Effect of oxygen on the production of abnormally high heats of interaction with hydrogen chemisorbed on gold

Abnormally high heats, exceeding 1600 kJ/mol (16 eV) per molecular oxygen, are generated by interaction of the oxygen with the hydrogen adsorbed on gold surfaces at 125 °C. The highest heats were observed during the interactions of fine gold particles supported on titanium oxide, approaching 1700 kJ/mol for three consecutive 100 nmol pulses of O₂ interacting with the adsorbed hydrogen atoms. The heats rapidly decrease after the hydrogen is consumed. It was also observed that the interactions of the gold particles with pure oxygen in the presence of noble gases, such as argon and helium, produced the heats markedly higher than those observed in the absence of noble gases. The abnormally high heats revealed by this work reach values from 3.5 to 6.1 times higher than the heats of formation of gaseous water from molecular hydrogen and oxygen.     

Heats of displacement of hydrogen from palladium by noble gases

It has been observed that noble gases, such as helium, neon and argon produce heat evolution when contacted with Pd powder partially saturated with hydrogen. These phenomena have been studied with flow-through adsorption microcalorimetry. The observed exothermic effects are comparable to those usually associated with the heat of sorption of hydrogen in palladium. It is suggested that the noble gases displace the adsorbed H species from the surface of Pd, causing their reabsorption in the Pd lattice with the exothermic heat of PdH bonds formation, or the formation of H₂, both heat evolutions being observed with a flow-through microcalorimeter.     

Hydrogen and noble gas interactions with iron nano-flakes

Exposure of pure iron nano-flakes to hydrogen generates a high heat evolution associated with hydrogen uptakes shown by flow-through microcalorimetry. A large part of the hydrogen was found to be irreversibly absorbed by the iron flakes at 220 °C and atmospheric pressure, but an increased desorption of hydrogen was achieved by noble gases, such as helium and argon. Thus the iron surfaces displayed strong affinity for hydrogen, but also, surprisingly, for the noble gases, which were found to be able to displace hydrogen from the iron surfaces.The uptake of hydrogen by the iron flakes was observed to reach 9 wt.% after exposure for 5 h, which may be of interest in hydrogen storage applications. Desorption with the help of argon may provide an acceptable method of hydrogen recovery.     

Preparation of ZnO nanopowders by thermal plasma and characterization of photo-catalytic property

Nano-sized zinc oxide (ZnO) powders were prepared via a thermal plasma process from micro-sized zinc powder while oxygen was employed as a reaction gas. Two different carrier gases, oxygen and argon, were evaluated and the flow rate of the reaction gas was controlled. The photo-catalytic activities of ZnO powders were evaluated by measuring the degradation of methylene blue (MB) in water under the UV and visible region. The prevailing goal of this study is to improve the photo-catalytic activity of nano-sized ZnO powders for the removal of environmental pollutants. The ZnO nanopowders were characterized by XRD, SEM, BET, and UV-vis spectrometry. Their mean crystallites sizes ranged from 26.5 nm to 48.6 nm. It was confirmed by a XRD analysis that the ZnO nanopowders had a high quality wurtzite structure. SEM and XRD results show that the size of the particles synthesized increased with an increase of the flow rate of the oxygen reaction gas. The powder obtained using the argon carrier gas with higher oxygen reaction gas flow rate was more rod-shape. The MB decomposition rates of the obtained ZnO nanopowders were studied under the UV and visible region. In the UV region, synthesized ZnO could decompose MB as well as commercial ZnO. However, in the visible region, the MB decomposition rate obtained using ZnO was much higher than that by commercial ZnO.     

Einfluß adsorbierter Gase auf Supraleitung und elektrische Leitfähigkeit dünner Thalliumschichten

Some effects of adsorbed gases on superconductivity and normal electrical conductivity of thallium films have been investigated. These films were 50 to 700 Å thick and were produced by condensation of thallium vapor on a crystalline quartz, plate at about 100 °K. At 3 °K adsorbed oxygen lowers the transition temperature and slightly increases the residual resistance. Heating of the film results in a steep increase of resistivity at about 15 °K and shifts the transition temperature to a considerably higher value. The changes in electrical conductivity and transition temperature increase with decreasing film thickness. With the thinnest films, the resistivity increases up to 50 per cent. The maximum shift of the transition temperature is 0·3 degrees. From the resistivity behavior, it can be inferred that the adsorbed oxygen molecules accept conduction electrons at 15 °K, thus changing the kind of their bond. This shows up in a decrease of the effective film thickness by 5 to 10 Å. Further, results of adsorption experiments with hydrogen, nitrogen and argon are reported. These results depend to a great extent on the purity of the gases.     

