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Low-cost and high-efficiency catalysts are of crucial importance for the electrocatalytic hydrogen evolution reaction (HER). Two-dimensional (2D) boron nitride (B–N) compounds formed by the combination of boron and nitrogen atoms of group III and V elements are promising candidates for electrocatalytic HER due to their significant electronic properties. Hence, an electrocatalyst is computer-aided designed with isolated single atoms of 3d, 4d, and 5d transition metals supported on 2D B–N (B2N, B5N3, and B7N5) monolayers to fabricate single-atom catalysts (SACs) with an excellent HER performance. Moreover, pH modulations are considered to improve the HER activity theoretically based on first-principles calculation. Our results indicate that B–N compounds surface doping with transition metal atoms can effectively enhance the HER catalytic performance over a wide range of pH. Among all SACs studied, Co-, Ti-, V-, Nb-, Ru-, Tc-, Zr-, and Os-embedded B2N, Sc-, Cr-, Mn-, Ti-, and Y-embedded B5N3, and Sc- and Mn-embedded B7N5 have excellent catalytic activity under acidic conditions, while Mo-, Ir-, Re-, Ta-, and W-embedded B2N and Ti- and Fe-embedded B7N5 show high catalytic activity under alkaline conditions. Interestingly, Hf@B2N and V@B5N3 systems exhibit promising catalytic activity under acidic, neutral, and alkaline conditions. Our work offers cost-effective candidates with a wide pH range HER performance for exploring ideal electrocatalysts. [ABSTRACT FROM AUTHOR]

Bragg interferometry (BI) is an imaging technique based on four-dimensional scanning transmission electron microscopy (4D-STEM) wherein the intensities of select overlapping Bragg disks are fit or more qualitatively analyzed in the context of simple trigonometric equations to determine local stacking order. In 4D-STEM based approaches, the collection of full diffraction patterns at each real-space position of the scanning probe allows the use of precise virtual apertures much smaller and more variable in shape than those used in conventional dark field imaging such that even buried interfaces marginally twisted from other layers can be targeted. With a coarse-grained form of dark field ptychography, BI uses simple physically derived fitting functions to extract the average structure within the illumination region and is, therefore, viable over large fields of view. BI has shown a particular advantage for selectively investigating the interlayer stacking and associated moiré reconstruction of bilayer interfaces within complex multi-layered structures. This has enabled investigation of reconstruction and substrate effects in bilayers through encapsulating hexagonal boron nitride and of select bilayer interfaces within trilayer stacks. However, the technique can be improved to provide a greater spatial resolution and probe a wider range of twisted structures, for which current limitations on acquisition parameters can lead to large illumination regions and the computationally involved post-processing can fail. Here, we analyze these limitations and the computational processing in greater depth, presenting a few methods for improvement over previous works, discussing potential areas for further expansion, and illustrating the current capabilities of this approach for extracting moiré-scale strain. [ABSTRACT FROM AUTHOR]

Epoxy dielectrics with high through-plane thermal conductivity (λ) hold great promise for applications in the thermal management of advanced power electronics. Intensive attempts have been made to improve the λ of epoxy by filling with boron nitride nanosheets (BNNSs). However, it remains a great challenge to achieve a satisfactory increased λ by a small amount of BNNS loading. Herein, we reported a new strategy to prepare epoxy dielectrics with internal three-dimensional phonon transport channels by vacuum freeze-drying and vacuum impregnation. Aramid nanofibers (ANFs) and BNNSs were used for the collaborative construction of a vertical interconnected thermal framework. The resultant ANF-BNNS/epoxy achieved a high through-plane λ of 0.87 W m−1 K−1 at only 1.43 vol. % BNNS, which is ∼17.1% higher than that of the BNNS/epoxy counterpart with even 18.34 vol. % randomly distributed BNNS. The increasing efficiency of λ of epoxy by ANF-BNNS is tenfold more than that of the conventional blending methods. In addition, the ANF-BNNS/epoxy composite also exhibits a low dielectric constant and low dielectric loss. The findings of this study offer an inspired venue to develop high-performance thermally conductive epoxy dielectrics with a minimal BNNS loading. [ABSTRACT FROM AUTHOR]

New properties can arise at van der Waals (vdW) interfaces hosting a moiré pattern generated by interlayer twist and strain. However, achieving precise control of interlayer twist/strain remains an ongoing challenge in vdW heterostructure assembly, and even subtle variation in these structural parameters can create significant changes in the moiré period and emergent properties. Characterizing the rate of interlayer twist/strain relaxation during thermal annealing is critical to establish a thermal budget for vdW heterostructure construction and may provide a route to improve the homogeneity of the interface or to control its final state. Here, we characterize the spatial and temporal dependence of interfacial twist and strain relaxation in marginally-twisted hBN/hBN interfaces heated under conditions relevant to vdW heterostructure assembly and typical sample annealing. We find that the ferroelectric hBN/hBN moiré at very small twist angles (θ ≤ 0.1 °) relaxes minimally during annealing in air at typical assembly temperatures of 170 ° C. However, at 400 ° C, twist angle relaxes significantly, accompanied by a decrease in spatial uniformity. Uniaxial heterostrain initially increases and then decreases over time, becoming increasingly non-uniform in direction. Structural irregularities such as step edges, contamination bubbles, or contact with the underlying substrate result in local inhomogeneity in the rate of relaxation. [ABSTRACT FROM AUTHOR]

Surface acoustic waves (SAWs) on piezoelectric insulators can generate dynamic periodic potentials inside one-dimensional and two-dimensional materials. These periodic potentials have been utilized or proposed for various applications, including acoustoelectric charge pumping. In this study, we investigate acoustoelectric charge pumping in graphene with very low electrostatic disorder. By employing a graphite top gate on boron-nitride-encapsulated graphene, we adjust the graphene carrier concentration over a broad range, enabling us to examine the acoustoelectric signal in both mixed-carrier and single-carrier regimes. We discuss the benefits of h-BN-encapsulated graphene for charge pumping applications and introduce a model that describes the acoustoelectric signal across all carrier concentrations, including at the charge neutrality point. This quantitative model will support future SAW-enabled explorations of phenomena in low-dimensional materials and guide the design of novel SAW sensors. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitride (h-BN) has excellent thermal conductivity and dielectric properties, which shows great potential for low-dimensional devices. However, mechanical properties of h-BN have not been comprehensively investigated through experiments. In this work, we conduct in situ direct tensile tests on freestanding single-crystal few-layer h-BN nanosheets with various layer numbers from 3 to 8, with an elaborate sample transfer and characterization protocol. Young's modulus of 573.8 ± 101.4 GPa and a tensile fracture strain up to 3.2% are revealed, which are comparable to its monolayer counterpart. Moreover, we find a tough-to-brittle transition in few-layer h-BN with the increase in layer number, which is attributed the interplay between the van der Waals interaction and in-plane covalent bonding. These findings could open up new possibilities in mechanical research of van der Waals materials and provide guidance for the design of h-BN-based devices and composites. [ABSTRACT FROM AUTHOR]

