Mechanical methods, thermogravimetry

The procedures of measuring changes in some physical or mechanical property as a sample is heated, or alternatively as it is held at constant temperature, constitute the family of thermoanalytical methods of characterisation. A partial list of these procedures is differential thermal analysis, differential scanning calorimetry, dilatometry, thermogravimetry. A detailed overview of these and several related techniques is by Gallagher (1992). 

Manometric and volumetric methods (kinetics) Thermogravimetry (kinetics from very thin films to thick scales stoichiometry) Electrical conductivity of oxides and allied methods (defect structures conduction mechanisms transport numbers) Radioactive tracers and allied methods (kinetics self diffusion markers)... 

In conclusion, according to the experimental results provided by the different electrochemical methods and by thermogravimetry, Hammouche et al. [82] suggest the following mechanism for oxygen reduction on La, xSrxMn03 d cathode ... 

Thermogravimetry is an attractive experimental technique for investigations of the thermal reactions of a wide range of initially solid or liquid substances, under controlled conditions of temperature and atmosphere. TG measurements probably provide more accurate kinetic (m, t, T) values than most other alternative laboratory methods available for the wide range of rate processes that involve a mass loss. The popularity of the method is due to the versatility and reliability of the apparatus, which provides results rapidly and is capable of automation. However, there have been relatively few critical studies of the accuracy, reproducibility, reliability, etc. of TG data based on quantitative comparisons with measurements made for the same reaction by alternative techniques, such as DTA, DSC, and EGA. One such comparison is by Brown et al. (69,70). This study of kinetic results obtained by different experimental methods contrasts with the often-reported use of multiple mathematical methods to calculate, from the same data, the kinetic model, rate equation g(a) = kt (29), the Arrhenius parameters, etc. In practice, the use of complementary kinetic observations, based on different measurable parameters of the chemical change occurring, provides a more secure foundation for kinetic data interpretation and formulation of a mechanism than multiple kinetic analyses based on a single set of experimental data. 

E 1640 (1999) Test method for assignment of the glass transition temperature by dynamic mechanical analysis E 1641 (1999) Test method for decomposition kinetics by thermogravimetry... 

The effect of the incorporation of HAP nanoparticles on the physicochemical properties of the nanofibrous membrane scaffold was investigated. The presence of ca. 30 nm nanohydroxyapatite in the composite nanofibrous membranes was confirmed by thermogravimetry, X-ray diffraction, and SEM. It was foimd that the alternative soaking surface mineralization method drastically influenced the mechanical properties of the nanofibrous membrane scaffold with a 88% and 94% drop in Yotmg s modulus and ultimate maximum stress (14). 

Thermogravimetry is also widely used both in studies of degradation mechanisms and for methods for service lifetime prediction measurements.TG lifetime prediction routines are available from instrument manufacturers. The routine calculates the activation energy by using a form of an Arrhenius equation (Eq. 6). 

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