查找使用阿拉丁产品的科研文献

Impact of Sintering Aid Type and Content on the Mechanical Properties of Digital Light Processing 3D-Printed Si3N4 Ceramics

Qing Qin,Lin Han,Gang Xiong,Zihan Guo,Junwei Huang,Yujuan Zhang,Zhen Shen,Changchun Ge

Digital light processing (DLP) 3D-printed Si₃N₄ ceramics, known for their exceptional performance, offer distinct advantages in meeting the high-strength and complex structural demands of industries such as aerospace, semiconductors, healthcare, automotive, energy, and machinery. However, due to Si₃N₄’s strong chemical stability, low diffusion rate, low self-sintering ability, and high melting point, achieving densification under conventional sintering conditions is challenging. As a result, sintering additives are essential to promote the sintering process, lower the sintering temperature, improve densification, and enhance performance. In this study, 45 vol% Si₃N₄ slurries were prepared using DLP 3D printing technology, incorporating nine different combinations of sintering additives, including aluminum oxide (Al2O3), yttrium oxide (Y2O3), and aluminum nitride (AlN), in various ratios with Si3N4. The slurries were then sintered at 1800 °C for 2 h under a 1 MPa N2atmosphere. Additionally, the phase composition, microstructure, grain distribution, and crack propagation of the materials. The results showed that a Si3N4to Al2O3and Y2O3ratio of 95:2.5:2.5 produced elongated β-Si3N4grain structures and enhanced density, achieving a maximum Vickers hardness of 12.88 ± 0.52 GPa. Additionally, the synergistic toughening effect of the rod-like β-Si3N4grains and sintering aids significantly improved the fracture toughness of the Si3N4ceramic matrix, with a flexural strength of 540.63 ± 10.05 MPa and a fracture toughness of 4.92 ± 0.07 MPa·m1/2. This study lays the foundation for the future application of 3D-printed Si3N4ceramics, optimization of sintering aid combinations at different ratios, and performance enhancement in extreme environments.

Effects of sintering temperature and sintering additive on microstructure, mechanical and dielectric properties of porous Si3N4 ceramics by gelcasting

Shuang Yin,Yao Zhang,Wei Wan,Xia Fang,Haiqiang Ma,Xinchun Xie,Tianyu Li,Xuewen Jiang,Aiwen Xie,Liqiang Liu,Cong Zhou,Ruzhong Zuo

Porous Si 3 N 4 ceramics were fabricated by combining gelcasting and pressureless sintering. The roles of sintering temperatures and sintering additives (Y 2 O 3 , Al 2 O 3 , and Y 2 O 3 -Al 2 O 3 ) in regulating phase composition, microstructure, sintering, mechanical, and dielectric properties of porous Si 3 N 4 ceramics were systematically studied. Compared with Y 2 O 3 and Al 2 O 3 , owing to the lower eutectic temperature, Y 2 O 3 -Al 2 O 3 was more effectively in promoting the particle rearrangement and dissolution-diffusion-reprecipitation processes during high-temperature sintering, leading to higher phase transformation degree of α→β-Si 3 N 4 , larger aspect ratio of columnar β-Si 3 N 4 grains, and higher densification of porous Si 3 N 4 ceramics. Furthermore, the increasing sintering temperature and the present β-Si 3 N 4 seeds within the raw powders were also conducive to phase transformation of α→β-Si 3 N 4 , β-Si 3 N 4 growth, and developing highly interlocking microstructure contributing to strengthening mechanical properties. At 10 wt% Y 2 O 3 and 5 wt% Al 2 O 3 , the complete phase transformation of α→β-Si 3 N 4 and sufficient β-Si 3 N 4 growth were achieved by pressureless sintering at 1750 ℃ for 1 h. The apparent porosity, bulk density, flexural strength , and fracture toughness of porous Si 3 N 4 ceramics reached 2.7%, 2.98 g/cm 3 , 450.9 MPa, and 4.35 MPa·m 1/2 , respectively, exhibiting superior mechanical properties. At 2 wt% Y 2 O 3 and 1 wt% Al 2 O 3, the resulting porous Si 3 N 4 ceramics had dielectric constant of 4.28–4.38 and dielectric loss tangent of 2.1 × 10 −3 -3.2 × 10 −4 throughout X-band, showing good microwave transmission properties. This study indicates that the gelcasting combined with pressureless sintering was proved to be a feasible method to prepare high-strength and low-dielectric porous Si 3 N 4 ceramics using Y 2 O 3 -Al 2 O 3 as sintering additives.