The in-plane thermal conductivity of hexagonal boron nitride (h-BN) with varying thicknesses is a key property that affects the performance of various applications from electronics to optoelectronics. However, the transition of the thermal conductivity from two-dimensional (2D) to three-dimensional (3D) h-BN remains elusive. To answer this question, we have developed a machine learning interatomic potential within the neuroevolution potential (NEP) framework for h-BN, achieving a high accuracy akin to ab initio calculations in predicting its thermal conductivity and phonon transport from monolayer to multilayers and bulk. Utilizing molecular dynamics simulations based on the NEP, we predict the thermal conductivity of h-BN with a thickness up to ∼100 nm, demonstrating that its thermal conductivity quickly decreases from the monolayer and saturates to the bulk value above four layers. The saturation of its thermal conductivity is attributed to the little change in phonon group velocity and lifetime as the thickness increases beyond four layers. In particular, the weak thickness dependence of phonon lifetime in h-BN with a nanoscale thickness results from its extremely high phonon focusing along the in-plane direction. This research bridges the knowledge gap of phonon transport between 2D and 3D h-BN and will benefit the thermal design and performance optimization of relevant applications. [ABSTRACT FROM AUTHOR]

In this study, the piezoelectric properties of scandium-alloyed gallium nitride (ScGaN), which is expected to be applied to microelectromechanical systems devices, are evaluated by first-principles calculations. The piezoelectric constant (d33) of GaN is found to increase by up to approximately 30 times upon the addition of 62.5 mol. % of Sc. The piezoelectric stress constant (e33) increases and the elastic constant (C33) decreases with increasing Sc content of ScGaN, driving the rise of d33. The improved piezoelectric properties of ScGaN compared with those of GaN are largely attributed to elastic softening, which is thought to be related to the transition from a wurtzite to hexagonal boron nitride (h-BN) structure driven by the change in bonding states between atoms caused by the addition of Sc to GaN. The crystal orbital Hamilton population analysis suggests that addition of Sc to GaN results in the combination of weaker Sc–N and Ga–N bonding, which makes the crystal structure unstable. This weakened bonding is thought to be the main cause of the destabilization of the wurtzite structure and transition to the h-BN structure of ScGaN. The elastic softening associated with this structural transition leads to the dramatic improvement in piezoelectric properties. [ABSTRACT FROM AUTHOR]

Packaging insulation materials with high thermal conductivity and excellent dielectric properties are favorable to meet the high demand and rapid development of third generation power semiconductors. In this study, we propose to improve the thermal conductivity of epoxy resin (EP) by incorporating a three-dimensional boron nitride thermally conductive network. Detailedly, polyurethane foam (PU) was used as a supporter, and boron nitride nanosheets (BNNSs) were loaded onto the PU supporter through chemical bonding (BNNS@PU). After immersing BNNS@PU into the EP resin, EP-based thermally conductive composites were prepared by vacuum-assisted impregnation. Fourier transform infrared spectrometer and scanning electron microscope were used to characterize the chemical bonding and morphological structure of BNNS@PU, respectively. The content of BNNS in BNNS@PU/EP composites was quantitatively analyzed by TGA. The results show that the thermal conductivity of the BNNS@PU/EP composites reaches 0.521 W/m K with an enhancement rate η of 30.89 at an ultra-low BNNS filler content (5.93 wt. %). Additionally, the BNNS@PU/EP composites have excellent dielectric properties with the frequency range from 101 to 106 Hz. This paper provides an interesting idea for developing high thermal conductivity insulating materials used for power semiconductor packaging. [ABSTRACT FROM AUTHOR]

In this work, the value and the polarity of the spontaneous and piezoelectric polarization have been investigated, as the use of two different reference structures for wurtzite-type group-III nitrides, namely, the zinc-blende and the layered-hexagonal crystal lattice, have resulted in different predictions. It was found that although the differences in value and polarity of the polarization for heterostructures such as wurtzite Al1−xScxN/GaN lead to similar interface sheet charges, a significant mismatch is observed when polarization reversal is considered. The interface sheet charge predicted before and after the polarization reversal in the wurtzite Al1−xScxN layer on GaN using the zinc-blende lattice as a reference predominantly shows a change in sign. When using the layered-hexagonal lattice as a reference, not only is the same polarity of the interface sheet charge maintained after polarization reversal, but it is even 30 times larger. In this case, the giant and positive spontaneous polarization values for metal-polar Al1−xScxN extracted from the ferroelectric switching, as well as the alignment of the piezoelectric polarization to it, were observed to be consistent with the predictions referenced to the layered-hexagonal lattice. Thus, it is concluded that the layered-hexagonal reference is not only more suitable for predicting the ferroelectric properties of wurtzite Al1−xScxN but should also be the correct reference when considering polarization reversal in heterostructures. If the significant increase in the interface sheet charge after polarization reversal is experimentally detected, it will allow the design and fabrication of novel devices for future high-frequency and power electronics applications. [ABSTRACT FROM AUTHOR]

In this research, we utilized density functional theory (DFT) computations to perform ab initio molecular dynamics simulations and static calculations on graphene, hexagonal boron nitride, and their heterostructures, subjecting them to strains, perturbations, twist angles, and defects. The gathered energy, force, and virial information informed the creation of a training set comprising 1253 structures. Employing the Neural Evolutionary Potential framework integrated into Graphics Processing Units Molecular Dynamics, we fitted a machine learning potential (MLP) that closely mirrored the DFT potential energy surface. Rigorous validation of lattice constants and phonon dispersion relations confirmed the precision and dependability of the MLP, establishing a solid foundation for subsequent thermal transport investigations. A further analysis of the impact of twist angles uncovered a significant reduction in thermal conductivity, particularly notable in heterostructures with a decline exceeding 35%. The reduction in thermal conductivity primarily stems from the twist angle-induced softening of phonon modes and the accompanying increase in phonon scattering rates, which intensifies anharmonic interactions among phonons. Our study underscores the efficacy of the MLP in delineating the thermal transport attributes of two-dimensional materials and their heterostructures, while also elucidating the micro-mechanisms behind the influence of the twist angle on thermal conductivity, offering fresh perspectives for the design of advanced thermal management materials. [ABSTRACT FROM AUTHOR]

Inquiring the isotopically engineered carrier transport in polar materials remains an open question. Herein, the phonon-limited drift carrier mobility of single-crystal cubic boron nitride is presented using first-principles calculations. Natural c-BN has the predicted electron mobility of 1230 and 760 cm2/V s by solving the iterative Boltzmann transport equation and self-energy relaxation time approximation, respectively. The hole mobility under the Boltzmann transport equation and self-energy relaxation time approximation is 193 and 105 cm2/Vs, respectively. Subsequently, the electron and hole mobilities at the stable isotope levels of boron and nitride are predicted, and nitride isotopes are found to be more effective than boron for carrier mobility. Those carrier mobilities further decrease with increasing temperature due to the strengthened electron–phonon interactions. Moreover, the phonon-assisted indirect optical absorption of c-BN is investigated by considering the contribution of phonons to the indirect electronic inter-band transitions. The predicted imaginary part of the dielectric function is in better agreement with previous experiments. This work aims to understand the role of phonons in determining the carrier mobility and indirect optical absorption of c-BN. [ABSTRACT FROM AUTHOR]

Two-dimensional magnetic materials have been increasingly studied and discussed in the field of spintronics due to their unique electronic properties, high spin polarizability, and a variety of magnetic properties. In this paper, we report a new two-dimensional bilayer hexagonal monolayer material bilayer hexagonal structure (BHS)-CrN2 by first-principles calculations. The BHS-CrN2 nanosheet is an intrinsic ferromagnetic semiconductor material, and the Curie temperature obtained by Monte Carlo simulation is 343 K. The absence of a significant imaginary frequency in the phonon spectrum indicates the dynamic stability of BHS-CrN2. After ab initio molecular dynamics simulation, the supercell of BHS-CrN2 remains a complete structure, indicating its thermal stability. The calculated elastic moduli satisfy the Born–Huang criterion, indicating that the BHS-CrN2 system has good mechanical stability. Interestingly, the compressive strain and O atom doping can transform the electronic structure of BHS-CrN2 from a semiconductor to a half-metal, and the Curie temperature of BHS-CrN2 can be further increased to 1059 K when a 5% tensile strain is applied. Furthermore, the BHS-CrN2 in the ferromagnetic state shows a significant in-plane magnetic anisotropy energy of 0.01 meV per Cr, and the CrP2 and CrAs2 show a large out-of-plane magnetic anisotropy energy of 0.207 and 0.988 meV per Cr, respectively. The results show that the intrinsic ferromagnetic semiconductor BHS-CrN2 has good stability, high Curie temperature, and tunable magnetic properties, which is a promising material for room-temperature spintronic devices. [ABSTRACT FROM AUTHOR]

