This thesis is made as it is submitted as a sum of published papers by the candidate. Aluminium hydroxides including gibbsite, boehmite and diaspore, are the major components, while iron hydroxides/oxides and kaolinite are the major impurities in bauxite. The dehydroxylation pathways during thermal activation of bauxite have been debated for decades. Phase transformation during thermal activation or calcination of bauxite to achieve high yields of alumina has been an important goal for the refining industry. This study deals with natural and synthetic aluminium and iron hydroxides using vibrational spectroscopy in conjunction with X-ray diffraction and electron microscopy, followed by the characterisation of the phase transformation in activated bauxite. In the Raman spectra, gibbsite shows four bands at 3617, 3522, 3433 and 3364 cm-1, and bayerite shows seven bands at 3664, 3652, 3552, 3542, 3450, 3438 and 3420 cm-1 in the hydroxyl stretching region. Five bands at 3445, 3363, 3226, 3119 and 2936 cm-1 for diaspore and four at 3371, 3220, 3085 and 2989 cm-1 for boehmite are present. The far infrared spectrum of boehmite resembles that of diaspore in the 300-400 cm-1 region. Boehmite has two characteristic bands at 366 and 323 cm-1 while diaspore has five at 354, 331, 250, 199 and 158 cm-1. The far infrared spectrum of gibbsite resembles that of bayerite in the 230-300 cm-1 region. Gibbsite shows three characteristic bands at 371, 279 and 246 cm-1 whereas bayerite shows six at 383, 345, 326, 296, 252 and 62 cm-1. The far infrared spectra are in-harmony with the FT-Raman spectra, allowing the study and differentiation of the stretching of AlO4 units to characterize these four alumina phases. The surface properties of kaolinite and gibbsite are studied using Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS). The FTIR-PAS spectra of kaolinite are recorded at mirror velocities of 0.05, 0.1, and 0.2 cm s-1, and compared to the gibbsite spectra recorded at mirror velocity of 0.2 cm s-1. It is found that the hydroxyl surface spectra are a function of depth. For the FTIR spectroscopy of thermal dehydroxylation of goethite to form hematite, the intensity of hydroxyl stretching and bending vibrations decreased with the extent of dehydroxylation of goethite. Infrared absorption bands clearly show the phase transformation between goethite and hematite, in particular the migration of excess hydroxyl units from goethite to hematite. Data from the band component analysis of FT-IR spectra indicate that the hydroxyl units mainly affect the a- plane in goethite and the equivalent c- plane in hematite. A larger amount of non-stoichiometric hydroxyl unit is found to be associated with a higher aluminium substitution. A shift to a higher wavenumber of bending and hydroxyl stretching vibrations is attributed to the effects of aluminium substitution associated with non-stoichiometric hydroxyl units on the a-b plane relative to the b-c plane of goethite. The dehydroxylation pathways of both the aluminium hydroxides and the impurities are intensively studied. Gibbsite completely decomposed at 250 °C, followed by boehmite and kaolinite at 500 °C. No phase transformations were observed for hematite, anatase, rutile or quartz up to 800 °C. Small amounts of gibbsite transformed to boehmite but the majority transformed to chi (χ) alumina, a disordered transition alumina phase, after dehydroxylation at 250 °C. The dehydroxylation pathways of crystalline gibbsite follow the orders: (a) gibbsite (&lt250 °C) to boehmite (250-450 °C) to gamma alumina (γ) (500-800 °C); or (b) gibbsite (&lt250 °C) to chi alumina (χ) (250-800 °C) to chi (χ) + kappa alumina (κ) (700-800 °C). Boehmite completely altered to gamma alumina (γ), while kaolinite altered to metakaolinite at 500 °C. The vibrational spectroscopy including FT-IR and FT-Raman, is a rapid, accurate and non-destructive technique in characterising both single and mixed mineral phases. In particular, the vibrational spectroscopy has shown its advantages over other techniques in terms of its sensitivity to hydroxyl groups. Future work on the simulation of bauxite dehydroxylation with emphasis on the studies of transition aluminas is proposed. The application of the advanced technique synchrotron x-ray spectroscopy, in addition to those techniques used in the present study, is recommended.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第22486号 / 農博第2390号 / 新制||農||1075(附属図書館) / 学位論文||R2||N5266(農学部図書室) / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 髙野 俊幸, 教授 和田 昌久, 教授 河本 晴雄 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

