查找使用阿拉丁产品的科研文献

Si3N4 Nanofibrous Aerogel with In Situ Growth of SiOx Coating and Nanowires for Oil/Water Separation and Thermal Insulation

Zongwei Tong,Baojie Zhang,Huijun Yu,Xiangjie Yan,Hui Xu,Xiaolei Li,Huiming Ji

Nanofibrous aerogels constructed by ceramic fiber components (CNFAs) feature lightweight, compressibility, and high-temperature resistance, which are superior to brittle ceramic aerogels assembled from nanoparticles. Up to now, in order to obtain CNFAs with stable framework and multifunctionality such as hydrophobicity and gas absorption, it is necessary to perform binding and surface modification processes, respectively. However, the microstructure as well as properties of CNFAs are deteriorated by the direct addition of binders and modifiers. To tackle these problems, we introduced a unique low-temperature (100 °C) chemical vapor deposition method (LTCVD) to achieve the cross-linking and hydrophobization of Si3N4 CNFA in only one step. More importantly, during the LTCVD process, SiOx coatings and nanowire arrays were in situ formed via vapor–solid (VS) and vapor–liquid–solid (VLS) mechanisms on the surface and intersection of Si3N4 nanofibers, which cemented the aerogel framework, endowed it with hydrophobicity, and improved its oxidation resistance at high temperature. Compared to most of its counterparts, the Si3N4/SiOx CNFA exhibited better mechanical properties, higher capability of oil/water separation (33–76 g·g–1), lower thermal conductivity (0.0157 W/m·K–1), and superior structural stability in a wide temperature range of −196–1200 °C. This work not only presents an excellent Si3N4/SiOx CNFA for the first time but also provides fresh insights for the exquisite preparation strategy of CNFAs.

Synergistic fabrication of FeSiAl/Si3N4 soft magnetic composites by two-step plasma-assisted ball milling and magnetic-field-induced orientation

Jun Wang,Kaixuan Li,Xinyu Zhao,Hongkang Zhao,Li Liu,Rui Wang,Zhaoyang Wu

Two-step plasma-assisted ball milling enables flaking and in situ Si 3 N 4 coating of FeSiAl powders. • Strongly bonded FeSiAl/Si 3 N 4 heterointerfaces are formed with Si–N, Si–O–N, and Fe–N/Al–N bonds. • Interfacial charge redistribution induces a built-in electric field and Schottky barrier. • Magnetic-field-assisted orientation builds ordered pathways for magnetic flux and heat conduction. • FeSiAl/Si 3 N 4 composites achieve high permeability, low core loss, and enhanced thermal conductivity simultaneously. To overcome the rapid permeability degradation, high eddy-current loss, and poor thermal management of FeSiAl soft magnetic composites under high-frequency and high-power conditions, a combined strategy of two-step plasma-assisted ball milling and magnetic-field-induced orientation was developed. The first plasma-assisted milling step transformed near-spherical FeSiAl powders into high-quality flakes, while the second step constructed a dense Si 3 N 4 coating layer, forming a tightly bonded core–shell structure. Interfacial analyses revealed the formation of Si–N, Si–O–N, and Fe–N/Al–N bonds. First-principles calculations further demonstrated interfacial charge transfer from FeSiAl to Si 3 N 4 , leading to strong Al–N covalent bonding, a built-in electric field, and a Schottky barrier, which effectively suppressed interparticle charge transport and reduced high-frequency eddy-current loss. Meanwhile, magnetic-field-induced orientation promoted the ordered arrangement of flaky particles, improving magnetic-flux continuity and heat-transfer pathways. The optimized composite containing 4 wt% Si 3 N 4 achieved an effective permeability of 93.4 at 1 MHz, a total core loss of 72.2 kW/m 3 at 50 mT and 100 kHz, and a thermal conductivity of 25.9 W·m −1 ·K −1 . This work provides a new route for designing soft magnetic composites for high-frequency, high-power-density power electronic devices. Download: Download high-res image (183KB) Download: Download full-size image

