Effect Of Hexagonal Boron Nitride Research Articles

Investigation of the Effect of Hexagonal Boron Nitride Addition on the Mechanical Properties of Flax Fiber-Reinforced Composite Materials

Hexagonal boron nitride (h-BN) has recently been utilized as a reinforcement in composite materials due to its properties such as hardness, thermal conductivity, electrical insulation, and strong chemical stability. The aim of this study is to investigate the effect of nano-sized hexagonal boron nitride (h-BN) on the mechanical properties of flax fiber-reinforced composite material. For this purpose, initially, hexagonal boron nitride was added to epoxy resin in different weight ratios and homogenized without agglomeration using ultrasonic treatment. Then, by employing the hand lay-up method, the mixture was applied to flax fiber fabrics and the flax fiber-epoxy composites were produced using the vacuum bagging method. Mechanical performance of the composites, produced with 0.5%, 1%, and 1.5% by weight of hexagonal boron nitride, was determined through tensile, flexural, shear, and compression tests. Experimental results indicated that the addition of hexagonal boron nitride to flax fiber epoxy composite material increased the flexural strength and modulus compared to the unreinforced flax fiber epoxy composite material. The highest flexural strength and modulus were observed in the samples with 1.5% by weight of hexagonal boron nitride (h-BN). Consequently, it can be considered that flax fiber-epoxy composite material with hexagonal boron nitride (h-BN) addition holds potential, especially for applications subjected to bending moments.

Effect of Nanoparticles and Microparticles of Hexagonal Boron Nitride on Structure, Thermal and Mechanical Stability of Lithium and Calcium Greases

Hexagonal boron nitride is being considered as an additive for greases due to its structure and physical and chemical properties. In the context of the application of such lubricants in real tribological systems, it is important to recognise the effect of hexagonal boron nitride not only on tribological properties, but also on other functional properties of this group of lubricants. In the present study, tests including dropping point, penetration and mechanical stability were carried out. Additionally, particular focus was placed on the properties of the additive itself, including particle size distribution and adsorption properties, as determined by scanning electron microscopy and low-temperature adsorption isotherms. The introduction of hexagonal boron nitride particles into lithium and calcium greases resulted in enhanced resistance to high temperature and prolonged mechanical stress. This phenomenon was attributed to the type of base grease and the modifications in the configuration of the grease's spatial network that ensued as a result of the incorporation of solid particles. It was found that an additive with a smaller particle size and a significant proportion of nanoparticle fractions, and a more developed porous structure, was more effective. Microscopic observations of the structure of the greases confirmed that the solid particles were deposited in the spatial network of the greases. The distribution of hexagonal boron nitride in the grease structure was found to be contingent upon the physical and chemical properties of the additive. Furthermore, the type of base grease, including the arrangement of the soap fibre network, was identified as a contributing factor.Graphical

Effect of Hexagonal Boron Nitride on Morphology, crystallinity and internal Exfoliation properties of Polypropylene melt and solid phases

ABSTRACT Polypropylene (PP) is one of the most important polymers widely used in different industries due to its many superior properties. Hexagonal boron nitride (hBN) is generally used in the electronic packaging industry and insulator material production due to its high thermal conductivity and low electrical conductivity. However, the lubrication properties have not yet been examined in the polymer matrix. The main purpose of this study is to examine the lubricating properties of hBN in the PP matrix and to expand its application areas. In this research, hBN/PP composites have been produced and characterized by scanning electron microscopy with an energy dispersive X-ray detector (SEM-EDX) and the differential scanning calorimeter (DSC), respectively. The linear viscoelastic behaviors (LVBs) and rheological properties of the hBN/PP composites have been investigated at 190°C by hybrid rheometer which had high temperature plate-plate geometry system; furthermore, the SEM has been used for searching hBN particles deformation, which was mechanical deformation and distribution into the PP. The oscillation sweeps tests have shown that the critical strain values and the gelation point of composites decreased with the increasing of the hBN content into the composites. Over the 10%, hBN addition into the PP elevated internal lubrication by the exfoliation of hBN plaques. The Williamson model and the discrete retardation spectrum (DRS) equation has been applied on the hBN loaded PP composites and the PP.

