Potassium niobate (KNbO3) is one of the most promising materials for the photocatalytic purification of water from pollutants. This is because the positions of the valence and conduction bands in KNbO3 are favorable for simultaneous redox half-reactions involving water and dissolved oxygen. Additionally, the ferroelectric properties of KNbO3 facilitate the separation of photogenerated charges under mechanical lattice stress, thereby increasing the quantum yield of photoreactions. The photocatalytic activity of materials depends on specific surface area and lattice microstrains, and optimizing these parameters can enhance the rate of photocatalytic reactions. In this study, for the first time, the influence of these parameters on the photocatalytic activity of KNbO3 was examined by varying the ball milling time. With increasing processing time, the specific surface area and lattice microstrains of KNbO3 continuously increased; however, an optimal process duration existed at which a balance between these parameters was achieved, ensuring the maximum photocatalytic response of KNbO3 under UV irradiation. After 60 min of ball milling, the specific surface area of KNbO3 increased 4.8-fold (from 0.82 to 3.93 m2 center dot g-1) and the lattice microstrains increased from 0.13% to 0.38%, leading to a 30% increase in photocatalytic activity in the decomposition of rhodamine B (RhB) (from 11.99 to 15.61 mg center dot g- 1 center dot h-1). When the milling time was increased to 80 min, the specific surface area increased to 6.35 m2 center dot g-1, and lattice microstrains reached 0.44%, but the photocatalytic activity decreased to 13.56 mg center dot g- 1 center dot h-1. These results imply that KNbO3 lattice microstrains have a major influence on the photocatalytic response.

High- and medium-entropy alloys (HEAs/MEAs) are promising reinforcement phases for lightweight composites due to their exceptional strength and thermal stability. Using molecular dynamics simulations with a machine learning interatomic potential, we screened 42 equiatomic Al–Cr–Fe–Co–Ni–Cu alloys, identifying CrFeCoNiCu as a top candidate for aluminum matrix composites. Surface energy calculations and Wulff construction predicted a rhombicuboctahedron inclusion morphology dominated by (111) and (110) facets. Atomistic compression testing revealed that the Al-10wt

This work proposes a new strategy for producing aluminum matrix composites with strong interfaces by forming additional reinforcing particles in situ through an aluminothermic reaction between the system components. Solgel synthesized high-entropy spinel-type (Cr0.23Mn0.22Fe0.22Co0.19Ni0.13)3O4 oxides (HEO) were added to Al nanopowder and the resulting mixture was subjected to high-energy ball milling (HEBM) and then spark plasma sintering (SPS). As a result of the aluminothermic reaction during SPS, HEO are partially reduced, providing excess oxygen for the formation of reinforcing Al2O3 nanoparticles, and the reduced metals react with Al with the formation of various intermetallic compounds (Al9Me2, Al5Me2, and Al2Me), which, in addition to HEO, serve as secondary strengthening phases. A new hexagonal AlMex phase with lattice parameters of approximately a = c = 1.76 nm has been well documented. HEBM has been shown to be an important step not only for uniform HEO distribution, but also for the aluminothermic reaction to occur at a relatively low temperature by improving the interaction between activated Al and HEO nanopowders. The maximum increase in hardness with the addition of HEO is 198 %, tensile strength 90 % (25 degrees C) and 97 % (500 degrees C), and compressive strength 220 % (25 degrees C) and 250 % (500 degrees C). Excellent mechanical properties are achieved at 500 degrees C: the ultimate tensile and compressive strength are 258 MPa and 410 MPa, respectively. The introduction of HEO also leads to a significant reduction in the coefficient of friction (from 0.7 (0 %) to 0.2 (3 %HEO)) and a noticeable reduction in dynamic wear (5.9-6.3 (3 % HEO) and 10.6-14.3 (5 %HEO) times depending on applied load). Thus, our research opens up exciting new possibilities for creating lightweight and high strength composites for use in the mid-temperature range.

