Huaqing Xie

Nanofluids, the fluid suspensions of nanomaterials, have shown many interesting properties, and the distinctive features offer unprecedented potential for many applications. This paper summarizes the recent progress on the study of nanofluids, such as the preparation methods, the evaluation methods for the stability of nanofluids, and the ways to enhance the stability for nanofluids, the stability mechanisms of nanofluids, and presents the broad range of current and future applications in various fields including energy and mechanical and biomedical fields. At last, the paper identifies the opportunities for future research.

Various suspensions containing Al2O3 nanoparticles with specific surface areas in a range of 5–124 m2 g−1 have been prepared and their thermal conductivities have been investigated using a transient hot-wire method. Nanoparticle suspensions, containing a small amount of Al2O3, have substantially higher thermal conductivity than the base fluid, with the enhancement increasing with the volume fraction of Al2O3. The enhanced thermal conductivity increases with an increase in the difference between the pH value of aqueous suspension and the isoelectric point of Al2O3 particle. For the suspensions using the same base fluid, the thermal conductivity enhancements are highly dependent on specific surface area (SSA) of nanoparticle, with an optimal SSA for the highest thermal conductivity. For the suspensions containing the same nanoparticles, the enhanced thermal conductivity ratio is reduced with the increasing thermal conductivity of the base fluid. The crystalline phase of the nanoparticles appears to have no obvious effect on the thermal conductivity of the suspensions. Comparison between the experiments and the theoretical model shows that the measured thermal conductivity is much higher than the values calculated using theoretical correlation, indicating new heat transport mechanisms included in nanoparticle suspensions.

Although the thermal properties of millimeter-sized carbon nanotube mats and packed carbon nanofibers have been readily measured, measurements for a single nanotube are extremely difficult. Here, we report a novel method that can reliably measure the thermal conductivity of a single carbon nanotube using a suspended sample-attached $T$-type nanosensor. Our experimental results show that the thermal conductivity of a carbon nanotube at room temperature increases as its diameter decreases, and exceeds $2000\text{ }\text{ }\mathrm{W}/\mathrm{mK}$ for a diameter of 9.8 nm. The temperature dependence of the thermal conductivity for a carbon nanotube with a diameter of 16.1 nm appears to have an asymptote near 320 K. The present method is, in principle, applicable to any kind of a single nanofiber, nanowire, and even single-walled carbon nanotube.

Multiwalled carbon nanotubes (CNTs) as produced are usually entangled and not ready to be dispersed into fluids. We treated CNTs by using a concentrated nitric acid to disentangle CNT aggregates for producing CNT nanofluids. Oxygen-containing functional groups have been introduced on the CNT surfaces and more hydrophilic surfaces have been formed during this treatment, which enabled to make stable and homogeneous CNT nanofluids. Treated CNTs were successfully dispersed into polar liquids like distilled water, ethylene glycol without the need of surfactant and into nonpolar fluid like decene with oleylamine as surfactant. We measured the thermal conductivities of these nanotube suspensions using a transient hot wire apparatus. Nanotube suspensions, containing a small amount of CNTs, have substantially higher thermal conductivities than the base fluids, with the enhancement increasing with the volume fraction of CNTs. For the suspensions with the same loading, the enhanced thermal conductivity ratios are reduced with the increasing thermal conductivity of the base fluid. Comparison between the experimental data and the theoretical model indicates that the thermal conductivities of nanotube suspensions seem to be very dependent on the interfacial layer that exists between the nanotube and the liquid.

A typical feature of polymer/fullerene based solar cells is that the current density under short-circuit conditions (Jsc) does not scale exactly linearly with light intensity (I). Instead, a power law relationship is found given by Jsc∝Iα, where α ranges from 0.85 to 1. In a number of reports this deviation from unity is speculated to arise from the occurrence of bimolecular recombination. We demonstrate that the dependence of the photocurrent in bulk heterojunction solar cells is governed by the build-up of space-charge in the device as a consequence of a difference in electron- and hole mobility. We have verified this for an experimental model system in which the mobility difference can be tuned from one to three orders of magnitude by changing the annealing treatment.

There has been an explosion of research into the physical and chemical properties of carbon-based nanomaterials, since the discovery of carbon nanotubes (CNTs) by Iijima in 1991. Carbon nanomaterials offer unique advantages in several areas, like high surface-volume ratio, high electrical conductivity, chemical stability and strong mechanical strength, and are thus frequently being incorporated into sensing elements. Carbon nanomaterial-based sensors generally have higher sensitivities and a lower detection limit than conventional ones. In this review, a brief history of glucose biosensors is firstly presented. The carbon nanotube and grapheme-based biosensors, are introduced in Sections 3 and 4, respectively, which cover synthesis methods, up-to-date sensing approaches and nonenzymatic hybrid sensors. Finally, we briefly outline the current status and future direction for carbon nanomaterials to be used in the sensing area.

Nanofluids, containing metal or nonmetal particles with nanometer sizes, exhibit much greater thermal conductivity than predictions. It has been proposed that interfacial structures formed by liquid molecule layering might play role. We investigated the impact of this interfacial nanolayer on the effective thermal conductivity of nanofluid. An expression for calculating enhanced thermal conductivity of nanofluid has been derived from the general solution of heat conduction equation in spherical coordinates and the equivalent hard sphere fluid model representing the microstructure of particle/liquid mixtures. The effects of nanolayer thickness, nanoparticle size, volume fraction, and thermal conductivity ratio of particle to fluid have been discussed. The predicted results are in good agreement with some recent available experimental data.

Ethylene glycol (EG) based nanofluids containing ZnO nanoparticles were prepared, and the thermal transport properties including thermal conductivity and viscosity were measured. The results show that the thermal conductivity of ZnO-EG nanofluids is independent of setting time from 20 to 360 min. The absolute thermal conductivity increases with temperature for different temperatures ranging from 10 to 60 °C, while the enhanced ratios are almost constant. The thermal conductivity of ZnO-EG nanofluids depends strongly on particle concentration, and it increases nonlinearly with the volume fraction of nanoparticles. The enhanced value of 5.0 vol.% ZnO-EG nanofluid is 26.5%, consistent with the prediction values by the combination of the aggregation mechanism with the Maxwell and Bruggeman models. The facts indicate that there is no magic physics behind nanofluids and the classical theories predict the measurements well. The rheological behaviors of the nanofluids show that ZnO-EG nanofluids with low volume concentrations demonstrate Newtonian behaviors, and for higher volume concentrations nanofluids, the shear-shinning behavior will be observed, because the effective volume fraction of aggregates is much higher than the actual solid volume fraction.

Electrochromic smart windows are regarded as a good choice for green buildings. However, conventional devices need external biases to operate, which causes additional energy consumption. Here we report a self-powered electrochromic window, which can be used as a self-rechargeable battery. We use aluminium to reduce Prussian blue (PB, blue in colour) to Prussian white (PW, colourless) in potassium chloride electrolyte, realizing a device capable of self-bleaching. Interestingly, the device can be self-recovered (gaining blue appearance again) by simply disconnecting the aluminium and PB electrodes, which is due to the spontaneous oxidation of PW to PB by the dissolved oxygen in aqueous solution. The self-operated bleaching and colouration suggest another important function of the device: a self-rechargeable transparent battery. Thus the PB/aluminium device we report here is bifunctional, that is, it is a self-powered electrochromic window as well as a self-rechargeable transparent battery.

We developed a facile technique to produce ethylene glycol based nanofluids containing graphene nanosheets. The thermal conductivity of the base fluid was increased significantly by the dispersed graphene: up to 86% increase for 5.0 vol % graphene dispersion. The 2D structure and stiffness of graphene and graphene oxide help to increase the thermal conductivity of the nanofluid. The thermal conductivity of graphene oxide and graphene in the fluid were estimated to be ∼4.9 and 6.8 W/m K, respectively.

Multi-walled carbon nanotubes (CNTs) as produced are usually entangled and not ready to be dispersed into organic matrix. CNTs were treated by mechano-chemical reaction with ball milling the mixture of potassium hydroxide and the pristine CNTs. Hydroxide radical functional groups have been introduced on the CNT surfaces, which enabled to make stable and homogeneous CNT composites. Treated CNTs were successfully dispersed into the palmitic acid matrix without any surfactant. Transient short-hot-wire apparatus was used to measure the thermal conductivities of these nanotube composites. Nanotube composites have substantially higher thermal conductivities than the base palmitic acid matrix, with the enhancement increasing with the mass fraction of CNTs in both liquid state and solid state. The enhancements of the thermal conductivity are about 30% higher than the reported corresponding values for palmitic acid based phase change nanocomposites containing 1 wt% CNTs treated by concentrated acid mixture.

Multi-walled carbon nanotubes (CNTs) were treated by using mechanochemical reaction method to enhance their dispersibility for producing CNT nanofluids. The thermal conductivity was measured by a short hot wire technique and the viscosity was measured by a rotary viscometer. The thermal conductivity enhancement reaches up to 17.5% at volume fraction of 0.01 for an ethylene glycol based nanofluid. Temperature has no obvious effects on thermal conductivity enhancement for the as prepared nanofluids. With an increase in thermal conductivity of the base fluid, the thermal conductivity enhancement of a nanofluid decreases. At low volume fractions (<0.4 vol%), nanofluids have lower viscosity than corresponding base fluid due to lubricative effect of nanoparticles. When the volume fraction is higher than 0.4 vol%, the viscosity increases with nanoparticle loadings. The prepared nanofluids, with no contamination to medium, good fluidity, stability, and high thermal conductivity, would have potential applications as coolants in advanced thermal systems.

Heat storage nanocomposites consisting of paraffin wax (PW) and multi-walled carbon nanotubes (MWNTs) have been prepared and their thermal properties have been investigated. Differential scanning calorimetric (DSC) results revealed that the melting point of a nanocomposite shifted to a lower temperature compared with the base material, with increasing the mass fraction of MWNTs, ϕw. With the addition of MWNTs, the latent heat capacity was reduced. The enhancement ratios in thermal conductivities of nanocomposites increase both in liquid state and in solid state with the increasing with ϕw when compared to the pure PW. For the composite with a mass fraction of 2.0%, the thermal conductivity enhancement ratios reach 35.0% and 40.0% in solid and in liquid states, respectively.

Graphene nanosheets/polyaniline nanofibers (GNS/PANI) composites are synthesized via in situ polymerization of aniline monomer in HClO4 solution. The PANI nanofibers homogeneously coating on the surface of GNS greatly improve the charge transfer reaction. The GNS/PANI composites exhibit better electrochemical performances than the pure individual components. A remarkable specific capacitance of 1130 F g−1 (based on GNS/PANI composites) is obtained at a scan rate of 5 mV s−1 in 1 M H2SO4 solution compared to 402 F g−1 for pure PANI and 270 F g−1 for GNS. The excellent performance is not only due to the GNS which can provide good electrical conductivity and high specific surface area, but also associate with a good redox activity of ordered PANI nanofibers. Moreover, the GNS/PANI composites present excellent long cycle life with 87% specific capacitance retained after 1000 charge/discharge processes. The resulting composites are promising electrode materials for high-performance electrical energy storage devices.

