Fabrication and Characterization of Porous Biphasic β-Tricalcium Phosphate/Carbonate Apatite Alginate Coated Scaffolds Ceram. Int. (IF 2.986) Pub Date : 2018-02-22 Yong Xuan Hui, Muhammad Iqbal Mazlam, Nurazreena Ahmad
In this research, biphasic β-tricalcium phosphate/carbonate apatite (β-TCP/CO3Ap) scaffolds incorporated with alginate were fabricated. Sodium alginate was extracted from local brown seaweed, Sargassum Polycystum via calcium alginate process. Biphasic β-TCP/CO3Ap scaffolds were fabricated by polymer reticulate method. β-TCP slurry was infiltrated into the polyurethane foam (PU) foam, then sintered up to 1300 °C, soaked for 4 hours and immediately quenched in still air to form biphasic β-TCP/α-TCP scaffold. Biphasic β-TCP/α-TCP scaffold was then transformed to biphasic β-TCP/CO3Ap scaffold by dissolution-precipitation reaction with 1 M of NaHCO3 at 170 °C for 1, 3 and 5 days. Biphasic β-TCP/CO3Ap scaffold from 5 days dissolution-precipitation reaction was chosen to incorporate with 1%, 3% and 5% of sodium alginate, respectively, as it has the highest composition of CO3Ap phase. FTIR and FESEM analysis confirmed the presence of characteristic functional groups of sodium alginate. Mechanical strength of biphasic β-TCP/CO3Ap scaffold improved by increasing the concentration of sodium alginate. The highest mechanical strength achieved was 26.38 kPa for biphasic β-TCP/CO3Ap scaffold with 5% sodium alginate coating and it was chosen to further study with the addition of 1%, 3% and 5% microspheres. FESEM analysis confirmed the attachment of microspheres on the surface of alginate/biphasic β-TCP/CO3Ap scaffold was successful.
Selective Laser Melting of Alumina: A Single Track Study Ceram. Int. (IF 2.986) Pub Date : 2018-02-21 Zhiqi Fan, Mingyuan Lu, Han Huang
Ceramics-based additive manufacturing is a complex process and the solidification mechanism and microstructural evolution are currently not fully understood. In this work, Al2O3 single tracks were formed using a customised selective laser melting (SLM) system equipped with a high power diode laser. The effects of laser energy density (LED) on geometry, microstructure and micro-mechanical properties of Al2O3 tracks were investigated. To better understand the solidification mechanism, a transient three-dimensional thermal model was developed for predicting the thermal behaviour of the melt pool. The results indicated the use of high LED gave rise to decreased viscosity and surface tension of the molten alumina and led to localised melting of the substrate. Both, in turn, enabled the formation of a continuous solidified track. The solidified tracks were primarily composed of columnar dendrite. When relatively high LED (≥25.7 kJ/m) was applied, equiaxed dendrite appeared along the central line near the track surface. The size of dendritic grains decreased with the decreased LED, attributed to the increased cooling rate at solidification interface. The micro-hardness of the solidified track was found to be inversely proportional to the grain size owning to grain boundary strengthening effect.
The effects of laser patterning 10CeTZP-Al2O3 nanocomposite disc surfaces: osseous differentiation and cellular arrangement in vitro Ceram. Int. (IF 2.986) Pub Date : 2018-02-21 Lidia Goyos-Ball, Catuxa Prado, Raquel Díaz, Elisa Fernández, Arnold Ismailov, Tero Kumpulainen, Erkki Levänen, Ramón Torrecillas, Adolfo Fernández
Customized square grid arrangements of different groove depths (1.0, 1.5 and 3.0 µm) and separations (10 and 30 µm) were successfully laser patterned, using a nanosecond pulsed fibre laser, on the surface of 10 mol% ceria-stabilized zirconia and alumina (10CeTZP-Al2O3) nanocomposite discs (diameter: 10 mm; thickness: 1.5 mm). The patterned surfaces and the in vitro biological response of osteoblasts (SAOS-2) towards them were thoroughly analysed. In terms of composition, the laser treatment was found to cause superficial monoclinic-tetragonal zirconia phase transformation and alumina evaporation. In vitro, the most effective grid configuration for osseous differentiation was found to be 1.5 µm groove depth and 10 µm groove separation, and confocal microscopy revealed that the cells show a tendency to be sorted as groove depth increases. It is thought that custom-made patterns could be produced to guide cell attachment in vivo, which could favour implant integration and reduce healing time.
Template-free synthesis of MgO mesoporous nanofibers with superior adsorption for fluoride and Congo red Ceram. Int. (IF 2.986) Pub Date : 2018-02-21 Zhichao Yu, Chonghe Xu, Kangkang Yuan, Xinzhu Gan, Haifeng Zhou, Xinqiang Wang, Luyi Zhu, Guanghui Zhang, Dong Xu
MgO mesoporous nanofibers were obtained by a template-free electrospinning method. The unique bumpy-structure was obtained on the surface of nanofibers that could enhance the surface area and provide more active sites for adsorption. The formation mechanism of the bumpy-structure has been investigated. The as-prepared MgO nanofibers with a high surface area of 194.17 m2 g−1 exhibited excellent adsorption capacities for fluoride of 237.49 mg g−1. Furthermore, the MgO nanofibers showed selective adsorption for different organic dyes and have superior adsorption capacity for Congo red (4802.27 mg g−1). The adsorption processes for both fluoride and Congo red were systematically investigated, which were found to follow the pseudo-second-order kinetic model. By comparison with the reported fabrication routes and adsorption capacities of mesoporous MgO, the synthesis process is simple, controllable and template-free, and the superior adsorption performance provided a potential adsorbent for the removal of fluoride and Congo red in wastewater treatment. The high surface area of the MgO mesoporous nanofibers might also promote its application in basic catalysis and other fields.
CO2 laser-assisted preparation of transparent Eu2Ti2O7 thin films Ceram. Int. (IF 2.986) Pub Date : 2018-02-21 Jan Mrázek, Jan Aubrecht, Filip Todorov, Jiří Buršík, Viktor Puchý, Robert Džunda, Soňa Vytykáčová, Ivan Kašík
We present a laser-assisted preparation of transparent europium-titanate Eu2Ti2O7 thin films with tailored structural and optical properties. We have evaluated the effects of the irradiation time on the structural and the optical properties of the films. This approach allows the preparation of nanocrystalline crack-free films and micro patterns. The amorphous thin films were prepared by a sol-gel method. The films were annealed by a CO2 laser beam for various time intervals. The laser irradiation induced a crystallization process that resulted in the formation of Eu2Ti2O7 nanocrystals. The nanocrystals regularly grew with increasing irradiation time reaching the size from 25 nm to 45 nm. A film of a thickness 480 nm exhibited an optical transmission of 91.9% that is close to the maximal theoretical limit. The film's refractive index at 632 nm was 2.26. A micrometric pattern was prepared by a direct laser writing followed by a wet chemical etching. Feasibility of the demonstrated approach, together with the high film's quality, and europium-titanate chemical resistivity open up many opportunities for advanced applications. The approach can be used for a preparation of protective coatings and integrated photonic devices such as planar optical waveguides and couplers.
Calcium phosphates grown on bacterial cellulose template Ceram. Int. (IF 2.986) Pub Date : 2018-02-21 C. Busuioc, C.D. Ghitulica, A. Stoica, M. Stroescu, G. Voicu, V. Ionita, L. Averous, S.I. Jinga
Bacterial cellulose membranes were employed as templates for calcium phosphates deposition by successive immersion in solutions of Ca(NO3)2·4H2O and (NH4)2HPO4, under ultrasonication. During the wet chemical reaction, mineral phases were loaded on bacterial cellulose fibrils, leading to precursor hybrid composites. These were subjected to a lyophilisation procedure in order to preserve the 3D porous aspect and afterwards to a thermal treatment with the aim of removing the polymeric phase and generating well crystallized structures. Different types of morphologies were achieved by varying the heating rate, as well as the calcination temperature and period. The as-prepared samples and the final ones were investigated from compositional and structural point of view through X-ray diffraction and Fourier-transform infrared spectroscopy and morphologically concerning by scanning electron microscopy. The magnetic properties were also evaluated in order to demonstrate the suitability of the obtained materials for the development of magnetic scaffolds dedicated to hard tissue applications.
Composite microstructures and piezoelectric properties in tantalum substituted lead-free K0.5Na0.5Nb1-xTaxO3 ceramics Ceram. Int. (IF 2.986) Pub Date : 2018-02-21 F. Jean, F. Schoenstein, M. Zaghrioui, M. Bah, P. Marchet, J. Bustillo, F. Giovannelli, I. Monot-Laffez
K0.5Na0.5Nb1-xTaxO3 (KNNT) (with x = 0.00, 0.05, 0.10, 0.20, 0.30, 0.50 and 1) ceramics are prepared by ball milling and two calcinations at 830 °C for 5 hours. Subsequent sintering of centimeter size pellets, 1–2 mm thick, is studied using conventional and spark plasma sintering techniques with various conditions. X-Ray diffraction and Raman spectroscopy phase identification reveal orthorhombic to tetragonal phase transitions occurring at about x = 0.50, associated to chemical disorder. Scanning electron microscope observations and associated energy dispersive X-ray spectroscopy analysis reveal some composite aspect of the ceramics. Substitution of niobium by tantalum, corresponding to x increase, decreases significantly the grain size but also the densification of the ceramics sintered by conventional sintering, while, enhancement of the piezoelectric properties is observed for both sintering techniques. Thanks to parameters optimization of the spark plasma sintering process, temperature-time-pressure, significant improvement of the relative density over 96%, is obtained for all the compositions sintered between 920 and 960 °C, under 50 MPa, for 5 to 10 minutes with heating rates of 100 ° C/min. High relative permittivity (εr = 1027), piezoelectric charge coefficient (d33 = 160 pC/N) and piezoelectric coupling factor (kp = 46%) are obtained in spark plasma sintered K0.5Na0.5Nb1-xTaxO3 composite ceramics, for x ranging between 0.10 and 0.30 and for some specific spark plasma sintering conditions. Thus, tantalum single element substitution on niobium site, combined with spark plasma sintering, is revealed to be a powerful combination for the optimization and the reliability of piezoelectric properties in KNN system.
