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1
Nadler, Jason Hayes. "The hydrogen reduction of iron and chromium oxides." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/19410.
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Ali, Iqbal 1948. "THE SURFACE CHEMISTRY OF CHROMIUM OXIDES IN AQUEOUS SOLUTIONS." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276486.
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A detailed study has been carried out to investigate the dissolution characteristics of unstabilized and stabilized CrO₂ particles. It has been found that on contact of CrO₂ with aqueous solutions, it dissolves by disproportionation reaction to HCrO₄ and Cr2O₃. XPS study has shown that stabilization of CrO₂ particles with bisulfite solution leads to the formation of Cr2O₃. However, because of agglomeration of the CrO₂ particles due to their magnetic properties, not all of the surface is completely stabilized. The electrokinetic characteristics of Cr(IV) and Cr(III) oxides in aqueous solutions have been investigated. Experiments suggest that sulfite ions chemisorb strongly on Cr₂O₃ particles. Experiments have also been carried out to study the adsorption of sodium dodecyl sulfate (SDS) on Cr₂O₃ particles. With increasing SDS concentration, Cr₂O₃ becomes less positively charged and ultimately negatively charged when the surfactant concentration exceeds 10⁻³ M. This suggests that SDS specifically adsorbs onto the oxide.
3
McIntosh, Monique Sandra. "Mechanisms and Factors Affecting Chromium Oxide Particle reduction in Iron-Chromium Honeycombs." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6934.
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In the production of iron chromium honeycombs, iron oxide and chromium oxide mixtures are reduced by hydrogen at elevated temperatures to produce a metallic alloy. The complete reduction of the iron oxide occurs prior to the reduction of the chromium oxide. The reduction of the chromium oxide particles within the iron matrix is affected by factors that include the diffusion of the reduced chromium away from the chromium oxide particle into the iron matrix, the diffusion of the gaseous reactants and products to and from the chromium oxide particles, and the porosity of the iron matrix, which changes as a result of sintering. The type of heat-treatment used, (isothermal or non-isothermal, i.e., holding at a specific temperature versus using a steadily increasing temperature) plays a vital role in how these factors will affect chromium oxide reduction.
Experimental data were used in conjunction with sintering and dissolution models to obtain an understanding of the environment in which the chromium oxide particles reduce as a function of heat-treatment. This understanding will assist in the development of more effective processing steps for the reduction of metallic honeycombs from oxide mixtures.
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Hillan, Marguerita Charlotte. "Investigations into steel substrate surface composition and the assessment of Cr. (VI) electrodeposit characteristics." Thesis, University of the West of Scotland, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365054.
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Rowley, Adrian. "Computer simulation of oxides." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298405.
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Lei, Yun School of Chemical Engineering & Industrial Chemistry UNSW. "Novel Fe2O3-Cr2O3 catalyst for high temperature water gas shift reaction." Awarded by:University of New South Wales. School of Chemical Engineering and Industrial Chemistry, 2005. http://handle.unsw.edu.au/1959.4/23321.
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The thesis is focused on the study of high temperature water gas shift catalysis, the identification of new improved catalysts and the study of the kinetics and mechanism of reaction over these catalysts. Rh-promoted Fe2O3-Cr2O3 was found to offer best performance which was significantly better than unpromoted catalyst over wide temperatures range. An extensive literature survey is first reported. Guidelines to develop new WGS catalysts are developed. As a result, the activities of precious metals supported on various oxides for high temperature WGS reaction have been tested. Rh(1wt%) doped Fe2O3/Cr2O3, exhibits the highest activity for WGS over a wide temperature range. 5wt%CuO/Fe2O3-Cr2O3, 1wt%Pt/Cr2O3, 1wt%Pt/Fe2O3-Cr2O3, 1wt%Pt/U3O8, 1wt%Pt/10%U3O8-Al2O3 and 1wt%Pt/5%V2O5-TiO2 fall into the second most active catalysts group, with an improved activity compared to commercial Fe2O3-Cr2O3 catalyst. It is clear that both the support/catalyst and the promoter can affect the efficiency of the WGS, leading to the obvious inference that the reaction rate is controlled at the promoter ??? support interface. Further kinetic studies and characterisation (TPR, TPD, pulse-adsorption (reaction)) on Rh/Fe3O4/Cr2O3 have been conducted. The study, conducted under conditions without inhibition from products of both forward and backward reactions, shows that the overall reaction rate expression is described as: 2 22 ??? =0.0041exp(???4042.6 ) 0.64 0.5 ???0.024 exp(???6022.9 ) 0.46 0.73 CO CO H O CO H r PP P P T T . Kinetics studies carried out under fuel reforming gas compositions shows that reaction rate expression changed when the temperature of reaction varied. The reaction rate equations at temperatures of 573K, 623K and 673K are derived as: 573K: 2 2 2 - 2.84 10-6 0.6 0.12 - 9.08 10-7 0.09 0.52 rCO = ?? PCO PH O ?? PCO PH 623K: 2 2 2 - 1.45 10-6 0.99 0.40 - 7.12 10-7 0.11 0.73 rCO = ?? PCO PH O ?? PCO PH 673K: -6 2 2 2 - = 4.37 ?? 10 0.86 0.41 -1.83 ??10-6 0.28 0.66 rCO PCO PH O PCO PH , The apparent activation energy was 61.7??2.5 kJmol-1 . TPR, TPD, TPO characterisation studies and reoxidation of catalysts by CO2 or H2O show that the active site for high temperature WGS reaction on Rh/Fe2O3/Cr2O3 is reduced magnetite Fe3O4 which dissociatively breaks down the H2O to form H* and OH* and adsorbs CO2. The deposited metal, Rh, acts as a promoter by facilitating the uptake of hydrogen (H2) and carbon monoxide (CO), desorption of H2 (at high temperature) and CO2.
7
Davies, G. H. "Adsorption and reaction of hydrogen cyanide on mixed copper and chromium oxides." Thesis, University of Bath, 1985. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.290991.
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The adsorption and interaction of HCN has been studied on (a) copper oxides on crystalline chromia, (b) mixtures of chromium (III) oxide and copper oxides on silica, and (c) mixtures of Cr(VI)O3 and CuO on silica. The adsorption and reaction of both HCN and C2N2 on Cr(VI)O3/SiO2 has also been studied. The work has involved gravimetric studies with a vacuum microbalance, infra-red spectroscopy of adsorbed species, and mass spectroscopic analysis of products. HCN contact at 293 K with both CuO/a-Cr2O3 and CuO-Cr2O3/SiO2 samples led to the slow release of cyanogen. The cyanogen reaction was shown to be occurring on the copper ions of the surface accompanied by reduction to cuprous hydroxide. Some HCN adsorption also occurred on this surface and on the chromia part of the surface without oxidation to cyanogen. On heating, some HCN was desorbed intact but most was oxidised to CO2 with some retention of nitrogen compounds on the surface. The infra-red work indicated that on the copper oxide part of the surface this oxidation occurred via an isocyanate, NCO, intermediate. On the chromia part of the surface HCN adsorption produced an amide species which decomposed to CO2 and N2. Pre-reduction of the surface suppressed cyanogen formation upon HCN adsorption, although considerable oxidation still occurred on heating. On Cr(VI)O3/Aerosil both HCN and C2N2 formed surface amides. On heating, there was some decomposition to CO2 and N2, as with Cr (III) oxide, but also in some cases sublimation of oxamide. With Cr(VI)O3-Cu(II)O/Aerosil, much less gaseous C2N2 was produced from HCN than on Cr2O3/CuO/Silica. This suggests that cyanogen was being preferentially adsorbed on the Cr(VI)O3. The results show the importance of the oxidation states of Cu and Cr in determining the surface reactions of HCN.
8
Luxton, Todd Peter. "Oxyanion Adsorption by Iron and Ruthenium Oxides: A Macroscopic, Spectroscopic, and Kinetic Investigation." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/28394.
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The adsorption and desorption behavior of trace element contaminants was evaluated
solids-goethite and ruthenium oxide. The importance of anion displacement as a mechanism
responsible for arsenic release from iron oxides was investigated on goethite. The adsorption
and polymerization of silicate on goethite was examined as a function of surface concentration
determine the influence of adsorbed silicate monomers and polymers on arsenite adsorption
desorption. A kinetic model was employed to describe arsenite adsorption and desorption
absence and presence of silicate. The potential environmental impacts of the research
discussed. Hydrous and crystalline ruthenium oxides were extensively characterized
traditional colloidal surface characterization techniques, dissolution experiments, and macro-
spectroscopic experiments. The two ruthenium oxide phases exhibited large specific
areas, a high density of reactive surface functional groups and the presence of multiple
oxidation states in both solids. Enhanced dissolution of hydrous ruthenium oxide occurred
presence of oxalate and ascorbate. While enhanced dissolution of the crystalline phase
only in the presence of oxalate at pH 3. Results from the dissolution experiments were
develop possible mechanisms for the oxalate and ascorbate promoted dissolution of ruthenium
oxides. Macroscopic adsorption studies of arsenate adsorption on both ruthenium oxides
examined over a broad pH (3-10) and initial solution concentration range (0.01 to
Results from the adsorption studies indicate arsenate forms a stable surface complex with
ruthenium oxide phases. Extended x-ray absorption fine structure spectroscopy and Pressurejump
relaxation studies indicates arsenate is specifically adsorbed the ruthenium oxide
Chromate adsorption on ruthenium oxides was investigated as a function of pH and
chromate solution concentration. Macroscopic adsorption studies and zeta
measurements suggest chromate forms an inner-sphere surface complex with both oxide
X-ray absorption near edge spectroscopy data indicates chromate (Cr(VI)) is reduced
chromium (Cr(III)) on the ruthenium oxide surface. Modeling of the first Cr shell indicated
two oxygen backscattering distances similar to the Cr-O atomic distances reported for
coordinated to Cr(VI) and Cr(III) providing additional evidence for Cr(VI) reduction.Ph. D.
