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...
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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.
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 ...
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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.
作者:
Huang, WenkaiXu, FuhuaLiu, XiangChina 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 fi...
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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.
A progressive oxidative damage model of c/Siccomposites, which is based on the oxidation mechanism and mechanical model of c/Siccomposites, is presented to simulate the damage process of c/Siccomposite under stress...
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A progressive oxidative damage model of c/Siccomposites, which is based on the oxidation mechanism and mechanical model of c/Siccomposites, is presented to simulate the damage process of c/Siccomposite 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/Siccomposites 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/Siccomposites 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.
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 ob...
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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.
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...
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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.
A small-scale plasma ablation facility was employed to test the c/c-Siccomposite material for investigating the thermal performance and ablation characteristics under two heat flux conditions, 3593.54 kW.m- 2 and 564...
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A small-scale plasma ablation facility was employed to test the c/c-Siccomposite 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.
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 photocatalyti...
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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.
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 a...
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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/Siccoating 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.
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