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      Optimizing Bi 2O 3 and TiO 2 to achieve the maximum non-linear electrical property of ZnO low voltage varistor

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          Abstract

          Background

          In fabrication of ZnO-based low voltage varistor, Bi 2O 3 and TiO 2 have been used as former and grain growth enhancer factors respectively. Therefore, the molar ratio of the factors is quit important in the fabrication. In this paper, modeling and optimization of Bi 2O 3 and TiO 2 was carried out by response surface methodology to achieve maximized electrical properties. The fabrication was planned by central composite design using two variables and one response. To obtain actual responses, the design was performed in laboratory by the conventional methods of ceramics fabrication. The actual responses were fitted into a valid second order algebraic polynomial equation. Then the quadratic model was suggested by response surface methodology. The model was validated by analysis of variance which provided several evidences such as high F-value (153.6), very low P-value (<0.0001), adjusted R-squared (0.985) and predicted R-squared (0.947). Moreover, the lack of fit was not significant which means the model was significant.

          Results

          The model tracked the optimum of the additives in the design by using three dimension surface plots. In the optimum condition, the molars ratio of Bi 2O 3 and TiO 2 were obtained in a surface area around 1.25 point that maximized the nonlinear coefficient around 20 point. Moreover, the model predicted the optimum amount of the additives in desirable condition. In this case, the condition included minimum standard error (0.35) and maximum nonlinearity (20.03), while molar ratio of Bi 2O 3 (1.24 mol%) and TiO 2 (1.27 mol%) was in range. The condition as a solution was tested by further experiments for confirmation. As the experimental results showed, the obtained value of the non-linearity, 21.6, was quite close to the predicted model.

          Conclusion

          Response surface methodology has been successful for modeling and optimizing the additives such as Bi 2O 3 and TiO 2 of ZnO-based low voltage varistor to achieve maximized non-linearity properties.

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          Most cited references22

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          Modeling and optimization I: Usability of response surface methodology

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            Response surface methodology

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              Development of a novel 96-microwell assay with high throughput for determination of olmesartan medoxomil in its tablets

              A novel 96-microwell-based spectrophotometric assay has been developed and validated for determination of olmesartan medoxomil (OLM) in tablets. The formation of a colored charge-transfer (CT) complex between OLM as a n-electron donor and 2, 5-dichloro-3, 6-dihydroxy-1, 4-benzoquinone (p-chloranilic acid, pCA) as a π-electron acceptor was investigated, for the first time, and employed as a basis in the development of the proposed assay. The proposed assay was carried out in 96-microwell plates. The absorbance of the colored-CT complex was measured at 490 nm by microwell-plate absorbance reader. The optimum conditions of the reaction and the analytical procedures of the assay were established. Under the optimum conditions, linear relationship with good correlation coefficient was found between the absorbance and the concentration of OLM in the range of 1-200 μg ml-1. The limits of detection and quantitation were 0.3 and 1 μg ml-1, respectively. No interference was observed from the additives that are present in the pharmaceutical formulation or from hydrochlorothiazide and amlodipine that are co-formulated with OLM in some formulations. The assay was successfully applied to the analysis of OLM in tablets with good accuracy and precision. The assay described herein has great practical value in the routine analysis of OLM in quality control laboratories, as it has high throughput property, consumes minimum volume of organic solvent thus it offers the reduction in the exposures of the analysts to the toxic effects of organic solvents, and reduction in the analysis cost by 50-fold. Although the proposed assay was validated for OLM, however, the same methodology could be used for any electron-donating analyte for which a CT reaction can be performed.
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                Author and article information

                Contributors
                Journal
                Chem Cent J
                Chem Cent J
                Chemistry Central Journal
                BioMed Central
                1752-153X
                2013
                10 August 2013
                : 7
                : 137
                Affiliations
                [1 ]Material Synthesis and Characterization Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia
                [2 ]Department of Physics, Faculty Science, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia
                Article
                1752-153X-7-137
                10.1186/1752-153X-7-137
                3751521
                23938168
                e85cf74f-daac-436b-9bd6-03f7e3def8c4
                Copyright © 2013 Abdollahi et al.; licensee Chemistry Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 19 May 2013
                : 6 August 2013
                Categories
                Research Article

                Chemistry
                optimization,zno-varistor,modeling,rsm,bi2o3,tio2
                Chemistry
                optimization, zno-varistor, modeling, rsm, bi2o3, tio2

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