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Effects of process parameters on morphology and distribution of externally solidified crystals in microstructure of magnesium alloy die castings 被引量:5
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作者 Meng-wu Wu Xiao-bo Li +1 位作者 Zhi-peng Guo Shou-mei Xiong 《China Foundry》 SCIE 2018年第2期139-144,共6页
During the cold-chamber high pressure die casting(HPDC) process, samples were produced to investigate the microstructure characteristics of AM60B magnesium alloy. Special attention was paid to the effects of process p... During the cold-chamber high pressure die casting(HPDC) process, samples were produced to investigate the microstructure characteristics of AM60B magnesium alloy. Special attention was paid to the effects of process parameters on the morphology and distribution of externally solidified crystals(ESCs) in the microstructure of magnesium alloy die castings, such as slow shot phase plunger velocity, delay time of pouring and fast shot phase plunger velocity. On the basis of metallographic observation and quantitative statistics, it is concluded that a lower slow shot phase plunger velocity and a longer delay time of pouring both lead to an increment of the size and percentage of the ESCs, due to the fact that a longer holding time of the melt in the shot sleeve will cause a more severe loss of the superheat. The impingement of the melt flow on the ESCs is more intensive with a higher fast shot phase plunger velocity, in such case the ESCs reveal a more granular and roundish morphology and are dispersed throughout the cross section of the castings. Based on analysis of the filling and solidification processes of the melt during the HPDC process, reasonable explanations were proposed in terms of the nucleation, growth, remelting and fragmentation of the ESCs to interpret the effects of process parameters on the morphology and distribution of the ESCs in the microstructure of magnesium alloy die castings. 展开更多
关键词 magnesium alloy high pressure die casting microstructure externally solidified crystals process parameters
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Atmospheric Pressure Plasma Processing of Fused Silica in Different Discharge Modes
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作者 李娜 辛强 +1 位作者 张鹏 王波 《Plasma Science and Technology》 SCIE EI CAS CSCD 2015年第7期567-573,共7页
One of the major advantages of utilizing atmospheric pressure plasma processing (APPP) technology to fabricate ultra-precision optics is that there is no subsurface damage during the process. In APPP, the removal fo... One of the major advantages of utilizing atmospheric pressure plasma processing (APPP) technology to fabricate ultra-precision optics is that there is no subsurface damage during the process. In APPP, the removal footprint and removal rate are critical to the capability and efficiency of the figuring of the optical surface. In this paper, an atmospheric plasma torch, which can work in both remote mode and contact mode, is presented. The footprints and the removal rates of both modes are compared by profilometer measurements. The influences of process recipes and substrate thickness for both modes are investigated through a series of experiments. When the substrate is thinner than 12 mm, the removal rate in contact mode is higher. However, the removal rate and width of the footprint decrease dramatically as the substrate thickness increases in contact mode. 展开更多
关键词 atmospheric pressure plasma processing remote mode contact mode removalfootprint removal rate
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Study on the Key Influencing Factors in Atmospheric Pressure Plasma Processing of Fused Silica
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作者 Na Li Bo Wang Hui-Liang Jin 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2014年第5期124-128,共5页
In order to get ultra-smooth fused silica surface without subsurface damage efficiently, the atmospheric pressure plasma processing( APPP) method has been developed. It is based on chemical reaction between active rad... In order to get ultra-smooth fused silica surface without subsurface damage efficiently, the atmospheric pressure plasma processing( APPP) method has been developed. It is based on chemical reaction between active radicals excited by plasma and workpiece surface atoms,so the subsurface damage caused by contact stress can be avoided and atomic-level precision can be ensured. In this paper,based on the spectral quantitative analysis theory,the influence laws on material removal rate by the key factors of APPP including the flow rate of reaction gases,the input power,the processing distance and time are discussed. In addition,the results that APPP can remove the damaged surface layer and do not introduce secondary damage are proved via the nanoindentation technology. 展开更多
关键词 atmospheric pressure plasma processing fused silica material removal rate surface quality
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Heat Transfer between Casting and Die during High Pressure Die Casting Process of AM50 Alloy-Modeling and Experimental Results
