Hg Vapor Pressure Research Articles

Mercury solubility measurements in natural gas components at high pressure

Saturated vapor pressure of elemental mercury (Hg) and Hg solubility in compressed gaseous methane, ethane, and carbon dioxide were investigated. The apparatus designed for this study was based on a flow method and equipped with a cold vapor atomic absorption survey meter to measure Hg concentration in gas phase. The saturated Hg vapor pressure ranged from 4.579 × 10−2 to 2.757 × 10−1 Pa at 278–298 K. The Hg solubility was measured up to 6.042 MPa for methane, 3.533 MPa for ethane, and 2.070 MPa for carbon dioxide at 268–303 K. The Hg mole fraction ranged from 4.842 × 10−9 to 8.683 × 10−7 in the vapor phase. The Hg solubility decreases with increasing pressure, and the pressure dependencies are similar in the three gases. The activation energy of Hg solubility was determined from the Arrhenius plot at the 1.55 and 3.55 MPa isobars. The activation energy at 1.55 MPa is about 60 kJ/mol·K for the three gases, similar to that at the saturated Hg vapor pressure. At 3.55 MPa the activation energy has the same value for methane but decreases to around 60 kJ/mol·K for ethane. The Peng–Robinson equation of state (PR-EOS) was used to correlate the saturated Hg vapor pressure and the Hg solubility in the vapor phase. The attractive parameter in the PR-EOS was fitted with the saturated Hg vapor pressure, and its temperature dependence was investigated using the van der Waals one-fluid mixing rule. The average absolute deviations were 0.322, 0.265 and 0.197 % for Hg solubility in gaseous methane, ethane and carbon dioxide, respectively. This investigation contributes to predicting mercury partitioning in natural gas processing facilities.

Strong Lines Emitted from Positive Column of Narrow Bore T2 Low-Pressure Ar-Hg Discharges

The electric field and absolute radiance of 13 strong lines in the positive column of narrow bore T2 (outer diameter 7 mm) low-pressure Ar-Hg discharges were measured experimentally, which includes 11 Hg lines ranging from 185 to 579 nm and 2 Ar lines of 811, 842 nm. The discharges were operated with different argon filling pressure ranging from 2 to 10 Torr (corresponding to 266 to 1333 Pa), for discharge currents 20-200 mA and cold spot temperature 20-80 °C (0.16-11.8 Pa Hg vapour pressure). The Koedam factors of important emission lines were also measured for various discharge parameters, in order to convert radiance to exitance, whereafter the radiant power of all the lines except 185 nm, could be calculated and their radiant efficiency could be compared as well. Considering the absorption of 185 nm radiation in air, the ratio of the radiance at 185 nm to that at 254 nm was measured instead of its Koedam factor for current 80-200 mA and cold spot temperature 20-60 °C. Therefore, 185 nm radiant power was derived indirectly from that of 254 nm in corresponding discharge conditions. According to our measured results, the argon pressure for the maximum production of 254 nm radiation is around 5 Torr. It is showed that the optimum cold spot temperature for 254 nm radiant efficiency is higher than 50 °C, which is consistent with the temperature dependence on the tube diameter. With increasing discharge current and cold spot temperature, 185 nm radiant power has the similar tendency to that of 254 nm, while the fraction of electrical power converted to 185 nm radiation increases slightly with these parameters. Generally, the ratio of radiant power at 185 nm to that at 254 nm is higher than 0.2. For evaluating the energy balance of the positive column as well as the luminous efficacy of the fluorescent lamp product, the radiant powers of other strong lines also has significantly effect though they are considerably smaller than that of 254 nm and 185 nm. Besides, it must be taken in consideration that mercury depletion on the axis of positive column is serious for T2 narrow tube discharge especially at low Hg vapour pressure and high current.

