Aluminum acetylacetonate has been reported as a precursor for the deposition of alumina films using different approaches. In this work, alumina-containing films were prepared by plasma sputtering this compound, spread directly on the powered lowermost electrode of a reactor, while grounding the substrates mounted on the topmost electrode. Radiofrequency power (13.56 MHz) was used to excite the plasma from argon atmosphere at a working pressure of 11 Pa. The effect of the plasma excitation power on the properties of the resulting films was studied. Film thickness and hardness were measured by profilometry and nanoindentation, respectively. The molecular structure and chemical composition of the layers were analyzed by Fourier transform infrared spectroscopy and energy dispersive spectroscopy. Surface micrographs, obtained by scanning electron microscopy, allowed the determination of the sample morphology. Grazing incidence X-ray diffraction was employed to determine the structure of the films. Amorphous organic layers were deposited with thicknesses of up to 7 mm and hardness of around 1.0 GPa. The films were composed by aluminum, carbon, oxygen and hydrogen, their proportions being strongly dependent on the power used to excite the plasma. A uniform surface was obtained for low-power depositions, but particulates and cracks appeared in the high-power prepared materials. The presence of different proportions of aluminum oxide in the coatings is ascribed to the different activations promoted in the metalorganic molecule once in the plasma phase.

The uranium molybdenum (U-Mo) alloys have potential to be used as low enriched uranium nuclear fuel in research, test and power nuclear reactors. U-Mo alloy with composition between 7 and 10 wt% molybdenum shows excellent body centered cubic phase (γ phase) stabilization and presents a good nuclear fuel testing performance. Hot rolling is commonly utilized to produce parallel fuel plate where it promotes the cladding and the fuel alloy bonding. The mechanical deformation generates crystallographic preferential orientation, the texture, which influences the material properties. This work studied the texture evolution in hot rolled U-Mo alloys. The U7.4Mo and U9.5Mo alloys were melted in a vacuum induction furnace, homogenized at 1000°C for 5 h and then hot rolled at 650°C in three height reductions: 50, 65 and 80%. The crystalline phases and the texture were evaluated by X-ray diffraction (XRD). The as-cast and processed alloys microstructures were characterized by optical and electronic microscopies. The as-cast, homogenized and deformed alloys have γ phase. It was found microstructural differences between the U7.4Mo and U9.5Mo alloys. The homogenized treatment showed effective for microsegregation reduction and were not observed substantial grain size increasing. The deformed uranium molybdenum alloys presented α, γ, θ texture fibers. The intensity of these texture fibers changes with deformation step.

NIELSEN, Guilherme F. Crystallographic texture of hot rolled and annealed uranium-molybdenum alloys. 2021. 144 p. Tese (Doutorado em Tecnologia Nuclear) -Instituto de Pesquisas Energéticas e Nucleares -IPEN/CNEN/SP. São Paulo.The Uranium-molybdenum alloys are a good candidate to be used as monolithic nuclear fuel in research, test, and also small power energy nuclear reactors. Hot rolling and annealing processes have been used for the production of monolithic fuels. The fuel production processes can generate crystallographic texture, which can modify the isotropic properties. Based on this, this work studied the preferred crystallographic orientation in hot rolled and annealed U-Mo alloys. The U7.4Mo and U9.5Mo alloys were melted in a vacuum induction furnace and then homogenized, hot rolled, and annealed. The alloys were characterized by optical and electronic microscopies. The crystalline phases were identified by X-ray diffraction. The macrotexture was analyzed by x-ray diffractometry and the microtexture was characterized by EBSD. The as-cast and processed alloys have the gamma phase.The best homogenization condition achieved was 1000 °C for 5 hours. The homogenized treatment showed effective for microsegregation reduction and substantial grain size increase was not observed. The deformed uraniummolybdenum alloys presented α, γ e θ fibers. The intensity of these texture fibers changed with rolling reduction. It was noted that the nucleation of recrystallized grains occurred in preferred locations. Recrystallized grains have crystallographic texture. Upon annealing, it was possible to verify that the microstructure in the annealed samples varies according to the degree of deformation and the annealing time. The deformation generated coincidence site lattice (CSL) grain boundaries.The movement of these special boundaries was observed with annealing.