Pressure broadening coefficients of the water vapor lines at 556.936 and 752.033 GHz

The air induced broadening coefficients of the pure rotational transitions of H₂O at 556.936 GHz (1₁₀←1₀₁), and 752.033 GHz (2₁₁←2₀₂) were measured by terahertz time-domain spectroscopy. The air broadening coefficient was determined to be for the 556.936 GHz line and for the 752.033 GHz line, respectively. The present broadening coefficients for the 556.936 GHz water line are significantly smaller than those of Markov and Krupnov [Measurements of the pressure shift of the 1(10)-1(01) water line at 556.936 GHz produced by mixtures of gases. J Mol Spect 1995:172;211-4] but relatively close to the values of the HITRAN database. The measured data may improve the accuracy of the abundance of water vapor retrieved from spectra obtained by the Odin/SMR satellite instrument. The effect on the satellite retrieval processing is discussed.     

Spectroscopic study of a TEA CO2 laser of the CO2/X,X=H2; N2/H2 type

The spectral output of a TEA CO₂ laser utilizing nonconventional CO₂/H₂ and CO₂/N₂/H₂ gas mixtures was analysed. A simultaneous multiline output in P-branch of the 00°110°0 transition was recorded. A domination of the P(18) line is typical for the first, and that of the P(20) line for the second gas mixture. The enhancement of the P(18) line intensity in spectra (different from P(20) line domination-CO₂/N₂/H₂ mixture) is explained primarily by a smaller contribution of the R(23) line gain (01¹111¹0 CO₂ band), to P(20) line (00°110°0 band). All measurements were conducted with a nondispersive optical cavity.     

Differential polarization of photoneutrons from deuterium

The differential polarization of photoneutrons from deuterium has been measured at lab reaction angles of 45° and 90° for incident unpolarized photons in the energy range 7 to 30 MeV. The polarization is measured by observing the left-right asymmetry in the elastic scattering of neutrons from a liquid-helium polarimeter which is used in conjunction with a nanosecond time-of-flight spectrometer. At the lowest energies, the ¹²C(n, n)¹²C reaction is used as an analyser. The left-right asymmetry is determined by using the spin-precession method, recently developed for use with a continuous energy spectrum of neutrons. Two independent difference experiments are carried out using C²H₂-CH₂ and H₂O-H₂O targets in order to detect possible target-dependent systematic errors. Departures from the predictions of current theories of the photo-disintegration of the deuteron are observed at both reaction angles.     

Vortex glass phase and flux creep in YBa2Cu3O y epitaxial film

Nonlinear I–V characteristics of YBa₂Cu₃O _y epitaxial film at different temperatures in a magnetic field of up to 5T and angles between the direction of the field and the a–b plane of 0°, 30°, 45°, 60°, and 90° were measured. We find that there are the vortex glass phase and vortex liquid phase in the mixed state. The flux creep exists in the vortex glass phase, and it obviously appears in the area around the boundary between the vortex glass phase and the vortex liquid phase.     

Magnetic properties of xNi0.53Cu0.12Zn0.35Fe1.88O4+(1−x)BaTiO3 nanocomposites

The nanocrystalline Ni_0.53Cu_0.12Zn_0.35Fe_1.88O₄ and BaTiO₃ powders were prepared using Microwave-Hydrothermal (M-H) method at 160 °C/45 min. The as synthesized powders were characterized using the X-ray diffraction (XRD) and Transmission Electron Microscope (TEM). The size of the powders that were synthesized using M-H system was found to be ∼30 and ∼50 nm for ferrite phase and ferroelectric phases, respectively. The powders were densified using microwave sintering method at 900 °C/30 min. The ferrite and ferroelectric phases were observed from XRD and morphology of the composites was observed with the Scanning Electron Microscope (SEM).The magnetic hysteresis loops were recorded using the Vibrating Sample Magnetometer (VSM).The frequency dependence of real (μ′) and imaginary (μ″) parts of permeability was measured in the range of 1 MHz-1.8 GHz. The permeability decreases with an increase of BaTiO₃ content at 1 MHz. The transition temperature (T_C) of ferrite was found to be 245 °C. The T_C of composite materials decreases with an increase in BaTiO₃ content.     

