Dissertations / Theses on the topic 'CNF catalyst'

Since there is a continuous shrinking of feature sizes in ultra-large scale integrated (ULSI) circuits, requirements on materials and technology are going to rise dramatically in the near future. In particular, at the interconnect system this calls for new concepts and materials. Therefore, carbon nanotubes (CNTs) are considered as a promising material to replace partly or entirely metal interconnects in such devices. The present thesis aims to make a contribution to the CNT growth control with the thermal chemical vapor deposition (CVD) method and the integration of CNTs as vertical interconnects (vias) in ULSI circuits. Different support/catalyst systems are examined in processes for catalyst pretreatment and CNT growth. The investigations focus on the catalyst formation and the interactions at the interfaces. Those effects are related to the CNT growth. To get an insight into interactions at interfaces, film structure, composition, and CNT growth characteristics, samples are extensively characterized by techniques like AFM, SEM, TEM, XRD, XPS, and Raman spectroscopy. Screening studies on nanoparticle formation and CNT growth with the well known system SiO2/Ni are presented. This system is characterized by a weak support/catalyst interaction, which leads to undirected growth of multi-walled CNTs (MWCNTs). By contrast, at the Ta/Ni system a strong interaction causes a wetting of catalyst nanoparticles and vertically aligned MWCNT growth. At the system W/Ni a strong interaction at the interface is found as well, but there it induces Stranski-Krastanov catalyst film reformation upon pretreatment and complete CNT growth inhibition. Studies on the SiO2/Cr/Ni system reveal that Cr and Ni act as a bi-catalyst system, which leads to a novel nanostructure defined as interlayer CNT (ICNT) structure. The ICNT films are characterized by well crystallized vertically aligned MWCNTs, which grow out a Cr/Ni layer lifted off as a continuous and very smooth layer from the substrate with the growth. Besides, this nanostructure offers new possibilities for the integration of CNTs in different electronic applications. Based on the presented possibilities of manipulating CNT growth, an integration technology was derived to fabricate CNT vias. The technology uses a surface mediated site-selective CVD for the growth of MWCNTs in via structures. Developments are demonstrated with the fabrication of via test vehicles and the site-selective growth of MWCNTs in vias on 4 inch wafers. Furthermore, the known resistance problem of CNT vias, caused by too low CNT density, is addressed by a new approach. A CNT/metal heterostructure is considered, where the metal is implemented through atomic layer deposition (ALD). The first results of the coating of CNTs with readily reducible copper oxide nanoparticles are presented and discussed
Aufgrund der kontinuierlichen Verkleinerung von Strukturen in extrem hoch integrierten (engl. Ultra-Large Scale Integration − ULSI) Schaltkreisen werden die Anforderungen an die Materialien und die Technologie in naher Zukunft dramatisch ansteigen. Besonders im Leitbahnsystem sind neue Materialien und Konzepte gefragt. Kohlenstoffnanoröhren (engl. Carbon Nanotubes − CNT) stellen hierbei ein vielversprechendes Material dar, um teilweise oder sogar vollständig metallische Leitbahnen zu ersetzen. Die vorliegende Arbeit liefert einen Beitrag zur CNT-Wachstumskontrolle mit der thermischen Gasphasenabscheidung (engl. Chemical Vapor Deposition − CVD) sowie der Integration von CNTs als vertikale Leitungsverbindungen (Via) in ULSI-Schaltkreisen. Verschiedene Untergrund/Katalysator-Systeme werden in Prozessen zur Katalysatorvorbehandlung sowie zum CNT-Wachstum betrachtet. Die Untersuchungen richten sich insbesondere auf die Katalysatorformierung und die Wechselwirkungen an den Grenzflächen. Diese werden mit dem CNT-Wachstum in Verbindung gebracht. Für Untersuchungen von Grenzflächeninteraktionen, Schichtstruktur, Zusammensetzung sowie CNT-Wachstumscharakteristik werden Analysen mit AFM, REM, TEM, XRD, XPS und Raman-Spektroskopie genutzt. Zunächst werden Voruntersuchungen an dem gut bekannten System SiO2/Ni zur Nanopartikelformierung und CNTWachstum vorgestellt. Dieses System ist gekennzeichnet durch eine schwache Wechselwirkung zwischen Untergrund und Katalysator sowie ungerichtetem Wachstum von mehrwandigen CNTs (MWCNTs). Im