• Title/Summary/Keyword: $Al_2O_3-mullite-SiC$

Search Result 70, Processing Time 0.027 seconds

Fabrication of $Al_2O_3/SiC$ Composite Through Oxidation of SiC (SiC의 산화에 의한 $Al_2O_3/SiC$ 복합체의 제조)

  • 김경환;이홍림;이형민;홍기곤
    • Journal of the Korean Ceramic Society
    • /
    • v.34 no.5
    • /
    • pp.535-543
    • /
    • 1997
  • The surface of SiC particles were partially oxidized to produce SiO2 layers on the SiC particles to prepare Al2O3/SiC composite by formation of mullite bonds between the grains of Al2O3 and SiC during sintering at 1$600^{\circ}C$. This process is considered to enable the sintering of Al2O3/SiC composite at lower temperature and also to relieve the stress, produced by thermal expansion mismatch between Al2O3 and SiC. In fact, Al2O3/SiC composite prepared by oxidation of SiC was observed to be more effectively sintered and densified at lower temperature. Maximum density, flexural strength and microhardness were obtained with 5.65 vol% of mullite content in Al2O3/SiC composite.

  • PDF

Solid-state reaction kinetics for the formation of mullite($3Al_2O_3{\cdot}2SiO_2$) from amorphous $SiO_2$ and ${alpha}-Al_2O_3$ (비정질 $SiO_2$${alpha}-Al_2O_3$부터 Mullite를 합성하기 위한 고체상태 반응속도)

  • 김익진;곽효섭;고영신
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.8 no.2
    • /
    • pp.332-341
    • /
    • 1998
  • Reaction kinetics for the solid - state reaction of ${\alpha}-Al_2O_3$with amorphous $SiO_2$to produce mullite ($3Al_2O_3;{cdot};2SiO_2$) was studied in the temperature range of 1450~$1480^{\circ}C$. Rate of kinetic reaction were determined by using $SiO_2$- coated $Al_2O_3$ compact containing 28.16 wt.% $SiO_2$and heating the reactant mixtures in MgO at definite temperature for various times. Amount of products and unreacted reactants were determined by X-ray diffractometry. Data from the volume fraction and ratio of peak intensities of mullite indicated that the reaction of ${\alpha}-;Al_2O_3$ with $SiO_2$to form $3Al_2O_3\;{\cdot}\;2SiO_2$ start between 1450 and $1480^{\circ}C$. The activation energy for solid-state reaction was determined by using the Arrhenius equation; The activation energy was 31.9 kJ/mol.

  • PDF

Preparation of Porous $Al_2O_3$-AIN-Mullite and $Al_2O_3$-AIN-SiC

  • Kim, Byung-Hoon;Na, Yong-Han
    • The Korean Journal of Ceramics
    • /
    • v.1 no.3
    • /
    • pp.147-151
    • /
    • 1995
  • Porous composite of $Al_2O_3$ and AIN based mullite and SiC can be prepared by alumium reaction synthesis and atmosphere controllied sintering in order to improve the durability of a gas filter body. The porous $Al_2O_3$-AIN-mullite, which has a strength of 168 kg/$\textrm{cm}^2$ and porosity of 51.59%, could be obtained by stmospheric firing at $1600^{\circ}C$ and the porous $Al_2O_3$-AIN-SiC with a porosity of 33% and strength of 977 kg/$\textrm{cm}^2$, could also be prepared. The average pore size has been changed from 0.2$\mu\textrm{m}$ in a reduction atmosphere and to 2$\mu\textrm{m}$ in an air atmosphere, respectively.

