Sustainable development in chemical engineering offers technical, industrially relevant solutions to environmental and economic issues. This work focuses on three specific issues; improving solvent selection and reducing costly experimentation, improving catalyst recovery while reducing reaction time, and producing commercial viable biofuels by cost effective pretreatments and valuable side product extractions. Novel solvent systems are a sustainable solution because they provide the ability to replace costly solvents with cheap, benign, and recyclable systems. Specifically, this work investigated the use of one novel solvent system, Gas Expanded Liquids (GXL).When a solvent is exposed to a gas in which it is miscible at modest pressures and temperatures, the liquid solvent becomes expanded, providing a unique tunable and reversible solvent with properties that can be much different then that of the solvent itself. If you apply this gas to a mixture of two liquids of a solid dissolved in a liquid phase, it can often provide a miscibility switch, aiding in separation, crystallization, and recovery of products or catalysts. In this work several different applications for organic solvents expanded with carbon dioxide were studied including miscibility switches for catalyst recycle, pretreatment of biomass for improved bio-ethanol production, and extraction of valuable chemicals from lignin waste in the pulp and paper industry. Solid solubility models to improve solvent selection and predict unique solvent mixtures during crystallization were also studied. The results reported here show promise for the use of GXL novel solvent systems and solid solubility models in many sustainable applications.

The study uses the Phase-field method to simulate the bubble behavior of liquid-solid interface in the solidification.The flow use the mass equation,momentum equation,and energy equation for simulating the variation of bubble. This pattern considers that three-phase of solid, liquid,and gas coexist with the different density and viscosity coefficient,and the external force considers surface tension and the gravity force. In addition,the mass transfer also can¡¦t neglect around interface. The result discuss the production of pore when the velocity of solidification is fast,but bubble leaves when the velocity of solidification is slow.

Abstract This research is focused on the condensation and phase transformation of NiO-TiO2, Co1-XO-NiO, and Co1-XO-MgO solid solution via dynamic laser ablation condensation and high temperature annealing. TiO2 rutile nanospheres with enhanced solid solution of NiO were synthesized via very energetic pulse laser ablation on clamped Ni/Ti target in oxygen for a very rapid heating/cooling, and hence pressure effect. Upon electron irradiation, the NiO-dissolved rutile (r) were partially transformed into 2(01 ) commensurate superstructure and Ni2(1+x)Ti1-xO4 spinel (s) following the crystallographic relationship [111]r//[012]s; (10 )r//(200)s. Alternatively, random NiTiO3 nanodomains were formed from amorphous regions in such a rapid decomposition process. In addition, the dense fluorite-type (f) derived TiO2 condensates dissolved up to 5 at% Ni2+ of the cations were synthesized via the same route. The nanocondensates less than 20 nm in size are nearly cubo-octahedral in shape and tended to transform martensitically to monoclinic (m) baddeleyite-type following the crystallographic relationship (100)f//(110)m; [001]f//[001]m. The condensates twice larger in size, with considerable matrix constraint, are nearly spherical in shape and consist of mosaic m-twin variants following complicated crystallographic relationships with each other and with the relic f-phase: (010)f//( 20)m; [001]f//[001]m. The charge and volume compensating oxygen vacancies due to NiO dissolution in the dense TiO2 condensates could facilitate the relaxation and amorphization process. Further more, pulse laser irradiation of Ni, Co, and Co-Ni (or Ni-Co) targets in an oxygen background gas produced nanocondensates with rock-salt type structure. Analytical electron microscopic observations indicated that such nanocrystals are cubic in shape for NiO and cubo-octahedral for Co1-xO and Ni1-xCoxO. The nanocrystals coalesced predominantly with {100} or {111} facets to form nano chain aggregates or closer packed manner. The Co1-xO was more or less oxidized as Co3-

