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Journal of Ceramic Science and Technology 1/2018
Vol. 9, No. 1 · March 2018
Microstructure and Phase Evolution of Cement-Bonded High-Alumina Refractory Castables for Porous Purging Plugs
Q. Wang, Y. Li, N. Xu, R. Xiang, S. Li
Pages 1-6 · DOI: 10.4416/JCST2017-00044
This work addresses the microstructure and phase evolution of four designed high-alumina refractory castables (containing ρ-Al2O3 or calcium aluminate cement as a binder source and 0 or 1 wt% microsilica). Various experimental tests (air permeability, linear change rate, apparent porosity, cold modulus of rupture, cold crushing strength, hot modulus of rupture, pore size distribution, X-ray diffraction and scanning electron microscopy) were conducted to characterize the castables. The results show that using cement as the binder has a significant effect on the properties of the refractory cast …
Effects of Stabilizer Content and Sintering Conditions on Y-TZP Ceramics made from Stabilizer-Coated Nanopowders
F. Kern, H. Strumberger, R. Gadow
Pages 7-18 · DOI: 10.4416/JCST2017-00049
Yttria-stabilized zirconia Y-TZP according to the state of the art has become a commodity applied in mechanical engineering and biomedicine. Besides the high strength typical for Y-TZP, the improved damage tolerance and fatigue strength are beneficial for components exposed to cyclic stress. In this study, Y-TZP materials were produced by means of hot pressing of nanoscale powders coated with yttria via a wet chemical route. Stabilizer contents were varied from 2.6 – 3 mol% Y2O3; sintering was carried out between 1250 °C and 1450 °C and 50 MPa axial pressure for 1 h. Samples were characterized …
Improving Optical Transmission of Spark-Plasma-Sintered YAG Ceramics: Effect of Powder Conditioning and Post-Treatments
R. Moronta Pérez, L. Boilet, P. Aubry, P. Palmero, L. Henrard, O. Deparis, V. Lardot, F. Cambier
Pages 19-28 · DOI: 10.4416/JCST2017-00052
Three YAG powders were densified by means of spark plasma sintering (SPS), with the aim of developing optically transparent ceramics. The influence of the physico-chemical characteristics of the powders (purity, agglomeration state and stoichiometry) on the sintering and the optical transmission was investigated. Depending on the powder type, different pre-treatments and/or post-treatments were necessary to increase both homogeneity and optical transmission of the densified parts. In the case of agglomerated powders, dispersion by ultrasonication was efficient and led to better homogeneity and …
Influence of the Oxygen Flow Rate on Gas Flow Sputtered Thermal Barrier Coatings
N. Rösemann, K. Ortner, M. Bäker, J. Petersen, G. Bräuer, J. Rösler
Pages 29-36 · DOI: 10.4416/JCST2017-00054
Porous thermal barrier coatings (TBC) reduce the thermal load of gas turbine components. State-of-the-art TBCs consist of partially yttria-stabilized zirconia (PSZ) and are deposited by means of thermal spray techniques or electron beam physical vapor deposition. In this paper, an alternative, innovative deposition technique (reactive gas flow sputtering – GFS) is investigated and the influence of process parameters on the microstructure and the suitability of GFS coatings as TBCs is discussed. PSZ coatings were deposited on polished FeCrAlY-alloy substrates, with varying substrate temperature …
Manufacturing of SiO2-Coated β-TCP Structures by 3D Printing using a Preceramic Polymer as Printing Binder and Silica Source
R. de Melo Bernardino, C. Wirth, S.L. Stares, G.V. Salmoria, D. Hotza, J. Günster
Pages 37-42 · DOI: 10.4416/JCST2017-00056
