Surface Studies of Heat-treated γ-Aluminas in the Adsorption of Sulfur Dioxide below Monolayer Coverage

1972 ◽  
Vol 50 (16) ◽  
pp. 2537-2543 ◽  
Author(s):  
R. W. Glass ◽  
R. A. Ross
Keyword(s):  
Sulfur Dioxide ◽  
Cross Sections ◽  
Nitrogen Adsorption ◽  
High Energy ◽  
Spherical Particles ◽  
Defect Centers ◽  
Heat Treated ◽  
Adsorption Desorption ◽  
Very High ◽  
Monolayer Coverage

Calorimetric heats of adsorption of sulfur dioxide at surface coverages from 0.1 to 3.5 µmol m−2 have been measured on a series of γ-aluminas heat-treated at 500, 700, and 900 °C. Essential features of the structures of the adsorbents have been characterized by analysis of nitrogen adsorption/desorption isotherms and by both direct and indirect electron microscopy.Heats of adsorption of 423 °K for adsorbed amounts of 0.1 µmol m−2 were 48.0, 59.0, and 85.0 kcal mol−1 for the 500, 700 and 900 °C samples, respectively. The values for the 500 and 700 °C samples fell rapidly with increasing coverage to around 19.0 kcal mol−1 at 3.2 to 3.3 µmol m−2, while the values for the 900 °C sample decreased slowly to 15.0 kcal mol−1 at the same coverage.The pores had circular cross sections and mean diameters of 25, 35, and 40 Å were observed for the 500, 700, and 900 °C samples, respectively. Examination of carbon/platinum replicas of the surface showed the presence of agglomerates of spherical particles approximately 400 Å in diameter.It is proposed that the high initial heats on the 500 and 700 °C samples are due to the formation of a sulfate-like species on the surface and at higher coverage extensive hydrogen bonding is present. The very high heats obtained on the 900 °C sample are believed to be due to interactions with high-energy defect centers in the oxide which were created by heat treatment.

Adiabatic Calorimetric Studies of the Adsorption of Sulfur Dioxide at 423 °K on Heat-treated Magnesias Characterized by Electron Microscopy

1972 ◽  
Vol 50 (17) ◽  
pp. 2817-2822 ◽  
Author(s):  
R. W. Glass ◽  
R. A. Ross
Keyword(s):  
Sulfur Dioxide ◽  
Nitrogen Adsorption ◽  
High Energy ◽  
Structural Features ◽  
Average Particle ◽  
Cubic Form ◽  
Transmission Electron ◽  
Heat Treated ◽  
Calorimetric Studies ◽  
Adsorption Desorption

Calorimetric heats of adsorption of sulfur dioxide at surface coverages from 0.2 to 7.7 μmol m−2 have been measured on a series of magnesias heat-treated at 600, 700, and 800 °C. Structural features of the adsorbents have been characterized by analysis of nitrogen adsorption–desorption isotherms and by transmission electron microscopy.Heats of adsorption at 423 °K for adsorbed amounts of 0.3 μmol m−2 were respectively, 86.0, 87.0, and 77.0 kcal mol−1 for the 600, 700, and 800 °C samples. The values for the 600 and 700 °C samples fell rapidly above a coverage of 2.0 μmol m−2 to around 44.0 kcal mol−1 at 5.0 to 7.0 μmol m−2, while the values for the 800 °C sample decreased continuously to 39.0 kcal mol−1 at the same coverage.Crystallite shapes tended increasingly towards the cubic form as the temperature of heat-treatment was increased and average particle sizes were 80, 240, and 320 Å for the 600, 700, and 800 °C samples, respectively.It is proposed that the very high heats obtained on all the samples are due to interactions with high-energy defect centers in the oxide and with the formation of magnesium sulfite initially, and magnesium sulfate towards monolayer completion.

