San Luis Potosí, Mexico
San Luis Potosí, Mexico

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Flores-Velez L.M.,Institute Metalurgia UASLP | Torres R.,Mexichem
Materials Characterization | Year: 2010

In this work, the sintering process of Portland cement was studied by combining thermomechanical analysis (TMA) and differential thermal analysis (DTA), together with X-ray diffraction (XRD) and scanning electron microscopy (SEM). Thermal analysis results employing both techniques indicted that phase transformations appeared at lower temperatures when CaF2 was incorporated in the raw materials. Besides, it was observed at high temperature that in some phase transformations TMA conducts to better resolution compared with the DTA measurements. Furthermore, mechanical properties and X-ray diffraction patterns corroborate the TMA and DTA results, corroborating that the final amount of alite (Ca3SiO5) is higher when a certain amount of CaF2 was present during the clinkerization process. © 2010 Elsevier Inc. All rights reserved.


Cardenas A.,Institute Metalurgia UASLP | Miranda J.M.,Institute Metalurgia UASLP | Espericueta D.,Institute Metalurgia UASLP
NACE - International Corrosion Conference Series | Year: 2012

The focus of this paper is to examine and review how applications of Electrochemical Chloride Extraction (ECE) affect the mortar mechanical properties. The mortar specimens were prepared with water/cement (w/c) ratio of 0.5 and contaminated with 5% of NaCl by mass of cement. A clean steel rod was centrally embedded in each specimen. The electrochemical treatments were based on different electrical current densities of 1, 3, 6 and 9 A/m 2 that were applied for 15 days. The state of corrosion was monitored before, during and after applying ECE regularly for two weeks. Selected samples from the cover zone of the untreated and treated specimens were taken to assess their chloride profiles. According to results of the compressive strength on mortars the mechanicals properties were not affected by ECE. ©2012 by NACE International.


Lomeli M.,Institute Metalurgia UASLP | Sanchez G.,Institute Metalurgia UASLP | Dominguez O.,Institute Metalurgia UASLP
Ceramics International | Year: 2015

The work presents the kinetic effect of nanometric BaF2 and CaF2 particles on kaolinite to mullite transformation. The kinetics were evaluated from dilatometric data using two different non-isothermal procedures: conversional model-fitting method and diffusional sintering analysis. From experimental data, the activation energy of mullite formation calculated from sintering (942 kJ/mol) and from conversional method (910 kJ/mol) were in good agreement with those values reported by other authors (mean value 1030 kJ/mol). After incorporation of 3 mol% of nanometric BaF2 and CaF2 in kaolinite and applying both analytical procedures, lower activation energies for mullite formation were obtained, assigning to the transformation the value of 635 kJ/mol for kaolinite/BaF2 and 428 kJ/mol for kaolinite/CaF2 composites. © 2015 Elsevier Ltd. and Techna Group S.r.l. All rights reserved.


Flores-Ramos A.,National Polytechnic Institute of Mexico | Dorantes-Rosales H.J.,National Polytechnic Institute of Mexico | Lopez-Hirata V.M.,National Polytechnic Institute of Mexico | Hernandez-Santiago F.,National Polytechnic Institute of Mexico | And 3 more authors.
Revista de Metalurgia | Year: 2014

Phase transformations in Zn-22%Al-2%Cu and Zn-22%Al-2%Cu-X (X = 1, 2 and 3%Ag) alloys during aging treatments . The study of phase transformations that take place in Zn-22%Al-2%Cu and Zn-22%Al-2%Cu-X (X = 1, 2 and 3%Ag) alloys was carried out using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Alloys were homogenized at 350 ° C during 10 days and quenched at ∼2 ° C. Subsequently, samples were aged at 200 ° C for different times. The initial microstructure consists in a matrix of fine equiaxial grains of α and η phases for all the alloys. Besides isolated particles of ε and Pdbl; were observed without and with Ag addition, respectively. During the aging, the four phase reaction, α + ε → η + τ', takes place to obtain the equilibrium η, α and τ' phases. However, the Ag addition promotes the formation of the Pdbl; phase, which retards or inhibits the four phase reaction. The stability of the Pdbl; phase is obtained with 3%Ag, which could improve the dimensional stability of the alloy for future industrial applications. © 2014 CSIC.


Dorantes-Rosales H.J.,National Polytechnic Institute of Mexico | Lopez-Hirata V.M.,National Polytechnic Institute of Mexico | Esquivel-Gonzalez R.,Valle de México University | Gonzalez-Velazquez J.L.,National Polytechnic Institute of Mexico | And 2 more authors.
Metals and Materials International | Year: 2012

The effect of the homogenizing temperature on phase transformations and hardening behavior was studied in a Zn-22Al-2Cu (wt%) alloy homogenized for 7 days at 315, 350, and 390 °C. The homogenized alloy was subsequently quenched and aged naturally at room temperature or artificially at 200 °C for different time periods. The β phase was unstable at room temperature and it decomposed through the β → α + η reaction during natural aging. An increase in the homogenizing temperature caused a decrease in the kinetics of the decomposition of the β phase in the alloy. Natural aging also caused an increase in the hardness due to the formation of nanometric grains with α and η phases and the presence of an intermetallic e phase. This result agrees with the time exponents (n) between 1.5 and 2.6, which were obtained using the Johnson-Mehl-Avrami-Kolmogorov equation for the decomposition of the β phase. The transformed fraction curves exhibited the fastest and slowest growth kinetics of the â phase decomposition at homogenizing temperatures of 350 and 390 °C, respectively. The artificial aging induced the formation of equilibrium phases and began a decrease in hardness due to the coarsening process of the equilibrium α, η, and τ' phases. © KIM and Springer.

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