• Carbon letters
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• 제14권1호
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• pp.55-57
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• 2013

The development of hollow carbon balls by $CO_2$ oxidation of two types of carbon blacks was studied. Super P (SP) and Denka Black (DB) were used for this study. Specific surface area (SSA), structural parameters, and microstructures were examined using Brunauer, Emmett and Teller apparatus, X-ray diffraction spectroscopy, and transmission electron microscope (TEM), respectively. The SSAs of both oxidized carbon blacks increased after oxidation. The SSAs of raw DB and SP were 73 $m^2/g$ and 60 $m^2/g$, respectively. Maximum SSAs of oxidized DB and SP were 152 $m^2/g$ and 253 $m^2/g$, respectively. The $d_{002}$ of DB and SP showed almost no change after oxidation. The Lc of raw DB ($38{\AA}$) and SP ($19{\AA}$) increased with increasing weight loss. The $L_c$ of SP increased up to $254{\AA}$ at 96% weight loss. The SSA increased about twice in DB (148 $m^2/g$) and about four times in SP (254 $m^2/g$) after 3 h oxidation compared with the original carbon blacks. Through TEM observation the outer parts of the oxidized carbon blacks showed a rigid shell structure and the inner parts looked empty. Generally it looked like an angular soccer ball, so we named it 'hollow carbon ball'. It is expected that the hollow carbon ball can be used as catalyst supports.

• Carbon letters
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• 제26권
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• pp.31-42
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• 2018

Adsorption is one of the best methods for wastewater purification. The fact that water quality is continuously decreasing requires the development of novel, effective and cost available adsorbents. Herein, a simple procedure for the preparation of a magnetic adsorbent from agricultural waste biomass and ferrofluid has been introduced. Specifically, ferrofluid mixed with wheat straw was directly pyrolyzed either by microwave irradiation (900 W, 30 min) or by conventional heating ($550^{\circ}C$, 90 min). Magnetic biochars were characterized by X-ray powder diffraction, $M{\ddot{o}}ssbauer$ spectroscopy, textural analysis and tested as adsorbents of As(V) oxyanion and cationic methylene blue, respectively. Results showed that microwave pyrolysis produced char with high adsorption capacity of As(V) ($Q_m=25.6mg\;g^{-1}$ at pH 4), whereas conventional pyrolysis was not so effective. In comparison to conventional pyrolysis, one-step microwave pyrolysis produced a material with expressive microporosity, having a nine times higher value of specific surface area as well as total pore volume. We assumed that sorption properties are also caused by several iron-bearing composites identified by $M{\ddot{o}}ssbauer$ spectroscopy ([super] paramagnetic $Fe_2O_3$, ${\alpha}-Fe$, non-stoichiometric $Fe_3C$, ${\gamma}-Fe_2O_3$, ${\gamma}-Fe$) transformed from nano-maghemite presented in the ferrofluid. Methylene blue was also more easily removed by magnetic biochar prepared by microwaves ($Q_m=144.9mg\;g^{-1}$ at pH 10.9) compared to using conventional techniques.

• 한국세라믹학회지
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• 제40권5호
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• pp.488-493
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• 2003

유기용매를 함유하는 염화니켈 수용액으로부터 Ni 미분말을 제조하였고 Ni 분말형성에 미치는 유기용매 첨가의 영향을 검토하였다. 모든 생성물들은 0.1~l.0 $\mu\textrm{m}$ 범위의 구형입자들이었고 입자들간의 응집은 관찰되지 않았다. 1-propanol이 40 vol% 첨가된 경우 분말의 입경감소와 균일성이 현저하였다. 이들 분말에 대한 평균입경과 비표면적은 각각 0.3 $\mu\textrm{m}$와 16.4 m$^2$/g이었다. 1-propanol의 첨가량이 증가함에 따라 hydrazine에 의한 환원반응시간은 감소하였고, 1-propanol이 40 vol%가 첨가된 경우 환원시간은 약 5분이었다. Ni 합성 분말은 32$0^{\circ}C$ 부근에서 산화되었고, 30$0^{\circ}C$ 부근에서의 중량 감소는 Ni(OH)$_2$의 탈수에 기인한 것이다.

