Novel piezoelectric thin film impact sensor: application in non-destructive material discrimination

We report on the design, development, and performance study of a packaged piezoelectric thin film impact sensor, and its potential application in non-destructive material discrimination. The impact sensing element employed was a thin circular diaphragm of flexible Phynox alloy. Piezoelectric ZnO thin film as an impact sensing layer was deposited on to the Phynox alloy diaphragm by RF reactive magnetron sputtering. Deposited ZnO thin film was characterized by X-ray diffraction (XRD), Atomic Force Microscopy (AFM), and Scanning Electron Microscopy (SEM) techniques. The d(31) piezoelectric coefficient value of ZnO thin film was 4.7 pm V-1, as measured by 4-point bending method. ZnO film deposited diaphragm based sensing element was properly packaged in a suitable housing made of High Density Polyethylene (HDPE) material. Packaged impact sensor was used in an experimental set-up, which was designed and developed in-house for non-destructive material discrimination studies. Materials of different densities (iron, glass, wood, and plastic) were used as test specimens for material discrimination studies. The analysis of output voltage waveforms obtained reveals lots of valuable information about the impacted material. Impact sensor was able to discriminate the test materials on the basis of the difference in their densities. The output response of packaged impact sensor shows high linearity and repeatability. The packaged impact sensor discussed in this paper is highly sensitive, reliable, and cost-effective.

Process Development for Functionalization of Cotton with Silver Nanoparticles Synthesized by Bio-based Approaches

Cotton is a widely used raw material for textiles but drawbacks regarding their poor mechanical properties often limit their applications as functional materials. The present investigation involved process development for one step coating of cotton with silver nanoparticles (SNP) synthesized using Azadirachta indica and Citrus limon extract to develop functional textiles. Addition of starch to functional textiles led to efficient binding of nanoparticles to fabric and led to drastic decrease in release of silver from fabricated textiles after ten washing cycles enhancing their environment friendliness. Differential scanning calorimetry, scanning electron microscopy, FT-IR analysis and mechanical studies demonstrated efficient binding of nanoparticles to fabric through bio-based processes. The functionalized textiles developed by the bio-based methods showed significant antibacterial activity against E. coli and S. aureus (with 99% microbial reduction). Present work offers a simple procedure for coating SNP using bio-based approaches with promising applications in specialized functions.

Growth and characterization of L-histidinium 2-nitrobenzoate single crystals: A new NLO material

Crystals of a new nonlinear optical (NLO) material, viz., L-histidinium 2-nitrobenzoate (LHNB) (1) were grown by slow evaporation of an aqueous solution containing equimolar concentrations of L-histidine and 2-nitrobenzoic acid. The structure of the title compound which crystallizes in the non-centrosymmetric monoclinic space group P2(1) was elucidated using single crystal X-ray intensity data. The UV-Vis-NIR spectrum of 1 reveals its transparent nature while the vibrational spectra confirm the presence of the functional groups in 1. The thermal stability and second harmonic generation (SHG) conversion efficiency of 1 were also investigated. (C) 2012 Elsevier GmbH. All rights reserved.

MECHANISM OF CELL LYSIS IN MICROFLUIDIC CHANNEL WITH INTEGRATED NANOCOMPOSITE ELECTRODES

This paper reports on the characterization of an integrated micro-fluidic platform for controlled electrical lysis of biological cells and subsequent extraction of intracellular biomolecules. The proposed methodology is capable of high throughput electrical cell lysis facilitated by nano-composite coated electrodes. The nano-composites are synthesized using Carbon Nanotube and ZnO nanorod dispersion in polymer. Bacterial cells are used to demonstrate the lysis performance of these nanocomposite electrodes. Investigation of electrical lysis in the microchannel is carried out under different parameters, one with continuous DC application and the other under DC biased AC electric field. Lysis in DC field is dependent on optimal field strength and governed by the cell type. By introducing the AC electrical field, the electrokinetics is controlled to prevent cell clogging in the micro-channel and ensure uniform cell dispersion and lysis. Lysis mechanism is analyzed with time-resolved fluorescence imaging which reveal the time scale of electrical lysis and explain the dynamic behavior of GFP-expressing E. coli cells under the electric field induced by nanocomposite electrodes. The DNA and protein samples extracted after lysis are compared with those obtained from a conventional chemical lysis method by using a UV-Visible spectroscopy and fluorimetry. The paper also focuses on the mechanistic understanding of the nano-composite coating material and the film thickness on the leakage charge densities which lead to differential lysis efficiency.

Aluminium coated carbon nanotube film for wavelength-selective surface

We report selective optical reflectance in an aluminium (Al) coated flexible carbon nanotube (CNT) thin film over a wide range of wavelengths (500-2500 nm). Selective-wavelength surface is achieved by coating CNT surfaces with Al thin film that presented a maximum optical reflectivity of similar to 65% in the infrared region. However, CNT film alone showed a reflectance of 15-20% over a larger range of wavelengths without any structural modification, which has not been realized so far. Moreover, a tailorable reflectance in CNT is shown to be achieved by tuning various parameters, namely, the porosity of the material, angle of an incident light, and refractive index of the materials. Owing to higher infrared reflectivity and thermal diffusivity, Al coated CNT presents a potential for a high efficiency solar collector. (C) 2013 AIP Publishing LLC.

