Preparation Of New Electrospun Nanofibers And Their Cyanate Ester Resin Matrix Composites

The excellent designability and synergistic effects make the composites become the fourthindependent category of materials follow-up to the metals, ceramics and polymers. Furthermore,compared with the macroscopic composites, nano-composites have outstanding performancefrom unique dimensional effects, quantum tunneling effects, and surface effects, which canbreathe new life into the field of composites. The inorganic nanofibers/resin matrix composite isthe important part of nano-composites. The performance of nano-composite not only depends onthe inorganic nanofibers and resin matrix, but also is greatly related to nanofibers dispersion andinterfacial adhesion in matrix. However, the manufacture process of high quality inorganicnanofibers is too costly, the sort and production of commercial inorganic nanofibers is limited.Meanwhile, how to keep good dispersion and desirable interfacial bonding of inorganicnanofibers in resin matrix without structural damage of nanofibers is still a challenge. We focuson these problems from inorganic nanofibers/resin matrix composite’s field in this dissertation,and raise five questions about the nano-composites.First, the various electrospun composite nanofibers have been prepared with keycomponents of tetraethyl orthosilicate (TEOS), titanium butoxide (TNBT), or zirconiumpropoxide (ZNP) respectively. Then the chemical and morphological stability of compositenanofibers in the air has been investigated and studied systematically during the electrospinningprocess and storage periods. The results show that moisture in the air will interact with theelectrospun composite nanofibers, and made a significant impact on ultimate morphology andperformance of the nanofibers. Hence, how to remain morphology and chemical properties ofcomposite nanofiber unchanged before the next steps, such as calcination and soak, are the basicrequirements for preparation of inorganic nanofibers with high production at low-cost. Bychoosing components in the electrospun composite nanofibers, the TNBT and ZNP in compositenanofibers can complete reaction of hydrolysis and polymerization during the electrospinningprocess. As the result, the as-spun composite nanofibers have excellent chemical and morphologystability, which can remain their morphology even after stored in the standard environment for15days, showing great potential in the large-scale preparation. Second, the influences of low-cost post-treatment, such as calcination and soak, on thestructure and morphology of electrospun composite nanofibers (TNBT(HAc) and ZNP(HAc)),which use TNBT and ZNP as key components respectively, have been investigated. Theformation mechanism of the composite nanofibers with special structures is worth studying. Theresults of the research show that the low-cost post-treatment can not only prepare titanium oxide(TiO2) nanofibers with rough surface, but also fabricate fiber-in-tube, solid and pure rutile-phasestructure TiO2nanofibers with a few simple steps. Meanwhile, for TNBT and ZNP can quicklyhydrolyze and polymerize in the air, it can be used conveniently to prepare TiO2and zirconiumoxide (ZrO2) nanofibers with core-shell structures by coating hydrolysis and polymerizationproducts from TNBT and ZNP.Third, using zirconium alkoxides as the key components in electrospun precursor materials,ZrO2nanofibers with controllable chemical properties and morphology were prepared by a newmethod based on electrospinning and sol-gel technology. The ZrO2nanofiber/cyanate ester (CE)resin composites with comprehensive properties were prepared by dispersing ZrO2nanofibercongeries in CE resin matrix. Through a standard electrospinning device and muffle, the porousZrO2nanofibers with different pore sizes and crystal structures can be prepared by calcining theelectrospun composite nanofibers at different temperatures. The ZrO2nanofibers congeries fromelectrospinning has a special structure, in which the relative positions of ZrO2nanofibers arefixed during the preparation process of ZrO2nanofiber/CE composites. As a result, theaggregation of ZrO2nanofibers can be avoided, and good dispersion of ZrO2nanofibers in thecan be gotten, leading to form ZrO2nanofiber/CE composites with excellent performance.Fourth, ZrO2nanofibers coated with nano-SiO2particles (SiO2@ZrO2) have been designedand prepared. The SiO2@ZrO2nanofibers not only have surface functional groups which willreact with the CE resin, but also can produce non-chemical mechanical interlocking effectsbetween the nanofibers and CE resin. The influence of SiO2@ZrO2nanofibers on the structureand properties of the SiO2@ZrO2nanofibers/CE composites was studied systematically. Theresults indicate that the SiO2@ZrO2nanofibers can obviously raise the bonding performance ofinterface layers between nanofibers and resin matrix, and consequently, improving performanceof the composite materials.Fifth, the copper-calcium titanate (CCTO) nanofibers have been firstly prepared byelectrospinning technique. The compositions of electrospinning precursor solutions have beencarefully studied. And the CCTO electrospun composite nanofibers have been successfully prepared by adding modifier (HAc) into the precursor solutions. The post-treatment on CCTOcomposite nanofibers has also been examined to distinguish the influence of process parameterson the structure and morphology of CCTO nanofibers. In addition, the dielectric properties ofpure-phase CCTO nanofibers and CCTO/CE composites have been measured and calculated. Theresults show that pure-phase CCTO nanofibers have different dielectric properties from theCCTO bulk materials.