Theoretical calculation and experimental investigation of interganular van-der Waals forces in ceramics

陶瓷晶间范德华力的理论计算与实验研究

• 批准号: 08455302
• 负责人: TANAKA Isao
• 金额: $ 2.43万
• 依托单位: KYOTO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 无数据
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08455302/
• 关键词: Si_3N_4; SiC; TEM; EELS; molecular orbital

Intergranular van-der Waals (vdW) force determines long range interaction of ceramics interfaces. It is effective over 10 hich is the order of the intergranular glassy film of Si_3N_4 ceramics. Such film is ubiquitous in Si_3N_4 ceramics but not in SiC.With recent improvement of high spatial resolution analytical electron microscopy, one can obtain electron energy-loss spectra (EELS) directly from the intergranular film. Since major features of the near edge structures of EELS (ELNES) can be ascribed to electronic dipole transitions from core orbitals to unoccupied band, accurate electronic calculations of the unoccupied band are necessary in order to interpret the experimental spectra.In the present study, we made first principle molecular orbital calculations by discrete variational (DV) Xalpha method using model clusters composed of Si, N and O.There were tow objectives. 1) Interpretation of spectral features of ELNES obtained from the film in terms of the local chemical bonding. 2) Theoretical calculation of intergranular vdWforces across the film. Parallel to these theoretical works, experimental efforts to characterize the intergranular glassy film have been made mainly by means of high spatial resolution electron microscopy.

晶间范德华 (vdW) 力决定陶瓷界面的长程相互作用。对于Si_3N_4陶瓷晶间玻璃膜的10量级以上是有效的。这种薄膜在Si_3N_4陶瓷中普遍存在，但在SiC中却没有。随着高空间分辨率分析电子显微镜的发展，人们可以直接从晶间薄膜中获得电子能量损失谱(EELS)。由于 EELS (ELNES) 近边缘结构的主要特征可归因于从核心轨道到未占据能带的电子偶极子跃迁，因此需要对未占据能带进行精确的电子计算以解释实验光谱。在本研究中，我们利用由Si、N和O组成的模型簇，通过离散变分（DV）Xalpha方法进行第一原理分子轨道计算。有两个目标。 1) 从局部化学键合角度解释从薄膜获得的 ELNES 光谱特征。 2) 薄膜上晶间 vdW 力的理论计算。与这些理论工作并行，主要通过高空间分辨率电子显微镜来表征晶间玻璃膜的实验工作。

项目成果

T.Nakayasu, T.Yamada, I.Tanaka, H.Adachi, and S.Goto: "Local Chemical Bonding around Rare Earth Ions in alpha and beta-Si_3N_4" J.Am.Ceram.Soc.(in press).

T.Nakayasu、T.Yamada、I.Tanaka、H.Adachi 和 S.Goto：“α 和 β-Si_3N_4 中稀土离子周围的局部化学键合”J.Am.Ceram.Soc.（出版中）。

I.Tanaka, T.Nakayasu, T.Yamada, and H.Adachi: "Local Chemical Bonding at Grain Boundary of Si_3N_4" Microstructures 96, Plenum press. (in press).

I.Tanaka、T.Nakayasu、T.Yamada 和 H.Adachi：“Si_3N_4 晶界处的局部化学键合”Microstructions 96，Plenum press。

H.Gu: "Structure and chemistry of intergranular films in Ca-doped Si_3N_4" Mater.Sci.Forum. 207-209. 729-732 (1996)

H.Gu：“Ca掺杂Si_3N_4中晶间薄膜的结构和化学”Mater.Sci.Forum。

I.Tanaka and H.Adachi: "Calculation of core-hole excitonic features on AlL_-edge x-ray-absorption spectra of alpha-Al_2O_3" Phys.Rev.B54 No.7. 4604-4608 (1996)

I.Tanaka 和 H.Adachi：“α-Al_2O_3 的 AlL_23> 边缘 X 射线吸收光谱的芯孔激子特征的计算”Phys.Rev.B54 No.7。

I.Tanaka: "First Principles Molecular Orbital Calculation of Electron Energy Loss Near Edge Structures of α-quartz" J.Phys.D.29. 1725-1729 (1996)

I.Tanaka：“α-石英边缘结构附近电子能量损失的第一原理分子轨道计算”J.Phys.D.29 1725-1729 (1996)。