Tungsten oxide tree-like structures

• Published in: Chemical physics letters Vol. 309; no. 5; pp. 327 - 334
• Main Authors: Zhu, Yan Qiu, Hu, Weibing, Hsu, Wen Kuang, Terrones, Mauricio, Grobert, Nicole, Hare, Jonathan P, Kroto, Harold W, Walton, David R.M, Terrones, Humberto
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 20-08-1999
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/S0009-2614(99)00732-0

An interesting micrometer scale tree-like structure has been generated by heating a W foil, partly covered by a SiO
2 plate, in an Ar atmosphere at ca. 1600°C. Upon sonication, the trees are broken into nanoneedles (ca. 5–50 nm wide and 20–200 nm long) and planar polyhedral nanoparticles (ca. 10–50 nm cross-section). Structural analysis, using ED, EDX, XRD, and HRTEM, showed that: (1) the trees consist of well-crystallised WO
x
phases (
x=0–3); (2) the nanoneedles are composed mainly of monoclinic W
18O
49 phases; and (3) the nanoparticles consist primarily of WO
3. The tree growth is thought to arise from the intrinsic crystalline feature of WO
x
, the planar defect or the shear structure of which is responsible for the breakdown of the trees.