• 한국재료학회지
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• 제16권3호
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• pp.173-177
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• 2006

Porous surfaced Ti implant compacts were fabricated by electro-discharging-sintering (EDS) of atomized spherical Ti powders. Powders of $50-100{\mu}m$ in diameter were vibratarily settled into a quarts tube and subject to a high voltage and high density current pulse in Ar atmosphere. Single pulse of 0.7 to 2.0 kJ/0.7 gpowder, from 150, 300, and $450{\mu}F$ capacitors was applied in less than $400{\mu}sec$ to produce twelve different porous-surfaced Ti implant compacts. The solid core formed in the center of the compact shows similar microstructure of cp Ti which was annealed and quenched in water. Hardness value at the solid core was much higher than that at the particle interface and particles in the porous layer, which can be attributed to both heat treatment and work hardening effects induced by EDS. Compression tests were made to evaluate the mechanical properties of the EDS compacts. The compressive yield strength was in a range of 12 to 304MPa which significantly depends on input energy. Selected porous-surfaced Ti-6Al-4V dental implant compacts with a solid core have much higher compressive strengths compared to the human teeth and sintered Ti dental implants fabricated by conventional sintering process.

• 한국재료학회지
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• 제11권10호
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• pp.895-899
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• 2001

Electrical properties of porous $BaTiO_3-based$ ceramics were investigated from the viewpoint of adsorbed oxygen. Namely, the effects of heat-treatment temperature ($450-600^{\circ}C$) and measuring atmosphere (oxygen and nitrogen) on the PTCR characteristics of the porous $BaTiO_3-based$ ceramics were investigated. It was found that the PTCR characteristics of the porous $BaTiO_3-based$ ceramics was developed at $\geq$55$0^{\circ}C$, and the magnitude of the PTCR characteristics increased with increasing heat-treatment temperature. It was also found that the magnitude of the PTCR characteristics in the porous $BaTiO_3-based$ ceramics increased in oxygen atmosphere, whereas decreased in nitrogen atmosphere during heating and cooling.

• 한국재료학회지
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• 제17권2호
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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.

• Journal of Electrical Engineering and Technology
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• 제5권1호
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• pp.146-150
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• 2010

A new type of dye-sensitized solar cell (DSC) based on a porous type Ti electrode without using a transparent conductive oxide (TCO) layer is fabricated for low-cost high-efficient solar cell application. The TCO-free DSC is composed of a glass substrate/dye-sensitized $TiO_2$ nanoparticle/porous Ti layer/electrolyte/Pt sputtered counter electrode. The porous Ti electrode (~350 nm thickness) with high conductivity can collect electrons from the $TiO_2$ layer and allows the ionic diffusion of $I^-/I_3{^-}$ through the hole. The vacuum annealing treatment is important with respect to the interfacial necking between the metal Ti and porous $TiO_2$ layer. The efficiency of the prepared TCO-free DSC sample is about 3.5% (ff: 0.48, $V_{oc}$: 0.64V, $J_{sc}$: 11.14 mA/$cm^2$).

• 한국분말재료학회지
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• 제18권1호
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• pp.41-48
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• 2011

As a pore precursor, carbon black with different content of 0 to 60 vol% were added to (Ba,Sr)$TiO_3$ powder. Porous (Ba,Sr)$TiO_3$ ceramics were prepared by pressureless sintering at $1350^{\circ}C$ for 1h under air. Effects of carbon black content on the microstructure and PTCR characteristics of porous (Ba,Sr)$TiO_3$ ceramics were investigated. The porosity of porous (Ba,Sr)$TiO_3$ ceramics increased from 6.97% to 18.22% and the grain size slightly decreased from $7.51\;{\mu}m$ to $5.96\;{\mu}m$ with increasing carbon black contents. PTCR jump of the (Ba,Sr)$TiO_3$ ceramics prepared by adding carbon black was more than $10^5$, and slightly increased with increasing carbon black. The PTCR jump in the (Ba,Sr)$TiO_3$ ceramics prepared by adding 40 vol% carbon black showed an excellent value of $9.68{\times}10^5$, which was above two times higher than that in (Ba,Sr)$TiO_3$ ceramics. These results correspond with Heywang model for the explanation of PTCR effect in (Ba,Sr)$TiO_3$ ceramics. It was considered that carbon black is an effective additive for preparing porous $BaTiO_3$ based ceramics. It is believed that newly prepared (Ba,Sr)$TiO_3$ cermics can be used for PTC thermistor.

• 한국분말재료학회지
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• 제22권2호
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• pp.122-128
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• 2015

In this study, titanium(Ti) meshes and porous bodies are employed to synthesize carbon nanotubes(CNTs) using methane($CH_4$) gas and camphene solution, respectively, by chemical vapor deposition. Camphene is impregnated into Ti porous bodies prior to heating in a furnace. Various microscopic and spectroscopic techniques are utilized to analyze CNTs. It is found that CNTs are more densely and homogeneously populated on the camphene impregnated Ti-porous bodies as compared to CNTs synthesized with methane on Ti-porous bodies. It is elucidated that, when synthesized with methane, few CNTs are formed inside of Ti porous bodies due to methane supply limited by internal structures of Ti porous bodies. Ti-meshes and porous bodies are found to be multi-walled with high degree of structural disorders. These CNTs are expected to be utilized as catalyst supports in catalytic filters and purification systems.

