The role of precursors on piezoelectric and ferroelectric characteristics of 0.5BCT-0.5BZT ceramic Ceram. Int. (IF 2.986) Pub Date : 2018-01-17 Atal Bihari Swain, V. Subramanian, P. Murugavel
Lead free piezoelectric ceramic 0.5(Ba0.7Ca0.3)TiO3−0.5Ba(Ti0.9Zr0.1)O3, which reveals a high piezoelectric coefficient was synthesized using two different precursors. The sample synthesized separately using ZrO2 and BaZrO3 as Zr-ion dopant precursor exhibits remarkable difference in characteristics. The dielectric studies revealed a clear ferroelectric transition at 95 °C for both the samples along with the expected tetragonal to orthorhombic and orthorhombic to rhombohedral transitions. The sample fabricated using BaZrO3 as precursor has lesser amount of secondary phases, and exhibits high density, large d33 (410 pC/N), and high remnant polarization (9.2 μC/cm2) which are suitable parameters for piezomechanical applications. On the other hand, the sample synthesized with ZrO2 as precursor yields the characteristic parameters suitable for energy storage applications such as large maximum polarization (17 μC/cm2), low remnant polarization (4.1 µC/cm2), large recoverable energy density (W = 164 mJ/cm3) with high percentage efficiency (74%). The studies illustrate the way of changing the physical properties of the piezoceramics towards selected applications by the choice of precursors.
Facile Synthesis of Graphene Oxide with Significant Enhanced Properties for Optoelectronic and Energy Devices Ceram. Int. (IF 2.986) Pub Date : 2018-01-17 Samia Aslam, Faiza Mustafa, Muhammad Ashfaq Ahmad
Graphite is a promising source for graphene and its derivatives (GO and RGO) but several lengthy processess are involved in the production and tuninng of its properties. In this work, graphene oxide nanosheets (GNSs) were synthesized by a one step, environment friendly and cost effective electrolysis technique. The GNSs were characterized by XRD, AFM, UV-vis-NIR, Raman, FTIR, photoluminescencespectroscopies and thermogravimetric analysis (TGA).The XRD patteren cofirmed the formation of GNSs. The UV-Vis anylsis confirmed quantumconfirnment effect in GNSs with increased band gap of 5.4 eV. PL spectrum showed emission peaks in visible to Infrared region.The sheets possessed excellent thermal stability confirmed from TGA analysis. The FTIR results verified the existence of oxygen-containing functional groups (OFGs) in the GNSs. The ID/IG≈0.85 I D / I G ≈ 0.85 obtained from Raman Spectra showed high quality GNSs with less defects. The AFM and SEM results showed wrinkles with high grain surface area and roughness.The obtained results showed significantly enhanced properties and indicated that synthesised GNSs sare cerdible potential candidates for optoelectronic devices including solar cells, supercapcitors, electrochemical and bio sensors, biomarkers and also suitable for low temperature fuel cells.
High sensitivity and selectivity of CaCu3Ti4O12-ZnO composites towards acetone gas at room temperature Ceram. Int. (IF 2.986) Pub Date : 2018-01-17 Mohsen Ahmadipour, Nik Akmar Rejab, Mohd Fariz Ab Rahman, Mohd Fadzil Ain, Zainal Arifin Ahmad
Detection of low concentration of acetone gas was carried out using porous CCTO-ZnO composites. The CCTO-ZnO composites were prepared via wet mixing method. The effects of ZnO (x = 0, 2, 6, and 10 wt.%) addition on the structural, morphological, and optical properties of CCTO-ZnO powder were investigated by XRD, FTIR, FESEM-EDAX, BET, UV-Vis, respectively, whereas the acetone gas sensing properties of CCTO-ZnO composites were studied by I-V characteristic. The XRD result showed a polycrystalline structure. The surface morphology of the powder exhibited a uniform distribution with intergranular porous microstructures. BET indicated average pore diameter (10.08, 10.70, 12.91, and 13.76 nm) and surface area (1.003 1.038, 1.594, and 2.029 m2g−1), respectively with increasing amount of ZnO. This is the cause for the reduction of optical transmittance and increase in their energy bandgap (1.97, 2.05, 2.08, and 2.10 eV). All samples depicted good transparency (≤ 80%) in the visible region. CCTO with the addition of 10 wt.% ZnO composite showed the highest sensitivity and selectivity towards 1 ppm acetone gas. The composites had 1% error from earlier stability performance, and can possibly be utilized for practically applied in the detection of acetone gas.
In situ synthesis of homogeneously dispersed SiC nanowires in reaction sintered silicon-based ceramic powders Ceram. Int. (IF 2.986) Pub Date : 2018-01-17 Yanhui Chu, Siyi Jing, Jikun Chen
The synthesis of homogeneously dispersed SiC nanowires in the ceramic powders arouses considerable interests due to its potential applications as reinforcements in the ceramic matrix composites. Herein, we reported a facile and novel approach to in situ synthesize homogeneously dispersed SiC nanowires in the reaction sintered silicon-based ceramic powders. The as-synthesized nanowires exhibited the single-crystalline 3C-SiC with diameters of 50–200 nm and lengths ranging from tens to over 100 μm. Combining further experimental results and thermodynamics analysis, we demonstrated the importance of the free silicon for the in situ synthesis of SiC nanowires in the reaction sintered silicon-based ceramic powders, since it increased the equilibrium vapor pressure of SiO gaseous product in the system.
Kinetics characterization of erbium-doped tellurite glass Ceram. Int. (IF 2.986) Pub Date : 2018-01-17 N. Elkhoshkhany, Eslam Syala
The thermal characteristics of the quaternary TeO2–ZnO –Na2O–Er2O3 glass system as a function of rising Er2O3 mol% have been studied from the kinetic point of view. Differential scanning calorimetry technique under non-isochronal conditions at various heating rates has been used to define the characteristic temperatures of the glasses (i.e glass transition, crystallization) in addition to the glass stability parameters. The activation energies required for both the glass transition and amorphous to crystalline transformation have been computed by different methods. The mode of the glass crystallization has been determined in terms of the Avrami kinetic constant to identify the crystallization succession. Quantitative analysis of the thermal characteristics and kinetic parameters of the glass were achieved in terms of cross-linking density, number of bonds, and the bond stretching force.
Low dielectric loss induced by coupling effects of donor-acceptor ions in (Nb+Al) co-doped rutile TiO2 colossal permittivity ceramics Ceram. Int. (IF 2.986) Pub Date : 2018-01-17 Yang Yu, Yu Zhao, Tian-Dong Zhang, Rui-Xuan Song, Yu-Lei Zhang, Yu-Long Qiao, Wei-Li Li, Wei-Dong Fei
Colossal dielectric properties in donor-acceptor co-doped rutile TiO2 ceramics have attracted increased interest in recent years. However, dielectric loss (tan δ) of (Nb+Al) co-doped TiO2 ceramics are quite scattered in the previous studies. Here, we show the dielectric properties of (Nb+Al) co-doped rutile TiO2 ceramics are sensitive to sintering and ageing technologies, which is related to the coupling behavior of acceptor-donor ions. Both permittivity and dielectric loss of as-sintered (Nb+Al) co-doped TiO2 ceramics are very large, and increase with the sintering time increasing. After ageing treatment at 900 °C, the dielectric loss of co-doped ceramics reduces from 139 to 0.15 in a wide frequency range. Based on the X-ray diffraction and complex impedance analyses, it can conclude that Nb5+-Al3+ pair formation during ageing treatment reduces the concentration of oxygen vacancy, resulting in the decreases of the conductivity and dielectric loss. The changes in dielectric response of (Nb+Al) co-doped TiO2 ceramics clearly suggest that ageing process is an effective way for the Nb5+ and Al3+ ions to form the Nb5+-Al3+ pairs. We believe that the coupling effect of donor-acceptor ions is a practical and feasible route to reduce the dielectric loss of (Nb+Al) co-doped TiO2 ceramics for high-energy-density storage applications.
Al doping influences on fabricating ZnO Nanowire Arrays: Enhanced Field Emission Property Ceram. Int. (IF 2.986) Pub Date : 2018-01-17 Yuanyuan Lv, Zhiyong Zhang, Junfeng Yan, Wu Zhao, Chunxue Zhai
Increase of free electrons concentration and decrease of defects density are the most desirable solution for stimulating the field emission property in semiconductor nanostructures. To implement this, herein we study the field emission efficiency of Al-doped ZnO nanowire arrays with different Al doping concentration, which were prepared by a simple facile hydrothermal method. The Al doping concentration plays a very important role on the structure, morphology, photoluminescence and field emission properties of the as-assembled samples. The results indicate that Al-doped ZnO nanowire arrays with Al doping concentration of 7 at.% exhibit the highest quality crystalline structure and lowest defect density relative to others samples thanks to the suitable modification of Al doping, and this led to the increase of free electrons concentration and decrease of defects density, which have an excellent field emission performance with the lower turn on field of 1.03 V/μm and higher field enhancement factor of 20658. This remarkable field emission performances of the Al-doped ZnO nanowire arrays may provide promising applications for different field emission devices.
