Experimental and Numerical Investigations on Softening Behavior of POM Under Cyclic Strain-Controlled Loading

In this paper, cyclic stress-strain behavior of POM was studied. Fatigue tests were carried out under symmetric uniaxial strain-controlled mode. In this case of loading conditions the material exhibited cyclic softening and with the increase of strain amplitude the total number of cycles to failure reduced dramatically. Additional fatigue tests were further performed under non-symmetrical uniaxial cyclic loading where specimens exhibited relaxation behavior and mean stress reached a zero value in continuous cycles. Experimental tests were performed using an INSTRON 8802 servo-hydraulic machine and the results obtained from the experiments were compared with numerical results. The numerical analysis was carried out by ABAQUS software using the following advanced plasticity models based on Von Mises criterion: isotropic hardening, linear kinematic hardening, and non-linear isotropic/kinematic hardening.     

Synthesis and application of amine functionalized silica mesoporous magnetite nanoparticles for removal of chromium(VI) from aqueous solutions

In this research, novel nanoparticles of Kit-6 mesoporous silica magnetite were synthesized with 9.6 nm pore diameter and 241.68 m² g^?1 surface area. The synthesized mesoporous magnetite nanoparticles (MMNPs) were functionalized with amine groups. Scanning electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy and nitrogen adsorption–desorption method confirmed the morphology and structure of the synthesized nanoparticles. The amine functionalized MMNPs were used for sorption of toxic chromate ions from aqueous samples. The effect of various experimental parameters (four factors at three levels) on the sorption efficiency of Cr(VI) was studied and optimized via Taguchi L₉ (3⁴) orthogonal array experimental design. At optimum conditions, the sorption of the Cr(VI) was best described by a pseudo second-order kinetic model with R² = 0.9999 and q_eq = 129.8 mg g^?1, suggesting chemisorption mechanism. Adsorption data were fitted well to the Langmuir isotherm and the synthesized sorbent showed complete ion removal with 185.2 mg g^?1sorption capacity.     

Three-Dimensional Simulation of Rolling Contact Fatigue Crack Growth in UIC60 Rails

In this article, a UIC60 rail with accurate geometry is studied by employing the finite element method. For this purpose, a three-dimensional elastic-plastic finite element model is conducted using model. In addition, the stress distribution of wheel-rail operation is acquired, and its effects on fatigue life are specified by damage mechanic methods. In the finite element model, the displacements and stress intensity factors (SIFs) are computed on the crack near the leading edge to calculate crack propagation trajectories and crack growth rate. The modified Paris model is used to estimate fatigue crack growth rates.     

一种新γ相氧化铝负载的铁铝双金属催化剂用于反向水煤气转化反应(英文)

In reverse water gas shift (RWGS) reaction CO₂ is converted to CO which in turn can be used to produce beneficial chemicals such as methanol. In the present study, Mo/Al₂O₃, Fe/Al₂O₃ and Fe-Mo/Al₂O₃ catalysts were synthesised using impregnation method. The structures of catalysts were studied using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, inductively coupled plasma atomic emission spectrometer (ICP-AES), temperature programmed reduction (H₂-TPR), CO chemisorption, energy dispersive X-ray (EDX) and scanning electron microscopy (SEM) techniques. Kinetic properties of all catalysts were investigated in a batch reactor for RWGS reaction. The results indicated that Mo existence in structure of Fe-Mo/Al₂O₃ catalyst enhances its activity as compared to Fe/Al₂O₃. This enhancement is probably due to better Fe dispersion and smaller particle size of Fe species. Stability test of Fe-Mo/Al₂O₃ catalyst was carried out in a fixed bed reactor and a high CO yield for 60 h of time on stream was demonstrated. Fe₂(MoO₄)₃ phase was found in the structures of fresh and used catalysts. TPR results also indicate that Fe₂(MoO₄)₃ phase has low reducibility, therefore the Fe₂(MoO₄)₃ phase signifificantly inhibits the reduction of the remaining Fe oxides in the catalyst, resulted in high stability of Fe-Mo/Al₂O₃ catalyst. Overall, this study introduces Fe-Mo/Al₂O₃ as a novel catalyst with high CO yield, almost no by-products and fairly stable for RWGS reaction.     

Phyto‐fabrication,purification, characterisation,optimisation, and biological competence of nano‐silver

Published studies indicate that virtually any kind of botanical material can be exploited to make biocompatible, safe, and cost‐effective silver nanoparticles. This hypothesis is supported by the fact that plants possess active bio‐ingredients that function as powerful reducing and coating agents for Ag+. In this respect, a phytomediation method provides favourable monodisperse, crystalline, and spherical particles that can be easily purified by ultra‐centrifugation. However, the characteristics of the particles depend on the reaction conditions. Optimal reaction conditions observed in different experiments were 70–95 °C and pH 5.5–8.0. Green silver nanoparticles (AgNPs) have remarkable physical, chemical, optical, and biological properties. Research findings revealed the versatility of silver particles, ranging from exploitation in topical antimicrobial ointments to in vivo prosthetic/organ implants. Advances in research on biogenic silver nanoparticles have led to the development of sophisticated optical and electronic materials with improved efficiency in a compact configuration. So far, eco‐toxicity of these nanoparticles is a big challenge, and no reliable method to improve the toxicity has been reported. Therefore, there is a need for reliable models to evaluate the effect of these nanoparticles on living organisms.     

Odorless,convenient and one-pot synthesis of thioethers from organic halides and thiourea

This review summarizes the most important advances in the synthesis of thioethers via the reaction of organic halides with thiourea as an odorless and nontoxic sulfur source during the period 2005 to May 2018. The reactions have been classified based on the type of catalysts.     

A selective catalyst for methanol conversion into light olefin with a high propylene to ethylene ratio

MSU-S catalyst, assembled from ZSM-5 zeolite seed (MFI), was synthesized with silica to alumina ratio 55 and characterized by XRD, NH3-TPD, BET and FT-IR techniques. It was tested in a vertical fixed bed reactor for selective production of light olefins from methanol (MTO) at temperatures of 400, 450 and 500 °C and WHSV of 1, 5 and 25 h^?1. After thorough investigation, it was found that WHSV=5 h^?1 and temperature of 500 °C are the optimum conditions for maximum light olefin yield, which was 52% with propylene to ethylene ratio of 4.57. Acidity of MSU-S was promoted by incorporation of phosphotungusticacid (HPW) and a direct method to reach high HPW dispersion and thermal stability. Maximum light olefin yield was observed over HPW-MSU-S at the optimum reaction conditions to be nearly 60% with propylene to ethylene ratio of 4.3.     

A Novelγ-Alumina Supported Fe-Mo Bimetallic Catalyst for Reverse Water Gas Shift Reaction

In reverse water gas shift (RWGS) reaction CO2 is converted to CO which in turn can be used to pro-duce beneficial chemicals such as methanol. In the present study, Mo/Al2O3, Fe/Al2O3 and Fe-Mo/Al2O3 c...