ISRN Ceramics The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Physical, Optical, and Spectroscopic Studies on MgO-BaO-B2O3 Glasses Tue, 24 Dec 2013 09:04:09 +0000 The mixed alkaline effect in double alkaline borate glasses MgO-BaO-B2O3 containing small proportions of copper oxide (CuO) has been studied. The glass samples are characterized by optical absorption, electron paramagnetic resonance (EPR), and Fourier transform infrared spectroscopy (FTIR). A red shift in optical absorption peaks with increasing MgO (decreasing BaO) concentration has been observed. The values of “” tensor and hyperfine “” tensor have shown inflections with glass composition. The number of spins and paramagnetic susceptibility () also exhibited mixed alkaline effect. The broadening of glass network with increase in MgO concentration is found from the FTIR spectra. Interestingly both density and molar volume have shown decreasing trend with glass composition. The optical band gaps exhibited a nonlinear compositional dependence. As expected, the glass samples possessed higher values of optical basicity (Λ), molar electronic polarizability (), and Urbach energy (). Samdani, Md. Shareefuddin, G. Ramadevudu, S. Laxmi Srinivasa Rao, and M. Narasimha Chary Copyright © 2013 Samdani et al. All rights reserved. Recent Progress in Chemically Bonded Phosphate Ceramics Mon, 25 Nov 2013 14:08:16 +0000 Chemically bonded phosphate ceramics have made an excellent progress in the last 10 years and are poised to be one of the major inorganic room-temperature setting materials for nuclear, structural, dental, and prosthetic applications. They are also poised to be the first inorganic industrial coatings for fire and corrosion protection applications. In 2004 the author in his book, Chemically Bonded Phosphate Ceramics, presented general theory, compositions, methods of fabrication, and preliminary commercial products that appeared in the market ten years ago. This paper reviews that background and presents advances of last ten years with an emphasis on the recent applications in the nuclear field. Arun S. Wagh Copyright © 2013 Arun S. Wagh. All rights reserved. Low Temperature Synthesis of α-Alumina with a Seeding Technique Tue, 05 Nov 2013 17:16:52 +0000 This paper reports a method for producing α-Al2O3 at low temperature, which uses a seeding technique. White precipitate of aluminum hydroxide, which was prepared with a homogeneous precipitation method using aluminum nitrate and urea in aqueous solution, was peptized by using acetic acid at room temperature and then transformed to a transparent alumina sol. To the alumina sol α-Al2O3 particles were added as a seed, and then the sol containing α-Al2O3 particles was transformed to an α-Al2O3-seeded alumina gel by drying the sol at room temperature. The nonseeded alumina gel was amorphous or fine crystallites even after being annealed at 600°C and was crystallized to γ-Al2O3 at 700°C. The α-Al2O3 seeding promoted crystallization of alumina gel to α-Al2O3. The promotion of crystallization was made remarkable with a decrease in α-Al2O3 particle size and an increase in α-Al2O3 particle content in weight for the final seeded alumina gel. With an α-Al2O3 particle size of 150 nm and an α-Al2O3 particle content of 5%, the seeded alumina gel was partially crystallized to α-Al2O3 by annealing at a temperature as low as 700°C and mostly at 900°C. Kazuhiro Inoue, Masachika Hama, Yoshio Kobayashi, Yusuke Yasuda, and Toshiaki Morita Copyright © 2013 Kazuhiro Inoue et al. All rights reserved. Preparation, Physicochemical Characterization, and Bioactivity Evaluation of Strontium-Containing Glass Ionomer Cement Tue, 10 Sep 2013 15:08:39 +0000 Background. Glass ionomer cements are one of the most important restorative materials in dentistry. One of the disadvantages of glass ionomer cements is their undesirable mechanical properties and bioactivity. Aim. The aim of this work was preparation and characterization of strontium-containing glass ionomer cement and evaluation of its bioactivity in the simulated body fluid. Materials and Methods. The ceramic component of glass ionomer cement was made by melting method. Scanning electron microscope (SEM) was used to study the size and the shape of glass particles. In order to determine the phase combination in the produced material, X-ray diffraction (XRD) analysis was carried out. The chemical composition of the glass was evaluated by X-ray florescence (XRF), and the surface area of the particles was determined using BET method. In order to investigate the biological properties of the glass, samples were immersed in simulated body fluid (SBF). Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) were used to recognize and confirm the apatite layer on the composite surface. Results and Conclusions. The result of X-ray diffraction (XRD) analysis confirmed the glassy structure of the produced ionomer cements. The result of XRF confirmed the presence of Sr in the chemical composition. Fourier transform infrared spectroscopy test and electron microscope confirmed the formation of apatite layer on the surface of material. The final result of this research was gaining glass ionomer cement containing Sr with improved bioactivity. Masomeh Khaghani, Ali Doostmohammadi, Zahra Golniya, Ahmad Monshi, and Ahmad Reza Arefpour Copyright © 2013 Masomeh Khaghani et al. All rights reserved. Experimental Investigation on Flowability and Compaction Behavior of Spray Granulated Submicron Alumina Granules Wed, 07 Aug 2013 07:55:29 +0000 Aqueous slurry with various solid loadings (up to 40 wt%) of alumina powder (D50 = 300 nm) with suitable rheological properties were spray dried into granules. Solid loading and feed rate of the slurry are found to have a prominent effect on the shape and size distribution of granules. Powder flow measurements exhibited a cohesive index of 28.45 signifying an extremely cohesive flow due to high surface area and irregular morphology. Finer sizes though it offers high geometrical surface area it leads to more surface contacts and hence, high interparticle friction. Spherical morphology achieved through optimum spray drying parameters significantly reduced the cohesive index to 6.45 indicating free flow behavior. Compaction studies of the spray-dried granules and corresponding plot of relative density versus compaction pressure revealed an agglomerate strength of 500 MPa followed by a plateau-like behavior reaching a maximum in the relative density of 59%-60% of the theoretical values. Abhisek Choudhary, Pandu Ramavath, Papiya Biswas, Nukala Ravi, and Roy Johnson Copyright © 2013 Abhisek Choudhary et al. All rights reserved. Evaluation of DLC, WC/C, and TiN Coatings on Martensitic Stainless Steel and Yttria-Stabilized Tetragonal Zirconia Polycrystal Substrates for Reusable Surgical Scalpels Tue, 07 May 2013 17:36:10 +0000 DLC, WC/C, and TiN coated SF 100 martensitic stainless steel and Yttria-Stabilized Tetragonal Zirconia Polycrystal (Y-TZP) surgical scalpels were tested, characterized, and comparatively evaluated with regard to chemical leach, micromorphology, and mechanical properties in order to evaluate their suitability as reusable surgical scalpels. Vickers microhardness (HV), Scratch Hardness Number (), and sharpening by grinding and cutting capabilities of all the coated scalpels were deemed appropriate for reusable surgical scalpels. However, coated Y-TZP scalpels demonstrated higher Vickers microhardness than martensitic stainless steel scalpels coated with the same coatings, except DLC coating on Y-TZP substrate that presented less adhesion than the other coatings. Uncoated and coated martensitic stainless steel scalpels presented corrosion and chemical leach when soaked for a defined period of time in a simulant physiological saline solution, while uncoated and coated Y-TZP scalpels did not present these drawbacks. Therefore, DLC, WC/C, and TiN coated SF 100 martensitic stainless steel surgical scalpels are unsuitable as reusable surgical scalpels, limiting their application to disposable scalpels only, as the uncoated ones, despite their higher microhardness and expected longer cutting capability duration. Based on these experimental results, WC/C and TiN coated Y-TZP scalpels can be proposed as candidates for reusable surgical scalpel applications. Stefano Pini, Roberto Groppetti, Claudio Mucchino, and Valentina Geretto Copyright © 2013 Stefano Pini et al. All rights reserved. Electrical Conduction in Ceramic by Complex Impedance/Modulus Spectroscopy Thu, 21 Mar 2013 12:00:56 +0000 The present work describes the piezoelectric, impedance, and conductivity studies of ; BNT-BT ceramics. The ceramics were prepared by conventional ceramic fabrication technique. X-ray diffraction data confirmed the formation of a pure compound in all the compositions. Williamson-Hall plot yielded the apparent crystallite sizes ~26–52 nm, and SEM micrograph showed grain sizes ranging between 1.8–3.5 μm for the material samples. Values of longitudinal piezoelectric charge coefficients of the samples poled under a dc electric field of about 2.5 kV/mm at 80°C/15 min indicated that their piezoelectric properties near the MPB are rather sensitive to the phase composition and reach preferred values at , where the relative content of the tetragonal phase is significantly higher than that of the monoclinic phase. Complex