Heterostructured TiO2/SnO2 fibrillar nanocomposites were synthesized by using electrospinning technology with the setup composed of a syringe pump with two parallel syringes on it and a rotating collector. The heterojunctions were formed between TiO2 and SnO2 nanofibers fast and efficiently on a large scale, after the fiberizing carrier polyvinylpyrrolidone (PVP) on the as-spun composite nanofibers was burnt away at 500°C. The samples were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflection spectroscopy (DRS), and photoluminescence spectra (PL), respectively. The results indicated that two kinds of small nanofibers with different diameters were interconnected to form heterojunctions. Photocatalytic tests displayed that the heterostructured TiO2/SnO2 nanofibers exhibited a much higher degradation rate of methylene blue (MB), rhodamine B (RhB), and 4-chlorophenol (4-CP) than that of bare TiO2 nanofibers or Evonik P25 under UV light irradiation. The enhanced photocatalytic activity could be attributed to the effective charge separation derived from the coupling effect of TiO2 and SnO2 nanocomposites.

Phase-transfer method has been applied for preparing stable kerosene based Fe3O4 nanofluids. Oleic acid was successfully grafted onto the surface of Fe3O4 nanoparticles by chemisorbed mode, which let Fe3O4 nanoparticles have good compatibility with kerosene. Pure cubic-phase Fe3O4 nanoparticles with an average diameter of 15 nm were obtained. The nanoparticles in nanofluids had the tendency to form larger clusters with the diameter of about 155 nm, and ultrasonication could not decrease the size of the clusters. The Fe3O4 nanofluids prepared by phase-transfer method do not show the previously reported “time-dependence of the thermal conductivity characteristic”, which indicates the stability of the nanofluids. In the temperature range from 10 to 60 °C, the thermal conductivities of the nanofluids track the thermal conductivities of the base liquid and the enhanced ratios are almost constant for the same loading. There is no clear behavior of the previously reported “the temperature dependence of the thermal conductivity”. The enhancement of the thermal conductivity increases linearly with the volume fraction of Fe3O4 nanoparticles and the value is up to 34.0% for 1.0 vol.% nanofluid. It is proposed that the soft cluster structure may be the reasonable explanation of the anomalously enhanced thermal conductivity.

Toluene, as a strong carcinogen, is widely found in the newly renovated rooms, shopping malls, and workshops. Photocatalytic oxidation has great superiority and application prospects for the degradation of toluene. However, low photocatalytic efficiency under visible-light irradiation arising from easy agglomeration of the solid catalysts hinders their photodegradation of toluene gas. In this work, heterostructured TiO2/WO3 photocatalysts were fabricated via an electrospinning technology combining the hydrothermal treatment. The special microstructure and composition allowed the photogenerated electrons quickly transfer from the TiO2 nanofibers to the WO3 nanorods, and thus effectively reduced the recombination of photogenerated electrons and holes. Coupling TiO2 with the narrow band-gap WO3 broadened the spectral response range of TiO2. The heterostructured TiO2/WO3 photocatalysts exhibited a remarkably higher degradation rate of toluene gas than that of the bare TiO2 nanofibers under visible-light irradiation. The photocatalysts were deposited onto the inner walls of the photoreactor and some nylon meshes. The meshes were also placed in the photoreactor in a direction perpendicular to the air flow. The meshes increased the contact between photocatalysts in solid phase and toluene in gas phase, and about 85.3% of the toluene had been degraded in the experimental conditions.

The present study reports the electrospun one-dimensional TiO2/graphene oxide (GO) composite nanofibers photocatalysts using polyvinylpyrrolidone (PVP) as a fiberizing carrier. Continuous TiO2 nanofibers segregated by the well-dispersed GO with the content even high as 5 wt% were obtained after the carrier PVP was burnt away at 500 °C. The observed lower excitonic intensity from photoluminescent study in the TiO2/GO samples than that in bare TiO2 nanofibers indicated that the recombination of photoinduced electrons and holes in TiO2 could be effectively inhibited in the composite nanofibers. Photocatalytic studies suggested that the TiO2/GO composite nanofibers showed higher mobility of charge carriers and enhanced photocatalytic activity than bare TiO2 nanofibers under visible light irradiation. In addition, photocatalytic performance of the TiO2/GO composites nanofibers was enhanced with increasing the GO concentration in the composite nanofibers. The results presented herein provide new insights into TiO2/GO composites materials as high performance photocatalysts with potential uses in environmental remediation.

In order to locate the optimal carrier concentrations for peaking the thermoelectric performance in p-type group IV monotellurides, existing efforts focus on aliovalent doping, either to increase (in PbTe) or to decrease (in SnTe and GeTe) the hole concentration. The limited solubility of aliovalent dopants usually introduces insufficient phonon scattering for thermoelectric performance maximization. With a decrease in the size of cation, the concentration of holes, induced by cation vacancies in intrinsic compounds, increases rapidly from ≈1018 cm-3 in PbTe to ≈1020 cm-3 in SnTe and then to ≈1021 cm-3 in GeTe. This motivates a strategy here for reducing the carrier concentration in GeTe, by increasing the mean size of cations and vice-versa decreasing the average size of anions through isovalent substitutions for increased formation energy of cation vacancy. A combination of the simultaneously resulting strong phonon scattering due to the high solubility of isovalent impurities, an ultrahigh thermoelectric figure of merit, zT of 2.2 is achieved in GeTe-PbSe alloys. This corresponds to a 300% enhancement in average zT as compared to pristine GeTe. This work not only demonstrates GeTe as a promising thermoelectric material but also paves the way for enhancing the thermoelectric performance in similar materials.

Solar energy absorption and storage have attracted extensive attention and a number of potential phase change materials have been reported. In the current work, new shape-stabilized phase change composite materials are designed, which can integrate high solar energy absorption, heat storage and thermal conductivity. The composite phase change materials are composed of copper foam (CF) as the supports, carbon material (graphene oxide and reduced graphene oxide (RGO)) as surface modifiers, paraffin and PEG10000 as organic phase change materials. CF modified by carbon materials provides a large number of active sites for the adsorption of phase change materials, which are stable and not easy to leak. The surface temperature of the composite phase change materials can rise to 70 °C within 200 s. Compared with the pure phase change material, the thermal conductivity of the CF/RGO/paraffin is increased by 300%. Its latent heat enthalpy is 111.53 J/g, the photothermal conversion efficiency is as high as 86.68%. Our approach not only provides a new way for facile manufacturing of high-performance composite phase change materials, but also integrates the processes of solar energy utilization, which exhibit good optical absorption performance, fast thermal response and excellent thermal storage capacity.

Graphene is one of the most attractive materials due to its unique features, including high aspect ratio, excellent mechanical, thermal, and optical features. Especially, graphene and its derivatives exhibit the significant photothermal effect and are among the prominent candidates for the utilization of solar energy. This article reviews the progress on photothermal applications of graphene and its derivatives. Graphene and its derivatives are expected to be good candidates for a host of applications, such as solar collector, solar-driven water evaporation, photothermal catalysis, photothermal therapy, and photothermal antibacterial. The commercial potential, challenges and research trends of graphene-based photothermal materials are also discussed.

As a typical phase-change material (PCM) with high heat storage capacity and wide distribution, hydrated salts play broad and critical roles in solar energy utilization in recent years. However, the leakage and supercooling problems of hydrated salts have been a constraint to their further practical applications. In the current work, the super-hydrophilic reduced graphene oxide (RGO) aerogels modified by konjac glucomannan (KGM) as supporting structural materials are prepared by the hydrothermal reaction-freeze-drying, which can effectively absorb and convert visible sunlight energy into thermal energy. In addition, the super-hydrophilic aerogels compounded with PCMs can ameliorate the shortcoming of leakage and suppress the supercooling temperature as low about 0.2-1.5 °C in the freezing process. Under 1 sun irradiation, the prepared sodium acetate trihydrate/KGM-modified graphene oxide aerogel (SAT/KRGO) composite PCM achieves a high photothermal conversion efficiency (86.3%) due to its good light absorption property. The number of cycles has no apparent effect on the supercooling of the composite materials, suggesting their stable thermal cycles and thermal storage.

Nanofluids as heat transfer fluids have shown huge potential in heat exchange systems. How to balance effective thermal conductivity, dispersion stability and viscosity has become one of crucial issues for the application of nanofluids. MXene nanosheets with high aspect ratio coupled with high thermal conductivity and hydrophilic properties are expected to be potential fluids fillers. In this study, comprehensive performance of ethylene glycol (EG) based nanofluids containing multilayer and delaminated single layer Ti3C2Tx MXene are investigated in detail. The thermal conductivity of nanofluids with 5 vol% of multilayer and single layer Ti3C2Tx increase by 53.1% and 64.9% compared with EG, respectively. It is interesting that the viscosity of 1 vol% of MXene nanofluids is much lower than those of graphene and multi-walled carbon nanotube with 0.1 vol% due to the excellent self-lubricating properties. Single layer Ti3C2Tx-EG nanofluids also exhibit excellent stability and no obvious sedimentation in 30 days. The detailed study on MXene nanofluids will provide a strategy for heat transfer fluids development.

Energy shortage, environmental and ecological issues have prompted a focus on effective solar energy utilization. Using composite phase change materials (PCMs) as an energy storage medium is an important method to achieve efficient solar energy conversion. Biomass materials are highly desirable for solar applications due to their wide range of sources, low cost, environment-friendly, and natural porous structure. In this study, cellulose is selected as a carbon source precursor. Three-dimensional (3D) directional cellulose-based carbon aerogels (CBCA) are constructed through an immersion expansion, orientation, freeze-drying, and carbonization process. Taking tert-butanol/ deionized water as co-solvent, the aerogel shows high specific surface and productivity as well as low structural shrinkage. 3D directional graphitized porous network and graphene guarantee excellent broadband absorption, efficient heat transfer pathways, and effective thermal storage ability. Stearic acid (SA) and graphene are melt blending, followed by a vacuum-impregnating process for the formation of 3D composite PCMs. The thermal storage capability of PCMs is greater than 96%, accompanied by the highest thermal conductivity of 1.17 W/(m·K) with 0.5 wt% graphene. Moreover, the highest light-thermal conversion efficiency can reach 90.3%. It also has a maximum light-thermal-electric energy conversion output power of 1.80 mW. This work provides a feasible, economical strategy for highly efficient solar energy storage and thermal energy utilization.

Stable ethylene-glycol-based nanofluids containing graphene oxide nanosheets have been prepared. The measurements of thermal conductivity indicate that the nanofluids have substantially higher thermal conductivities than the base fluid. The thermal conductivity enhancement depends strongly on the volume fraction of graphene oxide nanosheets and increases with the increasing loading. When the nanosheet loading is 5.0 vol%, the enhancement ratio is up to 61.0%. The thermal conductivity of the fluids remains almost constant for seven days, indicating their high stability. The level of enhancement is independent of temperature in the measured temperature range.

3D hierarchitectures (HAs) of BiOCl composed of 2D nanosheets, which intercross with each other, have been successfully synthesized by a template-free solvothermal method at 160 °C for 12 h. The morphology and compositional characteristics of the 3D HAs were investigated by various techniques. On the basis of characterization results, the growth of such 3D HAs has been proposed as an Ostwald ripening process followed by self-assembly. The growth and self-assembly of BiOCl nanosheets could be readily tuned with the molar ratio of urea to BiCl3·5H2O, which brought different morphologies and microstructures to the final products. The specific surface area and porosity of the 3D hierarchitectured (HAd) BiOCl also were investigated by using nitrogen adsorption and desorption isotherms. UV–vis spectra reveal that the band gap energies of the 3D HAs can be tuned from 3.05 eV to 3.32 eV. The as-prepared 3D HAd BiOCl showed much higher photocatalytic activity than that of the reported in the literature, which was evaluated by the degradation of Rhodamine-B (RhB) dye under ultraviolet light irradiation.

