Mechanical high-temperature properties and damage behaviour of refractory composites

粗晶耐火复合材料由于其在烧结过程中的低收缩、高温塑性和导电性，在混合建筑中具有很高的应用潜力，如用于可加热隔热材料或用作铸钢件的塞子。分项目3的目的是在第二个资助期内调查研究组内产生的复合材料和模型材料复合材料(混合隔热层和混合插头)的力学性能和损伤行为，这些复合材料和模型材料复合材料是以粗晶Al_2O_3为外壳，粗晶金属陶瓷复合材料(60%Nb或Ta和40%Al_2O_3)为高温电热核心。材料复合材料(I)粗晶Al_2O_3和(Ii)注浆工艺的复合材料、(Iii)海藻酸盐法的颗粒和(Iv)添加的颗粒的高温性能以及混杂复合材料的高温性能，如压缩强度、蠕变和应力松弛行为，将在与应用相关的温度范围内进行研究。此外，还将研究循环冷等静压(不同的压力和压力脉动)和随后的烧结制度(1600°C和1700°C)对子项目1中不同预合成颗粒的复合材料在1600°C以下的力学性能和损伤行为的影响。对于夹层结构，使用相同的复合颗粒。同样有趣的是，多孔复合材料的机械性能与子项目6中通过FAST烧结的样品的机械性能进行了比较，这些样品的孔隙率要低得多或可以忽略不计。此外，重点对断裂力学性能进行了研究。特别感兴趣的还有夹层结构中陶瓷/复合材料界面处的损伤行为。对有缺口和无缺口试件进行四点弯曲试验，研究金属陶瓷芯材和粗晶Al_2O_3覆层的损伤行为。除了声发射测量外，还将对夹层结构进行热成像研究，以检测夹层结构在加热和机械加载过程中陶瓷覆层的损伤发展情况。

Coarse-grained refractory composites have a high potential for applications in hybrid construction, such as in heatable heat shields or as plugs for steel casting due to their low shrinkage during sintering, plasticity at high temperatures and electrical conductivity. The aim of subproject 3 is to investigate in the second funding period the mechanical properties and damage behaviour of the composites and model material composites (hybrid heat shields and hybrid plugs) generated within the research group based on coarse-grained Al2O3 as outer shell and coarse-grained metal-ceramic composites (60% Nb or Ta and 40% Al2O3) as electrically heatable core at high temperatures. The high-temperature properties such as compressive strength, creep and stress relaxation behaviour of the individual components of the material composites (i) coarse-grained Al2O3 and the composites (ii) from the slip casting process, (iii) from granules of the alginate route and (iv) from additively manufactured granules, as well as of the hybrid composite are to be researched in the temperature range relevant to the application. In addition, the influence of cyclic cold isostatic pressing (different pressures and pressure pulsations) and subsequent sintering regimes (1600°C, 1700°C) on the mechanical properties and damage behaviour of the composites with different pre-synthesized grains from subproject 1 at temperatures up to 1600°C will be investigated. The same composite granules are used as for the sandwich structures. Of interest is also the comparison of the mechanical properties of the porous composites with the samples sintered in subproject 6 by means of FAST, which have a much lower or negligible porosity. In addition, the focus is on the fracture mechanical properties. Of particular interest is also the damage behaviour at the ceramic/composite interface in the sandwich structure. 4-point bending tests on notched and unnotched specimens will be used to investigate the damage behaviour of the metal-ceramic core and the coarse-grained Al2O3 cladding. In addition to the acoustic emission measurements, a thermographic investigation will also be applied to the sandwich structures to detect the damage development in the ceramic cladding of the sandwich structures during heating and mechanical loading.