Experimental and theoretical study of the reaction of the ethynyl radical with nitrous oxide, C2H + N2O

We investigated the rate constants and reaction mechanism of the gas phase reaction between the ethynyl radical and nitrous oxide (C(2)H + N(2)O) using both experimental methods and electronic structure calculations. A pulsed-laser photolysis/chemiluminescence technique was used to determine the absolute rate coefficient over the temperature range 570 K to 836 K. In this experimental temperature range, the measured temperature dependence of the overall rate constants can be expressed as: k(T) (C(2)H + N(2)O) = 2.93 × 10(-11) exp((-4000 ± 1100) K/T) cm(3) s(-1) (95% statistical confidence). Portions of the C(2)H + N(2)O potential energy surface (PES), containing low-energy pathways, were constructed using the composite G3B3 method. A multi-step reaction route leading to the products HCCO + N(2) is clearly preferred. The high selectivity between product channels favouring N(2) formation occurs very early. The pathway corresponds to the addition of the terminal C atom of C(2)H to the terminal N atom of N(2)O. Refined calculations using the coupled-cluster theory whose electronic energies were extrapolated to the complete basis set limit CCSD(T)/CBS led to an energy barrier of 6.0 kcal mol(-1) for the entrance channel. The overall rate constant was also determined by application of transition-state theory and Rice-Ramsperger-Kassel-Marcus (RRKM) statistical analyses to the PES. The computed rate constants have similar temperature dependence to the experimental values, though were somewhat lower.     

The experiments and correlations of the solubility of ethylene in toluene solvent

Polymer cyclic olefin copolymer (COC) is produced from the reaction of attaching ethyl groups to the norbornene monomer in liquid phase. The first step of process is dissolving ethylene in a liquid phase where toluene is present as a cosolvent. Thus, the solubility of ethylene in liquid toluene is the most important factor affecting the production of COC. In this study, the solubility of ethylene in toluene was measured in the temperature range from 323.15 to 423.15 K and pressure range from 5 to 25 bar. The experiments were conducted by the method of pressure decaying with a newly designed apparatus. The experimental results show that the solubility of ethylene in toluene increases with increasing pressure but decreases with increasing temperature.The experimental solubility data were expressed in the vapor–liquid equilibrium relationship and correlated fairly well by the bubble–pressure calculation with the Peng–Robinson equation of state (PR EOS) incorporated with the van der Waals one-fluid and the Zhong–Masuoka mixing rules with the consideration of binary interaction parameters. The results showed the van der Waals (vdW-1) mixing rule is slightly better than the Z–M mixing rule for pressure correlation but the Z–M mixing rule is slightly better for vapor composition correlation.A semi-empirical solubility equation with four parameters for the present binary system was proposed in this study. This proposed model estimates the solubility easier and as accurate as the PR EOS does for the present system.     

A kinetic study of the reactions of Fe+ with N2O, N2, O2, CO2 and H2O, and the ligand-switching reactions Fe+.X + Y --> Fe+.Y + X (X = N2, O2, CO2; Y = O2, H2O)

