摘要
二铝酸钙(CA_2)和六铝酸钙(CA_6)是CaO-Al_2O_3二元体系中两类重要化合物。二铝酸钙材料具有很低的热膨胀系数,在和其他高熔点、高膨胀系数材料(比如MgO、CaZrO_3等)复合时可以很好的降低复相材料的热膨胀系数低;六铝酸钙材料在高温还原气氛下有很好的稳定性、在碱性环境中有足够的抗侵蚀能力以及其在含氧化铁渣中具有低溶解性,被认为是一种有前途的高温材料,同时六铝酸钙具有六方片状晶体结构以及与刚玉相有很好的化学相容性和相近的热膨胀系数的特点,人们将之引入氧化铝陶瓷基质中来增韧氧化铝陶瓷。
本论文拟采用反应烧结法合成了CA_2、CA_6材料,并通过在刚玉质耐火材料基质中引入不同含量的CA_2、CA_6相,制备了CA_2/CA_6刚玉复相耐火材料,以期利用CA_2材料的低膨胀系数和CA_6材料的片状增韧机理来改善现有刚玉耐火材料的热震稳定性。本论文研究工作如下:
1.研究以轻质CaCO_3/活性氧化铝,纯铝酸钙水泥/活性氧化铝两种合成工艺路线,采用反应烧结法合成CA_2、CA_6材料,研究了反应原料、反应温度、成型压力对CA_2、CA_6材料烧结性能和物相变化的影响,观察和分析了CA_2、CA_6材料的显微结构,探讨了CA_6片状晶体结构的生长机理。
2.采用机压成型制备CA_2/CA_6刚玉复相材料。研究了纯铝酸钙水泥或CaCO_3加入量不同对CA_2/CA_6刚玉复相耐火材料的烧结性能、力学性能、物相组成、热膨胀性能及其显微结构的影响,并探讨了CA_2/CA_6刚玉复相材料的抗渣性能。
3.采用浇注成型方法制备CA_2/CA_6/刚玉复相材料。研究了纯铝酸钙水泥加入量对材料的烧结性能、力学性能、物相组成、热膨胀性能及显微结构的影响,并探讨了CA_2/CA_6/刚玉复相材料的抗渣性能。
Calcium dialuminate (CA2) and Calcium hexaluminate (CA6) occur at CaO-Al2O3 system as important compounds. Composites combining CA2 with high melting point and high thermal expansion materials such as MgO and CaZrO3 show a lower thermal expansion due to the low thermal expansion coefficient of CA2. CA6 is considered as a promising material for its well stability in reducing atmospheres, improved corrosion resistance to alkali and low solubility in slag containing Fe2O3. Furthermore, thanks to the hexagonal platelet structure, well chemical consistence and similar thermal expansion coefficient with corundum, CA6 is introduced into the matrix of corundum ceramic as toughening phase.
In this paper, CA2 and CA6 were synthesized respectively by reaction sintering and CA2/CA6/corumdom composite refractories were fabricated through adjusting the content of CA2 and CA6 in matrix in order to improve the thermal shock resistance of corundum refractories. What has been done in this paper is divided into three parts:
The first part focuses on the sintering properties and reaction mechanism of CA2 and CA6 synthesized by two processing routes-CaCO3/ -Al2O3 and pure calcium aluminate/ -Al2O3, respectively. The effect of raw materials and compact pressures and reaction temperatures on the sintering properties of the product was studied. The microstructures of CA2 and CA6 were observed and the plantlet structure growth mechanism of CA6 was discussed.
The second part focuses on the fabrication and properties of CA2/CA6//Al2O3 multiphase composites. The effect of the content of pure calcium aluminate or CaCO3 in the matrix on the sintering and mechanical properties , phase composition , thermal expansion, microstructure and slag resistance of CA2/CA6/Al2O3 multiphase composites were investigated.
The final part focuses on the fabrication and properties of CA2/CA6/Al2O3 castable. The effect of the content of pure calcium aluminate in the matrix on the sintering and mechanical properties, phase composition , thermal expansion, microstructure and slag resistance of CA2/CA6/Al2O3 composites were investigated.
