Synthesis Of SiC Quasi-One-Dimensional Nanomaterials And Design Of Vacuum Controlled Atmosphere Furnace Using Continuously Produce Nanomaterials

In recent years, a great of interests in wide band gap semiconductor of SiCquasi-one-dimensional nanomaterials have been attracted due to their distinctivemorphologies, novel properties and the great potential application in the optical,electrical and mechanical field. In this paper, the synthesis and microstructures of SiCquasi-one-dimension nanomaterials were studied systematically. Furthermore, duringthe fabrication experiment of SiC nanomaterials we find that the controlled atmospherefurnace usually has one oven, which has low efficiency and waste quantity of energy.So we design the three-oven controllable atmosphere furnace using continuouslyproduce nanomaterials. The main results are as follows:Theβ-SiC nanobelts with median ridge were synthesized for the first timethrough a solid-vapor-solid process using a mixture of milled Si and SiO₂ powders andC₃H₆ as the raw materials by chemical vapor reaction method in a vertical tube furnacewith graphite heater. Their microstructures were characterized by scanning electronmicroscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM),selected-area electronic diffraction (SAED) and high-resolution transmission electronmicroscopy (HRTEM). The results show that theβ-SiC nanobelts have obviousmedian, the lengths ofβ-SiC nanobelts are up to several tens of micrometers, and thetypical widths of the nanobelts are in the range of 1～1.5μm with thickness of about10～20nm. The surface of SiC nanobelts is fiat and the fringe is uniform along theirlength. These nanobelts are cubic structureβ-SiC single crystalline. A two-step growthprocess is proposed to account for the formation ofβ-SiC nanobelts with median ridge. Theβ-SiC coaxial nanocables with amorphous SiO₂ wrapping layers have beensynthesized at relatively low temperature by chemical vapor reaction in a homemadegraphite reaction cell by controlling the rate of Si and SiO₂ powders and otherpreparation conditions. Their microstructures were characterized by using a digitalcamera, SEM, TEM, EDX and XRD. The analysis results show that the center thinnernanowires of the coaxial nanocables are cubic structureβ-SiC single crystal core witha uniform diameter of 10～60nm, whereas the outside wrapping layer of the coaxialnanocable is an amorphous silicon oxide with tens of nanometers in thickness, andtheir lengths are up to several tens of micrometers. The vapor-liquid-solid (VLS)mechanism was proposed to elucidate the growth process ofβ-SiC/SiO₂ coaxialnanocables.The vacuum controlled atmosphere furnace using continuously producenanomaterials is made up of the furnace body, the heater, the heat preservation parts,the vacuum system, the seal system, the hydraulic pressure system, the water-coolingsystem, the providing vapor system, the control system, and other auxiliary parts. Thefurnace body is divided into three ovens, i.e. feeding, reacting and discharging. Theheat preservation and sealed transfer zones are provided between reacting oven andfeeding oven, and between reacting oven and discharging oven. So both the input andoutput of raw materials and products can be operated under thermal reaction cell,avoiding the rise and fall of temperature in the atmosphere furnace repeatedly.Therefore, only one process of rising temperature is enough to keep producing, whichincreases the production efficiency, decreases the cost of raw materials, and savesenergy, at the same time, the purity and quality of the production are guaranteed.Accordingly, the separation of physical place and superposition of time of the threeprocesses which are called input, reaction and output for short are realized.The vacuum controlled atmosphere furnace using continuously producenanomaterials has been designed and the ichnographies of the parts have been drawn.The structure sculpting and dynamic simulation have been finished by usingthree-dimensional simulation software Pro/Engineer and the dynamic simulationsoftware 3ds max, which greatly improves the designing level and efficiency andfurther confirms the correct theory and dependable design. This design successfullycombines the traditional design with the three dimensional simulation and processdynamic simulation design, which shortens design cycle, reduces design cost and fullymanifests the synchronization modern design idea of the design and the manufacture.In a word, the fabricatedβ-SiC nanobelts with median ridge andβ-SiC/SiO₂coaxial nanocables have great promising applications in field emission devices,nanoscale optoelectronic devices and nanocomposites. The design of vacuumcontrolled atmosphere furnace using continuously produce nanomaterials in this paper has obvious ingenuity in the processing technology areas of the nanomaterialsfabrication through vapor-phase method. So we have put in for invention patent onNovember eighth, 2006, the invention patent number is CN 200510104486.4.