A series of reactions involving Fe(+) ions were studied by the pulsed laser ablation of an iron target, with detection of ions by quadrupole mass spectrometry at the downstream end of a fast flow tube. The reactions of Fe(+) with N(2)O, N(2) and O(2) were studied in order to benchmark this new technique. Extending measurements of the rate coefficient for Fe(+) + N(2)O from 773 K to 185 K shows that the reaction exhibits marked non-Arrhenius behaviour, which appears to be explained by excitation of the N(2)O bending vibrational modes. The recombination of Fe(+) with CO(2) and H(2)O in He was then studied over a range of pressure and temperature. The data were fitted by RRKM theory combined with ab initio quantum calculations on Fe(+).CO(2) and Fe(+).H(2)O, yielding the following results (120-400 K and 0-10(3) Torr). For Fe(+) + CO(2): k(rec,0) = 1.0 x 10(-29) (T/300 K)(-2.31) cm(6) molecule(-2) s(-1); k(rec,infinity) = 8.1 x 10(-10) cm(3) molecule(-1) s(-1). For Fe(+) + H(2)O: k(rec,0) = 5.3 x 10(-29) (T/300 K)(-2.02) cm(6) molecule(-2) s(-1); k(rec,infinity) = 2.1 x 10(-9) (T/300 K)(-0.41) cm(3) molecule(-1) s(-1). The uncertainty in these rate coefficients is determined using a Monte Carlo procedure. A series of exothermic ligand-switching reactions were also studied at 294 K: k(Fe(+).N(2) + O(2)) = (3.17 +/- 0.41) x 10(-10), k(Fe(+).CO(2) + O(2)) = (2.16 +/- 0.35) x 10(-10), k(Fe(+).N(2) + H(2)O) = (1.25 +/- 0.14) x 10(-9) and k(Fe(+).O(2) + H(2)O) = (8.79 +/- 1.30) x 10(-10) cm(3) molecule(-1) s(-1), which are all between 36 and 52% of their theoretical upper limits calculated from long-range capture theory. Finally, the role of these reactions in the chemistry of meteor-ablated iron in the upper atmosphere is discussed. The removal rates of Fe(+) by N(2), O(2), CO(2) and H(2)O at 90 km altitude are approximately 0.1, 0.07, 3 x 10(-4) and 1 x 10(-6) s(-1), respectively. The initially formed Fe(+).N(2) and Fe(+).O(2) are converted into the H(2)O complex at approximately 0.05 s(-1). Fe(+).H(2)O should therefore be the most abundant single-ligand Fe(+) complex in the mesosphere below 90 km.     

Novel corresponding-states principle approach for the equation of state of isotopologues: H2(18)O as an example

The corresponding-states principle (CSP) has been considered for the development of the equations of state (EOS) of minor isotopologues that are usually unknown. We demonstrate that, for isotopologues of a given molecular fluid, a general extended multi-parameter corresponding-states EOS can be reduced to the three-parameter EOS, utilizing the critical parameters (temperature and density) and Pitzer's acentric factor as correlation parameters. Appropriate general CSP mathematical formalism and equations for constructing the EOS of minor isotopologues are described in detail. The formalism and equations were applied to isotopologues of water and demonstrated that the isotopic effect on the critical parameters and the acentric factor of H(2)(18)O can be successfully calculated from the EOS of H2O and experimental data on the isotope effects (liquid-vapor isotope fractionation factor and molar volume isotope effect). We have also shown that the experimental data on the vapor pressure isotope effect (VPIE) for 18O-substituted water are inconsistent within the framework of thermodynamics with the liquid-vapor oxygen isotope fractionation factor. The novel approach of CSP to isotopologues developed in this study creates a new opportunity for constructing the EOS of minor isotopologues for many other molecular fluids.     

Magnesium aminoethyl phosphonate (Mg(AEP)(H2O)): an inorganic-organic hybrid nanomaterial with high CO2:N2 sorption selectivity

The inorganic-organic hybrid magnesium aminoethyl phosphonate (Mg(AEP)(H(2)O), particle diameter: 20 nm; specific surface area: 322(10) m(2) g(-1); pore volume: 0.9(1) cm(3) g(-1)) shows reversible CO(2) sorption (152(5) mg g(-1)) at high pressure (≤110 bar). In contrast, N(2) uptake remains below 1.0(1) mg g(-1). Based on this selectivity (～100%) Mg(AEP)(H(2)O) expands the range of materials available for CO(2) capture.     

Experimental and modelling study of the recombination reaction H + O(2) (+M) --> HO(2) (+M) between 300 and 900 K, 1.5 and 950 bar, and in the bath gases M = He, Ar, and N(2)

The recombination reaction H + O(2) (+M) --> HO(2) (+M) was studied by laser flash photolysis in a high pressure flow cell, over the temperature range 300-900 K, the pressure range 1.5-950 bar and in the bath gases M = He and N(2). Earlier experiments by Hahn et al. (Phys. Chem. Chem. Phys. 2004, 6, 1997) in the bath gas M = Ar were also extended. The data were analyzed in terms of unimolecular rate theory employing new calculations of relevant molecular parameters. Improved energy transfer parameters for the bath gases M = He, Ar, N(2), and H(2)O could thus be obtained and complete falloff curves were constructed. In the case of water, the high pressure rates well connect with pulse radiolysis results obtained in supercritical water by Janik et al. (J. Phys. Chem. A 2007, 111, 79).     