The Effect of Heat Treatment of Silica Gels on the Calorimetric Heats of Adsorption of Sulfur Dioxide up to One-twentieth Monolayer Coverage at 423 °K

1972 ◽  
Vol 50 (8) ◽  
pp. 1241-1245 ◽  
Author(s):  
R. W. Glass ◽  
R. A. Ross
Keyword(s):  
Sulfur Dioxide ◽  
Nitrogen Adsorption ◽  
Silica Gels ◽  
Distribution Data ◽  
Heats Of Adsorption ◽  
Heat Treated ◽  
Adsorbed Complex ◽  
Adsorption Desorption ◽  
Limiting Values ◽  
Dual Site

Calorimetric heats of adsorption of sulfur dioxide have been determined at 423°K for a series of silica gels heat-treated at 240, 550, 700, 800, and 900 °C. At the lowest surface coverage of 0.01 μmol m−2, heats of 25 to 30 kcal mol−1 were observed. These values dropped rapidly with increasing coverage and approached "limiting" values of 6 to 7 and 12 kcal mol−1 for dehydroxylated and hydroxylated surfaces, respectively. To explain the results at lowest coverages an adsorbed complex involving multiple hydrogen bonds is proposed while at higher coverages it is suggested that single and dual site adsorbed species predominate for the dehydroxylated and hydroxylated surfaces, respectively. Sulfur dioxide adsorption isotherms on all gels at 423 °K obeyed the Langmuir equation.Adsorbents were characterized by nitrogen adsorption–desorption isotherms at 77 °K and pore size distribution data were calculated from the desorption branch.

scholarly journals Highest energy proton–nucleus cross-sections

2018 ◽  
Vol 33 (40) ◽  
pp. 1850242 ◽  
Author(s):  
L. Stodolsky
Keyword(s):  
Cosmic Rays ◽  
Cross Sections ◽  
High Energy ◽  
High Energy Proton ◽  
Proton Proton ◽  
Energy Proton ◽  
Black Disc ◽  
Simple Generalization ◽  
Very High Energy ◽  
Very High

The description of very high energy proton–proton cross-sections in terms of a “black disc” with an “edge” allows a simple generalization to highest energy proton–nucleus cross-sections. This results in a leading ln2W term and a ln W term whose coefficient depends linearly on the radius of the nucleus (W the c.m. energy). The necessary parameters are determined from the fits to p–p data. Since the coefficient of the ln W term is rather large, it is doubtful that the regime of ln2W dominance can be reached with available energies in accelerators or cosmic rays. However, the ln W term can be relevant for highest energy cosmic rays in the atmosphere, where a large increase for the cross-section on nitrogen is expected. Tests of the theory should be possible by studying the coefficient of ln W at p-nucleus colliders.

Low Surface Coverage Interactions of Sulfur Dioxide on Selected Transition Metal Catalysts from 273 to 423 °K

1971 ◽  
Vol 49 (17) ◽  
pp. 2832-2839 ◽  
Author(s):  
R. W. Glass ◽  
R. A. Ross
Keyword(s):  
Sulfur Dioxide ◽  
Transition Metal ◽  
Silica Gel ◽  
Surface Coverage ◽  
Nitrogen Adsorption ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
Hydrogen Bond Formation ◽  
Support Medium ◽  
Adsorption Desorption

Calorimetric beats of adsorption for sulfur dioxide at low surface coverages from 0.004 to 0.600 μmol m−2 on a number of supported transition metal catalysts have been measured between 273 and 423 °K mainly by an adiabatic technique. The catalysts included Fe2O3, Mn2O3, V2O5, MnSO4, and "NiS" ail supported on silica gel.Sulfur dioxide adsorption/desorption isotherms, nitrogen adsorption data, and chemical and infrared analyses were also determined to provide further ancillary information.Heats of adsorption at 423 °K for adsorbed amounts of 0.004 μmol m−2 varied with the adsorbent from nearly 39.0 for Mn2O3 on silica gel to 23.0 kcal mol−1 for the silica gel support medium. With increase in surface coverage to 0.600 μmol m−2 the heat values begin to steady at 6 to 7, 7 to 8, and 8 to 9 kcal mol−1 at 423, 373, and 323 °K, respectively, and less discrimination is observed among the various materials. Preadsorption of small amounts of sulfur dioxide on the supported oxides followed by oxygen admission caused sharp initial falls of as much as 7 to 8 kcal mol−1 in the heat values whereas preadsorption of oxygen followed by sulfur dioxide gave only slight heat increases of around 1 kcal mol−1.It is proposed that sulfur dioxide is chemisorbed on all surfaces with the strongest interactions occurring at the lowest coverages. Sulfates are formed on the oxides as confirmed by chemical analysis, and it is postulated that multiple hydrogen bond formation occurs on silica gel through the interaction of sulfur dioxide oxygen atoms with surface hydroxy groups.

