Co 2 P nanoparticles for microwave absorption

Microwave absorbing materials have critical roles in homeland and information security. In this study, we report for the first time Co2P nanoparticles as promising microwave absorbing materials. A large reflection loss peak of −39.3 dB, correlating to nearly 99.99% absorption efficiency, is obtained with a 1.10-mm-thick Co2P nanoparticle absorber. Important relationships are revealed between the reflection loss peak value (RLpeak), the reflection loss or absorption peak frequency (fpeak), and the reflection loss or absorption peak width (Δf10), with respect to the overall thickness of the Co2P nanoparticle absorber. The three important parameters that determine the microwave absorption can be approximately expressed with the following general formula: P = A + B/dn, where P is RLpeak, fpeak, or Δf10; d is the thickness of the Co2P nanoparticle absorber A (A is zero when P is fpeak or Δf10); and B and n are the fitting constants. A non-zero permeability of the Co2P nanoparticles slows the shift of fpeak to a lower value and decreases the narrowing of Δf10 as d increases, while RLpeak decreases in a wide thickness range. Because of this, the overall microwave absorbing performance can be well tuned with the thickness of the Co2P absorber, making Co2P nanoparticles as strong candidates for microwave absorption.