Effect of hexagonal boron nitride on structural, mechanical, and tribological behavior of polyamide 6/glass fibers (5 wt%) hybrid nanocomposites

Effect of hexagonal boron nitride on structural, mechanical, and tribological behavior of polyamide 6/glass fibers (5 wt%) hybrid nanocomposites

Thermal conductivity and orientation of liquid crystal polymer filled with boron nitride

This work focuses on the study of effect of hexagonal boron nitride (BN) on the self-orientation, rheology and thermal conductivity of thermotropic liquid crystalline polymer (LCP), which possesses a semirigid-rod molecular structure. The LCP/BN composites are prepared by extrusion and injection molding processes. The 2D-WAXD analysis evidences the presence of self-orientation and typical “skin-core” structure of LCP and LCP composites. As a consequence, there are abundant macro fibrils in the matrices. The role of the lateral dimension of BN on the properties of LCP was investigated. It is confirmed that BN with a larger lateral size can more effectively improve the TC and thermal stability of LCP. Being filled with 30% BN with a large lateral size of 50 μm, the thermal conductivity of LCP/BN50-30 composite is increased by 88.11% compared with pure LCP, in contrast, the increment ratio of 38.43% and 43.93% when the LCP is filled with BN with lateral size of 0.5 μm and 5.0 μm at the same loading.

Thermal and thermomechanical properties of boron nitride-filled acrylonitrile butadiene styrene (ABS) composites

The present study aims at investigating the effect of hexagonal boron nitride (hBN) nanoplatelets on the properties of acrylonitrile butadiene styrene (ABS) polymer. Composites containing 0-30 vol% hBN were prepared through batchwise melt compounding, which was followed by compression molding. Subsequently, the thermal and thermomechanical properties of the fabricated samples were investigated. The dynamic mechanical analysis (DMA) revealed that the storage modulus of the samples was markedly improved in the entire examined temperature range, while the glass transition temperature also gradually increased as a function of hBN content. According to the thermogravimetric analysis (TGA), the incorporated boron nitride particles enhanced the thermal stability of ABS composites, exhibiting a notably higher decomposition onset temperature. Additionally, the thermal conductivity of the ABS/hBN composites significantly increased by 570% when the hBN content was 30 vol%.

Observation of half-integer Shapiro steps in graphene Josephson junctions

We study quantum transport and AC Josephson effect of hexagonal boron nitride encapsulated graphene (BGB) Josephson junctions (JJs). Our experiments reveal the emergence of the half-integer Shapiro steps in the n-type regime with high electron carrier densities. We attribute this observation to the gate-tunable transmission probability of the graphene junction. Our numerical simulations are consistent with the appearance of half-integer Shapiro steps at high transparency, which suggests a skewed current phase relationship in the graphene JJ.

Synergistic effect of hexagonal boron nitride and carbon nanofibers on tribological behavior of nanolubricant

The lubrication of the wind bearings is crucial for maintaining the efficiency and lifetime of the wind turbines. In this work, nanolubricant samples containing hexagonal boron nitride (h-BN), carbon nanofibers (CNFs), and carbon nanotubes (CNTs) were prepared and applied to friction pairs to study the tribological properties at different speeds and under different loads. The polyalphaolefin (PAO) sample with 6 wt% of CNF and 6 wt% of h-BN demonstrated the lowest and most stable average friction coefficient of GCr15/40Cr pair. Considering reduction of both wear loss and friction coefficient, the sample with only CNF is more suitable for low-load and low-speed working conditions. While the sample loaded with both h-BN and CNF is more suitable for high-load and high-speed working conditions.

Corrosion and wear properties of h-BN-modified TC4 titanium alloy micro-arc oxide coatings

In this study, ceramic coatings were prepared on the surface of TC4 titanium (Ti) alloy by micro-arc oxidation (MAO). The morphology, element distribution and phase composition of MAO coatings were analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and other analytical methods. The effect of hexagonal boron nitride (h-BN) doping on the wear resistance and corrosion resistance of the MAO layer was studied. The results showed that the coating was mainly composed of rutile titanium dioxide (TiO2), anatase titanium dioxide and a small amount of h-BN. Furthermore, the composite coating containing h-BN was less porous than the particle-free coating. The test results showed that h-BN doping slightly affected the hardness of the MAO coating, and it was helpful in improving the thickness, corrosion resistance and wear resistance of the coatings. When the amount of h-BN was 3 g/l, the corrosion current density of the coating was the smallest. When the addition of h-BN was 1.5 g/l, the friction coefficient of the coating was the smallest. The wear mechanism was adhesive wear, accompanied by slight abrasive wear.

