American Dental Association Science & Research Institute, LLC, Chicago, Illinois, USA.
Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois, USA.
J Biomed Mater Res B Appl Biomater. 2020 Nov;108(8):3323-3330. doi: 10.1002/jbm.b.34668. Epub 2020 Jun 20.
Zirconia with 3 mol% yttria (3Y-TZP) has been used for dental crowns and bridges due to its excellent mechanical behavior. Performing fracture toughness testing on this nanograin material, however, can be a challenge. For reliable results, fracture toughness testing requires an extremely sharp notch in the test specimen that closely approximates a very sharp crack. This study was to investigate an alternative method to produce nanometer-sized notches, which are less than the average grain size of 3Y-TZP, during the preparation of single-edge V-notched beam specimens and report the resulting fracture toughness value.
We present a method using focused ion beam (FIB) milling to fabricate nanometer-sized notches in 3Y-TZP. The notch tip is <100 nm wide, which is smaller than the grain size, and is consistent throughout the thickness of the specimen.
The FIB-notched specimens show a much reduced average fracture toughness of 5.64 ± 1.14 MPa√m compared to 8.90 ± 0.23 MPa√m for the specimens without FIB-notches. The FIB-milling did not appear to create any monoclinic phase prior to fracture toughness testing. Fractures originated at the FIB-notches, and the notch size can be readily identified post-mortem using a microscope. A considerable amount of tetragonal-to-monoclinic phase transformation was observed throughout the fracture surfaces.
FIB milling provides an alternative method to fabricate nanometer-sized notches that are smaller than the grain size of tetragonal zirconia polycrystal. The fracture toughness determined using FIB-notches was ~5.64 MPa√m, smaller than the specimens with V-notches fabricated using saw blades.
氧化锆添加 3 摩尔%氧化钇（3Y-TZP）因其优异的机械性能而被用于制作牙冠和牙桥。然而，对这种纳米晶粒材料进行断裂韧性测试可能具有挑战性。为了获得可靠的结果，断裂韧性测试需要在试件上制备极其尖锐的缺口，该缺口要非常接近尖锐的裂纹。本研究旨在探讨一种替代方法，即在制备单边 V 型缺口梁试件的过程中制备纳米级的缺口，这些缺口小于 3Y-TZP 的平均晶粒尺寸，并报告由此产生的断裂韧性值。
我们提出了一种使用聚焦离子束（FIB）铣削在 3Y-TZP 中制备纳米级缺口的方法。缺口尖端的宽度小于 100nm，小于晶粒尺寸，并贯穿整个试件的厚度。
与未经 FIB 缺口处理的试件的 8.90±0.23MPa√m 相比，FIB 缺口处理的试件的平均断裂韧性明显降低至 5.64±1.14MPa√m。在进行断裂韧性测试之前，FIB 铣削似乎并未产生任何单斜相。断裂起源于 FIB 缺口，缺口尺寸可以在显微镜下进行尸检后很容易地识别。在整个断裂表面观察到相当数量的四方相向单斜相转变。
FIB 铣削提供了一种替代方法来制备纳米级的缺口，这些缺口小于四方氧化锆多晶的晶粒尺寸。使用 FIB 缺口确定的断裂韧性约为 5.64MPa√m，小于使用锯片制备的 V 型缺口试件。
