• Journal of Industrial Technology
• /
• v.28 no.A
• /
• pp.19-22
• /
• 2008

In recent years, much attention has been paid to "Photocatalytic oxidation" as an alternative technique, where the pollutants are degraded by UV-irradiation in the presence of a semiconductor suspension such as titanium dioxide. $TiO_2$ is the most often used photocatalyst due to its considerable photocatalytic activity, high stability, non-environmental impact and low cost. 1n this research, the photocatalytic degradation of humic acid, acetaldehyde and methylene blue in $UV/TiO_2$ systems has been stydied. The effect of calcination temperature for manufacturing of $TiO_2$ photocatalysts and type of photocatalysts on photodegradation has been investigated. Photocatalysts with various metal ions(Mn, Fe, Cu and Pt) loading are tested to evaluate the effects of metal ions impurities on photodegradation. The photodegradation efficiency with $Pt-TiO_2$ or $Fe-TiO_2$ or $Cu-TiO_2$ is higher than Degussa P-25 powder. However, the photodegradation efficiency with $Mn-TiO_2$ is lower than Degussa P-25 powder. The photocatalytic properties of the nanocrystals were strongly dependent upon the crystallinity, particle size, standard reduction potential of various transition metal and electronegativity of various transition metal. As a result photocatalysts with various metal ion loading evaluated the effect of photodegradation.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.17 no.1
• /
• pp.1-6
• /
• 2008

There are some methods that have been used to manage a degasing process in recent years, such as an injection method that uses aluminum molten metal powder and chemicals supplier and input method that supplies argon and nitrogen, or chlorine gas by using a gas blow-tube. However, these methods show some problems, and it shows that it is a difficult process to handle, pollution due to producing a lot of toxic gases like chlorine and fluoride gas, irregular effects, and lowering work efficiency due to the excessive processing time. The problems that are the most fatal are the producing a lot of sludge due to the reaction of aluminum molten metal with chemicals, loss of metals, and decreasing the life of refractory materials. In order to solve these problems, this paper develops a technology that is related to aluminum continuous casting molten metal and monolithic degasing apparatus. A degasing apparatus developed in this study improved the existing methods and prevented environmental pollution with smokeless, odorless, and harmlessness by using a new method that applies argon and nitrogen gas in which the methods used in the West and Japan are eliminated. The method developed in this study decreases the molten metal processing and settling time compared to the existing methods and improves the workers' health, safety, and environment because there is no pollution in processes.

• Proceedings of the KWS Conference
• /
• 2010.05a
• /
• pp.32-38
• /
• 2010

Hybrid material(ceramic+metal) processes were developed for micro filter using ceramics coating at metal filter surface by thermal spray method, micro hole drilling at ceramic coated filter surface by femtosecond laser, and fiber laser direct welding of ceramic and metal (SUS304, SM45C) by capillary effect. Thermal spray process was used for ceramic powders and metal filters. The used ceramic powders were $Al_2O_3+40TiO_2$(Metco 131VF) powder of maximum particle size $5{\mu}m$ and ${Al_2O_3}99+$(Metco 54NS) power of maximum particle size 45m. Ceramic coated filters using thermal spray method had a great influence on powder material, particle size and coating thickness but had a fine performance as a micro filter. CW fiber laser was used to drill the top ceramic layer and melt the bottom metal layer for joining applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.474-475
• /
• 2007

Wire electrical explosion(WEE) has been used for the production of fine metal particles. In WEE, electrical powder was stored and compressed into capacitor and released to produce fine particles through evaporation and condensation. In this study, the effect of applied voltage on the size of copper powders was investigated. High tension was added up to the explosion device by dividing 4 steps. At voltages lower than 5.2 kV, the fraction of powders finer than $44{\mu}m$ was almost negligible. The effectiveness of explosion increased sharply with increased voltage over 5.8 kV. At the highest voltage of 6.4 kV, more than 80% of explosion products were finer than $44{\mu}m$.

