Probing Aqueous Electrolytes with Fourier Spectrum Pulse-Echo Technique

The nature of variations of ultrasonic wave velocity(v) and attenuation constant({\alpha}) with the concentration(c) in aqueous solutions of NaCl, KCl and CsCl are investigated at room temperature(250C) at 1MHz and 2 MHz wave frequency. Fourier Spectrum Pulse-Echo (FSPE) technique is used to achieve better accuracy in measurement, particularly for {\alpha} measurement. In NaCl and KCl abrupt changes in the values of v and {\alpha} are noticed at particular solution concentrations whereas, for CsCl almost smooth variation in v is observed over the whole concentration range for both of the frequencies 1 and 2 MHz . The nature of variation in v and {\alpha} in these solutions are analyzed in view of other spectroscopic studies. The well-known Jones-Dole equation that explains the viscosity({\eta}) variation in many electrolyte solutions, offers satisfactory fits to the experimental velocity variation with parameter values characteristics of the sample

Effects of excess root applied silicon on Triticum aestivum and Zea mays under Aphis gossypii and Schistocerca gregaria herbivory and water-stressed conditions

Triticum aestivum (wheat) and Zea mays (maize) are two of the most important staple food and industrial crops used by developed and developing countries. Drought and pest attack often reduces wheat and maize production, causing huge economic losses. Silicon has been proposed to protect plants from several biotic and abiotic environmental stresses such as pest attack and drought. Silicon accumulation in plants can increase the abrasiveness of their leaves, potentially deterring herbivory by several important pest species, such as Aphis gossypii (aphids) and Schistocerca gregaria (locusts). Silicon accumulation in plants may also reduce transpiration rates and thus increase their drought tolerance. Here, the potentially protective effects of root silicon application to Triticum aestivum and Zea mays, against both water stress and herbivory by Aphis gossypii and Schistocerca gregaria, were investigated in a series of greenhouse experiments. Na2SiO3.9H2O (Sodium Meta Silicate) was used as a source of silicon. Experiments manipulated the impact of silicon on drought and controlled plants with and without pest species present; the influence of silicon application on herbivore performance and its potential interaction with water stress was also investigated. Aphid performance was evaluated by determining the change in the population growth rate over two weeks. The influence of silicon application on locust herbivory was determined by calculating the total damage to the plants over two weeks. Silicon application increased the abrasiveness of the leaves of both Triticum aestivum and Zea mays, and enhanced their resistance to Schistocerca gregaria herbivory; however the increased abrasiveness did not have an effect on Aphis gossypii performance. Additionally silicon accumulation enhanced drought tolerance when the temperature was kept between 20-25 °C, but it had no effect on plant biomass and plant photosynthetic rate when the green-house temperature was maintained between 40-45 °C. Silicon application to crop species provides a potentially cost-effective alternative to pesticides, and may increase drought tolerance in both C3 and C4 crop species

Probing aqueous electrolytes with Fourier Spectrum Pulse-Echo technique

The nature of variations of ultrasonic wave velocity(v) and attenuation constant(a) with the concentration(c) in aqueous solutions of NaCl, KCl and CsCl are investigated at room temperature(25 degrees C) at 1 MHz and 2 MHz wave frequency. Fourier Spectrum Pulse-Echo (FSPE) technique is used to achieve better accuracy in measurement, particularly for a measurement. Abrupt changes in the values of v and a are noticed at particular solution concentrations for NaCl and KCl but, for CsCl, almost smooth variation in v is observed over the whole concentration range both for 1 MHz and 2 MHz. The nature of variation in v and a in these solutions are analyzed in view of other spectroscopic studies. The well-known Jones-Dole equation that explains the viscosity (eta) variation in many electrolyte solutions, offers satisfactory fits to the experimental velocity variation with parameter values characteristics of the sample. (C) 2019 Elsevier B.V. All rights reserved

Effect of load in scratch experiments on soda lime silica glass

Today the technological applications of glass span from everyday life to many advanced areas. These advanced applications require very accurate grinding and polishing that involve controlled removal of glass to achieve micron or even sub-micron surface finish. The major bottleneck in this connection is that the material removal mechanisms during such processes are yet to be fully understood. Since grinding involves many single pass scratch processes happening simultaneously, to develop better understanding about the effect of the normal load in affecting the material removal mechanisms: a number of single pass scratch experiments were conducted on a commercially available soda lime silica glass as a function of various normal loads (2-15 N) at a constant scratch speed of 100 mu m.s(-1). The results showed that the tribological properties, the severity and the spatial density of damage evolution were sensitive to the applied normal loads and the resultant tensile as well as shear stresses. Extensive optical and scanning electron photomicrography of the surface and sub-surface deformation zones proved the existence of three distinct deformation zones in the immediate vicinity of the scratch grooves and led to the development of a qualitative model of the material removal mechanisms. (C) 2012 Elsevier By. All rights reserved

