O controle das características da escória de refino primário pode ser realizado pela adição de fluxantes, sendo comumente utilizado a Fluorita (CaF2), isto porque a Fluorita aumenta a solubilidade de CaO e, por conseguinte, aumenta a capacidade de desfosforação de escória. Apesar disso, alguns estudos advertem sobre o risco de liberação de gás tetra fluoreto de silício, que tem caráter nocivo para o meio ambiente. Outro problema relatado é o aumento do desgaste do revestimento refratário impactando nos custos de produção. Neste trabalho de mestrado o uso de Sodalita Nefelínica como fluxante foi comparado com a Fluorita em relação ao desgaste de refratários a base de MgO-C e à fluidez. Os ensaios consistiram em dopar escória de conversor LD com diferentes quantidades de Fluorita e Sodalita (1, 2, 3, 4 % em massa). Os resultados demonstraram que a Fluorita fornece uma escória com menor ponto de fusão e mais fluida, porém ela causa maior desgaste no revestimento refratário, mais que o dobro do desgaste causado pela Sodalita. Acredita-se que isso tenha ocorrido devido a Fluorita ser capaz de aumentar a dissolução tanto do CaO presente na escória quanto do MgO presente no refratário. Este processo é intensificado pela baixa viscosidade apresentada com este fluxante. / The control of the slag characteristics from primary refining can be accomplished by adding fluxes, being commonly used Fluorite (CaF2). This happens because the fluorite increases the solubility of CaO and thus increases the ability of the slag dephosphorization. Nevertheless, some studies warn about the risk of releasing silicon tetra-fluoride gas which has harmful character to the environment. Another problem reported is the increased wear of the refractory lining impacting on production costs. In this master dissertation the use of Sodalite Nepheline as flux was compared with Fluorite concerning MgO-C based refractories wear and fluidity. The tests consisted of doping LD converter slag with different amounts of Fluorite and Sodalite (1, 2, 3, 4 % mass). The results showed that the Fluorite provides a slag with a lower melting point and becomes more fluid, but it causes greater wear on the refractory lining, more than double the wear caused by Sodalite. It is believed that this has occurred due Fluorite be able to enhance the dissolution of the CaO in slag as well as MgO present in the refractory. This process is intensified by the low slag viscosity presented with this flux.

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The annular cement sheath plays a crucial role in ensuring well integrity by providing adequate zonal isolation, stabilizing the formation, and protecting the casing from corrosion. A majority of well integrity problems originate from oil well cement shrinkage and shrinkage-induced cracking, as well as cracking induced by other external stresses. The addition of expansive additives is a commonly used way to compensate for shrinkage. Compared to conventional ettringite-based and CaO-based expansive additives, MgO has many advantages including a thermally stable hydration product, relatively low water requirements for hydration, and designable expansion properties. These make MgO a promising candidate for delivering the desired expansion under the complex and variable underground wellbore environment. Self-healing materials which have the capability for autonomous crack repair are an attractive solution for addressing cracking problems in oil well cement. Engineered additions of healing agents for autonomic self-healing via a delivery system have been reported as effective ways to promote self-healing in cementitious materials. Microcapsules that can be easily added to cement pastes and dispersed through the cement matrix are considered particularly suitable for use in oil well cement. This research project investigates the efficacy of reactive MgO expansive additives to reduce shrinkage, and of sodium silicate microcapsules to improve the self-healing properties of oil well cement, and explores the feasibility of their combined use in a high temperature oil well environment. Three types of reactive MgOs from different reactivity grades, high reactivity N50, medium reactivity MAG-R, and low reactivity 92/200, were characterised in terms of their expansion characteristics in cement paste prisms cured in water, and further tested on their autogenous shrinkage reduction at 80oC. The highly reactive N50 could only partially compensate for autogenous shrinkage, while the less reactive MAG-R and 92/200 completely compensated for autogenous shrinkage. MAG-R and 92/200 also showed effective drying shrinkage reduction at 90% RH. The restrained expansion of MAG-R and 92/200 during an early age was found to significantly improve the cracking resistance of oil well cement. The free expansion of 92/200, with low reactivity, caused significant strength reduction, but under restrained conditions the effect was mitigated as its compressive strength was enhanced by confined expansion. The addition of MAG-R increased compressive strength under both free and restrained conditions. Two groups of sodium silicate microcapsules, T1 with rigid polyurea shells and T2 with rubbery polyurea shells, were characterised in terms of their thermal stability, alkalinity resistance and survivability during cement mixing, and the results verified their suitability for use in oil well cement at the high temperature of 80 oC. The effects of the two types of microcapsules on the self-healing performance of oil well cement at 80 oC were monitored using a variety of techniques. Oil well cement itself showed very little healing capability when cured at 80 oC, but the addition of microcapsules significantly promoted its self-healing performance, showing reduced crack width and crack depth, enhanced tightness recovery against gas permeability and water sorptivity, as well as strength recovery. Microstructure analyses of the cracking surface further verified the successful release of the sodium silicate core and its reaction with the cement matrix to form C-S-H healing products. Both groups of microcapsules showed comparable self-healing efficiency. Their different shell properties mainly influenced the strength of oil well cement, with rigid shell microcapsules causing less strength reduction than rubbery shell microcapsules. The overall performance of oil well cement containing both reactive MgO and microcapsules were evaluated. The combined addition of MgO MAG-R and T1 microcapsules showed similar expansion performance and self-healing efficiency compared to their individual use. The use of MgO MAG-R compensated for the strength reduction caused by the addition of microcapsules, achieving an overall improvement in the cement strength.

