Tritiation of amorphous and crystalline silicon using T <inf>2</inf> gas

Incorporation of tritium in hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si) at 250 °C using tritium (T 2) gas at pressures of up to 120 atm is reported. The tritium is stored in a surface layer which is approximately 150 and 10 nm for a-Si:H and c-Si, respectively. The concentration of tritium occluded in planar and textured c-Si is linearly dependent on the total surface area. The tritium is stable and the dominant tritium evolution occurs at temperatures above 300 °C. The concentration of tritium locked in a-Si:H and c-Si was 20 and 4 at. %, respectively. Self-catalysis appears to be important in the tritiation process. © 2006 American Institute of Physics

Power-scaling performance of a three-dimensional tritium betavoltaic diode

Three-dimensional diodes fabricated by electrochemical etching are exposed to tritium gas at pressures from 0.05 to 33 atm at room temperature to examine its power scaling performance. It is shown that the three-dimensional microporous structure overcomes the self-absorption limited saturation of beta flux at high tritium pressures. These results are contrasted against the three-dimensional device powered in one instance by tritium absorbed in the near surface region of the three-dimensional microporous network, and in another by a planar scandium tritide foil. These findings suggest that direct tritium occlusion in the near surface of three-dimensional diode can improve the specific power production. © 2009 American Institute of Physics

Hydrogen effusion from tritiated amorphous silicon

Results for the effusion and outgassing of tritium from tritiated hydrogenated amorphous silicon (a-Si:H:T) films are presented. The samples were grown by dc-saddle field glow discharge at various substrate temperatures between 150 and 300 °C. The tracer property of radioactive tritium is used to detect tritium release. Tritium effusion measurements are performed in a nonvacuum ion chamber and are found to yield similar results as reported for standard high vacuum technique. The results suggest for decreasing substrate temperature the growth of material with an increasing concentration of voids. These data are corroborated by analysis of infrared absorption data in terms of microstructure parameters. For material of low substrate temperature (and high void concentration) tritium outgassing in air at room temperature was studied, and it was found that after 600 h about 0.2% of the total hydrogen (hydrogen+tritium) content is released. Two rate limiting processes are identified. The first process, fast tritium outgassing with a time constant of 15 h, seems to be related to surface desorption of tritiated water (HTO) with a free energy of desorption of 1.04 eV. The second process, slow tritium outgassing with a time constant of 200-300 h, appears to be limited by oxygen diffusivity in a growing oxide layer. This material of lowest H stability would lose half of the hydrogen after 60 years. © 2008 American Institute of Physics

Development of a Compact 20 MeV Gamma-Ray Source for Energy Calibration at the Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory (SNO) is a real-time neutrino detector under construction near Sudbury, Ontario, Canada. SNO collaboration is developing various calibration sources in order to determine the detector response completely. This paper describes briefly the calibration sources being developed by the collaboration. One of these, a compact {sup 3}H(p,{gamma}){sup 4}He source, which produces 20-MeV {gamma}-rays, is described

Heterostructure Engineering of a Reverse Water Gas Shift Photocatalyst

To achieve substantial reductions in CO2 emissions, catalysts for the photoreduction of CO2 into value‐added chemicals and fuels will most likely be at the heart of key renewable‐energy technologies. Despite tremendous efforts, developing highly active and selective CO2 reduction photocatalysts remains a great challenge. Herein, a metal oxide heterostructure engineering strategy that enables the gas‐phase, photocatalytic, heterogeneous hydrogenation of CO2 to CO with high performance metrics (i.e., the conversion rate of CO2 to CO reached as high as 1400 µmol g cat−1 h−1) is reported. The catalyst is comprised of indium oxide nanocrystals, In2O3−x(OH)y, nucleated and grown on the surface of niobium pentoxide (Nb2O5) nanorods. The heterostructure between In2O3−x(OH)y nanocrystals and the Nb2O5 nanorod support increases the concentration of oxygen vacancies and prolongs excited state (electron and hole) lifetimes. Together, these effects result in a dramatically improved photocatalytic performance compared to the isolated In2O3−x(OH)y material. The defect optimized heterostructure exhibits a 44‐fold higher conversion rate than pristine In2O3−x(OH)y. It also exhibits selective conversion of CO2 to CO as well as long‐term operational stability