An analysis on changes in structure,tensile properties of polytetrafluoroethylene film induced by protons

Effect of 100 keV proton radiation on the structure and tensile properties of PTFE film was investigated. The change in structure before and after proton radiation was mainly evaluated by means of differential scanning calorimetry. The experimental results show that under radiation of 100 keV protons for the fluence less than 7×10¹⁵ p/cm², the DSC characteristics including the phase enthalpy of transformations at room temperature ΔH_rt1 and ΔH_rt2, the melting enthalpy ΔH_m1 and ΔH_m2, the crystallization exothermal enthalpy ΔH_c, and Tg II were decreased, while the melting temperature was increased a little with the fluence increase. The change in crystallization enthalpy ΔH_c indicated the increase of molecular weight of the PTFE film, but for 150 keV when the fluence exceeded the fluence of 10¹⁶/cm², the molecular weight decreased gradually. With increasing proton fluence, the thermal gravity loss was decreased, while the initial decomposition temperature increased, demonstrating that crosslinking of molecular chains occurred. With the increase of the proton fluence, for proton with energy less than 150 keV, the tensile fracture strength increased at first, but when the fluence exceeded 10¹⁶/cm², the tensile fracture strength showed a decreasing trend. While for the proton of 170 keV, the tensile fracture strength σ_f increased abruptly at the fluence of 2×10¹³/cm², with the fluence increasing further, the tensile fracture strength σ_f decreased gradually. The change of tensile properties could be related with the competition of branching crosslinking and the scission degradation.     

Surface Energy Characteristics of Polytetrafluoroethylene Bombarded with MeV Protons

Energy characteristics of the irradiated surface of a polytetrafluoroethylene film depend on the energy and fluence of bombarding MeV protons. Irradiation with 2–4 MeV protons leads to an increase in the surface free energy; 4 MeV protons at a fluence of 10¹⁵ proton/cm² increase the polarity of the polymer surface by 40 times due to the appearance of functional groups, the polarity enhancement being manifested in an increase in the acid–base component of the surface energy by more than a factor of 50. There is a correlation between the dispersion component of the surface energy and the degree of crystallinity of the near-surface layer of the polymer a period. They both grow symbatically in the case of bombardment with 1–2 MeV protons and decrease upon irradiation with 4 MeV protons. It has been found that dehydrofluorination results in carbonization of the irradiated surface, a decrease in the fluorine content, and an increase in the proportion of oxygen due to oxidation of the radicals generated by proton bombardment.     

Effect of bombardment with helium ions on the molecular-topological structure and elemental composition of the surface of polytetrafluoroethylene

Irradiation of a polytetrafluoroethylene (PTFE) film with accelerated (1–5 MeV) helium ions at a fluence of 10¹⁵ ion/cm² has been studied. The efficiency of carbonization, defined as a decrease in the fluorine content and an increase in the carbon content on the surface of the polymer, increases with the incident ion energy. A characteristic feature of the topological structure of PTFE is the presence of four high-meltingpoint crystalline modifications, the “branching points” of the pseudo-network of the amorphous matrix block, in addition to a low-melting-point modification with the melting onset temperature of 13°C. After bombardment with 3–5 MeV ions, only two crystalline blocks remain in the polymer and a cluster block, which was not present in the unirradiated polymer, appears. The overall mass fraction of the crystalline structure in the irradiated polymer (0.48) is below that in the initial polymer (0.66), indicating amorphization of its structure.     

Optical-limiting property of cyclic phenylacetylene oligomer synthesized under high pressure

The optical-limiting property of a new cyclic phenylacetylene oligomer was investigated. Toluene solutions of the oligomer contained within a quartz cell were irradiated with the pulse from frequency doubled Nd: Yag laser at 532 nm. At low input fluence, the transmittance of the toluene solution was constant and agreed well with that obtained by spectrophotometer. At high input fluence, the transmittance of the solution above a concentration of 5 wt % decreased with input fluence. The oligomer had an optical limiting property. As the concentration of the oligomer increased from 5 to 20 wt %, the threshold for optical limiting decreased. The threshold was independent of the molecular weight. The optical limiting property was analyzed by the following equation obtained according to the reverse saturable absorption mechanism; log(I₀/I) = K(I₀ - I) + A_g, where I₀ is the input fluence, I is the output fluence, K is a parameter depending on the absorption cross section and the relaxation time, and A_g is the absorbance of the ground state. © 1996 John Wiley & Sons, Inc.     

