Hydrogen-oxygen Flame Research Articles

Fabrication of Li 2O–B 2O 3–P 2O 5 solid electrolyte by aerosol flame deposition for thin film batteries

Amorphous Li 2O–B 2O 3–P 2O 5 thin films were prepared from an aqueous precursor solution of a LiNO 3 and BCl 3, POCl 3 by Aerosol Flame Deposition. The aqueous precursor solution of the LiNO 3 was first atomized with an ultrasonic vibrator (1.7 MHz), and B 2O 3 and P 2O 5 were synthesized from BCl 3 and POCl 3 by an oxygen–hydrogen flame. Their microstructure and electrical properties were investigated by SEM, XRD, Raman spectroscopy and impedance spectroscopy. XRD analysis revealed that a crystalline phase of LiCl was formed in the glass soot as well as amorphous boron and phosphorus oxides, and the crystalline LiCl found in deposited glass soot completely disappeared by heat treatment. The correlation between the structural modification of glass network, compositional variation and the conductivity was characterized by Raman spectroscopy. The glass electrolyte fabricated in this study exhibited a maximum conductivity of about 10 − 7 S/cm at 30 sccm flow rate of BCl 3 and POCl 3.

Promotion and inhibition of a hydrogen—oxygen flame by the addition of trimethyl phosphate

This paper gives results of numerical modeling of a laminar hydrogen—oxygen flame doped with trimethyl phosphate at various pressures and compositions of the combustible mixture. The calculations were performed using the PREMIX and CHEMKIN-II software packages. It was found that phosphorus-containing additives promoted the flame at subatmospheric pressures and inhibited it at atmospheric pressure. Kinetic analysis showed that catalytic recombination reactions were responsible for both phenomena. In the case of subatmospheric pressures, the promoting effect and its enhancement with increasing additive concentration were related to a flame temperature rise in the chemical-reaction zone due to catalysis of the recombination reactions by phosphorus-containing compounds. Increasing the additive concentration led to an increase in both the rate of the branching reaction H + O2 = OH + O and the rate of the chain termination reaction, but the increase in branching reaction rate prevails, resulting in an increase in the flame velocity. In the case of atmospheric-pressure flames, where the reaction-zone temperature is close to the adiabatic equilibrium value, the additive led to an increase in the rate of decay of active flame species and, hence, to a decrease in the flame propagation velocity with increasing additive concentration.

High-resolution line-shape spectroscopy during a laser pulse based on Dual-Broad-Band—CARS interferometry

A high-resolution spectroscopic method is developed for recording Raman spectra of molecular transitions in transient objects during a laser pulse with a resolution of ≈0.1 cm-1. The method is based on CARS spectroscopy using a Fabry—Perot interferometer for spectral analysis of the CARS signal and detecting a circular interferometric pattern on a two-dimensional multichannel photodetector. It is shown that the use of the Dual-Broad-Band—CARS configuration to obtain the CARS process provides the efficient averaging of the spectral—amplitude noise of the CARS signal generated by a laser pulse and, in combination with the angular integration of the two-dimensional interference pattern, considerably improves the quality of interferograms. The method was tested upon diagnostics of the transient oxygen—hydrogen flame where information on the shapes of spectral lines of the Q-branch of hydrogen molecules required for measuring temperature was simultaneously obtained and used.

Effect of silver addition on the formation and deposition of titania nanoparticles produced by liquid flame spray

In this study, liquid flame spray (LFS) was used to produce titania, silver and silver–titania deposits of nanoparticles. Titanium(IV)ethoxide (TEOT) and silver nitrate in ethanol solutions were used as precursors and sprayed into turbulent hydrogen–oxygen flame. Production rates of 1.5–40 mg/min of titania were used with silver additions of 1, 2, 4, and 8 wt% compared to titania. Nanoparticle deposits were collected by thermophoretic sampling at six different axial distances from the flame torch head: 3, 5, 10, 12, 15, and 20 cm, of which the all but the last one occurred inside the flame. The deposit samples were analysed by TEM and SAED analysis. The powder samples of the particles were also collected by electric precipitator to XPS and specific surface area analysis. Particle size and effective density after the flame in the aerosol were analysed with SMPS and ELPI. The results from the previous studies i.e. controlling the particle size by setting the production rates of the particles were seen to apply also for this binary system. Characterisation of the deposits showed that when the substrate is inserted into the flame, in the beginning of the flame the deposit is formed by gas phase deposition whereas further down the flame the particles are first formed in the gas phase and then deposited. The location of the transition from gas phase deposition to gas phase nucleation prior to deposition depends on chemical/physical properties (e.g. thermodynamics and gas phase interactions) of the precursor, precursor concentration in the flame and also flame temperature profile. Therefore, the deposit collection distance from the burner also affected the collected particle size and degree of agglomeration. The two component deposits were produced in two different ways: one-step method mixing both precursors in the same solute, and two-step method spraying each precursor separately. The particle morphology differs between these two cases. In one-step method the primary (dTEM) and agglomerate particle size (dSMPS) decreased with the amount of silver addition, verifying the fact that when present, the silver has a clear effect on the titania nanoparticle formation and growth.

