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Sangram Mazumder,박정규,Naboneeta Sarkar,이기성,Bijay Basnet,김익진 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.12
This paper reports the formation of carbon nanotubes (CNTs) reinforced porous Al2O3 ceramics by a novel combination ofthree processes. Porous ceramics are developed using direct foaming. Cobalt nanoparticles as catalysis agents aresimultaneously synthesized and dispersed by colloidal process to prepare the suitable catalyst material for carbon nanotubessynthesis. The catalytic chemical vapour deposition (CCVD) technique is used to directly synthesize CNTs within the porousceramics and the effect of growth time on the morphology, crystallinity and yield of CNTs are investigated. Hertzianindentations are used to evaluate the damage behaviour under constrained loading conditions. The mechanical behaviour fromindentation load-displacement curves is compared according to CNTs contents in the samples.
In situ CCVD synthesis of carbon nanotubes within zeolite crystal coated porous ceramic foam
MAZUMDER, Sangram,ZHAO, Wei,PARK, Jung Gyu,SARKAR, Naboneeta,KIM, Sukyoung,KIM, Ik Jin CERAMIC SOC OF JAPAN 2015 JOURNAL- CERAMIC SOCIETY JAPAN Vol.123 No.1438
<P>In this study, consolidated zeolite crystal coated porous ceramic foams containing a large quantity of carbon nanotubes (CNTs) within micro-metre sized pores were prepared. An alumina-silica porous ceramic body, having an average pore size of less than 100 mu m, was produced by the direct foaming technique. Well-shaped zeolite crystals having an average size of 180 nm were synthesized and homogeneously coated on the porous ceramic body by an in situ process. An Fe-supported zeolite/ceramic matrix, which is used for CNT synthesis, was prepared using ion-exchange by immersing the zeolite-coated porous ceramic body into FeCl2 aqueous solution. The CNTs were synthesized by a catalytic chemical vapour deposition (CCVD) process for four different reaction times. Both acicular-shaped and randomly bundled networks of multi-walled carbon nanotubes (MWCNTs) were synthesized using these different reaction times. Moreover, the yield of CNTs produced showed a tendency to increase with increasing reaction time. (C)2015 The Ceramic Society of Japan. All rights reserved.</P>
Influence of amphiphile on foam stability of Al2O3-SiO2 colloidal suspension to porous ceramics
Naboneeta Sarkar,박정규,서동남,Sangram Mazumder,Ashish Pokhrel,Christos G. Aneziris,김익진 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.4
The stabilization of wet foam is very important to avoid the instability caused by the large interfacial area at gas-liquid interface of colloid suspension. Propionic acid, a short chain carboxylic acid is used as foam stabilizer, which acts by modifying the particle surface and increases the wet foam stability. The characterization of Al2O3-SiO2 foams, namely Laplace pressure, foam stability, air content and bubble size are explored by changing the concentration of the amphiphile. Macroporous Al2O3- SiO2 ceramics with open or closed cells, average pore size of less than 100 μm and porosities within 43 and 51% was prepared by direct foaming process. The sample sintered at 1300 ℃ for 1 hour showed an adsorption free energy of 0.9 × 107 to 2.0 × 108 kTs and a Laplace pressure of 0.63 to 0.85 mPa, highlighting good wet foam stability of approximately 80-90%.
Stabilization of nano-particles in concentrated colloidal suspension to porous ceramics
Naboneeta Sarkar,박정규,Sangram Mazumder,김익진 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.2
This study presents a novel method to study the stabilization mechanism of wet foams in concentrated colloidal suspension. The thermodynamic instability of wet foam bubbles in water due to the large and highly energetic interfacial area is the main challenge of processing such foams from colloidal suspension. Smaller bubbles under pressure diffuse into larger bubbles. This is known as Ostwald ripening, and it results in coarsening of the wet foam. Hence, the bubble size distribution broadens. To optimize the bubble size and the stability of wet foam, the adsorption free energy and Laplace pressure of nano-particle stabilized colloidal suspensions are investigated. Porous ceramics with more than 90% wet foam stability can be prepared easily with this novel approach. The sintered foam shows a particle free energy of 1.7 × 108 ~ 3.2 × 108 kTs and pressure difference of 20 mPa to 25 mPa for colloidal Al2O3 and SiO2 particles with particle size of 40 nm and 20 nm respectively.