查找使用阿拉丁产品的科研文献

Enhanced atomic oxygen erosion resistance and wear resistance of epoxy nanocomposites with KH560-functionalized h-BN nanohybrids

Wu Yi-Ming,Hou Guo-Yuan,Fan Xin,Zhu Qian-Ye,Cui Ming-Jun,Ren Si-Ming

Polymer materials commonly employed in low Earth orbit (LEO) environments are highly susceptible to atomic oxygen (AO) attack, leading to severe degradation and deterioration of their properties. To address this challenge, 3-glycidyloxypropyltrimethoxysilane-modified hexagonal boron nitride (h-BN@KH560) nanohybrids were synthesized and incorporated into epoxy (EP) composites to enhance their AO erosion resistance. The resulting hexagonal boron nitride-based epoxy nanocomposites (FBN/EP) were systematically evaluated for their tribological performance and AO erosion resistance using a series of characterization techniques. The results demonstrated that the incorporation of h-BN@KH560 nanohybrids significantly improved the wear resistance and AO erosion resistance of the EP matrix. Specifically, the FBN 1.0 /EP nanocomposite exhibited an 86.1% reduction in wear rate compared to pure EP, while FBN 5.0 /EP nanocomposite achieved optimal AO erosion resistance, with a minimal erosion rate of 3.58 × 10 –24 cm 3 atoms −1 at an AO dose of 1.2 × 10 21 atoms cm −2 . These findings indicate that the incorporating content-induced distribution of h-BN@KH560 within the EP matrix strongly influences the wear resistance of FBN/EP nanocomposites, but there is a relatively minor effect on their AO erosion resistance. The enhanced AO erosion resistance is attributed to the synergistic barrier protection provided by h-BN@KH560 and the formed B 2 O 3 and SiO 2 layers under AO irradiation. This study offers a promising strategy for extending the service life of epoxy nanocomposites in harsh LEO environments. Graphical abstract

The structural design and oxidation resistance of high fracture toughness Si3N4/BN composites for elevated temperature application

Ningning Dong,Liuxin Chao,Yue He,Bangjun Li,Yun Zhu,Lu Liu,Guobing Ying

Si 3 N 4 /BN composites were fabricated via hot-pressing sintering, achieving outstanding mechanical properties with flexural strength of 623.41 MPa and fracture toughness of 10.22 MPa·m 1/2 - through structural optimization. Key factors contributing to these properties included the use of finer Si 3 N 4 powder, unidirectional fiber alignment, and an optimized fiber diameter of 0.95 mm, which enhanced densification. The residual strength of samples subjected to oxidation testing at 1000-1400 °C for 1-64 h was measured. Notably, samples oxidized at 1000 °C for 4 h exhibited a 5.04% increase in flexural strength compared to their room-temperature strength, attributed to SiO 2 healing the microcracks. At 1200 °C, needlelike Y 2 Si 2 O 7 crystals formed, while higher temperatures (up to 1400 °C) and prolonged oxidation led to their dissolution and the precipitation of platelike aluminosilicates. These microstructural transformations were found to critically influence the residual strength, highlighting the intricate relationship between oxidation conditions, phase evolution, and mechanical properties in Si 3 N 4 /BN composites.

Directional BN alignment via Fe3O4 with Tri-source engineered ATP for enhanced fireproofing performance of waterborne epoxy

