• Analytical Science and Technology
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• v.24 no.6
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• pp.503-509
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• 2011

Specific surface area is becoming a very important factor when newly developed advanced nano-materials are evaluated. But there have been many differences in results when measuring specific surface areas, depending on the measuring equipments and analysis method. To verify the reliability of the specific surface area measurement device supplied within the country, Round Robin Test (RRT) has been done at 21 affiliated research institutes. As a result, it was found that several institute had problems in measuring of gas adsorption amount in measuring equipment, and this proved the need for certified reference material (CRM). Furthermore, it was also found that the results from BET analysis is easily swayed by the analyst's subjectivism, and the calculated results may differ up to 16% in case of CRM I depending on the selection range of BET analysis. So this showed that a standard guideline for BET constant C value and fitting correlation coefficient R is needed, to properly select range in BET analysis. The experience in RRT, distribution of CRM, and standardized procedure would result in improved reliability in industrial processes, and thus, would contribute to the quality management, the productivity improvement, the safety evaluation, and the new material development.

• Analytical Science and Technology
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• v.13 no.1
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• pp.89-95
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• 2000

Three grades of activated carbon fibers (ACFs) were prepared from various precursors of plantic, synthetic, and mixed fabrics of viscose rayon and cotton. The ACFs an exhibited type I isotherms on the adsorption of nitrogen or argon. Micropore analysis revealed that the ACFs have uniform micropore size distribution in which their peak diameters were in the range of $5.6{\pm}0.3{\AA}$. The BET surface area of ACFs up to $1600m^2g^{-1}$ was proportional to the adsorption capacity of iodine. The BET values of the ACFs prepared were proportional to the burn-off degree of the products.

• Journal of the Mineralogical Society of Korea
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• v.15 no.3
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• pp.195-204
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• 2002

Mineralogy and the exposed surface area are two of the most important factors controlling dissolution and weathering rates of soils. The mixture of inorganic and organic materials of various size distributions and structures that constitute soils makes the calculation of weathering rates difficult. The surface area of soil minerals plays an important role in most of programs for calculating the weathering rates and critical loads. The Brunauer-Emmett-Teller (BET) measurement is recommended for the measurement of specific surface area. However, BET values measured without organic matter removal are in fact those far all the N2-adsorbed surface areas, including the surfaces covered and aggregated with organisms. Surfaces occupied by organisms are assumed to be more reactive to weathering by organic activities. Therefore, the BET surface area difference before and after organic removal depicts the area occupied by organisms. The present study shows that the BET values after organic matter removal using $H_2$O$_2$ are larger than those without removal by 1.68~4.87 $m^2$/g. This implies that BET measurement without organic removal excludes the reactive area occupied by organisms and that the area occupied by organisms in soils is much larger than expected. It is suggested that specific surface area measurement for calculating weathering rates of mineral soils should be made before and after organic matter removal. The results of a column experiment are presented to demonstrate the potential retarding influence that this organic matter may have on mineral dissolution and weathering.

• Journal of the Korean Ceramic Society
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• v.35 no.10
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• pp.1055-1060
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• 1998

The effects of particle size distribution have been investigated on the high frequency low loss Mn-Zn fer-rites. The particle size distribution was controlled by milling time. Zirconia ball and engineering plastic jar were employed to avoid iron contamination from the milling media. As increasing the milling time BET value was increased from 0.55 to 3.21m2/g and mean particle size was decreased from 2.1 $\mu\textrm{m}$ to 1.0$\mu\textrm{m}$ The large specific surface area of initial powder resulted in the high density of sintered core. However starting powders with high BET lead to inhomogeneous grain growth as well as poor electromagnetic pro-perties at sintering temperature above 1300$^{\circ}C$.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.149-149
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• 2023

미세플라스틱은 입자크기가 5 mm 이하인 플라스틱으로 정의되며, 수계로 유입된 미세플라스틱은 내분비계 교란물질로 작용하여 생태계에 환경독성을 유발하고 오염물질을 흡착·운반할 수 있는 독성 물질의 매개체로서 미세플라스틱의 위해성에 대한 우려가 증가하고 있다. 본 연구는 수용액에서 다양한 미세플라스틱의 납(Pb) 흡착특성을 평가하고 미세플라스틱의 비표면적에 따른 흡착 효과를 비교하고자 하였다. 플라스틱 종류 중 HDPE (High-density Polyethylene)와 PVC (Polyvinyl Chloride)를 각각 세 가지 크기(Group 1: 2.5 mm - 1.0 mm, Group 2: 1.0 mm - 0.3 mm, Group 3: < 0.3 mm)로 제조하여 분류하였으며, 미세플라스틱 입자크기의 비표면적은 BET(Brunauer, Emmett, Teller)분석을 통하여 측정하였다. 담수환경 조성을 위해 pH 7로 조절한 Pb 용액의 농도(0, 0.5, 1, 5, 10, 30 mg/L)별 흡착실험을 수행하였으며 실험결과를 3가지 흡착등온식(Langmuir, Freundlich, Sips 모델)을 사용하여 미세플라스틱에서 Pb 흡착 거동을 나타내었다. BET 분석 측정결과, PVC의 경우 Group 3 > Group 2 > Group 1 순으로 PVC의 입자크기가 작을수록 비표면적이 크게 나타났으며, HDPE 비표면적 또한 비슷한 경향을 보였다. HDPE와 PVC에서 Pb의 흡착은 Langmuir 모델(R² > 0.97)과 Freundlich 모델(R² > 0.82)보다 Sips 모델(R² > 0.98)이 흡착 거동을 설명하기에 가장 적합하였다. 최대흡착능(Q_m) 상수는 입자크기가 작아질수록 흡착능이 높아지는 추세를 보였으며, 흡착세기(K_F)와 흡착강도(n^-1)는 각 플라스틱의 Group 3(HDPE K_F = 0.028, PVC K_F = 0.032; HDPE n^-1 = 0.225, PVC n^-1 = 0.547)에서 가장 높게 나타났다. 본 연구를 통해 HDPE와 PVC에서 Pb의 흡착특성은 Sips모델로 설명이 가능했으며, 이에 따라 Pb 흡착과정에 복수의 흡착메커니즘이 작용하고 있음을 유추해볼 수 있었다. 미세플라스틱의 입자크기와 비표면적이 Pb 흡착량에 영향을 미치는 것을 알 수 있었으며, 미세플라스틱이 중금속을 흡착하여 생물체 내로 전이시킬 수 있는 매개체 역할의 가능성을 확인하였다.

