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A novel type of piezoelectric aluminium-based hybrid composite containing silicon carbide (SiC) and piezoelectric lead lanthanum zirconate titanate (PLZT) was prepared using powder metallurgy technique followed by sintering at 630 °C and hot extrusion at 500 °C. The volume fraction of PLZT particles varied as 0%, 5%, 10% and 15% with fixed weight 1 wt.% of SiC respectively in the composite and its effects on the microstructure as well as the damping nature of the composite were studied. The microstructure of composites was analysed by scanning electron microscope (SEM) and electron microprobe, and damping behaviour was investigated using Dynamic Mechanical Analysis (DMA) as function of temperature. Microstructural results attested the homogeneity of two different reinforcements in the composite and thus confirmed hot extrusion process had shown promising route for obtaining homogenous and dense metal matrix composites. DMA studies of homogenous hybrid MMCs indicated that the increase in wt.% of piezoelectric PLZT particles improved the damping properties. [ABSTRACT FROM AUTHOR]

Single phase yttria nanopowders for transparent ceramics were successfully prepared by using a novel approach called microwave-flash combustion technique. This technique involves the reaction of yttrium nitrate and urea in microwave oven for few minutes. The as-prepared precursor powder was later calcined at 1100 °C for 4h to form cubic crystalline yttria nanopowders. The as-prepared and calcined powders were analysed by such methods as thermogravimetry, Brunauer--Emmett--Teller surface area measurement, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results confirmed that the yttria powder synthesized by microwave-flash combustion was homogenanus and the particles size was in the range of 50-120 nm for calcined powders. [ABSTRACT FROM AUTHOR]

La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 − δ (LSCF) perovskite nanostructures were synthesised using a 42 kHz ultrasound assisted synthesis technique for the fabrication of electrodes in the intermediate and/or low temperature solid oxide fuel and electrolysis cells (SOFCs/SOECs). The obtained nanomaterials were dried at 110 °C followed by calcination in a normal atmosphere at various temperatures from 400 to 1000 °C for 2 h. Powder characteristics such as crystal structure, thermal decomposition, particle size and morphology were analysed. The transmission electron microscopy (TEM) study revealed the uniform equi-axial shape and growth of the obtained nanostructures with respect to the calcination temperature till 800 °C. The structural and chemical analyses confirmed the existence of LSCF and CoFe 2 O 4 phases. [ABSTRACT FROM AUTHOR]

In this study, intermetallic Nb3Sn of nanometer-sized grains was synthesized by powder metallurgy route. Elemental powders of Nb and Sn in the stoichiometric proportions were mechanically alloyed for 3h in a high-energy mill under a protective atmosphere of argon. X-ray diffraction patterns of milled powders confirmed the formation of a Nb(Sn) solid solution evidenced by the presence of Nb peaks only, which are shifted to higher angles. Rietveld refinements used to analyze this XRD pattern indicated a better fit when a tetragonal structure with the space group I4/mmm is used instead the Nb cubic lattice with space group Im-3m. Size-strain analysis from line-broadening of peak profiles by using "double-Voigt" approaches showed that the broadening is due to both a small crystallite size (around 6nm) and microstrains. Subsequent heat treatment of the Nb(Sn) powder mixture was required for the formation of the Nb3Sn ordered phase. X-ray diffraction patterns obtained after a thermal treatment at 700°C for 1h were fitted using a multiphase Rietveld refinement. Although the resulting powders are composed mainly by Nb3Sn (up to 87weight%), certain amount of other intermetallic phases like Nb6Sn5, NbSn2 and Nb and Sn oxides were also determined. In agreement with the Rietveld refinement analysis, microprobe analysis also revealed that changes in chemical composition at different sites of powder particles are preserved even after annealing at 700°C. Magnetic properties measured at 300K on resulted Nb3Sn powders evidenced the soft super paramagnetic materials nature through its magnetization hysteresis loops. [ABSTRACT FROM AUTHOR]

Cu-8 wt-%SmCo5 alloys were obtained through mechanical milling for novel industrial applications. Copper and SmCo5 powder mixtures were mechanically alloyed in a planetary ball mill to disperse SmCo5 fine particles in the copper matrix with the aim to modify the structural, mechanical, electrical and magnetic properties. The resulting alloyed powders were characterised as a function of milling time. Under the magnetic field, SmCo5 particles achieved Ms to improve the soft magnetic properties of copper-8 wt-%SmCo5 to be used in dielectromagnetic components. The magnetic properties of Cu-8 wt-%SmCo5 powders reached their optimum values after milling time ranging from 10 to 15 h. The consolidation of milled alloy powders was performed by uniaxial hot pressing at 923 K for 2 h under argon atmosphere to obtain dense compacts. The consolidation process resulted in good dense metal matrix composite materials with adequate properties of compression strength >900 MPa, 95 HRB in hardness, electrical conductivity up to 43% of that of the International Annealed Copper Standard (IACS) and magnetic properties such as coercive field, saturation and remanent magnetisation obtained at 218 Oe, 70·23 emu g-1 and 6·09 emu g-1 respectively at 300 K. The existence of a coercive field and a little magnetic memory of the consolidated system is a typical behaviour of magnetically soft materials. The variation of electric and magnetic properties and its dependence on structure strength change with milling time were discussed. [ABSTRACT FROM AUTHOR]

In this study, electroceramics PBN and PLZT along with SiC were included in Al-3.96 wt.% Mg (A514.0) master alloy. Ultrasonic cavitation (UST) and mechanical stirring (MS) were employed to improve wettability and dispersion during casting. Two composite systems were produced: PBN system (5 wt.% PBN + 1 wt.% SiC and 15 wt.% PBN + 1 wt.% SiC) and the PLZT system (follows the same designation). The influence of fabrication method on the microstructures, particle distribution and wettability as well as electroceramic impact on dynamo-mechanical properties of prepared composites were investigated. Optical microscope (OM) and scanning electron microscope (SEM) results indicate that the processing technique was effective as it promoted wettability and homogeneous dispersion of particles throughout the Al matrix. Dynamic mechanical analysis (DMA) study of the composites demonstrated that the addition of the functional particles to the Al alloy matrix improved damping capacity (Tan δ) at 200 °C. The composites exhibited an increase in Tan δ of 24.3 ± 0.3% and 91.4 ± 0.2% for 5 and 15 wt.% PBN + 1 wt.% SiC and an increase of 19.7 ± 0.5% and 42.5 ± 0.3% for 5 and 15 wt.% PLZT + 1 wt.% SiC, respectively, when compared to the aluminium alloy matrix. [ABSTRACT FROM AUTHOR]