• 한국세라믹학회지
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• 제32권4호
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• pp.507-515
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• 1995

The monolithic dry gels of the Li2O-Al2O3-TiO2-SiO2 system were prepared by the sol-gel technique using metal alkoxides as starting materials to obtain monolithic glass-ceramics at low temperature without melting. Activation energy for the crystal growth of the gel with 6.05% TiO2, nucleating ageng, for the preparation of Li2O-Al2O3-TiO2-SiO2 system glass-ceramic was 101.14kcal/mol. As a result of the analysis of DTA & XRD, it was confirmed that the crytallization of Li2O-Al2O3-TiO2-SiO2 system glass-ceramic was the most efficient when 6.05% TiO2, nucleating agent, was added. $\beta$-eucryptite solid solution crystals and $\beta$-spodumene solid solution crystals were detected in the sample heat treated above 85$0^{\circ}C$. The sintered gel heat treated at 85$0^{\circ}C$ had the specific surface area of 185$m^2$/g, the pore volume of 0.19cc/g and the average pore radius of 20.8$\AA$. This shows that the sintered gel is also comparatively porous material. In temperature range of 25~85$0^{\circ}C$ thermal expansion coefficient of the specimen which was crystallized for 10hrs at 85$0^{\circ}C$ was 6.7$\times$10-7/$^{\circ}C$, which indicated that the crystallized specimen was turned out to be the glass-ceramic with low thermal expansion.

• 한국지반환경공학회 논문집
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• 제11권1호
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• pp.53-59
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• 2010

해수 침적 조건에서 시멘트 수화물이 부식되는 화학적 열화과정은 콘크리트 구조물이나 주입공사 목적물에서 동일하다. 국내에서 사용되고 있는 MSG(Micro Silica Grouting)주입재는 실리카질 물질이 다량 함유된 혼합계 시멘트로서 분말도가 $8,000cm^2/g$ 이상으로 높기 때문에 수화활성도가 매우 크고, 고강도 및 고내구성을 특징으로 하며, $C_3A$ 함유량도 5% 이하로 내황산염시멘트 규격을 만족하는 내해수성 시멘트재로 평가된다. 따라서, 본 논문에서는 내해수성이 우수한 MSG와 국내에서 사용되고 있는 급결재를 조합하여 내해수성 특성을 실험적으로 평가하였다. 국내에서 일반적으로 규산계 고활성 급결재 또는 초속경시멘트계 무기질 급결재가 사용되고 있다. 이들 급결재와 MSG가 조합된 주입재의 호모겔 시편에 대해서 압축강도, 중량변화 및 길이변화 특성을 실험적으로 평가하여 내해수성이 우수한 주입재 조합을 제시하였다.

• 한국지반환경공학회 논문집
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• 제15권12호
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• pp.5-13
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• 2014

본 연구에서는 발포질석을 글리세롤로 코팅하여 인에 대한 흡착력을 높인 발포질석 흡착제 제조 및 인 제거능력을 평가하였다. 발포질석과 4 mol%의 황산을 포함한 글리세롤을 1:4 비율로 혼합 후 380, 580, $780^{\circ}C$로 가열하여 다공성 탄소층을 발포질석 표면에 부착하였다. $380^{\circ}C$로 가열한 질석의 경우 비표면적인 $53.1m^2/g$을 나타내었으며, TGA 분석을 통해 탄소성분의 산화로 인한 질량손실이 가장 큰 것으로 분석되었다. $380^{\circ}C$로 제조된 코팅 발포질석을 이용한 수용액 속의 인 제거를 흡착모델에 적용해보니 Langmuir 모델에 더 적합하며 여기로부터 구한 최대제거량은 714.3 mg/kg으로 기존 점토광물을 이용한 인 흡착연구결과보다 더 흡착용량이 뛰어난 것을 알 수 있었다.

• Journal of Ecology and Environment
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• 제31권3호
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• pp.213-223
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• 2008

The increasing area of abandoned rice fields could provide new opportunities for wetland restoration in Asia. However, it is unknown how quickly or completely abandoned rice fields will recover from agricultural disturbances. We assessed water quality and plant community succession in abandoned rice fields with different hydrology in a mountain valley to understand the effects of hydrological regime on recovery. Water level, soil redox potential, water quality, plant composition, and primary production were measured. The sites, coded as D6, N13, and N16, had been recovering for 6, 13, and 16 years by 2006. N13 and N16 have been recovering naturally whereas D6 has been drained with a nearby dike and was tilled in 2001. The typical hydroperiods of D6, N13, and N16 were no surface water, permanently flooded, and seasonally flooded, respectively. The major change in vegetation structure of both D6 and N13 was the replacement of herbaceous species by woody species. Drawdown accelerated this change because Salix koreensis grew better in damp conditions than in flooded conditions. Phragmites japonica reduced plot-level plant species richness. The removal efficiency of $NH_4-N$, $NO_3-N$, and $PO_4-P$ from water varied seasonally, ranging between -78.8 to 44.3%, 0 to 97.5%, and -26.0 to 44.4%, respectively. In summary, abandoned rice fields quickly became suitable habitat for native wetland plant species and improved regional water quality. Variation among our sites indicates that it is likely possible to manage abandoned rice fields, mostly through controlling hydrology, to achieve site-specific restoration goals.

