Study of Lightweight Ceramic Matrix-Less Syntactic Foam Composed of Cenosphere Using Spark Plasma Sintering

Lightweight materials are widely studied for their use in aerospace and automotive industries. Prior research has shown that cenospheres can be used to create porous ceramics. However, the impact of sintering conditions on cenosphere-based materials remains unclear. This gap motivated the current investigation into how sintering parameters affect material properties. No prior work had resolved the relationship between cenosphere size and compressive strength. The study builds on existing knowledge of ceramic sintering and foam structures. It was already known that cenospheres offer low density and high porosity. This paper aims to clarify the role of temperature and mould size in shaping final properties. The research fills a specific niche in lightweight composite development.

The study aimed to evaluate how sintering parameters influence the properties of cenosphere-based ceramic foams. The specific problem addressed is the lack of understanding about how temperature and mould size affect shrinkage and compressive strength. The motivation stems from the need for lightweight materials with controlled porosity. The authors propose to use spark plasma sintering to achieve precise material control. This approach allows for systematic variation of parameters. The goal is to identify optimal sintering conditions for desired material behavior. The study focuses on cenosphere size and sintering temperature as key variables. It was already known that cenospheres can form porous structures, but this work seeks to quantify the effects.

The researchers used spark plasma sintering to process cenosphere-based materials. They varied sintering temperatures from 900 to 1300 °C and tested three mould diameters: 20, 30, and 50 mm. Cenosphere sizes of 63-150 µm and 150-250 µm were examined. Sample shrinkage was measured during the sintering process. Apparent density was calculated based on sample dimensions and mass. Porosity was determined using water immersion and mercury intrusion techniques. Compressive strength was tested using standard mechanical testing protocols. The Rice model was applied to correlate compressive strength with porosity and density.

Shrinkage began at 900 °C and increased with higher temperatures. Apparent density rose from 0.97 to 2.3 g·cm^-3 in 20 mm moulds at 1050-1300 °C. In 30 mm moulds, density increased from 0.81 to 1.87 g·cm^-3 at 1050-1200 °C. In 50 mm moulds, density ranged from 0.54 to 0.75 g·cm^-3 at 1050-1150 °C. Total porosity dropped from 61.5% to 3.9% as sintering temperature increased from 1050 to 1250 °C. Open porosity decreased at lower temperatures, while closed porosity peaked at 1150 °C. Compressive strength increased from 11 MPa to 312 MPa in 20 mm moulds as temperature rose from 1050 to 1300 °C. These findings align with the Rice model's prediction of exponential dependence on porosity.

The authors propose that sintering temperature and mould size significantly influence cenosphere-based foam properties. They suggest that higher temperatures increase density and reduce porosity. The study indicates that compressive strength grows exponentially with decreasing porosity. The findings support the use of the Rice model to predict material behavior. The results suggest that 20 mm moulds produce the highest compressive strength. The study implies that larger moulds yield lower density materials. The authors propose that cenosphere size affects material performance. The research confirms that spark plasma sintering allows precise control over material properties.