Cracking cone fracture after cold compaction of argillaceous particles

Cold uniaxial pressing of powder into a green body is a common forming process used in ceramic and pharmaceutical industries. Argillaceous particles are used as a model system to investigate granule failure during compaction. Indeed, the volume enclosed between the die and punches is reduced and the powder consolidates until a final height is obtained or a prescribed compacting pressure is reached. Desired properties of the green body are high strength, uniform density, no defects and fracture. In this work an experimental investigation has been focused on the ‘cracking cone’ fracture in powder compacts. This includes studies of crack propagation and determination of operating conditions to avoid the green body fracture. The numerical modelling is implemented using a finite element method based on the Von Mises criterion. A case of simulation is presented to demonstrate the ability of the model to compute the distribution of the relative stresses.     

Preparation and characterization of CeO2–TiO2 support for Ru catalysts: Application in CWAO of p-hydroxybenzoic acid

The catalytic wet air oxidation of aqueous solutions of p-hydroxybenzoic acid has been carried out over CeO₂–TiO₂ supported ruthenium catalysts (Ru/Ce–Ti) at 140 °C and 50 bar of air. High activity of ruthenium supported catalysts was observed. It was found that the decrease of the molar ratio Ce/Ti from 3 to 1/3, improves the activity of Ru catalysts. The activity of the samples decreases in the following order: Ru/Ce–Ti (1/3) > Ru/CeO₂ ≈ Ru/TiO₂ > Ru/TiO₂DT51. Characterization of samples was performed by means of N₂ adsorption–desorption, XRD, UV–visible, TPR, SEM and TEM.     

NUMERICAL STUDY OF FLOW AROUND AN OSCILLATING DIAMOND PRISM AND CIRCULAR CYLINDER AT LOW KEULEGAN-CARPENTER NUMBER

In order to identify the influence of shape corners on the instantaneous forces in the case of oscillating bodies, the simulated flow field is compared for two kinds of cross sections: diamond prism and circular cylinder. For these two flow configurations, the same Reynolds number and a Keulegan-Carpenter are considered. To compute the dynamic flow field surrounding the body, the Navier-Stokes transport equations in a non-inertial reference frame attached to the body are considered. Hence, a source term is added locally to the momentum equation to take into account the body acceleration. The proposed model is solved using the PHOENICS code. For the oscillating circular cylinder, the simulated results are in good agreement with the experimental data available in the litterature. After validation of this proposed model, flow field for diamond prism is determined. For both bodies, the process of the vortex formation is similar, with the formation of a recirculation zone in the near-wake containing a symmetric pair of vortices of equal strength and opposite rotation. The length of recirculation zone varies approximately linearly with time. However, the in-line force coefficient of the oscillating diamond prism is found to be greatest, since the recirculation zone is longer compared with that of the oscillating circular cylinder.     

Multi-scales modelling of dynamic behaviour for discontinuous fibre SMC composites

The requirements of passive security, notably in the transport industry, impose to maximize the dissipation of the energy and to minimize the decelerations undergone by a vehicle and thus passengers due to violent shocks (crash). This paper aims at establishing efficient expected answers towards the preoccupations mainly emanating from transport industry. Currently, the behaviour laws implemented in the dynamic explicit schemes (RADIOSS, PAM-CRASH and LS-DYNA) do not integrate sufficiently the physical aspects in the material degradation, mainly the damage process, their kinetics, the variability and especially the heterogeneity of the composite materials microstructure. This paper deals with the development of a multi-scale predictive model coupling specific experimental methodologies and the micromechanical formulation of damage mechanisms in order to build constitutive laws for discontinuous fibre reinforced composites materials. The developed micromechanical modelling is based on an experimental methodology conducted over a range of strain rates from quasi static to 250 s⁻¹. The latter has enabled identifying local probabilistic damage criterion formulated through the Weibull’s statistical integrating the strain rate effect and describing the progressive interfacial debonding under rapid loading. The developed model has been validated to predict the stiffness reduction and the overall elastic visco-damage behaviour for SMC composite material. The model simulations agree well with high speed tensile tests and confirm that the damage threshold and kinetic in the SMC are mainly strain rate sensitive.     

Removal of organic load and phenolic compounds from olive mill wastewater by Fenton oxidation with zero-valent iron

Pre-treatment of olive mill wastewater (OMW) by Fenton Oxidation with zero-valent iron and hydrogen peroxide was investigated to improve phenolic compounds degradation and the chemical oxygen demand (COD) removal. Experimental procedure is performed with diluted OMW with COD 19 g/L and pH 5.2. The application of zero-valent Fe/H₂O₂ procedure allows high removal efficiency of pollutants from OMW. The optimal experimental conditions were found to be continuous presence of iron metal, acidic pH (2–4) and 1 M hydrogen peroxide solution. The experimental results show that the removal of 1 g of COD need 0.06 M of H₂O₂. At pH 1, the maximum COD removal (78%) is achieved after 1 h. Therefore, with a pH value within 2 and 4 the maximum COD removal reached 92%. Phenolic compounds are identified in treated and untreated OMW by gas chromatography coupled to mass spectrometry (GC–MS). The result shows a total degradation of phenolic compounds and an increasing biodegradability of treated OMW.     

