• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.376-376
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• 2016

Poly(ethylene oxide) (PEO)/functionalized bacterial cellulose nanowhiskers (f-BCNW) (0.1 wt%) composite nanofibers were fabricated by electrospinning process and the thermomechanical properties were significantly enhanced more than the PEO and PEO/bacterial cellulose nanowhiskers (BCNW) (0.1 wt%) composite nanofibers. The functionalization of BCNW (f-BCNW) was performed by microwave plasma treatment for effects of nitrogen functionalization of chemically-driven BCNW. The N-containing functional groups of f-BCNW enhanced chemical bonding between the hydroxyl groups of the polymer chains in the PEO matrix and diameter size of PEO/f-BCNW (0.1 wt%) composite nanofibers were decreased more than PEO and PEO/BCNW (0.1 wt%) composite nanofibers on the same concentration. The strong interfacial interactions between the f-BCNW nanofillers and polymer matrix were improved the thermomechanical properties such as crystallization temperature, weight loss and glass transition temperature (Tg) compared to PEO and PEO/BCNW composites nanofibers. The results demonstrated that N2 plasma treatment of BCNW is very useful in improving thermal stability for bio-applications.

• Journal of the Korean Wood Science and Technology
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• v.42 no.2
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• pp.119-129
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• 2014

This work undertook to prepare nanofibers of cellulose nanofibrils (CNF)/polyvinyl alcohol (PVA) composite by electrospinning, and characterize the electrospun composite nanofibers. Different contents of CNFs isolated from hardwood bleached kraft pulp (HW-BKP) by 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-mediated oxidation were suspended in aqueous polyvinyl alcohol (PVA) solution, and then electrospun into CNF/PVA composite nanofibers. The morphology and dimension of CNFs were characterized by transmission electron microscopy (TEM), which revealed that CNFs were fibrillated form with the diameter of about $7.07{\pm}0.99$ nm. Morphology of the electrospun nanofiber observed by field-emission scanning electron microscopy (FE-SEM) showed that uniform CNF/PVA composite nanofibers were manufactured at 1~3% CNF contents while many beads were observed at 5% CNF level. Both the viscosity of CNF/PVA solution and diameter of the electrospun nanofiber decreased with an increase in CNF content. The diameter and its distribution of the electrospun nanofibers helped explain the differences observed in their morphology. These results show that the electrospinning method was successful in preparing uniform CNF/PVA nanofibers, indicating a great potential for manufacturing consistent and reliable cellulose-based nanofibrils for scaffolds in future applications.

• Polymer(Korea)
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• v.35 no.6
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• pp.605-609
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• 2011

Composite nanofibers were prepared by electrospinning and thermal treatment from poly (vinylidene fluoride) (PVDF)-$SiO_2$ blend solution. The nanofibers were stacked on layers to produce fully interconnected pores. TEM micrographs and EDX spectra confirmed the presence of $SiO_2$ in the composite nanofibers. The porosity of nanofibers was effectively enhanced by the introduction of electrospinning technique. ATR-FTIR and XRD results revealed that PVDF in the composite nanofibers exhibited the mixture crystal structure of ${\alpha}$-phase and ${\beta}$-phase. The crystal structure of ${\alpha}$-phase and crystallinity increased by the thermal treatment. In addition, the mechanical properties, thermal stability and hydrophobicity were markedly amplified by the thermal treatment.

• Membrane Journal
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• v.27 no.3
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• pp.284-289
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• 2017

In this study, natural clay as a filler was systematically integrated into polysulfone nanofibers to prepare polysulfone/clay composite membranes with mechanical properties. The composite nanofibers were formed by electrospinning of a mixed precursor of polysulfone and clay. The pore size of the composite membranes was adjusted by simply controlling the number of layers of nanofibers. The overall membrane properties were examined by SEM, contact angle, pore characteristics, tensile strength and water flux. In particular, the presence of clay within the nanofibers was confirmed with SEM images and the mechanical property of the composite nanofiber membranes was examined by tensile strength measurements. Thus, the prepared composite membranes were expected to be utilized for water treatment system.

• Fibers and Polymers
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• v.5 no.2
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• pp.105-109
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• 2004

The synthesis of titanium dioxide nanofibers with 200-300nm diameter was presented. The new inorganic-organic hybrid nanofibers were prepared by sol-gel processing and electrospinning technique using a viscous solution of titanium isopropoxide (TiP)/poly(vinyl acetate) (PVAc). Pure titanium dioxide nanofibers were obtained by high temperature calcination of the inorganic-organic composite fibers. SEM, FT-IR, and WAXD techniques were employed to characterize these nanofibers. The titanium dioxide nanostructured fibers have rougher surface and smaller diameter compare with PVAc/TiP composite nanofibers. The anatase to rutile phase transformation occurred when the calcination temperature was increased from $600^{\circ}C$ to $1000^{\circ}C$.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.3-6
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• 2003

