Structural characteristics of silica sonogels prepared with additions of isopropyl alcohol

Wet silica gels with similar to 1.4 x 10(-3) mol SiO2/cm(3) and similar to 92 vol% liquid phase were obtained from sonohydrolysis of tetraethoxysilane (TEOS) with different additions of isopropyl alcohol ( IPA). The IPA/TEOS molar ratio R was changed from 0 to 4. Aerogels were obtained by supercritical CO2 extraction. The samples were analyzed by small-angle X-ray scattering (SAXS) and nitrogen adsorption. The wet gels exhibit mass fractal structure with fractal dimension increasing from D similar to 2.10 to D similar to 2.22, characteristic length xi decreasing from similar to 9.5 to similar to 6.9 nm, as R increases from 0 to 4, and an estimated characteristic length for the primary silica particles lower than similar to 0.3 nm. The supercritical process apparently eliminates a fraction of the porosity, increasing the mass fractal dimension and shortening the fractality domain in the mesopore region. The fundamental role of isopropyl alcohol on the structure of the resulting aerogels is to decrease the porosity and the pore mean size as R changes from pure TEOS to R = 4. A secondary structure appearing in the micropore region of the aerogels can be described as a mass/surface fractal structure, with correlated mass fractal dimension D-m similar to 2.7 and surface fractal dimension D-s similar to 2.3, as inferred from SAXS and nitrogen adsorption data.

Persistence of resinous cement residues in dentin treated with different chemical removal protocols

The aim of this study was to evaluate the persistence of resin cement residues after dentin surface cleaning with different alcohol-based solutions or an essential oil (eucalyptol). Forty bovine teeth were sectioned in order to expose pulp chamber dentin to be washed with 1.0 mL of 2.5% sodium hypochlorite (NaOCl), followed by 0.1 mL of 17% EDTA application for 3 min, and final irrigation with 2.5% NaOCl. The specimens were air dried and resin-based cement was rubbed onto the dentine surface with a microbrush applicator. After 15 min, the surface was scrubbed with a cotton pellet and moistened with different dentin cleaning solutions, compounding the following groups: G195% ethanol, G270% ethanol, G370% isopropyl alcohol, or G4eucalyptol. The dentin was scrubbed until the cement residues could not be visually detected. Sections were then processed for SEM and evaluated at x 500 magnification. Scores were attributed to each image according to the area covered by residual sealer, and data were subjected to KruskalWallis at 5% significance. Eucalyptol promoted the most adequate dentin cleaning, although no statistical difference was detected amongst the groups (P > 0.05), except between the eucalyptol and 70% ethanol groups (P < 0.05). All the evaluated dentin cleaning solutions were unable to completely remove the cement residues from the dentin surface. Microsc. Res. Tech., 2012. (C) 2012 Wiley Periodicals, Inc.

Room temperature co-precipitation of nanocrystalline CeO2 and Ce0.8Gd0.2O1.9-delta powder

This paper describes a simple method to co-precipitate CeO2 and Ce0.8Gd0.2O1.9-delta with ammonium hydroxide from solvents such as: water, ethylene glycol, ethyl alcohol and isopropyl alcohol. Characterization by Raman spectroscopy and XRD evidenced the formation of a solid solution of gadolinium-doped ceria at room temperature. Nanometric particles with crystallite size of 3.1 nm were obtained during synthesis using ethyl alcohol as solvent. This is a promising result compared with those mentioned in the literature, in which the smallest crystallite size reported was, 6.5 nm. (c) 2006 Elsevier B.V. All rights reserved.

Postharvest characteristics and treatments to overcome latex exuded from cut flowers of lotus

Lotus (Nelumbo nucifera Gaertn.) is a perennial herbaceous aquatic ornamental plant with potential to be used as a new cut flower for the Brazilian ornamental market. It shows exotic and attractive flowers and has a strong market appeal, once it is known as a symbol of purity, holiness and immortality. However, flowers have a short-vase life. Lotus flower stem exudes a large quantity of sticky milky sap from the cut surface, which is produced in laticifers, spatially associated with both xylem and phloem. It has been reported that latex coagulates on the cut surface preventing or reducing water absorption and reducing flowers' vaselife, requiring treatments to stop the flow of latex. The objective of this study was to report observations of lotus postharvest characteristics and evaluate treatments to overcome latex flow. The experiment was conducted as a complete randomized design with three replications of four stems in each vase and eight treatments; a control (distilled water), pretreatment of cut stem-ends with hot water (40° C/1 minute), boiling water (3 seconds), isopropyl alcohol 90% (10 minutes) or citric acid (pH = 2.8/1h) and, maintenance of stems in a holding solution of Tween® 20 (0.01%), citric acid (200 mg L-1) or Tween® 20 (0.01%) plus citric acid (200 mg L-1). Treatments had no significant effect on flowers vaselife which was only about three days, although isopropyl alcohol, hot and boiling water completely stopped latex flow. Cut stem-ends pretreated with citric acid (pH = 2.8/1 h) showed a significantly higher relative water content of petals compared to others treatments. The senescence symptom of lotus cut flowers was mainly characterized by abscission of turgid petals and dehiscence of stamens without any visual change of petal color and brightness.

