• 한국분말재료학회지
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• 제26권1호
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• pp.11-15
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• 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.

• 환경위생공학
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• 제14권2호
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• pp.46-55
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• 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.

• 대한환경공학회지
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• 제30권6호
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• pp.637-641
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• 2008

이 연구는 과염소산염 제거를 위하여 정수처리장에서 적용 가능한 맞춤분말활성탄 제조와 활성탄 종류에 따른 제거효율 은 비교하기 위하여 수행하였다. Cetyltrimethylammoniumchloride(CTAC)를 이용하여 활성탄에 흡착 전처리하면 과염소산염을 효과적으로 제거 할 수 있었다. 10,000 mg/L 맞춤분활성탄은 농도 5,000 mg/L CTAC 용액 500 mL에 5 g의 분말활성탄을 혼합하여 제조하였다. 맞춤분말활성탄을 이용하면 일반 분말활성탄에 비해 10 이상 높은 과염소산염 제거가 가능하였다. 맞춤 분말활성탄을 이용하여 과염소산염 제거 시 초기 접촉시간 15분은 접촉시간에 따라 잔류 과염소산염의 농도가 줄어들었으나 15분 이후에는 잔류농도의 변화가 거의 없었다. 맞춤분말활성탄 조제 시 활성탄의 요오드가에 따라서 과염소산염 제거능이 달랐는데 요오드가 1,083 mg/g 활성탄은 요오드가 944 mg/g 활성탄에 비해 4배 이상 높은 과염소산염 제거능을 보였다. 일반적으로 정수장에서 주입 가능한 분말활성탄 농도인 5 mg/L 범위의 맞춤분말활성탄 주입농도에서 50 $\mu$g/L의 과염소산염 농도를 15 $\mu$g/L까지 저감 가능하였다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2001년도 춘계학술강연 및 발표대회
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• pp.39-40
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• 2001

• 한국유체기계학회 논문집
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• 제18권2호
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• pp.43-47
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• 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.

• 한국분말재료학회지
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• 제9권4호
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• pp.235-244
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• 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.

• 산업경영시스템학회지
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• 제30권2호
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• pp.8-14
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• 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
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• 제5권1호
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• pp.37-50
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• 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.

• 자원리싸이클링
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• 제28권5호
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• pp.74-79
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• 2019

구리이온농도를 117.15 mg/L로 조절한 모의 광산배수용액 제조하고, 세멘테이션제로서 철분을 투입하여 세멘테이션 공정 중 구리이온제거효율에 대한 철분당량, 철분크기, 교반속도의 영향을 조사하였다. 교반속도가 200 rpm의 경우, 온도 $20^{\circ}C$에서 2 당량의 철분을 투입하면 90분에 51 %의 구리가 제거되었으나 16 당량의 철분을 투입하면 60분에 99 % 이상의 구리가 제거되었다. $48{\mu}m$ 이하와 $150{\mu}m$ 크기의 철분을 2당량 투입하여 구리제거율을 관찰한 결과 200 rpm에서는 큰 차이를 나타내지 않았으나 교반속도를 400 rpm으로 증가시킨 경우 두 입도 모두에서 구리제거효율을 크게 증가하였으며, 이는 200 rpm에서 철분의 입자가 응집되어 비표면적이 감소된 것이 원인으로 SEM분석을 통해 확인하였다. 교반속도 600 rpm, 반응온도 $20^{\circ}C$, $48{\mu}m$ 이하 철분 2 당량의 조건에서 60 분에 99 % 이상의 구리가 제거된 것을 확인하였다.

• 한국분말재료학회지
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• 제8권2호
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• pp.91-97
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• 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.