• Journal of Powder Materials
• /
• v.26 no.1
• /
• pp.11-15
• /
• 2019

In this study, a method to remove residual powder on a multi-layered graphene and a new approach to transfer multi-layered graphene at once are studied. A graphene one-step transfer (GOST) method is conducted to minimize the residual powder comparison with a layer-by-layer transfer. Furthermore, a residual powder removing process is investigated to remove residual powder at the top of a multi-layered graphene. After residual powder is removed, the sheet resistance of graphene is decreased from 393 to 340 Ohm/sq in a four-layered graphene. In addition, transmittance slightly increases after residual powder is removed from the top of the multi-layered graphene. Optical and atomic-force microscopy images are used to analyze the graphene surface, and the Ra value is reduced from 5.2 to 3.7 nm following residual powder removal. Therefore, GOST and residual powder removal resolve the limited application of graphene electrodes due to residual powder.

• Journal of environmental and Sanitary engineering
• /
• v.14 no.2
• /
• pp.46-55
• /
• 1999

This study compared the adsorption characteristics of heavy metal ions by crab shell, treated crab shell with 2N-HCl, treated crab shell with 4%-NaOH, chitin and chitosan.Using crushed crab shell, the heavy metal ions removal rates of $Cd^{2+}$ and $Zn^{2+}$ were about 70-80% in 45minutes, but the removal rates of $Cu^{2+}$, $Cr^{6+}$ and $Pb^{2+}$ was less than 10%, 10% and 30%, respectively. For the by-products crab shell by 2N-HCl treatment, it was shown that the removal rates of $Cu^{2+}$ and $Pb^{2+}$ were about 70-80% in 45minutes reaction. But, some problems were observed, that the contained protein in crab shell was changed into gel in the mixing solution after a few hours. For the by-products of crab shell by 4%-NaOH treatment, the removal rates of Pb and Zn were about 90% in 45 minutes, and those of capacity of chitin and chitosan powder was better than those of the other by-products. The more adding to the adsorbent dosages increased the removal rates, and the adsorption reaction was rapidly occurred in a few minute. Using 1.0 wt% chitin powder, the heavy metal removal rates were ordered $Cu^{2+}$(94%) > $Zn^{2+}$(89%) > $Cd^{2+}$(88%) > $Pb^{2+}$(77%) > $Cr^{6+}$(58%) in 45 minutes. Using 1.0 wt% chitosan powder, the heavy metal removal rates were ordered $Cu^{2+}$(99%) > $Pb^{2+}$(96%) > $Cd^{2+}$(79%) > $Zn^{2+}$(71%) > $Cr${6+}$(46%) in 45minutes. The degree of degree of deacetylation by prepared chitosan was 91%.The Freundlich adsorption isotherm of $Cu^{2+}$, $Cd^{2+}$ and $Zn^{2+}$, when it was applied to 1.0 wt% chitosan powder in minutes, can be acceptable very strictly. The equation constant (1/n) for $Cu^{2+}$, $Cd^{2+}$ and $Zn^{2+}$ were 0.54 0.41 and 0.23 respectively.

• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.6
• /
• pp.637-641
• /
• 2008

The aims of this research were to manufacture tailored powder activated carbon having a higher prechlorate removal efficiency and to compare perchlorate removal efficiency with different carbon materials for applying to the drinking water treatment plant. Activated carbon pre-loaded with cetyltrimethylammonium chloride(CTAC) has been researched to be an effective adsorbent for removing perchlorate in the water. 10,000 mg/L tailored powder activated carbon were manufactured by mixing 5.0 g of powder activated carbon(PAC) into 500 mL of 5,000 mg/L CTAC solution. The tailored powder activated carbon had 10 times higher perchlorate removal efficiency than virgin powder activated carbon. The residual perchlorate gradually decreased with the first 15 minute contact time with the tailored powder activated carbon, however, the longer contact time did not affect perchlorate removal. Tailored powder activated carbon by manufactured with 1,083 mg/g iodine value carbon had almost 4 times higher perchlarate removal efficiency than the 944 mg/g iodine value carbon. Dosage of 5 mg/L tailored powder activated carbon, which can adaptable dosage at the treatment plant, could decrease the perchlorate concentration from 50 $\mu$g/L to 15 $\mu$g/L.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2001.04a
• /
• pp.39-40
• /
• 2001

• The KSFM Journal of Fluid Machinery
• /
• v.18 no.2
• /
• pp.43-47
• /
• 2015

As water quality regulations have tightened, many studies to improve wastewater treatment efficiency have been performed. In this study, magnetite powder was used to maintain a high concentration of MLSS in lab-scale wastewater treatment system. After magnetite powder injection, MLSS concentration was above 8,000 mg/L and it was 3.2 times higher than control group(2,500 mg/L). In addition, nitrogen removal efficiency and phosphorus removal efficiency comparing with the control group was increased 20.5% and 11%, respectively.

