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Single-walled carbon nanotubes (SWCNTs, the mean diameter of 1.35 nm) were produced by a modified arc discharging furnace using a mixture powder of KCl and Co-Ni alloy as catalyst at 600°C. The hydrogen storage capacity of SWCNTs was enhanced by the mechanism of atom hydrogen spillover from the supported catalyst. The temperature effect on the hydrogen storage capacity of as-grown SWCNTs was investigated. The relative experiments of SWCNT hydrogen uptake and release were carried out by a high-pressure volumetric gas-adsorption measurement system. The experimental results indicated that the hydrogen storage capacity of SWCNTs increased with the environmental temperatures decreasing. The hydrogen storage capacity of SWCNTs was up to 1.73 wt% at 77 K for 2 hours under the pressure of 10 MPa, and the corresponding releasing hydrogen capacity is about 1.23 wt% under ambient pressure.

For the safe storage of zeolite wastes generated by the treatment of radioactive saline water at the Fukushima Daiichi Nuclear Power Station, this study investigated the fundamental properties of h...

In this paper, a numerical study of coupled heat and hydrogen transfer characteristics in an annular cylindrical hydrogen storage reactor filled with Mg2Ni is presented. An unsteady, two-dimensional (2-D) mathematical model of a metal hydride reaction bed of cylindrical configuration is developed for predicting the hydrogen storage capacity. The effect of volumetric radiation is accounted in the thermal model. Effects of hydride bed thickness, initial absorption temperature, hydride bed thermal conductivity, and hydrogen supply pressure on the hydrogen storage capacity are studied. A thinner hydride bed is found to enhance the hydriding rate, accomplishing a rapid reaction. At an operating condition of 20 bar supply pressure and 573 K initial absorption temperature, Mg2Ni stores about 36.7 g hydrogen per kg alloy. For a given bed thickness and an overall heat transfer coefficient, there exists an optimum value of hydride bed thermal conductivity. The present numerical results are compared with the experim...

The hydrogen isotope effects upon operation of a polymer electrolyte membrane fuel cell have been observed. The deuterium concentration in the exhaust hydrogen gas from the cell was found lower than that of the hydrogen gas fed to the cell, which indicated that the heavier isotope of hydrogen was preferentially oxidized at the anode. The overall hydrogen isotopic separation factor between the oxidized and non-oxidized hydrogen ranged from 3.46 to 3.99 and increased with decreasing flow rate of the feed gas or increasing rate of hydrogen utilization.

A new sensor for the detection of hydrogen at parts per million (ppm) levels was fabricated by coating a thin film of palladium-doped activated single-walled carbon nanotube on the inner wall of a glass tube. The response of the sensor was based on the changes in the impedance of the sensor upon the adsorption of hydrogen molecules. The linear dynamic range of the sensor was from 1 to 50 ppm. The relative standard deviation of six replicate analyses of 5 ppm of H2 was 2.1% and the limit of detection was 0.73 ppm for H2 species. Humidity, methane and hydrogen sulphide did not have any serious effect on hydrogen recognition. Also, no interfering effect was observed when 20-fold excess (mass/mass) of carbon dioxide or carbon monoxide was present with hydrogen.

Amorphous carbon nanotubes (ACNTs) were produced by a temperature-controlled arc discharging furnace with a mixture powders of Co-Ni (1:1wt%) alloy as catalyst and hydrogen as buffer gas. As-grown and treated ACNTs with a mean diameter of about 14nm for hydrogen storage and release experiments were studied in this paper. The test experiments of hydrogen uptake and release were carried out by a volumetric gas-adsorption measurement system. The results indicated that the hydrogen storage capacity of ACNTs was 1.1wt% at the pressure of 2.45MPa and room temperature. Around 50% of the adsorbed hydrogen gas of ACNTs could be released under a standard pressure and at room temperature.

