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CuO as sintering additive to Sr0.4Ca0.6La4Ti5O17 ceramics

100%

Manan A. , Shah L. A. , Attaullah

Materials Science Poland

2013

tom Vol. 31, No. 1

122-125

The effects of CuO addition on the sintering behavior and microwave dielectric properties of Sr0:4Ca0:6La4Ti5O17 ceramics were investigated. CuO was selected as a liquid phase sintering aid to lower the sintering temperature of Sr0:4Ca0:6La4Ti5O17 ceramics. With CuO addition, the sintering temperature of Sr0:4Ca0:6La4Ti5O17 ceramics was effectively reduced from 1550 °C to 1475 °C. The crystalline phase exhibited no phase difference and no second phase was detected at all addition levels. The electric permittivity was not significantly affected by various amounts of CuO addition and ranged from 52 to 54. Small values (<+7 ppm/K) of the temperature coeficient of resonant frequency were obtained for Sr0:4Ca0:6La4Ti5O17 ceramics. However, the unloaded quality factor Qu was strongly dependent upon the CuO concentration. Qu fo - 10500 GHz was obtained for Sr0:4Ca0:6La4Ti5O17 ceramics with 0.5 wt.% of CuO addition, sintered at 1475 °C.

Fabrication of Ag and Au nanoparticles in cross-linked polymer microgels for their comparative catalytic study

100%

Shah L. A. , Sayed M. , Siddiq M.

Materials Science Poland

2017

tom Vol. 35, No. 3

651--659

Three dimensional cross-linked polymer microgels with temperature responsive N-isopropyl acrylamide (NIPAM) and pH sensitive methacrylic acid (MAA) were successfully synthesized by free radical emulsion polymerization with different amounts of MAA. Silver and gold nanoparticles with the size of 6.5 nm and 3.5 nm (±0.5 nm), respectively were homogeneously reduced inside these materials by chemical reduction method at pH 2.78 and 8.36 for the preparation of hybrid materials. The samples were characterized by FT-IR, DLS and TEM techniques. The catalytic activity of the hybrid materials was investigated for the reduction of 4-nitrophenol (4-NP) using NaBH4 as reducing agent by UV-Vis spectroscopy. The hybrid polymer network synthesized at pH 8.36 showed enhanced catalytic efficiency compared to the catalysts synthesized at pH 2.78. In this study, it has been stated that the catalyst activity strongly depends on the amount of MAA, pH value during synthesis and the type of entrapped metal nanoparticles.