Zirconia Nanoparticles

deA combination of experiments and ab initio quantum-mechanical calculations has been applied to examine electronic, structural, and hyperfine interactions in pure and Ta-doped zirconium dioxide in its monoclinic phase (m-ZrO2). From the theoretical point of view, the full-potential linear augmented plane wave plus local orbital (APW + lo) method was applied to treat the electronic structure of the doped system including the atomic relaxations introduced by the impurities in the host in a fully self-consistent way using a supercell approach. Different charge states of the Ta impurity were considered in the study and its effects on the electronic, structural, and hyperfine properties are discussed. Our results suggest that two different charge states coexist in Ta-doped m-ZrO2. Further, ab initio calculations predict that depending on the impurity charge state, a sizeable magnetic moment can be induced at the Ta-probe site. This prediction is confirmed by a new analysis of experimental data.

The availability of zirconium dioxide (zirconia) ceramics in dentistry has expanded the range of designs and applications for all-ceramic restorations and increased its popularity. Nanoparticles (NPs) have attracted considerable attention owing to their unique properties and ease of production from variety of materials. Zirconia with enhanced properties can be achieved by doping with biocompatible material. The present study devised sol gel method for preparation of Fe 3 O 4 doped ZrO 2 nanoparticles (NPs). Zirconia sol is doped with pre-synthesized Fe 3 O 4 NPs. Structural characterizations have shown a mixture of monoclinic and tetragonal zirconia. An increase in crystallite size has observed with dopant concentration. Lattice contraction was observed for the Fe 3 O 4-doped zirconia samples. This lattice contraction results in volumetric change which leads to formation of tetragonal phase. Relative higher density (~6g/cm 3) has been observed which is perquisite for implantations and coatings. Magnetic properties reveal the mix paramagnetic and ferromagnetic behavior with low value of coercivity and magnetization.

Structure, phase transformations, grain growth, and defects of bare and alumina-coated nanoparticles of HfO(2) and ZrO(2) synthesized in a microwave-plasma process have been investigated by x-ray diffraction (XRD), transmission electron microscopy (TEM), and perturbed angular correlation (PAC) spectroscopy. The PAC technique was used to measure the electric quadrupole interactions (QIs) of the nuclear probes (181)Ta and (111)Cd in nanocrystalline HfO(2) and ZrO(2) as a function of temperature. For comparison, the QI of (181)Ta in the bulk oxides was determined in the same temperature range 300 K <= T <= 1550 K. The oxygen-metal ratio of the as-synthesized particles was determined by x-ray photoelectron spectroscopy to be in the range 1.4 <= x <= 1.8. A hydrate surface layer with a hydrogen content of 5-10 wt %, consisting of chemisorbed hydroxyl groups and organic precursor fragments, was detected by (1)H magic-angle spinning NMR. XRD and TEM show that bare n-ZrO(2), Al(2)O(3)-coated n-ZrO(2), and Al(2)O(3)-coated n-HfO(2) are synthesized in the tetragonal or cubic modification with a particle size d < 5 nm, whereas bare n-HfO(2) is mainly monoclinic. The grain growth activation enthalpy of bare n-ZrO(2) is Q(A) = 32(5) kJ/mol. Coating with Al(2)O(3) stabilizes the tetragonal over the monoclinic phase, both in hafnia and zirconia nanoparticles. While TEM micrographs of the native nanoparticles reveal a well-ordered cation sublattice, the observation of a broad QI distribution in the PAC spectra suggests a high degree of disorder of the oxygen sublattice. The gradual transformation of the disordered state and the phase evolution were studied by high-temperature QI measurements. Hafnia nanoparticles persist in the monoclinic (m) phase up to T <= 1400 K. In coated n-ZrO(2)/Al(2)O(3), the monoclinic and tetragonal (t) phases coexist over a large temperature range, whereas uncoated, initially tetragonal or cubic (t or c) n-ZrO(2) presents a sharp m <-> t transition. A "defect" component involving 30%-40% of the probe nuclei appears in the (181)Ta PAC spectra of all nanoparticles when these are cooled from high temperatures T >= 1200 K. The temperature dependence of this component can be reproduced by assuming that Ta impurities in hafnia and zirconia may trap electrons at low temperatures. The observation that the defect component appears only in nanoparticles with diameter d < 100 nm suggests that mobile electrons are available only in the surface region of the oxide particles, either from oxygen vacancies (V(O)) and/or V(O)-hydrogen donors at the interface of the nanoparticles and their hydrate layers. This conclusion is supported by the absence of a size effect for (111)Cd probes in HfO(2) and ZrO(2). The temperature dependence of the (181)Ta defect fraction is consistent with a Ta(+) impurity level at E(d) similar to 0.9 and 0.6 eV below the hafnia and zirconia conduction band, respectively.

Magnesium (Mg), and its alloys have good potential for using in biomedical applications due to its good
mechanical properties and biodegradability. However, the poor corrosion resistance and insufficient
mechanical stability of Mg in biological fluids have limited its clinical applicability. As a result, surface
modification techniques are being investigated to improve corrosion resistance for biomedical applications. In this study, a bioactive CaP film were deposited on the surface of the AZ31B magnesium alloy
via anodization with SBF solution used as the electrolyte with and without ZrO2 Nanoparticles (NPs).
The samples were evaluated and characterized in vitro to assess their degradation and cytocompatability behaviour via FE-SEM, electrochemical corrosion test, immersion test, and cell culture tests. The
results indicate that the AZ31B Mg alloy surface anodized in SBF with and without ZrO2 NPs consists of
CaP nanoplate leaf-like apatite structures and porous 3-D structures, respectively. The nanomorphology
showed uniform growth on the anodized surface that had created the porous layer on the surface of the
samples three days after immersion in the SBF solution. The formation of such nanostructures on the
anodized sample could provide the implant materials with extra biocompatibility. Moreover, this unique deposited layer can improve the corrosion resistance and cytocompatability of the Mg alloys, which make
it a promising material for use in biomedical applications

The availability of zirconium dioxide (zirconia) ceramics in dentistry has expanded the range of designs and applications for all-ceramic restorations and increased its popularity. Nanoparticles (NPs) have attracted considerable attention owing to their unique properties and ease of production from variety of materials. Zirconia with enhanced properties can be achieved by doping with biocompatible material. The present study devised sol gel method for preparation of Fe3O4 doped ZrO2 nanoparticles (NPs). Zirconia sol is doped with pre-synthesized Fe3O4 NPs. Structural characterizations have shown a mixture of monoclinic and tetragonal zirconia. An increase in crystallite size has observed with dopant concentration. Lattice contraction was observed for the Fe3O4-doped zirconia samples. This lattice contraction results in volumetric change which leads to formation of tetragonal phase. Relative higher density (~6g/cm) has been observed which is perquisite for implantations and coatings....