A stable δ- and β-bismuth trioxide was prepared at room temperature by vacuum vapor-phase oxidation. The average crystal size of products was 14.6 nm (by XRD), the d(0.5) value was in the range from 62 nm to 69 nm, ...A stable δ- and β-bismuth trioxide was prepared at room temperature by vacuum vapor-phase oxidation. The average crystal size of products was 14.6 nm (by XRD), the d(0.5) value was in the range from 62 nm to 69 nm, and geometric standard deviation(GSD) was from 1.42 to 1.64. The results show that δ-Bi2O3 is formed when quenching rates is rapid and β-Bi2O3 is formed when it is slow. The size of grains increases with rising reaction temperature, flow rate of carrier gas, residual pressure of system and longer growing time of grains.展开更多
Nanometer TiO 2 powders were obtained from TiOSO 4 and studied by XRD, TEM and BET. The result indicated that pH and heat treatment temperature have great effects on their grain size and crystal phase structu...Nanometer TiO 2 powders were obtained from TiOSO 4 and studied by XRD, TEM and BET. The result indicated that pH and heat treatment temperature have great effects on their grain size and crystal phase structure. Annealed at 500 ℃, nanometer TiO 2 with a specific surface area of 101.39 m 2 ·g -1 and a grain size about 10 nm were obtained(pH=5); and with a specific surface area of 95.48 m 2 ·g -1 and a grain size about 30 nm were obtained(pH=10). The research indicated that crystal phase transformation of rutile at 750 ℃made great promotion in grain size growth.展开更多
Nanometer TiO 2 powders were obtained from TiOSO 4 and studied by XRD, TEM and BET. The result indicated that pH and heat treatment temperature have great effects on their grain size and crystal phase structu...Nanometer TiO 2 powders were obtained from TiOSO 4 and studied by XRD, TEM and BET. The result indicated that pH and heat treatment temperature have great effects on their grain size and crystal phase structure. Annealed at 500 ℃, nanometer TiO 2 with a specific surface area of 101.39 m 2 ·g -1 and a grain size about 10 nm were obtained(pH=5); and with a specific surface area of 95.48 m 2 ·g -1 and a grain size about 30 nm were obtained(pH=10). The research indicated that crystal phase transformation of rutile at 750 ℃made great promotion in grain size growth.展开更多
Strengthening due to precipitation of Cu in the a-Fe matrix is an important phenomenon utilized in the design of HSLA steels. In the present work, the microstructure of supersaturated solid solution in Fe-1.18%Cu bina...Strengthening due to precipitation of Cu in the a-Fe matrix is an important phenomenon utilized in the design of HSLA steels. In the present work, the microstructure of supersaturated solid solution in Fe-1.18%Cu binary alloy was investigated by means of high resolution electron microscopy. The results indicated that the solid solution was heterogeneous, there were lots of Cu atom clusters, which consisted of diffractive stripe microstructure similar to twin crystal. Orientation deviation was observed between two （110）o planes in diffractive stripes, which results in light and shade contrast. Furthermore, formation mechanisms of the nanometre stripe microstructure were discussed in terms of the interaction of Cu and Fe atoms in the Fe-Cu binary alloys.展开更多
Cu precipitation behaviors in two Cu-bearing austenitic antibacterial stainless steels,type 304 and type 317L,were systematically studied by using relatively simple methods for materials analysis,including micro-hardn...Cu precipitation behaviors in two Cu-bearing austenitic antibacterial stainless steels,type 304 and type 317L,were systematically studied by using relatively simple methods for materials analysis,including micro-hardness,electrical resistivity,electrochemical impedance spectroscopy,X-ray diffraction and differential scanning calorimetry.The results indicated that after aging at elevated temperature,the micro-hardness, electrical resistivity,electrochemical impedance and lattice constant of the steel were all varied at different degrees due to the precipitation and growth of Cu-rich phases.The results also showed that the heat evolution during the process of Cu precipitation could be sensitively detected by means of differential scanning calorimetry,obtainning the starting temperature,peak temperature,peak area of the Cu-rich precipitation,and even the activation energy by calculation.The results confirmed that the Cu-rich phased precipitation in the Cu-bearing austenitic antibacterial stainless steel should be a thermal activation process controlled by Cu diffusion.All the materials analysis methods used in this study can be more simple and effective for application in R & D of the Cu-bearing antibacterial stainless steels.展开更多
The decomposed characteristic of nanometer ZnO precursor compound was studied. From the research, the decomposed temperature of nanometer precursor compound of ZnO is about 230 ℃ and it may be completely decompounded...The decomposed characteristic of nanometer ZnO precursor compound was studied. From the research, the decomposed temperature of nanometer precursor compound of ZnO is about 230 ℃ and it may be completely decompounded at 350 ℃. By means of the kinetics theory, the dynamics equation of precursor compound of nanometer ZnO was obtained. Activation energy is approximately 789.83±40 J·mol -1, reaction order is about 3, and pre-exponential factor is 0.0696 mg·s -1.展开更多
A study was conducted on the formation of a Cu-rich phase at the scale/steel interface of Cu-containing steel by high-temperature oxidation with varying amounts of A1 and Ni. Both A1 and Ni were found to help decrease...A study was conducted on the formation of a Cu-rich phase at the scale/steel interface of Cu-containing steel by high-temperature oxidation with varying amounts of A1 and Ni. Both A1 and Ni were found to help decrease the amount of the Cu-rich phase at the interface. Analysis of the effects by these elements was conducted in terms of the melting point of the Cu-rich phase, the solid solubility of Cu in austenite, the rate of oxidation, and the amount of Cu-rich phase occlusions in scales. Because of selective oxidation,in which A1 and Ni are oxidized more and less preferentially than Fe, respectively, A1 was weakly concentrated at the interface whereas Ni was more heavily concentrated in it. Thus, A1 exerted no effect on the melting point of the Cu-rich phase, whereas Ni raised its melting point. A1, which was applied at contents of less than 2.0%, decreased the solubility of Cu in austenite but this effect weakened at the interface during oxidation. By contrast,Ni increased the solubility of Cu, and this effect was strengthened with oxidation. Both A1 and Ni promoted internal oxidation and the formation of occlusions.展开更多
基金Project(03SSY4056) supported by the Bureau of Science and Technology of Hunan Province, China Project(04C034) supported by the Bureau of Education of Hunan Province, China
文摘A stable δ- and β-bismuth trioxide was prepared at room temperature by vacuum vapor-phase oxidation. The average crystal size of products was 14.6 nm (by XRD), the d(0.5) value was in the range from 62 nm to 69 nm, and geometric standard deviation(GSD) was from 1.42 to 1.64. The results show that δ-Bi2O3 is formed when quenching rates is rapid and β-Bi2O3 is formed when it is slow. The size of grains increases with rising reaction temperature, flow rate of carrier gas, residual pressure of system and longer growing time of grains.