impedance/modulus spectroscopic analyses indicated the presence of grain-boundary effect along with the bulk contribution and also confirmed the presence of non-Debye type of multiple relaxations in the materials. The temperature dependent electrical conductivity data suggest the negative temperature coefficient of resistance behaviour. The activation energy studies allow insight into the nature of the conduction mechanisms occurring in the materials system which are explained on the basis of hopping model of charge carriers. Ansu Kumar Roy, Kamal Prasad, and Ashutosh Prasad Copyright © 2013 Ansu Kumar Roy et al. All rights reserved. DSC and DC Conductivity of Bi2O3 · LiF · B2O3 Glasses Tue, 29 Jan 2013 09:52:30 +0000 Fluoroborate glasses with Bi2O3 content and having compositions Bi2O3 · ()LiF · 60B2O3 ( = 0, 5, 10, 15, and 20) are prepared using melt-quench technique. DSC characterization is carried out to observe glass transition temperature. Two such temperatures are observed for each of the reported samples. DC conductivity of the reported samples is studied with the variation in temperature from 313 K to 413 K by dividing this range into three regions, namely, low-, intermediate-, and high-temperature regions. DC conductivity responses for these temperature regions are explained using different conductivity models. Susheel Arora, Virender Kundu, D. R. Goyal, and A. S. Maan Copyright © 2013 Susheel Arora et al. All rights reserved. A Study of Parameters Affecting Wear Resistance of Alumina and Yttria Stabilized Zirconia Composite Coatings on Al-6061 Substrate Mon, 31 Dec 2012 09:24:30 +0000 In this investigation, a composite coating of alumina and yttria stabilized zirconia in equal proportion was developed on Al-6061 substrate using Atmospheric Plasma Spraying technique. Two commercially available powders of chemical composition Al 25Fe7Cr5Ni and Al2O330(Ni 20Al) were used as bond coats. The coating samples were subjected to abrasive wear test as per ASTM G99. From the results it was found that wear rate and coefficient of friction depend on various parameters such as microstructure, surface roughness, porosity, coating thickness, and hardness. It was also found that the mechanism of wear is mainly due to abrasion and once the bond coat is exposed to the disc, it loses material by adhesion. As the coating systems possess α-Al2O3 and ZrO2, they can be used for wear and heat resistant applications such as cylinder liner of internal combustion engines. N. Krishnamurthy, M. S. Prashanthareddy, H. P. Raju, and H. S. Manohar Copyright © 2012 N. Krishnamurthy et al. All rights reserved. Preparation and Catalytic Properties of Iron-Cerium Phosphates with Sodium Dodecyl Sulfate Wed, 26 Dec 2012 11:08:32 +0000 Iron phosphate was prepared from iron nitrate and phosphoric acid with sodium dodecyl sulfate at various stirring hours. The chemical composition of the obtained samples was estimated from ICP and XRD measurements. Particle shape and size distribution were observed by SEM images and laser diffraction/scattering methods. Further, the catalytic activity was studied with the decomposition of the complex between formaldehyde, ammonium acetate, and acetylacetone. The peaks of FePO4 were observed in XRD patterns of samples prepared in Fe/Ce = 10/0 and then heated at 600°C. Other samples were amorphous in XRD patterns. Iron-cerium phosphates had high catalytic activity for the decomposition of the complex. Hiroaki Onoda and Takeshi Sakumura Copyright © 2012 Hiroaki Onoda and Takeshi Sakumura. All rights reserved. Effect of Excess Silicon on the Formation of Ti3SiC2 Using Free Ti/Si/C Powders Synthesized via Arc Melting Wed, 19 Dec 2012 14:35:37 +0000 The aim of this study is to investigate the effect of excess silicon on the formation of from free Ti/Si/C powders synthesized via arc melting. The reactant mixture was prepared according to the off-stoichiometric ratio of 3Ti : ()Si : 2C, where (excess Si) varied from 0 to 0.5. Samples were analyzed using X-ray diffractometry (XRD), field-emission scanning electron microscopy (FESEM), and energy-dispersive spectroscopy (EDS). The relative density and porosity of products were calculated using the Archimedes method. Through optimization of the arcing schedules (time) and excess Si amounts, 86.9 wt% of with a relative density of 86% was obtained. For all products, was identified as the main phase, while TiC, , and were identified as secondary phases. grains were in the form of elongated platelets; they were nucleated and grew on the surface of equiaxed TiC grains. The microporosity present in the TiC-equiaxed grains affected the density and porosity of the products. Mohamad Johari Abu, Julie Juliewatty