检索结果-内蒙古大学图书馆

Investigation of the bulging mechanism of c/Sic coating through in situ optical observation and numerical simulation

引用

cERAMIcS INTERNATIONAL 2021年第14期47卷 20456-20466页

作者： Kong, Yi Zhang, Jinsong Yue, Mengkun Yue, Wen Qu, Zhe Wang, Xian Wei, Dong Gui, Yewei Tang, Yunlong Feng, Xue China Univ Geosci Sch Engn & Technol Beijing 100083 Peoples R China Tsinghua Univ Dept Engn Mech AML Beijing 100084 Peoples R China Tsinghua Univ Ctr Mech & Mat Beijing 100084 Peoples R China Inst Flexible Elect Technol THU Flexible Integrated Circuit Ctr Jiaxing 314006 Peoples R China China Aerodynam Res & Dev Ctr Sate Key Lab Aerodynam Mianyang 621000 Sichuan Peoples R China China Univ Geosci Beijing Zhengzhou Res Inst Zhengzhou 450001 Peoples R China

carbon fibre-reinforced silicon carbide composites (c/Sic) are a type of high-temperature structural ceramics that can be widely applied in aerospace, hypersonic aircraft, and military fields. However, the practical application of such materials in some complex high-temperature environments is still limited owing to drawbacks such as the bulging problem. In this study, the bulging of a c/Sic coating in a high-temperature wind tunnel is investigated. The surface data of specimens in the high-temperature arc wind tunnel were obtained using optical visualisation equipment, and the entire process of the formation of coating bulges, and their evolution and fusion is illustrated. Then, a fully coupled thermal fluid-solid simulation model is established, and the influence of defects on the internal heat transfer of materials is analysed. Further, the thermal fluid-solid coupling simulation technology is also used to analyse the bulging process of the coating to understand the mechanism of chemical reactions in defects between the coating and substrate. This work can serve as a guide for the screening and improvement of the material coating process.

关键词： c Sic coatings High temperature Bulging coupling simulation Defects

来源：评论

学校读者我要写书评

暂无评论

Superior hydrogen generation from sodium borohydride hydrolysis catalyzed by the bimetallic co-Ru/c nanocomposite

引用

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2021年第50期46卷 25376-25384页

作者： Huang, Wenkai Xu, Fuhua Liu, Xiang China Three Gorges Univ Engn Res Ctr Ecoenvironm Three Gorges Reservoir R Key Lab Inorgan Nonmetall Crystalline & Energy Co Coll Mat & Chem EngnMinist Educ Yichang 443002 Hubei Peoples R China

Sodium borohydride has been widely regarded as a promising hydrogen carrier owing to its greatly hydrogen storing capability (10.8 wt%), high weight density and excellent stability in alkaline solutions. Herein, we first design and synthesize a series of bimetallic M-Ru/c nanocomposites (including Fe-Ru/c, co-Ru/c, Ni-Ru/c and cu-Ru/c), via simply alloying of commercial Ru/c with nonprecious metal, for superior H2 evolution from the NaBH4 hydrolysis. The result exhibits that H2 generation is synergetically improved by alloying Ru/ c with co or Ni, while it is hindered by alloying Ru/c with Fe or cu. Indeed, co-Ru/c presents the highest efficient catalytic activity for H2 generation, with the TOF of 117.69 mol(H2)center dot molRu-1 center dot min-1, whereas Ru/c is only 57.08 mol(H2)center dot molRu-1 center dot min-1. In addition, the TOF of co-Ru/c reaches to 436.51 mol(H2)center dot molRu-1 center dot min-1 (96.7 L(H2)center dot gRu-1 center dot min-1) in the presence of NaOH. (c) 2021 Hydrogen Energy Publications LLc. Published by Elsevier Ltd. All rights reserved.

关键词： Sodium borohydride Hydrogen co-Ru c Bimetallic Hydrolysis

来源：评论

学校读者我要写书评

暂无评论

Preparation and characterization of hybrid Pd/c nanocomposites and their application in electrocatalytic activity

引用

FULLERENES NANOTUBES AND cARBON NANOSTRUcTURES 2021年第11期29卷 853-859页

作者： Wang, Hongxiang Jiangsu Vocat Coll Elect & Informat Sch Digital Equipment Huaian Peoples R China

An environment-friendly oxidation-reduction method was used to prepare Pd/c hybrid nanocomposites (Ncs) using carbon as host and Pd nanoparticles (NPs) as surface loading, and sodium citrate was used as a reducing agent. The structures and morphologies of the Pd/c hybrid Ncs were characterized by X-ray diffraction, transmission (high-resolution) electron microscopy (TEM, HRTEM), X-ray photoelectron spectroscopy and so on. The results demonstrated that the Pd NPs were deposited on the surface of the c sphere beads, and the Pd NPs were homogeneous and monodispersed. The results also indicated that the diameter of the Pd NPs was 3 +/- 0.5 nm and the Pd/c Ncs were 197 +/- 6.5 nm. In addition, the Pd/c Ncs showed improved electrocatalytic activity for formic acid oxidation in comparison with commercial Pd NPs through controlling the surface structures. So, the environment-friendly preparation method provided developmental direction to fabricate all kinds of metal/c hybrid Ncs architectures.

