Dissertations / Theses on the topic 'Titanium nitride'

Thin film coatings are used to improve the properties of components and products in such diverse areas as tool coatings, wear resistant biological coatings, miniature integrated electronics, micro-mechanical systems and coatings for optical devices. This thesis focuses on understanding the development of intrinsic stress and microstructure in coatings of the technologically important materials of aluminium nitride (AlN) and titanium vanadium nitride (TiVN) deposited by filtered cathodic arc deposition. Thin films of AlN are fabricated under a variety of substrate bias regimes and at different deposition rates. Constant substrate bias was found to have a significant effect on the stress and microstructure of AlN thin films. At low bias voltages, films form with low stress and no preferred orientation. At a bias voltage of -200 V, the films exhibited the highest compressive stress and contained crystals preferentially oriented with their c axis in the plane of the film. At the highest bias of -350 V, the film forms with low stress yet continue to contain crystallites with their c axis constrained to lie in the plane of the film. These microstructure changes with bias are explained in terms of an energy minimisation model. The application of a pulsed high voltage bias to a substrate was found to have a strong effect on the reduction of intrinsic stress within AlN thin films. A model has been formulated that predicts the stress in terms of the applied voltage and pulsing rate, in terms of treated volumes known as thermal spikes. The greater the bias voltage and the higher the pulse rate, the greater the reduction in intrinsic stress. At high pulsing and bias rates, a strong preference for the c axis to align perpendicular to the substrate is seen. This observation is explained by dynamical effects of the incident ions on the growing film, encouraging channelling and preferential sputtering. For the first time, the effect of the rate of growth on AlN films deposited with high voltage pulsed bias was investigated and found to significantly change the stress and microstructure. The formation of films with highly tensile stress, highly compressive stress and nano-composites of AlN films containing Al clusters were seen. These observations are explained in terms of four distinct growth regions. At low rates, surface diffusion and shadowing causes highly porous structures with tensile stress; increased rates produced Al rich films of low stress; increasing the growth rate further led to a dense AlN film under compressive stress and the highest rates produce dense, low stress, AlN due to increased levels of thermal annealing. Finally this thesis analyses the feasibility of forming ternary alloys of high quality TiVN thin films using a dual cathode filtered cathodic arc. The synthesised films show exceptional hardness (greater than either titanium nitride or vanadium nitride), excellent mixing of the three elements and interesting optical properties. An optimum concentration of 23% V content was found to give the highest stress and hardness.

Metal nitrides have gained interest due to their high melting point, mechanical resistance, thermal and electrical conductivity. To the best of our knowledge, titanium nitride (TiN) and molybdenum nitride (MoN) electrodes have always been prepared as thin films. However, thin film electrodes tend to delaminate or crack during preparation or usage which exposes the underlying substrate and increases their surface area. In addition, the vapour deposition techniques employed to prepare thin films can introduce contaminants to the samples. In this work we prepared solid metal nitride samples, characterised them with a range of physical methods and investigated their electrochemical properties. Our work demonstrates the feasibility of obtaining TiN and MoN from Ti and Mo foils and microwires via nitridation in a NH3 atmosphere. The process was confirmed using energy dispersive X-ray spectroscopy and X-ray diffraction (XRD). The XRD spectra also showed that hexagonal MoN and cubic Mo2N were obtained. This work also demonstrates the viability of fabricating solid TiN and MoN microelectrodes, microdisks and microbands, from the nitrided Ti and Mo samples. Hence a major objective of the project was to assess whether TiN and MoN could be used as alternatives to conventional microelectrode materials such as Pt, Au, and C. To the extent of our knowledge, MoN and TiN wires have never been used to construct microelectrodes. The electrochemical behaviour of the solid TiN and MoN microelectrodes is assessed using different redox mediators to cover a range of redox potentials. The cyclic voltammograms recorded with the untreated TiN microband electrodes showed that the redox processes at positive potentials were not electrochemically reversible. Yet, the electrochemical response was improved after etching the TiN surface with hydrofluoric acid vapour. In contrast, MoN microelectrodes exhibited sigmoidal shape cyclic voltammograms with a plateau region for all redox mediators even without surface treatment. The TiN and MoN microelectrodes exhibited good activity towards the oxygen reduction reaction recorded in pH 1, 7, 10, and 14. The TiN and MoN microelectrodes were also employed to assess their properties towards the reduction of peroxodisulfate, a very strong oxidising agent with a very complex reduction process. This study also employed bare Au, bare Pt, nanostructured Pt, and bismuth-adsorbed Pt microdisk electrodes to search for the electrode that produces a stable and preferably a diffusion-controlled current for the reduction of peroxodisulfate. Cyclic voltammograms with a plateau region were obtained with the nanostructured Pt, bismuth-modified Pt, HF-etched TiN, and MoN microelectrodes but not with the bare Au and bare Pt microelectrodes. However, only MoN microdisks demonstrated a stable steady-state current for the reduction of peroxodisulfate. To our knowledge, no group has observed cyclic voltammograms with a plateau region when employing bare electrodes for the reduction of peroxodisulfate. A linear relationship between the current and concentration was obtained with the MoN microdisk electrodes for concentrations above 0.1 mM. Similarly, the MoN microdisk electrode produced a diffusion-controlled current for scan rates between 5 and 50 V s-1. Overall, the MoN microelectrodes produced more reliable amperometric results than the TiN microelectrode. Thus, the MoN microelectrodes could be exploited as an alternative to the conventional Pt, Au, and C microelectrodes.

The use of ceramic has gradually increased over the past few years. Si3N4 is one of the most important ceramics used as structural material for high temperature applications. The practical use of advanced ceramics depends on the reliability of ceramic/metal joining techniques and the properties of the resulting interfaces. This work focuses on various aspects of diffusion bonding of Si3N4 to Ti as well as on the use of Ti-foil interlayer during the self-joining of Si3N4. Si3N4/Ti and Si3N 4/Ti-foil/Si3N4 combinations were diffusion joined by hot-uniaxial pressing and the microstructural characterization of the resulting interfaces was carried out by SEM, EPMA, and X-ray diffraction.
Diffusion bonding was carried out at temperatures ranging from 1200 to 1500ºC using different holding times, pressures, and surface roughness of the joining materials. The results showed that Si3N4 could not be bonded to Ti at temperatures lower than 1400ºC, however successful joining at higher temperatures. Joining occurred by the formation of a reactive interface on the Ti side of the joint. At temperatures greater than 1330ºC, liquid formation occurred by the interaction of Ti with Si promoting bonding, as well as the high affinity of Ti for Si resulted in rapid interface formation of silicides, initially Ti5Si3. EPMA and X-ray diffraction confirmed the presence of Ti5Si3, TiSi, and TiN at the interface. The surface roughness of the joining materials plays an important role since thicker interfaces were obtained for polished samples compared to as-ground samples. The interfaces grew in a parabolic fashion with the formation of various Ti-silicides (Ti5Si3 and TiSi) as well as Ti-nitride (TiN) at the interface.
Evaluation of joint strengths as a function of the experimental parameters such as, joining temperature and time was obtained by four-point bending test performed on Si3N4/Ti/Si3N4 joints. Strong joints were produced at joining temperatures greater than 1450ºC with average bend strength of more than 100 MPa. The maximum joint strength was obtained in samples hot-pressed at 1500ºC and 120 minutes reaching a value of 147 MPa.

