Rozprawy doktorskie na temat „Ball-milling”

Polymorphism and crystallinity are now recognised as important issues in drug development. This is shown by the increased amount of research in this area over recent years. In pharmaceutical development milling is an important unit operation for size reduction to improve powder handling, processing and dissolution rate. The aim of this thesis was to investigate the effect of ball milling (and cryo-milling) on the solid state properties, including amorphous drug formation, of pharmaceutical solids. Milling was carried out using an oscillatory ball mill (Mixer Mill MM301, Retsch GmbH & Co., Germany). In cryo-milling the milling jars were immersed in liquid nitrogen for three min before milling. XRPD was used as the main technique to evaluate the milled samples. Ranitidine hydrochloride (RAN) and indomethacin (INDO) were the model drugs used in this study. It was found that upon milling, RAN form 1 converts to RAN form 2 via an amorphous phase. A faster amorphization rate was observed when the crystalline samples were cryo-milled. Amorphous ranitidine hydrochloride was characterized to have a glass transition (T[g]) range of 13 to 30 �C and a crystallization exotherm (T[c]) between 30 and 65 �C. Conversion was found to occur faster when the temperature of the solid powder was greater than the T[c]. Under various storage conditions, similarly, crystallization of the amorphous phase mainly led to RAN form 2. However, some form 1 and amorphous phase was also detected on the XRPD diffractograms. Using partial least squares regression, the amount of solid form components in the ternary RAN mixtures were successfully quantified. RAN form 2 did not convert to form 1 under any milling (including cryo-milling) or storage conditions used in this study. Overall, RAN form 2 was found to be the thermodynamically stable form and the two (RAN) polymorphs are likely to be a monotropic pair. In a co-milling study of INDO and RAN, the two crystalline drugs were successfully converted into a single amorphous phase after 60 min of co-milling in a cold room (4 �C). The T[g] range (26-44 �C) was also characterized for these mixtures. DRIFTS spectra of the co-milled amorphous samples indicated an interaction had occurred between the carboxylic acid carbonyl (HO-C=O) and benzonyl amide (NC=O) of the INDO molecule with the aci-nitro (C=NO₂) of RAN. Depending on the ratio of INDO to RAN, in general, the amorphous mixtures were stable at 4 �C after 30 days of storage. Crystallization was faster when the binary mixtures were stored at higher temperature or contained higher amounts of RAN in the mixture. Although XRPD and DRIFTS suggested an interaction between the two drugs, co-crystal formation was not observed between INDO and RAN. Ball milling can be used to produce amorphous drug. The rate and extent of amorphization is dependent on the milling conditions. A faster rate of amorphization was observed when the crystalline drugs were cryo-milled. Amorphous drug formation can be made either alone or in combination with another crystalline drug. Amorphization could offer a significant improvement on the dissolution profile and the bioavailability of the poorly water soluble drug - indomethacin. Furthermore, ball milling can also be used to produce a homogenous mix between solids. The �goodmix� effect can be used for seed-induced crystallization or, when the XRPD or Raman data were combined with partial least squares regression, to create a reliable calibration model for quantitative analysis.

At Domfer Metal Powders, the ball milling operation is critical since it determines many characteristics of the final product, such as density, green strength, compressibility and dimensional change. Highly variable input material properties and operational procedures accompanied by poor product feedback frequency generate large variations in powder properties. The goal of the research is to develop a model-based control system for the ball milling process of metal powder. The following research objectives are aimed at reducing process variations while maximizing throughput: include ball mill physics into design and computer models, develop control strategies and computer architectures for real-time control, and develop process monitoring and fault diagnosis techniques.
Ball mill size reduction theory is presented as a basis for process characterization. Next, process physics are described along with the measurability and controllability of the variables. Then, plant trials are performed to define system behavior and performance specifications of variables and sensors. After that, a sampler for metal powder is developed to automate the entire sieve analysis process.
A new ball mill model is created for open-circuit dry ball milling of metal powders. The process model is a combination of rules, equations and heuristics and is implemented using an agent based architecture that can deal with multiple data streams and a network of related sub-models of different sizes and operating time scales.
The model architecture is integrated using a programmable logic controller. Control and monitoring algorithms are developed in low-level PC language. A performance plant trial validated the control system and demonstrated that ball milling product specifications, namely size distribution and apparent density, are achievable and maintainable at a 99.7% confidence interval. This new technology will endow Domfer with a serious lead in metal powder manufacturing.
Key words. model-based control, ball milling, metal powder.