Silica suspension and coating developments for Advanced LIGO

The proposed upgrade to the LIGO detectors to form the Advanced LIGO detector system is intended to incorporate a low thermal noise monolithic fused silica final stage test mass suspension based on developments of the GEO 600 suspension design. This will include fused silica suspension elements jointed to fused silica test mass substrates, to which dielectric mirror coatings are applied.The silica fibres used for GEO 600 were pulled using a Hydrogen-Oxygen flame system. This successful system has some limitations, however, that needed to be overcome for the more demanding suspensions required for Advanced LIGO. To this end a fibre pulling machine based on a CO2 laser as the heating element is being developed in Glasgow with funding from EGO and PPARC.At the moment a significant limitation for proposed detectors like Advanced LIGO is expected to come from the thermal noise of the mirror coatings. An investigation on mechanical losses of silica/tantala coatings was carried out by several labs involved with Advanced LIGO R&D. Doping the tantala coating layer with titania was found to reduce the coating mechanical dissipation. A review of the results is given here.

The chain character of the third self-ignition limit of hydrogen-oxygen mixtures and flame propagation at atmospheric pressure

It is shown that the characteristic time of the hydrogen-oxygen reaction without the participation of reaction chains is thousands of times longer than the characteristic time of heat removal from the reactor under third self-ignition limit conditions. As a result, reaction mixture self-heating does not exceed several degrees and, contrary to commonly accepted views, cannot cause thermal ignition. It is also shown that the reason for self-ignition under these conditions is the excess rate of chain branching compared with chain termination responsible for the formation of chain avalanches. For the same reason, layer-by-layer ignition during laminar flame propagation is also a chain process. Self-heating arises as a result of the development of chain combustion and strengthens chain avalanches. Explosion and detonation inhibition shows that chain avalanches play an important role in these processes.

Electrolysers for the formation of the hydrogen–oxygen flame used in the gas-flame treatment of materials (review)

Electrolysers for the formation of the hydrogen–oxygen flame used in the gas-flame treatment of materials (review)

Preliminary Investigation of the Supply of Chemical Species to an Aqueous Solution Using a Hydrogen−Oxygen Flame

A new method of supplying radical species to aqueous solutions using a hydrogen-oxygen flame is investigated. When a hydrogen-oxygen flame is directed on the surface of an aqueous solution, hydroxyl radicals (*OH) produced in the flame are extracted into the aqueous phase. The presence of *OH in the aqueous solution was confirmed by electron paramagnetic resonance with spin trapping using 5,5-dimethyl-1-pyrroline-N-oxide. The extraction of *OH into the aqueous solution was monitored using a quantitative analysis of hydrogen peroxide (H2O2). The effects of the hydrogen and oxygen gas flow rates, hydrogen/oxygen ratio, and atmosphere on H2O2 formation were studied. When the hydrogen-oxygen flame blew on a phosphate buffer solution (pH 6.7) under an Ar atmosphere, the concentration of H2O2 increased with the blowing time of the flame and the flow rate of hydrogen gas. Under air, nitrate and nitrite ions were formed in the aqueous phase in addition to H2O2, and the H2O2 concentration was lower than that under argon. The application of this new method to an aqueous solution of Cu(II)-ethylenediaminetetraacetic acid (EDTA) caused a remarkable decrease in the concentration of Cu(II)-EDTA and total organic carbon.

Hydrogen—Oxygen Flame as a Radical Source for Aqueous‐Phase Reaction: Carboxylation of Propylamine in Aqueous Formic Acid Solution

AbstractFor Abstract see ChemInform Abstract in Full Text.

Cu determination in crude oil distillation products by atomic absorption and inductively coupled plasma mass spectrometry after analyte transfer to aqueous solution

