Nanofiltration membrane cross‐linked by m‐phenylenediamine for dye removal from textile wastewater

In this work, m‐phenylenediamine (MPD) is used to prepare cross‐linked polyetherimide (PEI)‐based nanofiltration (NF) membrane for treatment of dye containing wastewater. The effects of dope solution composition, cross‐linking time, and dye concentration on membrane performance are investigated. Results indicate that the rejection of dye is increased with the increase of acetone concentration in the dope solution, cross‐linking time, and dye concentration. Meanwhile, membrane flux showed the opposite trend. With the aid of SEM and FTIR analysis, the cross‐linking between MPD and PEI is confirmed. The cross‐linked membrane has thicker and dense selective layer compared to the unmodified membrane. The cross‐linked NF membrane (PEI: 15 wt%; acetone: 20 wt%; cross‐linking time: 10 minutes) showed good performance in filtration of synthetic dye wastewater (Reactive Red 120, 1500 ppm) with 98% dye rejection and 0.013 L m^?2 hour^?1 of flux at relatively low operating pressure (60 psi).     

ToF‐SIMS observation of PTFE surfaces modified by α‐particle irradiation

The surface structure of polytetrafluoroethylene (PTFE) upon α‐particle irradiation has been investigated at doses in the range of 1 × 10⁷ to 1 × 10¹¹ Rad and compared with the surface structure of the unirradiated polymer. Both neat and 25% fiberglass content PTFE were studied. The samples, maintained at nominal room temperature, were irradiated in vacuum by 5.5 MeV ⁴He²⁺ ions generated in a tandem accelerator beam line. Static time‐of‐flight SIMS (ToF‐SIMS) was employed to probe chemical changes at the surface as a function of the irradiation level. In general, the data are indicative of increased cross‐linking at α‐doses less than 1 × 10⁹ Rad, followed by increased fragmentation and unsaturation at α‐doses greater than 1 × 10⁹ Rad. Throughout the irradiation regime, scission is a constant factor promoting cross‐linking, branching, and unsaturation. However, at α‐doses greater than 1 × 10¹⁰ Rad, extreme structural degradation of the polymer becomes evident and is accompanied by conversion to oxygen‐functionalized and aliphatic compounds. Thus, for PTFE in an α‐particle field, an upper exposure limit of ～10¹⁰ Rad is essential for nominal retention of molecular structure. Finally, a quantitative relationship between α‐dose and characteristic fragment ion intensity is developed. Copyright © 2005 John Wiley & Sons, Ltd.     

100 keV H+ ion irradiation of as‐deposited Al‐doped ZnO thin films: An interest in tailoring surface morphology for sensor applications

We report the influence of 100 keV H⁺ ion beam irradiation on the surface morphology, crystalline structure, and transport properties of as‐deposited Al‐doped ZnO (Al:ZnO) thin films. The films were deposited on silicon (Si) substrate by using DC sputtering technique. The ion irradiation was carried out at various fluences ranging from 1.0 × 10¹² to 3.0 × 10¹⁴ ions/cm². The virgin and ion‐irradiated films were characterized by X‐ray diffraction, Raman spectroscopy, atomic force microscopy, and Hall probe measurements. Using X‐ray diffraction spectra, 5 points Williamson‐Hall plots were drawn to deduce the crystallite site and strain in Al:ZnO films. The analysis of the measurements shows that the films are almost radiation resistant in the structural deformation under chosen irradiation conditions. With beam irradiation, the transport properties of the films are also preserved (do not vary orders of magnitude). However, the surface roughness and the crystallite size, which are crucial parameters of the ZnO film as a gas sensor, are at variation with the ion fluence. As ion fluence increases, the root‐mean‐square surface roughness oscillates and the surface undergoes for smoothening with irradiation at chosen highest fluence. The crystallite size decreases initially, increases for intermediate fluences, and drops almost to the value of the pristine film at highest fluence. In the paper, these interesting experimental results are discussed in correlations with ion‐matter interactions especially energy losses by the ion beam in the material.     

