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The edge-hydroxylated boron nitride nanosheets (BNNS) not only has excellent thermal stability, electrical properties, but also has high specific surface area, good dispersibility and compatibility. In this paper, edge-hydroxylated BNNS was obtained by stripping hexagonal boron nitride (h-BN) using wet chemical reaction method. The hydroxylated structure of the surface and formation mechanism of BNNS were analyzed, and the optimal controlled conditions were explored by orthogonal test. The results showed that the content of N element in the center of the BNNS (46.44 at. %) is significantly higher than that of B element in the edge of the sheets (33.10 at. %), and the content of O element in the edge of the sheets is nearly 30% higher than that in the center. It indicates that the edge of the BNNS introduces more oxygen than h-BN, the nitrogen atoms at the edge are replaced by oxygen atoms to achieve hydroxylation. When the mass ratio of h-BN and potassium permanganate is 1 g: 5 g, the reaction time is 9 h, and the reaction temperature is 60 °C, the obtained nanosheets have the best hydroxylation and good stripping effect. The average lateral size of the exfoliated nanosheets is 123 nm and only about three layers. [ABSTRACT FROM AUTHOR]

It has been shown that combining 2D materials in vertical or lateral heterostructures can significantly change and improve their electronic properties, making them more applicable for various purposes, e.g., nanoelectronics, spintronics, energy storage, catalysis etc. In this paper, we employ first principle calculations to investigate the influence of Li adsorption on lateral heterostructures composed of nanoribbons of graphene and hexagonal boron nitride. The results indicate the profound role of the nanoribbon interface. With respect to the sole graphene or boron nitride nanoribbons, Li atoms more strongly adsorb to their lateral interface due to the hybridization of electronic states. This leads to the severe changes in the electronic band structure. Our findings show that in the case of boron terminated zigzag nanoribbon interface, metallic character of the nanoribbon is changed upon Li adsorption. It opens an indirect bandgap of about 0.2 eV, showing that Li adsorption can be used for tuning electronic properties of the nanoribbons. [ABSTRACT FROM AUTHOR]

Boron nitride is a two-dimensional (2D) plate-like material with excellent thermal conductivity and lubricity. In this study, BN is introduced into Gutta-Percha (GP)/zinc oxide (ZnO) composites, and after orientation treatment, the GP@ZnO/BN composites with high TC and excellent fluidity are prepared. Moreover, the "skateboard effect" between BN plates and rod-like ZnO particles is proposed in this paper and confirmed, affording oriented GP@ZnO/5-BN lower shear viscosity (371.88 Pa·s) and higher thermal conductivity (1.65 Wm−1 K−1) than those of GP/ZnO composites. Specifically, in vitro experiments, with the assistance of the "skateboard effect," the lateral root canals filling depth (0.980 mm) of oriented GP@ZnO/5-BN composites exhibit 69.55, 49.62, and 49.16% deeper than that of commercial Bio Gutta-Percha points, MTWO Gutta-Percha points (VP), and PROTAPER universal Gutta-Percha points, respectively. Furthermore, the cytotoxicity level of the GP@ZnO/5-BN composites manifest 0–1 and the X-ray image of the GP@ZnO/5-BN composites depict similar radiopacity effect with DPP point, indicating that the oriented GP@ZnO/5-BN composites are safe and qualified as the commercial GP point materials. [ABSTRACT FROM AUTHOR]

Phonon polaritons in van der Waals materials show the strong electric confinement and low energy loss. Combining with the materials hexagonal boron nitride, hyperbolic phonon polaritons can be excited in two RS bands, which changes a lot in electric field distribution and transmission characteristics. In order to increase the tunability of hyperbolic phonon polaritons, a structure based on graphene/h-BN heterostructure has been formed in previous studies. In this paper, the electric field distribution and transmissivity characteristics are calculated and discussed based on grapheme–h-BN–graphene heterostructure. The results illustrate the excellent transmissivity tunability in 780 cm−1 incident wavenumber of type-I band and poor transmissivity tunability in 1368 cm−1 of type-II band. In addition, superior field-enhanced characteristic (115.76% transmissivity in 6 V external voltage) is shown in the structure. These excellent properties make such structure a promising component in future optoelectronic devices design. [ABSTRACT FROM AUTHOR]

This paper reports that a novel polyimide dielectric composite with three-dimensional (3D) thermally conductive networks and enhanced breakdown strength was firstly fabricated by filling with core-double-shell structured F-BA fillers. The F-BA particles were composed of nano-sized boron nitride (nBN) and polydopamine-coated spherical alumina (PDA@Al2O3). Moreover, to ameliorate interfacial compatibility between F-BA fillers and PI matrix as well as restrain phonons scattering during propagation, 1,6-Diisocyanatohexane (HDI) was innovatively used as "bridge agent" to connect and functionalize nBN and PDA@Al2O3 particles to generate core-double-shell structure. The results revealed that breakdown strength of PI dielectric composite with 25 wt % F-BA fillers was increased to 146.3 MV·m−1, showing an increment of 68.5% in comparison with that of pure PI. Furthermore, the thermal conductivity of F-BA/PI composite with 25 wt % F-BA fillers increases to 6.41 W/m·K of in-plane direction and 1.01 W/m·K of through-plane direction, respectively, which shows 36 and 6 times higher than polyimide of 0.18 W/m·K. For dielectric properties of F-BA/PI composite, the dielectric constant and loss are less than 3.5 and 0.02, respectively. Considering these properties, the prepared PI dielectric composite shows potential application in high-performance electronic devices. [ABSTRACT FROM AUTHOR]

In this paper, a novel type of micropore-rich boron nitride (BN) fibers (m-BNFs) was prepared by adding a surfactant hexamethylenetetramine in the traditional melamine-diborate (M·2B) precursor of conventional porous BN fibers (BNFs). As a result, extra micropore distribution could be introduced within m-BNFs bodies. Due to adding of the micropores, the CO2 capture capacities of the BN fibers were improved to be 2.85 mmol g−1, which were significantly higher than that of original porous BNFs. Also, these m-BNFs would have an enhanced adsorption capacity of methane, the amount of up to 0.71 mmol g−1. At the same time, these new m-BNFs materials showed excellent thermal stability, which would be more valuable for advanced gas adsorption working in a high-temperature environment in the future. [ABSTRACT FROM AUTHOR]

