Fabrication And Application Of Oxide Nanofibers By Blow Spinning

Nanofibers have attracted significant attention due to their special structure and multifunction,and oxide ceramic nanofibers have been extensively applied in various areas by the intrinsic properties of oxide materials.An efficient,universal,low-cost and safe method for fabricating nanofibers plays a fundamental role in scientific research and industrial application.Herein,large-scale manufacturing and assembling of oxide ceramic nanofibers through an efficient and novel blow spinning process is reported.The oxide ceramic nanofiber sponges exhibited excited resilience at both room temperature and high temperature.Moreover,the oxide ceramic nanofiber films and sponges by blow spinning achieved multiple applications,such as elasticity-dependent electrical resistance,photocatalytic activity,thermal insulation,gas sensor and particle matter filter.The main contents of this dissertation include:A variety of oxide ceramic?such as TiO₂,ZrO₂,SnO₂ and BaTiO₃?nanofibers were fabricated by using a novel blow spinning method.The diameters of the TiO₂ nanofibers can be controlled from 35-800 nm.The Oxide ceramic nanofiber sponges with densities varying from 8-40 mg/cm³ can be controlled by an air-permeable cage-like collector,with the porosity above 99.7%.The blow spinning method can be further improved,such as using hot gas to help solvent evaporation,special collector to get aligned nanofibers and multi-needles to blow spinning.Furthermore,the industrial scale for fabricating oxide ceramic nanofibers was achieved.The light-weight oxide ceramic nanofiber sponges exhibit resilience at both room temperature and high temperature,which avoids the sensitivity and brittleness to flaws of the traditional oxide ceramic nanofiber.At room temperature,the TiO₂ nanofiber sponge exhibits a residual strain of only 13%after about 50%strain for 100 cycles at room temperature,a residual strain of only 5%after about 23%strain for 10 cycles at 400 ^oC.Furthermore,the ZrO₂ nanofiber sponge also shows good resilience even at 800°C and1300°C.The energy dissipation mechanisms and grain size relationship of the mechanical properties are studied in the dissertation.In situ uniaxial compression in an SEM showed the detailed changes of the oxide ceramic nanofiber sponge.And the oxide ceramic nanofiber sponge can serve many functions,such as elasticity-dependent electrical resistance,photocatalytic activity,thermal insulation,and gas sensor.Ultra-light and resilient Al₂O₃ nanotube sponges were prepared by using blow spinning method combined with ALD technology.The thicknesses of tube walls vary from 5-50 nm,and densities of Al₂O₃ nanotube sponges vary from 0.68-2.45 mg/cm³.The nanotube sponge exhibits optical semi-transparent,heatproof property,and low thermal conductivity with high porosity.The mechanical property of this novel nanotube sponge was studied,such as amorphous Al₂O₃ and?-Al₂O₃ nanotube sponges,exhibiting a residual strain of 20%after 40%strain for 100 cycles and 50%strain for 10 cycles respectively.By blow spinning technology,a highly efficiency particulate matter filter which can be used at both room temperature and high temperature with resilient YSZ nanofiber sponge was prepared.At room temperature,it has 99.4%filtration efficiency for NaCl aerosol particles with diameter size of 20-600 nm,98.75%filtration efficiency for 20 nm particle matter,under an airflow velocity of 4.8 cm/s.At 750 ^oC,the YSZ nanofiber filter exhibits 99.97%filtration efficiency for PM_0.3-2.5,and 99.98%filtration efficiency for PM_2.5-10,under an airflow velocity of 10 cm/s.The filtration efficiency and pressure drop were discussed.A practical vehicle exhaust filter to capture PM with>98%filtration efficiency was also assembled.The highly flexible ITO nanofiber transparent electrode films were fabricated by blow spinning.Transmittance and resistance vary with the thickness of the nanofiber film.For example,the ITO nanofiber film exhibits 81%optical transmittance with the sheet resistance of 304?/sq.Furthermore,the sheet resistance of the ITO nanofiber film only increased by 18.4%when the bending radius decreased to 0.5 mm,and the resistance is slightly changed after 1000 times of bending cycles at 3.5 mm bending radius.