L'objectif de ce projet est d'explorer la possibilité d’utiliser des oxydes mixtes nanostructurés obtenus par broyage à haute énergie (HEBM en anglais) dans des capteurs de gaz des oxydes mixtes à haute performance et à faible coût. Les compositions chimiques, LaFeO3 et LaCoO3, ont été choisies en fonction de leurs propriétés intrinsèques de détection de gaz proposées dans la littérature. L'effet des paramètres de synthèse sur leurs performances de détection de gaz a été étudié. Ce projet est divisé en trois étapes. Dans la première étape, les paramètres de synthèse ont été optimisés pour obtenir des oxydes nanocristallins LaCoO3 à structure pérovskite. Un procédé de revêtement a ensuite été développé afin de déposer le matériau sous forme de poudre sur un substrat électriquement résistant et de créer un dispositif de détection. Cette méthode consiste en une simple étape d’enrobage où la poudre nanocristalline est mise en suspension dans une solution aqueuse à un pH ajusté avec précision et le substrat y est immergé jusqu'à l’obtention d’une couche continue et homogène. Les échantillons ont été ensuite séchés, conditionnés et les propriétés de détection ont été évaluées en mesurant essentiellement le comportement de la résistance électrique sous différentes compositions de gaz. Afin de comparer la méthode de fabrication des oxydes dans ce projet (broyage à boulets, BM) à d'autres méthodes de synthèse classiques, les mêmes compositions chimiques des pérovskites LaFeO3 et LaCoO3 ont été réalisées par la méthode sol-gel (SG) et par réaction à l’état solide (SSR). L'effet de la taille des particules sur les performances de détection du monoxyde de carbone par le LaCoO3 a été étudié. En comparant aux autres méthodes classiques, la technique par broyage à haute énergie a abouti à la plus petite taille des cristallites, environ 11 nm, alors que la SG et la SSR ont donné une taille de cristallites respectivement de 20 nm et 1 μm. Le taux de réponse maximale vis-à-vis au CO a été augmenté de 7% pour les échantillons par SSR à 17% pour la SG et jusqu’à 26% pour la BM, tout en conservant une surface spécifique stable pour les trois méthodes de synthèse. Dans la deuxième étape, la surface spécifique (SSA) des échantillons broyés par BM a été augmentée en utilisant une seconde étape de broyage. L'effet de la surface spécifique sur les performances de détection de gaz et sur la mobilité des atomes d'oxygène ainsi que sur leur capacité de désorption des oxydes mixtes a été examiné. Les matériaux synthétisés ont été caractérisés par diffraction des rayons X (XRD), par désorption du dioxygène à température programmée (TPD-O2) et par analyse de leur surface spécifique (BET). Les résultats de détection ont révélé l’effet positif d’une faible taille de cristallites associée à une grande surface spécifique sur les performances de détection de gaz. La surface spécifique de l'échantillon synthétisé par BM est passée de 4 m2/g à une valeur optimale de 66 m2/g grâce à la seconde étape de broyage. La pérovskite optimisée par deux étapes de broyage a montré le plus fort taux de réponse allant jusqu'à 75% pour 100 ppm de CO dans l'air sec à 125°C. Ce pourcentage est de quatre à dix fois supérieur à ceux obtenus par sol-gel et par réaction à l'état solide. La performance de détection de gaz du composé LaCoO3 ayant une taille de cristallites de 11 nm et une surface spécifique de 66 m2/g a été définie comme étant le matériau de référence pour d'autres améliorations. Dans la troisième étape, le potentiel de la méthode de BM dans l’obtention de composés chimiques dopés a été exploré par la synthèse de formulations ayant la forme La1-xCexCoO3 où le pourcentage de cérium et l'effet de ce dopage sur les propriétés de détection de gaz ont été évalués. L'effet de l'élément dopant sur la structure pérovskite a été étudié. Les composés dopés par le cérium ont montré un point de saturation de 10% dans la structure pérovskite et un ajout supplémentaire de Ce à ce pourcentage limite entraîne l’apparition de l'oxyde de cérium en tant qu'impureté et affecte la détection des gaz. La température de détection optimale du CO pour la formulation dopée a été trouvée à 100°C par rapport à 130°C pour la structure pérovskite de référence (LaCoO3). Parmi les oxydes mixtes dopés au Ce, la formulation La0.9Ce0.1CoO3 montre le meilleur taux de réponse (240%) qui est de quatre fois supérieur au taux de réponse du LaCoO3 pour une même concentration de CO. La TPD-O2, la TPD-CO et l’analyse de surface XPS ont été effectuées pour établir la relation entre la performance de détection et les propriétés physiques et chimiques des échantillons synthétisés. En outre, les pérovskites nanostructurées de la forme LaFeO3 ont également été synthétisées en utilisant la méthode HEBM. Cette formulation a été choisie pour sa sensibilité intrinsèque et pour sa capacité de détection du CO. Les propriétés de détection de cette formulation pour le méthane sont améliorées par un dopage au palladium. L’oxyde de Pd est imprégné sur la surface de l’oxyde nanostructuré LaFeO3. Ce dopage révèle l'effet de ce métal noble sur les performances de détection au méthane. Différentes masses d’oxyde de Pd ont été utilisées pour déterminer la quantité optimale à ajouter afin de maximiser la détection du méthane. Les composés nanostructurés dopés au Pd indiquent une bonne sensibilité au méthane à très basse température (<150°C), alors que pour la pérovskite pure de LaFeO3, la détection est inexistante dans cette gamme de température. Un pourcentage massique de 2% Pd pour le composé LaFeO3 montre un taux de détection maximum de 600% par rapport aux 300 ppm CH4 dans l'air. Cet oxyde dopé possède une taille de cristallite de 14 nm et une surface spécifique élevée de 46 m2/g. La capacité de stockage du méthane de la formulation dopée a été également évaluée en étudiant l'effet de l'élément de dopage sur la capacité d'adsorption et de sa relation avec la performance de détection d'échantillons synthétisés. Aucune activité catalytique n’a été observée pour les formulations dopées au Pd.
The aim of this project is to explore the possibility of exploitation of nanostructured mixed oxides obtained by HEBM technique in development of high efficient gas sensors in terms of performance and cost. LaFeO3 and LaCoO3 formulations were chosen as perovskite-based materials, based on their intrinsic sensing properties reported on the literature, to investigate the effect of synthesis parameters on their gas sensing performance. In the first step, synthesis parameters were optimized to obtain nanocrystalline LaCoO3 perovskite-oxide. A coating method was then developed in order to coat the sensing material in powder form on an electrically resistant substrate and to provide a sensing device. This coating method consisted of a simple wash-coating process where the nanocrystalline powder is put in suspension in an aqueous solution with an accurately adjusted pH and the substrate is dipped in until a continuous and homogeneous thick sensing layer is formed. The samples were then dried and conditioned and the sensing properties were evaluated basically by measuring electrical resistance behaviour of the device in different gas compositions. In order to compare the ball milling (BM) method with other synthesis methods, the same formulation was also obtained using sol-gel (SG) and solid-state reaction (SSR) methods. The effect of crystallite size on CO sensing performance of synthesized LaCoO3 was studied. Compared to the other methods, HEBM resulted in lowest crystallite size of 11 nm while the SG and SSR gave a crystallite size of 20 nm and 1 µm, respectively. While the specific surface area of all samples remained similar, the maximum response ratio was increased from 7% for SSR samples to 17% and 26% for SG and BM samples, respectively. In the second step, specific surface area (SSA) of milled materials was increased using a second milling process. The new synthesis process was called Activated Reactive Synthesis (ARS). The effect of surface area on gas sensing performance and oxygen mobility as well as oxygen desorption capacity of synthesized materials was investigated. Synthesized materials were characterized using XRD, TPD-O2 and BET. Gas sensing results revealed a positive effect of low crystallite size and high surface area on gas sensing performance of milled materials. Specific surface area of the BM sample was successfully increased from 4 m2/g to an optimum value of 66 m2/g by an ARS step. Improved BM material showed the highest response ratio of up to 75% for 100 ppm CO in dry air at 125°C, which is four and ten times higher than those obtained by sol-gel and solid-state reaction methods, respectively. The gas sensing performance of LaCoO3 samples with a crystallite size of 11 nm and a specific surface of 66 m2/g was set as a benchmark for further improvements. In the third step, the potential of ARS method in providing the doped formulations was explored by synthesizing La1-xCexCoO3 series doped with different amounts of cerium. The effect of cerium doping on perovskite structure and its gas sensing properties was then evaluated. Ce-doped formulations showed a saturation point at 10 at.% in the perovskite structure. The optimum CO sensing temperature for doped formulation was found to be 100°C compared to 130°C for pure perovskite. Among the Ce-doped formulations, La0.9Ce0.1CoO3 showed the best response ratio (240%) with respect to 100 ppm CO that was four times higher than the response ratio of pure LaCoO3. TPD-O2, TPD-CO and XPS were performed to find the relation between sensing performance and physical and chemical properties of synthesized samples. Further addition of Ce resulted in segregation of cerium oxide as a second phase (impurity) and deteriorated the sensing performance of the doped materials. Nanostructured LaFeO3 perovskite was also synthesized using ARS method. This formulation was chosen for its intrinsic hydrogen and CO sensing properties. The sensing properties of this formulation with respect to methane were improved by Pd doping. Pd oxide was impregnated on the surface of nanostructured and high surface of LaFeO3 to further enhance its methane sensing performance. Different amounts of palladium oxide were used to find the optimum level of doping. Doped formulations showed a good sensitivity to methane at very low temperature (<150°C) while pure LaFeO3 did definitely not show any sensing property with respect to methane at the same temperature range. LaFeO3 with 2 wt.% Pd with a crystallite size of 14 nm and a high specific surface area of 46 m2/g showed maximum response ratio of 600% with respect to 300 ppm CH4 in air. Methane storage capacity of doped formulation was evaluated to investigate the effect of doping element on adsorption capacity and its relation with the sensing performance of synthesized samples. No catalytic activity was observed for doped formulations.

