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반암(맥반석)으로 제조한 다공성 펠렛의 Ag 담지 및 항균 메디아로서의 적용
한요셉,김현중,신영섭,박재구,고재철,Han, Yo-Sep,Kim, Hyun-Jung,Shin, Young-Seop,Park, Jai-Koo,Ko, Jae-Churl 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.1
The porous pellets were prepared from porphyry by slurry foaming method. The effect of sintering temperatures on pore structure of porous porphyry pellets with different extension ratio ($E_R$) was investigated by specific surface area, water absorption and porosity, which changed with sintering temperatures. When the sintering temperatures increased from $975^{\circ}C$ to $1075^{\circ}C$, specific surface area and water absorption of the all samples decreased. In case of the sample with an equal sintering temperature, $E_R=3.0$ pellets had little influence on pore structure compared to the $E_R=2.0$ pellets. As a results, it was shown by SEM that facilitated formation of micro pores at $E_R=2.0$ pellets shrunk increasingly after sintering process. At $E_R=3.0$ and sintering temperature at $1025^{\circ}C$, optimum conditions of the porous porphyry porous pellets was found. Also, Escherichia coli removal efficiency of the silver-containing porphoyry porous pellets was measured for the feasibility as a antibacterial media. The antibacterial activity of prepared silver-containing sample was maintained above 90% for 40 days.
국내 바나듐함유 티탄철광 파분쇄 산물 중 바나듐, 티타늄, 그리고 철 자력선별 거동
한요셉,고병헌,김성민,백상호,Tsogchuluun Davaadorj,전호석 한국자원공학회 2021 한국자원공학회지 Vol.58 No.1
In this study, vanadium-titanium magnetite (VTM) ore was crushed and ground to effectively concentrate vanadium from the VTM ore. In addition, a wet magnetic separation experiment was performed for the fractured products, utilizing various grinding times at a low magnetic intensity (0.05 T). The degree of liberation of the VTM sample was predominantly due to grinding, and a duration of 15 min was set as the optimum grinding time. The best vanadium recovery was obtained from the sample milled for 15 min, achieving a vanadium grade of 1.05% and a recovery of 80.3%. To maximize the amount of vanadium recovered through magnetic separation, it is necessary to selectively separate magnetite and ilmenite as magnetic and non-magnetic mineral, respectively. 이 연구에서는 국내 바나듐함유 티탄철광(vanadium-titanium magnetite, VTM)내 효과적인 바나듐회수를 위하여 먼저 VTM의 파쇄 및 분쇄를 수행하였다. 그리고, 분쇄시간에 따른 산물에 대하여저자력 (0.05 T) 세기에서 습식 자력선별 실험을 수행하였다. 파분쇄에 의하여 VTM의 단체분리가크게 일어났으며, 15분 분쇄시간이 최적 분쇄시간으로 설정되었다. 게다가, 분쇄시간에 따른 분쇄산물의 자력선별 실험 결과, 15분 분쇄된 시료에서 가장 우수한 바나듐 회수가 가능하였으며, 바나듐 품위 1.05% 그리고 회수율 80.3%를 달성하였다. 자력선별에서의 최대 바나듐으로 회수하기 위해서는 선택적으로 자철석을 자성물질로 티탄철석을 비자성물질로서 효과적으로 분리해야 할 것이다.
