Piezoelectricity and Its Applications

The piezoelectric effect is extensively encountered in nature and many synthetic materials. Piezoelectric materials are capable of transforming mechanical strain and vibration energy into electrical energy. This property allows opportunities for implementing renewable and sustainable energy through power harvesting and self-sustained smart sensing in buildings. As the most common construction material, plain cement paste lacks satisfactory piezoelectricity and is not efficient at harvesting the electrical energy from the ambient vibrations of a building system. In recent years, many techniques have been proposed and applied to improve the piezoelectric capacity of cement-based composite, namely admixture incorporation and physical. The successful application of piezoelectric materials for sustainable building development not only relies on understanding the mechanism of the piezoelectric properties of various building components, but also the latest developments and implementations in the building industry. Therefore, this review systematically illustrates research efforts to develop new construction materials with high piezoelectricity and energy storage capacity. In addition, this article discusses the latest techniques for utilizing the piezoelectric materials in energy harvesters, sensors and actuators for various building systems. With advanced methods for improving the cementations piezoelectricity and applying the material piezoelectricity for different building functions, more renewable and sustainable building systems are anticipated

Initial Permeability Dependence on the Microstructural and Compositional Changes in Ni-Zn-Sc Ferrites

Observed variations in density, grain size and initial permeability (µic) in two series of Ni-Zn-Sc ferrites with varying concentrations of zinc and scandium have been discussed in terms of their microstructural and compositional changes. Initial amounts of scandium enhanced densification and sintering in both the series. Subsequent concentrations of only scandium caused reduction in µic in Series-I, whereas simultaneous substitutions of zinc and scandium together resulted an increase in µic in Series-II. Conclusions have been drawn towards the domination of the microstructural changes in series-I and compositional changes in series-II in the study of initial permeability

Densification, Grain Growth and Microstructure of Ni-Zn Ferrites

Ni0.65 Zn0.35 Fe2 O4, with high density and fine grain size, is a desirable composition for applications of high frequency switching power supplies. This composition has been studied under different sintering conditions. Observed changes in density, grain size and microstructure in these ferrites have been correlated to the volatilization of zinc from the samples at elevated sintering temperatures. Densification and grain growth are observed to be Arrhenius controlled rate processes with activation energies of 63.9 and 64.4 Kcal/mole respectively

Shape and size-controlled synthesis of Ni Zn ferrite nanoparticles by two different routes

Monodisperse Ni-Zn ferrite nanoparticles of different compositions have been synthesized using two different routes, such as sonochemical and polyol methods. In both the cases, the process was attempted in a single reaction in the absence of any surfactant and deoxygenated conditions. X-ray diffraction data on the samples confirmed formation of pure ferrite phase with spinel structure, and indicated that the sonochemical method produces highly crystalline particles compared to the polyol process. Transmission electron microscopy images reveal formation of different shapes, such as cubic, spherical, flower-like and amorphous depending on the method and composition of the ferrite. The magnetic properties of the synthesized Ni-Zn ferrite nanoparticles, measured by vibrating sample magnetometer at room temperature, show that the highest magnetization value was obtained for the composition of Ni0.5 Zn0.5 Fe2O4 in both the synthesis methods. The results of both the methods were discussed by correlating the structure to the magnetism at nanoscales. © 2014 Elsevier B.V. All rights reserved.

Enhanced Ferromagnetic Order in Mn Doped BiFeO3-Ni0.5Zn0.5Fe2O4 Multiferroic Composites

Multiferroic composites of 0.5 BiFeO3-0.5Ni0.5Zn0.5Fe2O4 and 0.5Bi0.95Mn0.05FeO3-0.5 Ni0.5Zn0.5Fe2O4 were prepared by combining sol-gel autocombustion and solid state methods. X-ray diffraction analysis of the composites reveals that the samples are formed as di-phase compounds while retaining the spinel phase for the Ni-Zn ferrite and perovskite phase for the Bi-ferrite. Fourier transform infrared spectroscopy measurements on the composites confirm their structures with the presence of Fe-O and Bi-O bonds. Dielectric measurements on the composites were used to discuss about the possible polarization/conduction mechanisms, phase transitions and magnetoelectric coupling. Room temperature ferroelectric and magnetic hysteresis loop studies on the samples ensure that the Mn doped composite exhibits enhanced remnant polarization as well as saturation magnetization compared to the undoped composite. Moreover, the Mn doping has further translated the composite into magnetically softened with coercivity almost close to zero. The obtained improvements in the dielectric and multiferroic properties of the composites are attributed to the corresponding structural modifications brought about by the Mn doping. Copyright © 2016 American Scientific Publishers All rights reserved.

Novel Planar Hall Sensor for Biomedical Diagnosing Lab-on-a-chip

International audienceThe underlying principle for magnetic biosensing has been elaborately described at first with the examples of different magnetoresistive sensing techniques. Then, the planar Hall resistance sensor has been shown as one of the best sensors for conducting magnetic bead detection experiments. While making an in depth study on the capabilities of a PHR sensor in different configurations and geometries, the sequence of narration ultimately has lead towards describing the evolution of hybrid AMR and PHR ring sensor in spin valve configuration with optimized performance for precise detection of even single magnetic bead. Biofunctionalization experiments were also conducted to ensure that our PHR sensor is capable of biomolecule recognition. Therefore, our present sensor can be used to promote for the biomolecular recognition and other molecular interaction detection. This novel planar Hall effect based sensor has been further demonstrated that it can be easily integrated into a lab-on-a-chip and is feasible for bead detection in the sensing current generated magnetic field (without the external applied magnetic field) so as to ensure it an efficient tool for high sensitive biomolecules recognition

Modified polyol route for synthesis of Fe3O4/Ag and alpha-Fe/Ag nanocomposite

We developed a new one-pot synthesis method for realizing silver coated magnetite nanocomposite by way of a modified polyol process. In this reaction, polyethylene glycol was used as a solvent media and it was observed to play a key role to act as a reducing agent, stabilizer as well as a linker for silver coating simultaneously. Further, we could successfully transfer the phase from Fe3O4/Ag to α-Fe/Ag by using the annealing system at 600°C in presence of hydrogen gas. X-ray diffraction data was independently used to confirm the formation of both the phases of Fe3O4/Ag and α-Fe/Ag. These Fe3O4/Ag and α-Fe/Ag samples were also characterized using transmission electron microscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy techniques and compared the results with those of seed Fe3O4 nanoparticles. The magnetic properties of the composites, Fe3O4/Ag and α-Fe/Ag with different Ag concentrations, along with the seed Fe3O4 nanoparticles were measured using vibrating sample magnetometer (VSM) at room temperature. Maximum magnetization values of 61.3 emu/g and 175.1 emu/g were observed for the samples with 1 mL Ag concentrations of Fe3O4/Ag and α-Fe/Ag, respectively. This new synthesis method looks to be a promising route for facile synthesis of different magnetic nanocomposites suitable for bioapplications. © 2014 Elsevier B.V. All rights reserved.1