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  • Cooperative effects of free volume and nanocrystallite on plastic deformation in bulk amorphous Al2O3–ZrO2–Y2O3
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-17
    Xiqing Xu; Mingchao Wang; Jing Xie; Chenxi Zhai; Hui Li; Xinghua Su; Xingang Wang

    Bulk amorphous Al2O3–ZrO2–Y2O3 samples are fabricated by hot pressing and heat treated at 750–950 °C to adjust the free volume and crystallinity degrees, and the cooperative effects of free volume and nanocrystallite on plasticity are explored. With increasing heat treatment temperature, the free volume decreases monotonically, and the nanocrystallization initiates above 800 °C. Under compression at 500 °C, the plastic strain is in linear correlation to the free volume for fully amorphous samples or amorphous/nanocrystalline composites, respectively. The larger free volume concentration is beneficial to the formation and propagation of shear bands, and achieves to larger plasticity. Although the amorphous/nanocrystalline composites have lower free volume, they display better plasticity than the fully amorphous samples, attributed to the microstress concentration at the interfaces between nanocrystalline and amorphous matrix. Due to the coexistence of tiny nanocrystallite and sufficient free volume, the sample heat treated at 850 °C exhibits the best plasticity with strain of 9.9%.

    更新日期:2020-01-17
  • Oxidation behaviour of coarse and fine SiC reinforced ZrB2 at re-entry and atmospheric oxygen pressures
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-17
    Rubia Hassan; Rishabh Kundu; Kantesh Balani

    ZrB2 composites reinforced with SiC of two different particle sizes (coarse ∼30 μm and fine ∼5 μm) were processed using spark plasma sintering. The oxidation behaviour of the synthesised composites was investigated at 1500 °C under two different partial pressures of oxygen. At higher oxygen partial pressure of 0.21 atm, coarse SiC reinforced ZrB2 composite developed thicker oxide layers as compared to fine SiC reinforced ZrB2 composite. The thicker silica layer formed provides an enhanced oxidation resistance for extended exposure periods of greater than 3 h. However, at lower oxygen partial pressure of 2 × 10−5 atm, fine SiC reinforced ZrB2 composite showed better oxidation resistance due to segregation of finer ZrO2 particles on the surface, which prevented inward transportation of oxygen.

    更新日期:2020-01-17
  • ZnO–C3N4 solar light -driven nanophotocatalysts on floating recycled PET bottle as support for degradation of oil spill
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-17
    Aysan Joodi; Somaiyeh Allahyari; Nader Rahemi; Shayan Hoseini; Minoo Tasbihi

    Oil spill from explosion of oil wells and tankers threatens the life of sea creatures. Photocatalytic oxidation of oil spills is a promising way due to its low cost, complete conversion and the capability of using free and abundant sunlight. For better interaction between oil, photocatalyst and the light, it is recommended to use floating photocatalysts. In this research, recycled drinking bottles made of polyethylene terephthalate (PET) were used as a floating support for C3N4 and ZnO photocatalysts. ZnO–C3N4/r-PET composite with various amounts of ZnO (0, 5, 10 and 15 wt%) were synthesized and characterized by means of X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM-EDX), N2-sorption isotherm (BET-BJH), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR) and UV–vis diffuse reflectance spectroscopy (UV–Vis DRS). The as-prepared ZnO–C3N4/r-PET nanocomposites were tested for the photocatalytic degradation of benzene. The results shown that by increasing the amount of ZnO, the particle size decreased, size distribution narrowed and a more homogenous morphology was observed. Moreover, pore volume, pore diameter and BET surface area increased. In details, ZnO crystallite size reduced from 32 nm in ZnO–C3N4/r-PET nanocomposite with 5 wt% of ZnO to 18 nm in similar nanocomposite with 15 wt% of ZnO. Increasing the ZnO amount, broadened the band gap but enhanced the light absorption in visible and UV regions. Good interaction between C3N4 and ZnO was confirmed in TEM images. The highest degradation performance was obtained in the presence of 15 wt% of ZnO In fact by decreasing the amount of ZnO in the ZnO–C3N4/r-PET composite, the photodegradation rate decreased significantly. Influence of operating parameters like pH, catalyst loading, benzene volume percent and simulated sea conditions on photodegradation of floating benzene were also studied in details.

    更新日期:2020-01-17
  • Fast drying of high-alumina MgO-bonded refractory castables
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-17
    V.S. Pinto; D.S. Fini; V.C. Miguel; V.C. Pandolfelli; M.H. Moreira; T. Venâncio; A.P. Luz

    Refractory producers face many challenges in terms of producing MgO-containing castables due to the high likelihood of magnesia to hydrate in contact with water, resulting in Mg(OH)2 generation. The expansive feature of this transformation affects the performance of such refractories, as (i) if this hydrated phase is not accommodated in the formed microstructure, ceramic linings with cracks and low green mechanical strength will be obtained; and (ii) if crack-free pieces are prepared, they should present low porosity and reduced permeability, which require special attention when heating these materials. In both cases, spalling/explosion may be favored during the drying step of MgO-containing compositions. Hence, this work investigated the ability of various additives in the optimization of the drying behavior of Al2O3–MgO castables. Vibratable compositions were tested after incorporating polymeric fibers (PF), an organic salt (OAS), SiO2-based additive (SM) or permeability enhancing active compound (MP) into the dry-mixtures. Various experimental measurements were performed to infer the role of the drying agents to prevent the samples' explosion and whether they would also influence other properties of the castables. As observed, OAS and MP helped to inhibit the MgO-bonded samples' explosion even under severe heating conditions (2–20 °C/min) and increased their green mechanical strength and slag infiltration resistance when compared to the additive-free composition. On the other hand, the addition of polymeric fibers (PF) or silica-based compound (SM) to the formulations was not able to prevent the castables' explosion when using a high heating rate and other side effects (samples’ cracking during drying at 110 °C, high linear expansion and increased slag penetration during corrosion tests) could also be observed when testing these materials. Thus, the selection of suitable drying agents is a key issue, as they may allow the development of MgO-bonded castables with enhanced properties and lower spalling risk during their first thermal treatment.

    更新日期:2020-01-17
  • Temperature dependence of the fracture strength of porous ceramic materials
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-17
    Ruzhuan Wang; Shu Wang; Dingyu Li; Weiguo Li; Chuanzeng Zhang

    In spite of the extensive use of porous ceramic materials in high-temperature applications, there are very few experimental and no theoretical studies on analyzing their temperature-dependent fracture behavior. In this work, in order to fill this research gap, a novel theoretical model for the characterization of fracture strength of porous ceramic materials with respect to temperature is proposed. The model considers the effects of the Young's modulus, specific heat capacity, volume fraction of pores, sizes of pore and flaw (critical flaw size). Further, through simplification the model can be used for the characterization of the strength of the dense ceramic materials. The models are verified by the obtained excellent agreements between the predictions and measurements. The experimentally observed phenomena are analyzed and explained according to the predicted results. Our analysis indicates that the temperature dependence of the fracture strength of the porous ceramic materials in vacuum is controlled by the Young's modulus and volume fraction of pores. While on high temperature oxidation the critical flaw size with respect to temperature should be considered. Furthermore, the temperature dependence of the strength of the dense ceramics is governed by the Young's modulus.

    更新日期:2020-01-17
  • Effect of sub and above-curie temperature annealing on the nanomechanical properties of PMN-PT piezoceramics
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-17
    V.S. Kathavate; B. Praveen Kumar; I. Singh; K. Eswar Prasad

    The domain configurations such as domain size, orientation, and interdomain spacing have a significant influence on the electromechanical properties of piezoelectric materials though their role on mechanical properties is not well understood. In this manuscript, we have systematically varied the domain configuration of polycrystalline lead magnesium niobate-lead titanate (PMN-PT) piezoceramics (by annealing them below and slightly above the Curie temperature, Tc) and determined the nanomechanical properties. Nanoindentation experiments performed on pristine, sub and above-Tc annealed samples in the peak load range of 1 mN–5 mN reveals a strong indentation size effect (ISE) in hardness, H. Further, it is observed that the sub-Tc annealed samples exhibit higher H and elastic modulus, E compared to the above-Tc annealed and pristine samples. In contrast to this, the piezoelectric constant, d33, decreases with increase in annealing temperature eventually approaches to “zero” for the above-Tc annealed samples, though both sub and above-Tc annealed samples have similar crystal structure. The microstructure and domain characterization indicate discernable differences in the domain structure suggesting that the differences in nano-mechanical and piezoelectric properties can be attributed to the changes in domain configurations. These results provide new insights about the novel way to engineer the domain configurations for tailoring mechanical and piezoelectric properties of the piezoceramics.

    更新日期:2020-01-17
  • Facile and inexpensive preparation method of iron phosphate from laterite residue
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-17
    Zhihe Cao; Baozhong Ma; Qiankun Jing; Peng Xing; Bao Liu; Chengyan Wang

    Laterite leach residue receives minimal attention, which causes severe environmental problems and resource wastage. In this paper, a facile and inexpensive method is proposed for preparing iron phosphate from laterite residues via phase transformation in phosphate medium. The laterite leach residue used in this study contains 59.2% Fe in the form of hematite. Based on the thermodynamic analysis of the system Fe2O3–H3PO4 and characterization of X-ray diffraction (XRD) and scanning electron microscope (SEM), phase transformation mechanism and operating conditions are determined. Phase transformation is divided into two stages, namely, dissolving and precipitating. Phase transformation should control pH-0.4 at first, which is beneficial to dissolving Fe2O3, and then increase pH to 1.8–3.9 to finish the precipitation of FePO4. In experiments, hematite can be completely transformed into iron phosphate at the following optimal conditions: 90 °C, 3.0 mol/L H3PO4, 3 h, and liquid-to-solid ratio of 10:1 mlL/g. XRD patterns and SEM images show that the crystal structure and pure phase of product match the standard iron phosphate well, and micro sheets aggregate to form a flowerlike morphology. Additionally, the initial discharge of the LFP synthesized by iron phosphate is 146.1 mAh g−1 at 0.1 C and shows good cycling performance at different C-rates. Electrochemical impedance spectroscopy shows that the Rct LFP synthesized by precursors is 80.83 Ω. The novel and facile method to treat laterite residue solves not only environmental problems of residue accumulation and wastage of iron resource but also improves the economic benefits of laterite.

