Efraín Rubio-Rosas

MgZnAl hydrotalcite-like compounds preparation by a green method: effect of zinc content

A series of MgZnAl hydrotalcite-like compounds with different zinc content (1–25 mass % of nominal zinc content) were prepared by a simple and environmentally-friendly method. The solids were characterized by X-ray powder diffraction (XRD), thermogravimetric (TG), nitrogen adsorption-desorption at −196°C (BET), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and CO2 temperature-programmed desorption (CO2-TPD). Transesterification of castor oil with methanol was selected as a probe reaction to stress the effect of zinc incorporation. From the XRD analysis of fresh samples it was demonstrated that the incorporation of zinc is feasible in the nominal range of 1–10 mass % while in the samples with higher zinc content, zinc nitrate and ZnO as secondary crystalline phases were observed. Furthermore, the analysis of samples calcined at 450°C indicated the coexistence of the ZnO and MgO crystalline phases. From the EDS and TG characterizations, the zinc percentage and thermal decomposition of the samples were determined. It was revealed that the samples exhibited the characteristic platy-like habit of hydrotalcite-like compounds. The BET analysis confirmed that the calcined samples presented an increment in their specific surface area values compared with the pristine ones. It was established that the amount of basic sites diminished with the zinc incorporation, which also affected the conversion degree of the transesterification reaction.

Morphological and chemical changes in human deciduous dentin after phosphoric acid, self-etching adhesive and Er: YAG laser conditioning

The morphological and chemical changes in deciduous dentin produced by different conditioning protocols were evaluated in this in vitro study. Eighty primary dentin samples were divided into eight groups (n = 10): G1, acid etching; G2, self‐etching adhesive; G3, G4, Er: YAG laser irradiation at 25.5 and 38.2 J cm−2, respectively; 10 Hz and spray irrigation. Groups 5, 6, 7, and 8 were irradiated at previous densities, and then phosphoric acid or self‐etching adhesive conditioning was applied. Scanning electron microscopy (SEM) and energy dispersive X‐ray spectroscopy (EDS) were used to evaluate chemical and morphological changes. Paired t‐test and One‐way ANOVA were used for statistical analysis (p ≤ 0.05). All samples showed different morphology with specific characteristics according to the conditioning protocol. Changing element concentration values are expressed in atomic percent (at %). After conditioning, there were statistically significant differences (p ≤ 0.05) for p at% and Ca/P in all groups; highlighting the following additional findings by group: G1, G7, and G8 showed changes in all elements studied, G2 presented a decrease in C at% and increased Ca at%, G3 and G4 exhibited at% changes in C, trace elements and Ca. Furthermore, G5 showed at% changes in O and trace elements; while G6 changes were observed on C at%, O at% and trace elements at%. Dentin morphology and chemical composition varied in accordance with the conditioning protocol, with characteristics specific for each one that could have clinical implications for the retention and bond strength performance of adhesive materials.

Changes in deciduous and permanent dentinal tubules diameter after several conditioning protocols: In vitro study

Innovators conditioning protocols are emerged in permanent dentin, however for deciduous dentin the information is limited; the aim of this study was to evaluate in vitro diameter of deciduous and permanent dentinal tubules after several conditioning protocols. Eighty dentin samples were distributed in sixteen groups (n = 5 p/g) and dentin surface was conditioned as follow: G1D/G1P acid etching; G2D/G2P, self‐etch adhesive; G3D/G3P, G4D/G4P, Er: YAG laser irradiation at 200 mJ‐25.5 J/cm2 and 300 mJ‐38.2 J/cm2, at 10 Hz under water spray respectively; G5D/G5P, G6D/G6P, G7D/G7P, and G8D/G8P were irradiated under the same energy densities followed phosphoric acid or self‐etch adhesive conditioning. The sample dentin of deciduous and permanent teeth was analyzed with scanning electron microscopy and tubule diameter was evaluated by Image Tools Scandium program. Data were subjected to one‐way analysis ANOVA to compare among groups with a level of significance at p ≤ .05. For deciduous dentin, diameters were from 1.52 ± 0.32 µm in G3D to 3.88 ± 0.37 µm in G1D; narrowest and widest diameter, respectively (p < .000). While permanent dentin tubules exhibited diameters from 1.16 ± 0.16/1.19 ± 0.12 µm in G7P/G8P to 2.76 ± 0.28 µm in G6P; narrowest and widest diameter, respectively (p < .000). All dentin conditioning protocols produced more open dentin tubules (diameter size) in deciduous dentin than permanent, specific conditioning protocols are required for each tissue (deciduous or permanent dentin), since same protocol produced stronger effects on primary dentin, which is important for dental clinical success in children and adolescents.

