Characteristics of heavy ion tracks in bubble detectors

Characteristics of tracks created by heavy ions in bubble detectors have been studied in detail by using four types of super long (23 cm), self-made bubble detectors and six species of high energy heavy ions: ¹²C, ²⁸Si, ⁴⁰Ar, ⁵⁶Fe, ⁸⁴Kr and ¹³²Xe. The following characteristics of heavy ion tracks in bubble detectors have been recognized:

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The wettability of poly(tetrafluoroethylene) by aqueous solutions of ternary surfactant mixtures

Contact angle measurements on poly(tetrafluoroethylene) (PTFE) surface were carried out for the systems containing ternary mixtures of cetyltrimethylammonium bromide (CTAB) and p-(1,1,3,3-tetramethylbutyl)phenoxypoly(ethylene glycols), Triton X-100 (TX100) and Triton X-165 (TX165). The aqueous solution of ternary surfactant mixtures were prepared by adding the third surfactant to the binary mixture of the surfactants where the synergetic effect in the reduction of the surface tension of water was determined, to compare the influence of the third surfactants on the values of surface tension of this binary mixture and the values of the contact angle on PTFE. The obtained results and calculations indicate that the ternary mixtures of CTAB + TX165 (αCTAB = 0.2, γ_LV = 60 and 50 mN/m) + TX100 (C = 10⁻⁸ to 10⁻² M) have the biggest efficiency of the reduction of contact angle of water on PTFE in comparison to aqueous solutions of the single surfactants and their binary and ternary mixtures. Also in the case of all studied ternary mixtures of surfactants at concentrations of the bulk phase corresponding to unsaturated monolayer at water-air interface the adsorption of surfactants at PTFE-water interface is different than that at water-air interface, but is the same at concentrations near the critical micelle concentration (CMC). Thus the linear dependences between γ_LV cos θ − γ_LV and cos θ − 1/γ_LV, in the range of concentration studied for all systems confirm the same adsorption at two interfaces only at C near the CMC.     

Studies on surface modification of poly(tetrafluoroethylene) film by remote and direct Ar plasma

Poly(tetrafluoroethylene) (PTFE) surfaces are modified with remote and direct Ar plasma, and the effects of the modification on the hydrophilicity of PTFE are investigated. The surface microstructures and compositions of the PTFE film were characterized with the goniometer, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Results show that the remote and direct plasma treatments modify the PTFE surface in morphology and composition, and both modifications cause surface oxidation of PTFE films, in the forming of some polar functional groups enhancing polymer wettability. When the remote and direct Ar plasma treats PTFE film, the contact angles decrease from the untreated 108-58° and 65.2°, respectively. The effect of the remote Ar plasma is more noticeable. The role of all kinds of active species, e.g. electrons, ions and free radicals involved in plasma surface modification is further evaluated. This shows that remote Ar plasma can restrain the ion and electron etching reaction and enhance radical reaction.     

Nitrogen plasma-based ion implantation of poly(tetrafluoroethylene): Effect of the main parameters on the surface properties

The surface of poly(tetrafluoroethylene) (PTFE or Teflon) was treated by nitrogen plasma-based ion implantation. Accelerating voltages between 15 and 30 kV, fluences between 1 × 10¹⁷ and 3 × 10¹⁷ cm⁻² and fluence rates between 3 × 10¹³ and 7 × 10¹³ cm⁻² s⁻¹ were applied. The effects of these main parameters were examined on the evolution of surface chemical composition, mean roughness, abrasive wear, wettability and surface electrical resistance. The aim was to obtain relationships, enabling to control the surface properties examined.The F/C atomic ratio determined by XPS strongly decreased, correlating inversely with voltage. The mean surface roughness characterized by topography measurements, increased, correlating directly with fluence and inversely with voltage. The wear volume obtained by multipass scratch tests did not show clear relationship with the main process parameters, however, it increased upon treatment with the increase of surface roughness and O/C atomic ratio. The water contact angle increased at low voltages and high fluences, due to preferential increase of roughness, and decreased at high voltages and low fluences, owing to intense defluorination and incorporation of N and O. The electrical resistance of the PBII-treated surfaces decreased by several orders of magnitude, showing a significant inverse correlation with fluence. It continued to decrease for samples exposed to air, primarily after treatments performed with low fluences, due to post-treatment type oxidation.     