Mohamed, and Zainal Arifin Ahmad Copyright © 2012 Mohamad Johari Abu et al. All rights reserved. Comparative Study of Indentation Size Effects in As-Sintered Alumina and Alumina Shock Deformed at 6.5 and 12 GPa Wed, 05 Dec 2012 08:39:53 +0000 Nanohardness of alumina ceramics determines its performance in all contact-related applications because the issue of structural integrity gets determined at the nanoscale of contact. In spite of the wealth of the literature, however, it is not yet known in significant details how the high-strain rate flyer-plate impact at different pressure affects the nanohardness of dense, coarse grain alumina ceramics. Thus, the load controlled nanoindentation experiments were performed with a Berkovich indenter on an as-received coarse grain (~10 μm), high density (~3.98 gm·cc−1) alumina, and shock recovered tiny fragments of the same alumina obtained from gas gun experiments conducted at 6.5 GPa and 12 GPa shock pressures with stainless steel flyer plates. The nanohardness of the as-received alumina was much higher than that of the 6.5 GPa and 12 GPa shock-recovered alumina. The indentation size effect (ISE) was the strongest in alumina shocked at 12 GPa and strong in alumina shocked at 6.5 GPa, but it was mild in the as-received alumina sample. These results were rationalized by analysis of the experimental load depth data and evidences obtained from field emission scanning electron microscopy. In addition, a rational picture of the nanoindentation responses of the as-received and shocked alumina ceramics was provided by a qualitative model. Riya Chakraborty, Anoop K. Mukhopadhyay, Keshaw D. Joshi, Amit Rav, Ashok K. Mandal, Sandip Bysakh, Sampad K. Biswas, and Satish C. Gupta Copyright © 2012 Riya Chakraborty et al. All rights reserved. Modeling of Viscosity and Thermal Expansion of Bioactive Glasses Tue, 04 Dec 2012 17:54:54 +0000 The behaviors of viscosity and thermal expansion for different compositions of bioactive glasses have been studied. The effect of phosphorous pentoxide as a second glass former in addition to silica was investigated. Consequently, the nonlinear behaviors of viscosity and thermal expansion with respect to the oxide composition have been modeled. The modeling uses published data on bioactive glass compositions with viscosity and thermal expansion. -regression optimization technique has been utilized for analysis. Linear and nonlinear relations are shown to establish the viscosity and thermal expansion coefficients associated with oxide components of the glasses under study. The modeling allows the calculation of viscosity for a given temperature and, accordingly, the fusion temperature of these glasses along with the coefficient of thermal expansion. The established model relations also suggest first- and second-order phosphorus-alkali and alkaline earth oxides interaction which is reflected on the model coefficient that calculates viscosity and thermal expansion. Saad B. H. Farid Copyright © 2012 Saad B. H. Farid. All rights reserved. Rare Earth-Doped SrTio3 Perovskite Formation from Xerogels Wed, 14 Nov 2012 11:58:24 +0000 A synthesis process of rare earth doped SrTiO3 by modified sol-gel technique is described. Impervious strontium titanate doped with rare earth was prepared by gelification and calcination of colloidal systems. Powders of thulium substituted strontium titanate (-δ, where ; 0.02; 0.05) were obtained through cohydrolysis of titanium, strontium, and thulium precursors by sol-gel method. The xerogel obtained from the evaporation of solvents was milled and calcinated at 1100°C to give a reactive powder. Pure and doped SrTiO3 dense disks were formed by uniaxial pressing. Thermogravimetry (TGA), differential scanning calorimetry (DSC) analysis, X-ray diffractometry (XRD), and scanning electron microscopy (SEM) have been used to study the microstructural evolution of amorphous xerogel into crystalline reactive and sinterable powders. Hardness was measured for each membrane by a Vickers microindenter. Dilatometric and TGA-DSC in pure CO2 flow tests have been performed to evaluate, respectively, the thermal and chemical stability of the material. The optimized preparation route has allowed to synthesize highly reactive easy sintering powders used for fully densified, impervious ceramics with high thermal and chemical stability at high temperature. Anastasia Rocca, Antonio Licciulli, Monia Politi, and Daniela Diso Copyright © 2012 Anastasia Rocca et al. All rights reserved. A Review on Infrared Spectroscopy of Borate Glasses with Effects of Different Additives Wed, 14 Nov 2012 09:55:46 +0000 Borate glasses are the technologically important class of glasses and play