• Journal of Magnetics
• /
• v.13 no.4
• /
• pp.144-148
• /
• 2008

The size and surface effects on the magnetism of a fcc Fe (001) surface was investigated by performing firstprinciples calculations on 3, 5, 7, and 9 monolayers fcc Fe (001) single slabs with two different two-dimensional lattice constants, ${\alpha}=3.44{\AA}$ (System I) and 3.65 ${\AA}$ (System II), using the all-electron full-potential linearized augmented plane wave method within a generalized gradient approximation. The surface layers were coupled ferromagnetically to the subsurface layer in both systems. However, the magnetism of the inner layers was quite different from each other. While all the inner layers of System II were ferromagnetically coupled in the same way as the surface layer, the inner layers of System I showed a peculiar magnetism, bilayer antiferromagnetism. The calculated spin magnetic moments per Fe atom were approximately 2.7 and 2.9 ${\mu}_B$ at the surface for Systems I and II, respectively, due to the almost occupied Fe d-state being in the majority spin state and band narrowing. The spin orientations of System I were out-of-plane regardless of its thickness, whereas the orientation of System II changed from out-of-plane to in-plane with increasing thickness.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.15 no.5
• /
• pp.202-207
• /
• 2005

We have investigated the relationship between a viscosity of the slip prepared from kaolin, quartz, $Mg(OH)_2$, etc and its influence on the speed of slip casting and the microsturcture of a sintered body. The speed of slip casting decreases as a viscosity of a slip decreases. The optimized viscosity range of a slip was found to be around $3.0\~17.0\;cP$. By careful controlling a viscosity of slip, homogeneous microstructure of outer surface layers, inner surface layers, intermediate layers, and inside layers were obtained by casting process. The specimen sintered at $1350^{\circ}C$ consists of a cordierite crystalline phase only as a constituent mineral.

• Bulletin of the Korean Chemical Society
• /
• v.28 no.4
• /
• pp.635-646
• /
• 2007

The reaction of gas-phase hydrogen atoms H with H atoms chemisorbed on a graphite surface has been studied by the classical dynamics. The graphite surface is composed of the surface and 10 inner layers at various gas and surface temperatures (Tg, Ts). Three chains in the surface layer and 13 chains through the inner layers are considered to surround the adatom site. Four reaction pathways are found: H2 formation, H-H exchange, H desorption, and H adsorption. At (1500 K, 300 K), the probabilities of H2 formation and H desorption are 0.28 and 0.24, respectively, whereas those of the other two pathways are in the order of 10-2. Half the reaction energy deposits in the vibrational motion of H2, thus leading to a highly excited state. The majority of the H2 formation results from the chemisorption-type H(g)-surface interaction. Vibrational excitation is found to be strong for H2 formed on a cold surface (~10 K), exhibiting a pronounced vibrational population inversion. Over the temperature range (10-100 K, 10 K), the probabilities of H2 formation and H-H exchange vary from 0 to ~0.1, but the other two probabilities are in the order of 10-3.

• Journal of Magnetics
• /
• v.13 no.4
• /
• 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.

• Applied Microscopy
• /
• v.26 no.3
• /
• pp.277-291
• /
• 1996

The structures of the egg envelope in fertilized eggs of three species of characidae, head and tail light fish (Hemigrammus ocellifer), black tetra (Gymnocorymbus ternetzi), and buenos aires tetra (Hemigrammus caudovittatus) were studied using light and electron microscopes. The fertilized eggs in all species were colorless, transparent, spherical and non-floted type. The egg envelopes have a single micropyle resembling the pathway of sperm in the area of the animal pole. The micropyle was surrounded by protruded lines of the egg envelope in a radiated form. Egg envelopes of fertilized eggs in both head and tail light fish and buenos aires tetra consisted of three distinct layers; an outer layer, a middle layer and an inner layer. And that of blacktetra consisted of two layers; an outer layer and an inner layer. Also, an outer layers of both head and tail light fish and black tetra were adhesive types but, in that of buenous aires tetra was non-adhesive type. An outer surface of egg envelope in black tetra was arranged by pores regularly. In that of head and tail light fish and buenos aires tetra have a rough side. An inner layer of egg envelope in fertilized eggs consisted of lamellae alternating with interlamellae of lower electron density; an inner layer of fertilized eggs in head and tail light fish consisted of three layers, that of black tetra was four layers, and that of buenos aires tetra was five layers.

• Fibers and Polymers
• /
• v.6 no.1
• /
• pp.6-12
• /
• 2005

Fiber surface morphologies and associated internal structures are closely related to its properties. Unlike other fibers including cotton, bast fibers possess transverse nodes and fissures in cross-sectional and longitudinal directions. Their morphologies and associated internal structures were anatomically examined under the scanning electron microscope. The results showed that the morphologies of the nodes and the fissures of bast fibers varied depending on the construction of the inner fibril cellular layers. The transverse nodes and fissures were formed by the folding and spiralling of the cellular layers during plant growth. The dimensions of nodes and fissures were determined by the dislocations of the cellular layers. There were also many longitudinal fissures in bast fibers. Some deep longitudinal fissures even opened the fiber lumen for a short way along the fiber. In addition, the lumen channel of the bast fibers could be disturbed or disrupted by the nodes and the spi­rals of the internal cellular layers. The existence of the transverse nodes and fissures in the bast fibers could degrade the fiber mechanical properties, whereas the longitudinal fissures may contribute to the very rapid moisture absorption and desorption.

