Effect of steaming on physical properties of aluminium hydroxide and aluminium oxide

1990 ◽  
Vol 55 (8) ◽  
pp. 1920-1927 ◽  
Author(s):  
Ro Yong Zun ◽  
Jaroslava Polednová ◽  
Květa Jirátová
Keyword(s):  
Physical Properties ◽  
Partial Pressure ◽  
Specific Surface ◽  
Surface Area ◽  
Water Vapour ◽  
Surface Properties ◽  
Specific Surface Area ◽  
Aluminium Hydroxide ◽  
Aluminium Oxide ◽  
Total Acidity

The effect of partial pressure of water vapour (50-750kPa) in air on physical properties of calcinated aluminium hydroxide AlOOH and aluminium oxide Al2O3 was examined. For both materials it was found that increasing pressure of water vapour leads to a decrease in the specific surface area and to an increase in the diameter of their mesopores. However, changes in the surface properties have not been identical: the total acidity of Al2O3 decreased whereas the acidity of calcinated AlOOH passed through a maximum. The total basicity of Al2O3 increased while that of AlOOH decreased.

scholarly journals Snow physics as relevant to snow photochemistry

2007 ◽  
Vol 7 (3) ◽  
pp. 5941-6036 ◽  
Author(s):  
F. Domine ◽  
M. Albert ◽  
T. Huthwelker ◽  
H.-W. Jacobi ◽  
A. A. Kokhanovsky ◽  
...  
Keyword(s):  
Physical Properties ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Quantitative Description ◽  
Field Measurements ◽  
Liquid Water Content ◽  
Reactive Gases ◽  
Snow Physics ◽  
Snow Photochemistry

Abstract. Snow on the ground is a complex multiphase photochemical reactor that dramatically modifies the chemical composition of the overlying atmosphere. A quantitative description of the emissions of reactive gases by snow requires the knowledge of snow physical properties. This overview details our current understanding of how those physical properties relevant to snow photochemistry vary during snow metamorphism. Properties discussed are density, specific surface area, optical properties, thermal conductivity, permeability and gas diffusivity. Inasmuch as possible, equations to parameterize these properties as a function of climatic variables are proposed, based on field measurements, laboratory experiments and theory. The potential of remote sensing methods to obtain information on some snow physical variables such as grain size, liquid water content and snow depth are discussed. The possibilities for and difficulties of building a snow photochemistry model by adapting current snow physics models are explored. Elaborate snow physics models already exist, and including variables of particular interest to snow photochemistry such as light fluxes and specific surface area appears possible. On the other hand, understanding the nature and location of reactive molecules in snow seems to be the greatest difficulty modelers will have to face for lack of experimental data, and progress on this aspect will require the detailed study of natural snow samples.

scholarly journals The effect of aluminium oxide on the reduction of cobalt oxide and thermostabillity of cobalt and cobalt oxide

2011 ◽  
Vol 9 (5) ◽  
pp. 834-839 ◽  
Author(s):  
Zofia Lendzion-Bieluń ◽  
Roman Jędrzejewski ◽  
Walerian Arabczyk
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Cobalt Oxide ◽  
Specific Surface Area ◽  
Hydrogen Reduction ◽  
Aluminium Oxide ◽  
Reduction Process ◽  
Oxide Phase ◽  
Recrystallization Process ◽  
Average Size

AbstractDuring precipitation and calcination at 200°C nanocrystalline Co3O4 was obtained with average size crystallites of 13 nm and a well developed specific surface area of 44 m2 g−1. A small addition of a structural promoter, e.g. Al2O3, increases the specific surface area of the cobalt oxide (54 m2 g−1) and decreases the average size of crystallites (7 nm). Al2O3 inhibits the reduction process of Co3O4 by hydrogen. Reduction of cobalt oxide with aluminium oxide addition runs by equilibrium state at all the respective temperatures. The apparent activation energy of the recrystallization process of the nanocrystalline cobalt promoted by the aluminium oxide is 85 kJ mol−1. Aluminium oxide improves the thermostability of both cobalt oxide and the cobalt obtained as a result of oxide phase reduction.

