共查询到20条相似文献,搜索用时 15 毫秒
1.
Imad Khlifi Octavian Pop Jean-Christophe Dupré Pascal Doumalin Marc Huger 《Journal of the European Ceramic Society》2019,39(13):3893-3902
Industrial magnesia-spinel bricks destined for thermal shock applications often show more flexibility and improved crack growth resistance. Components from the spinel structure group are usually added to promote microcracking coming from thermal expansion mismatch. This leads to the development of toughening mechanisms that are very effective in improving the crack propagation resistance.Magnesia-hercynite composites were investigated in order to highlight their fracture process, with regard to their microstructure, by using Digital Image Correlation (DIC). The direct measurement of displacement fields between digital images of the reference state and the deformed one has provided valuable information on material deformation during loading. The aim of this work was to investigate the fracture behaviour of refractories through the coupling of the Wedge Splitting Test (WST) and DIC. By using a refined DIC process transformation taking into account a discontinuity of displacement, called 2P-DIC, a more effective characterisation of the fracture behaviour was achieved. 相似文献
2.
Nianshun Zhao Huiqing Fan Xiaohu Ren Jiangwei Ma Jie Bao Yijun Guo Yunyan Zhou 《Journal of the European Ceramic Society》2019,39(14):4096-4102
A novel (0.67-x)BiFeO3-0.33BaTiO3-x(K0.5Nd0.5)TiO3 (KNT100x, x = 0.0, 0.02, 0.04, 0.06, 0.08 mol%) ceramics were fabricated and their microstructure and electrical properties were studied. All samples displayed a pseudo-cubic symmetry, and adding of KNT had little effect on grain size. The dielectric analysis displayed the dispersion increases with the addition of KNT compositions, showing strong relaxor properties. Besides, high dielectric constant (ε’) of 23000 and dielectric peak temperature (Tm) of 390 °C remain at 1 kHz in the x = 0.02 sample while the dielectric loss (tanδ) dropped below 0.5 in the range of 30–400 °C, showing excellent electrical insulation performance. In addition, doping of KNT had obvious influence on the strain, and a large strain (Smax) of 0.26% was obtained at x = 0.02 due to the increase of electrical insulation. More importantly, the strain at 50 kV cm?1 enhanced significantly with temperature increasing, reaching a maximum strain of 0.75% with a small hysteresis coefficient of 30% at 110 °C. Particularly, KNT02 exhibited excellent fatigue resistance within 105 fatigue cycles. Presumably these results are attributed to the coexistence of ferroelectric and non-ergodic relaxor domains and the thermally activated domain wall motion. 相似文献
3.
Mohammed N. Al-Aaraji Antonio Feteira Stephen P. Thompson Claire A. Murray David A. Hall 《Journal of the European Ceramic Society》2019,39(14):4070-4084
Solid solutions of 0.35(Ba,Ca)(Zr,Ti)O3-0.65(K0.5Bi0.5)TiO3 (BCZT-KBT) having various Ca and Zr contents were synthesized by solid state reaction. The sintered ceramics exhibited interesting features comprising core-shell type microstructures and relaxor ferroelectric behaviour. The influence of air-quenching on structure and electrical properties has been systematically investigated. The results indicate that the compositional heterogeneity in the shell regions, for the slow-cooled state, was reduced by air quenching. Improvements are evident in ferroelectric tetragonal phase content, accompanied by increased polarisation values and depolarisation temperatures. Comparing the results obtained for two BCZT compositions, it was demonstrated that the stability of the ferroelectric tetragonal phase in slow-cooled BCZT-KBT samples was improved for the ceramic with lower Ca and Zr concentrations, denoted x = 0.06, comparing with that for higher levels, denoted x = 0.15. Furthermore, the electric field-induced ferroelectric state in the quenched ceramic with x = 0.06 was found to be more stable during heating, yielding an enhanced depolarisation temperature. 相似文献
4.
