Investigation of the fracture mechanism and mechanical properties of polystyrene/silica nanocomposite in various silica contents

There is limited research on the effect of silica on the mechanical properties of polystyrene. For this lack of information, this study has focused on the fracture mechanism and mechanical properties of Polystyrene/silica nanocomposite. Transmission electron microscopy showed proper dispersion of nanoparticles in PS matrix in both low and high filler loadings. Scanning electron microscopy, TOM micrography, and non-contact surface profiler were used to study the fracture surface and fracture mechanism characteristics of the nanocomposite. It seems that the debonding mechanism is an important mechanism in toughening of Polystyrene/silica nanocomposites. In addition, mechanical behavior of the samples was investigated. Tensile, flexural, and compressive strength and also impact and plain-strain fracture toughness of nanocomposite samples showed different behaviors in low and high nanoparticle loadings and interestingly, we found an optimum value less than 2% for nanoparticle loading in which we observed the highest improvement in mechanical properties of the nanocomposite.     

Failure analysis of a heat-resistant stainless steel ring in a gas turbine burner

Journal of Mechanical Science and Technology - Hot gas path components in gas turbines are damaged by several mechanisms due to aggressive environments. In this research, the cracking of an insert...     

Prediction of mass transfer coefficients in an asymmetric rotating disk contactor using effective diffusivity

Mass transfer characteristics have been investigated in a 113 mm diameter asymmetric rotating disk contactor of the pilot plant scale for two different liquid–liquid systems. The effects of operating parameters including rotor speed and continuous and dispersed phase velocities on the volumetric overall mass transfer coefficients are investigated. The results show that the mass transfer performance is strongly dependent on agitation rate and interfacial tension, but only slightly dependent on phase flow rates. In this study, effective diffusivity is used instead of molecular diffusivity in the Gr?ber equation for estimation of dispersed phase overall mass transfer coefficient.The enhancement factor is determined experimentally and there from an empirical expression is derived for prediction of the enhancement factor as a function of Reynolds number. The predicted results compared to the experimental data show that the proposed correlation can efficiently predict the overall mass transfer coefficients in asymmetric rotating disk contactors.     

FLUORO/NO: A Nitric Oxide Donor with a Fluorescence Reporter

Nitric oxide (NO) plays significant signalling roles in cells; the controlled generation of NO is of therapeutic relevance. Although a number of methods for the delivery and detection of NO are available, these events are typically mutually exclusive. Furthermore, the efficiency of delivery of NO can be compromised by detection technologies that consume NO. Here, we report FLUORO/NO, an esterase‐activated diazeniumdiolate‐based NO donor with an in‐built fluorescence reporter. We demonstrate that this compound is capable of enhancing NO within cells in a dose‐dependent manner, accompanied by a similar increase in fluorescence. The compatibility of this tool to study NO‐mediated signalling as well as NO‐mediated stress is demonstrated. FLUORO/NO is a convenient tool that shows NO‐like activity and allows monitoring of NO release. This tool will help interrogate the redox biology of NO.     

Facile synthesis,morphology and structure of Dy<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles through electrochemical precipitation

The aim of this research was to introduce a new, facile and simple method for synthesis of Dy₂O₃ nanostructures at room temperature. For the first time, galvanostatic electrodeposition was used to synthesize Dy₂O₃ particles, and the influence of the current density on the structure and morphology of the product was studied. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET). The results show that the current density has little effect on the chemical composition but great effect on the structure and morphology of the samples. The average size of the particles decreases as the applied current density increases. The grain size of as-prepared samples decreases from 500 to 70 nm when the current density increases from 0.5 to 6.0 mA·cm^?2. To obtain oxide product, the as-prepared samples were heat-treated at 1,000 °C. The results show that the heat-treated samples have smaller particles. The XRD results show that the similar patterns are observed in the samples synthesized at different current densities, and the only difference from the JCPDS card is the ratio of peak intensities. With the increase in the current density, a decrease in the current efficiency is observed.     

Effect of Structural Parameters on Drop Size Distribution in Pulsed Packed Columns

The effect of packing type on drop size distribution in pulsed packed columns was investigated by means of different columns and three packing types with three liquid systems including n‐butyl acetate, toluene, and kerosene with water. These liquid systems cover a wide range of interfacial tensions. Also the influence of operating variables in terms of pulse intensity and volumetric flow rates of dispersed and continuous phases was examined. Pulse intensity, interfacial tension, and packing shape were found as the main important factors for drop size distribution while volumetric flow rates had no significant effect. Correlations are presented to predict drop distribution and mean drop size in pulsed packed columns.     

