Magnetocaloric Composite Materials And Polymer Electrolyte Based On Mesoporous Silica

Mesoporous silica materials have been widely used in material science,chemistry,biological sciences and many other fields.Because of a little of weak acid centers of mesoporous silica materials,they are almost catalytic inactive,so these cannot give full play to its superior performance as mesoporous materials.Therefore,by Embedding other atoms or atomic group into silica framework to form mesoporous composite material,or adding polymer to modified silica materials,they can broaden applied range of the mesoporous silica.Mesoporous silica become a hot issue in recent years.This dissertation studied silica and its modified materials from two aspects.In the first part,by using a certain amount of neutralβ-CD as stabilizing agent,high dispersionγ-Fe₂O₃ NPs with 16 nm can be prepared.High dispersionγ-Fe₂O₃ combined with Au nanoparticles（denoted asγ-Fe₂O₃-Au NPs）coated by mesoporous silica spheres（denoted as m-SiO₂）were synthesized by a facile one-pot method process.TEM images showed the ordered morphology,good dispersion,and uniform particle size ofγ-Fe₂O₃-Au NPs inside composite.Furthermore,XRD,M–H curves and N₂ sorption characterization etc confirmedγ-Fe₂O₃-Au@m-SiO₂ composite possessed good magnetic property,uniform mesoporous distribution and high surface area.The second aspect,through PVDF-HFP matrix and modified silica,we get functional nanocomposite gel polymer membrane SiO₂-SO₃Li/PVDF-HFP by using tape casting method.Above polymer membrane has important application in lithium ion battery and li-air Batteries.By SEM images,TEM images,elemental analysis,XRD,contact angle,electrochemical testing and battery test characterization methods,SiO₂-SO₃Li/PVDF-HFP membrane is uniform,and presents unique hexagonal porous channel.It possesses decreased crystallinity and increased amorphous area compared with PVDF-HFP membrane.This dramatically enhanced the segmental motion of polymer chains,which strengthened the movement of Lithium-ion.The ionic conductivity of SiO₂-SO₃Li/PVDF-HFP gel polymer electrolyte reached 7.64×10^-4 S.cm^-1 in 1 mol L^-1 LiTFSI/TEGDME and 2.58×10^-3 S.cm^-1 in 1 mol L^-1 LiPF₆/EC-DEC at T=20℃.The cell composed of SiO₂-SO₃Li/PVDF-HFP gel polymer electrolyte(1mol L^-1LiPF₆/EC-DEC electrolyte)showed 720 h of cycling at a current density of 0.5 mA cm^-2 in both directions for 1h which had a stable voltage response at 40 mV.The charging and discharging performance of the battery is superior to PVDF-HFP gel polymer electrolyte.