Thermo and photochromic properties of Na2O-WO3-SbPO4 glasses

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Disorder effects produced by the Mn and H incorporations on the optical absorption edge of Ga1-xMnxAs:H nanocrystalline films

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The optical absorption edge of nanocrystalline Ga(1-x)Mn(x)N films deposited by reactive sputtering

We have focused on the optical absorption edge of nanocrystalline Ga(1-x)Mn(x)N (0.00 <= x <= 0.18) films deposited by reactive RF magnetron sputtering. The films obtained are nanocrystalline with grain sizes of about 25 nm, having wurtzite structure and strong orientation texture in the c-axis direction. The optical characterizations of the absorption edges were obtained in the 190-2600 nm spectral range. The increase of the Mn content causes an increase of the absorption coefficient which can be clearly noticed at low energies, and a quasi-linear decrease of the optical gap. Broad absorption bands observed around similar to 1.3 and similar to 2.2 eV were associated with transitions between the Mn acceptor level and the valence and conduction bands, respectively. The observed changes in the optical properties due to the Mn incorporation observed in these nanocrystalline films are similar to those reported for ferromagnetic GaMnN single-crystal films.

Structural Characterization of Nanocrystalline Sb-Doped SnO2 Xerogels by Multiedge X-ray Absorption Spectroscopy

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Structural and optical properties of chlorinated plasma polymers

Amorphous hydrogenated chlorinated carbon (a-C:H:Cl) films were produced by the plasma polymerization of chloroform-acetylene-argon mixtures in a radiofrequency plasma enhanced chemical vapor deposition system. The main parameter of interest was the proportion of chloroform in the feed, R(C), which was varied from 0 to 80%. Deposition rates of 80 nm min (1) were typical for the chlorinated films. Infrared reflection-absorption spectroscopy revealed the presence of C-Cl groups in all the films produced with chloroform in the feed. X-ray photoelectron spectroscopy confirmed this finding, and revealed a saturation of the chlorine content at similar to 47 at.% for R(C)>= 40%. The refractive index and optical gap, E(04), of the films were roughly in the 1.6 to 1.7, and the 2.8 to 3.7 eV range. These values were calculated from transmission ultraviolet-visible-near infrared spectra. Chlorination leads to an increase in the water surface contact angle from similar to 40 degrees to similar to 77 degrees. (C) 2011 Elsevier B.V. All rights reserved.

Evaluation of Bulk and Surfaces Absorption Edge Energy of Sol-Gel-Dip-Coating SnO2 Thin Films

The absorption edge and the bandgap transition of sol-gel-dip-coating SnO2 thin films, deposited on quartz substrates, are evaluated from optical absorption data and temperature dependent photoconductivity spectra. Structural properties of these films help the interpretation of bandgap transition nature, since the obtained nanosized dimensions of crystallites are determinant on dominant growth direction and, thus, absorption energy. Electronic properties of the bulk and (110) and (101) surfaces are also presented, calculated by means of density functional theory applied to periodic calculations at B3LYP hybrid functional level. Experimentally obtained absorption edge is compared to the calculated energy band diagrams of bulk and (110) and (101) surfaces. The overall calculated electronic properties in conjunction with structural and electro-optical experimental data suggest that the nature of the bandgap transition is related to a combined effect of bulk and (101) surface, which presents direct bandgap transition.

Electronic structure and optical properties of BaMoO4 powders

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Structural and optical properties of CaTiO3 perovskite-based materials obtained by microwave-assisted hydrothermal synthesis: An experimental and theoretical insight

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Study of optical properties and molecular structure of plasma polymerized diethylene glycol dimethyl ether

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Wettability, optical properties and molecular structure of plasma polymerized diethylene glycol dimethyl ether

Modern industry has frequently employed ethylene glycol ethers as monomers in plasma polymerization process to produce different types of coatings. In this work we used a stainless steel plasma reactor to grow thin polymeric films from low pressure RF excited plasma of diethylene glycol dimethyl ether. Plasmas were generated at 5W RF power in the range of 16 Pa to 60 Pa. The molecular structure of plasma polymerized films and their optical properties were analyzed by Fourier Transform Infrared Spectroscopy (FTIR) and UltravioletVisible Spectroscopy, respectively. The IR spectra show C-H stretching at 3000-2900 cm(-1), C=O stretching at 1730-1650 cm(-1), C-H bending at 1440-1380 cm(-1), C-O and C-O-C stretching at 1200-1000 cm(-1). The refraction index was around 1.5 and the optical gap calculated from absorption coefficient presented value near 3.8 eV. Water contact angle of the films ranged from 40 degrees to 35 degrees with corresponding surface energy from 66 to 73x10(-7) J. Because of its favorable optical and hydrophilic characteristics these films can be used in ophthalmic industries as glass lenses coatings.

