BN Content Research Articles

Mechanical and Thermal Behaviour of Epoxy/Hexagonal Boron Nitride/Short Sisal Fiber Hybrid Composites

Hybrid composite i.e. surface modified hexagonal boron nitride (hBN) and short sisal fiber reinforced in epoxy matrix is fabricated using hand lay-up method. The effect of surface modified hBN filler and sisal fiber content on mechanical and thermal properties of epoxy based hybrid composites were investigated in this paper. The main aim of the investigation is to develop a material which can found its application in microelectronic components. As per the requirement of microelectronic industry, the material should possess high thermal conductivity. Hence, thermal conductivity of epoxy increases with increase in hexagonal boron nitride content. Inspite of insulative nature of sisal fiber, the study shows that its inclusion in combination with hBN enhances the thermal conductivity if the content of both the fillers were properly selected. Other thermal property like coefficient of thermal expansion and glass transition temperature appreciably improves when combination of fillers were added in epoxy matrix. Mechanical properties under study i.e. tensile strength and compressive strength also enhances when combination of sisal fiber and hBN were incorporated as compared to when single filler hBN were used. Hence, usage of hybrid filler as reinforcement in epoxy improve overall mechanical and thermal property of the developed material.

Enhanced thermal conductivity of natural rubber based thermal interfacial materials by constructing covalent bonds and three-dimensional networks

With the rapid development of electronic integration technology, the timely and efficient heat dissipation capacity has become increasingly important to ensure reliability and lifetime of electronics. Thermal interface materials (TIMs) were considered as the best candidate to tackle this issue. In this work, the three-dimensional structures with covalent bond connections of boron nitride/natural rubber (BN/NR) thermal interface composites were successfully prepared and its possessed an ameliorated through-plane thermal conductivity of 0.79 W m−1 K−1 when BN content were 25 wt%. The results demonstrated that three-dimensional network structures and chemical interactions between BN and NR had a significant contribution in reducing interfacial thermal resistance. Meanwhile, the sensitive thermal response, satisfactory electrical insulation and good mechanical properties made its own high probability for the TIMs applications. Importantly, this tactics created a new means to construct elastomer-based thermal management materials and applied for the electronic packing materials.

Achieving a high thermal conductivity for segregated BN/PLA composites via hydrogen bonding regulation through cellulose network

Normally, the effective dispersion of thermal conductive fillers is a prerequisite for ensuring thermally conductive networks formed in polymer composites. In this work, a facile method was provided by using cellulose to alter the distribution state of boron nitride (BN) for the preparation of high thermally conductive polylactic acid (PLA). After powder mixing and hot‐pressing process, the Cellulose@BN was located at the boundaries of PLA granules to form consecutive thermally conductive networks with more compact structure. Morphology observation and FTIR spectra confirmed that BN edges absorbed on the cellulose surface under the intermolecular hydrogen bond interaction between PLA and BN. At the BN content of 25 wt%, contrasted with traditional BN/PLA segregated polymer composites (SPCs), thermal conductivity coefficient of Cellulose@BN/PLA SPCs improved by 53.5% from 0.71 to 1.09 Wm−1 K−1. This enhancement could be attributed to the reason that the cellulose regulated stripe aggregation allowed the BN connect with each other more compact, thus a thermal conduction networks with reduced phonon scattering were formed.

Boron nitride for modification of rubber based on isoprene elastomer

The work studies vulcanization characteristics of elastomers based on isoprene rubber filled with carbon black N330 and boron nitride (BN). The influence of the boron nitride (BN) concentration on technological, dynamic, physical and mechanical properties of elastomers has been researched. The application of boron nitride for producing rubber with good properties has been considered. With a gradual increase of the inert filler BN concentration up to 35%, a decrease in the curing rate by 33% and polymer cross-link density by 26% is observed. Moreover, the start time of vulcanization increases by almost 300%, the optimal curing time by 200%.

Compressive properties and energy absorption response of cBN added Al composite foams

Abstract In this study, pure Al foam and 2, 5, 10 wt.% cubic boron nitride Al composite foams were manufactured to reveal the effects of cubic boron nitride addition on the properties of Al foam materials. Cellular morphology investigations and quasi-static compression test results were correlated with the effect of foaming agent behavior, compacting pressure, amount of ceramic addition, and compressive properties. The cubic boron nitride reinforced Al foams exhibited superior compressive properties and energy absorption behavior. The compressive properties were enhanced by increasing the cubic boron nitride content and compacting pressure. The maximum mechanical properties were achieved in 10 wt.% cubic boron nitride aluminum composite foams. The results revealed that these composite foams are possibly a candidate for specific high technology applications with high mechanical properties.

