Authors:B. Pacewska, A. Klepańska, P. Stefaniak, and D. Szychowski
Attempt was made to evaluate the usefulness of thermoanalytical methods, combined with X-ray phase analysis and chemical analyses,
for the study of thermal decomposition of waste materials to be subjected to thermal treatment.
The object of the studies were petrochemical waste materials intended to be decomposed in a rotary furnace. Results are given
of the studies of five selected waste materials.
Authors:T. Kaljuvee, M. Radin, D. Astahhov, and Y. Pelovski
TG-FTIR technique was used for identification of gaseous compounds evolved
at thermal treatment of six coal samples from different deposits (Bulgaria,
Russia, Ukraine). The experiments were carried out under dynamic heating conditions
up to 900C at heating rates of 5, 10 or 50 K min–1
in a stream of dry air. The emission of CO2, H2O,
CO, SO2, COS, methane, methanol, formic acid, formaldehyde,
acetaldehyde, chlorobenzene was clearly identified in FTIR spectra of the
samples studied. The formation of ethanol, ethane, ethylene and p-xylene, at least on the level of traces, was also
identified. At the heating rate of 5C min–1
the temperature of maximum intensities of the characteristic peaks of COS
was 270C, of formaldehyde, formic acid, ethane and methanol 330C,
of SO2, CO, acetic acid, ethylene and p-xylene
400C and of chlorobenzene 500C. At 10C min–1
and 50C min–1 these temperatures were
shifted, respectively, by 70–300C and 150–450C towards
higher temperatures and the respective absorption bands in FTIR spectra were,
as a rule, more intensive.
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.
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:F. Mezahi, H. Oudadesse, A. Harabi, A. Lucas-Girot, Y. Le Gal, H. Chaair, and G. Cathelineau
The dissolution kinetic and structural behaviour of natural hydroxyapatite (N-HA) and synthetic hydroxyapatite (S-HA) was
studied vs. sintering temperature and using ‘in vitro’ experiments. Obtained results highlight the chemical stability of N-HA. Any structural
modification was observed until 1200°C. In the fact S-HA undergoes some modifications. XRD diagrams show the tricalcium phosphate
(TCP) phase formation between 800 and 1100°C and tetracalcium phosphate (TetCP) phase formation at 1200°C. The ‘in vitro’
assay shows that the dissolution was occurred more in N-HA than in S-HA. The formed TCP activated the dissolution kinetic
and then the precipitation phenomena when a continuous dissolution of TetCP leaded to slow down the kinetic precipitation.
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:F. I. El-Hosiny, S. A. Abo-El-Enein, H. El-Didamony, and Kh. A. Khalil
Rice husk ash fired at different temperatures, 450, 700 and 1000°C, was mixed with different concentrations of lime (molar lime/silica ash ratio of 0.2, 0.5 and 1.0). Each dry mixture was first ground and hydrated in the suspension form (water/solid ratio = 10) for various time intervals within the range of 1 to 365 days. The surface properties of the unhydrated and hydrated samples were studied by means of nitrogen adsorption measurements. The results indicated that the surface areas and total pore volumes of unhydrated solid mixtures and hydrated lime-rice husk ash samples, prepared with lime/silica ash ratio of 1.0, decrease with increasing firing temperature of rice husk ash. The effect of varying the lime/silica ash ratio of the solid mixture on the surface area and pore structure was fully discussed. The results of surface area and pore volume measurements could also be related to the crystal structure of silica produced from rice husk ash.
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.