In the industry of metal cutting tools the conditions are extreme; the temperature can vary thousand degrees rapidly and the pressure can be tremendously high. To survive this kind of stress the cutting tool must be both hard and tough. In order to obtain these properties different coatings are used on a base of cemented carbide, WC-Co. Common coatings are hard ceramics like titanium nitride and titanium carbon-nitride with an outer layer of aluminium oxide. In this thesis the possibility of using titanium dioxide as an interlayer between titanium carbon-nitride and aluminium oxide to control the morphology and phase of aluminium oxide is investigated. Of the different aluminium oxide phases only the alpha-Al2O3 is stable. The titanium carbon-nitride coatings are made by CVD (chemical vapour deposition); also the alumina is deposited by CVD. The titanium dioxide was deposited by atomic layer deposition (ALD) which is a sequential CVD technique that allows a lower deposition temperature and better control of the film growth than CVD. The obtained thin films were analyzed using XRD, Raman spectroscopy, ESCA and SEM. To test the adhesion of the coatings the samples were sand blasted. A thin interlayer of titanium dioxide causes the aluminium oxide to grow as alpha-Al2O3, thinner TiO2 gave better adhesion.

Transition metal nitrides have recently garnered much interest as alternative materials for robust plasmonic device architecture including potential applications in solar absorbers, photothermal medical therapy, and heat-assisted magnetic recording. Titanium nitride (TiN) is one such potential candidate. One advantage of the transition metal nitrides is that their optical properties are tunable according to the deposition conditions. The controlled achievement of tunability, however, is also a challenge. Although the formation of TiN has been the subject of numerous previous studies, a thorough analysis of the deposition parameters necessary to form metallic TiN films optimized for plasmonic applications had not been demonstrated. Similarly, such TiN films had not been subjected to detailed optical measurements which could be used in FDTD device simulations to optimize plasmonic device designs. To be able to design, simulate and build robust and optimal device structures, in this work a systematic and thorough examination of the effect of varied substrates, temperatures, and reactive gas compositions on magnetron sputtered TiN was conducted. In addition, the effects of application of an additional substrate bias were studied. The resulting optical properties at visible to near-infrared frequencies were the focus of this thesis. The optical properties of each film were measured via spectroscopic ellipsometry with more "metallic” films demonstrating a larger negative value of the real part of the permittivity. These optical measurements were correlated with both the films’ deposition conditions and microstructural measurements including x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), and transmission electron microscopy (TEM) measurements; the different deposition conditions resulted in TiN and TiOxNy films with widely tunable optical responses. By sputtering under different conditions, the value of the real part of the permittivity was tuned from small positive values, through small and moderate negative values, and finally all of the way to large negative values which are comparable to those measured in gold. It was determined that both the chemical composition as well as the film crystallinity had a significant effect on the resulting properties with the most metallic films in general exhibiting a Ti:N ratio close to 1:1, low oxygen incorporation, more N bound as TiN rather than in oxynitride form, and better crystallinity. Increased substrate temperature in general increased the metallic character while application of a substrate bias reduced crystalline order, however also reduced oxygen incorporation and allowed for deposition of metallic TiN at room temperature. The close lattice match of TiN and MgO allowed for heteroepitaxial growth on this substrate under carefully controlled conditions. Finally, to demonstrate the viability of the optimized TiN thin films for plasmonic applications, three benchmark plasmonic structures were simulated using the measured, optimized optical properties including a plasmonic grating coupler, infrared nanoantennas, and a nanopyramidal array. The devices were successfully fabricated and preliminary measurements show promise for plasmonic applications for example in solar conversion and photothermal medical therapy.
Engineering and Applied Sciences - Applied Physics

The Thesis described within the scope of the Master Program is focused on cermets, which belong among cutting materials. The introductory portion of the Thesis presents the characteristics of cermets from the perspective of production, physical-mechanical characteristics, marking and usage in cutting. The core portion of the Thesis focuses on the role of cermets in the category of leading world producers of tools and instrumental materials, cutting evaluation, and the suggested working conditions of cermets in lathing operations. The working conditions are prepared for steel and cast iron. The conclusion of the Thesis focuses on a technical-economical analysis of cermets.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.
Includes bibliographical references (p. [116]-[127]).
This thesis reports an integrated optical wavelength specific switching device for applications in optical integrated circuits (OICs) based on micro electromechanical systems (MEMS). The device consists of a ring resonator add-drop filter and a conductive MEMS bridge which is actuated by electrostatic force. Introducing conductive material into the electromagnetic evanescent field of the ring waveguide results in loss in the propagating light within, disabling the resonance and the filtering capabilities of the ring resonator. Therefore, by actuating the MEMS bridge in and out of the waveguide's evanescent field, the filter can be toggled between the on and off states. One large problem that must be faced when fabricating and actuating a MEMS cantilever or bridge structure for this type of device is the residual stress that may deflect the structure in an undesired way. This is because the vertical displacement of the structure is crucial. In order to solve this problem, this thesis is based on the use of titanium nitride (TiN) as structural material for the bridge. Titanium nitride has very attractive mechanical properties as well as good conductivity, which makes it an ideal structural material for electrostatically actuated devices.
(cont.) Moreover, the residual stress within the material can be relieved by proper control of deposition conditions and/or post processing. This thesis focuses on the post process annealing of titanium nitride in order to eliminate the residual stress in the structure and obtain a fiat bridge profile. Titanium nitride MEMS bridge structures were fabricated and tested. Their deflection from a flat state and stress was measured and characterized, and a structure with minimal residual stress was successfully fabricated. The actuation of the MEMS bridge is also demonstrated, and its characteristics are analyzed. Also discussed is the possibility of extending the design of the MEMS switch to implement the three-electrode ultra-fast strain-induced switching and MEMS wavelength tuning of an integrated optical filter. A realistic design of these devices is proposed in context with the requirements imposed by the optical telecommunication industry, and fabrication methods are considered. Simulations have been conducted using finite element analysis and mode solving to establish the feasibility of these designs.
y Satoshi Takahashi.
S.M.

Titanium nitride coatings, because of their high hardness, resistance to corrosion and wear and gold-like appearance, are widely used in industrial applications ranging from coating of decorative items to protection of cutting and forming tools against wear and corrosion. Because of their excellent tribological properties especially their suitability in cutting, abrasive and erosive wear application, titanium nitride coatings have attracted considerable research. The suitability of TiN coatings as excellent tribological coatings is explained by their high hardness, good adhesion to steel substrate and chemical stability. However, there is one critical shortcoming which affects the use of TiN coatings in commercial products. It is that TiN coatings show high friction coefficients against some counterfaces.

