CERAMICS INTERNATIONAL
·
2021
·
IF 4.527
Shuang Yin,Dongliang Mao,Limei Pan,Xia Fang,Yang Wang,Tai Qiu,Jian Yang
The porous SiC–Si 3 N 4 composite ceramics with good EMW absorption properties were prepared by combination of gelcasting and carbothermal reduction. The pre-oxidation of Si 3 N 4 powders significantly improved the rheological properties of slurries (0.06 Pa s at 103.92 s −1 ) and also suppressed the generation of NH 3 and N 2 from Si 3 N 4 hydrolysis and reaction between Si 3 N 4 and initiator APS, thereby reducing the pore defects in green bodies and enhancing mechanical properties with a maximum value of 42.88 MPa. With the extension of oxidation time from 0 h to 10 h, the porosity and pore size of porous SiC–Si 3 N 4 composite ceramics increased from approximately 41.86% and 1.0–1.5 μm to 46.33% and ~200 μm due to the production of CO, N 2 and gaseous SiO, while the sintering shrinkage decreased from 16.24% to 10.50%. With oxidation time of 2 h, the Si 2 N 2 O fibers formed in situ by the reaction of Si 3 N 4 and amorphous SiO 2 effectively enhanced the mechanical properties , achieving the highest flexural strength of 129.37 MPa and fracture toughness of 4.25 MPa m 1/2 . Compared with monolithic Si 3 N 4 ceramics, the electrical conductivity , relative permittivity and dielectric loss were significantly improved by the in-situ introduced PyC from the pyrolysis of three-dimensional network DMAA-MBAM gel in green bodies and the SiC from the carbothermal reduction reaction between PyC and SiO 2 and Si 3 N 4 . The porous SiC–Si 3 N 4 composite ceramics prepared by the unoxidized Si 3 N 4 powders demonstrated the optimal EMW absorption properties with reflection loss of −22.35 dB at 8.37 GHz and 2 mm thickness, corresponding to the effective bandwidth of 8.20–9.29 GHz, displaying great application potential in EMW absorption fields.
研究领域:
材料科学
·
电子材料
✓ 已验证
产品关联
DOI
高影响因子
COMPOSITES PART B-ENGINEERING
·
2019
·
IF 6.864
Shanshan Xiao,Hui Mei,Daoyang Han,Laifei Cheng
SiC nw /C/Si 3 N 4 porous ceramic composites with layer-by-layer structure were successfully fabricated by freeze drying, carbonization and chemical vapor infiltration processes for excellent room and high temperature electromagnetic (EM) wave absorption properties . The sandwich-like structure within the layer and the capacitor model structure between the layers are formed inside of the composite, and these structures are beneficial to the EM wave consumption. The EM absorption properties are optimized by regulating the relative contribution of the polarization loss (primarily provide by SiC nw and defects in carbon phase) and the conductance loss (primarily offered by the conductive network formed by the carbon thin film). As an antioxidant protective layer, Si 3 N 4 ceramic coating is prepared on the outside of the carbon film . The prepared SiC nw /C/Si 3 N 4 porous composites show high absorption efficiency (exceed −39.7 dB), wide absorption band (cover the whole X band), small density (0.92 g/cm 3 ), thin thickness (2.9 mm), and excellent high-temperature stability (stable up to 873 K). The unique structures not only facilitate EM wave absorption, but also enable the composite a compressive strength of 168 MPa.
研究领域:
材料科学
·
电磁学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2020
·
IF 4.495
Weide Wang,Dongxu Yao,Hanqin Liang,Yongfeng Xia,Kaihui Zuo,Jinwei Yin,Yu-Ping Zeng
The effect of YH 2 on densification, microstructure, and thermal conductivity of Si 3 N 4 ceramics were investigated by adjusting the amount of YH 2 in the range of 0–4 wt% using a two-step sintering method. Native SiO 2 was eliminated, and Y 2 O 3 was in situ formed by a metal hydride reduction reaction, resulting in various Y 2 O 3 /SiO 2 ratios. Full densification of YH 2 -doped samples could be achieved after sintering at 1900 °C for 4 h. The Y 2 O 3 /SiO 2 ratio had a significant influence on the composition of crystalline secondary phases. Besides, the increased Y 2 O 3 /SiO 2 ratio is conducive not only to the grain growth but also to the reduction of activity of SiO 2 in the liquid phase, resulting in enlarged purified grains, reduced volume fraction of intergranular phases and increased Si 3 N 4 -Si 3 N 4 contiguity. Ultimately, the thermal conductivity increased by 29 % from 95.3 to 123.0 W m −1 K −1 after sintering at 1900 ℃ for 12 h by the substitution of Y 2 O 3 with YH 2 .
研究领域:
材料科学
·
热传导工程
✓ 已验证
DOI
高影响因子
Journal of Materials Chemistry A
·
2024
·
IF 10.7
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.
