No Jin Park

Effect of Initial Textures on Texture Formation in AA 3004 Sheets during Continuous Confined Strip Shearing and Subsequent Annealing

The effect of initial textures on the texture formation during continuous confined strip shearing (CCSS) and subsequent annealing was investigated in AA 3004 sheets. The CCSS tools were designed to provide a constant shear strain of the order of 0.5 per pass while preserving the original sheet shape. During the CCSS deformation, the initial texture disappeared, and shear texture components developed. However, the intensity of the shear texture components did not further develop with an increasing number of CCSS passes. The softer initial sample depicting the cube texture displayed the evolution of {111}//ND fiber orientations. Upon recrystallization annealing, the textures developed during CCSS were randomized through the suppression of oriented nucleation and selected growth which generally dominate the evolution of recrystallization texture in cold rolled aluminum alloy sheets.

Manufacturing of Cu-15.0Zn-8.1Al Shape Memory Alloy Using Spark Plasma Sintering

In order to control the grain size of Cu-15.0Zn-8.1Al shape memory alloy, the spark plasma sintering (SPS) technique was applied. The sintering processes were carried out under different atmospheres with a different powder size. The sintered bodies were denser under the Ar+4%H2 gas atmosphere than under the 100% Ar gas. By using the small-sized powders, the fine microstructure with average grain size of 2~3 was obtained. With the large-sized powders, the single martensitic phase was observed with the average grain size of 70~72 . When the starting powders with different sizes were mixed, it is confirmed that the average grain size of the manufactured alloys was 15 , but the distribution of grain size was not uniform.

Orientation of Island and Small Grains in Grain Oriented Electrical Steels

Grain oriented electrical steels should have low core loss and high magnetic flux density. These properties are closely related with sharpness of {110} texture after secondary recrystallization. This Goss texture develops by abnormal grain growth during secondary recrystallization annealing. Based on experimental results, a general suggestion which estimates the magnetic properties after secondary recrystallization from a primary recrystallized texture can be made. For a material to have better magnetic properties after secondary recrystallization, its primary recrystallized texture should have not only larger number of ideal Goss grains, but also lower frequency of low angle grain boundary around those Goss grains.

The Properties of ZnO Nanorods for Organic-Inorganic Solar Cell Fabricated by Wet Chemical Method

We made the ZnO nanorods using wet chemical method. it is so simple, economic and suitable for large-scale production, the quality of the arrayed ZnO nanorods fabricated using these methods are not as good as that of nanorods prepared via VLD, CVDand ED method. We demonstrate that the concentration of precursors have influence on the morphology and optical properties, growth density and its distribution of the arrayed ZnO nanorods can be effectively controlled by using suitable conditions. We tried to study suitable ZnO nanorods growth condition to apply to a organic-inorganic hybrid solar cell, and we made the solar cell and investigated the energy conversion efficiency etc.

The Synthesis of Magnetic Nano-Sized Iron Oxide from Liquid Solution by Adding Organic Components

Titanium silicon carbide (Ti3SiC2) is a remarkable material for its combination of the best properties of metals and ceramics. The high purity Ti3SiC2 ceramic has been prepared by infiltration sintering (IS), and the effect of a small amount of Si on Ti3SiC2 ceramic formation was investigated. The results show that the purity of Ti3SiC2 ceramic could be increased significantly and the sintering time for Ti3SiC2 could be decreased remarkably when proper amount of Si was added in the starting mixture. The Ti3SiC2 sintered compact with a purity of 99.2wt% and a relative density of 97% was obtained by the infiltration sintering from a starting mixture composed of n(Ti):n(Si):n(TiC) = 1:0.3:2 at 1500 °C with holding time of 2/3h.

