A Ni layer with a thickness of about 100 nm was sputtered on Cu substrates,followed by an ultrasonic seeding with nanodiamond suspension.High-quality diamond film with its crystalline grains close to thermal equilibri...A Ni layer with a thickness of about 100 nm was sputtered on Cu substrates,followed by an ultrasonic seeding with nanodiamond suspension.High-quality diamond film with its crystalline grains close to thermal equilibrium shape was deposited on Cu substrates by hot-filament chemical vapor deposition（HF-CVD）,and the sp2 carbon content was less than 5.56%.The nucleation and growth of diamond film were investigated by micro-Raman spectroscopy,scanning electron microscopy,and X-ray diffraction.The results show that the nucleation density of diamond on the Ni-modified Cu substrates is 10 times higher than that on blank Cu substrates.The enhancement mechanism of the nucleation kinetics by Ni modification layer results from two effects：namely,the nanometer rough Ni-modified surface shows an improved absorption of nanodiamond particles that act as starting points for the diamond nucleation during HF-CVD process;the strong catalytic effect of the Ni-modified surface causes the formation of graphite layer that acts as an intermediate to facilitate diamond nucleation quickly.展开更多
Deposition of diamond inside the trenches or microchannels by chemical vapor deposition （CVD） is limited by the diffusion efficiency of important radical species for diamond growth （H, CH3） and the pore depth of t...Deposition of diamond inside the trenches or microchannels by chemical vapor deposition （CVD） is limited by the diffusion efficiency of important radical species for diamond growth （H, CH3） and the pore depth of the substrate template. By ultrasonic seeding with nanodiamond suspension, three-dimensional （3D） penetration structure diamond was successfully deposited in cylindrical microchannels of Cu template by hot-filament chemical vapor deposition. Micro-Raman spectroscopy and scanning electron microscopy （SEM） were used to characterize diamond film and the effects of microchannel depth on the morphology, grain size and growth rate of diamond film were comprehensively investigated. The results show that diamond quality and growth rate sharply decrease with the increase of the depth of cylindrical microchannel. Individual diamond grain develops gradually from faceted crystals into micrometer cluster, and finally to ballas-type nanocrystalline one. In order to modify the rapid decrease of diamond quality and growth rate, a new hot filament apparatus with a forced gas flow through Cu microchannels was designed. Furthermore, the growth of diamond film by new apparatus was compared with that without a forced gas flow, and the enhancement mechanism was discussed.展开更多
A Ti interlayer with thickness about 300 nm was sputtered on Cu microchannels, followed by an ultrasonic seeding with nanodiamond powders. Adherent diamond film with crystalline grains close to thermal equilibrium sha...A Ti interlayer with thickness about 300 nm was sputtered on Cu microchannels, followed by an ultrasonic seeding with nanodiamond powders. Adherent diamond film with crystalline grains close to thermal equilibrium shape was tightly deposited by hot-filament chemical vapor deposition(HF-CVD). The nucleation and growth of diamond were investigated with micro-Raman spectroscope and field emission scanning electron microscope(FE-SEM) with energy dispersive X-ray detector(EDX). Results show that the nucleation density is found to be up to 1010 cm-2. The enhancement of the nucleation kinetics can be attributed to the nanometer rough Ti interlayer surface. An improved absorption of nanodiamond particles is found, which act as starting points for the diamond nucleation during HF-CVD process. Furthermore, finite element simulation was conducted to understand the thermal management properties of prepared diamond/Cu microchannel heat sink.展开更多
With the TiB2−SiC powders after spray granulation and vacuum calcination as raw materials,the TiB2−SiC coating was prepared by supersonic atmospheric plasma spraying(SAPS).The effects of spraying power and spraying di...With the TiB2−SiC powders after spray granulation and vacuum calcination as raw materials,the TiB2−SiC coating was prepared by supersonic atmospheric plasma spraying(SAPS).The effects of spraying power and spraying distance on the properties of the TiB2−SiC coating were investigated and the fabrication processing of SAPS was optimized.The results show that the sprayed powders after calcination have a uniform particle size distribution,good sphericity and enhanced fluidity.The coating prepared by the calcined powders has a dense structure and high deposition efficiency.When the calcined TiB2−SiC powders are used and the spraying power is 95 kW and the spraying distance is 150 mm during supersonic plasma spraying,the obtained TiB2−SiC coating behaves the best comprehensive performance with the porosity,microhardness,bonding strength and resistivity equal to 5.6%,3.57 GPa,18.3 MPa and 10.8 mΩ·cm,respectively.展开更多
基金Project(20110933K) supported by the State Key Laboratory of Powder Metallurgy,ChinaProject(2012QNZT002) supported by the Freedom Explore Program of Central South University,ChinaProject(CSUZC2012024) supported by the Open-End Fund for the Valuable and Precision Instruments of Central South University,China
文摘A Ni layer with a thickness of about 100 nm was sputtered on Cu substrates,followed by an ultrasonic seeding with nanodiamond suspension.High-quality diamond film with its crystalline grains close to thermal equilibrium shape was deposited on Cu substrates by hot-filament chemical vapor deposition（HF-CVD）,and the sp2 carbon content was less than 5.56%.The nucleation and growth of diamond film were investigated by micro-Raman spectroscopy,scanning electron microscopy,and X-ray diffraction.The results show that the nucleation density of diamond on the Ni-modified Cu substrates is 10 times higher than that on blank Cu substrates.The enhancement mechanism of the nucleation kinetics by Ni modification layer results from two effects：namely,the nanometer rough Ni-modified surface shows an improved absorption of nanodiamond particles that act as starting points for the diamond nucleation during HF-CVD process;the strong catalytic effect of the Ni-modified surface causes the formation of graphite layer that acts as an intermediate to facilitate diamond nucleation quickly.