9
Chan, Chun Man. "Transmission electron microscopy study of growth of oxide film in nanoparticles of Cr and Fe /." View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202003%20CHAN.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003.Includes bibliographical references (leaves 58-59). Also available in electronic version. Access restricted to campus users.
10
Dong, Pengli. "Measurements of the thermodynamic activities of chromium and vanadium oxides in CaO-MgO-Al2O3-SiO2 slags." Licentiate thesis, KTH, Materials Science and Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9940.
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In the present work, the thermodynamic activities of chromium and vanadium oxide in CaO-SiO2-MgO-Al2O3 slags were measured using gas-slag equilibration technique. The slag was equilibrated with a gas mixture of CO, CO2 and Ar gases enabling well-defined oxygen partial pressures in the gas mixture (PO2=10-3,10-4,10-5 Pa) at temperatures 1803, 1823K, 1873, 1923 K. The slags were kept in Pt crucibles during the equilibration and the duration of which was 20 h. From a knowledge of the thermodynamic activity of chromium and vanadium in Cr or V in Pt alloy, obtained from literature, and the oxygen partial pressure in the gas stream calculated by Thermo Calc software, the thermodynamic activity of chromium, vanadium oxide in the slags could be observed.An assessment of the experimental studies in earlier works reveal that, the activities of chromium at low chromium contents and vanadium in their respective alloys in platinum exhibits a strong negative deviation from ideality, the logarithms of activity coefficient of these elements were found to increase with increasing mole fractions of these metals in the Pt-alloys.Regarding the slag phase, all the chromium in the slags was assumed to be present in the divalent state in view of the low Cr contents and the low oxygen potentials employed in the present studies. Analogously, vanadium in the slag was assumed to be in the trivalent state in view of the low vanadium contents in the slag and the low oxygen partial pressure in the gas phase. Activity of chromium oxide, CrO decreases with increasing temperature and decreasing content of chromium oxide in slag and oxygen partial pressure in the gas phase. Activity of vanadium oxide, VO1.5 in slag phase shows a negative deviation from ideality. Activity coefficient of vanadium oxide shows a decrease with basicity of slag and the “break point” occurs at about slag basicity of 1 under the oxygen partial pressure of 10-3 Pa and temperature of 1873 K.A relationship for estimating the actual content of chromium, vanadium in slag as a function of activities of chromium or vanadium, temperature, oxygen partial pressure and slag basicity were developed from the present results, the agreement between the estimated and experimental values is satisfactory, especially at lower oxygen partial pressure.
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Bhandari, Narayan. "Investigations of the (Photo)Chemistry of Nano- and Micron-dimensioned Iron Oxides for Metal(loid) Remediation." Diss., Temple University Libraries, 2013. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/225174.
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ChemistryPh.D.
Anthropogenic activities and natural processes over time have led to the release of toxic heavy metal contaminants into the environment. As a consequence, there is an increasing number of illnesses caused by the exposure of humans to heavy metals and metalloids. The dissertation work presented here focused on the synthesis, characterization, and understanding of the surface chemistry, as well as the photo-reactivity, of a variety of iron (oxyhydr)oxide nano-materials that have relevance for the remediation of heavy metal contaminants, such as arsenic and chromium in aqueous environments. The research focused on the photo-induced reductive dissolution of a nano-dimensioned iron oxyhydroxide, ferrihydrite, in the presence of oxalate, the photo-induced arsenite oxidation, and the simultaneous redox transformation of arsenite and chromate in the presence of ferrihydrite and another environmentally relevant iron oxyhydroxide, goethite. The photo-reductive dissolution of ferrihydrite (using simulated solar radiation) in the presence of oxalic acid was investigated with surface sensitive in situ and ex situ techniques that included attenuated total reflectance Fourier transform infrared spectroscopy. Ferrihydrite at a solution pH of 4.5 exhibited an induction period where the rate of Fe(II) release was limited by a low concentration of adsorbed oxalate due to the site-blocking of carbonate that was intrinsic to the surface of the ferrihydrite starting material. The photo-induced decarboxylation of adsorbed oxalate also ultimately led to the appearance of carbonate reaction product (distinct from carbonate intrinsic to the starting material) on the surface. Ferrihydrite that was prepared under carbonate free condition showed a rapid release of Fe(II) upon irradiation and no induction period was observed. Arsenite [As(III)] oxidation in the presence of ferrihydrite and goethite was also investigated. Ferrihydrite or goethite when exposed to As(III) in the dark led to no change in the oxidation state of As(III) reactant. However, exposure of As(III) in the presence of ferrihydrite or goethite to simulated solar light resulted in the oxidation of As(III) and a reduction of surface Fe(III) leading to an overall increase in the total As removal. At a solution pH of 5, this conversion of As(III) to As(V) on ferrihydrite resulted in the partitioning of a stoichiometric amount of Fe(II) into the aqueous phase and the majority of the As(V) product remained bound to the ferrihydrite surface. In contrast, the As(III)/goethite system showed a different photochemical behavior in the absence or presence of dissolved oxygen. Under oxic conditions, in contrast to ferrihydrite, the majority of the As(V) product was in the aqueous phase and the relative amount of aqueous Fe(II) was significantly less than in the ferrihydrite circumstance. Experimental observations suggested that in the oxic environment, Fe(II) on the goethite surface was heterogeneously oxidized to Fe(III) by dissolved oxygen resulting in the formation of reactive oxygen species that led to the further oxidation of As(III) in solution. Similarly, various experimental investigations were conducted to test the simultaneous removal of As(III) and Cr(VI) from solution. Our results suggested that a surface mediated spontaneous electron transfer between As(III) and Cr(VI) occurred in the presence of Fe- and Al-(oxy)hydroxides. Both infrared and x-ray absorption spectroscopies were conducted to get more insight into the charge transfer reaction and mechanism of electron transfer reaction. In summary, the research discussed here should help to understand the details of oxidation/reduction reactions occurring at mineral-water interfaces. Perhaps more importantly, the methodologies discussed in this dissertation could potentially be novel and eco-friendly approaches for arsenite as well as hexavalent chromium remediation.
Temple University--Theses
12
Bergman, Ola. "Studies of oxide reduction and nitrogen uptake in sintering of chromium-alloyed steel powder." Licentiate thesis, KTH, Materials Science and Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9555.
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The powder metallurgy (PM) process route is very competitive for mass production of structural steel components with complex shape, due to efficient material utilisation, low energy consumption, and short overall production time. The most commonly used alloying elements are the processing friendly metals Cu, Ni and Mo. However, the prices for these metals are today high and volatile, which threatens to make the PM process less competitive compared to conventional metal forming processes. Consequently, there is a strong desire in the PM industry to increase the use of less costly alloying elements. Cr is an attractive alternative since it, besides low cost, provides high hardenability and also recyclable components. The drawback is that Cr has high affinity for oxygen, which makes oxidation and oxide reduction in PM processing of Cr-alloyed materials a challenging issue. Furthermore, the interaction between nitrogen and Cr-alloyed powder during processing is important to consider, since Cr also has high nitrogen affinity and is prone to form nitrides.
The aim of the research work presented in this thesis was to study oxide reduction and nitrogen uptake in sintering of Cr-alloyed steel powder. Water-atomized powder grades pre-alloyed with 1.5-3% Cr were used as test materials. Sintering experiments were performed in N2/H2 (90/10) atmospheres with test bars pressed to density 7.0-7.2 g/cm3. The oxygen content of the sintering atmosphere was varied and different sintering temperatures and cooling rates were applied. The experimental study has been complemented with thermodynamic calculations using the software Thermo-Calc.
The oxygen partial pressure should be below 4 x 10-18 atm in order to have reducing conditions during sintering at 1120°C of steel powder pre-alloyed with 3% Cr. With graphite added to the powder, conditions are reducing at higher oxygen partial pressures (up to 10-16 atm) due to favourable conditions locally in the material. Sintering at 1120°C for 30 minutes leads to incomplete reduction of Cr-oxides in the Cr-alloyed PM grades, but remaining oxides are not detrimental for mechanical properties of the PM components. Increased sintering temperature is beneficial for the oxide reduction kinetics and practically all oxides are reduced after sintering for 30 minutes above 1200°C. Nitrogen uptake by Cr-alloyed steel powder from N2-based sintering atmospheres is strongly dependent on the cooling rate applied after sintering. No nitrides appear in the sintered material and mechanical properties are not affected when normal cooling rates (0.5-1°C/s) are applied. Very low cooling rates (such as 0.05°C/s) may lead to grain boundary precipitation of Cr-nitrides in the sintered material.
