The thermophysical property of hollow silica spheres was studied by the experimental test 3 omega method, theoretical calculation and finite element simulation. The experimental values of the thermal conductivity, less than 0.02 Wm(-1) K(-1), indicated that the powder silica hollow spheres are indeed the high efficient heat-insulating materials. The influences of the particle size and packing density on the thermal conductivity were observed. Then the formula interpreting aerogels were used to calculate the thermal conductivity of hollow silica spheres. The calculated values were larger than the experimental ones. Moreover, ANSYS software was applied to develop a heat conduction model for this type materials based on their hollow structure features. The geometry of the materials was discrete and finite element analysis was performed. The simulated values were close to that of air and a little higher than the experimental and calculated ones. And the possible reasons causing such differences were proposed.
"Microspheres introduction into a composite material (CM) results in reduction of material density, compaction and heat conductivity. It has been proven that microspheres concentration and size as well as gaseous phase composition pose determining influence over the thermophysical properties of syntactic foams (Li et al., 2011; Loginova, 2010; Liao 2011). Binding agents in syntactic foams ensure mechanical strength and heat stability of a heat-insulating coating and additional anticorrosion activity when used on a base metal surface (Loginova, 2010). "
"The quantity and quality of introduced microspheres impact the heat-insulating properties of the material; herewith there are associated affects present: increase in viscosity and appearance or growth in system strength (Li et al., 2011; Loginova, 2010; Liao et al., 2011). A majority of filled systems studied demonstrate the critical filling level, above which there is a sharp change in rheological parameters and strength values (Varlamova et al., 2011). "
[Show abstract][Hide abstract] ABSTRACT: The article deals with heat-insulating coatings used in power industry. Special attention is paid to syntactic foams manufactured with the use of microspheres and various binding agents. Raw materials used in syntactic foams are analysed. Use of microspheres in syntactic foam structures defines their heat-insulating properties, ensures material density and heat conductivity reduction, whereas binding agents ensure mechanical strength and thermal stability of heat-insulating coating.
Modern Applied Science 12/2014; 9(4). DOI:10.5539/mas.v9n4p96
[Show abstract][Hide abstract] ABSTRACT: Silica hollow spheres treated by 3-aminopropyltriethoxysilane (KH550) and hydrochloric acid showed good compatibility with polyurethane due to the improved functional group matching and charge matching between them. The resultant composite thin film exhibited excellent thermal insulation (0.05 W m(-1) K-1) and light transmission (above 80%), which were quantitatively evaluated by thermo-resistance superposition method and UV-vis spectra, respectively. Moreover, finite element simulation was used to calculate thermal conductivity of the composite thin film. The simulated value was close to the experimental one, which confirmed the effectiveness of the modifications.
Douglas Rangel Goulart, Daniel Takanori Kemmoku, Pedro Yoshito Noritomi, Márcio de Moraes
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