• Title/Summary/Keyword: Crystallization rate

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Crystallization of $K_2O-SiO_2-TiO_2$ Glasses ($K_2O-SiO_2-TiO_2$ 계 유리의 결정화)

  • 김성식;박현수
    • Journal of the Korean Ceramic Society
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    • v.22 no.2
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    • pp.44-50
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    • 1985
  • The crystallization behavior of $K_2O-SiO_2$ glasses with added $TiO_2$ and the effect of $TiO_2$ on internal nuleation at temperature in the range of 875 to 121$0^{\circ}C$ have been investigated by means of X-ray diffractometry optical microscopy and scanning electron microscopy. The crystalline phase of these glasses identified by X-ray diffractometry is cristbalite. The scanning electron microspcopy reveals a two-phase layer of dendritic crystals and intersitial melt which grow from the surface at a constant rate, The observed crystallization rates are consistent with a diffusion-controlled mechanism. An equation relating viscosity and undercooling to growth rate is presented.

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A Study on Pd/Ni Mixed Metal Induced Lateral Crystallization (Pd와 Ni의 혼합물을 촉매로 이용한 금속 유도 측면 결정화에 관한 연구)

  • 최성희;윤여건;주승기
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2003.11a
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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

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SEPARATION OF CsCl FROM LiCl-CsCl MOLTEN SALT BY COLD FINGER MELT CRYSTALLIZATION

  • Versey, Joshua R.;Phongikaroon, Supathorn;Simpson, Michael F.
    • Nuclear Engineering and Technology
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    • v.46 no.3
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    • pp.395-406
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    • 2014
  • This study provides a fundamental understanding of a cold finger melt crystallization technique by exploring the heat and mass transfer processes of cold finger separation. A series of experiments were performed using a simplified LiCl-CsCl system by varying initial CsCl concentrations (1, 3, 5, and 7.5 wt%), cold finger cooling rates (7.4, 9.8, 12.3, and 14.9 L/min), and separation times (5, 10, 15, and 30 min). Results showed a potential recycling rate of 0.36 g/min with a purity of 0.33 wt% CsCl in LiCl. A CsCl concentrated drip formation was found to decrease crystal purity especially for smaller crystal formations. Dimensionless heat and mass transfer correlations showed that separation production is primarily influenced by convective transfer controlled by cooling gas flow rate, where correlations are more accurate for slower cooling gas flow rates.

Crystallization of Borosilicate Glasses for High-Strength Bulletproof Materials (고강도 방탄소재를 위한 Borosilicate 유리의 결정화)

  • Lee, Hyun-Suk;Shim, Gyu-In;Choi, Se-Young
    • Journal of the Korea Institute of Military Science and Technology
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    • v.16 no.3
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    • pp.358-364
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    • 2013
  • Borosilicate glass(GVB-Solutions in glass, 2mm, Germany) was prepared in the composition of $80.4SiO_2-4.2Na_2O-2.4Al_2O_3-13.0B_2O_3$. The 2-step crystallization was performed around $584^{\circ}C$ of glass transition temperature ($T_g$), and $774^{\circ}C$ of crystallization temperature($T_c$). The maximum nucleation rate was $8.8{\time}10^9/mm^3{\cdot}hr$ at $600^{\circ}C$ and the maximum crystal growth rate was 3.5nm/min at $750^{\circ}C$. The maximum mechanical properties were observed at 22.8% of volume fraction, the strength, hardness and fracture toughness was 555MPa, $752kg/mm^2$, $1.082MPa{\cdot}mm^{1/2}$. The crystal size of 177nm which has volume fraction of 22.8% showed maximum strength of 562MPa, it is about 157% higher than parent borosilicate glass. From these results, the crystallized borosilicate glass can be applied weight lighting of bullet proof materials.

Copolyester Studies (6) Thermal Properties of Poly(Ethylene Terephthalate) Modified by 5-Sulfoisophthalic Acid Sodium Salt (Polyester의 개질에 관한 연구 (6) 5-Sulfoisophthalic Acid Sodium Salt 로 개질된 Poly(Ethylene Terephthalate)의 열적 성질)

  • Tae Oan Ahn;Han Mo Jeong
    • Journal of the Korean Chemical Society
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    • v.31 no.6
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    • pp.582-589
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    • 1987
  • The thermal properties of poly (ethylene terephthalate) (PET) modified by 5-sulfoisophthalic acid sodium salt(SIAS) were studied. The glass transition temperature was increased, and the melting temperature and the crystallization rate were decreased as the content of SIAS unit was increased. The decrease of crystallization rate is thought to be due to the polar, bulky sulfonic acid sodium salt group which greatly retards the crystallization on to the growing crystal surface of the diffused polymer chain. The crystallization mechanism of copolyester is dependent on the content of SIAS unit and the three dimensional growth of crystal is hindered by the added SIAS unit.