The effect of cyclic heat treatment on the physicochemical properties of bio hydroxyapatite from bovine bone

This paper focus on physicochemical changes in bio-hydroxyapatite (BIO-HAp) from bovine femur obtained by calcination at high temperatures: 520–620 (each 20 °C) at 7.4 °C/min and from 700 to 1100 °C (each 100 °C) at three heating rates: 7.4, 9.9, and 11.1 °C/min. BIO-HAp samples were obtained using a multi-step process: cleaning, milling, hydrothermal process, calcination in an air atmosphere, and cooling in furnace air. Inductively Couple Plasma (ICP) showed that the presence of Mg, K, S, Ba, Zn, and Na, is not affected by the annealing temperature and heating rate. While Scanning Electron Microscopy (SEM) images showed the continuous growth of the HAp crystals during the calcination process due to the coalescence phenomenon, and the Full Width at the Half Maximum for the X-ray patterns for temperatures up to 700 is affected by the annealing temperature and the heating rate. Through X-ray diffraction, thermal, and calorimetric analysis (TGA-DSC), a partial dehydroxylation of hydroxyapatite was found in samples calcined up to 900 °C for the three heating rates. Also, Ca/P molar ratio decreased for samples calcined up to 900 °C as a result of the dehydroxylation process. NaCaPO4, CaCO3, Ca3(PO4)2, MgO, and Ca(H2PO4)2 are some phases identified by X-ray diffraction; some of them are part of the bone and others were formed during the calcination process as a function of annealing temperature and heating rate, as it is the case for MgO.

Third Congress on Materials Science and Engineering (CNCIM-Mexico 2012)

The Third Congress on Material Science and Engineering (CNCIM-Mexico 2012), which took place in Merida, Mexico, from 27 February to 2 March 2012 was organized by three research groups (cuerpos academicos) from the Universidad Autonoma de Yucatan: Ingenieria Fisica (UADY-CA-27), Modelado y Simulacion Computacional de Sistemas Fisicos (UADY-CA-101) and Quimica Fundamental y Aplicada (UADY-CA-32), in collaboration with the Centro de Investigacion y de Estudios Avanzados (Cinvestav-Merida). The First Congress in Material Science and Engineering (CNCIM-2010), was organized in Puebla, Mexico in February 2010. This was followed by CNCIM-2011 held in Toluca, Mexico in February 2011. The CNCIM-Mexico 2012 Conference consisted of plenary talks (8), invited talks (10), oral contributions (54) and poster presentations (70). The topics of the Conference were: Synthesis and Preparation of Materials: Organic and Inorganic Characterization of Materials: Novel Methods and Techniques Applications of Materials: Environment, Medicine, Pharmacy, Technology, Food and Renewable Energy New Materials: Composites, Nanostructures, and from Natural Sources Theory: New Methods and Computer Simulations We want to thank the Organizing Committee, the Institutions and Sponsors supporting the Conference, and everyone who contributed to the organization of this meeting, for their invaluable efforts in order to guarantee the complete success of this conference. Editors Romeo de Coss Centro de Investigacion y de Estudios Avanzados del I.P.N. (Cinvestav-Merida) A.P. 73 Cordemex 97310, Merida, Yucatan, Mexico decoss@mda.cinvestav.mx Gabriel Murrieta-Hernandez Universidad Autonoma de Yucatan Calle 60 No. 491-A, Centro Historico, C.P. 97000, Merida, Yucatan, Mexico murrieta@uady.mx Aaron Aguayo-Gonzalez Universidad Autonoma de Yucatan Calle 60 No. 491-A, Centro Historico, C.P. 97000, Merida, Yucatan, Mexico aguayo@uady.mx Efrain Rubio-Rosas Benemerita Universidad Autonoma de Puebla Ciudad Universitaria, Col. San Manuel, C.P. 72570, Puebla, Puebla, Mexico efrain.rubio@cuv.buap.mx Ernesto Chigo-Anota Benemerita Universidad Autonoma de Puebla Ciudad Universitaria, Col. San Manuel, C.P. 72570, Puebla, Puebla, Mexico ernesto.chigo@correo.buap.mx Enrique Vigueras-Santiago Universidad Autonoma del Estado de Mexico Instituto Literario No. 100, Col. Centro 50000, Toluca, Edo. de Mexico, Mexico vigueras@uaemex.mx Session Chairs Gabriel Canto Santana, Universidad Autonoma de Campeche. Enrique Vigueras Santiago, Universidad Autonoma del Estado de Mexico. Cesar Cab, Universidad Autonoma de Yucatan. Alejandro avila Ortega, Universidad Autonoma de Yucatan. Jesus Barron Zambrano, Universidad Autonoma de Yucatan. Maritza de Coss, Universidad Autonoma de Yucatan. Jorge A. Tapia Gonzalez, Universidad Autonoma de Yucatan. David Munoz Rodriguez, Universidad Autonoma de Yucatan. Mario Perez Cortes, Universidad Autonoma de Yucatan. Jesus Garcia Serrano, Universidad Autonoma del Estado de Hidalgo. Ruben Arturo Medina Esquivel, Universidad Autonoma de Yucatan. Cesar R. Acosta, Universidad Autonoma de Yucatan. Organizing Committee Aaron Aguayo Gonzalez, Universidad Autonoma de Yucatan. Gabriel Murrieta Hernandez, Universidad Autonoma de Yucatan. Alejandro Tapia Gonzalez, Universidad Autonoma de Yucatan. Cristian Carrera Figueiras, Universidad Autonoma de Yucatan. Heriberto Hernandez Cocoletzi, Benemerita Universidad Autonoma de Puebla. Ernesto Chigo Anota, Benemerita Universidad Autonoma de Puebla. Efrain Rubio Rosas, Benemerita Universidad Autonoma de Puebla. Enrique Vigueras Santiago, Universidad Autonoma del Estado de Mexico. Romeo de Coss, Centro de Investigacion y de Estudios Avanzados (Cinvestav-Merida). Organizers: Sponsors: