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1.
《Journal of the European Ceramic Society》2019,39(15):4645-4653
C/SiBCN composites with a density of 1.64 g/cm3 were prepared via precursor infiltration and pyrolysis and the bending strength and modulus at room temperature was 305 MPa and 53.5 GPa. The precursor derived SiBCN ceramics showed good thermal stability at 1600 °C and the SiC and Si3N4 crystals appeared above 1700 °C. The bending strength of the composites was 180 MPa after heat treatment at 1500 °C, and maintained at 40 MPa-50 MPa after heat treatment for 2 h at 1600 °C–1900 °C. In C/SiBCN composites, SiBCN matrix could retain amorphous up to 1500 °C and SiC grains appeared at 1600 °C but without Si3N4. The reason for no detection of Si3N4 was that the carbon fiber reacted with Si3N4 to form an interface layer (composed of SiC and unreacted C) and a polycrystalline transition layer (composed of B and C elements), leading to the degradation of the mechanical properties. 相似文献
2.
Lei Han Liang Huang Faliang Li Junkai Wang Yuantao Pei Yuan Zeng Quanli Jia Haijun Zhang Shaowei Zhang 《Ceramics International》2018,44(10):11088-11093
Si3N4/SiC porous ceramics were fabricated by a novel foam-gelcasting and microwave-assisted catalytic nitridation method at a temperature as low as 1273?K for 60?min or after only 10?min at 1373?K utilizing commercial Si and SiC with trace of impurity Fe (0.33?wt%) as starting materials. The Si3N4/SiC porous ceramics containing porosity of 68.54?±?0.73% which were fabricated at 1373?K for 10?min had flexural and compressive strengths of 5.28?±?0.17?MPa and 12.86?±?1.55?MPa. 相似文献
3.
Wei Zhou Rui-ming Yin Lan Long Heng Luo Wei-da Hu Yan-hong Ding Yang Li 《Ceramics International》2018,44(11):12301-12307
Si3N4 ceramics modified with SiC nanofibers were prepared by gel casting aiming to enhance the dielectric and microwave absorption properties at temperatures ranging from 25?°C to 800?°C within X-band (8.2–12.4?GHz). The results indicate that the complex permittivity and dielectric loss are significantly increased with increased weight fraction of SiC nanofibers in the Si3N4 ceramics. Meanwhile, both complex permittivity and dielectric loss of SiC nanofibers modified Si3N4 ceramics are obviously temperature-dependent, and increase with the higher test temperatures. Increased charges mobility along conducting paths made of self-interconnected SiC nanofibers together with multi-scale net-shaped structure composed of SiC nanofibers, Si3N4 grains and micro-pores are the main reason for these enhancements in dielectric properties. Moreover, the calculated microwave absorption demonstrates that much enhanced microwave attenuation abilities can be achieved in the SiC nanofibers modified Si3N4 ceramics, and temperature has positive effects on the microwave absorption performance. The SiC nanofibers modified Si3N4 ceramics will be promising candidates as microwave absorbing materials for high-temperature applications. 相似文献
4.
《Journal of the European Ceramic Society》2004,24(12):3409-3417
The Si/B/C/N/H polymer T2(1), [B(C2H4Si(CH3)NH)3]n, was reacted with different amounts of H3Al·NMe3 to produce three organometallic precursors for Si/B/C/N/Al ceramics. These precursors were transformed into ceramic materials by thermolysis at 1400 °C. The ceramic yield varied from 63% for the Al-poor polymer (3.6 wt.% Al) to 71% for the Al-rich precursor (9.2 wt.% Al). The as-thermolysed ceramics contained nano-sized SiC crystals. Heat treatment at 1800 °C led to the formation of a microstructure composed of crystalline SiC, Si3N4, AlN(+SiC) and a BNCx phase. At 2000 °C, nitrogen-containing phases (partly) decomposed in a nitrogen or argon atmosphere. The high temperature stability was not clearly related to the aluminium concentration within the samples. The oxidation behaviour was analysed at 1100, 1300, and 1500 °C. The addition of aluminium significantly improved the oxide scale quality with respect to adhesion, cracking and bubble formation compared to Al-free Si(/B)/C/N ceramics. Scale growth rates on Si/B/C/N/Al ceramics at 1500 °C were comparable with CVD–SiC and CVD–Si3N4, which makes these materials promising candidates for high-temperature applications in oxidizing environments. 相似文献
5.
