What are the properties of cenosphere products?

Cenosphere source will influence the eventual product properties including chemical composition, colour, particle size distribution, and particle density distribution. Processing will generally eliminate any important differences so that products are remarkable consistent.

The properties of both Tecfil grades is presented in the table bellow:

Physical Properties of Dirk Tecfil™

 

T 300

T 150

Particle size range

microns

5 - 300

5 - 150

Average size (approx)

microns

120

110

True particle density (S.G)

gm / cc

0.60 - 0.65

Bulk density

Kg /m3

370- 450

Particle form

 

Hollow Spheres

Colour

Grey

 

Hardness

mohs

5 - 6

K value

Wm-1 deg C-1

0.11

pH in water

 

6 - 8

Melting point

0C

1250

Sintering point

0C

900

Internal pressure

atmospheres

0.2

Physical properties: Under an optical microscope, the appearance is of shiny, colourless spheres relatively close in size. Some darker spheres with iron impurities occur, the proportion varying with source.

Electron microscopy reveals most of the particles as near-perfect spheres. A few are disfigured by blisters possibly pfa particles fused on to the surface of gas bubbles formed within the shell. Each individual size fraction exhibits a remarkably consistent average particle density, demonstrating that average wall thickness as a percentage of sphere diameter is essentially independent of particle size.

Comparisons are made with synthetic hollow glass spheres. Cenospheres are darker in colour and have a higher density. Their thicker walls result in higher crushing strengths so that cenospheres can be used in applications where synthetic spheres would break. Cenospheres also have a higher softening temperature - about 1,200oC compared with 600oC for the borosilicate glass, most commonly used in synthetic spheres.

Commercial grades: Properties of finished product grades reflect the raw material properties and the degree of processing. Most attention is paid in processing to accurate control of maximum particle size. Because of the low proportion of small diameter spheres in the raw material and the difficulty of extraction, yields of fine grades are low and such fine grades are consequently expensive.

While normal grades are centred around average particle densities of 0.7 kilograms per litre, specialist grades with lower densities such as 0.5 kg/l and 0.3 kg/l may be produced.