Increasing interests have been paid to nanofluids because of the intriguing heat transfer enhancement performances presented by this kind of promising heat transfer media. We produced a series of nanofluids and measured their thermal conductivities. In this article, we discussed the measurements and the enhancements of the thermal conductivity of a variety of nanofluids. The base fluids used included those that are most employed heat transfer fluids, such as deionized water (DW), ethylene glycol (EG), glycerol, silicone oil, and the binary mixture of DW and EG. Various nanoparticles (NPs) involving Al2O3 NPs with different sizes, SiC NPs with different shapes, MgO NPs, ZnO NPs, SiO2 NPs, Fe3O4 NPs, TiO2 NPs, diamond NPs, and carbon nanotubes with different pretreatments were used as additives. Our findings demonstrated that the thermal conductivity enhancements of nanofluids could be influenced by multi-faceted factors including the volume fraction of the dispersed NPs, the tested temperature, the thermal conductivity of the base fluid, the size of the dispersed NPs, the pretreatment process, and the additives of the fluids. The thermal transport mechanisms in nanofluids were further discussed, and the promising approaches for optimizing the thermal conductivity of nanofluids have been proposed.

Aluminum nitride nanoparticles (AlNs) have been found to be a good additive for enhancing the thermal conductivity of traditional heat exchange fluids. At a volume fraction of 0.1, the thermal conductivity enhancement ratios are 38.71% and 40.2%, respectively, for ethylene glycol and propylene glycol as the base fluids. Temperature does not have much influence on the enhanced thermal conductivity ratios of the nanofluids, though a volume fraction of 5.0% appears to signify a critical concentration for rheology: for <5.0 vol% for Newtonian behavior, and for >5.0 vol% for obvious shear-shinning behavior, for both ethylene glycol and propylene glycol.

Five kinds of oxides, including MgO, TiO2, ZnO, Al2O3 and SiO2 nanoparticles were selected as additives and ethylene glycol (EG) was used as base fluid to prepare stable nanofluids. Thermal transport property investigation demonstrated substantial increments in the thermal conductivity and viscosity of all these nanofluids with oxide nanoparticle addition in EG. Among all the studied nanofluids, MgO–EG nanofluid was found to have superior features, with the highest thermal conductivity and lowest viscosity. The thermal conductivity enhancement ratio of MgO–EG nanofluid increases nonlinearly with the volume fraction of nanoparticles. In the experimental temperature range of 10–60°C, thermal conductivity enhancement ratio of MgO–EG nanofluids appears to have a weak dependence on the temperature. Viscosity measurements showed that MgO–EG nanofluids demonstrated Newtonian rheological behaviour, and the viscosity significantly decreases with the temperature. The thermal conductivity and viscosity increments of the nanofluids are much higher than the corresponding values predicted by the existing classical models for the solid–liquid mixture.

Nanofluids containing graphene oxide nanosheets have substantially higher thermal conductivities than the base fluids. The thermal conductivity enhancement ratios with the loading 5.0 vol % are up to 30.2%, 62.3%, and 76.8%, when the base fluids are distilled water, propyl glycol and liquid paraffin, respectively. The enhancement ratios of the nanofluids are almost constant with the tested temperature varying, and they are reduced with the increasing thermal conductivity of the base fluids. Heat transport along the graphene oxide plane is proposed to be the major contributions to the increase in the thermal conductivity.

TiO2 nanoparticles about 20 nm in diameter in the form of anatase were prepared and characterized. The nanoparticles were successfully dispersed into a paraffin wax (PW) matrix without any surfactant. The differential scanning calorimetric instrument and the transient short hot-wire method were used to measure the thermal properties of the TiO2/PW composites. It is found that the phase-change temperature and latent heat capacity vary with TiO2 nanoparticles loading levels. When the loading is not over 1 wt%, the phase-change temperature drops, and the latent heat capacity increases. When the loading is over 2 wt%, the phase-change temperature increases, and the latent heat capacity drops. A significant increase in latent heat capacity is found around 0.7 wt% loading. The thermal conductivity of the composites increases monotonically with increasing TiO2 loading. But such a tendency tends to decrease when the loading is over 3 wt%.

Stable ethylene glycol based copper nanofluids were prepared through a two-step method, using polyvinyl pyrrolidone as dispersant, which was vital for the long-term stability of nanofluids. The substantial thermal conductivity enhancements were seen for the obtained nanofluids. For ethylene glycol based copper nanofluids with 0.5 vol.% at 50 °C, the enhancement ratio was up to 46%. The thermal conductivities depended strongly on the temperature of fluid, and the enhancement ratios increased along with the increasing temperatures. Brownian motions of Cu nanoparticles would play the key role on determining the effects of the temperature on thermal conductivity enhancement of nanofluids. The measured apparent thermal conductivity showed the time-dependent characteristic within 15 min. It indicated that the measurement should be made after 15 min at least to obtain the true thermal conductivities of ethylene glycol based copper nanofluids.

Homogeneous and stable nanofluids have been produced by suspending well dispersible multi-walled carbon nanotubes (CNTs) into ethylene glycol base fluid. CNT nanofluids have enhanced thermal conductivity and the enhancement ratios increase with the nanotube loading and the temperature. Thermal conductivity enhancement was adjusted by ball milling and cutting the treated CNTs suspended in the nanofluids to relatively straight CNTs with an appropriate length distribution. Our findings indicate that the straightness ratio, aspect ratio, and aggregation have collective influence on the thermal conductivity of CNT nanofluids.

α-MnO2 nanorod was prepared by chemical precipitation with surfactant as the structure-directing agent and subsequent heat treatment at 800 °C. The morphology and structure of the prepared α-MnO2 were investigated by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). It was revealed that the α-MnO2 nanorod was successfully synthesized without impurities and the diameter of the nanorod was less than 50 nm. In cyclic voltammetry and galvanostatical discharge–charge test, the α-MnO2 nanorod showed regular capacitive behaviors and good cycling stabilities and delivered a maximum capacitance of 166.2 F/g, which indicated that the α-MnO2 nanorod was a potential good electrode material for supercapacitor application.

Nanofluids offer the exciting new possibilities to enhance heat transfer performance. In this paper, experimental and theoretical investigations have been conducted to determine the effect of CuO nanowires on the thermal conductivity and viscosity of dimethicone based nanofluids. The CuO nanowires were prepared through a thermal oxidation method, and the analysis indicated that the as-prepared CuO nanowires had high purity, monocrystalline with a monoclinic structure and large aspect ratio compared to CuO nanospheres. The experimental data show that the thermal conductivity of the nanofluids increases with the volume fraction of CuO nanowires or nanospheres, with a nearly linear relationship. For the nanofluid with the addition of 0.75 vol.% CuO nanowires, the thermal conductivity enhancement is up to 60.78%, which is much higher than that with spherical CuO nanoparticles. The nanofluids exhibit typical Newtonian behavior, and the measured viscosity of CuO nanowires contained nanofluids were found only 6.41% increment at the volume fraction of 0.75%. It is attractive in enhanced heat transfer for application. The thermal conductivity and viscosity of CuO nanofluids were further calculated and discussed by comparing our experimental results with the classic theoretical models. The mechanisms of thermal conductivity and viscosity about nanofluids were also discussed in detail.

A remarkable synergistic effect between graphene sheets and alumina particles in improving the thermal conductive properties of the novel thermal grease is demonstrated. The use of hybrid size alumina filler leads to compact packing structure in the silicone base and hinders the aggregation of graphene to form clusters. The two-dimensional graphene with superb thermal conductivity can bridge the alumina particles to form more compact packing structure and provide faster and more effective pathways for phonon transport in thermal grease. These synergistic effects decrease the thermal boundary resistance and enhance the thermal conductivity of the thermal grease. The addition of graphene is only 1 wt.%, and the maximum thermal conductivity of the novel thermal grease is 3.45 W/m K. It is significantly improved compared with the thermal grease without graphene (2.70 ± 0.10 W/m K). With respect to the silicone base, an enhancement in thermal conductivity of 2553% is obtained. Meanwhile, a correction theoretical model is proposed by modifying Burggeman asymmetric model, and the model predictions are in reasonable agreement with the experimental values.

A chemical reduction method for preparing monodispersed pure-phase copper colloids in water and ethylene glycol has been reported. Owing to the reduction property of ethylene glycol, the reaction rate in ethylene glycol is higher than that in water. In addition, the amount of reducing agent can be reduced largely. Ascorbic acid plays roles as reducing agent and antioxidant of colloidal copper, due to its ability to scavenge free radicals and reactive oxygen molecules. Thermogravimetric results reveal that the as-prepared copper nanoparticles have good stability, and they begin to be oxidized at above 210 degrees C. Polyvinyl pyrrolidone works both as size controller and polymeric capping agents, because it hinders the nuclei from aggregation through the polar groups, which strongly absorb the copper particles on the surface with coordination bonds.

Four different methods, acid oxidation, mechanochemical reaction, ball milling, and grafting following acid oxidation, were used to treat multi-walled carbon nanotubes (MWCNTs). During treatment, hydroxyl groups, carboxylic groups, and amidocyanogen were introduced onto the surfaces of the MWCNTs. The MWCNTs were dispersed into palmitic acid (PA) to prepare phase change composites with high thermal conductivity. Both chemical treatment and ball milling help to break the MWCNT aggregates and to enhance their dispersibility. Measurements show that the thermal conductivity increase of the composites is highly dependent on the MWCNT pretreatment process. We propose that the difference in the interfacial thermal resistance between the MWCNTs and the matrix is due to the difference of the MWCNT surface state caused by different treatment processes. In all the MWCNT/PA composites, the one containing MWCNTs with hydroxyl groups, treated by a mechanochemical reaction, has the highest thermal conductivity increase, which, at room temperature, is up to 51.6% for a MWCNT addition of 1.0%.

Fabrication highly efficient photothermal conversion nanofluids is a fascinating topic in solar energy harvesting applications. Herein, we present TiN is an excellent alternative plasmonic nanofluid for solar thermal conversion. The optical absorption property and the photothermal conversion performance of titanium nitride (TiN) are superior to another five traditional materials such as carbon nanotube, graphene, Au, Ag and metal sulfide (CuS). Dual localized surface plasmon resonance (LSPR) effect between Au and TiN nanoparticles make the hybrid nanocomposite (Au/TiN) possess superior optical absorption to TiN at the same concentration. The maximal temperature rise of 100 ppm TiN after irradiation for 20 min is 14.2 °C. The photothermal conversion efficiency of TiN is much higher than another five conventional nanofluids. All Au/TiN nanofluids with different Au loadings show higher maximal temperature rise than TiN, indicating dual LSPR effect is beneficial for better photo-thermal conversion performance.

