Processing of nanostructured WC-Co and W-Co powders,modelling of Fe-Mn-Si alloy, swelling of Fe-Cu alloy, andmechanical properties and sintering of Fe-Mn-Si steels havebeen studied in the present thesis. W-Co precursors made by chemical synthesis were used toproduce nanostructured WCCo and W-Co powders by calcination,reduction and carburization. The phase constituents in thecalcined powders depend on temperature and atmospheres. Cobaltcan accelerate the reduction rate of the W-Co precursors as acatalyst, and cobalt influences the formation of intermediatephases during the reduction of the precursors. The ratio of carbon monoxide to carbon dioxide controlscarburization process, gives different intermediate phases andcarburization rates. There exist several intermediate phases: W6Co6C, W3Co3C, W2C due to varying carbon monoxide content in thecarburization gases. Nanostructured WC-Co powders with aparticle size of 20-50 nm have been obtained. The effect of silicon content on the particle sizedistribution of milled Fe-Mn-Si master alloy powders is muchmore significant than that of manganese content. A finer finalparticle size can be obtained in the alloy powders with highersilicon compositions. Long time milling results in theagglomeration of small particles. The grinding process can bedescribed using classic batch grinding equation based on thepopulation balance model. A swelling model for Fe-Cu alloyssintered at the temperatures above the melting point of copperhas been established based on the penetration mechanism. In themodel, the particle coordination number and heating rate wereused to express the porosity and the thickness of the diffusionlayers between iron and copper particles respectively. The effects of sintering temperature and time on theproperties of sintered steels have been studied. Fe-Mn-Simaster alloys made by cast-milling, atomizing, and acombination of atomization and milling have been covered. Themilled, and atomizationmilled alloy steels showed goodmechanical properties with small dimensional change. Transientliquid phase of the Fe-Mn-Si alloys accelerates densification,and offer fast diffusion of alloying elements. The addition ofa small amount of Fe-Mn-Si master alloy to Astaloy 85Mo powdercan lead to high strength with zero dimensional change. <b>Key words:</b>Processing; Modelling; Nanostructured powder;WC-Co; W-Co; Calcination; Reduction; Carburization; Particlesize; Sintered steel; Fe-Cu alloy; Swelling; Fe-Mn-Si masteralloy; Mechanical properties; Sintering parameters.

The present work reports a study of mechano-chemical synthesis (MCS) and mechano-chemical activation synthesis (MCAS) of nanostructured hydrides in the Mg-H, Mg-Al-H and Mg-B-H systems by controlled reactive mechanical alloying/milling (CRMA/CRMM) in the magneto-mill Uni-Ball-Mill 5. Regardless of the hydride systems, the morphologies of milled Mg-H, Mg-Al-H and Mg-B-H powders after a prolonged milling time can be characterized by dramatic particle size refinement and high tendency to form agglomerates. In the Mg-Al-H system, no successful synthesis of magnesium alanate has been achieved by MCS of the nanostructured magnesium alanate using four starting stoichiometric Mg-2Al mixtures. It is hypothesized that Al(Mg) solid solution in the initial stage (~10h) of CRMA and free Al(s) decomposed from solid solution as the milling time increases the initial stage inhibit the reaction to form magnesium alanate. In contrast to an unsuccessful synthesis in MCS process, a successful synthesis of the magnesium alanate and 2NaCl mixture by MCAS has been achieved. DSC and TGA analysis show that the decomposition of magnesium alanate occurs in a two-step reaction at the temperature ranges of 125-180 and 225-340°C. In the Mg-B-H system, when the Mg-2B mixture is made with the oxidized amorphous boron containing B2O3 then after a prolonged MCS time (200h), only nanometric γ- and β- magnesium hydrides are formed. In contrast, oxide-free amorphous boron in the original Mg-2B mixture prompts the formation of a resulting mixture of nanometric MgB2 and an amorphous phase containing hydrogen. Further annealing of the milled Mg-2B mixtures at ~100-400ºC under ~4-4.3 MPa of hydrogen for 20-100h does not result in the formation of ternary magnesium alanate. Alternatively, a powder mixture of 2NaBH4 and MgCl2 is used as a starting material to synthesize Mg(BH4)2 hydride. Amorphous Mg(BH4)2 phase might have been synthesized after MCAS process. However, the formation of Na(Mg)BH4 solid solution might prevent the synthesis of a large amount of Mg(BH4)2 hydride. Once the solid solution is formed, the amount of Mg will be insufficient to form a large amount of Mg(BH4)2 hydride.

