Fractal Characteristics of Pore Structures in GGBFS-based Cement Pastes

Kim, Jiyoung,Choi, Young Cheol,Choi, Seongcheol Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.428 No.-

<P><B>Abstract</B></P> <P>The present study evaluated pore surface fractal characteristics of high-strength cement pastes with different ground granulated blast-furnace slag (GGBFS) replacement ratios. Using the results of mercury intrusion porosimetry measurements, the surface fractal dimension in various pore-size ranges was calculated. Experimental results show that the fractal characteristics appeared in mesopores in range of 6–10nm and 10–25nm and larger capillary pores with sizes of more than 100nm. In larger capillary pores, as the GGBFS replacement ratio increased up to 65%, the surface fractal dimension and pore volume decreased, and they increased when the GGBFS replacement ratio increased from 65% to 80%. In contrast, higher GGBFS replacement ratios in mesopore regions resulted in an increased surface fractal dimension and pore volume. Furthermore, in the regions where fractal characteristics appeared, pore volume and the surface fractal dimension exhibited a proportional relationship. The ratio of the surface fractal dimension to the volume of larger capillary pores was strongly correlated with the compressive strength of the specimens.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pore surface fractal characteristics of GGBFS-based cement pastes were evaluated. </LI> <LI> Three pore-size ranges exhibited fractal characteristics. </LI> <LI> Pore volume and the surface fractal dimension were proportional. </LI> <LI> The ratio of the dimension to pore volume was correlated with compressive strength. </LI> </UL> </P>

Resin Capacity of Technical Woven Fabrics: Pore Volume and Pore Shape Simulation

Hamid Reza Sharafat,Mehdi Kamali Dolatabadi,Ali. A. A. Jeddi 한국섬유공학회 2020 Fibers and polymers Vol.21 No.11

Nowadays, technical woven fabrics are broadly utilized as reinforcement of composites. Resin capacity of wovenfabric is one of the main challenges in laminate fabrication. Resin diffusion during fabrication of the composite is extremelydepended on fabric micro-morphology. The geometry of weave unit cell and its pore are fundamental factors in evaluatingresin capacity and resin diffusion within fabrics. The main attempt of this study was obtaining an approach to evaluate resincapacity of a woven fabric via simulating pore shape and pore volume. For this purpose, four basic unit cells for all kind ofweaves were simulated with the two shapes of tow cross-section: lens and racetrack. Afterwards, 3D shape and volume oftheir pores were simulated using this approach. The proposed approach is established on the base of initial data of fabric suchas tow setts, tow titers, planar density and thickness of a technical fabric. To assess the simulation, three types of wovenfabrics namely, plain, twill and satin were impregnated by epoxy resin using vacuum infusion process. The volume fractionsof the matrix and fibers of real composites were compared with simulated ones. It was demonstrated that the approach withracetrack assumption led to high degree of convergence with experimental results. The maximum relative error of pioneeredmethod to evaluate volume of the pore in this condition exceeded up to 1.43 %. Suitable correlation between volumefractions of the pore and void was observed in experimental data. It is experimentally demonstrated that the void volumefraction of composite will be increased with decrease of pore volume due to difficulty of wetting. In this paper, it is illustratedthat the resin capacity of a woven fabric is a function of vacuum level in vacuum infusion process. For instance, resincapacity of a certain plain fabric could be reduced up to 10 % under 60 kPa (0.6 bar) of vacuum in contrast with steady stateof fabric at room atmosphere.

硅酸質系微分末混合 塗布防水材料가 시멘트모르터의 透水性 및 細孔量에 미치는 影響

김형무 서울産業大學校 1994 논문집 Vol.39 No.1

This paper describes the effect of siliceous coating on water permeability and pore volume of mortar substrate. Coefficient of permeability and pore volume were measured for evaluation of watertightness of the.. Coefficient of permeability and pore volume of coated mortar were obviously less than those of non-coated one. Effect of siliceous coating reached the inside 5 to 10mm of coated morta. Reduction of pore volume was caused by the decrease of capillary pores within the size range 0.1 to 1/μm. Relationship of them can be described by the equation y=3.25×10?x??, where y is coefficient of permeability and x is pore volume.