Gegensatz dazu hat bei dem System Ta/Ni eine starke Interaktion an der Grenzfläche eine Katalysatornanopartikelbenetzung und vertikales MWCNT-Wachstum zur Folge. Für das W/Ni-System gelten ebenfalls starke Interaktionen an der Grenzfläche. Bei diesem System wird allerdings eine Stranski-Krastanov-Schichtformierung des Katalysators und eine vollständige Unterbindung von CNT-Wachstum erreicht. Bei dem System SiO2/Cr/Ni agieren Cr und Ni als Bi- Katalysatorsystem. Dies führt zu einer neuartigen Nanostruktur, die als Zwischenschicht-CNT (engl. Interlayer Carbon Nanotubes − ICNTs) Struktur definiert wird. Die Schichten sind durch eine gute Qualität von gerichteten MWCNTs charakterisiert, die aus einer geschlossenen, sehr glatten und von den CNTs getragenen Cr/Ni-Schicht herauswachsen. Darüber hinaus bietet die Struktur neue Möglichkeiten für die Integration von CNTs in verschiedene elektronische Anwendungen. Auf der Grundlage der vorgestellten Manipulationsmöglichkeiten von CNT-Wachstum wurde eine Integrationstechnologie für CNTs in Vias abgeleitet. Der Ansatz ist eine oberflächeninduzierte selektive CVD von vertikal gerichteten MWCNTs in Via-Strukturen. Diese Technologie wird mit der Herstellung von einem Via-Testvehikel und dem selektiven CNT-Wachstum in Vias auf 4 Zoll Wafern demonstriert. Um das Widerstandsproblem von CNT-Vias, verursacht durch eine zu niedrige CNT-Dichte, zu reduzieren, wird eine Technologieerweiterung vorgeschlagen. Der Ansatz geht von einer CNT/Metall-Heterostruktur aus, bei der das Metall mit Hilfe der Atomlagenabscheidung (engl. Atomic Layer Deposition − ALD) implementiert wird. Es werden erste Ergebnisse zur CNT-Beschichtung mit reduzierbaren Kupferoxidnanopartikeln vorgestellt und diskutiert

The ability to fabricate a charge-driven water pump is a crucial step toward mimicking the catalytic ability of natural enzyme systems. The first step towards making this water pump a reality is the ability to make a carbon nanotube (CNT) membrane with uniform, 0.8 nm pore diameter. Proposed in this work is a method for synthesizing these carbon nanotubes via VPI-5 zeolite templated, transition metal catalyzed pyrolysis. Using a membrane composed of these CNTs, it is possible to get water molecules to flow single file at a high flow rate, and to orient them in such a way that would maximize their ability to be catalyzed. Additionally, using the ability to plate a monolayer of precious metal catalyst molecules around the exit to the membrane, catalyst efficiency can be maximized by making every catalyst atom come into contact with a substrate molecule. In this work, we also demonstrate the ability to plate a monolayer of precious metal catalyst atoms onto an insulating, mesoporous, support material. By combining these two chemical processes, it is possible to mimic the catalytic efficiency of natural enzyme systems.

Abstract Degradation of the support and sintering of catalyst nanoparticles inherently leads to a loss of functionality of catalyst materials in converters and sensors. Malfunction in such devices may lead to serious economic and environmental damage. The quest for novel and sustainable catalyst materials with better durability is thus ongoing. In this thesis, one-dimensional nanomaterials such as carbon nanotubes and titanium dioxide nanowires are studied and compared to their conventional zero-dimensional counterparts in regard to their structural and functional stability. With the combination of several catalyst nanomaterials and supporting surfaces, aging properties of more than 70 different materials are assessed by the means of X-ray diffraction, transmission electron microscopy and energy-dispersive X-ray analyses. Although CNTs were shown to be thermally the most stable carbonaceous supports for metal nanoparticles, they are, similar to other carbon supports, more sensitive to high temperatures than metal oxide supports and can suffer deactivation by catalytic oxidation and gasification even at moderate temperatures. In addition, the irradiation of the samples with e-beams caused the most dramatic changes in CNT based materials, where nanosized deformities (voids, channels) were formed when either nanoparticles or defects were present. The prepared nanocompositions have been utilized successfully in three different applications including (i) synthesis of hydrogen from ethanol via a steam reforming reaction, (ii) hydrogenation of citral to form value added chemicals and (iii) the application of advanced electrode materials in electric double-layer capacitors. Both CNT and TiO₂ nanowire based nanomaterials were shown to outperform their conventional nano- and microparticle based counterparts in the studied catalytic reactions, i.e. in citral hydrogenation and steam reforming of ethanol, respectively. Furthermore, nanostructured CNTs obtained by catalytic partial oxidation of the material showed an increased specific surface area, which could be exploited in supercapacitor electrodes with enhanced specific capacitance
