Corrosion resistance improvement of titanium base alloys

The corrosion resistance of the new Ti-6Al-4V-1Zr alloy in comparison with ternary Ti-6Al-4V alloy in Ringer-Brown solution and artificial Carter-Brugirard saliva of different pH values was studied. In Ringer-Brown solution, the new alloy presented an improvement of all electrochemical parameters due to the alloying with Zr; also, impedance spectra revealed better protective properties of its passive layer. In Carter-Brugirard artificial saliva, an increase of the passive film thickness was proved. Fluoride ions had a slight negative influence on the corrosion and ion release rates, without to affect the very good stability of the new Ti-6Al-4V-1Zr alloy.

Synthesis and characterization of Fe(III)-doped ceramic membranes of titanium dioxide and its application in photoelectrocatalysis of a textile dye

Pure and Fe(III)-doped TiO2 suspensions were prepared by the sol gel method with the use of titanium isopropoxide (Ti(OPri)4) as precursor material. The properties of doped materials were compared to TiO2 properties based on the characterization by thermal analysis (TG-DTA and DSC), X-ray powder diffractometry and spectroscopy measurements (FTIR). Both undoped and doped TiO2 suspensions were used to coat metallic substrate as a mean to make thin-film electrodes. Thermal treatment of the precursors at 400ºC for 2 h in air resulted in the formation of nanocrystalline anatase TiO2. The thin-film electrodes were tested with respect to their photocatalytic performance for degradation of a textile dye in aqueous solution. The plain TiO2 remains as the best catalyst at the conditions used in this report.

Titanium pigment in tissues of drug addicts: report of 5 necropsied cases

The aim of this report is to describe the anatomic-pathologic findings from necropsies of 5 drug addicts with titanium pigment in several organs after chronic intravenous injection of crushed propoxyphene hydrochloride tablets. Samples from liver, spleen, lungs, lymph nodes, and bone marrow were obtained, and after being grossly studied, they were submitted to evaluation using common light and polarized microscopy. In all 5 cases, a pigment with characteristics of titanium dioxide was found within tissue samples of the organs studied. Our findings suggest that research concerning titanium pigment within body tissues should be enhanced, considering the potential contribution of this morphologic data to forensic pathology.

MORPHOLOGICAL AND MICROMORPHOLOGICAL CHANGES IN THE STRUCTURE OF A RHODIC HAPLUDOX AS A RESULT OF AGRICULTURAL MANAGEMENT

In evaluation of soil quality for agricultural use, soil structure is one of the most important properties, which is influenced not only by climate, biological activity, and management practices but also by mechanical and physico-chemical forces acting in the soil. The purpose of this study was to evaluate the influence of conventional agricultural management on the structure and microstructure of a Latossolo Vermelho distroférrico típico (Rhodic Hapludox) in an experimental area planted to maize. Soil morphology was described using the crop profile method by identifying the distinct structural volumes called Morphologically Homogeneous Units (MHUs). For comparison, we also described a profile in an adjacent area without agricultural use and under natural regrowth referred to as Memory. We took undisturbed samples from the main MHUs so as to form thin sections and blocks of soil for micromorphological and micromorphometrical analyses. Results from the application of the crop profile method showed the occurrence of the following structural types: loose (L), fragmented (F) and continuous (C) in both profiles analyzed. In the Memory soil profile, the fragmented structures were classified as Fptμ∆+tf and Fmt∆μ, whose micromorphology shows an enaulic-porphyric (porous) relative distribution with a great deal of biological activity as indicated by the presence of vughs and channels. Lower down, from 0.20 to 0.35 m, there was a continuous soil volume (sub-type C∆μ), with a subangular block microstructure and an enaulic-porphyric relative distribution, though in this case more compact and with aggregate coalescence and less biological activity. The micromorphometrical study of the soil of the Memory Plot showed the predominance of complex pores in NAM (15.03 %), Fmt∆μ (11.72 %), and Fptμ∆+tf (7.73 %), and rounded pores in C∆μ (8.21 %). In the soil under conventional agricultural management, we observed fragmented structures similar to the Memory Plot from 0.02 to 0.20 m, followed by a volume with a compact continuous structure (C∆μ), without visible porosity and with few roots. In the MHUs under conventional management, reduction in the packing pores (40 %) was observed, mainly in the continuous units (C). The microstructure had well-defined blocks, with the occurrence of planar pores and less evidence of biological activity. In conclusion, the morphological and micromorphological analyses of the soil profiles studied offered complementary information regarding soil structural quality, especially concerning the changes in pore types as result of mechanical stress undergone by the soil.

