| Metal matrix composites?metal matrix composites?are composite materials with excellent properties obtained by mixing metals with other materials.The application of such materials is not only cost-effective,but also more suitable for a wider range of applications.Traditional metal matrix composites,because they cannot adapt to the harsher environments,will inevitably limit their practical applications.However,they combine the intrinsic physical properties inherent to metal substrates and their own high-performance reinforcing phases,such as CNTs?Carbon Nanotubes,CNTs for short?,carbon fibers.Ceramic materials,etc,can not only overcome the various problems faced by the current metal matrix composite materials,but also may be applied to high-tech fields.Adding the reinforcing phase to the metal matrix can greatly increase the hardness,tensile strength,elastic modulus,and other mechanical functions of the composite.In addition,the material's current-carrying limit,thermal conductivity and field transmitter energy will also be increased.The CNTs-reinforced metal matrix composites still have some problems of large-scale production and application,mainly including the following two points:1.The complete average separation of CNTs in the metal matrix;2.The high-quality joint status between the CNTs and the metal matrix.For this reason,the metal matrix composite material that simplifies the process flow and adapts to the development needs still has application prospect and research space.In this paper,combining three kinds of metal matrix composites,using different experimental methods and post-processing techniques.we obtained the results of three kinds of metal matrix composites in terms of electrical function,thermodynamic function and field emission performance.The following will briefly explain three Experimental results and conclusions of a kind of metal matrix composites.The first is a composite of CuNWs?Copper Nanowires?and CNTs.The composite film has the electrical properties of CuNWs and the mechanical properties of CNTs.The suitable composite film has excellent current-carrying limit,which is of great significance for the research of CNTs-enhanced Cu composite film materials.Theoretically,the electrical properties of composites are mainly affected by the composite composition and distribution ratio.Using the single variable method,the effect of reaction time,the purity of sodium hydroxide,the content of ethylenediamine and the reaction temperature of the water bath on the aspect ratio of CuNWs was analyzed.The increase in conductivity of CNTs was analyzed.The effects of sintering temperature,homogenization,annealing and mechanical reduction on the electrical properties of CNTs were investigated.After optimizing the CNTs and CuNWs,a series of composite films with different ratios of CNTs and CuNWs were prepared and the electrical functions of the composite films were experimentally demonstrated.The results showed that the conductivity of CuNWs was the best when the reaction time was1 h,sodium hydroxide was good in analytical grade,the content of ethylenediamine was1 mL and the water bath temperature was 70°C.When the sintering temperature was normal temperature,the homogeneous pressure was 500 MPa.The conductivity of CNTs is best when the quality is 3 times,the annealing temperature is 500°C,the holding time is 1h,the pressing force is 6N and the pressing time is 10min.When the volume content of CuNWs is 49.04%,the composite film has the best conductivity and the most current-carrying performance.Well,they reached 9.58*10-5?*m and 159.09A/cm2,respectively.Followed by Tin powder?Sn Powder,referred to as Sn?and CNTs composite materials.In order to investigate the thermodynamic function of the composites,the composites of CNTs and Sn were obtained via ball milling sintering and the influence of the difference in CNTs mass fraction on the hardness and thermal conductivity of the composites was studied.The results show that when the mass fraction of CNTs is 10%.the hardness of the composite reaches a maximum value of 466.68 HV,which is approximately 37.8 times that of pure Sn and the thermal conductivity is 1 W/m*k,which is approximately 3%of pure Sn.Appropriate CNTs content and low temperature annealing have a significant enhancement effect on the composites:10%mass fraction of CNTs increases the hardness of Sn after sintering at 200°C,but it is not good for the thermal conductivity of composites.Finally,it is a composite material composed of an aluminum sheet?Al flakes,referred to as Al?and CNTs.The combined electrophoresis and laser welding processes achieved good physical adhesion between the CNTs and the metal substrate without a binder,thereby preparing field emission cathodes formed of CNTs and Al composite materials.The short-wavelength pulsed laser was used to perform 2d welding on the Al metal surface.Under appropriate laser parameters,the microscopic morphology was observed.It was explained that the appropriate laser energy intensity could cause the base metal to produce a solid-liquid phase transition and change the microstructure of the metal surface.So as to promote the basic integration of CNTs into the metal surface and achieve a stable nano-connection,thus forming a field emission cathode composite.Membrane field transmitter energy measurements were performed on this composite material,the on-voltage drop was about 60%and the emission current density showed a solid promotion.It is due to the rapidity,stability and purity of the laser that the interface impedance after processing is reduced as well as the electron emission is easier.The above studies on the relevant properties of the three metal matrix composites provide reliable reference value and practical application guidance for promoting the related applications and research of metal matrix composites. |
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