Effect of Synergistic Modification of Building Materials Based on α-Hemihydrate Phosphogypsum by Portland Cement/H-PDMS on Water Resistance

Alpha-hemihydrate phosphogypsum (α-HPG) is a cementitious material obtained by dehydration of phosphogypsum (PG), a byproduct of phosphoric acid production. Poor water resistance of α-HPG has usually restricted its application in construction materials. In this study, hydroxy-terminated polydimethylsiloxane (H-PDMS) and Portland cement (PC) were used for the hydrophobic modification of α-HPG. The fluidity, setting times, compressive strength, flexural strength, ratio of compressive to flexural strength, water absorption rate, softening coefficient, pore structure, chemical information, and microstructure of the samples were measured to evaluate the modification effect of H-PDMS and PC. The results showed that H-PDMS and PC significantly improved waterproof properties of α-HPG and reduced its porosity, total pore area, and pore diameter. Specifically, PC provided the reactive group -OH that reacted with H-PDMS. Also, due to the coverage of hydrophobic -CH₃ groups, PG was given an overall hydrophobicity with a contact angle of 134° (1.5% H-PDMS). H-HPG (H-PDMS- and PC-modified α-HPG) hydrophobic material can be used in building materials with waterproof requirements and achieve the comprehensive utilization of solid waste PG.

Recent advances in femtosecond laser-structured Janus membranes with asymmetric surface wettability

Janus wettability membranes have received much attention because of their asymmetric surface wettability. On the basis of this distinctiveness from traditional symmetrical membranes, relevant scholars have been inspired to pursue many innovations utilizing such membranes. Femtosecond laser microfabrication shows many advantages, such as precision, short time, and environmental friendliness, over traditional fabrication methods. Now this has been applied in structuring Janus membranes by researchers. This review covers recent advances in femtosecond laser-structured Janus membranes with asymmetric surface wettability. The background in femtosecond laser-structured Janus membranes is first discussed, focusing on the Janus wettability membrane and femtosecond laser microfabrication. Then the applications of Janus membranes are introduced, which are divided into unidirectional fluid transport, oil-water separation, fog harvesting, and seawater desalination. Finally, based on femtosecond laser-structured Janus membranes, some existing problems are pointed out and future perspectives proposed.

A Contrastive Investigation on the Anticorrosive Performance of Stearic Acid and Fluoroalkylsilane-Modified Superhydrophobic Surface in Salt, Alkali, and Acid Solution

Stearic acid and fluoroalkylsilane are widely used in chemical modification to fabricate superhydrophobic surfaces in corrosion-resistant exploration. However, extensive works have just explored their anticorrosive performance in salt solution. Very rare work has focused on comparing their corrosion-resistant performance in corrosive solution (salt, alkali, and acid) systematically. In this study, two kinds of superhydrophobic surfaces were obtained on laser-processed rough IN304 surface after the stearic acid and FAS modification processes, respectively. The investigation and comparison of anticorrosion performance in salt, alkali, and acid electrolyte were carried out via potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The promotion mechanism or impairing mechanism was further proposed based on the results of surface wettability, surface morphology, and X-ray photoelectron spectroscopy. Besides, the long-term anticorrosion performance and the stability of surface wettability were also investigated. It is hoped that these research findings could provide an explicit guidance of suitable anticorrosion methods selection for metals in different kinds of corrosive solution (salt, alkali, and acid), which will further raise the promising prospect of functional surfaces for practical applications in industry.