Reactive Nanocomposite Materials Produced by Arrested Reactive Milling
Energetic formulations, in which metals are used as fuels or fuel additives, are characterized by high reaction enthalpies and temperatures, but relatively low reaction rates. In general, the rates are restricted by mass transfer processes controlling reaction between the metals and respective oxidizers. Agglomeration of metal particles further reduces their burn rates. New nanomaterials are being developed to reduce the impeding effects of mass transfer and accelerate the reactions. However, metal nanopowders are expensive, difficult to handle, and often contain substantial portion of oxide, reducing their bulk reaction enthalpy. In this research, micron scale, metallic powders were produced in which each particle is a three-dimensional, reactive nanocomposite. Specific material compositions include thermites, such as 2Al+M0O3, 2Al+3CuO, 2Al+Bi2O3, 3Zr+2Bi2O3, etc., highly energetic intermetallic, and metal-metalloid composites, e.g., 2B+Ti, B+Zr, etc. The materials are synthesized using arrested reactive milling (ARM; a high-energy ball milling technique derived from reactive milling. The process is inexpensive and readily scalable. The starting ingredients are regular, commercially available powders of metals or respective oxides, which are mixed and ball-milled. The specific milling dose is introduced as a parameter to describe the energy transferred from the milling media to the powder. During continuous milling of components for which the adiabatic temperature of reaction exceeds 1800 K, the exothermic reaction will occur spontaneously at a material-dependent critical milling dose. For ARM, the ball-milling is interrupted just before the critical milling dose is achieved and thus before the reaction is mechanically triggered. The resulting powders are compositionally uniform, individual particles, which are fully dense and contain the starting materials mixed on the scale of 100 nm or finer. These materials are extremely reactive and can be used in propellants, explosives, and pyrotechnics. A broad range of material compositions was produced because of the extreme versatility of the synthesis approach. Different laboratory experiments characterizing ignition and combustion of these materials were performed in which the new materials were compared to the currently used aluminum powders and powder mixtures. These experiments include constant volume explosion, lifted laminar flame, heated filament ignition, and other measurements. In addition, detailed thermal analysis measurements were performed and coupled with analyses of fully and partially reacted samples performed using x-ray powder diffraction and electron microscopy. The results of these latter experiments are analyzed in conjunction with the ignition and combustion measurements in order to establish the reaction kinetics and mechanisms for the new nanomaterials. An overview of the materials synthesis, properties, and results of the ignition and combustion measurements will be presented and discussed.
Energetic materials metal combustion metal ignition reaction kinetics explosives propellants pyrotechnics
Edward L. DREIZIN Mirko SCHOENITZ Mikhaylo A. TRUNOV Vern K. HOFFMANN Swati M. UMBRAJKAR Ervin BELONI
New Jersey Institute of Technology, Newark, NJ, USA
国际会议
西安
英文
3-14
2007-10-23（万方平台首次上网日期，不代表论文的发表时间）