论文标题:纳米级活性碳酸钙的制备
THE PREPARATION AND APPLICATI ON OF PEROVSKITETYPE OXIDE CATALST IN AIR ELECTRODE
论文作者 白鸽玲
论文导师 满瑞林,论文学位 硕士,论文专业 化学工艺
论文单位 中南大学,点击次数 111,论文页数 76页File Size3759k
2002-04-01论文网 http://www.lw23.com/lunwen_1265927/ 纳米,碳酸钙,碳化机理,晶形,表面改性
nanograde;calcium carbonate;carbonation reaction;crystal form; particle size;surface
纳米级碳酸钙是一种功能性的无机填料。它不但具有增加产品体积，降低产品成本的作用，而且还拥有优良的补强性能。本文对其制备工艺及表面改性进行了较为系统的研究。 本论文对制备纳米碳酸钙的关键反应及其机理进行了研究。跟踪测定了碳化反应过程的电导率和pH值的变化，归纳了碳化反应过程的基本特征，并给予讨论和解释。通过中断气体通入的碳化实验和添加晶种的碳化实验，对该解释进行了进一步验证。 在对纳米碳酸钙制备各主要影响因素进行了单因素实验的基础上，确定了制备纳米碳酸钙的最佳工艺条件：温度为10℃左右，二氧化碳浓度为30％～40％，氢氧化钙悬浮液浓度为8％左右，为工业生产提供了一定的参考。同时，本论文还对不同晶形碳酸钙的制备进行了研究。通过在碳化反应过程中向反应溶液加入不同种类的添加剂，制备出了立方形、球形、链状碳酸钙，且其平均粒径均小于100nm。此外，在碳化过程中还采用了超声波技术，对比实验结果可发现，在碳化过程中添加超声外场，能有效的减小碳酸钙的粒径，并使其粒径分布范围较窄。将制备的多种纳米碳酸钙产品作性能检测，结果显示，碳酸钙粒径均在100nm以下，pH值平均为8.81，沉降体积平均为5.11ml／g，白度(wj)平均为90.88，达到国家优质品标准。 最后，本文还对纳米碳酸钙的表面改性进行了研究，研制并采用了多种新型活化剂对纳米碳酸钙进行表面处理，考察、测定了改性后碳酸钙的吸油值、白度、活化度等性质，结果表明，改性后的纳米碳酸钙的活化率均达到100％，吸油值平均为46.8g／100g，白度(wj)平均为93.70，达到国家颁布标准。
Nanograde calcium carbonate is a kind of functional inorganic filler. It not only can increase the volume of product and decrease the cost, but also has excellent tefnj-or.ce character. In this paper, the preparation technology and surface mod/station are studied systematically.The key reaction, carbonation, and its mechanism of the preparation of nanograde calcium carbonate are studied. The basic character of carbonation reaction is discovered by monitoring the conductivity and pH value during the reaction. Some reasonable explanation and deduction are also given. Through the experiments of suspending gas and adding seed crystal, the explanation and deduction are verified.Based on the single-factor experiments of preparing nanograde calcium carbonate, the optimum technology conditions, which provide some consultation for industry, are found. The temperature of reaction is about 10癈. The volume concentration of CO2 is 30%~40% and the concentration of Ca(OH)2 is around 8%. Meanwhile, the preparations of different crystal form calcium carbonate are also studied in this paper. By adding different additive during carbonating process, cubic, spherical and chain calcium carbonate are prepared. Moreover, ultrasonic technique is used in the experiment. The result shows that the particle size of calcium carbonate can be decreased effectively by using ultrasonic, and the distribution of the particle size is narrow. Through examination, it can be easy found that the particle sizes of the calcium carbonate are less than 100nm and the average of pH value 8.81, the average subside volume 5.11nu/g,the average of the whiteness degree (Wj) 90.88. That means all of the calcium carbonate prepared reach the national standard of high-quality products.In the end, the surface activation of nanograde calcium carbonate is also studied. Several new activators are developed and used in the experiments, and some characters of the activation calcium carbonate are investigated and determined as following: the activation rate 100%, the average value of oil absorption 46.8g/100g, and the whiteness degree (Wj) 93.70. All the activation calcium carbonates prepared fit in with the nationalstandard.
|
