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Table 1 Mean and standard derivation values of electrochemical parameters of the as-sprayed coating and heat-treated graded coatings at different temperatures after electrochemical test
Coating Ecorr (mV) icorr (nA·cm-2) Rp (kΩ·cm2)
As-sprayed -576 ± 87a,b,c 142 ± 54a,b 72 ± 16a
Heat-treated (oC)
400 -598 ± 60a,b 134 ± 35a,b 87 ± 29a 500 -518 ± 46b,c 95 ± 25a,b 162 ± 33b,c
600 -464 ± 58c 83 ± 23a 178 ± 49c
700 -692 ± 77a 153 ± 39b 103 ± 22a,b
Number of samples is at least six in each subgroup.
Mean values followed by the same superscript letter in the same column are not significantly different (p > 0.05) according to Scheffe’s post-hoc multiple comparisons.
Figure 1. XRD patterns of the HA powder, monolithic HA coating, and graded coating (H:
apatite; A: α-TCP; B: β-TCP; C: CaO).
Figure 2. FTIR spectra of the HA powder, monolithic HA coating, and graded coating.
Figure 3. (a) Surface and (b) cross-sectional SEM micrographs and (c) elemental analyses of Ti, Ca and P through coating thickness of the graded coating.
(b)
50 µm (a)
40 µm
Figure 4. OCP of coated samples before and after cyclic fatigue. (a) HA coating without fatigue, (b) graded coating without fatigue, (c) graded coating with fatigue, and (d) HA coating with fatigue.
Figure 5. Typical polarization curves of coated samples before and after cyclic fatigue. (a) HA coating without fatigue, (b) graded coating without fatigue, (c) graded coating with fatigue, and (d) HA coating with fatigue.
Figure 6. XRD patterns (left) and FTIR spectra (right) of the as-sprayed coating (a) and heat-treated coatings at 400oC (b), 500oC (c), 600oC (d), and 700oC (e). (H: apatite; A: α-TCP; B:
β-TCP; C: CaO).
Figure 7. Open circuit potential-time (left) and typical polarization (right) curves of graded coatings before (a) and after heat treatment at 400oC (b), 500oC (c), 600oC (d), and 700oC (e) in deaerated HBSS at 37°C.
Figure 8. Scanning electron micrographs: as-sprayed coating (a) with gentamicin loading (b), the release of gentamicin for as-sprayed coating (c) and 600oC-treatment coating (d).
Figure 9. The release profiles of gentamicin as a function of time from coatings without (a) and with heat treatment at 600oC (b). The insert is the short-term release profiles.
出席國際學術會議心得報告
計畫編號 NSC 95-2314-B-040-011-MY2
計畫名稱 含胜肽分子之氫氧基磷灰石/鈦功能性漸鍍層之特性研究
出國人員姓名 服務機關及職稱
丁信智
中山醫學大學 口腔材料科學所 教授 會議時間地點 96/9/9-96/9/14 加拿大 Banff
會議名稱 第 58 屆國際電化學年會
發表論文題目 Electrochemical behavior of heat-treated hydroxyapatite/titanium composite coatings
一、參加會議經過
本次第 58 屆國際電化學年會在加拿大班夫國家公園內的班夫中心國際會議廳舉行。會議 發表分口頭及海報貼示，論文超過 1100 篇，會議期間每天早上 9 點有 1 小時的 plenary lecture，
邀請電化學領域大師專題報告。整個會議研討涵蓋與電化學相關的各種不同議題，如生物電 化學、感測器、鋰電池、材料腐蝕、生物燃料電池、電化學奈米科技、電催化等。並有電化 學儀器設備商同時參展，會場討論氣氛十分熱絡。在 9/12 下午大會有半日遊的活動，本人自 費參於 Lake Louise & Moraine Lake Tour，當晚並有晚宴。本人受第六屆亞洲電化學研討會主 辦單位林修正教授所託，攜帶 demo 至會場。
二、與會心得
此研討會主要是由國際電化學學會主導，來自美加、歐洲及亞洲地區（大陸、日本及韓 國）多位學者參與。台灣學者除我本人外，另有來自台灣科技大學化工系何國川教授實驗室 博士生、成大醫工張憲彰教授、中興吳靖宙教授、大同張敏興教授等參加。電化學研究為一 跨領域且理論、應用並重的學門，從與會中所發表的論文可知仍有相當大的研究空間。國際 趨勢除能源主題外，似乎逐漸朝向運用電化學理論於分子級奈米科技。這次本人的論文發表，
也與國外學者進行多次意見交流，並邀請數位國際友人參於台北第六屆亞洲電化學研討會。
台灣電化學研究人才散佈在各領域如化工、材料、醫工、化學等，不過並沒有一個直接的電 化學學會，但可喜的是經過數位教授努力，國際電化學學會支持，將在 2008，5/11-14 於台北 舉辦第六屆亞洲電化學研討會。期待未來能舉辦更多國際型會議。
Electrochemical Behavior of Heat-Treated Hydroxyapatite/Titanium Composite Coatings
Shinn-Jyh Ding*, Po-Jen Chien
Institute of Oral Materials Science, Chung-Shan Medical University, Taichung 402, Taiwan [email protected]
Hydroxyapatite (HA)-coated appliances plasma sprayed on the metallic substrates endow the orthopaedic and dental implants not only with bioactivity but also with a protective layer shielding the release of metal ions, in addition to bearing the loading. Nevertheless, the HA coating-metallic substrate bonding is still an unsolved problem for the long-term clinical use of the implant. To improve the coating-substrate bond strength and other properties, more recently, we developed functionally graded HA/Ti coatings consisting of an underlying Ti bond coat, the alternating layer, and an HA top-layer plasma-sprayed on titanium alloy substrates [1]. In this work, the major consideration was to examine the corrosion resistance of the potential graded coatings after various post-deposition heat treatments over 400-700oC at 100oC interval.
The results elicited that the heat treatment used led to recrystallization of amorphous calcium phosphate of as-sprayed coatings and gave rise to a higher crystallinity by a factor of 4-5 but temperature-sensitive bond strength. In contrast to the other three heat-treated coatings, the 500oC-treated specimen had the maximum bond strength that was comparable to the as-sprayed coating of about 23 MPa. After post-deposition heat treatment, plasma spray-induced layer defects such as porosity within coatings were effectively reduced. As for the electrochemical results, although there was no significant difference in corrosion potential between as-sprayed coating and heat-treated coating at 500oC, the current density of this heat-treated coating was significantly lower than that of the as-sprayed coating. Moreover, the heat-treated coating had a better corrosion-resistant ability with an increased polarization resistance value by approximately two times as compared to the as-sprayed specimen. Improved corrosion resistance was possibly due to a coating surface modification with higher crystallinity and less dissoluble non-apatite phases, as well as a reduction of coating defects [2] when the functionally graded coatings were subjected to post-deposition heat treatment.
On the basis of the data in this study, the heat treatment at 500oC for 1 h in air, endowing with increased crystallinity and the reduced defects without significantly reduced bond strength, provided a better corrosion protection than the other three treatment temperatures.
Reference
[1] C.C. Chen, T.H. Huang, C.T. Kao, S.J. Ding, J. Biomed. Mater. Res. 78B (2006) 146.
[2] C.C. Chen, T.H. Huang, C.T. Kao, S.J. Ding, Electrochim. Acta 50 (2004) 1023.
Acknowledgement to National Science Council of the Republic of China (grant No.
95-2314-B-040-011-MY2).