共查询到20条相似文献,搜索用时 31 毫秒
1.
Effect of Sintering Additives on Microstructure and Mechanical Properties of Porous Silicon Nitride Ceramics 总被引:2,自引:0,他引:2
Jun Yang Jian-Feng Yang Shao-Yun Shan Ji-Qiang Gao Tatsuki Ohji 《Journal of the American Ceramic Society》2006,89(12):3843-3845
Porous silicon nitride (Si3 N4 ) ceramics with about 50% porosity were fabricated by pressureless sintering of α-Si3 N4 powder with 5 wt% sintering additive. Four types of sintering aids were chosen to study their effect on the microstructure and mechanical properties of porous Si3 N4 ceramics. XRD analysis proved the complete formation of a single β-Si3 N4 phase. Microstructural evolution and mechanical properties were dependent mostly on the type of sintering additive. SEM analysis revealed the resultant porous Si3 N4 ceramics as having high aspect ratio, a rod-like microstructure, and a uniform pore structure. The sintered sample with Lu2 O3 sintering additive, having a porosity of about 50%, showed a high flexural strength of 188 MPa, a high fracture toughness of 3.1 MPa·m1/2 , due to fine β-Si3 N4 grains, and some large elongated grains. 相似文献
2.
Gui-hua Peng Min Liang Zhen-hua Liang Qing-yu Li Wen-lan Li Qian Liu 《Journal of the American Ceramic Society》2009,92(9):2122-2124
Silicon nitride ceramics were prepared by spark plasma sintering (SPS) at temperatures of 1450°–1600°C for 3–12 min, using α-Si3 N4 powders as raw materials and MgSiN2 as sintering additives. Almost full density of the sample was achieved after sintering at 1450°C for 6 min, while there was about 80 wt%α-Si3 N4 phase left in the sintered material. α-Si3 N4 was completely transformed to β-Si3 N4 after sintering at 1500°C for 12 min. The thermal conductivity of sintered materials increased with increasing sintering temperature or holding time. Thermal conductivity of 100 W·(m·K)−1 was achieved after sintering at 1600°C for 12 min. The results imply that SPS is an effective and fast method to fabricate β-Si3 N4 ceramics with high thermal conductivity when appropriate additives are used. 相似文献
3.
Tzer-Shin Sheu 《Journal of the American Ceramic Society》1994,77(2):499-504
An equilibrium Y-Si-O-N melt was infiltrated to eliminate the open porosity of reaction-bonded silicon nitride at 1600–1800°C. This oxynitride melt contained two equilibrium phases, a β-Si3 N4 solid phase and a liquid phase at high temperatures. Before infiltration, porous reaction-bonded silicon nitride compacts were heat-treated to completely transform to the β-Si3 N4 phase. After infiltration, the flexural strength of the reaction-bonded silicon nitride material increased from 200 to 600 MPa at 25°C, from 200 to 300 MPa at 1400°C in air. 相似文献
4.
Fei Chen Qiang Shen Faqiang Yan Lianmeng Zhang 《Journal of the American Ceramic Society》2007,90(8):2379-2383
A new method for preparing high bending strength porous silicon nitride (Si3 N4 ) ceramics with controlled porosity has been developed by using pressureless sintering techniques and phosphoric acid (H3 PO4 ) as the pore-forming agent. The fabrication process is described in detail and the sintering mechanism of porous ceramics is analyzed by the X-ray diffraction method and thermal analysis. The microstructure and mechanical properties of the porous Si3 N4 ceramics are investigated, as a function of the content of H3 PO4 . The resultant high porous Si3 N4 ceramics sintered at 1000°–1200°C show a fine porous structure and a relative high bending strength. The porous structure is caused mainly by the volatilization of the H3 PO4 and by the continous reaction of SiP2 O7 binder, which could bond on to the Si3 N4 grains. Porous Si3 N4 ceramics with a porosity of 42%–63%, the bending strength of 50–120 MPa are obtained. 相似文献
5.
Jun-Qi Li Fa Luo Dong-Mei Zhu Wan-Cheng Zhou 《Journal of the American Ceramic Society》2007,90(6):1950-1952
The influence of phase formation on the dielectric properties of silicon nitride (Si3 N4 ) ceramics, which were produced by pressureless sintering with additives in MgO–Al2 O3 –SiO2 system, was investigated. It seems that the difference in the dielectric properties of Si3 N4 ceramics sintered at different temperatures was mainly due to the difference of the relative content of α-Si3 N4 , β-Si3 N4 , and the intermediate product (Si2 N2 O) in the samples. Compared with α-Si3 N4 and Si2 N2 O, β-Si3 N4 is believed to be a major factor influencing the dielectric constant. The high-dielectric constant of β-Si3 N4 could be attributed to the ionic relaxation polarization. 相似文献
6.
