Effect of ZrB2 Particle Size on Pressureless Sintering of ZrB2 - ß-Sic Composites

Abstract

Zirconium diboride is an ultra high temperature ceramic material that leads this emerging class of materials because of its distinct combination of properties, including high melting temperature (> 3000 °C) and the lowest theoretical density (6.09 g·cm-3) among the borides. This combination of properties makes ZrB2 candidate for airframe leading edges on sharp-bodied reentry vehicles. In this work, the effect of particle size of ZrB2 on the pressureless sintering of ZrB2-SiC composites was studied, using ZrB2 powder with average particle size of 2.6 and 14.2µm. Four different vol% concentration of ß-SiC (0, 10, 20 and 30 vol%) were added to as-received and planetary milled ZrB2 powder. Samples were pressureless sintered at 2050 °C/1h in argon atmosphere. The reduction of initial ZrB2 particle size led to composites with better results of densification, mechanical properties and oxidation resistance regardless ß-SiC addition, showing relative densities around 92.5 %Theoretical Density (Td) and flexural strength and microhardness around 260 MPa and 17.5 GPa, respectively. Composites processed with as-received ZrB2 powder showed increasing in densification and flexural strength with the SiC content increasing. Relative density varied from 74.7 to 90.8 %TD and flexural strength from 102 to 241 MPa, for 0 and 30 vol% of SiC, respectively.

Ultrafast high‐temperature sintering of ZrB2

“…The increase in UHS time to 60 s seems to have allowed for the final stage of densification to be reached, with only a small fraction of closed porosity remaining. These results are in good agreement with reported results in the literature for other sintering processes, such as pressureless sintering and SPS 16,19,20 …”

“…These results are in good agreement with reported results in the literature for other sintering processes, such as pressureless sintering and SPS. 16,19,20 Figure 2G-I shows wider areas of the microstructures of the sintered ZrB 2 prepared with 60 s sintering time, showing regions at the center of the sample, away from the heat source (h), and the edge of the sample, close to the heat source (i). All these images exhibit a relatively homogeneous microstructure, indicating that there were no significant hot spots during the experiments across the sample throughout the lengths of roughly 1 mm, with just a few examples of porosity consistent with the density measured by Archimedes and some grain pullout from polishing.…”

The Oxidation Behavior of ZrB2-SiC Ceramic Composites Fabricated by Plasma Spray Process

“…The ZrB 2 synthesis process also provides possible explanations for the existence of this boron-containing step. Indeed, ZrB 2 is commonly produced from boron oxide, zirconium oxide, and carbon at temperatures above 2400 °C in an arc furnace by means of a process boron-carbothermal [ 30 ]. The following reaction (Equation (2)) occurs simultaneously: B 2 O 3 + ZrO 2 + 5 C → ZrB 2 + 5 CO …”

Non-catalytic applications of g-C3N4: A brief review

“…Using the SPS process in the manufacture of UHTCs will be very useful [31]. The SPS process has faced some challenges in cases in which powder has low sinter-ability, poor oxidation resistance, and low self-diffusion coefficient [32]. Some research has been carried out to solve the mentioned problems in order to improve the properties of parts manufactured with the SPS process by adding the g-C 3 N 4 as a sintering aid and reinforcement phase.…”