Kenichi Noguchi

Synthesis and Evaluation of Ceramic Materials. Tensile Fracture and Fracture Toughness of Y2O3-Stabilized ZrO2.

The tensile strength of yttria-stabilized tetragonal zirconia polycrystals (Y-TZPs) was measured and the fracture surfaces were analyzed by SEM-XMA. The fracture toughness, KIC, SEPB, and the crack extension resistance curve (R-curve) were evaluated by the single-edge-precracked-beam (SEPB) and the double cantilever beam (DCB) methods, respectively. The fracture toughness, KIC, slopel, evaluated from the tensile strength and the fracture surface analysis shows 3.4 to 3.7 MPa√m, which is much smaller than KIC, SEPB (5.0 to 5.2 MPa√m). The type of R-curve is a rising one, and KIC, slopel and KIC, SEPB are close to the initial and the saturated values of the R-curve, respectively. The fracture origins of the SEPB and the tensile test specimens are a relatively large precrack and a small natural flaw, respectivery. Therefore, the value of fracture toughness of the Y-TZPs with a rising R-curve depends on the size of fracture origin.

Strength Evaluation of Y2O3-stabilized Tetragonal ZrO2 Polycrystals with Scanning Laser Acoustic Microscopy

A scanning laser acoustic microscope, SLAM, was applied to measure an ultrasonic attenuation coefficient and detect the internal defects of Y2O3-stabilized tetragonal zirconia polycrystals(Y-TZP). Bend and tensile strength of the Y-TZP materials decreased with the increase of the attenuation coefficient and the number of macro-defects which were detected by SLAM, respectively, although a claer relation between bulk density and strength of Y-TZP materials was not given. SLAM can be the useful technique for nondestructive evaluation of the strength of Y-TZP.