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Journal of Ceramic Science and Technology 4/2016
Vol. 7, No. 4 · December 2016
Low-Temperature Degradation Behaviour and Mechanical Properties of a 3Y-TZP Manufactured from Detonation-Synthesized Powder
F. Kern, V. Lindner, R. Gadow
Pages 313-322 · DOI: 10.4416/JCST2016-00036
In recent years, yttria-stabilized zirconia Y-TZP has attracted considerable interest in the field of dental restoration. However, the state-of-the-art Y-TZP materials made from coprecipitated powders only just comply with the current standard in terms of fracture resistance and grain size. In this study a new nanoscale starting powder produced with detonation synthesis was applied to produce a fully dense specimen by means of hot pressing in the sintering temperature range between 1250 – 1500 °C. Mechanical properties, microstructure and phase composition were studied. Low-temperature degrada …
Anisotropic Fracture Toughness and Microstructure of Graphene-Reinforced TiC/Si3N4 Composite
Y. Zhang, Y. Zhang, G. Xiao, G. Xiao, C. Xu, C. Xu, M. Yi, M. Yi, X. Meng, X. Meng
Pages 323-328 · DOI: 10.4416/JCST2016-00032
Using the hot pressing sintering process, graphene-platelets (GPLs)-reinforced TiC/Si3N4 composite (GPLs/TiC/Si3N4) was prepared with the aim of improving its fracture toughness. Microstructure analysis shows that the pressure applied during the hot pressing sintering process leads to the orientational distribution of GPLs perpendicular to the pressing direction in the GPLs/TiC/Si3N4 composite. With the single-edge notched beam method, the fracture toughness of GPLs/TiC/Si3N4 was measured in the hot pressing direction (HPD) and perpendicular to the hot pressing direction (PHPD). The fracture t …
Structural, Electrical and Magnetic Properties of BiFe1-xYxO3 (0 ≤ x ≤ 0.6) Ceramics
A.A.A. Najm, A.H. Shaari, H. Baqiah, E. Bin Saion, L.K. Pah, C.S. Kien, M.M.A. Kechik
Pages 329-334 · DOI: 10.4416/JCST2016-00028
The effect of Y substitution on the microstructure, dielectric, magnetic and leakage current properties of BiFe1-xYxO3 (0 ≤ x ≤ 0.6) ceramics was investigated. The BiFeO3 phase that is dominant at x = 0.0 – 0.2 decreased with the increase of Y substitution. Other phases such as YFeO3 and Bi1.46Y0.54O3 emerged with Y substitution and became dominant in the range x = 0.3 – 0.4 and 0.5 – 0.6, respectively. The BiFe1-xYxO3 composites of rounded shape grains at x = 0.0 deformed at x = 0.1 – 0.3 and changed to melted-like grains at x = 0.4 – 0.6 with the incorporation of smaller grains at x = 0.5 an …
Microstructure and Mechanical Properties of Ternary Ceramic Composites with a ZrC-SiC Matrix
B.X. Ma, S.H. Xu
Pages 335-340 · DOI: 10.4416/JCST2016-00039
ZrC-SiC-ZrSi2 ternary ceramic composites were prepared by means of hot pressing. The effect of the ZrSi2 content on the microstructure and mechanical properties of the fabricated materials was investigated. It was found that the addition of ZrSi2 is effective in promoting the sinterability of ZrC-SiC-ZrSi2 ternary composites, and the highest relative density reaches 98.8 % when the ZrSi2 content is 10 vol%. ZrSi2 particles in the microstructure are characterized by an irregular shape with low dihedral angles, which is beneficial for the densification of the composites. The hardness of the comp …
Effects of Micro-Damage on the Nonlinear Constitutive Behavior of SiC/SiC Minicomposites
S. Zhang, S. Zhang, X. Gao, X. Gao, J. Chen, J. Chen, H. Dong, H. Dong, Y. Song, Y. Song, Y. Song, H. Zhang
Pages 341-348 · DOI: 10.4416/JCST2016-00040
The effects of matrix cracking, fiber/matrix interfacial debonding and fiber fracture on the nonlinear constitutive behavior of SiC/SiC minicomposites were studied. An in-situ tensile test was performed to detect the matrix cracking in real time. The macroscopic tensile test was also performed on the SiC/SiC minicomposites to obtain their stress-strain responses. Based on the test results, models of these types of damage were developed. The shear-lag model was adopted to simulate the stress-strain response of SiC/SiC minicomposites. The contributions of these types of damage to the nonlinearit …
Synthesis of Calcium Hexaboride Powder via Boro/Carbothermal Reduction with a Gel Precursor
D. Yilmaz Çakta, N. Koç, S. Turan
Pages 349-356 · DOI: 10.4416/JCST2016-00044
In this study, the synthesis of calcium hexaboride powder via boro/carbothermal reduction (BCTR) using a single-step-processed gel product prepared from commercial boric acid, readily available and low-cost D(-)-Mannitol and calcium carbonate was investigated. The gel product was characterized by means of Fourier Transform Infrared Spectroscopy (FTIR) and Simultaneous Thermal Analysis (STA). The effect of the boro/carbothermal reduction temperature and dwell time on the phase formation were examined with x-ray diffractometry and scanning electron microscopy. CaB6 synthesis was performed with t …