Discrepancies over the onset of surfactant monomer aggregation interpreted by fluorescence, conductivity and surface tension methods

Molecular probe techniques have made important contributions to the determination of microstructure of surfactant assemblies such as size, stability, micropolarity and conformation. Conductivity and surface tension were used to determine the critical aggregation concentration (cac) of polymer-surfactant complexes and the critical micellar concentration (cmc) of aqueous micellar aggregates. The results are compared with those of fluorescent techniques. Several surfactant systems were examined, 1-butanol-sodium dodecylsulfate (SDS) mixtures, solutions containing poly(ethylene oxide)-SDS, poly(vinylpyrrolidone)-SDS and poly(acrylic acid)-alkyltrimethylammonium bromide complexes. We found differences between the cac and cmc values obtained by conductivity or surface tension and those obtained by techniques which use hydrophobic probe.

Adsorption of hidrogen peroxide on the surface of silica - titania mixed oxide obtained by the sol-gel processing method

This work describes the sol-gel mixed oxide SiO2/TiO2 property, ST, as prepared, and submitted to heat treatment a 773 K, STC. SEM and EDS images show, within magnification used, a uniform distribution of the TiO2 particles in SiO2/TiO2 matrix. Both, ST and STC adsorb hydrogen peroxide on the surface and through EPR and UV-Vis diffuse reflectance spectra, it was possible to conclude that the species on the surface is the peroxide molecule attached to the Lewis acid site of titanium particle surface, alphaTi(H2O2)+. As the material is very porous, presumably the hydrogen peroxide molecule is confined in the matrix pores on the surface, a reason why the adsorbed species presents an exceptional long lived stability.

Proteoliposomes as matrix vesicles' biomimetics to study the initiation of skeletal mineralization

During the process of endochondral bone formation, chondrocytes and osteoblasts mineralize their extracellular matrix by promoting the formation of hydroxyapatite (HA) seed crystals in the sheltered interior of membrane-limited matrix vesicles (MVs). Ion transporters control the availability of phosphate and calcium needed for HA deposition. The lipidic microenvironment in which MV-associated enzymes and transporters function plays a crucial physiological role and must be taken into account when attempting to elucidate their interplay during the initiation of biomineralization. In this short mini-review, we discuss the potential use of proteoliposome systems as chondrocyte- and osteoblast-derived MVs biomimetics, as a means of reconstituting a phospholipid microenvironment in a manner that recapitulates the native functional MV microenvironment. Such a system can be used to elucidate the interplay of MV enzymes during catalysis of biomineralization substrates and in modulating in vitro calcification. As such, the enzymatic defects associated with disease-causing mutations in MV enzymes could be studied in an artificial vesicular environment that better mimics their in vivo biological milieu. These artificial systems could also be used for the screening of small molecule compounds able to modulate the activity of MV enzymes for potential therapeutic uses. Such a nanovesicular system could also prove useful for the repair/treatment of craniofacial and other skeletal defects and to facilitate the mineralization of titanium-based tooth implants.

Effect of modified clays on the structure and functional properties of biofilms produced with zein

The purpose of this study was to evaluate changes in the structure and some functional properties of biofilms added with modified clays (Cloisite® 15A and Cloisite® 30B) prepared by the casting method. The analysis of the microstructure of the films, scanning electron microscopy (SEM), Optical microscopy (MO), and Infrared Spectroscopy (FTIR) indicated that the addition of clay in the films resulted in the formation of a heterogeneous microstructure, microcomposite or tactoid. Due to the formation of a microcomposite structure, functional properties of the films added with both clays such as opacity, solubility, and permeability to water vapor (PVA), were not better than those of the control film. Thus, it was concluded that although it is possible to produce a film added with modified clays using the casting method, it was not possible to obtain intercalation or exfoliation in a nanocomposite, which would result in improved functional properties.

Effect of Brea Gum on the characteristics of wheat bread at different storage times

The effect of Brea Gum (BG) addition on a basic bread formulation is described. The aim of the study was to investigate the effect of BG on the characteristics of wheat bread in terms of changes in moisture, texture, retrogradation of amylopectin, and microstructure. Bread quality was assessed by the physical parameters (volume, specific volume index, width/height ratio, crumb moisture, color, and hardness) and crumb grain structure (total cell number, total cell area, average size of cells, and number of cells per unit area). The effect of BG on the characteristics of the crumb during 24, 48, and 72 hours of storage was determined according to changes in moisture, hardness, and amylopectin retrogradation. Furthermore, the microstructure of the crumb was analyzed by scanning electron microscopy (SEM). The results show the ability of BG to retain moisture in the bread crumb, which was expressed by the lower hardness of the bread crumbs with the addition of the hydrocolloid at 48 and 72 hours of storage. This effect was also evident in the microstructure.

