Thick composite magnetoelectric films by electrophoretic deposition

Electrophoretic deposition (EPD) from colloidal suspensions was utilized for the preparation of composite magneto-dielectric films on a conductive substrate. The present process is developed as a convenient forming process for the development of devices based on thick magneto-dielectric films [1]. The deposition parameters - using EPD - such as colloidal parameters, deposition voltage and deposition time and the post process parameters, such as drying velocity and sintering will be controlled. This work aims to control the fillers/matrix ratio during the deposition and obtain a good adhesion, compaction and functionality of the composite film after the heat treatment. Measurements results for the current transients during constant-voltage deposition and the correlated deposited mass are presented [2, 3].1] A.O. Karilainen, P.M.T. Ikonen, C.R. Simovski, S.A. Tretyakov, A.N. Lagarkov, S.A. Maklakov, K.N. Rozanov, and S.N. Starostenko, Experimental studies on antenna miniaturisation using magneto-dielectric and dielectric materials, IET Microw. Antennas Propag., vol. 5, no. 4, pp. 495–502, 2011. 2] C. Baldisserri, D. Gardini and C. Galassi, An analysis of current transients during electrophoretic deposition (EPD) from colloidal TiO2 suspensions, Journal of Colloid and Interface Science 347 (2010) 102–111 3] H. Farnoush, J.A. Mohandesi, D. H. Fatmehsari and F. Moztarzadeh, A kinetic study on the electrophoretic deposition of hydroxyapatite–titania nanocomposite based on a statistical approach, Ceramics International 38 (2012), 6753-676

Structure analysis of cobalt ferrite/titania composite

Magnetodielectric bulk composite of a magnetic phase and a dielectric one were tailored to tune the macroscopic properties of permittivity and permeability. The designing of heterostructure formed by magnetic and dielectric counterparts offers a versatile route for the production of isotropic composite material with unusual electromagnetic properties. This study investigates the microstructure of sintered titania (TO)/cobalt ferrite (CFO) composites related to compositional modifications. The crystalline structure was studied through the comparison of theXRD patterns withthe EDS analysis and the results of the image analysis done on the electron micrographs. The image analysis wasfundamental to verifythe XRD and EDS interpretations, and to measure the effective volume contentof the phasesafter heat treatment.Several TO/CFO ratios from 0.7 to 11.8were analyzed. The formation oftheternary compound (FCTO) was foundonly in the composite with the TO/CFO ratio equal or bigger than 3

Magneto-dielectric characterization of TiO2-CoFe2O4 derived ceramic composites

Dielectric permittivity (ε′), magnetic permeability (µ′) and dielectric and magnetic loss (tan δε and tan δµ, respectively) of magneto-dielectric cobalt ferrite-titania (CFO-TO) ceramic composites are determined from 200 to 300 MHz. The four different combinations of phases - that can be produced in the sintered composite, according to the starting CFO/TO molar ratio - allow to tune the macroscopic permittivity and permeability. For the first time impedance, miniaturization and magneto-dielectric loss of the four classes of composites are calculated and discussed. The displayed miniaturization factors between 4.4 and 8.2 in the very-high frequency (VHF) range corroborate their potential application as magneto-dielectric substrate materials for antennas. Remarkably, the ceramic composites characterized by 2 vol.% and 3 vol.% of CFO and TO, respectively, dispersed in Fe2CoTi3O10 (FCTO) matrix display a magneto-dielectric loss lower than 0.07 and a miniaturization factor of 4.8

Flexible composite films with enhanced piezoelectric properties for energy harvesting and wireless ultrasound-powered technology

In the last years, ultrasound energy harvesting has emerged as the most promising technique for wireless power supply of implanted medical devices. These devices require flexible piezoelectric materials with high piezoelectric response in the ultrasonic range. Here we report on bio-compatible NBT-BT/PVDF flexible composites, with variable filler content up to 50 vol%, prepared by a properly designed and optimized process, which incorporates in a complex connectivity pattern fully sintered NBT-BT crystalline powders in a PVDF matrix. The dielectric constant of the flexible composites increased from 10 of pure PVDF polymer to 110 of composite films with 50 vol% NBT-BT content, while the high frequency piezoelectric d33 constant increased from 0.2 pC/N to 33 pC/N for the same samples. The composite with 50 vol% NBT-BT exhibits the figure of merit for the harvested ultrasound energy d33g33 ≅ 1.54 × 10−12 m3/J, which is comparable to the figure of merit for the NBT-BT piezoelectric ceramic (1.8 × 10−12 m3/J) and higher than other reported results for random composites. Based on these results, this study provides an easy method to fabricate random flexible piezoelectric composites with enhanced high frequency piezoelectric response and high energy density harvested from an ultrasound source

Versailles project on advanced materials and standards (VAMAS) interlaboratory study on measuring the number concentration of colloidal gold nanoparticles

We describe the outcome of a large international interlaboratory study of the measurement of particle number concentration of colloidal nanoparticles, project 10 of the technical working area 34, "Nanoparticle Populations" of the Versailles Project on Advanced Materials and Standards (VAMAS). A total of 50 laboratories delivered results for the number concentration of 30 nm gold colloidal nanoparticles measured using particle tracking analysis (PTA), single particle inductively coupled plasma mass spectrometry (spICP-MS), ultraviolet-visible (UV-Vis) light spectroscopy, centrifugal liquid sedimentation (CLS) and small angle X-ray scattering (SAXS). The study provides quantitative data to evaluate the repeatability of these methods and their reproducibility in the measurement of number concentration of model nanoparticle systems following a common measurement protocol. We find that the population-averaging methods of SAXS, CLS and UV-Vis have high measurement repeatability and reproducibility, with between-labs variability of 2.6%, 11% and 1.4% respectively. However, results may be significantly biased for reasons including inaccurate material properties whose values are used to compute the number concentration. Particle-counting method results are less reproducibile than population-averaging methods, with measured between-labs variability of 68% and 46% for PTA and spICP-MS respectively. This study provides the stakeholder community with important comparative data to underpin measurement reproducibility and method validation for number concentration of nanoparticles

