AlC_4B_<24>及びAl_3C_2B_<48>結晶の合成

概要

論文の詳細を見る
AIC_4B_<24> and Al_3C_2B_<4> 8 crystals were prepared by the reaction between carbon and boron powders using a molten aluminium flux in an argon atmosphere. The conditions for obtaining these crystals with a relatively large size were established. As-grown AlC_4B_24 and Al_3C_2B_48 crystals were used for the study of oxidation in air at high temperatures, and also measurements of density, unit cell dimensions and Vickers microhardness. AlC_4B_<24> crystals were obtained together with crystals of Al_3C_2B_<48> or Al_4C_3. Al_3C_2B_<48> were prepared as twinned crystals of A and B phases, without accompanying α-AlB_<12>, β- AlB_<12> type, γ-AlB_<12> AlC_4B_<24> or Al_C_3 crystals. The optimum conditions for growing AlC_4B_<24> single crystals and Al_3C_2B_<48> crystals are the following atomic ratios of starting materials (C/B, Al/B), soaking temperature and soaking time; C/B= 9. 60/24, Al/B=144.24/24, 1500℃ and 5h for AlC_4B_<24> and C/B=0 24/24-0.48/24, Al/B=144.24/24, 1300℃ and 5h for Al_3C_2B_<48> respectively. Under these conditions, AlC_4B_<24>, single crystals, having a black color and metallic luster, were generally obtained in the form of a bipyramidal shape. On the other hand, the twinned crystals of Al_3C_2B_48 were yellowish brown and semitransparent, having a nearly spherical polyhedral shape with smooth planes. The largest crystals prepared have the maximum dimensions of about 2.1 mm×2.mm×2.2 mm (for AlC_4B_<24>) and 1.1 mm×1.1 mm×1.2 mm (for AlC_4B_<24>). Unit cell dimensions, Vickers microhardness (H_v) and densities (d_m) are as follows :AlC_4B_<24> ; a=8.892(2), b=9.112(1), c=5. 692(2) (Å), V=461.1(3) (Å^3). H_v =2500-2690 kgf/mm^2, d_m=2.55(1)g/cm^3 Al_3C_2B_<48> ; for A phase, a=12.377(2)_b=12. 627(1), c=5.079(1) (Å), V=793.8(1) (Å)〜a=12.363(2), b= 12.616(1), c=5.102(1) (Å), V=795. 8(2) (Å^3) ;for B phase, a=6.166(2), b=12.635(2), c=10.156(2) (Å), V=791.2(2) (Å^3)〜a=6.181(2), b= 12.622(1), c=10.161(1) (Å), V=792.7(2) (Å^3). H_v=2570-3050 kgf/mm^2, dm=2.59(2)g/cm^3 The oxidation reaction in air of AlC_4B_<24> and Al_3C_2B_<48> crystals began to proceed at about 760℃ and 710℃, respectively, and their oxidation products were found to be 9Al_O_3・2B2O_3(orthorhombic system) and B_2O_3(hexagonal system) phases.
社団法人日本セラミックス協会の論文
1990-12-01

AlC_4B_<24>及びAl_3C_2B_<48>結晶の合成

スポンサーリンク

概要

著者

関連論文

スポンサーリンク