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Nickel oxide thin films were obtained by a cost-effective chemical spray pyrolysis approach on glass substrates using nickel chloride as starting precursor with different deposition times. The X-ray diffraction investigation indicated that the obtained films were polycrystalline cubic structure with preferred orientation along (111) plane. Scanning electron microscopy images for sprayed NiO layers at deposition time of 5 and 10 min exhibit a porous structure with randomly oriented honeycomb like morphology. The optical direct band-gap energy Eg of sprayed NiO films was around 3.4–3.5 eV for all deposited samples and optical transmittance decreases with increasing the deposition time. Gas sensing performance was tested for the detection of nitrogen dioxide (NO2) at different operating temperatures and NO2 concentrations. It was found that the sprayed NiO thin film at deposition time of 5 min shows the maximum sensitivity of 57.3% for 20 ppm NO2 at 200 °C as operating temperature with good stability and selectivity. This study suggests that the sprayed NiO thin film is a good candidate material for NO2 detection at a relatively low operating temperature.

Few reports are displayed on relation between electrical characteristics of rocks and pressure. The objective of this article is the interpretation and modeling of experimental kaolinite specimens under various pressures (0- ~4.5 Kb, at ~50% humidity), and frequency (10 Hz - 10 kHz). Complex impedance measurements were performed for samples. At low pressure range (≤1 Kb); the reliance of the experimental capacitance and conductance on the pressure displays a considerable dependence on the applied pressure. Constant conductances are present at higher pressures. With rising pressure the capacitance decreases. These behaviors are interpreted by percolation theory. With the rise of pressure, the pore spaces decrease and conducting paths between grains increase. The behavior of capacitance and conductance with frequency is comparable with other reports as it will be discussed. Due to existence of water, it was supposed there is impedance at the kaolinite grain surfaces. Also, it was supposed the presence of charge movement and chemical reaction at surface grains. Renormalization group model as a member of the percolation group methods was used to interpret and model experimental data. We developed a model using four phases to analyze the probable deviations in electrical features that may control pressure.

Electrical properties of carbonate rocks from North Sinai, Egypt, were investigated experimentally in the frequency domain (100 Hz to 100 kHz). Changes between electrical properties were attributed to changes in mineral composition and texture of samples. Asymmetric mixture laws cannot describe electrical behavior of heterogeneous rocks in the mentioned frequency range. A theoretical pseudo-random renormalization group (PRNG) method was developed to model electrical behavior of rock mixtures. The main goal of this paper is to make forward and inverse modeling using PRNG method for the electrical properties as a function of frequency for carbonate rocks with texture. In PRNG method four phases were used to take into account the texture in the samples. Four phases are the best that we could use in the model. We are trying to increase the competence of the model in the near future. In these four phases mainly conducting constituents (silt and clay) and mainly insulating constituents (sand, air and carbonate) may coat each other. With appropriately chosen coatings for the four phases, the PRNG method can reasonably model the electrical properties of the samples in the measured frequency range. Thus, an inverse problem is used to find the detailed structure of the four phases, which leads to the measured electrical properties of the samples, taking into account the measured concentrations of the different constituents of the samples. The inverse problem is based on minimizing the misfit between the measured frequency response for the conductivity and the dielectric constant and those obtained theoretically from the PRNG method. It was shown that the texture plays an important role in determining the A.C. electrical properties of heterogeneous samples.

Detailed mineralogical and geochemical studies were carried out on the middle members of the black shales of the Duwi Formation (Quseir–Safaga province) to define their source rock, paleo-weathering, pollution impact and provenance of the sources. The studied black shales are highly fossiliferous and fissile. They are texturally classified as phosphatic marly mudstone microfacies. The black shale mineral composition is mainly composed of calcite, apatite, quartz, pyrite and clay minerals. The average values of Cu, Ni, Zn, Cr, V, As and Se and the ratios Rb/Sr and Cr/Ni in black shale are enriched compared to those of the Post-Archean Australian Shale (PAAS) values. Electrical properties of samples were measured using a non-polarizing electrode, at room temperature (∼18 °C), and relative atmospheric humidity of (∼35%), in the frequency range from 42 Hz to 5 MHz. The changes in electrical properties were argued to be due to the change in mineral composition. Generally, the electrical properties of rocks are changed due to many factors such as grain size, mineral composition, grain shape and inter-granular relations between grains. The dielectric constant decreases with frequency, and increases with conductor concentration. Also, the conductivity increases with the increase of conductor continuous paths between electrodes.

A frequency-domain membrane polarization impedance formula was suggested previously by Marshall and Madden for a sequence of ion selective and non-selective regions of equal cross-sections. We generalized the formula for the case of non-equal cross-sections and small Debye lengths (common case). This formula is a simplification of a general analysis of the impedance, given by Buchheim and Irmer, which is tedious for computations and does not give physical insight into the process. The obtained results are physically consistent for the effect of the different cross-sections on the limiting resistance at high frequencies. It is, also, consistent in behaviour with the chargeability formula given by Titov. The impedance model considering regions of non-equal cross-sections may be useful for modeling complex impedance of partially and fully water-saturated rocks. Our study also gives, in detail, the essential equations not given in Buchheim and Irmer derivation, while the lengthy intermediation steps are omitted. Some typing errors in the equations of the previous derivation are rectified. Our approach and formula for the impedance is more rigourous than the formula given by Bucker and Hordt.

