Dilatometry, bulk measurements

Using dilatometry in parallel with cyclic voltammetry (CV) measurements in lmolL 1 LiC104 EC-l,2-dimethoxy-ethane (DME), Besenhard et al. [87] found that over the voltage range of about 0.8-0.3 V (vs. Li/Li+), the HOPG crystal expands by up to 150 percent. Some of this expansion seems to be reversible, as up to 50 percent contraction due to partial deintercalation of solvated lithium cations was observed on the return step of the CV. It was concluded [87] that film formation occurs via chemical reduction of a solvated graphite intercalation compound (GIC) and that the permselective film (SEI) in fact penetrates into the bulk of the HOPG. It is important to repeat the tests conducted by Besenhard et al. [87] in other EC-based electrolytes in order to determine the severity of this phenomenon. 

Another approach to anisotropic materials is to measure the bulk expansion of material using dilatometry (Fig. 6). The technique was used extensively to study initial rates of reaction for bulk styrene polymerization in the 1940s, an experiment which the author has used in his thermal analysis class on TMA. By immersing the sample in a fluid (normally silicon oil) or... 

There are several methods available for the study of bulk crystallization, including dilatometry, differential scanning calorimetry, and x-ray diffraction. Optical microscopy is the most versatile method for the study of crystallization since the use of a trinocular permits the simultaneous measurement of bulk crystallization (using transmitted light intensity) and of crystal growth kinetics using direct observation. 

At cryogenic temperatures, no concentration changes are expected thus IR spectroscopy can be used to detect transitions in polymers by recording abrupt or discontinuous changes in intensities as a function of temperature. This IR type of molecular dilatometry should indicate the same transitions that are observed in bulk thermal expansion measurements. If certain IR absorptions are related to the various components or morphological structures present, then a probe of the thermal responses of these structures is available. Multiphase and copolymer systems can be easily studied by using IR spectroscopic analysis. 

---