Nuclear Techniques ›› 2020, Vol. 43 ›› Issue (1): 10204-010204.

• ACCELERATOR, RAY TECHNOLOGY AND APPLICATIONS •

### Study on the microstructure and defects of Al2O3/ZrO2 nano-composites by positron lifetime spectroscopy

Xuehui SHI Jianjian ZHAO Wenzeng GUO Xuelian WANG Zhu WU Yichu XU

1. School of Physics and Technology, Hubei Key Laboratory of Nuclear Solid State Physics, Wuhan University, Wuhan 430072, China
• Received:2019-04-11 Revised:2019-11-01 Online:2020-01-15 Published:2020-01-21
• Supported by:
National Natural Science Foundation of China(11675123)

Abstract: Background

Al2O3/ZrO2 nano-composites have excellent mechanical properties, high temperature stability and chemical stability, as well as good anti-irradiation effect. It is a potential nano-composites in practical industry.

Purpose

This study aims to investigate the microstructures and defects of Al2O3/ZrO2 nano-composites at different annealing temperatures (room temperature -1 000 ℃) by positron annihilation lifetime spectroscopy (PALS).

Methods

The Al2O3 and ZrO2 nanoparticle powder with a mass ratio of 1:1 was ball-milled for 10 h and then pressed into pellets under a pressure of 5 MPa for 2 min. PALS was employed for detecting open-volume defects while X-ray diffraction (XRD) and transmission electron microscope (TEM) were used as auxiliary comparison tools for analyzing microstructures under various annealing temperatures.

Results

XRD results showed that the grain sizes of Al2O3, ZrO2 and Al2O3/ZrO2 nano-composites remained unchanged with annealing temperature below 500 ℃. With the increasing of annealing temperature from 500 ℃ to 1 000 ℃, the grain sizes of ZrO2 and Al2O3/ZrO2 increased to 75 nm and 115 nm, respectively. PALS analysis showed that the main defects in the samples were vacancies, vacancy clusters and microvoids, and the defects mainly existed in the grain boundaries. When the annealing temperature was below 500 ℃, the total defect densities of the three samples were basically unchanged. Above 500 ℃, the open volume defects began to recover, and the change of ZrO2 was more obvious, while the stability of Al2O3/ZrO2 was higher because of inhibiting each other's grain growth. TEM images revealed that the grain size of nano-Al2O3 did not change with the annealing temperature below 500 ℃, but when the annealing temperature was higher than 500 ℃, the growth of nano-Al2O3/ZrO2 was slow and agglomeration occurred.

Conclusions

Both grain size and defect density of Al2O3/ZrO2 nano-composites remains unchanged with annealing below 500 ℃. Above 500 ℃, with the increase of annealing temperature, the grain of nano-Al2O3/ZrO2 grew slower than nano-ZrO2 and the openning volume defects began to recover which was confirmed by TEM observation.

CLC Number:

• TL99