PB/Au/CILE的制备与应用

混合离子液体(N-丁基吡啶六氟磷酸盐,[BuPy][PF6])与石墨粉,制备了离子液体碳糊电极(CILE),再采用电沉积法制得PB/Au/CILE修饰电极,研究了该修饰电极的电化学行为及其对H2O2的电催化,建立了H2O2的计时安培测定新方法。结果表明:在该修饰电极上PB产生了一对准可逆的氧化还原峰,并对H2O2表现出良好电催化作用,安培法测定H2O2的线性范围为5.0×10-6～1.55×10-4mol/L,检出限为1.0×10-6mol/L(S/N=3)。连续10次测定5.0×10-6mol/L H2O2峰电流的RSD为2.1%。     

Aerosol chamber study of optical constants and N2O5 uptake on supercooled H2SO4/H2O/HNO3 solution droplets at polar stratospheric cloud temperatures

The mechanism of the formation of supercooled ternary H(2)SO(4)/H(2)O/HNO(3) solution (STS) droplets in the polar winter stratosphere, i.e., the uptake of nitric acid and water onto background sulfate aerosols at T < 195 K, was successfully mimicked during a simulation experiment at the large coolable aerosol chamber AIDA of Forschungszentrum Karlsruhe. Supercooled sulfuric acid droplets, acting as background aerosol, were added to the cooled AIDA vessel at T = 193.6 K, followed by the addition of ozone and nitrogen dioxide. N(2)O(5), the product of the gas phase reaction between O(3) and NO(2), was then hydrolyzed in the liquid phase with an uptake coefficient gamma(N(2)O(5)). From this experiment, a series of FTIR extinction spectra of STS droplets was obtained, covering a broad range of different STS compositions. This infrared spectra sequence was used for a quantitative test of the accuracy of published infrared optical constants for STS aerosols, needed, for example, as input in remote sensing applications. The present findings indicate that the implementation of a mixing rule approach, i.e., calculating the refractive indices of ternary H(2)SO(4)/H(2)O/HNO(3) solution droplets based on accurate reference data sets for the two binary H(2)SO(4)/H(2)O and HNO(3)/H(2)O systems, is justified. Additional model calculations revealed that the uptake coefficient gamma(N(2)O(5)) on STS aerosols strongly decreases with increasing nitrate concentration in the particles, demonstrating that this so-called nitrate effect, already well-established from uptake experiments conducted at room temperature, is also dominant at stratospheric temperatures.     

A kinetic study of the reactions of Ca+ ions with O3, O2, N2, CO2 and H2O

The reactions between Ca(+)(4(2)S(1/2)) and O(3), O(2), N(2), CO(2) and H(2)O were studied using two techniques: the pulsed laser photo-dissociation at 193 nm of an organo-calcium vapour, followed by time-resolved laser-induced fluorescence spectroscopy of Ca(+) at 393.37 nm (Ca(+)(4(2)P(3/2)-4(2)S(1/2))); and the pulsed laser ablation at 532 nm of a calcite target in a fast flow tube, followed by mass spectrometric detection of Ca(+). The rate coefficient for the reaction with O(3) is essentially independent of temperature, k(189-312 K) = (3.9 +/- 1.2) x 10(-10) cm(3) molecule(-1) s(-1), and is about 35% of the Langevin capture frequency. One reason for this is that there is a lack of correlation between the reactant and product potential energy surfaces for near coplanar collisions. The recombination reactions of Ca(+) with O(2), CO(2) and H(2)O were found to be in the fall-off region over the experimental pressure range (1-80 Torr). The data were fitted by RRKM theory combined with quantum calculations on CaO(2)(+), Ca(+).CO(2) and Ca(+).H(2)O, yielding the following results with He as third body when extrapolated from 10(-3)-10(3) Torr and a temperature range of 100-1500 K. For Ca(+) + O(2): log(10)(k(rec,0)/cm(6) molecule(-2) s(-1)) = -26.16 - 1.113log(10)T- 0.056log(10)(2)T, k(rec,infinity) = 1.4 x 10(-10) cm(3) molecule(-1) s(-1), F(c) = 0.56. For Ca(+) + CO(2): log(10)(k(rec,0)/ cm(6) molecule(-2) s(-1)) = -27.94 + 2.204log(10)T- 1.124log(10)(2)T, k(rec,infinity) = 3.5 x 10(-11) cm(3) molecule(-1) s(-1), F(c) = 0.60. For Ca(+) + H(2)O: log(10)(k(rec,0)/ cm(6) molecule(-2) s(-1)) = -23.88 - 1.823log(10)T- 0.063log(10)(2)T, k(rec,infinity) = 7.3 x 10(-11)exp(830 J mol(-1)/RT) cm(3) molecule(-1) s(-1), F(c) = 0.50 (F(c) is the broadening factor). A classical trajectory analysis of the Ca(+) + CO(2) reaction is then used to investigate the small high pressure limiting rate coefficient, which is significantly below the Langevin capture frequency. Finally, the implications of these results for calcium chemistry in the mesosphere are discussed.     

