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After coal fly ash activation with alkaline NaOH solution by the hydrothermal method, it was possible to synthesize the zeolites type Cancrinite and Analcime. Slow positron beam experiments have been performed on two set of samples. One in which the NaOH concentration was varied and another one in which the synthesis temperature range was varied. The mineralogical composition was determined by X ray diffraction, the morphology of one of the zeolite samples as compared with the coal fly ash was observed by 3D X-ray imaging. Positron results suggest that increasing the NaOH concentration produces an increase in open volume and/or defects while increasing the temperature in the sample preparation diminishes it.
G.I. Supelano; C.A. Palacio; M. Weber; J. McCoy; J. Jennings; J.A. Mejía Gómez; C.A. Parra Vargas; C. Ortiz; K. Lynn. Study of fly ash based zeolite by using slow positrons. Materials Science and Engineering: B 2020, 263, 114890 .
AMA StyleG.I. Supelano, C.A. Palacio, M. Weber, J. McCoy, J. Jennings, J.A. Mejía Gómez, C.A. Parra Vargas, C. Ortiz, K. Lynn. Study of fly ash based zeolite by using slow positrons. Materials Science and Engineering: B. 2020; 263 ():114890.
Chicago/Turabian StyleG.I. Supelano; C.A. Palacio; M. Weber; J. McCoy; J. Jennings; J.A. Mejía Gómez; C.A. Parra Vargas; C. Ortiz; K. Lynn. 2020. "Study of fly ash based zeolite by using slow positrons." Materials Science and Engineering: B 263, no. : 114890.
Polyaniline (PANI) has recently gained great attention due to its outstanding electrical properties and ease of processability; these characteristics make it ideal for the manufacturing of polymer blends. In this study, the processing and piezoresistive characterization of polymer composites resulting from the blend of PANI with ultra-high molecular weight polyethylene (UHMWPE) in different weight percentages (wt %) is reported. The PANI/UHMWPE composites were uniformly homogenized by mechanical mixing and the pellets were manufactured by compression molding. A total of four pellets were manufactured, with PANI percentages of 20, 25, 30 and 35 wt %. Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to confirm the effective distribution of PANI and UHMWPE particles in the pellets. A piezoresistive characterization was performed on the basis of compressive forces at different voltages; it was found that the error metrics of hysteresis and drift were influenced by the operating voltage. In general, larger voltages lowered the error metrics, but a reduction in sensor sensitivity came along with voltage increments. In an attempt to explain such a phenomenon, the authors developed a microscopic model for the piezoresistive response of PANI composites, aiming towards a broader usage of PANI composites in strain/stress sensing applications as an alternative to carbonaceous materials.
Andrés Felipe Cruz-Pacheco; Leonel Paredes-Madrid; Jahir Orozco; Jairo Alberto Gómez-Cuaspud; Carlos R. Batista-Rodríguez; Carlos Andrés Palacio Gómez. Assessing the Influence of the Sourcing Voltage on Polyaniline Composites for Stress Sensing Applications. Polymers 2020, 12, 1164 .
AMA StyleAndrés Felipe Cruz-Pacheco, Leonel Paredes-Madrid, Jahir Orozco, Jairo Alberto Gómez-Cuaspud, Carlos R. Batista-Rodríguez, Carlos Andrés Palacio Gómez. Assessing the Influence of the Sourcing Voltage on Polyaniline Composites for Stress Sensing Applications. Polymers. 2020; 12 (5):1164.
Chicago/Turabian StyleAndrés Felipe Cruz-Pacheco; Leonel Paredes-Madrid; Jahir Orozco; Jairo Alberto Gómez-Cuaspud; Carlos R. Batista-Rodríguez; Carlos Andrés Palacio Gómez. 2020. "Assessing the Influence of the Sourcing Voltage on Polyaniline Composites for Stress Sensing Applications." Polymers 12, no. 5: 1164.
An adequate identification of physico-chemical properties of clay minerals is an important step to develop technological applications. In Colombia, a common issue is that the evaluation of raw materials with the preparation of the final product depend on empirical knowledge, it is common not to use any kind of technological tool to conduct any analysis. In contrast, the clay mixtures for this study were prepared and characterized by following a careful procedure to evaluate and control the qualities such as color of the final product. For this purpose, differential scanning calorimetry, magnetization, scanning electron microscopy, X-rays analysis, and positron annihilation lifetime spectroscopy techniques were applied. It is possible to conclude that the implementation scientific techniques in the sector of clay minerals may serve as a powerful tool, since preparing samples in an empirical way have been proved to lead to different qualities in the final product.
