A 2-kW COIL with a square pipe-array JSOG and nitrogen buffer gas

A 2-kW-class chemical oxygen-iodine laser (COIL) using nitrogen buffer gas has been developed and tested since industrial applications of COIL devices will require the use of nitrogen as the buffer gas. The laser, with a gain length of 11.7 cm, is energized by a square pipe-array jet-type singlet oxygen generator (SPJSOG) and employs a nozzle bank with a designed Mach number of 2.5. The SPJSOG has advantages over the traditional plate-type JSOG in that it has less requirements on basic hydrogen peroxide (BHP) pump, and more important, it has much better operational stability. The SPJSOG without a cold trap and a gas-liquid separator could provide reliable operations for a total gas flow rate up to 450 mmol/s and with a low liquid driving pressure of around 0.7 atm or even lower. The nozzle bank was specially designed for a COIL using nitrogen as the buffer gas. The cavity was designed for a Mach number of 2.5, in order to provide a gas speed and static temperature in the cavity similar to that for a traditional COIL with helium buffer gas and a Mach 2 nozzle. An output power of 2.6 kW was obtained for a chlorine flow rate of 140 mmol/s, corresponding to a chemical efficiency of 20.4%. When the chlorine flow rate was reduced to 115 mmol/s, a higher chemical efficiency of 22.7% was attained. Measurements showed that the SPJSOG during normal operation could provide a singlet oxygen yield Y greater than or equal to 55%, a chlorine utilization U greater than or equal to 85%, and a relative water vapor concentration w = [H2O]/([O-2] + [Cl-2]) less than or equal to 0.1.

Systematic study of the transfer of amino acids across the water/1,2-dichloroethane interface facilitated by dibenzo-18-crown-6

Facilitated ion transfer reactions of 20 amino acids with di.benzo-18-crown-6 (DB18C6) at the water/1,2-dichloroethane (W/DCE) interfaces supported at the tips of micro- and nano-pipets were investigated systematically using cyclic voltammetry. It was found that there were only 10 amino acids, that is, Leu, Val, Ile, Phe, Trp, Met, Ala, Gly, Cys, Gln (in brief), whose protonated forms as cations can give well-defined facilitated ion transfer voltammograms within the potential window, and the reaction pathway was proven to be consistent with the transfer by interfacial complexation/dissociation (TIC/TID) mechanisms. The association constants of DB 18C6 with different amino acids in the DCE (beta(0)), and the kinetic parameters of reaction were evaluated based on the steady-state voltammetry of micro- or nano-pipets, respectively The experimental results demonstrated that the selectivity of complexation of protonated amino acid by DB18C6 compared with that of alkali metal cations was low, which can be attributed to the vicinal effect arising from steric hindrance introduced by their side group and the steric bulk effect by lipophilic stabilization.

Studies of effect of phase volume ratio on transfer of ionizable species across the water/1,2-dichloroethane interface by a three-electrode setup

The electrochemical behavior of pyridine distribution at the water/1,2-dichloroethane interface with variable phase volume ratios (r=V-0/V-W) was investigated by cyclic voltammetry. The system was composed of an aqueous droplet supported on a Ag/AgCl disk electrode covered with an organic solution or an organic droplet supported on a Ag/AgTPBCl disk electrode covered with an aqueous solution. In this way, a conventional three-electrode potentiostat can be used to study an ionizable compound transfer process at a liquid/liquid interface with a wide range of phase volume ratios (from 0.0004 to 1 and from 1 to 2500). Using this special cell we designed, only very small volumes of both phase were needed for r equal to unity, which is very useful for the investigation of the distribution of ionizable species at a biphasic system when the available amount of species is limited. The ionic partition diagrams were obtained for different phase volume ratios.

Electrochemical recognition of alkali metal ions at the micro-water 1,2-dichloroethane interface using a calix[4]arene derivative

In this paper, a calix[4]arene derivative, 5,11,17,23-butyl-25,26,27,28-tetra-(ethanoxycarbonyl)-methoxy-calix[4]arene (L), is investigated as a host to recognize alkali metal ions (Li+, Na+, K+, Rb+ and Cs+) at the interface between two immiscible electrolyte solutions (ITIES). Well-defined cyclic voltammograms are obtained at the micro- and nano-water \ 1,2-dichloroethane (W \ DCE) interfaces supported at micro- and nano-pipets.

