bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced Anisotropic Damage Model Fully Coupled with Anisotropic Plasticity
Authors: Badreddine Houssem , Saanouni Khemais
Published: August 2015

In this work, a thermodynamically-consistent framework is used to formulate a non-associative finite strain anisotropic elastoplastic model fully coupled with anisotropic ductile damage. The finite strain assumption is considered using specific large strains kinematics based on multiplicative decomposition of the total transformation gradient and assuming a small elastic strains. The objectivity principle fulfillment is assumed using the well-known rotating frame formulation. The effective variables are defined to introduce the effect of the anisotropic damage on the other variables through the total energy equivalence assumption. The non-associative plasticity framework, for which equivalent stresses in yield function and in plastic potential are separately defined, allows better plastic anisotropy description. The evolution equations for overall dissipative phenomena are deduced from the generalized normality rule applied to the plastic potential while the consistency condition is still applied to the yield function. Applications are made to an RVE with generic material parameters by considering non-proportional loading paths. For each loading path the effect of the anisotropic plasticity on the damage evolution is studied in the context of finite strains.
Continuum Model of Deformation of Piezoelectric Materials with Cracks
Authors: Babich Dmytro , Bezverkhyi Olexander , Dorodnykh Tatiana
Published: August 2015

The present paper addresses the continuum model describing deformation and accumulation of microdamages in electroelastic materials based on the generalized Eshelby principle. The microdamageability is considered as a process of appearance of flat elliptic or circular microcracks randomly dispersed over volume, the concentration of which increases with a load. The Eshelby method is based on the principle of equivalence of the deformation energy of fractured piezoelectric materials and the energy of medium, which is modeling these materials as a continuous medium. The key point of this approach is to determine the densities of the released elastic and electric energy.
Brittle Damage in Initially Anisotropic Materials: A Model Accounting for the Induced Anisotropy and Unilateral Effects
Authors: Welemane Hélène , Goidescu Cristina , Kondo Djimédo , Pantalé Olivier , Karama Moussa
Published: August 2015

A new micromechanical modelling approach for brittle damage in initially orthotropic materials is presented. The proposed strain-based energy formulation allows to derive a fully anisotropic multilinear model for microcracked materials with arbitrary oriented defects. The thermodynamics framework provides a standard procedure for the damage evolution law. The new model explicitly accounts for the interaction between primary and induced anisotropies. Moreover, the very challenging issue of opening-closure effects (unilateral behavior) is addressed in this framework.
Different Numerical Time Integration Schemes for Elastoplasticity Coupled to Anisotropic Damage
Authors: Fassin Marek , Wulfinghoff Stephan , Reese Stefanie
Published: August 2015

Much effort has been put in the development of proper continuum damage mechanics models, in which damage is either represented as a scalar, vectorial or tensorial quantity. In this work the anisotropic damage theory of Lemaitre et al. (2000), which describes damage as a second order tensor, is utilized. Two numerical time integration algorithms, namely a fully implicit and a partially explicit scheme, are compared by means of finite element computations of a plate with a circular hole. The convergence behavior of the two algorithms is studied and compared regarding the number of time steps.
Micromechanical Damage Simulation to Obtain Effect of Coarse Grains Distribution on Mechanical Properties of Bimodal AL Using 2D XFEM
Authors: Hosseini-Toudeshky Hossein , Jamalian Maryam
Published: August 2015

In this paper, we focus on the stress-strain behavior prediction of the bimodal bulk Al5083 series which are comprised of ultra-fine grains (UFG) separated by coarse grain (CG) regions. The CGs in the UFG matrix effectively prevents microcracks from propagation, leading to enhance ductility and toughness while the strength remains high. In this work, initially, XFEM is implemented for bimodal materials considering various fracture criteria for brittle and ductile phases in maximum traction and cohesive law. Then the stress-strain behavior dependency of the model on the CG distribution in a constant volume fraction is investigated by extraction of RVEs from optical microscopy (OM) images of the real material. The solution convergence of such a problem with irregular geometry, plasticity and crack initiation-propagation demanded extreme efforts that accomplished by refining and arranging meshes as well as adding damage stabilizations. As a result of the above procedures, the sensitivity of the modeling procedure to various RVEs is obtained, the crack initiation-propagation pattern in microscale is predicted and consequently, the global stress-strain behavior result is calculated. It is shown that the predicted results are in good agreement with the available experimental results.
Recent Developments in Modelling of Progressive Damage in Fibre-Reinforced Composites
Authors: Chen Bo Yang , Tay Tong Earn
Published: August 2015

This paper provides an overview of recent developments in the modeling of progressive damage in fiber-reinforced composite laminates. Some insights into modeling the size effects of open-hole composite laminates under in-plane tension and compression, the significance of ply-blocking and delamination are discussed. Recent interest in the interaction and migration of matrix cracks and delamination, resulting in development of integrated XFEM-CE and floating node methods will also be presented.
Adaptive Zooming Method for the Simulation of Quasi-Brittle Materials
Authors: Llau Antoine , Jason Ludovic , Baroth Julien , Dufour Frédéric
Published: August 2015

