• 한국전기전자재료학회논문지
• /
• 제21권1호
• /
• pp.18-22
• /
• 2008

In this paper, the Ni-Co alloy was used for thermal stability estimation comparison with Ni structure. The proposed Ni/Ni-Co structure exhibited wider range of rapid thermal process windows, lower sheet resistance in spite of high temperature annealing up to $700^{\circ}C$ for 30 min, more uniform interface via FE-SEM analysis, NiSi phase peak. Therefore, The proposed Ni/Ni-Co structure is highly promising for highly thermal immune Ni-silicide for nano-scale MOSFET technology.

• Bulletin of the Korean Chemical Society
• /
• 제31권1호
• /
• pp.151-156
• /
• 2010

In this paper, we characterized bimetallic Pt-Ru/C alloy catalysts having four different compositions and compared the catalytic activities of the prepared alloys for CO oxidation. ICP-AES, EDS, XRD, TEM, and XAS were used to investigate the composition, degree of alloying, particle size, and electronic structure of the prepared Pt-Ru/C catalysts. Those results indicated the synthesis of the alloy catalysts with intended composition and uniform size. The electrochemical study of the characterized alloys showed higher catalytic activity for CO oxidation than that of the commercial Pt/C (E-TEK, Inc., 20 wt %) catalyst. Especially, it was shown that the alloy catalyst with Ru composition of 50 atomic % gave the highest catalytic activity for CO oxidation.

• 대한치과보철학회지
• /
• 제38권1호
• /
• pp.38-49
• /
• 2000

The purpose of this study was to evaluate the effects of thermocycling on the shear bond strength of Co-Cr alloy to denture base resin. PMMA denture base resin such as heat-cured $Vertex-RS^{(R)}$, self-cured $Vertex-SC^{(R)}$ and 4-META denture base resin such as heat-cured $Meta-Dent^{(R)}$, self-cured $Meta-Fast^{(R)}$ was bonded to Co-Cr alloy. Samples were divided into 3 groups : no thermocycling group as control, thermocycling between $5^{\circ}C\;and\;55^{\circ}C$ with 15 second dwell time as group 1, thermocycling with 1 minute dwell time as group 2. The shear bond strength was measured and the interface between metal and resin was observed by SEM. The results were as follows. 1. The shear bond strength decreased significantly according to thermocycling and dwell time(P<0.001). 2. The bond strength of Co-Cr alloy and 4-META denture base resin was significantly higher than that of Co-Cr alloy and PMMA denture base resin(P<0.001) 3. In SEM, there was no gap in control group, but there was much and large gap in group 1, 2. The longer dwell times, the lower bond strength. PMMA denture base resin had more gap than 4-META denture base resin in the interface. These results revealed that thermocycling decreased the bond strength between Co-Cr alloy and denture base resin and dwell time of thermocycling changed the effect of thermocycling. The results suggested that oral temperature change affect the bond strength of prosthesis.

• 한국전기전자재료학회논문지
• /
• 제14권2호
• /
• pp.163-168
• /
• 2001

This dissertation describes the development of a sensor for measuring microscopic displacement where we use CoFeSiB amorphous alloy magnetic ribbon having near zero magnetostrictive properties. For the development of the sensor, we first fabricate amorphous alloy magnetic ribbon, and then investigate its physical and magnetic properties. Finally, its possibility of practical application as a displacement sensor is discussed. The experimental samples were made of near zero magnetostrictive (Co$\_$0.94/Fe$\_$0.06/)$\_$9/Si$_2$B$\_$19/ alloy which were fabricated by a rapid liquid quenching method. As a results, we got amorphous alloy magnetic ribbons of 12㎛ in thickness, 10 mm in length, and 2.5 m in width. It was found that the crystallization temperature and the Curie temperature are around 451$\^{C}$ and around 441$\^{C}$ respectively. We couldn't observe any noticeable change of the impedance frequency of 10MHz, but observed the impedance change of 3.76 %/Oe at 100 MHz. The inductance was nearly stable over the frequency range of 1∼10 MHz, In addition, it was observed that the variation of the inductance and the impedance were linear within the displacement ranges of 20∼60㎛. As the results of the experiments, it is suggested that the displacement sensor which is fabricated by using amorphous alloy magnetic ribbon of (Co$\_$0.04/Fe$\_$0.06/)$\_$79/Si$_2$B$\_$19/ compound, can be used as a sensor to detect microscopic displacement.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.109-110
• /
• 2006

We have studied the effect of C/Ti atomic ratio of TiCx (x=0.5, 0.75 and 1.0) raw powder on the properties of the Ti-Mo-WTiC sintered hard alloy. The decrease of C/Ti atomic ratio accelerated the densification in the sintering process. The hardness was remarkably improved up to 1350HV with decreasing the C/Ti atomic ratio because of increase of TiCx phase volume content and its fine dispersion. From the results of electro-chemical tests in acid and 3% NaCl solutions, it was obvious that every alloy had excellent corrosion resistance, which meant about 200 times better than that of WC-Co cemented carbide.

