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  • Electric Field-Induced Changes in the Ferroelastic Behavior of (Na1/2Bi1/2)TiO3-BaTiO3
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-06-15
    Alexander Martin, Neamul H. Khansur, Kyle G. Webber

    In this study, the macroscopic mechanical behavior was characterized for poled and unpoled polycrystalline (1−x)(Na1/2Bi1/2)TiO3-xBaTiO3 (NBT-xBT) for compositions across the morphotropic phase boundary (MPB). Due to a field-induced ferroelectric phase transformation, NBT-xBT compositions near the MPB (x = 6 – 7 mol%) showed a significant decrease in the coercive stress for electrically poled samples. The apparent difference in mechanical behavior is suggested to be due to an irreversible electric-field-induced transformation to long-range ferroelectric order in the poled samples. The results indicate a significant difference in the critical stresses for the relaxor-ferroelectric transition and ferroelastic domain wall motion, which can have important effects on applications for lead-free ferroelectrics. To further illustrate this, a method was developed to electrically depole NBT-xBT at room temperature, resulting in an unpoled NBT-xBT material with long-range ferroelectric order. Mechanical testing revealed analogous macroscopic ferroelastic behavior to the poled samples, despite the lack of a piezoelectric response.

    更新日期:2018-06-15
  • A new series of low-temperature cofirable Li3Ba2La3(1-x)Y3x(MoO4)8 microwave dielectric ceramics
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-06-15
    Ruzhong Zuo, Yudong Xu, Min Shi, Weiqiong Li, Liangguo He

    A new series of Li3Ba2La3(1-x)Y3x(MoO4)8 microwave dielectric ceramics were prepared by a conventional solid-state reaction method. The Rietveld refinement results further confirm that Li3Ba2La3(1-x)Y3x(MoO4)8 belongs to a monoclinic system with space group C2/c. Scanning electron microscopy results reveal that Li3Ba2La3(1-x)Y3x(MoO4)8 ceramics can be well sintered at a low sintering temperature. In addition, the permittivity (εr) of Li3Ba2La3(1-x)Y3x(MoO4)8 ceramics was found to decrease gradually with increasing substitution content of Y3+, while the quality factor (Qxf) and temperature coefficient of resonant frequency (τf) increase with x monotonously. The x = 0.4 ceramic sintered at 700 °C for 4 h possesses optimum microwave dielectric properties of εr ~ 14.4, Qxf ~ 14,994 GHz (at 9.0 GHz) and τf ~ + 6.9 ppm/°C. Particularly, no chemical reaction between the matrix phase and Ag metal suggests that the Li3Ba2La1.8Y1.2(MoO4)8 ceramic might be a promising candidate for low-temperature co-fired ceramic applications.

    更新日期:2018-06-15
  • Microwave dielectric properties and infrared reflectivity spectra analysis of two novel low-firing AgCa2B2V3O12 (B = Mg, Zn) ceramics with garnet structure
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-06-15
    Junqi Chen, Ying Tang, Huaicheng Xiang, Liang Fang, Harshit Porwal, Chunchun Li

    Two Ag-containing microwave dielectric ceramics AgCa2B2V3O12 (B = Mg, Zn) with garnet structure were prepared through solid-state reaction method. Dense ceramics were obtained at low sintering temperatures, 665 °C for AgCa2Zn2V3O12 and 730 °C for AgCa2Mg2V3O12. Their microwave dielectric properties were characterized for the first time and analyzed by means of packing fraction, bond valence, octahedral distortion, Raman spectra and infrared reflectivity spectra. Both compounds displayed high chemical compatibility with Ag electrodes. Additionally, thermally stable ceramics with near-zero temperature coefficients of resonance frequency (τf) were achieved by forming ceramic composites with CaTiO3.

    更新日期:2018-06-15
  • 更新日期:2018-06-15
  • Fabrication and characterization of carbon fiber reinforced SiC ceramic matrix composites based on 3D printing technology
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-06-15
    Wei Zhu, Hua Fu, Zhongfeng Xu, Rongzhen Liu, Ping Jiang, Xinyu Shao, Yusheng Shi, Chunze Yan

    A novel method has been developed to fabricate carbon fiber reinforced SiC (Cf/SiC) composites by combining 3D printing and liquid silicon infiltration. Green parts are firstly fabricated through 3D printing from a starting phenolic resin coated carbon fiber composite powder; then the green parts are subjected to vacuum resin infiltration and pyrolysis successively to generate Cf/C preforms; finally, the Cf/C preforms are then infiltrated with liquid silicon to obtain Cf/SiC composites. The 3D printing processing parameters show significant effects on the physical properties of green parts and also resultant Cf/C preforms, consequently greatly affecting the microstructures and mechanical performances of the final Cf/SiC composites. The overall linear shrinkage of the Cf/SiC composites is less than 3%, and the maximum density, flexural strength and fracture toughness are 2.83 ± 0.03 g/cm3, 249 ± 17.0 MPa and 3.48 ± 0.24 MPa m1/2, respectively. It demonstrates the capability of making near net-shape Cf/SiC composite parts with complex structures.

    更新日期:2018-06-15
  • Tunable electrocaloric and energy storage behavior in the Ce, Mn hybrid doped BaTiO3 ceramics
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-06-14
    Shujuan Liu, Qidong Xie, Lixue Zhang, Yingying Zhao, Xuan Wang, Pu Mao, Jiping Wang, Xiaojie Lou

    The electrocaloric effect and energy storage property are tuned in the Ba1-xCexTi0.99Mn0.01O3 ceramics prepared by the solid state reaction method. The ceramics with lower Ce content (x = 0.005, 0.015) show a better ΔT and ΔT/ΔE response. The ceramics with higher Ce content (x = 0.030, 0.040, 0.045) represent the broader ΔT peaks (50 K–60 K), and the higher energy storage density and efficiency. The largest electrocaloric response (ΔTmax = 1.22 K, ΔT/ΔE = 0.41 K mm/kV) is found in the Ba0.995Ce0.005Ti0.99Mn0.01O3 ceramics, which is comparable or even higher than that of the most isovalent substituting BaTiO3-based ceramics reported before. The maximum energy storage density 0.11 J/cm3 (E = 30 kV/cm) is obtained for the Ba0.970Ce0.030Ti0.99Mn0.01O3 ceramics, with high efficiency of 65–88% over a wide temperature range of 72 K. This work may open more opportunities to design high electrocalaric and energy storage performance lead-free systems from the viewpoint of the heterovalent and size mismatch substitution.

    更新日期:2018-06-14
  • Low-temperature sintering and microwave dielectric properties of B2O3-added ZnO-deficient Zn2GeO4 ceramics for advanced substrate application
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-06-09
    Xing-Hua Ma, Sang-Hyo Kweon, Mir Im, Sahn Nahm

    ZnO-deficient Zn2-xGeO4-x ceramics with 0.05 ≤ x ≤ 0.15 were synthesized because a ZnO secondary phase is formed in the stoichiometric Zn2GeO4 ceramics synthesized using micrometer-sized ZnO and GeO2 powders. The Zn1.9GeO3.9 ceramic sintered at 1000 °C showed a homogeneous Zn2GeO4 phase with good microwave dielectric properties: εr of 6.8, Q × f of 49,000 GHz, and τf of -16.7 ppm/°C. However, its sintering temperature was still too high for it to be used as an advanced substrate for low-temperature co-fired ceramic devices. Therefore, various amounts of B2O3 were added to the Zn1.9GeO3.9 ceramics to reduce their sintering temperature. Owing to the formation of a B2O3-GeO2 liquid phase, these ceramics were well sintered at low temperatures between 925 °C and 950 °C. In particular, 15 mol% B2O3-added Zn1.9GeO3.9 ceramic sintered at 950 °C showed promising microwave dielectric properties for advanced substrates without the reaction with an Ag electrode: εr = 6.9, Q × f = 79,000 GHz, and τf = -15 ppm/°C.

    更新日期:2018-06-10
  • Structural Peculiarities of 0.67Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 Thin Films Grown Directly on SrTiO3 Substrates
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-06-06
    Urška Gabor, Matjaž Spreitzer, Hana Uršič, Elena Tchernychova, Zoran Samardžija, Wen J. Wu, Danilo Suvorov

    Growth of Pb(Mg1/3Nb2/3)O3–33PbTiO3 thin films by pulsed-laser deposition directly on non-conductive SrTiO3 substrates for d33-mode energy harvesters (EHs) was studied, as they offer a higher figure-of-merit than d31-mode EHs. It was found that a high defect density, present in the film grown at 0.13 mbar, is manifested in the form of splitting of the (00l) peaks in X-ray diffraction, which was avoided by raising the process pressure to 0.27 mbar. Nevertheless, both films grow in a combined 2D and 3D manner, and form out-of-phase boundaries (OPBs) with a PbO rock-salt structure between the as-grown islands. It was found that the overall composition of the sample with optimized structural and functional properties was Pb1.07Mg0.19Nb0.44Ti0.32O3, which is close to stoichiometric. The surplus of Pb is compensated by the formation of OPBs and Mg deficit maintains macroscopic electroneutrality. In-plane and out-of-plane relative permittivities of 1900 and 980, respectively, imply macroscopic out-of-plane polarization.

