Cobalt diselenide (CoSe2), a representative transition-metal chalcogenide (TMC), is attracting intensive interest as an anode material for lithium ion batteries (LIBs), in view of its high specific capacity based on the conversion reaction mechanism.
Polybenzoxazole (PBO) aerogels have such valuable properties as excellent thermal and chemical stability, good fire resistance, and electronic transmission. However, the current processes to produce these aerogels tend to be complex and inefficient, and they are difficult to process into complex shapes. In this paper, we report a strategy to prepare cross-linked PBO (cPBO) aerogels by the polybenzoxazine. The polybenzoxazine aerogels were obtained first and then converted into cPBO aerogels through heat treatment. The prepared cPBO aerogels not only had low thermal conductivity (0.030 to 0.039 W m −1 K −1 ) but also possessed excellent mechanical properties (compressive modulus of 84.68 MPa) and low dielectric properties (1.51 at 1 kHz). These are attributable to the intrinsic structure of cPBO and the high porosity of aerogels in general. Because small-molecule ortho-functionalized benzoxazine has good solubility and can be used to prepare homogeneous solutions with various solid contents, this preparation strategy avoids the defect of directly using PBO resin, which has poor solubility and poor processability. Moreover, the pores of the cross-linked polybenzoxazine aerogels can be retained to the greatest extent during heat treatment. The preparation process is simple, efficient, and has a good application prospect.
This paper proposes a novel cholesteric liquid crystal (CLC) film–based dual-probe fiber sensor to monitor volatile organic compound (VOC) gas. The sensor consists of a 2×2 multimode fiber coupler, in which the two output fiber ends are covered by two types of CLC films (CLCF) with different pitches. It can be observed that the reflection peak wavelengths of CLCs shift to the red side as the VOC gas concentration increases. The sensitivities of the two CLCFs are 8.435 nm·L/mmol and 14.867 nm·L/mmol to acetone, 14.586 nm·L/mmol and 29.303 nm·L/mmol to ethanol, respectively. In addition, the dependence of the peak wavelength shift of CLCF on the total concentration of the acetone and ethanol mixed gas at different mixing ratios is measured. The linear relationships between the peak shift of CLCFs, the total mixed gas concentration and acetone/ethanol ratio are calculated using the least-squares method. Therefore, this proposed dual-probe fiber optic sensor can distinguish the concentrations of acetone and ethanol in a mixed gas of acetone and ethanol.
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