Sintering and phase evolution of ?-Al2O3 with transition-metals addition at around ?-transition temperature

Ozawa, Masakuni; Katoh, Osamu; Suzuki, Suguru; Hattori, Yoshitaka; Yamamura, Misaho

doi:10.1007/bf00579251

Cited by 28 publications

(14 citation statements)

References 15 publications

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“…It has been reported that the rare earth additives can improve the properties of the catalysts and decrease the consumption of precious metals at the same time [10]. Fu et al had found in their work [7] that certain dopants, such as lanthana, can stabilize ceria and prevent its sintering.…”

Section: Introductionmentioning

confidence: 98%

The effect of La on Au-ceria catalyst for water gas shift reaction

et al. 2007

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For Au-ceria catalysts prepared by deposition-precipitation method, catalytic performance of water gas shift reaction was studied in different La loadings. In the complete doping range, ceria retains with its cubic fluorite structures. BET, XRD, H 2 -TPR, HRTEM studies showed that La doping can improve the activity of Au-ceria catalyst by stabilizing ceria and modifying its morphology. In addition, the test of catalyst stability evaluation also proved a better stability performance of Au-ceria catalyst can be realized by appropriate La doping.

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Section: Introductionmentioning

confidence: 98%

The effect of La on Au-ceria catalyst for water gas shift reaction

et al. 2007

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“…Recently, Ozawa et al also reported a similar phase transformation of ␥-Al 2 O 3 . [19] The morphology of extracted whiskers analyzed by XRD is shown in the SEM micrograph in Figure 2. The surface of the whiskers in Figures 2(a) and (b) is very smooth, because no detectable reaction occurred under these conditions.…”

Section: A Interfacial Reaction In Al 18 B 4 O 33 /Al Compositementioning

confidence: 99%

Effect of interfacial reaction on bending strength of Al18B4O33 whisker-reinforced aluminum composites

Yao

Sasaki

Jin

et al. 1998

Metall Mater Trans A

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The present study deals with the mechanism of the interfacial reaction and the microstructure of the interface in aluminum borate whisker-reinforced pure aluminum matrix composites prepared by a squeeze casting process. By means of X-ray diffraction analysis (XRDA), differential thermal analysis (DTA), scanning electron microscopy (SEM), and high resolution transmission electron microscopy (HRTEM), it has been found that no interfacial reaction occurred under the as-cast condition, whereas aluminum reacted with the whiskers when the composite was reheated at a temperature higher than 726 ЊC. The reaction produced ␥-Al 2 O 3 . Based on HRTEM observation, it is considered that the whiskers bond to the aluminum matrix directly after squeeze casting. The observation also shows that there is a specific orientation relationship between the reaction product and whisker, {002} Al 18 B 4 O 33 {220} ␥-Al 2 O 3 , ͗200͘ Al 18 B 4 O 33 ͗111͘ ␥-Al 2 O 3 , which leads to a coherent interface with a mismatch of less than 1 pct. The interfacial bonding state changed after heating under different conditions. Propagation of cracks in each interfacial state was observed by SEM, and the effects of the interfacial reaction on the bending strength were studied with the microstructure of the interface.

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“…The γ -to-θ and then α phase transition temperature is important for catalyst and catalyst-support materials used at high temperature, because the specifi c surface area decreases drastically at the transition, and catalytic activity is lost. Many investigators have reported the effects on the transition temperature of adding various cations 2, 3 . There have also been numerous studies dedicated to improving the thermal stability of γ-Al 2 O 3 because its phase transformations are thought to directly affect both the surface area and the number of active sites, which are very important with respect to its practical application.…”

Section: Introductionmentioning

confidence: 99%

Barium oxide as a modifier to stabilize the γ-Al₂O₃ structure

Pakdehi

Rasoolzadeh

Moghadam

2016

Polish Journal of Chemical Technology

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This research concentrated on the structural stability of γ-alumina (γ-Al 2 O 3 ) was investigated by a combination of differential thermal analysis, X-ray diffractometry and surface-area measurements. The γ -to-θ and then α phase transitions were observed as an exothermic peak at 1000°C-1400°C in the DTA curves. The role of barium oxide as a modifi er to stabilize γ-Al 2 O 3 structure has been investigated. XRD measurements show that after calcination at 1000°C for 2 h, a signifi cant fraction of the pure γ-Al 2 O 3 (BaO-free) transformed to θ-Al 2 O 3 while that the transition phase in alumina samples modifi ed by BaO have been reduced signifi cantly. Barium oxide, eliminate pentacoordinated aluminum ions through coordinative saturation and alter these ions into octahedral cations and effectively suppressed the γ -to-α phase transition in Al 2 O 3 , which concluded as improving the thermal stability and porous properties of the experimental samples.

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Sintering and phase evolution of ?-Al2O3 with transition-metals addition at around ?-transition temperature

Cited by 28 publications

References 15 publications

The effect of La on Au-ceria catalyst for water gas shift reaction

The effect of La on Au-ceria catalyst for water gas shift reaction

Effect of interfacial reaction on bending strength of Al18B4O33 whisker-reinforced aluminum composites

Barium oxide as a modifier to stabilize the γ-Al₂O₃ structure

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Sintering and phase evolution of ?-Al2O3 with transition-metals addition at around ?-transition temperature

Cited by 28 publications

References 15 publications

The effect of La on Au-ceria catalyst for water gas shift reaction

The effect of La on Au-ceria catalyst for water gas shift reaction

Effect of interfacial reaction on bending strength of Al18B4O33 whisker-reinforced aluminum composites

Barium oxide as a modifier to stabilize the γ-Al2O3 structure

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Product

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Barium oxide as a modifier to stabilize the γ-Al₂O₃ structure