Carbon nanotubes （CNTs） were coated by tungsten using metal organic chemical vapor deposition. Magnetic stirring was employed to disperse the W-coated CNTs （W-CNTs） in a Cu matrix, and then, the mixed powders were...Carbon nanotubes （CNTs） were coated by tungsten using metal organic chemical vapor deposition. Magnetic stirring was employed to disperse the W-coated CNTs （W-CNTs） in a Cu matrix, and then, the mixed powders were consolidated by spark plasma sintering. The W-CNTs obtained a uniform dispersion within the Cu matrix when the W-CNT content was less than 5.0vo1%, but high content of W-CNTs （10vol%） resulted in the presence of clusters. The W-CNT/Cu composites containing low content of W-CNTs （〈5.0vol%） exhibited a higher thermal conductivity than the sintered pure Cu, while the CNT/Cu composites exhibited no increase in thermal conductivity after the incorporation of uncoated CNTs. The W-CNT content was found to play a crucial role in determining the thermal conductivity of the W-CNT/Cu composites. The thermal conductivity of the W-CNT/Cu composites increased first and then decreased with the W-CNT content increasing. When the W-CNT content was 2.5vo1%, the W-CNT/Cu composite obtained the maximum value of thermal conductivity. The thermal resistance of the （W-CNT）-Cu interface was predicted in terms of Maxwell-Gamett effective medium approximation, and its calculated value was about 3.0× 10-9 m2.K.W-l.展开更多
SiC whiskers with 'rosary bead' morphology were synthesized using suitablesilicon source and carbon source through solid reaction at the temperature above 1537 K. Thediameter and length of the SiC whiskers wer...SiC whiskers with 'rosary bead' morphology were synthesized using suitablesilicon source and carbon source through solid reaction at the temperature above 1537 K. Thediameter and length of the SiC whiskers were about 0.1-1.0 μm and 20-100 μm, respectively. Thelargest diameter of their enlarged ends of the whiskers was about 0.2-1.0μm, and it gradually andsmoothly decreased to the size of the plain part of the whiskers. The results of X-ray diffractionanalysis show that the crystalline structure of the obtained SiC whiskers is β-SiC. It isconsidered that the SiC whiskers grow via a vapor-solid mechanism.展开更多
Abrasive wear characteristics of polyethylene, polystyrene,polymethylmethacrylate, nylon 1010 and polyvinyl chloride were investigated. The volume relativewear resistance coefficients of these thermoplastic polymers a...Abrasive wear characteristics of polyethylene, polystyrene,polymethylmethacrylate, nylon 1010 and polyvinyl chloride were investigated. The volume relativewear resistance coefficients of these thermoplastic polymers are 18%-35% (hardened and lowtemperature tempered steel 45 was used as a comparing material), and have a linear correlation withsquare roots of their cohesive energy densities. The coefficients of linear correlation is 0.949.Wear morphologies were observed by scanning electron microscope (SEM). Main wear mechanism of thethermoplastic polymers includes brittle breaking for the hard and brittle polymers & plowing andfatiguing for the soft and tough ones.展开更多
基金supported by the National High-Tech Research and Development Program of China (No.2009AA03Z116)the National Natural Science Foundation of China (No.50971020)
文摘Carbon nanotubes （CNTs） were coated by tungsten using metal organic chemical vapor deposition. Magnetic stirring was employed to disperse the W-coated CNTs （W-CNTs） in a Cu matrix, and then, the mixed powders were consolidated by spark plasma sintering. The W-CNTs obtained a uniform dispersion within the Cu matrix when the W-CNT content was less than 5.0vo1%, but high content of W-CNTs （10vol%） resulted in the presence of clusters. The W-CNT/Cu composites containing low content of W-CNTs （〈5.0vol%） exhibited a higher thermal conductivity than the sintered pure Cu, while the CNT/Cu composites exhibited no increase in thermal conductivity after the incorporation of uncoated CNTs. The W-CNT content was found to play a crucial role in determining the thermal conductivity of the W-CNT/Cu composites. The thermal conductivity of the W-CNT/Cu composites increased first and then decreased with the W-CNT content increasing. When the W-CNT content was 2.5vo1%, the W-CNT/Cu composite obtained the maximum value of thermal conductivity. The thermal resistance of the （W-CNT）-Cu interface was predicted in terms of Maxwell-Gamett effective medium approximation, and its calculated value was about 3.0× 10-9 m2.K.W-l.
文摘SiC whiskers with 'rosary bead' morphology were synthesized using suitablesilicon source and carbon source through solid reaction at the temperature above 1537 K. Thediameter and length of the SiC whiskers were about 0.1-1.0 μm and 20-100 μm, respectively. Thelargest diameter of their enlarged ends of the whiskers was about 0.2-1.0μm, and it gradually andsmoothly decreased to the size of the plain part of the whiskers. The results of X-ray diffractionanalysis show that the crystalline structure of the obtained SiC whiskers is β-SiC. It isconsidered that the SiC whiskers grow via a vapor-solid mechanism.
文摘Abrasive wear characteristics of polyethylene, polystyrene,polymethylmethacrylate, nylon 1010 and polyvinyl chloride were investigated. The volume relativewear resistance coefficients of these thermoplastic polymers are 18%-35% (hardened and lowtemperature tempered steel 45 was used as a comparing material), and have a linear correlation withsquare roots of their cohesive energy densities. The coefficients of linear correlation is 0.949.Wear morphologies were observed by scanning electron microscope (SEM). Main wear mechanism of thethermoplastic polymers includes brittle breaking for the hard and brittle polymers & plowing andfatiguing for the soft and tough ones.
