An Environmentally Friendly Nb–P–Si Solid Catalyst for Acid-Demanding Reactions

Here, we report the structural characteristics, the surface properties, and the catalytic performances of a Nb–P–Si ternary oxide material (2.5Nb2O5·2.5P2O5·95SiO2, 2.5NbP) in two reactions of importance for biomass valorisation and green industrial production: hydrolysis of inulin and esterification of oleic acid with polyalcohol for biolubricant production. High dispersion of the Nb centers, ascertained by UV–vis–DRS, 29Si, 31P, and 1H solid-state NMR spectroscopy, is the key point for the successful activity of 2.5NbP. Intrinsic and effective acidities of the sample were studied by FT-IR of adsorbed pyridine in the absence and presence of water and by volumetric titrations of the acid sites in cyclohexane and in water, to enlighten the nature and amount of acid sites in different environments. For both studied reactions, 2.5NbP catalyst exhibits water-tolerant acidic sites, mainly Brønsted ones, giving higher activity and better stability in the reaction medium than well-known niobium oxophosphate catalyst, which is considered one of the best water-tolerant acid catalysts

Investigation on Metal–Oxide Graphene Field-Effect Transistors With Clamped Geometries

In this work, we report on the design, fabrication and characterization of Metal-Oxide Graphene Field-effect Transistors (MOGFETs) exploiting novel clamped gate geometries aimed at enhancing the device transconductance. The fabricated devices employ clamped metal contacts also for source and drain, as well as an optimized graphene meandered pattern for source contacting, in order to reduce parasitic resistance. Our experimental results demonstrate that MOGFETs with the proposed structure show improved high frequency performance, in terms of maximum available gain and transition frequency values, as a consequence of the higher equivalent transconductance obtained

Corrosion of carbon steel in natural waters. Effect of oxygen and bicarbonate/carbon dioxide

The corrosive behavior of waters with different O content of 0.5-8 mg/L was detd. on mild steel specimens in a closed hydraulic circuit by the linear polarization resistance and impedance detns. Water compns. were fixed to differentiate the effect on corrosion rate of both the CO2 and HCO3-contents. The corrosion rate as function of O2 content shows 3 different behaviors. The corrosion rate increases with O2 contents 0-3 mg/L and is nearly const. with O2 from 4 to 8 mg/L, while there is a narrow range where the corrosion rate abruptly decreases. The corrosion rate for any O2 content, was more effected by the [HCO3-] than by {CO2}. An interpretation of these effects is given

Influence of temperature and humidity on ionic conduction of mixed metal hydroxides

Results of conductivity (ac) measurements are reported for synthetic mixed metal hydroxides as a function of temperature, ranging from 323 to 353°K, and relative humidity, ranging from 50 to 80%. The polycrystalline compacts of layered mixed hydroxides show protonic conductivities arising from the interlayer region. The conductivity is strongly dependent on the temperature, relative humidity and composition of mixed metal hydroxides. The conductivities are anisotropic with the direction of forming pressure owing to the preferential orientation of lamellar crystals, particularly evident with powders characterized by high crystal size. © 1988

FT infrared spectroscopy of the devitrification of lithium germanate glasses

A series of amorphous and crystalline lithium germanates containing up to 25 mol% Li2O, are studied by FTIR. The glasses are found to devitrify in a number of steps. In the primary step, above T-g. the glasses undergo a transformation with a strong exothermic effect which corresponds to almost no crystal growth. The nature of this process is investigated and discussed