Preparations And Characterization Of Several Carbon Nanotubes Composites And The Relative Applications

Nano technology is one of the most important technologies in the21century. Carbon nanotube(CNTs) has been paid much attention for its excellent properties and abroad application potential. As a new one-dimension material, CNTs exposed more excellent properties than traditional materials, which have the potential to be the ideal reinforce filler of advanced composite. Great research of CNTs reinforced polymer matrix or inorganic matrix composite has been done in recent years, which acquired a lot of achievements.To make a focused research on the preparation and its properties of CNTs compound with polymers or metals, the main work of this paper include the surface modification of CNTs and its compound with resin and silver in order to improve the mechanical and electronical properties of epoxide resin. The effect of CNTs and its compound with micro/nano iron powder on metal injection molding is researched. The rheological properties are evaluated to resolve some of the traditional problems in MIM industry.The main results can be summarized as follows:1. Prepared by ultrasonic and vacuum casting, CNTs can enhance the mechanical and electronical properties of epoxide resin with the content no more than1.7wt%. When CNTs content is0.75wt%, the tensile-strength, tensile-modules and the fracture extensibility of the composite increase18.2%,16.1%and85.5%respectively. The broken energy is absorbed by three parts, one is pulling Cnts out, the other is broken Cnts and the last one is debonding of Cnts and matrix. The values of the three parts are5kJ/m,1.1kJ/m2and0.18kJ/m2, respectively. Micro structure observation shows that with the adding of CNTs, the fracture surface of composite become more and more coarse, and the crack can not expand through the sample very easy. For these reason, the composite gains enhanced mechanical properties. The electron resistance drop down and two seepage threshold values appear when the content of CNTs is0.3wt%and1.1wt%.2. Additives of SDB is used to improve the separation of CNTs. Adding2.25wt%SDB can help to increase the tensile-strength, tensile-modules and the fracture extensibility of the composite by21.4%,26.0%and40.7%respectively. The two seepage threshold values appear when the additives content is0.4wt%and2.25wt%. Microstructure shows that after treated by additives, the CNTs disperse much better, the cracks expand even harder, and a dimple-like fracture shape appears.3. Two kinds of Ag/C compound nanotube are prepared by ball milling and chemical plating. When the milling-tube is25wt%, the tensile-strength, tensile-modules and the fracture extensibility of the composite increase19.6%,16.6%and15.3%. The seepage threshold values appear when the content is15wt%and31wt%. When the plating-tube is20wt%, the tensile-strength, tensile-modules and the fracture extensibility of the composite increase34.1%,33.3%and19.3%. The seepage threshold values appear when the content is llwt%and25wt%. Compared with milling Ag/C nanotube and pure CNTs, plating Ag/C nanotube can increase the mechanical and electronical properties to a greater extent for the reason that the plating nanotube can achieve a more uniform silver coat around CNTs, which will double the reinforce effect of the fillers.4. Micro iron/CNT compound powder is prepared by mechanical alloying and the traditional binder system was optimized. Proper content of the compound powder was added into optimized binders to prepare micro iron MIM feedstock. Study shows that the compound powders can increase the iron separation in the binders and improve powder loading to54vol%, of which the viscos activation energy E and strain sensitive factor n are16.5kJ/mol and0.39respectively. IR analyze shows CNTs can open the C=O bond, improve the connection of powders with binders.5. Nano iron compound CNTs is prepared by ultrasonic dispersing and mechanical alloying. Adding this compound powders with the ratio of nano iron and CNTs of20:1into traditional micro iron MIM feedstock can help to increase the powder loading to58vol%with the best rheological properties, when the viscos activation energy E and strain sensitive factor n are14.79kJ/mol and0.2and the micro structure has the lest defect. The compound powder can add some functional group on the benzene molecular, which can combine with other binders to improve the strength of the green product. Besides, it can strength connection effect of particles and binders, which to prevent the separation of particles and binders in MIM procedure.6. The toal nano iron powder MIM feedstock with CNTs is prepared and the related properties have been studied for the first time, which shows a pseudo-plastic behavior similar as micro iron feedstock. But, nano iron feedstock has a higher viscosity than that of micro iron feedstock in the same temperature or shear rate for its high surface area. When powder loading is35vol%, the viscos activation energy E and strain sensitive factor n are15.87kJ/mol and0.2. Calculation shows that feedstock system can reach the energy balance when the particle diameter is40nm and the powder loading is around33vol%, which is according to the experimental results.7. Thermal analyze of the total nano iron MIM feedstock with CNTs shows that the degrease stage has two steps, one is the PW decomposition with the weight lose of16wt%, the other is EVA decomposition with weigh lose of6%. This grease pattern can be applied into the real MIM operation.