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作者 Zhipeng GUO Shoumei XIONG +1 位作者 Sang-Hyun Cho Jeong-Kil Choi 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2008年第1期131-135,共5页
A method based on die casting experiments and mathematic modeling is presented for the determination of the heat flow density (HFD) and interfacial heat transfer coefficient (IHTC) during the high pressure die cas... A method based on die casting experiments and mathematic modeling is presented for the determination of the heat flow density (HFD) and interfacial heat transfer coefficient (IHTC) during the high pressure die casting (HPDC) process.Experiments were carried out using step shape casting and a commercial magnesium alloy,AM50.Temperature profiles were measured and recorded using thermocouples embedded inside the die. Based on these temperature readings,the HFD and IHTC were successfully determined and the calculation results show that the HFD and IHTC at the metal-die interface increases sharply right after the fast phase injection process until approaching their maximum values,after which their values decrease to a much lower level until the dies are opened.Different patterns of heat transfer behavior were found between the die and the casting at different thicknesses.The thinner the casting was,the more quickly the HFD and IHTC reached their steady states.Also,the values for both the HFD and IHTC values were different between die and casting at different thicknesses. 展开更多
关键词 Interfacial heat transfer coefficient High pressure die casting process AM50 Magnesium alloy
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Optimized Synthesis of Carbon Aerogels via Ambient Pressure Drying Process as Electrode for Supercapacitors
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作者 袁磊 CHANG Lijuan +5 位作者 FU Zhibing YANG Xi JIAO Xingli TANG Yongjian LIU Xichuan 王朝阳 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2015年第6期1325-1331,共7页
Carbon aerogels were synthesized via ambient pressure drying process using resorcinolformaldehyde as precursor and P123 to strengthen their skeletons. CO2 activation technology was implemented to improve surface areas... Carbon aerogels were synthesized via ambient pressure drying process using resorcinolformaldehyde as precursor and P123 to strengthen their skeletons. CO2 activation technology was implemented to improve surface areas and adjust pore size distribution. The synthesis process was optimized, and the morphology, structure, adsorption properties and electrochemical behavior of different samples were characterized. The CO2-activated samples achieved a high specific capacitance of 129.2 F/g in 6 M KOH electrolytes at the current density of 1 m A/cm^2 within the voltage range of 0-0.8 V. The optimized activation temperature and duration were determined to be 950 ℃ and 4 h, respectively. 展开更多
关键词 supercapacitors carbon aerogels ambient pressure drying process activation
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Influence of Pressure on the Annealing Process of β-Ca_2SiO_4(C_2S) in Portland Cement
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作者 高云鹏 董琬晴 +1 位作者 李工 刘日平 《Chinese Physics Letters》 SCIE CAS CSCD 2018年第3期48-51,共4页
Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-speciality grout. Dicalcium silicate (Ca2SiO4) is the primary constituent ... Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-speciality grout. Dicalcium silicate (Ca2SiO4) is the primary constituent of a number of different types of cement. The β-Ca2SiO4 phase is metastable at room temperature and will transform into β-Ca2SiO4 at 663K. In this work, Portland cement is annealed at a temperature of 950K under pressures in the range of 0-5.5 CPa. The high pressure experiments are carried out in an apparatus with six anvil tops. The effect of high pressure on the obtaining nano-size β-Ca2SiO4 (C2S) process is investigated by x-ray diffraction and transmission electron microscopy. Experimental results show that the grain size of the C2S decreases with the increase of pressure. The volume fraction of the C2S phase increases with the pressure as the pressure is below 3 CPa, and then decreases (P 〉 3 GPa). The nano-effect is very important to the stabilization of β-Ca2SiO4. The mechanism for the effects of the high pressure on the annealing process of the Portland cement is also discussed. 展开更多
关键词 Ca2SiO4 in Portland Cement Influence of Pressure on the Annealing process of SIO
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Surface-Driven High-Pressure Processing
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作者 Keith E. Gubbins Kai Gu +6 位作者 Liangliang Huang Yun Long J. Matthew Mansell Erik E. Santiso Kaihang Shi Malgorzata Sliwifiska-Bartkowiak Deepti Srivastava 《Engineering》 2018年第3期311-320,共10页
