Crystal engineering has advanced the strategies of design and synthesis of organic solids with the main focus being on improving the properties of the developed materials. Research in this area has a significant impact on large-scale manufacturing as industrial processes may give rise, at various stages, to stress-induced transformations and product modification. This thesis investigates the solid-state properties at play in the case of the surface and structural reorganization which results from the stress within a crystal during the drying of labile multicomponent organic solids. Chapter 1 introduces various concepts in solid-state chemistry and explores their application in the manufacture of solid pharmaceuticals. The significance of stress-induced transformations during the drying process is illustrated by reactions associated with crystal decomposition processes such as dehydration, desolvation and sublimation. The chapter also introduces carbamazepine (CBZ) multicomponent materials as models for the studies of stress-induced transformations. Chapter 2 presents the experimental section of the work and describes the materials, methods and equipment used for the study. Chapter 3 presents the analysis of the various crystal structures of CBZ. The crystal forms are classified with an emphasis on a comparison of intermolecular interactions, coformer arrangement, crystal packing and the geometric parameters of slip/cleavage planes within the crystals. Chapter 4 details the experimental methods for preparation of the samples. Cooling solution crystallization was the standard method which has been selected, and crystal habit and surface variations have been studied as a function of the solution concentration and the crystallization environment. Attention is given, in particular, to the preparation of carbamazepine dihydrate and the specific cocrystals carbamazepine cocrystals formed with benzoquinone and oxalic acid. Chapter 5 is devoted to the dehydration of carbamazepine dihydrate for samples prepared and examined in approximate 1-gram laboratory scale quantities. It explores the effect of vacuum, temperature, humidity and seeding on the surface and bulk properties of the products. Chapter 6 presents the solid-state characterization results obtained for samples crystallized at a much larger scale (ca. kilogram quantities) with a particular emphasis placed on their mechanical properties. It explores the comparison of large scaled batches with laboratory scale samples in order to obtain a greater understanding of how small-scale laboratory studies may be extrapolated to more commercial processes. Chapter 7 present results on the stress-induced transformations of carbamazepine solvates and cocrystals. It details the effect of thermal decomposition on the surface and bulk properties of the products, possible seeding effects, and the interconversion between carbamazepine dihydrate and carbamazepine benzoquinone cocrystal. Chapter 8 combines the research findings concerning the structural analyses of the materials in the context of current literature. Limitations related to the use of carbamazepine as a model and to the experimental set-up are also explored. In the final chapter conclusions are presented which correlate observations made on the crystallization and decomposition of multicomponent materials operating at small-scale to effects appropriate to manufacturing of pharmaceuticals at large scale.

The production of multi-component cement from clinker and two additives such as trass and blast furnace slag has now spread throughout the world. These additives are generally interground with clinker to produce a composite cement of specified surface area. The grinding stage is of great importance as it accounts for a major portion of the total energy consumed in cement production and also as it affects the quality of composite cements by the particle size distribution of the individual additives produced during grinding. This thesis study was undertaken to characterize the breakage properties of clinker and the additives trass and slag with the intention of delineating their grinding properties in separate and intergrinding modes. Single particle breakage tests were conducted by means of a drop weight tester in order to define an inherent grindability for the clinker and trass samples in terms of the median product size ( ). In addition, a back-calculation procedure was applied to obtain the breakage rate parameters ( ) of perfect mixing ball mill model using industrial data from a cement plant. Kinetic and locked-cycle grinding tests were performed in a standard Bond mill to determine breakage rates and distribution functions for clinker, trass and slag. Bond work indices of these cement components and of their binary and ternary mixtures were determined and compared. Attempts were made to use back-calculated grinding rate parameters to simulate the Bond grindability test. The self-similarity law was proved to be true for clinker and trass that their shapes of the self-similarity curves are unique to the feed material and independent of the grinding energy expended and overall fineness attained. The self-similar behaviour of tested materials will enable process engineers to get useful information about inherent grindability and energy consumption in any stage of the comminution process. The parameters, and indicating the degree of size reduction were defined with different theoretical approaches as a function of energy consumption by using single particle breakage test data of clinker and trass. The breakage distribution functions were found to be non-normalizable. On the other hand, the breakage rate functions were found to be constant with respect to time but variable with respect to changing composition in the Bond ball mill. These variations are critical in computer simulation of any test aiming to minimize the experimental efforts of the standard procedure. As a result of the back calculation of breakage rate parameters for clinker and trass samples in the Bond mill, no common pattern was seen for the variation of the rate parameters. Therefore, computer simulation of the Bond grindability test did not result in an accurate estimation of the Bond work index.

