Dental implants: Surface modification of cp-Ti using plasma spraying and the deposition of hydroxyapatite

The commercial pure titanium (cp-Ti) is currently being used with great success in dental implants. In this work we investigate how the cp-Ti implants can be improved by modifying the metal surface morphology, on which a synthetic material with properties similar to that of the inorganic part of the bone, is deposited to facilitate the bone/implant bonding. This synthetic material is the hydroxyapatite, HA, a calcium-phosphate ceramic. The surface modification consists in the application of a titanium oxide (TiO2) layer, using the thermal aspersion - plasma spray technique, with posterior deposition of HA, using the biomimetic method. The X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) and Diffuse Reflectance Infrared Fourier Transform (DRIFT) techniques have been used for characterizing phases, microstructures and morphologies of the coatings. The TiO2 deposit shows a mixture of anatase, rutilo and TiO2-x phases, and a porous and laminar morphology, which facilitate the HA deposition. After the thermal treatment, the previously amorphous structured HA coating, shows a porous homogeneous morphology with particle size of about 2-2.5 μm, with crystallinity and composition similar to that of the biological HA.

Erbium-activated HfO2-based waveguides for photonics

70SiO2 - 30HfO2 planar waveguides, activated by Er3+ concentration ranging from 0.3 to 1 mol%, were prepared by solgel route, using dip-coating deposition on silica glass substrates. The waveguides showed high densification degree, effective intermingling of the two components of the film, and uniform surface morphology. Propagation losses of about 1 dB/cm were measured at 632.8 nm. When pumped with 987 nm or 514.5 nm continuous-wave laser light, the waveguides showed the 4I 13/2→4I15/2 emission band with a bandwidth of 48 nm. The spectral features were found independent both on erbium content and excitation wavelength. The 4I13/2 level decay curves presented a single exponential profile, with a lifetime between 2.9-5.0 ms, depending on the erbium concentration.

Powder processing and In Vivo evaluation of a titanium porous coating implant

The processing of titanium porous coatings using powder metallurgy technique to achieve a porous structure that allows osseointegration with bone tissue was discussed. The porous microstructure exhibited micropores and interconnected macropores with size ranges that allowed bone ingrowth. The macropores in the coatings were originated from the binder evaporation while the micropore was related with the porous titanium powder and the low compaction pressure used. The in vivo evaluation indicated that osseointegration had occurred between the bone and porous material.

Evaluation of Ir-based modifiers in the simultaneous determination of As, Bi, Pb, Sb, and Se in milk by graphite furnace atomic absorption spectrometry

Different modifiers (IrCl3, W+IrCl3, Zr+IrCl 3) and coatings (Ir, W-Ir, Zr-Ir) were evaluated for the simultaneous determination of arsenic, bismuth, lead, antimony, and selenium in milk by graphite furnace atomic absorption spectrometry using the 'end-capped' transversely heated graphite atomizer (THGA). Integrated platform, pretreated with Zr-Ir as permanent modifier, was elected as the optimum surface modification resulting in up to 250 firings. Two additional recoatings were possible without significant changes in the analytical performance (750 firings). For 20 μL of matrix-matched standard solutions using diluted (1:10) milk samples, typical correlation coefficients between integrated absorbance and analyte concentration (5.00-20.0 μg/L) was always better than 0.999. The levels of the analytes found in commercial milk samples were lower than the limit of detection: 2.9 μg/L As, 2.9 μg/L Bi, 1.8 μg/L Pb, 1.9 μg/L Sb, and 2.5 μg/L Se. Recoveries were found within the following intervals: 88-114% for As, 89-118% for Bi, 89-113% for Pb, 91-115% for Sb, and 92-115% for Se. The relative standard deviations (n = 12) were ≤2% (As), ≤ 5% (Bi), ≤ 1.4% (Pb), ≤ 3% (Sb), and 5% (Se), and the respective calculated characteristic masses were 54 pg As, 55 pg Bi, 40 pg Pb, 56 pg Sb, and 51 pg Se.

Temporal evolution of sulfated zirconia sol-gel during dip coating: Analysis of mass drainage with time-varying refractive index

The formation of sulfated zirconia films from a sol-gel derived aqueous suspension is subjected to double-optical monitoring during batch dip coating. Interpretation of interferometric patterns, previously obscured by a variable refractive index, is now made possible by addition of its direct measurement by a polarimetric technique in real time. Significant sensitivity of the resulting physical thickness and refractive index curves (uncertainties of ±7 nm and ±0.005, respectively) to temporal film evolution is shown under different withdrawal speeds. As a first contribution to quantitative understanding of temporal film formation with varying nanostructure during dip coating, detailed analysis is directed to the stage of the process dominated by mass drainage, whose simple modeling with temporal t-1/2 dependence is verified experimentally. © 2006 Elsevier B.V. All rights reserved.

