Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2002. / Includes bibliographical references. / Ionized physical vapor deposition (IPVD) and electrochemical deposition (ECD) are two major thin film deposition processes in the microelectronics industry. The ion fluxes with high kinetic energies in IPVD process involve complex surface interactions that affect overall topology of the microscale features. Copper ECD process involves complex surface reactions and transport phenomena that ranges over different length scales. In this work, predictive simulation tools for these two processes have been developed by investigating the surface reaction and the transport phenomena in IPVD and ECD processes. In the IPVD process, molecular dynamics (MD) techniques with embedded-atom potentials are used to study the surface reactions for atoms with high impinging energies (30 - 50 eV). The surface reaction rates are combined with ballistic transport and level set methods. The resulting tool demonstrates the effect of the kinetic energy driven surface diffusion on the feature profile evolution. For the ECD process of copper, detailed surface kinetic mechanisms are developed based on the competitive adsorption/desorption model in the presence of three representative additives, poly ethylene glycol (PEG) and bis-(sodium sulfoprophyl) (SPS) and chloride. The proposed kinetic mechanism is capable of describing the synergistic effect of different additives on the copper deposition. Statistically designed experiments were performed with the rotating disk electrode (RDE) apparatus. A hydrodynamic model was developed for RDE and is used to fit the kinetic parameters that are independent of the transport effect. / (cont.) A reactor scale model is developed based on the Galerkin finite element method. The model includes momentum transport, transient mass transport, potential distribution and detailed surface kinetic mechanisms. The experimental film thickness uniformity on the blank wafer with commercial electrochemical deposition cell is compared with the simulation result. The reactor scale model is used to investigate the various effects on the film thickness uniformity including terminal effects and mass transport effects. The analysis shows the qualitative difference between two effects and how they can be eliminated. Also, the reactor scale simulation tool is used to model the pulse plating process. Improved performance of the pulse plating over the constant current operation suggests that the relaxation period is the critical parameter that determines the film thickness uniformity. A computationally efficient feature scale model is developed. Mass transport, potential distribution and detailed surface reactions are included in the model ... / by Gwang-Soo Kim. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2009. / Includes bibliographical references (p. 209-217). / Homogenous-charge, compression-ignition (HCCI) combustion is a new method of burning fuel in internal combustion (IC) engines. In an HCCI engine, the fuel and air are premixed prior to combustion, like in a spark-ignition (SI) engine. However, rather than using a spark to initiate combustion, the mixture is ignited through compression only, as in a compression-ignition (CI) engine; this makes combustion in HCCI engines much more sensitive to fuel chemistry than in traditional IC engines. The union of SI- and CI-technologies gives HCCI engines substantial efficiency and emissions advantages. However, one major challenge preventing significant commercialization of HCCI technology is its small operating range compared to traditional IC engines. This project examined the effects of fuel chemistry on the size of the HCCI operating region, with an emphasis on the low-load limit (LLL) of HCCI operability. If commercialized, HCCI engines will have to operate using standard commercial fuels. Therefore investigating the impact of fuel chemistry variations in commercial gasolines on the HCCI operability limits is critical to determining the fate of HCCI commercialization. To examine these effects, the operating ranges of 12 gasolines were mapped in a naturally-aspirated, single-cylinder HCCI engine, which used negative valve overlap to induce HCCI combustion. The fuels were blended from commercial refinery streams to span the range of market-typical variability in aromatic, ethanol, and olefin concentrations, RON, and volatility. The results indicated that all fuels achieved nearly equal operating ranges. The LLL of HCCI operability was completely insensitive to fuel chemistry, within experimental measurement error. The high-load limit showed minor fuel effects, but the trends in fuel performance were not consistent across all the speeds studied. These results suggest that fuel sensitivity is not an obstacle to auto-makers and/or fuel companies to introducing HCCI technology. / (cont.) Developing an understanding of what causes an HCCI engine to misfire allows for estimation of how fuel chemistry and engine operating conditions affect the LLL. The underlying physics of a misfire were studied with an HCCI simulation tool (MITES), which used detailed chemical kinetics to model the combustion process. MITES was used to establish the minimum ignition temperature (Tmisfire) and full-cycle, steady-state temperature (Tss) for a fuel as a function of residual fraction. Comparison of Tmisfire and Tss near the misfire limit showed that Tss approaches Tmisfire quite closely (to within ~ 14 K), suggesting that the primary cause of a misfire is insufficient thermal energy needed to sustain combustion for multiple cycles. With this relationship, the effects of engine speed and fuel chemistry on the LLL were examined. Reducing the engine speed caused a reduction in T, which allowed fuel chemistry effects to be more apparent. This effect was also observed experimentally with 2 primary reference fuels (PRFs): PRF60 and PRF90. At 1000 RPM, PRF60 obtained a substantially lower (~30%) LLL than PRF90, but at speeds >/= 1500 RPM, fuel ignitability had no effect on the LLL. Fuel chemistry was shown to influence the LLL by increasing both Tmisfire and Tss for more auto-ignition resistant fuels. However, the extent to which fuel chemistry affects these temperatures may not be equivalent. Therefore, the relative movement of each temperature determines the extent to which fuel chemistry impacts the LLL. / by John P. Angelos. / Ph.D.