Preparation, biocompatibility, and biotribological properties of TiN-incorporated graphite-like amorphous carbon bio-ceramic composite films Ceram. Int. (IF 2.986) Pub Date : 2018-01-17 D.G. Liu, L. Zheng, Y Liang, H. Li, J.Q. Liu, L.M. Luo, Y.C. Wu
In this work, TiN-incorporated graphite-like amorphous carbon (a-GLC) bioceramic films were successfully fabricated on Ti alloy (Ti6Al4V) using the magnetron sputtering technique. The biocompatibility and biotribological properties of the TiN/a-GLC-coated Ti alloy were evaluated. Based on the clinical application, the microstructure, biocompatibility, histomorphological observation, and mechanical properties were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, nanoindentation test, and in vitro and in vivo tests including MTT, cell adhesion test, and slice observation of hard tissues. These techniques confirmed that there was strong bonding between the Ti alloy and the TiN/a-GLC film. In addition, face-centered cubic TiN and hexagonal close-packed Ti were clearly detected in the TiN/a-GLC films. A partial nanocomposite structure, comprised of homogeneous nanoclusters and crystalline particles, was detected in the amorphous matrix. Cell adhesion and MTT test results indicated that the TiN/a-GLC film could promote cell attachment and proliferation. Phase composition and the film morphology were determined to be the crucial factors that contributed to the improved biocompatibility. The biotribological property test showed that the TiN/a-GLC film with a Ti content of 7.8 at% had the lowest coefficient of friction (COF) of 0.076 and the lowest wear rate of 1.76×10–6 mm3 (Nm)–1. The low COF was attributed to the superior mechanical properties of the TiN/a-GLC composite film. The TiN/a-GLC-coated Ti alloy implants were placed subcutaneously into rabbits for different time periods, and the tissue response decreased significantly as compared to that of the pure a-GLC film. The excellent biocompatibility and function reliability of the TiN/a-GLC bioceramic films showed that they are potential candidates for bone tissue implants.
Photoreactivity and mechanism of BiPO4/WO3 heterojunction photocatalysts under simulant sunlight irradiation Ceram. Int. (IF 2.986) Pub Date : 2018-01-17 Hua Lv, Xinxin Wu, Yumin Liu, Peng Zhang, Yafei Cao, Hao Ren
Considering the practical use, it is of important value to design full-spectrum photocatalysts that can absorb natural sunlight for photodegrading organic contaminants. A series of BiPO4/WO3 heterojunction catalysts with different WO3 contents were readily synthesized via a facile hydrothermal route. Under simulant sunlight irradiation, the photocatalytic activity of the as-prepared products was evaluated by degrading rhodamine B (RhB) solution. Results demonstrated that the most enhanced RhB degradation of 77.2% could be achieved in the BiPO4/WO3 composite with molar ratio of WO3 to BiPO4 to be 2:1, which was about 4.9 and 2.1 times higher than pure BiPO4 (15.9%) and WO3 (37.8%), respectively. During the photocatalytic process of BiPO4/WO3 composite, the photoinduced electrons in BiPO4 would transfer to WO3 while the photoinduced holes in WO3 could easily inject to BiPO4 through their intimate contact interfaces, thus leading to an efficient transfer and separation of interfacial charge carriers. Moreover, the interaction of BiPO4 and WO3 could also extend the region of the absorption spectrum, which then benefited the improvement of photocatalytic activity.
Highly nonlinear varistors fabricated by hot-dipping tin oxide thin films in Ta2O5 powder at different temperatures Ceram. Int. (IF 2.986) Pub Date : 2018-01-17 Qi Wang, Zhijian Peng, Yang Wang, Xiuli Fu
This work proposed a smart approach to fabricate highly nonlinear SnOx-Ta2O5 thin film varistors. During processing, tin oxide films in nanoscaled thickness were firstly deposited onto electrically conducting silicon wafers through radio frequency magnetron sputtering a sintered tin oxide ceramic target; and then, the obtained films were hot-dipped in Ta2O5 powder in a Muffle oven for 60 min at different temperatures. With the hot-dipping temperature increased from 300 to 800 °C, the nonlinear coefficient of the samples increased first and then decreased, reaching the maximum of 16.8 at 600 °C, which is a record in all the reported SnO2-based varistors and comparable with those of the most extensively investigated and commonly commercially applied ZnO-based ceramic varistors. Correspondingly, the leakage current decreased first and then increased, obtaining the minimum of 4.1 mA/cm2. Besides, the breakdown electric field increased first and then decreased, presenting the maximum of 0.0313 V/nm. Such nanoscaled thin film varistors would be promising in electrical and electronic devices working in low-voltage.
High Remnant Polarization, High Dielectric Constant and Impedance Performance of Nb/In Co-doped Bi0.49La0.01Na0.49Li0.01TiO3-δ Ceramics Ceram. Int. (IF 2.986) Pub Date : 2018-01-17 Mohsin Ali Marwat, Bing Xie, Malik Ashtar, Yiwei Zhu, Penyuan Fan, Haibo Zhang
The new ferroelectric oxides, Bi0.49La0.01Na0.49Li0.01Ti0.99(Nb1-xInx)0.01O3-δ (hereafter abbreviated as BLNLTN1-xIx), with x = 0.5–0.65 were fabricated using conventional solid state reaction method. The effects of Niobium (Nb) and Indium (In) as B-site substitutions on phase, microstructure, dielectric, ferroelectric, complex impedance and complex electric modulus properties were systemically analyzed. Hysteresis graphs indicated that BLNLTN0.5I0.5 comparatively have the highest remnant polarization (Pr) of about 49.83 µC/cm2. Moreover, the dielectric studies of BLNLTN0.5I0.5 showed the highest relative dielectric constant (εr) i.e. 4599.3 in comparison to all other compositions. In addition, it also indicated very small loss of <0.045 at 1 kHz over a broad range of temperature i.e. room temperature (RT) to 380 °C. By comparing BLNLTN0.5I0.5 with BNT, Pr and εr were increased 13.46% and 26.3%, respectively whereas coercive electric field (Ec) and tanδ were decreased 41.06% and 1.96%, respectively. The impedance analysis for BLNLTN0.5I0.5 revealed a gradual decrease in bulk resistance (Rb) with the increase in temperature. Also, it showed negative temperature coefficient of resistance (NTCR) property at 500–800 °C and a p°lydispersive non-debye type relaxation at 800 °C. The complex electric modulus analysis proved that effect is mainly due to the bulk grains. Their basic analysis i.e. XRD and SEM studies showed a single phase perovskite structure, spherical grain shape and decreasing average grain size trend with increasing x content. The overall analysis has confirmed the significance of Nb/In co-doping in Bi0.49La0.01Na0.49Li0.01TiO3-δ and showed it as a capable dielectric material for fabricating high-temperature ceramic capacitors.
Fabrication of Electrospun Mn1-xZnxMoO4 (x=2.5, 5, and 10% Zn) Nanofibers: Microstructure Parameters, Surface Morphology and Kramers-Kronig (KK) Analysis Ceram. Int. (IF 2.986) Pub Date : 2018-01-17 T. Ramezanpour, Hossein Mahmoudi Chenari, H. Kangarlou
Electrospun Mn1-xZnxMoO4 nanofibers (x=2.5, 5 and 10%), have been prepared by controlling the Zn concentration of a polymeric solution followed by calcination. The effects of Zn doping on structural, morphological, chemical characterization, and optical properties of the manganese molybdate nanofibers were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive analysis of X-rays (EDAX), BJH pore size and volume analysis, Fourier Transform Infrared (FTIR), and Reflectance spectrum in the wave length range of 200–1200 nm. XRD studies revealed the diffraction peaks are mainly assigned to the orthorhombic structure of the MoO3 phase. The microstructural investigation of the calcinated nanofibers has been achieved from the size-strain plot (SSP) model using X-ray diffraction profile analysis. The SEM images exhibit Zn-doped manganese molybdate ceramic nanofibers with diameters ranged from 60±10 to 90±10 nm after calcination at 400 °C. The optical property of the prepared nanofibers was also proposed according to the Kramers-Kronig model.
Effect of controlled segmentation on the thermal cycling behavior of plasma sprayed YSZ thick coatings Ceram. Int. (IF 2.986) Pub Date : 2018-01-16 Satish Tailor, Ankur Modi, S.C. Modi
This work is the 2nd part of the previous work done in the series; where, for the first time controlled segmentation crack densities have been developed manually in the coatings, even after the coating deposition. Atmospheric plasma sprayed (APS) Yttria-stabilized zirconia (YSZ)-coatings are deposited on Ni-based superalloy IN738. Thermal cycling performance was tested before and after the development of controlled segmentation crack densities in the coatings at 1150 °C for 500 cycles. In the present work, failure mechanisms in un-segmented coating and alongside the effect of controlled segmentation on the thermal cycling behavior of plasma sprayed YSZ thick coatings are investigated. Results show a promising strain tolerance behavior for the segmented coatings, whereas regular conventional (un-segmented) coating could not sustain at higher temperature after its thermal cycling test. Coating microstructures reveal that four types of coating failure were observed in un-segmented regular coating and it happened due to the formation of thermally grown oxide (TGO). Whereas, segmentation helps to control the excess formation of TGO and therefore a very thin layer of TGO was observed in segmented coating and obvious no coating failure or spallation occurred.
High transmittance in IR region of conductive ITO/AZO multilayers deposited by RF magnetron sputtering Ceram. Int. (IF 2.986) Pub Date : 2018-01-16 Kun-Lun Wang, Yan-Qing Xin, Ji-Feng Zhao, Shu-Mei Song, Sheng-Chi Chen, Ying-Bo Lu, Hui Sun
The widely commercial used transparent conductive oxides (TCOs), such as ITO, combine ideal transmittance in visible light region and low electrical resistivity. However, its transmittance in near infrared (NIR) region is very limited. In contrast, AZO as a promising candidate of ITO possesses better optical transmittance in NIR region but presents poor electrical properties. In order to extend the applications of TCO materials in NIR region, ITO/AZO multilayers were designed in this work. The influence of the AZO monolayer thickness on the film's optoelectronic properties in NIR region was investigated. The results show that with AZO monolayer thickness increasing, the film's electrical resistivity increases, but always lower than that of single AZO film. In addition, the film's transmittance in NIR region is greatly improved by increasing AZO monolayer thickness. In point of the figure of merit, all ITO/AZO multilayers present enhanced optoelectronic properties in NIR region with respect to single ITO film or single AZO film. When AZO monolayer thickness is about 6 nm, the optimal film is realized. Its resistivity is around 8.6 × × 10−3 Ω·cm, while its average transmittance in NIR region reaches 90.0%.
