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1、 毕业 论文 外文资料翻译 题 目 热处理对三种不同途径生产的 纳米粉氧化锆晶体结构和形态的影响 学 院 材料科学与工程 专 业 材料科学与工程 班 级 学 生 学 号 指导教师 二一 三 年 三 月 二 一 日 2 j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 1 9 5 ( 2 0 0 8 ) 178185 journal homepage: Effect of thermal treatment on the crystal structure and morphology of

2、zirconia nanopowders produced by three different routes M.M. Rashad , H.M. Baioumy Central Metallurgical Research and Development Institute, P.O. Box 87, Helwan, Cairo, Egypt article Article history: info abstract Zirconia ZrO2 nanopowders have been successfully prepared via three processing routes,

3、 namely, conventional precipitation (CP), citrate gel combustion (CGC) and microemulsion rened precipitation (MRP). The formed zirconia particles were characterized using X-ray diffraction analysis (XRD), scanning electron microscope (SEM), Fourier transformer infrared (FT-IR) spectroscopy and UVvis

4、ible absorption spectrum. The results showed that the CP route led to the formation of tetragonal ZrO2 phase with low crystallinity at 700 C and the formed tetragonal phase was transformed to monoclinic ZrO2 phase at temperatures ranged Received 24 May 2006 Received in revised form 22 April 2007 Acc

5、epted 23 April 2007 Keywords: Zirconia Synthesis Crystal structure Nanoparticles Characterization from 1000 to 1200 C. The CGC route led to formation of monoclinic phase without presence tetragonal phase species in the temperatures range from 1000 to 1200 C. In contrast, MRP technique led to the for

6、mation of tetragonal phase with high crystallinity compared with the other processing at 700 C and the produced tetragonal phase was inverted to cubic phase by increasing the calcination temperatures from 1000 to 1200 C. SEM showed that the morphology of the produced zirconia nanopowders changed acc

7、ording to synthesis routes and thermally treated temperatures. 2007 Elsevier B.V. All rights reserved. 1. Introduction Advanced ceramics known as ne ceramics are a diverse group of inorganic oxides such as zirconia, alumina, tita- nia and non-oxides like silicon carbide, boron carbide and silicon ni

8、tride. These materials are drawing attention as high technology materials because of their superior mechan- ical, thermal, electrical, chemical and optical properties. Zirconia ne ceramics have an impressive combination of properties such as high strength, hardness, toughness, corrosion resistance,

9、low co-efcient of friction and biocom- patibility. Nearly 80% of produced zirconia in the world is used in conventional applications such as refractories, pig- ments, glazers, opaciers, abrasives, etc. The ever-increasing numbers of ceramics applications have resulted in devel- oping of advanced tec

10、hnologies to process nanopowders zirconia (Galgali et al., 1995). The advanced applications of zirconia nanopowders are including transparent opti- cal devices, electrochemical capacitor electrodes, oxygen sensors, fuel cells and catalysts including photocatalysts (Srdic and Omorjan, 2001； Kongwudth

11、iti et al., 2003). Zir- conia catalyzes the hydrogenation of olens, isomerization of olens and epoxides and the dehydrations of alco- hols. When zirconia is used as support, various reactions Corresponding author. Tel.: +20 2 5010642/213； fax: +20 2 5010639. E-mail address: (M.M. Rashad). 0924-0136

12、/$ see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2007.04.135 3 j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 1 9 5 ( 2 0 0 8 ) 178185 179 such as Fischer-Tropsch synthesis, methanol synthesis and hydrodesulfurization have been reporte

13、d to proceed with higher activity and selectivity than with conventional sup- ports (Jung and Bell, 2000). It is well known that zirconia is a low absorption materials usable for coating in the near-UV (300 nm) or IR ( 8 m) regions. Typical applica- tions include near-UV laser and dielectric mirror

14、designs. In addition, about 95% of ferrule, the most important part of the optical ber connector is now made from zirconia ne ceramics. It is known that high quality of the ceramic is based on the excellent performance of zirconia powder (5). Preparing a ne and an agglomerate free zirconia powder is

15、 the rst and perhaps the most important step in obtaining a sintered zirconia ceramic of desirable microstructure and therefore mechanical properties. Various chemistry-based novel approaches have been taken for the preparation of zirco- nia powders including co-precipitation, hydrothermal, sol gel,

16、 sonochemical method, microemulsion and thermal decom- position processing (Ma et al., 2004； Wu et al., 2003； Lee et al., 1999； Tai et al., 2001； Djuricic et al., 1995； Bourell and Kaysser, 1993； Ward and Ko, 1993； Huang and Guo, 1992； Fang et al., 1997； Li et al., 1989； Juarez et al., 2000； Yashima

