共查询到20条相似文献,搜索用时 15 毫秒
1.
Xiaokai Li Yangyang Xu Xiaojian Mao Qiangqiang Zhu Junxi Xie Minghui Feng Benxue Jiang Long Zhang 《Ceramics International》2018,44(2):1362-1369
Highly transparent ZrO2-doped Y2O3 ceramics were successfully synthesized using the hot isostatic pressing (HIP) process. The effects of the ZrO2 content on the sintering behaviors, optical transmission spectra, Vickers hardness, grain size, size distribution, and Raman spectra were determined. The results indicated that decreased ZrO2 content could promote increased transmittance, red-shifted infrared cutoff wavelength, increased thermal conductivity, decreased Vickers hardness, and increased lattice ordering. According to the optical transmission spectra, the optimized ZrO2 content was 0.50 at%, at which point the ceramic exhibited a larger pre-sintering temperature range of 1650–1750 °C and the average grain size of 3.35 µm at 1750 °C. The grain size was significantly decreased at lower pre-sintering temperatures. Furthermore, a moderate Vickers hardness of 8.42 GPa and high thermal conductivity of 10.85 W/m K at room temperature were obtained for the optimized ceramic. 相似文献
2.
Edson Cezar Grzebielucka Adriana Scoton Antonio Chinelatto Sergio Mazurek Tebcherani Adilson Luiz Chinelatto 《Ceramics International》2010
Yttria-tetragonal zirconia polycrystal (ZrO2 + 4.5 mol% Y2O3) nanocrystalline powder was synthesized by two Pechini-type gel routes, the in situ polymerized complex (IPC) method and the PEG/AF method. FTIR spectra confirmed coordination of metal ions with the polymer by different routes, depending on the method used. The crystallite size of the powder increased from 5 nm to 8 nm when the temperature was increased from 450 °C to 600 °C and calcination times increased from 2 h to 24 h. The morphology of the powders differed only when the organic impurities were not completely eliminated. After calcination, the morphology of the powders produced by the two methods showed porous agglomerates composed of smaller particles. All the resulting microstructures were very similar, regardless of the method employed to obtain the powder or the calcination times and temperatures. 相似文献
3.
The microstructure and mechanical properties of ZrO2-2 mol% Y2O3 ceramics were studied on samples prepared by cold isostatic pressing and pressureless sintering. It was shown that the density of the alloy increases with increasing sintering temperature. The Vickers hardness decreases with the appearance of the monoclinic phase and increasing its content. Compared with the single tetragonal phase, the (t + m) dual-phase structure with microcracks has a much higher fracture toughness (16·5 MPa√m) because of a complex mechanism of toughening (transformation, microcracks and residual stresses). 相似文献
4.
Yanmei Kan Guojun Zhang Peiling Wang Omer Van der Biest Jef Vleugels 《Journal of the European Ceramic Society》2006,26(16):3607-3612
A suspension stabilizer-coating technique was employed to prepare x mol% Yb2O3 (x = 1.0, 2.0, 3.0 and 4.0) and 1.0 mol% Y2O3 co-doped ZrO2 powder. A systematic study was conducted on the sintering behaviour, phase assemblage, microstructural development and mechanical properties of Yb2O3 and Y2O3 co-doped zirconia ceramics. Fully dense ZrO2 ceramics were obtained by means of pressureless sintering in air for 1 h at 1450 °C. The phase composition of the ceramics could be controlled by tuning the Yb2O3 content and the sintering parameters. Polycrystalline tetragonal ZrO2 (TZP) and fully stabilised cubic ZrO2 (FSZ) were achieved in the 1.0 mol% Y2O3 stabilised ceramic, co-doped with 1.0 mol% Yb2O3 and 4.0 mol% Yb2O3, respectively. The amount of stabilizer needed to form cubic ZrO2 phase in the Yb2O3 and Y2O3 co-doped ZrO2 ceramics was lower than that of single phase Y2O3-doped materials. The indentation fracture toughness could be tailored up to 8.5 MPa m1/2 in combination with a hardness of 12 GPa by sintering a 1.0 mol% Yb2O3 and 1.0 mol% Y2O3 ceramic at 1450 °C for 1 h. 相似文献
5.
Thixotropic gels of the precursor powders of the titled compounds have been prepared by the addition of oxalic acid to the mixed solutions of metal salts at room temperature (≈ 27 °C). The clear sols of yttrium-zirconyl oxalate (YZO) and yttrium-cerium-zirconyl oxalate (YCZO) gelled within a few hours and were oven-dried at 40 °C. The various stages of gelation behaviour of the sols are explained on the basis of DLVO theory. By repeptizing the dried gel powders with water, concentrated sols were prepared. The gelation time as a function of chloride ion concentration is discussed for both sols. The nature of the temperature dependence of the dried gel powders was studied by means of thermogravimetric analysis and differential thermal analysis. Powder X-ray diffraction was used to study the crystallization behaviour of the dried amorphous gel powders. It is found that these powders crystallize in tetragonal phase when calcined at 850 °C for 1 h. Estimation of surface area and infra-red characterization have also been carried out for the prepared powders. 相似文献
6.
