京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21780号 / 工博第4597号 / 新制||工||1716(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 中村 正治, 教授 大江 浩一, 教授 村田 靖次郎 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Presented for the degree of Doctor of Science of University of the Uiituatersrand. October, 1964. / ffiy interest in iron metabolism was initially aroused in 1948 by a young patient with idiopathic haemochromatosis who was admitted to Professor Elliott*© ward while I was serving my medical internship, With the support of the Council for Scientific and Industrial Research it was possible to carry out radioisotopic studies on this patient and over the next four years a number of other subjects with the same disease ware investigated. As the study continued, attention was also directed to the siderosis which is so common in adult Bantu, and to the Iron overload which results from the administration of repeated blood transfusions to subjects with refractory anaemias. / IT2018

Iron oxyhydroxides are ubiquitous in surface environments, playing a key role in many biogeochemical processes. Their characterization is made challenging by their nanophase nature. Magnetometry serves as a sensitive non-destructive characterization technique that can elucidate intrinsic physical properties, taking advantage of the superparamagnetic behaviour that nanoparticles may exhibit. In this work, synthetic analogues of common iron oxyhydroxide minerals (ferrihydrite, goethite, lepidocrocite, schwertmannite and akaganéite) are characterized using DC and AC magnetometry (cryogenic, room temperature), along with complementary analyses from Mössbauer spectroscopy (cryogenic, room temperature), powder X-ray diffraction and scanning electron microscopy. It was found that all of the iron oxyhydroxide mineral nanoparticles, including lepidocrocite, schwertmannite and akaganéite were superparamagnetic and therefore magnetically ordered at room temperature. Previous estimates of Néel temperatures for these three minerals are relatively low and are understood as misinterpreted magnetic blocking temperatures. This has important implications in environmental geoscience due to this mineral group’s potential as magnetic remanence carriers. Analysis of the data enabled the extraction of the intrinsic physical parameters of the nanoparticles, including magnetic sizes. The study also showed the possible effect on these parameters of crystal-chemical variations, due to elemental structural incorporation, providing a nanoscale mineralogical characterization of these iron oxyhydroxides. The analysis of the intrinsic parameters showed that all of the iron oxyhydroxide mineral nanoparticles considered here have a common magnetic moment formation mechanism associated with a random spatial distribution of iv uncompensated magnetic spins, and with different degrees of structural disorder and compositional stoichiometry variability, which give rise to relatively large intrinsic magnetization values. The elucidation of the magnetic nanostructure also contributes to the study of the surface region of the nanoparticles, which affects the particles’ reactivity in the environment.

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Fe78_C.,r xSiioBj2 and Fe77S. xCr-,S i7S. Bjs (with x values ranging from 0 to 8) glassy metallic alloys have been produced in the form of both wires and ribbons using the rotating water bath melt spinning process and chill block melt spinning process, respectively. It was found that the Fe77.5C.,r,, ,S ii. 5B15s eries had better amorphousw ire forming ability than the Fe7g_XCrXSiloBs1e2ri es. However, in ribbon form, both series showed good castability as amorphous alloys. Selected mechanical properties of the glassy samples have been compared with those of high tensile steel wire. Both thermal and mechanical properties were found to be composition-dependent, especially on the Cr content, with the Fe77.X5.C rrSi7.5B1s5e ries wires being thermally more stable and strongert han their Fe7gX. CrrSiloB12c ounterparts. A new bend type fatigue testing machine that uses two pulleys (DP) has been developed to perform tests on the basis of tension-compression loading cycles. The results have been compared with those obtained by using an existing single pulley (SP) machine that performs only tensile-tensile loading cycles. Although the DP machine can impose compressive to tensile bend stresses at different constant mean stress, it was observed that, for low stress ranges and large constant mean stresses the machine performed equivalent bend tests to those using the SP machine. The fatigue performance of amorphous wires was improved on substituting Fe by Cr and on decreasing the constant mean stress. The high tensile (HT) steel wire apparently had better fatigue performance than amorphous wires in terms of stress range; however, when the results were expressed in terms of strain range, the fatigue performance of amorphous wires was slightly better than HT steel wires, as had been demonstrated in previous studies. It was observed that, when the DP machine performed compressive to tensile bending stress cycles, the fracture surfaces differed from those observed in the SP machine. Under tensile to tensile conditions, the fracture surfaces observed for samples tested in the DP machine were similar to those tested in the SP machine. Fracture mechanics analysis of the results suggests that embrittlement is occurring ahead of growing fatigue cracks in these amorphous wires.

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