Direct construction of interconnected Si3N4 nanowire networks for enhancing the thermal conductivity and mechanical performance of flexible composite films

Mengyi Li,Baokai Wang,Chang Yu,Mengyang Niu,Kunjie Yuan,Weiwei Xuan,Ming Yue,Lifeng Zhu,Kexin Chen,Qi Wang

With great advancements in foldable electronic devices, there has been growing interest in ultra-light and flexible composite films possessing high in-plane thermal conductivity. One-dimensional (1D) Si3N4 nanowires (Si3N4NWs) possess the advantages of high thermal conductivity, superior mechanical performance and easy to be directionally aligned to construct thermally conductive pathways, which have been considered one of the ideal fillers for preparing anisotropic composite films. However, 1D Si3N4NWs with high aspect ratios tend to aggregate and are difficult to be dispersed in polymer matrixes, while traditional dispersion approaches utilizing prolonged ball milling or strong mechanical mixing easily result in a significant reduction in the length of Si3N4NWs, making it difficult to fully exploit the advantages of high intrinsic thermal conductivity. Therefore, it is highly essential to prepare high-performance composite films without damaging the length of Si3N4NWs. In this study, we propose an innovative strategy for the direct construction of continuous thermally conductive networks composed of ultra-long Si3N4NWs. An entire piece of Si3N4NW paper was successfully synthesized, which was directly used to prepare composite films via a simple vacuum-impregnation combined with hot-pressing method. Since the high aspect ratio of Si3N4NWs was maximally preserved during the composite process, the prepared Si3N4NW/EP composite films exhibited a high in-plane thermal conductivity of 16.02 W m−1 K−1 at a filling fraction of 64.6 wt%. More importantly, the interconnected, ultra-long Si3N4NWs also provide composite films with flexibility and excellent mechanical strength, enabling promising applications in the thermal management of electronic devices.

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

Porous Si 3 N 4 ceramics hold great promise for high-temperature wave-transparent materials, but it is a significant challenge to achieve both a low dielectric constant and high mechanical strength. This study explores a method combining in-situ pre-gel casting and non-directional freeze-drying to produce high-porosity, uniform microstructure Si 3 N 4 ceramics. By adjusting gel concentration and pre-gelation time, ice crystal growth effectively restricted, resulting in a uniform pore structure. The resulting porous Si 3 N 4 ceramics exhibited low drying shrinkage (1.50 %) and high porosity (59.13 %), with a flexural strength of 119.48 MPa, surpassing porous ones produced by other wet forming processes. At 30 GHz, the dielectric constant was 2.45, and the dielectric loss was 5.65 × 10 −3 .

The effect of h-BN content on mechanical properties, microstructure and machinability of hot-pressed h-BN/Si3N4 composites

Song Wu,Yongfeng Xia,Ming Zhu,Jun Zhao,Dongxu Yao,Yu-Ping Zeng

Si 3 N 4 ceramics now face new applications and challenges in the semiconductor field. The preparation of h-BN/Si 3 N 4 machinable ceramics incorporating 5–30 vol% h-BN via hot-pressing was carried out. This study systematically explored how the varying h-BN content influenced the composite's microstructure, mechanical attributes, and machinability . The results showed that some of the h-BN was encapsulated by growing Si 3 N 4 grains to form an intragranular structure during the process of hot-pressing, while the remaining h-BN exhibited uniform distribution along grain boundaries. The Si 3 N 4 phase transition in composites was inhibited by excessive h-BN, accompanied by a higher decrease in densification. The sample containing 20 vol% h-BN exhibited the best comprehensive performance, with high mechanical strength and excellent machinability. The bending strength and fracture toughness remained high at 862 MPa and 10.3 MPa m 1/2 , and could be effortlessly machined with cemented carbide drills. Additionally, the machinability of the composites was systematically characterized through observations of crack propagation paths, fitting of R-curves, and mechanical drilling tests.

