Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1958. / Includes bibliographical references (leaves 63-64). / by Richard T. Nowak. / M.S.

This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2019 / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (pages 211-233). / Electrodeposition is a fascinating electrochemical phenomenon that contains deep physical insights and has broad practical applications. At the heart of the physics governing electrodeposition is a competition between a destabilizing force caused by surface crests growing more rapidly than surface troughs in a positive feedback loop and a stabilizing force arising from surface energy effects that prevent the surface from roughening excessively. The physical manifestation of this surface instability is the formation and propagation of dendrites. Some applications of electrodeposition include electroplating of metals such as copper and charging of next-generation high-energy-density metal batteries such as lithium metal batteries. From both theoretical and practical standpoints, it is important to understand how to control and exploit electrode-position. / In this thesis, we explore electrodeposition in a homogenized charged porous medium that contains a fixed background charge density, which affords us a new knob for controlling electrodeposition. In practice, such a background charge density can either naturally arise from ionization of surface functional groups or be generated through experimental techniques such as layer-by-layer deposition of polyelectrolytes on the pore surfaces. We investigate the theoretical aspects of electrodeposition in charged porous media in three different ways. First, we introduce a simple transport model that accounts for the background charge density and couple it with electrochemical reaction kinetics for electrodeposition. We then validate the coupled model by comparing predicted steady state current-voltage relations and linear sweep voltammetry with experimental data for copper electrodeposition in a variety of nanoporous media. / Second, we perform linear stability analysis on the model to understand how key system parameters such as the background charge density affect the linear stability of the metal surface. We then show good agreement between theoretical predictions and experimental observations of the critical and instability wavelengths for copper electrodeposition in cellulose nitrate membranes. Third, we carry out impedance analysis on the model and explain some intriguing features in the experimental impedance spectra for copper electrodeposition in anodic aluminum oxide membranes. Through these three different types of analysis, we demonstrate the predictive power and robustness of the theory despite its simplicity / by Edwin Sze Lun Khoo. / Ph. D. / Ph.D. Massachusetts Institute of Technology, Department of Chemical Engineering

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1999. / Includes bibliographical references (p. 259-275). / With the rapid advancement of computational science, modeling and simulation have become standard methods to study the behavior of complex systems. As scientists and engineers try to capture more detail, the models become more complex. Given that there are inevitable uncertainties entering at every stage of a model's life cycle, the challenge is to identify those components that contribute most to uncertainties in the predictions. This thesis presents new methodologies for allowing direct incorporation of uncertainty into the model formulation and for identifying the relative importance of different parameters. The basis of these methods is the deterministic equivalent modeling method (DEMM), which applies polynomial chaos expansions and the probabilistic collocation approach to transform the stochastic model into a deterministic equivalent model. By transforming the model the task of determining the probability density function of the model response surface is greatly simplified. In order to advance the representation method of parametric uncertainty. a theoretical study of polynomial chaos representation of uncertain parameters has been performed and an Adomian polynomial expansion for functions of random variables has been developed. While DEMM is applied to various engineering systems to study the propagation of uncertainty in complex models, a systematic framework is introduced to quantitatively assess the effect of uncertain parameters in stochastic optimization problems for chemical product and process design. Furthermore, parametric uncertainty analysis techniques for discrete and correlated random variables have been developed such that the deterministic equivalent modeling method can be applied to a broader range of engineering problems. As a result of these developments, uncertainty analysis can now be performed 2 to 3 orders faster than conventional methods such as Monte Carlo. Examples of models in various engineering systems suggest both the accuracy and the practicality of the new framework for parametric uncertainty analysis established in this thesis. / by Cheng Wang. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1999. / Includes bibliographical references (p. 305-322). / Separation processes are used extensively in the chemical process industries and by far the most common of these is distillation. Although several alternative strategies have been developed, distillation will likely remain dominant particularly for the largescale separation of non-ideal liquid mixtures. A topic of particular interest in recent years has been heterogeneous azeotropic distillation or heteroazeotropic distillation. This technique is commonly employed to separate azeotropic mixtures by introducing a heterogeneous entrainer that causes liquid-liquid phase separation. Although the design and simulation of heteroazeotropic systems is far more complicated than its homogeneous counterpart, heteroazeotropic distillation is often preferred due to the ease of recovery of the entrainer and the crossing of distillation boundaries due to the liquid-liquid phase split in the decanter. The topic of this thesis is the analysis of heteroazeotropic systems. Specifically, an algorithm has been developed which, under reasonable assumptions, will compute all homogeneous and heterogeneous azeotropes present in a multicomponent mixture predicted by the phase equilibrium model employed. The approach is independent of both the particular representation of the nonideality of the mixture and