    更新日期:2018-06-07
  • Re-examination of the β→γ transformation of Ca2SiO4
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-06-06
    Sofien Saidani, Agnès Smith, Youssef El Hafiane, Lotfi Ben Tahar

    Dicalcium silicate finds applications in different fields (cement, bio-ceramics, refractories). In the case of Portland cement, its interest is its lower sintering temperature compared to tricalcium silicate and therefore an interesting compound for low CO2 cements. Dicalcium silicate goes through different polymorphic forms, namely α, α'H, α'L, β and γ, as the temperature decreases. In theory, only the γ-phase is stable at room temperature. In a polycrystalline material, the different polymorphs can co-exist depending on several factors (sintering conditions, presence of impurities, grain size) and the interpretations given in the literature are sometimes contradictory. For cement applications, only the α, α' or β polymorphs react with water to give hydrates while γ does not. Therefore, this paper focuses specifically on the effect of grain size on the β to γ transformation. We also propose that the transformation is semi-reconstructive and not martensitic as suggested by some authors.

    更新日期:2018-06-07
  • Tunable Structural Transition and Multiferroic Properties of the Composite Thin Films through the Structural Transition of Magnetic Layer
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-06-06
    Guoqiang Tan, Zhengjun Chai, Yujuan Zheng, Zhongwei Yue, Wei Yang, Meiyou Guo, Huijun Ren, Ao Xia, Long Lv, Yun Liu

    The Bi0.9Er0.1Fe0.96Mn0.02Co0.02O3/Co1-xMnxFe2O4 (BEFMCO/CMxFO) thin films have been deposited by sol-gel method. Structural distortion is observed in the BEFMCO with the appearance of trigonal-R-3 m: H in the CMxFO. The enhanced multiferroic properties, well electrically writable and ferroelectric switching properties are obtained in BEFMCO/CMxFO thin films. The investigation indicates that the structural transformation of the CMxFO influences the structure and multiferroic properties of BEFMCO and the interfacial effects between BEFMCO and CMxFO layers. This transformation and Mn-doping cause the change of carriers, which solves the problem that the magnetic layer exacerbates the ferroelectric properties. It promotes to form the weak local electric field, which causes the weak interface effect, and brings out the weak resistive switching in the BEFMCO/CMxFO thin films. Therefore, it is believed that the BEFMCO/CMxFO films can offer a potentially tunable structural transformation of composite films for practical applications.

    更新日期:2018-06-07
  • Phase equilibria in the ZrO2-YO1.5-TaO2.5 system at 1250 °C
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-06-05
    Chandra A. Macauley, Abel N. Fernandez, Jason S. Van Sluytma, Carlos G. Levi

    The phase relationships in the ZrO2-YO1.5-TaO2.5 (ZYTO) system at 1250 °C—a temperature of interest for thermal barrier coatings applications—were investigated using precursor-derived powders. The system is bisected by a quasi-binary joining the tetragonal (t) ZrO2 and monoclinic (M’) YTaO4 solid solutions. The mutual solubility limits for these phases differ significantly depending on whether the third phase in equilibrium with t and M’ is fluorite or the orthorhombic (O) Zr6Ta2O17. More importantly, the tetragonal phase in equilibrium with fluorite is non-transformable to the monoclinic form upon cooling, whereas that in equilibrium with O, which has lower stabilizer content, is transformable. The behavior contrasts with that previously observed for the equilibrium at 1500 °C, wherein the t phase on both sides of the quasi-binary is non-transformable. The fluorite solid solution extends from the ZrO2-YO1.5 binary to the YO1.5-TaO2.5 binary at 1250 °C, as previously shown for 1500 °C.

    更新日期:2018-06-06
  • Investigation of chemical bonds in the ordered Ba3Zn(Nb2-xMox)O9+x/2 ceramics and its effects on the microwave performance
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-06-05
    Bowen Zhang, Lingxia Li

    1:2 ordered Ba3Zn(Nb2-xMox)O9+x/2(BZNM) ceramics with space group <img height="31" border="0" style="vertical-align:bottom" width="49" alt="View the MathML source" title="View the MathML source" src="https://origin-ars.els-cdn.com/content/image/1-s2.0-S0955221918303728-si1.gif">P3¯ml were prepared by solid-state method. The nature of chemical bonds in Ba3Zn(Nb2-xMox)O9+x/2(BZNM) ceramics was investigated for the first time. Firstly, the bond energy was closely related to the lattice vibration. High bond energy would lead to weak non-harmonic interactions, which were the main factors of improving Qf. Secondly, polarization of the chemical bond was the principal contributor to the relative permittivity of microwave ceramics. Compared with the traditional method, the calculated result based on the P-V theory reduced the error from 81% to 4.4%. Through the discussion, it was confirmed that the analysis method based on chemical bond was highly feasible and scientific in the microwave ceramics. At last, the system of Ba3Zn(Nb1.992Mo0.008)O9.004 sintered at 1435 °C for 6 h and annealed at 1300 °C for 10 h had excellent microwave dielectric properties: εr = 38.9, Qf = 102,931 GHz, τf = 19.2 ppm/°C, which, to our best knowledge, provided a alternative for the application of millimeter-wave communications.

    更新日期:2018-06-06
  • Influence of barium borosilicate glass on microstructure and dielectric properties of (Ba,Ca)(Zr,Ti)O3 ceramics
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-06-05
    Abdulkarim Z. Khalf, David A. Hall

    Barium borosilicate (BBS) glass was added as a sintering aid to (Ba0.7Ca0.3)TiO3-Ba(Ti0.8Zr0.2)O3 (BCZT) ceramics at levels from 2 to 15 wt%, yielding enhanced densification. The addition of BBS also induced changes in phase composition, from predominantly tetragonal to orthorhombic at room temperature. It is shown that the changes in phase content are caused by a shift of the orthorhombic to tetragonal phase transformation from below room temperature to ≈ 50 °C. An additional high temperature transition around 120 °C was also identified. These observations are interpreted in terms of the development of chemical heterogeneity associated with the redistribution of dopant elements (particularly Zr and Ca) through the liquid phase during sintering. The relative permittivity and electric field-induced polarisation values were generally degraded by the presence of the glass phase, but a reduction in ferroelectric hysteresis and improved densification behaviour have potential benefits in dielectric energy storage applications.

    更新日期:2018-06-06
  • Microstructural, mechanical and tribological properties of suspension plasma sprayed YSZ/h-BN composite coating
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-06-05
    Yongli Zhao, Yan Wang, Zexin Yu, Marie-Pierre Planche, François Peyraut, Hanlin Liao, Audrey Lasalle, Alain Allimant, Ghislain Montavon

    Brittleness, relative high friction coefficient and wear rate limit the applications of ceramic coatings as wear-resistant layers. However, because embedding additives with ceramic matrix has demonstrated to be an effective way to improve coating performances, different contents and size of h-BN were added into an YSZ suspension. Afterwards, the YSZ/h-BN composite coatings were manufactured by suspension plasma spray and their tribological analysis indicated that: i) the reduction of the friction coefficient and wear rate can be achieved by incorporating h-BN into YSZ coating. ii) finer h-BN particle is more helpful to enhance the tribological properties of the coating. iii) the optimum content is dependent on h-BN particle sizes. iv) when the contents and the size of the h-BN inclusion increase, the probability distribution of the micro-hardness can become bi-modal. Three worn surface conditions were summarized and their wear mechanisms were discussed as well.

    更新日期:2018-06-06
  • Digital Light Processing of Wollastonite-Diopside Glass-ceramic Complex Structures
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-06-04
    Johanna Schmidt, Hamada Elsayed, Enrico Bernardo, Paolo Colombo

    In this work, the possibility of shaping a glass-filled photosensitive polymer resin with Digital Light Processing (DLP) into a complex 3D structure and transforming it subsequently into a bioactive glass-ceramic scaffold was investigated. The influence of the printing conditions and the heat-treatment was studied using a 41 vol% glass-filled acrylated polymer resin. Scaffolds with designed architecture were turned into a wollastonite-diopside glass-ceramic at 1100 °C. They completely maintained their shape, exhibited no viscous flow and showed a homogenous linear shrinkage of around 25 %. At 83 vol% porosity structures with Kelvin cell design exhibited a compressive strength exceeding 3 MPa, demonstrating that the material is suitable for the fabrication of bioceramic scaffolds for bone tissue engineering applications.

