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.     

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.     

Investigation of ion transport in Li<Subscript>8</Subscript>ZrO<Subscript>6</Subscript> and Li<Subscript>6</Subscript>Zr<Subscript>2</Subscript>O<Subscript>7</Subscript> solid electrolytes

Lithium ionic conductivity and spin-lattice relaxation rates were measured in Li₈ZrO₆ and Li₆Zr₂O₇ solid electrolytes. It was found that the Li₈ZrO₆ solid electrolyte undergoes a transition to the superionic state in the temperature range 673–703 K. It was shown that Li⁺ ions are mobile in particular lattice positions of the Li₆Zr₂O₇ phase, and that ionic conductivity is monotonic at an activation energy of 79.4 kJ/mol.     

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.     

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.     

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.     

Phase Transitions in a Mixture of Amorphous C<Subscript>60</Subscript> and C<Subscript>70</Subscript> Fullerene Phases at High Temperatures and Pressures

Phase transitions in two types of amorphous fullerene phases (C₆₀–C₇₀ (50/50) mixtures and an amorpous C₇₀ fullerene phase) are studied via neutron diffraction at pressures of 2–8 GPa and temperatures of 200–1100°C. Fullerenes are amorphized by grinding in a ball mill and sintered under quasi-hydrostatic pressure in a toroidal-type chamber. Diffraction studies are performed ex situ. It is shown that the amorphous phase of fullerenes retains its structure at temperatures of 200–500°C, and amorphous graphite is formed at 800–1100°C with a subsequent transition to crystalline graphite. This process is slow in a mixture of fullerenes, compared to C₇₀ fullerene. According to neutron diffraction data, the amorphous graphite formed from amorphous fullerene phases has anisotropy that is much weaker in a fullerene mixture.     

Phase transition in a KPb<Subscript>2</Subscript>Br<Subscript>5</Subscript> crystal

Crystals of the KPb₂Br₅compound are investigated using polarized light microscopy and calorimetry. The birefringence and the angle of rotation of the optical indicatrix are measured in the temperature range 270–620 K. It is found that the KPb₂Br₅ crystal undergoes a first-order ferroelastic phase transition at temperatures T_0↑ = 519.5 K and T_0↓ = 518.5 K with a change in the enthalpy ΔH = 1300 ± 200 J/mol. This transition is accompanied by both twinning and the symmetry change mmm ? P2₁/c. It is revealed that the angle of rotation of the optical indicatrix exhibits an unusual behavior under variations in the temperature due to a strong temperature dependence of the birefringence.     

Chemiluminescent emission of CH*, C*<Subscript>2</Subscript>, OH*, and CO*<Subscript>2</Subscript> during the ignition of ethane behind reflected shock waves

The chemiluminescent emission from CH*, C*₂, OH*, and CO*₂ during the self-ignition of various mixtures of ethane with oxygen and argon behind reflected shock waves in the 1240–1790 K temperature range at a total concentration of the mixture М ₅ = (1 ± 0.2) × 10^?5 mol/cm³ is experimentally studied. It has been shown that the time-to-maximum in the emission intensity profiles is almost identical for all the emitters studied. How the pattern of the OH* emission profile changes with the temperature and mixture composition is examined. The CH* and C*₂ emission profiles demonstrate virtually symbatic behavior in the covered ranges of temperature, pressure, and equivalence ratio. It is established that the emission signals from OH* and CO*₂ appear earlier than the C*₂ and CH* emission signals. The numerical simulation predictions are found to be in close agreement with the experimental results.     

Crystallization kinetics of Al<Subscript>86</Subscript>Ni<Subscript>8</Subscript>Ho<Subscript>6</Subscript> amorphous alloy

We investigate the processes of crystallization and determined the structure and thermal properties of Al₈₆Ni₈Ho₆ amorphous alloy in a wide temperature range. A three-stage nature of the crystallization process upon heating to a temperature of 700 K is found. According to data of high-temperature X-ray diffraction analysis, the crystallization of an Al₈₆Ni₈Ho₆ amorphous ribbon is rather complex: aluminum crystallites grow in the amorphous phase to a temperature of 470 K, a Ho₃Ni₅Al₁₉ phase is formed above 563 K, and a HoAl₃ phase appears above 598 K. The phases of Ho₃Ni₅Al₁₉ and HoAl₃ are retained up to a temperature of 723 K. A three-stage kinetic model of the crystallization process with the reaction sequence is proposed based on calculations by multivariate nonlinear regression. The values of the total activation energy for each crystallization stage reach 239, 378, and 247 kJ/mol.     

