To see the other types of publications on this topic, follow the link: Metal hydroxides.
Dissertations / Theses on the topic 'Metal hydroxides'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Metal hydroxides.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Cheung, William M. L. (William Man Lung). "Artificial phosphodiesterases : dinuclear metal complexes with bridging hydroxides." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23875.
Full textAbstract:
The reactivities of two dinuclear metals complexes with bridging hydroxides for hydrolyzing phosphrite diesters have been examined.The second-order rate constants ($ rm k sp prime sb{hyd}/M sp{-1} s sp{-1}$) for the hydroxidecatalysed hydrolysis of bridging aryl methyl phosphates in di-$ mu$-hydroxodinuclear cobalt(III) complex ($ rm Co sb2( lbrack 9 rbrack aneN sb3) sb2(OH) sb2(OP(O)(OMe)(OAr) rbrack sp{3+}$ ( (9) aneN$ sb3$ = 1,4,7-triazacyclononane) and the corresponding free aryl methyl phosphates (25$ sp circ$C and 0.1 M ionic strength) obey the following Bronsted equations: eqalign{ rm log k sp prime sb{hyd} (free diester) = -0.70 pK sb{ rm a}-0.66 & quad rm(R = 0.996) cr rm log k sp prime sb{hyd} (bridging diester) = -1.40 pK sb{ rm a} + 14.4 & quad rm (R = 0.999) cr} hese linear free energy relationships suggest that the di-$ mu$-hydroxodinuclear cobalt(III) complex, irrespective of the leaving groups hydrolyzes the bridging phosphate diesters by the same mechanism. They also indicate that the complex provides greater rate-acceleration for hydrolyzing phosphate diesters with good leaving groups than with poor ones.
La(III) cooperates with hydroxide in hydrolyzing bis(4-nitrophenyl) phosphate (BNPP). The close agreement between the titration data and the pH-rate profile indicates that the active core of the catalyst is a dinuclear La(III) complex bridged by five hydroxide ions La$ rm sb2(OH) sb5 sp+.$ The mechanism proposed for $ rm La sb2(OH) sb5 sp+$-promoted hydrolysis of BNPP involves double Lewis acid activation and intramolecular nucleophilic catalysis of the bridging hydroxide.
2
Robins, Daniel Swaim. "Studies of molecularly designed layered double metal hydroxides /." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487854314870167.
Full text
3
Jakupca, Michael R. "Characterization and application of layered double metal hydroxides /." The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487863429096234.
Full text
4
Partridge, Robert Daniel. "Electrodeposition of mixed-metal hydroxides in the formation of ceramic films." Thesis, Manchester Metropolitan University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337846.
Full text
5
Mitchell, Sharon Jane. "Synthesis and characterisation of layered inorganic mixed metal oxides and hydroxides." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611671.
Full text
6
Ahmed, Yousif Hummaida. "Toxic waste treatment by slag cements." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336560.
Full text
7
Lakin, Nicholas Mark. "Electronic and microwave spectroscopy of indium(I) hydroxide." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259963.
Full text
8
Enman, Lisa. "Structure-Property Relationships in Mixed-Metal Oxides and (Oxy)Hydroxides for Energy Applications." Thesis, University of Oregon, 2019. http://hdl.handle.net/1794/24227.
Full textAbstract:
Metal oxides and (oxy)hydroxides, particularly those containing two or more metals have many uses as electronic materials and catalyst, especially in energy applications. In this dissertation, the structure-property relationships of these mixed-metal materials are explored in order to understand how these materials work and to guide design of materials with even higher efficiency for a given application. Chapter I introduces the materials and studies undertaken. Chapter II presents a fundamental analysis of the electronic and local atomic properties of mixed-transition-metal aluminum oxide thin films.
The final three chapters focus on water electrolysis for hydrogen production, which is limited in part by the slow kinetics of the oxygen evolution reaction (OER). Nickel-iron and cobalt-iron (oxy)hydroxides have been shown to be the most active in alkaline conditions. Although it is evident that Fe is essential for high activity, its role is still unclear. Chapter III investigates the role of Fe in NiOOH by comparing the effects of Ti, Mn, La, and Ce incorporation on the OER activity of NiOOH in base. Chapter IV evaluates the OER activity and Tafel behavior of Fe3+ impurities on different noble metal substrates. Chapter V describes the results of in situ and in operando X-ray spectroscopy experiments, which shows that the local structure around Fe atoms in Co(Fe)OOH changes during OER while that of Co stays the same. This work adds to the growing body of literature that suggests Fe is essential to the catalytic active site for the OER on transition-metal (oxy)hydroxides.
This dissertation contains previously published and un-published coauthored material.2020-01-11
9
Murad, T. M. A. "Investigation into hydrogen bonding configurations in metal oxide hydroxides, with special reference to gamma-FeOOH." Thesis, Swansea University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638279.
Full text
10
Fogg, Andrew Michael. "Structural, kinetic and synthetic studies of intercalation compounds." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297906.
Full text
11
Stevens, Michaela. "Fundamentals and Industrial Applications: Understanding First Row Transition Metal (Oxy)Hydroxides as Oxygen Evolution Reaction Catalysts." Thesis, University of Oregon, 2017. http://hdl.handle.net/1794/22633.
Full textAbstract:
Intermittent renewable energy sources, such as solar and wind, will only be viable if the electrical energy can be stored efficiently. It is possible to store electrical energy cleanly by splitting the water into oxygen (a clean byproduct) and hydrogen (an energy dense fuel) via water electrolysis. The efficiency of hydrogen production is limited, in part, by the high kinetic overpotential of the oxygen evolution reaction (OER). OER catalysts have been extensively studied for the last several decades. However, no new highly active catalyst has been developed in decades. One reason that breakthroughs in this research are limited is because there have been many conflicting activity trends. Without a clear understanding of intrinsic catalyst activity it is difficult to identify what makes catalysts active and design accordingly. To find commercially viable catalysts it is imperative that electrochemical activity studies consider and define the catalyst’s morphology, loading, conductivity, composition, and structure.
The research goal of this dissertation is twofold and encompasses 1) fundamentally understanding how catalysis is occurring and 2) designing and developing a highly active, abundant, and stable OER catalyst to increase the efficiency of the OER. Specifically, this dissertation focuses on developing methods to compare catalyst materials (Chapter II), understanding the structure-compositional relationships that make Co-Fe (oxy)hydroxide materials active (Chapter III), re-defining activity trends of first row transition metal (oxy)hydroxide materials (Chapter IV), and studying the role of local geometric structure on active sites in Ni-Fe (oxy)hydroxides (Chapter V). As part of a collaboration with Proton OnSite, the catalysts studied are to be integrated into an anion exchange membrane water electrolyzer in the future.
This dissertation includes previously published and unpublished co-authored material.10000-01-01
12
Wu, T. H. "Optimising cell voltage and understanding charge storage mechanism of transition metal oxides and hydroxides for aqueous supercapacitors." Thesis, University of Liverpool, 2016. http://livrepository.liverpool.ac.uk/3002214/.
Full textAbstract:
This study focuses on aqueous electrochemical capacitors (ECs) for optimising the cell voltage and understanding the charge storage mechanism of transition metal oxides and hydroxides. The first part discusses how to optimise cell voltage of symmetric and asymmetric ECs. In Chapter 4, a commercial activated carbon (ACS–679) was employed as an electroactive material to demonstrate the necessity of charge–balanced condition of aqueous symmetric ECs in order to improve the utilisation of electrochemically stable potential window of electroactive material. Besides, the effect of stable open–circuit potential on electroactive materials is also addressed here. The concept is on the basis of electrochemical charge–balance principle, therefore, it is believed to be applicable to all the symmetric ECs no matter what kind of material is used as electroactive material. The charge–balanced electric double–layer capacitors (EDLCs) was assembled to evaluate the acceptable cell voltage by means of electrochemical analyses, including cyclic voltammogram, constant current charge–discharge, electrochemical impedance spectroscopy and inductance–capacitance–resistance meter measurements. Moreover, charge–unbalanced EDLCs were used to demonstrate the necessity of charge balance in symmetric ECs since those exhibit lower cell voltage and specific energy compared with the charge–balanced case. Similarly, in Chapter 5, asymmetric ECs consisting of reduce graphene oxide and manganese oxide (RGO//MnOx) were employed as an example to establish criteria for determining the highest acceptable cell voltage of asymmetric ECs with excellent reversibility and capacitor−like behaviour. It is very useful to evaluate the practical specific energy of asymmetric ECs by understanding the highest acceptable cell voltage. Besides, RGO//RuO2 was also demonstrated to verify the validity of the proposed criteria. The second part probes the charge storage mechanism of transition metal oxides and hydroxides in aqueous ECs. In Chapter 6, a wide–ranging study on electrochemical activation from Mn3O4 to MnO2 in 0.5 M Na2SO4 medium were presented, which includes in operando monitoring of the structural evolution during the activation process via in situ Raman microscopy. Other advanced material characterisation techniques, such as powder X–ray diffraction, X–ray photoelectron spectroscopy, scanning electron and transmission electron microscopy, were also applied to analyse the as–prepared and activated MnOx. Due to the structural disordering of electrochemically activated birnessite−MnO2 and residual Mn3O4, the charge storage is attributable to the redox reaction between Mn(III) and Mn(IV) at outer surface active sites, rather than cations and/or protons intercalation into layer structures. In Chapter 7, the redox behaviours of γ−NiOOH/α−Ni(OH)2 in various electrolytes (LiOH, NaOH, KOH, CsOH and NH4OH) are discussed. The charge storage mechanism of γ−NiOOH/α−Ni(OH)2 was studied by means of EQCM and in situ Raman microscopy. Moreover, the computational simulation (DFT+U) based on EQCM results gives a better idea on the compositional changes in the first few potential cycles. The insertion/removal of Li+ does not alter the content of water inside the structure, while the insertion of Na+ and K+ leads to a significant removal of water. The removed water molecules cannot be reversibly re−inserted back into the nickel structure, leading to the loss of water molecules in Ni(OH)2 structure during charge–discharge process. The capability to retain water molecules inside the Ni(OH)2 is crucial for the stability of γ−NiOOH/α−Ni(OH)2 redox reaction.
13
Masikhwa, Tshifhiwa Moureen. "Synthesis and characterization of Co-based hydroxides and metal disulphides with various forms of carbon for supercapacitor applications." Thesis, University of Pretoria, 2016. http://hdl.handle.net/2263/60837.
Full textAbstract:
The aim and objectives of this work are to synthesize cobalt-based hydroxides and transition metal disulphides composites with carbon materials such as graphene foam and activated carbon by a facile and environmentally friendly hydrothermal technique for energy storage application. Because faradaic materials suffer from poor electrical conductivity and low electrochemical stability, while carbon materials are known to have good electrical conductivity and electrochemical stability, the combination of the two materials to make hybrid material should be able to improve the electrochemical properties of the composite material. Morphological, structural, surface area and compositions properties of the produced materials were evaluated and characterized using methods such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption isotherm (BET), Fourier transformation infrared spectroscopy (FTIR) and Raman spectroscopy. Electrochemical characterization involved cycling voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS) and cycling life were carried out in two (asymmetric device) and three-electrode configurations using 6 M KOH aqueous electrolyte and they all showed excellent electrochemical performance. For instance the asymmetric devices based on CoA-LDH/graphene foam//AEG gave specific capacitance of 101.4 F g-1 with a maximum energy density of 28 Wh kg-1 and a corresponding power density of 1420 W kg-1 at a current density of 0.5 A g-1 , VS2//AC gave specific capacity of 155 F g-1 and high energy and power densities of 42 Wh kg-1 and 700 W kg-1 respectively at current density of 1 A g-1.and MoS2_150 mg GF //AEG gave high specific capacitance of 59 F g-1 with maximum energy and power densities of 16 Wh kg-1 and 758 W kg-1 respectively at a current density of 1 A g-1 respectively . All these results showed the great potential of the hybrid materials derived from the incorporation of cobalt based hydroxides and transition metal disulphides with carbon for supercapacitor application.Thesis (PhD)--University of Pretoria, 2016.
