Effect of gamma irradiation on the light polarization variation of PMMA polymer

Analyzing the effect of ionized gamma irradiation on the optical parameters of materials is a solution for finding newer techniques in the field of detector and dosimeter systems. A PMMA (polymethylmethacrylate) polymer was radiated from a ⁶⁰Co source with a power of 1800 C and a constant dose rate of 1.44 kGy/h in three steps of 5, 25 and 61.2 kGy. The ionized gamma irradiation affected the refractive index of polymer and therefore it changes the polarization of the incident light. The difference in the polarization phase shift of the polymer depended on the dose it had been irradiated with.     

The effects of ceramic fillers on the PMMA-based polymer electrolyte systems

The effects of ceramics fillers on the polymethylmethacrylate (PMMA)-based solid polymer electrolytes have been studied using ac impedance spectroscopy and infrared spectroscopy. The polymer film samples were prepared using solution cast technique, tetrahydrofuran (THF) used as a solvent, and ethylene carbonate (EC) has been used as plasticizer. Lithium triflate salt (LiCF₃SO₃) has been incorporated into the polymer electrolyte systems. Two types of ceramic fillers, i.e., SiO₂ and Al₂O₃, were then implemented into the polymer electrolyte systems. The solutions were stirred for several hours before it is poured into petri dishes for drying under ambient air. After the film has formed, it was transferred into desiccator for further drying before the test. From the observation done by impedance spectroscopy, the room temperature conductivity for the highest conducting film from the (PMMA–EC–LiCF₃SO₃) system is 1.36 × 10⁻⁵ S cm⁻¹. On addition of the SiO₂ filler and Al₂O₃ filler, the conductivity are expected to increase in the order of ∼10⁻⁴ S cm⁻¹. Infrared spectroscopy indicates complexation between the polymer and the plasticizer, the polymer and the salts, the plasticizer and the salts, and the polymer and the fillers. The interactions have been observed in the C=O band, C–O–C band, and the O–CH₃ band. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7-9, 2006.     

Influence of 60Co gamma irradiation on the structural and optical properties of 2-aminopyridinium 4-nitrophenolate 4-nitrophenol crystals

In this article, effect of gamma irradiation on the structural and optical properties of 2-aminopyridinium 4-nitrophenolate 4-nitrophenol (2AP4N) has been reported. The grown crystals of 2AP4N were exposed to ⁶⁰Co gamma rays with a dose of 50 kGy and 100 kGy. The radiation-induced effects were analyzed using X-ray diffraction, FT-IR, UV–visible, photoluminescence techniques. The refractive index was determined using a long arm spectrometer. The structural properties of the pristine and irradiated crystals were studied using powder XRD. The peak intensity decrease after irradiation may be attributed to the formation of point defects. The UV visible study reveals that the energy gap has decreased after irradiation and then has increased for the higher dose. The intensity variation in the PL spectra is due to colour center mechanism. The SHG efficiency of 2AP4N crystals was found to be unaffected by gamma irradiation.     

Effect of storage time on the properties of PVA–KOH alkaline solid polymer electrolyte system

Polyvinyl alcohol (PVA) and potassium hydroxide (KOH) have been used to prepare alkaline solid polymer electrolytes (ASPE) films. The films were stored in a dry environment for 30 and 100 days. The highest room temperature conductivity for the PVA:KOH film with weight percentage ratio of 1:0.67 during storage for 30 and 100 days were (8.5±0.2)×10⁻⁴ and (1.3±0.1)×10⁻⁷ S cm⁻¹, respectively. The conductivity–temperature behaviour after 30 and 100 days of storage of the alkaline polymer electrolytes is Arrhenian and liquid-like. The structural, morphological and thermal studies of the ASPE films are also presented in this paper.     