关键词： carbon spheres Pd c hybrid structure nanocomposite electrocatalytic activity

来源：评论

学校读者我要写书评

暂无评论

Oxidation behaviour of Sic ceramic coating for c/c composites prepared by pressure-less reactive sintering in wet oxygen: Experiment and first-principle simulation

引用

cERAMIcS INTERNATIONAL 2021年第11期47卷 15337-15348页

作者： Zhang, Pengfei Zhang, Yulei Gai, Wenhan chen, Guohui Northwestern Polytech Univ Shaanxi Prov Key Lab Fiber Reinforced Light Compo State Key Lab Solidificat Proc Xian 710072 Peoples R China

Sic ceramic coating, for prevention of c/c composites against oxidation, was prepared by pressure-less reactive sintering to investigate the oxidation behaviour in an oxidising environment containing water vapour at 1773 K. The experimental results demonstrated that the oxidation behaviour of porous Sic ceramics could be divided into two stages, following the parabolic model, which was attributed to the variation in the contact area involved in the oxidation reactions. During the entire oxidation process, water vapour could accelerate the oxidation of the Sic ceramics, according to the weight change. By first-principle calculations, the accelerated oxidation rate of the Sic ceramics was attributed to weakened Si?O and Al?O bonds in the formed glassy scale, which were caused by hydroxide radicals from the water. Atomic thermal motions at high temperature could lead to the breakage of the network structure, promoting the diffusion and solution of oxidising gases. When the as-prepared Sic ceramics were applied as anti-oxidative coatings for the c/c composites, the Sic ceramic coating and c/c matrix could be sealed and protected faster per unit time, because water vapour was beneficial to the formation of a glassy layer. The weight loss of the c/c matrix could be attributed to unsealed microcracks inside the Sic coating in the initial stage.

关键词： c c composites Sic ceramic coating Oxidation behaviour Wet oxygen First-principles Molecular dynamics

来源：评论

学校读者我要写书评

暂无评论

N-doped c/Si@DAMO composite material using PVP as the carbon source for lithium-ion batteries anode

引用

IONIcS 2021年第10期27卷 4185-4196页

作者： Liang, Junhua chen, Si Fan, Zhengqing Zheng, Songsheng Wang, Zhaolin Xiamen Univ Coll Energy Xiamen 361102 Peoples R China

Silicon (Si) material, with high specific capacity (4200 mAh/g) and low discharge voltage, is considered as one of the most ideal, promising, and alternative anode materials in next-generation lithium-ion battery (LIBs). In order to resolve the internal drawbacks of Si and reduce the process cost, the Si recycled from the kerf waste of photovoltaic industry was used as raw material. A silane-coupling agent 3-2 (2-sminoethylamino) propyltrimethoxysilane (DAMO) and a binder (PAA) was used to prepare Si@DAMO composite material with cross-linked net structure. Then, the polyvinyl pyrrolidone (PVP) containing N element was coated on the Si@DAMO. After carbonization, the c/Si@DAMO composite material with cross-linked net structure was obtained. The as-prepared c/Si@DAMO anode delivered an initial capacity of around 2841.6 mAh/g, and it remained a reversible capacity of 2066.7 mAh/g after 200 cycles at the current density of 0.1 c. At the rate testing from 0.1 to 1 c, the discharge capacities were 2593.39 mAh/g, 2362.95 mAh/g, 2082.08 mAh/g, 1882.44 mAh/g, 1704.57 mAh/g, and 1545.32 mAh/g, respectively. It retained 2084.88 mAh/g when back to 0.1 c charge rate after 60 cycles. Therefore, it suggests that the as-prepared c/Si@DAMO is a potential anode material for LIBs.

