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(12) United States Patent (10) Patent No.: US 7,700,202 B2 Easler Et Al

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(12) United States Patent (10) Patent No.: US 7,700,202 B2 Easler Et Al US007700202B2 (12) United States Patent (10) Patent No.: US 7,700,202 B2 Easler et al. (45) Date of Patent: Apr. 20, 2010 (54) PRECURSOR FORMULATION OF A SILICON 6,261,509 B1 7/2001 Barnard et al. CARBDE MATERAL 2005/0205798 A1* 9/2005 Downing et al. ....... 250,390.11 (75) Inventors: Timothy E. Easler, San Diego, CA (US); Andrew Szweda, San Deigo, CA FOREIGN PATENT DOCUMENTS (US); Eric Stein, Poway, CA (US) JP 2000-1551.89 * 11/1999 (73) Assignee: Alliant Techsystems Inc., Minneapolis, MN (US) (*) Notice: Subject to any disclaimer, the term of this OTHER PUBLICATIONS patent is extended or adjusted under 35 Pramono et al. (“Helium Release and Physical property Change of U.S.C. 154(b) by 259 days. Neutron Irradiated alpha-SiC Containing B4C of Different 10B con centrations'), Journal of Nuclear Science and Technology, vol. 40, (21) Appl. No.: 11/357,716 No. 7, p. 531-536 (Jul 2003).* Phelps et al. (“Step Bunching Fabrication Constraints in Silicon (22) Filed: Feb. 16, 2006 Carbide'). Semiconductor Science and Technology, vol. 17, No. 5, (May 2002) pp. L17-L21.* (65) Prior Publication Data “New High-Performance SiC Fiber Developed for Ceramic Compos ites.” <http://www.lerc.nasa.gov/WWW/RT2001/5000/ US 2007/O189952 A1 Aug. 16, 2007 5100dicarlo 1.html>> 2001, 3 pages. (51) Int. Cl. (Continued) B32B 9/00 (2006.01) B32B 9/00 (2006.01) Primary Examiner Timothy M Speer C04B 3.5/52 (2006.01) Assistant Examiner—Jonathan C Langman C04B 3.5/56 (2006.01) (74) Attorney, Agent, or Firm TraskBritt (52) U.S. Cl. .......................... 428/698: 376/904: 501/88 (58) Field of Classification Search ................. 428/698: (57) ABSTRACT 501/92, 96.3, 96.4 See application file for complete search history. A precursor formulation of a silicon carbide material that (56) References Cited includes a ceramic material and a boron-11 compound. The ceramic material may include silicon and carbon and, option U.S. PATENT DOCUMENTS ally, oxygen, nitrogen, titanium, Zirconium, aluminum, or 3,801,447 A * 4, 1974 Heenan ...................... 376/.456 mixtures thereof. The boron-11 compound may be a boron-11 4,004,934. A * 1/1977 Prochazka ................... 501/90 isotope of boron oxide, boron hydride, boron hydroxide, 4,663,105 A 5, 1987 Sakai et al. boron carbide, boron nitride, borontrichloride, borontrifluo 4,744,922 A * 5/1988 Blakely et al. .............. 252/478 ride, boron metal, or mixtures thereof. A material for use in a 5,071,600 A 12/1991 Deleeuw et al. nuclear reactor component is also disclosed, as are Such com 5,366,943 A 1 1/1994 Lipowitz et al. ponents, as well as a method of producing the material. 5,395,783 A * 3/1995 Baumann et al. ............ 438,239 5,851,942 A 12/1998 Sacks et al. 8 Claims, 3 Drawing Sheets US 7,700,202 B2 Page 2 OTHER PUBLICATIONS com/news/newsreleasedetails.aspx?id=154, printed Jun. 3, 2009, 2 Certificate of Analysis and Conformance, Enriched Boron Oxide pageS. (11B2O3), EaglePicher Technologies, LLC., Quapaw, OK, Mar. 17. (11)B Enriched Boron Oxide Product Specification, Ceradyne, Inc., 2005, 2 pages. Document No. BP-SSSm-11B03, Feb. 21, 2008, 1 page. Ceradyne, Inc. Completes EaglePicher Boron LLC Acquisition, Ceradyne, Inc. New Release, Sep. 4, 2007. http://www.ceradyne. * cited by examiner U.S. Patent Apr. 20, 2010 Sheet 1 of 3 US 7,700,202 B2 U.S. Patent Apr. 20, 2010 Sheet 2 of 3 US 7,700,202 B2 FIG. 2 U.S. Patent Apr. 20, 2010 Sheet 3 of 3 US 7,700,202 B2 FIG. 3 ?i??i???????????????????????????????????à US 7,700,202 B2 1. 2 PRECURSORFORMULATION OF A SILICON instruments for detecting neutrons. However, 'B is unstable CARBIDE MATERAL and undergoes fission when irradiated, producing a gamma ray, an alpha particle, and a lithium ion. Therefore, when a FIELD OF THE INVENTION component formed from conventional SiC fibers is irradiated, the boron compound undergoes fission, which is accompa The present invention relates to a stable silicon carbide nied by outgassing and degradation of the SiC fibers or the (“SiC) material for use in the nuclear industry, such as in SiC bodies. As such, conventional SiC fibers are not suitable components of a nuclear reactor, as well as to Such compo for use in a component to be used in the nuclear industry, Such nents. More specifically, the present invention relates to a SiC as in a nuclear reactor. material that includes aboron-11 ("B") isotope, as well as to 10 It would be desirable to produce SiC fibers or SiC bodies a precursor and method for forming the SiC material, and that are more stable to irradiation for use in components to be components including the SiC material. used in the nuclear industry. For instance, it would be desir able to produce SiC fibers or SiC bodies that are useful in BACKGROUND OF THE INVENTION nuclear applications without outgassing or degradation. 