    更新日期:2020-01-17
  • Effect of annealing atmosphere (CO and N2 gas flow) on surface morphology and crystal quality of AlN buffer layer
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-17
    Cheng Cheng; Wei-Han Lai; Chun-Kai Huang; Cheng-Yi Liu

    In this study, the effect of the annealing atmosphere (N2–CO and pure N2 atmosphere) on the crystal quality, surface morphology, and surface O content of the annealed AlN buffer layers was studied. The FWHM of the (0002) plane of an XRD rocking curve showed that the screw dislocation density of the as-grown AlN film can be reduced by annealing in both N2–CO and pure N2 atmosphere. The AlN film showed an improvement in crystal quality under pure N2 annealing atmosphere. As annealing the AlN buffer layer improves the crystal quality, surface roughness, and surface O content of the AlN film, it should be well controlled for the subsequent growth of III-nitride layers. The surface oxidation that occurred on the AlN films during annealing in N2–CO atmosphere resulted in an increase in surface O content and surface roughness of the AlN films, which is undesirable for the subsequent growth of III-nitride layers. We observed that the surface O content (in the depth of 2-nm) of all annealed AlN films was reduced in the N2 annealing atmosphere, which could be due to the O outgassing from the AlN surface to the pure N2 annealing atmosphere. The O outgassing of the surface O content in the AlN surface layer was related to the volume of space in the annealing setups. However, a large volume of annealing space under pure N2 gas flow resulted in higher thermal decomposition on the annealing AlN films, leading to pits forming on the annealed AlN surface and a smearing of the original step-terrace structure. Therefore, we found that there is an optimal annealing atmosphere space in maintaining the original surface morphology and achieving low surface O content in the annealed AlN film.

    更新日期:2020-01-17
  • ZnO nanocrystal-coated MoS2 nanosheets with enhanced ultraviolet light gas sensitive activity studied by surface photovoltage technique
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-17
    Jiayu Wang; Jiahao Deng; Yunbo Li; Huan Yuan; Ming Xu

    In this paper, ZnO nanocrystals and MoS2/ZnO composites were fabricated by a simple sol-gel method and ultrasonic concussion. Several characterization techniques including XRD, TEM, XPS, Raman spectroscopy and surface photovoltage were employed to explore the samples. The doping of MoS2 nanosheet into the ZnO nanocrystal composites was studied for its effect on NO2 gas-sensitivity under UV irradiation at room temperature. Compared to gas sensors developed from pure ZnO, those developed from ZnO/MoS2 exhibited higher sensitivity with a reversible response. Surface photovoltage results suggest that these desirable sensing features can be attributed to MoS2/ZnO heterojunctions and an abundance of diffusion channels which reduce the energy barrier to promote ready transference and target gas adsorption/desorption. These results offer new opportunities to fabricate composite materials for gas sensors.

    更新日期:2020-01-17
  • Ordered mesoporous silica encapsulated carbon quantum dots and its application in Fe3+ detection
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-17
    Yufei Dong; Jianzhong Ma; Chao Liu; Yan Bao

    The nanocomposites prepared by the combination of SiO2 and carbon quantum dots (CQDs) have the advantages of low toxicity, high fluorescence intensity, high biocompatibility and good water solubility, which greatly broaden its application range. Nevertheless, if only SiO2 and CQDs are simply combined without any structural design, the stability of the nanocomposites will be poor, which will affect its practical application value. In this work, we first synthesized ordered mesoporous silica (OMS) rapidly in aqueous solution by a facile method (30 min), and then generated CQDs in situ in the mesoporous channels of OMS by hydrothermal method to obtain [email protected] fluorescent nanocomposites. The chemical structure and morphology of OMS and [email protected] were characterized by FT-IR, XRD, SAXRD and TEM, indicating that CQDs was successfully encapsulated in OMS. The stability test results of [email protected] indicate that CQDs can be stably present in the mesoporous channels of OMS, and the fluorescence intensity of [email protected] nanocomposites is almost independent of ionic strength, pH and storage time. The optical performance results show that the optimal excitation wavelength of [email protected] nanocomposites is about 340 nm, the emission wavelength is about 440 nm. Using [email protected] nanocomposites as fluorescent probes to detect Fe3+, it was found that [email protected] responded very quickly to Fe3+. The fluorescence quenching intensity of [email protected] has a good linear relationship with the concentration of Fe3+ in the range of 25–750 μM. Therefore, the trace amount of Fe3+ in solution can be calculated by measuring the relative magnitude of fluorescence intensity.

    更新日期:2020-01-17
  • Preparation and characterization of high flux alumina membrane supports by composite pore former method
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-17
    Yangfang Cheng; Yougen Yu; Cheng Peng; Jianqing Wu

    Pore formers are essential for preparation of high performance ceramic membrane supports. The removal of the pore former is a key process affecting the sintering rate and quality. To avoid excessive concentration of pore former removal at a certain temperature, we choose carbon black, sawdust and hydroxyethyl cellulose (HEC) as a composite pore former to prepare supports with high flux and sinter the supports rapidly. According to thermal analysis results of the three pore formers, we designed the ratio of sawdust/carbon black/HEC as 5/3/2. By tuning the firing temperature, pore former content and heating rate, the supports prepared with this method exhibited a pure water flux of 45.4 m3m−2h−1bar−1 and a bending strength of 46.2 MPa. The properties are highly dependent on the pore former content and slightly on the heating rate, which means that the composite pore former method can greatly reduce the time consumption without damage to the support quality. The corrosion experimental results also indicate the supports are quite resistant to strong acid and alkali corrosion. In summary, the composite pore former method is a promising way to fabricate supports with excellent performances and realize the fast firing of high porosity ceramic membrane supports.

    更新日期:2020-01-17
  • The hydration resistance, evolution mechanism of sol-coated aluminum and its effect on mechanical properties of SiC porous reticulated ceramics
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-16
    Xiong Liang; Yawei Li; Shaobai Sang; Qinghu Wang; Zhu He; Benwen Li

    As the key component for porous media burner, the sufficient strength of SiC reticulated porous ceramics (RPCs) is necessary due to the scour of hot flue gas. However, the SiC RPCs prepared with template replica method often exhibited serious oxidation and low strength when the foam was burnt out. In the present work, a sol-coated Al powder with high hydration resistance was introduced into the silicon carbide slurry to promote mullite formation in SiC skeleton, meanwhile reduce the SiC oxidation ratio of sample during the heat treatment. Firstly, the silica-sol coated Al with uniform silica-sol was successfully prepared via dip coating to improve the ability of hydration resistance of Al powder. Furthermore, sol-coated Al with spherical morphology improved rheological properties of silicon carbide slurry, including viscosity and rheological behavior. In addition, the evolution mechanism of sol-coated Al in SiC RPCs was revealed. The AlO2(g) and AlO(g) was first formed in the system, thus significantly reducing the SiC oxidation ratio in SiC RPC. The partial pressure of AlO(g) increased with the sintering temperature, the needle-shaped mullite formed at 1300 ○C when it dissolved in the microsilica, while lumpy mullite formed as SiC was the silica source in SiC RPCs. The addition of sol-coated Al was beneficial to optimize the microstructure of SiC skeleton, resulting in higher compressive strength of SiC RPCs.

    更新日期:2020-01-17
  • The effect of Ni12+ heavy ion irradiation on the optical and structural properties of BeO ceramics
    Ceram. Int. (IF 3.450) Pub Date : 2019-02-19
    A.E. Ryskulov; A.L. Kozlovskiy; I.A. Ivanov; V.V. Uglov; S.B. Kislitsin; M.V. Zdorovets

    The paper presents study results of structural and optical changes in heavy ion irradiated BeO ceramics. Irradiation was carried out on DC-60 heavy ion accelerator using Ni12+ ions with an energy of 100 MeV with irradiation fluence of 1013-1014 ions/cm2. It has been established that intensity decrease and shape change of OSL (Optically Stimulated Luminescence) curves for irradiated samples are caused by concentration increase of defects and amorphous inclusions, which affect ceramics reflectance. It has been determined that change in magnitude of atom displacements from lattice sites is exponential, which has great influence on crystal structure distortion and deformation in case of defect overlap regions formation at large irradiation fluences.

    更新日期:2020-01-16
  • Improvement of electrical performance by surface structure of Ni-material as a high-performance asymmetric supercapacitor electrode
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-16
    Damin Lee; NanasahebM. Shinde; Ji Cheng Ding; Jianjian Fu; Rakesh K. Sahoo; Hyun Woo Lee; Je Moon Yun; Heon-Cheol Shin; Kwang Ho Kim

    Binder-free Ni-material array electrodes on Ni-foam are fabricated using a facile hydrothermal method for high-performance supercapacitors. Instead of a binder, urea is added to increase the adhesion of Ni-foam as both the substrate and electrode material. In this paper, we present the contribution of urea to the formation of the material. The surface characteristics and the electrical properties of the Ni-material array change with the amount of urea. When 2.4 g of urea is added to the sample for the first time, a Ni(HCO3)2 microrod electrode is obtained; it shows large wire growth on the Ni-foam, which can be explained about the abnormal grain growth behavior because there is little energy barrier for atomic attachments with a disordered or rough interface atomic structure. Its specific capacitance is 346 F g−1 at a current density of 3 A g−1. In contrast, when the amount of urea is reduced to 0.8 g, a Ni2(CO3) (OH)2 array electrode is produced; it exhibits a nano-size wire array and a specific capacitance of 833.2 F g−1 at a current density of 3 A g−1. Thus, it is confirmed that the large surface area of Ni2(CO3) (OH)2 exhibits outstanding electrical properties. And, the fabricated asymmetric supercapacitor of Ni2(CO3) (OH)2 composite as the positive electrode and graphene as the negative electrode, which has a high energy density of 22.1 W h kg−1 at a power density of 673.1 W kg−1. In addition, this obtained asymmetric supercapacitor can turn on the LED light.

