粉煤灰基多孔莫来石陶瓷的性能优化及低温烧结
摘要
本文以粉煤灰，外加铝源（氧化铝、氢氧化铝）为主要原料，运用淀粉原位固化成型技术高温烧结制备了多孔莫来石陶瓷。并对其抗弯强度，显气孔率，体积密度进行了表征；运用扫描电子显微镜观察样品孔的孔径、形状和分布。利用X射线衍射仪，对样品进行了物相分析。实验表明氢氧化铝作为外加铝源相比氧化铝更易得到高强度的多孔莫来石陶瓷。
在此基础上加入少量的氟化铝，促进原位反应生成莫来石晶须，大大的改善了制得的多孔莫来石陶瓷的抗弯强度，提高了其力学强度。通过对样品微观形貌的分析表明添加氟化铝能够在较低的温度下形成高长径比的莫来石晶须，随着温度的升高，晶须明显变粗，这些高长径比的晶须相互搭建形成了一种咬合结构，这种结构对提高陶瓷的强度是有利的。同时证明氢氧化铝作为铝源相对于氧化铝更易制得高长径比的莫来石晶须，形成的这种咬合结构也更明显。氢氧化铝为铝源添加氟化铝使粉煤灰制备的多孔莫来石陶瓷（气孔率为40%左右）的抗弯强度由70MPa提高到120MPa。
为了更高层次的实现粉煤灰的利用价值，在较低的温度下得到高强度的莫来石陶瓷，节约能源。以粉煤灰，氢氧化铝，氟化铝为主要原料，并分别添加La_2O_3、Y_2O_3、MgO等烧结促进剂，探讨其在粉煤灰-氢氧化铝-氟化铝体系中促进低温烧结的效果。实验结果表明，La_2O_3、Y_2O_3、MgO等都实现样品的低温烧结。La_2O_3、Y_2O_3主要以低温下生成大量液相来实现烧结，但其价格较贵，而MgO主要以固溶产生缺陷促进烧结，氧化镁过量时（10wt%）虽然促进了致密化，却抑制了莫来石相的生成。最后，以铝矾土代替工业生产的铝源加入粉煤灰，加入3wt%，5wt%的氧化镁促进致密化制备多孔莫来石陶瓷，但物相仍以刚玉相和石英相为主。
本实验，通过配方及添加剂的选择，成功在较低温度下(1400℃)利用粉煤灰制备了具有较高强度的莫来石陶瓷，不仅节约了天然资源，实现了粉煤灰的潜在利用价值，而且有利于保护环境，为工业粉煤灰制备多孔莫来石提供实验和理论依据
Porous mullite ceramics were fabricated with flyash, aluminium source (alumina and aluminium hydroxide) as starting materials through starch consolidation method. The bending strength, apparent porosity was tested. Microstructure of the samples was observed by scanning electron microscopy (SEM). X-ray patterns of the samples were tested on X-ray diffractometer using CuKαradiation. The study indicated that Al (OH) 3 is more suitable to be used to prepare high strength mullite ceramics.
AlF3 as additive is helpful to form mullite whisker in a lower temperature. The whiskers constructed an interlocking structure, which enhanced the bending strength of the porous mullite ceramics. As a source of aluminium, Al(OH)3 was more suitable to fabricate needle-like mullite than A1_2O_3.The result shows that the strength of the porous mullite ceramics produced with Al(OH)3 and AlF3 were enhanced from 70MPa to 120MPa.
For to reduce the sintering temperature of the porose mullite ceramics produced with flyash, La_2O_3, Y_2O_3 and MgO were added in to promote the densification (at 1400℃)of the mullite ceramics fabricated by flyash-Al(OH)3-AlF3 system, respectively. The research indicated that all the additives (La_2O_3, Y_2O_3, MgO) can made the samples densification at 1400℃. The mechanism of promote densification of the additives is that La_2O_3 and Y_2O_3 formed liquid phase in a low temperature with reactants respectively, and MgO formed solid solution promoted densification. The mullitization process was restrained while added overmuch MgO(10wt%). With bauxite as alumina source and added MgO(3wt% or 5wt%) can’t produced mullite ceramics at 1400℃. The main phase in ceramics is corundum and quartz.
