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51.
为了探究等离子喷涂制备ZrB_2-SiC涂层组织结构疏松、致密性差的原因,采用去离子水对经过射流场加热的粉体进行收集,对比前后粉体的组织结构特征以及物相变化。设计单颗粒沉积试验探究粉体的熔化状态以及变形颗粒的形貌特征,并与等离子喷涂制备涂层进行对应分析。结果表明,由于"涡流效应"使得经过等离子射流场的ZrB_2-SiC粉体与卷入的氧气发生反应,粉体出现轻微氧化现象。经过等离子射流场后,ZrB_2-SiC粉体呈现3种形貌特征:表面光滑型、表面多孔型、表面团聚型。其原因与等离子射流温度场非均匀性以及粉体的飞行路径有关。变形颗粒呈现与之相对应的3种形貌特征:熔化充分颗粒、团聚堆积颗粒、以及介于两者间的半熔融半疏松颗粒。共晶组织包裹的ZrB_2颗粒容易在涂层中形成致密区,而团聚堆积的ZrB_2和SiC颗粒是涂层形成疏松区的主要原因。 相似文献
52.
Jin-Hao Yuan Wei-Ming Guo Yang Liu Shi-Kuan Sun Xiao-Ming Duan De-Chang Jia Hua-Tay Lin 《Journal of the American Ceramic Society》2022,105(3):1629-1634
The influences of different contents ranging 0–15 wt% of high-entropy boride (HEB) (Hf0.2Mo0.2Ta0.2Nb0.2Ti0.2)B2 on the mechanical properties of SiC-based ceramics using Al2O3-Y2O3 sintering additives sintered by spark plasma sintering process were investigated in this study. The results showed that the introduction of 5 and 10 wt% (Hf0.2Mo0.2Ta0.2Nb0.2Ti0.2)B2 could facilitate the densification and the grain growth of SiC-based ceramics via the mechanism of liquid phase sintering. However, the grain growth of SiC-based ceramics was inhibited by the grain boundary pinning effect with the addition of 15 wt% (Hf0.2Mo0.2Ta0.2Nb0.2Ti0.2)B2. The SiC-based ceramics with 15 wt% (Hf0.2Mo0.2Ta0.2Nb0.2Ti0.2)B2 showed the enhanced hardness (21.9±0.7 GPa) and high toughness (4.88±0.88 MPa·m1/2) as compared with high-entropy phase-free SiC-based ceramics, which exhibited a hardness of 16.6 GPa and toughness of 3.10 MPa·m1/2. The enhancement in mechanical properties was attributed to the addition of higher hardness of HEB phase, crack deflection toughening mechanism, and presence of residual stress due to the mismatch of coefficient of thermal expansion. 相似文献
53.
Fabrication of Low-Porosity Indium Tin Oxide Ceramics in Air from Hydrothermally Prepared Powder 总被引:1,自引:0,他引:1
Chandana P. Udawatte Kazumichi Yanagisawa 《Journal of the American Ceramic Society》2001,84(1):251-253
Compositionally homogeneous indium tin oxide (ITO) ceramics with low porosity were obtained successfully by sintering hydrothermally prepared powders. The fabrication technique began with the preparation of microcrystalline, homogeneously tin-doped (5 wt%) indium oxyhydroxide powder, under hydrothermal conditions. Low-temperature (∼500°C) calcination of the hydrothermally derived powder led to the formation of a substitutional-vacancy-type solid solution of In2 Sn1− x O5− y , and further heating of this phase at temperatures of >1000°C resulted in the formation of the tin-doped indium oxide phase, which had the C -type rare-earth-oxide structure. The sintering of uniformly packed, calcined powder compacts at 1450°C for 3 h in air resulted in low-porosity (∼0.7%) ITO ceramics. 相似文献
54.
