Thermal analysis, mass spectrometry, infrared spectrophotometry, X-ray phase analysis, scanning electron microscopy, and sorption methods were used in the study of thermal transformations of the products of partial hydrolysis of hydrous aluminium nitrate in ammonia medium. It has been found that the process of aluminium nitrate hydrolysis under the conditions applied and in the presence of ammonia gives boehmite as the main product, with some admixture of a basic salt.Aluminium oxide obtained from the products of partial hydrolysis of hydrous aluminium nitrate in ammonia medium at 550°C has a crystalline -Al2O3 structure. Its specific surface, as determined by low-temperature adsorption of nitrogen, exceeds 200 m2g–1. Features of the products are well developed mesopore structure and considerable ability of benzene adsorption. Calcination of the obtained aluminium oxide for 2 h at 900°C reduces its specific surface to about 110 m2 g–1.
Authors:R. Knubovets, Y. Nathan, S. Shoval, and J. Rabinowitz
The thermal transformations in phosphorites during flash calcination were investigated by FT-IR spectroscopy, X-ray diffraction
and chemical analyses. During flash calcination changes occur, both in the composition of the phosphorite and in the crystallochemistry
of the fluor-carbonate-apatite (francolite). The former changes include: decomposition of a great part of the calcite in the
rock and oxidation of organic matter. The latter changes include: partial removal of the structural carbonate; partial relocation
of the remaining carbonate ions in the apatite structure; a new arrangement of hydroxyl groups and fluorine on the hexagonal
axis; partial condensation of the orthophosphate groups and increase of crystallite sizes. Isomorphous substitution of PO4−3 in apatite by SO4−2 and SiO4−4 may take place.
Titanium raw materials play important role as a source of titanium and titanium dioxide. The investigation of the rate of
oxidation and phase transformation of titanium slag in static air atmosphere by use of thermogravimetry (TG) and X-ray diffractometry
(XRD) were presented. The investigation were carried out for three different particle size fractions to determine influence
of this parameter on rate of reaction. To estimate kinetic parameters was used the kinetic model of contracting volume. The
value of kinetic parameters show that influence of heating rate and particle size on rate of reaction is not so large. The
thermogravimetric investigations of the oxidation of titanium slag in air atmosphere shown that reaction proceeds in two stages.
The XRD investigation shown that titanium slag has the pseudobrookite structure and its diffraction pattern is very close
to the diffractogram of magnesium titanate MgTi2O5 and iron magnesium titanium oxide (Fe-Mg-Ti-O). At elevated temperature the structure of slag transforms to the ferric pseudobrookite
structure and excess titanium dioxide forms the rutile phase.
Authors:K. Gavrichev, A. Bolshakov, D. Kondakov, A. Khoroshilov, and S. Denisov
Differential scanning calorimetry, differential thermogravimetry, X-ray analysis and electronic microscopic studies of thermal
transformations of PbO2 were carried out. Formation of fine dispersed (less than 100 nm) particles of α-PbO was observed at PbO2 thermal decomposition at heating to 580°C. Reverse reaction of Pb3O4 formation from PbO was found at cooling and annealing at 400°C in air. At heating of α-PbO to 650°C the particle growth to
1 μm with formation of β-PbO took place. Thermal decomposition with formation of β-PbO particles with size from 0.3 to 1 μm
at PbO2 heating to 650°C was observed. Transition from PbO to Pb3O4 at cooling of sample heated to 650°C was not detected. Interpretation of observed phenomena from the point of view of particle
size influences on the shift of α-PbO↔β-PbO phase transition temperature and on the chemical activity of phases are presented.
This work focuses on the thermal and mineralogical transformations of red wall tile pastes. The pastes contain different amounts of calcareous and are prepared with Brazilian raw materials. Thermal transformations are evaluated by TG, DTG and DTA, dilatometric analysis, and X-ray diffraction. Four endothermic transformations were identified and interpreted as the release of physically adsorbed water, dehydration of hydroxides, dehydroxylation of kaolinite, and decomposition of carbonate. An exothermic transformation within the 925–950°C range is associated to crystallization of new phases such as calcium aluminosilicates and mullite. TG measurements indicate that the total mass loss of the pastes is dependent on the amount of calcareous addition. Dilatometric analysis indicates the onset of sintering at around 900°C, leading to shrinkage of the pellets. The thermal analysis results agree well with the X-ray diffraction.
Authors:Rattanai Baitahe, Naratip Vittayakorn, and Banjong Boonchom
, only mechanism of dehydration and condensation of the compound has been reported by Brandova et al. [ 20 ]. After a detailed literature survey, kinetic and thermodynamic studies of thermaltransformation of the compound have been not found anywhere. The
The aim of the present study was to determine the kinetic equations for the thermal transformations of precipitated iron oxides
and hydroxides, namely for the process of thermal dehydroxylation of goethite and consecutive of hematite crystal structure
growth as well as for the oxidation of magnetite to maghemite and its thermal transformation into crystalline hematite. The
investigations have been carried out using thermogravimetry (TG/DTG/DTA), X-ray powder diffractometry (XRD) and high temperature
powder diffractometry (HT-XRD). This presentation contains the continuation of our earlier works.
Authors:Rafał Janus, Piotr Natkański, Anna Wach, Marek Drozdek, Zofia Piwowarska, Pegie Cool, and Piotr Kuśtrowski
carbons are applied as the adsorbents for the removal of heavy metal ions and organic pollutants from aqueous solutions as well as volatile organic compounds (VOCs) from exhaust gases [ 5 – 7 ]. The mechanism of the PAN thermaltransformation during
Authors:S. A. Agranova, G. A. Polotskaya, N. A. Shirokov, V. G. Baranov, and Yu. N. Sazanov
The effect of introduction of the comonomer methylthiirane (MT) into the main chain of polyacrylonitrile (PAN) on the thermal transformations of the macromolecules in dilute DMF solution was studied. For this purpose, statistical copolymers of acrylonitrile and MT were synthetized and their pyrolysis in solution was investigated. It was found that introduction of the thioether group into the main chain of PAN results in essential changes in the thermal behaviour of the copolymers as compared to the homopolymer. The results of rheological, thermal and spectral studies on the solutions suggest that the direction of the thermochemical reaction changes on introduction of the thioether group into the PAN molecule. In such copolymers the reaction will preferably proceed by the -C≡N groups forming conjugated cyclic structures.