Grain Boundary Conformed Volumetric Mesh Generation from a Three-Dimensional Voxellated Polycrystalline Microstructure

We present a new comprehensive scheme for generating grain boundary conformed, volumetric mesh elements from a three-dimensional voxellated polycrystalline microstructure. From the voxellated image of a polycrystalline microstructure obtained from the Monte Carlo Potts model in the context of isotropic normal grain growth simulation, its grain boundary network is approximated as a curvature-maintained conformal triangular surface mesh using a set of in-house codes. In order to improve the surface mesh quality and to adjust mesh resolution, various re-meshing techniques in a commercial software are applied to the approximated grain boundary mesh. It is found that the aspect ratio, the minimum angle and the Jacobian value of the re-meshed surface triangular mesh are successfully improved. Using such an enhanced surface mesh, conformal volumetric tetrahedral elements of the polycrystalline microstructure are created using a commercial software, again. The resultant mesh seamlessly retains the short- and long-range curvature of grain boundaries and junctions as well as the realistic morphology of the grains inside the polycrystal. It is noted that the proposed scheme is the first to successfully generate three-dimensional mesh elements for polycrystals with high enough quality to be used for the microstructure-based finite element analysis, while the realistic characteristics of grain boundaries and grains are maintained from the corresponding voxellated microstructure image.     

Effect of Strain Aging on Tensile Behavior and Properties of API X60, X70, and X80 Pipeline Steels

The effect of strain aging on tensile behavior and properties of API X60, X70, and X80 pipeline steels was investigated in this study. The API X60, X70, and X80 pipeline steels were fabricated by varying alloying elements and thermomechanical processing conditions. Although all the steels exhibited complex microstructure consisting of polygonal ferrite (PF), acicular ferrite, granular bainite (GB), bainitic ferrite (BF), and secondary phases, they had different fractions of microstructures depending on the alloying elements and thermomechanical processing conditions. The tensile test results revealed that yielding behavior steadily changed from continuous-type to discontinuous-type as aging temperature increases after 1% pre-strain. After pre-strain and thermal aging treatment in all the steels, the yield and tensile strengths, and yield ratio were increased, while the uniform elongation and work hardening exponent were decreased. In the case of the X80 steel, particularly, the decrease in uniform elongation was relatively small due to many mobile dislocations in PF, and the increase in yield ratio was the lowest because a large amount of harder microstructures such as GB, BF, and coarse secondary phases effectively enhanced work hardening.     

Effect of oxide additives on the sintering behavior and electrical properties of strontium- and magnesium-doped lanthanum gallate

The effects of 14 different metal-oxide additives (metal = Mn, Fe, Co, Ni, Cu, B, Li, V, Zn, Si, Ca, Al, Bi, and Ba) on the sintering, phase purity, and electrical properties of strontium- and magnesium-doped lanthanum gallate (LSGM) are studied. The density, phase purity, and electrical conductivity depend closely on the sintering aids and sintering temperatures. The addition of V, Zn, Si, Co, and Fe improves the densification, phase purity, and electrical conductivity, with V showing the most promising effect on the low-temperature sintering of the phase-pure LSGM specimen with high conductivity.     

Preparation of poly-lactic acid nano/microparticles using supercritical anti-solvent with enhanced mass transfer

Supercritical anti-solvent precipitation with enhanced mass transfer (SAS-EM) was applied for the production of micro and sub-microparticles of poly-lactic acid (PLA). SAS-EM technique uses an ultrasonic vibrating surface to enhance mass transfer rate between supercritical CO₂ and solvent. Without applying ultrasonic power, which is same as SAS process, PLA particles with average diameters ranging between 1 μm and 3 μm were obtained. Using SAS-EM with the power supply of 200 W, spherical PLA particles smaller than 1 μm were obtained. The particle size was able to be controlled in the range of 0.4 μm–1.0 μm, by adjusting the power supply of ultrasonic field, the system pressure and temperature.     

Extraction of lanthanide ions from aqueous solution by bis(2-ethylhexyl)phosphoric acid with room-temperature ionic liquids

Extractions of five kinds of lanthanide metal ions by bis(2-ethylhexyl)phosphoric acid (DEHPA) with [1-Cn-3-methylimidazolium][PF₆](Cn = C₂, C₄) or [1-butyl-4-methylpyridinium][PF₆] were carried out under various DEHPA and HNO₃ concentrations from 0 to 1 M and under different temperature conditions from 298 to 333 K. These results were compared with those using the conventional organic solvent, hexane, in terms of their distribution coefficient values. Under all of the conditions in this study, the ionic liquid system shows more than three times greater extractability for lanthanide compared to when hexane was used. The distribution coefficient of lanthanide ions decreased as the length of the alkyl chain increased from the ethyl to the butyl. In addition, the imidazolium cation generally shows a higher distribution coefficient compared to the pyridinium cation in an ionic liquid. The concentration ratio of lanthanides and DEHPA resulted in an extraction affinity transition for lanthanides. Also evaluated in this study were issues related to the selectivity associated with the lanthanide mixture and the dependency of the ionic radius during lanthanide extraction.     

