The low-gravity environment aboard the space provides a unique platform for understanding crystal-growth-related phenomena that are masked by gravity on the Earth and for exploring new crystal growth techniques. We ha...The low-gravity environment aboard the space provides a unique platform for understanding crystal-growth-related phenomena that are masked by gravity on the Earth and for exploring new crystal growth techniques. We have characterized the wetting behavior of metal alloys and carried out melt growth of compound semiconductors under the support of materials science program in the SJ-10 recoverable satellite. We found that interfacial reaction plays a significant role in the interfacial evolution of Sn-based alloys. Detached growth of InAsSb was realized under microgravity, whereas during the terrestrial experiment the crystal and the crucible wall contact with each other. Moreover, the suppression of buoyancy-driven convection results in a more uniform composition distribution in the InGaSb and Bi_2Te_3-based semiconductor alloys.展开更多
Activities of space materials science research in China have been continuously supported by two main national programs.One is the China Space Station(CSS)program since 1992,and the other is the Strategic Priority Prog...Activities of space materials science research in China have been continuously supported by two main national programs.One is the China Space Station(CSS)program since 1992,and the other is the Strategic Priority Program(SPP)on Space Science since 2011.In CSS plan in 2019,eleven space materials science experimental projects were officially approved for execution during the construction of the space station.In the SPP Phase Ⅱ launched in 2018,seven pre-research projects are deployed as the first batch in 2018,and one concept study project in 2019.These pre-research projects will be cultivated as candidates for future selection as space experiment projects on the recovery of scientific experimental satellites in the future.A new apparatus of electrostatic levitation system for ground-based research of space materials science and rapid solidification research has been developed under the support of the National Natural Science Foundation of China.In order to promote domestic academic activities and to enhance the advancement of space materials science in China,the Space Materials Science and Technology Division belong to the Chinese Materials Research Society was established in 2019.We also organized scientists to write five review papers on space materials science as a special topic published in the journal Scientia Sinica to provide valuable scientific and technical references for Chinese researchers.展开更多
Experiments were carried out on carburizing and temperature rising of the semi steel melt in a plasma induction furnace.Influence of many factors, such as power supply mode,position of the plasma torch and bottom b...Experiments were carried out on carburizing and temperature rising of the semi steel melt in a plasma induction furnace.Influence of many factors, such as power supply mode,position of the plasma torch and bottom blown gas stirring,on heating efficiency and melt temperature distribution was studied. Melt temperature could be effectively controlled by plasma heating,and carbon content of semi steel melt increased from 1.92 % to 4.58 %, and the utilization rate of carbon reached up to 61.57 % during carburizing of the melt.展开更多
The virtual absence of gravity-dependent phenomena in microgravity allows an in-depth understanding of fundamental events that are normally obscured and therefore are difficult to study quantitatively on Earth.Of part...The virtual absence of gravity-dependent phenomena in microgravity allows an in-depth understanding of fundamental events that are normally obscured and therefore are difficult to study quantitatively on Earth.Of particular interest is that the low-gravity environment aboard space provides a unique platform to synthesize alloys of semiconductors with homogeneous composition distributions,on both the macroscopic and microscopic scales,due to the much reduced buoyancy-driven convection.On the other hand,the easy realization of detached solidification in microgravity suppresses the formation of defects such as dislocations and twins,and thereby the crystallographic perfection is greatly increased.Moreover,the microgravity condition offers the possibilities to elucidate the liquid/solid interfacial structures,as well as clarify the microstructure evolution path of the metal alloys(or composites)during the solidification process.Motivated by these facts,growths of compound semiconductors and metal alloys were carried out under microgravity by using the drop tube,or on the scientific platforms of Tiangong-2 and SJ-10.The following illustrates the main results.展开更多
