Sensitization of polymeric track detectors with carbon dioxide

The effect of CO₂ on the sensitivity of polymeric track detectors was studied. It has been found that the sensitivity of SR-90 is dependent on the amount of CO₂ dissolved in the polymer at the time of etching. It has been also found that CR-39 can be sensitized to some extent with an aging in CO₂. Since the sensitization in CO₂ is possible even a long time after the irradiation, the mechanism of the latent track formation by CO₂ is quite different from that by O₂. This would be the key to achieve the long term stability of polymeric track detectors such as SR-90 and CR-39.     

Mechanical properties of polymeric composites with carbon dioxide particles

Nanocomposites consisting of a polymethylmethacrylate or polystyrene matrix with embedded silicon dioxide nanoparticles surface-modified by silazanes have been prepared by melting technology. The influence of particles on viscoelastic properties of the nanocomposites has been studied using dynamic mechanical analysis. It has been revealed that the addition of 20 wt % of SiO₂ raises the flexural modulus of the nanocomposites by 30%.     

Absorption of pulsed CO2 laser radiation by air and carbon dioxide

An optoacoustical method is used in experimental study of nonlinearity in absorption of pulsed CO₂ laser radiation by air with CO₂ and H₂O added and pure CO₂. The laser pulse consists of frequencies related to several rotational transitions, generated simultaneously. Nonlinearity in absorption was detected for laser radiation levels above 0.2 MW/cm².Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 49–51, October, 1982.     

Single- and multi-photon absorption of carbon dioxide laser lines by SO2 and CO2 molecules

Summary We have used 60 rovibrational lines of a Lumonics TEA CO₂ laser to record the spectra of coincidence of SO₂ IR absorption with CO₂ laser emission. We extended the same type of investigation to CO₂ molecules and observed an absorption at practically all the rovibrational lines of the laser. We have also recorded the increase of absorption with pressure of the studied molecule and with its temperature. Our work reveals very accurately the fine structure of these absorptions that shows a clear discreteness in the intensities of the lines. Some implication of this discreteness in multiphoton absorption is also presented, through data that indicate very strong vibrational coupling between ground and excited electronic states of SO₂. The authors of this paper have agreed to not receive the proofs for correction.     

High pressure ignition delay times of H2/CO mixture in carbon dioxide and argon diluent

Ignition Delay Time (IDT) plays a significant role in combustion process of advanced power cycles such as direct-fired supercritical carbon dioxide (sCO₂) cycle. In this cycle, fuel and oxidizer are heavily diluted with carbon dioxide (CO₂) and autoignite at a combustor inlet pressure range of 10–30 MPa and a temperature range of 900–1500 K. A fuel candidate for sCO₂ power cycle applications is syngas (H₂/CO mixture); however, its ignition properties at these conditions are not studied. Moreover, the existing chemical kinetics models have not been evaluated for H₂/CO mixtures applications relevant to elevated pressure conditions and under large dilution levels of CO₂. Therefore, two tasks are performed in this study. First, IDTs of a H₂/CO=95:5 mixture at stoichiometric and rich (Φ=2) conditions are measured in a high-pressure shock tube under 95.5% CO₂ dilution level and at 10 MPa and 20 MPa for a temperature range of 1161–1365 K. For the experimental conditions considered in this work, Aramco 2.0, FFCM-1, HP-Mech and USC Mech II kinetic models are capable of capturing IDT data. Second, similar experiments are conducted by replacing the CO₂ dilute gas with Argon (Ar) to understand the chemical effect of CO₂ on IDT globally. Sensitivity analysis results reveal that for both diluents, reaction H + O₂(+M)=HO₂(+M) is the most important reaction in controlling ignition. Further, a rate of production analysis shows that CO₂ has a competing effect on OH radical production. On one hand, CO₂ accelerates the consumption of H radicals through H + O₂+CO₂→HO₂+CO₂ therefore hindering HO₂+HOH+OH reaction for OH production. On the other hand, CO₂ is shown to enhance OH production through H₂O₂+M=OH+OH+M. These kinetic effects from CO₂ cancel out, therefore CO₂ does not significantly alter the IDT globally when compared to the Ar bath case. This is confirmed by both experimental results and simulation.     

