No description available.

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.

Abstract The purpose of this study was to investigate the removal performance in oxidation of ammonia solution, synthesized concentration in range of 200 mg/l -1000 mg/l, in continuous WAO process over Cu/La/Ce catalyst. The operation parameters in WAO process were performed as follows: reaction temperature, influent velocity, initial concentration of ammonia and oxygen pressure. During the first stage WAO test, ammonia conversion only reached to 40.1% under the conditions performed as follows: initial concentration of ammonia in 400 mg/l, 12 of pH, 453 K of temperature, 3.0 MPa of total pressure and 3.0 ml/min of influent velocity. In the second stage experiments conducted by 453 K, pH 12, 3.0MPa and 400 mg/l, the ammonia conversion was above 86.2% over catalyst in WAO process. In addition, the conversion of ammonia were found to be 89%, 82.6%, 81.6% and 79.3% when the initial concentration were regulated in 200, 400, 800 and 1000 mg/l respectively; 91.4% conversion of ammonia could be obtained when temperature was raised at 473 K. The tests such as XRD, SEM, EDS, ICP-MS and EA were also determined. The kinetics of WAO over Cu/La/Ce catalyst in oxidation of ammonia solutions using Power-Rate Law was presented to calculate the apparent reaction order and activated energy.

No description available.

no / 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.

Apresenta uma metodologia para o projeto e fabricação de moldes para prensagem isostática de pó cerâmico (alumina) utilizando ferramentas computacionais CAD/CAE associadas à tecnologia de Prototipagem Rápida. O processo de prensagem isostática é simulado utilizando o método dos elementos finitos. Para a representação da compactação do pó cerâmico é utilizado o modelo de Drucker-Prager/cap e para a representação do comportamento do material elastomérico é utilizado o modelo hiperelástico de Mooney-Rivlin, ambos disponíveis no programa ABAQUS. Tal simulação visa obter o projeto do molde de forma mais rápida e precisa, ajustando-o até que se alcance um molde adequado para produzir um compacto com uma quantidade de sobrematerial ideal para o processo de usinagem a verde. Para isso utilizou-se como estudo de caso uma esfera cerâmica para implante de quadril. Um protótipo virtual do molde adequado obtido das simulações é então modelado e reproduzido em plástico ABS (Acrylonitrile Butadiene Styrene) pela tecnologia de Prototipagem Rápida FDM (Fused Deposition Modeling). Esse protótipo físico é a base para o desenvolvimento de matrizes rígidas e em silicone, que são utilizadas para a confecção da parte flexível do molde (matriz elastomérica) e de partes rígidas como a gaiola suporte obtidas por vazamento dos polímeros. Constatou-se a viabilidade da utilização da metodologia de projeto e fabricação do molde para prensagem isostática, considerando que as simulações mostraram-se bastante coerentes com os resultados experimentais obtidos de componentes prensados. / This work presents a methodology for the design and fabrication of ceramic powder isostatic pressing moulds using CAD and CAE tools and Rapid Prototyping. The isostatic pressing process was simulated using the finite element method. The compaction behavior of ceramic powder is described by the Drucker-Prager/cap constitutive model and the behavior of elastomeric material is described by the Mooney-Rivlin constitutive model within the commercial finite element software ABAQUS®. These simulations are required to adjust the mould design in order to suit the geometry of the compact and green machining allowance. For this study, it is used a case study consisting of pressing a ceramic sphere for hip implant stem. A virtual prototype was designed from the geometry obtained from the simulations and reproduced in Acrylonitrile Butadiene Styrene (ABS) polymer, using the Rapid Prototyping technology - Fused Deposition Modeling (FDM). Silicone moulds were obtained from the polymer prototype and used to aid in the making of the elastomeric bag and mould support cage. The methodology used in this investigation was validate considering that the simulations yield to a good agreement with measured manufactured components.