Effect of gamma rays irradiation on ferroelectric phase transition and domain defect interaction in lead meta niobate single crystal

The objective of our study is to identify the role of gamma rays to control the existing limit of ferroelectric nature of lead meta niobate (PbNb₂O₆) single crystals in terms of domain-defect interaction. The critical value of density of oxygen vacancy sites and average distance between two successive oxygen vacancies, which are responsible for ferroelectric nature in lead niobate single crystal have been calculated. The disappearance of Ferro electricity, which is associated with domain-defect interaction as well as an absence of obeying the Curie-Weiss law have been discussed in gamma rays irradiated lead meta niobate single crystal.     

Effect of molecular weight on conductivity of polymer electrolytes

The ionic conductivity, σ, of mixtures of poly(ethylene oxide) (PEO) and lithium bis(trifluoromethanesulfone)imide (LiTFSI) was measured as a function of molecular weight of the PEO chains, M, over the range 0.2-5000 kg/mol. Our data are consistent with an expression σ = σ₀ + K/M proposed by Shi and Vincent [Solid State Ionics 60 (1993)] where σ₀ and K are exponential and linear functions of inverse temperature respectively. Explicit expressions for σ₀ and K are provided.     

4H-SiC探测器的γ辐照影响研究

为研究4H-SiC探测器的抗γ辐照性能,使用40万Ci级的⁶⁰Co源对4H-SiC探测器进行了数次辐照,累积辐照剂量最大为1 MGy(Si),并在辐照后对4H-SiC的性能进行了测试。随着累积辐照剂量增加,4H-SiC探测器的正向电流增大,而反向电流恰好相反;根据4H-SiC探测器的正向I-V曲线可提取理想因子和肖特基势垒,理想因子从1.87增加到2.18,肖特基势垒从1.93 V减小至1.69 V;4H-SiC探测器对²⁴¹Am源产生的α粒子进行探测时,探测器的电荷收集率从95.65%退化到93.55%,测得能谱的能量分辨率由1.81%退化到2.32%。4H-SiC探测器在受到1 MGy(Si)的γ辐照后,与未受到辐照时相比,在探测能量为5.486 MeV的α粒子时能量分辨率和电荷收集率仅退化了28.18%和2.2%,仍具备优良的探测性能。     

The effect of gamma irradiation and shelf aging in air on the oxidation of ultra-high molecular weight polyethylene

This study has investigated the effect of shelf aging, for up to one year in air, on the properties of gamma-irradiated ultra-high molecular weight polyethylene (UHMWPE). A variety of techniques were used to characterize the properties of treated samples. Differential scanning calorimetery (DSC) was used to characterize the morphology. The extent of cross-linking in a polymer network was detected by swelling measurements. The durometer hardness test was used to measure the relative hardness of this material, and changes in density were also measured. Results from all these measurements were combined to explain the changes in the microstructure of the aged, irradiated UHMWPE. This study shows that crystallinity is increased with radiation dose and with aging due to chain scission, which leads to a reduction in the molecular weight of the material. This allows the chains to rearrange to form crystalline regions. Positron annihilation lifetime spectroscopy confirms these conclusions. Fractional free volumes have been deduced from lifetime parameters, which correlate with the data obtained by the other techniques.     

Hydrogen and oxygen generation with polymer electrolyte membrane (PEM)-based electrolytic technology

With dwindling liquid fuel resources, hydrogen offers a credible alternative. The use of hydrogen in a fuel cell offers the highest fuel conversion efficiency compared with all other technologies and it also has the potential to substantially reduce greenhouse gas and particulate emissions at least at the end-user sites. One of the major barriers to the introduction of the hydrogen economy and its wider acceptance is the lack of the rather costly hydrogen generation, transportation and distribution infrastructure to meet the local transport fuel demands. On-site or distributed hydrogen generation would remove the need for this up-front infrastructure requirements and assist with the early large-scale trials of the fuel cell technology for both transport and stationary applications and also introduction of the hydrogen economy. In this paper, the development of polymer electrolyte membrane electrolysis technology for on-site, on-demand hydrogen generation has been discussed. The major emphasis is given on reducing catalyst cost; interface design and modifications; interconnect materials, design and fabrication; and investigation of the sources of degradation. Stacks to 2 kW_{H 2} capacity have been constructed and tested and show initial efficiencies of >87% at 1 A cm⁻².     

