• 한국표면공학회지
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• 제50권3호
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• pp.192-197
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• 2017

A 6-way-cross consisting of a 2.75-inch CF flange was used as a main chamber on a PFEIFFER VACUUM TMP station based on a 67 l / sec turbo molecular pump and a diaphragm pump to produce a magnet array with a volume ratio of 5.5: 1.A 1-inch diameter copper target and graphite target were fabricated using MDX-1.5K from Advanced Energy Industries, Inc as a DC power supply. Ion current density of copper target and graphite target was measured by unbalanced magnetron sputtering. The basic pressure condition was $6.3{\times}10^{-7}mbar$ and the process pressure was Ar 50 sccm at $1.0{\times}10^{-2}mbar$ (7.5 mTorr) in the Ar atmosphere. Therefore, the relative density of copper ions reaching the substrate with the measured ion current density was derived.

• Computers and Concrete
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• 제15권6호
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• pp.973-987
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• 2015

The electrical resistivity of air-dried, saturated, and carbonated concretes with different mixture proportions was monitored to evaluate and quantify the influence of the age of the specimen, carbonation, and curing condition. After 28 days of curing, four prepared specimens were stored in a vacuum chamber with 5% $CO_2$ for 330 days to make carbonated specimens. Four of the specimens were placed in water, and four specimens were cured in air until the end of the experiments. It was observed that the electrical resistivity of the carbonated specimens increased as carbonation progressed due to the decrease of porosity and the increase of hydrated products. Therefore, in order to estimate the durability of concrete, its carbonation depth was used as the measurement of electrical resistivity. Moreover, an increase of electrical resistivity for air-dried and saturated concretes was observed as a function of age of the specimen. From the relationship between chloride diffusivity provided by Yoon et al. (2007) and the measurements of electrical resistivity, it is expected that the results well be of significant use in calibrating chloride diffusivity based on regular measurements of electrical resistivity during concrete construction.

• E2M - 전기 전자와 첨단 소재
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• 제10권5호
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• pp.425-433
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• 1997

BSCCO thin films have been fabricated by co-deposition at an ultralow growth rate using ion beam sputtering(IBS) method. The growth rates of the films was set in the region from 0.17 to 0.27 nm/min. MgO(100) was used as a substrate. In order to appreciate stable existing region of Bi 2212 phase with temperature and ozone pressure, the substrate temperature was varied between 655 and 82$0^{\circ}C$ and the highly condensed ozone gas pressure(PO$_3$) in vacuum chamber was varied between 2.0$\times$10$^{-6}$ and 2.3$\times$10$^{-5}$ Torr. Bi 2212 phase appeared in the temperature range of 750 and 795$^{\circ}C$ and single phase of Bi 2201 existed in the lower region than 785$^{\circ}C$. Whereas, PO$_3$dependance on structural formation was scarcely observed regardless of the pressure variation. And high quality of c-axis oriented Bi 2212 thin film with T$_{c}$(onset) of about 90 K and T$_{c}$(zero) of about 45 K is obtained. Only a small amount of CuO in some films was observed as impurity, and no impurity phase such as CaCuO$_2$was observed in all of the obtained films.lms.

• Applied Microscopy
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• 제47권1호
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• pp.55-62
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• 2017

This paper describes experiments aimed at characterizing the behavior of field electron emitters fabricated by coating carbon fibers with epoxylite resin. Polyacrylonitrile carbon fibers of type VPR-19, thermally treated at $2,800^{\circ}C$, were used. Each was initially prepared in a "uncoated" state, by standard electro polishing and cleaning techniques, and was then examined in a scanning electron microscope. The fiber was then baked overnight in a field electron microscope (FEM) vacuum chamber. Current-voltage characteristics and FEM images were recorded on the following day or later. The fiber was then removed from the FEM, coated with resin, "cured" by baking, and replaced in the FEM. After another overnight bake, the FEM characterization measurements were repeated. The coated fibers had significantly better performance than uncoated fibers. This confirms the results of earlier experiments, and is thought to be due in part to the formation of a conducting channel in the resin over layer. For the coated fiber, lower voltages were needed to obtain the same emission current. The coated fibers have current-voltage characteristics that show smoother trends, with greater stability and repeatability. No switch-on phenomena were observed. In addition, the emission images on the phosphor-coated FEM screen were more concentrated, and hence brighter.

