Ln2Zr2O7 (Ln = Nd, Gd)相轉變與矽氧化物薄膜對鋼片防蝕之研究

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Title:	Ln2Zr2O7 (Ln = Nd, Gd)相轉變與矽氧化物薄膜對鋼片防蝕之研究
Other Titles:	Phase transition in Ln2Zr2O7 (Ln = Nd, Gd) and corrosion protection of carbon steel by different alkoxysilanes
Authors:	李攸軒;Lee, Yu-Hsuen
Contributors:	淡江大學化學學系博士班高惠春;Kao, Huey-Chuen I.
Keywords:	相轉變;XANES光譜;防蝕;SAE1018鋼片;Ln2Zr2O7;phase transition;XANES;Sol-Gel;corrosion protection,SAE1018
Date:	2011
Issue Date:	2011-06-16 21:57:40 (UTC+8)
Abstract:	氧化物相轉變實驗以檸檬酸鹽前驅物法，鍛燒溫度為700-1400℃製備兩系列的A2B2O7氧化物，樣品起始組成為Ln2Zr2O7 (Ln = Nd、Gd)。所得到Nd 與Gd 系列單相樣品的鍛燒溫度分別低於900和1100℃為缺陷的螢石結構(DF)；鍛燒溫度分別高於1000和1200℃則為無序的焦綠石結構(DP)。隨著鍛燒溫度的上升，焦綠石相的有序程度增加，根據Arrehnius方程式所計算出的Nd系列樣品陽離子和陰離子熱活化能分別為0.27(1)和0.46(4) eV；Gd系列樣品的熱活化能分別為0.40(3)和1.44(4) eV。O K-edge吸收光譜圖顯示，532 eV 和536 eV兩個吸收峰分別為O (1s) 電子轉移至Zr (4d)的eg和t2g軌域。在Zr K-edge吸收光譜圖中，隨著鍛燒溫度的上升，晶場分裂能的增加，顯示Zr(4d)與配位基O (2p)軌域的互相影響增加，在焦綠石相中的ZrZr−O配位共價鍵比螢石相中的Zr−O配位共價鍵強。防鏽實驗以TEOS (tetraethoxysilane)、TMOS(tetramethoxysilane)、VTrMOS (vinyltrimethoxysilane)、APTrEOS (3-aminopropyltriethoxysilane)、PhTrEOS (phenyltriethoxysilane) 等五種矽氧化物藉由溶膠−凝膠法製備薄膜對鋼片表面防蝕之研究。在室溫中，將其中一種矽氧化物分別溶於(1) 苯胺、(2) NMP (N-methyl-2-pyrrolidone)、(3)苯胺和NMP中，並加入PMMA(polymethyl-methacrylate)混合反應，此為溶膠−凝膠溶液，接著以浸漬塗佈法將溶液塗佈於鋼片基材上。幾乎所有樣品薄膜硬度在一公斤鉛筆力的測試結果皆為9 H，附著力部分在膠帶測試下為 ≤ 5% 面積脫落。以苯胺、TMOS製備的薄膜具有最佳的防腐蝕效果，在35 °C、5%鹽霧測試結果可達2.0(1) x 103 h，厚度為12(1) μm；其腐蝕速率為0.005(1) mm/y。由實驗結果得知，使用四個Si−OR官能基比使用三個Si−OR官能基當溶膠−凝膠溶液的起始材料有較好的防蝕結果。 Two series of samples, Ln2Zr2O7 (Ln = Nd, Gd), were prepared by the polymeric citrate precursor method. Nd2Zr2O7 and Gd2Zr2O7 samples have fluorite phase if they are prepared at temperatures lower than 900 and 1100 °C, respectively. On the other hand, if the samples are prepared at temperatures higher than 1000 and 1200 °C, they have pyrochlore phase. Cation and anion ordering of the pyrochlore samples increases with increasing the preparation temperatures. Activation energies calculated on the log (σ⋅T) vs.(1/T) for the Nd2Zr2O7 and Gd2Zr2O7 on the cation ordering process are 0.27(1) and 0.40(3) eV, and on the O(3) site are 0.46(4) and 1.44(4) eV, respectively. The energy difference of the O K-edge absorption spectra at 532 and 536 eV was assumed to the crystal field splitting energy of the 4d orbitals (ΔE4d, t2g and eg) of the Zr ion. A correlation between ΔE4d and the strength of the interaction between Zr (4d) and O (2p) orbitals have been found. The same results can be found from the Zr K-edge absorption spectra.Five alkoxysilanes, such as, TEOS (tetraethoxysilane), TMOS (tetramethoxysilane), VTrMOS (vinyltrimethoxysilane), APTrEOS (3-aminopropyltriethoxysilane) and PhTrEOS (phenyltriethoxysilane) were employed for making protective films on a carbon steel substrate via sol-gel method. Three sol-gel solutions containing one alkoxysilane and either (1) aniline, (2) NMP (N-methyl-2-pyrrolidone), or (3) aniline and NMP were prepared. PMMA (polymethyl-methacrylate) is added to help the formation of a dip-coated film on the substrate. All of the films have corrosion resistance effect. Most of them have hardness of 9 H under 1 kg pencil test and only ≤ 5% areas are removed by the tape test. The best result is found in the film with a thickness of 12 μm prepared by TMOS and aniline. It sustains in the 5% salt mist for 2.0(1) x 103 h at 35 °C, equivalent to the corrosion rate of 0.005(1) mm/y. In general, films prepared by the TEOS and TMOS with four −OR have better anticorrosion effect than those made by the alkoxysilanes with three −OR functional groups.
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