Facile synthesis of nanosized sodium magnesium hydride, NaMgH₃

The ternary magnesium hydride NaMgH3 has been synthesised via reactive milling techniques. The method employed neither a reactive H2 atmosphere nor high pressure sintering or other post-treatment processes. The formation of the ternary hydride was studied as a function of milling time and ball:powder ratio. High purity NaMgH3 powder (orthorhombic space group Pnma, a=5.437(2) Å, b=7.705(5) Å, c=5.477(2) Å; Z=4) was prepared in 5 h at high ball:powder ratios and characterised by powder X-ray diffraction (PXD), Raman spectroscopy and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX). The products formed sub-micron scale (typically 200–400 nm in size) crystallites that were approximately isotropic in shape. The dehydrogenation behaviour of the ternary hydride was investigated by temperature programmed desorption (TPD). The nanostructured hydride releases hydrogen in two steps with an onset temperature for the first step of 513 K

Couscous manufacture in fluidized bed by wet agglomeration of wheat semolina

Agglomeration is a key unitary operation in a number of industries (pharmaceutical, chemical, food, civil engineering). The agglomeration process controls the structural characteristics and final properties of agglomerates. One of the activities involving food agglomeration is the production of  couscous by agglomeration of durum wheat semolina. Couscous is considered the most important traditional dish among the Maghreb people. The industrial process of couscous production includes various stages, the most important of which is wet granulation of semolina, which contributes to the quality of the final product. The agglomeration of cereal powders from different origins (durum wheat, maize and barley) has been performed in a variety of equipment such as high shear mixers, drum mills and fluidized beds. However, the agglomeration of semolina in fluidized beds has had very limited study. The purpose of this research is, therefore, to study couscous production using durum wheat semolina in a fluidized bed equipped with a spray nozzle. The fluidized bed has the advantage of generating strong particle movement and intense mixing to increase the size of the granules evenly throughout the mass used.The efficiency of this process is determined by the couscous yield defined as the mass ratio of couscous to raw material. The results showed that couscous can be produced from semolina by wet fluidized bed agglomeration with a specific effect of fluidification air flow, liquid flow, bed temperature and spray liquid properties on the couscous quality (size, brittleness and morphology) as well as on yield. The latter rose by 60% when the water containing flour was sprayed. Furthermore, the results of this study showed that granules size changes directly with the liquid flow rate, while temperature and air flow have an opposite effect. It was also found that changing binder components have an effect on the quality of the agglomeration of the product. Key words: Couscous, agglomeration, fluidization, semolina, friability, granulation, atomization, size enlargement, dryin

Modelling of Heat Transfer in a Fluidized Bed Reactor Irradiated Indirectly by Concentrated Solar Energy

AbstractA two phases model of air heating in bubbling fluidized bed of sand particles with concentrated solar radiation as source of energy is developed. This model is based on the Kato and Wen's model (1969) for the hydrodynamic aspect which was modified to take account the thermic aspect. Nine algebraic equations were established in permanent regime for different heat and mass balances as well as heat losses against surrounding media. The Newton Raphson's method was used to solve this system of equations. Results have shown that the model developed is able to predict the temperature profiles of gas and particles in the bubble and emulsion phases, the wall temperature along the reactor, the heat flux transferred to the bed and heat losses by forced convection and radiation to surrounding air. The effects of the fluidizing air velocity, total mass of particles and the wind velocity on the thermal behaviours were examined. Model predictions seem reasonable looking for its comparison agreement with bibliographical data

Field effect transistor with integrated microfluidic channel as pH sensor

International audienceThis paper presents an original design of chemical sensors with an integrated microfluidic channel. Targeted applications are pH-meters devices. The integration of the microfluidic channel allows decreasing the volume required for each measurement. The sensing part of the device consists of a field effect transistor (FET) with a suspended gate directly performed above the fluidic channel. Chemicals under test are driven through the sensing area between the electrical channel of the FET and the suspended gate. By this way products that flow in the microfluidic channel directly module the concentration of charges inside the transistor's gap and thus induce changes in the transfer characteristic. This paper describes the fabrication process and the technological choices for materials. Electrical tests, performed in air and in liquid, have shown a good behavior of the transistor, linked to a good mechanical sustain of the fluidic channel. The system is able to detect transition between air and liquid media. Moreover, it has shown a high sensitivity (about 300 mV/pH) to pH measurements

Adsorption of Algerian Asphaltenes onto Synthesized Maghemite Iron Oxide Nanoparticles

