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Lead-free piezoelectric materials and composites for high power density energy harvesting
Maurya, Deepam,Peddigari, Mahesh,Kang, Min-Gyu,Geng, Liwei D.,Sharpes, Nathan,Annapureddy, Venkateswarlu,Palneedi, Haribabu,Sriramdas, Rammohan,Yan, Yongke,Song, Hyun-Cheol,Wang, Yu U.,Ryu, Jungho,Pri Published for the Materials Research Society by th 2018 Journal of materials research Vol.33 No.16
<▼1><B>Abstract</B><P/></▼1><▼2><P>In the emerging era of Internet of Things (IoT), power sources for wireless sensor nodes in conjunction with efficient and secure wireless data transfer are required. Energy harvesting technologies are promising solution toward meeting the requirements for sustainable power sources for the IoT. In this review, we focus on approaches for harvesting stray vibrations and magnetic field due to their abundance in the environment. Piezoelectric materials and piezoelectric-magnetostrictive [magnetoelectric (ME)] composites can be used to harvest vibration and magnetic field, respectively. Currently, such harvesters use modified lead zirconate titanate (or lead-based) piezoelectric materials and ME composites. However, environmental concerns and government regulations require the development of a suitable lead-free replacement for lead-based piezoelectric materials. In the past decade, several lead-free piezoelectric compositions have been developed and demonstrated with promising piezoelectric response. This paper reviews the significant results reported on lead-free piezoelectric materials with respect to high-density energy harvesting, covering novel processing techniques for improving the piezoelectric response and temperature stability. The review of the state-of-the-art studies on vibration and magnetic field harvesting is provided and the results are used to discuss various strategies for designing high-performance energy harvesting devices.</P></▼2>
Ce<sup>3+</sup>-enriched core-shell ceria nanoparticles for silicate adsorption
Kim, Kijung,Seo, Jihoon,Lee, Myoungjae,Moon, Jinok,Lee, Kangchun,Yi, Dong Kee,Paik, Ungyu Published for the Materials Research Society by th 2017 Journal of materials research Vol.32 No.14
<▼1><B>Abstract</B><P/></▼1><▼2><P>Ce<SUP>3+</SUP> ions in ceria nanoparticles (NPs) play a role as reactive sites in the adsorption of silicate anions. However, the limited concentration of Ce<SUP>3+</SUP> ions in ceria NPs remains a major challenge in this regard. Herein, we report a simple strategy to synthesize Ce<SUP>3+</SUP>-enriched core-shell ceria NPs for enhanced adsorption of silicate anions. To increase the overall Ce<SUP>3+</SUP> concentration, a shell layer is composed of Ce<SUP>3+</SUP>-rich ultrasmall ceria NPs approximately 5 nm in size. The Ce<SUP>3+</SUP> concentration of such core-shell ceria NPs is increased by 12.7-17.1% relative to that of the pristine ceria NPs, resulting in increased adsorption of silicate anions. The Freundlich model fits the observed adsorption isotherm well and the constants of adsorption capacity (<I>K</I>F) and adsorption intensity (1/<I>n</I>) indicate higher adsorption affinity of the core-shell ceria NPs for silicate anions. We attribute these improvements to the increased Ce<SUP>3+</SUP> concentration contributed by the ultrasmall ceria coating. This strategy can be used for enhancing the reactivity of ceria materials.</P></▼2>
Kang, Joon-Koo,Park, Chee-Sung,Lee, Jae-Wung,Park, Gun-Tae,Kim, Hyoun-Ee,Choi, Jong-Jin Published for the Materials Research Society by th 2006 Journal of materials research Vol.21 No.6
<P>Highly (100)- and (111)-oriented lead magnesium niobate-lead zirconate titanate (PMN-PZT) films were deposited on Pt(111)/Ti/SiO2/Si substrates using a sol containing polyvinylpyrrolidone (PVP). The molar ratio of Zr/Ti in the PZT was fixed at 60/40, and the PMN content was changed in the range of 0-30 mol%. The films had a dense and columnar microstructure with a thickness of about 1 μm as a result of being spun four times. The crystallographic orientation of the films was controlled by adjusting the pyrolysis temperature; a (100) orientation was obtained by pyrolyzing at 300 °C and a (111) orientation by pyrolyzing at 350 °C. The electrical properties of the films were strongly dependent on the crystallographic orientation and PMN content. With increasing PMN content, the dielectric constant of all of the films increased. On the other hand, the remnant polarization of the (111)-oriented films decreased steadily with increasing PMN content, while that of the (100)-oriented films remained unchanged up to a PMN content of 20%. The piezoelectric coefficients of the (100)-oriented film were consistently higher than those of the (111)-oriented film with the same composition. The highest piezoelectric coefficient was observed for the (100)-oriented film with a composition of 0.2PMN-0.8PZT, indicating the morphotropic phase boundary between the rhombohedral PZT phase and the pseudocubic PMN phase is in the vicinity of this composition.</P>
Strain induced hardening and softening behaviors of deformed Cu and Cu-Ge alloys
Gong, Y.L.,Kim, H.S.,Ren, S.Y.,Zeng, S.D.,Zhu, X.K. Published for the Materials Research Society by th 2016 Journal of materials research Vol.31 No.5
<▼1><B>Abstract</B><P/></▼1><▼2><P>Herein, Cu and Cu-Ge alloys with different stacking fault energies (SFEs) are prepared via rolling at room temperature (RTR) and via a combination of high-pressure torsion (HPT) and RTR (HPT + RTR). The x-ray diffraction measurements reveal that the grain size, dislocation density, and twin density vary with the strain and SFEs. The tensile tests indicate that the strength of materials with medium SFEs increases initially and then slightly declines, while the ductility is enhanced by increasing the strain via HPT. In contrast, for low-SFE materials, enhanced strength and improved ductility may be achieved simultaneously through increasing the strain to a high level. The variation of strength with respect to strain is primarily dependent on the solute concentration and SFE. The underlying mechanisms governing the effect of strain and SFE on the microstructures and mechanical properties of the metals are also discussed.</P></▼2>