Volumetric thermal analysis of semicrystalline poly(ethylene terephthalate), PET, with different content of crystalline phase
was carried out using mercury-in-glass dilatometry. The effect of crystals on the thermal properties of amorphous phase (glass
transition temperature, Tg, thermal expansion coefficients, α) were determined. At cold-crystallization (106°C, up to 4 h), crystalline content of 2.4–25.3
vol.% was achieved. Increasing content of crystalline phase broadens the glass transition region and increases Tg. The change of thermal expansion coefficient during glass transition is lower than that predicted by the two-phase model,
which indicates the presence of a third fraction — rigid amorphous fraction (RAF), whose content steadily increases during
crystallization. However, its relative portion (specific RAF) is significantly reduced. Further significant decrease in specific
RAF appears after annealing at a higher temperature.
Authors:Y. Malghe, S. Dharwadkar, K. Krishnan, and K. Singh Mudher
The phase transitions in the LaCrO3 were studied using bulk dilatometry and high temperature X-ray diffractometry from room temperature to 1050 and 1200°C, respectively.
LaCrO3 was prepared at 500°C from oxalate precursor employing microwave heating technique. Bulk shrinkage measurements on LaCrO3 pellets were carried out using dilatometer designed and fabricated in our own laboratory. Dilatometric curves of LaCrO3 showed two peaks in ΔL/L vs. temperature curves in the range 200–400 and 800–1000°C, respectively. These phase transitions have been confirmed using
high temperature X-ray diffractometry. The role of simple technique like bulk dilatometry in detecting and monitoring the
polymorphic transformations in solids is discussed for lanthanum chromates.
The aim of the present work is to find relation between the state of ceramic coating of iron and the physical properties of
coated samples as a function of temperature. The iron samples coated by plasma assisted physical vapor deposition (PA PVD)
with layers of TiN were investigated with new technique – temperature modulated thermomagnetometry (TM TMAG) and thermal dilatometry
(TM DIL). From the irregular behavior of the thermal dilatation and magnetic susceptibility, the process of the coating degradation
can be resolved.
Authors:J. Tulliani, G. Pagès, G. Fantozzi, and L. Montanaro
By using a wet chemical route, pure calcium hexaluminate (CA6) was yielded, significantly lowering the reaction temperature and shortening the synthesis time if compared to usual industrial
procedures. owever, dilatometric studies performed on compacts made of the as-prepared powder, just after pre-heating at 450C,
has shown a superposition between sintering shrinkage and expansion related to CA2 formation, an intermediate phase formed during calcination and phase evolution to CA6. oupling of such opposite phenomena led to microcracking of the material, mainly if the heating rates (10C min-1) were high. However, lower heating rates (1-5C min-1) could quite avoid microcracking but also limit densification.
Two different porcelain compositions were studied: a soft and a hard
one. DTA, optical non-contact dilatometry and DSC were used to evaluate the
thermal behaviour of the porcelain compositions with the aim to master the
suitable thermal cycle for each. Results were interpreted on the basis of
mineralogy and microstructure: the amorphous phase, abundant in soft porcelain,
plays an important role on thermal expansion (8·10–6
K–1 for soft and 6·10–6
K–1 for hard at 1000°C). Thermal expansion
behaviour as function of firing time was also studied. Non-contact dilatometry
characterisation of porcelain bodies enable to master the suitable thermal
cycle for the sintering.
Application of temperature modulated dilatometry (TM DIL) to investigation on degradation of the adhesion between ceramic
films and the substrate is presented. Layers of titanium nitride deposited by plasma assisted physical vapour deposition (PA
PVD) methods on the Armco iron substrates were tested. This paper shows that the TM DIL method is helpful in determining the
usefulness of the titanium nitride covering of the cutting tools and machine parts.
Authors:A. Colantuono, S. Dal Vecchio, G. Mascolo, and M. Pansini
Powdered pressed compacts of different cationic forms of a natural chabazite were tested by dilatometry. The dilatometric curves of the various cationic forms displayed markedly different features, interpretable in terms of shrinkage by dehydration, thermal expansion, cation migration and thermal breakdown of the zeolitic structure.
The ternary compounds 14PbO·P2O5·2PbCl2 (R) and 29PbO·3P2O5·6PbCl2 (S), which are formed in the ternary system PbO-P2O2-PbCl2, were examined by dilatometry. Numerous, previously undescribed thermal and dilatational effects were observed to occur in these compounds under the influence of temperature.
Authors:P. Pustková, J. Shánělová, P. Čičmanec, and J. Málek
The structural relaxation of Ge38S62 glass has been studied by length dilatometry and calorimetry. The Tool-Narayanaswamy-Moynihan model was applied on obtained
data of structural relaxation and parameters of this model were determined: Δh*= 4832 kJ mol-1, ln(A/s)= -811, β= 0.70.1 and x=0.60.1. Both dilatometric and calorimetric relaxation data were compared on the basis of the fictive relaxation rate. It
was found that the relaxation rates are very similar and well correspond to the prediction of phenomenological model.
The decomposition processes of a carburised Fe–C alloy, a Fe–C, a Fe–Cr–C and commercial SAE 52100 cast alloys (with a C content
of about 1 mass%) have been studied by means of differential scanning calorimetry and dilatometry. The combination of these
two experimental techniques is very powerful and allows the identification of all the stages occurring during tempering. Activation
energies have been obtained by performing a Kissinger-like analysis and were used to infer the rate-determining step for each
stage of decomposition. This parallel investigation allowed to determine the effect of the alloying elements on the different
stages of tempering.