A method to simulate concrete structures (quasi-brittle material) with localized nonlinearities is presented. Based on Guyan’s condensation, it consists in replacing the elastic zones of the structure by their equivalent rigidities (super-elements). The nonlinear computation is then performed only on the zones of interest (ie, damaged). As new damaged zones may appear, the proposed method monitors the evolution of the system and re-integrates previously condensed areas if necessary. This method, applied on different tests cases, allows a substantial computation economy.
Prediction of Low Cycle Fatigue Life Using Cycles Jumping Integration Scheme
Authors: Labergere Carl , Saanouni Khemais , Sun Zhi Dan , Dhifallah Mohamed Ali , Li Yisa , Duval Jean Louis
Published: August 2015

In this paper, cycles jumping scheme integration is used to numerically integrate fully coupled constitutive equations in order to predict the low cycle fatigue life under cyclic loading. This procedure avoids the calculation of the full loading cycles (some millions of loading cycles) while considering the transient stages due to the hardening (at the beginning) and the high damage-induced softening during the last tens of loading cycles. The model parameters have been identified using the results obtained from a 316L steel cylindrical specimen subject to symmetric tension-compression loading path. The effects of the specimen size as well as the mesh size on the fatigue life prediction are investigated.
Stochastic Continuum Damage Mechanics Using Spring Lattice Models
Authors: Kale Sohan , Koric Seid , Ostoja-Starzewski Martin
Published: August 2015

In this study, a planar spring lattice model is used to study the evolution of damage variabledLin disordered media. An elastoplastic softening damage constitutive law is implemented which introduces a cohesive length scale in addition to the disorder-induced one. The cohesive length scale affects the macroscopic response of the lattice with the limiting cases of perfectly brittle and perfectly plastic responses. The cohesive length scale is shown to affect the strength-size scaling such that the strength increases with increasing cohesive length scale for a given size. The formation and interaction of the microcracks is easily captured by the inherent discrete nature of the model and governs the evolution ofdL. The proposed method provides a way to extract a mesoscale dependent damage evolution rule that is linked directly to the microstructural disorder.
A Study on the Collapse Mechanism of High Strength Concrete Columns Apply to Fiber-Cocktail
Authors: Kwon Ki Seok , Kim Heung Youl , Chae Seung Un , Cho Bum Yean
Published: August 2015

More high-rise structures are currently being constructed and correspondingly, the compressive strength of concrete has been increased. However, compared to conventional strength concrete the high strength concrete (HSC) exhibits coarse inner pore structure which blocks escape routes of vapour generated in the event of fire. This results in spalling and subsequently, are responsible for fire vulnerability of the structure. In addition, spalling phenomena is also affected by the section dimensions of HSC which is also another crucial factor from socio-economic considerations. Thus, this study was carried out to evaluate the fire resistance performance of hybrid fiber (i.e. steel-polypropylene-fibre)-reinforced HSC columns with different cross-section dimensions. The result of the fire resistance performance testing using 100MPa concrete showed that delay to failure was observed by approximately 76 per cent.
Experimental Study on Horizontal Shear Crack Control of Prestressed Corrugated Composite Beams
Authors: Chae Seung Un , Cho Bum Yean , Kweon Oh Sang , Kim Heung Youl
Published: August 2015

In case the structure is exposed to the high temperature, the lateral shear crack is the major cause exposing the steel bar to the high temperature and also the major cause of the collapse of buildings. In the study, in order to control the lateral shear crack, the presterssing using strands in a reverse direction of the lateral shear crack has applied and the fire resistance test of the PS corrugated web composite beam has been carried out, produced in a corrugated type of the steel to increase the efficiency of the prestressing. As a result of the test, the lateral shear crack introducing the PS has been reduced but it has been concluded that in case the strands are failed, the brittle failure can be taking place.
Radiation Induced Damage in Ductile Materials Subjected to Time-Dependent Stresses
Authors: Skoczeń Błażej , Ustrzycka Aneta
Published: August 2015

The problem undertaken in the present work concerns the kinetics of evolution of radiation induced damage under mechanical loads. Furthermore, coupling between the radiation induced nanodamage and the mechanically induced micro-damage is taken into account. The evolution of radiation induced damage is combined with the evolution of classical mechanically induced damage within the common framework of Continuum Damage Mechanics (CDM). Closed form analytical solutions for the problem of periodic irradiation combined with cyclic axial loads, corresponding to Rice & Tracey law was obtained.
Statistical Laws of Dynamic Fragmentation of ZrO2 Ceramics
Authors: Davydova Marina , Uvarov Sergey , Chudinov Vasiliy
Published: August 2015

Dynamic fragmentation of ceramic samples with different porosity were carried out using modified Hopkinson bar setup, which allow us to keep samples safe (in order to define fragment size distribution) and to measure fractoluminescence impulses occurred on the fracture surfaces (in order to establish the distribution of intervals between impulses). The analysis of experimental data reveals that the fragment size distribution and distribution of interval between fractoluminescence impulses obeys a power law, which exponent depends on ceramics porosity.
In Situ Dynamic Experiments and Modeling in Multiscale Kinetics of Damage-Failure Transition
Authors: Naimark Oleg
Published: August 2015

Scaling regularities that reveal the power law statistics of fragmentation and self-similarity of damage-failure transitions are linked to specific type of critical phenomena in ensembles of typical mesoscopic defects – structural-scaling transition. Taking into account nonlinearity of damage-failure transition the scaling effects were explained as the consequence of subjection of damage kinetics to the intermediate asymptotical (self-similar) solution. This solution has the nature of multiscale blow-up dissipative structures, represents the set of collective modes of defects responsible for the damage localization stage. Original in-situ experiments supported the assumption concerning the role of multiscale blow-up collective modes of defects in qualitative different scenario of dynamic crack propagation, failure of shocked materials, fragmentation statistics.
Evaluation of Cumulative Damage of RC Members under Repeated Impact Loading
Authors: Tamai Hiroki , Sonoda Yoshimi
Published: August 2015

