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The attainment of both high strength and toughness is the ultimate goal for most structural materials. Although ceramic material has been considered for use as a structural material due to its high strength and good chemical stability, it suffers from the limitation of low toughness. For instance, although Y2O3- stabilized tetragonal ZrO2 polycrystals (Y- TZPs) exhibit remarkable toughness among ceramics due to their phase transformation toughening mechanism, this toughness is still much weaker than that of metals. Here, we report Y- TZP- based ceramic materials with toughnesses exceeding 20 MPa m1/2, which is comparable to those of metals, while maintaining strengths over 1,200 MPa. The superior mechanical properties are realized by reducing the phase stability of tetragonal zirconia by tailoring the microstructure and chemistry of the Y- TZP. The proposed ceramic materials can further advance the design and application of ceramic- based structural materials. [ABSTRACT FROM AUTHOR]

Y2O3-stabilised ZrO2 (YSZ) ceramics have been used for various engineering applications since Garvie et al. discovered phase-transformation toughening in 1975. The performance of YSZ ceramics depends on the YSZ microstructure. In the present review, the tetragonal-to-cubic phase transformation and grain growth are first discussed, organised according to existing hypotheses of microstructure-development mechanisms in YSZ during sintering. We demonstrate that the phase transformation and grain growth can be most reasonably understood by a grain boundary segregation-induced phase transformation (GBSIPT) mechanism and that the solute-drag effect of Y3+ ions segregating along the grain boundaries, respectively. Next, the Al2O3-doping effect is discussed with emphasis on the microstructure-development behaviour in a small amount of Al2O3-doped YSZ, which is widely used in engineering applications. We further discuss the effect of GBSIPT on low-temperature degradation resistance and the effect of grain size on superplasticity, focusing on the nanocrystalline YSZ, which was created by applying the Al2O3-doping effect. [ABSTRACT FROM AUTHOR]

The attainment of both high strength and toughness is the ultimate goal for most structural materials. Although ceramic material has been considered for use as a structural material due to its high strength and good chemical stability, it suffers from the limitation of low toughness. For instance, although Y 2 O 3 -stabilized tetragonal ZrO 2 polycrystals (Y-TZPs) exhibit remarkable toughness among ceramics due to their phase transformation toughening mechanism, this toughness is still much weaker than that of metals. Here, we report Y-TZP-based ceramic materials with toughnesses exceeding 20 MPa m 1/2 , which is comparable to those of metals, while maintaining strengths over 1,200 MPa. The superior mechanical properties are realized by reducing the phase stability of tetragonal zirconia by tailoring the microstructure and chemistry of the Y-TZP. The proposed ceramic materials can further advance the design and application of ceramic-based structural materials.

Abstract: A systematic study of the influence of alumina (Al2O3) doping on the optical, electrical, and structural characteristics of sputtered ZnO thin films is reported in this study. The ZnO thin films were prepared on 1737F Corning glass substrates by R.F. magnetron sputtering from a ZnO target mixed with Al2O3 of 0–4 wt.%. X-ray diffraction (XRD) analysis demonstrates that the ZnO thin films with Al2O3 of 0–4 wt.% have a highly (002) preferred orientation with only one intense diffraction peak with a full width at half maximum (FWHM) less than 0.5°. The electrical properties of the Al2O3-doped ZnO thin films appear to be strongly dependent on the Al2O3 concentration. The resistivity of the films decreases from 74 Ω·cm to 2.2×10−3 Ω·cm as the Al2O3 content increases from 0 to 4 wt.%. The optical transmittance of the Al2O3-doped ZnO thin films is studied as a function of wavelength in the range 200–800 nm. It exhibits high transparency in the visible-NIR wavelength region with some interference fringes and sharp ultraviolet absorption edges. The optical bandgap of the Al2O3-doped ZnO thin films show a short-wavelength shift with increasing of Al2O3 content. [Copyright &y& Elsevier]

• The homogeneous sheet of Al 2 O 3 /CaO provides high specific surface area and abundant active sites. • The Al 2 O 3 /CaO exhibits excellent arsenic adsorption activity and anti-sintering ability. • Al top site of Al 2 O 3 /CaO is the dominant active site for As 2 O 3 adsorption. Calcium oxide (CaO), as a high temperature sorbent, has been widely applied in the field of heavy metal removal due to its low price and stable chemical properties, but CaO tends to sinter at high temperature, which affects the adsorption performance. In this work, Al 2 O 3 /CaO sorbent with resistance to sintering was synthesized via citric acid and calcine method, which was innovatively employed to the adsorption of As 2 O 3 combining experiment and theoretical analysis. The experimental results demonstrate that the adsorption capacity of untreated CaO reduces immensely with the temperature rising from 1073 to 1273 K, and arsenic adsorption capacity reduces from 303 to 50 mg/kg. Whereas, arsenic adsorption capacity of Al 2 O 3 /CaO almost maintains at high level and reaches to 534 mg/kg at 1173 K, which proves that the addition of Al 2 O 3 can improve the anti-sintering ability of CaO. Meanwhile, through density functional theory (DFT), the adsorption sites of Al 2 O 3 /CaO was further studied. Al site of Al 2 O 3 /CaO was found to be the main adsorption active site and electron transfer channel, which effectively facilitates the separation of lattice oxygen. Finally, the adsorption mechanism of As 2 O 3 on Al 2 O 3 /CaO was proposed. [ABSTRACT FROM AUTHOR]

• Sol-gel synthesized and heat-treated 40Fe x AlSi samples with ' x' of 10, 15, and 20 resulted in the precipitation of fayalite, hematite and maghemite NPs with photocatalytic properties. • The corresponding degradation rate constant k , following the first-order reaction kinetics, was 14.89 × 10−2 min−1 for 40Fe 2 O 3 -15Al 2 O 3 -45SiO 2 sample. • The presence of various crystalline phases that contain iron ions in mixed-valence states favors the formation of continuous pathways for uninterrupted polaronic transport which enhances an increase in DC conductivity. • Electrical conductivity and photocatalytic activity of the composites increase with the alumina content. The glass samples with the composition of 40Fe 2 O 3 - x Al 2 O 3 -(60− x)SiO 2 were prepared by sol-gel method. The samples were characterized by XRD, 80 K 57Fe Mössbauer spectroscopy, TEM, FTIR and impedance spectroscopy. In the glass samples with less than 10% alumina, fayalite and hematite were crystallized by addition of hercynite. Whereas nanoparticles of hematite (α-Fe 2 O 3) and maghemite (γ-Fe 2 O 3) doped with Al were confirmed with the increase of alumina contents (15% and 20%). The glass samples exhibit the electronic conduction which is explained by the polaronic conduction mechanism. It is noticed that the catalysts containing a mixture of hematite and maghemite nanoparticles showed higher photocatalytic degradation of Rhodamine B dye than those containing hematite alone. It is suggested from the characterizations of newly developed iron-containing aluminosilicate glass samples that the materials with several bandgaps and without dissolving itself should be developed in the future for water purification under visible light irradiation. [ABSTRACT FROM AUTHOR]