12003-67-7Relevant academic research and scientific papers
Large-scale, surfactant-free, hydrothermal synthesis of lithium aluminate nanorods: Optimization of parameters and investigation of growth mechanism
Joshi, Upendra A.,Jae, Sung Lee
, p. 3176 - 3184 (2007)
Lithium aluminate nanorods were successfully synthesized from Al 2O3 nanoparticles and lithium hydroxide by a simple, large-scale hydrothermal process without any surfactant or template. The various reaction parameters were optimized to achieve the maximum yield. The as-obtained nanorods had orthorhombic β-lithium aluminate structure with edges in the range of 40-200 nm and lengths of 1-2 μm confirmed by SEM, TEM, XRD, and NMR. Upon calcination at 1273 K for 12 h it transformed to γ-lithium aluminate, yet maintained the initial morphology, demonstrating the thermal stability. The ratio of lithium hydroxide to aluminum oxide showed a significant effect on the morphology as Li/Al = 1 gives microroses , whereas Li/Al = 3 and Li/Al = 15 gave microbricks and nanorods , respectively. Investigation of the mechanism showed that the nanorods were formed via a rolling-up mechanism. As we used all-inorganic raw materials and a simple synthetic procedure under mild conditions, the scale-up of this process for large-scale production should be very easy.
The influences of heat treatment on the structural properties of lithium aluminates
Ribeiro,Silva,Mohallem
, p. 857 - 864 (2001)
Two synthesis routes, sol precipitation and sol gelation, using aluminum isopropoxide and lithium nitrate as precursors have been used to prepare lithium aluminate. The sol precipitation method (LISOL) produced a mixture of γ-LiAlO2 and LiAl5O8, and sol gelation (LIGEL) produced pure γ-LiAlO2, both at 750°C. The density and specific surface area of the ceramic powders calcined at 1150°C were 2.72 g cm-3 and 6 m2 g-1, respectively, for the powders obtained by sol precipitation and 2.47 g cm-3 and 2 m2 g-1, respectively, for the powders obtained by sol gelation. The synthesized powders presented thermal stability over 600°C and the sintering process occurred in the temperature range of 600-1400°C. The absorbed heat by the material in this temperature range during DTA/TG experiment showed that the sintering process was more efficient when the powders were previously calcined over 550°C.
Cation coordination and Fe3+ luminescence in LiAlO2 polymorphs prepared by a hydrothermal method
Kutty,Nayak
, p. 249 - 262 (1999)
The polymorphs α-, β-, and γ-LiAlO2 were synthesized by a hydrothermal method. The as-prepared product obtained at 240 °C was β-LiAlO2, which converted completely to γ-LiAlO2 above 1000 °C. α-LiAlO2 was obtained by the decomposition of LiAl(OH)4·H2O prepared by imbibition of LiOH into LiAl2(OH)7·2H2O hydrothermally at 140 °C. Solid state MAS NMR (magic-angle spinning nuclear magnetic resonance) studies indicate that Li+ uniquely occupies octahedral sites in all the polymorphs. This observation indicates that the results of XRD and crystal structure studies on β- and γ-LiAlO2 reported in the literature that indicate the presence of Li- in the tetrahedral site are apparently in error with respect to Li+ coordination. The other cation, Al3+, occupied octahedral sites in α-LiAlO2 and tetrahedral sites in the β- and γ-LiAlO2. The Fe3+ doped in the various polymorphic forms of this compound was found to uniquely occupy the octahedral Li+ site. EPR spectrum of the Fe3+ doped in these polymorphs indicates that during the transformation this site is distorted. The Fe3+ photoluminescent emission maximum was different for each polymorph. The difference in the luminescence characteristics among the polymorphic forms is due to the change in the site symmetry because of the distortion of the octahedra occupied by Fe3+ across the phase transition. The infrared spectrum indicates that site symmetry is lowered during the phase transition.
Impact of the memory effect on the catalytic activity of Li-Al hydrotalcite-like compounds for the cyanoethylation reaction
Pavel,Zvoianu,B?rjega,Angelescu
, p. 1106 - 1111 (2010)
The target of this work is to investigate structural and textural modifications of Li-Al hydrotalcite-like compounds by memory effect and their impact on the catalytic activity of these solids for the cyanoethylation reaction. The samples have been characterized by XRD, FT-IR, TG-DTG, surface area and porous structure. The catalytic test results showed that the reconstruction of the hydrotalcite leads to a decrease of the catalytic activity compared to the parent hydrotalcite. This fact may be related either to the smaller specific surface area of the reconstructed form or to the leaching of Li+ during reconstruction. It has been also noticed that the calcination of Li-Al hydrotalcite leads to the formation of a α-LiAlO 2 stable phase.
