| Recently, amorphous carbon nanotubes (ACNTs) become focus for researchers. The walls of the ACNTs are composed of many carbon clusters featuring short-distance order and long-distance disorder. Amorphous carbon contains parts of the properties of both diamond and graphite. Due to differences in structure, the ACNTs have some potential applications which are different from crystalline carbon nanotubes’s. Therefore, preparation of amorphous carbon nanotubes and the development of its applications is a promising research.Through the study on carbon nanotues, people gradually realize that one-dimensional structural materials have special physical and chemical properties. TiO2nanotubes show broad applications in solar energy storage and utilization, photoelectric conversion, photochromism, photocatalytic degradation of pollutants in air and water. So, deep study on TiO2nanotubes has great strategic significance in solving the energy and environmental crisis.Attapulgite is a kind of natural hydrous magnesium-aluminum silicate mineral with a la-minated chain structure. Attapulgite is a typic one-dimensional nanomaterial. The diameter of attapulgite is in the range of nanosize. Suitable acidification treatment or heat treatment of attapulgite could increase its surface energy, which facilitates it adsorb organic micromole-cules. Attapulgite is a kind of hydrous magnesium-aluminum silicate mineral, so it can be dissolved by HF, strong acid and strong alkali. Having removed the attapulgite that as the template, the carbon or TiO2deposited on the external surface of the attapulgite formed a hollow tubular structure obtaining nanotubes.The innovation points of this thesis are:①utilization of natural nanomaterials attapulgite as the template, combined the template method and hydro-thermal method to obtain amorphous carbon nanotubes, combined the tem-plate method and sol-gel method to obtain TiO2nanotubes. The research ideas are new and unique which has not been reported before.②utilization of natural nanomaterials attapulgite as the template to prepare nanotubes materials proposed a novel method for the preparation of nanotube materials, and opened up new areas of the deep processing and utilization of attapulgite.The main work of this thesis were utilization of natural nanomaterials attapulgite as the template, combing the template method and hydro-thermal method to obtain amorphous car-bon nanotubes, combing the template method and sol-gel method to obtain TiO2nanotubes, characterization and test the as-prepared nanotubes, tentatively exploring the formation me-chanism of the amorphous carbon nanotubes and TiO2nanotubes. The whole text included two parts of research conclusions as follows:Ⅰ. Preparation, characterization and tentative exploration of the formation mechanism of the amorphous carbon nanotubes①Using attapulgite as the template, furfuryl alcohol as the carbon source, Combined the tem-plate method and hydro-thermal method to obtain amorphous carbon nanotubes. The X-ray diffraction patterns, the SAED pattern and Raman spectrum of the samples indicated that the as-prepared carbon material was amorphous. The scanning electron microscope (SEM) and transmission electron microscope (TEM) pictures showed that the as-prepared carbon material had nearly the same morphology and size of attapulgite and mainly had tubular and sheet appearances. The EDS spectrum showed that the chemical composition of the the as-prepared carbon nanotubes are mainly carbon, indicating that we obtained carbon nanotubes of high purity successfully. Brunauer-Emmett-Teller (BET) surface area analysis indicated that specific surface area of the as-prepared amorphous carbon nanotubes reaches up to503.1274m2/g. The adsorption-desorption curve and pore size distribution of the sample analysis results showed that there are micropore, mesopore and macropore in the as-prepared amorphous carbon nanotubes②The reasons why the carbon nanotubes are amorphous are not yet very clear. Here, a hypo-thesis was put forward. After acidification treatment, the specific surface area of attapulgite was increased and the adsorption ability of attapulgite was inhanced, which means attapul-gite can adsorbed organic micromolecules like furfuryl alcohol. During the process of Hy-drothermal synthesis, the water under high temperature and pressure had a strong oxidation ability and more extensive integration capabilities, which adsorbed the carbon firmly on the surface of the attapulgite. Having adsorbed the carbon source, the attapulgite was calcined under N2atmosphere. The attapulgite’s crystalline structure was gradually destroyed with the increasing temperature from600℃to800℃, simultaneouly the furfurly alcohol was carbonized and carbon nanotubes growed along the external surface of the attapulgite. Due to the gradual collapse of the attapulgite’s crystalline structure, the resultant carbons grow-ing upon the attapulgite exhibited disordered structure characteristics and amorphous car-bon nanotubes were finally obtained.Ⅱ. Preparation, characterization and tentative exploration of the formation mechanism of the TiO2nanotubes①Using attapulgite as the template, butyl titanate as the titanium source, Combined the tem-plate method and sol-gel method to obtain TiO2nanotubes. The X-ray diffraction patterns showed that TiO2nanotubes calcined at350℃had poor crystallinity, TiO2nanotubes cal-cined at more than550℃have high crystallinity and calcinations convert the TiO2nano-tubes from anatase to rutile. TiO2nanotubes calcined at350℃were anatase, TiO2nano-tubes calcined at350℃were mixture of rutile, TiO2nanotubes calcined at350℃were ru-tile. The scanning electron microscope (SEM) and transmission electron microscope (TEM) pictures showed that the TiO2nanotubes had nearly the same morphology and size of atta-pulgite and had obvious tubular appearances. The EDS spectrum showed that the chemical composition of the the as-prepared TiO2nanotubes are titanium and oxygen, indicating that we obtained TiO2nanotubes of high purity successfully. Brunauer-Emmett-Teller (BET) surface area analysis indicated that with the calcinations temperature rising, specific surface area of the as-prepared TiO2nanotubes decreased. This was because as the temperature rised, TiO2experienced phase transition, during which heat of in situ phase change accele-rated the growth of crystal grains and increased the size of the grains, resulting in the de-crease of the specific surface area of the as-prepared TiO2nanotubes. The adsorp-tion-desorption curve and pore size distribution of the sample analysis results showed that there are micropore, mesopore and macropore in the as-prepared TiO2nanotubes.②The formation mechanism of the TiO2nanotubes was speculated as follows:Attapulgite is negatively charged, so when it was mixed with cationic surfactant CTAB, the CTAB was adsorbed onto the surface of attapulgite as a result of electrostatic attraction.TiO2is also negatively charged, so CTAB was also adsorbed by the TiO2precursor. CTAB reduced the electrostatic repulsion between TiO2and attapulgite and connected TiO2and attapulgite to-gether as a bridge, which facilitated TiO2load on the surface of the attapulgite. Finally, after calcinations and removal of the template, TiO2nanotubes were obtained. |
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