    更新日期:2018-06-05
  • Phenomenological understanding of flash sintering in MnCo2O4
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-06-04
    Anshu Gaur, Mahamad Ahamad Mohiddon, Vincenzo M. Sglavo

    The dual role of electric field in the flash sintering process of conducting MnCo2O4 is demonstrated. The flash and conventionally sintered MnCo2O4 samples produced at different temperatures are characterized using energy dispersive X-ray and micro-Raman spectroscopy to elucidate the micro-level spatial distribution of evolved phases. Raman signal mapping over the two ways sintered samples exposes differently grown areas of cobalt oxide based secondary phase. Electrical conductivity of conventionally sintered sample is recorded as a function of temperature and E-field and is utilized to discover the charge carrier activation mechanism during the flash effect. The conductivity before the flash-onset is shown to be comparable to that occurs by Poole-Frenkel effect and Phonon-assisted tunneling i.e. by the mechanism that occurs before the dielectric breakdown of semiconductors and insulators. The observed results, finally, confirm that catalyst like drift action of E-field on cobalt oxide formation is responsible for enhancement in the flash-sintering.

    更新日期:2018-06-05
  • Fabrication and properties of dense α-cordierite glass-ceramic coating on porous BN/Si2N2O ceramic
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-06-04
    Yangshan Sun, Delong Cai, Zhihua Yang, Hailiang Li, Bo Niu, Wenjiu Duan, Dechang Jia, Yu Zhou

    α-Cordierite glass-ceramic coating was fabricated on the porous BN/Si2N2O ceramic by glass-ceramic method. The effect of the heating temperature on the phase composition, microstructure, mechanical properties, water resistance and dielectric properties of the coatings was investigated. A large amount of α-cordierite precipitated from the glass phase when the heating temperature was 1050 °C and the content of α-cordierite in the coating increased with increasing the heating temperature. The resulting α-cordierite glass-ceramic coatings had a good wettability and adhesion with the porous ceramic substrate. The coating/substrate interface was continuous without defects. When the heating temperature was 1050 ~ 1200 °C, the resulting coatings possessed positive mechanical properties and good water resistance due to the high densification. And the dielectric constant and loss tangent of the coated samples prepared at 1050 ~ 1200 °C were 4.1 ~ 4.3 and 0.005 ~ 0.01 respectively in the frequency of 21 ~ 36 GHz.

    更新日期:2018-06-05
  • Improving the sealing performance of glass-ceramics for SOFCs applications by a unique ‘composite’ approach: a study on Na2O-SiO2 glass-ceramic system
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-06-03
    Dewei Lin, Shengwei Tan, Fen Lin, Zhengwei Dong, Jiajia Yan, Dian Tang, Hsiwen Yang, Kongfa Chen, Teng Zhang

    The rigid nature of sealing glass-ceramics restricts the thermal cycling stability of Solid Oxide Fuel Cells (SOFCs), which thus evokes an interest in designing a sealing glass without crystallization under the operational condition of SOFCs. In this paper, we report that the sealing performance of 30Na2O-70SiO2 (in mole%) glass-ceramic can be significantly improved by Fe2O3 dopant through a composite approach. In particular, the crystallization in glass can be suppressed by appropriate Fe2O3 dopant amount (8 mole%), which results in the improved sealing property of glass. In addition, the glass modified with Fe2O3 shows good chemical compatibility with 8 mole% yttria-stabilized zirconia (8YSZ) electrolyte and metallic interconnect (430 stainless steel) in dual atmospheres. The possible mechanism for the improved sealing performance of 30Na2O-70SiO2 glass-ceramic by this unique composite approach is also discussed.

    更新日期:2018-06-04
  • Glass-ceramic oxidation protection of higher manganese silicide thermoelectrics
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-01-09
    M. Salvo, F. Smeacetto, F. D’Isanto, G. Viola, P. Demitri, F. Gucci, M.J. Reece

    A higher manganese silicide (HMS) thermoelectric, with composition MnSi1.74, densified by spark plasma sintering, was successfully coated with a glass-ceramic, in order to be used at temperatures higher than 500 °C. Compositional changes in both the HMS substrate and the glass-ceramic coating are reviewed and discussed with respect to the electrical properties of the uncoated and coated HMS before and after thermal cycles from RT to 600 °C in air. The formation of a Si-deficient layer (MnSi) on the uncoated HMS surface is due to the reaction between the HMS and oxygen at 600 °C, thus contributing to a lower power factor in comparison with the as-sintered HMS. Coated HMS samples (after thermal cycles RT-600 °C) show a lower electrical resistivity and a significantly higher power factor in comparison with the uncoated ones. The glass-ceramic coating is self-reparable at 600 °C, as demonstrated by the complete sealing of an induced scratch on its surface.

    更新日期:2018-06-03
  • Ultra-high temperature porous graded ceramics for solar energy applications
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-01-19
    R. Licheri, C. Musa, A.M. Locci, S. Montinaro, R. Orrù, G. Cao, L. Silvestroni, D. Sciti, N. Azzali, L. Mercatelli, E. Sani

    Porous graded materials (PGMs) consisting of ZrB2 are obtained by Spark Plasma Sintering (SPS) taking advantage of an asymmetric die configuration with changing cross section. Due to the temperature gradient established along the longitudinal direction, porosity changes up to about 26 vol.% were generated across the volume. The surface roughness of the resulting products increased as the holding temperature was reduced. Superior solar absorbance (α) and lower spectral selectivity (α/ε) properties were correspondingly obtained. PGMs displayed higher α and lower α/ε values with respect to highly dense samples produced using a constant cross section die. More important, these products exhibit similar or improved optical properties with respect to the reference SiC material. These findings are important in view of the development of a novel class of ceramics for solar energy applications, able to operate under higher temperature conditions while simultaneously satisfying optical, microstructural and mechanical needs.

    更新日期:2018-06-03
  • Role of the sintering atmosphere in the densification and phase composition of asymmetric BCZY-GDC composite membrane
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-01-31
    Daniel Montaleone, Elisa Mercadelli, Angela Gondolini, Matteo Ardit, Paola Pinasco, Alessandra Sanson

    Ceramic hydrogen separation membranes are promising devices to be integrated in industrial hydrogen-based technologies using fossil fuel as feedstock. Among all, BaCe0.65Zr0.20Y0.15O3-δ–Ce0.8Gd0.20O2-δ composite membrane is the most promising ceramic-ceramic system for such application. However, one of the main issues in Ba-containing perovskites is related to Ba loss at the high sintering temperature needed for the complete densification of the material. This work reports the influence of the sintering atmosphere and temperature on the membrane’s densification and phase purity. BaCeO3 (BC), BaCe0.65Zr0.20Y0.15O3-δ (BCZY) and a BaCe0.65Zr0.20Y0.15O3-δ–Ce0.8Gd0.20O2-δ (BCZY-GDC) mixture were used as Ba-sources to modify the sintering atmosphere. The more reactive BC and BCZY systems promoted a solid-state reaction between BCZY and GDC leading to an undesired single mix-phase enriched in barium on the membrane’s surface. The desired asymmetric architecture with the correct stoichiometry was obtained using BCZY-GDC as Ba-source and sintering the membrane at 1550 °C.

    更新日期:2018-06-03
  • SiC/MoSi2 based coatings for Cf/C composites by two step pack cementation
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-01-31
    Federica Bezzi, Federica Burgio, Paride Fabbri, Selene Grilli, Giuseppe Magnani, Elena Salernitano, Matteo Scafè

    In order to improve the oxidation resistance of Cf/Cs produced by chemical vapour infiltration, a multilayer coating based on silicon carbide and molybdenum disilicide was produced by two-step pack cementation technique. The inner SiC layer with a thickness up to 25 μm was obtained without promoted reaction additives by varying the composition, and thermal treatment conditions. The SiC/SiC-MoSi2 coating was produced with a thickness up to 80 μm by two step pack cementation, considering the effect of the inner layer characteristic. The enhancement of the oxidation resistance, observed in SiC/SiC-MoSi2 coated Cf/Cs by means of thermal analysis in flowing air up to 1500 °C, was due to the formation of SiO2 promoted by the passive oxidation of silicon carbide and molybdenum disilicide.

    更新日期:2018-06-03
  • Effect of synthetic method on CeZr support and catalytic activity of related Rh catalyst in the oxidative reforming reaction
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-02-02
    F. Basile, R. Mafessanti, A. Fasolini, G. Fornasari, E. Lombardi, A. Vaccari

    The production of hydrogen by oxy-reforming is a process coupling steam reforming and catalytic partial oxidation allowing a balance of endothermic and exothermic reaction and smoothing the temperature profile. Nevertheless, deactivation of the catalyst by carbon formation is still an issue favored by low O/C and Steam/C ratio used in the process. The development of a catalyst for the oxy-reforming process started with the study of the synthesis by water-in-oil microemulsion of Ce0.5Zr0.5O2, to obtain high oxygen storage capacity, a property that helps the removal of eventually formed carbon. The studied synthesis was able to provide the desired Ce0.5Zr0.5O2 with a good stability with temperature, while classical coprecipitation gives Ce0.6Zr0.4O2 phase. The catalysts were impregnated with 2.7% of Rh and tested in oxy-reforming using low residence time and reaction conditions able to discriminate the differences in catalyst activity. The catalyst prepared using microemulsion CeZr showed higher conversion and stability when compared with the one synthesized by coprecipitation. In particular, differently from the coprecipitated sample, the carbon formation was not present in the one prepared by microemulsion. The activity and stability were linked to the characterization features of the mixed oxides and the impregnated catalysts.

