Effect of compressive stress on the ferroelectric hysteresis behavior in 0-3 PZT-cement composites

Lead zirconate titanate (PZT)-cement composites of 0-3 connectivity were produced using 50% PZT vol. content. PZT-cement based composites are developed for use as sensors for smart concrete structures, however, these sensors would in real life be under a certain stress. The effect of stress on the ferroelectric polarization-electric field (P-E) hysteresis of the composites is reported in this present work. It was found that there was a small but noticeable reduction in the remnant polarization (P_ir) by ≈ 0.3-0.7 μC/cm² while the coercive field (E_ic) remained approximately the same when the stress was increased from 0 to 57 MPa.     

Acetylene sensor based on Pt/ZnO thick films as prepared by flame spray pyrolysis

ZnO nanoparticles loaded with 0.2-2.0 at.% Pt have been successfully produced in a single step by flame spray pyrolysis (FSP) technique using zinc naphthenate and platinum(II) acetylacetonate, as precursors dissolved in xylene and their acetylene sensing characteristics have been investigated. The particle properties were analyzed by XRD, BET, TEM, SEM and EDS. Under the 5/5 (precursor/oxygen) flame condition, ZnO nanoparticles and nanorods were observed. The crystallite sizes of ZnO spherical and hexagonal particles were found to be ranging from 5 to 20 nm while ZnO nanorods were seen to be 5-20 nm in width and 20-40 nm in length. In addition, very fine Pt nanoparticles with diameter of ∼1 nm were uniformly deposited on the surface of ZnO particles. From gas-sensing characterization, acetylene sensing characteristics of ZnO nanoparticles is significantly improved as Pt content increased from 0 to 2  at.%. The 2 at.% Pt loaded ZnO sensing film showed an optimum C₂H₂ response of ∼836 at 1% acetylene concentration and 300 °C operating temperature. A low detection limit of 50 ppm was obtained at 300 °C operating temperature. In addition, Pt loaded ZnO sensing films exhibited good selectivity towards hydrogen, methane and carbon monoxide.     

Triplex addressability as a basis for functional DNA nanostructures

Here, we present the formation of a fully addressable DNA nanostructure that shows the potential to be exploited as, for example, an information storage device based on pH-driven triplex strand formation or nanoscale circuits based on electron transfer. The nanostructure is composed of two adjacent hexagonal unit cells (analogous to naphthalene) in which each of the eleven edges has a unique double-stranded DNA sequence, constructed using novel three-way oligonucleotides. This allows each ten base-pair side, just 3.4 nm in length, to be assigned a specific address according to its sequence. Such constructs are therefore an ideal precursor to a nonrepetitive two-dimensional grid on which the "addresses" are located at a precise and known position. Triplex recognition of these addresses could function as a simple yet efficient means of information storage and retrieval. Future applications that may be envisaged include nanoscale circuits as well as subnanometer precision in nanoparticle templating. Characterization of these precursor nanostructures and their reversible targeting by triplex strand formation is shown here using gel electrophoresis, atomic force microscopy, and fluorescence resonance energy transfer (FRET) measurements. The durability of the system to repeated cycling of pH switching is also confirmed by the FRET studies.     

Improvement of the mechanical and thermal properties of silica‐filled polychloroprene vulcanizates prepared from latex system

In this work, well‐dispersed silica suspension having excellent storage stability was prepared by using an ultrasonic probe. The obtained silica suspension and curatives were added into the polychloroprene (CR) latex for preparing silica‐filled CR latex compounds having various silica loadings. Then, the silica‐filled CR vulcanizates were prepared via a dipping process. The thermal and mechanical properties of the dipped CR vulcanizates containing silica dispersed by using an ultrasonic probe were compared with those of the dipped CR vulcanizates containing silica dispersed by using a mechanical stirrer. By using thermogravimetric analysis, it could be seen that thermal resistance of the dipped CR films having silica prepared by ultrasonic probe is greater than that prepared by using the mechanical stirrer. This result corresponds well with their tensile strength after aging in the hot‐air oven. In addition, modulus, tensile strength, and tear strength of the vulcanizates prepared from CR latex compounds containing silica prepared by using the ultrasonic probe are obviously greater than those prepared by using the mechanical stirrer, especially at high silica loading. This is because the silica prepared using the ultrasonic probe is uniformly distributed and dispersed throughout the CR matrix, as can be observed in the scanning electron microscope micrographs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Fabrication and electrical properties of PC-PNZT-PVDF-GO composites

The objectives of this research are to fabricate and investigate new smart composites for the sensing and actuation applications in civil engineering. The fabrication and properties of cement-based piezoelectric ceramic composites are emphasized. However, cement-based piezoelectric composites are still difficult to obtain great electrical properties due to the evidence of some pores in the composites. Therefore, a novel approach to effectively improve their polarization of piezoelectric ceramic is to add a semiconductor (graphene oxide) and an insulator (polyvinylidene fluoride) phases between piezoelectric particles by the introduction of a small volume fraction of a third phase. Microstructure of the new composites was investigated using Scanning electron microscope (SEM). Dielectric permittivity and ferroelectric properties were then investigated.     

Reinforcing potential of micro- and nano-sized fibers in the starch-based biocomposites

Starch-based biocomposites reinforced with jute (micro-sized fiber) and bacterial cellulose (BC) (nano-sized fiber) were prepared by film casting. Reinforcement in the composites is essentially influenced by fiber nature, and amount of loading. The optimum amount of fiber loading for jute and bacterial cellulose in each composite system are 60 wt% and 50 wt% (of starch weight), respectively. Mechanical properties are largely improved due to the strong hydrogen interaction between the starch matrix and cellulose fiber together with good fiber dispersion and impregnation in these composites revealed by SEM. The composites reinforced with 40 wt% or higher bacterial cellulose contents have markedly superior mechanical properties than those reinforced with jute. Young’s modulus and tensile strength of the optimum 50 wt% bacterial cellulose reinforced composite averaged 2.6 GPa and 58 MPa, respectively. These values are 106-fold and 20-fold more than the pure starch/glycerol film. DMTA revealed that the presence of bacterial cellulose (with optimum loading) significantly enhanced the storage modulus and glass transition temperature of the composite, with a 35 °C increment. Thermal degradation of the bacterial cellulose component occurred at higher temperatures implying improved thermal stability. The composites reinforced with bacterial cellulose also had much better water resistance than those associated with jute. In addition, even at high fiber loading, the composites reinforced by bacterial cellulose clearly retain an exceptional level of optical transparency owing to the effect of the nano-sized fibers and also good interfacial bonding between the matrix and bacterial cellulose.     

Modeling the improved textural properties of purple waxy rice dried through fluidization

This study developed a mathematical model and gelatinization kinetic equation for drying rice through fluidization. This model was then applied to improve the softness and stickiness of non-milled waxy rice (NWR) to be comparable to those of milled waxy rice (MWR). The results demonstrate that the hardness value decreased and that the stickiness value increased with an increasing degree of starch gelatinization. The model and equation were validated based on their satisfactory R² values and were then used to predict the suitable degree of starch gelatinization and to recommend drying conditions. Compared to MWR, the simulated NWR had an equal hardness value and a larger stickiness value.