• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.7 no.3
• /
• pp.465-472
• /
• 1997

An extension of new test methods for surfaces with an apparatus based on photon-induced desorption and ionisation in the electric field, is constructed and tested, It also investigates how to show the efficiency of the arrangement adsorbates $H_2$ and He on W(110). The field emitter temperature was 80 K. The wavelength of light used was 193 nm with field strengths between 10 and 50 V/nm. Many ion fragments($CO^+, He^+, H_2^^+, H_2O^+, W^{3+}\; and\; W^{2+}$) were produced by an electronic stimulation of the adsorbate with the help of a photon energy of 6.4 eV at He and $H_2$/W(110). A transient recorder enables the registration of the entire mass spectrum.

• Journal of Welding and Joining
• /
• v.9 no.1
• /
• pp.23-31
• /
• 1991

Laser beam weldability of zircaloy-4was investigated using a pulsed Nd: YAG laser of 200W average power. Mechanical properties of laser and GTA bead-on-plate welded zircaloy-4 test specimens were compared. The influence of plasma generated during laser welding was analyzed and optimum laser welding parameters were investigated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.16 no.1
• /
• pp.1-4
• /
• 2003

The SiH$_4$soak step is widely used to prevent the WF$_{6}$ attack to the underlayer metal using the chemical vapor deposition (CVD) method. Reduction or skipping of the SiH$_4$soak process time if lead to optimizing W-plug deposition process on via. The electrical characteristics including via resistance and the structure of W-film are affected by the time of SiH$_4$soak process. The possibility of elimination of SiH$_4$soak process is confirmed In the case of W- film grown on the stable Ti/TiN underlayer.

• Resources Recycling
• /
• v.27 no.6
• /
• pp.3-10
• /
• 2018

Tungsten is a metal with high melting point and used as a raw material for the production of super alloys. Tungsten exists as $WO{_4}^{2-}$ in alkaline solution. As solution pH decreases, polymerization reaction of $WO{_4}^{2-}$ occurs to result in the precipitation of tungstic acid. The hydrometallurgical process for the recovery of tungsten from ores or secondary resources can be classified as acid and alkaline leaching. In selecting a process for the recovery of pure tungsten from secondary resources, the nature and concentration of impurities in the secondary resources and the manufactured tungsten materials should be considered.

• Korean Journal of Materials Research
• /
• v.25 no.6
• /
• pp.274-278
• /
• 2015

The possibility of using the chemical precipitation method of up-cycled ammonium paratungstate (APT) was studied and compared with the thermal decomposition method. $WO_3$ particles were synthesized by chemical precipitation method using a 1:2 weight ratio of APT: Di-water. For thermal decomposition, APT powder was heated for 4h at $600^{\circ}C$ in air atmosphere. The reaction products were characterized by X-ray diffraction (XRD), X-ray fluorescence spectrometer (XRF), particle size analyzer (PSA), and field emission-scanning electron microscopy (FE-SEM). Thermogravimetric analysis (TGA) of the up-cycled APT allowed for the identification of the sequence of decomposition and reduction reactions that occurred during the heat treatment. TGA data indicated a total weight loss of 10.78% with the reactions completed in $658^{\circ}C$. The XRD results showed that APT completely decomposed to $WO_3$ by thermal decomposition and chemical precipitation. The particle size of the synthesized $WO_3$ powders by thermal decomposition with 2 h of planetary milling was around $2{\mu}m$ During the chemical precipitation process, the particle size of the synthesized $WO_3$ powders showed a round-shape with ${\sim}0.6{\mu}m$ size.

• Journal of the Korea Convergence Society
• /
• v.12 no.4
• /
• pp.87-94
• /
• 2021

While the shielding substances of radiation shields in medical institutions are beginning to be replaced by environmentally friendly materials, radiation protection according to the shielding properties of environmentally friendly substances is becoming an important factor rather than the existing lead shielding properties. Tungsten and barium sulfate are representative shielding materials similar to lead, and are made in sheets or fiber form with eco-friendly materials. Ytterbium is an impermeable material used as a fluorine compound in the dental radiation field. This study aims to evaluate the shielding performance in the x-ray shielding area by comparing the shielding properties of ytterbium by energy band and that of existing eco-friendly materials. When three types of shielding sheets were fabricated and tested under the same process conditions, the shielding performance of the medical radiation area was about 5 % difference from tungsten. Furthermore, shielding performance was superior to barium sulfate. In the cross-sectional structure of the shielding sheet, there was a disadvantage that the arrangement of particles was not uniform. Ytterbium oxide showed sufficient potential as a medical radiation shielding material, and it is thought that it can improve the shielding performance by controlling the particle arrangement structure and particle size.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.1
• /
• pp.603-608
• /
• 2018

Although the voltage-applied discharge method is most widely used in the semiconductor and display industries, periodic management costs are incurred because the method causes defects due to the absorption of ambient fine dust and causes emitter tip contamination due to the discharge. The emitter tip contamination problem is caused by the accumulation of fine particles in ambient air due to the corona discharge of the ionizer. Fuzzy ball generation accelerates the wear of the emitter tip and deteriorates the performance of the ionizer. Although a mechanical cleaning method using a manual brush or an automatic brush is effective for contaminant removal, it requires management of additional mechanical parts by the user. In some cases, contaminants accumulated in the emitter may be transferred to the wafer or product. In order to solve this problem, we developed an ionizer for a clean environment that can remove the pencil-type emitter tip and directly ionize the surrounding gas molecules using the tungsten wire located inside the ion tank. As a result of testing and certification by the Korea Institute of Machinery and Materials, the average concentration was $0.7572particles/ft^3$, the decay time was less than two seconds, and the ion valance was 7.6 V, which is satisfactory.