Janus particles are colloidal particles for which one half of the surface has different attributes than the other half. One property of a spherical dielectric particle with half of its surface covered by a layer of another dielectric or metal is that it has a non-uniform scattering pattern when exposed to light. However, the angle with which the light is shone on the particle has a large effect on the scattering pattern produced. Thus it is important that we are able to orient these Janus particles. The orientation can be controlled if we apply an electric field to the particle for example. The movement of colloidal particles with an electric field is widely studied and this field is called dielectrophoresis. For a Janus particle, the calculations for the force and torque become complicated. The movement and rotation of these particles have been studied, however, no analytic solution has been found. In this report, we derive a semi-analytic description of the force and torque due to an external electric field on a spherical Janus particle. For this, first the potential due to an external electric field is determined and then the force and torque are calculated with two methods: the dipole approximation and the Maxwell Stress Tensor method. In the dipole approximation, there is no force on the Janus particle. But, there is a torque on the particle in the dipole approximation. Due to this torque, the Janus particle will orient itself such that its cap points in the direction perpendicular to the applied field. For the torque calculated with the Maxwell Stress Tensor, we get a similar result as in the dipole approximation. On the other hand, according to the calculations with the stress tensor, there is a relatively small force on the particle.

The behaviour of ODS 12Cr steel under thermal treatment is studied in this report at micro and macro level. ODS 12Cr steel is always in the ferrite phase and has a melting point at 1500 ºC. Before studying, the retrieved samples were metallographically prepared in four steps: mounting, grinding, mechanically polishing and electrolytically polishing. A measurement was done to analyse the effect of electrolytically polishing on bulk S and W parameters. This showed that mechanically polishing with 0.04 μm alumina particles has the same effect as electrolytically polishing. Next, the alloy was studied with three different measurement techniques: positron annihilation Doppler broadening spectroscopy, Vickers hardness test and positron lifetime measurements. Before these measurements the samples were annealed at selected temperatures for 10 minutes and naturally cooled. The Doppler broadening spectroscopy was done with the Variable Energy Positron beam (VEP) at the Reactor Institute Delft (RID). With this set-up the S and W parameter were measured at different im- plantation energies and converging bulk values of them were determined. The results were fitted with VEPFIT. This measurement was done in the as received state and after annealing from 200 ºC up to 1300 ºC in steps of 100 ºC. The Vickers hardness test was done with a load of 0.3 kgf and in the same temperature range as the VEP measurements but with steps of 200 ºC. A lifetime spectrum was measured in the as received state with two sample sandwiching a 22Na source packed with kapton. The average lifetime was determined by fitting the spectrum with LT 9.2. This measurement was repeated after annealing for 10 minutes from 200 ºC up to 700 ºC in steps of 100 ºC. The three different measurement techniques show corresponding results. Up to annealing temperatures of 1000 ºC the results stay constant. The bulk S and W parameters are respectively 0.475 and 0.078. The Vickers hardness stays at 395 HV and is comparable to literature values. The average lifetime is approximately 208 ps, which corresponds with defects with sizes comparable to or at least larger than that of divacancies. At this temperatures most thermal vacancies are trapped by the nano-oxide particles and are not able to liberate themselves which causes the constant results. At higher temperatures (larger than 1100 ºC) the thermal vacancy concentration increases and the vacancies gain enough energy to be liberated. This causes, in combination with oxide particles clustering, more defects in the material and explains the increasing bulk S value for temperatures up from 1100 ºC. The high bulk S values, compared with an iron alloy with less chromium, can also originate from clustering of chromium atoms. The surface S parameters are also increased in this temperature domain due to the formation of an oxide layer which can be seen with the naked-eye. Finally, the hardness value decreases to 374 HV after annealing at 1200 ºC which is a significant decrease and indicates that the pinning of the nano-particles decreases, resulting in grains growing easier.

Humanity needs to increase use of renewable sources of materials and energy. Biomass can be used for both of these needs. Cellulose is the main component of biomass. Understanding the multi-level hierarchical structure of cellulose holds the key tomultiple applications of this material. One of the promising applications of lignocellulsic biomass is the production of bioethanol as a replacement for fossil fuels. Yearly production of biomass could potentially supply enough bio-ethanol to completely replace gasoline. However, it would require dramatic increase in the efficiency of the bioethanol production. The main obstacle to the development of bioethanol production into a sustainable process is the recalcintrance of cellulose which was developed throughout entire plant evolution. In order to overcome this obstacle an important step was incorporated into the process, i.e. pretreatment of biomass. Amultitude of pretreatments have been developed and applied to disrupt the structure of lignocellulosic biomass. However it is still not clear, which structural parameters are responsible for the success of a certain pretreatment technique.@en

