Super insulating paper-honeycomb composite with silica-aerogels

Kurzfassung

Up to date stopping global warming seems to be impossible while actual attempts could not compensate growing CO2 output. Further activities are necessary. Not only changing the energy production from fossil fuels to solar ones but also alternatives in energy consumption are highly required to save the world. Therefore new high qualitative thermal super insulation materials are of critical importance to energy-efficiency wherever thermal losses have to be minimized for example building design, transportation or aircraft industry. Paper-honeycombs are cheap and widely used for all kinds of packaging. For most applications simple corrugated card boards are suitable. If more properties are required improvements are necessary. To get a thermal super insulating aerogels are suitable materials. During the last decade great progress has been developed to make aerogels easily tunable via synthesis conditions of the sol-gel process. It turns out that not only the mechanical strength is variable, but also the micro-, meso- and macrostructure can be adapted to applied needs. The densities of aerogels are ranging from 0.005-0.2 g/cm3, specific surface area is in the range of 100 - 2000 m2/g, low thermal conductivity under SATP conditions between 0.01-0.03 W/mK and they possess a high sound absorption. Due to these excellent properties aerogels are brilliant insulation materials. The combination of paper-honeycombs and silica aerogels gives an excellent composite material. In the beginning experiments embedding silica aerogels into paper-honeycombs failed as the aqueous or alcoholic solvents of the sol-gel process destroyed the structure of the honeycombs. Great effort was necessary to success. Firstly flexible and semi flexible silica aerogels and paper honeycombs as a reinforcing template material were synthesized. Further development is carried out to improve the properties of the composite material, the combination of silica aerogels with paper honeycombs. The challenges in the preparation of the composite material are 1. aerogels free on shrinkage, 2. aerogels free of cracks and 3. undestroyed paper-honeycombs structure. Within the presentation we will show newly achieved results. We can demonstrate that not only changing recipes in respect to molar ratios of precursors and solvents as well as catalysts are important but also processing parameters like stirring velocity and time, kind of propellers, temperature, time of hydrolysis and aging, and in addition process control during supercritical drying is a key factor to get fully intact reinforced composites. How important is the interaction of all these parameters for the material? Therefore especially manufacturing of the advanced aerogel materials and the materials characterization like improved mechanical strength, texture analysis, thermal conductivity, inflammability, permeability, BET and adsorptions will be on the focus of the presentation. The inspiring results recommend the composite material for several applications in the field of thermal super insulations.