热障涂层陶瓷层材料LnMgAl_(11)O_(19)(Ln=La,Nd)粉体的性能
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摘要
用共沉淀法制备LnMgAl_(11)O_(19)粉体,证明了提高沉淀温度和pH值可使前驱粉体的性能明显提高。应用差热分析和X射线法研究了磁铅石相的生成温度和粉体的结晶度;使用Scherrer公式并结合XRD谱计算了晶粒尺寸;用扫描电镜观察了各工艺参数的前驱粉体在1500℃时效5 h后的形貌;使用Malvern ZEN3600粒度仪和Manual measurement软件分析了粉体硬团聚的尺寸分布;用Nd_2O_3, Gd_2O_3, Sm_2O_3替代La_2O_3,研究了制备多种镁基六铝酸盐粉体的可行性。结果表明:在pH值为11.5、沉淀温度为60℃条件下制备的前驱粉体,其完全相变为纯LaMgAl_(11)O_(19)粉体的初始温度为1440℃,比在常温下沉淀的前驱粉体降低了150℃,磁铅石相的生成效率明显提高。在1500℃时效5 h的粉体其晶粒为纳米尺度。提高沉淀温度和pH值有利于减小晶粒尺寸和降低粉体的热导率。采用相同工艺参数可制备出纯NdMgAl_(11)O_(19)粉体,其晶粒尺寸略大于LaMgAl_(11)O_(19)粉体的尺寸。
Powders of LaMgAl_(11)O_(19)(lanthanum magnesium hexaaluminate) were synthesized via a two-step process, i.e. chemical co-deposition for precursor powders and then high-temperature calcination for final products. The quality of the precursor powders could be improved significantly by proper adjusting the co-deposition parameters such as increasing the deposition temperature and pH value. The formation temperature of magnetoplumbite-phase, the crystallinity and grain size of the prepared powders were characterized by differential thermal analysis and X-ray diffraction. The morphology of powders calcined at 1500℃ for 5 hours for various precursors was examined by scanning electron microscope,while their grain size distribution was inspected by Malvern ZEN3600 and Manual measurement. The feasibility of preparation of various magnesium hexaaluminate was tried by replacing La_2O_3 with Nd_2O_3,Gd_2O_3 or Sm_2O_3 respectively. The results show that the precursor powders, co-deposited from solution with p H=11.5 at 60℃, could be transformed into powders of plain LaMgAl_(11)O_(19)-phase after calcination at1440℃, which was 150℃ lower than those co-deposited at room temperature. The powders calcined at1500℃ for 5 hours were nano-sized, while rising the deposition temperature and p H value may be beneficial to decrease the grain size, therewith decrease the thermal conductivity of powders. Besides the grain size of NdMgAl_(11)O_(19) powders prepared with the same process parameters was slightly larger than that of LaMgAl_(11)O_(19) powders.
Powders of LaMgAl_(11)O_(19)(lanthanum magnesium hexaaluminate) were synthesized via a two-step process, i.e. chemical co-deposition for precursor powders and then high-temperature calcination for final products. The quality of the precursor powders could be improved significantly by proper adjusting the co-deposition parameters such as increasing the deposition temperature and pH value. The formation temperature of magnetoplumbite-phase, the crystallinity and grain size of the prepared powders were characterized by differential thermal analysis and X-ray diffraction. The morphology of powders calcined at 1500℃ for 5 hours for various precursors was examined by scanning electron microscope,while their grain size distribution was inspected by Malvern ZEN3600 and Manual measurement. The feasibility of preparation of various magnesium hexaaluminate was tried by replacing La_2O_3 with Nd_2O_3,Gd_2O_3 or Sm_2O_3 respectively. The results show that the precursor powders, co-deposited from solution with p H=11.5 at 60℃, could be transformed into powders of plain LaMgAl_(11)O_(19)-phase after calcination at1440℃, which was 150℃ lower than those co-deposited at room temperature. The powders calcined at1500℃ for 5 hours were nano-sized, while rising the deposition temperature and p H value may be beneficial to decrease the grain size, therewith decrease the thermal conductivity of powders. Besides the grain size of NdMgAl_(11)O_(19) powders prepared with the same process parameters was slightly larger than that of LaMgAl_(11)O_(19) powders.