The application of high pressure favors many chemical processes, providing higher yields or improved rates in chemical reactions and improved solvent power in separation processes, and allowing activation barriers to ... The application of high pressure favors many chemical processes, providing higher yields or improved rates in chemical reactions and improved solvent power in separation processes, and allowing activation barriers to be overcome through the increase in molecular energy and molecular collision rates. High pressures-up to millions of bars using diamond anvil cells-can be achieved in the laboratory, and lead to many new routes for chemical synthesis and the synthesis of new materials with desirable thermody- namic, transport, and electronic properties. On the industrial scale, however, high-pressure processing is currently limited by the cost of compression and by materials limitations, so that few industrial processes are carried out at pressures above 25 MPa. An alternative approach to high-pressure processing is pro- posed here, in which very high local pressures are generated using the surface-driven interactions from a solid substrate. Recent experiments and molecular simulations show that such interactions can lead to local pressures as high as tens of thousands of bars (1 bar=1×10^5 Pa), and even millions of bars in some cases. Since the active high-pressure processing zone is inhomogeneous, the pressure is different in dif- ferent directions. In many cases, it is the pressure in the direction parallel to the surface of the substrate (the tangential pressure) that is most greatly enhanced. This pressure is exerted on the molecules to be processed, but not on the solid substrate or the containing vessel. Current knowledge of such pressure enhancement is reviewed, and the possibility of an alternative route to high-pressure processing based on surface-driven forces is discussed. Such surface-driven high-pressure processing would have the advantage of achieving much higher pressures than are possible with traditional bulk-phase processing, since it eliminates the need for mechanical compression. Moreover, no increased pressure is exerted on the containing vessel for the process, thus eliminating concerns about materials failure. 展开更多
关键词 CONFINEMENT High pressure High pressure phase High pressure reaction High pressure manufacture High pressure chemical processing
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Optimization of pressurization process in low-pressure casting of a 5.4-ton gigantic C95800 copper alloy casting
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作者 Zi-ao Qiu Xin-yi Zhao +9 位作者 Chao-jun Zhang Jun-liu Yang Rui-yun Shi Tang-qi Lü Xiao-lei Yu Qiu-shi Chen Lin-lin Quan Lun-yong Zhang Fu-yang Cao Jian-fei Sun 《China Foundry》 SCIE EI CAS 2024年第6期717-726,共10页
During the low-pressure casting of extra-large size C95800 copper alloy components,traditional linear pressurization technique leads to a rapid surge of liquid metal inlet velocity at the regions where the mold cavity... During the low-pressure casting of extra-large size C95800 copper alloy components,traditional linear pressurization technique leads to a rapid surge of liquid metal inlet velocity at the regions where the mold cavity cross-section enlarges.This rapid increasement of liquid metal inlet velocity causes serious entrapment of gas and oxide films,and results in various casting defects such as the bifilm defects.These defects detrimentally deteriorate mechanical properties of the castings.To address this issue,an innovative nonlinear pressurization strategy timely matching to the casting structure was proposed.The pressurization rate decreases at sections where the cross-section widens,but it gradually increases as the liquid metal level rises.By this way,the inlet velocity remains below a critical threshold to prevent the entrapment of gas and oxide films.Comparative analyses involving numerical simulations and casting verification illustrate that the nonlinear pressurization technique,compared to the linear pressurization,effectively diminishes both the size and number of bifilm defects.Furthermore,the nonlinear pressurization method enhances the casting yield strength by 10%,tensile strength by 14%,and elongation by 10%.Examination through scanning electron microscopy highlights that the bifilm defects arising from the linear pressurization process result in the reduction of the castings’mechanical properties.These observations underscore the efficacy of nonlinear pressurization in enhancing the quality and reliability of gigantic castings,as exemplified by a 5.4-ton extra-large sized C95800 copper alloy propeller hub with complex structures in the current study. 展开更多
关键词 gigantic copper alloy casting C95800 low-pressure casting nonlinear pressurization process
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Nitrogen rejection from low quality natural gas by pressure swing adsorption experiments and simulation using dynamic adsorption isotherms 被引量:4
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作者 Xinran Zhang Hua Shang +2 位作者 Jiangfeng Yang Libo Li Jinping Li 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2022年第2期120-129,共10页
