Showing papers on "Chemisorption published in 1968"
TL;DR: In this paper, the chemisorption of various gases on the Pt(100) single crystal surface has been studied, using low energy electron diffraction (LEED), mass spectrometry, flash desorption and work function measurements, at gas pressures usually ⩽ 1 × 10−7 Torr and at temperatures between 25°C-1400°C.
253 citations
TL;DR: In this paper, the surface area and hydrogen chemisorption measurements made on palladium-black samples were used to determine surface areas of particles of a size where other techniques, such as electron microscopy, X-ray linebroadening and small-angle scattering, often fail through interference of the support.
228 citations
TL;DR: In this article, it was shown that two types of adsorption sites exist on the surface of porous silica glass (Corning code no. 7930) for the adaption of polar molecules, such as ammonia.
Abstract: It has been shown previously that two types of adsorption sites exist on the surface of porous silica glass (Corning code no. 7930) for the adsorption of polar molecules, such as ammonia. One site ...
177 citations
TL;DR: In this paper, the authors used low-energy electron diffraction to define the structure and the growth mechanism of the adsorbed layers of two-dimensional compounds, based on the mean distance between atoms.
177 citations
TL;DR: In this article, carbon dioxide chemisorption studies at 0 °C were used to determine the relative basicities of alkali-promoted reduced magnetite catalysts, showing that a higher surface basicity correlates with a lower methane selectivity in the Fischer-Tropsch synthesis.
175 citations
TL;DR: In this article, the phase distribution of equilibrated copper-nickel films with equal surface compositions has been analyzed and shown to be a constant multiplicity over the alloys of equal surface composition.
98 citations
TL;DR: In this article, the authors studied the chemisorption of hydrogen sulfide on some nickel catalysts in the temperature range 550-645 °C and showed that a saturation layer was formed at ratios above 5 × 10−6, approximately, and at ratios at 10−3 bulk sulfide (Ni2S3) was formed.
91 citations
TL;DR: In this paper, the authors measured the amount of water adsorbed and the area covered by oxygen in a graphon sample at 500°C to different carbon burn-off up to 70% in order to produce samples of varying active surface areas.
75 citations
TL;DR: In this paper, the authors focus on reactive collision at a gas-solid interface and gaseous atomic species containing unpaired electrons and present an approach of the gaseus atom corresponding to chemisorption.
Abstract: Publisher Summary This chapter focuses on reactive collision at a gas–solid interface and gaseous atomic species containing unpaired electrons For chemical interaction between surface and gaseous atoms, an approach of the gaseous atom corresponding to chemisorption is required Elucidation of the elementary processes associated with reaction requires, therefore, some information on the bond strengths between atoms and surfaces Desorption of an adatom represents essentially the reverse of the adsorption process Thus, either an atom or a diatomic molecule may be desorbed depending on the particular conditions In contrast to the catalytic recombination process, where the over-all chemical change is independent of the nature of the surface, chemical reactions between gaseous atoms and surface lattice atoms can involve an array of chemical processes Most of the atom detectors that fall into the first category transduce the heat of atom recombination into a temperature rise of a thermocouple or into an enthalpy change at constant temperature in a metal filament calorimeter
64 citations
TL;DR: In this article, the interaction of oxygen with a polycrystalline tungsten ribbon has been examined using electron stimulated desorption, and at least three binding states of adsorbed oxygen have been identified: a physically adorbed state which forms at 20° K, and two chemisorbed states designated β 1 and β 2.
61 citations
TL;DR: In this paper, a theoretical treatment of the observed experimental behavior of both the oxygen uptake and work function of the oxidized aluminum film can be accounted for by a two-stage reaction.
TL;DR: In this article, the authors compared the properties of diamond powders with different surface oxides and showed that about one third of the surface bonds can be saturated with H, F, Cl, Br and O.
TL;DR: In this paper, the effect of various absorbed gaseous species on the adhesion and friction of tungsten was investigated in a vacuum of 10−10 Torr with a hemispherical rider specimen contacting a flat.
Abstract: An investigation was conducted to determine the effect of various absorbed gaseous species on the adhesion and friction of tungsten. Experiments were conducted in a vacuum of 10−10 Torr with a hemispherical rider specimen [(100) tungsten] contacting a flat. The atomic planes of tungsten examined on the flat included the (100), (110), and the (210). The gases absorbed to these tungsten surfaces included hydrogen, oxygen, carbon dioxide, hydrogen sulfide, and a homologous series of hydrocarbons (methane through decane), as well as ethylene and acetylene. The results of the study indicate that the presence of any gas, even hydrogen, on the tungsten surface will reduce adhesion and friction. Less than a monolayer of oxygen adsorbed on tungsten is sufficient to reduce appreciably the friction of tungsten crystals. For hydrocarbons an increase in chain length (methane through decane) resulted in a progressive decrease in friction. Furthermore, with ethane, ethylene, and acetylene, friction decreased with an increase in the number of carbon‐to‐carbon bonds.
TL;DR: In this article, a combination of hydrogen chemisorption or X-ray diffraction line-broadening measurements, plus carbon monoxide chemisors, was used to estimate the relative amounts of nickel in comparatively large crystallites (∼50 A) and in an essentially atomic state of dispersion, as well as the specific surface area of the nickel in these two size ranges.
TL;DR: In this article, three forms of nitrogen adsorption have been detected: physical, weak, and strong chemisorption, and a conclusion has been made on the mechanism of nitrogen adaption on the basis of volumetric measurements of amount adsorbed and work function.
TL;DR: In this article, electric field effect on chemisorption of oxygen on zinc oxide, discussing electron transfer mechanism was discussed, and electron transfer was used to transfer electron from electron to zinc oxide.