Economic and environmental considerations have resulted in a worldwide drive to increase the cycle efficiency of fossil fired power plant. Boiler designs able to achieve significant efficiency increases already exist; the limiting factor is the performance of materials. As a result, much effort is currently being focussed on the development of enhanced materials to increase their operating temperature and/or pressure. The requirement that such materials should possess good thermal fatigue performance in addition to good creep performance dictates the selection of ferritic and martensitic steels for many components. Thus, most of the development effort in this field is currently focussed on martensitic steels that can operate beyond the current maximum plant design of 290 barg/580°C up to 335barg/630°C or even beyond. The most advanced conventional ferritic steels such as E911, P92, P122 and NF12 are 9-12% Cr martensitic steels and gain their creep strength from the tempered martensite structure and the precipitated carbides and nitrides. Their long term creep performance is ultimately limited by the rate at which these precipitates coarsen or otherwise transform over time at elevated temperature. This research work presents the development of an alternative alloy which aims to increase the high temperature long term creep performance by replacing the relatively low stability carbides and nitrides present in conventional ferritic steels with a thermodynamically more stable dispersion of titanium nitride particles. To overcome the solubility limitation on precipitating a significant level of fine titanium nitride and to remove the dimensional constraints of gas phase nitriding, the innovative technique being developed here is one of solid state nitriding using a nitride donor. The microstructure and properties of the titanium nitride strengthened steels have been assessed at each stage of the alloy development using a range of optical and electron microscope examination techniques and hardness, tensile and creep mechanical assessment techniques. The results have shown that the processing route plays an important role in the development of the titanium nitride particles and these in turn play an important role in the development of the grain structure. The initial evaluation of the creep rupture properties found them to be very poor, below that of the base material. This was due to two factors; relatively coarse titanium nitride particles and very fine grain size (due to the titanium nitride particles pinning) which resulted in extensive grain boundary sliding. This research, therefore, investigates the development of the entire processing route, including the development of powder metallurgy and spray forming procedures with the aim of achieving a homogeneous dispersion of fine titanium nitride particles to resist dislocation creep and the development of a coarse interlocking grain structure to resist grain boundary sliding. The achievements in the creep properties are presented in comparison with conventional ferritic creep resistant steels and advanced ferritic steels such as PM2000. The properties achieved are discussed, not only in relation to the beneficial aspects such as creep strength and the effect this has on boiler cycle efficiency, but also in relation to deleterious effects that are a consequence of reduced creep ductility. Finally, possible mechanisms to improve the properties as well as methods of reducing the production costs are assessed with a view to achieving the overall objective of developing a commercially viable material.

Titanium Aluminum Nitride (TiAlN) is an important industrial coating that improves hardness and corrosion resistance. The objective of the present work is to develop chemical methods which selectively remove TiAlN coatings deposited on Titanium substrates. The selected stripping solution consists of hydrogen perox¬ide (H2O2) and potassium oxalate (K2C2O4). Coupons of Ti-6-4 coated with a notional 10 micron thick coating of TiAlN were exposed to a stripping solution at varying temperature and compositions. Overall, it was found that increasing the temperature of reaction or the concentration of reactants led to an increase in stripping rate of the coating and substrate. The selectivity also increased with an increase in tempera¬ture or potassium oxalate concentration, but decreased with an increase in hydrogen peroxide concentration. The highest stripping rate that was obtained for the coating was of 39 µm/hr at a tempe¬rature of 75oC, a concentration of hydrogen peroxide of 5.9 mol/L and a potassium oxalate concentra¬tion of 0.226 mol/L. At the same conditions, uncoated samples were found to be stripped at a rate of 6.6 µm/hr. The best selectivity that was obtained was of 6.8, at a potassium oxalate concentra¬tion of 0.226 mol/L, a hydrogen peroxide concentration of 4.4 mol/L and a 75oC temperature. It was also found that the ratio of Ti:Al in the coating had a major effect on its chemical resistance to H2O2 and K2C2O4 mixtures.
Titanium Aluminum Nitride (TiAlN) est un revêtement industriel important puisqu'il améliore la dureté et la résistance à la corrosion. L'objectif de ce travail est de développer des techniques chimiques qui enlèvent de façon sé¬lective des revêtements de TiAlN déposés sur des substrats de Titane. La solution chimique sélection¬née consiste de peroxyde d'hydrogène (H2O2) et d'oxalate de potassium (K2C2O4). Des échantillons de Ti-6-4 couverts d'une couche de TiAlN d'une épaisseur notionnelle de 10 micromètres ont été exposés à plusieurs solutions chimiques avec des températures et concentrations variées. De façon générale, nous avons trouvé que si on augmentait la température de la réaction ou la concentration des réactants, cela faisait augmenter les vitesses de dégradation du revêtement et du substrat. La sélectivité augmentait aussi avec une hausse de la température ou de la concentration d'oxalate de potassium, mais diminuait avec une hausse de la concentration de peroxyde d'hydrogène. La plus haute vitesse de dissolution du revêtement qui a été obtenue était de 39 µm/hr à une température de 75oC, une concentration de peroxyde d'hydrogène de 5.9 mol/L et une concentration d'oxalate de potassium de 0.226 mol/L. À des conditions similaires, le substrat se dissolvait à une vitesse de 6.6 µm/hr. La meilleure sélectivité obtenue était de 6.8, à une concentration d'oxalate de potassium de 0.226 mol/L, une concentration de peroxyde d'hydrogène de 4.4 mol/L et une température de 75oC. Nous avons aussi trouvé que le ratio de Ti:Al dans le revêtement a un impact majeur sur sa résistance chimique aux solutions de H2O2 et de K2C2O4.

Hydrogen is a clean and sustainable form of carrier of energy that can be used in mobile and stationary applications. At present hydrogen is produced mostly from fossil sources. Solar photoelectrochemical processes are being developed for hydrogen production. Storing hydrogen can be done in three main ways: in compressed form, liquid form and by chemical bonding. Near term spaceport operations are one of the prominent applications for usage of large quantities of liquid hydrogen as a cryogenic propellant. Efficient storage and transfer of liquid hydrogen is essential for reducing the launch costs. A Two Stage Reverse Turbo Brayton Cycle (RTBC) CryoCooler is being developed at University of Central Florida. The cryocooler will be used for storage and transport of hydrogen in spaceport and space vehicle application. One part in development of the cryocooler is to reduce the friction and wear between mating parts thus increasing its efficiency. Tribological coatings having extremely high hardness, ultra-low coefficient of friction, and high durability at temperatures lower than 60 K are being developed to reduce friction and wear between the mating parts of the cryocooler thus improving its efficiency. Nitrides of high-melting-point metals (e.g. TiN, ZrN) and diamond-like-carbon (DLC) are potential candidates for cryogenic applications as these coatings have shown good friction behavior and wear resistance at cryogenic temperatures. These coatings are known to have coefficient of friction less than 0.1 at room temperature. However, cryogenic environment leads to increase in the coefficient of friction. It is expected that a composite consisting of a base layer of a hard coating covered with layer having an ultra-low coefficient of friction would provide better performance. Extremely hard and extremely low friction coatings of titanium nitride, molybdenum disulphide, TiN/MoS2 bilayer coatings, DLC and DLC/MoS2 bilayer coatings have been chosen for this application. TiN film was deposited by reactive DC magnetron sputtering system from a titanium target and MoS2 film was deposited by RF magnetron sputtering using a MoS2 target. Microwave assisted chemical vapor deposition (MWCVD) technique was used for preparation of DLC coatings. These composite coatings contain a solid lubricating phase and a hard ceramic matrix phase as distinctly segregated phases. These are envisioned as having the desired combination of lubricity and structural integrity. Extremely hard coatings of TiN and DLC were chosen to provide good wear resistance and MoS2 was chosen as the lubricating phase as it provides excellent solid lubricating properties due to its lamellar crystal structure. This thesis presents preparation; characterization (SEM and XRD), microhardness and tribological measurements carried out on TiN and TiN/MoS2 coatings on aluminum and glass substrate at room temperature. It also presents initial development in preparation of DLC coatings.
M.S.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science and Engineering