Microstructure and Electrical Properties of Co-Doped ZnO Varistors
S. Hamdelou, K. Guergouri, K. Guergouri
Pages 357-364 · DOI: 10.4416/JCST2016-00045
Varistor ceramics based on Co-doped ZnO nanopowders were prepared with the sol-gel method. The analysis of the structure shows that the ZnO:Co (1 mol%, 3 mol%, 5 mol% and 7 mol%) has a wurtzite structure without any second phase, the Co ions successfully substitute Zn sites in the ZnO lattice. The grain size of the obtained nanopowders varies between 36 and 210 nm. The microstructure and electrical properties of varistors made of these powders have been studied as a function of the sintering temperature, which ranged between 900 °C and 1075 °C. The varistors were sintered by means of the micro …
Higher Electronics Circuit Integrations within the Fractal Electronics Frontiers
V.V. Mitic, V.V. Mitic, V. Paunovic, Lj. Kocic
Pages 365-378 · DOI: 10.4416/JCST2016-00047
Knowledge of the morphology of ceramic grains and pores facilitates understanding of the sintering process. The real intergrain contact surfaces, as highly irregular objects, can only be adequately described by using fractal models. Both micro- and nanostructured shapes of grains and intergranular contacts can be easily reconstructed by using fractal analysis/modeling. Several variations of Coble's two-sphere model are reviewed in this paper. Further, the intergranular capacity model has been reexamined from the perspective of intergranular fractal formations. The area of grains' surface is ca …
Ablation-Resistant Composite Coating of HfC-TaC-SiC for C/C Composites Deposited by Supersonic Atmospheric Plasma Spraying
Y. Yang, K. Li, G. Liu, Z. Zhao
Pages 379-386 · DOI: 10.4416/JCST2016-00050
HfC-TaC-SiC multiphase coating was prepared on the surface of SiC-coated carbon/carbon composites by means of supersonic atmospheric plasma spraying. The morphology and microstructure of the HfC-TaC-SiC coating were characterized with XRD and SEM. The ablation resistance test was performed with an oxyacetylene torch. The results show that the surface of the coating is dense and rough. No crack can be found. The HfC-TaC-SiC coating could protect the substrate from ablation by the generated oxide compound layer. During ablation, the new compound Hf6Ta2O17 was generated, which had a single phase …
Experimental Investigation of the In-Plane Shear Behavior on Needled C/SiC Composites using Digital Image Correlation
G. Yu, X. Gao, Y. Song, Y. Song
Pages 387-396 · DOI: 10.4416/JCST2016-00052
In this study, the digital image correlation (DIC) technique was employed as a full-field measuring tool to analyze the in-plane shear deformation behavior of needled C/SiC composites. The non-linear in-plane shear stress-strain curve was obtained. The shear strain distribution and evolution were analyzed. The correlation between the shear strain distribution along the notches and the structure of needled preforms was investigated. The initiation and propagation of the cracks on the surface of shear specimens were studied. The failure mechanisms of needled C/SiC composites under shear loading …
Influence of Phosphoric Acid Treatment on the Photocatalytic Activity of Zinc Oxide
H. Onoda, Y. Sato
Pages 397-402 · DOI: 10.4416/JCST2016-00053
Zinc oxide is often used as a white pigment for cosmetics; however, it exhibits photocatalytic activity that causes the decomposition of sebum on the skin when exposed to the ultraviolet radiation in sunlight. In this work, zinc oxide was reacted with various concentrations of phosphoric acid for several hours to synthesize a novel white pigment for cosmetics. The chemical composition, powder properties, photocatalytic activities, colors, and smoothness of these pigments were studied. The obtained materials exhibited x-ray diffraction peaks relating to zinc oxide and phosphate after phosphoric …
Low-Temperature Preparation of Lanthanum Hexaboride Fine Powder via Magnesiothermic Reduction in Molten Salt
K. Bao, C. Liu, B. Yazdani Damavandi, S. Zhang
Pages 403-408 · DOI: 10.4416/JCST2016-00057
Lanthanum hexaboride (LaB6) fine powder was synthesized from La2O3 and B2O3 using a molten-salt-assisted magnesiothermic reduction technique. The effects of salt type, Mg amount, heating temperature and time on the synthesis were investigated, and the relevant reaction mechanisms discussed. Among the three chloride salts (NaCl, KCl and MgCl2) attempted, MgCl2 showed the best accelerating effect. When 20 mol% excessive Mg was used, phase-pure LaB6 particles of ∼ 200 and ∼ 100 nm were obtained respectively after 4 h heating at 1000 °C, and 5 h at 900 °C.
