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Journal of Ceramic Science and Technology 3/2016
Vol. 7, No. 3 · September 2016
Thermochemical Calculations of the Stability of Ti2AlC in Various Atmospheres
M. Stumpf, T. Fey, P. Greil
Pages 223-228 · DOI: 10.4416/JCST2016-00029
The thermochemical stability of the MAX phase Ti2AlC under vacuum, inert Ar, pure O2 and N2 and a reactive air atmosphere was explored based on thermochemical equilibrium calculations. A dataset on the enthalpy of formation, standard molar entropy and the temperature variation of the heat capacities of Ti2AlC and TiC0.5 was derived from thermochemical properties given in the literature and implemented in the software package HSC Chemistry. In inert atmosphere Ti2AlC decomposes peritectically into solid TiC0.5 and a liquid Al-rich phase at approximately 1673 °C whereas in vacuum (1 mPa) dissoci …
Production of β-Silicon Carbide Nanofibers using the Forcespinning® Method
A. Salinas, A. Altecor, M. Lizcano, K. Lozano
Pages 229-234 · DOI: 10.4416/JCST2016-00026
Silicon carbide (SiC) nanofibers were produced on a large scale using the Forcespinning® method. Non-oxide ceramics such as SiC are known for their low density, oxidation resistance, thermal stability, and wear resistance. The nanofibers were prepared using a solution-based method with polystyrene and polycarbomethylsilane as the precursor materials. Fiber spinning was performed under different parameters to obtain high yield, fiber homogeneity, and small diameters. The fibers were spun under a controlled nitrogen environment to prevent fiber oxidation. The resultant nonwoven nanofiber mats we …
Synthesis and Characterization of Nanoparticulate Crystallite Cobalt Ferrite for Permanent Magnet Applications
M.A. Ahmed, N.G. Imam, M.M. Hefny, and H.R. Gomaa
Pages 235-242 · DOI: 10.4416/JCST2015-00073
Nanoparticulate cobalt ferrite CoFe2O4 (COF) was successfully obtained at relatively low temperature by means of a facile chemical wet method, namely citrate auto-combustion. X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), Fourier Transform Infrared (FTIR), and Vibrating Sample Magnetometry (VSM) were carried out to study the structural and magnetic properties, respectively. The XRD results confirm the formation of single spinel phase of COF with an average lattice parameter (a) of 8.38 nm. XRD analysis revealed that the crystal size is about 43 nm, which is close to …
Microwave Dielectric Properties of (1-x)CaTiO3-x(Na0.5Nd0.5)TiO3 Ceramics
A.E. Reda, D.M. Ibrahim, D.A. Abdel Aziz
Pages 243-248 · DOI: 10.4416/JCST2015-00083
The crystal structures, phase compositions and the microwave dielectric properties of (1-x)Ca2+TiO3 - x(Na1+0.5 Nd3+0.5)TiO3 ceramics prepared by the conventional solid state route have been investigated. The formation of solid solution is confirmed in XRD patterns. A specimen using 0.92Ca2+TiO3-0.08(Na1+0.5Nd3+0.5)TiO3 (x = 0.08) sintered at 1250 °C/2 h possesses an excellent combination of microwave dielectric properties, (εr) = 31.8, a maximum (Qxf) value of 2·104 at 5 GHz. This may be related to the increase in density as well as the grain morphology, which led to a reduction in the dielec …
Sintering of Magnesia and Iron Oxide in Air and Flowing Nitrogen and its Corrosion Process by Molten Electrolyte
Y.B. Xu, Y.W. Li, J.H. Yang, S.B. Sang, Q.W. Qin
Pages 249-256 · DOI: 10.4416/JCST2015-00085
In the present paper, novel sidewall materials for aluminum reduction cells were prepared in air and nitrogen using magnesia and magnetite powders. The sintering behavior of the specimens and their corrosion resistance to electrolyte have been investigated. The results show that Fe3O4 phase is transformed into Fe2O3 at high temperatures in air, which in turn reacts with the MgO added to form MgFe2O4. For the specimens prepared in nitrogen, most of the Fe3O4 is reduced to FeO in specimens without MgO while all the specimens with added MgO are composed of FexMg1-xO only. The densification of the …
Crystal Structure, Raman Spectra and Dielectric Properties of Ca0.66Ti0.66La0.34Al0.34O3 Microwave Ceramics with Nd3+Additions
Y. Xu, R. Fu, Y. Yang, J. Cai, X. Gu, J. Fang
Pages 257-262 · DOI: 10.4416/JCST2016-00001
Ca0.66Ti0.66La0.34Al0.34O3 (CTLA) ceramics doped with Nd2O3 were prepared by means of the conventional solid-state reaction method. The Nd2O3 dopant was added in the range of 0.5 – 3.5 wt%. The dielectric properties, crystal structure and Raman spectra of the CTLA ceramics doped with Nd2O3 were investigated with the Hakki and Coleman's dielectric resonant, XRD and Raman spectroscopy method, respectively. It was found that Nd2O3 promotes the densification and enlarges the crystal cell volume of CTLA ceramics. Two chemical reaction defects emerge in CTLA ceramics with the substitution of Nd3+. N …
