Molecular dynamics of glycerol and glycerol-trehalose bioprotectant solutions nanoconfined in porous silicon

Glycerol and trehalose-glycerol binary solutions are glass-forming liquids with remarkable bioprotectant properties. Incoherent quasielastic neutron scattering (QENS) is used to reveal the different effects of nanoconfinement and addition of trehalose on the molecular dynamics in the normal liquid and supercooled liquid phases, on a nanosecond timescale. Confinement has been realized in straight channels of diameter D=8 nm formed by porous silicon. It leads to a faster and more inhomogeneous relaxation dynamics deep in the liquid phase. This confinement effect remains at lower temperature where it affects the glassy dynamics. The glass transitions of the confined systems are shifted to low temperature with respect to the bulk ones. Adding trehalose tends to slow down the overall glassy dynamics and increases the non-exponential character of the structural relaxation. Unprecedented results are obtained for the binary bioprotectant solution, which exhibits an extremely non-Debye relaxation dynamics as a result of the combination of the effects of confinement and mixing of two constituents

Humidity effect on baseline conductance and H₂S sensitivity of cadmium germanium oxynitride thick film gas sensors

International audienceCadmium germanium oxynitrides are excellent sensing materials for the detection of H2S. The effect of humidity on both the baseline conductance and the sensitivity to H2S of thick-film gas sensors was investigated. The devices were subjected to dry and moist (varying relative humidity (RH)) air. Results showed that, unlike most semiconductor gas detectors, the presence of moisture has no significant effect on conductivity nor on the sensitivity to H2S of cadmium germanium oxynitride sensors. Hypotheses on surface processes accounting for such insensitivity are given. It appears likely that the surface states involved in responses to changes in RH are different from those involved in the detection of other gases

Manufacturing of transparent ZnS ceramics by powders sintering

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Hot-pressed ZnS infrared ceramics: correlating precursor synthesis method to sinterability and transparency

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Experimental and numerical study of small lead acid batteries regeneration

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Utilization of (Cd,Zn)_2-xGeO_4-x-3yN_2y oxynitride as sensitive material for H₂S gas sensor

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Salt leaching using powder (SLUP) process for glass/chitosan scaffold elaboration for biomaterial applications

International audienceTissue engineering has emerged as an alternative approach to create bone tissue by growing cells on 3D scaffolding. The aim of this study was to synthesize a composite glass/chitosan (BG-CH) by using new salt leaching using powder (SLUP) process in order to control the porosity rate and then the chemical reactivity of the final product. SLUP process consists on the cavity creation with desired pore sizes. It does not require heat treatment. This process is based on washing out the NaCl particles used for that. It is due to its high solubility in aqueous media. This work focuses on the elaboration, physicochemical, and chemical reactivity studies of pure bioactive glass and bioactive glass associated with chitosan. A range of composite scaffolds with different bioactive glass/chitosan contents has been synthesized. NaCl with a distinct range size was used with the aim of optimizing the pore network. Obtained results show that the specific surface area and pore volume increase with increasing of chitosan and porogen content. The same observations for pore volume were registered. The obtained scaffolds had high porosity (90%) with good pore connectivity. SEM images revealed strong dependence of sizes and shapes of pores on the salt/composite ratios

Detection of propane by "GaON" thick-film gas sensors

The detection mechanism of propane by gallium oxynitride ("GaON") sensors was investigated. The electrical resistance of the sensors was monitored during propane exposure (0, 15, 30, 50 and 100 ppm) in dry and humid atmosphere (10% relative humidity at room temperature), at different oxygen concentrations (0, 2, 5, 10 and 20%). Temperature programmed desorption-mass spectrometry (TPD-MS) was used to investigate the species desorbing from the surface of "GaON" after exposure to propane at 250 degrees C and 350 degrees C. The detected species were propene, propane, CO, CO2, NH3 and H2O. This study demonstrates that the oxidative dehydrogenation (ODH) of propane on "GaON" can take place without oxygen in the gaseous phase, thus implying a redox Mars-van Krevelen mechanism, which involves the contribution of lattice oxygen and possibly nitrogen during the activation of propane on the sensor surface. (c) 2006 Elsevier B.V. All rights reserved