abstract: Various biologically inspired flow field designs of the gas distributor (interconnector... more abstract: Various biologically inspired flow field designs of the gas distributor (interconnector) have been designed and simulated. Their performance using Nafion-212 with humidified H[subscript 2] and Air at 80 °C with the ANSYS Fluent Fuel Cell module software was evaluated. Novel interdigitated designs were optimized by obeying biologically inspired branching rules. These rules allow for more mathematically formal descriptions of flow field designs, enabling relatively simple optimization. The channel to land ratio was kept equivalent between designs with typical values between 0.8 and 1.0. The pressure drop and the current density distribution were monitored for each design on both anode and cathode sides. The most promising designs are expected to exhibit lower pressure drop however, low pressure drop can also be an indication of potential water flooding at higher operating current density. A biologically inspired interdigitated design with 9 inlet channels exhibited reduced p...
A recently predicted two dimensional (2D) carbon allotrope, tetrahex-carbon consisting of tetrago... more A recently predicted two dimensional (2D) carbon allotrope, tetrahex-carbon consisting of tetragonal and hexagonal rings, draws research interests due to its unique mechanical and electronic properties. Tetrahex-C shows ultrahigh strength, negative Poisson ratio, a direct band gap and high carrier mobility. In this work, we employ first-principles density-functional theory calculations to explore the directional dependence of electronic properties such as carrier effective mass and mobility in tetrahex-C. Tetrahex-C demonstrates strong anisotropicity in effective mass of charge carrier and therefore its mobility (electric conductance) exhibits a strong orientation preference. More interesting, we find that such unique anisotropic carrier effective mass and mobility can be controlled by simple uniaxial strain. The orientation dependence of effective mass can be dramatically rotated by 90 degrees through applying uniaxial tensile strain beyond ~ 7% (11%) in the armchair direction for ...
The existence of a new two dimensional CN2 structure was predicted using ab-initio molecular dyna... more The existence of a new two dimensional CN2 structure was predicted using ab-initio molecular dynamics (AIMD) and density-functional theory calculations. It consists tetragonal and hexagonal rings with C-N and N-N bonds arranged in a buckling plane, isostructural to tetrahex-carbon allotrope. It is thermodynamically and kinetically stable suggested by its phonon spectrum and AIMD. This nanosheet has high concentration of N and contains N-N single bonds with an energy density of 6.3 kJ/g, indicating potential applications as high energy density materials. It possesses exotic mechanical properties with negative Poisson's ratio and an anisotropic Young's modulus. The modulus in the zigzag direction is predicted to be 340 N/m, stiffer than h-BN and penta-CN2 sheets and comparable to graphene. Its ideal strength of 28.8 N/m outperforms that of penta-graphene. The material maintains phonon stability upon the application of uniaxial strain up to 10% (13%) in the zigzag (armchair) di...
Two novel three-dimensional (3D) crystal structures of carbon (C) and germanium carbide (GeC2) we... more Two novel three-dimensional (3D) crystal structures of carbon (C) and germanium carbide (GeC2) were predicted using first-principles density-functional theory (DFT) calculations. These newly discovered 3D carbon allotrope and GeC2 are in the space group of Fmmm (space group number 69). Their crystal structures have unique tetragonal/hexagonal rings formed by either C or Ge/C atoms. Both structures were proven to be thermodynamically stable through the phonon spectrum calculations. The C allotrope is a semiconductor with a wide band gap of 3.65 eV predicted by the hybrid density functional HSE06 method, while GeC2 is metallic. The new C allotrope has a low mass density of 2.84 g/cm3. More importantly, it is proven to be energetically stable with cohesive energy less than -7.5 eV/atom which is lower than many other carbon allotropes implying the possibility to be fabricated in lab. Such a carbon crystal structure with a low mass density and wide band gap once synthesized would have wi...
Clathrates of the tetrel (Tt = Si, Ge, Sn) elements are host–guest structures that can undergo Li... more Clathrates of the tetrel (Tt = Si, Ge, Sn) elements are host–guest structures that can undergo Li alloying reactions with high capacities. However, little is known about how the cage structure affects the phase transformations that take place during lithiation. To further this understanding, the structural changes of the type VIII clathrate Ba8Ga16−δSn30+δ (δ ≈ 1) during lithiation are investigated and compared to those in β-Sn with ex situ X-ray total scattering measurements and pair distribution function (PDF) analysis. The results show that the type VIII clathrate undergoes an alloying reaction to form Li-rich amorphous phases (LixBa0.17Ga0.33Sn0.67, x = 2–3) with local structures similar to those in the crystalline binary Li–Sn phases that form during the lithiation of β-Sn. As a result of the amorphous phase transition, the type VIII clathrate reacts at a lower voltage (0.25 V vs Li/Li+) compared to β-Sn (0.45 V) and goes through a solid-solution reaction after the initial conv...
The existence of a new two dimensional CN2 structure was predicted using ab initio molecular dyna... more The existence of a new two dimensional CN2 structure was predicted using ab initio molecular dynamics (AIMD) and density-functional theory calculations.
