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排序方式: 共有1018条查询结果,搜索用时 218 毫秒
1.
《Journal of the European Ceramic Society》2022,42(15):7180-7186
In this work, drying of bodies prepared by gelcasting fine submicrometre-sized zirconia particles was studied and a drying process for defect-free bodies with large cross-sections was proposed. It was found that the cracking of large bodies could be prevented by reducing the monomer content and using appropriate non-volatile cosolvents. Glycerol and polyethylene glycols with different molecular weights were used as non-volatile cosolvents in aqueous ceramic suspensions. The complex effects of the individual cosolvents on the gelcasting process and, in particular, on the drying step were investigated and explained. The applicability of individual cosolvents for the gelcasting process were discussed and their optimal use was indicated. 相似文献
2.
Haitang Yang Zilong Lu Bixiong Bie Zeyu Fu Jianling Yue Xiaozhong Huang 《Ceramics International》2019,45(9):11395-11402
SiCf/PyC/SiC and SiCf/BN/SiC mini-composites comprising single tow SiC fibre-reinforced SiC with chemical vapor deposited PyC or BN interface layers are fabricated. The microstructure evolutions of the mini-composite samples as the oxidation temperature increases (oxidation at 1000, 1200, 1400, and 1600?°C in air for 2?h) are observed by scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction characterization methods. The damage evolution for each component of the as-fabricated SiCf/SiC composites (SiC fibre, PyC/BN interface, SiC matrix, and mesophase) is mapped as a three-dimensional (3D) image and quantified with X-ray computed tomography. The mechanical performance of the composites is investigated via tensile tests.The results reveal that tensile failure occurs after the delamination and fibre pull-out in the SiCf/PyC/SiC composites due to the volatilization of the PyC interface at high temperatures in the air environment. Meanwhile, the gaps between the fibres and matrix lead to rapid oxidation and crack propagation from the SiC matrix to SiC fibre, resulting in the failure of the SiCf/PyC/SiC composites as the oxidation temperature increases to 1600?°C. On the other hand, the oxidation products of B2O3 molten compounds (reacted from the BN interface) fill up the fracture, cracks, and voids in the SiC matrix, providing excellent strength retention at elevated oxidation temperatures. Moreover, under the protection of B2O3, the SiCf/BN/SiC mini-composites show a nearly intact microstructure of the SiC fibre, a low void growth rate from the matrix to fibre, and inhibition of new void formation and the SiO2 grain growth from room to high temperatures. This work provides guidance for predicting the service life of SiCf/PyC/SiC and SiCf/BN/SiC composite materials, and is fundamental for establishing multiscale damage models on a local scale. 相似文献
3.
《Ceramics International》2018,44(18):22473-22480
The compact green bodies, prepared via a novel solid-liquid mixing method of precursors, were successfully pyrolyzed to obtain the dense bulk SiAlCN ceramics at 1000 °C. It can be seen from their SEM that they have uniform and dense microstructure, indicating that this method can be used to prepare bulk ceramics. In order to verify that they can be used as sensor heads, their temperature-resistance characteristics and repeatability were tested. The results show that the conductive mechanism belongs to Arrhenius's Tailed-State and Extended-State in the temperature range of 500–650 °C and 650–930 °C, respectively. And it shows that SiAlCN ceramics can be used as the sensor heads for high-temperature sensors. 相似文献
4.
《Journal of the European Ceramic Society》2020,40(4):1111-1118
Highly textured TiB2 ceramics were prepared by slip casting an aqueous suspension in a magnetic field of 9 T, followed by sintering using Field Assisted Sintering Technology (FAST). Particle size refinement by ball milling improved both the degree of texturing and densification of the material (RD > 98 %). The sintered material exhibited a Lotgering orientation factor of 0.90, with the c-axis of TiB2 oriented parallel to the magnetic field and FAST pressing direction. The texturing effect induced by the uniaxial pressing was negligible. The textured TiB2 material exhibited a significant anisotropy in mechanical properties; the values of hardness and indentation elastic modulus measured along directions transverse to the c-axis of TiB2 were 37 % and 13 % higher than the ones measured along the c-axis direction. Moreover, the specific wear rate of a surface of textured TiB2 parallel to the field was one order of magnitude lower than a surface perpendicular to the field. 相似文献
5.
