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  • 1
    ISSN: 1432-0630
    Keywords: 79.20R ; 34.50 ; 34.70 ; 79.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Transient adsorption or skipping motion of silicon ions scattered under specular conditions from a Cu(111) surface is reported. The phenomena is identified on the basis of the observation of discrete energy loss peaks in the scattered positive and negative ion kinetic energy distributions, together with their behaviour upon variation of the crystal azimuth, incidence angle of the beam to the surface, and scattering angular distributions. Up to five reflections in a binding potential were seen. We propose that the beam is trapped following an energy loss, by electron-hole pair or plasmon excitation, which exceeds the incident beam energy component normal to the surface. The results lend strong support to the thesis that ion beam techniques can probe the family of potential surfaces upon which adsorption and reaction, at thermal energies, proceed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 8 (1987), S. 133-145 
    ISSN: 1572-9567
    Keywords: atmospheric effects ; coal ; heat capacity ; modeling ; water desorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract During the development of transferable measurement techniques for the heat capacity of raw coal, it was observed that the atmosphere in sealed sample cells affected the thermal behavior, particularly during the initial measurements. The model which had been used to represent the specific heat of coal did reproduce the results in air but failed to reproduce the deep exotherm of the thermograms obtained in nitrogen. The specific heat of coal has been determined in helium, argon, and carbon monoxide to provide insight into possible modifications to the model. The results of initial and repeat runs in the five different atmospheres and the impact of these results on the modeling are presented and discussed. The agreement between the experimental heat capacity and that predicted by the model, up to 500 K, is excellent and supports Merrick's predictions for the heat capacity of coal.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 6 (1985), S. 673-679 
    ISSN: 1572-9567
    Keywords: aggregate structure ; coal ; equation-of-motion method ; density dependence ; frequency spectrum ; “gel” model ; harmonic nearest-neighbor forces ; heat capacity ; hexagonal structure ; porous structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Coal is a sedimentary, organic “rock” which is almost never in a state of thermal equilibrium. Because of its importance, the thermal properties of this ill-characterized substance are of great interest. Recent work has shown that coal has many of the characteristics of a gel-type structure. We have made this observation the basis for a model study of the thermal properties of a gel system, using the equation-of-motion method to determine the density of states for the system and, thereby, its heat capacity. This model has one of the essential features of a model of coal, namely, a porous structure. With a hexagonal close-packed lattice as the basis for our gel, we have calculated the frequency spectrum for several particle densities. The disorder in the system has a marked effect on the frequency spectrum, shifting a larger number of modes from high to low frequencies. Also, for a gel with 3% vacancies, and in-plane, out-of-plane bond strengths at the ratio 2∶ 1, there is a further shift to lower frequencies and the two-peaked spectrum expected for such an anisotropic structure develops. The heat capacity is affected only at low temperatures. We conclude that the gel model provides a satisfactory basis for development as a model of coal.
    Type of Medium: Electronic Resource
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