Dissertations / Theses on the topic 'Ceramic powder injection moulding'

The literature concerning the injection moulding of engineering ceramics has been reviewed. This indicated that a number of claims had been made for the successful use of different organic binders during moulding and their removal prior to sintering. However, many of the claims were not supported by detailed/exact eScperimental evidence as to powder-binder compositions, moulding conditions, moulded properties, debinding times/cycles, or details of the structure and properties of the solid ceramic bodies produced. From the available information it was clear that there were few systematic and scientific investigations concerning the understanding of each stage of the injection moulding process. The present research programme has been carried out in two phases as follows. The first phase was concerned with the reinvestigation and re-evaluation of binder systems claimed to be successful for the injection moulding of alumina ceramics. The binders re-investigated included the thermoplastic-based binders such as polystyrene, polyacetal and atactic polypropylene and the water-based methylcellulose (Rivers) binder system. Alumina was chosen as the main powder to be investigated due to its simple handling and, highest applications amongst ceramic materials and on the basis that there is incomplete published work for almost every step of the injection moulding process. During the first stage of this work the optimum properties such as powder-binder compositions, mixing and moulding conditions, debinding properties, green and sintered densities provided by each binder system were determined. The results of these investigations showed that all the previous (re-evaluated) binder systems had major limitations and disadvantages. These included low volume loading (64 % maximum) of the alumina powder resulting in rather low sintered densities (96 % maximum-of theoretical density) and very long debinding times in the case of the thermoplastic-based binders. it ry low alumina volume loading (55 % maximum resulting in a 94 % . sintered theoretical density) and long moulding cycle time (- 5 min) along with adhesion and distortion problems during demoulding occurred in the case of the water-based methylcellulose binder system. Further work did not appear worthwhile. The newly developed binder systems have been used with a number of other powders such as zirconia, silicon nitride, silicon carbide, tungsten carbide-6 weight % cobalt and iron-2 weight % nickel, to establish- whether injection moulding is feasible. Optimum properties such as powder volume loadings, mixing, moulding, demoulding, moulded densities, debinding and some sintered density results showed that these new binder systems can also be used successfully for the injection moulding of other ceramic and metallic powders, although a fuller evaluation of the properties such as optimum sintered densities and mechanical properties is required.

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Real-time diagnostics of ceramic powder injection molding using a commercial micromolding machine was performed using ultrasound. Miniature ultrasonic sensors were integrated onto the mold insert. Melt front, solidification, temperature variation and part detachment of the feedstock inside the mold cavity were observed. It has been demonstrated that ultrasonic velocity in feedstock inside the mold cavity, the ultrasonic contact duration during which the part and mold are in contact, and holding pressure can be used to assist with optimization of injection and cooling parameters to minimize energy consumption and maximize process efficiency.Real-time diagnostics of ceramic powder injection molding using a commercial micromolding machine was performed using ultrasound. Miniature ultrasonic sensors were integrated onto the mold insert. Melt front, solidification, temperature variation and part detachment of the feedstock inside the mold cavity were observed. It has been demonstrated that ultrasonic velocity in feedstock inside the mold cavity, the ultrasonic contact duration during which the part and mold are in contact, and holding pressure can be used to assist with optimization of injection and cooling parameters to minimize energy consumption and maximize process efficiency.

A novel powder processing technique has been developed by combining conventional powder injection moulding with polymer co-injection moulding, to permit the in-situ surface engineering of metal or ceramic components as an integral step within the processing cycle. The new technique has been used to produce surface engineered iron based components with either corrosion resistant or wear resistant surfaces, and to produce alumina based components with toughened surfaces. The most critical factor for the feasibility of surface engineered components is that the sintering profiles of the skin and core materials must be well matched or differential shrinkage or delamination will result. A particular requirement of surface engineering is the ability to control the surface engineered skin profile. Polymer injection moulding modelling software was applied to predict the surface engineered skin profiles of the surface engineered metal/ceramic components. Successful skin profile prediction is dependent on the characterisation of the feedstock materials being injection moulded. Several feedstocks have been characterised for their material properties and first pass models developed to predict the feedstock material properties as a function of their individual material properties and mass or volume ratios. It has been demonstrated that the design of the feedstock composition and injection moulding process conditions can be optimised by the use of computer-based injection moulding modelling software to achieve the desired surface engineered skin profile. A methodology has been developed that outlines all the stages necessary for successful powder co-injection moulding.

Ceramic injection moulding is already established as a production technique for complex shaped ceramic components. However the process is limited to thin section mouldings generally not exceeding a wall thickness of 10 mm. The global objective of this work is to describe and understand the aetiology of defects which preferentially appear in thick injection moulded ceramics, and to find ways to overcome these problems. The following stages are examined mould-filling, solidification, binder removal and sintering. Different moulding techniques; conventional moulding, modulated pressure moulding, insulated sprue moulding and low hold pressure moulding were applied. Moulding thicknessw as systematicallyv aried (15,20,25, and 35 mm).. Hold pressures and times were closely controlled and found to be decisive processing parameters for defect creation. The use of insulated sprue moulding prevented void formation in 25 nun thick mouldings and the application of low and constant hold pressures (>5 MPa) led to a reduction of residuals tressesin the mouldings. An intensive study was carried out on the binder removal stage in which the catalytic removal of the polyacetal binder enabled removal of the binder from sections of 35 nun thickness. The reaction and transport kinetics during binder removal were studied and close observations were made out on various defects which could appear during interrupted binder removal. Differential shrinkage of the ceramic components during sintering was studied and could be tracked back to flow-induced particle alignment during mould filling. The sintering behaviour of the alumina feedstock used in this study was compared with an equiaxed zirconia powder injection moulding suspension. The phenomenon of jetting in large section mouldings and the creation of spherulites during solidification of the polymer were found to influence moulding structure.

