• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.327-327
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• 2011

A nonthermal bioplasma source was developed for application to human liquid fluids by making use of nano-size tungsten tips. Characteristics of the plasma source are investigated. Here we have used the AC voltage system. The bioplasma source generated by a tungsten tip with quartz tube and ground electrode is a low-temperature plasma without making any noticeable damage to cells at a low power operation. The breakdown voltage and current signals are measured by high voltage probe (Tektronix P6015A) and current probe (P6021). Variation of breakdown temperature near the tip electrode is larger than that in the neighborhood of ground electrode. Bubble formation during discharge has been recorded and investigated by using the high speed camera. The existence and behavior of hydroxyl and superoxide radicals are detected and measured by spectrometers. The electrical and optical properties of breakdown characteristics are also investigated.

• Journal of Advanced Marine Engineering and Technology
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• 제18권3호
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• pp.68-77
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• 1994

TIG welding process is applied for the active metal such as aluminum and titanium, also sometimes for overlay welding of superalloy. However the welding speed to be applied is very low because of the unstable bead formed in the region of high current and high welding speed. The present study was carried out to examine the basic phenomena of high speed TIG melt run welding by the 2% Th - W electrode(dia.3.2mm) of various tip shapes.

• Corrosion Science and Technology
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• 제14권2호
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• pp.59-63
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• 2015

Airless spray which is widely used for painting to ship blocks and hull sides is the coating method for attaching atomized paint material to the substrate using spray tip nozzle with compressed air. When the paint material which has high solid contents such as epoxy primer paint is atomized by passing through spray tip nozzle with high pressure, the nozzle composed of tungsten carbide(WC) undergoes the erosive wear, leading to widening of nozzle hole. The deformation of nozzle hole induces improper spray pattern and coating failures such as finger pattern and sagging because the conditions of spray pump pressure and paint flow rate for developing full spray pattern are changed. In this study, an appropriate replacement cycle of spray tip was predicted by measuring the erosive wear tendency as increasing the spraying time of epoxy primer paint.

• 대한기계학회논문집
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• 제6권2호
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• pp.113-120
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• 1982

In the previously reported Part I, the experimental results in frictional machining that finished medium carbon steel SM 50 C under 6 kinds of liquid atmospheres by using ceramic tip as a frictional tool was described. The present study reports the experimental results that all the machining conditions are same in the Part I except tool material changed ceramics into tungsten carbide. The ceramic tool material is a stable oxide and a non-metallic material, but the tungsten carbide has the metallic characteristics that adhere to carbon steel at about 750.deg.C. The present study shows th comparison of the experimental results for the above 2 kinds of frictional tool material.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.883-886
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• 2001

The mechanical properties such as the Young's modulus, damping ratio, vibration mode and hardness of the disk materials heat-treated under various conditions are measured, and the relations between there properties and the cutting characteristics such as early tip fracture are examined. The results obtained from this study are as follows. The circular saw with the V-Cr added disk has higher young's modulus and damping ratio than the saw with STC5 disk, preventing the early fracture of tungsten carbide due to the above properties. The circular saw with the disk which is subjected to the heat treatment at the quenching temperature of $830^{\circ}C$ and at the temperature of $550^{\circ}C$ have the best tool life and surface roughness.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제28회 추계학술대회
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• pp.313-322
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• 1998

Tappet has wear problems like scuffing or pitting because of high Hertzian contact stress by line contact type between cam and tappet. To overcome this wear problems, we developed the high wear resistant tappet. Developed tappet consists of WC base alloyed tip and steel body. These two parts were directly bonded each other at high temperature under vacuum condition. To estimate the wear resistance of tungsten carbide tappet, we perform the scuffing test and engine dynamo test. As the result, tungsten carbide tappet has better wear resistance than conventionally chilled iron tappet.

• Applied Microscopy
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• 제46권4호
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• pp.227-237
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• 2016

This investigation deals with the process of field electron emission from composite microemitters. Tested emitters consisted of a tungsten or carbon-fiber core, coated with a dielectric material. Two coating materials were used: (1) Clark Electromedical Instruments Epoxylite resin and (2) Epidian 6 Epoxy resin (based on bisphenol A). Various properties of these emitters were measured, including the current-voltage characteristics, which are presented as Fowler-Nordheim plots, and the corresponding electron emission images. A field electron microscope with a tip (cathode) to screen (anode) distance of 10 mm was used to electrically characterize the emitters. Measurements were carried out under ultra-high vacuum conditions with a base pressure of $10^{-6}$ Pascal ($10^{-8}$ mbar).

• 한국진공학회지
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• 제1권1호
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• pp.78-82
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• 1992

W(123) 표면위에 수소와 중소수가 흡착될 때 일함수의 변화를 장방출(Field Fmission) 방법으로 측정하였다. 78K에서 이 분자들이 흡착될 때 일함수의 변화는 처음에 는 증가하다가 최대치에 이른 후 감소하였고, 덮임율(coverage)이 증가함에 따라 포화되었 다. 텅스텐 tip의 온도를 200K까지 올렸을 경우에, 일함수의 변화가 최대가 되었을 때의 덮 임율은 78K일 때의 비해 낮은 덮임율 쪽으로 이동하였고, [011] 방향을 갖는 step 혹은 terrace에 의한 일함수의 효과도 동시에 관측되었다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.18-22
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• 2000

An experimental study was carried out to investigate the effect of nano-contact condition on the nano-adhesion phenomena. SPM(scanning probe microscope) tips with different radius of curvature were fabricated by a series of masking and etching processes. DLC(diamond-like carbon) and W-DLC (tungsten-incorporated diamond-like carbon) were coated on (100) silicon wafer by PACVD(plasma assisted chemical vapor deposition). Pull-off forces of Pure Si-wafer, DLC and W-DLC were measured with SPM(scanning probe microscope). Also, the same series of tests were carried out with the tips with different radius of curvature. Results showed that DLC and W-DLC showed much lower pull-off force than Si-wafer and Pull-off force increased with the tip radius.

• 반도체디스플레이기술학회지
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• 제10권2호
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• pp.115-119
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• 2011

A tip-type carbon nanotube(CNT)-based field emitter was studied to consider it as electron source for micro-focused x-ray tube. The CNT was grown directly on a metal (tungsten) substrate by using an inductively coupled plasma-chemical vapor deposition (ICP-CVD) method. Prior to CNT growth, the metal substrate was etched to have various tip angles from $10^{\circ}$ to $180^{\circ}C$ (flat-type). The morphologies and microstructures of all the grown CNTs were analyzed via field-emission SEM. Furthermore, the effects of substrate tip-angles on the emission properties of CNT-based field emitters were characterized to estimate the maximum current density, the turn-on voltage, and the spatial distribution of electron beams. Prolonged long-term stability testing of the CNT emitters was also performed. All the experiment results obtained from this study indicated why a tip-type CNT emitter, compared with a flat-type CNT emitter, would be more desirable for a micro-focused x-ray system, in terms of the emission current level, the focused beam area, and the emission stability.