New Strategies for Preparing NanoSized Silicon Nitride Ceramics 总被引:2,自引:0,他引:2
Xin Xu Toshiyuki Nishimura Naoto Hirosaki Rong-Jun Xie Yinchun Zhu Yoshinobu Yamamoto Hidehiko Tanaka 《Journal of the American Ceramic Society》2005,88(4):934-937
We report the preparation of nanosized silicon nitride (Si3 N4 ) ceramics via high-energy mechanical milling and subsequent spark plasma sintering. A starting powder mixture consisting of ultrafine β-Si3 N4 and sintering additives of 5-mol% Y2 O3 and 2-mol% Al2 O3 was prepared by high-energy mechanical milling. After milling, the powder mixture was mostly transformed into a non-equilibrium amorphous phase containing a large quantity of well-dispersed nanocrystalline β-Si3 N4 particles. This powder precursor was then consolidated by spark plasma sintering at a temperature as low as 1600°C for 5 min at a heating rate of 300°C/min. The fully densified sample consisted of homogeneous nano-Si3 N4 grains with an average diameter of about 70 nm, which led to noticeable high-temperature ductility and elevated hardness. 相似文献
7.
Processing of a Novel Multilayered Silicon Nitride 总被引:1,自引:0,他引:1
Yasuhiro Shigegaki Manuel E. Brito Kiyoshi Hirao Motohiro Toriyama Shuzo Kanzaki 《Journal of the American Ceramic Society》1996,79(8):2197-2200
A new type of silicon nitride with a layered structure of alternating dense and porous layers was obtained by addition of β-Si3 N4 whiskers to the porous layers. The materials consisted of dense layers 60 μm thick and porous layers 40 μm thick with a final porosity of about 30%. Highly anisotropic shrinkage behavior was observed during sintering. A large addition of whiskers to the porous layers resulted in layers with well-oriented and tightly tangled elongated grains, where porosity is represented by anisotropic shaped pores. 相似文献
8.
Branko Matovic Georg Rixecker Fritz Aldinger 《Journal of the American Ceramic Society》2004,87(4):546-549
This paper deals with the densification and phase transformation during pressureless sintering of Si3 N4 with LiYO2 as the sintering additive. The dilatometric shrinkage data show that the first Li2 O- rich liquid forms as low as 1250°C, resulting in a significant reduction of sintering temperature. On sintering at 1500°C the bulk density increases to more than 90% of the theoretical density with only minor phase transformation from α-Si3 N4 to β-Si3 N4 taking place. At 1600°C the secondary phase has been completely converted into a glassy phase and total conversion of α-Si3 N4 to β-Si3 N4 takes place. The grain growth is anisotropic, leading to a microstructure which has potential for enhanced fracture toughness. Li2 O evaporates during sintering. Thus, the liquid phase is transient and the final material might have promising mechanical properties as well as promising high-temperature properties despite the low sintering temperature. The results show that the Li2 O−Y2 O3 system can provide very effective low-temperature sintering additives for silicon nitride. 相似文献
9.
Porous 2H-Silicon Carbide Ceramics Fabricated by Carbothermal Reaction between Silicon Nitride and Carbon 总被引:2,自引:0,他引:2
Jian-Feng Yang Guo-Jun Zhang Naoki Kondo Ji-Hong She Zhi-Hao Jin Tatsuki Ohji Shuzo Kanzaki 《Journal of the American Ceramic Society》2003,86(6):910-914
Porous SiC ceramics were synthesized by sintering pressed and pressed/CIPed powder compacts of α-Si3 N4 , carbon (Si3 N4 :C = 1:3 mol as ratio), and sintering aids, at 1600°C for few hours to achieve a reaction, and subsequently sintering at a temperature range of 1750°–1900°C, in an argon atmosphere. High porosities from 45%–65% were achieved by low shrinkage with large weight loss. Formation of pure 2H-SiC phase via a reaction between Si3 N4 and carbon can be demonstrated by X-ray diffractometry. The resultant porous SiC samples were characterized by SiC grain microstructures, pore-size distribution, and flexural strength. This method has the advantage of fabricating high-porous SiC ceramics with fine microstructure and good properties at a relatively low temperature. 相似文献
10.
