Preparation And Modification Of Aluminum Borate One-Dimensional Nanomaterials

Aluminum borate one-dimensional nanomaterials attract much attention in Phyiscs,Chemistry,Materials and so on due to their excellent mechanical properties, chemical inertness, high temperature stability, low thermal expansion coefficient, and much lower cost compared to the traditional strengthening materials-SiC nanowires. In order to expand the application fields of the aluminum borate nanomaterials and further enhance the mechanical properties, it is worthy of completing and investigating the optional conditions to fabricate aluminum borate nanowires, carrying out the surface modification of refractory nanomaterials, etc. According to the problems of the present research of aluminum borate one-dimensional nanomaterials, the work that I have mainly done is as following.(1) We have systematically investigated the preparing process of aluminum borate nanowires. In fact, we groped the optional conditions to synthesize large-scale high yield aluminum borate nanowires. According to the synthesis process, we pay much attention to the key effects: the preparaion of precursor from sol-gel method and the additive of aluminum powder. The products show that the precursor can control the dimension and the aluminum powder can decrease the diameter and increase the aspect ratio. Using the optional conditions, the diameter of our products is 20-60 nm and the length is 1-2 um long.(2) Under the assistance of sucrose, we firstly got the high aspect ratio (upper than 100) aluminum borate arrays using the reaction between aluminum nitrate and boric acid at high temperature. We have also detailedly analyzed the experimental process and discovered that the sucrose played a crucial role in the growth of the nanowire bundles by supporting as a polymeric substrate and a type of adhesive template. Due to the function of the sucrose playing in the reaction, we proposed a rational mechanism for our products. The supporting document One supplies the systematical experiments and the experimental results. The supporting document Two supplies the extendable application of our method to the preparation magnesium borate (Mg₂B₂O₅) nanowire bundles. The results also show that our extendability is feasible in the preparation of Mg₂B₂O₅ nanowire bundles.(3) Multilayer nanowire webs of aluminum borate (Al₁₈B₄O₃₃) have been firstly synthesized by a solid-state reaction between boron, boron oxide, and aluminum oxide at high temperature without using any template or substrate. Alumina particles on micron-scale provided an in-situ reaction container, supplying a special environment for the self-oriented growth of the aluminum borate nanowires; the addition of boron should be responsible for the generation of the web morphology; the orientation could be maintained by a quenching treatment at the last step. Further experiments were carried out to investigate the morphological dependence on the reactant compositions. The possible growth mechanism for the nanowebs was also proposed and comfirmed by our systematical experiments.(4) We catch our clues from the pre-work of our group and my grope about quick lagre-scale preparation of BN-Al₁₈B₄O₃₃ nanocables, a facile method was firstly proposed to coat nanowires with BN by an epitaxial growth process. We took aluminum borate (Al₁₈B₄O₃₃) nanowire webs for example, our method had directly and completely coated Al₁₈B₄O₃₃ nanowire webs with BN. The BN-Al₁₈B₄O₃₃ nanocable webs could be obtained by the reaction of Al₁₈B₄O₃₃ nanowire webs, B₂O₃ and ammonia at 1200℃. The high-temperature stable Al₁₈B₄O₃₃ nanowire webs played as a template for the epitaxial coating of BN. The coating was characterized by the means of X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Infrared spectrum (IR) and High-resolution transmission electron microscopy (HRTEM). The typical thickness of the BN shells is～5 nm. The growth mechanism of the present BN-coated aluminum borate (Al₁₈B₄O₃₃) nanostructures was also proposed. The importance of our method is that it is not limited by the cruel properties of the core nanowires (comparing with the high temperature unstable Al₄B₂O₉), it has the large potential applications to extend it into a widely used method to uniformly coat refractory nanomaterials by BN, so as to modify the surface of the refractory nanomaterials.