BORON-SILICON-CARBON CERAMIC MATERIALS AND METHOD OF MAKING
A reaction bonded ceramic body that has 50% to 60%, by weight, boron carbide, and 20% to 30%, by weight, silicon carbide. The reaction bonded ceramic body has least a portion of the boron carbide reacted with silicon to become siliconized boron carbide. Also, a method of making a reaction bonded ceramic material. The method may include the steps of forming a green body from a mixture of boron carbide, carbon, and an organic binder, and contacting the green body with a liquid infiltrant comprising silicon. The infiltrant has a temperature of about 1625° C. to about 1700° C. Furthermore, a method of making a reaction bonded boron carbide ceramic body. The method includes the steps of forming a green body from a mixture of boron carbide, carbon, and an organic binder. The weight ratio of boron carbide to carbon in the green body may be about 5:5 to 1 or more. The method also includes siliconizing a first portion of the boron carbide to siliconized boron carbide by contacting the green body with a molten silicon infiltrant, where the infiltrant has a temperature of about 1625° C. to about 1700° C. The method may further include dissolving a second portion of the boron carbide in the silicon infiltrant, where at least some of the dissolved boron carbide is reprecipated as smooth particulates.
1 . A reaction bonded ceramic body comprising:
50% to 60%, by weight, boron carbide; and
20% to 30%, by weight, silicon carbide;
wherein at least a portion of the boron carbide has reacted with silicon to become siliconized boron carbide.
2 . The reaction bonded ceramic body of claim 1 , wherein the body comprises at least 10%, by wt., of the siliconized boron carbide.
3 . The reaction bonded ceramic body of claim 1 , wherein the body comprises at least 50%, by wt., of the siliconized boron carbide.
4 . The reaction bonded ceramic body of claim 1 , wherein the body comprises about 10% to 20%, by weight silicon.
5 . The reaction bonded ceramic body of claim 1 , wherein the ceramic body has a fracture toughness of about 3.5 MPa-m 1/2 or more.
6 . The reaction bonded ceramic body of claim 1 , wherein the ceramic body has a fracture toughness of greater than 5 MPa-m 1/2 .
7 . The reaction bonded ceramic body of claim 1 , wherein the ceramic body has a fracture toughness of about 6 MPa-m 1/2 or more.
8 . The reaction bonded ceramic body of claim 1 , wherein the ceramic body has a flexural strength of about 180 MPa or more.
9 . The reaction bonded ceramic body of claim 1 , wherein the ceramic body has a flexural strength of about 200 MPa or more.
10 . The reaction bonded ceramic body of claim 1 , wherein the ceramic body has a flexural strength of about 280 MPa or more.
11 . The reaction bonded ceramic body of claim 1 , wherein at least 10%, by wt., of the silicon carbide is β-SiC.
12 . The reaction bonded ceramic body of claim 1 , wherein at least 50%, by wt., of the silicon carbide is β-SiC.
13 . The reaction bonded ceramic body of claim 1 , wherein less than 50%, by wt., of the silicon carbide is α-SiC.
14 . The reaction bonded ceramic body of claim 1 , wherein less than 20%, by wt., of the silicon carbide is α-SiC.
15 . A method of making a reaction bonded ceramic material, the method comprising:
forming a green body from a mixture of boron carbide, carbon, and an organic binder; and
contacting the green body with a liquid infiltrant comprising silicon, wherein the infiltrant has a temperature of about 1625° C. to about 1700° C.
16 . The method of claim 15 , wherein the infiltrant contacts the green body in a low-pressure atmosphere having a pressure of about 100 mTorr or less.
17 . The method of claim 15 , wherein the green body comprises:
80% to 90%, by weight, boron carbide;
10% to 20%, by weight, free carbon.
18 . The method of claim 17 , wherein the free carbon comprises an organic binder.
19 . The method of claim 17 , wherein the free carbon comprises graphite.
20 . A method of making a reaction bonded boron carbide ceramic body, the method comprising:
forming a green body from a mixture of boron carbide, carbon, and an organic binder, wherein the weight ratio of boron carbide to carbon in the green body is about 5:5 to 1 or more;
siliconizing a first portion of the boron carbide to siliconized boron carbide by contacting the green body with a molten silicon infiltrant, wherein the infiltrant has a temperature of about 1625° C. to about 1700° C.; and
dissolving a second portion of the boron carbide in the silicon infiltrant, wherein at least some of the dissolved boron carbide is reprecipated as smooth particulates.
21 . The method of claim 20 , wherein the siliconzed boron carbide comprises B 12 C 2 Si, wherein a silicon atom replaces one of the carbon atoms in the carbon backbone of the boron carbide.
22 . The method of claim 21 , wherein the silicon atom replaces a middle carbon atom in the carbon backbone.
23 . The method of claim 20 , wherein the siliconzed boron carbide comprises B 12 CSi 2 , wherein two silicon atoms replace two carbon atoms in the carbon backbone of boron carbide.
24 . The method of claim 20 , wherein the smooth particulates of reprecipitated boron carbide lack a sharp edge.
25 . The method of claim 20 , wherein the smooth particulates of reprecipitated boron carbide are substantially spherical.
26 . The method of claim 20 , wherein the green body comprises about 85%, by wt., boron carbide and about 15%, by wt., carbon.
27 . The method of claim 20 , wherein the reaction bonded boron carbide ceramic body comprises less than 10%, by wt., unsiliconized boron carbide.
28 . The method of claim 20 , wherein the reaction bonded boron carbide ceramic body comprises more than 10%, by wt., silicon.
29 . The method of claim 20 , wherein the reaction bonded boron carbide ceramic body comprises more than 20%, by wt., silicon carbide.
30 . The method of claim 29 , wherein at least a portion of the silicon carbide is β-SiC.
31 . The method of claim 20 , wherein the reaction bonded boron carbide ceramic body comprises:
about 9.3%, by wt., unsiliconized boron carbide;
about 22.5%, by wt., silicon carbide; and
about 10.9%, by wt., silicon metal.