The aim of this study was to investigate the reaction behaviors of nanoscale Fe3O4 and H1/10-[Fe3O4]MgO slurry injection coupled with the electrokinectic (EK) process for remediation of NO3− and Cr6+ in saturated soil. To assure the above-mentioned nanomaterials were capable of reductively adsorbing inorganic pollutants (e.g., NO3− and Cr6+) in the acidic environment in the anode reservoir of the ek remediation system, an investigation on transformation of the concerned nanomaterials in different aqueous solutions (de-ionized water and simulated groundwater ) of different initial pHs (2 and 3.5) was conducted. Due to a high dose of nanoscale Fe3O4 and a resulting serious agglomeration while adsorbing NO3− and Cr6+, the characteristic peaks of the X-ray diffraction (XRD) analysis for nanoscale Fe3O4 remained the same after adsorption experiments. But the situations were quite different in the case of nanoscale H1/10-[Fe3O4]MgO, the characteristic peaks of £\-Fe2O3 in the XRD pattern were detected, confirming that this nanomaterial could reductively adsorb NO3− and Cr6+ in the acidic environment. The effectiveness of using polyacrylic acid (PAA) and soluble starch (SS) to stabilize nanoscale Fe3O4 and H1/10-[Fe3O4]MgO in different aqueous solutions containing humic acid was compared. It was found the former yielded a better stability. Therefore, PAA was chosen to prepare the slurries of target nanomaterials. Then slurry injection coupled with the EK process was tested for remediation of NO3- and Cr6+ in saturated soil. The results showed that the removal efficiency of NO3− was more than 90%, and the NO3− concentration in the anode reservoir was below Taiwan¡¦s Pollution Control Standards of type¢¹Groundwater for NO3−-N. Under the same test conditions, however, the removal efficiency of Cr6+ was unsatisfactory. This might be ascribed to acidification of soil near the anode resulting in high adsorption of Cr2O72− by soil. Thus, a solution to solve this problem has to seeked. The solution lies in how to enhance the contact of the above-mentioned nanomaterials with Cr6+ in the anode reservoir. One possibility is to use the nature of SS would hydrolyze in the acidic environment. Therefore, SS-stabilized nanomaterials in the acidic environment would hydrolyze resulting in the exposure of the soil nanomaterials therein. To this end, SS was used to replace PAA for nanomaterial slurry preparation for remediation of Cr6+. In addition, polarity reversal was practiced in the EK system to maintain a neutral ph of soil and increase the mobility of Cr6+ in soil. Finally, the result showed that nanoscale Fe3O4 and H1/10-[Fe3O4]MgO slurry injection coupled with the polarity reversal electrokinetic system could really enhance the removal efficiency of Cr6+ in the saturated soil. In summary, nanoscale Fe3O4 and H1/10-[Fe3O4]MgO slurry injection coupled with the EK process has been proven to be capable of remedying NO3− and Cr6+ in saturated soil. Meanwhile, the concept of reductive adsorption was realized in this work as well.

