Enhanced airborne sound absorption effect in poly(vinylidene fluoride)/(K0.5Na0.5)NbO3-nanofiber composite foams

Introducing electrical conductive function to discharge local piezoelectric effect is found effective for improving airborne sound absorption performance. In this work, instead of conductive fillers, a composite with two piezoelectric materials with opposite piezoelectric responses was explored aiming at enhanced sound absorption effect. Open-cell poly(vinylidene fluoride)/(K_0.5Na_0.5)NbO₃ (PVDF/KNN)-nanofiber composite foams were proposed and investigated for airborne sound absorption purpose. Structural and thermal analyses showed that the KNN nanofibers were well dispersed in the PVDF matrix and enhanced the degree of crystallinity of polar phase of PVDF. Significantly enhanced airborne sound absorption over a broad frequency range was observed in the PVDF/KNN-nanofiber composite foams, with increasing KNN nanofibers. One possible mechanism for the improved sound absorption with the piezoelectric KNN nanofibers with positive piezoelectric coefficient added in the PVDF matrix with negative piezoelectric coefficient is that electrical discharge could be facilitated for energy dissipation with the opposite charges generated through the piezoelectric effects in the two phases with opposite polarity. The experimental results show that the open-cell PVDF/KNN-nanofiber composite foams are promising for broadband airborne sound absorption application, and our analysis shed a light on the strategy in designing piezoelectric composite foam with high sound absorption performance.     

Keyword-based private searching on cloud data along with keyword association and dissociation using cuckoo filter

International Journal of Information Security - Outsourcing of data is a very common scenario in the present-day world and quite often we need to outsource confidential data whose privacy is of...     

Self-activated ‘green’ carbon nanoparticles for symmetric solid-state supercapacitors

Tuning of porosity and surface properties of nanoparticles especially on carbon-based nanomaterials, adopting a ‘greener’ or self-activation synthesis technique for electrical charge storage, is progressing. Herein, we report the self-activation of Teak wood sawdust in a nitrogen atmosphere at different activation temperatures to synthesize carbon nanoparticles. The activated carbon nanoparticles synthesized at 900 °C exhibits a maximum?~?360 m² g^?1 surface area with?~?2 nm average pore size diameter. Five electrolytes viz. KOH, KCl, Na₂SO₄, NaCl, and H₃PO₄ are used for studying the supercapacitance nature of the activated carbon nanoparticles in a 3-electrode configuration. A maximum specific capacitance of?~?208 F g^?1 @ 0.25 A g^?1 is obtained in 1 M KOH as the electrolyte. Two symmetric supercapacitors, aqueous (1 M KOH) and solid-state (PVA/KOH), are fabricated, and their performance difference is compiled. The solid-state symmetric supercapacitor performs in a wider voltage window (1.7 V) with a superior energy density of 27.1 Wh kg^?1 at a power density of 178 W kg^?1.

Graphical abstract

     

Intensity tunable optical limiting behaviour of an organic material 2-aminopyridinium succinate succinic acid single crystal

Journal of Materials Science: Materials in Electronics - A mixed solution of 2-aminopyridine and succinic acid, with a 1:1 molar ratio, was kept at room temperature to develop a 2-aminopridinium...     

Novel and simple methodology to fabricate porous and buckled fibrous structures for biomedical applications

Reproducible buckled and porous sub-micron diameter polycaprolactone (PCL) fibers were produced by simple electrospinning process for biomedical applications. In this study, six types of solvent combinations with different vapor pressures were used to study the effect of phase separation on the morphology of electrospun fibers. The fiber morphology, Infrared spectroscopy, water contact angle and tensile test were performed to study the material properties. It is evident that the fiber morphology was affected by solvent combinations used for the fabrication of sub-micron fibers. The solution viscosity, the collecting distance and the type of solvent combination used could be an optimum parameter for the generation of porous-buckled fibers with narrow pore size distribution. The simplicity of the set-up is the immense advantage for producing buckled and porous elastomeric fibers for tissue engineering applications. All the fibers were spun on a motionless collector plate to study the properties of fibers. The combination of surface pores with the buckled pattern could be of great importance in the field of biomedical engineering.     

Aloe vera incorporated biomimetic nanofibrous scaffold: a regenerative approach for skin tissue engineering

Aloe vera (AV) is one of the medicinal herbs with a well-established spectrum of wound healing, antimicrobial and anti-inflammatory property. AV-mediated therapeutics present significant tissue regenerative activity by modulating the inflammatory and proliferative phases of wound healing. The purpose of the present work was to combine the biological properties of AV and the advantages of electrospun meshes to prepare a potent transdermal biomaterial. The polycaprolactone (PCL) containing 5 and 10 wt % of lyophilized powder of AV was studied for electrospinning into nanoscale fiber mats and compared with PCL/Collagen blend for dermal substitutes. SEM revealed the average diameters of PCL, PCL-AV 5 %, PCL-AV 10 % and PCL/Collagen nanofiber scaffolds in the range of 519 ± 28, 264 ± 46, 215 ± 63 and 249 ± 52 nm, respectively. PCL-AV 10 % nanofiber scaffolds showed finer fiber morphology with improved hydrophilic properties and higher tensile strength of 6.28 MPa with a Young’s modulus of 16.11 MPa desirable for skin tissue engineering. The nanofibers were then used to investigate differences in biological responses in terms of proliferation and cell morphology of mice dermal fibroblasts. It was found that PCL-AV 10 % nanofibrous matrix favored cell proliferation compared to other scaffolds which almost increased linearly by (p ≤ 0.01) 17.79 % and (p ≤ 0.01) 21.28 % compared to PCL on sixth and ninth day. CMFDA dye expression, secretion of collagen and F-actin expression were significantly increased in PCL-AV 10 % scaffolds compared to other nanofibrous scaffolds. The obtained results proved that the PCL-AV 10 % nanofibrous scaffold is a potential biomaterial for skin tissue regeneration.     

A concurrent control architecture for autonomous mobile robots using Asynchronous Production Systems

The quest for efficient real-time response by autonomous robots in hazardous environments necessitates not only fast computational schemes in expert systems but also requires insights on high performance data structures and concurrent algorithms that lead to elegant problem-solving methods in the AI discipline. towards this objective, this paper presents an Asynchronous Production System (APS) of architecture capable of monitoring and processing real-time information.     

Studies on EVA‐Based Wax Fuel for Launch Vehicle Applications

A fuel for the hybrid rocket system was developed. The attempts made to improve the mechanical properties of wax by adding EVA (ethylene vinyl acetate) are illustrated. It was observed that the mechanical properties obtained by adding EVA to wax were dependent on the process of curing the fuel specimen. A proprietary method of curing the fuel specimen was established. The percentage elongation obtained with 20 % EVA and 80 % of wax was around 17 %, which was much higher than the values obtained with pure wax (4 %). It was observed from the study that the higher the percentage of EVA content in wax was, the better the mechanical properties were. Regression rate studies with EVA and wax combination were carried out. It was observed that the regression rate decreased upon addition of EVA in wax. This reduction was compensated by using a bluff body at the head end. The regression rate obtained with 20 % EVA and 80 % wax even with the use of bluff body is lower than that obtained with pure wax, but is around 3.5 times the regression rate obtained with polymeric fuels.