Large-area Piezoceramic Coating with IDT Electrodes for Ultrasonic Sensing Applications

In the present paper, the ultrasonic strain sensing performance of large-area piezoceramic coating with Inter Digital Transducer (IDT) electrodes is studied. The piezoceramic coating is prepared using slurry coating technique and the piezoelectric phase is achieved by poling under DC field. To study the sensing performance of the piezoceramic coating with IDT electrodes for strain induced by the guided waves, the piezoceramic coating is fabricated on the surface of a beam specimen at one end and the ultrasonic guided waves are launched with a piezoelectric wafer bonded on another end. Often a wider frequency band of operation is needed for the effective implementation of the sensors in the Structural Health Monitoring (SHM) of various structures, for different types of damages. A wider frequency band of operation is achieved in the present study by considering the variation in the number of IDT electrodes in the contribution of voltage for the induced dynamic strain. In the present work, the fabricated piezoceramic coatings with IDT electrodes have been characterized for dynamic strain sensing applications using guided wave technique at various different frequencies. Strain levels of the launched guided wave are varied by varying the magnitude of the input voltage sent to the actuator. Sensitivity variation with the variation in the strain levels of guided wave is studied for the combination of different number of IDT electrodes. Piezoelectric coefficient e(11) is determined at different frequencies and at different strain levels using the guided wave technique.

Polymer template-assisted microemulsion synthesis of large surface area, porous Li2MnO3 and its characterization as a positive electrode material of Li-ion cells

Lithium-rich manganese oxide (Li2MnO3) is prepared by reverse microemulsion method employing Pluronic acid (P123) as a soft template and studied as a positive electrode material. The as-prepared sample possesses good crystalline structure with a broadly distributed mesoporosity but low surface area. As expected, cyclic voltammetry and charge-discharge data indicate poor electrochemical activity. However, the sample gains surface area with narrowly distributed mesoporosity and also electrochemical activity after treating in 4 M H2SO4. A discharge capacity of about 160 mAh g(-1) is obtained. When the acid-treated sample is heated at 300 A degrees C, the resulting porous sample with a large surface area and dual porosity provides a discharge capacity of 240 mAh g(-1). The rate capability study suggests that the sample provides about 150 mAh g(-1) at a specific discharge current of 1.25 A g(-1). Although the cycling stability is poor, the high rate capability is attributed to porous nature of the material.

On Using Nanoporous Alumina Films as Tribological Coating

Anodization of aluminum alloys is a common surface treatment procedure employed for the protection against corrosion. A thin amorphous layer of alumina is formed on the surface of alloy, which seals the alloy surface from the surrounding. This alumina layer being harder than the base aluminum alloy can be useful as a tribological coating. But since this alumina layer is randomly formed with disordered voids and pores, predicting the mechanical properties is difficult. Specific anodizing conditions can be used to form highly ordered anodic nanoporous alumina films 1] on the aluminum alloy surface. These nanoporous alumina layer can be effectively used as a tribological coating, because of the highly ordered controllable geometry and the empty pores which can be used as reservoirs for lubricant.

Transverse elastic response of bundled coated cylinders

The overall elastic response of a bundle of coated cylinders is a major aspect of thermal, nuclear and automotive engineering designs. This paper extends the previous work on tubular bundles to assess the effect of coating material and thickness. A major contribution from this paper is determining the overall transverse elastic response of coated thick cylinders by extending the Michell stress function approach in conjunction with contact mechanics. Finite element results using contact elements pave the way for applying the contact stress boundary conditions for Michell analysis. Theoretical and finite element analyses overall give results consistent with the previous work, and the results also fall within the well-established Voigt-Reuss bounds. (C) 2013 Elsevier Ltd. All rights reserved.

Polymer Template Assisted Synthesis of Porous Li1.2Mn0.53Ni0.13Co0.13O2 as a High Capacity and High Rate Capability Positive Electrode Material

A porous layered composite of Li2MnO3 and LiMn1/3Co1/3Ni1/3O2 (composition: Li1.2Mn0.53Ni0.13Co0.13O2) is prepared by reverse microemulsion method employing a soft polymer template and studied as a positive electrode material. The precursor is heated at several temperatures between 500 and 900 degrees C. The product samples possess mesoporosity with broadly distributed pores of about 30 nm diameters. There is a decrease in pore volume as well as in surface area by increasing the temperature of preparation. Nevertheless, the electrochemical activity of the composite increases with an increase in temperature. The discharge capacity values of the samples prepared at 800 and 900 degrees C are about 250 mAh g(-1) at a specific current of 40 mA g(-1) with an excellent cycling stability. A value of 225 mAh g(-1) is obtained at the end of 30 charge-discharge cycles. Both these composite samples possess high rate capability, but the 800 degrees C sample is marginally superior to the 900 degrees C sample. A discharge capacity of 100 mAh g(-1) is obtained at a specific current of 1000 mA g(-1). The high rate capability is attributed to porous nature of the composite samples. (C) 2013 The Electrochemical Society. All rights reserved.