Equation of state for the NH3−H2O system

An equation of state (EOS) for the NH₃–H₂O system has been developed. This EOS incorporates a highly accurate end-member EOS and on an empirical mixing rule. The mixing rule is based on an analogy with high order contributions to the virial expansion for mixtures. Comparison with experimental data indicates that the mixed system EOS can predict both phase equilibria and volumetric properties for this binary system with accuracy close to that of the experimental data from 50°C and 1 bar to critical temperatures and pressures.     

Contribution to thermochemical studies of 0.8[xB_2O_3-(1-x)SiO_2]-0.2Na_2O glasses

Calorimetric measurements in 0.8[xB_2O_3-(1-x)SiO_2]-0.2Na_2O glasses and melts are performed in HF calorimetry at 298 K and lead borate calorimetry at 973 K,respectively.Mixing enthalpy is affected by both temperature and composition.At 298 K,the mixing enthalpies are slightly negative and components are miscible at that temperature in the whole composition range.At 973 K, the sign of the mixing enthalpies reflect the tendency to phase separation at silica-rich compositions,which is avoided for kinetic ...     

溶剂热法合成In2S3/CuSe核壳结构粉体

本文以氯化铜、氯化铟、硫脲、亚硒酸以及硒粉为原料,乙二醇及乙二胺为溶剂,采用常压溶剂热法制备了硫化铟为核硒化铜为壳(In2S3/CuSe)的核壳结构复合粉体。主要探讨了反应温度、不同反应原料以及不同表面活性剂对产物物相以及形貌的影响。通过采用X射线衍射(XRD)、扫描电镜(SEM)对产物的物相、形貌以及组成进行了表征。实验结果表明:常压溶剂热条件下可以制备得In2S3/CuSe复合粉体,其最佳反应工艺参数是:于160℃下合成In2S3粉体为核,于100℃下合成包裹在In2S3表面的CuSe粉体从而获得In2S3/CuSe核壳结构复合粉。在该工艺参数下合成产物的形貌主要由圆球状颗粒组成,粉体的粒径分布在1~2μm。此外,本文也通过添加不同种类表面活性剂对产物的形貌进行了控制。     

The collimation angle shift of desorbing product N2 in a steady-state N2O+CO reaction on Rh(110)

The angular distribution of desorbing product N2 was studied in N2O decompositions on Rh(110) in the temperature range of 60-700 K. The N2 desorption collimates along 62 degrees -68 degrees off normal toward either the [001] or [001] direction in a transient N2O decomposition below ca. 470 K or in the steady-state N2O+CO reaction above 540 K. In the steady-state reaction at the temperature from ca. 470 to 540 K, however, the collimation angle shifts from 62 degrees to 45 degrees with decreasing surface temperature. This angle shift is ascribed to the steric hindrance by coadsorbed CO because the N2 collimation in transient N2O decomposition at around 65 degrees is recovered in the range of 380-500 K by an abrupt CO pressure drop followed by the decrease in CO coverage. N2O is oriented along the [001] direction before dissociation. A scattering model of the nascent N2 by adsorbed CO is proposed, yielding smaller collimation angles.     