Using high-energy ball milling of metallic powders and Al2O3 nanopowder followed by spark plasma sintering, CrFeCoNiCu-x%Al2O3 (x = 0.1, 0.5, 1 and 3 wt%) composites with a thermally-stable hierarchical microstructure were prepared, in which micrometer-sized regions consisting of FCC1 (high-entropy alloy (HEA), a = 0.35 nm) and FCC2 (Cu-based oxide, a = 0.51 nm) nanograins and reinforcing Al2O3 nanoparticles are surrounded by Cu-rich layers (FCC3). The introduction of Al2O3 nanoparticles into CrFeCoNiCu HEA significantly altered the microstructure and improved its chemical, mechanical, and tribological properties. Doping with Al2O3 nano-particles resulted in: (i) an increase in the dispersion of structural components, (ii) an increase in the volume fraction of the Cu-rich phase, (iii) a significant decrease in the oxygen content in the Cu-rich phase, and (iv) a high dislocation density and an increase in the local stresses level. Al2O3 NPs located at grain boundaries hinder oxygen diffusion, which leads to the rapid formation of a dense Cr2O3 oxide layer during oxidation and a decrease in the oxide scale thickness. The addition of 1 wt% Al2O3 resulted in an increase in hardness by 27.5 %, compressive strength by approximately 29 % (both at 25 degrees C and at 750 degrees C), crack resistance and dynamic impact resistance by 64.3 (500 N) and 40.4 % (700 N), wear resistance by 6.2 (25 degrees C) and 3.4 (500 degrees C) times, and a 2fold decrease in the oxidation rate at 750 degrees C. After annealing at 750 degrees C, which resulted in complete relaxation of internal stresses, the composites exhibited fully plastic behavior under compression at 750 degrees C. The HEA-1 % Al2O3 composite achieved UCS25 degrees = 2197 MPa (annealed) and UCS750 degrees = 1328 MPa (not annealed).

A new original strategy for producing composite materials based on a high-entropy alloy (HEA) reinforced with oxide and boride nanoparticles (NPs) is proposed. For this purpose, amorphous boron was introduced into the CrFeCoNiCu powder mixture in amounts of x = 0.1, 0.5, 1, and 3 wt%, and the oxygen source was oxygen contained in the initial metal powder. For the first time, the important role of zirconia in phase formation, which enters the system during long-term high-energy ball milling (HEBM) using ZrO2 balls, has been revealed. CrFeCoNiCu (HEA) and CrFeCoNiCu-xB (HEA-xB) composites were prepared by HEBM and spark plasma sintering. The resulting HEA-xB materials have a hierarchical microstructure in which Cu-based interlayers (FCC3 phase) surround regions with a fine-grained (30-250 nm) microstructure consisting of two fcc phases, HEA (FCC1) and (Cu,Zr)Ox (FCC2), and a Cr3Cu phase. In addition, reinforcing borides M23B6 and fine oxides ZrO2, 10-25 nm in size, that have not reacted with Cu are present. For the first time in the CrFeCoNiCu HEA the formation of a cubic fluorite (Cu,Zr)Ox phase with a lattice parameter a = 0.48-0.51 nm is observed as a result of the interaction of Cu with ZrO2 and their stabilization in the cubic phase. The maximum ultimate compressive strength (UCS) of the HEA-0.5 %B composite is 1847 (25 degrees C) and 1206 MPa (750 degrees C). The important role of hightemperature annealing at 750 degrees C, which leads to significant changes in the microstructure and properties, is shown. After annealing, all samples showed an increase in UCS at 25 degrees C to a maximum value of 2079 MPa for the HEA-0.5 %B HEA and demonstrated high plastic deformation without failure up to a maximum applied load of 20 kN at 750 degrees C. The yield tensile strength at 25 degrees C (YTS25) of the B-free HEA sample after annealing increased from 500 to 700 MPa, and the HEA-B materials showed YTS25 values in the range of 500-580 MPa. The B addition in an amount of 0.1 and 0.5 wt% leads to a significant increase in impact wear resistance. In addition, the abrasive wear resistance of the HEA-1 %B and HEA-3 %B composites is an order of magnitude higher than that of the B-free counterpart. This opens up new possibilities for the creation of cost-effective and easily scalable technologies for producing HEA-based composites reinforced with dispersed oxides and borides.