In this study, the adsorption of Algerian asphaltene sample extracted from Hassi Messaoud oil field is conducted for the first time. The adsorption process was performed using novel synthesized iron oxide nanoparticles (γ-Fe2O3). γ-Fe2O3 Nanoparticles were in-house synthesized and characterized by an array of techniques using, Brunauer-Emmett-Teller (BET), high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The results showed that the synthesized nanoparticles have an average crystalline domain size around 10 nm and a specific surface area of 120 m2/g. The adsorption process of the Algerian asphaltenes took place in a batch mode by dissolving the asphaltenes in toluene at 25°C. Different initial concentrations of asphaltene solutions were used in this study, namely 100, 500, and 1000 ppm. During this adsorption, both isotherm and kinetic studies were investigated. The results showed that the synthesized iron oxide nanoparticles are promising nano-adsorbents that have a high affinity to remove the asphaltenes and the equilibrium was recorded after 15 min. The Solid-Liquid-Equilibrium (SLE) model was used to correlate the adsorption experimental data

Fabrication of field effect transistor with integrated microfluidic channel dedicated to the detection in liquid

Ce travail de recherche porte sur la réalisation de dispositifs électroniques spécifiques et originaux (Transistors à effet de champ à microcanaux) dédiés à la détection des espèces chimiques et biochimiques en milieu liquide. Ce dispositif s'appuie sur la technologie des transistors à grille suspendue (SGFET) déjà réalisés à l'IETR, en y apportant une amélioration majeure qui consiste en l'intégration au sein de la structure d'un canal microfluidique. Cette structure, nommée transistor à canal microfluidique intégré, doit permettre de conserver la forte sensibilité de détection du SGFET mais aussi de garantir le passage du liquide testé sous la grille. Cette architecture permet aussi d'augmenter sa robustesse et sa fiabilité tout en ne nécessitant que de très petits volumes de solutions. Des microcanaux avec un bon maintien mécanique ont été réalisés par micro-usinage de surface en utilisant différents matériaux comme couche sacrificielle. Ces canaux ont été intégré dans un FET et leurs accès microfluidiques ont été assurés en réalisant des ouvertures (inlet/outlet) par la face avant. Les tests électriques ont montré un bon fonctionnement de ces capteurs avec une grande sensibilité de mesure du pH mais le passage du liquide est alors majoritairement dû aux phénomènes de capillarité. Une amélioration sur l'architecture de la structure a été faite, en réalisant des ouvertures par la face arrière. Un bon fonctionnement avec une grande sensibilité de mesure de pH ont été présentés. Finalement, une structure hybride contenant une ouverture sur la face avant et une autre sur la face arrière, a été élaborée et les tests d'injection de la solution ont été un succès.This work presents the achievement of specific and original electronic devices (Field effect transistor with microfluidic channel), dedicated to the detection of chemical and biochemical species in liquid. This device relies on the technologies of suspended gate transistor, developed in IETR, with a major improvement in the structure by adjunction of a microfluidic channel integrated in the structure. This structure named transistor with integrated microfluidic channel must enable to guarantee the flow of liquid under the gate, while keeping the high sensitivity of the SGFET. This architecture also allows increasing its robustness and reliability while requiring only a very small amount of chemicals solutions. Microchannels with good mechanical properties were fabricated by surface micromachining using different materials as a sacrificial layer. These channels have been integrated into a FET and microfluidic accesses (inlet / outlet) were provided by making openings via the front face. Electrical tests showed good functioning of these sensors with high sensitivity of pH measurement. However in this case, liquid flow is mainly achieved by capillarity. An improvement on the architecture of the structure was made with opening on the rear face. A good behaviour with high sensitivity of pH measurement was presented. Finally, a hybrid structure containing one opening access in the front face and one on the rear face was elaborated and the injection of the solution was successful

OFDM-FBMC performance in presence of non-linear high power amplifier

Dans cette thèse une étude des performances des systèmes OFDM et FBMC/OQAM en présence d'amplificateur de puissance sans mémoire en terme de TEB est présentée. Ensuite, nous avons proposé une technique de linéarisation d'AP par pré-distorsion adaptative neuronale. Aussi, nous avons proposé deux techniques de correction des non-linéarités au niveau du récepteur.In our work, we have studied the impact of in-band non linear distortions caused by PA on both OFDM and FBMC/OQAM systems. A theoretical approach was proposed to evaluate the BER performance for the two systems. This approach is based on modeling the in-band non-linear distortion with a complex gain and an uncorrelated additive white Gaussian noise, given by the Bussgang theorem. Then, we have proposed different techniques to compensate this NLD either on the transmitter or the receiver sides