Size reduction processes, particularly fine grinding systems, in mineral processing and cement production plants constitute a great portion of energy consumption and operating costs. Therefore, the grinding systems should be designed properly and operated under optimum conditions to achieve productive and cost effective operations. The use of simulation based on kinetic mathematical models of grinding has proven useful in this respect. The kinetic models contain two essential parameters, namely, breakage rate and breakage distribution functions, that are to be determined experimentally, and preferably in laboratory, or by back-calculation from the mill product size distribution for a given feed size distribution. Experimental determination of the breakage parameters has been mostly carried out in laboratory batch mills using one-size-fraction material. The breakage rate parameter is obtained from the disappearance rate of this one-size-fraction material, while the breakage distribution parameters are estimated from the short-time grinding of the same material. Such laboratory methods using one-size fraction material, however, are not truly representative of industrial continuous mill operations where the mill contents have a distribution of particle sizes. There is evidence in the literature that the size distribution of the mill contents affects the breakage parameters. This thesis study was undertaken with the main purpose of investigating the effect of the size distribution of the mill hold-up on the brekage parameters of quartz and calcite minerals in lockedcycle dry grinding experiments. The locked-cycle and one-size-fraction experiments were performed in the Bond ball mill instrumented with a torque-measuring device. Different closing screen sizes were used in the locked-cycle work to produce different size distributions of the mill hold-up, and the operating conditions were changed in the one-size-fraction experiments to obtain different power draws. Particle breakage parameters were assessed for these changing conditions. Prior to the experiments related to the main purpose of the study, preliminary experiments were conducted for two reasons: (i) to find the power draw of the Bond mill in relation to the operating conditions with the intention of eliminating the use of costly torque-measuring devices by others
and (ii) to find the most accurate estimation method of breakage distribution functions among the three existing methods, namely, the &ldquo
zero-order production of fines&rdquo
method, the BII method, and the G-H method. The G-H method was found to be more appropriate for the current study. The locked-cycle grinding experiments revealed that the breakage rate function of coarse fractions increased with increasing proportion of fines in the mill hold-up. Breakage distribution functions were found to be environment-dependent and non-normalizable by size in one-size-fraction and locked cycle grinding experiments. It was concluded that the cumulative basis breakage rate function could sufficiently represent the breakage characteristics of the two studied materials in a wide range of operating conditions. Therefore, it would be more appropriate to evaluate the breakage characteristics of materials ground in ball mills by linearized form of the size-discretized batch grinding equation using single parameter instead of dealing with two parameters which may not be independent of each other.

The research work in this thesis has been devoted to understand the formation mechanism of single-crystalline and textured polycrystalline nanoparticles and nanoflakes of SmCo5 and Nd2Fe14B prepared by surfactant-assisted (SA) ball milling and to study their microstructural and magnetic properties. The nanoparticles and nanoflakes are promising candidates to be used as hard magnetic phase for the fabrication of high-energy-density exchange-coupled nanocomposite magnets. The influence of a range of different surfactants, solvents and milling parameters on the characteristics of ball-milled powder has been systematically investigated. Small fraction (~10 wt.%) of SmCo5 nanoparticles of average diameter 15 nm along with textured polycrystalline nanoflakes of average diameter 1 µm and average thickness of 100 nm were obtained after SA – ball milling of SmCo5 powder. Isolated single-crystalline particles (200-500 nm) and textured polycrystalline flakes (0.2-1.0 µm) of Nd2Fe14B have been prepared in bulk amount (tens of grams), after SA – ball milling of dynamic-hydrogen-disproportionation-desorption-recombination (d-HDDR) processed Nd2Fe14B powder. These single-crystalline Nd2Fe14B particles are promising for their microstructure for the fabrication of exchange-coupled nanocomposite permanent magnets. The SmCo5 and Nd2Fe14B flakes and particles were well aligned in magnetic field: the former showed [001] out-of-plane orientation while the latter showed [001] in-plane orientation. A maximum degree of texture values of 93 % and 88 % have been obtained for the magnetically-oriented SmCo5 flakes and Nd2Fe14B single-crystalline particles, respectively. SA – ball milling resulted in an increase of coercivity of SmCo5 particles from 0.45 T for un-milled powder to a maximum value of 2.3 T after 1 h of milling, further milling resulted in a decrease of the coercivity. The coercivity of SA – ball-milled Nd2Fe14B particles decreased drastically from 1.4 T for un-milled d-HDDR powder to 0.44 T after 0.5 h of milling, isolated single-crystalline particles (200-500 nm size) obtained after 4 h of SA – ball milling showed a coercivity of 0.34 T. The drastic decrease in coercivity of ball-milled Nd2Fe14B particles is attributed to the morphological change because the demagnetization in Nd2Fe14B magnets is governed by nucleation mechanism. A remarkable enhancement in coercivity from 0.26 T to 0.70 T for ethanol-milled sample and from 0.51 T to 0.71 T for oleic-acid-milled samples has been obtained after an optimum heat-treatment at 400 0C. An increase of α-Fe and Nd2O3 phase contents and a sharp change of lattice parameter c of Nd2Fe14B was observed when heat-treating above 400 0C. The change in lattice parameter at higher temperature is thought to be due to partial substitution of carbon atoms present in the surfactant or solvent, for boron atoms
Das Ziel dieser Arbeit ist es, den Mechanismus der Herstellung von einkristallinen und texturierten polykristallinen Nanopartikeln und Nanoflakes aus SmCo5 und Nd2Fe14B durch Tensid-gestütztes Kugelmahlen zu verstehen. Des Weiteren soll deren Gefüge und magnetische Eigenschaften untersucht werden. Die Nanopartikel sind vielversprechende Kandidaten zur Verwendung als hartmagnetische Phase in hochentwickelten, austauschgekoppelten Nanokomposit-Magneten. Der Einfluß der Art der verwendeten Tensid, Lösungsmittel sowie Mahlparameter auf die Eigenschaften der kugelgemahlenen Pulver wurde systematisch untersucht. Ein kleiner Anteil (~10 m.%) von SmCo5 Nanopartikeln mit mittlerem Durchmesser von 15 nm zusammen mit texturierten polykristallinen Plättchen mit mittlerem Durchmesser von 1 µm und mittlerer Dicke von 100 nm wurden nach Tensid-gestütztes Kugelmahlen erzeugt. Alleinstehende einkristalline Partikel (200-500 nm) und texturierte polykristalline Plättchen (0,2-1,0 µm) aus Nd2Fe14B wurden in größeren Mengen (einige 10 g) hergestellt. Das verwendete Ausgangspulver wurde hierbei durch dynamisches-Hydrierung-Disproportionierung-Desorption-Rekombination (d-HDDR) hergestellt und anschließend Tensid-gestütztes Kugelmahlen. Die genannten einkristallinen Nd2Fe14B Partikel sind ebenfalls vielversprechend als hartmagnetischer Bestandteil von austauschgekoppelten Nanokomposit-Magneten. Die SmCo5- und Nd2Fe14B-Plättchen und -Partikel wurden alle in einem Magnetfeld ausgerichtet: erstere zeigten aus der Ebende herauszeigende und letztere in der Ebene liegende [001]-Orientierung. Ein maximaler Texturgrad von 93% wurde für im Magnetfeld ausgerichtete SmCo5 flakes bzw. 88% für einkristalline Nd2Fe14B Partikel erzielt. Tensid-gestütztes Kugelmahlen führte zu einem Anstieg der Koerzitivfeldstärke von SmCo5 Partikeln von 0,45 T für ungemahlenes Pulver auf 2,3 T nach einer Mahldauer von 1 h. Weiteres Mahlen führte zu einem Abfall der Koerzitivfeldstärke. Die Koerzitivfeldstärke von Tensid-gestütztes Kugelmahlen Nd2Fe14B Partikeln verringerte sich stark von 1,4 T von ungemahlenem d-HDDR Pulver auf 0,44 T nach 0,5 h Mahlen. Freistehende einkristalline Partikel (200-500 nm groß), welche nach 4 h Tensid-gestütztes Kugelmahlen erhalten wurden, zeigten eine Koerzitivfeldstärke von 0,34 T. Der starke Abfall der Koerzitivfeldstärke von gemahlenen Nd2Fe14B Partikeln wird die morphologischen Veränderungen zurückgeführt, da die Ummagnetisierung nukleationsgesteuert ist. Ein bemerkenswerter Anstieg der Koerzitivfeldstärke von 0,26 T auf 0,70 T wurde für eine in Ethanol gemahlene Probe verzeichnet, sowie ein Anstieg von 0,51 auf 0,71 T für eine Probe, welche mit einer Zugabe von Oleinsäure gemahlen wurde. Beide Proben wurden einer optimierten Wärmebehandlung bei 400°C unterzogen. Bei höheren Temperaturen wurde für Nd2Fe14B ein Anstieg der Menge an α-Fe und Nd2O3 gefunden und eine sprungartige Veränderung des Gitterparameters c der Nd2Fe14B Phase. Die Veränderung des Gitterparameters wird auf die partielle Substitution von Kohlenstoffatomen des Tensid oder Lösungsmittels gegen Boratome zurückgeführt