Partitioning of atmospheric carbon dioxide over Central Europe: insights from combined measurements of CO 2 mixing ratios and their carbon isotope composition

Regular measurements of atmospheric CO ₂ mixing ratios and their carbon isotope composition (¹³C/¹²C and ¹⁴C/¹²C ratios) performed between 2005 and 2009 at two sites of contrasting characteristics (Krakow and the remote mountain site Kasprowy Wierch) located in southern Poland were used to derive fossil fuel-related and biogenic contributions to the total CO ₂ load measured at both sites. Carbon dioxide present in the atmosphere, not coming from fossil fuel and biogenic sources, was considered ‘background’ CO ₂. In Krakow, the average contribution of fossil fuel CO ₂ was approximately 3.4%. The biogenic component was of the same magnitude. Both components revealed a distinct seasonality, with the fossil fuel component reaching maximum values during winter months and the biogenic component shifted in phase by approximately 6 months. The partitioning of the local CO ₂ budget for the Kasprowy Wierch site revealed large differences in the derived components: the fossil fuel component was approximately five times lower than that derived for Krakow, whereas the biogenic component was negative in summer, pointing to the importance of photosynthetic sink associated with extensive forests in the neighbourhood of the station. While the presented study has demonstrated the strength of combined measurements of CO ₂ mixing ratios and their carbon isotope signature as efficient tools for elucidating the partitioning of local atmospheric CO ₂ loads, it also showed the important role of the land cover and the presence of the soil in the footprint of the measurement location, which control the net biogenic surface CO ₂ fluxes.     

Partitioning of atmospheric carbon dioxide over Central Europe: insights from combined measurements of CO2 mixing ratios and their carbon isotope composition

Regular measurements of atmospheric CO (2) mixing ratios and their carbon isotope composition ((13)C/(12)C and (14)C/(12)C ratios) performed between 2005 and 2009 at two sites of contrasting characteristics (Krakow and the remote mountain site Kasprowy Wierch) located in southern Poland were used to derive fossil fuel-related and biogenic contributions to the total CO (2) load measured at both sites. Carbon dioxide present in the atmosphere, not coming from fossil fuel and biogenic sources, was considered 'background' CO (2). In Krakow, the average contribution of fossil fuel CO (2) was approximately 3.4%. The biogenic component was of the same magnitude. Both components revealed a distinct seasonality, with the fossil fuel component reaching maximum values during winter months and the biogenic component shifted in phase by approximately 6 months. The partitioning of the local CO (2) budget for the Kasprowy Wierch site revealed large differences in the derived components: the fossil fuel component was approximately five times lower than that derived for Krakow, whereas the biogenic component was negative in summer, pointing to the importance of photosynthetic sink associated with extensive forests in the neighbourhood of the station. While the presented study has demonstrated the strength of combined measurements of CO (2) mixing ratios and their carbon isotope signature as efficient tools for elucidating the partitioning of local atmospheric CO (2) loads, it also showed the important role of the land cover and the presence of the soil in the footprint of the measurement location, which control the net biogenic surface CO (2) fluxes.     

Potentiometric carbon dioxide sensor based on thin Li3PO4 electrolyte and Li2CO3 sensing electrode

Potentiometric CO₂ gas sensors with thin-film lithium phosphate (Li₃PO₄) electrolytes were developed by using radio frequency (RF) magnetron sputtering. Li₂CO₃ and a mixture of Li₂TiO₃ and TiO₂ were used as sensing and reference electrodes, respectively. By using the RF sputtering deposition process, we obtained a dense, crystalline, thin-film Li₃PO₄ electrolyte with good adhesion on the Al₂O₃ substrate. The thin-film Li₃PO₄ electrolyte had good ionic conductivity, i.e., 2.15?×?10^?6 S cm^?1 at 500 °C, and its activation energy was 0.97 eV. The thin-film Li₃PO₄ electrolyte was suitable for the miniaturization of potentiometric CO₂ sensors. The thin-film potentiometric CO₂ sensor provided relatively good sensing response for overall CO₂ concentrations (500 to 3,000 ppm and 5 to 20 %) at 500 °C. The Nernstian slope of 78.2 mV/decade obtained for CO₂ concentrations from 5 to 20 % at 500 °C was close to the theoretical value (76.6 mV/decade). Although the sensor’s reading deviated from the theoretical value at low CO₂ concentrations (500 to 3,000 ppm), the sensor provided better sensing performance than a potentiometric CO₂ sensor with a thick electrolyte. As a result, it was assumed that the thin-film sensor could be used to monitor the overall concentration of CO₂ in the environment.     

