外文翻譯---利用穩(wěn)定劑包覆納米粉體技術(shù)制備ceo2和y2o3共穩(wěn)的全穩(wěn)定zro2的微波燒結(jié)（英文）

1、Journal of the European Ceramic Society 27 (2007) 689–693Microwave sintering of CeO2 and Y2O3 co-stabilised ZrO2 from stabiliser-coated nanopowdersS.G. Huang a,b, L. Li b, O. Van der Biest a, J. Vleugels a,?a Department

2、of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Heverlee, Belgium b School of Material Science and Engineering, Shanghai University, 149 Yanchang Road, Shanghai 20

3、0072, ChinaAvailable online 19 May 2006AbstractTetragonal ZrO2 polycrystalline (TZP) composites with 2 wt.% Al2O3 and co-stabilised with 1 mol% Y2O3 and (4, 6 or 8) mol% CeO2 were sintered at 1450 ?C for 20 min in a sing

4、le mode 2.45 GHz microwave furnace. For comparison, conventional sintering was performed in air at 1450 ?C for 20 min. The starting powder mixture was obtained by a suspension coating technique using yttrium nitrate, cer

5、ium nitrate and pure m-ZrO2 nanopowder. Fully dense material grades were obtained by both sintering methods. The influence of the composition and the sintering methods on the final phase composition and microstructure we

6、re investigated by X-ray diffraction and scanning electron microscopy. Finer and more uniform microstructures were observed in the microwave sintered ceramics when compared to the conventionally sintered samples. The fra

7、cture toughness increases with decreasing stabiliser content, whereas a reverse relation was found for the Vickers hardness. Comparable toughness and hardness values were obtained for the microwave and conventionally sin

8、tered samples. © 2006 Elsevier Ltd. All rights reserved.Keywords: ZrO2; Microwave processing; Sintering; Grain size; Mechanical properties1. IntroductionMicrowave sintering (MS) of ceramics is a novel tech- nique th

9、at gained much attention because of the rapid heating, enhanced densification rate, and improved microstructure. In MS, electromagnetic waves interact with ceramics, leading to volumetric heating by dielectric loss. When

10、 conventional sin- tering (CS), heat is transformed to the surface of the ceramic component and reaches the core by thermal conduction, produc- ing high temperature gradients and stresses. Such a volumetric heating of MS

11、 may result in ceramics with a more uniform and finer microstructure when compared to conventional sintering. Over the years, various structural ceramics and composites such as CeO2–ZrO2, Y2O3–ZrO2, and Al2O3 have been s

12、uc- cessfully microwave sintered.1–5 Recently, work by Zhao et al.1showed that full density of 12 mol% CeO2–ZrO2 and 3 mol% Y2O3–ZrO2 ceramics could be obtained by MS resulting in a high toughness of 10 MPa m1/2 for Ce-T

13、ZP and a high hardness? Corresponding author. Tel.: +32 16 321244; fax: +32 16 321992. E-mail address: jozef.vleugels@mtm.kuleuven.be (J. Vleugels).of 12.4 GPa for Y-TZP when sintered at 1450 ?C for 20 min. Travitzky et

14、al.2,3 found that 3 mol% Y-TZP and 2 mol% Y- TZP/20 wt.% Al2O3 composites fabricated by MS exhibited a higher density, superior mechanical properties, and a smaller grain size compared to CS. Using a multimode microwave

15、fur- nace with 2.45 GHz radiation, Xie et al.4,5 revealed that 99.5% theoretical density and a fracture toughness of 13.7 MPa m1/2were obtained for 5 wt.% CeO2 + 3 wt.% Y2O3 doped ZrO2 ceramics sintered at 1500 ?C for 15

16、 min. To improve the low strength of Ce-TZP and enhance the thermal stability of Y-TZP, co-stabilised ZrO2 with different CeO2 and Y2O3 content are fabricated. According to the reports by Huang and Li6,7 and Lin8,9 the r

17、atio of CeO2 and Y2O3 strongly influences the tetragonal ZrO2 (t) and cubic ZrO2 (c) phase content, leading to the significant difference in microstruc- ture and mechanical properties. The presence of c-ZrO2 largely decr

18、eases the mechanical properties of ZrO2 ceramics. The frac- ture toughness of 12 mol% CeO2–3 mol% Y2O3 co-stabilised ZrO2 obtained by pressureless sintering at 1450 ?C for 1–4 h is reported to be only 2.02–2.42 MPa m1/2.

19、6 The large amount of cubic phase, thermodynamically calculated to be 37 mol%, explains the very modest fracture toughness.60955-2219/$ – see front matter © 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jeur

20、ceramsoc.2006.04.040S.G. Huang et al. / Journal of the European Ceramic Society 27 (2007) 689–693 691around 1000 ?C, the heating rate increases rapidly although the absorbed power is the same whereas the output power of

21、the system concomitantly decreases. The cooling rate after sinter- ing, established by switching of the power supply, is much faster than during conventional sintering, shortening the total sintering cycle.3.2. Phase con

22、stitutionFig. 2 compares the X-ray diffraction data of the calcined 1Y8Ce2Al ZrO2 powder and polished surface of the microwave sintered 1YxCe2Al ceramics. After calcination at 800 ?C for 60 min, the 1Y8Ce2Al powder exhib

23、ited the same crystal struc- ture as that of the m-ZrO2 starting powder. The XRD patterns of the sintered ceramics reveal that all CeO2 and Y2O3 dissolved into the ZrO2, with the formation of tetragonal and/or cubicZrO2.

24、 It should be mentioned that it is almost impossible to dif- ferentiate the t- and c-ZrO2 phase by means of XRD, implying that the fully tetragonal samples might contain a minor amount of c-ZrO2, especially with higher s

25、tabiliser contents. According to the thermodynamic simulation, the 1Y4Ce2Al and 1Y6Ce2Al grades are fully tetragonal at 1450 ?C, whereas the 1Y8Ce2Al grade contains 5 mol% c-ZrO2.6,7 A relatively small amount of m-ZrO2 i

26、s measured in the 1Y4Ce2Al sample. The m-phase however can also be a result of the stress-induced transforma- tion during polishing. For the conventionally sintered 1YxCe2Al samples, the similar phase constitutions were

27、observed.3.3. MicrostructureTherepresentativemicrostructuresofthemicrowaveandcon- ventionally sintered 1YxCe2Al ceramics, sintered at 1450 ?CFig. 3. Microstructures of the microwave (MS) and conventionally (CS) sintered