Magnetoelastic effects in Jahn-Teller distorted CrF2_2 and CuF2_2 studied by neutron powder diffraction

We have studied the temperature dependence of crystal and magnetic structures of the Jahn-Teller distorted transition metal difluorides CrF$_2$ and CuF$_2$ by neutron powder diffraction in the temperature range 2-280 K. The lattice parameters and the unit cell volume show magnetoelastic effects below the N\'eel temperature. The lattice strain due to the magnetostriction effect couples with the square of the order parameter of the antiferromagnetic phase transition. We also investigated the temperature dependence of the Jahn-Teller distortion which does not show any significant effect at the antiferromagnetic phase transition but increases linearly with increasing temperature for CrF$_2$ and remains almost independent of temperature in CuF$_2$. The magnitude of magnetovolume effect seems to increase with the low temperature saturated magnetic moment of the transition metal ions but the correlation is not at all perfect

Palladium nanoparticles supported on fluorine-doped tin oxide as an efficient heterogeneous catalyst for Suzuki coupling and 4-nitrophenol reduction

Immobilization of palladium nanoparticles onto the fluorine-doped tin oxide (FTO) as support Pd/FTO, resulted in a highly active heterogeneous catalyst for Suzuki-Miyaura cross-coupling reactions and 4-nitrophenol reduction. The Pd/FTO catalyst has been synthesized by immobilization of palladium nanoparticles onto FTO via a simple impregnation method. ICP-MS analysis confirmed that there is 0.11 mmol/g of palladium was loaded successfully on FTO support. The crystallinity, morphologies, compositions and surface properties of Pd/FTO were fully characterized by various techniques. It was further examined for its catalytic activity and robustness in Suzuki coupling reaction with different aryl halides and solvents. The yields obtained from Suzuki coupling reactions were basically over 80%. The prepared catalyst was also tested on mild reaction such as reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). Pd/FTO catalyst exhibited high catalytic activity towards 4-NP reduction with a rate constant of 1.776 min(-1) and turnover frequency (TOF) value of 29.1 hr(-1). The findings revealed that Pd/FTO also maintained its high stability for five consecutive runs in Suzuki reactions and 4-NP reductions. The catalyst showed excellent catalytic activities by using a small amount of Pd/FTO for the Suzuki coupling reaction and 4-NP reduction

Switchable hydrophobic-hydrophilic layer obtained onto porous alumina by plasma-enhanced fluorination

Conventional lithographic printing processes using porous alumina for offset applications generally use “wet” routes. Recently “dry” processes have been developed which are based on a heat-induced hydrophilic/oleophilic conversion of one or more layers of the coating so that a stronger affinity to-wards ink or water fountain is created at the exposed areas with respect to the surface of the unex-posed coating. Treatments involving rf plasma-enhanced fluorination (PEF) constitute exceptional tools for modifying the surface properties of materials. Many advantages of these techniques can be indeed outlined, when compared to more conventional methods: room-temperature reactions, chemical modi-fications limited to surface only without changing the bulk properties, possible non-equilibrium reac-tions. The influence of PEF treatments on porous alumina layer used in printing plates has been tested with various fluorinated gases (CF4, C3F8 and C4F8) and characterized by XPS. The hydrophobic prop-erties of the fluorinated layer have been deduced from contact angle measurements. Using C4F8 rf-PEF treatment, the outmost surface of the hydrophilic alumina substrate used for lithographic printing is hydrophobized, or in other words, the hydrophilic substrate is converted into a support with hydro-phobic properties. Once being hydrophobized, the surface layer may be rendered hydrophilic using a heat pulse, thus giving rise to switchable hydrophobic-hydrophilic properties of the material

Structure cristalline des variétés basse et haute température de fluoferrite de rubidium Rb Fe F4

Rb Fe F₄ exhibits a reversible polymorphic transformation at 650° C : Rb Fe F₄α ⇆ Rb Fe F₄β. The crystal structures of the two forms α and ß have been determined. These two structures with very similar lattice energy present (FeF₄)n [with n negative charges] layers of ReO₃ type ; rubidium atoms are inserted between these layers.Rb Fe F₄ présente une transformation allotropique réversible à 650° C : Rb Fe F₄α ⇆ Rb Fe F₄β. Les structures des deux variétés α et ß ont été déterminées. Ces deux structures d'énergies réticulaires très voisines sont caractérisées par des feuillets [de charge -n] (FeF₄)n de type ReO₃ entre lesquels s'insèrent les atomes de rubidium.Tressaud A., Galy Jean, Portier Jean. Structure cristalline des variétés basse et haute température de fluoferrite de rubidium Rb Fe F4. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 92, 4, 1969. pp. 335-341

Influence of Fluorination On the Transport-properties of Some Series of Materials

The effect of fluorination on the transport properties of three classes of materials is presented. The intercalation of fluorine in graphitized carbon fibres drastically modifies their electrical behaviour. A wide range of conductivities is observed from sigma(300K) similar to 1.5 X 10(5) S cm(-1) for Csimilar to 14F to sigma(300K) similar to 10(2) S cm(-1) for C-<3F. A superconducting oxyfluoride La2Cu(O,C-F4.17 is obtained by the intercalation of fluorine species into the La2CuO4 lattice. Superconductivity can be attributed to a hole-doping process and the increase of the number of charge carriers is confirmed by the thermoelectric power results. In YBa2Cu3O7-delta ceramics, an enhancement of the critical current density results from a radiofrequency plasma treatment using CF4 gas

Systèmes magnétiques de basse dimensionnalité dans des fluorures de type usovite et jarlite

Dans le cadre d’une étude générale des systèmes magnétiques de basse dimensionnalité rencontrés dans les fluorures, nous décrivons ici de nouveaux composés isostructuraux de l’usovite Ba2CaMgAl2F14 et de la jarlite Sr6Na2MgAl6F32(OH)2. D’un point de vue magnétique, ces fluorures présentent un comportement caractéristique de chaînes ferrimagnétiques, ou, pour certains, de clusters ferrimagnétiques. Nous nous sommes efforcés de corréler structure et propriétés magnétiques, et de paramétrer ces propriétés grâce à des modèles théoriques originaux