91 |
Synthèse du LiXFePO4 par voie fondue et l’étude de la couche de carbone sur LiFePO4Dahéron, Benjamin 03 1900 (has links)
Le LiFePO4 est un matériau prometteur pour les cathodes des batteries au lithium. Il possède une bonne stabilité à haute température et les précurseurs utilisés pour la synthèse sont peu couteux. Malheureusement, sa faible conductivité nuit aux performances électrochimiques. Le fait de diminuer la taille des particules ou d’enrober les particules d’une couche de carbone permet d’augmenter la conductivité. Nous avons utilisé une nouvelle méthode appelée « synthèse par voie fondue » pour synthétiser le LiFePO4. Cette synthèse donne des gros cristaux et aucune impureté n’est détectée par analyse Rayon-X. En revanche, la synthèse de LiXFePO4 donne un mélange de LiFePO4 pur et d’impureté à base de lithium ou de fer selon l’excès de fer ou de lithium utilisé. La taille des particules de LiFePO4 est réduite à l’aide d’un broyeur planétaire et plusieurs paramètres de broyage sont étudiés. Une couche de carbone est ensuite déposée sur la surface des particules broyées par un traitement thermique sur le LiFePO4 avec du -lactose. L’influence de plusieurs paramètres comme la température du traitement thermique ou la durée du chauffage sont étudiés. Ces expériences sont réalisées avec un appareil d’analyse thermogravimétrique (ATG) qui donne la quantité de chaleur ainsi que la variation de masse durant le chauffage de l’échantillon. Ce nouveau chauffage pour la couche de carbone donne des échantillons dont les performances électrochimiques sont similaires à celles obtenues précédemment avec la méthode de chauffage pour la couche de carbone utilisant le four tubulaire. / LiFePO4 is a promising cathode material for Lithium-ion batteries. It
provides high thermal stability and is synthesized using low cost materials.
Unfortunately LiFePO4 suffers from a low electrical conductivity, which is harmful
to its electrochemical performance. Decreasing the particle size or coating the
particles with carbon increases the conductivity of the material. We have used a
new synthetic method called molten synthesis to synthesize LiFePO4. The molten
synthesis produces large crystals of LiFePO4 with no impurity detected via X-ray
diffraction analysis. Moreover, the synthesis of LiXFePO4 gives a mixture of pure
LiFePO4 and Li-based impurities or LiFePO4 and Fe-based impurities whenever
there is an excess of lithium or iron used. The particle size of the synthesized
material is reduced via a Planetary Mill and numerous milling parameters were
investigated. A carbon coating was then deposited on the surface of the milled
material by thermally treating LiFePO4 with β-lactose. The influences of several
parameters such as heat treatment temperature and/or heating duration were
studied. These experiments were performed using a thermogravimetric analysis
(TGA), which provides the amount of heat and weight change during the heating
of the sample. This new heating method for carbon coating gave rise to samples
with similar electrochemical performance data as to the previously established
heating method involving a tubular furnace.
|
92 |
Synthesis and characterisation of metal (Fe, Ga, Y) doped alumina and gallium oxide nanostructuresZhao, Yanyan January 2008 (has links)
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.
|
93 |
Contribution to the study of formation mechanisms of condensable by-products from torrefaction of various biomasses / Contribution à l’étude de mécanismes de formation des espèces condensables lors de la torréfaction de biomasses variéesRodriguez Alonso, Elvira 03 December 2015 (has links)
L’objectif des travaux est de mieux comprendre durant la torréfaction de différentes biomasses l’évolution chimique à la fois des phases solide et gaz. Des expériences de torréfaction ont été menées selon un profil de température dynamique entre 200 et 300°C, sous atmosphère inerte, sur du pin, du frêne, du miscanthus et de la paille de blé. La perte de masse et la formation des espèces condensables ont été analysées par ATG-GCMS, et l’évolution chimique de la phase solide par RMN du solide 13C CP/MAS. Trente espèces condensables ont été détectées ; la moitié a été formée dans l’ensemble de la gamme de température explorée et un tiers l’a été par toutes les biomasses. Les principaux phénomènes qui semblent associés à la dégradation du solide sont la décristallisation de la cellulose, une sévère dégradation de l’hémicellulose, la dévolatilisation des groupes acétyles, la conservation des groupes méthoxys et la formation d’un résidu solide. Il a été par ailleurs montré que perte de masse et évolution chimique du solide n’étaient pas directement corrélées pour différentes biomasses. A partir de ces résultats expérimentaux, un modèle conceptuel a été développé pour décrire la dégradation de la biomasse. Trente réactions ont été associées aux trois constituants macromoléculaires principaux que sont la cellulose, l’hémicellulose et la lignine, respectivement représentées par deux sucres en C5 et C6 et par trois unités detype H, G et S. Ce modèle présente l’originalité de s’appuyer sur une description détaillée de ces deux derniers constituants et de prévoir la formation de seize espèces condensables, cinq gaz permanents et six formes de char solide, grâce à des réactions ayant un sens chimique et équilibrées d’un point de vue stoechiométrique. / The objective of the present work is to better understand chemical evolution of both solid and gaseous phases during torrefaction of various biomasses. Torrefaction experiments were carried out with a dynamic profile of temperatures between 200 and 300°C, under inert atmosphere, for pine, ash-wood, miscanthus and wheat straw. Mass loss and formation of condensable species were analyzed by TGA-GC-MS, and chemical evolution of solid phase was characterized by 13C CP/MAS solid-state NMR. Thirty condensable species could be detected; a half of these species were formed during the whole temperature range, and a third were formed by all biomass types. The main phenomena that occurred in solid phase were found to be decrystallization of cellulose, severe degradation of hemicellulose, devolatilization of acetyl groups, conservation of methoxyl groups and charring. It was also found that mass loss and chemical evolution of solid were not directly correlated for different biomasses. Based on the experimental results, a conceptual model was developed to describe biomass degradation duringtorrefaction. Thirty reactions were determined for the three major macromolecular constituents, namely cellulose, hemicellulose – represented by C5 and C6 sugars – and lignin – represented by H, G and S units. The main innovations of this model are in thedetailed approach of hemicellulose and lignin compositions, as well as in the prediction of sixteen condensable and five permanent species, and six forms of solid char, through chemically meaningful and stoichiometrically valid reactions.
