Thermal analytical techniques, oxidative using

STA has been widely used in coal studies. Combustion of coal is highly sensitive to experimental conditions and TA experiments are usually associated with low reproducibility. STA markedly enhances coal combustion reproducibility and this feature accounts for its popularity as an analytical technique for studies of the thermal behavior of coals. In simple terms, the initial drying process of a coal can easily be separated from the subsequent oxidation, which in STA can be assigned directly to a dry weight . 

Hsuan, Y. G., Evaluation of the Oxidation Behavior of Polyethylene Guan, Z. Geomembranes using Oxidative Induction Time Tests, In Riga, A. T., Oxidative Behavior of Materials by Thermal Analytical Patterson, G.H. (Eds.) Techniques, ASTM Publication, 1997 ... 

Abstract Thermal analytical methods such as differential scanning calorimetry (DSC) have been successfully applied to neat petrodiesel and engine oils in the last 25 years. This chapter shows how DSC and P-DSC (pressurized DSC) techniques can be used to compare, characterize, and predict some properties of alternative non-petroleum fuels, such as cold flow behavior and oxidative stability. These two properties are extremely important with respect to the operability, transport, and long-term storage of biodiesel fuel. It is shown that the quantity of unsaturated fatty acids in the fuel composition has an important impact on both properties. In addition, it is shown that the impact of fuel additives on the oxidative stability or the cold flow behavior of biodiesel can be studied by means of DSC and P-DSC techniques. Thermomicroscopy can also be used to study the cold flow behavior of biodiesel, giving information on the size and the morphology of crystals formed at low temperature. 

The third block in Fig. 2.1 shows the various possible sensing modes. The basic operation mode of a micromachined metal-oxide sensor is the measurement of the resistance or impedance [69] of the sensitive layer at constant temperature. A well-known problem of metal-oxide-based sensors is their lack of selectivity. Additional information on the interaction of analyte and sensitive layer may lead to better gas discrimination. Micromachined sensors exhibit a low thermal time constant, which can be used to advantage by applying temperature-modulation techniques. The gas/oxide interaction characteristics and dynamics are observable in the measured sensor resistance. Various temperature modulation methods have been explored. The first method relies on a train of rectangular temperature pulses at variable temperature step heights [70-72]. This method was further developed to find optimized modulation curves [73]. Sinusoidal temperature modulation also has been applied, and the data were evaluated by Fourier transformation [75]. Another idea included the simultaneous measurement of the resistive and calorimetric microhotplate response by additionally monitoring the change in the heater resistance upon gas exposure [74-76]. 

This chapter reviews the various methods used to identify and characterize iron oxides. Most of these are non-destructive, i. e. the oxide remains unaltered while being examined. These methods involve spectroscopy, diffractometry, magnetometry and microscopy. Other methods, such as dissolution and thermal analysis destroy the sample being examined. Only the principle of each method is given here. The main weight is put on the information about Fe oxides which can be extracted from the analytical results obtained by the different techniques together with references to relevant studies. A detailed description of each technique can be found in the appropriate texts listed in each section. 

Thermal analysis methods are defined as those techniques in which a property of the analyte is determined as a function of an externally applied temperature. Regardless of the observable parameter measured, the usual practice requires that the physical property and the sample temperature are recorded continually and automatically and that the sample temperature is altered at a predetermined rate. Thermal reactions can be endothermic (melting, boiling, sublimation, vaporization, desolvation, solid-solid phase transitions, chemical degradation, etc.) or exothermic (crystallization, oxidative decomposition, etc.) in nature. Such methodology has found widespread use in the pharmaceutical industry for the characterization of compound purity, polymorphism, solvation, degradation, and excipient compatibility. ... 

Metal oxide and hydroxide systems serve many functions, including roles as pigments, in mineralogy, and also in catalysis. The classic techniques used in such investigations have included diffraction (especially X-ray diffraction XRD), thermal analysis, transmission electron microscopy, Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy (see also Chapters 2 and 4). Until the introduction of voltammetry in the analysis of immobilized microparticles, electrochemical studies had been confined to solid electrolyte cells (Chapter 12), normally functioning at elevated temperatures. Unfortunately, these studies proved to be inapplicable for analytical characterization, and consequently a series of systematic studies was undertaken using immobilized microparticles of iron oxides and oxide-hydrates (for reviews, see... 

---