the topology of the liquid-liquid region. Furthermore, the approach can be readily extended to handle any number of liquid and/or solid phases in equilibrium. Moreover, the heteroazeotrope finding algorithm can be extended to explore the phase equilibrium structure of a multicomponent mixture under system and/or property model parameter variation, including the detection of incipient homogeneous and heterogeneous azeotopes and the determination of the bifurcation values of the parameters where they appear, disappear, or switch between each other. The ability to predict the incipient homogeneous and heterogeneous azeotropes that may appear under different conditions or property parameter values can be incorporated into design algorithms to expand the number of alternative designs. Furthermore, the ability to systematically and efficiently explore the phase equilibrium structure is a valuable tool when fitting property model parameters, allowing the experimentalist to rapidly explore the capabilities and limitations of the phase equilibrium model. The techniques mentioned above are useful when analyzing heteroazetropic systems for design purposes. The second product of this thesis improves the efficiency of the actual simulation of the heteroazeotropic system (or any system for that matter). Specifically, a new class of automatic differentiation methods, known as 'subgraph reduction methods', have been developed that offer substantial improvement over existing techniques both in the increase in speed of the derivative evaluation and the reduction in memory required to store and evaluate the Jacobian matrix of a sparse system of equations. Furthermore, a variant of the subgraph reduction approach has been custom-tailored for use within an interpretive simulator architecture that dramatically increases speed and reduces memory requirements compared to other techniques commonly employed in this environment. / by John Eugene Tolsma. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1999. / Includes bibliographical references. / The feasibility of microstructuring polyelectrolyte multilayers has been established by using the layer-by-layer assembly technique in combination with patterned self-assembled monolayers (SAMs). SAMs of a carboxylic acid surface (COOH) and a triethylene glycol surface (EG) were used to promote and resist polyelectrolyte adsorption. respectively. Processing conditions necessary for the selective deposition of both weak and strong polyelectrolytes were established as a function of polyelectrolyte molecular weight. ionic content, ion type. and pH. Low molecular weight polyelectrolytes adsorbed more selectively on patterned SAM surfaces than high molecular weight polyelectrolytes. Strong polyelectrolytes multilayers of sulfonated poly(styrene) (SPS) and polydiallyldimethyl ammonium chloride (PDAC) required the addition of 0.1 M NaCl to the polyelectrolyte dipping solutions to optimize selective deposition. Adding 1.0 M NaCl to each polyelectrolyte solution and including a periodic drying step in the multilayer fabrication process reversed the templating ability of the COOH and EG SAMs for the SPS/PDAC multilayers. Weak polyelectrolytes such as linear (polyethylenimine) (LPEI), branched (polyethylenimine) (BPEI), poly(allylamine hydrochloride (PAH), poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) were adsorbed at pH 2.5. 4.8, 7, and IO on patterned COOH and EG SAMs to determine optimal patterned deposition conditions. Each polyacid and polyamine had a secondary interaction that changed the affinity of the multi layers for the COOH and EG surfaces. The technique was also extended to include an optically active dye in the multilayers. Imaging the patterned dye multilaycrs under a fluorescence microscope produced light emission from the selectively adsorbed dye molecules. The different conditions and interactions that produced selective deposition of polyelectrolyte multilayers were combined to build complex multilayer structures. A cladding structure was produced by depositing a blanketing layer of strong polyelectrolytes on preformed patterned multilayers. A different complex structure of polyelectrolytes was fabricated by selectively adsorbing a second polyelectrolyte system within the patterned structure of strong polyelectrolyte multilayers. This assembly was accomplished by utilizing secondary interactions of weak polyelectrolyte multilayers with the EG surface. / by Sarah L. Clark. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2018 / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 143-151). / DNA is a highly programmable molecule that can be designed to self-assemble into nearly arbitrary 2D and 3D nanoscale structures. DNA origami is a particularly versatile method to achieve complex molecular architectures. However, the rules for designing scaffolded DNA origami have not been well-formalized, which hinders both the investigation of characteristics of well- and poorly-folded structures as well as the participation of a larger scientific audience in DNA nanotechnology. In my thesis work, a fully automatic inverse design procedure DAEDALUS (DNA Origami Sequence Design Algorithm for User-defined Structures) has been developed that programs arbitrary wireframe DNA assemblies based on an input wireframe mesh without reliance on user feedback. This general, top-down strategy is able to design nearly arbitrary DNA architectures, routing the scaffold strand using a spanning tree algorithm and adding staple strands in a prescribed manner. The wireframe nanoparticles produced can use antiparallel crossover (DX) motifs, for robust selfassembly, parallel paranemic crossover (PX) motifs, for staple-free self-assembly, or a hybrid of the two, to minimize the number of staples required for folding to the ones necessary for functionalization. The thermodynamics of the self-assembly of these wireframe structures, and the effects of scaffold and staple routing, are investigated using quantitative PCR and FRET measurements, tracking fluorescence to elucidate global and local folding events. The framework developed should enable the broad participation of nonexperts in this powerful molecular design paradigm and set the foundation for further predictive models of DNA self-assembly. / by Sakul Ratanalert. / Ph. D. / Ph.D. Massachusetts Institute of Technology, Department of Chemical Engineering

