致密ZrO_2陶瓷板表面金属层的熔盐电解法制备
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摘要
致密ZrO_2陶瓷具有良好高温强度、耐磨性,以及导电、导热特性,而致密ZrO_2陶瓷板的表面金属化是改善其与金属间的钎焊润湿性,促进其应用的重要途径。熔盐电解法是一种通过加载电压直接将金属从其氧化物中还原实现金属冶炼的方法。在Ca Cl2-Na Cl混合熔盐中,以致密ZrO_2陶瓷板为阴极,石墨为阳极,在850℃,3.1 V电压条件下对致密ZrO_2陶瓷板进行电解,表面原位生成致密的锆金属层。采用X射线衍射(XRD)研究了不同电解时间、不同表层深度的物相组成,并计算分析表层不同深度电解产物的含量。结果显示,ZrO_2的电解脱氧冶金反应由外向内进行,形成ZrO_2,Zr3O和Zr共存的电解脱氧层。随电解时间增加,脱氧层的深度增加,表面氧含量减小。当电解时间超过8 h,在致密ZrO_2陶瓷板表面形成锆金属层。初步探讨了熔盐电解法机制,提出氧化锆陶瓷表面氧的离子化是受到了强制双电层吸引的设想。
The dense ZrO_2 ceramics have good high temperature strength,abrasion resistance,as well as conductive and thermal conductivity. Surface metallization of dense ZrO_2 ceramic plates is an important way to improve the brazing wettability between them and the metal. The molten salts electro-deoxidization is a metal smelting method to produce metal directly from metal oxide by loading voltage. By using CaCl_2-NaCl molten salts as electrolyte,dense ZrO_2 ceramics as cathode and graphite rod as anode,the ceramic plates were electrolyzed at 850 ℃ and 3. 1 V,and a Zr metal layer was obtained on the ZrO_2 ceramic plate by in-situ electro-deoxidization.The phase constitutions of the ceramics surfaces layers with different electro-deoxidization time,as well as in different depth,were studied by means of X-ray diffraction(XRD) techniques,and the contents of various phases were calculated. The result showed that the electro-deoxidization took place from surface of the ceramic plate,and an electro-deoxidization layer containing ZrO_2,Zr_3O and Zr formed. With increasing electrolysis time,the thickness of electro-deoxidization layer increased,and oxygen content decreased. When the electrolysis time exceeded 8 h,the zirconium metal layer was formed on the surface of the compact ZrO_2 ceramic plate. The mechanism of the electro-deoxidization was analyzed preliminarily. The hypothesis was proposed that the ionization of oxygen atoms resulted from zirconia surface being attracted by the forced electric double layer.
The dense ZrO_2 ceramics have good high temperature strength,abrasion resistance,as well as conductive and thermal conductivity. Surface metallization of dense ZrO_2 ceramic plates is an important way to improve the brazing wettability between them and the metal. The molten salts electro-deoxidization is a metal smelting method to produce metal directly from metal oxide by loading voltage. By using CaCl_2-NaCl molten salts as electrolyte,dense ZrO_2 ceramics as cathode and graphite rod as anode,the ceramic plates were electrolyzed at 850 ℃ and 3. 1 V,and a Zr metal layer was obtained on the ZrO_2 ceramic plate by in-situ electro-deoxidization.The phase constitutions of the ceramics surfaces layers with different electro-deoxidization time,as well as in different depth,were studied by means of X-ray diffraction(XRD) techniques,and the contents of various phases were calculated. The result showed that the electro-deoxidization took place from surface of the ceramic plate,and an electro-deoxidization layer containing ZrO_2,Zr_3O and Zr formed. With increasing electrolysis time,the thickness of electro-deoxidization layer increased,and oxygen content decreased. When the electrolysis time exceeded 8 h,the zirconium metal layer was formed on the surface of the compact ZrO_2 ceramic plate. The mechanism of the electro-deoxidization was analyzed preliminarily. The hypothesis was proposed that the ionization of oxygen atoms resulted from zirconia surface being attracted by the forced electric double layer.
引文
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[2]Liu M F,Guo Z C,Lu W C.Process of direct electrochemical reduction of Ti O2[J].The Chinese Journal of Nonferrous Metals,2004,14(10):1752.(刘美凤,郭占成,卢维昌.Ti O2直接电解还原过程的研究[J].中国有色金属学报,2004,14(10):1752.)
[3]Mellors G W,Senderoff S.Electrodeposition of coherent deposits of refractory metals[J].Journal of the Electrochemical Society,1965,112(3):266.
