Study On The Microstructure Of Different Metamorphic Deformed Coal Based On AFM

In recent years, the atomic force microscope(AFM) analysis technology is a new approach of researching on coal surface ultra microstructure. In this paper, by using AFM for different kinds of tectonic deformation of coal surface ultra microstructure(nano-level macromolecular aggregates with nanoscale pores)characteristics do Systematic research and analysis, and using the theory of fractal geometry and 3d surface roughness on the surface morphology structure of microscopic structure characterized.Research shows that the level of different coal metamorphism, Coal surface average roughness Sa and the root mean square value of Sq decreased,At the same time, kurtosis and skewness values Sku>3 and Ssk tends to 0. As metamorphic grade increases, arranged in a mesh grid structure tends to close, the increasing number of micropores. Under different mechanisms of tectonic stress, the ultrastructure of coal shows different characteristics of structure, namely the mesh grid structure appears the mutative trend to the peristaltic-like structure; from the pore structure analysis found that as the metamorphic grade increases, the micropores ratio continues to increase in coal, to anthracite stage adsorption capacity of the strongest. Under the brittle deformation mechanisms, tectonic stress promotes the growth of transition pore and mesopore, making coal gas diffusion flow capacity increased; Under ductile deformation mechanisms, the tectonic stress promotes the development of microporous and transitional pore to a certain extent, however, because of poor connectivity among pores and irregular pore shape, so that the gas migration pathways become "tortuous" and is not conducive to gas diffusive transport.Sa and Sq decreased, while the kurtosis and skewness values change also shows that the topography values are consistent. Ultrastructural differences of different metamorphism and deformation coals are due to metamorphism and deformation strength cause coal macromolecular structure appears to different evolution characteristics, while the deformation of macromolecular structure also makes nanoscale pores changed, namely, metamorphism enhances the degree of arrangedorderly and Regularity of macromolecular structure, meanwhile, tectonic stress not only lead to the changes in nanoscale pore structure, but also makes the macromolecular structure appears to ahead of evolution, yet coal macromolecular structure has different evolution patterns under the effect of metamorphism and deformation.Fractal dimensions were calculated deformation using power spectral density and box dimension method, quantitative description of the distribution and pore distribution of spatial frequency surface profile, along with the increase of metamorphic degree enhancement and the extent of structure, two kinds of fractal dimension is increased, the high frequency component wavelength topography space increased, surface profile details of the characteristics of complex, and the surface morphology of porous showed dense distribution.