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3D‐printing‐reinforced metal matrix composites are a promising avenue for fabricating materials to meet the demands of the 21st century. Ti–6Al–4 V has been a useful material in the aerospace and medical industries for decades due to its incredible strength‐to‐weight ratio, and now its suitability for additive manufacturing has made it even more desirable. One of the leading‐edge reinforcements being studied for metal matrix composites is carbon nanotubes due to their remarkable mechanical properties such as strength and elastic modulus. It is desirable to manufacture advanced metal matrix composites using advanced manufacturing techniques such as selective laser melting. Herein, the effect of 1 vol% carbon nanotube reinforcements on the microstructural evolution and properties of selective‐laser‐melt‐printed Ti64 and the interrelationships with laser energy density, laser power, and laser scan speed are investigated. The effectiveness of reinforcement and influence of printing parameters are assessed via microstructural and porosity analysis, and microhardness testing. Utilizing selective laser melting with a laser energy density of 60 J mm−3, a >99% dense Ti–CNT composite is manufactured with microhardness of 4.75 GPa—a 30% enhancement over its Ti64 counterpart. [ABSTRACT FROM AUTHOR]

Lead-free Bi(Mg1/2Ti1/2)O3-(Bi1/2K1/2)TiO3-(Bi1/2Na1/2)TiO3(BMT-BKT-BNT) ceramics have been shown to exhibit large electromechanical strains under high electric fields along with negligible fatigue under strong electric fields. To investigate the role of point defects on the fatigue characteristics, the composition 5BMT-40BKT-55BNT was doped to incorporate acceptor and donor defects on the A and B sites by adjusting the Bi/Na and Ti/Mg stoichiometries. All samples had pseudo-cubic symmetries based on x-ray diffraction, typical of relaxors. Dielectric measurements showed that the high and low temperature phase transitions were largely unaffected by doping. Acceptor doping resulted in the observation of a typical ferroelectric-like polarization with a remnant polarization and strain hysteresis loops with significant negative strain. Donor-doped compositions exhibited characteristics that were indicative of an ergodic relaxor phase. Fatigue measurements were carried out on all of the compositions. While the A-site acceptor-doped composition showed a small degradation in maximum strain after 106 cycles, the other compositions were essentially fatigue free. Impedance measurements were used to identify the important conduction mechanisms in these compositions. As expected, the presence of defects did not strongly influence the fatigue behavior in donor-doped compositions owing to the nature of their reversible field-induced phase transformation. Even for the acceptor-doped compositions, which had stable domains in the absence of an electric field at room temperature, there was negligible degradation in the maximum strain due to fatigue. This suggests that either the defects introduced through stoichiometric variations do not play a prominent role in fatigue in these systems or it is compensated by factors like decrease in coercive field, an increase in ergodicity, symmetry change, or other factors. [ABSTRACT FROM AUTHOR]

In the high-temperature ternary perovskite piezoelectric system x PbTiO3- y BiScO3- z Bi( Ni1/2, Ti1/2) O3 ( PT- BS- BNiT), the addition of bismuth to the A site and nickel to the B site leads to compositions that exhibit diffuse relaxor-like behavior. For these, depolarization temperature, not Curie point, is the critical value of temperature. Depolarization temperature ( Td) is defined as the temperature at which the steepest loss in polarization occurs. This temperature is observed in poled materials through two different methods: loss tangent measurements and in situ d33. Across the ternary system, multiple dielectric anomalies occurred which was observed in dielectric tests where the dielectric peak broadens and becomes frequency dependent as BNiT content increased. For different compositions, the value of Td ranged between 275°C-375°C. Values for the piezoelectric coefficient increased with temperature up to d33 = 1000 pC/N during in situ d33. High temperature (up to 190°C) and high field (up to 40 kV/cm) were also applied to test ferroelectric properties in these regimes. [ABSTRACT FROM AUTHOR]

In the high-temperature ternary perovskite piezoelectric system x PbTiO3- y BiScO3- z Bi( Ni1/2, Ti1/2) O3 ( PT- BS- BNiT), the addition of bismuth to the A site and nickel to the B site leads to compositions that exhibit diffuse relaxor-like behavior. For these, depolarization temperature, not Curie point, is the critical value of temperature. Depolarization temperature ( Td) is defined as the temperature at which the steepest loss in polarization occurs. This temperature is observed in poled materials through two different methods: loss tangent measurements and in situ d33. Across the ternary system, multiple dielectric anomalies occurred which was observed in dielectric tests where the dielectric peak broadens and becomes frequency dependent as BNiT content increased. For different compositions, the value of Td ranged between 275°C-375°C. Values for the piezoelectric coefficient increased with temperature up to d33 = 1000 pC/N during in situ d33. High temperature (up to 190°C) and high field (up to 40 kV/cm) were also applied to test ferroelectric properties in these regimes. [ABSTRACT FROM AUTHOR]

Abstract: High temperature ferroelectrics are an important aspect of piezoelectric material research for many energy related applications. Some of the desired properties are high Curie temperature, large remanent polarization, and large piezoelectric coefficients. Polycrystalline perovskite ceramics of the composition (1− x)[BiScO3 +Bi(Ni1/2Ti1/2)O3]− xPbTiO3 (BS-BNiT-PT), were synthesized using standard solid state processing. Room temperature X-ray diffraction revealed a perovskite phase with an observed transition from tetragonal to pseudo-cubic symmetry over the compositional range x =0.50–0.60. Compositions rich in PbTiO3 showed strong tetragonal distortions with characteristic first-order phase transitions. As the PbTiO3 content decreased dielectric measurements revealed large permittivities (er′~16,000) with relaxor characteristics up to 400°C. Ferroelectric hysteresis measurements revealed remanent polarizations as high as 31μC/cm2 at x =0.52 with relatively low coercive fields of 25kV/cm. The piezoelectric coefficients, mechanical quality, and planar coupling factors of the x =0.54 composition were 376pC/N, 13.4, and 0.148, respectively. [Copyright &y& Elsevier]