|
94 |
Síntese e caracterização de fósforos a base de silicatos de cálcio e magnésio dopados com európio e disprósio / Synthesis and characterization of phosphors based on calcium and magnesium silicates doped with europium and dysprosiumMISSO, AGATHA M. 25 May 2017 (has links)
Submitted by Marco Antonio Oliveira da Silva (maosilva@ipen.br) on 2017-05-25T17:33:34Z
No. of bitstreams: 0 / Made available in DSpace on 2017-05-25T17:33:34Z (GMT). No. of bitstreams: 0 / Fósforos a base de silicatos de Ca e Mg foram preparados pelo método sol-gel combinado com o processo de sais fundidos. O gel de sílica foi obtido a partir da solução de Na2SiO3 usando soluções de cloretos de európio, disprósio, cálcio e magnésio. Assim, estes cloretos foram homogeneamente distribuídos no gel. O gel obtido foi seco e tratado termicamente a 900°C por 1h para permitir a fusão dos sais presentes. Em seguida o material foi lavado com água até teste negativo para íons Cl- e seco em estufa a 80°C. A redução do európio para Eu2+ foi realizada em um forno sob atmosfera de 5% de H2 e 95% de Ar a 900°C por 3h para obter os fósforos de CaMgSi2O6:Eu2+ e CaMgSi2O6:Eu2+:Dy3+. Nos difratogramas de DRX das amostras, a diopsita foi identificada como fase cristalina principal e quartzo, como a secundária. Micrografias obtidas por MEV (microscopia eletrônica de varredura), das amostras, mostraram morfologia acicular, esférica, folhas e bastonetes das partículas e dos aglomerados . Curva de análise térmica (TGA-DTGA) revelou que a temperatura de cristalização do CaMgSi2O6:Eu2+ é próxima de 765°C. Estudos de espectroscopia de fotoluminescência foram baseados nas transições interconfiguracionais 4fN → 4fN-1 5d do íon Eu2+. O espectro de excitação apresentou banda larga relativa à transição de transferência de carga ligante metal (LMCT) O2- (2p) → Eu3+ na região de 250 nm e bandas finas oriundas das transições 4f → 4f do íon Eu3+ , mostrando a transição 7F0 → 5L6 em 393 nm quando a emissão é monitorada em 583,5 nm. E o espectro de emissão com excitação monitorada em 393 nm apresentou picos finos entre 570 e 750 nm característicos das transições 5D0 → 7 FJ (J = 0 - 5) do íon Eu3+ , indicando que o íon Eu3+ se encontra em um sítio com centro de inversão. Os resultados obtidos indicam que o método desenvolvido é viável na síntese de fóforos, CaMgSi2O6:Eu2+ e CaMgSi2O6:Eu2+:Dy3+ como foi proposto. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
|
95 |
Magnétisme coopératif dans des composés de coordination à base de Cu(II), Ni(II) et Co(II) et ligands imidazole carboxyliques / Cooperative magnetism in coordination compounds based on Cu(II), Ni(II) and Co(II) and imidazole carboxylic ligands / Magnetismo cooperativo en compuestos de coordinación basados en Cu(II), Ni(II) y Co(II) con ligandos imidazol carboxílicosArrué-Muñoz, Ramón 09 December 2014 (has links)
La présente thèse traite de la synthèse à température ambiante et pression atmosphérique de différents composés de coordination hybrides organique-inorganiques. La partie inorganique de ces composés est constituée d’éléments de transition de la première période 3dn divalents: cobalt, nickel et cuivre. Les ligands utilisés constituent la partie organique de ces composés. Les ligands employés sont l’acide-1H-imidazol-4-carboxilique (H2IMC) et l’acide-1H-imidazol-4,5-dicarboxílique (H3IMDC). La composante inorganique Mx+ est introduite dans le composé terminal en utilisant le précurseur métallique moléculaire M(hfac)2 (M = Cu2+, Co2+, Ni2+; hfac = 1,1,1,5,5,5- hexafluoro-2,4-pentanodione), précurseur utilisé afin d'obtenir un centre métallique acide facile à coordonner aux ligands imidazol carboxíliques dans des positions axiales. L’ensemble des composés a été caractérisé par l’étude des propriétés magnétiques, études thermogravimétriques et caractérisation structurale (résolution et affinement) sur échantillons pulvérulents. Dans la totalité des structures obtenues, le ligand imidazol carboxylique se lie à l’espèce métallique en positions équatoriales via l’élément azote du cycle et un élément oxygène du groupement carboxylique. Les mesures magnétiques montrent des déviations à la loi de Curie à basse température qui indiquent des phénomènes de coopération magnétique entre les centres métalliques. Ces centres métalliques ont été traités et modélisés en considérant, pour les composés contenant les éléments cuivre et nickel, un modèle de chaîne régulière qui a permis d’estimer la constante d’interéchange J. Pour les composés contenant l’élément cobalt, seule l’importante contribution orbitale (L≠ 0) à la propriété magnétique (état fontamental 4T1g en symétrie octaédrique) sans interaction inter espèces magnétiques a été prise en considération pour traiter les données. / This thesis work presents the synthesis at ambient temperature and pressure of different hybrids organic - inorganic coordination compounds. The inorganic portion is composed by transition elements from the first period 3dn divalent cobalt, nickel and copper. The selected ligands are the organic portion of these compounds, and there are the 1H-imidazol-4-carboxylic acid (H2IMC) and 