Thermochemical capture of carbon dioxide on lithium aluminates (LiAlO 2 and Li5AlO4): A new option for the CO 2 absorption
Avalos-Rendon, Tatiana,Casa-Madrid, Julio,Pfeiffer, Heriberte
, p. 6919 - 6923 (2009)
Lithium aluminates (LiAlO2 and Li5AlO4) were synthesized, characterized, and tested as possible CO2 captors. LiAlO2 did not seem to have good qualities for the CO2 absorption. On the contra
Local Coordination of Low-Spin Ni3+ Probes in Trigonal LiAl yCo1-yO2 Monitored by HF-EPR
Stoyanova, Radostina,Zhecheva, Ekaterina,Alcántara, Ricardo,Tirado, José L.
, p. 4053 - 4057 (2004)
The local coordination of low-spin Ni3+ probes in trigonal LiAlyCo1-yO2 was studied using high-frequency EPR spectroscopy. This technique allows distinguishing between two types of Ni3+ ions: Ni3+ ions in trigonal crystal field ( 2Eg ground state) and Ni3+ ions in tetragonal crystal field (2A1g ground state). When a Ni3+ ion is in a uniform Co environment, the orbitally degenerate state for Ni 3+ is preserved and the EPR spectrum of the ground vibronic doublet state can be observed (intermediate Jahn-Teller effect). The value of g 1 decreases as the mean M - O bond is contracted. The local tetragonal distortion can be observed for Ni3+ ions located in a mixed Co6-yAly environment. Along the progressive replacement of Co by Al, the strength of the crystal field for Ni3+ increases gradually and the extent of the tetragonal distortion displays a tendency to increase. The maximum effect of Jahn-Teller distortion is achieved when the Ni3+ ion falls in a pure Al environment.
Subsolidus phase relations in the Al2O3-Li 2O-Ta2O5 (Nb2O5) systems
Zuev
, p. 424 - 426 (2007)
The phase composition has been studied and an equilibrium phase diagram has been designed for the Al2O3-Li2O-R 2O5 (R = Ta or Nb) systems in the subsolidus region up to 1000°C and 85 mol % Li2/s
Metal nitrate/fuel mixture reactivity and its influence on the solution combustion synthesis of γ-LiAlO2
Iano?, Robert,Laz?u, Ioan,P?curariu, Cornelia
, p. 209 - 214 (2009)
The reactivity of LiNO3 and Al(NO3)3 with respect to urea and β-alanine was investigated. Experimental results proved that β-alanine is a more suitable fuel for LiNO3, whereas urea seems to be more adequate for
Hydrothermal routes to various controllable morphologies of nanostructural lithium aluminate
Hu, Linfeng,Qiao, Bin,Tang, Zilong,Zhang, Zhongtai
, p. 1407 - 1413 (2007)
The α-LiAlO2 powders have been successfully prepared by a hydrothermal route based on using the surfactant of heax-adecyltrimethyl ammonium bromide (CTAB) as the template. One-dimensional (1D) nanorods with higher and lower aspect ratio, 2D mesoporous microsheets were respectively observed with different concentration of the surfactants. A high specific surface area up to 151 m2/g was obtained by this method. The formation mechanism of the nanostructural lithium aluminate was proposed.
Sol-gel synthesis of lithium aluminate
Valenzuela, Miguel A.,Jimenez-Becerril, Jaime,Bosch, Pedro,Bulbulian, Silvia,Lara, Victor H.
, p. 455 - 460 (1996)
LiAlO2 was prepared by two sol-gel methods using simultaneous hydrolysis of the reagents: aluminum sec-butoxide/ lithium methoxide and aluminum sec-butoxide/LiOH. The resulting ceramic powders were compared with those prepared by two conventional methods (i.e., solid-state fusion and peroxide). The sol-gel method provided powders with a very high γ-LiAlO2 content after calcining at temperatures as low as 700°C when LiOH was used. The solids were characterized by AAS, DTA, TGA, XRD, and SEM.
