Phase separation in pyrex glass by hydrothermal treatment: evidence from micro-Raman spectroscopy

In this work, we investigated the formation of porous silica matrix obtained by hydrothermal treatment under saturated steam condition from Pyrex (R) glass. This investigation was carried out by scanning electron microscopy (SEM), infrared spectroscopy (IR), X-ray powder diffractometry (XRD) and Raman microscopy. We observed the presence of connected and homogeneously distributed pores in a non-crystalline silica phase and a detectable interface between silica and remnant glass phases resulting in a framework similar to asymmetric membranes. The results indicate that the process of phase separation takes place at lower temperature than that of glass-transition on the surface of the glass phase. Essential reaction between water and silica at supercritical condition together with the formation and leaching of soluble phase contribute to obtain porous silica matrix, (C) 2001 Elsevier B.V. B.V. All rights reserved.

Hydrothermal treatment of gadolinium oxide in presence of silica

Hydrothermal and solvothermal (isopropanol) treatments of gadolinium oxide and silica were investigated under different pressure and temperature conditions. Products were examined by infrared vibrational spectroscopy (IR), x-ray powder diffraction (XRD) and thermal analysis (DTA, TG). Hexagonal gadolinium hydroxide was obtained in hydrothermal conditions, even in presence of silica, while no change was observed from isopropanolic medium treatment. Hydrothermally treated samples are more reactive as precursors for solid state reactions in inorganic synthesis.

Porous silica matrix obtained from pyrex class by hydrothermal treatment: Characterization and nature of the porosity

A novel porous silica matrix has been prepared from Pyrex glass, using hydrothermal treatment under saturated-steam condition. This process makes it possible to obtain, in one step, a silica support formed of a homogeneously distributed and interconnected macropore microstructure. The new matrix contains silanol groups that can be used in reactions of surface modification to provide a hybrid material and a selective macrofiltration membrane, and also it can improve chemical inertness. The porous matrix is noncrystalline as obtained and, after thermal treatment at temperatures higher than 950degreesC, exhibits an X-ray pattern characteristic of alpha-cristobalite and low volume contraction. The present samples were characterized by scanning electron microscopy, mercury intrusion porosimetry, nitrogen adsorption-desorption isotherms, infrared spectroscopy, X-ray powder diffractometry, atomic absorption, and high-resolution solid-state nuclear magnetic resonance. The results present a new way of producing a macroporous silica matrix.

Anthracnose control and mango quality (Mangifera indica L.) cv. van dyke after hydrothermal and chemical treatment

Anthracnose causes severe damage to the mango skin. Therefore, there is need to do the post-harvest phytosanitary treatment of the fruits through soaking in fungicide solution, which associated with the hydrothermal treatment has resulted into improved benefits. The present work has aimed at studying anthracnose control and post-harvest quality of mangoes (Mangifera indica L.), cv. Van Dyke after hydrothermal treatment associated with chemical through the physical, physicochemical, chemical and phytopathologic analyses. The mangoes coming from the commercial orchard of the town of Jana ba-MG, of the 2000 crop, were harvested at the commercial maturation stage. After selection according to color uniformity, size and absence of mechanic and physiologic injuries, they were shipped in plastic boxes to the EPAMIG - CTNM - Nova Porteirinha - MG, fruit post-harvest laboratory, where the samples were submitted to the hydrothermal treatment in cold bath in solution containing the fungicides Thiabendazole (Tecto 400 mL/100L), Proclaraz (Sportak 10L/100L) and Imazalil (Magnate 200mL/100L). After air-drying, the fruits were packed in plastic trays and stored at room temperature (25 +/- 2 degrees C and RH 70%) for a 12-day period and evaluated as to the intrinsic quality characteristics every 4 days. The experiment was conducted a completely randomized with 8 treatments, 4 replicates and experimental unit consisting of 4 fruits. The variations of pH, total soluble solids, total titrable acidity and total soluble sugars have not endangered the organoleptic characteristics of mangoes cv. Van Dyke stored under room temperature (25 +/- 2 degrees C and RH 70%) till 8 days' storage. The association of the hydrothermal treatment with the chemical was efficient in fruit anthracnose control for till 12 days' storage. The fungicide Prochloraz (Sportak 110 mL/100L), associated with the hydrothermal treatment, completely inhibited the appearance of anthracnose symptoms.

