• Title/Summary/Keyword: Porous body

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Fabrication of Ti Porous body with Improved Specific Surface Area by Synthesis of CNTs (CNTs 합성을 통해 향상된 비표면적을 갖는 Ti 다공체의 제조)

  • Choi, Hye Rim;Byun, Jong Min;Suk, Myung-Jin;Oh, Sung-Tag;Kim, Young Do
    • 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.

Characteristics of Silicon Carbide Nanowires Synthesized on Porous Body by Carbothermal Reduction

  • Kim, Jung-Hun;Choi, Sung-Churl
    • 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.

A Study on the Behavior of Combustion Wave Propagation and the Structure of Porous TiNi Body during Self-propagating High-temperature Synthesis Process

  • Kim, Ji-Soon;Gjuntera, Victor E.;Kim, Jin-Chun;Kwon, Young-Soon
    • 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.

A Study on the Porous Glass-Ceramics in the Phosphate System (인산염계 다공질 결정화 유리에 관한 연구)

  • 박용완;현부성;김태호
    • 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.

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On the numerical simulation of perforated bluff-bodies: A CFD study on a hollow porous 5:1 rectangular cylinder

  • Xu, Mao;Patruno, Luca;Lo, Yuan-Lung;de Miranda, Stefano;Ubertini, Francesco
    • 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.

Microstructure Control of Porous Ceramics by Freeze-Drying of Aqueous Slurry (동결건조공정을 이용한 다공성 세라믹스의 미세구조 제어)

  • 황해진;문지웅
    • 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.

Biocompatibility of Low Modulus Porous Titanium Implants Fabricated by Spark Plasma Sintering (방전플라즈마소결법에 의해 제조된 저탄성 타이타늄 다공질체의 생체적합성 평가)

  • Song, Ho-Yeon;Kim, Young-Hee;Chang, Se-Hun;Oh, Ik-Hyun
    • 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.

Pore Structure and Mechanic:11 Property of Porous TiNi Biomaterial Produced by Self-Propagating High-Temperature Synthesis (고온자전합성법으로 제조된 다공성 TiNi 생체재료의 기공구조 및 기계적 특성)

  • 김지순;강지훈;양석균;정순호;권영순
    • 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 $99^{\circ}C$.

Preparation of Alumina Ceramics by Pressureless Powder Packing Forming Method (II) Characterization of Sintered Body Fabricated by Pressureless Powder Packing Forming Method (무가압 분말 충전 성형법을 이용한 알루미나 세라믹스의 제조 (II) 무가압 분말 충전 성형법에 의해 제조된 소결체 특성 관찰)

  • 박정형;성재석
    • 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.

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Micro-Porous Ceramics Using directionally $MgAl_2O_4/MgO$ eutectic crystals

  • Lee, Jong-Ho
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.15 no.6
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    • pp.229-233
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    • 2005
  • Novel process was tried to obtain micro-porous ceramic body containing continuous pore channel. $MgAl_2O_4/MgO$ eutectic fibers and rods have been grown successfully by the micro-pulling-down method, and the microstructures and optical characterizations of grown crystals were performed. $MgAl_2O_4/MgO$ eutectic fibers of $0.3{\sim}1mm$ in diameter and about 500 mm in length, and the rods having 5 mm in diameter with approximately 60 mm in length have been grown with the $6{\sim}120mm/hr$ of growth speed. The eutectic fibers showed homogeneous microstructure in which MgO fiber aligned to the growth direction in the $MgAl_2O_4$ (spinel) matrix. The grown crystals looked semitransparency under naked eyes. Optical and orientational characterizations were performed. The second phase of MgO (periclase) was easily removed by selective etching with hydrochloric acid, and then porous bodies were obtained.