Fluorescence line-narrowing spectroscopy is used to characterize the effect of metal cation codopants (Sr2+, La3+, Gd3+, Y3+, Lu3+, Sc3+, and Ga3+) on the state of aggregation of Eu3+ in sol−gel silica. Significant Eu3+ clustering occurs in samples doped only with Eu3+. The addition of codopants inhibits the clustering of Eu3+ and promotes better dispersion of Eu3+ in the glasses. The extent of the inhibition of clustering increases with field strength of the codopant and levels off at high field strength. The inhibition of clustering is correlated with the generation of strong crystal field bonding sites for Eu3+ in the presence of codopants. Characteristics of these sites include the presence of Eu−O−M (M = codopant) linkages and stronger interactions with the network-forming regions of the glass. Supporting luminescence decay and Raman spectroscopy measurements are also presented.

Sol-gel titania films were deposited on 316L stainless steel using titanium isopropoxide as a chemical precursor. Dipcoating

Fluorescence line narrowing and lifetime measurements are used to characterize the extents of clustering and hydroxyl quenching, respectively, in Eu3+-doped sol−gel silica glasses prepared using europium trifluoromethanesulfonate (triflate). A triflate ((CF3SO3)3Eu) rather than a traditional nitrate (Eu(NO3)3·6H2O) precursor is used as the rare earth ion dopant in order to determine the feasibility of effecting chemical dehydroxylation via in situ fluorination by incorporating fluorine directly as a ligand substituent of the Eu3+ precursor. In samples doped only with Eu3+, the use of the triflate precursor leads to no noticeable differences in hydroxyl quenching of Eu3+ fluorescence or Eu3+ aggregation relative to samples prepared with a nitrate precursor. Beneficial effects are observed, however, in samples codoped with Al3+ or Sr2+. When Al3+ or Sr2+ is included in the synthesis, a reduction in hydroxyl quenching of Eu3+ is observed when the triflate precursor is used relative to the nitrate precursor. In addition, (CF3SO3)3Al is found to be as effective at inhibiting Eu3+ clustering as the previously reported Al(NO3)3·9H2O and (C4H9O)2Al−O−Si(OC2H5)3 precursors. The effect of incoporating fluorine via FSi(OC2H5)3 is also briefly considered and gives mixed results which differ for nitrate and triflate Eu3+ precursors.

Sol-gel film in the SiO 2 -CaO-P 2 O 5 system was prepared from TEOS, TEP, alcohol and hydrated calcium nitrate in an acidic medium. The coatings were deposited on stainless steel using the dip-coating technique. After deposition, the composite was submitted to heat treatment, at different temperatures and exposure times to investigate the influence of such parameters on the surface morphology of the composite. The coated surfaces were characterized by AFM, SEM and FTIR. The present study showed that the formation of different textures (an important parameter in implant fixation) could be controlled by temperature and time of heat treatment.

Tissue engineering has evolved from the use of biomaterials for bone substitution that fulfill the clinical demands of biocompatibility, biodegradability, non-immunogeneity, structural strength and porosity. Porous scaffolds have been developed in many forms and materials, but few reached the need of adequate physical, biological and mechanical properties. In the present paper we report the preparation of hybrid porous polyvinyl alcohol (PVA)/bioactive glass through the sol-gel route, using partially and fully hydrolyzed polyvinyl alcohol, and perform structural characterization. Hybrids containing PVA and bioactive glass with composition 58SiO2-33CaO-9P2O5 were synthesized by foaming a mixture of polymer solution and bioactive glass sol-gel precursor solution. Sol-gel solution was prepared from mixing tetraethoxysilane (TEOS), triethylphosphate (TEP), and calcium chloride as chemical precursors. The hybrid composites obtained after aging and drying at low temperature were chemically and morphologically characterized through infrared spectroscopy and scanning electron microscopy. The degree of hydrolysis of PVA, concentration of PVA solution and different PVA-bioglass composition ratios affect the synthesis procedure. Synthesis parameters must be very well combined in order to allow foaming and gelation. The hybrid scaffolds obtained exhibited macroporous structure with pore size varying from 50 to 600 µm

One of the applications of selective surfaces is to improve performance of solar absorbers. The purpose of this work is to produces selective coatings with high absorption of solar radiation in the range of UV/Vis/NIR. It was prepared a selective surface composed of black chromium (Cr/Cr 2 O 3 ) deposited on substrates of AISI 304 stainless steel using the technique of electrolytic deposition for application in solar thermal absorbers. The great parameters for deposition consisted of a continuous electric current of 2A for 90s, at a constant temperature of 40°C. After deposition, the samples under went to a heat treatment at 600°C for 2h for oxidation. The coatings thicknesses were determined. From the SEM analysis coupled with EDS, it was found that the microstructures reported sample of cermets. The XRD results show diffraction peaks related to metallic chromium (Cr) and chromium oxide (Cr 2 O 3 ). Spectral absorptance values more 90.0% were found.

The effects of combustion thermal spraying parameters namely combustion pressure, feeding rate, and carrier gas on the wear resistance, friction coefficient, and Knoop hardness of poly (ethylene terephthalate) (PET) films were investigated. The PET coatings were characterized by measuring the wear coefficients by calowear-type testing, the friction coefficients by a pin-on-disk test, and Knoop hardness. The abrasive wear and friction coefficients of the coatings were compared with the values of a post consumer PET bottle chip reference sample. The structural characteristics of the coatings were investigated by X ray diffraction. Statistical analysis of the results allowed for the systematic characterization of the influence of the process variables mentioned above on the coating wear, friction, and microhardness values. Specifically, this study shows that the process parameters affect the wear coefficient and Knoop hardness significantly, but not the friction coefficient. The degree of crystallinity of the PET coatings varied from 20 to 26%. Keywords: thermal spray, PET, tribology*e-mail: rogerioxavier@yahoo.com.br, jose.branco@cetec.br, vilmaccosta@hotmail.com, calado@eq.ufrj.br 122 Nunes et al. Materials Researchparameters were 10 rpm, 14 mm trail diameter, 10-N load, 50 turns, and a traveled distance of 2,200 mm. Each sample was measured in triplicate. The samples were weighed before and after testing for calculation of mass loss. Wear testAbrasive wear was evaluated by calowear testing, which involves the interaction of a rotating steel sphere with the sample surface with alumina as an abrasive. A semi-spherical crater was formed on the contact surface of the sample. The wear rate was calculated from the crater dimension using Equations 2, 3, and 4:where D is the crater diameter, n the number of turns, R the sphere radius, V the lost volume, S the sliding distance, and Q the wear rate 12 .The wear coefficient (K) was calculated with the Archad equation 10 , where W is the applied load and H the hardness.The sliding distances of the sphere were 100, 200, 300, 500, and 1000 turns and the applied load was 13.7 N. Each sample was measured in triplicate. The crater diameter was measured by 3D profilometry. Results and Discussion Coating structureUsing an optical microscope, the presence of bubbles or pores at the substrate/coating interface and in the PET coating medium was not observed. However, they were observed on the coating-free surface. The formation of bubbles is explained in the following way. The final coating temperature was around 410 °C, below the degradation temperature of PET (420 °C). Apparently, the temperature reached by the deposited layers was sufficient for their complete coalescence between the substrate and the coating medium. Particle degradation was insignificant. This will be further discussed with the results of the infrared spectroscopy. Due to the heterogeneous size of the PET particles, the smallest ones probably melted, while the larger ones were semi-melted. During the natural cool...

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