BN/Ag hybrid nanomaterials (HNMs) and their possible applications as novel active catalysts and antibacterial agents are investigated. BN/Ag nanoparticle (NP) hybrids were fabricated using two methods: (i) chemical vapour deposition (CVD) of BN NPs in the presence of Ag vapours, and (ii) ultraviolet (UV) decomposition of AgNO3 in a suspension of BN NPs. The hybrid microstructures were studied by high-resolution transmission electron microscopy (HRTEM), high-angular dark field scanning TEM imaging paired with energy dispersion X-ray (EDX) mapping, X-ray photoelectron spectroscopy (XPS), and infrared spectroscopy (FTIR). They were also characterized in terms of thermal stability, Ag+ ion release, catalytic and antibacterial activities. The materials synthesized via UV decomposition of AgNO3 demonstrated a much better catalytic activity in comparison to those prepared using the CVD method. The best catalytic characteristics (100% methanol conversion at 350 °C) were achieved using the UV BN/Ag HNMs without preliminary annealing at 600 °C in an oxidizing atmosphere. Both types of the BN/Ag HNMs possess a profound antibacterial effect against Escherichia coli K-261 bacteria.

The influence of reinforcing AlN, AlB2 and BN phases, either individually or in combination, on the mechanical properties of Al-based composites fabricated via reactive ball milling of Al/BN, Al/B, and Al/Li3N powder mixtures, followed by their spark plasma sintering (SPS) was studied. An increase in tensile strength by 135% (25°C) and 185% (500°C) compared to pure Al was achieved in the Al/BN composites where BN, AlN, and AlB2 phases simultaneously formed. Density functional theory (DFT) calculations of the interface strength between Al and formed phases supported the experimental data. The obtained results demonstrated that the combination of reactive ball milling and SPS is a promising technique allowing for the formation of reinforcing phases from source materials.

BNNPs/Ag nanohybrids with an optimal amount of B2O3 demonstrated a higher catalytic activity.

Light (density <2.7g×cm−3) yet strong (tensile strength >350MPa) metal matrix composites (MMCs) are highly anticipated for aerospace and automotive industries. The MMCs application fields can be significantly expanded if they possess enhanced strength at elevated temperatures also. In the present study, Al-based composites loaded with either micro- or BN nanoparticles (BNMPs and BNNPs) with up to 10wt% of BN phase were produced via spark plasma sintering (SPS) of ball-milled Al-BN powder mixtures. A dramatic increase in the composite tensile strength compared to pure Al samples (up to 415%) was demonstrated during tensile tests both at 20°C and 500°C. BNMPs were found to be a more preferred additive compared with BNNPs due to the formation of more homogeneous and uniform morphologies within the ball-milled powder mixtures and resultant SPS products. The most impressive tensile strength of 170MPa at 500°C was achieved for an Al-7wt% BNMPs SPS composite, as compared to a value of only 33MPa for a pure Al SPS-produced sample. The reinforcement mechanism was uncovered based on detailed X-ray diffraction analysis, differential scanning calorimetry, Raman spectroscopy, scanning and high-resolution transmission electron microscopy and energy-dispersion X-ray analysis. Microscale BN, AlB2 and AlN inclusions acting within Al-matrices in the frame of Orowan strengthening mechanism, and pre-formed during ball-milling-induced pre-activation of Al-BN powder mixtures, finally crystallized during SPS processing and ensured the dramatically improved tensile strength and hardness of the resultant composites.