• Clean Technology
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• v.8 no.2
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• pp.61-66
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• 2002

Recycling method of red mud, byproduct from the aluminium manufacturing process, and paper sludge was investigated in order for them to be utilized as the adsorbent for the removal of volatile organic components(VOCs). Either high density polyethylene(HDPE) or low density polyethylene(LDPE) was added to facilitate the manufacture of adsorbents. The utilization of HDPE in the adsorbents increased the adsorption capacity due to the good physical properties, such as, BET and true density, compared with LDPE. BET values of the manufactured adsorbents were much lower than the commercial activated carbon ($10^{-2}-10^{-3}$). It may be due to the fact that the time for decomposition of the paper sludge was not enough during the manufacturing of adsorbents. But the specific adsorption capacity of the manufactured adsorbents (mole adsorbed per unit surface area) had much higher value than the commercial activated carbon (10-100). Therefore, it is important that BET of manufactured adsorbents needs to be increased to obtain the same adsorption capacity as the commercial activated carbon.

• Korean Journal of Materials Research
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• v.8 no.2
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• pp.114-119
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• 1998

등방성 피치계 탄소섬유를 Co$_{2}$gas중에서 등온산화시켜 활성탄소섬유를 제조하였다. 산화된 섬유의 비표면적은 BET장치를 이용하여 측정하였다. Burn-off가 증가하여도 반응속도는 크게 감소하지 않았으며, 80$0^{\circ}C$와 90$0^{\circ}C$에서 산화된 섬유의 비표면적은 40%-60%의 burn-off에서 급격히 증가하다가 60%이상에서 감소하였다. 110$0^{\circ}C$에서 산화된 시편은 40%이상 burn-off되어도 비표면적은 크게 증가하지 않고 60%를 지나서도 계속해서 표면적이 증가하는 현상을 나타내었다. 100$0^{\circ}C$에서 60.4%의 burn-off가 일어난 산화섬유의 비표면적은 3,614$m^2$/g로 가장 큰 값이 얻어졌다. 등방성 탄소섬유는 미세한 흑연결정립들이 무질서한 배향을 하고 있으며, 미세기공벽으로 작용할 수 있는 결정립층이 많기 때문에 활성탄소섬유 제조를 위한 원료로 적합하다고 판단된다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.154-154
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• 2016

다공성 수지상 구리분말은 그 구조적 특성으로 인해 다양한 촉매 분야에 사용되어왔으며, 본 연구에서는 전해도 금욕의 종류에 따라 수지상 구리의 표면적 특성에 대해 연구하였다. 도금욕의 종류($CuSO_4$, $CuCl_2$, $Cu_2P_2O_7$), 인가 전위, 도금시간(1, 5, 10, 30min)에 따른 수지상 형상을 비교하였다. SEM 이미지 분석 결과 황산구리와 염화구리 도금용액에서는 plate-like dendrite 형상이 관찰되었으며, 피로인산구리 도금용액에서는 needle-like dendrite 형상이 관찰되었다. 정전위 실험결과 도금용액별 한계전류밀도에서 음(-)의 방향으로 100mV 낮은 지점의 인가 전위 및 도금시간 10분에서 3가지 용액 모두 가장 미세한 수지상 입자가 관찰되었다. 도금용액별 겉보기 밀도 및 BET 비표면적을 측정해본 결과 미세한 수지상일수록 겉보기밀도는 낮게 비표면적은 크게 측정되었다. 가장 낮은 겉보기 밀도와 가장 높은 BET 비표면적을 가지는 용액은 염화구리 도금용액이었으며 그 값은 $0.951g/cm^3$, $1.8052m^2/g$이었다.

• 한국전기화학회:학술대회논문집
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• 2001.06a
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• pp.203-208
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• 2001

• Journal of the Mineralogical Society of Korea
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• v.15 no.4
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• pp.273-282
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• 2002

Al-pillared montmorillonite was synthesized from Na-saturated montmorillonite which was prepared by ionic substitution from Ca-montmorillonite of the Jabut mine, Gyeongiu City d(001), surface areas, and dehydration and ionic substitution properties have been compared for both Ca-montmorillonite and Al-pillared montmorillonite. d(001) spacings of Ca-montmorillonite and Al-pillared montmorillonite were 15.1 $\AA$ and $18.3\AA$, respectively. Dehydration took place before $350 ^{\circ}C$ in Ca-montmorillonite, whereas linealy up to $550^{\circ}C$ in Al-pillared montmorillonite. BET surface areas are 5～6 times larger in Al-pillared montmorillonite ($192 \m^2$/g) than Camontmorillonite. Ca-montmorilonite shows high selectivity for $Na^{＋}$ /, whereas Al-pillared montmorillonite for $Ca^{2＋}$ . The former shows decreasing d(001) spacing with increasing substitution of $Na^{＋}$ and irregular interstratified structure at high substitution of $Ca^{2＋}$ /, whereas the latter shows linear decreasing pattern in d(001) spacing with increasing $Ca^{ 2+}$.