a significant role in various applications. Borate glasses contain planar BO3 groups as structural units, rather than tetrahedral SiO4 groups. The oxygen atoms are, as in SiO2, again connected to two network-forming atoms, in case of boron. The radial distribution analysis describes the B2O3 glass structure as consisting of boroxol rings, that is, planar rings containing three boron atoms and three oxygen atoms. The network forming of the B2O3 and the SiO4 is affected with the addition of some metal cation additives Pb, Zn, Cd, and so forth. These additives also work as a network modifier and a nucleating agent for crystallization of glass. Therefore, the optical properties of the borate glasses have been changed significantly. Chandkiram Gautam, Avadhesh Kumar Yadav, and Arbind Kumar Singh Copyright © 2012 Chandkiram Gautam et al. All rights reserved. Contact Deformation of Alumina Wed, 14 Nov 2012 09:23:39 +0000 The study of contact-induced deformations during hardness evaluation and the subsequent damage mechanisms of alumina under low loads deserves significant importance for its applications as wear-resistant inserts, biomedical implants, thin films, and armour plates, because the contact-induced brittle failure is an issue of major scientific concern that prevents their widespread commercial applications. However, the studies on hardness of dense, coarse grain alumina at ultralow load, for example, 1 N, are still lacking. Therefore, the present study was conducted on a dense (~95% of theoretical) coarse-grain (~20 μm) alumina at a low peak load of 1 N with varying loading rates (10−3–100 N·s−1) applied in depth sensitive indentation experiments. The results showed profuse presence of multiple micro-pop-in and pop-out events possibly linked to dislocation nucleations underneath the indenter. The critical resolved shear stress () was found to enhance with the increase in applied loading rates. The occurrences of the localized shear deformation band formation and microcracking in and around the indentation cavity were explained in terms of the correlation between the nanoscale plasticity events, the small magnitude of (), the maximum shear stress () developed just underneath the indenter, and the dislocation loop radius (). Manjima Bhattacharya and Anoop Kumar Mukhopadhyay Copyright © 2012 Manjima Bhattacharya and Anoop Kumar Mukhopadhyay. All rights reserved. Study of PbTiO3-Based Glass Ceramics Containing SiO2 Sun, 04 Nov 2012 08:44:52 +0000 Glass samples with composition 50PbO : 25TiO2 : (25-X) B2O3 : XSiO2 (with X = 0, 1.5, 2.5, 3.5, and 5 mol%) were prepared by conventional quenching technique. These glass samples were converted to glass ceramics by the two-stage heat treatment schedule. Formation of ferroelectric lead titanate phase in the glass ceramics was confirmed from the XRD. The density, CTE, and dielectric constant of the glass and glass-ceramic samples were measured. The glass-ceramic sample containing 2.5 mol% SiO2 exhibited the highest dielectric constant. The SEMs of glass-ceramic samples were studied. The P-E hysteresis loop studies also revealed the highest remnant polarization for this sample, which has a potential for being developed for practical applications. V. K. Deshpande and V. U. Rahangdale Copyright © 2012 V. K. Deshpande and V. U. Rahangdale. All rights reserved. Use of Wollastonite as a Flux for Bone China Bodies Wed, 17 Oct 2012 11:45:09 +0000 The utilization of wollastonite as a flux in bone china was investigated in this work. Ceramic industry is always looking to optimize the use of fluxes as a way of reducing energy costs associated with firing. Wollastonite is added in ceramic formulations as an auxiliary flux and allows fast firing production. However, its use in bone china has not been tested before. In the present work, two formulations were prepared, comparing the traditional formulation to another in which the conventional flux (potash feldspar) was partially replaced by wollastonite. The firing behavior, technical properties, microstructure, and phase development were analyzed. A slip with wollastonite was also developed to analyze its rheology. Wollastonite body achieved a reduction of firing temperature, a large plateau for firing, and optimal slip stabilization for casting pieces. Lauren Arrussul Carús, Fabiana de Souza, and Saulo Roca Bragança Copyright © 2012 Lauren Arrussul Carús et al. All rights reserved. Template-Based Synthesis of Nanoporous Hydroxyapatite Wed, 17 Oct 2012 10:37:43 +0000 Hydroxyapatite (HAp) particles, a potential starting material for bone substitutes, with nanopores were synthesized in the presence of cetyltrimethylammonium bromide (CTAB) and P123 as cationic