High-Alumina Fly Ash-Based Ceramics: The “Bulletproof Vest” of High-Temperature Industries

High-alumina fly ash is a new type of fly ash with an alumina content exceeding 37%. It mainly contains alumina (38%–50%), silica, and iron oxide. Together, these components account for more than 80%.

In the combustion chambers of aerospace engines, gas temperatures can exceed 2,000 °C; in steel plants’ blast furnaces, molten iron and slag continuously erode the refractory lining. In such extreme environments, new ceramic materials transformed from industrial waste—high-alumina fly ash—are emerging as a “super protective suit” thanks to their outstanding high-temperature resistance.

Material Properties

The core of this material is mullite (Al₆Si₂O₁₃), which makes up more than 85% of its content. It forms a strong framework for heat resistance. The unique three-dimensional network structure of mullite crystals works like a natural honeycomb. It effectively blocks heat transfer. Its refractoriness reaches ≥ 1790 °C. This is like wearing one-third of the Sun’s surface temperature directly on your body. The compressive strength reaches 250 MPa. Each square centimeter can withstand 2.5 tons of pressure without deformation. This even surpasses some steels.

Performance Index	Traditional Refractory Brick	High-Alumina Fly Ash-Based Ceramic	Aerospace-Grade Carbon Fiber Composite
Refractoriness (°C)	1650	≥ 1790	1500
Compressive Strength (MPa)	150	250	120
Thermal Conductivity (W/m·K)	1.2	0.8	0.5

Manufacturing Process

Manufacturers first crush and purify high-alumina fly ash with Al₂O₃ content above 40%. They then form green bodies using dry-press molding. This is similar to traditional ceramic shaping but under a pressure of 200 MPa. That equals a 20-ton weight on an area the size of a fingernail.

Next, they sinter the material at 1400–1600 °C to produce porous ceramics. To further improve performance, they use hot-press sintering. This process increases density from 90% to 95%, making the structure more compact. It is like compressing loose sand into granite. By controlling the heating rate, they create uniformly distributed mullite crystals.

Application Scenarios

Blast furnace linings in steel plants: Traditional refractory bricks last about two years. The new ceramics extend service life to 3.2 years. This is a 60% improvement. As a result, downtime and maintenance costs decrease. A large steel plant saved 20 million yuan per year after adopting the material.

Aerospace engine combustion chambers: The material acts as an insulating layer. Its low thermal conductivity (0.8 W/m·K) can lower metal wall temperatures by over 300 °C. This creates a “fire-and-ice” shield between the combustion chamber and the metal wall.

Key areas of glass kilns: Under 1600 °C molten glass erosion, service life doubles compared to traditional materials. One glass manufacturer reduced kiln maintenance frequency by 40%.

Technological Breakthrough

By adding nano-SiO₂ (particle size < 50 nm), researchers increased the thermal shock resistance by four times. This modification is like weaving “nano spider silk” inside the ceramic: when exposed to sudden temperature changes, the nanoparticles absorb energy via stress-induced phase transformation, preventing crack propagation. Remarkably, these nanoparticles form a “nano-bridging” structure inside the ceramic, as if giving it a “bulletproof vest.”

Epic Powder

The advent of high-alumina fly ash-based ceramics not only solves a global challenge in industrial waste recycling but also sets a new benchmark in high-temperature protection materials. Built on a mullite framework and enhanced through nano-modification and advanced sintering, it achieves comprehensive breakthroughs in refractoriness, strength, and thermal shock resistance.

With expertise in ultrafine grinding, classification, and material modification, Epic Powder provides the precision particle processing technology that ensures the high-purity mullite phases and uniform nano-dispersion required for such advanced ceramics. By integrating Epic Powder’s grinding and classification solutions into the production process, these “super armors” are poised to drive greener, more efficient high-temperature industries, and support humanity’s exploration of even harsher environments with unparalleled reliability.