Fine structure of lignitous coals

The adsorption of nitrogen at 78°K and 195°K, as well as adsorption of carbon dioxide at 78°K, 273°K and 298°K was measured on non-activated and activated Beda lignitous coals. The original lignite sample was thermally heated at 400°, 500°, 600° and 800°. The sample was activated either with 10 and 25 per cent zinc chloride or with steam to burn-outs of 10 and 25 per cent. Zinc chloride activation increases the adsorption capacity and micropore volume but does not affect the pore size. Steam activation on the other hand, produces the same effect as zinc chloride activation in its initial stages and at a certain stage, gasification with steam also widens the already existing pores altering thus the porous structure of the material.     

Arsenic sorption on TiO2 nanoparticles: Size and crystallinity effects

Single solute As (III) and As (V) sorption on nano-sized amorphous and crystalline TiO₂ was investigated to determine: size and crystallinity effects on arsenic sorption capacities, possible As (III) oxidation, and the nature of surface complexes. Amorphous and crystalline nanoparticles were prepared using sol-gel synthesis techniques. For amorphous TiO₂, solute pH in the range of 4-9 had a profound impact on only As (V) sorption. As (III) and As (V) sorption isotherms indicated that sorption capacities of the different TiO₂ polymorphs were dependent on the sorption site density, surface area (particle size) and crystalline structure. When normalized to surface area, As (III) surface coverage on the TiO₂ surface remained almost constant for particles between 5 and 20 nm. However, As (V) surface coverage increased with the degree of crystallinity. X-ray absorption spectroscopic analysis provided evidence of partial As (III) oxidation on amorphous TiO₂ rather than crystalline TiO₂. The data also indicated that As (III) and As (V) form binuclear bidentate inner-sphere complexes with amorphous TiO₂ at neutral pH.     

Comparative Study of Fatty Acid Composition,Total Phenolics,and Antioxidant Capacity in Rapeseed Mutant Lines

There is limited variability within rapeseed germplasm in Morocco. Induced mutation was recently used to generate novel genetic variability and develop mutant lines combining desirable traits. In this context, nine promising advanced rapeseed M₂ mutant lines and the wild-type variety “INRA-CZH2” were evaluated for their seed oil content, fatty acid composition, total phenolic content (TPC), and free-radical scavenging activity (FRSA) by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 3-ethylbenzothiazoline-6-sulfonic acid (ABTS) methods. The results showed significant variability among all mutants in seed oil content (38.14–42.04%) and fatty acids (SAFA = 5.49–10.99%, MUFA = 50.33–71.62%, PUFA = 22.89–8.68%). The mutant H2M-5 exhibited the highest fraction of MUFA and the lowest proportion of SAFA and PUFA, while the mutant H2M-4 showed the highest SAFA and PUFA amounts and the lowest MUFA level. TPC varied from 2.16 to 4.35 mg GAE/100 g. The highest amount was found in the mutant H2M-1, which is about twice that of other mutants and the wild-type variety. FRSA differed significantly among the samples, and the variations observed for DPPH and ABTS methods were 40.5–59.28% and 40.31–59.86%, respectively. FRSA was positively correlated to TPC in the sampled oils (r = 0.801 and 0.802, P < 0.01). This is the first report emphasizing the biochemical potential of rapeseed varieties and novel mutants in Morocco. H2M-1, H2M-4, and H2M-5 were proposed for the Rapeseed National Breeding Program, as they showed higher levels in some biochemical traits of interest.     

Re-examination of the β→γ transformation of Ca2SiO4

Dicalcium silicate finds applications in different fields (cement, bio-ceramics, refractories). In the case of Portland cement, its interest is its lower sintering temperature compared to tricalcium silicate and therefore an interesting compound for low CO₂ cements. Dicalcium silicate goes through different polymorphic forms, namely α, α'_H, α'_L, β and γ, as the temperature decreases. In theory, only the γ-phase is stable at room temperature. In a polycrystalline material, the different polymorphs can co-exist depending on several factors (sintering conditions, presence of impurities, grain size) and the interpretations given in the literature are sometimes contradictory. For cement applications, only the α, α' or β polymorphs react with water to give hydrates while γ does not. Therefore, this paper focuses specifically on the effect of grain size on the β to γ transformation. We also propose that the transformation is semi-reconstructive and not martensitic as suggested by some authors.     

Characteristics of heat transfer and fluid flow in a channel with single-row plates array oblique to flow direction for photovoltaic/thermal system

This study has been carried out to investigate the characteristics of convective heat transfer and fluid flow for a single row of oblique plates array to the flow direction inside a channel. The flow inside the channel is laminar and the plates array have spanwise distance between the plates and heated by radiation. This configuration has been designed to be used for Photovoltaic/Thermal system (PV/T) applications. The theoretical results are validated with measured values, and a good agreement prevailed. The results show that an increase in the plate oblique angle (γ) in the range from 0 to 15 degrees, leads to an increase in the Nusselt number (Nu) up to a maximum value and then decreases. The oblique angle at the maximum value of Nu depends on the flow Reynolds Number (Re), and (?_w/?_pl), where (?_w/?_pl) is defined as the ratio of the plates’ spacing at zero oblique angle to the plate length. Furthermore, increasing (?_w/?_pl) results in a significant increase in the heat transfer coefficient depending on the values of Re, and plate oblique angle (γ). In addition, increasing (γ) from 0 to 15 degrees results in a decrease in the friction factor up to a certain value, after which the friction value approaches a constant value depending on Re value and (?_w/?_pl). It was found that for any value of the plate oblique angle (γ), the friction factor decreases with the increase of the values of (?_w/?_pl) and Re, respectively.     

Dispersion of cellulose crystallites by nonionic surfactants in a hydrophobic polymer matrix

Cellulose nanoparticles obtained by acid hydrolysis of cellulose paper were used to reinforce polystyrene composite films. The nonionic surfactant sorbitan monostearate was utilized to improve the dispersion properties of the hydrophilic cellulose in hydrophobic matrix and to prevent the formation of aggregates. Turbidity tests were used to measure dispersion stability of the cellulose crystallites in the hydrophobic solvent used in the composite manufacture. A correlation was found between the dispersion stability in solvent and the formation of aggregates in the polymeric composites. Nanocomposite films were processed using a casting/evaporation technique. Thermal and mechanical properties of processed composites were studied by differential scanning calorimetry (DSC) and dynamical mechanical analyses (DMA), respectively. The results showed that the optimum addition of surfactant produced better dispersion of the cellulose particles in the polystyrene matrix and improved the mechanical properties of the resulting composite due to an enhanced compatibility. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers