Master of Science / Food Science Institute / Jayendra K. Amamcharla / Milk protein concentrate (MPC) powders are high-protein dairy ingredients obtained from membrane filtration processes and subsequent spray drying. MPC powders have extensive applications due to their nutritional, functional, and sensory properties. However, their flow properties, rehydration behavior, and morphological characteristics are affected by various factors such as processing, storage, particle size, and composition of the powder. Literature has shown that knowledge about the powder flowability characteristics is critical in their handling, processing, and subsequent storage. For this study, FT4 powder rheometer (FT4, Freeman Technologies, UK) was used to characterize the flowability of MPC powders during storage. This study investigated the flowability and morphological characteristics of commercial MPC powders with three different protein contents (70, 80, and 90%, w/w) after storage at 25ºC and 40ºC for 12 weeks. Powder flow properties (basic flowability energy (BFE), flow rate index (FRI), permeability, etc.) and shear properties (cohesion, flow function, etc.) were evaluated. After 12 weeks of storage at 40ºC, the BFE and FRI values significantly increased (P < 0.05) as the protein content increased from 70 to 90% (w/w). Dynamic flow tests indicated that MPC powders with high protein contents displayed higher permeability. Shear tests confirmed that samples stored at 40ºC were relatively less flowable than samples stored at 25ºC. Also, the lower protein content samples showed better shear flow behavior. The results indicated that MPC powders stored at 40ºC had more cohesiveness and poor flow characteristics than MPC powders stored at 25ºC. The circle equivalent diameter, circularity, and elongation of MPC powders increased as protein content and storage temperature increased, while the convexity decreased as protein content and storage temperature increased. Overall, the MPC powders evidently showed different flow properties and morphological characteristics due to their difference in composition and storage temperature. Literature has shown various methods for determining the solubility of dairy powders, but it requires expensive instruments and skilled technicians. The front-face fluorescence spectroscopy (FFFS) coupled with chemometrics could be used as an efficient alternative, which is commonly used as fingerprints of the various food products. To evaluate FFFS as a useful tool for the non-destructive measurement of solubility in the MPC powders, commercially procured MPC powders were stored at two temperatures (25 and 40ºC) for 1, 2, 4, 8, and 12 weeks to produce powders with different rehydration properties, which subsequently influenced their fluorescence spectra. The spectra of tryptophan and Maillard products were recorded and analyzed with principal components analysis. The solubility index and the relative dissolution index (RDI) obtained from focused beam reflectance measurement was used to predict solubility and dissolution changes using fluorescence spectra of tryptophan and Maillard products. The solubility index and RDI showed that the MPC powders had decreased solubility as the storage time and temperature increased. The results suggest that FFFS has the potential to provide rapid, nondestructive, and accurate measurements of rehydration behavior in MPC powders. Overall, the results indicated that solubility and dissolution behavior of MPC powders were related to protein content and storage conditions that could be measured using FFFS.

Ce travail a pour objectifs d’évaluer le potentiel d'une technique spécifique de caractérisation des propriétés d'écoulement des poudres : le rhéomètre à poudre FT4. L'objectif est de pouvoir mettre en place une analyse complète sur les avantages, les inconvénients et les limites d'utilisation des tests, l'impact de la cohésion des poudres et la répétabilité des mesures. Tout d'abord, des efforts sont faits pour explorer les différences entre la consolidation test de FT4 et le tap-tap. Les résultats indiquent que la consolidation test de FT4 a une bonne répétabilité, mais il peut sous-estimer la compressibilité des poudres. Cette méthode peut être optimisée en améliorant sa procédure d'initialisation pour donner des résultats cohérents en tant que le tap-tap. Deuxièmement, le cisaillement test de FT4 est comparé avec Schulze Ring Shear Tester et Evolution Powder Tester. Cette comparaison indique que le cisaillement test de FT4 peut sous-estimer la cohésion des poudres. Par conséquent, les dimensions des accessoires doivent être optimisées. Enfin, une nouvelle technique de caractérisation a été mise au point. Dans cette méthode, les poudres présentent des mouvements périodiques et la période correspondant peut être liée aux propriétés d'écoulement des poudres. Cette méthode a une très bonne capacité à identifier et à catégorier les propriétés d'écoulement de la poudre dans les conditions de faible contrainte. / This research has been dedicated to evaluate the reliability of the FT4 and to improve the current tests for a better and convenient powder characterization. Firstly, efforts are made to explore the differences between the compaction test provided by the FT4 and the traditional tapped density measurement. Results indicate that the FT4 compaction test has good repetability but it may underestimate powder compressibility. This method can be optimized by improving its initialization procedure to give consistent results as the tapped density measurement. Secondly, the shear tests provided by the FT4 are evaluated by comparing with the methodologies provided by Schulze Ring Shear Tester and Evolution Powder Tester. This comparison indicates that the FT4 shear cell test may underestimate powder strength, especially when a cohesive powder sample is measured, which may cause blockage when using the FT4 method to design a silo. To overcome this shortage, the dimensions of the shear accessories should be optimized. Most importantly, a new characterization technique has been developed. ln this method, powder materials present periodic motions and the cycle time of the periodic flow can be linked to the powder flow properties. This method has very good capability to identify and classify powder flow properties under low stress conditions.