1H-imidazole-4,5-dicarboxylic acid (H3IMDC)2. The inorganic component Mx+ is introduced into the terminal compound by using the molecular metallic precursor M(hfac)2 (M=Cu2+, Co2+, Ni2+; hfac=1,1,1,5,5,5-hexafluoro-2,4-pentanodione) used to obtain an acidic metal center that coordinates easily to imidazol carboxylic ligands in axial positions. All compounds were characterized by studying their magnetic properties, thermogravimetric analysis and structural characterization (resolution and refinement) on powdered samples. In all these compounds, the imidazole carboxylic ligand is linked to the central metal ion in equatorial position, by the nitrogen atom from the imidazole ring, and an oxygen atom from the carboxylic group. The magnetic measurements have revealed deviations at low temperatures to the Curie law, suggesting magnetic cooperation phenomena between the metallic centers. For the copper and nickel based compounds, the magnetic data was analyzed considering a regular chain model that has led to obtain the value of the exchange coupling constant J. For the cobalt based compounds the treatment has been different. Only the important orbital contribution (L≠ 0) to the magnetic propierties (fundamental state 4T1g for octahedral symmetry) without interaction between the metallic centers was taken into account for the data treatment. / La presente tesis trata de la síntesis a temperatura ambiente y presión atmosférica de diferentes compuestos de coordinación híbridos órgano-inorgánicos. La parte inorgánica de estos compuestos está constituida por los elementos de transición divalentes del primer período 3dn: cobalto, níquel y cobre. Los ligandos utilizados constituyen la parte orgánica de estos compuestos. Los ligandos empleados son el ácido-1H-imidazol-4-carboxílico (H2IMC) y el ácido-1H-imidazol-4,5-dicarboxílico (H3IMDC). La componente inorgánica Mx+ ha sido introducida en los compuestos terminales utilizando el precursor metálico molecular M(hfac)2 (M = Cu2+, Co2+, Ni2+; hfac = 1,1,1,5,5,5-hexafluoro-2,4-pentanodiona), precursor utilizado con el fin de obtener un centro metálico ácido fácil de ser coordinado por los ligandos imidazol carboxílicos en las posiciones axiales. El conjunto de los compuestos obtenidos ha sido caracterizado mediante el estudio de sus propiedades magnéticas, análisis termogravimétrico y caracterización estructural (resolución y afinamiento) sobre muestras pulverizadas. En la totalidad de la estructuras obtenidas, el ligando imidazol carboxílico se une al metal en posiciones ecuatoriales a través del átomo de nitrógeno del anillo imidazol y un átomo de oxígeno del grupo carboxílico. Las medidas magnéticas muestran desviaciones de la ley de Curie a baja temperatura que indican fenómenos de cooperación magnética entre los centros metálicos. Estos centros metálicos han sido tratados y modelados considerando para los compuestos de cobre y níquel, un modelo de cadena regular que ha permitido estimar el valor de la constante de intercambio J. Para los compuestos de cobalto, se ha considerado la importante contribución orbital (L≠ 0) a la propiedad magnética (estado fundamental 4T1g en simetría octaédrica) sin interacción entre las especies magnéticas para el tratamiento de los datos.
|
96 |
Vliv aplikace lignitu na distribuci organického uhlíku v půdě / Influence of the Application of Lignite on the Distribution of Organic Carbon in SoilŠirůček, David January 2019 (has links)
This diploma thesis is focused on optimization of sequential chemical fractionation method to humeomics in order to be useful for determination of organic matter content and distribution and also organic elements in soil. Subsequently, the optimized method is used to assess the efect of lignite application as soil support on these soil characteristics. For these purposes, there were three source matrices of organic matter (lignite, soil and annual soil extraction after lignite application) fractionated by sequential chemical analysis. In parallel, these samples were also fractionated by classic alkaline extraction to obtain the so-called extractable fraction of organic matter (NOM). Individual fractions from sequential chemical fractionation as well as NOM samples were characterized by methods of elemental analysis (determination of organic elements), thermogravimetry (contents of ash, organic matter and moisture) and FTIR spektrometry (structural analysis). The results obtained from a large range of data from all humeomics fractions and NOM fractions showed that the method of sequential chemical fractionation gives higher yields of organic matter compared to classic alkaline extraction. Another indisputable advantage is the fact that the obtained fractions divided according to solubility and strenght of binding to soil inorganics can be better characterized by physical-chemical methods, which provides more detailed information about soil organic matter. The results of the work also show that in order for lignite as a support substance to significantly affect soil properties, a longer time, multiple sampling and repetition of individual fractionations would be needed.