Low-temperature thermal-expansion anomaly in Bi<Subscript>2</Subscript>Sr<Subscript>2</Subscript>CuO<Subscript>6</Subscript>

Single-crystal samples of the Bi_{2 + x}Sr_{2 ? x ? y}Cu_{1 + y}O_{6 + δ} system revealed anomalous (negative) thermal expansion in the temperature range 10–20 K. Magnetic fields of 1–3 T were found to strongly affect the position and width of the anomaly region. A thermal-expansion singularity was detected at temperatures T≈30–50 K, which may be related to the formation of a pseudogap.     

Electronic excitations in BeAl<Subscript>2</Subscript>O<Subscript>4</Subscript>, Be<Subscript>2</Subscript>SiO<Subscript>4</Subscript>, and Be<Subscript>3</Subscript>Al<Subscript>2</Subscript>Si<Subscript>6</Subscript>O<Subscript>18</Subscript> crystals

Low-temperature (T = 7 K) time-resolved selectively photoexcited luminescence spectra (2–6 eV) and luminescence excitation spectra (8–35 eV) of wide-bandgap chrysoberyl BeAl₂O₄, phenacite Be₂SiO₄, and beryl Be₃Al₂Si₆O₁₈ crystals have been studied using time-resolved VUV spectroscopy. Both the intrinsic luminescence of the crystals and the luminescence associated with structural defects were assigned. Energy transfer to impurity luminescence centers in alexandrite and emerald was investigated. Luminescence characteristics of stable crystal lattice defects were probed by 3.6-MeV accelerated helium ion beams.     

High-temperature heat capacity of stannates Pr<Subscript>2</Subscript>Sn<Subscript>2</Subscript>O<Subscript>7</Subscript> and Nd<Subscript>2</Subscript>Sn<Subscript>2</Subscript>O<Subscript>7</Subscript>

Oxide compounds Pr₂Sn₂O₇ and Nd₂Sn₂O₇ have been obtained by solid-phase synthesis. The effect of temperature on the heat capacity of Pr₂Sn₂O₇ (360–1045 K) and Nd₂Sn₂O₇ (360–1030 K) has been studied using differential scanning calorimetry. The thermodynamic properties of the compounds (changes in enthalpy, entropy, and the reduced Gibbs energy) have been calculated by the experimental data of C_p = f(T).     

The formation of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles in the oxidation of aluminum by water under sub- and supercritical conditions

Massive aluminum samples were oxidized by sub- and supercritical water with the formation of (AlOOH) _n and (Al₂O₃) _n nanoparticles. The release of H₂ began at 523 K when the reagents were heated uniformly to 700 K. The time lag of the beginning of oxidation was 140 s when supercritical water was injected into a reactor with aluminum samples at 665 K and 23.1 MPa. Oxidized aluminum powders were analyzed using a transmission electron microscope. Predominantly large (300–400 nm) α-Al₂O₃ particles were formed when supercritical water was injected into a reactor with aluminum. Smaller (20–50 nm) γ-Al₂O₃ particles were also observed in samples oxidized by water vapor under temperature increase conditions. Kinetic equations describing the rate of H₂ formation in the reaction of H₂O with aluminum were obtained. Possible nanostructuring mechanisms are discussed.     

Formation and dispersion of CO<Subscript>2</Subscript> after combustion in closed area

This study deals with the formation of carbon dioxide (CO₂) after combustion process and dispersion in a closed area. The formation and dispersion of CO₂ were numerically simulated and validated by experiment. Ethanol (C₂H₅OH) was chosen as a fuel for the combustion process. Numerical simulations were carried out by using Reynolds averaged Navier–Stokes (RANS) approach with k-ε and k-ω turbulent models. The combustion process was simulated using two methods. Species transport with chemical reactions was the first method, and the second method was the nonpremix combustion model based on the mixture fraction theory. There were done some sensitivity studies on the influence of the time step size and a resolution of computational grid. Results from numerical simulations were validated by experimental measurements, where the CO₂ concentration was measured by the non-dispersive infrared (NDIR) sensor at four points.     

