Title page for ETD etd-09132005-115831


Document Type Master's Dissertation
Author Ricco, Isabel Maria Moreira
URN etd-09132005-115831
Document Title Alternative oxidants and processing procedures for pyrotechnic time delays
Degree MEng (Chemical Engineering)
Department Chemical Engineering
Supervisor
Advisor Name Title
Prof W Focke
Keywords
  • detonator
  • antimony trioxide
  • lead chromate
  • silicon
  • burn speed
  • copper antimonite
  • time delay
  • pyrotechnic
Date 2004-12-12
Availability unrestricted
Abstract
This study was directed at the pyrotechnic time delay compositions that are used in detonator assemblies. The objectives were to:

--Investigate effective alternatives for the barium and lead-based oxidants currently used, maintaining the use of silicon as fuel

--Develop easy to use, realistic measurement techniques for burn rates and shock tube ignitability

--Determine the variables that affect burn rate, and

--Evaluate alternative processing routes to facilitate intimate mixing of the component powders.

Lead chromate and copper antimonite were found to be suitable oxidants for silicon in time delay compositions. They were ignitable by shock tubing, a relatively weak ignition source. The measured burn speeds for these systems showed a bimodal dependence on stoichiometry. Measured burn rates varied between 6-28 mm/s. Lead chromate is potentially a suitable alternative to the oxidant currently used in the medium burn rate commercial composition. It burns faster than copper antimonite. The latter is potentially a suitable replacement oxidant for the slow and medium compositions.

Antimony trioxide-based compositions exhibited unreliable performance with respect to ignition with shock tubing.

The addition of aluminium powder or fumed silica was found to reduce the burn rate. Increasing the silicon particle size (<3,5mm) also decreased the burn speed for copper antimonite and lead chromate compositions. Addition of fumed silica improved the flow properties of the lead chromate, copper antimonite and antimony trioxide powders allowing for easier mixing.

The silicon powder was found to react violently with water in alkaline solutions. This makes particle dispersion in a wet-mixing process problematic.

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