CORROSION BEHAVIOURS OF MgO-C REFRACTORIES: INCORPORATION OF GRAPHITE OR PYROLYTIC CARBON BLACK AS A CARBON SOURCE Ceram. Int. (IF 2.986) Pub Date : 2018-01-16 Tuba Bahtlı, Derya Yeşim Hopa, Veysel Murat Bostancı, Nesibe Sevde Ulvan, Serife Yalcın Yastı
In this study, corrosion behaviours of MgO-C refractories produced by the incorporation of carbon and pyrolytic carbon black obtained from waste tire pyrolysis under either argon or oxygen atmospheres were investigated. Moreover, the effect of porosity on the corrosion resistance of those refractories was studied. The microstructures of corroded refractories were characterized by Scanning Electron Microscopy (SEM)/EDX. Experimental studies indicated that refractories produced by the use of pyrolytic carbon black as a carbon source had higher amount of porosity due to their lower packing density and lower corrosion resistance than those of ones produced by the incorporation of graphite.
Structural ordering and microwave dielectric properties of Ba1-xLn2x/3(Co0.7Mg0.3)1/3Nb2/3O3 (Ln=La, Nd) ceramics Ceram. Int. (IF 2.986) Pub Date : 2018-01-16 Zhefei Wang, Chenyao Zhai, Jianfei Lu, Shilong Yin, Xuhong Wang, Lei Yu
(Ba1-xLn2x/3)(Co0.7Mg0.3)1/3Nb2/3O3 (0.01≤x≤0.04, Ln=La, Nd) ceramics were systhesized by solid-state reaction process and their sintering behavior, microstructure and microwave dielectric properties were investigated in this paper. The X-ray diffraction results show that all the samples exhibit a single peroskite phase except for the Nd-substituted compositions with x>0.02. The sinterability and grains distribution are improved by the La-substitution. Though the long range ordering degrees on B-site are similar in the Ln-substituted compositions, the size of ordered domains observed by HRTEM images are quite different. Compared with the Nd-subsituted compositions, the higher Q×f values in the La-substituted compositions are mainly attributed to the better densificaition and ordered domain structure with lower energy barriers. Both εr and τf values increase slightly with the increase of Ln-substitution. A good combination of microwave dielectric properties was obtained in the La-substituted composition with x=0.01: εr=32.5, Q×f=79812 GHz, τf =4ppm/°C.
Realizing white light emitting in single phased LaOCl based on energy transfer from Tm3+ to Eu3+ Ceram. Int. (IF 2.986) Pub Date : 2018-01-16 Huayu Bai, Yan Song, Dan Li, Qianli Ma, Xiangting Dong, Wensheng Yu, Ying Yang, Jinxian Wang, Guixia Liu, Tingting Wang
Herein, a set of tetragonal Tm3+, Eu3+ doped 3D umbrella-like LaOCl phosphors was synthesized to realize wide range white light emitting. The energy transfer between Tm3+ and Eu3+ ions was observed in LaOCl:Tm3+, Eu3+ system. Multiple evidences clarified conjointly the energy transfer properties involving overlap spectra, changes of emission spectra, and fluorescent decay times. The mechanism of energy transfer from Tm3+ to Eu3+ in the LaOCl host was discussed in detail. The emission spectrum of LaOCl:Tm3+, Eu3+ system contain blue light from Tm3+ transition, green and red light from Eu3+ transition, which involve three primary colors constituting white light. Thereby, under excitation at 229 nm, a relatively large range of adjustable white light emission can be reached due to the energy transfer from Tm3+ to Eu3+ in LaOCl host, when percentage of sensitizer and activator are adjusted. The finding clarifies these materials as promising for potential application in near ultraviolet based white light emitting diodes.
Synthesis of SnO/g-C3N4 visible light driven photocatalysts via grinding assisted ultrasonic route Ceram. Int. (IF 2.986) Pub Date : 2018-01-16 Baoyan Liang, Danhui Han, Changhong Sun, Wangxi Zhang, Qi Qin
SnO/Graphitic-C3N4 (g-C3N4) photocatalysts were prepared by a simple solid phase grinding-assisted ultrasonic synthesis technology. Results showed that SnO/g-C3N4 composites with moderate g-C3N4 exhibit nanosheet morphology. An intimate interface boundary exists between the g-C3N4 and SnO phases in the composites. The composites possess excellent photocatalytic activity. SnO/g-C3N4 exhibits optimum photocatalytic property (7.66%) and highest photoactivity, which could degrade 98% of methyl orange under visible-light irradiation within 80 min.
Development of a novel compressive h-BN based seal for planar intermediate temperature SOFC Ceram. Int. (IF 2.986) Pub Date : 2018-01-13 Xiaochun Wang, Wei Zhang, Ruizhu Li, JiaJun Yang, Dong Yan, Jian Pu, Bo Chi, Li Jian
A novel compressive boron nitride (h-BN) based seal has been developed for planar intermediate temperature solid oxide fuel cell (SOFC). It exhibited extremely low leakage rates and thermal cycling stability under simulated stack conditions. The h-BN based seal showed leakage rates of 0.01 sccm/cm under gas pressure of 6.8 kPa in the temperature range of 650 ~ 800 °C, and maintained similar leakage rates during 10 thermal cycles. The excellent sealing performance can be explained by oxidation of h-BN surface to form liquid B2O3 layers beyond the critical temperature of 700 °C. Two of compliant B2O3 glass layers were observed on the surface of the h-BN to adjoin well cell and metallic interconnect. The sandwich structure with liquid B2O3 layer on two sides of the h-BN seal could not only enhance interfacial adherence but also eliminate the gas leakage paths at SOFC operation temperature. The applicability of the h-BN based seal has also been verified by single cell test.
Fabrication of CeO2 Ceramic Spheres as a Surrogate of Nuclear Fuel by an Improved Microwave-assisted Rapid Internal Gelation Process Ceram. Int. (IF 2.986) Pub Date : 2018-01-13 Wei Tian, M.A. Pouchon, Hangxu Guo, Denglei Chen, Xiaojie Yin, Zhi Qin
CeO2 is a surrogate of PuO2 in nuclear fuel development. Uniform sized ceramic CeO2 spheres were fabricated by an improved internal gelation process which combined the in-situ instant mixing of room-temperature precursor solutions with microwave-assisted internal gelation. Chemical kinetics investigations showed that the gelation process sped up as the [HMTA]/[Ce4+] ratio, [OH-]/[Ce4+] ratio and temperature increased. However, to avoid cracking during the sintering process, the [HMTA]/[Ce4+] ratio should be limited at low value while [OH-]/[Ce4+] ratio should be sufficiently high. Besides, pressured water treatment was adopted to wipe off impurities in the gelled spheres before sintering. The microstructure and morphology of the prepared ceramic CeO2 spheres were also investigated. The improved microwave-assisted internal gelation process greatly simplifies the conventional sol-gel process and avoids secondary organic radioactive waste. It will be a potential method for the fabrication of MAs and Pu-containing ceramic nuclear fuel spheres in glove-box in future.
Role of MoSe2 on nanostructures WO3-CNT performance for photocatalytic hydrogen evolution Ceram. Int. (IF 2.986) Pub Date : 2018-01-13 M.B. Tahir, G. Nabi, T. Iqbal, M. Sagir, M. Rafique
Exploration of highly-efficient photocatalysts for H2 evolution is a great concern for fabricating sustainable green energy systems. In this contribution, unique and architectural nanostructured WO3-CNT @MoSe2 composites were developed through facile hydrothermal and wet-chemical co-precipitation method. Structural, morphological and optical properties were investigated using XRD, SEM, EDX, BET, Uv-Vis and PL spectroscopy. Experimental results demonstrate that photocatalytic activity increases with increasing coupling contents of MoSe2 upto 4% and for CNT-WO3 with 2at%. However, the further increment in content above this optimal level lessened the photocatalytic performance of composites. Higher photocatalytic activity towards hydrogen evolution is accredited to extended region of visible portion of solar light, large surface area and suppresses the charge carrier's recombination by synergistic effect between MoSe2 and WO3-CNT. Consequently, the as-prepared photocatalyst empowers potential applications for green hydrogen evolution.
Structural and Magnetic Behavior of Nanocrystalline Cr Doped Co-Mg Ferrite Ceram. Int. (IF 2.986) Pub Date : 2018-01-13 Priya Jadoun, Jyoti Sharma, Sudhish Kumar, S.N. Dolia, Deepak Bhatnagar, V.K. Saxena
Nanoparticles of Cr substituted Co-Mg ferrites with chemical composition Co0.5Mg0.5CrxFe2-xO4 (0≤x≤1) have been synthesized by sol-gel auto combustion route. Rietveld refined powder X-ray diffraction patterns confirmed nanocrystalline single phase formation of all the ferrite samples in the face centered cubic spinel structure in the space group of Fd3m (No. 192). Cr doping for Fe in the Co-Mg ferrite leads to monotonic decrease in the saturation magnetization at 300 K as well as at 5 K, which can be described due to the weakening of super exchange interaction because of the replacement of Fe3+ ions by weak magnetic Cr3+ ions at the octahedral site. Decrement observed in coercivity from 0.085 T to 0.044 T at room temperature with increase in Cr concentration is indicative of the decrement in the isotropic field. Coercivity follows the Kneller's law for Co0.5Mg0.5Fe2O4 ferrite within the temperature range 5 K − 300 K. Interestingly the saturation magnetization was observed to increase whereas the coercivity decreases with increase in the annealing temperature in Co0.5Mg0.5Cr0.6Fe1.4O4 ferrite.
