• 약학회지
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• 제29권4호
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• pp.176-182
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• 1985

As a part of the studies on adsorptive properties of Korean halloysite clays, Hadong white clays of premium grade were examined for geometric pore structured by mercury porosimetry and for specific surface areas by nitrogen adsorption according to the BET procedure. Three size fractions of the native clay sample were derived from passage BS #100, #200 and #325 meshes, respectively. Several parameters lhus observed in relation to the pore structures are shown below: 1. The size fraction of BS #100, #200 and #325 show internal pore volumes of 25.3, 30.2 and $35.0m^2g^{-1}$, respectively. 2. In the distribution curves of the cumulative pore volume against pore diameter, it has been shown that the larticle sizes, the steeper the distribution over the larger ranges of pore diameters. The converse is true the smaller particles. 3. Internal pore areas increase with decrease in pore sizes. It follows that the pores having diameters of $\leq$0.1$\mu\textrm{m}$ are responsible for more than 90% of the total pore area. 4. The behaviour of nitrogen adsorption can be best described by BET type IV isotherm. Further, the hysteresis loops of the adsorptiondesorption curves become narrower with decresing particle sizes. 5. The specific surface areas observed for the fractions of BS #100, BS #200 and BS #325 are 34.6, 35.4 and 43.2m $^2g^{-1}$, respectively. and the calcined clay of BS #325 has a specific surface area near $30.4m^2g^{-1}$.

• 폴리머
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• 제29권5호
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• pp.445-450
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• 2005

인체 보형물의 생체 재료로 사용할 목적으로 히아루론산 비드를 제조하였다. 히아루론산 수용액과 콩기름을 섞어서 얻어진 현탁상태에서 히아루론산을 1,3-butadiene diepoxide로 가교시켰다. 제조된 비드의 물성을 살펴보기 위해 직경, 표면적과 팽윤도를 측정하였고 전자현미경으로 표면상태를 관찰하였다. 가교제의 농도가 $5-12\;vol\%$ 범위에서 비드가 형성되었으며 제조된 비드는 단순분산성을 보였다. 히아루론산 농도 혹은 가교제 농도가 증가할수록, 가교 온도가 감소할수록, BET표면적과 팽윤도가 감소하였다. 혼합속도의 변화에 의해 비드의 물성은 거의 변하지 않았으나 비드의 크기는 효과적으로 조절되었다.

• Carbon letters
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• 제10권4호
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• pp.339-344
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• 2009

Henequen fiber was air-stabilized, carbonized, and steam-activated to obtain high surface area activated henequen fiber (AHF). Thermal behavior of henequen fibers has been studied by TGA. The structural morphology and characteristics were observed by SEM and BET surface area measurement. The yield of AHF from natural henequen was in the range of 20~25 wt%. Mesopores (2~2.5 nm) were developed on the AHF as the activation temperature was raised up to $700^{\circ}C$, and the band of mesopore size distribution moved to 15~30 nm when the activation were carried out at $900^{\circ}C$ for 30 min. The specific surface area and the total pore volume were about $1394\;m^2/g$ and $1.30\;cm^3/g$, respectively at this activation conditions.

• Journal of Forest and Environmental Science
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• 제23권1호
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• pp.51-55
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• 2007

본 연구는 염화아연을 이용한 화학약품 부활법으로 잣나무재 활성탄을 제조하기 위해 원료에 대한 화학약품부활제 비율의 영향을 검토하였다. 염화아연과 혼합한 목분은 질소분위기에서 상온에서 $600^{\circ}C$까지 1시간 열처리하여 중량변화를 측정하였다. 이 처리과정에 있어 활성탄 내부에 다양한 공극크기 분포와 표면특성이 확인되었다. 즉, 최대 BET 표면적과 총 공극체적은 목분에 대하여 염화아연의 비율이 5배인 경우였으며, 각각 그 값은 $1468m^2/g$와 1.74 cc/g이었다. 결론적으로 활성탄 제조시 화학약품부활제의 비율에 의해 활성탄의 특성이 뚜렷하게 차이가 나타나는 것이 확인되었다.

• 공업화학
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• 제29권3호
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• pp.318-324
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• 2018

본 연구에서는 물리적 활성화법인 수증기 활성화법을 이용하여 PAN (Polyacrylonitrile)계 활성탄소섬유를 제조하였다. 활성화는 온도와 시간을 변수로 하였으며, 활성화 온도(700, 750, $800^{\circ}C$)에 도달하였을 때 200 mL/min의 수증기 유량의 조건으로 PAN 탄소섬유의 활성화를 진행하였다. 제조된 활성탄소섬유의 기공구조를 분석하기 위하여 질소가스의 흡 탈 등온선을 통한 비표면적($S_{BET}$) 측정과 표면분석을 위한 AFM 분석을 실시하였다. 또한 인장시험을 실시하여 활성화 결과 형성된 기공구조가 섬유의 기계적 특성에 미치는 영향을 고찰하였다. 그 결과, 활성화 후 섬유의 비표면적($S_{BET}$)은 $448{\sim}902m^2/g$의 값을 나타냈으며, 인장강도는 58.16~84.92%, 탄성계수는 69.81~83.89%의 감소를 보였다.

