Preparation Of Electrospinning Nanofiber Composites And Research On Multi-band Electromagnetic Shielding

In recent years,with the incessant blossom of electronic science and technology,Electronic technology/equipment is widely used in all fields.But while we are enjoying the various conveniences that these bring us,due to the development of wireless electronic devices in the direction of intelligence,high frequency,density and multi-function,these electronic devices inevitably produce intertwined and different frequencies electromagnetic radiation/interference（EMI）during operating,which not only impacts the normalcy of delicate electronic fixing,the safe transmission of communication information,but also directly affects people’s health.Therefore,EMI shielding materials have become a research hotspot under the background of the rapidly developing information age.Although many successes have been realized,most of these lightweight and flexible EMI materials concentrate on the SE of single-band.In fact,sensitive electronic devices,used in practice,and human beings usually suffer the threatens from double-or multiple-bands of EMI.For example,human healthcare diagnose in hospital suffers the threaten from microwaves,X-rays,andγ-rays.Biotic tissue will be damaged by UV irradiation and high-energy microwaves.Therefore,the research of shielding materials with efficient,multi-band EMI shielding properties is very necessary.However,how to integrate multi-band shielding materials together effectively and exert the effect of 1+1 greater than 2 remains a great challenge.Based on the above content,this thesis uses electrospinning technology,hydrothermal synthesis,chemical deposition,ion exchange and other methods,and through the rational selection of functional materials,a series of composite nanofiber membranes have been prepared.And by adjusting the composition,morphology,construction of heterojunction/Schottky,synergy between components and thickness of materials,the electromagnetic shielding performance of the material in each wavelength band is improved.The details are as follows:1.Ternary PAN/Zn S/Ag₂S composite nanofibrous membranes（NMs）with efficient X-ray shielding properties were prepared by ion exchange reaction and electrospinning.The bilayer continuous Zn S shell and Ag₂S shell and the heterojunction contact between the double shells endow the PAN/Zn S/Ag₂S NM with high photoelectric effect and low Compton scattering,enabling the NM to achieve efficient X-ray shielding.Compared with the almost X-ray shielding disability of a single shell,the PAN/Zn S/Ag₂S composite nanofiber membrane exhibits a huge X-ray shielding advantage due to the cooperative effect between the components.The attenuation ability of PAN/Zn S/Ag₂S NM to X-ray is stronger than other common shielding materials（aluminum,lead and silver foils）,and its shielding ability gradually increases with the increase of thickness.When the thickness of PAN/Zn S/Ag₂S NM is 1.0 mm,the X-ray attenuation rate of PAN/Zn S/Ag₂S NM is as high as 93.8%at 30 ke V,showing excellent X-ray shielding ability.The PAN/Zn S/Ag₂S NM exhibits strong temperature tolerance from-196°C to 368°C,and still maintains good flexibility while achieving high-efficiency X-ray shielding performance.2.In order to achieve multi-spectral EMI shielding performance,we have prepared ternary P-W₁₈O₄₉-Ag composite nanofibrous membrane with strong multi-spectral EMI shielding ability（shielding bands covers microwave,infrared,and very short-wave X-ray）by solvothermal,electroless plating and electrospinning methods.The Schottky contact between the continuous bilayer(W₁₈O₄₉shell and the Ag shell)endows the P-W₁₈O₄₉-Ag NM with high photoelectric effect and low Compton scattering for efficient X-ray shielding.When the thickness of P-W₁₈O₄₉-Ag NM is 1.92 mm,the X-ray attenuation of P-W₁₈O₄₉-Ag NM is 99%at 30 ke V,and it drops to 30.6%at 100 ke V.Due to high electrical conductivity(～30400 S cm^-1)and porous structure,P-W₁₈O₄₉-Ag NM exhibits high shielding ability against microwaves（8–26.5 GHz）when the composite film thickness is 0.11 mm.In the full microwave band,the average EMI SE is 90.6 d B,and the highest EMI SE can reach 100.9 d B.The composite film also has good infrared stealth ability,which can achieve infrared shielding in a wide infrared region（2.5-20μm,15～150 THz）.Blend with the background.The micro/nano-scale pore structure,the air within the pores,and the nano-scale polymer（PAN）core enable the P-W₁₈O₄₉-Ag NM to have extremely low thermal conductivity(～0.11 W m^-1 K^-1),effectively reducing the the thermal conductivity of the composite film.It is worth noting that the composite membrane still exhibits good flexibility while achieving robust temperature tolerance from-196°C to 385°C.These remarkable features give our composite films great potential for building multi-band electromagnetic shielding materials at harsh temperatures.