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Carbon spheres with size of 50–300 nm were synthesized via a solvent-thermal reaction with calcium carbide and chloroform
as reactants in a sealed autoclave. The morphologies and microstructures of carbon spheres before and after high temperature
treatment (HTT) were characterized by X-ray diffractometry (XRD), scanning electronic microscopy (SEM), energy diffraction
spectroscopy (EDS), and transmission electron microscopy (TEM). The formation mechanism of carbon spheres was discussed. The
results indicate that the carbon spheres convert to hollow polyhedron through HTT. Carbon spheres are composed of entangled
and curve graphitic layers with short range order similar to cotton structure, and carbon polyhedron with dimension of 50–250
nm and shell thickness of 15–30 nm. The change of solid spheres to hollow polyhedron with branches gives a new evidence for
formation mechanism of hollow carbon spheres. 相似文献
2.
C/C-SiC composites with SiC island distribution were prepared via a new processing route. The fabrication process mainly included
silicon infiltration by ultrasonic vibration, chemical vapor deposition (CVD), siliconizing, liquid phase impregnation and
carbonization. The wear and friction properties were tested by an MM-1000 wet friction machine. The results show that SiC
phases are mainly distributed between carbon fibers and pyrocarbons as well as among the pryocarbons. The dynamic friction
coefficient of the composites decreases gradually from 0.126 to 0.088 with the increase of the surface pressure from 0.5 to
2.5 MPa at the same rotary speed. Furthermore, under the constant surface pressure, the dynamic friction coefficient increases
from 0.114 to 0.126 with the increase of the rotary speed from 1 500 to 2 500 r/min. However, the coefficient decreases to
0.104 when the rotary speed exceeds 4 500 r/min. During the friction process, the friction coefficient of C/C-SiC composite
is between 0.088 and 0.126, and the wear value is zero after 300 times brake testing.
Foundation item: Project(2006CB600901) supported by the Major State Basic Research and Development Program of China; Project(0991015) supported
by Guangxi Science Found, China; Project(200808MS083) supported by Guangxi Education Department Found 相似文献
3.
The droplet size distribution with large-holed compound sieve tray operating in the spray regime is measured by using a double electrical probes technique in a cold model column of 400 mm diameter. The results indicate that the hole F-factor Fo and surface tension are the main factors which influence the liquid dispersion expressed by the Sauter mean diameter D32. A correlation of D32 on surface tension, viscosity, F-factor, weir height and liquid flow rate is proposed. 相似文献
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