The strength of conventional aluminium alloys decreases rapidly above 150°C, which limits their applications at elevated temperature. Rapid solidified (RS) nanoquasicrystalline Al₉₃Fe₃Cr₂Ti₂ (at.%) alloy has previously shown outstanding mechanical performance and microstructural stability at elevated temperatures (>300°C). In order to obtain an outstanding Al-based material with very high strength in a broad range of temperature, it is proposed to produce a nanocomposite consisting of nano-size ceramic particles homogenously distributed in a nanoquasicrystalline alloy matrix. The main challenges of processing nanoquasicrystalline nanocomposites in ball milling are to prevent the metastable quasicrystalline phase from decomposition and to avoid the agglomerations of nano-size γ-Al₂O₃.

Silver (Ag) was loaded to three different kinds (P-25, NT-22, and TiO(OH)2) of titanium dioxide (TiO2) powders through adding three different quantities (4.6, 9.2, and 13.8 ml) of silver nitrate (AgNO3) solution by mechanical ball milling process. X-Ray diffraction analysis suggested that Ag was loaded on the TiO2 powders in the form of silver oxide (AgO). SEM, particle size, and BET surface area analyses revealed that TiO2 particles agglomerated after ball milling, resulting in the decrease of specific surface area of the TiO2 powders. Powders P-25, NT-22, and TiO(OH)2 degraded 94 %, 46 %, and 26 %, respectively of MO solution under 1 h UV irradiation. Increasing amount of Ag loading enhanced photocatalytic activity of TiO2 powders under UV irradiation. The best photocatalytic performance was achieved by 13.8 ml AgNO3 solution added NT-22 powders. Percent methyl orange (MO) degradation of 13.8 ml AgNO3 solution added P-25, NT-22, and TiO(OH)2 powders under 1 h UV irradiation was 85 %, 96 %, and 67 %, respectively. Contact angle measurements revealed that hydrophilic properties of TiO2 powders were also improved by Ag loading. Moreover, TiO2 powders gained antibacterial prospect after Ag addition. Ag loaded TiO2 powders could be used effectively for the applications requiring better photocatalytic activity and antibacterial effect.

High-energy ball milling was studied for the ex situ strengthening of aluminum (Al) with nanodiamond (ND). Al-ND metal matrix composite powders with 5 wt% and 10 wt% nanodiamond were synthesized by high-energy ball milling of the blended component powders. Stearic acid was used as a process control agent to minimize agglomeration of the powders upon milling. A uniform distribution of the ND reinforcement was successfully obtained after milling the powders for a period of ten hours with a ball-to-powder ratio of 30:1 in a SPEX 8000M ball mill. Composition and properties of the Al-ND composite was studied using energy dispersive spectrometry (EDS) mapping, scanning electron microscopy (SEM), X-ray diffraction (XRD), optical microscopy, and nanoindentation techniques.

Here we report on technical details of preparation of Si-Ge-based nanostructured thermoelectic materials by a mechnical alloying method. It has been shown that for a milling speed of 350 rpm a single Si-Ge phase is formed after milling time less than 6 h. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35302

An experimental ball-milling study was performed to compare the deagglomeration behavior and the evolution of the particle size distribution with increasing milling time of two relatively coarse WC powders used for the production of cemented carbide cutting tools. The WC-powders were found to have distinctly different particle size distributions and particle morphologies prior to milling. Lab-scale WC samples were made using a range of different process parameters and milling times. These were then analysed by means of microscopy, laser light scattering, gas adsorption BET analysis and X-ray powder diffraction, XRD, to attain particle size distribution, specific surface area and a mean crystal size, respectively. The results suggested a linear relation between log(particle size) and log(milling time) between 10 and 80 hours milling. The viscosity was shown to have a minor effect on the milling efficiency. Both the number of collisions of milling balls per unit time as well as the kinetic energy of the milling ball affected the size reduction; more collisions or higher energy resulted in a higher milling efficiency. The evaluation of the effect of the process parameters on milling efficiency was facilitated by the use of simple scaling factors. For example, all milling curves for samples with different WC amounts coincided when rescaling the milling time using a scaling factor based on the weight of the WC and milling balls. The same scaling factor could be used with success for rescaling the results from different trials obtained with laser light scattering, gas adsorption and XRD. The results of this work are useful for future work on modeling of the milling process which should lead to more accurate predictions of the outcome of milling unit operations.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.
Includes bibliographical references (leaf 41).
The hardness and percent crystallinity of Cu33Zr67 powder samples are measured through several cycles of a cyclic phase transformation during ball milling. Each are found to cycle with a period of approximately 320 minutes. Although significant chemical contamination was found in the milled specimens, the results shed some light on mechanical alloying theory and favor interpreting mechanical alloying as a driven alloys process.
by David Taylor Schoen.
S.B.

