【摘要】：近幾年來(lái),隨著納米科技的迅速發(fā)展,納米材料的應(yīng)用受到各個(gè)領(lǐng)域的廣泛關(guān)注,納米碳酸鈣作為一種優(yōu)質(zhì)填料和白色顏料,由于具有成本低、性能優(yōu)、無(wú)毒無(wú)味等特點(diǎn),廣泛應(yīng)用在橡膠、塑料、造紙、涂料、油墨、醫(yī)藥、化妝品等眾多行業(yè)。目前制備納米碳酸鈣的方法主要有：復(fù)分解法、碳化法、乳液法、凝膠法、非冷凍法。 真空冷凍干燥法制備的納米粉體具有微粒形狀規(guī)則、粒徑小而均勻、粒度分布窄、化學(xué)成分純、粒子間無(wú)硬團(tuán)聚、分散性好等特點(diǎn),因而受到關(guān)注。 所以本文不僅選用真空冷凍干燥方法制備納米碳酸鈣而且利用自行開發(fā)的真空冷凍干燥顯微鏡成功的觀測(cè)、記錄了溶液凍結(jié)蒸發(fā)的全過(guò)程,并且對(duì)溶液凍結(jié)蒸發(fā)的過(guò)程進(jìn)行了分析和研究。 本文利用碳酸氫鈣溶液為制備納米碳酸鈣的前驅(qū)體溶液,在同樣的條件下分別采用直接冷凍干燥方法和真空蒸發(fā)凍結(jié)方法制備粉體,通過(guò)X射線檢測(cè)和透射電鏡檢測(cè)發(fā)現(xiàn)所制備的粉體為多晶體,存在兩種晶體類型,粉體很純凈不含其它的雜質(zhì),粉體疏松多孔,采用上述兩種方法都能得到粒徑在50納米左右的碳酸鈣,用兩種方法得到的粉體從形貌到成份都沒有太大的區(qū)別,但是利用真空蒸發(fā)凍結(jié)方法就會(huì)節(jié)約很多的能源,這對(duì)以后對(duì)利用真空冷凍干燥方法制備納米碳酸鈣有很大的指導(dǎo)意義。 本文還設(shè)計(jì)實(shí)驗(yàn)探索如何防止溶液在真空蒸發(fā)凍結(jié)過(guò)程中的爆沸(除去溫度和壓力因素)。以純水為例通過(guò)實(shí)驗(yàn)可以得出結(jié)論：純水中的溶解氣體對(duì)自凍結(jié)過(guò)中的第一次爆沸有很大的影響,把經(jīng)過(guò)脫氣處理的水中放入瓷片會(huì)很有效的防止第二次爆沸時(shí)液體的飛濺。 本文完成了對(duì)真空冷凍干燥顯微鏡的開發(fā)工作,并對(duì)其結(jié)構(gòu)、工作原理和能夠在實(shí)際工作中的應(yīng)用進(jìn)行了詳盡的描述。利用凍干顯微鏡實(shí)現(xiàn)了對(duì)凍于過(guò)程的顯微觀測(cè),并對(duì)其溫度和壓強(qiáng)的紀(jì)錄,分析了液體凍結(jié)的結(jié)晶狀態(tài),通過(guò)控制系統(tǒng)對(duì)導(dǎo)熱塊的升溫和降溫掌握了溶液真空蒸發(fā)和真空冷凍干燥的微觀特點(diǎn),驗(yàn)證了在冷凍干燥過(guò)程中溶液的偏析,首次利用凍干顯微鏡直接觀測(cè)法測(cè)定了碳酸氫鈣溶液的共晶點(diǎn)和共熔點(diǎn)溫度。首次在顯微結(jié)構(gòu)上研究了碳酸氫鈣溶液的凍結(jié)過(guò)程,對(duì)以后利用真空冷凍方制備成分均勻,顆粒尺寸理想的粉體有著重要的影響。
[Abstract]:In recent years, with the rapid development of nanotechnology, the application of nano-materials has received extensive attention in various fields. As a kind of high-quality filler and white pigment, nano-calcium carbonate has the characteristics of low cost, excellent performance, non-toxic and tasteless, etc. Widely used in rubber, plastics, paper, paint, ink, medicine, cosmetics and many other industries. At present, the main methods of preparing nanometer calcium carbonate are: double decomposition, carbonation, emulsion, gel, non-freezing. The nano-powder prepared by vacuum freeze-drying method has the characteristics of regular particle shape, small and uniform particle size, narrow particle size distribution, pure chemical composition, no hard agglomeration between particles, good dispersion and so on. So this paper not only uses vacuum freeze drying method to prepare nanometer calcium carbonate, but also records the whole process of solution freezing evaporation by using vacuum freeze drying microscope developed by ourselves. The process of solution freezing evaporation is analyzed and studied. In this paper, calcium bicarbonate solution was used as the precursor solution to prepare nanometer calcium carbonate. Under the same conditions, the direct freeze-drying method and the vacuum evaporation freezing method were used to prepare the powders, respectively. X-ray and transmission electron microscopy showed that the prepared powder was polycrystalline, and there were two crystal types. The powder was pure and free of other impurities. The powder was porous and porous. Calcium carbonate with a particle size of about 50 nanometers can be obtained by either of the two methods. There is no great difference between the morphology and composition of the powders obtained by the two methods, but the vacuum evaporation freezing method will save a lot of energy. It is of great significance for the preparation of nano calcium carbonate by vacuum freeze drying. Experiments are also designed to explore how to prevent the solution from boiling during vacuum evaporation freezing (removing temperature and pressure factors). Taking pure water as an example, it can be concluded that the dissolved gas in pure water has a great influence on the first explosion and boiling in the self-freezing process. Putting the water treated by degassing into the porcelain chip will effectively prevent the spatter of the liquid during the second explosion. In this paper, the development of vacuum freeze-drying microscope is completed, and its structure, working principle and practical application are described in detail. The microscopic observation of freezing process was realized by using freeze-dried microscope, and the crystallization state of liquid freezing was analyzed by recording the temperature and pressure. The microcosmic characteristics of solution vacuum evaporation and vacuum freeze drying are grasped by the control system for the heating and cooling of the heat conduction block, and the segregation of the solution in the process of freeze-drying is verified. The eutectic point and eutectic point temperature of calcium bicarbonate solution were measured by the direct observation of freeze-dried microscope for the first time. The freezing process of calcium bicarbonate solution was studied for the first time in microstructure, which has an important effect on the preparation of powders with uniform composition and ideal particle size by using the vacuum freezing formula.
【學(xué)位授予單位】：東北大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2010
【分類號(hào)】：TB383.1

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