A nanofilm rotation method is developed to study the rotation of nanograins and the formation of various low energy interfaces. Epitaxial (100), (110), (111) and (112) NiO nanofilms are prepared by ion beam sputtering onto the (100), (110), (111) and (112) surfaces of NaCl single crystal. By overlapping of the above films with an angle difference, and annealing at relatively low temperatures 100 ¢Jthe nanograins are induced to rotate till a metastable interface is reached. The rotation process and the metastable interfaces are determined by transmission electron microscopy. Many new interfaces between mixed planes are found, and their orientation relationships and structures are analyzed. The study discovered eight groups of metastable orientation relations, respectively, which have not been reported in literatures. 2¡¦ orientation relationship is [11 ]( 10)//[01 ]( 11) 2¡¦¡¦ orientation relationship is [00 ]( 10)//[ 0 ]( 11) 4e1 orientation relationship is [13 ]( 12)//[110](00 1) 4¡¦ orientation relationship is [1 1]( 12)//[0 0](00 1) 4e2 orientation relationship is [13 ]( 12)//[100](00 1) 5¡¦ orientation relationship is [ 1 ]( 12)// [01 ] ( 11) 6¡¨ orientation relationship is [110]( 12)// [001] ( 10) 6¡¦¡¦¡¦ orientation relationship is [110]( 12)// [ 1] ( 10)

The stable interfaces between NiO and ZrO2 reached by nanofilms interface rotation method are reported in this study. Epitaxial nanofilms of NiO and ZrO2 were synthesized on single crystal NaCl (001), (011), (111) surfaces. All nanofilms are investigated by transmission electron microscopy and selected-area diffraction (SAD) patterns. Composite nanofilms were formed by overlapping nanofilms of NiO and ZrO2 at difference angles and thermally treated. The rotation process and final stable interfaces in the overlapped nanofilms are analyzed by SAD patterns. Orientation relationships and interface rotation are analyzed. This study found five new interfaces. (1) (001)N/ Z¡A[110]N//[110]Z (2) (001)N/ Z¡A[100]N//[110]Z (3) N/ Z¡A[110]N//[110]Z (4) N/ Z¡A[111]N//[110]Z (5) N/ Z¡A[001]N//[110]Z

This experiment use NaCl (001) single crystal as substrate, and the target is zinc oxide, to generate a-plane (112 ¡Â0) zinc oxide nanothim. The nanofilm is used as a buffer layer generating by Ion Beam Sputtering, and then increasing the thickness by Plasma sputtering. Part of specimens to proceed atmospheric heat treatment with different temperature and time, and part of specimens to change the ratio of the gas when the thin film is growth, then use of Transmission electron microscopy (TEM) and Photoluminescence (PL) as the analysis of film properties. The results of experiment, show that (112 ¡Â0) plane have more stringent conditions when generate of thin film, and easy to become the ring of electron diffraction with no-epitaxy .But finally we get a data what can generate a well a-plane ZnO thin film, the substrate temperature of 400 ¢X C, the sputtering time of 1 hour, Ar/O2 = 1.5. From the results of Photoluminescence, we find that there are zinc vacancies in ZnO thin film, probably there are too many oxygen atoms. While the heat treatment in nitrogen, zinc vacancies are reduced rapidly. Indicating that oxygen atoms within the film are reduced by nitrogen atoms or replace the position of the oxygen atoms.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19684号 / 工博第4139号 / 新制||工||1639(附属図書館) / 32720 / 京都大学大学院工学研究科機械理工学専攻 / (主査)教授 北村 隆行, 教授 立花 明知, 教授 鈴木 基史 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

This work outlines a series of developments and discoveries related to surface chemistry of controlled near-surface architectures. Through a combination of various X-ray spectroscopy techniques and innovative electrochemical fabrication techniques, valuable knowledge has been added to the fields of electrochemical fabrication, electrocatalysis, and fundamental surface chemistry. Described here is a specific new development in the technique of surface limited redox replacement (SLRR). This work, along with an accompanying journal publication1, reports the first-ever use of nickel as an intermediary for SLRR. In addition, this work identifies specific deviations from the nominal reaction stoichiometry for SLRR-grown films. This led to the proposal of a new reaction mechanism for the initial stages of the SLRR process, which will assist future fabrication attempts in this field. This work also discovered fundamental changes in Pt overlayer systems as the thickness of the overlayer on a gold support is increased from less than a single atomic monolayer to multilayer thicknesses. It was found that Pt overlayers below a certain threshold thickness exhibited increased affinity for hydroxyl groups, along with an increased propensity for formation of oxide and chloride species. These films were also studied for methanol, carbon monoxide, and ethylene glycol electro-oxidation. Finally, this work reports controlled surface architectures of Pt and Cu deposits on application-oriented TiO₂ nanotube arrays and Au-carbon supports.