Graphene oxide/polypyrrole nanowire composite material (GO/PPy) is synthesized using an in situ chemical polymerization method. The field-emission scanning electron microscope (FE-SEM) and transmission electron microscopy (TEM) results demonstrate that the PPy nanowires with 40 nm in diameter are uniformly dispersed on the surface of GO nanosheets, which greatly increases the surface area of the material and the charge transfer reaction. This two-dimensional structure exhibits better electrochemical performance than the pure individual components. According to the galvanostatic charge/discharge analysis, the GO/PPy composite has a good supercapacitive performance with a specific capacitance of 728 F g−1 at a discharge current density of 0.5 A g−1, higher than that of PPy nanowires (251 F g−1). At a discharge current density of 2.5 A g−1, the GO/PPy composite also has a high specific capacitance of 675 F g−1. Significantly, the GO/PPy electrode shows excellent cycling stability (7% capacity loss after 1000 cycles) due to the GO layer releasing the intrinsic differential strain of PPy chains during long-term charge/discharge cycles.

Carbon nanotubes (CNTs) with ultrahigh thermal conductivity and very large aspect ratio have been proposed as excellent dispersions for preparing nanofluids, a new kind of thermal performance enhanced heat transfer media. In the past decade, various techniques have been developed to produce homogeneous and long-term stable CNT contained nanofluids with or without using surfactants. The thermal performances including thermal conductivity, convective heat transfer coefficient, and boiling critical heat flux have been investigated. Efforts have been taken to elucidate the heat transfer mechanism in CNT nanofluids, and theoretical models have been proposed to predict the thermal conductivity enhancement of CNT nanofluids. This article aims to address the preparation techniques and the experimental and theoretical studies on the heat transfer charicteristics of CNT nanofluids.

This paper presents an experimental investigation of rheological and heat transfer properties of Al2O3 nanofluids based on the mixture of 45 vol.% ethylene glycol and 55 vol. % water. The Al2O3 nanofluids (volume fraction φ = 0.02) over 45 °C exhibit Newtonian behaviors, below 45 °C, they will be non-Newtonian fluids. The enhanced thermal conductivity ratios of the nanofluids with the volume fraction 1.0%, 2.0% and 3.0% are 3.8%, 7.7%, and 11.6% respectively, slightly larger than those predicted by the classic theoretical models. The heat transfer coefficients of the nanofluids with 1.0 vol.% and 2.0 vol.% have been found an increase up to 57% and 106%, respectively, when the Reynolds number is 2000.

Abstract Miniaturized power supplies, such as microsupercapacitors, are highly demanded in micro-electro mechanical systems (MEMS) and micro portable microdevices due to their superior cyclability, high power density, and considerable energy. In this study, we utilize ZIF-8 derived carbon as a source of active material to fabricate flexible microsupercapacitors via a simple electrophoresis method. The deposited ZIF-8 derived carbon particles with high surface area play a decisive role in achieving high electrochemical performances. The simple and straightforward process of electrophoretic deposition using ZIF-8 derived carbon particles generates porous carbon films on microsupercapacitors, which leads to a superior electrochemical performance.

Photothermal energy conversion and storage are crucial in solar collection systems. However, it is difficult for traditional media to balance high photothermal conversion, thermal conductivity and thermal energy storage. Considering the advantages of nanofluids (volumetric absorption systems) and PCMs (high latent storage density), we develop novel form-stable PCMs for solar collection systems and overcome the disadvantages of current systems, which take melamine sponge as supporting materials, paraffin wax as solid-liquid PCMs, reduced graphene oxide and zirconium carbide as solar absorption and thermal conduction additives. The results demonstrate that the rich network skeleton structure of reduced graphene oxide modified melamine sponge provides huge surface tension and capillary force to support paraffin wax for achieving the shape-stability before and after phase transition, and the latent enthalpy reaches 137 J/g. The composites PCMs with different content zirconium carbide show good photoabsorption, high thermal storage capacity and excellent heat transfer property. The photothermal conversion efficiency is up to 81% when doped with 0.01 wt% zirconium carbide. The maximum thermal conductivity of composites PCMs is 121% higher than that of paraffin wax. The reduced graphene oxide and zirconium carbide co-modified melamine sponge/paraffin wax composites show its great potential in solar energy utilization and storage.

Epoxy resin based thermal interfacial materials (TIMs) with high thermal conductivity have been obtained by filling Ag nanoparticle-decorated graphene nanosheets (GNSs) as thermal conductive fillers. The thermal conductivity (k) enhancement of epoxy resin based TIMs increases with the thermal filler loading. The more decoration of Ag nanoparticles on the GNS surfaces, the higher thermal conductivity enhancement of epoxy resin based TIM is. It is proposed that the bigger Ag nanoparticles acting as “spacers” increase the distance between the graphene sheets more than the smaller ones. It is not easy for graphene sheets to form stacked graphitic structures and the high specific surface area as well as other unique properties exhibited by 2D graphene are retained. Furthermore, the larger particle size is desired to minimize the scattering of phonons because of low interfacial thermal barrier. The obvious enhancement of thermal properties should be also attributed to the high intrinsic k of graphene and the effective thermal conductive networks forming by graphene and Ag nanoparticles. The synergistic effects including the stronger phonon Umklapp scattering, better phonon transmission trough the interfaces, decreasing Kapitza resistance, and decreasing ability of heat transfer by electrons result in the slight variation of k with the temperature. The weak temperature dependence of k is beneficial for TIM applications and can be obtained by controlling the addition of hybrid thermal fillers and quantity of decorated silver nanoparticles.

Generating water steam is a significant process for many fields. By combining heat localization and thin-film evaporation, a low-cost high-efficiency solar steam generator is proposed here. The measurements show that the energy efficiency is 78% at 1 kW/m2. Meanwhile, the experimental results agree well with our theoretical prediction based on thin-film evaporation theory. Besides, the dependence of efficiency on particle concentration and size are discussed. It’s found that the performance of the generator has a weak correlation to a few different particles (graphite, graphene, MoS2, and carbon nanotubes). This work offers a new in-depth understanding of high-efficiency solar steam generation and shows an example of using nanotechnology in practical application by a cheap and simple way.

Hydrogen production via steam reforming of the bio-oil from corn cob by fast pyrolysis with in situ CO2 sorption was investigated. The CaO obtained by calcining Ca(CH3COO)2·H2O showed the best CO2 adsorption efficiency among the three kinds of CaO from different precursors, and thus was selected as CO2 sorbent used in the sorption-enhanced steam reforming process. For the bio-oil steam reforming, when the liquid hourly space velocity was lower than 0.15 h−1, the yield and concentration of H2 tended to the maximum. With the comparison to the case without CO2 sorption, the yield and concentration of H2 with CO2 sorption were obviously improved with the carbon deposition effectively inhibited during the temperature range between 650 °C and 850 °C and the S/C range between 9 and 15. Through the sorption-enhanced steam reforming process, the highest hydrogen yield and concentration were obtained between 750 °C and 800 °C at S/C ratio of 12, and they were over 85% and 90%, respectively.

A novel excellent carbon-H2O nanofluid, nitrogen-doped graphitic carbon, has been discovered and prepared by using a facile metal-organic frameworks (MOFs) derived synthesis method. The obtained ZIF-8 (ZIF denotes zeolitic imidazolate framework) derived nitrogen-doped graphitic carbon (ZNG) analogs have high specific surface area of 580.2 m2 g−1 and show broad band absorption across the visible and near-infrared region. Au nanoparticles with the size of 2–5 nm are facilely and successfully deposited on the surface of nitrogen-doped graphitic carbon (Au/ZNG) via an impregnation-reduction method. The photothermal conversion tests indicate that both ZNG-H2O and Au/ZNG-H2O nanofluids show better photo-thermal performance and more awesome dispersion stability in water than conventional carbon nanofluids such as graphene and nitrogen-doped carbon nanotubes. Just as expected, Au/ZNG nanofluid shows obvious enhancement in photo-thermal performance due to the synergistic effect of the localized surface plasmon resonance (LSPR) Au nanoparticles and ZNG. This novel ZNG/water nanofluid is very attractive in working fluids for direct absorption solar collectors.

Abstract The basic task of railway signal work is to ensure safe and smooth transportation, improve transportation capacity, and improve transportation conditions and quality. Since it carries important information and control technology; it must be characterized by high security and high reliability. To address the aforementioned issues, this study uses a nonlinear technique to provide high-precision real-time detection of frequency shift signal parameters, based on an investigation of the sources of spectrum leakage in the FFT transformation. It not only reduces the sampling time but also the computation time when compared to the nonlinear method. This paper presents a frequency shift track circuit parameter based on nonlinear algorithm, studies the application of frequency shift signal parameter detection based on nonlinear algorithm, and simulates it with MATLAB. The experimental results show that the errors of center frequency, low frequency, and frequency offset are distributed in the range of ±0.05 Hz, ±0.005 Hz and ±0.15 Hz, respectively, which meet the parameters of frequency shift signal. The algorithm can meet the requirement of technical indexes and shorten the sampling time, which provides a theoretical basis for the design of the real-time frequency shift signal parameter tester.

Efficiency is an important factor in the utilization of solar energy. Direct absorption solar energy collectors (DASCs), a new generation collector of converting solar irradiation into heat directly by nanofluids, is regarded as a promising solution for capturing solar energy with high efficiency. Both good stability and high absorption ability are crucial for nanofluids to be an ideal working fluid of DASCs. In this work, we synthesize hyperstable Ti3C2Tx-H2O nanofluids as the working fluids of DASCs and investigate its photothermal conversion performance. The results show that the maximum conversion efficiency of thin-layer Ti3C2Tx nanofluids achieves 91.9% at a very low mass fraction of 0.02 wt%, which is higher than that of multi-layer Ti3C2Tx samples. Based on the experimental results, a simulation model is built to observe the radiation energy transformation in DASCs and results show that better photothermal performance of thin-layer MXene Ti3C2Tx stems from its stronger localized surface plasmon resonance (LSPR) effect. Besides, the coupling effect and the shape of Ti3C2Tx particles also play important roles in photothermal absorption and conversion. Based on our experimental and numerical results, the Ti3C2Tx-H2O nanofluids have great potential in solar energy harvesting.

The efficient reutilization of electrode materials in waste lithium-ion batteries (LIBs) is an urgent and tough problem that grows along with the rapid increase in the use of LIBs in various areas, including portable electronic products, electric vehicles and backup power supplies. Herein, we propose a promising way to recover the LiCoO2 positive electrode material from the recycled LIBs via structure restoration. The collected spent LiCoO2 powder is mixed with lithium salts and sintered to form a sophisticated layered structure. When Li2CO3 is added as the lithium source and the mole ratio of lithium to cobalt is controlled at 1.00 in the mixture, a layered structure of regenerated LiCoO2 could be preferably obtained at a calcination temperature of 800 °C. To improve the electrochemical performance of the regenerated LiCoO2, nanosized Al2O3 particles are coated on the surface of the regenerated LiCoO2. The Al2O3-coated and regenerated LiCoO2 demonstrates comparable properties to those of commercial LiCoO2 materials. The regeneration of spent LiCoO2 via structure restoration, which is demonstrated in the present study, provides an effective way to reuse cobalt metal directly without traditional leaching and re-synthesis procedures, which reduces energy consumption and contributes to the environmental protection.

