Boron-containing brushite cements (B-BC) for bone grafting based on B-substituted β-tricalcium phosphate (B-TCP) have been developed. The phase composition and microstructure of B-BC have been studied. It is shown that the crystalline phase of brushite is formed as a result of hardening of cements. The behavior of B-BC in physiological solution containing TRIS-buffer was studied. The strength of B-BC under compression 5 days after mixing is 22.5 ± 1 MPa. Studies of antibacterial activity against gram-negative strain E. coli ATCC25922 and gram-positive strain S. aureus ATCC25923 showed that boron containing brushite cement exhibits antibacterial activity against both strains, causing a decrease in the number of CFU after 3 h of incubation. In vitro studies of the developed B-BC were carried out, it was shown that the developed cements based on TCP and B-TCP are biocompatible and promising for use in bone tissue surgery.

Hydroxyapatite (HA) Ca 10 (PO 4 ) 6 (OH) 2 powders kept for 1 h with stirring in 0.25 M aqueous solutions of dihydrogen phosphates of ammonium NH 4 H 2 PO 4 , sodium NaH 2 PO 4 , and potassium KH 2 PO 4 were used to obtain ceramics. According to XRD data, there were no changes in the phase compositions of powders after such treatment. After firing at 900 – 1100°C the phase composition of ceramics based on HA Ca 10 (PO 4 ) 6 (OH) 2 powder treated with an aqueous solution of NH 4 H 2 PO 4 included β-tricalcium phosphate β-Ca 3 (PO 4 ) 2 and HA Ca 10 (PO 4 ) 6 (OH) 2 ; the phase composition of ceramics based on HA powder Ca 10 (PO 4 ) 6 (OH) 2 treated with an aqueous solution of NaH 2 PO 4 included sodium-substituted tricalcium phosphate Ca 10 Na(PO 4 ) 7 and HA Ca 10 (PO 4 ) 6 (OH) 2 ; the phase composition of ceramics based on HA powder Ca 10 (PO 4 ) 6 (OH) 2 treated with an aqueous solution of KH 2 PO 4 included potassium-substituted tricalcium phosphate Ca 10 K(PO 4 ) 7 and HA Ca 10 (PO 4 ) 6 (OH) 2 . The formation of biphasic ceramics occurred because of reduction in the Ca/P molar ratio of HA Ca 10 (PO 4 ) 6 (OH) 2 powder after treatment in aqueous solutions of dihydrogen phosphates of ammonium NH 4 H 2 PO 4 , sodium NaH 2 PO 4 , and potassium KH 2 PO 4 . Adsorption of cations and anions from solutions on the surface of HA particles, slight dissolution of HA in aqueous solutions of dihydrogen phosphates with acidic pH, as well as ion exchange of cations and anions in the HA structure for cations and anions from solutions were possible processes effecting change in the ratio of cations and anions in HA powder. The resulting ceramic composites contain biocompatible phases and can be recommended for creating bone implants.

Ceramics with post-firing (600 – 900°C) phase composition represented by calcium sulfate anhydrite CaSO 4 and sodium calcium sulfates (Na 0.8 Ca 0.1 ) 2 SO 4 and Na 6 Ca(SO 4 ) 4 was obtained from a powder mixture of sodium sulfate Na 2 SO 4 and calcium sulfate dihydrate CaSO 4 ∙ 2H 2 O with molar ratio CaSO 4 ∙ 2H 2 O/Na 2 SO 4 = 1. The phase composition of the powder mixture after homogenization (in acetone) in a planetary mill included, in addition to the initial salts, hydrated sodium calcium sulfate Na 4 Ca(SO 4 ) 3 ∙ 2H 2 O. On soaking in water for 5 and 60 min the weight loss of the ceramic sample fired at 700°C was equal to 15 and 75%, respectively. Na 2 O–CaO–SO 3 ceramics in the form of granules or complex structures obtained by means of 3D printing can be used as a removable (soluble or leachable) porogen and (or) a prototype of a porous space with specified architecture to obtain porous polymeric or inorganic materials.

The powder of hydrated calcium pyrophosphate Ca2P2O7 ⋅ xH2O containing potassium chloride KCl as a by-product was synthesized at room temperature from 0.5 M aqueous solutions of calcium chloride CaCl2 and potassium pyrophosphate K4P2O7 at a ratio of Ca/P = 1. The particle size of the powder with a shape close to isometric was 100–200 nm after synthesis and 0.5–1.0 μm after heat treatment at 700°C. Upon heating, KCl was retained in the powder up to 600°C, participating in the formation of new phases: potassium/calcium double pyrophosphate K2CaP2O7 and chlorapatite Ca3(PO4)3Cl in the range of 500–700°C and then K-substituted tricalcium phosphate Ca10K(PO4)7 at 800°C. The hydrated calcium pyrophosphate powder containing KCl as a by-product can be recommended for the manufacture of biocompatible multiphase ceramic materials, and the powder after heat treatment at 800°C can be used to obtain biocompatible materials using chemical bonding reactions.