Synthesis and characterization of poly (1‐vinyl‐3‐butylimidazolium‐co‐methyl methacrylate) gel polymer electrolytes for dye‐sensitized solar cells: Effect of structure and composition

Herein, three ionic liquid random copolymers (P) containing 1‐vinyl‐3‐butylimidazolium bromide (VBImBr) and methyl methacrylate (MMA) with various molar ratios were prepared using conventional free radical polymerization. Afterward, their corresponding chemically cross‐linked copolymers (XP) were formed similarly in the presence of polyethylene glycol dimethacrylate (PEGDMA). The synthesized copolymers were characterized using FT‐IR, ¹H NMR, and GPC. Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) results showed that the rigidity and thermal stability of the copolymers depended on the ionic liquid content as well as the degree of cross‐linking. Gel polymer electrolytes were then prepared via obtained copolymers in the presence of a constant amount of synthesized imidazolium‐based ionic liquid. Among the copolymers, the P3 with in feed VBImBr:MMA molar ratio of 70:30 and the cross‐linked 1%‐XP3 copolymer prepared with 1 mol% of PEGDMA exhibited the highest conductivity and diffusion coefficients for I₃^¯ and I^¯. The power conversion efficiency of the optimized linear and cross‐linked copolymers (P3 and 1%‐XP3) under the simulated AM 1.5 solar spectrum irradiation at 100 mW cm^?2 were 3.49 and 4.13% in the fabricated dye‐sensitized solar cells (DSSCs), respectively. The superior long‐term stability and high performance of the gel electrolyte containing 1%‐XP3 suggested it as commercial gel electrolyte for future DSSCs.     

Molecular modification of slightly cross‐linked HDPE: comparison of electron beam irradiation and peroxide treatments

The aim of this study is to investigate the changes in molecular structure of high density polyethylene after slightly cross‐linking with either electron beam irradiation or chemically with the peroxide method, by examining both the gel and sol parts of the polymer. Melt flow index and dynamic mechanical thermal analysis tests verify the cross‐linking process after each treatment method. Differential scanning calorimetry and Fourier transformed infrared tests, together with rheology and viscometry tests, show that the cross‐linking process has resulted in not only cross‐linking long chains but also chain scission of short chains, thus broadening the molecular weight distribution. Because these created short chains act like lubricants, cross‐linked chains flow easier. Therefore, the polymer remains processable according to the melt flow index test, and this will make the usage of slightly cross‐linked high density polyethylene in injection molding processes possible. Copyright © 2016 John Wiley & Sons, Ltd.     

Control of thermal cross‐linking reactions and the degree of crystallinity of syndiotactic 1,2‐polybutadiene

Thermal stability, crystallization, morphological development, subsequently melting, and crystallinity control of a syndiotactic 1,2‐polybutadiene sample were carefully carried out by thermogravimetry (TGA), polarized optical microscopy (POM), differential scanning calorimetry (DSC), temperature‐modulated differential scanning calorimetry (TMDSC), and wide‐angle X‐ray diffraction (WAXD), respectively. The experiments indicate that thermal cross‐linking reaction rates under nitrogen protection and in air are different for this polymer at temperature above 155 °C. Under nitrogen protection, the thermal cross‐linking reaction rate is delayed and the mechanism of melt crystallization obtained from the DSC results is in good accordance with that from POM observation. TMDSC results indicate that melting–recrystallization–melting model is more proper to explain the double melting events of this sample. At the same time, the evolution of the degree of crystallinity as the function of the time was investigated by WAXD profiles for the samples firstly crystallized at 145 °C for 1 h and then kept at 163 °C mediated between the temperatures of the double peaks. It shows that as prolonging the annealing time at 163 °C thermal cross‐linking reactions possibly occur, leading to gradual reduction of the apparent crystallite sizes, evaluated by Scherrer equation and the degree of crystallinity. The changing sequence of the relative intensity of the stronger four diffraction peaks with time due to thermal cross‐linking reactions is (111)/(201) > (210) > (010) > (200)/(110). © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2885–2897, 2005     

Surface analysis of high performance carbon/bismaleimide composites exposed to electron irradiation

