Subcategory: Materials Science
Cyerra Prevo - Grambling State University
Co-Author(s): Naidu Seetala and Owen Reedy, Grambling State University, Grambling, LA Thomas Key, HeeDong Lee, and Lawrence Matson, Wright-Patterson Air Force Base, Dayton, OH
Ultra-High-Temperature Ceramics (UHTCs) such as ZrB2 and HfB2 with incorporation of SiC are used to increase the temperature capability and durability for applications in leading edge of hypersonic vehicles, where extremely high heat fluxes generate very high temperatures and steep temperature gradients. Ultra-High-Temperature Ceramics (UHTCs) such as ZrB2 and HfB2 with incorporation of SiC are being considered as structural materials for applications in propulsion and thermal protection systems. We used high energy ball milling of the precursor powders to increase lattice distortion enhanced inter-diffusion, uniform distribution of SiC, and reduce grain growth during Spark plasma sintering (SPS). Here, we studied the effect of high energy ball milling of ZrB2 or HfB2 with 20 vol% SiC on the particle size and crystal micro-strain distribution. The powders of ZrB2 or HfB2 and 20 vol% SiC were mixed with about 1/3 weight SiC balls of 10 mm dia. in a stainless steel container with a 2 mm inner-layer coating of silicone based polymer. The mixing is performed in a glow box with Argon inert gas and sealed the container for high-energy planetary ball milling. The particle size distribution and crystal micro strain are examined after 24 hrs and 48 hrs of ball milling using Dynamic Light Scattering Technique and x-ray diffraction (XRD), respectively. The particle distribution obtained from the light scattering shows bi-model distribution. Upon ball milling the larger size particles decreased and the volume of smaller sized particles increased indicating some break down of larger particles due to high energy ball milling. The effect is much smaller for ZrB2 powders compared to HfB2 powders indicating HfB2 powders may be more brittle compared to ZrB2 powders. The XRD peaks shifted to lower 2Θ angle and broaden as the high energy ball milling time increases. Peak shift to lower angle indicates crystal lattice distortion to increase the lattice parameter and the broadening of the peak indicates either the crystalline grain size decreases A preliminary analysis is performed on the XRD data to estimate the micro-strain using the Williamson-Hall method . The crystal strain showed continuous increase with the increasing ball milling time for both samples. For future work on this project there is need of a detailed analysis of Ball milled powders and consolidated samples using Williamson-Hall plots. Analysis of x-ray diffraction spectra using MAUD software for phase compositions on hydrogenated nano-powder composites. Hydrogenation of ZrB2 nano-powders prior to SPS needs to be continued for reproducibility and improvement of the process. There is also need to find a new source of nano-powders since the quality of the precursors is very important to obtain desired final product. TGA oxidation studies will need to be performed to study the oxidation resistance of the composites.
Funder Acknowledgement(s): My research project is funded by the Air Force.
Faculty Advisor: Naidu Seetala, firstname.lastname@example.org
Role: I performed sample preparation by grinding and polishing the surfaces of the samples. I performed Hardness testing on the samples. Performed four-point bend test on samples. Looked at the surface of the samples under SEM microscope. Performed X-Ray Diffraction. Analyzed data from X-Ray Diffraction by using a Williamson-Hall Plot created in Excel.