Thermal conductivity of polyimide/AlN and polyimide/(AlN + BN) composite films prepared by in-situ polymerization

A series of polyimide/AlN composite films and polyimide/AlN/BN composite films with different contents were prepared by using polyimide as organic matrix, AlN and BN as inorganic fillers. The filling of the ALN + BN particles increases the dielectric constant, the breakdown strength, and the thermal conductivity of the film. After filling in 9 vol% AlN content, the thermal conductivity of the polyimide/AlN composite film was 0.675 W/(m·K), which was three times that of the pure PI film. The PI/AlN/BN composite film had a thermal conductivity of 0.711 W/(m·K) when the content of AlN and BN was 3 vol% and 6 vol%, When the inorganic packing particles are 3%, the tensile strength loss is small and the breakdown strength is increased to 180 kV/mm. The SEM image of PI film showed that when different contents of AlN particles were added to the matrix, whitening phenomenon may occur due to poor interface bonding ability, and the problem was improved after KH560 modification. The result showed that two fillers with different particle sizes formed a close-packing, which was beneficial to increase the number of thermal conduction paths, thereby improving the thermal conductivity. Overall, this paper prepared a series of PI thin films with high thermal conductivity and high insulation.

Enhancing the mechanical, wear and corrosion behaviour of stir casted aluminium 6061 hybrid composites through the incorporation of boron nitride and aluminium oxide particles

This research paper portrays the enrichment of mechanical, wear and corrosion properties of the Aluminium 6061 matrix composite by incorporating hybrid reinforcements. Aluminium 6061 alloy is stir casted with different proportions of boron nitride (BN), Aluminium oxide (Al2O3) and graphite particles. Tensile test reveals that the tensile strength and ductility for the Al 6061-30 BN -10Al2O3- 5C is improved due to the presence of higher BN content along with 10% Al2O3. Significant improvement in microhardness (63HV), compressive strength (187 Pa) and impact strength (12 J) for the Al 6061-30 BN -10Al2O3- 5C when compared with the bare Al 6061 alloy. The dispersion of BN with Al2O3 improved the wear resistance for the Al 6061-30 BN -10 Al2O3- 5 C composite, where as the unreinforced bare Al alloy has caused the major surface degradation resulting in poor wear property and the worn out surfaces are examined through the scanning electron microscope. The main wear mechanism is identified as adhesive wear. The corrosion test results clearly reveals that the corrosion resistance is higher for the Al 6061-30 BN -10Al2O3- 5C (−0.526 ± 0.004 V) with a lower current density of −0.983 ± 0.004 μA cm−2 than the other composites and bare Al 6061.

Структура и свойства композиционных компактов из высоколегированного порошка железа с добавками нитрида бора

The results of the research of structure and properties of a composite compact from 13 Cr – 2 Мо and BN powders depending on the concentration of boron nitride are provided. It is shown that adding boron nitride in an amount of more than 2% by weight of the charge mixture leads to the formation of extended grain boundary porosity and finely dispersed BN layers in the structure, which provides a high level of wearing properties of the material. The effect of boron nitride concentration on physical and mechanical properties is determined. It was found that the introduction of a small amount of BN (up to 2 % by weight) into the compacts leads to an increase in plasticity, bending strength, and toughness by reducing the friction forces between the metal powder particles during pressing and a more complete grain boundary diffusion process during sintering. The formation of a regulated structure-phase composition of powder compacts of 13 Cr – 2 Mо – BN when the content of boron nitride changes in them allows us to provide the specified physical and mechanical properties in a wide range. The obtained results of studies of the physical and mechanical characteristics of the developed material allow us to reasonably choose the necessary composition of the powder compact for sealing structures of the flow part of steam turbines, depending on their operating conditions.