Xuefan Zhou Zhongna Yan He Qi Lu Wang Siyu Wang Yuan Wang Chao Jiang Hang Luo Dou Zhang 《Journal of the European Ceramic Society》2019,39(7):2310-2317
In this work, the crystalline phase, domain structure, and electrical properties of [Bi0.5(Na0.84K0.16)0.5]0.96Sr0.04Ti1-xNbxO3 (x = 0.010–0.030) ceramics are investigated. Increasing the Nb content induces the phase transition from coexistent rhombohedral and tetragonal phases to a single pseudo-cubic phase, and the lamellar ferroelectric domains evolve into polar nanoregions. Decreased ferroelectric-to-relaxor transition temperature and enhanced frequency dispersion are found in the temperature-dependent dielectric constant and loss, implying a transition from the non-ergodic to ergodic relaxor state. The Nb substitution significantly degrades the long-range ferroelectric order with sharply decreased piezoelectric coefficients from ? 140 to ? 1 pC/N. However, a large strain of 0.32% at 5 kV/mm (normalized strain of 640 pm/V) is obtained around the critical composition of x = 0.0225. The composition of x = 0.030 shows good temperature insensitivity of the strain response, characterized by 308 pm/V with less than 15% reduction from 25 °C to 125 °C. 相似文献
5.
N. Al Nasiri N. Patra M. Pezoldt J. Colas W.E. Lee 《Journal of the European Ceramic Society》2019,39(8):2703-2711
Two rare earth monosilicates (Yb2SiO5, and Lu2SiO5) were deposited using a low-cost coating application method to produce a single-layer coating. RE- oxides slurries were dip coated on oxidised CMC samples and subsequently heat treated at high temperature to ensure reaction between SiO2 and RE-oxides to form the RE-monosilicate. A single, continuous, homogeneous thick coating of 25 μm was obtained. X-ray diffraction (XRD) confirmed formation of, RE-monosilicates in Yb and Lu silicate systems. Coated samples were exposed to 90% H2O static steam environment at 1350 °C for 25, 50, 100, and 150 h. Scanning Electron Microscopy (SEM) indicated that both coatings adhered strongly to the substrate. Coating thickness reduced from 22 μm to 11 μm for Yb-coating and 13 to 4 μm for Lu-coating with increasing corrosion time from 25 to 150 h, however there was no significant attack of the CMC for all steam exposure times. 相似文献
6.
M. Makarovic A. Bencan J. Walker B. Malic T. Rojac 《Journal of the European Ceramic Society》2019,39(13):3693-3702
In this work, BiFeO3-SrTiO3 (BFO-STO) solid solutions have been studied with particular emphasis on the problems related to conventional solid state synthesis of BFO-based systems. This method results in the formation of Bi-rich phase on grain boundaries and inhomogeneities inside the grains, similar to the core-shell microstructure previously reported for several BFO-based ceramic systems. Highly homogeneous and dense BFO-STO ceramics were prepared by mechanochemical activation-assisted synthesis. The as-prepared (x)BFO-(1-x)STO ceramics with 0.7 ≥ x≥ 0.575 exhibited high remanent polarization (30–50 μC cm?2) and a maximum d33 value of 69 pC N-1 at x = 0.625. It is shown that the compositions in the close proximity of the pseudocubic phase (x ≤ 0.6), however, exhibit pronounced aging of d33 coefficient with time, which is most probably related to the low stability of the domain structure after poling. The results of this study could further promote the processing optimization and compositional design of the BFO-STO and other BFO-based systems. 相似文献
7.