In order to remove N_(2) from low quality natural gas,a mathematical model has been established by Aspen adsorption,using the CH_(4)-selective sorbent silicalite-1 pellets.The dynamic adsorption isotherm was first sim... In order to remove N_(2) from low quality natural gas,a mathematical model has been established by Aspen adsorption,using the CH_(4)-selective sorbent silicalite-1 pellets.The dynamic adsorption isotherm was first simulated by breakthrough simulation of a CH_(4)/N_(2) mixture at different adsorption pressures and feed flow rates based on breakthrough experiments.The resulting simulated CH_(4) dynamic adsorption amounts were very close to the experimental data at three different adsorption pressures(100,200,and 300 kPa).Moreover,a single-bed,three-step pressure swing adsorption(PSA)experiment was performed,and the results were in good agreement with the simulated data,further corroborating the accuracy of the gas dynamic adsorption isotherm obtained by the simulation method.Finally,based on the simulated dynamic adsorption isotherm of CH_(4) and N_(2),a four-bed,eight-step PSA process has been designed,which enriched 75%(vol)CH_(4) and 80%(vol)CH_(4) to 95%(vol)and 99%(vol),and provided 99%(vol)recovery. 展开更多
关键词 Natural gas SILICALITE-1 Simulation Dynamic adsorption Pressure swing adsorption process
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Practical application of pressure regulating technology for fire district in Meiyukou Coal Mine
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作者 章庆丰 贾宝山 《Journal of Coal Science & Engineering(China)》 2008年第4期546-549,共4页
Based on the simulated laboratory experiment of pressure balance for fire ex- tinguishing,the pressure regulating technology was summarized for the fire district in Meiyukou Coal Mine.The technology includes three mea... Based on the simulated laboratory experiment of pressure balance for fire ex- tinguishing,the pressure regulating technology was summarized for the fire district in Meiyukou Coal Mine.The technology includes three measures for air pressure regulation, namely applying the pressure regulating chamber to balance the air pressure of fire district, increasing the air pressure of the working face,and filling the ground surface fractures.A good effect was obtained to prevent and extinguish the fire.When the measures fail to in- crease the pressure of working face or to regulate that of air chamber,the measure to fill the ground surface fractures will play an important role. 展开更多
关键词 fire district pressure regulating technology pressure regulating process pressure balancing ventilation
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Influence of Chemical Precleaning on the Plasma Treatment Efficiency of Aluminum by RF Plasma Pencil
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作者 Vadym PRYSIAZHNYI Pavel SLAVICEK +1 位作者 Eliska MIKMEKOVA Milos KLIMA 《Plasma Science and Technology》 SCIE EI CAS CSCD 2016年第4期430-437,共8页
This paper is aimed to show the influence of initial chemical pretreatment prior to subsequent plasma activation of aluminum surfaces.The results of our study showed that the state of the topmost surface layer(i.e.th... This paper is aimed to show the influence of initial chemical pretreatment prior to subsequent plasma activation of aluminum surfaces.The results of our study showed that the state of the topmost surface layer(i.e.the surface morphology and chemical groups)of plasma modified aluminum significantly depends on the chemical precleaning.Commonly used chemicals(isopropanol,trichlorethane,solution of Na OH in deionized water)were used as precleaning agents.The plasma treatments were done using a radio frequency driven atmospheric pressure plasma pencil developed at Masaryk University,which operates in Ar,Ar/O_2 gas mixtures.The effectiveness of the plasma treatment was estimated by the wettability measurements,showing high wettability improvement already after 0.3 s treatment.The effects of surface cleaning(hydrocarbon removal),surface oxidation and activation(generation of OH groups)were estimated using infrared spectroscopy.The changes in the surface morphology were measured using scanning electron microscopy.Optical emission spectroscopy measurements in the near-to-surface region with temperature calculations showed that plasma itself depends on the sample precleaning procedure. 展开更多
关键词 atmospheric pressure plasma plasma jet aluminum surface treatment surface processing chemical precleaning
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Experimental study on pressurized activated sludge process for high concentration pesticide wastewater 被引量:3
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作者 Zanfang Jin, Zhiyan Pan, Shangqin Yu, Chunmian Lin College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou 310032, China. 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2010年第9期1342-1347,共6页
