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In this work, ZnO films were deposited on titanium substrates by the sputtering technique for non-enzymatic glucose detection in an alkaline solution. The samples were grown using pulsed D.C. sputtering using a ZnO target; we remain... more
In this work, ZnO films were deposited on titanium substrates by the sputtering technique for non-enzymatic glucose detection in an alkaline solution. The samples were grown using pulsed D.C. sputtering using a ZnO target; we remain constant the power at 100 W and varied the deposition time in order of obtain films with different thickness. The properties of the samples were analyzed by X-ray diffraction (XRD), optical transmission, scanning electron microscopy (SEM), and electrochemical techniques. The results shown that the thickness of the samples varied with the deposition time. The electrochemical response studied by cyclic voltammetry revealed that the sensor response increased when the ZnO film thickness decreased. The electrochemical biosensing device showed a sensitivity of 7.65 ?A cm-2mM-1 with a linear response range of 3.3 mM to 11.0 mM.
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Research Interests: Engineering, Materials Science, Optoelectronics, Mott metal-insulator transition, Thin Film, and 13 morePhysical sciences, Chromium, Sputtering, Nickel, CHEMICAL SCIENCES, Room Temperature, Electrical Properties, Elsevier, Electrode, Electric Field, Electronics Devices and Circuits, non blocking I/O, and Induced Resistance
ABSTRACT RÉSUMÉ Le but de ce travail est d’améliorer les propriétés du kaolin DD3 calciné (Chamotte) par l’ajout de la dolomite et par conséquent de réduire le taux de phase vitreuse. Cette dernière se présente sous forme de cristobalite... more
ABSTRACT RÉSUMÉ Le but de ce travail est d’améliorer les propriétés du kaolin DD3 calciné (Chamotte) par l’ajout de la dolomite et par conséquent de réduire le taux de phase vitreuse. Cette dernière se présente sous forme de cristobalite entre 1100°C et 1400°C et sous forme d’une phase amorphe au dessus de 1400°C. Les mélanges entre 5 et 20% poids de dolomite ont été traités et frittés sous les mêmes conditions entre 1200°C et 1550°C. Les spectres DRX montrent qu’un ajout de 5 à 20 % poids en dolomite conduit, après frittage, à des céramiques composites formées principalement de phases : mullite, anorthite, spinelle et indialite (α-cordiérite). L’ajout de plus 10% poids de dolomite réduit le taux de la phase amorphe à 9.6% après frittage dans le domaine de températures 1200°C et 1500°C. Les céramiques obtenues sont caractérisées par : une densité apparente allant de 2,88 à 3,21 g/cm3, une très faible porosité, un module de rupture variant de 67 à 112 MPa et une micro-dureté Vickers de 9,1 à 10,67 GPa. ABSTRACT The mixtures between 5 and 20% weight of dolomite were treated and sintered under the same conditions between 1200°C and 1550°C. XRD Spectra show that the addition from 5 to 20% weight of dolomite led, after sintering, to form ceramic composite composed mainly of phases: mullite, anorthite, spinel and indialite (α-cordierite). The addition of dolomite more than 10% reduces the rate of the amorphous phase to 9.6% after sintering in the temperature range 1200°C and 1500°C. Ceramics obtained is characterized by: an apparent density in the range 2,88 to 3,21 g/cm3, a very low porosity, a module of rupture between 67 and 112 MPa and a Vickers microhardness from 9,1 to 10,67 GPa.
