• Journal of the Korean Crystal Growth and Crystal Technology
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• v.3 no.2
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• pp.99-106
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• 1993

A relationship $(T_c = -17.869C^2+1840.2C-46623)$ between Curie Temperature$(T_c)$ and (C), $Li_2O$ mole percent(%) was established from the measurement results of Curie temperature $(T_c)$) analysed by DTA(Differential Thermal Analysis) in the range from 48.50 to 49.00 $Li_2O$ mole %. Congruent melt composition of $LiTaO_3$ single crystal was to be 48.65 $Li_2O$ mole % and its Curie temperature was also determined to be $610{\pm}1^{\circ}C$ from the results of Curie temperature difference, ${\Delta}T (T_{c(Top)}-T{_c(Tail)})$ of Czochralski grown $LiTaO_3$ crystals and the distribution coefficient(k). The k was calculated from $LiO_2$ mole ratio of initial melt to final melt and initial crystal to final crystal in the range from 48.60 to 48.70 $Li_2O$ mole %.

• Polymer(Korea)
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• v.24 no.3
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• pp.333-341
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• 2000

Blends consisting of linear shape polylactic acid and star shape polylactic acid (L-PLLA/S-PLLA) have been prepared by melt and solution blending. The effect of blending method on the thermal properties and crystallization behavior of L-PLLA/S-PLLA blends has been investigated. The molecular weight decrease was revealed both in melt and solution blending. S-PLLA was found to be more stable than L-PLLA in the reduction of molecular weight during the course of blending due to its star shape structure. As a result, broad molecular weight distribution was obtained in solution blending. It was found that melting temperature and glass transition temperature decrease with increasing S-PLLA content. Blending method had large influence on the glass transition temperature of PLLA blends, while less effect on melting temperature. From DSC results, it can be noticed that solution blending is more effective blending method to obtain higher crystallinity than melt blending for S-PLLA and blend with higher S-PLLA content.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1365-1372
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• 2001

In the planar flow casting(PFC) process, the conditions of the melt puddle between nozzle and rotating wheel affect significantly the quality and dimensional uniformity of the downstream ribbon. For stable puddle formation, the nozzle is placed very close to the quenching wheel, so the surface-tension and wall-adhesion forces have an important effect upon the fluid flow.\`In this study the planar flow casting process has been mode]ed using the VOF method for free surface tracking. The transient puddle formation from the present analysis shows good agreements with the previous experimental results. Furthermore, the variation of melt temperature and the corresponding cooling rate of the melt have been examined. The present results also show how the melt puddle can be farmed on the rotating substrate, how the melt flows within the puddle, and how the changes of the process variables affect the puddle formation and its corresponding fluid flow and heat transfer behavior.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.3 no.2
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• pp.117-124
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• 1993

It was found that the basic principle of continuous crystal growth method was following as; the powder supplied from the feeding system is molten in the graphite crucible under the ambient gas. After forming the molten zone in the lower part of the crucible, the seed crystal is deeped into the melt and pulled down with the rotation so that the melt crystallized from the seed. When the lowering rate, rotation rate, feeding rate and temperature are correct, the single crystal can grow. The critical melt level, the feeding rate, the growth rate, the change of the shape of molten zone by the graphite susceptor and crucible, the position of work coil, the balance between the gravitational force of melt and the centrifugal force originated from the rotation of seed which are the variables of the crystal growth and the sintering phenomenon of melt surface were researched.

