Tunable whole visible region color emission, enhancing emission intensity and persistent performance of a self-activated phosphor:Na2CaSn2Ge3O12 Ceram. Int. (IF 3.057) Pub Date : 2018-07-18 Xinquan Zhou, Guifang Ju, Yang Li, Yahong Jin, Haoyi Wu, Yihua Hu
The composition and tunable luminescence properties of garnet phosphors are flexible because of their unique A3B2C3O12 structure. Garnet phosphors with tailored luminescence properties can be designed by varying in the A, B, and C cation sublattices. In this research, the self-activated long-persistent phosphor (LPP) Na2CaSn2Ge3O12 (NCSG) was successfully synthesized by a solid-state method. A series of dopants (Mn2+, Pr3+, Tb3+, and Dy3+) were selected as single-component emitters to tailor the emission color of the NCSG phosphor. NCSG emits in yellow at ~ 560 nm and in the near-infrared at ~ 790 nm with long-persistent luminescence (PersL). By doping with these ions, the PersL of the NCSG was significantly improved, and various colors covering the entire visible region from violet to the near-infrared were obtained. The trap types and depths were examined by electron paramagnetic resonance (EPR) and the thermo-luminescence (TL) glow curves. The EPR signals revealed that oxygen vacancies are the trap centers. The TL glow curves showed that the intrinsic and extrinsic luminescence centers both act as charge carrier recombination centers. Furthermore, the PersL mechanism of the NCSG and NCSG:R (R = Mn2+, Pr3+, Tb3+ and Dy3+) phosphors was discussed in detail. The strategies employed in this work can be an effective way to fabricate new multi-wavelength, garnet-based LPPs with potential applications.
Dielectric, conductivity and piezoelectric properties in (0.67-x)BiFeO3-0.33BaTiO3-xSrZrO3 ceramics Ceram. Int. (IF 3.057) Pub Date : 2018-07-18 Nianshun Zhao, Huiqing Fan, Xiaohu Ren, Jiangwei Ma, Jie Bao, Yijun Guo, Yunyan Zhou
A new type of (0.67-x)BiFeO3-0.33BaTiO3-xSrZrO3 (x = 0.00, 0.02, 0.04, 0.06, 0.08 wt%, abbreviated as SZ100x) ternary lead-free relaxation ceramic was prepared by a conventional mixed-oxide sintering method. The surface texture, dielectric, impedance, electrical conductivity and piezoelectric were studied in detail. It was found that three kinds of compounds are completely dissolved into a single structure with a pseudo-cubic (Pc) phase. Besides, scanning electron microscopy figures indicated that proper doping can make the ceramic system more compact while excessive SrZrO3 content would cause abnormal growth of the grain. In addition, the analysis of dielectric temperature spectra shown that the dielectric peaks gradually widen with an increase in x and the x = 0.04 sample has the strongest relaxation characteristics. Importantly, doping of SrZrO3 can greatly improve the impendence and electrical insulation characteristics. Besides, high strain value of 0.24% with the normalized strain value of 400 pm/V was obtained at x = 0.04, which was related to the relaxation response of the polar nanoregion under electric field.
Dosimetric properties of ZrO2 and ZrO2:Sm3+ exposed to beta rays Ceram. Int. (IF 3.057) Pub Date : 2018-07-18 H.S. Lokesha, Naveen Chauhan, K.R. Nagabhushana, Fouran Singh
This work investigates thermoluminescence (TL) and optically stimulated luminescence (OSL) properties of ZrO2 and ZrO2:Sm3+ (1 mol%) synthesized by solution combustion method. XRD measurement suggested that both the samples exhibit monoclinic phase. The average crystallite size measured using scanning electron microscopy is found to be ~ 60 nm. TL glow curve of ZrO2 had a prominent peak at 429 K and a less prominent (or smaller) peak at 510 K. On the other hand, ZrO2:Sm3+ had a broad glow peak at 460 K. TL glow curve intensity of all the peaks is found to increase linearly with beta dose (upto 16.4 Gy) for both samples. TL Trapping parameter are analyzed after deconvolution of TL glow curves using CCDA method. The recombination sites of glow peaks are investigated through TL emission spectrum. The 429 K peak show a band at 500 nm is attributed due to oxygen vacancies. Continuous Wave–OSL measurements (CW-OSL) suggests a linear increase in the intensity with beta dose for both samples. The decay curves are deconvoluted by using general order kinetics. CW–OSL decay curve has shown two components contributing to the OSL signal. The photoionization cross sections of ZrO2 and ZrO2:Sm3+ for two components are found to be 1.187 × 10−16, 6.255 × 10−18 and 1.303 × 10−16, 8.842 × 10−18 cm2 respectively. Linearly Modulated - OSL (LM-OSL) of ZrO2 exhibit broad peak and it is deconvoluted into 4 peaks. These results suggests the possibility of choosing suitable activator for development of new TL dosimeters.
Study of crystallographic, thermal and electrical properties of (Bi2O3)1-x-y(Tb4O7)x(Gd2O3)y electrolyte for SOFC application Ceram. Int. (IF 3.057) Pub Date : 2018-07-18 İsmail Ermiş, S.P.S. Shaikh
In this study, (Bi2O3)1-x-y(Tb4O7)x(Gd2O3)y (xTbyGdSBi) ternary solid solutions were synthesized via the solid-state synthesis technique. The phase structures of electrolytes were defined by X-ray powder diffraction (XRD) and differential thermal analysis/thermal gravimetric techniques (DTA/TG). The total electrical conductivity (σT) was measured with respect to the test temperature and doping concentration by using four-point probe technique (4PPT). Measurement results showed that δ-phase was obtained in test specimens and the conductivity of the electrolytes increased with increasing test temperature and decreasing amount of Gd2O3. The 5Tb5GdSBi ternary system had the highest conductivity value of 3.88 × 10−1 S cm−1 at 850 °C. Compared to the literature, the results from this study are reasonably promising.
Effect of the Al2O3/SiO2 Mass Ratio on the Crystallization Behavior of CaO-SiO2-MgO-Al2O3 Slags Using Confocal Laser Scanning Microscopy Ceram. Int. (IF 3.057) Pub Date : 2018-07-18 Zhanjun Wang, Il Sohn
The crystallization behavior of a CaO-SiO2-MgO-Al2O3 slag system with varying Al2O3/SiO2 mass ratios from 0.03 to 1.10 has been investigated using a confocal laser scanning microscopy (CLSM). The resulting continuous cooling transformation (CCT) and time-temperature-transformation (TTT) curves showed that the initial crystallization temperature increased and the incubation time for crystallization slightly decreased with increasing Al2O3/SiO2 ratio. The crystal growth rate first increased and then decreased with decreasing isothermal temperature. X-ray diffraction (XRD) analysis suggested that Ca2MgSi2O7 or Ca3MgSi2O8 precipitated as the primary phase at lower Al2O3/SiO2 ratios, while the Ca2Al2SiO7 phase was preferred at higher Al2O3/SiO2 ratios. The observed crystalline phases correlated well with the expected thermodynamic predictions from FactSage. In addition, structural analysis using 27Al magic angle spinning nuclear magnetic resonance (27Al MAS-NMR) microscopy of the as-quenched slags indicated the presence of a higher ratio of tetrahedral [AlO4]5-structural units with increasing Al2O3/SiO2 ratio, which enhanced the polymerization of tetrahedral [AlO4]5- and [SiO4]4- structural units to form Ca2Al2SiO7.
A hydrothermal etching route to synthesis of 2D MXene (Ti3C2, Nb2C): enhanced exfoliation and improved adsorption performance Ceram. Int. (IF 3.057) Pub Date : 2018-07-18 Chao Peng, Ping Wei, Xin Chen, Yongli Zhang, Feng Zhu, Yonghai Cao, Hongjuan Wang, Hao Yu, Feng Peng
2D MXenes have attracted extensive attentions owing to their anisotropy, high conductivity and other extraordinary properties. The popular preparation method of MXenes usually involves HF in high concentrations, which has seriously restricted their pervasive applications. In this work, a new hydrothermal route with low-toxicity etching agents (NaBF4, HCl) was used to synthesize Ti3C2 MXene (h-Ti3C2). Compared with the Ti3C2 prepared by the traditional HF etching method (t-Ti3C2), the h-Ti3C2 has the higher c lattice parameter, larger interlayer distance and larger BET specific surface area, because of the slow release mechanism during the hydrothermal process. The hydrothermal etching method not only avoided the use of high-concentration HF, but also was more efficient to prepare Ti3C2 flakes. Moreover, the hydrothermal etching route can be extended to other MXene materials, e.g. Nb2C. We demonstrated that the h-MXenes have better adsorption performance of methylene blue and methyl orange dyes. The hydrothermal etching route proposed in this study enabled the environmental benign and high efficiency exfoliation of MXenes, displaying the promise to facilely prepare 2D MXenes and paving a way to their widespread applications.
Electrical and mechanical properties of granular-fibrous carbon-carbon composites with recycled carbon fibres Ceram. Int. (IF 3.057) Pub Date : 2018-07-18 Marcel Zambrzycki, Janusz Tomala, Aneta Fraczek- Szczypta
In the following study, the electrical and mechanical properties of granular-fibrous carbon-carbon composites with short recycled carbon fibres have been investigated. The examined composites contained from 0 to 12 wt.% of three types of recycled carbon fibres that differ in length. The conducted study has proven that it is not the type of applied fibre, but rather the resultant porosity of composites that exerts the predominant influence on the electrical resistivity and mechanical properties of the tested materials. The curve fitting revealed mathematical formulas correlating the studied properties with the apparent density of the composite samples. Owing to the addition of the shortest carbon fibres, the mechanical and electrical properties were significantly improved (50.14% and 24.06% increase in modulus of elasticity and flexural strength respectively for the sample with 12 wt.% of the shortest fibres). A 21.39% decline in the resistivity (ϱ=161.26µΩ⋅m) of the composite containing 4% of shortest fibres was noted in comparison with the reference sample. Unlike powdered fibres, the addition of longer fibres caused an increase in porosity and deterioration of microstructure, which resulted in a significant decline in the key properties of the investigated composites.