• Journal of Powder Materials
• /
• v.7 no.4
• /
• pp.228-236
• /
• 2000

An investigation was carried out on the possibility whether the ball-milling process of low energy could successfully improve the packing density and flowability for MIM application in W-20wt%Cu system. In this study, W-20wt%Cu powder mixture was prepared by ball-milling. W powder was not fractured by low mechanical impact energy used in the present work during the critical ball-milling time, but the ductile Cu powder was easily deformed to the 3 dimensional equiaxed shape, having the particle size similar to that of W powder. The ball-milled mixture of W-20wt%Cu powder had the more homogeneous distribution of each component and the higher amount of powder loading for molding than the simple mixture of W-Cu powder with an irregular shape and a different size. Accordingly, the MIM W(1.75)-20wt%Cu powder compacts were able to be sintered to the relative density of 99% by sintering at $1400^{\circ}C$ for one hour.

• Journal of Powder Materials
• /
• v.5 no.4
• /
• pp.340-344
• /
• 1998

Along with the growth of conventional ferrous powder metallurgy (PM), PM of aluminum alloys has been intensively investigated in Japan. Although rapidly solidified aluminum alloy powder was first used in the USA,/sup 1)/ commercialization for consumer market was first realized in Japan./sup 2)/ In order to achieve the viable cost-performance including Near Net Shape (NNS) formability, we developed three processes, powder extrusion, powder forging and sintering. The new powder extrusion process does not use either capsulation or vacuum degassing. The new powder forging does not need lateral flow. The new sintering process does not use liquid phase. The performance achieved by the processes is outstanding mechanical or physical properties that has potential to substitute cast iron, steel, titanium Metal Matrix Composite (MMC) or Ingot Metallurgy (IM) aluminum alloys. Cooperation with customers, powder suppliers and research associations contributed to the advancement of PM aluminum alloys in Japan.

• Journal of Powder Materials
• /
• v.10 no.1
• /
• pp.51-56
• /
• 2003

To investigate the effect of the parameters of the plasma arc discharge process on the particle formation and particle characteristics of the iron nano powder, the chamber pressure, input current and the hydrogen volume fraction in the powder synthesis atmosphere were changed. The particle size and phase structure of the synthesized iron powder were studied using the FE-SEM, FE-TEM and XRD. The synthesized iron powder particle had a core-shell structure composed of the crystalline $\alpha$-Fe in the core and the crystalline $Fe_3O_4$ in the shell. The powder generation rate and particle size mainly depended on the hydrogen volume fraction in the powder synthesis atmosphere. The particle size increased simultaneously with increasing the hydrogen volume fraction from 10% to 50%, and it ranged from about 45nm to 130 nm.

• Journal of Welding and Joining
• /
• v.19 no.5
• /
• pp.481-485
• /
• 2001

Laser cladding processing allows rapid transfer of heat to the material being processed with minimum conduction into base metal. The effect of $CO_2$ laser cladding with high viscosity mixed powders was investigated. High viscosity mixed powder consists of bronze powder and flux that is used at a high temperature condition. The mixed powder has a high viscosity that it can be easily pasted over a curved or slope substrate. The device for mixed powder was designed and manufactured. It consists of the high viscosity mixed powder feeding system, the preheating system and the shielding gas system which prevents the clad layer from being oxidized. The results of experiment indicated that the feed rate of high viscosity mixed powder was important for later cladding with mixed powder feeding. The high viscosity mixed powder and substrate must be preheated to prevent porosity from breaking at the clad layer. The experimental result shows that the high viscosity mixed can be applied for laser cladding process.

• Journal of Navigation and Port Research
• /
• v.34 no.1
• /
• pp.27-31
• /
• 2010

In this paper, we developed an EM wave absorber having the absorption ability of more than 15 dB for port logistics RFID system by using AMP. Firstly, we fabricated EM wave absorber by using AMP and CPE(Chlorinated Polyethylene) with different composition ratios 80:20 wt.% and 85:15 wt.%. Secondly, we designed the optimum EM wave absorber using the calculated material constants obtained from measured input impedance of the samples. Therefore, EM wave absorber with absorption ability of 17.5 dB at 433 MHz when composition ratio of AMP:CPE=85:15 wt.% and thickness of 5.5 mm.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.985-986
• /
• 2006

Principal peculiarities of technology for applying coatings of metallic powders on internal surfaces of hollow cylindrical parts by centrifugal method with induction heating from internal surface of part are examined. It is shown that most effective checking and regulating method of sintered powder layer is monitoring the high-frequency current generator power upon contactless pickup indications of external surface temperature of rotating part.