Measuring the pressure in ultrahigh-pressure mercury arcs

Ultrahigh-pressure (UHP) mercury lamps are important as high-brightness light sources for digital projection. Hg pressures are usually above 20 MPa and difficult to measure. We have built special UHP lamps with a liquid Hg condensate in a temperature-controlled reservoir, allowing us to tune the Hg vapor pressure p between 14 and 30 MPa. As a simple measure for p, we recorded the width Δλ of the 546 nm Hg line while varying p and also the lamp current I and voltage U. The data define a function p(Δλ,I,U) that will deliver p to better than 3% from simple measurements of Δλ, I, and U for most UHP lamps in the important 100–200 W power range. The method is applied to sample lamps, yielding pressures up to 26 MPa and demonstrating how filled Hg amount, burning position, arc gap, and lamp power affect the pressure. The effective temperature of typical UHP lamps is found to be 2400 K. We also derive an improved characteristic U(d,p,I) for the dependence of the arc voltage on arc gap, pressure, and current for e...

A Nano-Selenium Reactive Barrier Approach for Managing Mercury over the Life-Cycle of Compact Fluorescent Lamps

Compact fluorescent lamps contain small quantities of mercury, release of which can lead to human exposures of potential concern in special cases involving multiple lamps, confined spaces, or young children. The exposure scenarios typically involve solid lamp debris that slowly releases elemental mercury vapor to indoor spaces. Here we propose and demonstrate a reactive barrier approach for the suppression of that mercury release, and demonstrate the concept using uncoated amorphous nanoselenium as the reactive component. Multilayer structures containing an impregnated reactive layer and a mercury vapor barrier are fabricated, characterized, and evaluated in three exposure prevention scenarios: carpeted break sites, disposal/recycling bags, and boxes as used for retail sales, shipping, and collection. The reactive barriers achieve significant suppression of mercury release to indoor spaces in each of thethree scenarios. The nanoselenium barriers also exhibit a unique indicator function that can reveal the location of Hg contamination by local reaction-induced change in optical properties. The article also presents results on equilibrium Hg vapor pressure above lamp debris, mathematical modeling of reaction and transport processes within reactive barriers, and landfill stability of nanoselenium and its reaction products.

Determination of Hg activity in Hg0.8Cd0.2Te liquid and solid solutions by a quasi-closed-space method

A quasi-closed-space method is proposed for accurately measuring the vapor pressure of a volatile component over solid compounds (solutions) and melts containing this component. The method is used to determine the equilibrium Hg vapor pressure pHg over the Hg0.8Cd0.2Te solid solution between 623 and 1268 K within the homogeneity range of HgCdTe and at its boundaries. The results indicate a jump in pHg and a break in its temperature dependence at about 920 K, corresponding to the onset of melting. Above 623 K, the total equilibrium excess of Te in solid homogeneous Hg0.8Cd0.2Te is close to the concentration of charged Hg vacancies, as determined by Hall effect measurements.

Fabrication of Au nanostructures in the process of amalgam formation followed by Au–Hg alloy thermal decomposition

Au films deposited under ultra-high vacuum conditions on air-cleaved mica substrates were exposed in situ to Hg vapor (residual gas pressure ∼1×10−7 Pa, with Hg vapor pressure of 0.24 Pa). This led to transformation of continuous gold film into isolated amalgam islands of nanometer scale. The changes of Au thin film surface topography caused by amalgamation carried out within ∼40 h were studied by the atomic force microscopy method, while the phase transition in the bulk of Hg-dosed Au films was monitored by means of X-ray diffraction. The island's morphology varies from irregular, ramified structures on terraces to compact shapes along the steps on the mica substrate. After thermal decomposition of the amalgam, thin gold films consisting of isolated Au nanostructures on mica can be obtained.

Power balance in highly loaded fluorescent lamps

Discrepancies reported in the literature between numerical predictions and experimental measurements in low-pressure Hg discharges at high current densities are considered. Elements of a one-dimensional fluid model and recent spectroscopic and Langmuir probe measurements are combined in a semi-empirical way to individually examine components of the positive column power balance and the discharge conductivity. At a Hg vapour pressure of 0.81 Pa (6.1 mTorr) and a current density of 300 mA cm−2, previous discrepancies in the power balance and discharge conductivity are simultaneously resolved by assuming a higher electron density than that obtained from the Langmuir probe measurements. This conclusion is supported by independent measurements of ion density reported in a companion paper. The importance of radial cataphoresis under these conditions, particularly with regard to radiation transport, is highlighted. This work is of particular interest for the design of fluorescent lamps operating at high current densities.