|
97 |
Biologischer Abbau organischer Substanz bei unterschiedlichem Wassergehalt in einem ModellversuchBirth, Volker 11 June 2019 (has links)
In der Landnutzung stellt die Bewertung der Versorgung mit organischer Bodensubstanz (OBS) eine besondere Herausforderung dar. Dabei wird der Einfluss der Bodenfeuchte aufgrund des globalen Klimawandels an Bedeutung gewinnen, da die Wasserverfügbarkeit Einfluss auf die Aktivität der bodenlebenden Mikroorganismen nimmt. Ziel der Arbeit waren daher Aussagen, inwieweit verschiedene Wassergehalte den biologischen Umsatz bei der Inkubation von Bodenproben mit unterschiedlicher Herkunft sowie organischer Düngung beeinflussen. In einem Modellversuch wurden Bodenproben ungedüngter Parzellen von drei deutschen Dauerfeldversuchen in einer zweifaktoriellen Blockanlage in Abhängigkeit von organischer Düngung (Weizenstroh, Stallmist) und Wassergehalt inkubiert. Die Experimente wurden in vier Feuchtigkeitsstufen mit 10, 40, 65 und 90 % der Feldkapazität über einen Zeitraum von 85 Tagen bei einer Temperatur von 25 °C realisiert. Zusätzlich sind vor und nach der Inkubation Thermogravimetrische Bodenanalysen (TGBA) durchgeführt worden.
Die Ergebnisse belegen einen mit dem Wassergehalt steigenden C-Umsatz, da die Aktivität von aeroben Mikroorganismen bis zur Wassersättigung des Bodens zunimmt. Die Steigerung war bei Zugabe von Weizenstroh höher als bei Stallmist, ohne Düngerzusatz signifikant niedriger. Gleichzeitig änderte sich die Dynamik der Abbauprozesse. Durch besonders trockene Verhältnisse wurde die Umsetzung verzögert, zudem sank die Umsatzrate langsamer. Ein dauerhafter Einfluss des Standorts auf den Umsatz der Düngemittel war dagegen nicht nachweisbar. Der biologische Abbau im Inkubationsversuch veränderte darüber hinaus die thermische Zerfallsdynamik. Die größten Veränderungen wurden nach Zugabe von Stroh festgestellt. Nicht geklärt werden konnte, ob in Böden mit höherer Versorgung durch organische Substanz gleiche Ergebnisse erzielt werden können. / In land use, the assessment of the supply of organic soil matter (OBS) is a particular challenge. The influence of soil moisture on global climate change will become increasingly important, as water availability influences the activity of soil-living microorganisms. The aim of the work is therefore to determine the extent to which different water contents influence the biological turnover during the incubation of soil samples with different origins as well as organic fertilisation. In a model experiment, soil samples from unfertilized plots of three German long-time field experiments were incubated in a two-factor block facility depending on organic fertilization (wheat straw, manure) and water content. The experiments were carried out in four humidity levels with 10, 40, 65 and 90 % of the field capacity over a period of 85 days at a temperature of 25 °C. In addition, thermogravimetric soil analyses (TGBA) were performed before and after incubation.
The results prove a C turnover increasing with the water content, since the activity of aerobic microorganisms increases until the water saturation of the soil. The increase was higher with the addition of wheat straw than with manure, without fertilizer significantly lower. At the same time, the dynamics of the degradation processes changed. Due to particularly dry conditions, conversion was delayed and the turnover rate fell more slowly. A lasting influence of the site on fertilizer turnover was not proved. In addition, the biological degradation in the incubation experiment changed the thermal decay dynamics. The largest changes were observed after the addition of straw. It could not be clarified whether the same results could be achieved in soils with a higher supply of organic matter.
