Zirconium diboride (ZrB2) is a good candidate among all nanocomposites of high-temperature ceramic matrix. The compound has wide applications in thermal protection systems of aerospace, ultrasonic planes, propellant parts and other industries such as plasma-arc furnace electrode and other components.
Dr. Mehdi Shahedi Asl, one of the coauthors of the paper on the research told Mehr News that developing of Zirconium diboride as a member of the high-temperature ceramic had been facing difficulties, inter alia, of attaining a full density of nonporous structure and high fracture toughness which “hits the ability to attract the energy and thus delaying the material decay.”
“We use nanographite flakes to improve full density and high fracture toughness in zirconium diboride-silicon carbide composites; we found that using nanographite flakes improved the high fracture toughness of the sample material up to 300 per cent, destroying almost all porosity of the sample,” Shahedi Asl told Mehr News.
“A proposed approach to reach at optimum structure of the composite is to use processes which use simultaneously high temperatures and external pressures to densify mixture powder; in the present study, we used hot pressing,” he added.
“Using nanographite flakes reduces the temperature necessary to densify the composite, thus bringing about lower energy consumption; improved mechanical properties of the sample raises the age and reliability of the sample,” said the researcher.
“Lower accepted sintering temperature of ZrB2 is the major barrier of developing nonporous samples; with adding nanographite flakes, nanoparticles react with oxide impurities of the surface and creates conditions for powder particles to bond better; nanoparticles, acting as a positive phase, destroy the high fracture toughness,” he detailed. “For microstructure and phase examinations, we used electron microscopy sweep and X-ray powder diffraction (XRD) methods; the hot pressed sample weight was determined using Archimedes method and to determine theoretical density, we used rule of mixtures,” Shahedi Asl detailed.
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