A universal hydrogen and deuterium liquefier

The design is given of an economical H₂ and D₂ liquefier which works by the boiling off of liquid He vapour. The decisive role played by the gas condenser in the operation of the liquefier is demonstrated. The relationships between the flow rates of He and of the liquefied gas are calculated and measured. The helium consumption is 2.85 l for liquefying 1 l of H₂ and 3.8 1 l of D₂, which agrees with the calculations.     

A very light and thin liquid hydrogen/deuterium heat pipe target for COSY experiments

A liquid hydrogen/deuterium heat pipe (HP) target is used at the COSY external experiments TOF, GEM and MOMO. The target liquid is produced at a cooled condenser and guided through a central tube assisted by gravitation into the target cell. An aluminum condenser is used instead of copper, which requires less material, improves conductivities and provides shorter cooling down time. Residual condenser temperature fluctuations in the order of ≈0.4 K are reduced by using thermal resistances between the cooling machine and the condenser of the heat pipe combined with a controlled heating power. A new design with only a 7-mm-diameter HP has been developed. The diameter of the condenser part remains at 16 mm to provide enough condensation area. The small amount of material ensures short cooling down times. A cold gas deuterium HP target has been designed and developed which allows protons with energy ?1 MeV to be measured. A 7-mm-diameter HP is used to fill a cooling jacket around the D₂ gas cell with LH₂. The D₂ gas is stabilized at 200 mbar to allow for thin windows. Its density is increased by factor 15 compared to room temperature.     

Heat capacity of H2 adsorbed on Ne and on D2 preplated graphite

We have performed heat capacity measurement on H₂ adsorbed on graphite preplated with either a monolayer of Ne or a monolayer of D₂, to search for low temperature 2D liquid H₂. We find evidence indicating that up to 80% of the Ne preplating is displaced by H₂, followed by H₂ growing on itself. This is in contrast to H₂ on D₂ preplated graphite in which H₂ grows on D₂ and possibly 2D liquid H₂ exists down to 5.74K.     

Four-photon spectroscopy of coherent molecular rotations in liquids in the 0–3 THz range

The spectra of free, low-frequency (0–3 THz) molecular rotations in liquid CCl₄, H₂O₂, D₂O, and H₂O, which coincide with the spectra of same molecules in the gas phase, have been observed for the first time by means of four-photon coherent laser spectroscopy. The spectra of water and hydrogen peroxide reveal resonances at the frequencies corresponding to rotational transitions involving the ground vibrational states of the ortho and para spin isomers of water.     

The melting curve of tetrahydrofuran hydrate in D2O

Melting points for the tetrahydrofuran/D₂O hydrate in equilibrium with the airsaturated liquid at atmospheric pressure are reported. The melting points were measured by monitoring the absorbance of the solution. Overall, the meltingpoint phase boundary curve is about 2.5 K greater than the corresponding curve for the H₂O hydrate, with a congruent melting temperature of 281±0.5 K at a D₂O mole fraction of 0.936. The phase boundary is predicted to within 5% if the assumption is made that the THF occupancy in the D₂O and H₂O hydrates is the same. We measure an occupancy of 99.9%. The chemical potential of the empty lattice in D₂O is estimated to be 5% greater than in H₂O.     

The dielectric constant of H2, D2, and HD in the condensed phases

Measurements have been made of the dielectric constant in the liquid and solid phases of H₂, D₂, and HD. Precise measurements were made in the liquid phase at saturated vapor pressure and compared with previous data. A study was made of the change in the dielectric constant upon solidification. Measurements were made in the solid phases of H₂ and HD from the solidifition point to about 0.02 K. Both solids exhibited temperature-dependent dielectric constants which were rather similar. The magnitude of the temperature dependence was found to be related to the concentration of molecules in the rotationalJ=1 state. The dielectric constant of HD was found to change quite dramatically between 1 and 2 K, while H₂ and D₂ show no similar change.     