Many semiconductors with broad solar spectrum absorption have always been pursuing for the effective photothermal conversion process. However, it is still a challenge to modulate the structural and bandgap of semiconductors to enhance the photothermal activity synergistically. In this work, facile prepared mesoporous CuO displays a narrower bandgap than non-porous CuO, leading to highly efficient solar-thermal conversion. Mesoporous CuO shows obvious broad and strong optical absorption, especially in the visible light region. It is noteworthy that the mesoporous CuO nanofluids exhibit good dispersibility in water. Different concentrations of mesoporous CuO nanofluids have higher temperature rise than non-porous CuO nanofluids. The photothermal conversion efficiency of 50 ppm mesoporous CuO/water nanofluid is 83.66%, compared with 58.86% for 50 ppm CuO/water nanofluid. Mesoporous CuO will bring a new paradigm for mesoporous metal oxide nanofluids as working fluids in direct absorption solar collectors.

Photothermal conversion, thermal energy transportation and storage are crucial in solar energy utilization. Due to the complexity of synthesis technology, it remains a hot issue to achieve the integration of high photothermal conversion, thermal conductivity and energy storage for phase change materials (PCMs) in recent years. As a typical carbon aerogel, reduced graphene oxide (RGO) aerogel exhibits the porous structure and outstanding properties, which makes RGO aerogel an attractive material for compounding with phase change materials. In this work, RGO aerogel is prepared by the hydrothermal-freeze drying method, which can effectively solve the issue of PCMs leakage. Oxygen-deficient TiO2 (TiO2-x) can further enhance the optical performance and improve the thermal conductivity of composite materials to 1.22 W/(m·K). The optimum TiO2-x content is 80%, which can obtain 89.9% photothermal conversion efficiency for TiO2-x/[email protected] TiO2-x/RGO aerogel will bring a new paradigm for PCMs as the working medium in absorption solar energy.

Solar thermal energy conversion and storage have gained more attention for solving energy crisis and environment issues. Phase-change materials with excellent thermal conductivity, high photothermal conversion efficiency, rapid heat storage and release, and good stability are required for solar thermal applications. In this study, three-dimensional (3D) interpenetrating network phase-change composites are fabricated by taking graphene-oxide (GO) aerogel (GA) containing a small amount of carbon nanotubes (CNTs) and carbon spheres (CSs) as support materials and vacuum impregnation melting polyethylene glycol (PEG) as the phase-change material. The 3D structure and abundant functional groups greatly improve the stability of phase-change composites. The addition of CNTs and CSs greatly increases the thermal conductivity and photothermal conversion capability of PCMs. Compared with pure PEG, thermal conductivity is increased by 181.58%, and photothermal conversion efficiency reaches 89.3%. Simulated results also confirm that GA-based phase change composites exhibit better thermal conductivity. Less thermal conductivity fillers and more phase-change material (96.4%) exhibit excellent thermal conductivity, high photothermal conversion efficiency, and a greater energy-storage density. The 3D phase-change composites are also applied for thermoelectric generation and show a stable output voltage of 35 mV for 300 s after removing the light source. The 3D interpenetrating network form-stable phase change composites based on black GA shows broad prospects in solar thermal energy applications.

Solar energy absorption, conversion, transportation and storage are crucial for high-efficiency solar thermal utilization. It is positive and promising to develop novel phase change materials (PCMs) with good shape stability, excellent photo-absorption and thermal-physical properties in the practical solar thermal application. Polymer supported PCMs with good heat transfer performance show an extensive application prospect. This research introduces a straightforward and practical strategy to prepare flexible poly (ethylene glycol) (PEG) form-stable phase change materials (FSPCMs) by taking cross-linked unsaturated polyester resin as skeleton and expanded graphite (EG) as thermal conductivity additive. The results show the FSCMs have excellent stability, thermal reliability and can be kept from leaking at 80 °C. The efficiency of photo-thermal conversion of FSPCMs doped with 7 wt % EG is up to 93.3%. The thermal conductivity is 1150% higher than PEG. Comparing to PEG, FSPCMs doped with 7 wt % EG can save time of 67.1% and 51.4% during the heating and cooling processes, respectively. The unsaturated polyester resin as common industry materials will provide more possibility for FSPCMs with enhanced thermal conductivity in practical solar thermal application.

Thermal interface materials (TIMs) are the key to solving heat dissipation problems in high-power electrical equipment. TIMs with high thermal conductivity and low thermal contact resistance (TCR) will enhance interfacial heat transfer. In this work, a phase-change mediated graphene composite hydrogel with low TCR and high thermal conductivity is designed. In addition, by introducing the hydrogel cross-linked network into the phase change material, the phase change material leakage problem is effectively solved. The thermal conductivity of the phase change hydrogel is enhanced by 324% from 0.3 Wm−1K−1 to 1.23 Wm−1K−1 at a filling rate of 7 wt% of graphene. The effects of temperature and pressure on phase change composite hydrogels are investigated. When the temperature is increased from 50 °C to 80 °C, TCR decreases rapidly from 90 K∙cm2/W to 0.2–0.5 K∙cm2/W, which is attributed to the improved interfacial wettability mediated by the phase change. When the pressure is increased from 10 Psi to 50 Psi with 80 °C, TCR decrease from 20 K∙cm2/W to 0.5 K∙cm2/W, improving interfacial contact and enhancing interfacial heat transfer. Combining a hydrogel with a cross-linked structure with the phase change material resulted in an excellent encapsulation of the phase change material. The thermal management performance of the phase change hydrogel is evaluated using infrared thermography and shows good thermal response behavior as the temperature rose to 68.7 °C after 120 s of heating. The strategy of combining phase change materials with hydrogels will provide new ideas for the design of TIMs.

Although graphene-based composites have been considered desirable candidates for thermal management applications, their poor electrical insulation restricts their further use in electrical insulation requiring occasions. Fluorinated graphene (FG), a new type of graphene-based material, attracts the attention of researchers due to its excellent electric insulation property. In this work, a novel fluorinated graphene aerogel/polydimethylsiloxane (FGA/PDMS) composite with a tightly-packed structure is constructed via freeze-drying and vacuum impregnation. The fabricated composite shows high compressibility and superior thermal conductivity of 1.41 W/(m·K) with a relatively low FGA loading of 0.28 wt%, 605.6% larger than the original PDMS. Meanwhile, it also maintains excellent insulation properties with an ultra-low electrical conductivity of 2.0 × 10−9 S/cm. 180 times smaller than graphene aerogel/PDMS. The practical excellent heat dissipation performance of the composite functioning as thermal interface material is also verified by a thorough study theoretically and experimentally. Furthermore, the FGA/PDMS composite also behaves with excellent flame retardant properties.

Knowledge distillation becomes a de facto standard to improve the performance of small neural networks. Most of the previous works propose to regress the representational features from the teacher to the student in a one-to-one spatial matching fashion. However, people tend to overlook the fact that, due to the architecture differences, the semantic information on the same spatial location usually vary. This greatly undermines the underlying assumption of the one-to-one distillation approach. To this end, we propose a novel one-to-all spatial matching knowledge distillation approach. Specifically, we allow each pixel of the teacher feature to be distilled to all spatial locations of the student features given its similarity, which is generated from a target-aware transformer. Our approach surpasses the state-of-the-art methods by a significant margin on various computer vision benchmarks, such as ImageNet, Pascal VOC and COCOStuff10k. Code is available at https://github.com/sihaoevery/TaT.

Fusing the camera and LiDAR information has become a de-facto standard for 3D object detection tasks. Current methods rely on point clouds from the LiDAR sensor as queries to leverage the feature from the image space. However, people discovered that this underlying assumption makes the current fusion framework infeasible to produce any prediction when there is a LiDAR malfunction, regardless of minor or major. This fundamentally limits the deployment capability to realistic autonomous driving scenarios. In contrast, we propose a surprisingly simple yet novel fusion framework, dubbed BEVFusion, whose camera stream does not depend on the input of LiDAR data, thus addressing the downside of previous methods. We empirically show that our framework surpasses the state-of-the-art methods under the normal training settings. Under the robustness training settings that simulate various LiDAR malfunctions, our framework significantly surpasses the state-of-the-art methods by 15.7% to 28.9% mAP. To the best of our knowledge, we are the first to handle realistic LiDAR malfunction and can be deployed to realistic scenarios without any post-processing procedure. The code is available at https://github.com/ADLab-AutoDrive/BEVFusion.

Photothermal energy conversion and storage based on organic solid-liquid phase change materials (PCMs) show huge potential in conquering discontinuous solar irradiation. It remains a challenge to fabricate integrated devices that take excellent photothermal conversion, heat transportation and energy storage into account. Here, we construct 3D oriented expanded graphite (EG) by compression induced graphite sheet self-assembly, then load the stearic acid (SA) to form oriented PCMs. The in-plane thermal conductivity, thermal response and energy storage density of 3D oriented PCMs are better than those of non-oriented PCMs under the same graphite mass faction and packing density. When the EG content is 20 wt%, the thermal conductivity of the oriented PCMs is 34.2% higher than that of the non-oriented PCMs and latent heat maintains above 159.36 J/g. We further prepare energy storage bricks and coordinate the heat conduction of oriented EG perpendicular to the axial direction of copper tube. The photothermal energy conversion efficiency of the energy storage brick reaches 95.3%, and the average powers during charging and discharging process are 2.1 kW and 2.4 kW, respectively. The design method for solar energy storage device improves the photothermal conversion efficiency, thermal conductivity and energy storage of PCMs, provides a simple and economical strategy for large-scale photothermal applications.

To achieve autonomous driving, developing 3D detection fusion methods, which aim to fuse the camera and LiDAR information, has draw great research interest in recent years. As a common practice, people rely on large-scale datasets to fairly compare the performance of different methods. While these datasets have been carefully cleaned to ideally minimize any potential noise, we observe that they cannot truly reflect the data seen on a real autonomous vehicle, whose data tends to be noisy due to various reasons. This hinders the ability to simply estimate the robust performance under realistic noisy settings. To this end, we collect a series of real-world cases with noisy data distribution, and systematically formulate a robustness benchmark toolkit. It can simulate these cases on any clean dataset, which has the camera and LiDAR input modality. We showcase the effectiveness of our toolkit by establishing two novel robustness benchmarks on widely-adopted datasets, nuScenes and Waymo, then holistically evaluate the state-of-the-art fusion methods. We discover that: i) most fusion methods, when solely developed on these data, tend to fail inevitably when there is a disruption to the LiDAR input; ii) the improvement of the camera input is significantly inferior to the LiDAR one. We publish the robust fusion dataset, benchmark, detailed documents and instructions on https://anonymous-benchmark.github.io/robust-benchmark-website.

In this research, the fracture characteristics and size effect of ultra-high performance fiber reinforced concrete (UHPFRC) are investigated by notched three-point bending beam test and meso-scale numerical simulation. Four series of geometrically similar UHPFRC notched-beams with different sizes were tested at quasi-static condition. Crack patterns during the fracture process were obtained by digital image correlation and the phenomenon of crack initiation, multiple cracking and crack localization were well captured. The macro-scale fracture properties are analyzed by double-K fracture model (DKFM) from the perspective of composite toughening. Results show that the initial fracture toughness evaluates the toughness of matrix and the increment from initial fracture toughness to unstable fracture toughness evaluates the toughening due to fiber bridging. The initial fracture toughness and unstable fracture toughness have no size effect and can be treated as material inherent. Experimental results also show a slight decreasing tendency of strength with the increasing of specimen size, which can be approximately fitted by size effect law (SEL). Then a meso-scale numerical model was developed by explicit representation of fibers and directly considering bond-slip relationship of fiber–matrix. Simulation results show that the meso-scale numerical model developed in this research can well simulate the fracture of UHPFRC in terms of crack patterns, fracture process zone, mechanical response and size effect. Parametric study was also conducted based on the meso-scale numerical model and the effects of fiber content, fiber orientation and interfacial bond strength on fracture performance and size effect are analyzed.

