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Angular distributions and total yields of atoms sputtered from bismuth targets by normally incident 10 keV -50 keV Ne+ and Ar+ ions have been measured both experimentally and by computer simulation. Polycrystalline Bi targets were used for experimental measurements. The sputtered atoms were collected on high purity aluminum foils under ultra-high vacuum conditions, and were subsequently analyzed using Rutherford backscattering spectroscopy. The Monte-Carlo based SRIM code was employed to simulate angular distributions of sputtered Bi atoms and total sputtering yields of Bi to compare with experiment. The measured sputtering yields were found to increase with increasing projectile energy for normally incident 10 keV - 50 keV Ne+ and Ar+ ions. The shapes of the angular distributions of sputtered Bi atoms demonstrated good agreement between experiment and simulation in the present study. The measured and simulated angular distributions of sputtered Bi exhibited an over-cosine tendency. The measured value of the degree of this over-cosine nature was observed to increase with increasing incident Ne+ ion energy, but was not strongly dependent on incident Ar+ ion energy. The differential angular sputtering yield and partial sputtering yields due to Ar ion bombardment of an inhomogeneous liquid Bi:Ga alloy have been investigated, both experimentally and by computer simulation. Normally incident 25 keV and 50 keV beams of Ar+ were used to sputter a target of 99.8 at% Ga and 0.2 at% Bi held at 40° C in ultra-high vacuum (UHV), under which conditions the alloy is known to exhibit extreme Gibbsian surface segregation that produces essentially a monolayer of Bi atop the bulk liquid. Angular distributions of sputtered neutrals and partial sputtering yields obtained from the conversion of areal densities of Bi and Ga atoms on collector foils were determined. The Monte-Carlo based SRIM code was employed to simulate the experiment and obtain the angular distribution of sputtered components. The angular distribution of sputtered Ga atoms, originating from underneath the surface monolayer, was measured to be sharply peaked in angle about the surface normal direction compared to the Bi atoms originating from surface monolayer. The simulation study produced contradicting results, where the species originating from surface monolayer was strongly peaked around the surface normal compared to the species originating from beneath the surface monolayer.

>Magister Scientiae - MSc / Hydrogen has high energy density and it is regarded as the future energy carrier. Hydrogen can be stored as a gas in high-pressure cylinders, as a liquid in cryogenic tanks and as a solid in metal hydrides. The storage of hydrogen in gas and liquid form has many limitations. Light metal hydrides show high energy density and are a promising and more practical mode of hydrogen storage. In particular, titanium and its alloys are promising metal hydrides for hydrogen storage due to their high affinity to hydrogen. The aim of this study is to investigate the effect of thermal annealing on hydrogen storage capacity of Ti-Pd multilayer systems. Ti-Pd multilayer films were prepared on CP-Ti (commercial pure Ti) and Ti6Al4V substrates using an electron beam evaporator equipped with a thickness monitor. The sequential deposition of layers Pd(50nm)/Ti(25nm)/Pd(50nm) was done at a constant deposition rate of 0.6 Å/s. The first batch of samples were thermally annealed at 550 °C in vacuum for two hours, the second batch of samples were annealed at 550 oC under H2(15%)/Ar(85%) gas mixture for two hours and the third series of samples was annealed under pure H2 gas at 550 oC for one hour. SEM showed relatively homogeneous and smooth topography of surfaces in as-deposited samples, while a rough textured surface was observed in both samples annealed under vacuum and under H2/Ar gas mixture. The samples annealed under pure H2 gas did not show any sign of crystallites grow but instead a relatively smooth surface with sign of etching. XRD revealed structural transformation as evidenced by the presence of PdTi2 phase in samples annealed under vacuum; in samples annealed under the gas mixture Pd2Ti was noted in addition to TiH2 and TiO2. While the TiH2 phase is an indication of hydrogen absorption, the TiPd2 phase suggests intermixing of the deposited layers and the presence of TiO2 is evidence of oxidation. The samples annealed under pure H2 gas showed only TiH2 with no trace of structural transformation. RBS confirmed the intermixing of layers in the samples annealed under vacuum and H2(15%)/Ar(85%) gas mixture, while samples annealed under pure H2 gas did not show any intermixing of layers. ERDA revealed an average H content of ~ 3.5 at.% in CP-Ti and ~6.2 at.% in Ti6Al4V for samples annealed under H2(15%)/Ar(85%) gas mixture. We recorded an hydrogen content of ~19.5 at.% in CP-Ti annealed under pure H2 while ~25.5 at.% was found in Ti6Al4V annealed under the same conditions. When the thickness of the Pd catalyst layers was increased to 100 nm (i.e. Pd (100 nm)/Ti (25 nm)/Pd (100 nm)), only ~ 12.5 at.% and 11.2 at. % hydrogen content was recorded in samples prepared on CP-Ti and Ti6Al4V alloy respectively, both annealed under pure hydrogen for one hour as above.