Multilayered interference coatings based on titanium- and zirconium nitride and designed for solar control have been prepared using reactive d c magnetron sputtering. Preparation effects and degradation mechanisms were investigated. It was shown that the quality of the nitride strongly depends on the degree of crystallinity in the underlying oxide. It has been shown that the nitride layer partly oxidizes as the top oxide layer is deposited. The degradation is enhanced with temperature. A thin sacrificial layer of aluminium deposited between successive depositions of nitride and oxide is shown to improve the optical performance of the coating as preparedm as well as after accelerated ageing tests. The optical properties of opaque and semitransparent films of zirconium nitride have been studied. A thorough investigation of the influence of composition, deposition rate, substrate temperature and film thickness on the optical response of the film was performed. Both photometric and ellipsometric methods were used to determine thicknesses and the optical constants at wavelengths ranging from 0.23 to 25 μm. The resulting values of n and k, in the wavelength intervals where these independent methods are applicable, have been shown to agree extremely well. The results so far indicate an even larger potential for zirconium nitride based solar control coatings as compared to the titanium nitride based. Access to optical constants derived from films of zirconium nitride of variable quality made multilayer modelling a powerful tool in the design and analysis of solar control coatings.

The measurement of pH value is crucial parameter in various fields like, drinking water monitoring, food preparation, biomedical and environmental applications. The most common device for pH sensing is the conventional pH glass electrode. While glass electrodes have several advantages, such as Nernstian sensitivity, superior ion selectivity, excellent stability, and extensive operating range, they have several key disadvantages. pH glass electrodes need to be stored in buffer solutions, they are fragile and have limited size and shape, making them impractical for some applications, such as being potentially used as miniature pH sensors for capsule endoscopy and ambulatory esophageal pH monitoring. To address these issues of limitations of glass electrodes, various metal oxides have been investigated and proposed as potential electrode materials for the development of pH sensors. Solid metal sensors offer unique features such as insolubility, stability, mechanical strength, and possibility of miniaturization. However, the main drawback of the metal oxide pH sensors is the interference caused by oxidizing and reducing agents present in some sample solutions. To reduce the redox interference, metal nitride solid sensors were investigated in this project with the potential for the development of high-sensitivity pH sensing electrodes. Metal nitrides are refractory, have high melting points and interstitial defects, and, at room temperature, they are chemically stable and resist hydrolysis caused by weak acids. There are many reports on different metal nitrides electrodes in literature, of which several have been previously investigated for use as pH sensors. Here, specifically, thin films of titanium nitride (TiN) were manufactured using radio frequency magnetron sputtering. The effect of sputtering parameters (e.g., thickness, sputter power, gas composition) were investigated to optimize the materials for use as pH sensor. Additionally, the underlining mechanism governing the pH sensitivity of these metal nitrides was investigated by examining the pH sensing properties (i.e., sensitivity, hysteresis, and drift) and the effect of redox agents. The successfully optimized material was then used to construct and demonstrate the concept of a solid-state pH sensor using an appropriate reference electrode. The solid-state TiN sensor paves the way for future development of a miniaturised pH sensor capsule for biomedical applications or lab-on-a-chip pH sensor for environmental and industrial applications. Expending the realms of pH monitoring, currently limited by the glass pH electrode.

The development of cheap industrial scale H2 production from renewable sources is highly desirable to meet our future clean-energy demands. One promising route is water splitting using solar radiation. In this thesis, the individual components of a photocatalytic system were explored with the aim of applying earth-abundant and industrially relevant catalyst materials for sustainable chemistry. A family of cobalt acetate compounds was examined as potential water and biomass oxidation catalysts, and TiN nanoparticles were investigated as co-catalysts for photocatalytic hydrogen evolution. A significant challenge for realising industrial scale water splitting is the development of efficient, stable, and earth-abundant catalysts for the water oxidation half reaction. Co(III) species have long been known to facilitate water oxidation and cobalt acetate has been employed as a versatile industrial oxidation catalyst of alkyl aromatic molecules over the last 60 years. This has inspired a series of investigations to evaluate several oligomers from a family of cobalt acetate compounds as water oxidation catalysts (WOCs). Three model Co(III) acetate oligomers of different nuclearity, the Co-cubane, [Co4(μ3-O)4(μ-OAc)4(py)4], Co-trimer, [Co3(μ3-O)(μ-OAc)6(py)3][PF6], and Co-dimer, [Co2(μ-OH)2(μ-OAc)(OAc)2(py)4][PF6] were assessed. Complementary to developing more efficient WOCs, an alternative approach is to employ sacrificial agents, such as aromatic molecules, that are more easily oxidised than water. The ability of cobalt acetate to oxidise a variety of lignin model compounds was also explored. Lastly, commercialised semiconductors (i.e. TiO2) are restricted to absorbing ~ 5% of the energy of the terrestrial solar spectrum. TiN nanoparticles were explored as co-catalysts with TiO2 (P25) for photocatalytic H2 evolution via MeOH reformation due to their unique optical properties.