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Dong, Qian. "Studies of transport in some oxides by gas phase analysis." Licentiate thesis, Stockholm, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-363.
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Obrovac, Mark Nikolas. "A model of the electrochemistry of chromium substituted lithium manganese oxides based on photoelectron spectroscopy valence band measurements." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq24888.pdf.
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Brown, Jared C. "UV Visible Spectra Analysis of High Temperature Water Gas Shift Catalysts Made from Iron, Lanthanum, Copper, and Chromium Oxides." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3222.
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Hydrogen is a vital component in several different chemical reactions as well as a potential fuel source for the future. The water gas shift (WGS) reaction converts CO and water to hydrogen and CO2. The objective of this work is to first, characterize the potential benefits of the addition of lanthanum oxide (lanthana) to the iron-chromium-copper (Fe-Cr-Cu) oxide catalysts industrially used in high temperature water gas shift processes, and second, analyze these catalysts using in-situ UV-Visible spectroscopy. The benefits of each component in the catalyst are discussed as well as potential benefits from the addition of lanthana. Lanthana is a rare earth oxide that dramatically increases the surface area of the iron based WGS catalysts, and small concentrations of other rare earth oxides (i.e. cerium) have been shown to increase the rate of desorption of CO2 from iron surfaces (Hu Yanping 2002). Lanthana has similar chemical properties to other rare earth oxides tested and has not been previously tested as an additive to the WGS catalyst. Therefore catalysts with 0, 1, 2, 5, 10, and 20 wt% lanthana were made via a co-precipitation method in order to measure changes in activity, physical stability, and thermal stability. Catalyst characterization techniques utilized include electron dispersive X-ray spectroscopy (EDX), temperature programmed reduction (TPR) with hydrogen, and nitrogen physisorption (BET). The kinetic analysis was performed utilizing both mass spectroscopy (MS) and gas chromatography (GC). The addition of 1 wt% lanthana to the Fe-Cr-Cu catalysts increases WGS reaction rates of the catalyst at 425°C and 350°C, however the 0% La catalyst has the highest rates at 375°C and 400°C. The 0% La catalyst shows significant drop off in rate at 425°C, suggesting that the lanthana provides a small thermal stabilizing, i.e. the addition of lanthana prevents catalyst sintering at higher temperatures. Traditionally, chromia acts as the sole thermal stabilizer in these catalysts. The addition of large amounts of lanthana inhibits the chromia stabilizing effect, however small additions of lanthana appear to have an additional catalyst promotional effect without interfering with the chromia thermal stabilization. The increased WGS reaction rates at higher temperatures could allow for greater throughput of reactants in industrial settings. Higher concentrations of lanthana decrease the activity due to what is believed to be disruption of the chromia stabilizing effect as well as reduced amount of the active phase of catalyst. In-situ UV-Visible analysis shows that the oxidation state of the iron in the catalyst has a direct correlation to the UV-Visible light absorbance of the surface of the iron catalyst. Extent of reduction is traditionally measured with a synchrotron which is significantly more expensive than UV-Vis spectroscopy. This study uses the more economical UV-Vis spectrometer to determine similar information. The lanthana doped catalysts show an over-reduction of iron during WGS conditions (i.e. rapid reduction of Fe2O3 to Fe3O4 and FeO).
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Weaver, Robert M. "Comparison of the Reactivity of Various Mn-Oxides With CrIIIaq: Microscopic and Spectroscopic Observations of Dissolution, Cr-sorption and Cr and Mn Redox Interactions." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/29365.
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The interaction between CrIIIaq and seven different Mn-oxides (6 monomineralic, 1 synthetic) have been observed in pH ~4.4 HNO3 and pH ~4.4 ~10-4M CrIIIaq solutions. For each mineral-solution interaction, the aqueous chemical concentrations (e.g. [Mn]aq, [Cr]aq, [CrVIaq]) were measured with time. Reacted samples were examined by XPS to determine if, and to what extent, the surface chemical states of Cr, Mn and O had changed. Microscopic observations of the reacted surfaces were obtained using AFM and high-resolution, low-voltage FESEM. The solubility of the Mn-oxides in the acidic, non-Cr bearing solutions varied inversely with the average Mn valence, but did not show systematic behavior with respect to the mineral structure type (e.g. tunnel, layer, framework). This trend was interpreted as resulting from the relative ability of an adsorbed proton to polarize surface Mn-O bonds, with the polarizability being in the order Mn2+-O > Mn3+-O > Mn4+-O. For samples reacted with CrIIIaq, the rate and extent of reductive dissolution was always greater than for acidic dissolution during the initial time period. The measured ratios of the [Mn]aq : [CrVI]aq were approximately in agreement with the values expected from the proposed stoichiometric reactions. Cr-uptake was observed to occur in undersaturated solutions as a result of adsorption, absorption and surface catalyzed precipitation. The chromium as detected by XPS was predominately CrIII, however pyrolusite contained both CrIII and CrVI. Previous studies have implicated a chromium surface precipitate to be responsible for the cessation of the CrIIIaq oxidation reaction. Our surface sensitive FESEM and AFM observations tend to suggest that Cr-uptake is by isolated site binding, very small (<30 nm) surface clusters or monolayer scale films. Cr-uptake was followed by slow Cr-release on several of the solids (particularly the layered solids) after a substantial portion of the total aqueous Cr had been converted to CrVIaq.
The oxidizing ability of the different Mn-oxides for CrIIIaq is evaluated with regards to the energy level of the redox couple (i.e. the redox potential) as compared with the Fermi energy level of the Mn-oxide. Although these energies were calculated rather than directly measured, the results indicate that electrons originating from adsorbed CrIII ions may be transferred into the conduction band or more likely, into available surface states. The presence of an initial limited quantity of electron accepting surface states likely explains the observation of a rapid initial CrIII-oxidation followed by much slower oxidation. The Mn-oxides that exhibited the greatest and longest lasting CrIII-oxidizing power were the Mn-oxides containing Mn3+, and in particular those containing Mn3+ and Mn2+. It is believed that the combined presence of a reducible Mn ion (e.g. Mn3+) and a highly soluble Mn2+ ion facilitates a sustained CrIII-oxidation reaction because fresh surface is exposed during the reaction.Ph. D.
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Abee, Mark Winfield. "Interaction of Acid/Base Probe Molecules with Specific Features on Well-Defined Metal Oxide Single-Crystal Surfaces." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/29011.
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Acid/Base characterizations of metal oxide surfaces are often used to explain their catalytic behavior. However, the
vast majority of these studies have been performed on powders or supported oxides, and there is very little information
available in the literature on the interaction of acid/base probe molecules with well-defined oxide surfaces of known
coordination geometry and oxidation state. The well-defined, single crystal surfaces of Cu2O (111), SnO2 (110), and Cr2O3
(1012) were investigated for their acid/base properties by the interactions between the probe molecules and the well-defined
surface features. The adsorption of NH3 at cation sites was used to characterize the Lewis acidity of SnO2 (110) and Cu2O
(111) surfaces. The adsorption of CO2, a standard acidic probe molecule, was used to characterize the Lewis basicity of the
oxygen anions on SnO2 (110), Cu2O (111) , and Cr2O3 (1012) surfaces. BF3, while not a standard probe molecule, has
been tested as a probe of the Lewis basicity of the oxygen anions on SnO2 (110) and Cr2O3 (1012).
By studying probe molecules on well-defined metal oxide surfaces with known coordination geometry and oxidation
state, an overall evaluation of NH3, CO2, and BF3 as probe molecules can be made using the surfaces studied. NH3 probed
differences in Lewis acidity of Sn cations on SnO2 (110), which had differences in coordination environments and oxidation
states. But, NH3 adsorption failed to provide any direct information on differences in Lewis acidity of Cu cations in different
local coordination geometries on Cu2O (111). CO2 is a poor probe of the Lewis basicity of oxygen anions on the metal oxide
surfaces studied here. CO2 does not strongly adsorb to either SnO2 (110) or Cu2O (111). On Cr2O3 (1012), CO2 does
interact with oxygen sites but in two different coordinations, which vary with surface condition, making a comparison of basicity
difficult. In the cases studied here, CO2 either does not adsorb, or it does not provide a clear set of results that can be related
simply to Lewis basicity. BF3 seems to be a much better probe of the Lewis basicity than CO2 for the well-defined metal
oxide surfaces studied here. On SnO2 (110) and Cr2O3 (1012), the boron atom of BF3 directly interacts with oxygen sites
by accepting their electrons. BF3 thermal desorption seems to provide a direct measure of the Lewis basicity of different
surface oxygen species as long as they are thermally-stable in vacuum.Ph. D.
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Aubertin, Nadine. "Caractérisation d'une nouvelle série d'oxysels à base de ferrate (VI) et application dans le traitement des eaux." Nancy 1, 1994. http://www.theses.fr/1994NAN10015.
