Lead-free Nanocomposites Research Articles

Enhanced Electroactive Phases in Bi3·3La0·7Ti3O12-poly (vinylidene fluoride) composites with Improved Dielectric Properties

Lead-free ceramic-polymer nanocomposites comprising poly (vinylidene fluoride) (PVDF) and homogeneously dispersed Bi3·3La0·7Ti3O12 (BLT) ceramic particles were synthesized using the solution casting method. The effect of BLT addition on the growth rate of different crystalline phases of PVDF was systematically investigated. X-ray diffraction analysis showed the presence of β-phase in all the composite samples. FTIR and Raman spectroscopy analysis also confirmed the enhancement in the electroactive β and γ phases with BLT addition. The fraction of β-phase i.e., F(β)% has been found to be 64.5% at 10 wt % BLT loading. The homogeneous distribution of ceramic particles in PVDF matrix was confirmed using field emission scanning electron microscopic analysis. The dielectric constant of the nanocomposites with 10 wt % of BLT loading can reach up to 53.5 at 100 Hz, which is attributed to the enhanced interfacial polarization and relative enhancement of electroactive phases of PVDF. The temperature-dependent dielectric measurement shows an enhancement in the dielectric constant with increasing temperature. The nanocomposites also exhibit excellent ferroelectric properties with enhancement in remanent polarization. This work suggests the possibility of enhancing the electroactive phases of PVDF with superior dielectric and ferroelectric properties. These lead-free nanocomposites may prove to have a tremendous potential in flexible sensors, data storage, and energy harvesting applications.

Investigation of physical properties of magnetoelectric LaFeO3–ErMnO3 lead-free nanocomposites

Magnetoelectric coupling has been investigated in lead-free nanocomposites of LaFeO3x–ErMnO3 (1−x) (x = 0.2 and 0.3) prepared by pyrophoric reaction process having piezomagnetic phase of LaFeO3 and piezoelectric phase of ErMnO3, while this nanocomposite reveals the signature of product property, i.e., Magnetoelectric coupling and magnetocapacitance effect (~ 50%) at room temperature attribute the enhancement of space charge polarisation of nanoparticles. Coexistence of both phases in nanocomposites is confirmed by X-ray diffraction technique. Electrical susceptibility corresponds to the domain wall motion due to electrostriction property. Temperature-dependent impedance analysis provides the evidence of space charge accumulation in nanocomposites exhibiting negative temperature coefficient resistance effect of the sample. The estimated activation energy from the Arrhenius fit suggests the hopping of carriers between La2+ and La3+ and Fe2+ and Fe3+ ions in the materials. The importance of the present study is the developing urge to know the details of magnetoelectric coupling and transport properties of a system for its technological applications.

Toward advanced gamma rays radiation resistance and shielding efficiency with phthalonitrile resins and composites

Abstract The phthalonitrile resins have claimed the leading place in the field of high performance polymers thanks to their combination of outstanding properties. The present work explores for the first time the gamma rays radiation resistance and shielding efficiency of the phthalonitrile resins and its related tungsten-reinforced nanocomposites. The primary goal of this research is to define the basic behavior of the phthalonitrile resins under highly ionizing gamma rays. The obtained results confirmed that the neat phthalonitrile resins can resist absorbed doses as high as 200 kGy. Meanwhile, the remarkable shielding efficiency of the phthalonitrile polymers was confirmed to be easily improved by preparing lead-free nanocomposites. In fact, the gamma rays screening ratio reached the exceptional value of 42% for the nanocomposites of 50 wt% of nano-tungsten loading. Thus, this study confirms that the remarkable performances of the phthalonitrile resins are not limited to the thermal and mechanical properties and can be extended to the gamma rays radiation and shielding resistances.

Piezoelectric and mechanical behavior of NaNbO3/PEKK lead-free nanocomposites

Lead-free piezoelectric nanocomposites based on poly(ether ketone ketone) (PEKK) and sodium niobate (NaNbO3) particles were elaborated. The presence of submicronic particles does not influence the thermal stability of the matrix so that no degradation phenomenon is observed before 500°C. The conservative mechanical modulus G′ increases linearly with the NaNbO3 fraction; this variation is well fitted by the Kerner model until 20vol%. Such nanocomposites remain ductile. The polarizing field required for obtaining piezoelectric nanocomposites is 12kV·mm−1 i.e. analogous with the one used for poling bulk ceramic. The value of the piezoelectric coefficient (d33=0.2 pC·N−-1 for 20vol% NaNbO3) is consistent with the Furukawa's model. This value is explained by the low PEKK permittivity. This low d33 is counterbalanced by the piezoelectric voltage constant (g33=103·10−3Vm·N−1) which is higher than the one of classical piezoelectric ceramic like PZT or BaTiO3.

Synthesis and Characterization of BNKT/ZnO Ferroelectric Lead-Free Nanocomposites

In this research, the effects of ZnO nanoparticles additive on crystallization behavior, dielectric and ferroelectric properties of Bi0.5(Na0.81,K0.19)0.5TiO3 ceramics were investigated. The samples were synthesized by solid state reaction technique, where powders were calcined at 850 °C for 4 h and ceramics were sintered at 1100-1150 °C for 4 h. Phase formation was determined by X-ray diffraction technique (XRD). The X-ray diffraction analysis of the ceramics suggests that all samples exhibited a perovskite structure. The dielectric properties under room temperature and various temperatures were also determined. Dielectric measurement data showed that the additive influenced dielectric constant and dielectric loss. Furthermore, the hysteresis loop behaviors slightly changed with increasing the nanoparticles contents.

Effects of NiO nanoparticles on electrical and magnetoelectric properties of BNT based ceramics

The properties of 0.94BNT-0.06BT/xNiO lead-free nanocomposites were investigated. The NiO additive influenced dielectric properties as well as the phase transition behavior of the samples. Dielectric properties under applied magnetic fields were also measured. After addition of the additive, the loss tangent could be controlled by an applied magnetic field. Furthermore, the P-E hysteresis loop changed from a normal hysteresis loop for the unmodified sample to a constricted loop for the x = 0.5 and 1.0 vol. % samples, and then became a lossy capacitor hysteresis loop for the x = 2.0 vol. % sample. These results suggest that NiO nanoparticles have a strong influence on the properties of the composites.

Reinforcements at nanometer length scale and the electrical resistivity of lead-free solders

In this study, the influence of a wide range of reinforcements (SnO 2, Cu, Y 2O 3, ZrO 2 + 8 mol.% Y 2O 3 and TiB 2) on the electrical resistivity of Sn–3.5Ag and Sn–3.5Ag–0.7Cu solders was investigated. The electrical resistivity test was conducted on the bulk samples of composite solders at ambient temperature. Results revealed that electrical resistivities of composites containing nanometer length scale reinforcement is not compromised for the optimal amount of reinforcement required to realize best tensile properties. This behavior was not displayed by composite containing micron size particles. The results of this study are expected to pave the way to develop lead-free nanocomposites especially for the industry using solid-state bonding technique.