15 SiC fibers are known in the art for providing mechanical BRIEF SUMMARY OF THE INVENTION strength at high temperatures to fibrous products, such as high temperature insulation, belting, gaskets, or curtains, or as The present invention relates to a precursor formulation of reinforcements in plastic, ceramic, or metal matrices of high a SiC material that includes a ceramic material and aboron-11 performance composite materials. To provide good mechani compound. As used herein, the term “SiC material refers to cal strength to these products or materials, the SiC fibers have SiC fibers, SiC bodies, or other forms of SiC ceramics, such a relatively high density (i.e., low residual porosity) and fine as monolithic SiC. SiC coatings, SiC thin substrates, or grain sizes. However, producing SiC fibers with these prop porous SiC ceramics. The ceramic material may include sili erties is difficult because the SiC fibers typically undergo con and carbon and, optionally, oxygen, nitrogen, titanium, coarsening or growth of crystallites and pores during a high 25 aluminum, Zirconium, or mixtures thereof. For the sake of temperature heat treatment. example only, the ceramic material may include SiC fibers, Sintering aids have been used to improve densification of silicon oxycarbide fibers, silicon carbon nitride fibers, silicon the SiC fibers and to prevent coarsening, allowing the SiC oxycarbonitride fibers, polytitanocarbosilane fibers, or mix fibers to be fabricated with high density and fine grain sizes. tures thereof. The boron-11 compound may be a boron-11 These sintering aids are typically compounds of boron. As 30 isotope of boron oxide, boron hydride, boron hydroxide, disclosed in U.S. Pat. No. 5,366,943 to Lipowitz et al., which boron carbide, boron nitride, borontrichloride, borontrifluo is incorporated by reference in its entirety herein, the SiC ride, boron metal, or mixtures thereof. The boron-11 com fibers are formed by converting amorphous ceramic fibers to pound may account for less than or equal to approximately polycrystalline SiC fibers. The ceramic fibers are heated in 2% by weight (“wt %) of a total weight of the precursor the presence of a sintering aid to produce the polycrystalline 35 formulation. Thus, while the present invention is referred to SiC fibers. The sintering aid is boron or a boron-containing for the sake of convenience in the singular as 'a' precursor compound, such as a boron oxide (“BO). An example of and “a” SiC material, it will be appreciated that a number of SiC fibers prepared by this process is SYLRAMICR), which is different SiC materials and precursors that may be used to available from COI Ceramics, Inc. (San Diego, Calif., an form a variety of materials are encompassed by the present affiliate of ATK Space Systems). 40 invention. Another method of forming SiC fibers is by spinning a The present invention also relates to a material for use in a polycarbosilane resin into green fibers, treating the green nuclear reactor component. The material includes a SiC mate fibers with boron, and curing and pyrolyzing the green fibers, rial and a boron-11 compound. The SiC material may be SiC as disclosed in U.S. Pat. No. 5,071,600 to Deleeuw et al. fibers, a SiC body, a SiC ceramic, a SiC coating, a SiC thin Other methods of forming SiC fibers are known, such as 45 Substrate, or a porous SiC ceramic. The boron-11 compound spinning organosilicon polymers into fibers, curing the fibers, may be one of the compounds previously described. The and ceramifying the fibers at elevated temperatures. However, boron-11 compound may account for from approximately 0.1 many of these methods undesirably introduce oxygen or wt % of a total weight of the material to approximately 4 wt % nitrogen into the SiC fibers. When these SiC fibers are heated of the total weight of the material. A layer of boron nitride that to temperatures above 1400° C., the oxygen or nitrogen is 50 includes the 'Bisotope (''BN”) may, optionally, be present Volatilized, causing weight loss, porosity, and decreased ten on a Surface of the material. sile strength in the SiC fibers. In addition to SiC fibers, SiC The present invention also relates to a method of producing bodies are known to be formed by molding SiC powder and a SiC material by converting a ceramic material to a SiC elemental carbon into a desired shape and heating the molded material in the presence of a boron-11 compound. The structure in a boron-containing environment. 55 ceramic material may be converted by heating the ceramic While many methods of producing SiC fibers (or SiC bod material in an environment that includes the boron-11 com ies) are known, components or products formed from con pound.
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