No description available.

O amido de milho é uma importante fonte de energia para os seres humanos e é muito utilizado em preparos de diversos pratos. Os grânulos de amido possuem estrutura semicristalina que sofre degradação em elevadas temperaturas e com presença de água. Com o objetivo de alterar a microestrutura dos grânulos de amido de milho, principalmente quanto à sua temperatura de gelatinização, foram realizados processos de aglomeração de três diferentes métodos e avaliadas as modificações ocorridas. Todas as partículas produzidas passaram por análises de DSC, FT-IR, DRX e MEV. O trabalho foi divido em três diferentes estudos. No Estudo I, foi realizada a aglomeração do amido de milho com solução de alginato de sódio por \"high shear\" com posterior secagem em leito fluidizado. A partícula depois de seca teve 99,5% de amido em sua composição. Os resultados mostraram que houve aglomeração nos grânulos de amido de milho; porém, devido à baixa fração de alginato de sódio nas partículas, elas não apresentaram diferenças significativas quanto à sua temperatura de gelatinização, sua estrutura e suas ligações, quando comparadas ao amido nativo. No Estudo II, em que foi realizada a aglomeração dos grânulos de amido de milho com solução de alginato de sódio e cloreto de cálcio, por \"dripping\", foram obtidas partículas com frações de (0, 50, 60, 70, 80 e 90)% de amido. As modificações aconteceram à medida em que se aumentou a quantidade de alginato de sódio da partícula. As partículas com maiores frações de amido não apresentaram alterações significativas em sua microestrutura e temperatura de gelatinização, quando comparadas ao amido de milho nativo. As partículas com menores frações de amido, ou seja, maiores teores de alginato de sódio, apresentaram alterações em sua microestrutura e cristalinidade, além de maiores temperaturas de gelatinização. No Estudo III, foi realizada a aglomeração do amido de milho com quitosana por \"dripping\" em soluções de diferentes molaridades de de hidróxido de sódio (NaOH). Dentre as principais modificações observadas, destaca-se o aumento da temperatura de gelatinização, em partículas que foram precipitadas em soluções alcalinas de NaOH com molaridade de (0,10 e 0,12) M. Para as concentrações molares de (0,14, 0,16, 0,18 e 0,20) M, de NaOH, observou-se que parte dos grânulos de amido de milho foram solubilizados pela solução alcalina, e que as frações sólidas remanescentes apresentaram-se na forma de partículas precipitadas de amido-quitosana, com aparência transparente e amarelada. Os processos de aglomeração do amido de milho nativo pelos métodos \"high shear\" e \"dripping\", utilizando-se soluções de alginato de sódio e quitosana, podem resultar em partículas resistentes à gelatinização, devido à atribuição de uma barreira física por estes ligantes, após as etapas de secagem. O aumento da concentração de alginato resultou em um aumento da temperatura de gelatinização, produzindo partículas de amido resistentes à degradação térmica. Adicionalmente, observou-se que o uso de soluções alcalinas diluídas de NaOH, também permitiu a produção de partículas resistentes à degradação térmica, por meio da precipitação da quitosana. O método \"dripping\" permitiu a produção de partículas com elevadas concentração de alginato ou quitosana, e foi o método mais indicado para a produção de partículas de amido resistentes à degradação térmica. As partículas aglomeradas pelo método \"high shear\" tiveram concentração de ligante (alginato de sódio) limitada a 0,5%, e não resultaram em partículas resistentes à degradação térmica. / Corn Starch is an important source of energy for humans and is widely used in food preparations. Starch granules exhibit a semicrystalline structure which undergoes degradation at high temperatures and the presence of water. In order to change the microstructure in corn starch granules, especially regarding its gelatinization temperature, three diferente methods of agglomeration processes were performed and changes of starch particles were studied. Every produced particle were analysed by DSC, FT-IR, XRD and SEM. The work was divided into three different studies. In Study I, agglomeration of corn starch was carried out with sodium alginate solution by \"high shear\" with subsequent fluidized bed drying. The dry contained was 99,5% starch in its composition. The results showed that the cornstarch granules agglomerated; however, due to the low fraction of sodium alginate in the particles, they showed no significant differences in gelatinization temperature, its structure and interactions when compared to native starch. In Study II, was performed the agglomeration of corn starch granules with sodium alginate solution and calcium chloride by dripping method and particles obtained contained (0, 50, 60, 70, 80 and 90)% (w/w) of starch. Modifications occurred with increasing the amount of sodium alginate in the particle. Particles with higher starch fractions showed no significant changes in its microstructure and gelatinization temperature, compared to the native corn starch. Particles with lower starch fraction, and higher concentrations of sodium alginate, showed changes in their microstructure and crystallinity, and higher gelatinization temperatures. In Study III, the agglomeration of cornstarch with chitosan by dripping in sodium hydroxide (NaOH) solutions of different molarities was evaluated. Among the main changes increases on the gelatinization temperature of particles precipitated in alkaline NaOH solutions with molarity (0,10 and 0,12) M was observed. For the molar concentrations (0,14, 0,16, 0,18 and 0,20) M NaOH, it was observed that some of granules corn starch were solubilised by the alkaline solution and the remaining solid fraction presented the form of precipitated particles of starch-chitosan with transparent and yellowish appearance. The native corn starch agglomeration processes by the methods \"high shear\" and \"dripping\", using solutions of sodium alginate and chitosan, can result in particles resistant to gelatinization due to the formation of a physical barrier of these ligands, after drying steps. Increasing the alginate concentration resulted in increase in the gelatinization temperature of starch, resulting in particles resistant to thermal degradation. Additionally, it was observed that the use of dilute alkaline solutions of NaOH allowed the production of thermal degradation resistant particles through precipitation of chitosan. The \"dripping\" method enabled the production of particles with higher concentrations of alginate or chitosan, and was the most suitable method for the production of starch particles resistant to thermal degradation. The particles agglomerated by \"high shear\" had binder concentration (sodium alginate) limited to 0,5%, and didi not result in particles resistant to thermal degradation.

