查找使用阿拉丁产品的科研文献

Graphene/h-BN Nanosheet/Nanosphere Composites Constructed by In Situ Laser Irradiation with Synergistically Improved Tribological Performance

Wei Li,Ting Luo,Changxu Zhu,Bin Zhang,Bingqiang Cao

Graphene/hexagonal boron nitride nanocomposites with different dimensions have great application prospects in the field of lubrication due to their unique layered structure and excellent mechanical properties. However, due to their complex synthesis process, easy agglomeration, and poor stability, graphene/hexagonal boron nitride nanocomposites have not yet been applied in lubricating applications. Herein, a simple and green in situ laser irradiation method is proposed to construct two-dimensional (2D) reduced graphene oxide (rGO) nanosheets and zero-dimensional (0D) hexagonal boron nitride nanosphere 2D/0D nanocomposite (L-rGO/h-BN). During the one-step laser irradiation in liquid, the GO nanosheets were reduced to rGO nanosheets. Meanwhile, the hexagonal boron nitride (h-BN) transformed from nanoflakes to nanospheres via a pulsed laser heating and reshaping process and embedded into the multilayer graphene nanosheets. The spherical h-BN nanoparticles as interlayer support can maintain the 2D graphene with a more stable layered structure, while the insertion of graphene sheets also effectively inhibits the agglomeration of the spherical h-BN nanoparticles. Therefore, a hierarchical 2D/0D layered rGO/h-BN nanocomposite was formed. Importantly, such composite nanoparticles can well disperse in the lubricating oil without significant precipitation for over 30 days and show remarkably improved tribological performance. This is due to the synergistic lubricant effect of the deposition repair effect from rGO nanosheets reducing wear and micro-bearing effect from h-BN nanospheres reducing friction by changing sliding friction into rolling friction.

C-doping into h-BN at low annealing temperature by alkaline earth metal borate for photoredox activity

Myonghak Ri,Kwanghak Choe,Kumchol Kim,Yan Gao,Zhiyong Tang

BCN (boron carbon nitride) nanosheets are promising photocatalyst materials for solar fuel production by visible light-driven water splitting and CO2 reduction due to their tunable band gap and unique properties. C-doping into h-BN by thermal annealing makes possible the preparation of BCN nanosheets with photocatalytic activity under visible light irradiation, but it generally requires a very high temperature (>1250 °C) from the thermodynamic viewpoint. Here, we report a new method to prepare BCN nanosheets with visible light-photocatalytic activity at lower annealing temperature (1000 °C) than equilibrium by adding alkaline earth metal compounds. BCN nanosheets formed in borate melt show a clear layered structure, tunable bandgap and photocatalytic activity for water splitting and CO2 reduction under visible light illumination. This provides a direction for doping other elements into h-BN at low annealing temperature by alkaline earth metal borates.

Aerogel Perfusion-Prepared h-BN/CNF Composite Film with Multiple Thermally Conductive Pathways and High Thermal Conductivity

Xiu Wang,Zhihuai Yu,Liang Jiao,Huiyang Bian,Weisheng Yang,Weibing Wu,Huining Xiao,Hongqi Dai

Hexagonal boron nitride (h-BN)-based heat-spreading materials have drawn considerable attention in electronic diaphragm and packaging fields because of their high thermal conductivity and desired electrical insulation properties. However, the traditional approach to fabricate thermally conductive composites usually suffers from low thermal conductivity, and cannot meet the requirement of thermal management. In this work, novel h-BN/cellulose-nano fiber (CNF) composite films with excellent thermal conductivity in through plane and electrical insulation properties are fabricated via an innovative process, i.e., the perfusion of h-BN into porous three dimensional (3D) CNF aerogel skeleton to form the h-BN thermally conductive pathways by filling the CNF aerogel voids. When at an h-BN loading of 9.51 vol %, the thermal conductivity of h-BN/CNF aerogel perfusion composite film is 1.488 W·m−1·K−1at through plane, an increase by 260.3%. The volume resistivity is 3.83 × 1014Ω·cm, superior to that of synthetic polymer materials (about 109~1013Ω·cm). Therefore, the resulting h-BN/CNF film is very promising to replace the traditional synthetic polymer materials for a broad spectrum of applications, including the field of electronics.Keywords:CNF aerogel;perfusion;h-BN;thermal conductivity;electrical insulation

