於超臨界二氧化碳流體中以無電鍍方法製備鎳硼合金之研究

• Main Authors: 王鴻宇, Wang, Hung-Yu
• Other Authors: 材料科學及工程學系碩博士班, 蔡文達, Tsai, Wen-Ta
• Format: Thesis
• Language: Chinese; English
• Published: 2009
• Subjects: electrochemical properties; supercritical carbon dioxide; mechanical properties; Ni-B alloys; Electroless nickel; 超臨界二氧化碳; 鎳硼合金; 無電鍍鎳; 電化學性質; 機械性質; Carbonic acid
• Online Access: http://ir.lib.ncku.edu.tw/handle/987654321/93152; http://ir.lib.ncku.edu.tw/bitstream/987654321/93152/1/

本研究試圖開發新一代無電鍍鎳技術，於無電鍍鎳系統中引入超臨界二氧化碳(以下簡稱sc-CO2)以製備鎳硼合金，利用包含掃描式電子顯微鏡(SEM)、原子力顯微鏡(AFM)、電子微探儀(EPMA)、X-ray繞射儀(XRD)、X-ray光電子能譜儀(XPS)、恆電位儀(Potentiostat)以及奈米壓痕測試(Nanoindentation)等儀器與實驗，來分析超臨界無電鍍製程與常壓無電鍍製程所製備之初鍍鎳硼合金鍍層(As-deposited)在材料性質上的差異，諸如鍍層表面形貌、鍍層成份、結晶結構、電化學性質與機械性質等，並探討經熱處理(Heat-treated)對鍍層性質的影響。此外，本研究亦討論界面活性劑濃度以及二氧化碳壓力對於超臨界無電鍍製程所析鍍之鍍層的性質影響。 利用SEM與 AFM觀察鍍層表面形貌觀察，發現於sc-CO2流體中析鍍之鎳硼合金鍍層具有較高的表面粗糙度，鍍層表面呈現細胞狀組織，其上存在?多小顆粒團聚的結構。此外，由於sc-CO2在高壓環境下溶入水中形成碳酸，降低鍍液pH值，因此使得sc-CO2無電鍍製程之鎳硼合金鍍層的析鍍速率下降而硼含量增加。電化學性質分析結果顯示，於sc-CO2無電鍍製程所製備之鍍層因為具有較少裂痕與孔洞，所以在0 5 M鹽酸水溶液環境中具有較高的腐蝕電位以及較低的陽極腐蝕電流密度。另一方面，在1 M之氫氧化鈉水溶液中，於sc-CO2流體中製備之鎳硼合金鍍層具有較高之腐蝕電位、較低之腐蝕電流密度與鈍化電流密度，顯示其抗蝕能力較佳。而在經過熱處理後，由於產生包括晶界與差排等缺陷，因此在0 5 M鹽酸水溶液環境中，常壓與sc-CO2流體中所析鍍之鎳硼合金鍍層的腐蝕電流密度與陽極極化電流密度都有上升的趨勢。 利用XPS分析鍍層的成份與化學組態，發現兩種製程(常壓無電鍍製程與sc-CO2無電鍍製程)所製備之鍍層中的鎳原子與硼原子皆以元素的型態存在，然而可以從sc-CO2無電鍍製程的鍍層中找到固溶於鎳基地相之碳原子的存在，顯示碳原子在此製程中可以被還原並固溶於鎳的晶格中，達到固溶強化的效果。由奈米壓痕測試作鍍層機械性質的分析結果亦顯示，sc-CO2製程可得到更高硬度之無電鍍鎳硼合金鍍層。XRD的分析結果顯示，兩種製程的初鍍鍍層呈現非晶質結構，而經過400℃熱處理一小時後，常壓製程之鍍層主要由結晶鎳、Ni3B與Ni2B析出相所組成，而sc-CO2製程之鍍層則以結晶鎳與Ni3B析出相為主。 改變界面活性劑(C12EO8)於鍍液中的濃度後，於sc-CO2流體中析鍍之無電鍍鎳硼合金鍍層表面粗糙度隨濃度增加而上升，顯示較高濃度之界面活性劑的條件下，sc-CO2與鍍液所形成的乳化型態可能影響了無電鍍的析鍍反應。而二氧化碳壓力的影響方面，實驗結果發現，由於壓力增加會提高sc-CO2在鍍液中的溶解度，因此產生更多量的碳酸於鍍液中而使得其pH值進一步降低；因此sc-CO2壓力提高時，所析鍍出之鍍層的性質變化皆與直接降低鍍液pH值後所析鍍之鍍層性質變化有類似的改變趨勢，而單純改變壓力對於鎳硼合金鍍層的影響則較不顯著。 This study proposes a new electroless nickel plating method by introducing supercritical carbon dioxide fluids to electroless Ni-B plating system (sc-CO2 EN-B) By using many analyses apparatus material properties of as-deposited and heat-treated films fabricated by normal EN-B and sc-CO2 EN-B process respectively were investigated and compared such as surface morphology chemical composition crystal structure electrochemical properties and mechanical properties In addition the effect of surfactant concentration and pressure on material characteristics of Ni-B films deposited with an emulsion of sc-CO2 was also discussed in this work An increase in surface roughness of the sc-CO2 EN-B films as compared with that formed in ambient pressure was observed by using AFM The surface morphology of sc-CO2 EN-B film presents cell-like feature with many small particles deposited on it The bath pH value deceased due to the formation and dissolution of carbonic acid when the sc-CO2 was presented in bath and caused a decrease in deposition rate and an increase in coating boron content Besides the less cracks and voids sc-CO2 EN-B films has higher corrosion potential and lower anodic current density than normal EN-B films in 0 5 M HCl solution Furthermore the anodic polarization characteristic of EN-B films in 1 M NaOH solution demonstrated that the passive current density decreases as deposited with an emulsion of sc-CO2 fluid After heat treatment(400℃ 1 hour) was performed the presence of the crystal defect like grain boundary and dislocation during crystallization caused an increase in corrosion current densities of two kinds of EN-B films in 0 5 M HCl solution Based on the results of XPS EN-B films contain the elementary nickel and boron no matter deposited in sc-CO2 or normal EN-B processes but the carbon was also found in sc-CO2 EN-B films which indicated that carbon might be reduced and formed solid solution with nickel base Because of the solid solution strengthening the hardness of sc-CO2 EN-B films is higher than normal EN-B films Furthermore the XRD results showed that as-deposited EN-B plated in the bath with or without the presence of sc-CO2 fluid were amorphous For the heat-treated EN-B films prepared at 400℃ for 1 hour the recrystallined Ni Ni3B and Ni2B precipitation phases were found in normal EN-B films moreover only the recrystallined Ni and Ni3B precipitation phases formed the crystal structure of the sc-CO2 EN-B films In addition with different concentrations of surfactant (C12EO8) in the bath the surface roughness increased with increasing C12EO8 concentration indicated that the emulsion characteristics of sc-CO2 and bath in the high C12EO8 concentration condition might influence the reaction process of electroless Ni-B deposition The rising of CO2 pressure increased the degree of the dissolution of sc-CO2 in bath meaning that lower the bath pH value which demonstrated the sc-CO2 EN-B films properties Comparing to the influence of reducing bath pH value directly the similar tendency was observed with the influence of increasing pressure by measuring the deposition rate and boron content of sc-CO2 EN-B films