Brookite TiO₂ is the most difficult TiO₂ polymorph to synthesize. The available methods in the literature to produce brookite nanostructures mostly use water-based techniques for the preparation of water-soluble Ti complexes first, followed by a hydrothermal growth of the brookite nanostructures. Besides its multi-step nature, achieving a single brookite phase and optimizing the aqueous growth environment are all issues to be hardly controlled. In this work, pure brookite TiO₂ nanorods are synthesized using tetrabutyl titanate Ti(OBu)₄ and Sodium Fluoride (NaF) as precursor materials in a simple non-aqueous one-pot solvothermal process. Alcoholysis of only Ti(OBu)₄ in ethanol resulted in pure anatase nanoparticles, while the addition of NaF was essential to promote the growth of highly pure brookite nanorods. The phase purity is confirmed by X-Ray Diffraction, Raman Spectroscopy, and High-Resolution Transmission Electron Microscopy. The growth mechanism is explained according to the Ostwald’s step rule, where Na⁺ ions are anticipated to have a potential role in driving the growth process towards the brookite phase.

Luminescent mesoporous Tb(OH)3@SiO2 core-shell nanospheres were synthesized through W/O microemulsion process at ambient temperature. The negatively charged silica favors a coating of the positively charged Tb3+ composite. Thus, silicon layer was adsorbed on the surface of Tb(OH)3 groups to form Tb-O-Si through electrostatic interaction. X-ray diffraction, field emission transmission electron microscopy (FE-TEM), energy-dispersive X-ray spectrometry, and Fourier transform infrared, UV/Visible, and photoluminescence spectroscopies were applied to examine the phase purity, crystallinity, surface morphology, and optical properties of the core-shell nanospheres. The FE-TEM results have revealed typically ordered mesoporous characteristics of the material with monodisperse spherical morphology in a narrow size distribution. The luminescent mesoporous core-shell nanospheres exposed remarkable splitting with broadening in the emission transition 5D4 → 7F5 (543 nm). In addition, the luminescent mesoporous core-shell nanospheres emit strong green fluorescence (from Tb3+) in the middle of the visible region under 325 nm (3.8) excitation. The luminescent mesoporous Tb(OH)3@SiO2 core-shell nanospheres can therefore be exploited as fluorescent probes in biomarkers or biolabeling, optical sensing, and drug delivery system. Further, these nanospheres could have potential use as scattering layers in dye-sensitized solar cells.

Ti-6Al-4V and Mg-AZ31 were bonded together using the Transient Liquid Phase Bonding Process (TLP) after coating both surfaces with zinc. The zinc coatings were applied using the screen printing process of zinc paste. Successful bonds were obtained in a vacuum furnace at 500 °C and under a uniaxial pressure of 1 MPa using high frequency induction heat sintering furnace (HFIHS). Various bonding times were selected and all gave solid joints. The bonds were successfully achieved at 5, 10, 15, 20, 25, and 30 min. The energy dispersive spectroscopy (EDS) line scan confirmed the diffusion of Zn in both sides but with more diffusion in the Mg side. Diffusion of Mg into the joint region was detected with significant amounts at bonds made for 20 min and above, which indicate that the isothermal solidification was achieved. In addition, Ti and Al from the base alloys were diffused into the joint region. Based on microstructural analysis, the joint mechanism was attributed to the formation of solidified mixture of Mg and Zn at the joint region with a presence of diffused Ti and Al. This conclusion was also supported by structural analysis of the fractured surfaces as well as the analysis across the joint region. The fractured surfaces were analyzed and it was concluded that the fractures occurred within the joint region where ductile fractures were observed. The strength of the joint was evaluated by shear test and found that the maximum shear strength achieved was 30.5 MPa for the bond made at 20 min.

N-BiVO₄ is a favorable photoelectrode candidate for a photoelectrochemical (PEC) water splitting reaction owing to its suitable energy level edge locations for an oxygen evolution reaction. On the other hand, the sluggish water oxidation kinetics of BiVO₄ photoanodes when used individually make it necessary to use a hole blocking layer as well as water oxidation catalysts to overcome the high kinetic barrier for the PEC water oxidation reaction. Here, we describe a very simple synthetic strategy to fabricate nanocomposite photoanodes that synergistically address both of these critical limitations. In particular, we examine the effect of a SnO₂ buffer layer over BiVO₄ films and further modify the photoanode surface with a crystalline nickel tungstate (NiWO₄) nanoparticle film to boost PEC water oxidation. When NiWO₄ is incorporated over BiVO₄/SnO₂ films, the PEC performance of the resultant triple-layer NiWO₄/BiVO₄/SnO₂ films for the oxygen evolution reaction (OER) is further improved. The enhanced performance for the PEC OER is credited to the synergetic effect of the individual layers and the introduction of a SnO₂ buffer layer over the BiVO₄ film. The optimized NiWO₄/BiVO₄/SnO₂ electrode demonstrated both enriched visible light absorption and achieves charge separation and transfer efficiencies of 23% and 30%, respectively. The photoanodic current density for the OER on optimized NiWO₄/BiVO₄/SnO₂ photoanode shows a maximum photocurrent of 0.93 mA/cm² at 1.23 V vs. RHE in a phosphate buffer solution (pH~7.5) under an AM1.5G solar simulator, which is an incredible five-fold and two-fold enhancement compared to its parent BiVO₄ photoanode and BiVO₄/SnO₂ photoanodes, respectively. Further, the incorporation of the NiWO₄ co-catalyst over the BiVO₄/SnO₂ film increases the interfacial electron transfer rate across the composite/solution interface.