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Formulation of mixed alumina/kaolin systems : Application to the elaboration of multi-layer materials by co-pressing

Rana Al Tahan

Abstract

Multilayer ceramic architectures generally exhibit improved mechanical properties in regards with individual monolithic constituents. In alumina-based materials, addition of kaolin can advantageously promote i) mullite crystallisation and ii) internal residual stresses by monitoring thermal expansion mismatch between layers. From powders prepared by freeze granulation whose formulations contain a reduce amount of organic additives, alumina/mullite composites shaped by uniaxial pressing have been developed and characterized. Two different kaolins are used in this study, with different characteristics in terms of crystallinity, grain shape, layering and basal/lateral face ratio. The originality of this work consisted in studying in detail the dispersion mechanisms of kaolinite suspensions in aqueous media by acoustophoresis, and in highlighting the relationship between kaolinite’s electrokinetic properties, physicochemical characteristics and thermal pretreatment between 200 and 800°C. The sintering properties of mixed alumina/kaolinite formulations were studied as a function of kaolinite crystallinity and content (0-25%vol). This thesis studies the integrated chain of a ceramic process, starting with the selection of kaolinite as a raw material (acoustophoresis, MAS NMR), its crystallochemical transformation into mullite (thermal analyses, dilatometry) and its incorporation into an alumina matrix for an original architecture of multilayer materials with modified properties of toughness and fracture resistance. The multi-layer materials developed show good interfacial adhesion despite the presence of a porous zone close to the layer interface. Compared to the monolithic materials, the most efficient multilayer configurations exhibit a failure stress improved by 30%.

Keywords

Kaolinite, Aluminous multilayer materials, Residual stresses, Co-Pressing, Mullite

Modified Freeze-granulation method for fabricating Li2TiO3 ceramic tritium breeding pebbles

Shufeng Zhang, Wei Lu, Youfu Jiang, Xinyu Gao, Delin Chu, Weihua Wang

Abstract

Lithium metatitanate (Li2TiO3) ceramic is an important candidate for tritium breeding material in fusion reactor blanket. Nevertheless, mass production has become an important factor restricting the application of Li2TiO3 pebbles. In this paper, freeze-granulation method is innovatively modified by drying frozen pebbles in acetone. The principle of modified freeze-granulation method is explained in detail. Influence of PVA content, sintering temperature and sintering time on mechanical performance of frozen pebbles dried in acetone are carefully discussed. The modified process could shorten the drying time in 30 min under the premise of good crushing load and thus conducive to improve the efficiency of mass production of tritium breeding ceramic pebbles potentially in the future. Finally, the Li2TiO3 pebbles present good sphericity, high average crushing load (38 N), abundant and uniform pores which are beneficial to tritium release.

Enhancing the density and crush load of Li2TiO3 tritium breeding ceramic pebbles by adding LiNO3-Li2CO3

Yichao Gong, Qingze Na, Chao Dang, Yijiang Yang, Mingxiang Tang, Zhanwen Liu, Guojun Zhang

Abstract

The fabrication of Li2TiO3 ceramic pebbles with satisfactory density and excellent crush load while maintaining a fine grain structure is one of the research objectives of solid tritium breeders. However, densification and grain refinement are often contradictory in lithium-containing ceramics during the sintering process. In this work, LiNO3-Li2CO3 was added during the preparation of Li2TiO3 green spheres by the wet process, and the formation of LiNO3-Li2CO3 molten salt resulted in the significant sintering improvement of Li2TiO3 ceramic pebbles. The addition of LiNO3-Li2CO3 increased the density of Li2TiO3 ceramic pebbles by 10.47 % (92.63 % vs. 82.16 %) and the crush load by more than four times (144.54 N vs. 28.2 N). ICP-OES analysis showed that the lithium content of the Li2TiO3 ceramic pebbles was slightly increased by the addition of LiNO3-Li2CO3. Overall, the difficulty of balancing grain refinement and densification in lithium-containing tritium breeders can be addressed by the proposed method.