研究领域:
材料科学
·
纳米技术
·
电子工程
✓ 已验证
产品关联
DOI
高影响因子
Materials Research Express
·
2024
·Vol. 11
·期 7
·075101
·
IF 1.8
Lina Zhan,Yao Zhang,Xuan Zhang,Yuzhibiao Xia,Yao Liu
The densification mechanism of CeO2 doped Si3N4 ceramics during spark plasma sintering (SPS) was investigated. The sintering process was observed to undergo significant densification at the intermediate stage of sintering (1435 °C–1816 °C), and the density and grain size of CeO2 doped Si3N4 ceramic were found to be greater than those of pure Si3N4 ceramic under the same sintering conditions. To determine the densification mechanism, a creep model was utilized to determine the densification mechanism which could be interpreted based on the values of the stress exponent (n) and the apparent activation energy (Qd). The results revealed that the Qd of pure Si3N4 (381.15 kJ mol−1) is higher than that of Si3N4-CeO2 powder (265.61 kJ mol−1). Moreover, the stress exponent n of Si3N4-CeO2 powder (1.12–1.33) was higher than that of pure Si3N4 powder (1.00–1.18). This can be attributed to the fact that the addition of CeO2 resulted in the formation of a liquid phase at the grain boundary which leading to a shift in the controlling mechanism from grain boundary diffusion to grain boundary sliding.
研究领域:
材料科学
·
陶瓷工程
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2015
·
IF 2.605
Na Sun,Xiangjun Meng,Zhenggang Xiao
In order to improve the dispersibility of nanoparticles in polymer matrix , a feasible processing way for grafting high density hydrophobic polymer on the surface of silicon nitride (Si 3 N 4 ) nanoparticles was carried out by an atom transfer radical polymerization (ATRP) method. The ATRP initiators were first immobilized on the surface of Si 3 N 4 nanoparticles by using 3-aminopropyltriethoxysilane coupling agent and 2-bromoisobutyryl bromide, and then the polymerization of methyl methacrylate was initiated and propagated on the surface of Si 3 N 4 nanoparticles by ATRP reaction. The chemical groups, size, morphology, grafting content, and colloidal thermal stability of PMMA–Si 3 N 4 particles were studied by Fourier transform infrared (FTIR), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). Results indicate that the grafting of polymer on the surface of Si 3 N 4 nanoparticles is successful and the grafting content of PMMA reaches 60.4%. Moreover, the grafted polymer chains have changed the surface properties of Si 3 N 4 nanoparticles and enhanced their dispersibility in organic media.
研究领域:
材料科学
·
高分子化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2022
·
IF 6.364
Haoqian Zhang,Feng Ye,Qiang Liu,Biao Zhang
Traditional layered broadband radomes are challenging to meet the needs of the high-temperature application, due to thermal mismatch between their layers. In this study, porous Si 3 N 4 ceramics with a novel continuous porosity gradient from 54.7% to 82.4% were achieved by lamellar gel-casting, freeze-drying, and subsequent sintering process. The porosity-graded structure in Si 3 N 4 ceramics shows no failure or cracks after sintering, benefiting from the low shrinkage after sintering at 1900 °C with the rapid sintering rate. The continuous porosity-graded structure without obvious interfaces was architected by ice crystal growth during solidification and the growth of rodlike β-Si 3 N 4 grains across the interfaces during sintering. This approach can be beneficial to designing high wave transmission performance at specific broadband for radome.
