The use of chlorine dioxide as an oxidant and/or disinfectant for drinking water treatment has been an alternative considered when utilities seek to control trihalomethane concentrations. However, concern regarding residual concentrations of chlorite and chlorate have resulted in limitations on applied chlorine dioxide dosages. This study describes the use of ferrous iron as a possible reducing agent for the elimination of residual chlorite from drinking water. / Master of Science

No description available.

Doctorat en Sciences / info:eu-repo/semantics/nonPublished

<p> An investigation has been made concerning the solubility of nitrogen in pure liquid iron, iron-carbon and ironaluminium alloys. A technique involving levitation melting and a rapid quench device has been used. The experimental data obtained have been expressed in terms of the interaction coefficients proposed by Wagner and Lupis and Elliott. The data have also been used to test the formalisms developed recently by Darken and Chipman. A simple model for liquid metal solutions in which the solutes may be considered "interstitial" has been developed and tested using the results of the present study and published data for a number of ternary solutions </p> / Thesis / Doctor of Philosophy (PhD)

No description available.

M.Sc. (50/50) Research project submitted to School of Chemical and Metallurgical Engineering, Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, South Africa July 2017 / This study and the work done involves investigating the effects of different parameters on the decarburization process of high carbon ferrochromium melts to produce medium carbon ferrochrome, and takes into account the manipulation of the different parameters and thermodynamic models based on actual plant data. Process plant data was collected from a typical plant producing medium carbon ferrochrome alloys using AODs. The molten alloy was tapped from the EAF and charged into the AOD for decarburization using oxygen and nitrogen gas mixtures. The gases were blown into the converter through the bottom tuyeres. Metal and slag samples and temperature measurements were taken throughout the duration of each heat. The decarburization process was split into two main intervals namely first stage blow (where carbon content in the metal bath is between 2-8 wt. % C) and second stage blow (carbon mass% below 2 wt. %). The first and second blow stages were differentiated by the gas flow rates whereby the first stage was signified by gas flow ratio of 2:1 (O2:N2), whilst the stage blow had 1:1 ratio of oxygen and nitrogen respectively. The effect of Cr mass% on carbon activity and how it relates to rate of decarburization was investigated, and the results indicated that an increase in Cr 66.54 – 70.5 wt. % reduced carbon activity in the metal bath from 0.336 – 0.511 for the first blowing stage. For the second blowing stage, the increase in Cr mass % of 67.22 – 71.65 wt. % resulted in an increase in C activity from 0.336 – 0.57. The trend showed that an increase in chromium composition resulted in a decrease in carbon activity and the same increase in Cr mass% resulted in reduced carbon solubility. Based on the plant data, it was observed that the rate of decarburization was time dependent, that is, the longer the decarburization time interval, the better the carbon removal from the metal bath. An interesting observation was that the change in carbon mass percent from the initial composition to the final (Δ%C) decreased from 10.18 – 8.37 wt. % with the increase in Cr/C ratio from 8.37 – 10.18. This effect was attributed to the chromium affinity for carbon and the fact that an increase in chromium content in the bath was seen to reduce activity of carbon. It was also observed that the effect of the Cr/C ratio was more significant in the first stage of the blowing process compared to the second blowing stage. A mass and energy balance model was constructed for the process under study to predict composition of the metal bath at any time interval under specified plant conditions and parameters. The model was used to predict the outcome of the process by manipulating certain parameters to achieve a set target. By keeping the gas flow rates, blowing times, gas ratios and initial metal bath temperature unchanged, the effect of initial temperature on decarburization in the converter was investigated. The results showed that the carbon end point with these parameters fixed decreased with increasing initial temperature, and this was supported by literature. The partial pressure of oxygen was observed to increase with decrease in C mass % between the first and second blow stages. For the second stage blow the partial pressure changed from 5.52*10-12 – 2.1*10-10 and carbon mass % increased from 0.754 – 2.99 wt. %. A carbon mass % of 7.87 had an oxygen partial pressure of 4.51*10-13 whilst a lower carbon content of 1.53 wt. % had an oxygen partial pressure of 8.06*10-11. The CO partial pressure however increased with increase in carbon composition in the metal bath. When the oxygen flow rate increased, a corresponding increase in the carbon removed (Δ%C) was observed. For the first stage of the blowing process, an increase in oxygen flow rate from 388.67 – 666.5Nm3 resulted in an increase in carbon removed from 5.06 – 7.28 wt. %. The second blowing stage had lower oxygen flow rates because of the carbon levels remaining in the metal bath were around +/- 2 wt. %. In this stage oxygen flow rates increased from 125 – 286.67 Nm3 and carbon removed (Δ%C) from 0.16 – 2.093 wt. %. The slag showed that an increase in basicity resulted in an increase in Cr2O3 in the slag. As the basicity increased from 0.478 – 1.281, this resulted in an increase in Cr2O3 increase from 0.26 – 0.68. Nitrogen solubility in the metal bath was investigated and it was observed that it increased with increasing Cr mass %. The increase in nitrogen solubility with increasing Cr mass % was independent of the nitrogen partial pressures. / MT2018