The rotationally-resolved absorption spectrum of formaldehyde from 6547 to 6804 cm

The room temperature absorption spectrum of formaldehyde, H₂CO, from 6547 to 6804 cm⁻¹ (1527-1470 nm) is reported with a spectral resolution of 0.001 cm⁻¹. The spectrum was measured using cavity-enhanced absorption spectroscopy (CEAS) and absorption cross-sections were calculated after calibrating the system using known absorption lines of H₂O and CO₂. Several vibrational combination bands occur in this region and give rise to a congested spectrum with over 8000 lines observed. Pressure broadening coefficients in N₂, O₂, and H₂CO are reported for an absorption line at 6780.871 cm⁻¹, and in N₂ for an absorption line at 6684.053 cm⁻¹.     

Mixed water/OH structures on Pd(1 1 1)

Chemisorbed O and water react on Pd(1 1 1) at low temperatures to form a mixed OH/H₂O layer with a (√3 × √3)R30° registry. Reaction requires at least two water molecules to each O before the (2 × 2)O islands are consumed, the most stable OH/water structure being a (OH + H₂O) layer containing 0.67 ML of oxygen, formed by the reaction 3H₂O + O → 2(H₂O + OH). This structure is stabilised compared to pure water structures, decomposing at 190 K as OH recombines and water desorbs. The (√3 × √3)R30° − (OH + H₂O) phase cannot be formed by O/H reaction and is distinct from the (√3 × √3)R30° structure formed by O/H coadsorption below 200 K. Mixed OH/water structures do not react with coadsorbed H below 190 K on Pd(1 1 1), preventing this phase catalyzing the low temperature H₂/O₂ reaction which only occurs at higher temperatures.     

Compact tunable mid-infrared laser source by difference frequency generation of two diode-lasers

Two continuous-wave single mode diode-lasers (Hitachi HL 7851G and Toshiba TOLD 9150) are applied as signal and pump sources for difference frequency generation (DFG) in an AgGaS2 crystal with a length of 30 mm. For 90° type I phase matching tunable mid-infrared laser radiation around 5 µm is obtained with an output power of up toP _DFG = 0.2 µW while the diode lasers are operated with powers of 30 and 50 mW at the center wavelengths 682 and 791 nm, respectively. The performance of the diode-laser-DFG system is shown as the absorption spectrum of CO for the P(28) rotational line around 2023 cm^–1 is probed in a 10cm long cell and in the exhaust of an engine.This research was supported by the Technologiestiftung Schleswig-Holstein under contract 94-35i.     

Interfacial reaction and electrical characteristics of Cu(RuTaNx) on GaAs: Annealing effects

This study elucidates the thermal stability and quasi ohmic contact characteristics of Cu(RuTaN_x) fabricated on a barrierless GaAs substrate. Cu(RuTaN_x) was prepared by cosputtering Cu, Ta, Ru, and N. The resistivity of the Cu(RuTaN_x)/GaAs structure annealed at 500 °C for 30 min was lower than that of the as-deposited structure, and the former was thermally stable up to 500 °C after 30 min of annealing. Further, the Cu(RuTaN_x)/GaAs structure exhibited electrical rectifying properties upon annealing at 550 °C for 10 min and revealed a quasi ohmic contact, as determined by the circular transmission line model (CTLM). The formation of quasi ohmic contact is further confirmed by transmission electron microscopy and energy dispersive X-ray spectroscopy.     

Crystal structure and Mössbauer spectroscopic study of FeSnF6·6H2O

Large single crystals of FeSnF₆·6H₂O were grown when aqueous hydrofluoric solutions of SnF₂ and FeF₂ were allowed to evaporate in air. Tin-119 Mössbauer spectroscopy at ambient temperature shows a single line at slightly negative isomer shift relative to CaSnO₃ at room temperature (=–0.380(6) mm/s, =0). This is characteristic of tetravalent tin octahedrally coordinated by fluorine. The X-ray crystal structure shows that tin(IV) is coordinated by 6 fluorine atoms, and Fe(II) by 6 water molecules. Both sites show a slight distortion from octahedral symmetry: the six distances are equal (Sn-Fe=1.941(3) Å and Fe-O=2.112(3) Å), whereas there are two values of angles (Fe-Sn-F=90.4(1)° and 89.6(1)°; O-Fe-O=91.1(1)° and 88.9(1)°). The material is an ionic compound [SnF₆]^2–[Fe(H₂O)₆]²⁺.     

