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Study of the Fabrification of One Dimensional Nanomaterial on the Anodic Alumina Template

Author: GuoJianZhang
Tutor: ZuoYu
School: Beijing University of Chemical Technology
Course: Materials Science
Keywords: anodic oxidation porous anodic alumina one-dimensional nano-material Wide band gap semiconductor Microstructure Growth mechanism
CLC: TB383.1
Type: PhD thesis
Year: 2008
Downloads: 511
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Abstract

Nanomaterials have at least one-dimensional size in the range of nanometer scale. The studies of nanomaterials started in the early 1980’s and have now become the hottest worldwide research fields. Nanostructured materials have many special mechanical, optical, electrical, magnetic, thematic and chemical properties due to their size effect, surface effect and quantum effect, thereby making them attractive for many new applications in many industry as well as high-technology fields. One-dimensional nanostructures have two-dimensional size in the range of nanometer scale, such as nanowires and naonotubes. Now the one-dimensional nanostructures have become the focus of intensive research owing to their novel physical, chemical, and biological properties as well as the potential applications in nanodevices. It is the foundation of the scientific research for one-dimensional nanomaterials to explore and develop the effective method for preparing one-dimensional materials. In this article, on the foundation of predecessor’s work, we studied the process for preparing the porous anodic alumina template and the alumina nanowires; we also forecast the hole regularity for the porous anodic alumina film using the BP neural network. Among the semiconductor materials which are suitable for high frequency, high temperature, high power and radio-resistance applications, silicon carbide （SiC） holds the most promising because of its wide energy band gap, high breakout field, high thermal conductivity and high drift velocity. The combination of these properties shows promise for next generation microelectronic devices and ICs fabricated in SiC.At present we prepared different appearance of SiC nanowires on the porous anodic alumina template by means of chemical vapor deposition, and discussed the influence of the preparation process to the product appearance. And the results can be summarized as follows:1、The porous anodic alumina template was successfully produced in H2SO4,H2C2O4 and H3PO4 by two-step anodization process. By controlling the aluminum sheet purity, the anodic voltage, the anodic time and the type of electrolyte, the diameter and regularity of the hole on the anodic alumina template can be controlled. For example, under a certain range of voltage, whether the use of sulfuric acid and oxalic acid or phosphoric acid as the electrolyte, the diameter and the regularity of the anodic alumina template increase with the voltage increasing; and the thickness also increases with the increasing oxidation time.2、By using the BP neural network forecast model and method which can be auto-adapted strongly, the regularity of the porous anodic alumina template was analytically studied, and the forecast result was consistent with the actual results. This provides a new approach for the performance identification and process optimization of porous anodic alumina template. Along with science development and technical progress, people will improve ANN the various inadequate in the practical applications. We believe firmly that ANN will obtain more widespread more thoroughly research in the material application research area.3、The metal oxide compound with good optical properties, electrical properties and other excellent features, has attracted the massive researcher’s attention. In this paper, By using the porous anodic alumina membrane which was prepared in sulfuric acid, oxalic acid and phosphoric acid electrolytes as the initial material, the tubular, the belt-shaped and the wire-like nano-structural materials can be obtained. The mechanism for different morphologies of the alumina nano-fibers were discussed. And the main reason was the special structure of the porous alumina template and the layer structure of a single cell different dissolved speed in dilute phosphoric acid4、SiC nanowires with fins were prepared on the surface of the anodic alumina membranes by simple chemical- vapor- reaction approach at 1350℃in an homemade reactor. Energy-dispersive X-ray spectroscopy （EDX）, X-ray spectroscopy （XRD）, transmission electron microscopy （TEM）, and selected area electron diffraction （SAED） indicated that the prepared nanostructures are cubic single-crystalline SiC nanowires. Field emission scanning electron microscope （FE-SEM） indicate that the prepared nanowires are composed of an inner core stem with a diameter of 50-60nm and an outer fins with a diameter of 100-110nm, the length of the nanowires are about several tens micrometers. The growth mechanism of the ordered nanowires is discussed.5、SiC nanorods and nano-chain have been synthesized at relatively low temperature and with no confined spaces via a new simple method—the vapor-chemical- reaction approach, in a homemade graphite reaction cell. A mixture of milled Si and SiO₂ and CH₄ were employed as starting materials. These two nanostructures were obtained respectively by controlling the rate of Si and SiO₂ powders and other preparation conditions. The analysis results show that both the nanorods and the center thinner nanowires of the coaxial nanochain with wrapping layers are cubic structureβ-SiC single crystalline, whereas the outside wrapping layer of the coaxial nanochain is an amorphous SiO₂. Two kinds of possible growth mechanisms for two different nanostructure are proposed.

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