Thermal shock resistance of air plasma sprayed thermal barrier coatings

The spallation resistance of an air plasma sprayed (APS) thermal barrier coating (TBC) to cool-down/reheat is evaluated for a pre-existing delamination crack. The delamination emanates from a vertical crack through the coating and resides at the interface between coating and underlying thermally grown oxide layer (TGO). The coating progressively sinters during engine operation, and this leads to a depth-dependent increase in modulus. Following high temperature exposure, the coating is subjected to a cooling/reheating cycle representative of engine shut-down and start-up. The interfacial stress intensity factors are calculated for the delamination crack over this thermal cycle and are compared with the mode-dependent fracture toughness of the interface between sintered APS and TGO. The study reveals the role played by microstructural evolution during sintering in dictating the spallation life of the thermal barrier coating, and also describes a test method for the measurement of delamination toughness of a thin coating. © 2014 Elsevier Ltd.

Study of Si/SiO2 hybrid antireflective coatings on SLD prepared by DSEBET - art. no. 69842P

We introduce a double source electron beam evaporation (DSEBET) technique in this paper. The refractive index coatings were fabricated on K9 glass substrate by adjusting the evaporation rates of two independent sources. The coatings, which were described by atomic force microscopy (AFM), show good compactness and homogeneity. The antireflective (AR) coatings were fabricated on Superluminescent Diodes (SLD) by DSEBET. The hybrid AR coatings on the facets of SLD were prepared in evaporation rates of 0.22nm/s and 0.75nm/s for silicon and silicon dioxide, respectively. The results of AFM and spectral performance of coated SLD show that DSEBET has a promising future in preparing the coatings on optoelectronic devices.

Ag surface plasmon enhanced double-layer antireflection coatings for GaAs solar cells

Surface plasmon enhanced antireflection coatings for GaAs solar cells have been designed theoretically. The reflectance of double-layer antireflection coatings (ARCs) with different suspensions of Ag particles is calculated as a function of the wavelength according to the optical interference matrix and the Mie theory. The mean dielectric concept was adopted in the simulations. A significant reduction of reflectance in the spectral region from 300 to 400 nm was found to be beneficial for the design of ARCs. A new SiO_2/Ag-ZnS double-layer coating with better antireflection ability can be achieved if the particle volume fraction in ZnS is 1%-2%.

Investigation on Fe, Mn, Zn, Cu, Pb and Cd fractions in the natural surface coatings sampled and surficial sediments collected in the Songhua River, China

Natural surface coatings sampled (NSCSs) from the surface of shingles and surficial sediments (SSs) in the Songhua River, China were employed to investigate the similarities and difference in fractions of heavy metals (Fe, Mn, Zn, Cu, Pb, and Cd) between NSCSs and SSs using the modified sequential extraction procedure (MSEP). The results show that the differences between NSCSs and SSs in Fe fractions were insignificant and Fe was dominantly present as residual phase (76.22% for NSCSs and 80.88% for SSs) and Fe-oxides phase (20.33% for NSCSs and 16.15% for SSs). Significant variation of Mn distribution patterns between NSCSs and SSs was observed with Mn in NSCSs mainly present in Mn-oxides phase (48.27%) and that in SSs present as residual phase (45.44%). Zn, Cu, Pb and Cd were found dominantly in residual fractions (>48%), and next in solid oxides/hydroxides for Zn, Pb and Cd and in easily oxidizable solids/compounds form for Cu, respectively. The heavy metal distribution pattern implied that Fe/Mn oxides both in NSCSs and SSs were more important sinks for binding and adsorption of Zn, Pb and Cd than organic matter (OM), and inversely, higher affinity of Cu to OM than Fe/Mn oxides in NSCSs and SSs was obtained. Meanwhile, it was found that the distributions of heavy metals in NSCSs and SSs were similar to each other and the pseudo-total concentrations of Zn, Cu, Pb and Cd in NSCSs were greater than those in SSs, highlighting the more importance for NSCSs than SSs in controlling behaviours of heavy metals in aquatic environments.