Studies on biaxial stretching of polypropylene film. IV. Overall orientation during one-step biaxial stretching and its application to the estimation of the principal refractive indices of isotactic polypropylene

Polypropylene film was biaxially stretched in one step in air at 140°C or 152°C, and the deformation was studied optically. A linear relation held between Δn_ss and v_A^?½ for v_A > 10, at both temperatures, where Δn_ss is the birefringence with respect to the normal to the film and v_A is the degree of stretching expressed as the factor by which the area of the film is increased. Extrapolation of data in this linear region yielded a value of 20 × 10^?3 for ?Δn_ss at infinite v_A. Since it is presumed that the polypropylene molecules lie completely parallel to the film surface when the film is stretched infinitely, ?Δn_ss at v_A^?½ = 0 must be just half Δn°, the intrinsic birefringence in the case of completely parallel orientation. Thus, Δn° must be 40 × 10^?3. This value was obtained experimentally in uniaxial stretching when the birefringence with respect to the direction of drawing was extrapolated to infinite extension. Similar relations held between n_p, the average of the refractive indices in the two stretching directions, and v_A, and between n_ss, the index normal to the film, and v_A. By similar extrapolations, (1/2)(n′_γ + n′_β) and n′_β = n*_α′ were estimated, and thence nα′ was obtained. Here, n′_α and n′_β are the refractive indices along the c axis (molecular chain axis) and b axis. All these optical parameters refer to a density of 0.900 g/cm³. Hence by applying a density correction to those values, the principal refractive indices and the intrinsic birefringence of polypropylene crystal were evaluated as follows: n_α = 1.5522, n_β = n*_α = 1.5106 and Δn_c° = 4.16 × 10^?3, where n*_α is the refractive index prependicular to the b and c axes of the crystal.     

Patterned immobilization of biomolecules by using ion irradiation‐induced graft polymerization

A new method for biomolecular patterning based on ion irradiation‐induced graft polymerization was demonstrated in this study. Ion irradiation on a polymer surface resulted in the formation of active species, which was further used for surface‐initiated graft polymerization of acrylic acid. The results of the grafting study revealed that the surface graft polymerization using 20 vol % of acrylic acid on the poly(tetrafluoroethylene) (PTFE) film irradiated at the fluence of 1 × 10¹⁵ ions/cm² for 12 h was the optimum graft polymerization condition to achieve the maximum grafting degree. The results of the fluorescence microscopy also revealed that the optimum fluence to achieve the maximum fluorescence intensity was 1 × 10¹⁵ ions/cm². The grafting of acrylic acid on the PTFE surfaces was confirmed by a fluorescence labeling method. The grafted PTFE films were used for the immobilization of amine‐functionalized p‐DNA, followed by hybridization with fluorescently tagged c‐DNA. Biotin‐amine was also immobilized on the acrylic acid grafted PTFE surfaces. Successful biotin‐specific binding of streptavidin further confirmed the potential of this strategy for patterning of various biomolecules. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6124–6134, 2009     

Photoacoustic monitoring of the mass removed in pulsed laser ablation

The mass Δm removed per pulse in laser ablation was shown to correlate with the acoustic signal A and the beam diameter ?. The functional forms of Δm(A, ?) were deduced for aluminum and polyvinyl chloride, for fluence ranging from 1.5 through 88 J cm^{− 2}. Δm so computed agreed with empirical values within experimental error. For samples whose mass is sensitive to environmental factors, off-line measurement of Δm was shown to be unreliable and real-time measurements such as acoustic monitoring became essential.     

DAMAGE OF SILICONE RUBBER INDUCED BY PROTON IRRADIATION

In this paper, the damage to methyl silicone rubber induced by irradiation with protons of 150 keV energy wasstudied. The surface morphology, tensile strength, Shore hardness, cross-linking density and glass transition temperaturewere examined. Positron annihilation lifetime spectrum analysis (PALS) was perfomed to reveal the damage mechanisms ofthe rubber. The results showed that tensile strength and Shore hardness of the rubber increased first and then decreased withincreasing irradiation fluence. The PALS characteristics τ_3 and I_3, as well as the free volume V_f, decreased with increasingirradiation fluence up to 10~(15) cm~(-2), and then increased slowly. It indicates that proton irradiation causes a decrease of freevolume in the methyl silicone rubber when the fluence is less than 10~(15)cm~(-2), while the free volume increases when thefluence is greater than 10~(15)cm~(-2). The results on cross-linking density indicate that the cross-linking induced by protonirradiation is dominant at smaller proton fluences, increasing the tensile strength and Shore hardness of the rubber, while thedegradation of rubber dominates at greater fluence, leading to a decrease of tensile strength and Shore hardness.     

