• Resources Recycling
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• v.12 no.6
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• pp.38-46
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• 2003

In this study, nano-sized Ni-ferrite and $Fe_2$$O_3$＋NiO powder was fabricated by spray pyrolysis process in the condition of 1kg/$\textrm{cm}^2$ air pressure using the Fe-Ni complex waste acid solution generated during the manufacturing process of shadow mask. The average particle size of the produced powder was below 100 nm. The effects of the reaction temperature, the concentration of raw material solution and the nozzle tip size on the properties of powder were studied. As the reaction temperature increased from $800 ^{\circ}C$ to $1100^{\circ}C$, the average particle size of the powder increased from 40 nm to 100 nm, the structure of the powder gradually became solid, yet the distribution of the particle size appeared more irregular. Along with the increase of the reaction temperature, the fraction of the Ni-ferrite phase were also on the rise, and the surface area of the powder was greatly reduced. As the concentration of Fe in solution increased from 20g/l to 200g/l, the average particle size of the powder gradually increased from 30 nm to 60 nm, while the distribution of the particle size appeared more irregular. Along with the increase of the concentration of solution, tie fraction of the Ni-ferrite phase was on the rise, and the surface area of the powder was greatly reduced. Along with the increase of the nozzle tip size, the distribution of the particle size appeared more irregular, yet the average particle size of the powder showed no significant change. As the nozzle tip size increased from 1 mm to 2 mm, the fraction of the Ni-ferrite phase showed no significant change, while the surface area of the powder slightly reduced. As the nozzle tip size increased to 3 mm and 5 mm, the fraction of the Ni-ferrite phase gradually reduced, and the surface area of the powder slightly increased.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.10
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• pp.986-993
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• 2010

In this study, sorption characteristics of thermally treated activated alumina (AA) for fluoride were investigated. Sorption experiments have been conducted in equilibrium and kinetic batch conditions. Also, effects of solution pH and anions on fluoride removal have been observed. The properties of thermally treated ( $700^{\circ}C$) activated alumina (AA700) and untreated activated alumina (UAA) were compared using field-emission scanning electron microscope, energy-dispersive spectrometry, X-ray diffractometer (XRD) analysis, and Brunauer-Emmett-Teller (BET) analysis. From the experiments using AA thermally treated at different temperatures (100, 300, 500, $700^{\circ}C$), it was found that at high fluoride concentrations (50, 100, 200 mg/L) the sorption capacity of thermally treated AA increased with increasing thermal treatment temperature. At an initial fluoride concentration of 200 mg/L, the sorption capacity of AA700 was 3.67 times greater than that of UAA. The BET analysis showed that the specific surface area of UAA was about 2 times larger than that of AA700. The XRD analysis indicated that UAA was composed of both boehmite (AlOOH) and bayerite ($Al(OH)_3$) while AA700 was $Al_2O_3$. The reason that fluoride sorption capacity of AA700 increased despite of decrease in specific surface area compared to UAA could be attributed to the change of crystal structure. The kinetic sorption test showed that fluoride sorption to AA700 arrived at equilibrium after 24 h. The equilibrium test demonstrated that the maximum sorption capacity of AA700 was 5.70 mg/g. Additional batch experiments indicated that fluoride sorption to AA700 was the highest at pH 7, decreasing at both acidic and basic solution pHs. Also, fluoride sorption to AA700 decreased in the presence of anions such as phosphate, nitrate, and carbonate. This study demonstrated that thermal treatment of AA at high temperature could increase its sorption capacity for fluoride.

• KSBB Journal
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• v.18 no.5
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• pp.412-417
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• 2003

We first investigated basic characteristics of reticulated polyurethane (PU) foams as microbial carriers. In general, the specific surface area of PU foams increases with respect to decreasing pore sizes. However, the number of microbes adhered on the unit surface of reticulated PU foams decreases with respect to decreasing pore sizes. Thus, as a result of totally considering all effects such as apparent density, hydrolysis rate, and adhesion, we can know that PU foams with 45 PPI is the most appropriate microbial carrier. In this study, we can also investigate the effect of various physico-chemical surface treatments on the adhesion of microbes on the surface of PU foams. We used a chitosan treatment, a PEI (Polyethylene Imine) treatment, a xanthane treatment and a plasma treatment. As a result of comparing all surface treatments, the plasma surface treatment was the best.