Working gases in thermoacoustic engines.

The best working gases for thermoacoustic refrigeration have high ratios of specific heats and low Prandtl numbers. These properties can be optimized by the use of a mixture of light and heavy noble gases. In this paper it is shown that light noble gas-heavy polyatomic gas mixtures can result in useful working gases. In addition, it is demonstrated that the onset temperature of a heat driven prime mover can be minimized with a gas with large Prandtl number and small ratio of specific heats. The gas properties must be optimized for the particular application of thermoacoustics; it cannot be assumed that high specific heat ratio and low Prandtl number are always desirable.     

Vitesse des ultrasons dans les gaz rares sous haute pression a la temperature de 298.15 K

By a Pulse Echoes Overlap Method, the speed of ultra sound has been worked out at 15 MHz for the complete noble gas series at temperature 298.15 K in a very wide density range (which corresponds at pressures up to 10 kbar for light noble gases). When the molar density and the isothermal compressibility coefficient are known, the ratio of specific heats can be deduced as a function of density. In the case of argon the evolution of both c_p and c_v has been obtained separately and a value of 3R is determined before the fluid-solid transition. These thermodynamical quantities have been compared with those derived from the numerical equation of state of Hansen for a Lennard-Jones fluid. One notices good agreement between predictions and experimental results for hot gases.     

Study of hysteresis behavior in reactive sputtering of cylindrical magnetron plasma

In order to make sufficient use of reactive cylindrical magnetron plasma for depositing compound thin films, it is necessary to characterize the hysteresis behavior of the discharge. Cylindrical magnetron plasmas with different targets namely titanium and aluminium are studied in an argon/oxygen and an argon/nitrogen gas environment respectively. The aluminium and titanium emission lines are observed at different flows of reactive gases. The emission intensity is found to decrease with the increase of the reactive gas flow rate. The hysteresis behavior of reactive cylindrical magnetron plasma is studied by determining the variation of discharge voltage with increasing and then reducing the flow rate of reactive gas,while keeping the discharge current constant at 100 m A. Distinct hysteresis is found to be formed for the aluminium target and reactive gas oxygen. For aluminium/nitrogen, titanium/oxygen and titanium/nitrogen, there is also an indication of the formation of hysteresis; however, the characteristics of variation from metallic to reactive mode are different in different cases. The hysteresis behaviors are different for aluminium and titanium targets with the oxygen and nitrogen reactive gases, signifying the difference in reactivity between them. The effects of the argon flow rate and magnetic field on the hysteresis are studied and explained.     

Interaction of Gaseous Reagents on Gold and Nickel Nanoparticles

The adsorption and interaction of hydrogen, carbon monoxide, and oxygen with gold and nickel nanoparticles is studied by scanning tunneling microscopy and spectroscopy. It is established that the HCO radical is formed on gold nanoparticles by the reaction between adsorbed H₂ and CO, which is subsequently oxidized by oxygen to water and CO₂. At the same time, after exposure to H₂ and CO, nickel nanoparticles coated with oxide are reduced. The formation of adsorbed HCO on such nanoparticles is not observed.     