    更新日期:2018-06-03
  • Oxygen transport, thermal and electrochemical properties of NdBa0.5Sr0.5Co2O5+δ cathode for SOFCs
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-02-02
    Adi Subardi, Kun-Yu Liao, Yen-Pei Fu

    In this study, the crystal structure, thermal, oxygen transport, electrical conductivity and electrochemical properties of the perovskite NdBa0.5Sr0.5Co2O5+δ (NBSC55) are investigated. In the temperature range of 250 °C–350 °C, the weight loss upon heating was due to a partial loss of lattice oxygen and along with a reduction of Co4+ to Co3+. The tend of weight-loss slows down as temperature increased above 350 °C indicating a reduction of Co3+ to Co2+ during this stage. The oxygen migration is dominated by surface exchange process at high temperature range (650-800 °C); however, the bulk diffusion process prevails at low temperature range (500–600 °C). For long-term testing, the polarization resistance of NBSC55 increases gradually form 3.13 Ω cm2 for 2 h to 3.34 Ω cm2 for 96 h at 600 °C and an increasing-rate for polarization resistance is around 0.22% h−1. The power density of the single cell with NBSC55 cathode reached 341 mW cm−2 at 800 °C.

    更新日期:2018-06-03
  • Copper-based electrodes for IT-SOFC
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-03-02
    Francesca Zurlo, Alessandro Iannaci, Vincenzo M. Sglavo, Elisabetta Di Bartolomeo

    Copper and gadolinium doped ceria (GDC) anode supported fuel cells were co-sintered at relatively low temperature (900 °C) and successfully tested in the intermediate temperature (IT) range. The GDC electrolyte densification was promoted by a compressive strain induced by increasing the anodic thickness and was evaluated by SEM investigation. Instead of more commonly used La0.8Sr0.2Fe0.6Co0.4O3-δ, strontium and copper-doped lanthanum ferrite La0.8Sr0.2Fe0.8Cu0.2O3-δ (LSFCu) mixed with 30 wt% GDC (LSFCu-GDC) was employed as cathodic material. Preliminary tests on Cu-GDC/GDC/LSFCu-GDC single cells showed promising results at temperature as low as 650 °C using hydrogen as fuel.

    更新日期:2018-06-03
  • Influence of oxygen partial pressure on the oxygen diffusion and surface exchange coefficients in mixed conductors
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-03-26
    P.-M. Geffroy, L. Guironnet, H.J.M. Bouwmeester, T. Chartier, J.-C. Grenier, J.-M. Bassat

    The performances of mixed ionic and electronic conductors is used in many applications, such as oxygen transport membranes or electrodes in solid oxide fuel cells. The performances of these systems depend mainly on two fundamental parameters including oxygen diffusion (DO) and the oxygen exchange coefficient (k). This work focuses on the impact of the oxygen partial pressure on oxygen diffusion and surface exchange coefficients of mixed conducting materials, as reported studies are scarce in the literature. In this way, two different mixed conducting materials are studied, namely, La0.6Sr0.4Fe0.6Ga0.4O3-δ, a perovskite-type material, and the nickelate La2NiO4+δ. The DO and k coefficients are determined by a specific oxygen permeation measurement and by the isotopic exchange depth profile method.

    更新日期:2018-06-03
  • Fabrication of dye-sensitized solar modules based on a prototyping pilot line and their integration into energy storage microsystems
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2017-11-10
    Giacomo Gorni, Isabella Zama, Christian Martelli, Luigi Armiento

    We successfully developed a prototyping pilot line for dye-sensitized solar modules up to 23 × 23 cm2. Dedicated ceramic materials were studied for large area application: we formulated a lead-free glass frit sealant with low softening point based on the ternary system Bi2O3-B2O3-ZnO and a TiO2 anatase screen-printable paste for semi-transparent photoanodes. Alongside traditional screen-printing, specific machines among which a thermal press, a dye injection equipment and an automatic electrolyte filler were designed and realized. A silver-free layout was adopted and the solar modules reached an efficiency close to 2%. Photovoltaic glass panels composed by interconnected DSSC modules were interfaced with custom integrated circuits to realize energy storage microsystems for two self-powered prototypes: a USB solar table for recharging of portable devices and a novel LED glass parapet for active night lighting are here presented.

    更新日期:2018-06-01
  • Zirconia nano-colloids transfer from continuous hydrothermal synthesis to inkjet printing
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2017-11-14
    M. Rosa, P.N. Gooden, S. Butterworth, P. Zielke, R. Kiebach, Y. Xu, C. Gadea, V. Esposito

    Water dispersions of nanometric yttria stabilized zirconia (YSZ) particles synthesized by Continuous Hydrothermal Synthesis are transferred into nano-inks for thin film deposition. YSZ nanoparticles are synthesized in supercritical conditions resulting in highly dispersed crystals of 10 nm in size. The rheology of the colloid is tailored to achieve inkjet printability (Z) by using additives for regulating viscosity and surface tension. Inks with a wide range of properties are produced. A remarkable effect of nanoparticles on the ink printability is registered even at solid load < 1%vol. In particular, nanoparticles hinder the droplet formation at low values of the printability while suitable jetting is observed at high Z values, i.e. Z ≈ 20. For the optimized inks, we achieve high quality printing with lateral and thickness resolutions of 70 μm and ca. 250 nm respectively, as well as self-levelling effect with a reduction of the substrate roughness. Densification is achieved at sintering temperatures below 1200 °C.

    更新日期:2018-06-01
  • Three-dimensional printed yttria-stabilized zirconia self-supported electrolytes for solid oxide fuel cell applications
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2017-11-15
    S. Masciandaro, M. Torrell, P. Leone, A. Tarancón

    Additive manufacturing represents a revolution due to its unique capabilities for freeform fabrication of near net shapes with strong reduction of waste material and capital cost. These unfair advantages are especially relevant for expensive and energy-demanding manufacturing processes of advanced ceramics such as Yttria-stabilized Zirconia, the state-of-the-art electrolyte in Solid Oxide Fuel Cell applications. In this study, self-supported electrolytes of yttria-stabilized zirconia have been printed by using a stereolithography three-dimensional printer. Printed electrolytes and complete cells fabricated with cathode and anode layers of lanthanum strontium manganite- and nickel oxide-yttria-stabilized zirconia composites, respectively, were electrochemical characterized showing full functionality. In addition, more complex configurations of the electrolyte have been printed yielding an increase of the performance entirely based on geometrical aspects. Complementary, a numerical model has been developed and validated as predictive tool for designing more advanced configurations that will enable highly performing and fully customized devices in the next future.

    更新日期:2018-06-01
  • Low temperature deposition of dense MnCo2O4 protective coatings for steel interconnects of Solid Oxide Cells
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-31
    B. Kamecki, J. Karczewski, T. Miruszewski, G. Jasiński, D. Szymczewska, P. Jasiński, S. Molin

    In this work manganese cobalt spinel (MnCo2O4) coatings were deposited on steel substrates by spray pyrolysis at 390 °C. This is at much lower temperatures than previously reported (typically in excess of 900 °C). It was possible to produce coatings with well controlled thickness (2-5-10 µm). The as-deposited coatings were evaluated for their microstructural changes and electrical conductivity up to 800 °C. Results confirm the formation of a single phase spinel with high density and electrical conductivity. Based on the obtained results, it might be concluded that spray pyrolysis is a very promising method to develop protective coatings for steel substrates at low temperatures overcoming limitations of many other methods.

    更新日期:2018-05-31
  • Enhanced microwave absorbance of oxidized SiCf/AlPO4 composites via the formation of a carbon layer on the SiC fibre surface
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-29
    Feng Wan, Jianhui Yan, Hongmei Xu

    A single-layer radar-absorbing structure active in the X-band (8.2 GHz to 12.4 GHz) was demonstrated by blending SiC fibres with an AlPO4 matrix material. The as-prepared SiCf/AlPO4 composites were oxidized at 1273 K for several hours to investigate the effects of oxidation on the dielectric and wave-absorbing properties. Scanning and transmission electron microscopy were used to characterize the morphology and microstructure of the composites. The AlPO4-SiO2 solid solution during oxidation promoted the formation of a complete carbon layer on the SiC fibre surface. The real and imaginary parts of the SiCf/AlPO4 composites increased from 4.2–4.4 to 5.9–7.1 and from 0.08–0.2 to 3.9–5.2, respectively, with increasing oxidation time from 0 to 10 h, respectively. When the thickness of the composites increased from 2.9 mm to 3.3 mm, the wave-absorbing property noticeably improved due to the formation of a carbon layer on the SiC fibre surface after oxidation.

