Magnetic, electric and thermal properties of cobalt ferrite nanoparticles

International audienceThe electric and magnetic properties as well as the thermal stability of CoxFe3-xO4 nanopowders, (0.

Nanoplastic production procedure for scientific purposes: PP, PVC, PE-LD, PE-HD, and PS

International audienceStudies on the environmental impact of nanoplastics face challenges in plastic analysis and a scarcity of nanoplastic materials necessary for the development of analytical techniques and experiments on biota impact. Here we provide detailed procedures for obtaining nanoparticles suspended in water for the most commonly used polymers: Polypropylene (PP), Polyvinylchloride (PVC), Low-and High-Density Polyethylene (PE-LD, PE-HD), and Polystyrene (PS). We dissolved larger size material to reprecipitate nanoparticles. For all plastic types, we obtained nanoparticles with a size between 50 and 300 nm, and a mainly spherical morphology. We verified that no irreversible agglomeration or coalescence of the particles occurred after 5 days of storage. The concentrations obtained in the final carrier solution were of the order of 10 9 particles mL-1. To prevent the persistence of reagents in the final carrier solution, a filtration step was implemented at the end of the process. The method proved unsuitable for Polyethylene Terephthalate (PET)

Electrical Properties of a CeO 2

The electrical conduction of a series of polycristalline [(1−x)CeO2⋅x/2Bi2O3] samples has been analyzed using electrical impedance spectroscopy, in the temperature range 25 to 750∘C. Samples have been prepared via a coprecipitation route followed by a pyrolysis process at 600∘C. For compositions x≤0.20, Ce1−xBixO2−x/2 solid solutions, with fluorite cubic structure, are obtained. In the composition range 0.30≤x≤1, the system is biphasic with coexistence of cubic and tetragonal structures. To interpret the Nyquist representations of electrical analyses, various impedance models including constant phase elements and Warburg impedances have been used. In the biphasic range (0.30≤x≤0.7), the conductivity variation might be related to the increasing fraction of two tetragonal β′ and β-Bi2O3 phases. The stabilization of the tetragonal phase coexisting with substituted ceria close to composition x=0.7 is associated with a high conduction of the mix system CeO2-Bi2O3

Implementation of an Embedded Sensor Based on Electrical Resistivity to Monitor Drying in Thick Concrete Structures

Electrical resistivity is a parameter sensitive to several properties of concrete, including water content, which is one of the key parameters governing concrete long-term durability. In this paper, the monitoring of the concrete water content profile throughout its entire thickness is discussed using an electrical approach as a measurement method. This is very relevant to applications requiring a centimeter resolution over a large thickness. The aim of this paper is to implement a multi-electrode embedded sensor in a concrete slab to determine the resistivity profile over concrete depth in order to monitor its drying. The sensor, designed as a printed circuit board (PCB), is integrated in two 30 cm thick concrete slabs. Different measurement configurations are presented. Following qualification in laboratory and controlled conditions, the study focuses on characterizing the sensor‘s response during the drying of the slabs. The results demonstrate the capability of the sensor to monitor concrete drying by measuring the resistivity profiles with a spatial centimetric resolution

Synthesis and microstructure of cobalt ferrite nanoparticles

International audienceCobalt ferrites (CoxFe3-xO4) nanoparticles with various compositions were synthesized by a new non-aqueous synthesis method. The cobalt ferrites were characterized by X-rays diffraction, and transmission electron microscopy coupled with energy dispersive spectroscopy. The nanoparticles are highly crystallized, with a homogeneous chemical composition. The particle size varies from 4 nm up to 7.5 nm, depending on the cobalt content. The smallest particles, with a size of 4 nm, are obtained for high cobalt content. These particles have also the highest micro-structural strain. Catalytic measurements were realized using Fourier Transform Infrared Spectroscopy. The lowest activation energy and the highest conversion rate are obtained for Co1.8Fe2.4O4, in the 400-500°C temperature range

Emission of metals under colloidal phase in wastes leachates : ICP-AES and SEM-EDX analysis

European Union is aiming to promote sustainable long-term progressive reduction of contaminant discharges to the environment. Potentially toxic elements and hydrophobic organic contaminants inputs and transfer of metals and organic contaminants to the environment occur from various sources: domestic, industrial and urban runoff. Different types of waste are extensively produced all over the word by industrial and domestic activities, but after disposal, their fate in the environment is poorly known, especially when pollutant release occurs under colloidal form. So, a general recommendation to protect the water and soil environment is that a biodegradability and fate assessment should be required for these various wastes, in order to determine subsequent implications for the environment. The complexity and variability in the composition of these wastes involve to study a large panel of them, since speciation of pollutants considerably depends on chemical composition, pH, Eh, ionic strength. Speciation, mobility and toxicity of these pollutants could be quite predictable in the aqueous or particulate phases, whereas their fate is unsure when they exist under colloidal form. Thus, it is of great interest to evaluate the composition of metals under colloidal form present in waste leachates in order to study the phase they are bound to, and finally predict their behavior and fate. In this context, 5 different wastes were studied: Bauxite residue, coastal marine sediments, sludge of wastewater treatment plant, crushed wastes and ashes from household incineration. After leaching, filtrations and measurement of element concentrations in the microfiltrate and ultrafiltrate fractions by Inductive Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), we used Scanning Electron Microscopy- Energy Dispersive X-ray spectroscopy (SEM-EDX) to specifically detect the phases bound to metals of colloidal size. Some answers dealing with emission of pollutants from wastes were given