Low-Temperature Synthesis of Ultra-High-Temperature Coatings of ZrB2 Using Reactive Multilayers

Dongwoo Lee,Gi-Dong Sim,Kechao Xiao,Joost J. Vlassak

doi:10.1021/jp505941g

Abstract

We demonstrate a route to synthesize ultra-high-temperature ceramic coatings of ZrB2 at temperatures below 1300 K using Zr/B reactive multilayers. Highly textured crystalline ZrB2 is formed at modest temperatures because of the absence of any oxide at the interface between Zr and B and the very short diffusion distance that is inherent to the multilayer geometry. The kinetics of the ZrB2 formation reaction is analyzed using high-temperature scanning nanocalorimetry, and the microstructural evolution of the multilayer is revealed using transmission electron microscopy. We show that the Zr/B reaction proceeds in two stages: (1) interdiffusion between the nanocrystalline Zr and the amorphous B layers, forming an amorphous Zr/B alloy, and (2) crystallization of the amorphous alloy to form ZrB2. Scanning nanocalorimetry measurements performed at heating rates ranging from 3100 to 10000 K/s allow determination of the kinetic parameters of the multilayer reaction, yielding activation energies of 0.47 and 2.4 eV for Zr/B interdiffusion and ZrB2 crystallization, respectively.

Highlights

ZrB2 is an ultra high-temperature ceramic (UHTC) with a unique set of properties, including an extremely high melting point, very high hardness, exceptional resistance to erosion, and excellent thermal and electric conductivity
Figure 2a depicts temperature as a function of time for typical DC scans performed on multilayer samples
The activation energy obtained by Samsonov et al was determined by measuring the thickness of ZrB2 in Zr/B diffusion couples exposed to temperatures in excess of 1,373 K

Summary

Introduction

ZrB2 is an ultra high-temperature ceramic (UHTC) with a unique set of properties, including an extremely high melting point, very high hardness, exceptional resistance to erosion, and excellent thermal and electric conductivity. AC measurements were performed on three different multilayer samples to measure the heat capacity, Cp, as a function of temperature, both before and after reaction. DC scanning measurements were performed on other multilayer samples to investigate the kinetics of the solid-state reaction.

Results

Conclusion