Hydroxyapatite/titania sol-gel coatings on titanium-zirconium alloy for biomedical applications

A simple sol–gel method was developed for hydroxyapatite/titania (HA/TiO2) coatings on non-toxic titanium–zirconium (TiZr) alloy for biomedical applications. The HA/TiO2-coated TiZr alloy displayed excellent bioactivity when soaked in a simulated body fluid (SBF) for an appropriate period. Differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction and scanning electron microscopy-energy dispersive spectrometry were used to characterize the phase transformations and the surface structures and to assess the in vitro tests. The HA/TiO2 layers were spin-coated on the surface of TiZr alloy at a speed of 3000 rpm for 15 s, followed by a heat treatment at 600 °C for 20 min in an argon atmosphere sequentially. The TiO2 layer exhibited a cracked surface and an anatase structure and the HA layer displayed a uniform dense structure. Both the TiO2 and HA layers were 25 μm thick, and the total thickness of the HA/TiO2 coatings was 50 μm. The TiZr alloy after the above HA/TiO2 coatings displayed excellent bone-like apatite-forming ability when soaked in SBF and can be anticipated to be a promising load-bearing implant material.

Biomimetic processing of nanocrystallite bioactive apatite coating on titanium-zirconium alloy

In this paper nanocrystallite apatite coating on TiZr substrate was prepared by a biomimetic process. Surface morphology, thickness, crystalline phases a~nd bond strength of the coating were investigated by SEM, XRD and tensIle test, respectively. Results show that the apatite coating exhibIts a nanocrystalIite structure with similar stoichiometry to that of natural bone. The apatite layer becomes thicker with the increasing of the SBF immersion time and is firmly adhered to the substrate with the highest average bond strength of 15.5 MPa. This nanocrystallite apatite coating is expected to bond to surrounding bone tissue directly in vivo after implantation.

Nature of new order rights to minerals : a rubikian exercise since passing the mayday rubicon with a cubic zirconium?

The Mineral and Petroleum Resources Development Act 28 of 2002 has created new categories of rights to "minerals" that may be granted to applicants by the Minister of Minerals and Energy. In this article the nature of these rights will be examined. The legislature has labelled prospecting rights and mining rights to minerals as limited real rights in the MPRD Act. The remaining rights to minerals are not labelled. Provision is made for registration or recording rights in the revived Mining Titles Registration Act 16 of 1967 (as amended). Registered rights are claimed to constitute a limited real right binding against third parties. Discrepancies and contradictions regarding the nature of rights to minerals are created by the two statutes. It is concluded that only upon clarification of the provisions of the two sister statutes, would the nature of rights to minerals be more evident. The proposed amendment of section 5(1) of the MPRD Act would be in line with property doctrine based upon the common law and is to be welcomed.

Cell biological responses of osteoblasts on anodized nanotubular surface of a titanium-zirconium alloy

Anodization of titanium and its alloys, under controlled conditions, generates a nanotubular architecture on the material surface. The biological consequences of such changes are poorly understood, and therefore, we have analyzed the cellular and molecular responses of osteoblasts that were plated on nanotubular anodized surface of a titanium-zirconium (TiZr) alloy. Upon comparing these results with those obtained on acid etched and polished surfaces of the same alloy, we observed a significant increase in adhesion and proliferation of cells on anodized surfaces as compared to acid etched or polished surface. The expression of genes related to cell adhesion was high only on anodized TiZr, but that of genes related to osteoblast differentiation and osteocalcin protein and extracellular matrix secretion were higher on both anodized and acid etched surfaces. Examination of surface morphology, topography, roughness, surface area and wettability using scanning electron microscopy, atomic force microscopy, and contact angle goniometry, showed that higher surface area, hydrophilicity, and nanoscale roughness of nanotubular TiZr surfaces, which were generated specifically by the anodization process, could strongly enhance the adhesion and proliferation of osteoblasts. We propose that biological properties of known bioactive titanium alloys can be further enhanced by generating nanotubular surfaces using anodization.

Zirconium, calcium, and strontium contents in magnesium based biodegradable alloys modulate the efficiency of implant-induced osseointegration

Development of new biodegradable implants and devices is necessary to meet the increasing needs of regenerative orthopedic procedures. An important consideration while formulating new implant materials is that they should physicochemically and biologically mimic bone-like properties. In earlier studies, we have developed and characterized magnesium based biodegradable alloys, in particular magnesium-zirconium (Mg-Zr) alloys. Here we have reported the biological properties of four Mg-Zr alloys containing different quantities of strontium or calcium. The alloys were implanted in small cavities made in femur bones of New Zealand White rabbits, and the quantitative and qualitative assessments of newly induced bone tissue were carried out. A total of 30 experimental animals, three for each implant type, were studied, and bone induction was assessed by histological, immunohistochemical and radiological methods; cavities in the femurs with no implants and observed for the same period of time were kept as controls. Our results showed that Mg-Zr alloys containing appropriate quantities of strontium were more efficient in inducing good quality mineralized bone than other alloys. Our results have been discussed in the context of physicochemical and biological properties of the alloys, and they could be very useful in determining the nature of future generations of biodegradable orthopedic implants.