Study of ionizable drugs transfer across the water/1,2-dichloroethane interface with phase volume ratio equal to unity using a three-electrode system

The electrochemical behavior of ionizable drugs (Amitriptyline, Diphenhydramine and Trihexyphenedyl) at the water/1,2-dichloroethane interface with the phase volume ratio (r = V-o/V-w) equal to 1 are investigated by cyclic voltammetry. The system is composed of an aqueous droplet supported at an Ag/AgCl disk electrode and it was covered with an organic solution. In this manner, a conventional three-electrode potentiostat can be used to study the ionizable drugs transfer process at a liquid/liquid interface. Physicochemical parameters such as the formal transfer potential, the Gibbs energy of transfer and the standard partition coefficients of the ionized forms of these drugs can be evaluated from cyclic voltammograms obtained. The obtained results have been summarized in ionic partition diagrams, which are a useful tool for predicting and interpreting the transfer mechanisms of ionizable drugs at the liquid/liquid interfaces and biological membranes.

Charge transfer across the water/nitrobenzene interface by three-electrode system

A droplet of aqueous solution containing a certain molar ratio of redox couple is first attached onto a platinum electrode surface, then the resulting drop electrode is immersed into the organic solution containing very hydrophobic electrolyte. Combined with reference and counter electrodes, a classical three-electrode system has been constructed, Ion transfer (IT) and electron transfer (ET) are investigated systematically using three-electrode voltammetry. Potassium ion transfer and electron transfer between potassium ferricyanide in the aqueous phase and ferrocene in nitrobenzene are observed with potassium ferricyanide/potassium ferrocyanide as the redox couple. Meanwhile, the transfer reactions of lithium, sodium, potassium, proton and ammonium ions are obtained with ferric sulfate/ferrous sulfate as the redox couple. The formal transfer potentials and the standard Gibbs transfer energy of these ions are evaluated and consistent with the results obtained by a four-electrode system and other methods.

Study of facilitated potassium ion transfer across a water vertical bar 1,2-dichloroethane interface using different phase volume ratio systems

A study of potassium ion transfer across a water \ 1,2-dichloroethane (W \ DCE) interface facilitated by dibenzo-18-crown-6 (DB18C6) with various phase volume ratio systems is presented. The key point was that a droplet of aqueous solution containing a redox couple, Fe(CN)(6)(3-)/Fe(CN)(6)(4-), with equal molar ratio, was first attached to a platinum electrode surface, and the resulting droplet electrode was then immersed into the organic solution containing a hydrophobic electrolyte to construct a platinum electrode/aqueous phase/organic phase system. The interfacial potential of the W \ DCE within the series could be externally controlled because the specific compositions in the aqueous droplet make the Pt electrode function like a reference electrode as long as the concentration ratio of Fe(CN)(6)(3-)/Fe(CN)(6)(4-) remains constant. In this way, a conventional three-electrode potentiostat can be used to study the ion transfer process at a liquid \ liquid (L \ L) interface facilitated by an ionophore with variable phase volume ratio (r = V-o/V-w). The effect of r on ion transfer and facilitated ion transfer was studied in detail experimentally. We also demonstrated that as low as 5 x 10(-8) M DB18C6 could be determined using this method due to the effect of the high phase volume ratio.

Study of electron-transfer reactions across an externally polarized water/1,2-dichloroethane interface by scanning electrochemical microscopy

A novel method to study electron-transfer (ET) reactions between ferrocene in 1,2-dichloroethane (DCE) and a redox couple of K3Fe(CN)(6) and K4Fe(CN)(6) in water using scanning electrochemical microscopy (SECM) with a three-electrode setup is reported. In this work, a water droplet that adheres to the Surface of a platinum disk electrode is immersed in a DCE solution. The aqueous redox couple serves both as a reference electrode on the platinum disk and as an electron donor/acceptor at the polarized liquid/liquid inter-face. With the present experimental approach, the liquid/liquid interface can be polarized externally, while the electron-transfer reactions between the two phases can be monitored independently by SECM. The apparent heterogeneous rate constants for the ET reactions were obtained by fitting the experimental approach curves to the theoretical values. These rate constants obey the Butler-Volmer theory i.e., them, are found to be potential dependent.

Investigation of ion transfer across the micro-water/nitrobenzene interface facilitated by a fullerene derivative

A functionalized fullerene derivative containing a monoaza-18-crown-6 moiety was investigated by facilitated ion (such as Li+, Na+, K+, NH4+, Mg2+, and Ca2+) transfer across the micro-water/nitrobenzene interface supported at the tip of a micropipet. The current responses were detected by cyclic voltammetry and Osteryoung square wave voltammetry, which demonstrated that the facilitated ion transfer does occur by an interfacial complexation-dissociation process. The diffusion coefficient of this compound in nitrobenzene was approximately (5.90 +/- 0.04) x 10(-7) cm(2) s(-1), which is 1 order of magnitude less than other common ionophores due to the large size of the molecule. The selectivity of this molecule toward the metal ions followed the sequence Na+ > Li+ > K+ > NH4+ > Ca2+ similar to Mg2+. In addition, this compound was also easy to form film at the water/nitrobenzene interface to inhibit the simple ion transfer of tetramethylammonium ion. However, the adsorption of this ionophore has less influence on the facilitated metal ion transfer.

