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ZrNi is considered a promising candidate for hydrogen storage and nickel-metal hydride rechargeable batteries (Ni-MH). The effect of creating zirconium and nickel vacancy defects on the dehydrogenation properties of ZrNiH3 is investigated by means of first-principles calculations. The results indicate that nickel vacancy is energetically more favorable to form in ZrNiH3 than zirconium vacancy, because of the lesser formation energy of Ni-vacancy. For both Zr and Ni vacancy defects, the formation enthalpy decreases with increasing the concentration of vacancy and, vice versa. In particular, it is found that with ~2.4% of zirconium vacancy defects or with ~4.5% of nickel vacancy defects in ZrNiH3, the formation enthalpy is around - 40 kJ/mol.H2, which is recommended by the U.S. Department of Energy (DOE). It is worth noting also that with slightly higher vacancy defects ~2.8 of Zr-vacancy or ~5.3% of Ni-vacancy in ZrNiH3, it becomes harder to store hydrogen in these systems without cooling. Moreover, the density of states (DOS) analysis indicates that the stability of ZrNiH3 decreases with increasing Zr-vacancy and Ni-vacancy concentrations, through the shrinkage in the size of the total DOS and shifting in the valence bands near to Fermi level.

Hybrid composites have been elaborated by incorporation of BaTiO3 (BT) inorganic nanoparticles into polyvinylidene fluoride (PVDF) polymer. BT–PVDF composite thick films with different volume fractions of BT (0%, 7%, 15%, and 30%) were deposited by spin-coating onto Pt/SiO2/Si substrates. The effects of the BT inorganic content in the PVDF polymeric matrix on the structural, dielectric, ferroelectric, and energy storage properties were investigated at room temperature. The crystal structure of the samples was identified by X-ray diffraction analysis, and their morphology was observed by scanning electron microscopy. Introduction of BT nanoparticles into the PVDF polymer led to a remarkable enhancement of the dielectric constant value and ferroelectric polarization. Additionally, the abnormal dielectric behavior observed for the composite with 30 vol.% BT nanoparticle volume fraction can be explained by the existence of a Debye relaxation domain at low frequency. Moreover, the stored energy density Wc was enhanced from 2.4 J/cm3 for pure PVDF polymer to 9 J/cm3 for the 30 vol.% BT nanoparticle volume fraction. Such BT–PVDF composite thick films are thus promising materials for the manufacture of electrostatic capacitors for electrical energy storage.

First-principles calculations based on Plane-Wave Self-Consistent Field (PWSCF) method, implemented in quantum espresso program, have been performed on ZrNiH3 substituted with transition metals (V, Ti, Fe, Mn, and Cr). The study aims to investigate the heat of formation in terms of material stability and desorption temperature. It is found that the substitution by transition metals, results in a significant enhancement in the thermodynamic properties accompanied by an increase of the volumetric and gravimetric hydrogen storage capacities. In addition, the obtained values of heat of formation and desorption temperature corroborate with that required by the U.S. Department of Energy (DOE) for stability and volumetric capacity criteria. Moreover, Mn and Fe elements are found to present the lowest substituting content (34%) to obtain optimum hydrogen storage characteristics (enthalpy of formation of - 40 kJ/mol.H2, decomposition temperature of 300 K and volumetric capacity of 134 g.H2/l), without affecting the electronic structure and the metallic character of ZrNiH3.

The partial oxidation of benzyl alcohol to benzaldehyde is a fundamental synthetic transformation in organic chemistry. However, the conventional oxidation methods pose many environmental problems such as the use of inorganic oxidants (chromates, permanganate and chlorinated oxidants) with high toxicity in organic media and the generation of a large amount of waste. In this work, we report a green approach for the oxidation of benzyl alcohol to benzaldehyde using bimetallic zirconium-nickel loaded on natural phosphate as heterogeneous catalyst with aqueous hydrogen peroxide as green oxidant under solvent-free conditions. The catalyst has been prepared by using a wet impregnation method and characterized by powder XRD and FT-IR studies. Compared to other works in literature, the developed catalyst showed relatively short reaction time (45 min), good yield (93%) and high recyclability without a significant loss in its activity.

