Calcined Alumina Ultrafine For High-Performance Refractories,can be used in castables with silica fume and reactive alumina powders, to reduce water addition, porosity and to increase strength, volume stability.
- Reactive Alumina
- Fused Alumina
- alumina ceramics
Short Description
Physical and chemical properties
Ceramic grade- Calcined Alumina
|
Properties Brands |
Chemical composition (mass fraction)/% |
effective density /（g/cm3）No less than |
α- Al2O3/% No less than |
||||
|
Al2O3 content is not less than |
Impurity content, not greater than |
||||||
|
SiO2 |
Fe2O3 |
Na2O |
Ignition Loss | ||||
|
JS-05LS |
99.7 |
0.04 |
0.02 |
0.05 |
0.10 |
3.97 |
96 |
|
JS-10LS |
99.6 |
0.04 |
0.02 |
0.10 |
0.10 |
3.96 |
95 |
|
JS-20 |
99.5 |
0.06 |
0.03 |
0.20 |
0.20 |
3.95 |
93 |
|
JS-30 |
99.4 |
0.06 |
0.03 |
0.30 |
0.20 |
3.93 |
90 |
|
JS-40 |
99.2 |
0.08 |
0.04 |
0.40 |
0.20 |
3.90 |
85 |
Alumina products with such calcined alumina powder as raw material have excellent mechanical strength, high hardness, higher electric resistivity and good thermal conductivity. The calcined alumina micropowder can be widely used in electronic equipment, structural ceramics, refractories,abrasives, polishing materials, et
Calcined aluminas are alpha-aluminas that consist primarily of sintered agglomerates of individual alumina crystals. The size of these primary crystals depends upon the degree of calcination and the agglomerate size on the subsequent grinding steps. The majority of calcined aluminas are supplied ground (<63μm) or fine-ground (<45μm). The agglomerates are not fully broken down during the grinding, which is a significant difference from reactive aluminas that are fully ground by a batch grinding process. Calcined aluminas are classified by soda content, particle size and degree of calcination. Ground and fine-ground calcined aluminas are used as a matrix filler to upgrade the product performance of formulations predominantly based on natural raw materials.
Calcined aluminas have a particle size similar to ground mineral aggregates and can therefore easily replace aggregates with lower purity. By increasing the overall alumina content of the mixes and improving their particle packing through the addition of fine alumina, the refractoriness and mechanical properties, such as hot modulus of rupture and abrasion resistance, are improved. The water demand of calcined aluminas is defined by the amount of residual agglomerates and the surface area. Therefore, calcined aluminas with low surface area are preferred as fillers in bricks and castables. Special calcined aluminas with higher surface area, can successfully replace clay as the plasticizer in gunning and ramming mixes. Refractory products modified by these products keep their good installation characteristics but show significantly reduced shrinkage after drying and firing.
Calcined Alumina
Calcined alumina powders are made by direct calcination of industry alumina or aluminum hydroxide at proper temperatures to transform into stable crystallineα-alumina, then grinding into micro-powders. Calcined micro- powders can be used in slide gate, nozzles, and alumina bricks. In addition, they can be used in castables with silica fume and reactive alumina powders, to reduce water addition, porosity and to increase strength, volume stability.
Calcined Aluminas for Refractories
Due to the excellent high temperature properties of a-Alumina, Calcined Aluminas are used in many refractory applications, both in monolithic and shaped products.
Product Performance
Depending on the degree of milling and crystal size, Calcined Aluminas serve a variety of different functions in refractory formulations.
Most important are:
• Upgrade product performance by increasing overall Alumina content of these formulations using natural raw materials in order to improve refractoriness and mechanical properties.
• Improve particle packing by increasing the amount of fine particles resulting in better mechanical strength and abrasion resistance.
• Form a matrix of high refractoriness and good thermal shock resistance by reacting with binder components like Calcium Aluminate Cement and / or clays.