The use of MWCNT to enhance oxygen reduction reaction and adhesion strength between catalyst layer and gas diffusion layer in polymer electrolyte membrane fuel cell

Kil, K.C.,Hong, S.G.,Park, J.O.,Pak, C.,Chang, H.,Paik, U. Pergamon Press ; Elsevier Science Ltd 2014 International journal of hydrogen energy Vol.39 No.30

The pore structure and pore volume of catalyst layer (CL) were controlled by utilizing multi-walled carbon nanotube (MWCNT). According to the increase in MWCNT ratio in CL, the primary pore (below 100 nm) volume concerning with the phosphoric acid penetration to the reaction site was decreased and the secondary pore (approximately 1 μm) volume relating with oxygen gas transportation was increased, respectively. However, the excessive addition of MWCNT was detrimental to electrochemical properties due to the difficulty of phosphoric acid penetration to the reaction site and the opposite influx of phosphoric acid to the secondary pore. Furthermore, the adhesion strength between CL and gas diffusion layer (GDL) was improved by only 10% addition of MWCNT. Therefore, it is suggested that the ratio of MWCNT in CL can be key role for obtaining the optimized pore volume, enhanced adhesion strength, and good performance of polymer electrolyte membrane fuel cell (PEMFC).

Optimized Assembly of Micro-/Meso-/Macroporous Carbon for Li–S Batteries

Qiong Tang,Heqin Li,Min Zuo,Jing Zhang,Yiqin Huang,Peiwen Bai,Jiaqi Xu,Kuan Zhou 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.2

In order to explore the effect of hierarchical porous carbon on the performances of Li–S batteries, we synthesized three kinds of micro-/meso-/macroporous carbon materials with different pore properties by facile hard-template method. Different from the majority of reports on porous carbon ensuing large specific surface area (SSA) and total pore volume, it was found that in the case of identically high sulfur content, the pore size distribution substantially influences the performances of Li–S batteries rather than the SSA and total pore volume. Furthermore, in the assembly of micro-/meso-/macropores, the micropore volume ratio to the total pore volume is dominant to the capabilities of batteries. Among the samples, the porous carbon carbonized with the precursor of sucrose at 950℃ presents the highest initial discharge specific capacity of 1327 mAh/g and retention of 630 mAh/g over 100 cycles at 0.2C rate along with the best rate capability. This sample possesses the largest micropore volume ratio of 47.54% but a medium SSA of 1217 m2 /g and inferior total pore volume of 0.54 cm3 /g. The abundant micropores effectively improve the conductivity of dispersed sulfur particles, inhibit the loss of sulfur series and enable the cathode to exhibit superior electrochemical performances.

염화아연 약품활성화를 이용한 음식물쓰레기로부터 활성탄 제조

강화영(Hwa Young Kang),이영동(Young Dong Lee),김세훈(Se Hoon Kim),박성봉(Sung Bong Park),정재성(Jae Sung Jung),박상숙(Sang Sook Park) 大韓環境工學會 2008 대한환경공학회지 Vol.30 No.9

활성탄을 제조하기 위하여 원료물질로서 음식물쓰레기를 이용하였다. 음식물쓰레기를 염화아연으로 약품활성화 하였다. 실험은 서로 다른 약품첨가비율(활성화제/음식물쓰레기), 활성화 온도, 그리고 활성화시간을 변수로 하여 수행하였다. 활성화물의 특성을 나타내기 위하여 요오드가와 메틸렌블루 가, BET 표면적, 세공 용적, 미세공 비율, 세공 직경, 수율 그리고 주사전자현미경관찰을 수행하였다. 로터리 킬른 반응로를 이용하여 염화아연 함침비 1.0배인 시료를 500℃에서 60분 동안 활성화하여 제조한 활성화물의 요오드가는 480 mg/g, 메틸렌블루 가는 95 mL/g, BET 표면적은 410 m2/g, 세공 용적은 0.248 cm3/g, 그리고 평균세공직경은 2.43 nm로 나타났다. 제조한 활성탄의 총 표면적중 미세공 면적 비율은 70.7%, 총 세공 용적 중 미세공 용적 비율은 53.2%를 나타냈다. It was studied to utilize wasted food as a starting material to produce for activated carbon. The wasted food was chemically activated with zinc chloride. Experiments were carried out at different chemical ratios(activating agent/wasted foods), activation temperatures, and activation time. The activated products were characterized by measuring the iodine and methylene blue number, the BET surface area, the pore volume, the micropore ratio, the pore diameter, the yields and the scanning electron microscope(SEM). For the products activated by impregnation ratio of 1.0 of ZnCl₂ at 500℃ for 60 min in a rotary kiln reactor had iodine number of 480 mg/g, methylene blue number of 95 mL/g, BET surface area of 410 m2/g, pore volume of 0.248 cm3/g, and average pore diameter of 2.43 nm, respectively. The activated carbon obtained had the contribution of micropore area of 70.7% to the total pore area and micropore volume of 53.2% to the total pore volume.

