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排序方式: 共有924条查询结果,搜索用时 6 毫秒
1.
Zeyu Zhao Jun Gao Yuqing Meng Kyle S. Brinkman Jianhua Tong 《Ceramics International》2021,47(8):11313-11319
The state-of-the-art protonic ceramic conductor BaZr0.8Y0.2O3-δ (BZY20) requires an extremely high sintering temperature (≥1700 °C) to achieve the desired relative density and microstructure necessary to function as a proton conducting electrolyte. In this work, we developed a cold sintering pretreatment assisted moderate-temperature sintering method for the fabrication of high-quality pure BZY20 pellets. BZY20 pellets with high relative density of ~94% were fabricated with a final sintering temperature of 1500 °C (200 °C lower than the traditional sintering temperature). A comparison with BZY20 control samples indicated that the proper amount of BaCO3 introduced on the BZY20 particle surface and the high green density achieved by cold sintering pretreatment were the main drivers for lowering the sintering temperature. The electrical conductivity measurement by electrochemical impedance spectroscopy showed that the as-prepared BZY20 pellets have a proton conductivity comparable to the state-of-the-art values. The cold sintering pretreatment outlined in this work has the potential to lower the sintering temperatures for similar types of protonic ceramic materials under consideration for a wide range of energy conversion and storage applications. 相似文献
2.
Bo Feng Yue Zhang Bingyang Li Shujuan Hu 《Journal of the American Ceramic Society》2019,102(2):855-866
Polymer-derived SiBCN, with superior thermal stability and amorphous activity, was introduced into ZrB2 powders. This sintering aid highly improved the sintering efficiency of ZrB2 ceramics at medium temperature (1000-1600°C), which showed a different service temperature range from that of traditional crystal additives. The microstructure and densification behavior of ZrB2–SiBCN samples were mainly studied. The polymer structural evolution including construction, rearrangement, and crystallization of the amorphous SiBCN network, made a large contribution to the densification of ZrB2 ceramics. The carbothermal reduction of pyrolysis carbon with oxide impurities could not only decrease the oxygen content, but also develop the activity of chemical bonds in SiBCN network. Diffusions and reactions at the interface also benefited the microstructure and consolidation of ZrB2–SiBCN ceramics. 相似文献
3.
Yihan Liang Siqi Xiang Tongye Li Chong Yu Ke Leng Xinfang Zhang 《Journal of the American Ceramic Society》2021,104(12):6131-6143
Implementing pressure-assisted flash sintering of ZnO powder without pretreatment by a new experimental configuration is presented. Rapid and energy-concentrated heating of electrode-sample-electrode area by induction heating allows preheating and flash sintering of loose-pack powder in the die with pressure assistance. Using an insulated die enables the current to flow through the sample during flash sintering. ZnO ceramics with a relative density of 95.1% can be achieved in less than 3 min. The whole process includes 104 s of preheating by a low-power induction heating device and 30 s of flash sintering assisted by a pressure of 26 MPa using the pulsed direct current (DC). The process characteristics of pressure-assisted flash sintering using the pulsed DC are discussed. The effect of pressure on densification and grain size is analyzed in detail, and some potential mechanisms are provided. 相似文献
4.
In this study, copper matrix composite materials with different ratios of carbon nanotubes were produced. The biggest problem faced in the production of carbon nanotube-reinforced composites is that carbon nanotubes do not distribute homogeneously in the matrix. A novel mixing technique was applied to overcome this problem. Hot pressing was used in sample production. A second high-pressure densification process was applied following the hot pressing process for enhancing the properties. The properties of both the hot-pressed specimens and the specimens to which a second high-pressure densification process was applied were characterized with the density measurements, microstructure examinations, and mechanical tests. The microstructure examinations showed that carbon nanotubes could be distributed homogeneously in the copper matrix with the mixing process applied. It was found out that the high-pressure densification process applied following the hot-pressing process increased the relative density and thus, all mechanical properties. 相似文献
5.
Jianwei Chen Huizhong Zhao Han Zhang Zhengkun Li Jiaqin Zhang 《Ceramics International》2018,44(6):6564-6572
Alkali resistance and thermo-mechanical properties of the transition zone of cement rotary kilns refractories are the key factors affecting their service life. Calcium alumino-titanate (CAT) containing bauxite-SiC composites were prepared using bauxite, SiC, CAT, Guang Xi white clay, α-alumina, and metallic silicon powder as starting materials and Al(H2PO4)3 as the binder. The effects of the CAT particle size on the phase composition, microstructure, thermo-mechanical properties, and alkali resistance of the CAT-containing bauxite-SiC composites during firing were investigated. The results reveal that the CAT particle size strongly affects the composites’ microstructure and sintering densification. With decreasing particle size, the particle-particle and particle-matrix interfacial bonding deteriorates gradually. When CAT particles are added, the specimens show higher strength, refractoriness under load, and residual rupture strength than the specimens with fine CAT powders. Specimens with fine CAT powders show lower coefficient of thermal expansion compared to the specimens with CAT aggregates. The alkali attack test confirms that the bauxite-SiC composite refractories with CAT aggregates show better alkali resistance than those with CAT fine powder. According to the alkali mechanism, 1) K vapors penetrate the specimen through the open and connected pores and cracks, 2) K vapors react with anorthite and corundum to form kalsilite accompanied by the formation of a liquid phase and new cracks. 相似文献
6.