TL;DR: In this paper, it was shown that the resonance at g = 2.10, developed upon heating of noble-metal-supported catalysts in hydrogen, results from the reduction of iron oxide to metallic iron also present on the supported catalyst.
TL;DR: In this paper, tritium tracer studies of the nature and reactivity of adsorbed 14C-ethylene were made using 5% alumina-supported palladium, rhodium, and platinum catalysts in a microcatalytic reactor between 20 ° and 200 °C.
TL;DR: Using chromatography, rates of chemisorption of hydrogen on a nickel catalyst were measured at 1 atm pressure and 243-297 °K as discussed by the authors, and the observed activation energy was 13.8 kcal/mole.
TL;DR: In this article, it was shown that the surface state due to chemisorbed oxygen determines the steady state photoconductivity and the equilibrium dark conductivity in the adsorbate ambient.
Abstract: The temperature dependence of the equilibrium conductivity and the temperature and illumination dependence of the steady‐state and transient photoconductivity of Cu and Cl doped sintered CdS layers are strongly affected by atmospheric oxygen. It is shown that the surface state due to chemisorbed oxygen determines the steady‐state photoconductivity and the equilibrium dark conductivity in the adsorbate ambient. Further, an oxygen chemisorption surface state, 0.9 eV below the conduction band, together with the associated surface space‐charge region cause the photocurrent to undershoot the equilibrium current upon cessation of illumination, and to overshoot the steady‐state photocurrent on reillumination.
TL;DR: In this article, a scheme for chromatographic thermodesorption apparatus and experimental conditions to obtain information on adsorbate-adsorbent interaction are presented and the effects of temperature conditions, amount of substance, and heating rate are discussed.
TL;DR: The results of the competitive hydrogenation of 14 pair combinations of cycloalkenes on alumina-supported platinum catalysts at 25.0° and 1 atm are reported in this paper.
TL;DR: In this article, it was shown that chemisorption of ions other than Ca 2+ and dissociation of surface OH groups provided a net negative charge of about 0.5 elementary charge unit per calcium adsorption site.
TL;DR: In this paper, the free-radical mechanism was replaced by the chemisorption mechanism, which assumes the dissociative adsorption of the organic halide on the silicon-copper double center (the silicon and the copper being joined by a chemical bond).
Abstract: The direct synthesis of organohalogenosilanes, particularly methyl- and phenylchlorosilanes, is the main process for the production of the monomers required for silicone polymers. This complex heterogeneous catalytic reaction involves the interaction of a gaseous component (the organic halide) with two solid components (silicon and copper), the relative quantities of which change as the reaction proceeds. The mechanism of the direct synthesis has not yet been conclusively established. The free-radical mechanism originally proposed supposes the formation of organic free radicals. On the other hand, the chemisorption mechanism suggested later postulates the dissociative adsorption of the organic halide on the silicon-copper double center (the silicon and the copper being joined by a chemical bond). The results obtained so far indicate that the chemisorption mechanism is of decisive importance, but it is not impossible that both mechanisms operate simultaneously.
TL;DR: In this paper, the inhibitive effect of nitrogen chemisorption on the adsorption of carbon monoxide has been studied over a singly and a doubly promoted iron synthetic ammonia catalyst.
TL;DR: In this article, a stable state behavior concerning oxygen reduction in alkaline medium has been examined, showing that the limiting factor is a surface-potential barrier which inhibits the oxygen chemisorption step.
TL;DR: In this article, low energy electron diffraction (LEED) and inelastic electron scattering (IES) measurements are used to characterize the chemisorption of hydrogen onto the Nb (110) surface.
Abstract: Low‐energy electron diffraction (LEED) and inelastic electron scattering (IES) measurements are used to characterize the chemisorption of hydrogen onto the Nb (110) surface. It is found that hydrogen chemisorbs readily at room temperature, causing no rearrangement or faceting of the surface, and with only small changes in the work function. Distinctive changes in the intensity curves indicate that the hydrogen is chemisorbed in a crystalline layer with the same lattice structure as the Nb (110). Removal of the hydrogen is easily accomplished by heating to 400°C, and residual gas measurements show a higher mass 1 peak than usual, indicating that the hydrogen is adsorbed as atoms. Changes in both the LEED intensity curves and in the IES measurements both suggest that the beam penetrates more deeply into the crystal when hydrogen is chemisorbed than for the clean surface.
TL;DR: In this paper, the e.s. signals from F, V and S centres have been measured in MgO over the fast neutron dose range from 5 × 1016 to 1020 fast neutrons cm-2.
Abstract: The e.s.r. signals from F, V and S centres have been measured in MgO over the fast neutron dose range from 5 × 1016 to 1020 fast neutrons cm–2. S centres are initially generated at a faster rate (% available sites per unit dose) than F centres but saturation concentrations of these isolated defects are similar. The specific surface areas of some MgO powders increase on neutron irradiation and this effect has been ascribed to a fragmentation of aggregates at grain boundaries. The fresh surfaces thus produced can play an important role in the radiation-induced reactivity of MgO towards oxygen. The height of the charge barrier produced by reaction of oxygen with F centres has been inferred from the chemisorption kinetics and is shown to be inversely proportional to the F centre concentration, in agreement with theory.
TL;DR: In this article, two specially designed infrared cells are described for use in studying chemisorption gas-solid reactions, and the gas phase spectrum of diisopropyl methyl phosphonate and dimethyl methylosphonate both before and after reaction with a transition metal solid, FeCl3, is shown.
Abstract: Two specially designed infrared cells are described for use in studying chemisorption gas-solid reactions. The gas phase spectrum of diisopropyl methyl phosphonate and dimethyl methyl phosphonate both before and after reaction with a transition metal solid, FeCl3, are shown, using these new cells. Assignments are made for all bands in the spectrum of these compounds.