tailieunhanh - Báo cáo hóa học: " Designing nanomaterials with desired mechanical properties by constraining the evolution of their grain shapes"

Tuyển tập các báo cáo nghiên cứu về hóa học được đăng trên tạp chí hóa hoc quốc tế đề tài : Designing nanomaterials with desired mechanical properties by constraining the evolution of their grain shapes | Tengen Nanoscale Research Letters 2011 6 585 http content 6 1 585 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Designing nanomaterials with desired mechanical properties by constraining the evolution of their grain shapes Thomas Bobga Tengen Abstract Grain shapes are acknowledged to impact nanomaterials overall properties. Research works on this issue include grain-elongation and grain-strain measurements and their impacts on nanomaterials mechanical properties. This paper proposes a stochastic model for grain strain undergoing severe plastic deformation. Most models deal with equivalent radii assuming that nanomaterials grains are spherical. These models neglect true grain shapes. This paper also proposes a theoretical approach of extending existing models by considering grain shape distribution during stochastic design and modelling of nanomaterials constituent structures and mechanical properties. This is achieved by introducing grain form . Example forms for 2-D and 3-D grains are proposed. From the definitions of form strain and Hall-Petch-Relationship to Reversed-Hall-Petch-Relationship data obtained for nanomaterials grain size and conventional materials properties are sufficient for analysis. Proposed extended models are solved simultaneously and tested with grain growth data. It is shown that the nature of form evolution depends on form choice and dimensional space. Long-run results reveal that grain boundary migration process causes grains to become spherical grain rotation coalescence makes them deviate away from becoming spherical and they initially deviate away from becoming spherical before converging into spherical ones due to the TOTAL process. Percentage deviations from spherical grains depend on dimensional space and form 0 minimum and 100 maximum deviations were observed. It is shown that the plots for grain shape functions lie above the spherical control value of 1 in 2-D grains for all .