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排序方式: 共有226条查询结果,搜索用时 27 毫秒
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《Journal of the European Ceramic Society》2022,42(4):1804-1814
Graphite–SiC micro-composites have been prepared in–house by carbothermal reduction process. Controlling the process parameters including the weight ratio of SiO2 to graphite as well as carbothermal reduction temperature during the micro-composite preparation favors the homogeneous formation of SiC with preferred morphologies like ribbons and whiskers/fibers. The micro-composite modified low carbon MgO-C refractories have exhibited significantly improved bulk properties over the standard composition. To understand the beneficial role of SiC reinforcement on hot strength performance under air oxidizing conditions, we propose a scaling parameter known as strength factor (fs) based on the ratio of hot strength (HMOR) to cold strength (CCS). Correlating the strength factor data (fs) with oxidative damage provides new insights into the reinforcing effects of distinct SiC morphologies in this new class of micro-composite fortified refractory systems over the standard compositions. 相似文献
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Zu Guoqing Lu Yukuan Yan Yi Zhang Xiaoming Zhao Jingwei Du Wei Ran Xu Jiang Zhengyi 《Metals and Materials International》2020,26(2):248-259
Metals and Materials International - The flow behaviour and microstructure characteristics of a ferritic stainless steel were investigated using plain strain compression test on a Gleeble 3500... 相似文献
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《International Journal of Hydrogen Energy》2020,45(53):28792-28799
The most ideal substitute for Pt/C to catalyze the oxygen reduction reaction (ORR) is the transition metal and nitrogen co-doped carbon-based material (TM-N-C). However, large particles with low catalytic activity are formed easily for the transition metals during high-temperature carbonization. Herein, PAN nanofibers uniformly distributed with FeCl3 were coated with SiO2 and then carbonized to obtain Fe–N–Si tri-doped carbon nanofibers catalyst (Fe–N–Si-CNFs). The SiO2 can further anchor the Fe atoms, thus preventing agglomeration during the carbonization process. Meanwhile, Si atoms have been doped in CNFs during this process, which is conducive to the further improvement of catalytic performance. The Fe–N–Si-CNFs catalyst has a 3D network structure and a large specific surface area (809.3 m2 g−1), which contributes to catalyzing the ORR. In alkaline media, Fe–N–Si-CNFs exhibits superior catalytic performance (E1/2 = 0.86 V vs. RHE) and higher stability (9.6% activity attenuation after 20000s) than Pt/C catalyst (20 wt%). 相似文献
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In this work, a one-step film formation method is demonstrated to obtain the patterned surface of an acrylate photocuring coating using nano-silica particles treated with a perfluoroalkoxysilane ((heptadecafluoro-1,1,2,2-tetra hydrodecyl) triethoxysilane) as a nanoadditive. Nanosilica particles were treated with perfluoroalkoxysilane and used in a UV-curable matrix. The typical patterns on the surface of the UV-cured films are revealed in AFM images. The surface properties of the cured films were investigated by measuring water contact angle and surface energy. The degree of conversion of the samples was obtained by FTIR analysis and pendulum hardness was measured using a Konig hardness meter. Scratch resistance of cured films was measured by standard scratch measuring pens. The characteristics obtained from AFM analysis showed that rough surface patterns in this system are controlled linearly by changes in the treated nano-particle concentration. The subtraction of surface energy of the cured film was clear and the water contact angle showed a 60% increase with the addition of a fluorinated nano-particle concentration. Surface hardness decreased and scratch resistance increased as the concentration of treated nanoparticles increased, while the final degree of conversion of the film remained unchanged. 相似文献
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《Ceramics International》2020,46(4):4256-4264