The surface tension of molten AlSi20 alloy has been measured by using the sessile drop method at 923―1123 K under argon atmosphere in both heating-up and cooling processes. The result shows that the surface tension o...The surface tension of molten AlSi20 alloy has been measured by using the sessile drop method at 923―1123 K under argon atmosphere in both heating-up and cooling processes. The result shows that the surface tension of this alloy decreases as long as temperature increases. The results of surface tension and contact angles in heating-up process have differences from those obtained in cooling process, because the metal microstructures have some changes at different temperatures based on the metal genetic theory. The surface tension of molten AlSi20 alloy and that of molten pure aluminum have been compared as well, and the temperature coefficient of AlSi20 alloy is slightly lower than that of Al. The result has been analyzed by the linear scanning analysis with ESEM. The concentration of silicon in most region of the bulk is lower than that of the surface and the addition of Si to pure Al decreases the surface tension of molten pure Al.展开更多
Wettability of molten Sn-Ag-Cu alloy on Cu substrate has been determined by sessile drop method, as well as its dependence on time and temperature. It was found that the evolution of contact angle at the alloy’s melt...Wettability of molten Sn-Ag-Cu alloy on Cu substrate has been determined by sessile drop method, as well as its dependence on time and temperature. It was found that the evolution of contact angle at the alloy’s melting point experienced four different stages. Especially, the contact angle was unstable and fluctuant in stage II, and gradually decreased in stage III mainly due to a chemical reaction between Sn-Ag-Cu alloy and Cu substrate. The contact angle decreased with increasing temperature, but increased slightly at 629 K, for another chemical reaction occurred. Interfacial characteristic has been further investigated by examining the sample’s cross section. Intermetallic compounds of Cu6Sn5 and β-Sn phase were found at the interface of Sn-Ag-Cu/Cu.展开更多
The reactive wetting kinetics of a Sn-30Bi-0.5Cu Pb-free solder alloy on a Cu substrate was investigated by the sessile drop method from 493 to 623 K.The triple line frontier,characterized by the drop base radius R wa...The reactive wetting kinetics of a Sn-30Bi-0.5Cu Pb-free solder alloy on a Cu substrate was investigated by the sessile drop method from 493 to 623 K.The triple line frontier,characterized by the drop base radius R was recorded dynamically with a high resolution CCD using different spreading processes in an Ar-H 2 flow.We found a good agreement with the De Gennes model for the relationship between ln(dR/dt) and lnR for the spreading processes at 493 and 523 K.However,a significant deviation from the De Gennes model was found for the spreading processes at 548 and 623 K.Our experimental results show a complicated temperature effect on the spreading kinetics.Intermetallics at the Sn-30Bi-0.5Cu/Cu interface were identified as Cu 6 Sn 5 adjacent to the solder and Cu 3 Sn adjacent to the Cu substrate.The intermetallic compounds effectively enhanced the triple line mobility because of reaction product formation at the diffusion frontier.展开更多
文摘The low-gravity environment aboard the space provides a unique platform for understanding crystal-growth-related phenomena that are masked by gravity on the Earth and for exploring new crystal growth techniques. We have characterized the wetting behavior of metal alloys and carried out melt growth of compound semiconductors under the support of materials science program in the SJ-10 recoverable satellite. We found that interfacial reaction plays a significant role in the interfacial evolution of Sn-based alloys. Detached growth of InAsSb was realized under microgravity, whereas during the terrestrial experiment the crystal and the crucible wall contact with each other. Moreover, the suppression of buoyancy-driven convection results in a more uniform composition distribution in the InGaSb and Bi_2Te_3-based semiconductor alloys.
基金Supports by the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences(XDA15013200,XDA15013700,XDA15013800,XDA15051200)the China’s Manned Space Station Project(TGJZ800-2-RW024)and the National Natural Science Foundation of China(51327901)。
文摘Activities of space materials science research in China have been continuously supported by two main national programs.One is the China Space Station(CSS)program since 1992,and the other is the Strategic Priority Program(SPP)on Space Science since 2011.In CSS plan in 2019,eleven space materials science experimental projects were officially approved for execution during the construction of the space station.In the SPP Phase Ⅱ launched in 2018,seven pre-research projects are deployed as the first batch in 2018,and one concept study project in 2019.These pre-research projects will be cultivated as candidates for future selection as space experiment projects on the recovery of scientific experimental satellites in the future.A new apparatus of electrostatic levitation system for ground-based research of space materials science and rapid solidification research has been developed under the support of the National Natural Science Foundation of China.In order to promote domestic academic activities and to enhance the advancement of space materials science in China,the Space Materials Science and Technology Division belong to the Chinese Materials Research Society was established in 2019.We also organized scientists to write five review papers on space materials science as a special topic published in the journal Scientia Sinica to provide valuable scientific and technical references for Chinese researchers.
