赤泥蜂窝陶瓷文献.docx

1、赤泥蜂窝陶瓷文献Fabrication of red mud honeycomb porous ceramics using dolomite as pore-forming agent ABSTRACTRed mud from aluminum industry was regarded as pernicious and poisonous industry waste around the world. In order to effectively utilize the intense alkaline slag, a novel red honeycomb ceramic was

2、developed successfully by extrusion molding using bauxite residues as raw materials, with bits of dolomite as pore forming agent. The aim of this research was to investigate the influences of amount of dolomite as well as of the sinter point on the mechanical strength, porosity, bulk density, crysta

3、lline phase and microstructure. The research shows that the relatively best comprehensive performance can be obtained by adding approximately 12% dolomite and using sintering temperature of 1175 ，leading to comprehensive strength, porosity, bulk density, medial pore diameter, about 14.5 MPa, 65 %, 0

4、.94 g/cm3, 5.2 m, respectively, which meet requirement of common honeycomb ceramic according to Chinese national standard. IntroductionRed mud (RM), generated by commercial alumina manufacturing produces, is gradually triggering serious environment issues due to its high alkalinity (11) 1-2. General

5、ly speaking, nearly two tons of red mud slurry will generate along with the production of one ton alumina and approximately three billion tonnes waste residues have so far stacked around the world 3. Most residues evacuated and disposed in huge landfills, which will occupy huge areas of land and con

6、taminating underground water 4. Siegfried et al. investigated the genotoxic effects of vanadium of red mud in higher plants. The results indicate that red mud not only cause genotoxic effect in plants but damage in human DNA. And the biggest environment catastrophe “Kolontar disaster” 5 allow people

7、 increasingly aware of that bauxite residues require treatment before they could release safely into the environment.Over the years, comprehensive work has been done to develop various measures for resource utilization and innocuity treatment of bauxite residues by the boffins in a variety of areas.

8、 Lu et al. 6 successfully synthesized a new foam ceramics by conventional ceramic sintering procedure using red mud as main raw materials with a spot of sodium silicate as the pore forming agent. Excellent mechanical strength, microstructure were obtained by adding about 40-50% bauxite residues. Lv

9、et al. 7 undertaken the research of developing the capacity of zirconium hydroxide-modified bauxite residues porous materials for removal of fluoride from aqueous solutions. The porous materials were prepared by an organic foam impregnation process with skyscraping red mud content about 60%, which h

10、as a maximum adsorption of fluoride at pH of 3.0 as well as equilibrium within 60 min. To consume numerous alkaline solid wastes, Yang et al 8. has developed unsintered construction materials from red mud wastes with the percentage composition about 20-40 , cured at ambient conditions. Results show

11、that the brick product reach the Chinese criterion of the 1st-class brick and show excellent durability in rigid climate conditions. As for utilizing red mud as catalyst support, Yang et al 9. fabricated multi-functional bauxite residues honeycomb ceramics by compression molding forming. The red mud

12、 honeycomb products reveal outstanding bending strength, water adsorption and porosity under the sintering temperature of 1075, which has a good advantage of application in environmental protection such as antibiosis, water filtration. In addition to the above, there are plenty of other research wor

13、k about water treatment 10-15, metal recovery 16, construction materials 17-21 and glass ceramic 22-24. However, less research has been reported on preparation of extrusion molding RM honeycomb ceramics.The present paper hammers at researching the feasibility to reuse bauxite residues in the product

14、ion of RM honeycomb ceramics. In the present study, the RM honeycomb ceramics are fabricated by various pilot-scale facilities such as vacuum kneader, vacuum pug mill, and extrusion molding machine, which are used as structural substrate in applications such as denitration,desulfuration and catalyti

15、c combustion. Mechanical properties, microstructure, and surface performance of the productions have been studied in this paper.Experimental detailMaterials The RM honeycomb ceramics were manufactured with red mud, dolomite, and additive as main raw materials. The primary composition of red mud and

16、dolomite supplied by QiXin Co.Ltd. is listed in Table 125. The additives include diaspore (Aluminium corp. of china Ltd.), fibre power (Yubang industrial ceramics co.Ltd., Zibo), CMC (Oubokai chemical co.Ltd., Tianjin), PVA (Zhonghe chemical co.Ltd., Tianjin), glycerol (Fuyu chemical co.Ltd., Tianji

17、n). In the procession of extrusion molding, the additive agents are critical for successful extrusion molding. As revealed in Table 2, 5% PVA were used as low temperature binder, 3% glycerol as lubricant, 2% CMC as plasticizer, 22% water as solvent 26, fiber powder and diaspore were used to improve

