Modifications Of Boron Nitride Research Articles

Achieving ultrahigh hole mobility in hydrogen-terminated diamond via boron nitride modifications

Wide-bandgap semiconductors with high carrier mobility are in great demand for high-power radio-frequency applications. In the past decades, extensive efforts have been devoted to investigating the carrier transport properties of hydrogen-terminated diamond (H-diamond), however, achieving its high hole mobility remains a challenge, thereby limiting the development of diamond electronic devices. Herein, we propose a novel strategy to increase the hole mobility of H-diamond by boron nitride (BN) clusters modifications. Amorphous BN clusters were deposited on high-quality H-diamond surfaces using magnetron sputtering. The modified H-diamond exhibits an ultrahigh hole mobility of 1100 cm2 V−1 s−1, over 10-fold higher than that of H-diamond prior to BN modification. Moreover, the BN-modified H-diamond also exhibits outstanding high-temperature tolerance and excellent thermal stability benefitting from the passivation effect of BN. At 380 K, it still maintains a hole mobility of 385 cm2 V−1 s−1. Even after annealing at 350 K for over 8 h, there are no noticeable variations in its carrier transport properties. The hole mobility enhancing mechanism and the factors influencing carrier transport properties of the BN-modified H-diamond are discussed using first principles calculations analysis. The developed BN-modified H-diamond opens up new possibilities for diamond-based radio-frequency electronic devices operating in challenging temperature environments.

Synchronously enhancing thermal conductivity and dielectric properties in epoxy composites via incorporation of functionalized boron nitride.

Polymer-like dielectrics with superb thermal conductivity as well as high dielectric properties hold great promise for the modern electronic field. Nevertheless, integrating these properties into a single material simultaneously remains problematic due to their mutually limited physical connotations. In this study, we developed high-quality thermally conductive epoxy composites with excellent dielectric properties. This was achieved by incorporating surface-functionalized microscale hexagonal boron nitride (BN) along with N-[3-(Trimethoxysilyl)propyl]ethylene diamine (DN) and N-[3-(Trimethoxysilyl)propyl]aniline (PN). In the resulting epoxy composite, microscale BN serves as the primary building block for establishing the thermally conductive network, while silica particles act as bridges to regulate heat transfer and reduce interfacial phonon-scattering. The prepared composites were thoroughly examined across various filler contents (ranging from 10 to 80 wt%). Among them, the DNBN/epoxy composite exhibited higher thermal conductivity (in-plane: 47.03 W m-1 K-1) at 60 wt% filler content compared to BN/epoxy (39.40 W m-1 K-1) and PNBN/epoxy (33 W m-1 K-1) composites. These results highlight the usefulness of surface modification of BN in improving compatibility between fillers and epoxy, ultimately reducing composite viscosity. Furthermore, the DNBN/epoxy composite at 60 wt% demonstrated superb dielectric constant (∼6.15) without compromising on dissipation loss (∼0.06). The strategy adopted in this study offers significant insights into designing dielectric thermally conductive composites with superior performance outcomes.

Enhanced flame retardancy of epoxy composites containing melamine polyphosphate‐modified boron nitride

AbstractSurface chemical modification of boron nitride could enhance the compatibility with polymers and improve flame retardancy performances. In this work, the double‐bond active sites were constructed on the surface of boron nitride modified by the γ‐methacryloyloxypropyl trimethoxysilane (KH570). Glycidyl methacrylate (GMA) was further grafted onto the surface of boron nitride via free radical polymerization. Finally, the flame retardancy melamine polyphosphate (MPP) was bonded to the surface of boron nitride by the ring opening reaction. This modification process was proved to be achieved by infrared spectroscopy and thermogravimetric test. The boron nitride modified by flame retardant were added into the epoxy matrix and cured to prepare flame retardant and thermal conductive composites. The flame retardant of the composites was studied by cone calorimetry, UL94 vertical combustion test and limiting oxygen index. The thermal conductivity of the composites was characterized by laser thermal conductivity instrument. The results showed that when the addition amount of flame retardancy MPP modified boron nitride in the composites was 20 wt%, the flame retardant rating of UL94 reached to V1; the limiting oxygen index was increased from 25.1 vol% of pure epoxy resin to 30.3 vol%; the PHRR of pure epoxy resin was reduced from 800 to 510 kW/m2 of composites; the thermal conductivity of the composites was enhanced from 0.21 W/m•K−1 of the pure epoxy resin to 0.82 W/m•K−1of the composites.

