Fig. 3

Three examples of Magnéli phases of titania suboxides identified in coal ash from US and Chinese coals. a–c A Ti _x O_2x−1 particle in bottom ash taken from a coal-fired power plant I, Kentucky, USA, in 2001 (No. 9 in Table 1): a bright field TEM image, b dark field TEM image, and c SAED pattern of the selected area in a, indicating a Ti₆O₁₁ particle. d–f A Ti _x O_2x−1 particle in fly ash taken from a coal-fired power plant in Xuzhou, China, in 2015 (No. 21 in Table 1): d bright field TEM image, e dark field TEM image, and f SAED pattern of the selected area in d, indicating a Ti₆O₁₁ particle. g–i A Ti _x O_2x−1 particle from fly ash taken from a southwest Virginia, USA, coal-fired power plant, USA, in 2014 (No. 3 in Table 1): g bright field TEM image, h dark field TEM image, and i SAED pattern of the selected area in g, indicating a Ti₈O₁₅ particle