Effect of deposition temperature on the mechanical, corrosive and tribological properties of mullite coatings Ceram. Int. (IF 2.986) Pub Date : 2018-01-12 Shuangjian Li, Xiaoqin Zhao, Yulong An, Wen Deng, Guoliang Hou, Enkang Hao, Huidi Zhou, Jianmin Chen
Thermal-sprayed ceramic coatings are used worldwide to provide protection from corrosion and wear on components. Nevertheless, they exhibit very poor tribological performance in corrosive conditions, primarily because the high porosity and low cohesive strength, resulting in severe corrosion of metal materials and wear of coatings. Herein, a series of mullite coatings are deposited on the surface of titanium alloys under different deposition temperatures and the splats behavior, mechanical properties, corrosion and wear performance of mullite coatings are studied. Results show that adjusting the deposition temperature can modify the splats behaviors, improve the microstructure and degree of crystallinity and enhance the hardness and cohesive strength. Owing to the improvements, the specimens deposited at higher temperatures have the excellent anti-corrosion and wear-resistant ability.
Improving Electrochemical Performance by Na, Mg and Al-Ion Doping of PbLi2Ti6O14 as Anode Materials for Li-Ion Batteries Ceram. Int. (IF 2.986) Pub Date : 2018-01-12 Runtian Zheng, Wenchao Bi, Haoxiang Yu, Xing Cheng, Haojie Zhu, Na Peng, Tingting Liu, Wuquan Ye, Jie Shu
In recent years, titanium-based oxides have attracted great attention in the research field of secondary Li-ion batteries. However, they suffer from poor electronic conductivity due to a huge band gap. In this paper, PbLi2Ti6O14 is fabricated by a simple one-step solid-state reaction method. To enhance its conductance and Li-storage capability, PbLi1.95Na0.05Ti6O14, PbLi1.95Mg0.05Ti6O14 and PbLi1.95Al0.05Ti6O14 are fabricated by Na, Mg and Al-ion doping. More impressively, PbLi1.95Al0.05Ti6O14 presents a superior reversible capability with a reversible charge capacity of 152.8 mAh g−1 after 100 cycles at current density 100 mA g−1. In addition, it also clearly demonstrates that PbLi1.95Al0.05Ti6O14 has good structural stability and electrochemical reversibility by in situ XRD observation. Besides, it also presents a high Li-ion diffusion coefficient of 1.978×10–12 cm2 s−1. All of these make it possible to become a superior performance anode material for Li-ion batteries.
The effect of La2O3 on the microstructure and mechanical properties of 12Ce-TZP Ceram. Int. (IF 2.986) Pub Date : 2018-01-12 Wen Zhang, Jinxiao Bao, Xiwen Song, Shengli An
The influence of La2O3 on the microstructure and mechanical properties of 12Ce-TZP was investigated. The 12Ce-TZP-xLa2O3 ceramics were synthesized by a conventional solid state reaction method. La2O3 addition has a significant influence on the phase composition and microstructure, as well as on the mechanical properties of all compacts. At lower La2O3 concentration (below 0.2 mol%), the microstructure refinement of the compact was obtained due to La2O3 segregation at the grain boundary, leading to a large improvement of both the hardness and strength. At higher concentration, the evolution of hardness and strength of all compacts were associated with zirconia stabilization effect and La2Zr2O7 precipitation at the grain boundary, as well as the appearance of monoclinic phase. Additionally, the transformation toughening mechanism played a dominant role in this system. Finally, an optimum combination of hardness and strength was obtained for the 0.5 mol% La2O3 containing compact.
Rare earth Sm3+ co-doped AZO thin films for opto-electronic application prepared by spray pyrolysis Ceram. Int. (IF 2.986) Pub Date : 2018-01-12 V. Anand, A. Sakthivelu, K. Deva Arun Kumar, S. Valanarasu, A. Kathalingam, V. Ganesh, Mohd Shkir, S. AlFaify, I.S. Yahia
Samarium co-doped aluminum zinc oxide (Sm:AZO) thin films were deposited on glass substrate by nebulizer spray pyrolysis technique with different Sm doping concentrations (0 at.%, 0.5 at.%, 1 at.% and 1.5 at%). X-ray diffraction patterns confirm the polycrystalline nature of prepared films with hexagonal crystal structure. The average crystallite size was found to be reduced with Sm doping due to increased lattice defects. The Raman spectra exhibited characteristic ZnO wurtzite structure confirmed through the presence of E2-high mode peak at 438 cm−1. The surface topology analysis revealed the uniformly distributed wheat shaped particles without any pinholes for 1 at.% Sm doped ZnO film. Sm:AZO films displayed high transparency which is around 90% and the energy gap of ~ 3.30 eV. Photoluminescence spectra of the thin films showed an UV emission peak at ~ 386 nm corresponds to near band edge (NBE) emission of bulk ZnO. Room temperature Hall Effect measurement showed that all the prepared films possess n-type conducting nature with low electrical resistivity (ρ) 4.31×10−4 Ω.cm for 1 at.% Sm doped film. The high figure of merit (ф) value of ~ 11.9 ×10−3 (Ω/cm)−1 was observed which indicates that the deposited films are highly suitable for opto-electronic device applications.
Synthesis and characterization of Na5M(MoO4)4 (M = Y,Yb) microwave ceramics for ULTCC applications Ceram. Int. (IF 2.986) Pub Date : 2018-01-12 Johnson Dhanya, Elattuvalappil Kalathil Suresh, Rajaram Naveenraj, Ravendran Ratheesh
Na5Y(MoO4)4 and Na5Yb(MoO4)4 ceramics are prepared by solid state ceramic route and structural characterization has been done using powder X-ray diffraction and Laser Raman spectroscopy techniques. The presence of MoO42- units in the crystal structure is confirmed from Raman spectra. The scanning electron micrographs of the sintered ceramic samples show dense microstructure. Na5Y(MoO4)4 ceramics exhibited a maximum sintered density of 3.6 g/cm3 at 600 °C with a dielectric constant of 7.8, quality factor (Q × f) of 56,800 GHz, and temperature coefficient of resonant frequency (τf) of −83 ppm/°C, whereas Na5Yb(MoO4)4 ceramics showed a maximum sintered density of 3.9 g/cm3 at 570 °C with a dielectric constant of 6.9, quality factor (Q × f) of 43,400 GHz, and temperature coefficient of resonant frequency (τf) of −68 ppm/°C. Powder X-ray diffraction and energy dispersive X-ray spectroscopic analyses of the co-fired samples confirm good chemical compatibility with aluminium electrode for Na5Yb(MoO4)4 ceramics and hence is a suitable candidate material for ULTCC applications.
Dielectric based energy storage capacity of sol-gel synthesized Sr-doped ZrTiO4 nanocrystallites Ceram. Int. (IF 2.986) Pub Date : 2018-01-12 Naadia Akhtar, Hafiz Muhammad Rafique, Shahid Atiq, Sana Aslam, Aamir Razaq, Murtaza Saleem
In this research work, we have studied the effect of substitution of Sr on the structural, morphological and impedance spectroscopic properties of Zr1-xSrxTiO4 (x = 0, 0.05, 0.10, 0.15 and 0.2), synthesized using sol-gel auto-combustion technique. The X-ray diffraction confirmed the orthorhombic phase. The Fourier transform infrared spectroscopy spectra confirmed that no organic content was present in the sample. Field emission scanning electron microscopic analysis reveals that the particle size reduces from 125 nm to 15 nm. Energy dispersive X-ray technique confirmed the presence of Zr, Ti, Sr and O in the matrix. Dielectric properties are measured at room temperature in the frequency range of 20 Hz to 20 MHz by using the impedance analyzer. Dielectric parameters have been studied by using Koop's theory and Maxwell-Wagner's Model. AC conductivity increases with the increase in frequency and with increasing Sr contents. The impedance plot shows the dominance of grain boundary resistance. Dielectric relaxation process has been studied using Modulus plot.
Large-scale and ultra-low thermal conductivity of ZrO2 fibrofelt / ZrO2-SiO2 aerogels composites for thermal insulation Ceram. Int. (IF 2.986) Pub Date : 2018-01-12 Jian He, Hangyuan Zhao, Xiaolei Li, Dong Su, Huiming Ji, Huijun Yu, Zhipeng Hu
The large-scale fibrous/aerogels composites are prepared by using zirconia fibrofelt (ZFF) as skeleton to give high strength and ZrO2-SiO2 aerogels (ZSA) as filler to give excellent thermal insulation through vacuum impregnation. The ZFF/ZSA with a low density of 0.302 g/cm3 and a high porosity (89%) exhibits large size of 180 mm in length, 180 mm in width and 25 mm in height which is larger than other fibrous aerogels. Meanwhile, the ZFF/ZSA exhibits high compressive strength of up to 0.17 MPa which is approximately six times higher than that of ZFF (0.028 MPa). The ZFF/ZSA shows a much lower thermal conductivity of 0.0341 W·m−1·K−1 at room temperature and 0.0460 to 0.096·m−1·K−1 during 500℃ and 1100℃ which are lower than that of conventional fibrous materials, indicating its excellent thermal insulation property in a wide temperature range, and the thermal insulation mechanism is analyzed. Thus, the large-scale, low density, high strength, and low thermal conductivity of ZFF/ZSA composites show enormous potential application in the fields of architecture, engineering pipes and aerospace for thermal insulation and protection.