    更新日期:2020-01-16
  • Relaxor ferroelectric (Na0.5Bi0.5)0.4Sr0.6TiO3-based ceramics for energy storage application
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-16
    Zhengyi Yang; Ying Yuan; Lei Cao; Enzhu Li; Shuren Zhang

    Lead-free (Na0.5Bi0.5)0.4Sr0.6TiO3-xK0.73Bi0.09NbO3 (abbreviated as NBST-xKBN) ceramics with perovskite structure were prepared by a conventional solid-state reaction method. NBST ceramics modified with KBN content demonstrate strong relaxor behavior. When x = 0.05, the optimal energy storage density (1.79J/cm3), improved recoverable energy efficiency (91.02%) and the maximum dielectric breakdown strength (22.2 kV/mm) are obtained. The discharge energy density of NBST-0.05KBN are measured under the electric field from 10 kV/mm to 16 kV/mm, exhibiting good discharge energy density (1.20J/cm3) at 16 kV/mm. Complex impedance plots of NBST-xKBN exhibit great resistivity of the ceramics. In all, these results indicate that NBST-xKBN is a potential candidate for energy storage applications.

    更新日期:2020-01-16
  • Influence of the atmosphere on the mechanical properties and slag resistance of magnesia-chrome bricks
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-16
    Gengfu Liu; Yawei Li; Tianbin Zhu; Yibiao Xu; Jun Liu; Shaobai Sang; Quanyou Li; Yuanjin Li

    Magnesia-chrome bricks are commonly used as the lining of smelters in copper and lead industry because of their resistance against the thermal, mechanical and chemical loads in the pyrometallurgical production process. In fact, the pyrometallurgical production process of lead-copper matte is generally a reducing process with plenty of coke and iron fillings as reducing agent, which implies that the magnesia-chrome bricks service in stronger reducing atmosphere. In this work, the microstructure, mechanical properties and slag resistance of such materials were investigated in reducing atmosphere to simulate the influence of the atmosphere on the properties of magnesia-chrome refractories. The results show that obvious increase in porosity and decrease in strength occurred to the magnesia-chrome samples after treating in reducing atmosphere. This is related to the structural damage of samples, in which Fe3+/Fe2+ within spinel (Mg, Fe)(Cr, Al, Fe)2O4 were partly reduced to metallic Fe under reducing atmosphere. Consequently, the slag penetrated much easily into the matrix of the samples. Moreover, the slag corrosion also aggravated due to the aggressive FeO in slag and the formation of magnesiowüstite in the penetration layer. Nevertheless, the high melt phases of spinel and forsterite were formed when the slag corrosion test was conducted in air atmosphere, thereby preventing further slag corrosion and penetration.

    更新日期:2020-01-16
  • Optical, electrical and magnetic properties of copper doped electrodeposited MoO3 thin films
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-16
    Rufus O. Ijeh; Assumpta C. Nwanya; Agnes C. Nkele; Itani G. Madiba; A.K.H. Bashir; A.B.C. Ekwealor; R.U. Osuji; M. Maaza; Fabian Ezema

    Copper-doped MoO3 thin films were prepared via electrodeposition technique. The techniques adopted for investigating the structural, optical, electrical and magnetic properties of both undoped and copper-doped MoO3 thin films include X-ray diffractometry, UV–visible spectroscopy, four-point probe and vibrating sample magnetometry respectively. Nanocrystalline homogenous grains with polycrystalline orthorhombic (α-MoO3) nature were obtained. The optical plots recorded decreased band gap energy from 3.44 eV to 3.27 eV, magnetic studies showed ferromagnetic properties of the doped samples while the electrical study revealed the highest conductivity of 1.5 Ωcm−1. Doping with Cu has the potentiality of increasing the conductivity of MoO3 thereby enhancing its application in photocells.

    更新日期:2020-01-16
  • Fe(III) modified Bi2O4 nano-rods for boosting photocatalytic performance through interfacial charge transfer effect
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-16
    Xuan Dai; Song Yan; Lishuang Cui; Lei Shi

    A novel Fe(III) modified Bi2O4 (Fe–Bi2O4) photocatalyst was prepared via the wet impregnation method, and measured through XRD, XPS, TEM, BET and DRS to analyze crystal structure, feature, textural and optical properties. Measurement results verified that Fe(III) formed nanoparticles loaded on the Bi2O4 nano-rod surface, which could attribute to accelerate photoinduced electrons efficient transfer and separation by interfacial charge transfer effect. When Fe–Bi2O4 photocatalyst was applied for decomposing rhodamine (RhB), the optimal photocatalyst (Fe–Bi2O4(45 wt%)) exhibited higher reaction rate constant in comparison to pure Bi2O4. Meanwhile, different radical scavengers tests revealed that h+ and ·O2− exhibited the major role in photocatalysis course. Finally, combined with above experimental results, a probable photocatalytic mechanism for Fe–Bi2O4 hybrid photocatalyst was presented.

    更新日期:2020-01-16
  • Incipient plasticity and dislocation loop evolution in rock-salt vanadium nitride
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-16
    Shayuan Weng; Xing Yue; Tao Fu; Xiang Chen; Xuesong Long; Xianghe Peng

    Incipient plasticity and dislocation loop (DL) evolution are two important plastic behaviors of ceramic materials. In this work, we performed molecular dynamics simulations of the nanoindentation on vanadium nitride (VN) surfaces with different Miller indexes to investigate the incipient plasticity, dislocation reactions, and the evolution of the DLs. It was found that the plasticity of VN proceeds by the nucleation and glide of partial dislocations, forming {111} stacking fault (SF). However, dislocation patterns of nanoindentation along different crystallographic orientations are quite different, which to be specific are dislocation flower for {001}, SF tripyramid for {111}, and symmetric inclined SF for {110} indentions. There are two kinds of reactions between the primary defects, including the movement of two parallel partial dislocations forming an extended dislocation, and the intersection of two unparallel SFs forming a stair-rod dislocation. The Thompson tetrahedron was extended to the illustration of the evolution of the microstructures in B1 crystalline VN during the nano-indentations on differently oriented surfaces.

    更新日期:2020-01-16
  • Fabrication of hierarchically micro/meso/macroporous silicon carbonitride ceramic using freeze casting method with a silsesquiazane precursor
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-15
    Tae-Hwan Huh; Young-Je Kwark

    Hierarchically porous silicon carbonitride (SiCN) was prepared using the freeze casting method with silsesquiazane (SSQZ) as a precursor. As SSQZ possesses a highly branched structure, it can provide a higher cross-linking degree than linear polysilazane and thereby, improve the structural stability. The porous SiCN can be produced without collapsing the pore structures by removing the organic groups during the pyrolysis process due to the high cross-linking degree. In this study, we used the freeze casting method to introduce macropores. In addition, the effects of glycidyl-POSS and 1,7-octadiene diepoxide as additional cross-linking agents on the formation of porous ceramics were investigated. The Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses showed that SSQZ with cross-linking agents demonstrated a higher cross-linking degree and was successfully converted to SiCN ceramics. As a result, the porous SiCN ceramics exhibited an improved structural stability, specific surface area, and pore volume.

    更新日期:2020-01-15
  • Impact of Eu3+ ion substitution on structural, magnetic and microwave traits of Ni–Cu–Zn spinel ferrites
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-15
    M.A. Almessiere; Y. Slimani; H. Güngüneş; V.G. Kostishyn; S.V. Trukhanov; A.V. Trukhanov; A. Baykal

    Partially europium (Eu) substituted Ni0.4Cu0.2Zn0.4EuxFe2-xO4 (0.0 ≤ x ≤ 0.10) nanostructured spinel ferrites (NSFs) were produced by sol-gel auto-combustion strategy. The XRD analyses verified the existence of the single-phase composition in all the investigated samples. The Mössbauer spectra were used to estimate the values of the line-width disparity, isomeric shift (IS), quadrupole splitting, and hyperfine magnetic field (HMF). The values of HMF of the A and B sites decreased with the rise in Eu substitutions. The paramagnetic contribution of the NSFs increased with the rise in Eu3+ contents. The S-parameters of the proposed NSFs were measured using co-axial method. The frequency dispersions of the permittivity and permeability were utilized to determine the reflection losses in the 1–20 GHz frequency range. The occurrences of the natural ferromagnetic resonance (NFMR) enabled substantial absorption of the electromagnetic energy ranged from 2.5 to 9.5 GHz. There was established a strong correlation between the level of chemical substitution (x) and amplitude-frequency characteristics of the studied spinel ferrites was established. Furthermore, the increase of Eu substitution strongly influenced the frequency characteristics of the NSFs. Anomalous changing of the resonant amplitude (more than 4 times) was shown. This can be explained by the appearance of indirect exchange interactions between Fe3+ (3 d5) and Eu3+ (4f6) electronic shells. Results revealed a potential for practical applications of such kinds of materials in functional radio electronic devices.