The spin-reorientation magnetic transitions in Ga-doped SmCrO3 Ceram. Int. (IF 3.057) Pub Date : 2018-07-18 H. Li, Y.Z. Liu, L. Xie, Y.Y. Guo, Z.J. Ma, Y.T. Li, X.M. He, L.Q. Liu, H.G. Zhang
Orthochromite SmCrO3 is known to show spin reorientation around 34 K and which was assigned as transition from Γ4 to Γ2. Our work reports the spin reorientation transitions in a series of Ga-doped SmCrO3: the spin reorientation transition from Γ4 to Γ2 at TSR2 = 88 K and another spin reorientation transition of Γ2 to Γ1 at TSR1 = 15 K were observed simultaneously when the content of Ga is 30%. Importantly, the evolution of spin reorientation transitions from the single spin reorientation of Γ4 → Γ2 to double ones of Γ4 → Γ2 → Γ1, and then to the single one of Γ2 → Γ1 is caused by the increase of Ga doping concentration. The M-T and M-H measurements have been made to study the temperature and magnetic field dependence of these spin reorientation transitions. These temperatures and doping dependence of spin reorientation transitions in RCrO3 (R = rare earth or yttrium) can appeal to the magnetic switching devices design based on these findings.
VO2(A) Nanorods: One-pot Synthesis, Formation Mechanism and Thermal Transformation to VO2(M) Ceram. Int. (IF 3.057) Pub Date : 2018-07-18 Liangmiao Zhang, Jianing Yao, Yunfeng Guo, Fang Xia, Yuanyuan Cui, Bin Liu, Yanfeng Gao
The monoclinic VO2(M) has promising applications in intelligent devices but its preparation still requires improvement to permit cost-effective mass production. In this work, we report a 2-stage approach for producing VO2(M) nanorods by (1) hydrothermal reduction of vanadium pentoxide by sodium bisulfate at 220 °C to form VO2(A), and (2) subsequent thermal activated phase transformation of VO2(A) to VO2(M) at 350–450 °C in vacuum. The obtained VO2(M) nanorods showed a reversible phase transition temperature at about 62.5 °C and a narrow thermal hysteresis width of 10 °C. The mechanism of the hydrothermal reduction was studied by combined ex situ microscopic and diffraction characterization of cooled samples as well as in situ PXRD experiments, in which the hydrothermal synthesis was monitored in real time by time-resolved diffraction datasets. It was found that the hydrothermal synthesis of VO2(A) is a 4-step process: (1) reduction of V2O5 to form VO2(B) nanoparticles, (2) oriented attachment of VO2(B) nanoparticles along the  direction, (3) formation of VO2(B) nanorods as a results of oriented attachments, and (4) hydrothermal transformation of the metastable intermediate VO2(B) nanorods to VO2(A) nanorods. This clear understanding of the mechanism will help the further optimization of synthesis temperature and time for preparing VO2(A). This method provides a low temperature thermal treatment alternative and hence helps the reduction of cost for the production of VO2(M), bring the mass application of VO2(M) one step closer.
Lead-less mesoscopic perovskite solar cells with enhanced photovoltaic performance by strontium chloride substitution Ceram. Int. (IF 3.057) Pub Date : 2018-07-18 Huanyu Zhang, Wenwu Liu, Rui Li, Mei Zhang, Min Guo
The substitution of toxic lead (Pb) in efficient perovskite solar cells (PSCs) is a key problem for commercialization. In this paper, strontium chloride (SrCl2)-doped lead-less PSCs were constructed successfully, and the effect of Sr substitution on the perovskite film formation and its photovoltaic property was investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible absorption, time-resolved photoluminescence (TRPL), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS) analyses. It is demonstrated that the introduction of Sr substitution changes the chemical composition of PbI2 precursors and reduces the excess PbI2 in the perovskite films. A 10 mol% Sr substitution in the PbI2 precursor solution can increase the absorbance of the resultant perovskite film and enhance the electron extraction at the “perovskite/TiO2” interface, thus increasing the device's short-circuit current density (Jsc) from 17.41 mA cm-2 to 19.45 mA cm-2. At the same time, Sr substitution can reduce the charge combination in the PSC, which allows the PSC to obtain a higher open-circuit voltage (Voc) of 1.08 V and fill factor (FF) of 0.74. Finally, the PSC prepared with 10 mol% Sr substitution exhibits a considerable power conversion efficiency (PCE) of 15.64%, showing an improvement of 18.9% compared to that of the pristine device.
Correlations between the Structural Characteristics and Enhanced Microwave Dielectric Properties of V–Modified Li3Mg2NbO6 Ceramics Ceram. Int. (IF 3.057) Pub Date : 2018-07-18 Gang Wang, Huaiwu Zhang, Xin Huang, Fang Xu, Gongwen Gan, Yan Yang, Dandan Wen, Jie Li, Cheng Liu, Lichuan Jin
Novel low-temperature fired Li3Mg2Nb1-xVxO6 (x=0.02−0.08) microwave dielectric ceramics were synthetized by the partial substitution of V5+ ions on the Nb5+ sites. The effects of V5+ substitution on structure and microwave dielectric properties were investigated in detail. XRD patterns and Rietveld refinement demonstrated that all of the samples exhibited a single orthorhombic structure. The structural characteristics such as the polarizability, packing fraction and NbO6 octahedron distortion were determined to establish the correlations between the structure and the microwave dielectric characteristics. The ɛr values presented a tendency similar to that of the polarizability. The high Q×f values were mainly attributed to the effects of the grain sizes and density rather than the packing fraction. The variation in the τf values was attributed to NbO6 octahedron distortion. Notably, the Li3Mg2Nb1-xVxO6 (x=0.02) ceramics sintered at 900 °C had outstanding microwave dielectric properties: εr=16, Q×f=131,000 GHz (9.63 GHz), and τf=−26 ppm/°C, making these ceramics promising ultralow loss candidates for low temperature co-fired ceramics (LTCC) applications.
Cutting temperature measurement using an improved two-color infrared thermometer in turning Inconel 718 with whisker-reinforced ceramic tools Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Jinfu Zhao, Zhanqiang Liu, Bing Wang, Yang Hua, Qingqing Wang
Great heat will generate in turning Inconel 718 with whisker-reinforced ceramic tools. The generated great heat damages the machined surface quality. More attentions have been paid to the methodologies for accurately measuring cutting temperature in the cutting zone. However, the current methodologies of measuring cutting temperature have the disadvantages of destroying temperature field, uncertain emissivity and low measuring accuracy. In this paper, an improved two-color infrared thermometer is developed and used to measure the maximum cutting temperature in the cutting zone. The contactless measurement and the eliminated emissivity effect can improve the authenticity of the measured maximum cutting temperature. The fast response time 10 ms and the high measuring accuracy of the improved two-color infrared thermometer can meet the requirements of measuring maximum cutting temperature. The measured maximum cutting temperature increases exponentially with the cutting speed. The improved two-color infrared thermometer can be adopted to more complicated situations by moving the reliable fixed tripod and convenient focusing. The improved two-color infrared thermometer is proved to be a convenient, effective and economic methodology for accurately measuring the maximum cutting temperature in the cutting zone.
Chalcogenide embedded quasi photonic crystal fiber for nonlinear optical applications Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Bikash Kumar Paul, Md. Abdul Khalek, Sujan Chakma, Kawsar Ahmed
In this article, a new quasi photonic crystal fiber (PCF) with chalcogenide ellipse core has been proposed. Fundamental optical transmission characteristics such as effective area, confinement loss, numerical aperture (NA), nonlinearity and power fraction has been investigated through the full vector finite element method (FV-FEM). The proposed model shows ultra low confinement loss of 2.08×10−5dB/m, significant NA of 1.2 × 10−8 dB/km and effective area of 1.42 × 10–12m2 in x-polarization mode. This shows a high nonlinearity of 4.72 × 104 W−1km−1. This raised model may play a vital role to sensing, biomedical imaging, fluorescence monitoring and optical signal processing and nonlinear applications.
Incorporation of monovalent cations into diopside to improve biomineralization and cytocompatibility Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 H. Rahmani, E. Salahinejad
This paper aims to evaluate the structure, bioactivity, biodegradation and cytocompatibility of diopside (CaMgSi2O6) doped with 2 mol% of Li, Na and K separately substituting for 1 mol% of Mg of diopside. An ethanolic, inorganic-salt coprecipitation method, followed by calcination at 900 °C, was used for synthesis. X-ray diffraction showed that the single-phase diopside structure is kept at this level of substitution; however, the crystallinity and lattice volume of diopside were changed depending on the size difference of the replacement components. According to in vitro biological studies, doping of all the alkali ions improves the bioactivity of diopside, with the highest and least effects obtained by K and Na, respectively. The MTT assay of osteoblast-like MG-63 cell cultures indicated that the cell viability and proliferation are improved as a result of using all the dopants, where the most enhancements were found for Na and K. It is eventually concluded that the incorporation of K into diopside ensures the optimal behaviors in terms of bioactivity and biocompatibility in vitro.
