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RISS 인기검색어
- 검색키워드
- 저자 : A. Hernández-Rangel (검색결과 5 건)
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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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Enrique Rocha-Rangel,Juan López-Hernández,José A. Rodríguez-García,Eddie N. Armendáriz-Mireles,Carlos A. Calles-Arriaga,W. J. Pech-Rodríguez,José A. Castillo-Robles 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.8
In this work, strontium titanate samples were prepared starting from SrCO3 and TiO2 powders mixture. Raw materials wereactivated mechanically in a planetary mill and then calcined at different temperatures (900 to 1300 oC). Powders after grindingwere analyzed by differential thermal analysis in order to follow the carbonate decomposition. On the other hand, samplesresulting from heat treatment were characterized by XRD, SEM and electrical measurements. XRD analysis determines thatSrTiO3 synthetized presents the cubic structure of perovskite. Complete reaction for SrTiO3 compound formation occurs at1200 oC. SEM observations indicate the presence of a microstructure with very small gran size and consequently a largenumber of grain boundaries. Electrical measurements suggest the formation of a material with high insulating capacity. Withthis evidence, it can be concluded that solid state reactions activated mechanically, proved to be an effective way to fabricatestrontium titanate compound with very fine microstructure and high insulating behavior.
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Curcumin-loaded Polycaprolactone/Collagen Composite Fibers as Potential Antibacterial Wound Dressing
E. San Martín-Martínez,Casañas-Pimentel,A. Almaguer-Flores,G. Prado-Prone,A. García-García,C. Landa-Solís,A. Hernández-Rangel 한국섬유공학회 2022 Fibers and polymers Vol.23 No.11
The development of wound dressings with therapeutical benefits is of great importance in skin tissue engineeringapplications, adding bioactive molecules into biomaterials is a strategy to achieve a better biological response. In this study,four different concentrations of curcumin (CUR; 5, 10, 15 and 20 by weight in relation to the PCL content) were incorporatedinto solutions composed of polycaprolactone (PCL) and collagen (COL) for the manufacture of electrospun fibers. The PCLCOL-CUR fibers were physicochemically characterized in terms of their morphology, wettability, degradation rate,mechanical behavior, and cumulative curcumin release. The in vitro biological properties of the composite membranes werealso evaluated. The results indicated that the membranes have diameters on average of approximately 200 nm. The wateruptake was adequate for exudates remotion in a wound, and the degradation rate of the fibers was highly appropriate toachieve complete skin tissue regeneration. The addition of CUR to composite membranes produced a significant increase inthe mechanical properties which indicate a satisfactory clinical handling. The incorporation of CUR produced a significantdecrease in the planktonic growth of S. aureus over time, however, the antibacterial effect against E. coli was limited, thepresence of CUR did not cause the inhibition of its growth. Finally, the viability of human dermal fibroblasts seeded on thetop of the membranes indicated the cytotoxic dosage effect of CUR, the two highest CUR concentrations produced asignificant loss of cell viability. Overall, our results suggested that the CUR-loaded PCL-COL composite membranes arepromising candidates for use as antibacterial dressings to enhance clinical wound management.
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Elizabeth Refugio-García,José G. Miranda-Hernández,José A. Rodríguez-García,Enrique Rocha-Rangel 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.3
The production of Al2O3/Ti/TiN functional materials through the nitriding in ammonia salts of previously Al2O3/Ti fabricated composites was achieved. The matrix for the preparation of the functional materials is to create an Al2O3-based composite that presents a fine and homogeneous dispersions of very fine metallic particles of Ti. After the nitriding, microstructural observations were carried out on the transverse zone of the materials’ surface showing the presence of a very thin film of about 20 μm of a constituent that was identified with the help of EDS as TiN. In addition, measurements of micro-hardness on the surface and in the core of the functional material were realized in order to determine the effect of nitride formation on the hardness.
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Fracture toughness enhancement for metal-reinforced alumina
Enrique Rocha-Rangel,Elizabeth Refugio-García,José G. Miranda-Hernández,Eduardo Terrés-Rojas 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.6
With the idea to determine ways of tailoring alumina (Al2O3) in order that one or more toughening mechanisms are activated in service, investigations about the production of Al2O3-based composites with different reinforcement metals and intermetallics have been carried out. The synthesis of composites materials has been made by means of both; liquid and solid pressureless sintering of an intensive mechanical mixture of powders. With the use of some metals in the chemical formulations, significant improvements in ceramic toughness have been reported. From the fracture toughness measurements and microstructural observations, it can be concluded that the toughening mechanism in Al2O3/metal reinforced composites is due to crack bridging and crack deflection. With the idea to determine ways of tailoring alumina (Al2O3) in order that one or more toughening mechanisms are activated in service, investigations about the production of Al2O3-based composites with different reinforcement metals and intermetallics have been carried out. The synthesis of composites materials has been made by means of both; liquid and solid pressureless sintering of an intensive mechanical mixture of powders. With the use of some metals in the chemical formulations, significant improvements in ceramic toughness have been reported. From the fracture toughness measurements and microstructural observations, it can be concluded that the toughening mechanism in Al2O3/metal reinforced composites is due to crack bridging and crack deflection.
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