• Journal of the Korean Society for Heat Treatment
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• v.21 no.1
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• pp.26-32
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• 2008

Effects of annealing treatment on microstructure and mechanical property of co-sputtered TiNi thin films were studied. As-deposited films showed amorphous state. However, above annealing temperature of $500^{\circ}C$ martensite phase (B19'), precipitate phase ($Ti_2Ni$) and a small amount of parent phase ($B_2$) were present, and phase transformation behaviors were three multi-step phase transformations $B19^{\prime}{\rightarrow}B_2$ and $B_2{\rightarrow}R-phase$ and $R-phase{\rightarrow}B19^{\prime}$. Increase of martensite transformation temperature, increase of microhardness and Young's modulus of TiNi films annealed above $500^{\circ}C$ were discussed in terms of precipitate phase.

• Journal of Magnetics
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• v.9 no.4
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• pp.101-104
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• 2004

The crystallization behaviours of nanocomposite made by a function of quenching rate (roller speed) were studied. The results showed that there was one step c$\mathbb{r}$ystallization process for the alloy quenched at roller speed of 32 m/s, which could be shown as, Am (amorphouse) + ${\alpha}-Fe/Nd_2Fe_{14}B$ ${\rightarrow}$ ${\alpha}-Fe/Nd_2Fe_{14}B$ . For the alloy quenched at roller speed of 40 m/s, there was steps crystallization process taking place at different temperatures, which could be shown as, Am ${\rightarrow}$ ${\alpha}-Fe/Nd_2Fe_{23}B_3+Nd_2Fe_{14}B+Am`$ ${\rightarrow}$ ${\alpha}-Fe/Nd_2Fe_{14}B$. The presence of transition phase ($Nd_2Fe_{23}B_3$) was harmful to get fine and uniform grain size during crystallization process. Uniform microstructures and high magnetic properties could be attained for the as-quenched alloy containing less amorphous phase and no presence of transition phase during annealing treatment. For the alloy prepared at roller speed of 32 m/s, the following properties were obtained, $B_r= 0.904 T,_iH_c = 801 kA/m, (BH)_{max} = 122 kJ/m^3 and M_r/M_s = 0.6$.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.47-50
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• 1999

The orientation mechanism of an amorphous $Bi_{2}$$Sr_{2}$$Ca_{2 x}$$Cd_{x}$$Cu_{3}$$O_{y}$ phase were studied by using the dilatometry. The amorphous $Bi_{2}$$Sr_{2}$$Ca_{2 x}$$Cd_{x}$$Cu_{3}$$O_{y}$ samples brought about a volume shrinkage at the onset of the crystallization of a $Bi_{2}$$Sr_{2}$$CaCu_{2}$$O_{6}$phase around $400^{\circ}C$. The random crystal growth of $Bi_{2}$$Sr_{2}$$CaCu_{2}$$O_{8}$ phase around $800^{\circ}C$. yielded a rapid volume expansion and after then samples shrinmed, accompanied with the crystal orientation. The$Bi_{2}$$Sr_{2}$$Ca_{2 x}$$Cd_{x}$$Cu_{3}$$O_{y}$ (x=0.4) sample exhibited the best-oriented structure because the liquid phase formed seemed to have the lowest viscosity which would contributed to the easy collapse of the card-house structure.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.6
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• pp.707-712
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• 2005

PRAM (Phase change random access memory) is one of the most promising candidates for next generation Non-volatile Memories. The Phase change materials have been researched in the field of optical data storage media. Among the phase change materials. $Ge_2Sb_2Te_5$ is very well known for its high optical contrast in the state of amorphous and crystalline. However the characteristics required in solid state memory are quite different from optical ones. In this study. the structural Properties of GeSbTe thin films with composition were investigated for PRAM. The 100-nm thick $Ge_2Sb_2Te_5$ and $Sb_2Te_3$ films were deposited on $SiO_2/Si$ substrates by RF sputtering system. In order to characterize the crystal structure and morphology of these films. x-ray diffraction (XRD). atomic force microscopy (AFM), differential scanning calorimetry (DSC) and 4-point measurement analysis were performed. XRD and DSC analysis result of GST thin films indicated that the crystallization of $Se_2Sb_2Te_5$ films start at about $180^{\circ}C$ and $Sb_2Te_3$ films Start at about $125^{\circ}C$.

• Korean Journal of Materials Research
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• v.6 no.8
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• pp.852-857
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• 1996

Crystallization characteristics of titanium oxide thin film during post-annealing of reactive sputter deposition were studied. Amorphous phases of as-deposited films were crystallized into rutile after annealing at $900^{\circ}C$ and anatase at $500^{\circ}C$, respectively when $O_2$ concentration during sputtering was more than 15%. However, rutile was the only phase obtainable after annealing if %$O_2$ was less than 10%. For these films, Magneli phase($Ti_nO_{2n-1}$) were crystallized below $500^{\circ}C$ at first place due to slow oxidation of nonstoichiometric films but $500^{\circ}{\sim}600^{\circ}C$ anatase with nonstoichiometry was crystallized for a short period. It was, therefore, concluded that crystal growth can proceed without phase transition if stoichiometric phase is formed at the first stage of crystallization, and that rutile, the most stable phase, was resulted from any oxygen deficient nonstoichiometric films.

