The wettability of Mg0 by liquid iron was studied using the sessile drop technique in vacuo at 1550°C. Specimens of vacuum-cast iron were melted on single crystals of optical-grade magnesium oxide. Tests were limited to two minutes because of iron volatilization. Chemical reaction at the liquid-vapor interface caused the contact angle to decrease from 117° to 65° during the first minute. Reaction between the iron and oxygen provided through the dissociation of Mg0 resulted in formation of an Fe0 layer over the drop surface. The Fe0 was drawn to the base of the drop where it accumulated as an annular Interfacial deposit. After solidification, the Fe0 decomposed to magnetite with separation of iron. Within the peripheral annulus the interface showed no sign of chemical attack. This effect was related to formation of a protective interfacial monolayer from electropositive impurities initially present in the iron. The major constituent of the monolayer appeared to be silicon although positive identification was not achieved. Chemical reaction occurred in each case where alloying additions to the iron of Ti, V, Cr, Nb, Ta, and Zr were made. Variation of contact angle with concentration was studied. Both V and Cr improved the wettability. The effect of Zr, Ti, Nb, and Ta on the wettability was not determined because oxide deposits around the basal periphery of the drops restricted expansion. Complete interfacial attack was observed with additions of Zr, Ti, and V whereas additions of Nb, Ta, and Cr resulted in an annular interfacial deposit around the drop perimeter similar to the pure Fe-Mg0 specimens. This phenomena supported the existence of an interfacial monolayer. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The microsegregation of Mn, Cu, Cr, Mo, Ni and Si has been measured in cast ductile iron and in ductile iron which has been quenched when partially solidified. Effective segregation coefficients have been determined for each of the elements, and used to calculate the segregation on the basis of the Scheil equation. The calculated values agree reasonably well with the values of the solute concentration as a function of the solid fraction measured in quenched samples. The microstructure of the solid phases during the solidification of ductile iron has been observed. Solidification of eutectic ductile iron begins with the independent nucleation of austenite and graphite in the melt. Later the graphite nodules are enveloped by austenite, and further solidification takes place by the thickening of the austenite layers enveloping the graphite. Isolated pockets of interdendritic melt are the last material to solidify. On the basis of the measured segregation of the different alloying elements, the mechanisms by which the segregation affects the microstructure are considered, and an explanation for the effect of segregation on the hardenability of ductile iron is proposed. A mathematical model of the solidification of eutectic ductile iron is formulated which includes heat flow, nucleation and growth of graphite nodules, and the segregation of Si. The model uses equilibrium temperatures given by the ternary Fe-C-Si equilibrium diagram. Using the mathematical model, cooling curves, nodule count and nodular size distribution are determined as a function of position in the casting sample. The results are compared to measured temperatures, nodule count and nodule size in rod castings of 12.5, 20 and 43mm radius. There is good agreement between the calculated and measured values for the 43mm radius rod, and not quite good agreement for the rods of smaller radii. The changes in solidification predicted by the model when some solidification parameters are varied are consistent with experimental observations with the same variation in the parameters. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

An investigation of the oxidation of solid iron by lead oxide-silica melts was undertaken between 850°C and 1000°C over a wide range of oxidising potentials. The experimental reaction rates were measured by a technique of electrical resistance measurements. In the intermediate range of concentration investigated (80-88 % wgt.PbO) the rate of oxidation was found to be proportional to the mole fraction of lead oxide in the melt, in other words, to the lead ion concentration. The rate determining step of iron oxidation by lead oxide-silica melts is supposed to involve lead cations in contrast with the oxidation of carbon where oxygen ions are involved. The apparent activation energy was found to be 50 ± 7 Kcal/mole. Two sets of activity data concerning the lead oxide in PbO-SiO₂ melts were available and were compared by processing the present results on iron oxidation and previous results on carbon oxidation by similar melts. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

A mathematical model has been developed to predict the operating behaviour of an SL/RN direct reduction kiln from a knowledge of the main process variables. The model is based on steady state principles and is capable of quantitatively describing the complex chemical reactions in the kiln such as reduction, Boudouard reaction, coal volatilization and combustion in the freeboard together with the mass and heat flows. Output from the model is in the form of axial profiles of gas, solids and wall temperatures, and concentrations in both the gas and the solid phases. Results from the model are in good agreement with measurements made on the 100 ton per day pilot kiln at the Steel Company of Canada. The influence of important process variables such as the type of coal, ore, degree of reduction, throughput etc. has been examined and predictions made regarding the operation of large commercial SL/RN kilns for sponge iron production. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

