• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.682-685
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• 2003

In this paper, we propose the method to measure the Young's modulus of carbon nano tube which was manufactured by chemical vapor deposition. We also made the tungsten tip by electrochemical etching process and the carbon nano tube which was detangled through ultra-sonication with isopropyl alcohol was attached to the tungsten tip. This tip which was composed of tungsten tip and carbon nano tube can be used in Young's modulus measurement by applying DC voltage with counter electrode. The attachment process and measurement of the deflection of carbon nano tube was done under optical microscope.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.581-584
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• 2003

The austenitic STS 304 stainless steel was turned to clarify the effects of tool geometry on the tool wear. The wear of TiN-TiCN-TiC-TiAlN coated tungsten carbide tool was the smallest, exhibiting larger wear in the order of Si-Al-O-N ceramic, TiN coated tungsten carbide, TiN-TiCN-TiN coated tungsten carbide, TiC-TiN cermet and M20 tungsten carbide tools at the same cutting conditions. The S-type tool of M20 with large approach angle showed the longest tool life of all tools used in this tests due to preventing the groove wear of the side cutting edge. The wear of the S-type tool with the rake angle of 15$^{\circ}$became smaller than with that of -5$^{\circ}$, but the tool with the nose radius of 0.8mm did not perform much better with increasing the rake angle.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.883-886
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• 1999

We deposited tungsten gate electrode on gate SiO$_2$by thermal LPCVD with WF$_{6}$, SiH$_4$ and H$_2$. The resistivity was ~10$\mu$Ωcm and exhibited good adhesion ability on oxide when the temperature was higher than 40$0^{\circ}C$. We find that, however, both the low-field current and the charge-trapping characteristics were inferior to the control devices. The oxide degradation by fluorine during the tungsten deposition must be minimized to use the tungsten as alternative gate electrode.e.

• Nuclear Engineering and Technology
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• v.48 no.3
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• pp.795-798
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• 2016

Transmission X-ray tubes based on carbon nanotube have attracted significant attention recently. In most of these tubes, tungsten is used as the target material. In this article, the well-known simulator Geant4 was used to obtain some of the tungsten target parameters. The optimal thickness for maximum production of usable X-rays when the target is exposed to electron beams of different energies was obtained. The linear variation of optimal thickness of the target for different electron energies was also obtained. The data obtained in this study can be used to design X-ray tubes. A beryllium window was considered for the X-ray tube. The X-ray energy spectra at the moment of production and after passing through the target and window for different electron energies in the 30-110 keV range were also obtained. The results obtained show that with a specific thickness, the target material itself can act as filter, which enables generation of X-rays with a limited energy.

• Explosives and Blasting
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• v.19 no.1
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• pp.101-110
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• 2001

Depleted uranium (DU) outperforms tungsten heavy alloys (WHA) by about 10%. Because of environmental and hence, political concerns, there is a need to improve WHA performance, in order to replace the DU penetrators. A technique of metal powder compaction by the detonation of an explosive has been applied to tungsten-titanium(W-Ti) powder materials that otherwise may be difficult to fabricate conventionally or have dissimilar, nonequilibrium, or unique me1astab1e substructures. However, the engineering properties of compacted materials are not widely reported and are little known especially for the "unique" composition of W-Ti alloy. To develop high-performance tungsten composites with superior ballistic attributes, it is necessary to understand, carefully document controlled experimental results, and develop basic computational models for potential composites with controlled microstructures. A detailed understanding and engineering application of W-Ti alloy can lead to the development of new structural design for engineering components and materials.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.3
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• pp.80-87
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• 2002

Tungsten carbide microshaft is used as micro-punch, electrode of MEDM (micro-electro-discharge machining), and micro-tool because it has high hardness and high rigidity. In this study, the tungsten carbide microshaft was fabricated using electrochemical machining. Concentration of material removal at the sharp edge and metal corrosion layer affect the shape of the microshaft. Control of microshaft shape was possib1e through conditioning the machining voltage and electrolyte concentration. By applying periodic voltage, material removal rate increased and surface roughness improved. The fabricated microshaft in $H_2 SO_4$ electrolyte maintained sharper end edge and better surface finish than those fabricated by other electrolytes.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.10
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• pp.56-64
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• 2003

The effect of tool geometry on the tool wear in turning the austenitic stainless steel, STS 304 was investigated. The wear of TiN-TiCN-TiC-TiAlN coated tungsten carbide tool was the smallest, showing larger wear in the order of Si-Al-O-N ceramic, TiN coated tungsten carbide, TiN- TiCN- TiN coated tungsten carbide, TiC-TiN cermet and M20 tungsten carbide tools at the same cutting conditions. The S-type tool of M20 with the larger side cutting edge angle showed the smallest tool wear in all tests due to preventing the groove wear of the side cutting edge. The wear of the S-type tool with the rake angle of $15^{\circ}$ became smaller than with that of $-5^{\circ}$, but the tool with the nose radius of 0.8mm did not perform much better with increasing the rake angle.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.157-157
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• 1999

Electrochromic tungsten oxide films were prepared by the electron beam deposition, and the dependence of the electrochemical stability and the optical properties on the titanium concentration, and on the annealing temperature, that was investigated. coloring and bleaching experiments were repeated by cyclic voltammetry in a propylene carbonate solution of LiClO4. Spectrometry was used to assess the stability of the transmittance in the degraded films. Tungsten oxide films with titanium contents of about 10~15 mol% were found to be most stable, undergoing the least degradation during the repeated for coloring and bleaching cycles. The reason for this small amount of degradation was the reduction of lithium ion trapping sites in the films, which results in an increased durability. Tungsten oxide films with titanium contents of about 20 mol% were annealed at 20$0^{\circ}C$ for 1 hour, and this results showed that durability of films were increased.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1259-1264
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• 2008

This paper presents an accelerated life test for burn out of tungsten filament of automotive halogen lamp. There are many failure modes and failure factors that associated with tungsten filament. But in this explain the dominant failure mode of tungsten filament is the bumout of the filament failure. At first, over voltage, high temperature, inrush current and vibration are selected as stress factors by using of two stage Quality Function Deploymeng(QFD). And we planed accelerated life test that has one factor(voltage) and three levels. By experiment it has absorbed that over voltage has an effect on the life of halogen lamp. Using ALTA programs, we estimated the common shpae parament of Weibull distribution, life-stress relationship and $B_{100p}$ life.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.1
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• pp.22-28
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• 1996

From the experimental study of Wire-Cut Electric Discharge Machining of STD-11 alloy steel and P-20 tungsten carbide, the characteristics such as hand drum form and discharge gap have been observed and evaluated for various conditions. Hand drum form can be improved when gap have been observed and evaluated for various conditions. Hand drum form can be improved when gap voltage and spark cycle become smaller, thickness become thinner, wire tension become larger and the no of cutting increases. When 60mm thickness tungsten carbide is cut in normal condition, hand drum form becomes larger due to the low conductivity machining allowance become slightly larger when peak discharge current and gap voltage become larger, or wire tension becomes smaller. Under the same condition, machining allowance of tungsten carbide is larger than alloyed steel by 1/100mm.