I.P. Jain

Microstructure change in poly(ethersulfone) films by swift heavy ions

PES membrane of thickness 25 microm was irradiated by Cl(9+) ions of energy 100 MeV at IUAC, New Delhi. Microstructure changes due to exposure to high-energy ions were investigated by Fourier transform infrared (FTIR) and ultraviolet/visible (UV/vis) absorption spectroscopies, X-ray diffraction technique and by dynamic mechanical analysis (DMA). A significant loss of crystallinity is observed by the XRD data. Particle size or grain size calculated using Scherrer formula indicates measurable change in particle size of irradiated samples. The polymer chain scissions and structure degradations are expected to occur for irradiated samples. Optical properties of the films were changed due to irradiation that could be clearly seen in the absorption spectra. FTIR does not show the remarkable change in the irradiated samples, but there is some change in the surface roughness observed by AFM.

Hydrogen in FeTi thin films by ERDA with Ag107 ions

Abstract Hydrogen content in hydride at various depths is very important. In the present work hydrogen content in hydrogenated FeTi thin films has been investigated by ERDA (Elastic Recoil Detection Analysis) using 160 MeV, Ag 107 ions. ERDA investigations have shown that FeTi thin films without exposing hydrogen have about 50 atm% of hydrogen content and after hydrogenation these films acquire 5–10 atm% of additional hydrogen. It was observed that the hydrogenation of irradiated films did not increase the hydrogen concentration further. It implies than a beam did not cause track formation in the sample at this energy.

Kinetics of hydrogen absorption in obliquely deposited FeTi thin films

Abstract FeTi thin films of thickness about 1000 A were obliquely deposited at 5 × 10 −5 Torr by thermal evaporation onto the glass substrate at room temperature. The resistance of the films deposited at different angles increases with the absorption of hydrogen and decreases with desorption. The resistance of the samples also increases with the angle of deposition. The change in resistance value is taken as a measure of amount of hydrogen absorbed in the samples. It is observed that the amount of hydrogen absorbed increases with the deposition angle which is due to an increase in the porosity of thin films.

Hydrogen absorption-desorption isotherms of La(28.9)Ni(67.55)Si(3.55)

Abstract Pressure–composition–temperature (P–C–T) isotherms of La(28.9)Ni(67.5)Si(3.55) which was fabricated by substitution of Ni by Si in LaNi5 at different temperature has been studied in the present work. It was found that the activation of the alloy is sufficiently easy. The saturation value of H/M of this alloy is about 1.0 for P–C–T at room temperature ( 293 K ). The H/M values were found to be 0.9, 0.85, 0.8 for P–C–T isotherms at 313, 323, 333 K , respectively, and equilibrium pressures were 1.01×10 5 , 1.41×10 5 , 1.71×10 5 , 2.12×10 5 Pa at these temperatures. The investigations show that the wt% of hydrogen in the alloy was about 1.75%. The maximum amount of hydrogen released by the alloy is in the temperature range 313– 343 K . For P–C–T curves the α+β phase decrease at higher temperatures. This makes it a better alloy for hydrogen storage for technological applications than LaNi5.

Hydrogen in obliquely deposited LaNi5 thin films

Abstract During the last decade, thin film metal hydride has become an emerging field of research. The effect of hydrogen charging/discharging on the electrical resistance of obliquely deposited (θ=0°,30°,45°,60°,75°) LaNi _5 thin films of thickness 130±0.5 nm was investigated. It was found that the activation of LaNi_5 thin films for hydrogen absorption is fairly simple. The change in resistance due to hydrogen absorption increases with the angle of deposition and decreases with desorption of hydrogen. Thin films deposited at large angle absorb more hydrogen than low angle deposited LaNi_5 films. This is due to the structure variation in these thin films as a result of “self-shadowing effect”. Hydrogen absorption/desorption is also fast for films deposited at higher angles.