    更新日期:2018-05-30
  • The microwave dielectric properties and crystal structure of low temperature sintering LiNiPO4 ceramics
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-29
    Ping Zhang, Shanxiao Wu, Mi Xiao

    The LiNiPO4 ceramic for the LTCC technology was prepared via the traditional solid-state reaction route and its dielectric properties were investigated for the first time. The best dielectric properties of LiNiPO4 ceramics with a εr of 7.18, Q×f value of 27,754 GHz and τf of -67.7 ppm/°C were obtained in samples sintered at 825 °C for 2 h. Rietveld refinement was firstly employed to study the crystal structure and dielectric properties of LiNiPO4 ceramics. Unfortunately, the relatively large negative τf was unfavorable to practical applications. Therefore, we introduced TiO2, which possessed a considerable positive τf, to obtain a desired τf value. The prepared LiNiPO4 ceramics with 15 wt% TiO2 sintered at 900 °C for 2 h exhibited excellent dielectric properties of εr~11.49, Q×f~10,792 GHz, τf~-2.8 ppm/°C. The Ag co-fired experiments confirmed the excellent chemical compatibility with LiNiPO4-TiO2 ceramics which might be potential dielectric LTCCs for high frequency applications.

    更新日期:2018-05-30
  • Dielectric and microwave absorption properties of divalent-doped Na3Zr2Si2PO12 ceramics
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-29
    Dan Chen, Luo Fa, Dongmei Zhu

    The work attempted to develop a new kind of high temperature microwave absorption material. Dense Na3Zr1.9M0.1Si2PO11.9 (M = Ca2+, Ni2+, Mg2+, Co2+, Zn2+) and Na3Zr2-xZnxSi2PO12-x (x = 0.1, 0.2, 0.3, 0.4) ceramics were prepared by solid-state reactions for phase, microstructure characterization and dielectric properties, microwave absorption properties analysis. Results show that the complex permittivity increases in all the divalent-doped Na3Zr2Si2PO12 ceramics. Na3Zr1.8Zn0.2Si2PO11.8 ceramic exhibits the highest complex permittivity and optimum microwave absorption performance. The lowest reflection loss is -28.1 dB at 9.88 GHz and the bandwidth is 4.14 GHz (8.26-12.4 GHz) with a thickness of 2.1 mm. It indicates that Na3Zr2Si2PO12 ceramic can be chosen as a potential candidate of microwave absorption material and the performance can be enhanced by divalent doping strategy.

    更新日期:2018-05-30
  • Dielectric breakdown toughness from filament induced dielectric breakdown in borosilicate glass
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-28
    Pia-Kristina Fischer, Gerold A. Schneider

    The dielectric breakdown strength of borosilicate glass was measured as a function of the length of a conducting filament in order to determine the critical energy release for the growth of a breakdown channel. The concept is similar to the experimental determination of the toughness in fracture mechanics and based on a Griffith type model for the electrical energy release rate in dielectric materials with space charge limited conductivity. By Focused-Ion-Beam-milling and Pt-deposition, up to 100 µm long conductive channels were fabricated in 163 µm thick borosilicate glass substrates. The dielectric breakdown strength of substrates with filaments longer than 30 µm could be very well described by a View the MathML source 1 f i l a m e n t   l e n g t h -dependence predicted by the model [1]. With these results for the first time a critical energy release rate for dielectric breakdown was determined being 6.30 ± 0.95 mJ/m.

    更新日期:2018-05-29
  • Application of asymmetric Si3N4 hollow fiber membrane for cross-flow microfiltration of oily waste water
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-28
    Hamidreza Abadikhah, Cai-Neng Zou, You-Zhi Hao, Jun-Wei Wang, Li Lin, Sayed Ali Khan, Xin Xu, Chu-Sheng Chen, Simeon Agathopoulos
    更新日期:2018-05-29
  • Ablation behavior of a novel HfC-SiC gradient coating fabricated by a facile one-step chemical vapor co-deposition
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-26
    Mingde Tong, Qiangang Fu, Lei Zhou, Tao Feng, Hejun Li, Tao Li, Kun Li

    To protect carbon/carbon composites against ablation at ultra-high temperature, a novel HfC-SiC gradient coating was fabricated by a facile one-step chemical vapor co-deposition. The phase composition, microstructure, bonding strength and ablation behaviour were investigated, and the mechanical properties of ablated coatings were characterized as well. The bonding strength of HfC-SiC gradient coating is 19.6 ± 0.5 N (176% higher than that of HfC coating). HfC-SiC gradient coating shows excellent ablation resistance under oxyacetylene flame. The mass and linear ablation rate of HfC-SiC coating were only 0.153 ± 0.02 mg·s-1 and −0.998 ± 0.08 μm·s−1, respectively. After ablation for 60 s, the hardness and elastic modulus of ablated HfC-SiC gradient coating are higher than those of ablated HfC coating. The excellent ablation resistance of HfC-SiC gradient coating results from its high bonding strength and the adhesion effect of Hf-Si-O sticky glass phase.

    更新日期:2018-05-27
  • Piezoelectric Properties of (1-x)BZT-xBCT System for Energy Harvesting Applications
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-24
    Dong-Jin Shin, Jinhwan Kim, Jung-Hyuk Koh

    In this study, we investigated (1-x)Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3 lead-free piezoelectric ceramics for energy harvester applications. The (1-x)BZT-xBCT ceramic is a promising lead-free piezoelectric material in the field of piezoelectric energy harvesting. Piezoelectric and energy properties of (1-x)BZT-xBCT ceramics were analyzed to confirm the possibility of using them as energy-harvesting materials. Especially, the vicinity of the phase convergence region was investigated to improve their piezoelectric properties. In the phase convergence region, cubic, rhombohedral, orthorhombic, and tetragonal regions co-exist within the narrow region. Near the phase transition region between the orthorhombic and tetragonal phase, the highest piezoelectric property d33 = 464 pC/N and the highest energy density of 158.5 μJ/cm3 were observed. This output energy density of 158.5 μJ/cm3 is the recorded highest value among lead-free ceramics. We found that the optimal sintering temperature was 1475 °C and the optimal composition was BZT-0.5BCT.

    更新日期:2018-05-25
  • Enhancing toughness and strength of SiC ceramics with reduced graphene oxide by HP sintering ☆
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-24
    Yihua Huang, Dongliang Jiang, Xianfeng Zhang, Zhenkui Liao, Zhengren Huang

    In this paper, the silicon carbide-reduced graphene oxide (SiC/rGO) composites with different content of rGO are investigated. The hot pressing (HP) at 2100 °C for 60 min under a uniaxial pressure of 40 M Pa resulted in a near fully-dense SiC/rGO composite. In addition, the influence of graphene reinforcement on the sintering process, microstructure, and mechanical properties (fracture toughness, bending strength, and Vickers hardness) of SiC/rGO composites is discussed. The fracture toughness of SiC/rGO composites (7.9MPam1/2) was strongly enhanced by incorporating rGO into the SiC matrix, which was 97% higher than the solid-state sintering SiC ceramics (SSiC) by HP. Meanwhile, the bending strength of the composites reached 625 M Pa, which was 17.3% higher than the reference materials (SSiC). The microstructure of the composites revealed that SiC grains were isolated by rGO platelets, which lead to the toughening of the composite through rGO pull out/debonding and crack bridging mechanisms.

    更新日期:2018-05-25
  • Oxidation of ß-SiC at high temperature in Ar/O2, Ar/CO2, Ar/H2O gas mixtures: kinetic study of the silica growth in the passive regime
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-24
    Mathieu Q. Brisebourg, Francis Rebillat, Francis Teyssandier

    The kinetics of silica growth during passive oxidation of SiC was studied using an original interferometric method carried out in a reactor specifically designed for that purpose. The influence of various oxidant species, O2, H2O, CO2 as well as their mixtures was investigated in a high temperature domain ranging from 1550 °C to 1850 °C at atmospheric pressure. This method is an efficient way to measure the various oxidation regimes usually described by the Deal-Grove model. Both the linear and parabolic rate constants are found to be independent of gas phase composition above 1700 °C, and to increase with oxygen partial pressure below 1700 °C for PO2 > 20 kPa. In the parabolic growth regime, we observed a transition from a low temperature interstitial-dominant to a high temperature network-dominant oxygen transport in the silica scale. The present results suggest the existence of a similar transition in the linear growth regime.