Plasma-Assisted Milling of FeSiAl/Si3N4 Soft Magnetic Composites: Frequency-Tuned Interfacial Coupling For Synergistic Magnetic, Electrical, and Thermal Performance

Liu Xuming,Xuan Dongpo,Li Kaixuan,Wang Jun,Wang Rui,Wu Zhaoyang

FeSiAl-based soft magnetic composites (SMCs) for medium- and high-frequency electromagnetic devices require high permeability, low core loss, and efficient thermal management. However, current insulation coating strategies are limited by poor coating continuity, weak interfacial adhesion, and insufficient thermal stability. In this work, FeSiAl/Si 3 N 4 SMCs were fabricated via two-step plasma-assisted milling (PAM) combined with magnetic-field-assisted orientation forming, with the vibration frequency in the second PAM step used to regulate the microstructure, interfacial characteristics, and overall performance of the composite powders and compacts. The results show that Si 3 N 4 was successfully introduced onto the powder surface while preserving the crystal structure of the FeSiAl matrix, thereby establishing chemically bonded interfaces involving Si–N, Si–O–N, and M–N (M = Fe, Al). First-principles calculations confirm that the FeSiAl(110)/Si 3 N 4 (120) heterointerface exhibits a binding energy of −5.08 J/m 2 , with its stability originating from charge transfer and the formation of Fe–N, Al–N, and Si–N bonds. As vibration frequency increased, the continuity of the Si 3 N 4 coating layer and the interlayer insulating network first improved and then deteriorated. The 1300 rpm sample exhibited an effective permeability of 99.8 at 1 MHz, with a decline of less than 2% over 1 kHz–1 MHz, together with a saturation magnetization of 165.2 emu/g, an electrical resistivity of 192.1 Ω m, a total core loss of 72.8 kW m −3 at 50 mT/100 kHz, and a thermal conductivity of 28.3 W m −1 K −1 . These results indicate that regulating the PAM frequency provides an effective route for coordinating the magnetic, electrical, and thermal properties of FeSiAl-based SMCs.

Enhanced electromagnetic wave absorption in (SiO2–C)f/(CrZrHfNbTa)C–Si3N4–SiBCN composite by defect engineering and gradient permittivity modulation

Yang Hu,Dewei Ni,Bowen Chen,Feiyan Cai,Xiaoyu Wang,Yanmei Kan,Yusheng Ding,Shaoming Dong

Structure and stealth integrated materials that simultaneously deliver mechanical loading and broadband electromagnetic wave (EMW) absorption performance are critical for next generation stealth aircraft. Although conventional carbon fiber reinforced ceramic matrix composites (C f /CMCs) exhibit outstanding load-bearing capacity, their inherent EMW reflection characteristics often fail to meet stealth requirements. This work proposes a multiscale design strategy synergizing microscopic defect engineering with macroscopic gradient permittivity modulation. Accordingly, (SiO 2 –C) f /(CrZrHfNbTa)C–Si 3 N 4 –SiBCN composite featuring self-adaptive impedance matching and multi-mechanism EMW absorption were successfully constructed. The material demonstrates acceptable load-bearing capacity (101 ± 5 MPa) while achieving a remarkably high effective absorption bandwidth (EAB) per unit thickness (2.68 GHz mm −1 ). More importantly, radar cross section (RCS) simulations reveal that the sample achieves a remarkable RCS reduction of 35.52 dB m 2 . This surpasses most reported materials system, demonstrating high practical application potential. Density functional theory calculations reveals that defect engineering (lattice distortion and point defects) in the sample constructs new polarization centers at the microscopic level, which significantly enhances polarization relaxation loss for improved EMW absorption. On the other hand, macroscopic structural design (SiO 2f -C f -SiO 2f ) significantly optimizes the impedance matching, which effectively broadens EAB. The multiscale design strategy overcomes the inherent conflict between strong EMW reflection and attenuation in carbon fibers, which provides a novel material solution for stealth aircraft.