Advanced hydrogen storage systems are needed to develop the next generation of portable batteries and vehicles. In this work, effect of oxygen and carbon vacancies in oxygen- and carbon-substituted hexagonal boron nitride (h-BN) nanocrystallites on hydrogen adsorption (H-ad) is investigated for the first time. For this purpose, BNOC nanomaterials containing 8-13 at% O and 3-6 at% C were synthesized from melamine-boric acid precursors in an ammonia-hydrogen atmosphere at moderate temperatures. The hydrogen-binding properties of h-BN-based nanomaterials strongly depend on the type of defects and the dopant present; therefore, hydrogen was used in the synthesis as an activator, creating active centers by removing oxygen and carbon. The resulting BNOC nanomaterials are characterized by low crystallinity, with crystallite sizes less than 2 nm. The best sample with a specific surface area of 1405.1 m(2)xg(-1), a specific pore volume of 0.779 cm(3)xg(-1), and a micropore volume of 0.517 cm(3)xg(-1) showed H-ad capacity of 5.2 wt% at T = 77.35 K and a pressure of 100 kPa. The pressed BNOC nanomaterials also exhibited decent volumetric H-2 uptake in the range of 16.7-18.7 g x L-1 for pellet densities in the range of 0.59-0.74 g x cm(-3). Density functional theory (DFT) calculations showed that H-ad up to 2.3 wt% at T = 77 K is only possible on pure BN, "armchair" carbon defects, and oxygen defects. H-ad up to 4.0 wt% is achievable on "zigzag" carbon defects at T < 70 K; above this temperature, hydrogen desorption occurs. H-ad from similar to 3 to 5.3 wt% at T = 77 K is thermodynamically favorable only for oxygen defects, above 5.3 wt%, the adsorption energy becomes positive, indicating the limit of hydrogen sorption. X-ray photoelectron spectroscopy (XPS) analysis suggests that the superior H-2 uptake of BNOC nanomaterials may be due to the hydrogen treatment-induced formation of active sites, such as oxygen and carbon vacancies. The obtained results not only demonstrate the promise of BNOC nanomaterials for hydrogen storage but also show the possibility of controlling structural defects to increase hydrogen uptake. Creating active sites through restructuring different types of vacancies may be a new strategy to improving hydrogen uptake.

The mechanical properties of spark plasma sintered Ni, such as hardness, tensile strength, compression resistance at 25 and 750 degrees C while maintaining good ductility and dynamic impact wear resistance were greatly improved by applying high-energy ball milling and introducing a small amount of amorphous boron as a reactive additive. An excellent combination of properties has been achieved by forming a submicron microstructure and nanocrystalline h-BN reinforcing layers.

A modern urgent task is to increase the upper limit of peak and operating temperatures of Al-based composites above 400 degrees C, which, due to the combination of low weight and high strength, are in demand in various power units and elements of load-bearing structures. To address this important problem, Al-based composites reinforced with 1, 3, 5, and 10 wt% of submicron Al2O3 particles were spark plasma sintered (SPS) using Al/Al2O3 composite microparticles obtained in microwave argon-plasma. When a mixture of submicron Al and Al2O3 particles is fed into the plasma reactor, the native oxide film on the Al surface is destroyed, Al melts, melt drops merge, and Al2O3 particles, the surface of which is cleaned of contamination by Ar+ ions, are captured by the melt, forming heterogeneous Al/Al2O3 microparticles with a strong Al/Al2O3 interface, which then become structural elements of SPS composites. The introduction of Al2O3 leads to a significant improvement in chemical, mechanical and tribological properties. With the addition of 10 wt% of Al2O3, hardness increases by 90% and ultimate compressive strength (UCS) by 143% (25 degrees C) and 111% (500 degrees C) while maintaining a high strain to failure of approximately 21.5%. Compared to the Al-Al2O3 composite sintered from the non-plasma treated powder, the UCS increases by 16% (25 degrees C) and 33% (500 degrees C). The Al-10%Al2O3 material shows significantly improved tribological characteristics due to the formation of an oxide-based tribofilm, which prevents intensive Al adhesion to the counterbody. In addition, due to the high density of Al2O3 particles, impact wear resistance increases by 2-3 times, the corrosion potential in a chloride-containing medium positively shifts by 110 mV, and the corrosion current density decreases by a factor of three. Achieving a UCS of 423 MPa at 500 degrees C while improving chemical and tribological properties can expand the high-temperature application of Al-based composites.

