Synthesis of Double Mesoporous Silica Nanoparticles and Control of Their Pore Size

Park, Dae Keun,Ahn, Jung Hwan Korea Electric Power Corporation 2021 KEPCO Journal on electric power and energy Vol.7 No.1

In this study, monodispersive silica nanoparticles with double mesoporous shells were synthesized, and the pore size of synthetic mesoporous silica nanoparticles was controlled. Cetyltrimethylammonium chloride (CTAC), N, N-dimethylbenzene, and decane were used as soft template and induced to form outer mesoporous shell. The resultant double mesoporous silica nanoparticles were consisted of two layers of shells having different pore sizes, and it has been confirmed that outer shells with larger pores (Mean pore size > 2.5 nm) are formed directly on the surface of the smaller pore sized shell (Mean pore size < 2.5 nm). It was confirmed that the regulation of the molar ratio of pore expansion agents plays a key role in determining the pore size of double mesoporous shells.

Pore size-controlled synthesis of PEG-derived porous TiO₂ particles and photovoltaic performance of dye-sensitized solar cells

Jo, Eun Hee,Chang, Hankwon,Kim, Sun Kyung,Roh, Ki‐,Min,Kim, Jiwoong,Jang, Hee Dong Elsevier 2014 Materials letters Vol.131 No.-

<P><B>Abstract</B></P> <P>Porous TiO<SUB>2</SUB> particles having a controlled pore size were synthesized from colloidal mixtures of TiO<SUB>2</SUB> nanoparticles and polyethylene glycol (PEG) via an aerosol templating method. The effect of a PEG addition on the pore properties of the as-prepared porous TiO<SUB>2</SUB> particles was systematically investigated. A larger amount of PEG led to porous TiO<SUB>2</SUB> particles with higher specific surface areas and total pore volumes originating from the removal of the PEG during a heat treatment. Furthermore, the photovoltaic characteristics of dye-sensitized solar cells (DSSCs) fabricated with porous TiO<SUB>2</SUB> photoanodes having different pore properties were estimated. The photovoltaic conversion efficiency of the DSSCs was found to be strongly dependent on the pore properties of the TiO<SUB>2</SUB> photoanode. The DSSC fabricated with the TiO<SUB>2</SUB> photoanode prepared with 0.25wt% of PEG showed the highest conversion efficiency of 6.17%, which was approximately 170% higher than that of DSSC fabricated with a TiO<SUB>2</SUB> photoanode without PEG.</P> <P><B>Highlights</B></P> <P> <UL> <LI> PEG-derived porous TiO<SUB>2</SUB> particles with a controlled pore size were synthesized by an aerosol templating method. </LI> <LI> The effect of the PEG addition on the pore properties was confirmed. </LI> <LI> Photovoltaic characteristics of DSSCs fabricated with the porous TiO<SUB>2</SUB> photoanodes were estimated. </LI> <LI> Porous TiO<SUB>2</SUB> photoanode enhanced the adsorption of dye and conversion efficiency. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Systematically Controlled Pore System of Ordered Mesoporous Carbons Using Phosphoric Acid as the In situ Generated Catalysts for Carbonization and Activation

Xing Jin,이창현,김진회,유대종,박찬호,손정국,김지만 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.8

We report on a facile synthesis of the ordered mesoporous carbon (OMC) materials with systematically controlled microporosity and mesoporosity simultaneously through the nano-replication route using phosphoric acid as the acid catalyst and activation agent. The use of phosphoric acid affects the pore structures of OMC materials, such as the formation of numerous micropores by activation of the carbon framework and the enlargement of mesopores by spontaneous phase separation during the carbonization. The mesopore sizes, surface areas, total pore volumes, and micropore volumes of the OMC materials are highly dependent on the phosphoric acid content and can be systematically controlled in the range 3.7–7.5 nm, 1027–2782 m2 g–1, 1.12–3.53 cm3 g–1 and 0.34–0.95 cm3 g–1, respectively. OMC materials with systematically controlled pore structures were successfully synthesized using phosphoric acid as the carbonization catalyst and mesoporous silica materials with cubic Ia3d and 2-D hexagonal mesostructures as the templates. The phosphoric acid in the synthesis of ordered mesoporous carbon materials acts as the chemical activating agent for micropore generation of the carbon framework and pore-expanding agent for controlling of mesopore size, in addition to functioning as the acid catalyst. The present synthesis pathway is very useful for preparing OMC materials with tunable mesopore sizes and well-developed microporosities at the same time.

