Microstructure and properties of zirconia-alumina composites fabricated via powder injection molding

Abstract

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.

Debinding behaviour and sintering temperature-dependent features of coloured zirconia fabricated by ceramic injection moulding

“…Normally the solvent-soluble binder is the key which always used in higher weight fraction compared to the others. Organic solvents, like hexane and n-heptane or even plain water, can possibly remove most of the majority binder [2][3][4] whereas the minority of the insoluble binder still exists to hold the powder compacts and promote handling ability before being burnt out while sintering.…”

Preparation of feedstock containing water-soluble binder for powder injection moulding of silver

“…The ratio between PEG and PVB was kept constant at 85:15 by weight. This PEG/PVB ratio was adapted from the previous works [14,15]. PEG provides appropriate feedstock viscosity that can flow into the mould cavity while PVB helps retain shape of components during and after water debinding.…”

“…The PEG/PVB composite binder was applied for injection moulding of a variety of powders to avoid the use of organic solvents. These include ceramic powders such as alumina, zirconia and alumina-zirconia composites [12,14,15] in addition to metal-ceramic composite materials such as stainless steel-tungsten carbide powder and tungsten carbide-nickel hardmetal powder [16,17]. The injection moulding of titanium alloys using the PEG/PVB binder system was also reported [13].…”