The porosity of refractory materials
Refractory materials have an important role in industries such as steelmaking, ceramics and glass manufacture. Refractory materials are typically inorganic, nonmetallic materials with low thermal conductivity and high resistance to thermal shock and extreme temperature changes. Porosity can have a significant impact on the properties of refractory materials. Porosity is the ratio of the volume of voids divided by the total volume of a material. It is an important parameter for understanding the mechanical and thermal properties of refractory materials.
There are three types of porosity in refractory materials: apparent porosity, real porosity and true porosity. Apparent porosity is the ratio of open and closed pores in a material’s non-porous portion. Real porosity is the ratio of open and closed pores in a material’s porous portion. True porosity is the ratio of closed pores to the total volume of the material. All three types of porosity are important parameters for determining the quality of refractory materials.
Porosity has a significant effect on the mechanical properties of refractory materials. For instance, pore size influences the strength of the material, while pore shape influences the thermal shock resistance of the material. The porosity also affects the thermal conductivity of the material, with open pores allowing increased thermal conductivity of heat-sensitive materials. Likewise, porosity can affect the resistance of refractory materials to abrasion, since the presence of open pores can lead to the formation of openings in the material that can increase the area on which abrasion can occur. In addition, porosity can affect the chemical properties of refractory materials, as it increases their susceptibility to corrosion and other forms of material decay.
The porosity of refractory materials can be determined by several different techniques. Traditional techniques such as the McBride-Luter ratio method, the Bates ratio method and the angularity index techniques are useful in determining the pore shape of refractories. Other methods such as X-ray imaging, mercury intrusion porosimetry and gas-solid adsorption can be used to determine the porosity of refractory materials.
The porosity of refractory materials can be manipulated in order to improve their properties. For instance, closed porosity can be reduced by adding particulate material such as quartz fines to the material, thereby reducing the number of closed pores and increasing the real porosity. Alternatively, some Refractory materials can be sintered at higher temperatures, which will reduce the number of open pores and increase the apparent porosity.
In summary, porosity is an important parameter for determining the properties of refractory materials. The three types of porosity – apparent porosity, real porosity and true porosity – are important for assessing the mechanical, thermal and chemical properties of refractory materials. Porosity can be manipulated to improve the material’s properties, and a variety of techniques can be used to accurately measure the porosity of refractory materials.
