INTERNATIONAL JOURNAL OF REFRACTORY METALS & HARD MATERIALS
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2018
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IF 2.606
Te Qi,Zhihao Zhao,Yongqiang Sun,Hangyuan Zhao,Xiaolei Li,Huiming Ji
Porous Si 3 N 4 ceramics with a unique interlocking microstructure have been fabricated by pressureless liquid-phase sintering with YbF 3 and CaF 2 sintering additives at a relatively low temperature (1550 °C). Phase transition and mass diffusion in the low-temperature sintering process are facilitated by YbF 3 and CaF 2 producing plenty of liquid phase owing to their extremely low melting points. As the content of YbF 3 increases from 8.0 wt% to 9.5 wt% and the CaF 2 decreases from 2.0 wt% to 0.5 wt%, the conversion rate of the phase transition from α-Si 3 N 4 to β-Si 3 N 4 increases from 71.1% to 81.2% and the largest average aspect ratio of the β-Si 3 N 4 grains reaches 10.05. At the same time, the porosity declines from 40.4% to 34.9% and the flexural strength increases from 168.5 MPa to 232.1 MPa.
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
·
2019
·
IF 3.45
Shuang Yin,Senchuan Jiang,Limei Pan,Lin Guo,Zhenghao Zhang,Jingxian Zhang,Xiaoyun Li,Tai Qiu,Jian Yang
Herein, a low–toxic N, N–dimethylacrylamide (DMAA) system was used in preparation of porous Si 3 N 4 ceramics by aqueous gelcasting, and variations in microstructure and properties with solid loading and calcination temperature were systematically investigated. In the considered solid loading range of 28–44 vol%, all the slurries exhibited superior rheological properties (≤145 mPa⋅s at 95.40 s −1 for 44 vol% solid loading) perfectly suitable for casting. With increasing solid loading, a decreased bulk density (1.71–1.69 g/cm 3 ), volume shrinkage (37.73–13.77%) and flexural strength (46.56–26.75 MPa) of green bodies were obtained, exhibiting better mechanical properties than those derived from the conventional acrylamide (AM) system. Regarding Si 3 N 4 ceramics with various solid loadings, the increase in calcination temperature favored the phase transformation α→β–Si 3 N 4 and β–Si 3 N 4 growth, however, the increased solid loading exhibited an inhibiting effect on those since mass transport in gas phase was blocked due to the disruption of pore connectivity. The resulting microstructure changes imparted Si 3 N 4 ceramics increasing flexural strength (110.36–367.88 MPa), fracture toughness (2.54–5.03 MPa⋅m 1/2 ), as well as decreasing porosity (54.21–41.05%) and pore size (0.38–0.33 μm). This work demonstrates the potential research value of DMAA system in preparing high–performance porous Si 3 N 4 ceramics through gelcasting technique.
研究领域:
材料科学
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陶瓷工程
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DOI
高影响因子
International Journal of Applied Ceramic Technology
·
2024
·
IF 1.8
Heng Zhang,Dongxu Yao,Yongfeng Xia,Yu-Ping Zeng
Porous Si 3 N 4 ceramics were prepared using the low-toxicity monomer HEMA (2-hydroxyethyl methacrylate) via a modified gel casting method. The rheological properties of Si 3 N 4 slurries were investigated. Triethanolamine with high activity was used as a catalyst and modifier for gelation reactions, effectively improving the curing rate and suppressing the inherent surface oxygen inhibition in such process systems. With an increase in solid loading of the slurry, the drying shrinkage (12.3% to 5.4%) significantly decreased, while the green body density (44.0%–49.0%) and flexural strength (9.65–16.46 MPa) increased, demonstrating an excellent mechanical strength. After sintering at 1700°C, the porous Si 3 N 4 ceramics prepared with 24–36 vol% solid loading slurry exhibited a flexural strength of 144.39–193.66 MPa and a porosity of 55.8% to 49.0%. The dielectric constant and loss tangent at 30 GHz ranged from 2.88 to 3.38 and 1.17–1.56 × 10 −3 , respectively. These ceramics show promising potential applications in high-performance structural ceramics and high-temperature wave-transparent materials.
