材料專業(yè)外文資料翻譯--熱處理對三種不同途徑生產(chǎn)的納米粉氧化鋯晶體結(jié)構(gòu)和形態(tài)的影響

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1、　　畢業(yè)論文外文資料翻譯　　題目熱處理對三種不同途徑生產(chǎn)的 　　納米粉氧化鋯晶體結(jié)構(gòu)和形態(tài)的影響　　學(xué) 院材料科學(xué)與工程 　　專業(yè) 材料科學(xué)與工程 &l

2、t;/p>　　班級 　　學(xué) 生 　　學(xué) 號 　　指導(dǎo)教師

3、 　　二〇一三年三月二一日　　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 ) 178–185　　journal homepage: ww

4、w.elsevier.com/locate/jmatprotec　　Effect of thermal treatment on the crystal　　structure and morphology of zirconia　　nanopowders produced by<p&

5、gt;　　three different routes　　M.M. Rashad ? , H.M. Baioumy　　Central Metallurgical Research and Development Institute, P.O. Box 87, Helwan, Cairo, Egypt<b&g

6、t;　　article　　Article history:　　info　　abstract　　Zirconia ZrO2 nanopowders have been succe

7、ssfully prepared via three processing routes,　　namely, conventional precipitation (CP), citrate gel combustion (CGC) and microemulsion　　re?ned precipitation (MRP). The formed zir

8、conia particles were characterized using X-ray　　diffraction analysis (XRD), scanning electron microscope (SEM), Fourier transformer infrared　　(FT-IR) spectroscopy and UV–visible

9、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 tr

10、ansformed to monoclinic ZrO2 phase at temperatures ranged　　Received 24 May 2006　　Received in revised form　　22 April 2007　　Accepted 23 Ap

11、ril 2007　　Keywords:　　Zirconia　　Synthesis　　Crystal structure

12、;　　Nanoparticles　　Characterization　　from 1000 to 1200 ? C. The CGC route led to formation of monoclinic phase without presence　　tetragonal phase species in t

13、he temperatures range from 1000 to 1200 ? C. In contrast, MRP　　technique led to the formation of tetragonal phase with high crystallinity compared with　　the other processing at 7

14、00 ? 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 pro

16、;　　1.　　Introduction　　Advanced ceramics known as ?ne ceramics are a diverse　　group of inorganic oxides such as zirconia, alumina, tita-&

17、lt;p>　　nia and non-oxides like silicon carbide, boron carbide and　　silicon nitride. These materials are drawing attention as　　high technology materials because of their superi

18、or mechan-　　ical, thermal, electrical, chemical and optical properties.　　Zirconia ?ne ceramics have an impressive combination　　of properties such as high str

19、ength, hardness, toughness,　　corrosion resistance, low co-ef?cient of friction and biocom-　　patibility. Nearly 80% of produced zirconia in the world is　　used

20、 in conventional applications such as refractories, pig-　　ments, glazers, opaci?ers, abrasives, etc. The ever-increasing　　numbers of ceramics applications have resulted in devel-

21、　　oping of advanced technologies to process nanopowders　　zirconia (Galgali et al., 1995). The advanced applications　　of zirconia nanopowders are including tr

22、ansparent opti-　　cal devices, electrochemical capacitor electrodes, oxygen　　sensors, fuel cells and catalysts including photocatalysts　　(Srdic and Omorjan, 2

23、001; Kongwudthiti et al., 2003). Zir-　　conia catalyzes the hydrogenation of ole?ns, isomerization　　of ole?ns and epoxides and the dehydrations of alco-　　hols

24、. When zirconia is used as support, various reactions　　Corresponding author. Tel.: +20 2 5010642/213; fax: +20 2 5010639.　　E-mail address: rashad133@yahoo.com (M.M. Rashad).</

26、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 ) 178–185　　179　　such as Fischer-Tropsch synthesis, methanol synthes

27、is and　　hydrodesulfurization have been reported to proceed with　　higher activity and selectivity than with conventional sup-　　ports (Jung and Bell, 2000). It

28、 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

29、 near-UV laser and dielectric mirror designs.　　In addition, about 95% of ferrule, the most important part　　of the optical ?ber connector is now made from zirconia<

30、p>　　?ne ceramics. It is known that high quality of the ceramic　　is based on the excellent performance of zirconia powder　　(5).　　Prepari

