Thermal step technique

Fig. 17 Three common thermal excitation schemes H (f) or T t) used in thermal wave techniques for the profiling of space charges (a) thermal wave method (LIMM), (b) heat pulse method, and (c) thermal step technique...

The third, thermal step technique, utilizes a steplike ehange of the surfaee temperature at one side of a dieleetric sample, while the opposite side is kept at its initial temperature. In this experiment, the applied temperature step ATit), initially restrieted to the surface near region, propagates and gradually changes toward a... 

Toureille A, Notingher P, Vella N, Malrieu S, Castellon J, Agnel S (1998) The thermal step technique an advanced method for studying the properties and testing the quality of polymers. Polym Int 46 81-92... 

Fig. 8. Outline of the time-scale of the processes observed during an electron transfer reaction observed through thermal lensing. Processes which occur in times below ca. 0.5 ps are very fast , beyond the temporal resolution of the thermal lensing technique they would appear as a step function in the kinetics of heat release. The slowest processes which would be observed in this case are the second-order recombinations of free ions, which take place in time scales of ps to several ms.

Organic/elemental carbon speciation is performed on yg-sized samples using a thermal evolution technique (11) in which carbon is evolved in 2 discrete steps at 400°C in He and at 650<>C in 10% 02/He, then measured as OO2 by nondispersive infrared (NDIR) spectroscopy (Beckman Model 865). 13c/12c measurements are made by... 

An attempt was made by Doblhofer et al. [210] to separate surface from bulk charging processes for thermally prepared Ru02 using the potential step technique. These authors [210] concluded that some bulk diffusion was involved, presumably involving protons, and estimated a diffusion coefficient of 10 19 cm2 s1. Weston and Steele [213] deduced a diffusion coefficient value for protons in porous powder electrodes of Ru02 which is approximately similar to the value of Doblhofer et al. [210]. Iwakura and co-workers [214], on the other hand, employed cyclic voltammetry in deduc-... 

We remark that much progress in our understanding of the very first thermalization step in large molecules such as dyes is exp>ected to follow the development of subpicosecond laser techniques. Unimolecular thermalization times in the 100-fs range have already been estimated. Femtosecond time resolution could also shed new light on the possible many-body contribution to near-resonant V-V transfer in simple dense systems. 

Examination of the residual solid from solubility samples is one of the most important but often overlooked steps in solubility determinations. Powder X-ray diffraction (PXRD) is the most reliable method to determine whether any solid state form change has occurred during equilibration. The sample should be studied both wet and dry to determine if any hydrate or solvate exists. Thermal analysis techniques such as differential scanning calorimetry (DSC) can also be used to identify any solid-state transformations, although they may not provide as definitive an answer as the PXRD method. Other methods useful in identifying any solid-state changes include microscopy, Raman and infrared spectroscopy, and solid-state NMR (Brittain, 1999). When changes in solid-state properties are identified in solubility studies, it is important to link the new properties to the properties of known crystal forms so the solubility result can be associated with the appropriate crystal form. 

The separating layer optical thicknesses were fixed (Fig. 3) about or AqU, where corresponds to the plasmon absorption maximum of a metallic nanoparticle monolayer in the KCl environment. These multilayer structures were fabricated by the thermal evaporation technique followed by deposition of metal and dielectric materials without breaking the vacuum between the evaporation steps. The structures grown by this technique are realized as a sequence of Ag island films separated by KCl intermediate layers of a subwavelength thickness. These data... 

This term can be applied to a number of techniques including static headspace, purge and trap, and thermal desorption. All of these techniques involve the extraction of a gaseous component from a solid or liquid sample. Static headspace is usually a one step technique where the componait of interest is extracted from the sample held in a closed vessel usually at elevated temperatures and then injected onto the GC. Purge and trap is a multistep technique where the compound of interest is extracted into a matrix and then thermally desorbed onto the GC for analysis. SPME used in conjunction with GC analysis could be considered a purge and trap technique. In thermal desorption, the sample is heated r idly and isolated using a cryogenic trap with the compounds isolated thermally desorbed. 

