The oxidation of two phase Cu Cr alloys containing 25% and 50% Cr prepared by powder metallurgy (PM) with a rather uniform two phase microstructure has been studied at 700～900 ℃ under oxygen pressure below the stabi...The oxidation of two phase Cu Cr alloys containing 25% and 50% Cr prepared by powder metallurgy (PM) with a rather uniform two phase microstructure has been studied at 700～900 ℃ under oxygen pressure below the stability of the copper oxides. The two PM alloys oxidized very slowly and formed only external Cr 2O 3 scales rather than undergoing an internal oxidation of chromium. This result is attributed mainly to a supply of chromium from the small Cr rich particles dispersed within the Cu rich phase. The oxidation kinetics of the two PM Cu Cr alloys approximately followed the parabolic rate law. The scaling rates are of the same order as those measured for pure chromium under the same oxygen pressure, but smaller than those for the alloys of similar composition prepared by normal arc melting techniques, whose compositions were largely non uniform. The results are interpreted in terms of the two phase nature of these alloys.展开更多
目的:研究并分析昆明市及周边地区高海拔条件下早产儿视网膜病变(retinopathy of prematurity,ROP)患儿母亲孕期的相关风险因素。方法:使用宽视野数字化眼底照相机(RetcamⅡ),对2010-05/2014-12到昆明市儿童医院眼科就诊的早产儿及部分...目的:研究并分析昆明市及周边地区高海拔条件下早产儿视网膜病变(retinopathy of prematurity,ROP)患儿母亲孕期的相关风险因素。方法:使用宽视野数字化眼底照相机(RetcamⅡ),对2010-05/2014-12到昆明市儿童医院眼科就诊的早产儿及部分足月小样儿(出生体质量均≤2000g)共1010例进行视网膜检查,收集ROP的发病数据及患儿母亲孕期相关资料,对所获得的各项数据进行统计学处理和分析。结果:早产儿1010例中发现ROP患儿139例278眼,患病率为13.76%,其中1期病变80例(57.55%),2期病变42例(30.22%),3期病变9例(6.47%),4期病变4例(2.88%),5期病变4例(2.88%)。阈值病变9例(6.47%)。ROP组与正常眼底组早产儿在出生体质量、胎龄、宫内窘迫、多胎妊娠方面的差异均有统计学意义(P<0.05)。结论:在昆明市高海拔低氧分压地区,ROP患病率为13.76%,低出生体重、小胎龄、宫内窘迫、多胎妊娠是ROP发生的主要孕期因素。展开更多
A new technology was put forward to deal with the carbonyl slag at low acidity and low oxygen pressure in the kettle. With the orthogonal experiments for analyzing the sequence of four factors and some single factor e...A new technology was put forward to deal with the carbonyl slag at low acidity and low oxygen pressure in the kettle. With the orthogonal experiments for analyzing the sequence of four factors and some single factor experiments for the best conditions. The best conditions are used for extracting nickel, cobalt and copper and enriching precious metals: the cupric ion concentration is 5 g/L; and pH=6; the sulfur coefficient is 1.4; the oxygen pressure is 0.08 MPa; the time bubbling oxygen is 20 min; the ratio of liquid to solid is 8:1; the leaching time is 2 h; the heating time is 2.5 h. The leaching rates of nickel and cobalt are more than 98% and that of copper is above 97%. Nickel and cobalt can be separated efficiently from copper and precious metals from the carbonyl slag. Moreover, its leaching liquor has less copper. Nickel and cobalt can be reclaimed only once. During the whole process, the leaching rates of Au and Ag are more than 99.9%, while other precious metals are still in the residue without any loss.展开更多
The influence of Ce addition on the oxidation behavior of 25Cr20Ni alloy at 950 oC under low oxygen partial pressure was inves-tigated. The oxidized samples were characterized by using X-ray diffraction （XRD）, scann...The influence of Ce addition on the oxidation behavior of 25Cr20Ni alloy at 950 oC under low oxygen partial pressure was inves-tigated. The oxidized samples were characterized by using X-ray diffraction （XRD）, scanning electron microscopy （SEM）, energy dispersive X-ray spectroscopy （EDS）, and scratch tester to obtain the oxide phases, morphology, thickness, composition and adhesion property of the oxide scales. The experiment results indicated that a small amount of Ce addition （0.02 wt.% or 0.05 wt.%） promoted oxidation resistance and inhibited the growth of the needlelike oxide. The Ce addition also decreased the formation of MnCr2O4 but promoted the SiO2 formation un-derneath the Cr2O3, which largely contributed to the improvement of oxide scale spallation resistance. For the sample with 0.3 wt.% Ce addi-tion, the oxidation rate significantly increased and the spallation resistance of the oxide scale decreased.展开更多
文摘The oxidation of two phase Cu Cr alloys containing 25% and 50% Cr prepared by powder metallurgy (PM) with a rather uniform two phase microstructure has been studied at 700～900 ℃ under oxygen pressure below the stability of the copper oxides. The two PM alloys oxidized very slowly and formed only external Cr 2O 3 scales rather than undergoing an internal oxidation of chromium. This result is attributed mainly to a supply of chromium from the small Cr rich particles dispersed within the Cu rich phase. The oxidation kinetics of the two PM Cu Cr alloys approximately followed the parabolic rate law. The scaling rates are of the same order as those measured for pure chromium under the same oxygen pressure, but smaller than those for the alloys of similar composition prepared by normal arc melting techniques, whose compositions were largely non uniform. The results are interpreted in terms of the two phase nature of these alloys.
