Browsing by Subject "XRD"

Non-communicable diseases such as cardiovascular diseases (CVDs) and erosive, unsustainable industrial fat-production methods pose two of the biggest threats to human health in great part of our planet. CVDs and obesity have been linked to diets high in fat and low in dietary fibre, pushing food manufacturers to adapt to more sustainable ingredients. For this reason, this research developed and researched about a new and sustainable plant-based oleogel intended to act as a substitute for saturated and hydrogenated fats. Its characterization was conducted through several techniques, including optical and field emission electron scanning microscopy, differential scanning calorimetry, Fourier transmission infrared spectroscopy, and synchrotron X-ray powder diffraction. The results showed that the build-up of the formation of the new oleogel was possible, while ensuring that both processing requirements and ingredients are readily available at food manufacturing plants, globally. These findings pose a great opportunity for plant-based fat-replacement formulations, through a sustainable approach. Considering previous studies, this novel system could potentially help in reducing the burden of obesity and CVDs, turning it into a functional food component. Further research on food applications and digestibility models could give more insight on the future applications of this fat-replacement system.

One of the main goals of materials research is to find the link between the properties of materials and their fundamental structures. The distinct properties of thin films, categorized as materials from a few single layers of atoms to some hundreds of nanometers, have enjoyed an unparalleled demand in modern device manufacturing, and thus the investigation of factors which determine thin film structure and morphology is a vital area of research. In the case of thin films, their final structures can often be connected back to the initial film formation stages, such as in the crystallographic growth competition during island growth and coalescence. In this thesis, thin film growth stages are studied from the perspective of how they are affected by impurities. From the initial diffusion of adatoms on a bare substrate; to the formation of islands, their growth and coalescence; to the mobility of grain boundaries and bulk diffusion leading to the formation of a fully continuous layer; impurities influence each of these thin film growth processes in a multifaceted way, either acting as growth inhibitors, promoters or potentially neutral agents. To this end, Ag and Cu thin films were synthesized by magnetron sputtering onto SiO_2/Si substrates, with thicknesses ranging from 3 nm to 30 nm using varied deposition conditions, with the addition of a 3 nm amorphous carbon layer to limit further restructuring and oxidation. Impurities were let into the deposition atmosphere via a controlled opening of a leak valve, corresponding to a step-wise increase of base pressure from 10^(-8) Torr to 10^(-6) Torr and finally 10^(-5) Torr. The full range of thin films was deposited with each base pressure (except for 10^(-5) Torr for Cu) using two deposition rates, around 0.1 Ås^(-1) and 2 Ås^(-1). Each film was characterized ex situ with ellipsometry, 4PP, XRD and AFM to map the morphological and microstructural evolution during film growth. It is found that impurities tend to inhibit island coalescence and initial grain growth, resulting in a reduction of continuous film formation thickness and average grain size, leading to the formation of flatter films with, in most cases, less surface roughness. In later stages, it is found that impurities may allow for more grain growth by their incorporation into the growing facets. In terms of crystal structure, it is shown that impurities have a more pronounced effect on (111) oriented grains, inhibiting their growth, thus altering the preferred growth orientations of Ag and Cu by allowing (200) grains to grow larger. Grain radii and equivalent ellipse distributions showed the different responses of Ag and Cu to impurities. Ag films showed more prominent effects when a lower deposition rate was used, highlighting the impact of impurities on diffusive processes, while Cu films exhibited more effects with the use of higher deposition rates, indicating that the role of impurities, in this case, was more significant after the formation of a continuous layer.