Search results for " composition"
showing 10 items of 1437 documents
Quantifying the Composition of Methylammonium Lead Iodide Perovskite Thin Films with Infrared Spectroscopy
2019
Lead halide perovskites (ABX3) are generally formed from a reaction of the lead halide salt (BX2) with the halide salt of the A cation (AX). The effects of varying film compositions as result of non-stoichiometric precursor ratios on electronic properties of halide perovskites are currently under debate. It is imperative, but experimentally challenging, to determine the chemical composition of thin films as a function of precursor ratio for a full understanding of the effect. Herein we report a precise quantification of the methylammonium (MA) content in differently fabricated films of MAPbI3 via infrared (IR) spectroscopy. We compare the thin film data to the first high quality dielectric …
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.
XAFS study of short range order in the heavily disordered MoxW1−wO3 oxides
1995
We have done comparative XAFS analysis on the MoK and WL 3 edges of polycrystalline Mo x W 1-x O 3 solid solutions. It was found that their structures are closely related to corner-shared WO 3 -type for x<0.9 while α-MoO 3 -type structure is present for x≥0.9. The obtained structural parameters for the first shell around metal ions allow to distinguish several structural phase transitions due to the change of composition. A set of subshells within the first shell was found, and they are in good agreement with Raman data
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…
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…
Characterization of Chemical Composition along the Molar Mass Distribution in Polyolefin Copolymers by GPC Using a Modern Filter-Based IR Detector
2013
Summary Gel permeation chromatography (GPC), also known as size exclusion chromatography (SEC), is the technique routinely used at high temperature to analyze the molar mass distribution in polyolefins. The distribution of comonomer along the molar mass distribution in a copolymer is a key microstructural feature that determines the macroscopic properties of the material, and thus, its range of possible applications and performance. The direct coupling of a modern filter-based infrared (IR) detector to a high temperature GPC instrument, by means of a heated flow-through cell, is here described. The analyses are carried out by recording the continuous IR absorbance chromatograms at selected …
Phase Composition and Morphology of Tungsten Oxide Nanoparticles Produced via a Pyrolytic Process
2018
The chemical synthesis is a leading route for the purposeful design of nanomaterials, whereas the tungsten oxides are employed in a variety of special applications. The production of nanomaterials by traditional synthetic methods is still a cumbersome multistep procedure. Here we propose an improved method to produce tungsten oxide nanoparticles via a pyrolytic process. A tungsten-containing precursor was prepared by liquid extraction using n-trioctylamine (C8H17)3N solution in toluene. We have shown that the conditions of thermal treatment of the W-based precursor determine the crystalline structure and nanomorphology of the final product. Monoclinic WO3 nanocrystallites are produced condu…
Aging of the surface of an Al-Cr-Fe approximant phase in ambient conditions: Chemical composition and physical properties
2003
ABSTRACTWe have investigated the surface properties of quasicrystalline and approximant phases in the Al-(Cu)-Cr-Fe system upon aging in ambient conditions. We found that some of these properties (like the electrochemical behavior, wetting or friction) slowly evolves with the length of exposure to normal atmospheric conditions, reaching a stable state only after several days. This report essentially focuses on one of these alloys, an Al65Cr27Fe8 approximant phase with g-brass structure. In a first part, we describe the effect of aging on the electrochemical behavior of this alloy and we propose an interpretation based on a simple electrical model of the oxidized surface. In a second part, w…
Influence of the Chemical Dissolution of MnS Inclusions on the Electrochemical Behavior of Stainless Steels
2005
Immersion of stainless steel containing a well-controlled density of MnS inclusions in 1 M NaCI, pH 3 leads to the chemical dissolution of these heterogeneities. This process was studied using in situ atomic force microscopy and the dissolution rate of MnS inclusions was estimated between 0.01 and 0.19 μm 3 /min. The effects of MnS dissolution on the chemical composition and the local electrochemical behavior of the specimen surface were investigated using secondary ion mass spectroscopy, X-ray photoemission spectroscopy, and the electrochemical microcell technique. It was shown that stable CrS and unstable FeSO 4 were formed. The size of the areas around MnS inclusions affected by the pres…
Structure of natural water-containing glasses from Lipari (Italy) and Eastern Rhodopes (Bulgaria): SAXS, WAXS and IR studies
1998
Abstract Two natural water-containing glasses with rhyolite composition originating from two different areas (perlite from Lipari, Italy, and expanded perlite from the Eastern Rhodopes, Bulgaria) have been characterised for chemical composition, atomic structure and specific surface area, with the ultimate goal of exploitation of volcanic glasses as carriers for heterogeneous metal catalysts. The two samples have similar chemical composition and total water content. The local structure, as determined by radial distribution function analysis of the wide angle X-ray scattering patterns, is similar, the medium-range structure being slightly more ordered for the Lipari glass. These results are …