R K Jain
Articles written in Bulletin of Materials Science
Volume 29 Issue 1 February 2006 pp 67-72 Alloys
The structural, electrical and thermodynamic properties of a La–Ni–Si [La = 28.9%, Ni = 67.5%, Si = 3.6%] alloy have been investigated. Powder XRD results show that the lattice constants and unit cell volume of the alloy increase after hydrogen storage. It was also found that the resistance of the alloy increased with dissolved hydrogen concentration. Hydrogen absorption pressure composition isotherms have also been investigated which show the presence of two single 𝛼 and 𝛽 regions and one mixed (𝛼 + 𝛽) phase. The thermodynamic parameters viz. the relative partial molar enthalpy (𝛥 𝐻) and relative partial molar entropy (𝛥 𝑆) of dissolved hydrogen, are found to be in the range 8–18 kJ (mol H)-1 and 25–63 JK-1 (mol H)-1. From the dependence of 𝛥 𝐻 on the hydrogen concentration, 𝑋, the different phases [𝛼, 𝛼+ 𝛽, 𝛽] and phase boundaries of the alloy-𝐻 system are identified. Thermal conductivity and diffusivity of La–Ni–Si and its hydride have been measured at room temperature by using TPS technique. Thermal conductivity was found to decrease due to absorbed hydrogen in the alloy.
Volume 30 Issue 2 April 2007 pp 153-156 Thin Films
The present work deals with the mixing of iron and silicon by swift heavy ions in high-energy range. The thin film was deposited on a 𝑛-Si (111) substrate at 10-6 torr and at room temperature. Irradiations were undertaken at room temperature using 120 MeV Au+9 ions at the Fe/Si interface to investigate ion beam mixing at various doses: 5 × 1012 and 5 × 1013 ions/cm2. Formation of different phases of iron silicide has been investigated by X-ray diffraction (XRD) technique, which shows enhancement of intermixing and silicide formation as a result of irradiation. 𝐼–𝑉 measurements for both pristine and irradiated samples have been carried out at room temperature, series resistance and barrier heights for both as deposited and irradiated samples were extracted. The barrier height was found to vary from 0.73–0.54 eV. The series resistance varied from 102.04–38.61 k𝛺.
Volume 39 Issue 1 February 2016 pp 41-46
The effect of high-temperature heat treatment on purity and structural changes of multiwalled carbon nanotubes (MWCNTs) were studied by subjecting the raw MWCNTs (pristine MWCNTs) to 2600°C for 60 and 120 min. Thermogravimetric analysis (TGA), X-ray diffraction, Raman spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to study the effect of heat-treatment duration on the purity and structural changes of MWCNTs. Results show that high-temperature heat treatment can be used to purify MWCNTs with proper optimization of treatment time. It was observed that 60 min heat treatment of raw MWCNTs imparts high purity and structural perfection to MWCNTs, while 120 min heat treatment imparts structural degradation to MWCNTs with collapse of the innermost shells. The present study indicates that metal impurities act as moderators in controlling the degradation of MWCNTs up to certain duration, and once the metal impurities escape completely, further heat treatment degrades the structure of MWCNTs.
Volume 42 | Issue 5
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