P. Val-Gómez A. del Campo F. Rubio-Marcos J.F. Fernández A. Moure 《Journal of the European Ceramic Society》2019,39(4):1011-1019
In this work a microstructural qualitative and quantitative study of spatial stress distributions in modified KNN ceramics (K0.44Na0.52Li0.04)1-xCox/2 (Nb0.86Ta0.10Sb0.04)O3, according to the polarization state is shown. X-ray diffraction reflects a perovskite crystalline structure with coexistence of Tetragonal and Orthorhombic phases (T/O). Confocal Raman microscopy shows that these crystalline phases are distributed in randomly micrometric regions through the ceramic volume. Tetragonal regions show higher piezoelectric coefficient and exhibit a higher micro-stress that hardens the ferroelectric response. By the contrary, the occurrence of orthorhombic micro-regions softened the ferroelectric behavior and reduced their piezoelectric coefficients. The ferroelectric response of ceramics is studied, where poling is also shown as a factor that affects the spatial micro-stress distributions. Finally, a model that relates the results obtained by Raman characterization with the ferroelectric properties and stress states is proposed. 相似文献
8.
《Journal of the European Ceramic Society》2017,37(15):5035-5043
Refractories with reduced brittleness show a pronounced deviation from linear elastic behaviour and an enhanced thermal shock resistance. This paper aims to study the influence of microstructure on the fracture behaviour of magnesia refractories. The wedge splitting test(WST), which enables stable crack propagation for quasi-brittle materials, was used to identify the fracture behaviour and evaluate the energy dissipation. The evaluation of the crack lengths of the magnesia and magnesia spinel materials during the entire cyclic WST is based on the localized strain evaluated using the digital image correlation (DIC). A significant fracture process zone develops in the magnesia spinel material. The relationship between the dissipated energy and the actual crack length, which was used to characterize the crack growth resistance, was determined. The refractory materials that showed reduced brittleness consume a small amount of energy for fracture initiation but a large amount of energy for further crack propagation. 相似文献
9.
This paper provides the first characterization of heat source field in the crack tip zone in carbon black filled natural rubber (NR). It focuses more especially on the calorific effects of strain induced crystallization (SIC). For this purpose, full thermal and kinematic fields are measured simultaneously. Initial image processing based on motion compensation enables us to track the temperature of any material point at the specimen surface. A second image processing stage, based on the heat diffusion equation, enables us to obtain the fields of heat sources produced and absorbed by the material during the test. The heterogeneity of the stretch states is analyzed from the kinematic measurements. In terms of heat production, crystallization acts in two opposite ways in the crack tip zone: the crystallization process produces additional heat, but crystallites act as fillers, which increases material stiffness in the crack tip zone. Moreover, the heat sources in the crack tip zone remain positive and small during unloading. This phenomenon is due to the production of mechanical dissipation and probably a continuation of the crystallization process. The results attained are compared with those recently obtained in non-crystallizing carbon black filled styrene butadiene rubber (SBR50). 相似文献
10.
The piezoelectric strain and resonance performance of 0.37BiScO3-0.6PbTiO3-0.03Pb(Mn1/3Nb2/3)O3 (BS-PT-PMN-xFe) ceramics with different amounts of Fe content addition were investigated from room temperature to 200 °C. Both the piezoelectric strain and resonance performance are improved by Fe addition in wide temperature range. Piezoelectric strain of BS-PT-PMN-xFe with 1 mol% Fe is 0.23%, which is comparable to that of BiScO3-PbTiO3 (BS-PT) ceramics, while the strain hysteresis is only one-third. At 200 °C, the high-field strain coefficient of BS-PT-PMN-Fe with 1 mol% Fe is as large as 700 pm/V. Variation of piezoelectric strain and hysteresis is clearly reducing by Fe addition. The maximum vibration velocity is enhanced up to approximately 1 m/s in 2 mol% Fe-modified BS-PT-PMnN-xFe ceramics, and the vibration velocity is stable from room temperature to 200 °C when the electric voltage magnitude was below 60 Vpp. These results indicate that BS-PT-PMN-xFe ceramics are potential candidates for high-temperature piezoelectric actuator application. 相似文献
11.