In this thesis, we present the phase-intensity conversion transmission method for the first time. We analyze phase-intensity conversion theory, laser diode noise, and EDFA noise. By experiment, we investigate the impact of the parameters in phase-intensity conversion such as light source linewidth, phase modulation index, dispersion magnitude, and EDFA on the system performance. We successfully demonstrated simultaneous transmission of one AM-VSB channel through intensity modulation and one QAM channel through phase modulation over 10 km single mode fiber using LiNbO3 external modulator. The system performance with CNR of 57~61 dB for the AM-VSB channel and BER of 6.8´10-9 for the QAM channel can be achieved. The demonstration and the experimental results confirm the feasibility of phase-intensity conversion techniques. Potentially, the phase-intensity conversion transmission method could be applied on optical encryption and decryption systems.

Attaching soft long side chain on conjugated polymers will form liguid cystal structure. Our research is to synthesis the polypyrrole with alkyl chains on nitrogen site and carbon site and observe the effects. We observe the phase transition by X-ray and DSC. But it is hrad to observe because of its absorbing light. Between observing, we just can find the liguid crystal transition on the polypyrrole with octadecane alkyl side chain on nitrogen site. Besides, we can find the 2.8Å and 3.2Å peaks By shearing and solvent casting. Such a phenomenon is common in conjugated polymers. But it is hard to explain. Besides, substituted on different sites will bring different results. Substituted on nitrogen site will lead to bigger d-sapcing than substituted on carbon site. This is because of the difference on co-planity. By the correlation function, we can realize that longer side chain, bigger fluctuation, but better layer structures.

The diffusional transformation kinetics of C-Mn steels during continuous cooling have been measured and predicted in this study for predicting the non-isothermal multi-stage cooling transformation kinetics. A suitable thermodynamic model is assessed for determining the driving force of austenite to ferrite transformation and the austenite/ferrite interface concentrations under various equilibrium constraints, which are essential to determine the diffusion-controlled transformation kinetics. The continuous cooling transformation (CCT) curves of C-Mn steels are determined using dilatometric method. Pham¡¦s empirical growth model is found most suitable for describing the start and finish transformation curve. The Avrami equation, common-used for isothermal transformation, is found to be applicable to the continuous cooling transformation. The Avrami exponents, nF and nP, for ferrite- and pearlite- dominant CCT, respectively, are close to the isothermal ones reported in the literature. The Avrami constant, b, increases with decreasing austenitizing temperature, indicating a fast progress of transformation. Combining Pham¡¦s empirical growth model with Avrami equation, the CCT kinetics of C-Mn steels can be predicated well. The examination on the microstructural evolution during CCT suggests that the transformation of austenite to grain boundary allotriomorphs of ferrite (GBAF) can be divided into (1) nucleation and growth (NG) stage, (2) growth only (site saturation, SS) stage, and (3) coalescence stage. In the NG stage, the oblate ellipsoid aspect ratio of GBAF remains 3:1 until all the nucleation sites are exhausted., i.e. the onset of SS stage, then gradually decreases in the SS stage. Once the aspect ratio approaches unity, the coalescence starts to operate. Based on this observation, a physical base model is developed for predicting the austenite to GBAF CCT. This model possesses the capability to predict the start and finish transformation temperatures, the fraction transformed, and the final ferrite grain size. Although such model failed to predict the whole range of CCT curve due to the fact that only the GBAF transformation is included at present stage, it is still highly recommended for microstructural control. In order to completely predict the whole CCT curves, a semi-empirical physical base model is adopted. In addition, the methodology to predict multi-stage cooling transformation from CCT curves is also derived based on additivity rule and the concept of ideal TTT diagram. Associated with the additivity rule and the concept of ideal TTT diagram, such empirical model is validated to be applicable for the prediction of CCT and step wise cooling transformation. The latent heat is calculated using thermodynamic software for the accurate control of cooling history of the medium carbon steels which usually releases an abundance of latent heat. Associated with the semi-empirical transformation model, the calculation of latent heat is integrated into a heat transfer model and successfully implemented in a mill operation.

