In the experiment, a heated carburizing gas mixture was sent over powdered cobaltosic oxide. Filamentous carbon is the main deposit that forms from this reaction when it is carried out at . When chlorobenzene is hydrodechlorinated over nickel and silica, highly ordered structures of filamentous carbon form. When potassium and bromine are present, this reaction can occur at temperatures as low as . This is because the potassium and bromine aided in restructuring the active sites, thus causing destructive chemisorption of the reactant and also causing the a precipitate of carbon to form. Adding potassium hydroxide to the mixture of nickel and silica in the reaction made little change to the yield of the reaction. However, the addition of potassium bromide significantly increased the yield. Other alkali metal bromides also allow the reaction and the formation of filamentous carbon to occur. Such alkali metal bromides include cesium bromide. Filamentous carbon can also be synthesized by decomposing chromium carbide at 100 to 200 megapascals and to . It has also been formed with a catalyst of cobalt and aluminum phosphate at 2 megapascals and to . The presence of ruthenium in this reaction lessens the yield of filamentous carbon. Filamentous carbon has been used to clean up oil spills. This works by the filaments bonding to crude oil. It is also used in light-weight composite materials that must have strength at high temperatures. Filamentous carbon has been known since at least 1890, when P. and L. Schützenberger observed it while passing cyanogen over red-hot porcelain. In the 1950s, it was discovered that the filaments could be produced by the reactions of gases such as hydrocarbons with metals such as iron, cobalt, and nickel. The first electron micrographs of tubular versions of the filaments appeared in 1952. Between the 1970s and the 1990s, filamentous carbon has been the subject of a number of research efforts. These studies included studies of the thermodynamic properties of the formation of the allotrope. The most significant study that took place during that time was conducted by Terry Baker in the 1970s and concerned keeping filamentous carbon from growing inside the cooling pipes of nuclear reactors.