This study showed that hydrodynamic particle breakage had potential as a method to help improve the disinfection of wastewater effluents. The physicochemical properties of flocs from four distinct effluents sources (combined sewer overflow, settled combined sewer overflow, primary effluent, and final effluent) were compared before and after hydrodynamic treatment. The use of hydrodynamic force to cause floc breakage was shown to be effective, though variable, across all source types. This variation in floc breakage did not have a significant impact on the UV disinfection achieved, as the UV dose kinetics were similar across samples from the same source type. The results of this study demonstrate how the physicochemical properties of floc are affected when exposed to shear force. These observations further the understanding of floc composition and behaviour when shear forces are applied while also providing evidence to indicate this process improves the performance of UV disinfection technology.

In the present work, the breakage of wastewater particles in orifice flow is investigated through numerical simulations. Using maximum strain rate along particle paths as the breakage criterion, breakage is predicted using computational fluid dynamics. The numerical simulations confirm that nominal orifice strain rate cannot explain the higher particle breakage in single-orifice systems compared to that of multi-orifice systems, instead particle breakage was found to correlate well with the maximum strain rates in the system. On the issue of effect of initial particle location on breakage, numerical modeling shows that particles travelling along the centerline are suspected to break less than those travelling near the wall. However, experiments designed to study the breakage of particles injected at various radial locations proved inconclusive. Finally, results suggest that while single orifice systems are ideal for strong particles, multi-orifice systems may be more effective in breaking weak particles.

In the present work, the breakage of wastewater particles in orifice flow is investigated through numerical simulations. Using maximum strain rate along particle paths as the breakage criterion, breakage is predicted using computational fluid dynamics. The numerical simulations confirm that nominal orifice strain rate cannot explain the higher particle breakage in single-orifice systems compared to that of multi-orifice systems, instead particle breakage was found to correlate well with the maximum strain rates in the system. On the issue of effect of initial particle location on breakage, numerical modeling shows that particles travelling along the centerline are suspected to break less than those travelling near the wall. However, experiments designed to study the breakage of particles injected at various radial locations proved inconclusive. Finally, results suggest that while single orifice systems are ideal for strong particles, multi-orifice systems may be more effective in breaking weak particles.

Particles exist in great abundance in nature, such as in sands and clays, and they also constitute 75% of the materials used in industry (e.g., mineral ores, formulated pharmaceuticals, dyes, detergent powders). When a load is applied to a bulk assembly of soil particles, the response of a geomaterial at the bulk (macro) scale, originates from the changes that take place at the particle scale. If particle breakage occurs, the shape and size of the particles comprising the bulk are changed; this induces changes in the contact network through which applied loads are transmitted. As a result, changes at the micro-scale can significantly affect the mechanical behaviour of a geomaterial at a macro-scale. It is therefore unsurprising that the mechanisms leading to particle breakage are a subject of intense research interest in several fields, including geomechanics. In this thesis, particle breakage of two dry granular materials is studied, both experimentally and numerically. The response of the materials is investigated under different stress paths and in all the tests grain breakage occurs. High resolution x-ray computed micro-tomography (XCT) is used to obtain 3D images of entire specimens during high confinement triaxial compression tests and strain controlled oedometric compression tests. The acquired images are processed and measurements are made of the temporal and spatial evolution of breakage, local variations of porosity, volumetric and shear strain and grading. The evolution and spatial distribution of quantified breakage including the resulting particle size distribution for the whole specimen and for specific areas, are presented and further related to the localised shear and volumetric strains that developed in the specimens. In addition, the discrete element method (DEM) was used to provide further micro-mechanical insight of the underlying mechanisms leading to particle breakage. Classical DEM simulations, using a Hertz-Mindlin contact model and non-breakable spheres, was first deployed to study the initiation and likelihood of particle breakage under oedometric compression. Moreover, a bonded DEM model was used to create clumps that represent each particle and simulate breakage of particles under single particle compression. The DEM model parameters were obtained from results of single particle compression test and the models were validated against the quantitative 3D information of the micro-scale, acquired from the XCT analysis.

