• Bulletin of the Korean Chemical Society
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• v.21 no.6
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• pp.577-582
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• 2000

Interdiffusion process at interfaces of chemically identical polymers (e.g., deuterated-nondeuterated pairs) with different molecular weights or polymers with similar physical properties, is studied here by varying the diffusion time. Considering the vacancy flux ($J_v$) and adopting the Cahn-Hilliard interracial energy in describing this system, we can see that the variation of the interfacial composition profile with time is asymetric and the interface moves towards the polymer with the lower molecular weight as interdiffusion progresses. Furthermore, interface shift $\Delta\chi$, which characterizes the interdiffusion between polymers, agrees well with the behaviors of the existing experimental data. We can also obtain the interface shift factor C, which can be converted into values of $D_s$ (self-diffusion coefficient of the smaller molecules), from the slopes of the linear fits to the data of the interface shift.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.1
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• pp.134-144
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• 2003

Reactive diffusion couples between Fe-5.8at.%Si and (Si wafer, $FeSi_2$, or FeSi alloy) were heat-treated at 1423k. The only layer of $Fe_3Si$ phase was formed in each diffusion couple. The width of $Fe_3Si$ layer was proportional to square root of diffusion time in each kind of diffusion couple. Growth rate of $Fe_3Si$ layer was relied on the concentration of Si in the supplied source of Si atoms. Interdiffusion coefficient of $Fe_3Si$ has been determined from the derived relation between growth rate constant and interdiffusion coefficient in this work. It was shown that the behavior of Kirkendall's void in $Fe_3Si$ layer was not affected by the kind of Si source. But solid solution $\alpha$ was formed in the diffusion couple between Fe-5.8 at.%Si and $Fe_3Si$ alloy. Kirkendall's voids in diffusional $\alpha$ were neglectively smaller than the case of $Fe_3Si$ phase growth.

• Journal of the Korean Ceramic Society
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• v.52 no.2
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• pp.133-136
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• 2015

The outward diffusion of $Na^+$ ions in iron-bearing soda lime silicate glass via oxidation heat treatment before the ion exchange process is artificially induced in order to increase the amount of ions exchanged during the ion exchange process. The effect of the addition process is analyzed through measuring the bending strength, the weight change, and the inter-diffusion coefficient after the ion exchange process. The glass strength is increased when the outward diffusion of $Na^+$ ions via oxidation heat treatment before the ion exchange process is added. For the glass subjected to the additional process, the weight change and diffusion depth increase compared with the glass not subjected to the process. The interdiffusion coefficient is also slightly increased as a result of the additional process.

• Fibers and Polymers
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• v.2 no.2
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• pp.98-107
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• 2001

The phase transition behavior isothermal micro-phase separation kinetics of polyester-based thermoplastic elastomer were studied using the synchrotron X-ray scattering(SAXS) method. The structural changes occurring during heating period were investigated by determining the changes of the one-dimensional correlation function, interfacial thickness and Porod constant. Based on the abrupt increases of the domain spacing and interfacial thickness, a major structural change occurring well below the melting transition temperature is suggested. Those changes are explained in terms of melting of the thermodynamically unstable hard domains or/and the interdiffusion of the hard and soft segments in the interfacial regions. SAXS profile changes during the micro-phase separation process were also clearly observed at various temperatures and the separation rate was found to be sensitively affected by the temperature. The peak position of maximum scattering intensity stayed constant during the entire course of the phase separation process. The scattering data during the isothermal phase separation process was interpreted with the Cahn-Hilliard diffusion equation. The experimental data obtained during the early stage of the phase separation seems to satisfy the Cahn-Hilliard spinodal mechanism. The transition temperature obtained from the extrapolation of the diffusion coefficient to zero value turned out to be about 147$\pm$$2^{\circ}$, which is close to the order-disorder transition temperature obtained from the Porod analysis. The transition temperature was also estimated from the inveriant growth rate. By extrapolating the inveriant growth rate to zero, a transition temperature of about 145$\pm$$\pm$$2^{\circ}$ was obtained.

• Journal of the Korean institute of surface engineering
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• v.48 no.6
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• pp.260-268
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• 2015

The thermal barrier coating (TBC) for inner wall of liquid-fuel rocket combustor consists of NiCrAlY as bonding layer and $ZrO_2$ as a top layer. In most case, the plasma spray coating is used for TBC process and this process has inherent possibility of cracking due to large difference in thermal expansion coefficients among bonding layer, top layer and metal substrate. In this paper, we suggest crack-free TBC process by using a precise electrodeposition technique. Electrodeposited Ni-P/Cr double layer has similar thermal expansion coefficient to the Cu alloy substrate resulting in superior thermal barrier performance and high temperature oxidation resistance. We studied the effects of phosphorous concentrations (2.12 wt%, 6.97 wt%, and 10.53 wt%) on the annealing behavior ($750^{\circ}C$) of Ni-P samples and Cr double layered electrodeposits. Annealing temperature was simulated by combustion test condition. Also, we conducted SEM/EDS and XRD analysis for Ni-P/Cr samples. The results showed that the band layers between Ni-P and Cr are Ni and Cr, and has no formed with heat treatment. These band layers were solid solution of Cr and Ni which is formed by interdiffusion of both alloy elements. In addition, the P was not found in it. The thickness of band layer was increased with increasing annealing time. We expected that the band layer can improve the adhesion between Cr and Ni-P.