Biocompatibility of Hydroxyapatite-Alumina and Hydroxyapatite-Zirconia Composites including Commercial Inert Glass (CIG) as a Ternary Component
B. Bulut, Z.E. Erkmen, E.S. Kayali
Pages 263-276 · DOI: 10.4416/JCST2016-00011
Hydroxyapatite (HA), chemical formula Ca10(PO4)6(OH)2, is a very popular bioceramic for orthopedic and dental applications. Although HA has excellent biocompatibility, its inferior mechanical properties make it unsuitable for load-bearing implant applications. Therefore, HA should be strengthened by a secondary phase to produce a composite that possesses robust mechanical properties. The aim of this study was to compare the microstructural and mechanical properties and biocompatibility of HA-Al2O3 and HA-ZrO2 composites with the addition of 5 and 10 wt% commercial inert glass (CIG) independent …
Sintering Behaviour of Fine Barium Titanate (BaTiO3) Powders Consolidated with the Pressure Filtration Method
Ł. Zych, A. Wajler, A. Kwapiszewska
Pages 277-288 · DOI: 10.4416/JCST2016-00016
Main aim of the study was the determination of the sintering behaviour of fine barium titanate powders consolidated with the pressure filtration method. Three commercial powders with primary particle size of 50, 100 and 200 nm were used. Relationships between particle size, characteristics of the consolidated bodies and their sintering behaviour were investigated. The far-reaching goal of the study was the production of transparent or translucent barium titanate, a material that is part of a group of transparent ferroelectric ceramics applied in electro-optical devices. Aqueous and propanol su …
Facile Synthesis and Characterization of MnxZn1-xFe2O4/Activated Carbon Composites for Biomedical Applications
J.C. Ríos-Hurtado, A.C. Martínez-Valdés, J.R. Rangel-Méndez, J.C. Ballesteros-Pacheco, E.M. Múzquiz-Ramos
Pages 289-294 · DOI: 10.4416/JCST2016-00020
The synthesis of MnxZn1-xFe2O4 ferrites (x = 0.4, 0.5 and 0.6) by means of the co-precipitation method is reported. Furthermore, a composite of Mn0.4Zn0.6Fe2O4/activated carbon was prepared with the mechanosynthesis method. The magnetic, structural, morphological and chemical properties were analyzed by means of VSM, XRD, SEM, FTIR and Boehm's titration. The heating capacity was evaluated under a magnetic field using solid-state induction heating equipment, in addition a hemolysis test was performed using human red blood cells. With regard to the synthesis of manganese-zinc ferrite, the result …
The Influence of Stabilizer Concentration on the Mechanical Properties of Alumina – 17 vol% Zirconia (0.6Y-2Y) Composites
F. Kern, S. Koummarasy, R. Gadow
Pages 295-300 · DOI: 10.4416/JCST2016-00034
Zirconia-toughened alumina (ZTA) with a zirconia content close to the percolation threshold has become the state-of-the art ceramic material for hip implants. In this study the stabilizer content in a ZTA with 17 vol% zirconia was varied between 0.6 – 2 mol% Y2O3 to understand more about the influence of the stabilizer concentration on mechanical properties, phase composition and formation of residual stress. It was found that fracture resistance reaches its maximum close to the stress neutral state where transformation stresses equilibrate residual cooling stresses while compressive stress in …
On the Synthesis of Low-Cost, Titanium-Based MXenes
C. Li, S. Kota, C. Hu, M.W. Barsoum
Pages 301-306 · DOI: 10.4416/JCST2016-00042
Herein we report methods to synthesize two MAX phases, Ti2AlC and Ti3AlC2, starting with rutile (TiO2), graphite and aluminum powders as raw materials. Adjusting the initial ratios of the raw materials led to the synthesis of multi-phase mixtures containing predominantly Ti2AlC-Al2O3 or Ti3AlC2-Al2O3. Free-standing Ti2CTx and Ti3C2Tx MXene films were successfully produced by etching the powders in a solution of hydrochloric acid with pre-dissolved lithium fluoride followed by sonication in water to produce colloidal suspensions of atomically thin MXene flakes. The Ti3C2Tx films produced from t …
Impact of Feedstock Nature on Thermal Conductivity of YSZ Thermal Barrier Coatings Obtained by Plasma Spraying
P. Carpio, P. Carpio, M.D. Salvador, R.Benavente, M. Miranda, A. Borrell, E. Sánchez
Pages 307-312 · DOI: 10.4416/JCST2016-00022
Yttria-stabilized zirconia (YSZ) coatings with low thermal conductivity were obtained using three different particle size distributions as starting powder: nano-, submicron- and bimodal submicron/nano-sized particles. On the one hand, these particles were reconstituted into micrometric, spray-dry agglomerates, which were subsequently deposited by means of conventional atmospheric plasma spraying (APS). On the other hand, the starting particles were dispersed in water and the resultant suspensions were deposited by means of suspension plasma spraying (SPS). The coatings were thermally treated t …