Iván Supelano García; Carlos Andrés Palacio Gómez; Julieth Alexandra Mejía Gómez; Carlos Arturo Parra Vargas. Physico-chemical characterization of clay mineral mixtures from Boyacá-Colombia. DYNA 2020, 87, 116 -122.
AMA StyleIván Supelano García, Carlos Andrés Palacio Gómez, Julieth Alexandra Mejía Gómez, Carlos Arturo Parra Vargas. Physico-chemical characterization of clay mineral mixtures from Boyacá-Colombia. DYNA. 2020; 87 (213):116-122.
Chicago/Turabian StyleIván Supelano García; Carlos Andrés Palacio Gómez; Julieth Alexandra Mejía Gómez; Carlos Arturo Parra Vargas. 2020. "Physico-chemical characterization of clay mineral mixtures from Boyacá-Colombia." DYNA 87, no. 213: 116-122.
A set of Nickel-Zinc ferrite samples (Ni1-xZnxFe2O4, x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were synthesized by the low-energy ball milling method with subsequent thermal treatment. Infrared, Raman and Mössbauer spectroscopies were used to analyze the lattice dynamics and structure of the prepared samples. Infrared studies showed a dominant absorption band ranging from 548 cm−1 to 592 cm−1 associated with cation-oxygen stretching vibrations at tetrahedral sites. The five Raman modes, predicted by factor group analysis, were observed in all spectra. All these spectra changed in symmetry because of the incorporation of Zn into the lattice, and the reordering of Fe, Ni and Zn ions in both, tetrahedral (A) and octahedral [B] sites. It is observed that Fe3+ ions located at tetrahedral sites are gradually displaced to octahedral sites by the increase of Zn2+ ions. Mössbauer spectra were collected for all samples at 295 K and at 18 K. The spectra were properly fitted by using a model that assumes that the average hyperfine magnetic field at the octahedral sites is due to a random substitution of magnetically interacting FeA3+ ions by diamagnetic ZnA2+ ions at the tetrahedral sites. It was found that the average supertransfered hyperfine field due to one FeA3+-O2+-FeB3+ superexchange interaction was equal to about 0.9 T at 18 K. The zinc contents at tetrahedral sites as obtained by Raman, Mössbauer and XRD techniques are compared and discussed.
Carlos Andrés Palacio Gómez; César Augusto Barrero Meneses; Juan Antonio Jaén. Raman, infrared and Mössbauer spectroscopic studies of solid-state synthesized Ni-Zn ferrites. Journal of Magnetism and Magnetic Materials 2020, 505, 166710 .
AMA StyleCarlos Andrés Palacio Gómez, César Augusto Barrero Meneses, Juan Antonio Jaén. Raman, infrared and Mössbauer spectroscopic studies of solid-state synthesized Ni-Zn ferrites. Journal of Magnetism and Magnetic Materials. 2020; 505 ():166710.
Chicago/Turabian StyleCarlos Andrés Palacio Gómez; César Augusto Barrero Meneses; Juan Antonio Jaén. 2020. "Raman, infrared and Mössbauer spectroscopic studies of solid-state synthesized Ni-Zn ferrites." Journal of Magnetism and Magnetic Materials 505, no. : 166710.
Coal fly ash (CFA) was obtained from the Sochagota TermoPaipa IV power plant in Boyacá Colombia. CFA was subjected to a hydrothermal activation with NaOH. Morphology, elemental and mineralogical composition and magnetic properties of the obtained products were studied by means of SEM-EDX, XRD and VSM. Activation with NaOH (4–5 M) between 80 and 150 °C for 24 h produced cancrinite zeolite; activation with NaOH at 2 and 3 M at 95 °C produced analcime zeolite. It was found out, that the synthesized zeolites exhibit a ferrimagnetic behavior due to iron coming from CFA. The magnetic response of the obtained products allows the use of these materials to environmental applications in aqueous medium. Adsorption test for methylene blue was performed for an analcime and cancrinite zeolite, the results show that equilibrium is reached after 60 min. The data of adsorption isotherms for analcime and cancrinite zeolite were fitted to Freundlich and Langmuir model, respectively. The synthesized zeolites from CFA were successfully used to remove methylene blue from aqueous solution.
