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Understanding mysteries of the material cohesion must pass through the mastery of the concept “chemical bonding”. However, the literature shows that the concept is perceived as abstract and difficult for students of all grade levels and academic .Among university students, in addition to the confusion caused by the plurality of chemical bonding models, the quantum approach is a source of major difficulties impeding the deep understanding of the concept. The research presented here consists of investigations with undergraduate students built around the fundamental concepts of the quantum model of the chemical bonding. The results show that the fundamental concepts of the quantum chemical bonding model are partially mastered.

For valorization and diversification of medicinal plants used in Comoros, we are interested in three species growth in this archipelago. Four essential oils were extracted from these plants and used in this study. Essential oils were obtained by hydrodistillation and analyzed by gas chromatography (GC) and GC–mass spectrometry (GC–MS). Sesquiterpene compounds are predominant in Piper borbonenseand Vetiveria zizanoidesessential oils but for Piper capenseessential oil, monoterpenes are predominant. Essential oils were investigated for their fungicidal activities against four fungi decay wood: Gloeophyllum trabeum(Persoon ex Fries) Murril (ATCC 11539), Poria placenta(Fries) Cooke sensu J. Eriksson (ATCC 9891), Coniophora puteana(Schumacher ex Fries) Karsten (ATCC 9351) and Coriolus versicolor(Linnaeus) Quélet (ATCC 12679). These essential oils showed an in important activity against all strains tested. However, the highest activity was observed in Vetiveriaand P. borbonenseessential oils.

The synthesis of two picket bismuth(III) porphyrins is reported, and their crystal structures are compared. The influence of the nature of the pickets, as well as their number, is discussed in terms of stability, kinetics of metalation, structure, and distortion of the porphyrin. Unexpectedly, the results indicate that the coordination sphere of bismuth is not affected by different types of distortion nor is the stability of the complex. For both types of complexes, the X-ray crystallography revealed that a single arm is actually in direct interaction with the bismuth cation, thereby allowing further functionalization on the porphyrin core as the linkage with immunoglobulins or anti-rabbit antibodies (both noted IgG), which have been used in diagnostic or therapeutic applications.

Thin films of rare earth oxides (REOs) have been deposited on stainless steel and quartz substrates by the metallo-organic chemical vapour deposition technique, using β-diketonate precursors. The structure and characteristics of the REO films were determined by scanning electron microscopy, X-ray diffraction, Auger electron spectroscopy, Secondary ion mass spectroscopy and X-ray photoelectron spectroscopy. The thicknesses of the coatings were determined by highly accurate weighing and by profilometry after a laser impact. Coated steel samples were oxidized at high temperature in isothermal and cyclic conditions to study the deposited rare earth element effect.

In this paper, an OMCVD method is used for local introduction of rare earth elements at chromia former alloy surfaces. Effect of such coatings on high temperature oxidation of two common stainless steels (AISI 304 and F17Ti) are comparatively tested in isothermal and cyclic conditions. In both cases, and particularly under cyclic conditions, a significant improvement of the high temperature behaviour is observed, depending on the rare earth element used for coating.

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The SiO2-CaO, SiO2-CaO-P2O5 and SiO2-CaO-P2O5-Ag2O glass systems were synthesized by the sol-gel technique and characterized with different techniques such as X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), and Environmental Scanning Electron Microscopy (ESEM). In vitro bioactivity tests were performed in Simulated Body Fluid (SBF). The antibacterial action of 65S5Ag (65%SiO2 + 24%CaO + 6%P2O5 + 5% Ag2O) is attributed exclusively to the leaching of Ag+ ions from the glass matrix. The activity of SiO2-CaO-P2O5-Ag2O was compared with that of its binary and ternary counterpart glass system. The concentrations of Ag-bioglass, in the range of 0.05 mg/mL of culture medium, were found to inhibit the growth of these bacteria.

Hydroxyapatite Ca10(PO4)6(OH)2 (HA) powder was successfully synthesized by a modified sol-gel method using a solution of calcium nitrate in ethanol, along with a solution of diammonium hydrogen phosphate in water and NH4OH as starting materials. The Ca/P molar ratio was maintained at 1.67. The powder was subjected to furnace and microwave heating to compare the decomposition of HA and study the crystallite sizes. It was found that microwave heated powders were pure HAP up to 230degC with absence of secondary phases. However, XRD patterns show that furnace heated powders convert completely to b-TCP when treated at 750degC and 1000degC. This result was confirmed by the absence of hydroxyl bands in the FT-IR spectra for these temperatures.