Triple‐faced polypropylene: Fire retardant,thermally stable,and antioxidative

A halogen‐free nitrogen‐rich additive was used to make polypropylene (PP) prepared for three different missions: fire retardancy, thermal stability, and antioxidative properties. The prepared additive was composed of a cyclodextrin, a nanohydroxyapatite, and a poly[[6‐[(1,1,3,3,‐tetramethylbutyl)amino]‐1,3,5‐triazine‐2,4‐diyl][(2,2,6,6‐tetramethyl‐4‐piperidinyl)imino]‐1,6‐hexanediyl[2,2,6,6‐tetramethyl‐4‐piperidinyl)imino] (SABO®STAB) integrated into a unique molecule, namely, BSDH. Fire retardancy performance of BSDH in PP was compared with that of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) commercially available additive in terms of cone calorimeter results. Thermal stabilities of PP/BSDH and PP/DOPO composites were compared by changes observed in pyrolysis activation energy values measured in thermogravimetric analysis under nitrogen atmosphere at various heating rates. Flame retardancy of PP/BSDH composite was reflected in a drop in the peak of Heat Release Rate by ca. 31% with respect to neat PP. Very interestingly, the results show that BSDH additive retarded thermal oxidation of PP macromolecular chains when compared with DOPO commercially available flame retardant, as signaled by a rise in oxidation induction time value as well as an increased early‐stage activation energy needed for thermal decomposition of PP in the presence of BSDH. J. VINYL ADDIT. TECHNOL., 25:366–376, 2019. © 2019 Society of Plastics Engineers     

Effect of strain rate and ball milling of reinforcement on the compressive response of magnesium composites

Effect of strain rate change and reinforcement ball milling on the compressive response of Mg composites is investigated in this work. Quasi-static response was determined using a servo hydraulic MTS machine while dynamic response was assessed by Split Hopkinson Pressure Bar. The presence of either as-received or ball milled Al particles significantly assisted in improving compressive response of Mg in both regimes, compared to monolithic Mg. In the quasi-static regime, the Mg/1.626Al composite containing ball milled Al particles exhibits significantly higher compressive yield strength, ultimate compressive strength and work of fracture of (+76, +87% and +58%) compared to monolithic Mg. However, with a fixed amount of Al, composites containing ball milled particles show a higher strength compared to composites containing as-received particles. Results also revealed that the tremendous increase in strain rate led to an increase in flow stress of all synthesized material while the failure strain was marginally compromised.     

A novel compact dual-wideband BPF with multiple transmission zeros and super wide upper stopband

In this article, a novel miniaturised dual-wideband bandpass filter (DWB-BPF) based on two different resonators including a quasi-spiral loaded multiple-mode resonator (QSL-MMR) and L-shaped transmission line (LS-TL) is presented. At the first step, in order to design a single wideband BPF filter with controllable transmission zeros near the centre frequency, the open circuit impedance parameter of quasi-spiral loaded resonator Z₂₁ is determined in terms of ABCD matrix. Then an equivalent circuit model of the proposed structure is derived and the impedance characteristic and electrical length of LS-TLs to achieve a DWB-BPF with excellent selectivity are calculated through even- and odd-mode analysis. The proposed filter possesses both compact and simple structure as well as two wide passbands with fractional bandwidth (FBW) of 70% and 22.8% for its first and second passbands, respectively. The proposed technique creates two transmission zeros at the lower and upper stopbands of each passband resulting in a very sharp roll-off accompanied by a wide stopband. Notably, the circuit size is reduced and the bandwidth is enhanced in comparison with its conventional counterparts. The theoretical performance of the filter is verified by the experimental one where a good agreement is reported between them.     

Ag/Amberlyst 15: Novel Adsorbent for Removal of Iodide Compounds From the Acetic Acid Solution

A laboratory-scale fixed-bed adsorption system was used to evaluate the capability of various adsorbents for removing methyl iodide from the acetic acid solution. Ag/Amberlite IR 120, Dowex R W50-X8, as well as a new adsorbent namely Ag/Amberlyst 15 were implemented to evaluate their removal efficiencies. Effect of process parameters such as temperature, flow rate of acetic acid solution, and resin's silver content were investigated. The experimental results indicated that a significant improvement in iodide compound removal efficiency can be achieved by using Ag/Amberlyst 15. The results also showed that the removal efficiency was increased with increasing the temperature as well as the resin's silver content, while the flow rate of acetic acid solution had a negative effect on this efficiency. The maximum removal efficiency was found to be 99% at temperature 24.5°C, flow rate 5.73 BV/h, and with Ag/Amberlyst 15 92% silver impregnated.