The group 11 metal adducts [HB{3‐(CF 3 ),5‐(CH 3 )Pz} 3 ]M(C 2 H 4 ) (M = Au, Ag, and Cu; Pz = pyrazolyl) have been synthesized via a metathesis process using [HB{3‐(CF 3 ),5‐(CH 3 )Pz} 3 ]Na and CF 3 SO 3 Cu, CF 3 SO 3 Ag, AuCl and ethylene. The related [HB{3‐(CF 3 ),5‐(Ph)Pz} 3 ]Ag(C 2 H 4 ) has also been synthesized using [HB{3‐(CF 3 ),5‐(Ph)Pz} 3 ]Na(THF), CF 3 SO 3 Ag and ethylene. These group 11 metal ethylene complexes are white solids and form colorless crystals. They have been characterized by NMR spectroscopy and X‐ray crystallography. The gold‐ethylene adduct [HB{3‐(CF 3 ),5‐(CH 3 )Pz} 3 ]Au(C 2 H 4 ) shows large upfield NMR shifts of the ethylene proton and carbon signals relative to the corresponding peaks of the free ethylene, indicating relatively high Au→ethylene backbonding. NMR chemical shift data suggest that the silver complexes of both the tris(pyrazolyl)borate ligands [HB{3‐(CF 3 ),5‐(CH 3 )Pz} 3 ] – and [HB{3‐(CF 3 ),5‐(Ph)Pz} 3 ] – exhibit the weakest interaction with ethylene as compared to the respective copper and gold complexes. X‐ray crystal structures reveal that the gold atom in [HB{3‐(CF 3 ),5‐(CH 3 )Pz} 3 ]Au(C 2 H 4 ) binds to scorpionate in κ 2 ‐fashion while the related silver adduct features a κ 3 ‐bonded scorpionate. [HB{3‐(CF 3 ),5‐(CH 3 )Pz} 3 ]Cu(C 2 H 4 ) has a scorpionate that binds to copper with two short Cu–N bonds and one long Cu–N distance.
Here we demonstrate the selective bulk scale synthesis of delaminated graphene sheets by a proper choice of magnetic field modulating an electric-arc.An ultra-high purity glassy graphite anode was sublimated in an argon atmosphere.Carbon nanotubes (CNTs), as well as graphene sheets were found inside the deposit formed on the cathode.Both the high purity CNTs as well as graphene sheets, with minimal structural defects, were synthesized separately by varying the strength and orientation of the external magnetic field generated by arrays of permanent magnets.The as-synthesized carbonaceous samples were characterized with the help of transmission electron microscopy, selected area electron diffraction (SAED), Raman spectroscopy (RS) and thermogravimetry for optimizing the highest selective production of delaminated graphenes.This optimization was done by varying the strength and orientation of the external magnetic field.The as-synthesized graphene sheets exhibited relatively high degree of graphitization and low structural defect density as confirmed by RS.They were found to exhibit higher oxidation temperature (767°C) than that of the carbon nanocrystalline (690°C) particles as inferred from the thermogravimatric analysis.Moreover, they were found to form 'scroll-like CNTs' at their edges on account of their surface energy minimization.This was confirmed by the SAED analysis.With this new technique, we could successfully synthesize delaminated graphenes at a rate of few g/h.
Nanocrystalline ZrO2 powder was synthesized by dc transferred arc thermal plasma reactor by homogeneous gas phase condensation mechanism. ZrO2 is an oxide ceramic with a high melting point, good chemical resistance and high mechanical strength. When doped with certain oxides, ZrO2 shows high ionic conductivity. ZrO2 is also recognized as a superior thermal barrier material. Thermal plasma synthesis of oxide nano materials shows pressure dependent crystalline phase and crystallite size. The X-ray diffraction analysis clearly shows that as the ambient oxygen gas pressure increases from 100 Torr to 1000 Torr the abundance of tetragonal phase goes on increasing. The morphology of the as synthesized ZrO2 powder was found to be spherical and independent on the ambient gas pressure as seen from the Scanning Electron Microscopy studies. The specific surface area of powder was calculated using the nitrogen gas adsorption Brunauer, Emmett, Teller surface area analysis technique and found no much variation.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
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