• Transactions of Materials Processing
• /
• v.29 no.6
• /
• pp.323-330
• /
• 2020

The surface region of a sheet metal may have different characteristics from the inner region because the surface region is less restricted than the interior. In addition, the grains on the free surface are less hardened because of surface adsorption of the dislocations, rather than piling up. In the case of bulk or thick sheet metals, this effect is negligible because the fraction of the surface region is much smaller than that of the inner region. However, this surface effect is important in the case of ultra-thin sheet metals. In order to evaluate the surface effect, tensile and bending tests were performed for the SS304 stainless steel with a thickness of 0.39 mm. The bending force predicted using the tensile behavior is higher than the measurement because of the surface effect. To account for the surface effect, the surface layer model was developed by dividing the sheet section into surface and inner layers. The mechanical behaviors of the two regions were calibrated using the tensile and bending properties. The surface layer model reproduced the bending behavior of the ultra-thin sheet metal.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2008.11a
• /
• pp.15-16
• /
• 2008

In case manufacturing COF, through hole should be made to be used for a pathway connecting the conductive layers of its both faces. In case Cu-plating inside of through hole with electroless plating way, contact between Cu and PI film gets bad to be fell apart from PI by the impact of applying to the electric devices. Therefore, after sputtering is applying on inner through hole, then a method to perform electroplating process. In this study, after changing sputtering condition to manufacture FCCL, we looked the changeability of the upper PI and inner hole Cu layers. Making use of RF Magnetron sputtering equipment, we coated Cu thin film and Cu-plated on it through electroplating. After cold-mounting the completed FCCL, we examined hole section through an optical microscope. From the result of test, with parameters deposition pressure and deposition time, both the thickness of the hole plated layer and PI plated upper layer increased at regular rate, increasing the thickness of Cu sputter layer. However, from the result of test in increasing RF-power, we could know the increment rate of hole plated layer is considerably greater than that of PI plated upper layer. Therefore, we finally acquired good result; if you want only to increase the plated layer of inner hole, it's much better to increase RF-power.

• Journal of Technologic Dentistry
• /
• v.27 no.1
• /
• pp.57-63
• /
• 2005

Experimental Ti-13%Zr and Ti-13%Zr-5%Cu alloys were made in an argon-arc melting furnace. The grade 2 CP Ti was used to control. To investigate the surface reaction layers produced by the reaction with mold materials and the influence of the reaction layers on the hardness of castings, A phosphate bonded $SiO_2$ base investment was used as mold material, and microstructure observation and hardness test were performed. The surface reaction layers of Ti-13%Zr and Ti-13%Zr-5%Cu alloys were thinner than that of CP Ti had a clearly multiple structure. A difference of the hardness between surface and inner of the Ti-13%Zr and Ti-13%Zr-5%Cu alloys became less than that of CP Ti. From the results, it was found that the Ti-Zr-(Cu) based alloys were possible to cast with $SiO_2$ base investment without the great changes of mechanical properties of the castings.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.135-135
• /
• 2015

Tubes are of extreme importance in industries as for fluid channels or wave guides. Furthermore, some weapon systems such as cannons use the tubes as gun barrels. To increase the service life of such tubes, a protective coating must be applied to the tubes' inner surface. However, the coating methods applicable to the inner surface of the tubes are very limited due to the geometrical restriction. A small-diameter cylindrical magnetron sputtering gun can be used to deposit coating layers on the inner surface of the large-bore tubes. However, for small-bore tubes with the inner diameter of one inch (~25 mm), the magnetron sputtering method can hardly be accommodated due to the space limitation for permanent magnet assembly. In this study, a new approach to coat the inner surface of small-bore tubes with the inside diameter of one inch was developed. Instead of using permanent magnets for magnetron operation, an external electro-magnet assembly was adopted around the tube to confine the plasma and to sustain the discharge. The electro-magnet was operated in pulse mode to provide the strong axial magnetic field for the magnetron operation, which was synchronized with the negative high-voltage pulse applied to the water-cooled coaxial sputtering target installed inside the tube. By moving the electro-magnet assembly along the tube's axial direction, the inner surface of the tube could be uniformly coated. The inner-surface coating system in this study used the tube itself as the vacuum chamber. The SS-304 tube's inner diameter was 22 mm and the length was ~1 m. A water-cooled Cu tube (sputtering target) of the outer diameter of 12 mm was installed inside of the SS tube (substrate) at the axial position. The 50 mm-long electro-magnet assembly was fed by a current pulse of 250 A at the frequency and pulse width of 100 Hz and 100 usec, respectively. The calculated axial magnetic field strength at the center was ~0.6 Tesla. The central Cu tube was synchronously driven by a HiPIMS power supply at the same frequency of 100 Hz as the electro-magnet and the applied pulse voltage was -1200 V with a pulse width of 500 usec. At 150 mTorr of Ar pressure, the Cu deposition rate of ~10 nm/min could be obtained. In this talk, a new method to sputter coat the inner surface of small-bore tubes would be presented and discussed, which might have broad industrial and military application areas.