• Title/Summary/Keyword: CoCr-based alloy

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Shear bond strength of luting cements to fixed superstructure metal surfaces under various seating forces

  • Ozer, Fusun;Pak-Tunc, Elif;Dagli, Nesrin Esen;Ramachandran, Deepika;Sen, Deniz;Blatz, Markus Bernhard
    • The Journal of Advanced Prosthodontics
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    • v.10 no.5
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    • pp.340-346
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    • 2018
  • PURPOSE. In this study, the shear bond strengths (SBS) of luting cements to fixed superstructure metal surfaces under various seating forces were investigated. MATERIALS AND METHODS. Seven different cements [Polycarboxylate (PCC), Glass-Ionomer (GIC), Zinc phospahate (ZPC), Self-adhesive resin (RXU), Resin (C&B), and Temporary cements ((RXT) and (TCS))] were bonded to a total number of 224 square blocks ($5{\times}5{\times}3mm$) made of one pure metal [Titanium (CP Ti) and two metal alloys [Gold-Platinum (Au-Pt) and Cobalt-Chrome (Co-Cr)] under 10 N and 50 N seating forces. SBS values were determined and data were analyzed with 3-way ANOVA. Pairwise comparisons and interactions among groups were analyzed with Tukey's simultaneous confidence intervals. RESULTS. Overall mean scores indicated that Co-Cr showed the highest SBS values ($1.96{\pm}0.4$) (P<.00), while Au-Pt showed the lowest among all metals tested ($1.57{\pm}0.4$) (P<.00). Except for PCC/CP Ti, RXU/CP Ti, and GIC/Au-Pt factor level combinations (P<.00), the cements tested under 10 N seating force showed no significantly higher SBS values when compared to the values of those tested under 50 N seating force (P>.05). The PCC cement showed the highest mean SBS score ($3.59{\pm}0.07$) among all cements tested (P<.00), while the resin-based temporary luting cement RXT showed the lowest ($0.39{\pm}0.07$) (P<.00). CONCLUSION. Polycarboxylate cement provides reliable bonding performance to metal surfaces. Resin-based temporary luting cements can be used when retrievability is needed. GIC is not suitable for permanent cementation of fixed dental prostheses consisting of CP Ti or Au-Pt substructures.

Effect on protective coating of vacuum brazed CMP pad conditioner using in Cu-slurry (Cu 용 슬러리 환경에서의 보호성 코팅이 융착 CMP 패드 컨니셔너에 미치는 영향)

  • Song M.S.;Gee W.H.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.06a
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    • pp.434-437
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    • 2005
  • Chemical Mechanical Polishing (CMP) has become an essential step in the overall semiconductor wafer fabrication technology. In general, CMP is a surface planarization method in which a silicon wafer is rotated against a polishing pad in the presence of slurry under pressure. The polishing pad, generally a polyurethane-based material, consists of polymeric foam cell walls, which aid in removal of the reaction products at the wafer interface. It has been found that the material removal rate of any polishing pad decreases due to the so-called 'pad glazing' after several wafer lots have been processed. Therefore, the pad restoration and conditioning has become essential in CMP processes to keep the urethane polishing pad at the proper friction coefficient and to allow effective slurry transport to the wafer surface. Diamond pad conditioner employs a single layer of brazed bonded diamond crystals. Due to the corrosive nature of the polishing slurry required in low pH metal CMP such as copper, it is essential to minimize the possibility of chemical interaction between very low pH slurry (pH <2) and the bond alloy. In this paper, we report an exceptional protective coated conditioner for in-situ pad conditioning in low pH Cu CMP process. The protective Cr-coated conditioner has been tested in slurry with pH levels as low as 1.5 without bond degradation.