Tricalcium phosphate (β-TCP) can be used as bone graft, exhibiting suitable bioabsorption and osteoconduction properties. The presence of silica may induce the formation of a hydroxyapatite layer, enhancing the integration between implant and bone tissue. Preceramic polymers present silicon in their composition, being a source of SiO2 after thermal treatment. Using the versatility of 3D printing, β-TCP and a polysiloxane were combined to manufacture a bulk β-TCP with a silica coating. For the additive manufacturing process, PMMA powder was used as passive binder for the β-TCP particles, and po …
Effect of Particle Size on the Blue Chromate Pigment CoAl2O4
Y. Wang, Q. Wang, Q. Chang, S. Hu, X. Wang, K. Yang
Pages 43-46 · DOI: 10.4416/JCST2017-00060
A stable ceramic ink for inkjet printing requires ultrafine pigment powders. However, the decreased particle size of the ceramic pigment has an uncertain effect on the chromate. To understand this effect, a series of CoAl2O4 powders with different particle sizes was prepared with the nitrate-glycine combustion method followed by bead milling. The results show that the average particle size (d50) of the CoAl2O4 powder decreases from 6.4 μm to 0.33 μm after milling for 10 h. The particle size has a clearly negative effect on the color of CoAl2O4 pigment. The chromate value changes from L* = 49.8 …
Effects of NH4VO3 on Properties and Structures of Cordierite Ceramics
W. Ning, Z. Tang, Z. Han, S. Ding, C. Xu, P. Zhang
Pages 47-52 · DOI: 10.4416/JCST2017-00063
To obtain cordierite ceramics with superior properties, different proportions of NH4VO3 were added to a preferred basic ceramic formula, the main raw materials of which included talc, kaolin, calcined kaolin, alumina, aluminum hydroxide and amorphous SiO2. The cordierite ceramics were manufactured by means of high-temperature sintering. The results show that the coefficient of thermal expansion of the cordierite ceramics is significantly reduced with the addition of 4 % NH4VO3; water absorption rate, apparent porosity and flexural strength of the ceramics were increased. The results of FT-IR, …
Controlled Preparation of Red-Light-Emitting (Y0.95Eu0.05)2O3 Phosphors and Vacuum Sintering of Transparent (Y0.95Eu0.05)2O3 Ceramics
B. Lu, B. Lu, B. Lu, H.M. Cheng, H.M. Cheng, H.M. Cheng, Z.G. Sun, L. Wang, J.G. Pan, J.G. Pan, J.G. Pan, H.B. Chen, H.B. Chen, H.B. Chen
Pages 53-60 · DOI: 10.4416/JCST2017-00066
A facile co-precipitation technique was employed for preparing well-dispersed (Y0.95Eu0.05)2O3 phosphors using ammonium hydrogen carbonate (AHC) as the precipitant, followed by vacuum sintering at the relatively low temperature of 1700 °C for 4 h to produce transparent (Y0.95Eu0.05)2O3 ceramics. The transparent (Y0.95Eu0.05)2O3 ceramic, with fine grain sizes of 12 – 14 μm, has a substantially smaller bandgap (∼ 4.45 eV) than the corresponding phosphor. Both the oxide powder and the transparent ceramic exhibit the typical 5D0→7F2 transition at ∼ 613 nm, corresponding to the Eu3+ emission upon U …
Effects of Growth Rate on Microstructure and Properties of Directionally Solidified Eutectic Ceramic Al2O3/MgAl2O4/ZrO2
Z. Chu, Z. Chu, S. Wang, S. Wang, J. Liu, J. Liu, J. Wang, J. Wang
Pages 61-68 · DOI: 10.4416/JCST2017-00076
Directionally solidified Al2O3/MgAl2O4/ZrO2 ternary eutectic ceramic was prepared by means of induction heating zone melting (IHZM), and the effects of the growth rate on the microstructure and properties of the solidified ceramic were investigated. X-ray diffraction (XRD) patterns showed that the eutectic rod contained Al2O3, MgAl2O4 and ZrO2 phases. The results of scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) demonstrated that Al2O3/MgAl2O4 constituted the matrix of the eutectic ceramic while rod-like ZrO2 was uniformly embedded in the matrix. The specimen morph …
