Improvements of the structural,thermal, and mechanical properties of structural adhesive with functionalized boron nitride nanoparticles

Investigations on the production and development of nanoparticle-reinforced polymer materials have been attracted attention by researchers. Various nanoparticles have been used to improve the mechanical, chemical, thermal, and physical properties of polymer matrix composites. Boron compounds come to the fore to improve the mechanical and thermal properties of polymers. In this study, mechanical, thermal, and structural properties of structural adhesive have been examined by adding nano hexagonal boron nitride (h-BN) to epoxy matrix at different percentages (0.5, 1, 2, 3, 4, and 5%). For this purpose, nano h-BN particles were functionalized with 3-aminopropyltriethoxysilane (APTES) to disperse the h-BN nanoparticles homogeneously in epoxy matrix and to form a strong bond at the matrix interface. Two-component structural epoxy adhesive was modified by using functionalized h-BN nanoparticles. The structural and thermal properties of the modified adhesives were investigated by scanning electron microscopy and energy dispersion X-ray spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis techniques. Tensile test and dynamic mechanical analysis were performed to determine the mechanical properties of the adhesives. When the results obtained from analysis were examined, it was seen that the nano h-BN particles functionalized with APTES were homogeneously dispersed in the epoxy matrix and formed a strong bond. In addition that, it was concluded from the experimental results that the thermal and mechanical properties of adhesives were improved by adding functionalized nano h-BN particles into epoxy at different ratios.     

Fabrication and magnetic properties of boron nitride nanocapsules encaging iron oxide nanoparticles

Boron nitride (BN) nanocapsules with iron oxide nanoparticles were fabricated by an arc discharge method, and the magnetic properties of these nanocapsules were investigated. High resolution electron microscopy showed that iron oxide nanoparticles of size 20 nm were encapsulated by boron nitride sheets of width 4 nm. Magnetization of the BN nanocapsules showed paramagnetism and the initial iron oxides showed ferromagnetism, which suggests the transformation into superparamagnetism by separating the iron oxide nanoparticles with BN sheets. The present work showed that the BN nanocapsules with magnetic nanoparticles can be produced and the effectiveness of the arc melting method was confirmed.     

The electrical and thermal properties of polyimide/boron nitride nanocomposite films

In the paper, the polyimide (PI)/boron nitride (BN) nanocomposites were prepared by in situ polymerization and exhibited enhanced electrical property and thermal stability. The structure of synthesized PI was confirmed by scanning electron microscopy, energy dispersive spectrometer, and Fourier transform infrared. The influence of doping concentrations on the relative permittivity, electrical conductivity, loss tangent, corona-resistant lifetime, and thermal stability of PI composites was investigated. Results showed that the relative permittivity of PI/BN composites increases after doping BN nanoparticles. It was noteworthy that both the electrical conductivity and loss tangent of PI composites were enhanced in low frequency (0–3000 Hz) and the situations were shifted in high frequency (>3000 Hz). It was observed that the corona-resistant lifetime of PI/BN composite with 20 wt% BN increases more than eight times. Moreover, significant improvements in the thermal stability of PI composites were achieved by addition of only a small amount of BN. The decomposition temperatures at 5 and 10% weight loss were 518.7 and 551.6 °C for 15 wt% doped PI/BN composite, respectively, which increases by 37.3 and 40.5 °C compared to those of pure PI. The resulting properties expand further the application range of polyimides.     

The effect of boron nitride nanosheets on the mechanical and thermal properties of aluminum nitride ceramics

The boron nitride nanosheets (BNNSs)/aluminum nitride (AlN) composites were prepared by hot press sintering at 1600°C. The microstructure, mechanical properties, and thermal conductivity of the samples were measured, and the effect of adding BNNSs to AlN ceramics on the properties was studied. It is found that the addition of BNNSs can effectively improve the mechanical properties of AlN. When the additional amount is 1 wt%, the bending strength of the sample reaches the maximum value of 456.6 MPa, which is 23.1% higher than that of the AlN sample without BNNSs. The fracture toughness of the sample is 4.47 MPa m^1/2, a 68.7% improvement over the sample without BNNSs. The composites obtained in the experiment have brilliant mechanical properties.     