引文
[1] Kopanda, J. E. and Maczura, G., Production process,Peoperties,and applications for calcium aluminate cements.In Alumina Chemical Science and Technology Handbook,ed. L. D. Hart. American Ceramics Society, Westerville.OH,1990,pp.171-184
[2] Parker, K. M. and Sharp, J.H., Refractory calcium aluminate cements. Trans. J. Br. Ceram. Soc., 1982, 8(2),35-42
[3] D.A.Jerebtsov,G.G.Mikhailov.Phase diagram of CaO-Al_2O_3 system, Ceram.Int.27 (2001) 25-28
[4] R.M.Cursetji and A.K.Chatterjee.User Friendly High Refractory CAC,ibid,467-476
[5] B.Hallstedt, Assesment of the CaO-Al_2O_3 system ,J.Am.Ceram.Soc.73(1)(1990)15-23
[6] P.J. Baldock, A.Parker, I.Sladdin,Xray powder diffraction data for calcium monoaluminate and
[7] D.W. Goodwin, A. J. Lindop,The crystal structure of CaO.2Al_2O_3, Acta Cryst.B 26(1970) 1230-1235
[8] D.Weber, A.Bischoff, Grossite(CaAl_4O_7)-a rare phase in terrestrial rocks and meteorites, Eur. J. Mineral 6(4)(1994)591-594
[9] E.R. Boyko, L. G. Wisnyi, The optical properties and structures of CaO.2Al_2O_3 and SrO. 2Al_2O_3, Acta Cryst. 11(1958) 444-445
[10] E.Cridal,S.De Aza,Proc.UNITECR Congress,Aachen,1991,pp.403-406
[11] S.Jonas, E Nadachowske, D.Szwagierczak, A new non-silicate refractory of low thermal expansion, Ceram. Int. 24(3)(1998)211-216
[12] S.Jonas, F.Nadachowski, D. Szwagierczak, Low thermal expansion refractory composites based on CaAl4O7, Ceram. Int. 25(1)(1999)77-84
[13] S.Jonas, F. Nadachowski, D.Szwagierczak, Refractory composites of deeply depressed thermal expansion, Key Eng.Mater.206(2)(2002)1169-1172
[14] K.Fukuda, K.Yamauchi, Anisotropic thermal expansion in CaAl_4O_7, J. Mater, Res. 17(5) (2002) 1050-1054
[15] Yoshikazu Suzuki,Tatsuki Ohji,Anisotropic thermal expansion of calcium dialuminate (CaAl_4O_7) simulated by molecular dynamics,Ceram.Int.23(1)(2003)107-113
[16] K.W.Harr.Relationship Between Mineral Phase C_4AF and CA in CAC with a High Iron Content, ibid, 121~127
[17] Nurse.R.W., Welch,J.H. and Majundar,A.J., The CaO-Al_2O_3 system in a moisture-free atmosphere. Trans.Br, Ceram.Soc., 1956.64,409-418
[18] Calcium Hexaaluminate in the system of CaO-Al_2O_3-SiO_2. AH., CCCP, 1949, 66(4):673~676.
[19] 高振昕.烧矾土中的六铝酸钙.硅酸盐学报.1982,10(2):216-220
[20] 高振昕、周宁生等。论不定形耐火材料的热反应与显微结构的形成与演变。2003年全国不定形耐火材料学术会议论文集,2003,P20~P37
[21] Linan An and Helen M. Chan, R-curve behavior of in-situ toughened Al_2O_3:CaAl_(12)O_(19) ceramic composites, J Am Ceram Soc, 1996, 79(12), 3142-48.
[22] Michael K. Cinibulk, Hexaluminates as a cleavable fiber-matrix interphase: synthesis, texture development, and phase compatibility, J Eur Ceram Soc, 2000, 20, 569-582.
[23] Sanchez-Herencia A J, Moreno R, Baudin, Fracture behavior of alumina-calcium hexaluminate composites obtained by colloidal processing, J Eur Ceram Soc, 2000,20, 2575-2583.
[24] Asmi D and Low I.M, Processing of an in-situ layered and graded alumina/calcium hexaluminate composite: Physical characteristics, J Eur Ceram Soc, 1998, 18, 2019-2024.
[25] Cristina Dominguez C, Chevalier J, Torrecilas R, et al, Microstructure development in calcium hexaluminate, J Eur Ceram Soc, 2001, 21,381-387.