Clustering of magnetic nanoparticles using a double hydrophilic block copolymer, poly(ethylene oxide)-b-poly(acrylic acid)

The use of a double hydrophilic block copolymer (DHBC), poly(ethylene oxide)-block-poly(acrylic acid) (PEO-b-PAA) to prepare magnetic nanoparticle (MNP) clusters was investigated. In this one-pot synthesis method, the DHBC controlled the particle growth and served as both stabilizer and clustering agent. Depending on the iron-to-polymer ratio, the synthesized particles can be in the form of colonies of small iron oxide particles or clusters of these particles with size larger than 100 nm. Compared to the previous reported result using random copolymers, the clusters prepared with DHBC were more compact and homogeneous. The yield of clusters increased when the amount of polymer added was limiting. Insufficient amounts of polymer resulted in the formation of bare patches on the magnetite surface, and the strong van der Waals attraction induced cluster formation.     

乙烯在Ni（110）表面吸附的几何结构

用理论计算的方法研究了不同覆盖度的乙烯在Ni（110）表面吸附的位置.乙烯的吸附几何结构在团簇计算中进行了局部优化.在低覆盖度下，单个乙烯分子占据了短桥位和顶位之间的中间位置.乙烯分子的C—C轴大致沿衬底的Ni原子链排列（即沿<110>晶向），C—C轴与衬底Ni（110）表面有10°的倾斜角.乙烯分子的C—C键的键长为0151nm.在高覆盖度下(05ML)，乙烯在Ni (110)上形成了有序的c（2×4）相，在一个表面元胞内的两个乙烯分子的吸附位置类似于低覆盖度时的结果，但乙烯分子的C—C 键键长分别为0142和0143nm.     

Rheological,thermal, and mechanical properties of poly(ethylene naphthalate)/poly(ethylene terephthalate) blends

Structural, Theological, thermal, and mechanical properties of blends of poly(ethylene naphthalate) (PEN) and poly(ethylene terephthalate) (PET) obtained by melt blending were investigated using capillary rheometry, differential scanning calorimetry (DSC), scanning electron microscopic (SEM) observation, tensile testing. X-ray diffraction, and ¹H nuclear magnetic resonance (NMR) measurements. The melt Theological behavior of the PEN/PET blends was very similar to that of the two parent polymers. The melt viscosity of the blends was between that of PEN and that of PET. Thermal properties and NMR measurement of the blends revealed that PEN is partially miscible with PET in the as molded blends, indicating that an interchange reaction occurs to some extent on melt processing. The blend of 50/50 PEN/PET was more difficult to crystallize compared with blends of other PEN/PET ratios. The blends, once melted during DSC measurements, almost never showed cold crystallization and subsequent melting and definitely exhibited a single glass transition temperature between those of PEN and PET during a reheating run. Improvement of the miscibility between PEN and PET with melting is mostly due to an increase in transesterification. The tensile modulus of the PEN/PET blend strands had a low value, reflecting amorphous structures of the blends, while tensile strength at the yield point increased linearly with increasing PEN content.     

Control of the temperature responsiveness of poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) copolymer using ultrasonic irradiation

Poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) (poly(NIPAM-co-HEMA)) is a temperature-responsive copolymer that is expected to be applicable as an advanced functional polymeric material in various fields. In this study, a novel method was developed to control the responsive temperature of poly(NIPAM-co-HEMA) using an ultrasonic polymerization technique. Initially, the behavior of the reaction was investigated using NIPAM and HEMA monomers under ultrasonic irradiation. A high ultrasonic power was found to produce a high reaction rate and low number average molecular weight of the copolymer. The polydispersity of the synthesized copolymer was approximately 1.5 for all ultrasonic powers examined. In the early stage of the reaction, the molar fraction of NIPAM in the copolymer was lower than the initial molar fraction of the monomers. It was concluded that ultrasonic irradiation affected the initiation reaction and polymer degradation, but did not affect the propagation reaction. Furthermore, the effect of the ultrasonic irradiation conditions on the temperature responsiveness of the copolymer was investigated. The lower critical solution temperature (LCST) of the copolymer was found to increase with increasing ultrasonic irradiation time. In addition, in the early stages of the reaction, the measured values of the LCST were higher than the estimated values using copolymer composition. This can be attributed to some parts of the copolymer chain possessing a higher NIPAM fraction than the overall fraction due to different reactivities of the monomers and terminated radicals. This hypothesis was indirectly verified by the synthesis of a block copolymer from the PNIPAM homopolymer and HEMA monomer.     

