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Carbon fiber-reinforced carbon matrix (C/C) composites were prepared by chemical vapor infiltration, and then they were subjected to silicon (Si) reactive melt infiltration to obtain C/C–SiC–Si composites. The ablation behavior of these two types of composites was evaluated by high-energy (500w) carbon dioxide laser irradiation under argon atmosphere. The depths and three-dimensional (3D) profiles of laser ablation holes were measured by laser confocal microscopy. The results showed that the depth of ablation hole of C/C composites gradually increased, and the ablation rate decreased with ablation time. The temperature distribution on C/C composite surface was simulated by 3D finite element analysis. The C/C–SiC–Si composites exhibited a rapid ablation rate during the ablation process within 7 s; however, no further ablation damage on carbon matrix was observed after 7 s. Si was found to dissipate energy through phase change, transpiration cooling, and smog attenuation. A laser ablation model was proposed based on the energy dissipation mechanism. C/C–SiC–Si composite showed better performance of laser ablation resistance in 100 s than pure C/C composite.

Recently, carbon fiber-reinforced silicon carbide (C/SiC) composites are considered important candidates for laser protection materials. In this paper, the ablation mechanism of C/SiC composites and their modified composites under laser irradiation was studied. ZrB2–MoSi2–SiC ternary-phase ceramic was successfully coated on C/SiC composites by using high velocity oxygen fuel (HVOF) technology, with Mo as transition layer. The evolution of phase and morphology of the composites was investigated by X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The ablation behavior of composites was investigated by laser confocal microscopy (LCM). The results showed that the ablation mechanism of composites was controlled by phase transformation, thermal reaction and thermal diffusion. The solid-liquid transition of ZrB2 and MoSi2 was the dominant factor. Thermal reaction and good thermal diffusivity of coatings were also important factors affecting the ablation performance. ZrB2–SiC– MoSi2/Mo coating failed when all phase transitions were completed and no continuous liquid phase was formed, followed by rapid damage of C/SiC substrate. The results of this work can provide theoretical guidance and research ideas for the design and application of laser protective materials.

A new protocol for the Cu(OAc)2-mediated cyanation of arenes using benzimidazole as the directing group with 2-(4-methylpiperazin-1-yl)acetonitrile as the cyano source was developed. A series of cyano derivatives were facilely and conveniently obtained in moderate to good yields by using this method. The C–H activation catalytic system was originally applied to the C(sp2)–H cyanation of the aryl/heteroaryl to synthesize 2-(1H-benzo[d]imidazol-2-yl)aryl nitriles. There were 19 new compounds in the synthesized 20 cyanide products. In this reaction, 2-(4-methylpiperazin-1-yl)acetonitrile as the cyano source was originally employed in the C(sp2)–H cyanation of the arenes. In addition, a fluorescent material 5a was obtained by derivative reactions of the obtained cyanide product 3.

We demonstrated an optical fiber sensor based on a cascaded fiber Fabry-Perot interferometer (FPI)-regenerated fiber Bragg grating (RFBG) for simultaneous measurement of temperature and strain under high temperature environments. The FPI is manufactured from a ∼74 µm long hollow core silica tube (HCST) sandwiched between two single mode fibers (SMFs). The RFBG is inscribed in one of the SMF arms which is embedded inside an alundum tube, making it insensitive to the applied strain on the entire fiber sensor, just in case the temperature and strain recovery process are described using the strain-free RFBG instead of a characteristic due-parameter matrix. This feature is intended for thermal compensation for the FPI structure that is sensitive to both temperature and strain. In the characterization tests, the proposed device has exhibited a temperature sensitivity ∼ 18.01 pm/°C in the range of 100 °C - 1000 °C and excellent linear response to strain in the range of 300 °C - 1000 °C. The measured strain sensitivity is as high as ∼ 2.17 pm/µɛ for a detection range from 0 µɛ to 450 µɛ at 800 °C, which is ∼ 1.5 times that of a FPI-RFBG without the alundum tube.

A series of π-conjugated molecules based on diimidazolepyridine derivatives were designed, synthesized by Suzuki coupling reaction and cyclization reaction and characterized. Diimidazolepyridine motif as the main structure could improve the thermal stability and optical property of the materials. All of the target compounds exhibited good thermal stabilities with T d values in the range of 416–490 °C. These compounds showed steady blue light emissions in the range of 424–478 nm and high quantum yields (0.33–0.69) in solution. Especially, compound 4f achieved appropriate energy gap (E g = 2.69 eV) and high fluorescence quantum yields (Φ f = 0.69) because of introducing electron-donating group, such energy gap was helpful to electronic transfer and transport. The materials have great potential for good electronic-transmission materials in OLEDs.

In this work, a simple fiber Fabry-Perot air-cavity interferometer (FPI) is formed by splicing a 246 μm long hollow core silica tube (HCST) between two single mode fibers (SMFs). In the thermal characterization test, the FPI exhibits limited linear range up to 700 °C in the first cycle of isochronal annealing treatment from room temperature up to 1000 °C. However, after a series of repeated isochronal thermal annealing, the temperature response of the proposed FPI is extended further to 1000 °C with a good thermal repeatability. Meanwhile, the annealed FPI has linear axial strain sensitivities up to 1000 μe from room temperature up to 800 °C. The proposed fiber structure is a potential sensor for high-temperature or stress measurement in aeronautical or metallurgical fields.

We have experimentally demonstrated an optical fiber Mach-Zehnder interferometer (MZI) structure formed by a few-mode photonic crystal fiber (PCF) for curvature measurement and inscribed a fiber Bragg grating (FBG) in the PCF for the purpose of simultaneously measuring temperature. The structure consists of a PCF sandwiched between two multi-mode fibers (MMFs). Bending experimental results show that the proposed sensor has a sensitivity of −1.03 nm/m−1 at a curvature range from 10 m−1 to 22.4 m−1, and the curvature sensitivity of the embedded FBG was −0.003 nm/m−1. Temperature response experimental results showed that the MZI’s wavelength, λa, has a sensitivity of 60.3 pm/°C, and the FBG’s Bragg wavelength, λb, has sensitivity of 9.2 pm/°C in the temperature range of 8 to 100 °C. As such, it can be used for simultaneous measurement of curvature and temperature over ranges of 10 m−1 to 22.4 m−1 and 8 °C to 100 °C, respectively. The results show that the embedded FBG can be a good indicator to compensate the varying ambient temperature during a curvature measurement.