Isochoric Heat Capacity Measurements for 0.5 H2O+0.5 D2O Mixture in the Critical Region

The isochoric heat capacity C _V of an equimolar H₂O+D₂O mixture was measured in the temperature range from 391 to 655 K, at near-critical liquid and vapor densities between 274.05 and 385.36 kgm^–3. A high-temperature, high-pressure, nearly constant-volume adiabatic calorimeter was used. The measurements were performed in the one- and two-phase regions including the coexistence curve. The uncertainty of the heat-capacity measurement is estimated to be ±2%. The liquid and vapor one- and two-phase isochoric heat capacities, temperatures, and densities at saturation were extracted from the experimental data for each measured isochore. The critical temperature and the critical density for the equimolar H₂O+D₂O mixture were obtained from isochoric heat capacity measurements using the method of quasi-static thermograms. The measurements were compared with a crossover equation of state for H₂O+D₂O mixtures. The near-critical isochoric heat capacity behavior for the 0.5 H₂O+0.5 D₂O mixture was studied using the principle of isomorphism of critical phenomena. The experimental isochoric heat capacity data for the 0.5 H₂O+0.5 D₂O mixture exhibit a weak singularity, like that of both pure components. The reliability of the experimental method was confirmed with measurements on pure light water, for which the isochoric heat capacity was measured on the critical isochore (321.96 kgm^–3) in both the one- and two-phase regions. The result for the phase-transition temperature (the critical temperature, T _{C, this work}=647.104±0.003 K) agreed, within experimental uncertainty, with the critical temperature (T _{C, IAPWS}=647.096 K) adopted by IAPWS.     

Thermal conductivity of liquid hydrogen filled foam

The effective thermal conductivities of silica aerogel foam [0.1(10)⁻³ kg m⁻³ nominal density] filled with liquid n-H₂, liquid n-D₂ and an equimolar mixture of liquid H₂D₂ were measured near 19.6 K. Our measured value of 97 mW m⁻¹ K⁻¹ for hydrogen filled foam is essentially the same as for the liquid alone. This result agrees with predictions for the thermal conductivity of porous systems which give a 2% enhancement in the effective thermal conductivity for this system relative to the liquid alone.     

Hydrogen adsorption on alkali metal surfaces: Wetting,prewetting and triple-point wetting

We report the results of a quartz microbalance study of the multilayer adsorption of H₂ and D₂ on sodium and on rubidium. On sodium H₂ and D₂ display the well known phenomenon of triple-point wetting. Interestingly low temperature adsorption isotherms of H₂ on the evaporated Na surface show sharp layering transitions. On rubidium a weaker substrate H₂ and D₂ undergo a wetting transition in the liquid phase followed by sharp presetting transitions away from liquid-vapor coexistence. The prewetting phase diagram of H₂ on Rb has been quantitatively mapped out.     

Numerical Study of a Multilayered Target for Muonic X-Ray Generation by Taking Time Delay of Muonic Atoms

The μd energetic atoms are produced by injection of fast muons into a solid hydrogen target of H ₂/D ₂, which contains a small amount of deuterium. A?solid layer of D ₂ has been frozen on H ₂/D ₂ for ion implantation. The target has been kept at low temperature ～3 K. Once ions are implanted into such a target in experiment, characteristic muonic X-rays are generated. Analyzing such X-rays is very useful for understanding nuclear shape of implanted ions. Here, X-ray yields have been determined by taking time delay of energetic μd(1s) atoms using an alternative kinetic approach. The introduced kinetic model describes recent experimental data well. There are reasonable agreements between obtained X-ray yields and those experimentally reported by Strasser et al.     