Regulatory Off-Gas Analysis from the Evaporation of Hanford Simulated Waste Spiked with Organic Compounds

After strontium/transuranics removal by precipitation followed by cesium/technetium removal by ion exchange, the remaining low-activity waste in the Hanford River Protection Project Waste Treatment Plant is to be concentrated by evaporation before being mixed with glass formers and vitrified. To provide a technical basis to permit the waste treatment facility, a relatively organic-rich Hanford Tank 241-AN-107 waste simulant was spiked with 14 target volatile, semi-volatile, and pesticide compounds and evaporated under vacuum in a bench-scale natural circulation evaporator fitted with an industrial stack off-gas sampler at the Savannah River National Laboratory. An evaporator material balance for the target organics was calculated by combining liquid stream mass and analytical data with off-gas emissions estimates obtained using U.S. Environmental Protection Agency (EPA) SW-846 Methods. Volatile and light semi-volatile organic compounds (<220 °C BP, >1 mm Hg vapor pressure) in the waste simulant were found to largely exit through the condenser vent, while heavier semi-volatiles and pesticides generally remain in the evaporator concentrate. An OLI Environmental Simulation Program (licensed by OLI Systems, Inc.) evaporator model successfully predicted operating conditions and the experimental distribution of the fed target organics exiting in the concentrate, condensate, and off-gas streams, with the exception of a few semi-volatile and pesticide compounds. Comparison with Henry's Law predictions suggests the OLI Environmental Simulation Program model is constrained by available literature data.

High temperature arsenic doping of CdHgTe epitaxial layers

AbstractExperimental results on solid‐state arsenic doping of the n‐type bulk and ISOVPE epitaxial CdXHg1‐XTe (X = 0.19 ÷ 0.3) alloys are presented. The arsenic doped thin epitaxial CdxHg1‐xTe films (nAs ≈ 5 · 1016 ÷ 1 · 1020 cm‐3; d = 2 ÷ 5 μm) obtained by RF sputtering in a mercury glow discharge were used as As diffusion sources. The arsenic diffusion and activation were carried out at temperatures T = 500 ÷ 600 °C under Hg vapour pressure. Immediately after the high temperature treatment all samples were annealed to annihilate point defects. The SIMS analysis was used for determination of the quantitative admixture distribution of As in the diffusion area. The arsenic electrical activity has been evaluated by means of differential Hall, resistivity and thermoemf measurements. The analysis of experimental data obtained as well as their comparison with previously obtained results has been performed. (© 2004 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Fabrication of (Hg,Re)Ba 2CaCu 2O y thin films on LSAT substrates by long heat treatment

We have succeeded in improving the superconducting properties of (Hg,Re)Ba 2CaCu 2O y ((Hg,Re)-1212) thin films on (LaAlO 3) 0.3–(SrAl 0.5Ta 0.5O 3) 0.7 (LSAT) substrates. The 300-nm-thick films were fabricated by repeating the two-step process. It was found that the formation reaction for the 1212 phase depends on the amount of Hg-vapor source or the Hg-vapor pressure. 220-nm-thick films were slowly grown on 80-nm-thick seed films in a low Hg-vapor pressure for a long duration of several tens hours (65 h). The films exhibited a flat surface and no appreciable outgrowths. Their T c values were 117–120 K and the J c values in a self-field were 4–6×10 6 A/cm 2 at 77 K. They were substantially higher than those of the films prepared by the previously reported process, i.e. rather fast growth in a high Hg-vapor pressure for several hours (5 h).

