Storti Enrico, Neumann Marc, Zienert Tilo, Hubálková Jana, Aneziris Christos Georgios
Institute of Ceramics, Refractories and Composite Materials, TU Bergakademie Freiberg, Agricolastraße 17, 09599 Freiberg, Germany.
Materials (Basel). 2021 Sep 22;14(19):5483. doi: 10.3390/ma14195483.
Full metal-ceramic composite beads containing different amounts of niobium and alumina, particularly 100 vol% alumina, 100 vol% niobium, and 95/5 vol% niobium/alumina, were produced by the alginate gelation process. The suspension for bead fabrication contained sodium alginate as gelling agent and was added dropwise into a calcium chloride solution to trigger the consolidation process. After debinding in air, sintering of the composite beads was performed under inert atmosphere. Samples in green and sintered state were analyzed by digital light microscopy and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. Investigations by mercury intrusion porosimetry revealed that pure alumina beads featured smaller pores compared to composite beads, although the open porosities were comparable. The fracture strength was evaluated on single beads. Contrary to the pure alumina, the composite beads showed a clear plastic deformation. Pure niobium beads showed a ductile behavior with very large deformations. XRD analyses revealed the presence of calcium hexaluminate and beta-alumina as minor phases in the alumina beads, while the composite ones contained about 25 wt% of impurities. The impurities comprised NbO arising from the oxidation, and β-NbC, from the reaction with the residual sodium alginate.
通过藻酸盐凝胶化工艺制备了含有不同量铌和氧化铝的全金属陶瓷复合珠，特别是100体积%氧化铝、100体积%铌以及95/5体积%铌/氧化铝的复合珠。用于制备珠子的悬浮液含有海藻酸钠作为胶凝剂，并逐滴加入氯化钙溶液中以引发固结过程。在空气中脱脂后，复合珠在惰性气氛下进行烧结。通过数字光学显微镜和配备能量色散X射线光谱仪的扫描电子显微镜对生坯和烧结状态的样品进行了分析。压汞法研究表明，尽管开孔率相当，但纯氧化铝珠的孔隙比复合珠小。对单个珠子评估了断裂强度。与纯氧化铝相反，复合珠表现出明显的塑性变形。纯铌珠表现出具有非常大变形的延性行为。X射线衍射分析表明，氧化铝珠中存在少量六铝酸钙和β-氧化铝，而复合珠含有约25重量%的杂质。这些杂质包括氧化产生的NbO以及与残留海藻酸钠反应生成的β-NbC。