This paper presents a feasibility study of cryo-adsorption systems using low temperature adsorption materials for the on-board storage of hydrogen in a fuel cell vehicle. Charge and discharge validation experiments were performed using a 5 L semi-vehicle size tank. The tank was larger than the conventional lab scale test tank in order to clarify issues and evaluate the potential of this system for practical vehicle applications, and to provide targets for material development. Our results show that cryo-adsorption has a potential of higher hydrogen storage capacity in term of compactness and lightness than conventional high pressure tanks, provided that high volumetric density adsorption materials are available. Our results show that it is possible to obtain acceptable charge and discharge performance. They also show the necessity for further basic investigations into the heat transfer behavior during the charge and discharge of cold hydrogen into the system. In general, this concept is suitable for application in the context of a liquid hydrogen distribution infrastructure, which is widely used in industrial gas delivery today and is also expected to play an important role in hydrogen delivery systems for the transport sector.

We reported a novel graphitized carbon coated Pt composite synthesized by one-pot TEOS polymerization-high temperature carbonation approach. Electrochemical measurements display that the obtained Pt/graphitized carbon (Pt@GC) shows high electrochemical activity toward hydrogen oxidation. Additionally, quartz crystal microbalance results for hydrogen adsorption indicate that Pt@GC has high performance of hydrogen storage. The synthesized Pt@GC composite shows significant potential applications in H2/O2 (air) fuel cell and hydrogen storage.

Experimentally, two types of samples (carbon nanotube – CNT, NbSe2) were tested and both irradiated by γ-rays and nonirradiated at two temperature levels — room temperature (293 K) and liquid nitrogen temperature (78 K). The irradiated samples were tested concerning the hydrogen absorption capability, and comparative analysis was done. It has been showed that CNT, NbSe2 are sustainable for irradiation. The increasing (∼15%) of hydrogen sorption-desorption capability for carbon nanotubes after irradiation treatment was demonstrated. Low temperature procedure of hydrogen storing showed the 2.9–3.5 mass% of hydrogen. The increasing of hydrogen storing in NbSe2 has not been observed.

In this article, liquefaction of hydrogen gas on platinum (Pt)-supported carbon nano-layers was investigated. In the experiments, H2PtCl6 was used as Pt precursor and to prepare the Pt catalytic reaction nano-layer. The required amounts of H2PtCl6 were mixed with 5 wt% carbon prepared by burning naphthalene in air. The catalyzed carbon and hydrogen gas was loaded into an autoclave. The autoclave was cooled using an external liquid nitrogen bath. After each run, non-liquefied hydrogen gas was vented, and then the autoclave was heated with an external heater for determining the liquefaction hydrogen in the reaction conditions. The yield of liquefied hydrogen was 7.4% weight of Pt-catalyzed carbon for 30 min.

The hydrogenation of aromatic components is of increasing interest due to the more stringent environmental legislation. In this work, the hydrogenation of toluene is approached as a part of the hydrogen storage in the form of liquid organic hydrides (methylcyclohexane). Storage of hydrogen in the form of liquid organic hydrides has been proposed involving methylcyclohexane. Hydrogen is generally regarded as a possible important future energy carrier for automotive and other applications. Hydrogen as an automotive fuel can be used in conventional internal combustion engines, but can also be applied in proton exchange membrane fuel cell vehicles. The catalytic experiments were made in a tubular pyrex glass fixed bed reactor (with a 20 mm diameter). The temperature range was between 150°C and 210°C under a total pressure of about 1 atm. Power law rate models were tested for the experimental data. All the models were analyzed with Analysis ToolPak Lineer Regression Method for the results. Model r = k...

Carbon based material and tungsten are used in ITER as plasma facing materials in the divertor region. Presumably, carbon-tungsten mixed materials will be formed on the surface of the inner components of the vacuum vessel. Therefore, it is necessary to understand incorporation phenomena of hydrogen into carbon-tungsten mixed materials. In this study, carbon-tungsten co-deposition layers were formed by sputtering method using hydrogen RF plasma. Hydrogen incorporation was investigated as a function of atomic ratio of carbon and tungsten contained in the layer. The obtained hydrogen retention was in the range between 0.16 and 0.83 as H/(C+W). The carbon ratio dependence on hydrogen incorporation was not observed It was found that the release behavior of the incorporated hydrogen changes depending on the atomic ratio of C and W in the layer.

