Overview
Metakaolin refractory material is produced by calcining kaolin clay at 650–800°C, transforming its crystalline structure into an amorphous aluminosilicate. This thermal activation enhances its reactivity and thermal stability, making it superior to raw kaolin in high-temperature environments. The material is widely adopted in industries requiring thermal insulation and chemical resistance, such as steel, cement, and glass manufacturing. Its pozzolanic properties also allow it to form strong ceramic bonds when fired, contributing to durable refractory installations.
Physical and Chemical Properties
Metakaolin refractories exhibit a low coefficient of thermal expansion (5–6 × 10⁻⁶/°C) and high porosity (15–30%), which collectively improve thermal shock resistance. Their amorphous structure provides a large surface area (10–25 m²/g), promoting better adhesion in binder systems. Chemically, the material is inert to most alkalis and acids except hydrofluoric acid. Its alumina content (typically 40–45%) ensures stability in oxidizing atmospheres, while silica (50–55%) contributes to viscosity control in molten slag environments.
Main Applications
Primary uses include linings for blast furnaces, rotary cement kilns, and glass tank regenerators. In foundries, metakaolin-based coatings protect molds from metal penetration. The material is also blended with other refractories like alumina or mullite to enhance workability. Emerging applications include waste incinerators and biomass energy plants, where its resistance to chlorine and sulfur compounds is critical. Some formulations serve as backup insulation behind dense refractory bricks to reduce heat loss.
Safety and Storage
Though non-toxic, fine metakaolin dust requires NIOSH-approved N95 respirators during bulk handling to prevent silicosis risks. Storage silos should maintain relative humidity below 60% to prevent moisture absorption, which can affect flowability and setting behavior. Spills should be cleaned with vacuum systems rather than dry sweeping. Fire protection is generally unnecessary as the material is non-combustible, but thermal decomposition above 1000°C may release trace crystalline silica.
B2B Procurement Guide
Industrial buyers should prioritize suppliers who provide detailed technical datasheets including PSD (Particle Size Distribution), impurity content (Fe₂O₃ <1.5%), and thermal conductivity data. Bulk shipments typically require 25kg multi-wall paper bags or big bags with moisture barriers. For refractory castables, verify the supplier’s metakaolin is pre-calcined to avoid shrinkage during in-situ dehydration. Sample testing for cold crushing strength (CCS >50 MPa) and permanent linear change (PLC <1% at 1400°C) is recommended before large orders.
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