Dióxido de titânio sol-gel: propriedades e comportamento eletrocrômico

Titanium dioxide was prepared by hydrolysis and polycondensation of titanium tetraisopropoxide. TiO2 films were obtained by spin coating of the precursor solution on ITO substractes (glass covered with indium doped tin oxide). Films were prepared using different temperatures and hydrochloric acid contents. The effect of the drying temperature of the films (100 or 400ºC) was also investigated. TiO2 films were characterized by cyclic voltammetry, chronoamperometry, ultraviolete-visible spectroscopy, scanning electron microscopy and X-ray diffractrometry.

Estudo do biomaterial Ti-6Al-4V empregando-se técnicas eletroquímicas e XPS

The Ti-6Al-4V alloy used as biomaterial has been used over the last years. The literature shows controversies concerning the kind and the chemical composition of the film naturally and elctrochemically formed on the surface of the titanium alloy. The presente work studies the film composition before and after the electrochemical polarization tests using the x Ray photoelectron spectroscopy (XPS) technique. The results showed that the film naturally formed on the metallic surface is constituted of a variety of oxides which do not cover the whole surface of the metallic alloy and therefore, metallic Ti, Al and V can be found on the uncovered areas. The tests of XPS made after the polarization up to 4V (SCE) showed that the electrochemically formed film is constituted only of TiO2 and that the peak current observed around 1,5 V (SCE) is due to the oxidation of any kind of titanium oxide or the growth of the film.

Síntese e caracterização de um composto VOPO4-DMA

A layered matrix, alpha-VOPO4.2H2O was used as host species to produce a VOPO4.dimethylacetamide intercalation compound. The oxovanadium matrix and the synthesized hybrid were characterized by elemental analysis, infrared spectroscopy, thermogravimetry, X-ray diffractometry and SEM microscopy. The X-ray diffraction patterns show that the VOPO4.dimethylacetamide compound is amorphous, but can be turned lamellar after a solubilization-crystallization process. The SEM micrographs obtained for the VOPO4-dimethylacetamide hybrid matrix show that the microstructure of VOPO4.2H2O is changed after reaction, with a delamination of the oxovanadium matrix.

Inativação por oxidação fotocatalítica de Escherichia coli e Pseudomonas sp.

This study presents the bactericidal activity of titanium dioxide photocatalysis, using as model Escherichia coli and Pseudomonas sp. cells. It was observed that the process efficiency is related to initial cell concentration, light intensity, UV irradiation exposure time, TiO2 concentration increase. The ultimate removal efficiency was above 99.9%.

Obtenção de titânio metálico com porosidade controlada por metalurgia do pó

Titanium is an attractive material for structural and biomedical applications because of its excellent corrosion resistance, biocompatibility and high strength-to-weight ratio. The high reactivity of titanium in the liquid phase makes it difficult to produce it by fusion. Powder metallurgy has been shown to be an adequate technique to obtain titanium samples at low temperatures and solid-phase consolidation. The production of compacts with different porosities obtained by uniaxial pressing and vacuum sintering is briefly reviewed. Powder particle size control has been shown to be very important for porosity control. Sample characterization was made using scanning electron microscopy (SEM) images.

Efecto de la naturaleza del precursor sobre las caracteristicas de las nanoparticulas de SnO2 sintetizadas

Tin oxide (SnO2) is widely used in industry as raw material for electronic devices, plating of different types of materials, for dyes and pigments, for electroplating, heterogeneous catalysis, etc. In this work SnO2 was obtained by a controlled precipitation method with special attention to the effects the tin precursor has on the microstructure of the final product. The most appropriate pH for obtaining SnO2 with the rutile structure as the main phase is 6.25 for SnCl2 and 6.40 for SnSO4. After heat treatment at 600 °C, particles of nanometric order (~10 - 30 nm approx) were obtained. The characterization of the solid phase was made by X-ray diffraction (XRD), thermal analysis (DTA/TG), transmission electron microscopy (TEM) and Fourier transformed infrared spectroscopy (FTIR).