O amido de milho é uma importante fonte de energia para os seres humanos e é muito utilizado em preparos de diversos pratos. Os grânulos de amido possuem estrutura semicristalina que sofre degradação em elevadas temperaturas e com presença de água. Com o objetivo de alterar a microestrutura dos grânulos de amido de milho, principalmente quanto à sua temperatura de gelatinização, foram realizados processos de aglomeração de três diferentes métodos e avaliadas as modificações ocorridas. Todas as partículas produzidas passaram por análises de DSC, FT-IR, DRX e MEV. O trabalho foi divido em três diferentes estudos. No Estudo I, foi realizada a aglomeração do amido de milho com solução de alginato de sódio por \"high shear\" com posterior secagem em leito fluidizado. A partícula depois de seca teve 99,5% de amido em sua composição. Os resultados mostraram que houve aglomeração nos grânulos de amido de milho; porém, devido à baixa fração de alginato de sódio nas partículas, elas não apresentaram diferenças significativas quanto à sua temperatura de gelatinização, sua estrutura e suas ligações, quando comparadas ao amido nativo. No Estudo II, em que foi realizada a aglomeração dos grânulos de amido de milho com solução de alginato de sódio e cloreto de cálcio, por \"dripping\", foram obtidas partículas com frações de (0, 50, 60, 70, 80 e 90)% de amido. As modificações aconteceram à medida em que se aumentou a quantidade de alginato de sódio da partícula. As partículas com maiores frações de amido não apresentaram alterações significativas em sua microestrutura e temperatura de gelatinização, quando comparadas ao amido de milho nativo. As partículas com menores frações de amido, ou seja, maiores teores de alginato de sódio, apresentaram alterações em sua microestrutura e cristalinidade, além de maiores temperaturas de gelatinização. No Estudo III, foi realizada a aglomeração do amido de milho com quitosana por \"dripping\" em soluções de diferentes molaridades de de hidróxido de sódio (NaOH). Dentre as principais modificações observadas, destaca-se o aumento da temperatura de gelatinização, em partículas que foram precipitadas em soluções alcalinas de NaOH com molaridade de (0,10 e 0,12) M. Para as concentrações molares de (0,14, 0,16, 0,18 e 0,20) M, de NaOH, observou-se que parte dos grânulos de amido de milho foram solubilizados pela solução alcalina, e que as frações sólidas remanescentes apresentaram-se na forma de partículas precipitadas de amido-quitosana, com aparência transparente e amarelada. Os processos de aglomeração do amido de milho nativo pelos métodos \"high shear\" e \"dripping\", utilizando-se soluções de alginato de sódio e quitosana, podem resultar em partículas resistentes à gelatinização, devido à atribuição de uma barreira física por estes ligantes, após as etapas de secagem. O aumento da concentração de alginato resultou em um aumento da temperatura de gelatinização, produzindo partículas de amido resistentes à degradação térmica. Adicionalmente, observou-se que o uso de soluções alcalinas diluídas de NaOH, também permitiu a produção de partículas resistentes à degradação térmica, por meio da precipitação da quitosana. O método \"dripping\" permitiu a produção de partículas com elevadas concentração de alginato ou quitosana, e foi o método mais indicado para a produção de partículas de amido resistentes à degradação térmica. As partículas aglomeradas pelo método \"high shear\" tiveram concentração de ligante (alginato de sódio) limitada a 0,5%, e não resultaram em partículas resistentes à degradação térmica. / Corn Starch is an important source of energy for humans and is widely used in food preparations. Starch granules exhibit a semicrystalline structure which undergoes degradation at high temperatures and the presence of water. In order to change the microstructure in corn starch granules, especially regarding its gelatinization temperature, three diferente methods of agglomeration processes were performed and changes of starch particles were studied. Every produced particle were analysed by DSC, FT-IR, XRD and SEM. The work was divided into three different studies. In Study I, agglomeration of corn starch was carried out with sodium alginate solution by \"high shear\" with subsequent fluidized bed drying. The dry contained was 99,5% starch in its composition. The results showed that the cornstarch granules agglomerated; however, due to the low fraction of sodium alginate in the particles, they showed no significant differences in gelatinization temperature, its structure and interactions when compared to native starch. In Study II, was performed the agglomeration of corn starch granules with sodium alginate solution and calcium chloride by dripping method and particles obtained contained (0, 50, 60, 70, 80 and 90)% (w/w) of starch. Modifications occurred with increasing the amount of sodium alginate in the particle. Particles with higher starch fractions showed no significant changes in its microstructure and gelatinization temperature, compared to the native corn starch. Particles with lower starch fraction, and higher concentrations of sodium alginate, showed changes in their microstructure and crystallinity, and higher gelatinization temperatures. In Study III, the agglomeration of cornstarch with chitosan by dripping in sodium hydroxide (NaOH) solutions of different molarities was evaluated. Among the main changes increases on the gelatinization temperature of particles precipitated in alkaline NaOH solutions with molarity (0,10 and 0,12) M was observed. For the molar concentrations (0,14, 0,16, 0,18 and 0,20) M NaOH, it was observed that some of granules corn starch were solubilised by the alkaline solution and the remaining solid fraction presented the form of precipitated particles of starch-chitosan with transparent and yellowish appearance. The native corn starch agglomeration processes by the methods \"high shear\" and \"dripping\", using solutions of sodium alginate and chitosan, can result in particles resistant to gelatinization due to the formation of a physical barrier of these ligands, after drying steps. Increasing the alginate concentration resulted in increase in the gelatinization temperature of starch, resulting in particles resistant to thermal degradation. Additionally, it was observed that the use of dilute alkaline solutions of NaOH allowed the production of thermal degradation resistant particles through precipitation of chitosan. The \"dripping\" method enabled the production of particles with higher concentrations of alginate or chitosan, and was the most suitable method for the production of starch particles resistant to thermal degradation. The particles agglomerated by \"high shear\" had binder concentration (sodium alginate) limited to 0,5%, and didi not result in particles resistant to thermal degradation.

