Authors:Mahmood Al Ramahi, Sándor Beszédes, and Gábor Keszthelyi-Szabó
structures such as EPS are converted into simple soluble organics. Pre-treatment techniques are suggested to facilitate the hydrolysis step in order to achieve faster disintegration and higher degradation efficiency. Specifically, hydrothermaltreatment has
Authors:P. Patrono, A. La Ginestra, C. Ferragina, M. A. Massucci, A. Frezza, and S. Vecchio
The Zr, Ti, Sn and Ge hydrogenphosphates, generally prepared in a crystalline form by the refluxing method, have been submitted to hydrothermal treatment at 180° and 300°C in order to observe if the preparation time can be shortened maintaining their chemical composition and their α-structure. Simultaneous TG and DTA together with XRD revealed to be very suitable techniques for the characterization of the obtained products.
Authors:S. Marinković, A. Kostić-Pulek, S. Durić, V. Logar, and M. Logar
Selenite was boiled in KCl solutions of different concentrations at the respective boiling temperatures and atmospheric pressure. The products were subjected to X-ray diffraction analysis, qualitative infrared analysis, differential thermal analysis and microscopic examination. The product obtained in 1.0 M KCl solution was the -form of calcium sulphate hemihydrate (-CaSO4·0.5H2O). In more concentrated KCl solution (1.5, 2.0, 2.5, 3.0, 3.5 or 4.0 M), the -form of calcium sulphate hemihydrate (-CaSO4·0.5H2O) was formed, and a reaction took place between KCl and CaSO4, which gave a double salt: potassium pentacalcium sulphate monohydrate (K2SO4·5CaSO4·H2O).
Authors:G. Dell’Agli, G. Mascolo, M. C. Mascolo, and C. Pagliuca
Summary Mechanical mixtures containing zirconia xerogel and increasing amount of crystalline yttria up to 40 mol%, were hydrothermally treated by microwave route at 110°C for 2h. All the treatments were performed in the presence of (KOH+K2CO3) mineralizer solution at concentration 0.2 M. Amorphous and hydrated ZrO2-Y2O3 solid solutions with yttria content up to 33.3 mol% (corresponding to Zr/Y molar ratio equal to 1), resulted after the hydrothermal treatments. A remarkable reduction of the surface area has been detected at increasing yttria content of the amorphous phases with a corresponding increase of the exothermic peak of crystallization. A mechanism of reaction for the formation of the amorphous solid solutions has been proposed.
Authors:R. C. Eerlingen, H. Jacobs, H. Van Win, and J. A. Delcour
Gelatinisation temperatures as a function of moisture content were determined for potato starch. The native starch was then hydrothermally treated at a temperature 3% (Kelvin degrees) below the gelatinisation peak temperature and at moisture levels varying from 20 to 67% (by weight). Gelatinisation temperatures, temperature ranges and enthalpy values were affected for all treated samples. However, two sample populations could be distinguished: those samples treated under ‘limited’ moisture conditions and other samples treated in the presence of ‘extragranular’ moisture. A two-step hydrothermal treatment further increased the gelatinisation temperature, but the effect of the second step was small in comparison to that of the first.
Authors:W. Wolski, E. Wolska, J. Kaczmarek, and P. Piszora
Products of hydrothermal treatment of the initial amorphous system MnxFe2−2x(OH)6−4x for 0≤x1 in 0.1x intervals, and products of their further thermal treatment, were examined by chemical analysis, X-ray, IR, and DTA techniques supported by magnetic measurements. After hydrothermal growth for lowx, hematite and goethite phases occurred. Although the goethite phase was still identifiable atx=0.6, formation of a solid solution with the isostructural groutite was not found. The ferrimagnetic spinel phase, which resists heating up to 400‡C, was present at 0.5≤x≤0.9. At higher temperatures, it transformed into the rhombohedral hematite type phase or into the cubic bixbyite phase. AtT≥900‡C, a ferrimagnetic spinel structure reappeared up tox=0.8. For x=0.9, the low- and high-temperature forms of the hausmannite phase occurred, forx= 1 passing from one form into another through Mn5O8 and partritgeite.
