Accuracy in determination of the temperature and partial pressure of CO<Subscript>2</Subscript> in CO<Subscript>2</Subscript>:N<Subscript>2</Subscript>:H<Subscript>2</Subscript>O:NO<Subscript>2</Subscript> mixtures by multiple-frequency laser probing

We present the results of analysis of the errors introduced by hot-band transitions 11¹0-01¹1, 03¹0-01¹1, 12⁰0-12⁰1 of the CO₂ molecule and the absorption lines of the H₂O and NO₂ molecules in determination of the temperature and partial pressure of CO₂, included in the gas mixture CO₂: N₂:H₂O: NO₂ at atmospheric pressure, by multiple-frequency laser probing using a CO₂ laser tunable over the lines of the 00⁰1-[10⁰0,02⁰0]_I,II ground-state laser transitions. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 810–815, November–December, 2007.     

Graphite gasification in high-temperature gas flows containing H<Subscript>2</Subscript>O and CO<Subscript>2</Subscript>

The rates of graphite gasification in interaction with high-temperature gas flows were compared. Carbon dioxide and a mixture of water vapor and argon taken in a 1:1 molar ratio were used as reagents. The reactor was a tube furnace; its temperature was varied from 1250 to 1400 K. The rates of graphite gasification in CO₂ and water vapor-argon mixture flows were approximately equal at 1250–1300 K, whereas, at 1350–1400 K, the water vapor-argon mixture exhibited higher reactivity than CO₂. The data obtained were approximated by Arrhenius dependences; the activation energy was found to be 153 kJ/mol for CO₂ and 248 kJ/mol for H₂O-Ar.     

Determination of an optimal five-gas combination in a sealed-off CO<Subscript>2</Subscript> laser

For obtaining the maximal output power, five lasing gas mixtures (CO₂, N₂, He, Xe and H₂) in a sealed-off CO₂ laser are optimized by applying a genetic algorithm and solving CO₂ laser kinetics equations. A comparison of numerical simulations shows that the optimal pressures of CO₂ and N₂ are 1.15 Torr and 7.32 Torr, respectively. Accordingly, the maximum laser power of 124 W is obtained by utilizing the optimal gas combination and an optimized resonator with a length of 1.2 m. Received: 14 August 2002 / Published online: 22 January 2003 The project supported by Zhejiang Provincial Natural Science Foundation of China (No. 602098). RID="*" ID="*"Corresponding author. Fax: +86-571/8832-0369, E-mail: chengch@mail.hz.zj.cn     

Photoluminescence of fluoroacrylate polymers impregnated with Eu(bta)<Subscript>3</Subscript> using supercritical CO<Subscript>2</Subscript>

Optical properties (photoluminescence and absorption) of Eu(bta)₃(B) _n (B = H₂O or 1,10-phenanthroline) polycrystalline powders and fluoroacrylate polymers (FAPs) impregnated with these compounds using supercritical CO₂ (SC CO₂) were investigated. It was established that impregnation of Eu(bta)₃phen into the FAPs using an SC CO₂ solution was difficult to achieve. The type of B (ancillary ligand) and the polymer matrix were shown to influence the temperature quenching of photoluminescence of Eu³⁺ ions in the range 25–100°C. A comparative analysis of quantum yields (λ_ex = 300 and 380 nm) and photoluminescence decay times (λ_ex = 337.1 nm) for Eu(bta)₃B _n and for Eu(bta)₃B _n -doped FAPs was performed.     

