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991.
Hao Wu Yukun Ren Tianyi Jiang Juzheng Chen Wenlong Wu Yang Lu Hongyuan Jiang 《International Journal of Applied Ceramic Technology》2022,19(6):2979-2989
Lightweight hollow ceramic microfibers/microparticles hold promising prospects in numerous applications. To date, it remains a challenge to develop a fabrication strategy that well balances product quality and efficiency. In this article, an all-aqueous microfluidic method was proposed to prepare tubular polymeric fiber as the preceramic template. The relevant dimensional parameters could be promptly regulated via simple flow rate control. This approach could serve as a general technical route to preparing different kinds of ceramics by switching the types of nanoparticles. Here, silica nanoparticles were introduced and the ceramic microfiber could be got via calcination. Afterward, the tubular silica microfiber was employed to synthesize geopolymer composite by mold casting. The chemically formed interfacial bonding between the silica microfiber and geopolymer matrix was confirmed by elemental analysis. The addition of 10% volume fraction silica microfiber could not only increase the flexural modulus of geopolymer composite by 3.5 times but also effectively inhibited crack propagation under thermal circumstances. 相似文献
992.
引发剂是调节氯乙烯悬浮聚合反应速率,并影响聚合放热、聚合周期和聚合釜生产能力的重要助剂。引发剂对氯乙烯悬浮聚合动力学的影响主要与引发剂的活性、用量有关。引发剂用量、加入方式和前后期使用比例等对树脂质量也有明显的影响。 相似文献
993.
Beiyue Ma Xinming Ren Zhi Gao Jialong Tian Zhouhua Jiang Wenyu Zan Jingkun Yu Fan Qian Yingnan Cao Gaofeng Fu 《International Journal of Applied Ceramic Technology》2022,19(3):1265-1273
Composite additives are an efficient means to improve the high-temperature stability and slag resistance of low-carbon MgO-C refractories. In this work, Al2O3-SiC powder was firstly synthesized from electroceramics waste by carbon embedded method at 1500°C, 1550°C, and 1600°C for 4 h, and then the as-synthesized Al2O3-SiC powder was used as an additive to low-carbon MgO-C refractories. The effects of its addition amounts of 0, 2.5 wt.%, 5.0 wt.%, and 7.5 wt.% on the properties of the refractories were investigated in detail. It was found that increasing the heat treatment temperature is beneficial to the phase conversion of mullite and quartz to alumina and silicon carbide in the electroceramics waste. Furthermore, the addition of Al2O3-SiC powder effectively improves the performance of low-carbon MgO-C samples, and the formation of spinel dense layer and high-viscosity isolation layer is the internal reason for the improvement of the oxidation resistance and slag resistance of low-carbon MgO-C samples. This work provides ideas for the reuse of electroceramics waste and presents an alternative strategy for the performance optimization of low-carbon MgO-C refractories. 相似文献
994.
Yuhan Ren Biao Zhang Junda Shao Jian Ye Qiang Liu Ye Gao Haoqian Zhang Zhaoxin Zhong Yang Wang Feng Ye 《International Journal of Applied Ceramic Technology》2022,19(5):2489-2499
Ceramics from porous Si3N4 and its derivatives SiAlON and Si2N2O were once considered the most promising high-temperature wave-transmitting materials. However, their large-scale application in the field of radomes is greatly restricted due to their poor oxidation resistance, high preparation costs, and expensive raw materials. Therefore, the development of low-cost porous oxide ceramics remains of significant interest to the field of high-temperature wave transmission. Surprisingly, mullite ceramics, which are representative of the Al2O3-SiO2-system of ceramics, are ultra-low-cost materials with the potential to replace ceramics from Si3N4 and its derivatives. In this paper, integrated porous Al2O3-SiO2-system ceramics were successfully prepared for load-bearing/wave-transmitting applications, using inexpensive calcined kaolin and alumina powder as the main raw materials. Calcined kaolin can provide seeds for the growth and development of mullite crystals in the ceramic system. High-strength and high-porosity ceramics were obtained with the mullite morphology controlled through the molar ratio of Al2O3 to SiO2 and the resulting content of mullite seeds. With increasing of mullite seed content, the length and radial width of mullite whiskers with “interlocking structure” gradually change from rod-shaped “long and thick” to needle-like “short and thin.” The prepared porous Al2O3-SiO2 ceramics have high flexural strength, fracture toughness, and good dielectric properties. 相似文献
995.