Microwave absorption performance of in situ synthesized Fe3O4-SiO2 hybrid fibres with enhanced environmental stability Ceram. Int. (IF 2.986) Pub Date : 2018-01-12 Ye Yuan, Yizhe Feng, Xu Zhao, Minglong Yang, Haibao Lu, Jianjun Li, Yunchen Du, Yibin Li, Xiaodong He
Fe3O4-SiO2 hybrid fibres were prepared by a combination of sol-gel and electro spinning techniques. The X-ray diffraction peaks of the fibres at 30.5, 35.5, 43.0, 57.0 and 62.6 correspond to the (220), (311), (400), (511) and (440) Fe3O4 planes and confirm the formation of Fe3O4 in the amorphous silica matrix. Si and Fe elemental mappings at the microstructural level were determined by scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry (EDS). The results reveal the uniform distribution of Si and Fe in the hybrid fibres. The Fe3O4-SiO2 hybrid fibres are immersed in the test hydrochloric acid solution with pH=1 and still can be magnetized and attracted to an external magnet after 6 hours in the solution. The heat- and flame-resistant performances of the hybrid fibres are demonstrated. Moreover, the prepared Fe3O4-SiO2 hybrid fibres display good microwave absorption performance in the range of relatively high frequencies. At a thickness of 5 mm, the bandwidth corresponding to reflection loss below −10 dB reaches approximately 11 GHz (7~18 GHz), covering the entire X-band (8.0~18.0 GHz) and Ku-band (12.0~18.0 GHz).
Optimized preparation of alumina based fillers for tuning composite properties Ceram. Int. (IF 2.986) Pub Date : 2018-01-12 Gamal Lazouzi, Marija M. Vuksanović, Nataša Z. Tomić, Miodrag Mitrić, Miloš Petrović, Vesna Radojević, Radmila Jančić Hainemann
Alumina based particles were prepared from aluminium chloride hydroxide as starting material by sol-gel technique. One series of particles was doped with ferrous oxide. Both series of particles were calcinated at three different temperatures: 700 °C, 800 °C and 900 °C. Poly(methyl methacrylate), PMMA, was used as a matrix and two different types of alumina based particles were added into the matrix to form the composites. All composites consisted of 3 wt. % of alumina based particles. The aim of this study was to examine whether and how the temperature of particle calcinaton affects the microhardness and mechanical properties of the composite. The particles were characterized by the X-ray diffraction (XRD) and physical absorption methods. The morphology of the composites was examined using a field emission scanning electron microscope (FESEM). The microhardness of composites was measured using a traditional Vickers hardness (HV) method. The mechanical characteristics of obtained composites were determined using tensile test and impact testing.
Electrochemical preparation of precursor phases for obtaining alpha-alumina from aluminium scrap Ceram. Int. (IF 2.986) Pub Date : 2018-01-11 J.C. García-Mayorga, G. Urbano-Reyes, M.A. Veloz-Rodríguez, V.E. Reyes-Cruz, J.A. Cobos-Murcia, J. Hernández-Ávila, M. Pérez-Labra
This work presents a study to obtain α-Al2O3 from thermal treatment of the precursor α-Al(OH)3 Al ( OH ) 3 (bayerite). The precursor was prepared from a cathodic electrosynthesis employing direct current (DC) and alternating current (AC) electrochemical techniques and using an aluminium solution prepared with scrap aluminium cans. Characterization techniques including X-ray diffraction (XDR), scanning electron microscopy (SEM) and thermogravimetric analysis (TG) were used to analyse the thermal behaviour, phase transformation, morphology and particle size of the products obtained. The range of potentials for electrodeposition was between −2.0 to 2.4 V with both DC and AC techniques. The presence of crystalline bayerite in the deposits obtained during all DC and AC experiments was observed, although a species of aluminium oxide (Al2.427O3.64) with AC was also identified. The surface morphology of the deposit with DC presented a compact uniform film, whereas with AC a granular form morphology with compact grains in the order of 1–3 μm was evident. In addition, the formation of an amorphous and low crystallinity bayerite precipitate was obtained from the solution, which presented a surface morphology of non-uniform fine grains and agglomerates. The thermal behaviour (TG) indicates three regions of change in the phase, which were verified via the thermal treatment; a transition of bayerite to η-Al2O3 in a temperature range between 290 and 300 ° C and subsequently to α-Al2O3 at a temperature of 1100 °C was determined. The α-Al2O3 presents high purity, a surface morphology with fine grains and agglomerates in the order of 1–10 μm and an appreciable porosity.
Influence of mechanical activation on functional properties of barium hexaferrite ceramics Ceram. Int. (IF 2.986) Pub Date : 2018-01-11 D. Kosanović, V.A. Blagojević, A. Maričić, S. Aleksić, V.P. Pavlović, V.B. Pavlović, B. Vlahović
Barium hexaferrite ceramics were prepared using mechanically activated mixtures of iron and barium titanate. The 60:40 mass% Fe:BaTiO3 powder mixtures were mechanically activated for different times (100–240 min) and sintered at 1100 and 1200 °C in order to determine the influence of mechanical activation of the precursor on the magnetic and dielectric properties of the resulting barium hexaferrite ceramics. The final product contained 84–89 mass% of Ba2Fe22.46O38Ti1.54 phase, with higher content corresponding to longer mechanical activation of the precursor. XRD and Raman measurements indicated that the remainder of the sample consists of leftover BaTiO3 and hematite, which was formed by the oxidation of iron during mechanical activation and sintering in air. Magnetic properties of samples sintered at 1200 °C are superior to those sintered at 1100 °C, which can be attributed to higher Ba2Fe22.46O38Ti1.54 phase content. The position of the Curie temperature in 350–420 °C temperature region is consistent with 0.8:1 ratio of Ti to Ba. Maximum magnetization was observed for samples activated for 120 min. Dielectric properties of samples sintered at 1200 °C showed a dependence on frequency, with a significant drop in relative permittivity with an increase in frequency in the low-frequency region, and relatively constant values of relative permittivity in the high-frequency region. The tangent loss showed a decrease with increase in frequency, where peaks corresponding to the resonance of the electron hopping frequency with the external field were observed in the samples corresponding to the longer mechanical activation. Dielectric properties showed relatively small changes for samples activated longer than 150 min.
A Comparative study to evaluate the Corrosion performance of Zr incorporated Cr3C2-(NiCr) coating at 900°C Ceram. Int. (IF 2.986) Pub Date : 2018-01-11 Lalit Ahuja, Deepa Mudgal, Surendra Singh, Satya Prakash
In this study zirconium incorporated Cr3C2-(NiCr) coating has been sprayed on three superalloys viz. Superni 718, Superni 600 and Superco 605 using D-gun technique. A comparative study has been carried out to check the cyclic oxidation in air and hot corrosion in simulated incinerator environment (40%Na2SO4-40%K2SO4-10%NaCl-10%KCl) for the coated specimens at 900 °C for 100 cycles. Oxidation kinetics has been established for all the specimens using weight change measurements. Corrosion products have been characterized using X-ray diffractometer (XRD) and scanning electron microscopy/energy-dispersive analysis (SEM/EDAX). Cr3C2-(NiCr)+0.2%wtZr coating provides very good corrosion resistance in air oxidation for all the three coated superalloys. As all the three coated superalloys shows parabolic behaviour with parabolic rate constant as 0.07×10-10 (g2cm-4s-1) for Superni 718, 0.43×10-10 (g2cm-4s-1) for Superni 600 and 0.3×10-10 (g2cm-4s-1) for Superco 605 This coating is also effective in the molten salt environment but coating on Co-based superalloy Superco 605 did not perform satisfactorily. The parabolic rate constants for coated Superni 718 is 0.61×10-10 (g2cm-4s-1), for coated Superni 600 is 6.72 ×10-10 (g2cm-4s-1) and for coated Superco 605 is 17.5 ×10-10 (g2cm-4s-1).
Highly effective photoelectrochemical performance of solar energy materials based on Ag2WO4-AgX (X=Cl, Br, I) sensitized TiO2 nanotube arrays Ceram. Int. (IF 2.986) Pub Date : 2018-01-11 Shaohua Zhang, Zhiyuan Liu, Yiqing Zhang, Shanmin Gao, Rencheng Jin, Qingyao Wang
The highly effective photoelectrochemical materials based on TiO2 nanotube arrays (TiO2 NTs) co-sensitized by Ag2WO4 and AgX (X=Cl, Br, I) were in-situ prepared by a successive ionic layer adsorption and reaction deposition of Ag2WO4 nanoparticles on TiO2 NTs followed by ion exchange to form Ag2WO4-AgX (X=Cl, Br, I) heterojunctions by a hydrothermal method. The deposition of Ag2WO4-AgX (X=Cl, Br, I) nanoparticles was investigated by XRD and SEM. The Ag2WO4-AgX (X=Cl, Br, I) sensitization significantly extended the inherent UV absorption of TiO2 NTs to the visible light region. The photoelectrochemical properties including the visible light photocurrent response and photoelectrocatalytic removal of methyl orange, rhodamine B and Cr(VI) were investigated in detail. The results indicated the TiO2 NTs/Ag2WO4-AgBr photoelectrode showed the optimal photoelectrochemical properties, which could be attributed to the excellent energy band structure and interface conductance.
Effect of TiO2 and CaF2 on the crystallization behavior of Y2O3-Al2O3-SiO2 glass ceramics Ceram. Int. (IF 2.986) Pub Date : 2018-01-11 Weiwei Zhu, Haifeng Jiang, He Zhang, Suqiu Jia, Yaodong Liu
The effects of TiO2 and CaF2 on the crystallization kinetics, microstructure, phase evolution and microhardness of Y2O3-Al2O3-SiO2 glass ceramics were investigated by differential scanning calorimetric (DSC), field emission scanning electron microscope (FESEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) techniques. The results show that the addition of TiO2 is effective to promote crystallization by decreasing the activation energy, refining the grain size and increasing the microhardness. However, the CaF2 plays an opposite role by increasing the activation energy, coursing the grain size and decreasing the microhardness. Furthermore, the addition of TiO2 induces bulk crystallization of Y2O3-Al2O3-SiO2 glass. On the contrary, the addition of CaF2 leads to surface crystallization and decreasing of thickness of surface crystallized layer.
