• Tribology and Lubricants
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• 제35권2호
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• pp.106-113
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• 2019

We investigated the application of tetrahedral amorphous carbon (ta-C) coatings to fabricate a glass lens manufactured using a glass molding process (GMP). In this work, ta-C coatings with different thickness (50, 100, 150 and 200 nm) were deposited on a tungsten carbide (WC-Co) mold using the X-bend filter of a filtered cathode vacuum arc. The effects of thickness on mechanical and tribological properties of the coating were studied. These ta-C coatings were characterized by atomic force microscopy, scanning electron microscopy, nano-indentation measurements, Raman spectrometry, Rockwell-C tests, scratch tests and ball on disc tribometer tests. The nano-indentation measurements showed that hardness increased with an increase in coating thickness. In addition, the G-peak position in the Raman spectra analysis was right shifted from 1520 to $1586cm^{-1}$, indicating that the $sp^3$ content increased with increasing thickness of ta-C coatings. The scratch test showed that, compared to other coatings, the 100-nm-thick ta-C coating displayed excellent adhesion strength without delamination. The friction test was carried out in a nitrogen environment using a ball-on-disk tribometer. The 100-nm-thick ta-C coating showed a low friction coefficient of 0.078. When this coating was applied to a GMP, the life time, i.e., shot counts, dramatically increased up to 2,500 counts, in comparison with Ir-Re coating.

• Journal of Periodontal and Implant Science
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• 제38권4호
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• pp.595-602
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• 2008

Purpose: Ti-6Al-4V alloy is widely used as an implant material because of its good biocompatibility and good mechanical property compared with commercial pure titanium. Otherwise, toxicity of aluminum and vanadium in vivo has been reported. Ti-8Ta-3Nb alloy is recently developed in the R&D Center for Ti and Special Alloys and it was reported that this alloy has high mechanical strength, no cytotoxicity and similar biocompatibility to commercial pure titanium, but many studies are needed for its clinical use. In these experiment, we carried out different surface treatment on each Ti-8Ta-3Nb alloy disks, then cultured cell on it and assessed biological response. Materials and Methods: cpTi, Ti-6Al-4V, Ti-8Ta-3Nb alloy disks were prepared and carried out sandblasting and acid etching (SLA) or alkali-heat treatment (AH) on the Ti-8Ta-3Nb alloy disks. We cultured primary rat calvarial cells on each surface and assessed early cell attachment and proliferation by scanning electron microscopy, cell proliferation, alkaline phosphatase activity. Result: The rates of cell proliferation on the cpTi, Ti-8Ta-3Nb AH disks were higher than others (p<0.05) and alkaline phosphatase activity was significantly enhanced on the Ti-STa-8Nb AH disks(p<0.05). Conclusion: Most favorable cell response was shown on the Ti-8Ta-3Nb AH surfaces. It is supposed that alkali-heat treatment of the Ti-8Ta-3Nb alloy could be induced earlier bone healing and osseointegration than smooth surface.

• E2M - 전기 전자와 첨단 소재
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• 제8권6호
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• pp.715-720
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• 1995

기계적 합금화법에 의한 비정질화 과정을 Ni-Ta계 및 Cu-Ta계에 대하여 조사하였다. Ni-Ta합금계는 혼합엔탈피가 음이나, Cu-Ta계는 혼합엔탈피가 양인 열역학적으로 대조적인 합금계이다. 볼밀 중 발생하는 원자구조 변화를 중성자회절법을 이용하여 관찰하였다. 두 합금게에 있어서 기계적 합금화에 의한 비정질상이 생성되었다. 비정질 Cu-Ta합금의 local원자구조를 혼합엔탈피가 크게 음인 Ni-Ta계의 결과와 비교하였다. 그 결과, 대조적 특성을 가진 두 합금계임에도 불구하고 원자크기가 작은 Ni 및 Cu가 bcc Ta의 결정격자 속으로 우선적으로 침입함으로써 비정질화가 진행됨을 알 수 있었다.

