Synergistic effect of α-Al2O3 and (NH4)3AlF6 co-doped seed on phase transformation, microstructure, and mechanical properties of nanocrystalline alumina abrasive

Li, Zicheng; Li, Zhihong; Zhang, Aiju; Zhu, Yumei

doi:10.1016/j.jallcom.2008.08.072

Cited by 17 publications

(9 citation statements)

References 31 publications

(33 reference statements)

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“…In the present study, the microstructure of the transformed coatings retained a porous, vermicular structure for all the annealing temperatures studied. This is in contrast to the sintering studies of seeded gels 16–24 where the advantage of the seeding is the attainment of dense equiaxed structures at lower temperatures relative to unseeded samples. As put forward by Dynys and Halloran, 14 the vermicular structure is the result of the negative volume change from δ‐ to θ‐alumina, coupled with the constraint of the continuous transformation front.…”

Section: Resultsmentioning

confidence: 80%

“…It was the work of Messing and colleagues 16–18 that first showed that seeding bohemite gels with α‐alumina powder resulted in an enhancement of the transformation kinetics, and sintering of the transformed alumina could be achieved at a significantly lower temperature relative to the unseeded gels. This approach has since been widely applied to sol–gel‐derived aluminas for a broad range of applications 20–24 …”

Section: Introductionmentioning

confidence: 99%

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Sol–Gel‐Derived Single‐Crystal Alumina Coatings with Vermicular Structure

Dutta¹,

Kim²,

Krentz³

et al. 2011

Journal of the American Ceramic Society

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Alumina sols were spin‐coated on {0001} (c‐plane) sapphire substrates. Heat treatment in air at temperatures varying between 1100° and 1400°C resulted in epitaxial conversion of the coating to α‐alumina. Seeded single‐crystal conversion could be achieved at temperatures as low as 1025°C at longer annealing times (18 h). The converted coatings were crack free, and exhibited a porous, vermicular microstructure that was attributed to the negative volume change during the γ to α alumina phase change, coupled with the volume constraint of the underlying sapphire substrate. Isolated regions of the coating that had delaminated from the substrate did not convert to {0001} sapphire, but instead remained polycrystalline after heat treatment. Single‐crystal islands that were not c‐plane oriented were occasionally observed at shorter times. It is suggested that such regions resulted from the random nucleation of α‐grains with a more rapid growth rate in the direction perpendicular to the substrate. The epitaxial conversion of alumina sol–gel coatings provides a potentially convenient method for generating patterned, single‐crystal ceramic substrates for a variety of applications.

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Section: Resultsmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Sol–Gel‐Derived Single‐Crystal Alumina Coatings with Vermicular Structure

Dutta¹,

Kim²,

Krentz³

et al. 2011

Journal of the American Ceramic Society

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“…It was only in 2008 when the first reports appeared about abrasive grains from nanocrystalline sintered corundum whose average grain size was below 100 nm [52][53][54] (60 nm [55]), which is produced with the sol-gel technology using the two-level sintering method in 1,150-1,300°C [52][53][54]. The grain growth is considerably limited through sintering temperature control and the application of compounds supporting sintering such as MgO-CaO-SiO 2 , during the last of the twolevel sintering stages.…”

Section: Nanocrystalline Sintered Corundummentioning

confidence: 99%

State of the art in production, properties and applications of the microcrystalline sintered corundum abrasive grains

Nadolny

2014

Int J Adv Manuf Technol

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The following article presents the current state of knowledge about technologies connected with microcrystalline sintered corundum against the backdrop of present abrasive products and the contemporary grains market. The complementary presentation of issues related to the microcrystalline sintered corundum abrasive grains, which constitute an important group of abrasives used in modern grinding technology, was given. The most important stages in the development of sintered corundum grains production technology, from the 1960s to current developments (nanocrystalline sintered corundum) in this field, were presented in chronological order. The production technology, properties, working conditions, wear phenomena and most important areas of application of such abrasive grains were described. Particular attention was paid to the wear phenomena of microcrystalline sintered corundum abrasive grains occurring during the grinding process. The collection of phenomena affecting the extension of the life of these types of grain in comparison with the white fused alumina grains were described. Moreover, forecasts concerning the development of abrasive grains of micro-and nanocrystalline sintered corundum were presented.

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“…There were some methods invented to decrease the transformation temperature to overcome the possibility of powder agglomeration problems by adding surfactants [8,13], the seeds [14][15][16], or mineralizers [9,13,[17][18][19][20][21][22][23]. Among them, the addition of mineralizer was proved to be an effective method.…”

Section: Introductionmentioning

confidence: 99%

The INFLUENCES OF FLUORIDES ON THE TRANSFORMATION OF Α -ALUMINA CRYSTALS

Tian¹

2017

Ceramics - Silikaty

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Influence of addition of aluminum fluoride (AlF 3) and ammonium fluoride (NH 4 F) on transformation of α-Al 2 O 3 from boehmite was investigated. Transformation of α-Al 2 O 3 occurred at about 1050°C and 950°C, when boehmite contained AlF 3 and NH 4 F additives respectively, which was 150°C and 300°C lower than that without any additives. The formed α-Al 2 O 3 consisted of clear, hexagonal plate-like particles about 2-3 µm in diameter and 200 nm in thickness. However, the formed hexagonal platelet particles gradually became blunt at edges and decreased in sizes at the higher calcinating temperatures. The transfer of α-Al 2 O 3 morphology was due to the diminution and disappearance of fluorine. The fluoride coated on the surfaces were firstly decomposed and then fluorine entered the lattices of crystals was volatilized. The fluoride with tiny particles attached on the surface had a same chemical bonding of F-Al-O with that in the lattices of crystals.

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Synergistic effect of α-Al2O3 and (NH4)3AlF6 co-doped seed on phase transformation, microstructure, and mechanical properties of nanocrystalline alumina abrasive

Cited by 17 publications

References 31 publications

Sol–Gel‐Derived Single‐Crystal Alumina Coatings with Vermicular Structure

Sol–Gel‐Derived Single‐Crystal Alumina Coatings with Vermicular Structure

State of the art in production, properties and applications of the microcrystalline sintered corundum abrasive grains

The INFLUENCES OF FLUORIDES ON THE TRANSFORMATION OF Α -ALUMINA CRYSTALS

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