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991.
This article presents a simple inexpensive method to measure flow and viscoelastic properties of calcium alginate hydrogels or gel solutions and is particularly suitable for quality control in small laboratory settings. This method can be considered an extension of the Melt Flow Index (MFI) method, which is routinely used in the polymer industry to indirectly determine the molecular weight of polymers. Results of alginate gels at various crosslinking densities obtained with this new test are compared to complex viscosity data obtained from a standard cone and plate rheometer, and demonstrate very good correlation. A mathematical model describing the apparent viscosity of the alginate gels in this test has also been developed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   
992.
Wear is one of the major problems faced in industry that reduces the life of industrial components and increases the operating costs. Therefore, hardfacing is widely employed by engineers to minimize components’ wear, in which single or multiple layers of hard material that mainly consists of carbides deposited on the base metal. However, these carbide-based materials suffer from solidification cracking due to lack of ductility. In this study, titanium carbide (TiC) reinforced alloy steel deposited using self-shielded flux cored arc welding technique. The microstructure and phase analysis in the hardfaced deposit by scanning electron microscope, energy dispersive x-ray and X-ray diffractometer revealed that the microstructure consists of finely distributed TiC within matrix of martensite and some retained austenite. Microhardness test and pin-on-disk wear test had shown that the clad deposit posses better hardness and wear resistance. Retained austenite formation and TiC precipitation were discussed in detail and correlated with the mechanical properties.  相似文献   
993.
994.
The complex perovskite Ba(Yb1/2Ta1/2)O3 has been prepared by the two-stage solid-state reaction method. Rietveld' refinement analysis indicates cubic perovskite phase with space group     . The 1:1 cation ordering at the B-site is revealed by the presence of (111) superlattice reflection in the X-ray diffraction pattern and further evidenced by the presence of A1g and F2g vibrational modes in the Raman spectra. The dielectric constant is measured to be 29.1, the product of quality factor and resonant frequency ( Q × f ) is found to be 32,000 GHz and the temperature coefficient of resonant frequency (τf) is 135 (ppm/°C) in the temperature range 30–70°C.  相似文献   
995.
Titanium dioxide (TiO2) nanotubes were fabricated by anodisation of titanium foil in 0.15 M ammonium fluoride in an aqueous solution of glycerol (90 % v/v). Electropolymerisation of pyrrole and deposition of gold nanoparticles on to the TiO2 nanotube array electrode were carried out by cyclic voltammetry (CV). Electrochemical characterization of the sensor was performed by CV and electrochemical impedance spectroscopy. The morphology of the electrode was studied after every step of modification using field emission scanning electron microscope and atomic force microscope. The sensor was tested for AA and other biomolecules in phosphate buffered saline solution of pH 7 using CV, differential pulse voltammetry and amperometry. The sensor exhibited very high sensitivity of 63.912 μA mM?1 cm?2 and excellent selectivity to ascorbic acid (AA) in the presence of other biomolecules such as uric acid, dopamine, glucose and para-acetaminophen. It also showed very good linearity (R = 0.9995) over a wide range (1 μM–5 mM) of detection. The sensor was tested for AA in lemon and found its concentration to be 339 mg ml?1.  相似文献   
996.
Two dimensional (2D) materials stacked with Van der waals bonding to obtain a heterostructure have always generated tailored physical and chemical properties. In this paper, the development and application of single-phase 2D Bi2MoO6-reduced graphene oxide (BMO-RGO) heterostructure by one-pot supercritical water (SCW) method is reported for the first time. The as-synthesized nanocomposite of BMO-RGO with single-phase orthorhombic crystal structure is confirmed by XRD. The 2D nanoflake morphology was observed under transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and Fourier transform infrared spectroscopy is performed to confirm the presence of BMO-RGO, RGO, and other functional groups, respectively. The specific capacities obtained through charge-discharge measurements from BMO and BMO-RGO heterostructure nanocomposites are compared and the optimization of RGO wt% is established. After 50 cycles, the capacity retention is around 202 mA h g?1 for BMO with 24 wt% RGO (BMO-24RGO) nanocomposite. This value is higher in comparison to pure BMO nanoflakes which have a capacity retention of 25 mA h g?1. These results show the influence of RGO content on the performance of electrochemical measurements when compared to pure BMO and BMO-24RGO electrodes. One-pot SCW synthesis is found to be a reliable method for the synthesis of BMO-RGO nanocomposite.  相似文献   
997.