A rich variety of hollow and solid (without internal hollow spaces) spherical boron oxynitride nanoparticles (BNO-NPs) with smooth or petalled surfaces were synthesized during a boron oxide-assisted chemical vapour deposition (BOCVD) process. Diverse BNO-NPs were obtained while utilizing different precursors, gas flow rates and synthesis temperatures in the range of 1200–1430 °C. The BNO-NP morphologies, atomic structures and spatially-resolved chemical compositions were studied by scanning (SEM) and transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray, Fourier-transform infrared and confocal Raman spectroscopy. Particle size distributions were measured using dynamic light scattering under visual microscopic control. A growth model of different spherical BNO-NP types based on the detailed analysis of physical–chemical processes at different BOCVD stages was proposed. A new type of spherical BNO-NPs of “hedgehog” morphologies with BN nanowires on their surfaces was first predicted in accordance with the designed model and then experimentally verified.

High-purity straight and discrete multiwalled boron nitride nanotubes (BNNTs) were grown via a boron oxide vapor reaction with ammonia using LiNO3 as a promoter. Only a trace amount of boron oxide was detected as an impurity in the BNNTs by energy-dispersive X-ray (EDX) and Raman spectroscopies. Boron oxide vapor was generated from a mixture of B, FeO, and MgO powders heated to 1,150 °C, and it was transported to the reaction zone by flowing ammonia. Lithium nitrate was applied to the upper side of a BN bar from a water solution. The bar was placed along a temperature gradient zone in a horizontal tubular furnace. BNNTs with average diameters of 30–50 nm were mostly observed in a temperature range of 1,280–1,320 °C. At higher temperatures, curled polycrystalline BN fibers appeared. Above 1,320 °C, the number of BNNTs drastically decreased, whereas the quantity and diameter of the fibers increased. The mechanism of BNNT and fiber growth is proposed and discussed.

Reactions of borates of alkali and alkaline earth metals with ammonia in a temperature range of 950–1250 °C are explored with respect to the nano-boron nitride syntheses. M2O(MO)·nB2O3 borates, where M2 = Li, Na, K, and M = Mg, Ca, Sr, Ba are studied for a molar ratio n = 0.5–5.0. It is found that various boron nitride (BN) nanostructures such as BN-nanotubes (BNNTs), graphene-like BN petals (BNGPs), and columnar porous BN (BNP) flakes grow depending on the borate composition and synthesis temperature. Both morphology and yield of BN-nanostructures depend on the basicity of the metal oxide and its fraction in the precursor borate. Borates of Li, Mg, and Ca demonstrate the highest ability to produce BNNTs. Borates of Na and K produce BNGPs in the whole range of investigated n values and temperatures. BNP flakes with pores of 10–100 nm are formed from Mg-borates with n > 3.

Boron nitride nanostructures (nanotubes, graphene-like petals, and columnar porous flakes) grew in reactions of alkali and alkaline earth borates with ammonia.

Fabrication of high strength yet light and low cost composite materials with good mechanical properties at room and elevated temperatures is a challenge that metallurgy and materials science communities are facing for many years, and no "dream material" has been developed so far. The primary goal of this study was to fabricate, characterize, and to carry out tensile tests on Al-based composite materials strengthened with commercially-available BN nanoparticles (BNNPs). The composites were fabricated by spark plasma sintering (SPS) technique. The structures of powder mixtures and composite materials, as well as their fracture surfaces, were studied by scanning and transmission electron microscopy. The influence of BNNPs content (0.5, 1.5, 3, 4.5, 6, and 7.5 wt%) and holding times (5, 60, and 300 min) at 600 °C during SPS on the tensile strength was investigated. A maximum increase in strength was observed for Al-based composites with 4.5 wt% of BNNPs. The sample demonstrated a 50% increase in tensile strength compared with pristine Al. Although the tensile tests performed at 300 °C revealed that the tensile strength became 20% lower than the strength at room temperature, it was, however, still 75% higher compared with that of the pure Al at 300 °C. In addition, at 300 °C the Al–BNNPs composites demonstrated a much higher value of yield stress, about 115 MPa, which is 190% higher than that of pure Al at the same temperature. The damping properties of Al–BNNPs composites were evaluated by temperature dependent internal friction (TDIF) measurements. The obtained results are discussed based on structural analysis and the TDIF data.