This letter reports on the measurements of the in-plane thermal conductivity and the electrical conductivity of a microfabricated, suspended, nanosized platinum thin film with the width of 260nm, the thickness of 28nm, and the length of 5.3μm. The experimental results show that the electrical conductivity, the resistance-temperature coefficient and the in-plane thermal conductivity of the nanofilm are greatly lower than the corresponding bulk values from 77to330K. The comparison results indicate that the relation between the thermal conductivity and the electrical conductivity of this nanofilm might not follow the Wiedemann–Franz law that describes the relation between the thermal conductivity and the electrical conductivity of a bulk metallic material.

A laser flash technique was applied to measure the thermal diffusivity along a multiwalled carbon nanotube (CNT) array in temperature range of −55–200°C. In the measurements, a nanosecond pulsed laser was used to realize noncontact heating and the temperature variations were recorded by an infrared detector. The experimental results show that the thermal diffusivity of the CNT array increases slightly with temperature in the −55–70°C temperature range and exhibits no obvious change in the 75–200°C temperature range. The CNT array has much larger thermal diffusivity than several known excellent thermal conductors, reaching about 4.6 cm2 s−1 at room temperature. The mean thermal conductivity (λ) of individual CNTs was further estimated from the thermal diffusivity, specific heat (Cp), and density (ρ) by using the correlation of λ=αρCp. The thermal conductivity of individual CNTs increases smoothly with the temperature increase, reaching about 750 W m−1 K−1 at room temperature.

A theoretical model which includes considerations of the effects of an interfacial nanolayer formed by liquid molecule layering on the particle/liquid interface and of micro-convection caused by thermal motion of nanoparticles has been proposed to calculate the effective thermal conductivity of nanofluids. This model accounts for the enhancement in effective thermal conductivity of a nanofluid with respect to the suspended nanoparticle size, volume fraction, temperature and thermal conductivities of the nanoparticle and base fluid. The predicted results are in good agreement with some recently available experimental data.

Single-walled carbon nanotubes (SWNTs) and double-walled carbon nanotubes (DWNTs) have been functionalized through the wet-mechanochemical reaction method. Results from the infrared spectrum and zeta potential measurements show that the hydroxyl groups have been introduced onto the treated SWNT and DWNT surfaces. Transmission electron microscope observations revealed that the SWNTs and DWNTs were cut short after being milled. SWNTs and DWNTs with optimized aspect ratio can be obtained by adjusting the ball milling parameters. Thermal conductivity enhancement of water-based nanofluids containing treated carbon nanotubes (CNTs) shows augmentation with the increase of temperature mainly due to the effects of an ordering liquid layer forming around the chemical surfaces of CNTs. Moreover, the thicker interfacial layer of water molecules on the surfaces of CNTs with smaller diameter, such as SWNTs, is in favor of greater thermal conductivity enhancement compared with the thinner one on the surfaces of DWNTs or MWNTs with larger diameter.

Multiwalled carbon nanotubes (MWNTs) were treated by concentrated acid combined with mechanical ball mill technology. The treated multiwalled carbon nanotubes (TCNTs) with functionalized surfaces and controlled morphologies were used to prepare silicon oil based nanofluids by using hexamethyldisiloxane as dispersant. Thermal conductivity results of the obtained nanofluids show that the collective effects, involving straightness ratio, aspect ratio, and aggregation of TCNTs, play a key role in the thermal conductivity of CNT nanofluids. This study suggests that the thermal characteristics of nanofluids might be manipulated by means of controlling the morphology of the additions, which also provide a promising way to conduct investigation on the mechanism of heat transfer in nanofluids. Reliable rheological properties of the prepared nanofluids were provided. It is important when the nanofluids are used in the potential heat exchange areas. The silicone oil based fluids behave in Newtonian manner in all the studied MWNT volume fractions and temperatures. The hexamethyldisiloxane added in silicone oil, in addition to decreasing the silicone oil viscosity, has little effect on the nanofluid rheological properties.

A green method was applied to prepare composites of multi-walled carbon nanotubes (MWNTs) decorated with silver nanoparticles (Ag-NPs). The MWNTs were functionalized by using mechanical ball milling technology in the presence of ammonium bicarbonate. The functionalized MWNTs were decorated with Ag-NPs by the traditional method of using a silver mirror reaction. Scanning electron microscopy (SEM) characterization showed that Ag-NPs distributed uniformly on the walls of MWNTs. The content and size of Ag-NPs could be controlled by adjusting the reducing time. The X-ray diffraction (XRD) patterns demonstrated that the Ag-NPs crystallized well. The resulting Ag/MWNT composites were used to prepare a water based nanofluid. The nanofluid showed higher thermal conductivity compared to that of a nanofluid containing MWNTs with functionalized surfaces.

Homogeneous and stable ethylene glycol based nanofluids containing low volume concentration diamond nanoparticles have been prepared. Diamond nanoparticles, purified and surface modified by the mixture acid, consist of the highly defective structure and the active functional groups on the surface. Ultrasound and the alkalinity of solution are beneficial to the deaggregate of soft diamond particle aggregation, and the diameters of purified nanodiamond are changed from 30–50 nm to 5–10 nm. The thermal conductivity enhancement decreases with elapsed time for 1.0 vol.% DNP–EG nanofluid at pH = 7.0. While for the stable nanofluids at pH = 8.5, there is no obvious thermal conductivity decrease within 6 months. The thermal conductivity enhancement values are up to 17.23% for the 1.0 vol.% nanofluid at 30 °C. Viscosity measurements show that the nanofluids demonstrate Newtonian behavior, and the viscosity significantly decreases with the temperature.

Stable nanofluids containing multi-walled carbon nanotubes (MWNTs) treated by concentrated acid and mechanical mill technology have been prepared. Water, ethylene glycol, glycerol, and silicone oil were used as base fluids. The rheological behaviors of the obtained nanofluids with different MWNT volume fractions and at different temperatures were investigated in details. The glycerol based and silicone oil based fluids behave Newtonian manner in all studied MWNT volume fractions and temperatures. The dispersant hexamethyldisiloxane added in silicone oil decreases the silicone oil viscosity but has no effect on the rheological properties of nanofluids. For the water based nanofluids, MWNTs act as lubricative function when the MWNT volume fraction is lower. Furthermore, for the ethylene glycol based and glycerol based fluid, almost no viscosity augmentation appears when the temperature is higher than 55°C.

The kinetics of Datong coal gasification in solid BF (blast furnace) slag using carbon dioxide as gasifying agent was studied between 1223 and 1423 K. The relative mass change during the gasification reaction was continuously monitored using a high-resolution thermogravimetric system. The influence of reaction temperature and coal/slag mass ratio in the reaction rate was analyzed. The reaction rate has a strong dependence on reaction temperature and coal/slag ratio. With increasing reaction temperature, carbon conversion, the peak value of reaction rate, the intrinsic surface reaction rate, and the reactivity index increases, and the time for complete carbon conversion decreased. The activation energy decreases with an increasing coal/slag ratio. When the coal/slag ratio is 1:0, the intrinsic the activation energy is 112 kJ/mol; however, when the coal/slag is 1:3, it is 53 kJ/mol. This indicates that BF slag is an active catalyst for carbon gasification. Reaction model Am (volume reaction model as proposed by Avrami-Erofeev) has the best fit on coal gasification using BF slag as heat carrier. The kinetic parameters applicable to the Am model different coal/slag ratios were obtained. The global rate equation that includes these parameters was developed.

Homogeneous and stable magnetic nanofluids containing γ-Fe2O3 nanoparticles were prepared using a two-step method, and their thermal transport properties were investigated. Thermal conductivities of the nanofluids were measured to be higher than that of base fluid, and the enhanced values increase with the volume fraction of the nanoparticles. Viscosity measurements showed that the nanofluids demonstrated Newtonian behavior and the viscosity of the nanofluids depended strongly on the tested temperatures and the nanoparticles loadings. Convective heat transfer coefficients tested in a laminar flow showed that the coefficients increased with the augment of Reynolds number and the volume fraction.

Thermodynamic analysis with Gibbs free energy minimization through Lagrange multiplier method was performed for coal gasification with steam using blast furnace (BF) slag as heat carrier and recycling its waste heat to produce hydrogen-rich gas (HRG). Simulations were carried out to study the operation temperature, pressure, S/C and BF slag basicity based on chemical equilibrium calculations. The optimal thermodynamic conditions were determined to improve hydrogen concentration and total syngas production as high as possible. The results suggested that the preferential conditions for HRG from Datong coal were achieved at 775 °C, atmospheric pressure and S/C of 2.0–3.0. Under these conditions, hydrogen concentration reached to 62.36% and the total gas production was 2.45 mol per mole of carbon in the coal. What's more, not only was the quality of HRG improved significantly, but also the BF slag waste heat was recycled effectively when using BF slag as heat carrier. The effect of BF slag basicity upon the gasification characteristics was also investigated, and the production of hydrogen increased significantly when basicity was 1.3.

Two kinds of silicone grease containing graphene nanoplatelets or reduced graphene oxide were prepared, and their thermophysical properties have been investigated. When the volume fraction was 1%, the reduced graphene oxide was the most effective additive to enhance the heat transfer properties of silicone, and graphene nanoplatelet was slightly inferior to the former. While when the concentration was enhanced, the viscosity of silicone grease containing reduced graphene oxide became very large due to its rich pore structure. Graphene nanoplatelet was efficient for the thermal conductivity enhancement of silicone grease, and it provided a thermal conductivity enhancement was up to 668% (loading of 4.25 vol.%). The experimental result is in excellent agreement with the recently developed theoretical model analyzing the thermal conductivity of isotropic composites containing randomly embedded GNPs, and it validates that graphene is an effective thermally conducting filler to let grease have high thermal conductivity with low filler content.

Polypyrrole (PPy) nanowires have been successfully grown on the surface of graphene oxide (GO) nanosheets by using a facile chemical method. The GO/PPy composites exhibit a predominant specific capacitance of 633 F/g at a current density of 1 A/g by charge/discharge analysis, in comparison with 227 F/g for pure PPy. The composites also show superior electrochemical rate capability and cycle stability. The attenuation of the specific capacitance is less than 6% after 1000 charge/discharge processes. The high specific capacitance and good stability of the GO/PPy composites are very promising for applications in electrochemical supercapacitor devices.

The steam reforming of four bio-oil model compounds (acetic acid, ethanol, acetone and phenol) was investigated over Ni-based catalysts supported on Al2O3 modified by Mg, Ce or Co in this paper. The activation process can improve the catalytic activity with the change of high-valence Ni (Ni2O3, NiO) to low-valence Ni (Ni, NiO). Among these catalysts after activation, the Ce-Ni/Co catalyst showed the best catalytic activity for the steam reforming of all the four model compounds. After long-term experiment at 700 °C and the S/C ratio of 9, the Ce-Ni/Co catalyst still maintained excellent stability for the steam reforming of the simulated bio-oil (mixed by the four compounds with the equal masses). With CaO calcinated from calcium acetate as CO2 sorbent, the catalytic steam reforming experiment combined with continuous in situ CO2 adsorption was performed. With the comparison of the case without the adding of CO2 sorbent, the hydrogen concentration was dramatically improved from 74.8% to 92.3%, with the CO2 concentration obviously decreased from 19.90% to 1.88%.