Die in der vorliegenden Arbeit untersuchten Metall-Keramik-Verbunde wurden mittels Pulverspritzgießen hergestellt. Unter Anwendung der teilautomatisierten Verfahrensoptionen Mehrkomponentenspritzgießen und Inmould-Labelling, welches u. a. die Verwendung tiefgezogener Grünfolien beinhaltete, wurden hierzu 2K-Prüfkörpergeometrien (Zugstab, Biegebruchstab, Ringverbund) und 2K-Demonstratoren (Innenzahnrad, Fadenführer, Greifer) jeweils bestehend aus Stahl 17-4PH und ZrO2 (3%Y2O3), im Co-Sinterverfahren unter H2-Atmosphäre bei 1350°C, entwickelt. Schlüssel zur Darstellung schwindungskonformer ZrO2- und Stahl 17-4PH-Formgebungsmassen war der Angleich der Pulverpackungsdichte. Untersucht wurde neben der Werkstoff- und Gefügeausbildung das sich während dem Formgebungs- und Sinterprozess ausbildende Metall-Keramik-Interface sowie die sich bevorzugt in diesem Bereich manifestierenden Verbundeigenspannungen. Neben der stoffschlüssigen Versinterung beider Partner konnte eine Steigerung der Verbundfestigkeit durch Legierungsmodifikation unter Ausschluss technologischer Fehlerquellen erreicht und spezifiziert werden.

Les contributions de cette thèse de doctorat sont focalisées sur les développements de formulations à base de polymères bio sourcés et déliantable à l’eau basés sur l’emploi d’acétate butyrate de cellulose (CAB) et de polyéthylène glycol (PEG). Ces nouvelles formulations ont été appliquées sur différentes nuances de poudres métalliques (invar) et céramiques (zircones). Ces matériaux possèdent une bonne stabilité dimensionnelle sous une large gamme de température imposée et possèdent de très bas coefficients d’expansion thermique.L’objective est l’étude et la compréhension du comportement des liants à base de CAB et PEG quand ils sont utilisés dans les variantes du procédé MIP (étapes de moulage avec ou sans pression, conditions particulières liées à la micro-injection, …) réalisées avec différentes nuances de poudres et différentes granulométries.Les caractéristiques intrinsèques de chaque CAB, leurs interactions avec le PEG et les poudres, l’influence de la nuance de poudre employée, ainsi que la granulométrie et la morphologie des poudres employées ont été étudiées et analysées en fonction du comportement final de la formulation développé et des taux de charges obtenues.L’homogénéité des mélanges développés, leurs taux de charge critique et maximal, ainsi que leurs comportements mécaniques, thermiques et rhéologiques ont été analysés et investigués par différentes études mécaniques, thermo et physico-chimiques. De nouvelles analyses chimiques et physiques ont été introduites par accroitre les connaissances sur les formulations développées. Les formulations optimales ont été validées pour différentes applications et avec l’emploi de différentes variantes du procédé MIP conduisant à l’élaboration de composants et de micro-composants PIM obtenus sans défauts et possédant d’excellentes propriétés fonctionnelles. L’étape de déliantage ainsi que l’étape de densification ont été optimisées en termes de cinétique et d’atmosphère aboutissant aux propriétés physiques et mécaniques escomptées pour l’ensemble des nuances de poudres considérées dans cette étude.En conclusion, les formulations développés des liants basées sur l’emploie de CAB et PEG sont exploitable au niveau de la recherche et au niveau industriel dans le procédé MIP. Elles apportent des améliorations par rapport aux liants conventionnels grâce à un procédé plus écologique. Cette première contribution représente une avancée significative dans l’émergence d’un procédé MIP plus écologique mais d’autres travaux futurs sont encore possibles
This PhD Thesis studied the use of binders based on cellulose acetate butyrate (CAB) andpoly(ethylene glycol) (PEG) in different type of materials, including a ceramic, the zirconiumsilicate, and a metallic alloy, the Invar 36. These materials share their low dimensionalstability with temperature with low coefficients of thermal expansion.The scope of this work is the study and comprehension of the behaviour of the mentionedbinder systems when they are employed in different PIM processes and under differentconditions and powder-types. With regard to this matter, different formulations were designedwith several types of PEG and CAB. These formulations were compared with commercialones. The intrinsic characteristics of each CAB were linked with the behaviour of the differentfeedstock also containing PEG and powder particles. The mixtures homogeneity, the optimumand critical solid loading and its flowability were assessed by torque and capillary rheology.Other complementary techniques such as electronic and light microscopy or the measurementof the mixtures densities by pycnometry were carried out to contrast rheology results. Thecompatibility between the feedstocks’ components and their thermal behaviour were analysedby calorimetry and thermogravimetry techniques. These methods were employed by the firsttime to determine the optimal solid loading.The optimal compositions were injected by using low or high pressures or by a micro injectionmoulding process. The debinding and sintering stages were optimised using severalatmospheres. Finally, the physical and mechanical properties of the final consolidated partswere measured.It could be concluded that the studied binder systems based on PEG and CAB presentedsuitable characteristics for PIM, providing improvements with respect to conventional bindersystems and by a more environmental friendly processing. However, that doctoral work wasjust a first approach to the use of these types of binder systems in PIM. Along this workseveral issues were detected and some topics regarding the processing should be furtherinvestigated to obtain the best of these binder systems