In this paper, porous mullite ceramics with strength increased were produced with flyash as raw materials at 1400℃by added additives and aluminium sources, and the bending strength were enhanced successfully. And then increase the industrious application of the porous mullite ceramics prepared from flyash.
在此基础上加入少量的氟化铝，促进原位反应生成莫来石晶须，大大的改善了制得的多孔莫来石陶瓷的抗弯强度，提高了其力学强度。通过对样品微观形貌的分析表明添加氟化铝能够在较低的温度下形成高长径比的莫来石晶须，随着温度的升高，晶须明显变粗，这些高长径比的晶须相互搭建形成了一种咬合结构，这种结构对提高陶瓷的强度是有利的。同时证明氢氧化铝作为铝源相对于氧化铝更易制得高长径比的莫来石晶须，形成的这种咬合结构也更明显。氢氧化铝为铝源添加氟化铝使粉煤灰制备的多孔莫来石陶瓷（气孔率为40%左右）的抗弯强度由70MPa提高到120MPa。
为了更高层次的实现粉煤灰的利用价值，在较低的温度下得到高强度的莫来石陶瓷，节约能源。以粉煤灰，氢氧化铝，氟化铝为主要原料，并分别添加La_2O_3、Y_2O_3、MgO等烧结促进剂，探讨其在粉煤灰-氢氧化铝-氟化铝体系中促进低温烧结的效果。实验结果表明，La_2O_3、Y_2O_3、MgO等都实现样品的低温烧结。La_2O_3、Y_2O_3主要以低温下生成大量液相来实现烧结，但其价格较贵，而MgO主要以固溶产生缺陷促进烧结，氧化镁过量时（10wt%）虽然促进了致密化，却抑制了莫来石相的生成。最后，以铝矾土代替工业生产的铝源加入粉煤灰，加入3wt%，5wt%的氧化镁促进致密化制备多孔莫来石陶瓷，但物相仍以刚玉相和石英相为主。
本实验，通过配方及添加剂的选择，成功在较低温度下(1400℃)利用粉煤灰制备了具有较高强度的莫来石陶瓷，不仅节约了天然资源，实现了粉煤灰的潜在利用价值，而且有利于保护环境，为工业粉煤灰制备多孔莫来石提供实验和理论依据
Porous mullite ceramics were fabricated with flyash, aluminium source (alumina and aluminium hydroxide) as starting materials through starch consolidation method. The bending strength, apparent porosity was tested. Microstructure of the samples was observed by scanning electron microscopy (SEM). X-ray patterns of the samples were tested on X-ray diffractometer using CuKαradiation. The study indicated that Al (OH) 3 is more suitable to be used to prepare high strength mullite ceramics.
AlF3 as additive is helpful to form mullite whisker in a lower temperature. The whiskers constructed an interlocking structure, which enhanced the bending strength of the porous mullite ceramics. As a source of aluminium, Al(OH)3 was more suitable to fabricate needle-like mullite than A1_2O_3.The result shows that the strength of the porous mullite ceramics produced with Al(OH)3 and AlF3 were enhanced from 70MPa to 120MPa.
For to reduce the sintering temperature of the porose mullite ceramics produced with flyash, La_2O_3, Y_2O_3 and MgO were added in to promote the densification (at 1400℃)of the mullite ceramics fabricated by flyash-Al(OH)3-AlF3 system, respectively. The research indicated that all the additives (La_2O_3, Y_2O_3, MgO) can made the samples densification at 1400℃. The mechanism of promote densification of the additives is that La_2O_3 and Y_2O_3 formed liquid phase in a low temperature with reactants respectively, and MgO formed solid solution promoted densification. The mullitization process was restrained while added overmuch MgO(10wt%). With bauxite as alumina source and added MgO(3wt% or 5wt%) can’t produced mullite ceramics at 1400℃. The main phase in ceramics is corundum and quartz.
In this paper, porous mullite ceramics with strength increased were produced with flyash as raw materials at 1400℃by added additives and aluminium sources, and the bending strength were enhanced successfully. And then increase the industrious application of the porous mullite ceramics prepared from flyash.
