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Journal of Ceramic Science and Technology 2/2018
Vol. 9, No. 2 · June 2018
Room-Temperature Mechanochemical Synthesis and Consolidation of Nanocrystalline HfB2-HfO2 Composite Powders
N. Akçamlı, N. Akçamlı, D. Ağaoğulları, Ö. Balcı, M. L. Öveçoğlu, İ. Duman
Pages 101-118 · DOI: 10.4416/JCST2017-00084
This study reports on the in-situ preparation of HfB2-HfO2 composite powders at room temperature by means of mechanochemical synthesis (MCS) from HfCl4-B2O3-Mg powder blends. The effects of milling duration and excess amounts of B2O3 and Mg reactants (20 and 30 wt%) on the HfB2 formation mechanism were investigated. After MCS and purification, HfB2, HfO2 and Mg2Hf5O12 phases were obtained. The Mg2Hf5O12 phase decomposed during the annealing treatment conducted at 1000 °C under Ar flow. The as-synthesized, purified, annealed and subsequently leached powders were characterized with an X-ray diff …
High-Temperature Measurements of Macroscopic Deformation Induced by Phase Changes: Application to Bauxite-Based Material
A. Coulon, E. de Bilbao, S. Brassamin, J. Poirier
Pages 119-126 · DOI: 10.4416/JCST2017-00085
High-temperature measurements of macroscopic deformation are of great interest for better understanding the behaviour of materials used in high-temperature processes. However, such measurements are still challenging when performed on very heterogeneous materials such as the bauxite-based material studied here. In this work, a high-resolution camera is used in combination with a high-temperature furnace to monitor the change in size of a bauxite-based sample. The technique is applied to measure the change in diameter induced by phase transformation of the material and by the impregnation of mol …
Alkali-Activated Materials Based on Callovo-Oxfordian Argillite: Formation, Structure and Mechanical Properties
C. Dupuy, C. Dupuy, A. Gharzouni, N. Texier-Mandoki, X. Bourbon, S. Rossignol
Pages 127-140 · DOI: 10.4416/JCST2017-00086
If accepted, the construction of Cigéo, a French geological disposal facility for radioactive waste, will lead to the excavation of a large quantity of Callovo-Oxfordian (COx) argillite. The valorization of this raw material by alkaline activation was studied. For this, COx argillite without and with thermal treatment at 750 °C using furnace and flash processes were investigated. These treatments led mainly to the dehydroxylation of clay minerals and the decomposition of carbonate compounds. The feasibility of the alkali-activated samples based on different argillite samples and their mixtures …
Effect of Submicron-Carbon-Containing MgO-C Refractories on Carbon Pickup of Ultra-Low Carbon Steel
Y. Liu, Y. Liu, L. Wang, G. Li, G. Li, G. Li, Z. Zhang, X. Xu, Y. Li, J. Chen
Pages 141-148 · DOI: 10.4416/JCST2017-00087
To reduce the carbon pickup of ultralow-carbon steel, the interaction between liquid steel and MgO-C refractories containing submicron carbon at 1600 °C was studied under laboratory conditions and compared with interaction of liquid steel with conventional MgO-C refractories containing flaky graphite. The results show that the carbon pickup in steel is provided by the spalling refractories, the penetration layer and the reaction of Al in steel with CO, which is generated from the reaction between MgO and C in refractories. The carbon supplied by spalling refractories might play a dominant role …
Electrical and Dielectric Properties of Isostatically Pressed Alumina-Based Electroporcelain
V. Trnovcová, M. Kubliha, I. Štubňa, Š. Csáki, Š. Csáki
Pages 149-154 · DOI: 10.4416/JCST2017-00089
The anisotropy of dc and ac conductivities and relative permittivity is studied in green, dehydroxylated, and fired, cold-isostatically pressed alumina-based electroporcelain. The dc conductivity, σdc, of green samples is isotropic and its temperature dependence contains two Arrhenius-like sections: below 140 °C, σdc = 5·10-2exp (-0.77/kT), and from 150 to 400 °C, σdc = 4·10-4exp (-0.56/kT), where σdc is in S/cm and conduction activation energies are in eV. The dc conductivity of dehydroxylated samples is also isotropic but much lower: below 200 °C, σdc = 1.7·10-3exp (-0.8/kT); above 210 °C, σ …
Enhanced Electrochemical Performance of Cu-Doped La2NiO4+δ Cathode for Solid Oxide Fuel Cells
H. Chen, H. Chen, X. Li, X. Du, H. Xie, L. Zhao, Y. Ling, Y. Ling
Pages 155-162 · DOI: 10.4416/JCST2017-0090
To illustrate the effect of Cu-doping in Ruddlesden-Popper-type La2NiO4+δ oxides, the crystal structure, interstitial oxygen formation, electrical conductivity, catalytic activity and chromium tolerance of La2NiO4+δ(LNO)and La2Ni0.9Cu0.1O4+δ(LNCO) are analyzed. XRD Rietveld and HT-TEM results confirm that both can be identified as Ruddlesden-Popper-type structures with tetragonal symmetry. Compared with non-doped LNO, LNCO has less interstitial oxygen, and its electrical conductivity decreases owing to the reduction of the carrier concentration. The effects on electrode performance are analyze …