and nonionic surfactants as the structuring units. Effect of nonionic surfactant concentration on surface areas is also investigated. Based on N2 adsorption-desorption isotherms investigation, surface area increased up to 50 m2/g by using P123 and 147 m2/g by using CTAB as porosity agent. Pore structure remained even after the removal of surfactant and calcinations at . E. Salimi, J. Javadpour, and M. Anbia Copyright © 2012 E. Salimi et al. All rights reserved. Electrical Properties and AC Conductivity of (Bi0.5Na0.5)0.94Ba0.06TiO3 Ceramic Mon, 15 Oct 2012 15:29:40 +0000 Lead-free perovskite (Bi0.5Na0.5)0.94Ba0.06TiO3 (BNBT06) was prepared by conventional ceramic fabrication technique at 1160°C/3h in air atmosphere. The crystal structure, microstructure, dielectric, polarization, piezoelectric properties, and ac conductivity of the sample were studied. X-ray diffraction data confirmed the formation of a single phase tetragonal unit cell. Williamson-Hall plot was used to calculate the lattice strain and the apparent particle size. The experimental relative density of BNBT06 was found to be ~96-97% of the theoretical one with an average grain size ~4 μm. Room temperature dielectric constant and loss factor at 1 kHz were found to be equal to 781 and 0.085, respectively. Longitudinal piezoelectric charge coefficient of the poled sample under 2.5 kV/mm at 80°C in silicone bath was found to be equal to 124 pC/N. Complex impedance and electric modulus spectroscopic analyses showed the dielectric relaxation in the material to be of non-Debye type. The Nyquist plots and conductivity studies showed the NTCR character of BNBT06. The correlated barrier hopping model (CBHM) as well as jump relaxation model (JRM) was found to successfully explain the mechanism of charge transport in BNBT06. The ac conductivity data were used to evaluate the minimum hopping length, apparent activation energy, and density of states at Fermi level. Ansu K. Roy, Amrita Singh, Karishma Kumari, K. Amar Nath, Ashutosh Prasad, and K. Prasad Copyright © 2012 Ansu K. Roy et al. All rights reserved. Study on Strength and Microstructure of Cement Pastes Containing Limestone Powder under Flowing Acid Solution Condition Mon, 15 Oct 2012 09:31:58 +0000 Different cement pastes containing limestone powder were prepared and soaked, respectively, in flowing acetic acid solution with pH value of 4 and sulfuric acid solution with pH value of 2. The strength and microstructure of the pastes after different flowing acid attack periods were investigated by using strength test, X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques in this study, which reveals the effect of limestone powder on flowing acid resistance mechanism of cement paste. Testing results show that the strength of pastes suffered flowing acid attack decreases with the increase of water-binder ratio and the content of limestone powder. In flowing acetic acid solution, calcium hydroxide and calcium carbonate react with acetic acid, which therefore made deterioration of pastes proceed from the exterior to the interior. In flowing sulfuric acid solution, although calcium hydroxide and calcium carbonate could react with sulfuric acid and form gypsum, the flowing liquid would dissolve it out and thus the crystallization of gypsum was difficult which would somewhat inhibit the swell of pastes. Shuhua Liu, Lihua Li, Zhigang Wang, Jiafeng Wang, and Meijuan Rao Copyright © 2012 Shuhua Liu et al. All rights reserved. Microstructural Modeling of Ni- Composites Using Object-Oriented Finite-Element Method Mon, 15 Oct 2012 08:49:59 +0000 This paper studied the mechanical and thermal properties of interpenetrating phase composites (IPCs) of Ni-Al2O3 using finite-element-based object-oriented program (OOFEM). It is difficult to model structure-property relationship in IPCs because of interpenetration of two or more phases. In order to understand the material behavior, OOFEM combines the microstructural data in the form microscopic images with the fundamental material properties (such as Young’s modulus or thermal conductivity of the constituent phases). Thermal conductivity, thermal expansion coefficient, and modulus of elasticity for the composites are examined using OOFEM and compared with other methods. The distribution of residual thermal stresses is also investigated. Neeraj Kumar Sharma, S. N. Pandit, and Rahul Vaish Copyright © 2012 Neeraj Kumar Sharma et al. All rights reserved. Chemical Synthesis and Properties of Novel Nanostructures and Microplatelets Fri, 28 Sep 2012 23:00:49 +0000 Bi2Se3 nanostructures, microsised fibre bundles, and platelets have been synthesised through a simple chemical spray pyrolysis route