• Carbon letters
• /
• 제15권1호
• /
• pp.1-14
• /
• 2014

Carbon nanofibers (CNFs) with diameters in the submicron and nanometer range exhibit high specific surface area, hierarchically porous structure, flexibility, and super strength which allow them to be used in the electrode materials of energy storage devices, and as hybrid-type filler in carbon fiber reinforced plastics and bone tissue scaffold. Unlike catalytic synthesis and other methods, electrospinning of various polymeric precursors followed by stabilization and carbonization has become a straightforward and convenient way to fabricate continuous CNFs. This paper is a comprehensive and brief review on the latest advances made in the development of electrospun CNFs with major focus on the promising applications accomplished by appropriately regulating the microstructural, mechanical, and electrical properties of as-spun CNFs. Additionally, the article describes the various strategies to make a variety of carbon CNFs for energy conversion and storage, catalysis, sensor, adsorption/separation, and biomedical applications. It is envisioned that electrospun CNFs will be the key materials of green science and technology through close collaborations with carbon fibers and carbon nanotubes.

• 한국산림과학회지
• /
• 제76권2호
• /
• pp.119-126
• /
• 1987

본 연구는 활엽수재(闊葉樹材)인 층층나무(Cornus Controversa Hemsl), 굴참나무(Quercus variabilis Blume) 및 산벚나무(Prunus sargentii Redher)를 시험편(試驗片)으로 하여 치수안정화효과(安定化效果)를 높일 수 있는 PEG 적정분자량(分子量)과 혼합방법(混合方法)을 혼합비 I, II, III, IV 및 V 중에서 찾는데 그 목적이 있었으며 실험결과는 다음과 같았다. 1. 목재내(木材內) PEG 주입율(注入率)은 비중에 따른 영향을 받았으며 굴참나무를 제외하고 만족할만한 주입율을 나타내어 적정혼합방법은 PEG V임을 알았다. 2. PEG V용액에서의 팽윤효과(澎潤效果)는 층층나무, 산벚나무에서 높았으며, 굴참나무의 팽윤효과(澎潤效果)를 높이기 위해서는 방수성약제(防水性藥劑)의 도장(塗裝)이 필요하다. 3. PEG V용액에서 산벚나무가 82.59%로 가장 높은 항수축능(抗收縮能)을 보였고 굴참나무가 62.79%로 가장 낮은 값을 보여 주었다. 4. 활엽수재(闊葉樹材)의 치수안정화(安定化)는 PEG의 혼합방법에 따라 커다란 차이를 나타내지 않았다. 5. 이상과 같은 실험결과를 종합 분석한 결과 비중이 높은 활엽수재(闊葉樹材)의 경우에는 PEG-400과 PEG-1000으로 혼합하되 외부인자를 충분히 고려할 필요가 있다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 하계학술대회 논문집
• /
• pp.295-296
• /
• 2009

There are various application of liquid crystal materials to devices, especially, blue phase liquid crystal (BPLC) and nano-structured liquid crystal mixture have been studied recently because BPs existing temperature range has been expanded by polymer-stabilization and liquid crystal has been confined in room which has certain coherence length so that their particular characters, such as fast response time and optically isotropic state at no electric field, could apply to advanced liquid crystal display devices. However, there is an crucial problem which is high operating voltage from low Kerr constant and limited electric field utilization using in-plain electric field. In this paper, we will analyze cell structure in the way of using electric field and show effective electric field utilization to reduce operating voltage.

• Transactions on Electrical and Electronic Materials
• /
• 제7권3호
• /
• pp.112-117
• /
• 2006

In this paper we present that the effects of polymer adsorption on stabilities and CMP performance of ceria abrasive particles. Characterization of ceria abrasive particles in the presence of poly(vinyl pyrrolidone) (PVP) was performed by the measurements of adsorbed amounts of PVP, average sizes, and the back scattering intensities of the ceria abrasive particles as functions of PVP molecular weight and PVP concentration. The ceria abrasive particles in the presence of PVP were used to polish $SiO_2\;and\;Si_3N_4$ films deposited on Si wafers in order to understand the effect of PVP adsorption on chemical mechanical polishing (CMP) performance, together with ceria abrasive particles without PVP. Adsorption of PVP on the ceria abrasive particles enhanced the stability of ceria abrasive particles due to steric stabilization of the thick adsorbed layer of PVP. Removal rates of the deposited $SiO_2\;and\;Si_3N_4$ films by the ceria abrasive particles in the presence of PVP were much lower than those in the absence of PVP and their magnitudes were decreased with an increase in the concentration of free PVP chains in the dispersion media. This suggests that the CMP performance in the presence of PVP could be mainly controlled by the hydrodynamic interactions between the adsorbed PVP chains and the free ones. Moreover, the molecular weight dependence of PVP on the removal rates of the deposited films was hardly observed. On the other hand, high removal rate selectivity between the deposited films in the presence of PVP was not observed.

