28 documents found, page 1 of 3
Thermal decomposition of δ-MoN and ε-Fe2N synthesized under concentrated solar ...
Cañadas, Inmaculada; Oliveira, Fernando Almeida Costa; Rodriguez, Jose; Shohoji, NobumitsuABSTRACT: Decomposition temperatures of δ-MoN and ε-Fe2N synthesized with flowing NH3 gas under concentrated solar radiation heating were evaluated by Differential Scanning Calorimetry (DSC) in Argon (Ar) gas environment. The measured decomposition temperature of δ-MoN and ε-Fe2N were dependent on the solar synthesis conditions, particularly either NH3 or N2 gas flow rate at temperature. Sample containing δ-MoN...
Synthesis of Non-Cubic Nitride Phases of Va-Group Metals (V, Nb, and Ta) from M...
Shohoji, Nobumitsu; Oliveira, Fernando Almeida Costa; Galindo, José; Rodriguez, Jose; Cañadas, Inmaculada; Fernandes, Jorge Cruz; Rosa, Luís GuerraABSTRACT: Using a high-flux solar furnace, loosely compacted powders of Va-group transition metal (V, Nb, and Ta) were reacted with stream of NH3 gas (uncracked NH3 gas) being heated by concentrated solar beam to a temperature (T) range between 600 and 1000 degrees C. From V, sub-nitride V2N (gamma phase) and hypo-stoichiometric mono-nitride VN possessing fcc (face-centered cubic) crystal lattice structure (del...
Influence of linear flow velocity of uncracked ammonia (NH3) gas on formation o...
Shohoji, Nobumitsu; Oliveira, Fernando Almeida Costa; Galindo, José; Fernandes, Jorge Cruz; Rodríguez, José; Cañadas, Inmaculada; Rosa, Luís GuerraABSTRACT: Nitriding experiments for powder specimens of Mo and Fe were carried out using a solar furnace SF40 at PSA (Plataforma Solar de Almería) in Tabernas (Spain) in uncracked ammonia NH3 gas (NH3 gas with suppressed extent of dissociation by flowing) aiming at determining the range of linear velocity v of NH3 gas flow to yield higher nitride phases, δ-MoN for Mo and ε-Fe2N for Fe. Standard solar exposure d...
Entropy terms in statistical thermodynamic analysis formula for non-stoichiomet...
Shohoji, NobumitsuABSTRACT: A series of statistical thermodynamic analyses were made since 1974 for different types of non-stoichiometric interstitial compounds MXx under simplifying a priori assumption of constant interaction energy E(X-X) between nearest neighbour interstitial atoms X within a homogeneity composition range of MXx at arbitrary temperature T [K]. Mode of distribution of X atoms in interstitial sites in MXx latti...
Suppressed hydrogen (H) solubility in body centered cubic vanadium (V) by alloy...
Shohoji, NobumitsuEquilibrium isothermal pressure-composition relationships reported for H solubility in body centered cubic (bcc) V1-yMyHx (M = Cr, Mo, Fe or Co) by Suzuki et al. recently on this journal were analyzed with statistical thermodynamics under a priori assumption of constant H-H interatomic interaction energy E(H-H) within homogeneity composition range of bcc V1-yMyHx phase at arbitrary temperature T. Results of the...
Low-temperature nitriding of VA-group metal powders (V,Nb,Ta) in flowing NH3 ga...
Fernandes, Jorge Cruz; Oliveira, Fernando Almeida Costa; Rosa, Luís Guerra; Rodríguez, José; Cañadas, Inmaculada; Magalhães, Teresa; Shohoji, NobumitsuOver the last two decades, we have been using concentrated solar beam as the reaction heat source for synthesizing carbides and nitrides of d-group transition elements in view of usage of ecological renewable energy source in place of conventional heat sources using electricity or gas. In recent works [1,2] nitriding of VIa-group metals (Cr, Mo, W) and Fe in stream of NH3 gas with suppressed extent of dissociat...
Low-temperature nitriding of VA-group metal powders (V,Nb,Ta) in flowing NH3 ga...
Fernandes, Jorge Cruz; Oliveira, Fernando Almeida Costa; Rosa, Luís Guerra; Rodríguez, José; Cañadas, Inmaculada; Magalhães, Teresa; Shohoji, NobumitsuOver the last two decades, we have been using concentrated solar beam as the reaction heat source for synthesizing carbides and nitrides of d-group transition elements in view of usage of ecological renewable energy source in place of conventional heat sources using electricity or gas. In recent works [1,2] nitriding of VIa-group metals (Cr, Mo, W) and Fe in stream of NH3 gas with suppressed extent of dissociat...
Nitriding VI-group metals (Cr, Mo and W) in stream of NH3 gas under concentrate...
Oliveira, Fernando Almeida Costa; Rosa, Luís Guerra; Fernandes, Jorge Cruz; Rodriguez, Jose; Cañadas, Inmaculada; Magalhães, Teresa; Shohoji, NobumitsuCarbides and nitrides of d-group transition metals are classified as refractory hard material and their industrial importance has been recognized for long. In recent years, unique functionalities including catalytic function and superconductivity are discovered for this group of materials to raise serious attention of materials researchers and engineers to refractory carbides and nitrides as novel functional ma...
Roles of unstable chemical species and non-equilibrium reaction routes on prope...
Shohoji, NobumitsuChemical species might be held in a state being away from equilibrium state, at least temporarily, as represented by non-graphitic carbon and gaseous ammonia NH3 with suppressed extent of dissociation by flowing. Such chemical species X in unstable state would possess chemical activity a(X) considerably higher than that of the same element in equilibrium (reference) state. In case of carbon, a(C) of amorphous c...
Roles of unstable chemical species and non-equilibrium reaction routes on prope...
Shohoji, NobumitsuChemical species might be held in a state being away from equilibrium state, at least temporarily, as represented by non-graphitic carbon and gaseous ammonia NH3 with suppressed extent of dissociation by flowing. Such chemical species X in unstable state would possess chemical activity a(X) considerably higher than that of the same element in equilibrium (reference) state. In case of carbon, a(C) of amorphous c...