In the civil and structural engineering field, there are so many problems regarding act of impact loading against some structures due to natural disaster. So it is important to evaluate the damage condition of them after impact loading, and to estimate the residual performance of them. This study is focused on a reinforced concrete (herein after called RC) structure such as caisson breakwater and rock-shed. In order to quantitatively evaluate the dynamic behavior and cumulative damage of RC members under low-velocity single and repeated impact loading, we conducted numerical approach by using the theory of Continuum Damage Mechanics (herein after called CDM). At the result, we clarified not only impact behavior of the members but also the relationship between cumulative kinetic energy of repeated impact loading and cumulative damage of the members. In addition, applicability limit of our model based on scalar damage modeling was clarified.
Influence of Specimen Geometry on Strain Localization Phenomena in Steel Sheets
Authors: Bao Chengheri , François Manuel , Le Joncour Léa
Published: August 2015

Strain localization in low carbon steel DC04 undergoing uniaxial tension is investigated by Electronic Speckle Pattern Interferometry (ESPI). The necking in the sheet specimens occurs by forming two narrow crossing bands. A model of strain rate distribution is used to extract quantitative information about the localization bands, such as bandwidths, bands orientations and their maximum strain rates. Thus, their evolutions are followed from the diffuse necking up to the rupture. The influence of specimen geometry on localization phenomenon is studied.
On the Use of the Generalized Eigenstrain Method in the Modeling of Coupling between Damage and Corrosion
Authors: Panicaud Benoit
Published: August 2015

The coupling between mechanical and chemical behaviors is investigated. The Generalized Eigenstrain Method is used and enables to take easily into account several couplings, such as damage and corrosion. Modeling is then performed and compared for different configurations. Chemical reactions and diffusion effects are thus described in order to improve accuracy of such a micromechanical time-dependent model. Application is then performed on a steel reinforced concrete material. Moreover, a particular and original coupling has been introduced, which is justified by thermodynamics arguments.
Multi-Phase Modelling of Concrete Affected by Sulfate Attack
Authors: Cefis Nicola , Comi Claudia
Published: August 2015

This study focuses on the modeling of damage in concrete subject to sulfate attack. The concrete is described as a multiphase material made of a solid skeleton, a fluid phase including water and air and an expanding phase, which exerts a pressure capable of damaging the concrete surrounding the reactive sites. The moisture content is computed through a simplified diffusion model, then a reactive-diffusion model allows for the computation of the expansive products of the reaction occurring between the aluminates of the cement paste and the incoming sulfate ions.
Influence of Alkaline Concentration on Physical Properties of Porous Geopolymer Using Silica Fume as Foaming Agent
Authors: Saikrasoon Anut , Jiemsirilers Sirithan , Laoratanakul Pitak
Published: August 2015

Porous geopolymer could be synthesized by using metakaolin and silica fume as foaming agent. The foam morphology was estimated in the function of water, silica fume content, and curing temperatures. Raw materials were mixed by Hobart mixer for 5 minutes and then poured in to cylinder mold after that cured at 70 degree celsius for 24 hours. During the synthesis process, the complex reaction would occur such as polycondensation and oxidation. These reactions affect to chemical and physical properties of porous sample. The parameters that mention above affect to density, physical, and chemical properties. The thermal conductivity of porous geopolymer that contained with 14 molal NaOH concentration yield the lowest values of 0.5101 W/mK and pore size distribution of 0.01-0.8 mm.Keywords: Porous geopolymer, thermal conductivity, metakaolin
Influences of Inhibitor and Firing Temperature on Efflorescence Reduction of Clay Products
Authors: Jindasuwan Sunisa , Chakornnipit Pim , Supothina Sitthisuntorn
Published: August 2015

For ceramic industry, efflorescence is undesirable and cannot be completely eliminated from the finished products. The efflorescence is caused by soluble salts in the raw material and mostly appears as white deposit at the product’s surface. In this research, the removal of sulfate in the raw materials was studied. In addition, the sulfate ions were immobilized by forming a water-insoluble compound. The sulfate ions in the raw materials and fired products were extracted by distilled water, and the concentration was determined by using a UV-visible spectroscopy following the ASTM C1580-09 standard. Three sources of the raw materials from Tambon Suan Phung, Ratchaburi, Tambon Mae Win and Mae Ta, Chiang Mai, were analyzed for sulfate concentrations. The clay from Tambon Suan Phung, Ratchaburi which had the highest sulfate concentration was selected for further study on the effect of inhibitor and firing temperature on efflorescence inhibition. To reduce solubility of the sulfate, three kinds of inhibitor, i.e. barium chloride, barium carbonate and barium hydroxide, were added into the raw material at various concentrations, i.e. 0.5, 1.0, 1.5 and 2.0 wt% and homogeneously mixed by ball milling followed by the addition of distilled water to prepare the clay slip. The clay products were mold casted to 1 x 1 x 3 inch3 in size. Then, they were fired at 800, 900 and 1000 °C. It has been revealed that the addition of barium carbonate at 2 wt%, which is the highest amount employed in this study, and firing temperature of 900 °C resulted in least sulfate leaching due to the formation of water-insoluble barium sulfate. To perform a field test, the fired samples with and without the addition of barium carbonate were immersed in water for 4 months. The efflorescence was observed on the sample without barium carbonate within the 1st month. In contrast, with the addition of barium carbonate, no efflorescence was observed after testing for 4 months.
Microstructure and Properties of Zirconia Toughened Alumina Fabricated by Powder Injection Moulding
Authors: Chuankrerkkul Nutthita , Charoenkijmongkol Rattanaporn , Somboonthanasarn Punnapa , Auechalitanukul Chiraporn , McCuiston Ryan C.
Published: August 2015