Image analysis of modified cellulose fibers from sugarcane bagasse by zirconium oxychloride

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Dielectric investigations of vanadium modified barium zirconium titanate ceramics obtained from mixed oxide method

Vanadium modified barium zirconium titanate ceramics Ba(Zr(0.10)Ti(0.90))O(3):2V (BZT:2V) were prepared from the mixed oxide method. According to X-ray diffraction analysis, addition of vanadium leads to ceramics free of secondary phases. Electrical characteristics reveal a dielectric permittivity at around 15,000 with low dielectric loss with a remnant polarization (P(r))of 8 mu C/cm(2) at 2 kV/cm. From the obtained results, we assume that vanadium substitution in the BZT lattice affects dielectric characteristics due to the electron-relaxation-mode in which carriers (polarons, protons, and so on) are coupled with existing dielectric modes. (C) 2009 Published by Elsevier B.V.

Waveguides and gratings fabrication in zirconium-based organic/inorganic hybrids

Sol-gel derived poly(oxyethylene)/siloxane organic/inorganic di-ureasil hybrids containing different amounts of methacrylic acid (McOH, CH(2)=C(CH(3))COOH)) modified zirconium oxo-clusters (Zr-OMc) were processed as thin films deposited in glassy substrates via spin coating and as transparent and shape controlled monoliths. Channel monomode waveguides and diffraction gratings were UV patterned using the Talbot interferometer and the Lloyd mirror interferometer experimental setups. The time dependence of the diffraction gratings efficiency was studied for hybrids containing different amounts of Zr-OMc. Finally, the number of propagating modes and the refractive index gradient within the waveguide region, determined as a Gaussian section located below the patterned channel, was evaluated and modeled, a maximum index contrast of 2.43 X 10(-5) being estimated.

Photoluminescence in amorphous zirconium titanate

Photoluminescence at room temperature was observed in amorphous zirconium titanate obtained from the polymeric precursor method. This was the first time in which PL was noticed in an amorphous compound made of two network formers. The PL spectra could be deconvoluted into two bands, whose center 1 was located from 540 nm to 552 nm and center 2 from 625 nm to 641 nm. The co-existence of fivefold and sixfold oxygen coordination of titanium and/or zirconium could be the origin of the radiative recombination of electron-hole pairs in amorphous ZT, which may be responsible for the emission of the photoluminescence.

Luminescence in semi-crystalline zirconium titanate doped with lanthanum

This paper aims to describe the synthesis of the semi-crystalline and crystalline powder of lanthanum doped with zirconium titanate (65/35), LZT through Pechini method. The analysis done by Raman demonstrated that semi-crystalline phase at 550 degrees C and crystalline phase after 600 degrees C were formed. The XRD pattern shows the ZrTiO4 phase formation demonstrating that La substitutions into the lattice take place. The calcined powder at different temperatures shows a semi-crystalline phase presenting photoluminescence effect when processed at low temperatures. From 300 to 400 degrees C a broadband is observed at 563 nm and 568 nm, respectively. Defects creation such as: Zr3+ center dot Vo(center dot center dot) and Ti3+ - V-O(center dot center dot), Zr and Ti replaced by La with vacancy formation, impurities and imperfections contributed to the photoluminescence effect. However, the main emission is due to a reverse Ti4+ -> O2- or/and Zr4+ -> O2- transition that occur within a regular titanate or zirconate eight-fold coordination [BO8-delta], B = Zr4+, Ti4+. (c) 2006 Elsevier B.V. All rights reserved.

Titanium and zirconium complexes containing sterically hindered hydrotris(pyrazolyl)borate ligands: synthesis, structural characterization, and ethylene polymerization studies

The synthesis, characterization and ethylene polymerization behavior of a set of Tp'MCl3 complexes (4, M = Ti, Tp' HB(3-neopentyl-pyrazolyl)(3)(-) (Tp(NP)); 5, M = Ti, Tp'= HB(3-tert-butyl-pyrazolyl)(3)(-) (Tp(tBu)); 6, M = Ti, Tp' = HB(3-phenyl-pyrazolyl)(3)(-) (Tp(Ph)); 7, M = Zr, Tp' = HB(3-phenyl-pyrazolyl)(3)(-) (Tp(ph)); 8, M = Zr, Tp' = HB(3-tert-butyl-pyrazolyl)(3)(-) (Tp(tBu))) is described. Treatment of these tris(pyrazolyl)borate Group IV compounds with methylalumoxane (MAO) generates active catalysts for ethylene polymerization. For the polymerization reactions performed in toluene at 60 degreesC and 3 atm of ethylene pressure, the activities varied between 1.3 and 5.1 X 10(3) g of PE/mol[M](.)h. The highest activity is reached using more sterically open catalyst precursor 4. The viscosity-average molecular weights ((M-v) over bar) of the PE's produced with these catalyst precursors varying from 3.57 to 20.23 x 10(5) gmol(-1) with melting temperatures in the range of 127-134 degreesC. Further polymerization studies employing 7 varying Al/Zr molar ratio and temperature of polymerization showed that the activity as well as the polymer properties are dependent on these parameters. In that case, higher activity was attained at 60 degreesC. The viscosity-average molecular weights of the polyethylene's decreases with increasing AI/Zr molar ratio. (C) 2003 Elsevier B.V. All rights reserved.

CONTRIBUTION TO THE STUDY OF ZIRCONIUM AND HAFNIUM ALPHA-HYDROXYCARBOXYLATES

A study of both zirconium and hafnium alpha-hydroxycarboxylates for analytical applications is presented, These compounds are studied by infrared spectroscopy, thermal analysis and X-ray diffractometry. dl-Mandelic, dl-p-bromomandelic and dl-2-naphthylglycolic acids are the more adequate reagents for gravimetric determinations of zirconium and hafnium, the ligands dl-2-hydroxyhexanoic and dl-2-hydroxydodecanoic acids were used for the first time and the results showed that they are also adequate reagents for the same purpose.