• 생명과학회지
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• 제17권9호통권89호
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• pp.1260-1265
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• 2007

자석으로 분리가 가능한 ${\alpha}-Amylase$가 코팅된 나노고분자를 제조하여 녹말의 분해공정에 활용하였다. 본 연구에서 개발된 고정화 효소의 안정성은 크게 증가하여 상온에서 200rpm으로 교반하면서 보관한 경우 30일 동안에 92.7%의 활성도를 유지하였다 . 고정화 효소를 자석을 이용하여 재사용한 경우 10 회 동안 사용했을 경우 95.2%의 활성도 회수율을 보 여 효소의 재사용 가능성을 확인시켜 주었다 . 고정화 효소 0.5mg을 사용하여 녹말 분해 공정 에 활용하였을 때 2 ml의 40 g/l 녹말 용액을 40분만에 완전히 분해 시켰다, 이러한 고정화 효소를 사용하여 연속 효소반응기를 개발하여 녹말 분해공정에 활용한 결과 체류시간을 1시간으로 하였을 때 녹말 30 g/l를 76% 분해시켜 산업적으로 활용 가능성을 보여 주었다.

• 한국분말재료학회지
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• 제26권4호
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• pp.334-339
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• 2019

To meet the current demand in the fields of permanent magnets for achieving a high energy density, it is imperative to prepare nano-to-microscale rare-earth-based magnets with well-defined microstructures, controlled homogeneity, and magnetic characteristics via a bottom-up approach. Here, on the basis of a microstructural study and qualitative magnetic measurements, optimized reduction conditions for the preparation of nanostructured Sm-Co magnets are proposed, and the elucidation of the reduction-diffusion behavior in the binary phase system is clearly manifested. In addition, we have investigated the microstructural, crystallographic, and magnetic properties of the Sm-Co magnets prepared under different reduction conditions, that is, $H_2$ gas, calcium, and calcium hydride. This work provides a potential approach to prepare high-quality Sm-Co-based nanofibers, and moreover, it can be extended to the experimental design of other magnetic alloys.

• Macromolecular Research
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• 제13권6호
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• pp.521-528
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• 2005

Electrospun polyacrylonitrile (PAN) nanofibers were carbonized with or without iron (III) acetylacetonate to induce catalytic graphitization within the range of 900-1,500$^{circ}C$, resulting in ultrafine carbon fibers with a diameter of about 90-300 nm. Their structural properties and morphologies were investigated. The carbon nanofibers (CNF) prepared without a catalyst showed amorphous structures and very low surface areas of 22-31 $m^{2}$/g. The carbonization in the presence of the catalyst produced graphite nanofibers (GNF). The hydrogen storage capacities of these CNF and GNF materials were evaluated through the gravimetric method using magnetic suspension balance (MSB) at room temperature and 100 bar. The CNFs showed hydrogen storage capacities which increased in the range of 0.16-0.50 wt$\%$ with increasing carbonization temperature. The hydrogen storage capacities of the GNFs with low surface areas of 60-253 $m^{2}$/g were 0.14-1.01 wt$\%$. Micropore and mesopore, as calculated using the nitrogen gas adsorption-desorption isotherms, were not the effective pore for hydrogen storage.

• Journal of Microbiology and Biotechnology
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• 제25권8호
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• pp.1291-1298
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• 2015

Five different polymer nanofibers, namely, polyaniline nanofiber (PANI), magnetically separable polyaniline nanofiber (PAMP), magnetically separable DEAE cellulose fiber (DEAE), magnetically separable CM cellulose fiber (CM), and polystyrene nanofiber (PSNF), have been used for the immobilization of lactase (E.C. 3.2.1.23). Except for CM and PSNF, three polymers showed great properties. The catalytic activities (k_cat) of the free, PANI, PAMP, and magnetic DEAE-cellulose were determined to be 4.0, 2.05, 0.59, and 0.042 mM/min·mg protein, respectively. The lactase immobilized on DEAE, PANI, and PAMP showed improved stability and recyclability. PANI- and PAMP-lactase showed only a 0-3% decrease in activity after 3 months of vigorous shaking conditions (200 rpm) and at room temperature (25℃). PANI-, PAMP-, and DEAE-lactase showed a high percentage of conversion (100%, 47%, and 12%) after a 1 h lactose hydrolysis reaction. The residual activities of PANI-, PAMP-, and DEAE-lactase after 10 times of recycling were 98%, 96%, and 97%, respectively.

• 방사선산업학회지
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• 제5권1호
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• pp.69-73
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• 2011

Polyamide 66 (PA66) nanofibers with Triallyl cyanurate (TAC) were obtained by electrospinning of formic acid and chloroform solution. Electron beam irradiation of PA66 nanofiber with and without TAC was carried out over a range of absorbed doses (20~100 kGy) in nitrogen. The characterization of the irradiated PA66 nanofibers and PA66 nanofibers with TAC was done by scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA) and universal testing machine (UTM). The results of the SEM image analysis confirmed that the morphology of PA66 nanofibers was not altered by electron beam. The amount of TAC in PA66 nanofiber with TAC was identified by $^1H-NMR$ analysis. The degradation temperature of PA66 nanofibers with TAC at an absorbed dose of 20~100 kGy was higher than the irradiated PA66 nanofiber without TAC. On the other hand, the decreasing rate of modulus of irradiated PA66 nanofibers with TAC was less than PA66 nanofibers.

