Vacuum-arc chromium-based coatings for protection of zirconium alloys from the high-temperature oxidation in air

Study of the oxidation behavior of CrN coating on Zr alloy in air

Nanoparticles coarsen in solution via atom-by-atom dissolution and reattachment (Ostwald ripening) or via crystallographically controlled attachment of discrete particles (oriented attachment). We coarsened anatase nanoparticles in hydrothermal solutions over the temperature range 105−250 °C and the pH range 1−12 and documented three distinct coarsening mechanisms controlled by solution pH. Anatase growth at pH > 11 occurs primarily by Ostwald ripening, yielding a wide particle size distribution. Over the pH range of 2 through 11, anatase grows both by oriented attachment and Ostwald ripening. At pH values <2, anatase simultaneously grows by oriented attachment and dissolves, precipitating as rutile. Oriented attachment is significant at values nearer to the pH of point of zero net proton charge (PZC), where anatase is very insoluble and has low surface charge. Rutile precipitation at low pH and anatase growth at high pH are promoted by enhanced Ti solubility at pH values far from the PZC. Understanding s...

Anatase Coarsening Kinetics under Hydrothermal Conditions As a Function of Ph and Temperature

The formation of rotation domains (RDs) in heteroepitaxy depends fundamentally on the relation of the crystal symmetries of substrate and epilayer. We assume well-defined crystallographic axes of substrate and epilayer along the growth direction and determine from group theory the number of RDs with crystallographically equivalent interfaces (CEIF) for all combinations of the two-dimensional (2D) point symmetries of substrate and epilayer, including cases of aligned and misaligned symmetry directions. Additional domains can arise from multi-domain substrates. Accidentally or nearly fulfilled additional symmetries of the substrate allow further domains with crystallographically inequivalent interfaces (CIIF). Schematic RDs for various rotation symmetries of substrate and epitayer.

Formation of epitaxial domains: Unified theory and survey of experimental results

ZrO 2 thin films were grown on TiN substrates by atomic layer deposition. A high dielectric constant (∼40) was obtained due to the formation of a high-temperature crystalline form, tetragonal or cubic. The origin of the formation of the high-temperature form was examined by depositing ZrO 2 films on two types of TiO 2 surfaces, anatase and rutile. Tetragonal or cubic ZrO 2 films were formed on both substrates. This suggests that growth-controlled selection is responsible for the formation of the metastable phase ZrO 2 , not the minimization of interfacial energy.

Atomic Layer Deposition of ZrO2 Thin Films with High Dielectric Constant on TiN Substrates

The TiO to anatase phase transformation has been studied by transmission electron microscopy in this Article. It is shown that prior formation of TiO from Ti film can induce the formation of anatase by thermal oxidation in air; otherwise only rutile is formed. Ti film deposited on the NaCl (001) surface is induced to form epitaxial TiO film by thermal oxidation in air. Further thermal oxidation in air partially transformed TiO into anatase (A) with a parallel orientation relationship of {200}A//{200}TiO. Detailed analysis of the lattice fringes image of the specimen reveals the presence of very high density of misfit dislocations. The TiO to anatase transformation is reversible as further annealing in a vacuum can turn the anatase back into TiO and eliminates the misfit dislocations. The transformation is analyzed in terms of the crystal structure, orientation relationship, and the dislocation distribution, which show that the TiO to anatase transformation is due to the close similarity between their stru...

Study of the TiO to Anatase Transformation by Thermal Oxidation of Ti Film in Air

http://www.nano.nsysu.edu.tw/nano/V2007/Papers/527_The%20oriented%20growth%20of%20zirconia%20thin%20films%20on%20NaCl%20(001)%20surface.pdf

The oriented growth of zirconia thin films on NaCl (0 0 1) surface

http://www.nano.nsysu.edu.tw/nano/V2007/Papers/204_Condensation%20of%20tetragonal%20zirconia%20polycrystals%20by%20reactive%20sputtering.pdf

Condensation of tetragonal zirconia polycrystals by reactive sputtering

Nanocrystalline -Zr condensates deposited by ion beam sputtering on the NaCl (1 0 0) surfaces and then annealed at 100–750 ◦ C in air. The phases present were identified by transmission electron microscopy to be nanometer-size -Zr + ZrO, -Zr + ZrO + c-ZrO2, c-ZrO2, c- + t-ZrO2, t-ZrO2, and t- + m-ZrO2 phase assemblages with increasing annealing temperature. The ZrO2 showed strong { 100 } preferred orientation due to parallel epitaxy with NaCl (1 0 0) when annealed between 150 and 500 ◦ C in air. The c- and t-ZrO2 condensates also showed (1 1 1)-specific coalescence among themselves. The c- and/or t-ZrO2 formation can be accounted for by the small grain size, the presence of low-valence Zr cation and the lateral constraint of the neighboring grains. © 2006 Elsevier B.V. All rights reserved.

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Sung-Wei Yeh

Papers

Study of the TiO to Anatase Transformation by Thermal Oxidation of Ti Film in Air

The oriented growth of zirconia thin films on NaCl (0 0 1) surface

Condensation of tetragonal zirconia polycrystals by reactive sputtering

Annealing induced oxidation and transformation of Zr thin film prepared by ion beam sputtering deposition

Low-temperature growth of (2 1 1 0) ZnO nanofilm on NaCL (0 0 1) surface by ion beam sputtering