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NiFe2O4 nanocomposite is a soft magnetic material with low saturation coercivity and magnetization but has high electrical resistivity making this material suitable for electric field applications. The purpose of this study was to determine the effect of NiFe2O4 composition on the electrical properties of NiFe2O4-PVDF nanocomposites prepared by the sol-gel method. Nickel Ferrite nanocomposites - polyvinylidene fluoride (NiFe2O4-PVDF) are made using the sol-gel method and then grown using a spin coating device on a glass substrate. NiFe2O4-PVDF nanocomposites are characterized using X-ray diffraction (XRD) which aims to determine the crystal system, whereas to determine the electrical properties of nanocomposite resistivity Four Point Probe are used. Based on the research conducted on the electrical properties of the NiFe2O4-PVDF nanocomposite, the resistivity value of the NiFe2O4- PVDF nanocomposite with variations in the composition of the PVDF used 10:10, 10:20, and 10:30 was 36.66913333 Ohm.m; 55,63242667 Ohm.m; and 20,85797333 (Ohm.m). While the results of the resistivity values of the nanocomposite NiFe2O4-PVDF with variations in the composition of NiFe2O4 used 10:10, 20:10, and 30:10 are 36,69613333 Ohm.m; 12.07853333 Ohm.m; and 9.616773333 (Ohm.m). It can be concluded that the greater the variation in the composition of NiFe2O4 and PVDF, the resistivity value decreases.

International audience; Herein, a novel polymeric porous membrane was developed, without the use of any organic solvent in the initial dope solution and using a biobased polymer derived from cellulose: Hydroxypropylcellulose (HPC). HPC was dissolved in water (20 wt%) and the phase separation was induced by increasing the temperature above the Lower Critical Solution Temperature (LCST) of the polymer solution, around 40 °C in the concentration range concerned in this study. To fix the membrane morphology and to prevent any resolubilization in water during filtration tests, a chemical crosslinking was performed using Glutaraldehyde. The phase diagram of HPC/water system was first studied and not only the cloud point but also the spinodal curves were determined using optical transmission techniques. It was exhibited that HPC phase diagram is very weakly dependent on concentration up to large concentrations and that the metastable region is very small, i.e. the cloud point and the spinodal curves are very close in a large range of concentration. The membrane stability was tested in water and some organic solvents, thus demonstrating the efficiency of the chemical crosslinking during membrane formation. The swelling and mechanical properties of HPC membranes were also investigated depending on the operating condition during membrane formation, showing that the temperature ramp during the membrane formation, from initial to final temperature, have a significant effect on the crosslinking efficiency and hence on the swelling properties. Finally, adding a porogen (PEG200) into the collodion, filtration tests were performed and exhibited that the membrane filtration properties depend on the temperature ramp as well, showing higher water flux for the highest temperature ramp tested.

International audience; Abstract This paper presents a new technique for making porous polymer membrane without using organic solvent from a nontoxic and biodegradable polymer, polyvinyl alcohol (PVA). This method consists first in inducing a phase separation in water – 10 wt% PVA solution, by increasing the temperature above the polymer cloud point temperature. A PVA with a degree of hydrolysis of 72% was selected according to its low cloud point temperature (47 °C for 10 wt% polymer) allowing saving energy. The second step of the preparation procedure corresponds to the stabilization of the structure by jointly cross-linking the polymer to stabilize the porous morphology and drying to evaporate the dilute phase. A chemical cross-linking reaction was performed using glutaraldehyde with a molar proportion (GA/monomer alcohol) of 0.04. Results showed that the cross-linking control was the key step to obtain porous membrane morphology. Consequently, the temperature and the catalyst volatility of the cross-linking reaction act directly on the final membrane morphology. Additionally, it was shown that the control of the relative humidity during the elaboration process had an effect on the porosity of the membrane skin layer as depicted by SEM pictures and filtration tests.

International audience