It is a great challenge for facile fabrication of thermal materials with both high thermal conductivity and excellent mechanical behaviors. Here, using tannic acid (TA) as a surface modifying agent, few-layer boron nitride nanosheets (BNNS) were effectively obtained by exfoliation of h-BN microplatelets through wet ball-milling. The existence of TA on the surface of BNNS also increased the dispersibility and stability in aqueous solution. By means of vacuum filtration of the dispersion of graphene oxide (GO) and BNNS, layered composite films of GO/BNNS were fabricated easily and at low cost. Because of the orderly orientation of GO and BNNS along the horizontal direction and high inherent thermal conductivity of the nanosheets used, a high in-plane thermal conductivity of 11.9 W/mK was reached with 80 wt% of BNNS. We also found that the thermal conductivity of the film could be further enhanced through adding 1.6 wt% PVA in the system to fill the voids between the nanosheets. The resulting composite film also exhibited excellent tensile strength of 41.0 MPa, flexibility potential for utilization on a curved surface, and electrical insulation up to 6.8 × 10 Ω cm. [ABSTRACT FROM AUTHOR]

Recent experiments with hexagonal boron nitride ( h-BN) have shown the successful covalent and non-covalent functionalization of these boron nitride nanostructures, especially nanosheets (BNNS). This paper explores the synthesis of several thiophene-based polymers with conjugated pendant groups and their reactions with BNNSs. Specifically, two phenyl carboxylic acid functionalized polythiophene polymers, poly[3-(4-methoxycarbonylphenyl)thiophene] and poly[3-(4-benzoic acid)thiophene], have been prepared and reacted with exfoliated BNNSs. The resulting complexes between the conjugated polythiophene polymers and the BNNS are reported and characterized by their reaggregation stability and by spectroscopic methods. [ABSTRACT FROM AUTHOR]

In this study, Boron Nitride Quantum Dots (BNQDs) are successfully synthesized via the hydrothermal method. Additionally, the hydrothermal method is employed to synthesize BNQDs decorated TiO2 nanograss (BNQDs/TiO2 NG) from BNQDs decorated TiO2 (BNQDs/TiO2). To validate the synthesis of different BNQDs samples, fluorescence spectroscopy (FL) is performed, revealing a strong quantum confinement effect resulting from variations in the precursor ratio. The bandgap energies of TiO2, BNQDs/TiO2, and BNQDs/TiO2 NG are determined using UV–Vis diffuse reflectance spectroscopy (UV-DRS), demonstrating a reduction in the band gap. A smaller band gap corresponds to a higher thermal conductivity, as there is a negative correlation between thermal conductivity and band gap energy. The study suggests that BNQDs/TiO2 NG exhibit higher thermal conductivity compared to TiO2 and BNQDs/TiO2. X-ray photoelectron spectroscopy (XPS) reveals the elemental composition of both BNQDs and TiO2, including Ti–O, B–N and B–O bonds. High Resolution Transmission Electron Microscopy (HR-TEM) is utilized to examine the morphological attributes of BNQDs/TiO2 NG. The crystalline structure of the synthesized composites is ascertained using X-ray diffraction (XRD). The photocatalytic degradation of methylene blue (MB) by TiO2, BNQDs/TiO2, and BNQDs/TiO2 NG under visible light is also compared. Based on the results, BNQDs/TiO2 NG is determined to be an effective material for treating wastewater containing organic dyes. [ABSTRACT FROM AUTHOR]

Perhaps the most defining feature of field-assisted sintering technology (FAST) is the application of an electric current, in addition to the uniaxial pressure, to create resistive heating in and around the sample region. However, with a few exceptions, most research takes this as an unchangeable part of the process. Here, this current flow has been directed to specific regions within the toolset, using boron nitride as electrically insulating material. This caused the heating to occur in differing regions within the Ti-6Al-4V sample and mould over four insulating configurations, with the shift in current density resulting in an extreme disparity in the final microstructures. The samples were imaged and analysed with deep learning in MIPAR, alongside comparisons with finite element analysis (FEA) models for 20 s and 5 min dwell times, to provide the technique with predictive capabilities for grain size and microstructure. The results gathered imply significant potential for this concept to improve the flexibility of FAST, and reduce negative effects such as undesirable temperature profiles in size scaling sintering for industry. [ABSTRACT FROM AUTHOR]

Spark plasma sintering (SPS) techniques have been intensively investigated for manufacturing of diverse materials. Numerous sintering methods have been researched to achieve a reduction of the sintering time, larger scale production, and significant energy savings. Usually, the traditional SPS methods need prohibitively high energy outputs to fabricate transparent ceramics. Previous studies showed that the SPS input power can be significantly decreased when an energy efficient configuration using a BN-coated graphite foils is used, but many samples obtained using this approach had cracks. The developed new thermally managed SPS (TM-SPS) results in the prevention of cracks, full densification, and uniform transparency in alumina. Furthermore, consumption is 17% lower in the developed new energy efficient SPS configuration compared to the traditional SPS configuration. Therefore, the developed TM- SPS method has potential for fabricating transparent ceramic of various materials with uniform transparency. A comprehensive three-dimensional fully coupled thermo-electro-mechanical finite element framework has been used for modeling the SPS with different energy configurations. [ABSTRACT FROM AUTHOR]

In recent years, various boron nitride (BN) based nanostructures have emerged as drug carriers for biomedical applications. Herein, the drug carrier potential of spherical BN nanoparticles was investigated with curcumin as a drug in the treatment of A549 lung cancer cells. Spherical boron nitride nanoparticles were synthesized in a single step by a nebulized spray pyrolysis (NSP) technique using boron trioxide [B2O3] and urea [CO (NH2)2] as precursors. Rietveld refinement revealed that the synthesized nanoparticles had hexagonal crystal structures with space group P63mc. The specific vibrational modes (B–N: 781 cm−1 and 1358 cm−1) and binding energy (B–N: 398.3 eV) confirmed BN formation. The NSP technique ensured that the nanoparticles had a spherical morphology with sizes in the range of 20–180 nm. Excellent curcumin encapsulation/loading efficiency was achieved and the bioavailability improved using a simple chemical surface modification of the BN nanoparticles. The cytocompatibility and cytotoxicity of the encapsulated BN nanoparticles in A549 lung cancer cells was evaluated in vitro using MTT assays. Further, the assessment of apoptosis in cells through flow cytometry confirmed that curcumin encapsulated BN nanoparticles showed significant A549 cell death, suggesting that BN nanoparticles can be a promising material as a drug carrier. [ABSTRACT FROM AUTHOR]

