Decanoic acid-palmitic acid/SiO2@TiO2 phase change microcapsules based on RBF model with excellent photocatalysis performance and humidity control property.

Abstract

The decanoic acid-palmitic acid composite phase change material compounds with SiO2 and TiO2 to prepare decanoic acid-palmitic acid/SiO2@TiO2 phase change microcapsules (D-P-SiO2@TiO2 PCM). The D-P-SiO2@TiO2 PCM could show efficient temperature regulation, remove pollutants through photocatalysis, and control air humidity. However, it is difficult to obtain the best experimental scheme directly using the traditional experimental setup due to the complicated photocatalytic-humidity performance. The radial basis function (RBF) model optimized the uniform experimental design parameters, and the D-P-SiO2@TiO2 PCM showed enhanced photocatalytic-humidity performance. The RBF-calculated preparation parameters were as follows: the molar ratio of decanoic acid-palmitic acid to tetraethyl silicate was 0.42, pH was 1.83, the molar ratio of deionized water to tetraethyl silicate was 98.15, while the molar rate of tetrabutyl titanate to tetraethyl silicate was 0.76. The degradation rate of gaseous formaldehyde by the RBF-optimized D-P-SiO2@TiO2 PCM was 69.57% after 6h, and the moisture content was between 0.0923 and 0.0940g·g-1 at 43.16-75.29% relative humidity (RH). The comparison between model optimization and the experiment sample prepared using the optimized parameters showed that the theoretical photocatalytic-humidity performance target value was 2.0502, and the tested target value was 2.0757. The error calculated from these two values was only 1.24%, and both were better than the best value of uniform experimental calculation. RBF mathematical model was proved to be an effective, convenient, and economic-saving method to simulate and predict D-P-SiO2@TiO2 PCM experimental design parameters. SEM and TEM analyses of the RBF-optimized D-P-SiO2@TiO2 PCM showed a uniform spherical structure, and the particle size analysis analyses was about 200nm. The DSC analysis showed the phase transition temperature range was between 16.97 and 28.94°C, within the comfort range of the human body. The UV-Vis investigations showed the absorption edge of the RBF-optimized D-P-SiO2@TiO2 PCM was 380nm, in line with the band gap structure of the TiO2 anatase phase. The thermogravimetric investigations showed that this composite was stable at normal temperature and pressure. After a 100 times hot-cold cycle, the quality of the RBF-optimized D-P-SiO2@TiO2 PCM maintained its stability, as the photocatalytic-humidity performance was almost the same. The N2-adsorption analysis showed it had a high specific surface area and irregular pore structures, which could help it regulate air humidity. Considering these results, the D-P-SiO2@TiO2 PCM, a new ecological functional material, would be used in the construction industry to improve the architectural ecological environment.