CO<Subscript>2</Subscript> activation on single crystal based ceria and magnesia/ceria model catalysts

Novel multifunctional ceria based materials may show an improved performance in catalytic processes involving CO₂ activation and reforming of hydrocarbons. Towards a more detailed understanding of the underlying surface chemistry, we have investigated CO₂ activation on single crystal based ceria and magnesia/ceria model catalysts. All model systems are prepared starting from well-ordered and fully stoichiometric CeO₂(111) films on a Cu(111) substrate. Samples with different structure, oxidation state and compositions are generated, including CeO_2-x/Cu(111) (reduced), MgO/CeO_2-x/Cu(111) (reduced), mixed MgO-CeO₂/Cu(111) (stoichiometric), and mixed MgO-CeO_2-x/Cu(111) (reduced). The morphology of the model surfaces is characterized by means of scanning tunneling microscopy (STM), whereas the electronic structure and reactivity is probed by X-ray photoelectron spectroscopy (XPS). The experimental approach allows us to compare the reactivity of samples containing different types of Ce³⁺, Ce⁴⁺, and Mg²⁺ ions towards CO₂ at a sample temperature of 300 K. Briefly, we detect the formation of two CO₂-derived species, namely carbonate (CO₃ ^2-) and carboxylate (CO₂ ^-) groups, on the surfaces of all investigated samples after exposure to CO₂ at 300 K. In parallel to formation of the carbonate species, slow partial reoxidation of reduced CeO_2-x/Cu(111) occurs at large doses of CO₂. The reoxidation of the reduced ceria is largely suppressed on MgO-containing samples. The tendency for reoxidation of Ce³⁺ to Ce⁴⁺ by CO₂ decreases with increasing degree of intermixing between MgO and CeO_2-x. Additionally, we have studied the stability of the formed carbonate species as a function of annealing temperature.     

A comparative study of Li<Subscript>2</Subscript>CO<Subscript>3</Subscript> modified carbon microbead anodes prepared by different synthetic routes for lithium-ion battery

Li₂CO₃ modified carbon microbead composites (LCO/CMB-T) with different covering amount are prepared by solvent evaporation and dipping method. LiCH₃COO are first used as lithium source, which can provide a precise control of Li₂CO₃ amount through varying dipping times or solution concentration. The morphology, structure, and covering amount are characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), and atomic absorption spectrometer (AAS). The dipping process can produce the samples with better surface coverage, more uniform coating, and higher Li₂CO₃ crystallinity, while the appropriate amount of Li₂CO₃ can help to decrease initial irreversible capacity and improve cell performance. Here, the sample with 1.07 % Li₂CO₃ prepared by dipping method shows the highest initial discharge capacity of 353.7 mAh g^?1 and coulombic efficiency of 89.5 %. The capacity retention is up to 82.1 % after 30 cycles.     

A miniature tunable TEA CO<Subscript>2</Subscript> laser using isotope <Superscript>13</Superscript>C<Superscript>16</Superscript>O<Subscript>2</Subscript> and <Superscript>12</Superscript>C<Superscript>16</Superscript>O<Subscript>2</Subscript>

A miniature tunable TEA CO₂ laser using isotope ¹³C¹⁶O₂ as the active medium is developed to extend the spectral range of CO₂ lasers for further application. The optimization of the energy parameters of the tunable TEA ¹³C¹⁶O₂ laser and the same laser using ¹²C¹⁶O₂ are studied. When a gas mixture (¹³C¹⁶O₂: N₂: He = 1: 1: 3) at a total pressure of 6.4 × 10⁴ Pa is used, the TEA ¹³C¹⁶O₂ laser of a 45-cm³ active volume obtains 51 emission lines in the [00⁰1–10⁰0] and [00⁰1–02⁰0] bands. The maximum pulse energy of the TEA ¹³C¹⁶O₂ laser is about 357 mJ. The same laser using the conventional gas mixture (¹²C¹⁶O₂: N₂: He = 1: 1: 3) at a pressure of 6.66 × 10⁴ Pa is measured to obtain 69 laser emission lines and the maximum pulse energy of laser radiation is about 409 mJ.     