Formation Mechanism of Elongated β–Si3N4 Crystals in Fe–Si3N4 Composite via Flash Combustion Ceram. Int. (IF 2.986) Pub Date : 2018-02-21 Bin Li, Guangqi Li, Junhong Chen, Haiyang Chen, Xinming Xing, Xinmei Hou, Yong Li
Elongated β–Si3N4 crystals have a significant influence on the mechanical property of Fe–Si3N4 composite. In this paper, the formation mechanism of elongated β–Si3N4 crystals in Fe–Si3N4 composite was investigated. During the preparation process, β–Si3N4 crystals developed in a spiral and layer growth mechanism in the dense areas. They kept growing from the dense areas and formed radially distributed elongated crystals with hexagonal prismatic morphology as time went on. As for the formation mechanism, the (100) crystal plane of β–Si3N4 from Si-N-O melt is mainly the vicinal crystal planes growth with different angles from the (100) crystal plane. At the later stage, the crystallization and the diffusion forces in Si-N-O molten phase decreased. However, the short range diffusion remained active and resulted in the gradient distribution of N content near the boundary. With the temperature decreasing, the disappearance of the short range diffusion implied the end of the crystallization process of the elongated β–Si3N4 crystals.
The effect of magnesium content on in vitro bioactivity, biological behavior and antibacterial activity of sol–gel derived 58S bioactive glass Ceram. Int. (IF 2.986) Pub Date : 2018-02-21 Amirhossein Moghanian, Arman Sedghi, Alireza Ghorbanoghli, Emad Salari
Bioactive glasses (BGs) have a great potential for bone replacement and regeneration in bone tissue engineering applications. In this research, first, sol–gel derived magnesium substituted 58 S BGs (MBGs) series composed of 60SiO2–4P2O5-(36-x) CaO- xMgO, (x= 0; 1; 3; 5; 8 and 10 mol.%) were synthesized and stabilized at 700 °C to eliminate the nitrates and prevent the crystallization of MBGs. MgO was substituted for CaO in the BG formula up to 10 mol% and the effect of Mg concentration on in vitro bioactivity and cellular properties of the MBGs were investigated by immersing them in simulated body fluid (SBF) followed by structural characterization using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) techniques. The effects Mg on proliferation and differentiation of osteoblastic MC3T3-E1 cells were also evaluated by 3-(4,5dimethylthiazol-2-yl)−2,5-diphenyltetrazolium bromide (MTT) and alkaline phosphate (ALP) activity. Results revealed that magnesium-substituted 58 S BG with 5 mol% MgO (BG-5) had the highest formation rate of hydroxyapatite (HA) while substitution of 8 mol% and10 mol% MgO (BG-8 and BG-10) lowered the bioactivity. MTT and ALP results confirmed that the substitution of the MgO up to 5 mol% increased both proliferation and differentiation of MC3T3-E1 cells, while more substitution had a negative effect and resulted in a decrease of proliferation and differentiation in BG-8 and BG-10. The result of antibacterial test showed that MBGs exhibited antibacterial effect against methicillin-resistant staphylococcus aureus (MRSA) bacteria. Taken together, results suggest that, among all the synthesized MBGs, sample BG-5 is a promising candidate as multifunctional biomaterial for bone tissue engineering with maximum cell proliferation and ALP activity, good bioactivity and high antibacterial efficiency against MRSA bacteria. Eventually, the BG-5 is suggested to be used in segmental defects in rat model in vivo.
Preparation of quaternary boro-phosphate multifunctional glasses and their structural, optical, switching and antibacterial properties Ceram. Int. (IF 2.986) Pub Date : 2018-02-21 Mahsa Baazm, Ehsan Soheyli, Mohammad Hossein Hekmatshoar, Arman Rostamzad, Abouzar Karami Cheragh Abad
In this paper, the glass composition of (1-x)P2O5-xB2O3-CuO-Li2O (x= 0, 5, 10, 15, and 20 mol%) was prepared and the effect of P2O5 substitution by B2O3 on their structural, optical, switching, and antibacterial characteristics was studied. FT-IR spectra showed that an increase in the B2O3 content leads to gradual erosion of the phosphate characteristic bonds, and the emergence of borate-related ones by creating new linkages between phosphate chains through P–O–B bonds and formation of highly cross-linked P3-O-B4 linkages. The incorporation of boron up to 20 mol%, also leads to an overall increase in glass transition temperature together with a decrease in the molar volume which both, implied improvement of glass stability. Optical studies revealed that all glasses are almost transparent in the UV-Vis region with high band gap energy about 3.83 eV, which experiences a red-shift with increase in the B2O3 concentration to 15 mol%. By calculating the wavelength-dependent optical parameters, however, it was found that the present glass composition with highest concentration of B2O3 shows refractive index near one and very negligible extinction coefficient (and imaginary optical dielectric function) at the visible region. These results support the great potential of the mentioned glass composition as a window layer. The analysis of the high electric field measurements demonstrated a wide range reduction in switching threshold voltage as the B2O3 content increases. This hints at their potential application as electrical-induced sensors. The antibacterial activity of x= 0 and x= 5 glass compositions has been examined by zone of inhibition measurements and it was found that they have potential applications as antibacterial agent.
Enhanced piezoelectric properties by reducing leakage current in Co modified 0.7BiFeO3−0.3BaTiO3 ceramics Ceram. Int. (IF 2.986) Pub Date : 2018-02-21 Shigang Huang, Qingning Li, Ling Yang, Jiwen Xu, Changrong Zhou, Guohua Chen, Changlai Yuan, Guanghui Rao
Co modified lead-free 0.7BiFeO3−0.3BaTiO3 (0.7BFO-0.3BT-xCo2O3；x =0, 0.3, 0.6, 0.9 and 1.2) piezoelectric ceramics were prepared by a conventional solid-state reaction. The effect of Co doping on the structural, piezoelectric properties and leakage current was investigated. A greatly reduced leakage current and dramatically improved piezoelectric properties were achieved in x=0.3 Co doped ceramic. The maximum d33=151 pC/N and kp= 0.32 were obtained at x=0.3 addition due to the co-effect of maximum applied poling electric field and large grain size. The X-ray photoelectron spectroscopy (XPS) analysis and complex impedance data indicated that the greatly reduced leakage current could be attributed to the effect of suppressing Fe2+ ion formation and promoting grain boundary resistance by Co doping. These results strongly suggest that low concentration of Co doping is a good strategy to improve the resistance and piezoelectric properties simultaneously in BFO-based lead-free piezoceramics.
Preparation of nanocrystalline MoSi2 with enhanced lithium storage by sol–gel and carbonthermal reduction method Ceram. Int. (IF 2.986) Pub Date : 2018-02-21 Jianguang Xu, Yu Zhang, Jinshun Qi, Yu Wang, Juhua Luo, Wei Yao
Herein nanocrystalline MoSi2 with enhanced lithium storage was successfully synthesized via a sol-gel and carbonthermal reduction method. Reduction of the gel mixture of Mo precursor and Si precursor by carbon at a desired temperature resulted in the formation of MoSi2 nanoparticles. The gel mixture was obtained through the hydrolysis of TEOS and ammonium molybdate and the polymerization of hydrolysis products of TEOS. The reducing agent carbon was produced via decarburition of sucrose's hydrolysis products, which have been wrapped in the gel during its formation process. Addition of HCl to the mixed solution controlled the hydrolysis and polymerization rate, and enabled the formation of a gel mixture with homogeneously distributed hydrolysis products of ammonium molybdate, TEOS and sucrose. This achievement likely generates a novel route to synthesize non-oxide compounds such as silicide, carbide through the sol–gel and carbonthermal reduction process. In addition, the as-received MoSi2 nanoparticles showed considerable activities in the reversible lithiation and delithiation process. When using as an anode for Li-ion batteries, MoSi2 nanoparticles delivered a specific capacity of 325 mAh g-1 at C/12 and showed an increasing capacity with cycling.
Microstructure and mechanical properties of hot pressed submicron TiB2 powders Ceram. Int. (IF 2.986) Pub Date : 2018-02-20 Zhezhen Fu, Rasit Koc
This paper studies the microstructure and mechanical properties of hot pressed submicron TiB2 powders. With the hot press temperature increasing from 1500 °C to 1800°C, the relative density increases and the sample maintains a single TiB2 phase. The powders are able to be sintered to a relative density of ~94.5% at the temperature of 1800°C. For the first time, unique elongated platelike grain structure, which has only been observed from transient liquid phase or reaction sintered borides, also forms at the sintering temperature of 1800°C. In addition, the sample sintered at 1800°C has a fine microstructure (elongated grain of ~0.3–3 µm) and high mechanical properties (hardness of ~27.6±2.3 GPa, flexural strength of ~560±49 MPa, and fracture toughness of ~6.5±0.2 MPa·m−1/2). Correlations between mechanical properties and microstructure are further discussed.
Sheet resistance dependence of fluorine-doped tin oxide films for high-performance electrochromic devices Ceram. Int. (IF 2.986) Pub Date : 2018-02-20 Kue-Ho Kim, Bon-Ryul Koo, Hyo-Jin Ahn
In the present study, we fabricated fluorine-doped tin oxide (FTO) films with different sheet resistances (~10 Ω/□, ~6 Ω/□, and ~3 Ω/□) prepared through the adjustment of deposition time during the horizontal ultrasonic spray pyrolysis deposition (HUSPD) and investigated the effect of electrochromic (EC) performances with different sheet resistances of the FTO films used as transparent conducting electrodes. The results demonstrated that, owing to the increased electrochemical activity, the decrease of sheet resistance accelerated switching speeds of the EC devices. However, for the coloration efficiency (CE), the FTO films with the optimum sheet resistance of ~6 Ω/□ exhibited the highest value as compared to the other samples. The improvement of the CE value can be mainly attributed to high transmittance modulation by the uniform surface morphology of the FTO films to reduce interfacial light-scattering between the WO3 films and FTO films. Therefore, our results provide a valuable insight into the improvement of the performance of the EC devices using the optimum sheet resistance (~6 Ω/□) of the FTO films.
