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Abstract—The effect of exposures in the range of 500–10 000 h at heating temperatures of 450–750°C on changes in the structure and properties of steel 08Kh18N10T has been studied. It has been found that, in the early stages of thermal aging at 450–550°C, the precipitates of finely dispersed carbides are formed, coherent with the austenitic matrix. With an increase in the holding time and aging temperature to 650°C, the sizes of Me23C6 carbide particles sharply increase, which, under a certain combination of temperature–time parameters, evolve into the σ phase with low coherence with the γ-solid solution. However, this phenomenon has little effect on the mechanical properties at room temperature. [ABSTRACT FROM AUTHOR]

Thermal aging of natural ester oil shows drastic reduction in partial discharge inception voltage (PDIV) and a significant variation is observed only above a certain aging time, under AC, DC, high frequency AC voltages and with harmonic voltages with different total harmonic distortion. Weibull distribution studies on PDIV measurements indicate a reduction in scale parameter (α) with increase in thermal aging temperature. A characteristic reduction in breakdown voltage was observed with the thermally aged ester oil, under AC, DC and standard lightning impulse voltage. The breakdown voltage variation with aged ester oil follows normal distribution. Ultraviolet (UV) analysis of ester oil thermally aged at 160°C has revealed a regular shift of the derived absorbance parameter to longer wavelengths. The interfacial tension and turbidity exhibits an inverse relationship with the thermally aged ester oil. Gas chromatography/mass spectrometric analysis of the thermally aged ester oil predicted the formation of more carboxylic acids and ketones with aging duration. The steady-state fluorescence on thermally aged ester oil exhibits a shift in its emission profile, which is in tandem with the UV absorption spectroscopic analysis. Fluorescence analysis can be adopted as a real-time monitoring tool in transformers, to understand the condition of liquid insulation. The viscosity dependence on the wavelength of derivative absorption maxima follows a direct relationship with the thermally aged natural ester oil.

Abstract: Zinc oxide with a diversity of well-defined morphologies was synthesized via a simple aqueous solution route by decomposing Zn x O y (OH) z precursor at suitable reaction conditions. Flower-like ZnO composed of rods was obtained by treating Zn x O y (OH) z precursor in the reaction solution at 90°C for 6h. The precipitate of layer-like Zn x O y (OH) z precursor was decomposed by drying at 90°C for 24h in air, resulting in the formation of ZnO microtubes. [Copyright &y& Elsevier]