• 한국세라믹학회지
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• 제53권6호
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• pp.597-603
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• 2016

Tantalum carbide, which is one of the ultra-high temperature ceramics, was deposited on graphite by low pressure chemical vapor deposition from a $TaCl_5-C_3H_6-Ar-H_2$ mixture. To maintain a constant $TaCl_5/C_3H_6$ ratio during the deposition process, $TaCl_5$ powders were continuously fed into the sublimation chamber using a screw-driven feeder. Sublimation behavior of $TaCl_5$ powder was measured by thermogravimetric analysis. TaC coatings have various phases such as $Ta+{\alpha}-Ta_2C$, ${\alpha}-Ta_2C+TaC_{1-x}$, and $TaC_{1-x}$ depending on the powder feeding methods, the $C_3H_6/TaCl_5$ ratio, and the deposition temperatures. Near-stoichiometric TaC was obtained by optimizing the deposition parameters. Phase compositions were analyzed by XRD, XPS, and Raman analysis.

• 한국식품조리과학회지
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• 제15권6호
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• pp.611-617
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• 1999

자동산화된 유지의 산패도와 돌연변이원성과의 관련성을 알아보고자 대우유를 $60{\pm}2^{\circ}C$에서 자동산화시키면서 과산화물가가 일정한 수치에 도달한 시료를 대상으로 Salmonella typhimurium 변이균주 중 구조이동형(frame shift) 변이균주인 TA98, TA1537과 염기치환형(base-pair substituent) 변이균주인 TA100, TA1535 및 102를 사용하여 Ames test를 수행하였다. TA98은 대사활성화법에서, TA100은 직접법에서, TA1535 및 TA1537은 직접법과 대사활성화법 모두에서 돌연변이 활성이 인정되었으나 TA102는 시료유지의 전자동산화기간에서 돌연변이 활성이 나타나지 않았다. 또한 돌연변이원성이 과산화물가가 높은 시기에 나타나 유지의 과산화물 함량과 돌연변이 활성간에 갚은 관련성이 있는 것으로 생각되었다.

• 기술혁신학회지
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• 제6권3호
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• pp.306-327
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• 2003

The importance of technology assessment(TA) is increasingly emphasized, however, the question of what is TA is ambiguous yet. This article traces the concept of TA, and tries to identify the its meaning and current issues. It argues that the ambiguity of TA concept is not tragedy, but blessing in its growth. We came to know that one should consider for a successful TA some issues : institutional conditions, methodology, functions and timeliness. And they should also be considered in the TA-building process of Korea which is now on.

• 한국식품위생안전성학회지
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• 제25권3호
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• pp.215-219
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• 2010

본 연구는 섬오갈피 뿌리 추출물을 이용하여 돌연변이 유발을 관찰하기 위해 S. typhimurium TA100, TA98, TA1535, TA1537과 E. coli WP2 uvr A를 이용해 Ames test을 하였고 또한 S. typhimurium TA100, TA98을 이용한 항돌연변이원 억제 시험을 시행하였다. Ames test에 필요한 시험물질들은 최고농도 결정을 통해 $5000\;{\mu}g$/plate, $2500\;{\mu}g$/plate, $600\;{\mu}g$/plate의 시험물질을 양성대조군, 실험군, 음성대조군을 비대사활성계와 대사활성계로 나누어 시험을 시행하였다. 시험 결과 모든 농도에서는 집락군의 일관성 있는 증가는 보이지 않았고 이 점으로 미루어 보아 복귀돌연변이는 일어나지 않았고 음성으로 판정하였다. 항돌연변이원 시험에서는 양성물질의 농도결정과 시험물질의 최고농도 결을 통해 양성대조군, 실험군, 음성대조군을 비대사활성계와 대사활성계로 시험을 하였고 시험결과 S. typhimurium TA100, TA98 두 균주 돌연변이 억제를 보였으며 TA98에서 더 높은 억제율을 보였다. 시험결과로 섬오갈피의 뿌리는 항돌연변이 억제효과에 탁월한 효과가 있음을 시사하였다.

