Soo Jin Park

Titanium dioxide nanofibers prepared by using electrospinning method

The synthesis of titanium dioxide nanofibers with 200–300 nm 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 °C to 1000 °C.

Synthesis and characterization of graphene oxide/carboxymethylcellulose/alginate composite blend films

In this work, graphene oxide/carboxymethylcellulose/alginate (GO/CMC/Alg) composite blends were prepared by a simple solution mixing-evaporation method. The resulting structure, thermal stability, and mechanical properties of the blends were investigated by wide-angle X-ray diffractometry, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, thermogravimetric analysis, and mechanical testing. The obtained findings revealed that CMC, Alg, and graphene oxide were able to form a homogeneous mixture. When compared to a CMC/Alg blend, the incorporation of 1 wt% graphene oxide improved the tensile strength and Youngs modulus by 40% and 1128%, respectively. In addition, the GO/CMC/Alg composite blend film showed a higher storage modulus than the CMC/Alg blend.

Eco-friendly synthesis, characterization and properties of a sodium carboxymethyl cellulose/graphene oxide nanocomposite film

A previously unreported nanocomposite (CMC/GO) high-performance film was prepared by a simple solution mixing-evaporation method. The structure, thermal stability, and mechanical properties of the composite films were investigated by wide-angle X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, thermogravimetry analysis, and mechanical testing. The results obtained from these different studies revealed that CMC and graphene oxide were able to form a homogeneous mixture. Compared with pure CMC, the tensile strength and Young’s modulus of the graphene-based materials were improved significantly upon incorporation of 1xa0wt% graphene oxide by 67xa0±xa06xa0% and 148xa0±xa05xa0%, respectively. In addition, the DMA composite films also showed a high storage modulus up to 250xa0°C.

Chitosan nanocomposite films: enhanced electrical conductivity, thermal stability, and mechanical properties.

A novel, high-performance Fe(3)O(4)/MWNT/Chitosan nanocomposite has been prepared by a simple solution evaporation method. A significant synergistic effect of Fe(3)O(4) and MWNT provided enhanced electrical conductivity, mechanical properties, and thermal stability on the nanocomposites. A 5% (wt) loading of Fe(3)O(4)/MWNT in the nanocomposite increased conductivity from 5.34×10(-5) S/m to 1.49×10(-2) S/m compared to 5% (wt) MWNT loadings. The Fe(3)O(4)/MWNT/Chitosan films also exhibited increases in tensile strength and modulus of 70% and 155%, respectively. The integral procedure decomposition temperature (IPDT) was enhanced from 501 °C to 568 °C. These effects resulted from a number of factors: generation of a greater number of conductive channels through interactions between MWNT and Fe(3)O(4) surfaces, a higher relative crystallinity, the antiplasticizing effects of Fe(3)O(4), a restricted mobility and hindrance of depolymerization of the Chitosan chain segments, as well as uniform distribution, improved dispersion, and strong interfacial adhesion between the MWNT and Chitosan matrix.

Design of quaternary logic gate using double pass-transistor logic with neuron MOS down literal circuit

A multi-valued logic (MVL) pass gate is an important element in configuring multi-valued logic. Multiple logical levels, which are different from binary pass gates, are required to be discriminated in MVL pass gates. In this paper, we designed the quaternary MIN (QMIN)/negated MIN (QNMIN) gate, and the quaternary MAX (QMAX)/negated MAX (QNMAX) gate using double pass-transistor logic (DPL) with neuron MOS (vMOS) threshold gates. In addition, we designed quaternary truncated sum (QTS) and quaternary truncated difference (QTD) gates using vMOS down literal circuits (DLC). The DPL improved the gate speed without increasing the input capacitance. It has a symmetrical arrangement and double-transmission characteristics. The threshold gates are composed of vMOS DLC. The proposed gates obtain the signal value, to realize various multi threshold voltage circuits. In this paper, these circuits use a 3 V power supply voltage and the parameters of the 0.35 /spl mu/m N-well 2-poly 4-metal CMOS technology. HSPICE simulation results are also presented.

