Weyl metal is regarded as a platform toward interacting topological states of matter, where its topological structure gives rise to anomalous transport phenomena, referred to as chiral magnetic effect and "negative" magneto-resistivity, the origin of which is chiral anomaly. Recently, the negative magneto-resistivity has been observed with the signature of weak anti-localization at x = 3 ∼ 4 % in Bi1−xSbx, where magnetic field is applied in parallel with electric field (E B). Based on the Boltzmann-equation approach, we find the negative magneto-resistivity in the presence of weak anti-localization. An essential ingredient is to introduce the topological structure of chiral anomaly into the Boltzmann-equation approach, resorting to semi-classical equations of motion with Berry curvature.

No abstract

Ohm's law is a fundamental paradigm in the electrical transport of metals. Any transport signatures violating Ohm's law would give an indisputable fingerprint for a novel metallic state. Here, we uncover the breakdown of Ohm's law owing to a topological structure of the chiral anomaly in the Weyl metal phase. We observe nonlinear I-V characteristics in BiSb single crystals in the diffusive limit, which occurs only for a magnetic-field-aligned electric field (E∥B). The Boltzmann transport theory with the charge pumping effect reveals the topological-in-origin nonlinear conductivity, and it leads to a universal scaling function of the longitudinal magnetoconductivity, which completely describes our experimental results. As a hallmark of Weyl metals, the nonlinear conductivity provides a venue for nonlinear electronics, optical applications, and the development of a topological Fermi-liquid theory beyond the Landau Fermi-liquid theory.

Removal of H2S by a commercially available zinc oxide sorbent was studied using a packed-bed reactor for desulfurizing the gas produced from steam-hydrogasification of carbonaceous materials. Experimental runs were conducted to monitor sulfur removal efficiency and H2S breakthrough time for the operation variables such as reaction temperature, steam content, space velocity, inlet H2S concentration, and sorbent particle size. For the inlet gas with 45 vol % steam content, the initial sulfur removal efficiency exhibited a maximum around 636 K. Varying the steam content of inlet gas affected the equilibrium of sorbent sulfidation in a reversible way, leading to the decrease of sulfur capture capacity of the sorbent as the steam content increased. Increasing the space velocity from 8 000 to 24000 h-1 decreased sulfur capture capacity significantly, indicating the deterioration of gas−solid contact in the reactor at the increased gas flow rates. Inlet H2S concentration was varied from 100 to 800 ppmv to reflect the diversity of steam-hydrogasifier feedstocks, which affected sulfur capture capacity of the sorbent in such a way that the extent of sorbent utilization was limited by the increased H2S concentration. Sorbent particle size was varied from 150−250 to 425−1000 μm to look into the effect of intraparticle mass transfer limitation. The particles greater than 425 μm exhibited the sulfur capture capacity that was limited by the reduced extent of sorbent utilization.

No abstract

No abstract

No abstract

Geologic carbon storage is considered as a requisite to effectively mitigate climate change, so large amounts of carbon dioxide (CO2) are expected to be injected in sedimentary saline formations. CO2 injection leads to the creation of acidic solution when it dissolves into the resident brine, which can react with reservoir rock, especially carbonates. We numerically investigated the behavior of reservoir-caprock system where CO2 injection-induced changes in the hydraulic and geomechanical properties of Apulian limestone were measured in the laboratory. We found that porosity of the limestone slightly decreases after CO2 treatment, which lead to a permeability reduction by a factor of two. In the treated specimens, calcite dissolution was observed at the inlet, but carbonate precipitation occurred at the outlet, which was closed during the reaction time of three days. Additionally, the relative permeability curves were modified after CO2–rock interaction, especially the one for water, which evolved from a quadratic to a quasi-linear function of the water saturation degree. Geomechanically, the limestone became softer and it was weakened after being altered by CO2. Simulation results showed that the property changes occurring within the CO2 plume caused a stress redistribution because CO2 treated limestone became softer and tended to deform more in response to pressure buildup than the pristine rock. The reduction in strength induced by geochemical reactions may eventually cause shear failure within the CO2 plume affected rock. This combination of laboratory experiments with numerical simulations leads to a better understanding of the implications of coupled chemo-mechanical interactions in geologic carbon storage.