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1.
The inhibition effect of Ag + ions on the photoanodic corrosion of CdS semiconductor electrodes has been studied in 0.5 M NaClO 4 + xM AgClO 4 solutions (0 x 10 −2, pH = 2) by means of potentiostatic current density-potential measurements, ac-impedance and atomic absorption. In the presence of Ag + ions in the solution a thin Ag 2S film of ca. 30–300 nm thickness is formed on the CdS surface due to the heterogeneous cation exchange reaction CdS + 2Ag + = Ag 2S + Cd 2+. The Ag 2S film formation is a transport controlled process which can be described by a parabolic rate law. From kinetic investigations in the temperature range (298 T 348 K) the activation energy of this process was determined to be about 62 kJ mol −1. Information about the morphology and composition of the surfaces was obtained from optical and scanning electron microscope investigations including EDAX. 相似文献
2.
A new class of polymer electrolytes, based on the interpenetrating polymer network approach, was obtained starting from functionalised macromers, of poly-ether nature, in the presence of a lithium salt (LiBF 4, LiClO 4, LiCF 3SO 3) and propylene carbonate (PC) or tetraethyleneglycol dimethylether (TGME), as plasticizers. The macromers were synthesised by living polymerisation employing a HI/I2 system as the initiator. The macromer has a polymerisable end group, which can undergo radical polymerisation, attached to a monodisperse poly-vinylether, containing suitable ethylene oxide groups for ion coordination. Monomers and macromers were characterised by FTi.r., u.v.–vis, 1H- and 13C-n.m.r. Self-consistent and easily handled membranes were obtained as thin films by a dry procedure using u.v. radiation to polymerise and crosslink the network precursors, directly on suitable substrates, in the presence of the plasticizer and the lithium salt. The electrolytic membranes were studied by complex impedance and their thermal properties determined by differential scanning calorimetry analysis. Ionic conductivities (σ) were measured for PC and TGME-based membranes at various plasticizer and salt contents as a function of T (60 to −20°C). LiClO4/PC/PE electrolytes, with 3.8% (w/w) salt and 63% PC, have the highest σ (1.15×10−3 and 3.54×10−4 S cm−1 at 20°C and −20°C, respectively). One order of magnitude lower conductivities are achieved with TGME; samples with 6% (w/w) LiClO4 and 45% (w/w) TGME exhibit σ values of 2.7×10−4 and 2.45×10−5 S cm−1 at 20°C and −20°C. 相似文献
3.
Condensation nuclei (CN) separated during winter 1982–1983 in Colorado consisted mostly of sulfates and chlorides, with nitrates practically absent. Nitrates were present in all precipitation (rain and snow). CN condensate collected in the presence of haze contained the largest amounts of SO 42− (1.7 × 10 −7 moles/ml), Cl (> 1.4 × 10 −7), and NO 3−(2.1 × 10 −8) recorded; the concentrations of the cations were > 2.2 × 10 −7 moles/ml of Na +, > 1.1 × 10 −7 of NH 4+, and > 2.6 × 10 −7 of K +. Nitrates were present in low concentrations in CN separated in the presence of fogs. The pH of the separated CN varied from 5.2 to 6.6; the pH of rain samples was between 4.6 and 5.3, and that of the snow samples was between 3.9 and 4.9. Analysis of single aerosol particles collected since 1979 showed the predominant anion to be sulfate. Nitrate ion-bearing aerosol particles were not detected on some days. 相似文献
4.
Bi 0.5(Na 1−x−yK xAg y) 0.5TiO 3 piezoelectric ceramics were prepared by conventional ceramic processes. X-ray diffraction patterns show a pure perovskite structure, indicating that the K + and Ag + ions substitute for the Na + ions in Bi 0.5Na 0.5TiO 3. The temperature dependence of the dielectric constant and dissipation factor shows all ceramics to experience two phase transitions: from ferroelectric to anti-ferroelectric and from anti-ferroelectric to paraelectric. The transition temperature from ferroelectric to anti-ferroelectric and the temperature at which the dielectric constant reaches its maximum value decrease with the increase of K + amount. At room temperature, the ceramics containing 17.5–20 mol% K + and 2 mol% Ag + exhibit high piezoelectric constant ( d33 = 180 pC/N) and high electromechanical coupling factor ( kp = 35%). 相似文献
5.
