Influence of Thermal Treatment on Kankara Kaolinite

In this work, the influence of thermal treatment on the structure of Kankara kaolinite was studied for the first time, using X-ray diffractogram (XRD), EDX, NanoSEM, FTIR-Attenuated Total Reflectance, DTA/TGA and BET surface area measurements. The treatment temperatures applied represents the peak of the transformation stages. The results show that surface area decreases with increase in temperature of treatment, while its crystal structure was transformed from the native kaolinite structure via the amorphous metakaolin to the typical mullite/crystobalite structure though with some unidentifiable peaks. The morphological studies showed that Kankara kaolinite is composed of nano-platelets of about 30nm thickness and in bundles of between 1 – 3 µm thicknesses with some marked variations/reductions as the treatment temperatures increases. The DTA/TGA result shows that the kaolinite undergoes dehydroxylation at 528.560C while been converted to metakaolin with a weight loss of about 14.4%. The presence of the characteristic OH, Al-OH, Si-OH and Si-O-Al bands were confirmed with the ATR studies which also showed the disappearance and subsequent appearance of new bands as the treatment temperature increased, this also affected the surface area and pore sizes of the transformation products

The Effect of Synthesis Parameters on the Catalytic Synthesis of Multiwalled Carbon Nanotubes using Fe-Co/CaCO3 Catalysts

Fe-Co bimetallic catalysts supported on CaCO3 were prepared by a wet impregnation, a deposition-precipitation and a reverse micelle method. The sizes of the Fe and Co particles were not affected by the Fe and Co sources (nitrate, acetate) when the wet impregnation and deposition-precipitation methods were used. ‘Clean’ multi-walled carbon nanotubes (MWCNTs) were obtained from all three Fe-Co synthesis procedures under optimal reaction conditions. The CNTs produced gave yields ranging from 623 % to 1215 % in 1 h under the optimal conditions, with similar outer diameters (o.d.) of 20–30 nm and inner diameters (i.d.) ~10 nm. The Fe/Co catalyst formedin the wet impregnation method revealed that the yield, diameter and purity of the CNTs were influenced by the C2H2/N2 ratio, time and temperature. All the methods gave high-quality CNTs after short reaction times but the quality deteriorated as the synthesis time was increased from 5 to 360 min. Indeed, the most influential parameter in controlling CNT purity, length and o.d. was found to be the synthesis time. The as-synthesized CNTs were purified using a single-step mild acid treatment process (30 % HNO3), which readily removed the support and metal particles.Keywords: Carbon nanotubes, synthesis, bimetallic catalyst, iron, cobaltPDF and Supplementry file attache

The Synthesis of Nitrogen-Doped Multiwalled Carbon Nanotubes Using an Fe-Co/CaCO3 Catalyst

ACVDmethod was used to prepare high-quality nitrogen-doped multiwalled carbon nanotubes (N-MWCNTs) using acetonitrile as the nitrogen and carbon source and acetylene as a carbon source over an Fe-Co/CaCO3 catalyst in the temperature range 700–850 °C. This represents a continuation of earlier work in which Fe-Co on CaCO3 was used to make undoped carbon nanotubes. The effect of synthesis parameters (growth temperature and CH3CN vaporization temperature) on the yield, size, quality, morphology and thermal stability of the N-MWCNTs was studied. The resulting materials were characterized by TEM,SEM, TGA, BET, XPS, CN elemental analysis and Raman spectroscopy. TEM analysis revealed that the nanotubes exhibit bamboo-like structures with rough surfaces and a relatively uniform diameter. The bamboo compartment distance decreased with increase in synthesis temperature due to the increased nitrogen content inN-MWCNTs. The SEM examination showed that at high synthesis temperatures carbon spheres (CSs) with chain-like morphology and large sizes were also formed along with the N-MWCNTs. The XPS and CN elemental analysis revealed that nitrogen atoms were successfully doped into the carbon walls. The amount of nitrogen incorporated in the N-MWCNTs varied with increasing growth time and CH3CN vaporization temperature.Keywords: Carbon nanotubes, CVD synthesis, nitrogen doping, acetonitrile, Fe-Co/CaCO3 catalyst PDF and supplemetary file attached

