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In this work, we have investigated the synergistic effect of micro- and nano-Ta2O5 fillers in the epoxy matrix on the thermal, mechanical, and radioprotective properties of the composites. Morphological analysis revealed uniform dispersion of fillers in the matrix. Both the thermal stability and tensile properties of matrices have enhanced in the presence of fillers. Although the nanocomposites showed significantly higher tensile strength and Youngs modulus compared to micro-composites, the enhancement in these properties was predominant at low loadings. Dynamic mechanical analysis indicated good interfacial adhesion and positive reinforcing effect on the matrix even at higher loading (30 wt%) of nano-Ta2O5. γ-Ray attenuation studies performed in the energy range of 0.356–1.332 MeV revealed better γ-ray shielding ability of nanocomposites compared to microcomposites at same weight fraction of fillers. In particular, γ-ray attenuation at 0.356 MeV for 30 wt% nano-Ta2O5 loaded epoxy composite was enhanced by around 13% compared to the microcomposite at the same loading. Increased surface-to-volume ratio of nanofillers and consequent increase in matrix-filler adhesion and radiation-matter interaction have manifested in an overall enhancement in the thermal, mechanical, dynamic mechanical, and radiation shielding characteristics of nano-Ta2O5/epoxy composites, proving them as promising γ-ray shields. 相似文献
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M. V. Muthamma S. G. Bubbly S. B. Gudennavar K. C. Shyama Narendranath 《应用聚合物科学杂志》2019,136(37):47949
Polymer composites, which are light in weight, cost effective, and less toxic, have potential applications in X-ray and γ-ray shielding and protection. In this work, we have explored the efficacy of poly(vinyl alcohol)–bismuth oxide composites as radiation shielding materials. Poly(vinyl alcohol) composites with different wt % (0–50) of bismuth were prepared by a simple solution casting technique. Structural and thermal characterization of these samples was carried out using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). TGA revealed the enhanced thermal stability of these composites. AC conductivity measurements and optical spectroscopy were used to analyze their electrical behavior. The composites showed low conductivity, and the energy gap obtained also showed their tendency to be insulators. The radiation attenuation properties were investigated using X-ray (5.895 and 6.490 keV) and γ-ray (59.54 and 662 keV) transmission measurements. The shielding efficiency of the composites increased with filler wt %. The 40 wt % composites exhibited mass attenuation coefficients of 122.68 and 93.02 cm2/g at photon energies of 5.895 and 6.490 keV, respectively, while the 50 wt % composites showed 1.57 and 0.092 cm2/g at photon energies of 59.54 and 662 keV, respectively. The effective atomic number quantifies the probability of interaction of radiation with matter. The effective atomic number of the composites calculated by the direct method was in good agreement with the theoretical value obtained from Auto-Zeff software. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47949. 相似文献
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Revanasiddappa Manjunatha Dodahalli Hanumantharayudu Nagaraju Gurukar Shivappa Suresh Jose Savio Melo Stanislaus F. D'Souza Thimmappa Venkatarangaiah Venkatesha 《Electrochimica acta》2011,(19):300
A selective electrochemical method is fabricated via layer-by-layer (LBL) method using both positively and negatively charged multi walled carbon nanotubes (MWCNTs) on poly (diallyldimetheylammonium chloride) (PDDA)/poly styrene sulfonate (PSS) modified graphite electrode, for the determination of acetaminophen (ACT) in the presence of dopamine (DA) and high concentration of ascorbic acid (AA). The modified electrode was characterized by cyclic voltammetry (CV) electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Experimental conditions such as pH, accumulation potential and time, effect of potential sweep rates and interferents were studied. In CV well defined peaks for AA, ACT and DA are obtained at 24, 186 and 374 mV, respectively. The separations of peaks were 210, 188 and 398 mV between AA and DA, DA and ACT and AA and ACT, respectively. The diffusion coefficient was calculated by chronocoulometric. Chronoamperometric studies showed the linear relationship between oxidation peak current and concentration of ACT in the range 25–400 μM (R = 0.9991). The detection limit was 5 × 10−7 mol/L. The proposed method gave satisfactory results in the determination of ACT in pharmaceutical and human serum samples. 相似文献
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Pavan S. Shivappa S. 《IEEE transactions on circuits and systems. I, Regular papers》2006,53(1):177-192
We examine the effects of transmission-line nonidealities like series loss, terminal impedance mismatch, circuit noise, and transconductor input and output capacitances on the performance of traveling-wave (TWA) and transversal finite-impulse response (FIR) filters. A general framework is presented for the analysis and simulation of such filters in the context of a real communication channel. Simulation results for adaptive equalizers operating at a data rate of 10 Gbps are given. Intuition is derived for the vastly superior performance of TWA-FIR filters. We also show that the effects of series losses can be counteracted in some measure by deliberately misterminating the transmission lines with a resistance lower than their characteristic impedance. 相似文献
