Abstract:With the urgent lightweight demand in the aerospace engineering and transportation industries, Al / Ti composite structures have attracted much interest due to their excellent performances compared with conventional materials. Computational simulations have contributed to the understanding of both fundamental and practical aspects of fabrication of such composites and studying of their properties. The present work reports the results of studies based on molecular dynamics simulations on the mechanical properti… Show more
“…The embedded atom method (EAM) was used to describe the Ni-Ni interactions [ 65 ], and AIREBO potentials were adopted for C-C interactions [ 66 ]. Both potential functions are well-known and can be effectively used for the simulation of various properties of metallic [ 67 , 68 ] and carbon structures [ 69 , 70 ].…”
In the present work, the thermal conductivity and thermal expansion coefficients of a new morphology of Ni/graphene composites are studied by molecular dynamics. The matrix of the considered composite is crumpled graphene, which is composed of crumpled graphene flakes of 2–4 nm size connected by van der Waals force. Pores of the crumpled graphene matrix were filled with small Ni nanoparticles. Three composite structures with different sizes of Ni nanoparticles (or different Ni content—8, 16, and 24 at.% Ni) were considered. The thermal conductivity of Ni/graphene composite was associated with the formation of a crumpled graphene structure (with a high density of wrinkles) during the composite fabrication and with the formation of a contact boundary between the Ni and graphene network. It was found that, the greater the Ni content in the composite, the higher the thermal conductivity. For example, at 300 K, λ = 40 W/(mK) for 8 at.% Ni, λ = 50 W/(mK) for 16 at.% Ni, and λ = 60 W/(mK) for 24 at.% Ni. However, it was shown that thermal conductivity slightly depends on the temperature in a range between 100 and 600 K. The increase in the thermal expansion coefficient from 5 × 10−6 K−1, with an increase in the Ni content, to 8 × 10−6 K−1 is explained by the fact that pure Ni has high thermal conductivity. The results obtained on thermal properties combined with the high mechanical properties of Ni/graphene composites allow us to predict its application for the fabrication of new flexible electronics, supercapacitors, and Li-ion batteries.
“…The embedded atom method (EAM) was used to describe the Ni-Ni interactions [ 65 ], and AIREBO potentials were adopted for C-C interactions [ 66 ]. Both potential functions are well-known and can be effectively used for the simulation of various properties of metallic [ 67 , 68 ] and carbon structures [ 69 , 70 ].…”
In the present work, the thermal conductivity and thermal expansion coefficients of a new morphology of Ni/graphene composites are studied by molecular dynamics. The matrix of the considered composite is crumpled graphene, which is composed of crumpled graphene flakes of 2–4 nm size connected by van der Waals force. Pores of the crumpled graphene matrix were filled with small Ni nanoparticles. Three composite structures with different sizes of Ni nanoparticles (or different Ni content—8, 16, and 24 at.% Ni) were considered. The thermal conductivity of Ni/graphene composite was associated with the formation of a crumpled graphene structure (with a high density of wrinkles) during the composite fabrication and with the formation of a contact boundary between the Ni and graphene network. It was found that, the greater the Ni content in the composite, the higher the thermal conductivity. For example, at 300 K, λ = 40 W/(mK) for 8 at.% Ni, λ = 50 W/(mK) for 16 at.% Ni, and λ = 60 W/(mK) for 24 at.% Ni. However, it was shown that thermal conductivity slightly depends on the temperature in a range between 100 and 600 K. The increase in the thermal expansion coefficient from 5 × 10−6 K−1, with an increase in the Ni content, to 8 × 10−6 K−1 is explained by the fact that pure Ni has high thermal conductivity. The results obtained on thermal properties combined with the high mechanical properties of Ni/graphene composites allow us to predict its application for the fabrication of new flexible electronics, supercapacitors, and Li-ion batteries.
The development of the microstructure during severe plastic deformation of an aluminum single crystal by complex shearing of the extruded tube (CSET) was studied in this paper. The research has demonstrated that even in a single crystal, an ultrafine-grained microstructure can be obtained during this one-step process. The size of the grains gradually changes and reaches the minimum size on the level of 1 μm at the inner surface of the resulting tube. Simultaneously, preferential orientations in individual parts of the deformed sample change in a complex way. The main mechanism affecting the final microstructure is continuous dynamic recrystallization. The microhardness also exhibits a gradient character with higher values at the inner surface of the tube compared to its center.
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