Study On Synthesis Of C@ZrSiO₄ Inclusion Pigment Via Non-Hydrolytic Sol-Gel Method

Black pigment is widely used decorative material due to its simplicity and elegance.Carbon black is believed to be a promising colorant owing to its non-pollution and high tinting ability.These merits make it be good candidate for black pigment.Although carbon black is easily oxidized at elevated temperature,zricon encapulated carbon black pigment is proposed to ensure its chromaticity.Moreover,there are few functional groups on the surface of carbon black particles,therefore,the affinity is low between carbon black and solvents,causing hardly coated by ZrSiO4.In this study,carbon black was empolyed as colorant,and SiO2 was firstly coated on its surface and then ZrSiO4 was coated again to form the C@SiO2@ZrSiO4 black pigment.SiO2 layer was beneficial to enhance the connection between the carbon and ZrSiO4 layer.Moreover,a novel C@ZrSiO4 inclusion pigment was prepared via non-hydrolytic sol-gel(NHSG)process by using TEOS as carbon source.The effects of surfactant type and content,pH value,TEOS/H2O molar ratio,precursor concentration,ZrSiO4 amount,Si/Zr ratio,Li/Si ratio and heat treatment,etc,on the synthesis and chromatic value of the inclusion pigment were studied by using X-ray diffraction(XRD),differential thermal and thermogravimetric analysis(DTA-TG),fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray photoelectron spectra(XPS),high temperature microscope and CIE color system.The experimental results indicated that:The carbon black particles can be well coated by SiO2 under the concentration of CTAB higher than 5×10--3 mol L-1,pH of 10,hydrolytic reaction time of 6 h,and subsequently followed by heating at 450℃ for 6 h under nitrogen atmosphere.The ZrSiO4 precursor was encapsulated on C@SiO2 particles under the concentration of 1 mol L-1,ZrSiO4/C ratio of 0.71.The xerogel was calcined under nitrogen atmosphere at 900℃ for 2 h to obtain C@SiO2@ZrSiO4 pigment.The middle SiO2 layer enhanced the connection between carbon black and ZrSiO4,and thus the L*value decreased from 51.77 to 33.72.When the concentration of ZrSiO4 precursor is lower than 1 mol L-1,ZrSiO4 dense layer can not be formed.If the precursor concentration is higher than this value,it is easy to cause opacifying effect.Carbon content has a great important influence on the chromatic value.As shown in XRD results,when the ZrSiO4/C ratio is lower than 0.71,too many carbon black particles influence the synthesis of ZrSiO4,resulting in the inpurities ZrO2 and SiO2.When it larger than 0.71,the ZrSiO4 layer is too thick,causing the poor chromatic performance.Therefore,the Si/Zr ratio of 1 was favorable to achieve the pure ZrSiO4 phase,whose L*value was lowest.It was found that the commercial carbon black was hardly dispersed in the solution.TEOS could be carbonized to small carbon black particles with high activity,which was easy to encapsulated by ZrSiO4.Therefore,a novel C@ZrSiO4 inclusion ceramic pigment was prepared via the NHSG method.When zirconium chloride was used as zirconium source,Si/Zr ratio of 1.2,Li/Si ratio of 0.3,the precursor concentration of 3 mol L-1,the C@ZrSiO4 pigment was achieved with great chromatic.performance,as L*=44.54.The XPS results showed that the stong chemical O-Si-C bonding between the ZrSiO4 and in-situ carbon was formed,which was beneficial to the inclusion.This inclusion pigment is low cost and simple preperation process,which broadens the selection of colorants of inclusion pigments,and also lays a good foundation for the production of cobalt-free black pigment.