• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.365-366
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• 2002

The sliding wear behavior of ultra high molecular weight polyethylene (UHMWPE) was examined on a novel low temperature degradation-free zirconia/alumina composite material and conventional alumina and zirconia ceramics used for femoral head in total hip joint replacement. The wear of UHMWPE pins against these ceramic disks was evaluated by performing linear reciprocal sliding and repeat pass rotational sliding tests for one million cycles in bovine serum. The weight loss of polyethylene against the novel low temperature degradation-free zirconia/alumina composite disks was much less than those against conventional ceramics for all tests. The mean weight loss of the polyethylene pins was more io the linear reciprocal sliding test than in the repeal pass rotational sliding lest for all kinds of disk materials. Neither the coherent transfer film nor the surface damage was observed on the surface of the novel zirconia/alumina composite disks during the test. The observed r,'stilts indicated that the wear of the polyethylene was closely related to contacting materials and kinematic motions. In conclusion, the novel zirconia/alumina composite leads the least wear of polyethylene among the tested ceramics and demonstrates the potential as lhe alternative materials for femoral head in total hip joint replacement.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.91-94
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• 2003

Ceramic femoral heads in the total hip replacement have been developed to reduce the polyethylene liner wear. Alumina and zirconia (3Y-TZP) are using in clinical application worldwide and there are many good test reports. However, alumina has a risk of catastrophic failure, and zirconia has the low temperature degradation in spite of enhanced fracture toughness. Recently, novel zirconia/alumina composite having low temperature degradation-free character and high fracture tough . was developed and it leads the lower wear 3f polyethylene than alumina and zirconia. In the present study, in order to optimise the microstructure of low temperature degradation (LTD)-free zirconia/alumina composite for the best wear resistance of polyethylene, various compositions of (LTD)-free zirconia/alumina composites were fabricated, and the sliding wear of UHMWPE against these novel composites were examined and compared with that against alumina and zirconia ceramics used for total hip joint heads.

• Journal of the Korean Applied Science and Technology
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• v.38 no.6
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• pp.1561-1567
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• 2021

In this study, we have studied synthesis of zirconia-alumina composite coating materials via a low-temperature sol-gel process. The zirconia-alumina composites were prepared by coating zirconia precursor, alumina precursor, and organosilane mixture on a polyethylene terephthalate substrate through three steps: sol-gel process, low-temperature photocuring process, and heat treatment process. The structural properties and element analysis of the composites were confirmed by FT-IR and XPS. The coated composite showed a transmittance of 96% or more in the visible light region with a wavelength of 420 nm or more and pencil hardness of 9H or more. In case of the composite of the molar ratio of zirconia and alumina of 1:4, the highest nanoindentation hardness was measured with 1.212 GPa.

• Bulletin of the Korean Chemical Society
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• v.23 no.8
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• pp.1127-1134
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• 2002

Fine ceramic particles of zirconia toughened alumina (ZTA), titania toughened alumina (TTA), and zirconia-titania toughened alumina (ZTTA) have been synthesized by ultrasonic spray pyrolysis (USP) at various temperatures from starting salt solutio ns of various compositions aiming for the development of catalytic material. These particles were characterized for properties such as shape, size and size distribution, diffraction pattern, and chemical and phase composition of elements by scanning electron microscopy (SEM), particle size analyzer (PSA), x-ray diffraction (XRD), and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Chemical compositions and sizes of ceramic composites have been controled by the stoichiometry of salt solutions and the flow rate of spraying solutions. The optimum experimental conditions for the various composite particle syntheses have been proposed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.355-361
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• 2004

Ceramic femoral heads in the total hip replacement have been developed to reduce the polyethylene liner wear, Alumina and zirconia (3Y-TZP) having the excellent tribological properties are coupled against acetabular cups of polyethylene and are used in clinical application worldwide. However, alumina has a risk of catastrophic failure, and zirconia has the low temperature degradation in spite of enhanced fracture toughness. Recently, novel zirconia/alumina composite is very attractive due to the low temperature degradation (LTD)-free character and high fracture toughness. In the present study, we focus on the wear of ceramic on ceramic, which are able to be used as femoral heads and acetabular cups. Therefore, LTD-free zirconia/alumina composites with three compositions are made in a form of disk and cylinder, and the wear of the composites is performed on pin-on-disk type wear tester. The wear is conducted with or without lubricant. All the composites fabricated with the different composition show the good wear resistance.