|
98 |
Corrélation entre le comportement électrique et les propriétés physico-chimiques des fils émaillés : vers l'origine de la défaillance de machines tournantes en conditions extrêmes / Origin of the failure occurring in high temperature electrical machines : a route to improve the electrical behavior of enamel wiresPetitgas, Benoit 26 June 2013 (has links)
Le sujet de cette thèse concerne les applications hautes températures, où les moteurs doivent être capables de fonctionner à 400°C pendant 2 heures, selon la norme en vigueur. Il convient dans ce type d’applications de disposer de matériaux assez stables pour que leurs propriétés isolantes restent inchangées, ce qui est le cas du fil émaillé PolyImide (PI). Ce fil émaillé pose néanmoins des problèmes économiques et de fournisseurs, d’où la nécessité de trouver d’autres alternatives. Ce travail de thèse a eu pour but de mettre au point et valider des techniques d’analyses (ATG / ATM / ATR-FTIR / DRS) adaptées au fil émaillé, et ce jusqu’à 400°C. Le PEI présente des propriétés insuffisantes pour ce type d’application car il se dégrade avant 350°C et perd ses propriétés d’isolation électrique. Le PAI est un matériau qui ne se dégrade que peu avant 400°C, et présente des caractéristiques électriques (propriétés diélectriques et de conduction) déjà plus proche du PolyImide. Nous avons pu établir la comparaison de deux PAI dont l’un est conventionnel et l’autre est un nanocomposite à base d’alumine. Ce dernier PAI est plus stable en température mais ne semble pas avoir de propriétés électriques très supérieures. Pour confronter les résultats expérimentaux obtenus dans des conditions particulières aux conditions réelles d’utilisation, des moteurs avec ces fils émaillés ont été fabriqués. Les moteurs équipés des fils PEI/PAI (fil standard) et PAI sont défaillants après 40 minutes au lieu de 2h, contrairement aux moteurs équipés de fil PI. La dégradation du PEI et le fluage du PAI, caractérisé au-delà de sa Tg (280°C), peuvent être la cause des dysfonctionnements de ces moteurs / This work is related to the high temperature application where motors have to withstand severe conditions - 400°C during 2 hours - according to the standard. Electrical insulation becomes a serious challenge for such application where materials have to remain stable, which is the case of PolyImide enameled wire. Other alternatives have to be found because this is a very expensive material with a small number of suppliers. The thermal, structural, mechanical and electrical properties of these systems have been investigated in-situ until 400°C by thermogravimetric analysis, ATR-FTIR microscopy, thermomechanical analysis, dielectric spectroscopy and DC voltage experiments. Dielectric spectroscopy has indicated a loss of insulating properties during the thermal cycle especially for PEI-containing enamels that degrades before 350°C. PAI enameled wires degrade just before 400°C, and electrical properties (dielectric properties and conductivity) are closer to PI‘s in this temperature range. A comparison between a conventional PAI and a PAI filled with nanoparticules of aluminium oxide has been made. The nanocomposite is thermally more stable but does not show better electrical behavior. To correlate all these results to the real test conditions (combined thermal, electrical and mechanical stresses), electrical motors have been fabricated using the enameled wires said before. They all breakdown after 40 minutes running, except motors made with PI enameled wires. The degradation of PEI ad the creeping of PAI up to its Tg (280°C) can explain the breakdown of these motors
|
99 |
Evaluation of novel metalorganic precursors for atomic layer deposition of Nickel-based thin films / Evaluierung neuartiger metallorganischen Präkursoren für Atomlagenabscheidung von Nickel-basierten DünnschichtenSharma, Varun 04 June 2015 (has links) (PDF)
Nickel und Nickel (II) -oxid werden in großem Umfang in fortgeschrittenen elektronischen Geräten verwendet. In der Mikroelektronik-Industrie wird Nickel verwendet werden, um Nickelsilizid bilden. Die Nickelmono Silizid (NiSi) wurde als ausgezeichnetes Material für Source-Drain-Kontaktanwendungen unter 45 nm-CMOS-Technologie entwickelt. Im Vergleich zu anderen Siliziden für die Kontaktanwendungen verwendet wird NiSi wegen seines niedrigen spezifischen Widerstand, niedrigen Kontaktwiderstand, relativ niedrigen Bildungstemperatur und niedrigem Siliziumverbrauchs bevorzugt. Nickel in Nickelbasis-Akkus und ferromagnetischen Direktzugriffsspeicher (RAMs) verwendet. Nickel (II) oxid wird als Transistor-Gate-Oxid und Oxid in resistive RAM genutzt wird.
Atomic Layer Deposition (ALD) ist eine spezielle Art der Chemical Vapor Deposition (CVD), das verwendet wird, um sehr glatte sowie homogene Dünnfilme mit hervorragenden Treue auch bei hohen Seitenverhältnissen abzuscheiden. Es basiert auf selbstabschließenden sequentielle Gas-Feststoff-Reaktionen, die eine präzise Steuerung der Filmdicke auf wenige Angström lassen sich auf der Basis. Zur Herstellung der heutigen 3D-elektronische Geräte, sind Technologien wie ALD erforderlich. Trotz der Vielzahl von praktischen Anwendungen von Nickel und Nickel (II) -oxid, sind einige Nickelvorstufen zur thermischen basierend ALD erhältlich.
Darüber hinaus haben diese Vorstufen bei schlechten Filmeigenschaften führte und die Prozesseigenschaften wurden ebenfalls begrenzt. Daher in dieser Masterarbeit mussten die Eigenschaften verschiedener neuartiger Nickelvorstufen zu bewerten. Alle neuen Vorstufen heteroleptische (verschiedene Arten von Liganden) und Komplexe wurden vom Hersteller speziell zur thermischen basierend ALD aus reinem Nickel mit H 2 als ein Co-Reaktionsmittel gestaltet. Um die neuartige Vorläufer zu untersuchen, wurde eine neue Methode entwickelt, um kleine Mengen in einer sehr zeitsparend (bis zu 2 g) von Ausgangsstoffen zu testen. Diese Methodologie beinhaltet: TGA / DTA-Kurve analysiert der Vorstufen, thermische Stabilitätstests in dem die Vorläufer (<0,1 g) wurden bei erhöhter Temperatur in einer abgedichteten Umgebung für mehrere Stunden wurde die Abscheidung Experimenten und Film Charakterisierungen erhitzt. Die Abscheidungen wurden mit Hilfe der in situ Quarzmikrowaage überwacht, während die anwendungsbezogenen Filmeigenschaften, wie chemische Zusammensetzung, physikalische Phase, Dicke, Dichte, Härte und Schichtwiderstand wurden mit Hilfe von ex situ Messverfahren untersucht.
