Journal of Ceramics The latest articles from Hindawi Publishing Corporation © 2016 , Hindawi Publishing Corporation . All rights reserved. Anisotropic Thermal Expansion of Zirconium Diboride: An Energy-Dispersive X-Ray Diffraction Study Wed, 31 Aug 2016 11:56:52 +0000 Zirconium diboride (ZrB2) is an attractive material due to its thermal and electrical properties. In recent years, ZrB2 has been investigated as a superior replacement for sapphire when used as a substrate for gallium nitride devices. Like sapphire, ZrB2 has an anisotropic hexagonal structure which defines its directionally dependent properties. However, the anisotropic behavior of ZrB2 is not well understood. In this paper, we use energy-dispersive synchrotron X-ray diffraction to measure the thermal expansion of polycrystalline ZrB2 powder from 300 to 1150 K. Nine Bragg reflections are fit using Pseudo-Voigt peak profiles and used to compute the and lattice parameters using a nonlinear least-squares approximation. The temperature-dependent instantaneous thermal expansion coefficients are determined for each -axis and -axis direction and are described by the following equations: = ( + × )/( × + ) and = ( + )/( + ). Our results are within range of previously reported values but describe the temperature anisotropy in more detail. We show that anisotropic expansion coefficients converge to the same value at about 780 K and diverge at higher temperatures. Results are compared with other reported values. William A. Paxton, Tevfik E. Özdemir, İlyas Şavklıyıldız, Terence Whalen, Hülya Biçer, Enver Koray Akdoğan, Zhong Zhong, and Thomas Tsakalakos Copyright © 2016 William A. Paxton et al. All rights reserved. Mechanical Properties of ZTA: Correlation with Structural Properties and Influence of Ageing Wed, 08 Jun 2016 09:39:45 +0000 We report the mechanical and thermal properties of industrial Zirconia Toughened Alumina (ZTA) composites for different compositions of zirconia and yttria, paying a special attention to possible ageing. As a result a correlation between the structural properties and the in-fine performances is obtained; in particular, depending on mechanical properties expected by the customer, optimum composites compositions are indicated. C. Exare, J.-M. Kiat, N. Guiblin, and V. Petricek Copyright © 2016 C. Exare et al. All rights reserved. Microelectrical Discharge Machining: A Suitable Process for Machining Ceramics Mon, 31 Aug 2015 12:52:51 +0000 Today ceramics are used in many industrial applications, for example, in the biomedical field, for high-temperature components or for cutting tools. This is attributed to their excellent mechanical and physical properties, as low density, high strength, and hardness or chemical resistance. However, these specific mechanical properties lead to problems regarding the postprocessing of ceramics. In particular, cutting processes require expensive tools which cause high manufacturing costs to machine ceramics. Consequently, there is a demand for alternative machining processes. Microelectrical discharge machining (micro-EDM) is a thermal abrasion process which is based on electrical discharges between a tool and a workpiece. The advantages of micro-EDM are more and more in focus for ceramic machining. These advantages include the process of being a noncontact technology, an independency of material brittleness and hardness, a low impact on the material, and the achievable microstructures. This paper presents the current state of investigations regarding micro-EDM of ceramics. Beside the process principle of EDM, the used procedures for machining ceramics and insulating ceramics are described. Furthermore several machining examples are presented to demonstrate the possibilities of the micro-EDM process with regard to the machining of ceramics. Andreas Schubert, Henning Zeidler, Ralf Kühn, and Matthias Hackert-Oschätzchen Copyright © 2015 Andreas Schubert et al. All rights reserved. Cubic Phases in the Gd2O3-ZrO2 and Dy2O3-TiO2 Systems for Nuclear Industry Applications Tue, 11 Aug 2015 06:42:16 +0000 Neutron absorbers are elements with a high neutron capture cross section that are employed at nuclear reactors to control excess fuel reactivity. If these absorbers are converted into materials of relatively low absorption cross section as the result of neutron absorption, they consume during the reactor core life and so are called burnable. These elements can be distributed inside an oxide ceramic that is stable