Chemical spray pyrolysis is utilized to deposit ZnO thin films with varied vanadium (V) contents, offering a simple, low cost and large-scale production deposition process. The effect of introducing V on structural, morphological, optical, electrical and magnetic properties of ZnO thin films is studied. XRD measurements reveal single phase ZnO polycrystalline layers with hexagonal wurtzite structure and high texturing along {002} plane. The incorporation of V into the ZnO lattice is confirmed through the XRD peaks shift towards a higher angle. Further, the SEM micrographs indicate morphological transformation from hexagonal nanoplates to spherical particles when increasing the V content from 2% to 10% nominally. All films are optically transparent in VIS and NIR spectral regions and the optical transmittance is strongly decreasing with increasing the V percentage. The magnetic measurement data shows paramagnetic behavior for the ZnO layer doped with 2% V while ZnO layer doped with 10% V shows a small ferromagnetic behavior. Additionally, the magnetoresistance measurement at 1.6 T shows positive values at room temperature and increased from 6% to 12% when increasing V amount.

The Electrical properties of substances respond quickly to slight changes according to the manner at which particles or grains are dispersed everywhere in the material (texture). Also, they react quickly to their conductor component concentrations. In this article, we will try to preserve the homogeneity of specimens. So, the sample elements (pure sand and pure hematite) are crushed separately, and different successive hematite (conductor) concentrations (East Aswan, in the Eastern Desert, Cairo, Egypt) mixed with pure sand. Different homogenous combinations and quantities of hematite put together, and electrical properties were measured. Measurements made for electrical properties at dry state condition at constant temperature (~20 °C). The frequency range used was 0.1 Hz - 10 5 Hz. The electrical spectrum, of the measurements, varies substantially according to measured frequency range and as stated by the composition or constitution or arrangement of specimens (sample texture). There are two conduction regions, as asserted by the conductivity that is determined by the frequency (two slopes). Permittivity increases linearly with increasing concentration. Permittivity is becoming smaller with the rising of the spectrum at a special rate. Electrical properties show universal Jonscher's law. The change in the specimens is the hematite conductor concentration (distributed homogeneously around sand grains) and probably the difference in the texture of specimens. Percolation theory is used to interpret the electrical properties of mixtures. Classical mixture formulas can be suggested to understand these homogeneous mixture samples.

The Jurassic sedimentary section in north Sinai is of a special interest in particular for its economic potentiality. The understanding of petrographical and electrical properties of these rocks is essential for investigating minerals and oil and water exploration. This paper presents a study of the petrographical and A. C. electrical properties of Jurassic carbonates. Electrical measurements have been conducted for twenty-nine (18) carbonate samples. The slight changes between samples in electrical properties were attributed to the changes in mineral composition, texture pore spaces and pore throat distribution of the samples. Electrical properties generally change with many factors (grain size, mineral composition, grain shape and facies). The dielectric constant decreases with frequency and increases with the presence of conductive solids (silt and clay) and its composition. The conductivity increases with the increase of conductor paths between electrodes. The main goal of this paper is to shed more light on interrelations between electrical properties (conductivity, dielectric constant and impedance as a function of frequency), petrography and mineral composition (carbonates that contain clays and quartz grains).

Electrical properties and X-ray diffraction of 20 hematite sandstone samples of the most economically interesting Egyptian iron ore deposits have been investigated. Samples were collected from two different areas in Egypt (Aswan and Bahariya). Complex impedance measurements in the frequency range from 10 Hz to 100 kHz were performed at room temperature (∼20 °C). The observed dielectric behavior was characterized by Maxwell–Wagner interfacial polarization at low frequencies and bulk polarization at relatively higher frequencies. The frequency dependence on conductivity shows a classical relaxation behavior followed Jonscher’s universal law. The measured electrical properties vary strongly with the frequency and sample composition. The difference in the electrical properties may be attributed to the fluctuations in the concentration of the sample constituents and to the degree of heterogeneity of the grains. The XRD-patterns of Egyptian iron ore deposits prove that the main phases are hematite and quartz.

AC electrical conductivity analysis for silica gel and silica gel-supported nickel (via 2, 5 and 8 wt.% Ni) and γ-alumina and γ-alumina-supported platinum (viz., 0.3 and 0.6 wt.% Pt) is carried out. Measurements were carried out in the frequency range from 0.1 Hz up to 100 kHz at room temperature (20 °C) and 1 V for estimating the effect of increasing Ni or Pt on its supports namely silica gel and γ-alumina. Electrical properties of such mesoporous materials reflect directly its ion exchange and interfacial catalytic activity. Assuming that Ni or Pt particles are optimally dispersed over the surface of its supports, this may give rise to an increase in the conductivity and dielectric constant of the studied system. Electrical properties of pure γ-Al2O3 and silica gel supports depend on metal content and frequency of the applied field. The observed increase in conductivity with the increase in metal loadings may be due to the increase in the mobility of the free charge carriers. These charge carriers diffuse in the bulk of pores and reach electrodes and discharge there giving rise to diffusion impedance (Warburg impedance). An equivalent circuit is deduced to describe the electrical behavior of the systems studied. It constitutes elements forming three mechanisms: ion exchange at interfaces, diffusion in the pores and high frequency effect (beyond the scope of this work). The study evidenced that the increase of metal content has a great effect on the electrical properties of the studied system.