In this study, mesoporous carbon-rich Mo4.8Si3C0.6/C/SiC ceramic nanocomposites were successfully prepared via a single-source precursor route, starting from allylhydridopolycarbosilane (AHPCS, SMP-10), bis(acetylacetonato) dioxomolybdenum (VI) [MoO2(acac)2], and divinylbenzene (DVB). Besides, polystyrene (PS) was used as a pore former. The obtained carbon-rich single-source precursor/PS mixtures were pyrolyzed at 1100°C, and then annealed at 1350°C-1600°C to fabricate a series of carbon-rich Mo4.8Si3C0.6/C/SiC ceramics comprised of high carbon content above 50 wt%. In comparison to the carbon-poor materials, the carbon-rich samples retain the higher specific surface area up to 214.6-304 m2/g at higher annealing temperatures (1350°C-1600°C) due to the enhancement of carbothermal reaction. The carbon-rich samples synthesized at 1500°C, denoted as SM/Mo/PS/DVB 2-1-4-2 1500 exhibit enhanced electrocatalytic performance with ultra-low overpotentials of 119 mV vs reversible hydrogen electrode at a current density of 10 mA cm−2 in acidic media, which is superior to that of the Mo4.8Si3C0.6/C/SiC ceramic (138 mV) with lower carbon content reported in our previous study. Therefore, our porous materials comprised of high carbon content and Nowotny phase (Mo4.8Si3C0.6, NP) are considered as promising catalysts for the hydrogen evolution reaction (HER). 相似文献
6.
《Ceramics International》2023,49(13):22022-22029
The in-situ controllable synthesis of AlN–SiC solid solution reinforcement in large-sized Al–Si3N4–Al2O3 composite refractory by two-steps nitriding sintering was examined. In the first step, a dynamic Al@AlN structure was constructed in the composite by pre-nitriding at 580 °C. During the subsequent sintering process, it cracked above ∼900 °C, and micronized Al cluster (mixture of droplets and vapor) was extracted out gradually. As a result, multiple AlN mesophases were formed through different reaction paths, including i) initial AlN shell formed by solid Al with N2, ii) reaction of Al cluster with N2, and iii) reaction of Al cluster with Si3N4 from 900 °C to 1500 °C. The Si3N4 precursor serves as both a solid nitrogen source and an active Si source, and the controllable reaction between Al and Si3N4 leading to uniformly distributed AlN and Si mesophases. AlN–SiC solid solution is significantly formed when liquid Si appears. The shell, granule and whisker SiC–AlN solid solution were observed mainly depending on the dynamic AlN mesophase. The SiC–AlN solid solution reinforced Al2O3 materials is a novel promising refractory for large-scale blast furnace lining. 相似文献
7.
Ling Li Chunfeng Liu Liangbo Sun Hongjiang Yu Xinhua Wang Xuanzhi Wang Jie Zhang 《Ceramics International》2018,44(7):7831-7836
Si3N4 ceramic was successfully joined to itself with in-situ formed Yb-Si-Al oxynitride glass interlayer. The joints were composed of three parts: (I) Si3N4 matrix, (II) oxynitride glass interlayer in which hexagonal or fine elongated β-sialon grains and a few ball-like β-Si3N4 grains exist, and (III) diffusion zone in Si3N4 matrix containing a thin dark layer and a ~ 25?µm thick bright layer. The seam owned similar microstructure to matrix and was inosculated with the matrix as a whole. The strength of the joint tended to increase with the increase of bonding temperature and reached the value of 225?MPa, when the joints were prepared at 1600?°C for 30?min under a pressure of 1.5?MPa. The high-temperature strength remained 94.7% and 75.2% of R.T. strength when the joints were tested at 1000?°C and 1200?°C, respectively. It may be contributed to the high softening temperature of the Yb-Si-Al oxynitride glass phase formed in the seam. Even suffered to the air exposure for 10?h at 1200?°C, the residual strength of the joints was still 143?MPa, attributed to the existence of YbAG phase. 相似文献
8.