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Research Interests: Philosophy and Humanities
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Not Available Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Return: Query Results Return items starting with number Query Form Database: Astronomy Physics... more
Not Available Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints
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Single-crystal X-ray diffraction studies are reported for 3,4-diphenyl-1,2,5-thiadiazoline 1,1-dioxide (I), 3,4-diphenyl-1,2,5-thiadiazolidine 1,1-dioxide(II) and 4-ethoxy-5-methyl-3,4-diphenyl-1,2,5-thiadiazoline 1,1-dioxide (III). Ab... more
Single-crystal X-ray diffraction studies are reported for 3,4-diphenyl-1,2,5-thiadiazoline 1,1-dioxide (I), 3,4-diphenyl-1,2,5-thiadiazolidine 1,1-dioxide(II) and 4-ethoxy-5-methyl-3,4-diphenyl-1,2,5-thiadiazoline 1,1-dioxide (III). Ab initio MO calculations on the electronic structure, conformation and reactivity of these compounds are also reported and compared with the X-ray results. A charge sensitivity analysis is performed on the results applying concepts derived from density functional theory, obtaining several sensitivity coefficients such
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We describe the development of a quantum key distribution (QKD) scheme based on ultrafast laser pumped sources of entangled photon pairs and the engineering of their entanglement properties. Though quantum entanglement has been shown to... more
We describe the development of a quantum key distribution (QKD) scheme based on ultrafast laser pumped sources of entangled photon pairs and the engineering of their entanglement properties. Though quantum entanglement has been shown to be a useful resource for quantum key distribution, little work has been carried out in making use of the full range of joint entanglement behavior present in hyper-entangled photon pairs. We consider the principal advantages of our QKD scheme in connection with the way it makes ...
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In the present work, Dynamical Mechanical Analysis (DMA) was employed in order to evaluate viscoelastic properties of polybutadiene (BR)/EPDM/Carbon black (CB) blends as a function of the strain amplitude. As expected, storage modulus,... more
In the present work, Dynamical Mechanical Analysis (DMA) was employed in order to evaluate viscoelastic properties of polybutadiene (BR)/EPDM/Carbon black (CB) blends as a function of the strain amplitude. As expected, storage modulus, G', of conductive samples presented a strong dependence on strain amplitude as described by the Payne effect. This effect appears in compounds at the electrical percolation threshold and is stronger as CB content is rinsed. However, linear viscoelastic region (LVR), a characteristic section of the curve which has had little attention in this type of studies, presented also a great dependence on CB concentration, i.e. LVR is shorter as carbon black content and, hence, the conductivity of samples, increases. Respect to the influence of the elastomeric ratio BR/EPDM, EPDM alone (ratio 0/100), which had the highest viscosity, was the only formulation without a significant G' dependence on strain at 15 % w/w of CB. Also, conductivity was measured before and after the deformation cycle, in such a way that these data were useful as an indication of the structure recovery. As electrical end mechanical hysteresis is related to the state of (CB) distribution these results are envisaged to balance mechanical and electrical stability.
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The destabilizing effect of deformation-induced heating on the cold drawing of polymeric films is investigated under adiabatic and plane-strain loading conditions. An approximate method, previously devised to study the steady-state cold... more
The destabilizing effect of deformation-induced heating on the cold drawing of polymeric films is investigated under adiabatic and plane-strain loading conditions. An approximate method, previously devised to study the steady-state cold drawing of polymers with viscoplastic properties, is further modified to incorporate the softening effects due to temperature. Parametric studies are carried out showing the interaction of material properties with the kinematics of the process.
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... Copyright © 2005 Elsevier BV All rights reserved. Permissions & Reprints. Modeling and experimental testing of the effect of solvent absorption on the electric properties of styrene butadiene rubber/carbon black... more
... Copyright © 2005 Elsevier BV All rights reserved. Permissions & Reprints. Modeling and experimental testing of the effect of solvent absorption on the electric properties of styrene butadiene rubber/carbon black chemical sensors. ...
