SiO2多次包裹对铋基黄色颜料的耐酸性和热稳定性的影响

Effect of silica layer multicoated on the acid resistance and thermal stability of bismuth-based yellow pigments

先用沉淀法合成了成分为Bi0.82V0.45Mo0.55O4和Na0.5Bi0.5(MoO4)的铋基黄色料,再用水解法对色料进行SiO2多次包裹,采用X射线衍射仪(XRD)、透射电子显微镜(TEM)、差热热重分析仪(DTA-TG)等技术对色料进行了表征。研究结果表明,SiO2多次包裹不改变色料的明度值L*,但色料的红/绿值a*和黄/蓝值b*略有下降,三次包裹后,色料仍呈现鲜艳的绿相黄,其色度L*、a*和b*值分别为79.26、-7.66和60.23;SiO2包裹次数越多,包裹层的孔隙率越少,包裹色料的耐酸性越好,三次包裹色料浸泡于1mol/L的盐酸中半小时损失量由未包裹色料的100%降至9.15%;未包裹色料在煅烧温度高于900℃后,部分物相向Bi4V2O11相转变,而SiO2一次包裹后,色料经1200℃煅烧后仍保持原物相;同时,SiO2致密包裹层的存在,减少了Bi的挥发,且包裹次数越多,孔隙率越少,Bi的挥发量也越少,耐温性也越好,三次包裹色料的耐温性由未包裹色料的600℃提升至1200℃。

In this study,silica layer multi-coated bismuth-based yellow pigments were successfully prepared by the hydrolysis method using the composition Bi0.82V0.45Mo0.55O4 and Na0.5Bi0.5(MoO4)prepared by the precipitation method.The as-obtained pigments were characterized by X-ray diffractometer(XRD),transmission electron microscope(TEM),differential thermal analysis(DTA)and thermogravimetric(TG)analysis.The results showed that the silica multi-coated did not change the brightness value(L*)of the pigments,however,the red/green value(a*)and the yellow/blue value(b*)decreased slightly.The pigments appeared still bright greenish-yellow and the chromaticity L*,a*,and b*were 79.26,-7.66,and 60.23,respectively,when thrice-coated.Besides,multi-coating could reduce the porosity of coating layers and improve acid resistance further.Compared with the uncoated pigments,the acid weight loss of thrice-coated pigments after half hour immersion in 1 mol/L hydrochloric acid declined from 100%to 9.15%.When the uncoated pigments were calcined higher than 900℃,part of the phase changed to Bi4V2O11,while the pigment which was once-coated with silica calcined at 1200℃,the phase maintained the original phase.At the same time,the presence of a dense coating with silica reduced the volatilization of Bi.Moreover,the porosity and the amount of Bi volatilization were gradually reduced,and the thermal stability was improved as the number of coated-layers increased.The thermal stability of the thrice-coated pigments was increased from 600℃to 1200℃with respect to the uncoated pigments.