Performance evaluation of polyamide TFC membranes: Effects of free volume properties on boron transport

Kim, Sung-Jo,Han, Doseon,Yu, Hye-Weon,O'Rourke, Brian E.,Kobayashi, Yoshinori,Suzuki, Ryoichi,Hwang, Moonhyun,Kim, In S. Elsevier 2018 Desalination Vol.432 No.-

<P><B>Abstract</B></P> <P>To comprehensively investigate the correlation between free volume properties (size and distribution) in the interior of polyamide (PA) active layer and mass transport mechanism, six polyamide thin film composite (TFC) membranes were characterized using positron annihilation lifetime spectroscopy (PALS). In case of pressurized filtration conditions, the rejection rate of boron across all PA membranes was found to be inversely proportional to the free volume size. The more boron transport occurred at the membrane containing larger free volume. In addition, the transition of the neutral boron transport mechanism from convection to diffusion was found to occur at a membrane free volume radius around 0.275nm within the applied pressure range (2 and 10bar), as verified by PALS and the dimensionless Peclet number. We believe that mass transport mechanism transition from convection to diffusion is caused by the compression of polyamide active layer due to applied hydraulic pressure (10bar), resulting in lowering the convective mass transport pathway inside polyamide active layer. These membrane free volume size criteria and experimental filtration results may subsequently be used as new design guidelines for the development of high boron rejection polyamide TFC membranes having a low energy consumption.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The free volume characterization of several polyamide membranes by PALS were performed to evaluate boron transport. </LI> <LI> The transition of boron transport mechanism was observed at a free volume radius around 0.275nm. </LI> <LI> Free volume properties measured by PALS could be used as new design criteria for high boron rejection membranes. </LI> </UL> </P>

계면활성제를 이용한 포화지층내 저비중 비수용성 유기용매의 제거거동에 관한 연구

이재원,박규홍,박준범,임경희 한국지반공학회 1999 한국지반공학회논문집 Vol.15 No.5

BTEX로 오염된 혼합토(사질토/점토)의 정화를 위한 계면활성제 기법의 적용성 및 제거효율에 대한 연구를 진행하였다. 초기농도 275mg/kg으로부터 1975mg/kg의 BTEX로 오염시킨 8개의 컬럼에 물, methyl alcohol과 계면활성제 용액을 주입하였고 이때 계면활성제와 첨가물의 혼합과 비혼합시에 대해 제거거동을 비교 분석하였다. 물을 이용한 흙 세척법의 적용 결과 850 간극부피의 물을 주입하여 98%의 제거 효율을 보였으나 8mg/kg 이하의 저농도에서는 더 이상 제거가 이루어지지 않고 일정한 양상을 가지는 tailing effect를 보였다. 본 실험 결과 가장 우수한 조건은3% ethyl alcohol과 3% SXS를 첨가한 4% SOFTANOL(equation omitted)-90을 간헐적으로 주입한 경우였으며 이 때 95 간극부피에서 99.5%의 제거효율을 보였다. 실험결과 물을 주입하였을 경우 850 간극부피를 주입한 반면, 계면활성제 적용시 95-165 간극부피에서 84.5%-99.5%의 제거효율을 보였는데 이는 계면활성제 기법을 오염된 지반 정화에 효율적으로 적용할 수 있음을 나타내는 것이다. Surfactant flushing for enhancing the removal of BTEX from contaminated sand/clay mixtures was investigated. Eight soil columns packed with relatively undisturbed BTEX contaminated soils, were leached with water, methyl alcohol and then flushed with surfactant with or without several additives. Initial concentrations of BTEX mixture range from 278mg/kg to 1975mg/kg. Initial BTEX removal efficiency was 98% when the contaminated soil was flushed with water of 850 pore volumes. Because of tailing effect, water flushing could not remove below 8mg/kg concentrations during the experimental period. Eventually, the most effective surfactant for flushing was turned out to be 4% SOFTANOL(equation omitted)-90 with 3% ethyl alcohol and 3% SXS. In interrupted flow conditions, the removal efficiency was 99.5% with the flushed water of 95 pore volumes. The BTEX mixture removed from the soil columns during the surfactant flushing ranges from 84.5% to 99.5% of the initial amount for both water leaching(850 pore volumes) and surfactant flushing(95-165 pore volumes), respectively. Test results indicated that surfactant flushing could enhance the removal of BTEX mixture from contaminated soils and could reduce the aqueous phase BTEX mixture concentration in leachate.