Vor der Evaluierung neuartiger Nickelvorstufen ein Benchmark ALD-Prozess war vom Referenznickelvorläufer (Ni (AMD)) und Luft als Reaktionspartner entwickelt. Das Hauptziel der Entwicklung und Optimierung von solchen Benchmark-ALD-Prozess war es, Standard-Prozessparameter wie zweite Reaktionspartner Belichtungszeiten, Argonspülung Zeiten, gesamtprozessdruck, beginnend Abscheidungstemperatur und Gasströme zu extrahieren. Diese Standard-Prozessparameter mussten verwendet, um die Prozessentwicklung Aufgabe (das spart Vorläufer Verbrauch) zu verkürzen und die Sublimationstemperatur Optimierung für jede neuartige Vorstufe werden. Die ALD Verhalten wurde in Bezug auf die Wachstumsrate durch Variation des Nickelvorläuferbelichtungszeit, Vorläufer Temperatur und Niederschlagstemperatur überprüft. / Nickel and nickel(II) oxide are widely used in advanced electronic devices . In microelectronic industry, nickel is used to form nickel silicide. The nickel mono-silicide (NiSi) has emerged as an excellent material of choice for source-drain contact applications below 45 nm node CMOS technology. As compared to other silicides used for the contact applications, NiSi is preferred because of its low resistivity, low contact resistance, relatively low formation temperature and low silicon consumption. Nickel is used in nickel-based rechargeable batteries and ferromagnetic random access memories (RAMs). Nickel(II) oxide is utilized as transistor gate-oxide and oxide in resistive RAMs.
Atomic Layer Deposition (ALD) is a special type of Chemical Vapor Deposition (CVD) technique, that is used to deposit very smooth as well as homogeneous thin films with excellent conformality even at high aspect ratios. It is based on self-terminating sequential gas-solid reactions that allow a precise control of film thickness down to few Angstroms. In order to fabricate todays 3D electronic devices, technologies like ALD are required.
In spite of huge number of practical applications of nickel and nickel(II) oxide, a few nickel precursors are available for thermal based ALD. Moreover, these precursors have resulted in poor film qualities and the process properties were also limited. Therefore in this master thesis, the properties of various novel nickel precursors had to be evaluated. All novel precursors are heteroleptic (different types of ligands) complexes and were specially designed by the manufacturer for thermal based ALD of pure nickel with H 2 as a co-reactant.
In order to evaluate the novel precursors, a new methodology was designed to test small amounts (down to 2 g) of precursors in a very time efficient way. This methodology includes: TGA/DTA curve analyses of the precursors, thermal stability tests in which the precursors (< 0.1 g) were heated at elevated temperatures in a sealed environment for several hours, deposition experiments, and film characterizations. The depositions were monitored with the help of in situ quartz crystal microbalance, while application related film properties like chemical composition, physical phase, thickness, density, roughness and sheet resistance were investigated with the help of ex situ measurement techniques.
Prior to the evaluation of novel nickel precursors, a benchmark ALD process was developed from the reference nickel precursor (Ni(amd)) and air as a co-reactant. The main goal of developing and optimizing such benchmark ALD process was to extract standard process parameters like second-reactant exposure times, Argon purge times, total process pressure, starting deposition temperature and gas flows. These standard process parameters had to be utilized to shorten the process development task (thus saving precursor consumption) and optimize the sublimation temperature for each novel precursor. The ALD behaviour was checked in terms of growth rate by varying the nickel precursor exposure time, precursor temperature and deposition temperature.
|
100 |
Evaluation of novel metalorganic precursors for atomic layer deposition of Nickel-based thin filmsSharma, Varun 17 February 2015 (has links)
Nickel und Nickel (II) -oxid werden in großem Umfang in fortgeschrittenen elektronischen Geräten verwendet. In der Mikroelektronik-Industrie wird Nickel verwendet werden, um Nickelsilizid bilden. Die Nickelmono Silizid (NiSi) wurde als ausgezeichnetes Material für Source-Drain-Kontaktanwendungen unter 45 nm-CMOS-Technologie entwickelt. Im Vergleich zu anderen Siliziden für die Kontaktanwendungen verwendet wird NiSi wegen seines niedrigen spezifischen Widerstand, niedrigen Kontaktwiderstand, relativ niedrigen Bildungstemperatur und niedrigem Siliziumverbrauchs bevorzugt. Nickel in Nickelbasis-Akkus und ferromagnetischen Direktzugriffsspeicher (RAMs) verwendet. Nickel (II) oxid wird als Transistor-Gate-Oxid und Oxid in resistive RAM genutzt wird.
Atomic Layer Deposition (ALD) ist eine spezielle Art der Chemical Vapor Deposition (CVD), das verwendet wird, um sehr glatte sowie homogene Dünnfilme mit hervorragenden Treue auch bei hohen Seitenverhältnissen abzuscheiden. Es basiert auf selbstabschließenden sequentielle Gas-Feststoff-Reaktionen, die eine präzise Steuerung der Filmdicke auf wenige Angström lassen sich auf der Basis. Zur Herstellung der heutigen 3D-elektronische Geräte, sind Technologien wie ALD erforderlich. Trotz der Vielzahl von praktischen Anwendungen von Nickel und Nickel (II) -oxid, sind einige Nickelvorstufen zur thermischen basierend ALD erhältlich.