Factors Affecting the Performance of Thermal Barrier Coatings in the Presence of V2O5 and Na2SO4
K.P. Jonnalagadda, R. Eriksson, R.L. Peng, X.-H. Li, S. Johansson
Pages 409-416 · DOI: 10.4416/JCST2016-00058
This study investigates the influence of temperature, salt concentration and thickness on the corrosion resistance of seven YSZ thermal barrier coatings in the presence of V2O5 and Na2SO4. For this study, a thick, high-porosity APS coating (670 µm) using hollow spherical powder (HOSP) and a thin, low-porosity APS coating (300 µm) using agglomerated and sintered (A&S) powder were fabricated. Corrosion tests were conducted at 750 °C and 900 °C with a mixture of Na2SO4 and V2O5 for four hours. At each temperature, salt concentrations of 4, 10 and 20 mg/cm2 were used. SEM and XRD investigations af …
Zirconia-Mullite Obtained from Co-Precipitated Zirconia-Mullite Composite Powders by SPS
H.Z. Li, Z.J. Li, X.D. Luo, J.Y. Gui, Z.P. Xie
Pages 417-422 · DOI: 10.4416/JCST2016-00059
The co-precipitation method is used to fabricate precursor powder. This powder is densified by means of the spark plasma sintering (SPS) technique at 1500 °C with a holding time of 7 min to prepare zirconia-mullite samples. Their density measures up to 97 % of the theoretical density, and the sintered mullite compacts exhibit better strength properties (289 ± 12 MPa) and Hv (9.99 GPa). The mode of fracture is changed with the addition of ZrO2 and extensive fine cleavages are observed on the grain surface. These cleavages join together to form steps, which can absorb more energy. The flexural s …
Silicon Nitride Ceramics with High Thermal Conductivity and Excellent Mechanical Properties Fabricated with MgF2 Sintering Aid and Post-Sintering Heat Treatment
F. Hu, F. Hu, L. Zhao, Z.P. Xie
Pages 423-428 · DOI: 10.4416/JCST2016-00065
Si3N4 ceramics were prepared with MgF2+Y2O3 as sintering aids by means of SPS, assisted by post-sintering heat treatment; these ceramics exhibited high thermal conductivity and excellent mechanical properties. The effect of the introduced MgF2 content and post-sintering heat treatment on the properties of Si3N4 ceramics was investigated in detail. It was found that the introduction of MgF2 had a positive impact on the growth of large elongated grains and the grain size of the Si3N4 ceramics. Compared to Si3N4 ceramics with Y2O3+MgO as sintering aids, the thermal conductivity, flexural strength …
Fabrication of Tin-Doped Indium Oxide Thin Films Using Aerosol Deposition
Y. Hasegawa, Y. Sato, S. Yoshikado
Pages 429-432 · DOI: 10.4416/JCST2016-00067
Tin-doped indium oxide (ITO) thin films are a key material for optical devices owing to their high electrical conductivity and high optical transparency. In this study, ITO thin films were formed on glass and sapphire substrates at room temperature using aerosol deposition (AD), and their crystal structure, resistivity, and optical properties were investigated. The films maintained the crystal structure of the source ITO particles used to form the films. For the glass substrate, the resistivity of the ITO films was approximately 3.0 × 10-3 Ω·cm. In addition, when the thickness was 0.24 μm, the …
Phase relations in the Si-Al-Pr-O-C system, including the SiC-Al2O3-Pr2O3, the Al2O3-Pr2O3-SiO2 and the SiC-Al2O3-Pr2O3-SiO2 subsystems, were determined by means of XRD phase analysis of solid-state-reacted samples fabricated by using SiC, Al2O3, Pr2O3 and SiO2 powders as the starting materials. Subsolidus phase diagrams of the systems were presented. Two Pr-aluminates, namely PrAlO3 (PrAP) and PrAl11O18 (β(Pr) β-Al2O3 type) were formed in the SiC-Al2O3-Pr2O3 system. SiC was compatible with both of them. Pr-silicates of Pr2SiO5, Pr2Si2O7 and Pr9.33Si6O26 (H(Pr) apatite type) were formed owing …
The Effect of Nano CuO as Sintering Aid on Phase Formation, Microstructure and Properties of Li2O-Stabilized β″-Alumina Ceramics
H. Ahmadi Moghadam, M. Hossein Paydar
Pages 441-446 · DOI: 10.4416/JCST2016-00075
