Investigation of Explosives

Investigation of Explosives PowerPoint PPT Presentation

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Explosives. Readily available if desire exists to createIn US it has become a weapon to criminals bent on revenge, destruction of commercial operations, or just plain mischief. Chemistry of Explosives. A chemical or mechanical action caused by combustion, accompanied by the creation of heat and the rapid expansion of gasesCharacterized by rapid rate of reaction and violent physical disruption of the surrounding environmentSudden build up of gas pressure.

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Investigation of Explosives

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1. Investigation of Explosives By Jennifer Hansen

2. Explosives Readily available if desire exists to create In US it has become a weapon to criminals bent on revenge, destruction of commercial operations, or just plain mischief

3. Chemistry of Explosives A chemical or mechanical action caused by combustion, accompanied by the creation of heat and the rapid expansion of gases Characterized by rapid rate of reaction and violent physical disruption of the surrounding environment Sudden build up of gas pressure

4. Detonation Exothermic reaction occurs so rapidly that oxygen in the air cannot participate in the reaction so many times the explosive has its own source

5. Oxidizing Agents A substance that supplies oxygen to a chemical reaction

6. Nitroglycerin Large Quantities of energy High explosive C3H5(NO2)3 When detonated by heatthe molecule decomposes with the oxygen recombining to form carbon dioxide, nitrogen, and water

7. In a small container the reaction explodes.. Shrapnel- high speed fragments of metal container of explosive

8. Outward rush of gases can.. Blast shrapnel and gases at a rate of 7,000 miles per hour This force can collapse walls, buildings, and objects in its path

9. Types of Explosives Low explosives Speed of Deflagration- very rapid oxidation reaction accompanied by the generation of a low intensity pressure wave that can disrupt the surrondings. Subsonic pressure wave High explosives Speed of detonation- extremely rapid oxidation reaction accompanied by a violent disruptive effect and an intense high speed shock wave

10. Low Explosive An explosive with a velocity of detonation less than 1,000 meters per second They produce propelling or throwing action that makes them suitable as propellants for ammunition or sky rockets

11. Black Powder Low Explosive 75% potassium Nitrate 15% Charcoal 10% Sulfur 3C+ S+ 2 KNO3? 3 CO2 + N2+ K2S Potassium Nitrate acts as the oxidizing agent.

12. Black powder is only harmful.. When confined!!

13. Safety Fuse Cord containing a core of black powder used to carry a flame at a uniform rate to an explosive charge Usually made of fabric or plastic

14. Smokeless powder Single-base An explosive consisting of nitrocellulose Nitrocellulose= nitrated cotton

15. Smokeless Power Double-base An explosive consisting of a mixture of nitrocellulose and nitroglycerin

16. Chlorate Mixtures Potassium chlorate mixed with sugar to make bomb with sulfuric acid Can also use Carbon Sulfur Starch Phosphorus Magnesium

17. Gas-Air Mixtures Natural gas can only explode within a range of air from 5.3-13.9% Too much or too little air will not allow it to combust

18. High Explosives An explosive with a velocity of detonation greater than 1,000 meters per second Examples TNT PETN RDX Dynamite Smashing or shattering effect on target

19. High Explosives Primary Explosive Ultrasensitive to heat shock or friction Detonate violently Referred to as primers Secondary Explosives Insensitive to heat, shock, or friction Military uses these TNT, PETN, RDX, tetryl

20. Dynamite Ironic that it was discovered by Alfred Nobel in 1867 Alfred Nobel is symbolic of humanities search for peace “Nobel peace prize”

21. Ammonium Nitrate Explosives For the most part have replaced dynamite Water gels, emulsions, and ANFO explosives Low cost very stable explosive Look like toothpaste with aluminum specks. Water resistant Can be derived from fertilizers

22. TATP Commonly used as a homemade device in the Middle East Acetone Hydrogen peroxide Acid catalyst like hydrochloric acid Friction and impact sensitive explosive London Bus destroyed by this explosive Reason why gels and liquids are not permitted on airplanes

23. Military High Explosives RDX most powerful and popular explosive is of a plastic dough-like consistency called composition or C-4

24. Detonating Cord A cordlike explosive containing a core of highly explosive material also called primacord

25. Detonators Blasting caps used for high explosives Electrical cap wired to a battery are also used when camouflaged in a suitcase Clocks Cell phones Ignition starters on cars

26. Collection and Analysis of Explosives The original blast sight will be obvious with a crater formed Collection of soil by blast site Wire mesh screens used to comb through debris Porous and non porous samples taken Look for detonator Gloves, shoe covers, overalls worn

27. Ion Mobility Spectrometer Uses vacuum to collect explosive residues from surfaces Once in the equipment the residues are vaporized by the application of heat The substances are exposed to a beam of electrons (beta rays) emitted by radioactive nickel and converted into electrically charged molecules or ions Those particles are sent through a magnetically charged tube The retention time can be a preliminary test for confirmation

28. Collection and Packaging Paint cans and airtight containers just like fire evidence

29. Analysis of Explosives First step is low power stereoscopic microscope to detect particles of unconsumed explosive Black powder and smokeless powder are easy to locate because of their size, color and shape High explosives are difficult to detect

30. After microscope examination Debris is washed with acetone to remove traces of explosives If a water-gel explosive is used the debris should be rinsed with water Color tests performed TLC (Thin layer Chromatography) run with known samples IR spectroscopy can also be used Xray diffraction GC/MS

31. Taggants Proposal to add fluorescent or magnetic tags to explosives for identification of manufacturer These tags could indicate where it was made and produced Switzerland only country adopt taggant program

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