Until the arrival of the theories of plate tectonics and seafloor spreading in the 1960s, the Earth’s mantle was generally believed to consist of peridotites of uniform composition. This view was shared by geophysicists, petrologists, and geochemists alike, and it served to characterize the compositions and physical properties of mantle and crust as “Sial” (silica-alumina) of low density and “S...

The electric, electronic, mechanical and thermal characteristics of high density electronic devices can be affected by the physico-chemical characteristics of base materials as well as by trace impurities. It is well known that soft errors caused by trace -emitting impurities are one cause of the faulty operation of electronic devices. This phenomenon was initially reported in May[1] in the 197...

Sintering with low frequency rf power (-50 M H z ) is a new technique with unique capabilities that has been used to sinter a variety of ceramic materials, including zirconia-toughened alumina, alumina, silicon carbide, and boron carbide. Processing with low frequencies offers many advantages compared to processing with conventional microwave frequencies (915 MHz and 2.45 GHz). Because of the l...

Monodisperse crystalline zero-valent iron, iron-nickel, iron-palladium nanowires were synthesised using template-directed electrodeposition methods. Prior to nanowire fabrication, alumina nanotemplates with controlled pore structure (e.g. pore diameter and porosity) were fabricated by anodising high purity aluminium foil in sulphuric acid. After fabrication of alumina nanotemplates, iron, iron-...

The quality of the refractories applied on integrated gasification combined cycle should be a key factor that affects both the reliability and the economics of gasifier operation. To enhance the workability of chromia/alumina castables, three types of ultrafine alumina powder were added to improve the workability. Densification behavior of such castables in the presence of ultrafine alumina was...

Despite the widespread use of amorphous aluminosilicates (ASA) in various industrial catalysts, the nature of the interface between silica and alumina and the atomic structure of the catalytically active sites are still subject to debate. Here, by the use of dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP SENS) and density functional theory (DFT) calculations, we show that o...

The phase transformation of aluminum hydrates yields various forms of alumina (d, q, K) and eventually alpha-alumina. The decrease in the specific surface area of alumina upon heat treatment is due to changes in crystalline structure and hence a decrease in the porosity of the material, Although the conversion of gamma-alumina to alpha-structure takes place with a lowering in surface area and p...

Using periodic density-functional theory (DFT), we investigated the structure and cohesive properties of the -alumina 11 tilt grain boundary, with and without segregated elements, as a model for the thermally grown oxide in jet engine thermal barrier coatings. We identified a new low-energy structure different from what was proposed previously based on electron microscopy and classical potentia...

The influence of NaNO2, HNO3 and H2SO4 on the structure and morphology of gamma-alumina was investigated by XRD, BET, SEM and FT-IR spectroscopy. Selected amounts of NaNO2, HNO3 and H2SO4 were added to a solution of aluminum isopropoxide (as a precursor for the boehmite synthesis). The boehmite samples were calcined at 350 and 600 ℃ to form the semi-crystalline high surface area gamma-Al2O3. Th...

background: some coincidental disorders with migraine have been introduced that may have role in its pathogenesis or aggravation. in this study we determined the relative frequency of hyperlipidemia as a coincidental disorder in patients affected by migraine. methods: a total of 102 migraine-affected patients according to international headache society (his) criteria and 103 control subjects ad...