Sandrine Gomes Elodie Petit Lawrence Frezet Jean-Marie Nedelec Ameni Gharzouni Sylvie Rossignol Guillaume Renaudin 《Journal of the American Ceramic Society》2020,103(10):5813-5824
The thermal behavior of a model MK-based K-geopolymer was investigated between room temperature and 1400°C in order to evaluate its potentiality for high-temperature applications. The purpose of our study was to monitor the behavior of a geopolymer during a temperature rise in order to better understand its variations with respect to temperature. The works from the present paper focus only changes in the porous network; it follows a first part devoted to variations in the mineral matrix. The results obtained here show that the geopolymer material preserves its porous integrity up to 800°C, while maintaining the reversibility of water exchanges corresponding to about 25 weight percent. Together with the results of part 1, the findings of this study allow us to affirm that geopolymer materials are only very little affected by temperatures up to 800°C, or even 900°C (keeping its mesoporous amorphous structure). 相似文献
7.
Saeed Ur Rehman Ahmad Shaur Hye-Sung Kim Dong Woo Joh Rak-Hyun Song Tak-Hyoung Lim Jong-Eun Hong Seok-Joo Park Seung-Bok Lee 《International Journal of Applied Ceramic Technology》2021,18(2):511-524
A dense Ce0.9Gd0.1O2−d (GDC) interlayer is an essential component of the SOFCs to inhibit interfacial elemental diffusion between zirconia-based electrolytes (eg YSZ) and cathodes. However, the characteristic high sintering temperature of GDC (>1400°C) makes it challenging to fabricate an effective highly dense interlayer owing to the formation of more resistive (Zr,Ce)O2 interfacial solid solutions with YSZ at those temperatures. To fabricate a useful GDC interlayer, we studied the influence of transition metal (TM) (Co, Cu, Fe, Mn, & Zn) doping on the sintering and electrochemical properties of GDC. Dilatometry data showed dramatic drops in the necking and final sintering temperatures for the TM-doped GDCs, improving the densification of the GDC in the order of Fe > Co > Mn > Cu > Zn. However, the electrochemical impedance data showed that among various transition metal dopants, Mn doping resulted in the best electrochemical properties. Anode supported SOFCs with Mn-doped, nano, and commercial-micron GDC interlayers were compared with regard to their performance and stability levels. Although all of the SOFCs showed stable performance, the SOFC with the Mn-doped GDC interlayer showed the highest power density of 1.14 W cm−2 at 750°C. Hence, Mn-doped GDC is suggested for application as an effective diffusion barrier layer in SOFCs. 相似文献
8.
Yong Hou Yu Wang Guo-Hua Zhang Kuo-Chih Chou 《Journal of the European Ceramic Society》2021,41(10):5201-5213
Fully dense and magnetically controllable glass ceramics was successfully synthesized by method of hot pressing using CaO-Al2O3-SiO2-Na2O glass powder and Fe3O4 powder as raw materials. The influences of sintering temperature and time, content and particle size of Fe3O4, as well as particle size of glass powder on the densification and magnetic properties of samples were investigated. It was found that the saturation magnetization gradually increased with increasing magnetite content. In addition, the samples containing smaller size magnetite particles had a higher coercivity. However, for samples using smaller size glass powder, magnetite particles could partially dissolve into the glass matrix, which led to the decrease of saturation magnetization and the increase of coercivity. It was also concluded that the precipitation of crystalline phase from smaller size glass powder caused the decrease of degree of densification, and after decreasing the sintering temperature, the degree of densification of product was enhanced. 相似文献
9.
为了解决软土地基上的构筑物沉降过大、承载力不满足等问题 ,很多学者依据Biot固结理论编制了大量的有限元程序。要在基本相同的计算量的前题下获得足够的精度 ,需要对有限元网格进行局部加密处理。作者提出的加密方法合理解决了接触单元和多级加载问题 ,并使用C ++Builder开发工具编制了加密程序 ,最后给出一个工程实例验证了方法的可行性。 相似文献
10.
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