Hydrogen exhibits the highest heating value per mass of all chemical fuels. Furthermore, hydrogen is regenerative and environmentally friendly. Hence, hydrogen storage is very important for humans. Hydrogen storage in metal hydrides is considered as one of the most attractive methods. In the present work, the hydrogen absorption-desorption behavior of the boron compounds has been compared. We present recent developments in the search for hydrogen-storage capacity of boron. Boron compounds have a very high energy density, much better than that of liquid hydrogen and also a lot safer. LiBH4 is a complex hydride that consists of 18 mass% of hydrogen. It has stability compared with other chemical hydrides and an easy conversion to H2. Thus, there are a good many reasons that hydrogen-storage materials for LiBH4 will be used in the future at many ranges for power sources. The future warrants further investigations of the B-H system from the viewpoint of hydrogen energy storage.

There are a few different approaches for hydrogen transportation and storage. Hydrogen can be stored as a compressed gas, as a liquid (at 20 K), and in solid state compounds. The first two methods are established technologies with several limitations, the most important being their energy intensive character. Hydrogen storage in metal hydrides is considered one of the most attractive methods. While hydrogen has many obvious advantages, there remains a problem with storage and transportation. Hydrides reduce the risk factors of gaseous or liquid hydrogen. The metal hydrides provide a safe method for fuel storage in hydrogen-powered vehicles. LiBH4 is a complex hydride which consists of 18% mass of hydrogen. Therefore, there are many reasons why hydrogen-storage materials, for example LiBH4, will be used in the future at many ranges. Hydride formation, reaction (absorption and/or chemisorption) between metal (M) and hydrogen (H2) is: M + nH2 MH2n+ Q.

We present a study of the adsorption of hydrogen on nanotube bundles and 4 different carbon fragment geometries as a function of their specific surface. The sorption process is investigated using grand canonical Monte Carlo methods in terms of the gravimetric and volumetric storage densities, as a function of radius, lattice spacing and temperature. The carbon fragments are contrived structures designed to study the effect of density and specific surface on physisorption of hydrogen on carbon nanostructures. They have a specific surface ranging from 2700 to 9220 m2/gr (with decreasing bulk density as the specific surface is increased). At low pressure, the gravimetric adsorbed density of hydrogen was observed to increase with the density of the carbon nanostructure. This trend is reversed at high pressure, where the specific surface available for adsorption plays a more important role. For physisorbed hydrogen, these results confirm that maximizing the specific surface of the adsorbent seems to remain the...

Hydrogen storage in alkali metal-graphite intercalation compounds (AGICs) prepared from cup-stacked carbon nanofibers (A-CNFs, A=K, Rb and Cs) was studied by means of thermal desorption of hydrogen. Hydrogen sorbed to stage-1 K-CNFs amounts to 0.067 dm^3 (STP) per gram of carbon component, most of which is fixed to KGIC as a chemical component.

Superactivated carbon and carbon nanotubes are both considered potential hydrogen carriers. Adsorption isotherms of H2 on activated carbon AX-21 and multi-wall carbon nanotubes were collected with a volumetric method for the temperature range of 77, 233–298 K and pressures up to 7 or 10 MPa. Based on the experimental data for 233–298 K, the limiting heats of adsorption of 7.6 and 1.8 kJ/mol were obtained for activated carbon and carbon nanotubes, respectively. The absolute adsorption was determined with a recently presented method, and the adsorption behavior of H2 on carbon nanotubes was thus reasonably explained. A comparison was given for the storage capacities of compression alone and of filling powder or pellets of the two materials. It was concluded that adsorption of H2 on carbon nanotubes is too weak to enhance storage, but activated carbon enhances storage capacity considerably. The weight percentage of hydrogen stored in carbon powder reaches 10.8% at 77 K and 6 MPa, including the quant...

Hydrogen storage property of Si-carbon nanotube composite was studied. It was found that the carbon nanotube coated Si particle was prepared by the decomposition of tetramethylsilane by using Ni catalyst. The obtained composite was consisted of the spherical Si particle with 300 nm diameter and the surface of Si particle was coated with carbon nanotube with 10 nm diameter. The obtained Si-carbon nanotube composite shows a fairly large hydrogen storage capacity of 2.5 wt%. The amount of storage H2 increased with increasing the preparation temperature and the largest hydrogen storage amount could be achieved at 1273 K for 6 h. Fairly large hydrogen storage capacity could be sustained after 3 cycles of adsorption and desorption.

