• 제목/요약/키워드: Forsterite

검색결과 43건 처리시간 0.025초

Sintering and grain growth in binary forsterite(Mg$_2$SiO$_4$)/spinel (MgAl$_2$O$_4$) system

  • Kim, Sungjin;Han, Young-Hwan;Cho, Kyeong-Sik
    • 한국결정성장학회지
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    • 제11권2호
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    • pp.78-84
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    • 2001
  • The binary forsterite($Mg_2SiO_4$)/spinel ($MgAl_2O_4$) system, a possible refractory for industrial applications, is investigated for their density and grain growth the same firing conditions as the each component material between $1400^{\circ}C$ and $1700^{\circ}C$ ($1650^{\circ}C$). The forsterite grain growth exponent is established to be equal to 5 for all compositions within this binary system. Generally; the spinel addition to forsterite inhibited the forsterite grain growth. The activation energies for the forsterite grain growth of the eight compositions(weight ratio of forsterite/spinel) within the binary system are determined to be: 952$\pm$79(95/5), 363$\pm$37(90/10), 219$\pm$21(80/20), 220$\pm$44(70/30), 112$\pm$16(50/50), 112$\pm$23(30/70), 198$\pm$26(10/90), and 121$\pm$12(5/95) KJ/mol. The more forsterite is contained within the binary system, the higher value the activation energy for forsterite grain growth. It is considered that the forsterite grain growth at the higher forsterite compositions are more inhibited by spinel than that of the lower forsterite compositions.

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고주파용 절록재료로서의 Forsterite 자기에 관한 연구(II) (Forsterite 자기 성질에 미치는 과잉 Mg 성분과 $BaCO_3$의 영향) (A Study on the Forsterite Porcelain as a High Frequency Insulator(II) (Influence of $BaCO_3$, excess MgO on the Properties of Forsterite Porcelain))

  • 이웅상;황성연
    • 한국세라믹학회지
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    • 제19권3호
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    • pp.205-214
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    • 1982
  • The method of lowering the sintering temperature and enlarging the range of sintering temperature in the manufacture of forsterite porcelain as a high frequency insulator was investigated. The four kinds of forsterite chamotte were calcinated at $1400^{\circ}C$. The forsterite bodies produced by adding $BaCO_3$ as a flux and 5% Kaolin as a bonding agent were heated in the range of sintering temperature. Sintering temperature tended to increase almost straightly as MgO exceded without $BaCO_3$. The range of sintering tem was at least $140^{\circ}C$. Specimens of MF-2-0, MF-2-A had superior mechanical strength and dielectric properties. The growing of the forsterite crystal was restricted and thus their grain size became fine and also the amount of crystal formation tended to decrease rapidly as $BaCO_3$ increased excessively.

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생체의용계측을 위한 극초단 Cr4+:Forsterite 레이저의 이론 해석 (Theoritical Analysis of Ultra Short Pulse Cr4+:Forsterite Laser for the Biomedical Applications)

  • 김신자;황대석;이승용;고대영;류광렬;이호근;이영우
    • 한국정보통신학회:학술대회논문집
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    • 한국해양정보통신학회 2004년도 춘계종합학술대회
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    • pp.335-338
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    • 2004
  • 본 논문에서는 생체 계측용 OCT의 광원으로 사용될 광대역 Cr4+:Forsterite 레이저의 동작 특성을 알아보기 위해 이론 해석과 수치 해석을 수행하였다. 수치해석에 사용된 Cr4+;Forsterite 매질 모델은 직경이 3mm이고, 길이는 5mm로 0.04%의 크롬 도핑 농도를 갖는다. 해석 결과에 의해 펌핑 광원이 600mW 일 때 발진하고, 펌핑 광원이 5W 부근일 때 포화된다는 것을 알 수 있었다.