Particle breakage can be significant in stirred vessels such as crystallizers. During crystallization, particle breakage can occur due to particle contact with other particles, the impeller, the suspension fluid, and/or the vessel. Such breakage produces fines and can cause filter plugging downstream. Although research has been conducted with respect to particle breakage, a comprehensive study is still needed to quantify the breakage occurring in stirred vessels. The overall goal of this research is to model the particle breakage occurring in a stirred vessel by analyzing the particle size and shape distributions that result from breakage. Breakage experiments are based on collision influences that affect the two dominant collisions types, crystal-to-crystal and crystal-to-impeller collisions. Results showed that the quantity of fines produced are affected by the solids concentration or magma density and suspension fluid utilized. Additionally, aqueous saturated solutions produced particle size distributions that differ from those obtained using a nonsolvent. Similar particle size distributions for two different materials (NaCl and KCl) are achieved in the same nonsolvent (acetonitrile) by adjusting the agitation rate using the Zwietering correlation to account for property differences; moreover, the same agitation rate adjustment produced similar distributions for KCl in acetone and acetonitrile which were both nonsolvents. However, modifications to the Zwietering correlation, such as changing the significance of the initial particle size, are proposed before this method of adjustment is deemed accurate. Number-based population modeling of particle breakage is achieved within 1-5% error for NaCl at each agitation rate investigated. Breakage modeling using a discretized population balance equation with Austin's equation for attrition and the power law form of the product function for fragmentation is a viable approach; however, more work is needed to increase the accuracy of this model.

