SYNTHESIS AND CHARACTERIZATION OF CERAMIC COMPOSITES DERIVED FROM EPPAWALA APATITE FOR AUTOMOTIVE AND INDUSTRIAL APPLICATIONS

Abstract

The Sri Lankan Eppawala rock phosphate deposit, found in the North Central province, is a non-renewable natural resource that does not replenish over humanly meaningful time scales. It contains nearly 34% to 40% phosphorous pentoxide (P2O5). Even though there are numerous viable and value-added phosphorous (P) industries, Sri Lanka exports rock phosphate as a raw material at lower prices to other developed nations. Considering its resource-related wealth, it is a timely requirement to obtain the proper compensation for this non-renewable resource. Therefore, it is crucial to consider developing and commercializing fresh P-related finds from the Eppawala rock phosphate deposit. In order to value add Eppawala high-grade rock phosphate (HERP), this dissertation thoroughly and critically discusses three patented innovative processes (sol-gel alcoholic route, solgel acidified route, and solid-state sintering technique) for synthesizing three patented nano-hydroxyapatite (HAp) ceramic varieties. It provides significant insights into processcomposites incorporating those synthesized HAp ceramic varieties withdifferent polymers [methyl methacrylate (MMA), 2-hydroxyethyl methacrylate (HEMA)], polyester, epoxy, glass fibers, silicon carbide (SiC) and boron nitride (BN) which can be used for several biomedical, automotive and industrial applications. Synthesized nanoHAp ceramic varieties and processed HAp incorporated composites were characterized using X-ray fluorescence spectroscopy (XRF), particle size analysis (PSA), X-ray diffraction spectroscopy (XRD), fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM with EDS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), tensile tests, and impact tests in order to find out composition, the size distribution of particles, crystallographic structure, identification of functional groups, the morphology of micro/nanostructures, glass transition temperatures, thermal stability, thermomechanical properties, tensile properties, and impact strength. American society for testing and materials (ASTM) standards were applied for all mechanical analyses. This dissertation compared those results with human hard tissues, commercial products, and literature according to their nature of applications. It has been concluded that HAp can be synthesized using the three routes to add value, HERP. These methods are highly cost-effective. Synthesized hexagonal, nano-HAp products perform similarly in chemical composition and structure to mammalian hard tissues via exhibiting different characteristics as bioceramic. The resulting composite materials obtained after reinforcing hydroxyapatite ceramic products with MMA and HEMA orderly for orthopedics and dentistry applications have proven that their performances are better than commercial products. It shows the highly profitable possibility of introducing Eppawala HAp products into the market as value-added bioceramic and its composites. Processed HAp incorporated E-glass fiber reinforced polyester matrix composites and ceramic (HAp/SiC/BN) incorporated epoxy matrix composites in this study demonstrate better properties than pure polyester and epoxy materials. Resulted composites can be used for automotive and aircraft applications. Also, it has confirmed the possibility of processing SiC and BN incorporated HAp composites under high temperatures (1600°C-1650°C), for other relevant industrial applications.