Apparatus including a magnetometer having a pair of U-shaped cores for extended lateral range electrical conductivity logging

Research of dielectric properties МOS-structures Si/Al 2O 3/Al on the basis of aluminium oxide layers received by the method of atomic layer deposition is carried out. Temperature-frequency dependences of real (e`) and imaginary (e``) components of complex dielectric permeability, di electric losses tanδ(f) and conductivity (σ ac) in the field of frequencies f = 1·10 -1–1·10 6 Hz are measured. It is established that in the examined structures the relaxation dispersion e` and e`` takes place. It is shown that dielectric losses in oxide layers are caused by relaxation polarization and through conductivity. It is found out that there is a hopping mechanism of conductivity with the frequency dependence of type σ ac ~ f 0.85. Parametres of spectrum of the localized states are estimated: radius of localization а = (3.66 ÷ 9.07) A, the Fermi-level density of states (N F) N F = (8.34 ÷ 31.44) ·10 19 эВ -1·м -3 and the spread of these states (∆E) ∆Е ~ (10 -2 ± 10 -3) эВ, average time and distance (r 0) jumps τ = 1 µs and r 0 = (75 ÷ 188) A. These features are explained in terms of structural properties of oxide layers.

Abstract Ac conductivity measurements and its analysis has been performed on x Bi 2 O 3 –(65− x )Li 2 O–20ZnO–15B 2 O 3 (0 ≤  x  ≤ 20) glasses in the temperature range 30–300 °C and a frequency range of 100 Hz to 1 MHz. The dc conductivity increased and the activation energy decreased with lithium content. The frequency dependent conductivity has been analyzed employing conductivity and modulus formalisms. The onset of conductivity relaxation shifts towards higher frequencies with temperature. The Almond–West conductivity formalism is used to explain the scaling behavior, and the relaxation mechanism is independent of temperature.

Electrolysis of molten lunar soil or rock is examined as an attractive means of wresting useful raw materials from lunar rocks. It requires only hat to melt the soil or rock and electricity to electrolyze it, and both can be developed from solar power. The conductivities of the simple silicate diopside, Mg CaSi2O6 were measured. Iron oxide was added to determine the effect on conductivity. The iron brought about substantial electronic conduction. The conductivities of simulated lunar lavas were measured. The simulated basalt had an AC conductivity nearly a fctor of two higher than that of diopside, reflecting the basalt's slightly higher total concentration of the 2+ ions Ca, Mg, and Fe that are the dominant charge carriers. Electrolysis was shown to be about 30% efficient for the basalt composition.

The determination of hydrologic parameters that characterize fluid flow through rock masses on a large scale (e.g., hydraulic conductivity, capillary pressure, and relative permeability) is crucial to activities such as the planning and control of enhanced oil recovery operations, and the design of nuclear waste repositories. Hydraulic permeability and electrical conductivity of sedimentary rocks are predicted from the microscopic geometry of the pore space. The cross-sectional areas and perimeters of the individual pores are estimated from two-dimensional scanning electron micrographs of rock sections. The hydraulic and electrical conductivities of the individual pores are determined from these geometrical parameters, using Darcy's law and Ohm's law. Account is taken of the fact that the cross-sections are randomly oriented with respect to the channel axes, and for possible variation of cross-sectional area along the length of the pores. The effective medium theory from solid-state physics is then used to determine an effective average conductance of each pore. Finally, the pores are assumed to be arranged on a cubic lattice, which allows the calculation of overall macroscopic values for the permeability and the electrical conductivity. Preliminary results using Berea, Boise, Massilon and Saint-Gilles sandstones show reasonably close agreement between the predicted and measured transport properties. 12 refs., 5 figs., 1 tab.