Molecular Simulation of H<Subscript>2</Subscript>O,CO<Subscript>2</Subscript>, and CH<Subscript>4</Subscript> Adsorption in Coal Micropores

Based on the chemical model of coal, slit micropores with different pore sizes are established and structures are optimized in the software of materials studio. As the temperature rises, absolute adsorption capacities of H₂O are slightly affected, while absolute adsorption capacities of CO₂ and CH₄ gradually decrease. As the fugacity rises, excess adsorption curves of CO₂ experience increase-decrease-gentle three stages, while the curves of CH₄ gradually decrease. With the increase of pore size, adsorption capacities of H₂O increase, while adsorption capacities of CO₂ and CH₄ gradually decrease. H₂O firstly adsorbs on the oxygen-containing functional group, so the walls of pore are the preferential area for H₂O, while CO₂ and CH₄ choose to adsorb on–C–C–, therefore the walls are the primary area for CO₂ and CH₄. Strong potential in micropores and hydrogen bond among water molecules will promote the water adsorption, while the adsorptions of CO₂ and CH₄ are only induced by the Van der Waals interaction, but the difference between adsorption density and bulk density of CO₂ and CH₄ decides the change of excess adsorption capacity.     

Oxidation of hydrogen sulfide and corrosion of stainless steel in gas mixtures containing H<Subscript>2</Subscript>S,O<Subscript>2</Subscript>, H<Subscript>2</Subscript>O,and CO<Subscript>2</Subscript>

The composition of volatile and solid products of oxidation of hydrogen sulfide and stainless steel in gas mixtures containing H₂S, O₂, H₂O, and CO₂ has been determined using mass spectrometry, x-ray diffraction analysis, and scanning electron microscopy. It has been shown that holding an H₂S–O₂ mixture at 301 K results in prevailing formation of elemental sulfur and iron sulfides in the form of porous hygroscopic crust on the reactor wall surface. Formation of gas-phase sulfur causes self-acceleration of the oxidation of hydrogen sulfide; the resulting water triggers corrosion of the reactor wall. Heating of the resulting sulfur-sulfide crust in O₂ medium is accompanied by formation of SO₂ and heat release at T > 508 K. After heating of the H₂S–CO₂ mixture to 615 K, H₂ and COS were found in the volatile reactants; no noticeable corrosion of the reactor wall has been detected. It has been established that addition of O₂ to the H₂S–CO₂ mixture and its heating to 673 K leads to formation of ferrous sulfates. The mechanisms of the observed processes are discussed.     

Microstructure and superconducting properties of the DyBaCuO ceramic doped with Na<Subscript>2</Subscript>CO<Subscript>3</Subscript>, NaCl,and KClO<Subscript>3</Subscript>

This paper reports on a study of the effect of doping with Na₂CO₃, NaCl, and KClO₃ salts on the microstructure and superconducting characteristics of ceramics with nominal compositions Dy_{1 ? x} M _x Ba₂Cu_{3 ? y} O_{7 ? δ} and DyBa₂Cu_{3 ? y} O_{7 ? δ} : M _x for M = Na, K; x = 0.2, 0.3, and y = 0, 0.2. The microstructure was characterized by transmission electron microscopy with local energy-dispersive x-ray in situ analysis (probe size ～1 nm). An analysis shows that none of the doping elements (Na, K, or Cl) enters into 123 grains in sizable amounts and that, as a result, the critical temperature of the superconducting transition remains practically constant in the range 90.0–93.5 K. Potassium and chlorine segregate at grain boundaries. It is shown that grain-boundary segregation of chlorine leads to a substantial increase in the superconducting critical current (by a factor 3–5 at 70 K) as compared to the undoped sample. The possible mechanisms accounting for the effect of Cl on intergrain critical current are discussed.     

Operational characteristics and power scaling of a transverse flow transversely excited CW CO<Subscript>2</Subscript> laser

Transverse flow transversely excited (TFTE) CO₂ lasers are easily scalable to multikilowatt level. The laser power can be scaled up by increasing the volumetric gas flow and discharge volume. It was observed in a TFTE CW CO₂ laser having single row of pins as an anode and tubular cathode that the laser power was not increasing when the discharge volume and the gas volumetric flow were increased by increasing the electrode separation keeping the gas flow velocity constant. The discharge voltage too remained almost constant with the change of electrode separation at the same gas flow velocity. This necessitated revision of the scaling laws for designing this type of high power CO₂ laser. Experimental results of laser performance for different electrode separations are discussed and the modifications in the scaling laws are presented.     