The Design of Group 4 Cyclopentadienyl, Olefin-Polymerisation Catalysts

This review focuses on Group 4 metallocenes and their use in the polymerisation of _-olefins. A brief overview of their history as well as theories concerning the mechanistic details of the polymerisation reaction precedes a discussion on the design of these polymerisation catalysts. This latter section will cover what effect metal, ligand and bridge choice has on polymerisation activity and the physical properties of the polymer produced. A major drawback to the use of these catalysts in industrial processes is related to the cost of their synthesis, the major problem here being the formation of an unwanted diastereomer during the synthetic process. The techniques employed to overcome these problems are therefore also reviewed. Lastly, the large volume of literature dealing with these catalysts makes it difficult to compare the polymerisation data of different catalysts and laboratories. The review therefore contains tables that attempt to collect the details of the most important polymerisation studies in a comparable and easy to reference manner South African Journal of Chemistry Vol.54 2001: 118-22

Solventless Substitution Reaction of Solid Phosphine Ligands with Ru(C5H4R)(CO)2I (R = H, Me)

The solventless reaction between Ru(C5H4R)(CO)2I (R = H, Me) and solid phosphine ligands [PPh3, P(p-MeOC6H4)3, P(m-MeC6H4)3, P(p-FC6H4)3, P(p-ClC6H4)3] was undertaken at various temperatures with all the reactions occurring in the melt phase. The reaction rates and type of products isolated are dependent on the electronic properties of the Cp-substituent and the para-substituent on the phosphine ligands. For the C5H4R moiety, when R = H the ligand substitution product Ru(C5H5)(CO)(PR3)I was obtained, and the ligand addition product [Ru(C5H4Me)(CO)2(PR3)]I was predominantly obtained when R = Me. The reaction rates are enhanced by para-substituted electron-donating phosphines. These results are similar to those obtained from studies utilizing benzene and xylene as solvents. The products have been characterized by FTIR and NMR spectroscopy and by MS. The complex Fe2(C5H5)2(CO)4 was found to act as a catalyst in all the melt reactions.Keywords: Solvent-free, ruthenium, cyclopentadienyl complexes, phosphinesPDF and Supplementry file attache

Tubular shaped composites made from polythiophene covalently linked to Prato functionalized N-doped carbon nanotubes

NatuurwetenskappeChemie & PolimeerwetenskapPlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]

Nanocomposites of gold and poly(3-hexylthiophene) containing fullerene moieties: Synthesis, characterization and application in solar cells

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Synthesis and characterization of single wall carbon nanotube-grafted poly(3-hexylthiophene) and their nanocomposites with gold nanoparticles

Please help populate SUNScholar with the full text of SU research output. Also - should you need this item urgently, please send us the details and we will try to get hold of the full text as quick possible. E-mail to [email protected]. Thank you.Journal Articles (subsidised)NatuurwetenskappeChemie & Polimeerwetenska

Synthesis of C-60-containing Polymers by Ring-opening Metathesis Co-polymerization of a C-60-cyclopentadiene Cycloadduct and N-(cycloheptyl)-endo-norbornene-5,6-dicarboximide and their Application in a Photovoltaic Device

A C-60-cyclopentadiene cycloadduct and N-(cycloheptyl)-endo-norbornene-5,6-dicarboximide were utilized as co-monomers in ring-opening metathesis polymerization (ROMP) reactions to afford a series of polymers containing C-60 in varying ratios. The polymerization reactions were catalyzed by the Grubbs second-generation ruthenium catalyst, and the co-polymers formed were investigated by spectroscopic and thermal techniques. The photovoltaic behavior of the new materials was studied by the construction of a simple sandwich-type photovoltaic cell. Under irradiation we concluded that the C-60 in the copolymers simultaneously accelerated both the charge separation in the polymer and the charge recombination between the electrons in the TiO2 and the electrolyte.213198212DST/NRF Centre of Excellence in Strong Materials,NRF [GUN 2053652]University of the Witwatersrand (University and Science Faculty Research Councils)NRF [GUN 2053652

Synthesis of C₆₀-containing polymers by ring-opening metathesis co-polymerization of a C₆₀-cyclopentadiene cycloadduct and <i>N</i>-(cycloheptyl)-<i>endo</i>-norbornene-5,6-dicarboximide and their application in a photovoltaic device

Please help populate SUNScholar with the full text of SU research output. Also - should you need this item urgently, please send us the details and we will try to get hold of the full text as quick possible. E-mail to [email protected]. Thank you.Journal Articles (subsidised)NatuurwetenskappeChemie & Polimeerwetenska