Monodisperse hollow silica nanospheres for nano insulation materials: synthesis, characterization, and life cycle assessment.

The application of manufactured nanomaterials provides not only advantages resulting from their unique properties but also disadvantages derived from the high energy use and CO(2) burden related to their manufacture, operation, and disposal. It is therefore important to understand the trade-offs of process economics of nanomaterial production and their associated environmental footprints in order to strengthen the existing advantages while counteracting disadvantages. This work reports the synthesis, characterization, and life cycle assessment (LCA) of a new type of superinsulating materials, nano insulation materials (NIMs), which are made of hollow silica nanospheres (HSNSs) and have great flexibility in modifying their properties by tuning the corresponding structural parameters. The as-prepared HSNSs in this work have a typical inner pore diameter of about 150 nm and a shell thickness of about 10-15 nm and exhibit a reduced thermal conductivity of about 0.02 W/(m K) because of their size-dependent thermal conduction at the nanometer scale. The energy and raw material consumption related to the synthesis of HSNSs have been analyzed by the LCA method. The results indicate that the recycle of chemicals, up-scaling production, and use of environmentally friendly materials can greatly affect the process of environmental footprints. New synthesis routes for NIMs with improved thermal performance and energy and environmental features are also recommended on the basis of the LCA study.