The present work reports a study of mechano-chemical synthesis (MCS) and mechano-chemical activation synthesis (MCAS) of nanostructured hydrides in the Mg-H, Mg-Al-H and Mg-B-H systems by controlled reactive mechanical alloying/milling (CRMA/CRMM) in the magneto-mill Uni-Ball-Mill 5. Regardless of the hydride systems, the morphologies of milled Mg-H, Mg-Al-H and Mg-B-H powders after a prolonged milling time can be characterized by dramatic particle size refinement and high tendency to form agglomerates. In the Mg-Al-H system, no successful synthesis of magnesium alanate has been achieved by MCS of the nanostructured magnesium alanate using four starting stoichiometric Mg-2Al mixtures. It is hypothesized that Al(Mg) solid solution in the initial stage (~10h) of CRMA and free Al(s) decomposed from solid solution as the milling time increases the initial stage inhibit the reaction to form magnesium alanate. In contrast to an unsuccessful synthesis in MCS process, a successful synthesis of the magnesium alanate and 2NaCl mixture by MCAS has been achieved. DSC and TGA analysis show that the decomposition of magnesium alanate occurs in a two-step reaction at the temperature ranges of 125-180 and 225-340°C. In the Mg-B-H system, when the Mg-2B mixture is made with the oxidized amorphous boron containing B2O3 then after a prolonged MCS time (200h), only nanometric γ- and β- magnesium hydrides are formed. In contrast, oxide-free amorphous boron in the original Mg-2B mixture prompts the formation of a resulting mixture of nanometric MgB2 and an amorphous phase containing hydrogen. Further annealing of the milled Mg-2B mixtures at ~100-400ºC under ~4-4.3 MPa of hydrogen for 20-100h does not result in the formation of ternary magnesium alanate. Alternatively, a powder mixture of 2NaBH4 and MgCl2 is used as a starting material to synthesize Mg(BH4)2 hydride. Amorphous Mg(BH4)2 phase might have been synthesized after MCAS process. However, the formation of Na(Mg)BH4 solid solution might prevent the synthesis of a large amount of Mg(BH4)2 hydride. Once the solid solution is formed, the amount of Mg will be insufficient to form a large amount of Mg(BH4)2 hydride.

<p>Processing of nanostructured WC-Co and W-Co powders,modelling of Fe-Mn-Si alloy, swelling of Fe-Cu alloy, andmechanical properties and sintering of Fe-Mn-Si steels havebeen studied in the present thesis.</p><p>W-Co precursors made by chemical synthesis were used toproduce nanostructured WCCo and W-Co powders by calcination,reduction and carburization. The phase constituents in thecalcined powders depend on temperature and atmospheres. Cobaltcan accelerate the reduction rate of the W-Co precursors as acatalyst, and cobalt influences the formation of intermediatephases during the reduction of the precursors.</p><p>The ratio of carbon monoxide to carbon dioxide controlscarburization process, gives different intermediate phases andcarburization rates. There exist several intermediate phases: W₆Co₆C, W₃Co₃C, W₂C due to varying carbon monoxide content in thecarburization gases. Nanostructured WC-Co powders with aparticle size of 20-50 nm have been obtained.</p><p>The effect of silicon content on the particle sizedistribution of milled Fe-Mn-Si master alloy powders is muchmore significant than that of manganese content. A finer finalparticle size can be obtained in the alloy powders with highersilicon compositions. Long time milling results in theagglomeration of small particles. The grinding process can bedescribed using classic batch grinding equation based on thepopulation balance model. A swelling model for Fe-Cu alloyssintered at the temperatures above the melting point of copperhas been established based on the penetration mechanism. In themodel, the particle coordination number and heating rate wereused to express the porosity and the thickness of the diffusionlayers between iron and copper particles respectively.</p><p>The effects of sintering temperature and time on theproperties of sintered steels have been studied. Fe-Mn-Simaster alloys made by cast-milling, atomizing, and acombination of atomization and milling have been covered. Themilled, and atomizationmilled alloy steels showed goodmechanical properties with small dimensional change. Transientliquid phase of the Fe-Mn-Si alloys accelerates densification,and offer fast diffusion of alloying elements. The addition ofa small amount of Fe-Mn-Si master alloy to Astaloy 85Mo powdercan lead to high strength with zero dimensional change.</p><p><b>Key words:</b>Processing; Modelling; Nanostructured powder;WC-Co; W-Co; Calcination; Reduction; Carburization; Particlesize; Sintered steel; Fe-Cu alloy; Swelling; Fe-Mn-Si masteralloy; Mechanical properties; Sintering parameters.</p>

