【百家大講堂】第198期：ZrO2基材料體系的實驗研究和熱力學(xué)模擬

　　講座題目：ZrO2基材料體系的實驗研究和熱力學(xué)模擬 

　　報  告 人：Fabrichnaya Olga 

　　時  　 間：2019年5月24日 上午8：30 -10 : 30

　　地  　 點：5號教學(xué)樓502-1 

　　主辦單位：研究生院、材料學(xué)院

　　報名方式：登錄北京理工大學(xué)微信企業(yè)號---第二課堂---課程報名中選擇“【百家大講堂】第198期：ZrO2基材料體系的實驗研究和熱力學(xué)模擬“

 

【主講人簡介】

 Fabrichnaya Olga，現(xiàn)任德國弗萊貝格大學(xué)教授,，她的主要領(lǐng)域涵蓋陶瓷系統(tǒng)的熱力學(xué)模型、相平衡的實驗研究,、熱分析和量熱法等。截止至今,，Olga教授已發(fā)表約150篇研究論文,，出版書籍一部，題為《Thermodynamic data, model and phase diagrams in multicomponent oxide systems》,。

Fabrichnaya Olga was born in 1960 in Moscow (Russian federation), graduated from Chemistry department of Moscow State University in 1983. In 1983 she was accepted as Ph. D. candidate in Institute of Geochemistry and Analytical Chemistry of USSR Academy of Sciences. She got Ph.D. in chemistry in 1988. In 1992 she went to work in cooperation project in Uppsala University, Sweden. In 1998 she got Ph. D. in mineralogy, petrology and geochemistry. In 1998-1999 she worked in Royal Institute of Technology, Stockholm, Sweden. From 1999 to 2006 she worked in Max-Plank-Institute in Stuttgart, Germany and Stuttgart University. From 2006 up to present time Olga Fabrichnaya is employed in Technical University of Freiberg, Germany. Her main research interests are thermodynamic modelling of ceramic systems, experimental investigation of phase equilibria, thermal analysis and calorimetry. She is a co-author of ~150 research papers and one book Fabrichnaya O., Saxena S.K., Richet P., Westrum E.F. (2004): “Thermodynamic data, model and phase diagrams in multicomponent oxide systems”, Springer Verlag, Berlin Heidelberg.

 

【講座信息】

本次講座將介紹ZrO2基材料體系的相平衡研究及熱力學(xué)模擬的實驗結(jié)果,。由于這些材料的廣泛應(yīng)用，其相關(guān)系的研究極為迫切,。由MgO穩(wěn)定氧化鋯（Mg-PSZ）增強的高合金奧氏體不銹鋼TRIP-鋼（相變誘導(dǎo)塑性）在壓縮中表現(xiàn)出非常高的比能吸收值,，是TRIP-基質(zhì)-復(fù)合材料的基礎(chǔ)。Mg-PSZ在變形過程中顯示出四方相到單斜相的馬氏體相變,，導(dǎo)致額外的強度增加,。由于氧化鋯顆粒和TRIP鋼之間的粘合增加，可添加少量TiO2改善復(fù)合材料的機械性能,。目前,，關(guān)于ZrO2-TiO2-MgO體系中相關(guān)系的信息很少，亟待研究,。這項工作的目的是對ZrO2-TiO2-MgO體系的相關(guān)系和熱力學(xué)數(shù)據(jù)庫開發(fā)的實驗研究,。稀土（RE）鋯酸鹽由于其極低的導(dǎo)熱性而作為TBC材料受到越來越多的關(guān)注。近年來發(fā)現(xiàn),，通過陽離子取代可以實現(xiàn)熱性能和機械性能的更多改進,。然而，關(guān)于相平衡的文獻數(shù)據(jù)主要用于二元RE2O3-ZrO2系統(tǒng),，RE2O3-RE'2O3-ZrO2系統(tǒng)的熱力學(xué)數(shù)據(jù)非常少,。這項工作的目的是對ZrO2-La2O3-Gd2O3和ZrO2-La2O3-Yb2O3系統(tǒng)的相關(guān)系和熱力學(xué)數(shù)據(jù)庫開發(fā)的實驗研究。使用共沉淀法通過滴加Zr（CH3COO）水溶液的混合物制備樣品,，Ti2（SO4）3和Mg（NO3）2到NH4OH水溶液中，然后蒸發(fā)和熱解,。對于含稀土體系Zr（CH3COO）4,，La（NO3）3·6H2O，Gd（NO3）3·6H2O和Yb（NO3）3·6H2O的樣品制備溶于水,，按所需比例混合并用作前體在NH4OH水溶液中共沉淀的溶液,。將獲得的沉淀物過濾并進行熱解,。對于所有考慮的系統(tǒng)，進一步的程序是相同的,。通過X射線粉末衍射鑒定長時間熱處理后穩(wěn)定的相組合,。通過差熱分析（??DTA）測定不變反應(yīng)的溫度。使用掃描電子顯微鏡結(jié)合分散X射線光譜法研究樣品微結(jié)構(gòu),?；谒@得的實驗數(shù)據(jù)，建立了在1550,1700和1900K溫度下ZrO2-TiO2-MgO體系的等溫截面,。對于具有螢石結(jié)構(gòu)的相,，發(fā)現(xiàn)了均勻性范圍的寬三元延伸。在βZrTiO4和四方ZrO2相中發(fā)現(xiàn)MgO的溶解度非常有限,，而在TiO2-MgO體系的中間體化合物中發(fā)現(xiàn)了更大的ZrO2溶解度,。在1550K下顯示出類似于δ-相Y4Zr3O12的低溫三元化合物。差熱分析顯示該相的穩(wěn)定性高達1631K,。測定了兩個共晶反應(yīng)的溫度和組成,。基于獲得的實驗結(jié)果,，使用CALPHAD方法優(yōu)化ZrO2-TiO2-MgO體系的熱力學(xué)參數(shù),。在ZrO2-La2O3-Gd2O3和ZrO2-La2O3-Yb2O3體系中，發(fā)現(xiàn)了三元體系中螢石相的廣泛延伸,。 Pyrochlore階段RE2Zr2O7形成連續(xù)固溶體（La,，Gd）2Zr2O7并且顯示出有限的Yb2O3溶解度（~20mol。％）,。 ZrO2-La2O3-RE2O3系統(tǒng)中的固態(tài)轉(zhuǎn)變表明在1673-1873 K范圍內(nèi)：（La,，Gd）2O3_A +螢石=（La，Gd）2O3_B + Pyrochlore為RE = Gd和螢石+ LaYbO3 = Pyrochlore +（Yb）對于RE = Yb,，La,，Zr）2O 3 + x_C。使用DTA測定這些轉(zhuǎn)化的溫度,?；谒@得的結(jié)果，評估所研究系統(tǒng)的熱力學(xué)參數(shù)并計算相圖,。"