We employ the molecular dynamics simulations to study the dynamics of acetanilide (ACN) molecules placed on a flat surface of planar multilayer hexagonal boron nitride. We demonstrate that the ACN molecules, known to be achiral in the three-dimensional space, become chiral after being placed on the substrate. Homochirality of the ACN molecules leads to stable secondary structures stabilized by hydrogen bonds between peptide groups of the molecules. By employing molecular dynamics simulations, we reveal that the structure of the resulting hydrogen-bond chains depends on the isomeric composition of the molecules. If all molecules are homochiral (i.e., with only one isomer being present), they form secondary structures (chains of hydrogen bonds in the shapes of arcs, circles, and spirals). If the molecules at the substrate form a racemic mixture, then no regular secondary structures appear, and only curvilinear chains of hydrogen bonds of random shapes emerge. A hydrogen-bond chain can form a zigzag array only if it has an alternation of isomers. Such chains can create two-dimensional (2D) regular lattices or 2D crystals. The melting scenarios of such 2D crystals depend on density of its coverage of the substrate. At 25% coverage, melting occurs continuously in the temperature interval 295–365 K. For a complete coverage, melting occurs at 415–470 K due to a shift of 11% of all molecules into the second layer of the substrate. [ABSTRACT FROM AUTHOR]

Graphene has been a subject of great interest not only due to its fascinating properties but also for being the pioneer among 2D van der Waals (vdW) materials. Hexagonal boron nitride, an isomorph of graphene and a wide gap insulator, is commonly referred to as white graphene. The combination of the insulating hexagonal boron nitride (h-BN) with other crystals to form heterostructures provide a path for engineering and manipulating new physics and device properties. In this work, we investigate the vdW heterostructures formed by assembling h-BN and lizardite, a clay-mineral that is abundant in nature and represents the most stable polymorph of the serpentine family. The optoelectronic properties of three distinct heterostructures are presented to discern the characteristics of the systems. We observe that unlike lizardite and h-BN which are insulators, all the three heterostructures exhibit a semiconducting nature. The direct gap of the heterostructure in which two h-BN sheets are simultaneously placed above and below the octahedral and tetrahedral layers also makes it relevant for optoelectronic devices. Additionally, unlike lizardite, the heterostructures demonstrate a polarization-dependent optical properties. The study of the assembled structures combining the clay-mineral with h-BN not only widens the spectrum of vdW heterostructures but also explores their potential within the context of the serpentine family. [ABSTRACT FROM AUTHOR]

We demonstrate a non-monotonic evolution of in-plane thermal conductivity of large-area hexagonal boron nitride films with thickness. Wrinkles and defects/impurities are present in these films. Raman spectroscopy, an optothermal non-contact technique, is employed to probe the temperature and laser power dependence property of the Raman active E2ghigh phonon mode, which, in turn, is used to estimate the rise in the temperature of the films under different laser powers. As the conventional Fourier law of heat diffusion cannot be directly employed analytically to evaluate the thermal conductivity of these films with defects and wrinkles, finite-element modeling is used instead. In the model, average heat resistance is used to incorporate an overall near-surface defect structure, and Voronoi cells with contact resistance at the cell boundaries are constructed to mimic the wrinkled domains. The effective in-plane thermal conductivity is estimated to be 87, 55, and 117 W/m K for the 2, 10, and 30 nm-thick films, respectively. We also present a quantitative estimation of the thermal resistance by defects and wrinkles individually to the heat flow. Our study reveals that the defects/impurities render a much higher resistance to heat transfer in the films than wrinkles. [ABSTRACT FROM AUTHOR]

A real-space method using generating integers is used to determine possible commensurate lattice Moiré patterns for a bilayer of two equal hexagonal lattices, which can in principle be extended to lattice mismatched bilayers. These Moiré patterns can be classified by a pair of relatively prime integers (n , m) , wherein a rotation θ (n , m) of the top hexagonal lattice maps its lattice vector (n , m) to (m , n) of the bottom lattice. Within this formulation, the area of the commensurate supercell is proportional to (n 2 + m 2 + n m) and the number of coincident lattice sites per supercell is given by (n − m) 2. Taking bilayer boron nitride (BN) as an example, we present how to systematically generate Moiré patterns and explore the differences in local chemistry in the interstitial region by impurity intercalation. Systematic calculations of the properties of intercalated 3d transition metals were performed in an h-BN (4 , 3) bilayer, corresponding to a rotation of 9.43 degrees. These calculations reveal that local symmetry in the intercalated region significantly affect the energetics and magnetization of the intercalated species. These results highlight that Moiré pattern physics is not limited to optoelectronic/electronic phenomena, such as interfacial exciton formation or magic angle superconductivity, but it also produces chemical and magnetic atomic site selectivity, which may play important roles in adsorption, catalysis, or quantum information. [ABSTRACT FROM AUTHOR]

Graphene-based field-effect transistors (FETs) are suitable for pH sensors due to their outstanding surface chemical properties and its biocompatibility. To improve the devices' stability and pH sensitivity, different sets of dielectric passivation layers composed of monolayer hexagonal boron nitride with and without aluminum oxide layers were evaluated. Non-linearities of the pH response were observed. Heterostructure FETs were derived from subtractive manufacturing of commercially transferred two-dimensional materials on four-inch SiO2/Si wafers via stainless steel and polypropylene masking. Phosphate solutions (10 mM) of varying pH were incubated on bare devices, whereby liquid-gating elucidated linear changes in the Dirac voltage of hBN/graphene (−40 mV/pH) that was smaller than a device consisting only of monolayer graphene (−47 mV/pH). Graphene-based FETs were passivated with aluminum oxide nanofilms via electron beam or atomic layer deposition and were observed to have distinct Raman spectral properties and atomic force microscopy topologies corroborating the hypothesis that morphological differences of the deposited aluminum oxide influence the pH-dependent electrical properties. Atomic layer deposition of aluminum oxide on the 2D sensing areas resulted in non-linear shifting of the Dirac voltage with respect to pH that evolved as a function of deposition thickness and was distinct between graphene with and without hexagonal boron nitride as a capping monolayer. The non-linear response of varying thickness of AlxOy on graphene-based FETs was progressively reduced upon basic wet etching of the AlxOy. Overall, passivated graphene-based transistors exhibit deposition-dependent pH responses. [ABSTRACT FROM AUTHOR]

Human urine phosphorus (existing in the form of phosphate) is a biomarker for the diagnosis of several diseases such as kidney disease, hyperthyroidism, and rickets. Therefore, the selective detection of phosphate in urine samples is crucial in the field of clinical diagnosis. Herein, we reported the phosphatase-like catalytic activity of few-layered h-BNNS for the first time. As the phosphatase-like activity of few-layered h-BNNS could be effectively inhibited by phosphate, a selective fluorescent method for the detection of phosphate was proposed. The linear range for phosphate detection is 0.5–10 µM with a detection limit of 0.33 µM. The fluorescent method was then explored for the detection of human urine phosphorus in real samples. The results obtained by the proposed method were consistent with those of the traditional method, indicating that the present method has potential application for urine phosphorus detection in clinical disease diagnosis. [ABSTRACT FROM AUTHOR]

