Advanced Materials Research Vol. 976

Abstract: In this work is presented a study of a piezoelectric energy harvesting device used for low power consumption applications operating at relative low frequency. The structure consists of a cantilever beam made by Lead Zirconate Titanate (PZT) layer with two gold electrodes for electrical contacts. The piezoelectric material was selected taking into account its high coupling coefficients. Different structures were analyzed with variations in its dimensions and shape of the cantilever. The devices were designed to operate at the resonance frequency to get maximum electrical power output. The structures were simulated using finite element (FE) software. The analysis of the harvesting devices was performed in order to investigate the influence of the geometric parameters on the output power and the natural frequency. To validate the simulation results, an experiment with a PZT cantilever with brass substrate was carried out. The experimental data was found to be very close to simulation data. The results indicate that large structures, in the order of millimeters, are the ideal for piezoelectric energy harvesting devices providing a maximum output power in the range of mW

Abstract: Copper complexes of dithiocarbamates ligands were obtained from RNH₂ (R = C₆H₁₃-, C₁₂H₂₅- y C₁₈H₃₇-) and an excess of CS₂ in the presence of NaOH. Sodium hexyldithiocarbamate is not possible to isolate from solution but the other two were obtained and characterizedby infrared spectroscopy, UV-vis and powder X-ray diffraction. Copper complexes were obtained in situ from ligand solution as greenish powders. All the complexes were characterized by infrared spectroscopy, UV-vis, powder X-ray diffraction and Scanning Electron Microscopy. The complexes show an amorphous phase in the case of DCu12 and nanocrystalline structure for DCu18, as observed in XRD.

Abstract: The objective of this study was to evaluate the influence of the synthesis conditions on the characteristics of carbon nanotubes (CNTs), to optimize the process parameters in the growth of CNTs. The CNTs were obtained by Chemical Vapor Deposition (CVD) at 800, 850 and 900 °C and carrier gas flow of 50, 80 and 110 ml/min from ferrocene and benzene during 1 h. The CNTs obtained were analyzed with a field emission scanning electron microscope (FESEM) JSM-7600F. The degrees of crystallinity of the samples were obtained through X-ray diffraction (XRD). The lengths of the CNTs were 3-120 microns and average diameters were 29-72 nm. The highest yields of CNTs were obtained with a flow rate of 80 ml/min and temperature of 850 °C. The diagrams illustrate XRD diffraction peaks corresponding to crystalline phases of graphite, Fe α and cementite (Fe₃C). The average CNTs walls were calculated with the Scherrer equation. The CNTs obtained with 50 ml/min carrier flow present an average of 40-42 walls, 80 ml/min-of 33-39 walls and 110 ml/min of 30-34 walls. These facts allow suppose that with a greater flow decreases the number of walls.

Abstract: The kaolin is an important component of a wide variety of industrial products, therefore kaolin samples of region mines Huayacocotla, Veracruz and Alumbres, Hidalgo were collected, these were treated to reduce the size particle employment an agate mortar and part of each one were analyzed using analytical techniques such as: absorption and emission atomic spectroscopy (AEAS), optical microscopy of polarization (OMP); X-rays diffraction (XRD); scanning electron microscopy (SEM); refractory test under ASTM standard C-24-79 using a pyrometric cone mold designed on ASTM standard C-24 and thermal test at different temperatures up to 1600 °C with heating and cooling rate of 2.5 °C·min^-1; thermogravimetric analysis (TGA) was carried out in a thermogravimetric analyzer with sample placed in alumina crucibles of high purity and the temperature was increased from room temperature up to 1000 °C with a heating rate of 10 oC·min^-1. Dates from elemental analysis were converted to percentage in oxides form of major elements. The analysis by OMP showed kaolin alteration degree in the region due to minerals such: plagioclase, feldspar and quartz, hydrothermal alteration of epithermal type represented by oxidation, sulfides (pyrite, galena) and association with chlorite. X-ray diffraction allowed determining to cristobalite (SiO₂) as majority phase in Huayacocotla and quartz (SiO₂) in Alumbres. Minority phases were observed in both areas such: dickite (Al₂O₃·Si₂O₅·(OH)₄), alunyte (KAl₃(OH)₆(SO₄)₂) and kaolinite (Al₂O₃·2SiO₂·2H₂O). Microanalysis with MEB showed kaolinite morphology, but structural formulas were not possible to determine due to impurities of Na, K, and Mg; those elements are present in clay complex group like: illite-alunite-dickite. Kaolin softening point was determined in 1300-1600 °C range, and it makes it feasible as refractory material of low and high temperature. Thermogravimetric analysis showed two decomposition areas, the first between 300-600 °C, which corresponds to crystallization water, and SO and SO₂ gases and the second from 700-1000 °C where an exothermic signal appears due to premullite phase formation.

Abstract: In this work, the dissolution of iridium was studied through a thermodynamic theoretic study with different concentrations of hydrochloric acid (HCl) and Iridium (Ir). Three different acid conditions and three different concentrations of iridium were analyzed: 1, 0.1 and 0.01 M HCl and 0.86, 0.021 and 0.002 M of iridium. The system 1 M HCl was the only one that presented soluble species of Ir. Results showed that as the Ir concentration diminished from 0.86 to 0.002 M, the pH range where it is possible to obtain Ir soluble species, increased (from 0-1.2 to 0-2). The presence of two Ir species (valences III and IV) for 0.021M and 0.002 M Ir concentrations was determined from the Pourbaix diagrams; while for the 0.086 M concentration, only the Ir (IV) species was observed. The Pourbaix diagrams showed that it is possible to obtain the species iridium (IV) from a potential range of 0.823 V vs SHE to 1.422 V vs SHE and at a pH between 0 and 1.2 in the 1 M HC1 solution.