Versailles project on advanced materials and standards (VAMAS) interlaboratory study on measuring the number concentration of colloidal gold nanoparticles

We describe the outcome of a large international interlaboratory study of the measurement of particle number concentration of colloidal nanoparticles, project 10 of the technical working area 34, "Nanoparticle Populations" of the Versailles Project on Advanced Materials and Standards (VAMAS). A total of 50 laboratories delivered results for the number concentration of 30 nm gold colloidal nanoparticles measured using particle tracking analysis (PTA), single particle inductively coupled plasma mass spectrometry (spICP-MS), ultraviolet-visible (UV-Vis) light spectroscopy, centrifugal liquid sedimentation (CLS) and small angle X-ray scattering (SAXS). The study provides quantitative data to evaluate the repeatability of these methods and their reproducibility in the measurement of number concentration of model nanoparticle systems following a common measurement protocol. We find that the population-averaging methods of SAXS, CLS and UV-Vis have high measurement repeatability and reproducibility, with between-labs variability of 2.6%, 11% and 1.4% respectively. However, results may be significantly biased for reasons including inaccurate material properties whose values are used to compute the number concentration. Particle-counting method results are less reproducibile than population-averaging methods, with measured between-labs variability of 68% and 46% for PTA and spICP-MS respectively. This study provides the stakeholder community with important comparative data to underpin measurement reproducibility and method validation for number concentration of nanoparticles

Versailles project on advanced materials and standards (VAMAS) interlaboratory study on measuring the number concentration of colloidal gold nanoparticles

We describe the outcome of a large international interlaboratory study of the measurement of particle number concentration of colloidal nanoparticles, project 10 of the technical working area 34, "Nanoparticle Populations" of the Versailles Project on Advanced Materials and Standards (VAMAS). A total of 50 laboratories delivered results for the number concentration of 30 nm gold colloidal nanoparticles measured using particle tracking analysis (PTA), single particle inductively coupled plasma mass spectrometry (spICP-MS), ultraviolet-visible (UV-Vis) light spectroscopy, centrifugal liquid sedimentation (CLS) and small angle X-ray scattering (SAXS). The study provides quantitative data to evaluate the repeatability of these methods and their reproducibility in the measurement of number concentration of model nanoparticle systems following a common measurement protocol. We find that the population-averaging methods of SAXS, CLS and UV-Vis have high measurement repeatability and reproducibility, with between-labs variability of 2.6%, 11% and 1.4% respectively. However, results may be significantly biased for reasons including inaccurate material properties whose values are used to compute the number concentration. Particle-counting method results are less reproducibile than population-averaging methods, with measured between-labs variability of 68% and 46% for PTA and spICP-MS respectively. This study provides the stakeholder community with important comparative data to underpin measurement reproducibility and method validation for number concentration of nanoparticles

Microstructure development in novel titania-cobalt ferrite ceramic materials

The system cobalt ferrite (CFO)–titania (TO) has been studied in view to produce new in situ ceramic composites by conventional solid state reaction. To synthesize the CFO–TO composite, the processing parameters are optimized to yield a reliable and repeatable homogeneous distribution of the phases. Composition, crystalline structure and microstructure of the sintered bodies were investigated by XRD, SEM, microprobe analysis; the image analysis was performed to quantify the phase volume content and grain size. The final compositions after sintering differ significantly from the starting ones as a consequence of the reaction of titania with the ferrite and the formation of a new ternary compound Fe2CoTi3O10 (FCTO). In this work we report for the first time the preparation of almost pure (about 95 vol%) single phase FCTO ceramics, its XRD patterns, and the microstructural characterization

Investigation of new magneto-dielectric titania-cobalt ferrite composites

Novel magneto-dielectric cobalt ferrite (CFO)- titania (TO) ceramic composites with composition (100-x)TO-xCFO with x ranging from 20 to 80 wt.% were prepared by conventional solid state reaction. Highly densified composites with two to three phases homogeneously distributed were obtained. The formation of a new ternary compound Fe2CoTi3O10 (FCTO) was observed only in composites having TO/CFO molar ratios equal to or larger than 2.2. The magneto-dielectric ceramic composites obtained can be classified by phases content in different classes with one of the starting CFO and /or TO always present; in the range of high CFO content the formation of CoTiO3 and Fe2O3 was detected. Magnetic permeability, dielectric permittivity (?') and losses (tan ?) were determined and correlated with the molar ratio of the dielectric and magnetic phases in the composites

Investigation of new magneto-dielectric titania-cobalt ferrite composites

Novel magneto-dielectric cobalt ferrite (CFO)- titania (TO) ceramic composites with composition (100-x)TO-xCFO with x ranging from 20 to 80 wt.% were prepared by conventional solid state reaction. Highly densified composites with two to three phases homogeneously distributed were obtained. The formation of a new ternary compound Fe2CoTi3O10 (FCTO) was observed only in composites having TO/CFO molar ratios equal to or larger than 2.2. The magneto-dielectric ceramic composites obtained can be classified by phases content in different classes with one of the starting CFO and /or TO always present; in the range of high CFO content the formation of CoTiO3 and Fe2O3 was detected. Magnetic permeability, dielectric permittivity (?') and losses (tan ?) were determined and correlated with the molar ratio of the dielectric and magnetic phases in the composites