• 한국미생물·생명공학회지
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• 제8권1호
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• pp.41-46
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• 1980

저분자량의 효소인 셀루라아제가 Sephadex G-100 gel chromatography를 사용하여 정제되었다. 정제된 성분의 생화학적 성질들이 조사되었는데 최적 PH와 온도가 각각 6.0과 5$0^{\circ}C$이었다. 서로 다른 결정도(crystallinity)를 갖고 있는 4가지 섬유소 기질의, 효소에 의한 가수분해가 측정되었다. 무정형(amorphous) 부분의 가수분해가 일어난 후에 결정화되어 있는 부분의 가수분해가 뒤따라온다는 것을 알 수 있었다. 효소가 섬유소 기질에 흡착되는 정도가 가수분해 반응에 미치는 영향을 보기 위해 흡착에 대한 연구가 수행되었다. 시간에 따라서 소분자량의 endo-glucanase가 여러가지섬유소 기질에 흡착되는 정도의 변화가 25분간 측정되었다. 무정형의 섬유소에 흡착되는 속도와 정도가 결정형 섬유소에 대한 그것들 보다 더욱 크게 나타났다. 이러한 결과는 endo-glucanase가 섬유소의 결정화 부분의 가수분해보다는 무정형부분의 가수분해에 대해서 더욱 중요한 역할을 한다는 것을 시사해 준다.

• 세라미스트
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• 제10권3호
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• pp.34-47
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• 2007

Photoinduced phenomena in non-crystalline insulators and semiconductors, specifically oxide and chalcogenide glasses, are briefly reviewed with some comments.

• 한국재료학회지
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• 제8권10호
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• pp.898-904
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• 1998

10-50wt% 범위의 W을 함유하는 Ni-W 합금을 전기도금에 의해 제조하였다. 합금 중의 W 량은 전류밀도가 증가함에 따라 증가하였다. 전류밀도가 50mA/${cm}^2$이하인 경우 Ni-W합금은 미세한 결정립을 갖는 Ni의 고용체이었으며, 전류밀도가 50mA/${cm}^2$이상인 경우 비정질상으로 변화하였다. 이들의 결정질$\longrightarrow$비정질 천이는 W량이 40-46wt%인 구간에서 일어났으며 반각폭이 3배이상으로 증가하였다. 결정질 합금의 격자상수는 평형상태도 상의 W의 고용한계(약 30wt%)를 초과하는 40wt%까지 연속적으로 증가하는 것으로 나타나 Ni이 W을 과고용하고 있는 상태인 것으로 밝혀졌다. 비정질 Ni-W 합금은 $400^{\circ}C$이상의 온도에서 열처리하면 강한 [111]방향성을 가지며 재결정하였으며, $800^{\circ}C$이상의 온도에서는 과고용된 W이 석출하였다. 합금조성 및 결정구조의 전류밀도 의존성을 이용하여 Ni-30%W과 Ni-50%W 합금층이 반복되는 결정질/비정질의 다층도금을 제조하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.403-404
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• 2012

We fabricated TFT devices with the GeSe channel. A single device consists of a Pt source and drain, a Ti glue layer and a GeSe chalcogenide channel layer on SiO2/Si substrate which worked as the gate. We confirmed the drain current with variations of gate bias and channel size. The I-V curves of the switching device are shown in Fig. 1. The channel of the device always contains amorphous state, but can be programmed into two states with different threshold voltages (Vth). In each state, the device shows a normal Ovonic switching behavior. Below Vth (OFF state), the current is low, but once the biasing voltage is greater than Vth (ON state), the current increases dramatically and the ON-OFF ratio is high. Based on the experiments, we draw the conclusion that the gate voltage can enhance the drain current, and the electric field by the drain voltage affects the amorphous-amorphous transition. The switching device always contains the amorphous state and never exhibits the Ohmic behavior of the crystalline state.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.280-281
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• 2011

We fabricated the devices of TFT type with the amorphous chalcogenide channel. A single device consists of a Pt source and drain, a Ti glue layer and a GeSe chalcogenide channel layer on SiO2/Si substrate which worked as the gate. We confirmed the drain current with variations of gate bias and channel size. The I-V curves of the switching device are shown in Fig. 1. The channel of the device always contains amorphous state, but can be programmed into two states with different threshold voltages (Vth). In each state, the device shows a normal Ovonic switching behavior. Below Vth (OFF state), the current is low, but once the biasing voltage is greater than Vth (ON state), the current increases dramatically and the ON-OFF ratio is about 4 order. Based on the experiments, we contained the conclusion that the gate voltage can enhance the drain current, and the electric field by the drain voltage affects the amorphous-amorphous transition. The switching device always contains the amorphous state and never exhibits the Ohmic behavior of the crystalline state.

