Effect of SPAN80 on the structure of emulsified aqueous suspensions

International audienceThe influence of an oil-soluble surfactant (SPAN80) on water in oil emulsions is investigated. The aqueous phase is a nanofluid consisting in a suspension of silica nanoparticles modified by CTAB. This aqueous solution, when emulsified in paraffin oil, is known to produce droplets with structural properties that depend upon the [CTAB]/[SiO 2 ] mixing ratio. For large mixing ratios, droplets have the usual spherical shape whereas for small ones, they are deformed and behave like stiff polymorphous objects. The present work focuses on the study of the robustness of this phenomenon when adding SPAN80 into the paraffin oil phase in a broad range of concentrations. Optical tomography microcopy is used to describe the structure of the emulsions. SPAN80 actually comes in addition to the stabilizing role of CTAB. It contributes in the decrease of interfacial tension and to a larger dispersity. For sufficiently large concentrations, emulsions are shown to always contain spherically shaped droplets. A similar phenomenology is observed for SDS/alumina aqueous suspensions. This suggests that the change from polymorphous to spherically shaped droplets is a general property of emulsified nanofluids in SPAN80/paraffin oil solutions

Proton tunnelling in the intramolecular hydrogen bond of 9-Hydroxyphenalenone

Inelastic neutron scattering spectra of the 9-hydroxyphenalenone and ring deuterated analogue reveal an intense band at 91 cm−1 with all characteristics anticipated for a tunnelling the transition of a (quasi)symmetric double minimum potential for proton transfer along the intramolecular hydrogen bond. This frequency is compared to those previously reported for similar systems

Study of the effect of a silver nanoparticle seeding layer on the crystallisation temperature, photoinduced hydrophylic and catalytic properties of TiO thin films deposited on glass by magnetron sputtering

The optimization of the photocatalytic activity and hydrophilic conversion of TiO is an active research area in the field of self-cleaning materials and energy storage/conversion. One major focus is the crystalline phase of TiO , known to be the most efficient of the anatase structures. Another issue is the decoration of TiO with noble metals, which act as charge carrier traps for electrons. The latter hinders or reduces the electron-hole recombination rate and often leads to a more efficient photocatalytic activity. In this paper, we describe how an interlayer consisting of 3-4nm silver nanoparticles (Ag-NPs) promotes TiO anatase crystallisation and has a positive effect on the photoinduced catalytic and hydrophylic properties of TiO thin films. Ag-NPs and TiO were deposited by magnetron sputtering in the same reactor in a two-step process: a) condensation of Ag-NPs produced in the gas phase thanks to a high-pressure discharge, and b) conventional TiO magnetron deposition in oxide mode. Four temperatures from RT to 288°C were investigated and film thickness was 80nm. Particle size and film structure were determined by TEM, HRTEM and XRD. Photocatalytic activities of the samples were tracked by the evaluation of the surface hydrophilicity after UV illumination and 24. hours post-illumination, and by UV-induced palmitic acid degradation

Synthesis and properties of LiNi0.5Mn0.5O2 cathode compounds prepared by successive freeze-drying and self-ignition

info:eu-repo/semantics/publishe

Transition from Spherical to Irregular Dispersed Phase in Water/Oil Emulsions

Bulk properties of transparent and dilute water in paraffin oil emulsions stabilized with sodium dodecyl sulfate (SDS) are analyzed by optical scanning tomography. Each scanning shot of the considered emulsions has a precision of 1 mu m. The influence of aluminum oxide nanoparticles in the structure of the water droplets is investigated. Depending on concentrations of SDS and nanoparticles, a transition occurs in their shape that changes from spherical to polymorphous. This transition is controlled by the SDS/alumina nanoparticles mixing ratio and is described using an identification procedure of the topology of the gray level contours extracted from each images. The transition occurs for a critical mixing ratio of R-crit approximate to 0.05 which does not significantly depend on temperature and electrolyte concentration. This structural change seems to be a general feature when emulsifying dispersions and most probably involves both interfacial and bulk phenomena

Raman study of the high-temperature phase transition of malonic acid

The Raman spectra of the high-temperature (α) phase of crystalline malonic acid, CH<SUB>2</SUB>(COOH)<SUB>2</SUB>, and its deuteriated derivative, CD<SUB>2</SUB>(COOD)<SUB>2</SUB>, have been investigated at 370 K in the wavenumber shift range 0-4000 cm<SUP>−1</SUP>. An assignment of the internal and external vibrations is given. Comparison of the infrared and Raman spectra of the α and β phases shows that the high-temperature phase ( α) consists of quivalent centrosymmetric dimer rings and that the corresponding space group is C<SUP>6</SUP><SUB>2h</SUB>—C2/c with molecules occupyging C<SUB>2</SUB> sites. The temperature dependence of various Raman lines, in particular those due to lattice modes, indicates that the phase transition is of first order and that during the transition, reorientation of the molecules about the c axis is strongly coupled with the low-frequency torsional (γOH...O) and librational modes