Applications of Fly Ash Microspheres

High Refractoriness: The primary chemical components of microspheres are silicon and aluminum oxides, with approximately 50–65% silica (SiO₂) and 25–35% alumina (Al₂O₃). Given that silica melts at 1,725°C and alumina at 2,050°C—both being highly refractory materials—microspheres exhibit exceptional refractoriness, typically ranging from 1,600–1,700°C. This makes them ideal for high-performance refractory applications.

Lightweight & Thermal Insulation: With thin, hollow walls and semi-vacuum interiors containing trace gases (N₂, H₂, CO₂, etc.), microspheres possess extremely low thermal conductivity. These "cenospheres" are not only lightweight (bulk density: 250–450 kg/m³) but also excellent thermal insulators (thermal conductivity: 0.08–0.1 W/m·K at room temperature), making them indispensable for lightweight insulation materials.

High Hardness & Strength: Formed as rigid vitreous bodies of silica-alumina mineral phases (quartz and mullite), microspheres achieve a Mohs hardness of 6–7 and static compressive strength up to 70–140 MPa. Their true density (2.10–2.20 g/cm³) rivals that of natural rock. Unlike porous lightweight materials (e.g., perlite, zeolite, diatomite) which suffer from poor hardness and strength, microspheres' robustness provides a competitive edge for high-strength applications.

Fine Particle Size & Large Specific Surface Area: Naturally occurring in the 1–250 μm range with a specific surface area of 300–360 cm²/g (comparable to cement), microspheres require no grinding for direct use. Their fine particle size meets the specifications of various products, whereas other lightweight insulators (e.g., perlite) lose insulation efficiency when ground to similar fineness due to increased density.

Excellent Electrical Insulation: Magnetically separated microspheres are highly effective insulators with non-conductive properties. Uniquely, their electrical resistance increases with rising temperatures—opposite to most insulators—enabling the production of high-temperature insulation components.