Opacifier
An opacifier is a substance added to a material in order to make the ensuing system opaque. An example of a chemical opacifier is titanium dioxide (TiO2), which is used as an opacifier in paints, in paper, and in plastics. It has very high refraction index (rutile modification 2.7 and anatase modification 2.55) and optimum refraction is obtained with crystals about 225 nanometers. Impurities in the crystal alter the optical properties.[1] It is also used to opacify ceramic glazes[2] and milk glass; bone ash is also used.
Opacifiers must have a refractive index (RI) substantially different from the system. Conversely, clarity may be achieved in a system by choosing components with very similar refractive indices.[3]
Glasses
Ancient milk glasses used crystals of calcium antimonate, formed in the melt from calcium present in the glass and an antimony additive. Opaque yellow glasses contained crystals of
For dental ceramics, several approaches are in use.
Opacifiers must also form small particles in the system. Opacifiers are generally inert.
X-ray opacifiers
In context of x-rays, opacifiers are additives with high absorption of x-rays; typically these are particles or compounds of lead, barium (often barium sulfate), tungsten, or other high atomic weight elements. Sometimes opacifiers are added to medical implants to make them visible under X-ray imaging. This is especially true in the case of most polymers which are often unrecognizable in the body when viewed using X-rays.
Rocket propellants
In
References
- .
- ^ Tin Oxide ( SnO2 ) Stannic Oxide – Properties and Applications, The A to Z of Materials.
- ISBN 81-203-2455-2.
- ISBN 9781135953171.
- ISBN 9781461412281.
- ^ US Army. Encyclopedia of Explosives and Related Items, vol.8