Japan started the national project“COURSE 50”for CO_(2) reduction in the 2000s.This project aimed to establish novel technologies to reduce CO_(2) emissions with partially utilization of hydrogen in blast furnace-ba...Japan started the national project“COURSE 50”for CO_(2) reduction in the 2000s.This project aimed to establish novel technologies to reduce CO_(2) emissions with partially utilization of hydrogen in blast furnace-based ironmaking by 30%by around 2030 and use it for practical applications by 2050.The idea is that instead of coke,hydrogen is used as the reducing agent,leading to lower fossil fuel consumption in the process.It has been reported that the reduction behavior of hematite,magnetite,calcium ferrite,and slag in the sinter is different,and it is also considerably influenced by the sinter morphology.This study aimed to investigate the reduction behavior of sinters in hydrogen enriched blast furnace with different mineral morphologies in CO-CO_(2)-H2 mixed gas.As an experimental sample,two sinter samples with significantly different hematite and magnetite ratios were prepared to compare their reduction behaviors.The reduction of wustite to iron was carried out at 1000,900,and 800℃ in a CO-CO_(2)-H2 atmosphere for the mineral morphology-controlled sinter,and the following findings were obtained.The reduction rate of smaller amount of FeO led to faster increase of the reduction rate curve at the initial stage of reduction.Macro-observations of reduced samples showed that the reaction proceeded from the outer periphery of the sample toward the inside,and a reaction interface was observed where reduced iron and wustite coexisted.Micro-observations revealed three layers,namely,wustite single phase in the center zone of the sample,iron single phase in the outer periphery zone of the sample,and iron oxide-derived wustite FeO and iron,or calcium ferritederived wustite'FeO'and iron in the reaction interface zone.A two-interface unreacted core model was successfully applied for the kinetic analysis of the reduction reaction,and obtained temperature dependent expressions of the chemical reaction coefficients from each mineral phases.展开更多
Polycrystalline silicon （poly-Si） thin film has been prepared by means of nickel-disilicide （NiSi2） assisted excimer laser crystallization （ELC）. The process to prepare a sample includes two steps. One step cons...Polycrystalline silicon （poly-Si） thin film has been prepared by means of nickel-disilicide （NiSi2） assisted excimer laser crystallization （ELC）. The process to prepare a sample includes two steps. One step consists of the formation of NiSi2 precipitates by heat-treating the dehydrogenated amorphous silicon （a-Si） coated with a thin layer of Ni. And the other step consists of the formation of poly-Si grains by means of ELC. According to the test results of scanning electron microscopy （SEM）, another grain growth model named two-interface grain growth has been proposed to contrast with the conventional Ni-metal-induced lateral crystallization （Ni-MILC） model and the ELC model. That is, an additional grain growth interface other than that in conventional ELC is formed, which consists of NiSi2 precipitates and a-Si. The processes for grain growth according to various excimer laser energy densities delivered to the a-Si film have been discussed. It is discovered that grains with needle shape and most of a uniform orientation are formed which grow up with NiSi2 precipitates as seeds. The reason for the formation of such grains which are different from that of Ni-MILC without migration of Ni atoms is not clear. Our model and analysis point out a method to prepare grains with needle shape and mostly of a uniform orientation. If such grains are utilized to make thin-film transistor, its characteristics may be improved.展开更多
基金based on results obtained from the“CO_(2)Ultimate Reduction System for Cool Earth 50(COURSE50)Project”commissioned by the New Energy and Industrial Technology Development Organization(NEDO)。
文摘Japan started the national project“COURSE 50”for CO_(2) reduction in the 2000s.This project aimed to establish novel technologies to reduce CO_(2) emissions with partially utilization of hydrogen in blast furnace-based ironmaking by 30%by around 2030 and use it for practical applications by 2050.The idea is that instead of coke,hydrogen is used as the reducing agent,leading to lower fossil fuel consumption in the process.It has been reported that the reduction behavior of hematite,magnetite,calcium ferrite,and slag in the sinter is different,and it is also considerably influenced by the sinter morphology.This study aimed to investigate the reduction behavior of sinters in hydrogen enriched blast furnace with different mineral morphologies in CO-CO_(2)-H2 mixed gas.As an experimental sample,two sinter samples with significantly different hematite and magnetite ratios were prepared to compare their reduction behaviors.The reduction of wustite to iron was carried out at 1000,900,and 800℃ in a CO-CO_(2)-H2 atmosphere for the mineral morphology-controlled sinter,and the following findings were obtained.The reduction rate of smaller amount of FeO led to faster increase of the reduction rate curve at the initial stage of reduction.Macro-observations of reduced samples showed that the reaction proceeded from the outer periphery of the sample toward the inside,and a reaction interface was observed where reduced iron and wustite coexisted.Micro-observations revealed three layers,namely,wustite single phase in the center zone of the sample,iron single phase in the outer periphery zone of the sample,and iron oxide-derived wustite FeO and iron,or calcium ferritederived wustite'FeO'and iron in the reaction interface zone.A two-interface unreacted core model was successfully applied for the kinetic analysis of the reduction reaction,and obtained temperature dependent expressions of the chemical reaction coefficients from each mineral phases.
基金Project supported by the National High Technology Development Program of China （Grant No 2002AA303250） and by the National Natural Science Foundation of China （Grant No 60576056）.
文摘Polycrystalline silicon （poly-Si） thin film has been prepared by means of nickel-disilicide （NiSi2） assisted excimer laser crystallization （ELC）. The process to prepare a sample includes two steps. One step consists of the formation of NiSi2 precipitates by heat-treating the dehydrogenated amorphous silicon （a-Si） coated with a thin layer of Ni. And the other step consists of the formation of poly-Si grains by means of ELC. According to the test results of scanning electron microscopy （SEM）, another grain growth model named two-interface grain growth has been proposed to contrast with the conventional Ni-metal-induced lateral crystallization （Ni-MILC） model and the ELC model. That is, an additional grain growth interface other than that in conventional ELC is formed, which consists of NiSi2 precipitates and a-Si. The processes for grain growth according to various excimer laser energy densities delivered to the a-Si film have been discussed. It is discovered that grains with needle shape and most of a uniform orientation are formed which grow up with NiSi2 precipitates as seeds. The reason for the formation of such grains which are different from that of Ni-MILC without migration of Ni atoms is not clear. Our model and analysis point out a method to prepare grains with needle shape and mostly of a uniform orientation. If such grains are utilized to make thin-film transistor, its characteristics may be improved.