Boron nitride nanotubes (BNNTs) are gaining interest for high temperature applications due to their thermal stability at elevated temperatures. Although BNNT temperature limits are well studied, there remains a gap in quantifying the high temperature failure mechanisms and oxidation kinetics. This study characterizes the oxidation mechanisms and kinetics of BNNTs and Al 2 O 3 -coated BNNTs, via atomic layer deposition (ALD), at temperatures between 850 and 1000 °C. ALD Al 2 O 3 surface coatings improved BNNT oxidation resistance by over an order of magnitude for coating thicknesses between 7 and 56 nm. However, the improved oxidation resistance of Al 2 O 3 -coated BNNTs decayed after prolonged exposure to oxygen at elevated temperatures, gradually reaching the same extent of oxidation as uncoated BNNTs after approximately 200 min at 900 °C. This behavior is attributed to the crystallization of as-deposited amorphous Al 2 O 3 coatings at elevated temperatures leading to densification, cracking, and exposure of BNNTs to the oxidizing environment. While Al 2 O 3 coatings did not completely prevent oxidation, a significant improvement in oxidation resistance was observed, extending the thermal stability of BNNTs. [ABSTRACT FROM AUTHOR]

With the continuous miniaturization and highly integrated development of modern electronics, thermal management materials with high thermal conductivity, good electrical insulating and flexibility are highly desired for the effective heat dissipation to maintain the reliable operations of electronic devices. However, enhancing thermal conductivity generally causes the deterioration of their mechanical properties and electrical insulation. Herein, combining the deformability of Galinstan-based liquid metal (LM) and good film-forming property of bacterial cellulose (BC), a series of thin and flexible boron nitride-based composite (BC/BNNS-LM) films was prepared via a facile vacuum-assisted filtration route. Benefiting from the directional arrangement of BNNS nanosheets, as well as gap-filling and bridging effects of deformable LM droplets, the resultant BC/BNNS-LM ternary nanocomposite film not only presents a high in-plane thermal conductivity of 66.1 W/m·K but also achieves excellent mechanical strength, flexibility and good dielectric property. These desirable properties confirm that the fabricated nanocomposite films have significant potential for effective heat dissipation in high-power-density electronics. [ABSTRACT FROM AUTHOR]

There exists more than one-third of the stock of buildings that do not meet energy-saving building standards, so there is an urgent need for breakthroughs in the field of green buildings. Herein, we successfully prepared boron nitride (BN) fiber aerogels by sol-gel, freeze-drying and high-temperature pyrolysis. When the molar ratio of C 3 N 6 H 6 to H 3 BO 3 was 1:2 and the roasting temperature was 1000 °C, the BN fiber aerogel was produced with high specific surface area (257.690 m2/g) and high porosity (99 %). BN fiber aerogels, with their low thermal conductivity (0.043 W/(m·K)) and stable mechanical properties (no change after 45 cycles at 30 % strain), offered possibilities for thermal insulation in green buildings. Its hydrophobic properties protect the wall from the natural environment. In particular, it had a solar reflectivity of 98.6 %, which exceeds most reflective coating materials, enabling the cooling of green construction on hot summer days. The high-temperature resistance of BN fiber aerogels could be applied in special environments such as blast furnace plants and thermoelectric power plants. [Display omitted] [ABSTRACT FROM AUTHOR]

Daytime radiative cooling material provides a low‐energy way of cooling because it can reflect sunlight and radiate heat without consuming any energy. However, there are still great difficulties in manufacturing low‐cost, high‐efficiency, sustainable, and biodegradable daytime radiative cooling materials. In this paper, poly (vinyl alcohol)/boron nitride (PVA/BN) composite aerogels were prepared by freeze‐drying technology. By adjusting the PVA concentration and BN content, the aerogel can achieve high sunlight reflectivity (96%), high mid‐infrared emissivity (96%) and good thermal insulation performance. Therefore, the temperature of the aerogel can be reduced to 12.5°C lower than the ambient temperature at night, and 5.5°C lower than the ambient temperature under the direct sunlight of 900 W/m2. This aerogel opens an environmentally sustainable pathway for radiative cooling applications. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO 2) is commonly used additive to improve the strength, hardness and coefficient of expansion properties of vitrified bonds. In this work, TiO 2 nanobelts were prepared through hydrothermal method, and the effect of TiO 2 nanobelts content on the microstructure and physical properties of vitrified bonds and vitrified bond CBN composites were systematically investigated. When the content of 0.2 wt% TiO 2 nanobelts and sintered at 660 °C, as-prepared nano-vitrified bonds exhibited the beneficial performance improvement. Specifically, the obtained coefficient of thermal expansion, flexural strength, microindentation hardness, and mobility are 5.37 × 10−6 °C−1, 85.96 MPa, 853.19 MPa, and 140.6 %, respectively. Moreover, the vitrified bonds with 0.2 wt% TiO 2 nanobelts addition is further used to optimize the performance of cubic boron nitride (CBN) composites. When sintered at 720 °C, the CBN composite samples depicted the excellent flexural strength, rockwell, porosity, and grinding ratio of 63.27 MPa, 61.5 HRB, 48.9 %, and 22.3, respectively. It can be attributed to the positive contribution of nano-vitrified bonds on the physical properties of CBN composites. This work is expected to contribute to the research on improving the performance of vitrified bonds with nano additives, and further obtain excellent performance nano-vitrified bond materials for the design and manufacturing of high-performance superhard abrasive tools. [ABSTRACT FROM AUTHOR]

In this study, the effect of hexagonal boron nitride (hBN) addition at different weight ratios to thermoplastic polyester elastomer (TPEE) reinforced with three different fiber types, namely carbon fiber (CF), glass fiber (GF) and basalt fiber (BF), on the mechanical, tribological and thermal properties of the composites was investigated. Adhesive wear test for tribological analysis, tensile and three-point bending tests for mechanical analysis, differential scanning calorimetry and thermogravimetric analyses for thermal investigation and scanning electron microscopy analysis for morphological evaluation were applied. The results showed that the addition of hBN to fiber-reinforced TPEE composites, regardless of the fiber type, and the increasing weight ratio of hBN improved the wear, mechanical and thermal properties of the composites. However, when comparing the synergistic effect of hBN when used simultaneously with fiber reinforcement on the basis of fiber type, CF was found to outperform GF and BF fiber types and hybrid reinforced composites containing 10 wt% hBN and CF to exhibit superior tribological, mechanical and thermal properties. It is also concluded that BF performs at a comparable level to GF and therefore can be used instead of GF in some applications. [ABSTRACT FROM AUTHOR]

Polypropylene (PP) has the advantages of corrosion resistance, easy processing, and low dielectric loss, but its low thermal conductivity limits the application of its composites in fields such as electronic packaging. To solve this problem, in this work, composite microspheres with the segregated structure were prepared by coating boron nitride nanosheets (BNNSs) on the PP surface by Pickering‐like emulsion method, and BNNSs@PP composites with three‐dimensional thermal conductivity network were obtained after molding. Due to the high thermal conductivity of BNNSs and the formation of perfect thermal conduction pathways, the thermal conductivity of the composites reached 1.71 W m−1 K−1 when the content of BNNSs was 10.1 wt%, which was a 713% increase in thermal conductivity for that of pure PP. At the same time, the mechanical properties of the composites were ensured. This method provides a simple and effective technique to improve the thermal conductivity of PP‐based thermally conductive composites, which has a wide application potential in electronic packaging. [ABSTRACT FROM AUTHOR]

