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RISS 인기검색어
- 검색키워드
- 저자 : Almanza-Robles J. M. (검색결과 3 건)
- 무료
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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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Thermal shock resistance of mullite/Sr-celsian/zirconia composites
Rodríguez-Salazar P.,Almanza-Robles J. M.,Cortés-Hernández D. A.,Escobedo-Bocardo J. C. 한국세라믹학회 2022 한국세라믹학회지 Vol.59 No.6
The thermal shock resistance of novel mullite /Sr-celsian /zirconia composites was studied. The eff ect of the Sr-celsian (15, 20, 25 wt.%) and ZrO 2 (5, 15, 25 wt.%) amounts on the thermal shock resistance, was evaluated. The composites were obtained at 1450 °C. Thermal shock resistance was performed by heating samples up to a selected temperature (∆ T = 200–1000 °C) and then suddenly immersed in water. After testing, the bending strength was evaluated and the results were statistically analyzed using Minitab with a confi dence level of 0.05. Pareto charts showed that Sr-celsian and zirconia content have the highest infl uence on fl exural strength after thermal shock. The highest thermal shock resistance was obtained for the composites with the highest amount of zirconia and Sr-celsian. Most of the composites showed a decrease in strength of around 75%. The strength of the composites with 20 or 25 wt.% of celsian and 25 wt.% zirconia increased at ∆ T of 1000 °C. The Pareto chart for these composites showed that zirconia has the highest eff ect on strength. A change in expansion is shown between 800 and 900 °C, indicating the transformation of monoclinic to tetragonal zirconia. This transformation generates microc- racks that defl ect cracks generated during thermal stress. Also, residual stresses are generated during cooling which plays a role in absorbing the energy of a generated crack. The strontium celsian forms an interlocked microstructure that improves strength. These composites are promising materials for applications in which sudden and extreme temperature changes occur.
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