    更新日期:2020-01-15
  • Corrosion behavior of Y2O3-doped mullite-ZrSiO4 coatings applied on C/C–SiC composites in the presence of moisture at temperatures of 1373–1773 K
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-15
    Tianxiao Qian; Yi Zeng; Xiang Xiong; Ziming Ye; Huilin Lun; Jinrun Hu; Yalei Wang; Zhongwei Zhang; Changhai Yan

    Commercial mullite powders show great potential for application in environmental barrier coatings. However, most of the commercial mullite powders contain amorphous silica, which produces volatile silicon hydroxide in hot steam. This leads to serious recession of mullite coatings in hot water vapor. In this study, a Y2O3-doped mullite-ZrSiO4 coating was fabricated on C/C–SiC composites using the slurry painting method. The addition of Y2O3 resulted in the elimination of the residual silica and derived-cristobalite in the commercial mullite powder, leading to the formation of a stable mullite-Y2Si2O7–ZrSiO4 coating. This indicates that Y2O3 can efficiently enhance the phase stability of commercial mullite at high temperatures. In addition, the corrosion behaviours of Y2O3-doped mullite-ZrSiO4 coatings were investigated at 1373, 1573, and 1773 K in a 95% H2O-5% O2 atmosphere. The coatings exhibited good corrosion resistance. The 15 mol% Y2O3 coating showed a weight loss rate of 1.62 wt % when exposed to hot steam for 10 h at 1573 K. This value is only 1/8th of that of the uncoated sample. Moreover, ZrSiO4 improved the water corrosion resistance of the Y2O3-doped mullite-ZrSiO4 coatings at 1573 K.

    更新日期:2020-01-15
  • Origin of colossal permittivity and low dielectric loss in Na1/3Cd1/3Y1/3Cu3Ti4O12 ceramics
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-15
    Zhanhui Peng; Xiaobin Zhou; Jitong Wang; Jie Zhu; Pengfei Liang; Xiaolian Chao; Zupei Yang
    更新日期:2020-01-15
  • Formation mechanism of MgSrAl10O17 and its effect on the mechanical performance of lightweight Al2O3–MgAl2O4 refractories
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-15
    YaLou Xin; HongFeng Yin; Yun Tang; HuDie Yuan; XiaoHu Ren; Kui Gao; QiFa Wan; YuChi Liu

    Lightweight Al2O3–MgAl2O4 refractories can be achieved by producing a density gradient structure which guarantees good slag resistance and low thermal conductivity. To further improve the mechanical properties of this material, in this study, in situ platelike structure was developed by adding different amounts of SrCO3 in the matrix. The phase composition, microstructure, physical and mechanical properties of the obtained lightweight refractories were characterized and evaluated. The results showed that besides corundum and spinel, platelike MgSrAl10O17 phase was also formed during reactive sintering. The well-developed MgSrAl10O17 phase possessing an interlocking structure formed grain-grain bridging with MgAl2O4, which significantly improved the mechanical performance of lightweight Al2O3–MgAl2O4 refractories. Although no obvious changes occurred in apparent porosity and bulk density of the specimen, the compressive strength and refractoriness under load were significantly improved after SrCO3 addition, which increased from ∼50 MPa to ∼80 MPa and 1589 °C–1656 °C, respectively. To better understand the relationship between microstructure evolution and improvement in performance, the formation mechanism of the MgSrAl10O17 phase and its reinforcement mechanism in the material were described in detail.

    更新日期:2020-01-15
  • Transparent Yb3+ doped phosphate glass-ceramics
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-15
    M. Hongisto; A. Veber; N.G. Boetti; S. Danto; V. Jubera; L. Petit

    Yb3+ doped oxyfluorophosphate glasses with the composition (98.75) [90NaPO3-(10-x) Na2O-xNaF] - 1.25Yb2O3 (in mol%) with x = 0, 2.5, 5, 7.5 and 10 were prepared using a standard melting process. The progressive replacement of Na2O by NaF leads to an increase in the number of Q2 units at the expense of the Q1 units. This increase in the polymerization of the glass network leads to a shift of the optical band gap to lower wavelength, to a slight increase in the intensity of the emission at 1000 nm and more importantly to a change in the glass crystallization process. Indeed, both surface and bulk crystallization were observed in the glass with x = 0 while surface crystallization only occurs when NaF is added in the phosphate network. The heat treatment leads to the precipitation of at least three crystalline phases: as x increases, the NaPO3 phase grows at the expense of Na5P3O10. All glasses precipitate the Yb containing crystal, NaYbP2O7 which leads to an increase in the intensity of the emission at 1000 nm compared to the emission at 975 nm. We show for the first time to the best of our knowledge that transparent Yb3+ doped phosphate glass-ceramics can be obtained within this glass system when free of NaF.

    更新日期:2020-01-15
  • Precision structural and phase analysis of boron carbide
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-15
    Joshua L. Watts; Henry J. Spratt; Peter C. Talbot; Jose A. Alarco; N.A. Raftery; Ian D.R. Mackinnon

    Structural analyses and phase quantification of solution-synthesised and commercially available boron carbide powders are conducted via Rietveld refinement of X-ray diffraction data. A fixed incidence parallel beam geometry is compared against the more commonly used Bragg-Brentano geometry. Fixed incidence parallel beam is found to have a significant advantage in phase quantification through the minimisation of peak aberrations due to the high X-ray transparency of boron carbide. The enhanced resolution and accuracy afforded by this technique allows for fundamental new insights into the phase content of boron carbide powders. Specifically, commercially obtained boron carbide powders are found to be multi-phasic, containing varying contents of both B∼4C and B∼6.5C phases. Solution-synthesised boron carbide produced in this study is found to comprise of B4.05C only. These findings have significant importance to the development of boron carbide for high-performance applications and present a potential avenue for the synthesis of high purity boron carbide powders with controlled stoichiometry.

    更新日期:2020-01-15
  • 更新日期:2020-01-15
  • Fine and high-performance B6.5C-TiB2-SiC-BN composite fabricated by reactive hot pressing via TiCN–B–Si mixture
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-14
    Junxiao Tang; Wei Ji; Jingjing Xie; Yunwei Shi; Yuexu Zhu; Qianglong He; Weimin Wang

    In this study, B6.5C-TiB2-SiC-BN composite was fabricated via reactive hot pressing from a powder mixture of TiCN, B, and Si. The reaction process of the powder mixture was investigated by heat treatment at elevated temperatures. The as-reacted powder products possessed a core-shell structure of TiB2 surrounded by h-BN. During densification, the h-BN in this structure acts as a diffusion channel and lubricant, which promoted the densification process. The extremely small size, fresh surface of in-situ formed phases, and uniform dispersion in synthesized powders also contributed to sintering. The designed reactive hot-pressing sintering effectively resolves the difficulty of obtaining uniformly-dispersed BN. The obtained bulk B6.5C-TiB2-SiC-BN composite ceramic shows high relative density (98.8%) and good comprehensive mechanical properties including hardness, bending strength, and fracture toughness of 19.6 GPa, 801 MPa, and 5.31 MPa m1/2, respectively.

    更新日期:2020-01-14
  • Improved microwave dielectric properties and sintering behavior of LiZnPO4 ceramic by Ni2+-ion doping based on first-principle calculation and experiment
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-14
    Rui Peng; Yongcheng Lu; Zhihua Tao; Daming Chen; Liang Shi; Qin Zhang; Yuanxun Li

    Theoretical calculation and experimental verification were performed to investigate the effect of Ni2+-ion substitution on the microstructure, sintering behavior, and microwave dielectric properties of LiZnPO4 ceramic. The crystal structure, electron density, formation energy, and vibration mode of the doped system were discussed on the basis of density functional theory. Samples were synthesized using the traditional solid-state reaction method and characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, network analysis, differentia-thermal and thermo-mechanical analyses, and Raman spectrometry. The substitution of Ni2+ ions to Zn2+ ions could modify the bond length, bond population, and electron distribution of ZnO4 tetrahedron. The vibration, microstructure, and sintering properties changed accordingly. The densification level and microwave dielectric properties improved (εr=5.57, Q×f = 63,951 GHz at 15 GHz, τf = -79.5 ppm/°C, relative density = 97.27%) when 4% (molar ratio) Zn2+ ions were replaced by Ni2+ ions sintered at 825 °C. The Ni2+-ion substitution could enhance the dielectric and sintering properties of LiZnPO4 ceramic.

    更新日期:2020-01-14
  • Construction of polypyrrole-wrapped hierarchical CoMoO4 nanotubes as a high-performance electrode for supercapacitors
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-14
    Aifeng Liu; Jianxin Tang

    For the creation of advanced electrochemical energy storage devices, a large challenge still remains in the designing and engineering of active electrodes with tailored nanoarchitectures and components that provide optimized electrochemical performances. In this study, CoMoO4@polypyrrole nano-heterostructures (NHs) are constructed by wrapping a polypyrrole (PPy) shell around the surface of CoMoO4 nanotubes (NTs) using a self-templated reaction and a subsequent in situ gas-phase polymerization reaction. CoMoO4 NTs possess a large amount of electroactive sites, short ion diffusion pathways, and provide sufficient buffering space. The PPy shell, on the other hand, is conductive, thereby allowing for efficient electron transport and fast charge transfer kinetics. By using their respective advantageous qualities for energy storage, along with the synergistic effect between the CoMoO4 NTs and PPy shell, the CoMoO4@PPy NHs electrode demonstrated improved specific capacitances of 1203 F g−1 at 2 A g−1 and 974 F g−1 at 20 A g−1, as well as 96% capacitance retention after 5000 cycles at 10 A g−1. Furthermore, asymmetric supercapacitor (ASC) fabricated using the CoMoO4@PPy//N-doped carbon NTs (N-CNTs) provided an energy density of 40.3 Wh kg−1 at a power density of 749 W kg−1. These results suggest the considerable potential of CoMoO4@PPy NHs for use in high-performance energy-storage devices.

