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

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 6 h, and the moisture content was between 0.0923 and 0.0940 g·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 200 nm. 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 380 nm, 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.

Photocatalytic degradation performance of gaseous formaldehyde by Ce-Eu/TiO2 hollow microspheres: from experimental evaluation to simulation.

Gaseous formaldehyde present indoors is often in low-medium concentration, as compared to that contained in manufactured products, but still poses great threat to human health. Thus, this work aims to fabricate Ce-Eu/TiO2 hollow microspheres, which showed excellent photocatalytic performance toward formaldehyde. Furthermore, photocatalytical degradation performance of Ce-Eu/TiO2 hollow microspheres toward formaldehyde was investigated. The kinetics of degradation mechanism of gaseous formaldehyde for different concentrations and different temperatures vs time were studied, and the simulation and experimental results were also compared. It was found that formaldehyde concentration had an effect on the degradation process, which was consistent with different kinetics reactions. At low concentration, the degradation rate was decided by the adsorption rate, and no accumulation of adsorbent occurred. This process was consistent with the first-order kinetics law, which was established by L-H dynamics theory and Arrhenius equation. At medium concentration, the degradation process of formaldehyde was controlled by both adsorption and photocatalysis, which was consistent with the power law model. The 3D model of formaldehyde degradation process by Ce-Eu/TiO2 hollow microspheres at different concentrations vs time was established, and the results showed that the simulation equations were in good agreement with the experimental results.

The Linear Hygroscopic Expansion Coefficient of Cement-Based Materials and Its Determination.

A crack caused by shrinkage could remarkably increase the permeability, heavily deteriorate the durability, and heavily deteriorate the service life of a concrete structure. However, different forms of thermal shrinkage can be predicted by directly applying a temperature load on a node. The prediction of moisture-induced stresses in cement-based materials by using the common finite element method (FEM) software is a big challenge. In this paper, we present a simple numerical calculation approach by using the proposed coefficient of hygroscopic expansion (CHE) to predict the moisture-induced deformation of concrete. The theoretical calculation formula of the linear CHE (LCHE) of cement-based material was deduced based on the Kelvin-Laplace equation and the Mackenzie equation. The hygroscopic deformation of cement mortar was investigated by inversion analysis; based on the results, the LCHE could be determined. Moreover, a case analysis of the application of LCHE to concrete is also conducted. The simulated results of concrete shrinkage were close to the experimental ones. As a whole, it is feasible to predict the drying shrinkage of concrete through simple calculation by using the proposed LCHE, which is also beneficial to the direct application of moisture loads on nodes in finite element analysis (FEA).