Synthesis of aminated glycidyl methacrylate grafted rice husk and investigation of its anion‐adsorption properties

In this study, we focused on the synthesis, characterization, and adsorption capacity testing of aminated glycidyl methacrylate grafted rice husk (RH‐g‐GMA–Am). Our goal was to obtain a high‐performance surface for the adsorption of various anions. Glycidyl methacrylate grafted rice husk (RH‐g‐GMA) was prepared by the graft copolymerization of glycidyl methacrylate with rice husk; the product was further subjected to an amination reaction. The surface properties, sorption characteristic functional groups, isotherm and kinetic studies, pore diffusion models, and effects of the temperature and pH on the material properties were studied under batch conditions. The IR spectroscopy results show additional surface functional groups for RH‐g‐GMA–Am. The adsorptions of and on RH‐g‐GMA–Am were found to follow pseudo‐second‐order kinetics; this indicated a possible dominant role played by chemisorption. The rate‐limiting step for mass transfer was found to be boundary layer diffusion. Furthermore, the sorption isotherms for and fit the Langmuir model. The amination of RH‐g‐GMA drastically increased the removal efficiency from 3 to 82% and from 6 to 93% for and , respectively. Moreover, RH‐g‐GMA–Am exhibited a better removal efficiency in the pH range of 4–6.5. Regeneration studies revealed that the surface of RH‐g‐GMA–Am could be regenerated repetitively by simple acid washing with an insignificant decrease in the active surface for consecutive adsorptions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43002.     

Effects of K2O Evaporation on the Structural Properties of KSbO3 Compounds

A specimen having a stoichiometric composition of KSbO₃·(KSb) calcined at 800°C has an R rhombohedral structure (RS), and changes to a Pn cubic structure (CS) when calcined at 1100°C. Finally, a <111>‐oriented rhombohedral phase is formed in the specimen calcined at 1230°C. K/Sb ratio decreases from 1.0 in RS, 0.93 in CS, and finally to 0.85 in <111>‐oriented rhombohedral phases. On the other hand, a specimen having a K‐excess composition of K_1.1SbO₃ calcined at 800°C shows a RS that is maintained in the K‐excess specimen calcined at 1230°C. The composition of these specimens is very close to KSb. Therefore, the RS with a space group of R is a stable form of KSbO₃. The formation of Pn cubic and <111>‐oriented R phases can be explained by the evaporation of K₂O during the calcination process at temperatures above 1100°C.     

Structural and Piezoelectric Properties of (Na1−xKx)NbO3 Platelets and Their Application for Piezoelectric Nanogenerator

(Na_1?xK_x)NbO₃ (NKN) platelets synthesized at 600°C for 12 h have an Amm2 orthorhombic structure. However, the structure of NKN platelets synthesized at 500°C is a mixture of R3m rhombohedral and Amm2 orthorhombic structures. The formation of a rhombohedral structure is attributed to the presence of OH^? and H₂O defects in the NKN platelets. The piezoelectric strain constant (d₃₃) of NKN platelets synthesized at 600°C for 12 h is 100 pmV^?1, whereas that of NKN platelets synthesized at 500°C is lesser (50 pmV^?1) due to the presence of these defects. Piezoelectric nanogenerators (PNGs) are fabricated using composites consisting of NKN platelets and polydimethylsiloxane. A large output voltage of 25 V and output current of 2.7 μA were obtained for the PNG with NKN platelets synthesized at 600°C for 6 h. This PNG shows a high output electrical energy of 3.0 μW at an external load of 5.1 MΩ.     

