The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
Zhichao Yang - One of the best experts on this subject based on the ideXlab platform.
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surfactant free preparation of mesoporous solid hollow boehmite and Bayerite microspheres via double hydrolysis of naalo2 and formamide from room temperature to 180 c
Journal of Colloid and Interface Science, 2020Co-Authors: Zhichao YangAbstract:Abstract The transformation from solid boehmite microspheres to hollow Bayerite microspheres at room temperature (25 °C) was successfully realized via the double hydrolysis of NaAlO2 and formamide (FA) solution. Effects of reaction time, temperature and FA dos on the transformation process were studied in detail. The results show that hollow boehmite microspheres were obtained via increasing the temperature above 120 °C and the FA dos above 12 mL; amorphous alumina hydrate, solid boehmite and hollow Bayerite microspheres were also obtained at 25 °C for 1 h, 2 h and 24 h reactions, respectively; solid Bayerite microspheres were obtained by decreasing the FA dos below 4 mL at 25 °C. Because of the slow change of pH from 12.9 to 8.7, simultaneous dissolution and regeneration for different aluminum hydroxide were the key factors for forming hollow boehmite/Bayerite microspheres. The Al yield for boehmite microspheres reached 41.4% at 25 °C for a 2 h reaction; when increasing the temperature to 180 °C, the Al yield for hollow boehmite microspheres with higher crystallinity increased to 82.7%. Moreover, the solid/hollow boehmite microspheres with high surface areas showed outstanding adsorption capacities of 751.9 mg/g and 694.4 mg/g, respectively, for Congo red. This significant transformation of structure and morphology provides an effective strategy for preparing mono-phase hydrated alumina with excellent adsorption performance.
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Surfactant-free preparation of mesoporous solid/hollow boehmite and Bayerite microspheres via double hydrolysis of NaAlO2 and formamide from room temperature to 180 °C.
Journal of Colloid and Interface Science, 2019Co-Authors: Zhichao YangAbstract:Abstract The transformation from solid boehmite microspheres to hollow Bayerite microspheres at room temperature (25 °C) was successfully realized via the double hydrolysis of NaAlO2 and formamide (FA) solution. Effects of reaction time, temperature and FA dos on the transformation process were studied in detail. The results show that hollow boehmite microspheres were obtained via increasing the temperature above 120 °C and the FA dos above 12 mL; amorphous alumina hydrate, solid boehmite and hollow Bayerite microspheres were also obtained at 25 °C for 1 h, 2 h and 24 h reactions, respectively; solid Bayerite microspheres were obtained by decreasing the FA dos below 4 mL at 25 °C. Because of the slow change of pH from 12.9 to 8.7, simultaneous dissolution and regeneration for different aluminum hydroxide were the key factors for forming hollow boehmite/Bayerite microspheres. The Al yield for boehmite microspheres reached 41.4% at 25 °C for a 2 h reaction; when increasing the temperature to 180 °C, the Al yield for hollow boehmite microspheres with higher crystallinity increased to 82.7%. Moreover, the solid/hollow boehmite microspheres with high surface areas showed outstanding adsorption capacities of 751.9 mg/g and 694.4 mg/g, respectively, for Congo red. This significant transformation of structure and morphology provides an effective strategy for preparing mono-phase hydrated alumina with excellent adsorption performance.
Ray L Frost - One of the best experts on this subject based on the ideXlab platform.
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xps study of the major minerals in bauxite gibbsite Bayerite and pseudo boehmite
Journal of Colloid and Interface Science, 2006Co-Authors: Theo J Kloprogge, Loc V Duong, Barry J Wood, Ray L FrostAbstract:Synthetic corundum (Al2O3), gibbsite (Al(OH)(3)), Bayerite (Al(OH)(3)), boehmite (AlO(OH)) and pseudoboehmite (AlO(OH)) have been studied by high resolution XPS. The chemical compositions based on the XPS survey scans were in good agreement with the expected composition. High resolution A12p scans showed no significant changes in binding energy, with all values between 73.9 and 74.4 eV. Only Bayerite showed two transitions, associated with the presence of amorphous material in the sample. More information about the chemical and crystallographic environment was obtained from the 0 Is high resolution spectra. Here a clear distinction could be made between oxygen in the crystal structure, hydroxyl groups and adsorbed water. Oxygen in the crystal structure was characterised by a binding energy of about 530.6 eV in all minerals. Hydroxyl groups, present either in the crystal structure or on the surface, exhibited binding energies around 531.9 eV, while water on the surface showed binding energies around 533.0 eV. A distinction could be made between boehmite and pseudoboehmite based on the slightly lower ratio of oxygen to hydroxyl groups and water in pseudoboehmite. (c) 2005 Elsevier Inc. All rights reserved.
