Self-Organization of Inorganic Soft Matter Membranous Structures Under The Microwave Heating

This chapter examines the differences between conservative and dissipative microwave-assisted self-organization. Using various imaging techniques (like microcolorimetry, microphotometry with 2D and 3D isophote maps, spectrozonal microimage profiling, and measurements of modulation transfer functions) and real-time correlation spectral microanalysis (with 2D FFT spectra, integral frequency or spatial characteristics, waveletgrams or scalograms with statistical image analysis), the main signatures that correspond to conservative or dissipative mechanism of self-organization were identified. For distinction and identification of the microbubbles and microdroplets formed during the microwave heating, integral frequency and spatial characteristics, real-time image correlations or correlograms, and time-resolved analysis of morphometric parameters (elongation, roundness, ellipticity, and convexity) were used. For distinction and identification of the crystallization products (during conservative self-organizations) like dendrites with different crystalline orientations, fractal spectra, column correlation graphs and angular correlograms were used. Multiparametric microstructure analysis performed both during and after the experiments, based on the high-resolution micrographs obtained by optical / polarization microscopy, allows to avoid application of complex analytical methods, such as operando scanning electron microscopy with X-ray microanalysis (unsuitable for the microwave heating experiments due to the possible SEM equipment damage) and to prevent subjective conclusions about the self-organization products arising from the limited capabilities of the standard optical methods. Application of various microscopic and microanalytical imaging techniques and real-time correlation spectral microanalysis of the structures obtained at different irradiation regimes allows to distinguish between the conservative or dissipative self-organization processes occurring in the inorganic colloidal precursor under the microwave irradiation. The resulting microstructures’ morphology, phase and chemical composition, as well as the degree of crystallinity depend on the irradiation time, microwave power, and the initial sol concentration. A possible mechanism of microwave-induced self-organization in inorganic colloids is proposed.