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Cette étude montre dans un premier temps qu'il est possible, à température ambiante et à l'état solide, de stabiliser le groupement feo#4#2# par substitution de fe(VI) par un atome x (x=s(+VI), cr(+VI), p(+V) et al(+III), par formation d'une solution solide k#2(fe#1##x,x#x)o#4. Nous avons montré que chromates et ferrates pouvaient constituer des solutions solides continues; avec les sulfates également, le sel de fer à oxyder a une incidence sur la teneur en fe(VI) du matériau fini; ainsi avec la jarosite, nous avons obtenu un mélange titrant a plus de 10% de fe(VI), alors qu'avec le sulfate ferreux, la teneur en fe(VI) n'excédait pas 7%. Les phosphates et aluminates sont moins favorables à la substitution des ferrates du fait de la charge différente des groupements tétraédriques. Au cours de ces différentes synthèses, nous avons également mis en évidence l'existence d'un nouveau sel ferrique de formule k#2feo(oh)#3 hydroscopique. Nous nous sommes intéressés, dans un deuxième temps, aux propriétés du sulfato-ferrate de potassium et plus particulièrement à sa stabilité thermique et sa stabilité en solution aqueuse. Nous avons dans un troisième temps, étudié l'efficacité des sulfato-ferrates de potassium dans le traitement des eaux usées urbaines d'une part et a potabilité d'autre part, en comparaison avec des réactifs couramment utilisés dans ce domaine, à savoir le chlorure ferrique et le sulfate d'aluminium hydrate. Les résultats obtenus quant à l'abattement de la D. C. O. , M. E. S. T. , phosphates, coliformes, métaux lourds, cyanures, pesticides et hydrocarbures sont de matière à envisager des tests à une plus grande échelle et ouvrent ainsi la voie à de nouvelles techniques de traitement des eaux
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Jeanneau, Justin. "Synthèse et propriétés physiques sous haute pression de composés à base de Cr4+." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY088.
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Après 25 ans de recherche sur les oxydes de cuivres supraconducteurs, les cuprates, la découverte d'une supraconductivité à haute Tc dans les pnictures à base de fer en 2008 a stimulé la recherche de nouveaux composés supraconducteurs. Les systèmes possédant un élément de transition 3d sont réellement intéressants en tant que potentiel nouveaux supraconducteurs. De plus, un composé antiferromagnétique (AFM) à haute température de Néel, de moment magnétique modéré et de structure cristallographique lamellaire (2D) semble essentiel pour atteindre les hautes Tc.Dans ce contexte de recherche, nous avons réinvestigué les propriétés physiques des membres n=1,2,3 et infini de la famille d'oxyde de chrome Ruddlesden-Popper (RP) Srn+1CrnO3n+1. Les résultats de plusieurs nouvelles études sur ces phases sont présentés telles que des expériences de diffraction de neutron sur poudre (DNP), de la diffraction des rayons-X en synchrotron sous pression et basse température, et des mesures de transport électriques sous pression. Bien que la supraconductivité n'ait pas été observée dans ces phases, nous reportons certains phénomènes physiques exotiques et intéressants tels qu'un effet "anti-Jahn-Teller" dans Sr2CrO4 à basse température et l'instauration d'un ordre orbital dans Sr3Cr2O7. Pour explorer de nouveaux composés à base de Cr dans lesquels la supraconductivité pourrait être potentiellement induite en changeant les interactions entre Cr dans les phases RP Sr2CrO4 et Sr3Cr2O7, de nouveaux chromates ont été synthétisés sous HP-HT par substitution de Sr2+ par d'autres éléments alcalino-terreux dans le but jouer avec l'effet de taille des cations (pression chimique). Pour la nouvelle phase RP n=1 Ca214, la substitution par un cation plus petit Ca2+ amène à un affaiblissement aussi bien du comportement isolant et que de l'ordre AFM. Concernant la synthèse de Ca327, cette phase n'a pu être obtenue, donnant lieu à la place à la nouvelle phase n=3 Ca4310. La substitution par un cation de rayon ionique plus grand du Ba2+ casse la structure RP et mène vers une nouvelle phase cubique à grand paramètre dont la structure a été résolue par tomographie en diffraction électronique. En 2014, la supraconductivité a été découverte dans le composé CrAs (2.2K à 0.8 GPa), soit le premier composé à base de Cr supraconducteur. Nous avons alors cherché un autre composé à base de Cr avec un TNéel relativement haute et moment magnétique modéré. En conséquence, nous avons travaillé sur un autre système similaire, le semiconducteur à gap étroit CrSb2. Nous avons observé une transition métal-isolant à partir de mesures de transport à 10GPa aussi bien pour des échantillons polycristallins que monocristallins que nous avons synthétisé. Nous mesurons aussi à cette pression une transition de phase par DRX en synchrotron. Finallement, une étude de DNP sous pression confirmera la dépendance en pression de l'ordre AFMAfter 25 years of research on the superconducting cuprates, the discovery of high Tc superconductivity in related iron based pnictides in 2008[1] has stimulated the search of new superconductors. In particular antiferromagnet (AFM) with high Néel temperature, moderate magnetic moments and with crystallographic 2D layers could be adequate parent phases for new unconventional superconductors. In particular, other systems with 3d transition elements are very interesting systems for potential new high Tc superconductors.In this context we have reinvestigated the physical properties of n=1, 2,3 and + members of the Srn+1CrnO3n+1Ruddlesden Popper (RP) series. We have successfully synthesized at HP-HT Sr2CrO4 (n=1), Sr3Cr2O7(n=2), Sr4Cr3O10 (n=3) and SrCrO3 (n=infinite). We present some results of several studies performed on these phases such as neutron powder diffraction, Synchrotron X-ray diffraction under high pressure and low temperature, electrical transport properties under high pressure. Even if no superconductivity was observed, interesting properties had been discovered such as an unusual “anti-Jahn-Teller” in Sr2CrO4 at low temperature or an orbital ordering in Sr3Cr2O7.To explore new Cr-based systems where superconductivity could potentially be induced by changing Cr-Cr interactions in the Sr2CrO4 and Sr3Cr2O7RP phases, new chromates have been synthesized under HP-HT by substituting Sr2+ with other alkaline earth elements in order to “play” with the cation size effect. For the n=1 RP Ca2CrO4 phase, substitution with Ca2+ as a replacing element lead to a weakening of both the insulating behavior and AFM ordering. Synthesis to form the n=2 RP Ca-based lead to the formation of the unexpected and new n=3 phase Ca4Cr2O10.Ba2+ as a replacing element broke the RP structure configuration and led to a new phase, whose crystal structure was solved using electron diffraction tomography.In 2014, superconductivity has been discovered in CrAs (Tc=2.2K at P=0.8GPa), the first superconducting Cr-based system. In this context, we have look for other AFM Cr-based system with relatively high Néel temperature and moderate Cr magnetic moment. In consequence, we investigated another system, the narrow-gap semiconductor CrSb2. We find a metal-insulating transition from transport measurement at 10 GPa for both polycrystalline and single crystals samples we synthesized. At this pressure, we also observed a phase transition on synchrotron XRD under pressure. Finally, pressure dependence of the AFM ordering had been established by NPD under high pressure
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Lockyer, D. M. "Adsorption and reaction of cyanogen with copper oxide, chromium oxide and copper oxide-chromium oxide surfaces." Thesis, University of Bath, 1988. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383244.
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Sakout, Mohammed. "Contribution de la spectrométrie X à l'étude des degrés d'oxydation du vanadium et du chrome dans les oxydes mixtes de structure spinelle." Rouen, 1989. http://www.theses.fr/1989ROUES002.
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Les déplacements chimiques expérimentaux observés à partir des spectres des oxydes simples et d'oxydes de Cr ou de V de structure spinelle à degré d'oxydation connu permettent d'établir une relation entre la valeur de ce déplacement chimique et le degré d'oxydation. Applications: 1) mise en évidence d'une très faible teneur en V (ii) dans les composés du système Fe(1+x)O(4) 2) dosage semiquantitatif du Cr (vi) dans les catalyseurs "chromite de cuivre"
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MALAGA, WALTER EDUARDO LAZO. "OBTAINING CHROMIUM OXIDE FROM FINE FECR HIGH-CARBON ALLOY." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=15410@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOO trabalho tem como motivação principal conciliar a crescente demanda de cromo em aplicações específicas com o aproveitamento de um resíduo industrial que está na forma de finos de baixo valor agregado. Desta forma, se estuda a possibilidade de recuperar o cromo, na forma de óxido, que está contido em finos da liga Fe-Cr Alto Carbono. Inicialmente, foi estudado o efeito das variáveis relevantes (temperatura, proporção dos reagentes) sobre a ustulação da liga com os hidróxidos de Na e Mg. Os resultados foram baseados na solubilização do produto ustulado e a subseqüente obtenção de uma solução rica em cromo separada de um composto rico em ferro. A etapa final envolve a precipitação do óxido de cromo. Os materiais envolvidos foram caracterizados por análise química, difração de raio-X e microscopia eletrônica de varredura. Os resultados qualitativos indicam a viabilidade do processo, mas, condições otimizadas devem ser identificadas visando uma maior eficiência do mesmo.
