A new technique for the simultaneous measurement of higher order harmonic of temperature wave under temperature scan was proposed.
The mathematical rule for the propagation of harmonies in the film shaped specimen was examined and the principle of Fourier
transform thermal analysis was theoretically and experimentally justified. This principle applied to a technique called ‘Fourier
transform thermal analysis’, makes it possible to determine simultaneously thermal diffusivity, heat capacity per unit volume
and thermal conductivity as a function of frequency and temperature. The results on thermoplastics were shown and the glass
transition and the crystallization were discussed.
Although thermogravimetric analysis (TG) has become an indispensable tool for the analysis and characterization of materials,
its scope is limited as no information is obtained about the qualitative aspects of the evolved gases during the thermal decomposition.
For processes involving mass loss, a powerful technique to provide this missing information is Fourier transform infrared
spectroscopy (FT-IR) in combination with TG. It supplies a comprehensive understanding of thermal events in a reliable and
meaningful way as data are obtained from a single sample under the same conditions.
The coupling TG/FT-IR is used in fuel analysis for the identification of residual volatiles, to determine their sequence of
release and to resolve thermogravimetric curves. In this work, the usefulness of TG/FT-IR for characterizing middle distillate
fuel residues is illustrated with some typical examples of recent application. A Bio-Rad FTS 25 FT-IR spectrometer coupled
with a TA Instruments TGA 2950 thermogravimetric analyzer was used for data aquisition.
The results obtained demonstrate the utility of this combined technique in determining the decomposition pathway of tarry
materials at various stages of pyrolysis, thereby allowing new insights into the complex thermal behaviour of hydrocarbon
Authors:Hantao Zou, Changhai Yi, Luoxin Wang, Hongtao Liu and Weilin Xu
Thermal decomposition of poly(lactic acid) (PLA) has been studied using thermogravimetry coupled to Fourier transform infrared
spectroscopy (TGA-FTIR). FTIR analysis of the evolved decomposition products shows the release of lactide molecule, acetaldehyde,
carbon monoxide and carbon dioxide. Acetaldehyde and carbon dioxide exist until the end of the experiments, whereas carbon
monoxide gradually decreases above the peak temperature in that the higher temperature benefits from chain homolysis and the
production of carbon dioxide. A kinetic study of thermal degradation of PLA in nitrogen has been studied by means of thermogravimetry.
It is found that the thermal degradation kinetics of PLA can be interpreted in terms of multi-step degradation mechanisms.
The activation energies obtained by Ozawa–Flynn–Wall method and Friedman’s method are in good agreement with that obtained
by Kissinger’s method. The activation energies of PLA calculated by the three methods are 177.5 kJ mol−1, 183.6 kJ mol−1 and 181.1 kJ mol−1, respectively.
We consider complex-valued functions f∊L1(ℝ+), where ℝ+:=[0,∞), and prove sufficient conditions under which the sine Fourier transform and the cosine Fourier transform belong to one of the Lipschitz classes Lip (α) and lip (α) for some 0<α≦1, or to one of the Zygmund classes Zyg (α) and zyg (α) for some 0<α≦2. These sufficient conditions are best possible in the sense that they are also necessary if f(x)≧0 almost everywhere.
Using pulse radiolysis, free radicals of ascorbic acid were generated by reactions of the primary radicals H and OH in acidic
and basic aqueous solutions. The formation and the decay of several radicals of ascorbic acid were detected by time resolved
Fourier transform electron spin resonance within a time interval of 100 ns to 1 ms. The rate constant of addition of H atoms
to ascorbic acid (1.3·108 dm3· mol−1·s−1) was directly determined by the change of line width of the low field line of the H atom in the presence of ascorbic acid.
The addition of OH radicals to ascorbic acid results in different radical structures, detected by highly resolved Fourier
transform ESR spectra.
The use of Fourier-transform near infrared spectroscopy (FT-NIR) to measure the content of protein, lipid and sugar contents of bakery products was investigated. The samples were dried, homogenized, sieved and measured in the wavelength range of 780–2500 nm. The calibration was based on partial least squares (PLS) regression with cross-validation. The performance of the final model was evaluated according to root mean square of cross-validation (RMSECV), root mean square error of estimation (RMSEE) and the determination coefficient (R2).The developed models use the ranges of 1100–1245 nm and 1590–2600 nm for protein determination, 1330–1840 nm and 2170–2350 nm for lipid, 1400–1630 nm, 2000–2170 nm and 2230–2570 nm for sugar determination, respectively. Protein, lipid and sugar could be determined directly with R2 values of 98.93, 99.07 and 98.81, and RMSECV values of 0.16 m/m%, 0.79 m/m% and 0.28 m/m%, respectively. It can be concluded that FT-NIR spectroscopy can be used for the routine determination of protein, lipid and sugar content of bakery products and it can contribute to the estimation of calorie content in a fast and non-destructive way.