Auxiliary Materials for High Borosilicate Glass Tubes
Generally, it includes clarifier, colorant, decolorizer, opacifier, flux and so on.
(1) Clarifier: When glass is melted, gas is decomposed to expel bubbles from glass melt. There are white arsenic, antimony oxide, nitrate, sodium antimonate, mirabilite and so on.
(2) Colouring agent: to make glass have various colors, usually transition metals such as Co, Ni, Mn, Cr, Cu, Fe, CdS, CdSe and Se, Au, Ag, etc.
(3) Decolorizing agents: chemical and physical decolorization. Chemical decolorization is the addition of oxidants to oxidize colored compounds into colorless or light colors. Physical decolorization is based on the principle of complementary color, adding colorants to offset the color of impurities such as FeO, Fe2O3, Cr2O3, and titanium dioxide. If iron oxide makes glass green, the colouring power will be weakened when nitrate and cerium oxide are added to oxidize iron to a high price. Se, Co, Ni and Mn can also be added to produce red-purple color, which is complementary to the blue-green color of Fe compound, but reduces the light transmittance.
(4) Emulsifier: When glass is cooled, it precipitates dense crystals, which scatters light and is opaque. Fluoride such as crystal, sodium fluosilicate and phosphate such as calcium phosphate are commonly used.