under irradiation and thus called inert. Cubic zirconium oxide is one of the preferred materials to be used as inert matrix. It is stable under irradiation, experiments very low swelling, and is isomorphic to uranium oxide. The cubic phase is stabilized by adding small amounts of dopants like Dy2O3 and Gd2O3. As both dysprosium and gadolinium have a high neutron cross section, they are good candidates to prepare burnable neutron absorbers. Pyrochlores, like Gd2Zr2O7 and Dy2Ti2O7, allow the solid solution of a large quantity of elements besides being stable under irradiation. These characteristics make them also useful for safe storage of nuclear wastes. We present a preliminary study of the thermal analysis of different compositions in the systems Gd2O3-ZrO2 and Dy2O3-TiO2, investigating the feasibility to obtain oxide ceramics useful for the nuclear industry. Maria Teresa Malachevsky, Diego Rodríguez Salvador, Sergio Leiva, and Claudio Alberto D'Ovidio Copyright © 2015 Maria Teresa Malachevsky et al. All rights reserved. The Effect of Thickness of Aluminium Films on Optical Reflectance Mon, 09 Feb 2015 13:24:24 +0000 In Uganda and Africa at large, up to 90% of the total energy used for food preparation and water pasteurization is from fossil fuels particularly firewood and kerosene which pollute the environment, yet there is abundant solar energy throughout the year, which could also be used. Uganda is abundantly rich in clay minerals such as ball clay, kaolin, feldspar, and quartz from which ceramic substrates were developed. Aluminium films of different thicknesses were deposited on different substrates in the diffusion pump microprocessor vacuum coater (Edwards AUTO 306). The optical reflectance of the aluminium films was obtained using a spectrophotometer (SolidSpec-3700/DUV-UV-VIS-NIR) at various wave lengths. The analysis of the results of the study revealed that the optical reflectance of the aluminium films was above 50% and increased with increasing film thickness and wavelength. Thus, this method can be used to produce reflector systems in the technology of solar cooking and other appliances which use solar energy. Robert Lugolole and Sam Kinyera Obwoya Copyright © 2015 Robert Lugolole and Sam Kinyera Obwoya. All rights reserved. Preparation, Structural, Electrical, and Ferroelectric Properties of Lead Niobate–Lead Zirconate–Lead Titanate Ternary System Wed, 04 Feb 2015 13:11:11 +0000 A ternary system of lead niobate–lead zirconate–lead titanate with composition xPN–yPZ–(x-y)PT where and , 0.25, and 0.35 known as PNZT has been prepared by conventional mixed oxide route at a temperature of 1100°C. The formation of the perovskite phase was established by X-ray diffraction analysis. The surface morphology studied by scanning electron microscopy shows the formation of fairly dense grains and elemental composition was confirmed by energy dispersive X-ray analysis. Dielectric properties like dielectric constant and dielectric loss ( and ) indicate poly-dispersive nature of the material. The temperature dependent dielectric constant () curve indicates relaxor behaviour with two dielectric anomalies. The poly-dispersive nature of the material was analysed by Cole-Cole plots. The activation energy follows the Arrhenius law and is found to decrease with increasing frequency for each composition. The frequency dependence of ac conductivity follows the universal power law. The ac conductivity analysis suggests that hopping of charge carriers among the localized sites is responsible for electrical conduction. The ferroelectric studies reveal that these ternary systems are soft ferroelectric. Rashmi Gupta, Seema Verma, Vishal Singh, and K. K. Bamzai Copyright © 2015 Rashmi Gupta et al. All rights reserved. Structural and Ferroic Properties of La, Nd, and Dy Doped BiFeO3 Ceramics Wed, 04 Feb 2015 06:11:57 +0000 Polycrystalline samples of Bi0.8RE0.2FeO3 (RE = La, Nd, and Dy) have been synthesized by solid-state reaction route. X-ray diffraction (XRD) patterns of Bi0.8La0.2FeO3 and Bi0.8Nd0.2FeO3 were indexed in rhombohedral (R3c) and triclinic (P1) structure, respectively. Rietveld refined XRD pattern of Bi0.8Dy0.2FeO3 confirms the biphasic (Pnma + R3c space groups) nature. Raman spectroscopy reveals the change in BiFeO3 mode positions and supplements structural change with RE ion substitution. Ferroelectric and ferromagnetic loops have been observed in the Bi0.8RE0.2FeO3 ceramics at room temperature, indicating that ferroelectric