碳纳米材料的模板法制备与结构表征

发布时间：2018-06-22 05:36

  本文选题：碳纳米材料 + 分子筛　； 参考：《太原理工大学》2010年博士论文

【摘要】：碳纳米管(Carbon nanotubes:CNTs)和洋葱状富勒烯(Onion-like fullerenes:NOLFs)等碳纳米材料自发现以来,以独特的结构和电学、磁学、力学、化学等特殊的性能,开辟了新的科学研究领域,在工程、电子、信息、能源、生物医药、化工和国防等领域具有潜在的应用前景。 本论文首先以简单的路径合成Li-ABW沸石分子筛,并采用传统的水热法以及非常规极浓体系、蒸汽相条件下分别合成MCM-41；然后在此模板上负载Fe做催化剂,采用化学气相沉积(Chemical Vapor Deposition,CVD)法合成了CNTs。另外,提出了由“聚合预成形+热处理成形”两步反应模板法合成NOLFs;并利用金刚石对顶砧实验技术(Diamond Anvil Cell,DAC)系统研究了NOLFs的高压性能。 研究的主要内容和结果如下： 1.分子筛合成 1)Li-ABW模板剂的合成 比较了相同晶化温度(150℃)、不同Li/Si摩尔比条件下合成沸石Li-ABW(Li/Si=1.5)和混合相Li-ABW+Li2SiO3(Li/Si=2.5)的晶体结构、焙烧相转变过程以及表观形貌等。结果表明：沸石Li-ABW可以在150℃的较低温度下用硅溶胶和异丙醇铝作原材料直接合成,其合成的最佳条件为：摩尔组成1.5Li2O：Al2O3：2SiO2：154H2O,150℃下晶化7天；当Li/Si摩尔比为2.5时,沸石从ABW纯相向ABW+Li2SiO3混合相转变。 2)MCM-41模板剂的合成 在M20(M=Li,Na,K)-Al2O3-SiO2-CTAB-H2O水热凝胶体系中,合成介孔(1.5-4nm)MCM-41分子筛。相对结晶速度为：K-MCM-41Na-MCM-41 Li-MCM-41.实验表明：K-MCM-41分子筛的晶体结构、吸附特性及热稳定性接近或优于Na-MCM-41分子筛. 在NaX-Na2O-A12O3-SiO2-CTAB-H20水热体系中合成MCM-41分子筛。实验表明：F-引入可加速MCM-41分子筛晶化速度；大量引入Br-影响MCM-41分子筛晶化。 在含辅助烷烃(正己烷、正庚烷、异辛烷)的水热体系中合成d100较大的MCM-41分子筛,d100值随辅助烃的碳数增加而增大。石油醚具有与前述烷烃类似的作用。水热体系中加入辅助烷烃使MCM-41分子筛的有序性降低,比表面积、孔体积略有减小。 在极浓体系中,由无定形凝胶Na2O-SiO2-CTAB-H2O合成MCM-41分子筛。CTAB/Si降至0.0125可以合成MCM-41分子筛,能有效地减少合成中CTAB的消耗。 用蒸气相法可以合成Si-MCM-41和Al-Si-MCM-41分子筛的纯相；蒸气相法可以明显地减少MCM-41分子筛制备过程中表面活性剂CTAB的消耗量；含有适量铝的样品比纯硅样品具有较高的热稳定性。 2.通过浸渍法制备了Fe/ABW.Fe/MCM-41和Fe/SBA-15分子筛催化剂,以其为模板,乙炔为碳源,Ar为保护气采用CVD法,考察了不同温度(600,700,800℃)、反应区域和分子筛载体对合成纳米碳材料的影响,另外,还考察了未负载任何催化剂的分子筛合成纳米碳材料以及实验中催化剂未经氢气还原合成纳米碳材料的结果。结果表明：在反应温度为700℃,三种不同的催化剂经H2还原后,在反应温度区催化生长出直径均匀(20-30nm)且晶化程度较好的CNTs. 3.模板法是一种具有创新性的制备NOLFs的方法,是以苯乙烯和丙烯酸等有机物单体为碳源,通过单体间的聚合反应使纳米金属颗粒包裹在内,形成内包金属NOLFs的前驱体；然后采用热处理方法将其转变为石墨化程度高的NOLFs,其核心为直径约60nm的铁纳米颗粒。通过场发射扫描电子显微镜和高分辨透射电子显微镜观察分析,结果表明：模板法制备NOLFs是一种十分新颖有效的制备方法,通过聚合反应和热处理成形这两步制备NOLFs,使NOLFs的形貌和大小具有高度可控的特点,对NOLFs的性能和应用研究非常重要。 4.采用电弧放电技术在液体中合成了高纯度的NOLFs和内包金属的NOLFs,并利用DAC对其高压Raman光谱进行了研究。结果表明,NOLFs的压力系数和弹性行为与多壁碳纳米管非常相似,且在20GPa高压下,没有发现同心石墨壳层结构的塌陷,说明NOLFs的硬度非常高,能够承受很大的压力。但DAC实验加压前后ID/IG比值的显著变化却从另一个侧面证明,尽管加压前后石墨壳层骨架结构没有发生塌陷,但还是存在诸如石墨层和金属核之间相界面结构的一定程度的结构破坏。
[Abstract]:Carbon nanotubes ( CNTs ) and onion - like fullerene ( NOLFs ) have developed new scientific research fields with unique structure and electrical , magnetic , mechanical and chemical properties , and have potential application prospects in the fields of engineering , electronics , information , energy , biological medicine , chemical engineering and national defense .