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Non-stoichiometric barium titanate (BaTiO3) powder of TiO2-excess compositions has been investigated using both reducing sintering and acceptor-doping. Crystalline phases were analysed by XRD. Attention has been paid to the analysis of the corresponding sintered microstructure by adopting scanning and transmission electron microcopy. Reducing sintering was in the low oxygen partial pressure, so as to dominate the oxygen-deficient. According to the defect chemistry, the purpose of acceptor-doping was the same as reducing sintering. We look out for phenomena which may be indicative that oxygen vacancies generated by acceptor-doping and reducing sintering have resulted in the metastable retention of high temperature hexagonal-BaTiO3 to an ambient temperature. In the Mg-doped study investigated the possibility that Mg2+ substitutes on Ti4+ site rather than the Ba2+ site, as expected from the radii. According to the unknown phase was indexed a supercell of MgTiO3, that showed evidence of Mg2+ dissolves in BaTiO3 and occupies the Ba2+ site. To reduce in a hydrogen atmosphere was a high dark conductivity. The Ti3+ content was determined via colorimetry. Because of the defect chemistry led to oxygen-deficient h-BaTiO3, i.e.BaTi1-xTixO3-x/2. The observed volume expansion behavior under Ar-H2 atmosphere demonstrates the possibility of having various microstructures via control of oxygen partial pressure. The transformation matrix described the relation between the two reciprocal lattices of the twinning. Investigation of reciprocal lattices was shown that ordering oxygen deficient on the BaO3 layer in the twin boundary. There was evidence of XRD patterns and surface energy that explained more and more twins in the microstructure via control of the low oxygen partial pressure. According to this theory, lamellae twins were generated by oxygen-deficient. The hexagonal phase might be also expressed as the cubic BaTiO3 containing twin boundary at BaO3 planes every three layers. That demonstrates the possibility of hexagonal phase retention in BaTiO3 was oxygen vacancies.

This study was to prepare nanoscale MgO using the homogeneous precipitation process and to investigate its destructive adsorption with dye wastewater of reactive black-5 and reactive blue-19. In addition, UV-vis Spectrophotometer, Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF/MS) and Gas Chromatograph/Mass Spectrometer (GC/MS) were used to analyze the intermediates resulting from destructive adsorption. Based on the results obtained, the destructive adsorption mechanisms for the treatment of dye wasterwater by nanoscale MgO were proposed in this study. In this work, the optimal operating conditions for nanoscale MgO synthesis were determined to be the following: (1) a chemical reaction time of 7 hr, (2) reaction temperature of 125¢J, (3) molar ratio of 9 for urea/MgCl2¡D6H2O, (4) water addition of 250 mL, (5) mixing intensity of 90 strokes per min, (6) calcination at 450¢J for 4 hr, (7) reflux time of 24 hr, (8) freeze-drying method, (9) two stage calcinations. Using these operating conditions one is able to prepare 2-D nanoscale MgO of hexagonal platelets with a thickness of 20-30 nm and BET surface area of 120-125 m2/g. The adsorption model of nanoscale MgO for RB-5 and RB-19 was fitted to the Langmuir equation and their adsorption capacity were 196.08 mg/g and 163.93 mg/g, respectively. Both of them were fitted to the pseudo-second-order kinetic model equation. The optimal operating conditions of nanoscale MgO for destructive adsorption of both dyes were determined to be the following: (1) an initial dye concentration of 1000 mg/L, (2) a nanoscale MgO dose of 15 g/L, (3) a vigorous mixing of 30 min, (4) no need of system pH adjustment. Under such conditions, chemical oxygen demand (COD) and American Dye Manufacturers Institute (ADMI) of RB-5 and RB-19 were lower than the textile effluent standards. According to the UV-vis spectrophotometer scanning results, the color removal of nanoscale MgO for RB-5 and RB-19 was good. At the same time, the absorbance of their second maximal peaks was decreased and some peaks were observed. Therefore, it proved that the model dyes were destroyed. Experimental results have shown that nanoscale MgO has a better performance of destructive adsorption on RB-5 than that of RB-19. This might be ascribed to the following reasons: (1) a greater molecular weight, (2) a longer molecule structure, (3) more sulfate ethyl sulfone groups for RB-5, and (4) a hard to be destroyed structure of anthraquinone for RB-19. The destructive adsorption of dye wastewater by nanoscale MgO presumably took place mainly on the surface active sites of nanoscale MgO, including anion/cation vacancies, superoxide anion, edge, corner, isolated OH, lattice bound OH and assiocited-OH groups. According to the results of MALDI-TOF/MS and GC/MS analysis, the relevant reaction mechanism for RB-5 could be divided into three stages: (1) adsorption and water-soluble groups exfoliation stage, (2) chromophor decomposition and decolorization stage, and (3) further degradation stage for light-color intermediates. On the other hand, the relevant reaction mechanism for RB-19 might involve only the adsorption and auxochrome exfoliation stage and chromophor decomposition and decolorization stage.

