D. MARTINEZ B. - Academia.edu (original) (raw)

Papers by D. MARTINEZ B.

Applied Surface Science, 2019

Modulated Infrared Radiometry is a photothermal technique which allows thermal characterization o... more Modulated Infrared Radiometry is a photothermal technique which allows thermal characterization of coatings. Thermal properties are determined by applying the "Extremum Method". Zr-ON films were deposited by sputtering to evaluate their thermal properties and the sensitivity of the method and its suitability for different film+substrate systems. Three factors were varied: i) composition/bonding: metallic Zr, crystalline metallic-type Zr-ON and disordered ceramic Zr-ON. The films were deposited in the metallic, reactive and poisoned regimes of the hysteresis curve; ii) each film was deposited simultaneously on three different substrates: high-speed steel, glass and silicon; iii) in each deposition batch, films with four different thicknesses were grown. Each film was deposited in the same batch with different thicknesses on top of different substrates. All of the parameters for which the model is sensitive to are explored in this matrix of 36 different samples. The thermal parameters of the films were calculated and the trends and values were examined. The trends were explained in terms of the microstructural/chemical characteristics of the films, and the influence of each substrate, depending on the film thickness. The obtained values agree with those found in literature, reflecting the nature of the films.

ABSTRACT In this work we report synthesis and characterization of RE2TiMgO6 (RE=Dy, Gd) double-pe... more ABSTRACT In this work we report synthesis and characterization of RE2TiMgO6 (RE=Dy, Gd) double-perovskite materials. Dy2TiMgO6 and Gd2TiMgO6 were prepared by the standard solid-state reaction recipe. Structural study of samples was carried out by X-ray diffraction measurements and Rietveld refinement. Results reveal that the material crystallizes in a monoclinic perovskite with space group P21/n. Experimental lattice parameters for Dy2TiMgO6 were a=5.3624(4) ° A, b=5.5973(2) °A and c=7.6794(2) A° , and for Gd2TiMgO6 a=5.3143(5) A° , b=5.5826(2) °A and c=7.6324(2) A° . From Rietveld analysis we also determine atomic positions, tilt angle, inter-atomic distances and site occupancies. Morphologic study was performed by Scanning Electron Microscopy experiments. Images show strongly coupled grains with mean size 3 ¹m. Measurements of magnetic susceptibility show that both compounds evidence paramagnetic behavior. The Curie-Weiss fitting supplies effective magnetic moments which are 98% in agreement with the theoretical predictions for the isolated rare earth elements for each compound.

Journal of Superconductivity and Novel Magnetism, 2012

The synthesis of the new high temperature superconductor system Yb 1.8 Sm 1.2 Ba 5 Cu 8 O 18 is r... more The synthesis of the new high temperature superconductor system Yb 1.8 Sm 1.2 Ba 5 Cu 8 O 18 is reported. The new material was produced using the standard solid-state reaction method. The structural characterization of the compound was performed by X-ray diffraction and Rietveld refinement using a polycrystalline sample of the material. Structural ordering corresponds to an orthorhombic structure, from the space group P mm2. The lattice parameters of the material are reported here. The superconducting nature of the material was determined by measuring the magnetization, as a function of its temperature, in the regime of low and mean field. A critical temperature value of T c ∼ 88 K was determined for Yb 1.8 Sm 1.2 Ba 5 Cu 8 O 18. The experimental results have shown that the production of a novel group RE 3 Ba 5 Cu 8 O 18 of high-T c superconductivity is possible, by substitution of RE instead of Y in the recently reported new superconductor material Y 3 Ba 5 Cu 8 O 18 .

Brazilian Journal of Physics, 2012

We report in-field kinetic energy results in the temperature region closely below the transition ... more We report in-field kinetic energy results in the temperature region closely below the transition temperature of two differently prepared polycrystalline samples of the superconducting cuprate SmBa2Cu3O 7−δ. The kinetic energy was determined from magnetization measurements performed above the irreversibility line defined by the splitting between the curves obtained according the ZFC and FC prescriptions. The results are analyzed in the intermediate field regime where the London approximation can be used for describing the magnetization. From the analysis, estimations were carried out for the penetration depth and the upper critical field of the studied samples.The difference between the kinectic energy magnitudes for the two studied samples is ascribed to effects from granularity.