• Applied Chemistry for Engineering
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• v.4 no.1
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• pp.94-102
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• 1993

The effects of temperature and of $Na_2O$ and $SiO_2$ contents on the crystallization of zeolite A were studied, by examining crystallization curves and particle size distributions of final products at various crystallization conditions. Crystallization process could be simulated adopting the assumptions of constant linear growth rate and equilibrium between amorphous solid phase and soluble species. Rate constants were determined by comparing the simulated crystallization curves with experimental data. Rate constant for linear growth increased with temperature and crystallization rate at different mole ratio of $Na_2O/H_2O$ correlated reasonably well with increase of soluble species. The rate constant of crystallization did not increase with increase in mole ratio of $Na_2O/H_2O$, but the rate of nuclei formation and the fraction of soluble species were enhanced. The rate constants for linear growth of zeolite A were determined as $0.07{\sim}0.24{\mu}m{\cdot}min^{-1}$ at these experimental conditions Apparent activation energy was estimated as $49kJ{\cdot}mol^{-1}$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.143-146
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• 1996

In (GeTe)$_{100-x}$(Sb$_2$Te$_3$)$_{x}$(x=33.5, 50, 66.5, 80 at.%) thin films, the optical properties of amorphous and crystalline thin film, XRD were studied. Also, the application for the phase change optical recording materials with the high stability and rapid erasing ability were studied. In the (GeTe)$_{100-x}$(Sb$_2$Te$_{3}$)$_{x}$ the transmittance was decreased with the increase of x. In all thin films, the transmittance was decreased and the reflectance was increased by annealing and particularly, the reflectance before and after annealing showed the large reflectance ratio. The XRD pattern, it was confined that these change of optical properties was due to the crystallization of amorphous thin films. The reflectance change was investigated using isothermal annealing condition.ion.ion.

• Laser Solutions
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• v.8 no.2
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• pp.13-20
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• 2005

Weldability is largely dependent on the phase evolution and the microstructure of the weld. For the weldability of the $Cu_{54}Ni_6Zr_{22}Ti_{18}$ bulk metallic glass, the crystallization affects the sensitivity of the weld to the brittle failure. In order to suppress the irreversible crystallization, Nd:YAG laser welding was chosen. The pulsed Nd:YAG laser was irradiated onto the BMG plate and the effects of the pulse shape [peak power intensity and pulse duration time] on the crystallinity were evaluated.

• Journal of Powder Materials
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• v.25 no.3
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• pp.246-250
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• 2018

In this study, we investigate the deformation behavior of $Hf_{44.5}Cu_{27}Ni_{13.5}Nb_5Al_{10}$ metallic glass powder under repeated compressive strain during mechanical milling. High-density (11.0 g/cc) Hf-based metallic glass powders are prepared using a gas atomization process. The relationship between the mechanical alloying time and microstructural change under phase transformation is evaluated for crystallization of the amorphous phase. Planetary mechanical milling is performed for 0, 40, or 90 h at 100 rpm. The amorphous structure of the Hf-based metallic glass powders during mechanical milling is analyzed using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Microstructural analysis of the Hf-based metallic glass powder deformed using mechanical milling reveals a layered structure with vein patterns at the fracture surface, which is observed in the fracture of bulk metallic glasses. We also study the crystallization behavior and the phase and microstructure transformations under isothermal heat treatment of the Hf-based metallic glass.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.7
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• pp.85-94
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• 1994

A high-resolution transmission electron microscopy study of the solid phase crystallization of the amorphous silicon thin films, deposited on SiOS12T at 52$0^{\circ}C$ by low pressure chemical vapor deposition and annealed at 55$0^{\circ}C$ in a dry N$_{2}$ ambient was carried out so that the arrangement of atoms in the crystalline silicon and at the amorphous/crystalline interface of the growing grains could be understood on an atomic level. Results show that circular crystalline silicon nuclei have formed and then the grains grow to an elliptical or dendritic shape. In the interior of all the grains many twins whose{111} coherent boundaries are parallel to the long axes of the grains are observed. From this result, it is concluded that the twins enhance the preferential grain growth in the <112> direction along {111} twin planes. In addition to the twins. many defect such as intrinsic stacking faults, extrinsic stacking faults, and Shockley partial dislocations, which can be formed by the errors in the stacking sequence or by the dissociation of the perfect dislocation are found in the silicon grain. But neither frank partial dislocations which can be formed by the condensation of excess silicon atoms or vacancies and can form stacking fault nor perfect dislocations which can be formed by the plastic deformation are observed. So it is concluded that most defects in the silicon grain are formed by the errors in the stacking sequence during the crystallization process of the amorphous silicon thin films.