Citrate precursors

In [20], the composition of the citrate precursor of CoFe204 is proposed as Co3Fe604(C6H607)8-6H20, i.e., two protons are detached from each molecule of citric acid, and the complex compound could be classified as an acidic salt. Distinct signatures of complex formation are obtained by means of infrared (IR) spectroscopy and nuclear magnetic resonance (NMR) for citrate complexes of iron and yttrium, potential precursors of YFe04 and... 

Prasad, S., Vijayalakshmi, A., Gajbhiye, N.S., Synthesis of ultrafine cobalt ferrite by thermal decomposition of citrate precursor, J. Therm. Anal. Calorim. 52, 5-10 (1998). 

The six-membered aromatic A ring originates from three units of malonyl-CoA, produced from citrate precursors through the activity of a cytosolic acetyl-CoA carboxylase (ACC) (Fatland and others 2004) (see Fig. 5.1). These three malonyl-CoA units are added through sequential decarboxylation condensation reactions and actually represent the first committed step toward flavonoid biosynthesis. 

A series of manganese-cerium oxide catalysts with different Mn/Ce atomic ratios was prepared by thermal decomposition of amorphous citrate precursors [5]. The samples were prepared by varying the ratio between the manganese and cerium salts. 

Balagopal, N. et al., Citrate precursor derived alumina-ceria composite powders, Ceram. Int., 18, 107, 1992. 

When a chelated nickel citrate precursor is used fi)r catalyst preparation strikingly different results are obtained. Only very small nickel oxide nanoparticles can be observed after calcination, which are situated inside the mesopores of the support material. As a... 

The various compositions of catalyst were synthesized using citrate precursor technique to get ultrafme particles. For example to get ZnFe204 the precursor Zn3Fe6(C6Hs07)8 I2H2O was calcined at 550° C for 5h to get final product. 

The average agglomerate size of catalysts using citrate precursor technique was around... 

Citrate method The amorphous citrate precursors were prepared using a similar procedure as given by Courty et al. [5]. Adequate amounts of La(N03)3-6H20 and A1(N03)3-9H20, from FLUKA (puriss p.a.), were dissolved in deionized water to obtain a 1.25 M solution. Citric acid monohydrate (FLUKA, puriss p.a.) was added to the solution, with a molar ratio citric acid / total cations = 1. The solution was concentrated in a rotary evaporator at 330 K and 20 mbar for 3 h. The viscous and vitreous product was finally dried in a vacuum stove at 370 K and 90 mbar for 20 h. After drying, a foaming precursor was obtained, which was calcined in air at 1070 K for 8 h, at 1170 for 12 h, and finally at 1370 K for 8 h. The support materials were crushed and sieved. The size fracrion between 100 and 300 pm was used for catalyst preparation. 

Fig. 46. Phase compatibilities in the Y(0/C03)-Ba(0/C03)-Cu(0/C03) system, from Karen and Kjekshus (1991), as seen by PXD after repeated firings of citrate precursors at (a) 800°C and (b) 900°C in oxygen of ambient pressure containing 40ppm COj. Phenomenological frontiers of the oxide carbonate stability are shown by dotted shading, those of carbonate stability by line shading.

Citrate method is probably the most widespread and the most effective route to create high-surface-area perovskites (Figure 18.4) [23]. Additionally, the decomposition of the amorphous citrate precursors leads to mixed oxides or solid solutions of high homogeneity. Although often considered as a sol-gel method, citrate is a specific route. The comparison of the two mild chemical... 

Liu, Q., Wan, L., Chen, M., et al. (2009). Dry Citrate-precursor Synthesized Nanocrystalline Cobalt Oxide as Highly Active Catalyst for Total Oxidation of Propane, J. Catal., 263, pp. 104-113. 

Shlyakhtin OA., Vinokurov A.L., Baranov A.N., Tretyakov Y.D. Direct synthesis of Bi-2212 by thermal decomposition of salt precursors. J. Supacond. 1998 11 507-514 SUeo E.E., Rotelo R., Jacobo S.E. Nickel zinc ferrites prepared by the citrate precursor method. Physica B 2002 320 257-260... 

Werde K.V., Mondelaers D., Vanhoyland G., Nelis D., Van Bael M.K., Mullens J., Van Poucke L.C., Van der Veken B., Desseyn H.O. Thermal decomposition of the ammonium zinc acetate citrate precursor for aqueous chemical solution depositions ofZnO.J. Mater. Sci.2002 37 81-88... 

Randhawa BS, Dosanjh HS, Kaur M (2009) Preparation of spinel ferrites from citrate precursor route. A comparative study. Ceram Int 35 1045-1049... 

Inexpensive Fe(III) precursors are used in sol-gel methods to substitute Fe(II) precursors. For example, a water-free sol-gel method using lauric acid as a surfactant has been used to prepare porous LiFeP04 with high specific surface area. Its reversible capacities at 5 C and 10 C are 142 and 125 mAh/g, respectively. In contrast, LiFeP04 prepared without the surfactant shows capacities of 146 and 90 mAh/g at C/10 and 5 C, respectively. Ferric citrate and LiH2P04 can also be used as primary materials to prepare a porous LiFeP04/C composite. In this sol-gel method, the citrate precursor... 

Amdouni N, Zarrouk H, Soulette F, Mien C (2003) LiAlyCoi y02 (0.0 < y < 0.3) intercalation compounds synthesized from the citrate precursors. Mater Chem Phys 80 205-214... 

Amdouni N, Zarrouk H, Julien CM (2003) Structural and electrochemical properties of LiCo02 and LiAlyCoi y02 (y = 0.1 and 0.2) oxides. A comparative study of electrodes prepared by the citrate precursor route. Ionics 9 47-55... 

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