and ferromagnetic ordering coexist in the ceramics at room temperature. The magnetic measurements at room temperature indicate that rare-earth substitution induces ferromagnetism and discerns large and nonzero remnant magnetization as compared to pristine BiFeO3. Ashwini Kumar, Poorva Sharma, and Dinesh Varshney Copyright © 2015 Ashwini Kumar et al. All rights reserved. Synthesis of β-SiC Fine Fibers by the Forcespinning Method with Microwave Irradiation Thu, 29 Jan 2015 12:46:27 +0000 A rapid method for synthesizing β-silicon carbide (β-SiC) fine fiber composite has been achieved by combining forcespinning technology with microwave energy processing. β-SiC has applications as composite reinforcements, refractory filtration systems, and other high temperature applications given their properties such as low density, oxidation resistance, thermal stability, and wear resistance. Nonwoven fine fiber mats were prepared through a solution based method using polystyrene (PS) and polycarbomethylsilane (PCmS) as the precursor materials. The fiber spinning was performed under different parameters to obtain high yield, fiber homogeneity, and small diameters. The spinning was carried out under controlled nitrogen environment to control and reduce oxygen content. Characterization was conducted using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The results show high yield, long continuous bead-free nonwoven fine fibers with diameters ranging from 270 nm to 2 µm depending on the selected processing parameters. The fine fiber mats show formation of highly crystalline β-SiC fine fiber after microwave irradiation. Alfonso Salinas, Maricela Lizcano, and Karen Lozano Copyright © 2015 Alfonso Salinas et al. All rights reserved. Coefficient of Thermal Diffusivity of Insulation Brick Developed from Sawdust and Clays Mon, 29 Dec 2014 06:23:11 +0000 This paper presents an experimental result on the effect of particle size of a mixture of ball clay, kaolin, and sawdust on thermal diffusivity of ceramic bricks. A mixture of dry powders of ball clay, kaolin of the same particle size, and sawdust of different particle sizes was mixed in different proportions and then compacted to high pressures before being fired to 950°C. The thermal diffusivity was then determined by an indirect method involving measurement of thermal conductivity, density, and specific heat capacity. The study reveals that coefficient of thermal diffusivity increases with decrease in particle size of kaolin and ball clay but decreases with increase in particle size of sawdust. E. Bwayo and S. K. Obwoya Copyright © 2014 E. Bwayo and S. K. Obwoya. All rights reserved. Modeling of Thermal and Mechanical Behavior of ZrB2-SiC Ceramics after High Temperature Oxidation Tue, 11 Nov 2014 07:37:02 +0000 The effects of oxidation on heat transfer and mechanical behavior of ZrB2-SiC ceramics at high temperature are modeled using a micromechanics based finite element model. The model recognizes that when exposed to high temperature in air ZrB2-SiC oxidizes into ZrO2, SiO2, and SiC-depleted ZrB2 layer. A steady-state heat transfer analysis was conducted at first and that is followed by a thermal stress analysis. A “global-local modeling” technique is used combining finite element with infinite element for thermal stress analysis. A theoretical formulation is developed for calculating the thermal conductivity of liquid phase SiO2. All other temperature dependent thermal and mechanical properties were obtained from published literature. Thermal stress concentrations occur near the pore due to the geometric discontinuity and material properties mismatch between the ceramic matrix and the new products. The predicted results indicate the development of thermal stresses in the SiO2 and ZrO2 layers and high residual stresses in the SiC-depleted ZrB2 layer. Jun Wei, Lokeswarappa R. Dharani, K. Chandrashekhara, Gregory E. Hilmas, and William G. Fahrenholtz Copyright © 2014 Jun Wei et al. All rights reserved. Preparation of Stable ZrB2-SiC-B4C Aqueous Suspension for Composite Based Coating: Effect of Solid Content and Dispersant on Stability Sun, 07 Sep 2014 12:18:44 +0000 ZrB2-SiC-B4C aqueous suspension has been prepared using poly(ethyleneimine) as a dispersant. Since increasing the solid content of suspension leads to high compaction and consequently low porosities through final coat, the effect of solid content has been studied. The dispersant and solid content were changed in the range of 0.3–1.5 wt.