- PostCharacterisation of droplet formation in spray drying of inhaled medicines(2022)Spray-drying is an established method for manufacturing of inhaled medicines. It facilitates the engineering of particles and control over various attributes of particle formation. An important step in this process is spraying, which is used to atomise the solvent solution into fine droplets. These atomised droplets are then dried in the presence of hot air to form particles. Spray dried particles have specific requirements when it comes to solid particle size and therefore control over particle size is one of the key factors necessary to the success of this technology. Spray formation and atomisation are however not well understood phenomenon and strong links between droplet formation and particle formation are found in theory. Hence, a good understanding of how droplet formation occurs and can be controlled is essential for the successful engineering of spray-dried particles. In this thesis, a Schlick 970 S4 nozzle was used to study the influence of composition on droplet size using formulations with different compositions of surface-active excipients and Active Pharmaceutical Ingredients (API). A Malvern Spraytec was used to determine the droplet size distribution at a selected range of flow parameters and changes in atomisation characteristics were studied by comparing the changes in droplet sizes for various formulations at the same flow parameters. The influence and effect of process parameters mainly liquid and gas flowrates on droplet formation are also studied and trends are plotted. It is found that gas flowrate is the primary parameter affecting the droplet formation and limitations on using the gas flowrate to manipulate the droplet size are identified. The main findings of this work indicate that the presence of surface-active excipients and API result in a reduction of droplet size and in turn solid particle size. This finding is further strengthened by correlating droplet size data with solid particle size data resulting in a good correlation for Dv50 and Dv90 values. Change in compositions ultimately result in changes to the physical properties of the solution namely, surface tension and viscosity. It is then explored how changes in surface tension and viscosity lead to changes in droplet size and strong correlations are observed. These strong correlations are then justified through mechanisms in theory and the cause effect relationship is identified. An attempt is also made using a high-speed camera to identify breakup mechanisms for use in future studies.
- PostSustainable Stimuli-Responsive Wound Dressing Made of Green Materials(2022)Non-healing chronic wound are wound that have a naturally high infection risk and produce an excess of exudate. To better treat these wounds, having a wound dressing that can absorb much of the exudate, keep the wound environment moist, and administer antibiotics when the wound is infected would be ideal. Here, a wound dressing that can absorb large amounts of exudate and locally administer drugs as a response to high pH commonly seen in infected wounds was prepared. First a carboxymethyl cellulose (CMC) aerogel scaffold was first prepared, using ethylene glycol diglycidyl ether (EGDE) as a cross-linker. The scaffold was then impregnated via diffusion or injection with naproxen-loaded pH-sensitive lignin nanoparticles (LNPs), synthesized using an anti-solvent method. Scanning electron microscopy (SEM) was used to investigate the morphology of the CMC gel as well as the shape and size of the synthesized unloaded and naproxen-loaded LNPs. The LNPs efficiency as drug-vehicles was investigated by loading the LNPs with naproxen and calculating the loading capacity and encapsulation efficiency of naproxen. Fourier Transform IR was used to investigate the cross-linking of CMC and EGDE and a tea bag test was used investigate the swelling capacity of the CMC gel. During the synthesis of the CMC gel, several parameters were varied. This resulted in aerogels with different morphologies and properties. Depending on the synthesis parameters, a swelling ratio between 28 and 623 g/g. A high swelling capacity was obtained by adding low concentrations of CMC and EGDE. The lowest swelling capacity was obtained by adding high EGDE concentrations and drying the gel via freeze-drying and oven-drying. Based on the SEM images of LNPs, unloaded and naproxen-loaded LNPs had a desired spherical shape with an average size of 71.6 and 81 nm, respectively. The size distribution was quite large for both LNPs between 31.5–127 nm for unloaded and 26.5–140 nm. The loading capacity of naproxen was around 10% while the encapsulation efficiency was around 48%. Based on the SEM images of the impregnated aerogels, no LNPs could be found. Either no LNPs were present in the sample taken or the LNPs have dissolved due to high pH.
- PostAnalysis of Multiphase Flow Centrifuge Decanter Separator Using CFD Simulations(2022)In the industry, it is common to encounter multiphase flow in many different applications in the oil and gas, food production and waste treatment industries. The nature of multiphase flow is extremely complex and is continuously developing in terms of methods and tools to perform analysis. One device in the industry involving mutiphase flow is the centrifuge decanter separator for sewage water treatment with the aim of separating fluid and solids. The centrifuge decanter in this study is a separator from Alfa Laval (AL). This study aims at analyzing the decanter by using computational fluid dynamics (CFD) as a simulation tool in combination with the field of multiphase flow modeling to understand the decanter’s different components and complex functions at high rotational speeds. This makes the decanter a very demanding topic for this type of research. The analysis of the phenomena was done through systematic changes in parameters, strategies and models. The Euler- Euler and Mixture multiphase models were used to predict the distribution of water and solids throughout the domain within the decanter separator and determine how efficient the separation process is in terms of the amount of exiting solids. Operation parameters such as the differential speed of the decanter parts and boundary conditions within the domain were analyzed and results were presented.
- PostStabilization of Uranium Nitride by Aluminum and Chromium Doping(2020)Uranium nitride is a promising accident tolerant fuel (ATF) candidate as it has great uranium density and thermal conductivity. The main downside is its inherent weakness to oxidation in mainly water and steam. In this work, uranium nitride was synthesized with 20% of total molar metal content as varying amounts of aluminum and chromium. The material was investigated in terms of oxidation performance and microstructure in order to asses the suitability of said dopants as an approach of stabilization. The material was synthesized as microspheres via the internal sol-gel process and carbothermal reduction at 1550 °C. Aluminum caused a change in microstructure and made the material more porous, which was believed to be the main reason why aluminum reduced oxidation performance during thermogravimetric analysis. This change was attributed to the tendency of aluminum to collect along the grain boundaries, potentially weakening grain adhesion. Only when chromium alone was added the oxidation temperature was increased. Added chromium not only caused caused cracking due to the release of gasses, but also surface formations due to the limited solubility of chromium in uranium nitride.