The application of a powder injection moulding process to the production of fully sintered hardmetal components has been studied. Salient, highly interdependent process variables investigated include; powder and binder characteristics, mixing techniques, feedstock rheological characteristics, mould design features, moulding parameters, debinding and sintering parameters. Fundamental studies were conducted to determine the effect of powder and binder characteristics on the powder loading capacity of feedstocks. Various methods of mixing were investigated. The most favourable methods were identified from the rheological response of their respective feedstocks as determined by capillary rheometry. Thermogravimetric analyses were used to; (a) identify binders and feedstocks essig beneficial debinding kinetics, (b) in the study of suitable debinding atmospheres and (c) to develop thermal debinding profiles for selected feedstocks. A spiral mould was used to assess the mouldability and optimum moulding parameters of selected feedstocks. Feedstock properties and mould design features which promoted moulding defects were identified and solutions developed. It was found that the maximum hardmetal powder loading achievable in a given feedstock was dependent on the powder size, size distribution and level of agglomeration. Low viscosity binders with high dielectric permittivities were found to promote highly loaded feedstocks. Feedstock viscosity increased with powder concentration. This relationship was modelled by a simple exponential power function over a narrow range of shear and powder concentration. Compounding methods utilising high shear melt mixing principles were found most effective in producing low viscosity feedstocks of consistent rheological response. Feedstock compositions of high powder concentrations and based on single, crystalline, wax binder systems were found to exhibit a high thermal dependence of viscosity, high activation energies of viscous flow, a high shear sensitivity and tended to segregate when subjected to shear. Such propensities were found detrimental to moulding behaviour. Spiral mould analysis revealed feedstock compositions were sensitive to changes in thermal parameters. Compositions based on multi-component binder systems were found most preferential in producing defect free mouldings of sound integrity and offered favourable debinding characteristics. Thermal debinding of mouldings was only completely effective by careful control of heating rates and when performed in hydrogen rich atmospheres. The reaction order and activation energy of the binder volatilisation was found to be dependent on the level of binder decomposition. Melt wicking was most effective using a hydrated magnesium aluminium silicate substrate. Sintered engineering components were produced by an injection moulding process with near theoretical densities and acceptable microstructures.

Slip casting and ceramic injection moulding are two techniques used in industry to produce advanced ceramics, which are ceramic parts with a good net shape, high complexity and of high strength. When slip or paste formulations are made up for use in these two shape forming techniques, it is often the binder that gives the formulation the flow characteristics and strength to be shaped and removed from the mould successfully with little or no defects. Water based binders are becoming more prominent in industry in recent times than traditional oil or wax based binders. They have a number of advantages including their low toxicity, easy and quick removal and good flow properties. Latex is a relatively new water based binder which has been used in a number of ceramic shape forming techniques in industry including gel casting and tape casting. Using a novel formulation of latex as a binder, which increases in viscosity following neutralisation and heat treatment, this thesis attempts to use this binder to form advanced ceramic parts using ceramic injection moulding and slip casting. Adaptations were made to latex formulations, ceramic mix formulations, and the choice of additives, and heating sequences in order to optimise the ceramic part production. It was shown that such binders, when mixed with ceramic, are able to form ceramic parts of reasonable quality and strength using ceramic injection moulding and gel casting. It is also thought that such binders can be further adapted to suit other shape forming techniques such as tape casting.

La pâte céramique étudiée, mélange de plusieurs polymères immiscibles : paraffine, EVA, cire de carnauba et d'une poudre minérale submicronique est utilisée dans le procédé d'injection. On s'est surtout attaché à corréler les propriétés rhéologiques à 130°C à la physico-chimie du system. Plusieurs paramètres ont été modifiés, - la fraction volumique, la composition du mélange de polymères et la nature de la poudre. On a montré que les molécules d'EVA et de carnauba sont adsorbées sur la surface de ZrO2, dans un rapport volumique de 2/1 et la poudre fait des inclusions dans la paraffine. Pour une fraction volumique >50% vol. , la pâte se comporte comme un solide et montre des propriétés de thixotropie – analysées avec un modèle développé par Piau. Un rhéomètre capillaire a été utilisé pour estimer la viscosité élongationelle, qui est très sensible (contraire à la viscosité de cisaillement), et clairement lié à la quantité d'EVA adsorbé
. The rheological properties of a ceramic paste, comprising several immiscible polymers : paraffin wax, EVA, carnauba wax, mixed with a mineral submicronic powder were investigated at 130°C. It is a prerequisite to master a forming process such as injection moulding and this was one of the pursued objectives. The other one was to relate these properties to the physico-chemical composition. Several parameters were modified i. E. - the vol. Solid fraction, the polymer blend composition and the nature of the powder. It was proved that EVA and carnauba molecules adsorb on ZrO2 surface, in a volume ratio 2/1 and the powder makes inclusions in the liquid paraffin. For a vol. Fraction >50%, a solid-liquid transition occurs - paste shows a thixotropic behaviour-analyzed with a model developed by Piau. A capillary rheometer was used to estimate the extensional viscosity, which is very sensitive (contrary to shear viscosity), and clearly related to the amount of adsorbed EVA

