【作者】 牛继南；

【导师】 强颖怀；

【作者基本信息】 中国矿业大学 ， 矿物材料工程， 2010， 博士

【摘要】 由于天然埃洛石在自然界中分布不均匀、赋存少、开采条件差,而且不同地区间形貌差异较大,因此Costanzo提出用高岭石来合成10?-埃洛石—即10?高岭石水合物。在常见的Costanzo法和Raythatha法中最明显的差别在于是否添加了氟化铵。为了解释这个差异并进一步理解高岭石水合机理,本文中细化对比了两种方法的各个步骤,结果发现水合过程的各个因素对两种方法的影响类似,但Costanzo法生成了更多的其他物质,而且氟化铵量越多水合物产率越小;同时根据氟置换层间羟基的模拟结果,认为水合过程中氟化铵的加入是不必要的;得到了目前实验范围内的最佳工艺,制备出了产率为91%的10?高岭石水合物。通过KD分别与甲醇、水作用的研究,以及前面两种方法的实验结果提出了高岭石的水合机理:即KD复合物层间的DMSO分子有至少三种类型,各型分子所受的高岭石片层限制和脱除速率不同,而且由于DMSO和甲醇与水的亲和力的明显不同,所以KD在和他们依次作用时能够形成水分子在层间的吸附,进而在高岭石塌陷时形成了水分子承担层间距的新结构,即形成了10?水合物。为了研究10?高岭石水合物的结构,利用分子动力学方法对层间水分子排布进行了模拟,结果发现除了I型洞水和II型连接水外还存在层间垂直分布的III型水分子,而且这些分子在层间主要以I—III、II—III型交替排列为主。通过对10?高岭石水合物形貌的观察,不仅发现了沿片状颗粒一侧的卷曲、沿相对两侧的卷曲,还发现了沿相邻两侧的卷曲;进一步的衍射结果表明这些卷曲中包含有a、b轴方向以外的其它卷曲,通过分析得到所有这几种晶向发生卷曲的难易程度为[110]>[010]=[310]=[3-10]>[100]>[1-10]。通过对高岭石结构的分析澄清了几种结构无序的成因;通过对高岭石晶体中层间羟基氟置换的研究,得到了层间氢键削弱时结构无序的变化情况;通过对高岭石有限片层卷曲时结构无序变化的分析(第八章),得到这些结构无序的变化情况和周期性体系中类似,而且几种无序中四面体弯曲和四面体起皱起主要作用,所以认为Singh关于高岭石片层卷曲的解释在一定程度上是正确的。为了验证铁置换八面体铝能否引起埃洛石的平板化,对不同铁分数的三水铝石和高岭石进行了能量最小化模拟。结果发现铁置换分数存在极限范围,在这个范围内,计算得到的埃洛石管径随铁的增加而增加,表明铁置换确实能缓解1:1层的不匹配,铁置换对四面体旋转和弯曲的影响也表明了这一点,进而认为能否将自然界中的平板状埃洛石起因归结于铁置换的关键是铁置换是否容易发生。该论文有图110幅,表21个,参考文献252篇。更多还原

【Abstract】 As the natural halloysite uneven distribution, less occurrence, poor mining conditions and large difference in morphology between different areas, Costanzo proposed to synthesize 10?-halloysite (viz. 10? kaolinite hydrate) from kaolinite. The most common methords of synthesizing hydrate are Costanzo method and Raythatha method, and the most obvious difference between them is whether ammonium fluoride will be added. In order to explain this difference and to further understand the mechanism of hydration of kaolinite, this work detailed and compared every step of two methods, it was found that every factor (except the quantity of ammonium fluoride) in the hydration process had similar impacts on two methods, but the Costanzo reaction generated more other products, and with the increase of ammonium fluoride, hydrate production decreased; according to the molecular simulation results author concluded that the adding of ammonium fluoride was not necessary in the hydration process of kaolinite; at the same time the optimum technics within the scope of the current experiment was gained to produce 10? hydrate with a yield high to 91%.Based on the study of the KD complex reaction with methanol and water respectively, and the results about two different methods, the hydration mechanism was proposed: DMSO molecules in KD complexe had at least three types, the restriction caused by kaolinite layers on each type and the speed removed from interlayer space were different, so water molecules would be absorbed on interlayer space, then the collapse of kaolinite layers stood by the interlayer water molecules resulting in a more stable 10? hydrate.In order to investigate the structure of 10? hydrate or 10?-halloysite, molcular dynamics method was used in simulating the arrangement of interlayer waters, the results showed that in addition to the hole water (type I) and connecting water (type II), there was also another water molecule, which almost keep vertical in interlayer space(type III); these three water molecules mainly arrange in I-III or II-III form alternately.By means of TEM observation, not only the curling along the single side, along the opposite sides were found, but also the curling along the adjacent sides,; further selected area diffraction analysis showed that the direction of these curling contain other orientations than a axis and b axis; the analysis of kaolinite structure revealed the degree of easiness to curl for all current orientations was [110]>[010] =[310] = [3-10 ]>[100]>[1-10].The cause of several disorders in kaolinite were clarified by means of analysizing of kaolinite structure; by means of study on the substitution of fluorine for interlayer hydroxyl in kaolinite crystal, the changing behavior of structure disorder was gained as the hydrogen bond was weakened; by means of analysizing the changing behavior of structure disorder in a single kaolinite layer the similar trend to the periodic system was gained for the changing of these disorders; tetrahedral bend and tetrahedral rotation might played the major roles in curling process, therefore author thought Singh’s interpretation about the curling mechanism of kaolinite layer to be correct in some extent.In order to test whether the substitution Fe for octahedral Al would cause the flattening of curling halloysite, gibbsite and kaolinite with different content of Fe were studied with the energy minimization method. The result showed there was a limit range of Fe substitution, the calculated radius of halloysite increased with the improvement of Fe substitution in the range, which revealed Fe substitution for octahedral Al could alleviate the dismatch of kaolinite 1:1 layer certainly, and the affect of Fe substitution on tetrahedral rotation and tetrahedral corrudation also indicated this point. Thus author thought whether the flattening of halloysite could be attributed to iron substitution, the key was whether the substitution of iron was easy to happen.The dissertation includes 110 figures, 21 tables and 252 references.更多还原