• International Journal of Fluid Machinery and Systems
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• 제7권2호
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• pp.54-59
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• 2014

Particle Image Velocimetry combined with developed image processing method is adopted to study the liquid-solid two phase flow in the centrifugal pump impeller with crystallization phenomenon. The tracer particle is used to follow the liquid phase, which has the diameter between 8 to $12{\mu}m$. The crystal particle precipitates from the sodium sulfate solution does change the wavelength of the laser, and which has great laser scattering characteristics. The diameter of the crystal particle is larger than $20{\mu}m$. Through calculating the diameter of the particles in the image, the tracer particle and the crystal particle can be distinguished. By analyzing the experimental result, the following conclusion has been obtained. During the delay period, there is not any crystal particle and the pump performance has not been changed. As the crystallization process begins, the crystal nuclei appears from the supersaturation solution and grows larger with temperature decreasing, which has the tendency of moving towards the pressure side. The characteristics of liquid-solid two phase flow with crystallization phenomenon in the pump are obtained according to analysis of experimental results, and some guiding advices are presented to mitigate the crystallization phenomenon in pump impeller.

• Carbon letters
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• 제7권2호
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• pp.87-96
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• 2006

This paper describes the physical properties of filled Nylon6 composites resin with nano-sized carbon black particle and graphite nanofibers prepared by melt extrusion method. In improving adhesions between resin and fillers, the surface of the carbon filler materials were chemically modified by thermo-oxidative treatments and followed by treatments of silane coupling agent. Crystallization temperature and rate of crystallization increased with increases in filler concentration which would act as nuclei for crystallization. The silane treatments on the filler materials showed effect of reduction in crystallization temperature, possibly from enhancement in wetting property of the surface of the filler materials. Percolation transition phenomenon at which the volume resistivity was sharply decreased was observed above 9 wt% of carbon black and above 6 wt% of graphite nanofiber. The graphite nanofibers contributed to more effectively in an increase in electrical conductivity than carbon black did, on the other hand, the silane coupling agent negatively affected to the electrical conductivity due to the insulating property of the silane. Positive temperature coefficient (PTC) phenomenon, was observed as usual in other composites, that is, temperature increase results conductivity increase. The dispersity of the fillers were excellently approached by melt extrusion of co-rotational twin screw type and it could be illustrated by X-ray diffraction and SEM.

• 한국결정성장학회지
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• 제12권4호
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• pp.210-214
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• 2002

$450^{\circ}C$ 이하에서 Cu를 이용한 전계 유도 방향성 결정화 공정을 통해 비정질 실리콘의 결정화 거동을 고찰하였다. 열처리와 동시에 전계를 인가하여 Cu가 증착된 패턴의 외부에서 Cu가 존재하지 않는 비정질 실리콘의 영역으로 측면 결정화를 유도하였다. 특히, Cu가 존재하지 않는 영역의 측면결정화는 (-) 전극 쪽에서 (+) 전극 쪽으로 방향성을 가지고 결정화가 진행되었다. 이러한 현상은 Cu와 Si가 반응 할 때, 주확산 종이 금속(Cu)이기 때문에 가능하다고 판단되었다. 또한, FALC 공정을 이용한 $350^{\circ}C$의 온도에서 결정화된 영역 내에 커다란 dendrites 형태의 가지가 형성되었고 전계 방향에 따른 측면 결정화가 진행되었음을 확인하였다. 결론적으로 $350^{\circ}C$의 매우 낮은 온도에서 30 V/cm의 전계 인가를 통해 12$\mu$m/h의 결정화 속도로 결정화가 가능함을 확인하였다.

• 한국세라믹학회지
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• 제29권12호
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• pp.956-962
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• 1992

The predominant sintering mechanisms of low firing temperature ceramic substrate which consists of borosilicate glass containing alumina as a filler are the rearrangement of alumina particles and the viscous flow of glass powders. In this system, sintering condition depends on the volume ratio of alumina to glass and on the particle size. When the substrate contains about 35 vol% alumina filler and the average alumina particle size is 4 $\mu\textrm{m}$, the best firing condition is obtained at the temperature range of 900∼1000$^{\circ}C$. The extensive rearrangement behavior occurs at these conditions, and the optimum sintering condition is attained by smaller size of glass particles, too. The formation of cristobalite during sintering causes the difference of thermal expansion coefficient between the substrate and Si chip. This phenomenon degradates the capacity of Si chip. Therefore, the crystallization should be prevented. In the alumina filled borosilicate glass system, the crystallization does not occur. This effect may have some relation with aluminum ions in alumina. For aluminum ions diffuse into glass matrix during sintering, functiong as network former.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.172-172
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• 2003

It has been known that Pd-MILC shows much faster and lower temperature crystallization than Ni-MILC but it can not be put into practice due to the quality issue of thus fabricated poly crystals. In this study, addition of Pd into Ni-MILC has been attempted in order to take advantages of the Pd-MILC without sacrificing of the Ni-MILC TFTs. It turns out that when 5% of Pd has been added to Ni for MILC, MILC growth rate increases two - three times faster than pure Ni-MILC. The MILC growth rate shows monotonic increase with increase the amount of Pd in Ni up to 50%. Even when small amount of Pd was added to Ni like 5%, crystallization phenomenon already follows the way of Pd-MILC. The Poly-W thus fabricated shows lower leakage current than pure Ni-MILC TFT without losing any amount of on-current This fact is very important in low temperature poly-TFTs because MILC-TFTs, especially suffer from the relatively high leakage current

