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Process parameter development of a Ti6Al4V-5wt%cr 3 c 2 metal matrix composite fabricated by Laser Powder Bed Fusion

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Procedia cIRP 2024年 124卷 104-109页

作者： Nompumelelo Nkosi Natasha Sacks Department of Industrial Engineering Stellenbosch University Stellenbosch 7600 South Africa

A process parameter strategy to manufacture a Ti6Al4V-5wt%cr 3 c 2 metal matrix composite using laser powder bed fusion was investigated. Several deposition strategies were developed and attempted to find dense, crack-free, non-porous composites with high hardness. Low energy densities resulted in composites with cracks and low hardnesses, while high energy densities resulted in crack-free composites with pores and relatively high hardness. While an optimal deposition parameter set was found to produce crack-free samples with good density and hardness, the samples still showed keyhole porosity. The addition of the cr 3 c 2 to Ti6Al4V stabilized the titanium-β phase since cr is a β stabilizer, and small amounts of Tic and the brittle ω phase were formed. The micro-hardness increased with the addition of the cr 3 c 2 due to the presence of the brittle phases. An annealing heat treatment led to an elimination of the ω phase which consequently decreased the hardness of the composite.

关键词： Metal Matrix composite Ti6Al4V chromium carbide Laser Powder Bed Fusion Hardness Microstructure cr 3 c 2 Titanium

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Advanced control-flow and concurrency in c∀

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SOFTWARE-PRAcTIcE & EXPERIENcE 2021年第5期51卷 1005-1042页

作者： Delisle, Thierry Buhr, Peter A. Univ Waterloo Cheriton Sch Comp Sci 200 Univ Ave West Waterloo ON N2L 3G1 Canada

c for all is a polymorphic, nonobject-oriented, concurrent, backwards compatible extension of the c programming language. This paper discusses the design philosophy and implementation of its advanced control-flow and concurrent/parallel features, along with the supporting runtime written in c for all. These features are created from scratch as ISO c has only low-level and/or unimplemented concurrency, so c programmers continue to rely on library approaches like pthreads. c for all introduces modern language-level control-flow mechanisms, like generators, coroutines, user-level threading, and monitors for mutual exclusion and synchronization. The runtime provides significant programmer simplification and safety by eliminating spurious wakeup and monitor barging. The runtime also ensures multiple monitors can be safely acquired in a deadlock-free way, and this feature is fully integrated with all monitor synchronization mechanisms. All control-flow features integrate with the c for all polymorphic type-system and exception handling, while respecting the expectations and style of c programmers. Experimental results show comparable performance of the new features with similar mechanisms in other concurrent programming languages.

关键词： c c∀ (cforall) coroutine concurrency generator monitor parallelism runtime thread

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

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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

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A Progressive Oxidative Damage Model of c/Sic composites under Stressed Oxidation Environments

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APPLIED cOMPOSITE MATERIALS 2021年第5期28卷 1609-1629页

作者： Ding, Junjie Sun, Zhigang chen, Xihui Niu, Xuming Jin, Yu Song, Yingdong Nanjing Univ Aeronaut & Astronaut State Key Lab Mech & Control Mech Struct Nanjing 210016 Peoples R China Nanjing Univ Aeronaut & Astronaut Coll Energy & Power Engn Jiangsu Prov Key Lab Aerosp Power Syst Nanjing 210016 Peoples R China Minist Ind & Informat Technol Key Lab Aeroengine Thermal Environm & Struct Nanjing 210016 Peoples R China

A progressive oxidative damage model of c/Sic composites, which is based on the oxidation mechanism and mechanical model of c/Sic composites, is presented to simulate the damage process of c/Sic composite under stressed oxidation environments. Firstly, the oxidation failure time of fibers was calculated according to the fiber stress and the fiber strength decline rule under stressed oxidation environments. Secondly, the stress redistribution and crack propagation around fracture fibers were given by combining the fracture position of fibers with the mechanical model, and the crack propagation would cause more fibers to be oxidized. Thirdly, the progressive oxidative damage process of c/Sic composites under stressed oxidation environments was simulated by repeating the cyclic process of fiber oxidation fracture and crack propagation around the fracture fibers. Finally, through the progressive oxidative damage model, the stress-strain curves and fracture morphology of the unidirectional c/Sic composites after stressed oxidation were predicted. The simulation results were correlated well with the experimental results, in terms of stressed oxidation life, stress-strain curve and variation law of fracture morphology, which indicated the reliability of the model.

