• Title/Summary/Keyword: ceramic particles

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Effect of the Raw Material and Coating Process Conditions on the Densification of 8 wt% Y2O3-ZrO2 Thermal Barrier Coating by Atmospheric Plasma Spray

  • Oh, Yoon-Suk;Kim, Seong-Won;Lee, Sung-Min;Kim, Hyung-Tae;Kim, Min-Sik;Moon, Heung-Soo
    • Journal of the Korean Ceramic Society
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    • v.53 no.6
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    • pp.628-634
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    • 2016
  • The 8 wt% yttria($Y_2O_3$) stabilized zirconia ($ZrO_2$), 8YSZ, a typical thermal barrier coating (TBC) for turbine systems, was fabricated under different starting powder conditions and coating parameters by atmospheric plasma spray (APS) coating process. Four different starting powders were prepared by conventional spray dry method with different additive and process parameter conditions. As a result, large- and small-size spherical-type particles and Donut-type particles were obtained. Dense structure of 8YSZ coating was produced when small size spherical-type or Donut-type particles were used. On the other hand, 8YSZ coating with a porous structure was formed from large-size spherical-type particles. Furthermore, a segmented coating structure with vertical cracks was observed after post heat treatment on the surface of dense structured coating by argon plasma flame at an appropriate gun distance and power condition.

Magnetic Abrasive Polishing Technology with Ceramic Particles (세라믹 입자를 이용한 자기연마가공 기술 사례)

  • Kwak, Tae-Soo;Kwak, Jae-Seob
    • Journal of the Korean Society for Precision Engineering
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    • v.30 no.12
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    • pp.1253-1258
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    • 2013
  • Ceramic particles as polishing abrasives are often used in a magnetic abrasive polishing process because they have strong wear resistance. Non-ferromagnetic ceramic abrasives should be mixed with ferromagnetic iron particles for controlling the mixture within a magnetic brush during the polishing process. This study describes the application of the ceramic particles for the magnetic abrasive polishing. The distribution of the magnetic abrasives attached on a tool varies with magnetic flux density and tool rotational speed. From the correlation between abrasive adhesion ratio in the tool and surface roughness produced on a workpiece, practical polishing conditions can be determined. A step-over for polishing a large sized workpiece is able to be selected by a S curve, and an ultrasonic vibration assisted MAP produces a better surface roughness and increases a polishing efficiency.

Evaluation of Microstructure and Mechanical Property of a Novel Ceramic Salt Core (세라믹 용융코어의 미세조직과 기계적 특성)

  • Lee, Jun-Ho;Lee, Dock-Young
    • Journal of Korea Foundry Society
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    • v.28 no.4
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    • pp.166-169
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    • 2008
  • This study deals about the development of fusible core with low melting temperature by addition of ceramic particles. A new concept of salt core was introduced to produce an integrated casting part having a complicated inner shape or requiring under-cut in high pressure die casting or squeeze casting process. The mechanical properties of fusible core were improved due to the addition of ceramic particles which helped to produce fine microstructure. The new technology for the preparation of new fusible core materials which possess high compression strength was established. Addition of ceramics particles increased the mechanical properties of fusible core materials. There was an increasing relationship between percentage of ceramic particles and mechanical strength was existed up to 60%.

Preparation and Characterization of a Layered Organic-inorganic Composite by the Electrophoretic Deposition of Plate-shaped Al2O3 Particles and Electrophoretic Resin (전기영동적층법을 통한 판상 알루미나 입자와 전기영동 수지의 배향 유무기 복합체 제조 및 물성평가)

  • Park, Hee Jeong;Lim, Hyung Mi;Choi, Sung-Churl;Kim, Younghee
    • Journal of the Korean Ceramic Society
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    • v.50 no.6
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    • pp.460-465
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    • 2013
  • Plate-shaped inorganic particles are coated onto a stainless steel substrate by the electrophoretic deposition of a precursor slurry which includes the inorganic particles of $Al_2O_3$ and polymer resin in mixed solvents to mimic the abalone shell structure, which is a composite of plate-shaped inorganic particles and organic interlayer binding materials with a layered orientation. The process parameters of the electrophoretic deposition include the voltage, coating time, and conductivity of the substrate. In addition, the suspension parameters are the particle size, concentration, viscosity, conductivity, and stability. We prepared an organic-inorganic composite coating with a high inorganic solid content by arraying the plate-shaped $Al_2O_3$ particles and electrophoretic resin via an electrophoretic deposition method. We analyzed the effect of the slurry composition and the electrophoretic deposition process parameters on the physical, mechanical and thermal properties of the coating layer, i.e., the thickness, density, particle orientation, Young's modulus and thermogravimetric analysis results.

Synthesis of Ceria Nanosphere by Ultrasonic Spray Pyrolysis

  • Kim, Jong-Young;Kim, Ung-Soo;Cho, Woo-Seok
    • Journal of the Korean Ceramic Society
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    • v.46 no.3
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    • pp.249-252
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    • 2009
  • Nanocrystalline ceria particles were prepared by using the ultrasonic spray pyrolysis method. The prepared ceria particles were found to be spherical and non-agglomerated by the SEM and TEM analyses. It was found that carrier gas influences the size and morphology. It was found that the air stream of carrier gas results in porous agglomerated structure of ceria abrasives, whereas solid nano-sphere can be obtained in a more oxidizing atmosphere.