Comparative sintering behaviour of MOX powders synthesized through the freeze granulation or dry-cogrinding routes

Guillaume Bernard-Granger, Florent Lebreton, Laure Ramond, Marion Le Guellec, Gabriella Cunha Costa Miranda, Abibatou Ndiaye, Thierry Gervais

Abstract

Two MOX powders containing 11 mol% Pu/(U+Pu) have been synthesized using the freeze granulation or dry-cogrinding routes. The sintering behaviour of green compacts has been investigated up to 1700 °C in an Ar/4.3 vol% H2 humidified with 1200 vpm H2O. The evolution of the sintering trajectory (grain size as a function of relative density) is identical up to approximately 94% relative density. Above this value, grain growth becomes significant in compacts made with the powder obtained by freeze granulation and densification becomes more modest. As for it, the sintering trajectory relating to the compacts shaped from the co-grinded powder continues up to approximately 97.5% relative density, without remarkable grain growth. Beyond this value, grain growth occurs and densification slows down. It has also been shown that the plutonium distribution is more homogeneous in the case of a sample sintered from the powder obtained by freeze-granulation (relative density around 97–99%).

Optimization of freeze granulation and sintering behavior of MgO granules for thermal interface materials

Hyojung Cho, Rokhyeon Kim, Haewon Jung, Joo-Hwan Han, In Chul Jung, Jungho Ryu

Abstract

Heat management of high-performance secondary batteries, used in various applications that require high charging and discharging rates, such as electric vehicles and electronic devices, has recently been attracting increased attention. One of the most popular heat management technologies involves the use of thermal interface materials (TIMs) for heat dissipation. TIMs are composites of thermally conductive granulated fillers uniformly dispersed in a polymer matrix. In this study, the freeze granulation process is optimized to prepare MgO granules with high thermal conductivity as an alternative to commercial alumina fillers for TIMs. The heat dissipation characteristics of TIMs are directly related to their thermal properties, size distribution, shape, density, and filler content. Therefore, a suspension is optimized with high solid content and low viscosity for proper spraying. The size distribution and sintered granule density are analyzed for various spraying distances and pressures to optimize the process for producing high-quality TIMs. Finally, a TIM with MgO granules formed by freeze granulation dispersed in silicone-based resin is fabricated, with a high thermal conductivity exceeding 5.425 W/m∙K (with an interfacial thermal resistance of 0.343 K∙ cm2/W) and low density of 2.78 g/cm3.

Design and Process Considerations in Spray Freeze Drying

Bernhard Luy, Matthias Plitzko, Howard Stamato

Abstract

Dynamic spray freeze drying combines spray freezing and rotary freeze drying to generate homogeneous, free-flowing lyophilized beads as a bulk intermediate product. This allows for filling on demand, with choices in dose strength and combinations of multiple active materials. Thus, the supply chain becomes highly flexible. This feature of handling bulk intermediate can significantly reduce time to market.

Production efficiency is enabled by using higher concentrated liquids yet maintaining fast reconstitution. Further processing with established solid dosage form technologies is possible, for example film coating for light or oxygen protection in diagnostic applications. The technology is built and tested in lab, pilot and production scale including its use for the manufacture of parenteral products, which is done in a fully contained process line. Industrial uses of the technology are in the areas of pharmaceuticals, diagnostics and medical devices, and specialty chemicals applications.

Compactability and sinterability of alumina granules made by spray freeze granulation drying and spray drying

Naoki Kondo, Akihiro Shimamura, Mikinori Hotta, Junichi Tatami, Shinya Kawaguchi

Abstract

The compactability and sinterability of alumina granules prepared by spray freeze granulation drying (SFGD) and spray drying (SD) were compared. The strengths of the granules made by SFGD and SD, densities of the green bodies and sintered bodies, pore size distributions of the green bodies, internal structures and strengths of sintered bodies made from SFGD and SD granules were evaluated. The strength of SFGD granules was lower than that of SD granules. The lower granule strength of the SFGD granules was advantageous to form a uniform structure without inter-granular pores in the green body, resulted in higher density and strength of the sintered body.