% and 45–55 vol.%, respectively, to assess the optimal conditions effect on stability and characteristics of suspension. Results of zeta potential measurements and rheological analysis at pH 7.8 showed that the composite suspension including 45 vol.% solid content and 1.5 wt.% dispersant was in stable state. Mehri Mashadi, Mohsen Mohammadijoo, Alireza Honarkar, and Zeinab Naderi Khorshidi Copyright © 2014 Mehri Mashadi et al. All rights reserved. Increasing Bending Strength of Porcelain Stoneware via Pseudoboehmite Additions Mon, 28 Apr 2014 11:19:59 +0000 Pseudoboehmite nanoparticles synthesized through the desulfation of Al2(SO4)3 were used to investigate the reinforcement of commercial porcelain stoneware. Fractured specimens investigated by SEM suggest that the added pseudoboehmite precursor generated a nanometric primary mullite phase dispersed in the porcelain glassy phase that limited and stopped the intergranular crack propagation. The porcelain modulus of rupture increased twice the value of the modulus of rupture (108 MPa) as compared with that samples without pseudoboehmite additions. Pseudoboehmite also led to increased densification of porcelain stoneware bodies up to 1250°C as shown by thermodilatometry data. Omar Aguilar-García, Rafael Lara-Hernández, Azucena Arellano-Lara, José L. Gil-Vázquez, and Jaime Aguilar-García Copyright © 2014 Omar Aguilar-García et al. All rights reserved. Durability Modeling of Environmental Barrier Coating (EBC) Using Finite Element Based Progressive Failure Analysis Wed, 09 Apr 2014 08:32:31 +0000 The necessity for a protecting guard for the popular ceramic matrix composites (CMCs) is getting a lot of attention from engine manufacturers and aerospace companies. The CMC has a weight advantage over standard metallic materials and more performance benefits. However, these materials undergo degradation that typically includes coating interface oxidation as opposed to moisture induced matrix which is generally seen at a higher temperature. Additionally, other factors such as residual stresses, coating process related flaws, and casting conditions may influence the degradation of their mechanical properties. These durability considerations are being addressed by introducing highly specialized form of environmental barrier coating (EBC) that is being developed and explored in particular for high temperature applications greater than 1100°C. As a result, a novel computational simulation approach is presented to predict life for EBC/CMC specimen using the finite element method augmented with progressive failure analysis (PFA) that included durability, damage tracking, and material degradation model. The life assessment is carried out using both micromechanics and macromechanics properties. The macromechanics properties yielded a more conservative life for the CMC specimen as compared to that obtained from the micromechanics with fiber and matrix properties as input. Ali Abdul-Aziz, Frank Abdi, Ramakrishna T. Bhatt, and Joseph E. Grady Copyright © 2014 Ali Abdul-Aziz et al. All rights reserved. Structural Evolution of Silicon Carbide Nanopowders during the Sintering Process Thu, 20 Mar 2014 17:41:26 +0000 Processes of sintering of silicon carbide nanopowder were investigated. Values of density ( g/cm3) and strength ( MPa) were obtained. Within the theory of dispersed systems, the temperature evolution of the materials structure was considered. The relationship between sintering temperature, characteristics of crystal structure and physical properties, in particular, density, and strength of aforementioned ceramics was established. It was concluded that it is necessary to suppress the anomalous diffusion at temperatures above 2080°C. Galina Volkova, Oleksandr Doroshkevych, Artem Shylo, Tetyana Zelenyak, Valeriy Burkhovetskiy, Igor Danilenko, and Tetyana Konstantinova Copyright © 2014 Galina Volkova et al. All rights reserved. Provenance Study of Archaeological Ceramics from Syria Using XRF Multivariate Statistical Analysis and Thermoluminescence Dating Tue, 11 Mar 2014 14:50:21 +0000 Thermoluminescence (TL) dating and multivariate statistical methods based on radioisotope X-ray fluorescence analysis have been utilized to date and classify Syrian archaeological ceramics fragment from Tel Jamous site. 54 samples were analyzed by radioisotope X-ray fluorescence; 51 of them come from Tel Jamous archaeological site in Sahel Akkar region, Syria, which fairly represent ceramics