We synthesized high-quality and oriented periodic mesoporous organosilica (PMO) monoliths through a solvent evaporation process using a wide range of mole ratios of the components: 0.17–0.56 1,2-bis(triethoxysilyl)ethane (BTSE): 0.2 cetyltrimethylammonium chloride (CTACl): 0–1.8 × 10 −3 HCl: 0–80 EtOH: 5–400 H 2O. X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images indicated that the mesoporous channels within the monolith samples were oriented parallel to the flat external surface of the PMO monolith and possessed a hexagonal symmetry lattice ( p6 mm). The PMO monolith synthesized from a reactant composition of 0.35 BTSE: 0.2 CTACl: 1.8 × 10 −6 HCl: 10 EtOH: 10 H 2O had a pore diameter, pore volume, and surface area – obtained from an N 2 sorption isotherm – of 25.0 Å, 0.96 cm 3 g −1 and 1231 m 2 g −1, respectively. After calcination at 280 °C for 2 h in N 2 flow, the PMO monolith retained monolith-shape and mesostructure. Pore diameter and surface area of the calcined PMO monolith sample were 19.8 Å, 0.53 cm 3 g −1 and 1368 m 2 g −1, respectively. We performed 29Si and 13C CP MAS NMR spectroscopy experiments to confirm the presence of Si–C bonding within the framework of the PMO monoliths. We investigated the thermal stability of the PMO monoliths through thermogravimetric analysis (TGA). In addition, rare-earth ions (Eu 3+, Tb 3+ and Tm 3+) were doped into the monoliths. Optical properties of those Eu 3+, Tb 3+ and Tm 3+-doped PMO monoliths were investigated by photoluminescence (PL) spectra to evaluate their potential applicability as UV sensors. 相似文献
6.
The kinetic study of the iodination of cinnamaldehyde and furfuraldehyde with hydrated monopositive iodine, produced by the interaction of aqueous I 2 solution and Ag + at μ = 0.3 (NaClO 4) was followed potentiometrically by using platinum gauge and saturated calomel electrode assembly. The reactions are of the first order with respect to both the substrate concentration (cinnamaldehyde and furfuraldehyde). They are also first order with respect to hydrated monopositive iodine, the iodinating agent. The reactions are independent of [Ag +] and [H +] in the solution in which the reactions have been studied. 相似文献
7.
Co and Co–P catalysts electroplated on Cu in sulfate based solution without or with an addition of H 2PO 2− ions were developed for hydrogen generation from alkaline NaBH 4 solution. The microstructures of the Co and Co–P catalysts and their hydrogen generation properties were analyzed as a function of cathodic current density and plating time during the electrodeposition. An amorphous Co–P electrodeposit with micro-cracks was formed by electroplating in the sulfate based solution containing H 2PO 2− ions. It was found that the amorphous Co–P catalyst formed at 0.01 A/cm 2 exhibited 18 times higher catalytic activity for hydrolysis of NaBH 4 than did the polycrystalline Co catalyst. The catalytic activity of the electrodeposited Co–P catalyst for hydrolysis of NaBH 4 was found to be a function of both cathodic current density and plating time, that is, parameters determining the concentration of P in the Co–P catalyst. Especially, Co–13 at.% P catalyst electroplated on Cu in the Co–P bath at a cathodic current density of 0.01 A/cm 2 for 1080 s showed the best hydrogen generation rate of 954 ml/min g-catalyst in 1 wt.% NaOH + 10 wt.% NaBH 4 solution at 30 °C. 相似文献
8.
