Papers by Keyword: Electric Conductivity

Abstract: The technology of applying the composite chrome-carbon coating to protect the conductive cathode pins in the aluminum industry is developed in this paper. The coating is based on the ability of fine-dispersed particles with size less than 0.5 micron.

Abstract: The main results of the study of the influence of man-made products of the metallurgical industry on the properties and structure of gypsum binder are presented. It has been proved that the introduction of man-made modifiers, metallurgical dust, and slag leads to an increase in the strength properties and electric conductivity of the material, but, over time, the waste efficiency decreases. The use of Portland cement as an activator leads to the formation of amorphous hydration products based on calcium hydrosilicates, which bind calcium sulfate crystals and provide an increase in the physicomechanical characteristics and electric behavior of the gypsum composite.

Abstract: The conditions for the synthesis of aluminum tungstate Al₂(WO₄)₃ and aluminum niobate AlNbO₄ were clarified using hydrothermal treatment and post-heating. Single-phase Al₂(WO₄)₃ can be synthesized through the hydrothermal treatment of the starting materials at a mixing ratio of Al:W = 5:5 at 250 °C for 5 h and post-heating at 840 °C for 6 h. The AlNbO₄ was synthesized using the same method, under a hydrothermal treatment of Al:Nb = 2:8 and post-heating. As a result of investigating the products under various mixing conditions based on the synthesis of pure Al₂(WO₄)₃ and AlNbO₄, Nb could not be doped into Al₂(WO₄)₃, but W-doped AlNbO₄ was synthesized. The electric conductivity was measured for several samples of sintered W-doped AlNbO₄, and the results showed that the electrical conductivity was improved within a higher temperature region by doping with W.

Abstract: The paper presents data on the temperature dependence of the conductivity of strontium bismuthate Sr₆Bi₂O₁₁. It is shown that the temperature dependence of conductivity cannot be described in the framework of existing models. It was found that at a temperature of about 400 K a change in the radius of localization of the charge carrier is observed.

Abstract: This work researches the impact of the temperature of compacted copper nanopowder on the amperage of the current flowing through the nanopowder sample. It was determined that upon reaching its oxidation temperature (~ 1900C), the copper nanopowder started conducting electricity, and at 280-320°C electric breakdown of sample was occurring. This is caused to irreversible processes taking place in nanomaterials during heating, such as sintering and mass-transfer, those processes leading to the formation of conductivity channels. This speaks in favor of an evident dependency between copper nanopowder conductivity and the chemical transformations taking place in it; this allows for recommending this research method for instant diagnostics of copper nanopowders.

Abstract: The effect of the Fe²⁺_B/Fe³⁺_B ratio (the ratio of divalent and trivalent iron ion in B position of the inverse spinel structure) in cermets on the electric conductivity and corrosion resistance of anodes was investigated. The experimental results showed that both the electrical conductivity and corrosion resistance are proportional to the Fe²⁺_B/Fe³⁺_B ratio on the surface of anodes because FeAl₂O₄ and NiAl₂O₄ are produced on the surface of the anode and Fe³⁺ in the NiFe₂O₄ is corroded preferentially during electrolysis.

Abstract: The work deals with the observation of microstructure and crack propagation from macro-indentation in a set of newly developed materials. Complex composites based on SiC matrix with 30, 40 and 50 wt. % of additives (Ti and NbC) were hot pressed at 1960 oC in air atmosphere under 30 MPa pressure for 1.5 hour. The microstructure and chemical composition were studied by SEM equipped with EDX analyzer. Hardness of the composites was evaluated by means of classic Vickers macro-indentation and fracture toughness was determined by the Anstis method. Indentation cracks were observed and their propagation was analyzed. The electrical conductivity as function of volume fraction of additives was determined.

Abstract: In this paper, we use PLASIMO to investigate the effect of discharge current on hydrogen plasma in the cascaded arc, the effects of discharge current on plasma properties were investigated. temperature, conductivity, and the distribution of electron density along the symmetry axis of hydrogen plasma is analyzed in the simulation area. The simulation results show that plasma temperature is 0.9503×104, 1.09862×104, 1.26675×104, 1.65102×104 K in the symmetry axis when the discharge current is 35, 50, 75 and 100A, meanwhile, electric conductivity is 1738.03, 2272.72, 2819.86, 3820.73 s/m.

Abstract: In this paper, we have presented a comprehensive study about the preparation, structure and electrical conductivity of Ag-doped La_1-x-ySr_xCu_yMnO_3-δ (0.05≤x≤0.4, y=0.1) ceramics. We first doped Ag into La_1-x-ySr_xCu_yMnO_3-δ compounds using a sol-gel method and then the gels were sintered at 1000°C by Muffle furnace. The structure variation was systematically characterized by the X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that that silver merged well into the lattice of La_1-x-ySr_xCu_yMnO_3-δ and z at.% Ag-doped La_1-x-ySr_xCu_yMnO_3-δ compounds precipitated only in one phase. As indicated by the conventional four-probe method and UV-Vis diffuse reflectance spectroscopic (DRS), the addition of Ag was dramatically effective in enhancing the electrical conductivity, whereas a slight effect of the addition of Ag on UV-Vis diffuse reflection was observed. Furthermore, the electrical conductivity increased with the enhanced sintering temperature within the temperature of 1000 °C, which proved that the dominant mechanism of the conductivity of Ag-doped ceramics was hole hopping transfer.

Abstract: The 10NiO-NiFe₂O₄ composite ceramics doped with NiO were prepared with the cold isostatic pressing-sintering process. The effects of NiO doping order on the density, bending strength and electrical conductivity of NiFe₂O₄ composite ceramics were studied. The results show that, doping excess 10wt% NiO before synthesis of NiFe₂O₄ composite (doping order one) and doping excess 10wt% NiO after synthesis of NiFe₂O₄ composite (doping order two), the former’s samples have a better relative density 88.9% and linear shrinkage rate 9.82%, which is increased by 7.12% and 3.6% compared with that of latter’s samples, respectively. At the same time, the former’s samples also have a better electric conductivity and reach 1.29S/cm at 1233K, which is higher about 13.15% than those latter’s samples. However, the bending strength of the former’s samples just has 76.28Mpa, which is lower about 15.41% than that of the latter’s samples 88.04Mpa.