  • PDF

Fabrication of Mullite-Bonded Porous SiC Using Ti3AlC2 MAX Phase

  • Septiadi, Arifin;Yoon, Dang-Hyok
    • Journal of the Korean Ceramic Society
    • /
    • v.56 no.2
    • /
    • pp.191-196
    • /
    • 2019
  • This study assessed the feasibility of a Ti3AlC2 MAX phase as an Al-source for the formation of a mullite bond in the fabrication of porous SiC tubes with high strength. The as-received Ti3AlC2 was partially oxidized at 1200℃ for 30 min before using to minimize the abrupt volume expansion caused by oxidation during sintering. Thermal treatment at 1100-1400℃ for 3 h in air led to the formation of Al2O3 by the decomposition of Ti3AlC2, which reacted further with oxidation-derived SiO2 on the SiC surface to form a mullite phase. The fabricated porous SiC tubes with a relative density of 48 - 62 % exhibited mechanical strengths of 80 - 200 MPa, which were much higher than those with the Al2O3 filler material. The high mechanical strength of the Ti3AlC2-added porous SiC was explained by the rigid mullite neck formation along with the retained Ti3AlC2 with good mechanical properties.

Preparation of Ultrafine Mullite Powder from Metal Alkoxides (금속 알콕사이드로부터 Mullite 초미분체의 제조)

  • Yim, Going;Yim, Chai-Suk;Kim, Young-Ho
    • Korean Journal of Materials Research
    • /
    • v.16 no.12
    • /
    • pp.719-724
    • /
    • 2006
  • Ultrafine mullite powder was prepared from aluminium-secbutoxide and tetraethyl orthosilicate(TEOS) in the molar $Al_2O_3/SiO_2$=3/2. Sol-gel method by partial hydrolysis technique, as it were, first, TEOS was partially hydrolysized and then mixed with Al-secbutoxide for complete hydrolysis was used. X-ray diffraction, infrared spectroscopy and transmission electron microscopy, etc. confirmed that the mullite powder prepared by this method is in the stoichiometric $Al_2O_3/SiO_2$ ratio. Al-Si spinel was formed at $980^{\circ}C$ and ultrafine mullite powder with about 20 nm particle size was obtained above $1,200^{\circ}C$. Also mullite powders calcined at $1,600^{\circ}C$ had a stoichiometric composition, $3Al_2O_3{\cdot}2SiO_2$ and the lattice constants of the mullite powders calcined above $1,200^{\circ}C$ were almost coincided with theoretical values.

Synthesis and Thermal Analysis of Mullite Whiskers in Al(OH)3-SiO2-AIF3 System (Al(OH)3-SiO2-AIF3계에서 뮬라이트 휘스커 합성과 열분석)

  • Lee Hong-rim;Lee Young-Woo;Lee Jung-Won;Kang Jong-Bong
    • Korean Journal of Materials Research
    • /
    • v.15 no.10
    • /
    • pp.644-651
    • /
    • 2005
  • The thermal analysis of $Al(OH)_3-SiO_2-AIF_3$ system was done. The thermal behaviors of components and the effect of moisture on the formation of mullite were investigated via TG-DTA and XRD analysis. The mixture of $Al(OH)_3,\;SiO_2,\;AIF_3$showed two endothermic peaks with drastic weight loss and one exothermic peak. Fluorotopaz was formed at $800^{\circ}C$ and turned into mullite completely at $1100^{\circ}C$. But the mixture $Al_2O_3$ of or dehydrated $Al(OH)_3$ and $SiO_2$ could not form mullite even at $1200^{\circ}C$ in which the crystalline phases were $\alpha-Al_2O_3$ ana cristobalite. It was found that the synthesized mullite was aciculate shaped single crystalline whisker.

Low-Temperatrue Synthesis of Mullite Powders by the Emulsion Technique (MgO-Al2O3-SiO2계 요업원료의 제조 및 소결특성 -에멀젼법에 의한 Mullite분체의 저온합성-)

  • 현상훈;이희수;송승룡
    • Journal of the Korean Ceramic Society
    • /
    • v.26 no.3
    • /
    • pp.361-370
    • /
    • 1989
  • Mullite powders were synthesized from the common solution of aluminum sulfate and sodium silicate solutions by the emulsion-hot kerosene technique. The reaction temperature and mechanism for mullitization and the characteristics of synthesized mullite powders were investigated. The effect of Na components introduced from sodium silicate solution on the physical property and microstructure of sintered mullite was also examined. It was proved that mullites were formed at 75$0^{\circ}C$ through the reaction mechanism of Na2O.2.2SiO2+3.3Al2(SO4)3longrightarrow1.1(3Al2O3.2SiO2)+Na2SO4+8.9SO3. Synthetic mullite powders consisted of the compositiion of 3Al2O3.2SiO2 and showed highly agglomeration of hollow spherical particles of 1${\mu}{\textrm}{m}$ diameter. The density and fracture toughness of sintered mullites were somewhat reduced because of the effect of a very small amount of residual Na components.