Six new silicon phases with direct band gaps were found through silicon atomic substitution of ca... more Six new silicon phases with direct band gaps were found through silicon atomic substitution of carbon in the known carbon structuresviahigh-throughput calculations.
abstract: Various biologically inspired flow field designs of the gas distributor (interconnector... more abstract: Various biologically inspired flow field designs of the gas distributor (interconnector) have been designed and simulated. Their performance using Nafion-212 with humidified H[subscript 2] and Air at 80 °C with the ANSYS Fluent Fuel Cell module software was evaluated. Novel interdigitated designs were optimized by obeying biologically inspired branching rules. These rules allow for more mathematically formal descriptions of flow field designs, enabling relatively simple optimization. The channel to land ratio was kept equivalent between designs with typical values between 0.8 and 1.0. The pressure drop and the current density distribution were monitored for each design on both anode and cathode sides. The most promising designs are expected to exhibit lower pressure drop however, low pressure drop can also be an indication of potential water flooding at higher operating current density. A biologically inspired interdigitated design with 9 inlet channels exhibited reduced p...
A recently predicted two dimensional (2D) carbon allotrope, tetrahex-carbon consisting of tetrago... more A recently predicted two dimensional (2D) carbon allotrope, tetrahex-carbon consisting of tetragonal and hexagonal rings, draws research interests due to its unique mechanical and electronic properties. Tetrahex-C shows ultrahigh strength, negative Poisson ratio, a direct band gap and high carrier mobility. In this work, we employ first-principles density-functional theory calculations to explore the directional dependence of electronic properties such as carrier effective mass and mobility in tetrahex-C. Tetrahex-C demonstrates strong anisotropicity in effective mass of charge carrier and therefore its mobility (electric conductance) exhibits a strong orientation preference. More interesting, we find that such unique anisotropic carrier effective mass and mobility can be controlled by simple uniaxial strain. The orientation dependence of effective mass can be dramatically rotated by 90 degrees through applying uniaxial tensile strain beyond ~ 7% (11%) in the armchair direction for ...
The existence of a new two dimensional CN2 structure was predicted using ab-initio molecular dyna... more The existence of a new two dimensional CN2 structure was predicted using ab-initio molecular dynamics (AIMD) and density-functional theory calculations. It consists tetragonal and hexagonal rings with C-N and N-N bonds arranged in a buckling plane, isostructural to tetrahex-carbon allotrope. It is thermodynamically and kinetically stable suggested by its phonon spectrum and AIMD. This nanosheet has high concentration of N and contains N-N single bonds with an energy density of 6.3 kJ/g, indicating potential applications as high energy density materials. It possesses exotic mechanical properties with negative Poisson's ratio and an anisotropic Young's modulus. The modulus in the zigzag direction is predicted to be 340 N/m, stiffer than h-BN and penta-CN2 sheets and comparable to graphene. Its ideal strength of 28.8 N/m outperforms that of penta-graphene. The material maintains phonon stability upon the application of uniaxial strain up to 10% (13%) in the zigzag (armchair) di...
Two novel three-dimensional (3D) crystal structures of carbon (C) and germanium carbide (GeC2) we... more Two novel three-dimensional (3D) crystal structures of carbon (C) and germanium carbide (GeC2) were predicted using first-principles density-functional theory (DFT) calculations. These newly discovered 3D carbon allotrope and GeC2 are in the space group of Fmmm (space group number 69). Their crystal structures have unique tetragonal/hexagonal rings formed by either C or Ge/C atoms. Both structures were proven to be thermodynamically stable through the phonon spectrum calculations. The C allotrope is a semiconductor with a wide band gap of 3.65 eV predicted by the hybrid density functional HSE06 method, while GeC2 is metallic. The new C allotrope has a low mass density of 2.84 g/cm3. More importantly, it is proven to be energetically stable with cohesive energy less than -7.5 eV/atom which is lower than many other carbon allotropes implying the possibility to be fabricated in lab. Such a carbon crystal structure with a low mass density and wide band gap once synthesized would have wi...
Clathrates of the tetrel (Tt = Si, Ge, Sn) elements are host–guest structures that can undergo Li... more Clathrates of the tetrel (Tt = Si, Ge, Sn) elements are host–guest structures that can undergo Li alloying reactions with high capacities. However, little is known about how the cage structure affects the phase transformations that take place during lithiation. To further this understanding, the structural changes of the type VIII clathrate Ba8Ga16−δSn30+δ (δ ≈ 1) during lithiation are investigated and compared to those in β-Sn with ex situ X-ray total scattering measurements and pair distribution function (PDF) analysis. The results show that the type VIII clathrate undergoes an alloying reaction to form Li-rich amorphous phases (LixBa0.17Ga0.33Sn0.67, x = 2–3) with local structures similar to those in the crystalline binary Li–Sn phases that form during the lithiation of β-Sn. As a result of the amorphous phase transition, the type VIII clathrate reacts at a lower voltage (0.25 V vs Li/Li+) compared to β-Sn (0.45 V) and goes through a solid-solution reaction after the initial conv...
The existence of a new two dimensional CN2 structure was predicted using ab initio molecular dyna... more The existence of a new two dimensional CN2 structure was predicted using ab initio molecular dynamics (AIMD) and density-functional theory calculations.
Six new silicon phases with direct band gaps were found through silicon atomic substitution of ca... more Six new silicon phases with direct band gaps were found through silicon atomic substitution of carbon in the known carbon structuresviahigh-throughput calculations.
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