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Muddiyada Vishnu Muthamma Shivappa Gudennavar Bubbly Shivappa Bharamappa Gudennavar 《应用聚合物科学杂志》2020,137(44):49366
Epoxy resin filled with suitable high Z elements can be a potential shield for X-rays and γ-rays. In this work, we present the γ-ray attenuation properties of epoxy composites filled with (0–30 wt%) Tantalum pentoxide (Ta2O5) and Ta2O5-Bi2O3, which were prepared by open mold cast technique. X-ray diffraction patterns showed crystalline peaks of Ta2O5 and bismuth oxide (Bi2O3) in the prepared epoxy-Ta2O5 and epoxy-Ta2O5-Bi2O3 composites. Homogeneity of the samples at higher filler wt% was revealed by SEM images. Mechanical characterization showed the enhanced mechanical strength of epoxy-Ta2O5-Bi2O3 composites compared to epoxy-Ta2O5. Higher storage modulus and glass transition temperature of the epoxy-Ta2O5-Bi2O3 composites showed enhanced stiffness and thermal stability when compared to neat and epoxy-Ta2O5. Decrease in the value of tan(δ) at higher content of filler loadings indicated the good adhesion between filler and matrix. Mass attenuation coefficients of epoxy-Ta2O5 (30 wt%) composites at γ-ray energies 59.54 and 662 keV were found to be 0.876 cm2 g–1 and 0.084 cm2 g–1, while that of epoxy-Ta2O5-Bi2O3 (30 wt% Bi2O3) composite were 1.271 cm2 g–1 and 0.088 cm2 g–1, respectively. The epoxy-5% Ta2O5-30% Bi2O3 composites with higher μ/ρ value and tensile strength may be a potential γ-ray shield in various radiation environments. 相似文献
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Pavuluri Srinivasu Sher Alam Veerappan V. Balasubramanian Sivan Velmathi Dhanashri P. Sawant Winfred Böhlmann Subhash P. Mirajkar Katsuhiko Ariga Shivappa B. Halligudi Ajayan Vinu 《Advanced functional materials》2008,18(4):640-651
Novel three dimensional cubic Fm3m mesoporous aluminosilicates (AlKIT‐5) with very high structural order and unprecedented loadings of Al in the silica framework have been successfully prepared for the first time by using non ionic surfactant as a template in a highly acidic medium. The obtained materials have been unambiguously characterized in detail by several sophisticated techniques such as XRD, N2 adsorption, HRTEM, HRSEM, EDS, elemental mapping, 27Al MAS NMR, and NH3‐TPD. We also demonstrate that the nature, and the amount of Al incorporation in the silica framework can easily be controlled by simply varying the nH2O/nHCl and the nSi/nAl ratios, and the Al sources in the synthesis gel. Among the Al sources examined, the Al isopropoxide (AiPr) is superior over other Al sources. 27Al MAS NMR results reveal that the amount of tetrahedral Al in the framework can be controlled by simply adjusting the nSi/nAl ratio in the synthesis gel, which increases with increasing the Al incorporation. One of the interesting findings in the work is the increase of the specific surface area, specific pore volume and the pore diameter of AlKIT‐5 with increasing the Al incorporation in the silica framework (up to nSi/nAl ratio of 10) while retaining the well‐ordered three dimensional cage type porous structure, and the mechanism for the unusual behavior has been discussed in detail. Finally, the acidity and the catalytic activity in the acetylation of veratrole of the AlKIT‐5 catalysts have been studied and the results have been compared with the several zeolites catalysts. Among the catalysts examined, AlKIT‐5(10) is found to be superior over the zeolites catalysts such as mordenite, zeolite H‐Y, zeolite H‐β, and ZSM‐5. 相似文献
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In the present work, we have explored the efficacy of bismuth (III) oxide (Bi2O3) loaded, calcium ion cross-linked solution cast sodium alginate composite films for radioprotective applications. Calcium ion cross-linking increased the water and chemical resistance, which further improved on introduction of Bi2O3 into the composites. The 40 wt% Bi2O3 loaded films showed good heat resistance with the peak degradation temperature reaching as high as 251°C. The Bi2O3 loaded composites showed enhanced tensile strength (TS) and Youngs modulus (YM). Compared to high-modulus polymers like epoxy, high-density polyethylene (HDPE) and poly (vinyl chloride) (PVC), these exhibit relatively greater extent of stretching before breaking. The γ-ray attenuation experiments showed that mass attenuation coefficients of the composites at various γ-ray energies increased with filler loading. These composites are effective in shielding γ-rays from radioactive sources like 137Cs, 22Na, 133Ba, and 60Co that are widely employed in several medical and industrial applications. The overall enhancement in thermal, mechanical, and radiation shielding characteristics of the composites may be attributed to the uniform distribution of the fillers in alginate matrix. These nontoxic sodium alginate/Bi2O3 composites can be used as soft and biodegradable radiation shields, which may be processed to wearable forms. 相似文献