Nanomechanical properties inside the scratch grooves of soda-lime-silica glass

Advanced applications of glass span the range from biomedical technology to special optical lenses to mobile phones and computers. Such advanced applications demand high-precision machining, which is like multiple single scratches occurring simultaneously on the glass surface. However, in spite of the wealth of literature on scratch deformation behavior of glass there is no significant information available on whether the nanomechanical properties are affected inside the scratch grooves. Therefore, nanoindentation experiments were deliberately conducted at a fixed load of 100 mN through the scratch grooves made at various applied normal loads (5-15 N) at a constant speed of 200 mu m s(-1) on polished soda-lime-silica (SLS) glass slides. The results showed that depending upon the applied normal load used to generate the scratch grooves, the nanohardness and Young's modulus inside the scratch grooves decreased by about similar to 30-60% from the corresponding data of the undamaged SLS glass due to the presence of sub-surface shear deformation and microcracking as observed by optical, scanning and field emission scanning electron microscopy. A model for microcracked brittle solids was utilized to explain these results

Investigation on sol-gel synthesized Ag-doped TiO2 cermet thin films

Undoped TiO2 and Ag-TiO2 (up to 23 at.% Ag) cermet thin films and polycrystalline powders have been prepared by sol-gel process. Their structure, composition, surface morphology and optical properties have been investigated by X-ray diffraction (XRD), differential thermal analysis (DTA), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and ultraviolet-visible spectroscopy (UV-VIS spectroscopy). It has been observed that while Ag does not form a solid solution with TiO2, it promotes the anatase to rutile phase transformation. The transformation temperature decreases from 827 degreesC for undoped TiO2 to about 650 degreesC for 23 at.% Ag-doped TiO2. SIMS analyses show that Ag is mostly present on the surface of the films. XPS studies confirm that these Ag are in the Ago state. Optical analyses show that with increasing Ag content, the refractive index (n) increases and the optical absorption behavior of the cermet films is modified, but the band gap of the anatase TiO2 is not influenced. (C) 2004 Published by Elsevier B.V

Aluminum nitride-single walled carbon nanotube nanocomposite with superior electrical and thermal conductivities

Development of aluminum nitride (AlN)-single walled carbon nanotube (SWCNT) ceramic-matrix composite containing 1-6 vol% SWCNT by hot pressing has been reported in this article. The composites containing 6 vol% SWCNT are dense (similar to 99% relative density) and show high dc electrical conductivity (200 Sm-1) and thermal conductivity (62 Wm(-1) K-1) at room temperature. SWCNTs contain mostly metallic variety tubes obtained by controlled processing of the pristine tubes before incorporation into the ceramic matrix. Raman spectroscopy and field emission scanning electron microscopy (FESEM) of the fracture surface of the samples show the excellent survivability of the SWCNTs even after high-temperature hot pressing. The results indicate the possibility of preparation of AlN nanocomposite for use in plasma devices and electromagnetic shielding

Effect of scratching speed on deformation of soda-lime-silica glass

The grinding and polishing of a fundamentally brittle material like glass to an utmost precision level for ultra-sophisticated applications ranging from mobile devices to aerospace as well as space shuttle components to biomedical appliances pose a big challenge today. Looking simplistically, the grinding and polishing processes are basically material removal by multiple scratching at a given speed. Unfortunately however, the role of the scratching speed in affecting the material removal mechanism in soda-lime-silica (SLS) glass is yet to be comprehensively understood. Therefore, the present work explores the surface and subsurface deformation mechanisms of SLS glass scratched under a normal load of 5 N at various speeds in the range of 100-1000 mu m s(-1) with a diamond indenter of similar to 200 mu m tip radius. The results show important roles of the time of contact, the tensile stress behind the indenter and the shear stress just beneath the indenter in governing the material removal mechanisms of the SLS glass

Improvement in hardness of soda-lime-silica glass

Hardness is a key design parameter for structural application of brittle solids like glass. Here we report for the first time the significant improvement of about 10% in Vicker's hardness of a soda-lime-silica glass with loading rate in the range of 0.1-10 N.s(-1). Corroborative dark field optical and scanning electron microscopy provided clue to this improvement through evidence of variations in spatial density of shear deformation band formation as a function of loading rate