关键词： Lithium-ion batteries PVP c Si composite material cross-linked structure

来源：评论

学校读者我要写书评

暂无评论

Flexural strength and wear resistance of c/c-Sic brake materials improved by introducing Sic ceramics into carbon fiber bundles

引用

cERAMIcS INTERNATIONAL 2021年第17期47卷 24130-24138页

作者： Ma, Xu Sun, Haodong Kou, Sijie Fan, Shangwu Deng, Juanli Zhang, Litong cheng, Laifei Northwestern Polytech Univ Sci & Technol Thermostruct Composite Mat Lab Xian 710072 Shaanxi Peoples R China Changan Univ Sch Mat Sci & Engn Xian 710064 Shaanxi Peoples R China

In this work, we adopted PIP technology to introduce Sic ceramics into the carbon fiber bundles of c/c-Sic composites. The obtained c/c-Sic composites containing PIP-Sic exhibited improved flexural strength. Meanwhile, the strength difference was reduced in in-plane and vertical directions. Fracture morphology revealed that the introduction of Sic into the fiber bundles broadened available toughening mechanism of the prepared composites. The braking performance of the materials was tested on an MM-1000 dynamometer. After braking at different speeds, we analyzed wear rates, variations in friction coefficient, and the morphological evolution of the friction surface. The results indicated that the introduction of Sic into the fiber bundles enhanced the abrasive resistance of local c/c regions, which yielded a significant reduction of the wear rates.

关键词： Polymer infiltration and pyrolysis (PIP) Sic c c-Sic composites Flexural strength Friction and wear

来源：评论

学校读者我要写书评

暂无评论

Sulfur-based mixotrophic denitrification with the stoichiometric S⁰/N ratio and methanol supplementation: effect of the c/N ratio on the process

引用

JOURNAL OF ENVIRONMENTAL ScIENcE AND HEALTH PART A-TOXIc/HAZARDOUS SUBSTANcES & ENVIRONMENTAL ENGINEERING 2021年第13期56卷 1420-1427页

作者： Yanez, Diana Guerrero, Lorna Borja, Rafael Huilinir, cesar Univ Santiago Chile Dept Ingn Quim Ave Libertador Bernardo OHiggins 3363 Santiago Chile Univ Tecn Federico Santa Maria Dept Ingn Quim & Ambiental Valparaiso Chile Inst Grasa CSIC Campus Univ Pablo de Olavide Seville Spain

The impact of the organic carbon to nitrate ratio (c/N ratio) on mixotrophic denitrification rate has been scarcely studied. Thus, this work aims to investigate the effect of the c/N ratio on the mixotrophic denitrification when methanol is used as a source of organic matter and elemental sulfur as an electron donor for autotrophic denitrification. For this, two initial concentrations of NO3--N (50 and 25 mg/L) at a stoichiometric ratio of S-0/N, and four initial c/N ratios (0, 0.6, 1.2, and 1.9 mg cH3OH/mg NO3- -N) were used at 25 (+/- 2) degrees c. The results showed that when using a c/N ratio of 0.6, the highest total nitrogen removal was obtained and the accumulation of nitrites was reduced, compared to an autotrophic system. The most significant contribution to nitrate consumption was through autotrophic denitrification (AuDeN) for a c/N ratio of 0.6 and 1.2, while for c/N = 1.9 the most significant contribution of nitrate consumption was through heterotrophic denitrification (HD). Finally, organic supplementation (methanol) served to increase the specific nitrate removal rate at high and low initial concentrations of substrate. Therefore, the best c/N ratio was 0.6 since it allowed for increasing the removal efficiency and the denitrification rate.

关键词： Mixotrophic denitrification c N ratio sulfur-based mixotrophic denitrification

来源：评论

学校读者我要写书评

暂无评论

Size effect of carbon fiber-reinforced silicon carbide composites (c/c-Sic): Part 1-bending load and statistical effects

引用

JOURNAL OF THE EUROPEAN cERAMIc SOcIETY 2021年第14期41卷 6805-6814页

作者： Flauder, Stefan Langhof, Nico Krenkel, Walter Schaffoener, Stefan Univ Bayreuth Ceram Mat Engn CME Prof Rudiger Bormann Str 1 D-95447 Bayreuth Germany

This study analyzed the influence of the sample volume, number of tested specimen, and testing method on the flexural strength of fabric-reinforced ceramic matrix composites. For this purpose, seven different batches of c/cSic were prepared with four different sample thicknesses to determine the flexural strengths and Weibull moduli by three-and four-point flexural tests. The result showed that c/c-Sic exhibits a size effect of strength under bending load because a decrease of measured flexural strength with increased specimen size was observed. This size effect was discussed regarding the Weibull weakest link approach and the concept of quasi-brittle materials. The determined Weibull moduli were comparable for the same load condition but dissimilar for the identical material if the load condition were changed from three-to four-point bending. Hence, the Weibull modulus was found to be not an inherent material constant for c/c-Sic and the Weibull weakest link approach seems not appropriate.

