Simultaneous Vaporization Research Articles

Vaporization of Zinc from Steel Scrap.

The rate of zinc vaporization from galvanized scrap was measured using a thermogravimetric apparatus along with chemical analysis. It is found that the rate of zinc vaporization is very fast in nitrogen and carbon monoxide atmospheres at temperatures higher then 950°C. At lower temperature rate decreases with decreasing temperature and is controlled by the gas phase mass transport. The simultaneous oxidation and vaporization of zinc occurs when the samples were heated in carbon dioxide and air. The current experimental results indicate that almost all of the zinc from scrap vaporizes during the heating process in a very short period of time after the temperature reaches above 850°C.

Surface tension influences on methanol droplet vaproiation in the presence of water

A computational model has been developed to study the influences of both temperature-and mass-fraction-driven surface tension forces on the transient vaporization of a methanol droplet in a hot environment containing water vapor. The model is based on the Navier-Stokes equations and includes variable transport and thermodynamic properties as well as simultaneous condensitation and vaporization. Numerical simulations have been carried out for practical flow conditions and intermediate Reynolds numbers. The results obtained show that surface tension forces dominate over surface shear forces and that the mass fraction-driven surface forces of water vapor are important during a significant portion of the droplet lifetime. The primary physical reasons for the dominance of the water-driven capillary forces are the low values of liquid mass diffisivity and the large variation of surface tension in water/alcohol mixtures. It is the conclusion of the paper that surface tenstion forces caused by surface mass fraction gradients of water should be included in alcohol droplet flows.

Optimization of a novel ETV system for solid sample introduction into an ICP and its application to the determination of trace impurities in SiC

The application of a novel electrothermal vaporization unit (ETV) for sample introduction into an inductively coupled plasma (ICP) is described. The system can be used for vaporizing both liquid and solid samples into an ICP or other excitation device. Exchangeable graphite cups can be used for rapid analysis of solid samples without any sample pretreatment. Free programmable, PC controlled heating cycles make it possible to use individual temperature programs to vaporize either organic or inorganic materials. By use of a computer operating parameters of the system, like ETV-temperature program, ETV-carrier gas flow rates, rf-power and observation height have been optimized with regard to the requirements of solid sampling. The system was first developed for steel analysis but was also used for investigation of environmental samples. An additional application of the system is the determination of impurities in ceramic materials like silicon carbide. Investigation indicated that PdCl 2 is a useful modifier for destruction of silicon carbide and simultaneous vaporization of the refractory impurities like aluminium, iron, vanadium and titanium. SiC samples from different manufacturers have been analysed. Concentration values of the elements investigated range from 8–950 μg g −1. On the assumption that the sample amount is about 5 mg, detection limits of the elements range from 0.3–4.4 μg g −1. Relative standard deviations of 2–14% have been found.

A Study On The Thermal Decomposition of Ba(tmhd)2 and Sr(tmhd)2

ABSTRACTDecomposition of Sr(tmhd)2 and Ba(tmhd)2 was investigated by thermogravimetric analysis, in-situ FTIR, and mass spectrometry. Both compounds decomposed following 3 steps: 1) decomposition of the ligands, 2) simultaneous vaporization and partial decomposition of metal-organics, and 3) decomposition of the vaporized metal-organics which existed as the oligomeric species.The Sr source decomposed at lower temperatures and in a narrower temperature range than the Ba source. Also, the gaseous oligomeric species from the Sr source decomposed relatively quickly while the corresponding species from the Ba source decomposed slowly over a long period. Such a difference between the two compounds is due to different bond energies between the metal atom and the ligands, as indicated by our FTIR results.

Direct determination of zinc in sea-water using electrothermal atomic absorption spectrometry with Zeeman-effect background correction: effects of chemical and spectral interferences

