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The research of electrolytic deposition of zirconia on dental Co-Cr alloy and on titanium
|關鍵字:||electrolytic deposition;電解沉積;Co-Cr alloy;titanium;corrosion;ion release;鈷鉻合金;鈦;腐蝕;離子釋出||出版社:||材料工程學研究所||摘要:||
本實驗中針對精密鈦專用包埋材，探討包埋材本身與鈦鑄造體性質。結果顯示包埋材Gilvest Ti的熱膨脹率在鑄造溫度200℃非常小，但是具有大的硬化膨脹率，可以補償鈦的鑄造收縮。包埋材Gilvest Ti熱膨脹率在溫度大於600℃時尺寸變化非常小，以及升溫和降溫路徑幾乎是可逆性，顯示可以降低包埋材之熱衝擊和避免包埋材因溫度變化太大造成之龜裂。
為了增加抗蝕性和減少金屬離子釋出，在牙科用鈷鉻合金表面利用電解沉積方法製作氧化鋯薄膜，並且分析鈷鉻合金表面氧化鋯薄膜之結構。原子吸收光譜分析證實具有氧化鋯薄膜之Co-Cr合金在人工模擬唾液中鈷和鉻離子釋出量相對降低。ESCA的結果顯示氧化鋯薄膜表層(surface layer)的鍵結能隨著退火溫度而改變，400℃、500℃和600℃的薄膜表層結構分別為非晶質(a)、正方晶(t)和斜方晶(m)。XRD結果顯示400℃、500℃和600℃的薄膜主體(film bulk)結構變化為m ® t ® m + t。TEM結果發現薄膜介層(interface layer)是次微晶粒，先後形成斜方晶和正方晶結構。這些不同的相變化主要是由於ZrO2在空氣中、薄膜主體或在Co-Cr合金表面上具有不同的表面能量。
Three chapters about dental materials were investigated in this study.
1.Properties of investment for precision castings
The aim of this chapter was to investigate the properties of investment for precision castings. The results indicated that the thermal expansion of investment Gilvest Ti is small, but the setting expansion is large enough to compensate the shrinkage of titanium casting. Besides, its thermal expansion at T ³ 600 ℃ was constant and its heating-cooling cycle was almost reversible. These two results can also reduce the thermal shock and then avoid the cracking of investments.
2.Properties and structures of electrolytic ZrO2 coating on dental Co-Cr alloys
This study was conducted to increase the corrosion resistance and to decrease the metal ion release of dental cobalt-chromium alloys by electrolytic ZrO2 thin coatings. The microstructure of electrolytic zirconia coated films on Co-Cr substrates were also examined. The AAS's results show that the ZrO2 coated Co-Cr alloys decrease the chromium ion level than that of uncoated Co-Cr alloy. According to the results of ESCA, the bonding energies of ZrO2 coating surface layer which changed with the annealing temperature from 400 oC, 500 oC to 600 oC are attributed to amorphous (a), tetragonal (t), and monoclinic (m) structure, respectively. The X-ray diffraction (XRD) of the coatings on the Co-Cr substrates annealed at 400, 500 and 600 oC revealed the major crystallization from m through t and then to m + t. However, the TEM observations clearly showed that the interface layer of the coatings was nanosize crystallites, first the formation of monoclinic and then with tetragonal ZrO2 structures. These different phase transformations are mainly due to different surface energy of ZrO2 coating in air, in bulk or on Co-Cr alloy.
3.Corrosion resistance of ZrO2 coating on cast titanium in fluoride containing solution.
Zirconia coatings were formed on pure titanium by electrolytic deposition. The aim of this chapter was to investigate the effect of electrolytic zirconia coating on the corrosion resistance of cast titanium in fluoride containing solution. The dynamic polarization curves indicated that titanium and ZrO2 coated specimen showed good resistance in artificial saliva and the latter is better. However, the corrosion resistance of uncoated and coated titanium was decreased with increasing the concentration of fluoride in artificial saliva. Also, the corrosion resistance of titanium and ZrO2 coated specimen was decreased seriously in high concentration of NaF and low pH value artificial saliva because HF was formed in acidic NaF solution.
|Appears in Collections:||材料科學與工程學系|
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