• Fibers and Polymers
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• v.6 no.1
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• pp.19-27
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• 2005

High-speed melt spinning of syndiotactic polystyrene was carried out using high and low molecular weight poly­mers, HM s-PS and LM s-PS, at the throughput rates of 3 and 6 g/min. The effect of take-up velocity on the structure and properties of as-spun fibers was investigated. Wide angle X-ray diffraction (WAXD) patterns of the as-spun fibers revealed that the orientation-induced crystallization started to occur at the take-up velocities of 2-3 km/min. The crystal modification was a-form. Birefringence of as-spun fibers showed negative value, and the absolute value of birefringence increased with an increase in the take-up velocity. The cold crystallization temperature analyzed through the differential scanning calorimetry (OSC) decreased with an increase in the take-up velocity in the low speed region, whereas as the melting temperature increased after the on-set of orientation-induced crystallization. It was found that the fiber structure development proceeded from lower take-up velocities when the spinning conditions of higher molecular weight and lower throughput rate were adopted. The highest tensile modulus of 6.5 GPa was obtained for the fibers prepared at the spinning conditions of LM s-PS, 6 g/min and 5 km/min, whereas the highest tensile strength of 160 MPa was obtained for the HM s-PS fibers at the take-up velocity of 2 km/min. Elongation at break of as-spun fibers showed an abrupt increase, which was regarded as the brittle-duc­tile transition, in the low speed region, and subsequently decreased with an increase in the take-up velocity. There was a uni­versal relation between the thermal and mechanical properties of as-spun fibers and the birefringence of as-spun fibers when the fibers were still amorphous. The orientation-induced crystallization was found to start when the birefringence reached -0.02. After the starting of the orientation-induced crystallization, thermal and mechanical properties of as-spun fibers with similar level of birefringence varied significantly depending on the processing conditions.

• Composites Research
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• v.26 no.4
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• pp.254-258
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• 2013

Polypropylene films reinforced with multi-walled carbon nanotubes and exfoliated graphite nanoplatelets were fabricated by extrusion, and the effects of filler type and take-up speed on the mechanical properties and microstructure of composite films were investigated. Differential scanning calorimetry revealed that the addition of carbon nanomaterials resulted in increased degree of crystallinity. However, increasing the take-up speed reduced the degree of crystallinity, which indicates that tension-induced orientations of polymer chains and carbon nanomaterials and the loss of degree of crystallinity due to rapid cooling at high take-up speeds act as competing mechanisms. These observations were in good agreement with tensile properties, which are governed by the degree of crystallinity, where the C-grade exfoliated graphite nanoplatelet with a surface area of $750m^2/g$ showed the greatest reinforcing effect among all types of carbon nanomaterials used. Scanning electron microscopy was employed to observe the carbon nanomaterial dispersion and orientation, respectively.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.06a
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• pp.275-280
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• 1997

We have investigated the deposition characteristics of (Ni0.8Fe0.2)20Ag80 thin films as a function of chamber pressure and nitrogen flow rate with scanning electron microscopy(SEM), atomic force microscopy(AFM), XRD and $\alpha$-step. The deposition rate of these film is decreased with increasing the chamber pressure and the nitrogen flow rate. With raising the chamber pressure, the growth mode of thin film is changed from island growth to columnar one, which is probably due to energy of atom. Contrary, the nitrogen flow rate is raised, growth mode is changed from columnar to island one. According to the XRD patterns, the preferred orientation is inhibited as the nitrogen flow rate is kept above 10 sccm, but that is nearly independent on the chamber pressure. When the chamber pressure decrease or the nitrogen flow rate increase, phase separation into permoally and silver is occured.

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.103-105
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• 2001

ZnO thin films on glass substrate were deposited by RF sputter with various $Ar/O_2$ gas ratio. Crystallinities, surface morphologies, and electrical properties of the films were investigated by XRD(x-ray diffractometer), and SEM (scanning electron microscopy) analyses. The facing targets sputtering system can deposit thin film at plasma free condition and change the deposition condition in wide range. We suggested that a very suitable $Ar/O_2$ gas of ratio should be 50/50 for preparation of high quality ZnO films with good C-axis orientation.

• Journal of the Korean Vacuum Society
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• v.10 no.1
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• pp.57-60
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• 2001

We prepared uniform CdS nanowire arrays ways with lengths up to 5 $\mu\textrm{m}$ and diameters as small as 20 nm by electrochemically depositing the semiconductor directly into the pores of anodic alumina films from an electrolyte containing $CdCl_2$ and S in dimethyl sulfoxide. The nanowire arrays were characterized by scanning electron microscopy and X-ray diffraction. The deposited materials are composed mainly of hexagonal CdS with (100) preferential orientation.

