Sinter-active nanocrystalline CeO<Subscript>2</Subscript> powder prepared by a mixed fuel process: Effect of fuel on particle agglomeration

A modified combustion process, namely a mixed fuel process making use of a mixture of two fuels, such as citric acid and glycine has been developed to prepare nanocrystalline ceria powders. The effect of the mixed fuel and the different fuel to oxidant ratios on the decomposition characteristics of the gels were investigated by simultaneous thermal analysis experiments. It was established from various characterization techniques that the ceria powder prepared through the mixed fuel process has got the optimum powder characteristics, namely, a surface area of 33.33 m²/g and a crystallite size of 14 nm compared to the powders produced through the combustion process using a single fuel like glycine or citric acid. Such powders when sintered at 1250°C resulted in pellets with densities in the range of 94–96% of theoretical density. In this paper, we have carried out systematic studies on the sintering of ceria powders prepared by different approaches. The sintered ceramic from mixed fuel batch, exhibited and retained relative density more than 95% up to 1250°C and this data clearly underscores the ability of this process in developing ceria ceramics with increased stability against reduction.     

Rapid breakdown anodization technique for the synthesis of high aspect ratio and high surface area anatase TiO2 nanotube powders

Clusters of high aspect ratio, high surface area anatase-TiO₂ nanotubes with a typical nanotube outer diameter of about 18 nm, wall thickness of approximately 5 nm and length of 5-10 μm were synthesized, in powder form, by breakdown anodization of Ti foils in 0.1 M perchloric acid, at 10 V (299 K) and 20 V (∼275 and 299 K). The surface area, morphology, structure and band gap were determined from Brunauer Emmet Teller method, field emmission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman, photoluminescence and diffuse reflectance spectroscopic studies. The tubular morphology and anatase phase were found to be stable up to 773 K and above 773 K anatase phase gradually transformed to rutile phase with disintegration of tubular morphology. At 973 K, complete transformation to rutile phase and disintegration of tubular morphology were observed. The band gap of the as prepared and the annealed samples varied from 3.07 to 2.95 eV with increase in annealing temperature as inferred from photoluminescence and diffuse reflectance studies.     

A new palladium catalyzed protocol for atom-efficient cross-coupling reactions of triarylbismuths with aryl halides and triflates

A new palladium catalyzed protocol for an atom-efficient cross-coupling reaction of triarylbismuths with aryl halides and triflates has been described. The palladium catalytic system with Cs₂CO₃ base was found to be very efficient in DMA solvent to furnish excellent yields of cross-coupled functionalized biaryls in short reaction times.     

Eigenvalue Bounds for the Orr—Sommerfeld Equation and their Relevance to the Existence of Backward Wave Motion—II

Results of the previous paper with this title ( M. B. Banerjee et al., Stud. Appl. Math. 103:43–50) are extended to the case of neutrally stable perturbations.     

A comparative study on thermoresponsive magnetic nanohydrogels: role of surface-engineered magnetic nanoparticles

A comparative study of thermoresponsive poly(N-isopropylacrylamide)(PNIPAAm)-chitosan (CS)-based magnetic nanohydrogels (MNHGs) encapsulating functionalized Fe₃O₄ nanoparticles (NPs) in terms of the parameters governing their suitability for real hyperthermia is reported. Iron oxide NPs functionalized with (a) citric acid (CA-Fe₃O₄), (b) ethylenediamine (Amine-Fe₃O₄) and (c) dimercaptosuccininc (DMSA-Fe₃O₄) have been synthesized and their encapsulation into MNHGs was obtained through physical encapsulation method. The structural characterizations of synthesized materials include X-ray diffraction, FT-IR, TGA, ICP-AES and X-ray photoelectron spectroscopy (XPS). Encapsulation of the functionalized NPs into MNHGs were observed in TEM micrographs, while SEM and AFM micrographs confirmed their spherical morphology (~250–300 nm). Lower critical solution temperature (LCST) variation was measured by UV–visible spectrophotometer and differential scanning calorimetry (DSC). MNHGs exhibited sufficient magnetization and heating ability for hyperthermia. Typically, hydrogels containing CA-Fe₃O₄ (50 mg/ml) raised the temperature of the medium to 43 °C, a suitable dose for in vivo application in tumor-bearing mice.     

Magnetism in FeNiW disordered alloys: Experiment and theory

We report here an experimental study of magnetization of FeNiW alloys at different compositions. We have studied variation of magnetization with temperature (at low external fields) and magnetic field (at low temperatures). The alloy shows para to ferromagnetic transitions across the composition range. We do not find any indication of the spin-glass phase. We have supplemented the experimental work with theoretical analysis using the first-principles tight-binding linear muffin-tin orbitals based augmented space recursion method. Our theoretical estimates of magnetic moment and Curie temperatures agree well with experiment. Our mean-field phase analysis also does not indicate the possibility of a spin-glass phase.     

The clemmensen reduction of α,β-unsaturated ketones

The deoxygenation of the α,β-unsaturated ketones (1) and (5) under the Clemmensen condition yielded the olefins (2) and (6) along with their respective dimers (3+4) and (8+9). The α , β-unsaturated ketone (13) under similar treatment yielded the olefin (14) in satisfactory yield but the dimer could not be characterized. The deoxygenation of the α,β-unsaturated ketones (10) and (16) under similar con- ditions afforded the olefins (12) and (15) respectively in satisfactory yield along with the rearranged olefins (11) and (17) respectively. Epox-idation of the olefin (17) followed by heating with p-toluenesulfonic acid yielded the ketone (18).     

Liouville Type Dilatonic Potential in Locally Rotationally Symmetric Bianchi I Model

Exact solutions are obtained for a special case of locally rotationally symmetric Bianchi I models consisting of a dilaton scalar field and a Liouville type dilatonic potential interacting with an electromagnetic field coupled with gravity, and the corresponding properties of the space-time are discussed.