Low Temperature Synthesis And Property Research Of MAX Phase Solid Solution

The MAX phase material,as a new type of ceramic material,has attracted much attention from researchers.This material combines the comprehensive properties of metal and ceramics,such as:high strength,high hardness,good oxidation resistance,good electrical and thermal conductivity and thermal shock resistance,etc.,in electrical contact materials,nuclear reactors,armor protection,microwave absorbent materials,aerospace and other fields have broad application prospects.Ti₃Al C₂ and Ti₃SiC₂ are both MAX phase materials that have been intvestigated extensively at present.However,the traditional synthesis method usually uses high temperature conditions and high energy consumption,which is not conducive to inhibiting the formation of competing phases.The existence of the competitive phase will affect the performance of the material and reduce the service time.In order to realize the efficient use of materials,add to other atoms in the M and A positions of the MAX phase to form MAX phase solid solution is a good way to strengthen the material.In this paper,two methods of pressureless sintering and element replacement reaction were used to prepare Ti₃Al（Sn）C₂ solid solutions.The Ti₃Al（Sn）C₂ solid solution is prepared by pressureless sintering process using elemental element powder as raw material at 1400℃.The synthesized product contains a certain amount of impurity phase Ti C and incompletely reacted Sn element.The element replacement reaction is different from pressureless sintering.The sintering temperature of the element replacement reaction is lower,the energy consumption is small,and there is no formation of a competing phase in the product.The Ti₃Al（Sn）C₂ solid solution was prepared by element replacement reaction using Ti₃Al C₂ and Sn Cl₂ as raw materials at a low temperature of 600℃.And the focus is on the effect of different initial raw material ratios,different sintering temperatures,and different holding times on the phase composition of Ti₃Al（Sn）C₂ solid solution.Combined with XRD and DSC analysis,the synthesis route of Ti₃Al（Sn）C₂ solid solution prepared by element substitution reaction is studied.In addition,the cyclic oxidation experiment was used to study the effect of Sn doping on the high temperature oxidation resistance of Ti₃Al C₂.The influence of Sn doping on the electromagnetic shielding performance of Ti₃Al C₂ was also explored.At the same time,the above two methods are also used to prepare Ti₃Si（Sn）C₂ solid solution.The results show that the pressureless sintering method can increase the sintering temperature to promote the reaction.The Ti₃Si（Sn）C₂ solid solution prepared at 1450℃has the highest purity,and the maximum solid solution content of Ti₃SiC₂ synthesized by this method for Sn is obtained.However,the Ti₃Si（Sn）C₂ solid solution was not synthesized by the element replacement reaction,and the reason was analyzed simply.In addition,this article also carried out related research on the synthesize and properties of(Ti_1-xW_x)₃SiC₂ solid solution.The pressureless sintering process was used to synthesize(Ti_1-xW_x)₃SiC₂ solid solution with Ti powder,W powder,Si powder,and C powder as raw materials and Al powder as an additive at two different temperatures of 1400℃and 1450℃for two hours.As a result,it was found that increasing the sintering temperature promotes the complete reaction.The effect of different W addition amount on the phase composition and microstructure of the synthesized product of the sample was studied,and the results showed that the maximum solid solution amount of W was 0.05.When an excessive amount of W is added,the main phase in the product will change,and the impurity phase will also increase.In addition,this paper uses a cyclic oxidation experiment to study the effect of W addition on the high-temperature oxidation resistance of Ti₃SiC₂ at a temperature of 800℃.The results show that a proper amount of solid solution W will improve the high-temperature oxidation resistance of Ti₃SiC₂.At the same time,the influence of different W solid solution content on the conductivity of Ti₃SiC₂ was also explored.