Made available in DSpace on 2016-12-08T17:19:34Z (GMT). No. of bitstreams: 1 Parte 01 - Revisao Bibliografica.pdf: 888360 bytes, checksum: 212c15e8818de6b2dfa60bb2cd835592 (MD5) Previous issue date: 2009-12-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The loss of an organ or a part of the body generates, besides the loss of function, social and psychological disorders. The materials used to replace bone fall into a class called biomaterials and should have physical and biological properties compatible with living tissue hosts. The objective of this study is to optimize the method of synthesis and characterization of a bone matrix of calcium phosphate nanostructured and nanocomposite calcium phosphate /SiO2n at concentrations of 1%, 2%, 3% and 5% by volume. Were carried out morphological characterization of nanoparticles, nanostructured mineral powders and biomaterials obtained by sintering at 1200 C/2h. Finally, studies were performed on the mechanical behavior of nanostructured biomaterials. The process of synthesis of nanostructured powders proved to be efficient and optimized, allowing to obtain the matrix of calcium phosphate and nanocomposites with silica gel. Silica gel influence the surface energy of the matrix of calcium phosphate and this phenomenon has influenced the particle size of the nanocomposites, phase transformation and sinterability of the matrix of calcium phosphate. Tests of mechanical properties showed that the increase in percentual silica gel in the phosphate matrix tends to reduce the mechanical strength (hardness, strength and fracture toughness). Only the nanocomposite with 1% silica showed improvement in mechanical properties after annealing. / A perda de um órgão ou de uma parte do corpo humano gera, além da perda da função, transtornos sociais e psicológicos. Os materiais utilizados na substituição de ossos enquadram-se em uma classe denominada de biomateriais e devem apresentar propriedades físicas e biológicas compatíveis com os tecidos vivos hospedeiros. Esse trabalho tem como objetivo otimizar o método de síntese e caracterização de uma matriz óssea de fosfato de cálcio nanoestruturada e de nanocompósitos fosfato de cálcio/SiO2n, nas concentrações de 1%, 2%, 3% e 5% em volume. Foram realizadas caracterizações morfológicas das nanopartículas, mineralógica dos pós nanoestruturados e dos biomateriais obtidos da sinterização a 1200ºC/2h. Por fim, foram realizados estudos sobre o comportamento mecânico dos biomateriais nanoestruturados. O processo de síntese de pós nanoestruturados mostrou-se eficiente e otimizado, permitindo a obtenção da matriz de fosfato de cálcio e dos nanocompósitos com sílica gel. A sílica gel influenciou na energia de superfície da matriz de fosfato de cálcio e esse fenômeno influenciou no tamanho de partícula dos nanocompósitos, transformação de fase e sinterabilidade da matriz de fosfato de cálcio. Os ensaios de propriedades mecânicas mostraram que o aumento do percentual de sílica gel na matriz de fosfato tende a reduzir a resistência mecânica (microdureza, flexão e tenacidade à fratura). Apenas o nanocompósito com 1% de sílica apresentou melhora nas propriedades mecânicas após o recozimento.

Apresenta uma metodologia para o projeto e fabricação de moldes para prensagem isostática de pó cerâmico (alumina) utilizando ferramentas computacionais CAD/CAE associadas à tecnologia de Prototipagem Rápida. O processo de prensagem isostática é simulado utilizando o método dos elementos finitos. Para a representação da compactação do pó cerâmico é utilizado o modelo de Drucker-Prager/cap e para a representação do comportamento do material elastomérico é utilizado o modelo hiperelástico de Mooney-Rivlin, ambos disponíveis no programa ABAQUS. Tal simulação visa obter o projeto do molde de forma mais rápida e precisa, ajustando-o até que se alcance um molde adequado para produzir um compacto com uma quantidade de sobrematerial ideal para o processo de usinagem a verde. Para isso utilizou-se como estudo de caso uma esfera cerâmica para implante de quadril. Um protótipo virtual do molde adequado obtido das simulações é então modelado e reproduzido em plástico ABS (Acrylonitrile Butadiene Styrene) pela tecnologia de Prototipagem Rápida FDM (Fused Deposition Modeling). Esse protótipo físico é a base para o desenvolvimento de matrizes rígidas e em silicone, que são utilizadas para a confecção da parte flexível do molde (matriz elastomérica) e de partes rígidas como a gaiola suporte obtidas por vazamento dos polímeros. Constatou-se a viabilidade da utilização da metodologia de projeto e fabricação do molde para prensagem isostática, considerando que as simulações mostraram-se bastante coerentes com os resultados experimentais obtidos de componentes prensados. / This work presents a methodology for the design and fabrication of ceramic powder isostatic pressing moulds using CAD and CAE tools and Rapid Prototyping. The isostatic pressing process was simulated using the finite element method. The compaction behavior of ceramic powder is described by the Drucker-Prager/cap constitutive model and the behavior of elastomeric material is described by the Mooney-Rivlin constitutive model within the commercial finite element software ABAQUS®. These simulations are required to adjust the mould design in order to suit the geometry of the compact and green machining allowance. For this study, it is used a case study consisting of pressing a ceramic sphere for hip implant stem. A virtual prototype was designed from the geometry obtained from the simulations and reproduced in Acrylonitrile Butadiene Styrene (ABS) polymer, using the Rapid Prototyping technology - Fused Deposition Modeling (FDM). Silicone moulds were obtained from the polymer prototype and used to aid in the making of the elastomeric bag and mould support cage. The methodology used in this investigation was validate considering that the simulations yield to a good agreement with measured manufactured components.

