Centro de investigación de Nanotecnología Aplicada (CNAP)Contiene la producción documental (impresa y audiovisual) del CNAPhttps://repositorio.umayor.cl/xmlui/handle/sibum/80102024-03-28T00:51:48Z2024-03-28T00:51:48ZSpin-lattice-dynamics analysis of magnetic properties of iron under compressiondos Santos, GonzaloMeyer, RobertTramontina, DiegoBringa, Eduardo M. [Univ Mayor, Fac Ciencias, Ctr Nanotecnol Aplicada, Chile]Urbassek, Herbert M.https://repositorio.umayor.cl/xmlui/handle/sibum/95072024-03-22T23:20:06Z2023-08-31T00:00:00ZSpin-lattice-dynamics analysis of magnetic properties of iron under compression
dos Santos, Gonzalo; Meyer, Robert; Tramontina, Diego; Bringa, Eduardo M. [Univ Mayor, Fac Ciencias, Ctr Nanotecnol Aplicada, Chile]; Urbassek, Herbert M.
Compression of a magnetic material leads to a change in its magnetic properties. We examine this effect using spin-lattice dynamics for the special case of bcc-Fe, using both single- and poly-crystalline Fe and a bicontinuous nanofoam structure. We find that during the elastic phase of compression, the magnetization increases due to a higher population of the nearest-neighbor shell of atoms and the resulting higher exchange interaction of neighboring spins. In contrast, in the plastic phase of compression, the magnetization sinks, as defects are created, increasing the disorder and typically decreasing the average atom coordination number. The effects are more pronounced in single crystals than in polycrystals, since the presence of defects in the form of grain boundaries counteracts the increase in magnetization during the elastic phase of compression. Also, the effects are more pronounced at temperatures close to the Curie temperature than at room temperature. In nanofoams, the effect of compression is minor since compression proceeds more by void reduction and filament bending-with negligible effect on magnetization-than by strain within the ligaments. These findings will prove useful for tailoring magnetization under strain by introducing plasticity.
2023-08-31T00:00:00ZSimulated nanoindentation into single-phase fcc FexNi1-x alloys predicts maximum hardness for equiatomic stoichiometryAlabd Alhafez, IyadDeluigi, Orlando R.Tramontina, DiegoRuestes, Carlos J.Bringa, Eduardo M. [Univ Mayor, Ctr Nanotecnol Aplicada, Chile]Urbassek, Herbert M.https://repositorio.umayor.cl/xmlui/handle/sibum/95062024-03-22T23:08:55Z2023-06-16T00:00:00ZSimulated nanoindentation into single-phase fcc FexNi1-x alloys predicts maximum hardness for equiatomic stoichiometry
Alabd Alhafez, Iyad; Deluigi, Orlando R.; Tramontina, Diego; Ruestes, Carlos J.; Bringa, Eduardo M. [Univ Mayor, Ctr Nanotecnol Aplicada, Chile]; Urbassek, Herbert M.
We investigate by molecular dynamics simulation the mechanical behavior of concentrated alloys under nanoindentation for the special example of single-phase fcc FexNi1-x alloys. The indentation hardness is maximum for the equiatomic alloy, x=0.5. This finding is in agreement with experimental results on the strength of these alloys under uniaxial strain. We explain this finding with the increase of the unstable stacking fault energy in the alloys towards x=0.5. With increasing Fe content, loop emission from the plastic zone under the indenter becomes less pronounced and the plastic zone features a larger fraction of screw dislocation segments; simultaneously, the length of the dislocation network and the number of atoms in the stacking faults generated in the plastic zone increase. However, the volume of twinned regions in the plastic zone is highest for the elemental solids and decreases for the alloys. This feature is explained by the fact that twinning proceeds by the glide of dislocations on adjacent parallel lattice planes; this concerted motion is less efficient in the alloys. Finally, we find that surface imprints show increasing pile-up heights with increasing Fe content. The present results will be of interest for hardness engineering or generating hardness profiles in concentrated alloys.