Transport characteristics of phonons and the specific heat of Y<Subscript>2</Subscript>O<Subscript>3</Subscript>:ZrO<Subscript>2</Subscript> solid solution single crystals

The temperature dependences of the specific heat and transport characteristics of phonons in single crystals of yttrium-stabilized zirconium dioxide Y₂O₃:ZrO₂ solid solutions have been studied. It has been shown that the temperature dependences of the specific heat at T > 5 K are almost identical at the degree of stabilization of a solid solution with an Y₂O₃ content of 5–20 mol %. Differences in the temperature dependences of the specific heat of samples from different sources at T < 5 K are due to the presence of low-energy two-level systems. The features of the transport characteristics of thermal phonons at liquid helium temperatures reflect not only the presence of two-level systems but also the scattering of phonons on low-dimensional domains of another phase coherently conjugate to the main phase of the Y₂O₃:ZrO₂ solid solution.     

Magnetic and magneto-lattice dynamics in GdMn<Subscript>2</Subscript>O<Subscript>5</Subscript>

The dynamics of magnetoelectric RMn₂O₅ crystals (R=Eu and Gd) was studied in the frequency and temperature ranges 20–300 GHz and 5–50 K, respectively. The crystals possessed magnetic and ferroelectric long-range order and had close transition temperatures, T_{N, C}?36 and 30 K for R=Eu and Gd, respectively. Mixed magneto-lattice excitations were observed in GdMn₂O₅; the excitations were most intense near the transition temperature T?30 K at frequencies close to the antiferromagnetic resonance frequencies of the Mn subsystem. Along with the antiferromagnetic resonance of the Mn subsystem, the ferromagnetic resonance of the Gd subsystem was observed in GdMn₂O₅ in an external magnetic field. No such dynamics was characteristic of EuMn₂O₅.     

Electron and electron-phonon effects in the quasi-two-dimensional molecular conductor θ-(BETS)<Subscript>4</Subscript>HgBr<Subscript>4</Subscript>(C<Subscript>6</Subscript>H<Subscript>5</Subscript>Cl): Optical studies at 300–15 K

This paper reports on a study of the polarized reflectance and optical conductivity spectra of the quasi-two-dimensional molecular conductor θ-(BETS)₄HgBr₄(C₆H₅Cl) within the 700–6500-cm^?1 region at 300–15 K and within the 9000–40 000 cm^?1 region at 300 K performed along two principal directions in the crystal plane parallel to the conducting layers of the BETS molecules. The IR spectra obtained at 300 K follow a close-to-Drude behavior, with strong broad features (1200–1400 cm^?1) due to electron-vibrational (vibronic) coupling (VC) superposed on the high Drude background. As the temperature is lowered in the range 180–80 K, in the spectra there appears a Lorentz term with ω_t=2900 cm^?1, as well as three additional VC-induced bands in the 800–1180-cm^?1 region, which disappear as the temperature is decreased further. The results obtained indicate the existence of unstable structural distortions along the two principal directions in the crystal, which are accompanied by the formation of a commensurate charge-density wave.     

Spherical shape BaO-ZnO-B<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> glass powders prepared by spray pyrolysis

Fine-sized BaO-ZnO-B₂O₃-SiO₂ (BZBS) glass powders were directly prepared by high temperature spray pyrolysis. The hollow glass powders prepared at low preparation temperature of 1000 °C had a low density of 2.65 g/cm³. However, the densities of the BZBS powders obtained at preparation temperatures of 1200 and 1400 °C were each 3.92 and 4.13 g/cm³. The mean size of the BZBS glass powders prepared by spray pyrolysis at preparation temperature of 1400 °C was 0.98 μm. The glass transition temperature (T_g) of the prepared BZBS glass powders was 518.9 °C. The dielectric layers formed from the prepared BZBS glass powders with a dense structure had a clean surface and a dense inner structure without voids at the firing temperature of 580 °C. The transparencies of the dielectric layers formed from the prepared BZBS glass powders were higher than 90% within the visible range. PACS 42.70.Ce; 85.60.Pg; 71.55.Jv