Polymer-Assisted Dispersion of Boron Nitride/Graphene in a Thermoplastic Polyurethane Hybrid for Cooled Smart Clothes.

The avoidance and mitigation of energy wastage have attracted increasing attention in the context of global warming and climate change. With advances in materials science, diverse multifunctional materials with high thermal conductivity have shown excellent energy-saving potential. In this study, a hybrid film exhibiting high thermal conductivity with excellent stretchability and washability was prepared. First, a simple surface modification of boron nitride (BN) was performed to realize a modified boron nitride (BNOH) filler. Next, an organic dispersant was synthesized to enhance the dispersion of BNOH and graphene nanoplatelets (GNPs) in the proposed composite. Subsequently, a simple procedure was used to combine the dispersed GNPs and BNOH fillers with thermoplastic polyurethane (TPU) to fabricate a hybrid structure. The hybrid films composed of BNOH–GNP/TPU with a dispersant exhibited a high thermal conductivity of 12.62 W m–1 K–1 at a low filler loading of 20 wt.%. This hybrid film afforded excellent stretchability and washability, as indicated by the very small thermal-conductivity reduction to only 12.23 W m–1 K–1 after 100 cycles of fatigue testing and to 12.01 W m–1 K–1 after 10 washing cycles. Furthermore, the cooling and hydrophobicity properties of the hybrid film were enhanced when compared with neat TPU. Overall, our approach demonstrates a simple and novel strategy to break the passive effect of traditional commercial cooling clothing by combining a high-thermal-conductivity film with an active cooling source to amplify the cooling effect and develop wearable cooled smart clothes with great commercial potential.

Improved Thermal Conductivity of Polymer Composites by Noncovalent Modification of Boron Nitride via Tannic Acid Chemistry

Improved Thermal Conductivity of Polymer Composites by Noncovalent Modification of Boron Nitride via Tannic Acid Chemistry

Enhanced thermal conductivity for polybenzoxazine matrix composites by constructing a hybrid conductive network and modification of fillers

Polyhedral oligomeric silsesquioxanes (POSS) and γ-glycidoxy propyl trimethoxy silane (KH560) were applied to modify boron nitride (BN) and boron nitride whisker (BNw), and modified BN (m-BN) and modified BNw (m-BNw) were added as thermally conductive fillers to polybenzoxazine (PBz) matrix to synthesize m-BN/m-BNw/PBz composite by hot press. The research results indicate that the modification of BN and BNw and the synergistic effect between m-BN and m-BNw can significantly improve the thermal conductivity of PBz composite. The thermal conductivity of PBz composite with 25 wt % m-BN and 25 wt % m-BNw reached to 1.27 W/mK, which is 35% higher than PBz composite with 50 wt % m-BN (0.94 W/mK), 76% higher than PBz composite with 50 wt % BN (0.72 W/mK), and also display excellent electrical insulation performance. The corresponding dielectric constant (ε) and dielectric loss (tan δ) were 3.83 and 0.0078, respectively. Besides, the Theat-resistance index (THRI) of PBz composite with 25 wt % m-BN and 25 wt % m-BNw is 242.26 °C, and the thermal degradation temperature at 30% weight loss (T30) is 557.72 °C, are higher than PBz matrix (224.46 and 498.88 °C). And the tensile strength of PBz composites with 25 wt % m-BN and 25 wt % m-BNw is 47.71 MPa.