• Macromolecular Research
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• 제8권3호
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• pp.103-115
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• 2000

The structural changes viewed from the molecular level have been investigated for the isothermal crystallization phenomena of polyethylene (PE) and the solvent-induced crystallization phenomenon of syndiotactic polystyrene (sPS) glassy sample. The data, which were collected by the time-resolved measurements of Fourier-transform infrared spectra, Raman spectra, synchrotron-sourced small-angle X-ray scattering, wide-angle X-ray scattering, and so on, were combined together to extract the detailed structural information in these phase transition phenomena. In the case of PE, the isothermal crystallization from the melt to the orthorhombic form was found to occur via the conformationally-disordered trans chain form, followed by the formation of the lamellar stacking structure of regular orthorhombic-type crystals. In the case of sPS, the amorphous chains in the glassy sample were found to enhance the mobility through the interaction with the injected solvent molecules, which act as a trigger to cause the conformational ordering from the random coil to the regular T$_2$G$_2$-type helical form. The thus created short helical segments were found to grow into longer helices, which gathered together to form the crystallites, as revealed by the organized coupling of the infrared, Raman and X-ray scattering data.

• 한국세라믹학회지
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• 제33권6호
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• pp.653-659
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• 1996

• 한국세라믹학회지
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• 제41권8호
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• pp.578-581
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• 2004

본 연구에서는 Palladium-Metal Induced Lateral Crystallization(Pd-MILC)과 Nickel-Metal Induced Lateral Crystallization (Ni-MILC)을 동시에 사용하여 Ni-MILC의 결정화 속도를 향상시키는 방법을 제안하였다 이 방법을 사용하여 기존의 Ni-MILC 보다 거의 4배나 빠른 결정화 속도인 15 $\mu$m/h를 얻을 수 있었다. Ni과 Pd의 간격이 좁을수록 Ni-MILC의 결정화 속도가 더 빨라졌으며 Pd두께, Ni두께에, 비정질 실리콘 너비와는 큰 의존관계가 없었다. 하지만 Pd이 Ni에 의해 덮혀져 Pd-MILC가 일어나지 못하는 경우에는 이러한 현상이 발견되지 않았다. 이는 Pd물질 그 자체가 Ni-MILC를 향상시키는 것이 아니라 Pd MILC가 진행되면서 발생하는 tensile stress에 의해 향상되는 것임을 의미한다. 이와 같은 현상들을 새로운 MILC mechanism으로 설명하였다.

• Advances in nano research
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• 제10권3호
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• pp.211-219
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• 2021

The evaluation of the corrosion resistance of titanium with a TiO2 nanotubes top layer was carried out (TiO2 NT). These nanostructures were evolved into anatase nanoparticles without heat treatment in an aqueous medium, which is a novel phenomenon. This work analyzes the layer between the nanotube bottom and the substrate, which is thin and still susceptible to corrosion. The bottom of TiO2 nanotubes having Fluor resulting from the synthesis process changed between amorphous to crystalline anatase with a crystallite size of about 4 nm, which influenced the corrosion rates. Four kinds of samples were evaluated. A) NT by Ti anodizing; B) NTSB for Ti plates, either modifying its surface or anodizing the modified surface; C) NT-480 for anodized Ti and heat-treated (480℃) for reaching the anatase phase; D) NTSB-480 for Ti plates, first, modifying its surface using sandblast, after that, anodizing the modified surface, and finally, heat-treated to 480℃ to compare with samples having induced crystallization and passivation. Four electrochemical techniques were used to evaluate the corrosion rates. The surfaces having TiO2 nanotubes with a sandblast pre-treatment had the highest resistance to corrosion.

• Acta Via Serica
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• 제3권1호
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• pp.11-25
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• 2018

The Renaissance is generally said to be the rebirth of the ancient civilizations of Greece and Rome, and was centered around Italy from the 14th to the 16th century. This includes the temporal peculiarity of the Renaissance as a sudden phenomenon after the Medieval Ages, and the spatial peculiarity of what happened only in Europe. However, if we remove the European-centered bias here, the horizon for interpreting the Renaissance becomes much wider. There have been claims that similar cultural phenomena resembling the Renaissance existed in other civilizations at the same time. This paper seeks to investigate two possibilities. The first is the possibility of a spatial expansion of the Renaissance. This suggests that the Renaissance was created by long-term exchanges with the Eastern, Middle and Western Hemispheres. The second is the possibility of a simultaneity of the Renaissance in the 14th and 16th centuries. This suggests that it was a global phenomenon that occurred in different civilizations. The Renaissance, therefore, was a crystallization of a complex of civilizations created by the crossing of various cultures along the Silk Road, and should be referred to as the 'Global Renaissance' instead of the 'Western Renaissance.'