Thermoelectric properties of carbon nanotube reinforced cement-based composites fabricated by compression shear Ceram. Int. (IF 2.986) Pub Date : 2018-01-11 Jian Wei, Yin Fan, Lili Zhao, Fei Xue, Lei Hao, Qian Zhang
Carbon nanotubes (CNTs) with weight percent of 5.0, 10.0 and 15.0% were added into the cement matrix to fabricate CNT reinforced cement-based composites (CNTs/CC) by mixing and dry compression shear methods. Seebeck coefficient, electrical conductivity and thermal conductivity of the as-received CNTs/CC were measured and analyzed in detail. The CNTs/CC exhibits the thermoelectric behavior of p-type semiconductor. CNTs were dispersed uniformly in cement matrix by compression shear stress, which promoted a relatively high electrical conductivity (0.818 S/cm) and Seebeck coefficient (57.98 μV/°C) of CNTs/CC. Combining with their lower thermal conductivity ranged from 0.734 to 0.947 Wm−1K−1, the CNTs/CC shows the highest thermoelectric figure of merit (ZT) has reached 9.33×10−5, Which is benefit to the applications in large-scale energy harvesting in the buildings and pavements with low cost in the future cities.
Effect of Nb/C ratio in the morphological, structural, optical and photocatalytic properties of novel and inexpensive Nb2O5/carbon xerogel composites Ceram. Int. (IF 2.986) Pub Date : 2018-01-11 Nicolas Perciani de Moraes, Rebeca Bacani, Maria Lucia Caetano Pinto da Silva, Tiago Moreira Bastos Campos, Gilmar Patrocínio Thim, Liana Alvares Rodrigues
This work explores the development of hybrid Nb2O5/carbon xerogel photocatalysts. The precursor materials used, such as tannin and recycled niobium scraps, enhance the economic and environmental aspects of the synthesis. The materials were characterized by diffuse reflectance spectroscopy, scanning electron microscopy, dispersive energy spectroscopy, infrared spectroscopy, Raman spectroscopy and X-ray diffraction. The photocatalytic action of the material was evaluated by methylene blue decomposition as determined by UV-visible spectroscopy. Anhydrous niobium oxide has a hexagonal structure. The X-ray profiles of the materials developed (XC-wNb) are similar to Nb2O5, confirming the presence of inorganic oxide in the matrix of these composites. The chemical elements that compose the samples are homogeneously distributed on the surface of the samples, confirming the dispersion of the oxide in the carbonaceous matrix. The XC-wNb absorbs radiation in a considerably wider range than inorganic oxides, in this case, for the entire wavelength range used in the experiments, thereby suggesting the synergistic effect of xerogel and niobium oxide on the optical properties of the XC-wNb samples. All XC-wNb presented photocatalytic activity under visible radiation, evidencing the beneficial coupling effect on the photocatalytic properties of the material. The XC-24Nb was the most effective photocatalyst at the wavelength used due its composition, morphological and photochemical properties. The methylene blue photodegradation is controlled to a greater extent by reaction with the OH•OH• radical. The XC-24Nb also presents high stability and reusability, which are optimal properties for industrial application.
Effects of the size of expanded polystyrene as a pore-former on the properties of insulating firebricks Ceram. Int. (IF 2.986) Pub Date : 2018-01-11 A. Ramezani, S. Nemat, S.M. Emami
The effect of the pore size on the properties of insulating firebricks was studied when different grain sizes of the expanded polystyrene (EPS) were used as an organic pore-forming agent. In particular, porous firebricks were produced by extruding of EPS and other materials. Due to the different grain sizes of EPS, insulating firebricks with different pore sizes were obtained. The results showed that the bricks with a smaller pore size (EPS 1.4 samples) had higher cold crushing strength. It is due to the higher continuity of the solid phase between the pores of the EPS 1.4 samples regarding EPS 2.8 bricks. Although the percent of reheat change of both EPS 2.8 and EPS 1.4 samples were nearly equal up to 1000 °C, EPS 2.8 bricks shrank faster than EPS 1.4 firebricks above 1000 °C. The thermal conductivity of the EPS 2.8 samples was higher than EPS 1.4 bricks. It can be concluded that in equal volume fraction of voids, the greater the number of pores of smaller size, the lower the thermal conductivity.
High temperature investigation of SiO2-Al2O3-ZnO-Na2O glass for ceramic-glaze: in-situ/ex-situ synchrotron diffraction and conventional approaches Ceram. Int. (IF 2.986) Pub Date : 2018-01-10 Andrea Bernasconi, Monica Dapiaggi, Jonathan Wright, Stefano Ceola, Stefano Maurina, Fernando Francescon, Alessandro Pavese
The temperature dependent behaviour of a complex aluminosilicate glass (SiO2-Al2O3-ZnO-Na2O system), which is a reference for ceramic glaze technology, has been determined, by combining techniques that cover a scale ranging from atomistic to macroscopic. The system shows a linear thermal expansion up to about 600 °C. The glass transition temperature is at 620 °C , as observed from Differential Scanning Calorimetry. Ex situ synchrotron diffraction experiments found a further transformation consisting of albite crystallization above 810 °C. This reaction is very slow and induces permanent structural modifications in the material at both intermediate and short ranges, as shown by in situ synchrotron diffraction experiments. These observations explain why ceramic glaze technology still faces challenges for large scale manufacturing and show the critical thermal range where interventions should be focussed . Eventually, melting takes place at 1190 °C, from hot stage microscopy.
Influence of LiBO2 Addition on the Microstructure and Lithium-ion Conductivity of Li1+xAlxTi2-x(PO4)3(x=0.3) Ceramic Electrolyte Ceram. Int. (IF 2.986) Pub Date : 2018-01-10 Hainan Bai, Jiulin Hu, Xiaoguang Li, Yusen Duan, Feng Shao, Takahiro Kozawa, Makio Naito, Jingxian Zhang
Concerning the safety problems of conventional Li-ion batteries with liquid electrolytes, it is crucial to develop reliable solid-state electrolytes with high ionic conductivity. Li1+xAlxTi2-x(PO4)3 (LATP, x=0.3) is regarded as one of the most promising solid electrolytes due to its high ionic conductivity and excellent chemical stability to humidity. Herein, a new strategy is proposed for improving the sintering behavior and enhancing the ionic conductivity of LATP by using LiBO2 as the sintering aid via liquid phase sintering. The as-prepared sample LATP with homogeneous microstructure and high relative density of 97.1% was successfully synthesized, yielding high total ionic conductivity of 3.5×10-4 S cm-1 and low activation energy of 0.39 eV at room temperature. It was found that the addition of LiBO2 could effectively enhance the densification and increase the ionic conductivity of LATP electrolyte, proving an effective way to synthesis LATP ceramics by a simple and reliable route.
Atomic force microscopy characterisation of alkali-silica reaction products to reveal their nanostructure and formation mechanism Ceram. Int. (IF 2.986) Pub Date : 2018-01-10 Chuanlin Hu, Bishnu P. Gautam, Dechen Shang, Fazhou Wang, Daman K. Panesar
Microscopic studies on alkali-silica reaction (ASR) products revealed two distinct forms of solid ASR products. However, their chemical and morphological aspects have not been adequately understood. This study provides a new insight into the nanostructure of ASR products as examined by atomic force microscopy (AFM). Results reveals that the surface microscale morphology of the rosette-like ASR product is associated with the loss of surface water, and the granular ASR product is formed by the accumulation of nanoscale particles with a typical size of around thirty nanometres. Moreover, the application of AFM provides evidence for the fluid nature of the granular ASR product at high moisture content.
Structure and ionic conductivity of Li7La3Zr2-xGexO12 garnet-like solid electrolyte for all solid state lithium ion batteries Ceram. Int. (IF 2.986) Pub Date : 2018-01-10 Shuqiao Hu, You-Fen Li, Ru Yang, Zijian Yang, Lege Wang
Lithium garnet-like structure with the substitution of Zr4+ sites by the same value of Ge4+ in the Li7La3Zr2O12 (LLZO) has been synthesized by a solid state reaction. The results indicate that doping Ge4+ in the LLZO was able to reduce the sintering temperature as well as increase the density of the pellets. The prepared samples Li7La3Zr2-xGexO12 with cubic garnet like structure were characterized by X-ray diffraction and Raman spectra. The lithium ionic conductivity of all components was characterized by AC impendence at 20 °C, and the high ionic conductivity can be obtained with 4.78×10−4 S/cm, while a low activation energy was only about 0.29 eV in the temperature range from 253-213 K. The solid electrolyte of Li7La3Zr2-xGexO12 possessed a wide electrochemical window. A full cell containing the Li7La3Zr1.7Ge0.3O12 electrolyte was assembled to test the electrical performance, which demonstrates that the first discharge capacity can reach up to 139.1 mA g−1 at 0.1 C and the discharge capacity remains at 140.6 mA g−1 after 20 cycles. These excellent performances indicate that Ge doping LLZO could be a promising electrolyte candidate for all solid state Li ion batteries.
Ceramic Metal Oxides with Ni2+ Active Phase for the Fast Degradation of Orange II Dye under Dark Ambiance Ceram. Int. (IF 2.986) Pub Date : 2018-01-10 Huihuang Chen, Julius Motuzas, Wayde Martens, João C. Diniz da Costa
Spraying power influence on microstructure and bonding strength of ZrSi2 coating for SiC coated carbon/carbon composites Ceram. Int. (IF 2.986) Pub Date : 2018-01-10 Fei Liu, Hejun Li, Shengyue Gu, Xiyuan Yao, Qiangang Fu
The objective of this current paper was to characterize the ZrSi2 coating deposited on the SiC coated carbon/carbon (C/C) composites by supersonic atmospheric plasma spraying (SAPS) at different spraying power. The microstructure, phase composition and bonding strength were investigated. In the process of spraying, a few of ZrSi2 powders were quickly oxidized to produce ZrO2, SiO2 and ZrSiO4 ceramic phases. These phases were randomly embedded in the ZrSi2 coating to enhance the mechanical performances of the coating to some extent. In addition, t-ZrO2 and c-ZrO2 phases formed above 1473 K might be converted into m-ZrO2 accompanied with 8% volume expansion, which can heal part of microcracks of the ZrSi2 coating. Therefore, only a few microcracks and pores at the spraying power of 40 kW were found at the surface of ZrSi2 coating and no penetrative cracks existed in the cross section. Meanwhile, the bonding strength of the interface between the ZrSi2 and the SiC coating reached up to 11 N at 40 kW. In short, the SAPS technology was deemed to be a useful method to deposit the ZrSi2 coating on SiC coated C/C composites with high performance.