The electrochemistry of cesium was investigated at mercury electrodes in the tri-1-butylmethylammonium bis((trifluoromethyl)sulfonyl)imide (Bu 3MeN +Tf 2N −) room-temperature ionic liquid (RTIL) by using cyclic staircase voltammetry, rotating disk electrode voltammetry, and chronoamperometry. The reduction of cesium ions at mercury exhibits quasireversible behavior with k0 = 9.8 × 10 −5 cm s −1 and = 0.36. The diffusion coefficient of Cs + in this RTIL was 1.04 × 10 −8 cm 2 s −1 at 303 K. Bulk deposition/stripping experiments conducted at a rotating mercury film electrode gave an average recovery of 97% of the electrodeposited Cs. The density, absolute viscosity, and equivalent conductance of Bu 3MeN +Tf 2N − were measured over the range of temperatures from 298 to 353 K. A polynomial equation describing the temperature dependence of the density is presented. Both the viscosity and conductance exhibited the non-Arrhenius temperature dependence typical of glass-forming liquids. The ideal glass transition temperature and the activation energies for viscosity and conductance were obtained by fitting the Vogel–Tammann–Fulcher (VTF) equation to the experimental data for these transport properties. 相似文献
9.
Kinetic studies were made on the polymerization of acrolein initated by potassium peroxodiphosphate (PP) in aqueous solution, in the presence and absence of Ag + ions. The rate of polymerization was found to depend on [M] 3/2 (M = monomer) and was independent of both [PP] and [Ag +]. The overall activation energy was calculated to be 4.8 kcal mol −1. A mechanism involving termination by PO 2-4 radicals is proposed and discussed. 相似文献
10.
Hydroxyapatite (Ca 10(PO 4) 6(OH) 2: HAP) was co-substituted with Ti(IV) and antibacterial ions (Ag +, Cu 2+ or Zn 2+) (HAPTiM), by coprecipitation and ion-exchange methods. Both HAPTiAg and HAPTiCu coated on porous spumous nickel film showed high efficiency for killing Escherichia coli and Staphylococcus aureus in the dark and under weak UVA irradiation, respectively. Moreover, their bactericidal activities were much higher than that of P25-TiO 2 film. The studies of ESR revealed that not only O 2− was formed on HAPTiM, HAPTi, HAP and P25-TiO 2 films under weak UVA irradiation, but also at ambient temperature without light O 2− was generated on HAPTiCu, HAPTiAg, and HAPTi. The redox couples of Cu 0/Cu 2+ and Ag 0/Ag + in the structure of HAPTiCu (Ag) caused the transfer of electron leading to the O 2− generation under the above conditions. The higher bactericidal activities of HAPTiM were due to the synergy of the oxidation role of the O 2− and the bacteriostatic action of antibacterial ions. The process of the damage of the cell wall and the cell membrane was directly observed by TEM, and further confirmed by the determination of potassium ion (K +) leakage from the killed bacteria. 相似文献
11.