Enhancement of the positive secondary ion yield during low‐energy,dual‐beam depth profiling of polytetrafluoroethylene with 1‐keV Cs+

This work documents the behaviour of the positive secondary ion yield of bulk polytetrafluoroethylene (PTFE) under dual‐beam depth profiling conditions employing 1 keV Ar⁺, Cs⁺ and SF₅⁺. A unique chemical interaction is observed in the form of a dramatic enhancement of the positive secondary ion yield when PTFE is dual‐beam profiled with 1 keV Cs⁺. The distinct absence of such an enhancement is noted for comparison on two non‐fluorinated polymers, polyethylene terephthalate (PET) and polydimethylsiloxane (PDMS). The bulk PTFE was probed using 15‐keV, ⁶⁹Ga⁺ primary ions in dual beam mode under static conditions; 1‐keV Ar⁺ (a non‐reactive, light, noble element), Cs⁺ (a heavier metallic ion known to form clusters) and SF₅⁺ (a polyatomic species) served as the sputter ion species. The total accumulated primary ion dose was of the order of 10¹⁵ ions/cm², which is well beyond the static limit. The enhancement of the positive secondary yield obtained when profiling with 1‐keV Cs⁺ far exceeds that obtained when SF₅⁺ is employed. An explanation of this apparent reactive ion effect in PTFE is offered in terms of polarisation of C? F bonds by Cs⁺ in the vicinity of the implantation site thereby predisposing them to facile scission. The formation of peculiar, periodic Cs_xF_y⁺ (where y = x ? 1) and Cs_xC_yF_z⁺ clusters that can extend to masses approaching 2000 amu are also observed. Such species may serve as useful fingerprints for fluorocarbons that can be initiated via pre‐dosing a sample with low‐energy Cs⁺ prior to static 15‐keV Ga⁺ analysis. Copyright © 2005 John Wiley & Sons, Ltd.     

Use of the vanadium(V)-xylenol orange mixture as an improved reagent for the spectrophotometric determination of traces of hydrogen peroxide

The reaction in V(V)-xylenol orange (XO)-H₂O₂ system was studied by spectrometry. On the addition of hydrogen peroxide to the mixture of vanadium(V) and XO (V-XO reagent), the absorption peak of V(V)-XO complex (λ_max = 582 nm) decreased significantly. The decrease in the absorbance (denoted as ΔA) was proportional to the concentration of hydrogen peroxide. The constant values of ΔA were obtained under the condition of [XO]/[V(V)] = 0.5 ~ 1.2 and in the pH 3.5 ~ 4.5 region. Based on these results, the conditions for the use of the V-XO reagent in the colorimetric determination of hydrogen peroxide were examined in detail. The V-XO reagent was found to be useful for the trace analysis of hydrogen peroxide with high sensitivity, and the data were little affected by the presence of some inorganic and organic substances. The lower limit of the determination is about 1 × 10^?6M.     

Absorbance‐Based Spectroelectrochemical Sensor for [Re(dmpe)3]+ (dmpe=dimethylphosphinoethane)

A spectroelectrochemical sensor was developed for [Re(dmpe)₃]⁺ as a nonradioactive analog for [Tc(dmpe)₃]⁺. The sensor consists of an optically transparent electrode (OTE) coated with a thin film of sulfonated polystyrene‐block‐poly(ethylene‐ran‐butylene)‐block‐polystyrene (SSEBS). Colorless [Re(dmpe)₃]⁺ was reversibly oxidized to [Re(dmpe)₃]²⁺ (λ_max=530 nm). [Re(dmpe)₃]⁺ preconcentrated by ion‐exchange into the SSEBS film, resulting in a 20‐fold increase in peak current compared to a bare OTE after 1 h of exposure to aqueous [Re(dmpe)₃]⁺ solution. Detection of [Re(dmpe)₃]⁺ at concentrations down to 2×10^?6 M was accomplished by electrochemical modulation of the complex and monitoring absorbance by attenuated total reflectance (ATR).     

