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排序方式: 共有3213条查询结果,搜索用时 15 毫秒
101.
《Ceramics International》2016,42(12):13601-13604
The crystallization and microstructure formation of glass with a Y2Si2O7-mullite eutectic composition were examined. A crystallization of Y2Si2O7 and the mullite phase due to phase separation occurred at 1174 °C, and a well-developed Y2Si2O7 facet crystal was formed. This sample was melted down and solidified via heat treatment at 1250 °C and 1300 °C, temperatures below the melting point of a Y2Si2O7-mullite eutectic. As a result of this solidification, a directional eutectic microstructure was formed. 相似文献
102.
《CIRP Annals》2019,68(1):349-352
This paper reports on a novel proprietary profiled rotary dresser which, in contrast with conventional tools, enables a controlled arrangement of geometrically defined abrasives over complex profiles. Output forces and abrasives’ wear were investigated during dressing and grinding tests. This showed a significant reduction in radial dressing forces (˜37%) and volumetric loss of material per grit (˜21%) when compared with conventional tools, together with low grinding forces and workpiece surface roughness variability for different wear conditions. The novel dresser proves the ability to obtain uniform wear rates along complex profiles, while allowing abrasive segment replacement to restore the dressing conditions. 相似文献
103.
104.
使用Levenberg-Marquardt训练函数的神经网络算法在复合材料板上进行声发射定位,采用声波到达时间作为输入向量,训练得到了到达各个传感器的声波触发时间与板上坐标的良好的映射关系。考虑到波形衰减,用传统的固定门槛提取的到达时间容易与实际情况偏差较大,讨论了一种相对准确的适合工程使用的到达时间提取方法。 相似文献
105.
对三维数字样机的技术现状进行了总结,归纳了传统二维总装图样的主要内容,分析以三维数字化总装出图代替二维总装图样的优势,提出三维数字化总装出图取代传统二维总装图样的技术方法,并对三维数字化总装出图的主要组成部分及表达形式进行阐述. 相似文献
106.
《Journal of the European Ceramic Society》2022,42(8):3542-3549
In this study, Ca/Tb co-doped HfO2 coatings were prepared by atmosphere plasma spraying. The chemical composition, morphology and infrared property of the coatings were characterized. The coatings possessed a layer-stacked morphology. When the Ca/Tb doping atomic ratio was 1:1, the phase of the coatings gradually changed from monoclinic to cubic with increasing the doping mass. The CTH2 coating had the highest emissivity which was 0.820 in 0.75–6.5 µm and 0.902 in 6.5–15 µm respectively. The enhancement in short band was mainly due to the introduction of Ca2+ and Tb3+ ions that generated oxygen vacancies in the lattice forming impurity levels within the forbidden band, moreover, the transfer of Tb3+ to Tb4+ increased the concentration of free electrons, which promoted the absorption of free carriers. The increase in long band attributed to the lattice distortion that reduced the lattice symmetry and strengthened the absorption of lattice polar vibration. 相似文献
107.
《Journal of the European Ceramic Society》2022,42(7):3127-3134
Diamond content is a key factor affecting diamond/SiC composite performance, especially thermal and mechanical properties, but the composite with high diamond content manufacturing is still challenging issues. Hot mold pressing combined with liquid silicon infiltration to make diamond/SiC composites with high diamond content and relative density has been proposed in this paper. In addition, the effect of diamond particle size on the maximization of diamond content as well as properties of the composites were evaluated. The experiment shows that the content of diamond in the composites increases with the increase of the diamond particle size. When the particle size of diamond is 400 µm, the volume fraction of diamond reaches 59.08%. The highest thermal conductivity (ddia= 300 µm) and highest bending strength (ddia= 50 µm) are 616.77 W/m K (It is the maximum TC of diamond/SiC prepared by pressureless infiltration at present) and 380 MPa, respectively. This work provides a novel and efficient preparation method for further improving the thermal conductivity of diamond/SiC composites. 相似文献
108.
《Journal of the European Ceramic Society》2022,42(5):2496-2504
A glass hollow fiber membrane coated with TiO2 was successfully synthesized by dip-coating and calcination. In addition, the effects of the calcination temperature, number of coating layers, and treatment method on the photocatalytic removal of methylene blue from wastewater by the membrane were investigated. The results showed that the TiO2-coated membrane calcined at 550 °C was uniform. It showed good photocatalytic and anti-fouling properties. As compared to the basement membrane, the TiO2-coated membrane showed significantly improved photocatalytic removal of methylene blue. It showed a methylene blue removal degree as high as 97.2% and could be recycled multiple times by a simple treatment. The methylene blue removal degree of the membrane remained 92.3-93.6% after five recycling operations. Therefore, the membrane prepared via the simple method proposed in this study could be used as an efficient photocatalyst to remove methylene blue from wastewater. 相似文献
109.
采用极限负荷准则,在考虑造粒喷头极限造粒能力的情况下,避开了尿素造粒喷头内复杂的流体力学问题的计算工作,给出了常压式旋转式尿素造粒喷头的参数确定方法。针对典型的年产400 kt尿素装置造粒喷头的设计过程及使用情况进行了计算,比较了斜孔喷头和直孔喷头在造粒塔内的不同喷洒效果,分析了众多文献中报道的塔内驼峰产生的原因和改进方向。在理论计算的基础上,讨论了带压式喷头和常压式喷头的工作原理和影响因素及各自在实际生产中的优缺点。 相似文献
110.
《Journal of the European Ceramic Society》2014,34(14):3319-3328
Silicon nitride materials containing 1–5 wt% of hexagonal boron nitride (micro-sized or nano-sized) were prepared by hot-isostatic pressing at 1700 °C for 3 h. Effect of hBN content on microstructure, mechanical and tribological properties has been investigated. As expected, the increase of hBN content resulted in a sharp decrease of hardness, elastic modulus and bending strength of Si3N4/BN composites. In addition, the fracture toughness of Si3N4/micro BN composites was enhanced comparing to monolithic Si3N4 because of toughening mechanisms in the form of crack deflection, crack branching and pullout of large BN platelets. The friction coefficient was not influenced by BN addition to Si3N4/BN ceramics. An improvement of wear resistance (one order of magnitude) was observed when the micro hBN powder was added to Si3N4 matrix. Mechanical wear (micro-failure) and humidity-driven tribochemical reaction were found as main wear mechanisms in all studied materials. 相似文献