Effect of gamma irradiation on chromate sorption over magnetite surface

Aqueous chromate sorption on suspended magnetite in the presence of gamma irradiation has been evaluated. Kinetics of chromate removal was evaluated using Lagergren's absorption model. Chromate removal with respect to the accumulated dose followed a Lagergren's pseudo-first-order kinetic model. A comparison of kinetics of chromate removal with respect to total accumulated dose for gamma irradiation experiment vis-à-vis with respect to time of treatment for different isothermal interactions has been undertaken. Rate constants indicate that the chromate removed per minute in isothermal equilibration at 80 °C is comparable to the chromate removed per kilogrey of gamma irradiation received. There is a redox interaction between the chromate and the ferrous of the suspended magnetite which was confirmed by X ray photo electron spectroscopy (XPS) analysis. This process reaches a saturation much before the consumption of entire ferrous ions of magnetite, indicating a passivating nature of the product. The effect of radiation on both chromate solution and dispersed magnetite to alter the redox process could be ascertained. Gaussian–Lorenzian peak fittings to the XPS data have been carried out to evaluate the chemical composition of the deposited chromium and the resultant change in the chemical composition of the iron in the oxide lattice. This indicated that the magnetite equilibrated with chromate under gamma irradiation resulted in a different surface composition as compared with the one obtained in absence of gamma irradiation. XPS data indicated the presence of hydroxyl group and oxide group attached to both iron and chromium moieties in case of irradiation, whereas only oxide group was seen with only temperature treatment.     

Preparation and characterization of the polymer electrolyte system ENR50/PVC/EC/PC/LiN(CF<Subscript>3</Subscript>SO<Subscript>2</Subscript>)<Subscript>2</Subscript> for electrochemical device applications

Polymer electrolytes containing epoxidised natural rubber (ENR50)/poly(vinyl chloride) (PVC) blend as a polymer host, a solvent mixture of ethylene carbonate (EC) and propylene carbonate (PC) as a plasticizer, and lithium imide, LiN (CF₃SO₂)₂, as a salt were studied. Polymer electrolytes that were obtained by solvent cast yielded solid dry rubbery films with a thickness range of 110–125 μm. Impedance spectroscopy, Fourier transform infra red (FTIR) spectroscopy, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were performed on these samples. The prepared solid polymer electrolytes exhibit ionic conductivities in the order 10⁻⁴ S cm⁻¹ at room temperature as expected. However, the physical properties of the electrolytes have improved significantly when optimal composition has been selected. Paper presented at the International Conference on Solid State Science and Technology 2006, Kuala Terengganu, Malaysia, Sept. 4–6, 2006.     

Electrochemical synthesis of ammonia based on doped-ceria-carbonate composite electrolyte and perovskite cathode

Electrochemical synthesis of ammonia was investigated using a cobalt-free La_0.6Sr_0.4Fe_0.8Cu_0.2O_3-δ-Ce_0.8Sm_0.2O_2-δ (LSFCu-SDC) composite cathode and SDC-ternary carbonate composite electrolyte. La_0.6Sr_0.4Fe_0.8Cu_0.2O_3-δ and Ce_0.8Sm_0.2O_2-δ were prepared via combined EDTA-citrate complexing sol-gel and glycine nitrate processes, respectively, and characterised by X-ray diffraction (XRD). Ammonia was successfully synthesised from wet hydrogen and dry nitrogen under atmospheric pressure using Ni-SDC, SDC-carbonate and LSFCu-SDC composites as anode, electrolyte and cathode respectively. Ammonia formation was observed at 400, 425, 450 and 475 °C and the maximum rate of ammonia production was found to be 5.39 × 10⁻⁹ mol s⁻¹ cm⁻² at 450 °C and 0.8 V. The AC impedance measurements were recorded before and after the ammonia synthesis in the range of temperature 400-475 °C. The formation of ammonia at the N₂ side together with stable current at 450 °C under constant voltage demonstrates that SDC-(Li/Na/K)₂CO₃ composite electrolyte exhibits significant proton conduction at a temperature around 450 °C.     