• Biomaterials and Biomechanics in Bioengineering
• /
• 제3권1호
• /
• pp.37-46
• /
• 2016

To maintain activity in a coenzyme/enzyme mixture system, such as ${\beta}$-nicotinamide adenine dinucleotide (NADH)/dehydrogenase, the water-soluble 2-methacryloyloxyethyl phosphorylcholine (MPC) polymers as an additive were synthesized and investigated for their stabilizing function. The inhibitor for the NADH/dehydrogenase reaction was spontaneously formed when the NADH was stored in the dehydrogenase solution. Therefore, we hypothesized that if the additive polymer could interact with an inhibitor without any adverse effect on the dehydrogenase, the activity in the NADH/dehydrogenase mixture could be maintained. We selected lactose dehydrogenase (LDH) as the enzyme, and the NADH was dissolved and incubated at $37^{\circ}C$ in the LDH solution containing the polymers. The phospholipid polymers used in this study were poly(MPC) (PMPC), poly(MPC-co-3-trimethylammonium-2-hydroxypropyl methacrylate chloride) (PMQ) and poly[MPC-co-potassium 3-methacryloyloxypropyl sulfonate ($MSO_3$)] ($PMMSO_3$). The poly($MSO_3$) was used as a reference. For the PMQ and $PMSO_3$ aqueous solutions, the activity of the NADH/LDH mixture system decreased with incubation time as the same level or lower than that in the Tris buffered solution in the absence of the polymers. However, for the poly($MPC-co-MSO_3$) ($PMMSO_3$) aqueous solution, the activity of the NADH/LDH mixed system was six times higher than that in the buffered solution even after a 3-days incubation. The LDH activity was 1.5-1.8 times higher in the presence of the $PMMSO_3$ compared with that in the $PMSO_3$ solution. The mixture of two polymers, poly(MPC) and poly($MSO_3$), did not produce any stabilization. Thus, both the MPC and $MSO_3$ units in the polymer chain had important and cooperative effects for stabilizing the NADH/LDH mixture.

• 한국고분자학회:학술대회논문집
• /
• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
• /
• pp.263-263
• /
• 2006

Poly (ethylene glycol)(PEG) - Poly (${\varepsilon}-caprolactone(CL)$) - Poly (D,L lactide(LA) (PCLA-PEG-PCLA) was synthesized by ring-opening polymerization to form temperature sensitive hydrogel triblock copolymer. The triblock copolymer was acrylated by acryloyl chloride. ${\beta}-amino$ ester was used as a pH sensitive moiety, in this study ${\beta}$- amino ester obtained from 1,4-butandiol diacrylate, and 4, 4' trimethylene dipiperidine, it have pKb around 6.6. pH/temperature sensitive penta-block copolymer (PAE-PCL-PEG-PCL-PAE) was synthesized by addition polymerization from acrylated triblock copolymer, 1,4-butandiol diacrylate, and 4, 4' trimethylene dipiperidine. Their physicochemical properties of triblock and penta-block copolymers were characterized by $^1H-NMR$ spectroscopy and gel permeation spectroscopy. Sol-gel phase transition behavior of PAE-PCL-PEG-PCL-PAE block copolymers were investigated by remains stable method. Aqueous media of the penta-block copolymer (at 20 wt%) changed from a sol phase at pH 6.4 and $10^{\circ}C$ to a gel phase at pH 7.4 and $37^{\circ}C$. The sol-gel transition properties of these block copolymers are influenced by the hydrophobic/hydrophilic balance of the copolymers, block length, hydrophobicity, stereo-regularity of the hydrophobic of the block copolymer, and the ionization of the pH function groups in the copolymer depended on the changing of environmental pH, respectively. The degradation and the stabilization at pH 7.4 and $37^{\circ}C$, and the stabilization at pH 6.4 and $10^{\circ}C,\;5^{\circ}C,\;0^{\circ}C$, of the gel were determined. The results of toxicity experiment show that the penta block copolymer can be used for injection drug delivery system. The sol?gel transition of this block copolymer also study by in vitro test ($200{\mu}l$ aqueous solution at 20wt% polymer was injected to mouse). Insulin loading and releasing by in vitro test was investigated, the results showed that insulin can loading easily into polymer matrix and release time is around 14-16days. The PAE-PCL-PEG-PCL-PAE can be used as biomaterial for drug, protein, gene loading and delivery.

• 한국막학회:학술대회논문집
• /
• 한국막학회 1995년도 추계 총회 및 학술발표회
• /
• pp.5-9
• /
• 1995

In the dry-jet-wet-spinning process of a hollow fiber membrane, the polymer solution is pumped into a coaxial tube, jet spinneret. The threadline emerging from the spinneret is stabilized by an internal coagulating medium(liquid or gas) as it emerges from the jet orifice. The nascent hollow thread is further stabilized in a quench bath as shown in Fig. 1. In this scheme, three mechanism of formatiota(temperature gradient, solvent evaporation, and solvent-nonsotvent exchange) can be combined. The changes which promote stabilization often play a dominant role in determining the ultimate fiber wall structure as well. Hence, in pratice, hollow fiber stabilization and development of membrane structure are commonly inseparable. However, fiber dimension(the inside diameter and wall thickness of the hollow fiber) is mainly a rheological problem and is determined by dope pumping rate, spinneret diatance from the coagulation bath, inner coagulant flow rate, and fiber draw-rate. Besides rheological phenomena play a prominent part in the final properties of the hollow fiber.