6.
《Journal of the European Ceramic Society》2005,25(8):1285-1291
The mechanical properties and thermal stability of the Al2O3/Er3Al5O12 (EAG) eutectic ceramics have been investigated at very high temperature. The emissive properties of this eutectic ceramics have also been measured and its possibilities of application to an emitter have been discussed. The present eutectic ceramic has excellent high-temperature strength characteristics, showing that tensile yielding stress is approximately 300 MPa at 1650 °C and superior thermal stability at 1700 °C in an air atmosphere. The present material shows strong selective emission bands at wavelength 1.5 μm due to Er3+ ion. The emission bands of this material are nearly coincident with the sensitive region of GaSb PV cell, therefore, the Al2O3/EAG eutectic ceramic can be regarded as one of the promising emitter materials in TPV systems. 相似文献
7.
《International Journal of Fatigue》2007,29(9-11):2040-2049
The fatigue-fretting damage parameter (FFDP) introduced by Ruiz is comprehensively discussed in this paper. Shortcomings and limitations of this criterion are presented resulting in a combined energetic-multiaxial enhancement (eFFDP). Specific frictional power was supposed to control the fretting damage and the critical plane approach is used to solve the multiaxial stress state in the fretting contact. The significance of the eFFDP is evaluated for the key–shaft–hub connection under combined torque and bend loading. Applying the analysis to recent fatigue tests, a comparison of stress and fretting parameters is made for different loading conditions including estimation of the fretting fatigue limit. 相似文献
8.
《Materials Letters》2007,61(14-15):3059-3063
In order to explore the tribological potential of the dual phase (DP) steel as a wear resistant material, the wear characteristics of the dual phase (DP) steel have been investigated with varying amounts of martensite from 43 to 81 vol pct, developed by varying holding time at the intercritical annealing temperature of 780 °C. Dry sliding wear tests have been conducted on DP steels using a pin-on-disk machine under different normal loads of 61.3, 68.5, 75.7 and 82.6 N and at a constant sliding speed of 1.20 m/s. At these loads, the mechanism of wear is mainly delamination, which has been confirmed by SEM micrographs of the subsurface and wear debris of the samples. Wear and friction properties have been found to be improved with increasing martensite volume fraction in dual phase steels. 相似文献
9.
《矿业科学技术学报(英文版)》2016,26(4):571-575
The content and the caking index of the heavy,the dense medium and the loose medium components of coal,obtained by extraction and stripping with CS_2/N-methyl-2-pyrrolidinone mixed solvent(1:1 by volume),were studied and correlated with the caking property of raw coals.Images of the three group components after heat treatment were analyzed.The results show that both caking index(G) and maximum thickness of plastic layer(Y) of coals have a good linear relationship with the content of the medium component;the dense medium and the loose medium components are the two key factors to determine the caking property of raw coals-they are the source materials of fluidity and swelling of coal,respectively;the heavy component without the swelling and fluidity was cohered by the other components;two new indexes,which can extend current understanding of the caking properties,were introduced. 相似文献
10.
《Synthetic Metals》2005,148(2):175-178
Data-storage and memory applications of conjugated polymers and organic semiconductors are generally probed by device current or dielectric properties to determine the storage and switching properties. In this article, we use photoluminescence as an alternate method of probing the states of the devices. We have fabricated such devices based on a polythiophene derivative, and recorded photoluminescence (PL) spectra during and after applying bias. The presence of localized charges on the backbone of the polymer has been found to modulate the PL intensity. Since the relaxation of the space charges is slow, we have shown that PL intensity can be used as a probe for memory applications to read the state of the device. PL as a probe for memory applications of polymeric materials offers an intrinsic advantage that the state can be read without affecting the device properties. 相似文献