L'étape de déliantage est une étape importante et parfois critique pour le procédé Moulage par Injection des Poudres. A cet effet, des analyses thermogravimétriques (TGA) ont été réalisées pour bien comprendre les mécanismes du déliantage thermique sous atmosphère imposée (Argon). Les méthodes de Kissinger et Ozawa ont été utilisées, en se basant sur les résultats des analyses thermogravimétriques, afin d’estimer les paramètres cinétiques nécessaires pour la simulation numérique, notre modèle se propose de décrire les phénomènes physiques liés à la dégradation du polymère, le transfert de chaleur de la déformation du composant pendant le déliantage thermique.La deuxième partie de la thèse est dédiée à la compréhension des mécanismes et du comportement du fritage des composants en tungstène sous une atmosphère d’hydrogène jusqu’à une température de 1 700°C. Des appareils expérimentaux, ont été mis en place afin de constituer une base de données physiques nécessaire pour l’identification des différents paramètres. L’identification de l’ensemble des lois de comportement a été réalisée en prenant en compte les spécificités physiques des poudres utilisées. Un modèle de comportement de type thermo élasto-viscoplastique est formulé pour représenter la loi de densification par diffusion solide, puis appliqué pour les différentes tailles de poudres de tungstène. La dernière étape consiste à valider des simulations numériques avec ABAQUS pour une meilleure détermination des densités et des retraits finaux des composants injectés
Thermal debinding is one of the most important steps In Powder Injection Moulding process. Thermogravimetric analyses (TGA) are employed to analyze the physics and kinetics of thermal debinding behaviour under argon atmosphere. The Kissinger and Ozawa method have been used to estimate the kinetic parameters from thermogravimetric experiments. To set up the numerical simulations of thermal debinding stage using finite element method, a coupled mathematical has been developed. The basic steps of the proposed model consist to solve the following sequences of coupled problems: themal degradation of binder coupled with heat transfer and deformation phenomena by finite element method using Comsol Multiphysics software.In the second part of this thesis, sintering behaviour of tungsten powders injection moulded component, under pure hydrogen atmosphere at temperature up to 1700°C. The experimental tests are used to determine the material parameters in the parameters in the viscoplastic constitutive law, which is incorporated with the identified parameters in order to simulate the final shrinkages and densities of tungsten injection moulded components during the sintering process. Comparison between the numerical simulations results and experimental ones, in term of shrinkages and sintered densities, shows a good agreement

Published Article
Metal injection moulding (MIM) offers advantages for mass production of components over conventional production methods for parts with complex shapes and large production runs. The MIM process includes mixing a fine metallic powder with a polymeric binder to produce a homogeneous feedstock. This enables the production of metallic components in a similar manner to plastic injection moulding. After undergoing a process of binder removal the components undergo a conventional sintering cycle. As significant shrinkage occurs (as much as 30%) this must be considered when designing the die cavity. This paper describes the design and manufacture of a die to produce tensile specimens. Extensive injection moulding trials to produce acceptable tensile components were undertaken. The complexities and possible implications of the design of a mould on the process are discussed. The outcomes of this research will be used by the CSIR for further development and application of the MIM technology for manufacture of high value components, such as dental implants.

This thesis focuses on the use of a design of experiment approach to examine the significance of process factors and interactions on the fabrication of micro- textured surfaces. The micro-textured surfaces examined contain pillar and hole features ranging from 80 – 2 micrometers in diameter. The processes examined are the deep reactive ion etching of silicon wafers for the production of silicon mould inserts and the micro-injection moulding of polypropylene, high density polyethylene and 316LS stainless steel replicate samples of the silicon mould insert. During the deep reactive ion etching of the silicon wafers the design of experiment approach was used to determine the significant of platen power, C4F8 gas flow and switching times to the presence of pillar undercut of 10 x 10, 5 x 5 and 2 x 2 micrometer pillars. Undercuts occur when the pillar base has a smaller cross-section than the apex of the pillar. Switching times was found to be the only statistically significant parameter for both 10 x 10 and 5 x 5 micrometer pillars. The design of experiment approach is used in the micro-injection moulding of polypropylene, high density polyethylene and 316LS stainless steel replicates to examine the significance of mould temperature, cooling time, holding pressure and injection speed on the part and buffer mass of the produce samples, the height and width of pillar on the replicate surfaces and the variation of the replicated pillars height and width from the original silicon mould insert. Examination of the high density polyethylene replicates found that mould temperature was the most significant factor regarding pillar dimensions (and variation from the silicon mould insert) across the range of pillar sizes. Upon examination of the polypropylene replicates it was found that the factor of most significance on pillar dimensions varied across the different pillar sizes. Holding pressure was identified as the most significant factor with regards to the 53 x 29 and 19 x 80 micrometer pillars. Injection speed was found to be most significant for the 25 x 25 and 19 x 29 micrometer pillars. Cooling time was found to be most significant with regards to the 30 x 10, 25 x 10, 20 x 10 and 15 x 10 micrometer pillars. While ii mould temperature was found to be most significant for the 20 x 20, 15 x 15 and 10 x 30 micrometer pillars. The interaction between mould temperature and injection speed was also found to be the most significant factor with regards to the 43 x 29 and 25 x 30 micrometer pillars. Examination of the 316LS replicates found that mould temperature was the most significant factor regarding pillar dimensions for 80 x 80 and 19 x 80 micrometer pillars. While holding pressure was found to be most significant to the 29 x 29 micrometer pillars and injection speed was identified as most significant to the 53 x 80 micrometer pillars. The samples produced during the design of experiment investigations were then used to examine the effect of surface texturing on droplet behaviour. Droplet contact angles were examined on polypropylene, high density polyethylene and silicon samples structured with 10 – 2 micrometer pillar. Initial droplet contact angles were found to be higher on the polypropylene samples than the high density polyethylene or silicon samples. With the lowest initial contact angles being found for the silicon inserts. Droplet ‘channelling’ and evaporation were examined on silicon, polypropylene, high density polyethylene and 316LS samples structured with micro-channel surface pillars and holes ranging from 80 – 2 micrometer in diameter. Contact pinning of the droplet to the surface via the three- phase contact-line was noted during observations of droplet ‘channelling’. This pinning effect was observed at all sample tilt angles (30 - 90 o ). With regards to droplet evaporation, the droplets were noted to evaporate evenly (with no or limited contact pinning) on all unstructured surfaces and the surfaces structured with hole features. On the surfaces structured with pillar features, the droplets appeared too evaporated along the surface gradient from the smallest pillars to the largest.