Kuk-Jin Hwang Miyoung Shin Young Wook Lee Myung-Hyun Lee Heesoo Lee Tae Ho Shin 《Journal of the European Ceramic Society》2019,39(15):4864-4873
The solid oxide membrane (SOM) process is an environmentally friendly and innovative technology that can produce valuable metals directly from their oxides. In the SOM process, a yttria-stabilized zirconia (YSZ) tube is normally immersed the molten salt containing dissolved metal oxides and oxygen anions that move to the SOM tube where they are reduced without any emission. However, the YSZ phase transition and yttrium dissolution by the reaction with the flux reduce the SOM stability and lifetime. Here, we investigated the effect of powder characteristics on YSZ stability in the SOM electrolysis environment. Thus, powder with good formability such as high flowability and tap/untap density showed a 2% decrease in electrical conductivity, but a 17% decrease in low formability powders. The cause of the degradation is the penetration of salt ions into the lattice and the elution of yttrium ions, which results in a phase transition. 相似文献
12.
Bo-Wei Xun Yu-Cheng Tang Jian-Yin Chen Bo-Ping Zhang 《Journal of the European Ceramic Society》2019,39(14):4085-4095
We reported a facile analysis and reduction of oxygen vacancy () in 0.7Bi(Fe1-xScx)O3-0.3BaTiO3 (0≤x≤0.08) ceramics. The leakage current mechanism was investigated intensively. Our results indicated that oxygen vacancies are the main cause for the high conductivity in BF-BT ceramics, and their concentration was quantitatively estimated from the Bi3+ content and the average oxidation state of iron. The concentration was effectively suppressed and the insulation resistance was enhanced by almost two orders of magnitude after doping 2%mol Sc3+. The enhanced insulation resistance contributed to excellent piezoelectric properties with d33 = 165 pC/N, TC = 505 °C, and kp = 26%. The proposed analysis method used to quantify the concentration provides valuable indications to reduce the leakage current density and improve the piezoelectric properties of BF-BT based ceramic. 相似文献
13.
Maxim Sokol Jian Yang Hrishikesh Keshavan Michel W. Barsoum 《Journal of the European Ceramic Society》2019,39(4):878-882
Alumina forming, oxidation and thermal shock resistant MAX phases are of a high interest for high temperature applications. Herein we report, on bonding and resulting interactions between a Ni-based superalloy, NSA, and two alumina forming MAX phases. The diffusion couples Cr2AlC/Inconel-718/Ti2AlC were assembled and heated to 1000 or 1100 °C in a vacuum hot press under loads corresponding to stresses of either 2 MPa or 20 MPa. The resulting interfaces were examined using X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Good bonding between Cr2AlC and NSA was achieved after hot pressing at 1000 °C and a contact pressure of only 2 MPa; in the case of Ti2AlC a higher temperature (1100 °C) and pressure (20 MPa) were needed. In both cases, a diffusion bond, in which mainly Ni and Cr out diffused from the NSA into the MAX phase and a concomittant out diffusion of Al from the latter, was realized with no evidence of interfacial damage or cracking after cooling to room temperature. The reactions paths were determined to be: Cr2AlC/Cr7C3/Cr7C3,β-NiAl/α-Cr(Mo)/NSA and Ti2AlC/Ti2AlC,Ti3NiAl2C/β-NiAl/α-Cr(Mo)/NSA. Twenty thermal cycles from room temperature to 1000 °C showed that Ti2AlC is a poor oxidation barrier for Inconel-718. However, in the case of Cr2AlC no cracks, delamination nor surface degradation was observed, suggesting that this material could be used to protect Inconel-718 from oxidation. 相似文献
14.