Atomic hydrogen storage by carbon nanotubes (CNTs) and highly oriented pyrolytic graphite (HOPG) has been studied using a flow catalytic reactor and an ultra-high vacuum surface science apparatus including scanning tunneling microscope (STM), respectively. Defect sites on CNTs as adsorption sites of atomic hydrogen are introduced by oxidation pretreatment using La catalyst. Pd catalysts are then deposited on CNT surfaces for dissociation of H2 into atomic hydrogen, which spills over to the defect sites. In the best case, 1.5 wt% of hydrogen is stored in the defective CNT with Pd particles at 1 atm and 573 K. In temperature programmed desorption (TPD) experiments, H2 starts to desorb at 700–900 K depending on the annealing temperatures of CNTs prior to hydrogen storage. On the HOPG surface, hot atomic hydrogen produced by dissociation of H2 using tungsten wire desorbs from graphite terraces at 400–700 K, which is much lower than that on CNTs. It is possible that one can decrease the desorption temperature by changing the method of H2 dissociation.

Although hydrogen has a great potential as clean energy, safe practical storage of hydrogen for applications such as fuel cells has been a major challenge. NaAlH4 is one of the metal hydrides, which are candidates for hydrogen storage in vehicles. However, the rather slow absorption/desorption kinetics is still a significant drawback. To alleviate this problem, purified NaAlH4 was ground with TiCl3, ZrCl4, or HfCl4. Desorption kinetics and capacities were observed under TPD-like operation. Absorption efficiency was determined by raising the temperature up to 125 °C. Of the three doped metals investigated for the positive effect on facilitating NaAlH4 decomposition, TiCl3 assists the best on the first reaction while ZrCl4 and HfCl4 do for the second one. Despite the kinetics enhancement directly involves with the ZrCl4 amount, there is a threshold of ZrCl4-content which affects. 6% ZrCl4 is considered as an appropriate amount to improve the hydrogen release because it simultaneously decreases the desorption temperature and gives the outstanding rate. In hydrogen desorption, ZrCl4 provides the most amount of released hydrogen, but for hydrogen absorption TiCl3-doped NaAlH4 possesses the highest capacity. It is believed that the metal size is one of the key factors resulting in such the behavior.

Hydrogen storage into multi-walled carbon nanotubes obtained by the decomposition of hydrocarbons using Ni-Li/SiO2 was investigated. The optimized reaction conditions for the synthesis of carbon nanotubes were 873K and W/F=40 g-cat.h/mol, and carbon nanotubes obtained by C2H6 decomposition were found to exhibit fairly large H2 storage capacity of 1 wt% at room temperature. The storage capacity increased with decreasing temperature and a capacity of 5 wt% was achieved at 77K, with 66% of adsorbed hydrogen being desorbable. Hydrogen adsorption by pi orbital in C-C bond coordination is proposed, observing both weakened Raman adsorption C-C peaks and the thermal release of CH4 after H2 storage.

We have investigated the effect of crystallization on the desorption of hydrogen atoms from nanostructured graphite by carrying out the hybrid molecular-dynamics simulation on model systems. It is shown by our simulation that the bond between hydrogen and carbon atoms becomes weaker due to the recrystallization of the nanostructured graphite and that the hydrogen dimer is formed with increasing temperature. We have thus found one possible mechanism of the hydrogen desorption from the nanostructured graphite.

