Thermal analysis in the form of electrical resistivity measurement is reviewed. It is useful for studying phase transitions and electrical conduction mechanisms. The resistivity can be the volume resistivity or the contact resistivity, as illustrated for the case of continuous carbon fiber polymer-matrix composites.
Authors:Veronika Vágvölgyi, R. Frost, M. Hales, A. Locke, J. Kristóf, and Erzsébet Horváth
The reaction of magnesium minerals such as brucite with CO2 is important in the sequestration of CO2. The study of the thermal stability of hydromagnesite and diagenetically related compounds is of fundamental importance to
this sequestration. The understanding of the thermal stability of magnesium carbonates and the relative metastability of hydrous
carbonates including hydromagnesite, artinite, nesquehonite, barringtonite and lansfordite is extremely important to the sequestration
process for the removal of atmospheric CO2. This work makes a comparison of the dynamic and controlled rate thermal analysis of hydromagnesite and nesquehonite. The
dynamic thermal analysis of synthetic hydromagnesite proves that dehydration takes place in two steps at 135 and 184°C, dehydroxylation
at 412°C and decarbonation at 474°C. Controlled rate thermal analysis shows the first dehydration step is isothermal and the
second quasi-isothermal at 108 and 145°C, respectively. In the CRTA experiment both water and carbon dioxide are evolved in
an isothermal decomposition at 376°C.
CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of magnesium carbonates
such as nesquehonite via approaching equilibrium conditions of decomposition through the elimination of the slow transfer
of heat to the sample as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of
non-isothermal nature reveal partial nesquehonite structure.
Many investigations and researches studied the reaction
ability between high explosive RDX and RDX with other chemicals. However,
accidents still occur and operating problems exist among the RDX manufacturing
process. This study utilized inherent safety concepts and DSC thermal analysis
to assess the incompatible reaction hazards of RDX during usage, handling,
storage, transporting and manufacturing. This assessment includes thermal
curve observations and kinetic evaluations. A decomposition mechanism of the
incompatible reaction is proposed. Among all the contaminants evaluated in
this study, the existence of ferrous chloride tetrahydrate, ferric chloride
hexahydrate and nitric acid shifted the main endothermic and exothermic reactions
of RDX. These contaminants further advanced the exothermic temperature onset
average by about 53, 46 and 61C, respectively. The summarized results
suggest that ferric oxide, ferrous chloride tetrahydrate, ferric chloride
hexahydrate, acetone solution and nitric acid can influence the reaction and
thermokinetic properties of RDX. These chemicals could induce potential hazards
by causing temperature control instability, heating and cooling systems failure,
and produce an unexpected secondary explosion. According to the conclusions
of this study, potential incompatible RDX hazards during usage and manufacturing
could be avoided.
Authors:S. N. Kreitmeier, G. L. Liang, D. W. Noid, and B. G. Sumpter
Thermal analysis by classical molecular dynamics simulations is discussed on hand of heat capacity of crystals of 9600 atoms. The differences between quantum mechanical and classical mechanical calculations are shown. Anharmonicity is proven to be an important factor. Finally, it is found that defects contribute to an increase in heat capacity before melting. The energy of conformational gauche defects within the crystal is only about 10% due to internal rotation. The other energy must be generated by cooperative strain. The conclusion is that the next generation of faster computers may permit wider use of molecular dynamics simulations in support of the interpretation of thermal analysis.
The thermal analysis of CoC2O42H2O, Co(HCOO)22H2O and Co(CH3COO)24H2O was carried out with simultaneous TG-DTG-DTA measurements under non-isothermal conditions in air and argon atmospheres.
The intermediates and the end products of decomposition were characterised by X-ray diffraction and IR and UV-VIS spectroscopy.
The decomposition of the studied compounds occur in several stages. The first stage of dissociation of each compound is dehydration
both in air and argon. The next stages differ in air and argon. The final product of the decomposition of each compound in
air is Co3O4. In argon it is a mixture of Co and CoO for cobalt(II) oxalate and cobalt(II) formate but CoO for cobalt(II) acetate.