Mingxing Zhou Ruihong Liang Zhiyong Zhou Xianlin Dong 《Journal of the European Ceramic Society》2019,39(6):2058-2063
The pyroelectric materials have immense applications in the uncooled infrared thermal detectors. However, owing to increasing environmental concerns due to Pb element, it is required to explore novel, high-performance, environmental-friendly pyroelectric materials. This is the first study to report about the pyroelectric properties of lead-free NaNbO3 ceramics, which displayed a high pyroelectric coefficient of 1.85 × 10?8 C cm-2 K?1 and figures of merit as Fi = 0.67 × 10?10 m V?1, Fv = 3.33 × 10?2 m2 C?1, and Fd = 5.32 × 10-5 Pa?1/2 at room temperature. Also, highly temperature-stable pyroelectric characteristics were also observed in NaNbO3 ceramics due to the high depolarization temperature of 280 ℃. The high pyroelectric properties and temperature stability were a result of the electric field induced irreversible phase transition from antiferroelectric to ferroelectric. Hence, we can conclude that lead-free NaNbO3 ceramics are a novel and promising candidate for pyroelectric detectors in a wide temperature range, especially for large area detectors and pyroelectric point detector. 相似文献
15.
Multi-principal component materials (MPCMs) are currently being investigated for use in high and ultra-high temperature environments. The design of oxidation resistant multi-component materials requires as input the oxidation behavior of each of the components. FactSage free energy minimization software and databases were used to calculate the equilibrium oxide phases and free energies of formation for the oxides of the Group IV, V and VI refractory metals, and their carbides, nitrides and borides. The results are summarized in Ellingham diagrams. Periodic trends were noted; Group IV elements form the most stable oxides with the highest melting temperatures (Tm), Group V elements form oxides with low Tm, and Group VI elements form gaseous oxide species. Oxygen diffusion data from literature for some of these oxides were also reviewed and summarized. The results are utilized to identify strategies for optimizing oxidation resistance of MPCMs for service at temperatures above 1700°C. 相似文献
16.
Jianhui Zhou Xiaotong Zhang Ying Yan Jianfeng Hu Hang Wang Yan Cai Jinqing Qu 《中国化学工程学报》2019,27(12):3043-3052
A novel antibacterial acrylate polymer composite modified with capsaicin was successfully synthesized by a two-step reaction. Capsaicin and acryloyl chloride were firstly esterified, and then applied to solution polymerization with acrylate monomers and styrene. The yield of the esterified products was about 85.3%. The polymer was characterized by Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), contact angle (CA) and antibacterial ring tests. The number-average molecular weight (Mn) of the polymer was 27214, based on the capsaicin-acrylate dosage of 6.5 wt%. The TGA revealed a stable thermal property. The contact angles of the polymers films on tinplate increased from 77.5° to 86.2° with the increasing amount of capsaicin-acrylate. The antibacterial tests demonstrated excellent antimicrobial capability of the polymers. 相似文献
17.
K. Praveen Nalla Sravani Rahul Jude Alroy G. Shanmugavelayutham G. Sivakumar 《Journal of the European Ceramic Society》2019,39(14):4233-4244
Conventional and solution precursor plasma spraying (SPPS) techniques were employed for developing gadolinium oxide doped lanthanum cerate ((La0.9Gd0.1)2Ce2O7, Gd-LC) based double-layered thermal barrier coatings (TBCs). Hot corrosion studies of the above coatings were carried out in molten Na2SO4 + V2O5 (1:1) environment at 900 °C. The state-of-the-art yttria-stabilized-zirconia (YSZ) coating was found to be completely delaminated after 120 h by forming yttrium vanadate (YVO4) and m-ZrO2. The accelerated delamination of YSZ can be attributed to the undesired phase transformation during exposure to corrosive species. Double-layered APS coatings were found to last for more than 300 h without densification of underlying YSZ layer and also, show better adherence with bond coat. SPPS Gd-LC coatings were found to be completely delaminated on densifying the underlying YSZ within 300 h. Lanthanum vanadate (LaVO4) was found to be the main corrosive product along with minor amounts of gadolinium vanadate (GdVO4) in Gd-LC double-layer coatings. 相似文献
18.
