Static and cyclic oxidation of Nb-Cr-V-W-Ta high entropy alloy in air from 600 to 1400℃

An oxidation resistance study has been made on Nb-Cr-V-W-Ta high entropy alloy in a range of temperature from 600 to 1400℃in air.Static oxidation study has been performed for either(a)12 or 24 h of heating time or(b)3 or 10℃/min heating rates to the desired oxidation temperature.Cyclic oxidation study conducted for three and a half days has been conducted at 600,700,and 800℃using 12 h of heating cycles.The alloy can withstand the cyclic oxidation process with only a reasonable loss of alloy.The identification of oxides indicates crystals of W and Ta oxides in cylindrical form while Nb and Cr oxides show a nodular or granular morphology at both 1000 and 1200℃while and additional of oxide of V in whisker forms at 1200℃.

Fabrication,characterization and optimization of high conductivity and high quality nanocrystalline molybdenum thin films

The present study investigated the influence of substrate temperature(Ts)and working pressure(P(Ar))on tailoring the properties of nanocrystalline(nc)molybdenum(Mo)films fabricated by radio-frequency magnetron sputtering.The structural,morphological,electrical and optical properties of nc-Mo films were evaluated in detail.The Mo films exhibited(110)orientation with average crystallite size varying from 9 to 22(±1)nm on increasing Ts.Corroborating with structural data,the electrical resistivity decreased from 55μΩcm to 10μΩcm,which is the lowest among all the Mo films.For Mo films deposited under variable P(Ar).the(110)peak intensity decrement coupled with peak broadening on increasing P(Ar).Lower deposition pressure yielded densely packed thin films with superior structural properties along with low resistivity of 15μΩcm.Optimum conditions to produce high quality Mo films with excellent structural,morphological,electrical and optical characteristics for utilization in solar cells as back contact layers were identified.

Effect of sintering temperature on the chemical bonding,electronic structure and electrical transport properties of β-Ga_(1.9)Fe_(0.1)O_(3) compounds

A model system,which is based on iron(Fe)doped gallium oxide(Ga_(2)O_(3))(Ga_(1.9)Fe_(0.1)O_(3)),has been considered to elucidate the combined effect of transition-metal ion doping and processing temperature on the chemistry,local structure and chemical bonding,and electrical transport properties of a wide band gap oxide(Ga_(2)O_(3)).The Ga_(1.9)Fe_(0.1)O_(3) compounds were synthesized using standard high-temperature solid state reaction method.The effect of processing conditions in terms of different calcination and sintering environments on the structural and electrical properties of Ga_(1.9)Fe_(0.1)O_(3) compounds is studied in detail.Structural characterization by Raman spectroscopy revealed that Ga_(1.9)Fe_(0.1)O_(3) compounds exhibit monoclinic crystal symmetry,which is quite similar to the intrinsic parental crystal structure,though Fedoping induces lattice strain.Sintering temperature(T_(sint))which was varied in the range of 900-1200℃,has significant impact on the structure,chemical bonding,and electrical properties of Ga_(1.9)Fe_(0.1)O_(3) compounds.Raman spectroscopic measurements indicate the proper densification of the Ga_(1.9)Fe_(0.1)O_(3) compounds achieved through complete Fe diffusion into the parent Ga_(2)O_(3) lattice which is evident at the highest sintering temperature.The X-ray photoelectron spectroscopy validates the chemical states of the constituent elements in Ga_(1.9)Fe_(0.1)O_(3) compounds.The electrical properties of Ga_(1.9)Fe_(0.1)O_(3) fully controlled by T_(sint),which governed the grain size and microstructural evolution.The temperature and frequency dependent electrical measurements demonstrated the salient features of the Fe doped Ga_(2)O_(3) compounds.The activation energy determined from Arrhenius equation is 0.5 e V.The results demonstrate that control over structure,morphology,chemistry and electrical properties of the Ga_(1.9)Fe_(0.1)O_(3) compounds can be achieved by optimizing T_(sint).