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Aluminum-silicon based hybrid composites reinforced with silicon carbide and graphite particles were prepared by liquid phase particle mixing (melt stirring) and squeeze casting. The thermal expansion and thermal conductivity behaviors of hybrid composites with various graphite contents (5.0; 7.5; 10 wt.%) and different silicon carbide particle sizes (45 µm and 53 µm) were investigated. Results indicated that increasing the graphite content improved the dimensional stability, and there was no obvious variation between the thermal expansion behaviors of the 45 µm and the 53 µm silicon carbide reinforced composites. The thermal conductivity of hybrid composites was reduced due to the enrichment of the graphite component.

DOI: http://dx.doi.org/10.5755/j01.ms.18.4.3093

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Background: Reinforcement of dental acrylics with fillers has yielded positive results. Different proportions of fillers have been added to strengthen the dental acrylics, but no consensus has been reached. Aim: The purpose of this study was to investigate the effects of the addition of different concentrations of yttria-stabilized zirconium (YSZ) obtained from the residues generated from the CAD-CAM milling of YSZ on the microstructure and mechanical properties of poly-methyl-methacrylate (PMMA)-YSZ composites. Materials and methods: Composite materials with different amounts (0.0 to 70.0% by weight) of recycled YSZ reinforced PMMA resin matrix were produced. Scanning electron microscope (SEM), energy dispersive electron spectrometer (EDS) and Fourier Transform Infrared Spectrometer (FTIR) were used for microstructural analysis. Among the mechanical properties, the Vickers microhardness test method for hardness, 2D profilometer for surface roughness and composite densities were evaluated by Archimedes method. Data were analyzed using a one-way analysis of variance (ANOVA) at a pre-set alpha of 0.05. Results: Microhardness and density increased until 60% by weight YSZ addition, while surface roughness remained unchanged but increased after 60% by weight YSZ addition. The addition of more than 60% by weight of YSZ caused agglomeration in the microstructures. The mechanical properties of poly-methylmethacrylate decreased with more than 60% YSZ by weight. Conclusion: Reinforcement of PMMA with residue zirconia powder will increase the usage chance of residue YSZ powder and provide a safer use of PMMA.