Synthesis of fluorene- and anthracene-based π-conjugated polymers and dependence of emission range and luminous efficiency on molecular weight

In the present work poly[9,9-dioctylfluorene-co-2-pentyl-9,10-bis(4-vinylphenyl)anthracene], a fluorene- and anthracene-based copolymer, is synthesized through a Heck coupling reaction. In order to synthesize polymers with high-molecular weight, DMF (P1), DMF/p-Xylene = 1/1 (P2), p-Xylene (P3), and 1,4-Dioxane (P4) are used as solvents, which are an important factor in the synthesis process. The number of average molecular weights (M_n) of the synthesized polymers P1–P4 do not differ significantly, standing at 22,309, 12,369, 29,192, and 39,464, respectively, while their weight average molecular weights (M_w) show considerable differences (i.e. 50,055; 24,042; 125,406; and 231,053). Polymers P1–P4 demonstrate little difference in the results of a thermal analysis, electrochemical analysis, UV–vis analysis, and photoluminescence (PL) spectrum measurement. With regard to electroluminescence (EL) spectrum measurement, however, P1 and P2 show main luminous peaks at 508 nm, while P3 and P4's luminous peaks are seen at 516 nm. Moreover, luminous shoulder peaks were red-shifted with increase of molecular weight of polymers from 460 to 544 nm. In this process, the luminous area is red-shifted from greenish-blue to yellowish-green. The I–V–L measurement results show that the maximum brightness of P1, P2, and P3 ranges from 164 to 303 cd/m² and their luminous efficiency is low at 0.031–0.054 cd/A. Meanwhile, the turn-on voltage of P4, having greater molecular weight, is 9.5 V, and its maximum brightness and corresponding luminous efficiency are 736 cd/m² and 0.08 cd/A, respectively, implying that the luminous efficiency of devices improves as the molecular weight becomes greater.     

NO presence effects on the reduction of N2O by CO over Al–Pd–Co oxide catalyst

Nitrous oxide (N₂O) is known as one of the greenhouse gases of which the emission levels are to be controlled and also an ozone-depleting material in the stratosphere. For more than a last couple of decades, various catalysts have been investigated for the reduction of N₂O emission. However, most of those catalysts require reaction temperatures as high as 450 °C even with the use of effective reducing agents. Furthermore, NO, which is usually present with N₂O, significantly interferes with the removal efficiency of N₂O. Al–Pd–Co oxide catalyst which is a type of mixed metal oxides (MMO) has shown 100% conversion of N₂O at temperatures as low as 200 °C using CO. This paper examines the effect of NO on the reduction of N₂O with CO over Al–Pd–Co oxide catalyst. The experiments were carried out in the temperature range of 100–500 °C with space velocity of 10,000–50,000 h^?1. Though the efficiency of N₂O reduction is decreased significantly when NO is present, the efficiency increases when sufficient CO is supplied. In this study, the reduction mechanisms of N₂O and NO by CO have been confirmed, and it was shown that MMO catalyst can simultaneously remove N₂O and NO using CO with high efficiency.     

Production of middle distillate through hydrocracking of paraffin wax over Pd/SiO2–Al2O3 catalysts

Pd/SiO₂–Al₂O₃ catalysts (Pd/SA-X) with different SiO₂ contents (X, wt%) were prepared for use in the production of middle distillate (C₁₀–C₂₀) through hydrocracking of paraffin wax. The effect of SiO₂ content of Pd/SA-X catalysts on their physicochemical properties and catalytic performance in the hydrocracking of paraffin wax was investigated. High surface area and well-developed mesopores of Pd/SA-X catalysts improved the dispersion of Pd species on the SiO₂–Al₂O₃ support. Acidity of Pd/SA-X catalysts determined by NH₃-TPD experiments showed a volcano-shaped trend with respect to SiO₂ content. Conversion of paraffin wax increased with increasing acidity of the catalyst, while selectivity for middle distillate decreased with increasing acidity of the catalyst. Yield for middle distillate showed a volcano-shaped curve with respect to acidity of the catalyst. This indicates that acidity of Pd/SA-X catalysts played an important role in determining the catalytic performance in the hydrocraking of paraffin wax. Among the catalyst tested, Pd/SA-69 with moderate acidity showed the highest yield for middle distillate.     

Structural estimation of particle arrays at air–water interface based on silica particles with well‐defined and highly grafted poly(methyl methacrylate)

Silica nanoparticles with well‐defined, highly grafted dense poly(methyl methacrylate) (MMA) were prepared by surface‐initiated activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) of methyl methacrylate with an initiator‐fixed silica particle in the presence of air. Two different polymerizations of MMA were carried out under the same conditions using tris[2‐(dimethylamino)ethyl]amine (Me₆TREN) and N,N,N′,N′,N″‐pentamethyldiethylene‐triamine (PMDETA) as the ligand, respectively. In the CuCl₂/PMDETA system, polymerization appeared to be more controlled with a lower polydisperisty compared with the CuCl₂/Me₆TREN system. The monolayer of these particles was formed at the air–water interface using Langmuir‐Blodgett (LB) technique. Multilayers of the particles were fabricated by repetition of LB depositing. A surface pressure–area (π–A) measurement and SEM observation were used to characterize the particle arrays. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Effects of film and substrate dimensions on warpage of film insert molded parts

Three‐dimensional flow and structural analyses were carried out for film insert injection molding to investigate warpage of film insert molded (FIM) parts with respect to variation of film and substrate thickness. Asymmetry of temperature distribution in the thickness direction was increased with increasing film thickness but decreased with increasing substrate thickness. Asymmetry of the in‐mold residual stress distribution in the FIM specimen was generated by the nonuniform temperature distribution, and it was increased with increasing film thickness but reduced with increasing substrate thickness. Warpage of the ejected FIM specimen was determined by relaxation of the asymmetric in‐mold residual stress distribution, and it was increased with increasing film thickness but reduced with increasing substrate thickness. Warpage of FIM specimens annealed at 80°C for 30 min showed complex behavior, and the behavior was understood by using factors such as degree of warpage of the ejected part, thermal shrinkage of the inserted film, and retardation of heat transfer. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers