High purity sintered tabular corundum material fine powder 180mesh

High purity sintered tabular corundum material fine powder 180mesh

• A pelletizer is used to form balls from fine calcined alumina continuously ground to maximise the green strength and forming capability of the alumina.

Use of an organic binder gives temporary cohesion. The addition of boron is possible to reduce soda during heating.

• The balls are dried before being loaded into the kiln. The key stage is the continuous sintering of the balls, with diameter from 6-26mm, at very high temperatures. In a 9m high vertical shaft kiln, for example, equipped with gas burners, temperatures can exceed 1900°C in the hottest zone. 

The balls take 15 hours to descend through the furnace, following a heating and cooling cycle.

After sintering the balls have low residual porosity because they have shrunk by 20%. 

• They are then crushed, ground, iron is removed magnetically, and finally screened into a range of grain size distributions from 45?m to 10mm.

• Tabular alumina is made up of grains of alpha alumina with a diameter of 50 to 300 ?m, formed by crystalline growth during sintering.

• It is dense, >3.55g/cm-3, and only slightly porous, < 5%.

• Its spherical porosity is mainly closed - water absorption: 1.5% - preventing cracks from spreading.

High purity tabular alumina can be produced (99.8% Al2O3, Na2O < 1000 ppm) aided by the absence of non-volatile mineral additions in the preparation of green balls. 

It is therefore very refractory and not subject to high temperature creep. 

? Chemical inertness – resistant to most alkalis and mineral acids

? High-density

? Low water absorption

? Extreme hardness

? High thermal conductivity

? Good resistance to thermal and mechanical shock

? High heat capacity

? High electrical resistance

? Excellent abrasion resistance