| Al_(65)Cu_(20)Co_(15)合金中准晶体的研究 | |
| 何伦雄 | |
| Subtype | 硕士 |
| Thesis Advisor | 郭可信 |
| 1988 | |
| Degree Grantor | 中国科学院金属研究所 |
| Place of Conferral | 中国科学院金属研究所 |
| Abstract | 对Al_(65)Cu_(20)Co_(15)合金进行了不同的凝固冷都处理，发现有四种不同的十边形准晶体存在。它们沿十次轴方向的周期分别为0.4, 0.8, 1.2和1.6nm。其中周期为0.8nm的十边形相是一种完整的、稳定的准晶体。加热这种十边形相生成了一种一维准晶体，它与母体十边形相关系密切，且沿原十次轴方向的周期变成0.4nm。这表明沿十次轴方向周期为0.4nm的十边形相是各种十边形相的基本结构。加热后样品中以CsCl类型的晶体结构为基的空位有序结构增多，共发现有τ_2, τ_3, τ_5, τ_8和τ_(13), τ_(21)六种型态。其中τ_(21)是第一次被观察到。角标的数值形成Fibonacci数列，表明K. Chattopadhyay对Al-Pd合金系中发现的空位有序结构解释为τ_∞是合理的。 |
| Other Abstract | Four different decagonal quasicrystalline phases are round in the Al_(65)Cu_(20)Co_(15) alloys. Their periodicities along the unique ten-fold axes are 0.4, 0.8, 1.2 and 1.6nm respectively. The founding of the periodicity of 0.8nm confirms the suggestion by X.Z. Li and K.H. Kuo that the decagonal phase with a periodicity of 0.4nm is the fundamental one. The decagonal phase with a periodicity of 0.8nm along the ten-fold axis is a perfect and stable quasicrystalline phase. The reciprocal space is more densely occupied by its diffraction spots than any other decagonal phases found before. After heating at 800 ℃ for 40hrs, part of the decagonal phase remains unchanged. A 1D quasicrystalline phase derived from the decagonal phase with a periodicity of 0.8nm is found after annealing the sample for 40hrs at 800 ℃. The 1D quasicrystal phase (with 2D translational symmetry) conjuncts the margin between the 2D decagonal phase (with 1D translational symmetry) and crystal structure (with 3D translational symmetry). The periodicity of the 1D quasicrystal phase along the original ten-fold axis of the matrix decagonal phase becomes to be 0.4nm. This furthermore confirms the suggestion by X.Z. Li et al. A series of vacancy ordered crystalline phases based on the CsCl-type structure are also found in this alloy system. These crystalline phases are derived from the 2D decagonal phase (with a periodicity of 0.8nm along the ten-fold axis) via the 1D quasicrystal. They are τ_2, τ_3, τ_5, τ_8, τ_(13) and τ_(21) phases. The subscripts are in a Fibonacci number sequence. Among them τ_(21) had not been observed before. The τ_(21) phase gives supports to K. Chattopadhyay's explanation of the vacancy ordered structure found in Al-Pd alloy system as τ_∞ if the subscript becomes infinitely large in a Fibonacci number sequence. |
| Pages | 34 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.imr.ac.cn/handle/321006/17335 |
| Collection | 中国科学院金属研究所 |
| Recommended Citation GB/T 7714 | 何伦雄. Al_(65)Cu_(20)Co_(15)合金中准晶体的研究[D]. 中国科学院金属研究所. 中国科学院金属研究所,1988. |
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