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Cooling, Heating, and Power (CHP) is an emerging category of energy systems consisting of power generation equipment coupled with thermally activated components. The application of CHP systems to residential and small commercial buildings is known as micro-CHP (m-CHP). This instructional module has been developed to introduce engineering students to m-CHP. In the typical engineering curriculum, a number of courses could contain topics related to m-CHP. Thermodynamics, heat transfer, HVAC, heat and power, thermal systems design, and alternate energy systems courses are appropriate m-CHP topics. The types of material and level of analysis for this range of courses vary. In thermodynamics or heat transfer, basic problems involving a m-CHP flavor are needed, but in an alternate energy systems course much more detail and content would be required. This instructional module contains both lecture material and a compilation of problems/exercises for both m-CHP systems and components.

Organic semiconductors (OSCs) have already been shown to have great potential to play an important role in the future of clean energy generation (organic solar cells) and provide energy efficient lighting (organic light-emitting diodes, OLED). Prior research has found that the light-emission efficiency of OLED is severely limited by the magnetic state (technically the spin-configuration) of the light-emission process. In this thesis, we work on the processes using external magnetic fields that can overcome these magnetic limitations. A major focus of this research is to enhance the performance of OLED, while at the same time to unravel the scientific mechanisms by which magnetic fields act on OSCs devices. Thermally activated delayed fluorescence (TADF) is a next-generation OLED emission technology which enables nearly 100% light-emission efficiency without using heavy precious metals. TADF characteristics depend on the probability of reverse intersystem crossing (RISC) from the triplet excited states (T1) to singlet excited states (S1). The conversion (T1 to S1) process depends strongly on spin dynamics, thus we predict a dramatic magnetic field effects (MFEs) in such TADF OLED devices. In subsequent experiments we observed that changes in TADF devices due to various forms of electrical stress can lead to enormous increases in magnetic field effects (MFEs) on the current (> 1400%) and electroluminescence (> 4000%). Our work provides a flexible and inexpensive pathway towards magnetic functionality and field sensitivity in current organic devices. Such OLED pave the way for novel magnetic sensitive OSCs devices with integrated optical, electronic and magnetic characteristics. Organic magnetoresistance (OMAR) has been observed to alter the current and efficiency of OLED without any ferromagnetic components. Here we utilizes slight alterations to the device properties, the addition of a radical-doped functional layer, in which the spin-relaxing effects of localized nuclear spins and electronic spins interfere, to address the assumption about the importance of the hyperfine interaction and to attempt to differentiate between the different models for OMAR. A feature where the magnitude of OMAR exhibits a plateau over a wide range of doping fraction was observed at all temperatures investigated. This phenomenon is well explained by a theory in which a single dopant spin strongly interacts, by exchange, with one of the bottleneck sites. A similar can be used to explain the efficiency increases observed in organic solar cells for certain doping fractions.