The problem of heat dissipation has become a key to maintain the operation state and extending the service time of electronic components. Developing effective thermal management materials and technologies is of great significance to solve this problem. Previously, passive cooling using phase change materials (PCMs) has been proposed as a thermal management method for electronic devices. In this work, a hybrid thermal management system coupling the heat storage of PCMs and the thermal conduction of high conductivity materials is designed toward thermal management of electronic devices. Specifically, ternary composite gels consisting of eicosane, styrene-ethylene-butylene-styrene (SEBS) and boron nitride (BN) are fabricated by liquid-phase blending and sol–gel transition toward the highly efficient thermal management of electronic devices. The van der Waals force between SEBS and eicosane and the π–π interaction between SEBS and BN enable the excellent form-stability of the ternary composite gels. Taking advantage of the merits of the functional components, the proposed ternary composite gels demonstrate a high thermal energy storage capacity of 157.5 Jg−1 and high thermal conductivity of 1.08 Wm−1 K−1. The ternary composite gels are applied in the thermal management of CPU and chip to reduce their working temperature via the synergistic effect of heat dissipation and heat storage. It is anticipated that the ternary composite gels create a state of the art alternative for the next-generation flexible and multifunctional thermal management devices. [ABSTRACT FROM AUTHOR]

The copper ion adsorption in wastewater treatment has gained increasing attention, which lies in the development of efficient adsorption materials. Herein, we demonstrated a novel class of macroscopic liquid-like three-dimensional (3D) graphene oxide (GO)-based derivatives for copper ion adsorption. To be specific, a supermolecular self-assembly process of GO in water induced by melamine and phytic acid, thus generating three-dimensional porous structural GO backbone. Then, the polyetheramine (M2070) and organosilane (KH560) were tethered via the covalent linkage, thus forming flexible oligomer species with silicon hydroxyl groups. Then, the oligomer species were attached to the surface of the GO backbone, yielding a novel class of black, homogenous GO-based derivatives. As expected, the liquid-like GO-based derivative presents the superior copper ion removal ability due to the synergistic effect of additions (melamine, phytic acid) and 3D porous structural backbone. More significantly, we presume that the rich libraries of organic oligomer species, together with other 2D nanosheets-based backbones (e.g., MXene, boron nitride, hydrotalcite, etc.), undoubtedly provide more convenience for the further construction of liquid-like 3D derivatives, eventually open a new era of advancing the development of novel adsorbents for heavy ions remove. [ABSTRACT FROM AUTHOR]

Supercapacitors appear to be attractive options for energy storage due to their high power density and lengthy cycling life. This work is focused on the design of reduced graphene oxide/hexagonal boron nitride (rGO/h-BN), via a hydrothermal method, as electrode materials for supercapacitor applications. Interestingly, the composite with rGO/h-BN 50:50 showed good capacity when compared to other ratios. Similarly, asymmetric supercapacitor devices were made up of rGO/h-BN and rGO as positive and negative electrodes, respectively, and nickel foam and stainless steel were used as a substrate. The nickel foam as substrate exhibits a high capacitance retention of 90% after 1000 cycles in a coin-cell configuration compared to stainless-steel substrate (71% after 500 cycles). Interestingly, a significant enhancement in the capacitance of Co3O4 was observed when incorporated with rGO/h-BN composite. The asymmetric supercapacitor made up of rGO/h-BN/Co3O4 delivered a good capacitance retention of 78% at 150 mA/g, after 5,000 cycles. As a result, h-BN/rGO-based composites with superlattice were synthesized using a hydrothermal approach as prospective materials for next-generation supercapacitor applications. [ABSTRACT FROM AUTHOR]

It is a long-term bottleneck to reasonably balance heat conduction and heat absorption for cost-effective thermal management applications. In the current study, a dual cooling polylactic acid (PLA) composite film was fabricated by subtly coating phase change materials of polyethylene glycol (PEG) onto the surface of thermally conductive fillers of hexagonal boron nitride (h-BN) (PEG@BN), where the thermal conductivity was greatly improved by decreasing the interfacial thermal resistance and the thermal transition of PEG was accelerated without any leakage. The thermal conductivity of (PEG@BN)/PLA at a low h-BN loading of 15.0 wt% was as high as 3.94 W m−1 K−1, which was enhanced by 87.6% and 1131.3% relative to uncoated PEG/BN/PLA and pure PLA, respectively. Meanwhile, the latent heat of (PEG@BN)/PLA at a PEG content of 20.0 wt% was 12.1 J g−1, exhibiting stable thermal performance. These results provide a paradigmatic strategy to develop dual cooling materials for efficient thermal management. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials like conventional graphene, hexagonal boron nitride (h-BN, monolayer), and transition metal dichalcogenides (2D TMDCs) have gotten a lot of attention lately because of their unparalleled possibilities for a variety of applications. MBenes, a family of two-dimensional (2D) transition metal borides, have recently attracted significant attention. Their elemental compositions, surface terminations, geometrical forms, and properties (chemical and physical) are unique and fascinating. These two-dimensional compounds hold promising potential for environmental applications because of their exceptional electrical conductivity, high hydrophilicity, rich surface chemistry, and outstanding stability. The newly discovered MBenes are incredibly stable, with isotropic and ultrahigh Young's modulus. Furthermore, MBenes have superior catalytic activity, optical and thermal properties. Given many potential MBenes, theoretical and experimental applications are expected soon. This review presents the synthetic approaches, properties (optical, thermal, mechanical, and electrochemical), and diverse applications of MBenes-based heterostructures. The numerous strategies for further investigation MBenes for applications in the energy sector (storage and conversion) are highlighted. [ABSTRACT FROM AUTHOR]