Tiivistelmä Katalyyttitukimateriaalin pilaantuminen ja katalyyttinanopartikkelien sintrautuminen johtavat siihen, että muuntajissa ja sensoreissa käytettävät katalyyttiset materiaalit eivät enää toimi, mikä voi aiheuttaa sekä vakavia taloudellisia haittoja että ympäristöhaittoja. Tämän vuoksi kehitetään uusia kestävämpiä katalyyttimateriaaleja. Tässä väitöskirjassa tutkittiin yksiulotteisia nanomateriaaleja, kuten hiilinanoputkia sekä titaanidioksidinanojohtimia ja verrattiin niiden rakenteellista ja toiminnallista stabiiliutta perinteisiin nollaulotteisiin vastineisiin. Erilaisten katalyyttinanomateriaalien ja tukimateriaalien yhdistelmien ikääntymistä arvioitiin röntgendiffraktion, läpäisyelektronimikroskopian ja energiadispersiivisen röntgenanalyysin avulla yli 70 erilaisesta näytteestä. Vaikka hiilinanoputket osoittautuivat termisesti stabiileimmaksi hiilipohjaiseksi tukimateriaaliksi metallinanopartikkeleille, ne ovat kuten kaikki hiilimateriaalit, metallioksiditukimateriaaleja herkempiä korkeille lämpötiloille. Hiilinanoputkipohjaiset katalyytit voivat deaktivoitua katalyyttisen hapettumisen tai kaasuuntumisen vuoksi jo kohtalaisissa lämpötiloissa. Lisäksi elektronisäteellä säteilytetyt nanopartikkelit tai pintavirheitä sisältävät hiilinanoputkipohjaiset katalyytit olivat tutkituista nanomateriaaleista herkimpiä muodostamaan nanorakenteita (koloja, kanavia). Valmistettuja nanokomposiitteja käytettiin onnistuneesti kolmessa eri sovelluksessa: i) vedyn valmistuksessa etanolista höyryreformointireaktiolla, ii) hienokemikaalien valmistuksessa sitraalin hydrauksella sekä iii) elektrodimateriaalina EDLC-kondensaattorissa. Sekä hiilinanoputki- sekä TiO₂-nanojohdinpohjaiset nanomateriaalit toimivat testatuissa katalyyttisissa reaktioissa (etanolin reformointi sekä sitraalin hydraus) paremmin kuin niiden perinteiset vastineet. Lisäksi superkondensaattorin ominaiskapasitanssia onnistuttiin nostamaan lisäämällä hiilinanoputkipohjaisen elektrodin ominaispinta-alaa katalyyttisella hapetusreaktiolla

ABSTRACT SYNTHESIS AND CHARACTERIZATION OF ETHANOL ELECTRO-OXIDATION CATALYSIS Demir-Kivrak, Hilal Ph.D., Department of Chemical Engineering Supervisor : Prof. Dr. Deniz Ü
ner Co-supervisor : Dr. Sadig Kuliyev October 2010, 196 pages In this study, the role of defects, the role of Sn in relation to defects, and the role of oxide phase of tin in ethanol electro-oxidation reaction were investigated. Firstly, adsorption calorimetry measurements were conducted on monometallic (1%Pt, 2%Pt, and 5%Pt) and bi-metallic (5% Pt-Sn) &gamma
-Al2O3 supported Pt catalysts. It was observed that while saturation coverage values decreased, intermediate heats remained same for Pt-Sn catalysts by the increasing amount of tin. The effect of particle size was investigated on Pt/C (pH=5), Pt/C (pH=11) catalysts at different scan rates. At high scan rates (quite above diffusion limitations), current per site activities were nearly the same for 20% Pt/C (E-Tek), Pt/C (pH=11), and Pt/C (pH=5) catalysts, which explained as electro-oxidation reaction takes place at the defects sites. Furthermore, the effect of support on ethanol electro-oxidation was investigated on CNT supported Pt catalyst. Results indicate that only the metal v dispersions improved ethanol electro-oxidation reaction and support did not have any effect on ethanol electro-oxidation reaction. Results on the 20% Pt-Sn/C (15:1 to 1:1 Pt: Sn atomic ratios) and 20% Pt-SnO2/C (6:1 and 1:1) catalysts indicated that ethanol electro-oxidation activity increased by increasing tin amount. For 20% Pt-Sn/C catalysts, Pt-Sn (6:1)/C indicated best activity. On the other hand, 20% Pt-SnO2 (6:1)/C catalyst was better than Pt-Sn (6:1)/C in terms of ethanol electro-oxidation activity due to the fact that there was low contact between Pt and tin oxide particles.

