微弧氧化與水熱法於鈦板之氫氧基磷酸鈣披覆

Abstract

本文以微弧氧化法於鈦板成長含鈣及磷之氧化膜，透過橫截面TEM解析其微結構，並探討後續水熱處理析出氫氧基磷酸鈣的機制。在β-甘油磷酸鈉及醋酸鈣電解液中，以定電流方式將鈦板陽極極化至350V，發現有微弧放電反應，同時鈦板表面生成含鈣及磷之多孔氧化層，其結晶相主要為銳鈦礦。經微弧放電生成的氧化膜呈現雙層結構，外層包括鈣/磷的結晶質與非晶質混和區域，非晶質區含有高含量的鈣及磷；內層為一多孔層，這些孔會隨著陽極膜向底材擴展而合併，形成氣孔層。電解液中β-甘油磷酸鈉含量的增加導致微弧氧化膜中鈣及磷含量的增加，但同時降低氧化膜鈣磷比與鍍層結晶程度。在磷酸根溶液中添加醋酸根和氫氧根皆可促進微弧放電反應，同時此兩種陰離子會使氧化膜產生不同形貌以及結晶結構。微弧放電成長的氧化膜在300℃進行2小時之水熱處理，無法獲得高結晶度之氫氧基磷酸鈣，添加碳酸氫鈉於水熱處理溶液後，析出高結晶性之單相氫氧基磷酸鈣。

Calcium and phosphorus-containing oxide film was made on commercially pure titanium plate using a microarc discharging oxidation method. The microstructure of the oxide film was characterized by cross-sectional transmission electron microscopy (TEM). Hydrothermal treatment was then performed on the oxide film for the precipitation of hydroxyapatite. Upon galvanostatic anodizing up to 350V at a current density of 50 mA/cm2 in the electrolyte consisting of β-glycerophosphate disodium(β-GP) and calcium acetate, microarc discharge was observed on titanium plates, leading to the formation of an oxide film mainly composed of anatase, and calcium and phosphorus species. Once microarc discharge occurred during anodizing, relatively large craters were observed on the oxide film, which generally comprised two layers:an outer overlay containing significant amount of Ca and P in a mixture of amorphous oxide and nanocrystalline anatase, and an inner oxide layer dotted with micropores contacting the substrate. Moreover, as the front of the oxide film propagated toward the substrate, these micropores tended to coalesce into cavities residing at the interface between the outer and inner layers. The oxide film contained more Ca and P, but lower Ca/P ratio, and displayed less crystallinity with increasing solution b-GP concentration. Both acetate and hydroxyl ions can enhance microarc discharging, while resulted in oxide films with different morphologies and crystal structure. Hydroxyapatite precipitates on the porous oxide film were nonuniform after 2 h of hydrothermal treatment at 300℃. In contrast, introducing sodium hydrocarbonate to hydrothermal treatment solution led to the formation of high density hydroxyapatite precipitates with improved crystallinity.