Papers by Keyword: Boehmite

Abstract: Mesoporous boehmite (γ-AlOOH) was synthesized from naturally occurring coal-bearing kaolinite (CBK) by direct sulfuric acid leaching and hydrothermal method to explore a new possible route to the synthesis of product with high value added using the CBK. The Brunauner-Emmett-Teller (BET) surface area and the average crystallite size of the γ-AlOOH powder could be controlled in the range from 6.3 to 192.5 m² g^-1 and from 5.5 to 14.4 nm, respectively, by varying the reaction temperature and reaction time. Owing to its porous structure and high surface area, the synthesized mesoporous γ-AlOOH powder exhibited better adsorption abilities for CR and fluoride in contrast to commercial boehmite, and it only took 20 min to reach removal efficiency of 99.6% for CR and 90.5% for fluoride, when the initial concentration of CR and fluoride was 100 and 10 mg L^-1, respectively.

Abstract: Investigations of microarc calcium phosphate (CaP) boehmite-containing biocoatings on the pure titanium (Ti) alloy were presented. There were discovered relationships of coating properties (morphology, elemental and phase composition, zeta-potential, wettability) on the boehmite deposition parameters. A variation of the modification parameters of boehmite nanoparticles deposition allowed producing hydrophilic boehmite-containing CaP coatings with the roughness of 2.2-3.1 μm and nanoscale morphology. The influence of boehmite nanoparticles on the surface zeta-potential of the coating was found.

Abstract: The surface modification of microarc calcium phosphate coatings by boehmite nanoparticles deposition was studied. The powder of aluminium nitride AlN was deposited on the microarc calcium phosphate coatings, and then the hydrolysis reaction was initiated. The boehmite (AlO(OH)) was formed as a result of the reaction. The influence of boehmite nanoparticles deposition on the properties of calcium phosphate microarc coatings (i.e. the morphology, elemental and phase composition, wettability) was studied. Experimental results show that the introduction of boehmite nanoparticles affects the surface morphology and wettability of the coating.

Abstract: Thermochemically activated aluminum trihydroxide (Al (OH)₃) is an important intermediate for ceramics, construction materials, catalysts, etc. Functional properties of materials based on Al (OH)₃ depend on its phase composition and porosity. A series of thermochemically activated Al (OH)₃ calcined at temperatures from 120 to 800 °C were studied by low-temperature N₂ sorption, XRD and thermal analysis. It was shown that transformation of gibbsite to boehmite occurs below 300 °C and is accompanied by increasing of specific surface area and pore volume. Transformation of boehmite to γ-Al₂O₃ proceeds above 400 °C. The sample calcined at 500 °C was shown to consist of monophase γ-Al₂O₃ with specific surface area of 206 m²/g and pore volume of 0.55 cm³/g.

Abstract: Polyvinylpyrrolidone (PVP)/boehmite nanocomposites fibers were successfully prepared by electrospinning using boehmite sol containing PVP as the spinning solution. Several techniques, including Fourier transform infrared (FT-IR), thermal gravimetric analyzer (TGA) and field emission scanning electron microscopy (FE-SEM) were used to characterize their ingredients, thermal properties and morphology. The results showed that PVP concentration exhibited significant effect on the PVP/boehmite nanofibers morphology. With increasing PVP concentration, the morphology changed from beaded, beaded fiber to uniform fiber. These PVP/boehmite nanofibers can be used as good candidates for continuously preparing uniform and compact alumina nanofibers.

Abstract: The morphology and particle size of boehmite play a decisive role on the application of alumina that derived from it. In this paper, we employed pseudoboehmite that produced from Al2 (SO4)3•18H2O and NH3•H2O at 70 °C, pH 7.5 as precursor to synthesize boehmite, and utilized different seeding when preparing pseudoboehmite and boehmite. To identify the influence of seeding on the microstructure of pseudoboehmite and boehmite, the products were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and BET. The results indicate that the pseudoboehmite seeding has a significant influence on the morphology and particle size of pseudoboehmite to which we should pay high attention. However, the boehmite seeding does not play the role of crystal nucleus as expected. The further intrinsic mechanism study is ongoing.

Abstract: Boehmite nanoparticles with different shapes and lengths were used in the preparation of the boehmite films and coatings, and as the fillers for an organic polymer. Then, it was investigated how the shapes and lengths of the particles reflected the characteristics of the films, coatings and fillers. The films were prepared by casting an aqueous sol of the nanoparticles on a Teflon-lined plate, drying and peeling. The coatings were fabricated on porous alumina tubes or graphite sheets by dipping the substrates into a sol of the nanoparticles. The boehmite-polyvinyl alcohol (PVA) composite films, in which the nanoparticles are fillers, were prepared by casting a mixture of a boehmite nanoparticle sol and PVA. The films, coatings and composites were characterized by TEM, TG-DTA, gas permeability, pore size distribution and thermal expansion measurements. In the films, fibrous particles with aspect ratios over 50 aggregated in parallel to each other to form slit-like micropores, on the other hand, plate- and rod-like particles with aspect ratios below 10 randomly aggregated to form meso pores. Corresponding to this, for the coatings on porous alumina tubes and graphite sheets, the fibrous particles gave much low gas permeability and high thermostability, respectively, compared with the plate-like and rod-like particles. For the boehmite-PVA composite films, the fibrous particles gave lower thermal expansion than the plate-like and rod-like particles.

Abstract: The boehmite sol is prepared with cheap inorganic salt Al(NO₃)₃ and NH₃H₂O. The anodized aluminum alloy was sealed with the boehmite sol. Influences of concentration of Al³⁺, pH and temperature of sol on the properties of sol and the sealed film were studied. The results shows that the viscosity of sol increases and the stability becomes lower with the increase of Al³⁺concentration and pH of sol. The viscosities of sol become lower with the rises of its temperature. The thickness of anodized film increases when sealed with boehmite sol. The thickness value of sealed film increases with the increase of the sol viscosity. The properties of sealed film are better while the color of sol is azury. The corrosion resistance of sealed film was enhanced with the pH rising from 5.5 to 7 at the same concentrate and temperature of sol. The corrosion resistance in acidic solution is improved remarkably for sol sealed film as the sol temperature rises up to 60°C. The time of changing colour for sol sealing film is longer than that of the film sealed by distilled water.

Abstract: Hydrothermal treatment method was proposed to prepare boehmite and the effect of precursors on the morphology of beohmite was investigated. On the coordinate effect of organic and inorganic flower-like AlOOH assembled by nano-plates can be obtained by Al(NO₃)₃ as precursor. 3D urchin-like AlOOH superstructures consisting of nanoribbons were produced from hydrate AlCl₃ as reagents. Dissolution and recrystallinity of intermediate product AlOCl caused this result. Globe and hollow sphere morphologies of beohmite were synthesized by Al₂(SO₄)₃ in a water-alcohol system. The formation mechanism is also because of the dissolution and recrystallinity of intermediate product sodium sulfate aluminum. Beohmite prepared by hydrothermal treatment was transformed to γ- Al₂O₃ at 600°C. The morphologies of γ- Al₂O₃ powders were still kept their original forms.

Abstract: Uniform and monodisperse boehmite (γ-AlOOH) nanosheets with a thickness of less than 20 nm have been prepared by the hydrothermal treatment of amorphous boehmite. XRD and FTIR analysis showed that boehmite nanosheets have uniform and high degree of crystallinity. SEM micrographs indicated that boehmite has a leaf-like morphology with high anisotropy (with a length of 0.25～1 m and a width of 50～100 nm).