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comparison of the raman spectra of Bayerite boehmite diaspore and gibbsite
Journal of Raman Spectroscopy, 2001Co-Authors: Ray L Frost, Huada Ruan, Theo J KloproggeAbstract:Gibbsite and Bayerite are alumina trihydrate (Al(OH) 3). Gibbsite occurs abundantly in nature, usually as a major mineral component in bauxite whereas Bayerite is rarely found in nature. Boehmite and diaspore are alumina oxohydroxide (AlOOH) and are two other important minerals in bauxite. The Raman spectra of these four minerals were obtained using a Fourier transform Raman spectrometer operating at 1064 nm. Bayerite spectrum shows five absorption bands, 3652, 3542, 3449, 3438, and 3421 cm-1 and the gibbsite spectrum shows four strong and sharp absorption bands, 3619, 3523, 3433 and 3363 cm-1 in the hydroxyl stretching region. Four broad bands, 3426, 3365, 3229 and 2935 cm-1 and three weak bands, 3420, 3216 and 3090 cm-1 are present in this region for diaspore and boehmite, respectively. The Raman bands correspond well with the infrared absorption bands at 3620, 3525 cm-1 for gibbsite, 3365 cm-1 for diaspore and 3423, 3096 cm-1 for boehmite and these bands are assigned to be Raman and infrared active. The spectra of Bayerite, gibbsite and diaspore are complex while the spectrum of boehmite only illustrates four absorption bands in the low frequency region. Common bands of RT-Raman spectra at 1019, 892, 816, 710, 568, 539, 506, 429, 395, 379, 321, 306, 255 and 242 cm-1 were observed for gibbsite, 1079, 1068, 898, 866, 545, 434, 388, 322, 292, 250 and 239 cm-1 for Bayerite, 705, 608, 446, 260 and 216 cm-1 for diaspore, and 674, 495 and 360 cm-1 for boehmite. The differences in the vibrational spectra of Bayerite, gibbsite, diaspore and boehmite are interpreted as being due to the differences in the molecular structure of these minerals.
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comparison of raman spectra in characterizing gibbsite Bayerite diaspore and boehmite
Journal of Raman Spectroscopy, 2001Co-Authors: Huada Ruan, Ray L Frost, J T KloproggeAbstract:High-quality Raman spectra were used for the characterization of alumina phases of gibbsite, Bayerite, diaspore and boehmite. The Raman spectrum of gibbsite shows four strong, sharp bands at 3617, 3522, 3433 and 3364 cm in the hydroxyl stretching region. The spectrum of Bayerite shows seven bands at 3664, 3652, 3552, 3542, 3450, 3438 and 3420 cm. Five broad bands at 3445, 3363, 3226, 3119 and 2936 cm and four broad and weak bands at 3371, 3220, 3085 and 2989 cm-1 are present in the Raman spectrum of the hydroxyl stretching region of diaspore and boehmite. The hydroxyl stretching bands are related to the surface structure of the minerals. The Raman spectra of Bayerite, gibbsite and diaspore are complex whereas the Raman spectrum of boehmite shows only four bands in the low-wavenumber region. These bands are assigned to deformation and translational modes of the alumina phases. A comparison of the Raman spectrum of bauxite with those of boehmite and gibbsite showed the possibility of using Raman spectroscopy for on-line processing of bauxites that contain a mixture of alumina phases.
Theo J Kloprogge - One of the best experts on this subject based on the ideXlab platform.
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xps study of the major minerals in bauxite gibbsite Bayerite and pseudo boehmite
Journal of Colloid and Interface Science, 2006Co-Authors: Theo J Kloprogge, Loc V Duong, Barry J Wood, Ray L FrostAbstract:Synthetic corundum (Al2O3), gibbsite (Al(OH)(3)), Bayerite (Al(OH)(3)), boehmite (AlO(OH)) and pseudoboehmite (AlO(OH)) have been studied by high resolution XPS. The chemical compositions based on the XPS survey scans were in good agreement with the expected composition. High resolution A12p scans showed no significant changes in binding energy, with all values between 73.9 and 74.4 eV. Only Bayerite showed two transitions, associated with the presence of amorphous material in the sample. More information about the chemical and crystallographic environment was obtained from the 0 Is high resolution spectra. Here a clear distinction could be made between oxygen in the crystal structure, hydroxyl groups and adsorbed water. Oxygen in the crystal structure was characterised by a binding energy of about 530.6 eV in all minerals. Hydroxyl groups, present either in the crystal structure or on the surface, exhibited binding energies around 531.9 eV, while water on the surface showed binding energies around 533.0 eV. A distinction could be made between boehmite and pseudoboehmite based on the slightly lower ratio of oxygen to hydroxyl groups and water in pseudoboehmite. (c) 2005 Elsevier Inc. All rights reserved.