We report that ultrastable faujasite-based ruthenium zeolites are highly active catalysts for N 2O decomposition at low temperature (120–200°C). The faujasite-based ruthenium catalysts showed activity for the decomposition of N 2O per Ru 3+ cation equivalent to the ZSM-5 based ruthenium catalysts at much lower temperatures (TOF at 0.05 vol.-% N 2O: 5.132 × 10 −4 s −1 Ru −1 of Ru-HNaUSY at 200°C versus 5.609 × 10 −4 s −1 Ru −1 of Ru-NaZSM-5 at 300°C). The kinetics of decomposition of N 2O over a Ru-NaZSM-5 (Ru: 0.99 wt.-%), a Ru-HNaUSY (Ru: 1.45 wt.-%) and a Ru-free, Na-ZSM-5 catalyst were studied over the temperature range from 40 to 700°C using a temperature-programmed micro-reactor system. With partial pressures of N 2O and O 2 up to 0.5 vol.-% and 5 vol.-%, respectively, the decomposition rate data are represented by: −dN 2O/d t=itk( PN2O) ( PO2) −0.5 for Ru-HNaUSY, −dN 2O/d t=k( PN2O) ( PO2) −0.1 for Ru-NaZSM-5, and −dN 2O/d t=k( PN2O) −0.2 ( PO2) −0.1 for Na-ZSM-5. Oxygen had a stronger inhibition effect on the Ru-HNaUSY catalyst than on Ru-NaZSM-5. The oxygen inhibition effect was more pronounced at low temperature than at high temperature. We propose that the negative effect of oxygen on the rate of N 2O decomposition over Ru-HNaUSY is stronger than Ru-NaZSM-5 because at the lower temperatures (<200°C) the desorption of oxygen is a rate-limiting step over the faujasite-based catalyst. The apparent activation energy for N 2O decomposition in the absence of oxygen is much lower on Ru-HNaUSY ( Ea: 46 kJ mol −1) than on Ru-NaZSM-5 ( Ea: 220 kJ mol −1). 相似文献
12.
This paper describes a pair of chemical reaction experiments developed for Rowan University's introductory course in chemical reaction engineering: an esterification reaction carried out in a packed bed, and a competitive reaction in which the kinetics were influenced by micromixing. The first experiment is the esterification of ethanol and acetic acid to form ethyl acetate. Students first examine this reaction in their organic chemistry class. The experiment developed in this project re-examines this reaction from a chemical engineering perspective. For example, the reaction is reversible and equilibrium-limited, but in the organic chemistry lab, there is no examination of the kinetics. The complementary chemical engineering experiment examines the relationship between residence time and conversion. The second experiment is a competitive system involving two reactions: 5I− + IO3− + 6H+ → 3I2 + 3H2O The first reaction is essentially instantaneous. Thus, when H+ is added as the limiting reagent, a perfectly mixed system would produce essentially no I2. Production of a significant quantity of I2 is attributed to a local excess of H+; a condition in which all H2BO3− in a region is consumed and H+ remains to react with I− and IO3−. In the spring of 2005, for the first time, both experiments were integrated into the undergraduate chemical reaction engineering course. This paper describes the use of the experiments in the classroom and compares the performance of the 2005 students to the 2004 cohort, for whom the course included no wet labs at all. 相似文献
13.
The previously described “redoxokinetic effect” is used to indicate the end-points of titrations of Fe 2+ with Cr 2O 72-, sulphuric acid with sodium hydroxide, AsO 2- with I 2 and Ag + with Cl −. With the first three systems an accuracy of 0·1 per cent is possible. The method is not suited to the fourth system. AbstractTitrations of sulphuric acid vs. sodium hydroxide at 0·1 N concentration and ferrous ammonium sulphate vs. potassium dichromate at 0·05 N concentration can be carried out with an accuracy of ±0·1 per cent using the redoxokinetic technique. A very sharp end-point was obtained in the case of iodine vs. arsenite titration at 0·1 N concentration. Silver nitrate vs. chloride titrations cannot be carried out by the redoxokinetic technique. Addition of MnSO4 to the extent of 50 g/l. of the solution enhances the precision considerably in the titration of dilute solutions of ferrous ammonium sulphate with dichromate. 相似文献
14.
