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

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.

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Study on the kinetics of process for obtaining cobalt nanopowder by hydrogen reduction under isothermal conditions

Izvestiya Vuzov Tsvetnaya Metallurgiya (Proceedings of Higher Schools Nonferrous Metallurgy) ◽

10.17073/0021-3438-2021-1-49-56 ◽

2021 ◽

Vol 1 (1) ◽

pp. 49-56

Author(s):

Hieр Nguyen Tien

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Hydrogen Reduction ◽

Average Particle Size ◽

Chemical Deposition ◽

Average Particle ◽

Isothermal Conditions ◽

Electron Microscopes ◽

Kinetics Of

The kinetics of metallic cobalt nanopowder synthesizing by hydrogen reduction from Co(OH)2 nanopowder under isothermal conditions were studied. Co(OH)2 nanopowder was prepared in advance by chemical deposition from aqueous solutions of Co(NO3)2 cobalt nitrate (10 wt.%) and NaOH alkali (10 wt.%) at room temperature, pH = 9 under continuous stirring. The hydrogen reduction of Co(OH)2 nanopowder under isothermal conditions was carried out in a tube furnace in the temperature range from 270 to 310 °C. The crystal structure and composition of powders was studied by X-ray phase analysis. The specific surface area of samples was measured using the BET method by low-temperature nitrogen adsorption. The average particle size of powders was determined by the measured specific surface area. Particles size characteristics and morphology were investigated by transmission and scanning electron microscopes. Kinetic parameters of Co(OH)2 hydrogen reduction under isothermal conditions were calculated using the Gray–Weddington model and Arrhenius equation. It was found that the rate constant of reduction at t = 310 °C is approximately 1.93 times higher than at 270 °C, so the process accelerates by 1.58 times for 40 min of reduction. The activation energy of cobalt nanopowder synthesizing from Co(OH)2 by hydrogen reduction is ~40 kJ/mol, which indicates a mixed reaction mode. It was shown that cobalt nanoparticles obtained by the hydrogen reduction of its hydroxide at 280 °C are aggregates of equiaxed particles up to 100 nm in size where individual particles are connected to several neighboring particles by contact isthmuses.

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SYNTHESIS AND CHARACTERIZATION OF FERROELECTRIC NANOCRYSTAL POWDERS OF SrBi2Ta2O9 BY A POLYMERIZABLE COMPLEX METHOD

International Journal of Modern Physics B ◽

10.1142/s0217979205031249 ◽

2005 ◽

Vol 19 (15n17) ◽

pp. 2514-2519 ◽

Cited By ~ 3

Author(s):

JIN-BO CHENG ◽

AI-DONG LI ◽

QI-YUE SHAO ◽

YUE-FENG TANG ◽

DI WU

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Thermal Analyses ◽

Water Soluble ◽

Complex Method ◽

Powder Synthesis ◽

Conventional Solid State Reaction ◽

Transmission Electron ◽

Average Size

Ferroelectric nanocrystal powders of SrBi2Ta2O9 (SBT) have been first prepared by a polymerizable complex (PC) route. The bismuth powder, strontium carbonate, and water-soluble tantalum oxalate solution were used as starting materials. Thermal analyses (TGA and DSC), x-ray diffraction (XRD), transmission electron microscopy (TEM), and conventional BET method were explored to characterize the structure, morphology, and specific surface area of PC-derived SBT powders calcined at 500-850 °C. As control samples, SBT powders were also fabricated by metalorganic decomposition (MOD) method. The XRD and TEM results indicate that high pure and well crystalline powders can be obtained at 650 °C with a average size of 50 nm. The PC-derived powder has much larger surface area than MOD-derived powder. The BET value of PC and MOD powder at 750 °C for 2h is 6.7 and 1.5m2/g, respectively. The specific surface area of powder prepared by conventional solid-state reaction is quite low, typically less than 1.5m2/g. Therefore, the feasibility of the polymerizable complex route is demonstrated in the powder synthesis of SBT with large surface area.

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Fabrication and Characterization of Cu Doped CeO2 by Hydrothermal Process for Antimicrobial Activity

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.391.114 ◽

2019 ◽

Vol 391 ◽

pp. 114-119 ◽

Cited By ~ 1

Author(s):

Yeon Bin Choi ◽

Jeong Hun Son ◽

Dong Sik Bae

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Hydrothermal Process ◽

Antibacterial Properties ◽

Reaction Times ◽

X Ray Diffraction ◽

Spherical Type ◽

Average Size

Cu doped CeO2 nanopowder was synthesized by hydrothermal process at 180°C for 2~10h. The average size and distribution of the synthesized Cu doped CeO2 nanopowder was controlled by reaction times. The crystallinity of the synthesized Cu doped CeO2 nanoparticles was investigated by X-ray diffraction (XRD). The morphology of the synthesized Cu doped CeO2 nanoparticles was observed by FE-SEM. The specific surface area of the synthesized Cu doped CeO2 nanoparticles was measured by BET. The crystal size of the synthesized Cu doped CeO2 nanoparticles decreased with decreasing reaction times. The average size of the synthesized Cu doped CeO2 nanoparticles was below 10nm and narrow, respectively. The shape of the synthesized Cu doped CeO2 nanoparticles was spherical type. The specific surface area of the synthesized Cu doped CeO2 nanoparticles increased with decreasing reaction times. Antibacterial properties of Cu doped CeO2 were analyzed by MIC method. The synthesized Cu doped CeO2 nanopowders showed antibacterial properties against E.coli and B.sub bacteria.