The aim of this article was to investigate the effects of electron irradiation in ultrahigh vacuum environment on the surface properties of high‐performance carbon/bismaleimide (BMI) composites used in aerospace. The changes in surface chemical composition with increasing irradiation fluence were studied by XPS. The evolution of surface morphology and surface roughness were observed by atomic force microscopy (AFM). The mass loss behavior occurring in the surface layer of the composites was examined. The results indicated that the electron irradiation in high vacuum caused rupture of chemical bonds and cross‐linking process in the surface layer, thereby leading to the mass loss behavior and the formation of carbonification layer in the surface of the carbon/BMI composites. The changes in the surface chemical composition were determined by a competing effect existing between the rupture of chemical bonds and the cross‐linking process at lower irradiation fluence, and by a degradation process only at higher fluence of electron irradiation. The surface morphology was altered and the surface roughness was increased significantly after electron irradiation. The mass loss ratio first increased obviously at lower fluences, and then reached a plateau value of 0.45% beyond 5 × 10¹⁵ cm^?2 fluence of electron irradiation. Copyright © 2011 John Wiley & Sons, Ltd.     

Effects of electron irradiation on poly(vinylidene fluoride–trifluoroethylene) copolymers studied by solid‐state nuclear magnetic resonance spectroscopy

The effects of electron irradiation on the molecular chemical structure, conformation, mobility, and phase transition of vinylidene fluoride (VDF) and trifluoroethylene (TrFE) copolymer have been investigated with variable‐temperature, solid‐state ¹⁹F nuclear magnetic resonance (NMR). It has been found that electron irradiation converts all‐trans conformations of both VDF‐rich and TrFE‐containing segments into dynamically mixed trans–gauche conformations accompanied by a simultaneous ferroelectric‐to‐paraelectric (or amorphous) transition. The variable‐temperature ¹⁹F magic‐angle‐spinning spectra results show that the paraelectric phase melts at much lower temperatures in irradiated films than in an unirradiated sample. Moreover, ¹⁹F NMR relaxation data (spin–lattice relaxation times in both the laboratory and rotating frames) reveal that electron irradiation enhances the molecular motion in paraelectric regions, whereas the molecular motion in a high‐temperature amorphous melt (>100 °C) is more constrained in irradiated films. Besides these physical changes, electron irradiation also induces the formation of several CF₃ groups. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1714–1724, 2006     

Cell inactivation studies on yeast cells under euoxic and hypoxic condition using electron beam from microtron accelerator

In the case of sparsely ionizing radiation such as electron, the dose rate and the pattern of energy deposition of the radiation are the important physical factors which can affect the amount of damage in living cells. In the present study, the differences in the cell survival efficiency and dose rate effect in diploid yeast strains Saccharomyces cerevisiae X2180 and Saccharomyces cerevisiae D7 under euoxic and hypoxic condition have been quantified. Irradiation was carried out using 8 MeV pulsed electron beam from Microtron accelerator. The dose per pulse and pulse width of the beam used was 0.6 Gy and 2.3 μs, respectively, which correspond to an instantaneous dose rate of 2.6 × 10⁵ Gy s⁻¹. For survival studies doses were delivered at a rate of 50 pulses per second (an average dose rate of 1,800 Gy s⁻¹). Fricke and alanine dosimeters were used to measure the dose delivered to the sample. A significant difference in the dose response has been observed under euoxic and hypoxic condition. Dose rate effect has been studied by changing the pulse repetition rate of the Microtron and the dose rate used was from 180 to 1800 Gy min⁻¹. A significant dose rate effect was observed under euoxic condition for Saccharomyces cerevisiae X2180 but the same was absent under hypoxic condition. The dose rate effect was absent for Saccharomyces cerevisiae D7 under both irradiation condition. The survival curves are found to be sigmoidal in shape under both condition but with a wider shoulder under hypoxic condition. The D₀ value and the Oxygen Enhancement Ratio (OER) at that point have been derived.     