Bionic modified h-BN loaded CeO2 nanoparticles to improve the anti-corrosion properties of composited epoxy coatings

Nanqi Shi,Zhike Li,Xin Li,Hongxin Luo,Shuzhen Dong,Haiyan Li

Hexagonal boron nitride (h-BN), as a two-dimensional lamellar material, has been paid more and more attention in the field of corrosion protection because of its excellent thermal stability, chemical stability and insulation. In order to solve the problem that h-BN is difficult to disperse in resin, inspired by the adhesion ability of mussel secretions, the surface of h-BN was modified with polydopamine (PDA) to improve the dispersion of the fillers in epoxy resin, and the prepared corrosion inhibition CeO 2 nanoparticles were loaded on the surface. A functional filler CeO 2 &PDA/h-BN with corrosion inhibition effect was prepared. The surface morphology , chemical structure and thermal stability of functional fillers were analyzed by SEM, FTIR, XRD and thermogravimetric analysis . The test results show that after 40 days of testing, the low-frequency impedance modulus of the epoxy composite coating is 15 times that of the pure epoxy resin, and the wear resistance properties also significantly improved. The anti-corrosion mechanism of the composite coating is analyzed, and the synergistic effect of h-BN's barrier ability and CeO 2 's corrosion inhibition ability is revealed. This paper provides an idea for the preparation of multifunctional h-BN composite anticorrosive filler.

Ag/BN/EVA Yarn Artificial Muscles with Low Drive Voltage, High Load Capacity, and High Energy Density

Shuolei Wang,Wenjun Wang,Zhonggui Zhang,Xiaojian Jiang,Ziyue Zhang,Hongyu Gao,Shi Xu,MD Zahidul Islam,Yaofeng Zhu,Yaqin Fu,Qingqing Ni,Yubing Dong

In this study, we developed composite fibers composed of silver (Ag)/boron nitride (BN)/ethylene-vinyl acetate copolymer (EVA) utilizing a combination of melt spinning–UV irradiation and chemical Ag-plating techniques. The inclusion of the BN filler was aimed to enhance the thermal conductivity and accelerate the response of EVA, while the application of a nano-Ag coating provided the fiber with high electrical conductivity. The results indicated that the electrical conductivity of the Ag/BN/EVA composite fiber achieved a notable value of 2.47 × 104 S/m. These composite fibers exhibited exceptional two-way shape memory properties, electrothermal conversion characteristics, and electrically driven actuation capabilities. Significantly, we demonstrated that by applying a voltage of merely 2.5 V, it was possible to precisely control the electrically reversible driving strain of the Ag/BN/EVA composite yarn by adjusting the energization time, resulting in an impressive energy density of 99.96 J/kg under a loaded weight (34.50 g), which is approximately 4107 times its own weight (0.0084 g). This led to the development of a composite yarn artificial muscle with a high load-bearing capacity, remarkable energy density, and low driving voltage requirements.

Foldcore sandwich structure formed by BN-coated graphene nanosheets grafted to SiC fibers with enhanced mechanical performance

Shuang Yi,Shubin Wang,Huiyu Yang

To improve the strong interface between fibers and ceramic matrix in silicon carbide (SiC) fibers reinforced in ceramic matrix composites (CMCs), tremendous efforts have been devoted to the fabrication of fiber coating. However, the design and preparation of these fiber coatings still remain a considerable challenge. In this study, we report a novel strategy to synthesize foldcore sandwich structure formed by boron nitride (BN)-coated graphene nanosheets (GNS) grafted to SiC fibers and analyze how the presence of GNS/BN composite coatings influences the mechanical performance of the fibers. In the fracture process, GNS-grafted SiC fibers coated with BN provide a specific wrinkled and malleable surface, which can be flattened and then broken in the early fracture stage. As a result, the fracture process is changed, resulting in enhanced mechanical performance. Our strategy could be further extended to the fabrication of other composite coatings on fibers with enhanced mechanical properties .