In a nuclear fusion reactor, tritium and its compounds must be recovered for the purpose of fuel recycling and hydrogen gas must be separated from a gas mixture with hydrogen compounds and other molecules. Proton-conducting ceramics have the proper characteristics to aid in this separation. The present paper describes the performance of a hydrogen pump using the one-end closed tube made of a proton-conducting ceramic (CaZr0.9In0.1O3-α, Effective electrode area: 47 cm2) at 800°C. Hydrogen gas was selectively extracted from Ar-H2 mixed gas at the rate of Faraday's low under an applied voltage of 3.5 V. This test apparatus could also electrolyze water vapor and/or decompose methane at the anode to generate hydrogen at the cathode. In the case of argon gas with 0.1% hydrogen, 0.1% methane and 1.2% water vapor, the hydrogen evolution rate was 0.34m1/min at 3.5 V. The current density was 1.2 mA/cm2 and the current efficiency was 79%. Experimental data suggest that water vapor has an important role for the hydro...

Hydrogen gas storage ability in carbon and boron nitride (BN) clusters was investigated by molecular orbital calculations. From single point energy calculations, H2 molecules would enter from hexagonal rings of C60 and B36N36 clusters and octagonal rings of B24N24 cluster because of lower energy barrier. Chemisorption calculation of hydrogen for BN clusters showed that hydrogen bonding with nitrogen atoms was more stable than that with boron atoms. Stability of H2 molecules in BN clusters seems to be higher than that of carbon clusters.

This study is a starting point for creating a new plastic recycling process. The process consists of two spouted bed reactors. In the first reactor, plastic chips are fed and instantaneously thermally decomposed into lower hydrocarbons (gas or vapor). In the second reactor, the hydrocarbons are further decomposed into carbon and hydrogen. Carbon can be utilized as carbon black, activated carbon and so forth. Hydrogen is a useful and clean fuel (no carbon dioxide evolution) and a raw chemical material. In this study, the decomposition of hydrocarbons (methane, ethane, propane, ethene and propene) was investigated to obtain basic data for the second reactor of the process. The hydrocarbons were decomposed in a fixed bed flow reactor packed with 1-mm-diameter α-alumina balls or 1-mm-diameter nickel-plated α-alumina balls, which were used as a decomposition catalyst. Carbon and hydrogen were the main products. The nickel-plated α-alumina balls gave a higher hydrogen production rate than the unplated α-alumina balls. This is caused by the dehydrogenation activity of nickel. For alkanes, the higher the carbon number, the greater the hydrogen production rate. For alkenes, a similar tendency was observed. The hydrogen production rate showed positive temperature dependency and positive hydrocarbon partial pressure dependency. The results obtained in this study showed that production of hydrogen and carbon is possible using the second reactor of the process we proposed.

Molecular dynamics simulations have been performed to study the mechanical properties of armchair-type single-walled and multiple-walled carbon nanotubes under tensile loading with and without hydrogen storage. Advanced bond order potentials were used in the simulations. Hydrogen molecules stored inside or outside nanotubes reduced the fracture strength of nanotubes. During the deformation, some C-C bonds were broken and reconstructed. If hydrogen. molecules were around, hydrogen atoms would compete with the carbon atoms, to form the H-C bonds, which reduces the mechanical strength of nanotubes. Such detrimental effect of hydrogen is enhanced if the curvature of the tubes is increased, or if hydrogen is stored in a multiple-walled carbon nanotube.

A tritium cleanup system has been conceptually developed for the large helical device (LHD) at the National Institute for Fusion Science. The system is a processing device employed to remove tritium from exhaust gas. In the exhaust gas discharged from the LHD in normal operation, the major part of tritium constituents should be in a form of hydrogen molecules because the fuel used in plasma experiments with the LHD is hydrogen molecules. From this viewpoint, we have designed a tritium cleanup system, which is characterized by tritium being removed and stored in a form of hydrogen molecules with less impurities, like oxygen and carbon, and its decomposition and the separation processes are introduced to convert various tritiated compounds into a form of hydrogen molecules of high purity. Besides these, there is another aspect in that getter materials are applied in both decomposition of tritiated compounds and storage of hydrogen molecules containing tritium.The system design is composed of three essential component parts: a hydrogen separator, a hydrogen absorbing vessel, and a decomposition process vessel. The hydrogen separator and the decomposition process vessel make a process loop repeat to remove hydrogen into a form of hydrogen molecules with less impurities. It ismore » important that 'less impurities' means having a less bad influence on hydrogen-absorbing materials used in the storage vessel.We think that the hydrogen separator will be manufactured by employing a palladium hydrogen purifier system, which is available in the marketplace, and the hydrogen storage vessel will also be manufactured by using hydrogen-absorbing alloys like titanium. Thus, the serious problem imposed on us is how to realize the decomposition process vessel. To develop the decomposition process vessel, we thought nonvolatile getter materials were promising and carried out performance tests of methane decomposition by the nonvolatile getter materials, where methane was used because it is hardly decomposed and there is little data for a flowing-gas system.The tritium cleanup system that was designed is presented. Also, a methane decomposition curve with ZrNi alloys used as one of the typical nonvolatile getter materials is shown, and the probability of the realization of the decomposition process vessel is examined.« less