Abstract While numerous publications deal with the properties and applications of porous silicon (PS), some of the related topics are not complete or could be investigated from different aspects. Therefore, the main objective of this thesis is to provide novel information associated with the optical and chemical properties of PS. For the investigations, various PS samples are manufactured by electrochemical dark etching of boron-doped p+-type Si wafers. Amongst others, (i) the wavelength-dependent refractive indices of freestanding PS monolayers having different porosities were obtained from optical transmission and reflection spectra in the 700–1700 nm wavelength range, and compared to those calculated from Bruggeman's effective medium approximation (EMA). The refractive indices of the PS samples are shown to be described well with the EMA. In addition, optical scattering at the air-PS interface was demonstrated. (ii) Multilayer stacks are created by alternating the porosities of PS layers within the same sample to form Bragg filters. The Bragg conditions of the filters are calculated and compared to optical transmission measurements. (iii) The oxidation of PS membranes in dry air is investigated with emphases on the reaction kinetics and on the structural changes of the porous matter. As revealed, oxidation proceeds faster in PS than in Si bulk. The formed SiO2 is amorphous and causes stress in the lattice of the residual Si skeleton. (iv) The effect of oxidation extent of PS layers on the growth mechanism of multi-walled carbon nanotubes (CNTs) is investigated. The density of the CNT network is found proportional to the oxidation extent of the substrates. (v) Finally, the chemically-reductive nature of PS is studied and exploited via the immersion plating method to deposit palladium and silver nanoparticles in the nanopores and on the surface of PS samples. The presented novel results have potential in silicon-based technologies, including integrated active and passive optical components (waveguides, filters, antireflection coatings, optical gas/liquid sensors), electronic devices (electrochemical gas/liquid sensors, diodes, field effect devices) and selective chemical catalysis (substrates, growth templates).

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Oxidative stress is involved in several neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis. Oxidative stress seems to be involved in the pathology of dementia/amnesia. It has been suggested that oxidative stress impairs the muscarinic cholinergic system triggering Alzheimer's disease. The muscarinic antagonist scopolamine has been used to induce amnesia in animals. This experimental model has been used in screening anti-amnesic drugs that could be useful for the treatment of dementia. The aim of this study was to evaluate the possible in vitro antioxidant effect of a series of pyrazoline derivatives newly synthesized: (1) 5-hydroxy-3-methyl-5-trifluoromethyl-4,5-dihydro-1H-carbaldehyde-pyrazole, (2) 5-hydroxy-3-methyl-5- trifluoromethyl-4,5-dihydro-1H-1-acetyl-pyrazole, (3) 5-hydroxy-3-methyl-5-trifluoromethyl-4,5-dihydro-1H-carboxyamide-pyrazole, (4) 5-hydroxy-3-methyl-5-trifluoromethyl-4,5-dihydro-1H-1-benzoyl-pyrazole, (5) 5-hydroxy-3-methyl-5-trifluoromethyl-4,5-dihydro-1H-1-(2- hydroxybenzoyl)-pyrazole and (6) 5-hydroxy-3-methyl-5-trifluoromethyl-4,5-dihydro-1H-1-(4-methoxybenzoyl)-pyrazole. Besides, considering the possible involvement of oxidative stress in dementia, the compound that was the most effective in vitro was assessed concerning to its ability to prevent the memory deficit and oxidative stress in a scopolamine-induced amnesia model. Compound (5) had the highest antioxidant capacity in vitro, since it reduced lipid peroxidation (TBARS) basal and stimulated by the pro-oxidants iron, hydrogen peroxide and sodium nitroprusside, having significant effects from 15 μM onwards (p<0.05). Compound (5) also protected against hydrogen peroxide-induced glutathione oxidation, with a significant effect at the concentration of 150 μM (p<0.05). This compound also had the highest total antioxidant activity, demonstrated by its ability to remove the radical 1,1-dyphenyl-2-pycrylhydrazyl (DPPH). Compounds (1) and (4) also reduced lipid peroxidation basal and stimulated by iron and sodium nitroprusside, having significant effects from 15 μM onwards (p<0.05). Compound (2) had the highest ability to reduce iron (p<0.05). Scopolamine administration 30 min before training session resulted in shorter latency to step-down during the test session of the inhibitory avoidance task (p<0.05). Pretreatment with pyrazole compound (5) had no effect per se on the step-down latency. However, pretreatment with compound (5) (100 μmol/kg) 30 min before scopolamine did prevent the amnesic effect of scopolamine (p<0.05). No significant effect of scopolamine or pyrazole treatment was observed on any of the oxidative stress markers evaluated (thiobarbituric acid reactive substances, non-protein sulfhydrylic groups content and activity of enzymes superoxide dismutase and catalase) suggesting that the protective effect of compound (5) was not related to a possible antioxidant activity. Results revealed that pyrazole compound (5) has in vitro antioxidant activity as well as neuroprotective activity in a model of amnesia. These findings suggest that compound (5) could be a promising drug for the treatment of Alzheimer´s disease. However, further studies are needed to elucidate the mechanisms involved in the antiamnesic effect of this compound, as well as its effect on other dementia models.