Thesis (M.S.) Massachusetts Institute of Technology. Dept. of Chemical Engineering, 1952. / Bibliography: leaf 34. / by Donald Owen Chessmore. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2001. / "June 2001." / Includes bibliographical references. / Population balances describe a wide variety of processes in the chemical industry and environment ranging from crystallization to atmospheric aerosols, yet the dynamics of these processes are poorly understood. A number of different mechanisms, including growth, nucleation, coagulation, and fragmentation typically drive the dynamics of population balance systems. Measurement methods are not capable of collecting data at resolutions which can explain the interactions of these processes. In order to better understand particle formation mechanisms, numerical solutions could be employed, however current numerical solutions are generally restricted to a either a limited selection of growth laws or a limited solution range. This lack of modeling ability precludes the accurate and/or fast solution of the entire class of problems involving simultaneous nucleation and growth. Using insights into the numerical stability limits of the governing equations for growth, it is possible to develop new methods which reduce solution times while expanding the solution range to include many orders of magnitude in particle size. Rigorous derivation of the representations and governing equations is presented for both single and multi-component population balance systems involving growth, coagulation, fragmentation, and nucleation sources. A survey of the representations used in numerical implementations is followed by an analysis of model complexity as new components are added. The numerical implementation of a split composition distribution method for multicomponent systems is presented, and the solution is verified against analytical results. Numerical stability requirements under varying growth rate laws are used to develop new scaling methods which enable the description of particles over many orders of magnitude in size. Numerous examples are presented to illustrate the utility of these methods and to familiarize the reader with the development and manipulations of the representations, governing equations, and numerical implementations of population balance systems. / by Darren Donald Obrigkeit. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 301-322). / Strong trends in chemical engineering have led to increased complexity in plant design and operation, which has driven the demand for improved control techniques and methodologies. Improved control directly leads to smaller usage of resources, increased productivity, improved safety, and reduced pollution. Model predictive control (MPC) is the most advanced control technology widely practiced in industry. This technology, initially developed in the chemical engineering field in the 1970s, was a major advance over earlier multivariable control methods due to its ability to seamlessly handle constraints. However, limitations in industrial MPC technology spurred significant research over the past two to three decades in the search of increased capability. For these advancements to be widely implemented in industry, they must adequately address all of the issues associated with control design while meeting all of the control system requirements including: -- The controller must be insensitive to uncertainties including disturbances and unknown parameter values. -- The controlled system must perform well under input, actuator, and state constraints. -- The controller should be able to handle a large number of interacting variables efficiently as well as nonlinear process dynamics. -- The controlled system must be safe, reliable, and easy to maintain in the presence of system failures/faults. This thesis presents a framework for addressing these problems in a unified manner. Uncertainties and constraints are handled by extending current state-of-the-art MPC methods to handle probabilistic uncertainty descriptions for the unknown parameters and disturbances. Sensor and actuator failures (at the regulatory layer) are handled using a specific internal model control structure that allows for the regulatory control layer to perform optimally whenever one or more controllers is taken offline due to failures. Non-obvious faults, that may lead to catastrophic system failure if not detected early, are handled using a model-based active fault diagnosis method, which is also able to cope with constraints and uncertainties. These approaches are demonstrated on industrially relevant examples including crystallization and bioreactor processes. / by Joel Anthony Paulson. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2005. / Includes bibliographical references. / Silk-inspired segmented polyurethanes containing flexible, hydrophilic segments with crystalline and liquid crystalline moieties were developed to mimic the hierarchical morphology of the continuous domain in and the superior mechanical properties of native spider silk. A series of polyurethane elastomers were designed with varying poly(ethylene oxide) (PEO)-containing soft segment lengths and hard segment contents. The incorporation of a hydrophobic poly(propylene oxide) (PPO) block and longer soft segment lengths (1900 g/mol) induced a higher degree of micro-phase segregation compared to PEO (1000 g/mol) soft segment polyurethanes of similar hard segment content. Segmented polyurethanes with longer PEO soft segment lengths (4600 g/mol) exhibited a lamellar morphology, which was driven by the high level of crystallinity in both the hard and soft