• Journal of the Korean institute of surface engineering
• /
• v.36 no.1
• /
• pp.1-8
• /
• 2003

In general, the microstructure in thin films was known to evolve in similar manner according to the energy striking the condensing film at similar homologous temperature, Th for the materials of the same crystal structure. The fundamental factors affecting particle energy are a function of processing parameters such as working pressure, bias voltage, target/sputtering gas mass ratio, cathode shape, and substrate orientation. In this study, Al, Cu, Pt films of the same crystal structure of face centered cubic (FCC) have been prepared under various processing parameters. The influence of processing variables on the microstructures and residual stress states in the films has been studied.

• Journal of the Korean Magnetic Resonance Society
• /
• v.8 no.1
• /
• pp.47-54
• /
• 2004

We have measured the linewidth and g-factor of EPR signals of the single crystal Mn$_{x}$Si$_{1-x}$ as a function of Mn-composition (0.4$\leq$x$\leq$0.9). We have investigated the linewidth of Mn$_{0.49}$Si$_{0.51}$ as a function of temperature (100 $\leq$ T $\leq$ 300 K). From these results EPR linewidth equation could be fitted for experimental data of EPR linewidth. This type of equation is similar to the shape of EPR linewidth of DMS (dulite magnetic semiconductor).or).r).

• Bulletin of the Korean Chemical Society
• /
• v.9 no.2
• /
• pp.98-101
• /
• 1988

A pure columnar cholesterogen based on the octasubstituted phthalocyanine $(PcH_2)$, S-(+)-2, 3, 9, 10, 16, 17, 23, 24-octakis[5-(dodecyloxy)-2-oxa-pentyl]-phthalocy anine(1a), is described. To evaluate a cholesteric character of 1a, the corresponding achiral $PcH_2$ 1b and the copper complex of chiral $PcH_2$ 1a (CuPc), S-(+)-2,3,9,10,16,17,23,24-octakis[4-(dodecyloxy)- 2-oxapentyl]-phthalocyanine(2a) were also prepared. The chiral 1a exhibited a typical cholesteric texture change in which the transition of platelet (blue phase) to fan-shape texture was observed (K－M－I), whereas the corresponding achiral 1b showed only a focal conic texture (K－ M－I). This is the first instance of a pure columnar cholesterogen observed with discotic liquid crystal systems.

• Journal of the Korean Society for Heat Treatment
• /
• v.4 no.4
• /
• pp.34-43
• /
• 1991

A small amount of misch metal and/or Zr was added as a dopant to 70.5wt----Cu-26wt----Zn-3.5wt----Al shape memory alloy in order to study the effect of grain refinement and heat treatments on the transformation behavior, stabilization of martensite, and shape memory ability. It was found that the addition of misch metal and Zr was very effective for reducing the grain size. The fracture mode has been changed from intergranular brittle fracture to ductile fracture with void formation and coalescence by the addition of misch metal and Zr. Aging of the ${\beta}$-phase decreases the $M_s$ temperature, but that of the martensite phase increases the $A_s$ temperature. The hysteresis of transformation temperature ${\Delta}T(A_s-M_s)$ has an increasing tendancy by grain refinement. The crystal structure of martensite was identified as monoclinic structure. As the grain size decreased, martensite stabilization more easily occured and the shape, memory ability has been reduced by the grain size refined.

• Journal of Korea Foundry Society
• /
• v.9 no.1
• /
• pp.58-66
• /
• 1989

The effect of heat treating temperature and ${\alpha}$ phase In the ${\beta}$ phase matrix were investigated for ${\beta}-CuZnAl$ shape memory alloys by tension test, fatigue test, and shape memory effect test. After heat treatment at $677^{\circ}C$, $750^{\circ}C$, $800^{\circ}C$ and $850^{\circ}C$ for 10 min. respectively, static fracture stress(${\sigma}_f$), fatigue fracture stress(${\tau}_{max}$) at $10^6$ cycle, and elongation(${\epsilon}_f$) was $24.2kg/mm^2$, $17.21kg/mm^2$ and 11.8%, respectively. As heat treating temperature decreased, fracture surfaces of the specimens were changed from the intergranular to the transgranular fracture mode. Especially, the a phase precipitated in the ${\beta}$ phase matrix had an effect on crack propagation and the fracture surface was characterized by dimple-like pattern when crack propagated in transgranular cracking mode. Precipitation of the ${\alpha}$ phase in the ${\beta}$ phase matrix lowered the transformation temperature by $10^{\circ}C$, and about 2.5 vol.% ${\alpha}$ phase did not affect the shape memory effect examined by the bending test.

• Korean Journal of Materials Research
• /
• v.16 no.2
• /
• pp.123-128
• /
• 2006

[ $BaMgAl_{10}O_{19}:Mn^{2+}$ ](BAM:Mn) phosphor particles with spherical shape were prepared by spray pyrolysis from colloidal solution with silica. The phosphor particles prepared by spray pyrolysis from aqueous solution had irregular morphology after high temperature post-treatment. On the other hand, the phosphor particles prepared from spray solution with colloidal silica had spherical shape after post-treatment. Colloidal silica used as additive improved the spherical shape and filled morphology of the precursor particles prepared by spray pyrolysis. The precursor particles with filled structure produced the BAM:Mn phosphor particles with spherical shape and non-aggregation characteristics after post-treatment at $1400^{\circ}C$ under reducing atmosphere. The phosphor particles prepared from colloidal solutions formed the crystal structure of BAM:Mn phosphor irrespective of the silica contents. The BAM:Mn phosphor particles prepared from aqueous and colloidal solutions had similar photoluminescence intensities under vacuum ultraviolet.