Chan Fu-wai = 非晶態鐵磁性鐵-磷-碳合金的製作 / 陳輔偉. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / Chan Fu-wai = Fei jing tai tie ci xing tie-lin-tan he jin de zhi zuo / Chen Fuwei. / Acknowledgments --- p.i / Abstract --- p.ii / Table of Content --- p.iv / Chapter Chapter 1: --- Introduction --- p.1 / Chapter 1.1 --- Nucleation --- p.1 / Chapter 1.1.1 --- Homogenous nucleation --- p.1 / Chapter 1.1.2 --- Heterogeneous nucleation --- p.4 / Chapter 1.2 --- The crystal growth --- p.5 / Chapter 1.2.1 --- The solid-liquid interface --- p.5 / Chapter 1.2.2 --- Lateral growth --- p.6 / Chapter 1.2.3 --- Continuous growth --- p.6 / Chapter 1.3 --- Non-equilibrium process --- p.8 / Chapter 1.3.1 --- Reduction of impurities --- p.8 / Chapter 1.3.2 --- Suppression of crystal growth --- p.8 / Chapter 1.4 --- The change in metallurgy --- p.9 / Chapter 1.4.1 --- The metallic glass --- p.9 / Chapter 1.4.2 --- The properties of glass --- p.10 / Chapter 1.4.3 --- The development of amorphous alloy --- p.11 / Chapter 1.5 --- Preparation methods of amorphous alloy --- p.12 / Chapter 1.6 --- The criterion of glass formation --- p.14 / Chapter 1.7 --- The study of this project --- p.15 / Reference --- p.16 / Figure --- p.19 / Chapter Chapter 2: --- Experiment --- p.36 / Chapter 2.1 --- Preparation --- p.36 / Chapter 2.2 --- Experimental procedure --- p.37 / Chapter 2.3 --- Sample analysis --- p.38 / Reference --- p.41 / Figure --- p.42 / Chapter Chapter 3: --- The formation of bulk ferromagnetic Fe-P-C amorphous alloy --- p.45 / Abstract --- p.45 / Introduction --- p.46 / Experiment --- p.47 / Result --- p.48 / Reference --- p.49 / Figure --- p.52 / Chapter Chapter 4: --- Compaction of bulk ferromagnetic Fe-P-C amorphous alloy --- p.57 / Abstract --- p.57 / Introduction --- p.58 / Experiment --- p.58 / Result --- p.60 / Reference --- p.61 / Figure --- p.62 / Chapter Chapter 5: --- Conclusion --- p.65

In this thesis the compounds Fe5SiB2 and Fe5PB2 have beensynthesized via high temperature synthesis, including arc melting anddrop synthesis. The structure for both compounds are of Cr5B3 typewith the space group I4/mcm. The cell parameters were refined toa = 5.5533 Å and c = 10.3405 Å for Fe5SiB2 and a = 5.4903 Å andc = 10.3527 Å for Fe5PB2. The saturation magnetization at roomtemperature for Fe5SiB2 has been measured to 138.8 Am2/kg and theanisotropy constant has been estimated to 79 kJ/m3. Theferromagnetic properties and the high anisotropy constant makesthese materials promising as permanent magnet materials, but moreinvestigations are necessary.