• Journal of Powder Materials
• /
• v.9 no.4
• /
• pp.235-244
• /
• 2002

The effects of residual impurities on solid state sintering of the powder injection molded (PIMed) W-15wt%Cu nanocomposite powder were investigated. The W-Cu nanocomposite powder was produced by the mech-ano-chemical process consisting of high energy ball-milling and hydrogen reduction of W blue powder-cuO mixture. Solid state sintering of the powder compacts was conducted at $1050^{\circ}C$ for 2~10 h in hydrogen atmosphere. The den-sification of PIM specimen was slightly larger than that of PM(conventional PM specimen), being due to fast coalescence of aggregate in the PIM. The only difference between PIM and PM specimens was the amount of residual impurities. The carbon as a strong reduction agent effectively reduced residual W oxide in the PIM specimen. The $H_2O$ formed by $H_2$ reduction of oxide disintegrated W-Cu aggregates during removal process, on the contrary to this, micropore volume rapidly decreased due to coalescence of the disintegrated W-Cu aggregates during evolution of CO.It can be concluded that the higher densification was due to the earlier occurred Cu phase spreading that was induced by effective removal of residual oxides by carbon.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.30 no.2
• /
• pp.8-14
• /
• 2007

The powder blasting process has become an important machining technique for the cost effective fabrication of micro devices. This process is similar to sand blasting, and effectively removes hard and brittle materials. A large number of investigations on the abrasive jet machining with such output parameters as material removal rate, penetration and surface roughness have been carried out and reported by various authors. To achieve higher surface roughness, to increase material removal rate and to identify the influence of blasting parameters on the output parameters, we use the taguchi method which is one of the design methods of experiments. We can select process parameters to optimize the blasting process of glass. Experimental results indicate that the taguchi method is useful as a robust design methodology for the powder blasting process.

• Advances in environmental research
• /
• v.5 no.1
• /
• pp.37-50
• /
• 2016

The main objective of this study is to evaluate adsorptive removal of Methylene Blue (MB) dye from aqueous solution using pumice powder. The effects of pH, adsorption time, agitation speed, adsorbent dose, and dye concentrations on dye adsorption were investigated. Process kinetics and isotherm model constants were determined accordingly. The results showed that adsorbent dose, dye concentration and agitation speed are the important parameters on dye adsorption and the removal of MB did not significantly change by varying pH. A total adsorption process time of 60 min was observed to be sufficient to effectively remove 50 mg/L MB concentration. The MB adsorption data obeyed both pseudo first order and second order kinetic models. Adsorption of MB by pumice fitted well both Langmiur and Freundlich isotherms ($R^2{\geq}0.9700$), except for 150 rpm agitation speed that system fitted only Langmiur isotherm. The results of this study emphasize that pumice powder can be used as a low cost and effective adsorbent for dye removal.

• Resources Recycling
• /
• v.28 no.5
• /
• pp.74-79
• /
• 2019

The effects of equivalent of iron powder, particle size, agitation speed on the removal efficiency of copper ion were investigated by adding iron powder as cementation agents to simulated mine drainage solution with 117.15 mg/L Cu ion. The 50 % of Cu was removed at 90 min with 2 equivalent of iron powder while more than 99 % of Cu was removed at 60 min with 16 equivalent at 200 rpm and $20^{\circ}C$. The removal efficiencies of Cu ion were not different using 2 equivalent of $48{\mu}m$ and $150{\mu}m$ iron powder, and the removal efficiency increased rapidly with increasing the agitation speed to more than 400 rpm. This lower removal efficiency resulted from agglomeration of iron powder observed by SEM, which could reduce the effective specific surface area. More than 99 % of copper ion was removed using 2 equivalent of $48{\mu}m$ iron powder at 60 min, 600 rpm and $20^{\circ}C$.

• Journal of Powder Materials
• /
• v.8 no.2
• /
• pp.91-97
• /
• 2001

The conventional debinding process in metal injection molding is very long time-consuming and unfriendly environmental method. Especially, in such a case of injection molded parts from hard and fine metal powder, such as WC-Co, an extremely long period of time is necessary in the conventional slow binder removal process. On the other hand, supercritical debinding is thought to be the effective method which is appropriate to eliminate the aforementioned inconvenience in the prior art. The supercritical fluid has high diffusivity and density, it can penetrate quickly into the inside of the green metal bodies, and extract the binder. In this paper, super-critical debinding is compared with wicking debinding process. Wax-based binder system is used in this study. The binder removal rate in supercritical $CO_2$ have been measured at $65^{\circ}C$, 75$^{\circ}C$ in the pressure range from 20 MPa to 28 MPa. Pores and cracks in silver bodies after sintering were observed using SEM When the super-critical $CO_2$ debinding was carried out at 75$^{\circ}C$, almost all the wax (about 70 wt% of binder) was removed in 2 hours under 28 MPa and 2.5 hours under 25 MPa.