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Title: Oxidized Metal Powders for Mechanical Shock and Crush Safety Enhancers

Abstract

The use of oxidized metal powders in mechanical shock or crush safety enhancers in nuclear weapons has been investigated. The functioning of these devices is based on the remarkable electrical behavior of compacts of certain oxidized metal powders when subjected to compressive stress. For example, the low voltage resistivity of a compact of oxidized tantalum powder was found to decrease by over six orders of magnitude during compaction between 1 MPa, where the thin, insulating oxide coatings on the particles are intact, to 10 MPa, where the oxide coatings have broken down along a chain of particles spanning the electrodes. In this work, the behavior of tantalum and aluminum powders was investigated. The low voltage resistivity during compaction of powders oxidized under various conditions was measured and compared. In addition, the resistivity at higher voltages and the dielectric breakdown strength during compaction were also measured. A key finding was that significant changes in the electrical properties persist after the removal of the stress so that a mechanical shock enhancer is feasible. This was verified by preliminary shock experiments. Finally, conceptual designs for both types of enhancers are presented.

Authors:
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
793313
Report Number(s):
SAND2002-0159
TRN: US200207%%95
DOE Contract Number:
AC04-94AL85000
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 1 Jan 2002
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE; ALUMINIUM; BREAKDOWN; COATINGS; DIELECTRIC MATERIALS; ELECTRICAL PROPERTIES; ELECTRODES; NUCLEAR WEAPONS; OXIDES; REMOVAL; SAFETY; TANTALUM

Citation Formats

GARINO, TERRY J. Oxidized Metal Powders for Mechanical Shock and Crush Safety Enhancers. United States: N. p., 2002. Web. doi:10.2172/793313.
GARINO, TERRY J. Oxidized Metal Powders for Mechanical Shock and Crush Safety Enhancers. United States. doi:10.2172/793313.
GARINO, TERRY J. Tue . "Oxidized Metal Powders for Mechanical Shock and Crush Safety Enhancers". United States. doi:10.2172/793313. https://www.osti.gov/servlets/purl/793313.
@article{osti_793313,
title = {Oxidized Metal Powders for Mechanical Shock and Crush Safety Enhancers},
author = {GARINO, TERRY J.},
abstractNote = {The use of oxidized metal powders in mechanical shock or crush safety enhancers in nuclear weapons has been investigated. The functioning of these devices is based on the remarkable electrical behavior of compacts of certain oxidized metal powders when subjected to compressive stress. For example, the low voltage resistivity of a compact of oxidized tantalum powder was found to decrease by over six orders of magnitude during compaction between 1 MPa, where the thin, insulating oxide coatings on the particles are intact, to 10 MPa, where the oxide coatings have broken down along a chain of particles spanning the electrodes. In this work, the behavior of tantalum and aluminum powders was investigated. The low voltage resistivity during compaction of powders oxidized under various conditions was measured and compared. In addition, the resistivity at higher voltages and the dielectric breakdown strength during compaction were also measured. A key finding was that significant changes in the electrical properties persist after the removal of the stress so that a mechanical shock enhancer is feasible. This was verified by preliminary shock experiments. Finally, conceptual designs for both types of enhancers are presented.},
doi = {10.2172/793313},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Jan 01 00:00:00 EST 2002},
month = {Tue Jan 01 00:00:00 EST 2002}
}

Technical Report:

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  • Temperature is notably the most difficult quantity to measure in shock compression experiments; however, it is critical for accurately constraining theoretical or tabular equations of state. Until now, the temperature achieved during the shock loading of porous materials could only be calculated. The technique presented in this report measures, for the first time, the shocked temperature of porous systems.
  • This investigation was undertaken primarily to obtain information concerning the chemical and structural homogeneity of mechanically alloyed powders and to determine under what conditions, if any, true solid solutions may be formed. Four different alloy systems were selected for study: (1) 50 w/o Cr - 50 w/o Mo, (2) Type 316 stainless steel, (3) 20.8 w/o Mn - 79.2 w/o Bi, and (4) a Beta-Ti alloy (Ti-11Cr-8Mn-5Mo-3Al). In both the Cr-Mo system and Type 316 stainless steel system, it was established by x-ray diffraction methods that the elemental components had become interdispersed on an atomic scale as a result ofmore » high-energy milling, but that a minimum threshold speed is necessary to obtain a significant degree of alloying. However, annealing studies on the milled powders provided strong indications that the solid solutions formed by mechanical alloying are very inhomogeneous from a chemical and structural point of view. Milling difficulties were encountered with the Beta-Ti and Bi-Mn powder systems which precluded any conclusions pertaining to structural or chemical homogeneity in these systems.« less
  • Following the results presented at the Second International Symposium on Power from Radioisotopes [Madrid, 29th May-1st June 1973] the present report describes the various tests: crush and internal pressures resistance of the radioisotopic sources as well as cremation at 1300 deg C (3370 deg F) performed on the sources, the thermoelectric batteries and the whole cardiac pacemaker.
  • Methods of obtaining essentially oxide-free powders Here evaluated by oxygen analyses, tensile tests, and microstructures of specimens made from reduced powders. The three techniques that effectively lowered the oxygen content of as-received powders at 1800 to 2150 deg F in a hydrogan atmosphere were tumbling the powder in a rotary furnace. heating with sodium hydride, and heating with carbon. Microstructures and tensile properties of several specimens made from rednced powder by pressing, sintering, and hot-swaging were nearly equivalent to those of wrought material. No consistent correlation existed between tensile properties and residual-oxygen content. (auth)
  • Carbon, hydrogen, and hydrogen plus carbon reduction of three oxidized nickel-base alloy powders (a solid solution strengthened alloy both with and without the gamma prime formers aluminum and titanium and the solid solution strengthened alloy NiCrAlY) were evaluated by thermogravimetry. Hydrogen and hydrogen plus carbon were completely effective in reducing an alloy containing chromium, columbium, tantalum, molybdenum, and tungsten. However, with aluminum and titanium present the reduction was limited to a weight loss of about 81 percent. Carbon alone was not effective in reducing any of the alloys, and none of the reducing conditions were effective for use with NiCrAlY.more » (Author) (GRA)« less