Spectroscopic evidence for radiation-induced crosslinking of poly(tetrafluoroethylene)

Direct spectroscopic evidence for radiation-induced crosslinking of poly(tetrafluoroethylene) (PTFE) is presented for all x-ray and electron dose levels above which it is possible to distinguish between deliberately introduced radiation damage and the x-ray damage inherent in obtaining an x-ray photoelectron spectrum (XPS). The C (1s) spectrum obtained after irradiation with 2 keV electrons for all doses greater than 1 μA-min/cm² consists of a four-peak spectrum identical to that previously obtained for plasma-polymerized tetrafluoroethylene and assigned to carbon atoms with variable numbers of bound F atoms (CF₃, CF₂, CF₁, and CF₀). X-ray irradiated PTFE can be fitted with the same four-peak spectrum. At or below an electron dose level of 1 μA-min/cm², the radiation damage is comparable to that produced by the x-ray dose necessary to obtain an XPS spectrum. The CF₁ and CF₀ components increase with increasing electron dose, and at high electron doses dominate the spectrum. With increasing dose the CF₃ component approaches a constant value while both the CF₂ component and the total F : C ratio decreases. These four components are those expected to result from radiation-induced crosslinking reactions of the polymer and are consistent with previous suggestions that crosslinking is the basis of radiation patterned adhesion to PTFE. © 1993 John Wiley & Sons, Inc.     

NMR and FTIR studies of coordinate-bonding and intramolecular and intermolecular hydrogen bonding in zinc(II)(3,5-diisopropylsalicylate)2

Carboxylate and salicylic OH coordinate bonding as well as intramolecular and intermolecular hydrogen bonding of bis-3,5-diisopropylsalicylatozinc(II), [Zn^II(3,5-DIPS)₂], with Lewis bases were studied to determine mechanisms accounting for antioxidant reactivity of Zn^II(3,5-DIPS)₂. Apparent thermodynamic parameters: K _eq, ΔS ⁰, ΔH ⁰, and ΔG ⁰ were determined for these equilibria with bonding of two molecules of dimethyl sulfoxide-d₆ (DMSO) or ethyl acetate-d₈ (EA) to the Zn^II using NMR and FTIR. We conclude that addition of two equivalents of DMSO or EA to non-polar solutions of Zn^II(3,5-DIPS)₂ results in bonding of DMSO or EA to Zn^II via sulfoxide or ester carbonyl oxygen atoms with ternary complex formation, leading to weakening of carboxylate and salicylic OH coordinate bonding to Zn^II and strengthening intramolecular hydrogen bonding between protons of salicylic OH groups and carboxylate oxygens. Subsequent addition of two or three additional equivalents of DMSO or EA leads to intermolecular hydrogen bonding between protons of salicylic OH groups.     

Medium energy,heavy and inert ion irradiation of metallic thin films: studies of surface nano‐structuring and metal burrowing

In context to the ion induced surface nanostructuring of metals and their burrowing in the substrates, we report the influence of Xe and Kr ion‐irradiation on Pt:Si and Ag:Si thin films of ~5‐nm thickness. For the irradiation of thin films, several ion energies (275 and 350 keV of Kr; 450 and 700 keV of Xe) were chosen to maintain a constant ratio of the nuclear energy loss to the electronic energy loss (S_n/S_e) in Pt and Ag films (five in present studies). The ion‐fluence was varied from 1.0 × 10¹⁵ to 1.0 × 10¹⁷ ions/cm². The irradiated films were characterized using Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The AFM and SEM images show ion beam induced systematic surface nano‐structuring of thin films. The surface nano‐structures evolve with the ion fluence. The RBS spectra show fluence dependent burrowing of Pt and Ag in Si upon the irradiation of both ion beams. At highest fluence, the depth of metal burrowing in Si for all irradiation conditions remains almost constant confirming the synergistic effect of energy losses by the ion beams. The RBS analysis also shows quite large sputtering of thin films bombarded with ion beams. The sputtering yield varied from 54% to 62% by irradiating the thin films with Xe and Kr ions of chosen energies at highest ion fluence. In the paper, we present the experimental results and discuss the ion induced surface nano‐structuring of Pt and Ag and their burrowing in Si. Copyright © 2016 John Wiley & Sons, Ltd.     