The investigation main motivation is to combine the growing chromium demand for specific applications with the reuse of a low value Cr-Fe-carbon alloy. Thus, it has been studied the possibility of recovering chromium, in the oxide form, from fines generated in the production of Fe-Cr High Carbon. Initially, the effect of relevant variables (temperature, ratio of reactants) on the alloy roasting with Na and Mg hydroxides, were studied. Then, the chromate solubilization followed by the chromium oxide precipitation have been carried out. The materials involved in the work have characterized by chemical analysis, DRX and MEV/EDS. The qualitative results indicated that the method can be applied but further experiments has to be carried out to optimize the process.
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Azad, Neelam. "Molecular mechanisms of chromium (VI)-induced apoptosis and malignant transformation." Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5041.
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Thesis (Ph. D.)--West Virginia University, 2007.Title from document title page. Document formatted into pages; contains ix, 103 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.
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Birnie, J. "Raman microscope determination of stress distributions in chromium oxide scales." Thesis, Open University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234525.
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Cole, Charles Randal. "Electron stimulated desorption of hydronium ions from chromium oxide surfaces." W&M ScholarWorks, 2005. https://scholarworks.wm.edu/etd/1539623480.
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The mass spectral peak observed at 19 amu in residual gas analyzers at very high (<10-6 Torr) and ultrahigh vacuum (<10 -9 Torr) has often been attributed to fluorine. Using Fourier Transform Mass Spectrometry, the hydronium ion, H3O+, has been fully resolved from F+ and its correlation to water vapor concentration was determined to be linear as expected for a gas phase process. The comparison of the mass 19 signals for a conventional quadrupole mass spectrometer and a Fourier transform mass spectrometer on the same vacuum chamber indicated hydronium was the source of mass 19.;The partial pressures of H2O in the very high vacuum range and higher suggest there is sufficient H2O density for the hydronium ions to form through ion-molecule interactions because hydronium formation was found to directly correlate with the H2O partial pressure. However, in a QMS at UHV, formation of H3O+ appears to occur principally by electron stimulated desorption (ESD). Introducing hydrogen into the system from 1 Langmuir exposure to saturation (1 x 10-6 Torr for 8 hours) increased the H3O + ESD yield detected by the QMS by as much as a factor of 10. The initial hydronium ESD cross section from a hydrogen saturated grid was estimated to be sigma ∼ 1 x 10-19, cm2.;TOF-SIMS sputter yields from the stainless steel grid of a quadrupole mass spectrometer also showed small signals of H3O+, as well as its constituents (H+, O+ and OH) and a small amount of fluorine as F-, but no F+ or F+ complexes (HF+, etc.). Using x-ray photoelectron spectroscopy, a small amount (0.4%) of fluorine was found in the surface of stainless steel. Electron bombardment reduces the fluorine bound in surface complexes, but not metal halides found below the surface. However, heating the sample eliminated the F 1s signal entirely, indicating that fluorine is not likely to be the source of mass 19 in residual gas analysis. Also, changes in the spectral shoulders on the O 1s and Cr 2P3/2 peaks show that hydrogen dosing stainless steel and chromium increases the amount of hydroxides at the surface, while heating and electron bombardment reduce them.
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Andronic, Laura Simona. "Photochemical metal organic deposition of layered materials of chromium oxide and lead oxide and of uranium oxide and cobalt oxide." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ61529.pdf.
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Dong, Yujung. "Geometric and Electronic Structure Sensitivity of Methyl and Methylene Reactions on α-Cr₂O₃ and α-Fe₂O₃ surfaces." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/39469.
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Structural and electronic effects in hydrocarbon reactions over metal oxides have been examined by comparing the reactions of methyl (-CH₃) and methylene (=CH₂) fragments on three different oxide single crystal surfaces: α-Cr₂O₃(101̅2), α-Cr₂O₃(0001), and α-Fe₂O₃(101̅2). The intermediates have been generated through the decomposition of halogenated hydrocarbons.
The primary reactions of methyl and methylene over α-Cr₂O₃ are methyl dehydrogenation to methylene, and methylene coupling (C-C bond formation) to ethylene (CH₂=CH₂). The different surface geometric structures of α-Cr₂O₃(101̅2) and (0001) lead to an increase in the activation barrier for methylene surface migration, a critical step in the coupling reaction, of 5.9 kcal/mol over the (0001) surface. For methyl dehydrogenation, differences in the local site pair (cation/anion) geometry and the proximity of surface lattice oxygen to the methyl group do not result in a significant difference in the barrier for dehydrogenation, suggesting that the surface anions play a minor role in the dehydrogenation of methyl on these surfaces.
Electronic differences in the Fe³⁺ (𝑑⁵) and Cr³⁺ (𝑑³) cations on structurally-similar α-Cr₂O₃(101̅2) and α-Fe₂O₃(101̅2) surfaces lead to major differences in reaction selectivity. α-Cr₂O₃(101̅2) is nonreducible under the reaction conditions of this study, but α-Fe₂O₃(101̅2) is highly reducible due to the difference in the d electron configuration. Hydrocarbons are formed over α-Cr₂O₃(101̅2), but nonselective oxidation products (CO₂, CO, H₂O) are formed over the stoichiometric α-Fe₂O₃(101̅2) surface along with surface reduction. Reduction of the α-Fe₂O₃(101̅2) leads to a shift in the product selectivity towards formaldehyde (CH₂O) and ethylene.
For the limited number of systems examined in this study, examples of geometric structure sensitive (methylene coupling) and structure insensitive (methyl dehydrogenation) reactions have been found on α-Cr₂O₃, and electronic effects are observed for the reactions on α-Cr₂O₃(101̅2) and α-Fe₂O₃. For the structure sensitive reaction, the differences in surface geometry impact the reactions kinetics over Cr₂O₃ but not the types of products formed, while the electronic differences give rise to dramatic changes in the selectivity associated with the very different products formed over α-Cr₂O₃(101̅2) and α-Fe₂O₃(101̅2).Ph. D.
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Shukri, Khalid. "Microstructure and response studies of chromium titanium oxide gas-sensitive resistors." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391673.
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CHEN, DONGSHENG. "Iron/Chromium Phase Decomposition Behavior in Oxide Dispersion Strengthened Ferritic Steels." Kyoto University, 2015. http://hdl.handle.net/2433/199417.
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Jones, Kimberley. "The application of iron oxide based photocatalysts in chromium photoredox chemistry." Thesis, University of Central Lancashire, 2011. http://clok.uclan.ac.uk/2811/.
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Chromium(VI) is a reactive and highly toxic pollutant species which is present in certain industrial effluent streams as well as sea water and polluted ground water. Chromium(III), however, is relatively inert and less toxic. Conventional methods used to eliminate Cr(VI) from aqueous phase include its reduction to Cr(III) at acidic pH by reaction with strong reducing agents such as thiosulphate, FeSO4 and SO2, followed by precipitation as hydroxide in alkaline media. However, this procedure is not suitable for Cr(VI) elimination in dilute aqueous solutions. Thus, semiconductor photocatalysis has been studied as a possible alternative. Photocatalysis is the process of using light to promote catalysis of reactions and normally involves the photoexcitation of a semiconductor catalyst. During photocatalysis, light of a wavelength corresponding to an energy greater than that of the band gap, Eg, of the material is incident on the catalyst, resulting in electrons being excited from the semiconductor valence band to its conduction band. These electrons can then reduce the Cr(VI) to Cr(III). The semi-conductor used consists of nanoparticulate iron oxide embedded in a clay matrix. Clays are micro-crystalline layered minerals. This gives rise to interlayer spaces in which the iron oxide is ‘grown’. The clay structure restricts the growth of the iron oxide, resulting in nano-particulate sized semiconductor particles. To monitor the changes in Cr(VI) concentration, a new, stable potentiometric method has been developed that involves the successful use of a gold electrode to measure Cr(VI) concentration, that has to date, not been reported elsewhere in literature. Results show that the nanocomposite does photo-reduce Cr(VI) to Cr(III) and does photo-oxidise ethanol. Modelling of the time dependence of the measured (photo-induced) potential has allowed for the extraction of key rate parameters for the Cr(VI) reduction process with a view to system optimisation.
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Medeiros, Angela Maria de Lemos. "SÃNTESE E CARACTERIZAÃÃO DE NANOPARTÃCULAS DE Cr2O3 ATRAVÃS DO MÃTODO SOL-GEL PROTÃICO." Universidade Federal do CearÃ, 2007. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=1093.
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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel SuperiorUltimamente as nanopartÃculas tÃm sido o foco principal dos pesquisadores. Esse empenho reside no fato de que novas e incomuns propriedades fÃsicas e quÃmicas, ausentes no mesmo material em tamanho macro e microscÃpico, sÃo observadas nessa nova escala. O direcionamento desse estudo à voltado à obtenÃÃo de nanopartÃculas de Ãxidos de cromo (Cr2O3) utilizando o mÃtodo sol-gel protÃico, tendo a gelatina como precursor orgÃnico e com o uso reduzir o custo de produÃÃo. Esse processo surge como uma nova alternativa para obtenÃÃo de Ãxidos com alta eficiÃncia e baixo custo. O interesse nesse material à devido Ãs diversas aplicaÃÃes como pigmentos verdes, revestimentos de materiais para proteÃÃo tÃrmica e principalmente como catalisador de inÃmeros produtos oriundos da indÃstria do petrÃleo, entre outras. AtravÃs dessa nova rota e utilizando um sal como fonte de cromo, foram obtidas partÃculas de tamanho mÃdio variando entre 20 e 60nm. Esses valores foram retirados de diferentes direÃÃes cristalogrÃficas atravÃs da tÃcnica de DifraÃÃo de Raios-X (DRX) e apÃs o refinamento da estrutura pelo mÃtodo Rietveld em diversas amostras preparadas em diferentes temperaturas. Outras tÃcnicas foram utilizadas para complementar os resultados obtidos pela DRX.
