Eco-friendly Geopolymer Composite Based on Non-heat-treated Phosphate Sludge Reinforced With Polypropylene Fibers

Silicon - Geopolymers produced with metakaolin (MK) and thermally untreated phosphate sludge (PS) are beneficial and environmentally advantageous materials, but their fragility limits its...     

Effect of toluene proportion on the yield and composition of oils obtained by supercritical extraction of Moroccan oil shale

Supercritical extraction of Tarfaya's oil shale by toluene revealed that the solvent proportion has a significant effect on the yield and the composition of the obtained oils. The analyses carried out on the recovered oils allowed to establish the optimal operating conditions giving the highest oil yields. In addition, it was observed that these oils contain a large proportion of aromatics compounds.     

Properties of metakaolin based geopolymer incorporating calcium carbonate

An alkaline solution, thermally activated kaolinite clay and a mineral additive (calcium carbonate) were mixed with the aim to elaborate a geopolymer material with physical and mechanical properties comparable to those of classical construction materials.The starting reagents were characterized by quantitative chemical analyses (XRF), mineralogical analyses (XRD), thermal gravimetric analyses (TGA), and grain size distribution measurements. The setting of the mixture (polymerization) was implemented by measuring the evolution of the viscosity as a function of time at different temperatures.The geopolymers were synthesized at a temperature of 40 °C. The investigation of the mechanical behavior reveals that these materials display acceptable characteristics: the flexural and compression strength are around 4.6 and 26 MPa respectively, for an added calcium carbonate over dry matter ration up to 12% by weight.The promising results exposed in this paper show that the geopolymer formulations can be adapted for applications in construction and civil engineering structures as an alternative to conventional materials.     

Influence of the experimental conditions on porosity and structure of adsorbents elaborated from Moroccan oil shale of Timahdit by chemical activation

This study records experiments undertaken to determine the suitable conditions for the use of the oil shale of Timahdit, as an adsorbent for water treatment. A simple process was proposed based on chemical activation. The preparation has been carried out by carbonization after impregnation of the precursor with phosphoric acid. The effect of different conditions of preparation on the specific surface area is discussed. These parameters are H3PO4/shale weight ratio, carbonization temperature, carbonization time and concentration of H3PO4. The properties and surface structure of the adsorbent were investigated by XPS and FT-IR. Their total surface acidity and basicity were also determined. The retention process of methylene blue (MB) by adsorbents has been studied. It was found that MHP2 and MHP7 have relatively high retention ability as compared to activated carbons.     

Production of activated carbon from a new precursor molasses by activation with sulphuric acid

Activated carbon has been prepared from molasses, a natural precursor of vegetable origin resulting from the sugar industry in Morocco. The preparation of the activated carbon from the molasses has been carried out by impregnation of the precursor with sulphuric acid, followed by carbonisation at varying conditions (temperature and gas coverage) in order to optimize preparation parameters. The influence of activation conditions was investigated by determination of adsorption capacity of methylene blue and iodine, the BET surface area, and the pore volume of the activated carbon were determined while the micropore volume was determined by the Dubinin-Radushkevich (DR) equation. The activated materials are mainly microporous and reveal the type I isotherm of the Brunauer classification for nitrogen adsorption. The activated carbons properties in this study were found for activation of the mixture (molasses/sulphuric acid) in steam at 750 degrees C. The samples obtained in this condition were highly microporous, with high surface area (> or =1200 m2/g) and the maximum adsorption capacity of methylene blue and iodine were 435 and 1430 mg/g, respectively.     

Mechanical behaviour in compression loading of 2D-composite materials made of carbon fabrics and a ceramic matrix

2D-carbon-carbon/ceramic composites, made from a 2D-carbon-carbon (2D-C-C) porous preform infiltrated with BN, SiC, TiC or B₄C, are mechanically characterized under compression loading in directions parallel or orthogonal to the carbon fabric layers. Three types of behaviour are observed: non-linear and time dependent behaviour, a quasi-linear domain and a pseudo-plastic behaviour related to damaging mechanisms. Underp-compression, the variations of the Young modulus as a function of compacity obey a parabolic or linear law depending on whether the material is weakly or highly densified. Undero-compression, an exponential law is observed whatever the densification degree. The variations of failure strength compacity follow similar laws. Phenomenological models are given which depict quite well the mechanical behaviours of the composites. Undero-compression, failure occurs as the result of damaging mechanisms taking place within the inter-layer ceramic bridges binding the fabric layers together. Underp-compression, a transition is observed, from interlayer delamination to intralayer failure, for a critical compacity of about 0.85 provided the infiltrated ceramic is strong enough (i.e. for SiC and TiC). Such a transition is assumed to also occur for 2D-C-C/B ₄ ^– C composites. On the contrary, for weak ceramic matrices (e.g. BN), failure inp-compression always occurs by delamination. The results suggest that the composite toughness could be increased by an optimization of the composite microstructure.     

Composite materials made from a porous 2D-carbon-carbon preform densified with boron nitride by chemical vapour infiltration

2D-C-C/BN composites (with a BN volume fraction (V _BN) up to 0.60) have been obtained by chemical vapour infiltration of hexagonal-BN from a BF₃-NH₃ mixture, within the pores of a 2D-C-C preform made of a stacking of carbon fabric layers which has been weakly consolidated with pyrocarbon. They were tested in compression on samples with the carbon fabric layers directed either parallel or perpendicular to the load axis. In the first case (p-direction), the compression behaviour is mainly elastic (at least for high enoughV _BN). Bothσ _∥ ^R andE _∥ increase regularly with risingV _BN, as the BN-layer deposited within the pores of the preform (mainly located between adjacent carbon layers) becomes thicker,ε _∥ ^R is weak and progressively decreases with increasingV _BN. In the second case (o-direction), the stress-strain curve exhibits both elastic and pseudoplastic domains whose respective extension depends onV _BN (or onV _p). The pseudoplastic behaviour is related to an irreversible microstructural damage of the interlayer C/BN filling.σ _⊥ ^R ,σ _⊥ ^E andE _⊥ increase with increasingV _BN (or decreasingV _p) according to parabolic laws,ε _⊥ ^R is much higher thanε _∥ ^R . The materials remain anisotropic even at highV _BN. Oxidation tests in air (or oxygen/argon mixtures) have shown that 2D-C-C/BN, incompletely densified (V _p ∼ 0.10) by BN, exhibit a weight loss (oxidation of the carbon skeleton) at low temperatures and a weight increase (oxidation of BN) above 900° C. Oxidation resistance is enhanced by increasingV _BN (which results in aV _p decrease) and decreasing oxygen partial pressure. It is predicted that a good oxidation protection of the carbon skeleton requires a full densification by BN (V _p ∼ 0) and will be effective at medium temperatures. The results of the present study could be easily extended to 2D-BN-BN composites.