Reversible thermochromic and thermal insulation performances of K2O·nSiO2 based fire-resistant glass via in-situ preparation

[Display omitted] •BMCS SiO2 nanoparticle has an onion-shaped core–shell structure.•K2O·nSiO2 based antifire material have a recyclable thermochromic characteristic.•The NH4+ was the key to have a thermochromic characteristic at a specific temperature.•The microporous insulation layer had an orange peel-like appearance with a hollow structure. We describe a low-cost method for synthesis of reversible thermochromic material which is considerable for energy-saving and fire-resistant applications. Here, K2O·nSiO2 based fire-resistant glass with excellent thermochromic performance was present by adding NH4+. This thermochromic material has been prepared via in-situ reaction using a newly SiO2 core–shell emulsion with high SiO2 solid content (52 wt%) and low viscosity (432.2 ± 10.9 mPa·s, 48 rpm) by the ball-milled method. These structural, morphological, optical, thermochromic and thermal insulation properties were systemically characterized. The color-changing and foaming mechanisms were further studied in detail. Onion-shaped core–shell structure and the folded morphology were clearly shown in scanning electron microscopy (SEM) micrographs. FTIR spectra was employed to characterize the difference between thermochromic material and control sample. The significant deviation appeared in visible region of this thermochromic fire-resistant glass during heating and cooling process with infrared thermography. The results shown that a small amount of NH4+ had endowed K2O·nSiO2 based fire-resistant glass with a reversible thermochromic characteristic at the specific temperature which was in accordance with the Boltzmann equation. Combined with TG-DSC analysis, fire insulation time was increased by microporous insulation layer with a sponge-like structure. A new routine toward the synthesis of multifunctional fire-resistant glass using on smart windows was provided in this work.