• 한국재료학회지
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• 제1권4호
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• pp.229-235
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• 1991

$Ta_2O_5$ 박막은 실리콘산화막, 실리콘질화막 박막에 비해 유전율은 높으나 누설전류밀도가 높고, 절연파괴강도가 낮아 DRAM의 커패시터용 재료로서 실용화가 되지 못하고 있다. 본 연구에서는 LPCVD법으로 형성시킨 $300{\AA}$ 두께의 $Ta_2O_5$ 유전체박막에 대해 후속열처리 또는 전극재료를 변화시켜 열악한 전기적 특성의 원인을 규명하고자 하였다. 그 결과 다결정 실리콘 전극의 경우 성막상태의 $Ta_2O_5$ 박막은 전극에 의한 환원반응에 의해 전기적 특성이 열화됨을 알 수 있었고, 이를 TiN 전극의 사용으로 억제시킬 수 있었다. 다결정 실리콘 전극의 경우 성막상태의 $Ta_2O_5$ 유전체는 누설정류밀도가 $10^{-1}A/cm^2$, 절연파괴강도가 1.5MV/cm 정도였으며, $800^{\circ}C$에서 $O_2$열처리를 하면 전기적 특성은 개선되나, 유전율이 낮아진다 TiN 전극을 채용할 경우 누설전류밀도 $10^{-6}~10^{-7}A/cm^2$, 절연파괴강도 7~12MV/cm 로 ONO(Oxide-Nitride-Oxide) 박막과 비슷한 $Ta_2O_5$ 고유전막을 얻을 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.242-244
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• 1996

The effects of $Co_{67}$C $r_{33}$ underlayer on the crystallographec and magnetic characteristics of the Co-Cr-Ta layer deposited on the underlayer was investigated. The diffraction intensity $I_{p(002)}$ of Co-Cr-Ta layers on the $Co_{67}$C $r_{33}$ layer was stronger than that of single layer and Co-Cr-Ta/Ti double layer. Therefore, the crystallinity of Co-Cr-Ta layer was improved by the $Co_{67}$C $r_{33}$ underlayers rather than Ti ones. However, the coercivity $H_{c}$ of Co-Cr-Ta layers deposited on $Co_{67}$C $r_{33}$ underlayer was as low as 250 Oe even at substrate temperature of 22$0^{\circ}C$. This $H_{c}$ decrease seems to be attributed to the effect of the $Co_{67}$C $r_{33}$ underlayer as well as interval time between deposition of the underlayer and the Co-Cr-Ta layer.yer.layer.yer.

• 한국전기전자재료학회논문지
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• 제11권12호
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• pp.1091-1098
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• 1998

Thermal stability of the electroless deposited Cu thin film was investigated. Cu/TaN/Si multilayer was fabricated by electroless-depositing Cu thin layer on TaN diffusion barrier layer which was deposited by MOCVD on the Si substrate, and was annealed in $H_2$ ambient to investigate the microstructure of Cu film with a post heat-treatment. Cu thin film with good adhesion was successfully deposited on the surface of the TaN film by electroless deposition with a proper activation treatment and solution control. Microstructural property of the electroless-deposited Cu layer was improved by a post-annealing in the reduced atmosphere of $H_2$ gas up to $600^{\circ}C$. Thermal stability of Cu/TaN/Si system was maintained up to $600^{\circ}C$ annealing temperature, but the intermediate compounds of Cu-Si were formed above $650^{\circ}C$ because Cu element passed through the TaN layer. On the other hand, thermal stability of the Cu/TaN/Si system in Ar ambient was maintained below $550^{\circ}C$ annealing temperature due to the minimal impurity of $O_2$ in Ar gas.