For the first time, the formation of Al@Al2O3 core-shell nanowires with a width of 50-160 nm and a length of 0.1-1.1 mu m was observed on the surface of oxidized Al particles when heated to 900 and 1000 degrees C. The nanowires were characterized by SEM-EDS, X-ray diffraction, XPS, and TEM. In addition, temperature-activated nanowire growth was monitored in-situ using TEM. Based on experimental observations and molecular dynamics simulations, an Al@Al2O3 core-shell nanowire formation model controlled by the pressure-assisted diffusion of Al2O intermediates was proposed. The modeling indicated the potential formation of Al2O suboxide molecules at the internal interface between Al2O3 shell and the Al melt at a temperature of 900 degrees C, followed by their diffusion through the nanopores of the oxide shell to the surface. There they underwent disproportionation into Al and Al2O3, which ultimately led to the formation of nanowires. The directed nanostructure growth from the surface is elucidated by the pressure gradient between the excess pressure inside the Al2O3/Al particles and the ambient pressure. The obtained results can be used in the creation of micro- and nanoelectronics products, for the manufacture of sensors and catalysts, as well as for the synthesis of Al-based composites reinforced with nanostructures.

Melanoma is the most aggressive form of skin tumor and leads to a high mortality (5.0-5.6 %) among all cancers. To increase efficiency of its treatment during local photodynamic therapy (PDT), we developed h-BN/n & sdot;MB heterostructures based on hexagonal boron nitride (h-BN) nanoparticles (NPs) and adsorbed methylene blue (MB) of various concentrations (n). Heterostructures containing 200 mg of MB per 1 g of h-BN (h-BN/200 MB), after their irradiation with an artificial sunlight source for 30 min, generated 3.7 x102 +/- 0.2 x103 mu M x mu g1 of reactive oxygen species (ROS) and reduced the viability of A-375 melanoma cells by 90 % after 48 h. The observed levels of oxidative and antitumor activity of the h-BN/200 MB hybrid material significantly exceed those of the individual system components, MB and h-BN. It is shown that MB adsorbed on h-BN NPs possesses enhanced stability and photooxidative activity. Adsorbed MB has almost not the dark phototoxicity inherent in the MB solution and demonstrates enhanced biocompatibility with normal fibroblasts Wi-38. The results demonstrate the promising potential of h-BN/n-MB heterostructures for melanoma PDT.

The development of hydrogen energy is capable of solving a number of important issues that modern society is facing, including global warming and various environmental impacts. Currently, there is an intensive search for natural sources of hydrogen as well as low-carbon techniques for mass production of hydrogen from natural gas, associated petroleum gas, and water. In parallel, efforts to develop technologies for the subsequent management of hydrogen are underway, and the creation of its safe and efficient storage is one of the highest priority goals. For the transportation and storage of hydrogen today, a number of solutions are offered, each of which has both positive and negative aspects. The boron nitride family of materials with high thermal and chemical stability, variability of morphologies, and flexibility of structure has been considered as a candidate for efficient hydrogen storage. This review offers to familiarize readers with the progress in the research and application of hexagonal boron nitride (h-BN), as well as BN-based materials in comparison with other materials, as promising hydrogen storage. Experimental and theoretical data obtained for different morphologies and internal structures were reviewed in relevance to the material`s sorption capacity with respect to hydrogen. Various approaches to improve the efficiency of hydrogen storage were analyzed, and the highest storage capabilities published were mentioned. Thus, BN-based materials are very promising as hydrogen storage, even for an automotive application, but the development of new mass production technologies should be carried out.

Fe 1 /h-BN single atom catalysts can be successfully synthesized using heat treatment of Fe phthalocyanine decorated h-BN in an oxygen atmosphere. Selectivity toward hydrocarbons can be controlled by the presence of Fe nanoparticles.

