Hollow corundum microspheres

The Hollow Corundum Microspheres (HCM) are made of aluminum oxide with purity of 99.6%, has a round shape with wide surface,

particle size from 5 to 180 microns, density from 0.8 to 2.0 gram per cm3, refractoriness 1800 °C and cold crushing

strength from 40 to 120 MPa.

In the photos taken by an optic and an electron microscope is visible a wide surface of HCM, a particle size and the crashing

walls of the HCM.

Main proporties of Hollow Corundum Microspheres:

Surface of the HCM is like an orange – it is very wide (to compare with glass bubble). The mix of big- and small-sized (160 microns and 20 microns) HCM and standard

grains of the fuzed white or red Al2O3 can help to obtain a porose matrix in filters or high porose grinding wheels with a pore size less than 0.1-10 microns.

Porose matrix for ceramic products

Pink alumina grain and HCM, small and big Grain and HCM_normal_normal Pink alumina grain and HCM, big and small size Bifractal dictribution of hollow corundum microspheres

An example of different distribution of alumina grains and HCM particles. Ceramics with a mix of big HCMs and small alumina grains and a mix of small HCMs and big

alumina grains will have absolutely different mechanical properties and porosity. Moreover, it is possible to gain other properties using a bifractal mix of big and small HCM.

Hollow Corundum Microspheres sized up to 180 microns which have a crush strength from 40 to 120 MPa allow to make the final products – for example, during producing

a crucibles, casting molds for molding or grinding wheels produced by isostatic or hot isostatic pressing the microspheres will not be crushed.

The final products with the addition of the microspheres obtain the low density, the low-heat-conductivity and the high mechanical crush strength.

By the spherical shape of microspheres the final product with HCM like ceramic crucibles, casting molds, grinding wheels or ceramic filters will have minimum reduction of blank

volumetric deformation while drying and sintering. Addition of 5-20% of the Hollow Corundum Microspheres allows to lower reduction of blank volumetric deformation after

sintering in 2-3 times in comparison with conventional materials.

Main application of HCM:

Type of Hollow Corundum Microspheres (HCM):

Analysis

Unit

HCM-S

HCM-L

Size

μm

5-100

70-180

Al2O3

%

99,7

Fe2O3

%

0,003

CaO

%

0,01

SiO2

%

0,025

Na2O

%

0,26

LOI

%

0,48

Bulk density

g/cm3

1.6-1.9