Physics
PhD
Unrestricted
14
Lovell, Jessica, and Sandra Levin. "Removal of hexavalent chromium in wastewater using granular ferric hydroxides." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-265899.
Full textAbstract:
This study took place in Malawi, south eastern Africa. Metal contamination of water and soil is a threat to the environment and human health and is a serious concern in many countries including Malawi. Blantyre is the city of commerce where most of the industry is located along the banks of the main rivers. Some of the industries produce wastewater, which due to poor access to wastewater treatment plants, is discharged without treatment into the environment. A match factory in Blantyre uses chromium as a colouring agent for match heads and very high concentrations of chromium(VI) have been measured downstream the factory with concentrations up to 56 mg/l, which is much higher than the WHO guidelines of 0.05 mg/l. Chromium(VI) mainly occurs as chromate CrO42- and dichromate Cr2O72- ions. They are both toxic and carcinogenic and can cause mutations and chromosomal aberrations. The aim of the study was to evaluate the efficiency of Granular Ferric Hydroxide (GFH) in adsorbing and removing chromium from an aqueous phase. Wastewater was collected from the match factory and by optimizing relevant parameters the removal efficiency was maximized. The parameters optimized were pH, dosage and contact time and the effect of initial concentration. After respective experiment, all samples were analysed for chromium using microwave plasma atomic emission spectroscopy (MP-AES). The optimum pH was chosen to 8.0, the dosage to 17.4 g GFH/l and the contact time to 2 hours for a 95% removal of total chromium in undiluted wastewater. The removal efficiency of the GFH was 2.84 mg Cr/g GFH. To implement wastewater purification with GFH a number of practical issues have to be taken into consideration. Above all, a sufficient stirring method has to be devised as the removal efficiency is much affected by improper stirring.Denna studie genomfördes i Malawi, sydöstra Afrika. Metallföroreningar i vatten och mark är ett stort problem i många länder, inklusive Malawi. Landets centrum för industri och handel ligger i Blantyre där de flesta av industrierna ligger längs med floderna. En del industrier genererar utsläppsvatten och på grund av dålig tillgång till vattenreningsteknik och vattenreningsanläggningar släpps mycket av det förorenade vattnet obehandlat ut i naturen. En tändsticksfabrik i Blantyre använder kromsalter för att färga tändstickshuvudena röda och höga koncentrationer av sexvärt krom har uppmätts nedströms fabriken. De uppmätta koncentrationerna var upp till 56 mg/l vilket är betydligt högre än WHO:s riktvärde på 0,05 mg/l. Sexvärt krom förekommer som kromat CrO42- och dikromat Cr2O72- joner vilka båda är mycket toxiska och cancerframkallande och därmed ett hot mot miljö och människor. Syftet med studien var att undersöka om granulära järnoxider (GFH) kunde användas som en adsorbent för att rena utsläppsvatten från kromater. Utsläppsvatten hämtades från tändsticksfabriken och genom att optimera relevanta parametrar kunde GFHns adsorbtionseffektivitet maximeras. Parametrarna som optimerades var pH, dos, kontakttid och initialkoncentration. Efter respektive experiment mättes kromkoncentrationen med mikrovågsplasma atomemissionsspektroskopi (MP-AES) Det optimala pH-värdet valdes till 8.0, dosen till 17.4 g GFH/l med en kontakttid på 2 timmar för en 95.3% reningsgrad på outspätt utsläppsvatten. Adsorptionseffektiviteten på GFHn var 2.84 mg Cr/g GFH. För att implementera vattenrening med GFH behöver flera praktiska aspekter tas med i beaktning. Framförallt är det viktigt med en bra omrörning för att GFHn ska kunna adsorbera effektivt.
15
Smythe, Nicole. "Reactivity studies of platinum(IV) hydroxide and methoxide complexes and the study of pincer palladium(II) complexes as potential catalysts for olefin epoxidation /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/8618.
Full text
16
Gómez, Suárez Adrián. "Synthesis and reactivity studies of mono- and diaurated species bearing N-heterocyclic carbene ligands." Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/6546.
Full textAbstract:
The use of Au-NHC complexes in homogenous gold catalysis has become very popular during the last 10 years. The work described in this thesis represents a modest contribution towards a better understanding of the reactivity of these fascinating complexes and the intermediate species involved during gold-catalysed transformations. There are two main themes that permeate the following chapters: a) synthesis and reactivity studies of monoaurated species and b) synthesis and reactivity studies of diaurated species. The main motivation for the work presented herein was to develop more efficient synthetic routes towards a series of gold complexes, such as [Au(NHC)Cl], [Au(NHC)(OH)] and [{Au(IPr)}₂(μ-OH)][X], in order to be able to further explore their reactivity. Chapter 2 constitutes the first approach that I had with the chemistry of Au-NHC complexes, and describes our efforts to evaluate how the use of a highly sterically demanding NHC ligand affects gold-catalysed transformations. Chapters 3 and 4 explore alternative, more efficient synthetic routes towards known Au- NHC complexes. For example, a new, highly robust protocol has been developed for the synthesis of [Au(NHC)X] (X = Cl, Br, I) complexes, which are the starting materials to prepare a wide range of Au-NHC based species. Moreover, as a result of our investigations it has been possible to isolate a series of [Au(NHC)(OH)] species and to gain some insight into the stability of these complexes. Chapters 5 and 6 describe the synthesis and applications of digold hydroxide species [{Au(IPr)}₂(μ-OH)][X] in a series of catalytic and stoichiometric transformations. For example, they have been used as silver-free catalysts for water-inclusive gold-catalysed transformations or to access key intermediates in gold catalysis, such as gem-diaurated and σ,π-digold-acetylide species. Finally, Chapter 7 combines what we learned about the reactivity of [{Au(IPr)}₂(μ- OH)][X] in order to develop for the first time a gold-catalysed transformation where two gold centres independently react with two substrate molecules to catalyse the hydrophenoxylation of alkynes.
17
Jennings, John Adam. "HETEROGENEOUS BASE METAL CATALYZED OXIDATIVE DEPOLYMERIZATION OF LIGNIN AND LIGNIN MODEL COMPOUNDS." UKnowledge, 2017. http://uknowledge.uky.edu/chemistry_etds/81.
Full textAbstract:
With the dwindling availability of petroleum, focus has shifted to renewable energy sources such as lignocellulosic biomass. Lignocellulosic biomass is composed of three main constituents, lignin, cellulose and hemicellulose. Due to the low value of cellulosic ethanol, utilization of the lignin component is necessary for the realization of an economically sustainable biorefinery model. Once depolymerized, lignin has the potential to replace petroleum-derived molecules used as bulk and specialty aromatic chemicals. Numerous lignin depolymerization strategies focus on cleavage of β-aryl ether linkages, usually at high temperatures and under reductive conditions.
Alternatively, selective benzylic oxidation strategies have recently been explored for lignin and lignin models. In this work, heterogeneous catalytic methods using supported base metals and layered-double hydroxides were evaluated for the oxidation of lignin models both before and after benzylic oxidation. Additionally, by studying putative reaction intermediates, insights were gained into the mechanisms of oxidative fragmentation of the model compounds.
Generally, it was found that after benzylic oxidation models were more susceptible to oxidative fragmentation. Indeed, several heterogeneous oxidation systems were found to convert lignin models to oxygenated aryl monomers (mainly benzoic acids and phenols) using inexpensive primary oxidants (i.e., hydrogen peroxide and molecular oxygen). Reactions were conducted at relatively mild temperatures and at low oxygen concentrations for the purpose of an easy transition to large-scale experiments. Finally, the catalytic systems that resulted in significant cleavage of lignin models were applied to a Kraft lignin. Oxidation of Kraft lignin resulted a mixture of products for which analytical data and increased solubility are consistent with interunit cleavage within the lignin macromolecule.
18
Richardson, Mickey Charles Braterman Paul S. "Layered double hydroxides as anion- and cation-exchanging materials." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-3623.
Full text
19
Ambadapadi, Sriram Braterman Paul S. "Study of substituted benzenesulfonate-containing layered double hydroxides and investigation of the hexamethylenetetramine route of LDH synthesis." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-3709.
Full text
20
Kosuri, Divya D'Souza Nandika Anne. "Polyethylene-layered double hydroxides and montmorillonite nanocomposites thermal, mechanical and flame retardance properties /." [Denton, Tex.] : University of North Texas, 2008. http://digital.library.unt.edu/permalink/meta-dc-6087.
Full text
21
Gemmell, Patrick. "Improvements in the precipitation of metal ions by magnesium hydroxide." Thesis, Durham University, 1998. http://etheses.dur.ac.uk/4653/.
Full textAbstract:
The removal of many metal ions from solution with bases by precipitation and filtration is well known. Due to it's limited solubility, Mg(OH)(_2) gives many benefits over the other commonly used bases in terms of safety and post-treatment processes such as residual mass and volume. The use of Mg(OH)(_2) as the base in these reactions, however, does not give satisfactory results in many cases, the levels of metal ions in solution after treatment remaining too high to allow discharge into public waterways. In order to aid these reactions, the use of extra reagents along with the base has been studied. These additives take the form of either donor ligands, e.g. PPh(_3), TMEDA, or other metal solutions, typically trivalent metals i.e. Fe(^3+), Al(^3+) or metal oxides i.e. Fe(_2)O(_3), Al(_2)O(_3).Following previous studies where P- and N-donor ligands, used in catalytic quantities had shown great increases in the %age of metal ions removed from complicated, multiple metal ion effluent systems, the reactions of individual metal ion solutions with these ligands showed disappointing results. After testing separate solutions of Cu(^2+) Fe(^2+) Ni(^2+), Zn(^2+), Pb(^2+) and Al(^3+), only Fe(^2+) showed the same improvements seen in the mixed ion systems. Decreases in %age of Cu(^2+) removed were observed for reactions including these ligands .Decreasing removal was seen with increasing ligand addition. This is due to the formation of soluble complexes which are unaffected by the pHs achieved in the reactions. The other metal ions tested showed little change for any addition of these ligand reagents. Addition of equivalent amounts of an easily precipitated metal ion, i.e. Al(^3+) or Fe(^3+), to a more difficult to treat metal ion solution, i.e. Ni(^2+) or Zn(^2+), gave large improvements on the removal of the ions by treatment with Mg(OH)(_2). Tenfold increases in removal of the ions were seen in the reactions, allowing dischargable concentrations to be achieved in far lower times than previously obtained. Addition of the M(III) solutions, while improving the metal ion removal, increased the amount of Mg(OH)(_2) required for treatment. An industrially available additive, containing Al and Fe sulphates, was tested in a similar fashion giving the same beneficial results. The use of identical amounts of base, with and without this additive showed that improvements in removal of metal ions were obtained even over increasing the relative amount of base added. To overcome this problem, the M(III) species were added in the form of oxides, e.g. Al(_2)O(_3). This removed the need for extra base but the results were disappointing compared to the addition of the M(III) ions as solutions, only ~10% increase in precipitation with a tenfold addition of oxide. None of these reactions achieved the Mg(OH)(_2) buffer pH of 10.5 even when large excesses were added. This has been attributed to coating of the solid Mg(OH)(_2) particles by precipitating M(II) hydroxides which prevented dissolution and kept the majority of the hydroxide from taking part in the reaction. The addition of the extra M(III) species provided preferential sites for the M(II) hydroxides to form on and thus allowed the reaction of all of the Mg(OH)(_2) added. The use of ultrasound to improve these reactions, both instead of and as well as the use of additives, was studied and was seen to give further improvement in these reactions. The ultrasound not only provided an increase in the energy of the systems through a general heating of the solution, but the physical forces created aided the break-up of both the solid Mg(OH)(_2) particles and any coatings that may have built up on them. The use of a 16kHz ultrasound probe produced large improvements in the removal of metal ions and when used in conjunction with M(III) additives dischargable concentrations were achieved in only 30 minutes. Through the use of various additives and conditions, Mg(OH)(_2) has been shown to be a viable option in the effluent treatment industry. The reactions were performed mainly on laboratory prepared solutions of the relevant metal ions, with commercially available Mg(OH)(_2) suspensions. The results were obtained from observation of the pH of the reaction mixtures and concentrations of the metal ions remaining in solution after filtration, determined by atomic absorption spectrophotometry.