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A device is introduced which are able to perform tension tests on nano materials, which works on the basis of a differential thermal dilatation of two of its components. This difference in dilatation is enough large to put the device in... more
A device is introduced which are able to perform tension tests on nano materials, which works on the basis of a differential thermal dilatation of two of its components. This difference in dilatation is enough large to put the device in operation when it is heating inside a Transmission Electron Microscope and stretching axi-symetric nano samples until breaking. The feasibility
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Several potentially conducting polymers, optically nonlinear polymers, and biomaterials contain heterocyclic structures. Reduction of the energy band gap of a conjugated polymer is a topic of considerable interest due to the possible... more
Several potentially conducting polymers, optically nonlinear polymers, and biomaterials contain heterocyclic structures. Reduction of the energy band gap of a conjugated polymer is a topic of considerable interest due to the possible elimination of doping in the preparation of highly conductive polymers. Control of the energy gap value of a polymer by molecular design could modify its optical, electronic and optoelectronic properties. Thiadiazoles and their derivatives are the structural basis of some of these polymeric materials. The results of the calculation of the HOMO-LUMO gap, the dipole moment and polarizability of thiadiazole oligomers in vacuo and in the presence of solvents are reported. The calculations are based on density functional theory using a specially tailored model chemistry. The potential utility of these materials for the development of chemical sensors is discussed.
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ABSTRACT An improved sensor capable of detecting and locating liquid hydrocarbon leaks on long pipelines is presented. A technique to optimize performance of microcurvature optical-sensor response is developed by modifying cross-linking... more
ABSTRACT An improved sensor capable of detecting and locating liquid hydrocarbon leaks on long pipelines is presented. A technique to optimize performance of microcurvature optical-sensor response is developed by modifying cross-linking density of the elastomer employed.
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ABSTRACT The coating process, of optic-fibers into a polymer matrix is a very difficult and delicate process due to the fragility of the fibers, which can get broken by the stresses and temperature imposed during processing. In this paper... more
ABSTRACT The coating process, of optic-fibers into a polymer matrix is a very difficult and delicate process due to the fragility of the fibers, which can get broken by the stresses and temperature imposed during processing. In this paper we introduce a new control system which is based on measurement of specific power changes in the laser transmitted signal thought the fiber. Those changes are produced by mechanical or thermal stresses on the fiber during processing. Those stresses normally generated by photoelastic effects on the fiber when it is pulled or heated, changing its optical properties. By a meticulous characterization of those effects we are able to establish a real time control system for the coating process, avoiding the deformation or even breaking of the fiber during coating.
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In the present work, the evolution of the electrical properties of two conductive composites when they come into contact with organic liquids is studied. The composites were elaborated with two butadiene based elastomers, a homopolymer... more
In the present work, the evolution of the electrical properties of two conductive composites when they come into contact with organic liquids is studied. The composites were elaborated with two butadiene based elastomers, a homopolymer (polybutadiene, PB) and a copolymer (styrene–butadiene–rubber, SBR). Both elastomers were loaded with carbon black (CB) and graphite (G). The results show that the resistivity of
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In the present work, Dynamical Mechanical Analysis (DMA) was employed in order to evaluate viscoelastic properties of polybutadiene (BR)/EPDM/Carbon black (CB) blends as a function of the strain amplitude. As expected, storage modulus,... more
In the present work, Dynamical Mechanical Analysis (DMA) was employed in order to evaluate viscoelastic properties of polybutadiene (BR)/EPDM/Carbon black (CB) blends as a function of the strain amplitude. As expected, storage modulus, G', of conductive samples presented a strong dependence on strain amplitude as described by the Payne effect. This effect appears in compounds at the electrical percolation threshold and is stronger as CB content is rinsed. However, linear viscoelastic region (LVR), a characteristic section of the curve which has had little attention in this type of studies, presented also a great dependence on CB concentration, i.e. LVR is shorter as carbon black content and, hence, the conductivity of samples, increases. Respect to the influence of the elastomeric ratio BR/EPDM, EPDM alone (ratio 0/100), which had the highest viscosity, was the only formulation without a significant G' dependence on strain at 15 % w/w of CB. Also, conductivity was measured b...
