Bone cements are widely used for the fixation of metallic prostheses in orthopaedics and to form replacements for skull defects in neurosurgery. Acrylic bone cements are based on a mixture of methyl methacrylate (MMA) and a fine powder of polymethyl methacrylate (PMMA). The polymerization of the bone cement occurs in contact with the bone and the prosthesis which act as the boundaries of a bulk polymerization reactor. The kinetic behaviour of the bone cement plays a fundamental role for the final performance of the implant.
Authors:Z. Lu, S. Chen, Y. Yu, J. Sun and S. Xiang
Thermal behaviour of tri(O,O'-diisopropyldithiophosphate)cobalt(III), Co(dptp)3 and bis (O,O'-diethyldithiophosphate)nickel(II), Ni(detp)2 and its adducts with pyridine, Ni(detp)2(py)2 or 4-methylpyridine, Ni(detp)(mpy)2 in a dynamic nitrogen atmosphere was investigated by TG-DTG and DSC techniques, which showed a medium endothermic peak for
the evolution process of pyridine(or 4-methylpyridine) and a strong exothermic peak for that of O,O'-diethyldithiophosphate.
The thermal stability and decomposition patterns for these compounds were compared and interpreted in terms of structural
features such as bond character and steric effects. The kinetic parameters and mechanisms of every decomposition stage involved
for all these complexes were obtained employing the non-isothermal kinetic analysis method suggested by Malek et al., which
showed the kinetics mechanism for pyrolysis of pyridine(or 4-methylpyridine) is an S-B empirical model with lower activation
energy, while that of O,O'-dialkyldithiophosphate is a diffusion model. These results are in accord with the fact that two
ligands are of different type.
In this research, pyrolysis and combustion behavior of three different oil shale samples from Turkey were characterized using
thermal analysis techniques (TG/DTG). In pyrolysis experiments, two different mechanisms causing mass loss were observed as
distillation and cracking. In combustion experiments, two distinct exothermic peaks were identified known low and high temperature
oxidation. On the other hand, determination of activation energies are required for the estimation of oil extraction conditions
from the oil shales. Differential methods are used to determine the activation energies of the samples where various f(α) models are applied from the literature. It was observed that the activation energies of the all oil shale samples are
varied between 13.1–215.4 kJ mol−1 in pyrolysis and 13.1–408.4 kJ mol−1 in combustion experiments which are consistent with other kinetic results.
Reactions with large negative enthalpy changes are often encountered in the chemical industry. Sometimes they give rise to
technical dangers and hazards, including explosions. This investigation concentrates on examination of adiabatic temperature-time-curves
and gives non-linear optimization procedures for obtaining kinetic parameters of simple decompositions,e.g. o-nitrobezaldehyde, two types of autocatalysis, consecutive reactions and competitive consecutive reactions. The advantage
of this computing method is that only differential kinetic equations are needed.
Authors:Dana Bogdan, J. P. Aycard, Mohamed Hnach, Elena Volanschi, Mihaela Hillebrand, V. Badescu, N. Dragoe and E. Segal
The thermal behaviour of some compounds derived from 5-phenylfuran-2,3-dione was studied. The thermoanalytical data relating to the decomposition steps and intermediates were completed with mass spectrometric analysis and infrared spectroscopy results. For some of the investigated reactions, the kinetic and structural data correlated satisfactorily.
Authors:Henry Kuo Feng Cheng, Nanda Gopal Sahoo, Xuehong Lu and Lin Li
matrix [ 7 , 10 ].
However, the detailed studies on the effects of nanoclay on the thermal kinetics of PP in the PPCNs have not been found in the literature. Therefore, in this work, the effects of nanoclay on the thermal decomposition and
kinetics and mechanism of nickel oxide reduction by hydrogen. This alternative theoretical model has been developed during the last 20 years [ 24 – 33 ] to explain the kinetics and mechanisms of thermal decompositions of solids. It is applied to metal oxide
The crystallization process of Li2B4O7 in the glass of stoichiometric composition, characterized by the crystal growth of pre-existing nuclei, was analyzed kinetically
by means of DTA. Because the number of pre-existing nuclei for the subsequent growth varies depending on the cooling rate
of the glass-forming melt and heating rate of the as-prepared glass, a modified Kissinger plot was applied for evaluating
the apparent activation energy to the crystal growth in the glass samples with three different thermal histories, i.e., the
pre-annealed, slowly quenched and quickly quenched glasses. The process was characterized by the three dimensional growth
of pre-existing nuclei with the apparent activation energy of ca 340 kJ mol−1.
A thermal analysis study on the reduction of iron oxide rich slags under different conditions is presented in this paper.
The effects of important process variables such as time, temperature, lime-silica ratio, FeO level in slag etc. are discussed.
It is shown that the mechanism of reduction by externally added graphite is different from that by a carbon saturated bath
although the activation energy values are similar.