ABSTRACT
The precise control of the ice crystal growth during a freezing process is of essential importance for achieving porous cryogels with desired architectures. The present work reports a systematic study on the achievement of multi-structural cryogels from a binary dispersion containing 50 wt% 2,2,6,6-tetramethylpiperidin-1-oxyl, radical-mediated oxidized cellulose nanofibers (TOCNs), and 50 wt% graphene oxide (GO) via the unidirectional freeze-drying (UDF) approach. It is found that the increase in the sol's pH imparts better dispersion of the two components through increased electrostatic repulsion, while also causing progressively weaker gel networks leading to micro-lamella cryogels from the UDF process. At the pH of 5.2, an optimum between TOCN and GO self-aggregation and dispersion is achieved, leading to the strongest TOCN-GO interactions and their templating into the regular micro-honeycomb structures. A two-faceted mechanism for explaining the cryogel formation is proposed and it is shown that the interplay of the maximized TOCN-GO interactions and the high affinity of the dispersoid complexes for the ice crystals are necessary for obtaining a micro-honeycomb morphology along the freezing direction. Further, by linking the microstructure and rheology of the corresponding precursor sols, a diagram for predicting the microstructure of TOCN-GO cryogels obtained through the UDF process is proposed.
ABSTRACT
As a promising candidate for large-scale energy storage systems, sodium-ion batteries (SIBs) are experiencing a rapid development. Organic conjugated carboxylic acid anodes not only have tailorable electrochemical properties but also are easily accessible. However, the low stability and electrical conductivity hamper their practical applications. In this study, disodium terephthalate (Na2 TP), the most favorable organic conjugated carboxylic acid anode material for SIBs, was proposed to integrate with graphene oxide (GO) by an anti-solvent precipitation process, which ensures the uniform and tight coating of GO on the Na2 TP surface. GO is electrochemically reduced during the first several cycles of the electrochemical measurement, which buffers the volume change and improves the electrical conductivity of Na2 TP, resulting in a better cyclic and rate performance. The incorporation of only 5â wt % GO onto Na2 TP leads to a reversible capability of 235â mA h g-1 after 100 cycles at a current rate of 0.1â C, which is the best among the state of the art organic anodes for SIBs. The one-step synthesis together with the low costs of the raw materials show a promise for the scalable preparation of anode materials for practical SIBs.
ABSTRACT
The breakthrough adsorption behaviors of gas phase trichloroethylene in a packed bed of activated carbon fibers (ACF) were investigated. The specific surface area of the ACF was 600 m2/g, 1400 m2/g and 1600 m2/g, respectively, and the concentration of trichloroethylene ranged from 270 mg/m3 to 2700 mg/m3. Results showed that the capacity of adsorption increased with increasing specific surface area, the relationship between the logarithms of 10% breakthrough time and concentration was approximately linear over the experimental range, the breakthrough time decreased with increasing temperature and humidity. The breakthrough curves at different inlet concentration or different temperature can be predicted by several simple theoretical models with good agreements.