[26] Curien, H., Guillemin, C. and Orcel ,J.et al.,L Hibonite,nouvelle espece minerale. Compt. Rend. Hebd.Seances Acad, Sci.,1958,242,2845-2847
[27] Hallstedt,B.,Assessment of the CaO-Al_2O_3 system.J.Am.Ceram.Soc.,1990,73,15-23
[28] Schmid, H. and Jonghe, L.C.,Structure and non-stoichiometry of calcium aluminates. Philos. Mag. A., 1983,48(2), 287-297
[29] Utsunomiya, A., Tanaka, K., Morikawa, H., Marumo, F.and Kojima, H Structure refinement of CaO-6Al_2O_3. J. Solid State Chem., 1989, 83(1), 8-19
[30] Iyi, N., Takekawa, S. and Kimura, S., Crystal chemistry of hexaluminates: β-Al_2O-3 and magnetoplumbite structures, J. Solid State Chem.,1989,83(1),8-19
[31] Balaji Venkateshwaran,etl.Low temperature dielectric properties of magnetoplumbite family of materials. International Journal of Inorganic Materials,1999(1)213-217
[32] H.Inoue, K. Sekizawa, etl. Changes of crystalline phase and catalytic properties by cation substitution in mirror plane of hexaluminate compounds. Journal of Solid State Chemistry. 1996,121,190-196
[33] Criado E, CA6_6耐火材料,国外耐火材料,1992,10, 58-63.
[34] Jose Luis Mendoza, Aaron Freese and Robert E. Moore. Thermalmechanical behavior of calcium aluminate composites. Ceramic Transactions Advanced in Refractories Technology. 1990.
[35] Vipin Kant Singh and Krishna Kumar Sharma, Low-Temperature Synthesis of Calcium Hexa-aluminate, Journal of American Ceramic Society. 2002 (4) 84:769-772.
[36] J.M.Tulliani,G..Pages,G..Fantozzi and L.Montanaro.Journal of Thermal Analysis and Calorimetry. Vol. 72(2003)1135-1140
[37] Vladimir V. Pimachenko and Valery V.Martynenko etl. Super Low Thermal Conductivity Heat Insulating Lightweight Material on the Basis of Calcium Hexaluminate. Proceedings of the Second International Symposium on Refractories, 2002:1188-1192.
[38] Van Garsel, etl. Long term high temperature stability of microstructure calcium hexaluminate based insulating materials. UNITECR.1999:181-186.
[39] Webb Janich, Maria, Suszczynski, et al. high temperature insulating refractory monolithics based on microporous aggregates. UNITECR.1999:177-180.
[40] B.M.Mohamed and J.H.Sharp.Kinetics of Formation Ca_(12)Al_(14)O_(33)(Dodecacalcium Heptaaluminate), ibid, 65-76
[41] M.A.Serry, N.M.Kalil and M.F.Zaaweah.Phase Evolution and Hydraulic Properties of Cement Castables Matrixes.Trans.Brit.Cer.Soc.,2001,4:171-176
[42] B.Touzo, D.Bell, K. L. Scrivener and C.Parr.Application of Calcium Aluminate Cement in Alumina-Spinel Castables.ibid,503-515
[43] D. Asmi, I.M. Low, B.H. O'Connor. Phase compositions and depth-profiling of calcium aluminates in a functionally graded alumina/calcium-hexaluminate composite. Journal of Materials Proceeding Technology. 2001, 118:219-224.
[44] Cdstina Dominguez, Jérome Chevalier, Ramon Torrecillas, Gilbert Fantozzi. Microstructure Development in Calcium.Hexaluminate. Journal of the European Ceramic Society, 2001,21: 381-387.
[45] Tulliani J M, pages G, Fantozzi G, Montanaro L, Dilatometry as a tool to study a new synthesis for calcium hexaluminate, J Therm Analys and Calorimet, 2003, 72, 1135-1140.
[46] Fuhrer M, Hey A and Lee W E, Microstructural evolution in self-forming spinel/calcium aluminate-bonded castable refractories, J Eur Ceram Soc, 1998, 18, 813-820.
[47] Chan Chen-Feng and Ko Yung-Chao, Effect of CaO content on the hot strength of alumina-spinel castables in the temperature range of 1000° to 1500℃, J Am Cerarn Soc, 1998, 81(11), 2957-2960.
[48] 李北星,于其俊,冯修吉.CaO—Al_2O_3系统铝酸钙矿物水化活性差异的SCC—DV—Xa方法研究.硅酸盐学报,1998,26(4):411-416.
[49] J.S.Moya, A.H.de Aza,H.ESteier, J.Requena and P.Pena,Scripta Metal.et Mat., 31 (1994) 1049.