As the electronic industry develops rapidly, the miniaturisation, integration and multifunctionality of electronic devices have resulted in a dramatic increase in power density, and the heat dispersal of electronic devices has attracted much attention. In this work, hydroxylated hexagonal boron nitride (BN-H) was obtained by hot alkali treatment, and boron nitride nanosheets (BNNS) with a thickness of about 4 nm were obtained by boric acid-assisted ball milling stripping. The effects of different types of fillers as well as filler contents on the thermally conductive and mechanical performance of organosilicon composites were also compared. Notably, when BN-H and BNNS thermally conductive fillers were added at 12 wt%, the thermally conductive coefficients of the composites were 0.4831 W·m−1·K−1 and 0.7131 W·m−1 K−1, respectively, which were 183% and 318% of higher than that for the pure silicone rubber (SR, with a thermally conductive coefficient of 0.1706 W·m−1·K−1). In addition, in respect of mechanical performance, the tensile strengths of SR/BN-H and SR/BNNS composites with a filling level of 12 wt% were 3.59 MPa and 3.89 MPa, respectively, and the storage moduli were 4501 MPa and 4583 MPa, respectively, which were improved to a certain extent compared with pure SR. The present work provides an effective way to develop organosilicone rubber composites with good thermal conductivity and mechanical properties by boric acid assisted ball milling to strip boron nitride in the field of electronics packages. [ABSTRACT FROM AUTHOR]

This document is a profile of Jinfa Chang, a new editorial board member of Frontier Reporters for the Chinese Journal of Chemistry. Chang is a professor at Northeast Normal University in China and has a background in chemistry, with a focus on electrocatalytic hydrogen energy-electric energy conversion. Chang's research aims to design and develop cost-effective, high-performance catalysts to accelerate the commercialization of hydrogen-related energy storage and conversion technologies. The lab pays particular attention to the electrocatalytic performance of electrode materials for fuel cells and water electrolysis under real-service conditions, with a specific interest in the reaction mechanism and structure-performance relationship. [Extracted from the article]

In this study, TiB 2 –TiC, TiB 2 –TiC-GNP, and TiB 2 -TiC-BN composites were produced via spark plasma sintering (SPS). The densification and sintering behavior, phase and Raman spectroscopy analyses, microstructural properties, Vickers microhardness, and wear behavior of the binary and ternary composites were investigated. The addition of various amounts of TiC to TiB 2 resulted in nearly complete densification. The TiB 2 –TiC-GNP specimens exhibited a relative density of more than 99 %; in contrast, the addition of BN did not contribute to the densification. The Vickers hardness of the GNP-added composites was ∼25 GPa, whereas hBN addition to the matrix decreased the hardness to ∼22 GPa (∼9 % decrease). According to the wear test, the addition of GNPs did not result in a significant change in the TiB 2 –TiC matrix; however, the addition of hBN increased the specific wear rate of the matrix by ∼100 %. The GNPs did not have a negative effect on the densification, microstructural, or mechanical properties, such as the Vickers hardness and wear resistance. Hence, they were determined to be a more suitable sintering aid for matrix composition than hBN. [ABSTRACT FROM AUTHOR]

A novel binary transition metal oxide (NiFe2O4) nanosphere catalyst with a diameter of 500 nm has been synthesized by the hydrothermal reaction, which can efficiently catalyze the formation of hexagonal boron nitride nanotubes (BNNTs) with high‐yield and large aspect ratio. Based on the temperature dependence of the product phase composition and microstructure, combined with results generated using single‐component catalysts, the BNNTs formation process can be summarized as follows: NiFe2O4 reacts with NH3 to generate Fe0.64Ni0.36, which dissolves to form a liquid‐phase Ni‐Fe alloy at high temperatures, where the B component in the precursor and the N atom formed by the decomposition of NH3 diffuse on the surface of the Ni‐Fe alloy; when the concentration of B and N exceed the saturation threshold, hollow BNNTs containing catalyst at the tips are precipitated. The formation process is dominated by a vapor‐liquid‐solid mechanism with tip‐growth mode, where the synergistic catalytic effect of the Ni‐Fe binary system promotes a high yield of large aspect ratio BNNTs. [ABSTRACT FROM AUTHOR]

[Display omitted] The electrocatalytic oxygen reduction reaction (ORR) is crucial for energy conversion systems such as fuel cells and metal-air batteries. Boron carbon nitrogen (BCN) is a novel functional material with a high specific surface area, excellent corrosion resistance, and outstanding electrochemical stability. These properties make BCN an effective ORR catalyst and a promising support for metal catalysts. This study leveraged the strong interaction between BCN and metals to anchor platinum nanoparticles (Pt NPs) onto the BCN surface (Pt/BCN), significantly enhancing the durability of traditional Pt/C catalysts in ORR. The half-wave potential of Pt/BCN is 0.927 V, higher than Pt/XC-72R (0.857 V) and commercial Pt/C (0.879 V). Notably, after 10,000 durability test cycles, the mass activity (MA) of Pt/XC-72R and commercial Pt/C decreased by 67 % and 75 %, respectively. Even after 50,000 cycles, Pt/BCN exhibited only a 54 % decrease in MA. Experimental data and density functional theory calculations confirmed increased electron transfer from Pt to the BCN support, indicating a strong electronic metal-support interaction (EMSI) between Pt and BCN. This strong EMSI effectively anchored the Pt NPs, preventing migration and aggregation during the ORR process. Consequently, our research introduces a novel electrocatalyst support material with significant potential for ORR and broader applications. [ABSTRACT FROM AUTHOR]

The current global warming, coupled with the growing demand for energy in our daily lives, necessitates the development of more efficient and reliable energy storage devices. Lithium batteries (LBs) are at the forefront of emerging power sources addressing these challenges. Recent studies have shown that integrating hexagonal boron nitride (h‐BN) nanomaterials into LBs enhances the safety, longevity, and electrochemical performance of all LB components, including electrodes, electrolytes, and separators, thereby suggesting their potential value in advancing eco‐friendly energy solutions. This review provides an overview of the most recent applications of h‐BN nanomaterials in LBs. It begins with an informative introduction to h‐BN nanomaterials and their relevant properties in the context of LB applications. Subsequently, it addresses the challenges posed by h‐BN and discusses existing strategies to overcome these limitations, offering valuable insights into the potential of BN nanomaterials. The review then proceeds to outline the functions of h‐BN in LB components, emphasizing the molecular‐level mechanisms responsible for performance improvements. Finally, the review concludes by presenting the current challenges and prospects of integrating h‐BN nanomaterials into battery research. [ABSTRACT FROM AUTHOR]

Epoxy resin, characterized by prominent mechanical and electric‐insulation properties, is the preferred material for packaging power electronic devices. Unfortunately, the efficient recycling and reuse of epoxy materials with thermally cross‐linked molecular structures has become a daunting challenge. Here, we propose an economical and operable recycling strategy to regenerate waste epoxy resin into a high‐performance material. Different particle size of waste epoxy micro‐spheres (100–600 μm) with core‐shell structure is obtained through simple mechanical crushing and boron nitride surface treatment. By using smattering epoxy monomer as an adhesive, an eco‐friendly composite material with a "brick‐wall structure" can be formed. The continuous boron nitride pathway with efficient thermal conductivity endows eco‐friendly composite materials with a preeminent thermal conductivity of 3.71 W m−1 K−1 at a low content of 8.5 vol% h‐BN, superior to pure epoxy resin (0.21 W m−1 K−1). The composite, after secondary recycling and reuse, still maintains a thermal conductivity of 2.12 W m−1 K−1 and has mechanical and insulation properties comparable to the new epoxy resin (energy storage modulus of 2326.3 MPa and breakdown strength of 40.18 kV mm−1). This strategy expands the sustainable application prospects of thermosetting polymers, offering extremely high economic and environmental value. [ABSTRACT FROM AUTHOR]