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2019 / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 329-334). / Distributions appear in many forms in models of chemical engineering systems. Such distributions account for microscopic variability in the system while simultaneously explaining its macroscopic properties. These macroscopic properties are often of practical engineering interest. Thus, it is valuable to be able to characterize the underlying distributions that affect them. Recently, in the mathematical programming literature, it was shown that it is possible to optimize a linear objective over a set of distributions by solving a specific type of convex optimization problem called a semidefinite program (SDP). From a theoretical perspective, SDPs can be solved efficiently. Furthermore, there exist several off-the-shelf codes designed specifically to solve SDPs. This thesis demonstrates how these theoretical and practical advancements can be applied to chemical engineering problems featuring distributions. Broadly speaking, it shows how, given limited information about a distribution, one can use SDPs to calculate mathematically rigorous bounds on various descriptions of that distribution. Two specific types of distributions are examined: particle size distributions and probability distributions arising in stochastic chemical kinetics, with the majority of the thesis covering the latter topic. The SDP-based bounding method described herein provides a rigorous solution to the long-standing "moment closure problem" arising in stochastic chemical kinetics. Moreover, it provides a means of analyzing of stochastic chemical kinetic systems which cannot be effectively analyzed using existing methods. The bounding method does have some limitations, and we present several refinements of the method aimed at overcoming these limitations. Finally, we discuss several ideas through which the bounding method may be further improved, which have not yet been explored. / by Garrett Ryan Dowdy. / Ph. D. / Ph.D. Massachusetts Institute of Technology, Department of Chemical Engineering

The tensile and fracture properties of alumina trihydrate (ATH) filled epoxy resins have been determined up to a maximum volume fraction of 0.33 with a cold setting curing agent (Epikure T) and up to V[sub]f=0.54 with a hot curing agent (piperidine). The effect of a reactive rubber on these properties, on its own and in ATH-filled composites have also been considered. All filled compositions showed a lower tensile strength than the unfilled resin. The largest effect occurred at low volume fractions, up to V[sub]f = 0.1, loadings higher than this did not reduce the strength any further. The addition of a rubber toughener (ATBN), to the ATH-filled composite, reduced the strength still further. The elongation to failure was also reduced. Young's modulus was increased and was in agreement with other studies and predictions of theoretical models. The Lewis and Nielsen equation was found to give a satisfactory approximation for both the ATH-filled and ATH-rubber compositions. The fracture energy (G[sub]lc) exhibited a maximum at a volume fraction of 0.1. The fracture toughness (K[sub]lc) increased linearly with increasing volume fraction of filler. Addition of ATBN rubber to ATH-filled composites increased G[sub]lc and K[sub]lc further. The results correlated well with the crack-pinning prediction of Green at high volume fractions but showed some deviation at low loadings. The theory of Green gave a break-away value, r, of 0.75 (compared to r=1.8-2.0 for alumina). Fracture toughness results are discussed in terms of crack-pinning and crack-blunting mechanisms. Experiments using model specimens suggested that failure in composites containing weak particles, such as ATH, was initiated by failure of the particle itself. These experiments showed that a polymer coating around the particles could improve the tensile strength by delaying fracture and then blunting any subsequent crack. Various methods for applying a polymer coating to the filler were investigated. These included: Spray drying, solvent deposition, mechanical mixing and in-situ polymerisation. The in-situ polymerisation route showed the most potential, but this needs further optimisation.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1997. / Includes bibliographical references (leaves 109-114). / by Doron Levin. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2007. / Vita. / Includes bibliographical references (leaves 154-168). / Hierarchically nanostructured materials exhibit order on multiple length scales, with at least one of a few nanometers. The expected enhancements for applications using these materials include improved mechanical, thermal and electrical properties; however, control of the morphology which governs material performance and fabrication remains a challenge. The development of novel quantitative characterization techniques is important to connect the underlying morphology to relevant processing parameters and macroscopic behavior. Rheological and morphological analysis can illustrate these governing structure-property relationships for hierarchically nanostructured materials based on "O-D" polyhedral oligomeric silsesquioxane (POSS) particles, "l-D" carbon nanotubes (CNTs), and "2-D" clay nanoparticles. We develop a technique, using small-angle X-ray scattering, which provides quantitative measurements of the morphological characteristics of CNT films, including shape, orientation, CNT diameter, and spacing between CNTs. The method reflects a locally averaged measurement that simultaneously samples from millions of CNTs while maintaining the necessary precision to resolve spatial morphological differences within a film. / (cont.) Using this technique we elucidate spatial variation in pristine films and study changes in the film structure as a result of mechanical manipulations such as uniaxial compression and capillarity-induced densification. We study the rheological properties of blends formed from POSS and clay nanoparticles incorporated into PMMA in shear and extensional flow fields. Relevant morphological parameters, such as volume fraction, aspect ratio of the clay particles, and POSS miscibility are determined using wide angle X-ray scattering and transmission electron microscopy. The interdependence between melt rheology and morphology are understood within a theoretical framework for percolated physical networks, providing for comprehensive guidance regarding the performance and processing of POSS and clay based nanocomposites. / by Benjamin Ning-Haw Wang. / Ph.D.