Study of the reaction step preceding sequential fission in the nuclear interaction (16.7 MeV/u) U+Au

The kinematical analysis of nuclear reactions between (16.7 MeV/u) ²³⁸U and ^nat.Au ions has been performed by using mica solid-state track detectors (SSNTD). The reaction products emanating from each isolated collision vertex were registered in the forward hemisphere with almost 2π angular coverage. It has been demonstrated previously that these tracks represent the second stage of a sequential fission process. In this paper the results of analysis pertaining to the first reaction step have been presented. Using a computer code based on the procedure of internal calibration it was possible to derive quantities like mass transfer, total kinetic energy loss, and scattering angles. It is shown that the mass flow and kinetic energy distribution between reacting partners interacting at different impact parameters during the first phase of the interaction decides the multiplicity of the final reaction products.     

Ionic conductivity of electrolytes based on star-branched poly(ethylene oxide) with high concentration of lithium salts

Electrolytes based on star-branched poly(ethylene oxide) with lithium bis(trifluoromethanesulfone)imide LiTFSI and lithium iodide salts were prepared by casting from solution. The electrical properties of electrolytes subjected to various heating and cooling runs were studied by impedance spectroscopy and impedance spectroscopy simultaneous with optical microscope observation. Differential scanning calorimetry was used for additional characterization. The results indicate that in electrolytes with high content of salt, values of ionic conductivity comparable to that of dilute electrolytes can be achieved. Moreover, electrolytes with high amount of salt seem to show weaker temperature dependence of conductivity. Promising results in terms of ionic conductivity were obtained for mixture of LiTFSI and lithium iodide. A few problems which may decrease the performance of studied system as a solid electrolyte were also identified, from which changes of physical properties of samples subjected to thermal cycles and aging seem to be the most important ones.     

Surface Modification of Poly(tetrafluoroethylene) Microporous Membranes by Acrylic Acid Liquid-Phase Graft Copolymerization

Air plasma-pretreated poly(tetrafluoroethylene) (PTFE) films were subjected to further surface modification by liquid-phase graft copolymerization with acrylic acid monomer (AAc). The surface compositions and microstructures of the modified films were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). An exterior graft copolymerization of AAc on the PTFE fiber was indicated by the SEM photographs. The XPS results indicated that the F/C atomic ratio of the membranes were 1.837 and 1.207, and the O/C atomic ratio were 0 and 0.112 for the original and liquid-phase grafted PTFE membranes, respectively. The pore size distributions of the treated and untreated PTFE membranes, measured by the bubble-point method, were much smaller than that of the untreated membrane.     

Ultrasound enhances lipase-catalyzed synthesis of poly (ethylene glutarate)

The present work explores the best conditions for the enzymatic synthesis of poly (ethylene glutarate) for the first time. The start-up materials are the liquids; diethyl glutarate and ethylene glycol diacetate, without the need of addition of extra solvent. The reactions are catalyzed by lipase B from Candida antarctica immobilized on glycidyl methacrylate-ter-divinylbenzene-ter-ethylene glycol dimethacrylate at 40 °C during 18 h in water bath with mechanical stirring or 1 h in ultrasonic bath followed by 6 h in vacuum in both the cases for evaporation of ethyl acetate. The application of ultrasound significantly intensified the polyesterification reaction with reduction of the processing time from 24 h to 7 h. The same degree of polymerization was obtained for the same enzyme loading in less time of reaction when using the ultrasound treatment. The degree of polymerization for long-term polyesterification was improved approximately 8-fold due to the presence of sonication during the reaction. The highest degree of polymerization achieved was 31, with a monomer conversion of 96.77%. The ultrasound treatment demonstrated to be an effective green approach to intensify the polyesterification reaction with enhanced initial kinetics and high degree of polymerization.     

An experimental study on the effect of mesoporous silica addition on ion conductivity of poly(ethylene oxide) electrolytes

Solid polymer electrolyte (SPE) composites, which are composed of poly(ethylene oxide) (PEO), mesoporous silica (SBA-15), and lithium salt were prepared in order to investigate the influence of SBA-15 content on the ionic conductivity of the composites. The ionic conductivity of the SPE composites was monitored by frequency response analyzer (FRA), and the crystallinity of the SPE composites was evaluated by using XRD. As a result, the addition of SBA-15 to the polymer mixture inhibited the growth of PEO crystalline domain, due to the mesoporous structure of the SBA-15. Also, the PEO₁₆LiClO₄/SBA-15 composite electrolytes show an increased ion conductivity as a function of SBA-15 content up to 15 wt.%. These ion conductivity characteristics are dependent on crystallinity with SBA-15 content.     