belonging to the Middle Bronze Age (2150 to 1600 B.C.) and the remaining three samples come from Mar-Takla archaeological site fairly representative of the Byzantine ceramics. We have selected four fragments from Tel Jamous site to determinate their age using thermoluminescence (TL) method; the results revealed that the date assigned by archaeologists was good. An annular 109Cd radioactive source was used to irradiate the samples in order to determine their chemical composition and the results were treated statistically using two methods, cluster and factor analysis. This treatment revealed two main groups; the first one contains only the three samples M52, M53, and M54 from Mar-Takla site, and the second one contains samples that belong to Tel Jamous site (local). Elias Hanna Bakraji, Rana Abboud, and Haissm Issa Copyright © 2014 Elias Hanna Bakraji et al. All rights reserved. Mechanical Behavior of Yttria-Stabilized Zirconia Aqueous Cast Tapes and Laminates Sun, 09 Mar 2014 09:31:56 +0000 Aqueous tape casting was used to produce yttria-stabilized zirconia films for electrolyte-supported solid oxide fuel cell (SOFC). Tape casting slurries were prepared varying the binder content between 20 and 25 wt%. A commercial acrylic emulsion served as binder. Rheological measurements of the two slurries were performed. Both slurries showed a shear-thinning behavior. Tapes with 25 wt% binder exhibited adequate flexibility and a smooth and homogeneous surface, free of cracks and other defects. Suitable conditions of lamination were found and a theoretical density of 54% in the laminates was achieved. Laminated tapes showed higher tensile strength compared to single sheets. Tape orientation has a significant influence on the mechanical properties. Tensile strength, elongation to strain, and Young’s modulus measured in samples produced in the direction of casting showed higher property values. V. Moreno, R. M. Bernardino, and D. Hotza Copyright © 2014 V. Moreno et al. All rights reserved. Alumina-Based Ceramics for Armor Application: Mechanical Characterization and Ballistic Testing Thu, 09 Jan 2014 13:10:52 +0000 The aim of this work is to present results of mechanical characterization and ballistic test of alumina-based armor plates. Three compositions (92, 96, and 99 wt% Al2O3) were tested for 10 mm thick plates processed in an industrial plant. Samples were pressed at 110 MPa and sintered at 1600°C for 6 h. Relative density, Vickers hardness, and four-point flexural strength measurements of samples after sintering were performed. Results showed that the strength values ranged from 210 to 300 MPa depending on the porosity, with lower standard deviation for the 92 wt% Al2O3 sample. Plates (120 mm × 120 mm × 12 mm) of this composition were selected for ballistic testing according to AISI 1045, using a metallic plate as backing and witness plates in the case of penetration or deformation. Standard NIJ-0108.01 was followed in regard to the type of projectile to be used (7.62 × 51 AP, Level IV, 4068 J). Five alumina plates were used in the ballistic tests (one shot per plate). None of the five shots penetrated or even deformed the metal sheet, showing that the composition containing 92 wt% Al2O3 could be considered to be a potential ballistic ceramic, being able to withstand impacts with more than 4000 J of kinetic energy. M. V. Silva, D. Stainer, H. A. Al-Qureshi, O. R. K. Montedo, and D. Hotza Copyright © 2014 M. V. Silva et al. All rights reserved. Influence of the Dopants on the Mechanical Properties of Alumina-Based Ceramics Wed, 25 Dec 2013 07:54:54 +0000 In the present study the mechanical properties of dense alumina-based ceramics obtained by two processing routes are investigated. The application of magnetic-pulsed compaction or hot pressing of the powder leads to a comparable combination of microhardness, elastic modulus, and fracture toughness. The insertion of Al into Al2O3 powder increases the microdistortions of the crystalline lattice, resulting in the sufficient decrease of indentation wear-resistance. The usage of ZrO2 or TiCN as dopants to alumina matrix improves slightly the mechanics of the composites with a noticeable decrease of the material lost by 30% compared to pure alumina at closely spaced arrays of indents. Regardless of the synthesis method, the ceramic grains were formed completely with the fracture travelling along the grain boundaries. Anton Sergeevich Kaygorodov, Vasily Ivanovich Krutikov, and Sergey