The hydrodynamic characteristics in aqueous solution at ionic strength I=0.2
of carboxymethylchitins of different degrees of chemical substitution have been determined. Experimental values varied over the following ranges: the translational diffusion coefficient (at 25.0°C), 1.1<10 7× D<2.9 cm 2 s −1; the sedimentation coefficient, 2.4< s<5.0 S; the Gralen coefficient (sedimentation concentration-dependence parameter), 130< ks<680 mL g −1; the intrinsic viscosity, 130<[ η]<550 mL g −1. Combination of s with D using the Svedberg equation yielded ‘sedimentation–diffusion' molecular weights in the range 40 000< M<240 000 g mol −1. The corresponding Mark–Houwink–Kuhn–Sakurada (MHKS) relationships between the molecular weight and s, D and [ η] were: [ η]=5.58×10 −3 M0.94; D=1.87×10 −4 M−0.60; s=4.10×10 −15 M0.39. The equilibrium rigidity and hydrodynamic diameter of the carboxymethylchitin polymer chain is also investigated on the basis of wormlike coil theory without excluded volume effects. The significance of the Gralen ks values for these substances is discussed. 相似文献
15.
Diffusion of ammonia and ammonium ions in sulphonic acid cation exchangers (gel Purolite SGC 100 × 10 MBH and macroporous Purolite C 160 MBH) from the solutions, representing the composition of “caustic condensate” (waste of nitrogen fertilizers production) is affected by pH of initial solution and structure of the matrix of cation exchanger. In gel matrix the effective intraparticle diffusivity ( Def) depends greatly on the solution pH because of shrinkage in alkaline and swelling in acidic medium: on decreasing the initial concentration of ammonia from 0.214 to 0.003 and increasing that of ammonium nitrate from 0 to 0.214 mol l −1 instead, the effect of ion exchange leads to a decrease in pH, resulting in swelling and increase in Def from 0.1 to 0.34 × 10 −10 for gel Purolite SGC 100 × 10 MBH and variation of 0.18–0.11 × 10 −10 m 2 s −1 for macroporous Purolite C 160 MBH (resistant to shrinkage and swelling). In Purolite C 160 MBH both macropore diffusivity (0.07–0.29 × 10−10 m2 s−1) and gel (solid phase) diffusivity (0.06–0.19 × 10−10 m2 s−1) are higher than micropore diffusivity (0.28–0.56 × 10−18 m2 s−1). With respect to the effective intraparticle diffusivity, resistance to nitric acid, used for the regeneration, and high concentration of ammonium nitrate in eluate (up to 110 g l−1), Purolite C 160 MBH has been installed for the conversion of ammonia and ammonium ions to ammonium nitrate reusable in the fertilizers production. This allows minimizing the economic loss and preventing the environmental contamination. 相似文献
16.
Ionic liquid–polymer gels were prepared by incorporating N-butyl- N-methylmorpholinium bis(trifluoromethanesulfonyl)imide (Mor 1,4TFSI) and poly(vinylidene fluoride)–hexafluoropropylene copolymer (PVdF(HFP)) using three different methods in order to observe the variation of ionic conductivities according to the presence of propylene carbonate (PC) and various weight ratios between Mor 1,4TFSI and gel polymer electrolyte (GPE). Ionic conductivities for each gel polymer electrolyte were measured with increasing temperature. Ionic conductivities of the GPEs increased with increasing temperature and weight ratio of Mor 1,4TFSI. In addition, the addition of PC into GPE led to the improvement of ionic conductivities. Thermogravimetric analysis (TGA) showed the suggested gel polymer electrolytes composed of only ionic liquid and polymer were stable up to approximately 400 °C. TGA and infrared spectroscopy data indicated that residual PC remains after evaporating PC in a vacuum oven, which did not affect the ionic conductivities. The GPEs containing PC displayed high conductivity (ca. 10 −2 S cm −1) at 60 °C. 相似文献
17.