Li2O-stabilized β″-alumina powder was synthesized in the double zeta process with Al2O3, Na2CO3 and Li2CO3 as the starting materials. The effect of nano CuO additive as the sintering aid on phase formation, microstructure, mechanical and electrical properties of Li2O-stabilized β″-alumina ceramics was investigated by means of x-ray diffraction (XRD), scanning electron microscope (SEM), biaxial flexure test (BFT) and ionic conductivity test. The results indicated that the fracture strength of the samples improved with the addition of a low concentration of nano CuO, which can be attributed to t …
Influence of MgAl2O4 Spinel Addition on Properties of Alumina-Chrome Refractory Prepared with Alumina-Chrome Slag
J. Wu, J. Liu, R. Li, Q. Zhen
Pages 447-454 · DOI: 10.4416/JCST2016-00076
Alumina-chrome refractory was developed using alumina-chrome slag of different grades (5 ∼ 3 mm, 3 ∼ 1 mm, 0.088 mm and 0.045 mm), with added micron-grade MgAl2O4 spinel powders. Batch materials were milled, pressed and sintered at 1500 °C with 22 h soaking. The refractory with 5 wt% MgAl2O4 exhibited the best properties in terms of bulk density and apparent porosity. In all the refractory samples, new phases were formed as a result of slag-refractory and copper-refractory interaction. With the addition of MgAl2O4 spinel, the corrosion resistance of the alumina-chrome refractory was improved …
Spray Freeze Granulation of Submicrometre α-Alumina Using Ultrasonication
S. Ghanizadeh, P. Ramanujam, B. Vaidhyanathan, J. Binner, J. Binner
Pages 455-462 · DOI: 10.4416/JCST2016-00078
Granulation is a key factor towards improvement of the flowability of fine ceramic powders to make them suitable for industrial dry pressing. Controlled granulation of fine alumina particles with a primary particle size of ∼ 150 nm was carried out using spray-freeze drying, which led to the production of flowable granules with high crushability. The fracture surface of uniaxially die-pressed green bodies made from granules with density values of ≥ 50 % of theoretical showed a uniform microstructure. Sintering experiments were performed using conventional single- and two-stage radiant heating m …
Annealing Temperature Effects on Structural and Hydrophilic Properties of Magnesium-Doped TiO2 Thin Films
M. Kumar, A. K. Gupta, D. Kumar
Pages 463-468 · DOI: 10.4416/JCST2016-00041
Magnesium-doped TiO2 thin films were deposited with the sol-gel spin coating technique. The effects of annealing on the structural and hydrophilic properties were studied. The films deposited on a Corning glass substrate were characterized by means of X-ray diffraction (XRD), UV-visible spectroscopy and Fourier transform infrared spectroscopy. The water contact angle was measured in order to investigate the hydrophilic property of the doped TiO2 films. It was observed that the crystallite structure of the doped TiO2 films improved significantly with increasing temperature. The formation of ana …
Crystallization Behavior, Microstructure and Magnetic Properties of B2O3-SiO2-Fe2O3-BaO-SrO Glass-Ceramics
M. Tavoosi, A. Ghasemi, D. Yousefi
Pages 469-476 · DOI: 10.4416/JCST2016-00063
The preparation and magnetic characterization of B2O3-SiO2-Fe2O3-BaO-SrO glass-ceramics were the goal of this study. In this regard, different mixtures of B2O3, SiO2, Fe2O3, BaO and SrO were melted in the temperature range 1200 – 1350 °C and were quenched between two sheets of cold steel. The as-quenched samples were annealed at 660 and 700 °C for 2 h. The prepared samples were then characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC) and a vibrating scanning magnetometer (VSM). According to the results obtain …
Synthesis of mesoporous Sr2MgSi2O7:Eu2+, Dy3+ energy storage carriers using cetyl trimethyl ammonium bromide as a template
X. Wei, J. Fan, X. Zhou, Y. Shen, X. Hu, G. Zuo
Pages 477-482 · DOI: 10.4416/JCST2016-00046
In this study mesoporous Sr2MgSi2O7:Eu2+, Dy3+ energy storage carriers were successfully prepared using cetyl trimethylammonium bromide (CTAB) as a template. Mesoporous Sr2MgSi2O7:Eu2+, Dy3+ can be obtained at a relatively low temperature of 950 °C with the addition of CTAB. The sample shows good porosity and energy storage performance. The pore diameter of the sample is distributed uniformly from 2 to 11 nm. The optical storage capability of the samples was investigated by studying the photoluminescence decay curves, which revealed that the afterglow time of the product could be improved by o …