In this letter, we dynamically investigate the resistive switching characteristics and physical mechanism of the Ni/ZrO2/Pt device. The device shows stable bipolar resistive switching behaviors after forming process, which is similar to the Ag/ZrO2/Pt and Cu/ZrO2/Pt devices. Using in situ transmission electron microscopy, we observe in real time that several conductive filaments are formed across the ZrO2 layer between Ni and Pt electrodes after forming. Energy-dispersive X-ray spectroscopy results confirm that Ni is the main composition of the conductive filaments. The ON-state resistance increases with increasing temperature, exhibiting the feature of metallic conduction. In addition, the calculated resistance temperature coefficient is equal to that of the 10–30 nm diameter Ni nanowire, further indicating that the nanoscale Ni conductive bridge is the physical origin of the observed conductive filaments. The resistive switching characteristics and the conductive filament's component of Ni/ZrO2/Pt device are consistent with the characteristics of the typical solid-electrolyte-based resistive random access memory. Therefore, aside from Cu and Ag, Ni can also be used as an oxidizable electrode material for resistive random access memory applications.

The effect of nitrogen doping by the NH3 plasma treatment approach on the resistive switching properties of a HfO2-based resistive random access memory (RRAM) device is investigated. Test results demonstrate that significantly improved performances are achieved in the HfO2-based RRAM device by nitrogen doping, including low operating voltages, improved uniformity of switching parameters, satisfactory endurance and long retention characteristics. Doping by nitrogen is proposed to suppress the stochastic formation of conducting filaments in the HfO2 matrix and thus improve the performances of the Pt/Ti/HfO2/Pt device.

In this paper, the pyrolysis performance and pyrolysis reaction kinetic characteristic of Fuxin coal and Fushun coal using solid blast furnace slag as heat carrier were studied. Parametric studies were conducted to understand the effects of coal type, heating rate and mass ratio of slag to coal on the performance of pyrolysis reaction. The most appropriate mechanism model of coal pyrolysis reaction was selected by methods of Coats-Redfern and Malek. The results showed that the increasing heating rate was beneficial to coal pyrolysis reaction. The characteristic parameters of these two coals increased significantly with the heating rate increasing. The function of slag on coal pyrolysis reaction depended on coal type and slag to coal ratio. Slag improved pyrolysis reaction when the coalification degree was higher and heating rate was lower. Slag had no influence on pyrolysis reaction or even had restraint when the coalification degree and the heating rate showed the opposite trend. Based on the kinetic analysis, the Chemical reaction model (C3 model) was confirmed as the most appropriate mechanism model to describe the pyrolysis of coal using solid slag as heat carrier. The thermal decomposition profiles calculated using the kinetic parameters were in good agreement with the experimental results.

Laser-induced electron tunneling underlies numerous emerging spectroscopic techniques to probe attosecond electron dynamics in atoms and molecules. The improvement of those techniques requires an accurate knowledge of the exit momentum for the tunneling wave packet. Here we demonstrate a photoelectron interferometric scheme to probe the electron momentum longitudinal to the tunnel direction at the tunnel exit by measuring the photoelectron holographic pattern in an orthogonally polarized two-color laser pulse. In this scheme, we use a perturbative 400-nm laser field to modulate the photoelectron holographic fringes generated by a strong 800-nm pulse. The fringe shift offers direct experimental access to the intermediate canonical momentum of the rescattering electron, allowing us to reconstruct the momentum offset at the tunnel exit with high accuracy. Our result unambiguously proves the existence of nonzero initial longitudinal momentum at the tunnel exit and provides fundamental insights into the nonquasistatic nature of the strong-field tunneling.

The working fluids with higher solar thermal conversion performance within broadband spectrum ranges are of great concern for direct absorption solar collectors (DASCs). Both metal nanoparticles with localized surface plasmon resonance (LSPR) effects and carbon nanomaterials have unique spectral absorption behaviors and have shown better photothermal performance in DASCs. In this paper, we attempted to prepare composite nanofluids including plasmonic bimetallic alloy and carbon nanomaterials to realize enhanced solar absorption and photothermal conversion performance. By taking ZIF-8-derived nitrogen-doped graphitic polyhedrons (ZNGs) as carrier, plasmonic bimetallic Ag-Au alloy nanoparticles were loaded on them by an impregnation-reduction method successfully. Ag-Au/ZNGs ethylene glycol nanofluids showed significant broadband absorption in the visible and near-infrared spectrum range at a lower concentration. Comparing to ethylene glycol, the photothermal conversion effeiency of all ZNGs nanofluids increased remarkablely. Plasmonic bimetallic Ag-Au alloy nanoparticles further improved the photothermal conversion efficiency, which was up to 74.35% for Ag-Au ZNGs nanofluids compared with 72.41%, 70.35% for Au/ZNGs, Ag/ZNGs respectively. This work presents a new way to enhance solar energy absorption and improve solar thermal conversion efficiency of nanofluids for DASCs.

In this study, thermal interface material is used in photovoltaic–thermoelectric coupling device to enhance the utilization of solar energy. An operating system including cooling equipment is established. The output performance evolutions of PV–TE​ coupling device are carried out based on thermal contact resistance under different experimental conditions. The PV–TE coupling devices combine with monocrystalline silicon PV cell and bismuth telluride TEG. Results show that adding TEG could minimize the PV cell temperature increase, hence improving PV cell performance effectively. Results also indicate that, with thermal interface material, the power generation by PV cells increases at least 14% and the power generation by TEG increases at least 60% due to the decreasing thermal contact resistance. Applying thermal interface material enhances the heat transfer in PV–TE coupling device.

Thermal contact resistance is a key bottleneck to restrict the rapid heat dissipation of electronic device. The wetting between two contact surfaces is one of the most important factors affecting the thermal contact resistance. Phase change thermal interface material can transform from solid state to molten state by heat inducing, which is an efficient way to reduce the thermal contact resistance. In this work, a novel form stable phase change thermal interface material of graphene/olefin block copolymer/paraffin filled with graphene (≤4.0 wt%) was designed. Furthermore, the influence of temperature and pressure on thermal contact resistance were studied, and the dominant position of thermal contact resistance and RTIMs in total thermal resistance was analyzed systematically. The results exhibit that thermal contact resistance decreases sharply from 8–20 Kcm2/W to 0.1–0.2 Kcm2/W for the temperature increases from 37 °C to 45 °C (50 Psi), with a drop of up to two orders of magnitude. This is because the wettability of the two contact surfaces is greatly improved by changing solid–liquid contact to solid–liquid contact. In addition, the thermal contact resistance decreases slightly with the increase of pressure (10–50 Psi, 48 °C). A small amount of graphene can significantly enhance the thermal conductivity of graphene/olefin block copolymer/paraffin, but the effect on thermal contact resistance is relatively weak. Moreover, critical thickness is proposed to quantitatively evaluate the dominant position of thermal contact resistance or RTIMs in total thermal resistance. It facilitates the quantitative analysis and optimization of thermal resistance in practical application.

Thermal contact resistance (TCR) between the thermal interface materials (TIMs) and the upper and lower contact surfaces plays an important role in the heat dissipation process of electronic devices. Moreover, TCR is mainly affected by temperature, pressure and fluidity of TIMs. When the critical operating temperature of the electronic device is reached, if solid-solid contact between two contact surfaces is changed into solid-liquid contact, TCR will be greatly reduced. Based on this idea, a novel form-stable phase change TIMs is proposed. The thermal conductivity of paraffin wax (PA) is improved by filling Al2O3 particles. The addition of olefin block copolymer (OBC) improves the stability and solves the leakage problem of PA. In addition, the effects of temperature and pressure on the TCR, especially near the phase transition point, are systematically studied. These results confirm that TCR of phase change Al2O3/OBC/PA is very sensitive to temperature. When the temperature rises from 37 °C to 41 °C, TCR of all samples decreases sharply from 10~20 K⋅cm2/Wto 1~2K⋅cm2/W. TCR of all samples decreases slowly with the increase of pressure (10~50 Psi, 45 °C) and is very close to the TCR of common thermal grease. Finally, when the mass fraction of Al2O3 is higher than 60 wt%, the thermal conductivity of the Al2O3/OBC/PA increases sharply with the increase of Al2O3. Therefore, form-stable Al2O3/OBC/PA is an important development direction to solve the heat dissipation in electronic technology.

A novel class of nano-encapsulated phase-change material (NEPCM) was produced using the suspension polymerization method with the core n-octadecane capsulated in the shell of poly(2,3,4,5,6-pentafluorostyrene). The morphology and components of the NEPCM were analyzed by the scanning electron microscopy, the X-ray diffractometer, and the Fourier-transform infrared spectroscopy. The thermal performance of various NEPCM samples was compared based on the measurements of the differential scanning calorimetry, the thermogravimetric analyzer, and the thermal conductivity meter. It is found that the NEPCM4 with shell/core mass ratio 1:2 has the best thermal performance among the tested samples with six different mass ratios. The measured melting enthalpy heat of (171.8 ± 2.2) J•g−1 for the NEPCM4 is the highest among all the tested capsules and the encapsulation efficiency for the NEPCM4 is also maximized at (76.1 ± 1.8)%. Capsule size variation in the prepared samples is small. The average size diameter of the NEPCM4 capsules is measured to be 490 ± 16 nm. The thermogravimetric investigation reveals that the initial weight-loss temperature for the NEPCMs is increased in comparison with that for the pure n-octadecane. The prepared nanocapsules exhibit excellent thermal stability and thermal properties, possessing enormous potentials to enable practical applications in thermal energy storage.

Direct absorption solar collector (DASC) is regarded as one of the most promising next-generation solar energy collection technology. Most researches focus on the photothermal performance of working fluids. While the optical boundary condition, which is another important factor influencing the efficiency of DASC, receives little attention. In this paper, the ethylene glycol based TiN nanofluids are used as the research objective. The temperature-dependent optical properties of nanofluids are experimentally investigated in detail, and when the temperature increases from 0 °C to 60 °C, the optical absorption performance of fluids could enhance ~50%, which means that the heated fluids has stronger absorption capability. To improve the photothermal conversion efficiency of collector system, two types of irradiation directions have been studied for the collector, and different heat transfer mode of each type has been experimentally analyzed. The experimental results show that the added nanoparticles can significantly enhance the photothermal conversion efficiency of solar collectors. When the concentration of TiN is 0.003 wt.%, the photothermal conversion efficiency of bottom irradiation mode achieves ~45%, much higher than that of side irradiation. However, the side irradiation collector can save ~40% of time to reach steady-state compared with the bottom irradiation collector. Moreover, two kinds of collectors have a uniform temperature field (~10 °C difference between different depth) over 1.0 cm irradiation depth. Consequently, the prospects for possible applications of ethylene glycol based TiN nanofluids in high-efficiency DASC are presented.

