The Characteristics of Black Powder

For about 500 years black powder enjoyed dominance as a propellant, explosive and igniter, and as the major firework ingredient its use remains unsurpassed. The prime reason for the longevity of black powder is its quickness , even at relatively low pressures, and this is brought about by manufacturing techniques (as described earlier) and the chemical reactivity of the constituents. 

Besides acting as a fuel, the finely-divided charcoal has a very high surface area which means that the substance can absorb appreciable quantities of sulfur dioxide (SO2) produced during combustion whilst allowing the remaining sulfur to perform more effectively as a fuel. 

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One of the characteristics of black powder is that it is a fast burning mixture. 

Black Powder. Black powder is mainly used as an igniter for nitrocellulose gun propellant, and to some extent in safety blasting fuse, delay fuses, and in firecrackers. Potassium nitrate black powder (74 wt %, 15.6 wt % carbon, 10.4 wt % sulfur) is used for military appHcations. The slower-burning, less cosdy, and more hygroscopic sodium nitrate black powder (71.0 wt %, 16.5 wt % carbon, 12.5 wt % sulfur) is used industrially. The reaction products of black powder are complex (Table 12) and change with the conditions of initia tion, confinement, and density. The reported thermochemical and performance characteristics vary greatly and depend on the source of material, its physical form, and the method of determination. Typical values are Hsted in Table 13. 

Although the compositions used in fountains are usually based on black powder propellant, the sparks that are responsible for the fountain effect originate from other substances within the composition. These substances are known as emitters and it is the physical and chemical properties of the emitters that determine the characteristics of the fountain. Various additives are also used to promote the visual effects or to cheapen the composition. 

The surface of a solid may differ in many ways from its bulk composition. Especially, such solids as commercial carbon black may contain minor amounts of impurities (such as aromatics, phenol, carboxylic acid). This would render surface adsorption characteristics different from that of pure carbon. It is therefore essential that, in industrial production, quality control of the surface from different production batch is maintained. Otherwise, the surface properties will affect the application. Another example arises from the behavior of glass powder and its adsorption character for proteins. It has been found that if glass powder is left exposed to the... 

Tsuchida et al. 213) showed that PVC solutions in tetrahydrofuran dehydrochlorinate when treated with sodium amide in liquid ammonia the product had many of the characteristics of polyacetylene and a conductivity of 10-4 S cm-1 but was an infusible black powder. It was found that reaction of PVC powder gave only limited dehydrochlorination of the surface. 

X-ray Data.—The structure of black phosphorus has been calculated from the X-ray reflection spectrum, using the powder method of Debye and Scherrer. It is a rhombohedral space-lattice having a characteristic angle of 60° 47, and a side of 5-96 A. The unit cell contains 8 atoms, and therefore the volume of the unit molecular aggregate is ... 

A large diffusion may be found also for composite materials, carbon, or metal based. In the first case different types of polymeric resins (thermoplastics, such as polypropylene, polyethylene, and PVDF, or thermosettings, such as epoxies and phenolics) are filled with carbonaceous powders (graphite or carbon blacks), to provide a material characterized by very high chemical stability in the fuel cell environment and satisfactory properties of electrical conductivity, but which cannot offer sufficient robustness at thickness lower than 2 mm. The metal composite plates are essentially based on combinations (sandwiches of different layers) of stainless steel, porous graphite, and polycarbonates, with the aim to exploit the characteristics of different materials. Their fabrication can be more complex but this is compensated by the possibility to incorporate other functional components, such as manifolds, seals, and cooling layers. 

Particle production from a flame process, especially soot and carbon black fabrication, has a history that can be traced to prehistoric times [1]. For several years, Titania and sihca powder have been produced industrially via a flame process [2]. As a continuous process, the flame method allows production at a high rate with controlled-particle characteristics that result in an inexpensive process for powder fabrication [3]. In addition, the abihty to control the fuel flow rate in flame is useful because it provides some control over the temperature at which a reaction can be carried out [3-5]. Generally, the characteristics of flame-made particles are highly crystalline, dense and free of impurities due to the high-temperature flame heat. 

High-rate electrode characteristics of V2O5 sol/carbon composites were studied. The V2O5 sol was prepared by a reaction between metallic vanadium and a hydrogen peroxide solution. The acetylene carbon black powder was added to the sol together with acetone in the form of a homogeneous suspension. A composite of amorphous V2O5 and carbon black was introduced into a macroporous nickel... 

With regard to the solid residue, the formation of solid products such as potassium carbonate, potassium sulfate, and potassium sulfide is characteristic for black powder. 

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