• Journal of Powder Materials
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• v.23 no.3
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• pp.235-239
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• 2016

This study is performed to fabricate a Ti porous body by freeze drying process using titanium hydride ($TiH_2$) powder and camphene. Then, the Ti porous body is employed to synthesize carbon nanotubes (CNTs) using thermal catalytic chemical vapor deposition (CCVD) with Fe catalyst and methane ($CH_4$) gas to increase the specific surface area. The synthesized Ti porous body has $100{\mu}M$-sized macropores and $10-30{\mu}m$-sized micropores. The synthesized CNTs have random directions and are entangled with adjacent CNTs. The CNTs have a bamboo-like structure, and their average diameter is about 50 nm. The Fe nano-particles observed at the tip of the CNTs indicate that the tip growth model is applicable. The specific surface area of the CNT-coated Ti porous body is about 20 times larger than that of the raw Ti porous body. These CNT-coated Ti porous bodies are expected to be used as filters or catalyst supports.

• Journal of the Korean Ceramic Society
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• v.55 no.3
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• pp.285-289
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• 2018

We synthesized silicon carbide (${\beta}-SiC$) nanowires with nano-scale diameter (30 - 400 nm) and micro-scale length ($50-200{\mu}m$) on a porous body using low-grade silica and carbon black powder by carbothermal reduction at $1300-1600^{\circ}C$. The SiC nanowires were formed by vapor-liquid-solid deposition with self-evaporated Fe catalysts in low-grade silica. We investigated the characteristics of the SiC nanowires, which were grown on a porous body with Ar flowing in a vacuum furnace. Their structural, optical, and electrical properties were analyzed with X-ray diffraction (XRD), transmission electron microscopy (TEM), and selective area electron diffraction (SAED). We obtained high-quality SiC single crystalline nanowire without stacking faults that may have uses in industrial applications.

• Journal of Powder Materials
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• v.17 no.1
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• pp.29-35
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• 2010

We produced cylindrical porous TiNi bodies by Self-propagating High-temperature Synthesis (SHS) process, varying the heating schedule prior to ignition of a loose preform compact made from (Ti+Ni) powder mixture. To investigate the effect of the heating schedule on the behaviour of combustion wave propagation and the structure of porous TiNi shape-memory alloy (SMA) body, change of temperature in the compact during SHS process was measured as a function of time and used for determining combustion temperature and combustion wave velocity. Microstructure of produced porous TiNi SMA body was observed and the results were discussed with the combustion characteristics. From the results it was concluded that the final average pore size could be controlled either by the combustion wave velocity or by the average temperature of the preform compact prior to ignition.

• Journal of the Korean Ceramic Society
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• v.32 no.7
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• pp.858-864
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• 1995

A porous glass-ceramics body was prepared in the phosphate system. The glass composition of 47.2CaO-22.2TiO2-30.6P2O5 (mol%) containing a few weight percent of ZrO2 was suitable for a mother glass of a porous glass-ceramics. The dense glass-ceramics body was made by a two-step heat treatment of the mother glass. The crystalline phases of the glass-ceramics were $\beta$-Ca3(PO4)2 and CaTi4(PO4)6. The $\beta$-Ca3(PO4)2 phase could be selectively leached out with HCl solution and thus a crystalline $\beta$-Ca3(PO4)2 skeleton was remained. The dimension and shape of the porous glass-ceramics were nearly the same as the those of the first formed glass. The specific surface area and average proe radius of the porous glass-ceramics were 19$m^2$/g and 22 nm, respectively.

• Wind and Structures
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• v.34 no.1
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• pp.1-14
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• 2022

In this work the flow through a hollow porous 5:1 rectangular cylinder made of perforated plates is numerically investigated by means of 2D URANS based simulations. Two approaches are adopted to account for the porous surfaces: in the first one the pores are explicitly modeled, so providing a detailed representation of the flow. In the second one, the porous surfaces are modeled by means of pressure jumps, which allow to take into account the presence of pores without reproducing the flow details. Results obtained by using the two aforementioned techniques are compared aiming at evaluating differences and similarities, as well as identifying the main flow features which might cause discrepancies. Results show that, even in the case of pores remarkably smaller than the immersed body, their arrangement can lead to local mechanisms able to affect the global flow arrangement, so limiting the accuracy of pressure jumps based simulations. Despite that, time-averaged fields often show a reasonable agreement between the two approaches.

