Study of small distorsions in Bi12MO20 oxides by simple exafs transmission technics

International audienceIn some Bi12 [A+xα B+yβ]O20 sillenite type phases the interatomic distances between oxygen and A or B cations located in tetrahedral sites of the lattice can be determined by EXAFS despite difficult recording conditions due to relatively low concentrations of A and B species in presence of strong absorbing bismuth

Structural study, thermal and physical properties of K2O-CaO-P2O5 phosphate glasses

Glasses of 50P2O5-xCaO-(50-x)K2O  (x= 0, 10, 20, 30, and 40 mol %) compositions were synthesized using the melt-quench procedure. The amorphous character of the prepared material was confirmed by X-ray diffraction (XRD) and Differential Scanning Calorimetry (DSC). Fourier Transform Infra-Red (FT-IR) and Raman spectroscopy are also carried out in order to determine the structural network evolution of the glassy materials with the composition. Besides, the physical properties of the glassy phosphate system were examined such as density and molar volume. The results showed that the increase of CaO content in phosphate glasses diminish the molar volume and raise the density and transition temperature. FTIR and Raman spectroscopy analysis demonstrate the formation of P-O-Ca bonds that substitute P-O-K bonds and the depolymerization of the phosphate chains. The formation of P-O-Ca bonds is in accordance with variations of glass transition temperature, (Tg), molar volume (Vm) and density (ρ). The former bonds are the origin of the partial glass-forming ability of Ca2+. In addition, an analysis of the surface morphology features was conducted using a Scanning Electron Microscopy (SEM) technique

Policing gender mobilities: interrogating the ‘feminisation of migration’ to Europe

This article proposes a gendered critique of the European Neighbourhood Policy, a framework that, amongst other things, aims to facilitate the mobility of migrants to the EU from the bordering countries. We highlight the ambivalences of European gender and migration regimes, and we take issue with the celebration of the ‘feminisation of migration’. The former fails to offer opportunities to women to safely embark on autonomous migratory projects, the latter contributes to reproduce traditional gender biases in the countries of origin as well as of destination. We conclude by suggesting that the EU critique to emigration countries for failing to tackle women’s discrimination is less than persuasive when assessed vis-á-vis with the curtailment on women’s independent mobility across European borders

Effectiveness and Compatibility of a Novel Sustainable Method for Stone Consolidation Based on Di-Ammonium Phosphate and Calcium-Based Nanomaterials

External surfaces of stones used in historic buildings often carry high artistic value and need to be preserved from the damages of time, especially from the detrimental effects of the weathering. This study aimed to test the effectiveness and compatibility of some new environmentally-friendly materials for stone consolidation, as the use thereof has been so far poorly investigated. The treatments were based on combinations of an aqueous solution of di-ammonium phosphate (DAP) and two calcium-based nanomaterials, namely a commercial nanosuspension of Ca(OH)2 and a novel nanosuspension of calcite. The treatments were applied to samples of two porous stones: a limestone and a sandstone. The effectiveness of the treatments was assessed using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, ultrasound pulse velocity test, colour measurements, and capillary water absorption test. The results suggest that the combined use of DAP and Ca-based nanosuspensions can be advantageous over other commonly used consolidants in terms of retreatability and physical-chemical compatibility with the stone. Some limitations are also highlighted, such as the uneven distribution and low penetration of the consolidants

Degradation of Alumina and Magnesia Chrome refractory bricks in Portland cement kiln – Corrected version*

In cement plants, the refractory products are particularly confronted to partially liquid oxide phases at temperature ranging between 900°C and 1700°C. All constituents of these products have to resist not only to thermal constraints, but also to the thermochemical solicitations which result from contact material/coating. In order to study the phenomenon of degradation of refractory bricks in cement kilns and to identify the causes of their degradation, we proceed to the examination of industrial cases in cement kiln. Many chemical tests of the degraded refractory bricks have been done and the results acquired were compared to the ones not used. The analysis of the results is doing using different techniques (Loss of ignition, X-ray Fluorescence, X-ray Diffraction). The results show that the degradation of the used bricks in the clinkering and cooling zone is due to the infiltration of aggressive elements such us sulphur, alkali (Na2O, K2O ...). The chemical interaction between the Portland clinker phases and refractory material has also an importance on the stability of the coating and consequently on the life of the refractories

Withdrawn article – Degradation of Alumina and Magnesia Chrome refractory bricks in Portland cement kiln

This paper published in MATEC Web of Conferences has been formally withdrawn. It should not be cited or referred to in the future. A corrected version replaces this article, see MATEC Web of Conferences 11 01048 (2014), DOI: 10.1051/matecconf/2014110104