Activated carbon modified by impregnation with iron (III) chloride solution (Fe‐ACs) were studied to try to raise their adsorption capacity for hydrogen sulfide, a malodorous substance. The surface area and pore volume of activated carbon were decreased by impregnation, but the amount of hydrogen sulfide adsorbed onto Fe‐AC was larger than that onto raw activated carbon (R‐AC). In particular, a large increase of the amount adsorbed onto Fe‐AC was noted at low equilibrium pressure. It was assumed that the increase of amount of hydrogen sulfide adsorbed onto Fe‐AC was due to the chemical interaction between iron (III) chloride on the pores in addition to the physical adsorption onto pores of activated carbon. Fe‐AC shows a high selectivity for hydrogen sulfide.

Hydrogen is taken up by a layer structured compound β-ZrNCl during its chemical vapor transport with NH4Cl in a sealed silica tube. The transported sample can be further hydrogenated by hydrogen spillover, and dehydrogenated by oxidation with Cl2 and KMnO4. The infrared absorption spectra indicate that the hydrogen is taken up in the double ZrN layer of β-ZrNCl, coordinating to a nitrogen atom. The second moments of 1H-NMR spectra suggest the formation of hydrogen pairs in β-ZrNCl. A motional line narrowing of the 1H-NMR spectrum was observed at temperatures around 200 K. The activation energy for the jumping motion of the hydrogen was determined to be 10.6 kJ/mol from the temperature dependence of the spin-lattice relaxation time. A possible structural model for the location of hydrogen was proposed.

A hydrogen probe made of nickel tubing has been used to monitor the release of hydrogen from coal liquid solvents at elevated temperatures and pressures. A knowledge of this release rate is helpful in determining the overall hydrogen balance for coal liquefaction operations, in choosing among alternative solvents and in evaluating the validity of model compounds. The hydrogen release was found for coal liquids to reach a constant value when the reactor temperature was steady. In the case of some model compounds the amount of hydrogen released continued to increase and equilibrium was not attained during a 10 hours measurement period. For the coal liquids the total pressure of the system was found to increase sharply with time indicating the production of gases other than hydrogen, while for the model compounds the total pressure increases were almost parallel to the increases of the hydrogen partial pressure. A correlation was developed for the percentage of hydrogen released with the aromatic fraction di...

State-of-the-art hydrogen separation technologies operate at/or near ambient temperatures and are not considered very effective with gases containing low concentrations of hydrogen (such as coal-gas) and are susceptible to common impurities such as H2S, H2O, and NH3. Energy Research Corporation is developing an alternate, versatile process for hydrogen separation from any hydrogen-containing gas. This novel process involves oxidation of hydrogen at a gas diffusion anode to hydrogen ions, transportation of the ions under applied electrical field to a cathode, and reduction of the hydrogen ions at the cathode to hydrogen gas. The device offers many attractive features, including high hydrogen recovery (>90%), high product purity (>99%), tolerance to a variety of impurities, flexible product pressure, efficient operation with very dilute gases, negligible pressure loss, and wide operating pressure range including atmospheric. The feasibility of this electrochemical hydrogen separation device (EHSD) ...

The differential permeation of hydrogen sulfide through a microporous Vycor-type glass membrane was found in the hydrogen and hydrogen sulfide separation system. Separation factors of less than 1.0 were obtained at 10°C under higher pressures of a feed gas mixture having a low hydrogen concentration.