Nitric oxide reduction by CO ON Rh(111): Temperature programmed reaction

The reaction of NO with CO on Rh(111) has been studied with temperature programmed reaction (TPR). Comparisons are made with the reaction of O₂ with CO and the reaction of NO with H₂. The rate-determining step for both CO oxidation reactions is CO(a) + O(a) → CO₂(g). Repulsive interactions between adsorbed CO and adsorbed nitrogen atoms lead to desorption of CO in a peak at 415 K which is in the temperature range where the reaction between CO(a) and O(a) produces CO₂(g). Thus the extent of reaction of CO(a) with NO(a) is less than that between CO(a) and O(a) due to the lower coverage of CO caused by adsorbed N atoms and NO. A similar repulsive interaction between NO(a) and H(a) suppresses the NO + H₂ reaction. CO + NO reaction behavior on Rh(111) is compared to that observed on Pt(111).     

Crystal structure and ferromagnetism of (n-C3H7)4N[CoFe(dto)3] (dto=C2O2S2)

Recently, we have discovered a new type of first order phase transition around 120 K for (n-C₃H₇)₄N[Fe^IIFe^III(dto)₃] (dto=C₂O₂S₂), where the charge transfer transition between Fe^II and Fe^III occurs reversibly. In order to elucidate the origin of this peculiar first order phase transition. Detailed information about the crystal structure is indispensable. We have synthesized the single crystal of (n-C₃H₇)₄N[Co^IIFe^III(dto)₃] whose crystal structure is isomorphous to that of (n-C₃H₇)₄N[Fe^IIFe^III(dto)₃], and determined its detailed crystal structure. Crystal data: space group P6₃, a=b=10.044(2) Å, c=15.960(6) Å, α=β=90°, γ=120°, Z=2 (C₁₈H₂₈NS₆O₆FeCo). In this complex, we found a ferromagnetic transition at T_c=3.5 K. Moreover, on the basis of the crystal data of (n-C₃H₇)₄N[Co^IIFe^III(dto)₃], we determined the crystal structure of (n-C₃H₇)₄N[Fe^IIFe^III(dto)₃] by simulation of powder X-ray diffraction results.     

Preparation of superhydrophobic films on titanium as effective corrosion barriers

Stable superhydrophobic films were prepared on the electrochemical oxidized titania/titanium substrate by a simple immersion technique into a methanol solution of hydrolyzed 1H,1H,2H,2H-perfluorooctyltriethoxysilane [CF₃(CF₂)₅(CH₂)₂Si(OCH₂CH₃)₃, PTES] for 1 h at room temperature followed by a short annealing at 140 °C in air for 1 h. The surface morphologies and chemical composition of the film were characterized by means of water contact angle (CA), field emission scanning electron microscopy (FESEM), atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). The water contact angle on the surface of this film was measured to be as high as 160°. SEM images showed that the resulting surfaces exhibited special hierarchical structure. The special hierarchical structure along with the low surface energy leads to the high surface superhydrophobicity. The corrosion resistance ability and durance property of the superhydrophobic film in 3.5 wt.% NaCl solution was evaluated by the electrochemical impedance spectroscopy (EIS). The anticorrosion properties of the superhydrophobic film are compared to those of unmodified pure titanium and titania/titanium substrates. The results showed that the superhydrophobic film provides an effective corrosion resistant coating for the titanium metal even with immersion periods up to 90 d in the 3.5 wt.% NaCl solution, pointing to promising future applications.     

