• 제목/요약/키워드: Heated glass

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A Study of Crystallization and Fracture Toughness of Glass Ceramics in the ZrO2·SiO2 Systems Prepared by the Sol-Gel Method (졸-겔법으로 제조한 ZrO2·SiO2계 결정화 유리의 결정화 및 파괴인성에 관한 연구)

  • Shin, Dae-Yong;Han, Sang-Mok;Kang, Wie-Soo
    • Journal of Industrial Technology
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    • 제20권A호
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    • pp.247-256
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    • 2000
  • Precursor gels with the composition of $xZrO_2{\cdot}(100-x)SiO_2$ systems (x=10, 20 and 30 mol%) were prepared by the sol-gel method. Kinetic parameters, such as activation energy, Avrami's exponent, n, and dimensionality crystal growth value, m, have been simultaneously calculated from the DTA data using Kissinger and Matusita equations. The crystallite size dependence on tetragonal to monoclinic transformation of $ZrO_2$ was investigated using XRD, in relation to the fracture toughness. The crystallization of tetragonal $ZrO_2$ occurred through 3-dimensional diffusion controlled growth(n=m=2) and the activation energy for crystallization was calculated using Kissinger and Matusita equations, as about $310{\sim}325{\pm}10kJ/mol$. The growth of $t-ZrO_2$, in proportion to the cube of radius, increased with increasing heating temperature and heat-treatment time. It was suggested that the diffusion of Zr4+ions by Ostwald ripening was rate-limiting process for the growth of $t-ZrO_2$ crystallite size. The fracture toughness of $xZrO_2{\cdot}(100-x)SiO_2$ systems glass ceramics increased with increasing crystallite size of $t-ZrO_2$. The fracture toughness of $30ZrO_2{\cdot}70SiO_2$ system glass ceramics heated at $1,100^{\circ}C$ for 5 h was $4.84Mpam^{1/2}$ at a critical crystaliite size of 40 nm.

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Influence analysis of heat treatment on crystalline structure of ZrO2-SiO2 glass precursor synthesized by sol-gel method (졸-겔법으로 합성된 ZrO2-SiO2 유리전구체의 결정화구조에 미치는 열처리의 영향분석)

  • Chun, Kyung-Soo
    • Analytical Science and Technology
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    • 제25권1호
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    • pp.3-6
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    • 2012
  • $xZrO_2-(1-x)SiO_2$ glass precursor with relatively high concentration of zirconium propoxide in metal alkoxide solution was obtained by sol-gel method and then heated at various temperature from 500 to $1,100^{\circ}C$ to investigate the effect of the thermal treatment on the crystalline structure of the glass precursor. Based on X-ray diffraction analysis, the crystalline peak was started to develop at temperature higher than $600^{\circ}C$, and the crystalline phase was considerably increased at $850^{\circ}C$ or higher. With increasing the thermal treatment temperature, the characteristic peaks, such as baddelyite, tetragonal-$ZrO_2$ and zircon, was shown at $35^{\circ}$, $50^{\circ}$ and $60^{\circ}$ of $2{\theta}$.

Effects of post-annealing and seeding layers on electrical properties of PLT thin films by MOCVD using ultrasonic spraying (후열처리 및 seeding 층이 초음파분무 MOCVD법에 의한 PLT 박막 제조 시 전기적 특성에 미치는 영향)

  • 이진홍;김기현;박병옥
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • 제12권5호
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    • pp.247-252
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    • 2002
  • $(Pb_{1-x}La_x)TiO_3$ (x = 0.1) thin films were prepared on ITO-coated glass substrates by metal organic chemical vapor deposition using ultrasonic spraying. Effects of the post-annealing and the seeding layer on crystallization, microstructures and electrical properties of thin films were investigated. Dielectric constants of films increased due to the modification of crystallization and the changing of a surface morphology by applying the post-annealing. In addition, as the application of PT seed- ing layer offered nucleation sites to PLT thin films, electrical properties of films were enhanced by the increase of crys-tallinity and grain size. The dielectric constant of the films post-heated for 60 min and with a seeding layer was 213 at 1 kHz.