Low-temperature PECVD of silicon dioxide on polymeric hydrogels

In this work, a complex investigation of the film surface composition and nanoscale mechanical properties, i.e. hardness and elastic modulus, of plasma-modified and silica-coated hydrogel thin films was carried out. Plasma treatment was performed in a reactive ion etching chamber (SF₆, CHF₃) at radio frequency (rf, 13.56 MHz) and in a plasma-enhanced chemical vapor deposition chamber (SiH₄/N₂, NH₃, N₂O) at radio frequency and dual frequency (13.56 MHz/100 kHz), respectively. The use of the dual-frequency configuration comprising two power supplies and operated in a switched mode enabled the investigation of the ion-bombardment influence on the polymer properties. For the application in silicon micromachined sensors best results were obtained by using a NH₃ or SiH₄/N₂ low-pressure plasma modification and a silica coating of the sensitive hydrogel film. PACS 81.05.Lg; 81.15.Gh; 81.65.Cf; 81.70.Bt     

Synthesis of novel promising materials via impregnation of crosslinked polymeric networks with metal complexes in supercritical carbon dioxide

Three types of polymers, phenol-formaldehyde copolymer and polypropyleneimine and polyamidoamine dendrimers, are synthesized using the polycondensation method. Mesoporous polymeric networks are formed by treating the above dendrimers with crosslinking agents. Impregnation of polymeric networks with rhodium acetylacetonate in supercritical carbon dioxide has been carried out for the first time and its optimal conditions have been determined. Using Raman spectroscopy, it has been shown that the metal content in polymer networks falls in the range 0.3–2.0 mass % depending on the type of the polymer and the crosslinking agent and on the crosslinking degree. Polymer samples including rhodium nanoparticles have been prepared by reducing immobilized rhodium acetylacetonate with molecular hydrogen. According to the preliminary data, the resulting samples possess extremely high activity as catalysts for hydrogenation of unsaturated compounds.     

Remote detection of sulfur dioxide by means of a CO2 laser

The possibility of remote detection of SO₂ in the 9-μm region of the spectrum by means of a TEA CO₂ laser was theoretically and experimentally investigated with regard to the real state of the atmosphere and the contribution of background concentrations of H₂O, CO₂ and NH₃ to absorption. For sounding along short paths (2L=2 km), the method of detection of small concentrations of SO₂ (at the MPC level) with the use of the lines of the CO₂-molecule regular transitions (00^o1–02^o0 band) has been devised and experimentally tested. It is shown that in sounding along longer paths (2L=6 km), a noticeable increase in sensitivity can be achieved by the generation lines of the CO₂-molecule sequential 00^o2–02^o1 band. B. I. Stepanov Institute of Physics of the National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 508–515, July–August, 1998.     

Surface chemistry of carbon dioxide

The review discusses how CO₂ surface chemistry has developed since the early 1950s. Emphasis is given to studies of well-characterized surfaces of metals, oxides and some more complex systems involving in particular alkali modified surfaces and also of coadsorbed molecules.     

Sonochemical reduction of carbon dioxide

Sonolysis of carbon dioxide dissolved in water was performed from a standpoint of reducing this material in atmosphere. During one hour of sonication, the amount of CO2 decreased to about half at 5 degrees C under CO2-Ar atmosphere. The decreasing rate for CO2 followed the order Ar > He > H2 > N2 and it was down with increasing temperature in the range of 5-45 degrees C. The most favorable concentration for reducing CO2 was 0.03 (mole fraction of CO2 in gas phase). This concentration in gas phase means an equal mixture of CO2 and Ar in water, because CO2 is more soluble than Ar. Since carbon dioxide dissolved in water would be partly ionized, the roles of ions on the sonolysis were also examined. Gaseous reaction products were CO, H2 and a small amount of O2. Carbon monoxide and hydrogen might be obtained from CO2 and H2O by sonolysis, respectively. Both gases are fuel and react each other to C1 compounds such as methanol, and so on. Therefore, irradiation of ultrasonic waves should be an important technique for reducing CO2.     

Rydberg states of carbon dioxide and carbon disulfide

The electronic absorption spectra of carbon dioxide and carbon disulfide have been reexamined. Model potential calculations have been used to calculate the energies of excited states in Rydberg approximation, and (npσ) and (npπ) Rydberg series have been assigned. For both molecules, the lowest excited ¹Π_g and ¹Π_u states are identified as Rydberg states. The lowest ${}^1\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ state is mainly Rydberg for CO₂, but contains some valence character for CS₂, There is no evidence for transitions to additional valence states of these symmetries.It is shown that $\text{LCAO}\text{MO}$ predictions about excited states can be misleading because of near-linear dependencies which arise in multicenter expansions. A consideration of the united atom orbitals for CO₂ and CS₂ predicts that there should be only the number of low-energy excited states which are found from the spectral analysis.     

