• Journal of the Korean Magnetics Society
• /
• v.9 no.3
• /
• pp.166-172
• /
• 1999

The magnetic properties between Mn-Ir antiferromagnetic layer and Ni-Fe ferromagnetic layer have been investigated in Mn-Ir/Ni-Fe/Zr on Si wafer formed by magnetron sputtering. Mn-Ir was sputtered from Ir chips and Mn target using D.C. power, Ni-Fe and Zr were deposited from Ni-Fe and Zr targets using D.C. power under Ar atmosphere. We studied the dependence of the magnetic properties on Ir content of Mn-Ir layer for Mn-Ir/Ni-Fe bilayer, and obtained the highest $H_ex$ of 219 Oe and the low $H_c$ of 30 Oe. And then focused on the effect of base pressure for Mn-Ir containing multilayers. Our experimental data showed that if the base pressure is higher than $3.0{\times}10^{-6}\;Torr$, the exchange anisotropy of Mn-Ir/Ni-Fe/Zr disappeared probably due to the grain refining of Mn-Ir film. In addition we have studied the dependence of Zr buffer on magnetic properties of Mn-Ir/Ni-Fe/Zr multilayers, and observed that Zr buffer about (111) texture and lower $H_c$ of Mn-Ir/Ni-Fe/Zr multilayer.

• Korean Journal of Metals and Materials
• /
• v.48 no.3
• /
• pp.194-202
• /
• 2010

Application of a stronger and more durable material for reactor pressure vessels (RPVs) might be an effective way to insure the integrity and increase the efficiency of nuclear power plants. A series of research projects to apply the SA508 Gr.4 steel in ASME code to RPVs are in progress because of its excellent strength and durability compared to commercial RPV steel (SA508 Gr.3 steel). In this study, the microstructural characteristics and mechanical properties of SA508 Gr.3 Mn-Mo-Ni low alloy steel and SA508 Gr.4N Ni-Mo-Cr low alloy steel were investigated. The differences in the stable phases between these two low alloy steels were evaluated by means of a thermodynamic calculation using ThermoCalc. They were then compared to microstructural features and correlated with mechanical properties. Mn-Mo-Ni low alloy steel shows the upper bainite structure that has coarse cementite in the lath boundaries. However, Ni-Mo-Cr low alloy steel shows the mixture of lower bainite and tempered martensite structure that homogeneously precipitates the small carbides such as $M_{23}C_6$ and $M_7C_3$ due to an increase of hardenability and Cr addition. In the mechanical properties, Ni-Mo-Cr low alloy steel has higher strength and toughness than Mn-Mo-Ni low alloy steel. Ni and Cr additions increase the strength by solid solution hardening. In addition, microstructural changes from upper bainite to tempered martensite improve the strength of the low alloy steel by grain refining effect, and the changes in the precipitation behavior by Cr addition improve the ductile-brittle transition behavior along with a toughening effect of Ni addition.

• Journal of the Korean Electrochemical Society
• /
• v.25 no.2
• /
• pp.81-87
• /
• 2022

In this study, the effect of alkylamine on copper electroplating was analyzed using cyclic voltammetry. When water-soluble alkylamines were added to the plating solution, the reduction reaction of Cu²⁺ was inhibited. The inhibition effect of 1,12-diaminododecane has been investigated at various concentrations and conditions of the plating solution. 1,12-diaminododecane was protonated in the acidic plating solution, and therefore, it did not act as a complexing agent for Cu²⁺. Accordingly, it was confirmed that the inhibiton effect of 1,12-diaminododecane was attributed to adsorption on the Cu surface. The adsorption of 1,12-diaminododecane exhibits two characteristics: (i) protonation and subsequent electrostatic attraction with anions pre-adsorbed on Cu surface, and (ii) direct adsorption on Cu surface via amine functional group. The adsorbed 1,12-diaminododecane caused three-dimensional growth and grain refining, as well as the inhibition effect, during Cu electroplating.

• Journal of the Korean Society for Heat Treatment
• /
• v.14 no.3
• /
• pp.160-166
• /
• 2001

The change of ribbon geometry, microstructure and shape recovery with Mn contents, wheel speed and various annealing temperature have been studied in Fe-X%Mn-5Cr-5Co-4Si (X%=15, 20, 24) shape memory alloy (SMA) ribbons rapidly solidfied by single roll chill-block melt-spinning process. The thickness and width of melt-spun ribbons are reduced, results in refining and uniformalizing grains with increasing wheel speed. In the ribbons melt-spun at a wheel speed of 15m/sec, both ${\varepsilon}$ and ${\alpha}^{\prime}$martensites are formed in ribbon 1 (15.5wt%Mn), while only ${\varepsilon}$ martensite is revealed in ribbon 2 (20.2wt%Mn) and ribbon 3 (23.5wt%Mn). The volume fraction of ${\varepsilon}$ martensite is decreased with increasing Mn contents, and those of ${\varepsilon}$ as well ${\alpha}^{\prime}$martensites are increased due to thermal stress relief and grain growth with increasing annealing temperature. Ms temperatures of the ribbons 1, 2 and 3 are fallen with increasing Mn contents. $M_s$ temperatures of the ribbons 1, 2 and 3 annealed at $300^{\circ}C$ for 3 min are risen abruptly, but are nearly constant even at higher annealing temperature, i.e., 400, 500 and $600^{\circ}C$ for 3 min. Shape recovery of the ribbons 1, 2 and 3 increased 30%, 52% and 69% with Mn contents, respectively. Shape recovery of ribbon 1 (15.5wt%Mn) formed ${\varepsilon}$ and ${\alpha}^{\prime}$martensites decreased because of the presence of ${\alpha}^{\prime}$martensite but those of ribbon 2 (20.2wt%Mn) and ribbon 3 (23.5wt%Mn) formed ${\varepsilon}$ martensite increased with increasing annealing temperature.

