Authors:E. Yörükoğulları, G. Yılmaz, and S. Dikmen
In this study, the zeolitic tuffs having clinoptilolite obtained from Bigadic region of western of Anatolia, Turkey were investigated
as regards to whether it is possible to be transformed into amorphous phase from them. At first, the zeolite tuffs rich in
clinoptilolite were characterized using XRD, DTA, TG, DSC, and FTIR standard methods. All the samples were heated at 110 °C
for 2 h and then were expanded within 5 min between the temperatures 1200 and 1400 °C. In addition, porosity and density were
determined. The resistance values of all the samples were measured in acidic and basic media. These samples were also analyzed.
As a result of this study, zeolitic tuffs in clinoptilolite were transformed into amorphous phase, and especially in chemical
industry were found convenient.
Heating and/or cooling of substances is one of the oldest and basic methods for preparing materials with defined properties.
This always leaves a definitive fingerprint of the thermal history. Beside knowing the structure we need to specify such materials
by their thermodynamic behaviour, i.e., stability/metastability, phase relations and transitions, particularly establishing
corresponding characteristic points. All this can be based on ordinary thermodynamics but its validity must be approved for
non-equilibrium conditions of temperature changes where equilibrium and kinetic effects overlap. The slower the phase transition
proceeds the greater is the deviation of the system state (kinetic curve) from its equilibrium state (equilibrium background).
This makes possible to locate the actual phase boundary between two states investigated, resulting in the so-called kinetic
phase diagrams. Most of modern technologies are intentionally based on non-equilibrium phenomena in order to create metastable/nonstable
phases of specific properties. In this sense thermal analysis is understand as the method for determining the sample state
on the basis of the sample interactions with the surroundings whose intensive parameters are controlled. Temperature is here
considered as a basic parameter that connects all thermophysical measurements and thermal treatments.
Authors:A. de Oliveira, J. Ferreira, Márcia Silva, Soraia de Souza, F. Vieira, E. Longo, A. Souza, and Iêda Santos
NiWO4 and ZnWO4 were synthesized by the polymeric precursor method at low temperatures with zinc or nickel carbonate as secondary phase.
The materials were characterized by thermal analysis (TG/DTA), infrared spectroscopy, UV–Vis spectroscopy and X-ray diffraction.
NiWO4 was crystalline after calcination at 350 °C/12 h while ZnWO4 only crystallized after calcination at 400 °C for 2 h. Thermal decomposition of the powder precursor of NiWO4 heat treated for 12 h had one exothermic transition, while the precursor heat treated for 24 h had one more step between
600 and 800 °C with a small mass gain. Powder precursor of ZnWO4 presented three exothermic transitions, with peak temperatures and mass losses higher than NiWO4 has indicating that nickel made carbon elimination easier.
Authors:István Dalmadi, Dávid Kántor, Kai Wolz, Katalin Polyák-Fehér, Klára Pásztor-Huszár, József Farkas, and András Fekete
., Berg, R. (2003) Combined high-pressure and thermaltreatments for processing of tomato puree: evaluation of microbial inactivation and quality parameters,
Innovative Food Science and Emerging Technologies
, 4, 377
Authors:Ion Sava, Ştefan Chişcă, Maria Brumă, and Gabriela Lisa
amide groups on the properties of partially imidized polyamidic acids as compared with those of the resulting polyimides, during different steps of thermaltreatment. Usually, the polarity of the surface influences the dielectric properties and the
H2SO4 and HCl processes accompanied by thermal treatments at different stages are described for the industrial extraction of alumina
from lateritic clay minerals, especially from kaolinite, an important component of lateritic bauxites. The effects of calcination
at high temperatures on the pretreatments of the raw lateritic materials, as well as on the thermal transformations of the
products (salts) resulting from the acid treatments of lateritic bauxites are analyzed. Beside energetic considerations, separation
methods of Al from Fe and from other lateritic-metallic components are emphasized in the extraction and purification processes.
The mechanism of a controlled HCl-extracting treatment performed on iron-bearing kaolinite is described, as well as its characterization
by IR and DTA ad hoc methods, enabling to distinguish between Al and Fe in the structure of lateritic kaolinite. The location
and quantification of Al in the structure of lateritic goethite is also considered.
The prepared amorphous
γ-ZrP\SiO2 composite had a complicated composition,
since a part of γ-ZrP is converted to α-form during the exfoliation
of it. The γ-ZrP\SiO2 composite have specific surface
area of 421 m2g–1.
The acidic P–OH groups of the lamellae species placed on the surface
(it is ≈1.0 meq g–1), do not destroy until
the temperature of 1030 K. During the thermal treatment the total mass loss
of 7.79% was found. This value corresponds to 0.42 mole of H2O
per molecule unit. The water loss process was found very slow, because of
the placing of bilamellar species in the composite.
The photoluminescence (PL) of barite is a noncharacteristic property and cannot be used for the investigation of its structure.
After thermal treatment of barite at 600°C several luminescent centers were observed, providing information about different
was determined from the vibrational structure and the long decay time of the luminescence band. Two different types of uranyl
were detected, thin films of uranyl mineral (most probably, reserfordin) and a solid solution of uranyl ion in barite crystal.
Characteristic green luminescence of UO
may be used as indicative feature for the prospecting of uranium deposits and for the sorting of barite ores with the aim
of cleaning from harmful U impurities. Eu2+ was determined from the spectral position, the half-width and the characteristic decay time of the luminescence band.
Mn2+ and Ag+ were determined by comparing luminescence bands spectral parameters to those of synthesized BaSO4−Mn and BaSO4−Ag. Fe3+ or Mn4+ were determined from the spectral-kinetic parameters of the luminescence bands.
irreversibly at 300 °C [ 14 , 15 ]. Above 400 °C, thermal reduction takes place [ 16 ], with Step II occurring in the range 460–570 °C, Step III in the range 700–800 °C, and Step IV above 1300 °C. The mechanism for these transitions in the thermaltreatment is
Authors:H. Oudadesse, A. C. Derrien, and M. Lefloch
In biomaterial field, the introduction of new types of composites presents a great interest for orthopaedic surgeons. In this work, geopolymers which are a family of aluminosilicates were synthesised and mixed with biphasic mixture (hydroxyapatite and of tricalcic phosphate). The optimised thermal treatment causes the reduction of pH to 7 units and favours the expansion of composites. Consequently, the increasing of porosity percentage was induced. These properties offer a good opportunity for applied composite as potential osseous biomaterial. To study the consequences of thermal treatment in the initial amorphous structure of composites some physico-chemical techniques like SEM, MAS-NMR and FTIR were employed. These methods permitted to evaluate the porosity, different links in composites and contributions of different groups of Si and Al before and after thermal treatment.