O estresse oxidativo está envolvido em diversas doenças neurodegenerativas importantes, tais como a doença de Alzheimer, a doença de Parkinson e a esclerose lateral amiotrófica. O estresse oxidativo parece estar envolvido na patologia da demência/amnésia, tendo sido sugerido que as alterações cerebrais decorrentes deste causam danos ao sistema colinérgico muscarínico e que desta forma desencadeiam a doença de Alzheimer. A escopolamina, um antagonista muscarínico, tem sido usado para induzir amnésia em animais, em um modelo experimental para a triagem de drogas que poderiam ser úteis no tratamento da demência. O principal objetivo deste estudo foi avaliar o possível efeito antioxidante in vitro de uma série de derivados pirazolínicos recém sintetizados: (1) 5-hidroxi-3-metil-5-trifluorometil-4,5-diidro-1H-carbaldeido-pirazol, (2) 5-hidroxi-3-metil-5- trifluorometil-4,5-diidro-1H-1-acetil-pirazol, (3) 5-hidroxi-3-metil-5-trifluorometil-4,5-diidro-1Hcarboxiamida- pirazol, (4) 5-hidroxi-3-metil-5-trifluorometil-4,5-diidro-1H-1-benzoil-pirazol, (5) 5-hidroxi-3-metil-5-trifluorometil-4,5-diidro-1H-1-(2-hidroxibenzoil)-pirazol e (6) 5-hidroxi-3-metil-5-trifluorometil-4,5-diidro-1H-1-(4-methoxibenzoil)-pirazol. Além disso, considerando o possível envolvimento do estresse oxidativo na demência, foi avaliada a capacidade do composto mais efetivo in vitro, em prevenir o déficit de memória e o estresse oxidativo em um modelo de amnésia induzida por escopolamina. O derivado pirazolínico (5) apresentou maior capacidade antioxidante in vitro, pois foi o mais efetivo para reduzir a lipoperoxidação (TBARS) basal e induzida pelos pró-oxidantes ferro, peróxido de hidrogênio e nitroprussiato de sódio, tendo efeitos significativos a partir de 15 μM (p<0,05). O composto (5) também protegeu a glutationa da oxidação induzida por peróxido de hidrogênio, tendo efeito significativo na concentração de 150 μM (p<0,05). Este composto também foi o que teve maior atividade antioxidante total, demonstrada pela sua capacidade de remover o radical 1,1-difenil-2-picrilhidrazil (DPPH). Os compostos (1) e (4) também reduziram a lipoperoxidação basal e induzida por ferro e nitroprussiato de sódio, tendo efeitos significativos a partir de 15 μM (p<0,05). O composto (2) apresentou a maior capacidade de redução de ferro (p<0,05). A administração de escopolamina 30 min antes do treino provocou amnésia, medida como a redução na latência para descer da plataforma no teste de esquiva inibitória (p<0.05). O pré-tratamento com o composto (5) 30 min antes da escopolamina não apresentou efeito per se na latência, mas preveniu o efeito amnésico da escopolamina, na dose de 100 μmol/kg (p<0.05). Não foi observado efeito significativo da escopolamina ou do composto (5) em qualquer dos marcadores de estresse oxidativo avaliados (substâncias reativas ao ácido tiobarbitúrico, grupos tiólicos não protéicos e atividade das enzimas superóxido dismutase e catalase), sugerindo que o efeito protetor do composto (5) não está relacionado à sua atividade antioxidante. Os resultados obtidos demonstram que o composto (5) apresenta atividade antioxidante in vitro e neuroprotetora em um modelo de amnésia, sugerindo que este composto pode ser promissor para o tratamento da doença de Alzheimer. No entanto, outros estudos são necessários para elucidar os mecanismos envolvidos na ação anti-amnésica deste composto, bem como o seu efeito em outros modelos de demência.

CO2 is a waste product from a number of human activities such as fossil fuel power generation, industrial manufacturing processes, and transport. The rising concentration of CO2 in the atmosphere is heating the planet’s surface via the well-established greenhouse effect; a mechanism for many irreversible climate change impacts. Coupled to this is the ever-increasing global pressure over the availability and access to fossil fuel reserves; the foundations of modern society. In recognition of this CO2 is gaining renewed interest as a carbon feedstock, a changing of attitude viewing it as an asset rather than waste. Carbon capture and utilisation (CCU) technologies are attempting to make use of it. However, little quantitative assessment work has been done to assessand verify such potentials. This thesis applies the principles and framework of the life cycle assessment (LCA) - environmental management tool to early stage CO2 utilisation laboratory processes. All processes employ engineered nanomaterials (ENM) to perform this function, a material class leading the way in the challenges of efficient and feasible CO2 chemistry. The LCA contribution in this thesis acts as a measuring and a guiding tool for technology developers, in the first instance to document the cradle-to-gate impacts of a number of formed ENMs. Appreciating the net environmental benefits of ENM uptake within society has yet to be wholly established, and the unavailability of data is recognised as a major factor. The work of this thesis will thus contribute to knowledge gaps, and be informative to wider community seeking to quantify technical performance benefits of ENMs in the context of net life cycle impact burdens. Finally the actual CCU processes are assessed, initially within the confines of the laboratory but further expanded for consideration at more industrially relevant scales. The potential for sound CCU performance were found achievable under best case conditions, with net GHG impact reductions over the life cycle, and the potential for lower impact carbon products, even carbon negative. However other environmental impacts such as ozone depletion, toxic emissions and the consumption of precious metalores are impacts that require consideration in the use of such technologies.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2016.