Structure and magnetic properties of multi-morphological CoFe2O4/CoFe nanocomposites by one-step hydrothermal synthesis Ceram. Int. (IF 2.986) Pub Date : 2018-02-19 Shichong Xu, Zhihe Wang, Rui Su, Na Han, Ailing Xie, Li Wang, Haibo Li
Multi-morphological CoFe2O4/CoFe nanocomposites have been synthesized using a facile hydrothermal process. The effects of hydrazine hydrate amount during hydrothermal reaction on the structure and magnetic property of the specimens were studied. With increasing hydrazine hydrate amount, the CoFe2O4 transformed to CoFe and the morphology of the specimen changed from granular particles to faceted particles. The saturation magnetization monotonically increased and the coercivity monotonically decreased with increasing hydrazine hydrate amount. The magnetic interactions, determining the magnetic properties of the composites, result from the dominant dipole coupling and relative weak exchange coupling between CoFe2O4 and CoFe nanoparticles. The CoFe2O4/CoFe nanocomposite prepared with 2 mL hydrazine hydrate exhibited the optimal magnetic properties, with the saturation magnetization of 81 emu/g and coercivity of 636 Oe.
ZnO/WO3 nanostructure as an efficient visible light catalyst Ceram. Int. (IF 2.986) Pub Date : 2018-02-19 Ahmed Khan Leghari Sajjad, Shamaila Sajjad, Anum Iqbal, Najam-ul-Athar Ryma
Highly photosensitive ZnO/WO3 photocatalysts were fabricated by wet impregnation of zinc oxide (ZnO) in different contents. Tungsten trioxide (WO3) was synthesized by hydrothermal route. The presence of ZnO inhibited the crystallization of WO3 and caused agglomeration of WO3 nanoparticles surface. The formation of Zn-O-W linkage was studied by X-ray photoelectron emission (XPS) and Fourier transforms Infra-red spectra (FTIR). These linkages were responsible for red shift of absorption peak of composites as compared to individual ZnO and WO3. The band gap was decreased due to incorporation of ZnO in WO3 which promoted the separation of photo-generated carriers. As a result, ZnO/WO3 composite showed extremely high efficiency for MO degradation in comparison with Degussa P25, pure ZnO and WO3. 2.0% ZnO/WO3 composite displayed the highest activity in photocatalytic decomposition of methyl orange (MO) dye.
Synthesis and Electrochemical Properties of α-LiVOPO4 as Cathode Material for Lithium-Ion Batteries Ceram. Int. (IF 2.986) Pub Date : 2018-02-19 Zhonggang Liu, Zhi Su, Hualing Tian
Triclinic α-LiVOPO4 with excellent electrochemical properties is prepared, using δ-VOPO4, LiNO3, and a highly conductive carbon material (acetylene black) as raw materials, by a two-step method, for the first time. Transmission electron microscopy reveals that the synthesized nanoscale α-LiVOPO4 is approximately 50–100 nm in size, and its surface is covered by 1.68-nm thick acetylene black, which not only improves the ionic conductivity of the material, but prevents material-size growth at high temperature, and particle agglomeration. In addition, the initial discharge capacity of α-LiVOPO4 sintered at 600 ℃ over 10 h is the highest, reaching 111.7 mAh·g−1 at 0.05 C. The capacity retention rate is 95.1%, which is 106.3 mAh·g−1 after 50 cycles.
A comparative study of synthesis and spark plasma sintering of YAG nano powders by different co-precipitation methods Ceram. Int. (IF 2.986) Pub Date : 2018-02-19 Mahsa Rahmani, Omid Mirzaee, Mohammad Tajally, Mohammad Reza Loghman-Estarki
Pure yttrium-aluminum-garnet (YAG) nano particles were synthesized via normal and reverse co-precipitation methods using nitrate starting solutions and ammonium hydrogen carbonate (AHC) as precipitator agent. The impact of titration method on the phase evolution, thermal behavior, precipitate's composition, morphology and chemical bonds of powders were studied by XRD, TG-DTA, FTIR, FESEM, TEM, EDS and BET analysis. The results revealed that in the normal method, the precipitates were composed of relatively dense particles compared with more homogenous fluffy precipitates with higher carbonate content obtained by the reverse method. The precursors achieved by the reverse method formed less agglomerated and smaller size YAG powders after calcination at 900 °C. Calcined nano powders were processed by spark plasma sintering (SPS) technique at 1350 °C for 10 min without any sintering aids or dispersive agents. The sintering of both powders led to a highly dense and fine submicron-structured YAG ceramic. However, the YAG ceramic produced by SPS of reverse co-precipitated nano powders showed higher transparency (43% at 680 nm and 58% in near-infrared range) and finer micro-structure (about 210 nm in grain size) as compared with normal co-precipitated nano particles.
Phase stability, thermo-physical properties and thermal cycling behavior of plasma-sprayed CTZ, CTZ/YSZ thermal barrier coatings Ceram. Int. (IF 2.986) Pub Date : 2018-02-19 Jinshuang Wang, Junbin Sun, Jieyan Yuan, Qiangshan Jing, Shujuan Dong, Bing Liu, Hao Zhang, Longhui Deng, Jianing Jiang, Xin Zhou, Xueqiang Cao
ZrO2 co-stabilized by CeO2 and TiO2 with stable, nontransformable tetragonal phase has attracted much attention as a potential material for thermal barrier coatings (TBCs) applied at temperatures >1200 °C. In this study, ZrO2 co-stabilized by 15 mol% CeO2 and 5 mol% TiO2 (CTZ) and CTZ/YSZ (zirconia stabilized by 7.4 wt.% Y2O3) double-ceramic-layer TBCs were respectively deposited by atmospheric plasma spraying. The microstructures, phase stability and thermo-physical properties of the CTZ coating were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric-differential scanning calorimeter (TG-DSC), laser pulses and dilatometry. Results showed that the CTZ coating with single tetragonal phase was more stable than the YSZ coating during isothermal heat-treatment at 1300 °C. The CTZ coating had a lower thermal conductivity than that of YSZ coating, decreasing from 0.89 W•m−1•K−1 to 0.76 W•m−1•K−1 with increasing temperature from room temperature to 1000 °C. The thermal expansion coefficients were in the range of 8.98×10−6 K−1 to 9.88×10−6 K−1. Samples were also thermally cycled at 1000 °C and 1100 °C. Failure of the TBCs was mainly a result of the thermal expansion mismatch between CTZ coating and superallloy substrate, the severe coating sintering and the reduction-oxidation of cerium oxide. The thermal durability of the TBCs at 1000 °C can be effectively enhanced by using a YSZ buffer layer, while the thermal cycling life of CTZ/YSZ double-ceramic-layer TBCs at 1100 °C was still unsatisfying. The thermal shock resistance of the CTZ coating should be improved; otherwise the promising properties of CTZ could not be transferred to a well-functioning coating.
Structure and morphology evolution in solid-phase synthesis lithium ion battery LiNi0.80Co0.15Al0.05O2 cathode materials with different micro-nano sizes of raw materials Ceram. Int. (IF 2.986) Pub Date : 2018-02-17 Shubiao Xia, Jian-Jun Liu, Fushao Li, Feixiang Cheng, Xue Li, Chengke Sun, Guo Hong
Solution-processed Nickel Oxide Hole Transport Layer for Highly Efficient Perovskite-based Photovoltaics Ceram. Int. (IF 2.986) Pub Date : 2018-02-17 Saemon Yoon, Dong-Won Kang
Solution processed NiOx is one of the promising hole transport layer (HTL) for planar perovskite solar cells, which can replace hygroscopic poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) HTL. In this study, we investigated effects of ethylenediamine (EDA) additive in NiOx precursor solution (nickel nitrate hexahydrate dissolved in ethyleneglycol) on optoelectronic and surface morphological properties of resultant solution processed NiOx films. By varying EDA content (0–10.0 v/v %) in the precursor, we could find out that adequate EDA additive (~5.0%) provide much reduced electrical resistivity and enhanced optical transmission compared with control NiOx film (No EDA) by suppressing formation of byproducts (i.e. nickel hydroxide). In addition, AFM surface topography showed much compact and dense deposition of NiOx film on ITO electrode. This contributed to improve charge transport properties and suppress charge recombination loss at ITO/perovskite interface, which provided strong enhancement in fill factor from 0.599 to 0.714 in the perovskite solar cells. As a result, a power conversion efficiency (PCE) was strongly increased from 13.9 (No EDA) to 16.7% (EDA 5.0%). This also outperformed the performance (14.3%) of device using PEDOT:PSS, which indicates that the adequate control of EDA additive for NiOx HTL could offer much promising photovoltaic performance.
Structural, hardness and toughness evolution in Si-incorporated TaC films Ceram. Int. (IF 2.986) Pub Date : 2018-02-17 Suxuan Du, Mao Wen, Lina Yang, Ping Ren, Qingnan Meng, Kan Zhang, Weitao Zheng
Ta–Si-C films were deposited by DC magnetron co-sputtering using TaC and Si targets in an Ar-discharge atmosphere. Increasing the current of Si target from 0.0 to 0.5 A led to a continuous increase of Si content from 0.0 to 30.8 at.%. The effects of Si content on microstructure were systematically investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). At low Si content (≤ 5.6 at.%), Si occupied C vacancies to form a solid solution Ta(C, Si). Further increasing the Si content, some Si atoms bonded with C atoms resulting in the formation of amorphous phase (a-C:Si), and the films presented a nanocomposite structure consisting of solid solution Ta(C, Si) surrounded by a-C:Si matrix. At the highest Si content (30.8 at.%), the film exhibited finally X-ray amorphous structures. The hardness (H) and fracture toughness (Kf) were observed to initially increase and then decrease as the Si content was increased. At 5.6 at.% Si, the film exhibited a maximum in H (44.9 ± 2.7 GPa) and Kf (3.61 ± 0.16 MPa m1/2), which can be ascribed to the formation of a solid solution. On further increasing the Si content, an amorphous phase gradually appeared, leading to a decrease in H and Kf.
