Elham Kamali Heidari

Electrospun Carbon Nanofibers with in Situ Encapsulated Co3O4 Nanoparticles as Electrodes for High-Performance Supercapacitors

A facile electrospinning method with subsequent heat treatments is employed to prepare carbon nanofibers (CNFs) containing uniformly dispersed Co3O4 nanoparticles as electrodes for supercapacitors. The Co3O4/CNF electrodes with ∼68 wt % active particles deliver a remarkable capacitance of 586 F g(-1) at a current density of 1 A g(-1). When the current density is increased to 50 A g(-1), ∼66% of the original capacitance is retained. The electrodes also present excellent cyclic stability of 74% capacity retention after 2000 cycles at 2 A g(-1). These superior electrochemical properties are attributed to the uniform dispersion of active particles in the CNF matrix, which functions as a conductive support. The onionlike graphitic layers formed around the Co3O4 nanoparticles not only improve the electrical conductivity of the electrode but also prevent the separation of the nanoparticles from the carbon matrix.

Sandwich-structured graphene–NiFe2O4–carbon nanocomposite anodes with exceptional electrochemical performance for Li ion batteries

Graphene–NiFe2O4–carbon nanocomposites with a sandwich structure are synthesized via the hydrothermal growth of NiFe2O4 nanoparticles on graphene sheets, followed by carbon coating. As a promising anode material for Li ion batteries, the nanocomposites deliver exceptional cycle stability of 1195 mA h g−1 after 200 cycles measured at 500 mA g−1. This value is among the highest reported so far for anodes containing similar NiFe2O4 nanoparticles. The synergy arising from the conductive graphene substrate, the well-dispersed, ultrafine NiFe2O4 nanoparticles and the protective carbon layer sustaining the sandwich together is responsible for this trait.

Nanocavity-engineered Si/multi-functional carbon nanofiber composite anodes with exceptional high-rate capacities

A facile and scalable electrospinning method is employed to fabricate in situ N-doped, porous graphitic carbon nanofibers (CNFs) containing Si nanoparticles surrounded by nanocavities as durable high-rate Li-ion anodes. Nanocavities are created within the graphitic carbon spheres by electroless etching of the Si nanoparticles, which function not only as buffer to accommodate the volumetric expansion of Si upon lithiation but also as a conducting network for fast electron/ion transport. The Fe3C catalyst simultaneously formed within the fiber promotes the formation of highly graphitic carbon structures while the nitric acid etchant in situ generates functional CNFs with numerous mesopores and oxygenated functional groups, offering extra reaction sites for Li ions. With the ameliorating structural features acting synergistically, the resultant C–Si/F–CNF electrode delivers an exceptional initial reversible capacity of 1548 mA h g−1 at 0.1 A g−1, and remarkable high-rate capacities of 770 and 580 mA h g−1 at 2.0 and 5.0 A g−1 after 70 cycles with excellent capacity retention.

Nanocasting Synthesis of Ultrafine WO3 Nanoparticles for Gas Sensing Applications

Ultrafine WO3 nanoparticles were synthesized by nanocasting route, using mesoporous SiO2 as a template. BET measurements showed a specific surface area of 700 m 2/gr for synthesized SiO2, while after impregnation and template removal, this area was reduced to 43 m 2/gr for WO3 nanoparticles. HRTEM results showed single crystalline nanoparticles with average particle size of about 5 nm possessing a monoclinic structure, which is the favorite crystal structure for gas sensing applications. Gas sensor was fabricated by deposition of WO3 nanoparticles between electrodes via low frequency AC electrophoretic deposition. Gas sensing measurements showed that this material has a high sensitivity to very low concentrations of NO2 at 250°C and 300°C.

Controlled synthesis of cobalt carbonate/graphene composites with excellent supercapacitive performance and pseudocapacitive characteristics

Cobalt carbonate hydroxide/graphene aerogel and cobalt carbonate/graphene aerogel (CCH/GA and CC/GA) composites are synthesized as supercapacitor electrodes via a one-pot hydrothermal method. Optimized processing conditions are established by controlling the composite composition and microstructure, and their influence on the capacitance performance of the electrodes is identified. A remarkable specific capacitance of 1134 F g−1 at a current density of 1 A g−1 is obtained for the optimal nanowire-shaped CCH/GA electrode, which is among the highest capacitance values of cobalt compound electrodes with or without nanocarbons reported so far. The electrode also delivers exceptional rate performance and cyclic stability benefiting from the pseudocapacitive characteristics of CC-based active materials and the highly conductive, interconnected 3D-structured GA. The CC/GA electrode presents a high capacity of 731 F g−1 under the same conditions. The ex situ XPS analysis identifies the reversible redox reactions of cobalt cations during charge/discharge cycles as the electrochemical mechanism responsible for the high pseudocapacitive properties of CC-based electrodes.

Nanocasting Synthesis of Ultrafine WO 3 Nanoparticles for Gas Sensing Applications

Ultrafine WO3 nanoparticles were synthesized by nanocasting route, using mesoporous SiO2 as a template. BET measurements showed a specific surface area of 700 m 2/gr for synthesized SiO2, while after impregnation and template removal, this area was reduced to 43 m 2/gr for WO3 nanoparticles. HRTEM results showed single crystalline nanoparticles with average particle size of about 5 nm possessing a monoclinic structure, which is the favorite crystal structure for gas sensing applications. Gas sensor was fabricated by deposition of WO3 nanoparticles between electrodes via low frequency AC electrophoretic deposition. Gas sensing measurements showed that this material has a high sensitivity to very low concentrations of NO2 at 250°C and 300°C.

Death-specific rate due to asthma and chronic obstructive pulmonary disease in Iran

Asthma and chronic obstructive pulmonary disease (COPD) could be considered as a major health problem in industrialized and developing countries. This study was designed to analyze the trends of mortality from asthma and COPD at national and subnational levels in Iran based on National Death Registry, from 2001 to 2015.

SYNTHESIS AND MANIPULATION OF WO3 NANO PARTICLES FOR GAS SENSING APPLICATIONS

Ultra fine WO3 nanoparticles were synthesized by nanocasting route, using mesoporous SiO2 as a template. BET measurements showed a specific surface area of 700m2/gr for synthesized SiO2 while after impregnation and template removal, this area was reduced to 43m2/gr for WO3 nanoparticles. HRTEM results showed single crystalline nanoparticles with average particle size of about 5nm possessing a monoclinic structure which is the favorite crystal structure for gas sensing applications. Alternative electric field was applied to align synthesized WO3 nanoparticles between electrodes. Gas sensing measurements showed that this material has a high sensitivity to very low concentrations of NO2 at 250°C.

Nanocasting Synthesis of Ultrafine WO3

Ultrafine WO3 nanoparticles were synthesized by nanocasting route, using mesoporous SiO2 as a template. BET measurements showed a specific surface area of 700 m 2/gr for synthesized SiO2, while after impregnation and template removal, this area was reduced to 43 m 2/gr for WO3 nanoparticles. HRTEM results showed single crystalline nanoparticles with average particle size of about 5 nm possessing a monoclinic structure, which is the favorite crystal structure for gas sensing applications. Gas sensor was fabricated by deposition of WO3 nanoparticles between electrodes via low frequency AC electrophoretic deposition. Gas sensing measurements showed that this material has a high sensitivity to very low concentrations of NO2 at 250°C and 300°C.