The dielectric properties of nano Si/C/N composite powder and nano SiC powder at high frequencies have been studied. The nano Si/C/N composite powder and nano SiC powder were synthesized from hexamethyldisilazane ((Me...The dielectric properties of nano Si/C/N composite powder and nano SiC powder at high frequencies have been studied. The nano Si/C/N composite powder and nano SiC powder were synthesized from hexamethyldisilazane ((Me 3Si) 2NH) (Me:CH 3) and SiH 4 C 2H 2 respectively by a laser induced gas phase reaction. The complex permittivities of the nano Si/C/N composite powder and nano SiC powder were measured between 8 2GHz and 12 4GHz. The real and imaginary parts of the complex permittivities of nano Si/C/N composite powder are much higher than those of nano SiC powder. The SiC microcrystalline in the nano Si/C/N composite powder dissolved a great deal of nitrogen. The local structure around Si atoms changed by introducing N into SiC. Carbon atoms around Si were substituted by N atoms. So charged defects and quasi free electrons moved in response to the electric field, diffusion or polarization current resulted from the field propagation. The high ε″and loss factor tgδ(ε″/ε′) of Si/C/N composite powder were due to the dielectric relaxation.展开更多
The effects of microwave sintering and conventional H2 sintering on the microstructure and properties of W-15Cu alloy using ultrafine W-15Cu composite powder fabricated by spray drying ＆ calcining-continuous reductio...The effects of microwave sintering and conventional H2 sintering on the microstructure and properties of W-15Cu alloy using ultrafine W-15Cu composite powder fabricated by spray drying ＆ calcining-continuous reduction technology were investigated. In comparison to the conventional HE sintering processing, microwave sintering to W-15Cu can be achieved at lower sintering temperature and shorter sintering time. Furthermore, higher performances in microwave sintered compacts were obtained, but high microwave sintering temperature or long microwave sintering time could result in coarser microstructures.展开更多
In the present work, composites of poly (methyl methacrylate)/titanium oxide nanoparticles (100/0, 97.5/2.5, 95/5, 92.5/7.5, 90/10 and 0/100 wt/wt%)were prepared to be used as bioequivalent materials according to thei...In the present work, composites of poly (methyl methacrylate)/titanium oxide nanoparticles (100/0, 97.5/2.5, 95/5, 92.5/7.5, 90/10 and 0/100 wt/wt%)were prepared to be used as bioequivalent materials according to their importance broad practical and medical applications. Thermal properties as well as X-ray diffraction analyses were employed to characterize the structure properties of such composite. The obtained results showed variations in the glass transition temperature (Tg), the melting temperature (Tm), shape and area of thermal peaks which were attributed to the different degrees of crystallinity and the existence of interactions between PMMA and TiO2 nanoparticle molecules. The XRD patterns showed sharpening of peaks at different concentrations of nano-TiO2 powder with PMMA. This indicated changes in the crystallinity/amorphosity ratio, and also suggested that the miscibility between the amorphous components of homo- polymers PMMA and nano-TiO2 powder is possible.The results showed that nano-TiO2 powder mix with PMMA can improve the thermal stability of the homo-polymer under investigation, lead- ing to interesting technological applications.展开更多
Two kinds of copper matrix composites reinforced respectively with nano-SiO2 and nano-AlN were prepared by powder metallurgy technique. The microstructure and properties of the composites were studied. The results sho...Two kinds of copper matrix composites reinforced respectively with nano-SiO2 and nano-AlN were prepared by powder metallurgy technique. The microstructure and properties of the composites were studied. The results show that the nano-SiO2 and nano-AlN distribution are uniform and the particulates also refine the grains. With the increase of nano-SiO2 and nano-AlN addition, the density of the both composites decreases, the resistivity increases, whereas the value of hardness reaches the maximum. Softening temperature of the two kinds of composites are above 700℃ which is very high in comparison with pure copper（about 400℃）. But with the same content of nano-SiO2 and nano-AlN particles, the hardness of Cu/AlN is much higher than that of Cu/SiO2, and the resistivity of Cu/AlN is close to that of Cu/SiO2. Thus the reinforcement effect of nano-AlN is better than that of nano-SiO2.展开更多