Doutoramento em Engenharia Mecânica
Neste trabalho foram produzidos nanocompósitos de AlSiC misturando alumínio puro com nano partículas de SiC com diâmetro de 45 – 55 nm, usando, de forma sequencial, a técnica da metalurgia do pó e a compactação por “ Spark Plasma Sintering”. O compósito obtido apresentava grãos com 100 nm de diâmetro, encontrandose as partículas de SiC localizadas, principalmente, nas fronteiras de grão. O nanocompósito sob a forma de provetes cilíndricos foi submetido a testes de compressão uniaxial e a testes de nanoindentação para analisar a influência das nanopartículas de SiC, da fração volúmica de ácido esteárico e do tempo de moagem, nas propriedades mecânicas do material. Para efeitos de comparação, utilizouse o comportamento mecânico do Al puro processado em condições similares e da liga de alumínio AA1050O. A tensão limite de elasticidade do nanocompósito com 1% Vol./Vol. de SiC é dez vezes superior à do AA1050. O refinamento de grão à escala nano constitui o principal mecanismo de aumento de resistência mecânica. Na realidade, o Al nanocristalino sem reforço de partículas de SiC, apresenta uma tensão limite de elasticidade sete vezes superior à da liga AA1050O. A adição de 0,5 % Vol./Vol. e de 1 % Vol./Vol. de SiC conduzem, respetivamente, ao aumento da tensão limite de elasticidade em 47 % e 50%. O aumento do tempo de moagem e a adição de ácido esteárico ao pó durante a moagem conduzem apenas a um pequeno aumento da tensão de escoamento. A dureza do material medida através de testes de nanoindentação confirmaram os dados anteriores. A estabilidade das microestruturas do alumínio puro e do nanocompósito AlSiC, foi testada através de recozimento de restauração realizado às temperaturas de 150 °C e 250 °C durante 2 horas. Aparentemente, o tratamento térmico não influenciou as propriedades mecânicas dos materiais, excepto do nanocompósito com 1 % Vol./Vol. de SiC restaurado à temperatura de 250 °C, para o qual se observou uma redução da tensão limite de elasticidade na ordem dos 13 %. No alumínio nanocristalino, a tensão de escoamento é controlada pelo efeito de HallPetch. As partículas de SiC, são segregadas pelas fronteiras do grão e não contribuem para o aumento de resistência mecânica segundo o mecanismo de Orowan. Alternativamente, as nanopartículas de SiC constituem um reforço das fronteiras do grão, impedindo o seu escorregamento e estabilizando a nanoestrutura. Deste modo, as propriedades mecânicas do alumínio nanocristalino e do nanocompósito de AlSiC poderão estar relacionadas com a facilidade ou dificuldade do escorregamento das fronteiras de grão, embora não seja apresentada prova explícita deste mecanismo à temperatura ambiente.
AlSiC nano composites were prepared by mixing pure Al and 50 nm diameter SiC nanoparticles using a powder metallurgy technique, followed by compression and spark plasma sintering. The final composites had grains of approximately 100 nm dimensions, with SiC particles located mostly at grain boundaries. The samples were tested in uniaxial compression and by nanoindentation in order to establish the effect of the SiC and stearic acid volume fraction, and the milling time on the mechanical properties. The results are compared with those obtained for pure Al processed under similar conditions and for AA1050 aluminum. The yield stress of the nano composite with 1 Vol. % SiC is more than ten times larger than that of AA1050. The largest increase is due to grain size reduction; nanocrystalline Al without SiC and processed by the same method has a yield stress 7 times larger than AA1050. Adding 0.5 Vol. % SiC increases the yield stress by an additional 47 %, while the addition of 1 Vol. % SiC leads to 50 % increase relative to the nanocrystalline Al without SiC. Increasing the milling time and adding stearic acid to the powder during milling lead to relatively small increases of the flow stress. The hardness measured in nanoindentation experiments confirms these trends, although the numerical values of the gains are different. The stability of the microstructure was tested by annealing samples to 150 oC and 250 oC for 2 h, in separate experiments. The heat treatment had no effect on the mechanical properties of all samples, except when treating the material with 1 Vol. % SiC at 250 oC, which led to a reduction of the yield stress by 13 %. In nanocrystalline Al, the flow stress is controlled by the HallPetch effect. As observed in this work, the added SiC particles segregate at grain boundaries and do not contribute to strengthening through the Orowan mechanism, rather pin the grain boundaries helping to stabilize the nanostructure of the material. Grain boundary sliding is expected to be important in both nanocrystalline Al and AlSiC, although we do not present explicit proof for the operation of this mechanism at room temperature.

Thesis (Ph. D. (Physics)) -- University of Limpopo, 2013.
A combination of ball milling experiments and ab initio calculations in this study successfully yielded results that shed light into understanding the fundamental basis for immiscibility and the concept of mechanical alloying in Ti-Mg system. In addition, the conditions for achieving extended solid solubility in elements that usually do not dissolve in each other under thermodynamic equilibrium conditions have been predicted using ultrasoft (US) and norm-conserving (NC) pseudopotentials. Hydostatic pressures required to stabilize ordered phases were determined. Our new systematic representation of martensitic transformation (MT) paths as a result of dislocation necessary to induce α→FCC, α→BCC and α→ω phase transitions led to, for the first time, a direct determination of CRSS and tensile strength for Ti and Mg HCP metals. Furthermore, a new ω phase which is less stable than α phase at 0 GPa is proposed. Based on this phase, α→ω deformation path which yielded the onset of uniaxial transition pressure of 4.167 GPa is reported. Attempts of synthesizing Ti-Mg solid solutions by means of Simoloyer high energy ball mill were not successful; however, nanocrystalline Mg-TiH2-x composites were instead formed. These results were attributed to quick formation of metastable Ti hydrides or cold welding at early stages of BM prior to alloying, thus serving as possible obstacles to forming such solid solutions. The deformed Ti crystals adsorbed H+ from the stearic acid leading to formation of metastable orthorhombic TiH2-x phase which later transformed to a tetragonal TiH2-x or even cubic TiH2 when stoichiometric amount of H2 had been adsorbed. Although the yield was significantly lower, the product of milling a mixture of coarse Mg and fine Ti particles was comprised of Ti particles adhering around ductile Mg particles in a core shell manner. The adhesion of the fine hard titanium particles on the surface of the large ductile magnesium particles impeded the further plastic deformation of the titanium particles, thus suppressing the formation of the faults necessary for mechanical alloying. Nanocrystalline Ti powder of about 40 nm was produced by 30h ball milling. During BM of Ti powder, solid-state transformation from HCP to FCC occurred in the presence of PCA with lattice parameters of 4.242 and 4.240 Å after 24 and 30 h, respectively, v due to protonation. When Ti powder was milled in the absence of PCA, no phase transformation was observed for both uninterrupted and interrupted milling cycles. In addition, nanocrystalline Mg powder with crystallite size varying between 60 and below 40 nm was produced by ball milling. However, no solid-state transformation took place even if the powder was milled for 90 h. Therefore, we evidently report for the first time that the interstitial H+ is the driving force for α → FCC phase transformation in ball milled Ti powder. Our theoretical results predicted the ω phase to be the ground-state structure of Ti at 0K and P=0 GPa, in support of other previously reported calculations. We noticed that the stability of the α phase was surpassed by that of the FCC lattice at ~ 100 GPa, corresponding with sudden sharp rise in c/a ratio, hence attributed to α → FCC phase transition. Similar results were obtained for Mg at 50 GPa, although in this case the crossing of lattice energies coincided with minimum c/a. However, using our proposed HCP→BCC MT path mechanism for Mg, it is evident that the minimum c/a at 50 GPa corresponds to a change in the preferred deformation slip from basal (below 10 GPa) to prismatic rather than phase transition. Nonetheless, the proposed MT model predicts that both elemental Ti and Mg prefer to deform via prismatic slip as indicated by lower shear stress as well as CRSS values compared to those calculated for basal slip. Theoretical findings from ab initio calculations on hypothetical ordered Ti-Mg phases indicated absence of intermetallic phases at equilibrium conditions, in agreement with experimental data. However, the formation becomes possible at 80 GPa and above with respect to c/a ratio but requires at least 200 GPa with respect to stable lattices. Using calculated heats of formation, elasticity and DOS, it has been possible to show that L12 TiMg3 could not form even at high pressure as 250 GPa. Nonetheless, both approaches indicate that forming an intermetallic compound between Ti and Mg requires a crystal structure change, α→FCC for Ti and HCP→BCC for Mg. Proposed DFT-based solid solution model for predicting phase stability and elastic properties of binary random alloys, with Mg-Li system serving as a test case, successfully yielded reliable results comparable to experimental data. This method was successfully applied to study an immiscible Ti-Mg system and the solubility limit vi was for the first time theoretically established. Based on formation energy of Ti-Mg solid solutions, our calculations predicted for the first time that the solubility of up to 60 and 100 at.% Mg into Ti with the use of USP and NCP, respectively, to be thermodynamically favourable with necessary lattice kinetics being the main challenge. Nonetheless, NCP proved to be reliable in predicting structural and elastic properties of disordered alloys.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Amidos modificados são utilizados pela indústria de alimentos por apresentarem melhor comportamento que amidos nativos. Modificações visando a redução do diâmetro granular para a obtenção de grânulos de tamanho similar aos da molécula de gordura tem sido de grande interesse, pois este amido modificado pode ser usado como substituto de gordura em diversas formulações. Para isso, o pré-tratamento enzimático pode ser usado para fragilizar a estrutura granular do amido e facilitar um posterior tratamento físico como a moagem, obtendo grânulos com menor diâmetro. O objetivo deste trabalho foi investigar o efeito da hidrólise enzimática seguida de moagem em moinho de bolas sobre as características estruturais e físico-químicas do amido de mandioquinha-salsa (Arracacia xanthorrhiza). Amido isolado de raízes de mandioquinha-salsa foi hidrolisado com α-amilase bacteriana e/ou amiloglucosidase fúngica, a 37 o C, em três diferentes condições: A: 40 SKB/g de α-amilase e 10 U/g amiloglucosidase por 36 h; B: 20 SKB/g de α-amilase e 5 U/g amiloglucosidase por 12 h; C: 5 U/g amiloglucosidase por 12 h. Após hidrólise os mesmos foram moídos por 1 e 2 h. Os amidos nativos e modificados foram analisados quanto à distribuição de tamanho de grânulos. Houve redução do diâmetro dos grânulos para todos os amidos tratados, mas a condição de hidrólise B foi a escolhida para a continuidade dos experimentos, por ter apresentado uma distribuição de tamanho de grânulos após moagem mais homogênea. Os amidos nativos e hidrolisados com 20 SKB/g de α-amilase e 5 U/g amiloglucosidase por 12 h foram analisados quanto a forma dos grânulos, distribuição do comprimento das cadeias laterais da amilopectina, distribuição do tamanho molecular dos componentes do amido, teor de amilose, difração de raios-X...
Modified starches are used by food industry because they have better performance than native starches. Modifications in order to reduce granular diameter to obtain granules of similar size to those of fat molecules has been of great interest, for this modified starch can be used as a fat substitute in various formulations. For this purpose, a enzymatic pretreatment can be used to weaken the granular structure of starch and facilitate a subsequent physical treatment such as grinding. The objective of this study was to investigate the effect of enzymatic hydrolysis followed by milling in a ball mill on the structural and physicochemical characteristics of Peruvian carrot (Arracacia xanthorrhiza) starch. Starch isolated from roots of Peruvian Carrot was hydrolyzed with bacterial α-amylase and fungal amyloglucosidase at 37 °C in three different conditions: A: 40 SKB/g of α-amylase and 10 U/g amyloglucosidase for 36 h; B: 20 SKB/g of α-amylase and 5 U/g amyloglucosidase for 12 h; C: 5 U/g amyloglucosidase for 12 h. After hydrolysis, the starches were ball milled for 1 and 2 h. The native and modified starches were analyzed for granular size distribution. There was reduction of the granular diameter for all modified starches, but the B condition of hydrolysis was choosen to continue the experiments because the starches modified in this condition displayed a more homogeneous granular size distribution after milling. The native and hydrolyzed with 20 SKB / g of α-amylase and 5 U / g amyloglucosidase for 12 h starches were analyzed for granule shape, distribution of branch chain length of amylopectin, molecular size distribution of the starch components, apparent amylose content, X-ray diffraction, thermal and pasting properties, swelling power and solubility. The native starch granules, analyzed in optical microscope... (Complete abstract click electronic access below)

