Pressure Mercury Vapor Research Articles

Amalgams for fluorescent lamps: Part I: Thermodynamic design rules and limitations

In compact fluorescent lamps, amalgams can be used to control the mercury vapour pressure inside the lamp. Since the optimal mercury vapour pressure and the coolest spot temperature of these lamps differ for each particular lamp configuration, it is desired to be able to design amalgams in such a way that a mercury vapour pressure versus temperature curve suitable for an optimal light-output is obtained for each particular lamp geometry. Using regular solution thermodynamics, relations have been derived between the mercury vapour pressure of the amalgam and the melting point, melting enthalpy and mercury interaction enthalpy of the underlying alloy. From these relations amalgam design rules and amalgam design limitations have been formulated.

Improvement in Fabrication of Hg-1223 Superconductor by Te-Doping

ABSTRACTThe sealed quartz tube method is one of the usual methods used for sintering mercury-based copper oxide superconductors. By this method, precursor pellets are inserted into the quartz tube together with certain mass ratio to the reagent sample pellets for controlling the mercury vapour pressure. A certain amount of excess HgO is required to ensure the fabricated sample to have the desired composition. In our research, it was found that if a small amount of TeO2 is added and mixed with the pulverized precursor after first calcination, Hg-1223 superconductors can be fabricated without using the precursor pellet and no excess HgO is required. Thus, the fabrication process can be simplified. As mercury and its oxide are toxic, if no excess Hg is involved, it is safe and good for the laboratory-environment. In this research, some amounts of 0.10 and 0.18 wt% (weigh percentage) of TeO2 were added into the precursor, it is shown that the critical temperature of the fabricated samples is comparable to that of the undoped Hg-1223 samples. For 0.10 wt% of TeO2, the Tc of the as-synthesized sample is about 116.7 K whereas the annealed Te-doped Hg-1223 is about 134.2 K. For 0.18 wt% of TeO2, the Tc of the as- synthesized and annealed samples are 115.8 K and 134.6 K, respectively. The phase structure of samples fabricated in this research has been analyzed by the X-ray diffraction technique. It shows that the Hg-1223 phase is dominated.

アマルガム封入蛍光ランプの管内水銀蒸気圧の測定

アマルガム封入蛍光ランプの管内水銀蒸気圧の測定

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.

Equilibrium vapour pressure of mercury from dental amalgam under loading conditions

Earlier studies have failed to establish a consensus on the amount of mercury vapour released from dental amalgam restorations. The purpose of this study was to accurately and quantitatively measure the equilibrium mercury vapour pressure from dental amalgam. The vapour pressure was measured using a quartz crystal microbalance as a function of the load from 0–5.4 MPa. Auger spectra were collected of the as-formed and argon ion sputter cleaned dental amalgam surface. For the as-formed surface the mercury vapour density is zero with no load and increases to 0.6 μg m -3 at 5.4 MPa. Following cleaning the mercury, vapour density increased to a maximum value of 15 μg m -3. The Auger spectra of the as-formed surfaces were dominated by features associated with carbon and oxygen. These spectral results in concert with the mercury vapour density measurements indicate that the oxide film on the as-formed surfaces inhibited the release of mercury vapour. The results of this experiment provide an upper limit for the amount of mercury vapour released by dental amalgams. Under conditions simulating the oral cavity this value would be reduced by oxides that form on the surface of dental amalgam restorations.

Equilibrium vapor pressure of mercury from dental amalgam in vitro

Objectives. The purpose of this study was to acquire reliable quantitative data on mercury vapor pressure above the surface of dental amalgam samples in both the as-formed and the abraded state.Methods. The equilibrium vapor pressure of mercury from dental amalgam was obtained using residual gas analysis in conjunction with a quartz crystal microbalance. The measurements were performed under ultrahigh-vacuum conditions.Results. Using the residual gas analyzer, the average mercury vapor pressures measured from the as-formed and abraded dental amalgam surfaces were 8 × 10−7 and 1.7 × 10−4 Pa, respectively. The corresponding vapor densities are: 6 × 10−2 μg/m3 and 14 μg/m3. The average mercury vapor pressures measured from the as-formed and abraded dental amalgam surfaces using the quartz crystal microbalance were: 2.4 × 10−6 and 1.0 × 10−4 Pa, respectively. The corresponding vapor densities are: 0.2 μg/m3 and 8 μg/m3.Significance. This project provides a measurement of the equilibrium vapor pressure of mercury from as-formed and abraded amalgam surfaces. By definition, the equilibrium vapor pressure provides the maximum density of mercury which can be present in the environment above the amalgam. The vapor density of mercury within the oral cavity must be less than this value due to the dynamic nature of the system.

