Stephen W. Sofie

Development of nanoalumina dust as insecticide against Sitophilus oryzae and Rhyzopertha dominica

This study aims to characterize and improve the insecticidal activity of nanostructured alumina dusts. To accomplish these goals, multiple solution based synthesis routes utilizing standard aluminum salt precursors were utilized to synthesize three unique types of alumina dust. These were compared with regards to morphology, particle size and surface area using electron microscopy and dynamic light scattering particle size analysis. Insect toxicity of the various dusts was assessed using two insect species that are pests of stored grain, Sitophilus oryzae and Rhyzopertha dominica. The dust synthesized using a modified glycine-nitrate combustion process consistently yielded greater mortality rates, and all dust types were more effective on S. oryzae than on R. dominica, although the difference varied across dust types. The data show that insecticidal activity is dependent on particle size, particle morphology and surface area but also indicated that minimizing particle size and maximizing surface area are not the sole dominant factors influencing efficacy. This study does however suggest that pesticide dusts can be engineered through modified synthesis to better target different insect species.

Electrical conductivity of Sr2−xVMoO6−y (x = 0.0, 0.1, 0.2) double perovskites

Electrical conductivity of Sr2-xVMoO6-y (x = 0.0, 0.1, 0.2) double perovskites has been investigated in a reducing atmosphere at temperatures up to 800 °C. This material has a key application in solid oxide fuel cell anodes as a mixed ion and electron conductor. A solid state synthesis technique was used to fabricate materials and crystal structure was verified through x-ray diffraction. Subsequent to conventional sintering in a reducing environment, elemental valence states were indentified through x-ray photoemission spectroscopy on the double perovskite material before and after annealing in a hydrogen environment. Samples exhibited metallic like conduction with electrical conductivities of 1250 S/cm (Sr2VMoO6-y′), 2530 S/cm (Sr1.8VMoO6-y″), and 3610 S/cm (Sr1.9VMoO6-y‴) at 800 °C in 5% H2/95% N2, with a substantial increase in conductivity upon cooling to room temperature. Room temperature electrical conductivity values for Sr1.9VMoO6-y‴ make it a candidate as the highest electrically conductive oxide...