Effect of Substituted Trifluoromethyl Groups on Thermal and Mechanical Properties of Fluorine-containing Epoxy Resin

In this study, 2-diglycidylether of benzotrifluoride (2-DGEBTF) and 4-diglycidylether of benzotrifluoride (4-DGEBTF) epoxy resins, which contained fluorine groups in the main chain, were synthesized. The resins were characterized by FTIR,1H NMR,13C NMR and19F NMR spectroscopy. The 2-DGEBTF and 4-DGEBTF epoxy resins were cured with triethylene tetramine (TETA), and the effect of the fluorine group on the synthesized epoxy resin on the cure behavior, thermal, and mechanical properties was investigated. The 2-DGEBTF/TETA system was more reactive than the 4-DGEBTF/TETA system, whereas the thermal stability factor i.e., the decomposition activation energy (Ed), of 4-DGEBTF/TETA was higher than that of 2-DGEBTF/TETA. These results can be explained by the decrease in cross-linking density and decomposition of the short side chains, resulting in the CF3 group at the para position. However, theKIC value of 4-DGEBTF/TETA was higher than that of 2-DGEBTF/TETA. This was attributed to the increase in flexibility in the epoxy backbone, resulting in a difference in steric hindrance and polarlizability.

Synthesis of polyacrylonitrile based nanoparticles via aqueous dispersion polymerization

ConclusionsIn this study, the aqueous dispersion polymerization of acrylonitrile, itaconic acid, and methyl acrylate has been successfully carried out using PVA as a steric stabilizer in the mixture of water and DMF medium. The formation and characterization of PAN-based nanoparticles were studied by the polymerization time and concentration of PVA. The chemical structure of the synthesized terpolymer of poly (AN-co-IA-co-MA) nanoparticle was confirmed using1H NMR, FTIR, and GPC spectra. All of the synthesized particles have the nonsmooth surface and relatively spherical shaped. The particle sizes were affected by the concentration of stabilizer concentration and reaction time. The stable PAN-based nanoparticles were successfully obtained when the concentration of the PVA increased from 5 to 15 wt% relative to the monomer and the average particle size decreased from 250 to 87 nm. The effects of PVA on the stabilization of particles and size variation are similar to the conventional stabilizers in the dispersion polymerization.

Influence of Oxyfluorination on Physicochemical Characteristics of Carbon Fibers and their Reinforced Epoxy Composites

The effect of oxyfluorination temperature on the surface properties of carbon fibers and their reinforced epoxy composites was investigated. Infrared (IR) spectroscopy results for the oxyfluorinated carbon fibers revealed carboxyl/ester (C=O) and hydroxyl (O−H) groups at 1632 and 3450 cm-1, respectively, and that the oxyfluorinated carbon fibers had a higher O-H peak intensity than that of the fluorinated ones. X-ray photoelectron spectroscopy (XPS) results indicated that after oxyfluorination, graphitic carbon was the major carbon functional component on the carbon fiber surfaces, while other functional groups present were C−O, C=O, HO−C=O, and C−Fx. These components improved the impact properties of oxyfluorinated carbon fibers-reinforced epoxy composites by improving the interfacial adhesion between the carbon fibers and the epoxy matrix resins.

The Effects of Cryomilling CNTs on the Thermal and Electrical Properties of CNT/PMMA Composites

In this study, the cryomilling of carbon nanotubes (CNTs) was carried out to accomplish better dispersion without using any hazardous chemicals. Accordingly, different samples of CNTs were prepared by varying the milling speed (10, 20, and 25 Hz) and time (5, 10, and 15 min) and incorporated into the poly(methyl methacrylate) (PMMA) matrix. The changes of the morphology were analyzed by utilizing a field emission scanning electron microscope (FESEM) and a high-resolution transmission electron microscope (TEM). Qualitative analysis of the cryomilled CNTs was carried out using Raman spectroscopy, and their surface area was determined via Brunauer–Emmett–Teller (BET) analysis. Subsequently, thermogravimetric analysis was conducted to evaluate the thermal properties, whereas the surface resistivity and electromagnetic interference shielding effectiveness for the electrical conductivity were also examined. It was observed that the composite with Cr-20-10 showed better thermal stability and lower resistivity in comparison to the others because, as the cryomilling time and frequency increased the distribution, dispersion and surface area also increased. Consequently, a better interaction between CNTs and PMMA took place.

Atmospheric chemical vapor deposition of graphene on molybdenum foil at different growth temperatures

Graphene was grown on molybdenum (Mo) foil by a chemical vapor deposition method at ndifferent growth temperatures (1000°C, 1100°C, and 1200°C). The properties of graphene nwere investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and Raman nspectroscopy. The results showed that the quality of the deposited graphene layer was naffected by the growth temperature. XRD results showed the presence of a carbide phase on nthe Mo surface; the presence of carbide was more intense at 1200°C. Additionally, a higher nI2D/IG ratio (0.418) was observed at 1200°C, which implies that there are fewer graphene layers nat this temperature. The lowest ID/IG ratio (0.908) for the graphene layers was obtained nat 1200°C, suggesting that graphene had fewer defects at this temperature. The size of the ngraphene domains was also calculated. We found that by increasing the growth temperature, nthe graphene domain size also increased.