With the extensive use of high-power electronic appliances, polymer-based thermal insulation composites with excellent thermal properties are utilized in the field of heat management with the aim of improving heat dissipation. Due to the high thermal conductivity and good electrical insulation, boron nitride (BN) is rendered as a superior candidate material for thermally conductive fillers. However, the thermal conduction of the composites is inevitably hampered by the interfacial resistance between BN and the polymer matrix. In this work, BN surface was modified by dopamine hydrochloride (PDA) and phenyltrimethoxysilane to enhance its interface compatibility with the polymer matrix. Meanwhile, by applying pressure to the composites during processing, BN grains inside the composite were well aligned to the direction parallel to the heat flow, thereby improving the through-plane thermal conductivity. When the filler content is fixed at 31 vol%, the thermal conductivity of the phenyl silicone rubber (PVMQ)-based composite prepared from modified BN (mark as M-BN/PVMQ) reaches 1.642 W/(m·K), nearly equal to nine times the value for the pure PVMQ matrix (0.18 W/(m·K)). Furthermore, in a nitrogen atmosphere, the initial decomposition temperature (T5%) reaches 512 °C, 172 °C higher than that of pure PVMQ (340 °C). The improved thermal stability of the composites prepared from modified BN resulted from the enhanced interfacial effect, which was analyzed by thermogravimetric infrared gas mass spectrometry system (TG-IR-GC/MS). The high thermal conductivity and stability enable the M-BN/PVMQ composite a promising material for thermal management. [ABSTRACT FROM AUTHOR]

The erosion and wear of gun barrels have always been engineering problems that affect the operational effectiveness of weapons. First, this report briefly introduces the formation of net cracks and turtle cracks that occur on the bore surface during launch. Then, influencing factors, including thermal factors, chemical factors, and mechanical wear, are analyzed, as well as their control measures. Based on these factors, erosion-reducing additive materials are comprehensively discussed. First, the early development of ERAMs, such as polyurethane, TiO2, and talc, is reviewed. Then, current ERAMs are discussed; they include improved lining TiO2-paraffin materials, polysiloxane materials, life extension repair materials, boron nitride nanomaterials, microcapsule composite particles, multifunctional carbonates, nitrogen-rich compounds, rare earth oxides and other metal oxides. The above discussion covers chemical composition, preparation method, micromorphology, erosion-reducing performance, combustion completeness, and compatibility with propellant. In addition, the erosion-reducing mechanism and principles of formula design are discussed. Finally, comprehensive analysis shows that ERAM technology is an effective way to slow erosion and wear with high efficiency. [ABSTRACT FROM AUTHOR]

A dense silicon carbide matrix composite reinforced by Hi-Nicalon fibers CVD coated with boron nitride and silicon carbide was fabricated by slurry impregnation and subsequent reaction sintering with molten silicon. The effect of the structure and the thickness of the silicon carbide layer of the fiber coating on the mechanical properties of the composite were investigated. That is, three types of silicon carbide layers, namely a dense structure with a thickness of 0.15 μm and two porous structures with a thickness of 0.15 μm and 0.48 μm, respectively, were investigated. As a result, excellent strength property of ceramic matrix composite (CMC) was obtained in the case of the dense silicon carbide (SiC) layer. The thickness effect of the SiC layer on the strength was smaller than that of the structure. [ABSTRACT FROM AUTHOR]

Highly flexible biocompatible materials that are both thermally conductive and electrically insulating are important for implantable and wearable bioelectronics applications. The ability to thermally process these materials into useful structures using additive manufacturing approaches opens up new opportunities for its use in bespoke structures. Here we investigate the three-dimensional (3D) printing of a medical-grade thermoplastic polyurethane (PU) elastomer, which is thermally insulating and enhance its thermal and mechanical properties through the incorporation of boron nitride (BN) as a filler. Via a simple solution compounding approach, a highly flexible and thermally conductive BN nanoparticle/ PU composite has been developed and subsequently processed into simple bio-scaffolds structures via a 3D pneumatic melt extrusion printing process. The addition of up to 20% w/w of BN to the PU significantly enhances the tensile modulus by 659%, from 1.74 to 13.2 MPa, while supporting high mechanical flexibility. The thermal conductivity of 20% w/w BN/PU composite increases by 74% with respect to the unmodified PU. The 3D printed BN/PU composite scaffolds exhibit good biocompatibility and cell attachment enhancement with L929 fibroblast cells. [ABSTRACT FROM AUTHOR]

Highly thermally conductive but electrically insulating polymer composites play an increasingly important role in thermal management applications due to their features of easy processing and lightweight. Herein, a unique segregated network, which consists of graphene nanoplatelets (GNP) and boron nitride fibers (BNF), was constructed in polypropylene (PP)-based composites via two-screw extrusion. The thermal conductivity and electrical insulation characteristic of the composites could be well controlled by adjusting the content and size of GNP and BNF. When PP was filled with 9wt% GNP and 30wt% short BNF, the highest thermal conductivity of 1.32 W/(m·K) was achieved in this work, which is about six times higher than the value of neat PP, while remained a good electrical insulating (as low as 2.98 × 10−9 S/m). It proposed that the unique segregated network, where the BNF play as a bridge to connect the scattered GNP, could benefit for phonons transmission but effectively interrupt electron conduction. Our work provides a facile method to design and fabricate the highly thermally conductive but electrically insulating composites applied in thermal management materials. [ABSTRACT FROM AUTHOR]

Functionalization of boron nitride (BN) materials with hydroxyls has attracted great attention to accomplish better performances at micro- and nanoscale. BN surface hydroxylation, in fact, induces a change in properties and allows expanding the fields of application. In this review, we have summarized the state-of-the-art in developing hydroxylated bulk and nanoscale BN materials. The different synthesis routes to develop hydroxyl BN have been critically discussed. What emerges is the great variety of possible strategies to achieve BN hydroxylation, which, in turn, represents one of the most suitable methods to improve the solubility of BN nanomaterials. The improved stability of BN solutions creates conditions for producing high-quality nanocomposites. Furthermore, new interesting optical and electronic properties may arise from the functionalization by OH groups as displayed by a wide range of both theoretical and experimental studies. After the presentation of the most significant systems and methodologies, we question of future perspective and important trends of the next generation BN materials as well as the possible areas of advanced research. Hydroxyl functionalization of boron nitride materials is a key method to control and enhance the properties and design new functional applications. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HA) is an ideal bone insert material due to its biocompatibility and osteoconductivity, but the poor mechanical properties limit its wide application in clinical practice. The aim of this work is to fabricate a novel composite that with similar porous structure to cortical bone and high mechanical properties by the addition of boron nitride (BN) and sintered in air at 1250 °C for 40 min. In mechanical properties, the maximum flexural strength, elastic modulus and fracture toughness are 94.04 MPa, 69.46 GPa and 1.16 MPa m1/2, respectively, which are improved by 20.56%, 12.87% and 8.41%, respectively. In the microscopy of surface and fracture surface, the porous structure similar to cortical bone is observed. There are microscale and nanoscale pores, and the pores present an interconnected structure. In vitro biocompatibility assessment, the addition of BN and its reaction product have no adverse effect on osteoblast viability, which even promotes osteogenic differentiation and mineralization. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitride nanosheets (h-BNNSs) are known to exhibit numerous prominent performances. However, scalable synthesis of h-BNNSs with a green, simple method has been difficult to achieve. In this study, xylitol-assisted discontinuous ball milling exfoliation (XADBME) of hexagonal boron nitride (h-BN) was proposed as a novel strategy for scalable synthesis of h-BNNSs. First, the high yield (above 80 wt%) could be achieved smoothly with this green chemistry method. Moreover, the as-synthesized h-BNNSs exhibited large lateral size, ultra-thin, defect-free. Lastly, the as-synthesized BNNSs and cellulose nanofibers (CNFs) were compounded to form a series of membrane materials. The mentioned membranes exhibited high in-plane thermal conductivity and prominent UV absorption characteristics. 70 wt% BNNS membrane [3.4 W(mK)−1] exhibited nearly 400% higher in-plane thermal conductivity than that of membrane without BNNS [0.7 W(mK)−1]. Thus, it shows promising applications in thermal management of electronic display screens, eye protection equipment, as well as portable mobile devices. [ABSTRACT FROM AUTHOR]