Zirconia toughened alumina (ZTA) ceramic has been fabricated by the powder injection moulding process. The ZTA ceramic, composed of 80 wt% alumina and 20 wt% zirconia, was mixed with a water-soluble, multi-component binder system. The binder ingredients were polyethylene glycol (PEG), polyvinyl butyral (PVB) and stearic acid (SA). Powder injection moulding was performed with powder loadings in the range of 48-52 vol%, using a laboratory-scale injection moulding machine. Water leaching was used for partial binder removal prior to thermal debinding and then sintering at 1650 °C for 2 hours. Microstructural examination of the ZTA ceramic revealed that zirconia inhibited alumina grain growth and, therefore, improved the mechanical and physical properties of the specimens. It was found that powder loading had an influence on density, hardness and strength of the specimens. A flexural strength of 334 MPa and hardness value of 2093 kg/mm2 was obtained from specimens injection moulded with 52 vol% powder loading feedstock. The highest sintered density achieved was 97% of the theoretical value.
Morphology and Phase Composition of Sol-Gel Derived Aluminum Borate Nanowhiskers
Authors: Sooksaen Pat
Published: August 2015

Aluminium borate nanowhiskers with varying aspect ratio were synthesized via sol–gel synthesis. The morphology of aluminum borate (Al4B2O9 and Al18B4O33) nanowhiskers could be controlled by varying the aluminum to boron (Al:B) molar ratio in the sol–gel derived precursors. Sintering temperatures (850 and 1100°C) and sintering times (4 and 32 hours) also affected the phase composition and size of the nanowhiskers. Citric acid was also added in the sol–gel derived precursors as a surface stabilizer for obtaining uniform finely dispersed nanostructures. Fine nanowhiskers were obtained by the calcination at 850°C, whereas higher temperature of 1100°C led to thicker and longer nanowhiskers and became rod-like crystals. The morphology and phase composition were investigated by field emission scanning electron microscope and X-ray diffraction. Chemical bond vibrations in the synthesized nanowhiskers were investigated by Fourier-transform infrared spectroscopy.
Metrodidazole In Situ Forming Eudragit RS Gel Comprising Different Solvents
Authors: Mahadlek Jongjan , Phaechamud Thawatchai
Published: August 2015

In situforming gel with solvent exchange mechanism is one of drug delivery systems for periodontitis treatment. The system is injected into the desired site then transforms into a gel state when the solvent diffuses out and aqueous diffuses in. Thein situforming Eudragit RSgels loading 1, 5 and 10%w/w metronidazole (MT) were developed in this study usingN-methyl pyrrolidone (NMP), 2-pyrrolidone and dimethyl sulfoxide (DMSO) as solvent. The viscosity of the gel systems in all solvents were increased as drug or polymer amount was increased with Newtonian flow behavior. Transformation into gel was evident after initiated the systems in phosphate buffer pH 6.8. NMP systems exhibited the lowest work of syringeability through 18 G syringe. Drug release from dialysis tube of DMSO systems was slower than that of NMP and 2-pyrrolidone systems, respectively. Antimicrobial activity againstStaphylococcus aureusof the systems comprising MT using NMP as solvent was greater than that using 2-pyrrolidone and DMSO, respectively, which the antimicrobial activity was increased as the drug amount was increased. Therefore, the solvent type affected the viscosity, gel formation, syringeability, drug release and antimicrobial activity of Eudragit RS systems. These developed systems sustained the drug release and inhibited the bacterial growth hence they were interesting systems for periodontitis treatment.
Preparation and Properties of PSZTM Ceramics with Different Methods
Authors: Boonruang Arjin , Ngernchuklin Piyalak , Daungdaw Saengdoen , Yongpraderm Nestchanok , Jeerapan Chalermchai
Published: August 2015

The PSZTM ceramics from Pb0.94Sr0.06(Zr0.52Ti0.48)O3doped with 0.1 mol% Mn were prepared by a solid state reaction and. Two different methods were used to calculate the amount of Mn-dopant into PSZT powder. One was calculated rely on B-site precursor represented byBmethod. The other was computed based on the amount of calcined PSZT calledCmethod. This study was to investigate the effect of the two different calculating formulations of Mn doped PSZT ceramics by B and C methods on phase formation, microstructure, physical and electrical properties. The results were observed that phase identification showed the formation of perovskite structure in both cases. Besides, the mechanical quality factor (Qm) of the PSZTM ceramics derived fromBmethod was two times higher than those fromCmethod. Nevertheless, the dielectric constant (K), piezoelectric coefficient (d33) and planar coupling coefficient (kp) of the PSZTM ceramics fromBmethod were slightly lower than those of derived fromCmethod. This could be drawn the conclusion that PSZTM with 0.1 mol% Mn prepared byBmethod can be used as hard-type piezoelectric material.
The Effect of Alumina/Glass Composite Composition on the Adhesion and Strength of a 96% Alumina Joint
Authors: Somton Kritkaew , Rodchom Mana , Dateraksa Kannigar , McCuiston Ryan C.
Published: August 2015