Tuning magnetic and high frequency dielectric behavior in Li-Zn ferrites by Ho doping Ceram. Int. (IF 2.986) Pub Date : 2018-01-10 Alina Manzoor, Muhammad Azhar Khan, Muhammad Yaqoob Khan, Majid Niaz Akhtar, Altaf Hussain
In the present study, the impact of holmium (Ho) substitution on structural, spectral, dielectric and magnetic behavior of Li1.2Zn0.4HoxFe2-xO4 (0.00≤x≤0.15) ferrites was investigated. The development of spinel phase and structural changes induced by Ho doping were confirmed by X-ray diffraction. The accommodation of Ho ions into spinel lattice was restricted for x≥0.06 as indicated by ortho phase (HoFeO3) traces. The decrease in lattice parameter (a) was attributed to the segregation of Ho ions on grain boundaries. FTIR spectra featured two intrinsic vibrational bands v1 (617 cm−1) and v2 (488 cm−1) for x=0 due to tetrahedral and octahedral vibrations respectively. The compositional dependence of force constants and bond lengths has explained on the basis of cations distribution and oxygen-cation bond distances of respective sites. The addition of Ho ions decreased the saturation magnetization and optimized the coercivity from 59 to 335 Oe, proposing these ferrites for magnetic recording media. Dielectric results for the entire range of frequency (1 MHz-3 GHz) revealed that ac conductivity increased from 3.5×105 to 1.8×106 (Ω-cm)−1 up to x=0.09 and then it decreased slightly for x=0.12. The effective contribution of grain-interior mechanism to dielectric behavior was confirmed by complex impedance study. The results of dielectric studies displayed that Ho doped lithium ferrites are suitable low loss potential materials for high frequency based applications.
Hydration evolution of MgO-SiO2 slurries in the presence of sodium metasilicate Ceram. Int. (IF 2.986) Pub Date : 2018-01-10 Yu Zhang, Yawei Li, Yajie Dai, Jun Liu, Yibiao Xu
In order to accelerate the formation of magnesium-silicate-hydrate gel (M-S-H), the sodium metasilicate was added into the MgO-SiO2 slurries. The effect of sodium metasilicate on the hydration process of MgO-SiO2 slurries was investigated in this work. It required a relatively small amount of sodium metasilicate to facilitate the formation of M-S-H and to surpress the brucite formation. In the early 24 hours, the M-S-H formed quickly due to the high concentration of magnesium ions and silicate species in solutions. With the further increasing of curing time, the M-S-H gel phase continuously grew. Furthermore, the sufficient silicate ions amount was favorable for the transformation of newly formed brucite to the M-S-H phase. The addition of sodium metasilicate influenced not only the reaction process but also the morphology of hydrates. Instead of the yolk-shell structure, the flower-like and stacked sheet-like M-S-H formed in the presence of sodium metasilicate.
Investigation on Ce3+ luminescence from different crystallographic sites, self energy transfer and abnormal thermal stability of nitrided Ba9Y2Si6O24: Ce3+ phosphor for W-LEDs Ceram. Int. (IF 2.986) Pub Date : 2018-01-10 Bing Peng, Kaixin Song, Huawen Wang, Shuangshuang Zhang, Weitao Su, Zhiqun Cheng
The nitrided Ba9Y2Si6O24: Ce3+ phosphors were prepared by the conventional high temperature solid state reaction. The site occupancy of Ce3+ ionic and its luminescent characteristics were clearly analyzed in Ba9Y2Si6O24 hosts by Rietveld refinement of XRD data, PL & PLE spectra analyses, as well as the first principle calculation. Compared with Ba9Y2Si6O24: Ce3+ phosphors, p-d orbital hybridization between N3--p and Ce3+-d orbital after the nitridation leads to red shifts of Ce(Ba(1))3+ and Ce(Ba(2,3))3+ lattice ionic emission peaks. Meanwhile, the self-energy transfer was pointed from Ce(Ba)3+lattice sites to Ce(Y)3+ lattice sites by the analysis of PL&PLE spectra and CIE chromaticity diagram. By optimizing the N3- concentration, there exists abnormal outstanding thermal-stability of nitrided Ba9Y2Si6O24: Ce3+ phosphors, its emission intensities at 453 K are higher than that of room temperature (293 K). The whole photoluminescent properties of nitrided Ba9Y2Si6O24: Ce3+ phosphors were superior to that of Ba9Y2Si6O24: Ce3+ phosphors without nitridation. It hints the nitrided Ba9Y2Si6O24: Ce3+ phosphors to be a promising candidate as a green phosphor for W-LEDs, and the nitridation technology might be an important feasible strategy to enhance and develop the luminescent properties for silicate and aluminates based phosphors.
Pressure dependent mechanical properties of calcium carbides Ceram. Int. (IF 2.986) Pub Date : 2018-01-10 Hong Jiang, Wei Dong, Xiao-Xue Qu, Kuan Cao, Yue-Hua Su, Chao Zhang
The mechanical properties of newly synthesized Ca2C3 and Ca2C under pressure have been studied by using the first-principles calculations with generalized gradient approximation. The equilibrium geometry, elastic stiffness constants, various moduli, and Pugh's ratio of the C2/m phase of Ca2C3 and the C2/m and Pnma phases of CaC2 are systematically studied. The elastic stiffness constants of C2/m-Ca2C3 under 0 GPa to 30 GPa, C2/m-Ca2C under 0 GPa to 7.5 GPa, and Pnma-Ca2C under 7.5 GPa to 30 GPa satisfy the Born−Huang mechanical criteria. The three phases of calcium carbides exhibit ductile characteristics. The surface constructions of bulk and Young's moduli illustrate the mechanical anisotropy of Ca2C3 and Ca2C. Our results are consistent with previously obtained experimental and theoretical data and have significant implications for the application of calcium carbides.
Effect of the calcium alumino-titanate particle size on the microstructure and properties of bauxite-SiC composite refractories Ceram. Int. (IF 2.986) Pub Date : 2018-01-10 Jianwei Chen, Huizhong Zhao, Han Zhang, Zhengkun Li, Jiaqin Zhang
Alkali resistance and thermo-mechanical properties of the transition zone of cement rotary kilns refractories are the key factors affecting their service life. Calcium alumino-titanate (CAT) containing bauxite-SiC composites were prepared using bauxite, SiC, CAT, Guang Xi white clay, α-alumina, and metallic silicon powder as starting materials and Al(H2PO4)3 as the binder. The effects of the CAT particle size on the phase composition, microstructure, thermo-mechanical properties, and alkali resistance of the CAT-containing bauxite-SiC composites during firing were investigated. The results reveal that the CAT particle size strongly affects the composites’ microstructure and sintering densification. With decreasing particle size, the particle-particle and particle-matrix interfacial bonding deteriorates gradually. When CAT particles are added, the specimens show higher strength, refractoriness under load, and residual rupture strength than the specimens with fine CAT powders. Specimens with fine CAT powders show lower coefficient of thermal expansion compared to the specimens with CAT aggregates. The alkali attack test confirms that the bauxite-SiC composite refractories with CAT aggregates show better alkali resistance than those with CAT fine powder. According to the alkali mechanism, 1) K vapors penetrate the specimen through the open and connected pores and cracks, 2) K vapors react with anorthite and corundum to form kalsilite accompanied by the formation of a liquid phase and new cracks.
Sintering behavior, phase evolutions and microwave dielectric properties of LaGaO3-SrTiO3 ceramics modified by CeO2 additives Ceram. Int. (IF 2.986) Pub Date : 2018-01-10 Zixing Wang, Changlai Yuan, Baohua Zhu, Qin Feng, Fei Liu, Jiwen Xu, Changrong Zhou, Guohua Chen
Crystal structures and microwave dielectric properties of (1-x) LaGaO3-x SrTiO3 (x=0.4, 0.5, 0.6) and 0.4SrTiO3−0.6LaGaO3-yCeO2 (y=0, 0.05, 0.1, 0.2) ceramics were investigated. As the x values increased, the orthorhombic changed to tetragonal perovskite structure at x=0.6 in LaGaO3-SrTiO3 system ceramics. However, numerous secondary phases were detected in LaGaO3-SrTiO3 system ceramics. Surprisingly, CeO2 additives could effectively suppress formation of secondary phases of 0.4SrTiO3−0.6LaGaO3 ceramics as Ce ions could be incorporated into host crystal lattices, leading to significantly improvement of optimal Q×f values from 35,354 GHz to 62,150 GHz. The Raman spectra exhibited that the modes associated with CeO2 phase became more obvious with increasing CeO2 additives. The 0.4SrTiO3−0.6LaGaO3−0.05CeO2 ceramics, sintered at 1475 °C/4 h, exhibited superior microwave dielectric properties with εr=32.9, Q×f =62,150 GHz and τf=−26.6 ppm/°C.
