Bioactivity of Mg-ion-implanted zirconia and titanium

Titanium and zirconia are bioinert materials lacking bioactivity. In this work, surface modification of the two typical biomaterials is conducted by Mg-ion-implantation using a MEVVA ion source in an attempt to increase their bioactivity. Mg ions were implanted into zirconia and titanium with fluences ranging from 1 x 10(17) to 3 x 10(17) ions/cm(2) at 40 keV. The Mg-implanted samples, as well as control (unimplanted) samples, were immersed in SBF for 7 days and then removed to identify the presence of calcium and phosphate (Ca-P) coatings and to characterize their morphology and structure by SEM, XRD, and FT-IR. SEM observations confirm that globular aggregates are formed on the surfaces of the Mg-implanted zirconia and titanium while no precipitates are observed on the control samples. XRD and FT-IR analyses reveal that the deposits are carbonated hydroxyapatite (HAp). Our experimental results demonstrate that Mg-implantation improves the bioactivity of zirconia and titanium. Further, it is found that the degree of bioactivity is adjustable by the ion dose. Mechanisms are proposed to interpret the improvement of bioactivity as a result of Mg implantation and the difference in bioactivity between zirconia and titanium. (c) 2006 Elsevier B.V. All rights reserved.

Probing into the catalytic nature of Co/sulfated zirconia for selective reduction of NO with methane

In this work, the structural and surface properties of Co-loaded sulfated zirconia (SZ) catalysts were studied by X-ray diffraction (XRD), N-2 adsorption, NH3-TPD, FT-IR spectroscopy, H-2-TPR, UV-vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and NO-TPD. NH3-TPD and FT-IR spectra results of the catalysts showed that the sulfation process of the support resulted in the generation of strong Bronsted and Lewis acid sites, which is essential for the SCR of NO with methane. On the other hand, the N-2 adsorption, H-2-TPR, UV/vis DRS, and XPS of the catalysts demonstrated that the presence of the SO42- species promoted the dispersion of the Co species and prevented the formation Of Co3O4. Such an increased dispersion of Co species suppressed the combustion reaction of CH4 by O-2 and increased the selectivity toward NO reduction. The NO-TPD proved that the loading of Co increased the adsorption of NO over SZ catalysts, which is another reason for the promoting effect of Co. (C) 2004 Elsevier Inc. All rights reserved.