Fine-tuning the pore size of mesoporous graphene in a few nanometer-scale by controlling the interaction between graphite oxide sheets

Lee, Jihye,Nankya, Rosalynn,Kim, Aran,Jung, Hyun Elsevier 2018 ELECTROCHIMICA ACTA Vol.290 No.-

<P><B>Abstract</B></P> <P>Mesoporous graphene (MG) was successfully synthesized by using the soft-template method with graphite oxide (GO) and triblock co-polymer (P123). The obtained MGs exhibit a high surface area as well as tuned pore parameters by preparing GO/P123 composite gel under different reaction conditions. Freeze-drying of the composite gel leads to physical interaction between the GO sheets, which induced the largest pores in MG. While, hydrothermal treatment can generate the chemical linkage between GOs through various reactions of oxygen functional groups on GOs, it facilitates the formation of relatively smaller and more uniform pores. Especially, the presence of a base catalyst under hydrothermal reaction accelerates the chemical reactions, which causes the smallest and most uniform pores. As controlling the interaction between GOs, the pore size of the MGs was easily fine-tuned in a few nanometer-scales never reported. Herein, the electrochemical performance was preliminarily tested as a supercapacitor among the various applications of MG. As a results, the hydrothermal treated sample shows the highest specific capacitance of 151.8 F g<SUP>−1</SUP> at a current density of 0.1 A g<SUP>−1</SUP>. Additionally, it exhibits excellent cycle stability with ∼96% retention of its initial capacitance at a current density of 3.0 A g<SUP>−1</SUP> even after 5000 cycles.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Effect of pore size in activated carbon on the response characteristic of electric double layer capacitor

Keiko Ideta,김두원,김태곤,Koji Nakabayashi,Jin Miyawaki,박주일,윤성호 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.102 No.-

The effect of pore size on the response characteristic of an electric double layer capacitor (EDLC) wasclosely examined. A series of phenol-resin-based activated carbon (AC) samples was prepared as averagepore size from 0.94 to 1.68 nm by KOH activation by varying the activation temperature andKOH/carbonized phenol-resin ratio. The impedance properties of pouch-type EDLC cells prepared usingAC samples were evaluated by applying an alternating current at 3 V between 10 mHz and 100 kHzfor confirming the response characteristic. The cell based on the AC with a largest pore size (1.68 nm)showed fast response frequency, and had a high dielectric relaxation time constant as calculated fromthe response frequency value. The AC with the largest pore size, which consisted of both micropores(>1 nm) and mesopores (2–4 nm), was confirmed to facilitate extremely low electrolyte-diffusion resistanceduring the formation of the electric double layer, implying that the large pores lead to fast andstable response frequency. The presented findings suggest that AC with a largest pore size as the electrodeleads to superior capacitance and response frequency characteristics in the alternating current thanthose of an AC with a smaller pore size.

기하학적 영상 처리를 이용한 나노 섬유 웹의 기공 분포 측정

김주용,이정해,임대영,변성원,Kim Jooyong,Lee Jung Hae,Lim Dae Young,Byun Sung Won 한국섬유공학회 2004 한국섬유공학회지 Vol.41 No.6

An image processing algorithm has been developed in order to anlyze the nanofiber web images from a high magnification microscope. It has been known that precise pore detection of thick webs is extremely difficult mainly due to lack of light uniformity, difficulty of fine focusing and translucency of nanofiber web. The serial morphological image processing techniques of edge detection, dilation, opening, skeletonization and dilation have been applied to images for accurate pore detection followed by connect-component labeling for computing mean pore size and standard deviation of pore sizes. The pore detection algorithm developed has been found to show excellent performance in characterizing the porous structure, thus being a promising tool for the on-line quality control of eletrospun fiber manufacturing.

A novel method for the pore size control of the battery separator using the phase instability of the ternary mixtures

Kim, L. U.,Kim, C. K. Wiley Subscription Services, Inc., A Wiley Company 2006 Journal of polymer science Part B, Polymer physics Vol.44 No.15

<P>The battery separator plays a key role in determining the capacity of the battery. Since separator performance mainly depends on the pore size of membrane, development of a technique for the fabrication of the membrane having controlled pore size is essential in producing a highly functional battery separator. In this study, microporous membranes having the desired pore size were produced via thermally-induced phase separation (TIPS) process. Control of the phase boundaries of polymer-diluent blends is the main concern in manipulating pore size in TIPS process, because pore size mainly depends on the temperature gap between phase separation temperature of the blend and the crystallization temperature of polymer. Microporous membranes having controlled pore size were produced from polyethylene (PE)/dioctyl phthalate (DOP) blends, PE/isoparaffin blends, and polymer/diluent-mixture ternary blends, that is, PE/(DOP/isoparaffin) blends. PE/DOP binary blends and PE/(DOP/isoparaffin) ternary blends exhibited typical upper critical solution temperature (UCST) type phase behavior, while PE formed a homogeneous mixture with isoparaffin above the crystallization temperature of PE. When the mixing ratio of polymer and diluent-mixture was fixed, the phase separation temperature of PE/diluent-mixture blend first increased with increasing DOP content in the diluent-mixture, went through a maximum centered at about 80 wt % DOP and then decreased. Furthermore, the phase separation temperatures of the PE/diluent-mixture blends were always higher than that of the PE/DOP blend when diluent-mixture contained more than or equal to 20 wt % of DOP. Average pore size of microporous membrane prepared from PE/DOP blend and that prepared from PE/isoparaffin blend were 0.17 and 0.07 μm, respectively. However, average pore size of microporous membrane prepared from ternary blends was varied from 0.07 to 0.5 μm by controlling diluent mixing ratio. To understand the phase behavior of ternary blend, phase instability of the ternary mixture was also explored. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2025–2034, 2006</P>

