用非等温热分析法研究了莫来石单相胶前驱体的结晶动力学,采用 XRD、TEM和27 Al-NMR 分析了前驱体向莫来石转化的微观结构变化。结果表明,前驱体在950℃开始形成莫来石晶体,结晶过程为以Avrami-Erofeev的随机形核和随后生长机制,动力学三因子：活化能Ea=1086.34 kJ/mol,指前因子A=9.33×1042 s-1,机理函数的微分表达式f(α)=n(1-α)[-ln(1-α)],其中n=3.37。结晶动力学为非均匀形核过程,形核速率I 随时间t 而下降；980℃左右主要以形核控制为主,1000℃左右则以核生长控制为主,晶粒的长大为扩散控制长大机制。
The crystallization kinetics of mullite from single-phase gel were studied using a non-isothermal ther-mal analysis method.The microstructure changes were investigated by X-ray power diffraction (XRD),trans-mission electron microscopy (TEM)and 27 Al nuclear magnetic resonance (NMR)spectroscopy.The results show mullite crystallization begins from 950 ℃.The crystallization process confroms to random nuclei produc-tion and the following unclei growth model of n-dimension Avrami-Erofeev.The activation energy Ea and the pre-exponential factor A of mullite crystallization are 1 086.34 kJ/mol and 9.33×1042 s-1,respectively.The differential expression of the corresponding mechanism function was f (α)=n(1-α)[-ln(1-α)] n-1 n ,n=3.37.The nucleation rates are non-uniform which decrease with the time t in crystallization process.Nuclea-tion was the dominant controlling step at about 980 ℃.Nucleation-growth becomes more predominant at about 1 000 ℃.The rates of the grain growth are controlled by diffusion.
参考文献
| [1] | Schneider H;Schreuer J;Hildmanna B .Structure and properties of mullite-a review[J].Journal of the European Ceramic Society,2008,28(2):329-344. |
| [2] | 李友芬,刘莉莉,杨建龙,王茜.掺杂锶对莫来石光谱特性的影响[J].功能材料,2010(z3):515-517,523. |
| [3] | Schneider H;Voll D;Saruhan B et al.Syntyesis and structural characterization of non-crystalline mullite pre-cursors[J].J Non-cryst Solid,1994,178(3):262-271. |
| [4] | Wei Wencheng;Halloran J W .Transformation kinetics of diphasic aluminosilicate gels[J].Journal of the American Ceramic Society,1988,71(7):581-587. |
| [5] | Li D X;Thornson W J .Mullite formation kinetics of a single-phase gel[J].Journal of the American Ceramic Society,1990,73(4):964-969. |
| [6] | Kiyoshi Okada;Jun-ichi Kaneda;Yoshikazu Kameshima .Crystallization kinetics of mullite from polymeric Al_2O_3-SiO_2 xerogels[J].Materials Letters,2003(21):3155-3159. |
| [7] | Douy A .Crystallisation of amorphous spray-dried precur-sors in the Al2 O3-SiO2 system[J].Journal of the European Ceramic Society,2006,26(8):1447-1454. |
| [8] | Tkalceca E;Ivankovica H;Nass R et al.Crystallization kinetics of mullite formation in diphasic gels containing different alumina components[J].Journal of the European Ceramic Society,2003,23(9):1465-1475. |
| [9] | Chen Yungfeng;Wang M C;Hon M H .Phase transfor-mation and growth of mullite in kaolin ceramics[J].Journal of the European Ceramic Society,2004,24(8):2389-2397. |
| [10] | Takei Takahiro .Crystallization Kinetics of Mullite in Alumina-Silica Glass Fibers[J].Journal of the American Chemical Society,1999(10):2876-2880. |
| [11] | Hulling J C;Messing G L .Epitactic nucleation of spinel in aluminosilicate gels and its effect on mullite crystalli-zation[J].Journal of the American Ceramic Society,1991,74(10):2374-2381. |
| [12] | Lee J S;Yu S C .Mullite formation kinetics of co-precipitated Al2 O3-SiO2 gels[J].Materials Research Bulletin,1992,27(4):405-416. |
| [13] | Okada K .Activation energy of mullitization from vari-ous starting materials[J].Journal of the European Ceramic Society,2008,28(2):377-382. |
| [14] | Guimin Zhang;Yucheng Wang;Zhengyi Fu .Transparent mullite ceramic from single-phase gel by Spark Plasma Sintering[J].Journal of the European Ceramic Society,2009(13):2705-2711. |
| [15] | 从长杰,罗仕婷,陶友田,张克立.ZnAc2·2H2 O在空气中的热分解动力学研究[J].高等学校化学学报,2005(12):2327-2330. |
| [16] | 周佳,何明中,张爱华,李淋,傅凤英.高岭土相转变的非等温动力学[J].无机化学学报,2010(07):1279-1283. |
| [17] | Bodart P R;Parmentier J;Harris R K et al.Alumin-ium environments in mullite and an amorphous sol-gel precursor examined by 27 Al triple-quantum MAS NMR[J].J Phys and Chem Solid,1999,60(2):223-228. |
| [18] | Fischer R X;Schneider H;Schmucker M .Crystal structure of Al-rich mullite[J].Am Miner,1994,79(9):983-990. |
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