Tuning the curing behavior of fluoroelastomer (FKM) by incorporation of nitrogen doped graphene nanoribbons (CNx-GNRs)

Graphene nanoribbons (GNRs), obtained by different methods from carbon nanotubes (CNTs) or graphene, are attractive materials for polymer nanocomposites due to their considerably high interfacial area, as compared to CNTs. Consequently, a better adhesion with a polymer matrix is anticipated for GNRs. Also, surface modification of these nanofillers, such as nitrogen doping, is known to be an efficient method to improve their properties. In this work, fluoroelastomers (FKM) were used as the polymer matrix to host GNRs. Undoped and nitrogen doped GNRs were synthesized from the parent multiwall carbon nanotubes (MWCNTs). MWCNT/FKM and GNR/FKM nanocomposites were prepared via a solution mixing/melt mixing protocol.     

Economic and air pollution effects of city council legislations on renewable energy utilisation in Tehran

Regarding the application of renewable energies, their infiniteness and no pollutant production are two important reasons for the universal acceptance. In this issue, calculation of the initial capital cost and the payback time are of crucial importance. Considering the significance of air pollution problem in the metropolis of Tehran and its related challenges, the Iranian government has been required to apply renewable sources. This research deals with the investigation of environmental and economic aspects, implementation of Tehran City Council Legislation (TCCL) considering the provision of 10–20% of required energies from new energies in buildings which were given permission in 2014. A large amount of the energy is consumed for different purposes such as water heating and to provide this need, a solar water heater (SWH) can be applied. In fact, by implementation of TCCL, the annual profit obtained by exporting extra natural gas to the neighbouring countries is 210,939.25$, which is a result of preserving 421,878.5?m³ natural gas. Furthermore, production of pollutants such as CO₂, SO₂, and NO_x reduced by 3045.40, 14.540, and 11.111 tons, respectively. Hence, reduction of environmental costs was calculated as 150,956.25$. Eventually, calculation of payback time for implementing SWH was obtained as 17 months.     

Enhancement of discharged energy density of poly(ethylene oxide) by soy protein isolate

Soy protein isolate (SPI) is used to modify energy storage performances of poly(ethylene oxide) (PEO). The pure PEO membranes are highly polar, but the extremely high energy loss led to very low discharged energy density for use. The addition of SPI in both high molecular weight PEO and low molecular weight PEO lead to greatly reduced polarization and stored energy density. However, it also largely reduces the current leakage and energy loss of the resulting membranes, leading to significantly enhanced discharged energy density. It is believed that the strong interactions between PEO and SPI are responsible for the energy storage properties aforementioned. Meanwhile, such interactions also result in a more brittle fracture behavior and reduced crystallinity of the PEO/SPI membranes. The enhanced discharged energy density and low energy loss suggest PEO/SPI membranes are promising dielectric materials for high efficiency energy storage applications where soluble and transient materials are desired. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45214.     

Effect of Low Concentration Sn Doping on Optical Properties of CdS Films Grown by CBD Technique

Thin and transparent films of doped cadmium sulfide (CdS) were obtained on commercial glass substrates by Chemical Bath Deposition (CBD) technique. The films were doped with low concentration of Sn, and annealed in air at 300 °C for 45 min. The morphological characterization of the films with different amounts of dopant was made using SEM and EDAX analysis. Optical properties of the films were evaluated by measuring transmittance using the UV-vis spectrophotometer. A comparison of the results revealed that lower concentration of Sn doping improves transmittance of CdS films and makes them suitable for application as window layer of CdTe/CIGS solar cells.     

