We present a study of chalcogenide glass fiber lasers doped with Dy 3+ , Pr 3+ or Tb 3+ that would operate in the mid-infrared wavelength range. A set of chalcogenide glass samples doped with different concentrations of rare earth ions is fabricated. The modeling parameters are directly extracted from FTIR absorption measurements of the fabricated bulk glass samples using Judd-Ofelt, Füchtbauer-Ladenburg theory and McCumber theory. The modeling results show that, for all the dopants considered, an efficient mid-infrared laser action is possible if optical losses are kept at the level of 1dB/m or below.

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How different catalysts would affect the evolution of char structure with increasing temperature during the pyrolysis of coal is fundamentally important for the clean utilization of coal. In this study, we applied in situ Raman spectroscopy and a fixed-bed reactor to characterize the evolution of char structure and product gas formation behavior. The results showed that the formation curves of the main gases presented two stages and the catalyst enhanced the pyrolysis significantly. The Raman spectra were fitted with a combination of four Lorentzian bands (D1, D2, D4, G) and one Gaussian band (D3) in the first-order region. Spectral parameters, such as band position, full widths at half-maximum (FWHM), and band area ratio, were used to characterize char structure. The D1 and G band FWHM and band area ratios I D1 /I G , I D3 /I G , and I D4 /I G increased with increasing temperature, while the D1 and G band positions and I G /I All decreased, indicating a decrease in the ordering of the char structure. The addition of catalyst led to a lower degree of char structural order. Thermogravimetric analysis was also used to measure the reactivity of char derived from pyrolysis, and the results showed a good correlation between reactivity indexes and I G /I All .

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To investigate the interactions between K2CO3 and coal char, a fixed-bed reactor was used to conduct catalytic pyrolysis and gasification of coal char. An in situ Raman spectroscopy system was applied to characterize the evolution of char structure. Three different ranks of Chinese coals were deashed first and pyrolyzed to chars before experiment. In catalytic pyrolysis of coal char, the release of CO proved that reactions occurred between K2CO3 and char and the release of a small amount of CO2 was connected with the oxygen content. In situ Raman spectra results showed that the char structure order decreased with rising temperature for the production of an intermediate. During the gasification process, the char structure order decreased first and then increased, attributed to the evaporation of K at high temperature. The ex situ data revealed that the intermediate did not exist at room temperature. For better understanding of the true form of chars at high temperature, an in situ Raman spectrometer is necessary.

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Incremental sheet forming (ISF) is a promising flexible manufacturing process, which has been tested in sheet forming of various metallic materials. Although ISF-based forming of thermoplastics is relatively new, it has drawn considerable interests and significant progress has been made in recent years. This paper presents a review of concurrent research on the emerging trend of thermoplastic-focused ISF processes. Attention is given to the processing conditions including process setup, process parameters and forming forces. The deformation mechanism and failure behaviour during ISF of thermoplastics are evaluated, which leads to detailed discussions on the formability, effect of different process parameters and the forming quality such as geometric accuracy, surface finish and other consideration factors in ISF of thermoplastics. A comparison of important similarities and differences between ISF of thermoplastic and metallic materials is made. Finally, a brief discussion is provided on the technical challenges and research directions for ISF of thermoplastic materials in the future.