• Tribology and Lubricants
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• v.5 no.2
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• pp.94-100
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• 1989

Friction and Wear behavior of continuous graphite fiber composites was studied for different fiber orientations against the sliding direction. The effect of fiber orientation on friction and wear of the composite and on the deformation of the counterface was investigated experimentally. Pin on disk type testing machine was built and employed to generate the friction and wear data. A graphite fiber composite plate was produced by the bleeder ply molding in an autoclave and machined into rectangular pin specimens with specific fiber orientations, i.e., normal, transverse, and longitudinal directions. Three different wear conditions were employed for two different periods of time, 24 and 48 hours. The wear track of the worn specimens and the metal counterface was examined with a scanning electron microscope (SEM) to observe the damaged fibers on the surface and wear film generation on the counterface. Wear mechanism of the composite during sliding wear is proposed based on the experimental results.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.5
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• pp.224-229
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• 2013

Vanadium oxide thin films were deposited on $c-Al_2O_3$ (001) substrate by in-situ RF magnetron sputtering. Oxygen partial pressure was adjusted to prepare thermochromic $VO_2$ phase. X-ray diffraction patterns and scanning electron microscopy convincingly showed that plate-like $V_2O_5$ grains were changed into round-shape $VO_2$ grains as oxygen partial pressure decreased. After the optimized deposition conditions were fixed, the effect of substrate temperature and orientation on the optical properties of $VO_2$ thin films was analyzed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.10
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• pp.1444-1453
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• 1993

비 구조적인 주면 환경에서 평면 팔레트(planar pallet)를 포크리프트(forklift)로 적재하거나 하역하기 위한 물류용 재료운송 로보트 시스템을 제안한다. 제안한 시스템은 음향(acoustic)센서와 시각(visual) 센싱데이타를 사용하여 팔레트에 지정된 2개의 스롯(slot)의 위치를 결정하고 포크리프트를 팔레트의 스롯에 인게즈(engage) 한다. 본 연구에서는 재료운송 시스템의 복잡성을 줄이기 위해서 폴라로이드(Poraloid) 음향센서의 3차원 거리 데이터와 CCD 카메라에서 얻은 2차원 시각 네이타를 통합하는 방법을 개발한다. 2개의 다른 소스로부터 얻은 데이타는 서로의 미비점을 보안하며 재료운송 로보트 시스템을제어하기 위한 효율적인 알고리즘을 제공한다. 카메라는 far-away vision 개념에 의한 음향센서의 선형 스캔닝(scanning) 대역을 우선 결정한다. 선형 스캔닝에 의하여 얻어지는 거리 데이타(range Map)는 least mean square방법을 사용하여 팔레트의 위치와 자세(position and orientation)를 결정한다(near vision). 팔레트에 대한 위치와 자세가 결정되면 다시 시각센서를 이용하여(close vision) 에지(edge)탐지와 Hough transfrom 기술을 적용하여 팔레트에 대한 포크리프트의 인게이지먼트 위치를 구한다. 개발된 시스템은 하드웨어와 소프트웨어로 구현하고 평가하며 실험적인 결과도 제시한다.

• Journal of information and communication convergence engineering
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• v.7 no.4
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• pp.530-534
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• 2009

C-axis-oriented ZnO thin films were successfully deposited on p-Si (100) in an RF magnetron sputtering system. Deposition conditions such as deposition power, working pressure, and oxygen gas ratio $O_2/(O_2+Ar)$ were varied. Crystalline structures of the deposited ZnO films were investigated by a scanning electron microscope (SEM) technique. Results show that the deposition parameters can have a strong impact on the preferred orientations and grain sizes of the deposited ZnO films.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.51 no.2
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• pp.77-81
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• 2002

In this study, PZT thin films were fabricated using sol-gel processing onto Si/$SiO_2$/Ti/Pt substrates. PZT sol with different Zr/Ti ratio(20/80, 30/70, 40/60, 52/48) were prepared, respectively. The films were fabricated by using the spin-coating method on substrates. The films were heat treated at $450^{\circ}C$, $650^{\circ}C$ by rapid thermal annealing(RTA). The preferred orientation of the PZT thin films were observed by X-ray diffraction(XRD), and Scanning electron microscopy(SEM). All of the resulting PZT thin films were crystallized with perovskite phase. The fine crystallinity of the films were fabricated. Also, we found that the ferroelectric properties from the dielectric constant of the PZT thin films were over 600 degrees, P-E hysteresis constant. And the leakage current densities of films were lower than $10^{-8}A/cm^2$. It is concluded that the PZT thin films by sol-gel process to be convinced of application for ferroelectric memory device.