The present invention relates to the synthesis of nanoscale powders and the consolidation of these powders into bulk solid materials without inducing any significant grain growth into the nanoscale materials.
In conventional polycrystalline materials the majority of the atoms are in an ordered crystalline structure in the grains with a small percentage of the atoms being in the grain boundaries separating the grains. In conventional materials the volume fraction of grain and interface boundaries rarely exceeds more than a few percent, and therefore, the bulk properties are not affected significantly. Conventional powders can be prepared by methods such as gas condensation, rapid solidification, sputtering, mechanical alloying/milling, conventional vapor deposition, (either physical vapor deposition, PVD, or chemical vapor deposition, CVD), plasma assisted PVD/CVD, electrodeposition, plasma processing and sol-gel processes.
Of all the processes listed, only inert gas condensation, plasma processes and mechanical alloying are used widely to synthesize nanoscale materials. The inert gas condensation process is currently used only as a research technique because the production rate of nanoscale materials is only few grams per minute via this route. Plasma processes also are costly and difficult to scale-up for large scale production of nanoscale materials. Due to process flexibility and ease in scaling-up, mechanical milling/alloying has been widely used for producing nanoscale materials. The combination of increased strength, improved toughness and lower density of nanoscale materials makes them extremely attractive for space and propulsions applications.
Historically titanium alloys are the baseline material for aircraft and space applications. Although conventional coarse-grain aluminum alloys are lighter than titanium, they lack the sufficient specific strength needed for many applications as space and propulsion materials. However, aluminum nanoscale materials provide a unique opportunity for aircraft, space and armor applications as the properties of nanoscale aluminum alloy, such as tensile strength, hardness and toughness are vastly improved over those of traditional coarse-grain materials. In addition, the cost is less than that of titanium alloys.
Thus, there exists a need for a process for making a nanoscale material and products therefrom.