• 한국재료학회지
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• 제22권6호
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• pp.321-327
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• 2012

The production of functional activated carbon materials starting from inexpensive natural precursors using environmentally friendly and economically effective processes has attracted much attention in the areas of material science and technology. In particular, the use of plant biomass to produce functional carbonaceous materials has attracted a great deal of attention in various aspects. In this study the preparation of activated carbon has been attempted from rice husks via a chemical activation-assisted microwave system. The rice husks were milled via attrition milling with aluminum balls, and then carbonized under purified $N_2$. The operational parameters including the activation agents, chemical impregnation weight ratio of the calcined rice husk to KOH (1:1, 1:2 and 1:4), microwave power heating within irradiation time (3-5 min), and the second activation process on the adsorption capability were investigated. Experimental results were investigated using XRD, FT-IR, and SEM. It was found that the BET surface area of activated carbons irrespective of the activation agent resulted in surface area. The activated carbons prepared by microwave heating with an activation process have higher surface area and larger average pore size than those prepared by activation without microwave heating when the ratio with KOH solution was the same. The activation time using microwave heating and the chemical impregnation ratio with KOH solution were varied to determine the optimal method for obtaining high surface area activated carbon (1505 $m^2$/g).

• 한국재료학회지
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• 제12권8호
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• pp.641-649
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• 2002

The redox properties of a homogeneously-precipitated $TiO_2$ rutile powder with a BET surface area of ~$200 m^2$/g, consisting of an acicular primary particle, were characterized using photocatalytic reaction in aqueous 4-chlorophenol, Cu-EDTA and Pb-EDTA solutions under ultraviolet irradiation, compared to those of commercial P-25 X$200 m_2$ powder with a spherical primary particle as well as home-made anatase $TiO_2$ powder with ~$200 m^2$/g BET surface area. Here, the anatase powder also includes mainly the primary particles very similar to the acicular shapes of the rutile $TiO_2$ powder. The rutile powder showed the fastest decomposition rate and the largest amount in the photoredor, compared with the anatase or P-25 powder, while the anatase powder unexpectedly showed the slowest rate and the smallest amount in the same experiments regardless of almost the same surface area. From results, the excellent photoredox abilities of this rutile powder appears to be due to specific powder preparation method, like a homogeneous precipitation leading to direct crystallization from the solution, regardless of their crystalline structures even when having the similar particle shape and surface area.

• 한국수소및신에너지학회논문집
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• 제31권1호
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• pp.1-7
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• 2020

The synthesis and catalytic activities over vanadium carbides were examined for ammonia decomposition reaction to produce the hydrogen. In particular, the comparison of vanadium nitrides were made on the ammonia decomposition reaction. The experimental data exhibited that BET surface areas ranged from 5.2 ㎡/g to 25.6 ㎡/g and oxygen uptake values varied from 3.8 μmol/g to 31.3 μmol/g. It is general that vanadium carbides (VC) were observed to be superior to vanadium nitrides for ammonia decomposition reaction. The primary reason for these differences were thought to be related to the extent of electronegativity between these materials. Most of vanadium carbide crystallites were exceeded by Pt/C crystallite. We assumed that the activities for vanadium carbide crystallites (VC) were comparable to or even higher than that determined for the Pt/C crystallite.

• 한국수소및신에너지학회논문집
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• 제30권1호
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• pp.1-7
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• 2019

The preparation and catalytic activities of various transition metal carbide crystallites (VC, MoC, WC) were examined in this study. In particular, the effect of different kinds of transition metal crystallites were scrutinized on the ammonia decomposition reaction. The experimental results showed that BET surface areas ranged from $8.3m^2/g$ to $36.3m^2/g$ and oxygen uptake values varied from $9.1{\mu}mol/g$ to $25.4{\mu}mol/g$. Amongst prepared transition metal carbide crystallites, tungsten compounds (WC) were observed to be most active for ammonia decomposition reaction. The main reason for these results were considered to be related to the extent of electronegativity between these materials. Most of transition metal carbide crystallites were exceeded by Pt/C crystallite. However, the steady state reactivities for some of transition metal carbide crystallites (WC) were comparable to or even higher than that determined for the Pt/C crystallite.

• 한국세라믹학회지
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• 제33권5호
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• pp.547-555
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• 1996

Porous alumina ceramics were fabricated by pseudo-boehmite phydosol-gel process within/without commercial $\alpha$-alumina particles average 1 and 40 micron respectively. The pore characteristics of fired specimens were studied by the measurement of bulk density total porosity thyermal analysis pore volume pore distribution BET area XRD and SEM. with increasing of firing temperature pore volume and BET surface area were decreased and the average pore size was increased to approximately 146$\AA$ upto 80$0^{\circ}C$ by de-watering of [OH] and formation of $\alpha$-alumina. The fired relative density of the alumina-dispersed specimen with average 1 micron particle was increased with the amounts of dispersed particle by bimodal packing theory which is compared to the ones of specimen including of average 40 micron particle. It was confirmed that the percola-tion threshold in porous ceramics with coarser particle (40 micron) has formed between the transformed-alumina from hydrogel and dispersed-alumina of above 50 vol% particle and the total porosity was increased at the threshold point above.