Search

We demonstrate an environmentally stable femtosecond laser for industrial application based on all polarization‐maintaining Yb‐doped laser and experimentally explore the effect of the net cavity dispersion (NCD) on output characteristics. The oscillator emits pulses with 5.1 ps and a 23 nm spectral bandwidth, then the pulse is compressed to 88 fs. The instabilities over 120 h gives 0.32% relative root mean square noise, indicating high stability of the pulse laser. With effective regulation of NCD, we obtained the maximum spectral bandwidth of 27 nm. Such broadband oscillator with compact all‐fiber configurations provide extremely high stability should be very attractive for long‐term industrial application. [ABSTRACT FROM AUTHOR]

Currently, the issue of improving the flame‐retardant performance of unsaturated polyester resin (UPR) has drawn a lot of attention. In this study, methyl vinyl di (1‐thio‐2,6,7‐trioxal‐1‐phosphabicyclo [2.2] octane‐4‐methoxy) silane (MVDOS) with P‐N‐Si‐based cage unit was synthesized, and it was utilized as a reactive flame‐retardant monomer to modify UPR. The UPR/MVDOS composites were prepared by introducing different ratios of MVDOS into UPR via the reaction of crosslink. The efficiency of the resulted composites was investigated by using the limiting oxygen index (LOI), vertical burning test, and cone calorimeter test. The results showed that the composites reached the V‐0 rate without dripping, and the LOI value was 29.1% when the content of MVDOS was as low as 18 wt%. Cone calorimeter tests revealed the peak of heat release and CO production of UPR/MVDOS‐18 were 238.2 KW/m2 and 0.0167 g/s, which were respectively lower than the ones of neat UPR. The introduction of MVDOS also increased the stability of UPR composites. Furthermore, the scattering electron microscopy, laser Raman spectroscopy, and X‐ray photoelectron spectroscopy studies revealed that the incorporation of MVDOS stimulated the UPR matrix to generate char layer with increased graphitization degree, which provided a good barrier to prevent heat and oxygen from being transferred and then protected the materials inside from further burning. This research provides a new way to obtain flame‐retardant UPR composites with high performance. [ABSTRACT FROM AUTHOR]

A one‐step solvothermal synthesis of hollow microspherical Bi2WO6 nanophotocatalyst was carried out for the first time under the collective action of potassium chloride (KCl) and polyvinylpyrrolidone (PVP). The physicochemical properties such as crystal structure, morphology, specific surface area, and optical properties of the material were characterized by means of XRD, SEM, EDS, UV‐vis, and BET. The effect of KCl and PVP on the morphology control of the product is discussed. Rhodamine B dye in wastewater was used as model pollutant, and the effect of hollow microspherical morphology on photocatalytic activity is discussed. The results presented here provide a simple, effective, and widely applicable approach for the rapid synthesis of special morphology Bi2WO6 by a one‐step method. [ABSTRACT FROM AUTHOR]

This work presents a novel and highly secure anticounterfeiting strategy based on core/shell upconversion nanocrystal (UCNC) hybrids with temperature‐responsive multicolor emissions. Opposite luminescent temperature‐dependences are found for active‐core@inert‐shell (thermal quenching) and active‐core@active‐shell (thermally induced enhancement) UCNCs. Accordingly, their hybrids are designed to show obvious color changes with increasing temperature under 975 nm excitation. Various color‐shifting pathways (from white to green, blue to green, etc.) are achieved by adjusting the core/shell NC combinations in the hybrids. Moreover, color changes of the printed patterns using the hybrid NC inks can be realized by the simple heating treatment, or by increasing the laser power and prolonging the irradiation time. The results indicate the great potential of these core/shell NC hybrids for anticounterfeiting applications with high‐level security and convenient authentication methods. Utilizing opposite luminescent temperature‐dependencies between upconversion nanocrystals with an inert and an active shell, respectively, hybrids are designed to show temperature‐responsive multicolor emission and used for producing highly secure color‐tunable anticounterfeiting patterns. Moreover, emission colors of the patterns can be tuned simply by hairdryer heating, increasing the laser power or prolonging the irradiation time. [ABSTRACT FROM AUTHOR]