Moisture Behavior of Thermal Insulation Coating Consisted of Vacuum-Hollow Nano-Ceramic Microspheres

Abstract

Nanotechnology-based thermal insulation materials have appeared in building industry in the last two decades. Among them thermal insulating coatings consisted of vacuum-hollow nano-ceramic microspheres are the subjects of most professional discussion. Most studies about these coatings focus only on examination of thermodynamic properties, because there is still no consensus in academic circles about thermodynamic processes inside nano-ceramic coatings. These professional discussions distract attention from other unknown but also important material properties, like behavior by contact with moisture. This paper summarizes the results of moisture behavior tests with nano-ceramic thermal insulation coatings which were conducted to determine the time trend of water absorption, as well as volume, mass and thermal insulation quality changes caused by increasing moisture content. Analyzing the results mathematical connections were found to describe the relation between water content, dimensional and thermal conductivity changes.

Thermodynamic Processes in Nanostructured Thermocoatings

“…Other sources publish much higher values (from 0.014 W/mK to 0.140 W/mK) and talk about their effective thermal conductivity which contains the internal and external convective heat transfer coefficients (hi and he) of the enclosed nanoscale pores inside the nanostructure. These details are often not confirmed by documented laboratory tests or refer to insufficiently introduced experiments (Orbán, 2015;Lakatos, 2016;Chukhlanov et al, 2017). Others calculate thermal conductivity of nanoceramic coatings from heat transfer coefficient (U-value) of a global building structure (Lakatos, 2016).…”

“…Spectral emissivity properties and reflective ability of nano-ceramic thermal insulation coatings were also tested and measured data demonstrated that coatings have the same radiant properties as standard building coatings (Čekon, 2012; Ádám et al, 2016). Based on GOST 23630.2-79 (Russian standard) using an IT-λ-400 instrument thermal conductivity of nano-ceramic coatings consisted of hollow inorganic microspheres measured to be 0.10-0.18 W/mK and the effective thickness of the thin-film insulation coating was determined at least 5 mm (that requires application of 4 layers of material at each layer thickness of 1-1.5 mm) (Chukhlanov et al, 2017).…”