Xubin Yang,Fei Zhong,Yingqing Zhan,Xin Zhang,Xinyu Bai,Jiawei Liu,Xulin Yang

The inherent flammability of epoxy resins (EP) limits their application in safety-critical areas. This study proposes a structurally ordered and synergistically flame-retardant strategy to address this issue. Initially, polydopamine (PDA) serves as a functional bridging layer to facilitate uniform deposition of Fe 3 O 4 nanoparticles onto boron nitride (BN) nanosheets, constructing a magnetically responsive interface. Subsequently, adenosine triphosphate (ATP) is introduced through copolymerization to form a novel composite flame retardant BN-Fe 3 O 4 @PATP (PATP is a copolymer of polydopamine and adenosine triphosphate). Under magnetic field induction, the BN loaded with Fe 3 O 4 nanoparticles achieves directional alignment within the epoxy resin matrix, forming an efficient physical thermal barrier. Simultaneously, the transition metal oxide Fe 3 O 4 can enhance the formation of residual charcoal. Furthermore, the acid source (phosphate groups), carbon source (polyhydroxy compounds), and gas source (amino groups) within ATP structure can generate an expanded char layer at high temperatures, thus improving its thermal shielding performance. Experimental results demonstrated significantly enhanced flame retardancy of the BN-Fe 3 O 4 @PATP/EP composite system compared to pure EP: peak heat release rate (PHRR), total heat release rate (THR), peak smoke release rate (PSPR), and total smoke release rate (TSR) were reduced by 39.8 %, 24.8 %, 36.8 %, and 44.3 %, respectively. Compared with pure epoxy and other epoxy composites, BN-Fe 3 O 4 @PATP/EP system also exhibits the lowest peak carbon monoxide (PCOPR) and carbon dioxide (PCO 2 PR) evolution rates, while the char residue rises significantly from 14.6 % (pure EP) to 28.8 %. By achieving magnetic field-induced ordered arrangement of BN combined with catalytic char-forming effect and intumescent flame-retardant mechanism, this work constructs a multifunctional flame-retardant system endowed with thermal insulation, smoke suppression, and toxicity reduction capabilities, providing a new strategy for the flame retardancy of EP.

Narrowband Blue Circularly Polarized Luminescence Emitter Based on BN-Doped Benzo[6]helicene with Stimuli-Responsive Properties

Meiyan Liu,Chenglong Li,Guanming Liao,Fenggui Zhao,Chunxia Yao,Nan Wang,Xiaodong Yin

Graphical Two 1,4-azaborinine [6]helicenes, H[6]BN1 and H[6]BN2 , exhibit blue fluorescence with narrow FWHMs below 31 nm and high PLQY up to 92 %. Desirable circularly polarized luminescence with g lum reaching 4~5×10 −4 and good configurational stability are relized for H[6]BN1 and H[6]BN2 . Mechanochromism occurs between H[6]BN1 ′s crystalline and amorphous states by modulationg π-π intermolecular interanctions. An turquoise OLED based H[6]BN1 is manufactured with the external quantum efficiency (EQE) of 3.18 %. Boron-doped helicenes, known for their unique electronic and photophysical properties, are of great interest for numerous applications. This research introduces two new azabora[6]helicenes, H[6]BN1 and H[6]BN2 , synthesized through an efficient method. These molecules have boron and nitrogen atoms in opposing positions, enhancing their distinctive attributes. Both helicenes show excellent emission properties, with H[6]BN1 and H[6]BN2 exhibiting narrowband blue fluorescence and circularly polarized luminescence (CPL), achieving g lum values of 4~5×10 −4 which is beneficial for chiroptical applications. The addition of a donor group, 3, 6-di-tert-butyl-9H-carbazole, in H[6]BN2 improves luminescence, likely due to enhanced molecular orbital overlap and electron delocalization. H[6]BN1 ′s needle-like single crystals exhibit mechanochromism, changing luminescent color from yellow to green under mechanical stress, which is promising for stimulus-responsive materials. In conclusion, this study presents a novel class of BN[6]helicenes with superior chiroptical properties. Their combination of electronic features and mechanochromism makes them ideal for advanced chiroptical materials, expanding the potential of helicene-based compounds and offering new directions for the synthesis of molecules with specific chiroptical characteristics.

Development of gradient cemented carbides with surface layers free of cubic phase via h-BN nitrogen source

Xu Xia,Chenyang Ma,Tianen Yang,Zhiyuan Ma,Yu Cao,Jiahuan He,Qiwen Zheng,Huaping Hong,Ji Xiong

This study investigates gradient cemented carbide with a cubic phase-free surface layer (CFL), commonly used as substrates for coated inserts to extend their service life. The tough gradient surface layer effectively prevents crack propagation, minimizing coating delamination and edge chipping. We propose using hexagonal boron nitride (h-BN) as a non-cubic nitrogen source for fabricating gradient cemented carbide with cubic (W,Ti)C, as a replacement for traditional cubic nitrogen sources. By employing powder metallurgy, we successfully created gradient cemented carbide with a CFL derived from h-BN. We also analyze the mechanism of gradient structure formation and characterize the microstructure, elemental distribution, and mechanical properties of the novel materials. The results demonstrate the feasibility of producing gradient cemented carbides with a CFL when h-BN is used as the nitrogen source. The crystal orientations at the gradient boundary are randomly distributed, showing no abrupt interface between the surface layer and the interior. Notably, titanium (Ti) and boron (B) are nearly absent in the surface layer, while cobalt (Co) shows higher concentration compared to the interior. The use of h-BN facilitates a nearly homogeneous titanium distribution in the subsurface zone, contrasting with the clustering seen when traditional cubic TiN is employed as the nitrogen source. Additionally, the thickness of the gradient surface layer can be effectively controlled by adjusting the h-BN levels, increasing with higher h-BN content in the raw materials. However, excessive h-BN addition facilitates abnormal WC phase growth in cemented carbides, and negatively affects transverse rupture strength despite the toughening effects of the cubic phase-free layer. Increased h-BN content also promotes the formation of TiB phases, which enhances the hardness of the cemented carbide.

