Preparation and Chromaticity Control of CoTiO3/NiTiO3 Co-Coated TiO2 Composite Pigments.

Yuan Chen,Ying Chang,Yuan Huang,Zhishun Wei,Wei Guo,Marie-Christine Record,Jiuxin Jiang,Pascal Boulet

doi:10.3390/ma15041456

Abstract

In this study, home-made amorphous TiO2 microspheres with good mono-dispersity and large numbers of mesopores on the surface were used as substrates. The intermediate microspheres were obtained by adding Co/Ni sources with different Co/Ni molar ratios in a water bath and making them react by water bath heating. By calcining the intermediate microspheres deposited on the TiO2 ones, a core–shell structured spherical CoTiO3/NiTiO3 inorganic composite pigment was prepared. The synthesized pigments were characterized by X-ray diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), laser particle size (LPS) analysis and colorimetry. The results show that when the calcination temperature is 800 °C and the Co/Ni molar ratio is 0.5:0.5, the pigments consist of a TiO2 core and outer ilmenite CoTiO3/NiTiO3 shell. Moreover, the surface of the product microspheres is smooth, and the particles are of regular sphericity with a uniform particle size of about 1.8 μm. The colorimetric analysis from the samples calcined at 800 °C shows color changes from yellow-green to dark green as the Co/Ni molar ratio increases (0.1:0.9 to 0.9:0.1). A Co/Ni molar ratio that is too high or too low results in the formation of by-products such as Co3O4 or NiO, respectively, which adhere to the product surface and affect the chromaticity of the product. This work has enabled the chromatic modulation of yellow-green inorganic pigments, providing a solution for the preparation of spherical inorganic pigments that are more suitable for industrial inkjet printing.

Highlights

Owing to excellent weather resistance, thermal stability and high hiding power, inorganic pigments are widely used in ceramics, high temperature materials, inks, coating materials and plastics [1,2,3,4,5]
All these results indicate that CoTiO3 green pigments and NiTiO3 yellow pigments can be synthesized by wet chemical methods below 1000 ◦C
XFi-grauyreD2iffsrhaoctwiosnthe X-ray diffraction (XRD) patterns of the products after calcination at 800 °C for samples wFiitghudreif2fesrheonwt Cs oth/Ne Xi mRDolparatrtaetrinoss.oAf tshsehporwonduinctFsiagfuterrec2aal,ciwnhateinonthaet 8C0o0/N◦Ci mfoorlsaarmraptlieos iws 0it.h1:0d.i9ff,etrheenpt rCood/uNctismmoalianrlyractioonss.isAtsosfhCoowTniOin3 aFnigdu/orre N2ai,TwiOh3e(nthtehediCffor/acNtiiomn opleaarkrsatoifo Ciso0T.i1O:03.9an, tdheNpiTroiOd3uacrtes mveariynslyimcoilnarsiisnt opfoCsiotiToinO),3NaniOd/aonrdNaniTaitOas3e(tThieOd2.iffraction peaks of CoTiO3 and NiTiO3 are very similar in position), NiO and anatase TiO2

Summary

Introduction

Owing to excellent weather resistance, thermal stability and high hiding power, inorganic pigments are widely used in ceramics, high temperature materials, inks, coating materials and plastics [1,2,3,4,5]. Compared to the solid phase reaction method, the wet chemical method requires a lower reaction temperature but tends to introduce impurities, and the synthesized pigments are not homogeneous in particle size and tend to agglomerate. Sekhar et al [26] obtained CoTiO3 by calcining precursors prepared by the sol-gel method at 700 ◦C, and Wang et al [17] synthesized NiTiO3 nano-yellow pigments by calcining organic polymer precursors of NiTiO3 at 600 ◦C and 800 ◦C. All these results indicate that CoTiO3 green pigments and NiTiO3 yellow pigments can be synthesized by wet chemical methods below 1000 ◦C

Methods

Results

Conclusion