Structural and magnetic properties of Ce-doped Strontium hexaferrite Ceram. Int. (IF 2.986) Pub Date : 2018-02-17 M.A. Almessiere, Y. Slimani, A. Baykal
Ce3+ ion substituted Sr-hexaferrite magnetic nanoparticles (MNPs), SrCexFe12-xO19 (0.0 ≤ x ≤ 0.5) MNPs, were fabricated by citrate sol-gel combustion approach. All products have been characterized using X-ray diffraction (XRD), Photoluminescence, scanning electron microscopy (SEM), elemental mapping (EDS), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) at 300 and 10 K. The XRD pattern presents effective substitution of Ce3+ on the sites of strontium hexaferrite lattice. With Ce3+ doping, the lattice parameters a is almost unchanged, whereas c is a little increases with increasing the dopant contents.The hysteresis loops M-H showed the ferromagnetic nature of all elaborated. The saturation magnetization (Ms) and the remnant magnetization (Mr) are reduced with increasing Ce amount. All the elaborated products presented typically squarness ratio (Mr/Ms) around 0.5, indicating the existence of non-interacting single domain MNPs with a uniaxial anisotropy. The anisotropy fields (Ha) are found to be very large proving that all products are magnetically hard. With increasing the Ce content, Ha increases which indicate the strengthening of magnetic properties. Consequently, the values of coercive field (Hc) are enhanced, leading these products to be utilized in many uses, such as recording media and permanent magnets. ZFC and FC magnetizations curves indicated shifts of the blocking temperature (TB) to lower temperatures with increasing Ce content. This is accredited to the reducing of particle size with Ce-substitution.
The effect of carbon and nickel additions on the precursor synthesis of Cr3C2-Ni nanopowder Ceram. Int. (IF 2.986) Pub Date : 2018-02-17 Kimmo Kaunisto, Minna Kotilainen, Marjaana Karhu, Juha Lagerbom, Tommi Vuorinen, Mari Honkanen, Minnamari Vippola, Erja Turunen
Decreasing crystal size to nanoscale is a proven method to enhance material properties. In this study, nanosize Cr3C2 and Cr3C2-Ni were synthetized and the reaction sequence was studied. Aqueous precursors using only water-soluble raw materials with varying carbon contents and a nickel addition were spray-dried. Glycine was used as a carbon source and chromium acetate hydroxide as a chromium source in the precursor solutions. Nickel nitrate hexahydrate was introduced as a nickel source to yield a metallic binder into the carbide nanopowder. Resulting powders were heat-treating to identify an applicable precursor composition producing the targeted Cr3C2 phase with crystal size of tens of nanometers. Thermal synthesis tests of the precursor powders to yield Cr3C2 took place at a temperature between 900 – 1300 °C under an Argon atmosphere. The synthesis of nanosize Cr3C2-Ni powder was successful at 1000 °C in 30 min, in a case of the best precursor. In order to produce the carbide phase with no residual oxide traces, relative carbon load has to be 48 wt.-%, while the stoichiometric amount of carbon in Cr3C2 is 13 wt.-%. When also introducing the nickel source into the precursor, an even higher carbon load was required. The carbon surplus needed to enable the Cr3C2 synthesis attributes to the non-homogeneity of the precursor composition. The chemical synthesis starting from water-soluble raw materials is a promising way of preparing nanosize Cr3C2-Ni with the targeted phase configuration.
Preparation of Ag@AgCl/g-C3N4/TiO2 Porous Ceramic Films with Enhanced Photocatalysis Performance and Self-cleaning Effect Ceram. Int. (IF 2.986) Pub Date : 2018-02-17 Xiang Lv, Tianhe Wang, Wei Jiang
We report a novel method to prepare translucent and stable Ag@AgCl/g-C3N4/TiO2 ceramic films having strong photocatalytic activities and self-cleaning capabilities under light irradiation. Colloidal silica was used as an inorganic binder and P25 TiO2 was added as a hydrophilicity enhancer without which a smooth coating was not achievable. Ag@AgCl of particle size around 30 nm, was synthesized by in-situ oxidation of nano-silver particles in porous g-C3N4/TiO2 films. Optimal conditions for Ag@AgCl/g-C3N4/TiO2 preparation in terms of strongest photocatalysis were established by tests on Rhodamine B degradation under visible and full spectral irradiations. A good adhesion strength of the porous films on glass substrate was achieved. Stability and reusability of the films were assessed by cycling tests. Possible photocatalytic mechanisms are proposed based on the basis of trapping experiments. Systematic characterization of the film suggests that the in-situ oxidation is an effective and practical method to produce nanoscale Ag@AgCl.
Effects of Ni addition on Properties of Vitrified Bond CBN Composites in Strong Magnetic Field Ceram. Int. (IF 2.986) Pub Date : 2018-02-17 Tianbiao Yu, Zhelun Ma, Xuezhi Wang, Boxue Song, Wanshan Wang
Properties of vitrified bond with varying Ni doping amounts were extensively investigated. Effects of Ni addition on microstructures and properties of vitrified bond cubic boron nitride (CBN) composites prepared in strong magnetic field were investigated for applications in CBN grinding tools. Vitrified bond was characterized using three-point bending, scanning electron microscopy, X-ray diffraction and other methods.The refractoriness, fluidity, and bending strength of vitrified bond were evaluated. Bending strengths, microstructures, and phase compositions of vitrified bond CBN composites achieved using conventional and strong electromagnetic sintering techniques were compared. Results show that the addition of Ni to vitrified bond CBN composites improved the fluidity and bending strength of the vitrified bond. Strong electromagnetic sintering improved the mechanical strength and pore structure of vitrified bond CBN composites. Moreover, the introduction of the strong magnetic field facilitated Ni migration and aggregation in vitrified bond, rotated abrasives, and formed new substances, thus increasing the stability of vitrified bond CBN composite thermal material. Also, strong magnetic field inhibit grain growth of non-magnetic and ferromagnetic materials with fine-grain effect.
Effects of sintering temperature and KBT content on microstructure and electrical properties of (Bi0.5Na0.5)TiO3-BaTiO3-(Bi0.5K0.5)TiO3 Pb-free ceramics Ceram. Int. (IF 2.986) Pub Date : 2018-02-17 Gang Liu, Wentao Jiang, Leiyang Zhang, Jing Cai, Ziyang Wang, Kaihua Liu, Xiaokui Liu, Yi Chen, Hongbo Liu, Yan Yan
A route exploring the morphotropic phase boundaries (MPB) region in (Bi0.5Na0.5)TiO3-BaTiO3-(Bi0.5K0.5)TiO3 ternary system has been designed based on the phase diagram. X-ray diffraction (XRD) has been performed to determine the phases of the prepared samples. The dielectric, ferroelectric, and piezoelectric properties of [(1-x) 0.9363(Bi0.5Na0.5)TiO3−0.0637BaTiO3]-x(Bi0.5K0.5)TiO3 (BNKBT100x) ternary lead-free piezoelectric ceramics are investigated as the functions of x and sintering temperature. When x was varied from 0 to 0.11, the BNKBT100x ceramics show single perovskite structure sintered at 1130 °C-1210 °C. These ceramics show large dielectric permittivity, small dielectric loss, and diffused phase transition behavior. Well-defined ferroelectric polarization-electric field (P-E) hysteresis loop and relative large piezoelectric and electromechanical coefficients are also found in these ceramics. When increasing x, the electrical performances first increase, then decrease. The same rule is found when varying the sintering temperature. The optimized composition and sintering temperature are finally obtained.
Effect of TGO thickness on the Thermal Barrier Coatings Life under Thermal Shock and Thermal Cycle Loading Ceram. Int. (IF 2.986) Pub Date : 2018-02-16 Kaveh Torkashvand, Esmaeil Poursaeidi, Maryam Mohammadi
Effect of thermally grown oxide (TGO) thickness on thermal shock resistance of thermal barrier coatings (TBCs) and also their behavior under a cyclic loading (including aging at maximum temperature) was evaluated experimentally. In order to form different thicknesses of TGO, coated samples experience isothermal loading at 1070 °C for various periods of times. Heat-treated samples were heated to 1000 °C and cooled down rapidly in water from the substrate side using a mechanical fixture. The life of samples was investigated as a function of TGO thickness. Furthermore, by performing an experiment the simultaneous effect of the TGO growth and thermal expansion mismatch– on the failure of thermal barrier coatings was evaluated. The results demonstrated that the presence of TGO with a thickness of 2 to 3 μm has a positive effect on the resistance against thermal shock.
Comparison between microwave and conventional sintering on the properties and microstructural evolution of tetragonal zirconia Ceram. Int. (IF 2.986) Pub Date : 2018-02-16 S. Ramesh, Ph.D, N. Zulkifli, C.Y. Tan, Y.H. Wong, F. Tarlochan, S. Ramesh, W.D. Teng, I. Sopyan, L.T. Bang, A.D. Sarhan
In this research, the comparison between microwave sintering and conventional sintering on the mechanical properties and microstructural evolution of 3 mol% yttria-stabilised zirconia were studied. Green bodies were compacted and sintered at various temperatures ranging from 1200 °C to 1500 °C. The results showed that microwave assisted sintering was beneficial in enhancing the densification and mechanical properties of zirconia, particularly when sintered at 1200 °C. It was revealed that as the sintering temperature was increased to 1400 °C and beyond, the grain size and mechanical properties for both microwave- and conventional-sintered ceramics were comparable thus suggesting that the sintering temperature where densification mechanism was activated, grain size was strongly influenced by the sintering temperature and not the sintering mode.
Effect of waste serpentine on the properties of basic insulating refractories Ceram. Int. (IF 2.986) Pub Date : 2018-02-16 A. Ramezani, S.M. Emami, S. Nemat
Basic insulating refractories were fabricated by the pressing route using dead-burned magnesia, pure calcined alumina, expanded perlite, and calcined waste serpentine as starting raw materials in four compositions from F1 to F4. Periclase and forsterite were major phases in F1 and F2 compositions, while spinel was also detected in the XRD patterns of F3 and F4 samples. Quantitative phase analysis showed that F4 sample sintered at 1450 °C has the highest forsterite content among all other samples. On the other hand, it has lower thermal conductivity compared to F1 to F3, and even lower than aluminosilicate IFBs with the same bulk density. It is concluded that forsterite is a highly insulating material, compared to periclase, corundum, periclase-spinel, aluminosilicates, such as mullite, etc.