Photonucleon Total Cross Sections at Very High Energy

1970 ◽  
Vol 25 (13) ◽  
pp. 902-902 ◽  
Author(s):  
W. P. Hesse ◽  
D. O. Caldwell ◽  
V. B. Elings ◽  
R. J. Morrison ◽  
F. V. Murphy ◽  
...  
Keyword(s):  
Cross Sections ◽  
High Energy ◽  
Total Cross Sections ◽  
Very High Energy ◽  
Very High

Measurement ofp−pinclusive cross sections at very high energy

1974 ◽  
Vol 9 (5) ◽  
pp. 1135-1161 ◽  
Author(s):  
L. G. Ratner ◽  
R. J. Ellis ◽  
G. Vannini ◽  
B. A. Babcock ◽  
A. D. Krisch ◽  
...  
Keyword(s):  
Cross Sections ◽  
High Energy ◽  
Very High Energy ◽  
Very High

scholarly journals GLUON SATURATION AND THE FROISSART BOUND: A SIMPLE APPROACH

2008 ◽  
Vol 23 (33) ◽  
pp. 2847-2857 ◽  
Author(s):  
F. CARVALHO ◽  
F. O. DURÃES ◽  
V. P. GONÇALVES ◽  
F. S. NAVARRA
Keyword(s):  
Cross Sections ◽  
High Energy ◽  
Simple Approach ◽  
Strong Interactions ◽  
Color Glass ◽  
Momentum Scale ◽  
Total Cross Sections ◽  
High Energies ◽  
Gluon Saturation ◽  
Very High

At very high energies we expect that the hadronic cross sections satisfy the Froissart bound, which is a well-established property of the strong interactions. In this energy regime we also expect the formation of the Color Glass Condensate, characterized by gluon saturation and a typical momentum scale: the saturation scale Qs. In this paper we show that if a saturation window exists between the nonperturbative and perturbative regimes of Quantum Chromodynamics (QCD), the total cross sections satisfy the Froissart bound. Furthermore, we show that our approach allows us to describe the high energy experimental data on [Formula: see text] total cross sections.

Photonucleon Total Cross Sections at Very High Energy.

1970 ◽  
Vol 25 (14) ◽  
pp. 979-979 ◽  
Author(s):  
W. P. Hesse ◽  
D. O. Caldwell ◽  
V. B. Elings ◽  
R. J. Morrison ◽  
F. V. Murphy ◽  
...  
Keyword(s):  
Cross Sections ◽  
High Energy ◽  
Total Cross Sections ◽  
Very High Energy ◽  
Very High

The Effects of Milling Methods on Doped LaCrO3 Nanopowder Prepared by Glycine Nitrate Process on Particle Size and Phase Transformation

2012 ◽  
Vol 428 ◽  
pp. 127-132
Author(s):  
Akbar Heidarpour ◽  
Ali Saidi ◽  
Mohamad Hasan Abbasi
Keyword(s):  
Particle Size ◽  
Phase Transformation ◽  
Nitrogen Adsorption ◽  
High Energy ◽  
Lanthanum Chromite ◽  
Second Phase ◽  
Transmission Electron ◽  
Particle Size Analyzer ◽  
Adsorption Desorption ◽  
Glycine Nitrate Process

In this study the effects of milling methods on particle size and phase transformation of strontium and nickel doped lanthanum chromite as an interconnect material for solid oxide fuel cells (SOFC) were investigated. Two compositions of La0.9Sr0.1Cr0.9Ni0.1O3 (LS10N10) and La0.7Sr0.3Cr0.9Ni0.1O3 (LS30N10) were synthesized by glycine nitrate process (GNP). The samples were characterized by means of X-ray diffraction, nitrogen adsorption–desorption, scanning and transmission electron microscope and laser particle size analyzer. Two different milling methods were used, namely, high-energy milling (HEM) and ball milling (BM) and the effects of these milling methods of as-synthesis powders on the particle size distribution, agglomeration behavior and phase transformation were also investigated. The results showed that BM caused reduction of particle size to submicron size with D50 value of 125 nm while HEM resulted in agglomeration. The obtained nanopowders, according to XRD results were single phase with perovskite type crystal structure and only in high content of Sr some SrCrO4 was detected. HEM caused the dissolution of the second phase in LS30N10.

Sign in / Sign up

Export Citation Format

Share Document