Pressurized biochemical process derived from traditional activated sludge processes is an innovative technology for wastewater treatment. The main advantage of the pressurized process is that the oxygen transfer barri... Pressurized biochemical process derived from traditional activated sludge processes is an innovative technology for wastewater treatment. The main advantage of the pressurized process is that the oxygen transfer barrier can be overcome by increasing the dissolved oxygen level. In this study, high concentration pesticide wastewater was treated by pressurized activated sludge process. It was found that the removal of chemical oxygen demand (COD) increased steadily with the increase of operating pressure, aeration time, and sludge concentration. When the operation pressure was 0.30 MPa and the aeration time was 6 hr, 85.0%-92.5% COD, corresponding to an effluent COD of 230-370 mg/L, was removed from an influent COD of 2500-5000 mg/L. The obtained outlet COD concentration was lower than 350-450 mg/L for the identical process operated under the atmospheric pressure. In addition, pressurized biochemical process could produce a higher COD volumetric loading rate at 5.8-7.6 kg COD/(m^3.day), compared with 2.0-2.8 kg COD/(ma.day) using the same equipment at the atmospheric pressure. The COD concentration followed a modified Monod model with Vmax 2.31 day-1 and Ks 487 mg/L. 展开更多
关键词 pressurized biochemical process pesticide wastewater activated sludge KINETICS
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Study on the physical basis of pressure and particle velocity combine processing 被引量:1
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作者 HUI Junying, LIU Hong, YU Huabing, FAN Minyi, LIANG Guolong (Underwater Acoustic Engineering Dept., Harbin Engineering University Harbin 150001) 《Chinese Journal of Acoustics》 2001年第3期203-212,共10页
Some basic studies of pressure and particle velocity combine processing such as correlation between them, average acoustic intensity processing, rotating and sharpening of directivity are described. Preliminary result... Some basic studies of pressure and particle velocity combine processing such as correlation between them, average acoustic intensity processing, rotating and sharpening of directivity are described. Preliminary results based on theoretical analysis and lake trail will lay a foundation for further research. 展开更多
关键词 Study on the physical basis of pressure and particle velocity combine processing
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A combined signal processing approach against coherent interference with pressure and particle velocity
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作者 HUI Junying, LI Chunxu, LIANG Guolong, LIU Hong (Harbin Engineering University Harbin 150001) 《Chinese Journal of Acoustics》 2001年第3期193-202,共10页
Comparing with traditional underwater acoustic system which only utilizes pressure information, combine sensor system processes pressure together with particle velocity information of sound field. More information ce... Comparing with traditional underwater acoustic system which only utilizes pressure information, combine sensor system processes pressure together with particle velocity information of sound field. More information certainly brings nicer processing result. By using spatial directional information collected by combine sensor, the Coherent Interference Energy Suppress (CIES) technology, which can effectively suppress coherent interference and detect linear spectrum signal and wide-band continuous-spectrum signal as well, is presented. Current research has shown favorite result, and further research is going on. 展开更多
关键词 A combined signal processing approach against coherent interference with pressure and particle velocity
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Study on Bamboo Treatment Technology with CuAz Preservative 被引量:2
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作者 QIN Shaoshan 1, 2 LIU Yanlong 1 LIU Junliang 1 1.College of Transportation and Civil Engineering, Beihua University, Jilin132013, P.R.China 2. Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091, P.R.China 《Chinese Forestry Science and Technology》 2008年第3期61-64,共4页
In order to research the effect of preservative penetrability, CuAz (copper azole) was used for the preservative, and pieces of Moso bamboo (Phyllostachys pubescens) were used for the experimental materials in this st... In order to research the effect of preservative penetrability, CuAz (copper azole) was used for the preservative, and pieces of Moso bamboo (Phyllostachys pubescens) were used for the experimental materials in this study. The vacuum pressure process was used to treat bamboo pieces. The results showed as follows: 1) Main treatment factors were preservative concentration and applied pressure; 2) In the same technology, both the retention and the weight proportion gain of the samples without node were less than those of ones with node, due to special structure of bamboo node; 3) For the samples without node, a good result could be gotten when the preservative concentration was from 1% to 2%, treatment pressure was 0.6 MPa, and treatment time was 30 min. And for the bamboo samples with node, a good result can be gotten when the concentration was 2%, treatment pressure was 0.4 MPa, and treatment time was 30 min. This study demonstrates that the interaction between preservative and bamboo can be improved by adjusting the parameters. 展开更多
关键词 CuAz Moso bamboo (Phyllostachys pubescens) preservation treatment penetrability vacuum pressure process
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