G.I. Supelano; Jairo Alberto Gómez Cuaspud; Luis Carlos Moreno-Aldana; C. Ortiz; C.A. Trujillo; C.A. Palacio; C.A. Parra Vargas; Carlos Andrés Palacio Gómez. Synthesis of magnetic zeolites from recycled fly ash for adsorption of methylene blue. Fuel 2019, 263, 116800 .
AMA StyleG.I. Supelano, Jairo Alberto Gómez Cuaspud, Luis Carlos Moreno-Aldana, C. Ortiz, C.A. Trujillo, C.A. Palacio, C.A. Parra Vargas, Carlos Andrés Palacio Gómez. Synthesis of magnetic zeolites from recycled fly ash for adsorption of methylene blue. Fuel. 2019; 263 ():116800.
Chicago/Turabian StyleG.I. Supelano; Jairo Alberto Gómez Cuaspud; Luis Carlos Moreno-Aldana; C. Ortiz; C.A. Trujillo; C.A. Palacio; C.A. Parra Vargas; Carlos Andrés Palacio Gómez. 2019. "Synthesis of magnetic zeolites from recycled fly ash for adsorption of methylene blue." Fuel 263, no. : 116800.
Leonel Paredes-Madrid; Arnaldo Matute; Carlos Palacio; Carlos Andrés Palacio Gómez. Understanding the effect of sourcing voltage and driving circuit in the repeatability of measurements in force sensing resistors (FSRs). Measurement Science and Technology 2019, 30, 115101 .
AMA StyleLeonel Paredes-Madrid, Arnaldo Matute, Carlos Palacio, Carlos Andrés Palacio Gómez. Understanding the effect of sourcing voltage and driving circuit in the repeatability of measurements in force sensing resistors (FSRs). Measurement Science and Technology. 2019; 30 (11):115101.
Chicago/Turabian StyleLeonel Paredes-Madrid; Arnaldo Matute; Carlos Palacio; Carlos Andrés Palacio Gómez. 2019. "Understanding the effect of sourcing voltage and driving circuit in the repeatability of measurements in force sensing resistors (FSRs)." Measurement Science and Technology 30, no. 11: 115101.
Samples of Nickel-Zinc ferrite, Ni1-xZnxFe2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0), were synthesized by a solid state reaction method. The morphology of four of the samples (x = 0.0, 0.4, 0.6 and 1.0) was observed with 3D X-ray imaging. The distortion caused by the increase of zinc in the ferrite structure and the respective movement of the trivalent (Fe) and divalent (Ni) ions from the tetrahedral- to the octahedral-sites cause some vacancies which act as positron traps. Doppler broadening of annihilation radiation experiments have been performed with a variable energy monoenergetic positron beam. The positron results as a function of the energy/depth implantation are presented in this work.
Carlos Andrés Palacio Gómez; Jedidiah Jacob McCoy; Marc H. Weber; Kelvin G. Lynn. Effect of Zn for Ni substitution on the properties of Nickel-Zinc ferrites as studied by low-energy implanted positrons. Journal of Magnetism and Magnetic Materials 2019, 481, 93 -99.
AMA StyleCarlos Andrés Palacio Gómez, Jedidiah Jacob McCoy, Marc H. Weber, Kelvin G. Lynn. Effect of Zn for Ni substitution on the properties of Nickel-Zinc ferrites as studied by low-energy implanted positrons. Journal of Magnetism and Magnetic Materials. 2019; 481 ():93-99.
Chicago/Turabian StyleCarlos Andrés Palacio Gómez; Jedidiah Jacob McCoy; Marc H. Weber; Kelvin G. Lynn. 2019. "Effect of Zn for Ni substitution on the properties of Nickel-Zinc ferrites as studied by low-energy implanted positrons." Journal of Magnetism and Magnetic Materials 481, no. : 93-99.