22
Balducci, Giulia. "Lightweight metal hydride-hydroxide systems for solid state hydrogen storage." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6534/.
Full textAbstract:
This thesis describes the preparation and characterisation of potential ‘modular’ solid state hydrogen storage solutions for on-board applications. The systems investigated throughout this work are based on reactions between light weight hydroxides and hydrides. In many senses light metal hydroxides can be seen as attractive candidates for hydrogen storage: they are low cost, present negligible toxicity and it is not possible to poison the fuel cell with decomposition products, unlike in nitrogen or boron containing systems. However, as the dehydrogenation products are the respective oxides, the major drawback of such systems lays in the fact the thermodynamics of rehydrogenation are not favourable for onboard applications. Hence, the system must be considered as a ‘charged module’, where the regeneration is performed ex-situ. Dehydrogenation can be achieved through reaction with light metal hydrides such as LiH or MgH2. A wide range of ‘modular’ release systems can be studied, however the most interesting in terms of theoretical gravimetric capacity, kinetics and thermodynamics within reasonable temperature range (RT - 350°C) use magnesium and lithium hydroxide and their hydrate forms. The present work focuses on the full investigation of three main systems: · Mg(OH)2 – MgH2 system · Mg(OH)2 – LiH system · LiOH(·H2O) – MgH2 system (both anhydrous and monohydrate LiOH were used) Mixtures of hydroxides and hydrides were prepared by manually grinding stoichiometric amounts of the starting materials. Further, nanostructuring the reactants was investigated as a means to control the dehydrogenation reaction and enhance the kinetics and thermodynamics of the process. Nanostructured Mg(OH)2 and LiOH(·H2O) have been successfully obtained using both novel and conventional synthetic routes. Reduction of the particle size of both hydrides was effectively achieved by mechanically milling the bulk materials. As detailed throughout Chapters 3, 4 and 5, promising results were obtained when employing nanosized reactants. The onset temperatures of hydrogen release were decreased and the overall systems performances enhanced. Particularly interesting results were obtained for the LiOH – MgH2 system, which exhibit a dramatic decrease of the onset temperature of H2 release of nearly 100 K when working with milled and nanostructured materials with respect to bulk reagents. All systems were characterised mainly by Powder X-ray diffraction (PXD) and simultaneous thermogravimetric analysis (TG-DTA) mass spectroscopy (MS). TG-DTA2 MS experiments were performed to obtain information on the onset and peak temperature of hydrogen release, weight loss percentage and nature and amount of the gases evolved during the reaction. Ex-situ PXD studies have been performed for each system in order to try and identify any intermediate species forming during the dehydrogenation process and ultimately propose a mechanism of H2 release. Since two fundamentally different types of reaction pathway could be proposed for the Mg(OH)2 – LiH system, powder neutron diffraction (PND) was employed for following the reaction in-situ. Developing a complete model of the dehydrogenation process in terms of mechanistic steps was found to be pivotal in order to understand and enhance such systems further.
23
Gibbs, Andrea Claire. "The hydrolytic coprecipitation of metals." Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295180.
Full text
24
Abbas, A. K. "Radiation-electron spin resonance studies on alkali-metal hydroxide aqueous glasses at low temperatures." Thesis, University of Salford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356173.
Full text
25
Trotochaud, Lena. "Structure-Composition-Activity Relationships in Transition-Metal Oxide and Oxyhydroxide Oxygen-Evolution Electrocatalysts." Thesis, University of Oregon, 2014. http://hdl.handle.net/1794/18312.
Full textAbstract:
Solar water-splitting is a potentially transformative renewable energy technology. Slow kinetics of the oxygen evolution reaction (OER) limit the efficiency of solar-water-splitting devices, thus constituting a hurdle to widespread implementation of this technology. Catalysts must be stable under highly oxidizing conditions in aqueous electrolyte and minimally absorb light. A grand goal of OER catalysis research is the design of new materials with higher efficiencies enabled by comprehensive understanding of the fundamental chemistry behind catalyst activity. However, little progress has been made towards this goal to date.
This dissertation details work addressing major challenges in the field of OER catalysis. Chapter I introduces the current state-of-the-art and challenges in the field. Chapter II highlights work using ultra-thin films as a platform for fundamental study and comparison of catalyst activity. Key results of this work are (1) the identification of a Ni0.9Fe0.1OOH catalyst displaying the highest OER activity in base to date and (2) that in base, many transition-metal oxides transform to layered oxyhydroxide materials which are the active catalysts. The latter result is critical in the context of understanding structure-activity relationships in OER catalysts. Chapter III explores the optical properties of these catalysts, using in situ spectroelectrochemistry to quantify their optical absorption. A new figure-of-merit for catalyst performance is developed which considers both optical and kinetic losses due to the catalyst and describes how these factors together affect the efficiency of composite semiconductor/catalyst photoanodes. In Chapter IV, the fundamental structure-composition-activity relationships in Ni1-xFexOOH catalysts are systematically investigated. This work shows that nearly all previous studies of Ni-based catalysts were likely affected by the presence of Fe impurities, a realization which holds significant weight for future study of Ni-based catalyst materials. Chapter V discusses the synthesis of tin-titanium oxide nanoparticles with tunable lattice constants. These materials could be used to make high-surface-area supports for thin layers of OER catalysts, which is important for maximizing catalyst surface area, minimizing the use of precious-metal catalysts, and optimizing 3D structure for enhanced mass/bubble transport. Finally, Chapter VI summarizes this work and outlines directions for future research.
This work contains previously published and unpublished co-authored material.2015-03-29
26
Stosiek, Christoph. "Struktur und Eigenschaften von nanoskopischen Metall(hydroxid)fluorid-Aluminiumoxid-Kompositen." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2010. http://dx.doi.org/10.18452/16162.
Full textAbstract:
Durch die Verwendung der fluorolytischen Sol-Gel Synthese ist es möglich, röntgenamorphe bzw. partiell nanokristalline Metallhydroxidfluoride und Metallfluoride zu erhalten. Diese Verbindungen unterscheiden sich in ihren Eigenschaften stark von „klassisch“ hergestellten, kristallinen Metall(hydroxid)fluoriden. In der vorliegenden Promotionsarbeit wurden deshalb in vier aufeinander folgenden Kapiteln sowohl die Synthese und Charakterisierung von Aluminium– und Magnesium(hydroxid)fluoriden beschrieben als auch die Auswirkung dieser Verbindungen auf das Phasentransformationsverhalten von böhmitischen Xerogelen zu Korund sowie ihre Wirksamkeit als Sinterhilfsmittel bei der Korundkeramikherstellung untersucht.The application of the fluorolytic sol-gel method with aqueous hydrofluoric acid enables the synthesis of X-ray amorphous or rather partially nanocrystalline metal hydroxide fluorides and metal fluorides. These compounds strongly differ in their characteristics from “classically” manufactured, crystalline metal hydroxide fluorides. In the present dissertation both, the synthesis and characterisation of aluminium and magnesium hydroxide fluorides were described and the effect of these compounds on the phase transformation behaviour from pseudoboehmites to corundum was examined as well as their effectiveness as sintering aid during the corundum ceramics production.
27
Brown, Neil J. "A multiattribute evaluation model for environmental compliance of existing metal hydroxide precipitation systems in the electroplating industry." Master's thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-01202010-020209/.
Full text
28
Tulyapitak, Tulyapong. "CURE AND MECHANICAL PROPERTIES OF CARBOXYLATED NITRILE RUBBER (XNBR) VULCANIZED BY ALKALINE EARTH METAL COMPOUNDS." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1158067153.
Full text
29
Ricknell, Jonas. "Recovery of valuable metals from spent HEV NiMH battery leach solutions." Thesis, KTH, Skolan för kemivetenskap (CHE), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-216397.