Selective Laser Sintering (SLS) is an additive manufacturing technique that builds 3D models layer by layer using a laser to selectively melt cross sections in powdered polymeric materials, following sequential slices of the computer-aided design (CAD) model. SLS generally uses thermoplastic polymeric powders such as polyamides. The resultant 3D-printed objects are often weaker in their strength compared to traditionally processed materials, due to their higher porosity. This paper described the process development of using melt-processable imide oligomers terminated with reactive 4-phenylethynylphthalic anhydride (4-PEPA) to conduct laser sintering (LS). The first successful 3D-printing of high temperature RTM370 thermoset polyimide carbon fiber composite was further post-cured to promote additional crosslinking for achieving higher temperature (Tg = 370°C) capability. Another novel imide oligomer, RTM385-SLS, formulated with a complex melt viscosity [h*] of ~104-105 poise is also suitable for LS. RTM385-SLS resin powder was mixed with 20-25% of hexagonal boron nitride (h-BN) and subjected to LS to print out "Green" specimens which could be further post-cured to afford a thermally conductive but electrically insulating composites with high Tg of 385°C. The cured composite specimens were then subjected to mechanical testing, thermal conductivity and porosity evaluation as well as SEM characterization. [ABSTRACT FROM AUTHOR]

Important technological advances in the mechanical manufacturing industry have increasingly generated good results with the turning of hardened materials, using polycrystalline cubic boron nitride (PCBN) tools, mainly replacing abrasive processes. The ability to meet project requirements without the need for multiple processes translates into cost reduction and increased productivity. Tool steels play varied and essential roles in various industrial applications, such as dies and punches for forming and cutting. Improvements in the performance of cutting tools are crucial to withstand the severe tribological conditions of the turning process of hardened materials. In this context, this work aimed to evaluate the performance of a PCBN tool in turning quenched and tempered AISI D2 steel, both in continuous cutting and interrupted cutting conditions, in the finishing operation with dry machining. The surface roughness was evaluated in the parameters (Ra, Rt, and Rz), the wear suffered by the tools, their mechanisms, and the morphological analysis of the chips. Tests were carried out with different cutting speeds (60, 130, 200, and 240 m/min), maintaining a constant feed rate of 0.15 mm/rev and a cutting depth of 0.2 mm. The results indicated that the most evident wear was crater and flank in the continuous cut, while in the interrupted cut, there was the presence of chipping and catastrophic failure. Wear mechanisms, such as adhesion (attrition), abrasion, and diffusion, were prominently observed. Furthermore, the tests showed that the increase in flank wear did not necessarily result in an increase in surface roughness, and that the wear mechanism changed with the increase in cutting speed. In the continuous cutting condition, the tool achieved more satisfactory performance, especially at higher cutting speeds (130, 200, and 240 m/min). In interrupted cutting, there is a predominance of catastrophic failure mainly in the ranges of 60 and 130 m/min and better performance at 200 m/min within the ranges evaluated. [ABSTRACT FROM AUTHOR]

Using mechanical activation of an oxide mixture containing 0.2 wt% hexagonal boron nitride, followed by high-temperature firing (1400–1500 °C), we prepared single-phase (La 0.2 Nd 0.2 Ho 0.2 Lu 0.2 Y 0.2) 2 ZrO 5 ceramic, a high-entropy oxide (HEO) analog of Gd 2 ZrO 5 , whereas we failed to obtain single-phase Gd 2 ZrO 5 under similar conditions: the material consisted of two phases, with the fluorite and bixbyite structures, like in the case of conventional synthesis or coprecipitation in previous work. Thus, the use of the HEOs allowed us to obtain a phase-pure compound with the fluorite structure at a markedly lower synthesis temperature. An important role was played by 0.2 wt% hyperstoichiometric hexagonal BN additions, which ensured considerable amorphization of the starting oxides. The start powders and resulting ceramics were studied by X-ray diffraction, SEM analyses and conductivity was measured by impedance spectroscopy method in dry and wet air. The highest proton conductivity, ∼2.5 × 10−5 S/cm at 630 °C, was offered by the (La 0.2 Nd 0.2 Ho 0.2 Lu 0.2 Y 0.2) 2 ZrO 5 HEO ceramic. The use of HEO analogs of various compounds can be helpful for not only assessing thermodynamic properties of ceramics (reduction in synthesis and polymorphic transformation temperatures), but also preparing proton conductors when it is necessary to enhance hydrating properties of the cation sublattice. [ABSTRACT FROM AUTHOR]

Organic luminogens play an indispensable role in optoelectronic devices, yet there is a pressing need to address their aggregation‐caused quenching (ACQ) and stability. Here we designed and prepared multilayered boron nitride nanosheets/fluorescein isothiocyanate (MBNNSs/FITC) composite phosphors with tunable photoluminescence by controlling the FITC content and annealing temperature. The research results indicate that MBNNSs/FITC with low or high loading of FITC is not conducive to enhancing the emission intensity of FITC, which can be attributed to the fact that low loading leads to a decrease in the content of fluorescent groups, while high loading promotes intermolecular aggregation of FITC dyes. Interestingly, the emission intensity of FITC in MBNNSs/FITC‐6 composite phosphors can be further enhanced by annealing treatment (200 °C), which can be ascribed to the suppression of the ACQ and effective energy transfer from the MBNNSs to the FITC. Moreover, the resultant composite phosphor displays outstanding thermal stability, remarkable photo stability and exceptional water‐resistance. This work provides a new design space for the development of non‐rare‐earth fluorescent materials using organic fluorescent dyes. [ABSTRACT FROM AUTHOR]

High‐performance sensors are in constant demand for health care and environmental protection. In this study, a sensitive paracetamol (PCM) sensor was designed by modifying glassy carbon electrode (GCE) with carbon‐doped boron nitride (BCN/GCE) nanosheets. The BCN nanosheets were synthesized using a molten‐salt method, which ensured the uniformity of size distribution. X‐ray diffraction and transmission electron microscopy results suggested that the carbon‐doping hardly changed the crystal structure and morphology of hexagonal boron nitride (HBN). However, the carbon‐doping can reduce the bandgap, increase the specific surface area and improve the electrical conductivity, which is attributed to the formation of abundant point defects in the BN crystal. These point defects modulate electronic structure and surface activity, and further improve the electrocatalytic properties of BN. The BCN nanosheets exhibited outstanding electrocatalytic activity in the oxidation of paracetamol (PCM). With the help of square wave voltammetry (SWV) method, the BCN/GCE demonstrated linear current response towards PCM covering the concentrations of 0.05–70 μM and 70–200 μM with a detection limit (LOD) of 0.0086 μM. The developed method also showed excellent selectivity and high stability. In addition, the BCN/GCE sensor worked well when it was applied to quantify PCM in actual samples. [ABSTRACT FROM AUTHOR]

