Effect of glycidyl methacrylate on the physical properties of wood–polymer composites

Chemical modification of pinewood was carried out by impregnating the wood with styrene as the impregnating monomer and in combination with a crosslinking monomer glycidyl methacrylate (GMA). Polymerization was carried out by catalyst heat treatment. Dimensional stability in terms of antiswell efficiency was determined and improved on treatment with polymer. Water uptake percentage was also improved for styrene‐GMA treated wood samples over styrene treated or untreated wood samples. Mechanical properties such as bending strength measured in terms of modulus of elasticity and modulus of rupture of polymer‐treated samples showed an improvement over untreated ones. Treatment also resulted an improvement in compressive strengths. Thermal properties of the wood samples were evaluated by thermogravimetric analyzer and differential scanning calorimeter. Biodegradability of the treated and untreated wood samples was determined and improvement was obtained on treatment. As a whole, styrene‐GMA treated wood samples showed more improvement over untreated or styrene‐treated samples. POLYM. COMPOS., 28:1–5, 2007. © 2007 Society of Plastics Engineers     

An electromechanical higher order model for piezoelectric functionally graded plates

Bidirectional flexure analysis of functionally graded (FG) plate integrated with piezoelectric fiber reinforced composites (PFRC) is presented in this paper. A higher order shear and normal deformation theory (HOSNT12) is used to analyze such hybrid or smart FG plate subjected to electromechanical loading. The displacement function of the present model is approximated as Taylor’s series in the thickness coordinate, while the electro-static potential is approximated as layer wise linear through the thickness of the PFRC layer. The equations of equilibrium are obtained using principle of minimum potential energy and solution is by Navier’s technique. Elastic constants are varying exponentially along thickness (z axis) for FG material while Poisson’s ratio is kept constant. PFRC actuator attached either at top or bottom of FG plate and analyzed under mechanical and coupled mechanical and electrical loading. Comparison of present HOSNT12 is made with exact and finite element method (FEM).     

Sample zone dynamics in peak mode isotachophoresis

We present a theoretical and experimental study of analyte preconcentration via peak mode isotachophoresis (ITP). We perform perturbation analysis of the governing equations that includes electromigration, diffusion, buffer reactions, and nonlinear ionic strength effects. This analysis relaxes the inherent numerical stiffness and achieves a fast solution to the transient sample evolution problem. In this model, we have incorporated a semiempirical relation to capture dispersion phenomenon within ITP interfaces. We also present a simple, closed-form analytical model that identifies key parameters governing the preconcentration dynamics in peak mode ITP. We have validated our models through a detailed experimental study performed in constant current conditions. The relevant governing experiment parameters were varied independently; namely, the leading electrolyte concentration, trailing electrolyte concentration, and current. Through our experimental study, we have identified optimum conditions to achieve high preconcentration ratio and sample accumulation rates. Our approach to the theoretical problem and experimental study provides useful guidelines in optimizing parameters such as detector location, ITP duration, and electrolyte composition in ITP preconcentration and separation assays.     

Wide area polycrystalline diamond coating and stress control by sp hot filament CVD reactor

This paper discusses large area uniform diamond coatings deposited in the sp³ Inc. Model 600 hot filament diamond deposition system (made by sp³ Inc., California, USA). This model combines proven hot filament thermal reactor technology with advanced controls to produce high quality polycrystalline diamond films over a maximum square area of 380 mm × 380 mm on a wide variety of substrate materials such as carbide-based cutting tools, wear surfaces, Si wafers, etc. The reactor is characterized using instrumented 300 mm Si wafers and modified, accordingly, to optimize performance on 300 mm diameter wafers or multiple 100 mm diameter wafers. Roles of temperature and other process parameters in stress formation and development in the diamond thin films, grown in a wide area hot filament deposition system, are discussed along with some of the ways of controlling these stresses on a production basis.     

Mapping the "forbidden" transverse-optical phonon in single strained silicon (100) nanowire

The accurate manipulation of strain in silicon nanowires can unveil new fundamental properties and enable novel or enhanced functionalities. To exploit these potentialities, it is essential to overcome major challenges at the fabrication and characterization levels. With this perspective, we have investigated the strain behavior in nanowires fabricated by patterning and etching of 15 nm thick tensile strained silicon (100) membranes. To this end, we have developed a method to excite the "forbidden" transverse-optical (TO) phonons in single tensile strained silicon nanowires using high-resolution polarized Raman spectroscopy. Detecting this phonon is critical for precise analysis of strain in nanoscale systems. The intensity of the measured Raman spectra is analyzed based on three-dimensional field distribution of radial, azimuthal, and linear polarizations focused by a high numerical aperture lens. The effects of sample geometry on the sensitivity of TO measurement are addressed. A significantly higher sensitivity is demonstrated for nanowires as compared to thin layers. In-plane and out-of-plane strain profiles in single nanowires are obtained through the simultaneous probe of local TO and longitudinal-optical (LO) phonons. New insights into strained nanowires mechanical properties are inferred from the measured strain profiles.     

