Thermodynamic and quality properties of lemon juice powder as affected by maltodextrin and Arabic gum

Sorption isotherms of lemon juice (LE) powders with and without additives-18% maltodextrin (MA) or 18% gum Arabic (GA) were determined at 20-50 degrees C. Addition of additives was shown to affect the isotherms in such a way that, at the same water activity, samples LE + GA and LE + MA presented lower equilibrium moisture content and were not so affected by varying temperature. The net isosteric heats of sorption of juice powders with additives were higher (less negative) than those of lemon juice powders, suggesting that there are more active polar sites in the product without addition of GA or MA. In general, the quality properties decreased with the addition of maltodextrin and gum arabic and it was obtained similar values for LE + GA and LE + MA.

Effects of powder preparation and sintering procedure on microstructure and dielectric properties of PLZT ceramics

PLZT ceramics belong to one of the very important groups of functional materials that make a basis for the production of a large range of electronic devices. The microstructure and properties of ceramics depend on the powder preparation and thermal processing conditions. Various techniques have been used to obtain chemically homogeneous and fine starting powders. PLZT powders have been prepared by two different production routes: by a modified Pechini method, using a polymeric precursor method (PMM) and by a partial oxalate method. A two-step sintering process, including a hot pressing, was carried out at 1100 and 1200degreesC Distinct phases obtained during the sintering process have been investigated by SEM and EDS techniques and dielectric properties such as permittivity and dielectric loss were measured in a frequency range from 1 to 20 kHz.. A significant difference in microstructure and dielectric properties, depending on powder origin and sintering procedure, has been noticed.

SYNTHESIS OF ULTRA-FINE CRYSTALLINE ZRXTI1-XO4 POWDER BY POLYMERIC PRECURSOR METHOD

Reactive ZrxTi1-xO4 (x=0.65, 0.50 and 0.35) powder was prepared by the polymeric precursor method. Studies by X-ray diffraction (XRD), nitrogen adsorption/desorption, and thermogravimetric analysis (TG) showed that powders with high crystallinity (>90%) and high surface areas (>40 m(2)/g) are obtained after calcination at 700 degrees C for 3 h. Infrared spectroscopy and XRD results showed that these titanates nucleate from the amorphous phase with no intermediate phases, at low temperature (450 degrees C).

Visible PL phenomenon at room temperature in disordered structure of SrWO4 powder

The SrWO4 (SWO) powders were synthesized by the polymeric precursor method and annealed at different temperatures. The SWO structure was obtained by X-ray diffraction and the corresponding photoluminescence (PL) spectra was measured. The PL results reveal that the structural order-disorder degree in the SWO lattice influences in the PL emission intensity. Only the structurally order-disordered samples present broad and intense PL band in the visible range. To understand the origin of this phenomenon, we performed quantum-mechanical calculations with crystalline and order-disordered SWO periodic models. Their electronic structures were analyzed in terms of band structure. The appearance of localized levels in the band gap of the order-disordered structure was evidenced and is a favorable condition for the intense PL to occur.

Processing and properties of Ag/BSCCO PIT tapes containing different proportions of silver metal powder

Monofilamentary tapes (150 pm thickness) were prepared by swaging and rolling silver tubes containing the Bi:2212 ceramic (granulation below 20 mum) and the silver powder (about 0.8 mum). The study has been made, among other samples, on tapes with nominal proportions of 0, 10 and 20 wt.% of silver. The samples were characterized by SEM, and by electrical measurements under varying applied magnetic field. The measurements of J(c) showed that the addition of 10 wt.% silver powder is very beneficent to this property, doubling the obtained values at 60 K, while the 20 wt.% tape presented very low J(c). The tape with no silver content showed to have a J(c) as high as 2.2 x 10(5) A/cm(2), at 4.2 K, zero applied magnetic field. (C) 2004 Elsevier B.V. All rights reserved.

Sugarcane molasses and yeast powder used in the Fructooligosaccharides production by Aspergillus japonicus-FCL 119T and Aspergillus niger ATCC 20611

Different concentrations of sucrose (3-25% w/v) and peptone (2-5% w/v) were studied in the formulation of media during the cultivation of Aspergillus japonicus-FCL 119T and Aspergillus niger ATCC 20611. Moreover, cane molasses (3.5-17.5% w/v total sugar) and yeast powder (1.5-5% w/v) were used as alternative nutrients for both strains' cultivation. These media were formulated for analysis of cellular growth, P-Fructosyltransferase and Fructooligosaccharides (FOS) production. Transfructosylating activity (U-t) and FOS production were analyzed by HPLC. The highest enzyme production by both the strains was 3% (w/v) sucrose and 3% (w/v) peptone, or 3.5% (w/v) total sugars present in cane molasses and 1.5% (w/v) yeast powder. Cane molasses and yeast powder were as good as sucrose and peptone in the enzyme and FOS (around 60% w/w) production by studied strains.

Sintering of ultrafine undoped SnO2 powder

The sintering process of nanometric undoped SnO2 powder was studied. No macroscopic shrinkage was observed during the sintening process. Grain growth kinetics investigation showed that surface diffusion is the dominant mechanism in the temperature range 500-1300 degreesC. For temperatures higher than 1300 degreesC, high weight loss was measured, suggesting evaporation-condensation as the dominant mass-transport mechanism. Thermogravimetric analysis (TG) and mass spectroscopy studies showed that the surface contamination of the SnO2 particles by chemical species like H2O, OH- and CO2, has a strong influence on the role of mass transport controlled by surface diffusion. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

X-ray powder diffraction analysis of a new palladium(II) amino acid complex

Powder X-ray diffraction data for a new palladium(II) amino acid complex, of composition PdC12H2ON2O4S2, are presented in this paper. Orthorhombic cell parameters are: a = 10.740 angstrom, b = 19.999 angstrom, and c = 5.2470 angstrom. (c) 2004 International Centre for Diffraction Data.

