• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.18.2-18.2
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• 2009

Ceramics have some properties that are unmatched by other kind of materials like metals or polymers. The ability of high thermal and chemical resistance and in case of being superior in specific mechanical properties makes the ceramic materials suitable for arange of applications. The microstructure and morphology of a material arguably permit the use of many advanced application otherwise difficult to achieve.Porous structures have some important applications in biomedical and environmental field. For human hard tissue reconstruction and augmentation procedure suitable biomaterials are used with a desirable porosity. A range of porous bioceramics were fabricated with tailored design to meet the demand of specific applications. Channeled and interconnected porosity was introduced in alumina, zirconia, and hydroxyapatite or tri calcium phosphate ceramics by different methods like multi-pass extrusion process, bubble formation in viscous slurry,slurry dripping in immiscible liquid, sponge replica method etc. The detailed microstructural and morphological investigations were carried out to establish the unique features of each method and the developed systems. For environmental filters the porous structures were also very important. We investigated a range of channeled and randomly porous silicon based ceramic composites to enhance the material stability and filtration efficiency by taking advantage of the material chemistry of the element. Detailed microstructural and mechanical characterizations were carried out for the fabricated porous filtration systems.

• Macromolecular Research
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• v.15 no.1
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• pp.65-73
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• 2007

Chitosan, fibroin, and hydroxyapatite are natural biopolymers and bioceramics that are biocompatible, biodegradable, and resorb able for biomedical applications. The highly porous, chitosan-based, bioceramic hybrid composite, chitosanlfibroin-hydroxyapatite composite, was prepared by a novel method using thermally induced phase separation. The composite had a porosity of more than 94% and exhibited two continuous and different morphologies: an irregularly isotropic pore structure on the surface and a regularly anisotropic multilayered structure in the interior. In addition, the composite was composed of an interconnected open pore structure with a pore size below a few hundred microns. The chemical composition, pore morphology, microstructure, fluid absorptivity, protein permeability, and mechanical strength were investigated according to the composition rate of bioceramics to biopolymers for use in tissue engineering. The incorporation of hydroxyapatite improved the fluid absorptivity, protein permeability, and tenacity of the composite while maintaining high porosity and a suitable microstructure.

• Journal of the Korean Ceramic Society
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• v.44 no.10
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• pp.574-579
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• 2007

Porous $Al_2O_3$ ceramics were prepared by the gelcasting foams method (a slurry foaming process) with acrylamide monomer. The foaming and gelation behavior was investigated with the parameters such as the type and concentration of surfactant, solid loading of slurry, and the concentrations of initiator and catalyst. Density, porosity, microstructure, and strength of the green and sintered samples were characterized. Of the four kinds of surfactants tested, Triton X-114 showed the highest foaming ability for the solid loading of 55-30 vol%. The gelation condition giving the idle time off min was found to set the foamed structure without significant bubble enlargement and liquid lamella thinning. The green samples were fairly strong and machinable and showed maximum strength of 2.4 MPa in diametral compression. The sintered samples showed densities of 10-36% theoretical (i.e. porosity 90-64%) with a highly interconnected network of spherical pores with sizes ranging from 30 to $600{\mu}m$. The pore size and connectivity increased but the cell strut thickness decreased with decreasing the solid loading. Flexural strength of 37.8-1.7 MPa was obtained for the sintered samples.

• Journal of the Korean Ceramic Society
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• v.49 no.6
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• pp.625-630
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• 2012

Highly porous silicon carbide (SiC) ceramics were fabricated from polysiloxane, SiC and carbon black fillers, AlN-$Y_2O_3$ additives, and poly (ether-co-octene) (PEOc) and expandable microsphere templates. Powder mixtures with a fixed PEOc content (30 wt%) and varying SiC filler contents from 0-21 wt% were compression-molded. During the pyrolysis process, the polysiloxane was converted to SiOC, the PEOc generated a considerable degree of interconnected porosity, and the expandable microspheres generated fine cells. The polysiloxane-derived SiOC and carbon black reacted and synthesized nano-sized SiC with a carbothermal reduction during a heat-treatment. Subsequent sintering of the compacts in a nitrogen atmosphere produced highly porous SiC ceramics with porosities ranging from 78 % to 82 % and a flexura lstrength of up to ~7 MPa.

• Korean Journal of Materials Research
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• v.16 no.11
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• pp.715-718
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• 2006

Porous hydroxyapatite (HAp) scaffolds have been prepared by using the slurry including HAp and magnesia based on the replication of polymer sponge substrate. The influence of MgO content in slurry on the pore morphology and size, density, porosity, and mechanical strength of porous HAp scaffolds was investigated. The obtained scaffolds with average pore sizes ranging 150 to 300 mm had open, relatively uniform, and interconnected porous structure regardless of MgO content. As the MgO content increased, the pore network frame of scaffolds became to be relatively stronger, even though the pore size was not much changed. The compressive strength of the scaffolds increased rapidly with the increase of MgO content because of increasing the pore wall thickness and density of the scaffolds. As a result, the porosity, density, and compressive strength of the porous HAp scaffolds prepared by the sponge method were significantly affected by the addition of MgO.