Tesis por compendio / [ES] En la actualidad, el modelado por deposición fundida (FDM) es el tipo de tecnología de fabricación aditiva más difundida y estudiada dada su facilidad de uso y economía de proceso. No obstante, debido a las anisotropías generadas durante el proceso aditivo, las piezas fabricadas mediante FDM presentan limitaciones en su uso funcional. Estas anisotropías dependen de los parámetros del proceso y pueden provocar variaciones dimensionales y cambios en las propiedades mecánicas de las piezas. Para mejorar dichas características, se puede recurrir a diversos post-procesos como el tratamiento térmico. Sin embargo, durante su aplicación se pueden producir variaciones dimensionales en las piezas tratadas que reduzcan o anulen su aplicabilidad industrial. En la presente Tesis Doctoral se ha abordado el estudio del comportamiento dimensional de piezas fabricadas mediante FDM sometidas a tratamiento térmico. Se ha evaluado una propuesta de mejora en el post-proceso consistente en el uso de un molde de polvo cerámico compactado alrededor de las piezas a fin de minimizar la aparición de deformaciones durante el tratamiento térmico. El estudio de las deformaciones durante el post-procesado térmico se ha focalizado en los dos materiales termoplásticos más empleados en FDM, el ácido poliláctico (PLA) y el acrilonitrilo butadieno estireno (ABS), de naturaleza semicristalina y amorfa respectivamente. Se han analizado las variaciones dimensionales sufridas por las piezas durante el tratamiento térmico, considerando la influencia de la orientación de las líneas depositadas, la temperatura del tratamiento y el uso del molde de polvo cerámico. Para evaluar la mejora aplicada en el post-procesado térmico, se ha definido y analizado la eficacia del molde con las mismas variables del estudio dimensional. A fin de poder predecir las deformaciones sufridas por las piezas tratadas y la eficacia del molde en un amplio rango de temperaturas, se ha realizado una aproximación polinómica con los resultados obtenidos experimentalmente. / [CA] Actualment, el modelatge per deposició fosa (FDM) és el tipus de tecnologia de fabricació additiva més difosa i estudiada atesa la facilitat d'ús i economia de procés. Això no obstant, a causa de les anisotropies generades durant el procés additiu, les peces fabricades mitjançant FDM presenten limitacions en el seu ús funcional. Aquestes anisotropies depenen dels paràmetres del procés i poden provocar variacions dimensionals i canvis a les propietats mecàniques de les peces. Per millorar aquestes característiques, es pot recórrer a diversos postprocessos com el tractament tèrmic. No obstant això, durant la seva aplicació es poden produir variacions dimensionals a les peces tractades que redueixin o anul·lin la seva aplicabilitat industrial. En aquesta Tesi Doctoral s'ha abordat l'estudi del comportament dimensional de peces fabricades mitjançant FDM sotmeses a tractament tèrmic. S'ha avaluat una proposta de millora en el post-procés consistent en l'ús d'un motlle de pols ceràmic compactat al voltant de les peces per tal de minimitzar l'aparició de deformacions durant el tractament tèrmic. L'estudi de les deformacions durant el post-processat tèrmic s'ha focalitzat en els dos materials termoplásticos més empleats en FDM, l'àcid poliláctico (PLA) i l'acrilonitrilo butadien estireno (ABS), de naturalesa semicristalina i amorfa respectivament. S'han analitzat les variacions dimensionals sofrides per les peces durant el tractament tèrmic, tenint en compte la influència de l'orientació de les línies dipositades, la temperatura del tractament i l'ús del motlle de pols ceràmic. Per avaluar la millora aplicada en el post-processat tèrmic, s'ha definit i analitzat l'eficàcia del motlle amb les mateixes variables de l'estudi dimensional. Per tal de poder predir les deformacions patides per les peces tractades i l'eficàcia del motlle en un ampli rang de temperatures, s'ha fet una aproximació polinòmica amb els resultats obtinguts experimentalment. / [EN] Nowadays, fused deposition modeling (FDM) is the most widespread and studied additive manufacturing technology due to its ease of use and process economics. However, due to the anisotropies generated during the additive process, FDM fabricated parts have limitations in their functional use. These anisotropies depend on the process parameters and can lead to dimensional variations and changes in the mechanical properties of the parts. Various post-processes, such as heat treatment, can be used to improve these characteristics. However, during its application, dimensional variations can occur in the treated parts that reduce or make their industrial applicability impossible. In this Thesis, the dimensional behavior of FDM parts subjected to heat treatment has been studied. A post-processing improvement proposal consisting of using a compacted ceramic powder mould around the parts to minimize deformations during the heat treatment has been evaluated. The study of deformations during thermal post-processing has focused on the two most widely used thermoplastic materials in FDM, polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS), with semi-crystalline and amorphous nature respectively. For this purpose, standard specimens coded according to different internal geometries were manufactured. The dimensional variations suffered by the parts during the heat treatment have been analyzed considering the influence of the orientation of the deposited lines, the material used, the treatment temperature and the use of the ceramic powder mould. To evaluate the thermal post-processing improvement, the effectiveness of mould has been defined and analyzed with the same variables of the dimensional study. To predict the deformations suffered by the treated parts and the efficacy of the mould in a wide range of temperatures, a polynomial approximation has been fitted to the results obtained experimentally. / Lluch Cerezo, J. (2023). Análisis y mejora del comportamiento dimensional de termoplásticos impresos en 3D mediante modelado por deposición fundida sometidos a un proceso de tratamiento térmico [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/194607 / Compendio