• Journal of Korea Foundry Society
• /
• v.17 no.1
• /
• pp.76-84
• /
• 1997

An investigation of the effects of transverse magnetic field on melt convection and macrosegregation in vertical Bridgman growth of Te doped InSb was carried out by means of microstructure observation, the measurement of Te distribution by Hall measurement, electrical resistivity measurement and X-ray analysis. Prior to the experiments, interface stability, convective instability and suppression of convection by magnetic field were examined. A thermosolutal convection in the Te doped InSb melt occurred in the examined growth condition without magnetic field. The effective distribution coefficient, $K_{eff}$, was about 0.35 without magnetic field, 0.45 with magnetic field of 2kG, and 0.7 at 4kG. It was found that the stronger the applied magnetic field was, the more the convection was suppressed.

• Journal of Korea Foundry Society
• /
• v.23 no.4
• /
• pp.204-211
• /
• 2003

Ti-3wt.%Nb(${\alpha}$type), Ti-20wt.%Nb(${\alpha}+{\beta}$,type) and Ti-40wt.%Nb(${\beta}$type) alloys were melted by vacuum are remelting. The specimens were homogenized at 1050$^{\circ}C$ for 24 hr and were then hot rolled to 50% reduction. Each alloys were solution heat treated at ${\beta}$ zone and ${\alpha}+{\beta}$, zone after homogenization, and then aged. The microstructural and hardness changes in Ti-Nb alloys with Nb contents were investigated by SEM, XRD and hardness tester. The microstructural change from equiaxied to acicular and the increase of ${\beta}$ phase in Ti-Nb alloys were obtained when the Nb content increased. The higher hardness value of ${\alpha}+{\beta}$type alloy was obtained compared to the other alloys.

• Journal of Korea Foundry Society
• /
• v.28 no.1
• /
• pp.31-36
• /
• 2008

Ti-Ni-Cu alloys are very attractive shape memory alloys for applications as actuators because of a large transformation elongation and a small transformation hysteresis. Rapidly solidified Ti-Ni alloy ribbons have been known to have the shape memory effect and superelasticity superior to the alloy ingots fabricated by conventional casting. In this study, solidification structures and shape memory characteristics of $Ti-Ni_{30}-Cu_{20}$ alloy ribbons prepared by melt spinning were investigated by means of DSC and XRD. Operating parameters to fabricate the amorphous ribbons were the wheel velocity of 55 m/s and the melt spinning temperature of $1500^{\circ}C$. The crystallization temperature was measured to be $440^{\circ}C$. The crystallized ribbons exhibited very fine microstructure after annealing at $440^{\circ}C$ for 10 minutes and $460^{\circ}C$ for 5 minutes and was deformed up to about 6.8% and 6.23% in ductile manner, respectively. Stress-strain curve of the ribbon exhibited a flat stress-plateau at 64 MPa and this is associated with the stress-induced a B2-B19 martensitic transformation. During cycle deformation with the applied stress of 220 MPa, transformation hysteresis and elongation associated with the B2-B19 transformation were observed to be $4.3^{\circ}C$ and 3.6%.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.378.1-378.1
• /
• 2014

In this study, we investigated that the resistance switching characteristics of Nb-doped HfO2 films with increasing Nb doping concentration. The Nb-doped HfO2 based ReRAM devices with a TiN/Nb-doped HfO2/Pt/Ti/SiO2 were fabricated on Si substrates. The Nb-doped HfO2 films were deposited by reactive dc magnetron co-sputtering at $300^{\circ}C$ and oxygen partial ratio of 60% (Ar: 16sccm, O2: 24sccm). Microstructure of Nb-doped HfO2 films and atomic concentration were investigated by XRD, TEM, and XPS, respectively. The Nb-doped HfO2 films showed set/reset resistance switching behavior at various Nb doping concentrations. The process voltage of forming/set is decreased and whereas the initial current level is increased in doped HfO2 films. However, the switching properties of Nb-doped HfO2 were changed above the specific doping concentration of Nb. The change of resistance switching behavior depending on doping concentration was discussed in terms of concentration of non-lattice oxygen and micro-structure of Nb-doped HfO2.

• Korean Journal of Materials Research
• /
• v.27 no.10
• /
• pp.544-551
• /
• 2017

In order to develop a new commercial Al-12%Si casting alloy with improved physical properties, we investigated the effect of adding Sr and TiB to the alloy. Al-12%Si alloys were prepared by die casting at $660^{\circ}C$. The eutectic temperature of the Sr-modified Al-12%Si alloy decreased to $9^{\circ}C$ and the mushy zone region increased. The shape of the Si phase changed from coarse acicula to fine fiber with the addition of Sr. The addition of TiB in the Al-12%Si alloy reduced the size of the primary ${\alpha}$-Al and eutectic Si phases. When Sr and TiB were added together, it worked more effectively in refinement and modification. The density of twins in the Si phase-doped Sr increased and the width of the twins was refined to 5 nm. These results are related to the impurity induced twinning(IIT) growth.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2002.08a
• /
• pp.628-631
• /
• 2002