TiO2表面氧空位对NO分子吸附的作用

采用程序升温热脱附(TPD)实验方法测定了NO在TiO2表面吸附后的脱附谱，利用分子轨道理论研究了TiO2吸附NO的原子簇模型及吸附前后的原子簇能级变化．结果表明，NO在TiO2表面吸附后可在两个峰值温度450和980K脱附出N2．TiO2表面经预覆氧处理后，N2的脱附量降低．吸附时NO中的O能够占据TiO2表面氧空位并与N脱离，而N原子则相互结合成为N2脱附．分子轨道理论计算证明在TiO2(110)表面能够存在氧空位并具备吸附NO的结构条件．     

Simulation study of argon adsorption on (0 0 1) faces of phyllosilicates

Grand Canonical Monte Carlo molecular simulations have been performed for argon and nitrogen adsorption on the basal surfaces of phyllosilicates without surface cations. The results have been compared with derivative isotherms analysis of experimental data. An optimization of the surface-Ar interaction has been performed by varying the oxygen atom LJ ?/k_B parameter and the optimized value was used to perform the nitrogen adsorption simulations. The analysis of the argon adsorption simulation indicates that adsorption mechanisms are more complex than may be suggested by experimental results obtained by low-pressure adsorption. The structure of the adsorbed film has a marked dynamic behaviour and the monolayer capacity strongly depends on the equilibrium relative pressure. For nitrogen adsorption, while high pressure behaviour is simulated adequately, some deviation is observed in low-pressure region of the isotherms suggesting that additional simulation and perhaps the use of a more sophisticated potential to model the nitrogen molecule can be necessary to understand fully the behavior of this gas on clay minerals.     

Is the thermodynamic behavior of the noble fluids consistent with the principle of corresponding states?

The applicability of the Principle of Corresponding States (PCS) for the noble fluids is discussed. We give the thermodynamic evidence for the dimerization of the liquid phase in heavy noble gases like argon, krypton etc. which manifests itself in deviations from the PCS. The behavior of the diameter of the entropy and the density is analyzed. It is shown that these characteristics are very sensitive to the dimerization process which takes place in the liquid phase of heavy noble gases.     

Study of the interaction of atomic particle fluxes with fine-grained media

The behavior of fine-grained (1–5 μm) boron and tungsten powders upon exposure to heat, electric field, and argon and hydrogen plasma ions is studied. A wide range of powder modifications caused by the above factors is sequentially considered. The driving forces and processes controlling the describedmodifications are presented.     

Assessment of pore structure parameters for polymer-templated mesoporous molecular sieves by means of nitrogen and argon adsorption

Pore size, wall thickness, and microporosity of polymer-templated mesoporous silica (PTMS) can be controlled by using different nonionic triblock copolymers as soft templates. The evolution of the pore structure of PTMS was studied by using nitrogen and argon adsorption at 77 K in addition to powder X-ray diffraction and transmission electron microscopy.     

铝和铝-锂合金的爆炸烧结试验研究

 本文研究了纯铝粉和快速凝固铝-锂合金粉的爆炸烧结工艺，测量了烧结体的密度，观察了烧结体内的微观组织和断口形貌。试验用粉末材料为水雾化铝粉、氮气雾化铝粉和氩气雾化铝-锂合金粉。试验时把粉末材料装在包套内，粉状炸药装在包套外的纸筒内，炸药从一端起爆。根据文中给出的爆炸烧结工艺参数的设计原则，通过系统地试验，已获得Φ17×70 mm的铝-锂棒材和Φ100×100 mm的纯铝棒材，相对密度超过98%，无中心孔（马赫孔）。微观组织和断口形貌观察结果表明：颗粒之间已达到焊接结合，结合区是由超细微晶组成，颗粒内部仍保持原始粉末的急冷组织。试验结果还表明：包套最终运动速度、包套内径、粉末材料强度、粉末材料表面氧化膜的厚度都是影响爆炸烧结质量的重要因素。     

Coexistence of non-registered monolayer and bilayer solid films: Statistical mechanics

A statistical mechanical theory is developed for low temperature solid monolayer and bilayer films of inert gases which are not in registry with the adsorbing substrate. The free energy is evaluated in terms of harmonic lattice vibrations of the solids, which is a quasiharmonic approximation. The lattice constant discontinuity in the transition under compression from the monolayer to the bilayer is found to be small, in accord with experiments on the adsorption of xenon and of krypton on silver and of argon on basal plane graphite. The calculations use realistic models for adatom interactions and substrate holding potentials in these three systems. At the bilayer formation, the lattice constant is still distinctly larger than that of the corresponding bulk solid under its vapor pressure. Thermodynamic functions of the phases at monolayer and bilayer coexistence are evaluated: the spreading pressure and the bilayer latent heat of adsorption are nearly constant along the coexistence curve for temperatures of 1 to 35 K. The calculated difference between the latent heats of adsorption of the monolayer and the bilayer is in good agreement with experimental data for the xenon/silver system, but it is smaller than the experimental difference for the krypton/silver and argon/graphite systems.     