Structure,morphology and dielectric properties of hexagonal boron nitride nanoparticles reinforced biopolymer nanocomposites

Hexagonal boron nitride nanoparticles (h-BNNPs)/Chitosan (CS)/Hydroxypropyl methylcellulose (HPMC) based ternary nanocomposites were prepared using solution casting method and characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analyses (TGA), Scanning electron microscopy (SEM) and Atomic force microscopy (AFM). The dielectric properties of CS/HPMC/h-BNNP nanocomposite films were also investigated as a function of frequency and temperature and a maximum dielectric constant of ~1200 was achieved at 5 wt % of h-BNNP loading in CS/HPMC blend matrix. The results from the structural, morphological and thermal studies revealed good interactions between h-BNNPs, CS and HPMC.     

Modification of hexagonal boron nitride nanoparticles with fluorosilane

Surfaces of hexagonal boron nitride (hBN) nanoparticles were modified with perfluorooctyl-triethoxysilane (FTS). Experiments were performed for 40–120 min in 70–150 °C range with FTS/hBN weight ratio in the range of 0.5–1.5. The products were analyzed by FT-IR, TGA, FESEM, HRTEM and EDX. Results of FT-IR analyses indicated that modification takes place in 80 min at 150 °C under reflux with a FTS/hBN ratio of 1.5. Presence of FTS on hBN nanoparticles was confirmed by the weight losses in TGA, and by TEM, TEM-EDX analyses.     

Interfacial modification of boron nitride nanoplatelets for epoxy composites with improved thermal properties

Interface is a critical factor in determining the properties of polymer composites. Generally, the physicochemical properties of the interface are closely associated with the surface chemistry of fillers. In this study, we report a simple method to fabricate boron nitride (BN) nanoplatelets using a sonication-centrifugation technique and investigate the effects of functionalization BN nanoplatelets on thermal properties of epoxy composites. Two methods have been used for functionalizing BN nanoplatelets: non-covalent functionalization by octadecylamine (ODA) and covalent functionalization by hyperbranched aromatic polyamide (HBP). The functionalized BN nanoplatelets were characterized by Fourier-transform infrared (FT-IR), nuclear magnetic resonance (¹H NMR), thermogravimetric analyzer (TGA), and transmission electron microscopy (TEM). Epoxy composites were fabricated by incorporating three kinds of fillers: BN nanoplatelets, BN nanoplatelets functionalized by ODA (BN-ODA), and BN nanoplatelets functionalized by HBP (BN-HBP). Our results show that the BN-HBP results in a strong interface and thus the composites exhibit significantly increased glass transition temperature, thermal decomposition temperature, thermal conductivity and dynamic thermal mechanical modulus. BN-ODA produced intermediate interface interaction, resulting in a moderate improvement of thermal properties. The composites with BN nanoplatelets show the least improvements of thermal properties.     

Highly-dispersible boron nitride nanoparticles by spray drying and pyrolysis

A spray drying and pyrolysis synthesis route was developed and it successfully prepared boron nitride (BN) nanoparticles with high dispersivity. During the experiment, the extremely rapid drying of the boric acid/urea solution during the spray-drying process resulted in the formation of homogeneous precursors, which was the key for the final pyrolysis synthesis of BN nanoparticles with high dispersibility and uniform diameters (~20 nm). Compared with boron nitride synthesized without using spray drying, the as-prepared BN nanoparticles possess higher specific surface area (145.01 m² g⁻¹) and larger pore volume (0.41 cm³ g⁻¹). Especially, we used the BN nanoparticles as lubricant and incorporated it into the liquid paraffin (LP). The experiment results show that the LP presents outstanding antifriction properties for a BN content of 1.5 wt%. These results suggest that the h-BN nanoparticles have significant potential applications in the field of tribology.     

Liquid crystal epoxy composites based on functionalized boron nitride: Synthesis and thermal properties

A composite was prepared by in-situ polymerization of liquid crystal epoxy (LCE₄) with a low dielectric and high thermal conductivity boron nitride (BN) filler, which the filler (f-BN) was surface-functionalized by γ-glycidoxypropyltrimethoxysilane (KH560) and aminopropylisobutyl polyhedral oligomeric silsesquioxane (NH₂-POSS). The surface-functionalized BN was more uniformly dispersed in LCE₄, which improved the interfacial compatibility between inorganic and organic phases. Compared with pure LCE₄, KH560, and NH₂-POSS modified f-BN/LCE₄ composites exhibited a higher glass transition temperature, better thermal stability, and higher thermal conductivity. For example, when the f-BN content reached 30 wt%, the energy storage modulus of the composite increased to 2580 MPa, and the glass transition temperature was 103°C. The thermal conductivity of this 30 wt% f-BN composite was 0.48 W m⁻¹ K⁻¹, 128.6% higher than that of pure LCE₄. In addition, thermal stability, low hygroscopicity, and dielectric properties of the composites were characterized and analyzed to explore the application prospects of f-BN/LCE₄ composites in electronic packaging and in high-performance microelectronic devices.     

