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RISS 인기검색어
- 검색키워드
- 저자 : E. Rocha-Rangel (검색결과 3 건)
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Synthesis by a solid state reaction of the Sr4Al6O12SO4 compound
J.A. Rodríguez-García,E. Rocha-Rangel,J. Torres-Torres,J. M. Almanza-Robles 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.3
The synthesis and formation of Sr4Al6O12SO4 in the system SrCO3-Al2O3-SrSO4 has been studied in the range of temperatures from 800 oC to 1400 oC using X-ray diffraction, thermo gravimetric, differential thermal and scanning electron microscopy analysis. Pellets of a mixture of 3 : 3 : 1 molar ratio of reactive grade Al2O3, SrCO3 and SrSO4 respectively were prepared, by solid state sintering, the reactive powders were thoroughly mixed under high energy ball-milling, uniaxially pressed into cylindrical samples and pressureless-sintered. Additionally the densities of some samples that were heat treated for 10 h at 1200, 1300 and 1400 oC were determined by the Archimedes method. The powder mixture was analyzed by TGA and DTA from room temperature to 1200 oC. XRD patterns indicated the formation of Sr3Al2O6 and SrAl2O4 as intermediate phases that nearly at the end of the process reacted with SrSO4 to form Sr4Al6O12SO4. The formation of Sr4Al6O12SO4 was complete at 1150 oC as XRD and DTA analysis indicated. An increase in the heat treatment time promotes the formation of Sr4Al6O12SO4at lower temperatures. The Sr4Al6O12SO4 powders were composed of spherical particles of small agglomerates. Results of density measurement indicated that only 80% of the theoretical density was reached for a treatment at 1400 oC of 10 h, which indicated the difficulty to obtain a dense material.
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Physical Properties of the Sr4Al6O12SO4 Ceramic Compound
J.A. Rodríguez-García,E. Rocha-Rangel,J. López Hernández,C.A. Hernández Bocanegra,A.L. Leal Cruz,J.M. Almanza Robles,J. Torres Torres 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.11
The Sr4Al6O12SO4 ceramic compound was synthesized by a solid state reaction starting from stoichiometric mixtures of 3 : 3 : 1 molar ratio of reactive grade of SrCO3, Al2O3 and SrSO4, respectively. Cylindrical samples were confirmed by uniaxial pressing at 100 MPa and were heat treated at 1400 oC during 4 hrs. Subsequently, the samples were ground and re-conformed in cylindrical shape samples by uniaxial pressing at 300 MPa. The new samples were heat treated at 1400 oC during 24 hrs. This process was done in order to increase density of the samples. The Sr4Al6O12SO4 ceramic compound was characterized by the study of its physical properties such as: density, micro-hardness, thermal expansion and stability, enthalpy of formation, magnetic properties and electrical conductivity. Experimental results show that the maximum density obtained for the Sr4Al6O12SO4 ceramic compound was 2.913 grcm−3, with thermal expansion coefficient of 10.12E−06(oC−1); it also presents an enthalpy of 2.3 KJmol-1 and an excellent thermal stability at elevated temperatures in different atmospheres. In addition, the Sr4Al6O12SO4 ceramic compound is neither electrically conductive nor magnetic.
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Microstructural evolution and fracture toughness of Al₂O₃/Ti composites
M. Vázquez-Villar,M. Romero-Romo,A. Altamirano-Torres,E. Rocha-Rangel 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.3
The effect of different additions of a metal (Ti) on the microstructure and fracture toughness of Al2O3-based ceramics, as well as the establishment of a route for their processing was analyzed in this study. The samples were prepared by means of mechanical milling and pressureless sintering in an argon atmosphere. Due to the fact of working with very small sizes of powders of both the metal and ceramic, it was possible to reach in sintered products greater values of densification than 95% of their relative density. Measurements of fracture toughness (KIC) evaluated by the fracture indentation method, indicate that this mechanical property had improved with some additions of Ti in the composite, for example KIC for pure alumina processed under the conditions of this study was 3.0MPa·m1/2, whereas, KIC for the composite with 3 vol % Ti was 4.1MPa·m1/2. The microstructure observed in a scanning electron microscopy shows the formation of small and fine metallic interpenetrating networks in the ceramic matrix, that improve in their formation with an increases of Ti in the composite. The effect of different additions of a metal (Ti) on the microstructure and fracture toughness of Al2O3-based ceramics, as well as the establishment of a route for their processing was analyzed in this study. The samples were prepared by means of mechanical milling and pressureless sintering in an argon atmosphere. Due to the fact of working with very small sizes of powders of both the metal and ceramic, it was possible to reach in sintered products greater values of densification than 95% of their relative density. Measurements of fracture toughness (KIC) evaluated by the fracture indentation method, indicate that this mechanical property had improved with some additions of Ti in the composite, for example KIC for pure alumina processed under the conditions of this study was 3.0MPa·m1/2, whereas, KIC for the composite with 3 vol % Ti was 4.1MPa·m1/2. The microstructure observed in a scanning electron microscopy shows the formation of small and fine metallic interpenetrating networks in the ceramic matrix, that improve in their formation with an increases of Ti in the composite.
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