Darüber hinaus haben diese Vorstufen bei schlechten Filmeigenschaften führte und die Prozesseigenschaften wurden ebenfalls begrenzt. Daher in dieser Masterarbeit mussten die Eigenschaften verschiedener neuartiger Nickelvorstufen zu bewerten. Alle neuen Vorstufen heteroleptische (verschiedene Arten von Liganden) und Komplexe wurden vom Hersteller speziell zur thermischen basierend ALD aus reinem Nickel mit H 2 als ein Co-Reaktionsmittel gestaltet. Um die neuartige Vorläufer zu untersuchen, wurde eine neue Methode entwickelt, um kleine Mengen in einer sehr zeitsparend (bis zu 2 g) von Ausgangsstoffen zu testen. Diese Methodologie beinhaltet: TGA / DTA-Kurve analysiert der Vorstufen, thermische Stabilitätstests in dem die Vorläufer (<0,1 g) wurden bei erhöhter Temperatur in einer abgedichteten Umgebung für mehrere Stunden wurde die Abscheidung Experimenten und Film Charakterisierungen erhitzt. Die Abscheidungen wurden mit Hilfe der in situ Quarzmikrowaage überwacht, während die anwendungsbezogenen Filmeigenschaften, wie chemische Zusammensetzung, physikalische Phase, Dicke, Dichte, Härte und Schichtwiderstand wurden mit Hilfe von ex situ Messverfahren untersucht.
Vor der Evaluierung neuartiger Nickelvorstufen ein Benchmark ALD-Prozess war vom Referenznickelvorläufer (Ni (AMD)) und Luft als Reaktionspartner entwickelt. Das Hauptziel der Entwicklung und Optimierung von solchen Benchmark-ALD-Prozess war es, Standard-Prozessparameter wie zweite Reaktionspartner Belichtungszeiten, Argonspülung Zeiten, gesamtprozessdruck, beginnend Abscheidungstemperatur und Gasströme zu extrahieren. Diese Standard-Prozessparameter mussten verwendet, um die Prozessentwicklung Aufgabe (das spart Vorläufer Verbrauch) zu verkürzen und die Sublimationstemperatur Optimierung für jede neuartige Vorstufe werden. Die ALD Verhalten wurde in Bezug auf die Wachstumsrate durch Variation des Nickelvorläuferbelichtungszeit, Vorläufer Temperatur und Niederschlagstemperatur überprüft.:Lists of Abbreviations and Symbols VIII
Lists of Figures and Tables XIV
1 Introduction 1
I Theoretical Part 3
2 Nickel and Nickel Oxides 4
2.1 Introduction and Existence 5
2.2 Material properties of Nickel and Nickel Oxide 5
2.3 Application in electronic industry 5
3 Atomic Layer Deposition 7
3.1 History 8
3.2 Definition 8
3.3 Features of thermal-ALD 8
3.3.1 ALD growth mechanism – an ideal view 8
3.3.2 ALD growth behaviour 10
3.3.3 Growth mode 11
3.3.4 ALD temperature window 11
3.4 Benefits and limitations 12
3.5 Precursor properties for thermal-ALD 13
3.6 ALD & CVD of Nickel – A literature survey 13
4 Metrology 17
4.1 Thermal analysis of precursors 18
4.2 Film and growth characterization 21
4.2.1 Quartz Crystal Microbalance 21
4.2.2 Spectroscopic Ellipsometry 24
4.2.3 X-Ray Photoelectron Spectroscopy 28
4.2.4 Scanning Electron Microscopy 29
4.2.5 X-Ray Reflectometry and X-Ray Diffraction 29
4.2.6 Four Point Probe Technique 20
5 Rapid Thermal Processing 32
5.1 Introduction 33
5.2 Basics of RTP 33
5.3 Nickel Silicides-A literature survey 33
II Experimental Part 36
6 Methodologies 37
6.1 Experimental setup 38
6.2 ALD process 41
6.2.1 ALD process types and substrate setups 41
6.2.2 Process parameters 41
6.3 Experimental procedure 42
6.3.1 Tool preparation 42
6.3.2 Thermal analysis and ALD experiments from nickel precursors 43
6.3.3 Data acquisition and evaluation 44
6.3.4 Characterization of film properties 46
7 Results and discussion 48
7.1 Introduction 49
7.2 QCM verification with Aluminum Oxide ALD process 49
7.3 ALD process from the reference precursor 50
7.3.1 Introduction 50
7.3.2 TG analysis for Ni(amd) precursor 51
7.3.3 Thermal stability test for Ni(amd) 51
7.3.4 ALD process optimization 52
7.3.5 Film properties 54
7.4 Evaluating the novel Nickel precursors 55
7.4.1 Screening tests for precursor P1 55
7.4.2 Screening tests for precursor P2 62
7.4.3 Screening tests for precursor P3 66
7.4.4 Screening tests for precursor P4 70
7.4.5 Screening tests for precursor P5 72
7.5 Comparison of all nickel precursors used in this work 74
8 Conclusions and outlook 77
References 83
III Appendix 101
A Deposition temperature control & Ellipsometry model 102
B Gas flow plan 105 / Nickel and nickel(II) oxide are widely used in advanced electronic devices . In microelectronic industry, nickel is used to form nickel silicide. The nickel mono-silicide (NiSi) has emerged as an excellent material of choice for source-drain contact applications below 45 nm node CMOS technology. As compared to other silicides used for the contact applications, NiSi is preferred because of its low resistivity, low contact resistance, relatively low formation temperature and low silicon consumption. Nickel is used in nickel-based rechargeable batteries and ferromagnetic random access memories (RAMs). Nickel(II) oxide is utilized as transistor gate-oxide and oxide in resistive RAMs.