Surface-modified boron nitride as a filler to achieve high thermal stability of polymer solid-state lithium-metal batteries

A polyethylene oxide composite polymer electrolyte with high thermal stability and mechanical strength was prepared via the modification of boron nitride. The modification was beneficial for the thermal conductivity, enhancing the thermal stability of the battery.

Особливості формування нанодисперсної зеренної структури в процесі РТ-спікання порошку гексагонального алмазу (лонсдейліту)

Results of an electron microscopic investigation of particles of lonsdaleite powder with additives of cubic diamond and polycrystalline specimens based on it at Р = 7,7 GPa in the temperature range 1700―1900 °С are presented. Lonsdaleite particles are characterized by a predominantly ternary texture [1120]l of different degree of perfection. Structural mechanisms of transformations in lonsdaleite particles, which cause the formation on nanograined structure in sintering, have been established. The initial stage is the mechanical dispersion of particles and dispersion as a result of plastic faulting deformation, which promotes their fragmentation without breakdown of continuity. The indicated processes lead to the destruction of texture in particles. Beginning from 1700 °С, the lonsdaleitecubic diamond phase transformation with the orientation ratio (111)dII (001)l occurs. It is realized within rods as elements of the substructure of lonsdaleite. At 1900 °С, the size of detected elements of the structure (grains) is 5―15 nm. Beginning from 2000 °С, the self-association of such grains into aggregates with sizes up to 70 nm and the subsequent process of coalescence of grains in aggregates with the formation of the monocrystalline state occur. The next stage of formation of the granular structure is caused by the formation of grain boundaries and development of collective recrystallization. After sintering at Т = 2100 °С, the grain size in specimens does not exceed 100 nm. It has been established that the transformation in lonsdaleite proceeds by structural mechanisms that are characteristic of wurtzite modifications of boron nitride and silicon carbide (strong disordering in the direction of the basal axis, plastic faulting deformation, and formation of multilayer polytypes during the hexagonal-to-cubic phase transformation). Keywords: lonsdaleite, particles, sintering, fragmentation, grains, coalescence.

Natural rubber composites with enhanced thermal conductivity fabricated via modification of boron nitride by covalent and non-covalent interactions

Hexagonal boron nitride (BN) platelets are often used as fillers to improve the thermal conductivity (λ) of polymer matrix composites thanks to their good insulation and relative high λ. However, the low compatibility between polymeric matrices and BN platelets results in interfacial phonon scattering, interfering with the composites' heat transfer. In this paper, functionalized BN platelets were first modified with poly(catechol/polyamine) (PCPA) and then grafted with bis-(γ-triethoxysilylpropyl)-tetrasulfide (Si69) to yield BN-PCPA-Si69/natural rubber (denoted as BN-PCPA-Si69/NR) composites. PCPA coating declined the interfacial phonon scattering between the matrix and fillers, while silane grafting improved the interfacial interaction via NR vulcanization with tetrasulfide bonds in Si69. In turn, these features led to improved dielectric characteristics, thermal conductivities, and mechanical properties. Among prepared samples, NR composite filled with 30% volume BN-PCPA-Si69 platelets content yielded a thermal conductivity 5.4-fold higher (λ = 0.81 W/mK) than that of neat NR (λ = 0.15 W/mK). The mechanical performances of BN-PCPA-Si69/NR composites also improved significantly with the maximum tensile strength reaching up 17.0 MPa. In sum, the proposed method looks inexpensive and feasible for the fabrication of high thermal conductive polymer composites for use in future advanced electronic devices, such as insulating and packaging electronic materials.

Casimir forces exerted by epsilon-near-zero hyperbolic materials

The Casimir force exerted on a gold dipolar nanoparticle by a finite-thickness slab of the natural hyperbolic material namely, the ortorhombic crystalline modification of boron nitride, is investigated. The main contribution to the force originates from the TM-polarized waves, for frequencies at which the parallel and perpendicular components of the dielectric tensor reach minimal values. These frequencies differ from those corresponding to the Lorentzian resonances for the permittivity components. We show that when the slab is made of an isotropic epsilon-near-zero absorbing material the force on the nanoparticle is larger than that induced by a hyperbolic material, for similar values of the characteristic parameters. This fact makes these materials optimal in the use of Casimir’s forces for nanotechnology applications.

