Investigation of phase transition of γ-alumina to α-alumina via mechanical milling method

Correia, Nuno; Mirhabibi, A.R.; Zolfonun, H.; Tahriri, Mohammadreza; Karimi, Meysam

doi:10.1080/01411590802008012

Cited by 55 publications

(44 citation statements)

References 29 publications

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“…10 were milled without the addition of α-Al 2 O 3 before milling, the results differ from the observations of Bodaghi et al (2008), and show that with the appropriate milling conditions, α-Al 2 O 3 can be produced mechanochemically without any seeding (Kostic et al, 2000). ZrO 2 contamination was also observed to increase as milling progressed as the intensity of the ZrO 2 peak increased with prolonged milling times.…”

Section: Characterisation Of Particle Morphology By Xrd Analysiscontrasting

confidence: 66%

“…Additionally, evidence of phase transformation due to milling, similar to that achieved by thermal dehydration of boehmite, has been reported in various works (Duvel et al, 2011;Wang et al, 2005). However Bodaghi et al (2008) observed no phase change in γ-Al 2 O 3 after 30 h of milling in the Fritsch Pulverisette 7 planetary ball mill but reported the occurrence of phase change of γ-Al 2 O 3 to α-Al 2 O 3 only after the addition of α-Al 2 O 3 seeds into the mill (Bodaghi et al, 2008). According to Bodaghi et al (2008) the α-Al 2 O 3 seeds act by reducing the transition temperature and activation energy for α-Al 2 O 3 to nucleate (Bodaghi et al, 2008).…”

Section: Introductionmentioning

confidence: 96%

“…However Bodaghi et al (2008) observed no phase change in γ-Al 2 O 3 after 30 h of milling in the Fritsch Pulverisette 7 planetary ball mill but reported the occurrence of phase change of γ-Al 2 O 3 to α-Al 2 O 3 only after the addition of α-Al 2 O 3 seeds into the mill (Bodaghi et al, 2008). According to Bodaghi et al (2008) the α-Al 2 O 3 seeds act by reducing the transition temperature and activation energy for α-Al 2 O 3 to nucleate (Bodaghi et al, 2008). It is therefore still necessary to carry out an in depth investigation into the effect of size reduction mechanisms brought about by different stress modes such as shear, impact, and compression on the surface and morphology or structure of the material.…”

Section: Introductionmentioning

confidence: 96%

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Effect of mill type on the size reduction and phase transformation of gamma alumina

Chauruka

Hassanpour

Brydson

et al. 2015

Chemical Engineering Science

118

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We study the effect of stress modes from three mills on structure of gamma-alumina. Extent of size reduction and mechanochemical effects are analysed. Jet milling is effective in size reduction and does not initiate mechanochemistry. Shear-induced phase transformation is observed in planetary ball mill. Transformation is by slip on alternate close packed oxygen layers from ccp to hcp. a b s t r a c tThe influence of stress modes and comminution conditions on the effectiveness of particle size reduction of a common catalyst support; γ-Alumina is examined through a comparative assessment of three different mill types. Air jet milling is found to be the most effective in reducing particle size from a d 90 of 37 mm to 2.9 mm compared to planetary ball milling (30.2 mm) and single ball milling (10.5 mm). XRD and TEM studies confirm that the planetary ball mill causes phase transformation to the less desired α-Alumina resulting in a notable decrease in surface area from 136.6 m 2 /g to 82.5 m 2 /g as measured by the BET method. This is consistent with the large shear stresses under high shear rates prevailing in the planetary ball mill when compared to the other mill types. These observations are consistent with a shear-induced phase transformation mechanism brought about by slip on alternate close packed oxygen layers from a cubic close packed to a hexagonal close packed structure.

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Section: Characterisation Of Particle Morphology By Xrd Analysiscontrasting

confidence: 66%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 96%

See 1 more Smart Citation

Effect of mill type on the size reduction and phase transformation of gamma alumina

Chauruka

Hassanpour

Brydson

et al. 2015

Chemical Engineering Science

118

View full text Add to dashboard Cite

show abstract

“…The unique physical and chemical characteristics of nanoparticles make them remarkably appropriate for creating new and improved devices [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. Quantum dots are semiconductor nanocrystals with various technical applications, especially in biology where they have been used in bio-labeling, bioimaging, and biomolecular detection [21,[27][28][29][30][31].…”

Section: Introductionmentioning

confidence: 99%

Determination of total aflatoxin using cysteamine-capped CdS quantum dots as a fluorescence probe

et al. 2016

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Aflatoxins form a class of potent carcinogens that contaminate a wide range of food products and can be fatal to humans and livestock. We have designed cysteamine-capped CdS quantum dots (QDs) to serve as aflatoxin photodetectors for use in agricultural industries. Water-soluble CdS QDs are synthesized through growth in a poly(vinyl alcohol) matrix using a chemical precipitation method. The prepared QDs are then characterized with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS), and transmission electron microscopy (TEM) analyses. The obtained results revealed that these CdS QDs have a 1-to 2-nm crystalline size, hexagonal wurtzite structure, and spherical morphology with a diameter less than 10 nm. Photoluminescence spectroscopy (PL) is performed to study the CdS QDs interactions with a standard solution of aflatoxins (B1, B2, G1, and G2 in a ratio of 5:1:5:1) in order to determine their effectiveness as aflatoxin detectors. A green emission peak is observed at 508 nm, with an intensity enhancement positively correlated with total aflatoxin concentration. The lower limit of detection for total aflatoxin concentration is found to be 0.05 ppb, well below international contamination allowances for food products. PL variations with aflatoxin concentration are best described by a Langmuir-type equation in the concentration range of this study (2.4-48 ppb).

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“…Although several approaches investigated ways of making these nanocrystals, methods of controlling the size, shape, and crystallinity and various parameters affecting the size and shape of these materials still need to be found [1][2][3][4].…”

Section: Introductionmentioning

confidence: 99%

Rapid mechanically activated solid-state synthesis of nanocrystalline α-Al2O3 using Fe2O3 and Al

Correia

Mirhabibi

Tahriri

2009

Powder Metall Met Ceram

Self Cite

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In this research, we demonstrate rapid mechanochemical synthesis of nanocrystalline α-alumina (α-Al 2 O 3 ) from a starting mixture of hematite (Fe 2 O 3 ) and aluminum (Al). The formation of α-Al 2 O 3 nanocrystallites occurs during the solid-state reaction and through the reduction treatment. Also in this paper, effects of milling time on the particle size and lattice strain of nanocrystalline α-Al 2 O 3 are investigated. The results indicate that complete reduction is reached only after 2 h of milling in a planetary mill and the crystallite size of obtained α-Al 2 O 3 is in general about 12 nm. Also, it is found that increasing the milling time can effectively decrease the nanocrystalline size and increase the lattice strain of α-Al 2 O 3 . Finally, the experimental results show appropriate homogeneity and dispersion of related nanocrystallites.

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Investigation of phase transition of γ-alumina to α-alumina via mechanical milling method

Cited by 55 publications

References 29 publications

Effect of mill type on the size reduction and phase transformation of gamma alumina

Effect of mill type on the size reduction and phase transformation of gamma alumina

Determination of total aflatoxin using cysteamine-capped CdS quantum dots as a fluorescence probe

Rapid mechanically activated solid-state synthesis of nanocrystalline α-Al2O3 using Fe2O3 and Al

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