An all-solid-state battery represents a promising solution for overcoming current lithium-ion batteries ’technological and safety limitations. However, the individual limitations of both inorganic and organic solid electrolytes hinder technological progression. Hybrid solid electrolytes hold the potential to surpass these limitations by integrating both the inorganic and organic phases. A comparative assessment was conducted between hybrid solid electrolytes produced via solvent and dry synthesis, to address potential solvent interactions during hybrid solid electrolyte production and prioritise sustainability. At 30°C, the comparative analysis demonstrates that the dry-processed PEO13LPSC10 hybrid solid electrolyte achieves a higher ionic conductivity of 1.61×10−5 S/cm, exceeding that of its solvent pro-cessed counterpart, which exhibits a conductivity of 1.51×10−5 S/cm. Conversely, for the PEO18LPSC10 hybrid solid electrolytes, the solvent processing method leads to a higher ionic conductivity, measured at 8.37×10−6 S/cm, in contrast to 7.61×10−6 S/cm observed for the dry-processed method. Thermal analysis indicates that heating above the polymer’s melting transition temperature leads to slow crystallisation in hybrid solid electrolytes using the dry method, resulting in two crystalline phases, as opposed to the single crystalline phase, which was observed using the solvent method. Both processing methods demonstrate homogeneity when comparing the top and bottom surfaces; however, an analysis of surface compositions between the two synthesis methods reveals distinct differences, as identified through. X-ray photoelectron spectroscopy. Moreover, decomposition is observed in both synthesis approaches but is more significant in solvent synthesis. The chemical stability of hybrid solid electrolytes produced by dry synthesis surpasses the solvent-based method. Further analysis through the dry method investigation reveals that an ethylene oxide to Li+ ratio of 10:1, and a Li6PS5Cl ratio of 10 wt%, yield the highest ionic conductivity among all studied hybrid solid electrolytes. This combination achieves an ionic conductivity of 3.35×10−5 S/cm at 30° C. Additionally, adding Li6PS5Cl and the alkali salt lithium bis(trifluoromethanesulfonyl)imide enhances the amorphous nature and mobility of the polymer, due to a plasticising effect on the organic matrix.

In this thesis, an algorithm to model the magnetic perturbation field caused by ships is designed and implemented. A systematic description of methods used for modelling the magnetic signature of ships is given. The algorithm fits coefficients of a prolate spheroidal harmonic expansion of the scalar potential of the magnetic field using a least angle regression method (LARS) modified to implement Lasso regularisation. A Monte Carlo method with model selection based on Akaike's information criterion (AIC) is used to select optimal parameters specifying the prolate spheroidal coordinate system centred on the ship. Furthermore, a method to restrict the degree and order of the harmonic expansion is presented and an extension of the scikit-learn module in Python is given. The predictive power of the model was verified using simulated test data, which showed that the designed model is able to make adequate predictions, but improvements are needed. Different analyses on the inputs of the model showed that the model is succesful for low levels of noise, but is susceptible to overfitting for higher levels of noise. Several recommendations for further research are made.

The aim of this thesis was to test the efficiency in practice of an analytical propagator with collision detection for N-body Keplerian systems. This can be used to simulate the evolution of a protoplanetary disk, which gives insight into how planetary systems form. The analytic propagator calculates collisions one by one, while a numerical propagator would compute each time step. The idea of using the analytic propagator is that collisions are rare in astronomical scales, such that jumping from collision to collision and calculating it, is more efficient than calculating all the time steps that are between collisions. Simplifying the orbits of the planetesimals into perfect Keplerian orbits, analytical solutions exist which are used by the analytic propagator. In this thesis, the runtimes of simulations were measured as well as other properties directly related to the runtime. The overall efficiency of the algorithm with respect to N seemed to be O(N3), which is one power less than previously predicted. The prediction was that the runtime of the full simulation is O(N2ε + N4s3/Ia3). Here ε is the maximum eccentricity, s/a is the ratio of a planetesimal's radius to the semi-major axis of its orbit, and I is the maximum inclination. This was calculated by estimating the total number of collisions to be O(N2s2/Ia2) and the runtime for each collision to be O(N2s/a). But the number of collisions turns from quadratic to linear in N, implying that above a certain N almost all planetesimals collide, which reduces the power of N by one. For comparison, the octree code has an algorithmic efficiency of O(N logN) per time step, and the number of steps for a fixed integration time grows as O(N4/3 log N).