In spite of the outstanding properties of boron nitride nanosheets (BNNSs), their applications may be limited due to counterproductive effect of the unavoidable defects in their structure. As such, tailoring the performance of these 2D nanostructures through defect engineering is of crucial importance. In this regard, we have probed the mechanical and thermal properties of defective BNNSs containing randomly distributed atomic vacancies and patterned point defects. For this purpose, molecular dynamic (MD) simulation is carried out to quantitatively explore the stress–strain response of the designed models under the uniaxial tensile loading. Additionally, thermal conductivity of the samples is examined by means of the non-equilibrium MD approach. The results indicate that only 2% of randomly distributed atomic vacancies would decrease both the Young modulus and thermal conductivity of BNNS by 13.7 and 44%, respectively. Furthermore, it is deduced that in addition to the defects content, their arrangement has also noticeable effects on the mechanical and thermal features of this 2D nanostructure. At the same defect content of 2.5%, it is shown that the presence of line defects transverse to the loading direction has the most damaging effect on the BNNS Young's modulus (i.e., 19.1%). This reduction is found to be 16.9 and 9.3% for the cases having randomly distributed vacancies and defects oriented parallel to the axial direction, respectively. Similar trend is also reported for the thermal conductivity of the defected structures. Moreover, to address the synergistic effects of mono-atomic vacancies, mechanical response of the BNNS samples containing double vacancy with different distances is thoroughly examined. In comparison with graphene, BNNS demonstrates to be less influenced by the defects and, therefore, is a potential candidate in applications such as polymer-based composites and efficient thermal management. This work provides some guidelines on promoting the BNNS multi-functional capabilities thorough its defect engineering. [ABSTRACT FROM AUTHOR]

Glass transition temperature (Tg) is important for the application of shape memory polymers (SMPs), and here shape memory polyimide (SMPI) with high Tg of 363 °C is reported. High shape recovery speed can improve reliability performance of SMP, and the introduction of modified boron nitride (M-BN) nanoparticles into SMPI matrix can enhance the recovery speed obviously. The faster recovery speed is mainly caused by the increase in thermal diffusivity, which enhances from 0.147 mm2 s−1 for primitive SMPI to 0.190 mm2 s−1 for the composite with 10% M-BN (SMPI/10% M-BN). Anti-wear capability is important for service life and performance reliability of materials, and wear rate decreases from 7.5 × 10−9 g N−1 r−1 for primitive SMPI to 0.83 × 10−9 g N−1 r−1 for SMPI/10% M-BN. The enhanced anti-wear capability is ascribed to high hardness, self-lubricating property and thermal conductivity of BN. Wear mechanism is studied, and it evolves from adhesive and fatigue wear for primitive SMPI to slight adhesive wear for SMPI/10% M-BN. [ABSTRACT FROM AUTHOR]

Boron nitride nanotubes (BNNTs) are one-dimensional dielectric and piezoelectric nanomaterials with non-cytotoxic properties and superb chemical and thermal stabilities. Regarding practical applications, a flexible, nanoporous, self-assembled film is one of the most low-cost usable structures. Here, we reveal a unique nanocatalyst-assisted ink spray coating method to synthesize 4.69-eV optical bandgap NTs and an easy mechanical peeling method to obtain an attractive nanoporous freestanding NT thin film with high flexibility and 91.45% porosity. Importantly, the piezoelectric d33 coefficient of the 90-nm-radius NT is 41.12 pm V−1, more than triple the value reported previously, due to the inner bamboo structure, and this coefficient is a function of radius. The nanoporous bamboo-type NT film shows excellent dielectric properties, with a relation dielectric constant of 5.15 and a dielectric constant of 9.78 for the solid type (ignoring air), which is more than triple the value of the cylindrical type. Moreover, the capacitance loss and electrical conductance versus frequency have great potential for a dielectric layer under high-frequency capacitance. Hence, bamboo-type BNNTs and their films can reasonably be widely applied in flexible electronic devices, high-precision piezoelectric sensors, and intelligent bioelectronic devices in harsh environments. [ABSTRACT FROM AUTHOR]

Within 40 min, hexagonal boron nitride (h-BN) was rapidly synthesized via microwave heating without using catalyst and protective gas. Melamine and boric acid were used as raw materials, and carbon fiber was utilized as microwave absorber, respectively. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM) were used to characterize the structures and morphologies of the samples. Results indicated that the whisker-like h-BN with diameters of 200–500 nm and lengths of 15–25 μm were successfully obtained. The specific surface area of the product was 510.941 m2 g−1. The maximum adsorption capacity for methylene blue solution of the as-obtained h-BN was high up to ~ 230 mg g−1 at room temperature. The excellent adsorption performance of the samples may be attributed to the oxygen-containing functional groups and defects formed during the high-energy microwave irradiation. [ABSTRACT FROM AUTHOR]