Thermal Performances of UHMWPE/BN Composites Obtained from Different Blending Methods

UHMWPE/BN composites were prepared by solvent mixing (SM) in this work, then were characterized by scanning electron microscope (SEM), Raman mapping, differential scanning calorimeter (DSC), thermogravimetric analysis (TG), and thermal conductivity meter to study the morphology, filler distribution, segregated structure, and thermal stability as well as thermal conductivity. Compared to the traditional melt mixing (MM), SM followed by molding contributes to the construction of segregated structures in UHMWPE composite. This segregated structure can greatly improve the thermal conductivity of the composites. The segregated structure of composites prepared by MM is destroyed by shearing. Moreover, the thermal stability of composites by SM is improved with the increment of BN content, which is better than that of samples by MM, probably resulting from the barrier function of the segregated structure.

Solid‐state shear milling method to prepare PA12/boron nitride thermal conductive composite powders and their selective laser sintering 3D‐printing

ABSTRACTThe selective laser sintering (SLS) is one of the most important 3D‐printing technologies. However, the challenges in SLS could be in the limited high material cost and single material performance. Development of high‐performance and multifunctional copowders suitable for SLS is of great importance. Here, polyamide 12 (PA12)/boron nitride (BN) thermal conductive copowders suitable for SLS were successfully prepared through solid state shear milling (S3M) technology in combination with cryogenic pulverization technology. The particle size, morphology, grafting reaction between PA12 and BN, rheology behavior, and coalescence behavior of the obtained PA12/BN copowders were carefully investigated. The optimal amount of silica flow additive (0.5 wt %) was determined to achieve the good powder flowability. Under the optimum 3D‐printing conditions, the fabrication of parts with high BN loading could be achieved. When BN content was at 40 wt %, the flexural strength could reach 10.6 MPa and the thermal conductivity could reach 0.55 W/m·k, 77% higher than that of pure PA12. After treated with phenolic epoxy resin, the tensile strength and flexural strength of the printed parts with 40 wt % BN loading could reach 14.2 and 25.6 MPa, which were 130 and 115% higher than those of the untreated 3D‐printed parts, respectively. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48766.

High thermal conductive shape-stabilized phase change materials of polyethylene glycol/boron nitride@chitosan composites for thermal energy storage

Phase change materials (PCMs) applied in the energy storage and temperature control system are crucial for energy conservation and environmental protection. In this work, boron nitride (BN)@chitosan (CS) scaffolds with three-dimensional (3D) porous structures were fabricated. And effective thermal conductive pathways could be created in the resultant scaffolds. By introducing polyethylene glycol (PEG) into the BN@CS scaffolds, composite PCMs with large latent heat of fusion and excellent shape-stability were obtained. In particular, a high thermal conductivity up to 2.77 W m−1 K−1 could be reached at a relatively low content of BN (27 wt%). Moreover, they also exhibited a satisfactory energy storage density of 136 J g−1. This work demonstrated a facile and environmentally friendly strategy to simultaneously achieve enhancement of thermal conductivity, high energy storage density, shape stability and outstanding thermal repeatability for composite PCMs, which held promising potential in waste heat recovery, cooling system and temperature control system.

A self-healing silicone/BN composite with efficient healing property and improved thermal conductivities

Polymer dielectric composites with excellent thermal conductivity have received increasing attention in the modern electronics industry due to their outstanding thermal management performance. However, conventional polymers used for the thermally conductive composites usually suffer from accidental mechanical failure, causing decrease in service life or loss of functionality. In this work, we prepared a self-healing silicone/BN composite simultaneous with high thermal conductivity, high self-healing efficiency and low electrical conductivity. Silicone cross-linked by DA adduct was used as polymer matrix and BN was used as thermally conductive filler. The self-healing silicone/BN composite exhibited a high self-healing efficiency of higher than 90% and an enhancement of 544% in thermal conductivity at BN content of 50 wt%. The self-healing composites presented excellent thermal management performance. The excellent self-healing properties were attributed to the thermal reversibility of the DA reaction and the flexibility of the siloxane molecules. In addition, the self-healing silicone/BN composite with 50 wt% of BN exhibited a low dielectric dissipation factor of 0.017 and an enhancement of 568% in tensile strength.

High thermal conductive epoxy based composites fabricated by multi-material direct ink writing

Thermal management is of importance to microelectronic industry. Owing to both excellent thermal conduction and electrical insulation, hexagonal boron nitride (BN) platelets are the widely-used thermal conductive fillers in polymers. Adding high content of BN can endow polymers high thermal conductivity, but in most cases, destroy the flexibility, failure strength as well as processability of the polymers significantly. Here, we report a multi-material 3D printing technique to prepare high thermal conductive epoxy based composites, by which BN platelets were assembled together in heat-conducting phase to form the dense, continuous thermal pathway. The BN platelets show excellent alignment along printing direction in epoxy matrix due to the shear-inducing effect of printing. The composites at filler loading of 20 wt% exhibit the thermal conductivity of 2.52 W·m−1·K−1 along printing direction. The thermal conductivity of the composites is in good agreement with the prediction of parallel model. It indicates that the composites with specific thermal conductivity can be prepared by tailoring the printing ratio of the heat-conducting phase to the matrix phase. Mechanical and insulating performance of the composites maintain good enough as well.

