Research On Application Of Ti₃C₂-based Comosite Materials In Wave Aborption And Seawater Desalination

Increasing electromagnetic radiation pollution and scarcity of fresh water resources are important issues that all countries in the world need to face.Therefore,the exploration of efficient microwave absorbing materials and seawater desalination materials is becoming more and more important.Ti3C2Tx material has high electrical conductivity,nano-scale thickness,large surface area,high surface atomic ratio,increased dangling bonds,interface polarization and multiple scattering,these propertites have become important absorbing mechanisms and made the material expected to become an excellent absorbing material;Ti3C2Tx material has some properties that include unique two-dimensional(2D)structure,high hydrophilicity,selective absorption and high light-to-heat conversion efficiency(?100%),which make Ti3C2Tx material has broad research prospects in seawater desalination.In this paper,Ti3C2Tx is used as the starting material,using different oxidation conditions to prepare Ti3C2Tx/TiOx composite by in-situ oxidation.After that,the oxidation mechanism,dielectric properties and absorbing properties of Ti3C2Tx/TiOx composites were studied.Electrostatic bonding is used to combine Ti3C2Tx with melamine formaldehyde resin,and then through high temperature and pressure carbonization to produce C-coated N-Ti3C2Tx ceramic material.At the same time,explore the excellent structure of the material,seawater desalination performance,salt resistance and acid rain corrosion resistance.The main research contents of this paper are as follows:(1)Ti3C2Tx/TiOx materials prepared under different oxidation conditions reveal the oxidation mechanism of Ti3C2Tx materials through microstructure analysis.During the oxidation reaction,as the degree of oxidation increased,the oxidation zone is different.In the initial stage of oxidation,the oxidation is mainly concentrated on the surface of Ti3C2Tx material and the corresponding Ti atoms combined to produce TiO2 which is a relatively stable rutile crystal form;As the degree of oxidation increased,the Ti-C bond in Ti3C2Tx material is opened.And the oxidation zone mainly reacts with Ti atoms(Ti2)with lower binding energy,and then reacts with Ti atoms(Ti1)with high binding energy.This process requires a lot of energy,and the TiO2 material formed by oxidation is not enough to form a stable rutile phase.Therefore,it appears in the anatase crystal form until the Ti atoms are completely oxidized.(2)Ti3C2Tx/TiOx materials prepared under air oxidation conditions.It can be found that from the structure the generated TiO2 particles are agglomerated and have larger sizes.Most of them appear in bulk form to form 3D/2D heterostructures with Ti3C2Tx materials.And with the increase of the degree of oxidation,the Ti3C2Tx material structure collapses and breaks to form defects.As the oxidation continued,the absorption performance will first increase and then decrease.Oxidation in a tube furnace at 250? for 1 hour forming heterostructure has the best absorption performance.When the material thickness is 2.4mm,the reflectivity of 8.5-11.5GHz is less than-10dB.(3)Water oxidation is the most mild.The size of TiO2 particles generated at 35? are existing small(in the form of nano-dots)and 2D Ti3C2Tx materials form an 0D/2D heterostructure.As the temperature increased to 50?,the size of TiO2 increase and agglomerated,so the heterogeneous interface of TiOx/Ti3C2Tx composite material is obviously enlarged,which leads to the improvement of its dielectric properties and microwave absorbing properties.(4)It is found that in the oxidation process of hydrogen peroxide solution,its microwave absorbing performance is relatively poor under different concentration conditions.The main reason is that the lower concentration of hydrogen peroxide solution is oxidized,resulting in less TiOx material,and the imaginary part of the complex permittivity of TiOx/Ti3C2Tx composite material system is relatively high,so that the material itself does not meet impedance matching,so there are fewer electromagnetic microwave entering the material,and most of the electromagnetic microwave are reflected on the surface of the material,and the electromagnetic absorption performance is not good;As the concentration of hydrogen oxide solution increased,because hydrogen peroxide itself has high oxidation properties,it will oxidize Ti in Ti3C2Tx materials to other valence states,destroy the Ti3C2Tx structure,and greatly reduce the imaginary part of the complex permittivity of the TiOx/Ti3C2Tx composite system,so that the material itself reduces the loss of electromagnetic microwave.(5)The TiOx/Ti3C2Tx material prepared by oxidation under the condition of sodium hydroxide solution,the sodium ions in the sodium hydroxide solution enter the material system,and the conductive particles contact each other so that the material formed a conductive channel and increased the dielectric constant of the material.An excessively high imaginary part of the dielectric constant will increase the electromagnetic microwave loss of the material,but at the same time it will reduce the impedance matching of the material.It has the best absorption performance when the sodium hydroxide solution concentration is 1mol/L for 1 hour,and when the material thickness is 6.5mm,it has the best absorption performance.(6)C-coated N-Ti3C2Tx ceramic material has a unique 3D/2D structure,which increased the spacing and porosity between Ti3C2Tx layers to increase and improve the rate of water supply and salt ion reflux.C-coated N-Ti3C2Tx ceramic material has high light absorption efficiency(89%),low heat reflectivity(0.37),and low thermal conductivity(0.21 W m-1 k-1).The C-coated N-Ti3C2Tx ceramic material can show higher evaporation rate(1.39 Kg·m-2 h-1)and higher light-to-heat conversion efficiency(83%)under a solar intensity.Under the condition of low salt water concentration(3.5wt%-9.5wt%),the evaporation rate is still maintained at 1.33 Kg m-2 h-1 in 1 hour,which shows,low salinity tolerance;The evaporator of C-coated N-Ti3C2Tx ceramic material can work stably and efficiently under peak daylight conditions of 7 days and 5 hours.Under simulated acid rain conditions,the C-coated N-Ti3C2Tx ceramic material still maintains high evaporation efficiency(evaporation efficiency is only reduced by 0.064 Kg-m-2 h-1)under 1500mm rainfall.