• Korean Journal of Materials Research
• /
• v.15 no.8
• /
• pp.496-502
• /
• 2005

Green-light emitting $BaMgAl_{10}O_{19}:Mn^{2+}$ (BAM:Mn) phosphor particles were prepared by spray Pyrolysis. The effect of reactor temperature and flow rate of carrier gas in the spray Pyrolysis on the morphology, crystallinity and photoluminescence characteristics under vacuum ultraviolet were investigated. The morphology of the as-Prepared Particles obtained by spray Pyrolysis had spherical shape and non-aggregation characteristics regardless of the reactor temperature. The spherical shape of the as-prepared Particles obtained by spray pyrolysis at low temperature disappeared after Post-treatment. On the other hand the as-Prepared Particles obtained by spray Pyrolysis at $1600^{\circ}C$ maintained spherical shape and non-aggregation characteristics after post-treatment at $1400^{\circ}C$ for 3 h under reducing atmosphere. The BAM:Mn Phosphor Particles Prepared by spray Pyrolysis at different reactor temperatures had pure crystal structure and high photoluminescence intensities under vacuum ultraviolet after post-treatment. BAM:Mn phosphor particles prepared by spray Pyrolysis at low How rate of carrier gas had complete spherical shape and filed morphology and high photoluminescence intensity after post-treatment under reducing atmosphere.

• Journal of Electrochemical Science and Technology
• /
• v.10 no.3
• /
• pp.276-283
• /
• 2019

Nitinol is an alloy of nickel and titanium. Nitinol is one of the shape memory alloys(SMA) that are restored to a remembered form, changing the crystal structure at a given temperature. Because of these unique features, it is used in medical devices, high precision sensors, and aerospace industries. However, the conventional method of mechanical machining for nitinol has problems of thermal and residual stress after processing. Therefore, the electrochemical machining(ECM), which does not produce residual stress and thermal deformation, has emerged as an alternative processing technique. In addition, to replace the existing experimental planning methods, this study used deep neural network(DNN), which is the basis for AI. This method was shown to be more useful than conventional method of design of experiments(RSM, Taguchi, Regression) by applying deep neural network(DNN) to electrochemical machining(ECM) and comparing root mean square errors(RMSE). Comparison with actual experimental values has shown that DNN is a more useful method than conventional method. (DOE - RSM, Taguchi, Regression). The result of the machining was accurately and efficiently predicted by applying electrochemical machining(ECM) and deep neural network(DNN) to the shape memory alloy(SMA), which is a hard-mechinability material.

• Journal of the Korean Society of Costume
• /
• v.50 no.7
• /
• pp.15-31
• /
• 2000

1. After the Chu Dynasty(周代), we can confirm the fish shape mark made of stones as the relics of the Chunkuk dynasty(戰國時代). In the Shu Dynasty(隋代), the system of bamboo and the rabbit shape mark made of silver into the fish shape mark. As it were, made of bamboo or siltier changed into the fish shape mark made of jade, gold, silver or wood. 2. In the Dang Dynasty(唐代), the used the fish shape credit mark made of jade, gold, silver, copper or textile, according to their classes. According to one's posit the man who wore purple, red coat, credit mark made a gold and silver. attached with putting them in fish bags. 3. In the Ryo Dynasty(遼代), there was also a system of attaching marks. The emperor was hanging the fish shape and the officials attached the double fish shape to the common dress. fish shape of jade. gold, amber, agate, silver or copper. without any fish bag. 4. The Song Dynasty(宋代) followed the system of the Dang Dynasty they used only the fish shape bags without marks in them. Hanging the fish shape bags made of gold and silver at the back side of the belt. 5. The Gin Dynasty(金代) carried out the system of made jade, gold or silver like the Dang, Song and Ryo Dynasty. In the Sejong Kingdom a system of paper card was carried out as the credit mark of the eighth and the ninth grade. 6. In the Ming Dynasty(明代), the military official general attached the golden, silver, ivory of jade, wood and copper cards with their positions and names. 7. Following the Dang Dynasty, Japan made of fish shape bags to their clothes. Colors of their fish shape marks were same as their clothes. They made the marks, such as crystal, cow's horn, lead and nickel and plated them with gold or silver. 8. In Korea, Pohai(발해) established the fish shape credit mark differed in material. gold, silver or copper according to their positions. We can confirm the Unified Silla(南國;統一新羅), carried out the system of attaching the fish shape in Chonma Chong(천마총), Golden Crown Chong(金冠塚), the King's 13-17 belt ring unearthed at the north part of Court South threat Chong(황남대총), the fish shape golden or silver, to their purple or red ceremonial coats. In the Koryo Dynasty(高麗), like the Dang, Song and Pohai, they attached the fish shape golden or silver marks, to their purple or red ceremonial coats.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.10 no.3
• /
• pp.177-184
• /
• 2000

The effect of the buyancy and thermocapillarity for differnent aspect ratio of flow field on melt motion and mass transfer has been numerically investigated in magnetic Czochralski crystal growth of silicon. During the process of crystal growth, the melt depth of crucible reduces so the aspect ratio of flow field also reduces. Therefore the shape of magnetic field of the flow field changes and the flow pattern also changes significantly. Together with the melt flow which forms the Marangoni convection (or thermocapillary flow) that comes from the inside the flow field, a flow circulation is observed near the corner close both to the crucible wall and the free surface. Due to this circulation, buoyancy effect has been turned out to be local rather than global. As the aspect ratio decreases, the radial component of the magnetic field prevails compared with the axial component in the flow field. Under the influence of this magnetic field, the melt flow and the temperature distribution in a meridional plane tend to depend on the radial position. As the aspect ratio decreases, the temperature gradient near the edge of the crystal decreases yielding smaller thermocapillarity, and the oxygen concentration near the crystal and the oxygen incorporation rate also decrease.