引文
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[3]Liu Z G,Ouyang J H,Xia X L,et al.Progress in research of novel rare-earth Zirconate materials[J].Mater.China,2011,30(1):32(刘占国,欧阳家虎,夏校良等.新型稀土锆酸盐材料研究进展[J].中国材料进展,2011,30(1):32)
[4]Mao Y N,GongA J,Qiu L N,et al.Preparation of Sm2O3doped La2Ce2O7ceramics for thermal barrier coatings by high temperature solid-state reaction[J].Chin.J.Eng.,2015,37:86(毛亚南,弓爱君,邱丽娜等.高温固相法制备Sm2O3掺杂La2Ce2O7热障涂层材料[J].工程科学学报,2015,37:86)
[5]Zhang H S,Zhu T,Wei Y.Research progress of perovskite and A2B2O7ceramics for thermal barrier coatings[J].Chin.Rare Earths,2010,31(4):75(张红松,朱涛,魏媛.钙钛矿及A2B2O7型热障涂层用陶瓷材料研究进展[J].稀土,2010,31(4):75)
[6]Ma W,Song F Y,Dong H Y,et al.Thermophysical properties of Y2O3and Gd2O3co-doped SrZrO3thermal barrier coating material[J].J.Inorg.Mater.,2012,27:209(马文,宋峰雨,董红英等.Y2O3与Gd2O3共掺杂SrZrO3热障涂层材料的热物理性能[J].无机材料学报,2012,27:209)
[7]Wu H D,Zhang J H,Zhou Z H,et al.Synthesis and lattice thermal expansion of magnetoplumbite structured Neodymium Magnesium Hexaaluminate[J].J.Chin.Ceram.Soc.,2017,45:930(吴红丹,张锦化,周志辉等.磁铅石结构NdMgAl11O19粉体的合成与晶格热膨胀[J].硅酸盐学报,2017,45:930)
[8]Machida M,Eguchi K,Arai H.Analytical electron microscope analysis of the formation of BaO?6Al2O3[J].J.Am.Ceram.Soc.,1988,71:1142
[9]Zhai Y Q,Li Y D,Meng M.Catalytic Combustion over hexaaluminate catalysts[J].Chin.Rare Earths,2004,25(5):58(翟彦青,李永丹,孟明.高温燃烧催化剂-六铝酸盐的结构、性质及制备[J].稀土,2004,25(5):58)
[10]Tian Y L,Qi F,Xie F,et al.Investigation progress on one novel thermal barrier coating[J].Nonferrous Met.(Extract.Metall.),2006,32(suppl.):41(田玉亮,齐峰,解峰等.一种新型热障涂层的研究进展[J].有色金属(冶金部分),2006,32(增刊):41)
[11]Qi F,Fan Z S,Sun D B,et al.Preparation of LaMgAl11O19spray powder-a new thermal barrier coatings material[J].J.Mater.Eng.,2006,(7):14(齐峰,樊自拴,孙冬柏等.新型热障涂层材料镁基六铝酸镧喷涂粉末的制备[J].材料工程,2006,(7):14)
[12]Ren Q,Wu X L,Wu J P.Application of determination of crystallinity of inorganic materials by XRD[J].Ceram.Sci.Art,2003,(3):18(任强,武秀兰,吴建鹏.XRD在无机材料结晶度测定中的应用[J].陶瓷科学与艺术,2003,(3):18)
[13]Friedrich C,Gadow R,Schirmer T.Lanthanum hexaaluminate-a new material for atmospheric plasma spraying of advanced thermal barrier coatings[J].J.Therm.Spray Technol.,2001,10:592
[14]Yu B L,Qi Q,Tang X F,et al.Effect of grain size on thermoelectric properties of CoSb3compound[J].Acta Phys.Sin.,2005,54:5763(余柏林,祁琼,唐新峰等.晶粒尺寸对CoSb3化合物热电性能的影响[J].物理学报,2005,54:5763)
[15]Gadow R,Lischka M.Lanthanum hexaaluminate-novel thermal barrier coatings for gas turbine applications-materials and process development[J].Sur.Coat.Technol.,2002,151-152:392
[16]Chen X L,Zhang Y F,Xu Z H,et al.Plasma-sprayed rare earth hexaluminate coatings[J].Therm.Spray Technol.,2009,1(2):43(陈小龙,张彦飞,许振华等.等离子喷涂稀土六铝酸盐热障涂层[J].热喷涂技术,2009,1(2):43)
[17]Bu H Y,Lu C.Research and development of cold spray technology[J].J.Mater.Eng.,2010,(1):94(卜恒勇,卢晨.冷喷涂技术的研究现状及进展[J].材料工程,2010,(1):94)
[18]Mallamaci M P,Sartain K B,Carter C B.Crystallization of calcium hexaluminate on basal alumina[J].Philos.Mag.,1998,77A:561