A time of flight MIEZE spectrometer, which employs radio frequency spin flippers with square pole shoes and a magnetic yoke is presented. These flippers can achieve higher fields than conventional resonant RF flippers, which employ an air core. High fields are crucial for the construction of a high resolution and compact MIEZE spectrometer. Setups using conventional and novel flippers are constructed for comparison and a variety of experiments to characterize MIEZE instruments. Evidence is presented which indicates that high field flippers are capable of generating a 100kHz MIEZE signal comparable to that obtained with a conventional setup. Furthermore the need for a fast and thin detector is demonstrated. In addition the shape of the MIEZE focal spot is determined to be Gaussian. Finally the importance of stable timing for time of flight MIEZE is demonstrated. This research is relevant for the implementation of MIEZE on the Larmor instrument at ISIS pulsed neutron source in the UK.

Nano-carriers have the potential to be an enormous game-changer in medicinal drug delivery systems. The polymeric nano-carriers used in this study are a product of the self-assembly of amphiphilic block copolymers, a complicated process which must be understood completely to finely tune the desired morphology for drug delivery. The goal of this thesis is to gain a better understanding of the self-assembly process of amphiphilic block copolymers. Specifically, it will focus on the ’opaque phase’ observed for poly(1,2-butadiene)-b-poly(ethylene oxide) (PBd-PEO) block copolymers, which seems to occur in the early stages of the self-assembly process. A nano-precipitation method has been developed at the TU Delft, which induces selfassembly and brings forward the opaque phase. The used block copolymer has a hydrophobic PBd block and a hydrophilic PEO block. This block copolymer dissolves well in acetone, but upon water (H2O) addition, it starts to self-assemble into spherical aggregates, useful for drug delivery. At small volumes of H2O, the opaque phase appears and disappears as more H2O is added. In this thesis, multiple samples have been prepared with the so-called Inverse Nanoprecipitation method and different experimental parameters among which the volume percentage of H2O present in the sample, have been varied. The samples have been studied using Visual Inspection, Dynamic Light Scattering and Spin Echo Small Angle Neutron Scattering. The experiments show that the time intervals between H2O addition do not affect the formation of aggregates, but rather the ‘when’ of adding the H2O. If this is added to the acetone before the block copolymer is dissolved, it affects the self-assembly process. A visual experiment showed that the opaque phase occurred 1.2±0.1 vol% H2O earlier than in previous research, which might be a result of the lower room temperature during this thesis. Another significant result might be that the addition of acetone-D6 or D2O affects the self-assembly process, which must be considered for future SESANS measurements. Lastly, during the opaque phase a strong temperature sensitivity is observed (which was already found in previous research at TU Delft, by E. Remmelts and further researched by R. Baaijens), high light scattering intensities are detected with DLS and for SESANS measurements the scattered neutron intensities were low. These observations all strongly point to a theory called ‘pre-micellization’, which gives a better understanding of the opaque phase.

This thesis contains the development of continuous Kepler orbit- and a discrete numerical integration-based collision detection algorithms in a system of LEO satellites, which in combination with collision algorithm form a simplified space debris evolution model. This model is then used to study the Kessler syndrome. The continuous and discrete algorithms get their names from the solutions of the Two Body Problem (TBP) and the methods for collision detection that they are based on; the analytical and continuous time solution of TBP resulting in the Kepler orbits and the numerical, discrete time Velocity Verlet integration of the TBP. The collision model consists of an algorithm for fragmentation collisions largely based on the NASA Standard Breakup Model and a method for elastic, random scattering collisions. Comparison between the continuous and discrete algorithms shows that on average both predict the same time to the first collision in a system of homogeneously distributed satellites. The algorithms differ in their efficiency depending on the number and the radius of the satellites in and the geometry of the system. For relatively small satellite numbers in large systems, the continuous algorithm is computationally more efficient. However, as more satellites or fragments result from previous collision, the continuous algorithm is outperformed by the discrete algorithm. Consequentially, its time complexity appears to be O(N2). Armed with this knowledge, the continuous algorithm is used to show that an initially small system of satellites is able to evolve into a large population of debris particles within several decades. Similarly, the discrete algorithm is used to show that an ordered collection of satellites in an homogeneously distributed system of debris-like particles exhibits the effect that a collision early on in the simulation can cause a cascade of collisions at a later stage. Hence Both the discrete and continuous algorithms predict a Kessler Syndrome and mimic predictions made by more advanced models from leading space agencies like NASA’s LEGEND, ESA’s DELTA and JAXA’s LEODEEM [Lio+13].Future research could focus on including atmospheric drag and gravitational perturbations to the continuous algorithm, thereby lengthening the time frame during which it can realistically simulate a system of satellites in LEO. To achieve this, it is suggested that one execute the calculations inherent to the algorithm in parallel on a GPU, as these are independent of each other.