German researchers have reported in the latest issue of the UK journal Nature that they have developed a new alloy smelting process that can turn solid metal oxides into block-shaped alloys in one step. The technology does not require melting and mixing the metal after it has been extracted, which helps reduce greenhouse gas emissions and conserve energy.

Researchers at the Max Planck Institute for Sustainable Materials in Germany used hydrogen instead of carbon as a reducing agent to extract the metal and form the alloy at temperatures far below the melting point of the metal, and have successfully produced low-expansion alloys in experiments. The low-expansion alloys are composed of 64% iron and 36% nickel, and can maintain their volume within a large temperature range, making them widely used in industry.

The researchers mixed the oxides of iron and nickel in the required proportion for low-expansion alloys, ground them evenly with a ball mill and pressed them into small round cakes. They then heated the cakes in a furnace to 700 degrees Celsius and introduced hydrogen. The temperature was not high enough to melt the iron or nickel, but was high enough to reduce the metal. Tests showed that the processed block-shaped metal had the typical characteristics of low-expansion alloys and had better mechanical properties due to its small grain size. Because the finished product was in the form of a block rather than powder or nanoparticles, it was easy to cast and process.

Traditional alloy smelting involves three steps: first, the metal oxides in the ore are reduced to metal by carbon, then the metal is decarbonized and different metals are melted and mixed, and finally, thermal-mechanical processing is carried out to adjust the microstructure of the alloy to give it specific properties. These steps consume huge amounts of energy, and the process of using carbon to reduce metals produces large amounts of carbon dioxide. The carbon emissions from the metals industry account for about 10% of the world’s total.

The researchers said that the byproduct of using hydrogen to reduce metals is water, with zero carbon emissions, and that the simple process has huge potential for energy savings. However, the experiments used oxides of iron and nickel of high purity, and the efficiency