Silicon nitridation mechanism in reaction‐bonded Si3N4–SiC and Si3N4‐bonded ferrosilicon nitride
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Menglong Long Yong Li Xiuming Jin Guisheng Yao Jialin Sun Ramachandran V. Kumar 《Journal of the American Ceramic Society》2018,101(9):4350-4356
Reaction‐bonded Si3N4–SiC and Si3N4‐bonded ferrosilicon nitride, with Si powder, SiC particles and Fe3Si–Si3N4 particles as raw materials, respectively, are prepared in flame‐isolation nitridation shuttle kiln with flowing N2 at 1723K. There is columnar β‐Si3N4 in both Si3N4–SiC and Si3N4‐bonded ferrosilicon nitride. However, fibrous α‐Si3N4 is only observed in Si3N4–SiC and Si3N4‐bonded ferrosilicon nitride contains much more Si2N2O than Si3N4–SiC. By analyzing the oxidation thermodynamics of Si and Si3N4, it is known that in the process of producing Si3N4–SiC, Si is oxidized first to gaseous SiO and fibrous α‐Si3N4 is generated with SiO and N2. The existence of SiO is the reason of low silicon nitridation rate. But in the process of producing Si3N4‐bonded ferrosilicon nitride, Si3N4 is easier to be oxidized than Si and Si2N2O is generated on the surface of Si3N4 hexagonal prisms in ferrosilicon nitride particles. Meanwhile, Si in raw materials forms new ferrosilicon alloys with Fe3Si, which decreases the temperature of liquid appearance and blocks some open pores in the samples, which stops the matter loss of nitridation. Liquid ferrosilicon alloys favors β‐Si3N4 generation from Si direct nitridation and fibrous α‐Si3N4 transformation, which used to exist in ferrosilicon nitride raw materials. 相似文献
9.
Boron nitride/silicon nitride (BN/Si3N4) composite ceramics were fabricated via the in-situ nitridation of boron (B) and silicon (Si) powders in forming gas (95%N2/5%H2) at 1390?°C. The effect of the B content on the phase composition, microstructure, density/porosity, machinability as well as mechanical properties of nitridized BN/Si3N4 composite ceramics was investigated. The addition of B slightly increased the nitridation degree of the Si and B powders mixture, and improved the ratio of the β-Si3N4 phase significantly at low B contents. B powders may have acted as a nucleating agent to promote the formation of β-Si3N4 crystals. A core-shell Si3N4/BN structure was revealed by the TEM technique, and the number of BN layers increased with the increase of the B content. The in-situ BN formed by the nitridation of B played a similar role with the BN directly added in enhancing the machinability of the BN/Si3N4 composite ceramics. The method of the in-situ nitridation of B is also effective to prepare SiC fiber-reforced BN/Si3N4 ceramic matrix 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.
Jiangbo Shan Ning Liao Yawei Li Dechang Jia Zhihua Yang Shaobai Sang 《Ceramics International》2019,45(3):3531-3540
The ultra-low cement bonded Al2O3-SiC-C castables were prepared with the introduction of a novel Si2BC3N antioxidant. The microstructure evolution and the mechanical properties were evaluated in coke bed and air atmosphere. Besides, the thermal properties, including thermal shock, hot modulus of rupture, oxidation and refractories under load, were comparatively investigated. The results show that the Si2BC3N powder together with B4C and Si can satisfy the oxidation resistance requirements over a full temperature range. Si2BC3N has mainly two effects depending on the treating temperature: 1) it protects the carbon from oxidation and increases the structure integrity when the specimens are treated below 1100?°C; 2) it stimulates the growth of SiC whiskers under 1400?°C due to the enhanced reaction between SiO and CO. Consequently, the CMOR and CCS of the Si2BC3N containing specimens have been improved attributing to the structural integrity and more SiC whiskers formation, regardless of the treating atmosphere. Besides, the thermal properties such as the hot modulus of rupture, thermal shock and refractories under load are also optimized with Si2BC3N addition. 相似文献
12.
Wei Zhou Yang Li Lan Long Heng Luo Yichen Wang 《Journal of the American Ceramic Society》2020,103(12):6822-6832
Carbon fibers reinforced Si3N4 composites with SiC nanofiber interphase (Cf/SiCNFs/Si3N4) were prepared by combining catalysis chemical vapor deposition and gel-casting process. Microstructures, mechanical properties, and electromagnetic wave absorption properties within X-band at 25°C-800°C of Cf/SiCNFs/Si3N4 composites were investigated. Results show that SiC nanofibers are combined well with Si3N4 matrix and carbon fibers, the fracture toughness is thus increased more than double from 3.51 MPa·m1/2 of the Si3N4 ceramic to 7.23 MPa·m1/2 of the as-prepared composites. As the temperature increases from 25°C to 800°C, Cf/SiCNFs/Si3N4 composites show a temperature-dependent complex permittivity, attenuation constant, and impedance. The relatively high attenuation capability of Cf/SiCNFs/Si3N4 composites at elevated temperature results in a great minimum reflection loss of −20.3 dB at 800°C with a thin thickness of 2.0 mm. The superior electromagnetic wave absorption performance mainly originates from conductive loss, multi-reflection, and strong polarization formed by the combined effects of carbon fibers and SiC nanofibers. 相似文献
13.