关键词： ceramic matrix composites (cMc) Bending test Weibull statistics c c-Sic Size effect of strength

来源：评论

学校读者我要写书评

暂无评论

Three-dimensional micro-pipelines high thermal conductive c/Sic composites

引用

cERAMIcS INTERNATIONAL 2021年第24期47卷 34333-34340页

作者： Zhang, Yunhai Liu, Yongsheng cao, Liyang Fang, Hui Liu, Bin cao, Yejie Wang, Jing chen, Jian Pan, Yu Northwestern Polytech Univ Sci & Technol Thermostruct Composite Mat Lab Xian 710072 Shaanxi Peoples R China Northwestern Polytech Univ Sch Aeronaut Xian 710072 Shaanxi Peoples R China Acad Mil Sci PLA China Natl Innovat Inst Def Technol Beijing 100071 Peoples R China Natl Univ Def Technol Coll Aerosp Sci & Engn Sci & Technol Scramjet Lab Changsha 410073 Hunan Peoples R China

carbon/silicon carbide (c/Sic) composites are usually regarded as thermal protective system materials and widely applied in hypersonic vehicles or ramjet. However, poor thermal conductivity of c/Sic composites, leading to severe heat concentration and thermal stress during the high-speed operation of hypersonic vehicle, limits their broad-range of practical applications. Modification with high thermal conductive fillers is an optional method;however, controllable dispersion and orientation of the fillers to construct continuous and ordered heat conductive channel has been proven to be a challenging task. Herein, based on high thermal conductivity fibers, a three-dimensional micro-pipeline preform was developed for the preparation of structure-function integrated c/Sic composites. The technical feasibility of the method, the characteristics of microstructures, and the thermal conductivity and bending strength of the as-obtained composites were systematically studied. Results revealed that the thermal conductivities of as-obtained composites reached 150.2 and 46.7 W m-1 K-1 for in-plane and out-of-plane direction, respectively. The bending strength obtained herein is 264.4 MPa, which is lower than that of polyacrylonitrile c/Sic composites. However, the fine control over the component and microstructure or densification could provide a higher value in the future research. In sum, the proposed method provides a convenient and feasible approach to prepare high thermal conductive c/Sic composites.

关键词： c Sic composites Micro-pipelines Thermal conductivity Bending strength Heat conductive channels

来源：评论

学校读者我要写书评

暂无评论

Elevated efficiency of c₃ photosynthesis in bamboo grasses: A possible consequence of enhanced refixation of photorespired cO₂

引用

GLOBAL cHANGE BIOLOGY BIOENERGY 2021年第6期13卷 941-954页

作者： Peixoto, Murilo M. Sage, Tammy L. Busch, Florian A. Pacheco, Haryel D. N. Moraes, Moemy G. Portes, Tomas A. Almeida, Rogerio A. Graciano-Ribeiro, Dalva Sage, Rowan F. Univ Fed Goias Programa Posgrad Biodiversidade Vegetal Inst Ciencias Biol Goiania Go Brazil Univ Toronto Dept Ecol & Evolutionary Biol 25 Willcocks St Toronto ON M5S 3B2 Canada Univ Birmingham Birmingham Inst Forest Res Sch Biosci Birmingham W Midlands England Univ Fed Goias Escola Agron Goiania Go Brazil Washington State Univ Sch Biol Sci Pullman WA 99164 USA

Bamboos are productive grasses that currently yield a high-quality wood and potentially an abundance of lignocellulose for bioenergy. All are c-3 grasses of warm habitats, where they are prone to significant photorespiratory inhibition and competitive suppression by c-4 grasses. Here, we investigate whether three bamboo species from the Brazilian cerrado (Dendrocalamus asper, Guadua angustifolia, and Guadua magna) exhibit unique adaptations that suppress photorespiratory costs and enhance photosynthetic efficiency. We evaluated photosynthetic efficiency of the bamboos and rice (Oryza sativa) by measuring c-*, the cO2 compensation point in the absence of mitochondrial respiration. At 25celcius, c-* averaged 2.81 Pa in each of the bamboo species, which is closer to a c-2 plant (2.71 Pa) than the c-3 plant rice (3.31 Pa). Assuming a chloroplast cO2 concentration of 200 mu mol mol(-1), this represents an 18% lower cost of apparent photorespiration in bamboo than rice. Light and transmission electronic microscopy of the bamboo leaves exhibited few organelles in the bundle and mestome sheath cells, and mesophyll (M) cells are deeply lobed with 99% of the cell periphery adjacent to intercellular air space covered by chloroplast and stromules. The chloroplast layer in bamboo M cells is thick, with mitochondria adjacent to or engulfed by chloroplasts. This arrangement slows cO2 efflux and facilitates refixation of photorespired cO2, which could explain the low c-* in the bamboos. The bamboos also had higher water use efficiency than rice, which may reflect efficient refixation of photorespired cO2.

关键词： Bambuseae c (*) c-3 photosynthesis cO2 refixation Dendrocalamus Guadua photorespiration water use efficiency

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：