Persistence of epoxy-based sealer residues in dentin treated with different chemical removal protocols

The presence of residual endodontic sealer in the pulp chamber may cause discoloration of the dental crown and interfere with the adhesion of restorative materials. The aim of this study was to compare the efficacy of different solvents in removing residues of an epoxy resin-based sealer (AH Plus) from the dentin walls of the pulp chamber, by scanning electron microscopy (SEM). Forty-four bovine incisor dental crown fragments were treated with 17% EDTA and 2.5% NaOCl. Specimens received a coating of AH Plus and were left undisturbed for 5 min. Then, specimens were divided in four groups (n = 10) and cleaned with one of the following solutions: isopropyl alcohol, 95% ethanol, acetone solution, or amyl acetate solution. Negative controls (n = 2) did not receive AH Plus, while in positive controls (n = 2) the sealer was not removed. AH Plus removal was evaluated by SEM, and a score system was applied. Data were analyzed by Kruskal-Wallis and Dunn tests. None of the solutions tested was able to completely remove AH Plus from the dentin of the pulp chamber. Amyl acetate performed better than 95% ethanol and isopropyl alcohol (p < 0.05), but not better than acetone (p > 0.05) in removing the sealer from dentin. No significant differences were observed between acetone, 95% ethanol, and isopropyl alcohol (p > 0.05). It was concluded that amyl acetate and acetone may be good options for cleaning the pulp chamber after obturation with AH Plus. SCANNING 35:17-21, 2013. © 2012 Wiley Periodicals, Inc. © Wiley Periodicals, Inc.

High-voltage electrophoretic deposition of preferentially oriented films from multiferroic YMn2O5 nanopowders

Processing of the YMn2O5 powder is very challenging, since it decomposes to YMnO3 and Mn3O4 at temperatures close to 1180 °C, while samples consolidation commonly demands high temperatures. The main goal of this work is to investigate a possibility to prepare thick films of YMn2O5, since their deposition generally requires significantly lower temperatures. Multiferroic YMn 2O5 was synthesized by the hydrothermal method from Y(CH3COO)3·xH2O, Mn(CH 3COO)2·4H2O and KMnO4 precursors. XRD, FE-SEM and TEM analysis showed that the obtained powder was monophasic, with orthorhombic crystal structure and columnar particle shape with mean diameter and length of around 20 and 50 nm, respectively. The obtained powder was suspended in isopropyl alcohol with addition of appropriate binder and deflocculant. This suspension was used for electrophoretic deposition of YMn2O5 thick films under the high-voltage conditions and electric fields ranging from 250 to 2125 V/cm. The films obtained at 1000 V/cm and higher electric fields showed good adhesion, particle packing, homogeneity and very low porosity. It was shown that the deposition in extremely high electric fields (KC=2125 V/cm) can influence the crystal orientation of the films, resulting in formation of preferentially oriented films. © 2012 Elsevier Ltd and Techna Group S.r.l.

Propriedades nanoestruturais de géis de sílica preparados com adiçoes de surfactante anionico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Síntese de aerogéis e xerogéis de sílica com troca de solvente e secagem a pressão ambiente

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo visando a otimização do solvente extrator e estudo preliminar sobre a quantificação da citocalasina D produzida pelo endófito Xylaria sp., usando a técnica de RMN de '1 SOB H'

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Tratamento a plasma de polímeros comerciais transparentes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Obtenção e caracterização de fibras poliméricas e cerâmicas pela técnica de “blow-spinning”

Pós-graduação em Ciência dos Materiais - FEIS

Avaliação da retençao de coroas de Ytrio-zircônia cimentadas à diferentes substratos, com quatro agentes cimentantes, após termociclagem

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeito da implantação iônica por imersão em plasmas sobre a bioatividade de titânio

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

Structure of Hydrophobic Ambient-Pressure-Dried Aerogels Prepared by Sonohydrolysis of Tetraethoxysilane with Additions of N,N-Dimethylformamide

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

Efeitos da interação e soluções utilizadas na prevenção da formação do precipitado originado pela interação do hipoclorito de sódio e do diglunato de clorexidina e a repercursão sobre a resistência de união de cimento obturador na dentina do canal radicular

Pós-graduação em Odontologia - FOAR