The application of chemical additives, known as grinding aids (GA), dates back to 1930 in the cement industry. As opposed to the cement industry, where the use of GAs is on the final processing step, it could be one of the first process steps in ore beneficiation. A few investigations addressed the GA applications in ore dressing; therefore, further studies are required to better understand the GA effects on the product properties and downstream separation processes. This thesis undertakes a comparative study on the dry grinding of magnetite and the resulting product characteristics with and without GAs. The main aim is to reduce energy consumption and to address some of the challenges associated with dry processing.  The effects of GAs on the dry batch ball milling of magnetite were examined to analyze the energy consumption (Ec), particle size distribution, flow properties, bulk properties, surface morphology, particle fineness, and surface chemistry of products. Their effects on the ground product were systematically explored by sieve analysis, powder rheology, BET surface measurements, optical microscopy analysis, and zeta potential measurements. Compared with the absence of GAs, the dry grinding efficiency of magnetite increased after using GAs; however, an optimal dosage exists based on the GA type. Among GAs which considered in this investigation (Zalta™ GR20-587 (Commercial GA) and Zalta™ VM1122 (Commercial viscosity aid) as well as sodium hydroxide), Zalta™ VM1122, a polysaccharide-based additive, was the most effective GA where by using this GA; the Ec decreased by 31.1% from 18.0 to 12.4 kWh/t. The PSD became narrower and finer (P80 decreasing from 181 to 142 µm), and the proportion of the particles (38–150 µm) increased from 52.5 to 58.3%. In general, the results reveal that at sufficient GA dosages, they reduce the average particle size, increase the specific surface area, and narrow the particle size distribution. However, an excessive amount of GAs could be detrimental to the grinding performance.  Further studies on powder rheology indicated that the used GAs resulted in improved material flowability compared to grinding without additives (in the examined dosage range). The rheology measurements by the FT4 Powder Rheometer showed strong linear correlations between basic flow energy, specific energy, and the resulting work index when GAs was considered for grinding. There was a strong correlation between the grinding parameters and flow parameters (r &gt; 0.93). These results confirmed the effect of GA on ground particles' flowability. Zalta™ VM1122 showed the best performance with 38.8% reduction of basic flow energy, 20.4 % reduction of specific energy, 24.6% reduction of aerated basic flow energy, and 38.3% reduction of aerated energy. The present investigation showed that the predominant mechanism of GAs is based on the alteration of rheological properties. Further investigation on the surface properties showed that using GAs could increase the surface roughness, which is beneficial for downstream processes such as froth flotation. Zalta™ VM1122 resulted in increased surface roughness and minimum microstructural defects from the optical microscope images. Furthermore, Zalta™ VM1122 (non-ionic) resulted in similar zeta potentials and pH values for the product compared to experiments without GA. These comparable product properties are advantageous as they minimize any potential negative effects on all possible downstream processes. / Kolarctic CBC (KO1030 SEESIMA)

During the pressing of powder mixtures to make cemented carbide tools, the degree to which the powder spreads to fill the die and to which it compacts is uncertain. This leads to inconsistent dimensions and densities in the finished product. This performance changes with the composition of the powder, including the amount of pressing agent in the mixture, the particle size distribution and particle shape. One way to quantify the degree to which powder will spread to fill the mold evenly is using the property called 'flowability'. There are several techniques by which flowability can be measured, and each technique does not always give results that are consistent with other techniques. It is, therefore, important to know what technique(s) predict(s) the final behavior of the powder in this application before it is used in quality assurance or to design a process. Additionally, powder size distribution and shape metrics are measured using dynamic image analysis to investigate if there is any relationship between key values of these properties and compaction behavior. In this study, static Angle of repose, Tap Density, Hall flow time and Powder rheometry were benchmarked against each other and against the dimensions of presses and liquid phase sintered tool inserts to understand which technique had the strongest dependence on the compactability, which was defined as the ratio of the tallest dimension in the insert to the smallest. After the study, the results showed that a more extensive particle size distribution improves the compaction properties and that the powders with a higher resistance to a rotating blade tend to have better compaction properties. On the other hand, a clear pattern for the results of all measurement methods and the correlation between the compaction behavior of the carbide