• 대한화학회지
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• 제42권1호
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• pp.42-50
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• 1998

산화티탄을 전극 재료로 사용하기 위해서는 투명하고 수용액에 안정한 재료가 필요하다.아세틸 아세톤 티탄(IV)으로부터 분사방법을 이용하여 산화티탄의 안정한 박막을 얻었다. 결정 모양은 구형을 나타내었으며, 결정의 크기는 온도가 증가함에 따라 증가하였고 두께는 감소하는 경향을 나타내었다. XRD 데이타로부터 아나타제 결정이 400$^{\circ}C$ 에서부터 얻어지기 시작함을 관찰하였다. 440$^{\circ}C$ 에서 만들어진 산화티탄이 고유 광전류가 최대값을 나타냈으며 가시광 영역에서 광전류가 증가하는 결과를 나타냈다. 가시광 영역에서의 광전류는 프탈로시아닌의 흡수 스펙트럼과 같은 ${\lambda}$max 위치에서 얻어졌고 이와 같은 결과는 프탈로시아닌의 결정 특성에 따른 광전류 특성으로 나타났다.

• 한국수소및신에너지학회논문집
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• 제13권4호
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• pp.259-269
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• 2002

A battery based on the lithium/elemental sulfur redox couple has the advantage of high theoretical specific capacity of 1,675 mAh/g-sulfur. However, Li/S battery has bad cyclic durability at room temperature due to sulfur active material loss resulting from lithium polysulfide dissolution. To improve the cycle life of Li/S battery, PEGDME (Poly(ethylene glycol) dimethyl ether) 500 containing 1M LiTFSI salt which has high viscosity was used as electrolyte to retard the polysulfide dissolution and nano-sized $Mg_{0.6}Ni_{0.4}O$ was added to sulfur cathode as additive to adsorb soluble polysulfide within sulfur cathode. From experimental results, the improvement of the capacity and cycle life of Li/S battery was observed( maximum discharge capacity : 1,185 mAh/g-sulfur, C50/C1 = 85 % ). Through the charge-discharge test, we knew that PEGDME 500 played a role of preventing incomplete charge-discharge $behavior^{1,2)$. And then, in sulfur dissolution analysis and rate capability test, we first confirmed that nano-sized $Mg_{0.6}Ni_{0.4}O$ had polysulfide adsorbing effect and catalytic effect of promoting the Li/S redox reaction. In addition, from BET surface area analysis, we also verified that it played the part of increasing the porosity of sulfur cathode.

• 공업화학
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• 제27권1호
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• pp.80-85
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• 2016

넓은 비표면적과 큰 기공 부피를 갖는 실리카에 다양한 아미노실란 화합물을 in-situ 중합법을 통해 기능화 후 이산화탄소 흡착 특성을 확인하였다. 이산화탄소 흡착 기능기로 아민기가 포함된 아미노실란 화합물이 사용되었다. 흡착제의 흡착 특성 분석을 위해 질소 흡 탈착 실험과 원소분석, in situ FT-IR, TGA를 이용하였다. 흡착제 합성 전후를 비교하였을 때 폴리아미노실란이 기능화되면 표면적과 기공부피 및 크기가 감소하였으며 실리카 기공 부피의 70%에 해당하는 폴리아미노실란 화합물을 기능화 시켰을 경우 기공 부피의 100% 기능화 보다 이산화탄소 흡착능이 향상되었다. 흡착 온도를 비교하며 $30^{\circ}C$보다 $75^{\circ}C$에서 폴리아미노실란 화합물의 열팽창과 자유부피 증가로 흡착능이 증가하였고, 2NS/NPS-2의 경우 기공 부피 70% 기능화와 흡착 온도 $75^{\circ}C$에서 9.2 wt%의 높은 $CO_2$ 흡착능을 보였다.