The current study reports on the improvement of mechanical properties of 3?mol% Y2O3 stabilized tetragonal ZrO2 (3Y-TZP) by introduction of tourmaline through ball milling and subsequent densification by pressureless sintering at 800, 1200, 1300, 1400?°C. Findings demonstrate that no matter which sintering temperature the 3Y-TZP ceramic containing 2?wt% tourmaline reach a maximum value in flexural strength and fracture toughness as compared to other composite ceramics. As the tourmaline content is 2?wt% and the sintering temperature is 1300?°C, the flexural strength and fracture toughness of the composite ceramics are the highest, increases of 36.2% and 36.6% over plain 3Y-TZP ceramic respectively. The unique microstructure was systematically investigated through X-ray diffraction, scanning electron microscopy, energy dispersive spectrum, and flourier transform-infrared. The strengthening and toughening mechanism of tourmaline in 3Y-TZP ceramic were also discussed. 相似文献
7.
P. A. Tikhonov M. Yu. Arsentev M. V. Kalinina L. I. Podzorova A. A. Ilicheva V. P. Popov N. S. Andreeva 《Glass Physics and Chemistry》2008,34(3):319-323
Powder precursors in the ZrO2-CeO2-Al2O3 and ZrO2-Sc2O3-Al2O3 systems are prepared by the sol-gel synthesis. It is revealed that the electrical conductivity of the sample doped with scandium
oxide is higher than the electrical conductivity of the sample doped with cerium oxide despite the higher content of the nonconducting
phase Al2O3 (corundum). The thermal expansion coefficients are determined for all the ceramic samples under investigation. It is established
that the Al2O3 dopant affects the thermal expansion coefficient. The ceramic materials studied can be used as solid-electrolyte sensors.
Original Russian Text ? P.A. Tikhonov, M. Yu. Arsent’ev, M.V. Kalinina, L.I. Podzorova, A.A. Il’icheva, V.P. Popov, N.S. Andreeva,
2008, published in Fizika i Khimiya Stekla. 相似文献
8.
Jihong She Peter Mechnich Martin Schmücker Hartmut Schneider 《Ceramics International》2001,27(8):687-852
Mullite ceramics were fabricated at relatively low temperatures from powder mixtures of -Al2O3 and quartz, with an Y2O3 addition. The mullitization process was analyzed by X-ray diffraction. The densification behavior was investigated as a function of the Y2O3 content, sintering temperature and holding time as well as mullite seeds. It has been shown that mullitization occurs via a nucleation and growth mechanism within an yttrious aluminosilicate glass, but lattice and grain-boundary diffusion becomes important during the densification process. Moreover, the incorporation of mullite seeds was observed to enhance both mullitization and densification. At 1400°C for 5 h or 1450°C for 2 h, 15 mol% Y2O3-doped and 5 mol% mullite-seeded specimens can be sintered to almost full density. 相似文献
9.
R.P. Yavetskiy V.N. BaumerN.A. Dulina Yu.I. PazuraI.A. Petrusha V.N. TkachA.V. Tolmachev V.Z. Turkevich 《Journal of the European Ceramic Society》2012,32(2):257-260
Y2O3:Eu3+ (1 at.%) translucent nanostructured ceramics with total forward transmission achieving ∼70% of the theoretical limit has been obtained by the transformation-assisted consolidation of custom-made cubic Y2O3:Eu3+ nanopowders under high pressure (HP). Sintering under the pressure of 7.7 GPa and temperatures in the 100-500 °C range leads to the partial cubic-to-monoclinic phase transition that results in two-phase Y2O3:Eu3+ nanoceramics. The average grain size of ceramics d ≤ 50 nm for both Y2O3:Eu3+ polymorph is comparable with crystallite size of initial nanopowders (d ∼ 40 nm), indicating that the grain growth factor is near unity. The phase compositions, morphology, densities, preliminary optical and luminescent properties of synthesized nanostructured ceramics have been studied. 相似文献
10.
R.M. Balestra S. Ribeiro S.P. Taguchi F.V. Motta C. Bormio-Nunes 《Journal of the European Ceramic Society》2006,26(16):3881-3886
The wetting of SiC plate by Y2O3/AlN additive was analysed using the sessile drop method. The wetting behaviour was observed by image capture system using a CCD camera during the heating, in argon atmosphere. The contact angle was measured as a function of temperature and time. After the wetting test the SiC plus additive samples were cut in order to observe the thickness plate cross section. The additive area and the interface between SiC and additive were analysed using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The wetting of SiC by Y2O3/AlN is influenced by the presence of a solid phase in some of the additive drops that depends mainly on the additive composition and consequently on the temperature. The measured contact angles were below 7°, reaching 0° for Y2O3/AlN additive tested at the eutectic composition, indicating a very good wettability of Y2O3/AlN on the SiC. 相似文献
11.