    更新日期:2018-05-24
  • Structural integrity and characteristics at lattice and nanometre levels of ZrN polycrystalline irradiated by 4 MeV Au ions
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-24
    Weichao Bao, Stuart Robertson, Ji-Xuan Liu, Guo-Jun Zhang, Fangfang Xu, Houzheng Wu

    We report an as-hot-pressed zirconium nitride polycrystalline with its primary crystal structure maintained no change but lattice defects and features were introduced at nanometre-scale after being irradiated by 4 MeV Au2+ with a total fluence of 5 × 1016/cm2. The variation of grey-level seen in backscattered electron images and electron backscattered diffraction maps directly evidenced the structure integrity of the polycrystalline ZrN is well maintained with no crystal structure change of ZrN. The irradiation depth had no relevance to crystal orientation, and Au deposition peaked at a depth of ∼0.58 μm with a near-Gaussian distribution. Within a depth <0.58 μm, long dislocation lines were developed with a Burgers vector of [0<img height="14" border="0" style="vertical-align:bottom" width="7" alt="View the MathML source" title="View the MathML source" src="https://origin-ars.els-cdn.com/content/image/1-s2.0-S0955221918303091-si1.gif">1¯]b/2 and density 3.2 × 1014 1/m2; beyond this depth, dislocation loops were formed with much higher density. In the ionization zone, cubic ZrO2 crystallites precipitated in a size of ∼5 nm. The irradiation damage processes are discussed based on the observed features.

    更新日期:2018-05-24
  • Lead-free high performance Bi(Zn0.5Ti0.5)O3-modified BiFeO3-BaTiO3 piezoceramics
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-23
    Gyung-Hyun Ryu, Ali Hussain, Myang-Hwan Lee, Rizwan Ahmed Malik, Tae-Kwon Song, Won-Jeong Kim, Myong-Ho Kim

    In this article, structure, dielectric, ferroelectric and piezoelectric properties of Bi rich Bi1.05(Zn0.5Ti0.5)O3-modified BiFeO3-BaTiO3 (BF-BT-xBZT) ceramics were investigated experimentally. Crystal structure, phase purity and microstructure were examined through X-ray diffractometry and scanning electron microscopy, respectively. The crystallographic results show the formation of single-phase solid solutions for all compositions except x = 10 mol%). The BF-BT modification through BZT instigates variation in grain size, enhancement in Curie temperature (TC) and field induced polarization and strain response. Large field induced strain of ~0.24% at low driving field along with a small hysteresis of ~38% was observed for 2 mol% BZT modified BF-BT ceramics. These investigated results signpost the potentiality of BF-BT-xBZT ceramics in high temperature piezoelectric device applications.

    更新日期:2018-05-24
  • Can ferrroelasticity be evaluated by nanoindentation?
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-23
    Wakako Araki, Xin Wang, Alan Atkinson

    The present study investigated the possibility of evaluating ferroelastic mechanical characteristics by spherical indentation. Finite element simulation of spherical indentation with a relatively large sphere of a ferroelastic-plastic material was performed using characteristic bulk data of a typical ferroelastic oxide (La-Sr-Co-Fe-O). The simulation results showed that the ferroelastic mechanical behaviour cannot be observed in the indentation load vs depth curve, but is clearly observable in the indentation stress vs indentation strain curve, which can be obtained reliably in experiments by estimating the contact radius using load-partial unloading sequences. The method can be reliable when the indentation stress is under the upper ferroelastic critical stress. Therefore, in principle ferroelastic mechanical characteristics could be evaluated by spherical indentation by obtaining the indentation stress vs indentation strain curve using partial unloading to estimate the contact radius, although the requirements are very difficult to satisfy in actual experiments.

    更新日期:2018-05-24
  • Large strain with low hysteresis in Bi4Ti3O12 modified Bi1/2(Na0.82K0.18)1/2TiO3 lead-free piezoceramics
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-22
    Pengyuan Fan, Yangyang Zhang, Qi Zhang, Bing Xie, Yiwei Zhu, Mosin Ali Mawat, Weigang Ma, Kai Liu, Jianzhong Xiao, Haibo Zhang

    In order to obtain BNT-based ceramic system with excellent electric-field-induced strain performance for actuator applications, a novel solid solution (100-x)Bi1/2(Na0.82K0.12)1/2TiO3-xBi4Ti3O12 ((100-x)BNKT-xBiT, x = 0-12 wt%) was designed and fabricated by solid state synthesis. The microstructure and related electrical properties of this material were systematically investigated. It was found that BiT is dissolved into the lattice structure of the BNKT, leading to a greater increase in the volatilization of Na and K, thus produce more A-site vacancies compared with the undoped BNKT. The 9 wt%BiT doped sample not only has sufficient A-site vacancies to destroy the long-range ferroelectric order of the base composition but also favors the presence of extremely stable relaxor phase at room temperature. Further, the ferroelectric-to-relaxor phase transition temperature TF-R can be effectively tuned to about 0 °C, giving rise to a large signal piezoelectric coefficient d*33 of 485 pm/V with a small hysteresis η of 23%.

    更新日期:2018-05-23
  • Parametric Studies of DD3R particles seeding on the modified surface of α-alumina support and synthesis of DD3R zeolite membrane
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-21
    Aynaz Meshkat, Mohammad Javad Vaezi, Ali Akbar Babaluo

    The effects of suspension concentration, number of coating stages and dipping time on seeding quality of DD3R particles on the ceramic supports were investigated. The supports were immersed in aqueous suspensions (0.1, 0.2 and 0.3 wt. %) of the DD3R seeds for three different dipping times 30, 90 and 240 s with different stages of 1, 2 and 3. The SEM analysis was used to study the quality of the seeded layers. The optimized seeding conditions of 0.2 wt. % suspension concentration, 2 number of coating stages and 30 s for dipping time leaded to obtain a uniform seeded layer with monolayer structure. The DD3R zeolite membrane was synthesized via hydrothermal method under the optimized seeding conditions. The XRD and SEM analyses confirmed the synthesis of DD3R membrane with proper quality. The single gas permeation results showed a good performance in the separation of CO2 from CH4.

    更新日期:2018-05-22
  • Perovskite stabilization in Fe- and Mg-doped Pb(Zn1/2W1/2)O3 and their dielectric characteristics
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-21
    Woo-Jun Lee, Nam-Kyoung Kim

    Stabilization of a perovskite structure by solid-state reaction in as-yet unreported Pb(Zn1/2W1/2)O3 ceramics was attempted with compositional modification. A wide range of fractions of Pb(Fe2/3W1/3)O3 were initially introduced into the host material, and 20 mol% Pb(Mg1/2W1/2)O3 was subsequently added to the resulting composition in order to enhance perovskite formation. The perovskite development yield of 62.5% (without any fraction of Pb(Fe2/3W1/3)O3 introduced) increased with Pb(Fe2/3W1/3)O3 contents and finally reached 99.9%. The lattice parameters of the perovskite structure in the cubic symmetry range decreased steadily from 0.4002 to 0.3979 nm with increasing Pb(Fe2/3W1/3)O3. The relative permittivity values of the ceramics increased from 72 to 4910 (1 MHz) with increasing Pb(Fe2/3W1/3)O3. By contrast, the dielectric maximum temperatures in the cubic perovskite range changed only slightly from -111 to −124 °C (1 MHz), quite insensitive to the compositional modification. Meanwhile, the phase transition changed gradually from sharp to diffuse modes with the Pb(Fe2/3W1/3)O3 substitution.

    更新日期:2018-05-22
  • Microstructural and optical properties of the ZnS ceramics sintered by vacuum hot-pressing using hydrothermally synthesized ZnS powders
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-19
    Ku-Tak Lee, Boo-Hyun Choi, Jong-Un Woo, Jeong-Su Kang, Jong-Hoo Paik, Byoung-Uck Chu, Sahn Nahm

    ZnS nanopowders annealed at low temperatures (≤550 °C) have a pure cubic structure, while a small amount of hexagonal phase formed in specimens annealed at temperatures ≥700 °C. The particle sizes of the ZnS nanopowders increased with the annealing temperature. ZnS ceramics that were sintered using ZnS nanopowders annealed at low temperatures (≤550 °C) exhibited low transmittance, because of their porous microstructure. ZnS ceramics that were synthesized using ZnS powders annealed at high temperatures (≥800 °C) containing large agglomerated particles, also exhibited low transmittance, due to the presence of a liquid phase. A carbonate absorption band was found from the ZnS ceramics with small grains, because carbon ions diffused from the graphite mold into the ZnS ceramics during sintering, probably through the grain boundaries, and formed carbonates. A ZnS ceramic that was sintered at 1020 °C using the nanopowders annealed at 750 °C exhibited dense microstructure, with a large transmittance, 68%, in the wavelength range 6.0–12 μm.

