Synthesis, In-situ Mechanical And Electrical Properties Of One-dimentional Carbide Nano-materials Generated From Plant Fibers

The physical and chemical properties of carbide nanomaterials are of interest for basic research and several technological applications due to their intrinsic material properties such as excellent chemical and thermal stability, high hardness, oxidation and corrosion resistance, and low electrical resistivity. These properties make carbide nanomaterials very useful as coating materials, cutting tools, superconductors, luminescent materials, and reinforcements in composites.The carbide nanomaterials are usually prepared by carbothermal reduction, thermal plasma, solvothermal, sol-gel, microwave heating, and self-propagating high temperature synthesis, however, these methods are complex and costly. In this dessertation, one-dimensional SiC, TiC and TaC nanomaterials were synthesized via a one-step, simple, convenient and cost effective carbothermal method using nature plant fibers including bamboo fibers, cotton fibers, coniferous wood fibers, and broad-leaved wood fibers as both the carbon source and the template. The growth mechanism, growth direction and microstructures of the as-prepared nanomaterials were investigated. The mechanical, electrical and photoluminescent properties were studied. The main contents can be summarized as fllows:1. One-dimensional (1D) SiC, TiC and TaC nanostructures were synthesized using nature plant fibers (bamboo fibers, cotton fibers, needlebush fibers, broad-leaved fibers, etc.) as both the carbon source and the template via a one-pot, convenient, low-cost, nontoxic, and mass production carbonthermal method. X-ray diffration (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersion spectroscopy (EDS) were applied to study their morphology, crystaline structure, growth direction and component.2. Photoluminescence (PL) property of the SiC nanowires was studied as well. The photoluminescence around 366 nm excited by 254 nm wavelength showed a blue shift compared to the 3c-SiC films'Blue - green fluorescence. In-situ atomic force microscope (AFM) three-point bending tests were performed to probe the mechanical properties of TiC nanowires. The measured Young's modulus of TiC NWs ranges from 394 to 468 GPa and the average modulus is 432±22 GPa. Electrical Doule-Layer Capacitors (EDLC) was assembled with TiC/C hybrid microstructures based on their remarkble electrical properties of TiC. In-situ AFM three-point bending tests were performed to probe the mechanical properties of TaC nanowires. These TaC nanowires exhibit high Young's modulus of 364.7 GPa, which is close to the spark plasma sintered TaC powders (335-469 GPa), higher than the reported value of 283 GPa for bulk TaC ceramics. In-situ TEM sliding probe technique was used to probe the electrical properties of single TaC NWs for the first time. The TaC nanowires show low electrical resistivity of 63.6μ?·cm. EDLCs were assembled with TaC/C hybrid microstructures based on the remarkble electrical properties of TaC.