Aesthetic and utilitarian properties of traditional ceramic wares as well as engineering properties of modern advanced ceramics are attained by maintaining an optimum temperature-time-atmosphere relationship, called firing schedule, in the kiln. The contribution of modern thermal analysis (TA) techniques such as TG/DTG, TG/EGA, TG/MS, DTA, DSC, TDA, etc. in 1) optimizing production steps by raw material quality control, by studying binder burn out, product densification, 2) in simulating appropriate preheating, firing and cooling schedules as well as 3) in developing shorter firing cycles has been extensively reported in recent literature. The paper will first discuss theoretical curves and energy required for ceramic firing and present from the literature selected examples of applications of thermal analysis in ceramic technology.
The research in thermal analysis and calorimetry, conducted by the author over the period 1964 to 1993, is summarised and
concisely reviewed. The major investigations have focussed on thermal analysis studies of coordination compounds, particularly
the metal dithiocarbamate complexes. A significant solution calorimetric study of some metal dithiocarbamate complexes has
also been undertaken. DSC has been applied to determine the sublimation enthalpies of many metal dithiocarbamate and metal
pentane-2,4-dionate complexes and solution calorimetry has been applied to study the thermochemistry of the latter group of
complexes. Thermal analysis investigations of several inorganic molten salt systems have been initiated. Thermometric titrimetry
has been applied to study metal-macrocyclic ligand systems in aqueous media and particularly those systems of environmental
significance. Temperature calibration standards for TMA have been proposed and TMA has been applied to study the mechanical
properties of several common inorganic compounds. DTA has been applied to study a wide variety of phenols and has subsequently
been applied as an analytical technique to determine the components of solid state phenol mixtures. Thermometric titrimetry
has been applied to determine the phenolic content of wines. A comprehensive thermal analysis study of Australian brown coal
has been undertaken, involving the DSC determination of coal specific energy, a TG/DTA study of the coal pyrolysis and combustion
processes and a TG/DTA and EGA study of the cation catalytic effect on the coal pyrolysis process. Thermal analysis and calorimetric
techniques have been extensively publicised and promoted by the publication of specialist reviews, the presentation of symposia
review papers and the oral presentation of short courses, particularly in the SE Asian region. This review essentially reveals
the diversity of possible application of thermal analysis and calorimetric techniques and the primary significance of thermodynamic
data in the fundamental rationalisation of chemical phenomena.
Authors:J. Orewczyk, S. Jasieńska, and S. Iwanczenko
This paper presents applications of thermal analysis to observe the course of reduction of acidic pellets, metallurgical substances
whose reducibility and strength are basic parameters of use in blast furnace processes. Both parameters depend on the mineral
composition of the samples. The investigations included determination of the chemical and phase compositions of the initial
samples and reduction products.
Research was conducted on acidic pellets from Połtawa (Poland), applied in the T. Sendzimir Steelworks (Poland), in comparison
with pellets from Brazil, Canada and Lebedyn (Russia).
Authors:L. Pane, E. Franceschi, L. De Nuccio, and A. Carli
Marine microalgae represent an essential link in the planktonic food web and some of them are commonly utilised in aquaculture
systems as food for larval and juvenile stages of fishes, crustacea and mollusca. However, the caloric content and the biochemical
composition of these microrganisms vary in relation to ageing and to several environmental conditions; so if the parameters
under which phytoplankton grow are not suitable, marine microalgae can supply small quantities of energy and essential nutrients.
The aim of this work was to study the effects of temperature on the marine planktonic alga Tetraselmis suecica using thermogravimetry (TG) and differential thermal analysis(DTA). Marked differences have been observed between exponentially,
stationary and senescence phases probably due to both the presence of different biomolecules produced during algal growth
and to the differences in the thermal properties of these intracellular molecules.
The paper deals with results of thermal analysis of low-alloyed chromium-molybdenum steel. The methods of analysis were dilatometry,
differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The Ac1 and Ac3 temperatures of the steel samples measured by dilatometry and DTA during the heating period were in good agreement. Generated
by cooling a martensitic structure first became apparent at 503 K. Tempering of the as-quenched samples showed the presence
of the second tempering stage in the region between 473 and 573 K. At that stage heat capacity decreased from 0.48 to 0.32
J g-1 K-1, as a result of conversion of transition carbide due to heat consumption. After normalization of the as-quenched samples
the heat capacity values were restored to between 0.42 and 0.47 J g-1 K-1 in the temperature range from 373 to 673 K.