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This paper introduces some latest developments regarding the X-ray imaging methodology and applications of the X-ray imaging and biomedical application beamline (BL13W1) at Shanghai Synchrotron Radiation Facility in the past 5 years. The photon energy range of the beamline is 8–72.5 keV. Several sets of X-ray imaging detectors with different pixel sizes (0.19–24 μm) are used to realize X-ray microcomputed tomography (X-ray micro-CT) and X-ray in-line phase-contrast imaging. To satisfy the requirements of user experiments, new X-ray imaging methods and image processing techniques are developed. In vivo dynamic micro-CT experiments with living insects are performed in 0.5 s (sampling rate of 2 Hz, 2 tomograms/s) with a monochromatic beam from a wiggler source and in 40 ms (sampling rate of 25 Hz, 25 tomograms/s) with a white beam from a bending magnet source. A new X-ray imaging method known as move contrast X-ray imaging is proposed, with which blood flow and moving tissues in raw images can be distinguished according to their moving frequencies in the time domain. Furthermore, X-ray speckle-tracking imaging with twice exposures to eliminate the edge enhancement effect is developed. A high-precision quantification method is realized to measure complex three-dimensional blood vessels obtained via X-ray micro-CT. X-ray imaging methods such as three-dimensional X-ray diffraction microscopy, small-angle X-ray scattering CT, and X-ray fluorescence CT are developed, in which the X-ray micro-CT imaging method is combined with other contrast mechanisms such as diffraction, scattering, and fluorescence contrasts respectively. Moreover, an X-ray nano-CT experiment is performed with a 100 nm spatial resolution. Typical user experimental results from the fields of material science, biomedicine, paleontology, physics, chemistry, and environmental science obtained on the beamline are provided.

It is of significance to understand the chemical content of carbon deposits in the large-scale two-stroke (LSTS) marine diesel engine because of adverse effect on the engine performance, oil consumption and emissions. In this work, two different combustion chamber deposits in an LSTS marine diesel engine were studied using thermogravimetry analysis (TGA), elemental analysis (EA) and synchrotron X-ray fluorescence (SXRF). One was on the piston top and the other on the piston land, termed PTCD and PLCD, respectively. For the PTCD sample, the 97% residue in the TGA and 1.4% carbon content in the EA indicated the main compositions of PTCD were metal salts or oxides and ashes, significantly different from the previous findings of the highest carbon content in deposits from the small four stroke engines. The different chemical content between PTCD and PLCD implied higher thermal load in the LSTS marine diesel engine led to a nearly complete thermal decomposition of PTCD. The higher calcium content in PTCD and PLCD indicated the additives of cylinder oil should be the main source of metal content of PTCD and PLCD. Calcium distribution in the SXRF results was indicative of the potential layered structure in PTCD and PLCD. In addition, the appearance of iron on the surface against the piston in PTCD and PLCD indicated iron oxides formation between carbon deposit and piston materials.

The three-dimensional structures of carbon deposits on piston surfaces in a large-scale two-stroke marine diesel engine have been nondestructively investigated using synchrotron X-ray microtomography. The results indicate that the piston carbon deposit (PCD) has a flat bottom surface where many irregular structures accumulate. Based on the microtomography, cross sections of the carbon deposit sample can be obtained in the direction perpendicular to the piston surface. A uniform deposition is found on the bottom surface of piston, where many tiny pores appear, which implies that a liquid film first forms on the piston surface and subsequent nucleation boiling occurs due to the high surface temperature. A significant decrease in the PCD density is observed when the PCD thickness is below a threshold of approximately 150 mu m. However, the PCD density remains almost unchanged from 150 to 1800 mu m. This result suggests that there should be different dominant formation mechanisms at these two stages. The local morphology, especially the approximately circular structure and the smooth boundary on the PCD surface, indicates that condensation should be the major factor controlling the formation of the PCD surface. However, the internal pores and minimal swelling on the surface could result from other mechanisms. (C) 2014 Elsevier Ltd. All rights reserved.

It is of significance that massive carbon deposit (CD) is observed in the combustion chamber of large-scale two-stroke marine diesel engine due to high thermal load, poor fuel quality, oil degradation and combustion and high particle emission. The structure and characteristics of CD have great influence on the engine performance and emissions. In this paper, we use synchrotron X-ray microtomography of Shanghai Synchrotron Radiation Facility to visualize the three dimensional structure of CD on the piston top land. Based on the quantitative image analysis, microstructure and pore characteristics of CD are investigated. The results show the CD thickness is around 1mm, half of clearance between cylinder liner and piston. However, the surface structure shows significant friction scratches, which suggests the oil film could be destroyed by the CD. The results of crackle distribution show that intensive crackle is located on the CD surface (inner and outer surfaces), while loosen crackle is found inside the CD. This implies that the crackle formation mechanism is different on the inner and outer surfaces. The analysis of pore connectivity indicated that most of cracks are connected, and the porosity is in the range between 10.9% and 12.8% in present experiments. In addition, small hole connected by cracks and the crackle could have impact on the absorption and desorption of unburnt emissions.