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In the present work, the effect of distribution of Carbon Black (CB) and rubber viscosity over the conductivity of rubber blend composites was studied. Preferential location of CB predicted by surface tension measurements and calculation... more
In the present work, the effect of distribution of Carbon Black (CB) and rubber viscosity over the conductivity of rubber blend composites was studied. Preferential location of CB predicted by surface tension measurements and calculation of interfacial energy (wetting coefficient) was corroborated by dynamic analysis (DMA) as well as bound rubber experiments. In this respect, the employment of the DMA technique to infer preferential distribution of CB, through the following of changes in the loss tangent (Tan δ), were proposed and successfully assessed in this study. A double percolation effect was evidenced by the appearance of a maximum in conductivity at relatively low EPDM content and CB concentration; however, when blend viscosity increases due to the addition of EPDM (the most viscous rubber), the double percolation effect is suppressed and the conductivity falls due to the prevailing dispersion effect of CB particles. According to these results, the blend viscosity was found ...
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Research Interests: Materials Engineering, Polymer Engineering, Electron Microscopy, Carbon, Morphology, and 13 moreNanocomposites, Nanoparticles, Polymerization, Emulsion polymerization, Polymer, Differential scanning calorimetry, Nanocomposite, Thermal Performance, Glass Transition, Glass Transition Temperature, Dynamic Mechanical Analysis, Mechanical Property, and Free radical polymerization
ABSTRACT In this work we develop an empirical method to calibrate the measuring head of a torque-rheometer to obtain the power-law parameters of polymer melts. This method is based on a similar analysis developed by Lee and Purdon.... more
ABSTRACT In this work we develop an empirical method to calibrate the measuring head of a torque-rheometer to obtain the power-law parameters of polymer melts. This method is based on a similar analysis developed by Lee and Purdon. However, in this work, only one geometrical parameter, with well-defined physical limits, is needed for calibration, instead of the two arbitrary parameters proposed by the previous authors. Moreover, this parameter is closely related to the ordinate of the logarithmic relationship between the torque (MT) and the angular velocity (S1), obtained from the torque-rheometer data. This allows us to define a calibration function for this parameter, which is used to evaluate the consistency index (m) of the melt. On the other hand, experimental results confirm the equivalence between the slope of the logarithmic values of torque and angular velocity obtained from the torque-rheometer data and those of shear stress vs. shear rate obtained from capillary rheometry. This further highlights the feasibility of evaluating the melt flow index (n) and the consistency index (m) from the torque-rheometer data.
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... Using Short Leather Fibers. II. Mechanical Characterization T. J. MADERA-SA"A, M. J. AGUILAR-VEGA*, A. UQUEZ ' , and F. VAZQUEZ MORENO* Centro de lnvestigacibn Cientifica de Yueath, AC AP 87 Cordemex, 97310, Mi.rida, Yueath,... more
... Using Short Leather Fibers. II. Mechanical Characterization T. J. MADERA-SA"A, M. J. AGUILAR-VEGA*, A. UQUEZ ' , and F. VAZQUEZ MORENO* Centro de lnvestigacibn Cientifica de Yueath, AC AP 87 Cordemex, 97310, Mi.rida, Yueath, M&o M. 0. W. RICHARDSON PTME. ...
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... The ASTM-D2807-78 (44) for to measure the chrome oxide content. ... Weight Percent Extractable in hexane (greases) 7.68 2 1.02 Humidity 12.11 2 1.87 Chrome-oxide 10.65 -+ 0.68 Proteins 62.64 t 2.05 (Nitrogen content) (10.32 t 0.35)... more
... The ASTM-D2807-78 (44) for to measure the chrome oxide content. ... Weight Percent Extractable in hexane (greases) 7.68 2 1.02 Humidity 12.11 2 1.87 Chrome-oxide 10.65 -+ 0.68 Proteins 62.64 t 2.05 (Nitrogen content) (10.32 t 0.35) Ashes (minerals) 6.88 -+ 0.22 ...
