Synthesis Of Boron Nitride Research Articles

Thermally stable and anti-corrosive polydimethyl siloxane composite coatings based on nanoforms of boron nitride

Coating technology has been emerged as a recognized and cost-effective approach in regard to mitigating issues that are linked to corrosion. We employed in-house synthesized boron nitride nanosheets (BNNS-CVD) and commercially available nanosized boron nitride (BN-nano) as fillers in this study to fabricate composite coatings with enhanced thermal stability and corrosion resistance. These fillers were dispersed in polydimethylsiloxane (PDMS) resin to develop composite coatings. The Fourier-transform infrared spectroscopy (FTIR), UV–visible spectroscopy, field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), and electrochemical impedance spectroscopy (EIS) were employed to characterize the prepared composite coatings. The FTIR analysis revealed a prominent absorption band around 1350 cm−1 that is indication of the distinctive B-N in-plane bending vibrations characteristic of boron nitride (BN). The FESEM images simultaneously confirmed the sheet-like morphology of both BN-nano and BNNS-CVD, which both found to be uniformly dispersed in the PDMS matrix. The EIS revealed that the composite films based on BNNS-CVD exhibited superior corrosion resistance compared to those based on BN-nano when exposed to a 3.5 wt% NaCl solution. Further, TGA profiles indicated that the composite films maintained their structural integrity up to 200 ℃ without degradation. Therefore, thermally stable and corrosion resistant coatings can be valuable for various new technology applications that involve corrosion issues.

Development of superhydrophobic and superoleophilic CNT and BNNT coated copper meshes for oil/water separation

In this research, chemical vapor deposition (CVD) method was used to synthesize boron nitride nanotube (BNNT) powder. This method involves heating multi-walled carbon nanotube (MWCNT) and boric acid in the presence of ammonia gas up to 1000 °C. Then MWCNT and synthetic BNNT were coated on the copper mesh via dip-coating method separately to prepare nano-structured membranes for efficient oil/water separation. Various analyzes were performed to identify the synthetic BNNT properties (X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and prepared coated membranes (FESEM, atomic force microscopy (AFM), water contact angle (WCA), oil contact angle (OCA) and oil/water separation process). Water and oil contact angle analyzes showed the super-oleophilic properties of both membranes with the underwater OCA of about 128°. For the separation process, a dead-end filtration setup was used, and free oil water mixture and o/w emulsion were prepared. So, in the separation process water was retained and decalin passed through both prepared membranes. The flux of CNT coated membrane was about 458 L m2 h−1, while this amount was 1834 L m2 h−1 for BNNT coated membrane and 99% separation efficiency was achieved by both of them. This four-fold increase in flux is due to the fact that the inner diameter of boron nitride nanotubes synthesized is four times larger than the inner diameter of MWCNT.

Synthesis and Modification of Boron Nitride nanotubes using ion implantation

In this work, Chemical Vapour Deposition (CVD) has been used to synthesize boron nitride (BN) nanostructures, particularly nanotubes, and selectively introduce defects into the lattice of the synthesized BN nanostructures through ion implantation. Scanning electron microscopy (SEM) images show clear evidence of BN nanostructures and BN nanotubes (BNNTs), with the latter appearing as long, thin structures with diameters ranging from ⁓30–80 nm. Raman analysis show an E2g mode of vibration assigned to hexagonal BN (h-BN) at 1366 cm−1 after ion implantation, with increased intensity. Grazing incidence X-ray diffraction (GIXRD) spectra revealed a prominent peak between 54 and 56°, corresponding to the (004) h-BN reflection, which was used to determine the average lattice parameter c⁓0.662 nm representing the stacking direction of the BN layers. The majority of the samples had broad peaks, indicative of a nanocrystalline material. The only exception was the sample grown at 1200 °C, which was found to have a Scherrer crystallite size >100 nm. In contrast, the rest of the samples had an average size of 3.5 nm. Notable observations in this study include a significant rise in the size of the Raman derived crystallite domains in the nanostructures synthesized at 1100 and 1200 °C after ion implantation with boron ions at fluence 5 × 1014 ions/cm2.

