• Journal of the Korean Wood Science and Technology
• /
• v.48 no.3
• /
• pp.405-413
• /
• 2020

Recycling of ionic liquid (1-ethyl-3-methylimidazolium acetate, [EMIM]Ac) after the pretreatment of Salix gracilistyla Miq. was conducted and the effect of the recycling number on the enzymatic saccharification yield was investigated. Enzymatic saccharification was performed using an enzyme cocktail (Acremonium cellulase and Optimash BG) at 50 ℃ for 72 h. All recycled [EMIM]Ac samples showed a lower amount of water soluble fraction than pure [EMIM]Ac. On increasing the recycling number from 1 to 4, the amount of water soluble fraction decreased from 18% to 15%. The X-ray diffraction pattern of the products pretreated with recycled [EMIM]Ac showed cellulose I crystalline polymorph. The crystallinity of the product pretreated with recycled [EMIM]Ac was 47-49%, which was lower than 33% of that with pure [EMIM]Ac. The yields of glucose and xylose decreased in the pretreatment with recycled [EMIM]Ac compared to that with pure [EMIM]Ac.

• Applied Chemistry for Engineering
• /
• v.3 no.2
• /
• pp.280-287
• /
• 1992

Aromatic liquid crystalline polyesters were synthesized from terephthalic acid(TPA), biphenyl dicarboxylic acid(BPA) and hydroquinone(HQ) by solution polymerization. Effects of TPA/BPA ratio(by mole %) on the thermal properties, thermal stability and textures of mesophases were investigated with DSC, TGA, cross-polarized microscopy and X-ray diffractometer. The synthesized polymers in this study were thermotropic and showed nematic textures. Melting temperature($T_m$) and isotropization temperature($T_i$) of polymer increased and thermal stabilities of polymer were improved with the content of BPA. Most of the polymers in this study had crystallinity more than 30%.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.11a
• /
• pp.55.1-55.1
• /
• 2011

Dye-sensitized solar cell(DSSC) have been considered one of the promising alternatives to conventional solar cells, because of their low cost, easy fabrication and relatively high energy conversion efficiency. However, although the cell offers reasonable efficiency at least 11%, the use of a liquid electrolyte placed technological challenges for achieving the desired durability and operational stability of the cell. In order to prevent or reduce electrolyte leakage considerable efforts have been made, such as p-type semiconductor or organic hole-transport material that better mechanical properties and simple fabrication processes. In this work, we synthesized solid-state electrolyte containing LiI and KI metal salt with starting materials of poly ethylene oxide to substitute liquid electrolyte enhance the ionic conductivity and solar conversion efficiency. Li+ leads to faster diffusion and higher efficiency and K+ leading to higher ionic conductivity. The efficiency of poly ethylene oxide/LiI system electrolyte is 1.47% and poly ethylene oxide/potassium electrolyte is 1.21%. An efficiency of 3.24% is achieved using solid-state electrolyte containing LiI and KI concentrations. The increased solar conversion efficiency is attributed to decreased crystallinity in the polymer that leads to enhanced charge transfer.

• Transactions on Electrical and Electronic Materials
• /
• v.11 no.4
• /
• pp.186-189
• /
• 2010

Nano-sized MgO single crystal powders have recently been reported to emit ultraviolet by stimulation of electrons in a vacuum. In this study, nanocrystalline MgO powders were applied to a xenon plasma flat fluorescent lamp (FFL) for a liquid crystal display backlight to improve its emission efficiency through the extra ultraviolet from the nano-MgO crystals. For comparison, a MgO nano-thin film was applied directly on the phosphors inside a lamp panel through e-beam evaporation. Adding MgO nano-crystal powders to the phosphors improved the luminance and efficiency of FFLs by around 20% and MgO nano-crystal coverage of 40% of the phosphor provided the best FFL emission characteristics; however, application of MgO thin film to the phosphors degraded the emission characteristics, even compared to FFLs without MgO. This was due to insufficient ultraviolet stimulation of the phosphors and the crystallinity and low secondary electron coefficient of the MgO.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.12
• /
• pp.4122-4126
• /
• 2012

Cellulose-graft-poly (L-lactide) (cellulose-g-PLLA) was successfully prepared via ring-opening polymerization (ROP) by using 4-dimethylaminopyridine (DMAP) as an organic catalyst in an ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl). The structure and morphology of the polymer was characterized by nuclear magnetic resonance (NMR) and transmission electron microscope (TEM). From wide-angle X-ray powder diffraction (WAXD) and degradation test (by acid, alkaline, PBS and enzyme solution), changes in the crystalline structure as a result of degradation was also investigated. The results indicated that materials which have low degree of crystallinity showing higher degradability, however, in acid liquor, enzyme solution, alkaline liquor and PBS system, the degradation rate of the polymer decreased by the above sequence. Moreover, with the further increase of graft degree of this material, its degradation degree decreased.

