Advances in the development of novel cobalt Fischer-Tropsch catalysts for synthesis of long-chain hydrocarbons and clean fuels.

Synthesis, properties, and applications of magnetic iron oxide nanoparticles

http://ntur.lib.ntu.edu.tw/bitstream/246246/172223/1/23.pdf

Characterization of cobalt oxides studied by FT-IR, Raman, TPR and TG-MS

Storage of ferrihydrite in aqueous suspensions at 24°C and pHs between 2.5 and 12 for as long as three years resulted in the formation of goethite and hematite. The proportions and crystallinity of these products varied widely with the pH. Maximum hematite was formed between pH 7 and 8, and maximum goethite at pH 4 and at pH 12. The crystallinity of both products, as indicated by X-ray powder diffraction line broadening and magnetic hyperfine field values and distribution widths, was poorer, the lower the proportion of the corresponding product in the mixture. The existence of two competitive formation processes is suggested: goethite is formed via solution, preferably from monovalent Fe(III) ions [Fe(OH)2+ and Fe(OH)4−], and hematite by internal rearrangement and dehydration within the ferrihydrite aggregates. This concept relates the proportions of goethite and hematite to the activity of the Fe(III) ion species in solution, and implies that conditions favorable for the formation of goethite are unfavorable for that of hematite and vice versa.

Effect of pH on the formation of goethite and hematite from ferrihydrite

This is an updated collation of magnetic parameters of rocks and minerals for geologists, geochemists, and geophysicists. Since the publication of the previous edition of Handbook of Physical Constants [74], two other collations have appeared [16, 18]. In addition, selected magnetic parameters have also been assembled [19, 22, 38, 41, 88]. Rather than produce a fully comprehensive collection, we have aimed for high-precision data obtained from wellcharacterized samples. Both tables and figures have been used for presenting the data, and best-fit equations have been provided for some of the displayed ata so that interpolations can be made easily. In an attempt to discourage the use of the outdated cgs system, all values are in the SI system (see Moskowitz, this volume). References have been cited for the sources used here. However, a more comprehensive bibliography has also been provided from which information can be extracted for samples which have not been included. The single-crystal constants and their variation with temperature and composition are for use by rock magnetists. Paleomagnetists and magnetic anomaly modelers have been provided with the magnetic properties of rocks and polycrystalline mineral samples. Lastly, we have made an effort to address the needs of environmental magnetism, a new group of researchers who require the values of sizeand

http://www.alaska-gold.com/RF003p0189.pdf

Magnetic Properties of Rocks and Minerals

Mössbauer studies of the morin transition in bulk and microcrystalline α-Fe2O3†

The M\"ossbauer spectra produced by ${10}^{\ensuremath{-}4}$-at.% ${\mathrm{Co}}^{57}$ and 0.5-at.% ${\mathrm{Fe}}^{57}$ doped in the normal spinels ${\mathrm{Co}}_{3}$${\mathrm{O}}_{4}$, Co${\mathrm{Rh}}_{2}$${\mathrm{O}}_{4}$, Co${\mathrm{Cr}}_{2}$${\mathrm{O}}_{4}$, Co${\mathrm{Mn}}_{2}$${\mathrm{O}}_{4}$, and Zn${\mathrm{Co}}_{2}$${\mathrm{O}}_{4}$ have been obtained. Based on properties of the spinel structure and on correlations with M\"ossbauer data from the natural-iron spinels, these spectra are interpreted in terms of the daughter and impurity iron being located on the tetrahedral and octahedral lattice sites. The charge state of the daughter iron is not always the same as that of the parent cobalt; instead, it is generally that of natural iron in the parallel spinel compounds ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$, Co${\mathrm{Fe}}_{2}$${\mathrm{O}}_{4}$, Fe${\mathrm{Co}}_{2}$${\mathrm{O}}_{4}$, Fe${\mathrm{Cr}}_{2}$${\mathrm{O}}_{4}$, Fe${\mathrm{Mn}}_{2}$${\mathrm{O}}_{4}$, and Zn${\mathrm{Fe}}_{2}$${\mathrm{O}}_{4}$. From this and other evidence, we propose that the daughter-iron's valence is determined primarily by the chemical bonding properties of iron (as distinct from cobalt) in the environment where it is created. Of the several models of spinel crystal chemistry, that of Goodenough and Loeb roughly accounts for our conclusions.

Mössbauer study of several cobalt spinels using Co 57 and Fe 57

The M\"ossbauer isomer shift of ${\mathrm{Au}}^{197}$ has been measured in samples of gold microcrystals supported in gelatin. The experimental isomer shift can be correlated with the lattice contractions observed in these microcrystals.

Dietrich Schroeer

Papers

Mössbauer studies of the morin transition in bulk and microcrystalline α-Fe2O3†

Mössbauer study of several cobalt spinels using Co 57 and Fe 57

Mössbauer isomer shift in gold microcrystals

Investigations of Charge States in Co 57 -Doped Oxides Using the Mössbauer-Effect and Delayed-Coincidence Techniques

Mössbauer study of Fe1 + xV2−xO4 spinels for the determination of cation distributions and magnetic structure☆