アルミナ/タングステンナノ複合材料の還元焼結 : 粉末プロセシング, 還元挙動及び微細組織

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Reduction behavior of tungsten oxide mixed with alumina powder and its sintering processes were investigated to fabricate Al_2O_3/W nanocomposites. Submicron-sized WO_3 powder could be obtained by a conventional ball-milling technique. Hygrometry analysis of Al_2O_3/WO_3 mixture revealed that WO_3 powder was reduced in two steps at 873 and 973 K. X-ray diffraction and transmission electron microscopy (TEM) analysis confirmed that Magneli phases, such as WO_2 and WO_x (x=2.89 to 2.92), were obtained by the reduction of WO_3 at 873 K. However, WO_3 was completely reduced to metallic W when reduction temperature was higher than 1173 K. A thermodynamic analysis qualitatively agreed with the experimental result that WO_2 and WO_x coexisted at intermediate temperatures. Reduction followed by hot-press sintering of Al_2O_3/WO_3 mixtures was carried out to obtain Al_2O_3/W nanocomposites. Agglomeration and/or incomplete reduction was found at high W content ; however, dense Al_2O_3/W composites with >98% of their theoretical density were obtained at low W content (i.e., <10 vol%). A microstructural investigation of the dense composite reveealed that it consisted of both micro- and nano-sized W dispersions. Furthermore, a large number of W particles of around 40 nm were found to be homogeneously dispersed in the Al_2O_3 matrix. These particles were much finer than the WO_3 particles obtained by ball-milling.
社団法人日本セラミックス協会の論文
2000-06-01

アルミナ/タングステンナノ複合材料の還元焼結 : 粉末プロセシング, 還元挙動及び微細組織

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