Microstructures and properties of polymer-derived hexagonal boron nitride fibers with initial gradient oxygen contents

Oxygen plays a crucial role in the synthesis of boron nitride (BN) and the preparation of BN ceramics. The effects of oxygen content on the microstructure and properties of BN fibers treated at 1600 °C have not been studied yet. In this work, polymer-derived BN fibers are cured at 300 °C under oxygen and pyrolyzed at 600 °C, 700 °C and 800 °C under ammonia as the pre-heated BN fibers. Then, these pre-heated BN fibers are treated at 1600 °C under nitrogen as the final BN fibers. The compositions and microstructures of the pre-heated and final BN fibers are investigated. As the pre-heated temperature increases, the oxygen contents of the pre-heated BN fibers decrease to 24 wt%, 17 wt% and 5 wt%, respectively. The structures of the pre-heated BN fibers transform from amorphous BN to turbostratic BN. The oxygen in the pre-heated BN fiber volatilizes as boron oxide during treatment at 1600 °C, promoting the formation and growth of h-BN in the final BN fiber, with the maximum grain size reaching 74 × 20 nm (La × Lc). As the grain size of the final BN fiber increases, the Young's modulus, density and oxidation resistance level of the BN fiber improve, and the dielectric properties decrease. The final BN fiber that underwent pre-heating at 700 °C has the best comprehensive properties, with a tensile strength of 1.11 GPa and a Young's modulus of 265 GPa. This study researches the relationship between composition, structure and performance, and provides a scientific basis for the preparation process of BN fibers.

Template-free synthesis of water-vapor stable porous 3D boron nitride

Due to its high thermal stability, dipolar structure, and easy synthesis porous boron nitride is a promising material in adsorption, catalysis, and gas storage. However, recent investigations showed that micro-mesoporous boron nitride is highly water-susceptible and reacts quickly with water to boron oxide and ammonia. Key parameters such as boron oxide content, crystallinity, and porosity primarily influence the water stability. Previous studies indicate that the synthesis of boron nitride without any microporosity could lead to a water-vapor stable product. Thus, this work pursues the template-free synthesis of solely meso-macroporous boron nitride. In order to achieve this, the influence of different nitrogen flow rates on the porosity of boron nitride was investigated. In addition, a pre-heating step was introduced which led to the successful synthesis of a meso-macroporous material. By varying the precursor ratio up to urea to boric acid 4–1, the porosity of the product was increased up to a BET surface area of 361 m2 g-1. To analyse the water stability, water-vapor adsorption was used. This enabled us to demonstrate the successful synthesis of highly water-vapor stable porous boron nitride.

Synthesis of Boron Nitride by Reduction of Boron Oxide with Aluminum in Nitrogen

The paper presents the results of studies of the self-propagating high temperature synthesis (SHS) of boron nitride via chemical reduction of boron oxide with aluminum in a nitrogen medium. The phase composition of the powder reaction products depending on the nitrogen pressure during the synthesis was studied by X-ray diffraction. It was found that SHS in the B2O3–Al system gives the BN–Al2O3 powder material containing 20–28 wt % hexagonal boron nitride depending on the nitrogen pressure. Microstructure examination showed that the obtained powder materials contains separate hexagonal BN particles with 3 μm size. The differences in the density and morphology of BN and Al2O3 determine the possibility of BN isolation from the obtained powder mixture by the pneumatic powder separation methods.

Synthesis of Boron Nitride by Reduction of Boron Oxide with Aluminum in Nitrogen

Synthesis of Boron Nitride by Reduction of Boron Oxide with Aluminum in Nitrogen

Calculating the penetration depth of reaction in chemical gas-phase deposition of boron nitride within porous bodies

The thermodynamic calculations conducted using the TERRA software package for the B–Cl–N–H system revealed that the inclusion of hydrogen into the B–Cl system significantly diminishes the thermodynamic stability of BCl3 with the possibility of boron formation in the condensed phase. On the other hand, the introduction of ammonia, which includes hydrogen, results in the synthesis of boron nitride across a broad temperature spectrum. The analysis of kinetic relationships uncovered three distinct regions in the boron nitride deposition process: K – kinetic region (up to 1400 K), D – diffusion region (above 1800 K) and T – transition region. The activation energy for the kinetic region was calculated as Ea = 134 kJ/mol. Within the temperature range of 1023–1123 K, linear dependences were observed. The computation of the penetration depth for the boron nitride deposition process assumed a gas mixture of boron trichloride, ammonia, and argon (BCl3 + NH3 + 30Ar). The results indicated that boron trichloride governs the extent of penetration. The depths of penetration for the chemical vapor infiltration boron nitride (CVI-BN) process, conducted at 0.1 kPa within the temperature range of 1100–1400 K, were determined for pore diameters of 1, 10, 30, 100, 200 and 300 µm. When porosimetry data for a specific preform is available, the acquired penetration depth relationships for the CVI-BN process under specific parameters and process temperatures facilitate the estimation of essential parameters for interphase formation using pyrolytic boron nitride.

Revealing Variable Dependences in Hexagonal Boron Nitride Synthesis via Machine Learning.