Fabrication and performance of calcium phosphate cement/small intestinal submucosa composite bionic bone scaffolds with different microstructures Ceram. Int. (IF 2.986) Pub Date : 2018-02-16 Tierong Bian, Kang Zhao, Qingnan Meng, Hua Jiao, Yufei Tang, Jing Luo
The microstructure of the tissue has a very important determining effect on its performance. Herein, two calcium phosphate cement (CPC)/small intestinal submucosa(SIS) composites bionic bone scaffolds with different microstructures were fabricated by rolling or/ and assembling method. The microstructure, 3D morphology, the crystal phase and mechanical properties of the scaffolds were investigated by micro CT, XRD, FIIR, SEM and electronic universal testing machines respectively. The results showed that the pore size of all scaffolds are in the range of 100~400 μm, which are beneficial to cells growth, migration, and tissue vascularization. Their porosity and the specific surface area were 14.53 ± 0.76%, 8.74 ± 1.38 m2/m3 and 32 ±0.58%, 26.75 ± 2.69 m2/m3 separately. The high porosity and the large specific surface area can provide a larger space and contact area for cells adhesion and proliferation. Meanwhile, compressive strength of the scaffolds soaked were 10 MPa and 27 Mpa, about 1.2 folds and 3.2 folds of the original scaffolds, respectively. The results are derived from different microstructures of the scaffolds and chemical bonds between SIS and new phases (hydroxyapatite), and the scaffolds performance steadily increased at near the physiological conditions. Finally, biocompatibility of the scaffolds was evaluated by CCK8, bionic microstructure scaffolds are nocytotoxicity and their biocompatibility is favorable. Based on the microstructure, compressive strength and cytotoxicity of the scaffolds, bionic Harvarsin microstructure CPC/SIS composite scaffold is expected to turn into a scaffold with the excellent porperties of real bone.
Influence of Er3+ substitution on the structural, magnetic, and magnetostrictive properties of cobalt ferrite synthesized from spent Li-ion batteries Ceram. Int. (IF 2.986) Pub Date : 2018-02-16 Changwei Dun, Guoxi Xi, Tingting Zhao, Ye Zhang, Yumin Liu, Li Yang
This study presents the effect of Er3+ substitution for Fe3+ at low concentrations on the structural, magnetic, and magnetostrictive properties of cobalt ferrite synthesized by sol–gel method using spent Li-ion batteries as raw materials. The XRD results confirm the formation of pure-phase cubic spinel structure with average crystallite sizes of 24.8 to 41.5 nm as obtained through the Scherrer formula. Although Er3+ substitution does not show any observable changes in morphology, the magnetic and magnetostrictive properties are strongly affected. Density measurements obtained by the Archimedes method reveal that the bulk density decreases and the porosity increases with Er3+ substitution because of the formation of intragranular pores during sintering. The saturation magnetization and coercivity of the samples obtained with a vibrating sample magnetometer are influenced by the incorporation of Er3+ at the B-sites. Magnetostriction and strain derivative curves show that Er3+ substitution makes cobalt ferrite more suitable for advanced magnetomechanical stress sensors and energy-efficient actuator devices.
Influence of Frequency and Temperature on Dielectric and Electrical Properties of Ca-Substituted Barium Iron Niobate Ceram. Int. (IF 2.986) Pub Date : 2018-02-16 Maalti Puri, Sukhleen Bindra Narang, Shalini Bahel
This paper presents the dielectric and electrical behavior of (Ba1-xCax)(Fe1/2Nb1/2)O3 (x = 0.0, 0.2, 0.6, 1.0) solid solutions. The dielectric and electrical properties were investigated with respect to variation in temperature (25°C to 250°C) and frequency (10 kHz to 970 kHz) using impedance analyzer. This study suggests that the relative permittivity increased with increase in Ca content up to x = 0.2 and then decreased for higher Ca concentration. Dielectric anomaly observed in Ɛr-T plots is frequency dependent which indicates that the relaxation in the system is due to electrons trapped in oxygen vacancies The occurrence of maxima of Z" and M" at different frequencies indicate the presence of Non Debye type relaxation in the studied materials. The purposed materials are potential candidate for multilayer capacitor applications.
Green facile synthesis of low-toxic superparamagnetic iron oxide nanoparticles (SPIONs) and their cytotoxicity effects toward Neuro2A and HUVEC cell lines Ceram. Int. (IF 2.986) Pub Date : 2018-02-16 Leila Gholami, Reza Kazemi Oskuee, Mohsen Tafaghodi, Abouzar Ramezani Farkhani, Majid Darroudi
Superparamagnetic iron oxide (Fe3O4) nanoparticles (SPIONs) were synthesized by co-precipitation using polyvinyl alcohol (PVA) as a capping agent under alkaline condition. The produced X-ray diffraction (XRD) pattern evidenced the presence of peaks corresponding to the inverse spinel structure of the prepared SPIONs. Debye-Scherrer and field emission scanning microscopy (FESEM) showed the prepared SPIONs to be well-defined with about < 50 nm size. Likewise, the superparamagnetic properties of the SPIONs measured by Vibrating Sample Magnetometer (VSM) showed high saturation magnetization (~ 65.36 emu/g). The in vitro cytotoxicity studies on Neuro2A and HUVEC cells have mentioned low toxic and non-toxic SPIONs, respectively in a range of concentrations (1.17–150 μg/ml), thus, we reckon that the synthesized SPIONs will have persistent utilization in different fields of medical applications.
Microstructure Evolution in Densification of SiC Ceramics by Aluminium Vapour Infiltration and Investigation of Mechanical Properties Ceram. Int. (IF 2.986) Pub Date : 2018-02-16 S.V. Amrut Raj, Dulal Chandra Jana, Prasenjit Barick, Bhaskar Prasad Saha
The densification and phase formation of 6 wt.% Y2O3 containing SiC compacts infiltrated by aluminium vapour were investigated. The densification of SiC powder compact occurred through infiltration of aluminium vapour formed through a reaction between alumina and carbon powders at 2000°C. Infiltrated specimens were evaluated concerning the density, phase, microstructure and mechanical properties including hardness and fracture toughness. X-ray diffraction studies showed the presence of yttrium aluminium garnet (YAG) and Al2O3 as the secondary phases along with other minor phases. Sectioning of the infiltrated specimen showed two regions: a dense layer starting from the surface of about 1 mm thickness followed by a porous structure at the core. The effect of infiltration depth on densification and evolution of microstructure are studied. Also, the changes in Vickers’ hardness and fracture toughness with the increase in specimen depth are discussed.
Fiber-reinforced one-part alkali-activated slag/ceramic binders Ceram. Int. (IF 2.986) Pub Date : 2018-02-16 Z. Abdollahnejad, M. Mastali, T. Luukkonen, P. Kinnunen, M. Illikainen
In the present experimental/numerical study, a combination of ceramic waste and ground-granulated blast furnace slag were used in the preparation of one-part alkali-activated binders. Moreover, the effect of fiber type and content on hardened-state properties and shrinkage was studied under two different curing conditions. In the first stage of this study water absorption, compressive strength, and flexural strength were assessed. Subsequently, the flexural performance of fiber-reinforced binders was simulated and predicted using finite element models under concentrated and distributed flexural loading, respectively. The experimental results showed that fibers improved mechanical properties, and enhancement was governed by fiber type and curing conditions. Moreover, the numerical results indicated that the developed fiber-reinforced binders offer a flexural load-carrying capacity in the range of 10 to 40kN/m2 and permissible service loads were well below the ultimate capacity.
Phase composition, Raman spectra, infrared spectra and dielectric properties of Li2MgTi1-x(Mg1/3Nb2/3)xO4 ceramics at microwave frequency Ceram. Int. (IF 2.986) Pub Date : 2018-02-16 C.H. Yang, H.T. Wu
The Li2MgTi1-x(Mg1/3Nb2/3)xO4 (0≤x≤0.5) ceramics were prepared by the conventional solid-state method. The relationship among phase composition, substitution amount and microwave dielectric properties of the ceramics was symmetrically investigated. All the samples possess the rock salt structure with the space group of Fm-3m. As the x value increases from 0 to 0.5, the dielectric constant linearly decreases from 16.75 to 15.56, which can be explained by the variation of Raman spectra and infrared spectra. The Q·f value shows an upward tendency in the range of 0≤x≤0.3, but it then decreases when x>0.3. In addition, the temperature coefficient of resonant frequency (τf) is shifted toward zero with the increasing (Mg1/3Nb2/3)4+ addition. By comparison, the Li2MgTi0.7(Mg1/3Nb2/3)0.3O4 ceramics sintered at 1400 °C can achieve an excellent combination of microwave dielectric properties: εr=16.19, Q·f=160,000 GHz and τf=−3.14 ppm/°C.
Enhancing thermal and mechanical response of aluminum using nanolength scale TiC ceramic reinforcement Ceram. Int. (IF 2.986) Pub Date : 2018-02-15 M. Penchal Reddy, M.A. Himyan, F. Ubaid, R.A. Shakoor, M. Vyasaraj, P. Gururaj, M. Yusuf, A.M.A. Mohamed, M. Gupta
In the present work, nano-sized titanium carbide (0.5, 1.0 and 1.5 vol.%) reinforced aluminum (Al) metal matrix composites were synthesized by powder metallurgy incorporating microwave sintering and hot extrusion. Microstructural, mechanical and thermal properties of hot extruded unreinforced aluminum and titanium carbide (TiC) reinforced aluminum composites are presented in this paper. X-ray diffraction (XRD) patterns and scanning electron microcopy (SEM) images show the homogeneous distribution of TiC nanoparticles in the Al matrix. The tensile and compressive strengths of Al composites increased with the increase in TiC content, while the ductility decreased. The CTE of Al composite decreased with the progressive addition of hard TiC nanoparticles. Overall, hot extruded Al 1.5 vol.% TiC nanocomposite exhibited the best combination of tensile, compressive, hardness and Young's modulus of 186±3 MPa, 416±4 MPa, 9.75±0.5 GPa and ~103 GPa, respectively. High tensile strength and good thermal stability exhibited by Al-TiC nanocomposites developed in this study show the potential for a variety of weight-critical engineering applications.
