Evaluation of genetic diversity among Tunisian grapevines by RAPD markers

Thirty-three native Tunisian grapevine varieties (Vitis vinifera L.), previously analysed with biochemical tools, were surveyed with RAPD markers, Eleven primers amplified 54 clear and unambiguous markers. Five groups of varieties were clearly resolved by UPGMA cluster analysis. These results allowed the discrimination of groups of varieties that could not be discriminated by biochemical analyses. In addition, the dendrogram obtained could be shown being independent from both the phenotypic characters and the origin of the accessions.

Synthesis and microstructure of cobalt ferrite nanoparticles

International audienceCobalt ferrites (CoxFe3-xO4) nanoparticles with various compositions were synthesized by a new non-aqueous synthesis method. The cobalt ferrites were characterized by X-rays diffraction, and transmission electron microscopy coupled with energy dispersive spectroscopy. The nanoparticles are highly crystallized, with a homogeneous chemical composition. The particle size varies from 4 nm up to 7.5 nm, depending on the cobalt content. The smallest particles, with a size of 4 nm, are obtained for high cobalt content. These particles have also the highest micro-structural strain. Catalytic measurements were realized using Fourier Transform Infrared Spectroscopy. The lowest activation energy and the highest conversion rate are obtained for Co1.8Fe2.4O4, in the 400-500°C temperature range

Effect of Fe substitution on structural and magnetic properties of Pr2Co7-xFex compounds

This work focuses on the synthesis, structure, and magnetic properties of Pr-Co-Fe compounds. Our previous study of Pr2Co7 alloys with high coercivity is shown that for samples annealed at Ta= 800 °C, the main phase is hexagonal of the Ce2Ni7 type structure. This leads to the formation of a magnetically hard Pr2Co7 phase; the coercivity being equal to 18 kOe at 293 K and 23 kOe at 10 K and important saturation magnetization. These performances are due to the combination of the complementary characteristics of 3d-itinerant and 4f-localized magnetism of Co and Pr, respectively. Its Curie temperature is about 600 K. The aim of this study is to follow the effect of partial substitution of Co by Fe on Pr2Co7-xFex structural and magnetic properties, where x =0.25, 0.50, 0.75 and 1. These compounds were synthesized by mechanical alloying. The Rietveld analysis of DRX shows that these intermetallics, annealed at Ta = 700 °C, adopt mainly hexagonal Ce2Ni7 type structure with P63/mmc group space. Moreover, it points out a lattice expansion along the c axis after Fe substitution for Co. Furthermore, these hexagonal phases possess magnetic properties more attractive than Pr2Co7, the Curie temperatures are higher than Pr2Co7 ones and the highest is obtained for x = 0.5 where TC = 760 K. This increase is due to the well-known electronic effect that invokes the reduction of antiferromagnetic coupling. These phases are particularly promising for permanent magnet applications

Effect of Fe substitution on structural and magnetic properties of Pr 2

This work focuses on the synthesis, structure, and magnetic properties of Pr-Co-Fe compounds. Our previous study of Pr2Co7 alloys with high coercivity is shown that for samples annealed at Ta= 800 °C, the main phase is hexagonal of the Ce2Ni7 type structure. This leads to the formation of a magnetically hard Pr2Co7 phase; the coercivity being equal to 18 kOe at 293 K and 23 kOe at 10 K and important saturation magnetization. These performances are due to the combination of the complementary characteristics of 3d-itinerant and 4f-localized magnetism of Co and Pr, respectively. Its Curie temperature is about 600 K. The aim of this study is to follow the effect of partial substitution of Co by Fe on Pr2Co7-xFex structural and magnetic properties, where x =0.25, 0.50, 0.75 and 1. These compounds were synthesized by mechanical alloying. The Rietveld analysis of DRX shows that these intermetallics, annealed at Ta = 700 °C, adopt mainly hexagonal Ce2Ni7 type structure with P63/mmc group space. Moreover, it points out a lattice expansion along the c axis after Fe substitution for Co. Furthermore, these hexagonal phases possess magnetic properties more attractive than Pr2Co7, the Curie temperatures are higher than Pr2Co7 ones and the highest is obtained for x = 0.5 where TC = 760 K. This increase is due to the well-known electronic effect that invokes the reduction of antiferromagnetic coupling. These phases are particularly promising for permanent magnet applications

Impact of carbon insertion on the microstructure and magnetic properties of nanocrystalline Pr2Co7 alloys

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Effect of stacking blocks on the low field magnetic refrigeration in nanocrystalline Pr2Co7 compound

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