Narrow Results

Partially aligned and oriented polyacrylonitrile(PAN)-based nanofibers were electrospun from PAN and SWNTs/PAN in the solution of dimethylformamide(DMF) to make the carbon nanofibers. The as-spun nanofibers were hot-stretched in an oven to enhance its orientation and crystallinity. Then it were stabilized at 250 °C under a stretched stress, and carbonized at 1000 °C in N₂ atmosphere by fixing the length of the stabilized nanofiber to convert them into carbon nanofibers. With this hot-stretched process and with the introduction of SWNTs, the mechanical properties will be enhanced correspondingly. The crystallinity of the stretched fibers confirmed by X-ray diffraction has also increased. For PAN nanofibers, the improved fiber alignment and crystallinity resulted in the increased mechanical properties, such as the modulus and tensile strength of the nanofibers. It was concluded that the hot-stretched nanofiber and the SWNTs/PAN nanofibers can be used as a potential precursor to produce high-performance carbon composites.

The WC–Co nanocomposites were synthesized by using a polymer precursor such as polyacrylonitrile, which severs as an in situ carbon source. The WC–Co nanocomposites formed are characterized by X-ray diffraction and electron microscopy. Nearly pure WC–Co nanocomposites with a particle size in the range of 60–80 nm have been obtained. The use of H₂ atmosphere enhanced the carbide formation and in turn reduced the reaction time (at high temperature). The phase purity of the products is strongly influenced by the processing conditions such as the firing temperature, time and atmosphere. This suggests that the process parameters have to be optimized before scaling up the process for commercial production.

One-step preparation method of metal-carbon nanocomposites based on bimetallic Co–Ru nanoparticles supported and IR carbonized polyacrylonitrile was proposed. IR pyrolysis of the precursor based on joint solution of polyacrylonitrile and metal compounds leads to the simultaneous formation of carbon support and bimetallic metal nanoparticles. The metal reduction occures due to the release of hydrogen during decomposition of backbone polymer chain. Furthermore, IR radiation shortens fabrication time significantly. It was shown that the presence of cobalt and ruthenium in the system provides the creation of alloy Co–Ru nanoparticles. In addition, cobalt provides a formation of structured carbon shells around bimetallic nanoparticles. The nanocomposites were tested as catalysts for the hydrogen production through ethanol steam reforming. The dependence of structural and functional properties on the metal loading was demonstrated. The high yield of hydrogen was recorded for all three samples, whereas the by-product yield was relatively low.

As a membrane process between ultraflitration (UF) and reverse osmosis (RO) nanofiltration is widely used in wastewater treatment, dye separation and desalination for its energy-efficient process. Layer-by-Layer (LbL) self-assembly technique is one of effective approaches to nanofiltration layer on support membrane via alternate deposition of building blocks by various non-covalent interactions. In order to extend the applications and improve the performance of LbLnanofiltration membrane, we induce organic-inorganic hybrid nanoparticles as the building block to fabricate nanofiltration composite membranes and focus on the effect of hybrid nanoparticles on self-assemble behavior, membrane structure and separation performance. Atom transfer radical polymerization (ATRP) initiator is anchored onto the surface of silica nanoparticles and initiate polymerization of N, N-dimethylaminoethyl methacrylate (DMAEMA). The PAN-based composite membranes are fabricated by LbL assembling of quaternized PDMAEMA@ SiO₂ (PMETAI@SiO₂) nanoparticles and PAA on hydrolyzed PAN ultrafiltration support membranes. The results indicate that the water flux has a maximum value with pH varying from 2.0 to 6.5. On the other hand, it shows opposite tendency with the increase of ion strength. The membrane exhibits high rejection of Congo red, which is contributed to small pore size and Donan effect.

Partially aligned and oriented polyacrylonitrile(PAN)-based nanofibers were electrospun from PAN and SWNTs/PAN in the solution of dimethylformamide(DMF) to make the carbon nanofibers. The as-spun nanofibers were hot-stretched in an oven to enhance its orientation and crystallinity. Then it were stabilized at 250 □ under a stretched stress, and carbonized at 1000 □ in N₂ atmosphere by fixing the length of the stabilized nanofiber to convert them into carbon nanofibers. With this hot-stretched process and with the introduction of SWNTs, the mechanical properties will be enhanced correspondingly. The crystallinity of the stretched fibers confirmed by X-ray diffraction has also increased. For PAN nanofibers, the improved fiber alignment and crystallinity resulted in the increased mechanical properties, such as the modulus and tensile strength of the nanofibers. It was concluded that the hot-stretched nanofiber and the SWNTs/PAN nanofibers can be used as a potential precursor to produce high-performance carbon composites.