Evidence of formation of ammonium perfluorononanoate/2H2O multilamellar vesicles: morphological analysis by rheology and rheo-2H NMR experiments

Rheology and rheo-(2)H NMR measurements are presented for 30 wt % ammonium perfluorononanoate (APFN)/(2)H(2)O mixture in the temperature range 20-70 °C. A first-order lamellar-to-nematic transition occurs at 42 °C, and a first-order nematic-to-isotropic transition occurs at 49 °C. Different rheological behaviors of the lamellar phase were observed with increasing the temperature. The lamellar structure at low temperature (Lα(-)) has a clear gel-like viscoelasticity, while at high temperature the lamellar structure (Lα(+)) has a liquid-like response. In this study we have observed for the first time, along with the lamellar phase of a surfactant containing fluorinated fatty acid, the formation of multilamellar vesicles (MLVs) ("onions") induced by shear. With the aid of nonlinear rheology and rheo-NMR techniques, onion formation was found to occur in both temperature regimes of the lamellar phase, but at different strain units. It is suggested that the lamellar phase consists of smectic structures in both Lα(-) and Lα(+), but with different percentages of defect density.     

Formation of abundant [Pb(H2O)]2+ by ligand-exchange reaction between [Pb(N2)n]2+ (n = 1-3) and H2O

Doubly charged lead monohydrate, [Pb(H2O)]2+, was predicted to be unstable in the gas phase, but it has recently been observed to form in low yield via ligand change between [Pb(CH3CN)]2+ and H2O [Shi, T.; Orlova, G.; Guo, J.; Bohme, D. K.; Hopkinson, A. C.; Siu, K. W. M. J. Am. Chem. Soc. 2004, 126, 7975-7980]. Here we report that abundant [Pb(H2O)]2+ is formed in the gas phase by ligand-exchange reaction between [Pb(N2)n]2+ (n = 1-3) and water after collisional activation. Density functional theory has been used to examine the ligand-exchange reaction profile. A comparison of the potential-energy surfaces between [Pb(N2)]2+ and [Pb(CH3CN)]2+ reacting with H2O provides strong evidence that the ligand-exchange reaction of [Pb(N2)]2+ with H2O to form [Pb(H2O)]2+ is more efficient than that of [Pb(CH3CN)]2+ with H2O.     

Thermal decomposition of monocalcium aluminate decahydrate (CaAl2O4.10H2O) investigated by in-situ synchrotron X-ray powder diffraction, thermal analysis and 27Al, 2H MAS NMR spectroscopy

The stability of monocalcium aluminate decahydrate, with the nominal composition CaAl(2)O(4).10H(2)O (CAH(10)), has a decisive role for the strength development and durability of cementitious materials based on high alumina cements. This has prompted an investigation of the thermal transformation of crystalline monocalcium aluminate decahydrate in air to an amorphous phase by in-situ synchrotron X-ray powder diffraction in the temperature range from 25 to 500 degrees C, by DTA/TGA, and (2)H, (27)Al MAS NMR spectroscopy. The decomposition includes the loss of hydrogen-bonded water molecules in the temperature range up to 175 degrees C, coupled with a reduction of the unit cell volume from 1928 A(3) at 25 degrees C, to 1674 A(3) at 185 degrees C. Furthermore, X-ray diffraction shows that CaAl(2)O(4).10H(2)O starts to transform to an amorphous phase at approximately 65 degrees C. This phase is fully developed at approximately 175 degrees C and it converts to crystalline CaAl(2)O(4) when heated to 1300 degrees C. The thermal decomposition in the temperature range from approximately 65 to approximately 175 degrees C involves both formation of an amorphous phase including AlO(4) tetrahedra and structural changes in the remaining crystalline phase.     