Gasification of porous carbon particle by carbon dioxide

The diffusive-kinetic model of porous carbon particles gasification is developed. The model considers the processes of heat and mass transfer both inside the porous particle and above it. Analysis of the model shows that heat and mass transfer have an influence to the gasification process to a marked degree. Gasification of carbon particle by carbon dioxide is impossible if particle temperature is lower about 850 K because concentration of carbon dioxide at the particle surface becomes lower than its equilibrium concentration. The rate of the carbon particle gasification is determined as a function of the porous particle internal surface area for different pressures and furnace temperatures.     

The quadrupole moments of carbon dioxide and carbon disulphide

The electric quadrupole moments of carbon dioxide and carbon disulphide have been measured through the birefringence induced in gaseous samples over a range of temperature. The value for CO₂, Θ = (-14·98 ± 0·50) × 10^-40 C m², is consistent with earlier measurements, showing that the temperature-independent hyperpolarizability contribution to the birefringence is insignificant. For CS₂, Θ = (+12·0 ± 0·6) × 10^-40 C m². The positive sign reflects the increased importance of the π electron contribution to Θ in CS₂.     

Muon diffusion in β-V2H

Hydrogen diffusion in the ordered hydride β-V₂H is mainly brought about by a minority fraction of interstitial atoms on antistructural sites. Recently, this mechanism was elucidated in a single crystal QNS study at temperatures close to the critical point (390 K≤T≤440 K) where already an appreciable amount of antistructural sites is occupied. Here we use the positive muon as a radioactive hydrogen tracer in order to show that the same diffusion mechanism is also valid at low temperatures (80 K≤T≤320 K) where the different jump processes are very slow and where the fraction of antistructural atoms is tiny but nevertheless dominates the long range diffusion.     

Mid-infrared polarization spectroscopy of carbon dioxide

The use of mid-infrared polarization spectroscopy (PS) for the detection of CO₂ has been demonstrated. The P(13) and P(14) resonances of the (0 0⁰ 0)→(1 0⁰ 1) transition of CO₂ were probed using a single-mode optical parametric generator system to produce a high-intensity laser beam at approximately 2.7 μm. The experiments were performed in an atmospheric pressure CO₂ jet and also in a sub-atmospheric pressure gas cell. The experimental results were compared with the results of the time-dependent density-matrix equations using direct numerical integration. The Zeeman-state structure of the upper and lower energy levels was included in the multi-state formulation of the density-matrix equations. Fifty-eight Zeeman states and two bath levels were included in the numerical analysis of the P(14) transition. The measured and calculated PS line shapes were in good agreement, and the absolute experimental signal level agreed with the theoretical calculation to within a factor of five. Received: 20 March 2002 / Revised version: 16 August 2002 / Published online: 11 December 2002 RID="*" ID="*"Present address: Innovative Scientific Solutions Inc., 2766 Indian Ripple Road, Dayton, OH 45 440, USA RID="**" ID="**"Corresponding author. Fax: +1-765/494-0539, E-mail: Lucht@purdue.edu RID="***" ID="***"Present address: School of Mechanical Engineering, Purdue University, W. Lafayette, IN 47807-2040 USA     

Mixed threefold and fourfold carbon coordination in compressed CO2

Carbon dioxide (CO2) has been recently reported to possess an amorphous form, named "carbonia," structurally similar to other group-IV oxide glasses. By combining ab initio constant pressure molecular dynamics, density-functional perturbation theory, and experimental IR spectra, we show that carbonia, and possibly also phase VI, is not SiO2-like, and that instead it is partially tetrahedral containing also a sizable amount of carbon in threefold coordination, but no sixfold octahedral coordination. Enthalpic considerations suggest that carbonia is a metastable intermediate state of the transformation of molecular CO2 into fully tetrahedral phases.     

Laser vaporization of carbon in the presence of carbon dioxide

2 . The dependence of the ion production on the laser ablation parameters is investigated and the expansion dynamics of the ablated species is studied through time and space resolved measurements of the ion yield. We discuss our observations on the basis of reactions involving neutral and ionized carbon-based species. Received: 11 March 1997/Accepted: 30 June 1997