A nanofilm rotation method is developed to study the rotation of nanograins and the formation of various low energy interfaces. Epitaxial NiO and Ag nanofilms are prepared by ion beam sputtering onto the (100), (110), (111) and (112) surfaces of NaCl single crystal. By overlapping of the above films with an angle difference, and annealing at relatively low temperatures the nanograins are induced to rotate till a stable interface is reached. The rotation process and the stable interfaces are determined by transmission electron microscopy. Many new interfaces between mixed planes are found, and their orientation relationships and structures are analyzed. The rotation speed increase with temperature and is fast above 200oC.

Recent advances in multilayer self-assembly have enabled the precise construction of nanocomposite ultrathin films on a variety of substrates, from large-area planar surfaces to nanoparticles. As a result, a wide range of physico-chemical properties may be represented by selecting from an array of surface preparations, molecules, assembly conditions, and post-assembly treatments. Such multilayer nanofilm assemblies are particularly attractive for use as specialized membranes for selective transport, which have many applications for separations, sensors, and drug delivery systems. In this work, nanocomposite ultrathin films built with layer-by-layer (LbL) self-assembly methods have been applied to surface modification to control interfacial behavior, including diffusion, anti-fouling, and biomimetic membranes. Transport and interfacial properties of nanocomposite membranes constructed using LbL self-assembly with synthetic and/or bio-polymers were characterized, and permeability values of clinically relevant small molecules through the nanofilms were determined. Correlations between permeability and film properties were also examined. Nanofilm coatings around 100nm thickness decreased diffusion coefficients of glucose up to five orders of magnitude, and were found to greatly affect enzymatic glucose sensor responses. Surface modification on top of the nanofilms with poly(ethylene glycol) provided anti-fouling effects. However, weak-weak polyelectrolyte multilayers (PEMs) should not be used to control transport due to their susceptibility under normal physiological conditions. Natural/biological polymers also provided multilayer film structures at the specific conditions, but their transport-limiting properties were not significant compared to synthetic PEMs. Even when covalently crosslinked, biological PEMs did not reduce the permeability of a small molecule. Finally, the predicting model of projecting analyte permeation through multi-phase nanocomposite films comprised with known diffusion coefficients was theoretically and experimentally evaluated. The modeling was matched reasonably well to experimental data. The outcomes will be the key knowledge or engineering principles to support future efforts in research and development. It is anticipated that the system developed for determining transport properties will provide a general platform for assessing new candidate materials. The theory developed will be useful in estimating transport properties of novel nanocomposite materials that may be interesting in a broad array of chemical and biological systems, from analytical separations to implantable biomedical applications, and will provide useful design rules for materials and fabrication process selection.

