Polymer track membranes for atmospheric pressure field extraction of ions from liquid solutions

An approach to the generation of gas phase ions by field extraction from liquid solutions has been investigated. The method uses a polymer membrane with nano-size channels as an interface between the liquid and the atmospheric pressure gas. Ions are produced by dissociation in the polar solvent and secondary ion-molecular reactions in the solution, which fills the channels of the membrane. Field extraction of the ions from the channels is stimulated by pulses of the electric discharge between the membrane and an adjacent electrode in the gas. The gas-phase ions are removed from the extraction zone by air flow and are detected by mass spectrometry. Possibilities of the membrane interface for generation of gas phase ions have been demonstrated from mass spectral investigation curried out for angiotensin II, gramicidin S and cytochrome C solutions. The current kinetics of the membrane ion source has been investigated to elucidate the mechanism of the ion extraction.     

Field evaporation of doubly charged ions from a polar liquid

The effect of charge on field evaporation of ions from polar liquids is considered. Using the electromembrane ion source, we performed mass-spectral analysis of field evaporation of ions from the solution of sodium sulfate in a water-glycerol mixture. The composition of doubly charged cluster ions in the field evaporation from glycerol is determined. The rates of the field evaporation of doubly charged ions and singly charged ions are compared. It is shown that the ion charge as well as its localization considerably influences the efficiency of field evaporation of ions from polar liquids.     

Field evaporation of impurity ions from a liquid gallium ion source

The charge states of ions emitted from a gallium liquid metal field ion (LMI) source contaminated with tin and copper have been measured. The results for tin show that the proportion of Sn²⁺ to Sn⁺ is much larger than is found for a LMI source of pure tin. A model in which Sn²⁺ is assumed to be produced by post-ionization of Sn⁺ is used to set an upper limit to the electric field at the point of emission. Its value is approximately equal to that predicted by field evaporation theory for a pure gallium source. Consequently the charge states of emitted impurity ions are determined by field strengths imposed by the main component.     

Generation of ions in a pulsed ion source with an interface based on a polymer track membrane

The time-of-flight spectra of ions generated during the extraction of negative ions from the KI solution in water–glycerin mixture by high-strength electric field pulses are studied using a source with an interface based on a polymer track membrane. It has been shown that the ions formed in secondary processes of bombardment of the membrane surface make a considerable contribution to the observed spectra. It has been found that the peaks of negative hydrogen ions have the highest intensity in the spectrum, indicating effective emission of these ions during the bombardment of polyethylene terephthalate by secondary ions with an energy of about 6 keV. The main trends in the modification of the membrane interface to reduce the fraction of secondary ions in the ion beam have been outlined.     

Irreversible adsorption from dilute polymer solutions

We study irreversible polymer adsorption from dilute solutions theoretically. Universal features of the resultant non-equilibrium layers are predicted. Two broad cases are considered, distinguished by the magnitude of the local monomer-surface sticking rate Q: chemisorption (very small Q) and physisorption (large Q). Early stages of layer formation entail single-chain adsorption. While single-chain physisorption times are typically micro- to milli-seconds, for chemisorbing chains of N units we find experimentally accessible times , ranging from seconds to hours. We establish 3 chemisorption universality classes, determined by a critical contact exponent: zipping, accelerated zipping and homogeneous collapse. For dilute solutions, the mechanism is accelerated zipping: zipping propagates outwards from the first attachment, accelerated by occasional formation of large loops which nucleate further zipping. This leads to a transient distribution of loop lengths s up to a maximum size after time t. By times of order the entire chain is adsorbed. The outcome of the single-chain adsorption episode is a monolayer of fully collapsed chains. Having only a few vacant sites to adsorb onto, late-arriving chains form a diffuse outer layer. In a simple picture we find for both chemisorption and physisorption a final loop distribution and density profile whose forms are the same as for equilibrium layers. In contrast to equilibrium layers, however, the statistical properties of a given chain depend on its adsorption time; the outer layer contains many classes of chain, each characterized by a different fraction of adsorbed monomers f. Consistent with strong physisorption experiments, we find the f values follow a distribution .Received: 13 January 2003, Published online: 8 July 2003PACS: 82.35.-x Polymers: properties; reactions; polymerization - 05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion - 68.08.-p Liquid-solid interfaces     

On the multi-spin magnon and spike solutions from membranes

Recently important classes of solitonic string solutions were obtained—giant magnons and single spikes. In previous study we showed the existence of giant magnon-like membrane solutions and studied their properties. In this paper we investigate classical rotating membranes representing analog of a specific class of string spiky solutions. Using the reduction to the Neumann–Rosochatius integrable system we find analog of the string single spike solutions. In contrast to the magnon-like solutions, this case is characterized with finite difference of energy and “winding number” and finite spins as well.     

Excimer state of a conjugate polymer (MEH-PPV) in liquid solutions

The conjugated polymer poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) is an important electrooptical material, which is useable as an excellent laser media. In this paper, we present the absorption and fluorescence spectral characteristics of MEH-PPV in a few organic solvents. The paper shows that MEH-PPV exists in an excimeric state in benzene, and that the laser action as shown here arises from a liquid excimeric state.     

X-ray scattering from polymer nematic liquid crystals

X-ray scattering from main chain polymer nematics is discussed from the point of view of its use in studying the ordering and fluctuations of the polymer chains that make up the nematic phase. An example of data from poly-γ-benzyl glutamate is given, with a discussion of the important features of the data, in terms of the current understanding of the nature of nematic ordering in main chain polymer systems. This includes analyses of the angular distribution function for the polymer segments, long wavelength fluctuations dictated by elastic phenomena, the effects of finite chain lengths, and effects due to the short range interactions and packing of the chains.     

