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Register a new userSingle- and Mixed-Phase TiO2 Powders Prepared by Excess-Hydrolysis of a Titanium Alkoxide
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To investigate excess-hydrolysis of titanium alkoxides, TiO2 powders were fabricated from titanium-tetra-isopropoxide using 6:1 and 100:1 H2O:Ti (r) ratios. Powders were dried and fired at a range of temperatures ( up to 800 C). Hydroxylation and organic content in powders were characterised using ATR-FTIR, laser Raman microspectroscopy, and elemental microanalysis; surface area and pore size distribution were evaluated using N2 gas adsorption; phase composition was analysed using XRD and laser Raman microspectroscopy; and crystallite size was evaluated by XRD, TEM and SEM. Results showed near-complete hydrolysis in a predominantly aqueous medium (r = 100), resulting in precipitated crystalline powders exhibiting brookite and anatase, which begin to transform to rutile below 500 C. Powders precipitated in a predominantly organic medium (r = 6) underwent partial hydrolysis, were highly porous and exhibited an amorphous structure, with crystallisation of anatase occurring at 300 C and transformation to rutile beginning at 500 to 600C.
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The thermal vacuum treatment effect on the optical absorption spectra of the TiO2 nanopowders, both pure and coated by the Ni-B clasters with the original electroless method was investigated. It was observed that the thermal treatment of pure TiO2 nanopowders does not change their optical absorption spectrum while after the coating of these powder particles by the Ni-B clasters the thermal treatment results in the increase of the optical light absorption in the visual region of spectrum. This points to the possibility of the significant improvement of the photocatalist efficiency of TiO2 nanopowders coated by the Ni-B clasters using the thermal treatment.
The preparation in thin film form of the known icosahedral phase in Ti-Ni-Zr bulk alloys has been investigated as a function of substrate temperature. Films were deposited by Pulsed Laser Deposition on sapphire substrates at temperatures ranging from room temperature to 350$^circ$C. Morphological and structural modifications have been followed by grazing incidence and $theta$-2$theta$ X-ray diffraction, transmission electron diffraction and imaging. Chemical composition has been analysed by Electron Probe Micro-Analysis. The in-depth variation of composition has been studied by Secondary Neutral Mass Spectroscopy. We show that Pulsed Laser Deposition at 275$^circ$C makes the formation of a 1 m thick film of Ti-Ni-Zr quasicrystalline textured nanocrystallites possible.
Single-domain particles of SrFe8Al4O19 were prepared by thermal treatment at 1473 K of porous products of citrate-nitrate auto-combustion, and the influence of synthesis time on the particle morphology and magnetic properties was studied. The procedure allows to obtain SrFe8Al4O19 particles with mean diameters 100 - 460 nm, and their coercivity ranges from 14.5 to 18.4 kOe, while ferromagnetic resonance frequencies vary from 149 to 164 GHz.
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