Role of Interfaces in Elasticity and Failure of Clay-Organic Nanocomposites: Toughening upon Interface Weakening?

Hydrocarbon Transportation in Heterogeneous Shale Pores by Molecular Dynamic Simulation

Shale oil in China is widely distributed and has enormous resource potential. The pores of shale are at the nanoscale, and traditional research methods encounter difficulty in accurately describing the fluid flow mechanism, which has become a bottleneck restricting the industrial development of shale oil in China. To clarify the distribution and migration laws of fluid microstructure in shale nanopores, we constructed a heterogeneous inorganic composite shale model and explored the fluid behavior in different regions of heterogeneous surfaces. The results revealed the adsorption capacity for alkanes in the quartz region was stronger than that in the illite region. When the aperture was small, solid-liquid interactions dominated; as the aperture increased, the bulk fluid achieved a more uniform and higher flow rate. Under conditions of small aperture/low temperature/low pressure gradient, the quartz region maintained a negative slip boundary. Illite was more hydrophilic than quartz; when the water content was low, water molecules formed a "liquid film" on the illite surface, and the oil flux percentages in the illite and quartz regions were 87% and 99%, respectively. At 50% water content, the adsorbed water in the illite region reached saturation, the quartz region remained unsaturated, and the difference in the oil flux percentage of the two regions decreased. At 70% water content, the adsorbed water in the two regions reached a fully saturated state, and a layered structure of "water-two-phase region-water" was formed in the heterogeneous nanopore. This study is of great significance for understanding the occurrence characteristics and flow mechanism of shale oil within inorganic nanopores.

Influence of the Surface State on the Interfacial Bonding Strength of the Cold-Rolled Brass/Carbon Steel Composite

To improve the interfacial bonding of dissimilar composites, the interaction mechanism between the surface state and severe plastic deformation to strengthen the interfacial bonding strength was revealed. In this study, the different surface states of the steel strip were designed by louver blade grinding (LBG) and diamond bowl grinding (DBG), and the cold-rolled composite method was developed to prepare the brass/carbon steel composite strips. The results show that the steel surface after DBG has a large roughness of 9.79 μm, a hard hardening layer of 6.2 GPa, and high cleanliness of 1.34 atomic % oxygen content, while that after LBG has a roughness of 1.31 μm, a hardening layer of 4.2 GPa, and an oxygen content of 2.37 atomic %. The large roughness promotes the breaking of the hardening layer; the hardening layer is beneficial to obtain sufficient interfacial stress to expose the fresh metal; and the high cleanliness reduces the barrier to the fresh metal and contributes to the bonding of the fresh metal. The interface of the cold-rolled brass/carbon steel composite strip after LBG and DBG is mechanical bonding and metallurgical bonding, respectively. In the process of the cold-rolling composite, large shear deformation occurs at the interface of brass and steel, resulting in a high concentration of vacancy and dislocation defects, which provides a channel for interdiffusion of atoms at the interface. Under the diffusion driving force provided by the cold-rolling shear deformation heat, a nanodiffusion layer with a thickness of 60 nm and high interfacial bond strength was formed.

Drained and undrained heat capacity of swelling clays

In microporous materials, poromechanical drained (open pore) and undrained (close pore) conditions play a role in the thermo-mechanical properties, which can also be affected by specific ion effects. Heat capacity...