关键词： Progressive oxidative damage model c Sic composites Stressed oxidation environments Oxidation fracture crack propagation Stress-strain curve

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3D flower-liked Fe₃O₄/c for highly sensitive magnetic dispersive solid-phase extraction of four trace non-steroidal anti-inflammatory drugs

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MIcROcHIMIcA AcTA 2021年第2期188卷 1-10页

作者： Xu, Xu Feng, Xue Liu, Zhen Xue, Shan Zhang, Lei Liaoning Univ Coll Chem 66 Chongshan Middle Rd Shenyang 110036 Peoples R China

A low cost-effective and simple synthesis method was adopted to acquire three-dimensional flower-like structure Fe3O4/c that has large specific area, suitable pore structure and sufficient saturation magnetism. The obtained Fe3O4/c exhibits outstanding preconcentration ability and was applied to extracting non-steroidal anti-inflammatory drugs from complex environmental and biological samples. The parameters of magnetic solid-phase extraction were optimized by univariate and multivariate methods (Box-Behnken design). The high degree of linearity from 2.5 to 1000.0 ng mL(-1) (R-2 >= 0.9976), the limits of detection from 0.25 to 0.5 ng mL(- 1) (S/N =3), and the limits of quantitation from 1.0 to 2.0 ng mL(- 1) (S/N =10) were yielded by adopting this novel method after the optimization. Moreover, the recoveries of non-steroidal anti-inflammatory drugs from 89.6 to 107.0% were acquired in spiked plasma, urine and lake samples. In addition, the adsorption of non-steroidal anti-inflammatory drugs on Fe3O4/c was explored by adsorption isotherms and kinetic studies. Furthermore, the adsorption mechanism for non-steroidal anti-inflammatory drugs by Fe3O4/c was proposed, which was hydrogen bonding and - interaction between non-steroidal anti-inflammatory drugs and Fe3O4/c.

关键词： 3D flower-like structure Fe3O4 c Magnetic solid-phase extraction NSAIDs Environmental and biological samples

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RMI- c/c-Sic-ZrSi2 composite serving in inert atmosphere up to 2100 °c: Thermal shock resistance, microstructure and damage mechanism

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cERAMIcS INTERNATIONAL 2021年第14期47卷 20371-20378页

作者： Tong, Yonggang Zhang, Hao Hu, Yongle Zhang, Peng Hua, Manyu Liang, Xiubing chen, Yongxiong Zhang, Zhibing Changsha Univ Sci & Technol Coll Automobile & Mech Engn Changsha Peoples R China Acad Mil Sci PLA China Natl Inst Def Technol Innovat Beijing Peoples R China

Thermal shock resistance (TSR) and related damage mechanism of c/c-Sic-ZrSi2 composites produced via Si-Zr alloy melt infiltration was investigated using a newly-developed equipment at superior high temperatures up to 2100 degrees c in an inert atmosphere. TSR was characterized by the residual strength and mass variation of the composites subjecting to thermal shock tests with different cycles and temperatures. Results indicated that TSR and damage of the composites were closely dependent on the testing cycles and especially temperatures. Strength of the composites was generally decreased with the increasing tested cycles. Slight strength reduction subjected to the low testing temperatures (< 1300 degrees c) were detected because almost no crack propagation occurred in the c-Sic-ZrSi2 matrix. At relatively higher temperatures (1300-1700 degrees c), thermal stress caused by temperature gradient and thermal expansion coefficient mismatch was greatly increased. consequently, matrix crack propagating into the intra fiber bundles and interfacial layers with much longer propagation paths were generated. Repeated thermal stress during cycled thermal shock tests weakened the interface bonding in the composites, and resulted in the delamination and interfacial debonding with obvious strength degradation. At ultrahigh temperatures (>= 1700 degrees c), matrix pores were produced due to ZrSi2 evaporation. combining effect by thermal stress and ZrSi2 evaporation caused severe damage to the composites with sharp strength reduction.

关键词： Thermal shock resistance Microstructure Damage Reactive melt infiltration c c-Sic-ZrSi 2 composites

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Thermal performance and ablation characteristics of c/c-Sic for thermal protection of hypersonic vehicle

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JOURNAL OF THE EUROPEAN cERAMIc SOcIETY 2021年第11期41卷 5427-5436页

作者： Shi, Yi-ang Zha, Bai-lin Su, Qing-dong Wang, Jin-jin Li, Si-ye Rocket Force Univ Engn Xian 710025 Peoples R China Project Management Ctr Beijing 100085 Peoples R China

A small-scale plasma ablation facility was employed to test the c/c-Sic composite material for investigating the thermal performance and ablation characteristics under two heat flux conditions, 3593.54 kW.m- 2 and 5644.86 kW.m-2. The morphology of post-test specimens was analyzed with the ablation rates calculated. The average mass ablation rates of two group specimens were 0.01735 and 0.10620 g.s-1 respectively with average linear ablation rate of 0.00680 and 0.09407 mm.s-s1. Specimen surface could be divided into three regions with typical layered structure characteristics. For the stagnation point ablation test, the structural deformation in the ablation surface area featured in vertical layering and lateral regionality, forming an ablation pit near the stagnation point. In the center region, sublimation occured primarily, accompanied by a serious jet scouring of the molten liquid phase, as well as a small amount of oxidation reaction;Jet erosion with thermal sublimation was the main factor for the mass loss in the transitional region;Thermochemical reactions were mainly carried out in the marginal region. The SiO2 generated from the thermochemical reaction of the material filled the interspace well and prevented the thermochemical reaction from penetrating deeper through the crack. The protective layer in the molten state with high viscosity reduced the damage of the high-speed jet impact material.