Impedance studies on polyacrylonitrile–CuX2–DMSO (X=Cl, Br, CF3SO3) solid polymer electrolyte

A series of polyacrylonitrile–dimethylsulfoxide–CuX₂ (X=CF₃SO₃⁻, Cl⁻, Br⁻), films (foils) were prepared by means of the solution cast technique. The thickness of the foils was between 0.04 and 0.09 cm and they contained 70–80 wt.% of the solvent. Conductivities of the solid electrolytes were obtained from impedance measurements. The conductivity increases with the increase of the salt content up to 8 wt.%; at higher concentrations (>8 wt.%) the conductivity is more or less stable, and reaches, in the case of Cu(CF₃SO₃)₂ and CuCl₂, the level of ca. 10⁻³ Ω⁻¹ cm⁻¹ at room temperature. The foils based on the CuBr₂ show even higher conductivity, close to 10⁻² Ω⁻¹ cm⁻¹ at room temperature, a value comparable to that characteristic for liquid solutions. The temperature variation of the conductivity for all the systems studied is of the Arrhenius type. The activation energy, determined from linear plots lnσ=f(T⁻¹), is of the order ca. 14 kJ mol⁻¹ for the PAN/CuBr₂/DMSO and of ca. 21 kJ mol⁻¹ for the PAN/CuCl₂/DMSO and the PAN/Cu(CF₃SO₃)₂/DMSO systems.     

Effect of branching in base polymer on ionic conductivity in hyperbranched polymer electrolytes

Novel hyperbranched polymer, poly[bis(diethylene glycol)benzoate] capped with a 3,5-bis[(3′,6′,9′-trioxodecyl)oxy]benzoyl group (poly-Bz1a), was prepared, and its polymer electrolyte with LiN(CF₃SO₂)₂, poly-Bz1a/LiN(CF₃SO₂)₂ electrolyte, was all evaluated in thermal properties, ionic conductivity, and electrochemical stability window. The poly-Bz1a/LiN(CF₃SO₂)₂ electrolyte exhibited higher ionic conductivity compared with a polymer electrolyte based on poly[bis(diethylene glycol)benzoate] capped with an acetyl group (poly-Ac1a), and the ionic conductivity of poly-Bz1a/LiN(CF₃SO₂)₂ electrolyte was to be 7×10⁻⁴ S cm⁻¹ at 80 °C and 1×10⁻⁶ S cm⁻¹ at 30 °C, respectively. The existence of a 3,5-bis[(3′,6′,9′-trioxodecyl)oxy]benzoyl group as a branching unit present at ends in the base polymer improved significantly ionic conductivity of the hyperbranched polymer electrolytes. The polymer electrolyte exhibited the electrochemical stability window of 4.2 V at 70 °C and was stable until 300 °C.     

Fuel quality and operational issues for polymer electrolyte membrane (PEM) fuel cells

Polymer electrolyte membrane (PEM) fuel cells are susceptible to degradation due to the catalyst poisoning caused by CO present in the fuel above certain limits. Although the amount of CO in the fuel may be within the permissible limit, the fuel composition (% CO₂, CH₄, CO and H₂O) and the operating conditions of the cell (level of gas humidification, cell temperature and pressure) can be such that the equilibrium CO content inside the cell may exceed the permissible limit leading to a degradation of the fuel cell performance. In this study, 50 cm² active area PEM fuel cells were operated at 55–60 °C for periods up to 250 hours to study the effect of methane, carbon dioxide and water in the hydrogen fuel mix on the cell performance (stability of voltage and power output). Furthermore, the stability of fuel cells was also studied during operation of cells in a cyclic dead end / flow through configuration, both with and without the presence of carbon dioxide in the hydrogen stream. The presence of methane up to 10% in the hydrogen stream showed a negligible degradation in the cell performance. The presence of carbon dioxide in the hydrogen stream even at 1–2% level was found to degrade the cell performance. However, this degradation was found to disappear by bleeding only about 0.2% oxygen into the fuel stream.     