Enhanced electromagnetic wave absorption properties of SiCN(Ni)/BN ceramics by in situ generated Ni and Ni3Si

Yanchun Tong,Chunmiao Liu,Chang Liu,Haibin Sun,Yurun Feng,Qiangqiang Hu,Hongying Zhang,Yujun Zhao,Xue Guo,Shigang Wu

In this paper, the SiCN(Ni)/BN ceramic with excellent electromagnetic wave (EMW) absorption performance was successfully prepared. The Ni and Ni3Si were in situ formed by the introduction of nickel acetylacetonate (NA), which effectively improved the impedance matching performance of SiCN(Ni)/BN ceramics. The EMW absorption properties of the SiCN(Ni)/BN ceramics showed a trend of first increasing and then decreasing with the increase in content of NA. When the NA content reached 7 wt%, the impedance matching range of SiCN-7 was optimal. The minimum reflection loss (RLmin) of SiCN-7 reached −53.47 dB at 4.2 mm and the effective absorption bandwidth (EAB) was 2.32 GHz at 3.48 mm. Through the analysis of electrical conductivity, it was found that the proportion of polarization loss in dielectric loss was more than 99%. It is worth noting that the radar cross section (RCS) value of SiCN-7 absorber was lower than that of the perfect electrical conductor (PEC) plate in the range of −90–90°, and showed a larger coverage angle, indicating that it possessed a good practical application prospect in the field of electromagnetic wave absorption.

Enhanced thermal conductivity and mechanical properties of BN@polymethylacrylimide/epoxy composites with self-assembled stable 3D network

Yang Wang,Ye Fang,Xudong Yang,Hongmin Cong,Zhengbai Zhao,Chao Yan

Constructing a three-dimensional (3D) network of fillers with high thermal conductivity is considered to be an effective strategy to obtain ideal thermal management materials (TMM). However, 3D filler network is often disrupted by the subsequent processing and forming processes , and it is difficult to incorporate high levels of fillers into lyophilized aerogels, which is a key factor limiting their widespread use. In this work, boron nitride@polymethylacrylimide/epoxy (BN@PMI/EP) composites with a stable 3D BN network were prepared by freeze-drying and hot-pressing. A water-soluble copolymer quaternary ammonium salt has been synthesized by the solution polymerization. BN@PMI aerogel was obtained by the freeze-drying of ammonium salt and BN solution, and thermal imidization. BN@PMI aerogel has a six-membered imine ring structure that can be loaded with a high content of BN, which ensures the stability of the 3D BN network structure and facilitates the subsequent impregnation of EP in vacuum, which is one of the innovations of this work.The stable and complete 3D BN network leads to the enhancement of thermal conductivity, and the out-of-plane and in-plane thermal conductivities of BN@PMI/EP reach 1.21 W·m –1 ·K –1 and 2.76 W·m –1 ·K –1 at BN loading of 40% (mass), respectively. Meanwhile, the excellent mechanical properties and results of finite element simulation and actual experiments confirm that BN@PMI/EP is a potential TMM.