关键词： c c-Sic composite material Ablation rates Ablation characteristics Thermal protection performance

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Design and fabrication of c-Mn_0.5cd_0.5S/cu3P ternary heterojunction catalyst for photocatalytic hydrogen evolution

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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2021年第59期46卷 30382-30392页

作者： Fang, Ningjie Song, Xincheng Zhang, Mingyue chu, Yinghao Sichuan Univ Coll Architecture & Environm Chengdu 610065 Sichuan Peoples R China Natl Engn Technol Res Ctr Flue Gas Desulfurizat Chengdu 610065 Sichuan Peoples R China

Photocatalytic hydrogen evolution from water splitting is a promising strategy to solve the energy demand of human beings. Here, we first designed a c-Mn0.5cd0.5S/cu3P ternary heterojunction catalyst for photocatalytic hydrogen production. The results show that the combination of c and cu3P can effectively improve the photocatalytic activity of Mn0.5cd0.5S. c-Mn0.5cd0.5S loading with 5 wt% cu3P exhibits the highest hydrogen evolution rate (44.1 mmol g(-1) h(-1)), which is 3.2 and 2.8 times higher than that of pure Mn0.5cd0.5S (13.7 mmol g(-1) h(-1)) and Mn0.5cd0.5S/3 wt%Pt (15.6 mmol g(-1) h(-1)), respectively. In addition, it shows a high hydrogen evolution rate (19.6 mmol g(-1) h(-1)) under visible light (>= 420 nm) irritation and the apparent quantum efficiency (AQE) is detected to be 3.2% at 420 nm. The enhanced photocatalytic activity can be attributed to the good conductivity of c and the formation of p-n heterojunction, which is beneficial for light harvesting and the separation and transportation of charge carriers. Besides, a possible mechanism is proposed. This work provides an effective way to improve the photocatalytic activity of Mn0.5cd0.5S by using non noble metal co-catalysts. (c) 2021 Hydrogen Energy Publications LLc. Published by Elsevier Ltd. All rights reserved.

关键词： Photocatalytic Hydrogen evolution c cu 3 P Mn 0 5 cd 0 5 S

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

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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

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双金属co/Zn-ZIFs中c3H6和c3H8吸附和扩散行为分子模拟研究

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化工学报 2025年

作者：齐昊王玉杰李申辉邹琦刘轶群赵之平北京理工大学化学与化工学院中石化(北京)化工研究院有限公司

基于第一性原理计算，构建出11种双金属有机框架co/Zn-ZIFs分子模型（1#、2#、3#等），每一种模型其各窗口结构相同，采用巨正则蒙特卡洛的方法研究了c3H6、c3H8分别在co/Zn-ZIFs上的吸附性能，通过吸附热分布、吸附位点、弱相互作用、... 详细信息

基于第一性原理计算，构建出11种双金属有机框架co/Zn-ZIFs分子模型（1#、2#、3#等），每一种模型其各窗口结构相同，采用巨正则蒙特卡洛的方法研究了c3H6、c3H8分别在co/Zn-ZIFs上的吸附性能，通过吸附热分布、吸附位点、弱相互作用、静电势及差分电荷密度等方法分析了c3H6、c3H8分别在co/Zn-ZIFs上吸附机理，并采用分子动力学计算了c3H6、c3H8分别在co/Zn-ZIFs窗口处的扩散特性。结果表明：c3H6、c3H8在co/Zn-ZIFs上的吸附主要作用在在配体咪唑环与甲基附近；一定范围内，升高温度、降低压力均有利于实现优先吸附c3H8，在环境温度为323 K，环境压力为0.5 bar下，3# co/Zn-ZIFs的c3H8对c3H6的理想吸附选择性最高，为1.25。c3H6、c3H8在6# co/Zn-ZIFs窗口处扩散自由能差值最大，为14.60 kJ/mol，c3H6、c3H8自扩散系数分别为3.910×10-10和1.445×10-12，c3H6/c3H8理想扩散选择性最高，为270.59。对于相同金属比例的不同co/Zn-ZIFs分子模型，具有相近的c3H6吸附量和c3H8吸附量，当占比少的金属原子呈相间分布时，c3H6、c3H8的扩散自由能最大，且c3H8与c3H6的扩散自由能差值变大，从而提升了c3H6/c3H8分离选择性。对于不同金属比例的co/Zn-ZIFs分子模型，具有相近的c3H6吸附量和c3H8吸附量，随着co/Zn比例上升，c3H8、c3H6分子的扩散自由能均逐渐增大，扩散阻力增大。结果对分析co/Zn-ZIFs分离c3H6/c3H8提供了极具价值的理论依据。

关键词：分子模拟 co/Zn-ZIFs c H /c H 吸附扩散

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