Study On The Fabrication And Properties Of Carbon Nanotubes/Aluminum Foam Composites

The aluminum?Al?foam can be used in the fields of aerospace,automobile and other industries due to its advantages of light weight,energy absorption,damping and sound absorption.However,the Al foam has some defects such as low strength and limited energy absorption capacity,which limits its extensive applications.Since the discovery of carbon nanotubes?CNTs?,they have been considered as ideal reinforcements of composite materials because of their light weight and excellent mechanical properties.Therefore,some researchers have explored CNTs reinforced Al foam composites to improve the mechanical properties of Al foams by the strengthening and toughening roles of CNTs.But the properties of the CNT/Al composite foams have not achieved the desired effect yet.There are still some problems such as the uneven dispersion of CNTs in the matrix and the limited improving degree of the mechanical properties and the low energy absorption efficiency of the composites.Thus,there is great significance to investigate the fabrication process and properties of the CNT/Al composite foams further.In order to improve the energy absorption and damping properties of CNT/Al composite foams,a process was designed and realized,that combined powder metallurgy,chemical vapor deposition?CVD?and the space-holder technique to fabricate novel CNT/Al composite foams.The influences of pressing pressure,process parameters to synthesize CNTs,pore forming methods on the preparation of CNT/Al composite foams were investigated.The energy absorption and damping properties of the CNT/Al composite foams were mostly analyzed.The study on the pressing pressure of the cold pressing process showed that,under the condition of 400MPa,the Al foam with strong binding ability and good compression performance could be obtained.After the removal of pore forming agent by dissolution-sintering method,under the conditions of adopting NiO as catalyst precursor,the synthesis temperature of 550°C and the Ni contents of 0.3wt.%,mesh CNTs with good morphology and high degree of graphitization were synthesized in-situ in the holes of Al foam by CVD.When the strain is 0.7,the energy absorbing ability of CNT/Al composite foams reached 47.3MJ/m³,compared with NiO/Al composite foams and pure Al foams,improving by 27.2%and 79.1%,respectively.Using the method of direct sintering and NiO as the catalyst precursor,the ideal temperature and catalyst content to synthesize CNTs were:550?and 0.2wt.%Ni.The energy absorbing ability of CNT/Al composite foams reached 46.5MJ/m³ at strain of 0.7.When using Ni?NO₃?₂ as the catalyst precursor,the optimal CVD parameters for the synthesis of CNTs were 550?and 0.3wt.%Ni,and the energy absorbing ability of CNT/Al composite foams was 16.8MJ/m³ at strain of 0.7.In comparison,CNT/Al composite foams fabricated by the dissolution sintering method and NiO as the catalyst precursor have better energy absorption property.The study on the damping properties of CNT/Al composite foams by single cantilever method in low frequency showed that,when the strain was 4.7×10^-4,damping values of CNT/Al composite foams reached 0.058;compared with NiO/Al composite foams and pure Al foams,the peak value of the internal friction peak of CNT/Al composite foams increased by 12.9%and 22.8%,respectively.