Effect of Air Gap Thickness on Top Heat Loss of a Closed-loop Oscillating Heat Pipe Solar Collector

  • Nguyen, Kim-Bao;Choi, Soon-Ho;Yoon, Doo-Ho;Choi, Jae-Hyuk;Oh, Cheol;Yoon, Seok-Hun
    • Journal of Advanced Marine Engineering and Technology
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    • 제33권7호
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    • pp.994-1002
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    • 2009
  • In this paper, effect of air gap thickness between absorber plate and glass cover on top heat loss of a closed loop oscillating heat pipe (CLOHP) solar collector was investigated. The CLOHP, which is made of copper with outer diameter of 3.2mm and inner diameter of 2.0mm, comprises 8 turns with heating, adiabatic and cooling section. The heating section of the heat pipe was attached to absorber plate which heated by solar simulator simulated by halogen lamps. The cooling section of the heat pipe was inserted into collector's cooling section that made of transparent acrylic. Temperatures of absorber plate, glass cover, and ambient air measured by K-type thermocouple and were recorded by MV2000-Yokogawa recorder. Top heat loss coefficients and top heat loss of the collector corresponding to some cases of air gap thickness were determined. The result of experiment shows the optimal air gap thickness for minimum top heat loss of this solar collector.

Micro Mold Fabrication and the Micro Patterning by RTP Process (Micro Mold 제작 및 RTP 공정에 의한 미세 패턴의 성형)

  • Kim H. K.;Ko Y. B.;Kang J. J.;Rhim S. H.;Oh S. I.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 한국소성가공학회 2004년도 추계학술대회논문집
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    • pp.294-297
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    • 2004
  • RTP(Rapid Thermal Pressing) is to fabricate desired pattern on polymer substrate by pressing patterned mold against the substrate heated around glass transition temperature. For a successful RTP process, the whole process including heating, molding, cooling and demolding should be conducted 'rapidly' as possible. As the RTP process is effective in replicating patterns on flat large surface without causing shape distortion after cooling, it is being widely used for fabricating various micro/bio application components, especially with channel-type microstructures on surface. This investigation finally aims to develop a RTP process machine for mass-producing micro/bio application components. As a first step for that purpose, we intended to examine the technological difficulties for realizing mass production by RTP process. Therefore, in the current paper, 4 kinds of RTP machines were examined and then the RTP process was conducted experimentally for PMMA film by using one of the machines, HEX 03. The micro-patterned molds used for RTP experiment was fabricated from silicon wafer by semi-conduct process. The replicated micro patterns on PMMA films were examined using SEM and the causes of defect observed in the replicated patterns were discussed.

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EO Performances of Flexible TN-LCD using in-situ Ultraviolet Exposure during Imidization of Polyimide on the Polymer Film

  • Moon, Hyun-Chan;Hwang, Jeoung-Yeon;Lee, Whee-Won;Seo, Dae-Shik
    • Transactions on Electrical and Electronic Materials
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    • 제6권3호
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    • pp.106-109
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    • 2005
  • We have investigated the generation of pretilt angle for a nematic liquid crystal (NLC) alignment with in-situ photoalignment method on polyimide (PI) surfaces using polymer films. Especially, we studied in-situ photoalignment changing heating temperature from $50^{\circ}C\;to\;120^{\circ}C$ on the polymer film. The LC aligning capabilities and pretilt angle on the polymer substrates were better than those on the glass substrate using in-situ photoalignment method. It is considered that this increase in pretilt angle may be attributed to the roughness of the micro-groove substrate induced by the in-situ photoalignment. As temperature of heated subtrate and UV exposure time increase, pretilt angle of the cell used polymer film increased. It is considered that the heating temperature of substrate is attributed to generate pretilt angle. Also, electro-optical performances of the in-situ photoaligned TN cell using the polymer substrate are almost the same as that of the TN cell using the glass substrate.

A Comparative Analysis on the Thermal Performance of Solar Vacuum Collector Tubes (진공관식 태양열 집열 튜브의 열성능 비교 분석)

  • Hyun, June-Ho;Chun, Won-Gee
    • Journal of the Korean Solar Energy Society
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    • 제23권3호
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    • pp.15-22
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    • 2003
  • This study deals with the collection of solar energy and its storage in evacuated tubular collector systems for different types of header design, flow passage and heat transfer devices. In order to elicit the most efficient combination of header design, flow passage, heat transfer hardware and operating conditions, a series of tests were done for the four different types of solar collectors utilizing vacuum tubes. The systems studied here either has the evacuated collector tubes with a metal cap on one end or the all-glass evacuated solar collector tubes These evacuated tubular collectors are known to be more efficient than the flat-plate ones in both direct and diffuse solar radiation. Test results show that the system comprised of the all-glass evacuated tubes with U-shaped copper pipes inside outperforms the other configurations. Especially, a rolled copper sheet tightly placed along the inner surface of each inner tube enhances heat transfer between the heated collector surface and the water contained in the U-shaped copper pipe.