In the last years, nanoparticles have becoming important to several researchers. This research reside in the fact that new and uncommon physical and chemical properties, absent in the same material in macro and microscopic size, are observed in this new scale. The subject of this study is obtaining chromium oxide nanoparticles (Cr2O3) by solâgel proteic process using gelatin as an organic precursor. This process appears as a new alternative for the synthesis of oxides for great applications with high efficiency and low cost. The interest in that material is due to the several applications such as green pigments, coverings of materials for thermal protection and mainly as catalyst of countless products originating from of the industry of the petroleum, among others. This new route, using chromium salt as chromium source, produces nanoparticles with average particle size between 20 and 60nm. These values were obtained for different crystallographic direction by means of X-Ray Diffraction (XRD) technique and the structure refinement by Rietveld method were applied in several samples prepared at different temperatures. Other techniques have been used in order to complement the XRD results.
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Barquist, Karna Nicole Larsen Sarah C. "Synthesis and environmental adsorption applications of functionalized zeolites and iron oxide/zeolite composites." [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/334.
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Li, Tao. "Reaction-bonding of Crâ†2Oâ†3 ceramics." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318804.
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Naisbitt, Simon Carl. "The effects of microstructure on the gas sensing properties of chromium titanium oxide." Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1444861/.
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The general principles relating to construction and operation of semiconducting metal oxide materials as gas sensitive resistors are discussed. The adsorbed oxygen model of sensor response is presented as the origin of the gas sensitivity of the conductivity of these materials. Microstructure is also noted to affect sensor response and various studies, simulations and models from the literature are presented and discussed. Based on a combination of the model developed by Williams et al. and the linear form of the empirical equation for sensor response the model that will be used in the present work is developed. Two batches of sensors made using two chromia raw material powders of differing particle size were obtained from City Technology Ltd. Groups of these sensors were sintered at different temperatures to generate sensors having different microstructures. The different sintering temperatures produced clear gradations in the microstructures of the sensors, observed using scanning electron microscopy. These sensors were then systematically tested to carbon monoxide (CO) and propane at a single operating temperature of 400 C. A further group of sensors created from the batch of sensors made from fine chromia raw material were sintered at a single temperature of 775 C but were operated at temperatures of 350, 400 and 450 C and tested to CO with exposures of 1800 second duration. The results of all the gas tests were successfully processed so as to obtain solutions to the microstructural model developed for the steady state and transient cases. The trends of the microstructural, sensitivity and time constant parameters with sintering temperature, microstructure, operating temperature and exposure length are successfully discussed with reference to how the model accounts for these trends. The unexpected or unusual results are explained in terms of potential inaccuracies in the model or how it has been applied in this work.
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York, Steven C. "Halocarbon Reactions on the Chromium (III) Oxide (1012) Surface." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/39182.
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A nearly stoichiometric, (1x1) Cr2O3 (1012) surface
was prepared from a single crystal of alpha-Cr2O3.
The five-coordinate cations exposed at the stoichiometric
surface dissociatively adsorb molecular oxygen to
form a (1x1), terminating chromyl (Cr=O) layer
that is stable to >1100 K. TDS and AES were used
to investigate the reactivity of the halo-alkanes
CFCl2CH2Cl, CF2ClCH2Cl, CF3CH2Cl, and CF2CH2F, in
addition to the halo-alkenes CFCl=CH2 and CF2=CH2.
The halo-alkanes CFCl2CH2Cl, CF2ClCH2Cl, and CF3CH2Cl
undergo 1,2-dihalo elimination similar to the Zn-catalyzed
dehalogenation of vicinal dihalides to form alkenes.
Some acetylene is also formed. The halo-alkenes
CFCl=CH2 and CF2=CH2 decompose to yield acetylene.
Halogen removed from the molecules remains bound
to the surface following TDS experiments and
eventually terminates the surface chemistry due
to site blocking of the cations. Reactivity is
directly related to the chlorine content of the
molecules investigated. Only CFCl2CH2Cl was
reactive on a chromyl-terminated surface.Ph. D.
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Feng, Jingxing. "Characterization of Native Oxide and Passive Film on Iron and Iron-Chromium Alloy." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406811146.
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Barquist, Karna Nicole. "Synthesis and environmental adsorption applications of functionalized zeolites and iron oxide/zeolite composites." Diss., University of Iowa, 2009. https://ir.uiowa.edu/etd/334.
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Silicalite-1 crystals and hollow tube structures were synthesized and functionalized with amine and sulfur containing groups. The adsorption behavior of metal ions (Pb2+, CrO4-) in aqueous solution was investigated on nanocrystalline zeolites functionalized with amines and thiols. Nanocrystalline zeolites with a diameter of 30-50 nm and external surface areas around 100 m2/g were functionalized with 3-aminopropyltriethoxysilane (3-APTES) and 3-mercaptopropyltrimethoxysilane (3-MPTMS). The materials were characterized by 29Si magic angle spinning nuclear magnetic resonance spectroscopy and x-ray diffraction. The adsorption of metal ions from aqueous solutions of Pb (NO3)2 and Na2Cr2O7 was measured by inductively coupled plasma-atomic emission spectroscopy. The effects of various conditions such as pH and concentration were studied to optimize adsorption. Adsorption on functionalized mesoporous silica (MS) was conducted for comparison to the functionalized zeolites.
Magnetic zeolite/iron composites were prepared using nanoscale and commercial faujasite zeolites. The composites were functionalized with amine groups to facilitate chromate adsorption under acidic conditions. The materials were characterized using nitrogen adsorption, scanning electron microscopy, thermogravametric analysis, FTIR spectroscopy, and Mossbauer spectroscopy. The adsorption of chromium was evaluated using inductively coupled plasma-optical emission spectroscopy (ICP/OES) to monitor solution chromium quantitatively. The removal of the composites with a magnet was demonstrated. The materials were then evaluated for the adsorption of Cr6+ using ICP-OES to detect chromium.
Iron containing zeolite composites were prepared using nanoscale faujasite zeolites. The composites were functionalized with amine groups and Fe ions to facilitate arsenate(As V) adsorption under a variety of pH conditions. The materials were characterized using nitrogen adsorption, X-ray diffraction, thermogravametric analysis and FTIR spectroscopy, and Mossbauer spectroscopy. The adsorption of arsenic was evaluated using inductively coupled plasma-optical emission spectroscopy (ICP/OES) to monitor solution concentration quantitatively. The removal of the composites with a magnet was demonstrated. Kinetics and pH dependence of the adsorption were studied.
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Bergman, Ola. "Studies of oxide reduction and nitrogen uptake in sintering of chromium-alloyed steel power /." Stockholm : Materialvetenskap, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9555.
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Hsieh, Man-Ching. "Application of Volatility Diagrams for Investigating Dry Etching Reactions of Chromium Oxide in LTCSS Processing." Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1307497361.
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Ma, Qiang. "Haloethane Reactions over the Chromia Cr₂O₃ (1012) Surface." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/34754.
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Ethyl iodide and ethyl chloride have been used as reactants to produce ethyl fragments on the stoichiometric α-Cr₂O₃ (1012) surface by means of thermal dissociation. Ethyl iodide is dissociated giving iodine adatoms and ethyl fragments bound to surface Cr cation sites, while ethyl chloride is dissociated giving chlorine adatoms and ethyl fragments. No oxygenated products are observed in thermal desorption, suggesting the 3-coordinate lattice oxygen on the stoichiometric α-Cr₂O₃ (1012) surface is very stable, and no nucleophilic attack occurs at the carbon atoms on surface ethyl fragments.
For both reactants, the only reaction products observed are ethylene gas (CH₂=CH₂), ethane gas (CH₃-CH₃), hydrogen gas (H₂) and halogen adatoms (Clads or Iads). In thermal desorption experiments, all the gas phase products from ethyl chloride are produced in a reaction-limited, high temperature desorption feature attributed to a rate limiting β-hydride elimination from surface ethyl fragments. Similar product desorption features are observed for the reaction of ethyl iodide. However, the reaction of ethyl iodide also produces ethylene and ethane via a low temperature, desorption-limited reaction channel. It is postulated that I adatoms produced in the reaction of ethyl iodide thermal desorption might somehow promote a low temperature route to products that Cl adatoms do not.Master of Science
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Ojelere, Olusola Oyedele [Verfasser]. "Homo- and Heterometallic Complexes of Vanadium and Chromium and their Conversion into Oxide Ceramics / Olusola Oyedele Ojelere." München : Verlag Dr. Hut, 2019. http://d-nb.info/1200754875/34.
