Evaluation of Hardness and Fracture Toughness in a Porcelain Stoneware with Pseudoboehmite Additions

O. Aguilar-García,S. Bribiesca-Vazquez,J. Zárate-Medina 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.1

The effect of pseudoboehmite additions to conventional stoneware porcelain is investigated. Green compacts were formed by slip casting of stabilized aqueous suspensions and then sintering at 1,150℃, 1,200℃ and 1,250℃. The phase evolution was followed by XRD, the densification degree was calculated from densities and the microstructures were studied by SEM. Hardness, H and fracture toughness, KIC were measured by Vicker’s indentation. When vitrification occurs the presence of the pseudoboehmite leads to a extra mullitization, which has two consequences: a volume expansion resulting in a high porosity and a decrease of the amount of liquid which causes problems with the densification, by these facts the pseudoboehmite particles decrease the fracture toughness of the bodies. The effect of pseudoboehmite additions to conventional stoneware porcelain is investigated. Green compacts were formed by slip casting of stabilized aqueous suspensions and then sintering at 1,150℃, 1,200℃ and 1,250℃. The phase evolution was followed by XRD, the densification degree was calculated from densities and the microstructures were studied by SEM. Hardness, H and fracture toughness, KIC were measured by Vicker’s indentation. When vitrification occurs the presence of the pseudoboehmite leads to a extra mullitization, which has two consequences: a volume expansion resulting in a high porosity and a decrease of the amount of liquid which causes problems with the densification, by these facts the pseudoboehmite particles decrease the fracture toughness of the bodies.

Mixture design to optimize the amount of deflocculants in aqueous porcelain precursor suspensions

O. Aguilar-García,S. Bribiesca-Vazquez,J. Zárate-Medina 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.2

The performance of dispersants poly(acrylic acid), a poly(methacrylic acid), sodium silicate, as well as binary and ternary deflocculant mixtures was compared for highly concentrated aqueous porcelain suspensions. These were formulated in ten stoneware recipes which were processed in the laboratory under fixed conditions, similar to those used in the ceramics industry, and viscosity measurements were made. The use of this methodology enabled the calculation of valid regression models (equations) relating viscosity with the contents of different deflocculant mixtures. The performance of dispersants poly(acrylic acid), a poly(methacrylic acid), sodium silicate, as well as binary and ternary deflocculant mixtures was compared for highly concentrated aqueous porcelain suspensions. These were formulated in ten stoneware recipes which were processed in the laboratory under fixed conditions, similar to those used in the ceramics industry, and viscosity measurements were made. The use of this methodology enabled the calculation of valid regression models (equations) relating viscosity with the contents of different deflocculant mixtures.

Solid State Luminescence Enhancement in π-Conjugated Materials: Unraveling the Mechanism beyond the Framework of AIE/AIEE

Shi, Junqing,Aguilar Suarez, Luis E.,Yoon, Seong-Jun,Varghese, Shinto,Serpa, Carlos,Park, Soo Young,Lü,er, Larry,Roca-Sanjuá,n, Daniel,Miliá,n-Medina, Begoñ,a,Gierschner, Johan American Chemical Society 2017 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.121 No.41

<P>Solid state luminescence enhancement (SLE) of conjugated organic materials has had a great impact in materials science, but a deep understanding has been rather limited to date. Here, we investigate a prototype example of SLE materials, cyano-substituted distyrylbenzene (DCS), by varying systematically and subtly the substitution pattern (inter alia of the position of the cyano-substituent) to give largely different photoresponse in fluid and solid solution as well in the crystalline state. The combination of quantitative (ultra)fast optical spectroscopic techniques, appropriate quantum-chemical methods, and structural (X-ray) data allows us to elucidate and rationalize all details of the SLE process, including steric versus electronic factors, radiative versus nonradiative decay channels, and intra- versus intermolecular contributions, providing a first holistic picture of SLE.</P>

Synthesis and characterization of YAG : Eu spray dryed powders

J. Zárate-Medina,R. López-Juárez,E. A. Aguilar-Reyes,J. Muñoz-Saldaña 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.1