Promising oxonitridosilicate phosphor host Sr3Si2O4N2: synthesis, structure, and luminescence properties activated by Eu2+ and Ce3+/Li+ for pc-LEDs

A novel oxonitridosilicate phosphor host Sr(3)Si(2)O(4)N(2) was synthesized in N(2)/H(2) (6%) atmosphere by solid state reaction at high temperature using SrCO(3), SiO(2), and Si(3)N(4) as starting materials. The crystal structure was determined by a Rietveld analysis on powder X-ray and neutron diffraction data. Sr(3)Si(2)O(4)N(2) crystallizes in cubic symmetry with space group Pa ?3, Z = 24, and cell parameter a = 15.6593(1) ?. The structure of Sr(3)Si(2)O(4)N(2) is constructed by isolated and highly corrugated 12 rings which are composed of 12 vertex-sharing [SiO(2)N(2)] tetrahedra with bridging N and terminal O to form three-dimensional tunnels to accommodate the Sr(2+) ions. The calculated band structure shows that Sr(3)Si(2)O(4)N(2) is an indirect semiconductor with a band gap ≈ 2.84 eV, which is close to the experimental value ≈ 2.71 eV from linear extrapolation of the diffuse reflection spectrum. Sr(3-x)Si(2)O(4)N(2):xEu(2+) shows a typical emission band peaking at ~600 nm under 460 nm excitation, which perfectly matches the emission of blue InGaN light-emitting diodes. For Ce(3+)/Li(+)-codoped Sr(3)Si(2)O(4)N(2), one excitation band is in the UV range (280-350 nm) and the other in the UV blue range (380-420 nm), which matches emission of near-UV light-emitting diodes. Emission of Sr(3-2x)Si(2)O(4)N(2):xCe(3+),xLi(+) shows a asymmetric broad band peaking at ~520 nm. The long-wavelength excitation and emission of Eu(2+) and Ce(3+)/Li(+)-doped Sr(3)Si(2)O(4)N(2) make them attractive for applications in phosphor-converted white light-emitting diodes.     

Pressure response of three-dimensional cyanide-bridged bimetallic magnets

Effects of pressure on the structures and magnetic properties of three types of 3-D cyanide-bridged bimetallic coordination polymer magnets, MnIICrIII ferrimagnet [Mn(en)]3[Cr(CN)6]2.4H2O (1; en = ethylenediamine), NiIICrIII ferromagnet [Ni(dipn)]3[Cr(CN)6]2.3H2O (2; dipn = N,N-di(3-aminopropyl)amine), and NiIIFeIII ferromagnet [Ni(dipn)]2[Ni(dipn)(H2O)][Fe(CN)6]2.11H2O (3), were systematically examined under hydrostatic pressure up to 19.8 GPa using a piston-cylinder-type pressure cell and a diamond anvil cell. The ferrimagnet 1 showed the reversible crystalline-to-amorphous-like phase change, and the magnetic phase transition temperature (TC) was reversibly changed from 69 K at 0 GPa to 126 K at 4.7 GPa. At higher pressure, the net magnetization was suppressed with increasing pressure, and the magnetic state at 19.8 GPa was assumed to be paramagnetic. The initial ferrimagnetic phase of 1 was not recovered after releasing the pressure from 19.8 GPa. The magnetic phase of 2 was reversibly converted between ferromagnetic and paramagnetic-like phase in the range 0 相似文献   

Determination of the rate constant for the OH(X2Pi) + OH(X()Pi) --> O(3P) + H2O reaction over the temperature range 293-373 K

The rate constant for the reaction OH(X2Pi) + OH(X2Pi) --> O(3P) + H2O has been measured over the temperature range 293-373 K and pressure range 2.6-7.8 Torr in both Ne and Ar bath gases. The OH radical was created by 193 nm laser photolysis of N2O to produce O(1D) atoms that reacted rapidly with H2O to produce the OH radical. The OH radical was detected by quantitative time-resolved near-infrared absorption spectroscopy using Lambda-doublet resolved rotational transitions of the first overtone of OH(2,0) near 1.47 microm. The temporal concentration profiles of OH were simulated using a kinetic model, and rate constants were determined by minimizing the sum of the squares of residuals between the experimental profiles and the model calculations. At 293 K the rate constant for the title reaction was found to be (2.7 +/- 0.9) x 10(-12) cm(3) molecule(-1) s(-1), where the uncertainty includes an estimate of both random and systematic errors at the 95% confidence level. The rate constant was measured at 347 and 373 K and found to decrease with increasing temperature.