Microrods of potassium niobate (KNbO3) were synthesized at 700, 800 and 900 °C by solid state reaction method and their structural, morphological, linear optical, nonlinear optical and magnetic properties were studied. X-ray diffraction and Rietveld refinement reveal that all the prepared KNbO3 samples belong to single phase orthorhombic structure with space group of Cm2m. Fourier transform infrared and Raman spectral analyses confirmed the Nb-O symmetric stretching vibrational modes of NbO6 octahedron. The grain growth direction (001) and inter planar spacing (0.38 nm) of KNbO3 were determined by high resolution transmission electron microscopy. Field emission scanning electron microscopy images revealed that KNbO3 are formed with nearly rod shape morphology with average diameter varying from 471 to 678 nm and length lies between 1.2 and 2.3 µm. X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy studies confirmed the presence of K, Nb and O elements in the KNbO3 matrix. UV–visible diffuse reflectance spectra showed that the band gap of KNbO3 microrods varies between 3.18 and 3.22 eV. The existence of blue (492 nm) and green (521 nm) emissions evidently showed the presence of oxygen vacancy in the samples. All the synthesized KNbO3 microrods exhibited relatively high SHG efficiency as compared with that of the standard KDP. Vibrating sample magnetometer analysis showed the existence of ferromagnetic behavior at room temperature. The saturation magnetization (Ms) of KNbO3 microrods lies between 0.015 and 0.012 emu g?1 and coercive field (Hc) varies in the range from 489 to 420 Oe.  相似文献   
998.
Dissolution inhibition capabilities of benzotriazole (BTAH) and ammonium dodecyl sulfate (ADS) are investigated, in combination with β-alanine, as a complexing agent for applications in electrochemical mechanical planarization (ECMP) of copper. Cu electrodissolution is induced by linear sweep voltammetry (LSV), and Fourier transform electrochemical impedance spectroscopy (FT-EIS) is combined with LSV to examine the relative roles of the electrolyte additives in governing the surface reactions of Cu under voltage activated conditions of ECMP. The experiments focus on the electrochemical rather than mechanical component of ECMP, and are designed to probe both the individual and combined effects of BTAH and ADS on Cu electro-dissolution in the absence of abrasion.  相似文献   
999.
Nicotinic acid (3‐pyridine carboxylic acid) is widely used in food, pharmaceutical, and biochemical industries. Compared to chemical methods, enzymatic conversion of 3‐cyanopyridine is an advantageous alternative for the production of nicotinic acid. This study is aimed to intensify the recovery of nicotinic acid using reactive extraction with organophosphorus solvating extractants such as tri‐n‐octyl phosphine oxide (TOPO) and tri‐n‐butyl phosphate (TBP). The distribution of nicotinic acid between water and phosphorus‐based solvents dissolved in various diluents and the comparison of extraction efficiency with pure diluents are studied at isothermal conditions. Pure diluents are not found to be good extracting agents and the maximum distribution coefficient (KD) obtained with 1‐octanol is 0.31. Experimental studies are carried out to investigate the effect of diluent, initial acid concentration, extractant type, and extractant composition on the degree of extraction. The maximum recovery of nicotinic acid is obtained by dissolving TOPO in MIBK at an initial nicotinic acid concentration of 0.10 kmol/m3. Solvation numbers and extraction equilibrium are also estimated with both TBP and TOPO.  相似文献   
1000.
Surface finish and surface hardness of the components play vital role in quality of products/components, in general and failure resistance, in particular. One of the finishing process involving surface plastic deformation that introduces compressive residual stresses and thereby improves fatigue resistance is “Burnishing”. Even though the burnishing process is widely employed, its process parameters were not systematically studied till date and not fully established for various important structural materials. The burnishing process parameters include force, speed, feed, and number of tool passes. In the present study, the data obtained from systematically conducted burnishing experiments are correlated with theoretical design using Taguchi method in case of EN series steels (EN 8, EN 24 and EN 31). The surface characterization employed includes optical microscopy, microhardness and magnitude of residual stress. The study revealed a one-to-one correlation between burnishing depth, increase in average microhardness and magnitude of compressive residual stresses and a peak in all these three at intermittent extent of burnishing (either after first or second pass) in all the three alloy steels.  相似文献   
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