Ballistic-resistant glass-ceramic and method of preparation

• US 4,473,653 A
• Filed: 08/16/1982
• Issued: 09/25/1984
• Est. Priority Date: 08/16/1982
• Status: Expired due to Fees

• Current Assignee: Boris L. Rudoi
• Original Assignee: Boris L. Rudoi
• Inventors: Rudoi, Boris L.
• Primary Examiner(s): McCarthy, Helen M.
• Application Number:
  US06/408,114
• Time in Patent Office: 771 Days
• Field of Search: 501/4, 501/7, 501/5, 501/10, 65/33, 65/134, 2/2.5, 428/911, 428/432
• US Class Current: 501/4
• CPC Class Codes: C03C 10/0027 containing SiO2, Al2O3, Li2O as main constituents
• CPC Class Codes: C03C 10/0045 containing SiO2, Al2O3 and MgO as main constituents
• CPC Class Codes: Y10S 428/911 Penetration resistant layer

Abstract

A composition and method of making a high strength semi-crystalline ceramic material of the lithium, aluminum, silicon oxides system type. The composition is characterized by a relatively narrow range of lithium, aluminum, silicon and potassium oxides to form a base glass batch and is modified by including a novel proportional combination of the catalysts or modifiers comprising the components TiO₂, ZrO₂ and SnO₂ and including one or more additives taken from a group consisting of B₂ O₃, MgO, Cr₂ O₃, CeO₂, V₂ O₅ and Na₂ O within specific percentage ranges.

The composition is formed and subjected to heat treatment within certain time and temperature steps to provide for the desired degree, size and type of crystalline formation (lithium disilicate, cristobalite, spinel) which exhibits the desired physical, mechanical and chemical properties which include a superior resistance to high speed projectiles for armor applications.

Claims

1. A semicrystalline ballistic-resistant glass-ceramic body having a plurality of fine-grained, randomly oriented inorganic crystals substantially uniformly dispersed in a glassy phase said crystals being formed by crystallization in situ from a glass body made from a base glass forming batch having a composition consisting essentially of by weight on an oxide basis:

78.5%-84.5% SiO₂, 9.5%-15% Li₂ O, 1%-6% Al₂ O₃ and 1.5%-4% K₂ O in a combination totaling 100% of the base glass batch and further including, on a weight basis calculated as a percentage of the total weight of said base glass batch, a combination of the group consisting of TiO₂, ZrO₂ and SnO₂ wherein the total of said combination of said group is not more than 5% and the weight ratio between them is approximately 3;

2;

1 respectively; and

including MgO between the range of 30% to approximately 50% of the amount of Al₂ O₃ on a weight basis in the composition and wherein the body is characterized by having lithium disilicate, cristobalite and spinel as the primary crystalline phases, a coefficient of thermal expansion which ranges from about 100 to 125×

10^-7 /°

C. (up to 800°

C.) and a density which ranges from about 2.45 to 2.50 gms/cc.

2. The semi-crystalline glass-ceramic body defined in claim 1 further including one or more oxides from the group consisting of 0-3.5% Na₂ O;

0-1.2% B₂ O₃ ;

0-1.5% CeO₂ ;

0-0.9% Cr₂ O₃ and wherein the total of Na₂ O and K₂ O is less than about 5%.

3. The semi-crystalline glass-ceramic body defined in claim 1 wherein the base glass composition consists essentially of the following percentages of components by weight on an oxide basis:

81.0-83.0% SiO₂ ;

11.0-13.0% Li₂ O;

1.5-4.0% Al₂ O₃ ;

1.5-3.0% K₂ O.

4. A method of making a semi-crystalline ballistic-resistant glass-ceramic body which comprises forming a molten body of glass consisting essentially of a base glass batch of the following components by weight percent, 78.5 to 84.5% SiO₂ ;

9.5 to 15% Li₂ O;

1 to 6% Al₂ O₃ ;

1.5 to 4% K₂ O, the sum of which totaling at least approximately between 95 to 97.5% of the total composition which also includes the combination of the group consisting of TiO₂, ZrO₂ and SnO₂ wherein the total of said combination of said group is not more than 5% on a weight basis as a percentage of the total weight of said base glass batch and the weight ratio of said group members relative to each other is 3;

2;

1, respectively; and

including MgO in the range between 30% to approximately 50% of the amount of Al₂ O₃ on a weight basis in the composition;

forming said molten body into a solid glass body;

then heating said solid body up to a temperature between 480-530 degrees centigrade and holding said temperature for a time period between approximately one to twenty-four hours for annealing purposes before cooling said body to room temperature;

then heating said annealed glass body up to approximately 480 to 530 degrees centigrade at a rate between approximately 1 to 5 degrees centigrade per minute, then continue heating said body at a rate between approximately 0.3 to 1.0 degrees centigrade to a temperature between 680 to 725 degrees centigrade and holding said temperature between said 680 to 725 degree centigrade range for a time period between approximately one-half to twenty-four hours;

then continuing to heat said body at a rate of temperature increase of 0.5 to 6 degrees centigrade until the temperature of said body reaches approximately 830 to 870 degrees centigrade, then holding said body within the last mentioned temperature range for approximately 5 minutes to 5 hours;

then cooling said body at a rate of approximately 0.5 degrees to 3 degrees centrigrade per minute to approximately 380-300 degrees centigrade;

then cooling is continued at a cooling rate of approximately 2 to 12 degrees centigrade per minute to room temperature and wherein the body is characterized by having lithium disilicate, cristobalite and spinel as the primary crystalline phases, a coefficient of thermal expansion which ranges from about 100 to 125×

10^-7 /°

C. (up to 800°

C.) and a density which ranges from about 2.45 to 2.50 gms/cc.