A comprehensive, transient three-dimensional model of a single-pass laser surface alloying process has been developed and used to examine the heat, momentum and species transport phenomena. A numerical study is performed in a co-ordinate system moving with the laser at a constant scanning speed. In this model a fixed grid enthalpy-porosity approach is used, which predicts the evolutionary pool development. In this model two extreme cases of alloying element and base metal combinations are considered based on their relative melting points. One extreme case is for an alloying element with its melting point much lower than that of the base metal. In this case the alloying element melts almost instantaneously. Hence it is assumed that the alloying element introduced on the melt pool surface is in the molten state. Thus, while solving the species conservation equation a species flux condition is used on the entire melt pool surface. This case is analysed for aluminium alloying element on iron base metal. The final species distribution in the melt pool as well as in the solidified alloy is predicted. The other extreme case is studied for an alloying element with its melting point relatively higher than that of the base metal. In this case all the alloying element particles on the melt pool surface will not melt. Only those particles which fall in the region on the melt pool surface where the local temperature is higher than the melting point of the alloying element will melt. The particles which fall away from this region are advected into the melt pool, due to a strong Marangoni convection on the melt pool surface. If a particle is advected into the inner region in the melt pool (where the temperature is higher than its melting point), it starts melting and thus the molten species mass gets distributed. Hence, the species flux condition at the entire surface of the melt pool is not valid. The particles are tracked in the melt pool by assuming the alloying particles to be spherical in shape and moving without any relative velocity with the surrounding fluid. Simultaneously, the temperature field inside the spherical particle is solved by assuming its surface temperature to be the local temperature in the melt pool. The amount of particle mass that fuses as it passes through a particular control volume is noted. The same procedure is repeated for a large number of particles initiated at various locations on the pool surface, and a statistical distribution of the species mass source in the entire pool is obtained. This species mass source distribution is then used to solve the species conservation equation. Nickel alloying element on aluminium base metal is used to illustrate this case. The numerical results obtained from the two cases are compared with the available experimental results. A qualitative matching is found between the numerical and experimental results.

Advanced nano-structured ferritic alloys (NFAs) containing a high density of ultra-fine (2-5 nm) nanoclusters (NCs) enriched in Y, Ti, and O are considered promising candidates for structural components in future nuclear systems. The superior tensile strengths of NFAs relative to conventional oxide dispersion strengthened (ODS) ferritic alloys are attributed to the high number density of NCs, which may provide effective trapping centers for point defects and transmutation products generated during neutron irradiation. This study consists of production, irradiation, and characterization of an advanced NFA, designated 14YWT, currently being developed at Oak Ridge National Laboratory (ORNL), in Oak Ridge, Tennessee. The purpose of this study was to characterize the tensile and fracture toughness properties of 14YWT produced during this project at ORNL before and after irradiation to evaluate it's resistance to radiation-induced changes in mechanical properties. Another alloy, designated 14WT, was produced during this project using identical production parameters used for 14YWT but without the Y2O3 addition during ball milling required for NC formation. Tensile and fracture toughness specimens were produced from both alloys and irradiated in small "rabbit" capsules in the High Flux Isotope Reactor (HFIR) at ORNL. Five other structural alloys that are currently being evaluated for applications in nuclear environments were irradiated and tested during this project to serve as comparison materials. Microstructural characterization was performed using optical microscopy, scanning electron microscopy, transmission electron microscopy, and atom probe tomography. Tensile strengths for 14YWT were found to be far superior to the other alloys for both irradiated and unirradiated conditions, with yield strength for 14YWT decreasing from ~1,450 MPa at 26°C to ~700 MPa at 600°C. Moderate radiationinduced hardening (50-200 MPa) and reduction in ductility was observed for 14YWT for all irradiation conditions and test temperatures. Fracture toughness results showed 14YWT in the unirradiated condition had a fracture toughness transition temperature (FTTT) around -150°C and upper-shelf K[subscript JIc] values around 175 MPa m. Results from irradiated 14YWT fracture toughness tests were found to closely mirror the unirradiated data and no shift in FTTT or decrease in K[subscript JIc] values were observed following neutron irradiation to 1.5 dpa at 300°C. Master curve analysis of the fracture toughness data show 14YWT to have a T[subscript o] reference temperature of -188 and -176°C in the unirradiated and irradiated condition, respectively, which is unprecedented for a high-strength dispersion strengthened ferritic alloy. The results from this study show 14YWT to be resistant to radiation-induced changes in mechanical properties and a promising candidate for structural applications in future nuclear systems. / text