A new hydrometallurgical process of chlorination-distillation at low temperatures about 100 °C was developed for recovery of valuable metal and environmental protection. This process was used to treat flue dust c...A new hydrometallurgical process of chlorination-distillation at low temperatures about 100 °C was developed for recovery of valuable metal and environmental protection. This process was used to treat flue dust containing arsenic and antimony and satisfactory results were obtained. Over 99% of arsenic and antimony were recovered, and high purity As2O3 and SbCl3 were produced. A metallic alcoholate technique was developed and proved to be of significant to the utilization of antimony resources. Using this technique, a number of antimony oxide powders were prepared, such as high purity and ultrafine Sb2O3, ultrafine Sb2O3-Sb2O5 and Sb2O3-SnO2 composite powders.展开更多
The effect of cationic additive on Cr/nanodiamond plating was studied.Chromium plating was performed in Sargent bath.Morphology of deposit was observed by scanning electron microscope(SEM);microhardness by hardness te...The effect of cationic additive on Cr/nanodiamond plating was studied.Chromium plating was performed in Sargent bath.Morphology of deposit was observed by scanning electron microscope(SEM);microhardness by hardness tester;wear rate by tribometer;amount of diamond in deposit by combustion method and passivity by potentiodynamic scan.Experimental results show that in the presence of cobalt cation,the amount of nanodiamond particle in the deposit is increased.With increasing diamond particle amount,the metallurgical,mechanical and electrochemical properties of Cr/nanodiamond deposit are improved.However,this improvement seems to be constrained.In the presence of 10 g/L of nanodiamond powder and 2.5 g/L of cobalt cation in the bath,the amount of diamond particle in deposit is increased by 4 times;and wear rate of Cr-Co/nanodiamond deposit is decreased by 2-3 times as compared with pure Cr/deposit.The passive current of Cr-Co/nanodiamond composite deposit is decreased from 18 to 8 μA.The morphology of Cr/nanodiamond is smooth remarkably in the presence of cobalt cation.展开更多
Spiky spherical nickel powder with sharp nano-tips on its surface is a kind of excellent fillers for developing pressure-sensitive cement-based composites/sensors for traffic detection,structural health monitoring,and...Spiky spherical nickel powder with sharp nano-tips on its surface is a kind of excellent fillers for developing pressure-sensitive cement-based composites/sensors for traffic detection,structural health monitoring,and border and military security.The sharp nano-tips on the surface of spiky spherical nickel particles can induce field emission and tunneling effects,which leads to the ultrahigh pressure-sensitive responses of the cement-based composites.In this paper,we systematically introduce research on nanotip-induced ultrahigh pressure-sensitive cement-based composites/sensors,with attentions to their pressure-sensitive property and sensing mechanism,pressure-sensitive characteristic model,and smart structure system for traffic detection.展开更多
文摘The dielectric properties of nano Si/C/N composite powder and nano SiC powder at high frequencies have been studied. The nano Si/C/N composite powder and nano SiC powder were synthesized from hexamethyldisilazane ((Me 3Si) 2NH) (Me:CH 3) and SiH 4 C 2H 2 respectively by a laser induced gas phase reaction. The complex permittivities of the nano Si/C/N composite powder and nano SiC powder were measured between 8 2GHz and 12 4GHz. The real and imaginary parts of the complex permittivities of nano Si/C/N composite powder are much higher than those of nano SiC powder. The SiC microcrystalline in the nano Si/C/N composite powder dissolved a great deal of nitrogen. The local structure around Si atoms changed by introducing N into SiC. Carbon atoms around Si were substituted by N atoms. So charged defects and quasi free electrons moved in response to the electric field, diffusion or polarization current resulted from the field propagation. The high ε″and loss factor tgδ(ε″/ε′) of Si/C/N composite powder were due to the dielectric relaxation.
基金Funded by the Project for Science and Technology Plan of Wuhan City(200910321092)the Youth Science Plan for Light of the Morning Sun of Wuhan City (200750731270)
文摘The effects of microwave sintering and conventional H2 sintering on the microstructure and properties of W-15Cu alloy using ultrafine W-15Cu composite powder fabricated by spray drying ＆ calcining-continuous reduction technology were investigated. In comparison to the conventional HE sintering processing, microwave sintering to W-15Cu can be achieved at lower sintering temperature and shorter sintering time. Furthermore, higher performances in microwave sintered compacts were obtained, but high microwave sintering temperature or long microwave sintering time could result in coarser microstructures.