18、bending strength 27,28. And then smooth, flat red mud honeycomb green body can be continuously extruded.Table 1Chemical composition of red mud and dolomite, wt.%.Raw materialsSiO2Al2O3Fe2O3CaOTiO2Na2OK2OMgOCO2LOIRed mud26.4317.8934.892.680.7212.180.370.10-11.70dolomite-0.2130.4-21.747.944.5*LOI(loss

19、 on ignition)Table 2Sample designation and primary compositions of RM honeycomb ceramics.sampleRed mud/wt.%Dolomite/wt.%Additiveswt.%PVAglycerolwatercmcFiber powerdiasporeRM176453222108RM272853222108RM3681253222108RM4641653222108Preparation.As illustrated in Fig. 1, the bauxite residues should be pr

20、eprocessed first (about 160 mesh), and mixed with dry additives by ball-milling for about 1 h, then kneaded by vacuum pugging mechine with the wet assistants for 30 mins. The paste materials need wrapped with cling film and banalized for approximately 24 h, and next extrusion molded to achieve green

21、-pressing of red mud honeycomb(32 mm). After drying in the shade for 48 h and desiccation at 100 for 1 h, the green body was sintered in muffle furnace. The sintering procedure was performed as the following procedure9,29: the green body need heated from ambient temperature to 500 at a heating rate

22、of 10 /min, held for 1 h, afterwards heated to 1000 at the rate of 5 /min, then ceaselessly heated to target temperature at the rate of 2/min, maintained for 1 h. Red mud and additive agents kneading puggingRM honeycomb Extrusion molding Aging for hours RM pasteFig. 1 Preparation ow chart for RM hon

23、eycomb ceramics.As shown in Fig. 2, cell channels and channels walls consist the structure of this red honeycomb ceramic, which was manufactured by a fixed extruding machine under normal barrel temperature and a honeycomb-shape die which has a square cell channel shaped in approximately 120 cells pe

24、r square inch and a wall thickness of about 800 m as well as outer wall thickness of 1 mm. And high ferric oxide content is sufficient to give the honeycomb green body a suitably red color and bright appearance.Fig. 2 Physical photographs of RM honeycomb ceramics. CharacterizationThe comprehensive s

25、trength of cylindrical honeycomb samples were conducted by electronic compressive strength testing machine(SGY- II, Testerking test instruments co.Ltd, Jinan ) with a loading rate of 5 mm/min. The measurement of porosity, water absorption capacity, bulk density of sintered honeycomb samples refer to

26、 Chinese national standard GB/T 25994-2010 30.The phase composition of sintered honeycomb sample was performed by Powder X-ray diffraction (BRUKER AXS GMBH D8 Focus) at 40 kV and 40 mA. The XRD graph conduct 2 from 10 80at a step size of 0.02 . The microstructure of fracture surface of sintered samp

27、les were observed by solid-image light microscope(BVM-300V, Batuo instrument co.Ltd, Shanghai) to get an overview about shape and size existing pores. The pore size was measured on a fracture of samples using an image image-pro plus.Results and discussion Mechanical property of RM honeycomb ceramicF

28、ig. 3 Effects of sintering temperature and dolomite content on bending strength. Fig. 3 illustrates the compressive strength of RM honeycomb ceramic samples containing different dolomite contents between 1100 and 1225. As exhibited in the diagram, the compressive strength of samples rises before the

29、y are reduced along with the fluctuation of temperaturer under the same dolomite content and by comparison of the four curves, the temperature needed for maximum crushing strength of the four fired bodies rises with the increase content of dolomite (sample RM4 has maximum compressive strength on 127

30、5). This is may primarily attributed to the justification that the free CaO and MgO content of the fired samples increases continuously with increase of dolomite content, while the conpressive strength decreases gradually31. The increase content of alkali metals restrains generation of diopside phas

31、e, promotes generation the hedenbergite phase, afterwards enlarges the sintering temperature. Fig. 4 Effects of sintering temperature and dolomite content on sample porosity.The porosity of the RM honeycomb ceramics at different pore forming agents between 1100 and 1225are shown in Fig. 4. On the tr

32、ansverse direction, the porosity of the sintered productions gravitates towards to present declining trends with the rise of sintering temperature under the same content, which is mainly because some of the glassy melts flow into the gap accumulated by crystal particles or micropore formed by CO2, these glassy phase has successfully bl