演讲题目:Assembly of CVD Graphene and Mechanical Properties
内容摘要
On the basis of CVD techniques that can produce large-area, high-quality, and crystallinity-controlled graphene samples, we studied their deformation by stretching, folding, and stacking, and the related mechanical properties. Specifically, 1) we developed a camphor-assisted method to free-stand centimeter-long ultrathin films and do tensile test.[1] By involving CVD monolayer graphene, the results showed that the Young’s modulus of centimeter-long monolayer graphene was around 700 GPa and the fracture strength was 3~5 GPa, far lower than the values of ~100 GPa for the micron sized graphene; 2) A centimeter-sized monolayer graphene film was folded to get a bilayer graphene film that has tunable interlayer twist; [2] 3) A folding method was used to assemble a laminated composite that has rich graphene folds. From the bending tests and modeling, it was found that the graphene folds reinforced the composite; [3] 4) A stacking method was used to assemble 100 layers of monolayer CVD graphene films to get a new carbon material that has low defect density, pure carbon content, highly ordered stacking manner in c axis direction, and ~50% interlayer twist structure. [4] The mechanical tests showed that it had significantly higher stiffness and fracture strength than other macroscale films made of solely graphene or graphite, along with a high in-plane electrical conductivity and thermal conductivity. 5) Experiments showed that the single-crystal monolayer CVD graphene exhibited a structural-directing effect that is, the highly crystalline graphene accelerates the carbonization and graphitization of polymers in a ‘catalytic’ manner. [5]
References
[1] B. Wang, R. S. Ruoff*., et al. Camphor-Enabled Transfer and Mechanical Testing of Centimeter-Scale Ultrathin Films, Advanced Materials 30, 1800888, 2018.
[2] B. Wang, R. S. Ruoff*., et al. Controlled Folding of Single Crystal Graphene, Nano Letters 17, 1467, 2017.
[3] B. Wang, N. Pugno*, R. S. Ruoff*, et al. Folding Large Graphene-on-Polymer Films Yields Laminated Composites with Enhanced Mechanical Performance, Advanced Materials 30, 1707449, 2018.
[4] B. Wang, B. Cunning*, R. S. Ruoff*, et al. Ultra-Stiff, Strong, and Highly Thermally Conductive Crystalline Graphitic Films with Mixed Stacking Order, Advanced Materials 31, 1903039, 2019.
[5] B. V. Cunning†, B. Wang†, R. S. Ruoff*. et al. Structure-Directing Effect of Single Crystal Graphene Film on Polymer Carbonization and Graphitization, Materials Horizons 6, 796, 2019.