This study has explored the CVD synthesis of carbon nanofibres (CNFs) using Eskom’s waste coal fly ash as a catalyst with acetylene and hydrogen as the carbon source and carrier gas, respectively. In the process, a possible growth mechanism for these carbon nanofibres was sought. CNFs were successfully synthesised from fly ash and were found to have an average diameter of 22±7 nm. The growth mechanism of these CNFs was studied using EDS, TEM and laser Raman spectroscopy. It was observed that CNFs grew via root growth on spherical particles of fly ash and by tip growth on irregular-shaped metal oxide agglomerates. Both of these were found, through EDS analysis, to be Fe-rich. CNFs were functionalised between 2-12 h under reflux at 110 °C using a 3:1 (v/v) combination of HNO3 and H2SO4 in order to introduce functional groups onto their surfaces to act as anchors for hydrophilic reactants. The functionalisation of these CNFs was studied using TEM, laser Raman spectroscopy, ATR-FTIR spectroscopy, PXRD, BET, XRF and TGA. ATR-FTIR spectroscopy showed that some carbonyl functional groups were present on the surfaces of these CNFs after functionalisation. The functionalised CNFs (fCNFs) were then treated using a simple hydrothermal method to deposit 10% (m/m) of TiO2 nanoparticles onto their surface. This hydrothermal method employed the drop-wise addition of TiCl4 to a cold water-fCNFs mixture, which was then refluxed at 115 °C for 2-12 h. Laser Raman spectroscopy confirmed the presence of both TiO2 (phase pure anatase) and CNFs. ATR-FTIR spectroscopy provisionally revealed the presence of covalent Ti-O-C bonds. Studies where the duration of exposure to TiCl4 and the functionalisation time of CNFs were examined showed that the particle size and agglomeration of the TiO2 nanoparticles did not affect the surface area of the CNF-TiO2 hybrids significantly. However, CNF-TiO2 hybrids which were shown by TGA to have high fly ash content were observed to have low surface areas. fCNFs functionalised at 2 h had the highest surface area, at all fixed durations of exposure to TiCl4 by comparison with fCNFs which had been functionalised for longer periods.
GR2016

碩士
國立中央大學
化學工程與材料工程研究所
98
Nanosized gold catalyst has been reported to be a good catalyst for the liquid phase hydrogenation reactions due to their excellent activity and selectivity. In this research, two investigations were carried out on the gold catalyst: the affection of cobalt oxides and palladium to gold catalysts. A series of Au catalysts supported on CoOx-TiO2 with various Co contents were prepared. CoOx-TiO2 support was prepared by incipient-wetness impregnation with aqueous solution of Co(NO3)2 on TiO2. Gold catalysts were prepared by deposition-precipitation method (DP) with 1 wt. % Au loading. The molar rations of Co to Ti were 0, 1/99, 6/94, 1/9, 2/8, 3/7 and 1.0, respectively. The catalysts were denoted as Au/CoOx-TiO2 (m), where m represented the atomic ratio of Co/Ti. Palladium was added as a second metal on TiO2 which were prepared by impregnation with aqueous solution of Pd(NO3)2. Gold catalysts were prepared by deposition-precipitation method (DP) with 1 wt. % Au loading. After preparation, the catalysts were reduced under H2 at 423oC for 2h and reduced by sodium borohydride in the methanolic solution (50/50 methanol/water) at 298K under vigorous stirring and used nitrogen stream to remove air. These catalysts were characterized by inductively-coupled-plasma-mass spectrometry (ICP-MS), X–ray diffraction (XRD), transmission electron microscopy(TEM), high resolution transmission electron microscopy(HR-TEM), X-ray photoelectron spectroscopy(XPS) and temperature programmed reduction (TPR). The catalytic properties of gold based catalysts were studied on hydrogenation of p–chloronitrobenzene (p-CNB). The conditions for hydrogenation reaction were 1.2 MPa H2 pressure, 353 K reaction temperature and 500 rpm stirring speed. Methanol was used as the solvent, the concentration of p-CNB was 0.2 M (2.54g p–CNB in 80 ml methanol) and the amount of gold based catalyst was 0.5g. The cobalt oxide in Au/CoOx-TiO2 plays the role of a textural promoter, prevents from sintering of gold particle, increased active sites, and then enhanced catalytic activity. Cobalt not only good in steric effect, but also be an electronic promoter, which donated partial electronic to Au. Au/CoOx-TiO2 (1:9) exhibited the highest activity among the series of Au/CoOx-TiO2. The Au-Pd/TiO2 catalyst which reduced by NaBH4 could reached 100% conversion at 180 min reaction time. The results showed that NaBH4 reduction could prevent Au0 from being oxidized, increased the active site. It could be concluded that suitable cobalt amount shows the best performance, and palladium could promote the conversion effectively.

