Edward L. Charsley

Studies on the ageing of a magnesium-potassium nitrate pyrotechnic composition using isothermal heat flow calorimetry and thermal analysis techniques

The ageing behaviour of a pyrotechnic mixture of magnesium and potassium nitrate has been followed at 50 °C and 65% relative humidity by isothermal heat flow calorimetry. Measurements have been carried out with samples in air and in an inert atmosphere. The main reaction product was found to be magnesium hydroxide. This has been determined quantitatively by thermogravimetry and the amount formed correlated with the measured cumulative heat of ageing. The results have been compared with those obtained for magnesium powder studied under the same conditions. In addition the influence of the ageing process on the pyrotechnic reaction has been studied by high temperature differential scanning calorimetry under ignition conditions and modulated temperature differential scanning calorimetry.

Development of a new instrument for performing microwave thermal analysis

This article describes the design and operation of a new thermal analysis instrument which uses microwaves to simultaneously heat and detect thermally induced transformations in samples with masses in the range of 50 mg to 0.5 g. The data acquisition and control software developed for the instrument support a range of experimental techniques including constant power, linearly ramped power, linearly ramped temperature, and various modulated methods. Microwave thermal analysis utilizes the fact that physical or chemical alterations in a material, caused by processes such as melting, decomposition, or solid-solid phase changes, cause variations in its dielectric properties. These can be revealed by a variety of means including changes in the sample temperature, the differential temperature, or the shape of the power profile during linear heating experiments. The scope of the instrument is demonstrated with the decomposition of basic copper carbonate. The large temperature increase (∼100 °C) observed on the f...

Qualitative and quantitative aspects of microwave thermal analysis

Thermally induced transformations in materials (e.g. melting, decomposition or solid‐solid phase changes) alter their dielectric properties and hence their ability to interact with a microwave field. This paper describes a new technique, microwave thermal analysis, where microwaves are used both to heat a material and as a means of detecting thermal transitions. Two approaches are described. The first is based on the changes in the temperature of a material when subjected to a constant microwave power and the second on the microwave power profile obtained when a material is heated in a controlled (linear) manner. Both approaches can provide qualitative and quantitative information on solid state processes. A classification is proposed for the different types of results found for various materials and transitions. The advantages and limitations of studying transitions and reactions using microwave energy are discussed. # 2000 Elsevier Science B.V. All rights reserved.

Microwave Thermal Analysis - A New Approach to the Study of the Thermal and Dielectric Properties of Materials

This paper describes a new instrument for performing thermal analysis using microwaves both as a form of heating and as a novel means of detecting thermally induced transformations in materials. Results are presented for a selection of processes including decompositions, dehydrations and phase changes. The capability of the instrument to be coupled with ancillary techniques such as EGA is also demonstrated.

Real-time analysis of peak shape : a theoretical approach to sample controlled thermal analysis

Abstract This paper describes a theoretical framework, based on real-time analysis of the shape of thermoanalytical peaks, for two new approaches to sample controlled thermal analysis (SCTA). These new methods have the common aim of effecting changes in the heating rate at a given point in a process (i.e. at a set value of α) irrespective of the absolute magnitude of the peaks produced by that process. This permits the automatic on-line optimisation of the resolution/experiment time ratio without the need for preliminary experiments.

MAGNETIC TEMPERATURE STANDARDS FOR TG

Magnetic transition temperatures, Tc, are measured by simultaneous TM/DTA for Alumel, cobalt, nickel, and three alloys of Ni and Co. The observed values of Tc are corrected using the values for the melting temperatures of pure metals used to define the International Temperature Scale. These corrections are based on the simultaneous melting of these pure metals alongside, but separate from, the magnetic sample. Nine investigators, using a wide variety of instrumentation, have made these measurements utilizing a standard protocol. The results are compared for several heating rates. It is planned to make these same magnetic materials ultimately available to the public for calibration of temperature of their TG instruments.

Gas concentration programming – a new approach to sample controlled thermal analysis

Abstract Sample controlled thermal analysis (SCTA) is the generic name used to describe a family of techniques where the heating rate is not pre-determined as in conventional thermal analysis, but altered as some function of a property of the sample (i.e. mass loss, rate of gas evolution, etc.). We demonstrate here a new form of SCTA, where the reaction rate for gas–solid reactions can be controlled by programming the concentration of the reactive gas whilst keeping the temperature constant.

Development and applications of a preparative scale sample controlled thermogravimetric system

The successful development of a high sensitivity SCTG system [1] resulted in the construction of a larger scale sample controlled thermobalance, which enables samples of 500 mg and above to be studied. One objective of the system was to allow the preparation, under precisely controlled thermal conditions, of sufficiently large amounts of coal chars that could then be characterised using a range of analytical techniques.

Thermal analysis of victorian brown coal

Abstract The proximate analysis of the five main lithotypes of Victorian brown coal has been obtained by theriaogravimetry. The data are compared with proximate analysis data for a typical European lignite and North American anthracite.

Development and applications of sample controlled thermomicroscopy

Sample controlled thermal analysis techniques such as constant rate transformation analysis or stepwise isothermal analysis, where the transformation rate of the sample itself is used to control the experiment, are becoming increasingly important [1]. The measurements are normally carried out using changes in the sample mass, sample dimensions or in the evolved gas, as the property used to control the experiment, and enable reactions to be studied in greater detail than is possible using linear heating techniques. A new approach is described here where a thermomicroscopy system has been developed to enable the intensity of the light reflected or transmitted by the sample to be used as the controlling signal [2].