Fine magnetic powder has been produced using the hydrogenation
disproportionation desorption and recombination (HDDR) process. The first goal of this work
involved an investigation of a range of disproportionation/desorption temperatures between
800 and 900°C with the purpose of optimizing the HDDR treatment for a Pr14Fe80B6 alloy.
The cast alloy was annealed at 1100°C for 20 hours for homogenization. The optimum
disproportionation temperature for achieving high anisotropy was 820°C. The influence of the
reaction temperature on the microstructure and magnetic properties of Pr14Fe80B6 HDDR
powders and magnets has been shown. A second stage of this study involved the
characterization, for each temperature, of the HDDR processed powder using X-ray
diffraction analysis. Samples of the HDDR material have been studied by synchrotron
radiation powder diffraction using the Rietveld method for cell refinement, phase
quantification and crystallite sizes determination. Scanning electron microscopy (SEM) has
also been employed to reveal the morphology of the HDDR powder.
Quantitative X-ray diffraction (the Rietveld Method) was used to quantify both the crystallite size (diffracting length) and precipitate size in several grades of microalloyed steels. The crystallite size calculated from diffraction profiles obtained from the rolling faces of X80 and X100 was found to decrease with decreasing coiling temperature. Quantitative X-ray diffraction analysis was also conducted on precipitate residues extracted (by matrix dissolution) from a Grade 100 microalloyed steel. A mean precipitate size of 4.8 nm was calculated for the fine (Nb, Mo, Ti, V) carbides observed in this steel. This value compares favourably with precipitate size measured using TEM and SANS analysis.
Thermolysis of [8,8-(PMe2Ph)2-nido-8,7-PtCB9H11] in boiling toluene solution results in an elimination of the platinum centre and cluster closure to give the ten-vertex closo species [6-(PMe2Ph)-closo-1-CB9H9] in 85% yield as a colourles air stable solid. The product is characterized by NMR spectroscopy and single-crystal X-ray diffraction analysis. Crystals (from hexane-dichloromethane) are monoclinic, space group P21/c, with a = 903.20(9), b = 1 481.86(11), c = 2 320.0(2) pm, β = 97.860(7)° and Z = 8, and the structure has been refined to R(Rw) = 0.045(0.051) for 3 281 observed reflections with Fo > 2.0σ(Fo). The clean high-yield elimination of a metal centre from a polyhedral metallaborane or metallaheteroborane species is very rare.
Dinuclear rhodium(I) η2:η2-cycloocta-1,5-diene (series a) and η2:η2-norborna-2,5-diene (series b) complexes with μ-RCOO- ligands, where R is linear C21H43 (complexes 1a, 1b), CH2CMe3 (2a, 2b), 1-adamantyl (3a, 3b) and benzyl (4a, 4b), have been prepared and characterized by spectroscopic methods. Structures of complexes 2b, 3a and 4a were determined by X-ray diffraction analysis. Complexes prepared show low to moderate catalytic activity in polymerization of phenylacetylene in THF giving high-cis-transoid polymers, but they show only oligomerization activity in dichloromethane.
Purification, crystallization, and preliminary X-ray diffraction analysis of rat kidney annexin V, a calcium-dependent phospholipid-binding protein.