Method thermally stimulated depolarization

Gun ko, V.M., Turov, V.V., Leboda, R., Zarko, V.I., Skubiszewska-Zi ba, J., and Charmas, B. 2007f. Adsorption, NMR and thermally stimulated depolarization current methods for comparative analysis of heterogeneous solid and soft materials. Langmuir 23 3184—3192. 

This book describes the applications of important new NMR spectroscopic methods to a variety of useful materials and compares them with results from other techniques such as adsorption, differential scanning calorimetry, thermally stimulated depolarization cmrent, dielectric relaxation spectroscopy, infrared spectroscopy, optical microscopy, and small-angle and wide-angle x-ray scattering. The text explores the application of NMR spectroscopy to examine interfacial phenomena in objects of increasing complexity, beginning with immodified and modified silica materials. It then describes properties of various mixed oxides with comparisons to individual oxides and also describes carbon materials such as graphite and carbon nanotubes. 

Another TL application is the analysis of the electronics states in materials, which are defined by both material and technology of its production. For example, for PS different contact methods to define the electronics states in metal/PS stmctures have been aheady applied thermally stimulated depolarization currents (TSDC) and thermally stimulated current (TSC) (Ciurea et al. 1998 Anastasiadis and Triantis 2000 Brodovoy et al. 2002), optical charging spectroscopy (OCS) (Ciurea et al. 2000), and deep-level transient spectroscopy (DLTS) (Pincik et al. 1999 Tretyak et al. 2003). The mentioned methods determine the parameters of traps related with both PS material and metal/PS interface and often differ from results obtained from TL experiments. Two advantages of the TL method are that it is contactless and it can reveal the energy distribution of both bulk and/or surface states. The obvious drawback of TL is that it can only be applied to luminescent materials. 

From a different study, it was seen that the transition behavior of blends of PVC with PMMA isotactic (i-PMMA) and syndiotactic (s-PMMA) was determined in the temperature range -150 °C to 130 °C by the thermally stimulated depolarization currents method (TSDC) and was found that the iPMMA and PVC formed an incompatible system over the entire concentration range, while in sPMMA/PVC blends, some compatibility probably existed but only for concentrations in sPMMA not higher than 10 wt% (Schurer et al., 1975 Verschueren et al., 1982). Hence it could be concluded that PVC was more miscible with syndiotactic PMMA than with isotactic PMMA. 

In series of publications [25,27,29,35-40] several methods were used for eharaeterization of the microphase structure of the semi-IPNs studied. Small-angle X-ray seattering (SAXS), differential scanning calorimetry (DSC) [27, 35-37], dynamic mechanical thermal analysis (DMTA) [27, 30-32], dielectric relaxation spectroseopy (DRS), and thermally stimulated depolarization currents (TSDC) [25, 39, 40] measurements have shown that pure PCN is characterized by a typical homogeneous structure, but for segmented LPU the microphase separation on the level of hard and soft domains due to their thermodynamic immiscibUity was denoted. As for semi-IPNs, the destruction of the microphase separated morphology of LPU was observed and the microphase separation between PCN and LPU phases, expected from the difference of solubility parameters, was not found. 

P. Pissis, A. Anagnostopoulou-Konsta, Protonic percolation on hydrated lysozyme powders studied by the method of thermally stimulated depolarization currents, J. Phys. D Appl. Phys. 23... 

More exotic —that is, so far, less frequently used—methods are also worth noting dielectric relaxation on which we have a whole chapter by Jozef Moscicki thermally stimulated depolarization " electro-optical behavior" (time dependence of transmitted light intensity under a low frequency electric field) thermo-optical analysis" " (temperature dependence of the transmission of light through birefringent... 

The advanced scattering methods,such as high resolution nuclear magnetic resonance techniques (HR-NMR), the NMR-spin diffusion, non-radiative energy transfer, excimer fluorescence, thermally stimulated depolarization current, small angle neutron scattering, SANS and FT-IR, are more appropriate for the task. For example, the NMR spin-lattice relaxation times, Tj, distinguishes > 2 nm and it may be used for either molten or solidified specimens " ... 

An alternative method to observe dielectric properties is termed thermal stimulated currents (TSC). This method involves polarization of a sample at high temperature (relative to Tg) and quenching to a temperature where depolarization is kineticaUy prevented in the time scale of the experiment. The temperature is then increased and the depolarization current is measured, yielding peak values associated with polymer transitions analogous to t", E" and tan S values obtained by conventional dielectric and dynamic mechanical measurements. The TSC spectra can reveal secondary relaxations, glass transitions and liquid or crystalline phase transitions and hquid crystalhne phase transitions. TSC has been applied to PBT/PC and PA6/ABS blends to study the intermixing of the components of the respective blends [58]. The TSC method is described in several references [59-61]. 

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