An alumina/glass composite was examined for use as a high-temperature ceramic adhesive for bonding of 96% alumina bodies. Four compositions of alumina and glass, 90:10, 80:20, 60:40, and 40:60 by wt.% were studied, referred to here as A, B, C, and D, respectively. Rectangular bend bars were produced from compositions A-D by die pressing. Two half-sized bend bars of 96% alumina were bonded together using pastes produced from compositions A-D. The sintering shrinkage, the phase analysis, the flexural strengths, and the fracture surfaces of the sintered bend bars were examined. The XRD analysis showed a decrease in the alumina and an increase in mullite as the glass content was increased. The dilatometric results found that the onset temperature for sintering shrinkage decreased as the glass content was increased. Composition C was found to have the highest flexural strength of 94 MPa, however the flexural strength of the adhesive joint sample, was only 36 MPa. Composition D had the lowest flexural strength of 43 MPa, but it had the highest flexural strength of the adhesive joint at 61 MPa. The increased adhesive strength of composition D could be due in part to penetration of the excess glass phase into the 96% alumina body. Therefore the flexural strength of the pure compositions alone could not be used to reliably predict the adhesive bond strength. The fracture surfaces of the adhesive joints showed increasing uniformity as the glass content increased, which indicated stronger adhesion.
Effect of Firing Temperature and Mo Doping on the Synthesis of Solar-Reflective Sm2Ce2O7 Yellow Pigment
Authors: Suwan Mantana , Sakchaikul Pantip , Yoriya Sorachon , Supothina Sitthisuntorn
Published: August 2015

Solar-reflective yellow pigment was synthesized by a solid-state reaction of the Sm2O3 and CeO2 in the presence of the (NH4)6Mo7O24 employed for the Mo doping. The raw materials were wet milled in acetone for 6 h to acheive a homogeneous slurry followed by calcination at 1100, 1300 and 1500 °C for 6 h. The effect of the Mo doping was investigated by adding 10, 15, 20, 25 and 30 wt.% (NH4)6Mo7O24. XRD analysis of the undoped product revealed the formation of Sm2Ce2O7 at 1300 °C along with the unreacted Sm2O3 and CeO2, and revealed the completed reaction at 1500 °C. The addition of (NH4)6Mo7O24 resulted in the formation of Sm2Ce2-xMoxO7+δ, where x = 0.02, 0.03, 0.04 and 0.05 depending on the amount of the Mo dopant employed. The doping also significantly affected the product’s color; it turned from ivory white to yellow with the increase of dopant content up to 20 wt.% and became dark green afterward. Increasing firing temperature from 1100 to 1500 °C led to brighter yellow due to the substitution of Mo6+ for Ce4+. At the optimum synthesis condition, i.e. 20 wt.% doping and 1500 °C firing temperature, the product was most yellowish and had 69.2 % near-infrared reflectance.
Comparison of Pyrolysis of Jatropha Cake with Different Catalysts Using PY-GC/MS
Authors: Jariyaphinyo Sirirak , Larpkiattaworn Siriporn , Chienthavorn Orapin
Published: August 2015

In this work, effect of different zeolite catalysts that reacted with jatropha cake residue to give pyrolysed products was studied. The products were separated and characterised by using pyrolysis gas chromatography-mass spectrometry (PY-GC/MS). A 4.0 mg of jatropha sample was put into the capsule sample holder of the pyrolysis-GC-MS instrument and the pyrolysis was performed at 500°C. Two separate experiments were carried out. In the first experiment the catalysts were Mordenite zeolite (30 mol/mol ratio of SiO2/Al2O3), Beta zeolite (37 mol/mol ratio of SiO2/Al2O3) and Pd/Al2O3. Each catalyst was mixed with jatropha cake with a ratio of 1:1 by weight. The jatropha cake pyrolysed with Mordenite zeolite gave the highest amount of aromatic hydrocarbons and the lowest amount of fatty acids than the products obtained from the other zeolites. In the second experiment, the amount of Mordenite zeolite was optimised for maximum production of aromatic hydrocarbon. The jatropha cake was mixed with increasing ratios of Mordenite zeolite of 1:2, 1:3 and 1:5 by weight. Improving the ratio of the zeolite increased the amount of aromatic hydrocarbon, while the yield of phenol and fatty acids components significantly decreased. To study the interrelation effect between two catalysts to the pyrolysis of jatropha cake, Mordenite zeolite and Pd/Al2O3, were mixed with different ratios of 1:1, 2:1 and 3:1 by weight, and the jatropha cake was pyrolysed with the mixed catalyst at the ratio of 1:1. Increasing the ratio of Mordenite zeolite in the mixed catalyst gave similar effect to those without Pd/Al2O3, except that the phenol component in the product reduced. To obtain the highest yield of desirable components, namely aromatic and aliphatic hydrocarbons, Mordenite zeolite was proved to be the most suitable catalyst with the ratio of 1:5 by weight.
Cu/ZnO Catalysts for Enhancing the Methanol Selectivity in Fischer-Tropsch Synthesis
Authors: Kongkinka Passakorn , Chatrewongwan Kittima , Saiwattanasuk Patraporn , Viravathana Pinsuda
Published: August 2015