Probing metabolic stability of CdSe nanoparticles: alkaline extraction of free cadmium from liver and kidney samples of rats exposed to CdSe nanoparticles

Cadmium selenide nanoparticles (CdSe NPs) exhibit novel optoelectronic properties for potential biomedical applications. However, their metabolic stability is not fully understood because of the difficulties in measurement of free Cd from biological tissues of exposed individuals. In this study, alkaline dissolution with tetramethylammonium hydroxide (TMAH) is demonstrated for selective determination of free Cd and intact NPs from liver and kidney samples of animals that were exposed to thiol-capped CdSe NPs. Aqueous suspensions of CdSe NPs (3.2 nm) were used to optimize the conditions for extracting free Cd without affecting NPs. Nanoparticles were found to aggregate when heated in TMAH without releasing any significant Cd to solution. Performance of the method in discriminating free Cd and intact NPs were verified by Dogfish Liver (DOLT-4) certified reference material. The samples from the animals were digested in 4 mL TMAH at 70 °C to extract free Cd followed by analysis of aqueous phase by ICP-MS. Both liver and kidney contained significant levels of free Cd. Total Cd was higher in the liver, while kidney accumulated mostly free Cd such that up to 47.9% of total Cd in the kidney was free Cd when NPs were exposed to UV-light before injection.     

Enhanced Hilbert–Huang transform and its application to modal identification

The well‐known Hilbert–Huang transform (HHT) consists of empirical mode decomposition to extract intrinsic mode functions (IMFs) and Hilbert spectral analysis to obtain time–frequency characteristics of IMFs through the Hilbert transform. There are two mathematical requirements that limit application of the Hilbert transform. Moreover, noise effects caused by the empirical mode decomposition procedure add a scatter to derivative‐based instantaneous frequency determined by the Hilbert transform. In this paper, a new enhanced HHT is proposed in which by avoiding mathematical limitations of the Hilbert spectral analysis, an additional parameter is employed to reduce the noise effects on the instantaneous frequencies of IMFs. To demonstrate the efficacy of the proposed method, two case studies associated with structural modal identification are selected. In the first case, through identification of a typical 3‐DOF structural model subjected to a random excitation, accuracy of the enhanced method is verified. In the second case, ambient response data recorded from a real 15‐story building are analyzed, and nine modal frequencies of the building are identified. The case studies indicate that the enhanced HHT provides more accurate and physically meaningful results than HHT and is capable to be an efficient tool in structural engineering applications. Copyright © 2012 John Wiley & Sons, Ltd.     

Investigating the acoustical properties of carbon fiber‐, glass fiber‐, and hemp fiber‐reinforced polyester composites

Wood is one of the main materials used for making musical instruments due to its outstanding acoustical properties. Despite such unique properties, its inferior mechanical properties, moisture sensitivity, and time‐ and cost‐consuming procedure for making instruments in comparison with other materials (e.g., composites) are always considered as its disadvantages in making musical instruments. In this study, the acoustic parameters of three different polyester composites separately reinforced by carbon fiber, glass fiber, and hemp fiber are investigated and are also compared with those obtained for three different types of wood specimens called poplar, walnut, and beech wood, which have been extensively used in making Iranian traditional musical instruments. The acoustical properties such as acoustic coefficient, sound quality factor, and acoustic conversion factor were examined using some non‐destructive tests based on longitudinal and flexural free vibration and also forced vibration methods. Furthermore, the water absorption of these polymeric composites was compared with that of the wood samples. The results reveal that the glass fiber‐reinforced composites could be used as a suitable alternative for some types of wood in musical applications while the carbon fiber‐reinforced composites are high performance materials to be substituted with wood in making musical instruments showing exceptional acoustical properties. POLYM. COMPOS., 35:2103–2111, 2014. © 2014 Society of Plastics Engineers     

Chemical vapor deposition synthesis of graphene on copper with methanol, ethanol, and propanol precursors

Large area, high quality graphene was synthesized from different liquid alcohols by chemical vapor deposition on copper foils in a tube furnace. The quality of the synthesized graphene was systematically investigated with various growth conditions. Alcohol vapor exposure times of 5 min and an average growth temperature of 850 °C yield continuous graphene monolayer films, as inferred from Raman spectroscopy. X-ray photoelectron spectroscopy shows that the oxygen moieties found in the source molecules have no measureable doping or oxidation effect in the synthesized graphene. Raman spectroscopy indicates that graphene films transferred to insulating substrates are of high quality. The field effect mobility of large area graphene transistors was measured at room temperature to be in the range 1800–2100 cm²/V s at carrier densities between 10¹¹/cm² and 10¹²/cm².