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Forsterite 소지에서 Zirconia 거동에 관한 연구

  • 이정로;이종근;오근호
    • 한국세라믹학회지
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    • 제24권4호
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    • pp.357-363
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    • 1987
  • This study consists of two powder preparation process. One is that the synthesized Forsterite at 1400$^{\circ}C$ mixed with Zirconia powder. Another, theoretical Forsterite composition mixed with Zirconia. These two Forsterite bodies were heat-treated at 1400$^{\circ}C$, 1450$^{\circ}C$. Synthesized Foresterite composition showed higher density, strength than Forsterite composite which was directly mixed with Zirconia KIC value was measured by Microhardness Indentation method. It shows the highest value when 15 weight percent Zirconia dispersed.

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고주파용 절록재료로서의 Forsterite 자기에 관한 연구(III) (Forsterite 자기의 미구조와 열팽창, 비저항과의 관계) (A Study on the Forsterite Porecelain as a High Frequency Insulator(III) (Microstrucrue, Thermal Expansion and Resistivity of the Forsterite Porcelain))

  • 이은상;황성연
    • 한국세라믹학회지
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    • 제20권4호
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    • pp.324-332
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    • 1983
  • In this studies resistivity thermal expansion and microstructure of the Forsterite Porcelain as a high frequency insulator were investigated. The body containing Zn-glass shows higher resistivity than any other body. The bodies containing K, Ba, Cd-glass respectively consist of fine crystals of mosaic type. The bodies containing Bi, Zn, Zr-glass repectively included more large crystals because of the grain growth and coherence of fine particles In the 4 series Forsterite containing excess MgO 0-6% the thermal coefficients of the bodies increased with the increasing of excess MgO and the bodies have conspicuously high thermal expansion coefficients when 15% excess $BaCO_3$ was added to. The resistivities of additive bodies of $BaCO_3$ 0, 5, 10% in Forsterite containg excess MgO 2% are higher than any other that of composition. Bacause the growing of Forsterite crystals was restrained with the increasing of excess MgO $BaCO_3$ their grain size became fine and their grain boundaries were decomposed and also the glass phase having high refractive inder was increased. The higher the firing temperature increased the more the process of crystal growing was progressed.

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고주파용 절연재료로서의 Forsterite 자기에 관한 연구 (I) (Forsterite의 결정질과 유리상) (A Study on the Forsterite Porcelain as a High Frequency Insulator (I) (Crystalline and Glassy Phases of Forsterite))

  • 이웅상;황성연
    • 한국세라믹학회지
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    • 제18권1호
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    • pp.13-22
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    • 1981
  • This study is to investigate the effective mineralizer in the manufacture of forsterite porcelain as a high frequency insulator. A mixture of $Mg(OH)_2$. and $SiO_2$.($\alpha$-Quartz) corresponding to the molar ratio of 2.0 MgO: 1.0 $SiO_2$ was prepared from the materials of high purity. It was heated to 140$0^{\circ}C$ at the rate of 20$0^{\circ}C$/hr, which was kept constantly for 1 hour, and one has made chamotte after cooling. Six kinds of glasses were prepared by an 0.1 atomic equivalent of K ions substitution-Ba, Bi, Zn, Cd, Zr-to the basic K-glass (0.333 $K_2O$.1.14 $SiO_2$) and were melted approximately at 150$0^{\circ}C$. The forsterite bodies were provided by adding each glass (10, 15, 20, 25, 30%) to the forsterite chamotte, which was fired at 1320, 1360, 1400, 144$0^{\circ}C$. (1 hr). One has examined the physical and dielectric properties for the specimens. The results of the experiments are as follows; 1. As for water absorption: Bodies were better vitrified with an addition and temperature change of Ba, Bi, Zn-glasses. The specimen containing Cd-glass showed deviation of slow decreasing, where as K-glass was completely not vitrified. 2. Bodies containing Ba, Zn, Bi-glasses appeared comparatively high Modulus of Rupture at 136$0^{\circ}C$, while containing Zr-glass had the highest Modulus of Rupture as the addition changes remarkably at 140$0^{\circ}C$. 3. It was estimated that 20-25% glass present in a forsterite bodies were in good conditions as for physical properties. 4. Specimens of Ba, Bi, Zr-glasses were superior as for dielectric properties, where among Ba-glass was most excellent. 5. Dielectric constant commonly increases in a slight gradient as firing temperature rises. 6. The petrographic examination showed that the bodies containing Ba, Bi-glasses had fine crystals, and were observed distinctly large mosaic crystals in the Zn-glass.