Investigation of proton transfer across the water/1,2-dichloroethane interface by o-phenanthroline using glass micro/nano-pipets and cyclic voltammetry

Facilitated proton transfer across the water/1,2-dichloroethane (DCE) interface supported on the tips of micro- and nano-pipets by o-phenanthroline (Phen) was studied by using cyclic voltammetry. The formed micro- and nano-liquid/liquid interfaces functioned as micro- and nano-electrodes under certain experimental conditions. The dependence of the half-wave potentials on the aqueous solutions acidities was studied and the ratio of association constants between Phen and proton in the aqueous and DCE phases was calculated by the method proposed by Matsuda et al.. The standard rate constant (k(0)) and the transfer coefficient (alpha) evaluated by using nano-pipets were equal to 0.183 +/- 0.054 cm/s and 0.70 +/- 0.09, respectively.

Fabrication of agar-gel microelectrodes and their application in the study of ion transfer across the agar-water 1,2-dichloroethane interface

In this paper, we describe a simple procedure to make agar-gel microelectrodes by filling micropipettes. These microelectrodes were used to study K+ transfer across the agar-water \ 1,2-dichloroethane interface facilitated by dibenzo-18-crown-6 (DB18C6), and the transfer of tetraethylammonium (TEA(+)). The results observed were similar to those obtained at micro-liquid \ liquid interfaces. The effect of various amounts of agar in the aqueous phase was optimized and 3% agar was chosen based on the potential window and solidification time. The different shapes of micro-agar-gel electrodes were prepared in a similar way. The fabricated agar-gel microelectrodes obey the classical micro-disk steady-state current equation, which is different from the behavior of a normal micropipette filled with aqueous solution without silanization. (C) 2001 Elsevier Science B.V. All rights reserved.

Scanning electrochemical microscopy study of electron transfer across the water/1,2-dichloroethane interface induced by common ions

In this work, we report the reverse electron transfer reaction between TCNQ in 1, 2-dichloroethane (DCE) and ferrocyanide in water. This process is a thermodynamic unfavorable reaction and the reverse electron transfer reaction can only be obtained by scanning electrochemical microscopy(SECM) in the presence of suitable potential-determining ions, which govern the interfacial potential difference. In our case, the potential determining ions are tetrabutylammonium ion(TBA(+)) and tetraphenylarsonium ion (TPAs+). The effects of the concentrations of TBA(+) and TPAs+ in two phases and other parameters have been studied in detail. The apparent heterogeneous rate constants(k(i)) were obtained under different values of K-p(K-p=c(i)(w)/c(i)(o)) for both cases by fitting the SECM approach curves with theoretical ones and the results showed that they were controlled by the interfacial potential differences. The relationship between apparent heterogeneous rate constants and the interfacial potential differences obeys Butler-Volmer theory.

INVESTIGATIONS OF HYDROLYSIS KINETICS OF ATROPINE SULFATE BY ELECTROANALYSIS AT THE WATER NITROBENZENE INTERFACE

The hydrolysis kinetics of atropine sulphate has been investigated by cyclic voltammetry at the water/nitrobenzene interface. The transfer process is diffusion controlled and the transfer species is a 1:1 proton-atropine complex. Two main factors, pH and temperature, which have notable effects on the hydrolysis rate, are illustrated. The most suitable pH for atropine to be preserved in aqueous solution and related parameters were estimated.

部分重力条件下气液两相流型研究

本文分析了"和平号"空间站气液两相流实验中获得的部分重力(0.1 g和0.014 g)条件下的流型特征及其相互转换条件,并将其和常重力与微重力两相流研究中较常用的流型转换模型的预测结果进行了比较.

Slug to annular flow transition of microgravity two-phase flow

A new model is developed for predicting the transition from the slug to annular flow of adiabatic two-phase gas/liquid flow in microgravity (mu g) environment. This model is based on the analyses of the effects of the surface tension and the gas inertia in a sense of more physical approach. The drift-flux model is applied to determine the gas void fraction near the transition region. The new model is compared with previous models and experimental data, and the results show the improvement in explanation of the experimental results.