《Journal of the European Ceramic Society》2020,40(3):622-629
Research into the high-temperature microstructural evolution of SiCN ceramic fibers is important for the aerospace application of advanced ceramic matrix composites in harsh environments. In this work, we studied the microstructural evolution of SiCN fibers with different C/N ratios that derived from polycarbosilane fibers at the annealing temperature range of 1400∼1600 °C. These results showed that the phase separation of SiCxNy phase and the two-dimension grain growth process of free carbon nanoclusters could be processed at the researched temperature range. As the annealing temperature increased to 1600 °C, the crystallization of amorphous SiC and Si3N4 could be detected. SEM and Raman analysis showed that the decomposition and carbothermal reduction of the Si3N4 phase at high temperatures played primary roles in contributing to the fiber strength degradation. Thus, a higher C/N ratio, which is beneficial for inhibiting the decomposition of amorphous Si3N4, helps SiCN fibers retain high tensile strength at high temperatures. 相似文献
14.
Crystallization Mechanism of CVD Si3N4–SiCN Composite Ceramics Annealed in N2 Atmosphere and Their Excellent EMW Absorption Properties
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Jimei Xue Xiaowei Yin Hongxing Pan Xiaofei Liu Litong Zhang Laifei Cheng 《Journal of the American Ceramic Society》2016,99(8):2672-2679
To tailor a new electromagnetic wave (EMW) absorbing material with lower reflection coefficient (RC) and larger operating frequency band, the CVD Si3N4–SiCN composite ceramics were prepared from SiCl4–NH3–C3H6–H2–Ar system and then annealed at the temperatures of 1400–1700°C in N2 atmosphere. Effect of the annealing temperatures on the microstructure, phase composition, permittivity, and microwave‐absorbing properties of the ceramic were investigated. Results showed that the CVD Si3N4–SiCN ceramics gradually crystallized into nanosized SiC grains, Si3N4 grains and graphite (T ≤ 1600°C), and then the grains grew up at T = 1700°C. The permittivity, dielectric loss, and electrical conductivity of as‐annealed CVD Si3N4–SiCN ceramics (T ≤ 1600°C) increased firstly due to the formation of conductivity and polarity network and the increase in nanograin boundary, and then decreased at 1700°C because of the growth of nanograins and the disappearance of nanograin boundary. The minimal RC and effective absorption bandwidth of the as‐annealed CVD Si3N4–SiCN ceramic at 1600°C was ?41.67 dB at the thickness of 2.55 mm and 3.95 GHz at the thickness of 3.05 mm, respectively, demonstrating that the totally crystallized CVD Si3N4–SiCN ceramic (T = 1600°C) had the superior microwave‐absorbing ability. 相似文献
15.
Si3N4 bonded SiC (Si3N4-SiC) is a conventional refractory material and has broad applications. In the present study, Si3N4-SiC refractory materials were systematically investigated in the copper-making environment. Si3N4-SiC was reacted with Cu, Cu2O, industrial matte, Cu2S and FeS melts at 1200 °C in argon gas atmosphere, and all samples were directly quenched in water after the experiments. Phase changes and compositions of the phases were measured by electron probe X-ray microanalysis. The present investigations demonstrate that Cu and Cu2S do not react with Si3N4-SiC at high temperatures and the wettability between this material and the melts is low. However, significant reactions occur between Si3N4-SiC and Cu2O, industrial matte and FeS. The results imply that Si3N4-SiC material has limited oxidation-resistance and can only be used under reducing conditions. 相似文献
16.
Xiaofang Wu Yong Li Peng Jiang Jialin Sun 《Journal of the American Ceramic Society》2022,105(3):2268-2276
In this study, alumina-based composite with 12 wt% Al and 16 wt% Si3N4 was designed to achieve the synthesis of 15R-Sialon reinforced alumina composite. To investigate the reaction mechanism, two-step sintered Al-Si3N4-Al2O3 samples at different temperatures ranging from 600°C to 1500°C were prepared and characterized via X-ray diffraction and scanning electron microscope (SEM). The results revealed that 15R-Sialon was synthesized at 1500°C through a novel liquid Si phase sintering and Si3N4 played as a precursor and a reactant. First, Si3N4 precursor reacted with Al to form intermediate phases AlN and Si, which were not further transformed below 1400°C. When the sintering temperature was 1500°C, the formed Si presented as a liquid phase, under the influence of which plate-like15R-Sialon was generated from Al2O3, residual Si3N4, and derived AlN. The obtained Si was also involved in the synthesis of 15R-Sialon and completely transformed. In addition to the AlN from Si3N4, the AlN deriving from the nitridation of Al may not react with liquid Si. Compared to 15R-Sialon from liquid Si, plate-like 15R-Sialon with smaller size was generated from AlN, SiO, and O2. 相似文献
17.