Turbomachinery operating on aircraft are often exposed to dusty or sandy environments during typical service. Engines on commercial and military flights operating in desert regions such as the Middle East or even Phoenix, Arizona can become severely damaged by ingesting dirt, grit, sand, and dust. Due to the high speeds, pressures, and temperatures, ingested particles can inflict erosion upon the blades, stators, and other components within the operating turbomachinery. Left unchecked, this erosion can lead to an increase in surge and stall probability while also contributing to higher service frequency and maintenance cost. Historically, particle-induced erosion is thoroughly documented and has been studied extensively; however, the underlying physics that govern the particle-surface interactions present in turbomachinery have remained elusive. The work described in this dissertation aims to describe a novel experimental technique used to measure and quantify particle-surface interactions characteristic of those present in turbomachinery. Specifically, the technique captures fully time-resolved trajectories of microparticles rebounding off a flat surface. It has been developed to measure the coefficient of restitution for particles of various material composition and shape incident on various surface materials at differing speeds and angles of incidence. The coefficient of restitution is a kinetic energy conservation metric that characterizes the amount of kinetic energy lost by particle during impact with a static surface and can be related to erosion extent and erosion mode. Many key findings were made during the experimental campaign that focused on particle bounce. It is shown that measuring fully-time resolved trajectories of bouncing particles leads to the highest quality coefficient of restitution data. Specifically, obtaining fully-time resolved trajectories allows for the stochasticity present in particle bounce to be measured and for the uncertainty in the coefficient of restitution to be fully characterized. It is shown that particle shape is not only the key driver that contributes to the stochasticity present in particle rebound, but also an important factor for determining the amount of plastic deformation that occurs on the flat surface. These findings are underscored in a novel coefficient of restitution model that accounts for the jagged particle shape present on typical particles and the plastic deformation of the surface material. This novel model also provides an analytical prediction of some of the stochasticity, or spread, present in coefficient of restitution measurements caused by particle shape. The modeled particle bounce and surface deformation is compared with experimental results. It is demonstrated that the new model accurately captures the slope of normal coefficient of restitution vs. normal velocity while surface deformation measurements can be used as an auxiliary validation for particle bounce models. In addition to measuring the coefficient of restitution for particle bounce, a novel measurement technique has also been developed to directly measure particle breakage. Along with the breakage probability of a particle, both the number and speed of the fragments for each broken breakage are measured. As expected, the breakage probability generally scales with normal velocity. It is shown that the average rebounding angle distribution for broken fragments is identical to that of bouncing particles for identical impact conditions. Moreover, average fragment velocities were shown to be about the same as that of bouncing particles. Finally, it is demonstrated that automated breakage detection allows for a significantly higher number of breakage events to be measured. This allows for the accuracy of the breakage probability measurement to be directly estimated with an uncertainty estimate. Raw results from the experimental study along with the novel coefficient of restitution model can be used to develop models for erosion in turbomachinery. Specifically, the coefficient of restitution is typically implemented in computational fluid dynamics (CFD) simulations to predict particle paths and induced erosion in turbomachinery. Currently, CFD simulation results do not agree with real-world erosion findings. This implies that the underlying physics governing erosion are not fully understood. Higher accuracy models, such as the one developed in this dissertation, coupled with empirical data can be leveraged to increase the accuracy of CFD simulations to predict erosion. In the long term, if erosion can be predicted, new engine designs can be developed that will be erosion resistant. These engines may feature new geometry to aid in expelling particles from an engine along with different materials that may be more erosion resistant. / Doctor of Philosophy / Erosion induced by particle ingestion has plagued aircraft since their inception. During operation within dusty environments, sand, dirt, and grit can be ingested into operating turbomachinery such as turbofan engines, turboshaft engines, and turbojet engines. High relative speeds between the rotating turbomachinery and particles coupled with high temperatures and pressures results in deformation and erosion of critical engine surfaces. Left unchecked, erosion of the engine can lead to significant safety concerns as engine failure can occur. Additionally, eroded engines require increased maintenance and servicing costs. While the effects of erosion have been extensively studied over the past few decades, the underlying physics that govern the erosion process have remained elusive. This work aims to elucidate some of the underlying physics that govern particle-surface interactions within turbomachinery. A novel experimental technique used to characterize particle bounce and particle breakage has been developed. Specifically, microparticles characteristic of those often ingested into engines are accelerated towards a flat surface made of materials often used in turbomachinery. A high-speed camera is used to image particle trajectories before and after impact and kinetic energy loss of each particle is measured. These measurements are used to compute the coefficient of restitution, which is a parameter that can be directly related to erosion location, extent, and mode. Additionally, the technique is also capable of detecting particle breakage and characterizing the number and speed of resulting fragments from the breakage event. The coefficient of restitution measurements are leveraged to draw key insights relating to irregular particle shape and deformation of the surface. These insights are then used to develop a novel coefficient of restitution and surface deformation model. This novel model accounts for the jagged particle shape characteristic of particles often ingested into turbomachinery. Moreover, the model also accounts for the stochasticity in coefficient of restitution measurement results induced by the jagged geometry. These contributions to the understanding of particle-surface interactions can significantly aid the development of erosion resistant designs for aircraft engines.

