Preparation Method of Sol-Gel Bimetallic Alloy
The sol-gel technique has long been used to prepare bimetallic alloys. This technique involves the mixing of an appropriate precursor solution with the second solution. The mixing step establishes a homogeneous solution. This technique has several advantages such as controlled mixing of the components, uniform fusion of the molten metal droplets, uniform dispersal of the particles and a homogeneous alloying of the components.
In the sol-gel route, the first step involves the preparation of an appropriate precursor solution. The precursor is usually some form of metal salt usually containing potassium, sodium, calcium and/or zinc. Such metal salts are dissolved in water to form a highly concentrated solution. The concentration of the metal salts in the solution is dependent on the composition of the bimetallic alloy.
The next step involves the addition of a second precursor solution. This solution contains the metal salts of the second component of the bimetallic alloy. This solution is added drop wise to the first precursor solution with stirring at an appropriate temperature and under an inert atmosphere. The temperature and atmosphere are critical to maintain the sol-gel reaction. If the temperature is too high, then the mixture will begin to solidify and the reaction will be incomplete. If the environment is too oxygen rich, then the reaction will produce metallic oxides leading to a decrease in alloying efficiency.
Once the two solutions are mixed, a precipitation reaction occurs in which the components of the bimetallic alloy divide into tiny droplets. These droplets contain the two metals in a way similar to the initial state of the alloy. Furthermore, the process produces very small droplets of bimetallic alloy, which will increase the alloying efficiency.
The precipitated droplets and the components of the two precursor solutions can then be separated by filtration. The precipitated droplets are then washed in order to remove any chemical impurities. After washing, the alloy is dried and then the process of sintering is started. This process involves applying heat to create a dense solid consisting of the original components in the bimetallic alloy. Sintering times and temperatures depend on the particular alloy created.
Finally, the sintered alloy is quenched in a coolant. This quenching step is important as it stabilizes the alloy while preserving its mechanical and chemical properties. After quenching, the alloy is ready for use. Bimetallic alloys prepared by the sol-gel route are known for their increased homogeneity and chemical homogeneity compared to those made by other methods. They also have better electrical, magnetic and structural properties, making them an ideal choice for many applications.