3-D microbattery electrolyte by self-assembly of oligomers

This paper reports the preparation and characterization of novel thin film electrolytes by UV cross-linking of poly(propylene glycol) diacrylate in the presence of polyetheramine (glyceryl poly(oxypropylene)triamine) and LiTFSI. The oligomeric surfactant polyetheramine facilitates self-assembly of the electrolyte, enabling it to be applied conformally onto a complex substrate which is necessary for 3D-microbatteries, while the acrylate network supplies mechanical stability. Conformal coatings onto LiFePO₄ electrodes and Cu nanopillars were confirmed by SEM. Ionic conductivities of 3.5 × 10^− 6 and 5.8 × 10^− 5 S/cm were measured at room temperature and 60 °C, respectively, at Li:O = 1:20 and PEA:PPGDA = 2:1 ratios. The electrochemical stability window test showed that the electrolyte is stable above 5.0 V vs. Li/Li⁺. Thermal analyses by TGA and DSC demonstrated that the polymer electrolyte is amorphous and thermally stable up to 300 °C.     

Effect of gamma irradiation on HPMC/ZnO nanocomposite films

The present work looks into the structural, chemical, mechanical, optical and thermal modification in ZnO nanoparticle incorporated hydroxypropyl methylcellulose (HPMC) polymer films, induced by gamma irradiation. The irradiation process was performed in a gamma chamber at room temperature using Cobalt-60 source (average energy of 1.25?MeV) at different doses: 0, 50, 100, 150 and 200?kGy. The modifications in structural, chemical, mechanical, optical and thermal properties, due to gamma irradiation in HPMC/ZnO nanocomposite films, have been studied using wide angle X-ray scattering (XRD), Fourier transform infrared spectroscopy, universal testing machine, ultraviolet–visible spectrophotometry and thermogravimetric analysis. It is found that gamma irradiation improves the mechanical and thermal properties of nanocomposite films.     

Effect of gamma irradiation on hydrothermally synthesized barium titanate nanoparticles

The effect of gamma irradiation on hydrothermally synthesized BaTiO₃ nanoparticles has been investigated. Gamma irradiation was carried out at room temperature from 0, 50, 100, 150, 200?kGy to a maximum dose up to 250?kGy, source being ⁶⁰Co gamma radiations. The structure, size and chemical changes of the BaTiO₃ were studied using X-ray diffraction, Fourier-transform infrared spectrophotometry (FTIR) techniques and scanning electron microscopy (SEM). The optical band gap has been computed by UV–Visible spectroscopy data. From the results obtained, it is evident that the gamma irradiation increases the crystallinity, whereas the particle size of BaTiO₃ nanoparticles is altered. UV–Visible spectroscopy shows a noticeable change in the energy band gap due to gamma irradiation. Significant changes in anharmonicity constant computed using FTIR data due to irradiation has been observed. SEM shows the size and deviation from uniformity of particles.     

Improving the surface properties of multi-walled carbon nanotubes after irradiation with gamma rays

The effects of gamma-irradiation on the modification of the surface and structure of multi-walled carbon nanotubes were studied. Gamma-irradiation affected the graphitization properties of functional groups, and decreased the diameter of multi-walled carbon nanotubes. The irradiated multi-walled carbon nanotubes with the absorbed dose of 100 kGy exhibited a larger specific surface area and microporous volume as compared with the other samples. The Raman spectroscopy and X-ray photoelectron spectroscopy showed that the interaction between the gamma-irradiation and the multi-walled carbon nanotubes with the absorbed dose of 150 kGy destroyed the nanostructure of carbons, leading to the formation of diamond-like structures and carbon oxides. In addition, gamma-irradiation with the absorbed dose of 100 kGy improved multi-walled carbon nanotubes graphitization and surface properties while at higher absorbed dose (150 kGy), it induced damaged structures (sp³ bonds and oxygen compositions).