Hydroxyapatite-Alumina composite powders, HAP-Al2O3, for biomedical applications were synthesized by neutralization method. Composites with different alumina content were prepared and calcined over the temperature range of 900-1300°C for 3 h. Effects of alumina content and calcination on the structural properties of powders were studied. The as-received powders and ceramics were characterized by various techniques (XRD, IR, SEM, TEM). Compressive strength of ceramics was determined using direct compressing. Results indicate that both crystallinity of the HAp-Al2O3 powders and the compressive strength increased with the temperature of calcination, but depending of the alumina content where the formation of β-TCP phase as secondary phase is detected after heat treatment. We notice that HAp-10Al2O3 offers the best mechanical strengths that can be improved by a high calcination temperature.

We study hydrogen storage properties of Nb doped ZrNiH3 using the first-principles calculations based on density functional theory (DFT). To achieve such calculations, we used full potential linearized augmented plane waves (FP-LAPW) method implanted in WIEN2K code. Total energy and density of states (DOS) are computed for Zr1-xNbxNiH3 (x = 0 and 0.1). It turns out that substituting 10% of zirconium by niobium in ZrNiH3 matrix involves a destabilization of the system. This destabilization is induced by the formation of a new hybridization between niobium and hydrogen atoms. Furthermore, the thermodynamic stability in terms of its energy of formation, as well as the capacity of the material to store hydrogen are discussed. Noteworthy that from FP-LAPW we report that Nb doped ZrNiH3 lower the desorption temperature to 305.77 K without significant reduction of the hydrogen storage capacity. This lowering of the temperature desorption makes the material very useful for hydrogen storage in solids.

The pyroelectric effect is commonly used to construct infrared radiation detectors. To pay attention to the possibility of using this phenomenon in materials based on relaxor-ferroelectric such as Pb(Mg1/3Nb2/3)1-xTixO3 (lead titanium-lead magnesium niobate), single crystals from solid solution were grown using modified Bridgman method with x taken three different range (x = 0.25, 0.33 and 0.40). In this work the operation principles for pyroelectric sensor and their properties are presented, with a brief review on the temperature stability of the Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN–xPT) single crystals. It was shown that the pyroelectric and dielectric properties are strongly dependent on composition (PT content), as well as the temperature variation. The investigations have revealed that the best choice for pyroelectric performances is oriented PMN–0.25 PT, although, the PMN–0.33 PT and PMN–0.40 PT owns much better temperature stability, and higher Curie temperature Tc. The PMN–xPT single crystals showed promising pyroelectric performances, they can be used as thermal sensors and may be associated with temperature management systems to improve the performance of solid state hydrogen reactors.

Thermal energy harvesting has great potential for environment-friendly self-powered devices. Materials based on relaxor-ferroelectric single crystals such as PMN-PT (lead titanium-lead magnesium niobate) have gained significant interest for their outstanding properties. In this context, single crystals from (1-x)PbMg1/3Nb2/3O3-xPbTiO3 solid solution were grown using the modified Bridgman method in the composition range of x = 0.25, 0.35, and 0.40. This paper presents a systematic comparison between (1-x)PMN-xPT single crystals and ceramics involving the effect of composition and the crystal orientation on thermal properties assuming a one-dimensional heat-flow process. Results demonstrate that thermal and pyroelectrical properties are intimately coupled to the chemical composition, where the studied single crystals have a good performances compared to their corresponding ceramics, which make them very promising for efficient cooling systems, and IR devices applications.

This study reports the enhanced mechanical resistance of the composite bioceramics of hydroxyapatite (HAP) and tricalcium phosphate (β-TCP) used as bone substitute. HAP/β-TCP mixture was prepared by wet mixing of powders and characterized. Effects of powder manufacturing and sintering temperature on the densification, microstructure and mechanical properties of the composite were studied. The rupture strength (σr) was calculated using the Brazilian test. At 1250 °C, the relative density and mechanical strength of the HAP/β-TCP ceramics reached the maximum value of 89% and 43 MPa, respectively. Experimental results were modeled by the finite element method to determine the stress distribution in the compacted disc.