Herein, we used dimethyl sulfoxide (DMSO) dispersion of aramid nanofibers (ANFs) as medium to exfoliate boron nitride nanosheets (BNNSs) from their bulk materials via a ball-milling route. The obtained BNNSs displayed large lateral sizes and were very clean without any contaminants. When milling under a high energy condition, many small-area nanosheets were appeared but the sample produced with high ANF concentration could still contain more large-size BNNSs. It was concluded that the DMSO is a good exfoliating medium for BNNSs due to the suitable viscosity, molecular weight, and polarity, while the introduction of ANFs can further improve the exfoliated sizes of BNNSs because of the buffering to impacting forces of milling balls. The ANF/BNNS composite exfoliated under high energy ball-milling and high ANF concentration gained the highest in-plane thermal conductivity of 27.23 W m−1 K−1 since the densified microstructure and the high dispersity, large lateral size, and high horizontal orientation of BNNSs. [ABSTRACT FROM AUTHOR]

Sub‐ambient cooling technologies relying on passive radiation have garnered escalating research attention owing to the challenges posed by global warming and substantial energy consumption inherent in active cooling systems. However, achieving highly efficient radiative cooling devices capable of effective heat dissipation remains a challenge. Herein, by synergic optimization of the micro‐pyramid surface structures and 2D hexagonal boron nitride nanoplates (h‐BNNs) scattering fillers, pyramid textured photonic films with remarkable solar reflectivity of 98.5% and a mid‐infrared (MIR) emittance of 97.2% are presented. The h‐BNNs scattering filler with high thermal conductivity contributed to the enhanced through‐plane thermal conductivity up to 0.496 W m−1 K−1 and the in‐plane thermal conductivity of 3.175 W m−1 K−1. The photonic films exhibit an optimized effective radiative cooling power of 201.2 W m−2 at 40 °C under a solar irradiance of 900 W m−2 and a daily sub‐ambient cooling effect up to 11 °C. Even with simultaneous internal heat generation by a 10 W ceramic heater and external solar irradiance of 500 W m−2, a sub‐ambient cooling of 5 °C can be realized. The synergic matching strategy of high thermal conductivity scattering fillers and microstructured photonic surfaces holds promise for scalable sub‐ambient radiative cooling technologies. [ABSTRACT FROM AUTHOR]

Polyimide (PI) is one of the most important engineering plastics, but its stability in aqueous environments is insufficient, which limits its anti‐corrosion efficiency. In this study, a novel P(VDF‐HFP)/SMT‐RS@BNNSs/PI composite coating is prepared by incorporating poly(vinylidene fluoride‐hexafluoropropylene) (P(VDF‐HFP)) and the exfoliated boron nitride nanosheets (BNNSs) which were highly co‐functionalized with two kinds of materials of the rosin and the soy‐maleic anhydride‐tannic acid adhesive molecules (SMT‐RS@BNNSs). The coatings are characterized in detail by using the XRD, FT‐IR, XPS, and SEM technologies. Electrochemical impedance spectroscopy (EIS) and polarization curve tests further evaluated the corrosion resistance of the coating. As results, the obtained P(VDF‐HFP)/SMT‐RS@BNNSs/PI coating with good adhesion (grade 1) to the low‐carbon steel plate displays a larger water contact angle of 93.10° compared to blank PI (75.5°) and SMT‐RS@BNNSs/PI (83.2°). The dispersed distribution and interaction of SMT‐RS@BNNSs can effectively reduce the phase separation between P(VDF‐HFP) and PI. Even after soaking in electrolyte for 15 days, the impedance modulus, corrosion current, and corrosion voltage of the P(VDF‐HFP)/SMT‐RS@BNNSs/PI coating are 1.568 × 1010 Ω cm2, 4.612 × 10−12 A cm−2, and 0.325 V, respectively. These properties are superior to those of the PI and SMT‐RS@BNNSs/PI coatings. It is believed that the excellent anti‐corrosive performance of this PI‐based composite will broaden the application fields of PI materials. [ABSTRACT FROM AUTHOR]

This study investigates the effects of boron nitride (BN) coating characteristics on the subsurface oxidation behavior of SiC/SiC composites in high‐temperature, water‐rich environments. Three types of coatings were examined: a crystalline stoichiometric BN, an amorphous BN, and a Si‐doped amorphous BN, the latter two containing 5–10 at% of oxygen and carbon. High‐resolution imaging and chemical analysis techniques were used to probe microstructural changes after oxidation at 1000°C for 1 or 12 h in flowing 20 vol% H2O, focusing on effects of coating thickness. Complementary chemical thermodynamic calculations and models for reaction‐ and transport‐controlled recession were used to interpret the experimental findings. Crystalline BN coatings produce open recession channels without forming borosilicate glass, a consequence of carbothermal reduction arising from C/CO produced through concomitant SiC oxidation. The combination of active oxidation and the relatively thick coatings in this system (ca. 1 µm) leads to a recession rate controlled by the intrinsic BN volatilization rate rather than the rate of gas transport. In contrast, amorphous coatings, both undoped and Si‐doped, readily oxidize to form borosilicate glasses that replace the BN. Broadly, the recession lengths increase with coating thickness. In the early stages, while the glass is boria‐rich and thus permeable to environmental oxidants, recession is controlled by the BN oxidation rate. As boria volatilizes, the silica concentration in the glass increases, eventually reaching the saturation limit and precipitating solid silica on the internal surfaces, essentially arresting further recession. [ABSTRACT FROM AUTHOR]

Highlights Boron nitride had emerged as an innovative thermally conductive filler, garnering increasing attention from researchers. However, there was a need to create new methods for efficiently producing functionalized boron nitride nanosheets with enhanced thermal conductivity and dispersion. In this study, a novel approach was introduced to utilize deep eutectic solvents as additives to facilitate the exfoliation of boron nitride nanosheets. This method offered significant advantages in terms of cost‐effectiveness (low additives level) and high yield (about 60%). Furthermore, the resulting epoxy resin composite material exhibited outstanding thermal conductivity and thermal management properties. The thermal conductivity of EP/d‐BNNS composites reached 1.02 W/mK at 20 wt% d‐BNNS loading. Additionally, the composite material demonstrated good thermal stability and low dielectric properties. This work demonstrated that this proposed approach represents an effective means for the scalable production of boron nitride nanosheets. The boron nitride nanosheets were obtained by deep eutectic solvents (DES) ball milling method. The exfoliated boron nitride exhibits superior dispersion stability. The thermal conductivity of EP composites is significantly improved. [ABSTRACT FROM AUTHOR]

The treatment of antibiotic wastewater is one of the environmental problems that humans must solve. Low-cost and high-activity photocatalysts are the key to the treatment of antibiotic wastewater environments. In this work, a single-layer coated TiO2/g-C3N4/BN (TCB) ternary composite heterojunction photocatalyst was successfully prepared. The appropriate amount of boron nitride (BN) was doped into the composite to form a I/II type double heterogeneous junction, which promoted the charge transfer and improved the separation efficiency of the photogenic carriers. Notably, a heterogeneous photocatalyst was constructed that could degrade tetracycline hydrochloride (TCH) in 30 min with a rapid degradation efficiency of 94.96%. When the light duration was increased to 60 min, the removal rate of TCH from aqueous solution could reach 99.16%. The reaction dynamics constant was 0.10128 s−1, which was 5.73 and 3.27 times higher than that of TiO2 and TiO2/g-C3N4, respectively. This work reveals the potential application of ternary composites with double heterojunction for photocatalytic degradation as well as provides a reference value for titanium matrix composites for antibiotic wastewater treatment. [ABSTRACT FROM AUTHOR]