• International Journal of Aeronautical and Space Sciences
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• 제13권2호
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• pp.221-228
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• 2012

An active compensation method for the deformation of composite structures using additional controllable metal parts is proposed, and its feasibility is experimentally investigated in a simulated space environment. Composite specimens are tested in a vacuum chamber, which is able to maintain pressure on the order of 10-3 torr and interior temperature in the range of ${\pm}30^{\circ}C$. The displacement-measuring interferometer system, which consists of a heterodyne HeNe laser and an interferometer, is used to measure the displacement of the whole structure. Meanwhile, the strain of the composite part and temperature of both parts are measured by fiber Bragg grating sensors and thermistors, respectively. The displacement of the composite structure is maintained within a tolerance of ${\pm}1{\mu}m$ by controlling the elongation of the metal part, which is bonded to the end of the composite part. Also, the possibility of fiber Bragg grating sensors as control input sensors is successfully demonstrated using a proper corrective factor based on the specimen temperature gradient data.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 제35회 춘계학술대회
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• pp.25-33
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• 2002

Effect of surface topography on the water wetting nature and micro/nano tribological characteristics of Si-wafer and PTFE was experimentally studied. The ion beam treatment was performed with a hollow cathode ion gun in different argon don dose conditions in a vacuum chamber to change the surface topography, Micro/nano tribological characteristics, water wetting angles and roughness were measured with a micro tribo tester, SPM (scanning prove microscope), contact anglemeter and profilometer, respectively. Results showed that surface roughness increased with the argon ion dose. The water wetting angle of tile ion beam treated samples also increased with the ion dose. Results also showed that micro-adhesion and micro-friction depend on the wetting characteristics of the PTFE samples. However, nano-triboloSical characteristics showed little dependence on the wetting angles. The water wetting characteristics of modified PTFE samples were discussed in terms of the surface topographic characteristics.

• 한국주조공학회지
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• 제30권3호
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• pp.100-110
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• 2010

The solidification sequence and formation of intermetallic phase of Fe-rich Al-Si-Cu alloy were investigated by using real-time imaging of synchrotron X-ray radiation. Effects of cooling rate during uni-directional solidification on the resultant solidification behavior was also studied in a specially constructed vacuum chamber in the SPring-8 facility. The series of radiographic images were complementarily analyzed with conventional analysis of OM and SEM/EDX for phase identification. Detailed solidification sequence and formation mechanisms of various phases were discussed based on real-time image analysis. The growth rates of $\alpha$-AlFeMnSi and ${\beta}-Al_5FeSi$ were measured in order to understand the growth behavior of each phase. It is suggested that real-time imaging technique can be a powerful tool for the precise understanding of solidification behavior of various industrial materials.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.29-33
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• 2004

This paper presents ESPI system for the measurement of thermal expansion coefficient of STS430 up to 1,000$^{\circ}C$. Existing methods, strain gauge and moire have the limitation of contact to object and do not supply the coefficient up to 800$^{\circ}C$. There needs to measure the data up to 800$^{\circ}C$, because heat resistant materials have high melting temperature up to 1,000$^{\circ}C$. In previous studies related to thermal strain analysis, the quantitative results are not reported by ESPI at high temperature, yet. In-plane ESPI and vacuum chamber for the reduction of air turbulence and oxidation are designed for the measurement of the coefficient up to 1,000$^{\circ}C$and speckle correlation fringe pattern images are processed by commercial image filtering tool-smoothing, thinning and enhancement- to obtain quantitative results, which is compared with references data. The comparison shows two data are agreed within 4.1％ blow 600$^{\circ}C$ however, there is some difference up to 600$^{\circ}C$. Also, the incremental ratio of the coefficient is changed up to 800$^{\circ}C$. The reason is the phase transformation of STS430 probably begins at 800$^{\circ}C$.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2004년도 학술대회지
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• pp.41-46
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• 2004

This study deals with the friction and wear characteristics of C-N coated spur gear. The PSII apparatus was built and a SCM415 test piece and test gear with steel substrate was treated with carbon nitrogen by this apparatus. The composition and structure of the surface layer were analyzed and compared with that of PVD coated TiN layer. It was found that both of friction coefficients of C-N coating and TiN coaling decreased with increasing load, however, C-N coating showed relatively lower friction coefficient than that of TiN coating. We was investigated the effect of C-N coating on hardness, friction and wear. The TiN coated gear showed more serious friction phenomena than that of C-N coated gear. It was considered that coating of TiN, which was conducted at a vacuum chamber at about $500^{\circ}C$ results in a tempering of base material that causes microstructure change, which in turn resulted in decreasing of hardness. The C-N coated gear and pinion had higher wear resistance that of TiN coated gear and pinion. C-N coating significantly improved the friction and wear resistance of the gear.

• 전기학회논문지P
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• 제58권4호
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• pp.476-482
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• 2009

This paper describes the development of capacitive sensor for the diagnosis of liquid dielectrics, which is widely used as the electrical insulating oil of transformer, circuit breaker, cable and etc. To survey the dielectric properties of the virgin and aged electrical insulating oils, we utilized the highly precise measuring system, using the principle of cross capacitance. The measured properties were used to determine the design factors of the sensor. Then the factors were optimized with the help of computational analysis. To evaluate diagnosis by the sensor, we performed accelerated thermal aging test about electrical insulating oils. The condition of aged specimens were investigated by measurements of relative permittivity i.e. capacitance change by capacitive sensor. And to evaluate the hysteresis characteristics with the change of temperature, we constructed a testing system, which was composed with vacuum drying oven, oil chamber and measuring instruments, such as LCR meter, MUX and so forth. Through the results of this investigation, we confirmed the superior characteristics of the newly developed sensor.