Mechanical properties of aluminum bonded joints reinforced with functionalized boron nitride and boron carbide nanoparticles

In the presented study, the effect of hexagonal boron nitride and hexagonal boron carbide nanoparticles on the strength of adhesively bonded joints was investigated experimentally. Hexagonal boron nitride nanoparticles were functionalized using 3-(aminopropyl) triethoxysilane to improve adhesion and increase the interaction between epoxy and nanoparticles. Similarly, h-B4C nanoparticles were functionalized by using 3-(glycidyloxypropyl) trimethoxysilane. New structural nano adhesives were produced by reinforcing the functionalized nanoparticles into epoxy at different proportions (0.5 wt.%, 1.0 wt.%, 2 wt.%, 3.0 wt.%, 4.0 wt.%, and 5.0 wt.%). Two different epoxies with different viscosity values (MGS-LR285 and Araldite 2011) were used as adhesives, and aluminum alloy (AA2024-T3) was chosen as an adherend. Tensile test was carried out to determine the failure load of the adhesive joints, and the fracture surface morphology was examined after the test Additionally, Scanning electron microscopy and energy dispersion X-ray spectroscopy (SEM-EDS) analysis was performed to observe the distribution of boron nanoparticles in the adhesives. The experimental results showed that the reinforcement of hexagonal boron nitride and boron carbide nanoparticles to the adhesives increased the joint strength substantially depending on the reinforcement ratio and viscosity of the adhesives. The maximum increase in failure loads was achieved by adding 1 wt.% functionalized boron nitride to high viscosity Araldite 2011 adhesive and 2 wt.% to low viscosity MGS-LR285 adhesive, and the ratio of increase in failure loads is 31% and 63%, respectively. Moreover, by adding 2 wt.% functionalized boron carbide nanoparticles to the Araldite 2011 and MGS-LR285 adhesives, the strength of the joints increased by about 27% and 70%, respectively.

Effect of hexagonal boron nitride (h-BN) addition on friction behavior of low-steel composite brake pad material for railway applications

In this study, low-steel composite friction materials containing different amount of h-BN were developed for railway vehicles. Addition of h-BN has no considerable effect on mechanical properties of the matrix structure. However, h-BN addition significantly affects friction and wear properties of the matrix material. While h-BN increases coefficient of friction of samples at low disk surface temperatures, it has a reverse effect after the temperature reaches to a critical level of 250–300 °C. Also, addition of 1.5 wt% h-BN to the matrix brings about more stable changes in friction coefficient during the braking periods under the extreme conditions as compared to the h-BN-free sample. Furthermore, low h-BN addition into the matrix results in better lubricity properties at relatively high temperatures.

Effect of h-BN nanoparticles on the tribological and rheological properties of API-Group I Oils

ABSTRACT The paper investigates the effect of hexagonal boron nitride (h-BN) nanoparticles on the tribological and rheological properties of the API-Group I lubricants i.e. Solvent neutral (SN)-500, Bright Stock (BS)-270, and thirdly a mixture of SN-500 and BS-270. The tribological properties of the base oils and the nanolubricants are studied using a four-ball tester and the experiments are carried out as per ASTM D4172 standard. It is observed that the addition of 0.25 wt.% h-BN nanoparticles improves the tribological properties of base oils. The wear scar diameter reduces by 2.51%, 19.78% and 3.17% for SN-500, BS-270, and BS+SN at 0.25 wt% h-BN nanoparticles concentration respectively. The rheological properties of the lubricants are measured on Anton Paar’s MCR 102. BS-270 depicts the maximum viscosity among the Group I oils equal to 289.14 mPa.s at 40 °C. Further, all the oils depict an increase in the dynamic viscosity with an increase in the concentration of nanoparticles.