• Advances in concrete construction
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• v.11 no.1
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• pp.81-88
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• 2021

Rice Husk Ash (RHA) geopolymer paste activated by sodium aluminate were characterized by X-ray diffractogram (XRD), scanning electron microscope (SEM), energy dispersion X-Ray analysis (EDAX)and fourier transform infrared spectroscopy (FTIR). Five series of RHA geopolymer specimens were prepared by varying the Si/Al ratio as 1.5, 2.0, 2.5, 3.0 and 3.5. The paper focuses on the correlation of microstructure with hardened state parameters like bulk density, apparent porosity, sorptivity, water absorption and compressive strength. XRD analysis peaks indicates quartz, cristobalite and gibbsite for raw RHA and new peaks corresponding to Zeolite A in geopolymer specimens. In general, SEM micrographs show interconnected pores and loosely packed geopolymer matrix except for specimens made with Si/Al of 2.0 which exhibited comparatively better matrix. Incorporation of Al from sodium aluminate were confirmed with the stretching and bending vibration of Si-O-Si and O-Si-O observations from the FTIR analysis of geopolymer specimen. The dense microstructure of SA2.0 correlate into better performance in terms of 28 days maximum compressive strength of 16.96 MPa and minimum for porosity, absorption and sorptivity among the specimens. However, due to the higher water demand to make the paste workable, the value of porosity, absorption and sorptivity were reportedly higher as compared with other geopolymer systems. Correlation regression equations were proposed to validate the interrelation between physical parameters and mechanical strength. RHA geopolymer shows comparatively lower compressive strength as compared to Fly ash geopolymer.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.11
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• pp.78-83
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• 1992

The current-voltage characteristics at SrO${\cdot}6Fe_{2}O_{3}$ electronic ceramics interfaces have been studied using cyclic voltammetric methods. The symmetrical and stable cyclic voltammograms, which indicate the same anodic and cathodic process, are obtained on the whole experiments. The approximate saturation current is 50$\mu$A but the value depends on the experimental processes of the electrode specimens. The current-voltage characteristics of SrO${\cdot}6Fe_{2}O_{3}$ electronic ceramics in dilute aqueous electrolytes or double deionized water are determined by the water adsorption process and the interconnected porosity effect. On the other hand, the current-voltage characteristics in relatively concentrate aqueous electrolytes are determined by the ionic adsorption process and the related electrical double layers. The SrO${\cdot}6Fe_{2}O_{3}$ electronic ceramics can be directly used as an electrochemically stabled resistor, electrode or a humidity sensor.

• Proceedings of the PSK Conference
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• 2003.04a
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• pp.302.2-303
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• 2003

For polymeric material for tissue engineering. chitosan was selected with benefit of high tissue compatibility attributed and wound healing through its activation of growth factors. And nonwoven chitosan fibrous matrix has well interconnected porosity. But chitosan itself has some of limitations in including rapid bone regeneration at initial states incorpor-ated of bioactive materials such as growth factors and ECM molecules. (omitted)

• Proceedings of the KOSOMBE Conference
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• v.1996 no.05
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• pp.221-222
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• 1996

In order to prepare the porous hydroxyapatite (HA) ceramics with different porosity, interconnectivity, mechanical properties, surface chemistry and tissue response, several methods have been developed. Of the different forms of Porous HA ceramics which were prepared by various methods, only the coralline HA has undergone major clinical applications in orthopaedic, maxillofacial and ophthalmic surgery. In this study, totally synthetic macroporous HA ceramics with various pore size distribution were prepared. It is shown that the new reticulate HA ceramics, comprised of interconnected voids surmunded by a web of ceramic, have a morphology which mimics that of human trabecular bone.

• Korean Journal of Materials Research
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• v.20 no.6
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• pp.331-337
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• 2010

A highly porous Biphasic Calcium Phosphate (BCP) scaffold was fabricated by the sponge replica method with a microwave sintering technique. The BCP scaffold had interconnected pores ranging from $80\;{\mu}m$ to $1000\;{\mu}m$, which were similar to natural cancellous bone. To enhance the mechanical properties of the porous scaffold, infiltration of polycaprolactone (PCL) was employed. The microstructure of the BCP scaffold was optimized using various volume percentages of polymethylmethacrylate (PMMA) for the infiltration process. PCL successfully infiltrated into the hollow space of the strut formed after the removal of the polymer sponge throughout the degassing and high pressure steps. The microstructure and material properties of the BCP scaffold (i.e., pore size, morphology of infiltrated and coated PCL, compressive strength, and porosity) were evaluated. When a 30 vol% of PMMA was used, the PCL-BCP scaffold showed the highest compressive strength. The compressive strength values of the BCP and PCL-BCP scaffolds were approximately 1.3 and 2MPa, respectively. After the PCL infiltration process, the porosity of the PCL-BCP scaffold decreased slightly to 86%, whereas that of the BCP scaffold was 86%. The number of pores in the $10\;{\mu}m$ to $20\;{\mu}m$ rage, which represent the pore channel inside of the strut, significantly decreased. The in-vitro study confirmed that the PCL-infiltrated BCP scaffold showed comparable cell viability without any cytotoxic behavior.