Afin de résoudre les problèmes environnementaux et énergétiques modernes, ces dernières années ont vu le développement de catalyseurs photocataytiques capables d’utiliser la lumière solaire. En effet, les possibles applications des semiconducteurs présentant des propriétés photocatalytiques dans les domaines de la production d’hydrogène ou la dégradation de polluants organiques ont généré un grand intérêt de la part de la communauté scientifique. Actuellement, les photocatalyseurs à base de dioxyde de titane (TiO₂) et de nitrure de carbone graphitique (g-C₃N₄) sont considérés comme les matériaux les plus étudiés pour leurs faibles coûts et leurs propriétés physico-chimiques exceptionnelles. Cependant, la performance photocatalytique de ces matériaux reste encore limitée, à cause de la recombinaison rapide des porteurs de charge et et d'une absorption limitée de la lumière. En générale, malgré des caractéristiques exceptionnelles, ces matériaux ne contribuent pas significativement à la séparation de charge et l’absorption de la lumière lorsqu’ils sont produits par des méthodes conventionnelles. L'objectif de cette thèse est de développer de nouvelles voies pour la production de matériaux efficaces basés sur TiO₂ et g-C₃N₄). Nous avons d'abord préparé de la triazine (CxNy) qui fonctionne comme un co-catalyseur d'oxydation ce qui facilite la séparation des paires «électron-trou» dans le système du photocatalyseur creux de type Pt-TiO₂-CxNy. La présence simultanée de Pt et de CxNy, qui servent comme co-catalyseurs de réduction et d'oxydation, respectivement, a permis une amélioration remarquable des performances photocatalytiques du TiO₂. De plus, nous avons développé une nouvelle approche, en utilisant un procédé de combustion de sphère de carbone assisté par l’air, pour préparer du C/Pt/TiO₂ . Ce matériau possède de nombreuses propriétés uniques qui contribuent de manière significative à augmenter la séparation « électron-trou », et en conséquence, à améliorer la performance photocatalytique. Dans le but de développer un matériau qui soit capable de fonctionner sous les rayons du soleil et dans l'obscurité, nous avons développé un photocatalyseur creux à double enveloppes : le Pt-WO₃/TiO₂-Au. Ce matériau a montré non seulement une forte absorption de la lumière solaire, mais aussi une séparation des charges élevée et une haute capacité de stockage d'électrons. Par conséquent, ce type de photocatalyseurs a montré une dégradation efficace des polluants organiques, à la fois sous la lumière visible (λ ≥ 420 nm) et dans l'obscurité. En ce qui concerne le g-C₃N₄, nous avons exploité la relation entre les lacunes d’azote et les propriétés plasmoniques des nanoparticules d’or (Au). Ce type de photocatalyseur du Au/g-C₃N₄ a été préparé en présence d’alcali suivi par une post calcination. En effet, les lacunes d’azote ainsi produites permettent le renforcement des interactions entre l’or et le g-C₃N₄ et des propriétés plasmoniques de l’or. Ces caractéristiques exceptionnelles renforcent l'utilisation efficace de l’énergie solaire ainsi que la séparation des paires « électron-trou », ce qui contribuent à la performance photocatalytique pour la production d'hydrogène du photocatalyseur. Afin d’améliorer la capacité d’absorption de la lumière visible de g-C₃N₄, une nouvelle voie de synthèse dénommée « poly-alcaline » a été développée. La possibilité d’ajouter du polyéthylèneimine (PEI) et de l’hydroxyde de potassium (KOH) pour générer de nombreux centres lacunaires en azote ainsi que des groupes hydroxyles dans la structure du matériau, a été explorée afin d’optimiser l’efficacité du matériau. De telles modifications ont démontré leurs capacités à réduire la bande interdite et à provoquer plus facilement la séparation de charges améliorant ainsi les propriétés photocatalytiques du photocatalyseur vis-à-vis de la production d’hydrogène. Cette méthode ouvre donc une nouvelle voie d’avenir pour préparer des photocatalyseurs nanocomposites efficaces possédant à la fois, une forte d’absorption de la lumière et une bonne séparation de charges.
Afin de résoudre les problèmes environnementaux et énergétiques modernes, ces dernières années ont vu le développement de catalyseurs photocataytiques capables d’utiliser la lumière solaire. En effet, les possibles applications des semiconducteurs présentant des propriétés photocatalytiques dans les domaines de la production d’hydrogène ou la dégradation de polluants organiques ont généré un grand intérêt de la part de la communauté scientifique. Actuellement, les photocatalyseurs à base de dioxyde de titane (TiO₂) et de nitrure de carbone graphitique (g-C₃N₄) sont considérés comme les matériaux les plus étudiés pour leurs faibles coûts et leurs propriétés physico-chimiques exceptionnelles. Cependant, la performance photocatalytique de ces matériaux reste encore limitée, à cause de la recombinaison rapide des porteurs de charge et et d'une absorption limitée de la lumière. En générale, malgré des caractéristiques exceptionnelles, ces matériaux ne contribuent pas significativement à la séparation de charge et l’absorption de la lumière lorsqu’ils sont produits par des méthodes conventionnelles. L'objectif de cette thèse est de développer de nouvelles voies pour la production de matériaux efficaces basés sur TiO₂ et g-C₃N₄). Nous avons d'abord préparé de la triazine (CxNy) qui fonctionne comme un co-catalyseur d'oxydation ce qui facilite la séparation des paires «électron-trou» dans le système du photocatalyseur creux de type Pt-TiO₂-CxNy. La présence simultanée de Pt et de CxNy, qui servent comme co-catalyseurs de réduction et d'oxydation, respectivement, a permis une amélioration remarquable des performances photocatalytiques du TiO₂. De plus, nous avons développé une nouvelle approche, en utilisant un procédé de combustion de sphère de carbone assisté par l’air, pour préparer du C/Pt/TiO₂ . Ce matériau possède de nombreuses propriétés uniques qui contribuent de manière significative à augmenter la séparation « électron-trou », et en conséquence, à améliorer la performance photocatalytique. Dans le but de développer un matériau qui soit capable de fonctionner sous les rayons du soleil et dans l'obscurité, nous avons développé un photocatalyseur creux à double enveloppes : le Pt-WO₃/TiO₂-Au. Ce matériau a montré non seulement une forte absorption de la lumière solaire, mais aussi une séparation des charges élevée et une haute capacité de stockage d'électrons. Par conséquent, ce type de photocatalyseurs a montré une dégradation efficace des polluants organiques, à la fois sous la lumière visible (λ ≥ 420 nm) et dans l'obscurité. En ce qui concerne le g-C₃N₄, nous avons exploité la relation entre les lacunes d’azote et les propriétés plasmoniques des nanoparticules d’or (Au). Ce type de photocatalyseur du Au/g-C₃N₄ a été préparé en présence d’alcali suivi par une post calcination. En effet, les lacunes d’azote ainsi produites permettent le renforcement des interactions entre l’or et le g-C₃N₄ et des propriétés plasmoniques de l’or. Ces caractéristiques exceptionnelles renforcent l'utilisation efficace de l’énergie solaire ainsi que la séparation des paires « électron-trou », ce qui contribuent à la performance photocatalytique pour la production d'hydrogène du photocatalyseur. Afin d’améliorer la capacité d’absorption de la lumière visible de g-C₃N₄, une nouvelle voie de synthèse dénommée « poly-alcaline » a été développée. La possibilité d’ajouter du polyéthylèneimine (PEI) et de l’hydroxyde de potassium (KOH) pour générer de nombreux centres lacunaires en azote ainsi que des groupes hydroxyles dans la structure du matériau, a été explorée afin d’optimiser l’efficacité du matériau. De telles modifications ont démontré leurs capacités à réduire la bande interdite et à provoquer plus facilement la séparation de charges améliorant ainsi les propriétés photocatalytiques du photocatalyseur vis-à-vis de la production d’hydrogène. Cette méthode ouvre donc une nouvelle voie d’avenir pour préparer des photocatalyseurs nanocomposites efficaces possédant à la fois, une forte d’absorption de la lumière et une bonne séparation de charges.
The utilization of solar light-driven photocatalysts has emerged as a potential approach to deal with the serious current energy and environmental issues. Over the past decades, semiconductor-based photocatalysis has attracted an increasing attention for diverse applications including hydrogen production and the decomposition of organic pollutants. Currently, titanium dioxide (TiO₂) and graphitic carbon nitride (g-C₃N₄)-based photocatalysts have been considered as the most investigated materials because of their low cost, outstanding physical and chemical properties. However, their photocatalytic performances are still moderate owing to the fast charge carrier recombination and limited light absorption. The main target of the research presented in this thesis is to develop novel routes to prepare efficient materials based on TiO₂ and g-C₃N₄. These materials possess prominent features, which contribute to address the fast charge separation and light absorption problems. We firstly have prepared triazine (CxNy) acting as an oxidation co-catalyst, which efficiently facilitates electron-hole separation in a Pt-TiO₂-CxNy hollow photocatalyst system. The co-existence of Pt and CxNy functioning as the reduction and oxidation co-catalysts, respectively, has remarkably enhanced the photocatalytic performance of TiO₂. Next, we have also developed a new approach employing the air- assisted carbon sphere combustion process in preparing C/Pt/TiO₂. This material possesses many salient properties that significantly boost the electron-hole separation leading to enhanced photocatalytic performance. In an attempt to design a material that can operate under sunlight and in darkness, we have introduced Pt-WO₃/TiO₂-Au double shell hollow photocatalyst. The material has shown not only strong solar light absorption but also efficient charge separation and electron storage capacity. As a result, this type of photocatalyst exhibits a high activity performance for the degradation of organic pollutants both under visible light (λ ≥ 420 nm) and in the dark. Regarding to g-C₃N₄, we have explored the relationship between nitrogen vacancies and the plasmonic properties of Au nanoparticles employing alkali associated with the post-calcination method to prepare Au/g-C₃N₄. In fact, the produced nitrogen vacancies in the structure of g-C₃N₄ essentially enhance the interaction at Au/g-C₃N₄ interface and the plasmonic properties of Au nanoparticles. These outstanding features contribute to enhance the utilization of solar light and electron-hole separation that prompt the photocatalytic performance towards hydrogen production. Finally, we have employed a novel poly-alkali route to prepare a strong visible light absorption photocatalyst-based g-C₃N₄. The co-existence of PEI and KOH, which induces numerous nitrogen vacancies and incorporated hydroxyl groups in the structure of the resulted material, has been explored for the first time. These modifications have been proved to narrow the bandgap and facilitate the charge separation leading to enhance the solar light-driven hydrogen production. This method also opens up a new approach to prepare efficient nanocomposite photocatalysts possessing both strong light absorption and good charge separation.
The utilization of solar light-driven photocatalysts has emerged as a potential approach to deal with the serious current energy and environmental issues. Over the past decades, semiconductor-based photocatalysis has attracted an increasing attention for diverse applications including hydrogen production and the decomposition of organic pollutants. Currently, titanium dioxide (TiO₂) and graphitic carbon nitride (g-C₃N₄)-based photocatalysts have been considered as the most investigated materials because of their low cost, outstanding physical and chemical properties. However, their photocatalytic performances are still moderate owing to the fast charge carrier recombination and limited light absorption. The main target of the research presented in this thesis is to develop novel routes to prepare efficient materials based on TiO₂ and g-C₃N₄. These materials possess prominent features, which contribute to address the fast charge separation and light absorption problems. We firstly have prepared triazine (CxNy) acting as an oxidation co-catalyst, which efficiently facilitates electron-hole separation in a Pt-TiO₂-CxNy hollow photocatalyst system. The co-existence of Pt and CxNy functioning as the reduction and oxidation co-catalysts, respectively, has remarkably enhanced the photocatalytic performance of TiO₂. Next, we have also developed a new approach employing the air- assisted carbon sphere combustion process in preparing C/Pt/TiO₂. This material possesses many salient properties that significantly boost the electron-hole separation leading to enhanced photocatalytic performance. In an attempt to design a material that can operate under sunlight and in darkness, we have introduced Pt-WO₃/TiO₂-Au double shell hollow photocatalyst. The material has shown not only strong solar light absorption but also efficient charge separation and electron storage capacity. As a result, this type of photocatalyst exhibits a high activity performance for the degradation of organic pollutants both under visible light (λ ≥ 420 nm) and in the dark. Regarding to g-C₃N₄, we have explored the relationship between nitrogen vacancies and the plasmonic properties of Au nanoparticles employing alkali associated with the post-calcination method to prepare Au/g-C₃N₄. In fact, the produced nitrogen vacancies in the structure of g-C₃N₄ essentially enhance the interaction at Au/g-C₃N₄ interface and the plasmonic properties of Au nanoparticles. These outstanding features contribute to enhance the utilization of solar light and electron-hole separation that prompt the photocatalytic performance towards hydrogen production. Finally, we have employed a novel poly-alkali route to prepare a strong visible light absorption photocatalyst-based g-C₃N₄. The co-existence of PEI and KOH, which induces numerous nitrogen vacancies and incorporated hydroxyl groups in the structure of the resulted material, has been explored for the first time. These modifications have been proved to narrow the bandgap and facilitate the charge separation leading to enhance the solar light-driven hydrogen production. This method also opens up a new approach to prepare efficient nanocomposite photocatalysts possessing both strong light absorption and good charge separation.