High-temperature thermoelectric properties of polycrystalline CaMn1-xNbxO3-δ Ceram. Int. (IF 2.986) Pub Date : 2018-02-15 J.W. Seo, G.H. Kim, S.-M. Choi, K. Park
The structural and thermoelectric (TE) properties of polycrystalline CaMn1-xNbxO3-δ (0.025 ≤ x ≤ 0.25) were studied with X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and electrical transport measurements, with an emphasis placed on the Nb5+ content. The CaMn1-xNbxO3-δ crystallized in an orthorhombic perovskite structure of the Pnma space group. The density and grain size of the CaMn1-xNbxO3-δ samples gradually decreased when Nb5+ ions substituted Mn4+ ions. The CaMn0.95Nb0.05O3-δ sample contained charge-ordered domains, stacking faults, and micro-twins. The substitution of Nb5+ for Mn4+ up to x = 0.15 led to an increase in electrical conductivity, mainly due to an increased electron concentration. The CaMn1-xNbxO3-δ samples with low Nb5+ contents (0.025≤x≤0.15) showed metallic behavior, whereas those with high Nb5+ contents (0.2≤x≤0.25) showed semiconducting behavior. The Nb5+ substitution lowered the absolute value of the Seebeck coefficient for the CaMn1-xNbxO3-δ samples due to an increased electron concentration. The largest power factor (1.19 × 10-4 Wm-1K-2) was obtained for CaMn0.95Nb0.05O3-δ at 800 °C. The partial substitution of Nb5+ for Mn4+ in CaMnO3-δ proved to be highly effective for improving high-temperature TE properties.
Drug and ion releasing tetracalcium phosphate based dual action cement for regenerative treatment of infected bone defects Ceram. Int. (IF 2.986) Pub Date : 2018-02-15 R. Jayasree, T.S. Sampath Kumar, Govindaraj Perumal, Mukesh Doble
Calcium phosphate cements (CPCs) are ideally suited for the local delivery of antibiotics in infected bone defects as they have multiple binding sites for loading various drugs. CPCs can also be substituted with ions such as Ag+, Zn2+, Mg2+, Sr2+, etc., to exhibit extended broad-spectrum antimicrobial activity. Strontium (Sr) in particular is known to enhance the new bone formation and decrease bone resorption. The current work aims to develop a dual action tetracalcium phosphate (TTCP) based cement which releases both the Sr2+ ion and ornidazole antibiotic drug for the treatment of bone infections. The TTCP with Sr2+ ion substitution was prepared by the solid state reaction method and it was used to form ornidazole loaded CPC. The ornidazole loaded cement prepared using 8 at. % Sr substituted TTCP (8SCPC-O) showed complete hydroxyapatite (HA) formation in phosphate buffered solution at the end of 1 week. Fine needle-shaped HA crystals were observed in 8SCPC-O cement. In vitro drug release studies showed an accelerated ornidazole release from the 8SCPC-O sample when compared to samples without Sr substitution. Ornidazole releasing cements were found to be biocompatible with skeletal myoblast (L6) cells. Antibacterial activity of ornidazole releasing cement was evident from day 1 onwards against E. coli. The above results suggest 8SCPC-O as a good candidate for treating local bone infections.
Fabrication of Ni-W-B4C composite coatings and evaluation of its micro-hardness and corrosion resistance properties Ceram. Int. (IF 2.986) Pub Date : 2018-02-15 Teng He, Yi He, Han Li, Zubo Su, Yi Fan, Ze He
Boron carbide (B4C) particles were embedded in nickel-tungsten (Ni-W) coatings by pulse current electrodeposition technique. Physical properties of the composite coatings were studied by XRD, SEM, EDS and Vickers micro-hardness instrument. Corrosion protection of the deposited films was investigated utilizing potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS). Results exhibited that the addition of B4C nanoparticles into the Ni-W alloy can significantly improve the surface morphology and the micro-hardness of the composite coatings. The corrosion resistance of Ni-W-B4C nanocomposite is much better than Ni-W alloy deposit, especially when the concentration of B4C nanoparticles is 2 g/L in plating bath, the obtained Ni-W-B4C composite coating has the best surface morphology, the highest micro-hardness and the excellent corrosion resistance.
In Situ synthesis of SiC-graphene core-shell nanoparticles using wet ball milling Ceram. Int. (IF 2.986) Pub Date : 2018-02-15 Jiangshan Zhang, Shufeng Yang, Zhixin Chen, Yi Yan, Jingwei Zhao, Jingshe Li, Zhengyi Jiang
A wet ball milling route was used to synthesise SiC-graphene core-shell nanoparticles in situ from graphite and SiC nanoparticles. Graphite flakes were gradually exfoliated into fresh graphene nanosheets (GNSs) without significant defects, which is attributed to mechanical shearing and moderate impaction forces between graphite flakes, milling balls and SiC nanoparticles during the wet milling. The non-destructive exfoliation is characterised by Raman, Fourier transform infrared and X-Ray photoelectron spectroscopies. The freshly produced GNSs are energetically unstable and thin enough to be flexible and this drives the in situ attaching and scrolling of GNSs on the SiC nanoparticles. The SiC nanoparticles and GNSs are well dispersed in the wet medium and the SiC nanoparticles are individually wrapped. It has been estimated that > 50% of the produced GNSs are wrapped around the SiC nanoparticles and these GNSs are generally ≤ 6 layers.
Fabrication of MgO-CaZrO3 refractory composites from Egyptian dolomite as a clinker to rotary cement kiln lining Ceram. Int. (IF 2.986) Pub Date : 2018-02-15 Emad M.M. Ewais, Ibrahim M.I. Bayoumi
Dolomite is used as basic lining for rotary cement kiln due its high refractoriness, corrosion resistance against basic environments and high coating performance, but its poor hydration resistance limits its use. In this work, Egyptian dolomite was converted into outstanding refractory magnesia-calcium zirconate composite (M-CZ) by the addition of 37.8 to 47.8 wt. % zirconia. The mixtures were milled, uni-axially formed and fired at a temperature of 1400–1550 °C for 2 hours. Thermal analysis, phase composition, microstructure, densification parameters, and other technological properties of the fired specimens were investigated. It was found that sintered M-CZ composite with bulk density (3.95 g/cm3), cold crushing strength (170 MPa), and high coating ability can be obtained by firing Egyptian dolomite with 37.8 wt. % zirconia at temperature 1500 °C with the formation of belite as a secondary product. This composite can be nominated to be produced on a large industrial scale.
Effect of Zn and Ti Co-doping on Structure and Electrical Properties of BiFeO3 Ceramics Ceram. Int. (IF 2.986) Pub Date : 2018-02-15 Jian-Hui Zhu, Jian-Qing Dai, Jie-Wang Xu, Xiao-Ya Li
In this paper, the effect of Zn and Ti co-doping on the structure, dielectric, ferroelectric and magnetic properties of BiFeO3 (BFO) ceramics have been studied. Co-doped BFO ceramics with different doping concentrations are prepared by using the sol-gel method. The structure, morphology and electrical properties of co-doped BFO ceramics are studied by using X-ray diffraction (XRD), scanning electron microscopy, impedance analyzer and ferroelectric test analysis system. Furthermore, the vibrating sample magnetometer (VSM) is used to investigate the magnetic properties. The structural transition from rhombohedral to tetragonal-like phase is observed with a high level of co-doping (x = 2.5%). In addition, higher content of Zn and Ti results in enhanced dielectric constant (ε) and reduced dielectric loss (tanδ). The highest remnant polarization of 0.4 μC/cm2 and coercive electric field of 15.5 kV/cm is demonstrated at x = 2.5%. The enhanced dielectric and ferroelectric properties can be attributed to the formation of defect complexes due to the Zn and Ti substitution.
Citrate- and glycerol triesters as novel dual-functional dispersants and plasticisers for ceramic processing Ceram. Int. (IF 2.986) Pub Date : 2018-02-15 S. Foghmoes, T. Klemensø, K. Brodersen, J.J. Bentzen, M. Della Negra
Short chained triesters of glycerol and citric acid were systematically investigated as novel dual-functional dispersants and plasticisers for use in ceramic processing. Additional systematic studies on a series of diesters having structural similarities with the citrate and glycerol triesters were performed to further assess the significance of specific functional groups for the stabilisation of suspensions. The overall purpose of this work consists in simplifying the formulation for ceramic processing slurries while at the same time limiting the environmental impact and toxicity. The use of multifunctional additives reduces the risk of unwanted interactions between different components. Additionally, the possible use of one additive in more than one role opens the opportunity for an overall reduction in the number and amount of chemicals and therefore reduction of costs and risks. For the citrate ester candidates, different alkoxy groups were tested as well as the acetylation on the hydroxyl group. The glycerol esters differed by the length of the carboxylic chain. Especially triethyl and tributyl citrate are proposed as promising dual-functional additives for ceramic processing. Specifically, for triethyl citrate the dual-function was finally demonstrated by producing a dense piece of 8YSZ through tape casting and subsequent sintering.