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comparison of the raman spectra of Bayerite boehmite diaspore and gibbsite
Journal of Raman Spectroscopy, 2001Co-Authors: Ray L Frost, Huada Ruan, Theo J KloproggeAbstract:Gibbsite and Bayerite are alumina trihydrate (Al(OH) 3). Gibbsite occurs abundantly in nature, usually as a major mineral component in bauxite whereas Bayerite is rarely found in nature. Boehmite and diaspore are alumina oxohydroxide (AlOOH) and are two other important minerals in bauxite. The Raman spectra of these four minerals were obtained using a Fourier transform Raman spectrometer operating at 1064 nm. Bayerite spectrum shows five absorption bands, 3652, 3542, 3449, 3438, and 3421 cm-1 and the gibbsite spectrum shows four strong and sharp absorption bands, 3619, 3523, 3433 and 3363 cm-1 in the hydroxyl stretching region. Four broad bands, 3426, 3365, 3229 and 2935 cm-1 and three weak bands, 3420, 3216 and 3090 cm-1 are present in this region for diaspore and boehmite, respectively. The Raman bands correspond well with the infrared absorption bands at 3620, 3525 cm-1 for gibbsite, 3365 cm-1 for diaspore and 3423, 3096 cm-1 for boehmite and these bands are assigned to be Raman and infrared active. The spectra of Bayerite, gibbsite and diaspore are complex while the spectrum of boehmite only illustrates four absorption bands in the low frequency region. Common bands of RT-Raman spectra at 1019, 892, 816, 710, 568, 539, 506, 429, 395, 379, 321, 306, 255 and 242 cm-1 were observed for gibbsite, 1079, 1068, 898, 866, 545, 434, 388, 322, 292, 250 and 239 cm-1 for Bayerite, 705, 608, 446, 260 and 216 cm-1 for diaspore, and 674, 495 and 360 cm-1 for boehmite. The differences in the vibrational spectra of Bayerite, gibbsite, diaspore and boehmite are interpreted as being due to the differences in the molecular structure of these minerals.
Nobuyoshi Koga - One of the best experts on this subject based on the ideXlab platform.
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A comparative study of the effects of decomposition rate control and mechanical grinding on the thermal decomposition of aluminum hydroxide
Journal of Thermal Analysis and Calorimetry, 2005Co-Authors: Nobuyoshi KogaAbstract:Two different processes of the thermal decomposition of synthetic Bayerite, i.e., the non-isothermal decomposition of mechanically ground sample in flowing N2 and the controlled rate thermal decomposition of crystalline Bayerite under vacuum, were investigated comparatively. In comparison with the conventional non-isothermal decomposition of crystalline Bayerite in flowing N2, the reaction temperature of the thermal decomposition was lowered by the individual effects of mechanical grinding of the sample and the reaction rate control. These decomposition processes indicated similar behavior characterized by the restricted changes of the specific surface area during the course of decomposition reaction and the formation of an amorphous alumina as the decomposition product. Different thermal behaviors were observed for those amorphous Al2O3 produced by the respective decomposition processes.
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controlled rate thermal decomposition of synthetic Bayerite under vacuum
Solid State Ionics, 2004Co-Authors: Nobuyoshi Koga, Shuto YamadaAbstract:Abstract Influences of the controlled decomposition rate and controlled residual pressure on the thermal decomposition process of synthetic Bayerite were investigated by applying a method of controlled rate evolved gas detection (CREGD). Comparing with the conventional process under linearly increasing temperature, the thermal decomposition process of the synthetic Bayerite at a controlled decomposition rate (∼10 −2 mg min −1 ) under controlled residual pressure (∼10 −3 Pa) was characterized by the lowered reaction temperature profile and small changes in the specific surface area of the sample during the course of reaction. Formation of an amorphous alumina as the decomposition product is another important result of the process control by the present CREGD. The amorphous alumina crystallizes to η-Al 2 O 3 at around 1100 K. It is worth noting that the characteristics of the reaction process under controlled rate conditions and the formation of amorphous alumina as the decomposition product are very similar to those of mechanochemically activated Bayerite under conventional linear heating.
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preparation and thermal decomposition of synthetic Bayerite
Journal of Thermal Analysis and Calorimetry, 2001Co-Authors: Nobuyoshi Koga, T Fukagawa, Haruhiko TanakaAbstract:The formation process of Bayerite, from an aqueous solution of sodium aluminate through enforced decomposition of aluminate ions by introducing CO2 gas and aging with mechanical stirring, was investigated by pH measurements of the mother solution during preparation reaction and characterization of precipitates obtained at various stages of preparation. An amorphous precipitate, produced initially by the reaction of introduced CO2, transformed to Bayerite via pseudoboehmite during aging. It was found that the crystalline particle size and morphology of the crystallized Bayerite change depending systematically on the preparation conditions. The reaction pathway of the thermal decomposition of the synthesized Bayerite was investigated by using thermoanalytical techniques.
