Articles you may be interested inIn situ structure characterization of Pb(Yb1/2Nb1/2)O3-PbTiO3 crystals under high pressure-temperature Appl.Structure and properties of superelastic hard carbon phase created in fullerene-metal composites by high temperature-high pressure treatment
Treatment of a fullerene soot extract and metal (Co) powder mixture under pressure of 5 and 8 GPa at 1000 °C leads to the transformation of fullerites into superelastic hard phase (SHP) and to simultaneous sintering of the powder mixture to nonporous composite material reinforced by the SHP particles. The structure of the SHP particles reveals a topological relation to the initial fullerite crystal morphology. Upon indentation, the SHP particles demonstrate an elastic recovery of up to 96%. The universal microhardness of the SHP particles HU = 26 GPa, and their microhardness HV = 35 GPa. A high ratio between the microhardness and elastic modulus (HV/E = 0.19-0.21) of the SHP particles makes them perspective candidates for design of materials with superior wear resistance and tribological properties.
Instrumented indentation methods have been used to study the effect of the loading rate and holding time at different maximum loads on the indentation characteristics of superelastic hard carbon particles reinforcing metal matrix composite materials. The properties of the carbon particles prepared in fullerite-metal powder mixtures by high-pressure synthesis substantially differ as a function of synthesis parameters (P, T) and the initial fullerite characteristics (C60 in crystalline or amorphous state). The indentation creep C
IT decreases with increasing F
max (500-2000 mN) and increases with holding time (60-600 s). The harder carbon particles formed from amorphous fullerite are characterized by higher indentation creep CIT and deeper penetration at constant load. Such creep behavior correlates with different elastic recovery characteristics of the particles upon indentation.
The electrical contact resistance and the electric erosion wear resistance of the composite mate rial consisting of a copper matrix reinforced by superelastic hard carbon are studied. The reinforcing of CM by carbon particles, which have a unique combination of mechanical properties (high microhardness of 30-35 GPa, elastic modulus of 180-200 GPa, and a high ratio of microhardness to elastic modulus (HV 50 /E > 0.15)), ensures good contact characteristics of the material. The minimum electrical contact resistance of CM is comparable with the electrical contact resistance of a reference sample made of gold. The electric erosion wear resistance of the CM is more than threefold that of chrome bronze, which is a widely used for high cur rent electrical contacts.
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