Cu/ZnO catalysts were studied to enhance the methanol selectivity in Fischer-Tropsch synthesis (FTS). By knowing that the methanol production from syngas (CO/H2) accelerated the crystallization of Cu and ZnO and led to the deactivation of the catalysts, a small amount of iron added to the catalyst could improve the catalyst stability by suppressing the crystallization of Cu and ZnO. The promotional effects of iron on the textural properties, reduction behavior, and structural changes of the Cu-based FTS catalysts were investigated by X-ray diffraction (XRD), X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). Their catalytic activity was measured at 10 bar and 190°C with H2/CO ratio of 2 and the FTS products were analyzed by GC. The product distribution was presented in terms of methanol, C1, C2-C4, and C5+ selectivity.
Visible Light Driven Photocatalytic Hydrogen Evolution by Lanthanum and Carbon-co-Doped NaTaO3 Photocatalyst
Authors: Husin Husni , Mahidin  , Zuhra  , Hasfita Fikri , Yunardi
Published: August 2015

Lanthanum and carbon co-doped sodium tantalum oxide, La-C-NaTaO3, are prepared by incorporating lanthanum and carbon into NaTaO3 cluster via a sol-gel technique using a sucrose as carbon source. The La-C-NaTaO3 prepared sample is calcined at a temperature of 700 °C. Effects of carbon contents on the crystal, shape, optical absorption response and activity of hydrogen production of the sample are evaluated. The crystal of La-C-NaTaO3 is characterized by XRD analysis. The results show that the XRD pattern of the La C co-doped NaTaO3 is found to be crystalline phase with monoclinic structure. From the analysis of SEM images, the particle size of the prepared powder is about 40-200 nm. The optical response is examined by diffuse reflectance spectra (DRS). It is depicted that the absorption edge of La-C-NaTaO3 crystalline shift to higher wavelength. The extension to the visible light absorption edge became drastic with increasing carbon content in the sample. The photocatalytic activity of La-C-NaTaO3 is examined from water-methanol aqueous solution under visible light irradiation. It is found that the photocatalytic activity of La-C-NaTaO3 depend strongly on the doping content of C, and sample La-C-NaTaO3 shows the highest photocatalytic activity for the water reduction. The optimum amounts of carbon to maximize the hydrogen evolution rate is to be 2.5 mol %. The La-C-NaTaO3 catalyst has high activity of H2 evolution of 40.0 [μmol h-1] and long time stability under visible-light irradiation, suggesting a promising utilization of such photocatalyst. La C co-doped NaTaO3 photocatalyst can be developed further in order to produce hydrogen as a green energy.
Utilization of Waste Enamel Venus Shell as Friendly Environmental Catalyst for Synthesis of Biodiesel
Authors: Buasri Achanai , Sriboonraung Teera , Ruangnam Kittika , Imsombati Pattarapon , Loryuenyong Vorrada
Published: August 2015

Calcium oxide (CaO) is one of the most promising heterogeneous alkali catalysts since it is cheap, abundantly available in nature, and some of the sources of this compound are renewable (waste material consisting of calcium carbonate (CaCO3)). In this study, the waste enamel venus shell was used as the raw material for CaO catalyst. The calcination of bio-waste was conducted at 900 °C for 2 h. The raw material and the resulting CaO catalyst were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and the Brunauer-Emmett-Teller (BET) method. The effects of reaction variables such as reaction time, microwave power, methanol/oil molar ratio, and catalyst loading on the yield of biodiesel were investigated by gas chromatograph-mass spectrometry (GC-MS). From the experimental results, it was found that the CaO catalysts derived from waste material showed good catalytic activity (the conversion of oil of nearly 93%, a very similar catalytic activity with laboratory CaO) and had high potential to be used as biodiesel production catalysts in transesterification of Jatropha Curcas oil with methanol.
Treatment of Textile Dyeing Wastewater by Electrocoagulation
Authors: Chantes Phutthamon , Jarusutthirak Chalor , Kanchanapiya Premrudee , Danwittayakul Supamas
Published: August 2015

Industrial wastewater discharged into environments has been a serious and crucial problem, especially the wastewater from textile industry. It is one of the most harmful wastewaters due to their dark color, high COD and biotoxicity. Electrocoagulation is a technically easy, convenient and quick process that uses an electric field to neutralize the surface charges of contaminants in wastewater leading to coagulation and sedimentation. In this work, electrocoagulation (EC) process employed in the removal of dyes from real Batik wastewater was optimized. The optimum process conditions (∼60% color removal) for laboratory-scale were found to be: anode/cathode = Fe/Al, treatment time = 10 minutes, and electrode gap = 2cm with 30 kWh.m-3 of energy consumption.
Fabrication of Zeolite Na-A and Activated Carbon Composites by Slip Casting for Drinking Water Filtration
Authors: Tepamat Thanakorn , Wasanapiarnpong Thanakorn , Sujaridworakul Pornapa , Mongkolkachit Charusporn
Published: August 2015