研究领域:
材料科学
·
陶瓷工程
·
航空航天工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF MATERIALS SCIENCE
·
2023
·Vol. 58
·期 23
·9395-9408
·
IF 4.5
Lin Yixuan,Qi Xiaoquan,Niu Guoqiang,Sun Qin,Ji Hongjun,Li Mingyu,Li Yufeng
Si 3 N 4 is a promising material for heat dissipation substrate due to its excellent thermal conductivity and mechanical properties. However, its application is limited by the difficulties in surface metallization. In this work, surface metallization of Si 3 N 4 ceramic substrate is realized by thick film method for the first time. Conductive silver paste containing Bi 2 O 3 -B 2 O 3 -ZnO glass frit as glass binder was prepared, and high-performance silver thick films were formed on Si 3 N 4 ceramic surface. The mechanical and electrical properties of silver films were significantly promoted with increasing sintering temperature, and silver films with high shear strength of 23.35 MPa and low resistivity of 3.41 μΩ·cm were obtained when sintered at 600 °C. In the meanwhile, the silver films exist high reliability under thermal cycles. The bonding between the silver thick film and Si 3 N 4 ceramic substrate was considerably enhanced as a result of interfacial reaction, forming Bi 2 Si 2 O 5 phase at the interface during sintering process. The formation mechanism was discussed and it is of great significance for the interfacial design in future studies. The results suggest that thick film method is a promising technology for obtaining high-quality surface metallization for Si 3 N 4 ceramic substrate. Graphical abstract
研究领域:
材料科学
·
电子工程
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2019
·
IF 3.45
Shuang Yin,Limei Pan,Xia Fang,Yufeng Li,Yanpu Li,Yongbao Feng,Tai Qiu,Jian Yang
In this study, the low–toxicity monomer N, N–dimethylacrylamide (DMAA), serving as both gelling agent and pore–forming agent, was adopted to fabricate porous Si 3 N 4 ceramics with a regulatable microstructure and property by aqueous gelcasting. Results indicate that monomer content played an important role in regulating and optimizing the properties of sintered bodies. With increasing monomer content (5.94–30.69 wt%), both slurry viscosity (maximum 0.14 Pa s at 95.40 s −1 ) and green body strength (11.35–49.23 MPa) exhibited monotonic increasing trends, demonstrating superior mechanical properties to those obtained using the neurovirulent acrylamide (AM) gelling system. The increased monomer content not only improved porosity, but also promoted α→β–Si 3 N 4 transformation as well as β–Si 3 N 4 grain growth through enhancing the connectivity of interlocking pores and accelerating the vapor phase transport during liquid–phase sintering. These variations in phase composition and microstructure derived from the varied monomer content further resulted in monotonic changes in porosity (40.32–51.50%), mean pore size (0.27–0.38 μm), flexural strength (202.77–132.15 MPa), fracture toughness (2.93–2.32 MPa m 1/2 ), dielectric constant (3.48–2.78) and loss (3.52–3.09 × 10 −3 ) at 10 GHz for sintered bodies, displaying an excellent comprehensive properties. This study suggests a promising prospect for DMAA in preparation of high–performance porous Si 3 N 4 ceramics by aqueous gelcasting.
研究领域:
材料科学
·
陶瓷工程
✓ 已验证
DOI
高影响因子
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2021
·
IF 5.302
Xinyi Gui,Mingfen Zhang,Puhao Xu,Guiwu Liu,Qinhan Guo,Xiangzhao Zhang,Haining Meng,Guanjun Qiao
Reactive air brazing of Si 3 N 4 ceramic was successfully achieved by using Ag-CuO filler metal. The effects of CuO content on the wettability of Ag-CuO/Si 3 N 4 system and the shear strength of Si 3 N 4 /Si 3 N 4 joint were investigated, and meanwhile the interfacial behavior was analyzed and discussed. Moreover, the work of adhesion, interfacial energy, and electronic properties of Ag/Si 3 N 4 , Ag/CuO and Ag/SiO 2 interfaces were evaluated by first-principles calculations. The Ag-CuO/Si 3 N 4 system transforms from no-wetting into wetting due to the oxidation of Si 3 N 4 substrate and the formation of SiO 2 layer on the substrate surface. The maximum average joint shear strength of over 50 MPa is obtained as the CuO content is 8 at.%. Compared with the Ag(111)/Si 3 N 4 (0001) interface, the Ag(110)/CuO(001) and Ag(110)/SiO 2 (001) interfaces show stronger interfacial bonding due to the formation of Ag-O ionic bond, indicating that the addition of CuO and the formation of SiO 2 contribute to the enhancement of interfacial bonding.
研究领域:
材料科学
·
计算化学
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2019
·
IF 3.45
Honghui Ding,Yuan Hu,Xiaolei Li,Zhihao Zhao,Huiming Ji
Porous Si 3 N 4 ceramics were fabricated by pressureless sintering at 1550 °C for 2 h with YbF 3 -MgF 2 composite sintering aids, systematically investigated for the effect of sintering aids addition on the microstructure and mechanical properties , further explored the formation process and sintering mechanism. The α-β phase transition rate of all samples approached 100% and MgF 2 showed a positive effect on the elongating of β-Si 3 N 4 crystal grains in morphology. The apparent porosity of porous Si 3 N 4 ceramics ranged from 34% to 39%. In addition, when 2.5 wt% YbF 3 was replaced by the same amount of MgF 2 , the flexural strength sharply increased to 298 MPa, an increase of ~49%, while the porosity increased to 37%, an increase of ~15%. With MgF 2 content increasing from 0 to 7.5 wt%, the structure factor reached a minimum of 3.23 when MgF 2 addition was 2.5 wt%, which demonstrated unparalleled superiority in mechanical properties compared with previous studies due to a more preferred form of morphology of connected rod-like β-Si 3 N 4 crystals network. Besides, our research indicated that MgF 2 addition could develop higher aspect ratio of β-Si 3 N 4 grains and had obviously positive effect on the elongating characteristic of β-Si 3 N 4 grains, which was related to the activation energy variation for nucleation on the different facets.
研究领域:
材料科学
·
陶瓷工程
✓ 已验证
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2024
·
IF 5.8
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.
研究领域:
材料科学
·
陶瓷工程
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）