• Journal of the Korean Ceramic Society
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• v.41 no.3
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• pp.229-234
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• 2004

In this study, we proposed new forming process for a porous ceramic body with unique pore structure. h tubular-type porous NiO-YSZ body with radially aligned pore channels was prepared by freeze-drying of aqueous slurry. A NiO-YSZ slurry was poured into the mold, which was designed to control the crystallization direction of the ice, followed by freezing. Thereafter the ice was sublimated at a reduced pressure. SEM observations revealed that the NiO-YSZ porous body showed aligned large pore channels parallel to the ice growth direction, and fine pores are formed around the outer surface of the tube. It was considered that the difference in the ice growth rate during the freezing process resulted in such a characteristic microstructure. Bilayer consisting of dense thin electrolyte film of YSZ onto the tubular type porous body has been successfully fabricated using a slurry-coating process followed by co-firing. It was regarded that the obtained bilayer structure is suitable for constructing electrode-support type electrochemical devices such as solid oxide fuel cells.

• Korean Journal of Materials Research
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• v.17 no.2
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• pp.107-114
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• 2007

Porous Ti compacts were fabricated by spark plasma sintering (SPS) method and their in vitro and in vivo biocompatibilities were investigated. Alkaline phosphatase (ALP) activity representing the activity of osteoblast was increased when osteoblast-like MG-63 cells were cultured on the Ti powder surface. Some genes related to cell growth were over-expressed through microarray analysis. The porous Ti compact with 32.2% of porosity was implanted in the subcutaneous tissue of rats to confirm in vivo cytotoxicity. 12 weeks post-operation, outer surface and inside the porous body was fully filled with fibrous tissue and the formation of new blood vessels were observed. No inflammatory response was confirmed. To investigate the osteoinduction, porous Ti compact was implanted in the femur of NZW rabbits for 4 months. Active in-growth of new bone from the surrounded compact bone was observed around the porous body. From the results, The porous Ti compacts fabricated by spark plasma sintering might be available for the application of the stem part of artificial hip joint.

• ETRI Journal
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• v.46 no.4
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• pp.571-580
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• 2024

A compact triple-band porous electromagnetic bandgap structure-loaded coplanar-waveguide-fed wearable antenna is introduced for applications of wireless body area networks. The porous structure is aimed to create a stopband or bandgap in the electromagnetic spectrum and increase breathability. The holes in the bottom electromagnetic bandgap surface increase the inductance, which in turn increases the bandwidth. The final design resonates at three bands with impedance bandwidths of 264 MHz, 100 MHz, and 153 MHz and maximum gains of 2.18 dBi, 6.75 dBi, and 9.50 dBi at 2.45 GHz, 3.5 GHz, and 5.5 GHz, respectively. In addition, measurements indicate that the proposed design can be deformed up to certain curvature and withstand human tissue loading. Moreover, the specific absorption rate remains within safe levels for humans. Therefore, the proposed antenna can suitably operate in the industrial, scientific, and medical, Bluetooth, Wi-Fi, and WiMAX bands for potential application to wireless body area networks.

• Journal of Powder Materials
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• v.10 no.1
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• pp.34-39
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• 2003

Porous TiNi bodies were produced by Self-propagating High-temperature Synthesis (SHS) method from a powder mixture of Ti and Ni. Porosity, pore size and structure, mechanical property, and transformation temperature of TiNi product were investigated. The average porosity and pore size of produced porous TiNi body are 63% and $216\mutextrm{m}$, respectively. XRD analysis showed that the major phase of produced TiNi body is B2 phase. Its average fracture strength and elastic modulus measured under dry condition were $22\pm2$ MPa and $0.18\pm0.01$GPa, respectively. It could be strained up to 7.3 %. The transformation temperatures determined by DSC showed the $M_s$ temperature of $67^{\circ}C$ and $A_f$ temperature of $99^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.32 no.1
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• pp.113-119
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• 1995

The green body was fabricated by a new forming method, pressureless powder packaing forming method, and the characteristics of sintered specimen were investigated. It was found that alumina ceramics prepared by the present method showed porous structure with narrow pore size distribution, and in case of abrasive powder sintered body, compared with dry-pressed specimen, had the nearly same density. Especially, the specimen prepared with spray-dried granules showed the characteristic that granules were not either deformed or fractured during forming and sintering process. Therefore, it was found that this new forming method was effective method in fabrication of porous ceramics on account of easy control of porosity and pore size and its high thermal stability.