【作者】 吴广州；

【导师】 杜丕一；

【作者基本信息】 浙江大学 ， 材料学， 2006， 硕士

【摘要】 珍珠是一种珍贵的有机宝石,颜色和光泽是决定其价值的两个最重要的因素,不同国家、不同民族的人对珍珠颜色有不同的喜好。市场上的珍珠主要是养殖珍珠,其颜色比较单一,不能满足人们的需求。另外,养殖珍珠个体往往存在光泽、颜色差异,必须要进行加工处理,以改进其颜色和光泽而达到宝石级商品的要求。染色是一个重要的优化处理方法,但国内外已有工艺生产出的染色珍珠还存在颜色稳定性差、易褪色,光泽易被侵蚀破坏等问题。染色珍珠在佩戴一定时间后会发生褪色,变得黯然无光。要解决这些问题,开发优质彩色珍珠制备技术十分必要。 本文对珍珠化学染色制备及机理进行了研究,对纳米改性TiO₂水性溶胶的制备进行了探讨,最后对染色珍珠的纳米TiO₂-聚合物协同改性及性能进行了分析。 文中首先,利用化学染色法对淡水养殖珍珠进行染色处理,得到了玫瑰红色、橙黄色、黑色等彩色珍珠。利用色彩分析仪、场发射扫描电镜对化学处理及染色过程中珍珠的色彩、光泽、微观形貌的变化进行了分析研究,对珍珠的染色机理进行了初步的探讨。结果表明,化学处理过程中在珍珠表面产生了一定数量的纳米微孔,而在染色过程中这些表面微孔则不断被修复,这个过程将直接影响珍珠的染色质量。 其次,利用无机盐溶胶-凝胶法（ISG）制备了水性过氧钛酸（peroxo titanic acid简写为PTA）溶胶,并进行水热处理制备含纳米锐钛矿晶粒的改性水性溶胶。利用XRD和FTIR对不同温度改性处理中物相及化学结构的变化进行了分析,利用TEM对所得纳米TiO₂颗粒的形貌和分布状态进行了观察。结果表明,Ti/H₂O₂比对PTA溶胶的形成有重要的影响,当Ti/H₂O₂比在1:3-1:4时能得到浅黄色半透明的稳定PTA溶胶。由不同处理工艺所得纳米TiO₂的TEM照片可以看出处理温度及时间对纳米TiO₂的数量及粒径有很大的影响,提高处理温度及延长处理时间都将有利于形成更多的纳米颗粒及促进颗粒的长大。同时随着处理温度的升高,时间的延长所得溶胶的稳定性降低。 最后,应用纳米TiO₂-聚合物协同改性处理工艺对染色珍珠进行改性,以提高染色珍珠的抗紫外褪色及抗腐蚀性能。利用紫外可见分光光度计对纳米TiO₂改性层的光透过性能进行表征,耐紫外褪色、耐汗液、耐酸液腐蚀试验对改性层及改更多还原

【Abstract】 Pearl is a precious organic gem, and the value of pearl mainly depends upon color and its luster. The person of the different nation, different race may have their distinct favor of different color of pearl. A great proportion of pearls that being sold on the market are cultured pearls. Yellow and write are two kinds of primary color of the cultured pearl, and these colors can not meet customers’ needs. On the other hand, the differences of color and luster between distinct pearls are very huge, it is necessary to carry out enhancing and treating on the pearls to make them fit the requirements as gem. The dyeing is an important method to processing of the cultured pearl. But many problems of the colored pearls that were processed by existing technology were appeared after wearing a period of time, the color and luster of the pearl might become unstable. The color of the pearl might fade because the photo-bleaching induced by UV-light in the sunshine, and its luster would become dim because the surface of the pearl was corrupted by the sweat, grease and other matters. So it is necessary to develop a novel processing method to produce high quality colored pearl.In this work, the preparation of chemical colorated freshwater cultured pearl and the mechanism of pearl dyeing processing were investigated;the preparation of nanosized anatase modified aqueous TiO₂ sol was discussed;nanosized TiO₂ particle-polymer co-modified colored pearl was successfully prepared and its protective effect against UV-induced bleaching and corrosion resistant was tested.In the first part of the paper, freshwater cultured pearl was colorated by two steps of chemical pretreatment and dyeing. The colored rose red, orange yellow and black pearls had been obtained by using C₂₈H₃₁CIN₂O₃, C₁₄H₁₄N₃NaO₃S and silver salt respectively. The reflectivity of the pearls was measured by visible spectrophotometer and its morphology was observed by field emission scanning electron microscopy. Then the mechanism of dye processing was discussed. Analyzing the SEM images of the pearl in different chemical treating and coloring time, the results indicated that some nanosized micorpores were generated on the pearl surface during the chemical pretreatment process, and these pores would be repaired by the dye. The quality of colored pearl was directly related with this process.Secondly, nanosized anatase modified aqueous TiO₂ sol was prepared through two steps: preparation of aqueous PTA （peroxo titanic acid） sol by ISG method from TiOSO₄, and then hydro-thermal modified in autoclave to form some nanosized anatase particle in the sol. The XRD and FTIR were used to detect the phase and chemical structure change during the process. Micrographs of TiO₂ particles were observed by TEM. Ti/H₂O₂ molar ratio could play as a very important factor during the preparation of PTA sol, and semi-transparent light yellow sol could be obtained when the ratio is1:3-1:4. TEM micrographs showed that the quantity and size of TiC^ particle increased with the hydro-thermal modification temperature change from 90 °C to 120°C, and prolong the treating time also could promote the formation of nano particle. The XRD pattern indicated that the higher temperature could promote the crystallization of anatase. On the other hand, with the increasing of modification temperature the stability of sol would become worse.Finally, nanosized TiC?2 particle-polymer co-modification technology was inducted to protect the colored pearl from UV-induced bleaching and improve its corrosion resistant. To measure the protective effect of the nanosized particle modified TiC>2 layer prepared in different condition, its UV radiation transmittance was measured by UV-Vis spectrophotometer. The results indicated that the quantity and size of nano particle and the thickness of modified layer were two important factors that could directly affect the protective effects of the modified layer. In order to improve the corrosion resistant of the pearl, a polymer co-modification layer was introduced after processing the nanosized particle modified TiC>2 layer. The heat treatment temperature could affect the reaction in the formation process of polymer. By heat treating in 120°C for 30-40 min a high visible light transmittance and low UV radiation transmittance co-modification layer was obtained. UV ageing test and corrosion test were used to confirm the performance of the nanosized TiC>2 particle-polymer co-modified colored pearls, the results prove that the performance of colored pearl was being markedly improved by the nanosized TiC>2 particle-polymer co-modification method.更多还原