Effect of gamma-ray irradiation on isothermal crystallization of biodegradable poly(ethylene succinate)

The effects of gamma-ray irradiation on the isothermal crystallization of biodegradable poly(ethylene succinate) (PESu) and the growth behavior of PESu spherulites have been studied by differential scanning calorimetry and polarized optical microscopy. The irradiation doses used in the study are 0, 200, 400, and 600 kGy. The kinetic parameters for the isothermal crystallization have been determined, using the Avrami relationship. The nucleation constants and activation energy for the growth of the PESu spherulites have been analyzed, using the Lauritzen-Hoffman growth theory. Triple melting points have been observed for all the irradiated PESu. The gamma irradiation has no observable effect on the Avrami exponent, and the composite rate constant increases first with the increase of the crystallization temperature, reaches maximum at the crystallization temperature of ~35 °C, and then decreases with the increase of the crystallization temperature for both the non-irradiated and irradiated PESu. There exists a transition of the growth of the PESu spherulites from regime II to regime III. Both the nucleation constants and activation energy increase with increasing the irradiation dose. The gamma irradiation increases the energy barrier for the migration of polymer chains.     

Study of projectile fragmentation in the reaction (158 A GeV) Pb + Pb using CR-39

The fragmentation of Pb ions at 158 A GeV energy produced in the interaction with Pb target has been studied using a CR-39 track detector. A stack comprising of 64 detectors was prepared such that a target of 1 cm thickness was sandwiched between the sheets of CR-39. The purpose of this exposure geometry was to calibrate CR-39 with respect to relativistic heavy ions as well as to study the fragmentation of Pb ions at 158 A GeV energy. The exposure was carried out at the SPS beam facility of CERN at normal incidence with a fluence of . Two detectors from the exposed stack have been selected for this study: one before and the other after the target material. After etching, the detectors were scanned using an optical microscope and the etched track lengths and the diameters of the track openings were measured manually. Considering that the lengths of tracks provide the best charge resolution for Z>65, we have measured track lengths for a sufficiently large number of fragments to identify individual charge states for 65<Z<83. The total charge-changing cross section has also been determined.     

Effect of the shell on the transport properties of poly(glycerol) and Poly(ethylene imine) nanoparticles

Dendritic core–shell architectures containing poly (glycerol) and poly (ethylene imine) cores and poly(lactide) shell (PG-PLA and PEI-PLA respectively) were synthesized. Analogous of these core–shell architectures containing the same cores but poly (L-lactide) shell (PG-PLLA and PEI-PLLA, respectively) were also synthesized. In this work PG and PEI were used as macroinitiator for ring opening polymerization of the lactid and L-lactide monomers. Different molar ratios of monomer to end functional groups of PG ([LA]/[OH]) and PEI ([LA]/[NHn] (n = 1 or 2)) were used to prepare the core–shell architectures with different shell thickness. These core–shell architectures were able to encapsulate and transport the small guest molecules. Their transport capacity (TC) depended on the type and thickness of the shells. TC of core–shell architectures containing PLLA shell was higher than that for their analogs containing PLA shell. The diameter of core–shell architectures was between 20–80 nm. The rate of release of guest molecules from chloroform solution of nanocarriers to water phase was investigated and it depended on the type of the core, shell and solvent.     

Structure-dependent magnetic susceptibility of sharp poly(ethylene oxide) fractions

Nine sharp fractions of poly(ethylene oxide) (PEO) glycol with number-average molar masses (M _n) in the range from 0.6 × 10³ to 20 × 10³ (PEO-0.6 to PEO-20) were characterized by magnetic susceptibility χ measured in the temperature interval 293 K to 378 K. In contrast to the liquidlike PEO-0.6 with temperature-invariant χ, the values of χ for each of the remaining solid samples, after the initial increase, exhibited two plateaus separated by a relatively narrow temperature interval of their second increase. The jumps of χ at lower and higher temperatures were attributed to a solid-state transition of unspecific nature and to the melting of the crystal fraction, respectively.