基金Project(21271188) supported by the Nature Science Foundation of China
文摘Deposition of diamond inside the trenches or microchannels by chemical vapor deposition （CVD） is limited by the diffusion efficiency of important radical species for diamond growth （H, CH3） and the pore depth of the substrate template. By ultrasonic seeding with nanodiamond suspension, three-dimensional （3D） penetration structure diamond was successfully deposited in cylindrical microchannels of Cu template by hot-filament chemical vapor deposition. Micro-Raman spectroscopy and scanning electron microscopy （SEM） were used to characterize diamond film and the effects of microchannel depth on the morphology, grain size and growth rate of diamond film were comprehensively investigated. The results show that diamond quality and growth rate sharply decrease with the increase of the depth of cylindrical microchannel. Individual diamond grain develops gradually from faceted crystals into micrometer cluster, and finally to ballas-type nanocrystalline one. In order to modify the rapid decrease of diamond quality and growth rate, a new hot filament apparatus with a forced gas flow through Cu microchannels was designed. Furthermore, the growth of diamond film by new apparatus was compared with that without a forced gas flow, and the enhancement mechanism was discussed.
基金Project(21271188) supported by the National Natural Science Foundation of China
文摘A Ti interlayer with thickness about 300 nm was sputtered on Cu microchannels, followed by an ultrasonic seeding with nanodiamond powders. Adherent diamond film with crystalline grains close to thermal equilibrium shape was tightly deposited by hot-filament chemical vapor deposition(HF-CVD). The nucleation and growth of diamond were investigated with micro-Raman spectroscope and field emission scanning electron microscope(FE-SEM) with energy dispersive X-ray detector(EDX). Results show that the nucleation density is found to be up to 1010 cm-2. The enhancement of the nucleation kinetics can be attributed to the nanometer rough Ti interlayer surface. An improved absorption of nanodiamond particles is found, which act as starting points for the diamond nucleation during HF-CVD process. Furthermore, finite element simulation was conducted to understand the thermal management properties of prepared diamond/Cu microchannel heat sink.
基金The authors are grateful for the financial supports from Guangdong Academy of Sciences Project(2018GDASCX-0402)of China,Yunnan Science and Technology Plan Project of China(2018IC080)the Natural Science Foundation of Hunan Province of China(2018JJ2524).
文摘With the TiB2−SiC powders after spray granulation and vacuum calcination as raw materials,the TiB2−SiC coating was prepared by supersonic atmospheric plasma spraying(SAPS).The effects of spraying power and spraying distance on the properties of the TiB2−SiC coating were investigated and the fabrication processing of SAPS was optimized.The results show that the sprayed powders after calcination have a uniform particle size distribution,good sphericity and enhanced fluidity.The coating prepared by the calcined powders has a dense structure and high deposition efficiency.When the calcined TiB2−SiC powders are used and the spraying power is 95 kW and the spraying distance is 150 mm during supersonic plasma spraying,the obtained TiB2−SiC coating behaves the best comprehensive performance with the porosity,microhardness,bonding strength and resistivity equal to 5.6%,3.57 GPa,18.3 MPa and 10.8 mΩ·cm,respectively.