Nikolaevich Paranin Copyright © 2013 Anton Sergeevich Kaygorodov et al. All rights reserved. Processing and Characterization of Yttria-Stabilized Zirconia Foams for High-Temperature Applications Thu, 19 Dec 2013 08:28:25 +0000 In this work ceramic foams of 3 and 8 mol% yttria-stabilized zirconia (3YSZ and 8YSZ) were manufactured by the replication method using polystyrene-polyurethane foams with pore sizes in the 7–10 ppi range. A second coating was carried out on presintered foams in order to thicken struts and hinder microstructural defects. The produced ceramic foams were structurally and thermomechanically characterized. Samples recoated with 3YSZ presented the highest relative densities () which contributed to a better mechanical and thermal behavior. Ana María Herrera, Amir Antônio Martins de Oliveira Jr., Antonio Pedro Novaes de Oliveira, and Dachamir Hotza Copyright © 2013 Ana María Herrera et al. All rights reserved. Effect of Anodic Current Density on Characteristics and Low Temperature IR Emissivity of Ceramic Coating on Aluminium 6061 Alloy Prepared by Microarc Oxidation Mon, 16 Dec 2013 14:27:21 +0000 High emitter MAO ceramic coatings were fabricated on the Al 6061 alloy, using different bipolar anodic current densities, in an alkali silicate electrolyte. We found that, as the current density increased from 10.94 A/dm2 to 43.75 A/dm2, the layer thickness was increased from 10.9 μm to 18.5 μm, the surface roughness was increased from 0.79 μm to 1.27 μm, the area ratio of volcano-like microstructure was increased from 55.6% to 59.6%, the volcano-like density was decreased from 2620 mm−2 to 1420 mm−2, and the γ-alumina phase was decreased from 66.6 wt.% to 26.2 wt.%, while the α-alumina phase was increased from 3.9 wt.% to 27.6 wt.%. The sillimanite and cristobalite phases were around 20 wt.% and 9 wt.%, respectively, for 10.94 A/dm2 and approximately constant around 40 wt.% and less than 5 wt.%, respectively, for the anodic current densities 14.58, 21.88, and 43.75 A/dm2. The ceramic surface roughness and thickness slightly enhanced the IR emissivity in the semitransparent region (4.0–7.8 μm), while the existing phases contributed together to raise the emissivity in the opaque region (8.6–16.0 μm) to higher but approximately the same emissivities. Mohannad M. S. Al Bosta, Keng-Jeng Ma, and Hsi-Hsin Chien Copyright © 2013 Mohannad M. S. Al Bosta et al. All rights reserved. Thermal Variation of Elastic Modulus on Nanocrystalline NiCuZn Ferrites Tue, 08 Oct 2013 13:23:08 +0000 The nanopowders of Ni0.38Cu0.12Zn0.5Fe2O4 with particle size, 20 nm have been synthesised using Microwave-Hydrothermal method and characterized. Then the ferrite samples were microwave sintered at different temperatures in an air atmosphere and characterized. The magnetic properties were measured at room temperature. The dielectric constant (), initial permeability () and quality factor () has been measured on sintered samples at 1 MHz. Thermal variation of initial permeability has been measured over temperature range of 300 K–600 K. A detailed study of elastic behaviour of NiCuZn ferrites has been under taken using a composite piezoelectric oscillator method over a temperature of 300 K–600 K. The room temperature elastic moduli is found to be slightly sample dependent and decreases with increasing the temperature, except near the Curie temperature, , where a small anomaly is observed. The internal friction at room temperature is also found to be more particle size dependent. The temperature variation of internal friction exhibits a broad maximum around 500 K, just below Curie temperature 530 K. The above observations were carried on in the demagnetized state; on the application of a 400 mT magnetic field allowed us to reach the saturated state of the sample at any of the measuring temperature. The anomaly observed in the thermal variation of elastic moduli and internal friction is explained with the help of temperature variation of magneto-crystalline anisotropy constant. S. R. Murthy Copyright © 2013 S. R. Murthy. All rights reserved. Mean-Field Approach to Dielectric Relaxation in Giant Dielectric Constant Perovskite Ceramics Wed, 25 Sep 2013 09:10:15 +0000 The dielectric properties of CaCu3Ti4O3 (CCTO) and A2FeNbO6 (AFN, A = Ba, Sr, and Ca) giant dielectric constant ceramics were investigated in the frequency range from 1 Hz to 10 MHz. The relaxation properties can be perfectly described by a polaron model, indicating that the dielectric