Development of correlations between process operation, granule structure and product properties - Influence of spray- and process parameters on internal structure and mechanical properties of ceramic granules

喷雾干燥陶瓷、金属或硬质合金颗粒必须满足规定的性能，并应设计良好，以便在粉末加工中进行后续处理和处理。尤其是良好的力学性能和均匀的喷雾干燥颗粒内部结构，对于由陶瓷块体材料模压成型的陶瓷零件的高质量和可靠性具有重要意义。除了复杂的喷雾悬浮特性影响颗粒结构从而影响颗粒的力学性能外，喷雾和干燥参数也会影响颗粒的这些特性。在SPP第二项目部分，确定了基本配方参数与悬浮剂性能之间的基本关系，以及悬浮剂性能与颗粒的结构和力学性能之间的关系。已有研究表明，有机添加剂的种类和性质对颗粒的内部结构和力学性能有很大的影响。结构的形成取决于这些添加剂的迁移和干燥行为。为了分析这些影响，需要一种合适的方法来量化颗粒结构中的添加剂分布。因此，第三个项目段的一个重要课题将是对先前开发的结构量化方法的资格鉴定。进一步的关键活动是研究不同的喷雾和干燥条件对颗粒结构的影响。这些研究将基于在不同尺寸的真实喷雾干燥器上的实验工作以及在单个液滴下的干燥实验。此外，还打算在喷雾干燥器内进行在线液滴尺寸测量。在这些试验中，将分析陶瓷悬浮液滴在实际工艺条件下的收缩和干燥行为，并考虑到不同的工艺参数。最后将评估所有已确定的配方、悬浮剂性能和工艺参数对内部结构和力学性能的影响。有了这些结果，就可以为产品设计形成详细的工艺知识，并为SPP内其他小组对喷雾干燥过程中的结构生成进行建模建立适当的数据集。

Spray dried ceramic, metallic or hard metal based granules have to meet defined properties and should be well designed for subsequent handling and treatment in powder processing. Especially well designed mechanical properties and homogeneous internal structure of spray dried granules are important for a high quality and reliability of ceramic parts formed by die pressing from ceramic bulk material. Besides the influence of complex spraying suspension properties on resulting granule structure and therefore on the mechanical granule properties, these granule properties will be influenced by spraying and drying parameters too. In second project section of SPP basic correlations between essential formulation parameters and suspension properties as well as correlations between suspension properties and resulting structure and mechanical properties of granules were identified. Previous results have shown, that kind and properties of organic additives have a strong influence on internal structure and resulting mechanical properties of granules. Structure generation is depending on migration and drying behavior of these additives. To analyze these effects a suitable method for quantification of additive distribution within the granules structure is necessary. Therefore an important topic in third project section will be the qualification of the previous developed method for structure quantification. Further key activities are investigations in dependence of granule structure on different spraying and drying conditions. These investigations will base on experimental works in real spray dryers of different size as well as drying experiments at single droplets. Furthermore an inline droplet size measurement within a spray dryer is intended. Within these tests shrinking and drying behavior of ceramic suspension droplets will be analyzed under real process conditions in consideration of varied process parameters. Finally all identified effects of formulation, suspension properties and process parameters on internal structure and mechanical properties will be evaluated. With these results it should be possible to form detailed process knowledge for product design as well as a suitable data set up for modeling of structure generation in spray drying process by other groups within SPP.