Preparation of ultrafine carbon spheres by controlled polymerization of furfuryl alcohol in microdroplets

Carbon microspheres with mean particle sizes of 0.7-1.2 μm were prepared by polymerization of furfuryl alcohol (FA) in H₂SO₄ solution droplets without any surfactant, followed by pyrolysis. FA was introduced by diffusion from FA-containing oil phase into the droplets formed in an interdigital micromixer. The oil to aqueous phase flow rate ratio and the FA and H₂SO₄ concentrations should be kept at medium values. A decrease in the total flow rate ratio, oil to aqueous phase flow rate ratio, or FA concentration results in small-sized carbon microspheres, and a decrease in the FA or H₂SO₄ concentration leads to formation of the carbon microspheres exhibiting rough surface. The carbon microspheres show good dispersity in ethanol and microporosity. Their particle sizes could be further reduced to 150 nm by using polyvinyl pyrrolidone, and their mesoporosity can easily be endowed by adding silica nanoparticles in the droplets.