文摘In the present work, composites of poly (methyl methacrylate)/titanium oxide nanoparticles (100/0, 97.5/2.5, 95/5, 92.5/7.5, 90/10 and 0/100 wt/wt%)were prepared to be used as bioequivalent materials according to their importance broad practical and medical applications. Thermal properties as well as X-ray diffraction analyses were employed to characterize the structure properties of such composite. The obtained results showed variations in the glass transition temperature (Tg), the melting temperature (Tm), shape and area of thermal peaks which were attributed to the different degrees of crystallinity and the existence of interactions between PMMA and TiO2 nanoparticle molecules. The XRD patterns showed sharpening of peaks at different concentrations of nano-TiO2 powder with PMMA. This indicated changes in the crystallinity/amorphosity ratio, and also suggested that the miscibility between the amorphous components of homo- polymers PMMA and nano-TiO2 powder is possible.The results showed that nano-TiO2 powder mix with PMMA can improve the thermal stability of the homo-polymer under investigation, lead- ing to interesting technological applications.
文摘Two kinds of copper matrix composites reinforced respectively with nano-SiO2 and nano-AlN were prepared by powder metallurgy technique. The microstructure and properties of the composites were studied. The results show that the nano-SiO2 and nano-AlN distribution are uniform and the particulates also refine the grains. With the increase of nano-SiO2 and nano-AlN addition, the density of the both composites decreases, the resistivity increases, whereas the value of hardness reaches the maximum. Softening temperature of the two kinds of composites are above 700℃ which is very high in comparison with pure copper（about 400℃）. But with the same content of nano-SiO2 and nano-AlN particles, the hardness of Cu/AlN is much higher than that of Cu/SiO2, and the resistivity of Cu/AlN is close to that of Cu/SiO2. Thus the reinforcement effect of nano-AlN is better than that of nano-SiO2.
文摘A new hydrometallurgical process of chlorination-distillation at low temperatures about 100 °C was developed for recovery of valuable metal and environmental protection. This process was used to treat flue dust containing arsenic and antimony and satisfactory results were obtained. Over 99% of arsenic and antimony were recovered, and high purity As2O3 and SbCl3 were produced. A metallic alcoholate technique was developed and proved to be of significant to the utilization of antimony resources. Using this technique, a number of antimony oxide powders were prepared, such as high purity and ultrafine Sb2O3, ultrafine Sb2O3-Sb2O5 and Sb2O3-SnO2 composite powders.
基金funded by KIMM' Project and KOFST (Brain Pool Program)
文摘The effect of cationic additive on Cr/nanodiamond plating was studied.Chromium plating was performed in Sargent bath.Morphology of deposit was observed by scanning electron microscope(SEM);microhardness by hardness tester;wear rate by tribometer;amount of diamond in deposit by combustion method and passivity by potentiodynamic scan.Experimental results show that in the presence of cobalt cation,the amount of nanodiamond particle in the deposit is increased.With increasing diamond particle amount,the metallurgical,mechanical and electrochemical properties of Cr/nanodiamond deposit are improved.However,this improvement seems to be constrained.In the presence of 10 g/L of nanodiamond powder and 2.5 g/L of cobalt cation in the bath,the amount of diamond particle in deposit is increased by 4 times;and wear rate of Cr-Co/nanodiamond deposit is decreased by 2-3 times as compared with pure Cr/deposit.The passive current of Cr-Co/nanodiamond composite deposit is decreased from 18 to 8 μA.The morphology of Cr/nanodiamond is smooth remarkably in the presence of cobalt cation.
文摘Spiky spherical nickel powder with sharp nano-tips on its surface is a kind of excellent fillers for developing pressure-sensitive cement-based composites/sensors for traffic detection,structural health monitoring,and border and military security.The sharp nano-tips on the surface of spiky spherical nickel particles can induce field emission and tunneling effects,which leads to the ultrahigh pressure-sensitive responses of the cement-based composites.In this paper,we systematically introduce research on nanotip-induced ultrahigh pressure-sensitive cement-based composites/sensors,with attentions to their pressure-sensitive property and sensing mechanism,pressure-sensitive characteristic model,and smart structure system for traffic detection.