Effect of Multiple loading sequence on in-phase thermomechanical fatigue hysteresis of silicon carbide fiber-reinforced ceramic-matrix composites
L. Li
Pages 163-174 · DOI: 10.4416/JCST2017-00095
In this paper, the effect of multiple loading sequence on the in-phase (IP) thermomechanical fatigue (TMF) hysteresis of silicon carbide fiber-reinforced ceramic-matrix composites (SiC-CMCs) has been investigated. Considering the coupling effects of multiple loading sequence, thermal cyclic temperature and applied cycle number, the fiber/matrix interface damage lengths have been determined based on the thermomechanical micromechanical stress field and fracture mechanics method. The relationships between the in-phase TMF hysteresis loops, multiple loading sequence, thermal cyclic temperature an …
Enhanced Magneto-Dielectric Properties of 0.6La0.1Bi0.9FeO3- 0.4BaTiO3/NiFe2O4 Composites Sintered with Powders Prepared with a One-Step Sol-Gel In-Situ Method
L. He, J. H. Wang, Z. T. Zhong, C. Zhang
Pages 175-182 · DOI: 10.4416/JCST2017-00096
0.6La0.1Bi0.9FeO3-0.4BaTiO3/NiFe2O4 (0.6LBFO-0.4BT/NFO) composite powders were firstly prepared using a simple one-step sol-gel in-situ method. The phase evolution with the calcination temperature was studied. The dense-sintered 0.6LBFO-0.4BT/NFO ceramics were synthesized, and the phase composition as well as the surface morphology were characterized. The dielectric and magnetic properties were measured. The results indicated that with increasing concentration of NFO, the ceramic composite shows an increased dielectric constant (ε’) while the dielectric loss tangent (tan δε) value decreases at …
Three-Dimensional Network ZnO/BaFe12O19 Composite Thick Films and their Microwave Absorption Properties
Y. Lin, J. Dong, Y. Liu, N. Han, L. Wang, H. Yang, J. Wang
Pages 183-192 · DOI: 10.4416/JCST2017-00097
ZnO/BaFe12O19 composite thick films with four different ZnO/BaFe12O19 mass fractions were synthesized with the tape-casting method in the presence of plate-like BaFe12O19 grains and sphere-like ZnO grains. Their phase composition, morphology and magnetic properties were analyzed by means of XRD, SEM and VSM, respectively. The microwave absorption properties were also investigated in the frequency range of 2 – 18 GHz, and the results show that the ZnO/BaFe12O19 composite thick films have multiple microwave attenuation peaks and their microwave absorption properties can be easily tuned by varyin …
Insulating Foams and Dense Geopolymers from Biochar By-Products
R. Farges, A. Gharzouni, B. Ravier, P. Jeulin, S. Rossignol
Pages 193-200 · DOI: 10.4416/JCST2017-00098
Pyrolysis is an innovative environmentally-friendly process to thermally treat biomass residues at low temperatures and in the absence of oxygen without releasing suspended particles, smoke or greenhouse gases. The obtained solid residue is called biochar. The aim of this work is to characterize four biochar by-products and to evaluate the feasibility of biochar-based geopolymer materials. For this, four types of biochar by-products, produced from wheat straw, miscanthus and wood, under different pyrolysis conditions were studied. First, the physical and chemical properties of the biochar by-p …
Tunable Temperature Range of Stress-Enhanced Electrocaloric Effects in Composition Gradient Bilayers
X. Sun, H. Huang, X. Ma, Y. Wen, Z.-M. Dang
Pages 201-208 · DOI: 10.4416/JCST2018-00002
We investigated a tunable temperature range of stress-enhanced electrocaloric effects in composition gradient bilayers by using the phenomenological Landau-Devonshire thermodynamic theory. A tunable temperature range of entropy change was obtained from 265 ∼ 270 K for the specific composition of BaSrTiO3 bilayers. Theoretical analysis shows that the external stress can tune the temperature range of electrocaloric effects from 220 K to 286 K, and the stress can tune the maximum temperature change 13 K per GPa. The thickness ratio of composition gradient films also can vary the adiabatic tempera …
Room-Temperature Structural and Dielectric Properties of Praseodymium-Doped SrBi2Nb2O9 Ceramics
M. Afqir, M. Afqir, A. Tachafine, D. Fasquelle, M. Elaatmani, J.-C. Carru, A. Zegzouti
Pages 209-214 · DOI: 10.4416/JCST2018-00004
In the present work, we studied the influence of substituting Pr for Bi on the structural and dielectric properties of SrBi2-xPrxNb2O9 (x = 0, 0.2) ceramics at room temperature. The samples were prepared by the solid-state reaction method. The XRD patterns of the doped sample corresponded well with those of the undoped samples. SEM revealed that the Pr doping brings significant change to the microstructure. The results obtained from different experimental dielectrics at room temperature are correlated to discuss the structure-property relationship with consideration of the internal microstruct …
