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1.
《Ceramics International》2019,45(10):13308-13314
The Si3N4 coating and Si3N4 coating with Si3N4 whiskers as reinforcement (Si3N4w-Si3N4) were prepared by chemical vapor deposition (CVD) on two-dimensional silicon nitride fiber reinforced silicon nitride ceramic matrix composites (2D Si3N4f/Si3N4 composites). The effects of process parameters of as-prepared coating including the preparation temperature and volume fraction of Si3N4w on the microstructure and mechanical properties of the composites were investigated. Compared with Si3N4 coating, Si3N4w-Si3N4 coating shows more significant effect on the strength and toughness of the composites, and both strengthening and toughening mechanism were analyzed. 相似文献
2.
Zhen-hua Liang Hai-long Zhang Liu-cheng Gui Jun Li Gui-hua Peng Guo-jian Jiang 《Ceramics International》2013
α/β Si3N4 composites with β-Si3N4 content ranging from 26% to 100% were hot-pressed with or without β-Si3N4 seeds, using MgSiN2 as additives, and their mechanical properties were investigated. When the α-Si3N4 content was over 58%, the microhardness of α/β Si3N4 composites was in the range of 23–24 GPa, and then the indentation hardness decreases with decreasing the content of α-Si3N4, whether with β-Si3N4 seeds or not. The toughness increased with increasing elongated β-Si3N4 grains, which improved fracture resistance by crack bridging, pull out or the crack deflection mechanism, and reached the maximum value of 7.0 MPa m1/2 with 1 wt% β-seeds. In comparison with α/β Si3N4 composite with a similar phase composition, the fracture strength was improved by adding β-Si3N4 seeds because of the relatively smaller grain sizes and higher toughness. The α/β Si3N4 composite with 5 wt% β-seeds showed a high strength of 1253 MPa, a high hardness of 20.9 GPa and a toughness of 6.9 MPa m1/2. 相似文献
3.
Kh.V. Manukyan S.L. Kharatyan G. Blugan P. Kocher J. Kuebler 《Journal of the European Ceramic Society》2009,29(10):2053-2060
The fabrication method and the mechanical and electrical properties of different MoSi2–Si3N4 composite materials were investigated. Commercially available individual compounds, one-stage combustion synthesized MoSi2–Si3N4 and submicron MoSi2 powders were used as starting materials, followed by hot pressing. It was found that the sintering atmosphere used, nitrogen or argon, had a significant effect on the phase composition, mechanical and electrical properties of the final materials. It was shown that in some cases partial nitridation of MoSi2 occurred with the formation of MoSi2–Mo5Si3–Si3N4 ternary composites. The electrical conductivity of the composites depends also on the microstructure of materials. It was shown that the composites fabricated using combustion synthesized MoSi2 powders (500 nm) are characterized by higher flexural strength at room temperature compared to those from commercial powders. On the other hand, the composites fabricated from the commercial powders had higher strength and fracture toughness at elevated temperatures (up to 1200 °C). For all composites, the strength decreased significantly at temperatures over 1000 °C due to the brittle–ductile transition of the MoSi2 phase. 相似文献
4.
Changxi Jiang Yinghua Zhuang Jianjun Wang Shengjun Liao Lijuan Zhou Shuang Li Yunxia Zhao 《International Journal of Applied Ceramic Technology》2022,19(5):2533-2544
Si3N4 ceramics with high thermal conductivity and outstanding mechanical properties were prepared by adding β-Si3N4 seeds and nanophase α-Si3N4 powders as modifiers. The introduction of β-Si3N4 seeds enhanced the growth of β-Si3N4 grains. Owing to the interlocked structure induced by the β-Si3N4 grains, the fracture toughness of Si3N4 ceramics reached a high value of 7.6 MPa·m1/2; also, the large-sized grains increased the contact possibility of Si3N4 grains, improving the thermal conductivity of Si3N4 ceramics (64 W/(m·K)). Because of the introduction of nanophase α-Si3N4, the flexural strength, fracture toughness, and thermal conductivity of the Si3N4 ceramics increased to 754 MPa, 7.2 MPa·m1/2, and 54 W/(m·K), respectively. According to the analysis of the growth kinetics of Si3N4 grains, the rapid growth of Si3N4 grains was ascribed to the reduction in the activation energy resulting from the introduction of β-Si3N4 seeds and nanophase α-Si3N4. 相似文献
5.