Full textAbstract:
As the demand on resources is increasing worldwide, the process of recycling material has become more important. The specific recycling of metals used in car batteries, and more specifically in the large batteries used in hybrid electric vehicles, is a rising concern where the industrially implemented recycling processes concerning these batteries that exist today are often highly pollutant and energy consuming. In the present study, an alternative hydrometallurgical recycling process of the previously and to some extent presently widely used battery type for hybrid electric vehicle applications, namely the Nickel Metal Hydride (NiMH) battery, has been investigated. The focus was to evaluate different routes of recovering Ni, Co, Mn, Zn, Al and residual Y from a NiMH battery leach solution as obtained in a priorly conducted leaching study. Three different possible products were chosen for closer investigation, a mixed metal hydroxide where all of the metals would be precipitated together, a new NiMH cathode material where a controlled precipitation of Ni, Co and Zn together would be implemented and last a pure Ni salt product where a selective separation of Ni from the other metals would be required. Two of the three products, the mixed metal hydroxide and the pure Ni salt, were found suitable for the specific system and it was concluded that a pure Ni salt production would be most justifiable. The separation of Ni from the other metals present in the solution was here proposedly achieved by an extraction process using supported liquid membranes. A mathematical model was used in Matlab in order to evaluate the separation efficiency and to determine the optimum process conditions for the extraction process and a hydroxide precipitation experimental study was conducted in order to determine both the process streams in the production of a mixed metal hydroxide and the solution behavior during the pH increase in the Ni salt production extraction process. The results suggested a low loss of valuable metals and due to this, both the process of producing a mixed metal hydroxide and the process of producing a pure Ni salt could be found to be economically justifiable.I samband med den ökande efterfrågan på råmaterial världen över så har processer för att återvinna material blivit mer och mer viktiga. Den specifika återvinningen av metaller som använts i bilbatterier, och än mer specifikt återvinningen av de stora batterier som används i hybridbilar är just nu en ökande oro då de rådande återvinningsprocesser som används idag ofta är högst energikrävande och har en stor förorenande inverkan på naturen. I denna studie har en alternativ hydrometallurgisk återvinningsprocess granskats i syfte att återvinna de metaller som används i nickelmetallhydridbatterier (NiMH) som brett har använts för just hybridbilsapplikationer. Fokus har legat på att utvärdera olika möjligheter att återvinna Ni, Co, Mn, Zn, Al och överbliven Y från en laklösning som är ett resultat av en tidigare genomförd lakstudie angående NiMH-batterierna. Tre möjliga produkter valdes för närmare granskning, en blandad metallhydroxid där alla metaller samutfälls ur lösningen, en ny NiMH-katod där en kontrollerad samutfällning av Ni, Co och Zn implementeras och sist ett rent nickelsalt där a selektiv separation av Ni från de övriga metallerna är nödvändig. Två av de tre produkterna, den blandade metallhydroxiden och det rena nickelsaltet, befanns vara lämpliga för det specifika systemet och slutsatsen drogs att en nickelsaltsproduktion var mest berättigad. Den föreslagna separationstekniken för att separera Ni från de andra metallerna i lösningen var en extraktionsprocess användandes av en vätskemembranteknik. En matematisk modell användes med hjälp av Matlab för att utvärdera separationseffektiviteten och för att bestämma optimala processförhållanden. En experimentell hydroxidutfällningsstudie genomfördes även för att bestämma både procesströmmarna i en produktion av en blandad metallhydroxid och för att undersöka lösningens beteende under pH-ökningen i den föreslagna produktionsprocessen av ett nickelsalt. Enligt resultaten är förlusten av värdefulla metaller låga i båda processerna och i enlighet med detta kunde både produktionsprocessen av en blandad metallhydroxid och av ett rent nickelsalt befinnas ekonomiskt hållbara.
30
Green, Lisa Marie. "Synthesis, characterization and reactivity of platinum(0)-tetraphosphion complexes and group VIII metal phosphine complexes coordinated to alkoxide and hydroxide ligands /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487331541709992.
Full text
31
Estes, Matthew J. "Corrosion of composite tube air-ports in kraft recovery boiler: Cr₂O₃, Fe₂O₃, NiO solubility in molten hydroxide." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/7027.
Full text
32
Del, Pilar Albaladejo Joselyn. "Zeolite-supported Cobalt Catalysts for Water Oxidation in Artificial Photosynthetic Systems." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1313603462.
Full text
33
Purushothaman, Bushan K. "DEVELOPMENT OF BATTERIES FOR IMPLANTABLE APPLICATIONS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=case1151609663.
Full text
34
Zhao, Yanyan. "Synthesis and characterisation of metal (Fe, Ga, Y) doped alumina and gallium oxide nanostructures." Queensland University of Technology, 2008. http://eprints.qut.edu.au/20529/.
Full textAbstract:
It is well known that nanostructures possess unique electronic, optical, magnetic, ferroelectric and piezoelectric properties that are often superior to traditional bulk materials. In particular, one dimensional (1D) nanostructured inorganic materials including nanofibres, nanotubes and nanobelts have attracted considerable attention due to their distinctive geometries, novel physical and chemical properties, combined effects and their applications to numerous areas. Metal ion doping is a promising technique which can be utilized to control the properties of materials by intentionally introducing impurities or defects into a material.
γ-Alumina (Al2O3), is one of the most important oxides due to its high surface area, mesoporous properties, chemical and thermal properties and its broad applications in adsorbents, composite materials, ceramics, catalysts and catalyst supports. γ-Alumina has been studied intensively over a long period of time. Recently, considerable work has been carried out on the synthesis of 1D γ-alumina nanostructures under various hydrothermal conditions; however, research on the doping of alumina nanostructures has not been forthcoming. Boehmite (γ-AlOOH) is a crucial precursor for the preparation of γ-Alumina and the morphology and size of the resultant alumina can be manipulated by controlling the growth of AlOOH.
Gallium (Ga) is in the same group in the periodic table as aluminum. β-Gallium (III) oxide (β-Ga2O3), a wide band gap semiconductor, has long been known to exhibit conduction, luminescence and catalytic properties. Numerous techniques have been employed on the synthesis of gallium oxide in the early research. However, these techniques are plagued by inevitable problems. It is of great interest to explore the synthesis of gallium oxide via a low temperature hydrothermal route, which is economically efficient and environmentally friendly.
The overall objectives of this study were: 1) the investigation of the effect of dopants on the morphology, size and properties of metal ion doped 1D alumina nanostructures by introducing dopant to the AlOOH structure; 2) the investigation of impacts of hydrothermal conditions and surfactants on the crystal growth of gallium oxide nanostructures. To achieve the above objectives, trivalent metal elements such as iron, gallium and yttrium were employed as dopants in the study of doped alumina nanostructures. In addition, the effect of various parameters that may affect the growth of gallium oxide crystals including temperature, pH, and the experimental procedure as well as different types of surfactants were systematically investigated.
The main contributions of this study are: 1) the systematic and in-depth investigation of the crystal growth and the morphology control of iron, gallium and yttrium doped boehmite (AlOOH) under varying hydrothermal conditions, as a result, a new soft-chemistry synthesis route for the preparation of one dimensional alumina/boehmite nanofibres and nanotubes was invented; 2) systematic investigation of the crystal growth and morphology and size changes of gallium oxide hydroxide (GaOOH) under varying hydrothermal conditions with and without surfactant at low temperature; We invented a green hydrothermal route for the preparation of α-GaOOH or β-GaOOH micro- to nano-scaled particles; invented a simple hydrothermal route for the direct preparation of γ-Ga2O3 from aqueous media at low temperature without any calcination.
The study provided detailed synthesis routes as well as quantitative property data of final products which are necessary for their potential industrial applications in the future. The following are the main areas and findings presented in the study:
• Fe doped boehmite nanostructures
This work was undertaken at 120ºC using PEO surfactant through a hydrothermal synthesis route by adding fresh iron doped aluminium hydrate at regular intervals of 2 days. The effect of dopant iron, iron percentage and experimental procedure on the morphology and size of boehmite were systematically studied. Iron doped boehmite nanofibres were formed in all samples with iron contents no more than 10%. Nanosheets and nanotubes together with an iron rich phase were formed in 20% iron doped boehmite sample. A change in synthesis procedure resulted in the formation of hematite large crystals. The resultant nanomaterials were characterized by a combination of XRD, TEM, EDX, SAED and N2 adsorption analysis.
• Growth of pure boehmite nanofibres/nanotubes
The growth of pure boehmite nanofibres/nanotubes under different hydrothermal conditions at 100ºC with and without PEO surfactant was systematically studied to provide further information for the following studies of the growth of Ga and Y doped boehmite. Results showed that adding fresh aluminium hydrate precipitate in a regular interval resulted in the formation of a mixture of long and short 1D boehmite nanostructures rather than the formation of relatively longer nanofibres/nanotubes. The detailed discussion and mechanism on the growth of boehmite nanostructure were presented. The resultant boehmite samples were also characterized by N2 adsorption to provide further information on the surface properties to support the proposed mechanism.
• Ga doped boehmite nanostructures
Based on this study on the growth of pure boehmite nanofibre/nanotubes, gallium doped boehmite nanotubes were prepared via hydrothermal treatment at 100ºC in the presence of PEO surfactant without adding any fresh aluminium hydrate precipitate during the hydrothermal treatment. The effect of dopant gallium, gallium percentage, temperature and experimental procedure on the morphology and size of boehmite was systematically studied. Various morphologies of boehmite nanostructures were formed with the increase in the doping gallium content and the change in synthesis procedure. The resultant gallium doped boehmite nanostructures were characterized by TEM, XRD, EDX, SAED, N2 adsorption and TGA.
• Y doped boehmite nanostructures
Following the same synthesis route as that for gallium doped boehmite, yttrium doped boehmite nanostructures were prepared at 100ºC in the presence of PEO surfactant. From the study on iron and gallium doped boehmite nanostructures, it was noted both iron and gallium cannot grow with boehmite nanostructure if iron nitrate and gallium nitrate were not mixed with aluminium nitrate before dissolving in water, in particular, gallium and aluminium are 100% miscible. Therefore, it’s not necessary to study the mixing procedure or synthesis route on the formation of yttrium doped boehmite nanostructures in this work. The effect of dopant yttrium, yttrium percentage, temperature and surfactant on the morphology and size of boehmite were systematically studied. Nanofibres were formed in all samples with varying doped Y% treated at 100ºC; large Y(OH)3 crystals were also formed at high doping Y percentage. Treatment at elevated temperatures resulted in remarkable changes in size and morphology for samples with the same doping Y content. The resultant yttrium doped boehmite nanostructures were characterized by TEM, XRD, EDX, SAED, N2 adsorption and TGA.
• The synthesis of Gallium oxide hydroxide and gallium oxide with surfactant
In this study, the growth of gallium oxide hydroxide under various hydrothermal conditions in the presence of different types of surfactants was systematically studied. Nano- to micro-sized gallium oxide hydroxide was prepared. The effect of surfactant and synthesis procedure on the morphology of the resultant gallium oxide hydroxide was studied. β-gallium oxide nanorods were derived from gallium oxide hydroxide by calcination at 900ºC and the initial morphology was retained. γ-gallium oxide nanotubes up to 65 nm in length, with internal and external diameters of around 0.8 and 3.0 nm, were synthesized directly in solution with and without surfactant. The resultant nano- to micro-sized structures were characterized by XRD, TEM, SAED, EDX and N2 adsorption.
• The synthesis of gallium oxide hydroxide without surfactant
The aim of this study is to explore a green synthesis route for the preparation of gallium oxide hydroxide or gallium oxide via hydrothermal treatment at low temperature. Micro to nano sized GaOOH nanorods and particles were prepared under varying hydrothermal conditions without any surfactant. The resultant GaOOH nanomaterials were characterized by XRD, TEM, SAED, EDX, TG and FT-IR. The growth mechanism of GaOOH crystals was proposed.
35
Onal, Mehmet Ali Recai. "Pressure Leaching Of Caldag Lateritic Nickel Ore." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615480/index.pdf.
Full textAbstract:
The purpose of this study was to investigate the process optimization of combined high pressure acid leaching (HPAL) and mixed hydroxide precipitation (MHP) route for the extraction of nickel and cobalt from Çaldag lateritic nickel ore. In order to extract nickel and cobalt values into pregnant leach solution (PLS), several process parameters of HPAL including acid load, temperature, leaching duration and particle size were investigated in comparative manner at constant solid concentration and agitation speed. After HPAL trials, it has been found that more than one combination of parameters offered higher than 90% extraction efficiencies for both nickel and cobalt. Among them, 0.325 kg/kg acid load, 250°
C, 1 hour duration and 100% -1 mm particle size was selected as the optimum conditions with 94.1% Ni and 94.0% Co extractions. A stock of PLS was prepared under the stated conditions that was treated by downstream operations in order to obtain MHP. Initially by two-stage iron removal of downstream operations major impurities iron, chromium and aluminum were nearly completely removed with acceptable nickel and cobalt losses from PLS. Then, the nickel and cobalt were precipitated by two-stage mixed hydroxide precipitation. In the first step of MHP, the optimum conditions were chosen as pH=7.10, 60°
C and 1 hour duration. The intermediate product obtained at these conditions contained 44.3% Ni, 3.01% Co with 3.06% Mn contamination. In summary, it was found that Ç
aldag nickel laterite ore was readily leachable under HPAL conditions and PLS obtained was easily treatable in order to produce saleable MHP.