Atomic Layer Deposition (ALD) is a special type of Chemical Vapor Deposition (CVD) technique, that is used to deposit very smooth as well as homogeneous thin films with excellent conformality even at high aspect ratios. It is based on self-terminating sequential gas-solid reactions that allow a precise control of film thickness down to few Angstroms. In order to fabricate todays 3D electronic devices, technologies like ALD are required.
In spite of huge number of practical applications of nickel and nickel(II) oxide, a few nickel precursors are available for thermal based ALD. Moreover, these precursors have resulted in poor film qualities and the process properties were also limited. Therefore in this master thesis, the properties of various novel nickel precursors had to be evaluated. All novel precursors are heteroleptic (different types of ligands) complexes and were specially designed by the manufacturer for thermal based ALD of pure nickel with H 2 as a co-reactant.
In order to evaluate the novel precursors, a new methodology was designed to test small amounts (down to 2 g) of precursors in a very time efficient way. This methodology includes: TGA/DTA curve analyses of the precursors, thermal stability tests in which the precursors (< 0.1 g) were heated at elevated temperatures in a sealed environment for several hours, deposition experiments, and film characterizations. The depositions were monitored with the help of in situ quartz crystal microbalance, while application related film properties like chemical composition, physical phase, thickness, density, roughness and sheet resistance were investigated with the help of ex situ measurement techniques.
Prior to the evaluation of novel nickel precursors, a benchmark ALD process was developed from the reference nickel precursor (Ni(amd)) and air as a co-reactant. The main goal of developing and optimizing such benchmark ALD process was to extract standard process parameters like second-reactant exposure times, Argon purge times, total process pressure, starting deposition temperature and gas flows. These standard process parameters had to be utilized to shorten the process development task (thus saving precursor consumption) and optimize the sublimation temperature for each novel precursor. The ALD behaviour was checked in terms of growth rate by varying the nickel precursor exposure time, precursor temperature and deposition temperature.:Lists of Abbreviations and Symbols VIII
Lists of Figures and Tables XIV
1 Introduction 1
I Theoretical Part 3
2 Nickel and Nickel Oxides 4
2.1 Introduction and Existence 5
2.2 Material properties of Nickel and Nickel Oxide 5
2.3 Application in electronic industry 5
3 Atomic Layer Deposition 7
3.1 History 8
3.2 Definition 8
3.3 Features of thermal-ALD 8
3.3.1 ALD growth mechanism – an ideal view 8
3.3.2 ALD growth behaviour 10
3.3.3 Growth mode 11
3.3.4 ALD temperature window 11
3.4 Benefits and limitations 12
3.5 Precursor properties for thermal-ALD 13
3.6 ALD & CVD of Nickel – A literature survey 13
4 Metrology 17
4.1 Thermal analysis of precursors 18
4.2 Film and growth characterization 21
4.2.1 Quartz Crystal Microbalance 21
4.2.2 Spectroscopic Ellipsometry 24
4.2.3 X-Ray Photoelectron Spectroscopy 28
4.2.4 Scanning Electron Microscopy 29
4.2.5 X-Ray Reflectometry and X-Ray Diffraction 29
4.2.6 Four Point Probe Technique 20
5 Rapid Thermal Processing 32
5.1 Introduction 33
5.2 Basics of RTP 33
5.3 Nickel Silicides-A literature survey 33
II Experimental Part 36
6 Methodologies 37
6.1 Experimental setup 38
6.2 ALD process 41
6.2.1 ALD process types and substrate setups 41
6.2.2 Process parameters 41
6.3 Experimental procedure 42
6.3.1 Tool preparation 42
6.3.2 Thermal analysis and ALD experiments from nickel precursors 43
6.3.3 Data acquisition and evaluation 44
6.3.4 Characterization of film properties 46
7 Results and discussion 48
7.1 Introduction 49
7.2 QCM verification with Aluminum Oxide ALD process 49
7.3 ALD process from the reference precursor 50
7.3.1 Introduction 50
7.3.2 TG analysis for Ni(amd) precursor 51
7.3.3 Thermal stability test for Ni(amd) 51
7.3.4 ALD process optimization 52
7.3.5 Film properties 54
7.4 Evaluating the novel Nickel precursors 55
7.4.1 Screening tests for precursor P1 55
7.4.2 Screening tests for precursor P2 62
7.4.3 Screening tests for precursor P3 66
7.4.4 Screening tests for precursor P4 70
7.4.5 Screening tests for precursor P5 72
7.5 Comparison of all nickel precursors used in this work 74
8 Conclusions and outlook 77
References 83
III Appendix 101
A Deposition temperature control & Ellipsometry model 102
B Gas flow plan 105
|
Page generated in 0.0646 seconds