The use of coarse-grained fill materials has grown significantly in recent years especially on account of their use in dams and transportation networks. This study investigates compressibility of various coarse-grained fill materials in dry and wet loading conditions in oedometer test. Four materials were used in the experiments, which falls into GP, GW, GM and GC categories respectively. GP material is a weathered rock obtained from Eymir Lake region. This material was chosen especially to be able to investigate degradation and particle breakage due to compaction and compression. GW, GM and GC materials were obtained by using the material called &lsquo / bypass&rsquo / which is a fill material used in the construction of metro of Eryaman. Using these four materials, large-scale double oedometer tests were carried out to investigate compressibility in both dry and wet conditions. The double oedometer testing technique is used to investigate the effect of soaking on compressibility behaviour of compacted fill materials. Various compactive efforts were used in the compaction stage to investigate the effect of compactive effort on compressibility and degradation of the four gravelly materials. Gradations of the post-test samples were obtained and particle breakage due to compaction using various compactive efforts and particle breakage due to compression were determined. It is found that amount of compression does not necessarily depend on the dry density of the material and fine fraction is also a dominating property regarding the compressibility in coarse-grained fill materials. The vertical strains induced by soaking are on the order of 12% - 20% of the compression measured in dry loading case for the well-graded coarse-grained fill materials tested. Besides, there is significant particle breakage in the compaction process and no further particle breakage in the oedometer test for GP material.

Milling is a common unit operation in industry for the purpose of intentional size reduction. Considerable amount of energy is consumed during a grinding process and much of the energy is dissipated as heat and sound, which often makes grinding into an energy-intensive and highly inefficient operation. Despite many attempts to interpret particle breakage during a milling process, the grindability of a material in a milling operation remains aloof and the mechanisms of particle breakage are still poorly understood. Hence the optimisation and refinement in the design and operation of milling are in great need of an improved scientific understanding of the complex failure mechanisms. This thesis aims to provide an in-depth understanding of particle breakage associated with stressing events that occur during milling. A hybrid of experimental, theoretical and numerical methods has been adopted to elucidate the particle breakage mechanics. This study covers from single particle damage at micro-scale to bulk comminution during the whole milling process. The mechanical properties of two selected materials, i.e. alumina and zeolite were measured by indentation techniques. The breakage test of zeolite granules subjected to impact loading was carried out and it was found that tangential component velocity plays an increasingly important role in particle breakage with increasing impact velocity. Besides, single particle breakage via in-situ loading was conducted under X-ray microcomputed tomography (μCT) to study the microstructure of selected particles, visualize the progressive failure process and evaluate the progressive failure using the technique of digital image correlation (DIC). A new particle breakage model was proposed deploying a mechanical approach assuming that the subsurface lateral crack accounts for chipping mechanism. Considering the limitation of existing models in predicting breakage under oblique impact and the significance of tangential component velocity identified from experiment, the effect of impact angle is considered in the developed breakage model, which enables the contribution of the normal and tangential velocity component to be rationalized. The assessment of breakage models including chipping and fragmentation under oblique impact suggests that the equivalent normal velocity proposed in the new model is able to give close prediction with experimental results sourced from the public literature. Milling experiments were performed using the UPZ100 impact pin mill (courtesy by Hosokawa Micron Ltd. UK) to measure the comminution characteristics of the test solids. Several parameters were used to evaluate the milling performance including product size distribution, relative size span, grinding energy and size reduction ratio etc. The collective data from impact pin mill provides the basis for the validation of numerical simulation results. The Discrete Element Method (DEM) is first used to model single particle breakage subject to normal impact loading using a bonded contact model. A validation of the bonded contact model was conducted where the disparity with the experimental results is discussed. A parametric study of the most significant parameters e.g. bond Young’s modulus, the mean tensile bond strength, the coefficient of variation of the strength and particle & particle restitution coefficient in the DEM contact model was carried out to gain a further understanding of the effect of input parameters on the single particle breakage behavior. The upscaling from laboratory scale (single particle impact test) to industrial process scale (impact pin mill) is achieved using Population Balance Modelling (PBM). Two important functions in PBM, the selection function and breakage function are discussed based on the single particle impact from both experimental and numerical methods. An example of predicting product size reduction via PBM was given and compared to the milling results from impact pin mill. Finally, the DEM simulation of particle dynamics with emphasis on the impact energy distribution was presented and discussed, which sheds further insights into the coupling of PBM and DEM.