蛍光灯用アマルガムの水銀蒸気圧-温度特性

蛍光灯用アマルガムの水銀蒸気圧-温度特性

Synthesis and Superconductivity of the HgBa 2Ca 2Cu 3O x superconductors

We produced the HgBa 2Ca 2Cu 3O 8+x (Hg-1223) superconductors by changing the composition, mercury vapor pressure and reaction temperature. We found that the high mercury pressure is essential for the formation of the Hg-1223 phase by preventing the decomposition of HgO at low temperature. This sample was characterized by the X-ray diffraction, Auger electron microprobe, AC susceptibility and resistivity measurement.

Synthesis and superconducting properties of HgBa2Ca2Cu3O8 +x

The influence of precursor composition, nominal mercury vapour pressure (PHg) and reaction temperature (t) on the formation of HgBa2Ca2Cu3O8 +x have been studied. By reducing the empty space inside the quartz tube, we could increase PHg higher than 200 atm and obtain samples containing only HgBa2Ca2Cu3O8 +x as the superconducting phase, with Tc(onset)= 134 K and Tc(zero)= 131 K.

Behavior of Mercury in High-Temperature Vitrification Processes

The Pacific Northwest Laboratory (PNL) has evaluated the waste processing behavior of mercury in simulated defense waste. A series of tests was performed under various operating conditions using an experimental-scale liquid-fed ceramic melter (LFCM). This solidification technology had no detectable capacity for incorporating mercury into its product, borosilicate glass. Essentially all the mercury fed to the melter was lost to the off-gas system as gaseous effluent. An ejector venturi scrubber condensed and collected 97% of the mercury evolved from the melter.Chemically, the condensed mercury effluent was composed almost entirely of chlorides, and except in a low-temperature test, Hg2Cl2 was the primary chloride formed. As a result, combined mercury accounted for most of the insoluble mass collected by the process quench scrubber. Although macroscopic quantities of elemental mercury were never observed in process secondary waste streams, finely divided and dispersed mercury that blackened all condensed Hg2Cl2 residues was capable of saturating the quenched process exhaust with mercury vapor. The vapor pressure of mercury, however, in the quenched melter exhaust was easily and predictably controlled with the off-gas stream chiller.These tests followed 12 earlier experiments performed at PNL to study the behavior of mercury during vitrification of simulated typical defense waste. The experiments were conducted using an experimental-scale spray calciner/in-can melter (SC/ICM) system plus a very similar off-gas system. Results with both the LFCM and SC/ICM technologies were essentially the same. Just as with the LFCM, the mercury was completely volatilized from the in-can melter system in all experiments. It reacted predominantly with halogens to form a fine particulate solid, most of which was deposited in the off-gas system piping.

Thermodynamic reactivity, growth and characterization of mercurous halide crystals

Thermodynamic calculations were carried out for the Hg-X-O system (X = Cl, Br, I) to identify the potential sources of contamination and relative stability of oxides and oxy-halide phases. The effect of excess mercury vapor pressure on the optical quality of mercurous halide crystal was studied by growing several mercurous chloride crystals from mercury-rich composition. The optical quality of crystals was examined by birefringence interferometry and laser scattering studies. Crystals grown in slightly mercury-rich composition showed improved optical quality relative to stoichiometric crystals.

Mercury porosimetry interpretation of fine and porous UO2 particles manufactured via the AUC process

Intrusion—extrusion curves from mercury porosimetry have been employed to construct condensation—evaporation isotherms. The usual limit of 1000 Å for pore size distribution from nitrogen adsorption has been extended to several hundred micrometers through the use of mercury isotherms. Vapor adsorption—desorption and mercury intrusion—extrusion are shown to be thermodynamically equivalent processes. The relationship between the hydraulic pressure needed to force mercury into a pore and the relative vapor pressure of mercury in the pore is derived.

Isovpe growth, post-growth annealing and characterization of Hg 1− xCd xTe layers

In this work we report on the isothermal vapour phase epitaxy of Hg 1− x Cd x Te films (with x ranging between 0.12 and 0.34) grown on (111 )Te oriented CdTe substrates. The post-growth annealing under mercury vapour pressure was performed in both open and closed systems. The morphological and electrical properties of the layers that are reported show mirror-like surfaces and mobility values ranging from 8 × 10 3 to 1.9 × 10 5 cm 2/Vs depending on the composition.