2023-06-16T00:00:00ZFast simultaneous electrochemical detection of Bisphenol-A and Bisphenol-S in urban wastewater using a graphene oxide-iron nanoparticles hybrid sensorPiña, SamuelSepúlveda, Pamela [Univ Mayor, Fac Ciencias, Ctr Nanotecnol Aplicada CNAP, Chile]García-García, AlejandraMoreno-Bárcenas, AlejandraToledo-Neira, CarlaSalazar-González, Ricardohttps://repositorio.umayor.cl/xmlui/handle/sibum/95012024-03-22T18:21:23Z2023-11-10T00:00:00ZFast simultaneous electrochemical detection of Bisphenol-A and Bisphenol-S in urban wastewater using a graphene oxide-iron nanoparticles hybrid sensor
Piña, Samuel; Sepúlveda, Pamela [Univ Mayor, Fac Ciencias, Ctr Nanotecnol Aplicada CNAP, Chile]; García-García, Alejandra; Moreno-Bárcenas, Alejandra; Toledo-Neira, Carla; Salazar-González, Ricardo
In this work, a novel and sensitive electrochemical sensor was developed for the simultaneous determination of low concentration levels of Bisphenol-A (BPA) and Bisphenol-S (BPS) in a secondary effluent from a wastewater treatment plant and surface water. The sensor design involved the utilization of a glassy carbon electrode that was modified with hybrid iron nanoparticles and a nanostructure of graphene oxide. The synthesized material displayed a stable heterostructure, facilitating efficient electronic transfer and exhibiting impressive electro-catalytic capacity. Furthermore, the sensor successfully detected anodic signals of BPA and BPS with a peak separation of 0.28 V, confirming its excellent performance. For method optimization, a chemometric tool based on a Central Composite Face (CCF) design response surface was employed. The optimized conditions yielded an analytical curve with a linear range of 15.0 to 120.0 mu mol L-1 for BPA, represented by the equation Iap (mu A)=-0.088 + 0.044 (mu A L mu mol-1) [cBPA], and 20.0 to 70.0 mu mol L-1 for BPS, represented by the equation Iap (mu A)=-0.367 + 0.025 (mu A L mu mol-1) [cBPS]. The detection and quantification limits for BPA were established at 12.05 and 36.51 mu mol L-1, respectively. Similarly, for BPS, the corresponding values were determined to be 11.63 and 35.24 mu mol L-1. The electrochemical method developed was validated by comparing it with the high-performance liquid chromatography coupled to diode array detector (HPLC-DAD) technique. Notably, the electrochemical method demonstrated to be successful in the simultaneous detection and quantification of BPA and BPS in a secondary effluent and surface water.
2023-11-10T00:00:00ZElectrochemical fabrication of nanowires poly (Indole-6-carboxylic acid) adorned with nanorod MnO2 for evaluation of its capacitive propertiesLorca-Ponce, J. [Univ Mayor, Fac Ciencias Ingn & Tecnol, Ctr Nanotecnol Aplicada, Chile]Cisterna, JonathanCattin, LindaBernede, Jean-ChristianLouarn, G.Ramírez, AMR.https://repositorio.umayor.cl/xmlui/handle/sibum/95002024-03-22T18:09:34Z2023-10-01T00:00:00ZElectrochemical fabrication of nanowires poly (Indole-6-carboxylic acid) adorned with nanorod MnO2 for evaluation of its capacitive properties
Lorca-Ponce, J. [Univ Mayor, Fac Ciencias Ingn & Tecnol, Ctr Nanotecnol Aplicada, Chile]; Cisterna, Jonathan; Cattin, Linda; Bernede, Jean-Christian; Louarn, G.; Ramírez, AMR.
A poly(indole-6-carboxy acid) nanowire composite with & beta;-MnO2 nanorod (6-PICA|& beta;-MnO2-NRs) was prepared by an electrochemical method and hydrothermal. The incorporation of & beta;-MnO2-NRs and the formation of 6-PICA nanowires are verified by SEM, TEM, Raman, powder XRD, and XPS, where the nanowires perform as an electroactive material and also as an environment to disperse the & beta;-MnO2 nanorods, at different concentrations. The study as a supercapacitor material shows that the specific capacitance of 6-PICA|& beta;-MnO2-NRs is 61.35 mFcm 2, higher than that of 6-PICA (43.01 mFcm 2) deposited on the ITO conductive glass electrode. These results indicate that the presence of pure phase & beta;-MnO2 in the form of nanostructure enhances the specific capacitance and ion diffusion in the charge-discharge process of 6-PICA at higher current densities without losing significant stability after 1000 cycles.
2023-10-01T00:00:00Z