Mechanical Behaviour of Zirconia-Toughened Alumina Laminates with or without Y-PSZ Intermediate Layers
M.D. Barros, P.L. Rachadel, M.C. Fredel, R. Janssen, D. Hotza
Pages 69-78 · DOI: 10.4416/JCST2017-00077
Zirconia-toughened alumina (ZTA) laminates with 5 vol% (95A) and 30 vol% (70A) of yttria-partially stabilized zirconia (Y-PSZ), as well as laminated composites with thick ZTA layers and thin Y-PSZ layers were developed and processed by means of tape casting followed by co-firing. The addition of 5 vol% Y-PSZ led to grain refinement, higher densification and an increase in mechanical properties compared to those of pure alumina. In contrast, the addition of 30 vol% Y-PSZ refined the alumina grains and formed clusters of zirconia. However, it promoted lower densification when compared to pure al …
Enhanced Mechanical and Electromagnetic-Wave-Absorption Properties of Ceramic Matrix Composites Fabricated by Novel Laser-Machining-Assisted CVI
J. Wang, Y. Liu, L. Cheng, X. Chen, Q. Zhou, Z. Hou, F. Ye
Pages 79-84 · DOI: 10.4416/JCST2017-00080
A novel technique based on laser-machining-assisted chemical vapor infiltration (LA-CVI) was proposed and developed to fabricate ceramic matrix composites (CMCs). The results showed that the compressive strength, the shear strength and the bending strength of the C/SiC composites increased by 50.7 %, 11.8 % and 17.8 %, respectively, compared with those of classical CVI-C/SiC composites. The improvement can be attributed to the reopening of the diffusion channels and formation of a dense band and a coating around the channels. On the other hand, the minimum reflection loss (RL) of the C/SiC com …
Microstructure and Properties of Carbon Block Refractories Containing Thermally Oxidized Anthracite for Blast Furnaces
T. Wang, S. Sang, Y. Li, Y. Xu, Q. Wang
Pages 85-92 · DOI: 10.4416/JCST2017-00081
Carbon block refractories containing thermally oxidized anthracite (TOA) and additives of Al and Si were prepared for use in blast furnaces. The TOA was obtained by treating electrically calcined anthracite (ECA) using the thermal oxidation method. It was then introduced into carbon blocks by partially or totally replacing the ECA raw materials. The microstructure and properties of carbon block refractories heated in a coke bed at 1400 °C were investigated. The results revealed that TOA accelerated the formation of β-SiC whiskers and β-Sialon phases in carbon block refractories because TOA has …
Reinforcement Mechanisms in Yttria-Ceria-Co-Stabilized Zirconia-Alumina-Strontium Hexaaluminate Composite Ceramics
F. Kern, A. Gommeringer
Pages 93-98 · DOI: 10.4416/JCST2017-00046
Composite ceramics with 1 mol% yttria and 6 mol% ceria co-stabilized zirconia matrix were reinforced with 10 vol% alumina and 10 vol% in situ-formed strontium hexaaluminate. Samples were shaped by means of slip casting in plaster molds and sintered in air for 3 – 72 h at 1500 °C. Full density and highest fracture resistance were achieved in overfired material while the maximum strength of 900 MPa was obtained at a dwell of 12 h. The high fracture resistance up to 10.4 MPa√m results from contributions of different reinforcement mechanisms: microcracking, crack bridging, crack deflection and – p …
Corrigendum to “Evaluation of Rheological and Thermal Behavior of Ceramic Materials during Liquid Phase Sintering with Numerical-Experimental Procedure”
H. Yaghoubi, E. Salahi, F. Taati
Pages 99-100 · DOI: 10.4416/JCST2017-00019-CORR
DOI of the original article: 10.4416/JCST2017-00019
The authors regret that in the original published version of this article the authors sequence was wrong. According to this we changed the order of E. Salahi to second place and H. Yaghoubi to first place.