Radial variations of Hg(63P J) in a narrow-diameter low-pressure Hg-Ar discharge

Two laser techniques are used to measure densities of mercury atoms in the three 63PJ states populated in the positive column of a narrow (13.7 mm diameter) low-pressure Hg-Ar dc discharge. Relative densities are obtained as a function of radial position using a saturated laser absorption technique, while on-axis absolute densities are measured using the hook method (an interferometric technique). Results are shown for two mercury vapor pressures and are compared with computer model predictions.

Modelling of low-pressure Ar+Hg discharge with high electric current densities

Deals with experimental and theoretical investigations on the characteristics of low-pressure Ar+Hg discharges with very high electric current densities. The positive column of these discharge systems is studied under the following conditions: noble gas pressure 7.7 Torr; tube radius 1.6 mm; cold-spot temperature 313-53 K (corresponding to a saturation mercury vapour pressure of 6-88 m Torr) and electric current 30-600 mA. It is found that the V-I characteristic of the positive column will be positive if the value of the current density is above a certain critical one. A six-level model which can fairly describe the depleted low-pressure Ar+Hg discharges is developed. The output of the theoretical model gives the whole macroscopic plasma properties such as the electric field strength, the electron temperature, the energy transfers of the various collision processes and the radiation output, etc. The E-I and Te-I characteristics calculated according to the model agree qualitatively with the measured results.

The pressure-temperature phase diagram of the HgTe system from dynamic mass loss measurements

A dynamic mass loss measurement technique was employed, for the first time, to establish the pressure-temperature phase diagram of the HgTe system. The mercury vapor pressures over HgTe samples of various compositions were determined at elevated temperatures in closed ampoules, using an automatic vacuum semi-microbalance and employing the lever principle. The width of the homogeneity range (50.06–50.25 at.% Te) of Hg 1− x Te(s), as determined in this work, is entirely on the tellurium-rich side of the phase diagram. For compositions within the homogeneity range, the mercury pressure depends on composition, temperature, and the sample-to-free volume ratio.

The Self-diffusivity of cadmium in Hg0·8Cd0·2Te

Abstract A radiotracer method has been used to determine the self-diffusivity D(Cd) of cadmium in Hg0·8Cd0·2Te between 230 and 500°C and as a function of mercury vapour pressure Phg above 280°C. At 280°C, D(Cd)αphg ½ Hg. At higher temperatures, D(Cd) is largely independent of pHg exceot near the maximum value of PHg At this maximum and, when D(Cd) is independent of pHg It is tentatively proposed that the self-diffusion mechanism is based on native defect complexes.

アマルガム封入電球形螢光ランプの水銀蒸気圧に関する考察

アマルガム封入電球形螢光ランプの水銀蒸気圧に関する考察

Mercury vapor streaming effect in McLeod gauges

In this paper the authors explain the experimental results, reported earlier, on the error made in measuring pressures below the vapor pressure of mercury with a McLeod gauge. Mercury vapor streaming effects the pressure measurement made by a cold trapped McLeod gauge. The percentage of errors in the pressure measured (i.e., Δp/P2%) agrees with Gaede’s transport theory and Takaishi’s kinetic theory of gas analysis of this problem. Below the vapor pressure of mercury the percentage error starts rising and rises to 10.3% forming a plateau and increases to 17%–19% below 2.67×10−3 Pa (2×10−5 Torr). This increase in pressure measurement error below 2.67×10−3 Pa (2×10−5 Torr) has been found to be in quantitative agreement with that predicted by Rambeau.

Variation of efficacy with arc tube bore and current in a high-pressure sodium lamp

The total wattage and voltage drop across a high-pressure sodium discharge in an arc tube constructed with three sections of different bores (4 mm, 5.7 mm and 7.4 mm) have been measured for three different currents (3A, 4A and 5A). The light intensity and visible region spectra were measured with a spectro-radiometer. The sodium and mercury vapour pressures were held constant throughout the experiment. This was achieved by using a large quantity of amalgam contained in a reservoir appended to the arc tube and submerging the reservoir in a bath of molten indium whose temperature could be independently fixed. The wattages and voltages across each section have been calculated, and a model used to calculate the spectra. There was good agreement between the calculated and measured total wattages, voltages and spectra for the nine combinations of current and bore. It has been determined that the efficacy increases by between 2% and 4.8% per mm of bore at constant current and by between 2.3% and 7.5% per A at constant bore. Throughout the experiment the wall temperatures varied between 1296 K and 1720 K. If the wall temperatures could have been held constant at 1500 K, it is predicted that the efficacy would have increased at rates between 8.8% and 11.7% per mm of bore and between −1% and 4% per A.