Transparent conductors as solar energy materials: A panoramic review

Platinum-based nanostructured materials: synthesis, properties, and applications.

Synthesis methods for nanosized hydroxyapatite with diverse structures.

Designer platinum nanoparticles: Control of shape, composition in alloy, nanostructure and electrocatalytic property

The present overview is intended to point the readers’ attention to the important subject of calcium orthophosphates. These materials are of the special significance because they represent the inorganic part of major normal (bones, teeth and dear antlers) and pathological ( i.e. those appearing due to various diseases) calcified tissues of mammals. Due to a great chemical similarity with the biological calcified tissues, many calcium orthophosphates possess remarkable biocompatibility and bioactivity. Materials scientists use this property extensively to construct artificial bone grafts that are either entirely made of or only surface-coated with the biologically relevant calcium ortho-phosphates. For example, self-setting hydraulic cements made of calcium orthophosphates are helpful in bone repair, while titanium substitutes covered by a surface layer of calcium orthophosphates are used for hip joint endoprostheses and as tooth substitutes. Porous scaffolds made of calcium orthophosphates are very promising tools for tissue engineering applications. In addition, technical grade calcium orthophosphates are very popular mineral fertilizers. Thus ere calcium orthophosphates are of great significance for humankind and, in this paper, an overview on the current knowledge on this subject is provided.

https://www.mdpi.com/1996-1944/2/2/399/pdf

Calcium Orthophosphates in Nature, Biology and Medicine

Templating of electrodeposited platinum group metals as a tool to control catalytic activity

The properties of Ca-deficient hydroxyapatite powder synthesized from calcium nitrate and ammonium hydrophosphate at 60°C, pH = 7, and Ca/P = 1.67, 1.61, and 1.48 are presented. After sintering at 1100°C for 6 h the phase composition of the ceramic based on these powders was represented by tricalcium phosphate (Ca/P = 1.48) or tricalcium phosphate hydroxyapatite (Ca/P = 1.67 and 1.61). The grain size of the ceramic was 100 – 1000 nm.

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Ca-deficient hydroxyapatite powder for producing tricalcium phosphate based ceramics

Conditions for hydroxyapatite (HAP) synthesis in aqueous solutions by hydrolysis of α-Ca3(PO4)2 were studied. Temperature exerts a substantial effect on the rate of α-Ca3(PO4)2 hydrolysis and also changes the morphology of the reaction products. At 40 °C, the plate-like intersecting (perpendicular to the surface of the initial particles) crystals of HAP grow. Their maximum size after the 24-h hydrolysis is 1–2 µm. Needle like HAP crystals are formed upon boiling of the suspension. The morphology observed for the HAP particles agrees well with the conclusions obtained by analysis of the kinetics of tricalcium phosphate hydrolysis.

Synthesis of hydroxyapatite by hydrolysis of α-Ca3(PO4)2

Ceramics based on calcium phosphates is known to be a prospective material for biomedical applications. Noticeable attention is paid to hydroxyapatite Ca10(PO4)6(OH)2 (HAp) due to its affinity to a bone mineral. It was recognized recently that Si-doped HAp is a highly promising material in sense of bioactivity improvement. In the frame of distinct research activity structured around this subject, some special problems are to be solved: (1) solubility of Si in the bulk of HAp lattice (and its limit) vs. segregation of Si to free surfaces and grain boundaries, (2) rationalization of Si effect on sintering of HAp ceramics, (3) charge compensation over aliovalent doping of HAp with Si and its interplay with thermal stability of HAp phase.

The work was focused on a fabrication of Si-HAp with Ca10(Po4)6-x(SiO4)x(OH)2-x (x=0..1) nominal composition and evaluation the effect of Si on sintering of HAp ceramics. The limit of Si solubility in HAp lattice was estimated to be not higher than x=0.1 in the formula above (at 1000 °C, according to XRD and SEM/EDX). The essence of the silicon influence consists in significant suppression of grain growth during the initial stage of sintering. Silicon doping reduces grain boundary mobility (increasing activation energy of lattice diffusion) along with the increase of pore mobility (in fact, increasing grain boundary diffusion). We believe that the effect of Si on sintering behaviour can be treated in terms of its segregation to grain boundaries, the phenomenon arising from a lattice instability of Si-HAp due to the charge compensation in the course of aliovalent doping.

Silicon-substituted hydroxyapatite ceramics (Si-HAp): densification and grain growth through the prism of sintering theories

InSb samples containing 022–142 wt % manganese were synthesized and identified The unit cell parameter decreased as the manganese concentration increased The samples contained microinclusions of manganese antimonides Electrical and magnetic measurements showed two ferromagnetic phases (In1−xMnxSb solid solution with Tc ∼ 7 K and MnSb with Tc ∼ 580 K) and a ferrimagnetic phase (Mn2Sb) The samples had p-type conductivity with a charge carrier concentration of about 1020cm−3 The semiconductor conductivity was observed at low temperatures and changed to the metal conductivity with temperature elevation

A. G. Veresov

Papers

Templating of electrodeposited platinum group metals as a tool to control catalytic activity

Ca-deficient hydroxyapatite powder for producing tricalcium phosphate based ceramics

Synthesis of hydroxyapatite by hydrolysis of α-Ca3(PO4)2

Silicon-substituted hydroxyapatite ceramics (Si-HAp): densification and grain growth through the prism of sintering theories

Ferromagnetism of manganese-doped InSb alloys