relaxation is intimately related to the hopping motion caused by localized charge carriers. Shanming Ke, Peng Lin, Haitao Huang, Huiqing Fan, and Xierong Zeng Copyright © 2013 Shanming Ke et al. All rights reserved. Mechanical Behaviour and Fracture Mechanics of Praseodymium Modified Lead Titanate Ceramics Prepared by Solid-State Reaction Route Thu, 29 Aug 2013 11:50:17 +0000 The praseodymium modified lead titanate ceramics with composition where = 0.04, 0.06, 0.08, and 0.10 prepared by solid-state reaction technique were subjected to indentation induced hardness testing method. The indentations were induced in the applied load ranging from 0.245 N to 4.90 N. The microhardness varies nonlinearly with load and was best explained by the concept of Newtonian resistance pressure as proposed by Hays and Kendall’s law. Crack propagation, fracture toughness (), brittleness index (), and yield strength () were studied to understand the effect of Pr content on various mechanical parameters. The load independent values were found to increase with the increase in praseodymium content. Vishal Singh, Shivani Suri, and K. K. Bamzai Copyright © 2013 Vishal Singh et al. All rights reserved. A Comprehensive Study on Gamma-Ray Exposure Build-Up Factors and Fast Neutron Removal Cross Sections of Fly-Ash Bricks Wed, 21 Aug 2013 11:06:01 +0000 Geometric progression (GP) method was utilized to investigate gamma-ray exposure build-up factors of fly-ash bricks for energies from 0.015 to 15 MeV up to 40 mfp penetration depth. The EBFs of the fly-ash bricks are dependent upon the photon energy, penetration depths, and the chemical compositions of the elements. Appreciable variations in exposure build-up factor (EBF) are noted for the fly-ash bricks. The EBFs were found to be small in low and high photon energy regions whereas very large in medium energy region. EBF of the bricks is inversely proportional to equivalent atomic number below 10 mfp for entire energy region of interest 0.015 to 15 MeV. The EBFs of fly-ash, brick of mud, and common brick were similar at 1.5 MeV photon energy. The EBF of the fly-ash bricks was found to be higher than that of the brick of mud, and common brick. The fast neutron removal cross sections of the fly-ash bricks, brick of mud, and common bricks were also calculated which were found to be in the same order. It is expected that this study should be very directly useful for shielding effectiveness of fly-ash brick materials and dose estimation. Vishwanath P. Singh and N. M. Badiger Copyright © 2013 Vishwanath P. Singh and N. M. Badiger. All rights reserved. Simple and Rapid Fabrication of Thin Films by a Chelate Route Wed, 12 Jun 2013 11:23:07 +0000 Na0.5K0.5NbO3 (NKN) thin films were prepared by a chelate route which offers the advantage of a simple and rapid solution synthesis. The route is based on the use of acetoin as a chelating agent. The process was optimized by investigating the effects of alkaline volatilization on film properties. While we observed no evidence of stoichiometry problems due to potassium volatilization loss during the heat treatments, thin films synthesized with insufficient sodium excess presented a potassium-rich secondary phase, which has a significant influence on the ferroelectric properties. We show that the amount of spurious phase decreases with increasing Na+ concentration, in such a way that a 20 mol% Na+ excess is necessary to fully compensate the volatilization loss that occurred during the heat treatment. In this way, NKN thin films annealed at 650°C presented a well-crystallized perovskite structure, no secondary phases, well-defined ferroelectric hysteresis loops ( μC/cm2,  kV/cm), and low leakage current density ( A/cm2 at 80 kV/cm). A. Fernández Solarte, N. Pellegri, O. de Sanctis, and M. G. Stachiotti Copyright © 2013 A. Fernández Solarte et al. All rights reserved. Structural Elucidation of Some Borate Glass Specimen by Employing Ultrasonic and Spectroscopic Studies Sun, 21 Apr 2013 08:21:05 +0000 Quantitative analysis has been carried out in order to obtain more information about the structure of two glass systems, namely, (B2O3-MnO2-PbO) (BML glass system) and (B2O3-Na2CO3-P2O5) (BSP glass system). Their structural elucidation has been carried out by studying the ultrasonic velocities (longitudinal velocities and shear velocities ) and density of these glass samples. The present investigation has been interpreted by focusing more on elastic and mechanical properties