La bioactivité des chitooligosaccharides semble dépendre des degrés de Nacétylation et de polymérisation ainsi que de la distribution des unités répétitives D-glucosamine et N-acétyl-D-glucosamine. Afin de préparer des structures parfaitement définies, nous avons développé une nouvelle méthode basée sur la synthèse chimique totale d’oligosaccharides pouvant être décrite en trois étapes :1- préparation de quatre monosaccharides jouant le rôle de donneurs et accepteurs de GlcN et GlcNAc2- formation des oligosaccharides protégés suite à la réaction de couplage d’un donneur de GlcN/GlcNAc avec un accepteur de GlcN/GlcNAc3- suppression des groupes protecteurs permettant l’obtention des chitooligosaccharides cibles.Un avantage important de cette stratégie vient de sa convergence. Ainsi, chaque structure protégée de chitooligosaccharide peut être convertie en un nouveau donneur ou accepteur de glycosyle par modification chimique, conduisant ensuite aux chitooligosaccharides de plus haut DP. / Bioactivity of chitooligosaccharides seems to depend on their degrees of Nacetylationand polymerisation but also the sequence of the D-glucosamine and Nacetyl-D-glucosamine units. To prepare well defined structures, we have developeda new method based on the total chemical synthesis of oligosaccharides describedin three stages:1- preparation of four monosaccharides playing the role of donors and acceptors ofboth GlcN and GlcNAc2- formation of protected oligosaccharides by the coupling reaction of oneGlcN/GlcNAc donor with one GlcN/GlcNAc acceptor3- removal of protecting groups to generate targeted chitooligosaccharidesAn important advantage of this strategy is based on its convergence. Thus, eachprotected chitooligosaccharide structure can be converted into a new glycosyldonor or acceptor, thanks to chemical modifications, and then leads to higher DPchitooligosaccharides

Some compounds, analogous to those found in naturally occurring systems, are found to possess chemotherapeutic activity. Some, in the form of their nucleoside or nucleotide derivatives, are valuable antimetabolites in that they may block normal RNA or DNA polymerisation, or may be incorporated into nucleic acids to form fraudulent, but not necessarily defective, polymers. Modification of natural ring systems, with a view to promoting chemotherapeutic activity is therefore of considerable interest; variation in the position and nature of the modification or ring substituent having a marked effect on chemotherapeutic activity. It is the purpose of this thesis to suggest methods for the facile synthesis of various uracils, pyrazoles and pyrazolo [3,4-d] - pyrimidines with alkyl, aryl and glycosyl substituents such that the nature of the ring substituents is easily varied. To this end a number of ethoxymethylene reagents were prepared which, by reaction with primary amines and hydrazines, would give acyclic intermediates capable of easy cyclisation into the uracil, pyrazole and pyrazolo [3,4-d] pyrimidine ring systems. Variation in the nature of specific substituents being determined by the choice of amine or hydrazine, other substituents being varied by modification of the original reagent.

This thesis describes Further studies on the utilisation of the diterpenoid natural product , 12-hydrxypodocarpa-8,11,13-trim 19-oic acid* (podocarpic acid) (1) . In particular it describes transformations of the C-ring to give suitable intermediates for the synthesis of optically active steroids and terpenoids. An investigation has been carried out on the Birch reduction of 12-methoxypodocarpa-8,11,13-trien-19-ol (8), and conditions for the optimum formation of the ketonic products (10) and (12) are suggested. The enones (25) and (26) have been synthesised from 12-hydroxypodocarpa-8,11,13-trien-19-oic acid (1) by sequences involving reduction of the aromatic ring followed by ring C transformations. Methyl 12-hydroxypodocarpa-8,11,13-trien-19-oate (3) has been converted in ca. 60% yield to the dextrorotatory C 13 methyl ether which has then been reduced in good yield to the enone (163). Potential routes for conversion of the enones (25), (26), and (163)into steroidal analogues are described. Initial steps in the transformation of the C 13 methyl ether(62) into an intermediate (176) suitable for the synthesis of (+)-a-onocerin (80) have been investigated. A preliminary study on the synthesis of the C 14 phenol (190) or its methyl ether (191) is also reported. * The numbering system used throughout this thesis is that proposed by J.W. Rowe (personal communication to Professor R. C. Cambie) in "The Common and Systematic Nomenclature of Cyclic Diterpenes", 3rd Revision, Oct. 1966, to be submitted to the IUPAC Commission on Organic Nomenclature (see page 144)