In order to make clear the coordinatively unsaturated sites (CUS) of Co–Mo/Al 2O 3 sulfided at high pressure, the temperature programmed desorption of NO adsorbed on Co–Mo/Al 2O 3 sulfided at high pressure was studied by DRIFT method. The intensity of two IR bands (1835 and 1785 cm −1) of adsorbed NO on Co–Mo/Al 2O 3decreased simultaneously up to 393 K. The higher frequency band disappeared at 393 K, while the lower frequency band remained even at 403 K. In the case of Mo/Al 2O 3, the intensities of two bands appeared at 298 K decreased monotonously with increasing temperature, and disappeared simultaneously over 433 K. In the case of Co/Al 2O 3, two bands disappeared simultaneously over 393 K. These results suggest that two kinds of nitrosyl species are formed on Co–Mo/Al 2O 3. One is dinitrosyl species adsorbed on CUS of Co, and the other is unidentified nitrosyl species. Comparing DRIFT spectra of Co–Mo/Al 2O 3 with those of a physical mixture of Mo/Al 2O 3 and Co/Al 2O 3, it is also suggested that the formation of the latter one correlates with the interaction between Co and Mo in Co–Mo/Al 2O 3. The unidentified nitrosyl species might be the key to explain the dependency of DRIFT spectrum of adsorbed NO on the pressure of sulfiding. 相似文献
18.
Gels of crosslinked β-cyclodextrin have been prepared using dimethylacetamide containing lithium, sodium and potassium triflate salts. Compositions were adjusted to produce materials with dry surfaces that showed no evidence of solvent leakage. Alternating current conductivity (σ) measurements of ion transport in these systems were made over the temperature range 290–360 K. Systems containing KCF3SO3 exhibited the best range of conductivity values from σ=10−4 S cm−1 (293 K) to σ=1.8×10−3 S cm−1 (360 K). These systems also show a linear dependence of log conductivity on 1/temperature, with activation energies for ion transport in the range 32–48 kJ mol−1. 相似文献
19.
This work deals with poly(ethylene oxide), PEO–MX (M=Li, K and Cs) amorphous electrolytes with −X–X −, [CF 3SO 2NCH 2(CH 2OCH 2) 2CH 2NSO 2CF 3] 2− (EDSA) and [CF 3SO 2NCH 2CH 2(CH 2OCH 2) 3CH 2CH 2NSO 2CF 3] 2− (TTSA) disulfonamide anions. These dianions have X − end-groups identical to anions [CF 3SO 2N(CH 2) 2OCH 3] − (MESA) and [CF 3SO 2N(CH 2) 3OCH 3] − (MPSA), one of which (MPSA) was reported to yield chelate-like associated species (presumably LiX 2− triplets) at concentrations above EO/Li=20 in PEO. This feature of LiMPSA, evidenced through glass transition temperature ( Tg) measurements, does not apply to Li 2EDSA and Li 2TTSA. Though none of these lithium salts form crystalline intermediate compounds with PEO, the limit of solubility of LiMESA (EO/Li=16) does not allow a clarification of this point for this salt. At lower concentrations, however, a conductivity comparison with the potassium and caesium salts shows that the apparent degree of dissociation ( = CLi+/ CLi) of LiMESA is comparable to that of LiMPSA. As opposed to both these salts and to some extent to Li 2EDSA, a much greater dissociation takes place for Li 2TTSA, the anion of which contains an inner, third ether group in its structure. 相似文献
20.
Layered -titanate materials, Na xM x/2Ti 1−x/2O 2 (M=Co, Ni and Fe, x=0.2–0.4), were synthesized by flux reactions, and electrical properties of polycrystalline products were measured at 300–800 °C. After sintering at 1250 °C in Ar, all products show n-type thermoelectric behavior. The values of both d.c. conductivity and Seebeck coefficient of polycrystalline Na 0.4Ni 0.2Ti 0.8O 2 were ca. 7×10 3 S/m and ca. −193 μV/K around 700 °C, respectively. The measured thermal conductivity of layered -titanate materials has lower value than conductive oxide materials. It was ca. 1.5 Wm −1 K −1 at 800 °C. The estimated thermoelectric figure-of-merit, Z, of Na 0.4Ni 0.2Ti 0.8O 2 and Na 0.4Co 0.2Ti 0.8O 2 was about 1.9×10 −4 and 1.2×10 −4 K −1 around 700 °C, respectively. 相似文献
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