Charge carrier generation and control on plasmonic Au clusters functionalized TiO2 thin films for enhanced visible light water splitting activity Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Adem Sreedhar, I. Neelakanta Reddy, Jin Hyuk Kwon, Jonghoon Yi, Youngku Sohn, Jin Seog Gwag, Jin-Seo Noh
We present the remarkable plasmon-enhanced photoelectrochemical (PEC) water splitting activity by swapping the gold (Au) clusters position at TiO2 interface. Specifically, we propose novel and strategic Au clusters functionalized TiO2 thin films (Au/TiO2 and TiO2/Au) as a potential photoelectrodes to regulate the charge carrier generation and transportation by creating progressive localized electric field and surface plasmon resonance platforms. Firstly, XRD results suggests that significant structural changes in the preferred (101) plane of anatase TiO2 with respect to Au (111). Furthermore, we have carried out XPS spectra to confirm the presence of Ti, O and Au anchoring sites. Moreover, FESEM images revealed successful distribution of Au clusters on and under the TiO2 surface. Interestingly, optical transmittance was effectively varied by the Au clusters position. As a result, C-V, I-V and I-t studies accurately demonstrated the establishing of localized electric field at the Au cluster-TiO2 interface, which yielded remarkable charge carrier generation and long-term stability by the Au/TiO2 photoelectrode than TiO2/Au. As evidenced from the above results, the tailored Au/TiO2 sequence exhibits superior PEC water splitting activity through establishing the trapping of incident light due to the confinement of Au clusters under the TiO2. Comprehensively, the optimization of the above findings represents an interesting route to develop the novel energy conversion devices for water splitting application.
Assembled porous Fe3O4@g-C3N4 hybrid nanocomposites with multiple interface polarization for stable microwave absorption Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Jieyi Yu, Fangli Chi, Yuping Sun, Junjie Guo, Xianguo Liu
Magnetic/dielectric composites can offer good electromagnetic impendence. However, the strategy for embodying strong absorbing ability and broad effective absorption band simultaneously is a significant challenge. Therefore, assembled porous Fe3O4@g-C3N4 hybrid nanocomposites have been designed and synthesized, in which porous Fe3O4 nanospheres assembled by ~3 nm Fe3O4 nanoparticles are surrounded by g-C3N4. The introduction of g-C3N4 improves dielectric loss ability at 2–18 GHz and magnetic loss ability at 2–10 GHz, and enhances attenuation constant, and increases electromagnetic impedance degree. These merits ensure that assembled porous Fe 3 O4/g-C3N4 hybrid nanocomposites deliver superior microwave absorption performance, such as effective absorption bandwidth, fE, (reflection loss less −10 dB) exceeding 5 GHz at 2.0–2.3 mm, the maximal fE of 5.76 GHz and minimal reflection loss of at least −20 dB with thickness ranging from 2.3 to 10.0 mm, avoiding the sensitivity of absorption properties to absorbing layer thickness. Stable microwave absorbing performance originates from multi-interfacial polarization, multi-reflection, enhanced electromagnetic loss capability, and good electromagnetic impedance. Our study offers a new idea for stable microwave absorber at 2–18 GHz.
Growth mechanism of YAG single crystal in planar waveguide by solid-state crystal growth method Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Ge Zhang, Benxe Jiang, Pande Zhang, Yiguang Jiang, Shuilin Chen, Long Zhang
In this paper, we researched the growth mechanism of solid-state crystal growth (SSCG) method in planar waveguide. The effect of tetraethyl orthosilicate (TEOS) inside YAG (yttrium aluminum garnet) ceramic matrixes on the YAG single-crystal growth was studied. The results indicated that the crystal growth increased with increasing TEOS content. Theoretical analysis confirmed that the solid-state crystal growth kinetics could be fitted by the Lifshitz–Slyozov–Wagner law. Additionally, the segregation of silicon was observed, the SSCG process with SiO2 effectively eliminated the pores in the YAG ceramic matrices via diffusion to the growth interface between the crystal and the ceramic. We successfully obtained high transparency YAG single crystal using the SSCG method, which transmittance value reached 83.62% at 1064 nm.
Effects of solution composition and electrophoretic deposition voltage on various properties of nanohydroxyapatite coatings on the Ti13Zr13Nb alloy Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Michal Bartmanski, Andrzej Zielinski, Beata Majkowska-Marzec, Gabriel Strugala
The purpose of the research was to establish the influence of the solution composition and the electrophoretic deposition voltage on the coating homogeneity and thickness, nanohardness, adhesion, corrosion resistance and wettability. The Ti13Zr13BNb alloy was coated by the electrophoretic technique with hydroxyapatite in a solution containing 0.1, 0.2 or 0.5 mg nanoHAp in 100 mL of suspension and at voltage 15, 30 or 50 V. The scanning electron and atomic force microscopies, polarization curves technique for corrosion assessment, nanoindentation and nanoscratch tests, and measurements of contact angle in simulated body fluid were performed. The obtained results revealed the complex and interrelated effects of both process determinants on the structure and properties of hydroxyapatite coatings, which were attributed to the role of the size, shape and content in suspension of hydroxyapatite particles.
In-situ preparation of MgFe2O4-GO nanocomposite and its enhanced catalytic reactivity on decomposition of AP and RDX Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Weimin Wang, Bo Liu, Kangzhen Xu, Yanqing Zu, Jirong Song, Fengqi Zhao
MgFe2O4-GO nanocomposite was successfully prepared by in situ growth method and characterized by XRD, FT-IR, Raman, SEM and TEM. MgFe2O4 nanoparticles were tightly anchored on the surfaces of GO sheets, and no separation of MgFe2O4 from GO sheets was found after ultrasound treatment for 10 minutes. GO sheets effectively prevent the aggregation of MgFe2O4 nanoparticles, and the particle size of MgFe2O4 is about 80 nm. Catalytic decomposition results show that the MgFe2O4-GO nanocomposite could obviously reduce the decomposition temperature and apparent activation energy of AP from 406.8 to 306.5 ℃ and from 161.0 to 116.6 kJ mol−1，respectively, and increase the decomposition heat of AP from 654.7 to 1183.2 J g−1. The thermal decomposition temperature of RDX was also reduced from 242.3 to 234.6 ℃. MgFe2O4-GO nanocomposite prepared by in situ growth method exhibits better catalytic decomposition performances than pure MgFe2O4, physical mixture MgFe2O4+GO and self-assembled MgFe2O4/GO.
Microstructure and mechanical properties of Al2O3-ZrO2 ceramic deposited by laser direct material deposition Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Fazhi Li, Xinwang Zhang, Changyou Sui, Jiazhu Wu, Haiying Wei, Yi Zhang
The thin-walled structures of Al2O3-ZrO2 ceramic were deposited using laser direct material deposition (LDMD). The effect of heat input on Al2O3-ZrO2 ceramics with different Al2O3/ZrO2 powder weight ratios were studied and the microstructures in different regions of the deposit were analysed. For the thin-walled structure with 85 wt% Al2O3 and 15 wt% ZrO2 (H1) hypoeutectic deposition, the grain growth angle increases with increasing heat input. From the frontier region to the central region, the microstructure was transformed from a columnar dendritic structure to a cellular structure. For thin-walled structure with 65 wt% Al2O3 and 35 wt% ZrO2 (H2) hypoeutectic deposition, the mean thickness of the banded structure increases with increasing heat input but decreased when the heat input was 124.3 J/mm. The minimum thickness of the banded structure was 0.16 mm. The microstructure of the frontier region exhibited cellular dendritic, while the amorphous structures appeared in the central region. The maximum hardness of the thin-walled structure with H1 hypoeutectic deposit was 21.4 GPa while the maximum fracture toughness of the H2 hypoeutectic deposit was 4.61 MPa m1/2. The fracture toughness was found to increases as the thickness of the banded structure decreases under high heat input. The results of this research provide some basis for attaining high quality Al2O3-ZrO2 ceramics by laser direct material deposition.
Structural, morphology and luminescence study of Er+3-doped garnet-type Li5La3Nb2O12 electrolytes as a potential new phosphor Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 A. Egaña, C. de la Torre Gamarra, M. Tardío, A. Várez, J.E. Muñoz-Santiuste
Erbium doped garnet-type Li5La3Nb2O12 electrolytes were synthesized by conventional solid state reaction in air at 900°C. Formation, microstructure and luminescence properties were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-VIS absorption and luminescence techniques. The limits of the Li5La3-xErxNb2O12 solid solution (0≤x≤0.05) were established by XRD and SEM. For x>0.05, garnet structure coexists with segregated Er2O3. Rietveld refinement of room temperature powder XRD patterns shows that this solid solution exhibits a cubic garnet structure (a ~ 12.79 Å and S.G. Ia-3d) and trivalent Er ions replace La cations in cubic coordination (located in 24c site). The typical green, red and infrared luminescence of Er3+ ions can be efficiently excited under several wavelength lights in the UV-VIS-NIR region. Optical measurements have been improved dispersing Li5La3-xEr-xNb2O12 powder in KBr pellets. Our results indicate the potentiality of rare earth doped Li5La3Nb2O12 garnets as a new family of phosphors.
Electroacoustic investigation of aqueous suspensions of raw materials for Al2O3-C refractories Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Kirsten Moritz, Nora Gerlach, Gert Schmidt, Christos G. Aneziris
The influence of the pH value and of an anionic polyelectrolyte on the zeta potential of different raw materials that are used for producing carbon-bonded alumina refractories was studied by measurements of the electrokinetic sonic amplitude (ESA). The following raw materials were investigated: alumina CT 3000 SG, tabular alumina T60/T64, modified coal tar pitch Carbores® P, graphite AF 96/97, carbon black LUVOMAXX® MT N-991 and RW micro-silica. The isoelectric points of these materials were identified, except for the graphite and the micro-silica, which exhibited a negative surface potential over the entire pH range investigated (pH 3–11). An anionic polyelectrolyte (Dolapix CA) was found to increase not only the value of the zeta potential of the oxides at the inherent suspension pH but also that of the graphite and the carbon black. Its addition to concentrated slurries containing a mixture of the investigated raw materials reduced the viscosity and resulted in a decrease in the apparent porosity of carbon-bonded alumina samples produced by pressure filtration. The suitability of the suspension composition for shaping large-sized samples by pressure slip casting and the high thermal shock resistance of the fabricated alumina-carbon refractory have been demonstrated.