31、ng a ?ne and an agglomerate free zirconia powder　　is the ?rst and perhaps the most important step in obtaining　　a sintered zirconia ceramic of desirable microstructure and</p&

32、gt;　　therefore mechanical properties. Various chemistry-based　　novel approaches have been taken for the preparation of zirco-　　nia powders including co-precipitation,

33、hydrothermal, sol gel,　　sonochemical method, microemulsion and thermal decom-　　position processing (Ma et al., 2004; Wu et al., 2003; Lee et al.,　　1999; Tai

34、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 et al.,

35、 1996;　　Yashima et al., 1994; Caruso et al., 1997; Chatterjee et al., 1992;　　Dodd and McCormick, 2002; Roy and Ghose, 2000; Kolen’ko et　　al., 2003; Noh et al

36、., 2003; Somiya and Akiba, 1999; Piticescu et　　al., 2001). The chemical precipitation (CP) method is a suitable　　low cost technique for the mass production compared with

37、;　　the other mentioned technique. The main drawback is that　　the particle size is not small and has in wide size distribution.　　Microemulsion re?ned precipitation (MRP

38、) gives better chem-　　ical homogeneity with controlling the particle size and size　　distribution. Citrate gel combustion (CGC) technique is used　　to obtain h

39、ighly uniform size and shape controlled nanopar-　　ticles.　　ZrO2 has three polymorphic phases; monoclinic (m), tetrag-　　onal (t) and cubic

40、(c). Because of its phase transformation　　from tetragonal to monoclinic around the temperatures range　　from 1100 to 2370 ? C, it is a challenging study with potentially

41、　　practical applications to prepare stabilized tetragonal ZrO2　　powders at low temperatures. Stabilization of t-ZrO2 phase　　is usually achieved by adding oxides of ytt

42、rium, magnesium,　　calcium, thorium, titanium, cerium and ytterbium (Piticescu　　et al., 2001; Jiang et al., 2001; Lascalea et al., 2004; Teterycz et　　al., 200

43、3; 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 temperatu

44、re　　up to the melting point at 2680 ? C. m-ZrO2 phase is stable　　below 1170 ? C and inverted to t-ZrO2 phase by increasing tem-　　perature over 1200 ? C. t-Zr

45、O2 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<p&

46、gt;　　about the change in the phase transformation and the mor-　　phology of the formed ZrO2 nanopowders that are produced　　by CP, CGC and MRP techniques. The present work aims at&

47、lt;/p>　　comparing the change in crystal structure, morphology, FT-IR　　spectra and UV–visible absorption spectrum of the produced　　ZrO2 nanopowders which are obtaine

48、d by these three process-　　ing routes at different calcination temperatures from 120 to　　1200 ? C.　　2.<p

49、>　　2.1.　　Experimental　　Materials and processing　　The materials used in the present work were, zirconyl chlo-　　ride

50、 ZrOCl2 ·8H2 O purchased from BDH Chemicals Ltd., Poole,　　England, sodium hydroxide and citric acid purchased from El-　　Nasr Pharmaceutical Chemical ADWIC, Egypt, n-pentanol

51、 and　　Triton X-100 (Serva Electrophoresis GmbH, Germany).　　To process ZrO2 powders by CP route, 10 g zirconium　　oxychloride octahydrate was dissolved in 100

52、ml bidistilled　　water using hot plate magnetic stirrer. The desired vol-　　ume of 2 M NaOH was added into the solution until pH　　10. After 15 min, the produce

53、d 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<p&g

54、t;　　rate of 10 ? C/min and kept at the respective temperature for　　1 h.　　To process ZrO2 powders by CGC method, 10 g of zir-　　conium oxych

55、loride 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.

56、;　　Then, the produced precursor was dried to 120 ? C overnight.　　The formed precursor was heated again to 500, 700, 1000 and　　1200 ? C at a rate of 10 ? C/min and kept

57、 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 mol

58、ar of　　Triton X-100 (non-anionic surfactant) was prepared by dissolv-　　ing in n-pentanol and the processed solution was divided into　　two parts, one part was

59、 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<p

60、>　　solutions were mixed together to precipitate zirconia hydrate　　at pH 10. The precipitated solution was ?ltered, washed, dried　　at 120 ? C, then calcined at different temper

61、atures from 500 to　　1200 ? C.　　2.2.　　Characterization　　The phase identi?cation and the crystallite