• Electrical & Electronic Materials
• /
• v.1 no.1
• /
• pp.54-61
• /
• 1988

This paper was a study on dielectric phenomena of the specimen, Polypropylene films which were annealled in air and quenched in liquid nitrogen after aging for 5[hr] in water of 100[.deg.C]. The specimen was measured in temperature range of 15-120[.deg.C] and in frequency range of 30-1x 10$^{6}$ [HZ]. As the results of the study, it was confirmed that the tacticity of specimen was isotactic structure, and the degree of cryatallinity of the specimens calculated by means of Natta's method from XRD (X-ray Diffraction) spectrum was 55[%]. And for dielectric relaxation, .betha. peak-the tan .delta. (spectrum around 20[.deg.C])-attributed due to amorphous regions, and .alpha. peak - the tan .delta. spectrum around 90[.deg.C]-due to crystalline regions. It was identified that the degree of crystallinity of the specimen quenched in the liquid nitrogen was increased to 55-65[%], and that of the specimen annealled in the air was decreased to 55-50[%]. And activation energy from dielectric loss spectra was obtained 34.5[kcal/mole] for .alpha. peak and 80.5[kcal/mole] for .betha. peak, respectively.

• Applied Science and Convergence Technology
• /
• v.24 no.4
• /
• pp.96-101
• /
• 2015

Quantitative evaluation of photocatalytic activity of oxide nanoparticles in aqueous solution is quite challenging in that the kinetic reaction rate is determined by a complicated interplay among various limiting factors such as light scattering and absorption, diffusion and adsorption of reactants in condensed liquid phase, photoexcited charge separation and recombination rate, and the exact nature of active sites determined by detailed morphology and crystallinity of nanocrystals. Here, we present our simple experimental results showing that the kinetic regime of a typical photocatalytic degradation experiment over UV-irradiated $TiO_2$ nanoparticles in aqueous solution is in that dominated by the photoactivity of $TiO_2$ and its concentration. This result lays a firm ground of using the measured kinetic reaction rate in evaluating photocatalytic efficiency of oxide nanocrystals under evaluation.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2002.08a
• /
• pp.523-525
• /
• 2002

The poly-Si thin film can be used in high mobility active matrix liquid-crystal display (AMLCD) and system on panel (SOP). In this paper, poly-Si thin films were grown by novel high temperature process on the molybdenum (Mo) substrate. By applying a high current above 48A on a Mo substrate. We obtained an improved crystalline Si films with the crystallinity over 80%. We exhibit the properties of structural and electrical properties of high temperature poly-Si thin film transistor on the Mo substrates.

• Journal of Hydrogen and New Energy
• /
• v.27 no.6
• /
• pp.747-752
• /
• 2016

Soot and harmful exhaust gas produced by liquid hydrocarbon fuel caused various environmental problems. In this study, soot characteristics produced by thermal decomposition of acetylene and diesel were analyzed, which are formed at different temperatures. These fuels were observed to produce particulate matters, and collected soot samples were observed by using TEM & SEM. These were found to be significantly different in structure and crystallinity.

• Particle and aerosol research
• /
• v.6 no.1
• /
• pp.37-46
• /
• 2010

Cu nano-colloid was prepared by wire electric explosion process under de-mineralized water and anhydrous ethanol. To control the properties of Cu nano-colloid, experimental conditions such as diameter of Cu wire and applied voltage were changed. The optimal Cu nano-colloid was prepared when the 0.1mm diameter of Cu wire with the applied voltage of 2000 V was used. The shape of Cu particles in colloid was spherical and the XRD result revealed that the phase of Cu particles was cubic phase. About 20nm Cu nanoparticles with high crystallinity were successfully prepared using wire explosion process under anhydrous ethanol and they showed more than 100 hours dispersion stability.