Cu was determined in a wide range of petroleum products from crude oil distillation using flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma mass spectrometry (ICP-MS). Different procedures of sample preparation were evaluated: (i) mineralization with sulfuric acid in an open system, (ii) mineralization in a closed microwave system, (iii) combustion in hydrogen–oxygen flame in the Wickbold's apparatus, (iv) matrix evaporation followed by acid dissolution, and (v) acidic extraction. All the above procedures led to the transfer of the analyte into an aqueous solution for the analytical measurement step. It was found that application of FAAS was limited to the analysis of the heaviest petroleum products of high Cu content. In ICP-MS, the use of internal reference method (with Rh or In as internal reference element) was required to eliminate the matrix effects in the analysis of extracts and the concentrated solutions of mineralized heavy petroleum products. The detection limits (in original samples) were equal to, respectively, 10, 86, 3.3, 0.9 and 0.4 ng g − 1 in procedures i–v with ETAAS detection and 10, 78, 1.1 and 0.5 ng g − 1 in procedures i–iii and v with ICP-MS detection. The procedures recommended here were validated by recovery experiments, certified reference materials analysis and comparison of results, obtained for a given sample, in different ways. The Cu content in the analyzed samples was: 50–110 ng g − 1 in crude oil, < 0.4–6 ng g − 1 in gasoline, < 0.5–2 ng g − 1 in atmospheric oil, < 6–100 ng g − 1 in heavy vacuum oil and 140–300 ng g − 1 in distillation residue.

Interactions of water vapor with oxides at elevated temperatures

Many volatile metal hydroxides form by reaction of the corresponding metal oxide with water vapor. These reactions are important in a number of high temperature corrosion processes. Experimental methods for studying the thermodynamics of metal hydroxides include: gas leak Knudsen cell mass spectrometry, free jet sampling mass spectrometry, transpiration and hydrogen–oxygen flame studies. The available experimental information is reviewed and the most stable metal hydroxide species are correlated with position in the periodic table. Current studies in our laboratory on the Si–O–H system are discussed.

Structural changes of various types of silica glass tube upon blowing with hydrogen–oxygen flame

Structural changes upon blowing with a hydrogen–oxygen flame were examined in three types of silica glass tube, containing <1, 200, and 1300ppm of OH (referred to as Samples I, II and III, respectively). The samples were studied by means of microscopic spectroscopy. Upon blowing, the OH concentration near the outside surfaces of Samples I and II increased, whereas that near the outside surface of Sample III decreased. On the basis of an analysis of the SiOH absorption band (by peak decomposition), changes in the distribution of free SiOH, H2O molecules, and hydrogen-bonded SiOH are discussed. The silica tube with a higher OH content has a lower fictive temperature as indicated by an IR absorption peak near 2260cm−1. After blowing, the fictive temperature of Samples II and III remained almost constant throughout the cross-section, while that of Sample I changed, ranging from 1400 to 1700K. The maximum fictive temperature was found at a depth of approximately 1000μm from the outside surface.

Measurement of Temperature and Concentration of OH Radicals in Combustion of Hydrogen and Ethanol by the Laser-Induced Fluorescence Technique

Diffusion combustion of ethanol and hydrogen and homogeneous combustion of hydrogen–oxygen mixtures are studied by the laser‐induced fluorescence technique in the linear regime and with signal saturation. Data on the flame temperature and OH concentration are obtained. The burning temperature of 3090 K for a stoichiometric O2–H2 mixture is in agreement with the known value. It is shown that the maximum concentrations of radicals in the hydrogen–air and stoichiometric hydrogen–oxygen flames are close to each other (4.4· 1016 cm-3).

Synchrotron photoionization measurements of combustion intermediates: the photoionization efficiency of HONO

The HONO radical has recently been observed by photoionization mass spectrometry in low-pressure hydrogen–oxygen flames doped with NO 2. The photoionization efficiency (PIE) spectrum has been measured between 10.83 and 11.63 eV. A Franck–Condon simulation using calculated geometries and force constants of the cation and neutral, and including the effects of Duschinsky rotation, is presented to describe the PIE as a function of photon energy. The simulated PIE is used as a fitting function to estimate the adiabatic ionization potential from the experimental data. The apparent ionization threshold of (10.97 ± 0.03) eV is in excellent agreement with calculated values and is consistent with published bracketing determinations of the proton affinity of NO 2.

VCSEL based detection of water vapor near 940 nm

A vertical-cavity surface-emitting laser (VCSEL) was used to study the absorption spectrum of water vapor in the 940 nm region. Measurements were performed in ambient air at room temperature and in a hydrogen–oxygen flame over the temperature range of 1500–1800 K. Several rotational absorption lines within the 2 ν 1+ ν 3 vibrational band were measured. The absorption spectra were well resolved, which demonstrates the feasibility of VCSEL-based spectroscopic measurements of water vapor at room and high-temperature in this spectral region. The results were in good agreement with the values obtained from the HITRAN-96 database.

Microscopic structure of nanometer-sized silica particles

We have studied the structure of nanometer-sized silica particles called fumed silica, which is a synthetic amorphous silicon dioxide produced by burning silicon tetrachloride in an oxygen-hydrogen flame, using infrared and Raman spectroscopies and a high-energy x-ray diffraction method. It has been demonstrated that the structure of fumed silica is not identical to that of the normal bulk silica glass in terms especially of the distribution of the size of silica rings. Three- and four-membered rings are more frequent in fumed silica than in the bulk silica glass. It has also been shown that the network structure of fumed silica is more flexible than that of the bulk one, probably explaining the reason why fumed silica can accommodate a large number of three- and four-membered rings in the structure.

