Metal solutions

Overview
Making solutions of known concentration is critical to ensuring reproducibility of results. Most scientists use molar concentration to describe solutions, and we will, too. The solutions we make will include several chemicals - the metal source, a stabilizing acid, and, for the inkjet printer, a mild explosive.

Metal Source
Caution: Some metal salts are extremely toxic. Always wear gloves and safety goggles when dealing with chemicals in the laboratory.

The metal source can be any water-soluble compound of the metal that will reliably pyrolyze to the metal oxide. In other words, the other atoms in solution should probably be limited to hydrogen, carbon, nitrogen, and oxygen. In the furnace, the hydrogen combines with oxygen (either from the atmosphere or from within the compound) to form water. Carbon will also combine with oxygen to form carbon dioxide. Nitrogen will form gaseous dinitrogen (which already comprises over 75% of the atmosphere). Two example decompositions are given below.

$$\mathrm{Mg(NO_3)_2 \longrightarrow N_2 + MgO + \frac{5}{2} O_2}$$

$$\mathrm{Na_2CO_3 \longrightarrow Na_2O + CO_2}$$

Stabilizing Acid
A small quantity of HNO3 is added to the solutions. The acidic conditions prevent reduction of the metal ions, helping to enhance the shelf life of stock solutions. The residual nitate ion in solution will not affect the composition of the metal oxide, for reasons described above.

Mild Explosive
When using the inkjet printer, ammonium nitrate is added to the aqueous solution. The thermal inkjet printer causes decomposition of the salt when the inkjet "fires," forming gaseous products that help expel the metal solution onto the substrate, preventing clogging of the printhead. The decomposition reaction is shown below.

$$\mathrm{NH_4NO_3 \longrightarrow N_2 + 2~H_2O + \frac{1}{2} O_2}$$