The coating of polymeric substrate polyetheretherketone (PEEK) with silver nanoparticles (AgNPs) was carried out by a wet chemical route at room temperature. The coating process was developed from the Tollens reagent and D-glucose as reducing agent. The resulting composite exhibited antimicrobial activity. The PEEK films were coated with a single layer and two layers of silver nanoparticles in various concentrations. The crystallographic properties of the polymer and the silver nanoparticles were analyzed by X-ray diffraction (XRD). Fourier transform infrared spectra (FTIR) show the interaction between the silver nanoparticles with the polymeric substrate. Transmission electron microscope (TEM) images confirmed the obtaining of metallic nanoparticles with average sizes of 25 nm. It was possible to estimate the amount of silver deposited on PEEK with the help of thermogravimetric analysis. The morphology and shape of the AgNPs uniformly deposited on the PEEK films was ascertained by the techniques of scanning electron microscopy (SEM) and atomic force microscopy (AFM), evidencing the increase in the amount of silver by increasing the concentration of the metal precursor. Finally, the antibacterial activity of the films coated with Ag in Escherichia coli, Serratia marcescens and Bacillus licheniformis was evaluated, evidencing that the concentration of silver is crucial in the cellular replication of the bacteria.
Andrés Felipe Cruz-Pacheco; Deysi Tatiana Muñoz-Castiblanco; Jairo Alberto Gómez Cuaspud; Leonel Paredes-Madrid; Carlos Arturo Parra Vargas; José Jobanny Martínez Zambrano; Carlos Andrés Palacio Gómez. Coating of Polyetheretherketone Films with Silver Nanoparticles by a Simple Chemical Reduction Method and Their Antibacterial Activity. Coatings 2019, 9, 91 .
AMA StyleAndrés Felipe Cruz-Pacheco, Deysi Tatiana Muñoz-Castiblanco, Jairo Alberto Gómez Cuaspud, Leonel Paredes-Madrid, Carlos Arturo Parra Vargas, José Jobanny Martínez Zambrano, Carlos Andrés Palacio Gómez. Coating of Polyetheretherketone Films with Silver Nanoparticles by a Simple Chemical Reduction Method and Their Antibacterial Activity. Coatings. 2019; 9 (2):91.
Chicago/Turabian StyleAndrés Felipe Cruz-Pacheco; Deysi Tatiana Muñoz-Castiblanco; Jairo Alberto Gómez Cuaspud; Leonel Paredes-Madrid; Carlos Arturo Parra Vargas; José Jobanny Martínez Zambrano; Carlos Andrés Palacio Gómez. 2019. "Coating of Polyetheretherketone Films with Silver Nanoparticles by a Simple Chemical Reduction Method and Their Antibacterial Activity." Coatings 9, no. 2: 91.
A series of Nickel-Zinc ferrite samples were synthesized by low-energy ball milling with subsequent thermal treatment in air at 1200 °C for 12 h. X-ray Diffraction patterns confirm the formation of the ferrite phases. Lattice parameters were found to increase almost linearly from 8.3366 Å to 8.4387 Å with the increment of zinc substitution. The oxygen parameters also increased and were found to closely follow an earlier proposed power law equation. The cation-oxygen bond lengths, suggest a gradual tetrahedral expansion and octahedral contraction with increasing Zn content. Additionally, the occupation of Zn2+ and Ni2+ ions in all samples has been determined by using the line intensity ratios of diffraction peaks together with a proposed general chemical formula. From the calculated cation distributions, it was found that the theoretical lattice parameters agree with the experimental ones. By using, the Williamson-Hall method, an average crystallite size of ∼36 nm was found.
Carlos Andrés Palacio Gómez; César Augusto Barrero Meneses; Arnaldo Matute. Structural parameters and cation distributions in solid state synthesized Ni-Zn ferrites. Materials Science and Engineering: B 2018, 236-237, 48 -55.
AMA StyleCarlos Andrés Palacio Gómez, César Augusto Barrero Meneses, Arnaldo Matute. Structural parameters and cation distributions in solid state synthesized Ni-Zn ferrites. Materials Science and Engineering: B. 2018; 236-237 ():48-55.
Chicago/Turabian StyleCarlos Andrés Palacio Gómez; César Augusto Barrero Meneses; Arnaldo Matute. 2018. "Structural parameters and cation distributions in solid state synthesized Ni-Zn ferrites." Materials Science and Engineering: B 236-237, no. : 48-55.