Design and Fabrication of FeSiCr@BN Soft Magnetic Composites with Improved Thermal Management and Core Loss Performance

Rui Wang,Kaixuan Li,Yang Liu,Zhaoyang Wu,Xingyi Wu,Shaogang Li,Li Liu

The optimization of FeSiCr soft magnetic composites remains a critical research area in the development of integrated molded inductors. Constructing dense insulation layers and achieving the ordered alignment of flaky magnetic powders are effective strategies to enhance their overall performance. Inspired by the structural design of fried chicken steak, this study synthesizes FeSiCr@boron nitride (BN) soft magnetic composites. By modifying with two-dimensional BN and employing magnetic field–assisted directional molding, the composites achieve orderly particle alignment and efficient insulation coating. Experimental results indicate that the thiol-modified BN (BN-s) insulation layer chemically bonded to the FeSiCr matrix, combined with the ordered alignment of flaky particles induced by magnetic orientation, substantially improves core loss performance and thermal management. The FeSiCr@BN soft magnetic composites with the optimal BN-s content of 4   wt% show a core loss of 398.5   kW/m 3 (30 mT/300   kHz), a thermal conductivity of 30.01   W·m −1 ·K −1 , a reduced operating temperature rise of 119°C, and an impressive resistivity increase from 0.08 to 10.17 Ω·m. This work presents a design strategy for soft magnetic composites, highlighting the promising applications of the prepared composites in electronic devices, power electronic systems, and smart grids.

Study of Nacre-like h-BN/waterborne polyurethane nanocomposite with high-thermal, mechanical and water resistance properties

Xiaoyan Gao,Nisar Ali,Meng Zhao,Guang Hu,Adnan Khan,Dandan Min,Lijing Zhang,Lingli Ni,Mohammed Albahri

Nacre-like polymer nanocomposites have become fascinating material nowadays because of their exceptional mechanical property. In this study, nacre-like waterborne polyurethane/hexagonal boron nitride (WPU/h-BN) nanocomposite with high-thermal, mechanical and water resistance has been successfully prepared via mechanical blending method. Owing to strong interfacial interactions and a nacre-like structure, the WPU/h-BN nanocomposite with a loading amount of 30 wt% exhibits excellent tensile strength of 27.3 MPa, compared with 4.16 MPa for pure WPU. Additionally, it has an exceptional maximum decomposition temperature of 443 °C and an outstanding water absorption ratio of 8.1 %. This approach of adopting h-BN and WPU to construct nacre-like structure may provide a new path for preparing high performance WPU strategies.

Enhancing Breakdown Field Strength and Energy Density in Sandwich-Structured P(VDF-HFP)/BT Films with BN Coating

Yinzhang Cheng,Xueting Bai,Zhenyu Lu,Ruijue Wang,Wei Wang,Ruizhou Guo,Yudong Xu,Zhipeng Lei

With the rapid development of communication, electronics, medical, and energy industries in modern society, film capacitors have garnered widespread attention and undergone significant growth. However, the low energy density (Ue) resulting from low breakdown strength (Eb) significantly limits the application of thin-film capacitors. In this work, we use a low-cost and effective dip-coating method to apply boron nitride (BN) layers onto the outer layers of poly(vinylidene fluoride-co-hexafluoropropylene)/barium titanate (P(VDF-HFP)/BT) composite films to prepare boron nitride-poly(vinylidene fluoride-co-hexafluoropropylene/barium titanate-boron nitride (BN-P(VDF-HFP)/BT-BN) composite films with a sandwich structure that exhibits extremely highEbandUe. The experimental results show that the sandwich-structured BN-P(VDF-HFP)/BT-BN films containing 7.5 wt% BT nanoparticles obtained 530 MV/mEband 18.12 J/cm3Ue, both of which are much higher than those of the corresponding monolayer films. In addition, the finite element simulation results show that the designed sandwich-structured films can reduce local field strength distortion, decrease leakage current, and suppress the development of breakdown channels, thereby significantly improvingEbandUe. In summary, this study presents a low-cost and effective method for enhancing the breakdown strength and energy density of thin-film capacitors.