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The Carbon Deposition during Iron Ore Reduction in Carbon Monoxide

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.625.243 ◽

2012 ◽

Vol 625 ◽

pp. 243-246

Author(s):

Shu Hua Geng ◽

Wei Zhong Ding ◽

Shu Qiang Guo ◽

Xiong Gang Lu

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Iron Ore ◽

Iron Reduction ◽

Carbon Deposition ◽

Reduction Process ◽

Ore Reduction ◽

X Ray ◽

Iron Ore Reduction

Iron ore reduction and carbon deposition in pure CO was investigated by using thermogravimetric (TG) method over the temperature range of 0-1200°C. The results of the work may be summarized as follows: in CO stream, carbon deposition occurred below 900°C, no carbon deposition was found above 1000°C. X-Ray analysis of the reacted sample indicated that the carbon deposition occurred with the iron was reduced. The iron reduction process and carbon deposition occurred simultaneously. The rate of carbon deposition changed with the transformation of iron oxides. The specific surface area and pore structure of reduced samples were analyzed. The specific surface area changed with the amount of carbon deposition.

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Effect of manganese on the thermostability and reducibility of cobalt nanomaterials.

MRS Proceedings ◽

10.1557/opl.2012.320 ◽

2012 ◽

Vol 1373 ◽

Author(s):

Zofia Lendzion-Bieluń

Keyword(s):

Specific Surface ◽

Surface Area ◽

Cobalt Oxide ◽

High Temperatures ◽

Specific Surface Area ◽

Small Addition ◽

Impregnation Method

ABSTRACTCobalt nanomaterials with promoters have been prepared by precipitation followed by calcination and impregnation method. The obtained materials are characterized by ICP, H2-TPR, BET and XRD. A small addition of manganese increases the specific surface area of cobalt nanomaterials and thermostability under reduction atmosphere. Bulk Co3O4 has been reduced in two steps (Co3+→Co2+→Co). A small addition of manganese to the cobalt oxide shifts the reduction peaks to high temperatures.

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Low Temperature Synthesis of Mesoporous SiC in Dual-Confined Spaces via Magnesiothermic Reduction

NANO ◽

10.1142/s1793292019501157 ◽

2019 ◽

Vol 14 (09) ◽

pp. 1950115 ◽

Cited By ~ 1

Author(s):

Zeng-Rong Wang ◽

Long Liu ◽

Xue Zhang ◽

Jia-Lin Xu ◽

Qiang Sun

Keyword(s):

Low Temperature ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Catalyst Support ◽

Reduction Process ◽

Carbon Matrix ◽

Carbon Composite ◽

Magnesiothermic Reduction ◽

Confined Spaces

Silicon carbide (SiC), especially mesoporous SiC has been in immense vogue for more than a decade because of its intriguing properties and wide applications. However, it is still challenging to synthesize mesoporous SiC with good structural integrality, large specific surface area and desirable porosity at a low temperature. In this study, we reported a “dual-confined spaces”-assisted synthesis of mesoporous SiC using well-assembled SiO2/carbon composite as precursor via a magnesiothermic reduction process. The well-crystallinity mesoporous SiC presented a mesopore structure with high specific surface area of 267.3 m2 g[Formula: see text] and large mesopore size of ca. 10[Formula: see text]nm can be directly fabricated at a temperature of at least 550∘C and the optimum synthesis temperature is 650∘C. During the synthesis, mesoporous carbon matrix and a pressure-tight stainless steel reactor were served as “dual-confined spaces” to avoid the aggregation of silica and the silicon residue left in the final SiC sample. Furthermore, the as-prepared mesoporous SiC showed prominent performance as catalyst support for the reduction of 4-nitrophenol to 4-aminophenol.

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Aluminium oxide primarily used for the production of aluminium. Determination of specific surface area by nitrogen adsorption

10.3403/30118280u ◽

2015 ◽

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Aluminium Oxide ◽

Nitrogen Adsorption ◽

Aluminium Determination

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

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19901920 ◽

1990 ◽

Vol 55 (8) ◽

pp. 1920-1927 ◽

Cited By ~ 1

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.

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