Abstract The main object of this thesis was to research injection mouldable 0–3 type ceramic polymer composites and their dielectric and magnetic properties in the GHz frequency region. The work has been divided into three sections. In the first section, two–phase ceramic polymer composites containing dielectric and magnetic fillers have been investigated and their characteristics analysed by reference to pre–existing mixing rules. The exploitation of these composites in miniaturizing devices, such as antennae, is presented and discussed. The second part describes three phase composites containing different nanosize additives (silver, silicon and alumina fibres) towards improving their dielectric properties. In the third part, some periodical and multilayer structures for ceramic polymer composite layers are proposed. In the case of two–phase ceramic polymer composites, with 37 vol.% of dielectric filler (Barium Strontium Titanate, BST) embedded into a thermoplastic polymer (ER140) matrix, the highest measured relative permittivity was 15 with a dielectric loss value of 0.008 at 1 GHz. With 43 vol.% of magnetic filler (hexaferrite, CO2Z) in ER182 matrix, the highest achieved relative permeability was 1.8 with a magnetic loss value of 0.077 at 1 GHz. Composites with Co2Z filler provide a 77% size reduction, and could thus be used advantageously in antennae. It was found that a 2–6 vol.% nanoaddition in BST–ER140 composites enhanced the relative permittivity drastically with only a minor effect on the dielectric losses. In particular, with only 2 vol.% addition of nanosize silver particles into the BST–ER140 composite, a 52% increase in the relative permittivity was obtained, with no significant change in the dielectric losses (tan δε = 0.004). Vertically and horizontally periodical dielectric composite structures comprising layers of different dielectric properties have been fabricated as well as multilayered structures containing dielectric and magnetic layers. The measurement results indicate that such multimaterial multilayer structures are good candidates for components with reduced dielectric and magnetic losses
Tiivistelmä Väitöstyön tavoitteena oli tutkia ruiskuvalettavien 0–3 –liitännäisten keraami-polymeerikomposiittien ominaisuuksia erityisesti niiden GHz-taajuusalueen dielektristen ja magneettisten ominaisuuksien kannalta. Työ on jaettu kolmeen osaan. Ensimmäisessä osassa on tutkittu kaksikomponenttisia keraami-polymeerikomposiitteja, joissa täytemateriaali on joko dielektristä tai magneettista materiaalia. Komposiittien ominaisuuksia on analysoitu jo olemassa olevien seosmallinnuskaavojen avulla. Komposiittien hyödyntämistä erilaisten sovellusten, kuten antennien, minityrisoinnissa on myös käsitelty. Toinen osa käsittelee kolmikomponenttisia komposiitteja, joissa lisäaineena on käytetty pieniä määriä nanomateriaaleja (hopea- ja piipartikkelit sekä alumiinioksidikuitu) tarkoituksena parantaa komposiitin dielektrisiä. Kolmannessa osassa on tutkittu periodisia ja monikerroksisia keraami- polymeerikomposiittirakenteita rakenteita. Kaksikomponenttisten keraami-polymeerikomposiittien tapauksessa suurin permittiivisyyden arvo 15 dielektristen häviöiden ollessa 0.008 (mittaustaajuus 1 GHz) saatiin komposiitille, jossa dielektristä täytemateriaalia (Barium Strontium Titanaatti, BST) oli 37 tilavuus-% termoplastisessa polymeerimatriisissa (ER140). Korkein saavutettu permeabiliteetin arvo 1.8 magneettisten häviöiden ollessa 0.077 (mittaustaajuus 1 GHz) saatiin komposiitille, jossa magneettista täyteainetta (hexaferriitti, Co2Z) oli 43 tilavuus-% ER182 -matriisissa. Tämä täyteaine mahdollistaa nykyistä jopa 77 % pienempien antennielementtien kehittämisen. Tukimuksessa todettiin 2–6 tilavuus-% nanomateriaalin lisäyksen BST-ER140 -komposiitteihin kasvattavan permittiivisyyttä merkittävästi juurikaan vaikuttamatta dielektrisiin häviöihin. Erityisesti 2 tilavuus-% hopeananopartikkeleiden lisäys BST-ER140 -komposiitteihin kasvatti permittiivisyyttä 52 % dielektristen häviöiden (tan δε =  0.004) kasvamatta. Työssä on myös tutkittu periodisesti (vertikaali ja horisontaali) koostettuja dielektrisiä komposiittirakenteita, jossa eri kerroksissa on erilaiset dielektriset ominaisuudet sekä monikerrosrakenteita, joissa vuorottelevat dielektriset ja magneettiset kerrokset. Mittaukset osoittivat, että monimateriaaliset monikerrosrakenteet ovat hyviä kandidaatteja komponentteihin, jotka vaativat pieniä dielektrisiä ja magneettisiä häviöitä