>Magister Scientiae - MSc / In the wide search for advanced materials for next generation lithium-ion batteries, lithium manganese orthosilicate, Li₂MnSiO₄ is increasingly gaining attention as a potential cathode material by virtue of its ability to facilitate the extraction of two lithium ions per formula unit, resulting in a two-electron redox process involving Mn²⁺/Mn³⁺ and Mn³⁺/Mn⁴⁺ redox couples. This property confers on it, a higher theoretical specific capacity of 333 mAhg⁻¹ which is superior to the conventional layered LiCoO₂ at 274 mAhg⁻¹ and the commercially available olivine LiFePO₄ at 170 mAhg⁻¹. Its iron analogue, Li₂FeSiO₄ has only 166 mAhg⁻¹ capacity as the Fe⁴⁺ oxidation state is difficult to access. However, the capacity of Li₂MnSiO₄ is not fully exploited in practical galvanostatic charge-discharge tests due to the instability of the delithiated material which causes excessive polarization during cycling and its low intrinsic electronic conductivity. By reducing the particle size, the electrochemical performance of this material can be enhanced since it increases the surface contact between the electrode and electrolyte and further reduces the diffusion pathway of lithium ions. In this study, a versatile hydrothermal synthetic pathway was employed to produce nanoparticles of Li₂MnSiO₄, by carefully tuning the reaction temperature and the concentration of the metal precursors. The nanostructured cathode material was further coated with a thin film of aluminium oxide in order to modify its structural and electronic properties. The synthesized materials were characterized by microscopic (HRSEM and HRTEM), spectroscopic (FTIR, XRD, SS-NMR, XPS) and electrochemical techniques (CV, SWV and EIS). Microscopic techniques revealed spherical morphologies with particle sizes in the range of 21-90 nm. Elemental distribution maps obtained from HRSEM for the novel cathode material showed an even distribution of elements which will facilitate the removal/insertion of Li-ions and electrons out/into the cathode material. Spectroscopic results (FTIR) revealed the vibration of the Si-Mn-O linkage, ascertaining the complete insertion of Mn ions into the SiO₄⁴⁻ tetrahedra. XRD and ⁷Li MAS NMR studies confirmed a Pmn21 orthorhombic crystal pattern for the pristine Li₂MnSiO₄ and novel Li₂MnSiO₄/Al₂O₃ which is reported to provide the simplest migratory pathway for Li-ions due to the high symmetrical equivalence of all Li sites in the unit cell, thus leading to high electrochemical reversibility and an enhancement in the overall performance of the cathode materials. The divalent state of manganese present in Li₂Mn²⁺SiO₄ was confirmed by XPS surface analysis. Scan rate studies performed on the novel cathode material showed a quasi-reversible electron transfer process. The novel cathode material demonstrated superior electrochemical performance over the pristine material. Charge/discharge capacity values calculated from the cyclic voltammograms of the novel and pristine cathode materials showed a higher charge and discharge capacity of 209 mAh/g and 107 mAh/g for the novel cathode material compared to 159 mAh/g and 68 mAh/g for the pristine material. The diffusion coefficient was one order of magnitude higher for the novel cathode material (3.06 x10⁻⁶ cm2s⁻¹) than that of the pristine material (6.79 x 10⁻⁷ cm2s⁻¹), with a charge transfer resistance of 1389 Ω and time constant (τ) of 1414.4 s rad⁻¹ for the novel cathode material compared to 1549 Ω and 1584.4 s rad-1 for the pristine material. The higher electrochemical performance of the novel Li₂MnSiO₄/All₂O₃ cathode material over the pristine Li₂MnSiO₄ material can be attributed to the alumina nanoparticle surface coating which considerably reduced the structural instability intrinsic to the pristine Li₂MnSiO₄ cathode material and improved the charge transfer kinetics.