This study was to investigate the reaction behavior of nanoscale [Fe3O4]MgO and trichlorothylene (TCE) in aqueous solutions. In addition, effects of environmental variables on TCE removal from a simulated groundwater system were investigated. At first, two types of metal oxide composites containing both nanoscale Fe3O4 and MgO (designated H-[Fe3O4]MgO and S-[Fe3O4]MgO, respectively) were prepared. Then they were characterized and verified by various apparatuses and methods including X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, specific surface area measurements. Since the substrate of S-[Fe3O4]MgO with a molar ratio of Fe3O4/MgO = 1/5 (designated S1/5-[Fe3O4]MgO) had a much greater specific surface area than that of the substrate of S-[Fe3O4]MgO with a molar ratio of Fe3O4/MgO = 5/5 (designated S5/5-[Fe3O4]MgO), S1/5-[Fe3O4]MgO was selected as the model composite for the treatment of TCE in this study. Results of batch tests showed that S1/5-[Fe3O4]MgO had the best treatment performance among various metal oxides and their composites. For an initial TCE concentration of 10 mg/L, however, only 45% removal could be achieved by 5.0 g/L of dispersed S1/5-[Fe3O4]MgO. Nevertheless, a greater removal efficiency could be obtained for a higher initial TCE concentration in a simulated groundwater system. Test results also showed that a lower temperature and higher pH would retard the relevant reaction rates in TCE removal. In the simulated groundwater system employed in this work, the existence of humic acid (< 10 mg/L) played an insignificant role in affecting the TCE removal. Analysis of TCE adsorption on S1/5-[Fe3O4]MgO in aqueous solution indicated that a Langmuir-type of chemical adsorption would have a better fit. Results of gas chromatography further showed the existence of small to trace amounts of TCE degradation products including cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, vinyl chloride, ethene and methane, etc. Thus, the relevant reaction mechanisms and pathways for the destructive adsorption were proposed.

This study was to investigate the reaction behavior of laboratory-prepared nanoscale adsorbents (Fe3O4 and H-[Fe3O4]MgO) and inorganic pollutants (NO3-, Cd2+and Cr6+) in simulated groundwater. First, Fe3O4 and the composites of nanoscale Fe3O4 and MgO were prepared using chemical co-precipitation method. Then they were characterized and verified by various apparatuses and methods including X-ray diffractometry, scanning electron microscopy, Zetasizer, and specific surface area measurements. Second, the nanoscale adsorbents were used to adsorb inorganic pollutants in simulated groundwater of different conditions. The relevant reaction behavior and mechanisms were also investigated. Results of this research showed that Fe3O4 and H-[Fe3O4]MgO had the greater adsorption amount when the initial concentration of inorganic pollutants was higher than lower. The adsorption rate of inorganic pollutants at 28¢J was greater than that of at 18¢J. The experimental results also showed that at a higher pH environment or the existence of humic acid in simulated groundwater would increase the removal efficiency of Cd2+, but decrease the removal efficiency of NO3- and Cr6+. Analysis of inorganic pollutants adsorption on nanoscale adsorbents in simulated groundwater indicated that a Langmuir-type of chemical adsorption and pseudo-second-order reaction kinetic equation would have better fit. In this study, it was also found that nanoscale adsorbents not only adsorbed inorganic pollutants but also reduced NO3- and Cr6+ to NO2-, NH4+, and Cr3+ at pH=3, respectively. Thus, the nanoscale adsorbents (Fe3O4 and H-[Fe3O4]MgO) prepared and were capable of reductively adsorbing inorganic pollutants (e.g., NO3- and Cr6+) for environmental remediation.

Catalytically relevant metal clusters were deposited on metal oxide supports. Palladium and gold were deposited on mixed morphology ZnO, and palladium was deposited on MgO(100). The materials were characterized with electron microscopy, photoluminescent spectroscopy, and X-ray photoelectron spectroscopy. The behavior of hydrogen on these materials, as well as bare ZnO, was studied using volumetric isotherms. The isotherms were used to determine the monolayer gas coverage, surface area, and heats of adsorption of hydrogen on these materials over the temperature range of approximately 8-13 K. At the temperatures and pressures studied, hydrogen physically adsorbed onto the materials. Additional investigations with inelastic neutron scattering were conducted on palladium decorated ZnO and bare ZnO. These revealed that hydrogen molecules on bare ZnO act as three dimensional free rotors, but hydrogen on palladium decorated ZnO acts as a two-dimensional planar molecule and undergoes a 6.2% bond length extension.