Influence of graphene nanosheets on stereocomplex crystallization behaviors of star‐shaped poly (D(L)‐lactide) stereoblock copolymer

The nanocompsites of star‐shaped poly(D‐lactide)‐co‐poly(L‐lactide) stereoblock copolymers (s‐PDLA‐PLLA) with two‐dimensional graphene nanosheets (GNSs) were prepared by solution mixing method. Crystallization behaviors were investigated using differential scanning calorimetry, polarized optical microscopy, and wide angle X‐ray diffraction. The results of isothermal crystallization behaviors of the nanocompsites clearly indicated that the GNS could remarkably accelerate the overall crystallization rate of s‐PDLA‐PLLA copolymer. Unique stereocomplex crystallites with melting temperature about 207.0°C formed in isothermal crystallization for all samples. The crystallization temperatures of s‐PDLA‐PLLAs shifted to higher temperatures, and the crystallization peak shapes became sharper with increasing GNS contents. The maximum crystallization temperature of the sample with 3 wt% GNS was about 128.2°C, ie, 15°C higher than pure s‐PDLA‐PLLA. At isothermal crystallization processes, the halftime of crystallization (t_0.5) of the sample with 3 wt% GNS decreased to 6.4 minutes from 12.9 minutes of pure s‐PDLA‐PLLA at 160°C.The Avrami exponent n values for the nanocomposites samples were 2.6 to 3.0 indicating the crystallization mechanism with three‐dimensional heterogeneous nucleation and spherulites growth. The morphology and average diameter of spherulites of s‐PDLA‐PLLA with various GNS contents were observed in isothermal crystallization processes by polarized optical microscopy. Spherulite growth rates of samples were evaluated by using combined isothermal and nonisothermal procedures and analyzed by the secondary nucleation theory. The results evidenced that the GNS has acceleration effects on the crystallization of s‐PDLA‐PLLA with good nucleation ability in the s‐PDLA‐PLLA material.     

Effects of gold‐induced crystallization process on the structural and electrical properties of germanium thin films

Gold‐induced (Au‐) crystallization of amorphous germanium (α‐Ge) thin films was investigated by depositing Ge on aluminum‐doped zinc oxide and glass substrates through electron beam evaporation at room temperature. The influence of the postannealing temperatures on the structural properties of the Ge thin films was investigated by employing Raman spectra, X‐ray diffraction, and scanning electron microscopy. The Raman and X‐ray diffraction results indicated that the Au‐induced crystallization of the Ge films yielded crystallization at temperature as low as 300°C for 1 hour. The amount of crystallization fraction and the film quality were improved with increasing the postannealing temperatures. The scanning electron microscopy images show that Au clusters are found on the front surface of the Ge films after the films were annealed at 500°C for 1 hour. This suggests that Au atoms move toward the surface of Ge film during annealing. The effects of annealing temperatures on the electrical conductivity of Ge films were investigated through current‐voltage measurements. The room temperature conductivity was estimated as 0.54 and 0.73 Scm⁻¹ for annealed samples grown on aluminum‐doped zinc oxide and glass substrates, respectively. These findings could be very useful to realize inexpensive Ge‐based electronic and photovoltaic applications.     

Characterization of a power bipolar transistor as high-dose dosimeter for 1.9–2.2 MeV electron beams

Results of the characterization studies on a power bipolar transistor investigated as a possible radiation dosimeter under laboratory condition using electron beams of energies from 2.2 to 8.6 MeV and gamma rays from a ⁶⁰Co source and tested in industrial irradiation plants having high-activity ⁶⁰Co γ-source and high-energy, high-power electron beam have previously been reported. The present paper describes recent studies performed on this type of bipolar transistor irradiated with 1.9 and 2.2 MeV electron beams in the dose range 5–50 kGy. Dose response, post-irradiation heat treatment and stability, effects of temperature during irradiation in the range from –104 to +22 °C, dependence on temperature during reading in the range 20–50 °C, and the difference in response of the transistors irradiated from the plastic side and the copper side are reported. DLTS measurements performed on the irradiated devices to identify the recombination centres introduced by radiation and their dependence on dose and energy of the electron beam are also reported.     