High thermal conductivity and high flame retardancy become necessary properties of thermally resistant thermosetting resins for many cutting-edge fields. However, building a phosphorus-free sustainable strategy is still a challenge; besides, sometimes high thermal conductivity and flame retardancy could not be simultaneously achieved, while sometimes they promote to each other, and no report focuses on explicating their relationship and mechanism. Herein, new resins with high thermal conductivity and greatly improved flame retardancy are developed through building phosphorus-free cross-linked network with three-dimensional porous framework based on boron nitride (BN) skeleton (sBN) and bismaleimide resin (BD). With the same loading of BN, sBN/BD has much higher thermal conductivity than the composite based on BN powders (BN/BD). For composites with 12.53 wt% of fillers (sBN or BN powders), the thermal conductivity of 5sBN/BD reaches 1.53 Wm−1 K−1, about 2.4 and 9.4 times of those of 5BN/BD and BD resin, respectively. The exploring relationship between flame retardancy and thermal conductivity shows that sBN/BD composites are somewhat easier to be ignited, and the flame propagation is faster, but under continuous heating, sBN/BD has much weaker burn strength and fewer smoke releasing compared with BN/BD. 5sBN/BD has about 51.9%, 47.5%, 42.5% and 54.8% lower peak heat release rate, total smoke release, specific extinction area and maximum smoke density than BD resin, respectively. The mechanism behind these interesting results is intensively discussed. [ABSTRACT FROM AUTHOR]

Double-network (DN) hydrogel which possesses many superior performances such as excellent toughness, viscoelasticity and self-healing ability has become promising biomaterials. However, lack of thermal conductivity and moderate adhesiveness has greatly limited their application as load-bearing cartilage substitutes. Boron nitride itself has good rigidity and thermal conductivity but poor water solubility. Hydroxylated boron nitride nanosheets (OH-BNNSs) which have been previously reported have good water solubility (~ 0.6 mg/mL) and to obtain a homogeneous and stable dispersion. In this work, we introduced OH-BNNS into DN hydrogel to obtain high thermal conductivity and toughness hydrogel. The DN hydrogel is a class of physically double-network hydrogel with hydrophobic association polyacrylamide (PAM) and partly crystalline polyvinyl alcohol (PVA). Impressively, the obtained PVA/PAM/BNNS composite hydrogel possesses super-flexibility, high toughness, good thermal conductivity, appropriate tissue adhesiveness and stimuli-free self-healing ability. Therefore, the composite hydrogel overcomes the poor mechanical strength and locally overheating issues as cartilage substitutes and may also become alternatives for antipyretic pastes. [ABSTRACT FROM AUTHOR]

In this study, the microstructural development and its effect on the thermal conductivity of polyamide/cyclic olefin copolymer (PA/COC) blends containing boron nitride (BN) particles were investigated. The co-continuous morphology of the BN-filled composites was confirmed by SEM images. The composite samples were prepared by a masterbatch method in order to localize the BN particles in the PA phase. The melt viscoelastic results have shown a liquid-solid transition at low-frequency range, indicating a three-dimensional percolated microstructure. However, the results have not shown a pronounced percolation in the thermal conductivity. These results have suggested that the sensitivity of the thermal conductivity of these composites to percolated microstructure is not as strong as the rheological behavior. A comparison made between the BN-filled PA and the blend composites with co-continuous morphology revealed a lower thermal conductivity for the PA-BN/COC compared to the PA/BN composites with the same BN concentration. Moreover, the values of thermal conductivity for the blend composites were found to be comparable with those predicted by a combination of Nielsen’s model (for filled polymers) and Wang’s model introduced for blends with co-continuous morphology. [ABSTRACT FROM AUTHOR]

Using laser surface modification, coatings of stainless steel 316 (SS316) alloy with 5 weight % hexagonal boron nitride (BN) were processed and then subjected to various tests to determine whether altering surface chemistry and microstructures via laser passes could enhance the mechanical performance of the coating. X-ray diffraction (XRD), scanning electron microscopy, Vickers hardness, and wear tests were used to characterize the coatings. It was hypothesized that the introduction of BN and modifying microstructures would influence hardness and wear resistance. The substrate was used as a control with a hardness of 178 ± 13 HV and a wear rate of 2.30 ± 0.04 × 10 mm/Nm. The addition of laser passes on the substrate slightly reduced wear rates while increasing hardness values by at least 12%. However, the addition of 5 wt% BN with no laser passes increased surface hardness by 85% to 329 ± 17 HV and reduced the wear rate by 38% to 1.43 ± 0.02 × 10 m/Nm. Modifying the composite's surface with one additional laser pass increased the surface hardness by 78% to 316 ± 6 HV and decreased the wear rate by 51% to 1.13 ± 0.01 × 10 mm/Nm. Two laser passes increased the composite's surface hardness by 71% to 304 ± 6 HV and decreased the wear rate by 55% to 1.04 ± 0.02 × 10 mm/Nm. Grain sizes were smaller in the coating when compared to the substrate and exhibited congruency at the coating-substrate interface. XRD analysis confirmed a major phase of austenitic stainless steel in the coating while containing a small amount of minor phase hexagonal BN. Our results indicate that both BN reinforcement and laser processing parameters can positively influence surface properties of these structures. [ABSTRACT FROM AUTHOR]

The influence of BN on the mechanical properties of carbon fibers was investigated. It is found that the Young's modulus of the derived carbon fibers becomes higher with BN amounts increasing through heat treatments at 1600-2350 °C, while the tensile strength increases at 1600 and 2000 °C and decreases at 2200 and 2350 °C with BN amounts increasing. Carbon fibers' modulus and strength are increased by 6.6 and 7.4 % at maximum, respectively. It can be interpreted that fiber modulus is mainly determined by the preferred orientation of graphene planes and the shear modulus between them, while the strength of carbon fibers strength is determined by not only the two factors but also defects. Through X-ray diffraction, Raman spectra, and scanning electron microscope analysis, it is noted that BN catalysis enhances the preferred orientation of graphene planes and makes little change on the shear modulus but generates more defects above 2000 °C for fierce reaction. [ABSTRACT FROM AUTHOR]

Absorption and scattering properties of pyrolytic boron nitride (pBN) have been characterized by infrared spectroscopy. The strong dielectric anisotropy predicted by first principles calculations is confirmed by measurements performed on a highly oriented pBN sample. Optical properties of textured samples elaborated by chemical vapor deposition were identified from normal hemispherical reflectance and transmittance spectra by applying modified two-flux and four-flux transport models. It is also shown that coating carbon-carbon composites used to build solar shields with a pBN layer having an optimal thickness could improve the protection performance. [ABSTRACT FROM AUTHOR]