International audience; The effect of Zr substitution by alkaline earth metals Mg, Be and post-transition metal Al on the evolution of hydrogen storage properties of ZrNiH 3 has been investigated by ab-initio calculations based on density functional theory. The stability of the quaternary hydrides is studied by the determination of the formation enthalpy and the desorption temperature. The obtained results indicate a reduction of the formation enthalpy as well as the desorption temperature , hence reflecting the enhancement of hydrogen storage properties of ZrNiH 3. Interestingly, each dopant (Mg, Be and Al) achieved its optimum substitution effect at a particular concentration, with Al and Be elements are found to exhibit the lowest substituting content 17% and 23% respectively and Mg with the highest concentration 85%, to achieve an ideal formation enthalpy (ΔH = −40 kJ/mol.H 2) and desorption temperatures (289 to 393 K), as required for practical use of proton exchange membrane fuel cells (PEMFC) without affecting the hydrogen storage capacity as seen in pure ZrNiH 3 .More-over, the electronic structure investigated by partial density of states (PDOS), reveals the metallic nature of Zr 1−x AM x NiH 3 (AM = Mg, Be and Al) hydrides. Highlights • The ZrNiH 3 hydride presents high stability and high decomposition temperature. • The stability decreases significantly when doping ZrNiH 3 with Mg, Be and Al. • The density of states reveals the metallic nature of Zr 1−x AM x NiH 3 hydrides. K E Y W O R D S density functional theory, hydrogen storage, Ni-MH batteries, thermodynamic properties, ZrNiH 3

Nowadays energy storage seems to be a vital point in any new energy paradigm. It has become an important and strategic issue, to ensure the energetic sufficiency of humanity. Indeed, hydrogen storage in solids has been proved and revealed as clean and efficient energy storage. Moreover, it can be thought as a seriously considered solution to enable renewable energy to be a part of our quotidian life. To achieve storing hydrogen in solid form, the present study aimed to concepts and simulates a solid-state hydrogen storage reactor (tank). An investigation of the parameters influencing the hydrogen storage performance is carried out. Meanwhile, to understand the physical phenomenon taking place during the storage of hydrogen, a 2D numerical modelling for a metal hydrides-based in hydrogen reactor is presented. A strong coupling between energy balance, kinetic law, as well as a mass momentum balance at sorbent bed temperature under a non-uniform pressure was resolved based on finite element method. The temporal evolutions of pressure, the raising temperature in the bed during the hydriding process as well as the impact of the hydrogen supply pressure within the tank are analysed and validated by comparison with the experimental work in literature, a good agreement is obtained. From an industrial point of view, this study can be used to design and manufacture an optimal solid-state hydrogen storage reactor.

Hydroxyapatite/zirconia powders were produced by soft chemistry and characterized by several techniques. The effects of the sintering temperature on the densification, microstructure and mechanical properties of the bioceramics were studied. The HAP-10%ZrO2 bioceramic was chosen for its specific advantages. Microstructural and textural characterization reveal disappearance of the microporosity in certain areas of the sample to form dense blocks whose size increases progressively as a function of the sintering temperature. Mechanical properties were assessed by the Brazilian and Vickers tests. Young and shear moduli were calculated from the longitudinal and transverse ultrasonic velocities, respectively. Above 1300°C, the mechanical strength, Vickers hardness, Young and shear moduli reach maximum values of 30 MPa, 2336 MPa, 81 GPa and 34 GPa, respectively. Rupture of the studied bioceramic is totally intergranular around 1300°C. We find that microstructure, porosity and the sintering process govern the development of the HAP-10%ZrO2bioceramic.

Ceramics arising from Pb(Mg1/3Nb2/3)1‑x TixO3 with composition near the morphotropic phase boundary (MPB) were prepared by the modified solid-state reaction method. The synthesized ceramics were characterized, and then the operating principles of pyroelectric and piezoelectric harvesters are reviewed. In addition, the dielectric behavior is measured to determine the dielectric constant and losses at different temperatures and frequencies. The typical behavior of a ferroelectric relaxer was observed by adding the PbTiO3 phase. The thermal properties are also analyzed by PPE calorimetry, presaging a one-dimensional heat-flow process. As a result, the dielectric and thermal behaviors of the as-prepared ceramics as well as their thermal stability are intimately linked to the PbTiO3 addition to PbMgl/3Nb2/3O3 phase. These materials exhibit good physical performances, which makes them promising candidates for pyroelectric micro-generators (PEG), cooling systems and infrared applications.

The recent developments in measurement technology have led to the installation of efficient monitoring systems on many bridges and other structures all over the world. Nowadays, more and more structures have been built and instrumented with sensors. However, calibration and installation of sensors remain challenging tasks. In this paper, we use a case study, Adige Bridge, in order to present a low-cost method for the calibration and installation of elasto-magnetic sensors on cable-stayed bridges. Elasto-magnetic sensors enable monitoring of cable stress. The sensor installation took place two years after the bridge construction. The calibration was conducted in two phases: one in the laboratory and the other one on site. In the laboratory, a sensor was built around a segment of cable that was identical to those of the cable-stayed bridge. Then, the sample was subjected to a defined tension force. The sensor response was compared with the applied load. Experimental results showed that the relationship between load and magnetic permeability does not depend on the sensor fabrication process except for an offset. The determination of this offset required in situ calibration after installation. In order to perform the in situ calibration without removing the cables from the bridge, vibration tests were carried out for the estimation of the cables’ tensions. At the end of the paper, we show and discuss one year of data from the elasto-magnetic sensors. Calibration results demonstrate the simplicity of the installation of these sensors on existing bridges and new structures.