The impact of polymer matrix blends on thermal and mechanical properties of boron nitride composites

To improve mechanical and thermal properties of a hexagonal boron nitride platelet filled polymer composites, maleic anhydride was studied as a coupling agent and compatibilizer. Injection molded blends of acrylonitrile butadiene styrene (ABS), high-density polyethylene (HDPE), and maleic anhydride with boron nitride filler were tested for thermal conductivity and impact strength to determine whether adding maleic anhydride improved interfacial interactions between matrix and filler and between the polymers. Adding both HDPE and maleic anhydride to ABS as the matrix of the composite resulted in a 40% improvement in impact strength without a decrease in thermal conductivity when compared to an ABS matrix. The best combination of thermal conductivity and impact strength was using pure HDPE as the matrix material. The effective medium theory model is used to help explain how strong filler alignment helps achieve high thermal conductivity, greater than 5 W/m K for 60 wt % boron nitride. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48661.     

Tribological and thermal properties of hexagonal boron nitride filled high‐performance polymer nanocomposites

High‐performance polymer nanocomposites based on poly(aryletherketone) (PAEK) as matrix and hexagonal boron nitride (h‐BN) nanopowder as reinforcement were fabricated using planetary ball mill followed by hot pressing. The addition of h‐BN (0–5 wt %) to the matrix enhanced the microhardness and thermal stability compared to pure matrix. For a constant sliding speed, the wear rate of the nanocomposites determined by using Pin‐on‐Disk tribometer was reduced approximately 22 times compared to pure matrix. The coefficient of friction of the nanocomposites is slightly increased but it is stable compared to that of pure matrix. It was also investigated that the thermal stability of the debris of the nanocomposites was decreased compared to the pure matrix and its nanocomposites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44409.     

Mechanical and thermal properties of wood‐plastic composites reinforced with hexagonal boron nitride

Mechanical, thermal, and morphological properties of injection molded wood‐plastic composites (WPCs) prepared from poplar wood flour (50 wt%), thermoplastics (high density polyethlyne or polypropylene) with coupling agent (3 wt%), and hexagonal boron nitride (h‐BN) (2, 4, or 6 wt%) nanopowder were investigated. The flexural and tensile properties of WPCs significantly improved with increasing content of the h‐BN. Unlike the tensile and flexural properties, the notched izod impact strength of WPCs decreased with increasing content of h‐BN but it was higher than that of WPCs without the h‐BN. The WPCs containing h‐BN were stiffer than those without h‐BN. The tensile elongation at break values of WPCs increased with the addition of h‐BN. The differential scanning calorimetry (DSC) analysis showed that the crystallinity, melting enthalpy, and crystallization enthalpy of the WPCs increased with increasing content of the h‐BN. The increase in the crystallization peak temperature of WPCs indicated that h‐BN was the efficient nucleating agent for the thermoplastic composites to increase the crystallization rate. POLYM. COMPOS., 35:194–200, 2014. © 2013 Society of Plastics Engineers     

Fabrication and mechanical properties of boron nitride nanotube reinforced silicon nitride ceramics

In this study, silicon nitride (Si₃N₄) ceramics added with and without boron nitride nanotubes (BNNTs) were fabricated by hot-pressing method. The influence of sintering temperature and BNNTs content on the microstructures and mechanical properties of Si₃N₄ ceramics were investigated. It was found that both flexural strength and fracture toughness of Si₃N₄ were improved when sintering temperature increases. Moreover, α-Si₃N₄ phase could transform into β-Si₃N₄ phase completely when sintering temperature rises to 1800 °C and above. BNNTs can enhance the fracture toughness of Si₃N₄ dramatically, which increases from 7.2 MPa m^1/2 (no BNNTs) to 10.4 MPa m^1/2 (0.8 wt% BNNTs). However, excessive addition of BNNTs would reduce the fracture toughness of Si₃N₄. Meanwhile, the flexural strength and relative density of Si₃N₄ decreased slightly when BNNTs were added. The related toughening mechanism was also discussed.     