Hybrid composite for drinking water filter aids were prepared by slip casting method. The slip was prepared from the mixture of 17.41% of zeolite Na-A, 17.41% of activated carbon, 0.35% of ZnO nanoparticles, 8.7% of phenolic resin, 0.54% carboxymethyl cellulose and 55.59% of reversed osmosis water. The slip was mixed in a high speed ball mill for 15, 30, 45 and 60 minutes and was then poured into plaster molds for 3 hours in order to maintain hollow casting. The green body was dried and fired at several of firing temperature of 600, 650, 700 and 750 °C. The major characteristics of the composite filter were characterized as: mechanical strength, morphology, pore diameter and ion exchange ability by three points bending, scanning electron microscopy (SEM), mercury porosimetry and inductive coupled plasma-optical emission spectroscopy (ICP-OES), respectively.
Homogeneous Precipitation Synthesis and Sintering of Magnesium Aluminate Spinel Nanoparticles
Authors: Serivalsatit Karn , Pornpatdetaudom Thanataon , Saelee Adison , Teerasoradech Sarut
Published: August 2015

A wide application of magnesium aluminate spinel powder has attracted a number of studies concerning the preparation of magnesium aluminate spinel powder. In this study, a precursor for magnesium aluminate spinel was synthesized by a homogeneous precipitation method using urea as a precipitant. The precursor and the calcined powders were characterized by X-ray diffractometry, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. After precipitation, the precursor was magnesium aluminium hydrate carbonate compound. By calcining, the precursor decomposed to MgO and an amorphous phase after calcining at 600°C. The formation of magnesium aluminate spinel via a reaction between MgO and the amorphous phase was observed after calcining over 800°C. The equiaxed magnesium aluminate spinel nanoparticles with particle size of 20-40 nm were obtained after calcining at 1100°C for 2 hours. Sinterability of the obtained magnesium aluminate spinel nanoparticles was also investigated by sintering compacts of magnesium aluminate spinel nanoparticles in the temperature interval of 1300-1650°C. Sintering temperature of 1600°C allowed the fabrication of dense magnesium aluminate spinel ceramics with relative density >95%.
Machined Surface Quality of Pre-Sintered Hardenable PM Steel
Authors: Khantisitthiporn Thawatchai , Morakotjinda Monnapas , Vetayanugul Bhanu , Tongsri Ruangdaj
Published: August 2015

The benefit of pre-sintered machining is to avoid machining difficulty of sintered parts especially hardenable PM steels. Pre-sintering treatments of green PM part at temperatures lower than the normal sintering temperature of 1120 °C result in green strength improvement high enough for machining. In this study, the influences of various pre-sintering temperatures and several machining conditions on machined surface quality of pre-sintered PM samples were investigated. The pre-sintered samples were machined by a turning process using a carbide cutting insert with varied cutting speeds at a fixed feed rate and depth of cut without cutting lubricant. Chromium alloyed PM steel (Astaloy® CrM) powder samples with (0.5 wt. %C) and without graphite (0 wt. % C) additions mixed with 1 wt. % of zinc stearate were prepared as green parts by cold compaction in a cylindrical die with diameter of 30 mm. Green density was about 7.00 g/cm3 and height of each sample was controlled by hydraulic pressure and powder weight of 80 g/sample. The green samples were treated by pre-sintering treatment before machining testing. Surface quality of each machined sample was evaluated by average surface roughness and surface texture by SEM analysis and the appearance of outlet edge breakout. The experimental results revealed that the pre-sintered samples with graphite addition showed better surface quality in terms of surface roughness and surface texture and small outlet edge breakout appearance. Moreover, at high pre-sintering temperatures of 900 and 1,000°C, the samples showed similar average surface roughness under the same turning conditions. The obtained surface textures were better than those of the samples pre-sintered at 700 and 800°C. The outlet edge breakout could not be found in the graphite-added samples pre-sintering at 1,000°C.
Microstructural and Phase Analysis of Service-Exposed Ni-Cr Alloy Turbine Blade
Authors: Hanafi Nuzul Hazwani Mohamad , Amrin Astuty
Published: August 2015

Ni-Cr superalloy has been widely used in turbomachinery equipments. Gas turbine blade made from Ni-Cr superalloys experience the effect of high temperature and stress during service which certainly cause various microstructural changes. It is found that the formation of spheroidal gamma prime (γ') phase replacing the cuboidal γ' phase and also the formation of M23C6 carbides along the grain boundaries. Numerous previous study has been conducted and reported that the microstructure of the turbine blade are being modified by service. This study involved assessing changes in blade microstructure and microhardness as a function of service time.
Sintered Titanium-Hydroxyapatite Composites as Artificial Bones
Authors: Moonchaleanporn Pongporn , Poolthong Nuchthana , Tongsri Ruangdaj
Published: August 2015

The design of engineered bone substitutes takes biocompatibility and mechanical compatibility into account as prerequisite requirements. Titanium (Ti) and hydroxyapatite (HA) with chemical formula of Ca10(PO4)6(OH)2, show good biocompatibility and are known as biomaterials. To combine metal powder (Ti) and ceramic powder (HA) as a composite material with mechanical properties comparable to those of natural bones needs strategy. In this work, powder metallurgy process was employed to produce Ti-HA composites, with nominal HA powder contents in the range of 0-100 vol.%. Mixtures of Ti and HA powders were pressed in a rigid die. Sintering was performed in vacuum atmosphere. The as-sintered specimens were tested on biocompatibility in a human-osteoblast cells. It was found that processing and materials parameters, including compaction pressure, control the composite microstructures and mechanical properties. Laboratory bone tissue culturing showed that a bone tissue could grow on the artificial bones (sintered Ti-HA composites).
Characterizations of Silicon Carbide Whisker-Filled in Benzoxazine-Epoxy Shape Memory Polymers
Authors: Likitaporn Chutiwat , Rimdusit Sarawut
Published: August 2015