Abstract: In this paper a study of wear behavior on nodular cast irons of the automotive industry is carried out. In different sections of two automobile parts, wear tests were performed using a tribometer pin-on-disk. Then, we calculated the density of nodules, volume fraction and nodularity without finding a relationship with the wear behavior. However, based on the concept of clusters of nodules, that integrate spatial distribution and size, we find that they play a major role in the wear behavior.

Abstract: It is important to develop scaffolds that resemble the extracellular matrix, thereby facilitating tissue regeneration. The objective of this work is to evaluate the biocompatibility of scaffolds of poly (L-lactide) with pure and grafted hydroxyapatite, at various concentrations of reinforcement, in Wistar Rat tissues, to evaluate the potential application on hard tissue regeneration. The biocompatibility tests were carried out in vivo in Wistar rats by implanting the material into the subcutaneous tissue and muscle from 1 to 14 weeks and evaluating the surrounding tissue stained with hematoxylin-eosin. All variants of scaffolds provoked an inflammatory response from mild to moderate, without showing necrosis. These results show that even if there is recognition of the implanted materials by the immune system, it does not provoke a violent response that damages the surrounding tissue, implying that the materials to be implanted for use in hard tissue can cause a mild reaction and tolerable long term effect that does not prevent their later use in hard tissue regeneration.

Abstract: The aim of this work is to report on the preparation of bismuth and gold nanoparticles ablating the corresponding target immersed in different liquid solutions: water and ethanol. The effect of the liquid environment and laser fluence used for ablation on the size and size distribution of the nanoparticles synthesized was investigated. The nanoparticle size was measured by transmission electron microscopy (TEM). In general terms, for both metals, the results obtained reveal smaller sizes as low as approximately 2 nm. The bismuth nanoparticles, as deposited, are highly crystalline in nature and, depending on the conditions of preparation, either Bi or Bi₂O₃ nanoparticles are obtained in both liquids. UV-Vis measurements show the typical band absorption characteristic of spherical particles of nanometric size. It is worth mentioning that the gold colloids obtained using water are very stable.

Abstract: In this paper we present the production of alternative industrial materials from the mining waste in the form of tailings, this study was made with the tailings of Dos Carlos, establishing 4 sampling zones, dividing them into three strata in the bottom, middle and top. The sampling method used is quartering, to homogenize the material and anticipate the possible use of it as a building material, having for this purpose 12 ceramic mixtures for subsequent treatment. Chemical composition was determined as 70.43% SiO₂, 7.032% Al₂O₃, 2.69% Fe₂O₃, 0.46% MnO₂, 3.98% K₂O, 3.34% CaO, 2.50% Na₂O, 56 grams per tonne of Ag y 0.6 grams per tonne of Au. In the mineralogical characterization the tailings presents silica, albite, berlinite, orthoclase and potassium jarosite as the main mineral phases, among other mineral phases in lesser concentration such as gypsum, calcite, anorthoclase, pyrite, sphalerite and galena. The determinations of the tailing material granulometry in the range of 60% in a size less than 270 mesh (53 μm). Afterwards, the alternative industrial materials were produced by using the tailings and heavy clay in order to give the composite a good green strength and plasticity during development, but above all to give it a compressive strength similar or higher than that of products derived from conventional processes. Keywords: Tailings, green strength, compressive strength, plasticity, heavy clays, alternative industrial materials.

Abstract: This paper presents the results of the adsorption of textile dyes in static systems, using adsorbent materials prepared from broccoli waste collected after harvest. The adsorption capacities of the non-activated lignocellulosic residue (BrocNat), the chemically activated waste using sodium hydroxide (BrocNaOH), the thermally activated at 823 K ash (AshBroc), and the chemically activated carbon using phosphoric acid at 673 K (CarBrocQ) were tested. Aqueous solutions containing cationic and anionic dyes as well as textile effluents generated after the dyeing process of a cotton-processing factory containing vat and reactive dyes were treated. Lignocellulosic materials were only effective in removing dyes when they were found in aqueous solution. The carbonaceous adsorbent CarBrocQ presented removal percentages close to 100% and between 13 and 75% for reactive and vat dyes contained in the effluents respectively. To accomplish the complete elimination of color from effluents containing vat dyes, these were treated before adsorption, using aluminum chlorohydrate and poly(acrylamide-co-sodium acrylate) as coagulant and flocculant agents, respectively. The COD of the effluent containing vat dyes was reduced up to 93% after both treatments were combined, and the removal of color was absolute. The high adsorption capacity of CarBrocQ occurs because of its high specific surface area, which was determined by N₂ adsorption to be 1177 m²g^-1. In the case of the lignocellulosic material, the specific surface area was determined by means of adsorption of methylene blue, and it was 485 m²g^-1 for both. The adsorption capacity of CarBrocQ was compared with that of commercial carbons, and proved to be similar. The adsorption results obtained indicate that broccoli waste can be used to prepare activated carbon with applications in the removal of dyes present in textile effluents.