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.

Microwave synthesis of YAG : Eu by sol-gel methodology

Yttrium-aluminum oxides are interesting compounds and they have been extensively used as host for lasers and phosphors, due to their stable physical and chemical properties. The fabrication of yttrium-aluminum garnet (YAG) has been investigated thoroughly. Single-crystal YAG is expensive and to produce it a new way has been investigated. This process consists of modifying the methodology of reagents mixture and the process of heating them. The microwave irradiation is used to heat-treat the oxide mixture. The traditional synthesis of YAG powders occurs through the reaction of aluminum and yttrium powders at high temperatures. With this work we investigated the preparation of YAG by non-hydrolytic sol-gel route as an alternative methodology to obtain yttrium-aluminum matrix from inorganic precursors (yttrium and aluminum chloride). The preparation of the gel was carried out in an oven-dried glassware. The AlCl3, YCl3 and ethanol were reacted in reflux under argon atmosphere. Europium III chloride was added as a structural probe. The powder was dried and heat-treated in modified microwaves. The samples were pre-treated at 50 and 800 C during I h and then heated in microwaves for 30 s, 2 and 4 min. The formation process and structure of the powders were studied by means of X-ray diffraction (XRD), photoluminescence (PL) and transmission electronic microscopy (TEM). XRD presents only picks corresponding to the YAG phase and confirmed by TEM. PL date showed that the YAG phase was formed in 2 min with the samples pre-treated at 50 C. For the samples pretreated at 800 degrees C, the YAG phase appears in 30s. The excitation spectra present a maximum of 394 nm corresponding to the L-5(6) level and emission spectra of Eu III ion present bands characteristic transitions arising from the D-5(0) -> F-7(J) (J= 1, 2, 3, 4) monifolds excited at their maximum. The magnetic dipole D-5(0) -> F-7(1) transition presents more intensity than the electric dipole D-5(0) -> F-7(2) transition. This methodology showed efficiency in obtaining YAG phase. (c) 2006 Elsevier B.V. All rights reserved.

Photoluminescence of crystalline and disordered BTO : Mn powder: Experimental and theoretical modeling

Disordered and crystalline Mn-doped BaTiO3 (BTO:Mn) powders were synthesized by the polymeric precursor method. After heat treatment, the nature of visible photoluminescence (PL) at room temperature in amorphous BTO:Mn was discussed, considering results of experimental and theoretical studies. X-ray diffraction (XRD), PL, and UV-vis were used to characterize this material. Rietveld refinement of the BTO:Mn from XRD data was used to built two models, which represent the crystalline BTO:Mn (BTO:Mn,) and disordered BTO:Mn (BTO:Mn-d) structures. Theses models were analyzed by the periodic ab initio quantum mechanical calculations using the CRYSTAL98 package within the framework of density functional theory at the B3LYP level. The experimental and theoretical results indicated that PL is related with the degree of disorder in the BTO:Mn powders and also suggests the presence of localized states in the disordered structure. (c) 2006 Elsevier B.V. All rights reserved.

Nanocoating of Al2O3 additive on ZrO2 powder and its effect on the sintering behaviour in ZrO2 ceramic

ZrO2 powder was coated with Al2O3 precursor generated by a polymeric precursor method in aqueous solution. The system of nanocoated particles formed a core shell-like structure in which the particle is the core and the nanocoating (additive) is the shell. A new approach is reported in order to control the superficial mass transport and the exaggerated grain growth during the sintering of zirconia powder. Transmission electron microscopy (TEM) observations clearly showed the formation of an alumina layer on the surface of the zirconia particles. This layer modifies the sintering process and retards the maximum shrinkage temperature of the pure zirconia.

X-ray powder diffraction analysis of methionine sulfoxide

Powder X-ray diffraction data for methionine sulfoxide, C5H11NO3S, obtained from the commercial amino acid, are presented in this work. Monoclinic cell parameters are: a = 15.500 Angstrom; b = 3.820 Angstrom; c = 13.490 Angstrom; 8=97.300 degrees. (C) 2001 International Centre for Diffraction Data.

Eu3+ as a spectroscopic probe in phosphors based on spherical fine particle gadolinium compounds

This work reports on the luminescence spectroscopy sensitivity in the determination of the phase purity in gadolinium compounds using Eu3+ as a probe. Cubic Gd2O3 and hexagonal Gd2O2S doped with Eu3+ spherical fine particles were obtained from doped gadolinium basic carbonates with morphological control and were also characterized by IR and XRD. Doped samples present Eu3+ characteristic transitions, with specific energy positions related to each phase. Emission and excitation spectra patterns were established for oxide and oxysulfide compounds, then oxysulfate and oxide impurities generated during oxysulfide preparation were monitored. From emission spectra some experimental intensity parameters were also calculated. All spectroscopic results reflect the presence or not of impurities in all compounds. (C) 2001 Elsevier B.V. Ltd. All rights reserved.