 

The experimental results for phase equilibrium study and thermodynamic modelling of the ZrO2-based system will be presented. Phase relations in the ZrO2-based systems are important because of various applications of these materials. High-alloyed austenitic stainless TRIP-steel (Transformation Induced Plasticity) reinforced by MgO stabilized zirconia (Mg-PSZ) exhibits extraordinary high values of specific energy absorption in compression and is the base of TRIP-Matrix-Composite material. The Mg-PSZ shows a martensitic transformation of tetragonal to monoclinic phase during deformation resulting in additional strength increase. Minor addition of TiO2 improves mechanical properties of the composite due to increase of bonding between the zirconia particles and the TRIP steel. Materials based on the ZrO2–TiO2–MgO system are also of interest due to their dialectical properties. Information on phase relations in the ZrO2–TiO2–MgO system was scarce and new experimental study was necessary. The aims of this work are experimental study of phase relations and thermodynamic database development for the ZrO2–TiO2– MgO system.  Rare earth (RE) zirconates attract more and more attention as TBC materials due to their extremely low thermal conductivity. In recent years it was found that even more improvement in both thermal and mechanical properties can be achieved via cation substitution. However, literature data on phase equilibria are available mostly for binary RE2O3–ZrO2 systems, with very little thermodynamic data for the RE2O3–RE’2O3–ZrO2 systems. The aims of this work are experimental study of phase relations and thermodynamic database development for the ZrO2– La2O3–Gd2O3 and ZrO2–La2O3–Yb2O3 systems Samples were prepared using the co–precipitation method by dropping the mixture of aqueous solutions of Zr(CH3COO)4, Ti2(SO4)3 and Mg(NO3)2 to the aqueous solution of NH4OH followed by evaporation and pyrolysis. For sample preparation in rare earth containing systems Zr(CH3COO)4, La(NO3)3·6H2O, Gd(NO3)3·6H2O and Yb(NO3)3·6H2O were dissolved in water, mixed in desired ratio and used as precursors solutions for coprecipitation in NH4OH aqueous solution. Obtained precipitates were filtrated and subjected to pyrolysis. The further procedure was the same for all considered systems. Phase assemblages stable after long heat treatment were identified by X-ray powder diffraction. Temperatures of invariant reactions were determined by differential thermal analysis (DTA). Sample microstructures were investigated using scanning electron microscopy combined with dispersive X-ray spectrometry. Based on the obtained experimental data, isothermal sections of the ZrO2–TiO2–MgO system at temperatures 1550, 1700 and 1900 K were established. Wide ternary extension of homogeneity range was found for phase with fluorite structure. Very limited solubility of MgO was found in beta ZrTiO4 and tetragonal ZrO2 phase, while more substantial solubility of ZrO2 was found in the intermediate compounds of the TiO2-MgO system. Low temperature ternary compound similar to δ-phase Y4Zr3O12 was revealed at 1550 K. Differential thermal analysis had shown stability of this phase up to 1631 K. Temperatures and compositions of two eutectic reactions were determined. Thermodynamic parameters of the ZrO2–TiO2–MgO system were optimized using CALPHAD approach based on the obtained experimental results. In the ZrO2-La2O3-Gd2O3 and ZrO2-La2O3-Yb2O3 systems wide extension of fluorite phase in ternary system was found. Pyrochlore phase RE2Zr2O7 forms continuous solid solutions (La,Gd)2Zr2O7 and demonstrates limited solubility of Yb2O3 (~20 mol.%). Solid state transformations were indicated in the ZrO2-La2O3-RE2O3 systems in the range 1673-1873 K: (La,Gd)2O3_A+Fluorite=(La,Gd)2O3_B +Pyrochlore for RE=Gd and Fluorite+LaYbO3=Pyrochlore+(Yb,La,Zr)2O3+x_C for RE=Yb. Temperatures of these transformations were determined using DTA. Based on the obtained results thermodynamic parameters of the investigated systems were assessed and phase diagrams were calculated.