The use of graphene‐based composite as anti‐corrosion and protective coatings for metallic materials is still a provocative topic worthy of debate. Nickel–graphene nanocomposite coatings have been successfully fabricated onto the mild steel by electrochemical co‐deposition technique. This research demonstrates the properties of nickel–graphene composite coatings influenced by different electrodeposition current densities. The effect of deposition current density on the; surface morphologies, composition, microstructures, grain sizes, mechanical, and electrochemical properties of the composite coatings are executed. The coarseness of deposited coatings increases with the increasing of deposition current density. The carbon content in the composite coatings increases first and then decreases by further increasing of current density. The improved mechanical properties and superior anti‐corrosion performance of composite coatings are obtained at the peak value of current density of 9 A dm−2. The incorporation of graphene sheets into nickel metal matrix lead to enhance the micro hardness, surface roughness, and adhesion strength of produced composite coatings. Furthermore, the presence of graphene in composite coating exhibits the reduced grain sizes and the enhanced erosion–corrosion resistance properties.
Fully dense disks, each consisting of a single crystal (111) plate of the relaxor‐based ferroelectric Pb(Mg1/3Nb2/3)O3‐35 mol% PbTiO3 (PMN‐35PT) embedded in a 0.48 ± 0.05 µm grain size polycrystalline matrix of the same composition, were formed by hot‐pressing at 950°C for 30 min under 20 MPa. Specimens were subsequently annealed to promote migration of the single‐crystal boundary through the polycrystal (a process termed seeded polycrystal conversion). An anneal of 10 h at 1150°C using PMN‐35PT packing powder resulted in minimal single‐crystal boundary migration, and was accompanied by matrix grain coarsening to 1.86 ± 0.20 µm. In contrast, an anneal of 10 h at 1150°C using PbZrO3 (PZ) sacrificial powder resulted in significant migration of the single‐crystal boundary through the polycrystal, accompanied by matrix grain coarsening to 13.3 ± 0.3 µm. The shape of the grown crystal relative to the seed plate was consistent with the <111> direction being the fastest growth direction. Based on the grown crystal dimensions, a lower bound <111> growth velocity of 0.14 mm/h was calculated. The increased boundary mobility in the specimen that was annealed using PZ sacrificial powder is attributed to a boundary‐wetting liquid PbO‐based second phase that formed during the anneal. This phase is believed to have formed via PbO absorption from the surrounding vapor phase due to a higher equilibrium PbO vapor pressure above PZ than above PMN‐35PT. The grown single crystal exhibited a promising <100> strain of 0.5% at an applied electric field of 4 MV/m.
Renalase, a novel monoamine oxidase, is emerging as an important regulator of cardiovascular, metabolic, and renal diseases. However, the mechanism of transcriptional regulation of this enzyme remains largely unknown. We undertook a systematic analysis of the renalase gene to identify regulatory promoter elements and transcription factors. Computational analysis coupled with transfection of human renalase promoter/luciferase reporter plasmids (5'-promoter-deletion constructs) into various cell types (HEK-293, IMR32, and HepG2) identified two crucial promoter domains at base pairs -485 to -399 and -252 to -150. Electrophoretic mobility shift assays using renalase promoter oligonucleotides with and without potential binding sites for transcription factors Sp1, STAT3, and ZBP89 displayed formation of specific complexes with HEK-293 nuclear proteins. Consistently, overexpression of Sp1, STAT3, and ZBP89 augmented renalase promoter activity; additionally, siRNA-mediated downregulation of Sp1, STAT3, and ZBP89 reduced the level of endogenous renalase transcription as well as the transfected renalase promoter activity. In addition, chromatin immunoprecipitation assays showed in vivo interactions of these transcription factors with renalase promoter. Interestingly, renalase promoter activity was augmented by nicotine and catecholamines; while Sp1 and STAT3 synergistically activated the nicotine-induced effect, Sp1 appeared to enhance epinephrine-evoked renalase transcription. Moreover, renalase transcript levels in mouse models of human essential hypertension were concomitantly associated with endogenous STAT3 and ZBP89 levels, suggesting crucial roles for these transcription factors in regulating renalase gene expression in cardiovascular pathological conditions.
Pb[(Mg1/3Nb2/3)0.65Ti0.35]O3 (PMN–35PT) powder was prepared using the columbite precursor method. Fully dense compacts were formed by hot‐pressing the powder at 950°C, and then the compacts were annealed at 1150°C for 5 and 10 h, respectively. Dielectric and piezoelectric properties of the as‐hot‐pressed and annealed samples were measured and correlated with microstructure. The as‐hot‐pressed material exhibited relaxor–ferroelectric‐like behavior, with a relatively low dielectric constant maximum measured at 1 kHz (Km@1kHz) of 8160. Annealing resulted in a transition to weak normal‐ferroelectric behavior, a shift in the dielectric maximum temperature from 190°C to 169°C, and a dramatic increase of Km@1kHz to a maximum value of 41 720 for the longer anneal. The as‐hot‐pressed microstructure was chemically heterogeneous, characterized by submicrometer‐sized regions of varying magnesium, niobium, and titanium content that likely originated from chemical heterogeneities that were present in the as‐prepared PMN‐PT powder. The as‐hot‐pressed properties have been explained as being the integrated response of many discrete ferroelectric responses as dictated for each of these regions by the local chemistry. The transition on annealing has been explained in terms of chemical homogenization to a near‐morphotropic phase‐boundary composition that is intrinsically weak normal‐ferroelectric. Differences in polarization‐versus‐electric‐field and strain‐versus‐electric‐field behavior between the hot‐pressed and annealed materials have been discussed in terms of differences in domain mobility.
Power generation from lead zirconate titanate (PZT) piezoelectric fibers in the form of 1–3 composites under application of an external force was investigated. Green fibers consisting of PZT powder dispersed in a cellulose binder were made by the Viscous Suspension Spinning Process (VSSP). The composites were made by firing sheets of parallel green PZT fibers at 1270 °C, and then laminating the sintered sheets in epoxy. Composites of several PZT fiber diameters (15, 45, 120, and 250 μm), with the fiber volume fraction fixed at ∼0.4, were investigated. Transducers comprised of electrode and poled plates of the composites, in which the plate thickness direction was in the fiber axis direction, were made. Power generation experiments were conducted by dropping a 33 g stainless steel ball onto the electroded face of each transducer from a height of 10 cm and recording the output voltage on an oscilloscope. A peak voltage of 350 V corresponding to 120 mW of peak power was obtained. The output voltage and power was the highest for the transducers made with the smallest diameter fibers (15μm) and increased with increasing of transducer thickness. The average piezoelectric coefficient, d33, of the transducers was about 300 pC/N and decreased with decreasing transducer thickness. In this paper, the power generation capability and dielectric properties of the laminated 1–3 fiber composites are discussed.
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