High Heat Resistance of the Structural Coloration of Colloidal Arrays with Inorganic Black Additives

Abstract

Structurally colored materials consisting of arrays of submicrometer-sized particles have drawn a great deal of attention because of their advantages, including low cost, low impact on human health as well as the environment, and resistance to fading. However, their low thermal stability is considered to be a critical issue for their practical use as colorants. Black-colored substances that can absorb the white color are added to colloidal array-type structurally colored materials to enhance their chromaticity. The poor thermal stability of commonly used black coloring additives, carbon black and Fe 3 O 4 nanoparticles, is a main factor that reduces the heat resistance of structural coloration. Here, we demonstrate the preparation of structurally colored materials with extraordinarily high heat resistance of coloration, up to 900 °C. Several metal oxides, i.e., calcium manganese-based oxide (CCMO), chromium−iron−cobalt−nickel oxide (CFCNO), and lanthanum manganite (LMO), are synthesized and employed as black additives for structurally colored coatings prepared by the electrophoretic deposition of spherical silica particles. When CCMO is used as a black additive, the coloration heat resistance of the film is stable up to 700 °C. On the other hand, the films maintain vivid structural colors after exposure to 900 °C temperatures when CFCNO and LMO are employed as black additives. On the basis of this finding, high heat resistance of structural colors requires both heat resistance of the black additives and nonreactivity with the components of the spherical particles used for colloidal arrays.

Manufacturing Large-scale Materials with Structural Color

“…A logical step to avoid this lower stability would be the use of broadband absorbers of oxides which could stand higher temperatures. This was indeed recently demonstrated by Yamanaka et al [90] who showed stable structurally colored samples up to a temperature of 900 °C in air.…”

In Situ Oxidizing Commercial Alloy to Achieve Selective Solar Absorption with High-Temperature Stability

“…It can be found in Figure that the reflectance spectra changed little after heating in the air at 600 °C for 144 h; the α̅ solar and ε̅ IR were almost constant at 0.817 and 0.098, respectively. These results indicated that SSAs prepared by high-temperature in situ oxidation had excellent thermal stability at 600 °C, which can be attributed to the Cr 2 O 3 with outstanding thermal stability. − …”

Optically Transparent and Color-Stable Elastomer with Structural Coloration under Elongation

“…Considering the coloring mechanism of conventional structurally colored materials, one would not typically think of using structural color to develop transparent, deformable elastomers that exhibit a particular hue. On the other hand, in our previous studies, − we have reported a number of systems in which the change in refractive index is isotropic due to the formation of short-range ordered aggregate structures of fine particles, resulting in little change in the hue of the structural color from any viewpoint. Even in such systems, if the distance of the short-range order changes with deformation of the material shape, the obtained hue will naturally change.…”

“…In this study, we have developed a transparent elastomer that exhibits an almost constant color regardless of elastomer deformation by utilizing the short-range ordered structure formed by fine particles. We have applied this system with short-range order in the refractive index to various systems since we first began studying it as a structurally colored material with little angular dependence. − In the present study, we found that composite silica particles with uniform particle sizes, when combined with a cross-linked poly­(2-methoxyethyl acrylate) (PMEA), a widely used biocompatible material, result in a transparent structurally colored composite elastomer whose hue hardly changes with elongation of the composite elastomer. The composite elastomer was also found to have high mechanical toughness due to the introduction of fine particles.…”