Boron carbide is known as a hard material; it possesses a unique complex of physical-mechanical properties and has diverse applications in industries. An expansion of its field of uses stems from the creation of boron carbide matrix nanocomposite materials. In view of this perspective, an effective liquid-charge synthesizing method for their components in nanopowder form has been proposed. This paper provides a focused review on advanced boron carbide matrix ceramic and metal-ceramic nanocomposites recently obtained by the authors using this method. Particular attention is paid to the characterization of boron carbide nanocomposites, including some ceramic borides, metallic alloys and also other metal-ceramic composites.

The results of the study of the production technology, phase composition, structure and physico-mechanical properties of metal-ceramic materials based on boron carbide and their components are presented. Boron carbide was obtained by direct synthesis from chemical elements using amorphous boron and carbon black. By mechanical dispersion, solid reagents were converted into an ultrafine state. Using a chemical method, nanoscale (70–80 nm) boron carbide was synthesised from suspension solutions of amorphous boron and liquid hydrocarbons. Boron carbide-based metal-ceramic composite powder B₄C–(Co–Ni–Ti) was obtained by mechanical dispersion of the constituent components. Based on results of studying of the temperature-dependence of wetting angle of boron carbide with Co–Ni–Ti metallic alloy, the compacting modes of metal-ceramic composite powders by plasma-spark sintering and hot pressing have been developed. The influence of the component content of the binder metal (alloy) on some physico-mechanical properties (linear expansion coefficient, hardness, and bending strength) of hardmetal-ceramic materials based on boron carbide was studied. It was found that the optimum content of the metal component in the composite is ∼ 25 wt-%. In the temperature range 300–600°C, the materials obtained are characterised by stable dimensional factors, since in this temperature range the thermal conductivity coefficient does not depend much on temperature. At room temperature, their bending strength is about 1 GPa. A new method of chemical synthesis of nanocrystalline ceramic compositions of boron carbide and titanium diboride using suspension solutions for the preparation of powders and their spark plasma sintering was also developed to obtain a compacted material of composition B₄C+30 wt-%TiB₂, which has a high hardness of 95 HRA (with maximum microhardness 45.6 GPa) and sufficient strength (with a bending strength of 834 MPa).

In the presented work, B₄C was irradiated with xenon swift heavy ions at the energy of 167 MeV. The irradiation of the substrate was done at room temperature to a fluence of 3.83 × 10¹⁴ ion/cm². The samples were then analyzed with the X-ray diffraction technique to study the structural modification, as it can probe the region of penetration of xenon atoms due to the low atomic number of the two elements involved in the material under study. The nano-cluster formation under ion irradiation was observed. Positron lifetime (PLT) calculations of the secondary point defects forming nanoclusters and introduced into the B₄C substrate by hydrogen and helium implantation were also carried out with the Multigrid instead of the K-spAce (MIKA) simulation package. The X-ray diffraction results confirmed that the sample was B₄C and it had a rhombohedral crystal structure. The X-ray diffraction indicated an increase in the lattice parameter due to the Swift heavy ion (SHI) irradiation. In B₁₂-CCC, the difference between τ with the saturation of H or He in the defect is nearly 20 ps. Under the same conditions with B₁₁C-CBC, there is approximately twice the value for the same deviation.

In the recently introduced phenomenological diatomic molecular model imagining the clusters as certain constructions of pair interatomic chemical bonds, there are estimated specific (per atom) binding energies of small all-boron planar clusters B_n, n = 1–15, in neutral single-anionic and single-cationic charge states. The theoretically obtained hierarchy of their relative stability/formation probability correlates not only with results of previous calculations, but also with available experimental mass-spectra of boron planar clusters generated in process of evaporation/ablation of boron-rich materials. Some overestimation in binding energies that are characteristic of the diatomic approach could be related to differences in approximations made during previous calculations, as well as measurement errors of these energies. According to the diatomic molecular model, equilibrium binding energies per B atom and B–B bond lengths are expected within ranges 0.37–6.26 eV and 1.58–1.65 Å, respectively.

The very high capture cross-section of (epi)thermal neutrons by the boron isotope ¹⁰B makes elemental boron and its compounds and composites prospective for serving as materials intensively interacting with neutron irradiation. In their nanostructured form, boron-rich materials reveal properties that improve their radiation-performance characteristics. In this regard, new technologies have been proposed for the synthesis of nanocomposites with matrices of boron carbide B₄C and hexagonal boron nitride h-BN. For the first time, boron carbide-tungsten and hexagonal boron nitride–(iron,magnetite) composites were obtained, respectively, in the form of layered/sandwich structures of components B₄C and W and h-BN nanopowders coated/intercalated with magnetic nanoclusters of iron Fe or magnetite Fe₃O₄. Studying of their chemical/phase composition, structure/morphology, and some other properties leads to the conclusion that the developed B₄C–W and h-BN–(Fe,Fe₃O₄) composites would be useful for solving important problems of boron-based neutron shielding and BNCT (Boron Neutron Capture Therapy), such as attenuating the gamma-radiation accompanying the absorption of neutrons by ¹⁰B nuclei and targeted delivery of ¹⁰B nuclei, as BNCT therapeutic agents, to tumor tissues using control by an external magnetic field, respectively.

The quasi-classical method for estimating the structural and energy parameters of crystals is justified. In the initial approximation, the charge-density and potential distributions are represented by step functions. As a result, the energy of the ground state of the crystal and the matrix elements of the secular equation determining its electronic structure can be expressed through finite sums. This approach makes it possible to avoid uncontrollable errors introduced in the truncation of infinite series, and the error of the approach itself does not exceed a few percent. The lattice constant a=2.64 Å and the band gap E _g =6.22 eV for two-dimensional boron nitride are determined by the quasi-classical method.