Lucun Guo

Normalized evaluation of thermal shock resistance for ceramic materials

A normalized method for evaluation of thermal shock resistance for ceramic materials was proposed. A thermal shock resistance index (TSRI), Г, in the range of 1 to 100, was introduced, based on a normalized formula obtained directly by a simple testing process of determining the changes in flexural strength before and after thermal shock cycles. Alumina ceramic was chosen as the model material and its thermal shock behavior was investigated systematically by water quenching. Based on the experiments on alumina ceramic, the thermal shock behaviors of other 19 types of ceramic materials ranging from porcelain, refractory ceramics to advanced ceramics including structural and functional ceramics were also evaluated, and their TSRIs, Γ, were derived. The dependence of Г on the coefficient of thermal expansion (CTE) of the materials was plotted, and it revealed that CTE is the most critical factor in affecting the thermal shock resistance for various ceramic materials. The effect of other factors such as porosity and fracture toughness on the index was also discussed.

Effect of pH on rheology of aqueous Al 2 O 3 /SiC colloidal system

The rheological behavior of aqueous Al2O3/SiC suspensions at different pH values was investigated by rheological measurement. Experimental results showed that at pH = 3–6, Al2O3 and SiC particles have opposite surface charges, and the binary suspensions have lower viscosity than the unary suspensions at shear rates of 0–300 s−1. Furthermore, at pH = 3–12, the stability of the Al2O3 component seemed to dominate the overall rheological behavior of the Al2O3/SiC binary suspensions. The tendency mentioned above showed little variations in various ionic strengths, particle diameters and component fractions.

Effect of transition metal oxides doping on Ce 0.9 Sm 0.05 Nd 0.05 O 1.95 solid electrolyte materials

The effect of transition metal oxides (TMOs) CoO1.5, FeO1.5 and MnO2 addition on Ce0.9Sm0.05Nd0.05O1.95 was studied. The crystal structures, microstructures, thermal expansion and electrical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), dilatometer and AC impedance spectroscopy, respectively. The results show that the TMOs addition remarkably promotes the densification of Ce0.9Sm0.05Nd0.05O1.95 and reduces the sintering temperature by ∼150 °C. The samples with TMOs addition sintered at 1450 °C exhibit higher conductivities than those sintered at 1500 °C. The maximum conductivity of 0.040 s.cm−1 at 700 °C was achieved with 1 mol% FeO1.5 doping when sintered at 1450 °C. In addition, the thermal expansion was linear for all the samples. The doping of TMOs does not appreciably change thermal expansion coefficient.