17、 et al., 1996； Yashima et al., 1994； Caruso et al., 1997； Chatterjee et al., 1992； Dodd and McCormick, 2002； Roy and Ghose, 2000； Kolenko et al., 2003； Noh et al., 2003； Somiya and Akiba, 1999； Piticescu et al., 2001). The chemical precipitation (CP) method is a suitable low cost technique for the m

18、ass production compared with the other mentioned technique. The main drawback is that the particle size is not small and has in wide size distribution. Microemulsion rened precipitation (MRP) gives better chem- ical homogeneity with controlling the particle size and size distribution. Citrate gel co

19、mbustion (CGC) technique is used to obtain highly uniform size and shape controlled nanopar- ticles. ZrO2 has three polymorphic phases； monoclinic (m), tetrag- onal (t) and cubic (c). Because of its phase transformation from tetragonal to monoclinic around the temperatures range from 1100 to 2370 C,

20、 it is a challenging study with potentially practical applications to prepare stabilized tetragonal ZrO2 powders at low temperatures. Stabilization of t-ZrO2 phase is usually achieved by adding oxides of yttrium, magnesium, calcium, thorium, titanium, cerium and ytterbium (Piticescu et al., 2001； Ji

21、ang et al., 2001； Lascalea et al., 2004； Teterycz et al., 2003； Panda et al., 2003； Zhang et al., 2004； Ai and Kang, 2004； Bhattacharjee et al., 1991). According to the change in thermal treatment, c-ZrO2 phase is stable at all temperature up to the melting point at 2680 C. m-ZrO2 phase is stable be

22、low 1170 C and inverted to t-ZrO2 phase by increasing tem- perature over 1200 C. t-ZrO2 phase is stable between 1170 and 2370 C by adding stabilized oxides (Stefanc et al., 1999). From our knowledge, little information in literature is found about the change in the phase transformation and the mor-

23、phology of the formed ZrO2 nanopowders that are produced by CP, CGC and MRP techniques. The present work aims at comparing the change in crystal structure, morphology, FT-IR spectra and UVvisible absorption spectrum of the produced ZrO2 nanopowders which are obtained by these three process- ing rout

24、es at different calcination temperatures from 120 to 1200 C. 2. 2.1. Experimental Materials and processing The materials used in the present work were, zirconyl chlo- ride ZrOCl2 8H2 O purchased from BDH Chemicals Ltd., Poole, England, sodium hydroxide and citric acid purchased from El- Nasr Pharmac

25、eutical Chemical ADWIC, Egypt, n-pentanol and Triton X-100 (Serva Electrophoresis GmbH, Germany). To process ZrO2 powders by CP route, 10 g zirconium oxychloride octahydrate was dissolved in 100 ml bidistilled water using hot plate magnetic stirrer. The desired vol- ume of 2 M NaOH was added into th

26、e solution until pH 10. After 15 min, the produced precipitate was ltered off, washed and dried at 120 C overnight. The dried ZrO2 nH2 O calcined at different temperatures from 500 to 1200 C at a rate of 10 C/min and kept at the respective temperature for 1 h. To process ZrO2 powders by CGC method,

27、10 g of zir- conium oxychloride octahydrate was dissolved in water. A stoichiometric amount of citric acid was added to the aque- ous solution. The mixture was evaporated to dryness at 60 C. Then, the produced precursor was dried to 120 C overnight. The formed precursor was heated again to 500, 700,

28、 1000 and 1200 C at a rate of 10 C/min and kept at the respective tem- perature for 1 h. For the MRP method, the authors employed n-pentanol as the oil phase and triton X-100 as the surfactant. One molar of Triton X-100 (non-anionic surfactant) was prepared by dissolv- ing in n-pentanol and the proc

29、essed solution was divided into two parts, one part was added to 10 g zirconyl chloride octahy- drate dissolved in small amount of water and the other part was used for preparation of 2 M sodium hydroxide. Both two solutions were mixed together to precipitate zirconia hydrate at pH 10. The precipita

30、ted solution was ltered, washed, dried at 120 C, then calcined at different temperatures from 500 to 1200 C. 2.2. Characterization The phase identication and the crystallite size of the pro- cessed ZrO2 nanopowders were characterized by Philips X-Ray Diffractometer PW 1730 with nickel ltered Cu K ra

31、diation ( = 1.5406 A) at 40 kV and 30 mA. The crystallite sizes of ZrO2 nanopowders were determined for the most intense peak (1 1 1) plane of ZrO2 crystals from the X-ray diffraction data using the Debye-Scherrer formula: dRX = k cos (1) where dRX is the crystallite size, k = 0.9 is a correction fa

32、ctor to account for particle shapes, the full width at half max- imum (FWHM) of the most intense diffraction plane, the wavelength of Cu target = 1.5406 A, and is the Bragg angle. The change in crystal morphologies of the ZrO2 particles produced at heated temperature 700 and 1000 C for differ- ent processing routes were examined by scanning electron microscopy (JEOL-JSM 5410 SEM). Specic surface area (SBET ) of