Tuning of Ferrimagnetic nature and Hyperfine Interaction of Ni2+ doped Cobalt ferrite nanoparticles for Power Transformer Applications Ceram. Int. (IF 2.986) Pub Date : 2018-02-15 K.M. Srinivasamurthy, Angadi V. Jagadeesha, S.P. Kubrin, Shiddaling Matteppanavar, D.A. Sarychev, P. Mohan Kumar, Haileeyesus Workineh Azale, B. Rudraswamy
Ferrites may contain single domain particles which gets converted into super-paramagnetic state near critical size. To explore the existence of these characteristic feature of ferrites, we have performed magnetization(M-H loop) and Mössbauer spectroscopic studies of Ni2+ substitution effect in Co1-xNixFe2O4 (where x=0, 0.25, 0.5, 0.75 and 1) nanoparticles were fabricated by solution combustion route using mixture of carbamide and glucose as fuels for the first time. As prepared samples exhibit spinel cubic structure with lattice parameters which decreases linearly with increase in Ni2+ concentration. The M-H loops reveals that saturation magnetization(Ms), coercive field(Hc) remanence magnetization(Mr) and magnetron number(ηB) decreases significantly with increasing Ni2+ substitution. The variation of saturation magnetization has been explained on the basis of Neel's molecular field theory. The coercive field(Hc) is found strongly dependent on the concentration of Ni2+ and decrease of coercivity suggests that the particles have single domain and exhibits superparamagnetic behavior. The Mössbauer spectroscopy shows two ferrimagnetically relaxed Zeeman sextets distribution at room temperature. The dependence of Mössbauer parameters such as isomer shift, quadru pole splitting, line width and hyperfine magnetic field on Ni2+ concentration have been discussed. Hence our results suggest that synthesized materials are potential candidate for power transformer application.
High-alumina refractory castables bonded with novel alumina-silica-based powdered binders Ceram. Int. (IF 2.986) Pub Date : 2018-02-14 A.P. Luz, S.J.S. Lopes, D.T. Gomes, V.C. Pandolfelli
In recent years, nano-binders (mainly colloidal suspensions) have been proposed as alternative materials for applications that require CaO-free refractory lining or improved mechanical behavior at intermediate temperatures (700 °C < T < 1200 °C). Despite the benefits of these suspensions, nano-bonded castables usually present limited green mechanical strength and different on site logistics to handle the liquid. Considering the availability of novel alumina-silica-based powdered binders, this work investigated the role of submicron alumina and SioxX®-Zero (both supplied by Elkem company) on rheological and mechanical properties of vibratable high-alumina castables, aiming to identify whether they can be suitable options to replace colloidal silica suspensions. Cold and hot mechanical strength and apparent porosity in the range of 110 up to 1400 °C, cyclic thermal shock resistance, creep tests and hot elastic modulus of the designed formulations were evaluated. According to the results, SioxX®-Zero-bonded compositions presented good flowability levels and their sintering process started around 800 °C. Adding boron carbide to the same formulations resulted in transient liquid sintering of the silica-containing refractories, which allowed the development of compositions with improved thermo-mechanical performance in the 600–1400 °C temperature range. Furthermore, the submicron alumina-bonded samples presented fast sintering, resulting in E values close to 200 GPa (the highest value so far registered in our lab for a coarse grain size formulation) after one heating-cooling thermal-cycle up to 1400 °C.
Sol-Gel Processed High-k Aluminum Oxide Dielectric Films for Fully Solution-Processed Low-Voltage Thin-Film Transistors Ceram. Int. (IF 2.986) Pub Date : 2018-02-14 Wenwen Xia, Guodong Xia, Guangsheng Tu, Xin Dong, Sumei Wang, Rui Liu
High-k oxide dielectric films have attracted intense interest for thin-film transistors (TFTs). However, high-quality oxide dielectrics were traditionally prepared by vacuum routes. Here, amorphous high-k alumina (Al2O3) thin films were prepared by the simple sol-gel spin-coating and post-annealing process. The microstructure and dielectric properties of Al2O3 dielectric films were systematically investigated. All the Al2O3 thin films annealed at 300–600 °C are in amorphous state with ultrasmooth surface (RMS~0.2 nm) and high transparency (above 95%) in the visible range. The leakage current of Al2O3 films gradually decreases with the increase of annealing temperature. Al2O3 thin films annealed at 600 °C showed the low leakage current density down to 3.9×10−7 A/cm2 at 3 MV/cm. With the increase of annealing temperature, the capacitance first decreases then increases to 101.1 nF/cm2 (at 600 °C). The obtained k values of Al2O3 films are up to 8.2. The achieved dielectric properties of Al2O3 thin films are highly comparable with that by vapor and solution methods. Moreover, the fully solution-processed InZnO TFTs with Al2O3 dielectric layer exhibit high mobility of 7.23 cm2 V−1 s−1 at the low operating voltage of 3 V, which is much superior to that on SiO2 dielectrics with mobility of 1.22 cm2/V−1s−1 at the operating voltage of 40 V. These results demonstrate that solution-processed Al2O3 thin films are promising for low-power and high-performance oxide devices.
Growth, microstructure, energy−storage and dielectric performances of chemical−solution NBT−based thin films: Effect of sodium nonstoichimometry Ceram. Int. (IF 2.986) Pub Date : 2018-02-14 C.H. Yang, Q. Yao, J. Qian, Y.J. Han, J. Chen
Na0.5+δBi0.5(Ti0.96W0.01Ni0.03)O3 thin films with various Na contents (abbreviated as Na0.5+δBTWN, δ=−3.0, −1.5, 0, 1.5%) were fabricated on ITO/glass substrates using a chemical−solution process. The effects of Na nonstoichiometry on the microstructure, insulating, ferroelectric and dielectric performances are investigated. The pure perovskite phase can be obtained in Na0.5BTWN and Na0.515BTWN, while for Na0.470BTWN or Na0.485BTWN, the main composition contains secondary phase of TiO2. The grain size increases from 30 nm at δ=−3.0% to 55 nm at δ=0%, then decreases to 52 nm with δ=1.5%. The leakage current of Na0.485BTWN sample is reduced dramatically in comparison with Na0.5+δBTWN (δ=−3.0, 0, 1.5%). The big recoverable energy−storage density of 63.1 J/cm2 and high energy−storage efficiency of 55.0% can be obtained for Na0.485BTWN due to the improved electric break−down strength and large difference value between the remanent polarization and maximum polarization. Enhanced dielectricity is achieved in Na0.485BTWN with a high tunability of 36.0% and a figure of merit of 4.0 at 450 kV/cm and 500 kHz. These results demonstrated that the crystallization, micrographs and energy storage and dielectric properties of Na0.5Bi0.5TiO3 are highly sensitive to low levels of Na−site nonstoichiometry.
Enhancement of density and ionic conductivity for Garnet-type Li5La3Ta2O12 solid electrolyte by self-consolidation strategy Ceram. Int. (IF 2.986) Pub Date : 2018-02-14 Pengcheng Zhao, Yu Xiang, Yan Xu, Yuehua Wen, Wenfeng Zhang, Xiayu Zhu, Meng Li, Zhaoqing Jin, Hai Ming, Gaoping Cao
Garnet-type Li5La3Ta2O12 (LLTaO) solid electrolyte is a potential candidate component for future all-solid-state batteries due to its extraordinary stability against the reaction with molten lithium. In contrast with traditional cold isostatic pressing (CIP) method, which generally pursues ultra-high pressure, this paper tries to enhance the density and ionic conductivity of LLTaO by self-consolidation strategy without the assistance of any pressing operations. A LLTaO bulk with a relative density of 95% is obtained. SEM images reveal that the bulk sample is assembled by large dense particles in size of tens of microns indicating that the interstitial space among the particles has been dramatically minimized. Accordingly, the total ionic conductivity and the bulk ionic conductivity at 30 °C are promoted up about one order of magnitude higher to 2.63×10−5 S cm−1 and 1.41×10−4 S cm−1, respectively. Moreover, the lithium ionic migration network in the crystalline unit cell of LLTaO is first explored from its assembled way. A hexagon-like basic unit with tetrahedral Li1 joint sites and Li1- - Li1 edges is identified. The tetrahedral Li1 sites act as crucial junctions for the transportation of lithium ions. This work would significantly stimulate the development of LLTaO electrolyte membrane technology.
Enhanced dielectric properties of three phase dielectric MWCNTs/BaTiO3/PVDF nanocomposites for energy storage using fused deposition modeling 3D printing Ceram. Int. (IF 2.986) Pub Date : 2018-02-14 Hoejin Kim, Jeffrey Johnson, Luis A. Chavez, Carlos A. Garcia Rosales, Tzu-Liang Bill Tseng, Yirong Lin
This research studied the effect of fused deposition modeling (FDM) 3D printing on three phase dielectric nanocomposites using poly(vinylidene) fluoride (PVDF), BaTiO3 (BT), and multiwall carbon nanotubes (CNTs). PVDF polymer and BT ceramics are piezo-, pyro- and di-electric materials extensively used for sensor and energy storage/harvesting applications due to their unique characteristic of dipole polarization. To increase dielectric property, CNTs have been recently utilized for uniform dispersion of BT nanoparticles, ultrahigh polarization density, and local micro-capacitor among matrix. It was proved that 3D printing process provides homogeneous dispersion of nanoparticles, alleviating agglomeration of nanoparticles and reducing micro-crack/voids in matrix which can potentially enhance their dielectric property than traditional methods. In this research, these three-phase nanocomposites are fabricated through FDM 3D printing process and characterized for dielectric property. Increasing both BT and CNT nanoparticles improves dielectric properties, while CNTs have a percolation threshold near 1.7 wt.%. The most desirable combination of dielectric constant and loss properties (118 and 0.11 at 1 kHz) is achieved with nanocomposites containing 1.7 wt.%-CNT/45 wt.%-BT/PVDF. These results provide not only a technique to 3D print dielectric nanocomposites with improved dielectric property but also large-scale electronic device manufacturing possibility with freedom of design, low cost, and faster process.