This research project investigates a new technique to efficiently mix crystalline solid additives with polymers by gentle ball milling with steel balls in the presence of carbon dioxide (C02) at 17 to 30°C and 1300 to 2500 psig. As the ball milling system is agitated, the steel balls transfer mechanical energy to the fluoropolymer and additive thereby converting them to powders. C02 is added into the chamber to expand the polymer and make it amenable to impregnation by the additive. At the end of the mixing process, a free flowing powder is produced consisting of the additive coated with fluoropolymer. The additives were extracted from the powders and intrinsic viscosity measurements were done on the remnant fluoropolymer. Viscosity studies showed that the virgin and post-ball milled fluoropolymers had similar intrinsic viscosities, hence similar molecular weights within experimental error limits. This implies that most of the polymer chains were simply disentangled during the mixing process and not broken. Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA) were done on the virgin polymer, the additives and the fabricated powders to determine the loading levels and to ascertain if there were any changes to the physical properties of the polymer. Scanning electron micrographs showed that some of the powder particles had additive particles stuck on the surface, but when these additives were washed off the surface of the powders with a suitable solvent that did not dissolve the polymer, DSC analysis showed the presence of additive incorporated into the polymer matrix.

In machining, the desired final shape is created in Computer Aided Design (CAD) environment and this information is forwarded to Computer Aided Manufacturing (CAM) phase in which the toolpath is generated and converted to machine specific commands for part manufacturing. The steps in CAD/CAM environments are geometry dependent only, and do not include the physics of the process. However, mathematical modeling of the machining operation gives the flexibility of identifying and resolving process related issues i.e. tool breakage, chatter vibrations and tolerance violations beforehand, which in turn leads to increased productivity. The first step of process modeling is to model the mechanics of the operation that leads to the prediction of the cutting forces experienced by the cutting tool and the workpiece. In this study the mechanics of ball-end tool which is commonly used to machine parts with free-form geometric features are studied. The main problem in ball-end milling mechanics is tool indentation which leads to inaccurate force prediction in tool axial direction, and has previously been solved experimentally only for specific cases. This thesis presents a generalized ball-end tool indentation detection and indentation force prediction model for any kind of work material and cutting tool geometry combinations. The static ball-end milling forces with indentation forces are predicted by developing an analytical cutting edge indentation model. The proposed model utilizes indentation mechanics of punch and wedge shape indenters, describes the required conditions for indentation occurrence and evaluates plastic and elastic contact pressures at the cutting edge and workpiece interface using the material properties of the workpiece. Cutting edge indentation mechanism is also studied through finite element (FE) modeling. A general FE model is obtained for the problem and results are reported only for the material cut in the thesis. The model proposed in the thesis has been verified experimentally. After integrating the developed indentation force prediction model into the cutting force model, predictions in tool axial direction are improved by 15-40% depending on type of the operation. The contribution of the thesis can be used in cutting force based ball-end milling process optimization and analysis for industrial applications.

Orientador: Célia Maria Landi Franco
Banca: Thais de Souza Rocha
Banca: Ana Carolina Conti e Silva
Resumo: Amidos modificados são utilizados pela indústria de alimentos por apresentarem melhor comportamento que amidos nativos. Modificações visando a redução do diâmetro granular para a obtenção de grânulos de tamanho similar aos da molécula de gordura tem sido de grande interesse, pois este amido modificado pode ser usado como substituto de gordura em diversas formulações. Para isso, o pré-tratamento enzimático pode ser usado para fragilizar a estrutura granular do amido e facilitar um posterior tratamento físico como a moagem, obtendo grânulos com menor diâmetro. O objetivo deste trabalho foi investigar o efeito da hidrólise enzimática seguida de moagem em moinho de bolas sobre as características estruturais e físico-químicas do amido de mandioquinha-salsa (Arracacia xanthorrhiza). Amido isolado de raízes de mandioquinha-salsa foi hidrolisado com α-amilase bacteriana e/ou amiloglucosidase fúngica, a 37 o C, em três diferentes condições: A: 40 SKB/g de α-amilase e 10 U/g amiloglucosidase por 36 h; B: 20 SKB/g de α-amilase e 5 U/g amiloglucosidase por 12 h; C: 5 U/g amiloglucosidase por 12 h. Após hidrólise os mesmos foram moídos por 1 e 2 h. Os amidos nativos e modificados foram analisados quanto à distribuição de tamanho de grânulos. Houve redução do diâmetro dos grânulos para todos os amidos tratados, mas a condição de hidrólise B foi a escolhida para a continuidade dos experimentos, por ter apresentado uma distribuição de tamanho de grânulos após moagem mais homogênea. Os amidos nativos e hidrolisados com 20 SKB/g de α-amilase e 5 U/g amiloglucosidase por 12 h foram analisados quanto a forma dos grânulos, distribuição do comprimento das cadeias laterais da amilopectina, distribuição do tamanho molecular dos componentes do amido, teor de amilose, difração de raios-X... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Modified starches are used by food industry because they have better performance than native starches. Modifications in order to reduce granular diameter to obtain granules of similar size to those of fat molecules has been of great interest, for this modified starch can be used as a fat substitute in various formulations. For this purpose, a enzymatic pretreatment can be used to weaken the granular structure of starch and facilitate a subsequent physical treatment such as grinding. The objective of this study was to investigate the effect of enzymatic hydrolysis followed by milling in a ball mill on the structural and physicochemical characteristics of Peruvian carrot (Arracacia xanthorrhiza) starch. Starch isolated from roots of Peruvian Carrot was hydrolyzed with bacterial α-amylase and fungal amyloglucosidase at 37 °C in three different conditions: A: 40 SKB/g of α-amylase and 10 U/g amyloglucosidase for 36 h; B: 20 SKB/g of α-amylase and 5 U/g amyloglucosidase for 12 h; C: 5 U/g amyloglucosidase for 12 h. After hydrolysis, the starches were ball milled for 1 and 2 h. The native and modified starches were analyzed for granular size distribution. There was reduction of the granular diameter for all modified starches, but the B condition of hydrolysis was choosen to continue the experiments because the starches modified in this condition displayed a more homogeneous granular size distribution after milling. The native and hydrolyzed with 20 SKB / g of α-amylase and 5 U / g amyloglucosidase for 12 h starches were analyzed for granule shape, distribution of branch chain length of amylopectin, molecular size distribution of the starch components, apparent amylose content, X-ray diffraction, thermal and pasting properties, swelling power and solubility. The native starch granules, analyzed in optical microscope... (Complete abstract click electronic access below)
Mestre