Effect of hexagonal boron nitride on the coefficient of frictions of organic-inorganic hybrid polymer thin films for metal surface coatings

Organic-inorganic hybrid coatings were developed via a sol-gel method using hexagonal boron nitride (h-BN) as a ceramic filler material incorporated into a polymeric matrix. To investigate the effects of h-BN on the properties of polymer-based coatings, parameters such as hardness, coefficient of friction, and hydrophobicity were investigated. Colloidal silica (CS), methyltrimethoxysilane (MTMS), water, and acid catalyst containing coatings were prepared by varying the content of h-BN from 10% to 25%. All the coatings were prepared with the same experimental procedure and coated on 1050 aluminum alloy plates. The compensating contents of MTMS and colloidal silica with a fixed molar ratio of MTMS and CS were set to be 1:1.2, and a specific amount of the catalyst was utilized. Coatings were examined by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDS). The most promising physical properties were determined to be the pencil hardness of 8B, adhesion strength of 5B, coefficient of friction of 0.332 N, and water contact angle of 114.75°. Therefore, it can be concluded that the h-BN improves the physical properties of polymeric coatings. In addition, this study demonstrates the effect of h-BN on the adherence of polymer matrix-based hybrid coatings.

Effect of Hexagonal Boron nitride Nanopowder Reinforcement and Mixing Methods on Physical and Mechanical Properties of Self-Cured PMMA for Dental Applications.

We report for the first time on the effect of biocompatible hexagonal boron nitride (h-BN) nanopowder reinforcement with different concentrations on the structural and mechanical properties of fabricated self-cured polymethyl methacrylate (PMMA) based dental materials (GC UNIFAST III). A comparison among the structural and mechanical properties between hand and ultrasonic mixing is also presented. Fabricated specimens were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), micro indentation, and flexural strength techniques. The ultrasonic mixing method provides better sample textures of the composite as compared to hand mixing. It is found that XRD and IR intensity of the peaks increases with the increase of h-BN concentration due to nanocomposite formation. The additions of h-BN nanoparticles to the acrylic resin enhanced the hardness and the flexibility values of the composites. Independently of the mixing method used, adding h-BN nanopowder relatively increases the Vickers Hardness numbers (VH) and Flexural Strength (FS) of the unmodified materials. However, using ultrasonic mixing method combined with h-BN nanopowder increases VH numbers to 300% and FS values to 550% with respect to the unmodified sample made by hand mixing. The results obtained are very encouraging and will support future research in vivo, to confirm whether PMMA loaded with h-BN nanoparticles is an improvement compared to current dental restorative materials.

In Vivo Assessment of the Effect of Hexagonal Boron Nitride Nanoparticles on Biochemical, Histopathological, Oxidant and Antioxidant Status

The aim of our study is to investigate the dose-dependent biological system effect of hexagonal boron nitride (hBN) nanoparticles, which is directly produced nanoscale, in vivo. Wistar albino rats (n = 80) weighing 200–250 g were divided into eight groups (n = 10). The acute effects of hBN NPs (i.v) on the rats were investigated by measuring the biochemical, hematological parameters and oxidant-antioxidant status. The results show that no significant change was observed in the hematological and biochemical parameters when the control group and other low dose groups were compared, except for the 1600 and 3200 µg/kg b.w. dose groups. Histological detection indicated that 1600 and 3200 µg/kg hBN NPs treatment could induce significant damage in the liver, kidney, heart, spleen and pancreas. With the findings obtained, it can be seen that hBN NPs cannot be evaluated independently of particle morphology, and that the hBN NPs used in this study may be suitable for biomedical applications where low doses between 50 and 800 µg/kg are not toxic.

Effect of hexagonal boron nitride (h-BN) inclusion on thermal characteristics of disc brake friction composites

Friction materials are developed keeping other ingredients constant and varying the weight percentage (wt%) of functional filler hexagonal boron nitride (h-BN) from 0 to 8 wt% and decreasing the space filler barite from 35 to 27 wt% in friction composites BN0, BN1, and BN2 respectively. Physical properties of these materials are measured as per Indian Standard (IS), and friction performance is studied using tribotester. Thermogravimetric analysis (TGA) with Differential scanning calorimetry (DSC) is carried out to find out the thermal behavior of friction composites at a higher temperature. The thermal conductivity values of these materials are measured using double-sided guarded hot plate apparatus. The addition of h-BN content enhances thermal conductivity from 0.86 W/mK to 1.40 W/mK. Effective thermal conductivity values of these multicomponent friction composites are also determined by analytical models and compared with experimentally measured values. Finally, to find out the thermal conductivity values of friction composites by the analytical method, the geometric mean model is modified with the introduction of the correction factor, which is based on the volume fraction of h-BN and temperature. Effective thermal conductivity values obtained by the modified geometric mean model agree well with measured values. The inclusion of h-BN improves physical properties, friction performance and thermal behavior of brake friction materials.

