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This study aimed to fabricate zirconia-alumina composites via powder injection molding and investigated the effects of alumina addition on microstructure as well as physical properties of the composites. Zirconia-alumina composites were prepared using polyethylene glycol (PEG) and polyvinyl butyral (PVB) as binders.  The powder loading was fixed at 38 vol%, and PEG: PVB binder weight ratio was fixed at 80:20.  Alumina content within ceramic component was varied at 0, 10, 20, 30, 40 and 50 vol% to observe the effect of alumina on the composite structures and properties. The injection molding was done at 190℃ followed by water debinding of PEG at 40℃. Thermal debinding of PVB at 450℃ was performed prior to sintering at 1450℃. From the density measurement via Archimedes’ method, the relative density of sintered samples was found to be highest at 10 vol% alumina and gradually lower at higher alumina content. The condition with highest density yielded the highest flexural modulus and flexural strength.  XRD indicated that tetragonal zirconia phase coexisted with alumina when alumina was added. Above 20 vol% alumina, monoclinic zirconia was also detected. The increased porosity in samples with high alumina content, as confirmed in SEM morphological observation, correlated with lower flexural strength and lower flexural modulus.  The results illustrated the feasibility of powder injection molding in the production of zirconia-alumina composites and the optimum condition in this study was 10 vol% alumina.

In this study, we utilized electrospun silica fibers (ESFs) as reinforcement in sandwiched nylon-6 composites. The silica fibers were fabricated via electrospinning of sol-gel precursor, prepared from tetraethyl orthosilicate. The process yielded non-woven silica fiber mats with fiber diameter about 350 nm, which is much smaller than conventional glass fibers. Each ESF mat was sandwiched in between two nylon-6 sheets and the layers were compression-molded to produce a composite sample. These composites were prepared with varying silica fiber content, approximately at 0, 0.5, 1.0, and 1.9 wt%. The ESF blended well and chemically bonded with the nylon matrix, as observed through scanning electron microscopy and Fourier transform infrared spectroscopy. Tensile tests revealed that tensile modulus and tensile strength increased with ESF content. Notch Izod impact test showed that impact strength also increased with ESF content. The tensile and impact properties were significantly improved, considering the use of such low silica fiber percentages, which could be due to ultra-fine fiber diameter and fiber continuity. From flexural test, however, flexural modulus and flexural strength decreased slightly by the addition of ESF. Specimen geometry and fabrication process play important roles in governing the composites mechanical behavior. POLYM. COMPOS., 00:000-000,

Silica fibers have been fabricated via sol-gel reaction and electrospinning. The precursor solution was prepared from tetraethyl-orthosilicate (TEOS), ethanol and aqueous hydrochloric acid. The viscous solution was electrospun at 15kV applied voltage and 20 cm tip-to-collector distance. The process yielded nonwoven sheet of silica fibers with good mechanical integrity. The silica fiber specimens were calcined at different temperatures: 400°C, 600°C and 800°C. Scanning electron microscope (SEM) observation reveals smooth and long fibers with average diameter below 0.5μm for all samples, both as spun and calcined. Fourier transform infrared spectroscopy (FT-IR) spectra show effects of calcination temperature on chemical structure of the fibers. Calcination results in the removal of organic residuals and leaving mostly silica content

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