The continuous hexagonal boron nitride (h-BN) coating with the ~100-350 nm thickness was produced from the aqueous solutions of the lithium and sodium borates. The saturated solution was applied on the silicon support by the spin coating, dried under the normal conditions and treated in the ammonia atmosphere under 1300 °C. Such method is a promising way for the fabrication of protection coating. For example, for the protection of the carbon products from an oxidation under high temperature atmosphere.

Continuous nanocrystalline coatings of hexagonal boron nitride ( h -BN) with a thickness of ~1000‒350 nm are prepared from highly concentrated aqueous solutions of lithium and sodium borates, which display good film-forming properties. The borate solutions were applied on silicon substrates by spin coating followed by drying in air and treatment in ammonia at a temperature of 1300°C. This method is deemed promising for creating protective coatings (e.g., for protecting carbon products from oxidation at elevated temperatures).

In this work, the interaction of a mixture of Al and BN nanopowder with hydrogen microwave plasma was studied. Using X-ray diffraction analysis, scanning and transmission electron microscopy, the formation of AlN and AlB2 nanocrystals as a result of short-term (~ 30 ms) interaction of Al vapor with h-BN was established. Obtained results also indicate the formation of hydrogenated hexagonal boron nitride h-BN-H. The critical shear stresses were calculated for the interfaces between BN and Al, AlB2, and AlN. Approaches for increasing the strength of the composite materials based on hexagonal boron nitride and aluminum are discussed.

Phosphates of the new formula type A5/3MgE4/3(PO4)3 (A = K, Rb; E = Ti, Zr) with a langbeinite structure have been synthesized via the sol-gel method followed by heat treatment and studied using X-ray diffraction, IR spectroscopy, and electron microscopy methods.

The phosphate–sulfate synthesis approach preventing the elimination of sulfur in the process of synthesis has been tested for NaBa6Zr(PO4)5SO4 as an example. The phase formation and thermal stability of phosphate–sulfate have been studied by X-ray diffraction and DTA-TG. The NaBa6Zr(PO4)5SO4 structure (space group I$$\overline 4 $$3d, a = 10.5449(3) Å, V = 1172.54(5) Å3, Z = 4) allied to the eulytite mineral has been refined by the Rietveld method. The structure is formed by wavy chains of edge-sharing (Na,Ba,Zr)O6-octahedra and (P,S)O4-tetrahedra sharing apices with the octahedra. Using thermal X-ray diffraction, it has been established that phosphate–sulfate is a strongly expanding material (αа = αb = αc = 13.3 × 10–6°C–1).

The formation of phases and the structure of phosphates in the M0.5 + xM′xZr2 − x(PO4)3 systems (M = Co, Mn; M′ = Ni, Cu; 0 ≤x ≤ 2) were studied. The formation of complex phosphate phases synthesized by the sol-gel method was investigated by X-ray diffraction, electron microscopy, microprobe analysis, and IR spectroscopy. The formation of limited solid solution crystallizing in the Sc2(WO4)3 structural type was established in the studied systems. The regularities of changes in their crystallographic characteristics depending on the chemical composition were elucidated. The crystal structure of Mn1.2Ni0.7Zr1.3(PO4)3 was refined by the Rietveld method using powder X-ray diffraction data (space group P21/n, Z = 4, a = 8.8317(13) Å, b = 8.9350(11) Å, c = 12.4893(17) Å, β = 90.027(26)°, V = 985.55(23) Å3). The obtained data on the formation of M0.5 + xM′xZr2 − x(PO4)3 solid solutions (M = Co, Mn; M′ = Ni, Cu) broadened the phase formation picture for the known phosphates with octahedral-tetrahedral {[L2(PO4)3]p−}3∞ type frameworks and characterized the general trends in the size dependence of the structure of phosphates and the limits of solid solutions.

Compounds Mn0.5Ti2(PO4)3 and Mn0.5Zr2(PO4)3 and Mn0.5+2xZr2 – x(PO4)3 (0 < x ≤0.35) solid solution were prepared by two variants of the sol-gel method using inorganic and organic reagents and were characterized using X-ray diffraction and IR spectroscopy. Mn0.5Ti2(PO4)3, a compound with an NaZr2(PO4)3 (NZP) structure, is formed at 600°C and is stable up to 950°C. Mn0.5Zr2(PO4)3 has dimorphism; its low-temperature phase having the Sc2(WO4)3 (SW) structure was prepared at 650°C, and the high-temperature NZP phase, at 1200°C. Mn0.5 + 2xZr2−x(PO4)3 solid solution crystallizes in an SW-type structure; it is thermally unstable at temperatures above 900°C. The thermal stability of samples decays as x rises. p ]The numbers of the stretching and bending vibrations in an $${\rm{PO}}_4^{3 - }$$ ion in the IR spectra of NZP and SW ortho-phosphates agree with factor-group analysis for space group R3̅ and P21/n. Structure refinement was carried out for the low-temperature Mn0.5Zr2(PO4)3 phase (space group P21/n, a = 8.861(3) Å, b = 8.869(2) Å, c = 12.561(3) Å, β = 89.51(2)°) and for the solid solution. The basis of the structures is a framework built of corner-sharing tetrahedra PO4 and octahedra ZrO6 or (Mn,Zr)O6. The framework interstices are occupied by cations Mn2+ in tetrahedral oxygen coordination. A comparative crystal-chemical analysis of the morpho-tropic series of M0.5Zr2(PO4)3 phosphates (M stands for a metal in the oxidation state +2) elucidated a relationship between structural features.