Cobalt-willemite and spinel as fractal blue nanopigments based on clinoptilolite zeolite: Synthesis, physical properties, and cool coating application

Abstract

Blue ceramic nanopigments have been achieved based on the clinoptilolite (CLNP) zeolite. CLNP has been used as a host precursor in conjunction with zinc oxide and cobalt chloride (CoCl2). The process compromised of ion exchange of Co+2 and Zn ions in the cages of zeolite and calcination after the drying process. The colored powders have been characterized by TGA-DTA, XRD, FTIR, surface area measurement (BET, BJH), UV–Vis–NIR, CIE-L∗a∗b∗ color measurements, FE-SEM and EDS. The results show that various intense blue color nanopigments are achieved based on the crystal structures of Co-willemite and spinel of Co-zinc aluminate and cobalt aluminate. The new structures are formed as a result of the heat-induced collapse of the CLNP structure and have the same shape, morphology, and fractal structure as the CLNP. Increased zinc and decreased cobalt content in the composition would be the best conditions for high-intensity peaks pattern and crystalline particle structure with intense blue color. The prepared blue pigment was coated on the surface of the ceramic tile, which showed a high reflectance in the NIR range. This means that the surface coated with the blue pigment can be recognized as a cool coating material.