Attempts at direct MS characterisation of additives in bulk polymer samples have centred on direct thermal adsorption of additives for the bulk polymer, followed by EI-MS, chemical ionisation (CI-MS) or field ionisation (FI-MS). However, this approach is linked to polymer additives that are stable or can provide meaningful fragment ions at elevated temperatures. Desorption/ionisation methods such as fast ion bombardment (FAB) [41], laser desorption [42, 43] and secondary ion MS (SIMS) have also been applied to the analysis of additives in bulk polymer samples. However, these single step techniques suffer to varying degrees from matrix interferences in the resulting mass spectra. 

Thermal analysis methods can be broadly defined as analytical techniques that study the behaviour of materials as a function of temperature [1]. These are rapidly expanding in both breadth (number of thermal analysis-associated techniques) and in depth (increased applications). Conventional thermal analysis techniques include DSC, DTA, TGA, thermomechanical analysis, and dynamic mechanical analysis (DMA). Thermal analysis of a material can be either destructive or non-destructive, but in almost all cases subtle and dramatic changes accompany the introduction of thermal energy. Thermal analysis can offer advantages over other analytical techniques including variability with respect to application of thermal energy (step-wise, cyclic, continuous, etc.), small sample size, the material can be in any solid form - gel, liquid, glass, solid, ease of variability and control of sample preparation, ease and variability of atmosphere, it is relatively rapid, and instrumentation is moderately priced. Most often, thermal analysis data are used in conjunction with results from other techniques. 

Following this book s step-by-step guidance, chemists and engineers new to thermal analysis techniques, whether in industry, government or academia, can quickly learn to use them to generate high-quality results. For more experienced researchers, the book enables them to expand their repertoire to include a broader range of sophisticated techniques and applications... 

The selection of best preparation conditions of catalyst is very important to obtain an excellent performance of the catalyst. The process of calcination and activation is the key step to determine the structure of catalysts dming preparation. Differential thermal analysis techniques can determine the specific conditions for various steps, such as the beginning and the end of the decomposition temperature and, suitable for calcining temperature etc. 

The relatively low-temperature headspace sam-pling/thermal desorption techniques are successfully utilised in particular to smdy odorous compounds in polymers. Although headspace methods offer quick analysis by simple means, they suffer from the fact that odorous volatiles may be present in such small amounts that a concentration step may be required before detection is possible. Bigger et al. [973] produced an odour... 

Bias-induced reverse piezoelectric response Broadband dielectric spectroscopy (BDS) Dielectric permittivity spectrum Dielectric resonance spectroscopy Elastic modulus Ferroelectrets Electrical breakdown Acoustic method Characterization Dynamic coefficient Interferometric method Pressure and frequency dependence of piezoelectric coefficient Profilometer Quasistatic piezoelectric coefficient Stress-strain curves Thermal stability of piezoelectricity Ferroelectric hysteresis Impedance spectroscopy Laser-induced pressure pulse Layer-structure model of ferroelectret Low-field dielectric spectroscopy Nonlinear dielectric spectroscopy Piezoelectrically generated pressure step technique (PPS) Pyroelectric current spectrum Pyroelectric microscopy Pyroelectricity Quasistatic method Scale transform method Scanning pyroelectric microscopy (SPEM) Thermal step teehnique Thermal wave technique Thermal-pulse method Weibull distribution... 

Step crystallization (SC), where a programmed step cooling is applied [33,38 0], and SSA, where a series of heating and cooling cycles are employed [33,41 8], are the two most frequently employed thermal fractionation techniques, and their comparative advantages and shortcomings have been reviewed [33]. The polymer chains are never physically separated during thermal fractionation and therefore the technique... 

Thermal analysis and calorimetry provide the opportunity for detailed analysis during each step of the manufacturing process. The isothermal microcalorimeter, with high sensitivity to measure very small changes, and rapid thermal analytical techniques which characterise materials, are powerful tools for such analyses. 

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