Two-step sintering was employed to consolidate nanocrystalline 8 mol% yittria stabilized zirconia processed by glycine-nitrate method. Results verified the applicability of this method to suppress the final stage of grain growth in the system. The grain size of the high density compacts (>97%) produced by two-step sintering method was seven times less than the pieces made by the conventional sintering technique. Up to ∼96% increase in the fracture toughness was observed (i.e. from 1.61 to 3.16 MPa m1/2) with decreasing of the grain size from ∼2.15 to ∼295 nm. A better densification behavior was also observed at higher compacting pressures. 相似文献
12.
The high-temperature wettability and interactions between NbSi-based alloys and Y2O3 ceramics with various microstructures were studied, based on which the corresponding mechanisms were discussed. The results showed that there was a characteristic transition during the high temperature wetting between the alloys and ceramics when the Y2O3 microstructure changed. The rate of spreading of molten NbSi-based alloys on the Y2O3 ceramics was relatively high when the level of open porosity was greater than 20.8%. As the level of open porosity of the Y2O3 ceramics increased from 6.9% to 27.8%, the initial and equilibrium contact angles between the alloys and ceramics increased from 81.3° to 110.0°, and from 60.5° to 93.2°, respectively. TiO and Ti2O phases formed within the alloy matrix of each wetting system. However, as the level of open porosity of the Y2O3 substrates increased, the Ti-oxide content initially gradually decreased and subsequently increased. The alloy in the system with the open porosity level of 20.8% contained the lowest Ti-oxide content while the system with the open porosity level of 6.9% contained the most. 相似文献
13.
Qing Yi Shengming Zhou Hao TengHui Lin Xiaorui Hou Tingting Jia 《Journal of the European Ceramic Society》2012,32(2):381-388
The paper reports the use of La2O3 and ZrO2 co-doping as a composite sintering aid for the fabrication of Tm:Y2O3 transparent ceramics. Two groups of experiments were conducted for investigating the influences of composite sintering aids on the microstructures and the optical properties of Tm:Y2O3 transparent ceramics in contrast to single La3+ and single Zr4+ doped Tm:Y2O3. Samples with composite sintering aids could realize fine microstructures and good optical properties at relatively low sintering temperatures. Grain sizes around 10 μm and transmittances close to theoretical value at wavelength of 2 μm were achieved for the 9 at.% La3+, 3 at.% Zr4+ co-doped samples sintered at 1500-1600 °C. The influences of the composite sintering aids on the emission intensities and the phonon energies of Tm:Y2O3 ceramics were also investigated. 相似文献
14.
Thomas Konegger Robert Potzmann Michael Puchberger Antje Liersch 《Journal of the European Ceramic Society》2011,31(15):3021-3031
Interactions between a poly(vinyl)silazane and Al2O3 or Y2O3-stabilised ZrO2 fillers were studied during the fabrication of polysilazane-derived bulk ceramics in order to investigate the influence of oxide fillers on resulting properties. Specimens were produced by coating of the filler powders with the polysilazane, warm-pressing of the resulting composite powders, and pyrolytic conversion in flowing N2 at various temperatures between 1000 °C and 1400 °C. Significant differences in densification were observed, depending on the filler used. Reactions between the polysilazane-derived matrix and Al2O3 or ZrO2 at temperatures ≥1300 °C resulted in the formation of Si5AlON7 or ZrSiO4, respectively. Reactivity in the polysilazane-derived component was a result of SiO2 contamination caused primarily by adsorbed species on the filler particle surface. Knowledge of polysilazane/filler interface processes is found to be decisive for the prediction of properties such as shrinkage and porosity, which heavily influence performance of a material. 相似文献
15.
Zhigang Jiang Le Zhang Fangzheng Zhen Qing Yao Wei Bu Tianyuan Zhou Yuelong Ma Rong Sun Hao Chen Yun Wang 《Ceramics International》2018,44(14):16859-16867
Well-dispersed Y2O3 powders were synthesized by a precipitation method from yttrium nitrate solution using (NH4)2SO4 and PEG4000 as the composite surfactant, and the dispersion mechanism of the composite surfactant was investigated in detail. Furthermore, the grain size, densification, mechanical and optical quality of as-prepared ceramics were also discussed. The dispersion state of both precursors and Y2O3 powders could be remarkably effected by the mass ratio of (NH4)2SO4 and PEG4000 during the liquid phase reaction process. When the function of electrostatic repulsion and the steric hindrance were combined properly, the aggregation state of powders could be effectively inhibited. With the addition of the mass ratio of 3:2 ((NH4)2SO4 to PEG4000), fine powders (130?nm) with high dispersion state were obtained. Meanwhile the Y2O3 ceramics with an average grain size of 3.65?µm were fabricated by sintering at 1750?°C for 8?h. 相似文献
16.