of glass specimen through ultrasonic study and the elemental analysis study through spectroscopic studies. The scanning electron microscopic (SEM) study was also carried out with a view to throwing more light on their morphological aspects. The results are corroborated in the light of the role of borate (B2O3) glasses in the formation of glassy structural network. S. Thirumaran and N. Karthikeyan Copyright © 2013 S. Thirumaran and N. Karthikeyan. All rights reserved. The Effect of Isostatic Pressing on the Dielectric Properties of Screen Printed Ba0.5Sr0.5TiO3 Thick Films Sun, 31 Mar 2013 15:24:56 +0000 Ba0.5Sr0.5TiO3 thick films with B2O3–Li2O glass sintering aid were prepared by the screen printing method on Al2O3 substrates. A 200 MPa isostatic pressure was applied to the films before sintering. After being sintered at 950 °C, lower porosity and denser microstructure was obtained compared with the films without isostatic pressing. The dielectric constant and dielectric loss were 238 and 0.0028, respectively. A tunability of 61.7% was obtained for the isostatic pressed films, a 27.8% enhancement compared to unpressurized films. These results suggest that isostatic pressing is an effective way to prepare dielectric thick films with dense microstructure, low dielectric loss, and high tunability. Siwei Wang, Lingling Zhang, Jiwei Zhai, and Fanglin Chen Copyright © 2013 Siwei Wang et al. All rights reserved. Grain Boundary Resistivity of Yttria-Stabilized Zirconia at 1400°C Tue, 12 Mar 2013 15:26:10 +0000 The grain size dependence of the bulk resistivity of 3 mol% yttria-stabilized zirconia at 1400°C was determined from the effect of a dc electric field  V/cm on grain growth and the corresponding electric current during isothermal annealing tests. Employing the brick layer model, the present annealing test results were in accordance with extrapolations of the values obtained at lower temperature employing impedance spectroscopy and 4-point-probe dc. The combined values give that the magnitude of the grain boundary resistivity  ohm-cm. The electric field across the grain boundary width was 28–43 times the applied field for the grain size and current ranges in the present annealing test. J. Wang, A. Du, Di Yang, R. Raj, and H. Conrad Copyright © 2013 J. Wang et al. All rights reserved. Experimental Study on LTCC Glass-Ceramic Based Dual Segment Cylindrical Dielectric Resonator Antenna Wed, 06 Mar 2013 10:32:11 +0000 The measured characteristics in C/X bands, including material properties of a dual segment cylindrical dielectric resonator antenna (CDRA) fabricated from glass-ceramic material based on B2O3–La2O3–MgO glass and La(Mg0.5Ti0.5)O3 ceramic, are reported. The sintering characteristic of the ceramic in presence of glass is determined from contact angle measurement and DTA. The return loss and input impedance versus frequency characteristics and radiation patterns of CDRA at its resonant frequency of 6.31 GHz are studied. The measured results for resonant frequency and return loss bandwidth of the CDRA are also compared with corresponding theoretical ones. Ravi Kumar Gangwar, S. P. Singh, Meenakshi Choudhary, D. Kumar, G. Lakshmi Narayana Rao, and K. C. James Raju Copyright © 2013 Ravi Kumar Gangwar et al. All rights reserved. Preparation and Characterization of Nano-Cadmium Ferrite Wed, 13 Feb 2013 18:58:54 +0000 Nano-hematite (α-Fe2O3) and nano-cadmium ferrite (CdFe2O4) are prepared using template-assisted sol-gel method. The prepared samples are analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Mössbauer spectroscopy techniques for structural and microstructural studies. Nano-α-Fe2O3 with particle size ~60 nm is formed at 500°C, while nano-CdFe2O4 with smaller particle size (~40 nm) is formed at 600°C. It is found that with a simple sol-gel process we can prepare nano-CdFe2O4 with better conditions than other methods: pure phase at lower sintering temperature and time (economic point) and of course with a smaller particle size. So, based on the obtained experimental results, a proposed theoretical model is made to explain the link between the use of the sol-gel process and the formation of nano-CdFe2O4 as a pure phase at low temperature. This model is based on a simple magnetostatic interaction between the formed nuclei within the solution leading to the formation of the stable phase at low temperature. S. M. Ismail, Sh. Labib, and S. S. Attallah Copyright © 2013 S. M. Ismail et al. All rights reserved.