Patent Publication Number: US-8113104-B2

Title: Ceramic components with diamond coating for armor applications

Description:
This application corresponds and claims priority to co-pending Canadian Patent Application Ser. No. 2,483,231, filed Sep. 30, 2004. The priority of this prior application is expressly claimed and its disclosure is hereby incorporated by reference in its entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to ceramic and ceramic matrix composite armor systems and specifically relates to the increase of hardness of the strike face using a diamond coating on the ceramic component. 
     Ceramic armor systems require two properties to be effective in their protection against projectiles. A first aspect of ceramic armor is the hardness of the ceramic. Ceramic armor systems are effective protection against armor piercing projectiles as the hardness of the ceramic exceeds that of the metal or steel of the projectiles. 
     A second consideration is the fracture toughness of the ceramic plate. Fracture toughness is an important characteristic for the ballistic performance of ceramic armor. 
     Ideally, a ceramic armor system would have a high hardness and a high fracture toughness. 
     In current applications, the ceramics of principal interest for protection against armor piercing projectiles are boron carbide, silicon carbide and aluminum oxide (alumina). Among these ceramics, boron carbide has the highest hardness, but quite a low fracture toughness. 
     Alumina is an alternative material that is used. Alumina has a lower hardness than boron carbide but when alloyed with a second phase, creating a ceramic-ceramic phase composite, it can exhibit reasonably high fracture toughness. However, this composite is still less hard than boron carbide. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to overcome the deficiencies of the prior art by providing a diamond coating on a ceramic component. Specifically, synthetic diamond dispersed into a silicate or a phosphate based slurry can be used for coating a monolithic armor plate for either personal protection or for tiles for a vehicle protection. This coating can then be heat treated to create a bond with the ceramic component. The diamond-coated ceramic exhibits better performance against armor piercing steel core projectiles than the ceramic component on its own. 
     The present invention therefore provides an armour plate comprising a ceramic base layer having an inner surface and an outer surface, the outer surface having bonded thereto at least one layer of a composite comprising diamond powder dispersed in a substrate bonded to said outer layer of said ceramic base layer. 
     The present invention also provides a method of increasing the hardness of a ceramic component comprising the steps of fabricating a diamond powder slurry by mixing a diamond powder with a base, applying the diamond powder slurry onto a strike face of said ceramic component, and hardening diamond powder slurry to form a bond between the diamond powder slurry and the ceramic component. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be better understood with reference to the drawings in which: 
         FIG. 1  shows a side cross-sectional view of a ceramic plate coated with the diamond coating of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Passive armor has the function of defeating and/or deflecting an impacting projectile. The present invention seeks to provide increased protection against armor piercing projectiles with a steel or other hard core for both vehicle and personal body armor. The present invention may be used for other purposes, as would be appreciated by those skilled in the art, including protection shields and building protection. 
     In a preferred embodiment of the invention, as illustrated in  FIG. 1 , a ceramic component  10  is used to defeat an armor piercing projectile. In a preferred embodiment, the ceramic component is composed of aluminum oxide (Alumina), silicon carbide, or a composite made therefrom. These ceramic components have a lower hardness than boron carbide but have an increased fracture toughness. 
     In order to improve the hardness of these ceramic components, a diamond coating  15  is added over the ceramic component  10 . By coating a ceramic component  10  with a diamond coating  15 , a higher hardness than boron carbide ceramics is accomplished. 
     Synthetic diamond, preferably in the 8-15 μm particle size can be used for coating monolithic armor plates for personal protection or tiles for vehicle protection. A diamond powder is dispersed into a hardenable slurry such as a silicate or a phosphate based slurry and in a preferred embodiment is sprayed onto the strike face of a ceramic component. The preferred silicate is calcium silicate, although other silicates such as sodium silicate may be used. As will be appreciated by one skilled in the art, other materials could also be used as long as a chemical adhesive or mechanical bond is achieved between these materials and the ceramic component  10 . 
     Once the ceramic component  10  has been sprayed with the diamond powder and silicate or phosphate slurry mixture, it is then hardened. In the case of most silicate or phosphate compounds, heat-treating at between 300° and 400° F. to form a chemical bond (silicate or phosphate bonding in the preferred embodiment) with the surface of ceramic component  10  is sufficient. However, it will be appreciated that other compounds may be hardened at different temperatures or by other means such as UV. curing or chemical catalysis, as will be apparent to one skilled in the art of laminating materials. 
     In one embodiment of the present invention, diamond is mixed with a liquid base such as calcium silicate in any proportion suitable for creating a protective diamond layer on ceramic component  10 . In a preferred embodiment it has been found that 5 g of diamond powder mixed with 10 g of silicate produces the desired results. However, this is not meant to be limiting. 
     The above therefore provides a diamond coated ceramic system which exhibits higher ballistic performance against armor piercing steel core projectiles. Through diamond coating, ballistic performance of boron carbide can be achieved in terms of the hardness of the ceramic component while still having the fracture toughness of alumina or silicon carbide based ceramics. Specifically, the inventors have found that a diamond coated ceramic component such as an alumina composite can be harder than a boron carbide plate while having a fracture toughness 6 (six) times greater than boron carbide. 
     It will be appreciated that multiple layers of coating may be applied, and that additional coatings or layers of other materials such antispall coatings, or UV protective coatings, may be applied over the diamond layer. 
     The above described embodiments are meant to be illustrative of preferred embodiments and are not intended to limit the scope of the present application. Also, various modifications, which would be readily apparent to one skilled in the art, are intended to be within the scope of the present application. The only limitations to the scope of the present application are set forth in the following claims.