K. Sachdev

Corrosion Behaviour of Amorphous and Nanocrystalline Ti60Ni40 in Aqueous HNO3 Solution

Potentiodynamic polarization studies were carried out on amorphous, nanocrystalline and crystalline states of the alloy Ti60Ni40 in 0.1 M HNO3, 0.5 M HNO3 and 1 M HNO3 aqueous solutions at room temperature. It was observed that the amorphous state exhibited higher corrosion current density than that by the nanocrystalline state. These results are corroborated by the weight loss studies performed on the different structural states of Ti60Ni40 alloy in 0.1 M HNO3, 0.5 M HNO3 and 1 M HNO3 aqueous media. Thus the nanocrystalline state is least prone to corrosion than the amorphous and the crystalline states.

Air oxidation of the bulk amorphous alloy Zr46.75Ti8.25Cu7.5Ni10Be27.5 studied by using a TGA

The oxidation in air of the bulk amorphous alloy Zr46.75Ti8.25Cu7.5Ni10Be27.5 in its amorphous state and the supercooled liquid state was studied in the temperature range of 588?633?K by using a thermogravimetric analyser (TGA). The oxidation kinetics of the alloy obeys the parabolic rate law during oxidation in its amorphous state as well as in the supercooled liquid state. The results were compared with those obtained in our previous study of the air oxidation of another well-known bulk alloy, Zr65Cu17.5Ni10Al7.5, in the temperature range of 591?684?K. The value of the parabolic rate constant (K) for the alloy Zr46.75Ti8.25Cu7.5Ni10Be27.5 (e.g. K=5.9? 10?9?g?cm?2?s?1/2 at 588?K) is about two orders of magnitude less than its value for the other bulk alloy Zr65Cu17.5Ni10Al7.5 (K=6.8? 10?7?g?cm?2?s?1/2 at 588?K), thus suggesting that the bulk amorphous alloy Zr46.75Ti8.25Cu7.5Ni10Be7.5 displays a better oxidation resistance in air than Zr65Cu17.5Ni10Al7.5.

SYNTHESIS AND HYDROGEN SENSING PROPERTIES OF CNT-ZnO NANOCOMPOSITE THIN FILMS

CNT-ZnO nanocomposite powders were synthesized by addition of carbon nanotubes (CNT) during the growth of ZnO nanoparticles using a wet-chemical method. These CNT-ZnO nanocomposites powder were then spin coated on corning glass substrates to obtain thin films which were characterized using X-ray diffraction, scanning electron microscopy and current voltage characteristics. Hydrogen sensing (50- 1000 ppm) carried out on pure and CNT-ZnO nanocomposites at operating temperature of 250 and 300°C in N2 atmosphere (0.4±0.03 mbar) revealed higher sensitivity in 2 wt.% CNT-ZnO nanocomposite thin film compared to the pure ZnO thin film.

Corrosion Behaviour of Ni[sub 78]Si[sub 8]B[sub 14] Alloy in 1 M NaCl Aqueous Medium at Room Temperature

Potentiodynamic polarization studies were performed on the air side and wheel side of the specimen Ni78Si8B14 in 1 M NaCl aqueous medium at room temperature. It was observed that the corrosion current density on the air side of the specimen was less than that of the wheel side of the specimen in 1 M NaCl aqueous medium. The amorphous nature of the air side and wheel side of the specimen Ni78Si8B14 was confirmed by X‐ray diffraction (XRD). The observed behaviour can be related to the surface morphology due to processing of the ribbons. It is suggested that the inferior corrosion resistance of the wheel side surface is attributed to higher concentration of quenched‐in defects due to higher cooling rate. Weight loss studies were also carried out in order to corroborate the polarization results. The results are discussed in the paper in the light of data reported in the literature.

A Comparative Study of Corrosion Behaviour of Amorphous and Nanocrystalline Ti60Ni40 in 0.5 M H2SO4 and 0.5 M HNO3 Aqueous Media

Corrosion studies were carried out using potentiodynamic polarization method on amorphous, nanocrystalline and crystalline states of the alloy Ti60Ni40 in 0.5 M H2SO4 and 0.5 M HNO3 aqueous media at room temperature. The nanocrystalline state of Ti60Ni40 was obtained by removing about 10 μm from the air side surface (crystalline state) by polishing. The presence of nanocrystalline phase was confirmed by X-ray diffraction (XRD). It was found from polarization results that the corrosion current density was higher in the amorphous state than in the nanocrystalline state in both 0.5 M H2SO4 and 0.5 M HNO3 aqueous media. These results are corroborated by the weight loss studies which were carried out in both of these media. Results are discussed in the paper in the light of data reported in the literature on similar type of alloys.