Influence of temperature on the lifetime of electronically excited uranyl ion: IV. Effect of isotope enrichment in low-temperature crystallization of partially deuterated aqueous solutions of sulfuric acid

The isotope effect manifested in phase transitions in deuterium-substituted aqueous solutions of sulfuric acid was found. The phase transitions occurring with variation of temperature of 0.5 M H₂SO₄ solution in H₂O, 0.5 M D₂SO₄ solution in D₂O, and their mixtures were studied by differential thermal analysis. Additional data on the phase transitions in these samples were obtained using chemiluminescence [low-temperature reaction of U(IV) with XeF₂] and τ-metry (measurement of the lifetime τ of uranyl ion UO₂²⁺ in the electronically excited state). The uranyl ion was used as a luminescence probe. The whole set of data obtained can be interpreted on the basis of the concept that a mixture of 0.5 M H₂SO₄ and 0.5 M D₂SO₄ solutions (H/D = 1), subjected to fast (10–15 K s⁻¹) cooling to 77 K followed by warming, contains a liquid phase in which the deuterium content in the temperature range 202–210 K is higher than that in the initial solution.     

Solubilities of ethylene,ethane, and carbon dioxide in mixed solvents consisting of methanol,acetone, and water

The amount of gas absorbed in a liquid solvent or solvent mixture is measured with a high-precision gas burette. Solubility coefficients (Henry and Ostwald coefficients) of C₂H₄ and C₂H₆ are determined at ambient temperature and atmospheric pressure (1) in the pure solvents C₃H₆O, CH₃OH, and H₂O; (2) in the three binary mixtures of the solvents as a function of the composition of the solvent mixture; and (3) in several ternary mixtures of arbitrary composition. The experimental data are presented in diagrams and tables.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Equation of State of He-H2 and He-D2 Dense Fluid Mixtures at High Pressures and Temperatures

The fluid variational theory is used to calculate the Hugoniot equation of state (EOS) of He, D₂, He + H₂, and He + D₂ fluid mixtures with different He:H₂ and He:D₂ compositions at high pressures and temperatures. He, H₂, and D₂ are the lightest elements. Therefore, the quantum effect is included via a first-order quantum correction in the framework of the Wigner-Kirkwood expansion. An examination of the reliability of the above computations is performed by comparing experiments and calculations, in which the calculation procedure used for He and D₂ is adopted also for He + D₂ and He + H₂, since no experimental data for the mixtures are available to conduct these comparisons. Good agreement in both comparisons is found. This result may be seen as an indirect verification of the calculation procedures used here, at least, in the pressure and temperature domains covered by the experimental data for He and D₂ used for comparisons, which is nearly up to 40 GPa and 10⁵ K. Also, the equation of state of He + H₂ fluid mixtures with different compositions is predicted over a wide range of temperatures and pressures.     

Distillation of hydrogen isotopes for polarized HD targets

We have developed a new cryogenic distillation system to purify Hydrogen-Deuteride (HD) gas for polarized HD targets in LEPS experiments at SPring-8. A small amount of ortho-H₂ (∼0.01%) in the HD gas plays an important role in efficiently polarizing the HD target. Since there are 1-5% impurities of H₂ and D₂ in commercially available HD gases, it is necessary to purify the HD gas up to ∼99.99%. The distillation system is equipped with a cryogenic distillation unit filled with many small stainless steel cells called “Heli-pack”. The distillation unit consists of a condenser part, a rectification part, and a reboiler part. The unit is kept at the temperature of 17-21 K. The Heli-pack has a large surface area that makes a good contact between gases and liquids. An amount of 5.2 mol of commercial HD gas is fed into the distillation unit. Three trials were carried out to purify the HD gas by changing temperatures (17.5 K and 20.5 K) and gas extraction speeds (1.3 ml/min and 5.2 ml/min). The extracted gas was analyzed using a gas analyzer system combining a quadrupole mass spectrometer with a gas chromatograph. One mol of HD gas with a purity better than 99.99% has been successfully obtained for the first time. The effective NTP (Number of Theoretical Plates), which is an indication of the distillation performances, is obtained to be 37.2±0.6. This value is in good agreement with a designed value of 37.9. The HD target is expected to be efficiently polarized under a well-controlled condition by adding an optimal amount of ortho-H₂ to the purified HD gas.     

