MAX Phase (Nb4 AlC3 ) For Electrocatalysis Applications

In search for novel materials to replace noble metal-based electrocatalysts in electrochemical energy conversion and storage devices, special attention is given to a distinct class of materials, MAX phase that combines advantages of ceramic and metallic properties. Herein, Nb4 AlC3 MAX phase is prepared by a solid-state mixing reaction and characterized morphologically and structurally by transmission and scanning electron microscopy with energy-dispersive X-ray spectroscopy, nitrogen-sorption, X-ray diffraction analysis, X-ray photoelectron and Raman spectroscopy. Electrochemical performance of Nb4 AlC3 in terms of capacitance as well as for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) is evaluated in different electrolytes. The specific capacitance Cs of 66.4, 55.0, and 46.0 F g-1 at 5 mV s-1 is determined for acidic, neutral and alkaline medium, respectively. Continuous cycling reveals high capacitance retention in three electrolyte media; moreover, increase of capacitance is observed in acidic and neutral media. The electrochemical impedance spectroscopy showed a low charge transfer resistance of 64.76 Ω cm2 that resulted in better performance for HER in acidic medium (Tafel slope of 60 mV dec-1 ). In alkaline media, the charge storage value in the double layer is 360 mF cm-2 (0.7 V versus reversible hydrogen electrode) and the best ORR performance of the Nb4 AlC3 is achieved in this medium (Tafel slope of 126 mV dec-1 ).

Magnetic and structural study of electric double-layered ferrofluid with MnFe(2)O(4)@γ-Fe(2)O(3) nanoparticles of different mean diameters: Determination of the magnetic correlation distance

Magnetic fluids based on manganese ferrite nanoparticles were studied from the structural point of view through small angle x-rays scattering (SAXS) and from the magnetic point of view through zero-field cooling and field cooling (ZFC-FC) and ac susceptibility measurements (MS). Three different colloids with particles mean diameters of 2.78,3.42, and 6.15 nm were investigated. The size distribution obtained from SAXS measurements follows a log-normal behavior. The ZFC-FC and MS results revealed the presence of an important magnetic interaction between the nanoparticles, characterized by a magnetic correlation distance Λ. The colloidal medium can be pictures as composed by magnetic cluster constituted by N interacting particles. These magnetic clusters are not characterized by a physical aggregation of particles. The energy barrier energy obtained is consistent with the existence of this magnetic clusters. Besides the magnetic interaction between particles, confinement effects must be included to account for the experimental values of the magnetic energy barrier encountered.

[Correlation between colonoscopy and histopathology of the colon in diverticular disease and the irritable colon syndrome]

In this study 29 patients were carriers of diverticular disease of the colons (DDC) and 29 patients with irritable bowel syndrome (IBS). The patients were diagnosed by means of a directed anamnesis standardized by the radiologic study of the colons. The methodology included, radiologic study of the colons, endoscopic examination of the colon (colonoscopy with biopsy) and anatomic pathologic examination of the fragments obtained in the endoscopy. It was tried, by means of colonoscopy with biopsy and anatomic pathological examination, to demonstrate, classify and relate, in agreement with pre-established criterion, the degree of intensity of the inflammatory process in the colic mucosa. According to the results we may conclude that: 1) colonoscopy in the studied inflammatory diseases is important for diagnosis, evaluation of the inflammatory process, identification of associated illness and material obtention for the anatomic pathological examination; 2) there is always a chronic inflammatory process, in variable degrees, of the colic mucosa in DDC and in IBS; 3) colonoscopy with biopsy and the anatomic pathological examination are adequate to diagnose with precision the degree of intensity of the chronic inflammatory process of the colic mucosa and the presence of associated disease in DDC and in IBS.