Some Aspects Regarding I. R. Absorbing Materials Based On Thin Alumina Films for Solar-Thermal Energy Conversion, Using X-Ray Diffraction Technique
Solar energy is the most “available”, ecological and clean energy. This energy can be used in active or passive mode. The active mode implies the transformation of solar energy into a useful energy. The solar energy can be transformed into thermal energy, using solar collectors. In these collectors, the active and the most important element is the absorber, material which performs the absorption of solar radiation and, in at the same time, limits its reflection. The paper presents some aspects regarding the IR absorbing material – a type of cermets, used as absorber in the solar collectors, by X Ray Diffraction Technique (XRD) characterization. Keywords—Alumina films, solar energy, X-ray diffraction.
Optimization of a solution-chemically derived solar absorbing spectrally selective surface
This thesis consists of two parts, one dominating part concerning spectrally selective solar absorbers and one dealing with thermal solar systems. The appended papers I to VIII concern the solar absorber part, papers dealing with the systems part have not been included in the thesis.A new spectrally selective absorber derived from a novel solution-chemistry method has been developed and optimized. The main objective was to investigate the potential of the spectrally selective surface. Some of the questions at issue were; would it be possible to create a suitable absorber composite using this method, how high selectivity could be obtained, could the performance be enhanced by using anti-reflection coatings, which was the optimal layer composition, would the thin films be durable and what was the structure and morphology like on a nano scale? The absorber consists of absorbing thin films of nickel nano-particles embedded in a dielectric matrix of alumina and an overlying anti-reflection film consisting of one of the following materials silica, hybrid-silica, alumina or silica-titania. Solution and sol-gel chemistry were used in the process. The thin films were spin-coated onto an aluminum substrate followed by a heat-treatment that generated the multi layer selective solar absorber. The optical constants for the thin film materials in question were determined. An optimal three layer structure was modeled using the experimentally determined optical constants. The theoretical three layer stack was experimentally confirmed and achieved a solar absorptance of 0.97 and a thermal emittance of 0.05 which definitely are commercially competitive values. The configuration of the three layer stack is: an 80%nickel-20%alumina film at the base, a 40%nickel-60%alumina film in the middle and a silica or hybrid-silica film at the top. The three layer absorber was subjected to high temperature and condensation accelerated ageing tests designed by IEA Task 27. The condensation test did not degrade the absorber whatsoever but the high temperature test did reveal some oxidation of the nickel particles. The oxidation occurs initially and then stops. A formed nickel-oxide layer hinders further oxidation. The level of oxidation is small and the absorber is qualified according to the IEA Task 27 test procedure.
Coronial Practice, Indigeneity and Suicide
All available data suggest that, like many other Indigenous peoples, Australian Aborigines are significantly more likely to kill themselves than are non-Aboriginal Australians. This statistical disparity is normally positioned an objective, ontological and undeniable social fact, a fact best explained as a function of endemic community disadvantage and disenfranchisement. This research explores the possibility that higher-than-normal Aboriginal suicide rates may also be a function of coronial decision-making practices. Based upon in-depth interviews with 32 coroners from across Australia, the following conclusions emerged from the data. First, coroners have differing perceptions of Indigenous capacity, and are less likely to have concerns about intent when the suicide is committed by an Indigenous person. Second, coroners have identified divergent scripts of Indigenous suicide, particularly its spontaneity and public location, and this supports rather than challenges, a finding of suicide. Third, the coronial perception of Indigenous life is a factor which influences a suicide determination for Indigenous deaths. Finally, the low level of Indigenous engagement with the coronial system, and the unlikelihood of a challenge to the finding of suicide by Indigenous families, means that a coronial determination of suicide is more likely.