Achieving a combination of high strength and ductility in metal-based composites is still a difficult task, and it is especially challenging in a wide temperature range. Here, nanoAl2O3/nanoAl composites with high tensile and compressive strength and excellent ductility at 25 and 500 °C were obtained using Al and Al2O3 nanopowders via a combination of high-energy ball milling (HEBM) and spark plasma sintering (SPS). Being about three times lighter than conventional high-strength steel (with a density of 2.7 g/cm3 vs. that of 7.8 g/cm3 for steel), the nanoAl2O3/nanoAl materials demonstrated tensile strength and elongation before failure comparable with those of steel. The nanoAl2O3/nanoAl composites were strengthened with two types of Al2O3 NPs, in situ formed, and introduced into the powder mixture. The resulting materials had a bimodal microstructure consisting of Al with micron and submicron grains surrounded by an Al/Al2O3 framework whose structural components were all in the size range of 20–50 nm. Among the studied compositions (0, 1, 2, 3, 4, 5, 10, and 20 wt.% of Al2O3), the Al-3%Al2O3 material showed the best thermomechanical properties, such as a tensile strength of 512 MPa and 280 MPa and a compressive strength of 489 MPa and 344 MPa at 25 and 500 °C, respectively, with an elongation to failure of 15–18%. These results show the promise of nanoAl2O3/nanoAl composites for use as small items in the automotive and aviation industries.

The photocatalytic activity of MoS2-based heterostructures largely depends on the thickness and orientation of the MoS2 component. The choice of suitable and commercially available substrates for the growth of MoS2 nanosheets (NSs) with tunable morphology is an important step towards application of new photocatalysts. We report a new facile two-step carbothermal-reduction-assisted CVD synthesis protocol to produce horizontally and vertically aligned MoS2 NSs on activated carbon (AC) granules. MoO3/AC pellets were first prepared by sonicating MoO3 and AC powders and then used as a substrate and Mo source to obtain MoS2/AC composites. A feature of the process is that MoO3 particles, prior to interaction with sulfur, undergo carbothermal reduction with the formation of Mo suboxides favorable for MoS2 growth. The thickness and orientation of MoS2 NSs strongly depend on the synthesis temperature. At 600°C, horizontally oriented triangular MoS2 NSs are formed on the surface of molybdenum oxide particles, and at 700°C, thin vertically oriented MoS2 NSs with a high aspect ratio (20×5000 nm2) are grown. The high photocatalytic activity of MoS2/AC composites during the decompositions organic dyes under UV radiation is associated with the thickness and orientation of MoS2 NSs. The vertical arrangement of the active edges intensifies the chemical interaction with the reagents, and the small NS thickness prevents the recombination of charges and facilitates their transfer to the surface. The obtained results open up new possibilities for the development of cost-effective and scalable MoS2-based photocatalysts with tunable thickness and orientation of MoS2 NSs on commercially available AC substrates using a carbothermal-reduction-assisted CVD approach.

New simple and scalable method for the synthesis of nanocrystalline Pt-containing hexagonal boron oxynitride (Pt/BN(O)) is proposed. At a minimum content of 0.0085 wt%, Pt is present only in the form of single atoms (SAs) and clusters. This sample demonstrates CO oxidation activity with specific CO2 productivity as high as 176 molCO2/gPt/h at 300 degrees C. The sample retains high catalytic activity after four cycles.

Ni-x%BN composites (x = 0.001, 0.05, and 0.1 wt%) with enhanced tensile and bending strength, as well as high ductility were fabricated by a combination of ball milling and spark plasma sintering. Material with 0.05 wt% of hexagonal BN (h-BN) nanoflakes show an increase in tensile strength of 26% (25 degrees C) and 63% (750 degrees C) compared to additive-free Ni counterpart and high ductility. Doping with h-BN increases the resistance to plastic deformation at both room and high temperatures. The bending strength of Ni-0.05%BN composite at room temperature has been increased by 121%. Small addition of h-BN leads to a decrease in the Ni grain size, and solid solution and grain boundary strengthening.