碩士
國立臺北科技大學
製造科技研究所
94
This paper proposes a mechanistic ball end mill cutting force model to estimate the ball end milling forces for inclined plane milling. The developed model that calculates the cutting forces based on a set of cutting force coefficients which depend on the material, the tool, the cutting conditions, the machining directions and the inclined angle of the milling surface. The developed ball end milling force models for inclined plane milling include rise milling ,downhill milling, and horizontal milling. This study uses the present cutting force model and the measured ball end milling forces data to obtain equivalent specific cutting force coefficients (C , C , and C ) for some cutting conditions. By substituting the cutting force coefficients into the present ball end milling force model, the milling force variation both on horizontal plane and inclined plane can be predicted. Finally, the present study also construct some parametric Bezier surfaces of cutting force coefficients in the CAD system by using finite experiment data of ball end milling, which is used to easily find out the cutting force coefficients for any inclined angle of ball end milling operation. In the present study, the cutting force model has been tested on aluminum alloy Al7075-T6 with micro grain carbide ball end mill ( 10 - 2 flutes). Validation tests have been carried out on planar surfaces milling and on inclined plane milling in some typical ball end milling conditions. The results show that the predicted cutting forces agreed well with the measured cutting forces.

碩士
國立成功大學
製造工程研究所
88
In this thesis, the effect of milling parameters on the ball-end milling forces is investigated by both the theoretical and experimental methods. In experimental aspect, the instantaneous cutting force signals and average cutting forces with different milling parameters in three orthogonal directions were measured by piezoelectric dynamometer. The objective of this thesis is to establish an algebraic model of cutting force system in the ball-end milling process. This objective is accomplished by systematically and analytically formulating the dominant dynamic components of three-dimensional cutting forces in the machining with helical multi-flute ball-end milling cutters. In this study, the ball-end milling cutting force model is developed to predict the instantaneous cutting force on given machining conditions. The basic concept involved in this thesis is the mathematical characterization of the cutter-workpiece interactions in terms of the chip width density function in an angular convolution expression. After the chip with density function is determined through the geometric model of cutter and workpiece engagement, differential cutting forces in three orthogonal directions are written in the angular domain. This solution is carried out by the convolution integration of the differential cutting forces along the helical flutes. A Laplace transformation for the convolution integral leads itself to a set of closed form expressions of the dynamic cutting force components in terms of process parameters, tool geometry, material characteristics and machining configuration. Finally, the tangential cutting pressure constant, proportionality coefficients and the estimated cutting forces were computed by the measured average cutting forces. It demonstrated that the theoretical results agreed well with the experimental results.

This dissertation focuses on the determination of the selection function parameters , a, , and  together with the exponent factors  and  describing the effect of ball size on milling rate for a South African coal. A series of batch grinding tests were carried out using three loads of single size media, i.e. 30.6 mm, 38.8 mm, and 49.2 mm. Then two ball mixtures were successively considered. The equilibrium ball mixture was used to investigate the effect of ball size distribution on the selection function whereas the original equipment manufacturer recommended ball mixture was used to validate the model. Results show that with the six parameters abovementioned estimated, the charge mixture is fully characterized with about 5 – 10 % deviation. Finally, the estimated parameters can be used with confidence in the simulator model allowing one to find the optimal ball charge distribution for a set of operational constraints.

碩士
國立中央大學
化學工程與材料工程研究所
96
LiFePO4 cathode materials with distinct particle sizes were prepared by a planetary ball-milling method. The effect of particle size on the morphology, thermal stability and electrochemical performance of LiFePO4 cathode materials was investigated. The ball-milling method decreased particle size, thereby reducing the length of diffusion and improving the reversibility of the lithium ion intercalation/deintercalation. It is worth noting that the small particle sample prepared using malonic acid as a carbon source achieved a high capacity of 160 mAh g-1 at a 0.1 C-rate and had a very flat capacity curve. However, the large particle sample decayed more dramatically in capacity than the small particle size samples at high C- rates. The improvement in electrode performance was mainly due to the nanometric fine particles, the small size distribution of the product, and the increase in electronic conductivity as a result of carbon coating. The structure and morphology of LiFePO4 samples were characterized with XRD, FE-SEM, TEM, EDS, and DSC techniques.

碩士
逢甲大學
機械與電腦輔助工程學系
104
This thesis presents an analysis on the effects of machining parameters on surface roughness in ball-end milling stainless steel S304, and thereby develops an experimental model. In the study, a Taguchi L8 table is first utilized to determine the dominant cutting parameters (that are feed, spindle speed, and path interval), and thereby the roughness models in the feed and the transverse directions are developed, respectively. Moreover, two different sets of cutting experiments with different-sized cutters (of which radii are 5 mm and 3 mm, respectively) are conducted to obtain the corresponding models, and consequently, the effect of cutter size is analyzed. Based on the proposed surface-roughness model, we can accurately describe and predict the surface roughness of machined part, and thereby, improve the machining accuracy and efficiency.

博士
國立成功大學
資源工程學系碩博士班
95
An experimental study has been conducted to evaluate the changes of montmorillonite under various conditions, such as different chemical ion exchange, alkylammonium, solvent (water and kerosene), intercalation by mixing and stirred ball-milling. Initial montmorillonite sample was prepared from raw bentonite/clay mined in Taitung, Eastern Taiwan. By the purification processes, it belongs to good grade in general clay resources. For the different alkylammonium conditions, the final organic montmorillonite has been obtained via two different straight-chain organic alkylammonium of treatment, namely: C12NH3+ and C18NH3+. The microstructure of the raw material and the products were examined by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The X-ray (XRD) results show that stirred ball-milling is an effective physical operation for breaking down the size of the clay particles and facilitating the intercalation of ammonium ions. The degree of the final products is noted that the increase in the layer space, from about 1.50 nm to 4.5 nm, and no obvious peak shape at 2θ = 2–10° over 72 hours. In order to achieve the commercial purpose, study on the effect of solvent (water and kerosene), intercalation by mixing and stirred ball-milling. The final product of exfoliated organic montmorillonite was obtained by treatment in water and kerosene systems. The optimum duration for stirred ball-milling was 6 h in both systems. In water the basal spacing increased gradually from 1.27 nm to 2.41 nm with dodecylammonium ions in the case of mixing and from 3.19 to 4.55 nm for dodecylammonium and hexadecylammonium ions during 2 h of ball-milling, respectively.