The determination of zinc in sea-water using an electrothermal atomic absorption spectrometry system with Zeeman-effect background correction is presented. The influence of various chloride and nitrate salts on the atomization signal of zinc was examined. In chloride medium particularly, the interference effect induced through losses of zinc chloride, by the thermohydrolysis of magnesium chloride and simultaneous generation of HCl during the pyrolysis step is noted. In nitrate medium, zinc is more stabilized by Mg > Ca > Na > NH+4. The effect of various inorganic and organic acids, used as chemical modifiers, on the atomization of zinc and background absorption signals in sea-water were examined. In unmodified sea-water, a Zeeman interference effect related to the vaporization of the chloride matrix leading to a systematic under-compensation and consequently to erroneous zinc concentration values was observed. In sea-water, modified with 1 mol l–1 nitric acid, a spectral Zeeman interference effect induced by the Zeeman splitting of the absorption bands of NO molecules generated during the decomposition–reduction of nitrate was observed; the induced over-compensation is eliminated by selective pyrolysis at about 850 °C. The chemical interference effect (25%) is related to the simultaneous vaporization of zinc and sodium oxides; the detection limit (3σ) being about 80 ng l–1 for a 10 µl injected volume of sea-water. In sea-water modified with 0.7 mol l–1 oxalic acid, there is no significant interference effect and the detection limit in this medium is about 60 ng l–1 for a 10 µl injected volume of sea-water.

Laser induced growth of Cd 1−xMn xTe and CdTeCd 1−xMn xTe superlattices

We report on the basic properties of Cd 1−xMn xTe and CdTeCd 1−xMn xTe multilayer structures and superlattices grown by pulsed laser evaporation and epitaxy (PLEE). Two computer controlled XeCl and Nd:YAG lasers are used for simultaneous or sequential vaporization of high-purity polycrystalline targets. The layers are grown on (001) oriented InSb and CdZnTe wafers held at a temperature in the range of 200 – 240 °C. In-situ reflection high energy electron diffraction, scanning electron microscopy, energy dispersive x-ray analysis, secondary ion mass spectroscopy, transmission electron microscopy and double crystal x-ray diffraction results have demonstrated that high quality PLEE layers and superlattices can be routinely grown.

Corrosion inhibition by ion beam induced vacuum carburization of tool steel

Drastic improvements of corrosion properties of a highly corrosive carbon steel material has been observed after N + ion bombardment and simultaneous vacuum vaporization of silicon oil. The combined effect of ion irradiation and controlled deposition results in a compact carbon-silicon layer, which due to the dynamic ion beam mixing process, is firmly attached to the substrate surface. Aqueous corrosion studies were done in both acetic acid and NaCl solutions. Improved corrosion properties were found by measuring the incubation time, i.e. the time of exposure in the liquid necessary to induce the first signs of corrosion attack. The improved corrosion characteristics are explained by the creation of the nonporous and highly adhesive carbon-silicon film acting as a protecting layer against chemical attack.

Silver-Indium-Cadmium Control Rod Behavior in Severe Reactor Accidents

Silver-indium-cadmium (Ag-In-Cd) control rod behavior in severe reactor accidents is examined with a goal of improving the methodology used to estimate reactor accident source terms. Control rod behavior in both in-pile and out-of-pile experiments is reviewed. A mechanistic model named VAPOR is developed that calculates the downward relocation and simultaneous vaporization behavior of the Ag-In-Cd alloy expected after control rod failure in a severe reactor accident. VAPOR is used to predict the release of silver, indium, and cadmium vapors expected in the Power Burst Facility (PBF) severe fuel damage (SFD) 1-4 experiment. In addition, a sensitivity study is performed to examine the effects of system pressure and flow rate on control rod vapor release. Although cadmium is found to be the most volatile constituent of the alloy, all of the calculations predict that the rapid relocation of the alloy down to cooler portions of the core results in a limited release for all three control rod alloy vapors. Results of the control rod and aerosol behavior in PBF test SFD 1-4 are presented. VAPOR calculations are found to compare much better with the control rod material release in test SFD 1-4 than empirical models that do not consider relocation of the alloy away from the hotter portions of the core. The timing and magnitude of control rod material release and the potential for control rod aerosol/fission product interactions during the early phase of a severe accident are dependent on the system pressure. A better understanding of control rod material behavior during the later in-vessel phase of the accident is needed to define more accurately both the magnitude of the aerosol source and the initial composition of molten material exiting the vessel in the event of lower vessel head failure.

Thermal Oxidation of Indium Phosphide

Despite industrial interest in producing a dielectric layer on indium phosphide, its thermal oxidation is not fully understood. This paper describes some results obtained from observing the oxidation reaction inisde a transmission electron microscope. At temperatures between 450° and 600°C, and are produced. Polycrystalline appears to be produced during simultaneous incongruent vaporization, which takes place above 362°C. At the early stages of the reaction, grows epitaxially on the , but later it transforms into polycrystalline .