Optical CO<Subscript>2</Subscript> Sensing with Ionic Liquid Doped Electrospun Nanofibers

The first use of electrospun nanofibrous materials as highly responsive fluorescence quenching-based optical CO₂ sensors is reported. Poly(methyl methacrylate) and ethyl cellulose were used as polymeric materials. Sensing slides were fabricated by electrospinning technique. A fiber-optic bundle was used for the gas detection. CO₂ sensors based on the change in the fluorescence signal intensity of ion pair form of 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS). The sensor slides showed high sensitivities due to the high surface area-to-volume ratio of the nanofibrous membrane structures. The preliminary results of Stern-Volmer analysis show that the sensitivities of electrospun nanofibrous membranes to detect CO₂ are 24 to 120 fold higher than those of the thin film based sensors. The response times of the sensing reagents were short and the signal changes were fully reversible. The stability of ion pair form of HPTS in the employed matrix materials was excellent and when stored in the ambient air of the laboratory there was no significant drift in signal intensity after 7 months. Our stability tests are still in progress.     

Production of collimated positronium by positron scattering from CO<Subscript>2</Subscript>, N<Subscript>2</Subscript> and Xe

The efficiency for collimated positronium production by charge-exchange in positron collisions with gaseous targets has been investigated in the range 20–396 eV. At 250 and 396 eV, CO₂ has been found to be approximately twice as efficient as N₂, the previous best neutralising gas at high energies. The efficiency from Xe, whilst lower at low energies, becomes comparable to that from H₂ at around 100–120 eV; at ∼250 eV, it is an order of magnitude lower.     

High-power high beam-quality multi-waveguide CO<Subscript>2</Subscript> amplifiers

The results from modeling the energy characteristics of a multi-waveguide power amplifier are presented. The optical schemes and calculations for the most promising circuits of multichannel waveguide CO₂ amplifiers are given. The amplifying system itself removes the problem of phase locking in individual channels of multichannel systems. The experimental results from the synchronization of arrays of multichannel waveguide CO₂ lasers allow the production of high-power (up to 15 kW) high beam-quality multibeam lasers. Technological lasers with such properties have yet to be produced anywhere in the world.     

Single enzyme nanoparticle for biomimetic CO<Subscript>2</Subscript> sequestration

Nanoparticle technology is being increasingly used in environmental sciences. We prepared single enzyme nanoparticle (SEN) by modifying the surface of carbonic anhydrase (CA) with a thin layer of organic/inorganic hybrid polymer. SEN-CA appears to be improving the stability of free enzyme. CA, as ubiquitously found enzyme, is involved in gaseous CO₂ sequestration and is being looked as a promising candidate for combating global warming. We report here physical characterization of SEN-CA using transmission electron microscope (TEM), Fourier-transform infrared analysis (FTIR), X-ray diffraction analysis (XRD), and energy dispersive X-ray (EDX). Average size of SEN-CA particles appears to be in the range of 70–80 nm. We also report the effect of SEN formation on the kinetic parameters of free CA such as Michaelis–Menten constant (K _m), maximum reaction velocity (V _max), and storage stability of free CA and SEN-CA. The V _max of SEN-CA (0.02857 mmol/min/mg) and free enzyme (0.02029 mmol/min/mg) is almost similar. K _m has decreased from 6.143 mM for SEN-CA to 1.252 mM for free CA. The stabilization of CA by SEN formation results in improved the half-life period (up to 100 days). The formation of carbonate was substantiated by using gas chromatography (GC). The conversion of CO₂ to carbonate was 61 mg of CaCO₃/mg of CA and 20.8 mg of CaCO₃/mg of CA using SEN-CA and free CA, respectively.     

Properties of powders produced by evaporating CeO<Subscript>2</Subscript>/Gd<Subscript>2</Subscript>O<Subscript>3</Subscript> targets exposed to pulsed-periodic radiation of a CO<Subscript>2</Subscript> laser

The characteristics (phase composition, grain shape, grain size distribution, and specific surface area) of Ce_0.78Gd_0.22O_2-δ nanopowders produced by exposing the target to pulsed CO₂ laser radiation are reported. Reasons for a threefold increase in the output of the experimental powder-preparation unit (up to 60 g/h) with the characteristic grain size (≈10 nm) remaining unchanged are discussed.     