This thesis describes Further studies on the utilisation of the diterpenoid natural product , 12-hydrxypodocarpa-8,11,13-trim 19-oic acid* (podocarpic acid) (1) . In particular it describes transformations of the C-ring to give suitable intermediates for the synthesis of optically active steroids and terpenoids. An investigation has been carried out on the Birch reduction of 12-methoxypodocarpa-8,11,13-trien-19-ol (8), and conditions for the optimum formation of the ketonic products (10) and (12) are suggested. The enones (25) and (26) have been synthesised from 12-hydroxypodocarpa-8,11,13-trien-19-oic acid (1) by sequences involving reduction of the aromatic ring followed by ring C transformations. Methyl 12-hydroxypodocarpa-8,11,13-trien-19-oate (3) has been converted in ca. 60% yield to the dextrorotatory C 13 methyl ether which has then been reduced in good yield to the enone (163). Potential routes for conversion of the enones (25), (26), and (163)into steroidal analogues are described. Initial steps in the transformation of the C 13 methyl ether(62) into an intermediate (176) suitable for the synthesis of (+)-a-onocerin (80) have been investigated. A preliminary study on the synthesis of the C 14 phenol (190) or its methyl ether (191) is also reported. * The numbering system used throughout this thesis is that proposed by J.W. Rowe (personal communication to Professor R. C. Cambie) in "The Common and Systematic Nomenclature of Cyclic Diterpenes", 3rd Revision, Oct. 1966, to be submitted to the IUPAC Commission on Organic Nomenclature (see page 144)

This thesis describes Further studies on the utilisation of the diterpenoid natural product , 12-hydrxypodocarpa-8,11,13-trim 19-oic acid* (podocarpic acid) (1) . In particular it describes transformations of the C-ring to give suitable intermediates for the synthesis of optically active steroids and terpenoids. An investigation has been carried out on the Birch reduction of 12-methoxypodocarpa-8,11,13-trien-19-ol (8), and conditions for the optimum formation of the ketonic products (10) and (12) are suggested. The enones (25) and (26) have been synthesised from 12-hydroxypodocarpa-8,11,13-trien-19-oic acid (1) by sequences involving reduction of the aromatic ring followed by ring C transformations. Methyl 12-hydroxypodocarpa-8,11,13-trien-19-oate (3) has been converted in ca. 60% yield to the dextrorotatory C 13 methyl ether which has then been reduced in good yield to the enone (163). Potential routes for conversion of the enones (25), (26), and (163)into steroidal analogues are described. Initial steps in the transformation of the C 13 methyl ether(62) into an intermediate (176) suitable for the synthesis of (+)-a-onocerin (80) have been investigated. A preliminary study on the synthesis of the C 14 phenol (190) or its methyl ether (191) is also reported. * The numbering system used throughout this thesis is that proposed by J.W. Rowe (personal communication to Professor R. C. Cambie) in "The Common and Systematic Nomenclature of Cyclic Diterpenes", 3rd Revision, Oct. 1966, to be submitted to the IUPAC Commission on Organic Nomenclature (see page 144)

This thesis describes Further studies on the utilisation of the diterpenoid natural product , 12-hydrxypodocarpa-8,11,13-trim 19-oic acid* (podocarpic acid) (1) . In particular it describes transformations of the C-ring to give suitable intermediates for the synthesis of optically active steroids and terpenoids. An investigation has been carried out on the Birch reduction of 12-methoxypodocarpa-8,11,13-trien-19-ol (8), and conditions for the optimum formation of the ketonic products (10) and (12) are suggested. The enones (25) and (26) have been synthesised from 12-hydroxypodocarpa-8,11,13-trien-19-oic acid (1) by sequences involving reduction of the aromatic ring followed by ring C transformations. Methyl 12-hydroxypodocarpa-8,11,13-trien-19-oate (3) has been converted in ca. 60% yield to the dextrorotatory C 13 methyl ether which has then been reduced in good yield to the enone (163). Potential routes for conversion of the enones (25), (26), and (163)into steroidal analogues are described. Initial steps in the transformation of the C 13 methyl ether(62) into an intermediate (176) suitable for the synthesis of (+)-a-onocerin (80) have been investigated. A preliminary study on the synthesis of the C 14 phenol (190) or its methyl ether (191) is also reported. * The numbering system used throughout this thesis is that proposed by J.W. Rowe (personal communication to Professor R. C. Cambie) in "The Common and Systematic Nomenclature of Cyclic Diterpenes", 3rd Revision, Oct. 1966, to be submitted to the IUPAC Commission on Organic Nomenclature (see page 144)