Silicon nitride (Si3 N4 ) ceramics, prepared with Y2 O3 and Al2 O3 sintering additives, have been densified in air at temperatures of up to 1750°C using a conventional MoSi2 element furnace. At the highest sintering temperatures, densities in excess of 98% of theoretical have been achieved for materials prepared with a combined sintering addition of 12 wt% Y2 O3 and 3 wt% Al2 O3 . Densification is accompanied by a small weight gain (typically <1–2 wt%), because of limited passive oxidation of the sample. Complete α- to β-Si3 N4 transformation can be achieved at temperatures above 1650°C, although a low volume fraction of Si2 N2 O is also observed to form below 1750°C. Partial crystallization of the residual grain-boundary glassy phase was also apparent, with β-Y2 Si2 O7 being noted in the majority of samples. The microstructures of the sintered materials exhibited typical β-Si3 N4 elongated grain morphologies, indicating potential for low-cost processing of in situ toughened Si3 N4 -based ceramics. 相似文献
11.
The kinetics of anisotropic β-Si3 N4 grain growth in silicon nitride ceramics were studied. Specimens were sintered at temperatures ranging from 1600° to 1900°C under 10 atm of nitrogen pressure for various lengths of time. The results demonstrate that the grain growth behavior of β-Si3 N4 grains follows the empirical growth law Dn – D0 n = kt , with the exponents equaling 3 and 5 for length [001] and width [210] directions, respectively. Activation energies for grain growth were 686 kJ/mol for length and 772 kJ/mol for width. These differences in growth rate constants and exponents for length and width directions are responsible for the anisotropy of β-Si3 N4 growth during isothermal grain growth. The resultant aspect ratio of these elongated grains increases with sintering temperature and time. 相似文献
12.
Sang-Hoon Rhee Jae Do Lee Doh-Yeon Kim 《Journal of the American Ceramic Society》2001,84(12):3040-3042
When a small amount of β-Si3 N4 seed particles is added during the preparation of Si3 N4 ceramics, a bimodal microstructure is obtained by sintering at 1760°C. When the specimen is further heat-treated at 1900°C to enhance the bimodal characteristic, the growth of large β grains is limited. The addition of a controlled amount of β seeds of uniform and large size is suggested to obtain the intended bimodal microstructure of Si3 N4 ceramics. 相似文献
13.
Jianren Zeng Yoshinari Miyamoto Osamu Yamada 《Journal of the American Ceramic Society》1991,74(9):2197-2200
Fine Si3 N4 -SiC composite powders were synthesized in various SiC compositions to 46 vol% by nitriding combustion of silicon and carbon. The powders were composed of α-Si3 N4 , β-Si3 N4 , and β-SiC. The reaction analysis suggested that the SiC formation is assisted by the high reaction heat of Si nitridation. The sintered bodies consisted of uniformly dispersed grains of β-Si3 N4 , β-SiC, and a few Si2 N2 O. 相似文献
14.
Fabrication of Low-Shrinkage, Porous Silicon Nitride Ceramics by Addition of a Small Amount of Carbon 总被引:4,自引:0,他引:4
Jian-Feng Yang Guo-Jun Zhang Tatsuki Ohji 《Journal of the American Ceramic Society》2001,84(7):1639-1641
Successful net-shape sintering offers a significant advantage for producing large or complicated products. Porous Si3 N4 ceramics with very low shrinkage were developed, in the present investigation, by the addition of a small amount of carbon. Carbon powders (1–5 vol%) of two types, with different mean particle sizes (13 nm and 5 μm), were added to α-Si3 N4 −5 wt% Y2 O3 powders. SiC nanoparticles formed through reaction of the added carbon with SiO2 on the Si3 N4 surface or with the Si3 N4 particles themselves. Such reaction-formed SiC nanoparticles apparently had an effective reinforcing effect, as in nanocomposites. Sintered Si3 N4 porous ceramics with a high porosity of 50%–60%, a very small linear shrinkage of ∼2%–3%, and a strength of ∼100 MPa were obtained. 相似文献
15.
Yongsheng Liu Litong Zhang Laifei Cheng Yongdong Xu Yi Liu 《International Journal of Applied Ceramic Technology》2010,7(1):63-70
Silicon nitride particle-reinforced silicon nitride matrix composites were fabricated by chemical vapor infiltration (CVI). The particle preforms with a bimodal pore size distribution were favorable for the subsequent CVI process, which included intraagglomerate pores (0.1–4 μm) and interagglomerate pores (20–300 μm). X-ray fluorescence results showed that the main elements of the composites are Si, N, and O. The composite is composed of α-Si3 N4 , amorphous Si3 N4 , amorphous SiO2 , and a small amount of β-Si3 N4 and free silicon. The α-Si3 N4 transformed into β-Si3 N4 after heat treatment at 1600°C for 2 h. The flexural strength, dielectric constant, and dielectric loss of the Si3 N4(p) /Si3 N4 composites increased with increasing infiltration time; however, the pore ratios decreased with increasing infiltration time. The maximum value of the flexural strength was 114.07 MPa. The dielectric constant and dielectric loss of the composites were 4.47 and 4.25 × 10−3 , respectively. The present Si3 N4(p) /Si3 N4 composite is a good candidate for high-temperature radomes. 相似文献
16.