Wafer-scale monolayer two-dimensional (2D) materials have been realized by epitaxial chemical vapor deposition (CVD) in recent years. To scale up the synthesis of 2D materials, a systematic analysis of how the growth dynamics depend on the growth parameters is essential to unravel its mechanisms. However, the studies of CVD-grown 2D materials mostly adopted the control variate method and considered each parameter as an independent variable, which is not comprehensive for 2D materials growth optimization. Herein, we synthesized a representative 2D material, monolayer hexagonal boron nitride (hBN), on single-crystalline Cu (111) by epitaxial chemical vapor deposition and varied the growth parameters to regulate the hBN domain sizes. Furthermore, we explored the correlation between two growth parameters and provided the growth windows for large flake sizes by the Gaussian process. This new analysis approach based on machine learning provides a more comprehensive understanding of the growth mechanism for 2D materials.

Pyrolyzed synthesis of boron nitride for photocatalytic degradation of indigo carmine studies

A non-metal type photocatalytic layered boron nitride (BN) material was synthesized by precursor conversion hydrothermal process followed by adequate temperature pyrolysis. The characterization of BN was performed through various analytical instrumental techniques. The results show that a hexagonal crystal structure BN with a strong BN bond was formed. The photocatalytic decolorization of indigo carmine (IC) dye was examined using synthesized BN with influencing factors like time, pH, catalyst, and dye concentration under ultra-violet light (UV) illumination. The decolorization efficiency was found to be 88%. The optimization of operating parameters was investigated and also found a model equation of decolorization efficiency through response surface methodology (RSM) based box - behnken design (BBD). The photocatalytic decolorization mechanism was suggested based on the experiments performed.

Preparation and Thermal Conductivity Enhancement of Boron Nitride Nano-Material PiG Composite

With the improvement of the conversion efficiency of LED chip and fluorescent material and the increasing demand for high-brightness light sources, LED technology has begun to move toward the direction of high-power. However, there is a huge problem that high-power LED must face with a large amount of heat generated by high power causing a high temperature thermal decay or even thermal quenching of the fluorescent material in the device, resulting in a reduction of the luminous efficiency, color coordinates, color rendering index, light uniformity, and service life of LED. In order to solve this problem, fluorescent materials with high thermal stability and better heat dissipation were prepared to enhance their performance in high-power LED environments. A variety of boron nitride nanomaterials were prepared by the solid phase-gas phase method. By adjusting the ratio of boric acid to urea in the raw material, different BN nanoparticles and nanosheets were obtained. Moreover, the control of catalyst amount and synthesis temperature can be used to synthesize boron nitride nanotubes with various morphologies. By adding different morphologies and quantities of BN material in PiG (phosphor in glass), the mechanical strength, heat dissipation, and luminescent properties of the sheet can be effectively controlled. PiG prepared by adding the right number of nanotubes and nanosheets has higher quantum efficiency and better heat dissipation after being excited by high power LED.

Boron nitride nanosheets modified with zinc oxide nanoparticles as novel fillers of dental resin composite

ObjectiveThe purpose of this study was to synthesize boron nitride nanosheets modified with zinc oxide nanoparticles (BNNSs/ZnO) and incorporate them as a novel inorganic filler to get an antibacterial dental resin composite. MethodsThe BNNSs/ZnO nanocomposites were synthesized via the hydrothermal method and characterized by Field Emission Scanning Electron Microscope (FESEM), Transmission Electron Microscopy (TEM), Energy Dispersive Spectrometer (EDS), X-ray Diffraction (XRD) and Fourier Transform-Infrared (FTIR) Spectroscopy. The BNNSs/ZnO or BNNSs were added into the experimental dental composite with different proportions, respectively. The mechanical and physical properties of the modified dental composite were evaluated. Their antibacterial activities were also assessed by quantitative analysis using Streptococcus mutans (S. mutans). ResultsThe BNNSs/ZnO nanocomposites were successfully synthesized, and the growth of ZnO nanoparticles (ZnO NPs) on boron nitride nanosheets was confirmed. The flexural strength (FS), flexural modulus (FM) and the compressive strength (CS) of all modified resin composites showed no change compared to the control group. The curing depth, degree of conversion, water absorption and solubility of the modified composites were still within the clinical requirement. The antibacterial rates of the modified composites were significantly increased compared to the control group, which can reach 98 % when 0.5 % BNNSs/ZnO was added. SignificanceThe modified dental resin composite with novel BNNSs or BNNSs/ZnO fillers shows significantly high antibacterial activity with suitable physicochemical and mechanical properties.

Turbostratic Boron-Carbon-Nitrogen and Boron Nitride by Flash Joule Heating.