• Journal of Conservation Science
• /
• v.35 no.5
• /
• pp.440-452
• /
• 2019

This research has analyzed SI, the traditional steel, and SIHS(SI + HS), SICS(SI + CS), and SINiS(SI + NiS), the materials that were produced through welding and reprocessing three modern steel- HS, CS, and NiS- that have different carbon content. The purpose of the analyzation was to improve the definition of the multi-layered pattern that appears in the forging process. In observing modified structures on the commissures of three modern steel that have different carbon component to the SI, SINiS produced the most significant multi-layered pattern as well as the excellent welding quality. The excellent welding quality was due to the content of nickel which helped the forge welding process with other materials. There was no significant difference in crystal grain per materials, and SICS showed the highest hardness. At the measurement of EPMA for commissures of the materials, SINiS showed the highest definition of the multi-layered pattern due to the nickel and carbon content. The results above showed that the carbon steel with nickel content is the best material for the most definite multi-layered pattern, expressed from the multi-layered structure which is a characteristic of traditional forge welding technology. It is expected that the result of this research can be utilized as the technical data in further researches regarding the relics excavated from ancient welding process and their multi-layered structure and patterns.

• Journal of Korea Foundry Society
• /
• v.39 no.2
• /
• pp.26-31
• /
• 2019

In this study, the mechanical characteristics and microstructure of hypereutectic Al-17Si-5Fe extruded alloys prepared by a rapid solidification process (RSP) were investigated. The hypereutectic Al alloy was fabricated by means of RSP and permanent casting. For RSP, the Al alloy melted at $920^{\circ}C$, cooling the specimens at a rate of $10^6^{\circ}C/s$ when the RSP was used, thus allowing the refining of primary Si particles more than when using permanent casting, at a rate of about 91%. We tested an extrusion RSP billet and a permanent-cast billet. Before the hot-extrusion process, heating to $450^{\circ}C$ took place for one hour. The samples were then hotextruded with a condition of extrusion ratio of 27 and a ram speed of 0.5 mm/s. Microstructural analyses of the extruded RSP method and the permanent casting method were carried out with OM and SEM-EDS mapping. The mechanical properties in both cases were evaluated by Vickers micro-hardness, wear resistance and tensile tests. It was found that when hypereutectic Al-17Si-5Fe alloys were fabricated by a rapid solidification method, it becomes possible to refine Si and intermetallic compounds. During the preparation of the hypereutectic Al-17Si-5Fe alloy by the rapid solidification method, the pressure of the melting crucible was low, and at faster drum speeds, smaller grain alloy flakes could be produced. Hot extrusion of the hypereutectic Al-17Si-5Fe alloy during the rapid solidification method required higher pressure levels than hot extrusion of the permanent mold-casted alloy. However, it was possible to produce an extruded material with a better surface than that of the hot extruded material processed by permanent mold casting.

• Korean Journal of Plant Resources
• /
• v.25 no.5
• /
• pp.624-632
• /
• 2012

As there have been lately many worldwide resource challenges such as potential exhaustion of fossil fuels, sudden rise of oil price and ever-rising grain pricing due to global food crisis, there have been more interests focused on recycling vegetable oils and fats into clean natural fuel and producing new resources based on waste cooking oil as a part of reusing waste resources. An Experiment was performed by using ratio of 50:50, 75:25 (w/w) mixture of based rapeseed oil, camellia oil, and olive oil. 50:50, 25:75 (w/w) mixture of based palm oil. The result was that the oleic acid ($C_{18:1}$) got the lowest percentage of 42.8%, when we combined the mixture of rapeseed oil and soybean oil. While the highest percentage of 72.1% was when the mixture of camellia oil and rapeseed oil were combined at 50:50 ratio. In 75:25 (w/w) case, mixture of rapeseed oil and soybean oil got the lowest. The highest ratio was the mixture of camellia oil and olive oil. Based on the component of palm oil, the total saturated fatty acid was decreased. It is expected that stabilizing oxidation through controlling of fatty acid after mixture and that liquidity at a low temperature. The acid value indicated that stabilizing oxidation got a range of highest to lowest. Camellia oil ranked as the highest, followed by olive oil, and the oil seeds as the lowest in rank. Controlling iodine value through mixture and improvement of stabilizing oxidation will provide a good quality. The quality of color has no significant change about mixture in ratio and maintenance. The reduction of the cost of refining process is expected by controling of mixture ratio at biodiesel production in the future.