Preparation Method of Submicrometer‐Sized α‐Alumina by Surface Modification of γ‐Alumina with Alumina Sol

Han, Kyoung Ran; Lim, Chang Sup; Hong, Mee-Jeong; Jang, Jae Won; Hong, Kug Sun

doi:10.1111/j.1151-2916.2000.tb01269.x

Cited by 21 publications

(4 citation statements)

References 12 publications

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“…-Alumina with desirable surface properties such as high surface area and mesoporous properties is most commonly used as a high-temperature catalyst or catalytic support and as a membrane [18]. The synthesis of alumina by sol-gel technique generally produces a mixture of alumina phases ( , and ) and these transform to a stable -alumina phase by heating at high temperature [10,[19][20][21]. In 2004, Macêdo et al, reported the synthesis of -alumina by sol-gel method from a saturated aqueous solution of aluminium nitrate using urea as neutralizing and hydrolysis control agent [22].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of β-Alumina Particles and Surface Characterization

Karim¹

2011

TOCOLLSJ

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Alumina was synthesized via sol-gel technique by the hydrolysis of aluminium ion controlled by urea in aqueous media. The resulting sol composed of Al(OH) 3 particles coalesced and became a transparent gel. The freshly prepared gel was heated at 280°C to obtain alumina particles. The obtained particles were found to be amorphous-alumina particles with high porosity, characterized by FTIR, XRD and S BET techniques. Electron micrograph shows that the particles are nano-sized having non-spherical shape. Comparatively higher magnitude of adsorption of cationic surfactant indicated that the surface of alumina particles is negatively charged.

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Section: Introductionmentioning

confidence: 99%

Synthesis of β-Alumina Particles and Surface Characterization

Karim¹

2011

TOCOLLSJ

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“…The transformation rate could be increased by several orders of magnitude. 14 Under a saturated water vapor pressure at 190°C, ␣-alumina with some amount of boehmite was obtained from seeded aluminum hydroxide by Sharma et al 10 On the other hand, Han et al 8 used an alumina sol that transformed to ␣-alumina to modify the surface of ␥-alumina powder particles as a precursor of nanosized ␣-alumina seeds. However, submicrometer ␣-alumina powders with different morphologies were achieved only after heat-treating the ball-milled powders at a relatively high temperature (ϳ1100°C).…”

Section: Introductionmentioning

confidence: 99%

Hydrothermal Synthesis of Submicrometer α‐Alumina from Seeded Tetraethylammonium Hydroxide‐Peptized Aluminum Hydroxide

Yang

Mei

Ferreira

2003

Journal of the American Ceramic Society

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Submicrometer α‐alumina powder was successfully synthesized from seeded aluminum hydroxide peptized with tetraethylammonium hydroxide (TENOH) and hydrothermally treated at 200°C, using α‐alumina particles as seeds. The powders were characterized by XRD, SEM, DTA‐TG, and BET analyses. Results showed that seeding could greatly enhance the transition to α‐alumina at 200°C without formation of other transient alumina phases. α‐Alumina with some amount of boehmite formed in the seeded samples, whereas boehmite was the exclusive phase formed in the nonseeded sample. The morphology of α‐alumina embedded in the boehmite matrix for the seeded samples suggests a direct transition from aluminum hydroxide to α‐alumina without the formation of transient alumina phases. The formation of α‐alumina in the seeded samples at temperatures as low as 200°C could be attributed to a favored nucleation in the TENOH‐peptized aluminum hydroxide and to the subsequent hydrothermal treatment that supplies the necessary activation energy for crystal growth. Transition of boehmite to α‐alumina in the hydrothermally treated samples with low‐seed contents was significantly promoted by heat‐treating the samples at 500°C.

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“…19 As in the case of seeded boehmite, [23][24][25] the number frequency and dispersion homogeneity of α-alumina seeds in PA-S and PA-S-Ca precursor gels is the key parameter controlling the size of the α-alumina grains, which in turn significantly affects the low-temperature sintering behavior. Thus, the low-temperature densification behavior of PA-S-Ca powders forming a finer-grained microstructure is the result of the synergistic effect between the α-alumina nanoparticles and Ca-dopant, which segregates to the grain boundaries during the transformation/sintering and hinders grain growth, leading to low-temperature full densification and a finer-grained microstructure.…”

Section: Fabrication Of Fine-grained Alumina Ceramicsmentioning

confidence: 99%

Densification of Ca-doped alumina nanopowders prepared by a new sol–gel route with seeding

Odaka

Yamaguchi

Fujita³

et al. 2008

Journal of the European Ceramic Society

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This paper demonstrates that the Ca-doped alumina nanopowders prepared by a new sol-gel route using polyhydoxoaluminum (PHA) and CaCl 2 solutions under α-alumina seeding represent a viable option for producing fine-grained ceramics. Appropriate conditions for producing Ca-doped alumina nanopowders suitable for low-temperature finer-grained densification were 0.10 mol% Ca-doping, 5 mass% α-alumina seeding and a calcination temperature of 900˚C. These conditions led to the formation of new nano-sized alumina powders, which consisted of ~80 nm α-alumina particles and γ-alumina nanoparticles. Using these Ca-doped nanopowders, fully densified alumina ceramics with a uniform microstructure composed of fine grains with an average grain size of 0.66 μm could be obtained at 1375˚C.Clearly, the Ca-doped nanopowders obtained here through the proposed sol-gel route are very suitable for fabricating dense, fine-grained alumina ceramics because an undoped sample with 5 mass% seeds led to a microstructure with an average grain size of 1.39 μm at 1375˚C.

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Preparation Method of Submicrometer‐Sized α‐Alumina by Surface Modification of γ‐Alumina with Alumina Sol

Cited by 21 publications

References 12 publications

Synthesis of β-Alumina Particles and Surface Characterization

Synthesis of β-Alumina Particles and Surface Characterization

Hydrothermal Synthesis of Submicrometer α‐Alumina from Seeded Tetraethylammonium Hydroxide‐Peptized Aluminum Hydroxide

Densification of Ca-doped alumina nanopowders prepared by a new sol–gel route with seeding

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