Perovskites and perovskite related materials are materials that are candidates for applications such as oxygen permeable membranes, cathodes for SOFC and high-temperature oxygen sensors. This arises from the potential high ionic conductivity and the chemical stability even at low partial pressures of oxygen. From an application point of view, it is important to have knowledge about the oxygen transport properties in these materials. Oxygen transport in mixed conducting oxides involves two inherently different processes; oxygen exchange between bulk gas and surface and solid state diffusion. The objective of this work has been to obtain fundamental understanding of these transport properties in mixed ionic and electronic conductors. For that purpose two materials systems with significant differences in electronic conductivty and oxygen vacancy concentration were chosen as objectives for the investigation, viz.: Sr-substituted LaCoO3 and Al-substituted SrTiO3.All transport properties (diffusion and surface exchange) have been assessed by electrical conductivity relaxation, and the work also evaluate the pros and cons using this specific method to obtain transport data for the materials in question.In the first two papers (Paper 1 and Paper 2) transport properties are derived for La1-xSrxCoO3-δ (x=0 (LC), 0.2 (LSC-02) and 0.5 (LSC-05)). In Paper 1 “chemical transport coefficients”, Dchem and kchem, are reported. More fundamental transport coefficients, such as oxygen component diffusion coefficient (DO) and vacancy diffusion coefficients (DV), are also deduced and discussed. Activation energies for DO and DV, were determined. The activation energies for DO varies from 279 kJ/mol for LC to 174-222 kJ/mol for LSC-02 and 90-105 kJ/mol for LSC-05, decreasing with increasing Srcontent. The activation energies for the vacancy diffusion coefficient, DV, are smaller than for the component diffusion coefficients and typical values are 77 kJ/mol for LC, 85 kJ/mol for LSC-02 and 75 kJ/mol for LSC-05, that is, almost independent of Sr-content. The enthalpies of vacancy formation decreases with increasing Sr content. The values are 206 kJ/mol for LC, 75 kJ/mol for LSC-02 and 15 kJ/mol for LSC-05, which agrees well with values reported in the literature. However, the vacancy diffusion coefficient showed an unexpected increase at high concentrations of oxygen vacancies, corresponding to δ=0.27-0.30. The phenomena with a PO2 dependent DV is discussed.In Paper 2, the oxygen surface exchange coefficient, k0, is derived from “chemical values” reported in Paper 1, and used as a basis to deduce probable reaction mechanisms associated with surface exchange. The temperature dependency plots showed that for the composition with x = 0.5, the k0 made a shift in activation energy from ~120 kJ/mol to ~15 kJ/mol above 950 °C. It is suggested that this significant shift in activation energy might be due to an oxygen adsorption/desorption mechanism on the surface becoming rate controlling at high temperatures. The composition with x=0.2 did not show this shift in activation energy. Relations between possible rate controlling reactions and reaction rates (k0) were established, and formed the basis for discussions on probable rate controlling processes. There are reasons to assume that for oxidation prosesses a rate controlling reaction involving a direct “installation” of an oxygen molecule into two vacancies is dominating, while a dissociation of an oxygen molecule generally gives a better description for a reduction process.In Paper 3 the oxygen transport properties in SrTi1-xAlxO3 (x=0 (ST), 0.02 (STA-02) and 0.05 (STA-05)) were determined in O2/N2 mixtures. In this contribution the electrical conductivity is also presented in a large PO2- interval (O2/N2- and CO/CO2-mixtures). Electrical conductivity for pure SrTiO3 (ST) in terms of PO2 applied well with defect chemistry reported in the literature. For the two Al-substituted compositions the electrical conductivity followed predicted behaviour at high and low PO2’s. However, in the medium PO2 range we were not able to describe the conductivity behaviour in terms of classical defect chemistry. Reasons for the discrepancy is discussed.Dchem for ST and STA-02 are reported and are, along with their corresponding activation energies, 187 and 104-180 kJ/mol, respectively, in good accordance with values from literature. Furthermore, values for the component diffusion coefficient, DO, and the vacancy diffusion coefficient, DV, are reported for ST at 950 °C, the only composition where oxygen vacancy concentrations are available in the literature. Values for kchem in STA-02 and STA-05 are also reported, and show pronounced PO2 dependencies. For STA-05 the activation energy for kchem is found to vary between 90 and 105 kJ/mol. Due to a high uncertainty, activation energies are not reported for STA-02.Reported Dchem and kchem values for related materials in literature indicate increasing numeric values with decreasing concentration of oxygen vacancies. It is reasoned that this is due to an ever increasing thermodynamic factor with decreasing population of vacancies. The implications for the component diffusion coefficient is discussed.In Paper 4 the oxygen transport properties in SrTiO3 pure and with Al were investigated in mixtures of CO/CO2. Dchem are reported for ST and STA-02 while kchem are reported for ST, STA-02 and STA-05. The Dchem showed a PO2-dependency, which can be explained by the variation in the thermodynamic factor. The introduction of Al in the sample increases the value of Dchem, probably due to the introduction of more oxygen vacancies. STA-02 showed a discrete increase in Dchem in the CO-rich atmospheres, this may be due to phase transition or phase separation at PO2 ~10-17 atm. The kchem showed a maximum at PCO/PCO2 = 1 for STA-02 and STA-05. This behaviour corresponds well with a rate controlling reaction involving a charged and adsorbed CO2 molecule. The same maximum is also reported in the literature for BaTiO3 wihtout and with 1.8 % Al and for La0.9Sr0.1FeO3.This work has examined chemical diffusion and surface exchange coefficients with electrical conductivity relaxation in two material systems with distinct differences in electrical conductivity and oxygen vacancy concentrations. The main focus has been to elucidate properties of the transport coefficients based on own measurements, but also include transport coefficients from other material systems from literature as references. The vacancy diffusion coefficients have been examined, showing that they increase with increasing concentration of oxygen vacancies in materials where the concentration of vacancies is high. No obvious reason for this behaviour has been found, however, it may be related to a change in activation energy. It is rather well established in the literature that for materials where the concentration of vacancies may be characterized as dilute, we should expect a DV independent of the population of vacancies. Finally, based on own results and data reported in the literature it appears that with respect to the oxygen surface flux the oxygen vacancy concentration seems to be the property of most importance. That is, for oxidation processes the oxygen exchange flux will increase with vacancy population.

This paper briefly describes the nature of remanence and anisotropy measurements using a spinner magnetometer. In the latter case, a known d.c. magnetic field is applied to the rotating sample. Broad features of the author's instrument and three methods of calibration are mentioned. The most important sources of electronic noise are given, as are estimates of the minim-maximum remanence and anisotropy signals that can be measured, and measurement times per specimen.