Interstitial fibrous-matted micron-scale aggregates of few-layered graphene nano-flakes, multi-layered carbon nanotubes, fullerenes, and fullerenoids have been found between quartz and potassium feldspar grains of slag-like high temperature and shock-metamorphosed rocks (polymictous sandstones) of the Dzharakuduk area (Kyzyl-Kum Desert, Uzbekistan). This is the first finding of few-layered graphene nano-flakes as well as multi-layered carbon nanotubes (with ~10 Å inner diameters) and their assemblages as mineral component of natural rocks. Amount of layers in natural few-layered graphene nano-flakes varied from 19 to 45. Mechanisms of few-layered graphene nano-flakes generation in natural rocks are discussed.

Abstract—A new method for obtaining the nanoscale hydroxyapatite with low crystallinity from aqueous solution of calcium malate Ca(C4H5O5)2 and ammonium hydrophosphate (NH4)2HPO4 at room temperature, molar ratio Ca/P = 1.67, and pH 9 was proposed. After synthesis and drying, the sample was a transparent composite with a matrix from the by-product of the reaction of organic nature containing nanoscale particles of calcium phosphate. The phase composition of the sample after thermal treatment at 900°C was represented by calcium hydroxyapatite.

Powder mixtures prepared by mechanical activation from synthetic hydrated acidic calcium phosphates Ca(H2PO4)2 · H2O and CaHPO4 · 2H2O were used to obtain resorbable ceramic in the system Ca (PO3)2–Ca2P2O7. The phase composition of the ceramic after firing in the interval 700 – 1000°C was represented by biocompatible and bioresorbable phases: calcium polyphosphate Ca(PO3)2, tromelite Ca4P6O19, and calcium pyrophosphate Ca2P2O7. The obtained materials can be used to fabricate resorbable implants for regenerative treatment of defects of bone tissue.

Interstitial fibrous nanoscale aggregates of multilayered carbon nanotubes, fullerenes, and fullerenoids were found in quartz and potassium feldspar grains of slag-like rocks (metamorphosed polymictic sandstones) of the Dzharakuduk area (Kyzylkum Desert, Uzbekistan). This is the first find of carbon nanotubes ~10 Å in diameter and their assemblages in natural rocks. Based on high-resolution transmitting and scanning electron microscopy, Raman spectroscopy and MS DTA, it is shown that carbon fullerenes are from 1–2 to 30–50 nm in diameter and carbon nanotubes are distinct in diameter (1–3 to 40–60 nm), length (7–10 to few hundreds of nanometers), and the amount of layers (2–3 to 40). Owing to electron transparency of carbon nanominerals and their magnification in one million times, we revealed morphological features of their zonal-sectorial structure and cut evolution.

X-ray amorphous powder was synthesized from a water solution of calcium acetate and a mixed-anionic \( \left({\mathrm{HPO}}_4^{2-}/{\mathrm{CO}}_3^{2-}\right) \) water solution, including ammonium hydrophosphate and ammonium carbonate, at room temperature without pH regulation. The powders synthesized from the mixed-anionic \( \left({\mathrm{HPO}}_4^{2-}/{\mathrm{CO}}_3^{2-}\right) \) solution can be recommended for fabricating composite materials with a polymer matrix or for obtaining ceramic containing tricalcium phosphate and calcite phases with firing temperature not exceeding 600°C.

A direct correlation was shown for the first time between mosaic irisation patterns in synthetic and natural precious opals (from Australia, Ethiopia, Honduras, Slovakia, and Russia) and their frustumational (lump or mosaic–cluster) inner structure by means of photoluminescence, X-ray phase analysis, IR and Raman spectroscopy, and scanning electron microscopy.

Chemical modification of the surface of basalt glass fiber has been considered, including diffusion-mode oxidation without formation of new crystalline phases and ion-exchange lithium enrichment. The effect of such a modification on the appearance of new surface formations during the hardening of composites that consist of the modified fiber and model nonorganing binding materials (mixtures of Ca3SiO5 and Ca3Al2O6 with water) has been analyzed. It has been shown that both ion-exchange lithium enrichment and diffusion-mode oxidation change the composition and the morphology of hydrosilicate and hydroaluminate particles that are formed on the surface from “individual hydraulically active phase–water” mixtures. They have also been shown to change the morphology of the very fiber that is in contact with the liquid phase of the binding material.

Ceramic based on calcium phosphates is obtained from powders synthesized from water solutions of calcium nitrate, ammonium hydrophosphate, and ammonium pyrophosphate as well as from a mixed-anionic solution containing simultaneously ammonium pyro- and orthophosphate in the molar ratio (NH4)2HPO4/(NH4)4P2O7 = 1. The ceramic obtained contains biocompatible bioresorbable phases and can be used to make implants used in regenerative methods for the treatment of bone tissue defects. This represents the first time synthesis from mixed-anionic solutions is used to obtain powders of calcium phosphates with significant quantities of each anion.

Powder mixtures are considered containing ammonium hydrophosphate and calcium carbonate intended for preparing biocompatible porous ceramic in the CaO–P2O5 system. Pore formation on heating in workpieces based on the powder mixtures in question occurs due to occurrence of gas liberation in the presence of melt in the NH3–H2O–CO2–CaO–P2O5 or CO2–CaO–P2O5 systems. Gas phase formation is due to liberation of gaseous water and ammonia, thermal hydrolysis of calcium polyphosphate, decomposition of calcium carbonate, and oxidation of carbonized organic compounds remaining within a powder mixture in the form of associated calcium carbonate synthesis reaction product.