Search results for "DECOMPOSITION"
showing 10 items of 766 documents
Submicrometer CaCuO2 and Ca2CuO3 particles from bimetallic formate precursors
1992
Abstract CaCuO2 and Ca2CuO3 are readily obtained by thermal decomposition of two new calcium and copper formates, CaCu(HCOO)4 and Ca2Cu(HCOO)6. These chemical-precursor based syntheses, while overcoming problems related to the stoichiometry of the final products, involve very short diffusion path lengths. This, in turn, results in soft treatments yielding pure phases constituted by submicrometer (≈0.4 μm) homogeneous particles.
NMR-investigation of the mechanism of silver mercaptide thermolysis in amorphous polystyrene
2007
Polymer-embedded silver clusters have been prepared by thermal decomposition of silver dodecylmercaptide previously dissolved in amorphous polystyrene. The morphology and structure of silver clusters have been determined by transmission electron microscopy (TEM) and large angle X-ray diffractometry (XRD), respectively. The mechanism involved in the thermolysis reaction was elucidated by different NMR techniques. The thermolysis produced thiol-derivatized silver clusters (i.e., silver clusters coated with a self-organized thiol monolayer, Agx(SC12H25)y) and had the effect of increasing the branching degree of polystyrene due to enhanced cross-linking.
TG/DTA-FTIR as a method for analysis of tall oil based rigid polyurethane foam decomposition gaseous products in a low oxygen environment
2020
Abstract This study is an investigation of the suitability of the thermogravimetry and differential thermal analysis method coupled with Fourier Transform Infrared spectrometry (TG/DTA-FTIR) for a thermal degradation gaseous product analysis of a rigid polyurethane-polyisocyanurate (PU-PIR) foam synthesised from high functionality tall oil fatty acids (TOFA) based polyols. The FTIR spectra of the TG-generated gaseous thermal degradation products of three PU-PIR formulations with varied high functionality TO based polyol content (45, 75 and 95 pbw) and a different tier of isocyanate (NCO) indexes (110, 150, 200, 300 and 400) for each formulation were compared to the spectra of a formulation …
Temperature- and illumination-induced charge-state change in divacancies of GaTe
2010
Temperature-dependent positron annihilation lifetime spectroscopy measurements have been performed in GaTe samples, with and without illumination. The average lifetime shows a monotonous temperature evolution but the lifetime decomposition shows a rich behavior. It is produced by two types of vacancy defects. The vacancy-type defects characterized by their shorter lifetime change their charge state below 100 K and when illuminating with light of an energy of 0.8 eV.
Ab initio thermodynamic study of (Ba,Sr)(Co,Fe)O3 perovskite solid solutions for fuel cell applications
2013
(Ba,Sr)(Co,Fe)O3 (BSCF) perovskite solid solutions are promising materials for solid oxide fuel cell cathodes and oxygen permeation membranes. Cathode performance strongly depends on the morphology of these materials remaining as a single phase or two-phase mixture. Combining ab initio calculations of the atomic and electronic structure of different supercells with thermodynamics of solid solutions, we have constructed and discussed phase diagrams of several important BSCF chemical compositions. It is demonstrated that in BSC cobaltite solid solution the spinodal decomposition may occur already at relatively low temperatures, while ferrite (BSF and SCF) solid solutions decompose at relative…
Pd2Mo3N: a new molybdenum bimetallic interstitial nitride
2001
The molybdenum bimetallic nitride Pd2Mo3N has been synthesized by ammonolysis of the stoichiometric mixture of low sized pure oxide crystallites (2PdO/3MoO3) as resulting from low temperature thermal decomposition of precursor powders obtained by freeze-drying of aqueous solutions of the appropriate metal salts. This compound has been characterized by elemental analysis, energy dispersive analysis of X-rays, X-ray diffraction, scanning electron microscopy (field emision) and thermogravimetry under oxygen atmosphere. Pd2Mo3N crystallizes in the cubic space group P4132 (no. 213) (Pd2Mo3N, a = 6.81770(3) A, Z = 4), and presents the unusual filled β-manganese structure. It is stable under oxyge…
Synthesis and thermoelectric characterisation of bismuth nanoparticles
2009
An effective method of preparation of bismuth nanopowders by thermal decomposition of bismuth dodecyl-mercaptide Bi(SC12H25)3 and preliminary results on their thermoelectric properties are reported. The thermolysis process leads to Bi nanoparticles due to the efficient capping agent effect of the dodecyl-disulfide by-product, which strongly bonds the surface of the Bi clusters, preventing their aggregation and significantly reducing their growth rate. The structure and morphology of the thermolysis products were investigated by differential scanning calorimetry, thermogravimetry, X-ray diffractometry, 1H nuclear magnetic resonance spectroscopy, scanning electron microscopy, and energy dispe…
Atomistic Theory of the Growth Mode for a Thin Metallic Film on an Isulating Substrate
2002
We have developed a novel theory for predicting the growth mode of a thin metallic film on an insulating substrate. Our theory combines ab initio electronic structure calculations for several ordered metal/insulator interfaces with varying metal coverage, with a thermodynamic method known in the theory of alloys. We illustrate this approach for an Ag film deposited on a MgO(001) substrate. Ab initio Hartree-Fock calculations predict a high mobility of adsorbed silver atoms on the perfect magnesia surface even at low temperatures. Our theoretical analysis clearly demonstrates that the growth of metal islands is predominant at the initial stage of silver deposition on MgO, which agrees with t…
Equilibrium phase behavior of polyethylene oxide and of its mixtures with tetrahydronaphthalene or/and poly(ethylene oxide-block-dimethylsiloxane)
2002
Liquid/solid and liquid/liquid (LL) transition temperatures were measured by means of an automated device that monitors the light passing through the systems as a function of T at different constant cooling or heating rates q. For pure polyethylene oxide (PEO) crystallization and melting temperatures depend on |q|0.3 and become identical at the equilibrium transition temperature Tm=61.0 °C in the limit of infinitely slow cooling/heating. The reduction of Tm for PEO dissolved in tetrahydronaphthalene (THN) yields information on the Flory–Huggins interaction parameter ξ between these two compounds; ξ results negative and decreases markedly with rising polymer concentration. A tentative explan…
Low temperature synthesis of monodisperse nanoscaled ZrO2with a large specific surface area
2012
Thermal decomposition of Zr(C(2)O(4))(2)·4H(2)O within an autoclave or in a conventional tube furnace at temperatures below 380 °C resulted in nano- and micron-sized ZrO(2), respectively. Reactions under autogenic pressure yielded monodisperse monoclinic (m) and tetragonal (t) ZrO(2) nanoparticles with an average diameter of ~8 nm and interconnected t-ZrO(2) nanoparticles with diameters of ~4 nm, depending on the synthesis temperature. Samples were characterised by X-ray diffraction (XRD), small angle X-ray scattering (SAXS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) associated with energy dispersive X-ray spectroscopy (EDS), Raman microspectroscopy and phot…