【作者】 贺国平；

【导师】 赵临远；

【作者基本信息】 广西师范大学 ， 无机化学， 2008， 硕士

【摘要】 近年来,核/壳复合粒子的设计和可控构筑已成为新材料和表面科学领域的研究焦点。由于核/壳粒子相比于单一组分材料表现出更优越的理化性能（如机械、化学、电学、磁学和光学方面）,而且,把贵重材料包覆在低廉的核体物质上可降低其生产成本。多种核/壳粒子已被制备出来,特别是壳层物为二氧化硅的复合粒子。水合二氧化硅外观呈白色,因在橡胶中有类似于炭黑的补强性能,所以俗称为白炭黑。它以密度小、比表面积大、分散性能好及优越的稳定性、补强性、增稠性和触变性等成为重要无机填料之一,广泛应用于橡胶、塑料、医药、涂料,日用化工等许多行业。因此,本课题根据“粒子设计”的新思想,探索白炭黑的绿色合成新工艺,以CaCO₃颗粒为核体、无定形SiO₂为壳层物试制出一种新型的白炭黑（我们称为ASNS,amorphous silica with novel particle structure）在某些应用中替代现有产品。在ASNS的生产工艺中,传统原料水玻璃、酸的消耗将减少90%以上,产品水洗、干燥的负担相应减轻,废水的生成量显著降低,基本上能够达到绿色化学和原子经济性的要求。并探索出一种新颖、快捷、可靠的测定无定形二氧化硅对碳酸钙包覆程度的新方法。这种核/壳材料测试技术的创新,对指导碳酸钙@白炭黑粒子的制备,确定最佳工艺条件,明确新产品的技术指标,都具有重要的实际应用价值。本文的主要工作如下:1.总结、分析了核/壳结构粒子的基本特性、制备方法、形成机理、表征方法和主要应用。这对核/壳复合材料的制备、结构性能和包覆机理的研究具有重要的指导意义。2.对三个不同厂家所生产的牙膏用二氧化硅磨擦剂的外观、pH值、热失重率、吸水量、硫酸盐含量、表观密度等六个方面的理化性质进行了测试和比较。3.研究了用非均相成核法在CaCO₃颗粒表面包覆无定形SiO₂的工艺。对影响包覆效果的Na2SiO₃溶液浓度、pH值、温度、CaCO₃颗粒的分散、物料混合方式等因素深入剖析。并从热力学和动力学方面探讨其包覆机理。4.研究了水溶液中亚甲基蓝（MB）与白炭黑之间的相互作用,考察了吸附时间、亚甲基蓝初始浓度、温度、pH值、盐的加入等因素对白炭黑吸附MB的影响,并探讨了吸附机理。实验结果表明,吸蓝量随初始浓度的增大而增大,随体系温度和盐浓度的升高而减小。还发现MB在较高pH条件下,因水解或形成二聚体对可见光的吸收率随pH升高不断降低的现象。根据此现象,本文提出,当pH值增大,白炭黑对MB吸附量增大的原因有两个:一是pH值越大,白炭黑表面负电荷量越多,因此对阳离子染料MB的吸附量增大;二是在高pH下,MB自身水解或形成二聚体导致吸附量测定结果偏高。由于MB是表征吸附剂吸附性能最常用的染料之一,该发现对于其它吸附体系的研究也具有参考价值。. 5.研究了碳酸钙对水溶液中亚甲基蓝的吸附作用,实验结果表明,碳酸钙对亚甲基蓝不吸附。因此,根据对MB的吸附性能不同可区分白炭黑和碳酸钙。6.采用亚甲基蓝吸附法测定无定形SiO₂对CaCO₃的包覆量和包覆率。这种快速、简便、直观、准确的测定方法对于指导核/壳粒子的生产具有重要的参考价值。更多还原

【Abstract】 In recent years, the design and controllable constructing of core-shell composite particles have become the focus of a study on a new materials and surface science. Various types of core-shell particles have emerged, especially, the shell material such as silica. Because such particles with core-shell structure often exhibit superior physicochemical properties （e.g. mechanical,chemical,electrical,magnetic and optical） to their single component counterparts, moreover, coating expensive shells on the inexpensive cores materials can lower the cost of the functional materials . With white external appearance,hydrated silicon dioxide has the similar function of reinforcing ability in rubber to carbon,so it is usally called white carbon black .For its low density,high specific surface area, fine dispersion,superior stability , reinforcing ability,thickening property and thixotropy inereasing etc.Silica has been one kind of important inorganic fillers, and widely used in many fields, such as rubber , plastic,medicine, pigment ,toothpaste and daily chemical industry. Thus, under the "particle design" new ideas,to attempts to regard amorphous SiO₂ as shell materials,regard CaCO₃ partiele as core materials to prepare a kind of new-type silica-gel filler, to explored the green synthetic process of silica, to produce a new type of silica （the amorphous silica with novel particle structure is called ASNS） as substitute for it’s existing products in some applications. It is the production process of ASNS that reduced the consumption of traditional raw materials of sodium silicate and acid by more than 90 percent, and reduced significantly the cost of washing and drying of products, and met basically the requirement of green chemistry and atom economy .We put forward a novel, rapid, reliable new method on determining the coated effect of calcium carbonate coated with amorphous silicon dioxide. It had practical application value for new measurement techniques of this core-shell material to guide the preparation of calcium carbonate @ silica,and to determine optimum conditions,and to definite technical index of a new product,and to establish enterprise standard. The main work of this dissertation are summed up as follows:1. In this paper we summarized and analyzed the basic characteristics, preparation method, formation mechanism, characterization methods and main application of core-shell particles. Which is of certain guiding significance for studying the preparation, structural performace and coating mechanism of core-shell composite materials.2. We tested and compared physicochemical properties （including the appearance , pH value, heat rate of weight loss, water absorption , sulphate content, the apparent density ）of three kinds of silica using for toothpaste abrasives produced by three different manufacturers.3. The technology of coating SiO₂ on the surface of CaCO₃ particles was studied by heterogeneous nucleation method. The influences of the solution concentration of Na2SiO₃ , the pH value, temperature of the system, the dispersion of CaCO₃ particles, blending way and adding rate were made a thorough analysis. The coating mechanism was studied through thermodynamics and dynamics.4. Studying on interaction of methylene blue（MB） in aqueous solution and silica, The effects of initial mass concentration of MB,adsorption time, temperature,pH value,salt on the MB adsorption of silical were also investigated. Experimental results have shown that increasing initial mass concentration of MB favors the adsorption while the acidic pH , temperature and salt go against the adsorption.It was found that the absorbance of visible light of methylene blue（MB） solution decreased at high pH beeause of hydrolysis or forming dimmer of MB. On the basis of this finding,we proposed that there were two reasons for the increasing removal of MB onto silica with the increasing pH value : One was the increasing negative charge on the silica surface with pH increasing and the other was the hydrolysis or dimmer forming of MB which causing the removal increase. As MB is one of the most popular dyes for characterization of various adsorbents, this finding may be also taken as reference to other adsorption system studies.5. The adsorption effect of the aqueous solution of methylene blue on calcium carbonate has been investigated. Experimental results have shown that no adsorption of methylene blue on calcium carbonate occurred. Therefore, according to different adsorption performances distinguishing between silica and calcium carbonate.6.The determination of the coating quantity and coating ratio of CaCO₃/SiO₂ core-shell particles by methylene blue spectrophotometric method. This rapid, simple, direct and accurate determination method has important reference value to guide the production of core-shell particles.更多还原