文摘Experiments were carried out on carburizing and temperature rising of the semi steel melt in a plasma induction furnace.Influence of many factors, such as power supply mode,position of the plasma torch and bottom blown gas stirring,on heating efficiency and melt temperature distribution was studied. Melt temperature could be effectively controlled by plasma heating,and carbon content of semi steel melt increased from 1.92 % to 4.58 %, and the utilization rate of carbon reached up to 61.57 % during carburizing of the melt.
基金Supports by the National Natural Science Foundation of China(U1738114)the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences(XDA15051200)+1 种基金the China's Manned Space Station Project(TGJZ800-2-RW024)the Chinese manned space flight pre-research project(030302)
文摘The virtual absence of gravity-dependent phenomena in microgravity allows an in-depth understanding of fundamental events that are normally obscured and therefore are difficult to study quantitatively on Earth.Of particular interest is that the low-gravity environment aboard space provides a unique platform to synthesize alloys of semiconductors with homogeneous composition distributions,on both the macroscopic and microscopic scales,due to the much reduced buoyancy-driven convection.On the other hand,the easy realization of detached solidification in microgravity suppresses the formation of defects such as dislocations and twins,and thereby the crystallographic perfection is greatly increased.Moreover,the microgravity condition offers the possibilities to elucidate the liquid/solid interfacial structures,as well as clarify the microstructure evolution path of the metal alloys(or composites)during the solidification process.Motivated by these facts,growths of compound semiconductors and metal alloys were carried out under microgravity by using the drop tube,or on the scientific platforms of Tiangong-2 and SJ-10.The following illustrates the main results.
基金the National Natural Science Foundation of China (Grant Nos. 50474043 and 50711140385)
文摘The surface tension of molten AlSi20 alloy has been measured by using the sessile drop method at 923―1123 K under argon atmosphere in both heating-up and cooling processes. The result shows that the surface tension of this alloy decreases as long as temperature increases. The results of surface tension and contact angles in heating-up process have differences from those obtained in cooling process, because the metal microstructures have some changes at different temperatures based on the metal genetic theory. The surface tension of molten AlSi20 alloy and that of molten pure aluminum have been compared as well, and the temperature coefficient of AlSi20 alloy is slightly lower than that of Al. The result has been analyzed by the linear scanning analysis with ESEM. The concentration of silicon in most region of the bulk is lower than that of the surface and the addition of Si to pure Al decreases the surface tension of molten pure Al.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50474043, 50711140385)
文摘Wettability of molten Sn-Ag-Cu alloy on Cu substrate has been determined by sessile drop method, as well as its dependence on time and temperature. It was found that the evolution of contact angle at the alloy’s melting point experienced four different stages. Especially, the contact angle was unstable and fluctuant in stage II, and gradually decreased in stage III mainly due to a chemical reaction between Sn-Ag-Cu alloy and Cu substrate. The contact angle decreased with increasing temperature, but increased slightly at 629 K, for another chemical reaction occurred. Interfacial characteristic has been further investigated by examining the sample’s cross section. Intermetallic compounds of Cu6Sn5 and β-Sn phase were found at the interface of Sn-Ag-Cu/Cu.
基金supported by the National Natural Science Foundation of China (50474043 and 50711140385)
文摘The reactive wetting kinetics of a Sn-30Bi-0.5Cu Pb-free solder alloy on a Cu substrate was investigated by the sessile drop method from 493 to 623 K.The triple line frontier,characterized by the drop base radius R was recorded dynamically with a high resolution CCD using different spreading processes in an Ar-H 2 flow.We found a good agreement with the De Gennes model for the relationship between ln(dR/dt) and lnR for the spreading processes at 493 and 523 K.However,a significant deviation from the De Gennes model was found for the spreading processes at 548 and 623 K.Our experimental results show a complicated temperature effect on the spreading kinetics.Intermetallics at the Sn-30Bi-0.5Cu/Cu interface were identified as Cu 6 Sn 5 adjacent to the solder and Cu 3 Sn adjacent to the Cu substrate.The intermetallic compounds effectively enhanced the triple line mobility because of reaction product formation at the diffusion frontier.
