Impact of Oxalate Ligand in Co-Precipitation Route on Morphological Properties and Phase Constitution of Undoped and Rh-Doped BaTiO3 Nanoparticles

In order to design and tailor materials for a specific application like gas sensors, the synthesis route is of great importance. Undoped and rhodium-doped barium titanate powders were successfully synthesized by two routes; oxalate route and classic route (a modified conventional route where solid-state reactions and thermal evaporation induced precipitation takes place). Both powders were calcined at different temperatures. X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX) and Brunauer-Emmet-Teller (BET) analyses are employed to identify the phases and polymorphs, to determine the morphology, the chemical composition and the specific surface area of the synthesized materials, respectively. The so-called oxalate route yields pure BaTiO3 phase for undoped samples at 700 °C and 900 °C (containing both cubic and tetragonal structures), while the classic route-synthesized powder contains additional phases such as BaCO3, TiO2 and BaTi2O5. Samples of both synthesis routes prepared by the addition of Rh contain no metallic or oxide phase of rhodium. Instead, it was observed that Ti was substituted by Rh at temperatures 700 °C and 900 °C and there was some change in the composition of BaTiO3 polymorph (increase of tetragonal structure). Heat-treatments above these temperatures show that rhodium saturates out of the perovskite lattice at 1000 °C, yielding other secondary phases such as Ba3RhTi2O9 behind. Well-defined and less agglomerated spherical nanoparticles are obtained by the oxalic route, while the classic route yields particles with an undefined morphology forming very large block-like agglomerates. The surface area of the synthesized materials is higher with the oxalate route than with the classic route (4 times at 900 °C). The presence of the oxalate ligand with its steric hindrance that promotes the uniform distribution and the homogeneity of reactants could be responsible for the great difference observed between the powders prepared by two preparation routes.

Mesoporous MnOx–CeO2 composites for NH3-SCR: the effect of preparation methods and a third dopant

In this study, an optimal oxalate route was used to obtain nickel/cobalt doped MnOx–CeO2 mixed oxides. Nickel doped MnOx–CeO2 showed excellent NH3-SCR activity and H2O + SO2 resistance.

Structural Characterization and Magnetic Properties of Undoped and Ti-Doped ZnO Nanoparticles Prepared by Modified Oxalate Route

Ti-doped zinc oxide and pure zinc oxide nanoparticles were synthesized by a modified oxalate route using Averrhoa carambola fruit juice as a natural source of oxalate. The characteristics of the precursors have been investigated by FTIR, TGA, and XRD. The results from the investigation revealed that the precursors are zinc oxalate and Ti-doped zinc oxalate which readily decompose at 450°C. The as-prepared precursors were calcined at 450°C for 4 hours, and the decomposition products have been characterized by XRD, SEM, EDX, and VSM. XRD results revealed crystallinity with hexagonal wurtzite structure, while the average grain size was found to be 26 nm for Ti-doped ZnO and 29 nm for ZnO, using calculations based on Debye-Scherrer equation. Furthermore, the morphological studies by SEM showed particle agglomeration, while the presence of Ti3+ in the zinc oxide lattice is indicated by EDS analysis. Finally the hysteresis loop from VSM results shows that Ti-doped ZnO exhibits ferromagnetism.

Synthesis and Characterization of CuO, TiO2, and CuO-TiO2 Mixed Oxide by a Modified Oxalate Route

Copper oxide (CuO), titanium oxide (TiO2), and Cu-doped TiO2 nanoparticles have been synthesized by pyrolysis of their corresponding precursors initially prepared by precipitation in aqueous solution using A. carambola fruit juice as a natural source of the precipitating agent (oxalate). The precursors were synthesized and characterized by FTIR, TGA, and PXRD. The results revealed that the precursors obtained were CuC2O4, TiO2(OH−)2C2O4, copper-doped titanium hydroxyl oxalate, and copper titanium hydroxyl oxalate. Complete decomposition for the as-prepared precursors containing titanium ions occurs at 600°C while impurity free copper oxalate decomposed at 450°C. The as-prepared precursors were decomposed and calcined at 600°C for 4 hours and the calcination products were characterized by XRD, SEM, and EDX. The results revealed the decomposition products to correspond to CuO, TiO2, Cu0.131Ti0.869O2, and CuO/TiO2.

Importance of porous structure and synergistic effect on the catalytic oxidation activities over hierarchical Mn–Ni composite oxides

Hierarchically porous manganese–nickel composite oxides (MNCOs) were successfully synthesized by an oxalate route and further applied for catalytic removal of benzene.