Enhanced thermal conductivity of CS/BN/Ti3O5 coatings to promote electron transport for ultra-sensitive fire sensing

Sijia Sun,Shuai Zhang,Mingzhu Pan

Intelligent fire warning system is a crucial protective equipment reduce fire hazards . A recent increasing concern is the development of sensitive fire warning materials that can be integrated with combustible materials to provide real-time alarms in the fire. However, current research on improving the sensitivity of fire warning sensors based on temperature-resistance response focuses on constructing continuous conductive networks. The effect of the heat transfer process is ignored, which limits the further improvement of alarm sensitivity. Here, we developed a strategy to improve thermal conductivity . Based on the chitosan (CS) conductive network in Ti 3 O 5 -based fire sensing system, aminated 2D h-BN nanosheets with high temperature resistance and ultrahigh in-plane thermal conductivity were further introduced. The h-BN improves the thermal conductivity of the fire warning coating from 1.43 W/m·K to 2.29 W/m·K. Intelligent fire warning sensors with ultra-sensitivity (1.16 s), low response temperature (170 °C), duration time (12 min) and durability (100 cycles) were successfully prepared by improving thermal conductivity to rapidly transfer heat to Ti 3 O 5 , which leads to a rapid decrease in resistance as the core mechanism. This work proposed an ingenious strategy for the construction of high fire safety and thermal conduction fireproof coatings, which revealed enticing prospects in the field of intelligent coatings.

Ag Nanoparticles Supported on h-BN/BiPO4 Heterostructures as a Photocatalyst for the Degradation of Rhodamine B

Yuting Li,Jiaming Song,Xin Zhao,Bingda Li,Zhuo Wang,Juanjuan Yang,Guoshuai Ban,Feng Teng,Jialong Ma,Chaoying Meng,Honggang Ye,Guangde Chen,Zhonghua Dai,Yu Cong

With increasing environmental pollution, the utilization of green techniques, such as photocatalysis, is required to degrade harmful sources without secondary pollution. In this study, we synthesized an efficient photocatalyst, i.e., a h-BN/BiPO4 heterostructure modified by Ag nanoparticles at the interface (Ag/BN/BPO) by photodeposition and a hydrothermal method, and investigated photocatalytic degradation performance for rhodamine B dye (RhB). It was found that 95% of RhB was removed by Ag/BN/BPO (optimal ratio) after 60 min of light exposure. Compared to BiPO4 and BN/BiPO4, the removal efficiency was improved by 50 and 30%, respectively. The high photocatalytic degradation activity of Ag/BN/BPO could be possibly attributed to the synergistic effect of the improved separation efficiency of electron–hole pairs by the special heterostructure design and the increased adsorption capacity due to the large specific surface area of the layered h-BN. This study provided a possible route for the development of highly efficient photocatalysts for the degradation of organic pollutants.

ZIF-derived carbon/BN/CMF composite PCM for enhanced latent thermal storage, photothermal conversion, and thermal insulation

Xiangfei Kong,Ruiming Nie,Jianjuan Yuan

Directional Assembly of Radicals to Methanol in CH4/H2O Plasma Mediated by BN-Confined Single Iron Atoms

Xiang Liu,Yongxin Fu,Ruidong Li,Yurong Yin,Jun Hu,Binran Zhao,Chengyi Dai,Xiaoxun Ma,Chunshan Song

Directly converting methane into high-value-added chemicals presents a significant challenge in catalysis. Nonthermal plasma (NTP) offers an efficient approach for direct methanol synthesis through methane activation. However, theoretical frameworks for designing catalysts under NTP conditions remain underdeveloped. It is quite difficult to control the assembly process of radical species on catalyst surfaces. A boron nitride (BN)-confined Fe single-atom catalysts (Fe-SACs) is synthesized by in situ anchoring in defect sites induced by mechanical ball milling. This catalyst is utilized for NTP-catalyzed direct methane-to-methanol conversion. The results demonstrate that the CH 3 OH yield increases by ≈2.5 times compared to conditions with NTP alone, while selectivity doubles. The experimental results and theoretical calculations indicate that ·OH radicals generated by the dissociation of H 2 O are rapidly adsorbed by Fe-SACs before annihilation. This process facilitates the stabilization of ·CH 3 species and enhances the kinetics of CH 3 OH assembly along the E-R reaction pathway. A design criterion is proposed for plasma-catalyzed radical adsorption intensification-directed assembly catalysts, offering a novel approach for the directional catalytic conversion of reactants through radical pathways.