The feasibility of gas phase deposition using a Ti alkoxide precursor for precise surface modification of catalysts was demonstrated by modifying a mesoporous alumina support with a Ti oxide overcoat. Titanium tetra-isopropoxide yields a Ti oxide layer that covers homogeneously the alumina surface. Uniformity of the deposited TiO₂ was verified by SEM-EDX, on both intra-particle and inter-particle levels. Only a few atomic layer deposition (ALD) cycles were required in order to obtain Ti contents with a relevance for industrial application. The pore size distribution of the overcoated catalyst support was barely affected by the coating process. Synthesized CoMo catalysts based on the Ti-alumina carrier showed up to 40% higher activity compared to a catalyst supported on pristine alumina, in hydroprocessing under industrial testing conditions. The TiO₂ coating appeared to be stable, showing no agglomeration characteristics after reaction as corroborated by TEM-EDX. ALD provides a scalable route with low waste generation for the production of precisely structured TiO₂-Al₂O₃ hydroprocessing catalyst supports.

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This work investigated the suppression of photocatalytic activity of titanium dioxide (TiO2) pigment powders by extremely thin aluminum oxide (Al2O3) films deposited via an atomic-layer-deposition-type process using trimethylaluminum (TMA) and H2O as precursors. The deposition was performed on multiple grams of TiO2 powder at room temperature and atmospheric pressure in a fluidized bed reactor, resulting in the growth of uniform and conformal Al2O3 films with thickness control at sub-nanometer level. The as-deposited Al2O3 films exhibited excellent photocatalytic suppression ability. Accordingly, an Al2O3 layer with a thickness of 1 nm could efficiently suppress the photocatalytic activities of rutile, anatase, and P25 TiO2 nanoparticles without affecting their bulk optical properties. In addition, the influence of high-temperature annealing on the properties of the Al2O3 layers was investigated, revealing the possibility of achieving porous Al2O3 layers. Our approach demonstrated a fast, efficient, and simple route to coating Al2O3 films on TiO2 pigment powders at the multigram scale, and showed great potential for large-scale production development@en

Stability of quantum dot (QD) films is an issue of concern for applications in devices such as solar cells, LEDs, and transistors. This paper analyzes and optimizes the passivation of such QD films using gas-phase deposition, resulting in enhanced stability. Crucially, we deposited alumina at economically attractive conditions, room temperature and atmospheric pressure, on (1,2-ethanediamine) capped PbSe QD films using an approach based on atomic layer deposition (ALD), with trimethylaluminum (TMA) and water as precursors. We performed coating experiments from 1 to 25 cycles on the QD films, finding that alumina formed from the first exposure of TMA. X-ray photoelectron spectroscopy points to the presence of oxygen-rich compounds on the bare QD films, most likely from entrapped solvent molecules during the assembly of the QD films. These oxygenated compounds and the amine groups of the organic ligands react with TMA in the first cycle, resulting in a fast growth of alumina. Using 10 cycles resulted in a QD film that was optically stable for at least 27 days. Depositing alumina at ambient conditions is preferred, since the production of the QD films is also carried out at room temperature and atmospheric pressure, allowing combination of both processes in a single go.

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To improve the thermal stability, Al₂O₃ has been successfully coated on a Y₃Al₅O₁₂:Ce³⁺ (YAG:Ce) phosphor powder host by using the Atomic Layer Deposition (ALD) approach in a fluidized bed reactor. Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray spectroscopy (EDX) analysis indicate that coating an Al₂O₃ thin layer by ALD is highly feasible. The luminescence properties (such as excitation and emission as well as quantum efficiency and UV-absorption of the coated YAG:Ce phosphor) were systematically analysed, with the further examination of the thermal resistance characteristics. The Al₂O₃ thin layer coating with precisely controlled thickness by ALD can obviously improve the luminescence intensity and greatly enhances the thermal stability of the YAG:Ce phosphor. It is suggested that the alumina coating with tailoring thickness seems not only to act like a barrier to decrease the thermal quenching, but also as a great help to promote the light absorption and transfer.

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