Abstract The x~ 1/8anomaly in the La-based cuprates had been puzzling since the discovery of high-Tc superconductors. Recently, the stripe phase which has attracted considerable attention in connection with many experiments, like neutron scattering, Raman and infrared(IR) spectra, Hall effect, thermoelectric power and magnetic susceptibility, etc. These results indicate that a crossover from one- to two-dimensional charge transfer accurs at x~1/8 . In this thesis, we synthesize two series of p-type superconductors La2-xSrxCuO4 and La1.4-xSrxNd0.6CuO4 by solid-state reaction. It has been well known that there is a marked drop in Tc - x phase diagram at x~1/8 in both systems. It is possible that this phenomenon is related to the stripe phase. This interesting question has motivated us to initiate the experiment of x-ray absorption near edge spectroscopy (XANES) to investigate the possibility of the electronic structure change caused by the stripe phase. It is found that the spectral weight of the hole carriers scales with the doping level x rather than with Tc . However, the charge stripe was observed in La1.4-xSrxNd0.6CuO4, but not in La2-xSrxCuO4. Our results also suggest that the formation of the stripe phase is not related to the structural phase transition in La1.4-xSrxNd0.6CuO4 consistent with earlier results. Comparisons are made between our results and those reported on the basic of the stripe phase scenario.

Optical measurement is a very important science in present times. Generally, optical interference is applied in precise measuring. In this thesis, we use the opto-electric properties of liquid-crystal layers and the phase-shifting shearing interferometer will be applied. Clear patterns should be figured when measuring optical properties traditional interferometers. A new interferometer called phase-shifting shearing interferometer was developed recently. It is not necessary to appear clear patterns in measurements. In application to this interferometer, the phase information got by way of shifting the reference lens that can control phase differences. Phase controlled in thus method is mostly by the step motor or the PZT installation. Now we replace this installation by liquid-crystal layers since the accuracy of liquid-crystal layers controlled by voltage is better than the mechanical installation. The measuring precision is improved wide. In this paper, we study the optical properties under the application both DC and AC voltage to a series of thickness of the liquid-crystal layer, and the suitable condition of liquid-crystal layers to apply to the phase-shifting shearing interferometer.

We have proposed and demonstrated a technique for the measurement of the wavefront of a diode laser beam with a large dynamic range. Our technique is a modified version of Hartmann and Shack-Hartmann wavefront sensor. The modified version is capable of providing a large dynamic range (180 degrees). The wavefront measurement exhibits a precision of ( 0.02 degrees), subject to a standard deviation governed by the diffraction limit (~£f/d). Using the physical measurement of the wavefront, we are able to reconstruct the electric fields of a diode laser beam at any location, including the far-field and near-field. The reconstructed electric fields were computed form the data of the intensity and the phase distribution by means of Fourier transform. The information about the electric field can be very useful in the design of microlens for the efficient coupling of light source into optical components. The results indicate that the wavefront sensor with large dynamic range can provide a reliable method for measuring the wavefront distributions of diode lasers with large divergence angles. However, the numerical near-field intensity is 150% deviated from the measured near-field intensity because of the inherent inaccuracy in the wavefront measurement. In this study, we have measured the near field intensity distribution directly with an objective and a CCD camera. We found that the distribution of the mode field was symmetric at a distance of 8£gm from a diode laser and the mode field diameter was 4.75£gm. Using the phase retrieval algorithms, the radii of the near-field wavefront in the vertical axis and the horizontal axis were 8£gm and 41£gm, respectively. Through the geometrical optics, the optimum curvatures of elliptic-cone-shaped lensed fiber for efficient coupling in the vertical axis and the horizontal axis were 4£gm and 20.5£gm individually. Once we know the optimum curvatures of elliptic-cone- shaped lensed fiber, we can fabricate it using grinding and fusing.

Thèse d'exercice : Médecine. Médecine générale : Université de Nantes : 2004. / Bibliogr. f. 99-101 [43 réf.].