Reversible thermochromic K2O·nSiO2-based anti-fire glass with bidirectional responsion and memory function

Abstract

We describe a low-cost method for the synthesis of reversible thermochromic K2O·nSiO2-based anti-fire materials with bidirectional responsion and memory function, which was significant for energy-saving and fire-resistant applications. Here, the reversible thermochromic (RTC) and inverted reversible thermochromic (IRTC) K2O·nSiO2-based anti-fire glass were prepared via an in-situ reaction using a high solid content and low viscosity SiO2 sol (HSLV SiO2 sol, 55 wt%). The morphological, thermochromic, thermal insulation, and memory performances were systematically characterized. The pincer-like structure, rod-like structure and the layered microporous morphology were clearly shown in scanning electron microscopy (SEM) micrographs. The color change, foaming, and memory mechanisms were further investigated in detail. The significant differences appeared in the visible region of RTC and IRTC K2O·nSiO2-based anti-fire glass during heating and cooling process. FTIR spectra were used to characterize the difference among RTC, IRTC and control samples. The results indicated that a small amount of NH4+ caused the K2O·nSiO2-based anti-fire glass to exhibit IRTC characteristics, and the continuous addition of polyhydric alcohols was the key to obtain RTC performance. The IRTC K2O·nSiO2-based anti-fire glass was suitable for the conservatories or greenhouses, and the RTC K2O·nSiO2-based anti-fire glass reduced the direct sunlight exposure to control the indoor temperature. Combined with morphological and Tg analysis, the thermal insulation performance was enhanced by a microporous insulating layer with a sponge-like structure. We also used the bidirectional reversible thermochromic performance to prepare a novel anti-fire glass component for construction with anti-counterfeiting function. This work provided a new approach for the application of multifunctional smart windows.