Microscopic Structure in Liquid Hydrogen and Deuterium: An X-Ray Scattering Study

The static structure factors S(Q) of liquid normal H₂ and D₂ have been measured in the wave-vector region 5 nm^–1<Q<30 nm^–1 through X-ray scattering using two independent sets of data. While the first set has been derived using a standard liquid diffraction geometry, the second has been worked out integrating the dynamic structure factors S(Q, ), measured through inelastic X-ray scattering spectroscopy. In the latter case the first spectral-moment sum rule has been used to obtain directly absolute static structure factor values. A comparison with quantum and classical Monte Carlo simulations shows that a quantitative agreement with the experimental data for both H₂ and D₂ can be obtained only if quantum effects are properly taken into account.     

Specific heats of solid hydrogen,solid deuterium,and solid mixtures of hydrogen and deuterium

Measurements have been made in the temperature range 0.5–5 K of the specific heats of pure solid H₂, pure solid D₂, and four solid mixtures of H₂ and D₂ with D₂ fractions between 15 and 95%, all of which systems had low concentrationc of molecules in the rotational stateJ=1. For the H₂,c=0.0023, and for the D₂,c=0.030. It was found that the observed specific heats could be described as the sum of three terms as follows. (1) A lattice specific heat. This was found to follow aT ³ function with _D =122 K for solid H₂ and _D=113.8 K for solid D₂. For the solid mixtures the lattice specifi heats have in first approximation values given by a weighted mean of the lattice specific heats of the pure components. (2) A Schottky term with a maximum at about 1.3 K for solid H₂ and 1.4 K for solid D₂, which can quantitatively be described in terms of electric quadrupole-quadrupole (EQQ) interactions in nearest-neighbor pairs and triples of molecules in the rotational stateJ=1. This term led to evaluation of , the EQQ interaction energy, giving /k=0.9 ± 0.1 K for solid H₂ and 0.93 ± 0.05 K for solid D₂. It was found, moreover, that in solid H₂ there was an appreciable enhancement with time of the number of clusters of molecules in the rotational stateJ=1 at the expense of the number of isolated singles of similar molecules, due to rotation diffusion. On the other hand no rotation diffusion was observed in solid D₂ or in the solid mixtures of H₂ and D₂, except possibly in those mixtures containing 85% H₂. (3) A second anomalous term occurring at temperatures below about 0.8 K and, by extrapolation, having its maximum below 0.5 K (the lowest temperature of our measurements). This anomaly was observed only in those samples containing D₂ and is, as yet, unexplained in detail. A further major conclusion from our results in the temperature range 0.5–5 K is that there was no evidence in the form of a sharp anomalous jump in the specific heat of any of the mixtures which could be interpreted as indicating the occurrence of isotopic phase separation. This absence of phase separation is noted, in spite of the fact that thermodynamically it is energetically favorable in the temperature range of observation.Work partially supported by a grant from the National Science Foundation and by contracts with the Office of Naval Research and DOD (Themis Program).     

Generation of neutron multigroup constants in the energy range –10 MeV for light and heavy water at four different temperatures

On the basis of the cross section models of neutron scattering in liquid H₂O and D₂O, which have been developed in the previous papers, we have generated eight sets of multigroup constants (energy-averaged cross sections) for each liquid at 5, 27, 52 and . The multigroup constants cover a wide energy range –10 MeV with 140 energy groups at equal logarithmic intervals and represent an angular scattering distribution by the Legendre polynomial expansion up to order 3. Major characteristics of neutron scattering inherent to liquid water are fully included in terms of coherent and incoherent properties and temperature-dependent quasi-elastic and inelastic scattering. These characteristics are assured by comparison with relevant experimental results of scattering cross section and also by neutron slowing-down and thermalization analysis in liquid H₂O and D₂O. It is shown that the present multigroup constants serve for analysis of neutron moderation from fission/spallation to ultra-cold energies, in combination with the already-generated ones for liquid ⁴He, H₂, D₂ and CH₄ and solid CH₄.     