Die in der vorliegenden Arbeit untersuchten Metall-Keramik-Verbunde wurden mittels Pulverspritzgießen hergestellt. Unter Anwendung der teilautomatisierten Verfahrensoptionen Mehrkomponentenspritzgießen und Inmould-Labelling, welches u. a. die Verwendung tiefgezogener Grünfolien beinhaltete, wurden hierzu 2K-Prüfkörpergeometrien (Zugstab, Biegebruchstab, Ringverbund) und 2K-Demonstratoren (Innenzahnrad, Fadenführer, Greifer) jeweils bestehend aus Stahl 17-4PH und ZrO2 (3%Y2O3), im Co-Sinterverfahren unter H2-Atmosphäre bei 1350°C, entwickelt. Schlüssel zur Darstellung schwindungskonformer ZrO2- und Stahl 17-4PH-Formgebungsmassen war der Angleich der Pulverpackungsdichte. Untersucht wurde neben der Werkstoff- und Gefügeausbildung das sich während dem Formgebungs- und Sinterprozess ausbildende Metall-Keramik-Interface sowie die sich bevorzugt in diesem Bereich manifestierenden Verbundeigenspannungen. Neben der stoffschlüssigen Versinterung beider Partner konnte eine Steigerung der Verbundfestigkeit durch Legierungsmodifikation unter Ausschluss technologischer Fehlerquellen erreicht und spezifiziert werden.:1 Einleitung und Zielstellung .................................................................................................5 2 Stand der Technik ..............................................................................................................6 2.1 Metall-Keramische-Verbundwerkstoffe und Werkstoffverbunde.....................................6 2.2 Werkstoffsystem ............................................................................................................6 2.2.1 Oxidkeramische Metall-Keramik-Verbunde.................................................................9 2.2.2 Nichtoxidkeramische Metall-Keramik-Verbunde........................................................15 2.3 Metall-Keramik-Interface..............................................................................................17 2.3.1 Stahl-Keramik-Komposite.........................................................................................21 2.3.2 Stahl-Keramik-Schichtverbunde................................................................................25 2.4 Konventionelle Verbindungs- und Fügetechnik.............................................................27 2.4.1 Kraft- und Formschluss.............................................................................................28 2.4.2 Lösbare Verbindungen .............................................................................................28 2.4.3 Nicht lösbare Verbindungen .....................................................................................29 2.4.4 Stoffschlüssige Verbindungen ..................................................................................30 2.5 Pulvertechnologische Verbindungs- und Fügetechnik ...................................................32 2.5.1 Co-Shaping..............................................................................................................34 2.5.2 Co-Firing..................................................................................................................38 2.6 Pulverspritzgießen........................................................................................................42 2.6.1 Prozesskette.............................................................................................................43 2.6.2 Werkstoffe...............................................................................................................45 2.6.3 Verfahrenscharakteristik...........................................................................................46 2.6.4 PIM in der industriellen Praxis ...................................................................................48 2.6.5 Mehrkomponentenspritzguss...................................................................................49 2.7 Prüfung und Spezifikation für spritzgegossene Metall-Keramik-Verbunde.....................52 2.7.1 zerstörende Prüfverfahren........................................................................................52 2.7.2 zerstörungsfreie Prüfverfahren .................................................................................55 2.7.3 Prädikative Methoden ..............................................................................................55 3 Experimenteller Teil..........................................................................................................57 3.1 Pulveranmusterung ......................................................................................................57 3.1.1 Feedstockherstellung und Charakterisierung ............................................................58 3.1.2 Grünfolienherstellung und Charakterisierung ...........................................................60 3.1.3 Thermische Analyse..................................................................................................62 3.2 Fertigungstechnologie..................................................................................................62 3.2.1 2-Komponentenpulverspritzgießen...........................................................................64 3.2.2 Folienhinterspritzen..................................................................................................64 3.2.3 Entbinderung und Sinterung ....................................................................................65 3.3 Werkstoff- und Verbundspezifikation...........................................................................66 3.3.1 Bestimmung der Dichte............................................................................................66 3.3.2 Dilatometrie.............................................................................................................66 3.5.2 Optische Interfaceanalyse.........................................................................................67 3.5.3 Mechanische Festigkeit ............................................................................................67 3.5.4 Röntgenographische Eigenspannungsanalyse ...........................................................68 4 Ergebnisdiskussion ...........................................................................................................70 4.1 Werkstoff- und Pulverauswahl .....................................................................................70 4.1.1 Untersuchungen zum Co-Sinterverhalten von Metall- und Keramikpulvern........................................................................................................78 4.1.2 Werkstoff- und Gefügeausbildung während der Co-Sinterung .................................85 4.2 Feedstock- und Bindersystem .......................................................................................92 4.2.1 Rheologische Eigenschaften .....................................................................................95 4.2.2 Thermisches Verhalten und Entbinderung ................................................................99 4.2.3 Verarbeitung von Feedstock und Grünfolie.............................................................101 4.3 Prüfkörperentwicklung...............................................................................................105 4.3.1 Gestaltungsoptionen..............................................................................................105 4.3.2 Verfahrensverifizierung ..........................................................................................106 4.3.3 Qualitative Bewertung der Verfahrensoption Inmould-Labelling..............................109 4.4 Werkstoffverbund.........................................................................................................112 4.4.1 Metall-Keramik-Interface........................................................................................112 4.4.2 Zugfestigkeit..........................................................................................................119 4.4.3 Verbundeigenspannungen .....................................................................................122 5 Zusammenfassung.........................................................................................................126 6 Literaturverzeichnis ........................................................................................................130 7 Abkürzungsverzeichnis...................................................................................................140 Anhang ................................................................................................................................141 A1 Spezifikation ZrO2-Feedstock Z1 .................................................................................142 A2 Spezifikation Stahl-17-4PH-Feedstock M1 ..................................................................143 A3 Rezeptur ZrO2-Folien ..................................................................................................144 A4 Rezeptur Stahl 17-4PH-Folien.....................................................................................145 A5 Prozessparameter – Spritzgießen (Bsp. Biegebruchstab 7x7x70mm)............................146 A6 Folienkonfektionierung – Bsp.- Demonstrator Greifer .................................................147 A7 Prozessautomatisierung – Bsp. Demonstrator Fadenführer..........................................148 A8 Spritzgegossene Demonstratoren – 2K-Spritzgießen...................................................149 A9 Spritzgegossene Demonstratoren – Inmould-Labelling................................................150 A10 Dilatometerschaubilder ..............................................................................................151 A11 Mikrozugproben ........................................................................................................152 A12 studentische Arbeiten ................................................................................................153

