1998) Effects of porosity and polymer matrix on the properties of piezoelectric ceramic/polymer composites, Ferroelectrics, 215:1, 123-130, Porous PZT was fabricated by conventional sintering process in the present study. Three kinds of polymer materials, with varying hardness, then were injected into the porous PZT to form a PZT/polymer composite with 3 ~~ 3 connectivity. Such properties as the dielectric constant, the coupling factor, and the hydrostatic piezoelectric constants were characterized. The effect of the polymer-phase hardness on the properties of the composites also was investigated.
A spray-formed Al 89 La 6 Ni 5 metallic glass matrix composite plate was obtained in thickness of 1 mm and diameter of 200 mm, comprising over 64% primary crystals (e.g. Al 11 La 3 ) uniformly dispersed in the glass matrix. The microstructure can not be achieved by annealing corresponding amorphous precursor. The crystals existing in the glass matrix were found to increase the hardness of the composite. Through nanoindentation test, the hardness and modulus of the composite at ambient temperature were found superior than its amorphous ribbon counterpart. The hardness of the composite was estimated with the rule of mixture from the constituents to be 4.4 GPa, which agreed well with the nanoindentation results. From loss modulus measurement and TMA test at elevated temperatures, a weak T g signal in the range of 213-240 C was revealed in the as-spray-formed composite. Furthermore, the dimension shrinkage of the composite was only 0.5% during the TMA test, which is much smaller than that of amorphous ribbon counterpart by up to 20%. The enhanced hardness by constituent second phases and the dimension stability of the composite are associated with their inherent microstructure, the primary crystals in particular.
Mg-based amorphous alloys exhibit maximum specific strength among bulk metallic glass systems. In this study, a bulk Mg 65 Cu 25 Y 10 deposit was produced successfully via spray forming process with higher cooling rate than conventional mold casting route. The deposit is 300mm in diameter, 10 mm in thickness and 650 g in weight.The average porosity is about 10%. The XRD and DSC results of the deposit look similar to that obtained from corresponding amorphous melt-spun ribbon. However, the measured composition of deposit varies slightly with the distance from substrate, which attribute to gravity effect of relative heavy element, like Y and Cu. The hardness of the deposit is higher than that of melt spun ribbons. The supercooled liquid region of the deposit determined from TMA technique is about 20K smaller than that obtained from DSC trace due to the stress induced nanocrystallzation occurred in the former. In addition, the volume reduction of deposit during TMA test was also smaller than that of ribbon and shows better dimension stability.
KEY WORDSBulk metallic glass, glass forming ability, spray forming, MgCuY ---
A composite transducer is fabricated, by stacking certain segments of poled piezoelectric ceramic, to satisfy multiple, conflicting design specifications. An electromechanical equivalent circuit that substantially facilitates the analysis of segmented systems, based on the Mason model is derived. To obtain the optimal solution to a specific design formulation, PSPICE programming techniques can be applied. An example of the application of PSPICE programming in the segmented transducer analysis is presented and the simulation results are in good agreement with the experimental measurements.
Mg bulk metallic glass rod, ribbon and composite plate were synthesized via injection
casting, melt spinning, and spray forming, respectively. The BMG composite plate has various
microstructure combinations, from fully amorphous phase to mixture of nanocrystals, crystals and
amorphous phase. XRD analyses were done on the rod and ribbon and throughout the vertical
locations of the plates at the maximum thickness. Glass transition temperature (Tg) and onset
crystallization temperature (Tx) were measured with DSC, and GFA (Glass Forming Ability) was
estimated with various GFA models. The microhardness of the spray-formed Mg-Cu-Gd layered
composite plate at various positions and Mg-Cu-Gd rod and ribbon were measured.
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