Dados como centro de anclaje topológico en una muestra superconductora

Solving the Ginzburg-Landau equations, we analyzed the vortex matter in a superconducting square with a Dimer structure of circular pinning centers generated by a pulsed heat source in the presence of an applied magnetic field. We numerically solved the Ginzburg-Landau equations in order to describe the effect of the temperature of the circular defects on the Abrikosov state of the sample. The pulsed laser produced a variation of the temperature in each defect. It is shown that an anomalous vortex-anti-vortex state (A-aV) appears spontaneously at higher magnetic fields. This could be due to the breaking of the symmetry of the sample by the inclusion of the thermal defects.Resolviendo las ecuaciones de Ginzburg-Landau, analizamos el estado de vórtice en un cuadrado superconductor con centros de anclaje circulares en forma de una estructura de Dados, generados por una fuente de calor pulsada y en presencia de un campo magnético aplicado. Resolvimos numéricamente las ecuaciones Ginzburg-Landau para describir el efecto de la temperatura de los defectos sobre el estado Abrikosov de la muestra. El láser pulsado produce una variación de la temperatura en cada defecto. Se muestra que un estado anómalo vórtice-anti-vórtice (A-aV), aparece espontáneamente hacia campos magnéticos altos. Esto podría deberse a la ruptura de la simetría de la muestra por la inclusión de los defectos térmicos

Surface evaluation of carbon steel doped with nitrogen ions

This study proposes by means of analytical characterization techniques, a structural evaluation of the surface modification of a ferrous material by three-dimensional ion implantation plasma technology. Carbon steel substrates immerse in a gaseous atmosphere, were surface-implanted with nitrogen ions via high voltage pulse discharges activated at a low-pressure range (“high vacuum”). The effect of the surface treatment on the structure, composition, and morphology of the substrates was verified by microscopy and spectroscopy techniques. From the micrographs obtained by scanning electronic microscopy and the analysis elemental by energy dispersive spectroscopy the morphology and nitrogen concentration of the treated and non-treated samples were analyzed and compared. As for the elemental analysis by energy dispersive spectroscopy, nitrogen concentration in the implanted substrates were detected and determined at a relatively low amount. In regard to the x-ray diffraction results, a decrease in the intensity of the (110), (200) and (211) planes of the treated substrate compared with the reference substrate, was observed. The analysis of phases-formation on the surface material performed by Raman spectroscopy, identified mainly ferric oxy-hydroxides typical uniform corrosion products.El presente trabajo de investigación propone mediante técnicas analíticas de caracterización, evaluar la estructura de materiales ferrosos modificados superficialmente mediante la tecnología plasma de implantación iónica tridimensional. Substratos de acero al carbono, inmersos en una atmosfera gaseosa, fueron implantados sobre la superficie con iones de nitrógeno por medio de la activación de una descarga pulsada de alto voltaje a bajas presiones. Se verificó el efecto del tratamiento superficial sobre la morfología, estructura y composición de las superficies implantadas con nitrógeno mediante técnicas microscópicas y espectroscópicas. Los resultados obtenidos por microscopia electrónica de barrido y espectroscopia de rayos X de energía dispersa muestran las morfologías y concentraciones de las especies presentes en la superficie de los substratos implantados y no implantados con iones de nitrógeno. Los espectros de difracción de rayos X muestran una disminución en la intensidad de los planos (110), (200), (211) del sustrato implantado con nitrógeno respecto al sustrato no implantado. Los espectros Raman muestran la formación de compuestos sobre los sustratos implantados con iones de nitrógeno, encontrándose principalmente fases de óxidos e hidróxidos de hierro, típicos productos de corrosión uniforme

Influence of the H2O content and the time on the formation of nanostructures in a chemical solution of H2O/HF/NH4F/EG

The influence of anodizing time on the length, morphology and photoelectrochem-ical properties of TiO2 Nanotubes has been investigated. An optimum anodizing time of 20 min at 20V leads to 220nm long of the nanotubes. By having a detailed control of the electric current one can know exactly the time in which the nanotubes grew and the time in which the process stopped. The FEG-SEM measures show the morphology of the nanotubes and how they come to separate and fall after a certain time. However, the growth of these, is uniform with little remaining material on the surface. For the solution of the anodizing process it is very important to control the amount of water, ethylene glycol and hydrofluoric acid. Small modifications in the solution change the growth time and size of the nanotubes

Experimental comparison of the effect of temperature on the vibrational and morphological properties of NixCo3-xO4 nanostructures

This work presents the experimental comparison of the effect of temperature and nickel addition on the synthesis of NixCo3-xO4 nanostructures x = 0.01, 0.04, 0.1, 0.16, using the sol-gel technique with final heat treatment at 600 °C and 800°C. X-ray diffraction (XRD) analysis indicates the formation of pure Co3O4 at 600 °C and the appearance of an additional residual NiO phase at 800 °C. The presence of this phase evidences a deviation in the peaks of the diffraction angle to lower ones generated by the difference in ionic radii, which is related to the insertion of larger ions (Ni2+) doped in the matrix of Co3O4. Scanning electron microscope (SEM) analysis indicates that there is a densification of the grains at higher temperatures, possibly associated with the thermal effect that generates greater interdiffusion. Fourier-transform infrared spectroscopy (FTIR) spectra show two main absorption bands with vibrations Co2+¬O, Co3+¬O and Ni¬O in 456 cm-1. The effect of doping generates a displacement in the bands that are evident in the Raman analysis, where the vibrational mode A1g at 600 °C is translated 28.07 cm-1. The values of SBET specific surface area indicate that as temperature increases, the surface area and volume of micropores decreases

Effect of nickel and rGO on the photocatalytic properties of Co3 xNixO4 prepared with citric acid and CTAB

This work summarizes the research about Co3 xNixO4 x = 0.0 (0%), 0.01 (1%), and 0.04 (4%) conducted with the addition of reduced graphene oxide, rGO, using two routes: with citric acid R1 (C₆H₈O₇, CA) and cetyltrimethylammonium R2 (C19H42BrN, CTAB) by sol-gel technique. The results show that the composite material ¿with rGO¿ enhanced the photocatalytic degradation of methylene blue (MB). According to the results, incorporating rGO into samples with low Ni concentrations of 1% and 4% and processed at 400 ◦C with R1, significantly increased their specific surface area to 31.372 m2.g-1 and 84.743 m2.g-1, respectively. The XRD technique shows the formation of pure cobalt spinel without associated secondary phases and with complete insertion of Ni into the structure. The presence of CA allows the formation of the oxide at lower temperatures. The results of the magnetic tests suggest that the samples obtained by the two synthesis routes present a paramagnetic behavior. The use of CTAB permits the formation of nanoparticles with low agglomeration. TEM images indicate that the sizes of the nanoparticles obtained in the synthesis are less than 20 nm. Thus, based on Raman spectroscopy, the vibrational modes corresponding to the Co3-xNixO4 structure were studied, identifying a broadening and displacement of the peaks with the addition of Ni. Moreover, the disappearance of the peaks corresponding to rGO and attributed to the coating of Co3-xNixO4 graphene nanoparticles was observed. The adsorption isotherms show the behavior of a mesoporous textured material. The diffuse reflectance indicates that R2 with a 1.72 eV value obtained the material with the smallest gap. In addition, the process identified that the existence of reduced graphene oxide increases the material's specific surface area, which plays a crucial role in MB degradation, outperforming the 4% Ni sample that degraded 39.65% in a two-hour treatment