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Spinel type CoFe2O4 thin films have been prepared, on stainless steel supports, by thermal decomposition of aqueous solutions of mixed cobalt and iron nitrates in 1:2 molar ratio at 400 °C. The electrochemical behaviour of the CoFe2O4/1 M KOH interface was investigated by cyclic voltammetry, chronoamperometry and impedance techniques. The studies allowed finding out the redox reactions occurring at the oxide surface. The results were compared with colloidal electrodes prepared by alkaline precipitation of Fe(II) or Fe(III) hydrous oxi-hydroxides on platinum electrodes. In addition, it has been concluded that the processes are diffusion-controlled and the diffusion of the hydroxide ion, through the oxide, acts as the rate-determining step. The diffusion coefficient of OH through the oxide film was determined using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy techniques.  相似文献   
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Spinel-type Fe x Co3−x O4 thin films with x = 0, 1, 2 and 3 were prepared, on stainless steel supports, using the thermal decomposition method at 400 °C. The X-ray diffraction patterns show the presence of a spinel-type structure with a low crystallinity. The electrochemical behaviour was investigated in 1 M KOH, using open-circuit-potential measurements and cyclic voltammetry. The studies allowed to observe the redox reactions occurring at the Fe x Co3−x O4 (x = 1 and 2) oxide surface, namely Fe3O4/Fe(OH)2 or Fe3O4/Fe2O3, Co3O4/CoOOH, Co(OH)2/CoOOH and CoO2/CoOOH by comparing the experimental data with those obtained for the Co3O4 and Fe3O4 films as well as with those referred to in the literature. The results show that iron ions play the major role in the solid-state surface redox transitions in the negative potential range, whereas the cobalt ions are the key species in the positive potential range. However, the contribution of each component, although small, has to be considered in both potential regions.  相似文献   
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In this paper, an approach for heart rate variability analysis during exercise stress testing is proposed based on the integral pulse frequency modulation (IPFM) model, where a time-varying threshold is included to account for the nonstationary mean heart rate. The proposed technique allows the estimation of the autonomic nervous system (ANS) modulating signal using the methods derived for the IPFM model with constant threshold plus a correction, which is shown to be needed to take into account the time-varying mean heart rate. On simulations, this technique allows the estimation of the ANS modulation on the heart from the beat occurrence time series with lower errors than the IPFM model with constant threshold (1.1% ± 1.3% versus 15.0% ± 14.9%). On an exercise stress testing database, the ANS modulation estimated by the proposed technique is closer to physiology than that obtained from the IPFM model with constant threshold, which tends to overestimate the ANS modulation during the recovery and underestimate it during the initial rest.  相似文献   
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Spinel type Co3O4 thin films, for the oxygen evolution reaction (OER) in 1 M KOH, have been prepared, on stainless steel supports, using the thermal decomposition method at 400 °C. The electrochemical behaviour of the oxide film/1 M KOH interface was investigated by cyclic voltammetry and impedance techniques. The impedance measurements were carried out at different positive potentials, from the open circuit potential to a potential in the OER region and the electrical equivalent circuit, L (R1Q1) (R2Q2) (R3Q3) was used to fit the experimental results. At each potential, a good correlation between experimental and simulated data is found, thereby validating the proposed equivalent circuit model. The roughness factor value determined in the potential region where the charge transfer reaction is negligible is similar to that obtained by cyclic voltammetry, with a value of 70 ± 2.  相似文献   
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Journal of Inorganic and Organometallic Polymers and Materials - This work aims to investigate the effect of nickel nitrate concentration on the size and antioxidant activity of nickel oxide...  相似文献   
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This work aims to optimize the antibacterial activity of iron oxide nanoparticles (IONPs) against both Gram-positive and Gram-negative bacteria. IONPs were greenly biosynthesized using Moringa oleifera leaves extract, and surface methodology (RSM) based on central composite design (CCD) was employed to investigate the combined effect of various experimental factors on the antibacterial activity of IONPs. The reaction and annealing temperatures besides precursor concentration were set as independent variables, while the antibacterial activity was set as a response to obtain the optimal conditions that maximizes IONPs antibacterial activity. Different characterization techniques such as UV–Vis, FTIR, XRD, SEM, and EDX were employed to study the properties of the biosynthesized nanoparticles. Meanwhile, the antibacterial activity was tested using the disk diffusion method. The characterizations results have confirmed the biosynthesis of Hematite (α-Fe2O3) nanoparticles of rhombohedral structure. The generated model has exhibited predicted values very close to the actual proving its validity to analyze and optimize the studied process. The model indicated that all the investigated parameters and their interactions have significantly affected IONPs antibacterial activity. An optimal antibacterial activity was achieved when biosynthesis factors at their lower levels (? 1). Furthermore, the effect of IONPs size on the antibacterial activity was studied and the results shown that the latter is significantly related to the nanoparticles size.

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