With recent advancements in energy conversion mechanisms, piezoelectric ceramics (1–x)PbMg1/3 Nb2/3Ο3-xPbTiΟ3 (1–x)PMN-xPT have demonstrated their abilities for converting mechanical vibrations into electricity. Three (1–x)PMN-xPT compositions were used in the present work with (x = 0.25, 0.31 and 0.33). The purpose of this paper is to investigate their piezoelectric performance as generators for energy harvesting applications. The energy harvester is numerically analyzed in this work. It consists of a piezoelectric bimorph clamped at one end to vibrating machinery, and a proof mass mounted on its other end. The energy harvester is also analyzed and experimental measurements of the harvested power are compared to the simulation results. A good agreement was observed between the experimental and the simulations results. According the application to exploit the vibrations of a hot air extractor, the results show that the harvested energy density of solid ceramics (1–x)PMN-xPT is 0.043 W/m2.

International audience; Lead-free functional oxides can be dedicated to numerous applications. Here a part of a complete study on ST and SCT ceramics dedicated to high-Q capacitors is presented, as well as some results on W and WO3 thin films dedicated to semiconductor gas sensors.

Calcium phosphate biomaterials were used to repair bone defects as prosthetic coatings. Powders and bioceramics from hydroxyapatite and β-tricalcium phosphate were fabricated using a low-cost process and characterized with different techniques. Their thermal stability and mechanical properties were investigated under water environment. This study was to investigate the effect of water moieties to cause permanent damage to calcium phosphate bioceramics by determining their mechanical properties changes.

We present an investigation of the mechanical properties of Al2O3-ZrO2 as duplex-structured materials using the finite element method (FEM). The creation of stress fields are a result of the material trying to dissipate mechanical energy that is being exerted on the biomaterial. By finite element modelling and the stress fields, as either compressive or tensile, we can understand how inclusions interact with each other bioceramic lattice containing alumina in the presence of different zirconia contents. The stress fields can be applied to various strengthening mechanisms in bioceramic. They can be created by adding several inclusions in alumina lattice.

In this study, the influence of powder manufacturing and sintering temperature on densification, microstructure and mechanical properties of dense β -tricalcium phosphate ( β -TCP) bioceramic has been studied. Densification results show that the β -TCP can be sintered at 1160 °C for 3 hours to have good density and high performance mechanic properties (Vickers hardness, toughness and Youngʼs modulus). X-ray diffraction and SEM microscopy are used to check the microstructure changes during the sintering temperature. The used processing of β -TCP ceramic improved its densification, microstructure homogeneity and mechanical properties.

Lead–free Sr[Formula: see text]CaxTiO3 ([Formula: see text]) ceramics were synthesized via a solid state reaction technique at room temperature. The effects of ionic substitutions in A-sites between strontium and calcium on the structural and dielectric properties were investigated. XRD technique was used to identify the crystal structure and to demonstrate the phase purity. SEM observations have shown homogeneous morphologies for all samples. Dielectric measurements were investigated for a wide range of frequency (100[Formula: see text]Hz–1[Formula: see text]GHz) and temperature (25[Formula: see text]C–250[Formula: see text]C). Strontium substitution by calcium has not only led to a decrease in the dielectric permittivity value, but also to the loss tangent value by a considerable factor. Interesting values of the quality factor and the quite constant value [Formula: see text] in extended frequency and temperature ranges show that SCT ceramic could be a real candidate for the development of monolithic ceramic capacitors dedicated to high-frequency lead-free components and/or to extremely high-temperature environments.

This paper reports the effects of processing densification on the mechanical properties of hydroxyapatite bioceramics. Densification of synthetic hydroxyapatite is conducted in the range 1000–1300 °C. X-ray diffraction and SEM microscopy are used to check the microstructure transformations. Vickers hardness, toughness and Young's modulus are analyzed versus the density and grain size. The sintering temperature and the particle size influence strongly the densification and the resulting mechanical properties. In addition, the critical sintering temperature appears around 1200 °C and the declined strength at the temperature up to 1200 °C is found sensitive to the dehydroxylation process of hydroxyapatite.