on glass substrates. Low substrate temperatures () favoured growth of nanostructures while elevated was accompanied by increased grain growth and formation of microsised platelets. The nanostructures were identified as nanorods, nanofibers, nanotubes, nanoflowers, and nanoneedles of various aspect ratios. There was an observed red shift of the optical band gap () with increased from 2.40 eV at 95°C to 1.25 eV at 360°C. Thermo probe measurements confirmed n-type conductivity with dark resistivities which followed a near exponential decline with elevated . The observed changes in optoelectronic properties existing in the different regimes were explained on the basis of microstructural and textural changes in the pristine clusters. Cosmas M. Muiva, Charles Moditswe, and T. Stephen Sathiaraj Copyright © 2012 Cosmas M. Muiva et al. All rights reserved. Synthesis, Structural, Electrical, and Thermal Studies of Pb1−𝑥Ba𝑥Nb𝟐O𝟔 (𝑥=𝟎.𝟎 and 𝟎.𝟒) Ferroelectric Ceramics Wed, 05 Sep 2012 11:38:36 +0000 The polycrystalline ceramic samples of lead barium niobate with general formula Pb1−𝑥Ba𝑥Nb2O6 (𝑥=0.0 and 0.4) were prepared by conventional solid state reaction method. The room temperature X-ray diffraction patterns reveal that both of the samples have orthorhombic crystal structure with space group Cm2m. The dielectric constant and dissipation factor were measured as a function of frequency (100 Hz-2 MHz) and temperature (RT-660K). The DC electrical conductivity of both the samples was measured from RT to 660 K. The activation energies calculated from log σ versus 1000/T curves in ferroelectric phase of the compounds are 1.09 eV for pure (𝑥=0.0) sample and 1.36 eV for Ba-substituted (𝑥=0.4) sample. The values of activation energies show that the substitution of Ba2+ ion on Pb2+ ion site increases the resistivity of pure PbNb2O6 (𝑥=0.0) ceramic. The modulated differential scanning calorimetry (MDSC) has been used to investigate the phase transition temperature of both the compounds and also to see the effect of Ba2+ ion substitution on the phase transition temperature, specific heat, and other thermal parameters of the compound. Shiv K. Barbar and M. Roy Copyright © 2012 Shiv K. Barbar and M. Roy. All rights reserved. Rietveld Structure Refinement and Cation Distribution of Cr𝟑+ Substituted Nanocrystalline Ni-Zn Ferrites Tue, 04 Sep 2012 11:09:52 +0000 Ferrite nanoparticles of Ni0.7Zn0.3Cr𝑥Fe2−𝑥O4 were prepared by a sol-gel autocombustion method. The prepared samples were shown to have a cubic spinel structure by applying the full pattern fitting of the Rietveld method. The unit cell dimension, discrepancy factor, and interatomic distance have been determined. As the Cr3+ content x increases, the unit cell dimensions and crystallite size are decreased. The IR spectra show two absorption bands in the wave number range of 400 to 600 cm−1. A. A. Birajdar, Sagar E. Shirsath, R. H. Kadam, S. M. Patange, D. R. Mane, and A. R. Shitre Copyright © 2012 A. A. Birajdar et al. All rights reserved. Mechanochemical Synthesis of Fluorapatite-Zinc Oxide (FAp-ZnO) Composite Nanopowders Sun, 02 Sep 2012 08:37:50 +0000 Fluorapatite-zinc oxide (FAp-ZnO) composite nanopowders were successfully prepared via mechanochemical process. Characterization of the products was carried out by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) analysis, energy dispersive X-ray spectroscopy (EDX), and field-emission scanning electron microscopy (FE-SEM) techniques. Results revealed that in the absence of ZnO which produced by hydrothermal method, the single-phase FAp had high-crystalline structure with appropriate morphological features. Furthermore, after 5 h of milling in the presence of 5 wt.% ZnO, FAp-5 wt.% ZnO, composite nanopowders with no impurity phase was obtained. Structural studies illustrated that the milling up to 5 h was not accompanied by a remarkable change in the structural features. Moreover, the gained composite powders presented an average crystallite size of about 40 nm for FAp. The FE-SEM observations indicated that the experimental outcome had a cluster-like structure which consisted of several small particles. Finally, results propose a new approach to prepare commercial amounts of novel FAp-based composite nanopowders with high quality and suitable structural and morphological features. Bahman Nasiri-Tabrizi and Abbas Fahami Copyright © 2012 Bahman Nasiri-Tabrizi and Abbas Fahami. All rights reserved. Characterization, Acid Activation, and Bleaching Performance of Ibeshe Clay, Lagos, Nigeria Thu, 01 Mar 2012 09:12:38 +0000 This paper investigated the possibility of using clay characterization as a major tool to predict its suitability for bleaching of