• Journal of the Korean Ceramic Society
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• v.25 no.3
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• pp.284-292
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• 1988

Alumina-zirconia composite powders for the purpose of improving fracture toughness and thermal shock resistance of alumina were prepared by the emulsion-kerosene drying method. The average particle size of composite powders was less then 1 $\mu\textrm{m}$ and their shapes were spherical. It was shown that the average particle size of composite powders decreased with the concentration of metal-salt in solution and the amount of span 80 added when preparing emulsions. The structure of all zirconia in composite powders heat-treated at 1200$^{\circ}C$ was a tetragonal form at room temperature. This result implied that fine zirconia particles were homogeneously dispersed in the alumina matrix.

• Journal of Powder Materials
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• v.10 no.5
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• pp.310-317
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• 2003

Two-component ceramic (alumina-zirconia) composites were fabricated by a soft-solution process in which polyethylene glycol (PEG) was used as a polymeric carrier. Metal salts and PEG were dissolved in ethyl alcohol without any precipitation in 1:1 volume ratio of alumina and zirconia. In the non-aqueous system, the flammable solvent made explosive, exothermic reaction during drying process. The reaction resulted in formation of volume expanded, porous precursor powders by a vigorous decomposition of organic components in the precursor sol. The PEG content affected the grain size of sintered composites as well as the morphology of precursor powders. The difference of microstructure in sintered composite was attribute to the solubility and homogeneity of metal cations in precursor sol. At the optimum amount of the PEG polymer, the metal ions were dispersed effectively in solution and a homogeneous polymeric network was formed. It made less agglomerated particles in the precursor sol and affected on uniform grain size in sintered composite.

• Journal of the Korean Ceramic Society
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• v.30 no.7
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• pp.571-577
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• 1993

The effect of $\alpha$-Al2O3 seeding on preparation of zirconia/alumina gel fragment prepared by sol-gel processing was characterized through XRD, SEM, TG/DTA and IR analysis. Aluminum isopropoxide and zirconium butoxide were used as starting materials. $\alpha$-Al2O3 seeding restrained grain growth of alumina and zirconia, and decreased tetragonal to monoclinic phase transformation of zirconia on cooling. Therefore, fine zirconia-toughened alumina composite having the relative sintered density of about 98% of theoretical at 140$0^{\circ}C$ for 2h could be obtained.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1475-1482
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• 1994

Compositionally triphasic boehmite-silica-zirconia composite gels were prepared by a multiphasic sol-gel route. Phase-formation characteristics and densification behavior of the gel compacts were examined with and without $\alpha$-Al2O3 seeding. In the unseeded triphasic gels, both $\alpha$-Al2O3 and mullite crystallize simultaneously at 130$0^{\circ}C$. On the other hand, the $\alpha$-Al2O3 seeding selectively induces the formation of corundum phase ($\alpha$-Al2O3) at a significantly lower temperature (~110$0^{\circ}C$) and facilitates an epitaxial growth of $\alpha$-Al2O3 between 1100~130$0^{\circ}C$. The densification of alumina-mullite-zirconia composite (derived from the triphasic gels) was also enhanced by the $\alpha$-Al2O3 seeding, and this was attributed to the delayed crystallization of mullite in the $\alpha$-Al2O3 seeded gel.

• Journal of the Korean Ceramic Society
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• v.48 no.2
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• pp.152-159
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• 2011

The green and hard machining characteristics of dental ceramics are of great interest to dental industry. The green bodies of TZP/$Al_2O_3$ composites were prepared by the cold isostatic pressing, and machined on the CNC lathe using PCD (polycrystalline diamond) insert under various machining conditions. With increasing nose radius of PCD insert, surface roughness initially increased due to increased cutting resistance, but decreased by the onset of sliding fracture. The lowest surface roughness was obtained at spindle speed of 1,300 rpm and lowest feed rate. Hard bodies were prepared by pressureless sintering the machined green bodies at several temperatures. The grinding test for sintered hard body was conducted using electroplated diamond bur with different grit sizes. During grinding, grain pull out in the composite was occurred due to thermal expansion mismatch between the alumina and zirconia. The strength of the composite decreased with alumina contents, due to increased surface roughness and high monoclinic phase transformed during grinding process. The final polished samples represented high strength by the elimination of a phase transformation layer.