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Rapid Synthesis of W–Cr Solid–Solution by Dielectric-Barrier Discharge-Plasma-Assisted Ball Milling
S. F. Hong,Z. C. Lu,Y. H. Liu,Q. M. He,W. Jiang,M. Q. Zeng 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.12
Supersaturated solid–solutions in a W–Cr alloy system were fabricated by conventional milling and plasma milling. The differentextension mechanisms of the solid solubility that were created by ball milling with and without discharge plasma werestudied. The solid–solubility of Cr in W for the P-milling W–Cr alloy system was higher, which indicates that plasma millingpromotes the formation of W(Cr) solid–solution more easily than conventional milling. According to Miedema’s model, inthe W–Cr alloy system, the free-energy change to form a W(Cr) solid solution by plasma milling is reduced compared withconventional milling because of the heating effect of the discharge plasma. Therefore, a higher stored energy in the grainboundaries and dislocations of the W–Cr nanograins during plasma milling makes it easier to overcome the thermodynamicbarrier in the formation of a solid–solution, when compared with conventional milling.
M. Q. Zeng,J. L. Tu,M. Zhu,W. Wang,J. W. Liu,Z. C. Lu 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.9
The effects of plasma discharge intensity on the microstructure evolution of ball-milled tungsten (W)–carbon (C)–cobalt (Co)mixtures and the formation mechanism of ultrathin plate-like tungsten carbide (WC) grains prepared by ball milling with andwithout plasma discharge were investigated. It was found that increasing the plasma discharge intensity during ball millingobviously promoted the formation of a thin flake-like W phase because of the electroplasticity effect and simultaneouslylowered the carburization temperature between W and C. A combination of high hardness and transverse rupture strength of92.9 HRA and 3659 MPa, respectively, was obtained for the WC–8Co alloy fabricated by plasma milling at a gas pressure of5 × 103 Pa with a dielectric barrier discharge layer thickness of 3 mm. These properties were mainly attributed to the markedlylowered activation energy of the WC phase and generation of highly oriented ultrathin plate-like WC grains by plasma milling. The combination of the flake-like structure of the plasma-milled W aggregate and high specific interfacial area and shortdiffusion distance of W/C were readily inherited by the ultrathin plate-like WC grains in the sintered WC–Co hardmetals.
X.-C. LU,L.-B. JI,W. CHEN,Z. HUANG 한국자동차공학회 2007 International journal of automotive technology Vol.8 No.1
The effect of the di-tertiary butyl peroxide (DTBP) additive on the heat release rate and emissions of a homogeneous charge compression ignition (HCCI) engine fueled with high Research Octane Number (RON) fuels were investigated. The experiments were performed using 0%, 1%, 2%, 3%, and 4% (by volume) DTBP-RON90 blends. The RON90 Fuel was obtained by blending 90% iso-octane with 10% n-heptane. The experimental results show that the operation range was remarkably expanded to lower temperature and lower engine load with the DTBP additive in RON90 fuel. The first ignition phase of HCCI combustion was observed at 850 K and ended at 950 K while the hot ignition occurred at 1125 K for all fuels at different engine working conditions. The chemical reaction scale time decreases with the DTBP addition. As a result, the ignition timing advances, the combustion duration shortens, and heat release rates were increased at overall engine loads. Meanwhile, the unburned hydrocarbon (UHC) and CO emissions decrease sharply with the DTBP addition while the NOx emissions maintain at a lower level.
X. LU,Z. HUANG,W. ZHANG,D. LI 한국자동차공학회 2005 International journal of automotive technology Vol.6 No.1
The purpose of this paper is to experimentally investigate the engine pollutant emissions and combustion characteristics of diesel engine fueled with ethanol-diesel blended fuel (bio-diesohol). The experiments were performed on a single-cylinder DI diesel engine. Two blend fuels were consisted of 15% ethanol, 83.5% diesel and 15% solublizer (by volume) were evaluated one without cetane improver (E15-D) and one with a cetane improver (E15-D+CN improver). The engine performance parameters and emissions including fuel consumption, exhaust temperature, lubricating oil temperature, Bosch smoke number, CO, NOx, and THC were measured, and compared to the baseline diesel fuel. In order to gain insight into the combustion characteristics of bio-diesohol blends, the engine combustion processes for blended fuels and diesel fuel were observed using an Engine Video System (AVL 513). The results showed that the brake specific fuel consumption (BSFC) increased at overall engine operating conditions, but it is worth noting that the brake thermal efficiency (BTE) increased by up to 1-23% with two blends when compared to diesel fuel. It is found that the engine fueled with ethanol-diesel blend fuels has higher emissions of THC, lower emissions of CO, NOx, and smoke. And the results also indicated that the cetane improver has positive effects on CO and NOx emissions, but negative effect on THC emission. Based on engine combustion visualization, it is found that ignition delay increased, combustion duration and the luminosity of flame decreased for the diesohol blends. The combustion is improved when the CN improver was added to the blend fuel.
Predication of Epoxy Resin Curing Process by Avrami Theory
Kim, S W,Shim, M J,Lu, M G 한국공업화학회 1997 응용화학 Vol.1 No.1
The cure behavior of DGEBA-MDA system was investigated under both isothermal and dynamic conditions. A detailed analysis of the cure process has been made utilizing the Avrami expression. The kinetic parameters were obtained from the isotherms and were in good agreement with the results from other analytical methods. Then those parameters were used to predict the behavior of the system for nonisothermal conditions.