    更新日期:2018-05-19
  • Crystallization, structure and properties of MgO-Al2O3-SiO2 highly crystalline transparent glass-ceramics nucleated by multiple nucleating agents
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-19
    Lei Han, Jun Song, Changwei Lin, Jianlei Liu, Taoyong Liu, Qian Zhang, Zhiwei Luo, Anxian Lu

    Generally, highly crystalline transparent glass-ceramics possess excellent physical and chemical properties compared to organic and other inorganic optical materials. We have successfully prepared highly crystalline transparent glass-ceramics in the MgO-Al2O3-SiO2 system by "extreme-time" nucleation & "finite-time" crystallization processes using P2O5, ZrO2 and TiO2 as multiple nucleating agents. The results revealed that the crystallization of glass is controlled by a three-dimensional interfacial crystal growth process. These glass-ceramics mainly consisted of cordierite crystals with a residual glassy phase, and crystallinity increased with crystallization time, but light transmittance decreased with crystallization time due to enlarged grain sizes. EDS mapping revealed a uniform distribution of elements within the glass-ceramic. In the optimal preparation condition (825 °C/96 h + 990 °C/3 h), these glass-ceramics exhibited a high crystallinity (87.3 vol. %), high transmittance (78 %), and excellent mechanical properties. This work provides a roadmap for preparing highly crystalline transparent glass-ceramics for applications in optical engineering.

    更新日期:2018-05-19
  • Novel Glass-ceramic SOFC Sealants from Glass Powders and a Reactive Silicone Binder
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-19
    Hamada Elsayed, Hassan Javed, Antonio G. Sabato, Federico Smeacetto, Enrico Bernardo

    The processing of sintered ceramics is often conditioned by the debinding step. The binders may determine some defects in the final product directly, by causing some gas evolution even at an advanced state of densification, due to incomplete decomposition at low temperature, or indirectly, by offering poor adhesion between particles, so that ‘green’ compacts may be easily damaged. The present investigation is aimed at exploring a novel concept for sintered glass-ceramics, based on the adoption of a silicone polymer as reacting binder, providing an abundant ceramic residue after firing. A glass belonging to the CaO-MgO-Al2O3-SiO2 system, already studied as a sealant in solid oxide fuel cell (SOFC) planar stack design, was reproduced in form of ‘silica-defective’ variants, featuring a SiO2 content, in the overall formulation, reduced up to 15 wt%. The overall silica content was recovered by mixing powders of the new glasses with the silicone: upon firing in air, the interaction between glass powders and polymer-derived silica led to glass-ceramics with the same assemblage than those formed by the reference glass and with a CTE of 9.5 × 10-6 K-1. The new approach has been successfully applied to the manufacturing of glass-ceramic seals as joining materials for solid oxide cells.

    更新日期:2018-05-19
  • Functional coatings for titanium casting molds using the replica technique
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-19
    Lisa Freitag, Stefan Schafföner, Christina Faßauer, Christos G. Aneziris

    The quality of titanium cast parts depends not only on the corrosion reaction of the mold in contact with the titanium alloy melt, but also on the dimensional accuracy and the surface quality of the investment casting mold. Usually, the ceramic mold is produced by dip-coating. This contribution investigated the coating properties of green calcium zirconate (CaZrO3) coatings produced by the replica technique. Thus, the effect of different coating slurries as well as different coating technologies on important coating properties was analyzed. In all cases, centrifuging and spraying produced thinner coatings compared to dip-coating. Using an appropriate coating slip, particularly centrifuging revealed a cohesive homogeneous coating surface and is therefore a promising technology for the production of functional coatings for titanium casting molds.

    更新日期:2018-05-19
  • Synthesis and characterization of PrxZr1-xSiO4 (x=0-0.08) yellow pigments via non-hydrolytic sol-gel method
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-19
    Ting Chen, Jianrui Zha, Xiaojun Zhang, Xiaobo Hu, Weihui Jiang, Zhixiang Xie, Wan Jiang

    Yellow inorganic pigments PrxZr1-xSiO4 (x = 0-0.08) have been prepared by a novel non-hydrolytic sol-gel (NHSG) method at 750 °C for 2 h. Replacing Pr4+ for Zr4+ in ZrSiO4 increased the cell volume and changed the color from white to yellow gradually. The Si―O―Zr and Si―O―Pr bands were observed in the FT-IR spectra of xerogel, indicating it could reach homogeneous mixing at the atomic level. Therefore, it promoted the solid solution reaction between Pr and zircon at low temperature. The samples exhibit high doping limitation (x = 0.08) and brilliant yellow hue (b* = 69.48) in contrast with the previously reported praseodymium zircon yellow pigments. The intense of yellow hue was increased with increasing the Pr doping content due to the increase of Pr4+/Pr3+ species. After applying on bisque ceramic tiles, the pigment exhibited excellent coloration, high thermal stability and low solubility in molten glazes, indicating its potential application in ceramic decoration.

    更新日期:2018-05-19
  • Optimising dopants and properties in BiMeO3 (Me = Al, Ga, Sc, Y, Mg2/3Nb1/3, Zn2/3Nb1/3, Zn1/2Ti1/2) lead-free BaTiO3-BiFeO3 based ceramics for actuator applications
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-17
    Shunsuke Murakami, Nihal Thafeem Ahmed Faheem Ahmed, Dawei Wang, Antonio Feteira, Derek C. Sinclaira, Ian M. Reaney

    A crystallochemical framework is proposed based on electronegativity difference (en) and tolerance factor (t) to optimise the BiMeO3 dopants and therefore the piezoelectric and electrostrictive response in BaTiO3-BiFeO3 based ceramics. Compositions in the series 0.05Bi(Me)O3-0.25BaTiO3-0.7BiFeO3 (BMe-BT-BF, Me: Y, Sc1/2Y1/2, Mg2/3Nb1/3, Sc, Zn2/3Nb1/3, Zn1/2Ti1/2, Ga, and Al) were fabricated using solid state synthesis and furnace cooled. Scanning electron microscopy and X-ray diffraction revealed that only Bi(Mg2/3Nb1/3)O3 and BiScO3 dopants, which lie in a narrow range of en vs. t, form homogeneous ceramics, free from secondary phases reflected in their superior piezoelectric coefficients (d33 ~145 pC/N). All other BiMeO3 additions exhibited either secondary phases (Y) and/or promoted a two-phase perovskite matrix (Zn, Ga and Al). The promising initial properties of BiScO3 doped compositions prompted further studies on 0.05BiScO3-(0.95-x)BaTiO3-(x)BiFeO3 (BS-BT-BF, x = 0.55, 0.60, 0.625, 0.65, and 0.70) ceramics. As x increased the structure changed from predominantly pseudocubic to rhombohedral, resulting in a transition from a relaxor-like to ferroelectric response. The largest d33* (465 pm/V) was achieved for x = 0.625 under 5 kV/mm at the crossover from relaxor to ferroelectric behaviour. BS-BT-BF with x = 0.625 showed >0.3% strain under 6 kV/mm up to 175 °C, demonstrating its potential for actuator applications.

    更新日期:2018-05-18
  • Energetic design of grain boundary networks for toughening of nanocrystalline oxides
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-17
    Arseniy Bokov, Shenli Zhang, Lin Feng, Shen J. Dillon, Roland Faller, Ricardo H.R. Castro
    更新日期:2018-05-18
  • The influences of stoichiometry on the sintering behavior, optical and scintillation properties of Pr:LuAG ceramics
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-14
    Zewang Hu, Xiaopu Chen, Jiawei Dai, Haohong Chen, Yun Shi, Huamin Kou, Tengfei Xie, Zhaoxiang Yang, Lexiang Wu, Yubai Pan, Martin Nikl, Jiang Li

    Sintering aids may enter the host lattice, create defects, and seriously deteriorate the scintillation properties of ceramic scintillators. In this study, the 0.3at%Pr:LuAG ceramics with different excess of Lu were fabricated by the solid-state reactive sintering without aids. The influences of stoichiometry on the sintering behaviors, optical and scintillation properties of the ceramics are systematically studied. The results show that the stoichiometric ceramics experience an abnormal grain growth during sintering. The Lu excess can restrain the abnormal grain growth of the ceramics because of the impurity drag effect. The excess Al2O3 as optical scattering centers, can also pin in the grain boundary to limit the fast migration of the grain boundaries. The light yield value of the as-sintered ceramics decreases with the increase of Lu content. After air-annealing, the ceramics with appropriate excess of Lu can achieve better optical quality and higher light yield compared to the stoichiometric Pr:LuAG ceramics.

    更新日期:2018-05-14
  • Direct and converse piezoelectric grain-size effects in BaTiO3 ceramics with different Ba/Ti ratios
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-11
    Bo-Wen Dai, Peng Zheng, Wangfeng Bai, Fei Wen, Lili Li, Wei Wu, Zhihua Ying, Liang Zheng

    The grain-size effects of the direct piezoelectric coefficient (d33) and the converse piezoelectric coefficient (d33*) of BaTiO3 ceramics with different Ba/Ti ratios were systematically explored. It was found that both d33 and d33* exhibited strong grain size (g) dependences for BaTiO3 ceramics with various Ba/Ti ratios. Although d33 showed similar grain-size dependence for all the Ba/Ti ratios, two entirely different grain-size dependence of d33* were observed. By carefully examining the microstructure and ferroelectric properties of the ceramics, the variations of domain configurations and maximum polarization of BaTiO3 ceramics with different Ba/Ti ratios were considered to be responsible for the different grain-size dependence of d33 and d33*, respectively.

