Synthesis and Characterisation of Cobalt Ferrite Coatings for Oxygen Evolution Reaction

In this paper, two novel procedures based on powder sedimentation, thermal treatment, and galvanostatic deposition were proposed for the preparation of porous cobalt ferrite (CoFe2O4) coatings with a metallic and organic binder for use as catalysts in the oxygen evolution reaction (OER). The electrochemical properties of the obtained electrode materials were determined as well, using both dc and ac methods. It was found that cobalt ferrite coatings show excellent electrocatalytic properties towards the oxygen evolution reaction (OER) with overpotential measured at a current density of 10 mAcm−2 from 287 to 295 mV and a Tafel slope of 35–45 mVdec−1. It was shown that the increase in the apparent activity of the CoFe2O4 coatings with an organic binder results mainly from a large electrochemically active area. Incorporation of the nickel binder between the CoFe2O4 particles causes an increase in both the conductivity and the electrochemically active area. The Tafel slopes indicate that the same rate-determining step controls the OER for all obtained coatings. Furthermore, it was shown that the CoFe2O4 electrodes exhibit no significant activity decrease after 28 h of oxygen evolution. The proposed coating preparation procedures open a new path to develop high-performance OER electrocatalysts

Non-destructive method of determination of elastic properties and adhesion coefficient of different coating materials

Purpose: The paper presents a non-destructive method of determination of Young’s modulus and adhesion coefficient of different coating materials (metallic coatings, polymer, composite etc.). Some of the results obtained by applying this method are discussed in detail. Design/methodology/approach: The presented method consists in measuring the dynamic response of the examined material in the form of a flat rectangular bar subjected to external periodic mechanical stress i.e. the so called vibrating reed technique. General equations describing elastic properties of the sample consisting of a substrate and a deposited coating are derived and discussed in detail. Findings: It was shown that the application of the proposed approach to the metallic, polymeric and composite coatings allowed to obtain a quantitative data concerning the change of both the elastic properties and the adhesion coefficient with a change of: coating thickness, measurement temperature, chemical composition of coating, surface preparation or in the case of epoxy resin coatings with a change of curing time or curing temperature. Research limitations/implications: The proposed method can be applied in many scientific problems in the field of coating materials (e.g. elastic properties of porous coating, crystallization of amorphous coating, adhesion of different polymeric coatings). Practical implications: It was shown that the described method can be successfully used in optimisation of some technological processes of deposition of different coatings on metallic substrate. Originality/value: The paper presents methodology of a non-destructive approach to determination of elastic properties and adhesion coefficient of coating materials with an overview of some applications already publish and also the new ones. Especially interesting are the results concerning the influence of surface preparation on adhesion coefficient which are published for the first time. Keywords: Coating materials; Elastic properties; Young’

Effect of the Boron Addition on the structure of the Ni-Mn-Co-In alloys

Series of Ni45:5xCo4:5Mn36:6In13:4Bx (at.%, x = 0, 0.05, 0.1, 0.5, 1.0) polycrystalline magnetic shape memory alloys produced by the induction melting were examined in terms of the structure and transition temperatures. The structure of the alloys was determined by the X–ray diffraction and transmission electron microscopy. Scanning electron microscopy and electron backscattering diffraction techniques were applied to obtain the microstructure and texture of alloys. Boron addition promotes nucleation of the second Co–rich and In–poor phase as well as causes decrease of the martensitic transformation temperatures

Preparation and magnetic characteristics of Co1−δZnδFe2O4 ferrite nanopowders

In the present paper the Co1 Zn Fe2O4 (0 1) ferrite nanopowders with a spinel type structure were synthesized using a chemical co-precipitation technique with constant flow rate FR = 120 cm3/min at three different reaction temperatures i.e. Tr = 50 C, 70 C and 90 C. Magnetic and structural characteristics of the obtained materials were investigated by means of X-ray diffraction method, transmission electron microscopy and vibrating sample magnetometer. In the course of studies hysteresis loops M( 0H) and the relations of magnetization M7T (determined at 0H = 7 T), squareness ratio S and the Néel temperature TN versus Zn content were determined and discussed in detail. It was shown that for < 0:6 the increase in reaction temperature Tr results in a significant increase of the measured magnetic characteristics. In particular, in the case of Co0:8Zn0:2Fe2O4 ferrite nanopowder magnetization M7T reaches maximal value of about 80 emu/g

Synthesis and Magnetic Properties of CuCr1:65Se4 Nanoparticles

CuCr1:65Se4 nanoparticles crystallize in the monoclinic Cr2Se3-type structure of the space group I2=m. The average crystallite size basing on the line broadening is less than 10 nm. With decrease of the size of grains a change from ferromagnetic to ferrimagnetic order, a lack of the magnetization saturation and a strong spin orbit coupling visible in the large value of the Landé factor g = 2:72 are observed. The change in magnetic order is caused by the change of the crystalline symmetry from the cubic phase to monoclinic one

Preparation and Magnetic Characteristics of Co 1-δ

In the present paper the Co1 Zn Fe2O4 (0 1) ferrite nanopowders with a spinel type structure were synthesized using a chemical co-precipitation technique with constant flow rate FR = 120 cm3/min at three different reaction temperatures i.e. Tr = 50 C, 70 C and 90 C. Magnetic and structural characteristics of the obtained materials were investigated by means of X-ray diffraction method, transmission electron microscopy and vibrating sample magnetometer. In the course of studies hysteresis loops M( 0H) and the relations of magnetization M7T (determined at 0H = 7 T), squareness ratio S and the Néel temperature TN versus Zn content were determined and discussed in detail. It was shown that for < 0:6 the increase in reaction temperature Tr results in a significant increase of the measured magnetic characteristics. In particular, in the case of Co0:8Zn0:2Fe2O4 ferrite nanopowder magnetization M7T reaches maximal value of about 80 emu/g

Magnetic properties and structure of the Ni-Co-Mn-In alloys with the boron addition

Series of Ni45:5xCo4:5Mn36:6In13:4Bx (at.%, x = 0, 0.05, 0.1, 0.5, 1.0) polycrystalline magnetic shape memory alloys were examined in terms of the magnetic properties, structure and transition temperatures. Depending on the boron concentration single or two phase alloys microstructures were observed. Additionally, the martensitic transformation temperatures decreases with the boron addition. Magnetic-field induced transformation occurs for the alloys with the boron addition up to 0.1 at.%. For alloys with 0.5 and 1.0 at.% of B transformation is hindered