Search results for "MINERALOGY"

Impact of granularity on transport properties of mechanically stressed La0.67Ca0.33MnO3 films

2001

Abstract (La,Ca)MnO 3 is one of so called collosal magnetoresistive materials and it is of interest to correlate its transport properties to film growth in order to optimize its performance. Two-hundred nanometers thick (100)La 0.67 Ca 0.33 MnO 3 films were grown by laser ablation on (100)SrTiO 3 , (100)LaAlO 3 and (100)(LaAlO 3 ) 0.3 +(Sr 2 AlTaO 6 ) 0.7 substrates. The films were granular in structure with low angle boundaries between the grains. The volume of the unit cell was considerably smaller for films grown on a SrTiO 3 substrate than on LaAlO 3 . At temperatures higher than the one where the spins order, the strongest response of resistivity on temperature ρ ( T ) was measured for…

Effects of ZrO2 precursors on the synthesis of V-ZrSiO4 solid solutions by the sol-gel method

1992

The preparation of V-ZrSiO4 solid solutions starting from different ZrO2 precursors by using sol-gel methods is reported. The starting materials were hydrolysed and the dried gels were fired at a temperature between 500 and 900 °C with soaking times of 12h. The organic character of zirconia precursors was stronger, i.e. the starting material had more carbon atoms, a higher temperature was necessary to make the first crystalline phase appear (ZrO2(tetragonal)) and the temperature range for the whole phase transformation was narrower. In all dried gel samples the presence of infrared bands which might be associated with either Si-O-Zr or Si-O-V was not observed. On the other hand, some bands …

Production and Properties of Lead Scandoniobate Ferroelectric Ceramics Doped with Rare-Earth Oxides

2001

Physico-chemical characterization of perlite of various origins

1985

Abstract Pearlstones (perlite) from Sardinia (Italy). Milos (Greece) and Siberia (USSR) have been evaluated in terms of chemical composition, phase analysis, iron distribution, morphology and thermal properties, for application as raw material in zeolite synthesis.

Microtextural Analyses of the Ni/NiO System after High Temperature Oxidation

2002

Integrated analytical methodologies for the study of corrosion processes in archaeological bronzes

2011

Abstract The investigations on structure and micro-chemical composition of archaeological metal alloys are needed in archaeometry. The aim of this study is devoted both to acquire information about their provenance and production technology, and to improve our understanding about the corrosion processes. In this paper we present the study of the corrosion phenomena of bronze samples, laboratory-made according to binary, ternary and quaternary alloys typical of Roman archaeometallurgical production through an integrated methodology based on the use of non or micro invasive physical techniques. Among the analysed samples, two were artificially aged through burial in the archaeological site of…

Low temperature catalytic combustion of propane over Pt-based catalyst with inverse opal microstructure in microchannel reactor

2007

A novel Pt-based catalyst with highly regular, periodic inverse opal microstructure was fabricated in a microchannel reactor, and catalytic testing revealed excellent conversion and stable activity for propane combustion at low temperatures.

SEM and XPS studies of titanium dioxide thin films grown by MOCVD

1998

Abstract The metal organic chemical vapour deposition (MOCVD) method was used to prepare titanium dioxide thin films. Thin films of TiO2, about 100 nm thick, were deposited on (100)Si and (1102)Al2O3 sapphire substrates using titanium isopropoxide (Ti(OC3H7)4) as metal organic precursor. The morphology of the films and the presence of impurities on the thin films surfaces were studied using respectively, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The influence of the growth parameters such as the deposition temperature, the carrier gas (nitrogen) flow rate and the presence of an additional oxygen flow on the characteristics of the titanium dioxide films h…

Physical rock matrix characterization: Structural and mineralogical heterogeneities in granite

2008

AbstractEvaluation of the transport and retardation properties of rock matrices that serve as host rock for nuclear waste repositories necessitates their thorough pore-space characterization. Relevant properties to be quantified include the diffusion depth and volume adjacent to water conducting features. The bulk values of these quantities are not sufficient due to the heterogeneity of mineral structure on the scale of the expected transport/interaction distances. In this work the 3D pore structure of altered granite samples with porosities of 5 to 15%, taken next to water conducting fractures at 180 200 m depth in Sievi, Finland, was studied. Characterization of diffusion pathways and por…

Formation of calcium containing minerals in the low temperature dolomite ceramics

2011

In order to elaborate low temperature dolomite ceramics, potentially suitable for the production of building materials, local low carbonate clay and dolomite siftings were used as a raw materials. Relationship between mechanical properties, mineral composition and firing temperature kept in the range of 600-800° C were established. According to the obtained data it was detected that the optimal burning temperature, giving the highest crushing strength (40 MPa) was around 700-750° C, optimal proportion of dolomite and clay expressed as ratio between CaO and Al2O3 - 2.5 wt%. Gradual formation of C3A occurs during firing, yielding C4AHX, i.e. mainly C4AH13 after hydratation of obtained composi…