Conductive polymer composites are manufactured by randomly dispersing conductive particles along an insulating polymer matrix. Several authors have attempted to model the piezoresistive response of conductive polymer composites. However, all the proposed models rely upon experimental measurements of the electrical resistance at rest state. Similarly, the models available in literature assume a voltage-independent resistance and a stress-independent area for tunneling conduction. With the aim of developing and validating a more comprehensive model, a test bench capable of exerting controlled forces has been developed. Commercially available sensors—which are manufactured from conductive polymer composites—have been tested at different voltages and stresses, and a model has been derived on the basis of equations for the quantum tunneling conduction through thin insulating film layers. The resistance contribution from the contact resistance has been included in the model together with the resistance contribution from the conductive particles. The proposed model embraces a voltage-dependent behavior for the composite resistance, and a stress-dependent behavior for the tunneling conduction area. The proposed model is capable of predicting sensor current based upon information from the sourcing voltage and the applied stress. This study uses a physical (non-phenomenological) approach for all the phenomena discussed here.
Leonel Paredes-Madrid; Carlos A. Palacio; Arnaldo Matute; Carlos A. Parra Vargas. Underlying Physics of Conductive Polymer Composites and Force Sensing Resistors (FSRs) under Static Loading Conditions. Sensors 2017, 17, 2108 .
AMA StyleLeonel Paredes-Madrid, Carlos A. Palacio, Arnaldo Matute, Carlos A. Parra Vargas. Underlying Physics of Conductive Polymer Composites and Force Sensing Resistors (FSRs) under Static Loading Conditions. Sensors. 2017; 17 (9):2108.
Chicago/Turabian StyleLeonel Paredes-Madrid; Carlos A. Palacio; Arnaldo Matute; Carlos A. Parra Vargas. 2017. "Underlying Physics of Conductive Polymer Composites and Force Sensing Resistors (FSRs) under Static Loading Conditions." Sensors 17, no. 9: 2108.
K.M. Mostafa; P.R. Calvillo; J. De Baerdemaeker; K. Verbeken; C.A. Palacio; D. Segers; Y. Houbaert; Carlos Andrés Palacio Gómez. Physical, microstructural and mechanical study of isochronal annealing of deformed commercial iron. Journal of Alloys and Compounds 2016, 656, 378 -382.
AMA StyleK.M. Mostafa, P.R. Calvillo, J. De Baerdemaeker, K. Verbeken, C.A. Palacio, D. Segers, Y. Houbaert, Carlos Andrés Palacio Gómez. Physical, microstructural and mechanical study of isochronal annealing of deformed commercial iron. Journal of Alloys and Compounds. 2016; 656 ():378-382.
Chicago/Turabian StyleK.M. Mostafa; P.R. Calvillo; J. De Baerdemaeker; K. Verbeken; C.A. Palacio; D. Segers; Y. Houbaert; Carlos Andrés Palacio Gómez. 2016. "Physical, microstructural and mechanical study of isochronal annealing of deformed commercial iron." Journal of Alloys and Compounds 656, no. : 378-382.
This paper reports the production of YBa\(_{2}\)Cu\(_{3-x}\)Fe\(_{x}\)O\(_{7-\delta }\) (0.05 \(\le x\) \(\le \) 0.12) superconducting system by using the standard solid-state reaction technique. A Rietveld refinement of the experimental X-ray diffraction patterns allows the determination of the lattice parameters and the phase composition of the studied system; the mean present phase shown is an orthorhombic phase Pmmm. Magnetic and transport properties are typical for superconducting samples. In this paper, magnetic susceptibility fluctuations are studied in the limit of weak magnetic fields. For each of the samples, the best fit of the experimental data of \(\Delta \chi \)/T, in the limit of weak magnetic fields in function of the reduced temperature, allowed us to obtain the values of \(A_\mathrm{s}\) (diamagnetism of Schmidt) and \(B_\mathrm{LD}\) (LD parameter). The Lawrence–Doniach model (LD) has been used for the fluctuation analysis. It is demonstrated, by means of the analysis of the thermal fluctuations, that the YBa\(_{2}\)Cu\(_{3-x}\)Fe\(_{x}\)O\(_{7-\delta }\) system has an excellent 2D scaling behavior (BLD).
G. I. Supelano; Jorge Luiz Pimentel Jr.; C. A. Palacio; Carlos Andrés Palacio Gómez; R. Menegotto Costa; Fania Danitza Caicedo Mateus; D. Martinez Buitrago; Jairo Roa-Rojas; F. Mesquita; C. A. Parra Vargas. Weak Field Magnetic Susceptibility Fluctuations Above the Superconducting Transition YBa $$_{2}$$ 2 Cu $$_{3-x}$$ 3 - x Fe $$_{x}$$ x O $$_{7-\delta }$$ 7 - δ (0.05 $$\le x$$ ≤ x $$\le $$ ≤ 0.12). Journal of Low Temperature Physics 2015, 182, 141 -152.