Beam profile measurement with CR-39 track detector for low-energy ions

A CR-39 track detector was successfully used to measure the outline of thin low-energy ion beams. After the etching, the surface of the detector was examined with an observation system composed of a Normarski microscope, a CCD camera and a digital image processing computer. Beam images obtained with the system were in good agreement on the outline of the beam formed with a beam aperture. Also, the resolving power in the beam outline measurement was roughly explained from the consideration of the ion range and the etch-pit growth in the chemical etching for the CR-39 detector.     

Field emission pressure sensors with non-silicon membranes

We report on the fabrication of cold cathode emitter and the design parameter simulation of a functional field emission-based pressure sensor. This device comprises a membrane made of metallic compound acting as the anode in front of a flat cold cathode emitter. First, the mechanical deflection of a diaphragm under selected input pressures is modeled. The current density distribution in the deflected diaphragm is then calculated using realistic field emission characteristics from fabricated sulfur doped boron nitride (S-BN) cold cathode device. The total current output was found by integrating the measured current density of the fabricated electron emitter device over the entire diaphragm area of the membrane as function of external pressure. The results show that conventional silicon membranes would pose problems when implemented in a real field emission device, and show how the use of unconventional materials (i.e., TiN) can help overcome these problems.     

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模拟了锂铅合金中氚提取技术,在采用流体力学建立代数模型的基础上,开展了旋转喷嘴鼓泡法提取锂铅合金中氢的研究。研究结果表明：锂铅熔融温度越高,氢提取累计效率越高;鼓泡床气含率受叶轮孔径影响不大,只是在较高的氦气流速下,采用小孔径时的气含率略高于大孔径,但孔径越小,气泡比表面积越大;随着氦气流速的增加,液态锂铅流循环强度明显增加,氢提取速率加快;喷头转速对氢提取影响有限。     

旋转喷嘴鼓泡法提取液态锂铅合金中的氢

模拟了锂铅合金中氚提取技术,在采用流体力学建立代数模型的基础上,开展了旋转喷嘴鼓泡法提取锂铅合金中氢的研究。研究结果表明：锂铅熔融温度越高,氢提取累计效率越高;鼓泡床气含率受叶轮孔径影响不大,只是在较高的氦气流速下,采用小孔径时的气含率略高于大孔径,但孔径越小,气泡比表面积越大;随着氦气流速的增加,液态锂铅流循环强度明显增加,氢提取速率加快;喷头转速对氢提取影响有限。     

Adsorption of phenolic compounds from aqueous solutions using carbon nanoporous adsorbent coated with polymer

Phenolic compounds are a widespread class of water pollutants that are known to cause serious human health problems; and the demand for effective adsorbents for the removal of toxic compounds is increasing.In this work adsorption of phenol, resorcinol and p-cresol on mesoporous carbon material (CMK-1) and modified with polyaniline polymer (CMK-1/PANI) has been investigated in attempt to explore the possibility of using nanoporous carbon as an efficient adsorbent for pollutants. It was found that CMK-1/PANI exhibits significant adsorption for phenolic derivatives. Batch adsorption studies were carried out to study the effect of various parameters like adsorbent dose, pH, initial concentration and contact time. From the sorption studies it was observed that the uptake of resorcinol was higher than other phenolic derivatives. Freundlich and Langmuir adsorption isotherms were used to model the equilibrium adsorption data for phenolic compounds.     

Polypropylene track membranes as a promising material for targets with polarized protons

Polypropylene track membranes made by irradiation of polypropylene films with a beam of high-energy heavy ions followed by chemical etching of latent ion tracks are proposed for being used as a polarized target material. To give membranes paramagnetic properties needed for allowing dynamic polarization of nuclei, the nitroxyl radical 2,2,6,6-tetramethylpiperidine-1-oxyl was introduced in the samples by the thermal diffusion technique. Using the electron paramagnetic resonance method, we obtained information on paramagnetic centers in the polymer matrix of the membranes and determined the nitroxyl radical concentration and rotational mobility of the spin probe in them.     

Viscosity of concentrated polymer solutions

In investigations of the Newtonian viscosity of polymer fluids, two concentration regions have received the major attention. One is the dilute solution where the contributions of the individual solute entities are essentially additive with only small interaction perturbations. The other is the bulk polymer or plasticized melt. We are concerned here with the broad intermediate region.     

Turbulent dynamics of polymer solutions

We study properties of dilute polymer solutions. The probability density function (PDF) of polymer end-to-end extensions R in turbulent flows is examined. We show that if the value of the Lyapunov exponent lambda is smaller than the inverse molecular relaxation time 1/tau then the PDF has a strong peak at the equilibrium size R0 and a power tail at R>R0. This confirms and extends the results of J. L. Lumley [Symp. Math. 9, 315 (1972)]. There is no essential influence of polymers on the flow in this regime. At lambdatau>1 the majority of molecules is stretched to the linear size R(op)>R0, which can be much smaller than the maximal length of the molecules due to their back reaction.     

Extraction of ions from polar solutions by high-strength electric field pulses

Extraction of ions from solutions of salts in ethylene glycol and water-glycerol mixture by high-strength electric field pulses is investigated. The conditions for stable extraction of ions from a polar liquid in the pulsed regime are ensured by using a track membrane with channels of a nanosize diameter as the interface between the liquid solution and vacuum. The possibility of barrier-free field evaporation of ions from polar liquids in electromembrane ion source for mass-spectrometric analysis of solutions is considered.