Fabrication of a novel high electrical conductivity Si3N4 matrix composite with Cu three-dimensional network structure by spark plasma sintering

Dandan Wu,Yufu Yan,Zijun Liu,Chengyong Wang

Silicon nitride (Si 3 N 4 ) ceramic matrix conductive composite materials have shown great promise as conductive layer materials for electrical transmission components. However, existing conductive phases struggle to form a three-dimensional (3D) interconnected network in Si 3 N 4 matrix, resulting in poor electrical conductivity . This study proposed a spark plasma sintering (SPS) process utilizing Si 3 N 4 as the substrate and Cu particles as the reinforcement phase to fabricate a novel electrical conductivity Si 3 N 4 /Cu composite material. The results indicated that the diffusion of Si atoms in Si 3 N 4 facilitated the formation of copper silicide (Cu i Si) interface between the two constituents during sintering, creating a strong chemical bonding for high conductivity. Simultaneously, composite materials with optimized Cu content formed a 3D interconnect network structure, providing a continuous path for electrical conduction. At Cu content of 30 vol%, the Si 3 N 4 /Cu composite exhibited a satisfying electrical conductivity of 295.37 S/m, which was 14 orders of magnitude higher than that of Si 3 N 4 . The composites also demonstrated a percolation phenomenon, with a theoretical percolation threshold of Cu particles at just 0.1 vol%, an order of magnitude lower than that of carbon reinforcement particles . Furthermore, an integrated design featuring external insulation and internal conductivity was achieved by wrapping a Si 3 N 4 insulation layer around the conductive Si 3 N 4 /Cu composites. The fabricated insulation layer exhibited higher resistivity (1.12×10 14 Ω) and a lower wear rate (1.3×10 −6 mm 3 /N·m) compared to some contemporary insulation ceramics, while the conductive layer had a lower calorific value , making them excellent candidates for electrical transmission component materials.

WITHDRAWN: Porous Si3N4 ceramics with uniform microstructure fabricated by in-situ pre-gel casting combined with non-directional freeze-drying

Heng Zhang,Dongxu Yao,Ming Zhu,Yongfeng Xia,Jun Zhao,Yu-Ping Zeng

A high-safety lithium-ion battery electrospun separator with Si3N4-assisted sulfonated poly(ether ether ketone) for regulating lithium flux

Xilong Wang,Xiaogang Cui,Bin He,Qian Zhao,Yujue Wang,Dan Xiao,Yan Meng,Taotao Gao,Kui Li

The uncontrolled lithium (Li) dendrite growth significantly impacts the safety performance of polymer separators. To mitigate this growth, this study introduces Si 3 N 4 into sulfonated poly(ether Ether Ketone) (SPEEK) and prepares Si 3 N 4 /SPEEK composite separators via electrospinning. At the interface between the Si 3 N 4 /SPEEK separator and the Li anode, the Si nanowires that form impede Li dendrite growth, thereby enhancing the electrochemical performance of lithium-ion batteries (LIBs). The Li deposition test of the 10 % Si 3 N 4 /SPEEK separator can operate for 1000 h without short-circuiting. Additionally, the LiFePO 4 ||Li cell with the 10 % Si 3 N 4 /SPEEK separator shows improved initial discharge capacity (157.8 mAh g −1 at 1C) and superior rate performance (125 mAh g −1 at 10C). Moreover, the nano-scale Si 3 N 4 endows the separator with robust thermal and mechanical properties. The FLIR observations reveal that the 10 % Si 3 N 4 /SPEEK separator maintains uniform thermal distribution and structural integrity even at 300 °C, ensuring safe battery operation at high temperatures. The additional load of the 10 % Si 3 N 4 /SPEEK separator can reach 10.2 mN, which enhances the puncture resistance of the separator. This work provides a solid approach for the application of SPEEK as a high-safety and high-rate LIB separator.