Hexagonal boron nitride (h-BN) is a promising material for nanophotonics. Intrinsic and artificially induced defects in h-BN films, flakes, and nanoparticles are potential candidates as quantum emitters at room temperature. However, the energy structure and the methods for controlling these defects are still unclear. In this paper, we have obtained single-photon sources in ultrafine h-BN nanoparticles fabricated by a cost-effective ammonothermal dehydration. We demonstrate quantum-dot-like emission using photon autocorrelation and fluorescence intensity trace measurements in the red range. The results obtained using low-power near-ultraviolet coexcitation reveal the distinctive photophysical properties of fluorescent defects in the synthesized h-BN nanoparticles. We show that quantum emitters in nanoparticles can be switched from dark to bright mode by coexcitation photocontrol. The observed effects in nanoparticles were explained by various mechanisms of metastable state disabling. We also report a 2-fold improvement in the contrast of fluorescence images from h-BN nanoparticles under low-intensity laser scanning coexcitation. The research results can be used to develop efficient solid-state photon sources, as well as in nanoscopy employing biocompatible fluorescent nanoparticles.

The use of nanoparticles (NPs) to modify the surface of cotton fabric is a promising approach to endowing the material with a set of desirable characteristics that can significantly expand the functionality, wear comfort, and service life of textile products. Herein, two approaches to modifying the surface of hexagonal boron nitride (h-BN) NPs with a hollow core and a smooth surface by treatment with maleic anhydride (MA) and diethylene triamine (DETA) were studied. The DETA and MA absorption on the surface of h-BN and the interaction of surface-modified h-NPs with cellulose as the main component of cotton were modeled using density functional theory with the extended Perdew-Burke-Ernzerhof functional. Theoretical modeling showed that the use of DETA as a binder agent can increase the adhesion strength of BN NPs to textile fabric due to the simultaneous hydrogen bonds with cellulose and BN. Due to the difference in zeta potentials (-38.4 vs -25.8 eV), MA-modified h-BN NPs form a stable suspension, while DETA-modified BN NPs tend to agglomerate. Cotton fabric coated with surface-modified NPs exhibits an excellent wash resistance and high hydrophobicity with a water contact angle of 135° (BN-MA) and 146° (BN-DETA). Compared to the original textile material, treatment with MA- and DETA-modified h-BN NPs increases heat resistance by 10% (BN-MA fabric) and 15% (BN-DETA fabric). Cotton fabrics coated with DETA- and MA-modified BN NPs show enhanced antibacterial activity against Escherichia coli U20 and Staphylococcus aureus strains and completely prevent the formation of an E. coli biofilm. The obtained results are important for the further development of fabrics for sports and medical clothing as well as wound dressings.

In this work, the photocatalytic activity and sorption capacity of heterogeneous structures AgCl/h-BN obtained by the polyol method were studied in comparison with the initial micron-sized h-BN powder. The chemical and phase composition, as well as the surface microstructure, were analyzed by scanning electron microscopy, energy dispersive spectroscopy, X-ray phase analysis, and X-ray photoelectron spectroscopy. High photocatalytic activity and sorption ability of heterogeneous structures AgCl/BN in the reaction of the organic dye methylene blue decomposition under ultraviolet irradiation were demonstrated. Keywords: heterogeneous materials, photocatalysis, hexagonal boron nitride, silver chloride.

Due to its unique physical, chemical, and mechanical properties, such as a low specific density, large specific surface area, excellent thermal stability, oxidation resistance, low friction, good dispersion stability, enhanced adsorbing capacity, large interlayer shear force, and wide bandgap, hexagonal boron nitride (h-BN) nanostructures are of great interest in many fields. These include, but are not limited to, (i) heterogeneous catalysts, (ii) promising nanocarriers for targeted drug delivery to tumor cells and nanoparticles containing therapeutic agents to fight bacterial and fungal infections, (iii) reinforcing phases in metal, ceramics, and polymer matrix composites, (iv) additives to liquid lubricants, (v) substrates for surface enhanced Raman spectroscopy, (vi) agents for boron neutron capture therapy, (vii) water purifiers, (viii) gas and biological sensors, and (ix) quantum dots, single photon emitters, and heterostructures for electronic, plasmonic, optical, optoelectronic, semiconductor, and magnetic devices. All of these areas are developing rapidly. Thus, the goal of this review is to analyze the critical mass of knowledge and the current state-of-the-art in the field of BN-based nanomaterial fabrication and application based on their amazing properties.