62、 size of the pro-　　cessed ZrO2 nanopowders were characterized by Philips X-Ray　　Diffractometer PW 1730 with nickel ?ltered Cu K radiation　　?( = 1.5406 A) at

63、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&

64、lt;p>　　using the Debye-Scherrer formula:　　dRX =　　k　　cos Â　　ˇ&l

65、t;/b>　　(1)　　where dRX is the crystallite size, k = 0.9 is a correction factor　　to account for particle shapes, ˇ the full width at half

66、 max-　　imum (FWHM) of the most intense diffraction plane, the　　?wavelength of Cu target = 1.5406 A, and Â is the Bragg angle.　　The change in crystal mor

67、phologies of the ZrO2 particles　　produced at heated temperature 700 and 1000 ? C for differ-　　ent processing routes were examined by scanning electron　　micro

68、scopy (JEOL-JSM 5410 SEM). Speci?c surface area (SBET ) of　　180　　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 )

69、178–185　　samples was determined by BET surface area analyzer (Nova　　2000 series, Quantachrome Instruments, UK).　　UV–visible absorption spectrums of the proce

70、ssed ZrO2　　powders using three processing routes at calcination temper-　　ature 1000 ? C were measured using CECIL CE 7200 UV double　　beam spectrophotometer.&

71、lt;/p>　　Vibration spectrum of the crystalline ZrO2 powders at　　calcination temperature 1000 ? C for the different processing　　techniques in KBr were recorded on Fou

72、rier Transformer and　　Pye-Unicam SP 300 instrument.　　3.　　Results and discussion　　The XRD patterns of the ZrO2 nanopow

73、ders products syn-　　thesized by precipitation (CP), citrate gel combustion (CGC)　　and microemulsion re?ned precipitation (MRP) techniques at　　different therm

74、al treatment from 120 to 1200 ? C were shown　　in Figs. 1–3. It is clear that the processed samples synthe-　　sized at temperature 120 ? C were amorphous in the three&l

75、t;p>　　processing techniques and it was also nearly amorphous for　　the produced ZrO2 powders of the precursor sample pow-　　der which treated at the temperature 500 ? C in case

76、of CP　　method. XRD studies also showed that the transformation of　　ZrO2 precursors to the crystalline tetragonal phase (JCPDS #49-　　1642) occurred as the cal

77、cination temperatures were increased　　Fig. 2 – XRD patterns of the produced ZrO2 powders by CGC　　method at 120, 500, 700, 1000 and at 1200 ? C for 1 and 3 h.

78、　　between 500 and 700 ? C for heating time 1 h. The crystallite　　sizes of formed single-phase t-ZrO2 nanopowders as calcu-　　lated from XRD analyses using Debye-Scherrer formula o

79、f　　the most intense peaks (1 1 1) plane were in the range of　　32.90, 10.18 and 20.97 nm at 700 ? C for CP, CGC and MRP　　methods, respectively. The presence o

80、f tetragonal phase in as-　　prepared ZrO2 and the powder formed at low temperature is　　attributed to the fact that the speci?c surface free enthalpy　　of tetra

81、gonal ( = 0.77 J/m2 ) is smaller than that of mono-　　clinic ( = 1.13 J/m2 ). The large surface area of as-synthesized　　nanopowders becomes a thermodynamic barrier for t-ZrO2</

82、p>　　to m-ZrO2 phase transformation. Consequently, tetragonal　　phase is remained. Liang et al. (Liang et al., 2003) explained the　　formation of tetragonal phase at l

83、ow temperature is attributed　　to that the structure of zirconia precursor is regarded as　　hydrous zirconia (ZrO2 ·nH2 O) and the schematic structure unit

84、;　　has 16 zirconium atoms, 20 non-bridging hydroxogroups, 22　　bridging oxide bond and 20 coordinated water and based on　　this model, the following equations is obtained by increa

85、sed　　the temperature up to 700 ? C:　　[Zr16 O22 (OH)20 (H2 O)20 ] · xH2 O　　Naturally dried　　?→<p&g

86、t;　　[Zr16 O22 (OH)20 (H2 O)20 ] + xH2 O　　(2)　　Fig. 1 – XRD patterns of the produced ZrO2 powders by CP　　method at 120, 500, 700, 1000 and

87、at 1200 ? C for 1 and 3 h.　　[Zr16 O22 (OH)20 (H2 O)20 ]?→16ZrO2 + 30H2 O　　heat　　(3)　　j o u r n a l