Microstructure and mechanical properties of highly dense Si3N4 ceramics with ZrN–AlN–Re2O3 (Re=Yb, Y, Nd, Ce, La) additives

Jun-Wei Huang,Xiao-Feng Dong,Xiao-An Lv,Xiao-Na Ren,Chang-Chun Ge

The Si 3 N 4 ceramics with ternary ZrN–AlN–Re 2 O 3 (Re=Yb, Y, Nd, Ce, La) and ZrN–AlN system as sintering additives were prepared by hot-pressed sintering with vacuum environment at 1750°C-30min–30MPa. Subsequently, the effect of the ternary additives system with 2 wt% Re 2 O 3 on phase transformation, grain boundary phases, microstructure, and mechanical properties of the Si 3 N 4 ceramics were investigated firstly. All samples achieved the high β-Si 3 N 4 phases transformation (≥98.86%), while the grain boundary phases Re x Zr 1-x O (4-x)/2 and Yb 2 Si 2 O 7 were detected in the sintered Si 3 N 4 ceramics with Re 2 O 3 additives. Additionally, compared with Si 3 N 4 ceramic not contain Re 2 O 3 additives, the Si 3 N 4 ceramics added Re 2 O 3 additives presented the textured microstructure with more elongated rodlike β-Si 3 N 4 grains based on the XRD and SEM results. Consequently, the sample S-Ce with added CeO 2 additive shows the highest relative density of 99.85% and optimal fracture toughness of 8.75 ± 0.36 MPa m 1/2 . The sample S–Nd with added Nd 2 O 3 additive presented a highest bending strength of 1061.78 ± 41.76 MPa. Sample S–Yb with added Yb 2 O 3 additive presented the maximum Vickers hardness of 16.35 ± 0.07 GPa. The results of this study can provide a helpful reference for the preparation of high-performance Si 3 N 4 ceramics.

Effect of the ratio of Y2O3 and MgSiN2 sintering additives on the microstructure, thermal and mechanical properties of Si3N4 ceramics

Yun Liu,Ruixiang Liu,Yuanhang Zheng,Jixue Zhao,Tianyi Sui,Xiaolei Li,Bin Lin

To investigate the mechanism of the influence of the sintering additive ratio on the microstructure evolution of silicon nitride (Si 3 N 4 ) ceramics, Si 3 N 4 ceramics were prepared by gas pressure sintering using different ratios of Y 2 O 3 /MgSiN 2 as additives. Varying the ratio of Y 2 O 3 /MgSiN 2 changed the composition of the liquid phase, thereby affecting the densification process and phase transformation rate of Si 3 N 4 ceramics, and ultimately changing their microstructure. The reduction in the Y 2 O 3 /MgSiN 2 ratio raised the N/O and Si/O ratios in the system, which increased the liquid phase viscosity. The Si 3 N 4 grain distribution varied from "normal to bimodal". In the case of increasing the proportion of MgSiN 2 and prolonging the sintering time, more of the glass phase evaporated, which reduced the content of the low thermal conductivity phase and increased the continuity of Si 3 N 4 /Si 3 N 4 . Therefore, Si 3 N 4 ceramics with 1 wt% Y 2 O 3 and 5 wt% MgSiN 2 exhibited excellent properties after sintering at 1900 °C for 12 h, with thermal conductivity, bending strength , and fracture toughness of 106.7 Wm −1 K −1 , 776 MPa, and 11.66 MPa m 1/2 , respectively.