Effects of particle size and dispersion methods of In2O3‐SnO2 mixed powders on the sintering properties of indium tin oxide ceramics 下载免费PDF全文
Fangsheng Mei Tiechui Yuan Ruidi Li Libo Zhou Kai Qin 《International Journal of Applied Ceramic Technology》2018,15(1):89-100
Three group samples were used to investigate the effects of particle size and dispersion methods of In2O3‐SnO2 mixed powders on the sintering properties of ITO ceramics by BET, SEM, XRD, and EPMA, etc. High‐density (99.8% of TD) ITO ceramics, with dimensions of 350 × 250 × 8 mm3 for the industrial application, were obtained by the mixed powders of In2O3 calcined at 1000°C and SnO2 with BET 6.0 ± 0.5 m2/g and collocation use of ball mill for 300 minutes, stirred mill for 60 minutes, and sand mill for 3 minutes. The results indicate that: (i) the larger the SnO2/In2O3 particle size ratio, the higher the density of ITO ceramics, (ii) the dispersion of mechanical ball‐mill methods for nanosized In2O3 and SnO2 powders is beneficial to the densification and structural homogeneity, and (iii) the smaller the relative grain size, the more uniform the distribution of grain size. 相似文献
55.
56.
Sintering of the NiFe2O4-10NiO/xNi Cermet 总被引:1,自引:0,他引:1
The sintering behavior of NiFe2 O4-10NiO/xNi cermet which was used as the most prospective inert anode materials for aluminum electrolysis was studied by examining the effects of raw powder particle size, sintering temperature, and the contents of Ni. The results show that fine particle size enables the powder to have high driving force for sintering. High temperature is beneficial to densification, but the ultra-high temperature does harm to the improvement of the density. The samples of NiFe2O4-10NiO/SNi has the highest relative density of 97.28 % when it is sintered at 1 350 ℃, but it decreases to 95.23 % when sintered at 1 400 ℃. Low addition of Ni has a great help to the sintering of NiFe2 O4-10NiO matrix. When the samples are sintered at 1 350 ℃ and the mass fraction of Ni is 5%, the highest relative density is gained, but the density decreases with the further increase of Ni contents. The low density of the sintered samples of NiFe2 O4-10NiO/17Ni is attributed to the high volume fraction of pores. 相似文献
57.
通过脱水处理制度的研究,确定了合适的升温速度范围和明显发生与不发生封孔致密化的边界温度。利用电子衍射技术,研究了α—FeOOH的微晶和颗村之间的取向关系,并对孔洞成行排列进行了解释。 相似文献
58.
Yanping Zhou Hanrui Zhuang Shulin Wen 《Journal of Materials Synthesis and Processing》1999,7(1):35-39
On the basis of phase relationships in the Ca–Si–Al–O–N system, a Ca––sialon ceramic was synthesized using the hot-pressing technique. The reaction sequences and densifications of the Ca––sialon vs. firing temperatures have been characterized in detail. The present experiments reveal a reaction sequence as follows: at 1250°C the reactant mixture started to soften, at 1300°C a gehlenite phase was produced, at 1500°C the gehlenite phase was resolved into a liquid phase and a Ca––sialon started to form, and at 1600°C the formation of Ca––sialon was complete. The product was stable and almost entirely single phase Ca––sialon. Accompanying to the above sequences, densification also proceeded via a liquid-phase sintering, particle rearrangement, solution–reprecipitation, and grain growth process. In the final microstructure elongated grains of Ca––sialon were obtained, improving the fracture toughness of this Ca––sialon ceramic. 相似文献
59.
60.
By synthesizing reactive powders via a self-sustaining combustion synthesis, the glycine-nitrate process, the gadolinium-doped celia (GDC) with the chemical formula Ce0.8Gd0.2O1.9 was prepared. The resultant powders were dispersed with the terpineol as the dispersant through different methods such as ball milling and high-shear dispersing. Coagulation factor (CF) was used to mark the degree of agglomeration on the nano-scale GDC in this work. The effect of agglomeration on the densification behavior at different sintering temperatures was investigated. The studies indicated that agglomeration retarded the densification at the sintering stage. The powders with better dispersion exhibited a higher sintered density at the same temperature. After effective dispersion treatment, GDC could be fully densified at the sintering temperature of 1300 ℃. The densification temperature was significantly lower than those reported previously. The high sintering kinetics of the ceramics was obtained based on the agglomeration control. 相似文献