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
·
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
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陶瓷工程
✓ 已验证
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2024
·
IF 5.8
Zhilei Wei,Wenqi Xie,Jiabin Hu,Zhejian Zhang,Biao Zhang,Lei Zhao,Yanjun Li,Bo Wang,Zhongqi Shi
Unidirectional porous (UP) Si 3 N 4 ceramics are promisingly applied in high-temperature filtration devices. However, traditional techniques exhibit the drawbacks of high energy consumption and difficult to control the pore structures. Herein, a novel technique of freeze casting combined with combustion synthesis was proposed to prepare the UP Si 3 N 4 ceramics using Si powder and Si 3 N 4 diluent as raw materials. The effects of Si 3 N 4 diluent content and solid loading on the phase composition, microstructure and permeable/mechanical/filtration properties were investigated systematically. The results showed that the porosity and structure wavelength of UP Si 3 N 4 ceramics with uniform microstructures can be tailored in a wide range of 50.8–86.0 % and 21.7–45.6 μm, respectively. The products exhibited anisotropic compressive strength, good permeable and filtration properties. This novel route with the advantages of energy-saving and high efficiency offers new insights for fabricating UP ceramics.
研究领域:
材料科学
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陶瓷工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2016
·
IF 3.014
Feng Wang,Jinwei Yin,Dongxu Yao,Yongfeng Xia,Kaihui Zuo,Hanqin Liang,YuPing Zeng
Porous Si 3 N 4 ceramics were fabricated through gelcasting followed by pressureless sinter at 1690 °C. Oil-in-water (O/W) Si 3 N 4 suspensions were prepared by mixing paraffin O/W emulsion and Si 3 N 4 suspensions, sodium alginate was used as gelling agent. The casted suspensions were quickly gelled by spraying calcium chloride aqueous solution onto the surface, thus oil was enwrapped into the green bodies. The porous Si 3 N 4 ceramics had spherical-shaped pores both with and without adding O/W emulsion. As changing the O/W emulsion content in the suspension, porous Si 3 N 4 ceramics with high open porosity of 60.1–63.9% and flexural strength of 44.5–34.6 MPa were obtained.
研究领域:
材料科学
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陶瓷工程
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产品关联
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
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2019
·
IF 4.175
Shuang Yin,Limei Pan,Kai Huang,Tai Qiu,Jian Yang
Porous Si 3 N 4 ceramics with bimodal hierarchical pore structures were fabricated through combining aqueous gelcasting and adding pore–forming agent method wherein a low–toxic monomer N, N–dimethylacrylamide (DMAA) and spherical pore–forming agent polystyrene sphere (PS) were respectively applied. The results demonstrated that PS size and content played an important function in regulating microstructure and properties of slurries, green and sintered bodies. The slurry viscosity increased sharply with the introduction of fine PS and reached a maximum of 1.78 Pa⋅s when adopting 7 wt% PS with d 50 = 2.51 μm. Fine PS addition caused higher porosity in green bodies than coarse one, resulting in a significant reduction in bending strength from 28.50 MPa to 11.50 MPa, however, overall, demonstrating high enough strength for mechanical processing. The formed spherical pores from PS in ceramic matrix facilitated high porosity and highly crosslinked microstructure, thus contributing to lowering dielectric constant and loss. With PS size increasing, the dominant role in mechanical properties was transferred from porosity to microstructure, whilst dielectric properties were merely controlled by porosity and spherical pores. The porosity, bending strength, fracture toughness, dielectric constant and loss at 15 GHz varied in ranges of 36.34–52.91%, 258.42–101.21 MPa, 6.02–3.38 MPa⋅m 1/2 , 4.29–2.98 and 1.48–1.18 × 10 −3 , respectively, displaying an excellent comprehensive properties.