domains. As the hard segment content (26 - 47 wt%) was increased, the crystallinity of the hard domains was enhanced, yielding a shift in the morphology of the continuous domain from soft segment continuous to hard segment continuous or an interconnected microstructure. The mechanical behavior of these systems was affected by the continuous domain morphology. Hysteresis and initial moduli increased, and extensibility decreased as the hard segment size was varied from 26 to 47 wt% in the PEO-PPO-PEO-containing polyurethanes. The pure PEO (1000 g/mol) soft segment polyurethane exhibited enhanced extensibility, tensile strength, and toughness compared to the PEO-PPO-PEO segmented polyurethanes, which was attributed to the presence of load-bearing crystallites. / (cont.) Shearing of the highly ordered and hydrogen-bonded hard domains resulted in orientation of the hard blocks at a preferential angle (±70⁰) to the stretch direction during tensile deformation. Strong alignment and strain-induced birefringence of the soft segment chains was identified in the pure PEO 1000 soft segment polyurethane, which supported the observed mechanical behavior. An ordered mesophase was observed in the PEO-PPO-PEO soft segment polyurethane in which the soft block formed the continuous domain. The hard segments aligned ±30̊ to the elongation direction within the hard domain as a result of the hydrogen-bonded network structure. Dramatic reductions ( [approx.] 16-fold decrease in toughness and [approx] 6-fold decrease in extensibility) in mechanical properties were found in PEO-PPO-PEO soft segment polyurethane/Laponite nanocomposites. The soft segment mobility was restricted in these nanocomposites, diminishing the ability for strain-induced ordering and hindering slippage of the soft segment chains during deformation. Regions of exfoliated Laponite alternated with intercalated-and-flocculated clay regions. These findings were rationalized in terms of preferential attraction of the hydrophilic, PEO-based soft block to the hydrophilic Laponite discs, leading to the intercalated-and-flocculated structures. However, the Laponite particles also interact with the polar hard domains, which has been assigned to the observed exfoliation. Poly(gamma-benzyl-L-glutamate) (PBLG)-PEO-PBLG copolymers were developed using custom-synthesized, diamine-terminated PEO 1000. / (cont.) These copolymers exhibited both alpha-helix and beta-sheet conformations, depending on the PBLG block length. Only low molecular weight segmented polyurethanes were obtained using these liquid crystalline copolymers due to the possible low reactivity of the amine end-groups and cyclization within the PBLG block. / by LaShanda Teresa James-Korley. / Ph.D.

Thesis (M.S.) Massachusetts Institute of Technology. Dept. of Chemical Engineering, 1951. / Bibliography: leaf 71. / by Robert T. Hucks, Jr. and William P. Thomson. / M.S.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1967. / Lacking leaves 22, 23, 25, 26, 33. Vita. / Bibliography: leaves 382-386. / by Hugh B. Hales. / Sc.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1938. / Includes bibliographical references (leaf 46). / by Jean Irwin Wagner. / M.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2002. / Includes bibliographical references. / Ab initio calculations were used to determine the H20-CH4 potential energy surface (PES) accurately for use in modeling gas hydrates. Electron correlation was found to be treated accurately by the second-order Moller-Plesset method (MP2). However, a large basis set, cc-pVQZ, was found to be necessary in order to compute the binding energies to within 0.1 kcal/mol of the basis set limit. In order to sample accurately the PES, the H2O-CH4 energy of interaction was computed at 18,000 points. For these computations to be feasible, a new method was developed in which all 18,000 points were computed using MP2/6-3 1++G(2d,2p) and then corrected to near the accuracy of MP2/cc-pVQZ. The PES calculated from the six-dimensional numerical potential agrees very well with far infrared vibration-rotation-tunneling spectroscopic data and experimental second virial coefficient data at the potential minimum and larger separations. In order to study the application of different potential forms to describe phase equilibrium for Structure I gas hydrates, molecular computations were performed and results were compared. Although simple potential forms can be fit satisfactorily to experimental P-T data for ethane and cyclopropane hydrates using the van der Waals and Platteeuw model, they fail to predict accurately cage occupancies of methane hydrates. Predicted phase equilibria and cage occupancies for methane hydrates using the ab initio potential are in close agreement with experimental P-T data and measured cage occupancies. The comparison showed that only the first-principles ab initio potential is able to physically characterize both the microscopic and macroscopic behaviors of methane hydrates. / (cont.) Various sets of thermodynamic reference properties currently available in the literature were examined by applying the van der Waals and Platteeuw model to predict monovariant 3-phase equilibria for hydrate forming binary mixtures from 260 to 320 K. Experimental uncertainties were found to be large enough to cause significant changes in the prediction of dissociation pressures. The ab initio methane-water intermolecular potential was used to obtain the reference properties with significantly small deviations, and the resulting parameters are able to give the best prediction of phase equilibria over the entire temperature range. / by Zhitao Cao. / Ph.D.