Physicochemical studies on ZnO-Al2O3 system

Mouśa, M. A.; Diefallah, El-Hussieny M.; Abdel-Fattah, A.A.; Omran, Z. A.

doi:10.1007/bf00587651

Cited by 6 publications

(2 citation statements)

References 17 publications

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“…Although franklinite has been observed to precipitate from aqueous Fe 3+ and Zn 2+ at ambient temperatures at an Fe 2+ /Zn 2+ mole ratio of at least two (43), it typically forms at temperatures ranging from 500 to 800 °C depending on precursors (44). Gahnite was shown to form from a ZnO-Al2O3 system at 600 °C (45). Thermodynamic analysis (Supporting Information) demonstrates that gahnite and franklinite are indeed sparingly soluble.…”

Section: Resultsmentioning

confidence: 99%

Heavy Metal Immobilization through Phosphate and Thermal Treatment of Dredged Sediments

Ndiba

Axe

Boonfueng

2008

Environ. Sci. Technol.

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Disposal of dredged sediments is expensive and poses a major challenge for harbor dredging projects. Therefore beneficial reuse of these sediments as construction material is highly desirable assuming contaminants such as heavy metals are immobilized and organics are mineralized. In this research, the effect of the addition of 2.5% phosphate, followed by thermal treatment at 700 degrees C, was investigated for metal contaminants in dredged sediments. Specifically, Zn speciation was evaluated, using X-ray absorption spectroscopy (XAS), by applying principal component analysis (PCA), target transformation (TT), and linear combination fit (LCF) to identify the main phases and their combination from an array of reference compounds. In dredged sediments, Zn was present as smithsonite (67%) and adsorbed to hydrous manganese oxides (18%) and hydrous iron oxides (15%). Phosphate addition resulted in precipitation of hopeite (22%), while calcination induced formation of spinels, gahnite (44%), and franklinite (34%). Although calcination was previously used to agglomerate phosphate phases by sintering, we found that it formed sparingly soluble Zn phases. Results from the U.S. EPA toxicity characteristic leaching procedure (TCLP) confirmed both phosphate addition and calcination reduced leachability of heavy metals with the combined treatment achieving up to an 89% reduction.

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Section: Resultsmentioning

confidence: 99%

Heavy Metal Immobilization through Phosphate and Thermal Treatment of Dredged Sediments

Ndiba

Axe

Boonfueng

2008

Environ. Sci. Technol.

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“…The chemical growth kinetics for the formation of these ZnO NWalls is explained in the succeeding section. It has been reported that ZnAl 2 O 4 is lower in electrical conductivity than ZnO and other oxide mixtures [18].…”

Section: Optical Characteristicsmentioning

confidence: 99%

Sonochemical approach for rapid growth of zinc oxide nanowalls

et al. 2012

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The sonochemical process drives chemical reactions with sound fields by creating extraordinarily high density of energy, pressure and temperatures. The process resulted in a number of unexpected chemical species and thought-provoking results in the recent past. In this paper, we present a new sonochemical approach to synthesize ZnO (zinc oxide) nanowalls (NWalls) on aluminum and alumina coated substrates at room ambient conditions. We achieved highly dense and uniform ZnO NWalls in areas that are coated with Al or Al 2 O 3 (alumina). The synthesis process was shown not to occur on Si, SiO 2 , Cr, or Ag surfaces. A series of experiments on understanding the growth kinetics offers detailed insight into the growth dynamics over time. Photoluminescence (PL) measurements, UV Vis spectroscopy, and SEM-EDS results confirm NWalls composed of crystalline ZnO that are formed via Al assisted growth induced by phase transformations under extraordinary pressure, temperature, and chemical growth kinetics. The chemical growth method as reported here, is applicable to arbitrary A.P. Nayak · A.M. Katzenmeyer · M.S. Islam ( ) substrates coated with an Al thin film. We demonstrate the applications of the as-formed NWalls in UV photoconductors and gas sensors.

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