National Chemical Laboratory

About: National Chemical Laboratory is a facility organization based out in Pune, Maharashtra, India. It is known for research contribution in the topics: Catalysis & Nanoparticle. The organization has 8891 authors who have published 14837 publications receiving 387600 citations.

Structural studies on NiO-CeO2-ZrO2 catalysts for steam reforming of ethanol

Abstract: The influence of Ce/Zr ratio on the redox behavior of Ni in a series of NiO-CeO2-ZrO2 catalysts was investigated using in situ electron paramagnetic resonance (EPR), diffuse reflectance UV-visible (DRUV-visible) and X-ray photoelectron spectroscopy (XPS). At all concentrations, a small amount of Ni (species I) substitutes in the fluorite lattice. Superparamagnetic, nanosize Ni crystallites (species II) were found in samples with 1–5 wt.% NiO and ferromagnetic, larger Ni crystallites (species III) were detected in samples with 20 wt.% or more NiO when contacted with hydrogen. Ce promoted the reduction of Ni. The reducibility of Ni decreased in the order: I>III>II. At steam reforming conditions (in the presence of H2+H2O+hydrocarbon/alcohol at 773 K), the extent of Ni reduction varies in the order: H2+alkane>H2+alcohol>H2 alone. Catalytic activity and especially stability in the steam reforming of bio-ethanol (containing 5 ppm S) correlates with the type III Ni species and is influenced by both the Ni-content and the Ce/Zr ratio in the support. A catalyst of composition NiO (40 wt.%)-CeO2 (30 wt.%)-ZrO2 (30 wt.%) maintained its activity for more than 500 h without deactivation.

Electrostatically controlled diffusion of carboxylic acid derivatized silver colloidal particles in thermally evaporated fatty amine films

Abstract: We have recently demonstrated that carboxylic acid derivatized silver colloidal particles can be incorporated in thermally evaporated fatty amine films by immersion of the films in the silver sol and that the process is controlled through electrostatic interactions [Sastry, M.; Patil, V.; Mayya, K. S. Langmuir 1997, 13, 4490]. In this paper, we analyze the influence of colloidal particle concentration, solution pH, and film thickness on the kinetics of cluster incorporation in thermally evaporated fatty amine films obtained from quartz-crystal microgravimetry (QCM) measurements in terms of a one-dimensional (1-D) Fickian-type diffusion model. Although it is found that 1-D diffusion adequately represents the cluster mass uptake kinetics observed using QCM, an interesting film-thickness dependence on the diffusivity was observed. The nature of the cluster-diffusion curves were quite different for amine films annealed prior to immersion in the colloidal solution. In these cases, the 1-D-diffusion model with ...

Superior field emission properties of layered WS2-RGO nanocomposites.

Abstract: We report here the field emission studies of a layered WS2-RGO composite at the base pressure of ~1 × 10−8 mbar. The turn on field required to draw a field emission current density of 1 μA/cm2 is found to be 3.5, 2.3 and 2 V/μm for WS2, RGO and the WS2-RGO composite respectively. The enhanced field emission behavior observed for the WS2-RGO nanocomposite is attributed to a high field enhancement factor of 2978, which is associated with the surface protrusions of the single-to-few layer thick sheets of the nanocomposite. The highest current density of ~800 μA/cm2 is drawn at an applied field of 4.1 V/μm from a few layers of the WS2-RGO nanocomposite. Furthermore, first-principles density functional calculations suggest that the enhanced field emission may also be due to an overalp of the electronic structures of WS2 and RGO, where graphene-like states are dumped in the region of the WS2 fundamental gap.