Excessive human exposure to toxic gases can lead to chronic lung and cardiovascular diseases. Thus, precise in situ monitoring of toxic gases in the atmosphere is crucial. Here, we present an artificial olfactory system for spatiotemporal recognition of NO2 gas flow by integrating a network of chemical receptors with a near-sensor computing. The artificial olfactory receptor features nano-islands of metal-based catalysts that cover the graphene surface on the heterostructure of an AlGaN/GaN two-dimensional electron gas (2DEG) channel. Catalytically dissociated NO2 molecules bind to graphene, thereby modulating the conductivity of the 2DEG channel. For the energy/resource-efficient gas flow monitoring, trust-region Bayesian optimization algorithm allocates many sensors optimally in a complex space. Integrated artificial neural networks on a compact microprocessor with a network of sensors provide in situ gas flow predictions. This system enhances protective measures against toxic environments through spatiotemporal monitoring of toxic gases. [ABSTRACT FROM AUTHOR]

Thermal energy storage, particularly through Phase Change Materials (PCMs), is gaining significant attention for its ability to enhance storage capacity and thermal conductivity. PCMs help alleviate the strain on renewable energy sources and stabilize load fluctuations. This study integrates a novel combination of LiNO3-NaSO4·10H2O-NaCl with boron nitride into Flat Plate Collectors (FPCs) to boost system performance. This Composite Phase Change Material (CPCM) increases latent heat value by up to 245.80 kJ, enhancing thermal decomposition and absorption rates while reducing heat losses. Boron nitride improves thermal conductivity by 25%, from 1.378 W/m·K to 5.543 W/m·K, increasing the CPCM's charging rate. The specific heat capacity rises from 4.2 J/g·°C to 5 J/g·°C at a maximum temperature of 90°C. As a result, the collector's efficiency improves by 15%, achieving an overall system efficiency of 88%. Water serves as the heat transfer fluid, and simulations are conducted using Python in Anaconda Jupyter Notebook. [ABSTRACT FROM AUTHOR]

Highlights The development of epoxy resin (EP) potting material with high thermal conductivity (TC) and excellent electrical insulating properties plays an important role in the development of drive motors to high specific power and high voltage. In this study, a simple preparation method is presented to solve the problem of low content filler settling and low TC of EP. Firstly, small‐sized perfluoroalkyltrimethoxysilane surface‐treated nanodiamond (ND) and large‐sized hydroxylated boron nitride (BN) were adsorbed together using hydrogen bonding to construct “Sesame Cookie”‐like structures. The heterostructure filler with different “sesame” contents were obtained by modulating the ND:BN ratio, and were filled into high‐temperature resistant AG70 EP at a fixed mass ratio of 20 wt.%. By surface treatment, the dispersibility of fillers in EP was improved, and the settling problem of low content fillers was solved. Finally, when the ratio of ND: BN is 1:2, the TC value of EP composite reached 0.94 W·m−1·K−1, which was 348% higher than pure EP, and the composite possessed good electrical insulating properties. In addition, the heat‐resistance temperature of the composite exceeded 200°C, which ensured the stable operation of the drive motor. This study presents new ideas for the exploitation of EP potting materials with high TC and excellent electrical insulating properties. Heterostructure filler is constructed using hydrogen bonding. Dispersion of the filler in the EP is improved by surface treatment. The TC value of the EP composite increased by 348%. The heat‐resistant temperature of the EP composite is more than 200°C. The EP composite has excellent insulating properties. [ABSTRACT FROM AUTHOR]

Van der Waals (vdW) heterostructures comprising of transition metal dichalcogenides (TMDs) and hexagonal boron nitride (h‐BN) are promising building blocks for novel 2D devices. The vdW epitaxy provides a straightforward integration method for fabricating high‐quality TMDs/h‐BN vertical heterostructures. In this work, the vdW epitaxy of high‐quality single‐crystal HfSe2 on epitaxial h‐BN/sapphire substrates by chemical vapor deposition is demonstrated. The epitaxial HfSe2 layers exhibit a uniform and atomically sharp interface with the underlying h‐BN template, and the epitaxial relationship between HfSe2 and h‐BN/sapphire is determined to HfSe2 (0001)[12¯${\mathrm{\bar{2}}}$10]//h‐BN (0001)[11¯${\mathrm{\bar{1}}}$00]//sapphire (0001)[11¯${\mathrm{\bar{1}}}$00]. Impressively, the full width at half maximum of the rocking curve for the epitaxial HfSe2 layer on single‐crystal h‐BN is as narrow as 9.6 arcmin, indicating an extremely high degree of out‐plane orientation and high crystallinity. Benefitting from the high crystalline quality of HfSe2 epilayers and the weak interfacial scattering of HfSe2/h‐BN, the photodetector fabricated from the vdW epitaxial HfSe2 on single‐crystal h‐BN shows the best performance with an on/off ratio of 1 × 104 and a responsivity up to 43 mA W−1. Furthermore, the vdW epitaxy of other TMDs such as HfS2, ZrS2, and ZrSe2 is also experimentally demonstrated on single‐crystal h‐BN, suggesting the broad applicability of the h‐BN template for the vdW epitaxy. [ABSTRACT FROM AUTHOR]

Unlocking the full potential of hydrogen as a clean fuel requires overcoming the challenge of efficient storage. A promising method involves utilizing metals decorated, high surface area materials for hydrogen storage. We employed density functional theory (DFT) calculations to investigate how H 2 molecules interact with h-BNNT decorated by alkali metals (AM) and transition metals (TM). The h-BNNT's stability is confirmed by negative cohesive energy, positive phonon dispersion curves, and room temperature AIMD calculations. Our calculations reveal that the adsorption energies of H 2 molecules on AM/TM decorated h-BNNT fall within the physisorption regime. Notably, Na, K, and Au decorated surfaces can store up to seven H 2 molecules each, while Cu and Ag atom can bind up to eight. Li atom, however, can only accommodate six H 2 molecules around it. We also predicted that under optimal conditions, h-BNNT decorated with a high concentration of AM/TM could achieve a hydrogen storage capacity of 3.77–6.72 wt%. This highlights the potential of decorated h-BNNT as a material for hydrogen storage medium. [Display omitted] • Alkali and transition metals decorated on hexagonal boron nitride nanotubes (h-BNNTs) are promising for hydrogen storage medium. • Single alkali metals (AM) and transition metals (TM) adsorbed six to eight H 2 molecules. • The average adsorption energy per H 2 molecule on AM/TM decorated h-BNNT is in the range of −0.177 to −0.299 eV/H 2. • Gravimetric weight percentage capacity (wt%) is in the range of 3.77–6.72 % for hydrogen storage. [ABSTRACT FROM AUTHOR]

Efficient and compact single photon emission platforms operating at room temperature with ultrafast speed and high brightness will be fundamental components of the emerging quantum communications and computing fields. However, so far, it is very challenging to design practical deterministic single photon emitters based on nanoscale solid‐state materials that meet the fast emission rate and strong brightness demands. Here, a solution is provided to this longstanding problem by using metallic nanocavities integrated with hexagonal boron nitride (hBN) flakes with defects acting as nanoscale single photon emitters (SPEs) at room temperature. The presented hybrid nanophotonic structure creates a rapid speedup and large enhancement in single photon emission at room temperature. Hence, the nonclassical light emission performance is substantially improved compared to plain hBN flakes and hBN on gold‐layered structures without nanocavity. Extensive theoretical calculations are also performed to accurately model the new hybrid nanophotonic system and prove that the incorporation of plasmonic nanocavity is key to efficient SPE performance. The proposed quantum nanocavity single photon source is expected to be an element of paramount importance to the envisioned room‐temperature integrated quantum photonic networks. [ABSTRACT FROM AUTHOR]