• Resources Recycling
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• v.23 no.1
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• pp.40-47
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• 2014

Feasibility of utilizing unburned carbon residue in coal ash as a potential precursor for the production of activated carbon was assessed to seek for solution to recycle unburned carbon residue. The unburned carbon concentrate generated from the 4 stages of cleaner flotation has a grade of 87% carbon. The crystalline impurities in the concentrate included quartz and mullite. Unburned carbon had a low specific surface area of $10m^2/g$, which might be related to a high degree of coalification of domestic anthracite coal. Carbon particles were mostly porous and have a turbostratic structure. When 1g of carbon was activated with 6g of KOH powder, the highest specific surface area value of $670m^2/g$ was achieved. Low wettability of unburned carbon particles, which was resulted from high temperature combustion in a boiler, might cause poor pore formation when they were activated by KOH solution. The activated carbon produced in this study developed micropores, with an equivalent quality of general-purpose activated carbon made from coal. Hence, it is concluded that chemically treated unburned carbon can be used for water purification or an alternative to carbon black as it is.

• KSBB Journal
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• v.8 no.5
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• pp.431-437
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• 1993

Active carbon which has the smallest bulk and wet density was found as the best support media among 4 different kinds of materials(celite, natural zeolite, Pusuk stone, active carbon) to make a proper fluidized-bed with small energy consumption. Its minimum and optimum fluidization velocity were found as 0.03cm/sec and 0.25cm/sec, respectively. As organic loading rate for methane fermentation was increased, CODcr removal efficiencies of all the media were decreased. But, CODcr, removal efficiencies of active carbon was maintained more than 90% in this experimental range of the organic loading rate. Larger amount of microorganism was adsorbed on the active carbon which has very high specific surface area. At the organic loading rate of 16g CODcr,/l day, its adsorbed cell mass was 157mg/g. Comparing natural zeolite with roast celite, adsorbed cell mass did not increase in proportion to specific surface area of the media. Even though roast celite has the same specific surface area as the Pusuk stone, its organic removal ability was superior to that of the Pusuk stone, which explains that the relatively great surface roughness and the positive surface charge are important for cell adsorption. It was concluded that the support media for anaerobic fluidized reactor should have small wet density and small fuidization velocity, if possible, in order to increase cell adsorption by reducing the fluid shear stress.

• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.304-309
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• 1999

Aluminum-pillared clay was prepared by the intercalation of Al-hydroxy oligomer into domestic bentonite. The solid products are characterized by XRD, nitrogen adsorption/desorption, EDX, and SEM. The solid products show relatively high specific surface areas in the range of $104{\sim}228m^2/g$, and their specific surface area, micropore surface area, and micropore volume increase with increasing the mole ratio of OH/Al. From the results of pore size distribution calculated by BJH equation, it was found that aluminum-pillared clay also contains much mesopore near $40{\AA}$. These results indicate that Al-hydroxy oligomer was intercalated into bentonite, and aluminum oxide was pillared among the layers of bentonite, and micropore and mesopore was finally developed into layers. As OH/Al mole ratio increases, the thermal stability of aluminum-pillared clay increases. This result can be explained by the fact that the density of layers is increased due to the formation of aluminum pillars.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1520-1522
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• 1996

전기 이중층 콘덴서는 일반적인 콘덴서와 백업용 이차 전지의 중간적 성격을 갖는 디바이스로서 직류 전압 인가시 전하는 진해액과 활성탄의 계면에 전기이중층을 이루며 축적된다. 본 논문에서는 탄화 및 활성화 조건을 달리하여 활성탄 전극을 제조하고 세공 면적, 비표면적, 겉보기 밀도차 기공율을 측정,검토하였으며 여러가지 유기 용매에 tetraethylammonium tetrafluoroborate를 각각 첨가하여 제조한 전해액의 전기전도도를 정하고 이들 전해액과 활성탄 전극을 이용하여 전기 이중층 콘텐서를 제작한 후 정전용량, 활성탄 전극의 안정 전위, 체적용량 밀도, 중량용량 밀도 등을 검토하였다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.13.1-13.1
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• 2009