Synergetic effect of thermal conductivity and flame retardancy of cyanate ester composites containing DOPO and BN with great dielectric properties

DOPO and boron nitride (BN) fillers with different particle sizes and several loadings were employed to improve the properties of cyanate ester (CE) resin. The effects of BN content and particle size on the thermal conductivity of the BN‐DOPO/CE ternary composites were discussed. The influence of enhancing the thermal conductivity of the ternary composites on their flame retardancy was studied. The consequences showed that increasing the thermal conductivity of BN‐DOPO/CE composites had an active impact on their flame retardancy. Approving flame retardancy of the ternary composites was certified by the high limiting oxygen index (LOI), UL‐94 rating of V‐0, and low heat release rate (HRR) and total heat release (THR). For instance, in contrast with pure CE matrix, peak of HRR (pk‐HRR), average of HRR (av‐HRR), THR, and average of effective heat of combustion (av‐EHC) of CEP/BN0.5 μm/10 composite were decreased by 51.7%, 33.8%, 18.7%, and 18.9%, respectively. Thermal gravimetry analysis (TGA) showed that the addition of BN fillers improves the thermal stability of the composites. Moreover, the ternary composites possess good dielectric properties. Their dielectric constants (ε) are less than 3, and dielectric loss tangent (tgδ) values are lower than neat CE resin.

Porous boron nitride/polyimide composite films with high thermal diffusivity and low dielectric properties via high internal phase Pickering emulsion method

This work offers a simple fabrication of porous boron-nitride-(BN)/polyimide-(PI) composite films with high thermal diffusivities and low dielectric constants by combining high-internal-phase Pickering emulsification (HIPPE) and subsequent hot-pressing. BN nanoparticles in composite foams were well dispersed and three-dimensionally connected following the surface of the PI skeleton used as the polymer matrix. The BN contents in the BN/PI composite foams were adjusted in the range of 20–80wt%. The porosities of the composite films were controlled according to the hot-pressing conditions such as the temperature. The porous BN/PI composite films exhibited high thermal diffusivities of 0.059–1.033mm2/s and low dielectric constants of 2.08–3.48 at 1GHz for BN contents of 20–80wt%. In particular, the BN/PI composite films had extremely low dielectric loss values, close to zero (<0.002) at high frequencies regardless of the BN content and pressing conditions.

New BN/SiOC aerogel composites fabricated by the sol-gel method with excellent thermal insulation performance at high temperature

Although pure silicon oxycarbide (SiOC) aerogels have unique properties of low density and high temperature resistance, they are still difficult to apply at a large scale due to brittleness. To overcome this drawback, a strong boron nitride/silicon oxycarbide (BN/SiOC) aerogel composite with high-temperature resistance and thermal insulation was prepared by the sol-gel method and pyrolysis of the precursor aerogel. The microstructural, mechanical and thermal insulation properties of the composites were investigated, and the effect of the BN content on the microstructure and properties was also clarified. The results indicate that the obtained mesoporous composites exhibit low thermal conductivity (0.04–0.20 Wm−1 K−1) and high-temperature resistance (∼1300 °C). As the BN content increased from 0 to 15 vol %, the compressive strength of the composites increased from 2.2 to 20.3 MPa. The obtained composites exhibit considerable promise in high-temperature thermal insulation applications.

Facile Liquid-Exfoliation Process of Boron Nitride Nanosheets for Thermal Conductive Polyphthalamide Composite.

In this study, we describe the fabrication of thermally conductive composites based on a polyphthalamide (PPA) matrix by the exfoliation of hexagonal BN nanosheets (BNNs) via the melt-mixing method. Boron nitride (BN) particles were hydroxyl groups surface-treated with sodium hydroxide (NaOH). Compared with existing BN peeling experiments, we successfully produced BNNs that are simpler, more economical, and have an excellent aspect ratio. For the same weight content of BN and BNNs, PPA/BN composites surface-treated with high aspect ratio BNNs have a high in-plane and through-plane thermal conductivity because of the intercalation of the hydroxyl group surface treatments between BN and PPA, which not only increases the wettability but also provides a good heat transfer path. Moreover, wide and thin BNNs are evenly dispersed inside the PPA/BN composite to provide excellent heat transfer paths in both in-plane and through-plane directions.

