Chemical & Metallurgical
Applications of Metal Powders
In metallurgy, obtaining the correct ratio of metals in an alloy mixture is paramount in controlling the resulting properties and performance of the components manufactured from that mixture. Oftentimes this entails adding metals of known composition in solid bars, rods, or powder form to a molten mixture prior to casting in order to obtain the correct composition. To ensure that these compositional modifiers are evenly mixed and dispersed they must completely melt and dissolve. For this reason, and to do so in an energy efficient manner, pre-mixed alloys are often utilised in cases where the alloy used has a lower melting point than the highest melting metal in the mixture. For example, to prepare an alloy that is ten percent titanium and ninety percent aluminum, one would intuitively think to simply add the titanium, with a melting point of 1668 oC to a molten bath of aluminum which melts at 882 oC. The titanium will not melt and dissolve at the melting point of the aluminum bath. However, by adding and pre-mixed alloy that is mostly titanium with ten percent aluminum, this master alloy now has a melting point nearly the same as the aluminum bath and will dissolve and evenly mix. These pre-mixed alloys are referred to as master alloys.
Copper powder is a simple yet extremely versatile tool in fine chemicals processing. While there are an array of compounds capable of inducing chemical reactions that can build up molecular structures by piecing together molecules through the formation of new carbon to carbon bonds, copper and its derivatives are catalysts of choice for a number of chemical transformations due to its cost effectiveness and ease of handling. As an example, The Ullmann Reaction uses copper powder as a catalyst to couple two hydrocarbon molecules together into a single entity via formation of a new carbon to carbon bond. By contrast, the Grignard reaction accomplishes synonymous results but does so using magnesium metal, which can be flammable and can react with water to produce explosive hydrogen gas. These types of chemical reactions whereby molecules are pieced together through formation of new stable carbon to carbon bonds are crucial processes employed to produce pharmaceuticals, plastics and additives, explosives, and countless other functional materials.
Copper powder, and tin to an extent, function as both catalysts and reagents in a range of chemical reactions. In some applications they function in their elemental form, but for a whole host of other scenarios these metals are reacted with other molecules or compounds to form reactive but sufficiently stable intermediate organometallic compounds. Using these pre-formed intermediates usually improves efficiencies and reduces waste in multicomponent chemical process flows such as those required to construct complex pharmaceutical active ingredients.
Refining and Precious Metal Recovery
A common technique to recover precious metals from complex mixtures such as ores or electronic waste is to soak or wash the material in concentrated acid. Precious metals such as gold and platinum become oxidised into a soluble salt form and dissolve into the acidic solution. All remaining solid material is removed by filtration. The acid solution is neutralized and the precious metal salts are converted back to their neutral metal form by addition of a reducing agent. Copper powder is sometimes used as this reducing agent to recover higher value materials such as gold, platinum, and palladium.