Experimental synthesis and density functional theory investigation of radiation tolerance of Zr3(Al1‐xSix)C2MAX phases

Eugenio Zapata‐Solvas,Alexander Chroneos,David C Parfitt,Michael E Fitzpatrick,Na Ni,Denis Horlait,William E Lee,Stavros‐Richard G Christopoulos

doi:10.1111/jace.14742

Abstract

AbstractSynthesis, characterization and density functional theory calculations have been combined to examine the formation of the Zr3(Al1–xSix)C2 quaternary MAX phases and the intrinsic defect processes in Zr3AlC2 and Zr3SiC2. The MAX phase family is extended by demonstrating that Zr3(Al1–xSix)C2, and particularly compositions with x≈0.1, can be formed leading here to a yield of 59 wt%. It has been found that Zr3AlC2 ‐ and by extension Zr3(Al1–xSix)C2 ‐ formation rates benefit from the presence of traces of Si in the reactant mix, presumably through the in situ formation of ZrySiz phase(s) acting as a nucleation substrate for the MAX phase. To investigate the radiation tolerance of Zr3(Al1–xSix)C2, we have also considered the intrinsic defect properties of the end‐members. A‐element Frenkel reaction for both Zr3AlC2 (1.71 eV) and Zr3SiC2 (1.41 eV) phases are the lowest energy defect reactions. For comparison we consider the defect processes in Ti3AlC2 and Ti3SiC2 phases. It is concluded that Zr3AlC2 and Ti3AlC2 MAX phases are more radiation tolerant than Zr3SiC2 and Ti3SiC2, respectively. Their applicability as cladding materials for nuclear fuel is discussed.

Highlights

They were initially studied in the 1960s,1 interest in the Mn+1AXn phases (n=integer, M=early transition metal; A=group 13-16 element and X=C or N) was regenerated by the report on the remarkable properties of Ti3SiC2 nearly two decades ago.[2]
The lattice parameters refined for the ZrC phases are similar in the first three samples and are equal to the lowest reported ones for ZrC1–x, which suggests that highly substoichiometric ZrC1–x is formed with x%0.4.31 From Rietveld refinements, when Si/(Si + Al)=0, Zr3AlC2 is present as a residual phase (7 wt%) (Table 1)
This study has considered the powder synthesis of Zr3(Al1– xSix)C2 MAX phases

Summary

Introduction

They were initially studied in the 1960s,1 interest in the Mn+1AXn phases (n=integer, M=early transition metal; A=group 13-16 element and X=C or N) was regenerated by the report on the remarkable properties of Ti3SiC2 nearly two decades ago.[2] This was followed by the synthesis of numerous ternary[3] or quaternary solid solution MAX phases,[4,5] which shared these metallic and ceramic properties (high elastic stiffness, high melting temperature, high thermal shock resistance, good machinability, high thermal, and electrical conductivity).[2,6,7,8,9,10,11,12] Such properties drive their technological importance and are attributed to their structure, which consists of the stacking of n “ceramic” layer(s) interleaved by an A “metallic” layer.[2,6,7,8].

Objectives

Methods

Results

Conclusion