M.Sc. / Bracketing the depositional age of the Gamagara/Mapedi to Lucknow and Olifantshoek succession in Griqualand West is important because it not only represents one of the oldest known red bed successions in the world but also hosts some of the first well preserved lateritic soil profiles and carbonates with heavy 13C values traditionally correlated with the so-called Lomagundi carbonate carbon excursion. In addition the ancient supergene very large high-grade hematite iron ore deposits of the Sishen-Postmasburg area on the Maremane dome are associated with the erosional unconformity at the base of the Gamagara Formation (a lateral equivalent of the Mapedi Formation). However, the depositional age of especially the Gamagara/Mapedi to Lucknow succession is under dispute because it has been considered a) correlative to the lower part of the Waterberg Group in the Transvaal area, with the implication that it is younger than the Bushveld Complex with an age of ~2,054 Ga, and b) correlative to the Dwaalheuwel-Magaliesberg succession of the pre-Bushveld Pretoria Group of the Transvaal Supergroup in the Transvaal area. The upper age limit of the Gamagara/Mapedi to Lucknow succession is defined by 1,92 Ga felsic volcanics in the overlying Neylan-Hartley succession of the Olifantshoek Group. The Hartley Lava Formation is overlain by Volop quartzites. This study involves age determinations of detrital zircon populations extracted from the basal Doornfontein conglomerate member of the Gamagara/Mapedi succession, and quartzites of the Gamagara/Mapedi, Lucknow, Neylan, Hartley and Volop Formations at various localities in Griqualand West. Based on field work, three unconformity-bound sequences are defined, namely the Gamagara/Mapedi-Lucknow, Neylan-Hartley and Volop sequences. Most interestingly quartzites of the Gamagara/Mapedi-Lucknow sequence contain abundant zircons with ages similar to that of the Bushveld Complex at ~2,054-2,06 Ga in addition to zircons as young as ~1,98-2,01 Ga. An exception is results on one sample of the Doornfontein Member analyzed so far (it is from the Rooinekke iron ore mine south of Postmasburg) that contains only zircons that are older than the Bushveld Complex with a rather prominent youngest population bracketed between 2,2 Ga and 2,32 Ga. The youngest detrital zircon populations in the Neylan-Hartley sequence are either slightly older than the Hartley lava or contain zircons with similar age to Hartley felsic lavas at 1,92 Ga. This sequence thus appears to have developed immediately prior to and coeval with Hartley volcanism. The overlying Volop sequence contains abundant zircons as young as ~1,89 Ga. The results clearly illustrate that the Gamagara/Mapedi to Lucknow succession is certainly not a lateral correlative of the pre-Bushveld Dwaalheuwel-Magaliesberg succession of the Pretoria Group. Rather it should be considered time-equivalent lower parts of the Waterberg Group in the Transvaal area. This implies that the heavy carbonate carbon excursion known from the Lucknow Formation is at least 100 my. younger than the one known from the upper part of the Silverton Formation along the contact with the overlying Magaliesberg Quartzite. There are thus at least three heavy carbonate carbon excursions, known from Paleoproterozoic cover successions of the Kaapvaal Craton in southern Africa, namely one in the ~2.35 Ga Duitschland Formation, a second in the ~2,1 Ga Silverton Formation of the Pretoria Group of the Transvaal Supergroup and the third in the ~1,98-1,92 Ga Lucknow Formation. It is further known that carbonates with normal open marine 13C values of close to zero occur in stratigraphic intervals between each of the heavy carbonate carbon excursions. The only unit that may still be correlated with part of the Pretoria Group is the Doornfontein Member at the base of the Gamagara/Mapedi succession. The correlation of this unit with the base of the Dwaalheuwel Formation and the Hekpoort paleosol of the Pretoria Group thus remain possible but analyses of additional samples are needed to make sure that the conglomerate, and by implication the ancient supergene Sishen-type iron ore deposits, does not also postdate the Bushveld Complex.

Iron-deficiency anemia is probably the commonest deficiency disease in infants and children throughout the world today. This prevalence is indeed surprising as the condition can be readily detected. Moreover, iron medication is cheap and for many years has been known to be effective in the prephylaxis and treatment of iron-deficiency anemia. In America, reportedly the most health-conscious of all countries, Guest and Brown (1957) have reported that the incidence, in at least one centre, is as high today as it was twenty years ago. If this is true in a country where practicing physicians are well primed about the importance of adequate nutrition, it is likely that in less-privileged communities there is probably greater failure to recognize or correct this deficiency state.