Wetting and reaction of BN-SiO2 ceramic by molten Ti-40Ni-20Nb (at.%) filler alloy

The wetting behavior and the interfacial reactions of molten Ti-40Ni-20Nb (at.%) filler alloy on the BN-SiO2 ceramic were investigated by the a sessile drop method at 1453 K under a vacuum atmosphere. Results demonstrated that a good wettability with final contact angles of approximately 44°–15° was obtained. Interfacial microstructure examinations revealed that the Ti-40Ni-20Nb filler alloy reacted with the BN-SiO2 ceramic, which resulted in the formation of TiN, TiB, Ti5Si3 and Ti3O5 at the interface. The wetting process of the Ti-40Ni-20Nb filler alloy on the BN-SiO2 ceramic was identified into 3 stages: (i) rapid decreasing stage, (ii) sluggish spreading stage and (iii) final equilibrium stage. In order to reveal the essence of the reactive wetting, the wettability of the Ti-40Ni-20Nb (at.%) filler alloy on the BN-SiO2 ceramic with three different BN contents were investigated. For the Ti-40Ni-20Nb/BN-SiO2 system, the wettability mainly depended on the final interfacial chemistry of the system but the intensity of the interfacial reactions. The final contact angle of the Ti-40Ni-20Nb filler alloy on the BN-SiO2 ceramic decreased as the BN content in the ceramic was increased from 20% to 80%.

Modulating topological structure of carbon nanotube/cyanate ester-boron nitride/cyanate ester multi-layered composites for enhancing dielectric properties, breakdown strength and energy density

Constructing multi-layered structures based on insulating layers and conductor/polymer composites is proved to be an effective strategy of preparing high dielectric constant conductor/polymer composites with suppressed dielectric loss, high breakdown strength and high energy density; however, up-to-date, researches are mainly focused on three-layer structures, the influence of the layer number on dielectric properties, breakdown strength and energy density of multi-layered composites has not been clearly elaborated yet. Starting from a typical three-layer structure composite (CBC) with outstanding integrated performance using carbon nanotube (CNT)/cyanate ester resin (CE) and hexagonal boron nitride (BN)/CE composites as C layer and B layer, respectively, new four-layer structure (CBCB) and five-layer structure (CBCBC and BCBCB) composites were fabricated to reveal the role and mechanism of layer number and BN content, consequently finding a new technique to get multi-layered composites with better integrated performances. Results show that when the content of BN in B layer is 20 wt%, the five-layer structure composite (CBC20BC) achieves the highest energy density, about 6264% higher than that of 0.4CNT/CE, this improvement of energy density is the maximum value among all multi-layered composites based on conductor/polymer layer reported so far. In addition, the dielectric constant of CBC20BC composite is as high as 352 (100 Hz), and the breakdown strength of CBC20BC composite is 1.4 times of that of CBC composite. The mechanism behind these excellent integrated performances is that the increase in layer number not only enhances the interfacial polarization, but also extends the length and tortuosity of breakdown path.

Achieving High Thermal Conductivity in Epoxy Composites: Effect of Boron Nitride Particle Size and Matrix-Filler Interface.

For the thermal management of high watt density circuit layers, it is common to use a filled epoxy system to provide an electrically insulating but thermally conducting bond to a metal substrate. An epoxy-thiol system filled with boron nitride (BN), in the form of 2, 30 and 180 µm platelets, has been investigated with a view to achieving enhanced thermal conductivity. The effect of BN content on the cure reaction kinetics has been studied by differential scanning calorimetry and the thermal conductivity of the cured samples has been measured by the Transient Hot Bridge method. The heat of reaction and the glass transition temperature of the fully cured samples are both independent of the BN content, but the cure reaction kinetics is systematically affected by both BN content and particle size. These results can be correlated with the thermal conductivity of the cured systems, which is found to increase with both BN content and particle size. For a given BN content, the thermal conductivity found here is significantly higher than most others reported in the literature; this effect is attributed to a Lewis acid-base interaction between filler and matrix.