Effect of surface heat transfer coefficient gradient on thermal shock failure of ceramic materials under rapid cooling condition Ceram. Int. (IF 2.986) Pub Date : 2018-02-14 Limin Chen, Anzhe Wang, Suo Xiangbo, Ping Hu, Xinghong Zhang, Zhengjun Zhang
A rapid thermal processor (RTP) device as well as quenching technique is employed to systematically investigate the effect of surface heat transfer coefficient (h) gradient on thermal shock failure of a hot-pressed ZrB2-based ceramic. Two typical kinds of quenchant with different surface h gradients during quenching tests, water and boiling water, are used for this study. When water as the cooling medium, two different cooling modes of indirect contact cooling by RTP device and direct contact cooling by quenching are also studied. The experimental results and related numerical simulations illustrate that surface h gradient plays an important role in thermal shock failure. This study confirms the previous presumption that the combination of body temperature gradient and surface h gradient leads to thermal stress damage and thermal shock failure. Under water quenching condition, water phase changes form bubbles randomly and produce great surface h gradient. Accordingly, critical body temperature gradient (V(max)c) is small (~270 °C s−1). Under aqueous polymer quenching condition, the introduction of polymer chains into water lowers the random formation of steam bubble and mediates the surface h gradient. The corresponding V(max)c hence become larger (~500 °C s−1). Under boiling water quenching condition, there is no surface h gradient and V(max)c is even larger (> 600 °C s−1). This study provides useful complementary information for understanding the thermal shock behavior and gives suggests for predicting materials performance in actual service.
Novel Fe2O3-doped glass /chitosan scaffolds for bone tissue replacement Ceram. Int. (IF 2.986) Pub Date : 2018-02-14 Emad El-Meliegy, Mostafa Mabrouk, Sara A.M. El-Sayed, Bothaina M. Abd El- Hady, Mohamed R. Shehata, Wafaa M. Hosny
In this study quaternary bioglass system (BG) SiO2–CaO–Na2O–P2O5 doped with Fe2O3 was prepared by the sol–gel method. Furthermore, 3D scaffolds were designed through blending Fe2O3 -doped bioglass with chitosan to obtain various compositions of scaffolds by the freeze-drying technique. The thermal behavior, morphological properties, porosity (%), mechanical properties and physicochemical properties of BG and scaffolds were evaluated by DSC/TGA, TEM, SEM, liquid displacement method, universal testing machine, XRD and FTIR. In addition, the in vitro bioactivity of the prepared scaffolds was studied in phosphate buffer saline (PBS) through the determination of PBS ions concentrations, as well as the degradation and the observation of precipitated calcium phosphate layer by SEM coupled with EDX and FTIR behavior. The cell viability of the prepared scaffolds was conducted against Baby Hamster Kidney fibroblasts (BHK-21) cell line. The presence of Fe2O3 decreased the Tg (from 513 to 390 oC) and the size decreased (from 20.89–50.81 to 13.92–27.87 nm). The scaffolds porosity (%) decreased upon Fe2O3 doping but the mechanical strength increased. Cell viability results for the designed scaffolds demonstrated acceptable cell viability compared with normal cells. Therefore, the designed scaffolds are promoted as regenerated materials that can be used for bone tissue replacement.
Molten salt synthesis and characterization of lead-free (1-x)Na0.5Bi0.5TiO3-xSrTiO3 (x=0, 0.10, 0.26) whiskers Ceram. Int. (IF 2.986) Pub Date : 2018-02-14 Xuefan Zhou, Zhong Wu, Chao Jiang, Hang Luo, Zhongna Yan, Dou Zhang
In this study, Na0.5Bi0.5TiO3-xSrTiO3 (NBT-xST, x=0, 0.10, 0.26) whiskers were synthesized by a two step molten salt method using Na2Ti6O13 whiskers as templates. The crystalline phase, morphology, microstructure, composition and ferroelectric characteristic of the whiskers were investigated in details. The topochemical transformation from Na2Ti6O13 structure to NBT-xST perovskite structure was found to occur by structural rearrangement of the edge sharing octahedra into vertex sharing octahedra. The prepared polycrystalline NBT-xST whiskers possessed high aspect ratio with diameter of 500–800 nm and length of 5–10 μm. The PFM investigations confirmed the favourable piezoelectricity of NBT whiskers while the NBT-0.26ST whiskers displayed relaxor-ferroelectric characteristics at room temperature, exhibiting the potential of NBT-xST whiskers for fabricating high performance micro/nano-devices.
Evolution of microstructure and electrical properties of Aurivillius phase (CaBi4Ti4O15)1-x(Bi4Ti3O12)x ceramics Ceram. Int. (IF 2.986) Pub Date : 2018-02-14 Bo Wu, Jian Ma, Wenjuan Wu, Min Chen
(CaBi4Ti4O15)1-x(Bi4Ti3O12)x (CBT-xBIT) Aurivillius phase ceramics were synthesized by the conventional solid reaction method. The evolution of the structure and the electrical properties of CBT-xBIT ceramics were systematically investigated. Due to the enhanced spontaneous polarization induced by internal stresses on the Bi2O2 layers in the CBT-xBIT structure, the optimal piezoelectric coefficient (d33~13 pC/N) was obtained in the ceramics with x=0.3 while exhibiting a relatively good thermal stability in the temperature range of 20 ~ 700 °C. The dc resistivity (ρdc) of the CBT-xBIT ceramics exhibited a higher value (≥109 Ω·cm) at room temperature, and the tan δ value of CBT-xBIT within the temperature range of 20 ~ 500 °C maintained stability as a result of the domain structure and point defect concentration in the ceramics. In addition, a distinctive double dielectric peak anomaly was observed in the εr-T curves of the CBT-xBIT (0.3, 0.5 and 0.7) ceramics, and it plays a remarkable role in the thermal stability of the piezoelectricity of CBT-xBIT ceramics. As a result, such research can benefit high temperature practical piezoelectric devices.
Influence of a few important parameters on the rheological behaviour of silicon carbide nanoparticles dispersed aqueous suspension Ceram. Int. (IF 2.986) Pub Date : 2018-02-13 Prasenjit Barick, Rahul Mitra, Bhaskar Prasad Saha
In this study, investigations have been carried out on the effect of a few important parameters such as molecular weight and concentration of dispersant (polyethyleneimine) as well as that of pH on the rheological behaviour of aqueous suspension comprising silicon carbide (SiC) nanoparticles. In addition to this, the effect of particle size and addition of finer SiC particles on the rheological behaviour of SiC suspension have been examined. It is observed that viscosity of suspension increases with the increase in molecular weight of dispersant and decreases as the concentration of dispersant increases. Further, it is noticed that viscosity of the suspension progressively increases below the pH≈7.6 and above the pH≈9.3, indicating that minimum viscosity i.e. maximum stabilization of suspension is obtained within the pH range of≈7.6-9.3. It has been observed that variation of SiC particle size from submicrometer to nanometer range and addition of nanometric SiC powder in SiC suspension containing coarser particles increase the viscosity significantly.
Mechanical properties and thermal shock resistance of Si2BC3N ceramics with ternary Al4SiC4 additive Ceram. Int. (IF 2.986) Pub Date : 2018-02-13 Ning Liao, Dechang Jia, Zhihua Yang, Yu Zhou, Yawei Li
Dense Si2BC3N ceramics were prepared through SPS sintering the amorphous Si2BC3N and Al4SiC4 powders obtained from mechanical alloying. The phase compositions, microstructures, and mechanical properties, as well as the thermal shock resistance were investigated. In addition, evaluations of oxidation and the ablation resistance were also preceded. The results show that Al4SiC4 phase can be detected at 1200 and 1400 °C under pressureless sintering. However, Al4SiC4 can be decomposed to AlN and SiC phases under higher temperatures. As for the bulk Si2BC3N ceramics, the Al4SiC4 additive induce the development of turbostratic BN(C) plates and improve the relative density consequently. Besides, the Al4SiC4 plates are embedded in the matrix of ceramics. Therefore, the mechanical properties and thermal shock resistance are improved apparently with the addition of additive. Meanwhile, the additive containing composites have superior ablation resistance than the pristine Si2BC3N ceramics due to their higher relative density.
Magnesium ferrite nanoparticles as a magnetic sorbent for the removal of Mn2+, Co2+, Ni2+ and Cu2+ from aqueous solution Ceram. Int. (IF 2.986) Pub Date : 2018-02-13 A.I. Ivanets, V. Srivastava, M.Yu. Roshchina, M. Sillanpää, V.G. Prozorovich, V.V. Pankov
Cyclic cold isostatic pressing and improved particle packing of coarse grained oxide ceramics for refractory applications Ceram. Int. (IF 2.986) Pub Date : 2018-02-13 Stefan Schafföner, Jens Fruhstorfer, Susann Ludwig, Christos G. Aneziris
This study investigated the cold isostatic pressing of coarse grained alumina refractories applying either a cyclic pressure increase or a cycling at maximum pressure. Additionally the effects of the maximum pressure and the particle size distribution on physical, mechanical and thermomechanical properties were analyzed. The cyclic pressure increase resulted in a slightly higher apparent density and lower apparent porosity. A cycling at maximum pressure decreased the median pore size to some extent. Remarkably, an optimized particle size distribution resulted in a lower apparent porosity, lower median pore size and in a higher Young's modulus before and after thermal shock together with a slightly lower relative decrease of the Young's modulus. A higher pressing pressure which decreased the apparent porosity did not affect the Young's modulus. Thus, apparently the optimized particle size distribution improved the particle packing which was associated with a smaller median pore size. This smaller pore size increased the number of pores relative to the total porosity, which then acted as points of crack initiation and crack deflection limiting the length of propagating cracks in case of thermal shock. Thus, tailoring the pore size distribution is a promising starting point to improve the thermomechanical properties of refractories.
Structural, electrical and magnetic properties of (110)-oriented BF-BZT-ST Films Ceram. Int. (IF 2.986) Pub Date : 2018-02-13 Caimin Meng, Bobo Tian, Haoliang Wang, Shuo Sun, Hong Shen, Tie Lin, Jian Yu, Jinglan Sun, Xiangjian Meng, Junhao Chu
Highly (110)-oriented BiFeO3-Bi(Zn/Ti)O3-SrTiO3 thin films were prepared on conductive Nb doped SrTiO3 substrates by pulsed laser deposition. The results demonstrate that the films show a pure perovskite phase with R3c symmetry. The films have a low dielectric loss, and a typical multiferroics character, possessing both of ferroelectric and ferromagnetic properties. The reduced dielectric loss is attributed to thermodynamic stabilization and charge compensation mechanisms in the BiFeO3 system. The remnant polarization (Pr) and the remnant magnetization (Mr) are ~ 46.2 μC/cm2 and ~ 4.6 emu/cm3 respectively.
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