OPTIMIZATION OF TECHNOLOGICAL MODES OF OBTAINING THE SOL-GEL METHOD, HIGH-PURITY SILICA WITH PARTICLES OF NANOSCALE LEVEL

Sol-gel with sonochemical process and sol-gel method were used for the fabrication of photocatalytic TiO2 powder and the properties of the TiO2 powder thus prepared were examined and compared. For the synthesis of TiO2 powder, the starting material was Ti-butoxide and H2O and the reaction was carried out at 80 °C in a sol-gel method. On the other hand, Ti-butoxide was reacted with H2O in an ultrasonic frequency of 23 kHz with ultrasonic powers of 800 W for two hours. After evaporation, 24 hours aging time was kept at 400 °C in both cases, the final product appeared was the anatase phase. Ultrasonic chemical method was found to be excellent for flocculation and crushing effects where as in sol-gel method, the product obtained was of high purity and high homogeneity. Sol-gel with sonochemical process has found to be excellent for flocculation and crushing effects. From Sol-gel method, the size of TiO2 particles produced were found to be about 20 nm, spherical, homogeneous while severe agglomeration. In contrast, by sonochemistry method, the size of TiO2 particles produced were about 10 ~ 22 nm size and it has shown more photocatalytic activity than sol-gel sample which is about 28.7 % greater efficiency

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Synthesis of YBa2Cu3O7-δ Using Oxalate Precursors and Sol-Gel Method

Advances in Science and Technology ◽

10.4028/www.scientific.net/ast.47.37 ◽

2006 ◽

Vol 47 ◽

pp. 37-42 ◽

Cited By ~ 3

Author(s):

Angel Bustamante D. ◽

Ana M. Osorio A. ◽

Luis De Los Santos V. ◽

Hilda Carhuancho A. ◽

J.C. González G. ◽

...

Keyword(s):

Aqueous Solution ◽

Oxalic Acid ◽

High Purity ◽

Sintering Temperature ◽

Ac Susceptibility ◽

Sol Gel ◽

Secondary Phases ◽

Gel Method ◽

Sol Gel Method ◽

Quantum Design Squid Magnetometer

In this work we present the results about the preparation of the superconductor YBa2Cu3O7-δ (Y123) by sol-gel method using oxalate precursors. Samples were prepared by dissolving stoichiometric mixtures of Y(OOCCH3).4H2O, Ba(OOCCH3)2 and Cu(OOCCH3)2.H2O acetates in aqueous solution of oxalic acid, HCOO-COOH. The particulate sols obtained (2g.) were divided in two parts (1g. each one), from which the first one (sample A) was grinded, pellet, calcined (860°C) and sinterised at 860°C in oxidizing atmosphere, the second part (sample B) was grinded, pellet, calcined at 880°C and finally sinterized at 880°C in the same conditions, the XRD revels the superconductor Y123 is formed in the first sample, but coexisting with remarkable presence of the secondary phases: CuO, BaCu3O4, BaCO3 and BaCuO2, while in sample B the XRD reveals the obtention of high purity monophase Y123, the ac susceptibility measurement using a Quantum Design (SQUID) magnetometer indicates TC(onset)=92K for this sample, moreover the Rietveld refinement was done taking the orthorhombic Pmmm Y123 spatial group as a model, this suggest the cell´s parameters a=3.839Å, b=3.899 Å and c=11.702Å as reported in the literature. Therefore for the preparation of Y123-superconductor using oxalate precursors, the optimus sintering temperature is 880°C.

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