Nanjing Tech University

About: Nanjing Tech University is a education organization based out in Nanjing, China. It is known for research contribution in the topics: Catalysis & Membrane. The organization has 21827 authors who have published 21794 publications receiving 364050 citations. The organization is also known as: Nangongda & Nánjīng Gōngyè Dàxúe.

Diameter and helicity effects on static properties of water molecules confined in carbon nanotubes

Abstract: The behavior of water in carbon nanotubes has recently received increasing attention since some theoretical work has shown that nanotubes have the potential to be used as proton-conducting pores for a variety of biological applications. The properties of a nanotube strongly depend on its diameter and helicity; therefore, their influences on the behavior of water molecules confined in carbon nanotubes have to be fully examined for a better understanding of nanotube's potential biological applications. In this work, molecular dynamics simulations were performed under ambient conditions for armchair and zigzag type nanotube segments of various diameters submerged in water. The results indicate that single-file water chains as the basis of fast proton conduction can be formed only in narrow nanotubes (0.676–0.811 nm diameter). The formation of ice-like water structures inside nanotubes might be sensitive to potential models and corresponding parameters. Obvious variation in average number of H-bonds per molecule can occur only in narrow carbon nanotubes, which is expected to significantly affect the diffusion rate of confined water. The extent of confinement phenomena is dominated by tube diameter. Tube helicity rarely affects the static properties of confined water.

Accelerated carbonation and performance of concrete made with steel slag as binding materials and aggregates

Abstract: Steel slag has been used as supplementary cementitious materials or aggregates in concrete. However, the substitution levels of steel slag for Portland cement or natural aggregates were limited due to its low hydraulic property or latent volume instability. In this study, 60% of steel slag powders containing high free-CaO content, 20% of Portland cement and up to 20% of reactive magnesia and lime were mixed to prepare the binding blends. The binding blends were then used to cast concrete, in which up to 100% of natural aggregates (limestone and river sands) were replaced with steel slag aggregates. The concrete was exposed to carbonation curing with a concentration of 99.9% CO2 and a pressure of 0.10 MPa for different durations (1d, 3d, and 14d). The carbonation front, carbonate products, compressive strength, microstructure, and volume stability of the concrete were investigated. Results show that the compressive strength of the steel slag concrete after CO2 curing was significantly increased. The compressive strengths of concrete subjected to CO2 curing for 14d were up to five-fold greater than that of the corresponding concrete under conventional moist curing for 28d. This is attributed to the formation of calcium carbonates, leading to a microstructure densification of the concrete. Replacement of limestone and sand aggregates with steel slag aggregates also increased the compressive strengths of the concrete subjected to CO2 curing. In addition, the concrete pre-exposed to CO2 curing produced less expansion than the concrete pre-exposed to moist curing during the subsequent accelerated curing in 60 °C water. This study provides a potential approach to prepare concrete with low-carbon emissions via the accelerated carbonation of steel slag.

Two orders of magnitude enhancement in oxygen evolution reactivity on amorphous Ba0.5Sr0.5Co0.8Fe0.2O3-δ nanofilms with tunable oxidation state.

Abstract: Perovskite oxides exhibit potential for use as electrocatalysts in the oxygen evolution reaction (OER). However, their low specific surface area is the main obstacle to realizing a high mass-specific activity that is required to be competitive against the state-of-the-art precious metal-based catalysts. We report the enhanced performance of Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) for the OER with intrinsic activity that is significantly higher than that of the benchmark IrO2, and this result was achieved via fabrication of an amorphous BSCF nanofilm on a surface-oxidized nickel substrate by magnetron sputtering. The surface nickel oxide layer of the Ni substrate and the thickness of the BSCF film were further used to tune the intrinsic OER activity and stability of the BSCF catalyst by optimizing the electronic configuration of the transition metal cations in BSCF via the interaction between the nanofilm and the surface nickel oxide, which enables up to 315-fold enhanced mass-specific activity compared to the crystalline BSCF bulk phase. Moreover, the amorphous BSCF-Ni foam anode coupled with the Pt-Ni foam cathode demonstrated an attractive small overpotential of 0.34 V at 10 mA cm-2 for water electrolysis, with a BSCF loading as low as 154.8 μg cm-2.

High-Efficiency Water-Transport Channels using the Synergistic Effect of a Hydrophilic Polymer and Graphene Oxide Laminates

Abstract: Graphene oxide (GO) laminates possess unprecedented fast water-transport channels. However, how to fully utilize these unique channels in order to maximize the separation properties of GO laminates remains a challenge. Here, a bio-inspired membrane that couples an ultrathin surface water-capturing polymeric layer (<10 nm) and GO laminates is designed. The proposed synergistic effect of highly enhanced water sorption from the polymeric layer and molecular channels from the GO laminates realizes fast and selective water transport through the integrated membrane. The prepared membrane exhibits highly selective water permeation with an excellent water fl ux of over 10 000 g m −2 h −1 , which exceeds the performance upper bound of state-ofthe-art membranes for butanol dehydration. This bio-inspired strategy demonstrated here opens the door to explore fast and selective channels derived from 2D or 3D materials for highly effi cient molecular separation.