Polyolefins are the most important commodity polymers today. Their end use properties polymers depend primarily on their molecular weight (MWD) and chemical composition (CCD) distributions. Several characterization techniques are used to analyze the microstructures of the polyolefins. High-temperature gel permeation chromatography (GPC) is the most widely used technique for MWD determination. Temperature rising elution fractionation (TREF) and crystallization analysis fractionation (CRYSTAF) are routinely used for CCD measurement. There have been significant improvements over the last few years on CCD characterization techniques for polyolefins with the introduction of crystallization elution fractionation (CEF) and high-temperature thermal gradient interaction chromatography (HT-TGIC). The main objective of this thesis was to conduct systematic studies on HT-TGIC and CEF to provide a better understanding on the separation mechanism of these new techniques and to find out operational conditions that enhance the resolution of the measured CCDs. The effects of cooling rate, adsorption/desorption temperature range, heating rate and sample size on HT-TGIC fractionation were investigated using polyethylene and ethylene/1-octene copolymers made with metallocene catalyst. It was found out that HT-TGIC was relatively insensitive to the cooling rate within the range investigated in this study. However, the obtained profiles depended strongly on the heating rate applied during the desorption cycle. Chromatograms measured under faster heating rates were broader and had lower resolutions, supposedly due to co-desorption effects. Analysis of polyolefin blends by HT-TGIC showed that sample volume was a very important parameter affecting peak separation of the blend components; reducing the volume of the injected sample can be used to minimize the degree of co-adsorption and co-desorption effects. The effect of solvent type on HT-TGIC analysis was investigated using o-dichlorobenzene (ODCB), 1,2,4-trichlorobenzene (TCB), and chloronaphthalene (CN). Polyolefin blends were analyzed using these solvents and the best resolution was obtained iv when ODCB was used as the mobile phase. The profiles obtained using TCB and CN were similar and both were strongly affected by the co-adsorption and co-desorption phenomena. HT-TGIC profiles of ethylene homopolymers and ethylene/1-octene copolymers were also compared with the equivalent CEF profiles. Interestingly, it was found out that the differences between the profiles measured by these techniques decreased as the comonomer content increased, with CEF systematically measuring sharper profiles for samples with low 1-olefin comonomer content. A new method was also developed to quantify the degree of co-crystallization of polyolefin blends analyzed by CEF and was used to quantify operating conditions that influenced co-crystallization. The results showed that co-crystallization can be minimized using slower cooling rates, but heating rates play a less important role. A detailed study on the effect of CEF operating conditions on CCD resolution was also conducted using industrial LLDPE resins that have broad MWDs and CCDs. Cooling rate and solvent flow rate during the cooling cycle significantly affect the degree of co-crystallization of CEF profiles. However, varying the heating rate does not have a marked impact on these separations. The CEF profiles of these resins were compared with the equivalent HT-TGIC profiles, showing that CEF provided better peak separation than HT-TGIC. Finally, a new mathematical model was developed to simultaneously deconvolute the MWD and CCD of polyolefins made with multiple site-type catalysts such as Ziegler-Natta catalysts. The model was applied to several industrial linear low-density polyethylene (LLDPE) resins to estimate the minimum number of active site types, the number average molecular weight, the average comonomer mole fraction, and the mass fraction of soluble and non-soluble polymer made on each site type.

A new analytical technique to measure the chemical composition distribution (CCD) of polyolefins, crystallization elution fractionation (CEF), was introduced in 2006 during the First International Conference on Polyolefin Characterization. CEF is a faster and higher resolution alternative to the previous polyolefin CCD analytical techniques such as temperature rising elution fractionation (TREF) and crystallization elution fractionation (CRYSTAF) (Monrabal et al., 2007). Crystallization elution fractionation is a liquid chromatography technique used to determine the CCD of polyolefins by combining a new separation procedure, dynamic crystallization, and TREF. In a typical CEF experiment, a polymer solution is loaded in the CEF column at high temperature, the polymer is allowed to crystallize by lowering the solution temperature, and then the precipitated polymer is eluted by a solvent flowing through the column as the temperature is raised. CEF needs to be calibrated to provide quantitative CCD results. A CEF calibration curve consists of a mathematical relationship between elution temperature determined by CEF and comonomer fraction in the copolymer that could be estimated by Fourier transform infrared spectroscopy (FTIR) and carbon-13 nuclear magnetic resonance (13C NMR). Different comonomer types in ethylene/α-olefin copolymers will have distinct calibration curves. The main objective of this thesis is to obtain CEF calibration curves for several different ethylene/α-olefin copolymers and to investigate which factors influence these calibration curves. A series of homogeneous ethylene/α-olefin copolymers (1-hexene, 1-octene and 1-dodecene) with different comonomer fractions were synthesized under controlled conditions to create CEF calibration standards. Their average chemical compositions were determined by 13C NMR and FTIR and then used to establish CEF calibration curves relating elution temperature and comonomer molar fraction in the copolymer.