The influence of gas phase composition on the process of Au–Hg amalgam formation

Interaction of thin Au films deposited on a glass substrate with Hg vapor at 298 K was studied. The influence of gas phase composition on the kinetics of the amalgamation process was examined. Several gas atmospheres were tried: vacuum (residual gases pressure ∼1×10 −7 Pa, with Hg vapor pressure 0.24 Pa), H 2, Ar and air at pressure around 101 kPa. The electrical resistance measurements in the process of Au–Hg amalgam formation were correlated with the atomic force microscopy investigations of amalgam surface structure and X-ray diffraction spectra of the bulk. The results of these studies clearly demonstrate the influence of gas phase composition on the kinetics of the amalgamation process. The experimental data are compared with theoretical calculations of the kinetic processes occurring at the thin Au film surface.

Recent progress in epitaxy of Hg-HTS thin films on oxides and metals

We recently developed a cation-exchange process and using it obtained high-quality epitaxial Hg-based high-temperature superconducting films. Unlike the conventional thermal-reaction process that needs to comply with the stringent requirements of chemical phase equilibrium, cation exchange was found to be a simple kinetic process that can be carried out in a large processing window based on the principle of atomic perturbation. Since this process can be carried out in a large processing window of the Hg-vapor partial pressure, we further developed a batch process for scaling up Hg-HTS tapes in long length and a crucible technique for scaling up to large area.

Resistivity and hall effect in the ab-plane of high TcHgBa 2CaCu 2O 6+y epitaxial films

By using of high quality HgBa 2CaCu 2O 6+y (Hg-1212) epitaxial films the resistivity and the normal state Hall effect in ab-plane have been studied. These properties indicate that Hg deficient Hg-1212 is an under-doped superconductor. In post annealing experiments we found that Hg can diffuse out from and into the films at 350°C depending on the Hg vapor pressure. The Hg deficient films show degraded superconductivity. Through annealing them in Hg atmosphere we recovered completely their superconductivity. Using these Hg-1212 films with different cation vacancy contents the relationship between T c and the Hall coefficient was studied. 1/R H was found to have T-linear behavior above a crossover temperature Y * and a weakended T-dependencebelow T *. This interesting behavior may be attributed to a pseudo-gap.

Quenching of (Cd,Mn,Hg)(Te,Se) Polycrystals by the Hot Isostatic Pressure Method and Crystal Growth

A II‐VI diluted magnetic semiconductor of crystal with 0.1 < x < 0.3, 0.1 < y < 0.3, 0 < z ≦ 0.02 has a high Hg vapor pressure at a temperature of crystal growth from a melt and has also temperature‐composition phase diagrams with a wide solid solution. The composition dependence of a figure of merit F (rotation/absorption) ≧ 250°/dB at 0.38 T at 0.98 μm was improved by adding selenium. A quenched‐annealed ingot with compositional uniformity in both the axial and radial directions was scaled up for large size (20 mm diam by 15 mm length) by the hot isostatic pressure method in which a sealed quartz ampul was subjected to a high external pressure of argon gas. Using this quenched‐annealed polycrystal ingot, a crystal with compositional homogeneity in the axial direction has been grown by a zone‐melt method for the first time. © 2000 The Electrochemical Society. All rights reserved.

Crystal growth of Cd 1− x−yMn xHg yTe 1− zSe z by a zone-melt method using a pressurized cast ingot

II–VI diluted magnetic semiconductor of Cd 1− x−y Mn x Hg y Te 1− z Se z crystal ( 0.1<x , y <0.3, 0⩽z⩽0.02 ) has a high Hg vapor pressure at a temperature of crystal growth from a melt and also has temperature–composition phase diagrams with a wide solid solution. A quenched polycrystal ingot starting from a stoichiometric Cd 1− x−y Mn x Hg y Te 1− z Se z melt was scaled up to a large size (20 mm diameter by 30 mm length) using a high-pressure synthesizing furnace, where a sealed quartz ampoule is subject to a high external pressure of argon gas (e.g. 14.0 MPa at 1060°C). Using this quenched polycrystal ingot, a large oriented single crystal has been grown by the zone melt method (ZM) for the first time. It has a large size (20 mm diameter by 25 mm length), low insertion loss (0.2 dB at 0.98 μm) and compositional uniformity both in the axial and radial directions.