Light-emitting boron nitride nanoparticles encapsulated in zeolite ZSM-5

We report strong visible photoluminescence (PL) at room temperature from BN nanoparticles encapsulated in ZSM-5. The investigation of powder X-ray diffraction, X-ray photoelectron spectroscopy, adsorption of N₂, UV–Vis absorption, and PL spectra shows that BN nanoparticles have been successfully encapsulated in ZSM-5. Intense blue PL can be obtained from the BN/ZSM-5 sample. Analysis of PL spectra leads us to propose that the luminescence may originate from the bound excitons at the defects or impurities in the BN nanoparticles, a quasi-direct-gap semiconductor material transferred from indirect-gap BN by encapsulation in ZSM-5.     

基于变径-变压塔的甲醇/氯仿二元共沸物精馏分离过程热集成与动态控制

研究了基于变径-变压塔(VDC-PSD)联合处理二元共沸物甲醇-氯仿分离过程的热集成,基于Aspen dynamics对动态控制方案进行了仿真验证,并通过改进控制结构实现了对进料流量和进料组成在±20%扰动下的自动控制;在没有增加控制难度的情况下,带有热集成的VDC-PSD可以实现热量的综合利用,提高PSD的经济性。     

Preparation and properties of boron nitride nanosheets/cellulose nanofiber shear-oriented films with high thermal conductivity

A highly thermally conductive boron nitride nanosheets/cellulose nanofiber (BNNS/CNF) oriented film was prepared by doctor blading method via mechanical shear-induced orientation. The SEM images for cross-sectional parts showed that BNNS were well aligned within the film, forming a good layered structure. The XRD results further confirmed the high orientation effect of BNNS. Due to the excellent thermal stability of BNNS and its good physical barrier effect on the matrix after the orientation treatment, the thermal stability of shear-oriented films was largely improved. Resulting from the shear-induced orientation, BNNS were closely contacted with each other, forming a good thermally conductive pathway within the CNF matrix. Thus the influence of the interfacial thermal resistance was dramatically reduced, and the thermal conductivity of shear-oriented films increased in proportion to filler loading. With 50 wt% BNNS, the thermal conductivity of the shear-oriented film reached 24.66 W/(m·K), which exhibited 1106% enhancement compared to the pure CNF.     

Optical and electrical properties of boron nitride oxide films

Polycrystalline boron nitride oxide (BNO) films are synthesized by RF magnetron sputtering. It is found that the bandgap of the BNO film increases with increasing oxygen composition. The bandgap energy as wide as 5.5 eV is obtained with oxygen composition of 17%. The electrical resistivity is estimated to be as high as 10¹³ Ωcm. Metal/BNO/metal structures are fabricated with various metals such as Ni, Cu and Al, and electrical characterization are performed for metal/BNO contacts. The true Schottky barrier heights are estimated for metal/BNO contacts. The true Schottky barrier height decreases with increasing metal work function. This behavior of the Schottky barrier height suggests that the BNO film has p-type electrical conduction.     

Mechanical and dielectric properties of functionalized boron nitride nanosheets/silicon nitride composites

Uniformly dispersed boron nitride nanosheets (BNNSs) reinforced silicon nitride (Si₃N₄) composites were prepared by surface modification assisted flocculation combined with SPS sintering. In order to improve the dispersibility of the BNNSs in the composites, the liquid phase stripped BNNSs are surface functionalized by a two-step covalently modification. The amino-modified BNNSs (NH₂-BNNSs) and Si₃N₄ powders have opposite surface potential, mixed evenly by electrostatic interaction during flocculation. The results showed that mechanical properties of Si₃N₄ composites were obviously enhanced by adding NH₂-BNNSs. The fracture toughness and bending strength of Si₃N₄ composites added 0.75 wt% NH₂-BNNSs were increased by 34% and 28%, respectively, compared with monolithic Si₃N₄. Toughening mechanisms are synergistic action of the torn, pull-out or bridging of BNNSs and crack deflection mechanisms with microstructural analyzes. The dielectric properties of the Si₃N₄ ceramics are also improved after the addition of NH₂-BNNSs.