$Al_2O_3$ capping layer and MgO protective layer were deposited by electron beam evaporation method using single crystal source. Thickness of the capping layer, $Al_2O_3$, was varied from 5 nm to 10 nm. Surface morphology was observed by SEM and AFM before and after hydration. And microstructure of deposited $Al_2O_3$ layer and chemical shift of electron binding energy were also observed by high resolution TEM and XPS, respectively, after hydration. From these results, it was found that Mg atoms diffused into $Al_2O_3$ layer, reacted with moisture and formed $Mg(OH)_2$ during hydration. As thickness of $Al_2O_3$ increased, extent of hydration increased. $Al_2O_3$ capped MgO thin films and uncapped MgO thin films were deposited on AC-PDP test panel to characterize discharge properties. Although $Al_2O_3$ has poor discharge properties rather than MgO, because of many hydrated species on the surface of MgO, similar discharge properties were observed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.18 no.6
• /
• pp.515-520
• /
• 2005

CMP(chemical mechanical polishing) process has been attracted as an essential technology of multi-level interconnection. Also CMP process got into key process for global planarization in the chip manufacturing process. In this study, potentiodynamic polarization was carried out to investigate the influences of $H_2O_2$ concentration and metal oxide formation through the passivation on tungsten and titanium. Fortunately, the electrochemical behaviors of tungsten and titanium are similar, an one may expect. As an experimental result, electrochemical corrosion of the $5\;vol\%\;H_2O_2$ concentration of tungsten and titanium films was higher than the other concentrations. According to the analysis, the oxidation state and microstructure of surface layer were strongly influenced by different oxidizer concentration. Moreover, the oxidation kinetics and resulting chemical state of oxide layer played critical roles in determining the overall CMP performance. Therefore, we conclude that the CMP characteristics tungsten and titanium metal layer including surface roughness were strongly dependent on the amounts of hydrogen peroxide oxidizer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1996.05a
• /
• pp.63-67
• /
• 1996

In this paper, effect of MnO$_2$ addition(0, 0.1, 0.2, 0.3, 0.5wt%) on the microstructure, dielectric and piezoelectric properties of [xPMW - (0.15-x) PNN] - [yPT-(0.85-y)PZ] (x=0, 0.01, 0.02, 0.03, 0.05, y = 0.35, 0.40, ().425, 0.45, 0.5) were investigated. When Ti/Zr ratio was 1.0, dielectric and piezoelectric properties were highest value. With PMW 2mol%, dielectric constant, dielectric constant (d$\_$33/, d$\_$31/) and electromechanical coupling factor (kp, k$\_$31/) were highest values of 1995, 479, 186(x10$\^$-12/C/N), 0.61, 0.36, respectively. With the addition of MnO$_2$, dielectric constant, electromechanical coupling factor (kp, k$\_$31/) were decreased, but with 0.3wt% MnO$_2$, eletromechanical coupling factor was highest value of 0.63. With the addition of MnO$_2$, mechanical quality(Q$\_$m/ was increased.

• Journal of Korea Foundry Society
• /
• v.28 no.5
• /
• pp.226-230
• /
• 2008

본 논문에서는 공정조성 부근의 Al-Si 합금의 미세구조에 미치는 전자기교반(EMS)의 영향에 대하여 연구하였다. 초정 a 상의 형상에 미치는 전자기교반의 세기의 영향을 조사하기 위하여 각각 교반장치에 60, 80,및 120V의 전압을 가하여 미세조직을 관찰하였다. 60V 이하의 전압이 인가되었을 때 전자기교반의 효과가 나타나지 않은 반면에, 80V 이상의 전압으로 5초 이상 인가되었을 때 구상화된 초정 a 상을 얻을 수 있었다. 인가된 전압이 120V일 때 초정 a 상은 보다 균일한 분포를 가지며 구상화 되었다. 전자기교반의 세기와 함께 교반시간의 영향을 확인하기 위하여 교반시간을 증가시키면서 미세조직을 관찰하였다. 또한 초정 a 상의 형상에 미치는 주조변수의 영향에 대해서도 실험하였다.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.29 no.6
• /
• pp.754-760
• /
• 1996

Effects of washing and additives on the texture of squid surimi gel which has been known to hard to gelation due to high protease activities and many water solubles were studied by SDS-PAGE, compression test, jelly strength and transmission electron microscopy analysis (TEM). Myosin (205 kDa) heavy chain was the major protein in water soluble fractions. It was impossible to make a gel after washing of the minced squid meat. These results suggested that squid (Todarodes pacificus) minced meat does not need a washing for good jelly products. $3.0\%$ of bovine plasma protein (BPP) produced the hardest gel ($16\%$ harder than the control) among the additives including egg white (EW), potato extracts (PE) and transglutaminase-K (TG-K) by compression test (P>0.05). Microstructure of control, $2\%$ EW and $4\%$ TG-K treated gels showed a sponge-like structure with more vacant space. Gels containing $3\%$ BPP formed the most rigid and arranged networks. Those results indicates that poor gel-network formation Was due to the degradation of myofibrillar proteins by proteases contained in the minced meat, which result in non-interlinkage.