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Reuse Technology of LiCl Salt Waste Generated from Electrolytic Reduction Process of Spent Oxide Fuel (전해환원공정발생 LiCl 염폐기물 재생기술)

  • Cho, Yung-Zun;Jung, Jin-Seok;Lee, Han-Soo;Kim, In-Tae
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.8 no.1
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    • pp.57-63
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    • 2010
  • Layer crystallization process was tested for the separation(or concentration) of cesium and strontium fission products in a LiCl waste salt generated from an electrolytic reduction process of a spent oxide fuel. In a crystallization process, impurities (CsCl and $SrCl_2$) are concentrated in a small fraction of the LiCl salt by the solubility difference between the melt phase and the crystal phase. Based on the phase diagram of LiCl-CsCl-$SrCl_2$ system, the separation possibility by using crystallization was determined and the molten salt temperature profile during layer crystallization operation was predicted by using mathematical calculation. In the layer crystallization process, the crystal growth rate strongly affects the crystal structure and therefore the separation efficiency. In the conditions of about 20-25 l/min cooling air flow rate and less than 0.2g/min/$cm^2$ crystal flux, the separation efficiency of both CsCl and $SrCl_2$ showed about 90% by the layer crystallization process, assuming a LiCl salt reuse rate of 90wt%.

Crystallization Behavior of Poly(ethylene terephthalate)/Ethylene-Methyl acrylate-Glycidyl methacrylate Copolymer Blend (폴리에틸렌테레프탈레이트/에틸렌-메틸아크릴레이트-글리시딜 메타크릴레이트 공중합물 블렌드의 결정화 거동)

  • 성상엽;이종관;이광희;진병석
    • Polymer(Korea)
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    • v.25 no.6
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    • pp.848-854
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    • 2001
  • The crystallization behavior of poly (ethylene terephthalate) (PET) /ethylene-methyl acrylate-glycidyl methacrylate copolymer (E-MeA-GMA) blend was studied. The extent of reaction and the reaction rate between PET and E-MeA-GMA were measured with torque rheometer, FT-IR and SEM. The effects of the grafting reaction on the crystallization behavior were investigated with DSC and time-resolved light scattering (TR-LS) techniques. The morphological change at the lamellar level was also examined by using a small angle X-ray scattering (SAXS) method.

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Solid Phase Crystallization Kinetics of Amorphous Silicon at High Temperatures

  • Hong, Won-Eui;Kim, Bo-Kyung;Ro, Jae-Sang
    • Journal of the Korean institute of surface engineering
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    • v.41 no.2
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    • pp.48-50
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    • 2008
  • Solid phase crystallization (SPC) of amorphous silicon is usually conducted at around $600^{\circ}C$ since it is used in the application of flat panel display using thermally susceptible glass substrate. In this study we conducted SPC experiments at temperatures higher than $600^{\circ}C$ using silicon wafers. Crystallization rate becomes dramatically rapid at higher temperatures since SPC kinetics is controlled by nucleation with high value of activation energy. We report SPC kinetics of high temperatures compared to that of low temperatures.

Crystallization Kinetics of $PbO-TiO_2-SiO_2-B_2O_3$ Glasses by DSC (DSC에 의한 $PbO-TiO_2-SiO_2-B_2O_3$계 유리의 결정화 속도)

  • 손명모;이승호;이헌수;박희찬
    • Journal of the Korean Ceramic Society
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    • v.32 no.12
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    • pp.1331-1336
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    • 1995
  • The glass-ceramics for ferro-electric were made from compositions of 70PbO.16TiO2.8SiO2.4B2O3.2AlPO4 (wt%) and 67.5PbO.20TiO2.8.5SiO2.2B2O3.2AlPO4 (wt%). The crystallization kinetics for PbTiO3 crystalline phase formation from glass was studied using non-isothermal DSC techniques. The values of activation energy, ΔE using variables of heating rate and temperature were calculated at various reaction fractions obtained from peak area over DSC. The results indicated that activation energy was lowest at 60% reaction fractions and the activation energy of glass containing 20.0 wt% TiO2 is higher than that of glass containing 16.0 wt% TiO2. The crystallization mechanism was three dimensional growth (n=4).

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Effects of nucleating agents and plasticizers on the crystallinity and crystal structure of PLA(PolyLactic Acid) (핵제 및 가소제 첨가에 따른 PLA(PolyLactic Acid)의 결정화도 개선 및 결정구조에 관한 연구)

  • Park, Eun-Jo;Park, Hern-Jin;Kim, Dong-Hak
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.1
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    • pp.914-920
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    • 2015
  • In this paper, the crystal structure and the crystallinity of PLA(PolyLactic Acid) were studied. PLA is a eco-friendly thermoplastic which completely decomposed by microorganisms, but has low thermal stability and low degree of crystallinity. The low crystallization rate makes the cycle time of injection molding longer and the degree of crystallinity lower. It is a very big disadvantage comparing the other thermoplastics. We improved the degree of crystallinity and the crystallization rate by introducing nucleating agents and plasticizer, and discussed the mechanism.