Identification of cell‐nucleation mechanism in foam injection molding with gas‐counter pressure via mold visualization

The mechanisms of cell nucleation and growth are investigated in foam injection molding (FIM) using gas‐counter pressure (GCP). An in‐situ mold visualization technique is employed. The application of GCP suppresses cell nucleation, and prevents the blowing agent from escaping during mold‐filling. The inherent structural heterogeneity in the regular FIM can be improved because of the uniform cavity pressure when employing GCP. The cavity pressure profiles show much faster pressure‐drop rates using GCP, because the single‐phase polymer/gas mixture has a lower compressibility than the two‐phase polymer/bubble mixture. Therefore, both the cell nucleation and growth rates are significantly increased through a higher pressure‐drop rate on the removal of the GCP. The effect of GCP magnitude on the cell morphology is explored. When the GCP is lower than the solubility pressure, bimodal foaming occurs. As the GCP increases above the solubility pressure, the cell density increases because of the higher pressure‐drop rate. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4035–4046, 2016     

Effect of Sintering Temperature on Thermoelectric Properties of p‐Bi2Te3 Alloys Produced by Gas Atomization

In this research, p‐type Bi₂Te₃–75% Sb₂Te₃ thermoelectric alloy powders were produced by gas atomization and subsequently sintered by hot pressing at different temperatures. The grain growth of the hot‐pressed samples was observed with increasing sintering temperature from 380°C to 460°C. The compressive strength increased with increasing hot‐pressing temperature due to the high relative density of bulk samples obtained at high temperatures. The effect of sintering temperature on thermoelectric (TE) properties was studied. The maximum power factor 3.48 mW/mK² was obtained for the sample hot pressed at 420°C due to the resulting high electrical conductivity and enhanced Seebeck coefficient values.     

Mechanical Properties of Submicrometer‐Grained Transparent Yttria Ceramics by Hot Pressing with Hot‐Isostatic Pressing

Here, we report the fabrication and mechanical properties of submicrometer‐grained (0.29–0.58 μm) transparent yttria ceramics by hot pressing combined with hot‐isostatic pressing. The effects of the grain size on the microhardness and the fracture toughness were studied. An unusual decrease of the fracture toughness with an increase in the grain size was revealed, which may be attributed to the different grain size dependence of the fracture behavior of the ZrO₂‐doped yttria ceramics compared to that of other yttria ceramics. The microhardness and fracture toughness of the transparent yttria ceramics were found to be better than those of the large‐grained yttria ceramics.     

The shrinkage properties of red pine wood assessed by image analysis and near-infrared spectroscopy

This work focused on the shrinkage and drying stress of red pine (Pinus densiflora) wood during kiln drying and investigated transverse shrinkage and moisture changes in thin specimens using digital image analysis and near-infrared spectroscopy, respectively. The effect of specimen thickness, which ranged from 1 to 10?mm on shrinkage, was analyzed under drying conditions with restrained stresses. The shrinkage due to moisture content was presented in the form of an exponential function and a linear function above and below the fiber saturation point, respectively. A shorter existence of the moisture gradient increased the transverse shrinkage. The tangential and radial shrinkage at the tissue level in 30-µm (longitudinal) thick slices was measured and compared with the shrinkage of above specimens with difference thicknesses. The transverse shrinkage of 1-mm-thick specimen is similar to the shrinkage measured using 30-µm-thick slice.     

Application of Gurson Model for Evaluation of Density‐Dependent Mechanical Behavior of Polyurethane Foam: Comparative Study on Explicit and Implicit Method

Recently, liquefied natural gas (LNG) is a focus of interest around the world for several reasons, and LNG cargo containment systems (CCS) increase in quality to prevent loss of LNG during shipping. For insulation of CCS, polyurethane foam (PUF), an outstanding insulation material, is commonly used. However, until now, although its mechanical properties are relatively good, the material is not considered as a structural member under compressive loading, principal load direction in CCS. Moreover, as PUF is a porous material by mixing and foaming, its mechanical properties depend on voids, which is a dominant parameter for density. Therefore, in the present study, nonlinear behavior of PUF is described using Gurson model with a novel technique, i.e., an acceleration factor. The model expresses the behavior through the volume fraction of voids with consideration of the density effect to evaluate structural performance using user‐defined material subroutine with explicit and implicit methods.