Preparation and characterization of novel environmentally friendly Al2O3/SiO2/CaO ceramic foams Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Luca Bertolla, Zdeněk Chlup, Peter Tatarko, Ondrej Hanzel, Oldřich Ševeček, Pavla Roupcová, Ivo Dlouhý
Low–cost Al2O3-SiO2-CaO ceramic foams were prepared using a novel and simple reactive foaming process. The foamed green bodies were produced by mixing aluminium powder and calcium hydroxide in an aqueous solution of sodium silicate and sintered in an argon atmosphere using a pressureless electric current assisted process (T = 800 °C). An additional thermal treatment was performed in air using a conventional furnace (T = 1050 °C) in order to oxidize the residual metallic phases. The resulting foams exhibited open porosity, densities ranging from 0.50 to 0.65 g/cm3 and wide pore size distribution (0.04–400 μm). The compressive strength and thermal diffusivity of these foams ranged from 2.12 to 1.01 MPa and from 0.27 to 0.45 mm2s-1, respectively, which indicate their suitability as thermal insulator materials.
Tribological characterization of bioactive zirconia composite layers on zirconia structures Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 M. Buciumeanu, D. Faria, J. Mesquita-Guimarães, F.S. Silva
The aim of this paper was to evaluate the tribological performance of bioactive zirconia composite layers applied by press and sinter method on yttria-stabilized zirconia (YSZ) substrates. Two types of bioactive zirconia composite layers were tested, zirconia reinforced by 10 vol% of HAp and by 10 vol% of β-TCP. The wear tests were carried out in Phosphate Buffered Saline (PBS) solution at 37 ± 2 ºC using a ball-on-plate configuration. The wear mechanisms of the samples were identified by SEM/EDS. Fracture toughness, hardness and roughness were also evaluated. Results indicated that the tribological performance was not affected by the addition of bioactive materials. The specific wear rates were within the same order of magnitude and no change in the coefficient of friction was observed among all samples. These results show that this new approach based on the use of a bioactive zirconia composite layer on zirconia substrate, is a promising solution for implants, as it is possible to maintain the high tribological properties of zirconia and in the same time to improve bond between living tissue and implant, as the HAp and β-TCP are acting as bioactive sites.
Impregnated active layer combustion synthesis of nano MgFe2O4 using green template Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Khalil Kohsari H., Reza Norouzbeigi
Nano-Magnesium ferrite (MgFe2O4) powders have been prepared by a modified combustion synthesis method named impregnated active layer combustion (IALC). The effects of five important parameters such as main fuel to oxidizer ratio (F/O), main fuel type, added fuel type, template type and main fuel (Added F/MF) to the added fuel ratio have been studied using Taguchi design. Xylitol, D-mannitol, ethylene diamine tetra acetic acid (EDTA) and diethylene triamine penta acetic acid (DTPA) were used as fuels. Besides, waste newspaper and platanus orientalis leaf (POL) were used as new green templates. Samples were characterized by XRD, XRF, SEM, TEM, BET and VSM analyses. Results showed that the average crystallite size of the sample prepared under optimized condition (mixture of Xylitol and DTPA as fuel, POL as template, and Added F/MF ratio of 0.75) was 17.66 nm. The result was confirmed by TEM. The saturated magnetization of the optimum sample was 21 emu/g and the specific surface area was 15.377 m2/g.
Porous Polymer Derived Ceramic (PDC)-Montmorillonite-H3PMo12O40/SiO2 Composite Membranes for Microbial Fuel Cell (MFC) Application Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Vignesh Ahilan, Michaela Wilhelm, Kurosch Rezwan
Ceramic membranes can serve as viable alternatives to the less mechanically stable polymeric membranes utilized in microbial fuel cells (MFCs). In this work, a series of polymer-derived ceramic (PDC) proton exchange composite membranes with large ion exchange capacity (IEC) values, high cation transport numbers, and low oxygen diffusion coefficients have been synthesized at various pyrolysis temperatures using a pressing technique. These materials were composed of a polysiloxane matrix mixed with proton-conducting fillers such as montmorillonite and H3PMo12O40/SiO2 at different ratios. By tuning the average pore sizes of the membranes between 0.1 and 1 μm and their hydrophilic/hydrophobic characteristics, the maximum IEC of 0.6072 mequiv/g and cation transport number of 0.6988 were obtained, which is 67% and 72% of polymeric nafion performance, respectively. In addition, the minimal oxygen mass transfer coefficient achieved by this approach was equal to 5.62×10−4 cm/s, which is very close to the commercial nafion membrane value. The fabricated PDC composite membranes meet all the essential criteria required for their use in MFC applications and represent a high potential to overcome limitations of polymeric membrane.
Niobium and Zinc Doped Titanium-Tin-Oxide Solid-Solution Ceramics: Synthesis, Structure and Electrical Characterization Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 T.B. Ivetić, D.L. Sekulić, J. Papan, I.O. Gúth, D.M. Petrović, S.R. Lukić-Petrović
This paper describes the processing, microstructure, optical and electrical properties of the nanocrystalline (NC) niobium and zinc doped titanium-tin-oxide (TTO:NZ) based ceramics. Variety of techniques was employed (X-ray diffraction, scanning electron microscopy, energy dispersive, Raman and impedance spectroscopy) in the characterization of the obtained TTO:NZ, which confirmed the formation of NC solid-solution matrix with Ti0.8Sn0.2O2 composition. A specific highly dense (approximately 97% of the theoretical density was reached) varistor like microstructure (matrix metal-oxide grains surrounded by the grain-boundary regions) and accordingly resembling electrical properties (breakdown electric field of approximately 130 V/mm and nonlinearity coefficient ofα≈ 6.5) were achieved through double cation doping and elected condition of the mechanochemical solid-state synthesis. Impedance response analysis of TTO:NZ ceramics by means of an equivalent electrical circuit based on the brick-layer model for polycrystalline materials revealed the presence of two temperature dependent electrical relaxation phenomena of the non-Debye type as well as the negative temperature coefficient of resistance behavior.
Properties of Selective Laser Melted Alumina-Spodumene Composite Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 M.X. Gan, C.H. Wong
Based on previously established process conditions, we successfully selectively laser melted and characterised the properties of alumina-spodumene composite. Additively manufacturing sample parts of this composite using various layer thicknesses revealed different printing defects. For example, at layer thickness of 50 µm, we observed delamination of the part from the substrate plate. Poor interlayer bonding, however, was found when the layer thicknesses used were 100 µm and 150 µm. With the addition of alumina, the flexural strength of the samples doubled. It was also found that heat treating the composite has negligible effect on the properties. Additionally, compared to using large layer thicknesses, printing with 50 µm layer thickness produced parts with the lowest amount of porosities. Furthermore, x-ray diffraction analysis detected crystallinity in the as-printed samples due to the addition of alumina particles and crystallisation from constant heat input. This article shows that selective laser melting of ceramic-glass-ceramic composite is possible.
The effect of phosphorus on the formation of mullite whiskers from citric acid activated kaolin Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Chenyang Zhang, Shuxin Lu, Zhijie Zhang, Mingfeng Zhong, Yuqin Li, Xia Huang, Wei Xu, Da Wang, Liming Wang
Mullite with an aspect ratio of 82.08 was prepared by adding 4.5 wt% Ca3(PO4)2 to citric acid activated kaolin. Phosphorus (P) has a significant role in the formation of well-developed mullite whiskers. The mechanisms were discussed based on X-ray diffraction, FTIR, SEM, EDS and 31P MAS NMR. The addition of P decreases the quartz content, but increases the liquid phase content. When the Ca3(PO4)2 content is less than 4.5 wt%, the main types of P in glass phase are Q1 and Q2; with increasing P content, the aspect ratio of mullite increases. When the Ca3(PO4)2 content is higher than 4.5 wt%, a higher polymerization degree of P (Q3) appears; however, the aspect ratio of mullite decreases. Therefore, the range of P contents enhancing the formation of mullite whiskers is narrow.
AMBIENT WEATHERING OF STEELMAKING LADLE SLAGS Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Marcos N. Moliné, Walter A. Calvo, Analía.G. Tomba Martinez, Pablo G. Galliano
During cooling and permanence outside, the solidified slag involved in the refinement process taking place in the steelmaking ladles suffers attack by environmental components such as water vapor and gaseous CO2 (weathering). The reactions involved are hydration and carbonation, and as a consequence, the pulverization of the slag occurs. In the present paper, the results of a study of the degradation of a typical steelmaking ladle slag over a period of eighteen weeks (126 days) are reported. To monitor the slag evolution, several experimental techniques were used, some of them rarely employed in this context, after dividing the initial slag batch in four granulometric fractions between > 7.2 mm and < 1.4 mm: granulometry by sieving, X-ray fluorescence (XRF), X-ray diffraction (XRD), and thermogravimetric (TGA) and thermal differential (DTA) analyses. As was already known, the main elements responsible for the slag degradation are free lime, followed by calcium aluminates and magnesia. It was also found that anhydrous and hydrated calcium aluminates are concentrated in the finest granulometric fractions and contribute to the generation of fines mainly during the final stage of hydration. The high percentage of particles smaller than 1.4 mm, with cementitious properties provided mainly by the presence of anhydrous calcium aluminates, are promising characteristics for alternative reusing of the studied ladle slag. Furthermore, slag weathering mechanisms are critical for understanding other steelmaking processes in which the slag is deeply involved, such as the protective role of the remaining thin slag layer against decarburation of ladle or converter working lining refractory bricks.