《Ceramics International》2020,46(2):1760-1765
In this study, SiAlON–Si3N4 composite ceramic are prepared by direct nitridation and investigated to overcome the limitations associated with ceramic Si3N4, which includes the difficulty in fabricating ceramic Si3N4 into shaped parts for use in the human body. Phase composition and microstructure of the SiAlON–Si3N4 composites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively, and the porosity, bulk density, compressive strength, and ion release were also measured. The biological properties were evaluated by bone cell cultures on the ceramic surfaces. Results show that Si4Al2O2N6 is formed by the reaction of Al, Si, and Al2O3 with nitrogen at high temperature that forms Si3N4, thereby fabricating SiAlON–Si3N4 composite ceramics. Some α-Si3N4 grains underwent a phase transition from α-to β-Si3N4 fiber at high temperature. Porosity of the samples increases with increasing Si3N4 content, while the bulk density of the samples decreases. The compressive strength increases and then slightly decreases with increasing Si3N4 content. Water leaching experiments of the SiAlON–Si3N4 composite ceramics reveal that the composites exhibit outstanding chemical stability. Studies using bone cell culture indicate that the cells present a fusiform and extend two or three thin pseudopodia. The phenomena demonstrate that MC3T3-E1 cells have excellent growth activity and have the potential ability to proliferate to osteocytes on the surfaces of the samples, thus suggesting that SiAlON–Si3N4 based ceramics are biocompatible and could be implemented as a potential bone-repairing material. 相似文献
6.
Si3N4–TiN composite powders were obtained by in situ pyrolysis of polytitanosilazane. Dense Si3N4–TiN composites were prepared by hot-pressing at 1800 °C under 20 MPa for 2 h without sintering additive. Crystallization of amorphous PTSZ powders occurred between 1400 and 1500 °C with major phases, α-Si3N4, β-Si3N4, and small amount of phase TiN. Mechanical properties and microstructure of Si3N4–TiN composites were characterized. The results showed that the mechanical strength was 620 MPa, the fracture toughness was 7.8 MPa m1/2 and the Vickers hardness was 8.5 GPa. SEM analysis indicated that Si3N4–TiN composite possessed excellent fracture toughness because TiN grains produced by in situ pyrolysis were well dispersed in Si3N4 matrix. 相似文献
7.
《Journal of the European Ceramic Society》2002,22(6):963-971
Silicon nitride–silicon oxynitride in situ composites were fabricated by plane-strain-compressing dense silicon nitrides, starting from 93 wt.% ultrafine β-Si3N4 and 7 wt.% cordierite, at 1600 °C under a constant load of 40 MPa and subsequent annealing at 1750 °C for 30 min. The resulting composites featured a microstructure of elongated Si2N2O grains (∼0.64 μm in diameter and ∼5.5 in aspect ratio) dispersed in a fine-grained β-Si3N4 matrix (∼ 0.30μm in diameter and ∼3.5 in aspect ratio), with the amount of Si2N2O, which had relatively strong textures, being strain-dependent. The mechanical properties were found to be improved due to the development of elongated Si2N2O grains, the texture formation, and the coarsening of β-Si3N4. Fracture toughness, however, was still low (∼5.2 MPa m1/2) for these composites in comparison to self-reinforced silicon nitrides, resulted from the strong Si2N2O-matrix interfacial bond and nearly equiaxed β-Si3N4 with a small grain size. Anticipated property anisotropies were clearly observed as a result of the textured microstructure. 相似文献
8.
《Ceramics International》2017,43(3):3435-3438
Graphene nanoribbons (GNRs) were obtained by unzipping multiwall carbon nanotubes (MWCNTs). Three different silicon nitride-carbon nanostructures were prepared by spark plasma sintering (SPS): ceramic composites that contained 1 wt% carbon nanofibers (CNFs), 1 wt% MWCNTs and 1 wt% GNRs respectively. The α to β-Si3N4 transformation ratio and thermal diffusivity of GNR/Si3N4 composites were higher than both CNF/Si3N4 composites and MWCNT/Si3N4 composites. Furthermore, the higher thermal diffusivities of GNR/Si3N4 composites can primarily be attributed to the higher number of elongate β-Si3N4 grains. 相似文献
9.