Titanium and boron nitride and carbide, titanium diboride were synthesized by carbothermic reduction as single phase as well as mixtures intended to form composite materials. The aim of the project is to study the physical chemistry of carbothermic reduction for the production of pure nonoxide ceramic powders and also for the in-situ formation of ceramic/ceramic partially-densified composites. The thermodynamic and kinetic factors that govern the phase constituents are discussed and the effect of processing parameters on the morphology and extent of reduction are also established. The first part of the present investigation is aimed at the production of titanium nitride, carbonitride and carbide powders and the in-situ formation of TiN/TiC partially-densified composites by the carbothermic reduction of titania in suitable nitriding atmospheres. The investigation includes the aspects of the thermodynamics and kinetics of the nitriding reaction and points out the reaction mechanism by identifying the phase formed after the nitridation process. The microstructures produced after the reduction-nitridation process have been correlated with the thermodynamic and kinetic parameters. The synthesized titanium nitride powder was identified as the carbonitride phase, Ti(CxN1_x), having a range of composition. The rate of reduction of TbO2 was found to be determined by the rate of oxygen diffusion in the sub-oxide lattice and the derived value of activation energy in the temperature range 1473K to 1773K from the Arrhenius plot is 120 kJ-mole-1 of T102. TI305 was found as a high temperature precursor phase for the formation of titanium nitride. The use of iron chloride as catalyst and activated charcoal in the mixtures of oxide increased the yield of titanium nitride phase by enhancing the rate of reduction of titanium oxides. The morphology of titanium carbonitride particles was dependent upon the reactivity of carbon and the temperature. The calculated equilibrium phase fields were found to be in agreement with the experimental data and provide a means to select the variables for the reduction condition for designing a required ceramic microstructure. The microstructure of boron nitrides is closely related to the structural chemistry of carbon and nitriding agent. The main aim of the second part of the project was to synthesize boron nitride and carbide powders and whiskers by carbothermic reduction of boric anhydride (6203) in nitrogen atmosphere and also to understand a relation between the processing parameters and the phases produced. The effect of processing conditions such as the gas composition, reactivity of carbon, reaction temperature and time as well as the composition of starting materials on the synthesis of boron nitride and carbide phases were studied. The reactivity of carbon, B/C ratio and gas composition were the most important variables that determined the formation, structure and morphology of the nitride. During the nitridation process, boron carbide phase also formed and played a significant role. The investigation also reports the evidence for the formation of metastable forms of BN i. e wurtzite and cubic BN. We also report the results of the solubility of nitrogen in C-saturated B4C structure. The third part of the present work is aimed at the production of TiB2 powders. Aspects of the formation of two or three ceramic phase mixtures were also examined together with the relative stability of the single phase mixed diborides with respect to pure diboride phase. The central aim of this part is to establish the mechanism of the synthesis reaction leading to the formation of uniform size of titanium diboride crystals. Titanium boride (TiB2) powder was produced in the powder form by the reduction of ingredient oxides with carbon via a gas-solid phase reaction. For the production of the composite microstructure, the nitrogen partial pressure was found to be the most critical factor. In the composite microstructure, the titanium nitride particles have a submicrometer size whereas the boride particle size is only a few micrometers with predominantly hexagonal morphology. Some calculated equilibrium phase fields have been experimentally verified. The empirical verification is a useful tool to establish the correctness of the calculated phase diagram. The theoretical approach therefore enables to identify the condition for the formation of phase mixtures. The constituent phases depend on the reduction conditions. For example, nitrides in equilibrium with Ti62 can only form above a critical nitrogen partial pressure whereas TiC or B4C form in the inert atmospheres. This result is applicable to all other ceramics. The investigation also shows the viability of production of the composite powder mixture via the oxide co-reduction technique. The synthesis of TIB2/TiN, TiB2ýC, TB2/TN/BN and mixed diboride composites is possible by employing the reduction route.

