自支撑金刚石厚膜三方向三点弯曲断裂韧性对比研究

摘要/Abstract

摘要： 采用直流电弧等离子体喷射和微波等离子体化学气相沉积法制备了三片直径为125 mm、厚度大于1 mm的自支撑金刚石膜。通过SEM、XRD、Raman、CT等检测手段对样品进行了形貌、物相表征,进一步通过激光预制裂纹方法研究了缺陷和晶粒尺寸对生长面、形核面及侧面三个方向断裂韧性的影响。结果表明,在金刚石薄膜沉积过程中,许多缺陷(包括孔隙)被引入薄膜中,特别是较厚膜中靠近生长面一侧的孔隙尺寸可以达到微米级,这会影响不同方向载荷下的断裂韧性。由于近生长面的晶粒尺寸最小,自支撑金刚石膜在生长面形成的裂纹具有最大断裂韧性,分别为7.8、8.3和9.2 MPa·m^1/2。对于较薄的样品,侧面裂纹的断裂韧性介于生长面和形核面之间,这与晶粒尺寸关系一致,表明断裂韧性受晶粒尺寸的影响。然而,当厚度超过0.8 mm时,生长侧附近的孔隙数量会增加,导致较厚的金刚石薄膜的断裂韧性最小(5.4 MPa·m^1/2)。本研究为金刚石上施加载荷方向的选择提供了指导。

关键词: 金刚石厚膜, 断裂韧性, CVD, 研磨, 缺陷, 晶粒尺寸

Abstract: Three free-standing diamond films with 125 mm in diameter and thickness exceeded 1 mm were deposited using DC arc plasma jet and microwave plasma chemical vapor deposition. In order to reduce the influence of sample size on the results of fracture toughness, diamond film samples were cut into square cross-sections. Morphology and phase were characterized by SEM, XRD, Raman, CT, et al. Influences of defects and grain size on fracture toughness in three directions of growth surface, nucleation surface and edge surface were studied. The results indicate that during the growth process, many defects (including pores) are introduced into the film. Especially, on the side near the growth surface in thicker films, the size of pores reaches the micrometer level, so that affects the fracture toughness under different directional loads. Due to the smallest grain size, all diamond free-standing films have the maximum fracture toughness at growth surface, which are 7.8, 8.3, and 9.2 MPa·m^1/2, respectively. For thinner samples, the fracture toughness of edge surface cracks is between growth surface and nucleation surface. This is consistent with the relationship between grain size, indicating that fracture toughness is influenced by grain size. However, when the thickness exceeds 0.8 mm, the number of pores near the growth side will increase, resulting in the smallest fracture toughness (5.4 MPa·m^1/2) of diamond films with thicker side. This study provides guidance for selecting the direction of load application.

Key words: diamond thick film, fracture toughness, CVD, grinding, defect, grain size

中图分类号:

罗晓航, 许光宇, 李利军, 张永康, 张亚琛, 吴海平, 安康. 自支撑金刚石厚膜三方向三点弯曲断裂韧性对比研究[J]. 人工晶体学报, 2024, 53(12): 2085-2093.

LUO Xiaohang, XU Guangyu, LI Lijun, ZHANG Yongkang, ZHANG Yachen, WU Haiping, AN Kang. Comparison on Three-Point-Bending Fracture Toughness of Free-Standing Diamond Thick Films from Three Directions[J]. JOURNAL OF SYNTHETIC CRYSTALS, 2024, 53(12): 2085-2093.

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