Far-field coalescence effects in polydisperse spray jet diffusion flames

When dense sprays are formed by a twin-fluid atomizer, inertial coalescence takes place in the jet far-field as the flow decelerates. A novel theoretical examination of the effects of this phenomenon on polydisperse spray diffusion flames is presented. Tambour's sectional equations are used to represent the spray which undergoes simultaneous vaporization and coalescence. The droplet size spectra are divided into ten sections between 0 to 160 μm in diameter, where the mass of a 20 μm droplet is taken as a single monomer. Inter- and intra-sectional coalescence effects are accounted for as well as droplet transfer to the gaseous phase and transfer of droplets from higher sections to lower sections through vaporization. Then, Spalding's “Genmix” computer code is employed to solve the fluid flow and species governing equations, which are coupled to the sectional spray governing equations. A parametric study reveals the possibility of altering the flame height, temperature and quantity of fuel droplets that escape combustion as a result of the way in which coalescence may hinder vaporization.

The Vaporization of the Various Trace Components from Aluminoborosilicate Glass

Abstract The simultaneous vaporization of dopants in aluminoborosilicate glass was investigated by means of mass spectrometry using a Knudsen cell. The detected chemical species were Na, K, Ni, Zn, Rb, Ag, Te, TeO2, and Cs in the temperature range of 650–800°C. Their vapor pressures were 10−6–10−4 Pa. The activation energy of vaporization was discussed in relation to the electrostatic force between the vaporizing specie and oxygen. However, lithium, alkali-earth metal elements, alomst all the transition metal elements (such as Fe, Cr, and Ru), and rare-earth metal elements were not detected in the vapor phase, though they were contained in the glass matrix.

Laser irradiation of human atherosclerotic obstructive disease: Simultaneous visualization and vaporization achieved by a dual fiberoptic catheter

Received for publication Apr. 2, 1982; accepted May 4, 1982. Reprint requests: Garrett Lee, M.D., Cardiovascular Medicine, Suite 202. UCD Professional Bldg., 4301 X St., Sacramento, CA 95817. The use of laser energy to produce controlled thermal injury to coronary atherosclerotic obstructive plaques, thereby widening vascular luminal diameter, has been demonstrated histologically.‘,’ The application of fiberoptic bundles to view internally the blood vessels of living dogs has been described.‘,” To illustrate the practicality and potential of using the laser to enhance vessel patency, a flexible catheter equipped with both fiberoptic viewing capabilities and a quartz fiber for laser delivery (Trimedyne, Inc., Arlington Heights, Ill.) was inserted into normal aorto-iliac arteries in living dogs (Fig. 1, left) and into human cadavers with diseased arteries (Fig. 1, right, and Fig. 2). A fatty hyalinized diseased area adjacent to the lumen was viewed and targeted for laser irradiation (Fig. 2, left). Following a 3-second 7 W burst from an argon ion laser source, a vaporized patent area was produced which can be visualized through the fiberoptic

Interactions of steep-fronted pressure waves with a heterogeneous combustion field

Prcssore-fime-position relations and the simuiitaneous determination of other important combustion parameters have been theoretically and experimentally performed. These results were generated along a rocket combnsior axis during propagation of a strong shock wave running back and forth through an heterogeneous combustion field and reflecting ai the combustor ends. The initial steady*state condition is recognized as being that of a Siquid bipropeiilant droplet spray combustion within the burner, limited by their simultaneous vaporization. Substantial interaction effects between the different axial distributions of mass, impulse, and energy sources, affecting the local energy release and the onset and behavior of a sawtooth-like pressure wave have been investigated. In order to study the pressure-time behavior at different burner locations a short shock tube was mounted in the opposite direction to the combustion gas flow at the downstream end of the combustor. This pulse generator functions as an additional external source of pulse energy to initiate the upstreamrunning shock. Therefore a single steep-fronted pressure pulse could enter the combustor axialiy at any time during the run. The governing unsteady differential equations of the gaseous phase have been solved by applying the numerical Lax-Wendroff two-step procedure, including the simultaneous bipropellant vaporization and the wave reflection at the injector end of the combustor. The initial conditions, as given by solving the steady-state problem at first, were filled to corresponding measurements of the local combustion efficiency. This paper compares some of the recently achieved theoretical results with the corresponding experiments.