Improvement of critical current density in Sb-doped HgBa 2Ca 2Cu 3O 8+ δ superconductor prepared by Hg vapour diffusion process

Antimony-doped Hg-1223 superconductors have been synthesised from the reaction of a Sb-doped precursor with elemental Hg vapour released from a reactant in sealed silica tubes (the Hg vapour diffusion process). The Hg vapour pressure can be controlled by a small addition of Se in the reactant bars. The phase purity and microstructure of the material have been characterised by XRD and SEM and the superconducing properties measured by electrical resistance and AC susceptibility. High quality superconducting material can be fabricated by this Hg vapour diffusion process with a suitable Se addition in the reactant bars. The microstructure reveals dense, plate-like grains with reduced void formation, when compared with material prepared by a solid state reaction route. Resistance and AC susceptibility measurements give a T c of 132 K. The diffusion process route significantly enhances the intergrain critical current density ( J c= 2.5×10 7 Am −2 at 77 K and zero field) and reduces the degradation of J c in a magnetic field.

Investigation of Moving Striations in a Low-Pressure Hg–Ar Discharge: II. Study of the Mechanism for the Occurrence

It is considered that moving striations appearing in a low-pressure Hg–Ar ac discharge is caused by the steep rise of electron temperature Tt near the reignition region due to the decrease in Hg vapor pressure.

Investigation of Moving Striations in a Low-Pressure Hg–Ar Discharge: I. Evaluation of Electron Temperature near the Reignition Region

When discharge tubes filled with low-pressure Hg–Ar gas are operated on a commercial ballast (at 50 or 60 Hz),they generate moving striations with decreasing ambient temperature. It was considered, in previous studies, that this phenomenon is caused by the high electron temperature in the reignition region of ac discharges below the ambient temperature. Saturated Hg vapor pressure decreases with decreasing ambient temperature. As a result, it is considered that the kinetic energy of electrons consumed for the excitation and ionization of Hg atoms decreases rapidly and the electron temperature of the high-energy part Tt, based on the assumption of a non-Maxwellian distribution function for energetic electrons, is raised above the excited or ionized levels of Ar gas. It is thought that this steep rise of the electron temperature in the reignition region induces the unstable discharges. It is confirmed by ac discharge simulation that the maximum of Tt values increases with decreasing in ambient temperature and Ar filling pressure.

Investigation of Hg 1-X Cdx te epitaxial vapor phase growth under isothermal conditions

The Hg 1. x Cd x Te layers were grown by vapor phase epitaxy on Cd-terminated {111} CdTe single crystal substrates from a HgTe solid source under isothermal conditions in a semi-closed system with controlled Hg vapor pressure. The growth kinetics were investigated in the temperature region from 420?C to 550?C with different source to substrate spacings, varying from 1 to 11 mm. It was found that the dependence of the growth rate on temperature could be well described by an Arrhenius type equation with an activation energy of 80 kJ/mol in the investigated temperature interval. The activation energies for the crystallization were the same for all the investigated source to substrate spacing.This activation energy value points to the importance of a solid-state diffusion process in the Hg 1-x Cdx Te/CdTe epitaxial couple obtained by isothermal growth under the given experimental conditions.

Optimization of mercury vapour pressure for high-frequency electrodeless light sources

Radiation qualities of mercury high-frequency electrodeless light sources (HFELSs) of natural and 202 isotope abundance of 99.8% have been studied in order to optimize filling and operation of the source. The optimal mercury vapour pressure in a high-frequency electrodeless inductive coupled discharge is estimated. A qualitative explanation of the excitation and ionization processes is given. An application of nonlinear multiparameter chi-square line shape fitting in order to find the true profile of spectral lines and equipment influence is presented. We demonstrate that, by appropriate selection of both the HF-oscillator working mode and Hg vapour pressure, it is possible to change the intensity and profile of the spectral lines quickly, making the use of the mercury HFELSs in various applications possible.