Abstract
Different kinds of aluminosilicate minerals were employed to fabricate CoAl2O4 hybrid pigment for studying its formation and coloring mechanism. It revealed that the color of the obtained hybrid pigments was determined by the content of Al2O3 and lightness of clay minerals. The higher the Al2O3 content and the lightness of clay minerals, the better the color parameters of hybrid pigments. During the preparation of hybrid pigments, CoAl2O4 nanoparticles were confined to be loaded on the surface of the aluminosilicate minerals, which effectively prevented from the aggregation and the size increase of CoAl2O4 nanoparticles. What's more, aluminosilicate mineral might be an ideal natural aluminum source to compensate the aluminum loss due to the dissolution of Al(OH)3 at alkaline medium during precursor preparation, keeping an optimum molar ratio of Co2+/Al3+ for formation of spinel CoAl2O4 pigments in the process of high-temperature crystallization.
Highlights
AB2O4 spinel complex oxides usually are used as ceramic materials, inorganic pigments, magnetic materials, catalysts and gas-sensitive materials (Ren et al, 2014; Yoneda et al, 2016; Zou and Zheng, 2016; Álvarez-Docio et al, 2017; Chafi et al, 2017; Rani, 2017; Tang et al, 2017), the most famous one of them is cobalt aluminate (CoAl2O4)
It is observed that the L∗ value of hybrid pigments firstly increases with the increase of the calcining temperatures, and it decreases as the temperature is above 1,100◦C
In order to obtain the blue color, the calcining temperature for preparation of CoAl2O4 pigments without Kaol must be above 1,200◦C (Figure S2, see ESI), but its color properties (L∗ = 37.41, a∗ = −0.52, b∗ = −41.14) are poor compared with Kaol-HP prepared at 1,100◦C (L∗ = 48.11, a∗ = 2.64, b∗= −63.75)
Summary
AB2O4 spinel complex oxides usually are used as ceramic materials, inorganic pigments, magnetic materials, catalysts and gas-sensitive materials (Ren et al, 2014; Yoneda et al, 2016; Zou and Zheng, 2016; Álvarez-Docio et al, 2017; Chafi et al, 2017; Rani, 2017; Tang et al, 2017), the most famous one of them is cobalt aluminate (CoAl2O4). The relevant formation and coloring mechanism of the CoAl2O4/clay mineral hybrid pigments was still not clear.
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