50 keV H+ ion beam irradiation of Al doped ZnO thin films: Studies of radiation stability for device applications

Thin films of Al doped ZnO (Al:ZnO) were deposited on two substrates (Si and glass) at room temperature and 300°C using DC magnetron sputtering. These films were bombarded with 50 keV H⁺ beam at several fluences. The pristine and ion beam irradiated films were analysed by X‐ray diffraction, Raman spectroscopy, scanning electron microscopy, and UV‐Vis spectroscopy. The X‐ray diffraction analysis, Hall measurements, Raman and UV‐Vis spectroscopy confirm that the structural and transport properties of Al:ZnO films do not change substantially with beam irradiation at chosen fluences. However, in comparison to film deposited at room temperature, the Al:ZnO thin film deposited at 300°C shows increased transmittance (from 70% to approximately 90%) with ion beam irradiation at highest fluence. The studies of surface morphology by scanning electron microscopy reveal that the ion irradiation yields smoothening of the films, which also increases with ion fluences. The films deposited at elevated temperature are smoother than those deposited at room temperature. In the paper, we discuss the interaction of 50 keV H⁺ ions with Al:ZnO films in terms of radiation stability in devices.     

Preparation and properties of novel fluorosilicone thermoplastic vulcanizate with cross‐linking–controlled core‐shell structure

A new fluorosilicone thermoplastic vulcanizate (TPV) composed of poly(vinylidene fluoride) (PVDF), silicone rubber (SR), and fluororubber (FKM) was successfully prepared through dynamic vulcanization. The morphological structure of the TPVs had core‐shell elastomer particles dispersed in a continuous PVDF matrix. Furthermore, the cross‐linking of core‐shell structure was controlled by adopting different curing agent. The effect of cross‐linking–controlled core‐shell structure on the morphology, crystallization behavior, stress relaxation test, solvent‐resistant properties of the obtained TPVs were investigated. It was found that the shell cross‐link had a significant influence on the crystallinity of the PVDF phase. The core‐shell bicross‐linked TPV was found to provide the lowest rate of relaxation. An obvious stress softening phenomenon was observed in the uniaxial loading‐unloading cycles in tension. The bicross‐linked TPV had good solvent resistant properties. The tensile strength of the bicross‐linked TPV was still 12 MPa even after immersed in butyl acetate for 48 hours.     

A study of dosimetry characteristics of GAF DM-1260 radiochromic films

The dosimetric characteristics of gamma-ray, x-ray and electron irradiated GAF-DM-1260 radiochromic film have been studied, and the dependence of radiation-induced film absorbance on irradiation temperature and reading temperature and the changes of the absorption spectrum peaks at different reading temperatures and absorbed doses (3×10¹ to 5×10⁴ Gy) are reported. It is shown that the responses are independent of the gamma-ray dose rate in the dose rate range considered in the experiment. The film response characteristics as a function of the absorbed dose to ⁶⁰Co gamma irradiation at the spectrophotometric reading wavelengths of 400, 580, 600, 650 and 670 nm and two absorption peaks are determined as well as the response characteristics to the electron beam at the reading wavelength of 400 nm. The results demonstrate that the film responses to gamma rays, x-rays and a 3.8 MeV electron beam are equivalent, over the absorbed dose rate range of about 0.8 Gy·s⁻¹ to 5×10⁸ Gy·s⁻¹. Some advice and points of view about the dosimetric characteristics of the film and some problems in usage are provided according to the experimental results.     

Effect of electron beam irradiation on dynamic mechanical,thermal and morphological properties of LLDPE and PDMS rubber blends

The effect of electron beam irradiation on the blends of linear low-density polyethylene (LLDPE) and poly dimethyl siloxane rubber (PDMS) prepared over a wide range of compositions starting from 70:30 to 30:70 (LLDPE: PDMS) by varying the radiation doses from 50 to 300 kGy has been studied. The dynamic modulii and dielectric strength of the blends increase on irradiation at 100 kGy as compared to that for the unirradiated blends. Degree of crystallinity and melting behaviour remain unchanged upon irradiation upto a dose of 100 kGy, beyond which it decreases. Thermal stability increases with increase in the proportion of PDMS rubber in the blend as well as on irradiation at 100 kGy. The phase morphology of the blends examined under the SEM exhibit two phase morphology before electron beam irradiation, whereas single phase morphology is observed after electron beam irradiation due to intra- as well as inter-molecular crosslinking leading to a miscible system.     