36
Adán, Mas Alberto. "Advanced metal graphene composite electrodes for a new generation of electrochemical energy storage devices." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0181/document.
Full textAbstract:
Actuellement, les supercondensateurs sont au centre de beaucoup de recherches. Ils offrent une solution potentielle pour le stockage réversible de l´énergie que ce soit pour le domaine spatial, aéronautique ou encore le transport (véhicules hybrides). Un axe de recherche important, visant à augmenter les densités d'énergie et de puissance, est consacré aux systèmes oxydes de métaux de transition /charbon actif (C) asymétriques. Les systèmes à base de RuO2 présentent les capacités les plus élevées, supérieures à 700 F/g, mais leur coût et leur toxicité limitent leur application aux petits appareils électroniques. Des oxydes moins coûteux tels que les oxydes de cobalt (notamment Co3O4), MnO2, V2O5, Fe3O4, NiO, Ni(OH)2, ainsi que des polymères conducteurs électroniques, ont été étudiés de manière approfondie au cours des dernières décennies jusqu’à être utilisés, pour certains, dans des dispositifs commerciaux. Mais aucun système n’a été aussi étudié que le C / MnO2. En effet, il a été démontré que ce dernier est particulièrement intéressant car il peut fonctionner dans des milieux aqueux à des tensions pouvant aller jusqu’à 2V tout en gardant une bonne stabilité électrochimique durant le vieillissement. Néanmoins, les performances du système, en particulier en termes de densité de puissance, sont limitées à cause de la mauvaise conductivité électronique du MnO2. Il est possible de surmonter ce problème en ajoutant à l’oxyde de manganèse, des matériaux conducteurs à base de carbone (noir de carbone, nanotubes de carbone…) ou encore, en développant des stratégies de greffage ou de décoration plus élaborées. La combinaison d’oxydes avec des espèces carbonées est très largement rapportée dans la littérature alors que le mélange d’oxydes de différente nature l’est beaucoup moins. Nous proposons dans ce projet de synthétiser et de développer des matériaux originaux améliorant, par un effet synergique, les propriétés intéressantes du manganèse, du cobalt et de l'oxyde / hydroxyde de nickel. Les inconvénients de chaque composant étant compensés par les bonnes propriétés complémentaires des autres. Nous cherchons à réunir en un seul matériau (ou composite), le bon comportement pseudocapacitif du manganèse, la bonne conductivité électronique associée aux oxydes de cobalt, la grande capacité de l'hydroxyde de nickel ainsi que les propriétés de conduction du carbone. Ce projet de doctorat vise à concevoir et à fabriquer de nouvelles classes d'électrodes composites hybrides basées sur des assemblages de graphène (pour la capacitance renforcée à double couche) et d'oxydes poreux de métaux de transition (pour une capacité faradique supplémentaire due à de multiples processus rédox réversibles). Les avantages combinés du graphène et des oxydes de métaux de transition permettront aux supercondensateurs à haute densité d'énergie de travailler dans des électrolytes aqueux respectueux de l'environnement ce qui est, aujourd’hui, un besoin reconnuSupercapacitors are the focus of much research at the present time. They offer a potential solution for reversible energy storage in the fields of space, aircrafts or transportation (hybrid vehicles). An important research line, aiming at increasing both energy and power densities, is devoted to asymmetric transition metal oxides / activated carbon (C) systems. RuO2-based devices exhibit the highest capacitance, more than 700 F/g, but their cost limits the applications to small electronic devices. Less expensive oxides such as cobalt oxides (especially Co3O4), MnO2, V2O5, Fe3O4, NiO, Ni(OH)2, as well as electrically conducting polymers, have been extensively studied in the past decades, or used in commercial devices; they EACH exhibit each drawbacks and advantages with regard to applications. But no system has been investigated as much as the C/MnO2 one, which is particularly interesting because it can work in aqueous media at tensions up to 2 V, and high stability in ageing has been demonstrated. Nevertheless, the performances of the system, especially in terms of power density, are limited by the poor electronic conductivity of MnO2. This problem is usually solved by simply mixing conductive carbon materials (carbon black, CNTs…) with MnO2 or by developing more elaborated grafting or decoration strategies. The combination of oxide and carbonaceous species is widely reported in the literature, whereas combining oxides with different natures is less frequently encountered. We propose in this project to synthesize and develop original materials enhancing, through a synergistic effect, the interesting properties of manganese, cobalt and nickel oxide/hydroxide, the drawbacks of each component being overbalanced by the good complementary properties of the other components. We aim at gathering in one single material (or composite), the good pseudocapacitive behavior of manganese, the good electronic conductivity associated to cobalt oxides, the high capacity of nickel hydroxide, as well as the enhanced conduction properties of carbon. The present PhD project aims at designing and manufacturing new classes of hybrid composite electrodes based on assemblies of graphene (for enhanced double layer capacitance) and porous transition metals oxides (for additional faradaic capacitance due to multiple reversible redox processes) directly applied on metallic current collectors. The combined advantages of graphene with those of transition metals oxides will enable supercapacitors with high energy density, working in environmentally friendly aqueous electrolytes, which are an acknowledged need
A procura crescente de energia em setores distintos, como residencial, transporte e industrial, bem como a proliferação de fontes renováveis de produção de energia, exigem novos e mais eficientes dispositivos de armazenamento de energia. Consequentemente, tem-se observado um interesse crescente na produção e engenharia de materiais para armazenamento de energia. Muito dos esforços de R&D estão centrados no desenvolvimento de materiais nanoestruturados que possam responder aos requisitos da aplicação, tais como densidade de energia, densidade de potência e estabilidade face à ciclagem do dispositivo. Presentemente são muitos os materiais investigados como potenciais candidatos para elétrodos para dispositivos de armazenamento de energia por via eletroquímia, nomeadamente baterias, condensadores, pseudocondensadores ou supercondensadores. O objetivo do presente trabalho é produzir e estudar novos materiais com uma resposta eletroquímica intermédia entre um elétrodo típico de supercondensador e um elétrodo típico de bateria, também conhecidos como elétrodos híbridos. Por essa razão, selecionaram-se hidróxidos e óxidos de níquel e cobalto devido à sua elevada atividade eletroquímica e baixo custo. Estes materiais foram combinados com derivados de grafeno, que exibem alta condutividade e elevada área superficial ativa. Portanto, este trabalho foca a síntese e caracterização fisico química e eletroquímica de hidróxidos e óxidos de níquel-cobalto nanoestruturados e sua combinação com óxido de grafeno reduzido para aplicações de armazenamento de energia. A síntese foi efectuada por duas vias distintas: eletrodeposição e exfoliação. A eletrodeposição é usada para obter hidróxidos e óxidos de níquel-cobalto em combinação com óxido de grafeno reduzido. Os resultados evidenciam um efeito sinérgico quando o óxido de grafeno reduzido é combinado com o (hidr)óxido de níquel- cobalto, isto é, um aumento na capacidade, condutividade e estabilidade do compósito quando comparado com o (hidr)óxido de níquel-cobalto. Neste trabalho é dada especial atenção à espectroscopia de impedância eletroquímica que foi utilizada para avaliar os fenômenos que ocorrem durante a carga e descarga contínua e compreender os processos que ocorrem no material ativo e que resultam na sua degradação. O hidróxido de níquel-cobalto é também preparado por exfoliação, em meio aquoso, por meio da intercalação de lactato, enquanto o tetra-butilamónio é utilizado na exfoliação do óxido de níquel-cobalto. A resposta eletroquímica é avaliada em diferentes eletrólitos após reconstrução. Os resultados revelam a influência das espécies intercaladas durante o processo de exfoliação: quando a exfoliação é realizada para fins de armazenamento de energia, as espécies intercaladas e a força da interação com o material ativo devem ser consideradas de antemão para evitar o bloqueio superficial ou inibição da interação elétrodo-eletrólito. Os resultados mostraram que a exfoliação é uma rota promissora para aumentar a área de superfície ativa dos materiais, um parâmetro crítico no desempenho eletroquímico dos materiais dos eletrodos. Nesta dissertação é também estudado o mecanismo de carga-descarga do hidróxido de níquel-cobalto, que ainda não está completamente entendido. Assim, compreender esse mecanismo é um passo crítico para otimizar a morfologia e o desempenho do material e para projetar futuros dispositivos de armazenamento de energia. Para esclarecer os processos que ocorrem durante a carga, aplica-se o modelo de Mott-Schottky foi aplicado parade modo a avaliar a variação da conductividade do material e da sua capacidade na interface elétrodo-eletrólito. [...]
37
Halvachizadeh, Jaleh. "The Investigation of Reactions of Atomic Metal Anions with Small Hydrocarbons and Alcohols in the Gas Phase." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30646.
Full textAbstract:
Hydrocarbons are an abundant resource of carbon and hydrogen. For example, fossil can be used to produce useful organic compounds. However hydrocarbons seem to be inert. Thus, the activation of the C-H bond is a popular research area. Metals play the main role in most catalysts that convert hydrocarbons to starting materials in industry. The study of metals is important because the properties of the metal core greatly influences the reactivity of a catalyst.1
The study of the chemistry of metals in the gas phase provides valuable information about the properties of metals. This information can be expanded to the chemistry of metals in the condensed phase. Furthermore, it is often both more accurate and more manageable to study the profile of a reaction in the gas phase than in the condensed phase.2,3
There are many studies about metal cations in the gas phase due to ease of their production. However metals have low electronegativity, limiting the study of gas phase metal anions. Recently, a simple and efficient method to generate atomic metal anions was developed at the University of Ottawa in Dr. Mayer's research laboratory.4-6 Atomic metal anions of Fe-, Co-, Cu-, Ag-, Cs- and K- were generated in an electrospray ionization (ESI) source of a mass spectrometer (MS).
In this thesis study generated metal anions were reacted with small hydrocarbons of pentane, 1-pentene, 2-pentene and 1-pentyne to investigate the role of different metal anions in the activation of the C-H bond. Also metal anions were reacted with small alcohols of 1-butanol, 2-butanol and 2-methyl-2-propanol to compare the results.
Metal anions showed a variety of reactions with these hydrocarbons and alcohols. Fe- was the only metal anion to show the electron transfer reaction, indicating that alcohols are more electronegative than Fe- and less electronegative than other metal anions. Fe-, Co- and Ag- showed the complex formation reaction. All metal anions showed the deprotonation reaction. A deprotonation reaction follows the harpoon mechanism, the long range proton abstraction7, and depends on the gas phase acidity of fragments. The most informative reaction observed was the dehydrogenation reaction because a metal-containing fragment is observed as a product in the spectrum of this reaction. The observation of a metal-containing fragment in the spectrum is significant because it emphasizes the important role that metal anions play in this reaction. This suggests that a dehydrogenation reaction involves metal insertion into a C-H bond. Among the transition metal anions, it was observed that Fe- and Cu- are more reactive than Co- and Ag- with regards to the dehydrogenation reaction, probably because Fe- and Cu- have a greater hydrogen affinity than Co- and Ag- that facilitates the hydrogen abstraction reaction. Another reason could be that Fe- and Cu- have a greater gas phase acidity that leads to a more stable intermediate in the course of the reaction. The results of this thesis study revealed that Cs- and K- could not abstract H from these substrates, probably due to the absence of occupied d orbitals that would facilitate insertion into a C-H bond.