Thermally activated delayed fluorescence (TADF) has been proposed as a pathway to achieve high efficiency organic light-emitting diodes (OLEDs) without the use of heavy metal atoms in molecular structures. Many different factors can be decisive for efficient light emission from TADF emitters. However, a complete picture of the working mechanisms behind TADF is still missing and further research exploring novel material and device ideas is required. This thesis aims to extend the understanding of TADF emitter and OLED design considerations by investigating photophysical properties of novel materials as well as fabricating, optimizing and characterizing devices. TADF emitters have great potential of being used in OLEDs because they allow for high quantum efficiencies by utilizing triplet states via reverse intersystem crossing (RISC). In small molecules this is done by spatially separating the frontier orbitals, forming an intramolecular charge-transfer state (iCT) and leading to a small energy difference between lowest excited singlet and triplet states (Δ𝐸ST). In polymer emitters, sufficient frontier orbital separation is harder to achieve, and typical strategies usually include adding known TADF units as sidechains onto a polymer backbone. In this thesis, a novel pathway of TADF polymer design is explored. A shift from a non-TADF monomer to TADF oligomers is explored. The monomer shows non-TADF emission and the delayed emission is shown to be of triplet-triplet annihilation (TTA) origin. An iCT state is formed already in the dimer, leading to a much more efficient TADF emission. This is confirmed by an almost two-fold increase of photoluminescence quantum yield (PLQY), a decrease in the delayed luminescence lifetime and the respective spectral line shapes of the molecules. Recently, intermolecular effects between small-molecule TADF emitters have been given more attention, revealing strong solid-state solvation or aggregation induced changes of sample performance. Implications of this on device performance are not yet fully covered. A thorough investigation of a novel TADF emitter 5CzCO2Me is conducted. Steady-state emission spectra reveal a luminescence redshift with increasing emitter concentration in a small molecule host. In all investigated concentrations, the emission profile remains the same, thus the redshift is attributed to the solid-state solvation effect. The highest photoluminescence quantum yield (PLQY) is achieved in the 20 wt% sample, reaching 66 %. The best OLED in terms of current-voltage-luminance and external quantum efficiency parameters is the device with 60 wt% emitter concentration, reaching maximal EQE values of 7.5 %. It is shown that the emitter transports holes and that charge carrier recombination does not take place on the bandgap of the host, but rather, a mixed host-guest concentration dependent recombination is seen. The hole transporting properties of 5CzCO2Me allows for a new dimension in tuning the device performance by controlling the emitter concentration.

Polymer matrix composites (PMC's) are now being used more and more extensively and over wider ranges of service conditions. Large changes in pressure, chemical environment or temperature influence the mechanical response of such composites. In the present effort, we focus on temperature, a parameter of primary interest in almost all engineering applications. In order to design composite structures without having to perform extensive experiments (virtual design), the necessity of establishing theoretical models that relate the macroscopic response of the structure to the microscopic properties of the constituents arises. In the first part of the present work, a new stiffness versus temperature model is established. The model is validated using data from the literature. The influence of the different polymer's properties (Molecular weight, crystallinity, and filler content) on the model are studied by performing experiments on different grades of four polymers PMMA, PEEK, PPS, and PB. This statistical model is proven to be applicable to very different polymers (elastomers, thermoplastics, crystalline, amorphous, cross-linked, linear, filled, unfilledâ ¦) over wide temperature ranges (from the glassy state to the flow region). The most attractive feature of the proposed model is the capability to enable a description of the polymer's mechanical behavior within and across the property transition regions. In order to validate the feasibility of using the model to predict the mechanical response of polymer matrix composites, the stiffness-temperature model is used in various micromechanical models (rule of mixtures, compression models for the life prediction of unidirectional PMC's in end-loaded bendingâ ¦). The model is also inserted in the MRLife prediction code to predict the remaining strength and life of unidirectional PMC's in fatigue bending. End-loaded fatigue experiments were performed. A good correlation between theoretical and experimental results is observed. Finally, the model is used in the Classical Lamination Theory; some laminates were found to exhibit stress reversals with temperature and behaved like thermally activated mechanical switches. / Ph. D.

The performance of a combined vapor-compression cycle/ORC is evaluated using waste-heat from a diesel generator. A flat plate microchannel heat exchanger is employed to provide energy exchange between the diesel exhaust stream and an oil loop, which provides energy to a boiler. This study finds an increased diesel duty corresponds with an increased cooling capacity, for a maximum of 5 kW of cooling (with 13.5 kWe diesel load). System COP is reduced with a higher input power due to limitations in the cooling cycle. A number of solutions are identified to increase the COP and cooling capacity. A new microchannel heat exchanger to recovery heat is designed to increase performance compared to the previous version. / Graduation date: 2012