vegetable oil, namely, palm oil. The clay sample collected from Ibeshe deposit was characterized by X-ray diffraction (XRD). The results of the XRD showed that the clay is composed of dioctahedral kaolinite and dickite, silica, ilmenite, and merlinite. The compositional analysis using atomic absorption spectroscopy (AAS) showed that the Na2O : CaO ratio is 0.22, a value less than one and indicative of the absence of bentonite which presence, just like montmorillonite, confers bleaching activity to clays. Furthermore, the SiO2 : Al2O3 ratio of 1.12 (greater than one) is suggestive of a clay suitable not for bleaching but for zeolite development. Actual laboratory tests for bleaching performance evaluation confirmed the prediction above that the clay indeed has poor bleaching action as shown by percent colour reduction. The colour reduction for natural clay was 9.1%. This value only increased to 27.3% after 3M HCl activation, a value still very low for effective bleaching. M. A. Usman, V. I. Ekwueme, T. O. Alaje, and A. O. Mohammed Copyright © 2012 M. A. Usman et al. All rights reserved. Impedance and Electrical Modulus Study of Microwave-Sintered SrBi2Ta2O9 Ceramic Sun, 12 Feb 2012 09:07:53 +0000 Bismuth layered structure SrBi2Ta2O9 ceramic is prepared by the microwave sintering technique via solid state route at 1100°C for 30 mins. X-ray diffraction analysis is used to analyze the phase purity, which identifies the orthorhombic structure with A21am space group. The fracture surface of the sintered pellet is visualized by scanning electron microscopy. Impedance spectroscopy is used to analyze the sample behavior as a function of frequency and temperature. Impedance and modulus study reveals the temperature-dependent non-Debye type relaxation phenomenon. The Nyquist plot shows a single arc representing the grain effect in the material, and the conductivity increases with increase in temperature. The Nyquist plot is fitted with an equivalent circuit, and the simulated parameters are well agreed with the calculated parameters. Arrhenius plot shows two different activation energies at below and above 300°C which identifies the phase transition of SrBi2Ta2O9 ceramic. The fatigue property is explained by the basis of activation energies, which shows that SBT sintered by microwave technique is more fatigue resistant than conventional sintering. V. Senthil, T. Badapanda, A. Chandra Bose, and S. Panigrahi Copyright © 2012 V. Senthil et al. All rights reserved. Remediation of Polluted Water Using Natural Zeolitic Aluminosilicates/Lateritic Clay Ceramic Matrix Membrane Wed, 08 Feb 2012 13:40:31 +0000 Microporous ceramic matrix membranes were prepared with complementary proportions of locally available zeolitic aluminosilicate materials and other abundant lateritic clay minerals. The membranes cast as circular disks (22.78 mm diameter and 2.11 mm thickness) were treated with silver nitrate solution to discourage microbial growth on their surface and then sintered at 900±5∘C for about 20 hours. Antimicrobial microfiltration process showed 87.24% to 100% bacterial rejection depending on the material combination ratio. Elemental characterization of the membrane materials was done using ion beam analysis (IBA) technique of particle induced X-ray emission (PIXE), while the physicochemical behaviour of the ceramic membranes was carried out through the analysis of the filtered water samples using atomic absorption spectroscopy (AAS), total dissolved solids (TDS), microbial, and pH analyses. Compositional characterization of raw materials showed comparatively low contents of impurities, such as Fe and Ca, in the raw materials, but with high SiO2/Al2O3 ratios for the raw material which is important for zeolitic material synthesis. Regularly porous microstructure of mean pore diameter of between 50 nm and 100 nm was observed from the analyzed images obtained from ZEISS Supra 40 scanning electron microscope. E. Ajenifuja, O. O. Akinwunmi, M. K. Bakare, J. A. Ajao, I. F. Adeniyi, and E. O. B. Ajayi Copyright © 2012 E. Ajenifuja et al. All rights reserved. The Stiffness of Syntactic Metal-Matrix Composites: A Statistical Model Mon, 06 Feb 2012 13:15:01 +0000 Stiffness estimates of unloaded isotropic particulates are made by a new analytical model, when reinforcements are either compact or hollow spheres. A statistical extension of this model is described when stiffness predictions involve loading of syntactic composites. A simple experimental routine is also proposed for monitoring the microballoons fracture upon brittle syntactic metal-matrix composites tensile loading. J. D. Botas and H. Águas Copyright © 2011 J. D. Botas and H. Águas. All rights reserved.