G. N. Subbanna

The Effect of Crystallinity on the Reversible Discharge Capacity of Nickel Hydroxide

The higher reversible discharge capacity exhibited by (bc: badly crystalline)‐nickel hydroxide compared to that of β‐nickel hydroxide can be attributed to the presence of regions characterized by turbostratic disorder in the former. These regions comprise the α‐modification of nickel hydroxide existing in an interstratified form within the sample. The α‐motifs in the are anion‐free, but hydrated, by virtue of which hydroxide exhibits a higher water content (11% by weight) compared to the β‐form (<1%).

Homogeneous precipitation from solution by urea hydrolysis: a novel chemical route to the α-hydroxides of nickel and cobalt

Homogeneous precipitation from solution by hydrolysis of urea at elevated temperatures (T= 120 °C) yields novel ammonia-intercalated α-type hydroxide phases of the formula M(OH)x(NH3)0.4(H2O)y(NO3)2 –x where x= 2,y= 0.68 for M = Ni and x= 1.85, y= 0 for M = Co. These triple-layered hexagonal phases (a= 3.08 ± 0.01 A, c= 21.7 ± 0.05 A) are more crystalline than similar phases obtained by chemical precipitation or electrosynthesis. This method can be adapted as a convenient chemical route to the bulk synthesis of α-hydroxides.

Electroless nickel hydroxide: synthesis and characterization

An electroless method of nickel hydroxide synthesis through the complexation-precipitation route which yields a fine particle material having a specific surface area of 178 m2 g−1 has been described. The morphology of this material as revealed by electron microscopy is distinctly different from the turbostratic nature of electrosynthesized nickel hydroxide. While the long range structure as shown by the X-ray diffraction pattern is similar to that of β-Ni(OH)2, the short range structure as revealed by infrared spectroscopy incorporates characteristics similar to that of α-Ni(OH)2. Cyclic voltammetry studies show that the electroless nickel hydroxide has a higher coulombic efficiency (>90%), a more anodic reversible potential and a higher degree of reversibility compared to the electrosynthesized nickel hydroxide and conventionally prepared nickel hydroxide.

On the existence of a nickel hydroxide phase which is neither α nor β

A novel phase of nickel hydroxide with an average interlayer spacing 5.4–5.6 A has been synthesized which is neither α nor β type but is an interstratification of both. It ages to the β form in strong alkali. These observations have implications on the dissolution–reprecipitation mechanism suggested for the α→β transformation of nickel hydroxide.

Pd-coated Ni nanoparticles by the polyol method: an efficient hydrogenation catalyst

Pd-coated Ni nanoparticles of 50 ± 15 nm size are prepared by the polyol method and characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and thermogravimetry analysis. Surface coverage of Pd on Ni particles is less than a monolayer for 0.5 and 1 at% Pd-coated Ni. Quantitative conversion of nitrobenzene to aniline is observed over these Pd-coated Ni particles at 27 °C under one atmospheric pressure of hydrogen. 0.5 and 1 at% Pd-coated Ni exhibits 10 times greater activity than that of typical colloidal palladium and platinum catalysts and 2.5 times higher activity than commercial 5 wt% Pd/C.

Novel electrosynthetic route to calcium phosphate coatings

Adherent calcium phosphate coatings have been electrosynthesized on stainless steel substrates by cathodic reduction of an aqueous acidified solution of calcium nitrate and diammonium hydrogenphosphate. The as-deposited coating is of the calcium hydrogen phosphate dihydrate which ages in an alkaline buffer to yield adherent coatings of the more useful calcium hydroxyapatite. This simple one step synthesis can be adapted for the fabrication of conformal calcium phosphate coatings on metal endoprostheses and provides an inexpensive alternative to such conventional coating techniques as laser ablation and rf sputtering.

Disorder in layered hydroxides: synthesis and DIFFaX simulation studies of Mg(OH)2

Powder X-ray diffraction (PXRD) patterns of magnesium hydroxides precipitated under different conditions exhibit characteristic non-uniform broadening of Bragg peaks which cannot be explained merely on the basis of Scherrer broadening. The broadening is shown to arise due to interstratification and turbostratic disorder.

Stabilization of α-nickel hydoxide in the presence of organic additives: chemical route to bulk synthesis

Organic molecules such as glucose or lactose mediate the synthesis and stabilize α-nickel hydroxide in a simple precipitation reaction, while, in the absence of these additives, β-nickel hydroxide is formed. The additives are not incorporated in the product phase.

Low temperature synthesis, structure and properties of alkali-doped La2NiO4, LaNiO3 and LaNi0.85Cu0.15O3 from alkali hydroxide fluxes

Abstract We report a low-temperature synthesis of La1.95Na0.05NiO4 from NaOH flux, La0.97K0.03NiO3 and La0.95K0.05Ni0.85Cu0.15O3 phases from KOH flux at 400xa0°C. Alkali-doped LaNiO3 can be prepared in KOH, but not in NaOH flux and La2NiO4 can be prepared in NaOH, but not in KOH flux. The flux-grown oxides were characterized by powder X-ray Rietveld profile analysis and electron microscopy. Sodium doped La2NiO4 crystallizes in orthorhombic structure and potassium doped LaNiO3-phases crystallizes in rhombohedral structure. La1.95Na0.05NiO4 is weakly paramagnetic and semiconducting while La0.97K0.03NiO3 and La0.95K0.05Ni0.85Cu0.15O3 show Pauli paramagnetic and metallic behavior.

Synthesis, structure and magnetic properties of Ln1 − xAxMnO3 (Ln = Pr, Nd; A = Na, K) from NaCl or KCl flux

Na- or K-substituted