Fabrication Of Diamond Composites By Spark Plasma Sintering

Diamond/Si、Diamond/Si/Ti、Diamond/B/Ti and Diamond/B/Co composites havebeen successfully fabricated by Spark plasma sintering （SPS）-reactive synthesis method. Ithas been reported that under the absence of oxygen atmosphere, micron-grade diamondparticles are susceptible to allotropic reconversion to graphitic sp2or amorphous carbondiamond began to transform into graphite at the sintering temperature of750°C, and atthe temperature of1400°C, graphitization of diamond occurs on the surface of thediamond particles which reduced the mechanical properties of the composites. SPS to acertain extent inhibited the chance of the graphitization of diamond due to its shortsintering time. To further avoid the emerging of the graphite as a separate phase, thecarbide forming elements of Si、Ti、Co、B reacted with carbon （diamond and graphite）generating the intermediate formation of SiC、TiC and B₄C chemically bonded diamondcomposites. Moreover, Si、Ti、Co would melt at the sintering temperature which benefitedthe infiltrating to the intervals of the diamond particles, thereby the relative densities ofthe composites were enhanced and the reactions between the carbide forming elementsand diamond was promoted.The results showed that the Diamond/Si、 Diamond/Si/Ti、 Diamond/B/Ti andDiamond/B/Co composites which were fabricated by SPS-reactive synthesis methodpossessed excellent mechanical properties. Especially, the relative densities and thebending strengths of the D/Si/Ti composites sintered at1650°C has achieved up to99%and440MPa respectively. And the results analyzed by XRD and Raman indicated that thegraphite emerged as a separate phase in the composites until the temperature up to1700°C at which the graphitization of diamond would occur inevitably, demonstrating theeffective consumption of graphite by the carbide forming elements.