• Title, Summary, Keyword: Gel casting

Search Result 57, Processing Time 0.037 seconds

Fabrication of Silicon Nitride Ceramics by Gel-Casting and Microwave Gas Phase Reaction Sintering(I) : Silicon Gel-Casting (Gel-Casting 및 마이크로파 기상반응소결에 의한 질화규소 세라믹 제조에 대한 연구(I) : Gel-Casting에 의한 실리콘 성형체의 제조)

  • Bai, Kang;Woo, Sang-Kuk;Han, In-Sub;Seo, Doo-Won
    • Journal of the Korean Ceramic Society
    • /
    • v.48 no.5
    • /
    • pp.348-353
    • /
    • 2011
  • By gel-casting, the silicon-polymer green bodies were prepared for silicon nitride ceramics, sintered by microwave gas phase reaction. Considering the viscosity and the idle time of slurries, we decided the operational conditions of related processes, and the optimum concentrations of raw materials powders, organic monomers, cross-linker, dispersant, initiator, and catalyst. So we could get the machinable green bodies, having about 50 MPa of bending strength without cracks by selecting drying conditions carefully.

Effect of Particle Size on Zirconia Gel-Casting Process

  • Kim, In-Woong;Lee, Sang-Jin
    • Journal of the Korean Ceramic Society
    • /
    • v.52 no.6
    • /
    • pp.449-454
    • /
    • 2015
  • The fabrication process of zirconia gel-casting was studied to obtain dense zirconia on a large scale or with complicated shapes. As an experimental parameter, two different particle sizes ($0.1{\mu}m$ and $0.7{\mu}m$) of zirconia powder were applied to the gel-casting process. The viscosity behavior of slurries incorporating 40 vol% of zirconia powder was examined as a function of the dispersant content and the solid load to determine the optimum dispersion conditions. In addition, the gelation time with an initiator, the de-binding behavior, and the main factors affecting densification were examined. The densification of the gel-casted zirconia green body depended on the mixing ratio between the monomer and the dimer and on the zirconia particle size. A green body with a small particle size of $0.1{\mu}m$ showed less densification, with a relative density of 93%. This may be due to the excess number of bubbles created through interactions between the larger particle surface and polymer additives during the ball-milling process.

Processing of Porous Ceramics with a Cellular Structure Using Polymer Beads

  • Ha, Jung-Soo;Kim, Chang-Sam
    • Journal of the Korean Ceramic Society
    • /
    • v.40 no.12
    • /
    • pp.1159-1164
    • /
    • 2003
  • Two processing routes (i.e., the gel casting and polymer preform routes) using polymer beads were studied to fabricate porous ceramics with a cellular structure. The gel casting route, comprising the gel casting of a ceramic slurry mixed with polymer beads, was found to be inadequate to produce porous ceramic bodies with a interconnected pore structure, due to complete coating of the slurry on the polymer beads, which left just isolated pores in the final sintered bodies. The polymer preform route, involving the infiltration of a polymer beads preform with the ceramic slurry, successfully produced porous ceramics with a highly interconnected network of spherical pores. The pore size of 250-300 $\mu\textrm{m}$ was demonstrated and the porosity ranged from 82 to 86%. This process is advantageous to control the pore size because it is determined by the sizes of polymer beads used. Another feature is the avoidance of hollow skeleton, giving a high strength.

Effects of particle size on processing variables and green microstructure in gelcast alumina green bodies (겔-케스팅한 알루미나 성형체에서 출발입도가 공정변수 및 성형 미세구조에 미치는 영향)

  • Ha, Chang-Gi;Kim, Jae-Won;Jo, Chang-Yong;Baek, Un-Gyu;Jeong, Yeon-Gil
    • Korean Journal of Materials Research
    • /
    • v.11 no.10
    • /
    • pp.869-878
    • /
    • 2001
  • Alumina $(Al_2O_3)$ green bodies were fabricated by gel-casting using three kinds of alumina with different particle size (mean particle size: 4.6 $\mu\textrm{m}$, 0.32 $\mu\textrm{m}$, 10nm). The effects of particle size on gel-casting process and green microstructure were investigated. The optimum dispersion conditions using ammonium salt (D-3019) as dispersant were 0.2 wt% (4.63 $\mu\textrm{m}$), 0.5 wt% (0.32 $\mu\textrm{m}$), and 5.0 wt% (10 nm), in high solid loading. The optimum solid loading of each starting material for gel-casting was obtained as 59 vol% (4.63 $\mu\textrm{m}$), 57 vol% (0.32 $\mu\textrm{m}$), 15 vol% (10 nm), depending on particle size, indicating that nano-size particle (10 nm) represent lower solid loading as high specific surface area than those of other two starting materials. The drying at ambient conditions (humidity; $\thickapprox$90%) was performed more than 48hrs to enable ejection of the part from the mold and then at $120^{\circ}C$ for 2hrs in an air oven, showing no crack and flaw in the dried green bodies. The pore size and distribution of the gelcast green bodies showed the significant decrease with decreasing particle size. Green microstructure was dependent on the pore size and distribution due to the particle size, and on the deairing step. The green density maximum obtained was 58.9% (4.63 $\mu\textrm{m}$), 60% (0.32 $\mu\textrm{m}$), 47% (10 nm) theoretical density (TD), and the deairing step applied before gel-casting did not affect green density.