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Characteristics of Cr(III)-based Conversion Coating Solution to Apply Aluminum Alloys for Improving Anti-corrosion Properties

  • Shim, Byeong Yun;Kim, Hanul;Han, Chang Nam;Jang, Young Bae;Yun, Jeong Woo
    • Journal of the Microelectronics and Packaging Society
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    • v.23 no.4
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    • pp.79-85
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    • 2016
  • It is imperative to find environment-friendly coatings as an alternative to the currently used hexavalent chromate conversion coatings for the purpose of improving the anti-corrosion properties of aluminum alloys. Hence, in this study, the corrosion properties of a trivalent chromate conversion coating solution are analyzed and measured. Because of the presence of multiple components in trivalent chromate conversion coating solutions, it is difficult to control plating, attributed to their mutual organic relationship. It is of significance to determine the concentrations of the components present in these coatings; hence, qualitative and quantitative analysis is required. The coating solution contained not only an environment-friendly component chromium(III), but also zirconium, fluorine, sulfur, and potassium, in the coating film. These metals are confirmed to produce a film with improved corrosion resistance to form a thin layer. The excellent corrosion resistance for the trivalent chromate solution is attributed to various inorganic and organic additives.

Analysis on the Fuel Cell Performance by the Impedance Method (임피던스법을 적용한 연료전지의 성능평가)

  • Kim, Gwi-Yeol
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.20 no.10
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    • pp.918-923
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    • 2007
  • Fuel cell is a modular, high efficient and environmentally energy conversion device, it has become a promising option to replace the conventional fossil fuel based electric power plants. The high temperature fuel cell has conspicuous feature and high potential in being used as an energy converter of various fuel to electricity and heat. Corrosions in molten electrolytes and the electric conductivity across the oxide scale have crucial characteristics. When molten salts are involved, high temperature corrosions become severe. In this sense, corrosions of alloys with molten carbonates have the most severe material problems. Systematic investigation on corrosion behavior of Fe/21Cr/Ti or Al alloy has been done in (62+38)mol% (Li+K)$CO_3$ melt at $650^{\circ}C$ using the electrochemical impedance spectroscopy method. It was found that the corrosion current of these Fe-based alloys decreased with increasing Al or Ti. And Al addition improved the corrosion resistance of this type of specimen and more improvement of corrosion resistance was observed at the specimen added with Al.

High Temperature Tribology Behavior of 4YSZ Coatings Fabricated by Air Plasma Spray (APS) and Electron Beam Physical Vapor Deposition (EB-PVD) (플라즈마 용사 및 전자빔 물리기상 증착법으로 제조된 4YSZ 코팅의 고온마찰마모 거동)

  • Yang, Young-Hwan;Park, Chan-Young;Lee, Won-Jun;Kim, Sun-Joo;Lee, Sung-Min;Kim, Seongwon;Kim, Hyung-Tae;Oh, Yoon-Suk
    • Journal of Surface Science and Engineering
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    • v.46 no.6
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    • pp.258-263
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    • 2013
  • 4 mol% Yttria-stabilized zirconia (4YSZ) coatings are fabricated by Air Plasma Spray (APS) and Electron Beam Physical Vapor Deposition (EB-PVD) with top coating of thermal barrier coating (TBC). NiCrAlY based bond coat is prepared as 150 ${\mu}m$ thickness by conventional APS (Air Plasma Spray) method on the NiCrCoAl alloy substrate before deposition of top coating. Each 4YSZ top coating shows different tribological behaviors based on the inherent layer structures. 4YSZ by APS which has splat-stacked structure shows lower friction coefficient but higher wear rate than 4YSZ by EB-PVD which has columnar structure. For 4YSZ by APS, such results are expected due to the sliding wear accompanied with local delamination of splats.

