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As a phase change material, erythritol has two main disadvantages: low thermal conductivity and high supercooling degree. In this study, we proposed a novel erythritol/graphene composite phase change material, and its thermal properties were predicted by molecular dynamics simulation. The effects of the graphene mass fraction, size and number of layers on the thermal conductivity and phase transition characteristics, including the melting point and supercooling degree, were analyzed. The mechanism behind the above phenomena was revealed from a micro perspective. The results show that graphene can not only improve the thermal conductivity of the composites but also reduce the supercooling degree, thus improving the thermal properties of erythritol. The thermal conductivity of the composites increases with increasing graphene amount, size and number of layers. When the mass fraction of graphene increased to 8 wt%, the thermal conductivity doubled. The melting point of erythritol can be effectively controlled by changing the amount, size and number of layers of graphene. This study can provide guidance for the design and application of erythritol-based composite phase change materials.

Erythritol as a phase change material (PCM) has the advantage of extremely high latent heat, excellent thermal stability. However, its low thermal conductivity and easy leakage greatly limit its practical application, so the development of novel shape-stabilized PCM with high thermal conductivity is of great significance. In this paper, thermal conductivity, melting point and adsorption properties of hierarchical porous diamond/erythritol composite PCM were calculated using molecular dynamics simulation. When the load of erythritol is 12.91 wt%, the thermal conductivity can reach 2.06 W ⋅m−1K−1, which is 207% higher than that of pure erythritol. The phonon vibration of erythritol plays an important role in the composite. Erythritol enhanced the mass transfer and shared part of the heat flux, which acted as an auxiliary heat channel. With the increase of load, the melting point increased and tended to bulk erythritol. The flexibility of erythritol in confined space was better, resulting in lower melting point than that in free space. The advantage of hierarchical porous diamond was verified by calculating centroid position of erythritol and interaction energy between host and guest. Significantly, the meso pore is conducive to heat and mass transfer, and the micro pore has stronger interaction with the core material.

We experimentally demonstrated the all-fiber erbium-doped Q-switched fiber laser based on the evanescent field interaction with lead sulfide (PbS) as saturable absorber (SA). The SA was fabricated by depositing the dispersion of PbS nanoparticles onto the taper of the microfiber with a diameter of ∼10 μm. The intensity-dependent nonlinear optical absorption of SA was investigated, and its saturation intensity and modulation depth were ∼3 MW/cm2 and ∼30.9 %, respectively. By incorporating the SA into the erbium-doped fiber laser (EDFL), stable Q-switched pulse at the central wavelength of 1558.68 nm can be obtained when the pump power was increased from 30 mW to 220 mW. The repetition rate frequency was increased from 17.21 kHz to 71.72 kHz, meanwhile, the pulse duration exhibited a decreasing trend from 10.67 μs to 2.74 μs and the signal-to-noise ratio was 48.31 dB. The maximum pulse energy was 53.24 nJ when pump power at 200 mw. On account of the results of the work, the PbS nanoparticles demonstrated a potential application value as an SA for fiber laser.

Studies have identified that the methanogenic consortia live in bituminous and lignite coal beds. The two main goals of this study are to verify the existence of the consortia in anthracite and to determine whether this high rank coal bed could provide nutrients for the methanogenic consortia. Research has confirmed that types of methanogenic consortia live in the Qinshui basin and use some compounds in anthracite as carbon sources to yield biogas. Maceral analysis confirmed that volatile matter is a controlling factor in the biological methane yield process. The CH 4 and CO 2 yield process showed that the methanogenic consortia can degrade volatile matter in anthracite into bio-methane in situ. This study confirmed that the methanogenic consortia bio-degradation process can work on anthracite to increase the CH 4 concentration in the Qinshui basin, which is located in the Shanxi province and is an important methane-producing coal seam in China. It was estimated that approximately 3.0 × 10 − 2 ~ 4.0 × 10 − 2 m 3 /kg of methane can be generated in the Qinshui basin by microbial bio-degradation.