Synthesis of Monolithic Gel to Bulk glass-Ceramic in Multicomponent Li2O-Al2O3-SiO2 System (Sol-Gel법에 의한 Li2O-Al2O3-SiO2계 괴상겔 및 결정화유리의 합성)

  • 양중식;작화제부
    • Journal of the Korean Ceramic Society
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    • 제25권5호
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    • pp.541-551
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    • 1988
  • The purpose of this investigation was to prepare multicomponent monolithic Li-Al-Si gels of composition(mol%) 16.67 Li2O-16.67 Al2O3-66.67 SiO2 and to convert the gels to monolithic glass-ceramic at low temperature without melting. The hydrolysis, DTA, TGA, TMA, SEM, pore distribution, density and the activation energy for crystallization of the glass-ceramic formation with rawmaterials of which tetraethl orhosilicate of networkforming cation(Si) is partially hydrolyzed, aluminum isoproxide and lithium methoxide prepared by Li-metal react with methanol were studied. The results were as follows : 1) Monolithic gels which were added with additional water, resulting in a total water content 2.5 to 3.0 times the stoichiometric amount required to fully hydrolyze the alkoxides. 2) Specimens were dried to form crylinders 60mm in length and 40mm in diameter in about 800 hrs at 5$0^{\circ}C$. 3) $\beta$-eucryptite crystals and $\beta$-spodumene crystals were detected in samples heated above 75$0^{\circ}C$. 4) Within the temperature and range of 25-50$0^{\circ}C$ and 1,00$0^{\circ}C$ the thermal expansion coefficient for crystallized samples were shown as 2.6-5.7$\times$10-7/$^{\circ}C$ and 7.4-12.5$\times$10-7/$^{\circ}C$, respectively. 5) The activation energy for the crystal growth was 11.01kcal/mol at 794$^{\circ}C$ to 85$0^{\circ}C$.

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HNO3 Etching Properties of BaO-B2O3-ZnO-P2O5 System of Barrier Ribs in PDP (플라스마 디스플레이 패널의 격벽용 BaO-B2O3-ZnO-P2O5계의 HNO3를 이용한 에칭 특성)

  • Jeon, J.S.;Kim, J.M.;Kim, N.S.;Kim, H.S.
    • Korean Journal of Materials Research
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    • 제16권4호
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    • pp.235-240
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    • 2006
  • We investigated the effect of ZnO filler on the microstructure of $BaO-B_2O_3-ZnO-P_2O_5$ glass system to find an etching mechanism of barrier ribs. The sintering behavior of composites heated in the temperature range $560-600^{\circ}C$ was studied by volumetric shrinkage rate and microstructure. The etching test was carried out in $HNO_3$ solution at $50^{\circ}C$ for 10 min. The volumetric shrinkage of sintered sample decreased with the increased firing temperature because of the formation of two crystals. Glass and ZnO filler react forming the $BaZn_2(PO_4)_2$ crystal phases during the sintering process. Etching phenomenon of sintered samples by $HNO_3$ showed that the $BaZn_2(PO_4)_2$ crystal phase was strongly leached compared to glass matrix, crystal phases and fillers. Therefore, the control of interface by condition of sintering is so important to achieve etching effect in barrier ribs.

A Molecular Dynamics Study on the Liquid-Glass-Crystalline Transition of Lennard-Jones System (한 Lennard-jones 시스템의 액체-유리-결정 전이에 관한 분자동역학 연구)

  • Chang, Hyeon-Gu;Lee, Jong-Gil;Kim, Sun-Gwang
    • Korean Journal of Materials Research
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    • 제8권8호
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    • pp.678-684
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    • 1998
  • By means of constant- pressure molecular dynamics simulations, we studied the liquid- glass- crystalline transition of a system composed of Lennard- Jones particles with periodic boundary conditions. Atomic volume and enthalpy were calculated as functions of temperature during heating and cooling processes. The Wendt- Abraham ratio derived from radial distribution function and the angular distribution function characterizing short range order were analyzed to distinguish between liquid, glass and crystalline states. A liquid phase resulting from a slow heating of an initial fee crystal amorphized on fast quench, but it crystallized on slow quench. When slowly heated, the amorphous phase from fast quench crystallized into an fee structure. A system with free surface was shown to melt from the surface inward at a lower temperature than bulk system and to have a strong tendency for crystallization even during a fast quench from a liquid state.

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