Fe doped δ-MnO2 nanoneedles as advanced supercapacitor electrodes Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Qi Gao, Jinxing Wang, Bin Ke, Jingfeng Wang, Yanqiong Li
Fe-doped δ-MnO2 nanoneedles have been successfully synthesized via a hydrothermal method as electrode materials. The morphologies of as-synthesized samples were characterized by SEM and the role of Fe3+ as a structure directing agent on the formation of MnO2 nanoneedles was investigated. The electrode exhibits maximum specific capacitance of 627.3 F g−1 at a current density of 1 A g−1, far exceeding the capacity of MnO2 monomers. Furthermore, the capacitance retention was measured to be 94.2% after 3000 cycles, showing remarkable cycling stability. The activation of Fe3+ in δ-MnO2 nanoneedles attributes to the enhancement of electrode conductivity and electrochemical performance. In principle, the results indicate the potential application of our samples in supercapacitor electrodes.
Comparative studies on microstructures, strengths and reliabilities of two types of AlN direct bonding copper substrates Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Xin Wei, Haixian Xu, Jun Zhan, Hao Zhang, Ye Cao, Song Cui, Wenming Tang
Oxidation of AlN ceramic plates was performed via two different techniques of Cu2+ activation followed by oxidation and direct oxidation. Two types of AlN direct bonding copper (DBC) substrates were then fabricated by combining the pre-oxidized Cu foils with the AlN plates. The interface structures, the peel strengths, and the temperature cycling reliabilities of the samples are investigated. The results showed that after Cu2+ activation followed by oxidation, rod-like CuAl2O4 particles were distributed on the dense α-Al2O3 layer oxide layer of the AlN plates. This microstructure is beneficial in improving the interface bonding strength and the wettability of the AlN-DBC substrates. Interface layers of both the AlN-DBC substrates were composed of two sublayers of Cu2O+CuAlO2 and residual Al2O3. During the peeling process, fractures occurred in the AlN plates for the Cu2+ activated and oxidized AlN-DBC substrates, but at the interface layer for the directly oxidized AlN-DBC substrates. The peel strength and the temperature cycling performance of the Cu2+ activated and oxidized AlN-DBC substrates were higher than the directly oxidized AlN-DBC substrates.
Processing and mechanical properties of nonstoichiometric TiCx (0.3≤x≤0.5) Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Zhichao Zhang, Changjian Geng, Yujiao Ke, Cui Li, Xiaochen Jiao, Yucheng Zhao, Hu Tang, Mingzhi Wang
Titanium carbide (TiC) has been considered as one of the most significant metal carbides for manufacturing a new generation of cermets. However, overhigh sintering temperature results in that dense sintered-bulk of TiC without metal binders is hard to realize at relative low temperature, which limits its applications. Here, we prepared nonstoichiometric TiCx (0.3≤x≤0.5) powers with carbon vacancy defects by mechanical alloying (MA) and then sintered into a cylindrical compact at high temperature and high pressure (HTHP). The mechanical properties of nonstoichiometric TiCx were obtained by an indentation method. Vickers hardness of TiC0.3, TiC0.4 and TiC0.5 compacts are 15 GPa, 25 GPa and 24 GPa, fracture toughness of TiC0.3, TiC0.4 and TiC0.5 are 6 MPa·m1/2, 3.8 MPa·m1/2 and 3.5 MPa·m1/2, respectively. Our studies indicate that introduction of carbon vacancies dramatically reduces the sintering temperature because of diffusion paths provided by carbon vacancies, without the deterioration of the mechanical properties. The successful synthesis of TiCx bulks may provide a low-temperature sintering route for refractory ceramic compounds such as VC, NbC and WC, etc.
Abrasion resistance and thermal conductivity of ZrO2-containing bauxite refractories in the transition zone of a cement kiln Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Bo Ren, Yawei Li, Mithun Nath, Shu Yan, Qinghu Wang
To substitute bauxite-SiC refractories which are currently used in transition zone of cement kilns, this paper aims to fabricate novel working lining with lower thermal conductivity and outstanding abrasion resistance. For this purpose, a composite refractory material, based on the incorporation of zircon and fused zirconia-mullite (FZM) into bauxite-based refractories is fabricated. The addition of both zircon and FZM led to superior thermal insulation performance despite their different abrasion behaviours. In particular, specimen containing zircon possesses lower cold crushing strength and accordingly inferior abrasion resistance, as compared to bauxite-SiC refractories. By comparison, incorporation of FZM powder resulted in the best abrasion resistance, as it is related to the improved fracture toughness which retard the propagation of crack, thereby preventing the material form spallation. ZrO2-containing bauxite refractories can be promising materials to satisfy the new request of cement rotary kilns.
Comparison of synthesis and spark plasma sintering of YAG nano particles by variation of pH and precipitator agent Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Mahsa Rahmani, Omid Mirzaee, Mohammad Tajally, Mohammad Reza Loghman-Estarki
Yttrium aluminum garnet ceramics with a wide range of technological and industrial applications have attracted great attention owing to their remarkable mechanical, thermal and optical features. The properties of transparent or translucent YAG ceramics with wide-ranging applications notably depend on the features of the starting particles which is directly affected by synthesis conditions. In this study, yttrium aluminum garnet precursors (YAG) were obtained by reverse co-precipitation method from a mix solution of aluminum and yttrium nitrates using ammonium hydrogen carbonate (AHC) and ammonia water (AW) solutions as precipitator agents. The effect of pH on the chemical composition and phase analysis of the precursors synthesized by different precipitants was explored, leading to the formation of precursors with the proper stoichiometric ratio of YAG phase. The phase evaluation process, thermal behavior, microstructures and other characteristics were compared for the two precipitants by ICP, XRD, FTIR, TG-DTA, BET, FESEM, TEM and EDX analysis. The results revealed that unlike AW, using AHC as precipitant at high pH values caused deviation from the YAG stoichiometric ratio. In the pH value of 7, both precipitants produced homogenous precipitates and pure YAG at a calcination temperature of 900 °C while the powders obtained by AHC exhibited more dispersity and fewer aggregates. Sub-micron-grained YAG ceramics were obtained by SPS method at 1380 °C for 10 min using amorphous nano particles without adding any sintering aids. Compared with ceramics produced using synthesized powders by AW, the ceramic of co-precipitated powders by AHC showed higher density (99.9%) and transparency (33% at 680 nm and 50% at 1100 nm).
Preparation of mullite/B4C composites: A comparative study on the effect of heating methods Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Ehsan ghasali, Ebrahim Karimi Saeidabadi, Masoud alizadeh, Ali Fazili, Hosein Rajaei, Alireza Jam, Houman Kazemzadeh, Touradj Ebadzadeh
The present study investigated preparation of the mullite/B4C composites through microwave and spark plasma sintering processes. A high-energy ball mill was used to mix the nono-sized mullite and B4C powders in ethanol media for 10 min. The mixed nano-sized powders were pelletized and sintered by microwave (MW) and spark plasma sintering (SPS) processes at 1500 and 1300 °C, respectively. The XRD results revealed the reactions between mullite and B4C, and also the formation of SiC, Al2O3, Si phases in SPS sintered sample. The identified crystalline phases in the microwave sintered sample were mullite and B4C. Samples sintered in SPS reached almost full density and showed improved mechanical properties (the hardness of 16.29 ± 0.2 GPa, bending strength of 348 ± 21 MPa and fracture toughness of 3.01 ± 0.18 MPa m−1/2) than those sintered in microwave. The microstructural investigations showed the formation of needle-like mullite at some areas of sample sintered in SPS with a uniform distribution of B4C in mullite matrix alongside pore-free microstructure. The microstructure of microwave sintered sample contained a large number of pores.
Fabrication of TiO2/Cu hybrid composite films with near zero TCR and high adhesive strength via aerosol deposition Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Myung-Yeon Cho, Dong-Won Lee, Won-Jung Kim, Yong-Nam Kim, Sang-Mo Koo, Daeseok Lee, Kyoung-Sook Moon, Jong-Min Oh
Room-temperature fabrication of TiO2/Cu composite films for embedded passive components were attempted via aerosol deposition process. XRD analysis and observation of internal microstructures revealed that TiO2/Cu composite films using 500 nm-sized TiO2 had further tight bonding between particles compared to 25 nm-sized TiO2, due to effect of initial TiO2 particle size on densification of internal microstructures. Then, to optimize their adhesive strength and temperature coefficient of resistance (TCR), electrical and mechanical properties of TiO2 (500 nm)/Cu composite films with different content of TiO2 were evaluated for applications as advanced composite film resistors. Results showed that TiO2/Cu (50 wt%/50 wt%) composite films had sufficient electrical resistivity (5.8 ×10−3 Ω cm), excellent near-zero TCR (−3 ppm/℃), and improved adhesive strength (~ 7.37 N/mm2) resulting from proper coexistence of anchoring bonds and mechanical interlocking formed during deposition.
Effect of uniaxial stress on phase transitions and dielectric properties of potassium niobate ferroelectric single crystal Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Tao Zhang, Qiang Wu, Fu-ping Zhang, Jia Yang, Gao-min Liu, Xing Wu
The uniaxial compression stress dependence of the phase transitions and dielectric properties of a potassium niobate (KNbO3) ferroelectric crystal were investigated using Landau–Ginsburg–Devonshire phenomenological theory. The results showed that (1) uniaxial stress along c could induce a spontaneous polarization change from the c direction to the c or c directions and from the c, c directions to the c direction; (2) the cubic to tetragonal and the tetragonal to orthorhombic phase transition temperatures increased, while the orthorhombic to rhombohedral phase transition temperature decreased as the uniaxial stress was increased; and (3) spontaneous polarization increased as the uniaxial stress was increased for the tetragonal and orthorhombic phases. The uniaxial stress dependence of the dielectric susceptibility also showed that a flatter Gibbs free energy profile corresponds with a greater expandability, contractibility, and rotationality of the polarization (which indicates a higher dielectric susceptibility), while a steeper Gibbs free energy profile corresponds with a reduced expandability, contractibility, and rotation of the polarization (which indicates a lower dielectric susceptibility).