The temperature-invariant values of χ_n in the melt state above T _m pass through a minimum for the sample PEO-2.0 and then increase again with (M_n) to a limiting value χ_∞ = ?0.622 × 10^?6. It is concluded that a considerable contribution of the molar-mass-dependent “paramagnetism” χ_P = χ ^? χ_d (where χ_d is the diamagnetic contribution estimated by Kirkwood's equation) to the total magnetic susceptibility of PEO fractions reflects distortions of the spherical symmetry of the electron shells around chain atoms resulting from the discontinuous change of both inter- and intrachain interactions as the (M_n) increases through and above the critical crossover molar mass (M_cr ) = 2 × 10³.     

铕(Ⅲ)-4-乙烯基吡啶共聚物稀土高分子配合物的合成及其光物理行为的研究

以4-乙烯基吡啶（4VP）与甲基丙烯酸甲酯（MMA）的共聚物为配体，并以邻菲洛啉（Phen)及2，2′-联吡啶（Bipy)小分子配体协同反应，与Eu(Ⅲ）配位，合成了稀土高分子配合物；通过FTIR表征了配合物的结构；通过紫外光谱与荧光光谱的测定，较充分地研究了稀土高分子配合物光致发光的光物理过程，实验结果表明，4-乙烯基吡啶共聚物通过吡啶环上的氮原子与稀土离子可直接配位；小分子配体的协同配位，可使稀土离子配位数趋于满足，且由于小分子配体能有效地加强能量吸收及分子内的能量传递，大大增强了配合物的荧光强度。     

Star-shaped oligo(ethylene glycol) ethers (OEGE) as a new type of plasticizer for polymer gel electrolytes

Star-shaped oligo(ethylene glycol) methyl ethers (three and four arm molecules of various molecular weights) were synthesized and characterized with regard to viscosity, thermal transitions, ability to solvate the electrolyte LiCF₃SO₃ and the ionic conductivity of their LiCF₃SO₃ solutions in comparison to linear oligo(ethylene glycol) methyl ethers. Polymer gel electrolytes were prepared by photopolymerization of tri(ethylene glycol) dimethacrylate (EG₃DMA) or its copolymerization with the polar comonomer cyanomethyl methacrylate (CyMA) in the presence of the oligo(ethylene glycol) ethers mentioned above and of the electrolyte LiCF₃SO₃. The gels were characterized concerning their thermal transitions, thermo-mechanical properties, their ability to solvate the electrolyte and their ionic conductivity. In comparison to the linear plasticizers the star-shaped ones show a distinctly lower tendency to crystallize, which is even completely suppressed in several cases. Intensified ion association was found in LiCF₃SO₃ solutions of the star-shaped plasticizers, if the number of the ethylene glycol units per arm was lower than 4. Therefore, the conductivity of the solutions and the gels was lower than that with linear plasticizers at room temperature. The modification of the polymer matrix by copolymerization with 20 mol% CyMA resulted in a maximum of the ionic conductivity σ≈1×10⁻⁵ S/cm of gels with star-shaped plasticizers at 25 °C.     

Electrochemical characteristics of the dimercaptan-poly(ethylene oxide) grafted polyaniline electrodes

The electrochemical and transport properties of the 2,5-dimercapto-1,3,4-thiadiazole (DMcT)/poly(ethylene oxide) (PEO) grafted polyaniline electrodes and the DMcT/polyaniline electrode interfaced with the poly(acrylonitrile) (PAN) based solid-polymer-electrolyte (SPE) containing lithium perchlorate and ethylene carbonate were studied. Compared with the electrochemical and transport properties of the DMcT/polyaniline electrode, the capacitance and voltammetric current density, obtained by cyclic voltammetry, were increased for the electrode with low grafted polyaniline (less than 3 mol. %), while decreased when the applied copolymers were highly grafted ones. The charge transfer resistance obtained from impedance measurements was much smaller in the DMcT/PEO grafted polyaniline electrode than that in the DMcT/polyaniline electrode, and more pronounced reduction of charge transfer resistance was observed for the electrode with low grafted polyaniline. The diffusion coefficient of lithium cation in the electrode was increased when the PEO grafted polyaniline was used as an electrode material, however, the increase of the diffusion coefficient was less significant at higher graft degrees. All these changes in electrochemical and transport characteristics by the employment of PEO chains upon polyaniline backbones were attributed to the enhancement of lithium ion solvation and enlarged free volume in the electrode.