An emerging category of energy systems, consisting of power generation equipment coupled with thermally-activated components, has evolved as Cooling, Heating, and Power (CHP). The application of CHP systems to buildings has developed into a new paradigm ? Cooling, Heating, and Power for Buildings (CHP-B). This instructional module has been developed to introduce undergraduate engineering students to CHP-B. In the typical ME curriculum, a number of courses could contain topics related to CHP. Thermodynamics, heat transfer, thermal systems design, heat and power, alternate energy systems, and HVAC courses are appropriate for CHP topics. However, the types of material needed for this mix of courses vary. In thermodynamics, basic problems involving a CHP flavor are needed, but in an alternate energy systems course much more CHP detail and content would be required. This series of lectures on CHP-B contains both a stand-alone CHP treatment and a compilation of problems/exercises.

Ein vielversprechendes Design für organische lichtemittierende Dioden (OLEDs) verwendet eine Wirt-Gast-Strategie durch Dispergieren einer kleinen Menge eines hocheffizienten Emitters (der Gast) in eine passende Transportmatrix (der Wirt). Die Aufgabe des Wirts ist den Exzitonentranport zum Emitter sicherzustellen und den Zerfall von Triplet-Exzitonen zu verhindern, und damit eine hohe Bauteilperformance zu erreichen. Die vorliegende Arbeit konzentriert sich auf die Beziehung zwischen Molekülstruktur und optoelektrischer Eigenschaften von Carbazol/Dibenzothiophen-Derivaten. Die Untersuchung umfasst sieben dieser Derivate für den Wirt, bei denen die Carbazoleinheit als Donator und die Dibenzothiopheneinheit als Akzeptor fungiert, wobei beide durch einen oder mehrere Phenylabstandshalter verbunden sind. Diese Wahl der Wirtsmaterialien erlaubt es den Einfluss der erweiterten Phenylabstandshalter und der unterschiedlichen molaren Verhältnisse von Akzeptor zu Donator zu untersuchen. Es ergab sich, dass eine kürzere Phenylabstandshalterlänge die Bauteilperformance durch eine größere Löcher- und Elektronendichte in der Emitterschicht verbessert; und ein 1:1 Carbazol-zu-Dibenzothiophen-Verhältnis der Bauteilperformance zuträglich ist, da es zu einem Ladungsträgergleichgewicht in der Emitterschicht führt. Diese Arbeit zeigt, unter Verwendung dieser Wirtsmaterialien, blaue FIrpic-basierte phosphoreszierende OLEDs (PhOLEDs) und grüne 4CzIPN-basierte thermisch aktivierte verzögerte Phosphoreszenz (TADF) OLEDs. Die blauen PhOLEDs und grünen TADF OLEDs mit mDCP zeigten Effizienzen von 43 cd/A (18.6%) beziehungsweise 66 cd/A (21%). / A particularly interesting organic light-emitting diodes (OLEDs) design adopts a host-guest strategy by dispersing a small amount of highly efficient emitter (the guest) into an appropriate transport matrix (the host). The host is utilized to transfer excitons to the emitter and to prevent triplet exciton quenching, thus high device performance can be achieved. The present thesis focuses on the relationship between the molecular structure and opto-electrical properties of carbazole/dibenzothiophene derivatives. The investigation encompasses seven of these derivatives for the host, in which the carbazole unit acts as a donor and the dibenzothiophene as an acceptor while they are linked through phenyl spacer(s). This choice of host materials enables to assess the impact of extended phenyl spacers and different acceptor to donor molar ratios. It was found that decreasing the phenyl spacer length enhances the device performance due to the larger both hole and electron densities in the emitting layer; and a 1:1 carbazole to dibenzothiophene ratio is favorable for device performance, since it balances the charge carriers in the emitting layer. Using these host materials, the work presented in this thesis demonstrates high-performance blue FIrpic-based phosphorescent OLEDs (PhOLEDs) and green 4CzIPN-based thermally activated delayed fluorescence (TADF) OLEDs. The blue PhOLEDs and green TADF OLEDs with mDCP showed efficiencies of 43 cd/A (18.6%) and 66 cd/A (21%), respectively.