A simple and green method is developed to prepare hexagonal boron nitride （h-BN）/poly（vinyl alcohol） （PVA） nanocomposites by using water as a common solvent ofh-BN nanosheets and PVA. The obtained h- BN/PVA nanocomposites are highly transparent, and have significantly improved mechanical and thermal properties. They may outperform nano-clay and nano-alumina/PVA nanocomposites as flexible optoelectronic devices, optical windows and heat-releasing materials operated in oxidative or corrosive environment.
In this paper, a purely mechanical model for the thermoelastic behavior of a bimorph microbeam is presented. The thermoelastic coupling problem of the microbeam is converted to a mechanical problem by simply replacing the thermal stress in the beam with a bulk force and a surface force. Thermoelastic deformation of the bimorph microbeams with constraints frequently used in micro-electro-mechanical systems (MEMS) devices has been derived based on this model and is characterized by FEA simulation. Coincidence of the results from theory and simulation demonstrates the validity of the model. The analysis shows that a bimorph microbeam with a soft constraint and a uniform temperature field has a larger thermoelastic deformation than that with a hard constraint and a linear temperature field. In addition to the adoption of materials with large CTE mismatch,thickness ratio and length ratio of the two layers need to be optimized to get a large thermoelastic deformation.