Tese de Doutoramento Ciência e Engenharia de Polímeros
The present work was focused on the development of new polymeric binder compounds for eco-sustainable powder injection moulding (PIM) process. Consequently, water debinding was a requirement once it is a lower environmental impact technology, economically attractive and less hazardous than the conventional catalytic, thermal or solvent debinding. Furthermore, the understanding of the influence of the binder composition on the overall process, from feedstock compounding to final sintered parts, and the development of a structured engineering methodology for new PIM binders was also aimed. The research program was carried out with AISI 316L stainless steel powder and developed in two main parts: i) characterisation of feedstock formulations and consequent discrimination; and ii) study of the influence of the developed binders in a pilot-scale process. The binder compositions followed a classic design based on a thermoplastic blend, using polyethylene glycol as selected as the water soluble main constituent. The influence of the other binder components, such as back-bone polymers, lubricants and surfactants, was assessed and a reference framework to relate binder formulation and PIM processing was developed. Moreover, promising binder compositions, to produce dimensional stable and precision sintered parts in a high densified and low contaminated sintered stainless steel, are proposed. As a result, a metallocene polyethylene base formulation is proposed as the ultimate binder to produce sintered parts with higher mechanical properties and minimum part defects. The results confirm the importance of the binder and demonstrate the influence of its composition in PIM process and support an innovative methodology to develop or optimise ecofriendly binders in an industrial environment.
O objectivo principal deste trabalho é o desenvolvimento de sistemas de ligantes poliméricos eco-sustentáveis para moldação por injecção de pós (PIM). Consequentemente, extracção aquosa foi considerada como um requisito, uma vez que é um processo com menor impacto ambiental, economicamente atractivo e menos nocivo para a saúde no trabalho, comparativamente com as soluções correntes de degradação catalítica, térmica ou por extracção com solventes. Adicionalmente, o trabalho teve como objectivos complementares, o aprofundamento do conhecimento sobre o processo PIM, em particular a compreensão da influência da formulação do ligante, desde a preparação do feedstock até à sinterização, e o desenvolvimento de uma metodologia de engenharia para a produção de novos ligantes. O programa de investigação assentou na utilização de um pó de aço inoxidável AISI 316L e foi implementado em duas partes principais: i) caracterização das formulações e consequente discriminação; ii) estudo da influência da composição dos ligantes num processo à escala-piloto. As formulações dos ligantes seguiram o conceito mais usual, baseado numa mistura termoplástica, usando polietilenoglicol como constituinte principal hidrossolúvel. O plano de trabalho permitiu o estudo da influência dos componentes minoritários, como os polímeros de estrutura, os lubrificantes e os agentes de superfície, bem como o desenvolvimento de um quadro de referência capaz de relacionar formulação e processamento em PIM. Foram identificadas algumas composições capazes de produzirem peças sinterizadas com elevada precisão dimensional e baixa variabilidade, num material com elevada densificação e baixa contaminação. O ligante com polietileno metalocénico, como polímero de estrutura, permitiu a obtenção de peças sinterizados com propriedades mecânicas satisfatórias e incidência de defeitos miníma. Os resultados confirmam a importância do ligante e a sua influência no processo de moldação por injecção de pós, e permitem propor uma metodologia inovadora para o desenvolvimento ou optimização de ligantes capaz de ser utilizada em ambientes industriais.

碩士
國立高雄應用科技大學
模具系碩士在職專班
102
The purpose of this study is to develop a zirconia micro gear with hardness higher than 1200 Hv using micro powder injection molding technology. A micro gear was designed first and Moldex3D analysis was carried out to find the best gating system for molding this gear. The green part was molded with Battenfeld microsystem 50 micro injection molding machine while Taguchi method was utilized to determine the best parameter settings. The green parts were further gone through debinding and sintering processes to complete the micro gear replication process. Results from the Taguchi method showed that the optimal molding parameters are spraying of release agent , packing speed 2 mm / s, injection speed 120 mm / s, male mold temperature 60℃, the female mold temperature 60℃, melting temperature 170℃, and the cooling time 20 sec. The ANOVA results indicated that cooling time, male mold temperature, and spraying of release agent influenced the molding quality most while packing speed and injection speed had no significant effect on the micro gear quality in this study.