High shear melt granulation (HSMG) is an established technology for a production of densified granules. In this project, it was used as a novel solvent-free method for the preparation of cocrystals. Cocrystals produced by HSMG were compared to those prepared by Hot Melt Extrusion (HME) to investigate the influence of variable parameters and conditions on the process of cocrystal conversion. The potential for the active control of cocrystals polymorphism utilising the intrinsic properties of lipids was also investigated in this project. Different cocrystal pairs were prepared by both cocrystallisation methods using glycol derivative polymers. Thermal analysis, powder X-ray diffraction and Raman spectroscopy were used as analytical techniques to determine the cocrystal yield and purity. The results obtained from HSMG suggest that sufficient binder concentrations (above 12.5% w/w) in a molten state and continuous shearing force are necessary to achieve a complete cocrystals conversion. Further increase in binder concentration (15% w/w) was found to provide more regular shape and smooth surface to the prepared spherical granules. Cocrystals preparation by HME was achievable after introducing a mixing zone to the extruder configuration (Conf B and Conf C) providing densified extrudates containing pure cocrystals. In conclusion, HSMG was found as a versatile technique for the preparation of pure pharmaceutical cocrystals embedded in polymer matrix within a spherical shape granule of smooth surfaces, providing additional desirable characteristics. Intensive surface interaction, enhanced by sufficient mixing under optimal parameters, was found as a key influencing factor in cocrystallisation. Cocrystals polymorphism was actively controlled by employing the intrinsic properties of polymers and lipids.