A parametric study on the buckling of functionally graded material plates with internal discontinuities using the partition of unity method

In this paper, the effect of local defects, viz., cracks and cutouts on the buckling behaviour of functionally graded material plates subjected to mechanical and thermal load is numerically studied. The internal discontinuities, viz., cracks and cutouts are represented independent of the mesh within the framework of the extended finite element method and an enriched shear flexible 4-noded quadrilateral element is used for the spatial discretization. The properties are assumed to vary only in the thickness direction and the effective properties are estimated using the Mori-Tanaka homogenization scheme. The plate kinematics is based on the first order shear deformation theory. The influence of various parameters, viz., the crack length and its location, the cutout radius and its position, the plate aspect ratio and the plate thickness on the critical buckling load is studied. The effect of various boundary conditions is also studied. The numerical results obtained reveal that the critical buckling load decreases with increase in the crack length, the cutout radius and the material gradient index. This is attributed to the degradation in the stiffness either due to the presence of local defects or due to the change in the material composition. (C) 2013 Elsevier Masson SAS. All rights reserved.

Performance of an ionomer blend-nanocomposite as an effective gas barrier material for organic devices

A new, flexible, gas barrier material has been synthesized by exfoliating organically modified nano-clays (MMT) in the blends of Surlyn (PEMA) using a copolymer of vinyl alcohol (EVOH) and demonstrated as a gas barrier material. The materials were characterized by Fourier transform infra red (FTIR) and UV-visible spectroscopy, differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA) and tensile studies. The oxygen and water-vapor permeabilities of the fabricated films were determined by calcium degradation test and a novel permeability setup based on cavity ring down spectroscopy, respectively. Hierarchical simulations of these materials helped us to understand the effect of intermolecular interactions on diffusivities of oxygen and water molecules in these materials. Schottky structured poly(3-hexylthiophene) based organic devices were encapsulated with the fabricated films and aging studies were carried under accelerated conditions. Based on permeability test results and accelerated aging studies, the fabricated PEMA/EVOH/MMT composites were found to be effective in decreasing the permeabilities for gases by about two orders of magnitude and maintaining the lifetime of organic devices.

Preparation and electrochemical performance of porous hematite (alpha-Fe2O3) nanostructures as supercapacitor electrode material

Porous alpha-Fe2O3 nanostructures have been synthesized by sol-gel route. The effect of preparation temperature on the morphology, structure, and electrochemical stability upon cycling has been studied for supercapacitor application. The discharge capacitance of alpha-Fe2O3 prepared at 300 A degrees C is 193 F g(-1), when the electrodes are cycled in 0.5 M Na2SO3 at a specific current of 1 A g(-1). The capacitance retention after 1,000 cycles is about 92 % of the initial capacitance at a current density of 2 A g(-1). The high discharge capacitance as well as stability of alpha-Fe2O3 electrodes is attributed to large surface area and porosity of the material. There is a decrease in specific capacitance (SC) on increasing the preparation temperature. As iron oxides are inexpensive, the synthetic route adopted for alpha-Fe2O3 in the present study is convenient and the SC is high with good cycling stability, the porous alpha-Fe2O3 is a potential material for supercapacitors.

Fatigue crack propagation at concrete-concrete bi-material interfaces

This paper presents experimental and analytical studies on fatigue crack propagation in concrete-concrete cold jointed interface specimens. Beams of different sizes having jointed interface between two concretes with different elastic properties are tested under fatigue loading. The acoustic emission technique is used for monitoring the fatigue crack growth. It is observed that the interface having a higher moduli mismatch tends to behave in a brittle manner. The CMOD compliances at different loading cycles are measured and the equivalent crack lengths are determined from a finite element analysis. An analytical model for crack growth rate is proposed using the concepts of the dimensional analysis. (C) 2014 Elsevier Ltd. All rights reserved.

Green colored nano-pigments derived from Y2BaCuO5: NIR reflective coatings

A green colored nano-pigment Y2BaCuO5 with impressive near infra-red (NIR) reflectance (61% at 1100 nm) was synthesized by a nano-emulsion method. The developed nano-crystalline powders were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), UV-vis-NIR diffuse reflectance spectroscopy and CIE-L*a*b* 1976 color scales. The XRD and Rietveld analyses of the designed pigment powders reveal the orthorhombic crystal structure for Y2BaCuO5, where yttrium is coordinated by seven oxygen atoms with the local symmetry of a distorted trigonal prism, barium is coordinated by eleven oxygen atoms, and the coordination polyhedron of copper is a distorted square pyramid CuO5]. The UV-vis spectrum of the nano-pigment exhibits an intense d-d transition associated with CuO5 chromophore between 2.1 and 2.5 eV in the visible domain. Therefore, a green color has been displayed by the developed nano-pigment. The potential utility of the nano-pigments as ``Cool Pigments'' was demonstrated by coating on to a building roofing material like cement slab and PVC coatings. (C) 2014 Elsevier Ltd. All rights reserved.