88、 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 ) 178–185　　181　　Fig. 3 – XRD patterns of the produced ZrO2 powders by MRP</p&

89、gt;　　method at 120, 500, 700, 1000 and at 1200 ? C for 1 and 3 h.　　When ZrO2 ·nH2 O is heated up to about 300 ? C, the　　metastable tetragonal zirconia is observed

90、 compared to its　　stable temperature around 1100–2370 ? C. The amorphous to　　tetragonal phase transformation is attributed to the loss of　　water from the amo

91、rphous hydrous zirconia resulting from　　the release of water of hydration and the production of water　　via oblation. Both processes lead to a reduction in the BET sur-

92、　　face area of the calcined solid and a consequent increase in　　the average particle size (Jung and Bell, 2000). Table 1 showed　　that the relation between the crystalli

93、te size and the surface　　area of the obtained ZrO2 nanopowders produced by differ-　　ent techniques. For CP method, when the crystallite sizes of　　the produce

94、d powders increased from 7 nm for the precursor　　thermally treated at 500 ? C to 32.90 nm at 700 ? C. The surface　　area of amorphous zirconia produced at 120 ? C was 250 m2 /g<

95、;/p>　　which was decreased to 230 m2 /g for the precursor thermally　　treated at 500 ? C and decreased again to 180 and 20 m2 /g for the　　precursor thermally treated

96、at 700 and 1000 ? C, respectively.　　For CGC method, the BET speci?c surface area of amorphous　　zirconia was 280 m2 /g then decreased to 210 m2 /g (crystallite

97、;　　size was 10.18 nm) for the precursor treated at 700 ? C then to　　60 m2 /g for the sample treated at 1000 ? C (crystallite size was　　41.2 nm). Moreover, for MRP method, the BET

98、 speci?c surface　　area was also 280 m2 /g then decreased to 200 m2 /g (crystallite　　size was 21 nm) and 45 m2 /g (crystallite size was 57.8 nm) for　　the prec

99、ursors annealing at 700 and 1000 ? C, respectively.　　The tetragonal phase then inverted to pure monoclinic　　phase (JCPDS #37-1484) by increasing the temperature up to

100、　　1000–1200 ? C for 1 h in case of CP and CGC techniques. Trans-　　formation from the tetragonal to monoclinic phase have been　　attributed to the relative stability of th

101、ese two phases depend　　on the sum of the free energies from particle surface, bulk　　and strain contribution (Jung and Bell, 2000). Because of the　　lower bulk

102、 free energy of m-ZrO2 and the lower surface free　　energy of t-ZrO2 , the latter phase is stabilized below a critical　　particle size for a given temperature. This critical size i

103、s esti-　　mated to be 10 nm at 298 K. In the absence of particle strain,　　this thermodynamic description has been found to give the　　correct temperature for t

104、he tetragonal to monoclinic phase　　transformation for the particles ranging from 9 nm to 10 m.　　The phase transformation occurred when the size of zirconia

105、particles is equal to or greater than the critical size determined　　from an analysis of the thermodynamic stability of small parti-　　cles of t- and m-ZrO2 . The validity of a pur

106、ely thermodynamic　　explanation has been questioned since several investigations　　have observed t-ZrO2 that is larger than the critical particle　　size by talk

107、ing into account factors such as domain boundary　　stresses, nucleation embryos, anionic vacancies and adsorbed　　cations and anions, all of which contribute to the stabiliza-</

108、p>　　tion of t-ZrO2 . On these factors, the effects of external strain　　and the adsorbed ionic species on the surface free energy of　　zirconia can be accommodated wi

109、thin the thermodynamic　　theory for the tetragonal to monoclinic phase transforma-　　tion. In addition, the phase transformation of zirconia starts　　from its s

110、urface region and then gradually develops into the　　bulk. The tetragonal phase in the surface region is dif?cult　　to stabilize. Treatment at progressively higher temperature</

111、p>　　in absence of strain is accompanied by loss of surface area.　　Moreover, when hydrous zirconia inverted to t-ZrO2 , zirconia　　Table 1 – Crystallite size (Cs) and

112、 the speci?c surface area SBET values of zirconia nanopowders synthesized by CP, CGC　　and MRP methods at different calcination temperatures　　Temperature (? C)

113、;　　Cs (nm)　　120　　500　　700　　1000

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