Shape memory polymers (SMPs) are polymer materials that can fix the temporary shape and then recover to their original permanent shape by external stimulation, i.e. applied heat. In this research, shape memory polymer composites (SMPCs) from benzoxazine (BA-a)-epoxy binary systems reinforced with adamantine silicon carbide whisker (SiCw) are investigated. The SiCw contents are controlled to be in range of 0 to 15% by weight. All specimens were fabricated by compression molding technique. The results revealed that the shape memory polymer composites showed higher glassy state storage modulus with increasing amount of the whisker suggesting substantial reinforcement effect of the whisker used. The glass transition temperature (Tg) was also improved from 102°C of the based polymer to the value about 122°C with the addition of about 15% by weight of the silicon carbide whisker. Finally, shape recovery stress systematically increased from the value about 1.5MPa of the unfilled polymer matrix to the value about 3.2MPa with an addition of 15% by weight of the silicon carbide whisker. The positive effect on thermal stability from SiCw addition is expected from the modification and will be reported in this work.
Effect of Particle Sizes on Film Formation Behavior of Hevea brasiliensis Natural Rubber Latex
Authors: Churinthorn Nut , Nimpaiboon Adun , Sakdapipanich Jitladda , Ho Chee Cheong
Published: August 2015

Natural Rubber (NR) latex obtained from Hevea brasiliensis contains a wide particle size distribution. The aim of this study is to investigate the effect of small rubber particles (SRP) and large rubber particles (LRP) on the characteristics of film formation. The rubber particle with different mean diameters can be separated by centrifugation at various speeds to prepare SRP and LRP latex. The average size of SRP and LRP were characterized by light scattering technique to show that the size of SRP was in the range of 0.20 μm, while that of LRP was larger with the wide distribution. SRP and LRP latex were dried at room temperature to study the film formation behaviors. The results showed that the film compaction time increased with increasing the particle size of NR. Furthermore, the rubber film were aged at room temperature for 3 weeks in order to observe the surface morphology using atomic forced microscopy (AFM) by tapping mode. The AFM images showed that SRP readily formed a coalescence film, while LRP showed individual particles on the surface of film at 24 h of storage time. The surface of both SRP and LRP films was smoother after storage. However, LRP film still showed individual particles on the surface after 3 weeks of storage time.
Effect of Various Extracted Solvent on DPPH Radical Scavenging Activity of Natural Rubber
Authors: Siriwong Suwimon , Rungvichaniwat Adisai , Klinpituka Pairote
Published: August 2015

Four types of extracted solvents i.e. mixtures of chloroform:acetone, chloroform:methanol, cyclohexane:acetone and cyclohexane:methanol, in the volume ratio of 4:1 were used to dissolve the natural rubber. Two grades of natural rubber i.e. air dry sheet (ADS) and ribbed smoked sheet No.3 (RSS3) were investigated. The rubber solution was purified by separated the rubber out with methanol. The non-rubber solution was then quantitative analyzed to verify 2,2-diphenyl-1-picryhydrazyl (DPPH) radical scavenging activity using Oxicount-Antioxidant kit test and also calculated the term of half maximal effective concentration (EC50). The plasticity retention index (PRI) was also investigated in order to compare the ageing properties of the rubber and their antioxidant activity. Furthermore, various rubbers i.e. ADS, RSS3 and Standard Thai Rubber 20 (STR20) were collected during early period of yearly tapping seasons to analyze the DPPH radical scavenging activity and EC50. It was found that the mixture of cyclohexane and methanol showed the highest DPPH radical scavenging activity and lowest EC50. RSS3 showed higher DPPH radical scavenging activity than that of ADS which the higher antioxidant activity also displayed the higher PRI values. It also found that during the early period of yearly tapping seasons, DPPH radical scavenging activity of RSS3 was found higher than that of ADS and STR20, respectively when extracted by mixture of cyclohexane and methanol.
Functionalization of Styrene-Butadiene Rubber and Skim Latex by Photo-Catalytic Reaction Using Nanometric TiO2 Film as a Photocatalyst
Authors: Nijpanich Supinya , Nimpaiboon Adun , Sakdapipanich Jitladda
Published: August 2015

Functionalization of rubber latex is used to improve some weak properties. One method of functionalization is chemical modification by a photo-catalytic reaction. In this work, the functionalization of styrene-butadiene rubber (SBR) and skim latex were carried out under UV irradiation in the presence of TiO2 film, which was double spin-coated on a glass petri-dish, followed by calcination at 550°C. The structural characterization of functionalized rubber latex was analyzed by FTIR and NMR techniques. In the case of SBR latex, the hydroxyl group was observed after exposure to 80W of UV irradiation in the presence of H2O2 at concentration of 20% by weight of dry rubber. However, the gel formation derived from cross-linking as a side reaction obstructed the further characterization of microstructure and limited the applications of latex and solid rubber. In the case of skim latex, the effect of pH, H2O2 concentration and UV irradiation time were studied. It was found that the functionalization was successful after exposure to low power of UV irradiation for 1 h in the presence of H2O2 at concentration of 5-10% by weight of dry rubber. The weight-average molecular-weight (Mw) slightly decreased from 2x106 to 1x106 g/mol.