The Research On Functional Applications Of Gallium-Based Liquid Metals

As an emerging high-tech material,liquid metal with both fluid and metal characteristics not only derives many rich and unique physical and chemical properties,but also provides a vast research space for the exploration of science and technology.And it has made a series of breakthrough achievements in the fields of chemistry,biology,materials,physics,modern electronic engineering and additive manufacturing in recent years,known as"the second revolution of human utilization of metals".Expanding the cross-fertilization with different fields based on the profound understanding of physical and chemical properties of liquid metals and solving the problems existing in other fields are the issues that need to be faced and considered for the future development of liquid metals.Based on the excellent flexible conductivity,self-healing ability,fluid properties and catalytic properties of dynamic metal atoms,the application advantages of gallium based liquid metal in flexible electronic devices,metal-polymer functional elastomers and organometallic catalysis are explored in detail in this paper.The problems of mechanical damage of electrodes in flexible electronic devices,complex technology of constructing three-dimensional elastic conductive network and metal catalyst passivation are improved.The main research contents are as follows:(1)One kind of room-temperature self-healing elastomer(SH-PDMS,repair efficiency of 95%at 6 h)with imine bonds as repair crosslinking points is designed,and a highly self-healing electret nanogenerator(SENG)is constructed by combining liquid metal with SH-PDMS substrate through a simple coating process.Benefited from the flexibility of liquid metal,the composite electrode has the advantages of mechanical tolerance,deformation conductivity stability and substrate binding ability.And these advantages can prevent the performance degradation of flexible electronic devices caused by electrode peeling.With the synergy of the instantaneous healing ability of liquid metal and room temperature self-healing elastomer SH-PDMS,SENG can recover its initial performance and maintain stable signal output performance even after multiple mechanical damages by repairing itself.This greatly extends the service life of the device.In addition,the preparation and application of SENG are diverse and flexible.It can not only transform mechanical energy into electrical energy to power microelectronic devices,but also be used for physical signal detection,such as the human body movement and even weak pulse beat.(2)Based on the fluidity and microsphere expansion properties of liquid metal,this chapter proposes a new strategy to build a lightweight conductive liquid metal elastomer from inside out in one step to solve the problems of tedious preparation process,difficult formation of conductive network,high metal consumption and heavy device mass of metal-polymer composite conductive elastomer.By heating the composite precursor of liquid metal and microspheres at a fixed volume,the microsphere will expand and squeeze the liquid metal to flow and fill the gap between the microspheres.Meanwhile,the contact part between the microspheres will also be plasticized and achieve one-step construction of a metal polymer bicontinuous three-dimensional network skeleton.Moreover,a force-resistance sensor and a finite element simulation system are used to explain how a liquid metal conductive network is formed in the polymer phase and how the formation of a three-dimensional conductive network is influenced by the internal mechanical sintering force and the liquid metal content generated by the microsphere expansion.This strategy is not only simple and universal(other types of low-melting point liquid metals are also suitable,such as gothium,Wood alloys and Field alloys),but also requires only 3 vol%liquid metals to build a metal-polymer double continuous three-dimensional network skeleton structure in one step(density<0.3g/cm~3,and the conductivity of 4 vol%liquid metal can reach 3.8×10~4S/m).This is much better than the currently reported liquid metal elastomers(which usually consume>40 vol%liquid metal).By selecting the appropriate metal,the rigidity and shape memory function of the foam can be adjusted by changing the temperature.Based on the characteristics of lightweight,reversible rigidity regulation,simple process,low cost,stable mechanical properties and electrical conductivity,this functional conductive elastomer has shown strong application value in different fields of life.(3)In order to solve the problems of low catalytic site density and poisoning inactivation of solid-phase metal catalysts,this chapter proposes a mechanical ball milling method to assist liquid metals to catalyze organic molecule C-C coupling to prepare functional polymers,based on the physical properties and metal activity of liquid metal flow.Through orthogonal experiments and finite element simulation simulation,the catalytic advantages of liquid metal flow catalysts are proved.Under the mechanical force,liquid metal catalysts are not only easily broken into countless nanoparticle to increase the reaction interface with the reactant;but also the interface of nanometal flow can accelerate the adsorption rate of the catalytic interface and improve the reaction rate.In addition,based on the advantages of mechanical chemistry and gallium-based liquid metals,a series of functional organic polymers that are difficult to prepare by solution have been successfully prepared.And a reasonable catalytic mechanism is proposed through the study of product structure analysis and reaction process.The prepared functional polymers have shown certain application values in the fields of lithium-ion batteries and fluorescence luminescence.Importantly,the use of liquid phase metal catalysts in organic synthesis not only improves the shortcomings of solid phase metal catalysts,but also makes people have a new understanding of homogeneous catalytic system.In summary,this thesis explores the application and significance of liquid metals in different fields based on the in-depth konwledge of their physical and chemical properties.It not only breaks the boundaries between disciplines and promotes the development and converegence of multiple disciplines,but also provides guidance for the application expansion of new materials.