Utilizing the heat energy of exhaust gases is a promising application of thermoelectric generator (TEG), which can convert low grade thermal energy into electricity. The annular thermoelectric generator (ATEG) is thought to be much more feasible for cylindrical heat source compared to the flat-plate thermoelectric generator (FTEG) in reference to the compatibility. Nevertheless, the quantitative comparison is lacking to clarify the prevalent geometry of TEG for cylindrical heat source. In this work, the performances of ATEG and FTEG are compared in detail with varying inlet temperature, velocity and the convective heat transfer coefficient when cylindrical heat source is applied. The turbulent heat source is described by the standard κ-ɛ functions together with the two-equation heat transfer model, while the output power and conversion efficiency of the ATEG and FTEG are calculated by solving the coupled thermo-electric equations. Our results showed that the output powers and the conversion efficiencies of ATEG and FTEG both increase with the increase of the inlet velocity, temperature, and the convective heat transfer coefficient. The conversion efficiency of ATEG is always higher than that of FTEG. The conversion efficiency of ATEG becomes even larger than that of FTEG when inlet temperature and/or convective heat transfer coefficient are relatively larger. In contrast, the output power of ATEG has no obvious difference with that of FTEG. This study addressed the condition when the ATEG has obvious advantage compared to the FTEG with cylindrical heat source applied. Our results suggest the annular TEG is better choice for cylindrical hot source especially when the inlet temperature and/or convective heat transfer coefficient are relatively larger. It could be a helpful guide for choosing suitable geometry of TEGs for energy harvesting in complex condition.

Solar-driven evaporation is a promising technology for freshwater production. However, traditional photothermal materials mainly focus on the issues of energy efficiency and versatility. The high cost of materials and the deterioration of solid material properties caused by salt accumulation hinder severely restricting industrialization. To solve these problems, a kind of flexible non-woven fabric loaded with reducing graphene oxide ([email protected]) is designed and prepared in this paper, which can remove the salts formed by evaporation through a simple washing process to clean and recycle the fabric. A bridge-shaped evaporation system is designed and established to form a co-evaporation mode on the upper and lower sides while avoiding heat loss to bulk seawater. Under the simulated sunlight (1.0 kW m−2), a high evaporation rate of 1.54 kg m−2 h−1 and a high evaporation efficiency of 97.83% are obtained. The outdoor solar evaporation experiment under natural sunlight shows that the average evaporation rate of [email protected] is 1.10 kg m−2 h−1. [email protected] provides a new way for low-cost, high-efficiency, large-scale solar seawater desalination because of superior solar thermal conversion performance and high evaporation rate.

CD47 is ubiquitously expressed on the surface of cells and plays a critical role in self-recognition. By interacting with SIRPα, TSP-1 and integrins, CD47 modulates cellular phagocytosis by macrophages, determines life span of individual erythrocytes, regulates activation of immune cells, and manipulates synaptic pruning during neuronal development. As such, CD47 has recently be regarded as one of novel innate checkpoint receptor targets for cancer immunotherapy. In this review, we will discuss increasing awareness about the diverse functions of CD47 and its role in immune system homeostasis. Then, we will discuss its potential therapeutic roles against cancer and outlines, the possible future research directions of CD47- based therapeutics against cancer.

Thermal energy harvesting and storage with phase change materials (PCMs) have attracted extensive exploration in solar-thermal utilization. Solving leakage issue of PCMs and improving the energy absorption, storage and transport are facing great challenges. As a typical aerogel with porous structure and strong light absorption, carbon aerogel (CA) becomes an attractive support material for PCMs. In this work, the carbon aerogels reinforced melamine foam (CA/Foam) were prepared by sol-gel polymerization, freeze drying and carbonization. To further optimize the pore structure and optical properties, CO2 activation is implemented to obtain the super black reinforced melamine foam, which is named as activated CA/Foam (ACA/Foam). After vacuum adsorption of PW, the prepared paraffin wax/activated carbon aerogel/foam (PW/ACA/Foam) maintains high thermal storage density of 143.4 J/g and shows excellent thermal stability, which can effectively solve the shortcoming of PCMs leakage due to rich pore structure. Encouragingly, the photothermal conversion efficiency of PW/ACA/Foam composite material can reach 92.1% with 5% weight fraction of resorcinol and formaldehyde in the precursor solution. The thermal conductivity of PW/ACA/Foam is 0.71 W/(m·K), 97.2% higher than pure PW, which will be the potential material for composite PCMs applied in solar energy utilization.

Antibiotic wastewater contains not only conventional pollutants but also high concentrations of antibiotics and the resulting pollutants, such as antibiotic resistant microorganisms and antibiotic resistant genes (ARGs). If not properly treated, the antibiotic wastewater will further induce the spread of antibiotic resistant microorganisms and ARGs in the environment. In this study, an up-flow anaerobic sludge bed (UASB)-anoxic/aerobic (membrane bioreactor) process (A/O(MBR)) was built to treat oxytetracycline (OTC) wastewater. Results showed that the removal efficiencies of OTC decreased from 72.92% to 59.60% when the OTC concentration increased from 25 mg/L to 50 mg/L. Increasing OTC concentration from 0 to 50 mg/L, the chemical oxygen demand (COD) removal efficiencies decreased from 97.47% to 95.05%. Nevertheless, the total nitrogen removal efficiency increased from 55.53% to 85.33%. Bacteroides and Azospira dominated in UASB and A/O(MBR) respectively with the relative abundance of 20.76% and 18.51% at 50 mg/L OTC. Both ARGs in the UASB and O(MBR) increased with the rise of OTC concentration and reached 3.44 × 109 and 7.61 × 108 copies/mL respectively at 50 mg/L OTC. And the corresponding mobile gene elements (MGEs) reached 4.29 × 108 and 3.58 × 108 copies/mL. The membrane presented an effective pollutants removal efficiency with the interception efficiencies for ARGs and MGEs reaching 90.86% and 87.91%, respectively.

To achieve the goal of carbon neutrality, efficient use of solar energy is feasible and imminent. The selection of phase change materials (PCMs) as energy storage media is an effective way to achieve practical utilization to solve the uncontinuity and unstability of solar energy. Solid-solid PCMs (SS-PCMs) have attracted attention due to their advantages of stable shape, no phase separation, and no corrosion. In this paper, cheap raw material pentaerythritol (PE) is selected as the energy storage medium. Titanium nitride (TiN) with localized surface plasmon resonance is used as light absorber and thermal conductive filler. The results show that phase transition enthalpy of 0.2 wt% TiN-composite phase change materials (CPCMs) is still as high as 287.8 J/g, which maintains 96.06 % energy storage density of PE. In addition, thermal conductivity of 0.2 wt% TiN-CPCMs is increased by 109.48 %, and photo-thermal conversion efficiency is as high as 90.66 %. Simultaneously, a thermoelectric harvester integrating thermoelectric generator (TEG) with SS-PCMs is proposed. The average maximum power of the TiN-CPCMs-TEG system is 59.26 % higher than that of the PE-TEG system. Total energy of system is also increased by 58.99 %, which lays the foundation for the application of mid-temperature heat collection engineering.

With the popularization of regional integrated energy system, there are a large number of integrated energy suppliers and consumers in regional integrated energy market. Transactions between integrated energy suppliers and consumers can create substantial social benefits, and the reasonable price mechanism will become very critical. In addition, low carbonization has become one of the goals of integrated energy market construction. Therefore, a price mechanism for regional integrated energy market considering carbon emissions is designed. First, based on the linear price function, a non-cooperative game model of integrated energy suppliers and consumers in the regional integrated energy market considering carbon emission is established. Further, a price mechanism is designed using the Nash equilibrium of the non-cooperative game. To protect the privacy of the market members, a distributed algorithm is proposed to solve the integrated energy trading model. Finally, numerical simulations are carried out to verify the validity of the proposed price mechanism, and the impact of carbon price changes is revealed through sensitivity analysis.

Two laboratory-level biological aerated filters (BAF) were constructed to explore their treatment capacity for simulated antibiotic wastewater at high (1 - 16 mg/L) and low (0 - 0.5 mg/L) concentrations. Results showed that BAF was capable of removing both sulfonamides and tetracyclines with an efficiency of over 90 % at 16 mg/L. The main mechanism for removing antibiotics was found to be biodegradation followed by adsorption. Paenarthrobacter was identified as the key genus in sulfonamides degradation, while Hydrogenophaga played a crucial role in tetracyclines degradation. Antibiotics resistant genes such as intI1, sul1, sul2, tetA, tetW and tetX were frequently detected in the effluent, with interception rates ranging from 105 - 106 copies/mL. The dominated microorganisms obtained in the study could potentially be utilized to enhance the capacity of biological processes for treating antibiotics contaminated wastewater. These findings contribute to a better understanding of BAF treating wastewater containing antibiotics and resistant genes.

This article deals with recent progress including the authors’ work concerning the molecular design, synthesis, purification, characterization and physical properties of seven types of multiphase copolymers of styrene (S) and ethylene oxide (EO), namely, PS–PEO diblock copolymers, PS–PEO–PS and PEO–PS–PEO triblock copolymers, star-shaped block copolymers, multiblock copolymers, PEO–g-PS, PS–g-PEO graft copolymers and five types of alkyl (meth)acrylate and ethylene oxide multiphase copolymers as well as other types of block and graft copolymers from ethylene oxide and diene or other vinyl (or acrylic) monomer.

A transient short hot wire technique (SHWT) is developed for simultaneous determination of the thermal conductivity and thermal diffusivity of various materials such as liquids, gases or powders. A metal wire with (or without) insulation coating serves both as a heating unit and as an electrical resistance thermometer and the wire is calibrated using water and toluene with known thermophysical properties. This SHWT includes correlation of the experimental data with numerically simulated values based on a two-dimensional heat-conduction model. For the measurements with proportional relation between temperature rise and logarithmic heating time interval, the thermal conductivity and thermal diffusivity are obtained from the slope and the intercept of the measured temperature rise and those of calculated non-dimensional temperature rise by including the heat flux and the properties of the wire. For the measurements with nonlinear relation between temperature rise and logarithmic heating time interval, the thermal conductivity and thermal diffusivity are extracted from a curve fitting method by using the downhill simplex method to match the experimental data and the numerical values. This technique is applied here using air as a testing sample. The effect of natural convection is investigated and the accuracy of this measurement is estimated to be 2% for thermal conductivity and 7% for thermal diffusivity.

Nanofluids, nanoparticle suspensions prepared by dispersing nanoscale particles in a base fluid, have been gaining interest lately due to their potential to greatly outperform traditional thermal transport liquids. Diamond has the highest thermal transport capacity in nature and diamond particles are often used as filler in mixtures for upgrading the performance of a matrix. It is reasonable to expect that the addition of diamond nanoparticles (DNPs) would lead to thermal performance enhancement in a base fluid. In this study, homogeneous and stable nanofluids composed of DNPs as the inclusions and a mixture of ethylene glycol (EG) and water as base fluid have been prepared. Acid mixtures of perchloric acid, nitric acid and hydrochloric acid were employed to purify and tailor the DNPs to eliminate impurities and to enhance their dispersibilty. Ultrasound and the alkalinity of solution are beneficial to the deaggregation of the soft DNP aggregations. The thermal conductivity enhancement of the DNP nanofluids increases with DNP loading and the thermal conductivity enhancement is more than 18.0% for a nanofluid at a DNP volume fraction of 0.02. Viscosity measurements show that the DNP nanofluids demonstrate Newtonian behaviour, and the viscosity significantly decreases with temperature. With increasing volume fraction of DNPs, the convective heat transfer coefficient increases first, and then decreases with a further increase in the volume fraction of DNPs. The nanofluid with a volume fraction of 0.005 has optimal overall thermal performance.