• 한국수소및신에너지학회논문집
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• 제16권4호
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• pp.334-342
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• 2005

200-300 nm 직경을 지닌 폴리비닐리덴 플루오라이드 초극세 섬유를 전기방사법으로 제조하였다. 이들을 불응화시킨 후, $800-1800^{\circ}C$ 온도에서 탄화시켜 PVdF 계 탄소나노 섬유를 제조하여 구조 및 기공분석을 하였다. 이들은 20-30 nm 크기의 탄소입자로 이루어져 있으며 탄소나노입자는 1 nm이하의 슬릿형 나노기공을 지니고 있었다. 탄화온도가 증가함에 따라 비표면적은 $1500^{\circ}C$에서 $414\;m^2/g$로 감소하였으나, $1800^{\circ}C$에서는 $1300\;m^2/g$로 급격히 다시 증가하였으며 1 nm 이하의 나노기공만을 지닌 탄소섬유가 얻어졌다. 비표면적 및 기공특성과 수소저장특성을 관계를 조사하기 위하여 Magnetic Syspension Balance(MSB)를 사용한 중량법으로 평가한 이들의 수소저장능은 0.04-0.4wt%이었다.

• KSBB Journal
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• 제25권5호
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• pp.466-470
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• 2010

본 연구에서는 자석으로 분리가 가능한 polyaniline nanofiber (PAMP)를 개발하여 선택적인 에탄올 흡착 및 탈착공정을 활용하여 에탄올을 농축하였다. 개발된 PAMP는 용액 중에 있는 에탄올을 80%이상 흡착하였다. 자석을 활용하여 PAMP에 흡착된 에탄올의 회수가 가능하였으며, 물리적인 힘을 통하여 에탄올 탈착이 가능하여 에탄올의 회수가 용이하였다. 본 연구에 개발된 PAMP는 지속적인 재활용이 가능하였다. 본 연구에서 PAMP를 10회 반복 사용하였을 때 PAMP의 에탄올 흡착율은 최초 사용한 경우의 92%를 유지하여 PAMP를 지속적으로 활용할 수 가능성을 확인하였다. 본 연구에서 개발된 PAMP를 사용하여 46 g/L의 저농도 에탄올을 197.6 g/L의 고농도 에탄올로 농축이 가능하였다.

• 마이크로전자및패키징학회지
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• 제23권2호
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• pp.57-63
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• 2016

We developed a flexible and micro-thick electromagnetic interference (EMI) shielding nanofabric layer that also functions as a water resisting and heat sinking material. Electrospinning followed by a simple heat treatment process was carried on to produce the EMI-shielding Ni/C hybrid nanofibers. The ambient oxygen partial pressure ($pO_2$ = 0.1, 0.7, 1.3 Torr) applied during the heat treatment was varied in order to optimize the effectiveness of EMI-shielding by modifying the size and crystallinity of the magnetic Ni nanoparticles distributed throughout the C nanofibers. Permittivity and permeability of the nanofibers under the electromagnetic (EM) wave frequency range of 300 MHz~1 GHz were measured, which implied the EMI-shielding effectiveness (SE) optimization at $pO_2$ = 0.7 Torr during the heat treatment. The materials' heat diffusivity for both in-plane direction and vertical direction was measured to confirm the anisotropic thermal diffusivity that can effectively deliver and sink the local heat produced during device operations. Also, the nanofibers were aged at room temperature in oxygen ambient for water resisting function.

• 방사선산업학회지
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• 제9권1호
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• pp.15-20
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• 2015

Carbon fiber has received much attention owing to its properties, including a large surface-to-volume ratio, chemical and thermal stability, high thermal and electrical conductivity, and high mechanical strengths. In particular, magnetic nanopowder dispersed carbon fiber has been attractive in technological applications such as the electrochemical capacitor and electromagnetic wave shielding. In this study, the nickel-oxide-nanoparticle dispersed polyacrylonitrile (PAN) fibers were prepared through an electrospinning method. Electron beam irradiation was carried out with a 2.5 MeV beam energy to stabilize the materials. The samples were then heat-treated for stabilization and carbonization. The nanofiber surface was analyzed using a field emission scanning electron microscope (FE-SEM). The crystal structures of the carbon matrix and nickel nanopowders were analysed using X-ray diffraction (XRD). In addition, the magnetic and electrical properties were analyzed using a vibrating sample magnetometer (VSM) and 4 point probe. As the irradiation dose increases, the density of the carbon fiber was increased. In addition, the electrical properties of the carbon fiber improved through electron beam irradiation. This is because the amorphous region of the carbon fiber decreases. This electron beam effect of PAN fibers containing nickel nanoparticles confirmed their potential as a high performance carbon material for various applications.

• 한국세라믹학회지
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• 제46권1호
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• pp.74-80
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• 2009

Electrospinning process is the useful and unique method to produce nanofibers from metal precursor and polymer solution by controlled viscosity. In this study, the NiZn ferrite nanofibers were prepared by electrospinning with a aqueous metal salts/polymer solution that contained polyvinyl pyrrolidone and Fe (III) chloride, Ni (II) acetate tetrahydrate and zinc acetate dihydrate in N,N-dimethylformamide. The applied electric field and spurting rate for spinning conditions were 10 kV, 2 ml/h, respectively. The obtained fibers were treated at $250^{\circ}C$ for 1 h to remove the polymer. Finally, the NiZn ferrite fibers were calcined at $600^{\circ}C$ for 3 h and annealed at $900{\sim}1200^{\circ}C$ in air. By tuning the viscosity of batch solution before electrospinning, we were able to control the microstructure of NiZn ferrite fiber in the range of $150{\sim}500\;nm$ at 770 cP. The primary particle size in $600^{\circ}C$ calcined ferrite fiber was about 10 nm. The properties of those NiZn ferrite fibers were determined from X-ray diffraction analysis, electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, thermal analysis, and magnetic measurement.