The behavior and mechanism of in-situ synthesis of the auxiliary electrode for sulfur sensor were investigated in this work, aiming for better application of calcium aluminate system in synthesizing the auxiliary electrode used for sulfur sensor. The in-situ reaction experiment was developed. In addition, the thermodynamic and kinetic calculations were adopted to further study the in-situ reaction possibility and the reaction rate. The results indicated that the value of lg(a[S]/a[O]) should be greater than a particular value to ensure the occurrence of the in-situ reaction. After immersion into the molten iron, the CaS phase was synthesized in the calcium aluminate system. The relationship between the reaction rate and reaction time was exponential, and the initial reaction rate was affected by the CaO content incorporated in the calcium aluminate system and the sulfur content in the molten iron. The initial in-situ reaction rate greatly increased with the increase of the CaO content and sulfur content. For example, the initial reaction rate was as high as 14.87 s-1 when the calcium aluminate system containing 60 wt% of CaO and for a sulfur content of 0.077 wt% in the molten iron. Moreover, the reason that the sulfur sensor fabricated by the ZrO2(MgO) tube with the calcium aluminate coating with different components had the same response time when measuring the different sulfur contents in the molten iron was further explained. 相似文献
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《中国稀土学报(英文版)》2020,38(11):1190-1200
Herein, a new mechanism involving Lewis acid-oxygen vacancy interfacial synergistic catalysis for aniline N,N-diethylation with ethanol was proposed, and the SO42−/Ce0.84Zr0.16O2–WO3–ZrO2 catalyst (SCWZ) with both Lewis acid sites and oxygen vacancies was synthesized by the hydrothermal method, which shows better catalytic activity than the reported solid acidic catalysts. Besides, the SO42−/ZrO2 (SZ) and SO42−/WO3–ZrO2 (SWZ) catalysts were also prepared and compared with SCWZ to investigate the synergistic effect of each component. The SO42− and WO3 mainly generate Lewis acid by bonding with ZrO2, which is beneficial for the fracture of the N–H bond in aniline. The Ce0.84Zr0.16O2 solid solution mainly plays a vital role in generating the oxygen vacancies as the interface active species, which can participate in stripping –OH from ethanol, then the carbocation will also be released, which only needs 1.3805 kcal/mol energy, calculated by density functional theory (DFT), to be input. In comparison, the traditional reaction mechanism needs the Brønsted acidic sites to promote the protonation of ethanol, then dehydration and subsequent formation of carbocation followed, and 108.6846 kcal/mol energy needs to be input, which is far higher than that of the new mechanism. The apparent activation energy (Ea) over SCWZ was measured by experiment to be 34.09 kJ/mol, which is much lower than that of SWZ (47.10 kJ/mol) and SZ (54.37 kJ/mol), illustrating comparatively preferable kinetics for SCWZ than that of SWZ and SZ. Besides, the conversion of aniline and selectivity to N,N-diethylaniline over SCWZ reach almost 100% and 73%, respectively. The SCWZ can be renewed for 4 times without rapid deactivation, and the longevity of SCWZ is longer than that of SWZ and SZ, as the loaded SO42− and tetragonal ZrO2 are stabilized by Ce0.84Zr0.16O2 and WO3, respectively. 相似文献
9.
《Journal of the European Ceramic Society》2022,42(2):672-681
Two types of MgO-C refractories with tight particle grading and non-tight particle grading were prepared according to Andreasen's continuous packing theory. Fracture behaviors were investigated using wedge splitting tests combined with digital image correlation method and acoustic emission techniques. The results indicated that MgO-C refractory with non-tight particle grading treated at 1400 ℃ had more in situ phases (e.g., AlN and MgAl2O4) and exhibited less brittleness than specimens with tight particle grading even though they had similar nominal tensile strengths. In contrast, specimens with non-tight particle grading had greater horizontal strain under various loading stages, reflecting their better ability to resist rupture deformation. In addition, more microcracks were initiated earlier in the pre-peak region, and more energy was consumed. The decrease in coarse particles and corresponding increase in fine powder content increased the interface between particles, benefiting for reducing the local stress concentration and improving the thermal shock resistance of refractories. 相似文献
10.
《Journal of the European Ceramic Society》2022,42(12):4866-4880
In order to solve the challenge of recyclability of tantalum substrates in high temperature oxidation environments, a novel MoSi2-WSi2-HfSi2-TiSi2 composite ceramic coating containing an Nb interlayer was prepared on the surface of tantalum substrate by a three-step method. The mix ceramic silicide coating exhibited superior performance and effective protection for 10.2 h at 1800 °C, possibly due to the formation of an outer SiO2-HfO2-HfSiO4 composite oxide film with low oxygen permeability, moderate viscosity and thermal expansion coefficient, as well as good self-healing ability. Furthermore, the coating successfully passed 537 thermal cycles from room temperature to 1800 °C. The presence of Nb interlayer significantly mitigated the thermal mismatch between the ceramic coating and the tantalum substrate, and the bidirectional diffusion of Nb element during the high temperature oxidation and thermal shock process further reduced the tendency of the coating to crack. 相似文献