Journal of Superconductivity and Novel Magnetism, 2013

Journal of Physics: Conference Series, 2014

The irreversibility line in the H−T plane divides the irreversible and reversible behaviour of th... more The irreversibility line in the H−T plane divides the irreversible and reversible behaviour of the magnetization which is of importance for the characterization of high T c superconductors. In this work, we report the production of Y 1-X Lu X Ba 2 Cu 3 O 7-δ (X=0.4, 0.5 and 0.6) superconducting system using the usual solid state reaction method. The irreversibility line H-T plane for the Y 1-X Lu X Ba 2 Cu 3 O 7-δ polycrystalline sample was investigated. The curves of magnetization ZFC (cero field cooled)-FC (field cooled) were measured in magnetic fields between 100 Oe and 4000 Oe, and allowed to obtain the values for irreversibility and critical temperatures.

In this paper, we analyze the structural, morphological, and magnetic properties of CaMn 1−x Mo x... more In this paper, we analyze the structural, morphological, and magnetic properties of CaMn 1−x Mo x O 3 (x = 0.08, 0.10, 0.12) system prepared by the usual solid-state reaction method. The results obtained by scanning electron microscopy (SEM) show an appropriate sintering process, and energy dispersive spectroscopy (EDS) shows that there is not a presence of strange elements. The X-ray diffraction analysis (XRD), through the Rietveld method, reveals that samples crystallize in a Pnma (62) orthorhombic structure, with an increase in the unit cell volume as a function of Mo concentration. Curves of magnetization zero field cooling (ZFC)-field cooling (FC) in a temperature range of 50 to 350 K show similar paramagnetic behavior of every applied field above 110 K in each one of the Mo doping. Below this temperature, the magnetic response becomes ferromagnetic. The antiferromagnetic transition was analyzed by fitting of the Curie-Weiss law. An increase in total effective magnetic moment and Neel temperature, ranging from 200 to 295 K, is observed when Mo concentration increases in CaMn 1−x Mo x O 3 (x = 0.08, 0.10, 0.12) system.

Fitoterapia, 2002

The hyaluronidase inhibitory activity of different fractions obtained from aqueous extract of bla... more The hyaluronidase inhibitory activity of different fractions obtained from aqueous extract of blackberry fruits was evaluated. We found that only fractions F3 and F7 inhibit the tested enzyme. ... Blackberry (Rubus fruticosus B.), from rosaseae family, is a small tree with red-blackish fruit containig ...

Journal of chromatography. B, Analytical technologies in the biomedical and life sciences, 2016

Human antithrombin is a blood derivative widely used in the treatment of coagulation dysfunction.... more Human antithrombin is a blood derivative widely used in the treatment of coagulation dysfunction. Affinity chromatography using heparin (HEP) derivatives is usually used for antithrombin purification. In this study, an affinity procedure based on a magnetic Dacron-HEP composite is proposed. Dacron was firstly converted to Dacron-hydrazide and magnetised by co-precipitation with of Fe(2+)/Fe(3+) (mDAC). HEP was activated by carbodiimide and N-hydroxysuccinimide and covalently linked to mDAC (mDAC-HEP). EDX and infrared spectra analyses confirmed each synthesis step of mDAC-HEP. This composite exhibited superparamagnetism behaviour. Human plasma was incubated with mDAC-HEP (fresh and stored over a long period) and washed with phosphate buffer containing increasing concentrations of NaCl. Human plasma antithrombin activity was reduced by approximately 20% in the presence of the 1.0M NaCl fraction, and this eluate was able to prolong coagulation time (aPTT) using both preparations. Elec...