    更新日期:2018-05-11
  • Energy Efficient Lightweight Periclase-Magnesium Alumina Spinel Castables containing Porous Aggregates for the Working Lining of Steel Ladles
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-11
    Wen Yan, Guiyuan Wu, Sanbao Ma, Stefan Schafföner, Yajie Dai, Zhe Chen, Jiangtao Qi, Nan Li

    This study presents a new lightweight periclase-magnesium alumina spinel castable (LPSC) for the working lining of steel ladles using porous periclase-spinel aggregates to replace conventional dense magnesia aggregates. The porous periclase-spinel aggregates were produced by an in-situ decomposition technique resulting in an apparent porosity of 23.3% and a median pore size of 5.66 μm. Scanning electron microscopy revealed a better porous aggregate/matrix interface bonding in the LPSC, which significantly improved its strength and thermal shock resistance. Additionally, the higher amount of micropores of the porous aggregates in the LPSC absorbed more penetrated slag from the matrix, which enhanced the slag resistance. Thus, compared with conventional castables, the LPSC had a lower bulk density of 9.2–10.8% and a lower thermal conductivity of 18.8% (1000 °C) while at the same time a higher strength, thermal shock resistance and slag resistance was achieved.

    更新日期:2018-05-11
  • Microstructure of (Hf-Ta-Zr-Nb)C High-Entropy Carbide at Micro and Nano/Atomic Level
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-09
    Ján Dusza, Peter Švec, Vladimír Girman, Richard Sedlák, Elinor G. Castle, Tamás Csanádi, Alexandra Kovalčíková, Michael J. Reece

    A High Entropy (Hf-Ta-Zr-Nb)C Ultra-High Temperature Ceramic (UHTC) was fabricated by ball milling and Spark Plasma Sintering (SPS) with a density of 99%. The microstructure characteristics were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) in combination with electron back scattered diffraction (EBSD) and transmission electron microscopy (TEM). Atomic structure and local chemical disorder was determined by means of scanning transmission electron microscopy (STEM) in conjunction with energy dispersive X-ray spectroscopy (EDS). According to the results, high purity, dense and homogeneous high entropy carbide with Fm-3 m crystal structure was successfully produced. The grain size ranged from approximately 5 µm to 25 µm with average grain size of 12 µm. Chemical analyses proved that all grains had the same chemical composition at the micro as well as on the nano/atomic level without any detectable segregation. The approximately 1.5 nm thin amorphous grain boundary phase contained impurities that came from the starting powders and the ball milling process.

    更新日期:2018-05-09
  • A Novel SiC-Based Microwave Absorption Ceramic with Sc2Si2O7 as Transparent Matrix
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-08
    Hanjun Wei, Xiaowei Yin, Zexin Hou, Fengrui Jiang, Hailong Xu, Minghang Li, Litong Zhang, Laifei Cheng

    For enhancing the dielectric and electromagnetic wave (EMW) absorption ability, SiC-Sc2Si2O7 ceramics were fabricated by introducing SiC into porous Sc2Si2O7 ceramics through precursor infiltration and pyrolysis (PIP). The Sc2Si2O7 powders were synthesized by sol-gel method and Sc2Si2O7 ceramics were prepared by pressure-less sintering. The results indicate that SiC nano-crystalline and turbostratic carbon derived from polycarbosilane distributed uniformly in electrically insulating matrix (Sc2Si2O7 matrix), resulting in tunable dielectric permittivity and EMW absorbing properties. Additionally, the content of C-rich SiC can be efficiently adjusted by PIP times. The SiC-Sc2Si2O7 ceramic showed excellent microwave absorption performance when the content of C-rich SiC was 25.3 wt. %. A minimum reflection coefficient of -51.3 dB was obtained at 9.56 GHz with the specimen thickness of 3.6 mm. The effective absorption bandwidth covered 3.6 GHz (from 8.7 to 12.3 GHz). The excellent microwave absorption abilities of SiC-Sc2Si2O7 ceramic were mainly attributed to uniform distribution of C-rich SiC in Sc2Si2O7 matrix. The special structure can improve the impedance matching and enhance microwave absorption performance. Moreover, the defects, interfaces and conductive network existed in the materials, which can synergistically improve the EMW absorption ability.

    更新日期:2018-05-09
  • Electron Microscopy Study of Pd, Ag, and Cs in Carbon Areas in the Locally Corroded SiC Layer in a Neutron-Irradiated TRISO Fuel Particle
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-07
    Haiming Wen, Isabella J. van Rooyen, John D. Hunn, Tyler J. Gerczak

    A detailed electron microscopy study was performed on focused ion beam-prepared lamellae from different locations relative to a crack across the inner pyrolytic carbon layer of a neutron-irradiated tristructural isotropic-coated particle. The distribution and composition of fission products across the inner pyrolytic carbon and silicon carbide (SiC) layers were studied. Previously, this crack was identified in the particle that released significant inventory fractions of cesium and silver during irradiation and displayed localized palladium pileup with SiC degradation. In this study, carbon areas were found in the SiC layer close to the crack tip and they had precipitates that consisted mostly of palladium silicides or palladium, with silver and/or cadmium frequently identified. Results confirmed that areas in the SiC layer close to the crack tip with localized accumulation of palladium were corroded by palladium, forming pure carbon areas and palladium silicide that provided pathways for silver, cadmium and cesium migration.

    更新日期:2018-05-08
  • High permittivitty (La0.5Sr0.5)CoO3-δ- La(Co0.5Ti0.5)O3-δ ceramic composites for next generation MIM capacitors
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-07
    Deepa Rajendran Lekshmi, Thomas Letang, Kuzhichalil Peethambharan Surendran

    Dielectrics with low capacitance loss and high relative permittivity are of high demand in metal-insulator-metal (MIM) capacitor that offers higher level of miniaturization, flexibility and performance. In order to achieve high relative permittivity, developing ceramics with metallic inclusions, has been suggested as a working strategy. But such materials may have high leakage currents and often lack thermal stability. With the objective for MIM applications, a series of (1-x)La(Co0.5Ti0.5)O3-δ-x(La0.5Sr0.5)CoO3-δ ceramics [x=0.0, 0.02, 0.04, 0.06, 0.08, 0.1, 0.2, 0.3, 0.4, 0.5, 1] were developed. The crystal structure analysis was performed for La(Co0.5Ti0.5)O3-δ, (La0.5Sr0.5)CoO3-δ and 0.5La(Co0.5Ti0.5)O3-δ-0.5(La0.5Sr0.5)CoO3-δ using X-pert High Score Plus. The composite with x=0.5 in (1-x)La(Co0.5Ti0.5)O3-δ-x(La0.5Sr0.5)CoO3-δ showed a maximum relative permittivity of 4920 with promising ac electrical resistivity (~202 Ω-cm). The thermal, electrical and dielectric properties together suggest that the composition 0.5La(Co0.5Ti0.5)O3-δ-0.5(La0.5Sr0.5)CoO3-δ is suitable for MIM capacitors in DRAM and RF devices.

    更新日期:2018-05-08
  • Degradation mechanisms of a self-healing SiC(f)/BN(i)/[SiC-B4C](m) composite at high temperature under different oxidizing atmospheres
    J. Eur. Ceram. Soc. (IF 3.411) Pub Date : 2018-05-04
    Xin’gang Luan, Yun Zou, Xiaohu Hai, Hui Bai, Qing Zhang, Ralf Riedel, Laifei Cheng

    Chemical vapor-infiltrated self-healing SiC(f)/BN(i)/[SiC-B4 C](m) composite specimens were exposed at 1300 °C for 300 h at atmospheric pressure under two different oxidizing atmospheres (i.e., wet (12%H2O:8%O2:80%Ar) and dry (0.01%O2:99.99%Ar)) representative of rich and poor oxidizing conditions, respectively. Mechanical testing, microstructural observations, and element analyses were performed on the treated specimens. The flexural strength retentions of the specimens were 47.9 and 39.4% under wet and dry oxygen conditions, respectively. The SiC and B4 C matrices were severely oxidized under wet oxygen conditions, whereas the BN interphase remained intact. The BN interphase and the B4 C layered phase were both partially oxidized under dry oxygen conditions. Thus, the SiC(f)/BN(i)/[SiC-B4 C](m) composites exhibited improved oxidation resistance under wet oxygen atmospheres as compared to dry oxygen conditions as a result of the formation of borosilicate glasses. In addition, two different degradation mechanisms for the composites during the oxidation process were discussed.

    更新日期:2018-05-04
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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