In this work, we investigate the relation between the diffusion behavior of Ti1-xAlxN at elevated temperatures and the microstructure. Thinfilm samples are synthesized by reactive co-sputtering with two cathodes. One cathode equipped with Ti target is connected to a highpower impulse magnetron sputtering (HiPIMS) power supply, and the other cathode equipped with Al target is operated with a directcurrent power source. The spinodal decomposition of cubic metastable Ti1-xAlxN controlled by thermally activated diffusion is observe fordiffusion behavior. Various HiPIMS pulsing frequencies are used to achieve different microstructure, while altered power applied to Altarget is used to change the Al content in films. In the phase composition analysis achieved by GI-XRD, the right-shift of (111) film peakalong with increasing Al-power is observed. A saturation of the right-shift and h-AlN peaks are also observed at certain Al-power. Thechemical composition determined by ERDA shows trends of reducing Al solubility limit in metastable phase and O contamination upondecreasing the pulsing frequency. More N deficiency is found in samples deposited with higher frequency. In the 500 Hz and 250 Hzsamples deposited into similar composition and thickness, no apparent difference of the microstructure is observed from the SEM crosssectionalimages. From HT-XRD, we observe higher intensity of TiO2 and h-AlN peaks in 500 Hz sample at elevated temperature ascompared with 250 Hz one. From the reduction of O contamination, denser Ti1-xAlxN films are able to be deposited with lower HiPIMSpulsing frequency. In addition, the higher intensity observed in HT-XRD patterns indicates that the 500 Hz sample is more open todiffusion and therefore allows the new formed phases to grow in larger grains.

TiN is used commercially as a wear resistant coating on cutting tools and as a diffusion barrier in microelectronics. TiN has gained increased interest as a material for MEMS, however there has been very little work carried out in the area of patterning and releasing TiN for use as a structural MEMS material. This thesis presents an investigation into the patterning and release of filtered arc deposited TiN thin films using surface micromachining techniques. Two novel strategies are presented for patterning TiN thin films and are achieved using excimer laser micromachining and photolithographic wet-etching. TiN was deposited onto single crystal Si and Cr and Cu sacrificial layers on Si. The use of Cr as a sacrificial layer was found to facilitate the best quality patterning of the TiN and hence the majority of the work involved using Cr sacrificial layers. TiN was deposited using partial filtration and full filtration and differences in the ability to selectively laser pattern the TiN from the Cr sacrificial layer are presented. Various analytical techniques were employed to investigate the origin of the difference in laser patterning the TiN thin films. The establishment of TiN and Cr as a novel material combination for surface micromachined MEMS was extended by etching the Cr sacrificial layer to facilitate the release of TiN stress-measurement structures. The major finding of this thesis is that filtered arc deposited TiN thin film on Cr can be used as a material combination to surface micromachine freestanding TiN structures as high quality patterning and etch selectivity can be achieved using both excimer laser micromachining and photolithographic wet-etching.

This thesis describes the synthesis, characterization and photocatalytic applications of carbon nitride (C3N4) and titanium dioxide (TiO2) materials. C3N4 was prepared from the thermal decomposition of a trichloromelamine (TCM) precursor. Several different reactor designs and decomposition temperatures were used to produce chemically and thermally stable orange powders. These methods included a low temperature glass Schlenk reactor, a high mass scale stainless steel reactor, and decomposition at higher temperatures by the immersion of a Schlenk tube into a furnace. These products share many of the same structural and chemical properties when produced by these different methods compared to products from more common alternate precursors in the literature, determined by infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and elemental analysis. C3N4 is capable of utilizing light for photocatalysis due to its moderate band gap (Eg), measured to be between 2.2 and 2.5 eV. This enables C3N4 to be used in the photocatalytic degradation of organic dyes and the production of hydrogen via the water-splitting reaction. C3N4 degraded methylene blue dye to less than 10% of its initial concentration in less than an hour of UV light illumination and 60% under filtered visible light in 150 minutes. It also degraded methyl orange dye to below 20% in 70 minutes under UV light and below 60% in 150 minutes under visible light. Using precious metal co-catalysts (Pt, Pd, and Ag) photo-reduced onto the surface of C3N4, hydrogen was produced from a 10% aqueous solution of triethanolamine at rates as high as 260 μmol h-1 g-1. C3N4 was also modified by mixing the precursor with different salts (NaCl, KBr, KI, KSCN, and NH4SCN) as hard templates. Many of these salts reacted with TCM by exchanging the anion with the chlorine in TCM. The products were mostly prepared using the high temperature Schlenk tube reactor, and resulted in yellow, orange, or tan-brown products with Eg values between 2.2 and 2.7 eV. Each of these products had subtle differences in the IR spectra and elemental composition. The morphology of these C3N4 products appeared to be more porous than unmodified C3N4, and the surface area for some increased by a factor of 4. These products demonstrated increased activity for photocatalytic hydrogen evolution, with the product from TCM-KI reaching a peak rate as high as 1,300 µmol h-1 g-1. C3N4 was coated onto metal oxide supports (SiO2, Al2O3, TiO2, and WO3) with the goal of utilizing enhanced surface area of the support or synergy between two different semiconductors. These products typically required higher temperature synthesis conditions in order to fully form. The compositions of the SiO2 and Al2O3 products were richer in nitrogen and hydrogen compared to unmodified C3N4. The higher temperature reactions with C3N4 and WO3 resulted in the formation of the HxWO3 phase, and an alternate approach of coating WO3 on C3N4 was used. The degradation of methyl orange showed a significant increase in adsorption of dye for the composites with SiO2 and Al2O3, which was not seen with any of the individual components. The composite between C3N4 and TiO2 showed improved activity for hydrogen evolution compared to unmodified C3N4. The surface of TiO2 was modified by the reductive photodeposition of several first row transition metals (Mn, Fe, Co, Ni, and Cu). This process resulted in the slight color change of the white powder to shades of light yellow, blue or grey. Bulk elemental analysis showed that these products contained between 0.04-0.6 at% of the added metal, which was lower than the targeted deposit amount. The Cu modified TiO2 had the largest enhancement of photocatalytic hydrogen evolution activity with a rate of 8,500 µmol h-1 g-1, a factor of 17 higher than unmodified TiO2.

碩士
長庚大學
光電工程研究所
99
The experiment of measuring Titanium Nitride (TiN) and TiN/Gold is using attenuated total reflectance (ATR), and analyzing the property of surface plasma resonance. The best thickness of TiN we got is 35 nm. We got the related parameters, by using Drude model. But Composed of titanium nitride nitrogen 2p orbitals and Ti 3d electron orbital electronic bonding of metal - nonmetal compounds, the electric concentration is less than gold, making the resistance is higher, resulting surface plasma resonance(SPR) doesn’t good performance of gold, showing a worse space dots per inch . If we choose TiN as a measuring tool, it make a misunderstanding the cause easily. Therefore, in the outer layer of gold film on the SPR membrane to produce the original interface compounds - and the air from the compound - metal into the air - the air, increasing the concentration of free electrons, the surface of the titanium nitride to improve the electrical properties of the objective.