The gas response enhancement from ZnO film for H2 gas detection

ZnO thin films were prepared by thermal oxidation of Zn metal at 400 °C for 30 and 60 min. The XRD results showed that the Zn metal was completely converted to ZnO with a polycrystalline structure. The sensors had a maximum response to H₂ at 400 °C and showed stable behavior for detecting H₂ gases in the range of 40 to 160 ppm. The film oxidized for 60 min in oxygen flow exhibited higher response than that of the 30 min oxidation which was approximately 4000 for 160 ppm H₂ gas concentration. The sensing mechanism was modeled according to the oxygen-vacancy model.     

Valence band and band gap photoemission study of (1 1 1) In2O3 epitaxial films under interactions with oxygen, water and carbon monoxide

Synchrotron radiation ultraviolet photoemission experiments at photon energies of 150 and 49 eV were performed on an epitaxial layer of (1 1 1) In₂O₃ with good crystallinity as established by a standard scanning probe and diffraction methods. Valence band (VB) and band gap photoemission spectra were monitored under separate oxygen, water and carbon monoxide exposures (100 L) at different activation temperatures within the range utilized for chemiresistive gas sensors (160-450 °C). Large changes in photoemission response within the whole VB were observed for all gases. Regular shifts of the valence band edge relative to the Fermi energy were found under gas exposures on two kinds of surface (partially reduced or partially oxidized), and are interpreted as changes of surface potential. Treatments in oxygen resulted in upward band bending (∼0.5 eV at T = 320 °C). Regardless of activation temperature, treatments in water resulted in downward band bending, but with small changes (<0.1 eV). Reduction properties of carbon monoxide were observed only at high temperatures of T ? 370 °C. At temperatures of 160 and 250 °C unusual “oxidizing” behavior of CO was observed with upward band bending of ∼0.7 eV (160 °C). Oxidizing and reducing effects of the gas interactions with the (1 1 1) In₂O₃ surface in all cases were accompanied by a corresponding behavior, i.e., a decrease or increase in photoemission response from so-called defect states in the band gap near the top of the valence band. The increases of photoemission within a band gap with maxima at binding energies (BE) of 0.4 (O₂-induced peak) and 1.0 eV (CO-induced peak) were, respectively, found for interactions with O₂ and CO for low temperatures (T = 160 and 250 °C). These responses were ascribed to acceptor-like electronic levels of O₂ and CO chemisorption states, respectively. A definite split of the top VB peak (BE ∼ 4.0 eV) was found under CO dosing at 160 °C. Established knowledge of the CO interaction with the (1 1 1) In₂O₃ surface explains earlier revealed acceptor-like behavior of In₂O₃ film conductivity during CO detection at operational temperatures lower than 250 °C through the formation of acceptor-like electronic levels of adsorbed CO molecules.     

H uptake kinetics of FeTi films coated with Ni

The H₂ storage material FeTi can be fully charged through a Ni coating in the course of hours. A mild activation, either by long H₂ exposure at RT, or annealing in 35 mbar H₂ at 150 °C, leads to a full uptake in minutes. The enhancement of the uptake rate after activation is caused by a reduction of the Ni-oxide surface. Ni does not limit the hydrogen uptake rate once the surface is clean. However, the Ni surface is sensitive to contamination, as for instance by CO adsorbed from air.     

Adsorption of CO and C2H4 on Rh-loaded thin-film dysprosium oxide

A dysprosium oxide thin film was deposited on Ru(0 0 0 1) by vapor depositing Dy in 2 × 10⁻⁷ torr O₂ while the Ru was at 700 K. The film was ca. 5 nm thick and produced a p(1.4 × 1.4) LEED pattern relative to the Ru(0 0 0 1) substrate. The adsorption and reaction of CO and C₂H₄ adsorbed on Rh supported on the Dy₂O₃ film were studied by TPD and SXPS. The CO initially reacted with loosely bound oxygen in the substrate to produce CO₂. After the loosely bound oxygen was removed, the CO adsorbed non-dissociatively in a manner similar to what is seen on Rh(1 1 1). C₂H₄ adsorbed on the Rh particles and underwent progressive dehydrogenation to produce H₂ during TPD. The C from the C₂H₄ reacted with the O in Dy₂O₃ to produce CO. CO dissociation on the Rh particles could be promoted by treating the Dy₂O₃ with C₂H₄ before CO exposure.     