Improving Anodes for Lithium Ion Batteries

As energy demands increase for applications such as automotive, military, aerospace, and biomedical, lithium-ion battery capacities are forced to increase in a corresponding manner. For this reason, much research is directed toward the development of improved battery anodes. Carbon nanotubes (CNTs), silicon, tin, and nanocomposites with these metals are the leading candidates for the next generation of lithium-ion battery anodes, leading to capacities 3 to 10 times that of graphite alone. This review looks at some of the studies addressing high capacity lithium-ion battery anodes.     

Propagation of rayleigh waves in transversely isotropic generalized thermoelastic diffusion

This paper is devoted to the study of propagation of Rayleigh waves in a homogeneous, transversely isotropic, thermoelastic diffusive half-space that is subjected to stress-free, thermally insulated/isothermal, and chemical potential boundary conditions in the context of the generalized theory of thermoelastic diffusion. The Lord and Shulman theory, where thermal and thermomechanical relaxation as well as diffusion relaxation are governed by two different time constants, is selected. Secular equations for surface wave propagation in the considered media are derived. The amplitudes of surface displacements, temperature change, and concentration are computed. The paths of the surface particles are determined. Transverse isotropy and diffusion effects on the phase velocity, group velocity, and attenuation coefficient are presented graphically.     

Rayleigh-Lamb Waves in Transversely Isotropic Thermoelastic Diffusive Layer

Propagation of plane harmonic thermoelastic diffusive waves in a homogeneous, transversely isotropic, thin elastic layer of finite width is studied, in the context of the theory of coupled thermoelastic diffusion. According to the characteristic equation, three quasi-longitudinal waves, namely, quasi-elastodiffusive (QED) mode, quasi-mass diffusion (QMD) mode, and quasi-thermodiffusive (QTD) mode can propagate in addition to quasi-transverse waves (QSV) mode and the purely quasi-transverse motion (QSH) mode, which is not affected by thermal and diffusion vibrations, gets decoupled from the rest of the motion of wave propagation. The secular equations corresponding to the symmetric and skew symmetric modes of the layer are derived. The amplitudes of displacements, temperature change, and concentration for symmetric and skew symmetric modes of vibration of the layer are computed numerically. Anisotropy and diffusion effects on the phase velocity, attenuation coefficient, and amplitudes of displacements, temperature change, and concentration are presented graphically in order to illustrate and compare the results analytically. Some special cases of the frequency equation are also deduced and compared with the existing results.     

Particle aggregation rate in a microchannel due to a dilute suspension flow

Particle-laden flow in a microchannel results in cluster formation and growth on the channel surface and the cluster growth, due to aggregation of polystyrene microparticles, has been investigated in this study. In particular, the initial stage of cluster growth is examined, where particle–cluster interaction is the dominant growth mechanism. Both experimental measurements and theoretical considerations were utilized to explore the functional dependence of the cluster growth rate on the following parameters: suspension void fraction, flow shear strain rate, and channel-height to particle-diameter ratio. The growth rate of an average cluster is found to increase linearly with suspension void fraction which is consistent with previous reports. The growth rate coefficient is found to obey a power-law relationship with respect to the shear strain rate, and predictions based on the modernized flocculation theory agree well with the experimental results. Furthermore, the growth rate coefficient obeys a power-law relationship with respect to the channel-height to particle-diameter ratio as well, qualitatively similar to other reported studies. However, to our knowledge, the exponent value estimated in this study does not agree with any previously published values; this disagreement is likely due to differences in experimental conditions.     

Surface roughness optimization of cold-sprayed coatings using Taguchi method

In this paper, Taguchi L 18 orthogonal array have been employed for depositing the electro-conductive coatings by varying various process parameters, i.e., substrate material, type of powder feeding arrangement, stagnation gas temperature, stagnation gas pressure, and stand-off distance. The response parameter of the coatings so produced is measured in terms of surface roughness. The optimum process parameters are predicted on the basis of analyses (ANOVA) of the raw data and signal to noise ratio. The significant process parameters in order of their decreasing percentage contribution are: stagnation pressure, stand-off distance, substrate material, stagnation temperature of the carrier gas, and feed arrangement of the powder particles, respectively.