Vol 52, No 4 (2016)

This paper reviews advances in the fabrication of calcium phosphate materials for injured bone tissue regeneration. We examine the key features of rapid prototyping for the fabrication of porous ceramic scaffolds with tailored architectures, the technology of biopolymer-based composite materials reinforced with calcium phosphate particles, and the fabrication of porous scaffolds via cement route.

The recrystallization of detonation nanodiamond in the presence of hydrogen-containing fluids has been studied at pressures from 6 to 8 GPa and temperatures above 1000°C. Electron microscopy and Xray diffraction data demonstrate that, in the presence of a hydrogen-containing fluid, nanocrystalline diamond recrystallizes to micron dimensions. We discuss the mechanism underlying the influence of hydrogencontaining media on the growth of diamond nanocrystals.

Bi_2–хLa_хFe₄O₉ and Bi₂Fe_4–2xTi_xCo_xO₉ ferrites have been prepared by solid-state reactions at a temperature of 1073 K. X-ray diffraction data indicate that, in the Bi_2–хLa_хFe₄O₉ system, the limiting degree of La³⁺ substitution for Bi³⁺ ions in Bi₂Fe₄O₉ does not exceed 0.05 and that the limiting degree of substitution in the Bi₂Fe_4–2xTi_xCo_xO₉ system lies in the range 0.05 < x < 0.1. The specific magnetization and specific magnetic susceptibility of the samples have been measured at temperatures from 5 to 300 K in a magnetic field of 0.86 T. The field dependences of magnetization obtained for the Bi_2–хLa_хFe₄O₉ and Bi₂Fe_4–2xTi_xCo_xO₉ ferrites at temperatures of 300 and 5 K demonstrate that partial isovalent substitution of La³⁺ for Bi³⁺ ions in Bi₂Fe₄O₉ and heterovalent substitution of Ti⁴⁺ and Co²⁺ ions for two Fe³⁺ ions leads to partial breakdown of the antiferromagnetic state and nucleation of a ferromagnetic state.

A new method has been proposed for the synthesis of catalytically active 80 wt % SnO₂ + 20 wt % CeO₂ materials supported on glass fiber, which involves the use of an ethanolic film-forming solution based on cerium(III) nitrate and salicylic acid, with the addition of tin(IV) chloride. We have studied the morphology of the materials thus prepared and assessed their catalytic activity for the deep oxidation of methane. The results indicate that the appreciable catalytic activity of the materials is ensured by their uniform distribution over the support surface and the small oxide aggregate size ( 10 μm), which is due to the use of the filmforming solution of the proposed composition.

A process has been proposed for hydrophobizing an inorganic porous material consisting of silica fibers using fluoroalkane dissolution in supercritical carbon dioxide. The process allows one to produce thin, homogeneous polymer coatings both on the surface and in the bulk of the material, ensuring that the material has excellent hydrophobic properties, which significantly improves its performance parameters and extends its potential application field.

We have studied the effect of hot-pressing conditions (different pressure rise rates and isothermal holding temperatures in the range 1450–1550°C) on the microstructure of ceramics produced from nanopowder with the composition Ce_0.09Zr_0.91O₂/MgAl₆O₁₀/γ-Al₂O₃ (20.6, 37.4, and 42.0 wt %, respectively). Firing at 1450°C for 1 h made it possible to obtain fine-grained ceramics with less than 3 μm in grain size. The compaction pressure rise rate was shown to be a key parameter under such thermal conditions (20 + 10°C/min → 1450°C). Grain growth was prevented most effectively when the maximum load, 30 MPa, was reached at a temperature of 1000°C. Under such conditions, the grain size was 0.4–0.8 μm and the relative density reached 98.8%.

Using ion-beam and rf magnetron sputtering of oxide targets, we have grown thin ZrO₂ coatings on 12Kh18N10T high-temperature steel substrates. Depending on the deposition technique, amorphous or crystalline (t + c) coatings have been obtained. The amorphous zirconia retains a disordered structure and high microhardness values up to 600°C. Its crystallization leads to a sharp drop in its microhardness and peeling from the substrate. The initially crystalline coating retains continuity and high microhardness values despite the t → с phase transition at 600 and 700°C. Only annealing at 800°C or higher temperatures reduces its microhardness. This is tentatively attributed to the influence of the substrate.

The temperature dependences of the Hall coefficient, electrical conductivity, and thermoelectric power for a eutectic InSb + MnSb composite have been studied in the temperature range from 80 to 700 K. Electron-microscopic results confirm that the system is in a two-phase state and consists of an InSb matrix and needle-like MnSb metallic inclusions. The inclusions are surrounded by interfacial zones ~0.3 μm in width. The observed anisotropy in the transport properties of the material is attributed to a short-circuiting effect of the metallic inclusions. Interpretation in terms of effective medium theory with allowance for the interfacial zones suggests that they make a significant contribution to the electrical conductivity anisotropy.

This paper discusses the problems of ensuring compatibility and functionality of admixtures with cements. We analyze the methodology—developed on the principles of continuity and superpositions—of functional kinetic analysis of the effect of admixtures on the hardening of cement systems using calorimetric monitoring of early hardening stages and illustrate the possibility of using this methodology by the examples of the technologies of summer ready mix and mass concretes, assessing the levels of the effect of admixtures on the hardening kinetics of cements.