Papers by Author: Ming Zhi Wang

Abstract: Onion-like carbon (OLC) was fabricated by annealing nanodiamond at temperatures ranging from 500°C to 1400°C. At 800°C, nanodiamond was completely transformed into amorphous carbon. At 900°C, OLC began appearing. As the annealing temperature increased from 1000°C to 1200°C, OLC particles size became larger and larger and the amorphous carbon coexisted in the center of the OLC particle became less and less. At 1400°C, all the amorphous carbon was transformed into the OLC.

Abstract: SiC/Ti3SiC2/TiC composites were fabricated by means of pressureless sintering using the 3TiC/2.2Si/0.2Al as raw materials. At the temperatures from 1000°C to 1200 °C, the main phase of the composite synthesized was Ti3SiC2. At the same time, there was a small amount of TiC and SiC existing. The composite had loose microstructure. At the temperature of 1300 °C, the TiC and Ti3SiC2 were the primary phases. And the SiC was the second phase. The SEM images showed that there were two kinds of microstructures in the composite. One was the Ti3SiC2 and the TiC platelets on its surface, another one was the TiC and the SiC equixed grains in its interior.

Abstract: Polycrystalline cubic boron nitride (PCBN) is formed by sintering cubic boron nitride particles (cBN) at high temperature and high pressure. In this process, a network of cBN particles is formed by intergrowth and bridging between the particle phases. The response of the aggregate to applied stresses in process such as hard machining, will therefore principally involve the deformation of this skeletal structure. In this work, the microstructure and hot hardness and adhesion properties of three high-density PCBN aggregates were comparatively studied. The results were correlated to their cutting performance and wear modes in machining a carbide-based hardfacing material.

Abstract: In this paper, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and sintering process were used to characterize Cu-Fe compound powders milled for different times. The increment of defects and the change of granularity, grain size and crystal structure were discussed. Mechanical Alloying (MA) influence on the sintering of Cu-Fe compound powders was analyzed. The results showed that, the refinement of the powders and the increment of defects such as interface and dislocation induced the energy storage. The stored energy released in the sintering process, which reduced the activation energy of vacancy and the activation energy of diffusion. So the sintering temperature was reduced and the structure, strength and hardness of specimens were improved.

Abstract: Fracture surface and surface of two kind of membrane of antibacterial bone china, which includes 3% and 5% of weight of composite phosphate containing rare earth respectively, were characterized by SEM and nanoindenter, respectively. Nanohardness and nanoscale friction coefficients were measured by nanoindenter. Friction coefficients were conducted at the maximal load being 300un,500un,1000un and scratching speed 15um/s, 0.75um/s, 0.5um/s, respectively. The nanohardness and friction coefficients of ceramic membrane including 3% and 5% of rare earths are 2.03GPa,0.18282 and 8.54GPa,0.051998, respectively. The two kind of ceramic membrane has stable nanotribology property. Obvious plastic flow and pile-up scratch impression of ceramic membrane including 3% rare earths is observed by AFM in situ imaging, but scratch impression of 5% has no plastic flow and take on the sink-in topography. Nanohardness and friction coefficients of this two kind of ceramic membrane have strong relationships each other but weak relations with elastic modulus.