文摘Nanometer TiO 2 powders were obtained from TiOSO 4 and studied by XRD, TEM and BET. The result indicated that pH and heat treatment temperature have great effects on their grain size and crystal phase structure. Annealed at 500 ℃, nanometer TiO 2 with a specific surface area of 101.39 m 2 ·g -1 and a grain size about 10 nm were obtained(pH=5); and with a specific surface area of 95.48 m 2 ·g -1 and a grain size about 30 nm were obtained(pH=10). The research indicated that crystal phase transformation of rutile at 750 ℃made great promotion in grain size growth.
文摘Nanometer TiO 2 powders were obtained from TiOSO 4 and studied by XRD, TEM and BET. The result indicated that pH and heat treatment temperature have great effects on their grain size and crystal phase structure. Annealed at 500 ℃, nanometer TiO 2 with a specific surface area of 101.39 m 2 ·g -1 and a grain size about 10 nm were obtained(pH=5); and with a specific surface area of 95.48 m 2 ·g -1 and a grain size about 30 nm were obtained(pH=10). The research indicated that crystal phase transformation of rutile at 750 ℃made great promotion in grain size growth.
基金Item Sponsored by National Natural Science Foundation of China (50361001)
文摘Strengthening due to precipitation of Cu in the a-Fe matrix is an important phenomenon utilized in the design of HSLA steels. In the present work, the microstructure of supersaturated solid solution in Fe-1.18%Cu binary alloy was investigated by means of high resolution electron microscopy. The results indicated that the solid solution was heterogeneous, there were lots of Cu atom clusters, which consisted of diffractive stripe microstructure similar to twin crystal. Orientation deviation was observed between two （110）o planes in diffractive stripes, which results in light and shade contrast. Furthermore, formation mechanisms of the nanometre stripe microstructure were discussed in terms of the interaction of Cu and Fe atoms in the Fe-Cu binary alloys.
文摘Cu precipitation behaviors in two Cu-bearing austenitic antibacterial stainless steels,type 304 and type 317L,were systematically studied by using relatively simple methods for materials analysis,including micro-hardness,electrical resistivity,electrochemical impedance spectroscopy,X-ray diffraction and differential scanning calorimetry.The results indicated that after aging at elevated temperature,the micro-hardness, electrical resistivity,electrochemical impedance and lattice constant of the steel were all varied at different degrees due to the precipitation and growth of Cu-rich phases.The results also showed that the heat evolution during the process of Cu precipitation could be sensitively detected by means of differential scanning calorimetry,obtainning the starting temperature,peak temperature,peak area of the Cu-rich precipitation,and even the activation energy by calculation.The results confirmed that the Cu-rich phased precipitation in the Cu-bearing austenitic antibacterial stainless steel should be a thermal activation process controlled by Cu diffusion.All the materials analysis methods used in this study can be more simple and effective for application in R & D of the Cu-bearing antibacterial stainless steels.
文摘The decomposed characteristic of nanometer ZnO precursor compound was studied. From the research, the decomposed temperature of nanometer precursor compound of ZnO is about 230 ℃ and it may be completely decompounded at 350 ℃. By means of the kinetics theory, the dynamics equation of precursor compound of nanometer ZnO was obtained. Activation energy is approximately 789.83±40 J·mol -1, reaction order is about 3, and pre-exponential factor is 0.0696 mg·s -1.
文摘A study was conducted on the formation of a Cu-rich phase at the scale/steel interface of Cu-containing steel by high-temperature oxidation with varying amounts of A1 and Ni. Both A1 and Ni were found to help decrease the amount of the Cu-rich phase at the interface. Analysis of the effects by these elements was conducted in terms of the melting point of the Cu-rich phase, the solid solubility of Cu in austenite, the rate of oxidation, and the amount of Cu-rich phase occlusions in scales. Because of selective oxidation,in which A1 and Ni are oxidized more and less preferentially than Fe, respectively, A1 was weakly concentrated at the interface whereas Ni was more heavily concentrated in it. Thus, A1 exerted no effect on the melting point of the Cu-rich phase, whereas Ni raised its melting point. A1, which was applied at contents of less than 2.0%, decreased the solubility of Cu in austenite but this effect weakened at the interface during oxidation. By contrast,Ni increased the solubility of Cu, and this effect was strengthened with oxidation. Both A1 and Ni promoted internal oxidation and the formation of occlusions.