    更新日期:2020-01-14
  • Complex impedance and Raman spectroscopy of Na0.5(Bi1-xDyx)0.5TiO3 ceramics
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-13
    Manal Benyoussef; Moneim Zannen; Jamal Belhadi; Bouchaib Manoun; Jean-Luc Dellis; Abdelilah Lahmar; Mimoun El Marssi

    In this work structural refinement, complex impedance spectroscopy (CIS) and Raman spectroscopy have been investigated on Na0.5(Bi1-xDyx)0.5TiO3 (xDyNBT) ceramic systems with x = 0, 2, 5 and 15%. The pure NBT, 2DyNBT and 5DyNBT compounds crystallize in a rhombohedral R3c structure while the 15DyNBT composition crystallizes in an orthorhombic Pnma structure. We reported that dysprosium addition affects the phase transition temperatures as well as the dielectric losses. The electrical transport at high temperatures was investigated using the CIS over a wide frequency range (10–106 Hz). The studied samples showed a non-Debye type process, with a short-range relaxation for the pure NBT and a coexistence of both localized and long-range relaxations of charge carriers for the 2DyNBT and 5DyNBT compounds. For the high concentration, 15DyNBT, a short-range relaxation is observed. Moreover, using a brick-layer model we discuss the resistance and capacitance of the different contributors (grain and grain boundaries) in our samples. High temperature Raman spectroscopy investigation was performed in order to follow the temperature evolution of the structural transformations on ferroelectric compounds. Anomalies in the temperature evolution of the vibrational modes are seen to correlate well with the temperature transitions observed from dielectric measurements.

    更新日期:2020-01-14
  • The influence of vacancy defects on elastic and electronic properties of TaSi (5/3) desilicides from a first-principles calculations
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-13
    Jiaying Chen; Xudong Zhang; Caihong Ying; He Ma; Jun Li; Feng Wang; Hui Guo

    As so far, the investigation and application of transition metal silicon-based materials have attracted wide attention. Tantalum-based silicides are one of the most important silicon-based high-temperature materials. But the brittle behavior hinders their wide applications. Here, the influence of vacancies on mechanical properties, brittle/ductile behavior and electronic properties of Ta5Si3 desilicides has been investigated using the first-principles calculations. The vacancy formation energy, elastic constants, elastic moduli, brittle/ductile behavior and electronic behavior of the perfect Ta5Si3 and Ta5Si3 with vacancies were comparatively calculated and discussed, respectively. The thermodynamic data and phonon dispersions demonstrate that the available Ta vacancies in Ta5Si3 can exhibit the better stability than Si atomic vacancies in Ta5Si3 desilicides. In addition, although the vacancies weaken the hardness of the parent Ta5Si3, the vacancies improve the brittle behavior of the parent Ta5Si3. Especially, the Ta-Va1 vacancy in Ta5Si3 induced brittle-to-ductile transition for parent Ta5Si3 desilicides. The electronic structures explain the mechanism of the different vacancies effect on mechanical properties.

    更新日期:2020-01-14
  • Osteogenic silver oxide doped mesoporous bioactive glass for controlled release of doxorubicin against bone cancer cell line (MG-63): In vitro and in vivo cytotoxicity evaluation
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-13
    Muhammad Saif ur Rahman; Muhammad Asif Tahir; Saima Noreen; Muhammad Yasir; Muhammad Bilal Khan; Tahir Mahmood; Ali Bahadur; Muhammad Shoaib
    更新日期:2020-01-13
  • Impact of surfactant ratios on mesostructured MnFe2O4 nanocomposites and their photocatalytic performance
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-13
    Reda M. Mohamed; Adel A. Ismail

    Synthesis of mesoporous MnFe2O4 nanocomposites employing a simple one-pot approach of manganese acetate with ferric nitrate at varying surfactant F127 triblock copolymer molar ratios from 0.0075 to 0.020 was conducted, and their impacts on the physical properties, morphology, crystallinity, and photocatalytic performance were investigated. TEM images of the synthesized mesoporous MnFe2O4 nanocomposites exhibit a quasi-spherical structure with 15-20 nm diameters. The lattice spacing of the MnFe2O4 plane (311) was determined by ∼ 0.256 nm, implying the construction of the cubic MnFe2O4 lattice structure. Interestingly, the obtained mesoporous MnFe2O4 nanocomposites have a large surface area of 227 m2/g for the first time. The total pore volume and average pore diameter were measured ∼6.0 nm and 0.33 cm3/g, respectively. The photocatalytic performance of the mesoporous MnFe2O4 nanocomposites for degradation of ciprofloxacin (CIP) was boosted from 50% to 100% by increasing surfactant F127 molar ratios from 0.0075 to 0.020. The photodegradation rate of the synthesized photocatalyst at 0.020 surfactant F127 molar ratio is higher two times than that of the synthesized one at 0.0075 molar ratio. Such high photocatalytic performance of mesoporous MnFe2O4 nanocomposite at high surfactant F127 molar ratio as compared with other samples might be referred to some effects like generation high •OH concentration, reduction of light scattering as a result of large pore volume and high surface area, or a rapid diffusion of the CIP to the active sites through the mesoporous structure.

    更新日期:2020-01-13
  • Mechanical and thermal properties of Graphene nanoplates (GNPs)/Lithium aluminosilicate (LAS) composites: An analysis based on mathematical model and experiments
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-13
    Guansheng Ma; Yibo Chen; Long Xia; Yufeng Zhan; Bo Zhong; Hua Yang; Longnan Huang; Li Xiong; Xiaoxiao Huang; Guangwu Wen

    The Graphene nanoplates (GNPs)/Lithium aluminosilicate (LAS) glass-ceramic composites were produced by hot-pressing sintering in vacuum condition. The flexural strength, fracture toughness, and thermal conductivity of the composites with different GNPs contents were investigated. The flexural strength and thermal conductivity reached maximum (137.17 ± 6.50 MPa and 1.98 W·m−1·K−1) when the content of GNPs increased to 2 wt%. When the GNPs content reached 3 wt%, fracture toughness reached maximum (5.45 ± 0.20 MPa·m1/2), which has obvious improvement compared with pure LAS glass-ceramic (1–2 MPa·m1/2). The mathematical models were induced to further investigate the effects of the agglomeration and content of GNPs on mechanical and thermal properties of the composite. The results show that the agglomeration of GNPs weakens the mechanical properties of the composites by reducing the energy dissipation of GNPs pull-out. The interfacial thermal resistance between the GNPs and LAS decreases initially followed by increasing, which will affect the thermal conductivity of the composites. This new material system will further expand the field of LAS ceramics in the future.

    更新日期:2020-01-13
  • Significantly enhanced dielectric and energy storage performance of AlN/KNbO3/PVDF sandwich-structured composites via introducing the AlN/PVDF insulating layers
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-13
    Qinzhao Sun; Pu Mao; Lixue Zhang; Jiping Wang; Yingying Zhao; Fang Kang

    Dielectric composites with a high dielectric constant and electric breakdown strength are highly desired for the excellent energy storage behavior of the microelectronic and electric power systems. Sandwich-structured composites with an insulating layer can provide a pathway to improve the dielectric and energy storage performance, and in general, the fillers design and volume control of the insulating layer are very important. Herein, we present a novel designed sandwich-structured aluminum nitride/potassium niobate/poly(vinylidene fluoride) (AlN/KNbO3/PVDF) nanocomposites by the solution-casting and hot-pressing process. The effect of the introduction of an insulating phase AlN in the two outer layers and a different KNbO3 volume fraction in the middle layer on the dielectric properties and energy storage behavior of the sandwich-structured composites were investigated in detail. The results demonstrate that dielectric constant, electric breakdown strength, energy storage density and discharged efficiency of the AlN/KNbO3/PVDF sandwich-structured composites are significantly enhanced. Moreover, a high energy density of 10.54 J/cm3 and a superior discharged energy efficiency of 70% at the electric breakdown strength of 337 MV/m are achieved in the sandwich-structured nanocomposites with 1 vol% KNbO3 in middle layer and with 1 vol% AlN in the outer layers, which are much higher than the conventional single-layered KNbO3/PVDF composites. It is indicated that the introduction of insulating layers in sandwich-structure composites can improve the electric breakdown strength and discharge efficiency, as confirmed by analyzing results of the finite element simulations. This work may provide an effective approach to develop excellent performance dielectric composites for electrical energy storage applications.

    更新日期:2020-01-13
  • Rapid sintering method for highly conductive Li7La3Zr2O12 ceramic electrolyte
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-13
    Li Yang; Qiushi Dai; Lei Liu; Dingsheng Shao; Kaili Luo; Sidra Jamil; Hong Liu; Zhigao Luo; Baobao Chang; Xianyou Wang

    Solid electrolytes could address the increasingly urgent safety and energy density concerns of lithium-ion batteries. Among several kinds of solid electrolytes, Ta-doped Li7La3Zr2O12 (Ta-LLZO) became a research hotspot because of its high Li-ion conductivity and chemical stability against Li-metal and air. However, the preparation of high quality LLZO ceramic electrolyte via conventional air ambient sintering method is still a big challenge due to the serious “Li-loss” and abnormal grain growth phenomenon during the long-time high-temperature sintering process. Herein, a new rapid ultra-high-temperature air ambient sintering method without mother powder (MP) is put forward for the preparation of high quality Ta-LLZO ceramic electrolyte. The rapid sintering strategy can effectively restrain “Li-loss”. Furthermore, it is demonstrated that the none-mother-powder method is superior to traditional mother-powder method. Ta-LLZO ceramics sintered without MP via this rapid sintering method own small grain size, tight grain boundary, dense microstructure and high conductivity. Specifically, the Ta-LLZO ceramic sintered at 1360 °C for 10 min without MP exhibits high conductivity (8.5 × 10−4 S cm−1 at 25 °C) and high relative density (97%), which equate those made by hot pressing sintering method. Without MP, the sintering process can avoid a lot of material waste and simplify the operation process. Moreover, the rapid sintering process can sharply shorten sintering time and reduce energy consumption. Therefore, this low-cost high-efficient sintering strategy can be effectively used in the large-scale production of high-quality Ta-LLZO ceramic electrolyte.