Estudo da influência dos íons K+, Mg2+, SO4 2- e CO3 2- na cristalização biomimética de fosfato de cálcio amorfo (ACP) e conversão a fosfato octacálcico (OCP)

The crystallization of hydroxyapatite (HA) in aqueous solution can be described by the mechanism ACP → OCP → HA. In this work, it was studied the influence of K+, Mg2+, SO4 2- AND CO3 2- ions in the formation of ACP and in its conversion to OCP, using biomimetic coatings on metallic substrates of commercially pure titanium (Ti c.p.). The results showed that Mg2+ and CO3 2- ions favored both the formation of ACP and its conversion to OCP. Differently, K+ and SO4 2- ions did not influence the formation of ACP and, consequently, interfered in the conversion to OCP.

The significance and determination by image analysis of microcrack density in hard chromium plating

It is well known that the microcrack density is a fundamental parameter in hard chromium electroplating. The chemical and mechanical properties of this coating are widely dependent on its microcrack density. In this paper a simple image analysis procedure to determine microcrack density is presented in order to demonstrate it as a fundamental tool to estimate the fatigue, corrosion and wear behavior, as well as the residual stress field of a coated component. For this purpose, the image analysis procedure was carried out on two kinds of hard chromium plating - one called accelerated (high velocity of deposition and fluoride-free) and the other conventional (with fluoride). The coatings were applied on samples of AISI 4340 aeronautical steel, which is widely used in aircraft landing gear components. To characterize the practical significance of this study, the microcrack density results were related to the fatigue, wear and corrosion behavior from previous study and to the residual stress field in the coatings.

Turning of compacted graphite iron using commercial tiN coated Si 3N4 under dry machining conditions

Due to their high hardness and wear resistance Si3N4 based ceramics are one of the most suitable cutting tool materials for machining hardened materials. Therefore, their high degree of brittleness usually leads to inconsistent results and sudden catastrophic failures. Improvement of the functional properties these tools and reduction of the ecological threats may be accomplished by employing the technology of putting down hard coatings on tools in the state-of-the-art PVD processes, mostly by improvement of the tribological contact conditions in the cutting zone and by eliminating the cutting fluids. However in this paper was used a Si3N4 based cutting tool commercial with a layer TiN coating. In this investigation, the performance of TiN coating was assessed on turning used to machine an automotive grade compacted graphite iron. As part of the study were used to characterise the performance of cutting tool, flank wear, temperature and roughness. The results showed that the layer TiN coating failed to dry compacted graphite iron under aggressive machining conditions. However, using the measurement of flank wear technique, the average tool life of was increased by VC=160 m/min.The latter was also observed using a toolmakers microscope and scanning electron microscopy (SEM).

Influence of cerium (IV) ions on the inorganic and organic phase for preparation of a siloxane-PMMA based film on tin plate substrate

Tinplate is one of the most widely used food canning materials, however, there are significant problems related to the use of tinplate cans, such as alterations in sensory features affecting food quality and corrosion phenomena of the canning material. To avoid corrosion problems different methods have been used for the passivation of tinplate such protective lacquers or different kinds of corrosion inhibitors (chromate and dichromate). However, chromates and dichromates are extremely harmful to the environment and can cause carcinogenic tumors to humans. An option, protective coatings obtained by the sol-gel process, act as a physical barrier, which isolates the surface of metal protecting from the corrosive agents. The aim of this work is to study the influence of addition of cerium (IV) ions in the inorganic and organic part of sol-gel processing in the formation of hybrid coatings based on siloxane-PMMA on tin plate. The coatings were obtained by dip-coating technique and evaluated by open circuit and impedance measurements, linear polarization and polarization curves obtained in 3.5% NaCl solution. The results have clearly shown the improvement on the protective properties of the Ce 4+ modified film when added into the organic phase, which can be due to the formation of a more uniform and densely reticulated siloxane-PMMA film. © 2009 by NACE International.

In vivo evaluation of porous titanium implants with biomimetic coating

The osseointegration of porous titanium implants was evaluated in the present work. Implants were fabricated from ASTM grade 2 titanium by a powder metallurgy method. Part of these implants were submitted to chemical and thermal treatment in order to deposit a biomimetic coating, aiming to evaluate its influence on the osseointegration of the implants. The implants were characterized by Scanning Electron Microscopy (SEM), Electron Dispersive X-Ray Spectroscopy (EDS) and Raman Spectroscopy. Three coated and three control (uncoated) implants were surgically inserted into thirty albino rabbits' left and right tibiae, respectively. Tibiae samples were submitted to histological and histomorphometric analyses, utilizing SEM, optical microscopy and mechanical tests. EDS results indicated calcium (Ca) and phosphorous (P) at the surface and Raman spectra exhibited an intense peak, characteristic of hydroxyapatite (HA). Bone neoformation was detected at the bone-implant interface and inside the pores, including the central ones. The mean bone neoformation percentage in the coated implants was statistically higher at 15 days, compared to 30 and 45 days. The mechanical tests showed that coated implants presented higher resistance to displacement, especially after 30 and 45 days.