Electrochemical modification of the porosity and zeta potential of montmorillonitic soft rock

Wang, Dong,Kang, Tianhe,Han, Wenmei,Liu, Zhiping,Chai, Zhaoyun Techno-Press 2010 Geomechanics & engineering Vol.2 No.3

The porosity (including the specific surface area and pore volume-diameter distribution) of montmorillonitic soft rock (MSR) was studied experimentally with an electrochemical treatment, based on which the change in porosity was further analyzed from the perspective of its electrokinetic potential (${\zeta}$ potential) and the isoelectric point of the electric double layer on the surface of the soft rock particles. The variation between the ${\zeta}$ potential and porosity was summarized, and used to demonstrate that the properties of softening, degradation in water, swelling, and disintegration of MSR can be modified by electrochemical treatment. The following conclusions were drawn. The specific surface area and total pore volume decreased, whereas the average pore diameter increased after electrochemical modification. The reduction in the specific surface area indicates a reduction in the dispersibility and swelling-shrinking of the clay minerals. After modification, the ${\zeta}$ potential of the soft rock was positive in the anodic zone, there was no isoelectric point, and the rock had lost its properties of softening, degradation in water, swelling, and disintegration. The ${\zeta}$ potential increased in the intermediate and cathodic zones, the isoelectric point was reduced or unchanged, and the rock properties are reduced. When the ${\zeta}$ potential is increased, the specific surface area and the total pore volume were reduced according to the negative exponent law, and the average pore diameter increased according to the exponent law.

가교도가 조절된 세공충진 이온교환막의 제조 및 전기화학적 응용: Part I. 전 바나듐 레독스 흐름전지

이지은,박예린,김도형,강문성 한국막학회 2017 멤브레인 Vol.27 No.5

본 연구에서는 얇은 폴리에틸렌 계 다공성 필름(두께 = 25 μm)에 이오노머를 충진시킨 세공충진 이온교환막을 개발하였으며 이를 적용한 전 바나듐 레독스 흐름전지의 충방전 특성을 고찰하였다. 특히 분자 크기가 다른 가교제를 혼합함 으로써 이온교환막의 가교도 및 자유체적을 적절히 제어하여 저저항 및 저 바나듐 투과도를 나타내는 이온교환막을 제조하 고자 하였다. 실험 결과, 제조된 세공충진 이온교환막은 상용막 대비하여 동등 수준의 우수한 전기화학적 특성을 나타내었다. 또한 바나듐 이온 투과도 및 전 바나듐 레독스 흐름전지 성능 평가 실험을 통해 얇은 막 두께에도 불구하고 상용막 대비하여 낮은 바나듐 이온 투과도와 높은 충방전 효율을 나타냄을 확인하였다. In this study, we have developed pore-filled ion-exchange membranes (PFIEMs) filled with ionomer in a thin polyethylene porous film (thickness = 25 μm) and investigated the charge-discharge characteristics of the all vanadium redox flow battery (VRFB) employing them. Especially, the degree of crosslinking and free volume of the PFIEMs were appropriately controlled to produce ion-exchange membranes exhibiting both the low membrane resistance and low vanadium permeability by mixing crosslinking agents having different molecular size. As a result, the prepared PFIEMs exhibited excellent electrochemical properties which are comparable to those of the commercial membranes. Also, it was confirmed through the experiments of vanadium ion permeability and VRFB performance evaluation that the PFIEMs showed low vanadium ion permeability and high charge-discharge efficiency in comparison with the commercial membrane despite their thin film thickness.