Phenol-formaldehyde-resin-based activated carbons with controlled pore size distribution for high-performance supercapacitors

Talreja, Neetu,Jung, SungHoon,Yen, Le Thi Hai,Kim, TaeYoung Elsevier 2020 Chemical engineering journal Vol.379 No.-

<P><B>Abstract</B></P> <P>Carbon-based materials with a controlled pore size distribution are highly desirable to achieve fast diffusion of electrolytes and enhance supercapacitor performance. Here, we report a method to effectively control porosity of the phenol formaldehyde (PF) resin-based carbons along with pore volume and pore size distribution using a combined metal templating and physical/chemical activation approach. The combined metal templating and physical/chemical activation approach allows the precise control of the pore size of the carbons. PF resin synthesized by suspension polymerization was used as a carbon source and metal ions (Fe<SUP>+</SUP> and Zn<SUP>+</SUP>) were used as templating agents. The pore size could be superbly tuned in the 2–50 nm range by varying the metal ion. Carbonization and CO<SUB>2</SUB> activation of the metal-embedded PF resins yielded carbon microparticles (M-CMP), which turned into carbon microparticles (M-CMP-S) having mesopores in the range of 35–51 nm by sonication and KOH activation. The specific capacitances of Fe-CMP-S and Zn-CMP-S were as high as 132 and 152 F g<SUP>−1</SUP> (58 and 74 F cm<SUP>−3</SUP>) in ionic liquid electrolyte with energy densities of 56 and 64 Wh kg<SUP>−1</SUP>, respectively. In organic electrolyte, the Zn-CMP-S showed the specific capacitance of 136 F g<SUP>−1</SUP> with a maximum power density of 709 kW kg<SUP>−1</SUP>. Adjustable pore size of the M-CMP-S facilitated the diffusion of electrolyte ions into the electrode, thereby achieving supercapacitor with high energy and power density.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Porous carbons with a controlled porosity and large pore volume were developed. </LI> <LI> Control over porosity was enabled by combined metal templating and activation. </LI> <LI> The resulting carbons were used as electrodes for supercapacitors. </LI> <LI> The supercapacitors showed both high energy density and power density. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

New continuous process developed for synthesizing sponge-type polyimide membrane and its pore size control method via non-solvent induced phase separation (NIPS)

Kim, Myeongsoo,Kim, Gunhwi,Kim, Jinyoung,Lee, Daero,Lee, Sangrae,Kwon, Jinuk,Han, Haksoo Elsevier 2017 Microporous and mesoporous materials Vol.242 No.-

<P><B>Abstract</B></P> <P>In this study, the improvement of synthesizing method of sponge-type polyimide (PI) membrane and its newly developed pore size control techniques are mainly described. The sponge-type polyimide membrane with large pore size (0.1–10 µm) and high permeability was successfully synthesized by using non-solvent phase separation method (NIPS) in continuous process and its full polyimidization is confirmed via Fourier-transform infrared technique. The theoretical approach in this research induced by Jurin's law which describes the height of a liquid within a thin capillary tube. In this theory, the pore size of membrane is highly influenced by the interactive tension between the polymer and solvents during synthesizing process of polymer membrane. There are two ways of controlling pore size established from Jurin's law. The validity of the application of Jurin's law was proven via comparison with theoretical and experimental data. Its inner structure of membrane and pore size are identified by field emission-scanning electron microscopy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Synthesis of sponge-type polyimide membrane for continuous system using non-solvent phase separation (NIPS) method. </LI> <LI> Two ways of controlling pore size established from Jurin's law. </LI> <LI> Comparison of pore size with theoretical and experimental data. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Microstructure and Pore Size Control of Silica Membrane for Gas Separation at Elevated Temperatures

Lee Kew-Ho,Sea Bongkuk,Lee Dong-Wook The Membrane Society of Korea 2005 Korean Membrane Journal Vol.7 No.1

Among ceramic membranes developed to date, amorphous silica membranes are attractive for gas separation at elevated temperatures. Most of the silica membranes can be formed on a porous support by sol-gel or chemical vapor deposition (CVD) process. To improve gas permselectivity of the membrane, well-controlled pores having desired size and chemical affinity between permeates and membrane become important factors in the preparation of membranes. In this article, we review the literature and introduce our technologies on the microstructure to be solved and pore size control of silica membranes using sol-gel and CVD methods.