A study on cytotoxicity of Ti-Nb alloys (Ti-Nb계 합금의 세포독성에 관한 연구)

  • Park, Hyo-Byeong
    • Journal of Technologic Dentistry
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    • v.25 no.1
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    • pp.89-94
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    • 2003
  • The use of titanium alloys as biomaterials is increasing due to their superior biocompatibility and enhanced corrosion resistance compared to conventional stainless steels and cobalt-based alloys. Ti-6Al-4V ($\alpha+\beta$type) alloy instead of pure titanium ($\alpha$type) is being widely used as biomaterials has some characteristics such as high fatigue strength, tensile strength and corrosion resistance. It also has similar characteristics to Ti in inducing bony ingrowth. But it has been reported recently that the vanadium element expresses cytotoxicity and carcinogenicity and the aluminium element is related with dementia of Alzheimer type and neurotoxicity. In order to overcome their detrimental effects, $\beta$-phase stabilizer Nb was chosen in the present study. CP-Ti(ASTM grade 2), Ti-3wt.%Nb($\alpha$type), Ti-20wt.%Nb ($\alpha+\beta$type) and Ti-40 wt.%Nb($\beta$type) alloys were melted by vacuum arc furnace. Biocompatibility of Ti-Nb alloys was evaluated by cytotoxicity test. The results can be summarized as follows: 1. For the cytotoxicity test, Ti-Nb alloys showed excellent biocompatibility compared to CP-Ti(ASTM grade 2), 316L STS and Co-Cr alloys.

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Thermal Durability of 4YSZ Thermal Barrier Coating Deposited by Electron Beam PVD (전자빔을 이용한 물리기상증착법으로 제조된 열차폐용 4 mol% YSZ 코팅의 내열특성)

  • Park, Chanyoung;Yang, Younghwan;Kim, Seongwon;Lee, Sungmin;Kim, Hyungtae;Lim, Daesoon;Jang, Byungkoog;Oh, Yoonsuk
    • Journal of Powder Materials
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    • v.20 no.6
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    • pp.460-466
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    • 2013
  • 4 mol% Yttria-stabilized zirconia (4YSZ) coatings with $200{\mu}m$ thick are fabricated by Electron Beam Physical Vapor Deposition (EB-PVD) for thermal barrier coating (TBC). $150{\mu}m$ of NiCrAlY based bond coat is prepared by conventional APS (Air Plasma Spray) method on the NiCrCoAl alloy substrate before deposition of top coating. 4 mol% YSZ top coating shows typical tetragonal phase and columnar structure due to vapor phase deposition process. The adhesion strength of coating is measured about 40 MPa. There is no delamination or cracking of coatings after thermal cyclic fatigue and shock test at $850^{\circ}C$.

Effect of Sintering Condition on Tensile Strength of Fe-based Non-equiatomic High Entropy Alloy (철계 비동일분율 고엔트로피 합금의 인장 강도에 미치는 소결 조건 영향)

  • Seo, Namhyuk;Jeon, Junhyub;Kim, Gwanghun;Park, Jungbin;Son, Seung Bae;Lee, Seok-Jae
    • Journal of Powder Materials
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    • v.28 no.3
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    • pp.221-226
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    • 2021
  • We fabricate the non-equiatomic high-entropy alloy (NE-HEA) Fe49.5Mn30Co10Cr10C0.5 (at.%) using spark plasma sintering under various sintering conditions. Each elemental pure powder is milled by high-energy ball milling to prepare NE-HEA powder. The microstructure and mechanical properties of the sintered samples are investigated using various methods. We use the X-ray diffraction (XRD) method to investigate the microstructural characteristics. Quantitative phase analysis is performed by direct comparison of the XRD results. A tensile test is used to compare the mechanical properties of small samples. Next, electron backscatter diffraction analysis is performed to analyze the phase fraction, and the results are compared to those of XRD analysis. By combining different sintering durations and temperature conditions, we attempt to identify suitable spark plasma sintering conditions that yield mechanical properties comparable with previously reported values. The samples sintered at 900 and 1000℃ with no holding time have a tensile strength of over 1000 MPa.