Influência do arcabouço hidroestratigráfico nas ocorrências de arsênio em águas subterrâneas ao longo do corredor termal do rio Uruguai (Argentina - Brasil - Uruguai)

The Thermal Corridor of Uruguay River is located in the triple border of Argentine, Brazil and Uruguay, and shows an intense economic thermal tourism activity, mainly based on groundwaters from Guarani Aquifer System (GAS). Recent studies have pointed out the occurrence of high concentrations of arsenic (>10 μg/L) in GAS groundwater in this area. The complex geological and hydrogeological framework in the area is associated to the Paraná Basin geological evolution south of the Assuncion-Rio Grande Arch; it encompass paleozoic marine sequences and continental sequences permian/eotriassic to mesozoic in age, which are covered by basaltic lavas of Serra Geral Formation. Iron oxide coatings have been described in sandstones of Buena Vista and Sanga do Cabral formations, which underlie GAS units. Arsenic occurrence is associated to sodium bicarbonate groundwater with pH values over 8.0. Arsenic is released to groundwater by desorption from iron oxides/hydroxides, as result of the higher pH of these waters, indicating that arsenic is released from the units that underlie GAS units. Increase in chromium and uranium concentrations are also related to high pH groundwaters, thus indicating special care on using groundwater from this region.

Cutting performance of diamond coated Si3N4 tool during turning

Silicon nitride cutting tools have been used successfully for machining hard materials, like: cast irons, nickel based alloys, etc. However these cutting tools with diamond coating present little information on dry turning operations of gray cast iron. In the present work, Si3N4 square inserts was developed, characterized and subsequently coated with diamond for dry machining operations on gray cast iron. All experiments were conducted with replica. It was used a 1500, 3000, 4500 m cutting length, feed rate of 0.33 mm/rev and keeping the depth of cut constant and equal to 1 mm. The results show that wear in the tool tips of the Si3N4 inserts, in all cutting conditions, was caused by both mechanical and chemical processes. To understand the tool wear mechanisms, a morphological analysis of the inserts, after experiments, has been performed by SEM and optical microscopy. Diamond coated PVD inserts showed to be capable to reach large cutting lengths when machining gray cast iron. © (2010) Trans Tech Publications.

Crystallization and optical properties of CCTO thin films under pressure influence

CCTO thin films were deposited on Pt(111)/Ti/SiO 2/Si substrates using a chemical (polymeric precursor) and pressure method. The pressure effects on the CCTO thin films were evaluated by XRD, FEG-SEM and optical properties. Pressure films were found to be more homogeneous and dense than chemical deposition films. Pressure also leaded to an increase in the photoluminescence emission; it is suggested that the displacement of Ti in the titanate clusters, favors the charge transference from TiO 6 to [TiO 5V o z], TiO 5V o z] to [CaO 11V o z] and [TiO 5V o z] to [CuO 4] x. The low synthesis temperature used in the pressure method allows the deposition of films on less expensive substrates (i.e. glass, aluminum, polymer and others).

Study of polypropylene surface modification by air dielectric barrier discharge operated at two different frequencies

In this work, air dielectric barrier discharge (DBD) operating at the line frequency (60 Hz) or at frequency of 17 kHz was used to improve the wetting properties of polypropylene (PP). The changes in the surface hydrophilicity were investigated by contact angle measurements. The plasma-induced chemical modifications of PP surface were studied by X-ray photoelectron spectroscopy (XPS) and Fourier-transformed infrared spectroscopy (FTIR). The polymer surface morphology and roughness before and after the DBD treatment were analyzed by atomic force microscopy (AFM). To compare the plasma treatment effect at different frequencies the variation of the contact angle is presented as a function of the deposited energy density. The results show that both DBD treatments leaded to formation of water-soluble low molecular weight oxidized material (LMWOM), which agglomerated into small mounts on the surface producing a complex globular structure. However, the 60 Hz DBD process produced higher amount of LMWOM on the PP surface comparing to the 17 kHz plasma treatment with the same energy dose. The hydrophilic LMWOM is weakly bounded to the surface and can be easily removed by polar solvents. After washing the DBD-treated samples in de-ionized water their surface roughness and oxygen content were reduced and the PP partially recovered its original wetting characteristics. This suggested that oxidation also occurred at deeper and more permanent levels of the PP samples. Comparing both DBD processes the 17 kHz treatment was found to be more efficient in introducing oxygen moieties on the surface and also in improving the PP wetting properties. © 2012 Elsevier B.V. All rights reserved.

Study of the influence of the rare earth elements (Ce3+ and Ce4+) concentration on the siloxanes coating applied on the copper surface

This work studied the influence of the rare earth (Ce3+ and Ce4+) elements concentration in polysiloxane flints deposited on copper by dip-coating process, and evaluated their resistance in a 3.5 wt.% NaCl medium. Classical electrochemistry techniques were used as open circuit potential, polarization curves and electrochemical impedance spectroscopy. The results revealed that by adding low concentration of Ce4+ ions, the coating prevents the electrolyte uptake any longer retarding the substrate degradation consequently. ©The Electrochemical Society.