  • PDF

Effect of Additives on Mechanical Properties of Alumina Bushing Fabricated by Gel-Casting

  • Hwang, Kwang-Taek;Cheong, Deock-Soo
    • Journal of the Korean Ceramic Society
    • /
    • v.46 no.6
    • /
    • pp.653-656
    • /
    • 2009
  • Alumina bushing used for manufacturing glass fiber was fabricated by gel-casting which can fabricate complex forms. When solid loading is increased, density was increased and shrinkage and absorption were decreased. The sample loading with 57 vol% solid was optimum for alumina suspension, which showed the best physical properties. The cast sample was sintered at $1550{^{\circ}C}$ for two hours with sintering additive, $Y_2O_3$. The result showed that the alumina bushing with $Y_2O_3$ sintering additive has a density of 98%, shrinkage of 11% and bending strength of 196 kg/$cm^2$.

Morphology and Swelling Behaviors of PVA/Gelatin Blend Membranes Prepared Under High Electric Field (고전장하에서 제조된 PVA/Gelatin 블렌드막의 구조와 팽윤거동)

  • Huh, Yang-Il;Yun, Hyung-Ku
    • Polymer(Korea)
    • /
    • v.30 no.6
    • /
    • pp.563-567
    • /
    • 2006
  • Poly(vinyl alcohol) (PVA) and gelatin (GEL) blend membranes were prepared by solution casting method under a high electric field. SEM observation of the membrane showed that gelatin rich domains were elongated and oriented to the direction of the applied electric field in PVA matrix. This can be attributed to the electrostatic emulsifying effects due to a reduction in interfacial tension. In addition, it was observed through WAXD and swelling measurements that the degree of crystallinity of membranes increased with applied electric field strength. This may be interpreted to be caused by the orientation effect of GEL domains in the blend membrane, and the self-annealing effect due to some heat generated from high electric field during casting.

Microstructures and Drying of the Alumina Green Body by the Gel-Casting Method (Gel-Casting으로 제조한 알루미나 성형체의 건조와 미세구조)

  • 오창준;이홍림
    • Journal of the Korean Ceramic Society
    • /
    • v.31 no.12
    • /
    • pp.1467-1474
    • /
    • 1994
  • The effects of the dispersion, drying, and binder burning-out on the green-microstructures of gelcasted alumina were studied. The slip consisting of 55 vol% alumina powder and 5 wt% organic materials was well-dispersed by adding 0.28 wt% polyelectrolyte polymer. Green bodies were dried at >85% relative humidity at room temperature. Green-microstructures were observed to be depended on the heating rate during binder burnout. Constant drying rate was not observed in drying process of gelcasted alumina. Sintered body showed its relative density higher than 99% when it was sintered at 1$600^{\circ}C$ for 2 hours.

  • PDF

Fabration of PLC susbstrate by slurry filling and sandblasting Method (Tape casting 법과 Sandblasting 법을 이용한 광소자용 기판 제조 (1))

  • Cho, Yun-Hui;Kim, Young-Seog;Lee, Young-Ho
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • /
    • pp.341-345
    • /
    • 2001
  • In this study, nano-sized powders of $Si0_2-0^{\sim}15mol%B_2O_3$ composition were prepared by sol-gel processing method using TEOS(Tetra ethyl ortho silicate) and $H_3BO_3$ solution. The powders were tape-cast on High silicate glass sheet(HSG) substrate and sintered to form a layer of undercladding for the planar light wave module, During the sol-gel processing, $H_2O/Si$ mole ratio were varied to modify the size of the powders in a range from 600 to 75nm. The dispersion of the powder was modified by changing the pH of the slurry. Sintering temperature of the tape was observed to decrease with the size of the powder and the $B_2O_3$ content in the powder. When the silica powders of 75-125nm in diameter containing 15mol% $B_2O_3$ were used, 98 TD% was obtained at $1250^{\circ}C$, which is approximately $300^{\circ}C$ reduction in sintering temperature compared with micrometer-sized powders.

  • PDF

Fabration of PLC susbstrate by slurry filling and sandblasting Method (Tape casting법과 Sandblasting법을 이용한 광소자용 기판 제조 (1))

  • 조윤희;김응석;이용호
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • /
    • pp.341-345
    • /
    • 2001
  • In this study, nano-sized powders of SiO$_2$-0∼15mo1%B$_2$O$_3$ composition were prepared by sol-gel processing method using TEOS(Tetra ethyl ortho silicate) and H$_3$BO$_3$ solution. The powders were tape-cast on High silicate glass sheet(HSG) substrate and sintered to form a layer of undercladding for the planar light wave module. During the sol-gel processing, H$_2$O/Si mole ratio were varied to modify the size of the powders in a range from 600 to 75nm. The dispersion of the powder was modified by changing the pH of the slurry. Sintering temperature of the tape was observed to decrease with the size of the powder and the B$_2$O$_3$ content in the powder. When the silica powders of 75∼125nm in diameter containing 15mo1% B$_2$O$_3$ were used, 98 TD% was obtained at 1250$^{\circ}C$, which is approximately 300$^{\circ}C$ reduction in sintering temperature compared with micrometer-sized powders.

  • PDF