• Polymer(Korea)
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• v.37 no.2
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• pp.204-210
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• 2013

Effects of additives (lubricant and antioxidant) and melt-blending condition (temperature, time and rotor speed) on the mechanical properties of polypropylene-based wood polymer composites (WPCs) were investigated. WPCs were prepared by melt-blending followed by compression molding. To understand melt-blending procedure, torque change of the WPC melt-blend was monitored. Maleic anhydride modified PP and nanoclay were used as a compatibilizer and a reinforcing filler, respectively. UTM and izod impact tester were used to measure the mechanical properties of the WPCs and a color-difference meter was used to measure the discoloration of the WPCs according to melt-blending condition. The mechanical properties showed that the optimized melt-blending condition was $170^{\circ}C$, 15 min, and 60 rpm. The mechanical properties of the WPCs decreased with increasing lubricant and antioxidant content. The two step method, adding wood flour later separately during melt-blending, was more effective than the typical one step method for improving the mechanical properties of the WPCs.

• Journal of Korea Foundry Society
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• v.43 no.6
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• pp.271-278
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• 2023

In the present study, A356 melt degassing experiments were conducted under various impeller rotation speed and inert gas flow rate conditions to determine changes in the melt temperature, composition and density during a degassing treatment. The melt temperature was found to decrease gradually as the degassing time increased, but a clear correlation between the impeller rotation speed or inert gas flow rate and the melt heat loss could not be confirmed. Regardless of the impeller rotation speed or inert gas flow rate, the Mg and Ti contents in the A356 melt scarcely changed, even after degassing for more than 10 minutes, while Sr contents decreased at the maximum degassing rate of 70 ppm. From a quantitative analysis of the degassing rate under each experimental condition based on the hydrogen concentration in the melt derived from the melt density and the degassing model equation, the inert gas flow rate was found to affect the degassing rate rather than the impeller rotation speed under the degassing operation condition employed in the present study.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.06a
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• pp.35-38
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• 1998

The momentum, heat and mass transport in the melt of several sizes of crucibles are calculated using a three dimensional numerical simulation technique with and without the k-$\varepsilon$ turbulent model. When turbulent model is not used, non-axisymmetric profiles of velocity, temperature and oxygen concentration appear in the melt of all sizes of crucibles. Axisymmetric profiles are obtained when the k-$\varepsilon$ model is adopted.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.2
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• pp.206-212
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• 2009

The pressurized spray system with nitrogen gas was designed to fabricate the spherical AN(ammonium nitrate) particles. When AN melt was sprayed from a nozzle with equivalent diameter of 0.28mm into an ambient dry air, the ligament breakup mechanism of the molten AN was found to be responsible for the droplet formation(or disintegration) of AN melt. In the experimental range of spray temperature with $170{\sim}200^{\circ}C$ and atomization pressure with $0.1{\sim}0.4MPa$, the spherical AN particles with mean diameter of $130{\sim}250{\mu}m$ were obtained.

• Journal of Korea Foundry Society
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• v.25 no.2
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• pp.102-108
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• 2005

The ability and fading behavior of inoculant in ductile cast iron melt and the effect of minor element on them were investigated. The result obtanied on nodularization and the performance of inoculant were more distinct when the melt was treated and held at the high temperature range of $1450{\sim}1500^{\circ}C$ than at the lower one of $1350{\sim}1400^{\circ}C$. The performance of 5.2%Mg-Fe-Si alloy was the best of 4 nodularizers. That of Fe-75%Si(I) alloy was better than other 4 inoculants. The performance of the Fe-75%Si(I) inoculant was deteoriated by the addition of sulfur or bismuth. On the other hand, that was improved by the addition of cerium, even though its extent was not big.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1537-1541
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• 2007

We injection molded a wedge type of plate with micro prizm patterns on its surface and investigated the fidelity of replication of the micro pattern depending on the process parameter such as mold temperature, melt temperature, injection rate or packing pressure. The size of the size of the $90^{\circ}$ prizm pattern is $50{\mu}m$ and the size of the plate is about 300㎜${\times}$200㎜. The thicknesses are 2.6㎜. and 0.7mm at each edge of the wedge type of plate. The fidelity of the replication turned out quite different according to the process parameters and location of the patterns on the plate. We measured the cavity pressure and temperature in real-time during the molding to analyze the effect of the local melt pressure and temperature on the micro pattern replication.