Lei Guo Chenglong Zhang Qing He Zhihua Li Jianxing Yu Xichun Liu Fuxing Ye 《Journal of the European Ceramic Society》2019,39(4):1496-1506
REPO4 (RE = Gd, Nd, La) ceramics with a monazite structure were fabricated by a chemical co-precipitation and calcination method. Hot corrosion tests were carried out in V2O5+Na2SO4 molten salt at 800 °C, 900 °C and 1000 °C for 2 h and 10 h. The temperature and heat duration had little effect on the type of corrosion products in this study. However, GdPO4 and REPO4 (RE = Nd, La) revealed different hot corrosion behavior. Exposed to the molten salt, GdVO4 and Gd4(P2O7)3 formed as the corrosion products for the GdPO4 case, while an RE(P,V)O4 (RE = Nd, La) solid solution was generated for NdPO4 and LaPO4 cases. The formation of the solid solution had less damage to the original microstructure, which benefited the hot corrosion resistance of the ceramics. From the crystallographic characteristics of rare earth phosphates/vanadates and a thermodynamics perspective, the hot corrosion mechanisms of REPO4 (RE = Gd, Nd, La) are discussed. 相似文献
19.
Karim Hentour Viviane Turq Alicia Weibel Florence Ansart Jean-Michel Sobrino Julien Garcia Pierre-François Cardey Christophe Laurent 《Journal of the European Ceramic Society》2019,39(4):1304-1315
Carbon-alumina coatings on stainless steel were prepared by a sol-gel route. The dispersion of the commercial graphite flakes by an ultrasonic bath, an ultrasonic probe and a high-shear mixer, produce thinner flakes, few-layered-graphene and bi-layer-graphene (BLG), respectively. The coatings were examined by optical and electron microscopy, interferential rugosimetry, optical profilometry and Raman spectroscopy. The friction coefficient against a steel ball is decreased by a factor of 5–7 and the wear volume is reduced by a factor of 6–38 compared to a pure alumina coating. The best results correspond to the sample prepared using the high-shear mixer. Delamination of the graphite flakes into BLG during the friction test provides the system with debris suitable for tribofilm building up and lubrication but it is better to already have carbon dispersed as BLG in the coating before the test, notably because the carbon surface area available is much higher. 相似文献
20.
Miguel de la Luz-Asunci n Eduardo E. P rez-Ram rez Ana L. Mart nez-Hern ndez Victor M. Castano V ctor S nchez-Mendieta Carlos Velasco-Santos 《中国化学工程学报》2019,27(4):912-919
The adsorption capacities for the removal of hexavalent chromium from aqueous solutions by six carbon nanomaterials have been evaluated. Single-walled and multi-walled carbon nanotubes as received and after oxidation treatment, graphene oxide and reduced graphene oxide are the materials with different dimension and functionalization compared in this research. Carbon nanotubes have been modified using hydrogen peroxide as oxidizing agent under microwave radiation. The oxidation treatment on carbon nanotubes has a positive effect increasing the adsorbent–adsorbate interaction. Rate-controlling mechanisms and equilibrium data are analyzed using non-linear models. Non-linear method is proposed as the most suitable method for determining the kinetic and equilibrium parameters. The values of adsorption energy(E) obtained from the Dubinin–Radushkevich isotherm,have been found around 0.371 and 0.870 k J·mol~(-1), indicating physical adsorption. Therefore, the pseudo-second order model represents better the kinetic experimental data. The results show that the Langmuir isotherm provides a slightly better fit to the experimental data compared with the Freundlich isotherm, indicating homogeneous distribution of active sites on carbon nanomaterials and monolayer adsorption. The separation factors RLare found in the range of 0–1, suggesting that the adsorption process is suitable for all adsorbents. The mechanisms for hexavalent chromium removal have been proposed as electrostatic interactions and hydrogen bonding. 相似文献