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Synthesis of Forsterite with High Q and Near Zero TCf for Microwave/Millimeterwave Dielectrics

  • Ohsato, Hitoshi;Ando, Minato;Tsunooka, Tsutomu
    • 한국세라믹학회지
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    • 제44권11호
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    • pp.597-606
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    • 2007
  • With the advent of ubiquitous age, the high quality dielectric materials have been required for the wireless communications available to the millimeterwave as well as microwave frequencies. The utilizable region for the frequency has been expanding to the millimeter-wave region because of the shortage of radio frequency (RF) resources. These high frequencies would be expected for ultra high speed LAN, ETS and car anti-collision system on the intelligent transport system (ITS) and so on. Silicates are good candidates for microwave/millimeterwave dielectrics, because of their low dielectric constant ${\epsilon}_r$ and high quality factor (High Q). Forsterite ($Mg_2SiO_4$) is one of the silicates with low ${\epsilon}_r$ of 6.8 and Q f of 240000 GHz. In this paper, we reviewed following three categories for synthesis of forsterite: (1) Synthesis of high Q forsterite (2) Adjust the temperature coefficient of resonant frequency $TC_f$ (3) Diffusion of $SiO_{4^-}$ and Mg-ions on the formation of forsterite.

포스테라이트계 유전체의 마이크로파 유전특성 (Microwave dielectric properties of Forsterite based Ceramics)

  • 김동영;이홍열;전동석;이상석
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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    • pp.279-282
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    • 2003
  • For the millimeter-wave dielectrics, Forsterite-based ceramics were produced. Pure forsterite ceramics($Mg_2SiO_4$) shows porous micro-structure and very low Q*f values, which is not suitable for the dielectrics for the millimeter-wave band. Several sintering aids including $Al_2O_3$, $Li_2CO_3$, $Li_2SiO_4$, were added to the forsterite ceramics in order to produce dense low-loss dielectrics. Among these additives, $Li_2CO_3$ is the most effective sintering aids. Several sub-components including NiO, ZnO, $SnO_2$, $TiO_2$, were added to enhance the microwave dielectric properties. $TiO_2$ is the most effective additive to enhance the dielectric properties at microwave bands. The simultaneous addition of $TiO_2$ and $Li_2CO_3$ increases Q*f value over 170,000, which can be used as dielectrics in millimeter-wave bands.

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The Synthesis of Vanadium-Doped Forsterite by the $H_2O_2$-Assisted Sol-Gel Method, and the Growth of Single Crystals of Vanadium-Doped Forsterite by the Floating Zone Method

  • 박동곤;Mikio Higuchi;Rudiger Dieckmann;James M. Burlitch
    • Bulletin of the Korean Chemical Society
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    • 제19권9호
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    • pp.927-933
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    • 1998
  • Polycrystalline powder of vanadium-doped forsterite (Vδ $Mg_2SiO_4$) was synthesized by the $H_2O_2$-assisted sol-gel method. The vanadium dopant, which was added as VO$(OMe)_3$ in methanol, went through several redox reactions as the sol-gel reaction proceeded. Upon adding VO$(OMe)_3$ to a mixture of $Mg(OMe)_2$ and Si$(OEt)_4$ in methanol, V(V) reduced to V(IV). As hydrolysis reaction proceeded, the V(IV) oxidized all back to V(V). Apparently, some of the V(V) reduced to V(IV) during subsequent gelation by condensation reaction. The V(IV) remained even after heat treatment of the gel in highly oxidizing atmosphere. The crystallization of the xerogel around 880 ℃ readily produced single phase forsterite without any minor phase. Using the polycrystalline powder as feeding stock, single crystals of vanadium-doped forsterite were grown by the floating zone method in oxidizing or reducing atmosphere. The doping was limited in low level because of the high partitioning of the vanadium in liquid phase during melting. The greenish single crystal absorbed visible light of 700∼1100 nm. But, no emission was obtained in near infrared range.