Olive mill wastewater degradation by Fenton oxidation with zero-valent iron and hydrogen peroxide

The degradation of olive mill wastewater (OMW) with hydroxyl radicals generated from zero-valent iron and hydrogen peroxide has been investigated by means of chemical oxygen demand (COD) and phenolic compounds analyses. The effects of the H2O2 dose, the pH and the organic matter concentration have been studied. The optimal experimental conditions were found to have continuous presence of iron metal, acid pH (2.0-4.0), and relatively concentrated hydrogen peroxide (9.5M). Coloration of OMW disappeared and phenolic compound decreased to 50% of initial concentration after 3h reaction time. The application of zero-valent Fe/H2O2 procedure permitted high removal efficiencies of pollutants from olive mill wastewater. The results show that zero-valent Fe/H2O2 could be considered as an effective alternative solution for the treatment of OMW or may be combined with a classical biological process to achieve high quality of effluent water.     

Combustion with mixed enrichment of oxygen and hydrogen in lean regime

A low global richness of combustion is interesting from an ecological and economic point of view as it helps to limit fuel consumption. In fact, the consequences of the combustion in poor mode are the appearance of local or global flame extinctions, energy loss by radiation and change in flame structure. The flammability limits of the diffusion methane flame can be resolved by the enrichment of the combustion air with oxygen or the use of the pure oxygen as oxidant as well as the addition to hydrogen in natural gas. Moreover, the use of oxygen and hydrogen as previously mentioned allow working in low ranges of richness while maintaining good flame stability. For a constant burner power of 15 kW, the reduction of the richness involves an increase in the oxidizer flow rate injected into the combustion reaction. In this present study, the variation of the richness, the fuel enrichment with hydrogen and the oxidant enrichment with oxygen are shown as major parameters where they have direct influences on the flow dynamic, the flame structure and the pollutant emissions.The Chemiluminescence of OH* radical and the PIV (Particle image velocimetry) are used in this work to characterize the flame structure, the stability and the dynamics of the flame. The measurement of pollutant emissions effected by a gas analyzer. The enrichment in oxygen and hydrogen provides a stable flame, which is well attached to the burner for the following richness values: 0.7, 0.8, 0.9 and 1. The reduction of the richness promotes the mixture quality of the reactants and leads a reduction in CO₂ and CO concentration. By contrast, the decrease of the richness supports the formation of NOx.     

Sol–gel reverse micelle preparation and characterization of N-doped TiO2: Efficient photocatalytic degradation of methylene blue in water under visible light

A series of N-substituted titanium (IV) 2-ethyl-1,3-hexanediolate Ti(C₃₂H₆₈O₈) precursor were synthesized by the sol–gel reverse micelle (SGRM) method. The ethylene diaminetetraacetic acid (Na₂EDTA) has been used as a source of nitrogen n species. The obtained solids were calcined at 500 ?C for 1 h to obtain photoactive phases. The effect of nitrogen content (N/Ti = 0.025; 0.03; 0.05 atomic ratios) is examined. The materials were characterized by XRD, BET, TG/DTA and UV–vis reflectance spectroscopy (DRS). Photocatalytic decolourisation of methylen blue (MB) in aqueous solution was carried out using nano, doped TiO₂. Experimental results revealed that N/Ti = 0.05 atomic ratio N-doped TiO₂ required shorter irradiation time for complete decolourisation of MB than pure nano TiO₂ and commercial (Degussa P-25) TiO₂.     

Integrated geo-microbial and trace metal anomalies for recognition of hydrocarbon microseepage in petroliferous regions: case of El Hajeb oilfield in the South East of Tunisia

Abstract

In this work we attempt to identify the geomicrobial fingerprints alongside with trace metals anomalies, and to explore whether the geomicrobial signatures are correlated with trace metals in El Hajeb oilfield in Tunisia. 51 soil samples are collected in grid pattern of 1?×?1?km interval. After incubating soil samples with propane in mineral salt medium, we count the propane oxidizing bacteria abundance ranged from nil to 2.44?×?10⁵ cfu/g of soil sample. It was found that the concentrations of trace elements are enormously increased when they are compared with the natural background concentrations of metals in soils.     

Investigation of dyes degradation intermediates with <Emphasis Type="Italic">Scytalidium thermophilum</Emphasis> laccase

Scytalidium thermophilum laccase was able to successfully decolourise Congo Red, Bromo-Cresol Green, Malachite Green, Phenol Red and Indigo Carmine under optimised conditions. The cited dyes belonging to three different classes were named azo, triarylmethane and indigoid. The decolourisation rates were 100, 95, 76, 57 and 22 mg h⁻¹ U⁻¹ for Indigo Carmine, Malachite Green, Bromo-Cresol Green, Congo Red and Phenol Red, respectively. The degradation products were characterised by UV–vis and FT-IR techniques, and their cytotoxicity was monitored. UV–visible absorption spectra and FT-IR analysis showed a complete degradation of Congo Red, Bromo-Cresol Green and Malachite Green, a partial degradation of Phenol Red and a transformation of Indigo Carmine. Toxicity study revealed that most of the treated dyes were less toxic than those before treatment, especially for Malachite Green. In fact, Scytalidium thermophilum laccase degraded Malachite Green into non-toxic products. Scytalidium thermophilum laccase constitutes a powerful tool for effective bioremediation of rich-dye textile effluents and was, therefore, found worthy of investigation for potential applications in restoration work and other biotechnological uses.