Avances En Ciencias E Ingenieria, 2011

Se reporta la caracterización del nuevo sistema superconductor Yb 0,5 Ho 0,5 Ba 2 Cu 3 O 7-δ pert... more Se reporta la caracterización del nuevo sistema superconductor Yb 0,5 Ho 0,5 Ba 2 Cu 3 O 7-δ perteneciente a la familia de cupratos de alta temperatura TR123; el material fue producido utilizando el método de reacción de estado sólido (SSR) con una temperatura de sinterizado de 910 °C. Se muestra la caracterización morfológica referente al comportamiento granular utilizando la técnica de Microscopía electrónica de barrido (SEM); la caracterización estructural, se logra sometiendo la muestra a difracción de rayos X (DRX) y se obtienen los parámetros estructurales implementando el método de refinamiento Rietveld en el software GSAS, el material resulta poseer celdas unitarias ortorrómbicas tipo perovskita con un comportamiento superconductor que se evidencia en la curva de resistividad como función de la temperatura cuya derivada presenta un punto crítico en el valor correspondiente a la temperatura crítica Tc 92,61 K.

Avances En Ciencias E Ingenieria, 2011

Se reporta la caracterización del nuevo sistema superconductor Yb 0,5 Ho 0,5 Ba 2 Cu 3 O 7-δ pert... more Se reporta la caracterización del nuevo sistema superconductor Yb 0,5 Ho 0,5 Ba 2 Cu 3 O 7-δ perteneciente a la familia de cupratos de alta temperatura TR123; el material fue producido utilizando el método de reacción de estado sólido (SSR) con una temperatura de sinterizado de 910 °C. Se muestra la caracterización morfológica referente al comportamiento granular utilizando la técnica de Microscopía electrónica de barrido (SEM); la caracterización estructural, se logra sometiendo la muestra a difracción de rayos X (DRX) y se obtienen los parámetros estructurales implementando el método de refinamiento Rietveld en el software GSAS, el material resulta poseer celdas unitarias ortorrómbicas tipo perovskita con un comportamiento superconductor que se evidencia en la curva de resistividad como función de la temperatura cuya derivada presenta un punto crítico en el valor correspondiente a la temperatura crítica Tc 92,61 K.

Applied Surface Science, 2019

Modulated Infrared Radiometry is a photothermal technique which allows thermal characterization o... more Modulated Infrared Radiometry is a photothermal technique which allows thermal characterization of coatings. Thermal properties are determined by applying the "Extremum Method". Zr-ON films were deposited by sputtering to evaluate their thermal properties and the sensitivity of the method and its suitability for different film+substrate systems. Three factors were varied: i) composition/bonding: metallic Zr, crystalline metallic-type Zr-ON and disordered ceramic Zr-ON. The films were deposited in the metallic, reactive and poisoned regimes of the hysteresis curve; ii) each film was deposited simultaneously on three different substrates: high-speed steel, glass and silicon; iii) in each deposition batch, films with four different thicknesses were grown. Each film was deposited in the same batch with different thicknesses on top of different substrates. All of the parameters for which the model is sensitive to are explored in this matrix of 36 different samples. The thermal parameters of the films were calculated and the trends and values were examined. The trends were explained in terms of the microstructural/chemical characteristics of the films, and the influence of each substrate, depending on the film thickness. The obtained values agree with those found in literature, reflecting the nature of the films.

ABSTRACT In this work we report synthesis and characterization of RE2TiMgO6 (RE=Dy, Gd) double-pe... more ABSTRACT In this work we report synthesis and characterization of RE2TiMgO6 (RE=Dy, Gd) double-perovskite materials. Dy2TiMgO6 and Gd2TiMgO6 were prepared by the standard solid-state reaction recipe. Structural study of samples was carried out by X-ray diffraction measurements and Rietveld refinement. Results reveal that the material crystallizes in a monoclinic perovskite with space group P21/n. Experimental lattice parameters for Dy2TiMgO6 were a=5.3624(4) ° A, b=5.5973(2) °A and c=7.6794(2) A° , and for Gd2TiMgO6 a=5.3143(5) A° , b=5.5826(2) °A and c=7.6324(2) A° . From Rietveld analysis we also determine atomic positions, tilt angle, inter-atomic distances and site occupancies. Morphologic study was performed by Scanning Electron Microscopy experiments. Images show strongly coupled grains with mean size 3 ¹m. Measurements of magnetic susceptibility show that both compounds evidence paramagnetic behavior. The Curie-Weiss fitting supplies effective magnetic moments which are 98% in agreement with the theoretical predictions for the isolated rare earth elements for each compound.