Larvicidal activity of Illicium difengpi BN Chang (Schisandraceae) Stem Bark and its Constituent Compounds against Aedes aegypti L

Y Liu,XC Liu,QY Liu,C Niu,ZL Liu

Breakdown Characteristics of BN Modified Silicone Gel Composite Insulation Materials under High du/dt Voltage

Dazhi Su,Bowen Tang,Shuoyan Ren,Hengxin Zhong,Zhiqian Liu,Ju Tang,Fuping Zeng

With the development of wide bandgap power semiconductor devices represented by silicon carbide (SiC) to higher voltage levels and faster switching speeds, the reliability of packaging insulation is facing severe challenges. In this paper, the strategy of modifying silicone gel by nano boron nitride (BN) doping is proposed, and the breakdown characteristics of composite insulation materials under high du/dt voltage are studied. The experimental results show that the breakdown voltage of composite insulating materials with different BN doping mass fractions decreases significantly with the increase of voltage rise rate. The doping of BN can effectively improve the high du/dt breakdown voltage of the composite insulating medium, and the modification effect is the most significant when the doping mass fraction of BN is 2%. Further combined with molecular simulation studies, it is found that the change in energy level structure of composite insulating materials under the action of electric field will lead to an increase in the number of carriers, which will accelerate the initiation of avalanche breakdown under high du/dt conditions. The doping of BN changes the charge transport mechanism of the composite material, and enhances the polarization of the molecular chain, thus exhibiting better insulation performance under high du/dt conditions. This study provides important data support and theoretical basis for the development of new high-performance insulation materials for new generation power device packaging.

Mussel-inspired immobilization of BN nanosheets onto poly(p-phenylene benzobisoxazole) fibers: Multifunctional interface for photothermal self-healing

Qing Shao,Zhen Hu,Xirong Xu,Long Yu,Dayu Zhang,Yudong Huang

The composites with interfacial self-healing ability are smart and promising materials in the future. Although some approaches have been used to heal the micro-cracks in composite materials, it is still a great challenge to develop a versatile strategy to fabricate multifunctional interface for self-healing. Here, boron nitride nanosheets (BN) are immobilized onto PBO fibers by facile polydopamine (PDA) chemistry. Benefiting from the photothermal effect of BN-PDA, the obtained surface layer displays interfacial self-healing properties under Xenon light irradiation.

Enhanced Breakdown Strength and Thermal Conductivity of BN/EP Nanocomposites with Bipolar Nanosecond Pulse DBD Plasma Modified BNNSs

Yan Mi,Jiaxi Gou,Lulu Liu,Xin Ge,Hui Wan,Quan Liu

Filling epoxy resin (EP) with boron nitride (BN) nanosheets (BNNSs) can effectively improve the thermal conductivity of BN/EP nanocomposites. However, due to the few hydroxyl groups on the surface of BNNSs, silane coupling agent (SCA) cannot effectively modify BNNSs. The agglomeration of BNNSs is severe, which significantly reduces the AC breakdown strength of the composites. Therefore, this paper uses atmospheric pressure bipolar nanosecond pulse dielectric barrier discharge (DBD) Ar+H2O low temperature plasma to hydroxylate BNNSs to improve the AC breakdown strength and thermal conductivity of the composites. X-ray photoelectron spectroscopy (XPS) shows that the hydroxyl content of the BNNSs surface increases nearly two fold after plasma modification. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) show that plasma modification enhances the dehydration condensation reaction of BNNSs with SCA, and the coating amount of SCA on the BNNSs surface increases by 45%. The breakdown test shows that the AC breakdown strength of the composites after plasma modification is improved under different filling contents. With the filling content of BNNSs increasing from 10% to 20%, the composites can maintain a certain insulation strength. Meanwhile, the thermal conductivity of the composites increases by 67% as the filling content increases from 10% (SCA treated) to 20% (plasma and SCA treated). Therefore, the plasma hydroxylation modification method used in this paper can provide a basis for the preparation of high thermal conductivity insulating materials.Keywords:bipolar nanosecond pulse;low temperature plasma;hydroxylation modification;BN nanosheets;nanocomposites;breakdown strength;thermal conductivity