Orientational ordering in solid D2 from NMR studies. II. The cubic ordered phase

An NMR study in the cubic phase of D₂ which exhibits long-range orientational order is reported. The spin systems in both para D₂ (with angular momentum J=1 and spinI=1) and in ortho D₂ (with J=0 andI=2) were investigated. The integrated intensity ratio of theI=1 andI=2 components in the solid echo, the NMR line shapes obtained by Fourier transforming the solid echoes, and the longitudinal relaxation times for theI=1 andI=2 systems are presented. Samples with D₂ concentrationX between 0.69 and 0.62 were studied over the temperature range 0.12<T<4 K. Measurements were carried out before and after repeated thermal cycling through the ordering transition to study the effect of this cycling on the temperature dependence of the relaxation times. The complex behavior of these relaxation times was found to be similar to that in cubic H₂ at a comparable concentration, and the interpretation of this behavior is discussed. Over most of the temperature range, the relaxation time of theI=2 spins is larger than that of theI=1 spins and is believed to be determined by cross-relaxation with the latter, whose intrinsic spin-lattice relaxation is observed. However, at low enough temperatures, the relaxation time for theI=2 spins is found to be shorter than that for theI=1 spins, and this observation cannot be understood on the basis of predictions. Furthermore, theI=2 relaxation time in this temperature region is found to depend on the position within the NMR line. Another observation not yet understood is that the ratio of the integrated intensitiesS(I=1)/S(I=2) in the solid echo is smaller than the theoretically predicted one by about 20%. The NMR line shapes for theI=1 spins in the ordered phase obtained from pulse measurements are compared with those from continuous-wave methods and to those from H₂.     

Preparation and optimization of a low cost,high breakage resistance ceramic proppant special for the coal-bed methane

A kind of low cost, high breakage resistance ceramic proppant special for exploitation of the coal-bed methane is successfully produced. The producing conditions are optimized through orthogonal experimental design method. The breakage resistance results of the orthogonal analyses show the best condition of this kind of ceramic proppant is A₄B₃C₃D₂, which means sintering temperature of 1350 °C, manganese mineral powder content of 5 wt.%, weight ratio of 75/25 (second grade bauxite to mujie clay), and holding time of 3 h. The ceramic proppants under this very condition of A₄B₃C₃D₂ are then prepared and their phase structure and microstructure are characterized subsequently. X-ray diffraction pattern exhibits that mullite and corundum are the main crystallographic phases. Scanning electron microscopy illustrates the A₄B₃C₃D₂ sample is with non-porous morphology and small amount of corundum grains and liquid phase, which play the role of improving strength. It reveals the orthogonal experimental design is a feasible optimization method and the ceramic proppant made under the condition of A₄B₃C₃D₂ is a promising material for exploiting the coal-bed methane resources.     

A Bipyridyl Covalent Organic Framework with Coordinated Cu(I) for Membrane C3H6/C3H8 Separation

Covalent organic frameworks (COFs) mixed matrix membranes (MMMs) combining individual attributes of COFs and polymers are promising for gas separation. However, applying COF MMMs for propylene/propane (C₃H₆/C₃H₈) separation remains a big challenge due to COF inert pores and C₃H₆/C₃H₈ similar molecular sizes. Herein, the designed synthesis of a Cu(I) coordinated COF for membrane C₃H₆/C₃H₈ separation is reported. A platform COF is synthesized from 5,5′-diamino-2,2′-bipyridine and 2-hydroxybenzene-1,3,5-tricarbaldehyde. This COF possesses a porous 2D structure with high crystallinity. Cu(I) is coordinated to bipyridyl moieties in the COF framework, acting as recognizable sites for C₃H₆ gas, as shown by the adsorption measurements. Cu(I) COF is blended with 6FDA-DAM polymer to yield MMMs. This COF MMM exhibits selective and permeable separation of C₃H₆ from C₃H₈ (C₃H₆ permeability of 44.7 barrer, C₃H₆/C₃H₈ selectivity of 28.1). The high porosity and Cu(I) species contribute to the great improvement of separation performance by virtue of 2.3-fold increase in permeability and 2.2-fold increase in selectivity compared to pure 6FDA-DAM. The superior performance to those of most relevant reported MMMs demonstrates that the Cu(I) coordinated COF is an excellent candidate material for C₃H₆ separation membranes.