When exposed to attack by moisture, macroscopic defect-free materials (MDFs) undergo mass and phase changes. The nature of
such changes was studied thermoanalytically. Attacked samples differ from non-attacked samples in the degradation of classical
cement hydrates (TG, below 200C) and calcium carbonate (TG, DTA, 550-650C). Quantitative assessment favours the hypothesis
of the impregnation/barrier effect due to the incorporation of polyphosphate glass into the structure of the MDFs. The identity
of the thermal decomposition of attacked and non-attacked samples in the range 250-400C demonstrates the resistance of cross-linked
sections of polymer and clinker constituents to the effects of moisture.
Crystallization of fat droplets in complex emulsions, which differed only by the initial structure of proteins, was studied by differential scanning calorimetry, before and after application of a whipping process. Upon cooling at 5 or 1°C min–1, the temperature needed to initiate fat crystallization was lower, and one more distinguishable crystallization peak was detected in emulsions containing caseins, in comparison with the emulsion containing pure whey proteins. Furthermore, the whipping process was accompanied by more protein depletion from the fat droplet surface, less resistance to coalescence, and a lower supercooling effect in the emulsion based on pure whey proteins.
Authors:Lisardo Núñez Regueira, M. Núñez, M. Villanueva, and B. Rial
The influence of agents originated in a municipal landfill on the thermal degradation of a polymeric system composed of a
diglycidyl ether of bisphenol A (n=0) and 1,2-diaminecyclohexane was studied by thermogravimetric analysis (TG) in order to obtain the lifetime of this material
before and after being attacked. The different data obtained were analyzed to check the resistance of these materials to chemical
attack and the possibility of their use as coating materials in plants where those reagents were present. At the optimum temperature
of service for this material, 373.16 K, the lifetimes obtained from the experimental results were 2633 years and 2135 years,
A logical approach to electron transport studies for barrier conduction in layered structures was adopted by thermally stimulated
discharge current (TSDC) measurement. The scope and applicability of this technique to the evaluation of the thermoelectric
parameters of relaxation time, detrapping energy and depolarization rates are demonstrated here. These are characterized by
the controlling factors of layer resistance and the resultant thermal and voltage gradients which apply to the drift of electrons
arising from both dipolar and interfacial charges. The methodologies used in this study are suitable for parametric evaluation
of structured electronic devices.
Heating a milligram-sized sample of material at a constant heating rate is usually achieved by controlling the temperature
of an electric-resistance furnace with a proportional integral derivative (PID) controller. Here we present a new method for
constant-rate heating that is based on a semi-empirical mathematical expression relating sample temperature, heating rate,
and electric power supplied to the furnace. This method uses PID control only for second-order corrections of the heating
rate. The linearity of the sample temperature vs. time curves obtained by applying this method to a simple furnace setup is the same as the linearity of the curves generated
by modern commercial thermogravimetric analyzers.
A thermal analysis method that separately reproduces the gas and condensed phase processes of flaming combustion in a single
laboratory test is described. Anaerobic pyrolysis of solid plastics at a constant heating rate and complete thermal oxidation
(nonflaming combustion) of the evolved gases provides the rate, amount, and temperatures over which heat is released by a
burning solid. A physical basis for the method, the test procedure, and the relationship of flammability parameters to fire
response and flame resistance of plastics are described.
The sulfidation behavior of Fe20Cr and Fe20Cr0.7Y alloys in H2–H2S atmospheres at 700 and 800C was determined by thermogravimetry. Isothermal measurements were carried out and the sulfidation
kinetics were evaluated from the mass gain vs. time curves. The reaction products were examined in a scanning electron microscope
and the compositions of micro-regions were determined using energy dispersive spectroscopy and X-ray diffraction. Yttrium
addition increased the sulfidation resistance of the FeCr alloy.
Authors:A. Gatti, A. Rastelli, S. Ribeiro, Y. Messaddeq, and V. Bagnato
Due to their excellent aesthetics, photopolymers
have been extensively used in several dentistry applications. However, several
problems are reported, e.g. low mechanical and abrasion resistance, shrinkage
during polymerization, etc. Properties of the final restorations are intrinsically
related to the polymerization stage, which can be conveniently studied by
photocalorimetry. In the present work the polymerization reaction and the
filler content of different photocurable commercial dental methacrylate-based
composites were studied by means of photocalorimetry and thermogravimetry,
respectively. The results show that the values of curing rate, the heat of
polymerization and the filler content vary significantly from one composite
The thermal behaviour
of 2- and 4-biphenylmethanol were studied by differential scanning calorimetry
(DSC). It was found that the 2-isomer shows a relatively strong resistance
to crystallisation, and that it easily vitrifies on cooling. Oppositely, 4-biphenylmethanol
readily crystallizes on cooling. The slow molecular mobility of 2-biphenylmethanol
in the amorphous solid state was studied by DSC and by thermally stimulated
depolarisation currents (TSDC). Both techniques indicate that 2-biphenylmethanol
is a relatively strong glass-former, with a fragility index of ~50 in
the Angell's scale.
Authors:S. Rao, K. Lal, S. Narasimhan, and Jaleel Ahmed
A method has been developed for the removal of cesium from the aqueous radioactive waste using a composite ion-exchanger consisting
of Copper-Ferrocyanide Powder (CFC) and Polyurethane (PU) Foam. Polyvinyl acetate has been used as a binder in the preparation
of CFC-PU foam. The physical properties of CFC such as density, surface area, IR stretching frequency and lattice parameters
have been evaluated and also its potassium and copper(II) content have been estimated. Optimization of loading of CFC on PU
foam has been studied. The CFC-PU was viewed under microscope to find out the homogeneity of distribution. Exchange capacities
of the CFC-PU foam in different media have been determined and column studies have been carried out. Studies have been undertaken
on extraction of cesium from CFC foam and also on digestion of spent CFC-PU foam and immobilization of digested solution in
cement matrix. The cement matrices have been characterized with respect to density, bio-resistance and leaching resistance.