Photoluminescence study of silicon solar cells irradiated with large fluence electrons or protons

In order to investigate the anomalous degradation of space silicon solar cells which was found in large fluence region, photoluminescence measurements are carried out for the cells irradiated with 1 MeV electrons with a fluence exceeding 1×10¹⁶ e/cm² and 10 MeV protons with a fluence exceeding 1×10¹³ p/cm². For both irradiation, the intensity of boron-related bound exiton line decreases with fluence and it disappears at the fluences where the anomalous degradation occurs. The dominant defect is a complex of an interstitial carbon and an interstitial oxygen (C_I–O_I). The generation of five-vacancy-defects was also observed for the proton irradiation. Variations of photoluminescence line intensity are discussed in terms of displacement damage dose calculated based on non-ionizing energy loss (NIEL).     

Effect of bombardment with helium ions on the molecular-topological structure and elemental composition of the surface of Kynar polyvinylidene fluoride resin

A polyvinylidene fluoride film has been bombarded with accelerated (1–5 MeV) helium ions at a fluence of 10¹⁵ ion/cm². Unlike the completely amorphous structure of the unirradiated polymer, the weight fraction of the crystalline modification in the irradiated polymer is 0.86–0.90, which is indicative of the efficient conversion of the amorphous structures of the polymer pseudo-network into the crystalline ones. Irradiation with 1-MeV ions leads to the greatest changes in the fraction of the crystalline modification and the glass-transition and flow temperatures of the polymer. The detachment of fluorine and the surface carbonization of the irradiated polymer occur under the ion beam.     

铀(Ⅵ)与不对称希夫碱配合物的合成和热分解反应动力学

邻苯二胺与5－氯－2－羟基二苯酮、邻香草醛作用合成了一种不对称希夫碱配体C₂₇H₂₁N₂O₃Cl（H₂L）。在正丁醇和甲醇体系中硝酸铀酰与该配体反应合成了一种固体希夫碱配合物[UO₂(HL)(NO₃)(H₂O)]·H₂O。通过元素分析、IR、UV、¹H NMR、TG-DTG及摩尔电导率分析等手段对合成的配合物进行了表征,用非等温热重法研究了铀(Ⅵ)配合物的热分解反应动力学,推断出第三步热分解的动力学方程为：d α /d t = A · e^{- E/RT} ·3/2[(1- α )^-1/3-1]^-1,得到了动力学参数E和A。并计算出了活化熵△S^¹和活化吉布斯自由能△G^¹。     

Effect of 200 keV proton irradiation on the properties of methyl silicone rubber

The effects of 200 keV proton irradiation on methyl silicone rubber were studied. The changes in surface morphology, mechanical properties, cross-linking density, glass transition temperature, infrared attenuated total reflection spectrum and mass spectrum indicated that, at lower fluence, the proton irradiation induced cross-linking, resulting in an increase in tensile strength and hardness of the methyl silicone rubber. However, at higher proton fluence, radiation-induced degradation, which decreased the tensile strength and hardness, became dominant. A macromolecular-network destruction model for silicone rubber irradiated with protons was proposed.     

Investigation of O7+ swift heavy ion irradiation on molybdenum doped indium oxide thin films

Molybdenum (0.5 at%) doped indium oxide thin films deposited by spray pyrolysis technique were irradiated by 100 MeV O⁷⁺ ions with different fluences of 5×10¹¹, 1×10¹² and 1×10¹³ ions/cm². Intensity of (222) peak of the pristine film was decreased with increase in the ion fluence. Films irradiated with the maximum ion fluence of 1×10¹³ ions/cm² showed a fraction of amorphous nature. The surface microstructures on the surface of the film showed that increase in ion fluence decreases the grain size. Mobility of the pristine molybdenum doped indium oxide films was decreased from ～122 to 48 cm²/V s with increasing ion fluence. Among the irradiated films the film irradiated with the ion fluence of 5×10¹¹ ions/cm² showed relatively low resistivity of 6.7×10^?4 Ω cm with the mobility of 75 cm²/V s. The average transmittance of the as-deposited IMO film is decreased from 89% to 81% due to irradiation with the fluence of 5×10¹¹ ions/cm².     

The Effect of –(C6F4)– on the Surface Free Energy of Main‐Chain Liquid Crystalline and Crystalline Polymers

Novel fluorinated main‐chain liquid‐crystalline/crystalline polymers were prepared through thin film polymerization to investigate the effect of –(C₆F₄)– on the surface free energy. The fluorine in the phenyl rings does not lower the total surface free energy of the thin copolymer films, compared to those without fluorine. Interestingly, the Lewis acid components (γ⁺) of the surface free energy of the fluorine‐containing polymers increase with an increase in the –(C₆F₄)– content, indicating the increasing electron accepting character of the surface.