• 한국입자에어로졸학회지
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• 제7권3호
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• pp.79-85
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• 2011

Porous $TiO_2-SiO_2$ particles were synthesized by co-assembly of nanoparticles of $TiO_2$ and $SiO_2$ in evaporating aerosol droplets. Poly styrene latex (PSL) particles were employed as a template of porous particles. Flowrate of dispersion gas, weight ratio of $TiO_2/SiO_2$ and $SiO_2$ concentration in the precursor, and PSL size were chosen as process variables. The morphology, crystal structure, chemical bonding, and pore size distribution were analyzed by FE-SEM, XRD, FT-IR, BET. The morphology of porous $TiO_2-SiO_2$ particles was spherical and the average particle size range were from 1 to $10{\mu}m$. The particles were composed of meso and macro pores. The average particle diameter and pore volume of the as prepared particles were dependant on process variables. It was found that UV-Vis absorption of the porous particles was comparable with pure $TiO_2$ nanoparticles even though $TiO_2/SiO_2$ ratio is low in the porous particles.

• 한국세라믹학회지
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• 제41권7호
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• pp.548-554
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• 2004

슬러리 발포법을 이용하여 다공성 실리카 지지체를 제조하였으며, 지지체 표면에 졸-겔법을 이용하여 TiO$_2$을 코팅하였다. TiO$_2$ 코팅층에 대한 XRD, SEM 및 BET 측정 결과, 열처리 온도가 50$0^{\circ}C$에서 TiO$_2$의 anatase 결정상이 나타나기 시작하여, $700^{\circ}C$에서 그 피크가 최대가 되었다. 이 때 결정 성장한 TiO$_2$ 입자의 크기는 약 1$mu extrm{m}$ 정도로 판명되었다. 또한, 촉매지지체로 활용성을 검토하기 위해 TiO$_2$코팅 전후로 지지체의 굽힘 강도와 기체 투과율을 측정하였다. 강도의 경우, 코팅 전 2.4 MPa에서 이후 3.9∼4.3MPa로 증가하였으나 열처리 온도의 영향에 의한 변화는 나타나지 않았다. 한편, 투과율은 코팅 전 770${\times}$$10^{-13}$ $m^2$에서 코팅 후 363${\times}$$10^{-13}$ $m^2$로 감소하였고 열처리 온도의 증가와 함께 감소하는 것으로 나타났다.

• 한국재료학회지
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• 제18권5호
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• pp.229-234
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• 2008

Porous Ti implant samples were fabricated by the sintering of spherical Ti powders in a high vacuum furnace. To increase their surface area and biocompatibility, anodic oxidation and a hydrothermal treatment were then applied. Electrolytes in a mixture of glycerophosphate and calcium acetate were used for the anodizing treatment. The resulting oxide layer was found to have precipitated in the phase form of anatase $TiO_2$ and nano-scaled hydroxyapatite on the porous Ti implant surface. The porous Ti implant can be modified via an anodic oxidation method and a hydrothermal treatment for the enhancement of the bioactivity, and current multi-surface treatments can be applied for use in a dental implant system.

• 대한토목학회논문집
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• 제42권2호
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• pp.163-170
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• 2022

본 연구에서는 다양한 TiO₂ 적용방법이 포러스 콘크리트의 질소산화물 제거성능 및 흡음특성에 미치는 영향을 조사하였다. 포러스 콘크리트 배합과정에서 TiO₂를 단순 혼입하는 방법, 바텀애쉬 골재에 TiO₂를 전처리하고 이를 이용하여 포러스 콘크리트를 제조하는 방법, 마지막으로 제조된 포러스 콘크리트에 TiO₂ 용액을 도포하는 방법으로 TiO₂ 적용 포러스 콘크리트를 제조하였다. 실험결과 TiO₂의 단순 혼입은 TiO₂의 함량이 증가함에 따라 압축강도를 감소시켰으며, 공극률은 증가시키는 것으로 관찰되었다. TiO₂ 함침 바텀애쉬 골재를 이용하는 경우 압축강도는 기존 포러스 콘크리트와 유사하지만 공극률이 감소하는 것으로 나타났다. 마지막으로 표면 도포 방법의 경우 공극률은 유사하였으나 강도가 증가하였다. 질소산화물 제거성능에서 TiO₂를 표면 도포한 샘플이 가장 높은 효율을 보였으며, TiO₂를 단순 혼입한 샘플들보다 바텀애쉬 골재에 전처리한 샘플에서 더 높은 질소산화물 제거성능이 관찰되었다. 흡음성능의 경우 TiO₂를 단순 혼입한 경우 공극률과의 상관관계를 확인할 수 있었지만, 다른 적용방법의 경우 일정한 경향이 발견되지는 않았다.