Effect of Rolling Temperature on the Evolution of Microstructure, Texture, and Mechanical Properties of AZ31 Mg Alloy

Magnesium alloys have attracted a great deal of attention and have been extensively studied, but there is still a major obstacle to their practical application, namely, their poor formability at room temperature, which basically originates from their insufficient number of slip systems. The development of a microstructure and/or texture that is more conducive to formability is one promising solution that could improve their formability. In the present work, the microstructures, textures, and tensile properties of AZ31 Mg alloys are studied following extrusion and full annealing and rolling at 100 and 300°C. After full annealing, a strong ∥ED fiber texture and a weak + ∥ED fiber texture (c-axes in the radial direction) were developed. After 40% rolling at 100°C, many deformed twins were observed and a relatively weak texture was developed. The basal poles were split and rotated about 20° to the rolling direction (RD). During 60% rolling at 300°C, dynamic recrystallization (DRX) took place and a strong ∥ND fiber texture was developed, and this had an influence on the alloys’ poor formability at room temperature.

Correlation between Texture at Primary Recrystallized State and Magnetic Properties in Grain Oriented Electrical Steels

Desirable magnetic properties for grain oriented electrical steels are low core loss and high magnetic flux density. These properties are closely related with sharpness of {110} texture. This Goss texture develops by abnormal grain growth during secondary recrystallization annealing. Based on experimental results, a general suggestion which estimates the magnetic properties after completion of secondary recrystallization from a primary recrystallized texture can be proposed. For a material to have better magnetic properties after completion of secondary recrystallization, it should have a primary recrystallized texture in which there are not only large number of ideal Goss grains, but also lower frequency of low angle grain boundary around those Goss grains.

The Influence of 0.1% Sc Addition on the Microstructure and Texture Development in Al-Zn-Mg-Cu-Zr Alloys

In this study, the microstructure and the texture development in Al–Zn–Mg–Cu–Zr alloys with/without 0.1%Sc has been investigated after extrusion, cold rolling, and aging treatment. After aging treatment, in Al alloy without Sc recrystallized equiaxed grains are obtained, while in Al alloy with Sc fine grains with an average size of 0.1~0.3 μm are obtained. After cold rolling, in case of the sample from the cross section (CS) to which Sc was added, texture with {112}<111>(Cu) + weak {123}<634>(S) component was developed while in case of the sample from longitudinal section (LS) to which Sc was added, texture with strong β-fiber + {110}<001>(Goss) components was developed. In case of CS and LS without Sc, texture of β-fiber was developed. After solid solution treatment and aging treatment, Al alloys (LS and CS) with Sc had rolling texture while Al alloys without Sc had random texture. The role of these differently developed textures in the plastic behavior, such as the normal anisotropy r-value (the plastic strain ratio) and planar anisotropy r-values are discussed.

Effect of Film Thickness on the Annealing Texture in Sputtered and Electroplated Cu Films

For optimum fabrication and usage of Cu films, an understanding of the relationship between processing and microstructure is required. The existence of twins is another significant factor for texture development in Cu films. Texture character and strength in the Cu film is dependent on the twin boundary development that is a function of processing conditions and film thickness. In this study, determination of grain growth and texture in the sputtered and electroplated Cu films during annealing was performed for films of 100, 480 and 850 nm in thickness deposited on a Ta(25 nm)/Si wafer. The texture was measured by X-ray pole figure. The effect of film thickness on the annealing texture in the sputtered and electroplated Cu films is examined and discussed.

The Texture Effect on Diffusion Barrier Property on TiN Films between Copper and Si Wafer

TiN thin films are widely used as a coating material due to their good mechanical and conductivity properties, high thermal properties, strong erosion and corrosion resistance. Also TiN has been used in Si devices as a diffusion barrier material for Al and Cu-based metallization. The uniform and dense structure of thin films is influenced by the texture of films. It was good to have uniform and dense structure and bad to have an open columnar structure in TiN thin films. Therefore, the property of diffusion barrier of the TiN films in semiconductor also is related to the texture and microstructure of TiN coated layer. In this study, the relationship between the texture and microstructure and the best diffusion barrier propertiy of TiN coated films (by PVD and MOCVD) on semiconductor devices (Cu/TiN/SiO2/Si layer) were investigated under different processing conditions and textures. The property of diffusion barrier for Cu of physical vapor deposited TiN thin films is better than that of metal organic chemical vapor deposited TiN thin films. Also the property of diffusion barrier for Cu of (111) textured TiN thin films is better than that of (200) textured TiN thin films.