In this paper , the Li - ABW zeolite molecular sieve was synthesized by a simple path , and MCM - 41 was synthesized under the condition of vapor phase by using conventional hydrothermal method and unconventional polar concentration system .
In addition , the high voltage performance of NOLFs was studied by means of diamond Anvil Cell ( DAC ) system .

The main contents and results of the study are as follows :

1 . Molecular sieve synthesis

1 ) Synthesis of Li - ABW Template Agent

The crystal structure of Li - ABW ( Li / Si = 1.5 ) and Li - ABW + Li2SiO3 ( Li / Si = 2.5 ) were synthesized from Li - ABW ( Li / Si = 1.5 ) and Li - ABW + Li2SiO3 ( Li / Si = 2.5 ) at the same crystallization temperature ( 150.degree . C . ) .
When the molar ratio of Li / Si was 2.5 , the zeolite was transformed from ABW pure opposite ABW + Li2SiO3 .

2 ) Synthesis of MCM - 41 Template Agent

The mesoporous ( 1.5 -4 nm ) MCM - 41 molecular sieve was synthesized in the hydrothermal gel system ( M = Li , Na , K ) - Al2O3 - SiO2 - CTAB - H2O . The relative crystallization velocity was : K - MCM - 41 Na - MCM - 41 Li - MCM - 41 . The experimental results show that the crystal structure , adsorption characteristics and thermal stability of K - MCM - 41 molecular sieve are close to or better than those of Na - MCM - 41 molecular sieve .

The MCM - 41 molecular sieve was synthesized in hydrothermal system of NaX - Na2O - Al2O3 - SiO2 - CTAB - H2O .
Large amounts of Br - affect the crystallization of MCM - 41 molecular sieve .

In the hydrothermal system containing auxiliary alkane ( n - hexane , n - heptane and isooctane ) d100 , the d100 was synthesized and the d100 value increased with the increase of the carbon number of the auxiliary hydrocarbon . The petroleum ether has the similar effect as the above - mentioned alkane . The addition of the auxiliary alkane to the hydrothermal system decreases the ordering of MCM - 41 molecular sieve , the specific surface area and the pore volume decrease slightly .

The MCM - 41 molecular sieve was synthesized from amorphous gel Na _ 2O - SiO _ 2 - CTAB - H2O by amorphous gel Na _ 2O - SiO _ 2 - CTAB - H2O . The MCM - 41 molecular sieve could be synthesized by reducing CTAB / Si to 0.0125 , which could reduce the consumption of CTAB .

The pure phase of Si - MCM - 41 and Al - Si - MCM - 41 molecular sieve can be synthesized by vapor phase method .
the vapor phase method can obviously reduce the consumption of surfactant CTAB during the preparation of MCM - 41 molecular sieve ;
Samples containing an appropriate amount of aluminum have higher thermal stability than pure silicon samples .

2 . Fe / ABW . Fe / MCM - 41 and Fe / SBA - 15 molecular sieve catalysts were prepared by impregnation . The effects of different temperatures ( 600 , 700 , 800 鈩，

本文编号：2051798