생활(生活) 폐기물(廢棄物) 소각재(燒却材) 슬래그를 이용(利用)한 메조포러스 실리카 합성(合成) : NaOH 농도(濃度)의 영향(影響)
한요셉,정종훈,박재구,Han, Yo-Sep,Jung, Jong-Hoon,Park, Jai-Koo 한국자원리싸이클링학회 2010 資源 리싸이클링 Vol.19 No.1
생활 폐기물 소각재 슬래그를 출발원료로한 메조포러스 실리카의 합성에 미치는 NaOH 영향에 대해 조사하였다. 기계적 분쇄를 통해 활성화된 소각재 슬래그에 대한 추출 공정은 농도가 다른 NaOH 용액을 이용한 알칼리 처리로 수행하였다. 분쇄시간 그리고 NaOH 용액 농도가 증가 할수록 소각재 슬래그로부터 추출되는 Si 추출량은 증가하였다. 합성된 메조포러스 실리카의 물리적 특성(기공크기, 비표면적 그리고 총 기공부피)은 BET, SEM, TEM 그리고 small-angle XRD 분석을 통하여 평가하였다. 합성된 메조포러스 실리카는 대략 7 nm 기공크기의 hexagonal 구조를 가진 SBA-15로 판명되었다. NaOH 용액 농도가 증가됨에 따라 합성된 메조포러스 실리카는 비표면적 및 기공 부피도 증가하였다. 반면, 거의 동일한 Si 이온 농도로 제조된 메조포러스 실리카의 경우, 3M NaOH로 제조된 샘플에 비해 4M NaOH로 제조된 샘플의 비표면적 및 기공 부피가 감소하였다. 이는 과량의 Na 이온이 mesophase 형성을 방해하여 미반응되어 남아있는 Si 이온이 합성되어진 mesophase의 벽 두께를 증가시키는 것으로 확인되었다. It was investigated that effects of NaOH concentration on synthesis of mesoporous materials using municipal solid waste incinerator ash slag (MSWI-ash slag). In order to increase the purity and maximize the amount of extracted Si content the raw MSWI-ash slag was mechanically activated. Extraction of Si from the MSWI-ash slag was carried out by alkali treatment using concentrated NaOH solution, which varied from 1M to 4M. Physical properties (i.e., pore size, specific surface area and total pore volume) of the synthesized mesoporous silica were also evaluated as a function of NaOH concentration via BET, SEM, TEM and small-angle X-ray scattering analyses. Over the entire range of NaOH concentration investigated (i.e., 1-4M), the synthesized mesoporous materials were determined to be SBA-15, which exhibited a hexagonal structure with the pore size of approximately 7 nm. On the other hand, specific surface area and total pore volume increased with NaOH concentration up to 3M while the values decreased at 4M, indicating that the optimal NaOH concentration for the synthesized mesoporous silica was approximately 3M. Further comparison analysis between two conditions (3M versus 4M) showed that the decrease in two physical properties at 4M NaOH concentration was likely due to the potential inhibition by excess Na ions on the formation of mesophase and the consequent increase of pore wall thickness by remaining Si ions.
다공성 실리카 지지체 제조 및 Sol-Gel 법에 의한 TiO2 코팅
한요셉,박재구 한국세라믹학회 2004 한국세라믹학회지 Vol.41 No.7
A sol-gel method was applied to coat TiO2 on porous silica prepared using slurry foaming method from silica. From the results of XRD, SEM, and BET, the anatase phase was firstly observed at the coated supports with the heated of 500oC. The coated supports with the heated of 700oC had the maximum anatase peak, and the particle size of coated TiO2 was about 1 mm. Bending strength and gas permeability of the porous silica were measured for the feasibility as a catalytic supports. In case of the uncoated porous materials with the strength of 2.4MPa, the strength increased to 3.9~4.3MPa after the coating process regardless of the heating temperature. On the other hand, the permeability of the uncoated porous materials decreased from 770 ´ 10-13 m2 to 363 ´ 10-13 m2 after the coating process, and it decreased with the increasing heating temperature. Key words : Porous silica, TiO2 coating, Heating temperature, Pore structure, Strength, Permeability
College Majors in Limited Supply: The Case of Private Universities in Korea
한요셉 한국경제학회 2022 The Korean Economic Review Vol.38 No.3
The distribution of college majors often shows signs of rigidity despite evident changes in the world of work. As a possible explanation for the distribution rigidity in the Republic of Korea, this study focuses on supply-side restrictions, specifically a region-based cap on university enrollment. Using the national-level demand change for each major as an instrument for program-level demand change, this study finds a systematic difference between regulated and unregulated private universities in the responsiveness of program size to student demand. Analyses using sharp changes in regulatory status confirm that the enrollment regulation slows internal adjustments, showing the need for regulatory reform.