Metal hydrides provide an efficient and safe method for storing hydrogen. Hydrogen can be stored indefinitely and released as needed for a number of energy usages. The commercially available alloys for storage are LaNi5-based, FeTi-based, and Mg-based alloys. In this paper we conduct an overall review of these alloys and compare them with other alloys, and in particular with zirconium based binaries and pseudobinaries. Also described in this paper is the apparatus required for hydrogen absorption and desorption experiments.

The hydrocarbon formation of carbon materials exposed to hydrogen atoms and ions is reviewed. It turns out that surface conditions and modification play a major role in hydrocarbon formation. Graphite exposed to hydrogen plasma exhibits surface properties similar to those of amorphous hydrogenated carbon films and redeposited carbon films. The total chemical erosion yield of these carbon materials is similar for thermal atomic hydrogen and for energetic hydrogen ions, reaching maximum values of --0.1 eroded carbon per incoming hydrogen. However, the spectrum of formed hydrocarbons is determined by the energy of the impinging hydrogen.

The hydrogen induced clusters in a dense lithium vapour are studied. It is shown that for temperatures T ⪆ 2400 K and hydrogen atom pressures PH 0·01 torr almost all hydrogen is present in the bound state as LigH clusters. The possibility of the experimental observation of these clusters is discussed.

Investigations of the compatibility of steam generator or heat exchanger materials of a high-temperature nuclear reactor with both the primary and the secondary media of the coolant circuits were conducted. This includes studies on the metal-water reaction, the hydrogen generation involved, and the permeation of the hydrogen into the primary circuit. Permeating hydrogen can cause oxide film reduction on the primary side of the tubes and decarburization of the material. Other phenomena of interest are the possible deposition of carbon and/or the carburization of the steel by the small amounts of carbon monoxide present in the inert helium, used as coolant gas. In addition, the hydrogen permeation under low partial pressures was investigated. The hydrogen release rates (due to the metal-water reaction) were determined for several types of steels for different temperatures. The results served as a basis for an estimate of the hydrogen delivery from the secondary circuit into the primary circuit and its influence on the required gas purification capacity. An attempt is made to explain the irregularities of the hydrogen release rates observed. It appears that the carburization problem is not of major significance under the low carbon monoxide concentrations that must be expected in the coolantmore » under normal operation conditions.« less

The behavior of hydrogen in liquid sodium containing relatively large amounts of oxygen were investigated with the aid of the hydrogen sensor of niobium membrane. The partial pressure of the hydrogen in liquid sodium at hot zone of a cold-trapped natural circulation sodium loop was measured as functions of temperatures of the cold trap and the hot zone of the loop. It was observed that at constant cold trap temperature the partial pressure of hydrogen in sodium increases with increasing the hot zone temperature. This study also showed that, keeping the temperature of hot zone constant, a logarithmic plot of hydrogen concentration calculated from the equilibrium hydrogen partial pressure vs. the reciprocal temperature of cold trap yields a straight line whose slope is nearly equal to that on the solubility of sodium hydroxide in sodium. Finally, it was observed that the permeation of hydrogen in sodium through a niobium membrane is a process controlled by diffusion. But the permeability for hydrogen in nio...

The plasmo of a hydrogen stream maintained in a microwave field has been shown to be an excellent and reliable source of atomic hydrogen. In addition, at low gas pressures the atomic hydrogen stream contains little if any sensible heat or enthalpy. Numerous accounts have been reported on the use of atomic hydrogen as a reactant with both inorganic and organic substances. Often the intermediates or products from such reactions could not have been synthesized as effectively, if at all, by other means.

The effect of pressure on hydrogen entry into steel has been investigated by studying the rate of permeation of hydrogen through a thin Fe diaphragm. The results indicate that as the pressure increases the surface coverage of hydrogen atoms, which determines the rate of hydrogen permeation, becomes increasingly controlled by the rate of diffusion of hydrogen dissolved in the aqueous solution. Above 250 atm. the linear increase in the permeation rate appears to be due to the effect of pressure on the state of hydrogen segregated at voids in the metal. The work is of significance in relation to the cathodic protection of steel structures immersed at depth in the sea.