Keywords

Granule, Spray dry, Spray freeze granulation dry, Compactability, Sinterability, Density, Pore

Spray-freeze-drying as emerging and substantial quality enhancement technique in food industry

Poornima Singh, Vinay Kumar Pandey, Rahul Singh, Aamir Hussain Dar

Abstract

Spray freeze drying is an emerging technology in the food industry with numerous applications. Its ability to preserve food quality, maintain nutritional value, and reduce bulk make it an attractive option to food manufacturers. Spray freeze drying can be used to reduce the water content of foods while preserving the shelf life and nutritional value. Spray freeze-drying of food products is a process that involves atomizing food into small droplets and then flash-freezing them. The frozen droplets are then placed in a vacuum chamber and heated, causing the liquid to evaporate and the solid particles to become a dry powder. Spray freeze drying has become a valuable tool for the food industry through its ability to process a wide range of food products. This review’s prime focus is understanding spray freeze-dried approaches and emphasizing their applicability in various products.

Keywords

Food products, Fruits & vegetables, Shelf life, Spray freeze drying

Development of an Inhalation Dry Powder Preparation Method without Heat-drying Process

Takaaki Ito

Abstract

Biopharmaceuticals, including therapeutic genes and proteins, are characterized by highly-targeted, specific action and flexible pharmacological design and have a rapidly growing market share; however, because of high molecular weight and low stability, injection is the most common delivery route of biopharmaceuticals. Thus, pharmaceutical innovations are required to provide alternative delivery routes for biopharmaceuticals. Pulmonary drug delivery via inhalation is a promising approach, particularly for targeting local diseases of the lung, because it can exert therapeutic effects in small doses and can noninvasively and directly deliver drugs to airway surfaces. However, biopharmaceutical inhalers must ensure that the biopharmaceuticals maintain their integrity as they are subjected to several types of physicochemical stress, such as hydrolysis, ultrasound, and heating, at various stages during the process from manufacturing to administration. In this symposium, I present a novel dry powder inhaler (DPI) preparation method without heat-drying, with the goal of developing biopharmaceutical DPIs. Spray-freeze-drying is a nonthermal drying technique that produces a powder with porous shapes; this powder has suitable inhalation characteristics for DPI. A model drug, plasmid DNA (pDNA), was stably prepared as a DPI using the spray-freeze-drying process. Under dry conditions, the powders maintained high inhalation characteristics and maintained pDNA integrity for 12 months. The powder induced pDNA expression in mouse lungs that exceeded at higher levels than the solution did. This novel preparation method is suitable for DPI preparation for various drugs and may help expand the clinical application of DPIs.

Keywords

dry powder inhalers; gene delivery; hyaluronic acid; spray-freeze-drying.

Effects of magnetic field-assisted liquid carbon dioxide spray freezing on the quality of honeydew melon

Qiyong Jiang, Min Zhang, Arun S. Mujumdar, Sunlong Gan

Abstract

The effectiveness of static magnetic fields with different intensities (5, 10, 15 mT) combined with liquid carbon dioxide spray freezing (LCSF) technique in improving the quality of frozen honeydew melon was investigated. The results showed that LCSF with magnetic fields above 10 mT significantly improved ice nucleation and quality of frozen melons compared to conventional −20 °C freezing, −80 °C freezing and LCSF method without magnetic field assistance (P < 0.05). 15 mT strength static magnetic field assistance suggested the best results, with a 15.0% reduction in total freezing time, 17.7% increase in average freezing rate, 26.6% reduction in drip loss, and better maintenance of sample quality compared to LCSF. These findings demonstrate that LCSF with static magnetic field assistance is promising in improving the quality of frozen foods.

Keywords

Magnetic field, Liquid carbon dioxide, Honeydew melon, Freezing