Turbostratic layers in 2D materials have an interlayer misalignment. The lack of alignment expands the intrinsic interlayer distances and weakens the optical and electronic interactions between adjacent layers. This introduces properties distinct from those structures with well-aligned lattices and strong coupling interactions. However, direct and rapid synthesis of turbostratic materials remains a challenge owing to their thermodynamically metastable properties. Here, a flash Joule heating (FJH) method to achieve bulk synthesis of boron-carbon-nitrogen ternary compounds with turbostratic structures by a kinetically controlled ultrafast cooling process that takes place within milliseconds (103 to104 K s-1 ) is reported. Theoretical calculations support the existence of turbostratic structures and provide estimates of the energy barriers with respect to conversion into the corresponding well-aligned counterparts. When using non-carbon conductive additives, a direct synthesis of boron nitride is possible. The turbostratic nature facilitates mechanical exfoliation and more stable dispersions. Accordingly, the addition of flash products to a poly(vinyl alcohol) nanocomposite film coating a copper surface greatly improves the copper's resistance to corrosion in 0.5 m sulfuric acid or 3.5 wt% saline solution. FJH allows the use of bulk materials as reactants and provides a rapid approach to large quantities of the hitherto hard-to-access turbostratic materials.

In situ synthesis of boron nitride “nanonoodles” based epoxy nanocomposites with enhanced thermal and dielectric properties

AbstractThe development of low loading fraction nanoscale reinforcements that can be used to improve the dielectric and thermal properties of a polymer remains a challenge by the reason of the insurmountable difficulties with exfoliation and dispersion of polymer nanocomposites. Here, we combined noodle‐like boron nitride nanoribbons (BNNRs) with epoxy resin (EP) by a facile in situ synthesis. The hydroxyl and amino on the BNNRs surface can not only improve dispersibility but also conduct the formation of EP with BNNRs by the in situ ring‐opening reaction. The thermal behavior, dielectric properties, and thermal conductivity of BNNRs/EP nanocomposites with different BNNRs contents were investigated. At an extremely low BNNRs loading fraction of 1 wt%, the thermal conductivity of the nanocomposite increased 48%, which is attributed to the long continuous heat conduction path formed by the strong integration of BNNRs and EP. In addition, the electrical breakdown strength increased from 95.58 to 159.17 kV·mm−1 as the BNNRs content increased, while the nanocomposites maintained acceptable dielectric properties. The results indicate the potential for BNNRs as a new class of nanofiller for dielectric polymers.

Low-Temperature Synthesis of Boron Nitride as a Large-Scale Passivation and Protection Layer for Two-Dimensional Materials and High-Performance Devices.

Two-dimensional materials (2DMs) with extraordinary electronic and optical properties have attracted great interest in optoelectronic applications. Due to their atomically thin feature, 2DM-based devices are generally sensitive to oxygen and moisture in ambient air, and thus, practical application of durable 2DM-based devices remains challenging. Here, we report a novel strategy to directly synthesize amorphous BN film on various 2DMs and field-effect transistor (FET) devices at low temperatures by conventional chemical vapor deposition. The wafer-scale BN film with controllable thickness serves as a passivation and heat dissipation layer, further improving the long-term stability, the resistance to laser irradiation, and the antioxidation performance of the underneath 2DMs. In particular, the BN capping layer could be deposited directly on a WSe2 FET at low temperature to achieve a clean and conformal interface. The high performance of the BN-capped WSe2 device is realized with suppressed current fluctuations and 10-fold enhanced carrier mobility. The transfer-free amorphous BN synthesis technique is simple and applicable to various 2DMs grown on arbitrary substrates, which shows great potential for applications in future two-dimensional electronics.

Mixing nitrogen-containing compounds for synthesis of porous boron nitride for improved porosity, surface functionality, and solid base catalytic activity

Porous boron nitride was synthesized using boric acid with urea and/or hexamethylenetetramine (HMTA) via pyrolysis method. X-ray diffraction and Fourier transform infrared measurements indicated that the synthesized boron nitride has a turbostratic structure with both amino and hydroxyl group on the surface. The synthesis using a mixture of two nitrogen-containing precursors was found to not only significantly increase the porosity, but also improve the surface functionality. X-ray photoelectron spectroscopy and B K-edge and O K-edge X-ray absorption fine structure measurements revealed that the proportion of amino and hydroxyl groups on the surface increased with increasing concentration of HMTA during synthesis. Solid-state 11B nuclear magnetic resonance spectroscopy indicated that all samples contained trigonal B-N, trigonal B-O and tetrahedral B-O sites, and that samples prepared with high concentrations of HMTA had less tetrahedral B-O sites, suppressing the formation of BOx species as byproducts. Solid base catalytic activity was evaluated through Knoevenagel condensation, and the catalytic performance was significantly improved by synthesizing boron nitride catalyst using a mixture of the two nitrogen-containing precursors. The enhancement of the activity was influenced by the development of the pore structure as well as the emergence of functional groups on the surface.