《Ceramics International》2016,42(15):16448-16452
The formation mechanism and thermodynamics of Si3N4 in reaction-bonded Si3N4-SiC materials were analyzed. There are two kinds of Si3N4, fibroid α-Si3N4 and columnar β-Si3N4, which are formed by different processes in Si3N4-SiC materials. Silicon reacts with oxygen, forming gaseous SiO and reducing oxygen partial pressure. SiO(g) diffuses from central to peripheral sections of blocks and reacts with nitrogen, thus forming Si3N4, mainly in peripheral sections. The reaction between silicon and oxygen causes the consumption of oxygen and leads to low oxygen partial pressure in the sintering system, which allows silicon to react with nitrogen directly generating Si3N4in situ. SiO(g) reacts with nitrogen forming Si3N4 at both central and peripheral sections of block. The non-uniform distribution of Si3N4 and uneven microstructure is caused by the generation process, indicating that it is unavoidable in Si3N4-SiC composites. 相似文献
10.
Changlian Chen Xin Liang Maya Luo Shicong Zhou Jiayou Ji Zhiliang Huang Man Xu 《Ceramics International》2019,45(5):5922-5926
Porous Si3N4-bonded SiC ceramics with high porosity were prepared by the reaction-sintering method. In this process, Si3N4 was synthesized by the nitridation of silicon powder. The X-ray diffraction (XRD) indicated that the main phases of the porous Si3N4-bonded SiC ceramics were SiC, α-Si3N4, and β-Si3N4, respectively. The contents of β-Si3N4 were increased following the sintering temperature. The morphology of Si3N4 whiskers was investigated by scanning electron microscope (SEM), which was shown that the needle-like (low sintering-temperature) and rod-like (higher sintering-temperature) whiskers were formed, respectively. From low to high synthesized temperature, the highest porosity of the porous Si3N4 bonded SiC ceramic was up to 46.7%, and the bending strength was ~11.6?MPa. The α-Si3N4 whiskers were derived from the reaction between N2 and Si powders, the growth mechanism was proved by Vapor–Solid (VS). Meanwhile, the growth mechanism of β-Si3N4 was in accordance with Vapor–Solid–Liquid (VSL) growth mechanism. With the increase of sintering temperature, Si powders were melted to liquid silicon and the α-Si3N4 was dissolved into the liquid then the β-Si3N4 was precipitated successfully. 相似文献
11.
Fei Li Wei Cui Zhaobo Tian Jie Zhang Songmo Du Zhanglin Chen Shijia Zhang Kexin Chen Guanghua Liu 《International Journal of Applied Ceramic Technology》2022,19(6):2957-2962
Si3N4 powders were prepared by combustion synthesis with 1- and 3-μm α-Si3N4, β-Si3N4 diluent and BN inert diluent. The maximum temperatures of samples with boron nitride (BN) as a diluent are about 1500–1600°C lower than that of samples with α-Si3N4 and β-Si3N4 as diluents are about 1600–1800°C. Moreover, the newly formed α-Si3N4 contents in the synthesized products with BN as diluent over 90 wt% are much higher than those with α-Si3N4 and β-Si3N4 as diluent about 20–40 wt%. The strip-like α-Si3N4, rod-like β-Si3N4 grains, and radiative shaped grains can be observed in the synthesized products. Finally, the effect of the diluent on the α-phase content of combustion synthesized Si3N4 is discussed, which provides key guidance for preparing Si3N4 powders with high α-phase content. 相似文献
12.
《Journal of the European Ceramic Society》2003,23(8):1175-1182
Mean-field micromechanics model, the rule of mixture is applied to the prediction of the thermal conductivity of sintered β-Si3N4, considering that the microstructure of β-Si3N4 is composed of a uniform matrix phase (which contains grain boundaries and small grains of Si3N4) and the purified large grains (⩾2 μm in diameter) of Si3N4. Experimental results and theoretical calculations showed that the thermal conductivity of Si3N4 is controlled by the amount of the purified large grains of Si3N4. The present study demonstrates that the high thermal conductivity of β-Si3N4 can be explained by the precipitation of high purity grains of β-Si3N4 from liquid phase. 相似文献
13.
Tatevik Minasyan Le Liu Yaroslav Holovenko Sofiya Aydinyan Irina Hussainova 《Ceramics International》2019,45(8):9926-9933
Lattice structures, their shape, orientation, and density make the critical building blocks for macro-scale geometries during the AM process and, therefore, manipulation of the lattice structure extends to the overall quality of the final product. This work reports on manufacturing of MoSi2-Si3N4 ceramic lattices through a selective laser melting (SLM) approach. The strategy first employs the production of core-shell structured MoSi2/(10-13?wt%)Si composite powders of 3–10?μm particle size by combustion synthesis followed by SLM assembly of MoSi2/Si lattices and their further nitridation to generate MoSi2-Si3N4 mesostructures of designed geometry. Experimental results revealed that the volumetric energy density of SLM laser has remarkable influence on the cell parameters, strength, porosity and density of lattices. Under compressive test, samples sintered at a higher laser current demonstrated a higher strength value. Selective laser melting has shown its potential for production of cellular lattice mesostructures of ceramic-based composites with a low content of a binder metal, which can be subsequently converted into a ceramic phase to produce ceramic-ceramic structure. 相似文献
14.