    更新日期:2020-01-13
  • Multi-scale defects in ZnO thermoelectric ceramic materials co-doped with In and Ga
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-13
    Anh Tuan Thanh Pham; Tuyen Luu Anh; Ngoc Kim Pham; Hanh Kieu Thi Ta; Truong Huu Nguyen; Dung Van Hoang; Hoa Thi Lai; Vinh Cao Tran; Jong-Ho Park; Jae-Ki Lee; Sungkyun Park; Ohtaki Michitaka; Su-Dong Park; Hung Nguyen Quang; Thang Bach Phan
    更新日期:2020-01-13
  • Effect of Si alloying content on the microstructure and thermophysical properties of SiC honeycomb/Al–Mg–Si composites prepared by spontaneous infiltration
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-13
    Zhejian Zhang; Bangzhi Ge; Wenqi Xie; Zhilei Wei; Wanli Yang; Yanjun Li; Zhongqi Shi

    Directional SiC honeycomb/Al–Mg–Si composites with different Si alloying contents (2–12 wt%) were prepared by spontaneous infiltration. The effect of Si alloying content on the phase composition, microstructure and thermophysical properties of the composites were investigated. The results showed that the equilibrium contact angles between the SiC ceramic and different Al alloys were in the range of 60.5–72° at 1273 K, benefitting the infiltration process. Meanwhile, the Si alloying content not only changed the phase composition of the composites, but also influenced the microstructure of the infiltrated Al alloys, especially changing the microstructure of Mg2Si phase from small flake-like eutectic phase (Mg2SiE) to large polygon-like primary phase (Mg2SiP). Due to the anisotropic feature of SiC honeycomb and the tunable phase composition and microstructure of the infiltrated Al alloys, the composites exhibited anisotropic and tailored thermophysical characteristics. The composites with the Si alloying content of 7 wt% possessed the optimum properties, with the highest TC of 140.95 W m−1 K−1 in axial direction and relatively low CTE of 11.1 × 10−6/K in radial direction. Additionally, the reduction of anisotropy of composites’ CTEs in two principal directions with the increase of Si alloying content was also discussed.

    更新日期:2020-01-13
  • Facile synthesis of g-C3N4/BiOClxI1-x hybrids with efficient charge separation for visible-light photocatalysis
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-13
    Xinyue Sun; Yi Du; Zhongfu Li; Shunwei Chen; Yibing Feng; Nan Jiang; Yang Liu; Jiajia Wang; Haoyu Li

    At present, most common catalysts are faced with the problem of high cost and only visible light response. Graphitic carbon nitride (g-C3N4) consists of elements C and N that are sufficiently abundant in the world and has visible light responses, but the electron-hole recombination rate of this photocatalyst is high. In this work, we directly prepare a series of g-C3N4-bismuth oxyhalides composites via facile in-situ deposition. Bismuth oxides with different chloro-iodine ratios (BiOClxI1-x) are prepared, followed by g-C3N4 deposition, setting up interfaces and improving photogenic charge carriers transfer. By testing the compositions, Cl:I = 8:2 in BiOClxI1-x and 10% of g-C3N4 doping amount enable the best photocatalytic performance of the samples. Under visible light irradiation, the degradation rate of rhodamine B (RhB) reaches 99% within 40 min. Through a variety of tests, the photogenerated hole (h+) and superoxide radical (•O2−) are found to play key roles in the degradation process. Cl element doping and heterojunction building improve the photocatalysis capacity of g-C3N4 and broaden the visible-light response of pure BiOI.

    更新日期:2020-01-13
  • Effect of SiO2 content on Y-TZP/Al2O3 ceramic-nanocomposite properties as potential dental applications
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-13
    Seyedhamidreza Rahimi; Fariborz SharifianJazi; Amirhossein Esmaeilkhanian; Mostafa Moradi; Amir Hossein Safi Samghabadi

    Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) have been widely applied in fixed partial prostheses as well as dental uses i.e. a substructure for crowns. However, Y-TZP has limited applications, which is due to the presence of defects in its microstructure introduced during the manufacturing process. Accordingly, due to Y-TZP limitations, the novel (X)Y-TZP- 20Al2O3-(80-X) SiO2 (X = 65, 70 and 75) ceramic nanocomposites were successfully fabricated via the powder metallurgy method. X-ray diffraction (XRD) patterns of commercial powders showed the stabilization of monoclinic zirconia (ZM) by increasing the silica content. In order to determine the fracture load and micro-bending strength, the three-point bending test was used at ambient temperature. The fractography analysis was applied to evaluate the fracture behavior of the crack path. The Scanning electron microscopy (SEM) test was performed to study the particle size of powders and monitor the fracture surface. The obtained phases prior to the failure of ceramics were alumina, tetragonal-zirconia, and monoclinic-zirconia. Both tetragonal-zirconia and alumina were presented on the cross-section of cracked samples. The obtained results showed that the specimen with 15% silica showed the best thermal properties as well as micro-shear bonding and bending strength which prove its potential for dental applications.

    更新日期:2020-01-13
  • Physical and in-vitro evaluation of ɛ-Fe3N@Fe3O4 nanoparticles for bioapplications
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-13
    Asnit Gangwar; S.S. Varghese; A. sharma; Sher Singh Meena; C.L. Prajapat; M.K. Viswanadh; K. Neogi; M.S. Muthu; N.K. Prasad

    Recently the core-shell nanostructures are employed for various applications. In this trend, ɛ-Fe3[email protected]3O4 (INIO) magnetic nanoparticles (core/shell structured) were synthesized by a solvothermal process followed by calcination. The X-ray diffraction (XRD), selected area diffraction pattern (SAEDP), X-ray photoelectric spectroscopy (XPS) and Mössbauer spectroscopy validates the formation of the spherical core-shell structure of the ɛ-Fe3[email protected]3O4 nanoparticles having size range (5–32 nm). The saturation magnetization values for the sample at ±2 T field were around 128 and 99 Am2/kg at 5 and 300 K respectively. The values were higher than the known values for iron oxide nanoparticles. The pluronic acid (F-127) based ferrofluid of these nanoparticles, displayed excellent stability (Zeta potential values) and good heating ability (external AC magnetic fields). The best specific loss power was found to be around 90 W/g at 23 mT field. The cell viability with human lung adenocarcinoma A549 cells was observed to be 88 and 85% at 1 mg/mL for these nanoparticles after the treatment for 24 and 48 h respectively.

    更新日期:2020-01-13
  • Effects of ultrafine WC on the densification behavior and microstructural evolution of coarse-grained WC-5Co cemented carbides
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-13
    Rengui He; Bin Li; Pinghua Ou; Chenghui Yang; Hailin Yang; Jianming Ruan

    The effect of ultrafine WC on the macroscopic shrinkage behavior and microstructural evolution of coarse-grained WC-Co cemented carbides during sintering was studied. WC-Co composite powders containing mixture of ultrafine (300 nm) and coarse (6.0 μm) WC powders were prepared using a novel sol-gel process. The results indicate that ultrafine WC addition enhanced shrinkage in the composite powder compacts during solid state sintering, while its influence on densification process in liquid-phase sintering can be ignored. The microstructural evolution confirmed that ultrafine WC addition promote the spreading of cobalt binder and the formation of WC-Co agglomerate in initial state of sintering. And, ultrafine WC addition resulted in a more uniform densification in the solid state sintering. Mechanisms of the enhanced shrinkage include the accelerated spreading of Co due to shortened diffusion distances and the increased surface diffusion velocity, and the activated sintering of WC skeleton due to grain boundary sliding.

    更新日期:2020-01-13
  • Influence of Cr and W addition on microstructure and mechanical properties of multi-step sintered Mo2FeB2-based cermets
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-13
    Hao Wu; Yong Zheng; Jiajie Zhang; Guotao Zhang; Zheng Ke; Xiangyu Xu; Xuepeng Lu

    The influence of Cr and W addition on microstructure and mechanical properties of Mo2FeB2-based cermets, prepared by multi-step sintering, is systematically evaluated by XRD, SEM, EDS, and TEM. After liquid-phase sintering, the final microstructure of Cr-doped Mo2FeB2-based cermets is similar to that of traditional Mo2FeB2-based cermets. The cermet, with 2.5% Cr content, exhibits superior comprehensive mechanical properties, i.e., Rockwell hardness, transverse rupture strength (TRS) and fracture toughness of 87.6 HRA, 2179 MPa and 21.7 MPa m1/2, respectively. In contrast, for W-doped Mo2FeB2-based cermets, a large amount of W-enriched (Mo,Fe,W)3B2 solid solutions precipitated around undissolved Mo2FeB2 particles, resulting in the formation of black core/gray rim structure. Particularly, a transition layer, with several atomic layer thickness, is observed between (Mo,Fe,W)3B2 rim phase and Fe-based binder phase, which corresponds to B-deficient (Mo,Fe,W)3B2−x orthorhombic boride phase. Moreover, the lattice mismatch between (Mo,Fe,W)3B2 and (Mo,Fe,W)3B2−x is found to be 1.9%. When doped with 5 wt% W, Mo2FeB2-based cermet exhibit superior comprehensive mechanical properties with Rockwell hardness of 84.6 HRA, TRS of 2088 MPa and fracture toughness of 24.4 MPa m1/2. The increase of fracture toughness (KIC) can be ascribed to the presence of W-rich transition layer.

    更新日期:2020-01-13
  • Infrared barriering behavior of reduced graphene oxide aerogel/ antimony tin oxide-polyaniline hybrids
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-13
    Hongan Li; Magdalena Sztukowska; Hongli Liu; Hongyuan Dong; Dorota Małaszkiewicz; Hai Zhang; Xiao Wang

    Our previous work reported for the first time that antimony tin oxide (ATO) nanoparticles were prepared by using reduced graphene oxide aerogels (rGOA) three-dimensional network as scaffolds. In this study, we encapsulated the hybrid aerogels as a whole by conducting polyaniline (PANI) to investigate the effect of the introducing of PANI on microstructure and performance of rGOA/ATO-PANI hybrids. Characterization of the as-prepared samples were performed by scanning electron microscopy (SEM), fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), Raman spectroscopy, ultraviolet visible near infrared spectroscopy (UV–VIS–NIR) and compressive stress. The electrochemical performances of hybrids were also investigated as well. The results showed that PANI was successfully grafted on rGOA/ATO and formed a compact film, which could further improve the conductivity of the hybrids and infrared absorption performance. The PANI had crystalline phases, and corresponding diffraction peaks were found in rGOA/ATO-PANI, which further indicated that PANI grafted on the surface of rGOA/ATO. The mechanical, electrochemical, infrared barriering performance of rGOA/ATO-PANI were improved as well.

