Methods for making aluminum nitride armor bodies

Abstract

A method of making aluminum nitride armor bodies is provided. The method starts with low cost bulk raw material, in the form of aluminum or aluminum alloy, cryogenically mills the raw material into a precursor powder, which is essentially free of oxides and other undesirable impurities. The precursor powder is formed into a pre-form using low cost, short residence time molding processes. Finally, the pre-form is exposed to a nitriding process to convert the pre-form into the aluminum nitride armor body. In this manner, the method avoids the use of high cost aluminum nitride as a starting material and avoids the need for the high cost, single axis densification processes of the prior art.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application Ser. No. 61 / 406,801, filed Oct. 26, 2010, the contents of which are incorporated by reference herein in their entirety.BACKGROUND OF THE DISCLOSURE[0002]1. Field of the Disclosure[0003]The present disclosure relates to armor bodies such as, but not limited to, plates, bar shapes, and / or complex structures. More particularly, the present disclosure is related to methods for producing a low cost, high efficiency, high yield aluminum nitride material and forming armor bodies therefrom.[0004]2. Description of Related Art[0005]Armor bodies are often assembled into a protective panel or system, which have been used to protect buildings, vehicles (air, land, or water), and people from projectiles. When used to protect buildings, people, and vehicles, the armor plates have been made from variety of materials such as metal, ceramic, fiber composite, glass, and others materials.[00...

AI Technical Summary

Benefits of technology

[0021]The process in some embodiments of the present disclosure includes placing the aluminum into a grinding mill equipped with a center line powered shaft having a multitude of orthogonal bars, preferably made of or coated with or shielded with ceramics. Typically, the mill will be filled up to about 50% or more of its volume with each media and aluminum, to a level covering the upper bar. Then, liquid nitrogen will be poured in and the mill will be covered. Some of the nitrogen will sublime, further lowering the temperature of the liquid. Upon addition of the liquid nitrogen, the materials will to some degree thermal shock and upon rotation of the shaft, the thermal shock and transition from ductile to brittle materials will provide very quick attrition of the aluminum. Typically, the shaft will rotate between 50 and 400 RPM.

[0022]Advantageously, during the milling according to the present disclosure, the energy in the mill, or the attrition zone, is very low at the circumference and at the center of the mill near the shaft. Most of the attrition and energy is found in the middle of the orthogonal bars. In this case since the shaft, in a preferred embodiment the orthogonal shafts will be metal fitted with zirconia or silicon nitride covers, never comes into anything with strength, hardness or fracture toughness exceeding th

Problems solved by technology

Thus, the process of the present disclosure results in an aluminum nitride body, which starts with pure aluminum or aluminum alloy powder and lacks the expensive high temperature, high pressure densification process of the prior art.

Because the bonds created by

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