Anhydrite/aerogel composites for thermal insulation

Abstract

High performance thermal insulating composite materials can be produced with mineral binders and hydrophobic aerogel particles through a hydrophilization process for the latter with surfactants. The present study is focused on the development of aerogel/calcium sulfate composites by the hydrophilization of hydrophobic silica aerogel particles through a polymer-based surfactant. Its effects on the microstructure and hydration degree are examined as well as their relation to the resulting mechanical and physical properties. Results show that composites with an around 60 % of aerogel by volume can achieve a thermal conductivity \30 mW/m 9 K. Interestingly, a surfactant addition of 0.1 % by wt% of the water in the mixtures provides better material properties compared to a surfactant wt% addition of 5 %. However, it has been found around 40 % entrained air, affecting the material properties by reducing the binder and aerogel volume fractions within the composites. Moreover, gypsum crystallization starts to be inhibited at aerogel volume fractions [35 %. Towards material optimization, a model for the calculation of thermal conductivity of composites and an equation for the compressive strength are proposed.

Properties of multifunctional composite materials based on nanomaterials: a review

“…The fraction of aerogel in the composite of 60% by volume possessed thermal conductivity less than 30 mW (m K) À1 . 67 Thermal insulation is especially important for energy storage in a thermal power plant. Xu et al 68 developed a ceramic composite material for this purpose based on hollow silica powders and alumina bers.…”

Stability Relevant Properties of an SiO2 Aerogel-Based Rendering and Its Application on Buildings

“…This is achieved with an appropriate surfactant (surface active agent), which creates a hydrophilic coating surrounding the granules. An investigation in this respect, on a composite insulation material based on hydrophobized aerogel granules and anhydrite binder, has been reported by Sanz-Pont et al [18], who detail the role of the surfactant with respect to the formation of water-based slurries, despite the hydrophobic surface of the aerogel granules. The negative impact of this hydrophilic coating is an increase in water uptake, and hence an increase in the overall thermal conductivity.…”

“…The negative impact of this hydrophilic coating is an increase in water uptake, and hence an increase in the overall thermal conductivity. The mentioned authors [18] tried to keep a balance between the amount of surfactant and water entering the granules. An influential parameter in this respect is the size distribution of the granules.…”

Polystyrene nanofibers for nonwoven porous building insulation materials

“…The synthesis of aerogels is a complex multistage process, which requires stages of sol formation, gelation, surface hydrophobization, due to their extreme hydrophilicity, and drying . Pure aerogels have weak mechanical stability and must be enforced with organic or inorganic binder or envelope, which reduces their insulation performance . There is, hence, a demand for the development of alternative robust and low‐cost materials capable to satisfy the building insulation requirement by significantly reducing the heat flow through the walls.…”