An attempt has been made to assign empirical formulae and possible ion exchange site for the antimonates of Zr(IV), Sn(IV)
and Cr(III). On the basis of analytical data, exchange capacity, infra-red and thermoanalytical investigations these ion exchangers
have the compositions as: ZrO2·0.5 Sb2O5·5.1 H2O, SnO2·2.5 Sb2O5·15 H2O and Cr2O3·5Sb2O5·31 H2O. Water molecules shown is the total water present which includes both water of constitution and water of crystallization.
The H+ attached to anionic part of the exchanger, i.e., Sb−OH is the possible site for cation exchange. However, the general shape
of curves in McKay Plot and the dependence of Kd values on the concentration of metal ions in solution at constant pH suggest
more than single possible exchange site.
This paper reports a comparative study of the non-isothermal decompositions of the heteropolyacids HPM and HPVM, with structures
consisting of Keggin units (KUs). Non-isothermal analysis at low heating rates demonstrated the existence of 4 crystal hydrate
species, depending on the temperature. The stability domains of the anhydrous forms of HPM and HPVM were found to be 150–380°C,
respectively. Processing of the TG curves obtained at different heating rates by the Ozawa method revealed that the decomposition
of anhydrous HPM takes place according to a unitary mechanism, whilst for anhydrous HPVM two mechanisms are observed. Thus,
the first part of the constitution water is lost simultaneously with the departure of vanadium from the KU as VO2+, while the second part is lost at higher temperatures as in the case HPM.
The mixtures of CuCl2 and KC1 with Cu to K molar ratios from 0.2 to 2.0 were analysed by thermogravimetry in air and argon atmosphere under different
conditions. The samples differed in the temperature of their preparation. Conclusions were drawn concerning the phase changes
and the constitution of the CuCl2−KC1 system.
High alumina cement (HAC) concrete undergoes with ageing a change in mineral constitution known as conversion which may be accompanied by a loss in strength. The amount by which this change in composition has gone, measured by the ratio of CaO·Al2O3·10 H2O to Al2O3·3 H2O is known as the degree of conversion (Dc). The faster the conversion goes the greater the loss in strength.
Authors:Piotr Szynkaruk, Marek Wesolowski, and Malgorzata Samson-Rosa
Thermal decomposition of magnesium salts of organic acids used in medicine (Mg acetate, Mg valproate, Mg lactate, Mg citrate,
Mg hydrogen aspartate, Zn hydrogen aspartate) was analyzed by thermoanalytical, calorimetrical, and computational methods.
Thermoanalytical studies were performed with aid of a derivatograph. 50-, 100-, and 200-mg samples were heated in a static
air atmosphere at a heating rate of 3, 5, 10, and 15 °C min−1 up to the final temperature of 700–900 °C. By differential thermal analysis (DTA), thermogravimetry (TG), and derivative
thermogravimetry (DTG) methods, it has been established that thermal decomposition of the salts under study occurs via two
stages. The first stage (dehydratation) was distinctly marked on the thermoanalytical curves. Calorimetrical studies were
carried out by using of a heat-flux Mettler Toledo differential scanning calorimetry (DSC) system. Ten milligram samples of
compounds under study were heated in the temperature range from 20 to 400 °C at a heating rate of 10 and 20 °C min−1 under an air stream. The studies showed that the values of transitions heats and enthalpies of dehydration for investigated
salts varied with the increasing of heating rate. For chemometric evaluation of thermoanalytical results, the principal component
analysis (PCA) was applied. This method revealed that points on PC1 versus PC2 diagrams corresponding to the compounds of
similar chemical constitution are localized in the similar ranges of the first two PC’s values. This proves that thermal decomposition
reflects similarity in the structure of magnesium salts of organic acids.
Authors:V. Amicarelli, G. Baldassarre, and L. Liberti
Granular activated carbon loaded with aniline,o-nitroaniline oro-nitrophenol, regenerated at relatively low temperature (450° in N2 atmosphere), shows losses of cyclic adsorption performances (about 5 % per cycle) comparable to those occurring with standard thermal regeneration (950° in controlled atmosphere). Adsorbate build-ups and related surface modifications have been determined.
The aim of this study is to investigate the influence of some monovalent counter-ions (NH4+, K+ and Cs+) on thermal behavior of polyoxometalates derived from H3PMo12O40 (HPM) and H4PVMo11O40 (HPVM) by replacing the protons. The IR and UV-VIS-DRS spectra of some acid and neutral NH4+, K+, Cs+ salts, which derived from HPM and HPVM, confirmed the preservation of Keggin units (KU) structure. The X-ray diffraction
spectra clearly showed the presence of a cubic structure. The non-isothermal decomposition of studied polyoxometalates proceeds
by a series of processes: the loss of crystallization water; the loss of O2 accompanying with a reduction of V5+→V4+ and Mo6+→Mo5+; the loss of constitution water started at 360C for HPVM salts and 420C for HPM salts; the decomposition of ammonium ion
over 420C with NH3, N2 and H2O elimination and simultaneous processes of reduction (V5+→ V4+ and Mo6+→ Mo5+ or Mo4+) associating with endothermic effects; reoxidation of Mo5+, Mo4+ and V4+with a strong exothermic effect; destruction of KU to the oxides: P2O5, MoO3 and V2O5 and the crystallization of MoO3.
Authors:B. Teitelbaum, T. Yagfarova, K. Aleyev, M. Khasanov, and F. Gafurov
TMA has been used to investigate the thermomechanical behaviour of six series of elastomers in connection with their chemical
constitution and physical structure. The elastomers, were synthesized from an NCO-terminal pre-polymer, based on oligo (ethylene
adipate), 1,4-butanediol and 2,4-toluylene diisocyanate, by curing with systems of two agents: a bifunctional one (1,4-butanediol,
bistethylene glycol)terephthalate, or monoethanolamine), and a trifunctional one (1,1,1-trimethylolpropane or diethanolamine).
The TMA results are presented as due to the superposition of the chemical cross-linking and the physical network, formed through
microphase segregation. The TMA suggests that diethanolamine unexpectedly acts as a chain extender, rather than a cross-linking
Authors:Dan Gao, Chong Woon Cho, Le Ba Vinh, Jin Hyeok Kim, Young Ho Kim, and Jong Seong Kang
distribution of chemical constitutions. Nonetheless, how to more exactly to explain the difference between the individual samples in the same cluster was found to be a complication of HCA. From the point of view, the chemical pattern recognition approaches