Study of improved VOCs sensing properties of boron nitride quantum dots decorated nanostructured 2D-ZnO material

Volatile organic compounds (VOCs) are continuously launched into the atmosphere from the industries and our daily activities. They can be categorized into 7 different types. A representative gas of each of these categories is sensed and studied in this manuscript. Pure 2D material or semi-conducting material proves to be the inefficient gas sensor. However, composite of certain materials can have good efficiency in gas sensing applications. When 2D ZnO (ZnO nanoplates) was decorated with hydrothermally synthesized boron nitride quantum dots (BNQDs), the sensing response was appreciable. XRD, HRTEM, and SAED were utilized for the sample characterizations. It was observed that the response of the ZnO-BNQDs sensor was appreciable towards gases like methanol, chlorobenzene, toluene, n-heptane, isoprene, ethyl acetate, and formaldehyde. The stability was good over a period of 2 months. The catalytic behavior of BNQDs helped to improve the response of ZnO towards the VOCs.

CVD synthesis of boron nitride from a solid precursor

Here we report on the studies of the controllable synthesis of large area boron nitride films by the resistive heating method on a metal substrate without using a dangerous boron and nitrogen containing gases. In our original home-made CVD setup, we used the copper foil as a metal catalytic substrate. With the solid precursor of ammonia borane, the boron nitride films were synthesized under low pressure conditions and at a growth temperature of about 1000°C. We obtained the films with an area of up to 1x1 cm2 by varying the synthesis parameters. The quality of boron nitride films was characterized using Raman spectroscopy and X-ray spectroscopy.

Thermal diffusivity measurement of boron nitride by photoacoustic spectroscopy

A photoacoustic spectrometer (PAS) is a very common method to measure non-radiative decay. When modulated electromagnetic light interacts with any solid powder sample, their thermal energy production is due to non-radiative decay. Then acoustic noise is produced due to temperature difference which is formed by the periodic heat transfer from the optical source. In this work, we have fabricated a PA cell and a pre-amplifier circuit and optimized them by parametric studies to get the desired signal. For the optimum signal, the volume of the cell cavity is found to be 5.30 × 10-6 m3. We have successfully synthesized Boron nitride (BN) by simple hydrothermal method with NH4Cl (Sample I) and without NH4Cl (Sample II). The XRD and FESEM data confirm the crystal phase and morphological structure of the synthesized material. The thermal diffusivity of sample I is obtained (7.22–8.31) × 10-6 m2/s. Similarly, for sample II, the thermal diffusivity is found to be (7.38–8.72) × 10-6 m2/s.

Boron nitride nanosheets incorporated polyvinylidene fluoride mixed matrix membranes for removal of methylene blue from aqueous stream

This study aims to synthesize boron nitride nanosheets (BNNS) incorporated polyvinylidene fluoride (PVDF)-based membranes using phase inversion method for removal of methylene blue (MB) from water. We start with density functional theory (DFT) calculations to get a first order estimate of absorption capacity of PVDF and BNNS-PVDF for MB, which reveal the probability of attaining higher adsorption capacity of MB for BNNS-PVDF than PVDF. Experimentally, the loading of the BNNS has been optimized by varying it from 0.5 to 2.0 wt%. The morphological characterization shows higher roughness with increased loading and highest void density for PVDF + 1 wt% BNNS. The corresponding SBET obtained is 28 m2/g. Further, the highest pure water flux (1160 l m-2 h-1), porosity (87.68%) and mechanical strength (1.8 MPa) also confirm that the membrane loaded with 1.0 wt% BNNS is optimum. The maximum adsorption capacity of the optimized BNNS-PVDF membrane has been found to be (142.86 mg g-1) that is 2.2 times higher than the PVDF membrane (65.36 mg g-1) and is largely in line with our DFT simulations. Moreover, the thermodynamic studies reveal that the adsorption is favorable at high temperatures and the reaction is endothermic in nature. The membrane exhibits good separation and regeneration behavior. Additionally, the optimized membrane shows excellent continuous flow adsorption of simulated MB contaminated aqueous stream and 100% removal of 10 ppm MB solution is achieved. These results reveal that the synthesized membrane loaded with 1.0 wt%. BNNS is a potential candidate for MB remediation from the aqueous stream.