引文
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[2]林介东,莫乾凯,江潮全,电厂粉煤灰综合利用技术,粉煤灰综合利用,2002,10(1): 31~33
[3]王智,粉煤灰活性激发基本系统中石灰因素的研究:重庆;重庆建筑大学,1998
[4]孔文俊,粉煤灰资源化途径探讨,大自然探索,1995, 14(51): 58~62
[5]黄兆龙,湛渊源,粉煤灰的物理和化学性质,粉煤灰综合利用,2003,2(4):3~8
[6] Yang YF, Gai GS, Fan SM, etal, Research on surface inorganic modification of mineral filler, Journal of china university of mining and technology, 2005, 34(3):179~283
[7]胡广君,钱建明,张立群,新型橡胶填料-空心玻璃微珠,特种橡胶制品,2002, 23(6): 14~17
[8]盖国胜等,微纳米颗粒复合与功能化设计,北京:清华出版社,2008. 174~175
[9]王爱勤,粉煤灰三大效的研究及其在三峡工程中的应用:南京;东南大学,1999
[10] Manz OE,全球粉煤灰大规模利用现状,国际电力,2000,4(2): 57~60
[11] Ketsarin P, Matthias W and Michael K, A new approach to the production of bricks made of 100% flyash. 2001
[12]张相峰,焦有宙,岳建芝等,粉煤灰资源化及其在路面工程中的应用,河南农业大学学报,2000,(1): 81~84
[13]李祥生,李璠,刘光华,国内外从粉煤灰提锗现状,江苏化工,2000,(12): 22~23
[14] Rubel A, Andrews R, Gonzalez R et al, Adsorption of Hg and NOx on coal by-products, Fuel, 2005, 84: 911~916
[15] Grover M, Narayanaswamy MS, Removel of hexavalent chromium by adsorption on flyash, 2nst Eng (India), 1982, 1: 36~39
[16]马宗庆,燃煤电厂粉煤灰综合利用高技术产业的发展思路,电力建设,2011, 3(22): 43~50
[17]孔文俊,粉煤灰资源化途径探讨,大自然探索,1995,51(14): 58~62
[18]陈冬,陈南春,莫来石的研究进展,矿产与地质,2004, 2: 18~22
[19]杜晶,高纯莫来石合成的研究:[硕士学位论文],西安;西安建筑科技大学,2004
[20]张桂敏,王玉成,傅正义等,莫来石低温合成及结构组成变化,硅酸盐学报,2008, 36(11), 1542~1547
[21]薛茹君,煤系高岭岩水热法合成超细莫来石粉,中国非金属矿工业导刊,2005,1: 17~19
[22]朱新文,江东亮,谭寿洪,低温固相反应合成莫来石的研究,中国粉体技术,2000, 6: 118~121
[23] Dong YC, Feng XF and Feng XY et al, Phase evolution and sintering characteristics of porous mullite ceramics produced from the flyash-Al(OH)3 coating powders, Journal of Alloys and Compounds, 2008, 460: 651~657
[24] Dong YC, Feng XF and Feng XY et al. Preparation of low-cost mullite ceramics from natural bauxite and industrial waste fly ash, Journal of Alloys and Compounds, 2008, 460:599~606
[25] J.H. Li, H.N. Ma and W.H. Huang, effect of V2O5 on the properties of mullite ceramics synthesized from high-alumium flyash and bauxite, journal of Hazardous materials, 2009, 1669: 1535~1539
[26]邓建欣,李兆前,艾兴,晶须增韧陶瓷基复合材料的进展,材料导报,1994,9(5),72~75
[27]袁建君,刘智恩,韩玉,莫来石晶须制备新工艺与生长机理,无机材料学报,1996:35~39
[28]王洪彬,莫来石晶须合成及其生长机理研究:[硕士论文],山东;山东大学,2006
[29] Hoffman D.W., Roy R., Komameni, S., Diphasic xerogels, a new class of materials: phase in the system Al2O3-SiO2, J. Am. Ceram Soc, 1984, 67: 468~471
[30]徐明霞,崔峰,超微莫来石粉制备新工艺,硅酸盐学报,1991,1: 80~85
[31] Nishu K, Ykoyama T, Characteritation of amorphous aluminosilicate formed by adsorption of silicic acid on aluminium hydroxide, Abstract of 27th symposium on the Basic Science of Ceramics, 1989,1: 808~809
[32] Sacks MD, Bozkurt N, Fabrication of mullite and mullite-matrix composites by transient viscous sintering of composite powders, J. AM. Ceram, Soc, 1991, 74:2428~2437
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