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Lawrence, P. J. "The role of defects and impurities at surfaces, interfaces and in the bulk of chromium(III) oxide." Thesis, University of Bath, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384627.
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Jin, Tongan. "Interactions of the Air Electrode with Electrolyte and Interconnect in Solid Oxide Cells." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/39223.
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The interactions between different components of solid oxide cells (SOCs) are critical issues for achieving the tens of thousands of hourâ s goal for long-term performance stability and lifetime. The interactions between the ceramic electrolyte, porous ceramic air electrode, and metallic interconnect materials â including solid state interfacial reactions and vaporization/deposition of some volatile elements â have been investigated in the simulated SOC operating environment. The interactions demonstrate the material degradation mechanisms of the cell components and the effects of different factors such as chemical composition and microstructure of the materials, as well as atmosphere and current load on the air electrode side. In the aspect of materials, this work contributes to the degradation mechanism on the air electrode side and provides practical material design criteria for long-term SOC operation.
In this research, an yttria-stabilized zirconia electrolyte (YSZ)/strontium-doped lanthanum manganite electrode (LSM)/AISI 441 stainless steel interconnect tri-layer structure has been fabricated in order to simulate the air electrode working environment of a real cell. The tri-layer samples have been treated in dry/moist air atmospheres at 800°C for up to 500 h. The LSM air electrode shows slight grain growth, but the growth is less in moist atmospheres. The amount of Cr deposition on the LSM surface is slightly more for the samples thermally treated in the moist atmospheres. At the YSZ/LSM interface, La enrichment is significant while Mn depletion occurs. The Cr deposition at the YSZ/LSM interface is observed.
The stoichiometry of the air electrode is an important factor for the interactions. The air electrode composition has been varied by changing the x value in (La0.8Sr0.2)xMnO3 from 0.95 to 1.05 (LSM95, LSM100, and LSM105). The enrichment of La at the YSZ/LSM interface inhibits the Cr deposition. The mechanisms of Cr poisoning and LSM elemental surface segregation are discussed.
A 200 mA·cm-2 current load have been applied on the simulated cells. Mn is a key element for Cr deposition under polarization. Excessive Mn in the LSM lessens the formation of La-containing phases at the YSZ/LSM interface and accelerates Cr deposition. Deficient Mn in LSM leads to extensive interfacial reaction with YSZ forming more La-containing phase and inhibiting Cr deposition.Ph. D.
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Engweiler, Jörg C. "Titania based vanadia, chromia and tungsten oxide catalysts prepared by grafting /." [S.l.] : [s.n.], 1995. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10960.
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Kestell, Gayle M. "Model of chromium poisoning in the cathode of a solid oxide fuel cell using the lattice Boltzmann method." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/41286.
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The metallic interconnect of a solid oxide fuel cell (SOFC) contains chromium in order to protect the metal from the corrosive environment in the fuel cell. Unfortunately, the chromium introduces chemical instability in the cathode as it migrates from the interconnect to the pores in the cathode. A model was developed previously in Asinari et al. [1] and Kasula et al [2] to model the flow of particles in a fuel cell electrode. To learn more about the migration of the chromium, the previous code is modified in this thesis work to include the effects of the chromium. The model uses Kinetic Theory to simulate the fuel cell at a mesoscopic scale. The discretized form of the Lattice Boltzmann equation is modified for enhanced performance and for use on a parallel processing system.
With the new model, the migration of the chromium in the cathode and the performance degradation of the fuel cell are predicted.Master of Science
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Shen, Fengyu. "Study of Perovskite Structure Cathode Materials and Protective Coatings on Interconnect for Solid Oxide Fuel Cells." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/74973.
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Solid oxide fuel cells (SOFCs) are promising devices to convert chemical energy to electrical energy due to their high efficiency, fuel flexibility, and low emissions. However, there are still some drawbacks hindering its wide application, such as high operative temperature, electrode degradation, chromium poisoning, oxidization of interconnect, and so on.
Cathode plays a major role in determining the electrochemical performance of a single cell. In this dissertation, three perovskite cathode materials, La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), Ba0.5Sr0.5Co0.2Fe0.8O3 (BSCF), and Sm0.5Sr0.5Co0.2Fe0.8O3 (SSCF), are comparatively studied through half-cells in the temperature range of 600-800 ºC. Sm0.2Ce0.8O1.9 (SDC) block layer on the yttria-stabilized zirconia (YSZ) electrolyte can lead to smaller polarization resistances of the three cathode materials through stopping the reaction between the cathodes and the YSZ electrolyte. SDC is also used as a catalyst to increase the oxygen reduction reaction (ORR) rate in the LSCF cathode.
In addition, interconnect is protected by CoxFe1-x oxide and Co3O4/SDC/Co3O4 tri-layer coatings separately. These coatings are demonstrated to be effective in decreasing the area specific resistance (ASR) of the interconnect, inhibiting the Cr diffusion/evaporation, leading higher electrochemical performance of the SSCF-based half-cell. Only 1.54 at% of Cr is detected on the surface of the SSCF cathode with the Co0.8Fe0.2 oxide coated interconnect and no Cr is detected with the Co3O4/SDC/Co3O4 tri-layer coated interconnect.
Finally, single cells with LSCF, BSCF, and SSCF as the cathodes are operated in the temperature range of 600-800 °C fueled by natural gas. BSCF has the highest power density of 39 mW cm-2 at 600 °C, 88 mW cm-2 at 650 °C, and 168 mW cm-2 at 700 °C; LSCF has the highest power density of 263 mW cm-2 at 750 °C and 456 mW cm-2 at 800 °C. Activation energies calculated from the cathode ASR are 0.44 eV, 0.38 eV, and 0.52 eV for the LSCF, BSCF, and SSCF cathodes respectively, which means the BSCF cathode is preferred. The stability test shows that the BSCF-based single cell is more stable at lower operative temperature (600 °C) while the LSCF-based single cell is more stable at higher operative temperature (800 °C).Ph. D.
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Dyer, Philip William. "Studies on molecular Oxo and Imido complexes of the group 6 metals and supported chromium oxide polymerisation catalysts." Thesis, Durham University, 1993. http://etheses.dur.ac.uk/5778/.
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This thesis describes studies directed towards the preparation of bis (imido) complexes of the Group 6 metals containing olefin, phosphine, acetylene, and alkyl ligands with particular emphasis on their relationship with Group 4 bent metallocenes. The polymerisation mechanism of the Phillips catalyst (CrO(_3)/SiO(_2)) is examined using XPS (X-Ray Photoelectron Spectroscopy) and in situ mass spectroscopy. Chapter 1 highlights properties of some of the important ligand classes that are used throughout the remainder of this thesis. Chapter 2 describes a high yield one-pot synthesis of molybdenum bis (imido) complexes of the type Mo(NR')(NR")Cl(_2).DME. In addition a number of attempts to extend this strategy to other metals are described, including a novel synthesis of the chromium complex [Cr(_2)Cl(_9)] [NHEt(_3)](_3). Chapter 3 describes the synthesis, characterisation, and reactivity of the bis (imido) bis (phosphine) complexes Mo(NAr)(_2)(PMe(_3))(_2) and [Mo(N(^t)Bu)(µ-N(^t)Bu)(PMe(_3))](_2). Further studies on bis (imido) olefin complexes of the type Mo(NAr)(_2)(PMe(_3))2(η(^2)-C(_2)H (_2)) and Mo(N(^t)Bu)(_2)(PMe(_3))(η(^2)-C(_2)H(_4)) was undertaken and concentrated on their structural relationship to Group 4 metallocene species. Chapter 4 describes the preparation, structure, and reactivity of some bis (imido) acetylene complexes Mo(NR)(_2)(PMe(_3)) (PhC=CR’) (R= Ar, (^t)Bu; R'= Ph, H). Preparation of bis (imido) alkyls was undertaken in attempts to generate benzyne and alkylidene derivatives. Chapter 5 studies the Phillips polymerisation catalyst using XPS and mass spectroscopy. Model systems were used to probe reactive surface species their use reveals a number of features that are difficult to observe with the actual catalyst. Aspects of molecular chemistry have been examined which are believed to relate directly to the heterogeneous system allowing a possible polymerisation mechanism to be postulated. Chapter 6 gives experimental details for Chapters 2-5. Philip William Dyer (November 1993)
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Segerdahl, Karin. "The breakdown of the protective oxide on 11% chromium steel : the influence of water vapour and gaseous KCl /." Göteborg : Chalmers university of technology, 2003. http://catalogue.bnf.fr/ark:/12148/cb40125707m.
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Pillay, Kriveshini. "A kinetic and mechanistic study on the oxidation of chromium oxide in pure chemicals and in ferrometallurgical slags." Master's thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/5415.