In this work, poly(ethylene oxide) nanofibers were fabricated by electrospinning to prepare nanofibers-reinforced composites. And the PEO powders-impregnated composites were also prepared to compare with physicochemical properties of nanofibers-reinforced composites. Morphology and fiber diameter of PEO nanofibers were determined by SEM observation. Mechanical interfacial properties of the composites were investigated in fracture toughness tests and interlaminar shear strength (ILSS) test. As a result, the fiber diameter decreased in increasing applied voltage. However the optimum condition for the fiber formation was 15 ㎸, resulting from increasing of jet instability at high voltage and the prepared PEO nanofibers were useful in fiber reinforced composites. The PEO-based nanofibers-reinforced composites showed an improvement of fracture toughness factors ($K_{IC} and G_{ IC}$) and ILSS, compared to the composites impregnated with PEO powders. These results were noted that the nanofibers had higher specific surface area and larger aspect ratio than those of the powder, which played an important role in improving the mechanical interfacial properties of the composites.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.4
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• pp.171-175
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• 2005

A new type of supercapacitor was constructed by using carbon nanofibers (CNFs) and DAAQ (l,5-diaminoanthraquinone) oligomer. DAAQ was deposited on the carbon nanofibers by chemical polymerization with ammonium peroxodisulfate (($NH_4)_2S_2O_8$) as oxidant in the 0.1 M $H_2SO_4$. Polymerization reaction was carried out with constant sonication. From the analysis, it is clear that surface of carbon nanofibers was quite uniformly coated with DAAQ. The performance characteristics of the supercapacitors have been evaluated using Cyclic Voltammetry. CNFs/DAAQ based composite electrode showed relatively good electrochemical behaviors in acidic electrolyte system. CNFs/DAAQ composite electrode showed relatively good capacitance (7 Ah/kg) compared to conventional capacitors in the range of $-0.4\~0.4$.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.70-70
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• 2010

Cerium oxide nanofibers have been of great interest in fundamental level study. We fabricated polyvinylpyrollidone (PVP) and cerium nitrate nanofibers composite applying a mixed solution of PVP and cerium nitrate hydrate (Ce(NO3)3) with various cerium concentration from 8.87 to 35.5wt% by electrospinning process. Electrospinning method is a simple and cost-effective process to make nanoand submicro nanofiber fabrication. We applied 0.69 kV/cm of electric field between the capillary and a drum collector covered with aluminum foil. Cerium oxide nanofibers were obtained after calcination of PVP/Ce(NO3)3 nanofibers composite at 573, 873 and 1273K, which were chosen by thermal gravimetry analysis. The obtained nanofibers were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS). When the viscosity of the electrospinning solution was high named over 60 cP, only nano and submicro-sized cerium oxide fibers were collected. X-ray photoelectron spectroscopy (XPS) was performed for investigation of the chemical nature of the obtained ceria nanofibers. After we calcined the PVP/ceria nanocomposites, metallic cerium was oxidized to cerium oxide including ceria.

• Journal of the Korean Applied Science and Technology
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• v.25 no.3
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• pp.341-346
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• 2008

Cellulose nanofibers from microfibril cellulose (MFC) was prepared by hydrobromic acid (HBr) treatment at different concentrations. Polyvinyl alcohol (PVA) composite films at various loading level of nanofibers were manufactured by a film casting method. The analysis of degree of polymerization (DP), crystallinity ($X_c$) and molecular weight ($M_w$) of cellulose after acid treatment was conducted. The mechanical and thermal properties of the cellulose nanofibers reinforced PVA films were characterized using tensile tests and thermogravimetric analysis (TGA). The DP and $M_w$ of MFC by HBr hydrolysis considerably decreased, but $X_c$ showed no significant change. After acid hydrolysis, the diameter of cellulose nanofibers was in the range of 100 to 200 nm. The thermal stability of the films was steadily improved with the increase of nanofiber loading. There was a significant increase in the tensile strength of PVA composite films with the increase in MFC loading. Finally, 5 wt.% nanofiber loading exhibited the highest tensile strength and thermal stability of PVA composite films.

• Journal of the Korean Ceramic Society
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• v.37 no.6
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• pp.569-575
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• 2000

Fabrication of carbon fiber reinforced composites was carried out by hand lay-up method. Carbon nanofibers and SiC nanofibers were used as filler in the composites fabrication. Carbon nanofibers, one of the new carbon materials, have 5∼500 nm in diameter and 5-10 nm in length. SiC nanofibers were modified by silicon monoxide vapor with carbon nanofibers. The composites were carbonized at 1000$^{\circ}C$ in a nitrogen atmosphere, and then densified by molten pitches impregnated in vacuum. Multiple cycles of liquid pitch impregnation and carbonization were carried out to obtain a desired density. The composites were characterized by density, microstructure. The inter-laminar shear strength (ILSS) test was performed for mechanical properties. For the new application, the microwave reflective proeprty of composites was investigated. Dielectric constant and permeability spectrum were measured in 12∼18 GHz frequency ranges. On the basis of the wave propagation theory in a lossy media, the reflection loss from the composite inter-layer was predict as a function of frequency.