Youren Xu Chao M. Huang Waltraud M. Kriven Avigdor Zangvil 《Journal of the American Ceramic Society》1994,77(8):2213-2216
The microstructure of a pressureless sintered (1605°C, 90 min) O'+β' SiAlON ceramic with CeO2 doping has been investigated. It is duplex in nature, consisting of very large, slablike elongated O' grains (20–30 μm long), and a continuous matrix of small rodlike β' grains (< 1.0 μm in length). Many α-Si3 N4 inclusions (0.1–0.5 μm in size) were found in the large O' grains. CeO2 -doping and its high doping level as well as the high Al2 O3 concentration were thought to be the main reasons for accelerating the reaction between the α-Si3 N4 and the Si-Al-O-N liquid to precipitate O'–SiAlON. This caused the supergrowth of O' grains. The rapid growth of O' crystals isolated the remnant α–Si3 N4 from the reacting liquid, resulting in a delay in the α→β-Si3 N4 transformation. The large O' grains and the α-Si3 N4 inclusions have a pronounced effect on the strength degradation of O'+β' ceramics. 相似文献
17.
Jian-Feng Yang Yoshihisa Beppu Guo-Jun Zhang Tatsuki Ohji Shuzo Kanzaki 《Journal of the American Ceramic Society》2002,85(7):1879-1881
Single-phase β'-SiAlON (Si6− z Al z O z N8− z , z = 0–4.2) ceramics with porous structure have been prepared by pressureless sintering of powder mixtures of á-Si3 N4 , AlN, and Al2 O3 of the SiAlON compositions. A solution of AlN and Al2 O3 into Si3 N4 resulted in the β'-SiAlON, and full densification was prohibited because no other sintering additives were used. Relative densities ranging from 50%–90% were adjusted with the z -value and sintering temperature. The results of X-ray diffraction, scanning electron microscopy, and transmission electron microscopy analyses indicated that single-phase β'-SiAlON free from a grain boundary glassy phase could be obtained. Both grain and pore sizes increased with increasing z -value. Low z -value resulted in a relatively high flexural strength. 相似文献
18.
Fengxia Li Li Fu Xiaojian Ma Changhui Sun LianCheng Wang Chunli Guo Yitai Qian Yitai Qian 《Journal of the American Ceramic Society》2009,92(2):517-519
Starting from Si powder, NaN3 and different additives such as N -aminothiourea, iodine, or both, Si3 N4 nanomaterials were synthesized through the nitridation of silicon powder in autoclaves at 60°–190°C. As the additive was only N -aminothiourea, β-Si3 N4 nanorods and α-Si3 N4 nanoparticles were prepared at 170°C. If the additive was only iodine, α-Si3 N4 dendrites with β-Si3 N4 nanorods were obtained at 190°C. However, when both N -aminothiourea and iodine were added to the system of Si and NaN3 , the products composed of β-Si3 N4 nanorods and α, β-Si3 N4 nanoparticles could be prepared at 60°C. 相似文献
19.
Mamoru Mitomo Yoh-ichiro Sato Nobuo Ayuzawa Isamu Yashima 《Journal of the American Ceramic Society》1991,74(4):856-858
Plasma etching of β-Si3 N4 , α-sialon/β-Si3 N4 and α-sialon ceramics were performed with hydrogen glow plasma at 600°C for 10 h. The preferential etching of β-Si3 N4 grains was observed. The etching rate of α-sialon grains and of the grain-boundary glassy phase was distinctly lower than that of β-Si3 N4 grains. The size, shape, and distribution of β-Si3 N4 grains in the α-sialon/β-Si3 N4 composite ceramics were revealed by the present method. 相似文献
20.
Gui-hua Peng Guo-jian Jiang Wen-lan Li Bao-lin Zhang Li-dong Chen 《Journal of the American Ceramic Society》2006,89(12):3824-3826
α/β-Si3 N4 composites with various α/β phase ratios were prepared by hot pressing at 1600°–1650°C with MgSiN2 as sintering additives. An excellent combination of mechanical properties (Vickers indentation hardness of 23.1 GPa, fracture strength of about 1000MPa, and toughness of 6.3 MPa·m1/2 ) could be obtained. Compared with conventional Si3 N4 -based ceramics, this new material has obvious advantages. It is as hard as typical in-situ-reinforced α-Sialon, but much stronger than the latter (700 MPa). It has comparable fracture strength and toughness, but is much harder than β-Si3 N4 ceramics (16 GPa). The microstructures and mechanical properties can be tailored by choosing the additive and controlling the heating schedule. 相似文献