Effect of addition of pigments and opacifier on the hardness, absorption, solubility and surface degradation of facial silicone after artificial ageing

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evaluation of the physical and chemical properties of two commercial and three experimental root-end filling materials

Objective. The aim of this study was to evaluate the pH, calcium release, setting time, and solubility of two commercially available mineral trioxide aggregate (MTA) cements (white MTA Angelus and MTA Bio), and of three experimental cements (light-cured MTA, Portland cement with 20% bismuth oxide and 5% calcium sulfate, and an epoxy resin-based cement).Study design. For evaluation of pH and calcium ion release, polyethylene tubes with 1.0 mm internal diameter and 10.0 mm length were filled with the cements and immediately immersed in flasks containing 10 mL deionized water. After 3, 24, 72, and 168 hours, the tubes were removed and the water from the previous container was measured for its pH and calcium content with a pH meter and an atomic absorption spectrophotometer. For analysis of the setting time, Gilmore needles weighing 100 g and 456.5 g were used, in accordance with the American Society for Testing and Materials specification no. C266-03. Solubility of each cement was also tested.Results. All the cements were alkaline and released calcium ions, with a declining trend over time. After 3 hours, Portland cement + bismuth oxide and MTA Bio had the highest pH and light-cured MTA the lowest. After 1 week, MTA Bio had the highest pH and light-cured MTA and epoxy resin-based cement the lowest. Regarding calcium ion release, after 3 hours, Portland cement + bismuth oxide showed the highest release. After 1 week, MTA Bio had the highest. Epoxy resin-based cement and light-cured MTA had the lowest calcium release in all evaluation periods. Regarding setting times, white MTA Angelus and MTA Bio had the shortest, Portland cement + bismuth oxide had an intermediate setting time, and the epoxy resin-based cement had the longest. The materials that showed the lowest solubility values were the epoxy resin-based cement, Portland cement + bismuth oxide, and light-cured MTA. The highest solubility values were presented in white MTA Angelus and MTA Bio.Conclusions. The white MTA Angelus and MTA Bio had the shortest setting times, higher pH and calcium ion release, and the highest solubility. In contrast, the epoxy resin-based cement and light-cured MTA showed lower values of solubility, pH, and calcium ion release. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010; 110: 250-256)

Evaluation of the propylene glycol association on some physical and chemical properties of mineral trioxide aggregate

Duarte MAH, Alves de Aguiar K, Zeferino MA, Vivan RR, Ordinola-Zapata R, Tanomaru-Filho M, Weckwerth PH, Kuga MC. Evaluation of the propylene glycol association on some physical and chemical properties of mineral trioxide aggregate. International Endodontic Journal, 45, 565570, 2012. Abstract Aim To evaluate the influence of propylene glycol (PG) on the flowability, setting time, pH and calcium ion release of mineral trioxide aggregate (MTA). Methodology Mineral trioxide aggregate was mixed with different proportions of PG, as follows: group 1: MTA + 100% distilled water (DW); group 2: MTA + 80% DW and 20% PG; group 3: MTA + 50% DW and 50% PG; group 4: MTA + 20% DW and 80% PG; group 5: MTA + 100% PG. The ANSI/ADA No. 57 was followed for evaluating the flowability and the setting time was measured by using ASTM C266-08. For pH and calcium release analyses, 50 acrylic teeth with root-end cavities were filled with the materials (n = 10) and individually immersed in flasks containing 10 mL deionized water. After 3 h, 24 h, 72 h and 168 h, teeth were placed in new flasks and the water in which each specimen was immersed had its pH determined by a pH metre and the calcium release measured by an atomic absorption spectrophotometer with a calcium-specific hollow cathode lamp. Data were analysed by using one-way anova test for global comparison and by using Tukeys test for individual comparisons. Results The highest value of flowability was observed with MTA + 20% DW and 80% PG and the lowest values were found with MTA + 100% DW. They were significantly different compared to the other groups (P < 0.05). The presence of PG did not affect the pH and calcium release. The MTA + 100% PG favoured the highest (P < 0.05) pH and calcium release after 3 h. Increasing the PG proportion interfered (P < 0.05) with the setting time; when used at the volume of 100% setting did not occur. Conclusion The addition of PG to MTA-Angelus increased its setting time, improved flowability and increased the pH and calcium ion release during the initial post-mixing periods. The ratio of 80% DW 20% PG is recommended.

Physicochemical properties of endodontic sealers of different bases

Objective: To assess the setting time (ST), flow (FL), radiopacity (RD), solubility (SB) and dimensional change following setting (DC) of different sealers (AH Plus (R), Polifil, Apexit Plus (R), Sealapex (R), Endomethasone (R) and Endofill (R)) according to American National Standards Institute/American Dental Association (ANSI/ADA) Specification 57. Material and methods: Five samples of each material were used for each test. For ST, cast rings were filled with sealers and tested with a Gillmore needle. For FL, the sealer was placed on a glass plate. After 180 s, another plate with 20 g and a load of 100 g were applied on the material, and the diameters of the discs formed were measured. In RD, circular molds were filled with the sealers, radiographed and analyzed using Digora software. For SB, circular molds were filled with the sealers, a nylon thread was placed inside the material and another glass plate was positioned on the set, pressed and stored at 37 degrees C. Samples were weighed, placed in water, dried and reweighed. The water used for SB was analyzed by atomic absorption spectrometry. For DC, circular molds were filled with the sealers, covered by glass plates and stored at 37 degrees C. Samples were measured and stored in water for 30 days. After this period, they were dryed and measured again. Results: Regarding ST, AH Plus (R), Apexit (R) and Endofil (R) sealers are in accordance with ANSI/ADA standards. Endomethasone's manufacturer did not mention the ST; Polifil is an experimental sealer and Sealapex (R) did not set. Considering RD, SB and DC, all sealers were in accordance with ANSI/ADA. The spectrometric analysis showed that a significant amount of K+ and Zn2(+) ions was released from Apexit Plus (R) and Endofill (R), respectively. Conclusion: Except for DC, all other physicochemical properties of the tested sealers conformed to ANSI/ADA requirements.

Synthesis of (Ca,Nd)TiO3 powders by complex polymerization, Rietveld refinement and optical properties

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)