에어로젤은 인류가 개발한 소재 중에서 가장 가벼운 고체로, 기공률이 90%이상이고 비표면적은 ~1000m2/g, 기공의 크기는 10nm 크기로 이루어진 나노기공 물질이다. 1931년에 Kisley가 물유리로부터 실리카 에어로젤을 합성한 이래로 실리카 에어로젤에 대한 연구가 가장 많이 이루어져왔으며, 단열소재, 흡음재, 체렌코프우주선 디텍터, 반도체의 초저유전소재, 유출된 석유의 정제, 촉매 등에 대한 응용에 대해서도 연구가 많이 이루어져 왔다. 그리고TiO2와 같은 광촉매 에어로젤 소재, 카본 에어로젤 소재등 다양한 나노기공 소재에 대해서도 연구가 이루어지고 있으며, 카본 에어로젤의 경우 나노기공과 비표면적을이용한 전기이중층 커패시터 (EDLC)에 대한 연구도 이루어지고 이다. 본 연구에서는 첫째로, 실리카 에어로젤에 대한 연구결과를 소개하고 이의 단열소재로서의 응용가능성에대하여 언급하고자 한다. 실리카 에어로젤 나노기공 소재의 경우, 기공크기가 10nm크기로 매우 작고 공기의 자유이동길이와 거의 비슷하여서 대류에 의한 열전달을 낮출 수 있으며, 낮은 고체함량으로 인하여 포논에 의한 열전달을 낮출 수 있기 때문에 단열소재로서 최고의 성능을 나타낸다. 하지만, 문제는 높은 기공률로 인한 기계적인 취약성이 문제이다. 따라서 이를 보완하기 위항 섬유로 에어로젤을 보강할 수 있는데, 이를통하여 에어로젤 나노기공소재와 섬유보강에 의한 복합화에 대하여 말하고자 한다. 또 다른 하나의 연구방법은유기-무기 하이브리드 나노기공 소재를 합성하는 것이다. 여기서는하나의 방법으로 MTEOS-TEOS의 하이브리드화와 초임계 건조공정에 의한 나노기공 소재에 대한 연구결과를소개하고자 한다. 마지막으로 카본 에어로젤 나노기공소재의 합성과 나노기공 구조의 제어 및 물성평가에 대한 것을 말하고자하는데, 본 발표에서는 레소시놀과 포름알데히드를 촉매에 의한 중합반응을 통하여 유기 에어로젤 소재를 합성하고 분위기에서탄소화 공정을 통하여 카본에어로젤을 합성하였다. 또한 금속 니켈을 도입하는 것에 의하여 탄소/니켈 복합 하이브리드 에어로젤 소재를 합성하고 슈퍼커패시터 전기화학 특성에 대한 연구결과를 발표하고자 한다.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1517-1519
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• 1999

FED용 형광체로 사용되는 $ZnGa_2O_4$를 Glycine Nitrate Process로 합성하여 고상 반응법으로 합성한 $ZnGa_2O_4$ 분말과 비교 분석하였다. 또한 Glycine Nitrate Process로 제조시 Mn의 doping 농도를 변화시키면서 각각의 조성비에 따른 발광특성을 알아보았다. TGA 측정 결과 GNP법으로 합성된 $ZnGa_2O_4$의 경우약 $300^{\circ}C$이상에서 무게감량이 없으며, XRD 상분석 결과 연소반응 후 이미 상형성이 이루어짐을 알 수 있었다. PL측정을 결과 GP(Glycine Nitrate Process)로 제조된 $ZnGa_2O_4$ 분말의 발광효율이 고상 반응법으로 제조된 분말보다 우수하였으며, 균일하고 비표면적이 큰 단일상임이 관찰되었고, 더 작은 에너지와 시간으로 제조할 수 있는 장점이 있었다.

• Korean Journal of Materials Research
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• v.6 no.3
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• pp.264-274
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• 1996

자체연소반응법에 의하여 탄화붕소(B4C)를 합성함에 있어서 자체적으로는 반응이 이루어지지 않아서 간접점화법인 화학로법(Chemical Furnace)으로 합성을 하였으며, 성형압력과 몰비를 변수로 하여 연소온도 및 연소속도의 변화를 측정하였다. 성형밀도가 이론밀도의 70%에서 연소온도와 연소속도가 가장 높았으며, 몰비에 대한 영향은 표준비였을 때 연소온도와 연소속도가 가장 높았다. 그리고 성형밀도에 따른 입자의 크기변화는 성형밀도가 높을수록 입자의 크기는 작아졌으며 따라서 비표면적은 커졌다.