De nouveaux électrocatalyseurs avec nanofilm de platine pour la réaction de réduction de l'oxygène avec application dans des piles à combustible à membrane échangeuse de protons ont été développés. Ces catalyseurs comprennent des films minces de platine déposés sur des réseaux de nanofibres de carbone. Des supports de nanofibres de carbone et de nanobrosse ont été préparés par électrofilage suivi de traitements thermiques pour la stabilisation et la graphitisation. Une méthode innovante d’électrodéposition pulsée à surpotentiel élevé a été développée pour le dépôt de nanofilm de platine sur des supports de nanofibres de carbone et de nanobrosse, ainsi que sur du graphite pyrolytique hautement orienté dont la planéité permet de caractériser le dépôt avec microscopie à force et électronique. Ces approches ont conduit à des électrodes en nanofibres autosupportées avec une porosité qui a été accordée à un matériau de plus en plus dense d'un côté à l'autre, où le côté présentant la plus grande surface était utilisé pour déposer du platine. Les électrodes ont été caractérisées ex situ en utilisant voltampérométrie cyclique, en démontrant une activité plus élevée pour la réaction de réduction de l'oxygène et une durabilité contre des cycles de tension plus élevée que les catalyseurs classiques au platine sur carbone. Ces électrodes ont été assemblés directement avec une membrane et une anode et caractérisés in situ dans une pile à combustible. Des films minces de platine ont également été préparés à la surface des nanofibres de nickel en utilisant le nouvelle approche de l'échange galvanique assisté par micro-ondes ; divers paramètres expérimentaux ont été étudiés pour déterminer leur effet sur l'échange et la morphologie du platine. Les fibres de nickel@platine résultantes ont présenté une électroactivité élevée pour la réaction de réduction d'oxygène et ont été caractérisées comme des électrocatalyseurs non supportés à la cathode d'un assemblage d'électrodes à membrane; des travaux supplémentaires sont nécessaires pour les stabiliser contre la perte de nickel de l’électrocatalyseur vers l’électrolyte. / Novel platinum thin film electrocatalysts for the oxygen reduction reaction of proton exchange membrane fuel cells were developed. These catalysts comprise platinum thin films deposited on carbon nanofibrous webs. Carbon nanofibres and nanobrush supports were prepared by electrospinning followed by thermal treatments for stabilisation and graphitisation. An innovative pulsed high overpotential electrodeposition method was developed to deposit platinum thin films both on carbon nanofibre and nanobrush supports, and also on highly oriented pyrolytic graphite, the planarity of which allowed detailed characterisation of the conformity, contiguity and thickness of the platinum films using atomic force and electron microscopy. These approaches led to self-standing nanofibre electrodes with porosity that was tuned to increasingly dense material from one side to the other, where the side presenting highest surface area was used to deposit platinum. The electrodes were characterised ex situ using cycling voltammetry where they demonstrated higher activity for the oxygen reduction reaction and greater durability on voltage cycling than conventional platinum on carbon catalysts. They were also assembled directly with a membrane and anode and characterised in situ in a single fuel cell. Thin platinum films were also prepared at the surface of nickel nanofibres using a novel approach to galvanic exchange assisted by microwaves, and a range of experimental parameters was investigated to determine their effect on the extent of exchange and the resulting platinum morphology. While the resulting nickel@platinum core@shell fibres demonstrated high electroactivity for the oxygen reduction reaction and were characterised as unsupported electrocatalysts at the cathode of a membrane electrode assembly, further work is required to stabilise them against nickel leaching from the catalyst to the electrolyte.

This dissertation concerns the development, fabrication and integration in a gas sensing microdevice of a novel 3-dimensional (3D) nanostructured metal-oxide semiconducting film that effectively merges the benefits of inorganic nanomaterials with the simplicity offered by non-lithographic electrochemistry-based preparation techniques. The film is synthesized via the porous-anodic-alumina-assisted anodizing of an Al/Nb metal bilayer sputter-deposited on a SiO2/Si substrate and is basically composed of a 200 nm thick NbO2 layer holding an array of upright-standing spatially separated Nb2O5 nanocolumns, being 50 nm wide, up to 900 nm long and of 8109 cm2 population density. The nanocolumns work as semiconducting nano-channels, whose resistivity is greatly impacted by the surface and interface reactions. Either Pt or Au patterned electrodes are prepared on the top of the nanocolumn array using an innovative sensor design realized by means of microfabrication technology or via a direct original point electrodeposition technique, followed by selective dissolution of the alumina overlayer. For gas-sensing tests the film is mounted on a standard TO-8 package using the wire-bonding technique. Electrical characterization of the 3D niobium-oxide nanofilm reveals asymmetric electron transport properties due to a Schottky barrier that forms at the Au/Nb2O5 or Pt/Nb2O5 interface. Effects of the active film morphology, structure and composition on the electrical and gas-sensing performance focusing on sensitivity, selectivity, detection limits and response/recovery rates are explored in experimental detection of hydrogen gas and ammonia. The fast and intensive response to H2 confirms the potential of the 3D niobium-oxide nanofilm as highly appropriate active layer for sensing application. A computer-aided microfluidics simulation of gas diffusion in the 3D nanofilm predicts a possibility to substantially improve the gas-sensing performance through the formation of a perforated top electrode, optimizing the film morphology, altering the crystal structure and by introducing certain innovations in the electrode design. Preliminary experiments show that a 3D nanofilm synthesized from an alternative Al/W metal bilayer is another promising candidate for advanced sensor applications. The techniques and materials employed in this work are advantageous for developing technically simple, cost-effective and environmentally friendly solutions for practical micro- and nanodevices, where the well-defined nano-channels for charge carriers and surface reactions may bring unprecedented benefits.