Aluminium alloys, including both foundry and wrought alloys, have been extensively used for light-weight structural and functional applications. A grain refined as-cast microstructure is generally highly desirable for either subsequent processing ability or mechanical properties of the finished components. In this thesis, the grain refined microstructures in Al alloys have been achieved by intensive melt shearing using the melt conditioning by advanced shearing technology (MCAST) without deliberate grain refiner additions. Such grain refinement has been attributed to the enhanced heterogeneous nucleation on the dispersed oxide particles. It has been established that the naturally occurring oxides in molten Al alloys normally have a good crystallographic match with the a-Al phase, indicating the high potency of oxide particles as the nucleation sites of the a-Al phase. The governing factors for these oxide particles to be effective grain refiners in Al alloys have been proposed, including the achievement of good wetting between oxide particles and liquid aluminium, a sufficient number density and uniform spatial distribution of the dispersed oxide particles, and near equilibrium kinetic conditions in liquid alloys. In the present study, near equilibrium kinetic conditions can be achieved by intensive melt shearing using a twin screw mechanism, which has been confirmed by the observed equilibrium a-AlFeSi phase in a cast Al alloy and the transformation from g- to a-Al2O3 at 740±20oC under intensive shearing. For different alloy systems, depending on the alloy system, and melting conditions, due to the particular types of oxide formed and its crystallographic and chemical characteristics, the nucleation site of the nucleated phase is different. Specifically, MgAl2O4 relative to MgO, and a-Al2O3 relative to g-Al2O3, have higher potency as heterogeneous nucleation sites of a-Al phase in Al alloys. In future, the modification of the crystallographic match, and of the other surface characteristics related to the interfacial energy between the specific oxides and nucleated phase by trace alloying addition through segregation to the interface between oxides and nucleated phases combined with physical melt processing (such as intensive shearing in the present study) should be investigated in more detail.

High shear mixing offers a promising solution for particle dispersion in a liquid with intensive turbulence and high shear rate, and has been widely used in the chemical, food and pharmaceutical industries. However, a practical high shear mixing process has not yet been adapted to solve the particle agglomeration in metallurgy due to the high service temperature and reactive environment of liquid metal. In this study, the effect of high shear mixing using the newly designed rotor-stator high shear device have been investigated with both Al and Mg matrix composites reinforced with SiC particles through casting. The microstructural observation of high shear treated Al and Mg composites show improved particle distribution uniformity in the as-cast state. Increased mechanical properties and reduced volume fraction of porosity are also obtained in the composite samples processed with high shear. With the melt conditioning procedure developed for twin roll casting process, two distinct solutions has been provided for thin gauge Mg strip casting with advanced microstructure and defect control. The melt conditioning treatment activates the MgO as heterogeneous nuclei of α-Mg through dispersion from continuous films to discrete particles. Thus enhanced heterogeneous nucleation in the twin roll casting process not only refines the α-Mg grain size but also eliminates the centre line segregation through equiaxed grain growth and localized solute distribution. The grain refinement of the α-Mg through SiC addition has also been studied through EBSD and crystallographic approaches. Two reproducible and distinct crystallographic orientation relationships between α-SiC (6H) and α-Mg have been determined: [1010]SiC//[2113]Mg, (0006)SiC//(1011)Mg, (1216)SiC//(2202)Mg and [0110]SiC//[1100]Mg, (0006)SiC// (0002)Mg, (2110)SiC//(1120)Mg.

