Synthesis, magnetic and optical properties of core/shell Co1-xZnxFe2O4/SiO2 nanoparticles

The optical properties of multi-functionalized cobalt ferrite (CoFe2O4), cobalt zinc ferrite (Co0.5Zn0.5Fe2O4), and zinc ferrite (ZnFe2O4) nanoparticles have been enhanced by coating them with silica shell using a modified Stöber method. The ferrites nanoparticles were prepared by a modified citrate gel technique. These core/shell ferrites nanoparticles have been fired at temperatures: 400°C, 600°C and 800°C, respectively, for 2 h. The composition, phase, and morphology of the prepared core/shell ferrites nanoparticles were determined by X-ray diffraction and transmission electron microscopy, respectively. The diffuse reflectance and magnetic properties of the core/shell ferrites nanoparticles at room temperature were investigated using UV/VIS double-beam spectrophotometer and vibrating sample magnetometer, respectively. It was found that, by increasing the firing temperature from 400°C to 800°C, the average crystallite size of the core/shell ferrites nanoparticles increases. The cobalt ferrite nanoparticles fired at temperature 800°C; show the highest saturation magnetization while the zinc ferrite nanoparticles coated with silica shell shows the highest diffuse reflectance. On the other hand, core/shell zinc ferrite/silica nanoparticles fired at 400°C show a ferromagnetic behavior and high diffuse reflectance when compared with all the uncoated or coated ferrites nanoparticles. These characteristics of core/shell zinc ferrite/silica nanostructures make them promising candidates for magneto-optical nanodevice applications

Magnetic properties of CoFe(2)O(4) synthesized by solid state, citrate precursor and polymerized complex methods: A comparative study

CoFe(2)O(4) ferrite was synthesized by solid state, citrate gel precursor and polymerized complex methods. Both the solid state method and the polymerized complex method at high temperatures produced micron-sized cobalt ferrite particles. Citrate precursor method and polymerized complex method at low temperatures produced nanosized particles. Using these three techniques, particle size in the range of 30-530 nm could be obtained. Magnetic properties of these samples were found to depend strongly on the particle size. Saturation magnetization was found to decrease marginally with increase in particle size whereas the coercively was found to increase exponentially from 219 Oe to 1625 Oe as the particle size was reduced from 530 nm to about 30 nm. The variations in the magnetic properties are attributed to the grain size effects and cation redistribution. The present work shows that magnetic properties could be tuned over a wide range, by changing the synthesis conditions. (c) 200

Corrosion Mechanism Suggested Based on Electrochemical Analysis and SVET for Uncoated Tinplate and Post Coated With a Hybrid Film

<div><p>The tinplate, used in the packaging sector and formed from a metal substrate, comprises a steel base which has undergone a surface treatment to produce a thin layer of FeSn2, a tin layer and an oxide tin layer. Currently, packaging using surface treatment is based on the use of chromates because these metals provide an excellent corrosion resistance. Nontoxic alternatives to pre-treatments have been developed in recent years to replace the chromate process. The aim of this work is to analyze the performance of a new hybrid organic-inorganic film obtained from sol-gel consisting of the alkoxide precursors 3-(Trimethoxysilylpropyl)methacrylate (TMSM) and tetraethoxysilane (TEOS) with the addition of cerium nitrate with the scanning vibrating electrode technique (SVET), and electrochemical and morphological characterizations. Moreover, the evolution of the corrosion of the substrate was evaluated to propose a mechanism of corrosion. The results showed a galvanic coupling between the Sn/SnO2 coat (cathode) and the defects exposed at the ferrous base (anode). The organic-inorganic hybrid film containing a cathodic corrosion inhibitor was able to retard the corrosion of the tinplate.</p></div

New approaches to the study of spinel ferrite nanoparticles for biomedical applications

This chapter is prepared into six different sections. The first part will provide a brief introduction of spinel ferrite nanoparticles synthesis, the use of chelating agents in the sol-gel method, and applications of spinel ferrite nanoparticles in biomedical fields. The second part will cover an overview of the structure and magnetism of spinel ferrites. The third part will present a summary of different types of chelating agents. The fourth part will provide information of the sol-gel synthesis for ceramic nanoparticles. The fifth part will focus on the preparation of cobalt ferrite nanoparticles by sol-gel methods using polyvinyl alcohol (PVA) and citric acid (CA) as chelating agents. The influence of chelating agents on the physical properties and antibacterial property of cobalt ferrite nanoparticles will be highlighted in the last part. A discussion on chelating agent-metal ion formation and the antibacterial mechanisms of spinel ferrite nanoparticles will be presented

Effect of organic precursor in hybrid sol–gel coatings for corrosion protection and the application on hot dip galvanised steel

Sol-gel coating material with enhanced corrosion protection for zinc-coated steel has been obtained through the incorporation of mono-phenol and bi-phenol organic precursors in an epoxide functionalised-silica-zirconia matrix. The effect of the presence of the organic precursors in the baseline formulation has been studied; sol stability has been examined by viscosity evolution; gel densification stage has been studied by differential scanning calorimetry (DSC); material composition has been analysed by Fourier transform infrared spectroscopy (FTIR) and X-ray spectroscopy (XPS); coating thickness and roughness has been measured by profilometry. Corrosion performance in three artificial weathering tests showed outstanding performance in the delay of zinc and steel corrosion products emergence, and electrochemical impedance spectroscopy (EIS) measurement permitted the identification of the coating presenting the most promising properties in terms of corrosion protection. Developed coatings have shown outstanding contribution to service life extension of zinc-coated parts.The authors thank the support of the Basque Government for EMAITEK 2017 program and the ELKARTEK project NG-FAB16 (contract number KK2016-00025). The authors thank CIC BiomaGUNE and Luis Yate for XPS characterisation