AMA StyleG. I. Supelano, Jorge Luiz Pimentel Jr., C. A. Palacio, Carlos Andrés Palacio Gómez, R. Menegotto Costa, Fania Danitza Caicedo Mateus, D. Martinez Buitrago, Jairo Roa-Rojas, F. Mesquita, C. A. Parra Vargas. Weak Field Magnetic Susceptibility Fluctuations Above the Superconducting Transition YBa $$_{2}$$ 2 Cu $$_{3-x}$$ 3 - x Fe $$_{x}$$ x O $$_{7-\delta }$$ 7 - δ (0.05 $$\le x$$ ≤ x $$\le $$ ≤ 0.12). Journal of Low Temperature Physics. 2015; 182 (5-6):141-152.
Chicago/Turabian StyleG. I. Supelano; Jorge Luiz Pimentel Jr.; C. A. Palacio; Carlos Andrés Palacio Gómez; R. Menegotto Costa; Fania Danitza Caicedo Mateus; D. Martinez Buitrago; Jairo Roa-Rojas; F. Mesquita; C. A. Parra Vargas. 2015. "Weak Field Magnetic Susceptibility Fluctuations Above the Superconducting Transition YBa $$_{2}$$ 2 Cu $$_{3-x}$$ 3 - x Fe $$_{x}$$ x O $$_{7-\delta }$$ 7 - δ (0.05 $$\le x$$ ≤ x $$\le $$ ≤ 0.12)." Journal of Low Temperature Physics 182, no. 5-6: 141-152.
Carlos Andrés Palacio Gómez; G I Supelano García; C A Palacio; C A Parra Vargas. Production and structural and magnetic characterization of a Bi1-xYxFeO3(x = 0, 0.25 and 0.30) system. Journal of Physics: Conference Series 2015, 614, 012003 .
AMA StyleCarlos Andrés Palacio Gómez, G I Supelano García, C A Palacio, C A Parra Vargas. Production and structural and magnetic characterization of a Bi1-xYxFeO3(x = 0, 0.25 and 0.30) system. Journal of Physics: Conference Series. 2015; 614 ():012003.
Chicago/Turabian StyleCarlos Andrés Palacio Gómez; G I Supelano García; C A Palacio; C A Parra Vargas. 2015. "Production and structural and magnetic characterization of a Bi1-xYxFeO3(x = 0, 0.25 and 0.30) system." Journal of Physics: Conference Series 614, no. : 012003.
Carlos Andrés Palacio Gómez; J. Antonissen; C.A. Palacio; E. De Grave. Effects of Si as alloying element on corrosion resistance of weathering steel. Corrosion Science 2012, 59, 198 -203.
AMA StyleCarlos Andrés Palacio Gómez, J. Antonissen, C.A. Palacio, E. De Grave. Effects of Si as alloying element on corrosion resistance of weathering steel. Corrosion Science. 2012; 59 ():198-203.
Chicago/Turabian StyleCarlos Andrés Palacio Gómez; J. Antonissen; C.A. Palacio; E. De Grave. 2012. "Effects of Si as alloying element on corrosion resistance of weathering steel." Corrosion Science 59, no. : 198-203.
The structural changes of rapidly-quenched amorphous Mg–Cu–Y alloys during time-dependent room-temperature embrittlement were investigated. A continuous reduction in enthalpic content with time, corresponding to a loss in free volume, and radial atomic distances obtained from synchrotron X-ray diffraction experiments imply an overall reduction in volume. Two distinct lifetimes were found by positron annihilation lifetime spectra, with the longer-lifetime component (attributed to areas of larger free volume) vanishing after an ageing time corresponding roughly to the time of embrittlement. Coincidence Doppler broadening suggests that the immediate environment of the annihilation sites is not altered during ageing. The mechanical behaviour correlates with the structural changes in the alloy. The densification observed is assumed to influence the sharp ductile-to-brittle transition in these Mg-based glasses, and the abrupt change in bending ductility is found to result from disappearing large free volume.
