High resolution nanoscale chemical analysis of bitumen surface microstructures

Surface microstructures of bitumen are key sites in atmospheric photo-oxidation leading to changes in the mechanical properties and finally resulting in cracking and rutting of the material. Investigations at the nanoscale remain challenging. Conventional combination of optical microscopy and spectroscopy cannot resolve the submicrostructures due to the Abbe restriction. For the first time, we report here respective surface domains, namely catana, peri and para phases, correlated to distinct molecules using combinations of atomic force microscopy with infrared spectroscopy and with correlative time of flight—secondary ion mass spectrometry. Chemical heterogeneities on the surface lead to selective oxidation due to their varying susceptibility to photo-oxidation. It was found, that highly oxidized compounds, are preferentially situated in the para phase, which are mainly asphaltenes, emphasising their high oxidizability. This is an impressive example how chemical visualization allows elucidation of the submicrostructures and explains their response to reactive oxygen species from the atmosphere.

Bitumen Morphology as Observed by Phase-Detection Atomic Force Microscopy

An analysis of the microstructure of several modified bitumen shown by phase detection Atomic Force Microscopy (AFM) is presented here. The phase detection and topographic AFM images, displayed three different types of microstructure: the so-called catana phase domains (beelike structures) dispersed in the peri-phase are present in most of the cases; para-phase domains are also observed in the neighbourhood of both catana and peri-phases. These results are consistent with the picture of bitumen as a heterogeneous mixture, as one should expect. The proportions of all these phases display a rather strong dependence on the nature of the modified bitumen considered, on the concentration of the modifier, as well as on the amount of aging of the mix.

Tunability modeling and experiments for BaTiO3-based solid solutions

In this paper, the electric field dependence of the dielectric constant in some BaTiO3-based ferroelectrics is theoretically described by means of the Landau-Ginzburg-Devonshire (LGD) theory and its? approximations valid for low polarizations (Johnson?s equation and even-power relation) when the sample is in its ferroelectric state and by a model considering random non-interacting dipolar units in a double well potential for the paraelectric state. High-voltage tunability data were obtained at room temperature for BaZr0.10Ti0.90O3 and Ba0.70Sr0.30TiO3 ceramics. The data were well fitted by using the Johnson?s approximation for the ferroelectric-relaxor BaZr0.10Ti0.90 O3 and satisfactory for the Ba0.70Sr0.30TiO3 ceramics, close to its ferro-para phase transition. For the last one, the non-interacting dipolar units model allows to determine the average dipolar moment.

STABILISATION OF PARAELECTRIC PHASE BY STRONG CUBIC AND QUARTIC PHONON ANHARMONICITIES IN KDP CRYSTAL

Considering cubic and quartic phonon anharmonic interactions into the pseudospinphonon coupled mode model of Kobayashi6 expressions for shift, width, soft mode frequency and hence Curie temperature, dielectric susceptibility, Curie-Weiss constant and dielectric (tangent) loss have been evaluated for ferroelectric KDP. The method of retarded double-time thermal Green’s function and the treatment of Dyson’s equation have been used in the development. It is shown that cubic and quartic phonon anharmonic interactions render real value to the soft mode frequency in the para-phase. Results are in agreement with the experimental results of others.