Fine powders of zirconia were prepared by employing combustion method with varying fuel to precursor molar ratios. The zirconia powders contained more amount of monoclinic phase as the fuel content was increased. This aspect was studied using XRD, IR and UV-vis diffuse reflectance techniques. The surface acid-base properties of these samples were also investigated by indicator titration method. The catalytic activity was probed with transfer hydrogenation reaction in liquid phase. It was found that combustion synthesized zirconia did not provide required active sites for transfer hydrogenation reactions in liquid phase unlike hydrous zirconia.

Gangavarapu Ranga Rao

Department Of Chemistry

H. Ranjan Sahu

Catalyst activity

combustion

Hydrogenation

infrared radiation

Powders

Reflection

Surface chemistry

Synthesis (chemical)

ultraviolet radiation

X ray diffraction analysis

FINE POWDERS

Molar ratios

MONOCLINIC PHASES

Zirconia

Fulltext

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Characterization of combustion synthesized zirconia powder by UV-vis, IR and other techniques

Bulletin of Materials Science

Solution combustion synthesis has been used for the preparation of finely dispersed copper oxide, copper and copper-nickel bimetallic particles. The structure and morphology of the materials are studied by XRD and SEM techniques. The fuel content in the combustion mixture is found to be a crucial factor in controlling the formation of oxide and metal particles. Starting with copper nitrate trihydrate as oxidizer (O) and carbohydrazide as fuel (F), we obtained CuO (F/O=0.75-1), mixed valence copper oxides. CuO+Cu2O, (F/O=1.0-1.5) and metallic Cu (F/O=2). At very low fuel content (F/O=0.5), a polymeric phase of copper hydroxide nitrate is isolated from the combustion residue. We also report the use of a new organic fuel N-tertiarybutoxy- carbonylpiperazine for the preparation of Cu, Ni and CuNi bimetallic particles. © 2004 Elsevier B.V. All rights reserved.

Materials Letters

Synthesis of CuO, Cu and CuNi alloy particles by solution combustion using carbohydrazide and N-tertiarybutoxy-carbonylpiperazine fuels

A series of ceria-incorporated zirconia (Ce1-xZrxO2, x = 0 to 1) solid solutions were prepared by employing the solution combustion synthesis route. The products were characterized by XRD and UV-Vis-NIR diffuse reflectance spectroscopy. The materials are crystalline in nature and the lattice parameters of the solid solution series follow Vegard's law. Diffuse reflectance spectra of the solid solutions in the UV region show two intense bands at 250 and 297 nm which are assigned respectively to Ce3+ ← O2- and Ce4+ ← O2- charge transfer transitions. The two vibrational bands in 6960 cm-1 and 5168 cm-1 in the NIR region indicate the presence of surface hydroxyl groups on these materials.

Proceedings of the Indian Academy of Sciences: Chemical Sciences

XRD and UV-Vis diffuse reflectance analysis of CeO2-ZrO2 solid solutions synthesized by combustion method

In this paper, we have reported the chemical synthesis of thermally stable mesoporous nanocrystalline zirconia with high surface area using a surfactant-assisted hydrothermal approach. We have employed different type of surfactants such as CTAB, SDS and Triton X-100 in our synthesis. The synthesized nanocrystalline zirconia multistructures exhibit various morphologies such as rod, mortar-pestle with different particle sizes. We have characterized the zirconia multistructures by X-ray diffraction study, Field emission scanning electron microscopy, Attenuated total refection infrared spectroscopy, UV-Vis spectroscopy and photoluminescence spectroscopy. The thermal stability of as synthesized zirconia multistructures was studied by thermo gravimetric analysis, which shows the high thermal stability of nanocrystalline zirconia around 900 degrees C temperature.

Journal of Nanoscience and Nanotechnology

Synthesis of Mesoporous Nanocrystalline Zirconia by Surfactant-Assisted Hydrothermal Approach

Highly thermally stable three-dimensional spongelike mesoporous CexZr1-xO2 solid solutions consisting of nanometer size particles with different Ce/Zr compositions were synthesized by a modified sol-gel procedure using a triethanolamine/water mixture as a solvent to be used in liquid Knoevenagel condensation reaction. These materials were investigated in detail by means of X-ray diffraction (XRD), Raman spectroscopy, chemical analysis, X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and adsorption microcalorimetry. The XRD, HRTEM and XPS studies proved the presence of nanocrystalline CexZr1-xO2 solid solutions. These solid solutions showed excellent chemoselectivity in the classical Knoevenagel reaction. The large pore sizes (around 10 nm) highlight the possibility of using CexZr1-xO2 as a support material for versatile catalytic systems. The results obtained from NH3 and SO2 adsorption microcalorimetry experiments successfully demonstrated the incorporation of ZrO2 into the CeO2 lattice resulting in both acidic and basic surface sites in a mixed oxide matrix. © 2009 Elsevier Inc. All rights reserved.

Journal of Catalysis

Knoevenagel condensation reaction over acid-base bifunctional nanocrystalline CexZr1-xO2 solid solutions

Nanocrystalline zirconium oxide powder has been prepared by the glowing combustion method using sucrose as the fuel and zirconyl nitrate as an oxidant in aqueous solution. The oxidant-to-fuel ratio was optimized (0.2) to prepare nanocrystalline zirconia. The influence of calcination temperature on the phase evolution of zirconia was also studied. The prepared powder was characterized by X-ray diffraction (XRD), fourier-transform infrared spectroscopy, thermal analysis, Raman spectroscopy, particle size analysis, scanning electron microscopy, transmission electron microscopy (TEM), and surface area analysis. Powder XRD pattern itself clearly revealed the presence of metastable tetragonal phase at room temperature. Raman spectrum revealed the presence of both tetragonal and monoclinic phases. TEM and surface area studies confirmed that the particles were in the nanoregime (5-30 nm). © 2010 The American Ceramic Society.

Journal of the American Ceramic Society

Preparation and Characterization of Nanocrystalline Zirconia Powders by the Glowing Combustion Method

Reduction of NO by CO catalysed by Rh/CeO2-ZrO2 solid solutions is investigated with the aim to elucidate the role of the CeO2-ZrO2 supports in modifying the activity of supported Rh. Two distinct kinetic regimes, characterised by different activation energies are observed below and above 500 K. It is proposed that below 500 K the reduction of NO occurs at the expenses of a concomitant oxidation of Ce3+ sites. In this model, the supported metal activates the reducing agent favouring the efficiency of Ce4+/Ce3+ redox couple. The influence of a high temperature reduction (H2, 1073 K) is also investigated. Such a treatment, which increases the reducibility at low temperatures of the CeO2-ZrO2 solid solution, promotes the efficiency of the catalysts at low temperatures, confirming the important role of the Ce4+/Ce3+ redox couple in determining the activity of the catalyst. © 1998 Academic Press.

Reduction of NO by CO over Rh/CeO2-ZrO2 catalysts: Evidence for a support-promoted catalytic activity

Alkylphenols when dehydrated over thoria at 500 °C gave diaryl ethers as main products. In addition to diaryl ethers, minor products were also formed, which were identified as xanthene and substituted xanthenes. Xanthenes were also formed in the reactions of phenol with alcohols over thoria. A mechanism is proposed for the formation of xanthenes. © 1980.

Journal	Bulletin of Materials Science
Publisher	Indian Acad of Sciences, Bangalore
ISSN	02504707
Open Access	Yes