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Nanocrystalline TiO2/SnO2 composites for gas sensors

An International Forum for Thermal Studies

Journal of Thermal Analysis and Calorimetry
Authors:
M. Radecka
,
A. Kusior
,
A. Lacz
,
A. Trenczek-Zajac
,
B. Lyson-Sypien
, and
K. Zakrzewska

Introduction Metal oxides, such as TiO 2 , SnO 2 , ZnO, WO 3 , and Fe 2 O 3 , are well known for their remarkable ability to change the electrical resistivity in response to oxidizing and reducing gases. Gas sensing properties

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Investigation of RuO2-IrO2-SnO2 thin film evolution

A thermoanalytical and spectroscopic study

Journal of Thermal Analysis and Calorimetry
Authors:
Elizabet Horváth
,
J. Kristóf
,
L. Vázquez-Gómez
,
Á. Rédey
, and
V. Vágvölgyi

Abstract  

The thermal evolution process of RuO2–IrO2–SnO2 mixed oxide thin films of varying noble metal contents has been investigated under in situ conditions by thermogravimetry-mass spectrometry (TG-MS), infrared emission spectroscopy (IR) and cyclic voltammetry (CV). The gel-like films prepared from aqueous solutions of the precursor compounds RuOHCl3, H2IrCl6 and Sn(OH)2(CH3COO)2–xClx on titanium metal support were heated in an atmosphere containing 20% O2 and 80% Ar up to 600C. Chlorine evolution takes place in a single step between 320 and 500C accompanied with the decomposition of the acetate ligand. The decomposition of surface species formed like carbonyls, carboxylates and carbonates occurs in two stages between 200 and 500C. The temperature of chlorine evolution and that of the final film formation increases with the increase of the iridium content in the films. The anodic peak charge shows a maximum value at 18% iridium content.

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Abstract  

The formation mechanism of thermally prepared IrO2/SnO2 thin films has been investigated under in situ conditions by thermogravimetry combined with mass spectrometry (TG-MS) and infrared emission spectroscopy (IRES). Mixtures of varying composition of the precursor salts (SnCl22H2O dissolved in ethanol and IrCl33H2O dissolved in isopropanol) were prepared onto titanium metal supports. Then the solvent was evaporated and the gel-like films were heated in an atmosphere containing 20% O2 and 80% Ar to 600C. The thermogravimetric curves showed that the evolution of the oxide phases take place in several decomposition stages and the final mixed oxide film is formed between 490 and 550C, depending on the noble metal content. Mass spectrometric ion intensity curves revealed that below 200C crystallization water, residual solvent, and hydrogen-chloride (formed as a result of an intramolecular hydrolysis) are liberated. The decomposition of surface species (surface carbonates, carbonyls and carboxylates) formed via the interaction of the residual solvent with the precursor salts takes place up to 450C as evidenced by emission Fourier transform infrared spectrometry.

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Reaction Kinetics, Mechanisms and Catalysis
Authors:
C. Munteanu
,
M. Caldararu
,
V. Bratan
,
P. Yetisemiyen
,
G. Karakas
, and
N. I. Ionescu

importance for oxidation reactions and can be easily followed by measuring the electrical properties in operando conditions. SnO 2 is among the oxides frequently used as a gas sensors and as a component of oxidation catalysts [ 1 – 6 ]. However

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Abstract  

The surface properties of gallium oxide and tin dioxide supported on alumina or titania have been studied by adsorption microcalorimetry. The differential heats of adsorption of various pollutant adsorbates such as sulfur dioxide, nitrogen monoxide, nitrogen dioxide and also ammonia were measured on these catalytic surfaces. NH3, SO2, NO2 are strongly adsorbed while NO is only physisorbed. The supported Ga2O3 samples show a slight decrease in acidity as probed by ammonia adsorption, compared to alumina or titania. The addition of SnO2 decreases the number of strong acid sites but creates a few weak and medium strength acid sites on alumina and does not modify the acidity of titania. In all cases, the basicity, probed by SO2 adsorption, is very strongly affected by the deposition of Ga2O3 or SnO2. The differential heats of NO2 adsorption remain nearly constant on all samples. The heats of adsorption are discussed as a function of the coverage and of the amount of guest oxide.

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-oxide catalysts, which have similar performance to supported precious metals, is still an attractive and important topic but with great challenge [ 2 , 4 , 5 ]. SnO 2 is an n-type semiconductor, which has been extensively and intensively studied in gas

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Abstract  

TG and DTA studies on Me3SnO2PCl2, Me2Sn(O2PCl2)2 and Ph3SnO2PCl2 were carried out under dynamic argon atmosphere. The results show that the decomposition proceeds in different stages leading to the formation of Sn3(PO4)2 as a stable product. This compound was characterized by IR spectroscopy. Decomposition schemes involving reductive elimination reactions were proposed.

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focus on the effects of size and shape on melting, glass transition, and Kauzmann temperatures of SnO 2 nanoparticles. The size-dependent glass transition is an important parameter for any phase transition process and is related to the thermodynamical

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Abstract  

Heterogeneous isotope exchange between hydrated stannic oxide and stannous chloride in 0.1M HCl solution has been studied as a function of the stannic oxide, stannous chloride, and chloride ion concentrations, and temperature. The exchange process is a second-order reaction, which is independent of the chloride ion concentration, with a mean rate constant, k, of 2.31 dm3 mol–1·min–1. The activation energy of the isotope exchange process was found to equal 3.62 kcal·mol–1. Possible use of this system, SnCl2/SnO2·xH2O, as basis for a113Sn-113mIn generator is suggested.

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