Metal oxide powder mix forms a ceramic flameproof coating Metal Tech News – January 12, 2022
While it may seem counterintuitive to consider lava as a source of inspiration for preventing homes and businesses from going up in smoke, researchers in Australia and China have drawn inspiration from this molten rock in the development of a better flame retardant.
To prevent buildings from going ablaze, manufacturers have added flame retardants to plastic, wood, and steel building materials for decades. These additives, however, can be toxic and expensive.
To make a better flame retardant, researchers led by Pingan Song, a chemist at the University of Southern Queensland, Springfield, turned to lava for inspiration.
Before cooling and forming igneous rocks, molten lava is made of metal and oxygen-containing glasses that are not only tolerant of heat, but also flow when heated. When exposed to intense heat, they form a ceramic char layer that prevents flames and lessens heat from reaching the material underneath
To replicate this natural process, Song and his colleagues used three components to make their own char.
First, they created a mixture of several metal oxide powders – aluminum, silicon, calcium, and sodium –that begins to melt at about 350 degrees Celsius (662 degrees Fahrenheit), which is lower than the temperature of most flames, forming a glasslike sheet. Next, the researchers added tiny flakes of boron nitride, which flow easily and help fill any spaces between the metal oxides as the glass forms. Finally, they added a fire-retardant polymer, which acts as a binder to glue the rest of the mixture to whatever it's coating.
The resulting mixture was dissolved into water and sprayed on a variety of surfaces such as rigid foam insulation, wood, and steel.
The team then broke out a butane torch and blasted each coated material with a 1,100C (2,010F) flame for 30 seconds.
When heated by the torch, the coating spewed out nonflammable gases, such as carbon dioxide. As it did, a uniform, noncombustible char layer was formed that blocked flames from spreading to the materials underneath.
The novel flame retardant protected rigid polymer foam commonly used to insulate homes better than more than a dozen widely used retardants, the researchers report today in the science journal, "Matter."
The lava-inspired coating also "offers exceptional fire protection for solid wood and steel."
Given these results, coupled with the fact that the materials used are non-toxic, this new material holds promise for preventing catastrophic and lethal fires in homes and workplaces.