Synthesis and mechanical properties of highly porous ultrafine-grain Si3N4 ceramics via carbothermal reduction-nitridation combined with liquid phase sintering

Qiang Zhi,Bo Wang,Shan Zhao,Zhao Zhang,Yu-Chen Deng,Nan-Long Zhang,Jian-Feng Yang

Highly porous Si 3 N 4 ceramics have been prepared via a novel carbothermal reduction-nitridation (CRN) reaction between carbon nanotubes (CNTs) and SiO vapor in a N 2 atmosphere. The green bodies consisted of 49.0 wt% CNT, 40.4 wt% α-Si 3 N 4 as seed and 10.6 wt% Y 2 O 3 as sintering additive, and SiO powders were located under the green bodies during sintering. By heating at temperatures ranging from 1550 to 1650 °C, fibrous β-Si 3 N 4 nanograins were obtained. Complete reaction was achieved after soaking at 1650 °C, and a mean grain diameter of approximately 290 nm and aspect ratio of as high as 20 were obtained, and a porosity of 73% was reached due to the low density of the green bodies. The bending and compressive strengths were up to 62 MPa and 82 MPa, respectively, which were higher than the values in the literature, as a result of the fine elongated fibrous β-Si 3 N 4 grains. It should be noted that the Si 3 N 4 ceramics exhibited a large strain to failure and ‘pseudoplastic’ deformation behavior during the compressive test, which was attributed to the high porosity.

Preparation, mechanical and thermal properties of Si3N4 ceramics by gelcasting using low–toxic DMAA gelling system and gas pressure sintering

Shuang Yin,Senchuan Jiang,Limei Pan,Chao Liu,Yongbao Feng,Tai Qiu,Jian Yang

In this work, Si 3 N 4 ceramics were fabricated through an aqueous gelcasting method using a low–toxic monomer called N, N–dimethylacrylamide (DMAA) followed by gas pressure sintering at 1850 °C for 2 h under 6 MPa N 2 atmosphere. The effect of solid loading on performance of slurries, green and sintered bodies was investigated systematically. The results show that the slurries with a solid loading as high as 50 vol% (viscosity 0.17 Pa.s at 100 s –1 ) were achieved. With the increase of solid loading (30–50 vol%), the green bodies exhibited a monotonically decreased, however high enough in general, flexural strength of 16.50–11.52 MPa, which was comparable to that of widely–used neurovirulent acrylamide (AM) gelling system. In regard to the sintered bodies, increasing solid loading significantly promoted sintering and improved mechanical properties and thermal conductivity as a result of the increased density, bimodal distribution structure, as well as suitable interfacial bonding strength . The best performance parameters of Si 3 N 4 ceramics, bulk density of 3.25 g/cm 3 , apparent porosity of 0.67%, flexural strength of 898.92 MPa, fracture toughness of 6.42 MPa m 1/2 , Vickers hardness of 2.81 GPa, and thermal conductivity of 34.69 W m –1 K –1 , were obtained at 50 vol% solid loading. This work renders low–toxic DMAA gelling system promising prospect in preparation of high–performance Si 3 N 4 ceramics by gelcasting.

Active metal brazing of Si3N4/Cu joint via a Cu-Sn-Ti filler: oxygen participation tailored interfacial microstructure and mechanical properties

Wei Feng,Jian Zhang,Yong Xiao,Peng Cao,Guoqiang Luo,Qiang Shen

Active metal brazing of Si 3 N 4 /Cu joints typically forms a rigid TiN/Ti 5 Si 3 interface that suffers from significant thermal mismatch. This study demonstrates an alternative strategy for engineering the interfacial reaction pathway using a (Cu20Sn) 100-x Ti x filler. A distinct Cu 2 Ti 4 O interfacial layer formed through oxygen participation in the interfacial reaction during brazing. Thermodynamic analysis reveals that the Ti-O reactions possess a significantly greater driving force than conventional Ti-N and Ti-Si reactions. The resulting Cu 2 Ti 4 O phase establishes a beneficial coefficient of thermal expansion (CTE) gradient across the joint, thereby effectively mitigating interfacial thermal stress. Joint brazed with 5 wt% Ti achieved the highest shear strength of 137.3 MPa, which is attributed to the optimized morphology of a discontinuous Cu 2 Ti 4 O layer and the reduced brittle CuSn 3 Ti 5 precipitation. These results demonstrate a new approach for interfacial engineering of non-oxide ceramic joints, confirming that trace oxygen can act as an effective microstructural modifier.