Synthesis of a novel single-source precursor for HfC ceramic and its feasibility for the preparation of Hf-based ceramic fibres Ceram. Int. (IF 2.986) Pub Date : 2018-01-10 Jun Cheng, Xiaozhou Wang, Jun Wang, Hao Wang
The growing popularity of ultra-high-temperature ceramics inspired us to prepare Hf-based ceramic fibres by sequential melt hand-drawing, ultraviolet (UV) crosslinking, and pyrolysis of a novel polymeric precursor synthesised by co-polymerisation of HfCl4, ethylenediamine, and allylamine. The above precursor featured a backbone comprising Hf–N and CH=CH groups and exhibited good melt spin ability due to having a relatively linear-chain structure, an optimal molecular weight (Mn = 2569 g/mol), and a suitable softening point (135−155 °C), being easily melt-drawn into green fibres (diameter = 25 μm) and exhibiting a high ceramic yield of 46.38 wt% at 1500 °C. UV curing of green fibres at room temperature and their subsequent pyrolysis in an inert atmosphere at 1200 and 1600°C afforded Hf-based ceramic fibres (diameter = 13 μm), indicating the great potential of the above precursor and the prepared ceramic fibres for ceramic matrix composites used in high-temperature applications.
Effects of atom- and phase-scale compressive stress on fracture toughness in yttrium-doped lanthanum zirconate solid solutions Ceram. Int. (IF 2.986) Pub Date : 2018-01-10 Yanfei Wang, Ping Xiao, Huan Yang, Siqing Wang, Rongjun Liu, Yingbin Cao
The poor fracture toughness of cubic pyrochlores has severely blocked their wide application. To toughen them, a series of yttrium dopants have been introduced to lanthanum zirconate, creating atomic or phase-scale compressive stress dependent on the concentration of dopants. We find bigger substitutional dopants, rather than smaller ones, can toughen cubic ceramics, attributing to the dominance of an imposed atomic compressive stress to surroundings over the local one near normal point defects. For special point defects such as oxygen vacancies or interstitials, the local stress in their vicinity could become dominant given an adequate concentration. Despite of the pyrochlore/fluorite intermixture possessing evidently reduced grains, it only exhibits intermediate fracture toughness, suggesting negligible grain refining effects on toughening. Further, a random distribution of atomic compressive stress induced by disordered oxygen vacancies is beneficial to toughening. This research highlights the atomic compressive stress on toughening, providing guidance for future design of novel thermal barrier coatings.
First-Principles Study on ZnV2O6 and Zn2V2O7: Two New Photoanode Candidates for Photoelectrochemical Water Oxidation Ceram. Int. (IF 2.986) Pub Date : 2018-01-10 H. Sameie, A.A. Sabbagh Alvani, N. Naseri, S. Du, F. Rosei
We used first principles calculations based on density functional theory with generalized gradient approximation to investigate and compare the structural, electronic and optical properties of two photoanode materials, ZnV2O6 and Zn2V2O7, for use in photocatalytic water splitting. After geometry optimization, the calculated structural parameters evince a satisfactory agreement with the reported experimental results indicating that the used method and conditions are suitable. The electronic structures demonstrate that both photocatalysts possess favorable band gaps (2.31 and 2.52 eV) and appropriate band edge positions for oxygen evolution reaction under solar radiation. The relatively light effective masses at the valence band maximum and conduction band minimum are expected to result in enhanced photocatalytic activity due to lower recombination probability of the photogenerated electrons and holes. The analysis of electronic density of states reveal that the higher coordination number of vanadium in ZnV2O6 with respect to Zn2V2O7 causes more delocalisation of bands owning to lower V-V and O-O distances in conduction and valence bands, respectively. Moreover, the origins of features that appear in solar energy harvesting characteristics (dielectric function and optical absorption coefficient) have been discussed for solar water splitting in detail.
Effect of Ti amount on wear and corrosion properties of Ti-doped Al2O3 nanocomposite ceramic coated CP titanium implant material Ceram. Int. (IF 2.986) Pub Date : 2018-01-09 O. Çomaklı, M. Yazıcı, T. Yetim, A.F. Yetim, A. Çelik
Al2O3 and Ti-doped Al2O3 nanocomposite ceramic coatings were prepared by using a sol-gel dip-coating process. Corrosion and wear resistance of Al2O3 ceramic coatings in relation to Ti amount were carried out using pin-on-disc tribotester, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Surface characterizations before and after the corrosion and wear tests were investigated by the scanning electron microscope (SEM) and X-ray diffraction (XRD) and hardness analysis. The results of corrosion and wear tests exhibited that the corrosion and wear resistance of nanocomposite ceramic coatings became better than uncoated samples. Also, corrosion and wear resistance of nanocomposite ceramic coatings improved with Ti doping content increased.
Fully Dense Hot Pressed Calcium Cobalt Oxide Ceramics Ceram. Int. (IF 2.986) Pub Date : 2018-01-09 Nidhi Puri, Ram P. Tandon, Ajit K. Mahapatro
Parametric optimization of dry sliding wear and friction of germanium doped lead calcium titanate borosilicate glass ceramic Ceram. Int. (IF 2.986) Pub Date : 2018-01-09 Sangeeta Das, S.S. Gautam, C.R. Gautam, Abhishek Madheshiya, U.S. Dixit
In this study, specific wear rate (SWR) and coefficient of friction (COF) of the synthesized samples in 55[(PbxCa1−x)O.TiO2]−44[2SiO2.B2O3]−1Ge with (0≤x≤0.7 mol%) system of glass ceramics was optimized using Taguchi method. The ASTM standards were used for preparing the samples for friction and wear tests on a pin-on-disc tribometer. The glass ceramic samples were used as pin materials that slid against a disc made up of EN32 steel. For assessing the tribological properties of the glass ceramics, three control factors, viz. material-compositions with varying fraction of x (x=0.0, 0.1, 0.3, 0.5 and 0.7 mol %), sliding speeds (2.61, 3.14, 3.66, 4.18 and 4.71 m/s) and loads (10, 15, 20, 25 and 30 N) were considered in an L25 orthogonal array design. The optimum input parameters for the minimum SWR and COF were selected based on signal to noise ratios and main effect plots. Analysis of variance (ANOVA) revealed that the sliding speed and lead oxide content of the material are the most contributing factors on SWR and COF, respectively. The optimization for minimizing the SWR and COF was carried out and confirmed. The surface morphologies of the tested glass ceramic sample were studied using scanning electron microscope (SEM) and the elemental analysis of the samples was done using energy dispersive analysis of X-rays (EDAX). The Vickers hardness at the free surface of the glass ceramic samples increased up to 9.59 mol % of lead oxide with the maximum hardness of 23.59 GPa. The compressive strength of glass ceramic samples could reach up to 190 MPa.
Modelling shear behaviors of 2D C/SiC z-pinned joint prepared by chemical vapor infiltration Ceram. Int. (IF 2.986) Pub Date : 2018-01-09 Yi Zhang, Litong Zhang, Jiangyi He, Chao Chen, Laifei Cheng, Yongsheng Liu
Progressive failure model is developed to investigate shear behaviors of 2D C/SiC z-pinned joint prepared by chemical vapor infiltration (CVI). It includes progressive failure model of 2D C/SiC composites and cohesive model of faying plane, in order to describe joint nonlinear shear behaviors and z-pin shear-off failure mode, respectively. All cohesive parameters are directly obtained from mechanical properties of 2D C/SiC composites. Results show that the model can almost reproduce joint shear behaviors and z-pin shear-off failure process. Joint failure results from coupled fiber tensile and fiber–matrix shearing damages at faying plane. The model also successfully demonstrates that joint shear properties can be effectively improved by changing z-pin density and diameter. The relationship between joint properties and mechanical properties of 2D C/SiC composites are subsequently obtained with the model. In this sense, joint shear strength increases with cohesive or in-plane shear strengths of 2D C/SiC composites.
Effects of Tb doping on structural and electrical properties of 47(Ba0.7Ca0.3)TiO3 –0.53Ba(Zr0.2Ti0.8)O3 thin films at various annealing temperature by pulsed laser deposition Ceram. Int. (IF 2.986) Pub Date : 2018-01-09 Haowei Lu, Lizhu Liu, Jiaqi Lin, Wenlong Yang, Ling Weng, Xiaorui Zhang
The ceramic thin films of 47(Ba0.7Ca0.3)TiO3–0.53Ba(Zr0.2Ti0.8)O3 (BCZT) + x (x=0.2, 0.3, 0.4 and 0.5) mol % Tb were grown on Pt(111)/Si substrates with various annealing temperature by pulsed laser deposition. The XRD spectra confirm that Tb element can enhance the (l10) and (111) orientations in ceramic films. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images show that Tb-doping can increase particle size effectively. The surface of Tb-doped film annealed at 800 ℃ is uniform and crack-free, and the average particle size and mean square roughness (RMS) are about 280 nm and 4.4 nm, respectively. Comparing with pure BCZT, the residual polarization (Pr) of 0.4 mol % Tb-doped film annealed at 800 ℃ increase from 3.6 to 9.8 μC/cm2. Moreover, the leakage current density value of Tb doped films are one order of magnitude (5.33×10−9−1.97×10−8 A/cm2 under 100 kV/cm) smaller than those of pure BCZT films (1.02×10−7 A/cm2).
The effects of in situ formation of Y3Al5O12 on property improvement of magnesium aluminate spinel refractories Ceram. Int. (IF 2.986) Pub Date : 2018-01-09 Jiangbo Liu, Zhoufu Wang, Xitang Wang, Hao Liu, Yan Ma
Magnesium aluminate spinel is widely used in cement rotary kilns, in the iron and steel industries, as well as in glass melting furnaces due to its excellent performance and chemical stability at both room temperature and elevated temperatures.In spite of these advantages, there are some practical problems during production of magnesium aluminate spinel refractories due to their poor sinterability: poor mechanical properties and poor creep resistance. These issues can cause problems during service. This study improved the sinterability of spinel refractories and in turn improved mechanical properties while decreasing the creep rate. This was done by forming a second low creep rate phase of yttrium aluminum garnet in the matrix structure. The addition of Y2O3 and reactive Al2O3 accelerated the densification process and increased the cold strength. There was a significant increase in the hot modulus of rupture due to the formation of YAG or the solid solution with spinel.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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