  • PDF

Microstructure and Mechanical Properties of Platelet Reinforced Mullite-Zirconia Composites (Platelet 강화 Mullite-Zirconia 복합체의 미세구조와 기계적 성질)

  • 박상엽
    • Journal of the Korean Ceramic Society
    • /
    • v.29 no.10
    • /
    • pp.757-764
    • /
    • 1992
  • The platelet reinforced mullite-zirconia composites were prepared by pressurelss sintering with addition of Al2O3 or SiC platelets. The sintered density of 10 vol% Al2O3 platelet reinforced mullite-zirconia composite was 98.3% at 1700$^{\circ}C$. The fracture strength (290 MPa) and fracture toughness (4.9 MPa$.${{{{ SQRT { m} }}) in the Al2O3 platelet reinforced mullite-zirconia composite were enhanced compared with those of mullite-zirconia due to the crack deflection and load transfer effect of platelets. Whereas, the SiC platelet reinforced mullite-zirconia composite sintered at 1650$^{\circ}C$ showed relatively lower density (95.7%), fracture strength (170 MPa), and fracture toughness (3.9 MPa$.${{{{ SQRT { m} }} than the Al2O3 platelet reinforced mullite-zirconia composite.

  • PDF

Synthesis of Mullite Whiskers by Vapor-Solid Reaction in the System of Al(OH)3-SiO2-AlF3 (Al(OH)3-SiO2-AlF3계에서 기상-고상반응에 의한 뮬라이트 휘스커 합성)

  • Lee, Hong-Lim;Kang, Jong-Bong
    • Journal of the Korean Ceramic Society
    • /
    • v.43 no.6 s.289
    • /
    • pp.376-382
    • /
    • 2006
  • In the $Al(OH)_3-SiO_2-AlF_3$ system, leaf-shaped fluorotopaz was first formed at $800^{\circ}C$ and mullite whisker was formed at $1,100^{\circ}C$. The mass transportation of Al and Si as gas phase, the fast reaction and growth, and the absence of liquid phase existence in mullite whisker showed that the formation and growth of mullite was from the solid-vapor reaction.

A Study on the Preparation of MgO-Al2O3-SiO2 System Ceramic Powders by Spray Pyrolysis Method (분무열분해법에 의한 MgO-Al2O3-SiO2계 화합물의 분체합성 및 그 특성)

  • 박정현;박찬욱;조경식
    • Journal of the Korean Ceramic Society
    • /
    • v.25 no.4
    • /
    • pp.397-407
    • /
    • 1988
  • Spinel, mullite and cordierite powders have synthesized from Mg(NO3)2.6H2O, Al(NO3).9H2O and SiCl4 solution by spray pyrolysis method. The two-fluid nozzle was used as an atomizer. The powders of sinel and mullite were synthesized above 80$0^{\circ}C$, but the cordierite composition was noncrystalline for all synthersizing temperature. Those noncrystalline powders were crystallized to $\alpha$-cordierite during calcining at 130$0^{\circ}C$ for 2hrs. The synthesized spinel, mullite and cordierite powders seem to be consisted of agglomerated hollow spherical particles. For all powders, the particle size ranged from submicron to about 3${\mu}{\textrm}{m}$ and mean particle size was about 1.4${\mu}{\textrm}{m}$ in diameter. The specific surface area values of spinel, mullite and cordierite powders were maximum for powders prepared at 100$0^{\circ}C$, and those were 45.9, 25.8 and 13.6$m^2$/gr, respectively.

  • PDF