Effect of hydrogen absorption on electrical resistance and hall effect charge carrier concentration in FeTi, FeTiSz, TiNi and TiNiSez thin films

Abstract The FeTi and TiNi thin films were obliquely deposited at 45°, under 10 −5 torr pressure onto a glass substrate by thermal evaporation. The layers of sulphur and selenium were coated on FeTi and TiNi thin films, respectively. The resistance variation and Hall charge carrier concentration were measured before and after hydrogenation. It was suggested that the hydrogen takes electrons from the metal and also that the hydrogen absorption was greater in thin films deposited in a parallel direction to the vapour beam than those films deposited perpendicularly to the direction of vapour beam.

The effect of a sulfur layer on FeTi thin films obliquely deposited for hydrogen storage

Abstract FeTi thin films of thickness of 730 A were obliquely deposited at different deposition angles θ (θ = 0°, 30°, 45°, 60° and 75°) under 5 × 10−5 torr pressure by thermal evaporation onto the glass substrate at room temperature. A layer of sulfur of thickness 115 A was deposited on the FeTi thin film. It was found that the resistance of the FeTi thin films increases with deposition angle and with the absorption of hydrogen, and decreases with desorption. The sulfur layer on the FeTi thin film was found to produce a marked improvement in the properties of thin films for hydrogen storage, and charging and discharging rate becomes faster in comparison to FeTi thin films.

Hydrogen absorption in Al doped MmNi5

There are many hydrogen storage alloys, but the MmNi5 family of alloys is of great importance as it has good properties for technological uses like hydrogen capacity, plateau pressure, repeatability and ease of activation. In the present paper we describe the hydrogen absorption mechanism of two samples of MmNi4.5Al0.5, having two different misch metal compositions. Sample-1 with misch metal composition (La 22%, Ce 52%, Nd 15% and Pr 11%) and sample-2 with misch metal composition (La 27.13%, Ce 51.57%, Nd 15.8%, Pr 5.50%). These two samples have a variation of the composition of misch metals in MmNi4.5Al0.5. The absorption–desorption cycles in these two samples have been studied in temperatures ranging from room temperature, 30°C to 85°C. H/M ratio of these samples was measured using a volume displacement method. It was found that the H/M ratio for the two samples have slight differences, varying from 0.06 to 0.8 in sample-1, and from 0.08 to 1.0 in sample-2, showing that sample-2 has the better composition of misch metal for hydrogen storage. The H/M for sample-1 becomes 0.8 at 80 psi of the hydrogen pressure while for sample-2 it attains a value of 1.0 at 30 psi. The time taken for activation of sample-2 was found to be small compared to sample-1, and the plateau pressure in sample-2 was found to be lower than sample-1. Therefore sample-2 has better hydrogen absorption–desorption properties and is therefore better for the technological uses of hydrogen energy.

The effect of selenium layer coating and temperature dependence on TiNi thin films obliquely deposited for the hydrogen absorption mechanism

Abstract TiNi thin films of thickness 800 A were obliquely deposited at different angles of θ [ θ = 0°, 30°, 45°, 60° and 75°] layer by layer under 5 × 10 −5 torr pressure by thermal evaporation onto the glass substrate at room temperature. A layer of selenium of thickness 110 A was coated on the TiNi thin films. It was found that the resistance of the TiNi thin films increases with deposition angle and with absorption of hydrogen. The selenium layer coated on TiNi thin film was found to produce a marked improvement in the properties of hydrogen storage and charging rate also becomes faster. The rate of hydrogen absorption increases with temperature at lower range, but at higher range of temperature absorption of hydrogen decreases at 1 atm hydrogen pressure.

Electrical conductivity of ion irradiated Ge20Se80-xBix thin films

Abstract Amorphous chalcogenide semiconductor Ge20Se80−xBix thin films have been bombarded with 75 MeV Ni ions at room temperature. The ion irradiation induced effects on the electronic properties have been monitored by DC conductivity measurements over a temperature range of 77– 476 K . The electrical conductivity and conduction activation energy changes on irradiation.