碩士
國立中央大學
化學工程與材料工程學系
105
Nano-palladium catalyst has been reported to have high activity for hydrogenation reaction but selectivity of main product, p-chloroaniline (p-CAN), was low. In this study, gold-palladium bimetals were loaded on spherical silica to form the egg-shell catalyst and used different ratio of Au/Pd metal on silica to carry out the p-CNB hydrogenation reaction. All the catalysts were characterized by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS). The condition of hydrogenation reaction was room temperature as reaction temperature, 0.55MPa as H2 partial pressure and at 300 rpm stirring rate. The average particle size of Pd-Au/SiO2 fresh catalyst was smaller than that of Pd/SiO2 and the active metals were highly dispersed on SiO2 support surface. In the early stage of reaction, metals still maintained high dispersion. The main reason is adding gold as promoter can prevent metals from agglomeration and dispread Pd to single active site. However, after long time on the stream, metals agglomeration on silica surface and larger particle size were observed and resulted in decrease in active metals and lead to deactivation. Besides, the activity of catalyst was significantly decreased but selectivity of p-CAN was not obvious change in p-CNB hydrogenation reaction. Therefore, metals composition was not serious change after the reaction.

A study of the effect of catalyst properties on the synthesis of carbon nanotubes (CNTs) is done in this thesis. Three different metal alloy catalysts, Fe/Ti, Ni/Ti, Co/Ti, have been studied. Various atomic concentrations and thicknesses were cosputter deposited on clean Si wafers using AJA Orion 4 RF Magnetron sputter deposition tool at 5mtorr and 17��C, and the films were characterized using a scanning electron microscope, Energy-dispersive X-ray spectroscopy. All the alloys have been annealed at 650��C and 3 torr in an argon atmosphere at 100 SCCM, followed by ammonia gas plasma etch at different powers at 3 torr and 50 SCCM NH��� flow in a modified parallel plate RF chemical vapor deposition tool for 1 minute. The influence of plasma power, thickness of catalyst and concentration of Ti the secondary metal in the alloy composition, on the surface morphology of the catalyst are investigated by characterizing them with atomic force microscopy. The study has shown that the surface roughness is affected by Ti concentration, thickness and plasma power. The 35 W power NH��� plasma produced rougher surfaces when compared to the 75 W NH��� plasma. The result is interpreted as follows: ion bombardment leads to greater etching of the catalyst surface. Thus, plasma power must be optimized for catalyst thin film and etch time. The study has provided an in depth analysis and understanding of the various factors that influence catalyst surface morphology which can be applied into further study for optimizing parameters for synthesis of single walled CNTs. Following this, a study on catalysts for CNT synthesis was performed using Plasma enhanced chemical vapor deposition and characterized by scanning electron microscope. CNTs were synthesized on Ni, Ni-Ti, Co, Co-Ti and Fe catalyst. Ni, Ni-Ti catalyst produced forest like vertically aligned CNTs whereas Co, Co-Ti produced vertically aligned free standing CNTs. The growth was dense and uniform across the substrate. Initial growth runs on Fe, Fe-Ti alloy did not produce any CNTs until catalyst was restructured with a thicker Ti under layer after an investigation using Secondary ion mass spectrometry of suspected Fe catalyst poisoning due to reaction with Si substrate. A room temperature run was carried out on annealed and plasma etched Ni catalyst and no CNTs were produced indicating the importance of substrate temperature of CNTs. A deeper understanding of factors of influence on CNTs such as catalyst types, structure/morphology, and substrate temperature has been achieved with this study.
Graduation date: 2013

碩士
國立東華大學
化學系
100
N-Heterocyclic Carbenes (NHCs) was a stable carbene, which was strong σ-donor character and considered to be of low toxicity. Triptycene was a very rigid structure, and we used triptycene as a ligand to synthesize the stable NHCs 1、2, and make it becomes a palladium (Pd) complex then into use of cross-coupling reactions. We found the ligands 1-di (1) and 2-di (2) are active catalytic ligands which can giving the good results to react with aryl halides and heterocyclic halides then catalyzed the Sonogashira reaction with aryl alkynes . Under different conditions, the ideal yield could up to 99%. We also test the catalytic recycling of 1, and it can be used in 3 to 5 times in different conditions.