Ping Zhang Yi-Han Li Li Chen Mao-Jie Zhang Yang Ren Yan-Xu Chen Zhi Hu Qi Wang Wei Wang Liang-Yin Chu 《Frontiers of Chemical Science and Engineering》2022,16(6):939
This work reports on a simple microfluidic strategy to controllably fabricate uniform polymeric microparticles containing hierarchical porous structures integrated with highly accessible catalytic metal organic frameworks for efficient degradation of organic contaminants. Monodisperse (W1/O)/W2 emulsion droplets generated from microfluidics are used as templates for the microparticle synthesis. The emulsion droplets contain tiny water microdroplets from homogenization and water nanodroplets from diffusion-induced swollen micelles as the dual pore-forming templates, and Fe-based metal-organic framework nanorods as the nanocatalysts. The obtained microparticles possess interconnected hierarchical porous structures decorated with highly accessible Fe-based metal-organic framework nanorods for enhanced degradation of organic contaminants via a heterogeneous Fenton-like reaction. Such a degradation performance is highlighted by using these microparticles for efficient degradation of rhodamine B in hydrogen peroxide solution. This work provides a simple and general strategy to flexibly combine hierarchical porous structures and catalytic metal-organic frameworks to engineer advanced microparticles for water decontamination. 相似文献
996.
Yuemin Lin Yuanyuan Zhang Renfeng Nie Kai Zhou Yao Ma Mingjie Liu Dan Lu Zongbi Bao Qiwei Yang Yiwen Yang Qilong Ren Zhiguo Zhang 《Frontiers of Chemical Science and Engineering》2022,16(12):1782
Ultra-dispersed Ni nanoparticles (7.5 nm) on nitrogen-doped carbon nanoneedles (Ni@NCNs) were prepared by simple pyrolysis of Ni-based metal–organic-framework for selective hydrogenation of halogenated nitrobenzenes to corresponding anilines. Two different crystallization methods (stirring and static) were compared and the optimal pyrolysis temperature was explored. Ni@NCNs were systematically characterized by wide analytical techniques. In the hydrogenation of p-chloronitrobenzene, Ni@NCNs-600 (pyrolyzed at 600 °C) exhibited extraordinarily high performance with 77.9 h–1 catalytic productivity and > 99% p-chloroaniline selectivity at full p-chloronitrobenzene conversion under mild conditions (90 °C, 1.5 MPa H2), showing obvious superiority compared with reported Ni-based catalysts. Notably, the reaction smoothly proceeded at room temperature with full conversion and > 99% selectivity. Moreover, Ni@NCNs-600 afforded good tolerance to various nitroarenes substituted by sensitive groups (halogen, nitrile, keto, carboxylic, etc.), and could be easily recycled by magnetic separation and reused for 5 times without deactivation. The adsorption tests showed that the preferential adsorption of –NO2 on the catalyst can restrain the dehalogenation of p-chloronitrobenzene, thus achieving high p-chloroaniline selectivity. While the high activity can be attributed to high Ni dispersion, special morphology, and rich pore structure of the catalyst. 相似文献
997.
998.
Hongwan Jiang Lin He Zhongwei Ren Gang Zhan Zhongfei Zou 《The International Journal of Advanced Manufacturing Technology》2018,98(5-8):1069-1080
The loose layer can appear on the rake face of a turning tool under certain cutting conditions and have an important influence on the rake face wear. In this paper, wear morphology and wear mechanism of loose layer on the rake face of the original turning tool and the new cemented carbide micro groove turning tool developed independently during the cutting process are studied, by the combination of theoretical analysis and cutting test. And the relationships between the diffusion wear and the adhesive wear of the loose layer on the rake face of the new micro groove turning tool are further analyzed and revealed. The research results show that the loose layer on the rake face of two turning tools is caused by the diffusion wear, which is formed by the brittleness-weakening of tool material in the region resulting from elements diffusion. Meanwhile, the wear degree of the rake face of tools is aggravated by the mutual promotion of diffusion wear and adhesive wear. In the normal wear stage, the degree of looseness and brittleness of the rake face of the original turning tool is greater than the one of the micro groove turning tool. In the severe wear stage, cobalt elements in the rake face of the two turning tools are dissolved and diffused in varying degrees, which further aggravates the brittle-weakening of materials in the region. But the degree of loose brittleness of the rake face of the original turning tool is still greater than the one of the micro groove turning tool. It can be concluded that the micro groove on the rake face of the new turning tool can improve the rake face wear to a certain extent. 相似文献
999.
1000.