Journal of Superconductivity and Novel Magnetism, 2012

The synthesis of the new high temperature superconductor system Yb 1.8 Sm 1.2 Ba 5 Cu 8 O 18 is r... more The synthesis of the new high temperature superconductor system Yb 1.8 Sm 1.2 Ba 5 Cu 8 O 18 is reported. The new material was produced using the standard solid-state reaction method. The structural characterization of the compound was performed by X-ray diffraction and Rietveld refinement using a polycrystalline sample of the material. Structural ordering corresponds to an orthorhombic structure, from the space group P mm2. The lattice parameters of the material are reported here. The superconducting nature of the material was determined by measuring the magnetization, as a function of its temperature, in the regime of low and mean field. A critical temperature value of T c ∼ 88 K was determined for Yb 1.8 Sm 1.2 Ba 5 Cu 8 O 18. The experimental results have shown that the production of a novel group RE 3 Ba 5 Cu 8 O 18 of high-T c superconductivity is possible, by substitution of RE instead of Y in the recently reported new superconductor material Y 3 Ba 5 Cu 8 O 18 .

Brazilian Journal of Physics, 2012

We report in-field kinetic energy results in the temperature region closely below the transition ... more We report in-field kinetic energy results in the temperature region closely below the transition temperature of two differently prepared polycrystalline samples of the superconducting cuprate SmBa2Cu3O 7−δ. The kinetic energy was determined from magnetization measurements performed above the irreversibility line defined by the splitting between the curves obtained according the ZFC and FC prescriptions. The results are analyzed in the intermediate field regime where the London approximation can be used for describing the magnetization. From the analysis, estimations were carried out for the penetration depth and the upper critical field of the studied samples.The difference between the kinectic energy magnitudes for the two studied samples is ascribed to effects from granularity.

Journal of Superconductivity and Novel Magnetism, 2013

Journal of Physics: Conference Series, 2014

The irreversibility line in the H−T plane divides the irreversible and reversible behaviour of th... more The irreversibility line in the H−T plane divides the irreversible and reversible behaviour of the magnetization which is of importance for the characterization of high T c superconductors. In this work, we report the production of Y 1-X Lu X Ba 2 Cu 3 O 7-δ (X=0.4, 0.5 and 0.6) superconducting system using the usual solid state reaction method. The irreversibility line H-T plane for the Y 1-X Lu X Ba 2 Cu 3 O 7-δ polycrystalline sample was investigated. The curves of magnetization ZFC (cero field cooled)-FC (field cooled) were measured in magnetic fields between 100 Oe and 4000 Oe, and allowed to obtain the values for irreversibility and critical temperatures.

In this paper, we analyze the structural, morphological, and magnetic properties of CaMn 1−x Mo x... more In this paper, we analyze the structural, morphological, and magnetic properties of CaMn 1−x Mo x O 3 (x = 0.08, 0.10, 0.12) system prepared by the usual solid-state reaction method. The results obtained by scanning electron microscopy (SEM) show an appropriate sintering process, and energy dispersive spectroscopy (EDS) shows that there is not a presence of strange elements. The X-ray diffraction analysis (XRD), through the Rietveld method, reveals that samples crystallize in a Pnma (62) orthorhombic structure, with an increase in the unit cell volume as a function of Mo concentration. Curves of magnetization zero field cooling (ZFC)-field cooling (FC) in a temperature range of 50 to 350 K show similar paramagnetic behavior of every applied field above 110 K in each one of the Mo doping. Below this temperature, the magnetic response becomes ferromagnetic. The antiferromagnetic transition was analyzed by fitting of the Curie-Weiss law. An increase in total effective magnetic moment and Neel temperature, ranging from 200 to 295 K, is observed when Mo concentration increases in CaMn 1−x Mo x O 3 (x = 0.08, 0.10, 0.12) system.

