MnNH4P2O7-Based Coating for High Temperature Assessment on the Surfaces of Cement Composites

This study examines the implementation of an MnNH4P2O7 (ammonium manganese III pyrophosphate)-based coating on structural elements to obtain temperature information with color changes. Based on the MnNH4P2O7 material, a coating was prepared and deposited on cement mortar surfaces. Heat experiments were then conducted to evaluate the thermochromism on the fabricated samples. The coated samples exhibited a superior irreversible thermochromic property at 400 °C with a color change from dark violet to light grayish blue at the heated surface. The color changes were retrieved at each temperature using a digital camera, and the change in color properties was evaluated in the RGB and L*a*b* color spaces using image processing techniques. With increasing temperature from room temperature, the RGB values were almost constant until 200 °C. At higher temperatures, the color changes started to accelerate until 400 °C. The values showed a 167%, 567%, and 49% increase in R, G, and B values, respectively, at 400 °C. In the L*a*b* color space, when the temperature was increased from room temperature to 400 °C, the L*a*b* values showed an increase of 211%, a decrease of 94%, and an increase of 78%, respectively.