Preparation Of Tungsten Nanowires And Nano-tungsten Carbide By Applying Mesoporous Carbon Nanotube As Template

Due to their excellent properties,tungsten(W)and tungsten based materials are considered as a kind of most important material in fields like industry,military and scientific research.However,the intrinsic brittleness of W restricts its further application.Fortunately,one-dimensional nano-W(W nanowire,Wn)could be the best choice of toughen phase for W and W based materials since it has excellent properties(higher elasticity modulus of 225±20 GPa,higher hardness of 6.2±1.7 GPa and higher strength of extension of 27.5?32.8 GPa).Whereas,a preparation method for Wn that no catalyst is involved and could realize large-scale preparation and morphology controllable has seldom been reported.Besides,as far as we know,as a kind of important industrial catalyst,nano-tungsten carbide is still unable to be prepared with controllable shape and size.In addition,another important nanomaterial-mesoporous carbon nanotubes(mCNTs)feature with unique mesoporous shell and hollow tube structure,which means materials could be adsorbed into the hollow tube via the mesoporous in the shell and controllable developed to be one-dimensional material.Therefore,mCNTs could be the ideal template to prepare one-dimensional nanomaterials.However,the intrinsic hydrophobicity of mCNTs limits its further application.Hence,we applied mCNTs as template to prepare Wn.Hydrophilia modification of the template was first processed on the premise of ensuring template's integrity.After that,filling of the template with AMT by wet chemical method and the hydrogen reduction of ammonium metatungstate(AMT)were studied systematically.W nanowire with controllable shape was successfully prepared and the preparation was no catalyst involved.Finally,Wn has been introduced to bulk tungsten as toughen phase,and it has been used as precursor to prepare nano W2C.This work includes:(1)Shell integrity of mCNTs has been kept while it has been modified to be hydrophilic successfully,mixture of strong acid,diluted HNO3,H2O2 and mixture of H2O2 and NH3 H2O were used as oxidizing agent and introduced different hydrophilic groups to mCNTs;(2)Based on the capillarity of mesoporous,property of AMT aqueous solution and filling mechanism of mCNTs have been studied systematically.First time realized the large-scale encapsulation of mCNTs at room temperature,and AMT nanorods/mCNT(AMTn/C)has obtained,which means AMT has been encapsulated into the hollow core of mCNTs at room temperature successfully;(3)X-ray diffraction,thermogravimetry-mess spectrum and filed emission scanning electron microscopy were applied in this part,AMT reduction process and the parameter impacts to product were studied systematically.Morphology controllable and non-catalyst involved mechanism of tungsten nanowires was proposed,and tungsten nanowires were first time prepared by no catalyst and morphology controllable method.Besides,output of tungsten nanowires could be enlarged for this preparation method;(4)W nanowires has been first time doped into bulk W,results revealed that morphology of W nanowire has been kept after sintering and the Wn crossed the grain boundary,which indicated that W nanowire could toughen bulk W,and preliminary property study of the doped bulk W confirmed this result.(5)tungsten nanowire/mCNTs(Wn/C)and tungsten nanodots/mCNTs(Wnd/C)have been used as precursor of nano-tungsten carbide,W2C nanorod and WC nanodot were obtained after the heat treatment of the precursors.It has been realized to controllable prepare nano-tungsten carbide and W2C nanorod was first time prepared.Besides,peroxidase-like property of the obtained nano-tungsten carbide was detected,especially the property of W2C was the first time to be detected and result reveal that it has excellent catalytic property.