• Corrosion Science and Technology
• /
• 제7권3호
• /
• pp.145-151
• /
• 2008

Material degradation such as high temperature oxidation of metallic material is a severe problem in energy generation systems or manufacturing industries. The metallic materials are oxidized to form oxide films in high temperature environments. The oxide films act as diffusion barriers of oxygen and metal ions and thereafter decrease oxidation rates of metals. The metal oxidation is, however, accelerated by mechanical fracture and spalling of the oxide films caused by thermal stresses by repetition of temperature change, vibration and by the impact of solid particles. It is therefore very important to investigate mechanical properties and adhesion of oxide films in high temperature environments, as well as the properties in a room temperature environment. The oxidation tests were conducted for Ni and Ni-Co alloy under high temperature corrosive environments. The hardness distributions against the indentation depth from the top surface were examined at room temperature. Dynamic indentation tests were performed on Ni oxide films formed on Ni surfaces at room and high temperature to observe fractures or cracks generated around impact craters. As a result, it was found that the mechanical property as hardness of the oxide films were different between Ni and Ni-Co alloy, and between room and high temperatures, and that the adhesion of Ni oxide films was relatively stronger than that of Co oxide films.

• 한국전기전자재료학회논문지
• /
• 제23권12호
• /
• pp.988-995
• /
• 2010

In this study the (Alnico, Sm-Co) bonded magnets were fabricated by mixing the Sm-Co added alnico alloy powders with epoxy resin and binder, appropriately. Also, the hybrid ring magnets of (Alnico, Sm-Co)/Sr-ferrite were fabricated by coupling the Sr-ferrite composite layer with an (Alnico, Sm-Co) magnet. The magnetic properties of (Alnico, Sm-Co) ring magnets were varied with the amount of Sm-Co powders. The addition of Sm-Co powders increased a remanent induction($B_r$) and coercive force($_BH_C$), while decreasing a surface flux density and repulsive distance. The surface flux density and repulsive distance for the (Alnico, Sm-Co) ring magnet increased with a magnetizing voltage up to about 160 V and reached an apparent saturation point. Also, the measurements of temperature and moisture characteristics showed that the surface flux densities of N-S poles and repulsive distance decreased a little within 4% after 10 days passed.

• Journal of Magnetics
• /
• 제13권4호
• /
• pp.115-119
• /
• 2008

The authors predicted that $Co_2HfSi$, a $Co_2$-based full Heusler alloy, is being a half-metallic ferromagnet by first-principles calculations using the all electron full-potential linearized augmented plane wave method which adopts the generalized gradient approximation. The integer value of the calculated total magnetic moment of 2.00 ${\mu}_B$ per formula unit and a spin gap of 0.69 eV in spin down state confirmed the half-metallicity of bulk $Co_2HfSi$. For the $Co_2HfSi$(001) surface, we considered two possible surface terminations, namely, Co terminated and HfSi terminated surfaces. It was found that half-metallicity was retained at the HfSi-terminated surface but not at the Co-terminated surface. The magnetic moment of surface Co atoms in the Co-terminated surface was slightly lower than that of Co atoms in deep inner-layers, whereas the magnetic moments of Hf and Si atoms at the HfSi-terminated surface were almost same as those in deep inner-layers.

• 열처리공학회지
• /
• 제36권3호
• /
• pp.128-136
• /
• 2023

In this study, the effects of heat treatment on the nano-scale creep behavior of CoCrFeMnNi high-entropy alloy (HEA) processed by high-pressure torsion (HPT) was investigated through nanoindentation technique. Nanoindentation experiments with a Berkovich indenter were performed on HPT-processed alloy subjected to heat treatment at 450℃, revealing that the hardness of the HPT-processed alloy (HPT sample) significantly increased with the heat treatment time. The heat treatment-induced microstructural change in HPT-processed alloy was analyzed using transmission electron microscopy, which showed the nano-sized Cr-, NiMn-, and FeCo-rich phases were formed in the HPT-processed alloy subjected to 10 hours of heat treatment (HPT+10A sample). To compare the creep behavior of HPT and HPT+10A samples, constant load nanoindentation creep experiments were performed using spherical indentation indenters with two different radii. It was revealed that the predominant mechanism for creep highly depended on the applied stress level. At low stress level, both HPT and HPT+10A samples were dominated by Coble creep. At high stress level, however, the mechanism transformed to dislocation creep for HPT sample, but continued to be Coble creep for HPT+10A sample, leading to higher creep resistance in the HPT+10A sample.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2002년도 제5회 압출 및 인발가공 심포지엄
• /
• pp.43-49
• /
• 2002

A7003 alloy has characteristics of their excellent weldability, high corrosion resistance and superior plastic working however the broadening of application for the alloy has been hampered by the lower extrudability associated by Mg content. For improvement of extrudability and enhanced recovery efficiency during Al scrap recyeling, it has been generally practiced to reduce Mg content in A7003 alloy. Therefore, it is necessary to investigate the influence of Mg content on mechanical strength and extrudability of A7003 alloy. For efficient material processing which has small amounts, life cycle assessment in material processing(MLCA) is evaluated. The quantitative analysis of energy requirements and $CO_2$ emission for production of A7003 extruded bar are estimated with different Mg content and billet pre-heating process (heating source by light oil or LPG). In particular, the estimation of energy requirements was performed within shipping and gating range (except the mining and extraction stages)to investigate the influence of the variables on energy requirements and $CO_2$ emission in detail. As Mg content increased, the flow stress and the extrusion pressure for A7003 alloy increased. It has been thought that an increment in extrusion pressure with increasing Mg content is caused by the solid solution hardening of Mg atoms in the matrix and increment in volume fraction of intermetallic compound, $Mg_2Si$. The extrudability and the tensile strength are equal to, or above that of conventional A 7003 alloy even the content of Mg varied from $1.1wt.\%\;to\;0.5wt.\%$ alloy. This means that minimizing the content of Mg in A7003 alloy can enhance recovery efficiency during Al scrap recycling. It can be quoted that rather than Mg content energy source for billet heating is a prime factor to determine the atmospheric $CO_2$ emission.