Cenospheres (Fly Ash Microspheres, Lightweight)
Key Features
- Lightweight hollow ceramic spheres — density 0.4–0.8 g/cc at very low cost
- Excellent thermal stability to 1200°C — fire-resistant applications
- Natural thermal and acoustic insulation properties
- Spherical morphology reduces compound viscosity vs. irregular fillers
- Cost-effective alternative to synthetic hollow glass microspheres
Cenospheres are hollow aluminosilicate ceramic spheres recovered from the fly ash byproduct of coal-fired power plant combustion. These natural hollow spheres have a true density of approximately 0.4–0.8 g/cc and outer diameters of 10–300 µm, making them a cost-effective lightweight filler alternative to synthetic hollow glass microspheres.
Cenospheres' hollow structure provides lightweight properties, thermal insulation (thermal conductivity 0.05–0.10 W/m·K), and acoustic insulation benefits. The ceramic aluminosilicate composition provides excellent thermal stability (stable up to 1200°C), chemical resistance, and fire resistance compared to polymer-based hollow fillers. The smooth, spherical morphology reduces compound viscosity relative to irregular mineral fillers at equal volume fraction.
In FRP composites, cenospheres are used for density reduction in structural laminates, thermal insulation panels, fire-resistant composites, and as a lightweight extender in putties and repair compounds. The gray to off-white color and variable particle properties (as a natural byproduct) make cenospheres generally more suitable for structural and non-cosmetic applications than the consistent, high-brightness hollow glass microspheres. At considerably lower cost than engineered hollow glass spheres, cenospheres are the economical choice for lightweight composites where strict color or particle size control is not critical.
Specifications
| Parameter | Value |
|---|---|
| Appearance | Gray to off-white hollow spheres |
| True density | 0.4–0.8 g/cc (typical batch ~0.6 g/cc) |
| Particle size range | 10–300 µm |
| Chemical composition | SiO₂ ~55–65%, Al₂O₃ ~25–30% |
| Compressive strength | ~2000–5000 psi |
| Wall thickness (approx.) | 2–6 µm |
| Median particle size (d50) | ~80–120 µm |
| Maximum service temperature | 1200°C |
| Thermal conductivity (bulk) | 0.05–0.10 W/m·K |
Applications
FAQ
Cenospheres are natural byproducts (recovered from fly ash) with variable density, color, and properties. They are less consistent between batches but significantly cheaper than engineered hollow glass microspheres. Glass microspheres are synthetically manufactured with controlled, consistent density, size, and crush strength, making them preferred for precision, high-performance, or cosmetic applications. For structural lightweight filling where consistency is not critical, cenospheres are the economical choice.
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