Effects of deposition time on properties of CaCu3Ti4O12 thin film deposited on ITO substrate by RF magnetron sputtering at ambient temperature Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Mohsen Ahmadipour, Mohd Fadzil Ain, Solleti Goutham, Zainal Arifin Ahmad
CaCu3Ti4O12 (CCTO) thin film was deposited on ITO substrate using radio frequency (RF) magnetron sputtering at various deposition times (1–4 h). The significant effects of deposition time on the structural, morphological, optical and electrical properties were systematically investigated using XRD, AFM, FESEM, UV–Vis, and Hall Effect measurements. XRD study showed that all sputtered films have cubic structure. Higher deposition times of up to 4 h enhanced the film's crystallinity, as demonstrated by the increase in peak intensity and incremental change in crystal size (from 19.5 to 23.6 nm). Roughness (Ra) and root mean square (RMS) values were found to increase from 1.99 to 5.15 nm and 2.66–6.68 nm, respectively, when deposition times were increased. The surface morphology of CCTO thin films were found to be smooth, compact, and densely island-shaped in structure. The film thickness increased from 270 to 330 nm with increase in deposition time. Increase in deposition time also affected the optical transmittance values which declined to 70% at the visible range and the optical energy band gap which decreased from 3.76 to 3.29 eV. At 4 h deposition time, the films showed lower resistivity (of 8.22 Ω/sq), and higher Hall mobility (78.43 cm2/Vs) and carrier concentration (9.84 × 1015 cm−2). The conclusion drawn from this study revealed that by controlling the deposition time, better properties of CCTO thin films can be achieved.
Effect of Co content on microstructure and mechanical properties of ultrafine grained WC-Co cemented carbide sintered by spark plasma sintering Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 Kui Liu, Zhenhua Wang, Zengbin Yin, Liyan Cao, Juntang Yuan
The WC-Co cemented carbides with 4 wt%~14 wt% Co content were fabricated by spark plasma sintering. The effect of Co content on microstructure and mechanical properties of WC-Co cemented carbide were analyzed. The results showed that the grain size of cemented carbide with different Co content was in 220–380 nm. As the Co content increased, the density, fracture toughness and flexural strength of cemented carbide increased, but the hardness gradually decreased. The hardness decreased by approximately 1.6 GPa with per 2 wt% increase of the Co content when the Co content was below 10 wt%. The optimal comprehensive mechanical properties was optimal when Co content was 8 wt%. The hardness, fracture toughness, and flexural strength were 19.87 GPa, 12.27 MPa m1/2 and 1834 MPa, respectively. The cemented carbide fabricated in this paper are more excellent compared to the commercial cemented carbides.
Higher intra-granular and inter-granular performances of YBCO superconductor with TiO2 nano-sized particles addition Ceram. Int. (IF 3.057) Pub Date : 2018-07-17 E. Hannachi, Y. Slimani, F. Ben Azzouz, A. Ekicibil
The impact of titanium oxide (TiO2) nanoparticles addition on the intra-granular and inter-granular properties of YBa2Cu3O7-y (Y-123) were thoroughly investigated. Specimens were produced through the solid-state reaction (SSR) route by adding small contents of TiO2 nano-entities. The phase identification was studied using the X-ray diffraction (XRD). The microstructure and the chemical composition were examined by scanning electron microscope (SEM) technique coupled with energy dispersive X-ray spectroscopy (EDXS) system. The electrical resistivity measurements were done using the conventional four probe technique. The intra-granular, inter-granular and transport critical current densities of the synthesized specimens were explored through measurements of magnetization, ac-susceptibility and current-voltage, respectively. The possible pinning mechanisms predominant in synthesized compounds are estimated. The obtained results show that small amount of TiO2 nanoparticles improves the flux pinning capacity in Y-123 material.
Perovskite oxide-based nanohybrid for low-temperature thin-film solid oxide fuel cells fabricated via a facile and scalable electrochemical process Ceram. Int. (IF 3.057) Pub Date : 2018-07-14 Beom-Kyeong Park, Han Gil Seo, WooChul Jung, Jong-Won Lee
High-performance electrodes for energy conversion systems can be achieved through the selection of materials with appropriate functionality as well as fabricating the desired nanoarchitectures. Nanohybrids of metal and perovskite metal oxide have a great potential as electrodes owing to the combined advantages of the active constituents; however, the controlled hybridization in nanoscale is hindered by the conflicting nature of the metal and perovskite oxide, and it should involve cost-, energy- and time-intensive fabrication techniques. Here, we report an electrochemical process as a facile, cost-effective, and scalable route to fabricating metal–perovskite metal oxide nanohybrids with tailored architectures. We successfully fabricate a Pt@LaCoO3 nanohybrid that consists of a conformal LaCoO3 nanonetwork on a nanoporous Pt thin-film framework. We examine this nanohybrid as an electrode for thin-film-based, low-temperature solid oxide fuel cells and demonstrate that the synergistic nanostructuring of Pt@LaCoO3 leads to exceptionally high oxygen reduction activity at reduced operating temperature and high stability.
A zeta potential and rheology study using electroacoustic spectroscopy on aqueous boron carbide suspensions Ceram. Int. (IF 3.057) Pub Date : 2018-07-10 Maxwell Dawes, Stuart Blackburn, Richard Greenwood
The zeta (ζ) potential of moderately concentrated (at 15 vol. %) boron carbide (B4C) suspensions were characterised using electroacoustic spectroscopy. This technique has been validated for use in this application by correlating the ζ-potential to the suspension viscosity (at 30 vol. %) across a range of pH values. Zeta potential has been shown to be effective in determining differences in B4C powders, reported to be nominally of the same specification in terms of particle size distribution and X-ray diffraction data. The isoelectric (IEP) points for three different as-received B4C powders were found to be 4, 7 and less than 2.5. The study showed that differences in ζ-potential across the powders can be minimised via heat treatment, which produced suspensions all with an IEP below 2.5. The study also established the effect of an anionic and a cationic dispersant on ζ-potential and rheology, demonstrating that excess dispersant from a ζ-potential perspective was required to obtain the lowest viscosity. The study concluded that as-received B4C powders most likely contain contaminants of a cationic nature and that electroacoustic spectroscopy is a useful tool in determining their behaviour in aqueous suspensions.
A study of fine-grained ceramics based on complex oxides ZrO2-Ln2O3 (Ln = Sm, Yb) obtained by Spark Plasma Sintering for Inert Matrix Fuel Ceram. Int. (IF 3.057) Pub Date : 2018-07-10 D.A. Mikhailov, A.I. Orlova, N.V. Malanina, A.V. Nokhrin, E.A. Potanina, V.N. Chuvil’deev, M.S. Boldin, N.V. Sakharov, O.A. Belkin, M.Yu. Kalenova, E.A. Lantcev
Fine-grained ceramics based on solid solitions of ZrO2-x-Ln2O3 (where Ln = Sm, Yb), which are used to simulate inert matrix fuel (IMF), were obtained by colloidal chemical synthesis of powders and their Spark Plasma Sintering (SPS). It has been established that the SPS activation energy (Qs) for fine-grain ceramics based on ZrO2 corresponds to the activation energy of oxygen diffusion on grain boundaries of zirconium oxide (zirconia). We have demonstrated that introducing oxides of samarium (Sm2O3) and ytterbium (Yb2O3) into zirconia decreases SPS activation energy and stabilizes the phase composition of zirconia. Ceramics with densities up to 100% were obtained by the following modes of SPS: sintering temperature 1000–1250 °C, sintering time 6–10 min. Hydrolysis testing in the static mode (Т = 20 °C, P = 1 atm) in distilled water revealed no leaching of lanthanide ions at detection thresholds of 5 ppm for Sm ions and 0.1 ppm for Yb ions.
Effect of synthesis method and morphology on the enhanced CO2 sensing properties of magnesium ferrite MgFe2O4 Ceram. Int. (IF 3.057) Pub Date : 2018-07-10 Sumangala T.P., Isabelle Pasquet, Lionel Presmanes, Yohann Thimont, Corine Bonningue, N. Venkataramani, Shiva Prasad, Valérie Baco-Carles, Philippe Tailhades, Antoine Barnabé
The synthesis and characterization of magnesium ferrite MgFe2O4 prepared by co-precipitation and sol gel combustion is reported. Structural characterization showed that all the samples have single spinel phase. The co-precipitated sample exhibits smaller grains and twice higher BET surface than the sol gel combustion samples. The powder was shaped to dedicated chemo-resistive home-made sensors devices. The electrical properties and sensing properties towards carbon dioxide of both MgFe2O4 powders were studied. The type of charge carriers were analysed on the basis of the change in resistance in the presence of air and argon. The sensing response towards CO2 was found to be dependent on the morphology of the powder sample and the CO2 concentration. A high response of 36% towards 5000 ppm of CO2 was reached which is good for this gas. The key role of the Mg ions modulating the electrical properties is discussed.
A facile strategy for preparation of magnetic graphene oxide composites and their potential for environmental adsorption Ceram. Int. (IF 3.057) Pub Date : 2018-07-10 Yan Liu, Hongye Huang, Defu Gan, Linru Guo, Meiying Liu, Junyu Chen, Fengjie Deng, Naigen Zhou, Xiaoyong Zhang, Yen Wei
Over the past decades, graphene oxide (GO) and its composites with organic and inorganic compenents have gradually become one of the most popular carbon nanomaterials, on account of multitudinous advantages, including great conductivity, excellent thermal stability and large specific surface area. In particular, the magnetic GO based composites have been extensively investigated for various applications owing to their combined advantages from both GO and magnetic nanoparticles. Although many strategies have been developed for preparation of magnetic GO based composites, a facile and efficient strategy is still rarely reported. In this work, we developed a direct, ultrafast, green and non-toxic strategy for scalable production of GO–Fe3O4 hybrids for the first time. Compared with conventional preparation methods, this strategy only requires a simple one-step reaction and would produce no pollutants in the whole reaction process. Furthermore, it could convincingly demonstrate the successful preparation of GO–Fe3O4 hybrids with outstanding properties through a series of characterization techniques. Finally, the outstanding performance of GO–Fe3O4 hybrids in adsorption experiments has been also demonstrated. Results indicated that these GO–Fe3O4 composites are potentially used for environmental adsorption.