The AlN/MAS/Si3N4 ternary composites with in-situ grown rod-like β-Si3N4 were obtained by a two-step sintering process. The microstructure analysis, compositional investigation as well as properties characterization have been systematically performed. The AlN/MAS/Si3N4 ternary composites can be densified at 1650 °C in nitrogen atmosphere. The in-situ grown rod-like β-Si3N4 grains are beneficial to the improvement of thermal, mechanical, and dielectric properties. The thermal conductivity of the composites was increased from 14.85 to 28.45 W/(m K) by incorporating 25 wt% α-Si3N4. The microstructural characterization shows that the in-situ growth of rod-like β-Si3N4 crystals leads to high thermal conductivity. The AlN/MAS/Si3N4 ternary composite with the highest thermal conductivity shows a low relative dielectric constant of 6.2, a low dielectric loss of 0.0017, a high bending strength of 325 MPa, a high fracture toughness of 4.1 MPa m1/2, and a low thermal expansion coefficient (α25–300 °C) of 5.11 × 10?6/K. This ternary composite with excellent comprehensive performance is expected to be used in high-performance electronic packaging materials. 相似文献
15.
Hajime Kiyono Yuho Miyake Yusuke Nihei Tomoki Tumura Shiro Shimada 《Journal of the European Ceramic Society》2012,32(7):1413-1417
A Si3N4 composite containing needle-like TiN particles (7 vol%) was fabricated. Needle-like TiN particles several micrometers long were synthesized using NH3 nitridation of TiO2 nanofiber, which was obtained using hydrothermal treatment. A mixed powder of α-Si3N4 and the needle-like TiN particles with additives was hot pressed at 24 MPa and 1850 °C for 1 h in N2 atmosphere. Mechanical properties of the composite were compared with those of a composite containing rounded TiN particles and a monolithic β-Si3N4 ceramic. The Si3N4 matrix of the composites containing TiN was mainly a-phase, suggesting that the α–β phase transformation of Si3N4 was inhibited by the presence of TiN. Although fracture strength of the composites was lower, fracture toughness was comparable to that of monolithic β-Si3N4 ceramics. Hardness of the composites was about 19 GPa and was greater than that of the monolithic β-Si3N4 ceramic. 相似文献
16.
《Journal of the European Ceramic Society》2007,27(5):2153-2161
The fabrication and properties of electrically conductive Si3N4–MoSi2 composites using two different sintering additive systems were investigated (i) Y2O3–Al2O3 and (ii) Lu2O3. It was found that the sintering atmosphere used (N2 or Ar) had a critical influence on the final phase composition because MoSi2 reacted with N2 atmosphere during sintering resulting in the formation of Mo5Si3. The electrical conductivity of the composites exhibited typical percolation type behaviour and the percolation concentrations depended on the type of sintering additive and atmosphere used. Metallic-like conduction was the dominant conduction mechanism in the composites with MoSi2 content over the percolation concentrations due to the formation of a three-dimensional percolation network of the conductive MoSi2 phase. The effect of the sintering additives on the electrical and oxidation properties of the composites at elevated temperatures was investigated. Parabolic oxidation kinetics was observed in the composites with both types of additives. However, the Lu2O3-doped composites had superior oxidation resistance compared to the composites containing Y2O3–Al2O3. It is attributed to the higher eutectic temperature and crystallisation of the grain boundary phase and the oxidation layer in the Lu2O3-doped composites. 相似文献
17.
《Ceramics International》2017,43(3):3238-3245
In this study, SiC coating for C/C composites was prepared by pack cementation method at 1773 K, and MoSi2-SiOC-Si3N4 as an outer coating was successfully fabricated on the SiC coated samples by slurry method at 1273 K. The microstructure and phase composition of the coatings were analyzed. Results showed that a porous β-SiC inner coating and a crack-free MoSi2-SiOC-Si3N4 coating are formed. Effect of Si3N4 content on the oxidation resistance of the coated C/C composites at 1773 K in air was also investigated. The weight loss curves revealed that introducing the appropriate proportion of Si3N4 could improve the oxidation resistance of coating. The MoSi2-SiOC/SiC coated C/C sample had an accelerated weight loss after oxidation in air for 20 h. However, the coating containing 45% Si3N4 could protect C/C composition from oxidation for 100 h with a minute weight loss of 0.63%. 相似文献
18.