    更新日期:2020-01-13
  • Eco-friendly and cost-effective synthesis of ZnO nanopowders by Tapioca-assisted sol-gel route
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-12
    Willians Lopes de Almeida; Fabiano Severo Rodembusch; Nilson S. Ferreira; Vânia Caldas de Sousa

    This study presents a low-cost method for obtaining nanometric zinc oxide (ZnO) by sol-gel route assisted by cassava starch (Tapioca). In this procedure, ZnO nanopowders (∼20 nm and 59 nm according to XRD) were obtained after 2 h of calcination at 500oC. The cassava starch played a fundamental role during the sol-gel synthesis allowing the obtention of ZnO nanopowders (ZnOT) with crystallite size three times smaller than the ones without cassava starch (ZnO). SEM and TEM images corroborate the idea that Tapioca inhibited crystal growth in ZnOT when compared to the ZnO obtained from the same methodology. The synthesis of the obtained ZnOT was studied by FTIR and the results point to a possible interaction between zinc cations and C–O groups of glucose molecule that arises from the starch hydrolysis; thus, showing that Tapioca works as a good chelating agent, as well as presenting a very low cost.

    更新日期:2020-01-13
  • Synthesis of in-situ mullite foam using waste rice husk ash derived sol by slip-casting route
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-12
    S.K.S. Hossain; Ram Pyare; P.K. Roy

    In this study, mullite foam ceramic is synthesized via a simple slip-casting method without using any pore producing additive or agent, in order to avoid the emission of greenhouse gases (mainly CO2) from the matrix. Waste rice husk ash (RHA) extracted sol (solid contain ∼7.5 wt%) as an alternative of conventional silica sources along with active alumina is used for the preparation of slip-casting slurry. About 22 wt% solid containing slurry is casted in the plaster of paris (POP) mold. The casting mass is dried at 110 °C and fired at 1100 °C, 1200 °C, 1250 °C, 1300 °C, 1350 °C, and 1400 °C. Several properties like phases, microstructure, porosity, density, mechanical strength, and thermal conductivity are comprehensively investigated with the foam samples. At 1250 °C fired sample is retained mullite dominating phase in the matrix. The single-phase mullite is formed at 1300 °C fired sample with 75.99% total porosity, 11.07 MPa compressive strength, and thermal conductivity of 0.153 W/m·k. Furthermore, the strength value and thermal conductivity are increased and porosity is reduced with the increasing firing temperature. The obtained results exhibit that the waste RHA derived sol is capable to produce low-temperature in-situ mullite foam through slip-casting route without generating the pollutants (mainly CO2↑).

    更新日期:2020-01-13
  • Surface integrity, fatigue performance and dry sliding wear behaviour of Si3N4–TiN after wire-electro discharge machining
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-12
    V.P. Srinivasan; P.K. Palani

    Silicon nitride–titanium nitride (Si3N4–TiN) ceramic composite was machined by wire-electro discharge machining (WEDM) to characterize the surface integrity and to investigate its effect on fatigue performance. Dry sliding wear behaviour of Si3N4–TiN sliding against EN32 steel was also tested. The polished and machined surfaces were examined for finding the hardness. The wire-EDM cut surface was examined with scanning electron microscope (SEM) for obtaining its microstructure. The wire-EDM of silicon nitride–titanium nitride produced a rough recast surface with different types of defects like micro-cracks, micro-pores, globules, droplets and surface craters. The material deposition to work specimen after machining was scrutinized by EDAX composition analyzer. The polished surface and wire-EDM cut surface were examined for determining the fatigue performance and it was observed that a deficiency of 25–35% in fatigue life in wire-EDM cut surface than that of the polished surface. Also, the wire-EDM cut surface exerts very high tensile residual stress compared to the polished surface. From the results, it is evident that the polished surface exhibits better surface finish and fatigue life, higher wear resistance and micro-hardness than that of the machined surface.

    更新日期:2020-01-13
  • Fabrication of amorphous silica coating on graphite substrate by laser cladding
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-11
    Ning-ning Ma; Jian Chen; Zheng-ren Huang; Ya-jie Li; Meng Liu; Xue-jian Liu; Zhong-ming Chen

    An amorphous silica coating was prepared on graphite substrate by laser cladding to improve the ablation resistance using a silicon interlayer as a transition layer. The laser cladding processes were carried out in the air atmosphere, which can simplify production conditions. The amorphous silica coating is uniform and dense, combining well with the graphite substrate. There is no obvious boundary between the silicon transition layer and the silica coating. Ablation test demonstrates that the silica coating has excellent performance compared to the uncoated graphite, and the silica-coated graphite has a weight loss of 2.17% after 80 min. After the ablation test, the silica coating still has a uniform and dense microtopography.

    更新日期:2020-01-13
  • CdTe quantum dots prepared using herbal species and microorganisms and their anti-cancer, drug delivery and antibacterial applications; a review
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-11
    Maryam Akbari; Mahdi Rahimi-Nasrabadi; Saeid pourmasud; Mohammad Eghbali-Arani; Hamid Reza Banafshe; Farhad Ahmadi; Mohammad Reza Ganjali; Ali Sobhani nasab

    One of the developing areas of nanotechnology is the production and application of nanoscale materials, with large surface/volume ratios, which provides them with the specific properties. Cadmium telluride (CdTe) is a typical nanomaterial, which has been the subject of various studies due to its large bandwidth and excitation binding energy, which make it suitable for various purposes like anti-inflammatory, wound healing, antioxidant, antifungal and antibacterial applications. The large quantities toxic chemicals and harsh conditions required for preparing CdTe, led to great interest in developing green methods. This review provides a comprehensive overview of the research on the green biological synthesis and characterization of CdTe. It is also important to consider the increasing interest in the area of production of CdTe QDs (Quantum dots) for drug delivery, bioimaging and anti-cancer applications. One green approach for producing CdTe nanocrystals is the application of metabolic activity of living organisms. Intra and extra-cellular biosynthesis can occur through a biomimetic approach based on feeding organisms with cadmium and telluride precursors. Yet there are huge gaps in our knowledge on the toxic effects of nano-scale CdTe particles on single organisms and the mechanism there of and to guarantee the safe application of CdTe, further work needs to be done on assessing the long-term effects of nano-sized CdTe particles at low quantities.

    更新日期:2020-01-13
  • Core-shell structured CaO aggregate prepared by granulating with Al chelating compound and its hydration resistance
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-11
    Jinhu Wang; Yaowu Wei; Bingrong Li; Mengrui Li; Nan Li

    A preparation method of core-shell structured CaO aggregates and its hydration resistance were investigated in this paper. Ca(OH)2 granules were obtained by granulation method and then soaked in Al chelating compound (hereinafter called ACC) ethanol solution, after that Ca(OH)2 granules were fired at different temperatures. The obtained CaO granules were characterized by measurements of crystalline phase formation, bulk density, apparent porosity, hydration resistance, pore size distribution, cylindrical crushing strength and microstructural analysis. It can be seen from the results that core-shell structured CaO granules with excellent hydration resistance can be prepared after treated with ACC and a protective shell layer was found on the surface of the granules. The ACC promoted the liquid phase sintering of CaO granules, which led to the grain growth and increased the density of granules. CaO grains were bonded by the tricalcium aluminate (C3A) and the apparent porosity of the aggregate was reduced after heating, that decreased the contact area of CaO with water vapor.

    更新日期:2020-01-13
  • Precisely controlled carbothermal synthesis of spherical β-Si3N4 granules
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-11
    Si-Yuan Sun; Zhi-peng Xie; Ke-Xin Chen

    High purity spherical β-Si3N4 particles were synthesized via an efficient carbothermal reduction–nitridation strategy by precise regulation. The results showed that nano-sized reactants with an appropriate ratio was significant for acquiring Si3N4 granules with pure β phase. c/a,b-axis length ratio of the β-Si3N4 particles could be adjusted by using various additives. Fine spherical β-Si3N4 particles can only be obtained with the help of CaO additive by L-S mechanism. Moreover, variations of underlying reaction mechanisms when changing the raw materials were comprehensively revealed. Owing to the high purity and fine spherical morphology, as-obtained β-Si3N4 powders are promising fillers for preparing resin-based composites with high thermal conductivities.

    更新日期:2020-01-13
  • Synthesis of V2O5-Doped and low-sintered NiCuZn ferrite with uniform grains and enhanced magnetic properties
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-11
    Xueying Wang; Dainan Zhang; Gang Wang; Lichuan Jin; Jie Li; Yulong Liao; Huaiwu Zhang; Shiyuan Wang

    NiCuZn ferrites with high permeability and low magnetic loss have great application potential in high-frequency electronics. In this study, the excellent magnetic properties of (Ni0.2Cu0.2Zn0.6O)1.03(Fe2O3)0.97 ferrites are explored by doping low-melting point V2O5. The results demonstrate that the introduction of V2O5 can promote grain growth, reduce pores between grains, and obtain a denser microstructure of NiCuZn ferrites. NiCuZn ferrites with high permeability (μ’≈693.2), high saturation magnetic flux density (Bs = 325.1 mT), high remanence (Br = 174.3 A/m), high Q value (∼47.60), and low coercivity (Hc = 69.06 A/m) are obtained when the samples are sintered at 900 °C. However, when excessive V2O5 is added, the presence of the non-magnetic V2O5 liquid phase weakens the magnetic properties and deteriorates the grain uniformity. A dense and uniform NiCuZn ferrite sample with excellent magnetic properties can be obtained by doping 0.50 wt% V2O5. The results indicate that V2O5 can be a good candidate for low-temperature sintering.