YAG compounds doped with Eu have been successfully synthesized by spray drying a solution of precursor nitrates. Aluminum and yttrium nitrates, europium oxide, ethylene glycol and citric acid were used as reagents. The resultant solution was fed to a spray dryer to obtain precursor powders, which were in turn heat treated at 800, 850 and 900oC and characterized by X-ray diffraction. Morphology of the synthesized powders was observed by scanning and transmission electron microscopy. Results showed that the crystallization temperature of the powders is below 850oC without the presence of intermediate phases. The powders consist of spherical agglomerates constituted of primary particles of 40 nm diameter approximately. YAG compounds doped with Eu have been successfully synthesized by spray drying a solution of precursor nitrates. Aluminum and yttrium nitrates, europium oxide, ethylene glycol and citric acid were used as reagents. The resultant solution was fed to a spray dryer to obtain precursor powders, which were in turn heat treated at 800, 850 and 900oC and characterized by X-ray diffraction. Morphology of the synthesized powders was observed by scanning and transmission electron microscopy. Results showed that the crystallization temperature of the powders is below 850oC without the presence of intermediate phases. The powders consist of spherical agglomerates constituted of primary particles of 40 nm diameter approximately.

First Molecular Characterization of Colletotrichum sp. and Fusarium sp. Isolated from Mangrove in Mexico and the Antagonist Effect of Trichoderma harzianum as an Effective Biocontrol Agent

Mayra I. Grano-Maldonado,Rosalio Ramos-Payan,Fernando Rivera-Chaparro,Maribel Aguilar-Medina,José, Geovanni Romero-Quintana,Amparo Rodrí,guez-Santiago,Mario Nieves-Soto 한국식물병리학회 2021 Plant Pathology Journal Vol.37 No.5

The aim of this study was to characterize potential fun- gal species affecting mangrove species in Mexico. The phytopathogens were identified based on morphologi- cal and molecular characteristics using internal tran- scribed spacer (ITS1/ITS4) primers then sequenced and compared with the other related sequences in GenBank (NCBI). Three fungal species were identified as Colletotrichum queenslandicum (Weir and Johnst, 2012) from black mangrove (Avicennia germinans); Colletotrichum ti (Weir and Johnst, 2012) from white mangrove (Laguncularia racemosa) and buttonwood mangrove (Conocarpus erectus); Fusarium equiseti (Corda) from red mangrove (Rhizophora mangle). In addition, C. ti and F. equiseti were identified from man- go Mangifera indica L. sampled close by the mangrove area. This study provides first evidence of anthracnose on four mangrove species caused by Colletotrichum and Fusarium species in the “Términos” coastal lagoon in Campeche State southern Mexico. This is the first time that C. queenslandicum and C. ti are reported in Mexico. F. equiseti has not been reported affecting M. indica and R. mangle until the present work. Little is known regarding fungal diseases affecting mangroves in Mexico. These ecosystems are protected by Mexican laws and may be threatened by these pathogenic fungus. This is the first report of the effect of Trichoderma harzianum TRICHO-SIN as an effective biological con- trol against of Colletotrichum and Fusarium species.

Optimal area for rectangular isolated footings considering that contact surface works partially to compression

Victor Bonifacio Vela-Moreno,Arnulfo Luévanos-Rojas,Sandra López-Chavarría,Manuel Medina-Elizondo,Ricardo Sandoval-Rivas,Carmela Martínez-Aguilar 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.4

This paper presents a new model to obtain the minimum area of the contact surface for rectangular isolated footings, considering that the contact surface works partially to compression (a part of the contact surface of the footing is subjected to compression and the other is not in compression or tension). The methodology is developed by integration to obtain the axial load “P”, moment around the X axis “Mx” and moment around the Y axis “My”. This document presents the simplified and precise equations of the four possible cases of footing subjected to uniaxial bending and five possible cases of footing subjected to biaxial bending. The current model considers the contact area of the footing that works totally in compression, and other models consider the contact area that works partially under compression and these are developed by very complex iterative processes. Numerical examples are presented to obtain the minimum area of rectangular footings under an axial load and moments in two directions, and the results are compared with those of other authors. The results show that the new model presents smaller areas than the other authors presented.