Preparation and Performance of Inverse, Reversible Thermochromic K 2 O·nSiO 2 ‐Based Fire‐Resistant Glass

An inverse, reversible thermochromic K 2 O·nSiO 2 ‐based fire‐resistant glass was developed through a low‐temperature in situ reaction using NH 4 HCO 3 as a multifunctional additive. The glass changed from white and opaque at room temperature (∼20–25°C) to colorless and transparent at ∼60°C, reaching a transmittance of 90.51 ± 0.32% and maintaining stable thermochromic behavior over 1000 thermal cycles. NH 4 HCO 3 incorporation increased the compressive stress at 66.7% strain from 2.6 ± 0.1 to 6.8 ± 0.2 MPa, accompanied by enhanced silicate‐network connectivity as revealed by Raman spectroscopy. During high‐temperature exposure, NH 4 HCO 3 promoted multistage foaming and hierarchical micro‐/nanoscale pore formation within the expanded barrier layer. The resulting pore‐within‐pore architecture increased the tortuosity of heat‐transfer pathways and suppressed structural collapse. After 60 min of fire exposure, the average unexposed‐side temperature remained well below the prescribed limit of 160°C. This work provides a practical strategy for integrating adaptive optical regulation, mechanical reinforcement, and high‐temperature thermal protection within a single inorganic glass system.