Synthesis And Performance Research Of Mixed Metal Oxide Pigments

Inspired by the structural feature of ruby and sapphire, a series of novel non-toxic andenvironmental-friendly composite oxide pigments composed of stable oxide （e.g. alfa-Al₂O₃etc.） as matrix and small amount of doping ions whose d-d transition, d-f transition, f-ftransition and charge transfer confer various colors on the pigments have been prepared. Thenovel composite oxide pigments are expected to be used to manufacture color fibers in meltspinning process so that waste water emit by textile printing and dyeing process can bereduced.First, green and yellow pigments were prepared at high calcination temperatures viahomogeneous precipitation method by doping chromium and cerium ions into Y₃Al₅O₁₂matrix. Second, blue and green pigments were synthesized at high calcination temperaturesvia sol-gel method by doping cobalt and nickel ions into ZnAl₂O₄matrix. The pigmentsamples were characterized by using XRD, UV-Vis-NIR spectroscopy, IR spectroscopy, XPS,SEM, particle size analysis and colorimetric methods. The effects of different amount ofdoping ions and calcination temperatures on the crystal structure and color properties wereinvestigated. The mechanism of color development was also analyzed. XRD analysis clearlyindicates that the crystalline phases of the two kinds of pigments are yttrium aluminum garnetand zinc aluminum spinel, respectively. The UV-Vis-NIR diffuse spectra results demonstratethat the subtle variations on coordination environments around the doped ions could changethe transition of the doped ions and the corresponding color changes. The L^*a^*b^*value of thepigments were measured by using colorimeter. To test whether the pigments are stable or not,the chemical stability of the samples, the pigment samples were soaked in concentratedhydrochloric acid for twenty-four hours and the supernatant fluids were analysis by usingICP-AES method. The result indicates that metal ions are hardly to be released from thepigments. The SEM measurements and particle size analysis results show that the sizes ofpigment particles are around200nm. Preliminary experiments were carried by blending thepigments with polypropylene by using melt spinning technique. Good dispersion of thepigments in polymeric host was confirmed by X-ray CT testing. The above resultsdemonstrate that the novel pigments are stable, and friendly to environment. They areexpected to play an important role to reduce waste water emission in manufacturing colorfibers.