Evaluation of mechanical properties of tubular LSFCO perovskite membranes at elevated temperatures in reactive environments

This paper reports the mechanical properties of tubular membranes of mixed conducting La_0.2Sr_0.8Fe_0.8Cr_0.2O_3-δ (LSFCO) perovskites at elevated temperatures. Strength, measured in a C-ring test over a temperature range of 22°-1000 °C in three different environments - air, 100% N₂, and 90% CO₂/10% CO mixtures - showed a decreasing behavior with increasing temperature and severity of reducing conditions. A maximum strength value of 340 MPa and a minimum of 105 MPa were observed at room temperature and at 1000 °C, respectively, in CO₂/CO environment. Fractography was used to characterize the flaws and changes in fracture mode. Results indicate that the observed changes in strength and fracture morphology are associated with non-equilibrium segregation of elements when exposed to the reducing environment.     

The influence of temperature (20-1000 °C) on binary mixtures of solid solutions of CH3COOLi·2H2O-MgHPO4·3H2O

Thermally induced phase transitions (20-1000 °C) in the substrates and binary mixtures of CH₃COOLi·2H₂O(1)-MgHPO₄·3H₂O(11) have been analysed. Changes taking place on dehydration and thermal dissociation of binary mixtures prepared with percent molar ratios of 90-10% were studied by differential thermal analysis (TG, DTG, DTA), IR-spectroscopy and WAXS.The above-mentioned substrates changed their structure when heated for 1 h at 500 or 1000 °C. CH₃COOLi·2H₂O(1) (ID: 23-1171) changed the structure at 500 °C to that of Li₂CO₃ (ID: 22-1141), while at 1000 °C the structure was impossible to analyse as the compound reacted both with porcelain and with platinum (crucible materials). MgHPO₄·3H₂O(11) (Newberyite, ID: 35-780, 19-762) changed its structure at 500 °C to amorphous phase and at 1000 °C to Mg₂P₂O₇ (ID: 32-626).The following compounds were assayed in the respective binary mixtures heated at 500 °C for 1 h: 70% (1)-30%(11): LiMgPO₄ (ID: 18-735), MgO (ID: 4-829); 50%(1)-50%(11): LiMgPO₄ (ID: 18-735), Li₃PO₄ (ID: 25-1030); 30%(1)-70%(11): LiMgPO₄ (ID: 32-574); binary mixtures heated at 1000 °C contained the following compounds: 70%(1)-30%(11): LiMgPO₄ (ID: 32-574,18-735), Li₃PO₄ (ID: 15-760,25-1030), MgO (ID: 4-829); 50%(1)-50%(11): LiMgPO₄ (ID: 32-574, 18-735), MgO (ID: 4-829); 30%(1)-70%(11): LiMgPO₄ (ID: 18-735, 32-574), Mg₂P₂O₇ (ID: 22-1152, 8-38), Li₄SiO₄ (37-1472).     

Effect of H2 and O2 plasma etching treatment on the surface of diamond-like carbon thin film

In this study, we investigated the surface properties of diamond-like carbon (DLC) films for biomedical applications through plasma etching treatment using oxygen (O₂) and hydrogen (H₂) gas. The synthesis and post-plasma etching treatment of DLC films were carried out by 13.56 MHz RF plasma enhanced chemical vapor deposition (PECVD) system. In order to characterize the surface of DLC films, they were etched to a thickness of approximately 100 nm and were compared with an as-deposited DLC film. We obtained the optimum condition through power variation, at which the etching rate by H₂ and O₂ was 30 and 80 nm/min, respectively. The structural and chemical properties of these thin films after the plasma etching treatment were evaluated by Raman and Fourier transform infrared (FT-IR) spectroscopy. In the case of as-deposited and H₂ plasma etching-treated DLC film, the contact angle was 86.4° and 83.7°, respectively, whereas it was reduced to 35.5° in the etching-treated DLC film in O₂ plasma. The surface roughness of plasma etching-treated DLC with H₂ or O₂ was maintained smooth at 0.1 nm. These results indicated that the surface of the etching-treated DLC film in O₂ plasma was hydrophilic as well as smooth.