Tribological Behavior of Polydiethylsiloxane (PDES) in a Si3N4 and M50 System under Low Temperatures from −80 to 25 °C

Junhao Han,Yong Tang,Luo Yue,Xianzhen Ma,Hao Jia,Ningxia Liu,Pengpeng Bai,Yonggang Meng,Yu Tian

Lubricants must exhibit good tribological behavior at low temperatures to ensure reliable startups in very cold regions. This study investigates the performance of lubricants, with a specific focus on their capacity for high-temperature lubrication and ensuring reliable low-temperature startup in engines. Experiments were conducted to assess the friction and wear characteristics of polydiethylsiloxane in conjunction with a Si3N4 ball and M50 (8Cr4Mo4V) steel across a temperature range of −80 °C to 25 °C. The results indicate that the coefficient of friction, as determined through friction and wear tests at various temperatures, remained below 0.1. As temperatures progressively decreased, the system’s friction coefficient increased, and wear volumes recorded at 25 °C and −60 °C were 9749.513 µm³ and 105.006 µm³, respectively, culminating in lubrication failure at −100 °C. This failure is primarily attributed to the increased viscosity and decreased mobility of polydiethylsiloxane at extremely low temperatures. Additionally, the reduced temperature increases the strength of the quenched steel, leading to hard particles or protrusions on the material’s surface, which collide with the Si3N4ball during friction, causing adhesion and spalling. Despite this, polydiethylsiloxane forms a stable protective oil film on the surface, enhancing the system’s lubrication performance. However, below −80 °C, this oil film begins to tear, leading to diminished lubrication efficacy. This study provides valuable data supporting the field of cryogenic lubrication.

Preparation of porous β-Si3N4/Si5AlON7 composite ceramics for digital light processing and study of mechanical and dielectric properties

Yaru Qin,Chenyu Zhao,Yujie Huang,Jiguang Dong,Xingyu Yang,Chenglong Shi

Porous β-Si 3 N 4 /Si 5 AlON 7 composite ceramics are anticipated to serve as high-temperature wave-transparent materials, yet the fabrication of high-performance porous β-Si 3 N 4 /Si 5 AlON 7 composite ceramics remains a significant challenge. Addressing this issue, this study introduces a technique for crafting high-performance porous β-Si 3 N 4 /Si 5 AlON 7 composite ceramics. This method involves the homogeneous blending of SiO 2 and Si 3 N 4 powders, followed by digital light processing and high-temperature liquid-phase sintering at 2000 °C. The impact of SiO 2 content on various properties of the ceramic slurry and the resultant ceramics was thoroughly examined, including rheology, curing depth, microstructural morphology, phase composition, flexural strength, hardness, dielectric constant, and dielectric loss. It was observed that a SiO 2 content of 30 % enables the slurry to fulfill the criteria for digital light processing, leading to the production of porous β-Si 3 N 4 /Si 5 AlON 7 composite ceramics that exhibit outstanding mechanical and dielectric properties. Specifically, these ceramics demonstrated a flexural strength of 149.2 ± 7.2 MPa and a hardness of 11.8 ± 1.1 GPa. Moreover, at a frequency of 10 GHz, the ceramics exhibited a dielectric constant of 4.02 and a dielectric loss of 0.11, highlighting their potential as high-temperature wave-transparent materials.

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.

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

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

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.

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.