• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.97.1-97.1
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• 2012

Porous ceramics are widely used for applications such as catalysis supports, gas distributors and filters such as DPF. For these purpose, it is important to have proper porosity controlling pore structure while maintaining mechanical and thermal properties. In this work, we have prepared the porous ceramic structures made of reaction bonded silicon nitride with hierarchical pore structures. Uni-directionally aligned pore channels, which are mostly filled with ${\beta}$-Si3N4 whiskers, were achieved by an ice-templating method. The structures of the pore channels and the walls are controllable by the processing conditions, such as solid concentration, freezing rate of the slurry, and additives. We have investigated and characterized the influences of the conditions on the microstructures and the properties, such as porosity, pore size distribution, lamellar thickness, wavelength, and orientations. The compressive strength test and flow test was performed to determine the structural integrity and air permeability.

• Journal of Powder Materials
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• v.23 no.3
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• pp.189-194
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• 2016

We report a facile method for preparing KIT-1 mesoporous silicates with two different macroporous structures by dual templating. As a template for macropores, polystyrene (PS) beads are assembled into uniform three dimensional arrays by ice templating, i.e., by growing ice crystals during the freezing process of the particle suspension. Then, the polymeric templates are directly introduced into the precursor-gel solution with cationic surfactants for templating the mesopores, which is followed by hydrothermal crystallization and calcination. Later, by burning out the PS beads and the surfactants, KIT-1 mesoporous silicates with macropores are produced in a powder form. The macroporous structures of the silicates can be controlled by changing the amount of EDTANa4 salt under the same templating conditions using the PS beads and inverse-opal or hollow structures can be obtained. This strategy to prepare mesoporous powders with controllable macrostructures is potentially useful for various applications especially those dealing with bulky molecules such as, catalysis, separation, drug carriers and environmental adsorbents.

• Carbon letters
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• v.18
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• pp.24-29
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• 2016

High pollutant-loading capacities (up to 319 times its own weight) are achieved by three-dimensional (3D) macroporous, slightly reduced graphene oxide (srGO) sorbents, which are prepared through ice-templating and consecutive thermal reduction. The reduction of the srGO is readily controlled by heating time under a mild condition (at 1 10⁻² Torr and 200℃). The saturated sorption capacity of the hydrophilic srGO sorbent (thermally reduced for 1 h) could not be improved further even though the samples were reduced for 10 h to achieve the hydrophobic surface. The large meso- and macroporosity of the srGO sorbent, which is achieved by removing the residual water and the hydroxyl groups, is crucial for achieving the enhanced capacity. In particular, a systematic study on absorption parameters indicates that the open porosity of the 3D srGO sorbents significantly contributes to the physical loading of oils and organic solvents on the hydrophilic surface. Therefore, this study provides insight into the absorption behavior of highly macroporous graphene-based macrostructures and hence paves the way to development of promising next-generation sorbents for removal of oils and organic solvent pollutants.

• Polymer(Korea)
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• v.39 no.1
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• pp.151-156
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• 2015

Herein, novel porous structures were fabricated from monomer solutions of dimethylsiloxane and benzene by directional crystallization in twice. First, a honeycomb-like structure was fabricated by $1^{st}$ directional crystallization of solvent. By infiltration of the solution and subsequent $2^{nd}$ directional crystallization, novel structures of different pores in the honeycomb-like structure were fabricated. The porous materials prepared by the repeated directional crystallization have higher indentation modulus and hardness than those of the samples prepared by single directional crystallization. When a higher solution concentration was used in $2^{nd}$ directional crystallization, the maximum increase (indentation modulus: 2140% increase, indentation hardness: 2330% increase) was obtained. On the other hand, porosity and contact angle were lower in the samples from $2^{nd}$ directional crystallization than those from $1^{st}$ directional crystallization. A large decreases was observed, when a relatively high concentration was used in $2^{nd}$ directional crystallization (porosity: 21% decrease, contact angle: 36% decrease).