Fitoterapia, 2002

The hyaluronidase inhibitory activity of different fractions obtained from aqueous extract of bla... more The hyaluronidase inhibitory activity of different fractions obtained from aqueous extract of blackberry fruits was evaluated. We found that only fractions F3 and F7 inhibit the tested enzyme. ... Blackberry (Rubus fruticosus B.), from rosaseae family, is a small tree with red-blackish fruit containig ...

Journal of chromatography. B, Analytical technologies in the biomedical and life sciences, 2016

Human antithrombin is a blood derivative widely used in the treatment of coagulation dysfunction.... more Human antithrombin is a blood derivative widely used in the treatment of coagulation dysfunction. Affinity chromatography using heparin (HEP) derivatives is usually used for antithrombin purification. In this study, an affinity procedure based on a magnetic Dacron-HEP composite is proposed. Dacron was firstly converted to Dacron-hydrazide and magnetised by co-precipitation with of Fe(2+)/Fe(3+) (mDAC). HEP was activated by carbodiimide and N-hydroxysuccinimide and covalently linked to mDAC (mDAC-HEP). EDX and infrared spectra analyses confirmed each synthesis step of mDAC-HEP. This composite exhibited superparamagnetism behaviour. Human plasma was incubated with mDAC-HEP (fresh and stored over a long period) and washed with phosphate buffer containing increasing concentrations of NaCl. Human plasma antithrombin activity was reduced by approximately 20% in the presence of the 1.0M NaCl fraction, and this eluate was able to prolong coagulation time (aPTT) using both preparations. Elec...

Avances En Ciencias E Ingenieria, 2011

Se reporta la caracterización del nuevo sistema superconductor Yb 0,5 Ho 0,5 Ba 2 Cu 3 O 7-δ pert... more Se reporta la caracterización del nuevo sistema superconductor Yb 0,5 Ho 0,5 Ba 2 Cu 3 O 7-δ perteneciente a la familia de cupratos de alta temperatura TR123; el material fue producido utilizando el método de reacción de estado sólido (SSR) con una temperatura de sinterizado de 910 °C. Se muestra la caracterización morfológica referente al comportamiento granular utilizando la técnica de Microscopía electrónica de barrido (SEM); la caracterización estructural, se logra sometiendo la muestra a difracción de rayos X (DRX) y se obtienen los parámetros estructurales implementando el método de refinamiento Rietveld en el software GSAS, el material resulta poseer celdas unitarias ortorrómbicas tipo perovskita con un comportamiento superconductor que se evidencia en la curva de resistividad como función de la temperatura cuya derivada presenta un punto crítico en el valor correspondiente a la temperatura crítica Tc 92,61 K.

Avances En Ciencias E Ingenieria, 2011

Se reporta la caracterización del nuevo sistema superconductor Yb 0,5 Ho 0,5 Ba 2 Cu 3 O 7-δ pert... more Se reporta la caracterización del nuevo sistema superconductor Yb 0,5 Ho 0,5 Ba 2 Cu 3 O 7-δ perteneciente a la familia de cupratos de alta temperatura TR123; el material fue producido utilizando el método de reacción de estado sólido (SSR) con una temperatura de sinterizado de 910 °C. Se muestra la caracterización morfológica referente al comportamiento granular utilizando la técnica de Microscopía electrónica de barrido (SEM); la caracterización estructural, se logra sometiendo la muestra a difracción de rayos X (DRX) y se obtienen los parámetros estructurales implementando el método de refinamiento Rietveld en el software GSAS, el material resulta poseer celdas unitarias ortorrómbicas tipo perovskita con un comportamiento superconductor que se evidencia en la curva de resistividad como función de la temperatura cuya derivada presenta un punto crítico en el valor correspondiente a la temperatura crítica Tc 92,61 K.