Reduction Extraction Method for Determining the Enthalpies of Decomposition Reactions of Different Boron Nitride Modifications

Pulsed (7–10 sec) reduction extraction in a helium gas carrier stream has been used for the first time to determine the standard enthalpies and the internal energies of thermal dissociation reactions for various modifications of boron nitride (BN) with and without carbon. The temperature dependences of the weight content of nitrogen extracted from nanosized (4–10 nm) and microsized (<1; 4–5 μm) BN powders in the range 2100–4000 K with a step of ~200 ± 25 K have been established. Nitrogen extraction from layered BN modifications (graphene and graphite structures) begins at 2400–2500 K and reaches 100% at 3500 K. The thermal decomposition curve for nanoand micropowders of dense BN modifications (wurtzite and sphalerite structures) is similar to that for the layered modifications and is shifted toward the high-temperature region by 900 K. The standard enthalpies of decomposition reactions for different BN modifications have been determined: 231 kJ/mole for graphene-like, 249 kJ/mole for graphite-like, 296 kJ/mole forwurtzite-like, and 391 kJ/mole for sphalerite-like modifications.

Surface modification of boron nitride by bio‐inspired polydopamine and different chain length polyethylenimine co‐depositing

We established a novel, easy, and versatile method of obtaining diverse and controllable interphases between epoxy resin and fillers. The method involved the co‐deposition of polydopamine (PDA) and polyethyleneimine (PEI) with different molecular lengths on boron nitride (BN) surface. The obtained PDA/PEI‐modified BN composites showed significantly improved mechanical properties, including tensile strength, toughness, and elongation at break. For example, the tensile strength, fracture toughness, and elongation at break of EP composite increased by 51%, 132%, and 170% compared with EP when the PEI molecular weight was 10 000, respectively. These results suggested that the interphases between BN and EP matrix can be adjusted by changing the molecular lengths of grafted modifiers, thereby offering a new method for the reasonable designing and exploitation of the BN‐based composite materials.

Mussel-inspired modification of boron nitride for natural rubber composites with high thermal conductivity and low dielectric constant

Owing to the development of modern micro-electronic devices, polymer composites with high thermal conductivity and low dielectric constant have become increasingly important. Herein, a combination of covalent and non-covalent modification was used to functionalize boron nitride (BN) platelets via first deposition with poly(dopamine) (PDA) followed by grafting with γ-methacryloxypropyl trimethoxy silane (KH570) (denoted as BN-PDA-KH570). The as-prepared BN-PDA-KH570 platelets were incorporated into the natural rubber (NR) matrix to prepare thermal conductive composites. After modification with PDA-KH570, the BN platelets were uniformly dispersed into the NR matrix, which is beneficial for improving the thermal conductivity of NR. The interfacial thermal resistance of the composites was also reduced due to the stronger interfacial interaction via vulcanization of NR with double bonds in KH570. Thus, the NR composites filled with 30 vol% BN-PDA-KH570 platelets exhibited a relatively high thermal conductivity of 0.39 W/mK, which is about 1.5 times and 4 times of 30 vol% BN/NR composite (0.26 W/mK) and pure NR (0.10 W/mK), respectively. In addition, the BN-PDA-KH570/NR composites exhibited a low dielectric constant (3.51 at 100 Hz) and a low dielectric loss tangent (0.25 at 100 Hz), which holds promising applications as thermal management materials for electronic devices.

