Papers by Keyword: Zirconia Composite

Abstract: A trend in the development of WC based cemented carbides and zirconia based ceramic composites is grain size refinement and more narrow grain size distributions of the starting powder, in order to accomplish higher hardness and abrasive wear resistance. The current work reports the results of dry sliding wear experiments on laboratory-made electrically conductive ZrO2-WC composites and commercially available WC-Co based cemented carbides, which have been manufactured and finished by rough cutting wire EDM with consecutive execution of gradually finer EDM regimes. Tribological data are obtained using a small-scale pin-on-plate test rig. Wear tracks are analyzed by surface scanning topography and scanning electron microscopy, revealing that the outer extensions of the wear tracks exhibit some differences in wear behavior compared to the central parts.

Abstract: Bioactive Mg-PSZ composites were developed by using wollastonite ceramics either as a constituent of the composite formulation or as a bioactive bed during the biomimetic treatment in simulated body fluids. The zirconia composites were prepared by uniaxial pressing of powder mixtures and sintered at 1550oC in air. Wollastonite containing zirconia/alumina composites were also sintered at 1350oC. The composites were immersed in SBF for 7 days on a bed of wollastonite powder and then re-immersed in 1.5SBF for 7 days. Tests were also performed with no wollastonite bed. A highly bioactive surface was observed on the Mg-PSZ/CaSiO3 and Mg-PSZ/Al2O3 composites. A homogeneous apatite layer was detected on the Mg-PSZ/CaSiO3 composites immersed for only 7 days in SBF. No apatite was formed on the Mg-PSZ/Al2O3/CaSiO3 composite. During the sintering mechanism at either 1550 or 1350oC small amounts of aluminosilicate phases are formed. These phases inhibited the apatite formation.

Abstract: The sliding wear behavior of ultra high molecular weight polyethylene (UHMWPE) was examined on four different compositions of novel low temperature degradation-free zirconia/alumina (Z/A) composite material used for a femoral head in total hip joint replacement. The wear of UHMWPE pins against these Z/A composite disks were evaluated by performing the linear reciprocal sliding and repeat pass rotational sliding tests for one million cycles in a bovine serum. The novel low temperature degradation (LTD)-free tetragonal zirconia polycrystal (TZP)/alumina composite (90(5.3Y, 4.6Nb)-TZP/10Al2O3) induced the less wear amount of UHMWPE than the other Z/A composites. Linear reciprocal motion wore more the UHMWPE pin than did repeat pass rotational motion for all disk materials. It was observed that few transfer film on the sliding track of Z/A composite disks and the matching contact surfaces of pins had relatively less scratch. Getting rid of transfer film, there is no change of surface roughness on the sliding track of Z/A composite disks. This novel Z/A composite (90(5.3Y, 4.6Nb)-TZP/10 Al2O3) demonstrates the potential as an alternative material for the femoral head in total hip replacement.

Abstract: This study evaluated the wear performance of cobalt-chromium, zirconia and alumina/zirconia composite heads against moderately crosslinked ultra-high-molecular-weight polyethylene liners under different temperature conditions. A temperature control unit was utilized to allow direct cooling/heating the head components at 4, 20, 37 and 45 °C in addition to the conventional no temperature control method. Results showed that the polyethylene wear was affected by the coolant temperature. The CoCrMo and the alumina/zirconia groups had similar wear rate without temperature control, however, the CoCrMo group generated 50% more wear than the alumina/zirconia group did when the coolant temperatures were above 20 °C. The zirconia group had the lowest wear rate of the three groups in all temperature conditions. The monoclinic phase content of the zirconia heads were about 0.2 M% before the test and 6.0 M% after the test, while the X-ray diffraction remained similar before and after the test in alumina/zirconia composite heads. The current study was able to reproduce the phase transformation of zirconia ceramics as reported in some clinical retrieval reports. A temperature control feature is recommended in a wear study in order to better simulate implant wear performance under the physiological condition in human body.