High resolution polarization spectroscopy and laser induced fluorescence of CO<Subscript>2</Subscript> around 2μm

High resolution Infrared Polarisation Spectroscopy (IRPS) and Infrared Laser Induced Fluorescence (IRLIF) techniques were used to probe CO₂/N₂ binary gas mixture at atmospheric pressure and ambient temperature. The probed CO₂ molecules were prepared by laser excitation to an overtone and combination ro-vibrational state (12⁰1, J=15) of CO₂, centred at 4988.6612 cm^-1. IRPS and IRLIF line profiles were recorded for several CO₂/N₂ binary mixtures. The observed IRLIF line shapes have the expected Lorentzian form while the observed IRPS line shapes are narrower by a factor of two than those recorded with the IRLIF and appear to have a Lorentzian-cubed profile. The recorded line profiles provide measurements of the pressure-broadening coefficient directly at atmospheric pressure. The Full-Width-Half-Maxima (FWHM) pressure broadening coefficients are measured, based on IRLIF, to be 0.2174±0.0092 cm^-1atm^-1 and 0.1327 ±0.0077 cm^-1atm^-1 for self- and N₂ collision broadening, respectively. The broadening coefficients obtained based on IRPS were measured to be ~8% larger than those obtained with IRLIF.     

Measurement on CO<Subscript>2</Subscript> solution density by optical technology

The optical technology based on Mach-Zehnder interferometry was successfully applied to a high-pressure liquid CO₂ and water system to measure CO₂ solution density. Experiments were carried out at a pressure range of from 5.0 to 12.5 MPa, temperatures from 273.25 to 284.15 K, and CO₂ mass fraction in solution up to 0.061. CO₂ solution density data were obtained from two sets of experiments. These data were calculated through the fringe shifts induced by density changes inside of the high-pressure vessel, which were directly recorded during the experiments, and a modified version of Lorentz-Lorenz formulation. The experimental results indicated that the density ratio of CO₂ solution to that of pure water at the same pressure and temperature is monotonically linear with the CO₂ concentration in the solution. The slope of this linear function, calculated by the experimental data fitting, is 0.275.     

Electromechanical properties of Pb<Subscript>3</Subscript>Ga<Subscript>2</Subscript>Ge<Subscript>4</Subscript>O<Subscript>14</Subscript> piezoelectric crystals grown from solution in a melt

Single crystals of lead gallium germanate Pb₃Ga₂Ge₄O₁₄ are grown from their own solution melts. The propagation of bulk acoustic waves is investigated, and the elastic, piezoelectric, and dielectric constants are calculated. The temperature dependences of the dielectric constants of this compound are analyzed.     

Effect of SO<Subscript>2</Subscript> and CO<Subscript>2</Subscript> additives on the cycle performances of commercial lithium-ion batteries

The effects of SO₂ and CO₂ additives in electrolytes on the cycle properties of liquid-state Al-plastic film lithium-ion batteries were first investigated. The experimental electrolytes were added with different amounts of SO₂ and CO₂. The baseline electrolyte was 1 mol L⁻¹ LiPF₆ in ethylene carbonate/dimethylcarbonate/ethyl-methyl carbonate (1:1:1, by volume), and graphite was used as anode. The main analysis tools were cycling test, rate capability, internal resistance test, low-temperature performance, and thermal stability. The results showed that both of the additives could promote to form an excellent solid electrolyte interface film on the surface of graphite anode, leading to excellent cycle performances, the capacity retentions of CO₂ and S5 were 94% and 97% after 400 cycles, respectively. Besides, the results also exhibited that the electrochemical performances of internal resistance, rate capability, low-temperature performance, and thermal stability were not changed significantly by the use of SO₂ and CO₂ as electrolyte additives.