V. M. Ievlev

Effect of Thermal Annealing on Electrical Properties of Si-LiNbO3

The substructure and electrical properties of the films with the thickness up to 2.0 µm deposited on Si by the methods of the radio frequency magnetron and ion-beam sputtering of a LiNbO3 target have been investigated. It has been established that in thermally annealed samples an activated conduction mechanism with variable jump distance takes place. As a result of thermal annealing a decrease in the charge localization centers (CLC) in the LiNbO3 films from Nt=3·1018cm-3 to Nt=3·1016cm-3 occurs.

Heat-treatment induced evolution of the morphology and microstructure of zirconia prepared from chloride solutions during

The properties of hydrous zirconia prepared from ZrOCl2 solutions were studied as functions of precipitation pH and subsequent heat treatment. Precipitation at pH ≤ 6 yields hydrous zirconia containing excess sorbate anions (Cl−), and at pH ≥ 7, ammonium ions. This difference considerably affects the thermolysis and morphology of the resulting samples. The samples prepared at pH ≥ 7 have far better developed surfaces. The morphological and structural evolution of hydrous zirconia samples during heat treatment is described. The involved processes are interpreted. At initial stages, the major process is the formation of metastable tetragonal ZrO2, which transforms to the monoclinic phase during subsequent heating.

Formation of thin foil of the ordered Pd-Cu solid solution with a CsCl-type lattice during magnetron sputtering

Among Pdbased membrane alloys (1), the Pd-Cu system has long attracted attention for deep hydrogen purification. This system is distinguished by the for� mation of a CsCltype ordered solid solution ( β phase) (2) in a rather narrow composition range close to Pd- 40 wt % Cu. It is accepted (3) that the CsCltype lattice, as compared to the less dense fcc lattice of the disordered solid solution ( α) phase), and, respectively, the shorter distance between octahedral voids (involved in hydro� gen diffusion) are responsible for a lower barrier for diffusion and a manyfold enhancement of hydrogen permeability. According to the results of numerous experimental studies summarized in (3), the hydrogen diffusion activation energy is 0.035 eV in the ordered solid solution, 0.325 eV in the disordered solid solu� tion, and 0.23 eV in palladium. The hydrogen diffu� sion coefficient at 300 K in the β phase is almost four orders of magnitude higher than in the α phase and two orders of magnitude higher than in Pd (3). Thus, the first, major, way of improving the perfor� mance of a Pd-Cu alloy membrane is to increase hydrogen permeability through ordering of the solid solution. The kinetics and mechanism of solid solu� tion ordering have been studied for more than three

Silicide formation during heat treatment of thin Ni-Pt and Ni-Pd solid-solution films and Pt/Ni bilayers on (111)Si

It is shown that isothermal heat treatment of (Ni-Pt)/Si and Pt/Ni/Si heterostructures leads to the formation of oriented Ni-and Pt-based silicide solid solutions. Owing to the three equivalent azimuth orientations in the basic lattice orientation relationship for the Si-Ni1−xPtxSi system, the resulting silicides have a nanocrystalline substructure. The stability of the substructure is due to the optimal interfacial lattice match and near-special grain-boundary misorientations. The silicide phases Ni1−xPtxSi and Pt1−yNiySi (or Ni1−xPdxSi and Pd1−yNiySi) may undergo segregation, having the same lattice orientation. In both systems, the segregation is associated with the predominant Ni diffusion. The second component (Pt) is shown to stabilize the orthorhombic Ni-based silicide and to prevent NiSi2 formation. Photon processing accelerates diffusion and leads to the formation of phase-pure Ni1−xPtxSi solid solutions.

Additive Technologies for Making Highly Permeable Inorganic Materials with Tailored Morphological Architectonics for Medicine

The review discusses methods to manufacture osteoconductive inorganic materials based mainly on calcium phosphates with given macroscopic porosity using rapid prototyping. Requirements for composition and morphological architectonic of these materials are considered, and three-dimensional printing techniques that are most often used to achieve this are described.

Hardness and microplasticity of nanocrystalline and amorphous calcium phosphate coatings

The hardness of thin (1.0–4.0 μm) hydroxyapatite coatings with different structures (nanocrystalline, amorphous-crystalline, and amorphous) grown by rf magnetron sputtering on Ti and Si plates has been studied using the nanoindentation method. All the grown structures are characterized by the strain which has reversible and irreversible components. The hardness of nanocrystalline coatings (about 10 GPa) corresponds to the average hardness of hydroxyapatite single crystals. The structure of nanocrystalline coatings in the indentation zone and outside it has been investigated and changes in the structure under the indenter have been revealed using high-resolution transmission electron microscopy. From a comparison of the hardnesses of coatings with different structures and based on an analysis of the intragranular structure, it has been assumed that the plastic deformation occurs according to a dislocation-free mechanism. The plastic deformation is interpreted in terms of the cluster representation of the hydroxyapatite structure and amorphous calcium phosphates of the same elemental composition and cluster-boundary sliding during the deformation.

Effect of photon irradiation on the process of recrystallization of thin metallic films

Recrystallization of thin polycrystalline films of Au, Pt, and Pd obtained by thermal evaporation and condensation in a vacuum on silicon plates that are not warmed up and are coated on both sides with silicon oxide has been studied by transmission electron microscopy. It has been established that the rate of normal grain growth in such films is higher upon photon treatment by the radiation of power xenon lamps (spectral region of 0.2–1.2 μm) than upon heat treatment. A quantitative estimate of the effect revealed indicates a change in the mechanism of the process that controls migration of grain boundaries. The effect is connected with the possible activation of hypersonic waves owing to the coexistence of phonon and electron excitations localized in nanosized regions of metallic films.

Sputtering condition effect on structure and properties of LiNbO3 films

Polycrystalline LiNbO3 films were grown on various substrates by the radio-frequency magnetron sputtering (RFMS) method and ion-beam sputtering (IBS) method at different sputtering conditions. Films formed on the substrates situated within erosion zone (plasma effect) manifested textured structure. When plasma effect became insignificant only LiNbO3 films with random size orientation were formed during the RFMS process and IBS process with an increase in the size of the crystallites. Reactive gas pressure as part of plasma effect has a profound effect on the films’ properties. When gas pressure was increased greatly, grain size declined two fold and the average surface roughness of the grown films doubled. At the higher gas pressure Li-poor phase LiNb3O8 appeared along with LiNbO3 during the growth process. As a result, the film texture disappeared. Single phase LiNbO3 films with two-axes (epitaxial) texture are formed on (111)Ag epitaxial film during the RFMS process at the ion assisted conditions.

Influence of ripening time on the properties of hydroxyapatite-calcium carbonate powders

Abstract80 wt % hydroxyapatite + 20 wt % calcium carbonate composite powders have been synthesized through precipitation from aqueous solutions. Increasing the ripening time of the precipitate in the mother liquor leads to partial calcium carbonate dissolution and the formation of carbonate-substituted hydroxyapatite and improves its crystallinity. In addition, the specific surface area of the powders increases from 83.2 to 238.7 m2/g. The powders ripened for 14 and 21 days show the best sinterability.

On the substructure of compact ceramics based on hydroxyapatite

Hydroxyapatite Ca10(PO4)6(OH)2 (HA), space group of symmetry Р63/m, is a key calcium phosphate employed for the manufacture of biologically active ceramic materials for medical purposes used to recon� struct bone tissue defects [1]. Therefore, the views on the intragrain substructure, the structure of internal