The work to be presented in this thesis took pl ace while I was working as a registrar in the department of radio-isotope diagnosis at Groote Schuur Hospital. During this period, I became interested in the ferrokinetic technique for attempting to quantitate normal and abnormal erythropoietis, and the possible development of these techniques so as to allow more accurate quantitation of the data. At the time the study started, the department was offering standard ferrokinetic investigations to aid in the diagnosis of abnormal haematological states. These studies did not, I felt, provide adequate information for the referring clinician, particularly in regard to ineffective erythropoietic activity.

No description available.

No description available.

The organometallic Lewis acid [(η5-C5H5)(CO)2Fe]BF4 reacts with excess dry diethyl ether at low temperatures to form the novel labile complex [(η5-C5H5)(CO)2Fe(OEt2)]BF4 which in turn serves as a precursor in the syntheses of various cationic dicarbonylcyclopentadienyliron complexes. The reactions of [(η5-C5H5)(CO)2Fe(OEt2)]BF4 with various 1-alkylamines, α,ω-diaminoalkanes, N-heterocyclics and heterofunctional amine ligands, as well as olefins, have been investigated. Reactions with 1-alkylamines and α,ω-diaminoalkane ligands lead to a series of novel monuclear and dinuclear complexes of the types [(η5-C5H5)(CO)2FeL]BF4 and [{(η5-C5H5)(CO)2Fe}2(μ-L)](BF4)2, respectively. The reaction of [(η5-C5H5)(CO)2Fe(OEt2)]BF4 with N-heterocyclic ligands such as 1,3,5,7-tetraazaadamantane (HMTA) and 1,4-diazabicyclo[2.2.2]octane (DABCO) give dinuclear complexes [{(η5-C5H5)(CO)2Fe}2(μ-L)](BF4)2 and monuclear complexes [(η5-C5H5)(CO)2FeL]BF4 (L = HMTA, DABCO). Its reaction with 1-methylimidazole (1-meIm) affords only the monuclear complex [(η5-C5H5)(CO)2Fe(1-meIm)]BF4 in which the coordination of 1-methylimidazole is via the sp2-N. The reaction with heterofunctional amine ligands is highly regioselective with the cation [(η5-C5H5)(CO)2Fe]+ showing higher affinity for NH2 than π-bonded, O or CN functionalities. Besides amines, [(η5-C5H5)(CO)2Fe(OEt2)]BF4 reacts with olefins and HCOOH to form complexes of the type [(η5-C5H5)(CO)2Fe(η2-olefin)]BF4 and [{(η5-C5H5)Fe(CO)2}2(μ-OCHO)]BF4, respectively. For comparison of steric and electronic effects, analogous pentamethylcyclopentadienyl amine complexes were synthesized from the THF complex [{η5-C5(CH3)5}(CO)2Fe(THF)]BF4. The reaction of 3-aminoprop-1-ene with the etherate complexes [(η5-C5R5)(CO)2Fe(E)]BF4 (R = H: E= Et2O; R = CH3: E = THF) led to air stable complexes [(η5-C5R5)(CO)2Fe(NH2CH2CHCH2)]BF4 (R = H, CH3), which in turn react with a mole equivalent of the etherate complexes to give dinuclear complexes of the type, [(η5-C5R5)(CO)2Fe(NH2CH2CHCH2)Fe(CO)2(η5-C5R'5)](BF4)2 (R not necessarily equal to R'). They also undergo halogenation to give the chiral dihalopropylamino complexes [(η5-C5R5)(CO)2Fe(NH2CH2CH(X)CH2(X))]BF4 (R=H, CH3; X = Cl, Br). The reaction of the dinuclear complex [{(η5-C5H5)(CO)2Fe}2(NH2CH2CHCH2](BF4)2 with NaI in acetone gives [(η5-C5H5)(CO)2Fe(NH2CH2CHCH2)]I and [(η5-C5H5)Fe(CO)2I]. All these complexes have been fully characterized by 1H NMR, 13C NMR, IR spectroscopy and elemental analysis. The mass spectra of 1-aminoalkane and diaminoalkane complexes have also been recorded and are discussed. The structures of 16 synthesized compounds have been confirmed by single crystal X-ray crystallography. Most of the amine complexes are water-soluble and some undergo counteranion exchange with sodium tetraphenylborate in both aqueous and organic media to give BPh4- salts. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2011.