Oxide films in aluminium melts are unavoidable. A new technology developed by BCAST suggests breaking films into small fragments or particles which play a role as the grain refiner. Mechanical breakage is realised by using a high-shear mixer (HSM) with the rotor-stator impeller. In the presented thesis, the positive role of small oxide particles is shown by the computer modelling. The defragmentation potency of HSM is demonstrated by physical modelling with powders checked by optical analyses (microscopy) and SEM (Scanning Electron Microscopy). The flow has been analysed by optical recording and by PIV (Particle Image Velocimetry) to find the best conditions to cause a satisfying oxides distribution in all volume of liquid metal processed by the HSM. A new model to estimate the mixed volume has been proposed and checked by experiments with liquid metals. The model was checked by the PIV observations and by direct experiments in the liquid metal and is found to be in good agreement with reality. Optimisation methods are considered and a new design of HSM is proposed according to the experimental findings. This design improves the uniformity of mixing in the pseudo-cavern volume and exhibits the dispersion efficiency better than the design used currently by BCAST. Understanding and development of high shear technology for liquid metals processing is an important part of BCAST research and is of great interest for industry. Up to now, this method was found to give good experimental results but it was a lack of information about physical basics behind this process. The goal of this thesis is to answer why and how to apply HSM in metallurgy and to propose new condition and design solutions associated with the specific requirements of the liquid metal process.

Results of a study of the influence of impeller speed on the strength, structure and morphology of granules produced in a type of high shear mixer granulators are reported. Calcium carbonate particles (Durcal 65) have been granulated in a Cyclomix with a capacity of 5 L. An aqueous solution of polyethylene glycol was used as the binder. The granules produced have been dried and their structure visualized using X-ray micro-tomography equipment, Nanotom, with a resolution of less than 1 μm. It is shown that the operation of the granulator at high impeller tip speeds produces granules with a higher strength and lower porosity than those produced at medium and low impeller speeds. Two different granule micro-structures and morphologies are produced at high and low impeller speeds. Structure descriptors such as phase volume fraction (as representative of porosity), chord length distribution and auto-correlation function (as indices of homogeneity of structure) are used to quantify the internal structure of granules in 3D, which in turn affects the granule strength.

Results of a study on the influence of process parameters such as impeller speed, granulation time and binder viscosity on granule strength and properties are reported. A high shear granulator (Cyclomix manufactured by Hosokawa Micron B.V., The Netherlands) has been used to produce granules. Calcium carbonate (Durcal) was used as feed powder and aqueous polyethylene glycol (PEG) as the binder. The dried granules have been analysed for their strength, density and size distribution. The results show that increasing the granulation time has a great affect on granules strength, until an optimum time has been reached. The underlying cause is an increase in granule density. Granules are consolidated more at higher impeller speeds. Moreover, the granule size distribution seems not to be affected significantly by an increase in impeller speed. Granules produced with high binder viscosity have a considerably lower strength, wide strength distribution due to poor dispersion of binder on the powder bed. Binder addition methods have showed no considerable effect on granule strength or on granule size distribution.

A novel method for manufacturing granules with a large particle at their core, referred to as seeded granules, is presented. As an example, calcium carbonate powders (Durcal) of different grades are used as primary particles and polyethylene glycol (PEG) as liquid binder in high shear granulators of different scales (Cyclomix, manufactured by Hosokawa Micron B.V., The Netherlands). The conditions giving rise to seeded granulations are specified in the form of an operational regime map. It is found that the seeded structure is strongly dependent on the impeller speed and the primary particles size distribution. It is shown that a Stokes number of around 0.1 represents the optimal dynamic conditions in the given example for producing seeded granules, regardless of the scale of the granulator.