Preparation And Properties Of Ti₃C₂T_x Reinforced Silver Matrix Composite Electrical Contact Materials

Ag-based electrical contacts are extremely important components in the low-voltage switch system,affecting the operation and safety of the entire system.Since the last century,Ag/Cd O with excellent performance has been widely used in the industry.However,with the urgent global demand for environmentally friendly materials,the production and use of Ag/Cd O electrical contacts that generate harmful Cd vapor during service have been gradually restricted by various countries.Because of its excellent electrical and thermal conductivity,two-dimensional derivative Ti₃C₂T_x of Ti₃Al C₂ is expected to replace Cd O as the reinforcing phase of silver-based electrical contact materials and enter commercial applications.In this paper,based on chemical etching methods,by changing the process parameters,preparing Ti₃C₂T_x and adjusting its structure,the effect of structure evolution on the structure and performance of Ag/Ti₃C₂T_xcomposite electrical contact materials is investigated.Based on the synthesis of phase-pure Ti₃Al C₂ parent material（≥97%）by pressureless sintering technology,a chemical etching method is used to prepare Ti₃C₂T_xpowders with different structures and surface functional groups by controlling the etching time.As the etching time increases,the powder gradually transforms from three-dimensional Ti₃Al C₂ to a mixed structure combining two-dimensional and three-dimensional（0.5h-pe Ti₃C₂T_x,1h-pe Ti₃C₂T_x）,and finally into a two-dimensional sheet multilayer structure（6h-pe Ti₃C₂T_x and 12h-pe Ti₃C₂T_x）.Ag/10wt.%Ti₃Al C₂,Ag/10wt.%xh-pe Ti₃C₂T_x（x=0.5,1,6,12）composites were successfully prepared,and the influence of the reinforced phase structure on the structure and properties of the composites at different sintering temperatures were also explored.With the increasing etching time,the reinforcing phase in the Ag matrix gradually evolved from a spherical shape to a ribbon shape.In the process of gradually changing the structure of the reinforced phase material from mixed structure combining two-dimensional and three-dimensional to a two-dimensional multi-layer structure,the peeling of the Al atomic layer causes the irregular density changes of the Ag-based composite material;the structural change of the reinforced phase material also leads to a decrease in hardness and tensile strength;the intrinsic conductivity of Ti₃C₂T_x is better than Ti₃Al C₂,leading to a decrease in the resistivity of the composite material.The Ag-Al interface diffusion damages the resistivity of the composite material during the rising temperature,but it is beneficial to the improvement of hardness,tensile strength and elongation.A comprehensive comparison shows that Ag/0.5h-pe Ti₃C₂T_x prepared at 800℃has an excellent comprehensive performance,taking account of electrical conductivity and mechanical properties.Its resistivity is as low as 27.87×10^-3μm·Ω,and its hardness and tensile strength are 124 HV and 153.87 MPa,respectively.Preferably,Ag/0.5h-pe Ti₃C₂T_x and Ag/12h-pe Ti₃C₂T_x composite bulk materials are tested for arc erosion resistance under national standard conditions（GB/T 14048.4-2020,400V/100A/AC-3）.Compared with the Ag/12h-pe Ti₃C₂T_x electrical contacts（4782failures,not up to the standard）,the Ag/0.5h-pe Ti₃C₂T_x electrical contacts have an effective operation of 7458 times（over the standard 6000 times）.After arc erosion,the surface of the Ag/0.5h-pe Ti₃C₂T electrical contact is flat,and the oxidation products are significantly reduced compared to the Ag/12h-pe Ti₃C₂T_x electrical contact.This is mainly due to the effectively restricting of Ag-Al by multi-dimensional mixed structure at high temperatures.Ti₃C₂T_x structure regulation improves the organization and performance of Ag/Ti₃C₂T_x composites.Although there is still a gap between the arc erosion resistance of Ag/Ti₃C₂T_x electrical contacts and that of Ag/Ti₃Al C₂ electrical contacts,it provides a way for the composition design and performance optimization of environment-friendly new electrical contact reinforcing phase material in the future.