Thermal conductivity enhancement of polyimide films filled with BN and AlN fillers

A series of polyimide (PI) composite films were prepared using PI as matrix and boron nitride (BN) and aluminum nitride (AlN) as the doped phases. The modification of the thermal conductive filler particles was characterized by Fourier transform infrared (FTIR). The results showed that the silane coupling agent KH550 was successfully coated on the surface of BN and AlN. X-ray photoelectron spectrometer characterization was used to further prove that silane coupling agents were successfully attached to BN and AlN surfaces, forming a new chemical bond. Scanning electron microscope (SEM) was used to analyze the dispersion of filler particles in the matrix. It was found that agglomeration phenomenon occurred when the content of BN particles were high, but this problem was improved after the surface modification of BN. The breakdown field strength and volume resistivity of PI/BN composite film increased first and then decreased with the increase of BN content and reached the maximum when the volume fraction of BN was 5%, which was 191.53 kV/mm and 8.832 × 1013 Ω·m, respectively. When the BN content was 9 vol%, the thermal conductivity of the PI/BN composite film was 0.496 W/(m·K), which was 1.4 times larger than that of the pure PI film. The thermal conductivity of the PI/BN/AlN composite film at the BN and AlN contents of 5 vol% and 1 vol%, respectively, is 0.144 W/(m·K) higher than that of 7 vol% PI/BN. It indicated that the synergistic effect of the composite fillers played a significant role, and at the same time, under the premise of ensuring higher thermal conductivity, the amount of thermally conductive particles could be reduced to some extent. After the surface modification of the filler particles, the properties of the composite film showed the same trend compared with the unmodified one, while the only difference was that there was a certain increase in the numerical value.

Surface modification of boron nitride via poly (dopamine) coating and preparation of acrylonitrile‐butadiene‐styrene copolymer/boron nitride composites with enhanced thermal conductivity

A biology‐inspired approach was utilized to functionalize hexagonal boron nitride (h‐BN), to enhance the interfacial interactions in acrylonitrile‐butadiene‐styrene copolymer/boron nitride (ABS/BN) composites. The poly (dopamine), poly (DOPA) layer, was formed on the surface of BN platelets via spontaneously oxidative self‐polymerization of DOPA in aqueous solution. The modified BN (named as mBN) coated with poly (DOPA) was mixed with ABS resin by melting. The strong interfacial interactions via π‐π stacking plus Van der Waals, both derived from by poly (DOPA), significantly promoted not only the homogeneous dispersion of h‐BN in the matrix, but also the effective interfacial stress transfer, leading to improve the impact strength of ABS/mBN even at slight mBN loadings. A high thermal conductivity of 0.501 W/(m·K) was obtained at 20 wt% mBN content, reaching 2.63 times of the value for pure ABS (0.176 W/(m·K)). Meanwhile, the ABS/mBN composites also exhibited an excellent electrical insulation property, which can be expected to be applied in the fields of thermal management and electrical enclosure.

Work Function Characterization of Potassium-Intercalated, Boron Nitride Doped Graphitic Petals

This paper reports on characterization techniques for electron emission from potassium-intercalated boron nitride modified graphitic petals. Carbon-based materials offer potentially good performance in electron emission applications owing to high thermal stability and a wide range of nanostructures that increase emission current via field enhancement. Furthermore, potassium adsorption and intercalation of carbon-based nanoscale emitters decreases work functions from approximately 4.6 eV to as low as 2.0 eV. In this study, boron nitride modifications of graphitic petals were performed. Hexagonal boron nitride is a planar structure akin to graphene and has demonstrated useful chemical and electrical properties when embedded in graphitic layers. Photoemission induced by simulated solar excitation was employed to characterize the emitter electron energy distributions, and changes in the electron emission characteristics with respect to temperature identified annealing temperature limits. After several heating cycles, a single stable emission peak with work function of 2.8 eV was present for the intercalated graphitic petal sample up to 1000 K. Up to 600 K, the potassium-intercalated boron nitride modified sample exhibited improved retention of potassium in the form of multiple emission peaks (1.8 eV, 2.5 eV, and 3.3 eV) resulting in a large net electron emission relative to the unmodified graphitic sample. However, upon further heating to 1000 K, the unmodified graphitic petal sample demonstrated better stability and higher emission current than the boron nitride modified sample. Both samples deintercalated above 1000 K.

