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Structural Analysis of TiC and TiC-C Core-Shell Nanostructures Produced by Pulsed-Laser Ablation

Journal of Materials Science and Chemical Engineering 2023年第7期11卷 1-13页

作者： Luis Enrique Iniesta Piña Miguel Ángel Camacho López Rafael Vilchis Néstor Víctor Hugo Castrejón Sánchez delfino reyes contreras Mestría en Ciencia de Materiales Facultad de Química Campus Rosedal Universidad Autónoma del Estado de México Toluca México Laboratorio de Fotomedicina Biofotónica y Espectroscopía Láser de Pulsos Ultracortos Facultad de Medicina Universidad Autónoma del Estado de México Toluca México Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM Toluca México TecNM/Tecnológico de Estudios Superiores de Jocotitlán Jocotitlán México Laboratorio de Acústica y Nanomateriales Facultad de Ciencias Campus el Cerrillo Universidad Autónoma del Estado de México Toluca México

This paper reports on the ablation process of a pure Ti solid target immersed in a C-enriched acetone solution, leading to the production of titanium carbide (TiC) and Ti-C core-shell nanostructures. The used route of synthesis is generally called pulsed laser ablation in liquid (PLAL). The presence of carbon structures in the solution contributed to the carbon content in the produced Ti-based nanomaterials. The atomic composition of the produced nanostructures was analyzed using SEM-EDS, while TEM micrographs revealed the formation of spherical TiC and core-shell nanostructures ranging from 40 to 100 nm. The identification of atomic planes by HRTEM confirmed a 10 nm diameter C-shell with a graphite structure surrounding the Ti-core. Raman spectroscopy allowed for the identification of D and G peaks for graphite and a Raman signal at 380 and 600 cm−1, assigned to TiC. The results contribute to the state-of-the-art production of TiC and Ti-C core-shell nanostructures using the PLAL route.

关键词： Laser Ablation TiC Nanoparticles Core-Shell Nanoparticles Pulsed Laser

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Changes in the Electrical Resistivity of Thin-Films for Polymer Composites Induced by Heating-Cooling Cycles

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材料科学与工程（中英文B版） 2012年第12期2卷 601-610页

作者： Susana Hemandez Lopez Enrique Vigueras Santiago Miguel Mayorga Rojas delfino reyes contreras Research and Develop Laboratory on Advances Materials (LIDMA) Chemistry Faculty Autonomous University of Mexico State Paseo Col6n esquina Paseo Tollocan s/n Toluca C.P. 50000 Mdxico Sciences Faculty Autonomous University of Mexico State Av. lnstituto Literario 100 Col Centro Toluca C.P. 50000 Mgxico

This paper is focus on the analysis of the electrical resistivity of polymer composites respect to the temperature when samples are under heating-cooling cycles in two type of experiments namely: (1) at three different heating rates and (2) an isothermic one. Three different films S1, S2 and S3 of Polystyrene + 22 wt% CB were submitted to several heating-cooling cycles until a reversing process of the resistivity behavior was reached for each film. The heating was performed from room temperature, RT (24 °C) to 120 °C at rates of 1, 2 and 5 °C/min, respectively. A fourth film S4 was exposed to isothermic-heating-cooling cycles, consisting on heat from RT to 120 oC (at 2 °C/min) and keep the film at 120 °C for 2.5 hours. The cooling rate was 0.2 °C/min for all samples. Results show that the cycle"s number for reaching the electrical stability of films were strongly dependent on the heating rate more than the kind of process (continuous or isothermic). Main analysis shows that as a lower the heating rate (1 °C/min) the number of heating-cooling cycles for reaching the reversibility (electrical stability) are less (6 cycles in our case) than those for higher heating rates (9 and 12 cycles). Results are explained in terms of the redistribution of carbon black particles due to the composite′s structural and thermal relaxation; in other words the dynamic polymer chain mobility during the heating process and the chain relaxation process during the cooling one.

关键词：高分子复合材料加热速率薄膜材料冷却循环电阻率分析样品松弛过程聚合物链

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Morphological Characterization in Wild Species of Heliconias(Heliconia spp)in Mexico

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American Journal of Plant Sciences 2017年第6期8卷 1210-1223页

作者： Carlos Hugo Avendano-Arrazate Jorge Alberto Arrazate-Argueta Simitrio Ortíz-Curiel Esaú Moreno-Pérez Leobardo Iracheta-Donjuan delfino reyes-López Manuel Grajales-Solís Misael Martínez-Bola?os Moises Cortés-Cruz National Forestry Crops and Livestock Research Institute(INIFAP)-Experimental Station Rosario IzapaTuxtla ChicoMexico Postgraduate College Postgraduate in EdafologyMontecilloMexico Autonomus University of Chapingo Departament of FitotecniaChapingoMexico Autonomus University of Puebla TeziutlanMexico National Genetic Resources Center–INIFAP TepatitlanMexico

In Mexico, the utilization of native heliconias germplasm for preservation and genetic improvement purposes, has been limited partly because of the unawareness between their population similarities and differences, and because of the degree of genetic divergence that exists among the interspecific and intraspecific ecotypes originated from different regions of the humid tropics. The objective of the present study was to morphological characterization wild species of the genus Heliconias in Mexico through some qualitative and quantitative morphological descriptors. Fifty-five qualitative and quantitative morphological characters were studied in 25 accessions from 11 native species. Characters of plant, leaf, inflorescence, flower, fruit, and seed were taken into account. Data was analyzed by Principal Component Analysis (PCA) and Hierarchical Cluster Analysis. Two analyses were carried out: the first one was for the 25 accessions that included characters of flower (55 variables), whereas the second was for only 19 accessions (66 variables) concluded until seed. The first six components explained a 69.4% of the total variation based on PCA. The variables which contributed most significantly were: leaf length (p < 0.001), limb width (p < 0.001), limb's petiole length (p < 0.001), pseudostem thickness (p < 0.05)/width at 60 cm (p < 0.05), rachis width (p < 0.05)/thickness (p < 0.001), second bract width (p < 0.001), growth (p < 0.001) and type of inflorescence (p < 0.05), petiole (p < 0.05) and peduncle length (p < 0.05), rachis color (p < 0.05), and wax in limb (p < 0.05) and in pseudostem (p < 0.05). Thirty-eight descriptors were suggested to differentiate wild species of heliconias in Mexico.

关键词： Heliconia Morphological Descriptors Principal Components

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