Growth kinetics of tin oxide nanocrystals in colloidal suspensions under hydrothermal conditions

Colloidal suspensions of tin oxide nanocrystals were synthesized at room temperature by the hydrolysis reaction of tin chloride (II), in an ethanolic solution. The coarsening kinetics of such nanocrystals was studied by submitting the as-prepared suspensions to hydrothermal treatments at temperatures of 100, 150 and 200 degrees C for periods between 60 and 12,000 min. Transmission electron microscopy (TEM) was used to characterize the samples (i.e. distribution of nanocrystal size, average particle radius and morphology). The results show that the usual Ostwald ripening coarsening mechanism does not fit well the experimental data, which is an indicative that this process is not significant for SnO2 nanocrystals, in the studied experimental conditions. The morphology evolution of the nanocrystals upon hydrothermal treatment indicates that growth by oriented attachment (OA) should be significant. A kinetic model that describes OA growth is successfully applied to fit the data. (c) 2006 Elsevier B.V. All rights reserved.

Stable colloidal suspensions of nanostructured zirconium oxide synthesized by hydrothermal process

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

Behavior of Peruvian carrot (Arracacia xanthorrhiza) and cassava (Manihot esculenta) starches subjected to heat-moisture treatment

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

Titanate nanotubes produced from microwave-assisted hydrothermal synthesis: Photocatalytic and structural properties

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Facile synthesis and characterization of ZrO2 nanoparticles prepared by the AOP/hydrothermal route

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

Uso de tratamento hidrotérmico e ácido clorídrico na qualidade de lichia 'Bengal'

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

Hyperfine interaction in Zn-Al layered double hydroxides intercalated with conducting polymers

Organic-inorganic hybrid materials based on the assembly between inorganic 2D host structure and polymer have received considerable attention in the last few years. This emerging class of materials presents several applications according to their structural and functional properties. Particularly, among others, layered double hydroxides (LDHs) provide the opportunity of preparing new organically modified 2D nanocomposites. Pyrrole carboxylic acid derivatives, namely 4-(lH-pyrrol-1-yl)benzoate, 3-(pyrrol-i-yl)-propanoate,7-(pyrrol-1-yl)-heptanoate, and aniline carboxylic acid derivative, namely 3-aminobenzoic acid, have been intercalated in LDHs of intralamellar composition Zn2Al(OH)(6). The LDHs were synthesized by the co-precipitation method at constant pH followed by hydrothermal treatment for 72 h. The materials were characterized by powder X-ray diffraction patterns (PXRD), transmission electron microscopy (TEM) thermogravimetric analysis (TGA), and electron spin resonance (ESR). The basal spacing found by the PXRD technique gives evidence of the formation of bilayers of the intercalated anions. ESR spectra present a typical signal with a superhyperfine structure with 6 + 1 lines (g = 2.005 +/- 0.0004), which is assigned to the interaction between a carboxylate radical from the guest molecules and a nearby aluminium nucleus (I = 5/2) from the host structure. Additionally, the ESR data suggest that the monomers are connected to each other in limited number after thermal treatment. (c) 2007 Elsevier Ltd. All rights reserved.

Effect of annealing on the semicrystalline structure of normal and waxy corn starches

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

Gadolinium-doped cerium oxide nanorods: novel active catalysts for ethanol reforming

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

Photolumiscent Properties of Nanorods and Nanoplates Y2O3:Eu3+

Nanorods and nanoplates of Y2O3:Eu3+ powders were synthesized through the thermal decomposition of the Y(OH)(3) precursors using a microwave-hydrothermal method in a very short reaction time. These powders were analyzed by X-ray diffraction, field emission scanning electron microscopy, Fourrier transform Raman, as well as photoluminescence measurements. Based on these results, these materials presented nanoplates and nanorods morphologies. The broad emission band between 300 and 440 nm ascribed to the photoluminescence of Y2O3 matrix shifts as the procedure used in the microwave-hydrothermal assisted method changes in the Y2O3:Eu3+ samples. The presence of Eu3+ and the hydrothermal treatment time are responsible for the band shifts in Y2O3:Eu3+ powders, since in the pure Y2O3 matrix this behavior was not observed. Y2O3:Eu3+ powders also show the characteristic Eu3+ emission lines at 580, 591, 610, 651 and 695 nm, when excited at 393 nm. The most intense band at 610 nm is responsible for the Eu3+ red emission in these materials, and the Eu3+ lifetime for this transition presented a slight increase as the time used in the microwave-hydrothermal assisted method increases.

Preparation of silica with controlled pore sizes for enzyme immobilization

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