The straightforward non-covalent functionalization and solubilization of hexagonal boron nitride nanosheets (BNNSs) has been achieved by reacting either polythiophene or polyvinylpyrrolidone polymers with exfoliated BNNSs. The BNNSs apparently form strong π-π stacking interactions with the polymers to yield stable derivatized nanosheets with modified properties. A number of polythiophene polymers functionalized with carboxylic acid groups that are connected to the thiophene subunit by varying numbers of CH2-hydrocarbon linker units have also been tethered to the exfoliated BNNSs. These BNNS-polythiophene-(CH2 )n -COOH structures have been further coordinated to pre-formed TiO2 nanoparticles to form more complex BNNS-polythiophene-(CH2)n-COO-TiO2 hybrid nanomaterials through covalent binding between the TiO nanoparticle surface and the carboxylic acid functional group of the BNNS-polythiophene unit. These novel structures have been characterized by SEM, TEM, FTIR, UV-Vis, and other spectroscopic data. [ABSTRACT FROM AUTHOR]

We report on spectroscopic study of pyrolytic hBN (pBN) by means of time- and energy-resolved photoluminescence methods. A high purity pBN samples (though low crystallinity) allow complementary information about excited states involved into the luminescence process. We affirm our recent conclusions about the impurity-related nature of most of fluorescence bands in microcrystalline hBN. In addition, a broad band centred at 3.7 eV previously not considered because of its superposition with an intense structured impurity emission is attributed to the radiative recombination of deep DAPs. [ABSTRACT FROM AUTHOR]

Multi-walled boron nitride (BN) nanotubes having cylindrical structure were synthesized employing the mechanothermal process. In this process hexagonal boron nitride powder (hBN) was first ball milled for 50–100 h using a high-energy ball mill and the ball-milled samples were annealed in N2 atmosphere for about 10 h in the temperature range of 950–1300 °C. The BN nanotubes exhibited a well-crystallized hexagonal structure with about 25–40 nm in diameter and up to 1 μm length. These BN nanotubes were well characterized using various techniques, such as, XRD, SEM, TEM and Raman Spectroscopy. [ABSTRACT FROM AUTHOR]

The thermal stability of polyol-ester-based thermal pastes is evaluated by weight loss, viscosity and thermal contact conductance measurements. A high degree of thermal stability has been attained by using a half-hindered phenolic primary antioxidant and a thiopropionate secondary antioxidant. By using either carbon black or boron nitride particles as the solid component, a thermally conductive paste with a high degree of thermal stability has been attained. The antioxidants cause the residual weight (excluding the solid component) after oven aging at 200 °C for 24 h to increase from 36 to 97 wt.%. They cause the viscosity not to increase upon heating and they reduce the thermal cracking tendency. They do not affect the thermal contact conductance measured across mating surfaces that sandwich the paste. The use of a fully-hindered phenolic primary antioxidant is less effective. Both carbon black and boron nitride serve as antioxidants in the presence of either primary antioxidant or secondary antioxidant at 200 °C, though, in most cases, they degrade the thermal stability in the presence of both primary and secondary antioxidants, particularly at 220 °C. Below 180 °C and in the presence of primary and secondary antioxidants, boron nitride is particularly effective in promoting the thermal stability. Boron nitride paste shows an estimated lifetime of 19 years at 100 °C, compared to 1.3 years for the carbon black paste, and 0.10 year for commercial polyol-ester-based Arctic Silver 5. Carbon black paste has a lower tendency for cracking after heating than boron nitride paste, due to the low volume fraction of the solid component. [ABSTRACT FROM AUTHOR]

Formation of hexagonal boron nitride by carbothermic reduction of boric oxide under nitrogen atmosphere at 1500 °C was investigated. Experiments were performed for durations in the range of 15 min to 3 h. Reaction products were subjected to powder X-ray diffraction analysis, chemical analysis and were examined by scanning electron microscope. Formation of hexagonal boron nitride was found to be complete in 3 h with most forming in the initial 2 h. Boron carbide was found to exist in the reaction products of the experiments in which hexagonal boron nitride formation was not complete. The aim of this study was to investigate the role of boron carbide in the carbothermic production of hexagonal boron nitride. For this purpose, conversion reaction of boron carbide into hexagonal boron nitride was studied. Boron carbide used in these experiments was produced in the same conditions that hexagonal boron nitride was formed, but under argon atmosphere. It was found that formation of hexagonal boron nitride from boron carbide—boric oxide mixtures was slower than activated carbon—boric oxide mixtures. It was concluded that boron carbide is not a necessary intermediate product in the carbothermic production of hexagonal boron nitride. [ABSTRACT FROM AUTHOR]

The second and third order elastic constants and pressure derivatives of second order elastic constants of hexagonal boron nitride have been obtained using the deformation theory. The strain energy derived using the deformation theory is compared with the strain dependent lattice energy obtained from elastic continuum model approximation to get the expressions for second and third order elastic constants. Higher order elastic constants are a measure of anharmonicity of crystal lattice. The six second-order elastic constants and the ten non-vanishing third order elastic constants and six pressure derivatives of hexagonal boron nitride are obtained in the present work and are compared with available experimental values. The second order elastic constant C11 which corresponds to the elastic stiffness along the basal plane of the crystal is greater than C33. Since C33 being the stiffness tensor component along the c-axis of the crystal, this result is expected from a layer-like material like boron nitride (BN). The third order elastic constants of hexagonal BN are generally one order of magnitude greater than the second-order of elastic constants as expected of a crystalline solid. The pressure derivative d C33/d p obtained in the present study is greater than d C11/d p which indicates that the compressibility along c-axis is higher than that along ab-plane of hexagonal BN. [ABSTRACT FROM AUTHOR]

Batch to batch and within batch variations, and the influence of fiber architecture on room temperature physical and tensile properties of BN/SiC coated Hi-Nicalon and Sylramic SiC fiber preform specimens were determined. The three fiber architectures studied were plain weave (PW), 5-harness satin (5HS), and 8-harness satin (8HS). Results indicate that the physical properties vary up to 10 percent within a batch, and up to 20 percent between batches of preforms. Load-reload (Hysteresis) and acoustic emission methods were used to analyze damage accumulation occurring during tensile loading. Early acoustic emission activity, before observable hysteretic behavior, indicates that the damage starts with the formation of nonbridged tunnel cracks. These cracks then propagate and intersect the load bearing “0°” fibers giving rise to hysteretic behavior. For the Hi-Nicalon preform specimens, the onset of “°” bundle cracking stress and strain appeared to be independent of the fiber architecture. Also, the “0°” fiber bundle cracking strain remained nearly the same for the preform specimens of both fiber types. TEM analysis indicates that the CVI BN interface coating is mostly amorphous and contains carbon and oxygen impurities, and the CVI SiC coating is crystalline. No reaction exists between the CVI BN and SiC coating. [ABSTRACT FROM AUTHOR]