Effect of Addition of Process Control Agent (PCA) on the Nanocrystalline Behavior of Elemental Silver during High Energy Milling

Mechanical Alloying (MA) or High Energy Milling has been a subject of great interest for last few decades. However, in the majority of the cases the investigations are confined to areas like alloying in binary or multi-component systems from premixed powders. Very little work has been reported on high-energy milling of pure metals. There are some reports on mechanical alloying of pure metals that undergo polymorphic transformation on milling, but relatively few papers have been reported in the literature pertaining to attrition milling of pure metals, which do not fall under this category. One such attempt has been made in this investigation by subjecting a noble metal like silver with fcc crystal structure to attrition milling. The present work deals with the investigation of the effect of addition of a process control agent (PCA) on the nanocrystalline behavior of elemental silver powder subjected to high energy milling in an attritor. Elemental silver powder was subjected to attrition milling with and without addition of stearic acid as PCA. The powder samples drawn at periodic intervals during the course of milling were subjected to characterization using techniques like XRD, SEM and DSC. The variation in particle shape morphology, crystallite size and lattice strain as a function of PCA was studied.     

Effect of reduction on graphitization behavior of mesophase pitch-derived carbon fibers

Chemically reduced solid-state mesophase pitch carbon fibers below 1000 °C in a flow of hydrogen gas were treated up to 3000 °C in an argon atmosphere in order to evaluate the effect of hydrogen on the graphitization behavior. Major phenomena observed during the reduction process are chemical transformation from an ether to a hydroxyl group (corresponding to the rupture of the C-O-C bond) and their subsequent evolution as gases. Finally, oversupplied hydrogen might be utilized to satisfy the dangling bond. For the sample heat treated at 3000 °C, the low crystallinity indicates that hydrogen atoms covalently bonded to the end planes of graphitic layers act as an effective barrier to crystallite growth.     

A periodic DFT study on adsorption of small molecules(CH4,CO,H2O,H2S,NH3)on the WO3(001) surface-supported Au

Gas molecules(such as CH4,CO,H2O,H2S,NH_3)adsorption on the pure and Au-doped WO3(001)surface have been studied by Density functional theory calculations with generalized gradient approximation.Based on the the calculation of adsorption energy,we found the most stable adsorption site for gas molecules by comparing the adsorption energies of different gas molecules on the WO3(001)surface.We have also compared the adsorption energy of five different gas molecules on the WO3(001)surface,our calculation results show that when the five kinds of gases are adsorbed on the pure WO3(001)surface,the order of the surface adsorption energy is CO>H2S>CH4>H2O>NH3.And the results show that NH3 is the most easily adsorbed gas among the other four gases adsorbed on the surface of pure WO3(001)surface.We also calculated the five different gases on the Au-doped WO3(001)surface.The order of adsorption energy was found to be different from the previous calculation:CO>CH4>H2S>H2O>NH3.These results provide a new route for the potential applications of Au-doped WO3 in gas molecules adsorption.     

Nitrogen containing barium titanate: Preparation and characterisation

The purpose of this work is to study the incorporation of nitrogen into barium titanate at oxygen sites by ammonolysis. The nitrogen content of the resulting barium titanate powders strongly depends on the flow rate of ammonia and the ratio Ba/Ti. The amount of resulting oxygen vacancies is lowered by co-doping with fluoride and tantalum.By avoiding an excess of BaO and exchanging 10 mol% Ti by Ta it is possible to produce powders with nitrogen content of more than 1 wt%. Partial substitution of barium oxide by barium fluoride also increases the nitrogen content. The nitrogen containing powders are colored and show an additional absorption at 500 nm measured in the UV/vis reflectance spectrum. The concentrations of nitrogen and fluorine in the samples were determined using ion-sensitive electrodes. X-ray powder diffraction shows the composition of the powders. The thermal stability was investigated by thermogravimetric analysis, and in order to calculate the specific surface area the three-point BET method was used.