<PAGE>
                                                                 EXHIBIT 10(n)


                                                      Dated: September 26, 1995

                          PATENT ASSIGNMENT OF SECURITY


     WHEREAS, Nuclear Metals, Inc., a Massachusetts corporation ("Borrower"),
owns the patent and patent applications shown on the attached SCHEDULE I (the
"Patents"), for which there are recordings or applications in the United
States Patent and Trademark Office under the numbers shown on SCHEDULE I; and

     WHEREAS, pursuant to (i) a Credit Agreement dated as of March 3l, 1995
by and among the Borrower, State Street Bank and Trust Company ("Bank") and
Carolina Metals, Inc. ("CMI"), a wholly-owned subsidiary of the Borrower, as
amended by First Amendment to Credit Agreement dated as of June 30, 1995
("Amendment"); (ii) a certain letter agreement dated the date hereof by and
among the Borrower, the Bank and CMI; and (iii) a Joint Security Agreement
dated as of March 31, 1995 by and among the Borrower, the Bank and CMI, as
amended by the Amendment and the First Amendment to Joint Security Agreement
dated the date hereof (as further amended, modified, supplemented and/or
restated from time to time, the "Security Agreement"), the Borrower is
obligated to the Bank; and

     WHEREAS, pursuant to the Security Agreement, the Borrower has granted to
the Bank a security interest in the Patents, all proceeds thereof, all rights
corresponding thereto and all reissues, divisions, continuations, renewals,
extensions and continuations-in-part thereof, and the recordings and
applications therefor and applications therefor and all goodwill of the
business to which each of the Trademarks relates.

     NOW, THEREFORE, for good and valuable consideration, receipt of which is
acknowledged, the Borrower does hereby assign unto the Bank and grant to the
Bank a security interest in and to the Patents and recordings and
applications therefor, which assignment and security interest shall secure
all of the "Obligations" as defined in the Security Agreement in accordance
with terms and provisions thereof.

     The Borrower expressly acknowledges and affirms that the rights and
remedies of the Bank with respect to the assignment and security interest
granted hereby are more fully set forth in the Security Agreement.


<PAGE>

     IN WITNESS WHEREOF, the parties hereto have executed this Patent
Assignment under seal as of on the date first above written.

Dated:  Boston, Massachusetts           NUCLEAR METALS, INC.
      September 26, 1995


Witness:                           By:    /S/ JAMES M. SPIEZIO
                                      -------------------------------
                                   Name:  James M. Spiezio
                                   Title:  V.P. Finance
     /S/ FRANK S. HAMBLETT
------------------------------


Witness:                           STATE STREET BANK AND TRUST
                                     COMPANY

                                   By:    /S/ WILLIAM R. DEWEY IV
-------------------------             ------------------------------
                                   Name:  William R. Dewey IV
                                   Title:  Vice President



<PAGE>


                          COMMONWEALTH OF MASSACHUSETTS

Suffolk, ss.                                           September 26, 1995

     Then personally appeared, before me, the above-named James M. Spiezio
the V. P. Finance of Nuclear Metals, Inc. and acknowledged the foregoing
instrument to be the free act and deed of said corporation.

                                      /S/ TONI-ANN PEPPE
                                   ---------------------------------------
                                   Notary Public

                                   My Commission Expires:  May 24, 2002



                          COMMONWEALTH OF MASSACHUSETTS

Suffolk, ss.                                           September 26, 1995

     Then personally appeared, before me, the above-named William R. Dewey IV
the Vice President of State Street Bank and Trust Company and acknowledged
the foregoing instrument to be the free act and deed of said corporation.

                                      /S/ TONI-ANN PEPPE
                                   ---------------------------------------
                                   Notary Public

                                   My Commission Expires:  May 24, 2002



<PAGE>

                                                                      SCHEDULE I



     PATENT NO.             DATE OF PATENT

     4,824,478                  04/25/89

     4,837,375                  06/06/89

     5,417,778                  05/23/95

     5,421,916                  06/06/95