Some metal anions not only can insert into a C-H bond of alcohols but also can insert into a C-O bond of alcohols to form metal hydroxide anions. Alcohols are more reactive than hydrocarbons with regards to reactions with metal anions because they contain a functional group.
This thesis study shows that some atomic metal anions are able to activate the C-H bond and abstract two hydrogens to form a double bond in hydrocarbons. It is probable that the electronic configuration, gas phase acidity and hydrogen affinity of the metal anions governs their reactivity.
38
Nilsson, Anna. "Optimering av den kemiska reningen vid Fläskebo deponi." Thesis, Uppsala University, Department of Earth Sciences, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-88841.
Full textAbstract:
Landfill leachate contains a variety of contaminants and is created when rainwater percolates the landfill. For landfill management the leachate is the main issue that can cause problems to the environment. At the landfill of Fläskebo, Renova AB treats the leachate in a local treatment plant. The treatment consists of a chemical treatment step with chemical precipitation, flocculation, sedimentation and filtration, and a final step with a carbon and peat filter. Renova has to ensure that the condition of the leachate reaches the regulation set for the landfill before it is released to the recipient. This regulation has not yet been established and a final suggestion will be given to the county administrative board in spring 2006.
In this master thesis the chemical treatment of Fläskebo is optimized. A comparison between the control program and the regulation was made to estimate the contamination of the leachate. Also the effectiveness of the two steps is evaluated. For optimization, the leachate was first tested in a laboratory with different coagulants and flocculants.
The purpose was to increase the precipitation of particles and metals; arsenic, cadmium, chromium, mercury, lead, copper, nickel and zinc through sweep floc coagulation and hydroxide precipitation. After the laboratory tests the precipitation was tested in the treatment plant with higher pH and coagulant. Also the process control for sodium hydroxide was examined.
The leachate had a small content of organic matter and nutrients, but had a large content of halogenated substances (AOX) and the heavy metals nickel and copper. High concentrations of contaminants were reduced better than low concentrations in the two treatment steps. The carbon and peat filter material also caused an increase of the arsenic content in the leachate after filtration. From the laboratory work the results showed a better reduction of metals with iron-chloride, PlusJÄRN and the anjonic polyacrylamid, Fennopol A. Because of the high content of chloride the iron- sulphate, PurFect was chosen for further tests. The optimal pH for the heavy metals arsenic, zinc, copper and nickel was between pH 9 and 9, 5. The precipitation in the treatment plant showed better results with sodium hydroxide and a higher pH, pH 9 in the flocculation basin. An increase of the coagulant PurFect from 202 mg/l to 225 mg/l meant only a higher chemical cost. The process control of sodium hydroxide showed an oscillating and unstable control performance, which may lead to a higher consumption of chemicals.
Lakvatten har varierande föroreningsgrad och karaktär och bildas då regnvatten perkolerar igenom en deponi. För en deponiverksamhet är lakvattnet den huvudsakliga påverkan på den omgivande miljön. Vid en av Renova ABs deponier, Fläskebo, utanför Göteborg sker reningen av vattnet i den lokala reningsanläggningen. Reningen består av kemisk fällning, flockning, sedimentering och filtrering samt ett kol- och torvfilter. För att få släppa ut lakvattnet har Renova just nu ett prövotidsvillkor på lakvattnets kvalité och till våren 2006 skall förslag på slutgiltiga utsläppsvillkor lämnas till Länsstyrelsen.
I detta examensarbete har den kemiska reningen av lakvattnet från Fläskebo optimerats utifrån lakvattnets karaktär. Lakvattnets föroreningsgrad bedömdes efter en jämförelse av analysresultatet inom kontrollprogrammet och riktvärdena i prövotidsvillkoret. Dessutom utvärderades effektiviteten i varje enskilt reningssteg, den kemiska reningen och kol- och torvfiltret. För optimering av den kemiska reningen testades lakvattnet först på lab med olika fällnings- och flockningsmedel. Uppgiften var att öka partikelfällningen och reducera metallerna arsenik, kadmium, krom, kvicksilver, bly, koppar, nickel och zink i lakvattnet genom svepkoagulering och hydroxidfällning.
Utifrån resultaten på lab testades sedan fällningen i full skala, pH höjdes i flockningsbassängen och så även dosen fällningsmedel till vattnet. En inledande undersökning av regleringen av lutdosering gjordes med några stegsvarsexperiment.
Lakvatten innehöll låga halter av organiskt material och närsalterna kväve och fosfor, medan de halogena ämnena (AOX) och tungmetallerna nickel och koppar var höga. De båda reningsstegen, kemisk rening och kol- och torvfiltret var generellt bra på att rena föroreningar i höga koncentrationer men var sämre vid låga. Kol- och torvfiltret ökade koncentrationen i vattnet av arsenik genom materialets interna läckage. I fällningsförsöken gav järnkloriden, PlusJÄRN och den anjoniska polyakrylamiden, Fennopol A bäst resultat i att avskilja metaller. Järnsulfaten PurFect gav näst bäst resultat och valdes istället för järnkloriden för vidare försök då kloridhalten i lakvattnet redan var högt. Optimalt pH för arsenik, zink, koppar och nickel var inom pHintervallet 9 och 9,5. Fällningen i full skala ute i verket visade ett bättre resultat vid tillsatt lut och ett högre pH (pH 9) i flockningsbassängen. Däremot betydde en höjning av fällningskemikalien från 202 mg/l PurFect till 225 mg/l enbart en ökad kemikaliekostnad och en överdosering. Det visade sig dessutom att lutregleringen var svängig och på gränsen till instabil. Regulatorn bör därför ses över så att risken för ökad kemikaliekonsumption och kostnader minskar.
39
Blin, Benoit. "Etude de la reduction de l'hydroxyde de coblat ii par les polyols et application a la preparation de poudres de cobalt microniques et submicroniques." Paris 7, 1987. http://www.theses.fr/1987PA077093.
Full text
40
Ayturk, Mahmut Engin. "Synthesis, annealing strategies and in-situ characterization of thermally stable composite thin Pd/Ag alloy membranes for hydrogen separation." Worcester, Mass. : Worcester Polytechnic Institute, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-042307-012951/.
Full textAbstract:
Thesis (Ph.D.)--Worcester Polytechnic Institute.Keywords: composite Pd and Pd/Ag membranes, alloying, Pd/Ag barrier, intermetallic diffusion, bi-metal multi-layer BMML deposition, electroless plating kinetics, high temperature x-ray diffraction, aluminum hydroxide surface grading, porous sintered metal supports, hydrogen separation. Includes bibliographical references (leaves 279-296 ).
41
Sterley, Anna, and Daniel Thörnkvist. "The feasibility of using macroalgae from anaerobic digestion as fertilizer in Grenada : A literature study of the potential use of residue as fertilizer in Grenada, and a complementary laboratory study to evaluate the biogas potential." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-284111.
Full textAbstract:
Coastal areas in Grenada and the Caribbean are experiencing an abundance of stranded macroalgae. Climate change and eutrophication are probable causes of this inconvenience. This leads to logistic and economic dilemmas for the Caribbean societies. Research of methods to benefit from the algal bloom is therefore valuable for a sustainable future in these countries. Studies of biogas and fertilizer production are initiated around the world, but a large scale production is absent. Therefore, this thesis scrutinize the requirements for producing biofertilizer from biogas by examine the content of macroalgae and the conditions in Grenada. To achieve this, a literature study and a miniature biogas experiment were conducted. Grenada would presumably benefit from substituting synthetic fertilizer with biofertilizer from macroalgae utilized in biogas production. The positive aspects includes the recirculation of nutrients, development of renewable energy and autonomous fertilizer production. Further research of the definite macroalgae content is essential to determine the exact extent and conditions of the fertilizer utilization.Kustområden i Grenada och Karibien är drabbat av större mängder strandade makroalger. Klimatförändringar och övergödning är de huvudsakliga orsakerna till denna olägenhet. Detta leder till logistiska och ekonomiska problem för samhällen i Karibien. Det är därför av värde att forska på metoder för att försöka nyttja algblomningen, för en hållbar framtid i dessa länder. Studier på biogasproduktion och gödselmedelstillverkning av makroalger har utvecklats på senare tid, men en storskalig produktion är fortfarande frånvarande. Därför ska denna avhandling granska kriterierna för att använda biogödsel från biogasproduktion genom att undersöka makroalgernas innehåll, och Grenadas förutsättningar för att genomföra detta. För att uppnå detta så har en litteraturstudie och ett mindre biogasexperiment genomförts. Grenada skulle förmodligen dra fördel av att byta ut syntetiskt gödningsmedel med biogödningsmedel från biogasproduktion med makroalger. De positiva aspekterna av detta är recirkulationen av näringsämnen, etablering av förnyelsebara energikällor, samt självständig gödselproduktion. Vidare forskning på det exakta innehållet i makroalger är väsentligt för att kunna bestämma utsträckningen och förhållandena för gödselmedelsanvändningen.
42
Ghisi, Mirela. "Determinação de Cu e Fe em Biodiesel por Espectrometria de Absorção Atômica com Atomização Eletrotérmica e Estudo do Efeito Catalítico destes Metais sobre a Estabilidade Oxidativa do Biodiesel." Universidade Federal do Maranhão, 2011. http://tedebc.ufma.br:8080/jspui/handle/tede/918.
Full textAbstract:
Made available in DSpace on 2016-08-19T12:56:36Z (GMT). No. of bitstreams: 1
MIRELA GHISI.pdf: 1324849 bytes, checksum: 5d9ca5c5a49c366f3bf4959e2e942a14 (MD5)
Previous issue date: 2011-05-16Conselho Nacional de Desenvolvimento Científico e Tecnológico
The metals content in biodiesel is directly related with the raw material used and also with the utilized biodiesel production method. In this work, an evaluation of the main metals present in biodiesel samples from different sources was done. The qualitative analysis of the metal content was assessed using the Inductively Coupled Plasma Mass Spectrometry technique after sample digestion in microwave oven. The main metals identified in the analyzed biodiesel samples were Al, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sr and Zn. Metals like Ag, As, Ba, Cd, Co, Tl and V have not significant presence in the samples. Among these, Cu and Fe were selected due to their relevance and importance in oxidative process of biodiesel, to the development of an analytical methodology to be used in the determination by Electrothermal Atomic Absorption Spectrometry, and also evaluate the effect of these metals over the oxidative stability of the soy biodiesel. The samples were prepared with tetramethylammonium hydroxide (TMAH), and the pyrolysis and atomization temperatures were optimized pyrolysis and atomization curves. The high pyrolysis temperature adopted, 1000 oC, certainly minimized potential interferences, but calibration had to be carried out with aqueous standard solutions in the presence of the TMAH. The detection limits in the sample (3s, n=10), were quite low 15 ng g-1 and 24 ng g-1 for Cu and Fe, respectively. Seven biodiesel samples, produced from different raw materials, including vegetable seed, waste frying oil and animal fat were analyzed. Accuracy was validated by applying the recovery test (recoveries from 105% to 120%) and through comparison with the obtained results by High Resolution Continuum Source Electrothermal Atomic Absorption Spectrometry. The precision, expressed by the relative standard deviation, was better than 3% for Cu and than 7% for Fe. Copper could be quantified in two and Fe in three of the seven samples. The biodiesel sample from fodder turnip was especially rich in the analytes in comparison to the other samples. The influence of metals Cu and Fe on soy biodiesel oxidative stability was evaluated by Rancimat method through induction period, according with the Standard EN 14112. The metals Cu2+ and Fe3+ were added to the biodiesel samples in the form of theirs salts, and different storage times of the samples were evaluated. Due to the catalytic behaviour of these metals, the oxidative stability of the samples was affected, even under low metal concentrations. Compared to Cu2+, the effect over the biodiesel stability was higher when Fe3+ was added.