• 방사선산업학회지
• /
• 제7권2_3호
• /
• pp.167-170
• /
• 2013

Lignin can be a valuable natural chemical resource. Structurally, lignin is a three-dimensional polymer made up of condensed C-C bonds and some ether linkages, most of which are not readily degraded. In this study, lignin carbonization under various electron beam pretreatment conditions was characterized through a thermogravimetric analysis (TGA), X-ray diffraction (XRD) and Raman spectroscopy. Lignin stabilization was controlled by various doses of electron beam irradiation corresponding to 50, 100, 200, 500 and 1,000 kGy; the carbonization process was performed under a nitrogen gas atmosphere at $1000^{\circ}C$ for 1 h. The TGA results showed that a 1,000 kGy lignin dose increased the residue weight from 39.96% to 45.23%, compared to non-irradiated lignin. This observation is in agreement with the XRD and Raman spectroscopy results, in which the two theta degrees and the degree of crystallization were improved by increasing the electron beam irradiation.

• Journal of the Korean Wood Science and Technology
• /
• 제3권1호
• /
• pp.3-15
• /
• 1975

How to stabilize wood against shrinking and swelling in variable atmospheric moisture conditions is important to the wood-using industry and a challenge to research. Polyethylene glycol stabilize wood by bulking the fiber. PEG also serve as a chemical seasoning agent, suppress decay in high concentrations, and have slight effect on physical properties, gluing or finishing. The study designed to determine the effect of PEG-400 on the dimensional stabilization of local hardwoods for wood carvings that could supply a greatly expanding tourist trade and making curved furniture parts, lamp stands and other decorative objects, and possible gunstock. The species examined were 6 species, Seo-Namoo (Carpinus laxiflora), Cheungcheung-Namoo (Cornus controversa), Gorosae-Namoo (Acer mono), Karae-Namoo (Juglans mandshurica), Jolcham-Namoo (Quercusserrata) and Sanbud-Namoo (Prunus sargentii), used as block of 5cm thick radially to the grain, 7cm wide tangentially, and 70cm long parallel to the wood grain. All these test piecies were conditioned above the fiber saturation point before impregnation. The stabilization effects were determined for PEG-400 treated woods in a 50 percent solution for 20 days. The following conclusions were obtained. PEG retentions increased with treating time. It was more effective to treat at 60$^{\circ}C$ than at room temperature. In degree of PEG-400 impregnation on species, Cheungcheung-Namoo havinglow specific gravity had the highest retentions, 68.77% but the lowest, 56.33% was shown in Jolcham-Namoo with high specific gravity. Specific gravity of treated wood increased considerably with effectiveness of polymer loading. The increases in specific gravity were 5.36 to 13.16 percent. The highest was Jolcham-Namoo, the lowest Karae-Namoo. On the dimensional stability, a 40 percent of effectiveness of polymer loading was just as effective as 60 percent in reduction in water absorptivity (RWA), antishrinkage efficiency (ASE) and antiswelling efficiency (AE), and from over 60 percent they increased more rapidly. Also species response varied considerably. ASE was 30.12 to 69.97 percent tangentially and 27.86 to 56.37 percent radially, AE 34.06 to 73.76 percent tangentially and 30.11 to 70.12 percent radially, and RWA 42.31 to 65.32 percent. No differences in volume swelling among the 6 species were observed. Its values were ranged from 14.98 to 19.55 percent and also increased with PEG retentions. On the mechanical properties, the strengths very much decreased with PEG-400 loadings as shown in Figure 12; that were 11.41 to 22.90 percent in compression, 21.61 to 34.35 percent in bending and 22.83 to 36.83 percent in tensile strength. PEG retention in cell wall was less than 1 percent and the most of PEG were immersed in cell lumen. Except for Korae-Namoo, effectivenesses of polymer loading were as much high as 61.58 to 75.02 percent. This is believed to be due to the effect of PEG-400 on excellant dimensional stability of treated woods.

• 접착 및 계면
• /
• 제14권3호
• /
• pp.146-159
• /
• 2013

본 연구에서는 $350^{\circ}C$에서 4 min 이내로 빠르게 등온 안정화공정을 통해 얻어진 레이온직물의 화학조성, 물리적 특성, X-선 회절 패턴, 열안정성 그리고 직물 형상에 미치는 초음파세척 및 화학전처리의 영향을 조사하였다. 안정화공정 동안 레이온직물에서 발생하는 중량감소와 열수축을 줄이고 안정화반응을 촉진시키기 위하여 안정화공정 전에 레이온직물을 먼저 초음파 세척하고 $NH_4Cl$, $Na_3PO_4$, $H_3PO_4$ 및 $ZnCl_2$로 화학전처리 공정을 수행하였다. 결과는 초음파세척 및 화학전처리가 안정화된 레이온직물의 중량감소, 열수축, 미세구조 변화, 탄소함량, 열안정성, 및 직물 형상에 영향을 주었으며, 사용한 안정화시간과 화학전처리제의 종류에 의존하였다.