Formation of Asperites on the Plate-like Alumina Particles by Molten-salt Method (Molten-salt 방법에 의해 합성되는 판상형 알루미나 분말 표면에 돌기형성 거동)

  • Lee, Yoon Joo;Kim, Bo Yeon;Shin, Dong-Geun;Kim, Soo Ryong;Kwon, Woo Teck;Kim, Younghee
    • Journal of the Korean Ceramic Society
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    • v.51 no.6
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    • pp.560-565
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    • 2014
  • Alumina nano-asperites were grown on plate-like alumina particles of which the surface had been covered with a capping agent to control the asperite formation sites on the particles. Utilized alumina source for asperite was nano sized ${\gamma}$-alumina, which was prepared by calcination of $Al(OH)_3$ at $600^{\circ}C$; silica suspension was used as the capping agent. Plate like alumina particles were covered by silica suspension and continuously heat-treated to $900^{\circ}C$ with nano sized ${\gamma}$-alumina, as the source material, under molten-salt atmosphere. Asperite growing site were controlled by the degree of coating of the capping agent; 10-20 nanosize of ${\theta}$-alumina were formed on the particle surface. On the other hand, alumina particles without capping agent were observed to undergo only step-like crystal growth during heat-treatment.

A Study on Packing of Regular Particles - Preparation of Dense Sintered Silicon Carbide (1) - (규칙입자의 충전 -치밀된 탄화규소 소결체의 제조(제 1 보)-)

  • 문병훈;남건태;최상욱
    • Journal of the Korean Ceramic Society
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    • v.31 no.9
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    • pp.989-994
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    • 1994
  • This study aims at finding the closest packings of regular shape particles such as sphere, circle rod and hexagonal rod type. As the ratio of particle size to container lowered to less than 1/10, the wall effect decreased gradually. The tap density of spherical particles with almost orthorhombic arrangement was 59.5%, while those of circle rod and hexagonal rod type particles were 63.5% and 63.0% respectively. And it was decreased with increasing the aspect ratio of regular particles. The tap density of binary mixtures was larger than that corresponding to the monosized particles packing by about 15%. The tap density of ternary mixtures was larger than that of corresponding to the packing of binary mixtures by about 9%. This work employed the binary mixture of 60% coarse particles and 40% fine particles with size ratio of 1.0 to 1/10 and the ternary mixture of 60% coarse particles, 20% medium and 20% fine particles with size ratio of 1:1/10:1/400 respectively.

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Distribution Analysis of TRISO-Coated Particles in Fully Ceramic Microencapsulated Fuel Composites

  • Lee, Hyeon-Geun;Kim, Daejong;Lee, Seung Jae;Park, Ji Yeon;Kim, Weon-Ju
    • Journal of the Korean Ceramic Society
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    • v.55 no.4
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    • pp.400-405
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    • 2018
  • FCM nuclear fuel, a concept proposed as an accident tolerant fuel in light water reactors, consists of TRISO fuel particles embedded in a SiC matrix. The uniform dispersion of internal TRISO fuel particles in the FCM fuel is very important for improving the fuel efficiency. In this study, FCM sintered pellets with various volume ratios of TRISO-coated particles were prepared by hot press sintering. The distribution of TRISO-coated particles was quantitatively analyzed using X-ray ${\mu}CT$ and expressed as a dispersion uniformity index. TRISO-coated particles were most uniformly dispersed in the FCM pellets prepared using only overcoated TRISO particles without mixing of additional SiC matrix powder. FCM pellets with uniformly dispersed TRISO particle volume fraction of up to 50% were prepared using overcoated TRISO particles with varying thickness.

Sintering and Characterization of SiC-matrix Composite Including TRISO Particles (TRISO 입자를 포함하는 SiC 복합소결체의 소결 및 특성 평가)

  • Lee, Hyeon-Geun;Kim, Daejong;Park, Ji Yeon;Kim, Weon-Ju
    • Journal of the Korean Ceramic Society
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    • v.51 no.5
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    • pp.418-423
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    • 2014
  • Fully ceramic micro encapsulated (FCM) nuclear fuel is a concept recently proposed for enhancing the stability of nuclear fuel. FCM nuclear fuel consists of tristructural-isotropic (TRISO) fuel particles within a SiC matrix. Each TRISO fuel particle is composed of a $UO_2$ kernel and a PyC/SiC/PyC tri-layer which protects the kernel. The SiC ceramic matrix is created by sintering. In this FCM fuel concept, fission products are protected twice, by the TRISO coating layer and by the SiC ceramic. The SiC ceramic has proven attractive for fuel applications owing to its low neutron-absorption cross-section, excellent irradiation resistivity, and high thermal conductivity. In this study, a SiC-matrix composite containing TRISO particles was sintered by hot pressing with $Al_2O_3-Y_2O_3$ additive system. Various sintering conditions were investigated to obtain a relative density greater than 95%. The internal distribution of TRISO particles within the SiC-matrix composite was observed using an x-ray radiograph. The fracture of the TRISO particles was investigated by means of analysis of the cross-section of the SiC-matrix composite.

Adsorption of Colloidal Silica Particles on a Glass Substrate

  • Sim, Soo-Man
    • Journal of the Korean Ceramic Society
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    • v.39 no.11
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    • pp.1011-1016
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    • 2002
  • Colloidal particles of silica (100 nm in size) were electrostatically dispersed and adsorbed on a glass substrate coated with silica sol or alumina sol. Stability of the suspensions and microstructure of the adsorbed particle layers were discussed in terms of total potential energies between the particles and the substrate. Well-dispersed suspension resulted in a layer with densely packed and regularly arranged particles, whereas less stable suspension resulted in a porous layer with loosely packed and irregularly arranged particles. Despite repulsive interactions between the particles and the substrate coated with silica sol, the observed adsorption can be attributed to chemical bonds formed at the interface between the particle and silica sol. In contrast, the adsorption of the particles on the substrate coated with alumina sol formed a layer with strongly adhered and densely packed particles, due to large attractive interactions between the particles and alumina sol.