Analytical electron microscopy was carried out on BN-coated 125 μm single crystal Al2O3 fiber reinforced NiAl matrix composites fabricated by diffusion bonding. NiAl was observed to react with BN to form a layer of AlN with a thickness of about 100 nm at the NiAl/BN interface during fabrication of the composite. The BN layer, deposited on Al2O3 fibers using chemical vapor deposition, exhibited a turbostratic structure with {002} planes of BN showing highly preferred orientation. Perfect bonding was obtained at the BN/Al2O3 interface with the BN {002} basal planes locally parallel to the surface of Al2O3. [ABSTRACT FROM AUTHOR]

X-ray powder diffraction and quantitative texture analysis have been employed to study the crystallographic relation of parent and product phases in direct transformations of graphite-like BN polymorphs into diamond-like BN phases at a pressure of 7.7 GPa and temperatures up to 2600 K. It has been found that the transformation of both CVD-produced bulk slightly textured turbostratic BN (tBN) and highly textured graphite-like hexagonal BN (hBN) results in a preferred orientation of the crystallites of the new cubic BN (cBN) due to the (111)cBN ∥ (001)tBN, hBN epitaxial relation. Phase transformation of a CVD-produced bulk highly textured rhombohedral BN (rBN) results in the formation of highly textured wurtzitic BN (wBN) according to the (100)wBN ∥ (001)rBN crystallographic relation. [ABSTRACT FROM AUTHOR]

Boron nitrogen (BN) films with the different cubic phase content were deposited on Si and fused silica substrates by radio frequency bias sputtering from a hexagonal BN target by using a two-stage deposition process. The BN films were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and UV-visible transmittance and reflection measurements. The optical absorption coefficient α and the refractive index n were calculated from the transmittance and reflection spectra. With increasing the c-BN content the absorption edge shifts to the higher energy, indicating that the optical band gap of the BN films increases with cubic BN content. The optical absorption behavior of BN films shows characteristics of amorphous materials. The dependence of α on the photon energy was fitted by the Urbach tail model and the band-to-band transition model at the two different energy regions, and the optical band gap of the BN films were obtained from the fits. In addition, the refractive index indicates obvious difference for the BN films with different cubic phase content. [ABSTRACT FROM AUTHOR]

The changes in nucleation behaviour upon addition of Boron Nitride (BN), Talc and Hydroxyapatite (HA) to poly( p-dioxanone) (PPDX) were monitored by DSC and Polarised Optical Microscopy (PM). Self-nucleation DSC studies evidenced the existence of the usual three self-nucleation domains depending on the self-nucleation temperature ( Ts) employed. By far the best nucleation agents for PPDX were its own self-nuclei and this result was independent of the presence or absence of any of the other nucleating agents employed; once Domain II was reached, self-nucleation dominated the nucleation process. BN and Talc were able to nucleate PPDX, thereby increasing its nucleation density, its dynamic crystallisation temperature upon cooling from the melt ( Tc) and its enthalpy of crystallisation (Δ Hc). BN was a better nucleating agent than talc. HA on the other hand caused an “antinucleation” effect on PPDX characterised by a decrease in its nucleation density, a decrease in its Tc and in Δ Hc. Isothermally crystallised PPDX exhibited large banded spherulites whose morphology changed as a function of crystallisation temperature from single banded structures with a very clear Maltese cross to double banded spherulites. PPDX also shows a change in growth regime upon increasing crystallisation temperature (from Regime III to Regime II) according to the kinetic interpretation of growth rate data. BN did not cause any significant modification of the spherulitic growth kinetics (in Regime II) except for a small decrease in surface free energy of PPDX crystals (σe). On the other hand HA was found to increase the spherulitic growth rate and the overall crystallisation rate of PPDX, this increase was caused by a degradation process experienced by the polymer during the treatments involved in isothermal crystallisation that was only present in the samples with HA. It is postulated that the interaction between the phosphate groups on the surface of HA and the ester groups of PPDX are responsible for both the antinucleation effect and the catalysis of the hydrolytic degradation of PPDX. [ABSTRACT FROM AUTHOR]

A transmission electron microscope study has been made of a silicon nitride component with 6 w/o yttrium oxide as a sintering aid hot isostatically pressed (HIP) with an encapsulation glass of borosilicate. The TEM study concentrated on the interface region between ceramic and glass. Two different types of hexagonal boron nitride were formed near the interface. One, with a textured structure, seemed to nucleate heterogeneously on the surfaces of silicon oxynitride grains. The (001) planes of the crystals extended outwards, giving a thickness of approximately 0.5 microns. The other type formed as hexagonally shaped grains separate from the first type and appeared to have grown as several segments in different directions around a nucleus. In each segment BN layers are parallel to each other and perpendicular to their common [001]BM direction. This second type of BN crystal was also detected a little further from the surface within the silicon nitride. The volume fraction of additive glassy phase tended to be lower in this surface region than in the bulk. Possible mechanisms of prevention of encapsulation glass penetration into the porous ceramic component during HIP were discussed. [ABSTRACT FROM AUTHOR]

Mechanical properties of high purity polycrystalline cBN sintered bodies synthesized by the direct conversion method under high pressure and high temperature have been investigated by hardness and transverse rupture strength (TRS) measurement in the temperature range of 20–1200 °C. It was confirmed that the hardness and TRS of the polycrystalline cBN depends strongly on the cBN grain size and the amount of residual (compressed) hBN in the sintered body. The fine-grained (<0.5 μm) and high purity (cBN > 99.9%) polycrystalline sintered body synthesized at 7.7 GPa, 2200–2400°C has highest hardness and TRS at any temperature. The TRS of the sintered body shows a positive temperature dependence up to 1200 °C. The high hardness and high TRS at high temperature of the fine-grained high purity polycrystalline cBN suggest that the sintered body has high potential in cutting tool uses. [ABSTRACT FROM AUTHOR]