Chemical sintering of TiO2 based photoanode for efficient dye sensitized solar cells using Zn nanoparticles Ceram. Int. (IF 3.057) Pub Date : 2018-07-10 Muhammad Shakeel Ahmad, A K Pandey, Nasrudin Abd Rahim, Syed Shahabuddin, S.K. Tyagi
Recombination reactions due to poor inter-particle contact at lower temperatures (<450°C) is a bottle neck for cost effective flexible dye sensitized solar cells (DSSCs). In this study, TiO2sintering to Coble initial stageat low temperatures has been achieved with low melting point zinc (Zn) metal nanoparticles. Zn nanoparticles showed improved inter-particle contact by formation of necks due to high surface diffusion at relatively lower temperatures (200°C). Addition of Zn nanoparticles showed comparable, rather improved efficiency at 200°C compared to reference TiO2photoanode fabricated at 450°C due to neck formation and surface plasmonic resonance (SPR) effect. Morphological studies revealed high contact formation between TiO2 and Zn nanoparticles. Electrochemical impedance and Uv-vis spectroscopy showed improvements in charge transfer and light absorption activity respectively. Structural studies showed no any detectable change in phase due to high surface diffusion and capillary forces produced by Zn nanoparticles at the TiO2/Zn interface.
Synthesis and characterization of Sr1-xLaxMnO3/SiOC nanocomposites decorated with 1D nanostructures for high temperature CO2 splitting Ceram. Int. (IF 3.057) Pub Date : 2018-07-10 Eva Casado, Beatriz García, Aitana Tamayo
1D nanostructures of Lanthanum Strontium Manganite (LSM) are tested as thermochemical catalyst for CO2 splitting. The manganite precursors were incorporated into a ceramic silicon oxycarbide (SiOC) matrix at two different stages during its synthesis to form the nanocomposites. As a result, the LSM nanostructures decorate the large-size pores of the SiOC matrix in form of 1D nanofibers and nanowires. At the same time, the formation of the SiOC units decreases because of the incorporation of these LSM. Moreover, the synthetic strategy strongly affects the surface parameter related to apolar interactions. It turns out that the surface fractal constant of the nanocomposite determines the reactivity of the LSM materials towards CO2. This reactivity has been verified by collecting the spectra of the gases involved in the thermochemical reactions and determining the relative CO2 concentration as a function of the temperature.
In situ synthesis and mechanism of mullite-silicon carbide composite ceramics for solar thermal storage Ceram. Int. (IF 3.057) Pub Date : 2018-07-10 Hao Cheng, Fen Ye, Jianfeng Wu, Wei Shi, Senglin Leng, Sizhan Wu
SiC combined with mullite ceramic, which is an important thermal storage material in solar thermal power generation systems, was synthesized in situ by semidry pressing and carbon-buried sintering of mixtures containing andalusite, calcined bauxite, kaolin, talc and SiC. The effects of the SiC addition and sintering temperature on the physical properties, crystal phases, microstructure, thermal shock resistance, thermo-physical properties and oxidation resistance of the specimens were studied. The results indicate that the formula W-1 (SiC content: 20%) sintered at 1540 °C has the best performance, yielding a bending strength of 36.46 MPa, the completion of 30 cycles of the thermal shock test without cracking and an increase in the bending strength by 136.86%. The silicon carbide on the surface of the specimen is oxidized to produce a dense SiO2 protective film, which effectively prevents the oxygen from incorporating into the interior of specimen and further oxidation. Potentially, the mullite-silicon carbide composite ceramics could be applicable as materials for solar thermal storage devices.
Double Crystal Symmetries and Magnetic Orderings in co-substituted (Y and Mn) Bismuth Ferrite Ceram. Int. (IF 3.057) Pub Date : 2018-07-10 Rabichandra Pandey, Lagen Kumar Pradhan, Pawan Kumar, Manoranjan Kar
The effect of double crystal symmetries on the magnetic property of Bi1-xYxFe1-xMnxO3 has been reported in the present article. The impurity phases (i.e. Bi2Fe4O9, Bi25FeO39 etc.) have been significantly reduced with the co-substitution of Y and Mn in Bi and Fe sites respectively. Rietveld refinement of the X-ray Diffraction patterns reveals the mixed crystal structure of Rhombohedra (R3c space group) as well as Orthorhombic (Pbnm space group) crystallographic symmetry. Percentage of R3c crystal symmetry decreases and Pbnm crystal symmetry increases with the increase in co-substitution of Y and Mn. Peak position in Raman spectra shifts as well as increase the peak broadening with the increase in percentage of co-substitution. It reveals the structural changes in the co-substituted BFO and supports to the XRD analysis. Magnetization has been found to increase with co-substitution and maximum was observed for x=0.075 compound. A correlation between the crystal symmetries and magnetic property has been established systematically. A phase diagram has been reported by correlating the crystal symmetries and magnetic parameters of co-substituted BFO.
Influence of operating temperature on Li2ZnTi3O8 anode performance and high-rate charging activity of Li-ion battery Ceram. Int. (IF 3.057) Pub Date : 2018-07-10 Akbar I. Inamdar, Abu Talha Aqueel Ahmed, Harish S. Chavan, Yongcheol Jo, Sangeun Cho, Jongmin Kim, Sambhaji M. Pawar, Bo Hou, SeungNam Cha, Hyungsang Kim, Hyunsik Im
The temperature-dependent performance of a Li2ZnTi3O8 (LZTO) anode and the ultrafast-charging activity of a Li-ion battery were investigated. The LZTO anode operates at different temperatures between −5 and 55 °C and in this work its sustainability is discussed in terms of storage performance. It delivered a discharge capacity of 181.3 mAhg−1 at 25 °C, which increased to 227.3 mAhg−1 at 40 °C and 131.2 mAhg−1 at −5 °C. The variation in the discharge capacity with temperature is associated with the reaction kinetics and the change in internal resistance. It showed a capacity retention of 64% and a coulombic efficiency of 98% over 500 cycles. Exhibiting a discharge capacity of 107 mAhg−1, the LZTO anode was sustainable over 100 charge-discharge cycles at an ultra-high charging rate of 10 Ag−1. The reaction kinetics estimated from a cyclic voltammetry analysis at high scan rates revealed a capacitive-type storage mechanism.
High-performance phosphorus-modified SiO/C anode material for lithium ion batteries Ceram. Int. (IF 3.057) Pub Date : 2018-07-10 Fan Song, Xuelin Yang, Shouzheng Zhang, Lu-Lu Zhang, Zhaoyin Wen
The phosphorus-modified SiO/C (PSC) composite is successfully prepared by a facile solid-state sintering route. Low-cost and eco-friendly anthracite and red phosphorus are respectively used as carbon source and phosphorus source. The obtained PSC powders present an amorphous nature. The introduced P plays a bridge role between SiO particles and C to relieve the stripping of carbon layer from SiO particles during cycle. As an anode for lithium ion battery, compared with the sample (SC) without P-incorporation, the PSC electrode delivers a much higher initial charge capacity of 846.2 mAh g−1 at 0.1 A g−1 and shows a better rate capability of 545.6 mAh g−1 at 0.5 A g−1 even after 300 cycles. The higher initial coulomb efficiency, larger reversible capacity and better cyclic performance are attributed to the early formation of SEI film, increased the electrical conductivity, improved structural stability and reduced charge transfer resistance.
Dielectric response and thermistor behavior of lead-free x NaNbO3 - (1-x) BiFeO3 electroceramics Ceram. Int. (IF 3.057) Pub Date : 2018-07-10 Y. Saad, I. Álvarez-Serrano, M.L. López, M. Hidouri
The electroceramics of the x NaNbO3 - (1-x) BiFeO3 (x = 0.15, 0.25, 0.50, 0.75, 0.85, 1) system (NBNFO) have been prepared at moderate temperatures (600 °C). Microstructural analysis from high resolution electron microscopy reveals the existence of small crystals (10–150 nm), which agglomerate leading to micro-sized crystals. All the NBNFO compounds show perovskite-type structure and a transition from rhombohedral (S.G. R3c) to orthorhombic (S. G. P21ma) mean macroscopic symmetry takes place for x = 0.50, as analyzed by refinement of XRD data. Nevertheless, at the microstructural scale, the system can be described by a compositional-segregation picture in which structural heterogenetiy is present. The materials show a positive temperature coefficient of resistivity (PTCR)-thermistor behavior above room temperature for x ≥ 0.50, up to maxima temperature values of 410, 393, 405 and 463 K for x values of 0.50, 0.75, 0.85 and 1, respectively. Above these temperatures, in the NTCR temperatures-region, conduction and polarization phenomena are analyzed from impedance and modulus formalisms in terms of two mechanisms implying different charge carriers: polaron hopping and/or diffusion of cation and oxygen vacancies. The activation energy values, Ea, corresponding to these processes are of about 0.50 and 1 eV, respectively. Finally, in the dielectric response displayed by the NBNFO ceramics, the development of a FE contribution as x increases is detected, which can be interpreted considering microstructural features.
Photoluminescence properties of zirconium and hafnium germanates obtained through different chemical routes Ceram. Int. (IF 3.057) Pub Date : 2018-07-10 V.V. Lozanov, V.E. Prokip, V.R. Shayapov, A.S. Berezin, N.I. Baklanova
Scheelite-type germanates ZrGeO4 and HfGeO4 were synthesized via ceramic and co-precipitation routes. The photoluminescence properties of the obtained germanates were studied. Under excitation at 250 nm, all samples showed a broad multi-color luminescence emission within the range from 2.0 to 3.5 eV. The dependence of the photoluminescence properties of the synthesized germanates as a function of the parameters of preparation, type of metal cation, and preliminary mechanical treatment is discussed. Hafnium and zirconium germanates, due to their good properties of bright and tunable photoluminescence, good photostability and chemical inertness, can be considered as promising fluorescent agents.