Authors:Ana Carla S. L. S. Coutinho, Solange A. Quintella, A. S. Araujo, Joana M. F. Barros, Anne M. G. Pedrosa, V. J. Fernandes Jr., and M. J. B. Souza
Nanoporous silica with narrow pore size distribution has attracted increasing attention as a novel material for separations and reactions involving large molecules. SBA-15 has been synthesized in an acidic medium using a triblock copolymer as template. In this work, the SBA-15 was synthesized by the hydrothermal treatment at 373 K for 48 h, of a gel with the following overall molar composition: 1.0TEOS:0.017P123:5.7HCl:193H2O, where TEOS is tetraethyl orthosilicate and P123 is poly(ethylene oxide, propylene oxide and 1,4-dioxane). The obtained material was characterized by thermogravimetry, X-ray diffraction, infrared spectroscopy and BET surface area. A kinetic study using the model free model was accomplished in the stage of decomposition of the template (P123). The obtained value of the apparent activation energy was ca. 131 kJ mol−1.
Authors:Y. Zhao, R. Frost, Veronika Vágvölgyi, E. Waclawik, J. Kristóf, and Erzsébet Horváth
Yttrium doped boehmite nanofibres with varying yttrium content have been prepared at low temperatures using a hydrothermal
treatment in the presence of poly(ethylene oxide) surfactant (PEO). The resultant nanofibres were characterized by X-ray diffraction
(XRD) and transmission electron microscopy (TEM). TEM images showed the resulting nanostructures are predominantly nanofibres
when Y-doping is less than 5%; in contrast Y-rich phases were formed when doping was around 10%.
The doped boehmite and the subsequent nanofibres/nanotubes were analyzed by thermogravimetric and controlled rate thermal
analysis methods. The boehmite nanofibres produced in this research thermally transform at higher temperatures than boehmite
crystals and boehmite platelets. Boehmite nanofibres decompose at higher temperatures than non-hydrothermally treated boehmite.
Iron doped boehmite nanofibres with varying iron content have been prepared at low temperatures using a hydrothermal treatment
in the presence of poly(ethylene oxide) surfactant. The resultant nanofibres were characterized by X-ray diffraction (XRD),
and transmission electron microscopy (TEM). TEM images showed the resulting nanostructures are predominantly nanofibres when
Fe doping is no more than 5%; in contrast nanosheets were formed if Fe doping was above 5%. For the 10% Fe doped boehmite,
a mixed morphology of nanofibres and nanosheets were obtained. Nanotubes instead of nanofibres were observed in samples with
20% added iron. The Fe doped boehmite and the subsequent nanofibres/nanotubes were analysed by thermogravimetric and differential
thermogravimetric methods. Boehmite nanofibres decompose at higher temperatures than non-hydrothermally treated boehmite and
nano-sheets decompose at lower temperatures than the nanofibres.
Authors:A. La Ginestra, P. Patrono, A. Frezza, C. Mancini, M. Massucci, and S. Vecchio
Pure and mixed Ge and Sn hydrogenphosphates, prepared either by refluxing in 8M H3PO4 or by hydrothermal treatment at 180° or 300°C, have been characterized in terms of chemical composition and thermal behaviour
and also tested as catalysts in the 1-butene isomerization, in order to correlate acidic properties with preparation method.
Solid solutions for every composition in this system are formed only when using the refluxing method, as proved by X-ray and
TG-DTA data. The hydrothermal treatments are strongly influenced by the hydrolysability of the Ge phosphate: in almost all
the samples, where Ge was present, GeOHPO4 was identified on TG-DTA curves by the endothermic H2O weight loss at 700°–800°C. The acidic properties of the various materials decrease as GeOHPO4 content increases.