In vitro study of fracture strength of provisional crown materials

  • Karaokutan, Isil;Sayin, Gulsum;Kara, Ozlem
    • The Journal of Advanced Prosthodontics
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    • v.7 no.1
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    • pp.27-31
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    • 2015
  • PURPOSE. The purpose of this report was to evaluate the effect of the fabrication method and material type on the fracture strength of provisional crowns. MATERIALS AND METHODS. A master model with one crown (maxillary left second premolar) was manufactured from Cr-Co alloy. The master model was scanned, and the data set was transferred to a CAD/CAM unit (Yenamak D50, Yenadent Ltd, Istanbul, Turkey) for the Cercon Base group. For the other groups, temporary crowns were produced by direct fabrication methods (Imident, Temdent, Structur Premium, Takilon, Systemp c&b II, and Acrytemp). The specimens were subjected to water storage at $37^{\circ}C$ for 24 hours, and then they were thermocycled (TC, $5000{\times}$, $5-55^{\circ}C$) (n=10). The maximum force at fracture (Fmax) was measured in a universal test machine at 1 mm/min. Data was analyzed by non-parametric statistics (${\alpha}$=.05). RESULTS. Fmax values varied between 711.09-1392.1 N. In the PMMA groups, Takilon showed the lowest values (711.09 N), and Cercon Base showed the highest values (959.59 N). In the composite groups, Structur Premium showed the highest values (1392.1 N), and Acrytemp showed the lowest values (910.05 N). The composite groups showed significantly higher values than the PMMA groups (P=.01). CONCLUSION. Composite-based materials showed significantly higher fracture strengths than PMMA-based materials. The CADCAM technique offers more advantages than the direct technique.

Evaluations of Si based ternary anode materials by using RF/DC magnetron sputtering for lithium ion batteries

  • Hwang, Chang-Muk;Park, Jong-Wan
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.08a
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    • pp.302-303
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    • 2010
  • Generally, the high energy lithium ion batteries depend intimately on the high capacity of electrode materials. For anode materials, the capacity of commercial graphite is unlike to increase much further due to its lower theoretical capacity of 372 mAhg-1. To improve upon graphite-based negative electrode materials for Li-ion rechargeable batteries, alternative anode materials with higher capacity are needed. Therefore, some metal anodes with high theoretic capacity, such as Si, Sn, Ge, Al, and Sb have been studied extensively. This work focuses on ternary Si-M1-M2 composite system, where M1 is Ge that alloys with Li, which has good cyclability and high specific capacity and M2 is Mo that does not alloy with Li. The Si shows the highest gravimetric capacity (up to 4000mAhg-1 for Li21Si5). Although Si is the most promising of the next generation anodes, it undergoes a large volume change during lithium insertion and extraction. It results in pulverization of the Si and loss of electrical contact between the Si and the current collector during the lithiation and delithiation. Thus, its capacity fades rapidly during cycling. Si thin film is more resistant to fracture than bulk Si because the film is firmly attached to the substrate. Thus, Si film could achieve good cycleability as well as high capacity. To improve the cycle performance of Si, Suzuki et al. prepared two components active (Si)-active(Sn, like Ge) elements film by vacuum deposition, where Sn particles dispersed homogeneously in the Si matrix. This film showed excellent rate capability than pure Si thin film. In this work, second element, Ge shows also high capacity (about 2500mAhg-1 for Li21Ge5) and has good cyclability although it undergoes a large volume change likewise Si. But only Ge does not use the anode due to its costs. Therefore, the electrode should be consisted of moderately Ge contents. Third element, Mo is an element that does not alloys with Li such as Co, Cr, Fe, Mn, Ni, V, Zr. In our previous research work, we have fabricated Si-Mo (active-inactive elements) composite negative electrodes by using RF/DC magnetron sputtering method. The electrodes showed excellent cycle characteristics. The Mo-silicide (inert matrix) dispersed homogeneously in the Si matrix and prevents the active material from aggregating. However, the thicker film than $3\;{\mu}m$ with high Mo contents showed poor cycling performance, which was attributed to the internal stress related to thickness. In order to deal with the large volume expansion of Si anode, great efforts were paid on material design. One of the effective ways is to find suitably three-elements (Si-Ge-Mo) contents. In this study, the Si based composites of 45~65 Si at.% and 23~43 Ge at.%, and 12~32 Mo at.% are evaluated the electrochemical characteristics and cycle performances as an anode. Results from six different compositions of Si-Ge-Mo are presented compared to only the Si and Ge negative electrodes.

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