A presença de metais no biodiesel está diretamente relacionada com a matéria-prima utilizada e também com o processo utilizado para a obtenção do biodiesel. Neste trabalho realizou-se uma avaliação dos principais metais presentes em amostras de biodiesel provenientes de diferentes fontes. A análise semi-quantitativa nas amostras de biodiesel foi realizada utilizando a técnica de Espectrometria de Massa com Plasma Indutivamente Acoplado após a digestão das amostras em micro-ondas. Os principais metais identificados nas amostras de biodiesel analisadas são Al, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sr e Zn. Metais como Ag, As, Ba, Cd, Co, Tl e V não estão presentes em concentrações significativas nessas amostras. Em função de sua relevância e importância em processos oxidativos do biodiesel, selecionou-se Cu e Fe para o desenvolvimento de uma metodologia analítica para a determinação destes por Espectrometria de Absorção Atômica com Atomização Eletrotérmica e também a avaliação do efeito destes metais sobre a estabilidade oxidativa do biodiesel de soja. As amostras foram preparadas com hidróxido de tetrametilamônio (TMAH), e as temperaturas de pirólise e atomização foram otimizadas através de curvas de pirólise e atomização. A alta temperatura de pirólise adotada, 1000 oC, certamente ajudou a minimizar possíveis interferências; porém, a calibração teve de ser realizada com padrões aquosos na presença de TMAH. Os limites de detecção (3s, n = 10), na amostra, foram baixos, 15 ng g-1 e 24 ng g-1 para Cu e Fe, respectivamente. Sete amostras de biodiesel, produzidas de diferentes matérias-primas, incluindo óleos vegetais, óleo de fritura e gordura animal foram analisadas. A exatidão foi avaliada através do teste de recuperação (recuperações de 105% a 120%) e através da comparação com os resultados obtidos por Espectrometria de Absorção Atômica de Alta Resolução com Fonte Contínua e Atomização Eletrotérmica. A precisão, expressa pelo desvio padrão relativo foi melhor que 3% para Cu e que 7% para Fe. Cobre pôde ser quantificado em duas e Fe em três das sete amostras. A amostra de biodiesel proveniente do nabo forrageiro era especialmente rica nos analitos comparada às outras amostras. A influência dos metais Cu e Fe sobre a estabilidade oxidativa do biodiesel de soja foi avaliada pelo método Rancimat através do período de indução, de acordo com a Norma EN 14112. Os metais Cu2+ e Fe3+ foram adicionados nas amostras de biodiesel na forma de seus sais, e foram avaliados diferentes tempos de armazenamento das amostras. Devido ao efeito catalítico destes metais, a estabilidade oxidativa das amostras analisadas foi reduzida mesmo na presença de baixas concentrações dos metais. O efeito do Fe3+ sobre a estabilidade do biodiesel foi significativamente maior quando comparado ao Cu2+.
43
Niklasson, Lovisa. "Characterization of the gas composition inside NiMH batteries during charge using GC-MS." Thesis, Uppsala universitet, Oorganisk kemi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-347525.
Full textAbstract:
The aim of the project was to develop a method to measure and studythe degree of activation of the negative electrode (MH) in a NiMH battery.This was done by characterization of the gases produced during charge of a battery – O2 and H2 – using a Gas Chromatograph. The current applied in the very first charge of the battery was varied in order to examine how this affects the gas evolution. In the developed method, batteries were charged to 8Ah with 9A, after which a gas sample was taken and analyzed with Gas Chromatography. An additional goal was to use the method to examine the difference in activation between virgin and recycled negative electrode material. A module charged stepwise with 0.07C followed by 0.2C had the lowest share of H2 after two cycles, indicated best activation. However, a higher amount of H2 in the beginning of the activation process could possibly enhance the degree of activation during the following cycles. The method indicated that the module with recycled MH was better activated than the virgin MH. To improve the technique, repeated measurements to get better statistics should be done. Gas samples should be taken at dV/dt=0 in order to take samples at same SoC. The charge current should be adjusted so that the same C rate is always used. This would make the results easier to interpret.
44
Baqué, David. "Perturbations anthropiques du réseau hydrographique du Bassin de la Garonne, cas des métaux et des nitrates." Toulouse 3, 2006. https://tel.archives-ouvertes.fr/tel-00128208.
Full textAbstract:
52000 km2 au Mas d’Agenais), fait l’objet de pressions anthropiques liées aux activités humaines agricoles, domestiques et industrielles. Le prélèvement des eaux de la Garonne et de ces principaux affluents sur une année hydrologique a permis de détecter des enrichissements significatifs pour un grand nombre d’éléments en trace métalliques (ETM : Pb, Cr, Ni, Cu, Zn…). Il s’avère que la plus part de ces éléments métalliques en quantité de trace (ppb) sont éventuellement transportés sous forme particulaire par les rivières. De nombreux arguments vont dans le sens d’une source majeure diffuse de pollution à l’origine de ces enrichissements : les pluies. Toutefois, certains enrichissements spécifiques liés à des activités industrielles locales sont observées (cas du Cr sur l’Agout). Les bilans des flux [entrée (pluies), sortie (exutoire)] ont mis en évidence le stockage de certains métaux, vraisemblablement dans les sols et les sédiments du lit de la Garonne. Le suivi des flux d’éléments dissous majeurs (NO3-, Cl-, SO42-, Mg2+, Ca2+, K+, Na+) et plus spécialement des nitrates, en période de basses eaux estivales (50 m3/s), dans les eaux d’un tronçon de Garonne Toulousaine, a permis la caractérisation et la quantification des apports anthropiques spécifiques en NO3-, Cl-, K+ et Na+ liés à cette agglomération. Certains de ces éléments, nitrates et potassium, sont partiellement éliminés tout au long de ce tronçon. Cette consommation peut être attribuée à l’activité biologique qui se développe dans le lit de la Garonne (développement du biofilm) dans ces périodes critiques où les eaux sont plus anoxiques (moins oxygénées). L’étude plus spécifique du devenir des nitrates dans une zone humide riveraine de la Garonne (site de Monbéqui) a mis en exergue les capacités de ces sites à éliminer ce composé azoté. .The Garonne’s basin, the second largest French basin (52000 km2 at Mas d’Agenais), is subject to anthropogenic pressures dues to agricultural, domestics and industrials humans activities. A one-year hydrological sampling of the Garonne’s and if its tributary’s water highlights significant enrichments for a large type of trace metal elements (TME : Pb, Cr, Ni, Cu, Zn…). It appears that most of those metals elements in trace quantity (ppb) have a particular transport in the river. Many arguments speaking in favour for a one major diffuse source pollution origin of those enrichments: the rains. However, some specific enrichments due to local industrial activities are observed (case of Cr in the Agout). The balance flux [enter : rains), out : the outlet of the catchment basin] show a storage of some metals, probably in soil and in the river bed sediments. The follow-up of majors flux elements (NO3-, Cl-, SO42-, Mg2+, Ca2+, K+, Na+) and especially of nitrate, in a Garonne stretch upstream to downstream of the Toulouse urban area was performed at a summer low water level period. The anthropic contribution to the river water composition from the urban area was estimated and indicated that NO3-, Cl-, K+ and Na+ represent the most important contributions of the anthropic inputs. Some of those elements, nitrates and potassium, are partially eliminated along this stretch. This looses may be attributed to biological activity (grow of biofilms) that appears in the Garonne river bed, especially in this critical period of anoxic water conditions (less oxygen). .
45
"Synthesis of transition metal oxides and hydroxides by soft-chemistry routes." 2009. http://library.cuhk.edu.hk/record=b5894090.
Full textAbstract:
Chan, Mui.Thesis (M.Phil.)--Chinese University of Hong Kong, 2009.
Includes bibliographical references.
Abstract also in Chinese.
