2000 Fiscal Year Final Research Report Summary
Creation of biomaterials having good mechanical properties with application of biomimetics function
| Project/Area Number |
11650724
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Structural/Functional materials
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| Research Institution | Sophia University |
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Principal Investigator |
NOZUE Akira Sophia University, Faculty of Science and Technology, Professor, 理工学部, 教授 (80146802)
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| Co-Investigator(Kenkyū-buntansha) |
SUZUKI Hiroshi Sophia University, Faculty of Science and Technology, Research Associates, 理工学部, 助手 (30154579)
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| Project Period (FY) |
1999 – 2000
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| Keywords | biomimetics / self-healing / Ti alloys / apatite |
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| Research Abstract |
(1) Alkali treatment and coating with composition gradient function
Ti-6Al-4V alloys were machined for CT specimen, polished and introduced fatigue pre-crack of 5 mm, after heat-treated with standard process. These specimens were immerged for a NaOH solution of 5 mol/l for 24 h. Then these specimens were heat-treated at 600℃ for 1 h to stabilize this alkali process. After this alkali process, these specimens were immerged in simulated body flood (SBF).
(2) Coating process
The formation of apatite and TiO_2 phases has been identified on the surface of specimens, which are alkali-treated and then immerged in SBF, by means of Thin Film X Ray Diffraction. By using the Auger electron spectroscopy, the element gradient exists at the surface of the specimens which are alkali-treated. From the spectroscopy, it is confirmed that the surface possesses the much volume fraction of O element and Ti concentration increases from the surface into the internal site. This length of the element gradient is about 400 nm.
(3) Expression of self-healing
The formation of element gradient causes self-healing at a pre-crack of the specimens, which are alkali-treated and then immerged in SBF, in order to add the biocompatibility at the surface. Fracture toughness is increased in 10 MPa m ^<1/2> due to the coating process of the element gradient. This increase of fracture toughness may be understood from the extrinsic toughening mechanism. On loading, Ti alloy of the matrix is yielded because of the relatively low yield strength with comparison of the coating zone of the high yield strength and then the crack tip of the pre-crack is blunted. As a result, stress intensity factor K is decreased, which expresses that the fracture toughness of this specimen is apparently increased.
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