文摘目的:研究并分析昆明市及周边地区高海拔条件下早产儿视网膜病变(retinopathy of prematurity,ROP)患儿母亲孕期的相关风险因素。方法:使用宽视野数字化眼底照相机(RetcamⅡ),对2010-05/2014-12到昆明市儿童医院眼科就诊的早产儿及部分足月小样儿(出生体质量均≤2000g)共1010例进行视网膜检查,收集ROP的发病数据及患儿母亲孕期相关资料,对所获得的各项数据进行统计学处理和分析。结果:早产儿1010例中发现ROP患儿139例278眼,患病率为13.76%,其中1期病变80例(57.55%),2期病变42例(30.22%),3期病变9例(6.47%),4期病变4例(2.88%),5期病变4例(2.88%)。阈值病变9例(6.47%)。ROP组与正常眼底组早产儿在出生体质量、胎龄、宫内窘迫、多胎妊娠方面的差异均有统计学意义(P<0.05)。结论:在昆明市高海拔低氧分压地区,ROP患病率为13.76%,低出生体重、小胎龄、宫内窘迫、多胎妊娠是ROP发生的主要孕期因素。
文摘A new technology was put forward to deal with the carbonyl slag at low acidity and low oxygen pressure in the kettle. With the orthogonal experiments for analyzing the sequence of four factors and some single factor experiments for the best conditions. The best conditions are used for extracting nickel, cobalt and copper and enriching precious metals: the cupric ion concentration is 5 g/L; and pH=6; the sulfur coefficient is 1.4; the oxygen pressure is 0.08 MPa; the time bubbling oxygen is 20 min; the ratio of liquid to solid is 8:1; the leaching time is 2 h; the heating time is 2.5 h. The leaching rates of nickel and cobalt are more than 98% and that of copper is above 97%. Nickel and cobalt can be separated efficiently from copper and precious metals from the carbonyl slag. Moreover, its leaching liquor has less copper. Nickel and cobalt can be reclaimed only once. During the whole process, the leaching rates of Au and Ag are more than 99.9%, while other precious metals are still in the residue without any loss.
基金supported by the Basic Research Program of the State Key Laboratory of Heavy Oil Processing (200809),China University of Petroleum, Beijing, China
文摘The influence of Ce addition on the oxidation behavior of 25Cr20Ni alloy at 950 oC under low oxygen partial pressure was inves-tigated. The oxidized samples were characterized by using X-ray diffraction （XRD）, scanning electron microscopy （SEM）, energy dispersive X-ray spectroscopy （EDS）, and scratch tester to obtain the oxide phases, morphology, thickness, composition and adhesion property of the oxide scales. The experiment results indicated that a small amount of Ce addition （0.02 wt.% or 0.05 wt.%） promoted oxidation resistance and inhibited the growth of the needlelike oxide. The Ce addition also decreased the formation of MnCr2O4 but promoted the SiO2 formation un-derneath the Cr2O3, which largely contributed to the improvement of oxide scale spallation resistance. For the sample with 0.3 wt.% Ce addi-tion, the oxidation rate significantly increased and the spallation resistance of the oxide scale decreased.