To realize cost-effectively manufacture of high-performance Si3N4 porous ceramic, a ferrosilicon nitride porous ceramic with an optimized interlocking structure was synthesized by flash combustion synthesis using FeSi75 powder as raw material. And the technology has been improved in many ways to ensure stable industrial production. The theoretical combustion temperature of FeSi75 in N2(g) is up to 4608K, while Si3N4 is unstable. Both adding diluent and designing the preheat temperature of nitrogen are taken to control synthesis temperature below 1600 °C. During synthesis, the Fe–Si liquid phase and SiO(g), which are essential for the selective growth of elongated columnar β-Si3N4 and whisker α-Si3N4 respectively, are formed firstly. Then, nitriding proceed in multiple ways. N diffuses through Fe–Si(l) and reacts with Si to form β-Si3N4, and the growth of elongated β-Si3N4 in Fe–Si liquid follows the dynamic ripening model, which is very fast and effective. Thus, an interlocking structure composed of elongated β-Si3N4 with an aspect ratio above 20 is reached. There is also an indirect nitridation reaction, that is, FeSi75 preferentially reacts with trace O2 in atmosphere to form SiO(g), which is further nitrided to form needle-like α-Si3N4. Needle-like α-Si3N4 is interspersed in the well-developed columnar β-Si3N4, making the structure stronger. Fe finally exists in the form of Fe3Si, which binds the surrounding elongated Si3N4 to form a sea-urchin like unit, making the structure more stable and strengthened. Through control of these reactions, optimizations in microstructure are reached, and the annual output of has reached 25,000 tons. The reaction model is established. 相似文献
19.
Qiang Zhi Bo Wang Shan Zhao Zhao Zhang Yu-Chen Deng Bao-Qiang Hou Nan-Long Zhang Jian-Feng Yang 《Ceramics International》2021,47(6):8113-8122
Si3N4 ceramic with ultrafine fibrous grains are expected to exhibit remarkable mechanical properties. In this work, highly porous Si3N4 ceramic monoliths composed of ultrafine fibrous grains were developed via a novel vapor-solid carbothermal reduction nitridation (V-S CRN) reaction between SiO vapor and green bodies comprised of carbon nanotubes (CNTs), α-Si3N4 diluents and Y2O3 in a N2 atmosphere. The unique fibrous grains-interconnected structure was developed through in-situ formation of Si3N4 and following liquid phase sintering. The porous Si3N4 monoliths with porosity of 61–78% was developed by controlling the contents of α-Si3N4 diluents and densities of the CNT green bodies. With increasing of the α-Si3N4 contents, Si3N4 fibrous grains with an aspect ratio of approximate or higher than 20 could be achieved, and the grains were gradually refined. For the samples with 40 wt% α-Si3N4, the minimum mean grain diameter and pore size of 164 nm and 0.79 μm were achieved, respectively, and the resultant porous Si3N4 monolith exhibited a flexural strength of as high as 73–102 MPa with the porosity of 61–73%, which is much higher than that of the reported in literature. The improvement of mechanical strength could be attributed to the densely interconnected bird's nests structure formed by the ultrafine fibrous grains. The effects of the α-Si3N4 diluents on the resulting porous Si3N4 monolith via this method were analyzed. 相似文献
20.
Haize Jin Dechang Jia Zhihua Yang Yu Zhou 《Journal of the European Ceramic Society》2021,41(4):2579-2586
Si2N2O composites were achieved via direct ink writing technique and pressureless sintering. The design and optimization of inks and the effect of mass ratio of Si3N4 and SiO2 on the phase composition, microstructure, mechanical properties and dielectric properties of composites were systematically investigated. The inks exhibit superior stability and printability. Increasing SiO2 content facilitated densification and enhancement of mechanical property. The generation of β-Si3N4 and Si2N2O and the nucleation of cristobalite were restrained by high content SiO2. The ceramic composites with the flexural strengths from 74.1MPa to 104.9MPa and low dielectric constant (≤4.68) were fabricated. This strategy provides a systematic reference for synthesis of high-performance porous Si2N2O composites based on the DIW. 相似文献