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With the increasing number of underground engineering construction projects such as coal mining, tunnel, and subway, water inrush disasters occur more and more frequently. Inspired by the phenomenon of microbial mineralization and diagenesis, microbial-induced calcium carbonate precipitation (MICP) is used to repair cracks in cement-based materials, which provides a new idea to solve the problem of water inrush. To investigate the self-healing properties of microbial capsules, this paper selected epoxy resin E-51 cured by DMP-30 as the wall material and Bacillus pasteurii as the core materials for experiments. In this paper, a single-factor method was adopted to determine the optimal preparation process of microbial capsules and the oil-phase separation method to prepare the microbial capsules. The effects of various factors on the experimental results under different core-wall ratios, reaction time, reaction temperatures, and agitation rates were analyzed. Microbial capsules were analyzed by Fourier transform infrared spectroscopy and optical microscopy to explore the functional groups and features of microbial capsules. The experimental results showed that the microbial capsules achieved the best performance with a core-to-wall ratio of 1 : 3, a reaction temperature of 50°C, a reaction time of 40 min, and a stirring rate of 300 rpm. Meanwhile, we determined the spore survival rate of microbial capsules and finally studied the waterproofness, storage stability, and rupture under the pressure of microbial capsules. We concluded that microbial capsules have high-efficiency and self-healing properties.

Microbial Induced Calcite Precipitation (MICP) is a biochemical process widely found in nature, also known as microbial mineralization. This paper investigates whether this process can help promote the intelligent reinforcement and repair of underground projects such as mines and tunnels. We selected Bacillus sphaericus and Bacillus mucilaginosus as the research objects. The former has an outstanding urease production ability, and the latter can secrete carbonic anhydrase in vitro. Bacillus mucilaginosus was introduced into the culture solution of Bacillus sphaericus in the most suitable culture environment, and the changes of mineralization rate and mineralization yield of Bacillus sphaericus were observed and analyzed. The results revealed that, to maintain the highest growth rate of Bacillus sphaericus, the optimal pH value was between 7 and 8, the optimal urea concentration was 0.5 mol/L, the optimal Ca2+ concentration was 0.6 mol/L, and the optimal Luria-Bertani (LB) culture concentration was 20 g/L. The amount of biomineralized calcium carbonate precipitated in the double bacteria solution can reach 1.89 times the amount of the precipitation in the Bacillus sphaericus solution under the same conditions. It concludes that the introduction of Bacillus mucilaginosus can effectively increase the mineralization yield of Bacillus sphaericus without affecting the mineralized products.

The conductive polymers PEDOT:PSS coated Li1.20[Mn0.53Ni0.13Co0.13Nb0.01]O2 cathode materials were synthesized via using the sol-gel method, followed by the wet solution process. And the X-ray diffraction (XRD), Rietveld refinement, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) were adopted to investigate the morphology and constituents of as-prepared cathode materials. The results demonstrated that a PEDOT:PSS layer was uniformly distributed on the surface of bulk Li1.20Mn0.54Ni0.13Co0.13O2 with Nb5+ doping successfully. And the PEDOT:PSS surface coating and Nb5+ doping modifications showed a significant improvement on the electrochemical properties of cathode. In particular, the 2 wt% PEDOT:PSS coated Li1.20[Mn0.53Ni0.13Co0.13Nb0.01]O2 delivered a supernal discharge capacity of 145.6 mAhg−1 at 5C high rate and retained a high capacity retention of 90.8% after 200 cycles at 45 °C, which were more superior than those of the pristine cathode (90.2 mAhg−1 and 80.7%). The enhanced electrochemical properties could be attributed to the facilitation of Lithium ions diffusion, the lower cation mixing and restriction of the side reactions between cathode surfaces with electrolyte by the Nb5+ doping and PEDOT:PSS coating.