    更新日期:2020-01-13
  • Mechanical activation for soft synthesis of bismuth silicates
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-11
    Yu. Belik; T. Kharlamova; A. Vodyankin; V. Svetlichnyi; O. Vodyankina

    Bismuth silicates are intensively investigated for their applications as condensers, sensors, data storage and optical devices, and photocatalysts. An increased interest in bismuth silicates stimulates developing new methods of their preparation. Synthesis of complex compounds in dry solid powder mixtures in the course of mechanical activation with the absence of any solvent and long-time high-temperature treatment is an attractive method in terms of “green” chemistry and time-effective one-stage approaches. In the present study, mechanical treatment of the mixtures of bismuth(III) compounds and silica with different Bi/Si atomic ratio is applied to prepare the Bi2SiO5, Bi4Si3O12, and Bi12SiO20 bismuth silicates. The effect of Bi precursor and milling time on the bismuth silicate formation in the course of mechanical treatment is investigated. The effect of subsequent thermal treatment of the activated mixture on the phase composition of the samples is also considered. The results obtained show the opportunity for the mechanochemical synthesis of γ-Bi12SiO20 and metastable Bi2SiO5 directly in the course of milling of α-Bi2O3 and SiO2·nH2O mixtures at room temperatures. The formation of target Bi4Si3O12 is shown to occur via the solid-phase reactions between Bi2SiO5 formed during the milling and silica unreacted in the course of subsequent thermal treatment at moderate temperature (<600 °C). Based on the results obtained, the possible pathways of phase evolution during the mechanical activation and subsequent thermal treatment are proposed.

    更新日期:2020-01-13
  • Stress design of a laminated MoSi2/Cr coating under particle impact and high temperature environment
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-11
    Dou Hu; Qiangang Fu; Lei Zhou; Yuyu Zhang; Guangpeng Zhang

    A protective laminated MoSi2/Cr coating was deposited on SiC coated carbon/carbon composites by plasma spraying. Under particle impact environment, the Cr interface layer could relax stress concentration and rapidly relieve impact stress by 30% in the laminated coating layer by layer, thus keeping inner layers intact according to the experiment and simulation results. Under thermal shock condition, sudden change of thermal stress induced by the Cr interface layer could also help change the crack propagation path, thus keeping the coated sample without mass loss after 30 thermal cycles between 1500 °C and room temperature. After 157 h oxidation at 1500 °C in static air, the Cr interface layer could also inhibit the formation of penetrating cracks and convert the oxidation mechanism of parabolic mass loss law in MoSi2 coating to linear mass loss law at the final oxidation stage.

    更新日期:2020-01-13
  • Synthesis, characterization, mechanical and biological properties of biocomposite based on zirconia containing 1393 bioactive glass with hydroxyapatite
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-11
    Sushma Yadav; Preetam Singh; Ram Pyare

    Zirconia substituted 1393 bioactive glass and hydroxyapatite containing biocomposite were synthesized and sintered to investigate their effect on bioactivity and cell proliferation. The substituted bioactive glass was synthesized by the sol-gel method. Afterward, hydroxyapatite (synthesized by co-precipitation method) was mixed with bioglass in different ratios and sintered at two temperatures (600 °C and 1000 °C) to study the effect on phase, bioactivity, cell proliferation, and mechanical strength. In terms of bioactivity, biocomposites show dissolution and apatite formation in SBF. An increase in density and compressive strength was observed due to the incorporation of glass with hydroxyapatite. Cell proliferation was studied by MTT assay over MG63 cell lines and results indicate that an increase in sintering temperature promotes cell proliferation and found maximum for BG_H80 (sintered at 600 °C) and BG_H50 (sintered at 1000 °C). Due to an increase in sintering temperature crystallization in composites improved the density, compressive strength and cell proliferation and became suitable material for biomedical application.

    更新日期:2020-01-13
  • Synthesis of BaTiO3 nanoparticles by sol-gel assisted solid phase method and its formation mechanism and photocatalytic activity
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-11
    Lijie Mi; Qiankang Zhang; Haiwang Wang; Zhengjie Wu; Yongxiang Guo; Yuanming Li; Xinyu Xiong; Kefan Liu; Weijie Fu; Yuan Ma; BingZhu Wang; XiWei Qi

    In this paper, a new sol-gel-assisted solid-phase method for the preparation of nano BaTiO3 ceramics is proposed to solves the shortcomings of too high temperature in solid-phase preparation and NO2 pollution produced by sol-gel method. The TiO2 precursor gel is used to encapsulate BaCO3, which can effectively reduce the temperature during calcination. In this study, XRD, FT-IR, XPS, TEM, SEM and TGA-DSC were used to explore the structure and evolution of samples at different stages. In addition, the crystallization and growth process of BaTiO3 were further studied. Then the energy band structure and electron hole recombination of different samples were analyzed by UV–Vis and PL spectra. Finally, the photocatalytic activity of different samples was investigated by photolytic water experiment. The results showed that BaTiO3 was initially generated at 600 °C and pure phase BaTiO3 was generated at 800 °C. In the photolytic water experiment, the samples calcined at 700 °C showed the best photocatalytic performance, with a hydrogen production rate of 43.74 μmol/g/h.

    更新日期:2020-01-13
  • Comparative study of TiAlN coatings deposited by different high-ionization physical vapor deposition techniques
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-11
    Liangliang Liu; Wei Tang; Lin Zhou; Zhongcan Wu; Qingdong Ruan; Xiaoyuan Li; Abdul Mateen Qasim; Suihan Cui; Tijun Li; Ricky KY. Fu; Xiubo Tian; Zhongzhen Wu; Paul K. Chu

    In physical vapor deposition (PVD), the energy and incident angle of ions can be adjusted easily by applying an electromagnetic field so that coatings with different structures and properties can be produced. In this work, several high-ionization coating techniques are employed to deposit TiAlN coatings to compare the effectiveness of each technique and resulting coating properties. The continuous high-power magnetron sputtering (C-HPMS) technique shows advantages in the deposition rate and coating performance. In addition, a deposition rate of 400 nm/min is achieved by C-HPMS, whereas those of high power impulse magnetron sputtering (HiPIMS) and arc ion plating (AIP) are 85 nm/min and 225 nm/min, respectively. The coating also shows a particle-free and dense morphology with a smaller surface roughness of 22.4 nm. Owing to efficient ionization, the TiAlN coating deposited by C-HPMS has a high hardness of 33.2 GPa which is comparable to those prepared by AIP and HiPIMS but with small residual stress. The results provide valuable information on how to choose the proper techniques and parameters to produce coatings with the desirable adhesion strength, tribological properties, as well as corrosion resistance.

    更新日期:2020-01-13
  • Facile fabrication of SrAl2O4:Eu2+, Dy3+ hollow microsphere by a chemical induction self-transformation process
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-11
    Dong Xu; Dajuan Lv; Fei Guo; Guotan Zhang; Honghai Wang; Liangming Xiong; Jie Luo; Weiming Wang; Hongyi Jiang

    For the first time, SrAl2O4:Eu2+, Dy3+ hollow microsphere is successful synthesized via a newly developed sol-gel synthetic method combined with the self-transformation process of chemical induction. In this approach, researchers are able to get this gel in seconds, and after it is immersed in the isopropanol at the temperature of 60 ºC, the SrAl2O4:Eu2+, Dy3+ hollow microsphere precursors can be synthesized through the self-transformation of chemical induction. The outer surface of SrAl2O4:Eu2+, Dy3+ hollow precursors (diameter in 1–2 μm) is similar to sea urchins, which consists of randomly clustered and interconnected nanoplatelets. SrAl2O4:Eu2+, Dy3+ hollow microsphere phosphors can be synthesized by calcining SrAl2O4:Eu2+, Dy3+ hollow microsphere precursors at an appropriate temperature. The optimum calcination temperature of the SrAl2O4:Eu2+, Dy3+ hollow microsphere phosphors is 1050 ºC, which have a well hollow-core construction and sea urchin-like outer surface. The photoluminescence spectra and luminance decay analysis indicate that the SrAl2O4:Eu2+, Dy3+ hollow microsphere phosphors have satisfactory persistent phosphorescence. The specific surface area, mean diameter of pores, as well as pore volume of the sample heated at 1050 ºC are 139.52 m2/g, 1.29 cm3/g and 37.08 nm, respectively.

    更新日期:2020-01-13
  • Synthesis of Fe3O4 nanoparticles of various size via the polyol method
    Ceram. Int. (IF 3.450) Pub Date : 2020-01-11
    Ah Hyun Oh; Hye-Yeong Park; Yeon-Gil Jung; Sung-Churl Choi; Gye Seok An

    The superparamagnetic Fe3O4 magnetic nanoparticles have attracted a considerable amount of attention in biomedical fields such as drug delivery, MRI contrast, and hyperthermia treatment. To enable these varied applications of Fe3O4 nanoparticles, it is essential to synthesise them in various sizes, from several nanometres to several hundred nanometres. The synthesis of superparamagnetic Fe3O4 nanoparticles was carried out using the polyol method, which is based on the polar polyol and synthesis was attained via a stepwise phase transformation. The concentration of sodium acetate (NaOAc) used to control the rate of hydrolysis of iron precursor and the molar ratio of the iron precursor and water were controlled to vary the size of Fe3O4 particles. It was found that the particle size decreased as the concentration of NaOAc increased and decreased even more when the molar ratio of the iron precursor was decreased. Particles ranging from 11 nm to 338 nm in size were produced using this method. The correlation between starting materials, particle size, and morphology was thus investigated from these results.

    更新日期:2020-01-13
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