The microstructure and electrical properties of ZnO-Bi2O3-based varistor ceramics doped with different Sc2O3 content sintered at 1100 °C were investigated. The results showed that the nonlinear coefficient of the varistor ceramics with Sc2O3 were in the range of 18-54, the threshold voltage in the range of 250-332 V/mm, the leakage current in the range of 0.1-23.0 μA, with addition of 0-1.00 mol% Sc2O3. The ZnO-Bi2O3-based varistor ceramics doped with Sc2O3 content of 0.12 mol% exhibited the highest nonlinearity, in which the nonlinear coefficient is 54, the threshold voltage and the leakage current is 278 V/mm and 2.9 μA, respectively. The results confirmed that doping with Sc2O3 was a very promising route for the production of the higher nonlinear coefficient of ZnO-Bi2O3-based varistor ceramics, and determining the proper amounts of addition of Sc2O3 was of great importance. 相似文献
17.
Yihua Huang Dongliang JiangJingxian Zhang Qingling LinZhengren Huang 《Ceramics International》2011,37(8):3523-3529
Transparent Nd:Y2O3 ceramic was obtained by sintering mono-sized spherical powder. The powder was prepared by homogeneous precipitation method in aqueous media using urea to regulate the pH. The structure and morphology of the powder were investigated by TG-DTA, XRD, SEM and IR spectrum. The effect of aging temperature, time, and the concentration of urea, [Y3+], and [Nd3+] were investigated. Results showed that the obtained precursor was R2(OH)CO3·H2O (R = Y, Nd), and the least size of mono-sized spherical yttria particles was 72 nm by a microwave oven method after calcinations at 850 °C for 4 h. After dry press and CIP, the particles accumulated closely, and no defects can be detected in the green body. 相似文献
18.
Jinshuang Wang Junbin Sun Qiangshan Jing Bing Liu Hao Zhang Jieyan Yuan Shujuan Dong Xin Zhou Xueqiang Cao 《Journal of the European Ceramic Society》2018,38(7):2841-2850
The properties of ZrO2 co-stabilized by CeO2 and TiO2 ceramic bulks were investigated for potential thermal barrier coating (TBC) applications. Results showed that the (Ce0.15Tix)Zr0.85-xO7 (x?=?0.05, 0.10, 0.15) compositions with single tetragonal phase were more stable than the traditional 8YSZ at 1573?K. These compositions also showed a large thermal expansion coefficient (TEC) and a high fracture toughness, which were comparable to those of YSZ. However, the phase stability, fracture toughness and sintering resistance of the CeO2-TiO2-ZrO2 system showed a decline tendency with the increase of TiO2 content. The TEC of the ceramic bulks decreased with increase of TiO2 content as well because the crystal energy was enhanced with increasing substitution of Zr4+ by smaller Ti4+. The (Ce0.15Ti0.05)Zr0.8O2 had the best comprehensive properties among the (Ce0.15Tix)Zr0.85-xO2 compositions as well as a low thermal conductivity. Therefore, it can be explored as a TBC candidate material for high-temperature applications. 相似文献
19.
Yttria- and ceria-doped tetragonal zirconia polycrystals ((Y, Ce)-TZP) with compositions 2·5 mol% YO1·5-4 mol% CeO2---ZrO2, 4 mol% YO1·5-4 mol% CeO2---ZrO2, and 2·5 mol% YO1·5-5·5 mol% CeO2---ZrO2 were prepared from zirconia sols obtained hy hydrolysis of ZrOCl2 solution, and their sintering, microstructure and thermal stability were studied. Sintered bodies with 99% TD were obtained by firing at 1400°C for 2 h in air. The grain size of (Y, Ce)-TZP increased with decreasing Y2O3 content in Y2O3---CeO2---ZrO2. (Y, Ce)-TZP was resistant to tetragonal-to-monoclinic (t → m) phase transformation during low temperature ageing as compared with 3Y-TZP. 相似文献
20.
Two-step sintering behavior of titanium-doped Y2O3 ceramics with monodispersed sub-micrometer powder
Two-step sintering of titanium-doped Y2O3 was carried out using monodispersed sub-micrometer powder. The effect of titanium dopant concentration on the sinterability and kinetic window of constant grain-size sintering were examined. The titanium doping improves the sinterability of the Y2O3 powder, which broadens the sintering kinetic window and lowers sintering temperature. The Vickers hardness was also enhanced as the doping concentration of titanium was increased, assuming the same grain size. 相似文献