Abstract --- p.i
Abstract (Chinese) --- p.iii
Declaration --- p.v
Acknowledgement --- p.vi
Table of Contents --- p.viii
List of Tables --- p.xiv
List of Figures --- p.xv
Chapter Chapter 1: --- Introduction
Chapter 1.1 --- Overview --- p.1
Chapter 1.2 --- Soft-Chemistry --- p.7
Chapter 1.2.1 --- Sol-Gel Method --- p.7
Chapter 1.2.2 --- Co-precipitation --- p.9
Chapter 1.2.3 --- Microemulsion --- p.10
Chapter 1.3 --- Application of Hydrothermal/Solvothermal Methods in Materials Synthesis --- p.12
Chapter 1.3.1 --- Fundamentals of Hydrothermal and Solvothermal Methods --- p.12
Chapter 1.3.2 --- Advantages of Hydrothermal/Solvothermal Methods in contrast to Conventional Synthetic Approaches --- p.13
Chapter 1.3.3 --- Hydrothermal and Solvothermal Preparation of Materials --- p.14
Chapter 1.4 --- Application of Transition Metal Oxides As Functional Materials --- p.15
Chapter 1.5 --- Aim and Scope of Work --- p.16
Chapter 1.6 --- References --- p.17
Chapter Chapter 2: --- Solvothermal and Hydrothermal Template Free Synthesis of ZnO Microspheres
Chapter 2.1 --- Introduction --- p.23
Chapter 2.2 --- Experimental Section --- p.25
Chapter 2.2.1 --- Synthesis of ZnO Microspheres by Solvothermal Method --- p.25
Chapter 2.2.2 --- Synthesis of ZnO Microspheres by Hydrothermal Method --- p.26
Chapter 2.2.3 --- Doping ZnO Microspheres with Silver or Gallium by Solvothermal Method --- p.26
Chapter 2.2.4 --- Characterization --- p.27
Chapter 2.2.5 --- Measurement of Photocatalytic Activity --- p.29
Chapter 2.3 --- Results and Discussion --- p.30
Chapter 2.3.1 --- X-Ray Diffraction Analysis --- p.30
Chapter 2.3.1.1 --- ZnO-HT and ZnO-ST --- p.30
Chapter 2.3.1.2 --- ZnO-ST: Effect of Different Concentrations of Zinc Acetate --- p.33
Chapter 2.3.1.3 --- Doping ZnO-ST with Silver or Gallium --- p.34
Chapter 2.3.2 --- SEM study --- p.36
Chapter 2.3.2.1 --- ZnO-HT and ZnO-ST --- p.36
Chapter 2.3.2.2 --- ZnO-HT-Different Volume Ratios of Ethylene Glycol to Water --- p.37
Chapter 2.3.2.3 --- ZnO-ST --- p.39
Chapter 2.3.2.3.1 --- Different Volume Ratios of Benzyl Alcohol to Ethylene Glycol --- p.40
Chapter 2.3.2.3.2 --- Different Concentrations of Zinc Acetate --- p.41
Chapter 2.3.2.3.3 --- Different Concentrations of Urea --- p.42
Chapter 2.3.3 --- TEM Study --- p.44
Chapter 2.3.3.1 --- TEM and HRTEM of ZnO-HT --- p.44
Chapter 2.3.3.2 --- TEM and HRTEM of ZnO-ST --- p.45
Chapter 2.3.3.3 --- TEM Images of Ga-Doped ZnO-ST --- p.47
Chapter 2.3.3.4 --- TEM Images of Ag-Doped ZnO-ST --- p.49
Chapter 2.3.4 --- Nitrogen Adsorption and Desorption --- p.50
Chapter 2.3.5 --- X-Ray Photoelectron Spectroscopy --- p.52
Chapter 2.3.5.1 --- XPS Study of ZnO-ST --- p.52
Chapter 2.3.5.2 --- XPS Study of ZnO-HT --- p.54
Chapter 2.3.5.3 --- XPS Study of Silver Doped ZnO-ST --- p.56
Chapter 2.3.5.4 --- XPS Study of Gallium Doped ZnO-ST --- p.58
Chapter 2.3.6 --- FR-IR Spectra --- p.60
Chapter 2.3.7 --- Photocatalytic Activity on Degradation of Methylene Blue --- p.61
Chapter 2.3.8 --- Proposed Formation Mechanism for ZnO-ST --- p.64
Chapter 2.3.9 --- Proposed Formation Mechanism for ZnO-HT --- p.68
Chapter 2.3.10 --- Optical Property of ZnO Microspheres --- p.69
Chapter 2.4 --- Conclusion --- p.73
Chapter 2.5 --- References --- p.74
Chapter Chapter 3: --- Synthesis of Hierarchical Porous Lithium Niobate Submicrometer Rods
Chapter 3.1 --- Introduction --- p.79
Chapter 3.2 --- Experimental Section --- p.81
Chapter 3.2.1 --- Characterization --- p.82
Chapter 3.3 --- Results and Discussion --- p.83
Chapter 3.3.1 --- X-Ray Diffraction Analysis --- p.83
Chapter 3.3.2 --- SEM Study --- p.86
Chapter 3.3.2.1 --- Surfactants Dependent Morphologies Change --- p.86
Chapter 3.3.2.2 --- Concentrations of CTAB --- p.87
Chapter 3.3.2.3 --- Time Dependent Morphologies Change --- p.88
Chapter 3.3.3 --- TEM Study --- p.91
Chapter 3.3.5 --- XPS Analysis --- p.93
Chapter 3.3.6 --- BET Analysis --- p.96
Chapter 3.3.7 --- Proposed Formation Mechanism --- p.97
Chapter 3.3.7.1 --- Effect of Microemulsion --- p.97
Chapter 3.3.7.2 --- Effect of CTAB --- p.98
Chapter 3.3.7.3 --- Ostwald Ripening --- p.99
Chapter 3.3.7.4 --- Formation of LiNi3O8 --- p.101
Chapter 3.4 --- Conclusion --- p.102
Chapter 3.5 --- References --- p.103
Chapter Chapter 4: --- Flower-Like α-Nickel Hydroxide synthesized by hydrothermal method
Chapter 4.1 --- Introduction --- p.106
Chapter 4.2 --- Experimental Section --- p.108
Chapter 4.2.1 --- Synthesis of Nickel Hydroxide by Hydrothermal Method --- p.108
Chapter 4.2.2 --- Characterization --- p.109
Chapter 4.3 --- Results and Discussion --- p.111
Chapter 4.3.1 --- X-Ray Diffraction Analysis --- p.111
Chapter 4.3.2 --- SEM Study --- p.115
Chapter 4.3.3 --- TEM and HRTEM Study --- p.116
Chapter 4.3.4 --- XPS Analysis --- p.117
Chapter 4.3.5 --- FT-IR Analysis --- p.119
Chapter 4.3.6 --- BET analysis --- p.120
Chapter 4.3.7 --- Proposed Formation Mechanism of the Flower like α-Ni(OH)2 --- p.122
Chapter 4.4 --- Conclusion --- p.123
Chapter 4.5 --- References --- p.124
Chapter Chapter 5: --- Conclusions and Future Work
Chapter 5.1 --- Conclusions --- p.127
Chapter 5.2 --- Future work --- p.129
46
Momodu, Damilola Y. "Investigation of metal hydroxides graphene composites as electrode materials for supercapacitor applications." Thesis, 2015. http://hdl.handle.net/2263/50281.
Full textAbstract:
The aim and objectives of this work are to optimize the synthesis of metal hydroxides - graphene foam (GF) composites using different configurations of graphene with a facile and environmentally friendly solvothermal technique for energy storage applications. The evaluation of the morphological, structural, surface area and compositional properties of the composites were carried out with the techniques such as field emission-electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Raman spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy. The results show the existence of interlaced sheets of metal-hydroxides-graphene composites with sufficient surface area necessary for efficient charge storage. The main reason for incorporating graphene foam (GF) into these metal hydroxides in this study was due to its unique mechanical properties, good conductivity and large surface area which offer the possibility for an enhanced deposition/adsorption of the active metal hydroxides both in-situ and as a supporting template for practical applications. The electrochemical properties of the synthesized composite electrodes modified with different graphene foam nanostructures were thus explicated in a 3-electrode system (with Ag/AgCl as reference electrode)and they all showed excellent electrochemical performance. The overall results clearly demonstrated an excellent potential of graphene based composite electrode materials for energy storage applications.Thesis (PhD)--University of Pretoria, 2015.
tm2015
Physics
PhD
Unrestricted
47
De, Kock Luéta-Ann. "Hybrid ion exchanger supported metal hydroxides for the removal of phosphate from wastewater." Thesis, 2015. http://hdl.handle.net/10210/15093.
Full textAbstract:
Ph.D. (Chemistry)Phosphorus in the form of phosphate needs to be removed from the aqueous environment as it is primarily responsible for eutrophication of water bodies. In an attempt to limit the discharged of phosphorus into the aqueous environment, the phosphate discharge limits for wastewater treatment plants have been decreased. These limits are not easily or economically met by current phosphorus removal technologies. In addition phosphorus is a non-renewable resource. To ensure the ongoing quality of water bodies and security of food production it is vital that phosphate in water be removed and recovered. In order to address these issues, novel hybrid metal oxide ion exchange resins based on Fe(III), Cu(II), Mn(IV and Ti(IV) oxides have been prepared and their phosphate adsorption characteristics determined.
48
Hung, Sheng-Hsiung, and 洪聖雄. "Electronic and magnetic structure of layered metal hydroxides and topological phase transition in Lanthanide hexaborides." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/09929950747803671869.
Full textAbstract:
碩士國立清華大學
物理系
103
We use VASP code which is based on density functional and plane wave method to study the electronic structure of layered metal hydroxides, and topological phase transition of Lanthanide hexaborides. Some of layered metal hydroxides have antiferromagnetic insulator band structures. Lanthanide hexaborides have wide physics properties, such as Kondo effect or strong correlated f electrons. We try to find the most stable spin structure of Cobalt hydroxides and Iron hydroxides and topological phase transition of Lanthanide hexaborides with Hubbard +U parameters.
49
Wu, Tzu Ho, and 吳子和. "Optimising cell voltage and understanding charge storage mechanism of transition metal oxides and hydroxides for aqueous supercapacitors." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/ggds6x.
Full textAbstract:
博士國立清華大學
化學工程學系
104
This study focuses on aqueous electrochemical capacitors (ECs) for optimising the cell voltage and understanding the charge storage mechanism of transition metal oxides and hydroxides. The first part discusses how to optimise cell voltage of symmetric and asymmetric ECs. In Chapter 4, a commercial activated carbon (ACS–679) was employed as an electroactive material to demonstrate the necessity of charge–balanced condition of aqueous symmetric ECs in order to improve the utilisation of electrochemically stable potential window of electroactive material. Besides, the effect of stable open–circuit potential on electroactive materials is also addressed here. The concept is on the basis of electrochemical charge–balance principle, therefore, it is believed to be applicable to all the symmetric ECs no matter what kind of material is used as electroactive material. The charge–balanced electric double–layer capacitors (EDLCs) was assembled to evaluate the acceptable cell voltage by means of electrochemical analyses, including cyclic voltammogram, constant current charge–discharge, electrochemical impedance spectroscopy and inductance–capacitance–resistance meter measurements. Moreover, charge–unbalanced EDLCs were used to demonstrate the necessity of charge balance in symmetric ECs since those exhibit lower cell voltage and specific energy compared with the charge–balanced case. Similarly, in Chapter 5, asymmetric ECs consisting of reduce graphene oxide and manganese oxide (RGO//MnOx) were employed as an example to establish criteria for determining the highest acceptable cell voltage of asymmetric ECs with excellent reversibility and capacitor−like behaviour. It is very useful to evaluate the practical specific energy of asymmetric ECs by understanding the highest acceptable cell voltage. Besides, RGO//RuO2 was also demonstrated to verify the validity of the proposed criteria. The second part probes the charge storage mechanism of transition metal oxides and hydroxides in aqueous ECs. In Chapter 6, a wide–ranging study on electrochemical activation from Mn3O4 to MnO2 in 0.5 M Na2SO4 medium were presented, which includes in operando monitoring of the structural evolution during the activation process via in situ Raman microscopy. Other advanced material characterisation techniques, such as powder X–ray diffraction, X–ray photoelectron spectroscopy, scanning electron and transmission electron microscopy, were also applied to analyse the as–prepared and activated MnOx. Due to the structural disordering of electrochemically activated birnessite−MnO2 and residual Mn3O4, the charge storage is attributable to the redox reaction between Mn(III) and Mn(IV) at outer surface active sites, rather than cations and/or protons intercalation into layer structures. In Chapter 7, the redox behaviours of γ−NiOOH/α−Ni(OH)2 in various electrolytes (LiOH, NaOH, KOH, CsOH and NH4OH) are discussed. The charge storage mechanism of γ−NiOOH/α−Ni(OH)2 was studied by means of EQCM and in situ Raman microscopy. Moreover, the computational simulation (DFT+U) based on EQCM results gives a better idea on the compositional changes in the first few potential cycles. The insertion/removal of Li+ does not alter the content of water inside the structure, while the insertion of Na+ and K+ leads to a significant removal of water. The removed water molecules cannot be reversibly re−inserted back into the nickel structure, leading to the loss of water molecules in Ni(OH)2 structure during charge–discharge process. The capability to retain water molecules inside the Ni(OH)2 is crucial for the stability of γ−NiOOH/α−Ni(OH)2 redox reaction.
50
Pineda, Cedeno Leslie William. "Germanium-, Tin-, Lead-, and Bismuth-Containing β-Diketiminato Complexes for the Synthesis and Structural Characterization of Hydroxide, Carboxylic Acid, Heterobimetallic Oxide, Transition Metal-Main Group, Hydride and Halide Compounds." Doctoral thesis, 2006. http://hdl.handle.net/11858/00-1735-0000-0006-B0D1-0.
Full text