碩士
逢甲大學
機械工程學所
100
Surface roughness is one of the most important performance indices for precision machining. This thesis presents an analysis on the effects of cutting parameters on surface roughness in ball-end milling process. The surface roughness in both feed direction and transverse direction is investigated. The cutting parameters include the feed, the spindle speed, the path interval, and the angle between the surface normal and the tool axis. In the study, 13 and 19 sets of data are conducted to establish empirical models for surface roughness in the feed and the transverse directions, respectively. Based on the proposed model, we can predict the surface roughness, design the tool paths and cutting parameters, and consequently, improve the machining quality and efficiency.

碩士
逢甲大學
機械與電腦輔助工程學系
102
By ball-end milling processes, mold of conic lens is fabricated on steel surface. With the plastic materials being heating to melt and filling the mold, conic lens is formed as plastic material cooling and solidifying. Quantitative analysis by laser image is investigated. Different incident angles will produce different images. The lens can change the laser spot to line image. It shows the conic lens has function of cylindrical lens. Moreover, it can further split the laser spot to cross line image which is “X” shape. It is obvious that the conic lens has various functions which belong to lenses having different conic surfaces respectively. From this study, it is found that CNC machining can fabricate conic lenses successfully. It can be used to machine lenses with complex surface practically.

碩士
大同工學院
機械工程研究所
86
The purpose of this research is to investigate what kind of cutting parameterswould affect the milling forces, when we use the ball-end milling cutter tomachine the free-form surfaces. The statistical experiment method is utilizedto establish the milling forces model of ball-end milling cutter and toinvestigate the effects of cutting parameters on milling forces withindifferent cutting conditions in accordance with the milling force models.The experimental results show that the milling force models are of goodreliability.In this study, the experimental design is adopted to plan the experiment.The experimental factors, including spindle speed, feed, axial depth of cut,radial depth of cut and position angle, are taken into consideration toinvestigate the effects on milling forces. In the experimental design, thematrix is planned by means of Response Surface Methodology and Taguchi Method.The experimental results are analyzed by statistical software package.Firstly, the experimental results which are analyzed by the analysis ofvariance can be practiced to assess the prominence among experimental factors.And then utilizing a second-order mathematical model, which is called canonicalanalysis, to model the mathematical relationship between cutting conditionsand milling forces. It is anticipated that the model is able to predictmilling forces over a wide variety of cutting conditions. The experimentalresults show that those significant factors, which will affect the millingforces, are in sequence to be the axial epth of cut, spindle speed,position angle and finally the feed rate. The model is also proved in goodagreement with experimental results. Finally, an optimum method is adoptedto search the optimal cutting conditions in the process of machining free-formsurfaces. These results are to provide the process planner with a guidance inselecting machining conditions.

碩士
國立東華大學
材料科學與工程學系
97
The transformation pathway of anatase TiO2 in high-energy planetary ball-milling was studied. Anatase powders were first milled using stainless ball/jar with the additive of ethanol alcohol for 10 mins to 12 hrs, followed by structure characterization by X-ray diffractometer (XRD) and analytical electron microscope (AEM). XRD revealed complicated phase assemblages in all milled powders, including residue anatase, the transitional TiO2-II phase and the final product of rutile. In the powders milled for up to ~7 hrs, the TiO2-II phase contents could reach ~50-60%. In addition to the above three polymorphs, AEM further identified a fourth monoclinic TiO2 (B) phase in the as-milled TiO2 powders . This TiO2 (B) phase occurs either as isolated nanosized particles or as thin lamellae of ~2-35 nm in thickness in the mixed-phase anatase-TiO2 (B) or TiO2 (B)-TiO2-II particles. Electron diffraction patterns showed that the mixed-phase powders follow specific crystallographic orientation relationships: <010>A ∥<010> B、{103}A ∥{-201} B for anatase-TiO2 (B); <-22-1>Ⅱ∥<010> B 、{10-2}Ⅱ∥{-20-2}B for TiO2 (B)-TiO2-II; <010>II ∥<111>R for TiO2-II – rutile, all of which being formed by sequential shear deformation of TiO2 polymorphs in high-energy milling. These observations, together with the well-known shear transformation of TiO2-II to rutile, unequivocally establish the anatase to rutile transformation pathway during high-energy milling process as: anatase => TiO2 (B) => TiO2-II => rutile, and open the doorway for the future mass production of nano-sized mixed-phase TiO2 powders with various phase assemblages and unique photocatalyst properties.

碩士
逢甲大學
機械與電腦輔助工程學系
104
This thesis presents an analysis on the effects of machining parameters on surface roughness in ball-end milling medium carbon steel S45-C, and thereby develops an experimental model. In the study, a Taguchi L8 table is first utilized to determine the dominant cutting parameters (that are feed, spindle speed, and path interval), and thereby the roughness models in the feed and the transverse directions are developed, respectively. In addition, the analyses of different parameter ranges and different machine tools are conducted. Based on the proposed surface-roughness model, we can accurately describe the surface roughness in ball-ended milling, and thereby, improve the machining accuracy and efficiency.

碩士
國立臺北科技大學
資源工程研究所
103
Hydrogen energy is one of the most important clean energy, and currently many subjects about the manufacture and storage of hydrogen are studied. This research focused on producing hydrogen by silicon in NaOH(aq), and the produced hydrogen was used to generate electricity via a fuel cell. The effects of various factors on hydrogen production rate and yield were explored. The experimental results show that increasing pH and temperature or stirring solution were helpful to increase hydrogen generation rate. Using ultrasonic vibration could significantly reduce the incubation time to obtain hydrogen. In addition, the faster hydrogen generation and the shorter incubation time could be obtained by using the smaller silicon particles. In the study, we adopted ball milling to shape the silicon and discussed some milling effects on shaping were systematically investigated. By the ratio of Si:0.5 mmZrO2 =1:10 and 600 rpm-milling for 10 hr, the size of silicon reduced from 44 μm to 312 nm. Finally, we used the silicon slurry waste to produce hydrogen, and applied the hydrogen to generate electricity by a fuel cell successfully.

碩士
國立中正大學
機械工程所
94
The critical part industry in mold, automobile manufacture and aircraft industry are developing vigorously. The geometry of a workpiece is getting complicated and the requirement for the precision of the workpiece surface is upgrading. And the surface precision is directly influenced by cutting forces, so the investigation of the cutting force becomes an important issue. Thus, the aim of this study is focused on the cutting force coefficients identification and the predicted of the cutting forces while the milling test is performed with Aluminum 6061-T6 which is in common use. In this study, the Taguchi Method is used to design the cutting tests. The effect of the feed per flute on the cutting forces is analyzed via the experimental results. The cutting force coefficients are identified by the Recursive Least Square Method with the experimental results of the end mill. The cutting parameters of AL6061-T6 are predicted by the identified cutting forces coefficients. Finally, the cutting forces in ball end mill are predicted by the model proposed in [9] with the predicted cutting parameters of AL6061-T6. The numerical results are compared with experimental results, and some conclusions are summarized as follows: The results show that the cutting forces for end milling process can be successful predicted by using the identified cutting force coefficients. And the predicted forces are very close to the measured forces. Furthermore, the cutting parameters of Aluminum 6061-T6 can be determined and used to predict the cutting forces in ball end milling process. And the predicted cutting forces are conformed to approximate to the measured forces.