Alumina ceramics are crucial for high-performance applications, such as turbine blades, due to their excellent thermal stability and mechanical properties. However, existing fabrication methods often fail to balance strength, porosity, and dimensional precision. This study partially fills this research gap through a systematic investigation of calcium oxide (CaO) doping effects on alumina ceramic cores fabricated via ceramic stereolithography, with controlled doping ratios and sintering parameters. A ceramic paste was prepared using coarse and fine Al 2 O 3 particles mixed with CaO as a sintering aid, followed by debinding and sintering to achieve optimal mechanical properties. The results show that CaO doping significantly enhances the flexural strength of alumina cores while maintaining porosity levels between 20% and 30% and controlling the sintering shrinkage rate to about 5%. Additionally, CaO doping alters the microstructure by inhibiting the transformation of spherical fine particles into flaky grains, improving sintering activity. However, as the CaO doping content increases, the bending strength increases, while the shrinkage rate of the material also tends to increase, resulting in a reduction in the overall porosity. This has a negative impact on the control of the manufacturing precision of turbine blades. Thus, although CaO doping improves strength and microstructure, achieving necessary dimensional control requires further optimization of doping content and sintering conditions.
Shaobo Yang,Yujie Ma,Jiali Li,Sijie Kou,Bo Chen,Chidong Liu,Juanli Deng,Shangwu Fan
Nowadays, Y 2 O 3 –Al 2 O 3 –SiO 2 (YAS) glass joining is considered to be a promising scheme for nuclear-grade continuous silicon carbide (SiC) fiber reinforced SiC matrix composites (SiC/SiC). CaO has great potential for nuclear applications since it has low reactivity and low decay rate under nuclear irradiation. In this paper, the effect of CaO doping on the structure, thermophysical properties , and crystallization behavior of YAS glass was systematically studied. As the CaO doping content increased, the number of bridge oxygens and the viscosity at high temperatures reduced gradually. After heat treatment at 1400 °C, the main phases in YAS glass were β-Y 2 Si 2 O 7 , mullite , and SiO 2 (coexistence of crystalline and glass phases), while that with 3.0% CaO doping turned into a single glassy phase under the same treatment conditions. Moreover, a structural model and the modification mechanism were proposed, which provided a theoretical basis for the subsequent component design and optimization.
CaO-doped γ-Al2O3 beads were prepared by an alginate assisted sol–gel method, followed by grafting with alkyl groups and impregnation of NbCl5 to construct multi-functionalized γ-Al2O3 beads for efficient catalytic conversion of glucose to 5-hydroxymethylfurfural (5-HMF). Doping with CaO improved the binding capacity of the catalyst with glucose and increased the Lewis acid amount. However, a high CaO content would cover the Lewis acid sites of γ-Al2O3, resulting in a lower isomeric conversion of glucose to fructose. When the C8–Ca(10%)–γ-Al2O3 catalyst was loaded with Nb2O5, intermediate fructose was consumed rapidly resulting in complete conversion of glucose, which indicated that conversion of glucose to 5-HMF involved the isomeric conversion of glucose to fructose followed by dehydration of fructose to 5-HMF. This was necessary to balance hydrophilic isomerization reactions with restraining the rehydration of 5-HMF by hydrophobic modification. This is similar to the reaction in which a medium with a certain amount of water was beneficial for glucose isomerization. Under the synergistic effect of Lewis acid provided by γ-Al2O3 and Brønsted acid offered by Nb2O5, C8–Ca(10%)–γ-Al2O3–Nb(3%), a glucose conversation rate of 100% and the highest yield of 5-HMF (68.4%) were achieved in the reaction medium with a dimethylsulfoxide/H2O (V/V) ratio of 4 : 1, a catalyst amount of 33 mg, a reaction temperature of 140 °C and a reaction time of 4 h.
危险品化学品经营许可证（带存储）