Estudo prévio de uma unidade industrial para produção de vinagrete sólido

Este trabalho consiste num estudo prévio tendo em vista o projeto de uma unidade industrial para a produção de vinagrete sólido. O produto em causa, o vinagrete sólido, assume-se como inovador, colocando-se como uma alternativa fácil para o tempero de saladas e potenciando novos sabores agradáveis ao paladar que cativem o consumidor. O trabalho inclui o estudo do processo, com descrição das etapas de preparação, os balanços mássicos, a descrição das peças de equipamento, a implantação fabril e uma breve estimativa do investimento necessário

Sistema para realização de medidas de luminescência com excitação por Raios X

In this work is presented a versatile system for X-ray excited optical luminescence (XEOL) measurements. The apparatus was assembled from a sample holder connected to an optical fiber responsibly for the acquisition of the scintillation signal. The spectrum is registered with a CCD coupled in a spectrograph provided with diffraction gratings. The system performance was analyzed by exciting GdAlO3:Eu3+ 3.0 at.% with X-rays from a diffractometer and measuring the emission spectra. The system can be used to obtain precise and reliable spectroscopic properties of samples with various conformations without the loss of the required safety when dealing with ionizing radiations

Determination of the local site occupancy of Eu3+ ions in ZnAl2O4 nanocrystalline powders

Once lanthanides-doped ZnAl2O4 have attracted attention for highly efficient phosphors and due to the complexity of this system, this work is focused in the understanding of the local site occupancy of the doped ions in the spinet structure by using Eu3+ as a spectroscopic probe. Europium(III)-doped ZnAl2O4 nanocrystalline powder samples were prepared by the Pechini method. Different heat treatment temperatures and doping levels were investigated. No impurities of residual Eu2O3 were observed for the samples with Eu3+ doping levels up to 10 at.%, indicating that the doping ions are diluted into the host. The luminescence spectroscopy from the Eu3+ ions revealed the Eu3+ ions might occupy at least two non-centro-symmetric sites and that the occupation ratio might be dependent on the heat treatment or doping level. It is observed that one site is related to a high covalent environment while at the other the ionic character prevails. This behavior is in agreement with the luminescence lifetime results. The decay curves were fitted according to double first-order decay model and it was confirmed the covalence difference between the two sites and also the population variation with the doping level. There are strong evidences that the europium ions substitute for the aluminum ones in the normal spinel structure. It cannot be disregarded that the dopant ions may be present on the surface of the particles. (C) 2011 Elsevier B.V. All rights reserved.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Luminescence of europium(III) and manganese(II) in barium and zinc orthosilicate

The aim of this work is to report on the luminescence properties of BaZnSiO4 activated by Eu3+ and Mn2+ ions. Doped and undoped powder samples were prepared by solid-state reaction starting from oxides and carbonates or Ba2SiO4:Eu3+ and Zn2SiO4:Mn2+ precursors. X-ray diffraction powder data, IR vibrational, and UV-vis luminescence spectroscopies were carried out. Results showed that doped and undoped samples from both types of precursors have the same structure and crystallize with a superstructure of hexagonal kalsilite. Vibrational spectroscopy has confirmed the formation of a silicate group, which outlines differences between products and silicate precursors. The observed luminescence assigned to Eu3+ and Mn2+ transitions covered most parts of the visible spectrum, an important requirement for phosphors in fluorescent low-pressure mercury vapor lamps

SILICA MORPHOLOGY CHARACTERIZED BY SEM - THE EFFECTS OF THE SOLVENT TREATMENT AND THE DRYING PROCESS

Scanning electron microscopy (SEM) was used to investigated the effects of volatile solvents (such as water, propanone, ethanol, methanol or ethyl ether), treatment and drying processes, microwave ovens, drying ovens, and vacuum desiccators or freeze driers, on silica morphology. Silica gel was obtained from diluted sodium silicate (1:5 w/w SiO2:H2O). The results showed that the drying process based on freeze drying is more efficient for structural conservation of the precipitate. Treatment with volatile solvents does not change the shape of the aggregates, but has an important role in the determination of aggregate surface roughness

Protetores solares

Health problems related to UV radiation can be minimized by the appropriate use of sunscreens. Different kinds of sunscreens are reported in the literature, even though there is a misleading denomination among them and few discussions are presented about how they work. This paper describes some important aspects in order to understand sunscreen phenomena such as: solar radiation effect, type of solar filters, protection mechanism, formulations and solar protection factor (SPF). Moreover the importance of Chemistry and the interdisciplinary studies related to sunscreens and cosmetic researches are emphasized.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Adaptações em forno de microondas doméstico para utilização em laboratório

Domestic microwave oven was modified for laboratory applications. Electronic system was made for controlling magnetron irradiation time. Exhaustion and air circulation systems were installed to clean the internal oven atmosphere during operation. The cavity walls were coated with aluminized thermal paint to avoid chemical corrosion. These modifications allowed the usage of the oven for drying and processes using reflux.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Morphological evolution of zinc oxide originating from zinc hydroxide carbonate

Zinc oxide can be obtained by thermal decomposition of hydrozincite, a topochemical reaction. This work reports the relation between zinc oxide morphology and the precursor zinc hydroxide carbonate precipitation time. The morphological evolution was monitored by SEM, IR and XRD. Zinc oxide obtained from initially precipitated hydrozincite consists of porous spherical aggregates and shows a single Zn-O IR vibrational band. At longer periods of precipitation time the aggregates were transformed into spherulitic-shaped zinc oxide particles showing the Zn-O split vibrational band. X-ray patterns show that the hexagonal zinc oxide phase is substantially increased as a function of hydrozincite precipitation time. © 1997 Elsevier Science S.A