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... the Fabrica de Vestimenta y Equipo (FAVE-SEDENA) of Mexico City. After washing and drymg the waste was grounded in a Paganini-Diconet Miller, POLYMER COMPOSITES, AUGUST 1998, Vol. 19, No. 4 431 Page 2. Tomas J. Madera-Santana, Albert0... more
... the Fabrica de Vestimenta y Equipo (FAVE-SEDENA) of Mexico City. After washing and drymg the waste was grounded in a Paganini-Diconet Miller, POLYMER COMPOSITES, AUGUST 1998, Vol. 19, No. 4 431 Page 2. Tomas J. Madera-Santana, Albert0 Campos Torres, and ...
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ABSTRACT In order to evaluate the possible use of short leather fibers to produce leather-like composites, five kilograms of fibers (extracted from leather wastes) were modified by in situ emulsion polymerization of methyl methacrylate... more
ABSTRACT In order to evaluate the possible use of short leather fibers to produce leather-like composites, five kilograms of fibers (extracted from leather wastes) were modified by in situ emulsion polymerization of methyl methacrylate (MMA). This treatment was performed in order to increase the compatibility of leather fibers with several commodity polymers used in the shoe and furrier industries. The chemical modification was carried out by aqueous emulsion polymerization initiated by a redox system (potassium persulfate and sodium metabisulfite). The effects of the monomer and redox initiator content as well as the reaction temperature were evaluated. The modified short leather fibers were characterized by instrumental techniques such as Infrared Spectroscopy (IR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), X-ray Diffraction and Scanning Electronic Microscopy (SEM). The results show that the polymer is formed on the exterior of fibers (deposited fraction) as well as in the interior (by grafting or forming interpenetrated networks). The treatment significantly improves the thermal stability of fibers. It also reduces their water adsorption capacity, as a coating of PMMA is produced over the leather surface, as microscopic analysis has revealed. The last characteristic could be an advantage in certain applications.
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Page 1. Study of the Flow Behavior of Polymer-Natural Fiber Suspensions in the Power Law Validity Range ALFRED0 m QUEZ t , JAFET QUXJANO, and ROLAND0 HOS Centro de Investigdn Cientiia de Ymath Unidad de MateMles ...
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The paper presents distributed fiber optic bending sensor for petroleum hydrocarbon leak detection based on coherent optical frequency domain reflectometry (C-OFDR) technique. In order to introduce bending losses a sensitive polymer,... more
The paper presents distributed fiber optic bending sensor for petroleum hydrocarbon leak detection based on coherent optical frequency domain reflectometry (C-OFDR) technique. In order to introduce bending losses a sensitive polymer, which reversibly swells under hydrocarbon influence is employed. In this work we used lumped reflectors, namely fiber Bragg gratings, placed between distributed sensitive elements. Design of proposed sensor utilizes
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ABSTRACT A model to determine the structural stability and cation configuration of Aurivillius phases is presented. Structural stress caused by elastic coupling between the (M2O2) and (An−1BnO3n+1) substructures that form the phase and... more
ABSTRACT A model to determine the structural stability and cation configuration of Aurivillius phases is presented. Structural stress caused by elastic coupling between the (M2O2) and (An−1BnO3n+1) substructures that form the phase and the electrostatic attraction forces between them are considered. The model suggests that the cation exchanges observed in these substructures result from a balance between the cohesive electrostatic energy and the disruptive elastic coupling energy. The model explains and predicts the cation configuration of Aurivillius phases of type (Bi2−xPbxO2)(PbyBi1−y)n−1BnO3n+1, where the cation exchange between M and A sites is of Bi3+ ↔ Pb2+ type. The PbBi2Nb2O9 phase is taken as a case study. This material has been studied quantifying this cation exchange and several theoretical models have been developed to explain the phenomenon. The cation equilibrium configuration determined by the present model is much more accurate than previous studies. Furthermore, a precise explanation of this phenomenon is provided.
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Page 1. Incorporation of Silver/Carbon Nanoparticles into Poly(methyl methacrylate) via In Situ Miniemulsion Polymerization and Its Influence on the Glass-Transition Temperature ERIKA I. LO´ PEZ-MARTÍNEZ,1 ALFREDO MA ...