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Bibliography: leaves 103-108.Chromium can exist in a number of oxidation states but the environmentally stable forms are trivalent (Cr(III)) and hexavalent (Cr(VI)) chromium. These two forms are noted for their different degrees of toxicity and mobility. Hexavalent chromium is more toxic and mobile and has been responsible for a number of illnesses in humans (Sheehan et. al., 1991). Elemental chromium and its compounds have a variety of uses in the industrial sector. The ferrometallurgical industry in particular makes use of chromium since this element imparts properties such as hardness and strenght to stainless steel. However, this industry also produces slags that contain residual amounts of chromium oxide (Cr[2]O[3]) along with other constituents such as calcium oxide (CaO). Thermodynamic data from the literature, has shown that Cr[2]O[3] can undergo oxidation at ambient temperature when in contact with CaO and atmospheric oxygen (Kilau and Shah, 1984; Hattori et al., 1978). Furthermore, the oxidation of Cr[2]O[3] in the presence of Ca(OH)[2] has also been observed at ambient temperature (Petersen, 1998).
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Bartie, Neill J. "The effects of temperature, slag chemistry and oxygen partial pressure on the behaviour of chromium oxide in melter slags." Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16255.
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Thesis (MScIng)--University of Stellenbosch, 2004.ENGLISH ABSTRACT: This thesis details results obtained in an experimental study conducted to determine the effects of operating temperature, oxygen partial pressure, bulk chromium oxide content and bulk FeOx/MgO ratio on the solubility of chromium oxide in melter type slags in the platinum industry. Two PGM-containing layers in the Bushveld Complex in South Africa, the Merensky and UG2 reefs, are currently being mined for the extraction of base metals and platinum group metals (PGM). While the Merensky reef is a pyroxenitic layer, the UG2 reef is a platiniferous chromitite seam. Due to a gradual depletion in Merensky ore reserves, platinum producers have been moving towards the processing of more UG2 concentrates, which are higher in chromium oxide content. The technical difficulties associated with the smelting of concentrates with high chromium oxide contents is a matter of concern. The formation of chromite spinels in melts increases liquidus temperatures and viscosities and subsequently hampers tapping of slags and mattes from furnaces. Bottom build-up from the smelting of high chromium oxide containing concentrates could reduce effective furnace volume. From the literature reviewed it was found that very few published investigations covered melt compositions and oxygen partial pressures similar to those encountered in the platinum industry. Relevant studies were found to deal with significantly lower bulk chromium oxide and iron oxide contents. It became clear that a need exists for information on the behaviour of chromium oxide and its effects on phase chemistry and stability in melter slags. It was decided to study the phase equilibria through drop-quench experiments using six synthetic slags with bulk FeOx/MgO ratios between 0.6 and 1.9 and bulk chromium oxide contents between 1.2 and 7 wt%. Temperatures investigated were 1400, 1500 and 1600°C. The oxygen partial pressure was varied between 6.8x10-10 atm at 1400°C to8.3x10-5 atm at 1600°C. Experiments were conducted in a sealed vertical tube furnace and the required oxygen partial pressure in the furnace tube was maintained by controlling the flow rates of purified CO and CO2 gas mixtures through the tube. Reaction products were quenched after a reaction time of between 20 and 24 hours, depending on temperature, and the phase compositions were analysed by microprobe. The experimental study revealed that chromium oxide partitions very strongly into the spinel phase relative to the liquid phase, especially at lower temperatures, and higher oxygen partial pressures and bulk chromium oxide contents. The solubility of chromium oxide in the liquid phase was found to increase with increasing temperature and decreasing oxygen partial pressure. An increase in bulk chromium oxide contents of 1 wt%, under otherwise constant conditions, resulted in an increase in slag liquidus temperature of approximately 100°C over the range of temperatures investigated. At 1500°C and bulk chromium oxide contents of 3.7 and 6.4 wt% a reduction in oxygen partial pressure from 1.1x10-5 to 1.1x10-7 atm resulted in increases in soluble chromium oxide of 0.9 and 2.0 wt%, respectively. A further decrease in oxygen partial pressure to 6.7x10-9 atm resulted in increases in soluble chromium oxide of 2.8 and 4.7 wt%, respectively. Experimental results were compared to values predicted by the multi-phase equilibrium (MPE) model developed by CSIRO, and found to agree well. Slag basicity was not varied experimentally and therefore the model was used to predict its effect on the solubility of chromium oxide in the liquid phase and the stability of crystalline phases. At constant temperature, an increase in basicity resulted in a decrease in the solubility of chromium oxide in the liquid phase as well as stabilisation of the spinel phase. It was concluded that practicable combinations of one or more of four main factors, namely increased operating temperature and decreased bulk chromium oxide content, slag basicity and oxygen partial pressure, should be applied and evaluated in a plantenvironment to optimise furnace operation. The MPE model would be a valuable tool in predicting the outcomes of such investigations.
AFRIKAANSE OPSOMMING: Hierdie tesis detaileer die resultate wat verkry is uit ‘n eksperimentele studie uitgevoer om die effek van bedryfstemperatuur, die parsiële druk van suurstof, die algehele chroomoksied inhoud en die algehele FeOx/MgO verhouding op die gedrag van chroomoksied in smelter slakke in die platinum industrie te bestudeer. Twee PGM-bevattende ertslae in die Bosveldkompleks in Suid Afrika, die Merensky en UG2 riwwe, word huidiglik gemyn vir die ekstraksie van basismetale en platinumgroep metale (PGM). Die Merensky rif is ‘n piroksenitiese laag terwyl die UG2 rif ‘n platinumbevattende chromitiet laag is. As gevolg van ‘n geleidelike afname in reserwes van Merensky erts beweeg platinumprodusente al meer na die verwerking van groter hoeveelhede UG2 erts. Die tegniese probleme wat gepaard gaan met die smelting van konsentrate met hoë chroomoksied inhoud kan ‘n rede tot kommer wees. Die vorming van chromiet spinelle in die slak- en matfases verhoog likuidus temperature en viskositeite en bemoeilik die tap van hierdie fases uit oonde. Die opbou van soliede fases verlaag ook die effektiewe oondvolume. Uit die literatuurstudie is gevind dat gepubliseerde studies waarin slak samestellings en parsiële suurstofdrukke wat betrekking het op die platinumindustrie bespreek is, baie beperk is. Dit is gevind dat relevante navorsing gedoen is met aansienlik laer algehele chroom- en ysteroksied konsentrasies. Gevolglik het dit duidelik geword dat ‘n behoefte bestaan vir inligting oor die gedrag van chroomoksied in oonde en die effekte daarvan op fasechemie en –stabiliteit in smelter slakke. Daar is besluit om eksperimente uit te voer deur die gebruik van ses sintetiese slakke met algehele FeOx/MgO verhoudings tussen 0.6 en 1.9 en algehele chroomoksied konsentrasies tussen 1.2 en 7.0 % (op ‘n massabasis). Temperature van 1400, 1500 en 1600°C en suurstof parsiële drukke tussen 6.8x10-10 atm by 1400°C en 8.3x10-5 atm by 1600°C is ondersoek. Eksperimente is uitgevoer in ‘n geseëlde vertikale buisoond en dievereiste suurstofdruk in die oond is gehandhaaf deur beheer van die vloeitempos van gesuiwerde CO en CO2 gas deur die oond. Reaksieprodukte is in water geblus na ‘n reaksietyd van tussen 20 en 24 ure, afhangende van die reaksietemperatuur. Fasesamestellings is bepaal deur mikrosonde analises. Die eksperimentele studie het bewys dat chroomoksied baie sterk in die spinelfase konsentreer relatief tot die vloeistoffase, veral by laer temperature, suurstofdrukke en algehele chroomoksied konsentrasies. Dit is gevind dat die oplosbaarheid van chroomoksied in die vloeistoffase toeneem met toenemende temperatuur en afnemende suurstofdruk. ‘n Toename in die algehele chroomoksied konsentrasie van 1 massa%, onder andersins onveranderde toestande, het ‘n toename van ongeveer 100°C in likuidus temperature veroorsaak tussen 1400 en 1600°C. By 1500°C en algehele chroomoksied konsentrasies van 3.7 en 6.4 massa%, het ‘n verlaging in suurstofdruk vanaf 1.1x10-5 tot 1.1x10-7 atm respektiewelike toenames in die chroomoksied oplosbaarheid van 0.9 en 2.0 massa% veroorsaak. ‘n Verdere verlaging in suurstofdruk tot 6.7x10-9 atm het respektiewelike toenames in chroomoksied oplosbaarheid van 2.8 en 4.7 massa% veroorsaak. Eksperimentele resultate is vergelyk met waardes wat voorspel is deur die multifase ewewigsmodel (MPE), ontwikkel deur CSIRO, en goeie ooreenstemming is gevind. Verskillende slak basisiteite is nie eksperimenteel ondersoek nie en daarom is die model gebruik om die effek daarvan op die oplosbaarheid van chroomoksied in die vloeistoffase asook die stabiliteit van kristallyne fases te bepaal. By konstante temperatuur het ‘n toename in slak basisiteit ‘n afname in chroomoksied oplosbaarheid veroorsaak en die spinelfase gestabiliseer. Die aanbeveling is gemaak dat ‘n kombinasie van een of meer van vier hooffaktore, naamlik hoër bedryfstemperature en laer algehele chroomoksied konsentrasies, slak basisiteit en suurstofdruk, in die praktyk toegepas en geëvalueer moet word om sodoendeoptimum bedryfkondisies te bepaal. Die multifase ewewigsmodel is ‘n nuttige instrument wat gebruik kan word om die resultate van sulke ondersoeke te voorspel.