The Active Oxidation of Si and SiC in the Viscous Gas‐Flow Regime

The active oxidation of Si and was investigated in the viscous gas‐flow regime. Kinetics were measured as a function of temperature and oxygen partial pressure using thermogravimetric techniques. Active oxidation was initiated by exposing oxide‐free samples to low oxygen partial pressures in gas mixtures. Oxidation rates were found to be controlled by oxygen transport through the gaseous boundary layer. Active oxidation of Si was found to occur in two distinct stages rather than in only one as expected. Linear sample weight losses were observed during the first stage; however, in the second stage unusual and destructive behavior was observed in the form of extremely rapid sample weight gains. This phenomenon was interpreted in terms of a simultaneous vaporization and condensation process. No such behavior was observed during active oxidation.

An Alternative to Accurate Pyrometry in Distinguishing Concurrent Vaporization Reactions. Postulated Results Using the Vaporization of Gold in Analyzing the Vaporization of Beryllium Oxide in Water Vapor.

For the transpiration determination of vaporization properties whose interconsistency is critical, the simultaneous vaporization of a reference substance such as uncontaminated gold is suggested as an alternative to accurate pyrometry. Calculations suggest that gold would be superior to all but the most accurate pyrometry in the temperature range 1700 to 2300 K. An application to seeking unreported gaseous hydrates of beryllia is illustrated by calculations based on estimated thermodynamic parameters.

Some characteristics of chemical reactions in vaporizing hybrid systems

The author's method [1] of analyzing transport processes associated with the injection of a fuel-oxidizer mixture into a laminar boundary layer through a porous plate can be extended to the case of sublimation of a surface in a high-temperature gas flow. Such conditions may develop in hybrid (combined) systems in which a mixture of fuel and oxidizer from the vaporizing element must mix and react with an external oxidizer flow. Preliminary results [2–4] indicate that in “pure” systems (in which oxidizer is not mixed with the solid propellant) the reaction kinetics have secondary significance as compared with the transport processes in the boundary layer and in the majority of cases can be ignored for all practical purposes. However, in other hybrid systems and, in particular, where a certain amount of oxidizer is mixed with the solid propellant, the reaction kinetics may acquire considerable importance. The methods of analyzing transport processes in hybrid systems proposed in [3,4], although they supplement one another, do not give a sufficient description. The present method of theoretical investigation of hybrid systems, although based on a diffusion interaction mechanism, permits a somewhat better understanding of the kinetic laws thanks to the assumption of two reaction fronts. As shown in [1], this is conditioned by the fact that in the case of simultaneous vaporization of the fuel and oxidizer components the mixture temperature may reach the critical reaction temperature T* (condition of formation of the first front) before complete stoichiometry is achieved. If the mass velocity of the fuel component is greater than the stoichiometric value corresponding to the presence of oxidizer in the mixture, the occurrence of a second reaction front will be determined by attainment of the full stoiehiometric relation between the mass flow of fuel unreacted in the first front and the external oxidizer flow.

Size Distribution and Velocity of Ethanol Drops in a Rocket Combustor Burning Ethanol and Liquid Oxygen

Single jets of ethanol were studied photomicrographically inside a rocket chamber as they broke up into sprays of drops which underwent simultaneous acceleration and vaporization with chemical reaction occurring in the surrounding combustion gas stream. In each rocket test-firing, liquid oxygen was used as the oxidant. Both drop velocity and drop size distribution data were obtained from photomicrographs of the ethanol drops taken with an ultra-high speed tracking camera developed at NASA, Lewis Research Center.

ELECTRICALLY FUSED FORSTERITE‐OLIVINE, I‐II*

AbstractNorth Carolina olivine was melted in the electric arc‐resistance furnace, with simultaneous reduction of the iron (fayalite) components, to form a product consisting essentially of crystalline forsterite. The forsterite obtained from olivine by reduction was contaminated by clinoenstatite or a siliceous glass unless MgO or CaO was added to the charge. Silica, present in excess of orthosilicate proportions, was not eliminated by carbon reduction. Simultaneous reduction or vaporization of MgO prevented increase in the MgO to SiO2 ratio by carbon reaction. Addition of theoretical amounts of MgO to the melt to produce forsterite completely eliminated the clinoenstatite and siliceous glass and resulted in an abrupt increase in high‐temperature load‐bearing strength. The presence of lime was detrimental to high‐temperature load‐bearing strength.