[4]Yan X Y,Fray D J.Production of niobium powder by direct electrochemical reduction of solid Nb2O5in a eutectic Ca Cl2-Na Cl melt[J].Metal Trans.B,2002,33(10):685.
[5]Li Q Y,Du J H,Xi Z P.Preparation of zirconium by electro-deoxidization in molten salt[J].Rare Metal Materials and Engineering,2007,36(S3):390.(李晴宇,杜继红,奚正平.金属锆的熔盐电脱氧制备[J].稀有金属材料与工程,2007,36(S3):390.)
[6]Kuznetsov S A.Electrochemistry of refractory metals in molten salts:Application for the creation of new and functional materials[J].Pure Appl.Chem.,2009,81(8):1423.
[7]Qiu G H,Wang D H,Ma M,Jin X B,Chen G Z.Electrolytic synthesis of Tb Fe2from Tb4O7and Fe2O3powders in molten Ca Cl2[J].Journal of Electroanalytical Chemistry,2006,589(3):139.
[8]Du J H,Xi Z P,Li Q Y,Li Z X,Tang Y.Preparation of Ti Fe alloy by electro-deoxidization in molten salt[J].Rare Metal Materials and Engineering,2008,37(12):2240.(杜继红,奚正平,李晴宇,李争显,唐勇.熔盐电解还原制备Ti Fe合金[J].稀有金属材料与工程,2008,37(12):2240.)
[9]Xie H W.Preparation of Al and alloys in low temperature molten salt[D].Shenyang:Northeastern University,2009.98.(谢宏伟.低温熔盐电解制备铝及合金[D].沈阳:东北大学,2009.98.)
[10]Liao C F,Luo L S,Wang X,Tang H.Preparation for Al-Nd intermediate alloy by molten-salt electrolysis method and its mechanism[J].The Chinese Journal of Nonferrous Metals,2015,25(12):3523.(廖春发,罗林生,王旭,汤浩.熔盐电解制备铝钕中间合金及其机理[J].中国有色金属学报,2015,25(12):3523.)
[11]Li Z Q,Hu L,Lu J,Liu N,Han M.Progress in mutual influences between substances during preparation of alloy via molten salt electro-deoxidation[J].Chinese Journal of Rare Metals,2016,40(11):1169.(李泽全,胡玲,卢姣,刘楠,韩梅.熔盐电脱氧法制备合金时物质间相互影响的研究进展[J].稀有金属,2016,40(11):1169.)
[12]Chen G Z,Fray D J.Voltammetric studies of the oxygen-titanium binary system in molten calcium chloride[J].Electrochem.Soc.,2002,49:455.
[13]Suzuki R O.Direct reduction processes for titanium oxide in molten salt[J].JOM,2007,59(1):68.
[14]Suzuki R O.Calciothermic reduction of Ti O2and in situ electrolysis of Ca O in molten Ca Cl2[J].Phys.Chem.Solids,2005,66(2-4):461.
[15]Mohandas K S,Fray D J.Electrochemical deoxidation of solid zirconium dioxide in molten calcium chloride[J].Metallurgical and Materials Transactions B,2009,40B(10):685.
[16]Wu T,Xiao W,Jin X B,Liu C,Wang D H,Chen G Z.Computer-aided control of electrolysis of solid Nb2O5in molten Ca Cl2[J].Physical Chemistry Chemi-cal Physics.2008,10(13):1809.
[17]Peng J J,Jiang K,Xiao W,Wang D H,Jin X B,Chen G Z.Electrochemical conversion of oxide precursors to consolidated Zr and Zr-2.5Nb tubes[J].Chemistry Materials,2008,20(23):7274.
[18]Li Z Q,Bai C G,Chen X L,Tao C Y.Conductivity of a Ti O2cathode in the FFC process and analysis of its influencing factors[J].Journal of Chongqing University,2008,31(11):1323.(李泽全,白晨光,陈小亮,陶长元.FFC工艺中阴极Ti O2的导电性及影响因素分析[J].重庆大学学报,2008,31(11):1323.)
[19]Wu X R,Jia Z J,Ma H Y,Liao S D,Wang B G.Fundamentals of electrochemistry(Ⅲ)——electrical double layer model and its development[J].Energy Storage Science and Technology,2013,2(2):152.(吴旭冉,贾志军,马洪运,廖斯达,王保国.电化学基础(Ⅲ)——双电层模型及其发展[J].储能科学与技术,2013,2(2):152.)
[20]Wang C Z.Solid Electrolyte and Chemical Sensors[M].Beijing:Metallurgical Industry Press,2000.14.(王常珍.固体电解质和化学传感器[M].北京:冶金工业出版社,2000.14.)