The effect of hexagonal boron nitride on wear resistance under two and three-body abrasion modes of polyetherketone composites

This investigation was performed to study the effect of hexagonal boron nitride (hBN) on abrasion wear behaviour of polyetherketone (PEK) composites. PEK composite were examined for two-body abrasive wear (2-BAW) with silicon carbide abrasive paper and three-body abrasive wear (3-BAW) test with silica sand according to ASTM standards. The Taguchi L9 design of experiment was employed to optimize the wear operating parameters. The optimized conditions with 10 N load, 320 grit size and 10 wt% of hBN resulted minimum specific wear rate (Ks). Unfilled PEK portrayed better impact strength, hardness, lower density and lower Ks under 3-BAW. However, 10 wt% of hBN was beneficial under 2-BAW condition. The SEM micrographs were analyzed to probe the wear mechanism involved in the abrasion process. Surface roughness (Ra) value measured was compared with Atomic Force Microscopy (AFM) and it was found that both the values are in good agreement. Multi-objective optimization by ratio analysis (MOORA) was implemented to rank the overall performance of PEK composites under study.

Effect of Dielectric Environment on Excitonic Dynamics in Monolayer WS2

AbstractAn experimental study on the effect of hexagonal boron nitride (h‐BN) underlay and cap layers on excitonic dynamics in monolayer WS2 is reported. A monolayer WS2 flake is fabricated by mechanical exfoliation. By using a dry transfer technique, three regions of the sample are obtained: WS2 directly on SiO2, WS2 on h‐BN, and WS2 sandwiched by two h‐BN flakes. Photoluminescence measurements show higher yield and narrower linewidth of the h‐BN/WS2/h‐BN region. Transient absorption measurements reveal that the top h‐BN layer enhances the exciton formation, prolongs the exciton lifetime, and slightly affects the exciton–exciton annihilation. By performing spatially resolved transient absorption measurements, exciton diffusion coefficients of about 100, 40, and 26 cm2 s−1 for the regions of WS2, h‐BN/WS2, and h‐BN/WS2/h‐BN, respectively, are obtained. The suppression of exciton diffusion by h‐BN is attributed to the additional phonon scattering mechanisms introduced by h‐BN, which decreases the exciton mean free path and thus the diffusion coefficient. The findings provide useful information for designing and understanding the effect of h‐BN layers interfacing with 2D semiconductors.

Effect of hexagonal boron nitride on the thermal and dielectric properties of polyphenylene ether resin for high-frequency copper clad laminates

As the base material of the printed circuit boards (PCBs), copper clad laminates (CCLs) with high thermal conductivity, low dielectric loss and high peel strength have been greatly desired especially for the upcoming 5G age. In this study, hexagonal boron nitride (hBN) was firstly introduced into the polymer insulating filler (Polyphenylene ether resin, PPER) of copper clad laminates for high frequency applications. The as-obtained CCLs exhibited a high thermal conductivity up to 1W/m·K and a low dielectric loss of ~4×10−3. Meanwhile, the interface tailoring of hBN was also tried by SiO2 coating, which enhanced the peel strength to a maximum value of 1.1N/mm, but changed the thermal conductivity behavior of the CCLs from the Agari's linear model to the modified quadratic model due to the interfacial thermal resistance effect of SiO2 coating on hBN. Moreover, the flexural strength and water absorption were also tested. The results revealed that, comparing with the related composite materials reported in literature and commercial products, the CCLs obtained in this paper have outstanding advantages in thermal and dielectric properties, validating the high potential of the present CCLs for use in high frequency PCBs.

Theoretical investigation of the effect of hexagonal boron nitride on perfect absorption in infrared regime

In this paper, we theoretically studied that the perfect interferenceless absorption in hexagonal boron nitride can be realized at different wavenumbers and incident angles. For examples, the absorption can reach 0.999 in the wavenumber band 500–750 cm−1 when the angle of incidence is 70°, and the absorption can beyond 0.9999 in the wavenumber band 1800–2400 cm−1 when the angle of incidence is 59.5°. The orientation of the optical axis provides an active way to manipulate the optical properties of the hexagonal boron nitride. This method does not only work for hexagonal boron nitride, but also works for other anisotropic materials. The results of this paper will give us a comprehensive understanding of hexagonal boron nitride.