Jiangong Li - One of the best experts on this subject based on the ideXlab platform.
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low temperature synthesis of single crystal alpha alumina platelets by calcining Bayerite and potassium sulfate
Journal of Materials Science & Technology, 2011Co-Authors: Xinghua Su, Jiangong LiAbstract:Single-crystal alpha alumina (α-Al 2 O 3 ) platelets were synthesized by calcining a powder mixture of Bayerite (α-Al(OH) 3 ) and potassium sulfate (K 2 SO 4 ) at 900°C. The crystalline phase evolutions and morphologies of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The synthesized samples mainly consisted of single-crystal α-Al 2 O 3 platelets with a diameter of 0.5–1.5 μm and a thickness of 50–150 nm. Moreover, with 3, 5, and 8 wt% (referred to the obtained alumina) α-Al 2 O 3 seeds adding into the powder mixture of Bayerite and potassium sulfate, the average diameter of α-Al 2 O 3 platelets can be reduced to 450, 240, and 220 nm, respectively. It is found that the sequence of the phase transformation is the Bayerite (α-Al(OH) 3 ) → boehmite (γ-AlOOH) → γ-Al 2 O 3 → α-Al 2 O 3 . Further analysis indicated that K 2 SO 4 can promote the phase transformation from γ-Al 2 O 3 to α-Al 2 O 3 and the formation of single-crystal α-Al 2 O 3 platelets might be attributed to the liquid phase K 3 Al(SO 4 ) 3 .
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Effect of Potassium Sulfate on the Low‐Temperature Formation of Alpha Alumina Platelets from Bayerite
Journal of the American Ceramic Society, 2010Co-Authors: Xinghua Su, Suqiang Li, Jiangong LiAbstract:The effect of potassium sulfate (K2SO4) on the phase transformation from Bayerite [α-Al(OH)3] to α-Al2O3 has been studied. K2SO4 and γ-Al2O3 react and form K3Al(SO4)3. Decomposition of K3Al(SO4)3 can supply the α-Al2O3 seeds for heterogeneous nucleation, accelerate the transformation from the γ-Al2O3 to α-Al2O3, and lower the formation temperature of α-Al2O3. α-Al2O3 particles grow into hexagonal platelets in the presence of the liquid phase K3Al(SO4)3. The α-Al2O3 platelets obtained by a 900°C calcination of the Bayerite and K2SO4 mixture have an average diameter of 1 μm and an average diameter/thickness ratio of 10.
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effect of potassium sulfate on the low temperature formation of alpha alumina platelets from Bayerite
Journal of the American Ceramic Society, 2010Co-Authors: Xinghua Su, Suqiang Li, Jiangong LiAbstract:The effect of potassium sulfate (K2SO4) on the phase transformation from Bayerite [α-Al(OH)3] to α-Al2O3 has been studied. K2SO4 and γ-Al2O3 react and form K3Al(SO4)3. Decomposition of K3Al(SO4)3 can supply the α-Al2O3 seeds for heterogeneous nucleation, accelerate the transformation from the γ-Al2O3 to α-Al2O3, and lower the formation temperature of α-Al2O3. α-Al2O3 particles grow into hexagonal platelets in the presence of the liquid phase K3Al(SO4)3. The α-Al2O3 platelets obtained by a 900°C calcination of the Bayerite and K2SO4 mixture have an average diameter of 1 μm and an average diameter/thickness ratio of 10.
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thermal decomposition of grinding activated Bayerite
Materials Research Bulletin, 2009Co-Authors: Xuelian Du, Xinghua Su, Yanqin Wang, Jiangong LiAbstract:Abstract Bayerite [α-Al(OH) 3 ] was ground for 2 h and its structure change was characterized. Soft grinding reduces the grain size of Bayerite, causes a lattice distortion in Bayerite, and accelerates the phase transition from Bayerite to the stable phases. With addition of α-Al 2 O 3 seeds, calcining the ground Bayerite at 300 °C leads to the onset of the α-Al 2 O 3 formation. The onset temperature and the completion temperature of the transformation to α-Al 2 O 3 in the ground Bayerite are about 800 and 150 °C lower than the onset temperature and the completion temperature of the transformation to α-Al 2 O 3 in the unground Bayerite, respectively. The thermal decomposition of the ground Bayerite undergoes the α-Al(OH) 3 → γ-AlOOH → γ-Al 2 O 3 → α-Al 2 O 3 path without the formation of the θ-Al 2 O 3 transition phase. The effect of soft grinding on the structure of Bayerite and the final thermal decomposition product of Bayerite will be discussed.
