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951.
Summary The thermal behavior of KH2PO4, NaH2PO4 and Na2HPO4 under non-isothermal conditions using TG method with different heating rates was studied. The values of the reaction rate were processed by means of Friedmans differential-isoconversional method. A dependence of the activation energy vs. conversion was observed. Therefore a procedure based on the compensation effect (suggested by Budrugeac and Segal) was applied. A less speculative data processing protocol was offered by the non-parametric kinetics method suggested by Serra, Nomen and Sempere. Three steps were observed by non-isothermal heating: a dehydration, a dimerization and a polycondensation. The differences in the intimate reaction mechanism are determined by the initial number of water molecules. 相似文献
952.
Employing hot tungsten filament to thermal dissociate molecular hydrogen,we generated gas phase atomic hydrogen under ultra-high vacuum(UHV)conditions and investigated its interaction with Pt(111) surface.Thermal desorption spectroscopy(TDS)results demonstrate that adsorption of molecular hy- drogen on Pt(111)forms surface Had species whereas adsorption of atomic hydrogen forms not only surface Had species but also bulk Had species.Bulk Had species is more thermal-unstable than surface Had species on Pt(111),suggesting that bulk Had species is more energetic.This kind of weakly- adsorbed bulk Had species might be the active hydrogen species in the Pt-catalyzed hydrogenation reactions. 相似文献
953.
Ahmad Shaabani Abbas Rahmati Soheila Naderi 《Monatshefte für Chemie / Chemical Monthly》2007,138(6):553-557
Summary. Reaction of triphenylphosphine and an electron deficient acetylenic ester in the presence of strong N–H acid such as alkyl
and aryl sulfamides or acetamide produces phosphorous ylides at room temperature in CH2Cl2. The aryl sulfamide phosphoranes undergo a smooth transformation reaction in boiling toluene and produce iminophosphoranes. 相似文献
954.
Crown ethers were reacted with HN-proton-donor molecules to obtain crystalline molecular host-guest complexes. It was found that complexes with crown ethers of different structure are formed, depending on the linear dimensions and mode of steric shielding of active centers of the proton-donor molecules.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 12, 2004, pp. 2030–2033.Original Russian Text Copyright © 2004 by Wang, Ganin.This revised version was published online in April 2005 with a corrected cover date. 相似文献
955.
Soonam Park Feng Liao John M. Larson Steven L. Girshick Michael R. Zachariah 《Plasma Chemistry and Plasma Processing》2004,24(3):353-372
A molecular beam mass spectrometry system for in situ measurement of the concentration of gas phase species including radicals impinging on a substrate during thermal plasma chemical vapor deposition (TPCVD) has been designed and constructed. Dynamically controlled substrate temperature was achieved using a variable thermal contact resistance method via a backside flow of an argon/helium mixture. A high quality molecular beam with beamtobackground signal greater than 20 was obtained under film growth conditions by sampling through a small nozzle (75 m) in the center of the substrate. Mass discrimination effects were accounted for in order to quantify the species measurements. We demonstrate that this system has a minimum detection limit of under 100 ppb. Quantitative measurements of hydrocarbon species (H, H2, C, CH3, CH4, C2H2, C2H4) using Ar/H2/CH4 mixtures and silicon species (Si, SiH, SiH2, SiCl, SiCl2, Cl, HCl) using Ar/H2/SiCl4 mixtures were obtained under thermal plasma chemical vapor deposition conditions. 相似文献
956.
Armin Presser Olaf Kunert Irmgard P?tschger 《Monatshefte für Chemie / Chemical Monthly》2006,26(1):365-374
Several improved approaches for the preparation of tetra-O-benzyl-α-D-glucopyranosyl bromide and tetra-O-pivaloyl-α-D-glucopyranosyl bromide are discussed. The importance of these compounds, which are useful glycosyl donors, was demonstrated
by successful preparation of cholesteryl glucopyranosides in an almost neutral medium without the formation of orthoesters.
In addition, accurate 1H and 13C NMR resonance assignments of the synthesized cholesteryl glycosides were performed by 2D NMR spectroscopy. 相似文献
957.
Daniela Schlemmer E. R. de Oliveira M. J. Araújo Sales 《Journal of Thermal Analysis and Calorimetry》2007,87(3):635-638
Conventional plastics has a
large impact in increasing the environment’s pollution. That’s
why the interest has turned towards novel partially and completely biodegradable
polymers. In this work, blends of polystyrene and thermoplastic starch with
glycerol and Buriti (Mauritia flexuosa
L.) oil as plasticizers were prepared. Samples were analyzed using TG/DTG
and DSC techniques. The TG results indicated that the blends with Buriti oil
are thermally more stable than those with glycerol. The DSC analysis that
Buriti oil provides a higher degree of plasticization of PS, compared to the
blends plasticized using glycerol under the studied conditions. 相似文献
958.
Maurer HH Tenberken O Kratzsch C Weber AA Peters FT 《Journal of chromatography. A》2004,1058(1-2):169-181
A liquid chromatographic-mass spectrometric assay with atmospheric pressure chemical ionization (LC-APCI-MS) is presented for screening for, library-assisted identification (both in scan mode) and quantification (selected-ion mode) of the beta-blockers acebutolol, diacetolol, alprenolol, atenolol, betaxolol, bisoprolol, bupranolol, carazolol, carteolol, carvedilol, celiprolol, esmolol, labetalol, metoprolol, nadolol, nebivolol, oxprenolol, penbutolol, propranolol, sotalol, talinolol and timolol in blood plasma after mixed-mode (HCX) solid-phase extraction (SPE) and separation by reverse-phase liquid chromatography with gradient elution. The validation data were within the required limits. The assay was successfully applied to authentic plasma samples allowing confirmation of diagnosis of overdose situations as well as monitoring of patients' compliance. 相似文献
959.
960.
Three fractions of SiC platelets were characterized using polarizing microscopy, X-ray diffraction, high resolution Auger electron spectroscopy (AES), electron spectroscopy for chemical analysis (ESCA) and scanning electron microscopy with energy dispersive analysis (SEM/EDX). The chemical analysis of the three fractions is given. The determination of the SiC polytypes (4H, 6H, 15R, 3C) was done and has been correlated with the chemical analysis. The results of the X-ray diffraction investigations confirm the polarizing microscopy observations. Using microanalytical techniques important conclusions about the impurity elements (e.g. B, Al, Fe) and their local distribution could be drawn. Most of them were found to be present on the outermost surfaces of the platelets. Some conclusions concerning the processing of the platelets are suggested.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday 相似文献