Structural change of OH-free fused quartz tube by blowing with hydrogen–oxygen flame

The effect of blowing with a hydrogen–oxygen flame on the structure of an OH-free fused quartz tube was studied by microscopic spectroscopy. The number of OH groups increased within 1000 μm from the outside surface (OSS). The peak decomposition of the IR absorption at around 3600 cm −1 showed that most OH structures were ‘free SiOH’ without the hydrogen bond, and H 2O molecules were also distributed throughout the cross section. The distribution of the fictive temperature, T F, in the cross section was measured from the peak position of infrared absorption at ≈2200 cm −1. T F before blowing was ≈1420 K, which is near the strain point, except in the region within 200 μm from the OSS, where T F steeply decreases approaching the OSS. After blowing, the values of T F became greater than those before blowing, increasing steeply from the OSS and having a maximum at ≈1000 μm. The steep change near the OSS must be caused by the shorter structural relaxation time due to the SiOH introduced by blowing and H 2O vapor in the flame. The distribution of the intensities of Raman bands at 495 (D 1) and 606 cm −1 (D 2) derived from the planar four- and three-member rings was also measured.

Experimental and numerical analyses of magnetic effect on OH radical distribution in a hydrogen-oxygen diffusion flame

The effect of magnetic field on OH radical distribution in a hydrogen-oxygen diffusion flame was experimentally and numerically investigated to explore the possibility of combustion control by magnetic force. In experiments, a coaxial type of burner was set between the magnet pieces. Two-dimensional (2D) cross-section distributions of OH* chemiluminescence intensity and OH fluorescence intensity were obtained with spectroscopic techniques using a CCD camera and a Planar Laser-Induced Fluorescence (PLIF) system, respectively. It was clearly seen that the high-density regions of OH* and OH radicals axisymmetrically migrated toward the central axis of the flame due to the influence of the magnetic field. In numerical simulations, such a phenomenon was qualitatively reproduced by solving the equations of reactive gas dynamics and magnetism. As a result, it was found that the magnetic force does not directly and selectively induce the diffusion velocity (the relative velocity) of OH itself. Alternatively, the magnetic force acting on O 2, whose mass density and magnetic susceptibility are much larger than those of other chemical species, causes the change in the mean velocity (the mass-average velocity) of mixture gas to transport the OH radical distribution indirectly and passively.

Influence of Four Kinds of Gradient Magnetic Fields on Hydrogen-Oxygen Flame

To explore the possibility of flame control by magnetic force, the influence of four kinds of gradient magnetic fields on OH density distribution in a hydrogen-oxygen jet diffusion flame was investigated by numerically solving the equations of reactive gasdynamics and magnetism. Vertically decreasing (case 1), vertically increasing (case 2), horizontally decreasing (case 3), and horizontally increasing (case 4) gradients of magnetic field were considered as model configurations. According to the numerical analysis, because the mass density and the magnetic susceptibility of O 2 gas are much higher than those of other chemical species, the surrounding air containing a lot of O 2 gas is strongly influenced by the magnetic force, and the magnetically induced airflow changes the OH distribution in the flame indirectly. The direction and magnitude of the OH density change significantly depends on the configurations of the gradient magnetic field. Specifically, in cases 1, 3, and 4, the OH distribution migrated to the inside of the flame, but in case 2, it moved toward the outside. However, when the horizontally decreasing gradient of the magnetic field was set up near the burner outlet, as in case 3, the OH density change becomes largest among those in the four cases.

Numerical analysis of a hydrogen-oxygen diffusion flame in vertical or horizontal gradient of magnetic field

The magnetic force is essentially in proportion to the mass density and the magnetic susceptibility of paramagnetic chemical species and the gradient of magnetic field. In this study, the effect of magnetic field on OH radical distribution in a hydrogen-oxygen diffusion flame was investigated by numerically solving the equations of reactive gasdynamics and magnetism to explore a possibility of combustion control by magnetic force. Particularly, we attempted the analysis for three kinds of cases with different spatial distributions of the magnetic field: Case 1 is without the magnetic field, Case 2 is under the vertical gradient of magnetic field, and Case 3 is under the horizontal gradient of magnetic field. According to the analysis, because the mass density and the magnetic susceptibility of O 2 are much larger than those of other chemical species in the peripheral region of the flame, O 2 was strongly influenced by the magnetic force in that region. Consequently, this force induced the flow of gas including a large amount of O 2 and indirectly changed the OH distribution in the flame. The horizontal magnetic gradient (Case 3) was about 1.2 times more effective in the OH density change than the vertical gradient (Case 2).