Patent Publication Number: US-2010107816-A1

Title: Method of making metal flakes

Description:
The invention relates to a method of making metal flakes by kinetic milling. 
     Metal flakes produced in this manner are used in large-scale industrial applications as pigments, solders, protective coatings, electromagnetic shielding, antifouling coatings, or biokinetically active coatings, etc. 
     Such methods are generally known from the prior art. Traditionally, metal flakes are currently produced by low- or high-kinetic milling methods, also known as “mechanical alloying” or “high-kinetic processing,” from only one predetermined base material. The base material is typically a metal in the form of water- or a gas-atomized powder. 
    
    
     Based on the prior art the object of the invention is to further improve a known method of making metal flakes in that it is also suitable for making metal flakes having improved properties. 
     The object is attained by the method defined in patent claim  1 . The method is characterized in that at least one further alloying additive is provided in addition to the metal base material, and that making the metal flakes is carried out by kinetic milling of the base material together with the at least one alloying additive such that the base material is mechanically alloyed with the one alloying additive. 
     The core of the invention is therefore that not only one, but at least two materials, e.g. the base material and an alloying additive, are used in the high-kinetic milling process and are then together mechanically alloyed into alloy metal flakes by the milling process. In this manner the high-kinetic milling process enables the creation of novel materials, particularly also ductile compounds that cannot be produced in the conventional fusion metallurgical manner. These are in particular saturated and over-saturated mixed crystal formations (superalloys), saturated, metastable, or quasicrystalline intermetal phase materials such as amorphous or partially amorphous materials. Contrary to known materials, the novel flake materials produced according to the invention have improved optical, electrical, chemical, electromagnetic, electrochemical, mechanical, biokinetic, or improved hydraulic properties. The materials produced according to the invention are used for example as pigments, solders, protective coatings, electromagnetic shielding, antifouling coatings, or as biokinetically active coatings, etc. 
     According to a first embodiment of the invention the base material is a metal such as aluminum, nickel, copper, palladium, silver, gold, or lead, each having a cubic face-centered Kfz lattice structure, or titanium, iron, cobalt, zinc, or molybdenum, the latter elements having a cubic space-centered KRZ lattice structure. 
     As an alternative a metallic alloy may also be used as the base material. 
     The alloying additive additionally used according to the invention is preferably also a metal, further preferably one of the metals mentioned above, or an oxide, a carbide, or a nitride. 
     However, the alloying additive additionally used according to the invention may also be carbon nano tubes CNT, and/or fibrous materials (fibers) such as fiber glass or Kevlar fibers, and/or polymers such as polytetrafluoroethylene (PTFE). The fibrous materials have a geometric function, for example it is incorporated into the metal structure of the base material, preferably as a whole by the mechanical alloying. For this purpose a suitable tempering of the alloy process is required. Furthermore, a ductile matrix is in particular necessary with the use of the fibrous materials. 
     All stated alloying additives may be mechanically alloyed either individually, or in any desired combination with each other. 
     The kinetic milling process is either a high- or low-energy kinetic milling process. 
     Advantageously, the method according to the invention enables making a novel material by mechanical alloying of a metal (base material) together with an alloying additive in the form of at least one further metal, or a non-metal.