• 한국전기전자재료학회논문지
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• 제32권5호
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• pp.376-381
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• 2019

In this work, we evaluated the structural, electrical and optical properties of $Ge_8Sb_2Te_{11}$ and Cu-doped $Ge_8Sb_2Te_{11}$ thin films prepared by rf-magnetron reactive sputtering. The 200-nm-thick deposited films were annealed in a range of $100{\sim}400^{\circ}C$ using a furnace in an $N_2$ atmosphere. The amorphous-to-crystalline phase changes of the thin films were investigated by X-ray diffraction (XRD), UV-Vis-IR spectrophotometry, a 4-point probe, and a source meter. A one-step phase transformation from amorphous to face-centered-cubic (fcc) and an increase of the crystallization temperature ($T_c$) was observed in the Cu-doped film, which indicates an enhanced thermal stability in the amorphous state. The difference in the optical energy band gap ($E_{op}$) between the amorphous and crystalline phases was relatively large, approximately 0.38~0.41 eV, which is beneficial for reducing the noise in the memory devices. The sheet resistance($R_s$) of the amorphous phase in the Cu-doped film was about 1.5 orders larger than that in undoped film. A large $R_s$ in the amorphous phase will reduce the programming current in the memory device. An increase of threshold voltage ($V_{th}$) was seen in the Cu-doped film, which implied a high thermal efficiency. This suggests that the Cu-doped $Ge_8Sb_2Te_{11}$ thin film is a good candidate for PRAM.

• 한국재료학회지
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• 제24권1호
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• pp.60-65
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• 2014

Fe-based amorphous coatings were fabricated on a soda-lime glass substrate by the vacuum kinetic spray method. The effect of the gas flow rate, which determines particle velocity, on the deposition behavior of the particle and microstructure of the resultant films was investigated. The as-fabricated microstructure of the film was studied by field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HR-TEM). Although the activation energy for transformation from the amorphous phase to crystalline phase was lowered by severe plastic deformation and particle fracturing under a high strain rate, the crystalline phases could not be found in the coating layer. Incompletely fractured and small fragments 100~300 nm in size, which are smaller than initial feedstock material, were found on the coating surface and inside of the coating. Also, some pores and voids occurred between particle-particle interfaces. In the case of brittle Fe-based amorphous alloy, particles fail in fragmentation fracture mode through initiation and propagation of the numerous small cracks rather than shear fracture mode under compressive stress. It could be deduced that amorphous alloy underwent particle fracturing in a vacuum kinetic spray process. Also, it is considered that surface energy caused by the formation of new surfaces and friction energy contributed to the bonding of fragments.

• Transactions on Electrical and Electronic Materials
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• 제13권6호
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• pp.322-325
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• 2012

Crystalline silica was synthesized by annealing amorphous silica at $1,300^{\circ}C$ or $1,400^{\circ}C$ for various times, and the crystallinity was estimated by X-ray diffraction (XRD) analysis. In order to prepare a low dielectric material, epoxy/crystalline silica composites were prepared, and the effect of silica content on the dielectric properties was studied under various functions of frequency and ambient temperature. The dielectric constant decreased with increasing crystalline silica content in the epoxy composites, and it also decreased with increasing frequency. At 120 Hz, the value of 5 wt% silica decreased by 0.25 compared to that of 40 wt% silica, and at 23 kHz, the value of 5 wt% silica decreased by 0.23 compared to that of 40 wt% silica. The value increased with increasing ambient temperature.

• IMMUNE NETWORK
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• 제13권3호
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• pp.94-101
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• 2013

Amorphous silica particles, whose applications are increasing in many biomedical fields, are known to be less toxic than crystalline silica. In this study, the inflammatory effects of amorphous silica nanoparticles were investigated using 30-nm amorphous silica nanoparticles and human peripheral blood mononuclear cells (PBMCs) or purified monocytes. As a result, production of IL-$1{\beta}$ and IL-8 were increased. In addition, the mitochondrial reactive oxygen species (ROS) was detected, which may lead to mitochondrial membrane disruption. Most importantly, inflammasome formation was observed. Therefore, these results provide immunological information about amorphous silica nanoparticles and suggest that amorphous silica nanoparticles can evoke innate immune reactions in human monocytes through production of IL-$1{\beta}$ and IL-8.

• Journal of Magnetics
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• 제3권3호
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• pp.78-81
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• 1998

Large magneto crystalline anisotropy energy and demagnetization energy of rare earth-transition metal (RF-TM) alloys play roles of bottlenecks towards their commercial applications for giant magnetostrictive and blue wavelength magneto optical recording materials, respectively. To solve the above problems, boron is added into amorphous RE-TM alloys to produce its electron transferring. The boron added amorphous RE-TM alloys show novel magnetic and magneto-optical properties as follows; 1) an amorphous $(Sm_{33}Fe_{76})$97B3 alloy obtains the magnetostriction of$ -550{times}10^{-6}$ at 400 Oe compared with saturation magnetostriction of$ -60{\times}10^{-6}$ in conventional Ni based alloys, 2) an amorphous$ (Nd_{33}Fe_{67})_{95}B_5$ alloy increases effective magnetic anisotropy to$ -0.5{\times}10^{-6} ergs/cm^3 from -3.5{\times}10^6 ergs/cm^3$ without boron, which correspond to the polar Kerr rotation angles of 0.52$^{\circ}$and 0.33$^{\circ}$, respectively. These results attribute to selective 2p-3d electron orbits exchange coupling (SEC).