CHEMICALLY STRENGTHENED LITHIUM ALUMINOSILICATE GLASS HAVING HIGH STRENGTH EFFECTIVE TO RESIST FRACTURE UPON FLEXING FROM IMPACT OF HIGH VELOCITY PROJECTILES

• Main Authors: SPINELLI IAN M, VARSHNEYA ARUN K
• Format: Patent
• Language: English
• Published: 15.03.2007
• Subjects: ARMOUR; ARMOURED OR ARMED VEHICLES; ARMOURED TURRETS; BLASTING; CHEMICAL COMPOSITION OF GLASSES, GLAZES, OR VITREOUSENAMELS; CHEMISTRY; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GLASS; HEATING; JOINING GLASS TO GLASS OR OTHER MATERIALS; LAYERED PRODUCTS; LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT ORNON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM; LIGHTING; MEANS OF ATTACK OR DEFENCE, e.g. CAMOUFLAGE, IN GENERAL; MECHANICAL ENGINEERING; METALLURGY; MINERAL OR SLAG WOOL; PERFORMING OPERATIONS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS,MINERALS OR SLAGS; SURFACE TREATMENT OF GLASS; TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION; TECHNICAL SUBJECTS COVERED BY FORMER USPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS; TRANSPORTING; WEAPONS

Chemically strengthened lithium aluminosilicate glass is characterized by a surface compression of at least 100,000 psi and a compression case depth of at least 600 microns. The glass also may be characterized by a compression at 50 microns below a surface of the glass that is at least 30,000 psi. A method of making this glass includes providing a lithium aluminosilicate glass having a composition comprising (in weight %): Li2O in an amount ranging from 3 to 9%, Na2O+K2O in an amount not greater than 3%, and Al2O3 in an amount ranging from 7 to 30%. The composition provides the glass with an annealing point temperature of at least 580° C. A mixed potassium and sodium salt bath is provided comprising predominantly potassium salt. A ratio of moles of sodium salt to moles of potassium salt in the mixed salt bath can range from 1:10 to 1:2. The temperature of the salt bath is maintained in a range of 450° C. up to an annealing point temperature of the glass. The glass is immersed in the salt bath for a period ranging from 2 to 96 hours. The inventive glass has high strength effective to resist fracture upon flexing from impact of high velocity projectiles and includes: bullet-resistant glass, blast-resistant glass, glass for armored defense vehicles, windows for government buildings, windows for monuments, windows for vehicles, train transparencies, aircraft transparencies, hurricane-resistant windows, earthquake-resistant windows, bank teller windows, display cases, and ATM touch panels.