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 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
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
The composite coating was prepared by thermal spray welding after making composite powder,which is composed of Ni-based self-melted alloy and AlOceramic powder including nano,sub-micron and micron powders.The influenc...The composite coating was prepared by thermal spray welding after making composite powder,which is composed of Ni-based self-melted alloy and AlOceramic powder including nano,sub-micron and micron powders.The influences of contents and sizes of AlOon the structure and wearability were investigated.The results show that the wear resistance of the coating would be increased greatly by adding AlO,but the spray weldability decreases with increasing AlOcontent.So there is an optimal content of AlOpowder.The composite coating with AlOnano or sub-micron powder of 0.5% has the best abrasive resistance,while the optimal content of AlOmicron powder is 1 %.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
The aging-hardening kinetics of powder metallurgy processed 2014Al alloy and its composite have been studied. The existence of n-SiC particulates leads to the increase of peak hardness. Interestingly, the aginghardeni...The aging-hardening kinetics of powder metallurgy processed 2014Al alloy and its composite have been studied. The existence of n-SiC particulates leads to the increase of peak hardness. Interestingly, the aginghardening peak of the composite takes place at earlier time than that of the unreinforced alloy. Transmission electron microscopy（TEM） studies indicated that the major precipitation phases are Al_5Cu_2Mn_3 and θ′（Al_2Cu）. Besides, Ω phase appeared in both specimens at peak hardening condition, which has been rarely observed previously in aluminum metal matrix composites without Ag. Accelerated aging kinetics and increased peak hardness may be attributed to the higher dislocation density resulted from the mismatch of coefficients of thermal expansion between n-SiC and 2014Al matrix. The results are beneficial to fabricating high performance composites for the application in automobile field such as pistons, driveshaft tubes, brake rotors, bicycle frames, railroad brakes.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 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.
基金Item Sponsored by Provincial Natural Science Foundation of Jiangsu of China(BK2000012)
文摘The composite coating was prepared by thermal spray welding after making composite powder,which is composed of Ni-based self-melted alloy and AlOceramic powder including nano,sub-micron and micron powders.The influences of contents and sizes of AlOon the structure and wearability were investigated.The results show that the wear resistance of the coating would be increased greatly by adding AlO,but the spray weldability decreases with increasing AlOcontent.So there is an optimal content of AlOpowder.The composite coating with AlOnano or sub-micron powder of 0.5% has the best abrasive resistance,while the optimal content of AlOmicron powder is 1 %.
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.
基金Financial support by the National Basic Research Program of China(“973”Program,No.2012CB619600)the National Natural Science Foundation of China(No.51474111)+2 种基金the Science and Technology Development Project of Jilin Province(No.20160519002JH)support came from the Fundamental Research Funds for the Central Universities(JCKY-QKJC02)the Chang Bai Mountain Scholars Program(2013014)
文摘The aging-hardening kinetics of powder metallurgy processed 2014Al alloy and its composite have been studied. The existence of n-SiC particulates leads to the increase of peak hardness. Interestingly, the aginghardening peak of the composite takes place at earlier time than that of the unreinforced alloy. Transmission electron microscopy（TEM） studies indicated that the major precipitation phases are Al_5Cu_2Mn_3 and θ′（Al_2Cu）. Besides, Ω phase appeared in both specimens at peak hardening condition, which has been rarely observed previously in aluminum metal matrix composites without Ag. Accelerated aging kinetics and increased peak hardness may be attributed to the higher dislocation density resulted from the mismatch of coefficients of thermal expansion between n-SiC and 2014Al matrix. The results are beneficial to fabricating high performance composites for the application in automobile field such as pistons, driveshaft tubes, brake rotors, bicycle frames, railroad brakes.