Hanjun Wei Xiaowei Yin Xiaolin Dang Litong Zhang Laifei Cheng 《Ceramics International》2018,44(18):22784-22793
For enhancing the absorption ability of dielectric and electromagnetic wave (EMW), C-rich SiC NWs /Sc2Si2O7 ceramics are successfully fabricated through in-situ growth of SiC nanowires (NWs) into porous Sc2Si2O7 ceramics by precursor infiltration and pyrolysis (PIP) at 1400?°C in Ar. SiC NWs are in-situ formed in the pore channels via a vapor-liquid-solid (VLS) mechanism, the relative complex permittivity increases notably with the content of absorber (C-rich SiC NWs), which tune the microstructure and dielectric property of C-rich SiC NWs/Sc2Si2O7 ceramics. Meanwhile, the minimum reflection coefficient (RC) of C-rich SiC NWs/Sc2Si2O7 ceramic decreases from ?9.5?dB to ??35.5?dB at 11?GHz with a thickness of 2.75?mm, and the effective absorption bandwidth (EAB) covers the whole X band (8.2–12.4?GHz) when the content of absorber is 24.5?wt%. The results indicate that Sc2Si2O7 ceramics decorated with SiC NWs and nanosized carbon have a superior microwave-absorbing ability, which can be contributed to the Debye relaxation, interfacial polarization and conductivity loss enhanced by in-situ formed SiC NWs and nanosized carbon phases. The C-rich SiC NWs /Sc2Si2O7 ceramics can be a promising microwave absorbing materials within a broad bandwidth. 相似文献
18.
Shangwu Fan Yifan Ning Xu Ma Chuan Yang Liuyang He Juanli Deng Laifei Cheng Litong Zhang 《Ceramics International》2018,44(13):15200-15207
FeSi2 modified C/C-SiC composites (C/C-SiC-FeSi2) are fabricated by chemical vapor infiltration (CVI) combined with reactive melt infiltration (RMI) with FeSi75 alloy. The effects of high-temperature annealing (1600?°C, 1650?°C, 1700?°C) on the microstructure and performance of C/C-SiC-FeSi2 are investigated. With the elevation of annealing temperature, the porosity of the composites and the content of SiC increase due to the evaporation of liquid Si and the further reaction of Si and C. The mechanical performance gradually decreases due to the catalytic graphitization of the carbon fiber, the high porosity and the thermal residual stress (TRS) caused by thermal mismatch of different phases. The coefficient of thermal expansion and thermal diffusivity slightly decrease with increasing annealing temperature for the increase of porosity. However, the friction performance of the heat treated materials at high braking speed are greatly improved attributing to the increase of SiC content and the capturing and storage function of pores on hard particles. 相似文献
19.
Dongxu Yao Huanbei Chen Kai-hui Zuo Yongfeng Xia Jinwei Yin Hanqin Liang Yu-Ping Zeng 《Ceramics International》2018,44(11):11966-11971
The high temperature strength and fracture behavior of porous Si3N4 ceramics prepared via reaction bonded Si3N4 (RBSN) and sintered reaction bonded Si3N4 (SRBSN) were investigated at 800–1400?°C. The weight gain after oxidation for 15?min and the microstructure of the edge and center of the fracture surface clearly show that the internal oxidation of porous SRBSN is unavoidable with porosity of ~ 50% and mean pore size of 700?nm. The oxidation of Si3N4 and intergranular Y2Si3O3N4 phase may responsible for the high temperature strength degradation of SRBSN. Porous Si3N4 ceramics prepared with addition of 1?wt% C showed low strength degradation at temperature >?1200?°C. 相似文献
20.
Bingying Xie Li Ma Dezhi Gao Xiao Lin Yu Liu Yujun Zhang Hongyu Gong 《Ceramics International》2018,44(8):8795-8799
ZrB2 powders were successfully prepared via carbothermal reduction of ZrO2 with H3BO3 and carbon black under flowing argon. By introducing SiC species into reaction mixtures, the effects of SiC addition on phase composition and morphology of ZrB2 powders thermally treated at different temperatures were investigated. The resultant samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS). The highly pure ZrB2 with the mean size of 5?µm could be obtained at 1600?°C for 90?min and the grains presented columnar shapes. After addition of SiC, ZrB2 revealed relatively better crystallinity and finer particle size. Regular columnar ZrB2 grains ranging from 1 to 2?µm were seen existing after reaction at 1500?°C for 90?min. 相似文献