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.

Control of Porosity by Using Isoreticular Zeolitic Imidazolate Frameworks (IRZIFs) as a Template for Porous Carbon Synthesis

Abstract: Herein, by using isoreticular zeolitic imidazolate frameworks (IRZIFs) as a template, we report the synthesis, morphology, and gas adsorption properties of porous carbon synthesized by a nanocasting method at 1000 °C, in which furfuryl alcohol (FA) was used as a carbon source. By using IRZIFs with variable porosity as templates, we could achieve control over the carbon porosity and H(2) and CO(2) uptake. The resultant microporous carbon C-70, synthesized by using ZIF-70 as the template, is the most porous (Brunauer-Emmett-Teller (BET) surface area 1510 m(2) g(-1)). Carbon C-68, synthesized by using ZIF-68, has moderate porosity (BET surface area 1311 m(2) g(-1)), and C-69, synthesized by using ZIF-69, has the lowest porosity in this series (BET surface area 1171 m(2) g(-1)). The porous carbons C-70, C-68, and C-69, which have graphitic texture, have promising H(2) uptake capacities of 2.37, 2.15, and 1.96 wt %, respectively, at 77 K and 1 atm. Additionally, C-70, C-68, and C-69 show CO(2) uptake capacities of 5.45, 4.98, and 4.54 mmol g(-1), respectively, at 273 K and 1 atm. The gas uptake trends shown by C-70, C-68, and C-69 clearly indicate the dependence of carbon porosity on the host template. Moreover, the as-synthesized carbons C-70, C-68, and C-69 show variable conductivity.

Two ferromagnetic phases with different spin states of Mn and Ni in LaMn 0.5 Ni 0.5 O 3

Abstract: A ferromagnetic transition below 280 K is observed in the temperature variation of the magnetization, measured using high magnetic fields, for samples of ${\mathrm{LaMn}}_{0.5}{\mathrm{Ni}}_{0.5}{\mathrm{O}}_{3}$ synthesized by the high-temperature solid-state reaction method. On the other hand, two well-defined magnetic transitions, at $\ensuremath{\sim}150$ and $\ensuremath{\sim}280\mathrm{K},$ are observed in low-field zero-field-cooled (ZFC) magnetization ${(M}_{\mathrm{ZFC}})$ measurements on these samples, indicating the possibility for the existence of two different ferromagnetic phases of the compound. ${\mathrm{LaMn}}_{0.5}{\mathrm{Ni}}_{0.5}{\mathrm{O}}_{3},$ synthesized by a low-temperature method, shows a single magnetic transition at $\ensuremath{\sim}150\mathrm{K}$ for samples annealed below $500\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ and a single magnetic transition at 280 K for samples annealed above $1000\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ in the low-field ${M}_{\mathrm{ZFC}}$ measurements. Broad or multiple magnetic transitions are observed for the low-temperature samples annealed in the temperature range $500--1000\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$ High-temperature magnetic susceptibility, powder x-ray-diffraction, and core-level x-ray photoelectron spectroscopic studies on the single-phase samples (annealed at 400 and $1300\ifmmode^\circ\else\textdegree\fi{}\mathrm{C})$ indicate that the nanocrystalline material (obtained at $400\ifmmode^\circ\else\textdegree\fi{}\mathrm{C})$ with spin states of Mn and Ni as ${\mathrm{Mn}}^{4+}$ and ${\mathrm{Ni}}^{2+}$ undergoes a magnetic transition below 150 K, whereas high temperature $(1300\ifmmode^\circ\else\textdegree\fi{}\mathrm{C})$ annealed material with spin states like ${\mathrm{Mn}}^{3+}$ and low-spin ${\mathrm{Ni}}^{3+}$ becomes ferromagnetic below 280 K. A charge disproportionation of the type ${\mathrm{Mn}}^{4+}+{\mathrm{Ni}}^{2+}\ensuremath{\rightarrow}{\mathrm{Mn}}^{3+}+{\mathrm{Ni}}^{3+}$ takes place when the low-temperature synthesized ${\mathrm{LaMn}}_{0.5}{\mathrm{Ni}}_{0.5}{\mathrm{O}}_{3}$ is annealed above $500\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$ The results give evidence for the existence of two different phases of ${\mathrm{LaMn}}_{0.5}{\mathrm{Ni}}_{0.5}{\mathrm{O}}_{3}$ with different crystal structures and different spin states of Mn and Ni.