Effect Of ZrO2 Addition Research Articles

Reaction sintering and mechanical properties of B4C with addition of ZrO2

The effect of ZrO2 addition on sintering behavior and mechanical properties of both hot-pressed and pressureless-sintered B4C was investigated. The addition of ZrO2 improved the densification behavior of B4C remarkably via a reaction with the B4C to form ZrB2 at elevated temperatures. When B4C was densified at 2000 °C by hot pressing, only a small amount (approximately 2.5 vol%) of ZrO2 was necessary to achieve a full densification. Excellent mechanical properties (hardness, elastic modulus, flexural strength, and fracture toughness) were observed in those specimens. As the amount of ZrO2 was increased further, the mechanical properties were reduced, except for the fracture toughness, apparently due to the formation of too much ZrB2 in the specimen. Without the applied pressure, larger amounts of ZrO2 should be added to obtain a body with high relative density. When the B4C was sintered at 2175 °C with addition of 10 vol% ZrO2, the specimen has a density higher than 95% of the theoretical, and hardness and flexural strength of 25 GPa and 400 MPa, respectively.

Effect of ZrO2 addition on strength and dilation behaviour of cordierite ceramics

Effect of ZrO2 addition on strength and dilation behaviour of cordierite ceramics

Superconductivity in YBa2Cu3O7- delta -ZrO2 systems

The effect of ZrO2 addition on the superconducting properties of YBa2Cu3O7- delta superconductors has been investigated by temperature-resistance measurements and X-ray diffraction studies. The results revealed that ZrO2 additions up to 2.0 wt.% do not have any detrimental effect on the superconducting properties of YBa2Cu3O7- delta . It is also found that the widely accepted procedure of slow cooling or annealing at 600 degrees C for several hours for oxygenation of samples is not essential to obtain superconductivity in the Zr-doped samples. The superconducting transition (92 K) was obtained by directly quenching the doped specimen from the sintering temperature of 950 degrees C in an oxygen atmosphere. The tetragonal to orthorhombic transformation took place within seconds in the doped samples, indicating that the rate of oxygen absorption has been tremendously increased in the ZrO2-doped YBa2Cu3O7- delta . Undoped samples quenched in air were always tetragonal and non-superconducting.

Phase Transformation Kinetics in the System Bismuth Oxide‐Zirconia

The effect of ZrO2 addition on the phase transformation of Bi2O3 was studied with powder X‐ray diffraction and differential thermal analysis. Samples containing higher than a few mole percent ZrO2 were obtained as the metastable β phase (tetragonal) at room temperature when they were cooled at 20°C/min from 800°C where the δ phase (fcc) is stable. When the same samples were cooled at the same rate from 1000°C, which is above the solidus, they formed the stable α phase (monoclinic) at room temperature. Evidence for the relatively higher solubility of ZrO2 in the α phase is discussed to explain this observation.

Zirconia Particle Coarsening and the Effects of Zirconia Additions on the Mechanical Properties of Certain Commercial Aluminas

The effects of ZrO2 additions on the mechanical properties of four commercial aluminas have been studied, and the changes in intergranular and intragranular ZrO2 particle sizes during aging have been determined for one of the aluminas. In this ceramic, the intercranular and intragranular ZrO2 particles coarsen obeying t1/2 and t1/3 kinetics, respectively. Changes in strength of the aluminas with additions of ZrO2 are shown to be related to changes in the Al2O3 matrix microstructure. Differences in toughness of the resulting composites are explained in terms of the different size and morphology of the intergranular ZrO2 particles and the operation of several toughening mechanisms, with transformation toughening a relatively minor contributor.