D.I. Uhlenhaut; F.H. Dalla Torre; Alberto Castellero; C.A.P. Gomez; N. Djourelov; G. Krauss; Bernd Schmitt; B. Patterson; J.F. Löffler. Structural analysis of rapidly solidified Mg–Cu–Y glasses during room-temperature embrittlement. Philosophical Magazine 2009, 89, 233 -248.
AMA StyleD.I. Uhlenhaut, F.H. Dalla Torre, Alberto Castellero, C.A.P. Gomez, N. Djourelov, G. Krauss, Bernd Schmitt, B. Patterson, J.F. Löffler. Structural analysis of rapidly solidified Mg–Cu–Y glasses during room-temperature embrittlement. Philosophical Magazine. 2009; 89 (3):233-248.
Chicago/Turabian StyleD.I. Uhlenhaut; F.H. Dalla Torre; Alberto Castellero; C.A.P. Gomez; N. Djourelov; G. Krauss; Bernd Schmitt; B. Patterson; J.F. Löffler. 2009. "Structural analysis of rapidly solidified Mg–Cu–Y glasses during room-temperature embrittlement." Philosophical Magazine 89, no. 3: 233-248.
Positron transmission experiments were performed on free-standing poly(methyl-methacrylate) (PMMA) and polystyrene (PS) films of nanometric thicknesses made by spin coating. The power_law equation z1/2(E) )=(α/ρ)En was determined from the measurements of the S-parameter as a function of the positron implantation energy. These transmission experiments indicate that n = 1.90(±0.08) and α = 1.33(±0.10) μg cm-2 which deviates from the values found by Algers et al. (n = 1.71(±0.05) and α = 2.8(±0.2) μg cm-2) and the commonly used parameters (n = 1.6 and α = 4.0 μg cm-2).
Carlos A. Palacio; Jérémie De Baerdemaeker; Danny Segers; Khaled M. Mostafa; Dries Van Thourhout; Charles Dauwe; Carlos Andrés Palacio Gómez. Positron Implantation and Transmission Experiments on Free-Standing Nanometric Polymer Films. Materials Science Forum 2008, 607, 105 -107.
AMA StyleCarlos A. Palacio, Jérémie De Baerdemaeker, Danny Segers, Khaled M. Mostafa, Dries Van Thourhout, Charles Dauwe, Carlos Andrés Palacio Gómez. Positron Implantation and Transmission Experiments on Free-Standing Nanometric Polymer Films. Materials Science Forum. 2008; 607 ():105-107.
Chicago/Turabian StyleCarlos A. Palacio; Jérémie De Baerdemaeker; Danny Segers; Khaled M. Mostafa; Dries Van Thourhout; Charles Dauwe; Carlos Andrés Palacio Gómez. 2008. "Positron Implantation and Transmission Experiments on Free-Standing Nanometric Polymer Films." Materials Science Forum 607, no. : 105-107.
C.A. Palacio; J. De Baerdemaeker; D. Van Thourhout; C. Dauwe; Carlos Andrés Palacio Gómez. Emission of positronium in a nanometric PMMA film. Applied Surface Science 2008, 255, 197 -200.
AMA StyleC.A. Palacio, J. De Baerdemaeker, D. Van Thourhout, C. Dauwe, Carlos Andrés Palacio Gómez. Emission of positronium in a nanometric PMMA film. Applied Surface Science. 2008; 255 (1):197-200.
Chicago/Turabian StyleC.A. Palacio; J. De Baerdemaeker; D. Van Thourhout; C. Dauwe; Carlos Andrés Palacio Gómez. 2008. "Emission of positronium in a nanometric PMMA film." Applied Surface Science 255, no. 1: 197-200.
C. Dauwe; C. Bas; C.A. Palacio; Carlos Andrés Palacio Gómez. Formation of positronium: Multi-exponentials versus blob model. Radiation Physics and Chemistry 2007, 76, 280 -284.
AMA StyleC. Dauwe, C. Bas, C.A. Palacio, Carlos Andrés Palacio Gómez. Formation of positronium: Multi-exponentials versus blob model. Radiation Physics and Chemistry. 2007; 76 (2):280-284.
Chicago/Turabian StyleC. Dauwe; C. Bas; C.A. Palacio; Carlos Andrés Palacio Gómez. 2007. "Formation of positronium: Multi-exponentials versus blob model." Radiation Physics and Chemistry 76, no. 2: 280-284.