碩士
國立雲林科技大學
機械工程系碩士班
90
This study that described experiments and researches are about mold flow、 appearance of cooling 、 shrinkage and sink marks of the Ceramic Injection molding (CIM). First imitates by C-MOLD, so thermal diffusivity (α) of feedstock is 2.8 multiple of PP and flow property is worse, it must provides more injection pressure and speed when injection to overcome cooling faster of feedstock and get better quality of products. If thickness of products too thin, it will be cooling faster. And we might get lower value of hardness and worse quality of finished products. Also found that it will improve by mold open a little and gain on thickness in a short time when Injection Compression Molding (ICM). Mold design must think about the change of shrinkage rate of each stage and magnify sizes in advance. And doing the best control for the final products precision. From experiments of CIM, the sizes of shrinkage rate each stage are sintered(17.74%)>debinded(2.03%)>green part(0.44%) . This study chooses Al2O3 feedstock to experiment and measure products property of density of sintered part and shrinkage of thickness by the Taguchi’s method. The biggest factors of Injection Molding (IM) are packing pressure and injection speed. The biggest factors of ICM are compression molding and melt temperature. From the result, said again that feedstock differences of fill property from plastics, the importance of injection speed and melt temperature. The research of surface sink marks, IM provides smaller packing pressure effect, and ICM provides well mixed mold compression to reduce shrinkage. So, the sink marks of ICM is smaller than IM.

碩士
國立雲林科技大學
機械工程系碩士班
94
This study is to develop the micro fabrication technology to produce a nozzle-array plate for fuel injection system of SI engines. It involves micro electro-discharge machining (M-EDM) and micro ceramic powder injection molding (MCPIM) technique. Because the pitch of 180um is quite small, a reverse-duplication M-EDM was used to manufacture micro cavity which has 4 micro pillars at once. The diameter of each pillar is about 300um. To reduce manufacture cost and keep higher precision and accuracy, micro injection molding was used to do the mass production. For CIM, lower mold temperature results in faster build-up of frozen layer, which in terms to prohibit the material to fill into the micro features. And this causes lower degrees of replication of CIM. Thus a vario-thermal injection molding (VTIM) system was developed and it provides higher mold temperatures to help the polymer melt fill into micro structures more like liquid and improve the degrees of replication of micro features. In order to study the effects of different processing conditions on the diameter shrinkage of green parts, Taguchi’s design method of experiments was applied to achieve meaningful results in fewer times of experiments. From the ANOVA analyses, less shrinkage of diameter was mainly affected by the initial mold temperature. Higher mold temperature result in thinner or even none frozen layer, which helps improve the degrees of duplicating the micro features. It also helps improve the bonding strength of weld lines which occur behind the micro holes. The debonding process is to separate the binding filler from the green part and has a strong effect on the success rate of final parts. In this work, commercial pellets and recommended thermal debonding procedures were applied. More studies are still needed to achieve better debonding contents and conditions in the near future. After that, brown parts were put in higher temperature oven for final sintering. Shrinkage during sintering was usually around 12~20% and affects the dimensions and precision of final parts. After sintering, similar experiments were done in measuring diameter shrinkage of sintered parts. Again, the most significant factor to the diameter shrinkage is the initial mold temperature. Higher mold temperature help polymer melt to flow and reduce the shear strain rate and stress, which can improve sintering quality. The average diameter of micro pillars was 310um and the average diameter of sintered holes was about 270um. Average hole shrinkage is about 13%, which is less than 16.6% of overall shrinkage of sintered parts. This work has successfully produced thin nozzle-array plates by integration of M-EDM and ceramic injection molding. Further studies to test its spraying performance on a SI engine are on the way and better results are expected.

Powder injection molding (PIM) is widely used to manufacture complex-shaped ceramic and metal components in high production volumes. In order to design and fabricate PIM components, it is important to know a number of material properties at different powder- polymer compositions. In this thesis, several predictive models for estimating rheological, thermal and mechanical properties as a function of powder-polymer mixtures were evaluated using experimental data obtained from the literature. Based on this survey, models were selected for predicting rheological, thermal and mechanical properties for aluminum nitride-polymer mixtures at various volume fractions of powder using experimental measurements of unfilled and filled polymers. The material properties were estimated for two aluminum nitride powder-polymer mixtures and used in mold-filling simulations. These results will provide new perspectives and design tools for identifying useful material compositions, component geometry attributes, and process parameters while eliminating expensive and time-consuming trial-and-error practices prevalent in PIM.
Graduation date: 2013

A new material system was developed for fabricating the combustion engine of an unmanned aerial vehicle. The material system consisted of a mixture of nanoscale and microscale particles of silicon nitride. Magnesia and yttria were used as sintering additives. The powders were mixed with a paraffin binder system. The binder-powder was analyzed for its properties and molding attributes. The study involved several steps of the development and processing. These steps include torque rheometery analysis, mixing scale-up, property measurements of binder-powder, injection molding, binder removal, sintering, scanning electron microscopy analysis and mechanical properties measurements. Simulations of the injection molding process were conducted to assess the feasibility of manufacturing a ceramic engine and to determine its optimal process parameters. The model building required for the simulation was based on flow and solidification behavior data compiled for the binder-powder mixture. The simulations were performed using the Moldfow software package. A design of experiments approach was set up in order to gain an understanding of critical process parameters as well as identifying a feasible process window. Quality criteria were then analyzed in order to determine the optimal production parameters. The study resulted in the successful development of design parameters that will enable fabrication of silicon nitride engine components by powder injection molding.
Graduation date: 2012