研究领域:
材料科学
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陶瓷工程
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产品关联
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
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陶瓷工程
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产品关联
DOI
高影响因子
International Journal of Materials Research
·
2024
·Vol. 115
·期 6
·391-399
·
IF 0.7
Haiqing Li,Yanru Wang,Runze Liu,Shuming Wang
Due to their special structure and many excellent properties, porous Si 3 N 4 ceramics have a wide range of potential applications as a new structural and functional integrated material. In the present study, porous Si 3 N 4 ceramics with excellent bending properties and satisfactory porosity were prepared by the gel-casting method. The variations in porosity, bending strength, fracture morphology and phase composition of the porous Si 3 N 4 ceramics with different weight fractions of La 2 O 3 –MgO sintering additive were investigated. The results showed that the density of porous Si 3 N 4 ceramics increased linearly with the increase of sintering additive content. When the content of sintering additive increased from 2.5 wt.% to 10 wt.%, the porosity of porous ceramics decreased from 30 % to 10 %. With the increase of sintering additive content, the bending strength of the samples first increased and then decreased. When the sintering additive content was 5.0 wt.%, the average bending strength of the samples reached a maximum of 240.88 MPa, and scanning electron microscopy and X-ray diffractometry results showed that β-Si 3 N 4 particles with well-developed pores and a maximum aspect ratio of 5.8 were formed in the porous silicon nitride ceramics. This study provides a reference for the preparation of porous Si 3 N 4 ceramics with good bending properties and porosity.
研究领域:
材料科学
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陶瓷工程
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产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2021
·
IF 4.527
Chao Wang,Xu Wang,Binglei Wang,Guozheng Xiao,Ruiqing Qiao,Fan Zhang,Yu Bai,Yizhuo Li,Yusheng Wu,Zhanjie Wang,Hongjie Wang
A dense β-Si 3 N 4 coating toughened by β-Si 3 N 4 nanowires/nanobelts was prepared by a combined technique involving chemical vapor deposition and reactive melt infiltration to protect porous Si 3 N 4 ceramics in this work. A porous β-Si 3 N 4 nanowires/nanobelts layer was synthesized in situ on porous Si 3 N 4 ceramics by chemical vapor deposition, and then Y–Si–Al–O–N silicate liquid was infiltrated into the porous layer by reactive melt infiltration to form a dense composite coating . The coating consisted of well-dispersion β-Si 3 N 4 nanowires/nanobelts, fine β-Si 3 N 4 particles and small amount of silicate glass . The testing results revealed that as-prepared coating displayed a relatively high fracture toughness, which was up to 7.9 ± 0.05 MPa m 1/2 , and it is of great significance to improve thermal shock resistance of the coating. After thermal cycling for 15 times at ΔT = 1200 °C, the coated porous Si 3 N 4 ceramics still had a high residual strength ratio of 82.2%, and its water absorption increased only to 6.21% from 3.47%. The results will be a solid foundation for the application of the coating in long-period extreme high temperature environment.
研究领域:
材料科学
·
表面工程
✓ 已验证
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
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陶瓷工程
✓ 已验证
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2024
·
IF 5.1
Guang-Xin Mao,Jia-Min Wu,Chong Tian,Chun-Lei Liu,Xin Lin,Fen Wang,Hai-Sheng Xu,Yu-Sheng Shi
Porous Si 3 N 4 ceramics are widely applied in aerospace and mechanical fields owing to their excellent properties. Furthermore, vat photopolymerization (VPP) technology can fabricate Si 3 N 4 components with complicated structures and high precision, but its layer-by-layer printing method leads to poor mechanical properties of ceramics. In this study, porous Si 3 N 4 ceramics with a porosity of 28.41 % strengthened by directional β-Si 3 N 4 were fabricated by combining VPP technology and seeding method. Rheological behavior and curing properties of the slurry were explored, and the influence of β-Si 3 N 4 content on the mechanical properties of printed Si 3 N 4 ceramics was investigated systematically. With the increase of β-Si 3 N 4 content, the orientation degree of β-Si 3 N 4 grains increased gradually, while fracture toughness and flexural strength of the ceramics exhibited a trend of increased first and then decreased and Vickers hardness gradually decreased. As β-Si 3 N 4 content increased to 5 wt%, the fracture toughness and flexural strength of porous Si 3 N 4 ceramics were improved from 4.23 MPa m 1/2 and 214.7 MPa–5.65 MPa m 1/2 and 272.0 MPa, respectively. Therefore, this work indicates that vat photopolymerization combined with seeding method is a promising approach for the fabrication of porous Si 3 N 4 ceramics with high performance and complex structures.
研究领域:
材料科学
·
机械工程
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产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）