| 摘要 |
An object made of a glass which changes size continuously when submitted to increasing corpuscular radiation only up to a certain limiting dose of radiation, is treated with radiation of an intensity to produce such a dose of radiation at the surface. This produces a compression or tension near the surface with a corresponding tension or compression within the article according as the glass expands or contracts under irradiation. The irradiation may be effected by electrons, protons, deuterons, tritons, alpha particles, nuclei of lithium or other elements, or neutrons. The particles may be accelerated or originate in nuclear reactions. The glass may contain an element such as boron or lithium which undergoes, under neutron bombardment, nuclear transformation with the emission of energetic particles. The natural boron may be enriched with boron 10, or the natural lithium with lithium 6. Glasses which expand when irradiated may contain:- .SiO2.10-70% .Al2O3.0-20% .B2O3.0-50% .Li2O+Na2O+K2O.0-30% .MgO+CaO+SrO+BaO.0-30% .PbO.0-85%, such that SiO2+B2O3+Al2O3 < 85%, M2O+MO+PbO > 15%, and the content of B2O3, when present, is above 10% and of Li2O, when present, is above 10%, M2 and M representing alkali and alkaline earth metals respectively. An example of such a composition is:- .SiO2.47% .B2O3.20% .PbO.9.5% .Li2O.23.5% Glasses which contract when irradiated may contain:- .SiO2.50-99% .Al2O3.0-20% .B2O3.0-50% .Li2O+Na2O+K2O.0-20% .MgO+CaO+SrO+BaO.0-30% .PbO.0-20% such that SiO2+B2O3+Al2O3 > 75% M2O + MO + PbO 0-25%, and the content of B2O3, when present, is above 1% and of Li2O, when present, is above 10%. An example of such a composition is:- .SiO2.80% .B2O3.4.3% .K2O.1% .Na2O.14.7% The irradiation treatment may be applied to modify the stresses existing in tempered glass. |