Exploitation of petroleum waste sludge with local bauxite raw material for producing high-quality refractory ceramics Ceram. Int. (IF 3.057) Pub Date : 2018-07-10 N.M. Khalil, Yousif Algamal, Qayid M. Saleem
The aim of this work is to exploit the petroleum waste sludge, through mixing with different quantities of the natural raw bauxite, present in abundance in Al zubierah area in Saudi Arabia, to manufacture high-quality refractory ceramics for use at high temperature applications. Seven batches were prepared using different weight proportions of local bauxite and petroleum waste sludge (100-0 wt%), (80–20Wt%), (60-40 wt%), (50- 50 wt%), (40–60 wt%), (20–80 wt%) and (0–100 wt%), respectively referred to M1, M2, M3, M4, M5, M6 and M7, the samples were prepared through solid-state technique to form cylindrical bodies by means of hydraulic pressing. The prepared bodies were dried and fired at different temperatures up to 1600 °C. The chemical and mineralogical compositions of raw bauxite and petroleum waste sludge were investigated using X-ray fluorescence (XRF) and X-ray diffraction (XRD) techniques. Their microstructure was depicted using scanning electron microscope (SEM) attached with energy dispersive X-ray unit (SEM+EDAX). The various technological properties of the ceramics bodies fired at different temperature (800–1600 °C) were tested. These properties involve; sintering parameters (bulk density and apparent porosity) tested using kerosene displacement method, the linear change tested by measuring the dimension shrinkage, mechanical properties (cold crushing strength) tested using an automatic compression machine as well as the refractory properties; permanent linear change, thermal shock resistance, refractoriness (Segar cone test) and load- bearing capacity. All tests were carried according to the international standard specifications. The chemical analysis using (XRF), and mineralogical investigation using (XRD), confirm that the petroleum waste sludge composed mainly from barite mineral (BaSO4), kaolinite (Al2(Si2O5(OH)4) and quartz (SiO2) while raw bauxite composed mainly from bohmite (AlO(OH)), gibbsite (Al(OH)3) and kaolinite. According to the International Standards, the used bauxite belongs to the high-quality bauxite grade (HQB). The firing temperature affects differently on the shape of the prepared bodies i.e., while the ceramics bodies prepared from M1-M5 keep their forms even at 1600 °C those of M6 and M7 have been fused at only 1400 °C. The technological properties of the prepared ceramic bodies are influenced by both firing temperature and the content of petroleum waste sludge. Ceramic bodies of M3 batch composed of 60 wt. % of bauxite and 40 wt. % of petroleum waste sludge was considered as the optimum among the investigated samples since they satisfy the requirement of the International Standards of refractory ceramics. This work is doubly valuable since it uses an available and cheap raw bauxite and consumes petroleum waste sludge (decreasing air pollution) to produce high-quality refractory ceramics with economic impact.
Thermally tunable terahertz magnetic responses of TbFeO3 ceramic Ceram. Int. (IF 3.057) Pub Date : 2018-07-10 Xinxi Zeng, Lingling Wu, Xiaoqing Xi, Bo Li, Ji Zhou
Terahertz (THz) radiation produces complex and intriguing interactions with many of the magnetically ordered materials. We introduced a THz time-domain spectroscopy with a temperature control attachment to investigate thermally tunable terahertz magnetic responses of TbFeO3. Ferromagnetic (FM) resonances and antiferromagnetic (AFM) resonances were excited simultaneously at T = 3–290 K. The performance of temperature effect on resonances was assessed by their transmittance, resonant frequency shifts and a defined quality factor (Q-factor, Q = ν0/Δν). Transmittance, defined Q-factor and frequency shifts were introduced to assess the thermally tunable performances of terahertz magnetic responses. Overall increased transmittance, increased Q-factor and blue shifts were observed as temperature cools. This will be beneficial to the THz spectroscopic application in controlling responses of various materials.
Novel hybrid material based on Mg2+ and SiO44- co-substituted nano-hydroxyapatite, alginate and chondroitin sulphate for potential use in biomaterials engineering Ceram. Int. (IF 3.057) Pub Date : 2018-07-10 Katarzyna Szurkowska, Anna Zgadzaj, Marzena Kuras, Joanna Kolmas
Pure hydroxyapatite (HA), HA enriched in Mg2+ ions (Mg-HA) and SiO44- ions (Si-HA), as well as a co-substituted sample (MgSi-HA), were synthesized using the precipitation method and systematically characterized according to various analytical methods. The degree of substitution was examined by inductively coupled plasma optical emission spectrometry (ICP-OES). The chemical structure of the samples was determined by mid-infrared spectroscopy (FT-IR) and solid-state nuclear magnetic resonance (ssNMR). The powder X-ray diffractometry (PXRD) method was used for the phase identification and characterization of unit cell parameters. An evaluation of the crystal morphology was carried out by transmission electron microscopy (TEM). All of the samples turned out to be cytocompatible, as confirmed by an in vitro test on the BALB/c 3T3 fibroblasts cell line. Moreover, the MgSi-HA sample was used to prepare granules based on sodium alginate and chondroitin sulphate. A new method of crosslinking using Mg2+ ions was developed. The low-porous granules obtained from this process were then characterized using scanning electron microscopy (SEM).
Feasibility of ZrC-W composite used as a tool of friction stir welding: first principles calculations and experiment Ceram. Int. (IF 3.057) Pub Date : 2018-07-11 Song Wang, Xingwen Fan, Xianfeng Yang, Qiao Zhang, Kaipeng Wu, Da Li
In this work, the feasibility of ZrC-W composite used as a tool of friction stir welding was investigated by first-principle calculation and mechanical test. A theoretical calculation (including interfacial atomic structure, the work of adhesion of interfaces, density of states and interfacial charge distribution) was performed on ZrC (100)/W (100) interfaces based on the method of the density function theory, and the results show that a strong C-W bond is formed at the interface and ZrC/W interfaces exhibit a mixture of covalent, metallic and ionic characteristic. Furthermore, ZrC–W composite was produced by powder metallurgy method. The composite had a Vickers hardness of 1290HV, and a mass loss rate of 0.046 g/h at 600℃, which indicates that ZrC-W has an excellent wear resistance. The calculated and experiment results gained in this study can provide an evidence that the application of ZrC-W composite used as a tool material of friction stir welding is feasible.
0.37BF-0.31PMN-0.32PT: A superior piezo-/pyro-/ferro-electric ternary ceramic at MPB Ceram. Int. (IF 3.057) Pub Date : 2018-07-11 Abhilash J. Joseph, Nidhi Sinha, Sahil Goel, Abid Hussain, Binay Kumar
A near morphotropic phase boundary composition 0.37BF-0.31PMN-0.31PT has been synthesized using the conventional solid-state reaction method. Scanning electron microscopy revealed a dense microstructure of the ternary ceramic system. A high piezoelectric coefficient (d33⁎ = 572 pm/V) was revealed from the displacement-voltage curve (butterfly loop). An excellent pyroelectric response was displayed by the ceramic in the temperature range of 30–80 °C. Good saturated ferroelectric loops with good fatigue resistant characteristic and high value of remanent polarization (Pr = 60.62 μC/cm2) and coercive field (Ec = 18.77 kV/cm) were obtained for the synthesized ceramic. Apart from the conventional method used for reporting the Pr value, which is normally larger than the practically usable (remanent) polarization component, true-remanent hysteresis task was used to isolate the non-remanent component and hence reveal the true-remanent component of polarization which was found to be ~ 80% that of the conventional Pr value suggesting low leakage contributions in the ternary ceramic system. Time-dependent compensated hysteresis task was performed to study the resistive-leakage nature of the ceramic, which is a frequency dependent parameter.
INFLUENCES OF THE PROCESSING METHOD AND SINTERING TEMPERATURE ON THE TRANSLUCENCY OF POLYCRYSTALLINE YTTRIA-STABILIZED TETRAGONAL ZIRCONIA FOR DENTAL APPLICATIONS Ceram. Int. (IF 3.057) Pub Date : 2018-07-11 Chuin Hao Chin, Andanastuti Muchtar, Che Husna Azhari, Masfueh Razali, Mohamed Aboras
The achievement of a high esthetic value in polycrystalline yttria-stabilized tetragonal zirconia (Y-TZP)-based dental restorations is hindered by the low translucency of Y-TZP. Thus, this study investigated the effects of processing method and sintering temperature on the translucency of Y-TZP for dental applications. Wet (slip casting) and dry (cold isostatic pressing) processing methods were used. Y-TZP specimens were fabricated by applying the processing methods and sintering at different temperatures (1450 °C–1650 °C). The mechanical, morphological, and optical properties of the Y-TZP specimens were examined and compared. The specimens were benchmarked with a commercial Y-TZP, namely, Cercon©. Results showed that wet processing produced higher mechanical properties and translucency than dry processing. This finding can be mainly attributed to the higher capability of wet processing than dry processing in alleviating the agglomeration in Y-TZP. Among the several specimens that were tested, the slip-casted Y-TZP that was sintered at 1600 °C showed the optimum mechanical properties (99.5% density and 12.7 GPa hardness) and translucency (35% light transmission) for dental applications. Furthermore, the light transmission achieved in this study was approximately three times higher than that of the commercial Y-TZP (13%), thereby indicating a potential alternative to replace the commercial Y-TZP. Highly translucent Y-TZP with excellent mechanical properties was developed in this study through wet processing with a sintering temperature of 1600 °C. The developed Y-TZP can be an alternative to commercial products to produce a highly esthetic dental restoration.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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