Nano-sized CoxMg1−xAl2O4(x= 0, 0.1, 0.2, 0.4, 0.6, 0.8, and 1) inorganic pigments were synthesized via combustion method usingβ-alanine, as a single and novel fuel, at 800°C in open furnace. The obtained powders were characterized by means of X-ray diffraction (XRD), energy dispersive X-ray (EDX) elemental analysis, diffuse reflectance spectrum (DRS), CIEL*a*b* color measurements, and scanning electron microscope (SEM). XRD patterns show that all calcined powders have single phase cubic spinel structure. EDX analysis revealed the composition of desired spinels. The diffuse reflectance spectra of the CoxMg1−xAl2O4(x> 0) pigments confirmed the presence of tetrahedrally coordinated Co2+ions in the spinel lattice. The colorimetric data pointed out the formation of blue pigments (forx> 0), corresponding to highly negative values ofb*, and the bluest color was produced forx= 0.8 and 1. SEM images showed nanoparticles with less than 30 nm crystallite size and flakes-like appearance of all synthesized powders.
Nanocrystalline cobalt aluminate spinel, CoAl2O4, was prepared via a microwave‐assisted solution combustion process applying various mixtures of urea, glycine, and starch as a novel mixed fuel. The effects of starch addition (0, 10, 20, and 30 wt%) on the physical characteristics (e.g. crystallite size and colour) of the blue nano pigments were also investigated. The resultant powders were characterised by means of X‐ray diffraction, scanning electron microscopy, electron dispersive X‐ray analysis, and CIE L*a*b* colour measurements. The presence of a CoAl2O4 spinel lattice after calcination of precursors at 600 °C was confirmed by X‐ray diffraction patterns, and the crystallite sizes were ca. 10–39 nm. Colorimetric data pointed to the formation of bright‐blue pigments at low levels of starch addition. Scanning electron microscope images showed that starch enrichment reduced the agglomeration and size of synthesised nanoparticles.
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