Gold Cementation by Dendritic Zinc Powders in Percolation Mode

2020 ◽  
Vol 989 ◽  
pp. 543-547
Author(s):  
K.D. Naumov ◽  
Vladimir G. Lobanov
Keyword(s):  
Particle Size ◽  
Physical Properties ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
High Specific Surface Area ◽  
Alkaline Solutions ◽  
Wide Range ◽  
Zinc Powders ◽  
Cyanide Solutions

In present article gold cementation features from cyanide solutions using dendritic zinc powders are studied. The powders were obtained by electroextraction from alkaline solutions. Powders with different physical properties were obtained by means of change in current density (from 0.5 to 2 A/m2) and NaOH concentration in solution (from 100 to 400 g/dm3) at the constant zinc concentration (10 g/dm3). The physical properties of mentioned powders were studied using SEM (Jeol JSM-6390LA), BET (Gemini VII 2390) and laser diffraction (Sympatec HELOS & RODOS). It is shown that electrolytic powders have high specific surface area, which is 1.8–2.6 times larger than the surface area of ​​the zinc powder currently used for cementation. At that electrolytic powders particle size is 8-22 times larger than the particle size of powder currently used for cementation. The reason of high specific surface area is the electrolytic zinc powders dendritic structure. It was found that the obtained powders precipitate gold from cyanide solutions with a greater efficiency in a wide range of productivity. Laboratory unit simulating Merrill-Crow technology was used for cementation. Immediately ahead conducting the experiments, Na2SO3 was added to the solution in excess to remove dissolved oxygen. Zinc powders were plated by dendritic lead before loading into the laboratory setup by cementation. Lead was added as acetate (Pb (CH3COO)2). The consumption of lead acetate was 10% by weight of zinc. Correlation between the powders physical properties and the gold extraction is shown.

scholarly journals Mixture Design Approach on the Physical Properties of Lignin-Resorcinol-Formaldehyde Xerogels

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Chris D. Castro ◽  
Germán C. Quintana
Keyword(s):  
Physical Properties ◽  
Specific Surface ◽  
Bulk Density ◽  
Surface Area ◽  
Specific Surface Area ◽  
Black Liquor ◽  
Adsorptive Capacity ◽  
Gel Formation ◽  
Soda Pulping ◽  
Catalyst Content

Organic xerogels were functionalized by incorporating sugarcane bagasse lignin from soda pulping black liquor, not used so far in this materials, with the aim of introducing new functional groups on traditional gels that could improve its adsorptive capacity. Two mixing designs were applied to identify the reactive combinations that allow a well gel formation and to adjust models that predict physical properties. The designs study five components: resorcinol (R, 0.04–0.3), lignin (L, 0.004–0.14), formaldehyde (F, 0.08–0.17), water (W, 0.45–0.8), and NaOH (C, 0.0003–0.0035). The first experimental design was an extreme vertices design and its results showed shrinkage between 4.3 and 59.7 and a bulk density from 0.54 to 1.3; a mass ratioLR/Fnear 1.5 was required for gel formation. In the second design a D-Optimal was used to achieve better adjusted coefficients and incorporate the largest possible amount of lignin in the gels. Bulk density varies from 0.42 to 0.9, shrinkage varies from 3.42 to 25.35, and specific surface area reaches values of 451.86 m2/g with 13% lignin and 270 m2/g with 27% lignin. High catalyst content improves lignin dissolution and increase shrinkage and bulk density of xerogels and bulk density. Lignin contributes to reducing shrinkage and specific surface area due to his compact and rigid structure.

scholarly journals Analysis of the sorption properties of different soils using water vapour adsorption and potentiometric titration methods

2016 ◽  
Vol 30 (3) ◽  
pp. 369-374 ◽  
Author(s):  
Kamil Skic ◽  
Patrycja Boguta ◽  
Zofia Sokołowska
Keyword(s):  
Specific Surface ◽  
Cation Exchange ◽  
Surface Charge ◽  
Surface Area ◽  
Water Vapour ◽  
Potentiometric Titration ◽  
Specific Surface Area ◽  
Cation Exchange Capacity ◽  
Exchange Capacity ◽  
Sorption Properties

Abstract Parameters of specific surface area as well as surface charge were used to determine and compare sorption properties of soils with different physicochemical characteristics. The gravimetric method was used to obtain water vapour isotherms and then specific surface areas, whereas surface charge was estimated from potentiometric titration curves. The specific surface area varied from 12.55 to 132.69 m2 g−1 for Haplic Cambisol and Mollic Gleysol soil, respectively, and generally decreased with pH (R=0.835; α = 0.05) and when bulk density (R=−0.736; α = 0.05) as well as ash content (R=−0.751; α = 0.05) increased. In the case of surface charge, the values ranged from 63.00 to 844.67 μmol g−1 Haplic Fluvisol and Mollic Gleysol, respecively. Organic matter gave significant contributions to the specific surface area and cation exchange capacity due to the large surface area and numerous surface functional groups, containing adsorption sites for water vapour molecules and for ions. The values of cation exchange capacity and specific surface area correlated linearly at the level of R=0.985; α = 0.05.

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