tools could not be discerned. In conclusion, the study showed that it is possible to determine a relationship between the results of measurement methods and the compaction behavior of powders. By using simple tests to predict the compactability properties, both money and time can be saved on the research of new, improved powder. Furthermore, the implementation of this study can lead to even better pressing and compactibility properties in the future for cemented carbide tools. / Vid pressning av pulverblandningar för tillverkning av hårdmetallverktyg är det osäkert i vilken grad pulvret sprider sig för att fylla matrisen och i vilken grad det komprimeras. Detta leder till inkonsekventa dimensioner och densitet i den färdiga produkten. Denna prestanda förändras med pulvrets sammansättning, inklusive mängden bindemedel som finns i blandningen, partikelstorleksfördelningen och partikelformen. Ett sätt att kvantifiera i vilken grad pulvret sprids för att fylla formen jämnt är att använda den egenskap som kallas "flytbarhet". Det finns flera tekniker för att mäta flytbarhet, och varje teknik ger inte alltid resultat som överensstämmer med andra tekniker. Det är därför viktigt att veta vilken eller vilka tekniker som förutsäger pulvrets slutliga beteende i denna tillämpning innan den används i kvalitetssäkring eller för att utforma en process. Vidare mäts pulvrets partikelstorleksfördelning och form med dynamisk bildanalys för att undersöka om det finns något samband mellan nyckelvärden för dessa egenskaper och komprimeringsbeteendet. I den här studien jämfördes statisk rasvinkel, tappdensitet, hallflödestid och pulverreometri samt med dimensionerna på pressar och sintrade verktygsinsatser i vätskefas för att förstå vilken teknik som hade det starkaste beroendet på kompatibiliteten, vilket definieras som förhållandet mellan den högsta dimensionen i insatsen och den minsta. Efter studien visade resultaten att en mer omfattande partikelstorleksfördelning förbättrar komprimeringsegenskaperna och att pulver med högre motståndskraft mot ett roterande blad tenderar att ha bättre komprimeringsegenskaper. Vidare kunde inte ett tydligt mönster för resultaten för alla mätmetoder och sambandet på komprimeringbeteendet för hårmetallverktygen urskiljas. Sammanfattningsvis visade studien på att det går att använda sig av mätmetoder för att kunna urskilja ett samband mellan resultaten på mätmetoderna och pulvers kompaktibillitetsegenskaper. Genom att använda sig av enkla mätningar för att kunna förutsäga kompaktibilitetsegenskaper samt komprimeringsbeteende kan både pengar respektive tid sparas. Vidare kan genomförandet av denna studie i framtiden leda till ännu bättre pressnings- samt kompaktibilitetsegenskaper för hårdmetallverktyg.

Additive manufacturing with the use of metals have been a steadily increasing field, being able to create products with a higher degree of complexity than traditional processing techniques. SLM is a popular AM process that uses metal powder as feedstock, and one of the key components of this process is the powder rheology. In recent years the use of a powder rheometer has been shown to be a good way of evaluating powder rheology of metal powders used within AM processes, but there is a clear lack of standardised tests and methods. In this study the Compressibility, Permeability, and Aeration test for 316L powders used within SLM processes was evaluated with a FT4 powder rheometer. 15 powders that had undergone printing in SLM processes were studied. This showed that the compressibility test had the best results in differentiating the bad preforming powders, thereafter the Aeration test. The Permeability test wasn’t able to differentiate the bad preforming powders with the settings used. This study demonstrates that some tests with a powder rheometer can evaluate the powder performance in SLM processes, but further research to evaluate the tests and standardise the settings are needed for clearer test results. / Additiv tillverkning med metall är ett område som stadigt ökat i intresse, främst på grund av möjligheten att producera produkter med en mycket högre grad av komplexitet i jämförelse med traditionella processmetoder. SLM är en populär AM process som använder metallpulver som råmaterial, och en av huvudkomponenterna för processen är pulvrets reologi. Under senare år har användningen av en pulver-reometer visat sig ett bra sätt att utvärdera pulver-reologi för metallpulver som används inom AM, men det finns en klar avsaknad av standardiserade test och metoder. I denna studie utvärderas Kompressabilitet, Permeabilitet, och Aerabilitet testen för 316L pulver producerade för SLM processer med en FT4 pulver-reometer. 15 pulver som genomgått SLM printing studerades. Studien visar att kompressabilitets testets utfall bäst överensstämde med det som setts under SLM processen, och bäst urskilde pulvren som fungerat dåligt att printa med, därefter Aerations testet. Permeabilitets testet kunde inte urskilja de sämre pulvren med de inställningarna som användes. Studien demonstrerar att vissa test och index samlade med ett pulver reometer är mer tillförlitliga än andra när det gäller för att utvärdera pulvrets prestanda inom SLM processer, men vidare forskning och studier krävs för att utvärdera testen och standardisera inställningar baserat på pulvret som testas.