Preparation of hydrophobic polyvinyl alcohol aerogel via the surface modification of boron nitride for environmental remediation

Macroscopic polyvinyl alcohol (PVA) aerogel is of great interest in environmental remediation due to its low cost and easy fabrication. However, the hydrophily of PVA aerogel limited its application in oil-water separation. In this work, boron nitride (BN)-modified PVA aerogel has been successfully prepared by a cost-effective frozen-drying method. PVA plays a role as a scaffold of aerogel to support BN nanosheets which can modify the surface properties of PVA aerogel, resulting in a dramatic change of wettability from hydrophily (0°) to hydrophobicity (94.9°–100.8°). Moreover, the obtained BN-modified PVA aerogel possesses a favorable porous structure, low density (41.8–60.0mg/cm3) and good adsorption capacity (12–38g/g), which make it a promising wastewater treatment material. Importantly, PVA aerogel with other functions can be easily fabricated through coupling with other inorganic materials by this strategy, which can provide various promising applications for environmental remediation.

Silane surface modification of boron nitride for high thermal conductivity with polyphenylene sulfide via melt mixing method

Polyphenylene sulfide (PPS) is a promising engineering polymer, which is used for various industrial applications. In this study, we developed a highly thermally conductive PPS composite containing boron nitride (BN) as a thermally conductive ceramic filler. (3‐Aminopropyl) triethoxysilane was doped onto the surface of hydroxyl‐functionalized BN using a simple sol–gel process. The modified BN particles were embedded in a PPS matrix via a melt mixing process using a twin extruder to form BN‐Si composites. The maximum thermal conductivity 3.09 W/m·K was exhibited by the surface‐modified BN‐Si containing 60 wt%. This value was 116% higher than the thermal conductivities of the pristine BN and PPS matrix, respectively. The surface‐treated composites also showed an improved storage modulus because of an improvement in the interfacial adhesion and interaction between the BN filler and the PPS matrix. Copyright © 2017 John Wiley &amp; Sons, Ltd.

Surface modification of boron nitride by reduced graphene oxide for preparation of dielectric material with enhanced dielectric constant and well-suppressed dielectric loss

Adding conductive filler is an effective way to enhance the dielectric constant while usually also increases the dielectric loss of polymer. In this study, we demonstrated that polymer composites with much improved dielectric constant while maintaining ultra-low dielectric loss could be achieved via using hybrid filler and controlling the dispersion of conductive filler in polymer matrix. To do this, the graphene oxide was designed to be immobilized on the surface of large-sized insulating hexagonal boron nitride (h-BN) via electrostatic self-assembly, and afterwards introducing this hybrid filler into epoxy accompanied with chemical reduction. In this case, since the reduced graphene oxide (rGO) sheets were fixed on the surface of h-BN, rGO sheets were well separated from each other even at high loading. Hence not only significantly enhanced dielectric constant was observed, but also a very low dielectric loss comparable to that of neat epoxy was achieved. This low dielectric loss was believed to be ascribed to both embedded insulating network of h-BN to inhibit the mobility of charge carrier and well-separated rGO sheets via immobilization. In addition to obviously improved dielectric properties, the nanocomposites also exhibited good thermal conductivity. We believe that this special structure will provide a new thought for fabricating dielectric materials with much enhanced dielectric constant as well as well-suppressed dielectric loss.

Fluid synthesis and structure of a new polymorphic modification of boron nitride

A new previously unknown phase of boron nitride with a hardness of 0.41–0.63 GPa has been pre-pared by the supercritical fluid synthesis. The presence of a new phase is confirmed by the X-ray spectra and IR absorption spectra, where new reflections and bands are distinguished. The fundamental reflection of the X-ray diffraction pattern is d = 0.286–0.291 nm, and the characteristic band in the infrared absorption spectrum is observed at 704 cm−1. The X-ray diffraction pattern and the experimental and theoretical infrared absorption spectra show that a new synthesized boron nitride phase can be a cluster crystal (space group 211) with a simple cubic lattice. Cage clusters of a fullerene-like morphology B24N24 with point symmetry O are arranged in lattice sites.