碩士
國立交通大學
材料科學與工程系所
93
In this work, the interfacial reactions in the TiN/Ti diffusion couple were investigated. TiN/Ti diffusion couples were annealed at temperatures ranging from 1000 to 1500℃in argon atmosphere for 36hours. The microstructures of the reaction interface were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), and analytical transmission electron microscopy (TEM/EDS). Phases of ε-TiN(tetragonal) was observed from TiN-side to Ti-side of the diffusion couple after reaction at 1000℃ for 36 hours. After reaction at 1300℃ for 36 hours , ε-TiN(tetragonal) and α-TiN0.3(hexagonal)were observed from TiN-side to Ti-side, and ε-TiN were formed by the peritectoid reaction. However, after reaction at 1400℃ for 36 hours, the needle-like Ti2N was precipitated. Finally, α-TiN0.3 did not exist after reaction at 1500℃ for 36 hours, but lath-like α-Ti was precipitated in the two-phase region.

Thesis (M.S.)--University of Wisconsin--Madison, 1989.
Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 67-70).

碩士
國立交通大學
材料科學與工程系所
97
In this work, the aluminization and oxidation reactions of Titanium Nitride (TiN) were investigated. TiN samples were annealed by using the pack cementation method at temperatures ranging from 850 to 1150℃in argon atmosphere for 10hours. The microstructures of the reaction interface were characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM). Phases of AlN(hexagonal) and TiAl3(tetragonal) were observed in the aluminized layer after reaction at 850℃ for 10hrs. However, Phase of TiN(cubic) was addationally formed in the aluminized layer after reaction at 1150℃ for 10hrs. After the optimum pack cementation treatment, the coated specimens were oxidized at 1000℃ up to 250 hrs in air. After oxidation, the TiN which was aluminization- treated at 850℃had batter oxidation resistance than the untreated TiN because of more AlN proportions relative to TiAl3 so as to form a continuous and dense Al2O3 protection layer. On the contrary, the TiN which was aluminized at 1000 or 1150℃had poor oxidation resistance than the untreated TiN. On the one hand, this is because TiAl3 would be oxidized to form TiO2/ Al2O3 mixed layers without offering better oxidation resistance. On the other hand, less amount of AlN would not be able to form a continuous Al2O3 protection layer.

碩士
國立虎尾科技大學
機械設計工程系碩士班
106
In this paper, an aluminum matrix containing titanium nitride particles was fabricated by an in situ process in which nitrogen gas reacts with titanium in the liquid melt to form TiN. The tensile and yield strength increased by up to 20% after the formation of TiN particles in the Al alloy matrix, whilst the hardness increased by up to 27%. The abrasive and sliding-wear resistance increased with the in situ process and direct addition of the TiN particles. TiN particles of aluminum alloy composite material with in situ process and the direct addition of TiN aluminum alloy composite material have significantly increased tensile strength and fatigue resistance. Among them, TiN aluminum alloy composite material in situ process has better tensile strength and fatigue resistance than the direct addition of TiN aluminum alloy composite material. The reason is that TiN particles with aluminum alloy composite material in situ process is smaller than the commercial TiN powder, and integrate with aluminum matrix strongly. Moreover, there is no flaw between TiN particles and aluminum matrix. It makes TiN particles of aluminum alloy composite material with in situ process have higher fatigue resistance,and the wearability of TiN particles of aluminum alloy composite material with in situ process is superior to the direct addition of TiN particles aluminum alloy composite material.

碩士
國立臺北科技大學
光電工程系
106
In this study, titanium nitride nanorod arrays with different thicknesses were deposited with glancing angle deposition technique by DC magnetron sputtering and argon-nitrogen mixed gas. Titanium nitride nanorod arrays with different columnar angles and thicknesses were deposited at a flow ratio of argon and nitrogen with ratio of (Ar (sccm): N2 (sccm) = 30:3.5). X-ray Photoelectron Spectroscopy (XPS) and X-ray Diffractometer (XRD) were used to derive the chemical analysis and lattice orientation of TiN nanorod array, respectively. Both p-polarized and s- polarized transmittance and reflectance spectra of each TiN nanorod array at angles of incident from +700 to -700 were measured. The absorption peaks associated with the Longitudinal Plasmon Mode (LPM) and the Transverse Plasmon Mode (TPM) in the p-polarized and s-polarized absorbance spectra were investigated. The absorptions of two modes were compared with a silver nanorod array with similar rod length. The difference between TiN and Ag nanorods array is discussed by analyzing the lattice orientation and intrinsic electromagnetic property of deposited TiN nanorods. The Finite-Difference Time-Domain (FDTD) is also applied to understand the mechanism of plasmonic modes in the TiN nanorods.

碩士
國立交通大學
材料科學與工程學系所
105
This thesis focuses on the study of nitriding process on different TiO2 templates by using microwave plasma. One of the templates is a 50 nm thick amorphous TiO2 film coated by atomic layer deposition on Si (100), and the other is single crystalline TiO2 of rutile structure in (001). The formed TiN is characterized for its microstructure with crystal orientation and chemical bonding. In the first part of this thesis, the evolution of the amorphous TiO2 for nitridation under different microwave plasma process conditions will be presented. Plasma nitriding processes have been performed with three different gases including N2 / H2 mixture, N2 / CH4 mixture, and pure N2. The second part is devoted to plasma nitriding of rutile TiO2 single crystal in (001) under similar conditions for nitriding amorphous TiO2 / Si. Finally, the results on the single crystal TiO2 will be compared with those on the amorphous TiO2 / Si. The morphology, crystallinity and chemical bonding of TiN after nitridation of TiO2 were characterized by using scanning electron microscopy, high-resolution x-ray diffraction, x-ray photoelectron spectroscopy, and transmission electron microscopy and scanning transmission electron microscopy. The results show that the nitrogen plasma with hydrogen can have a higher nitriding rate, while it may have a more significant etching effect. After nitridation of the amorphous TiO2 on Si, polycrystalline TiN in <001> preferred orientation is formed. In contrast, epitaxial TiN can be successfully obtained upon nitridation of the single crystalline TiO2. In the use of nitrogen-hydrogen plasma nitriding, the surface of rutile TiO2 can be nitrided to (011) TiN, and the orientation relationship can be indicated by <110> TiO2 // <100> TiN. In addition, the (001) TiN will be produced when replacing nitrogen-hydrogen plasma to nitrogen-carbon plasma, the epitaxial relationship is <110> TiO2 // <110> TiN and (001) TiO2 // (001) TiN. Finally, for the pure nitrogen plasma, epitaxial (011) TiN is obtained with the same relationship with TiO2 as for the nitrogen-hydrogen plasma.

碩士
國立交通大學
電子工程系所
96
A dielectric response theory was used to study the inelastic cross sections for electrons crossing the indium nitride and titanium nitride surface. The inelastic cross sections contain information on both the surface and volume excitations. Parameters in the extended Drude dielectric function were determined from the fits of this function to experimental optical data. Theoretical derivations of the differential inverse inelastic mean free path (DIIMFP) and inverse inelastic mean free path (inverse IMFP) for either incident or escaping electrons were made for different electron energies, crossing angles, and electron distances relative to the crossing point at the surface. Dependences of the calculated DIIMFP and inverse IMFP on electron energy, crossing angle, and electron distance were analyzed. Surface excitation parameter (SEP), which describes the total probability of the surface excitations for the electrons moving outside the solid, was also calculated for different electron energies and crossing angles. The energy and angular dependences of the calculated SEPs were also analyzed.