Photo‐Modification of Melanin by a Mid‐infrared Free‐electron Laser

Melanin is rigidly constructed by several nitrogen‐containing aromatic rings, and its excess accumulation in skin tissue is closely associated with melanosis. Although visible lasers (wavelength: 600–1000 nm) are conventionally used for the photo‐thermolysis of melanocyte, several pigmented nevi are difficult to be treated. Here, we propose an alternate method for targeting the molecular structure of melanin using an infrared free‐electron laser (FEL) tuned to 5.8 μm that corresponds to the stretching vibrational mode of carboxylate group. A drastic morphological change on the black‐colored surface of melanin powder was observed after the pulse irradiation with power energy of 500 mJ cm^?2, and the minimum irradiation time for damage to the morphology was 1.4 s. Analyses by mass spectroscopy, infrared spectroscopy, and ¹³C‐nuclear magnetic resonance implied that a pyrrole group was removed by the FEL irradiation. In addition, the FEL irradiation dispersed almost all of the melanoma cells from a culture solution without any influence on other ingredients in the medium, and one‐cell analysis by infrared microscopy showed that the structure of melanoma could be substantially damaged by the irradiation. This study proposes the potency of intense mid‐infrared laser as novel alternative way to reduce melanin.     

Investigation of irradiation dose rate on curing characteristics of carbon fiber/polymer composites by low‐energy electron beam

During in situ low‐energy electron beam (E‐Beam) curing for carbon fiber‐reinforced polymer composite, prepregs undergoes 3 sequenced curing processes, namely E‐Beam‐induced curing, postray curing after irradiation, and thermally induced curing. In this study, the irradiation dose rate (IDR) is demonstrated to be influential on the redistribution of the curing portions in the 3 curing stages and directly influences the interlaminar bonding quality of the stepwise cured laminates. Differential scanning calorimetry results showed that higher IDR resulted in higher temperature of irradiated prepregs, and hence, a higher degree of curing was induced by the E‐Beam within a dose range of 0 to 500 kGy as compared to lower IDRs, which decreased the interlaminar physical adhesive quality between layers. Analysis indicates that other than pure physical adhesion between uncured layers, postray curing can further enhance the interlaminar shear strength for cured laminates by introducing cross‐layer chemical bonding in the interlaminar zone.     

Sensitizing DNA Towards Low‐Energy Electrons with 2‐Fluoroadenine

2‐Fluoroadenine (^2FA) is a therapeutic agent, which is suggested for application in cancer radiotherapy. The molecular mechanism of DNA radiation damage can be ascribed to a significant extent to the action of low‐energy (<20 eV) electrons (LEEs), which damage DNA by dissociative electron attachment. LEE induced reactions in ^2FA are characterized both isolated in the gas phase and in the condensed phase when it is incorporated into DNA. Information about negative ion resonances and anion‐mediated fragmentation reactions is combined with an absolute quantification of DNA strand breaks in ^2FA‐containing oligonucleotides upon irradiation with LEEs. The incorporation of ^2FA into DNA results in an enhanced strand breakage. The strand‐break cross sections are clearly energy dependent, whereas the strand‐break enhancements by ^2FA at 5.5, 10, and 15 eV are very similar. Thus, ^2FA can be considered an effective radiosensitizer operative at a wide range of electron energies.     

Chemical dosimeters for electron beam dosimetry of microtron accelerator

The variable energy microtron at Mangalore University has been used to study the effect of radiation on different materials and biological systems. While studying the effects of radiation, it is essential to have complete knowledge of absorbed dose. In the present study the dose due to 8 MeV electron beam from microtron accelerator has been calculated using chemical dosimeters. The uniformity of dose distribution at various points of the irradiation area also has been calibrated. From the dosimetry studies it is observed that there is a linear relation between dose and electron numbers over a wide range of absorbed doses. It is evaluated that the electron counts of about 1.15 × 10¹⁴ corresponds to an absorbed dose of 100 Gy and a field size of about 4 × 4 cm is available at 30 cm distance from the beam exit window over which the dose distribution is uniform.