Variable angle spectroscopic ellipsometry and its applications in determining optical constants of chalcogenide glasses in infrared

The principle of variable angle spectroscopic ellipsometry（VASE） and the data analysis models, as well as the applications of VASE in the characterization of chalcogenide bulk glasses and thin films are reviewed. By going through the literature and summarizing the application scopes of various analysis models, it is found that a combination of various models, rather than any single data analysis model, is ideal to characterize the optical constants of the chalcogenide bulk glasses and thin films over a wider wavelength range. While the reliable optical data in the mid-and far-infrared region are limited, the VASE is flexible and reliable to solve the issues, making it promising to characterize the optical properties of chalcogenide glasses.

Synthesis of RE-Ag,Al-RE-doped sol-gel glass and films for solar cells

The paper dealt with the study of fluorescence properties of sol-gel systems doped with rate-earth ions and co-doped with silver. The general problem for these types of inorganic phosphors was a very low absorbance in the visible range. Therefore, a sensitizer of luminescence of the rare-earth ions should be selected and used. The sensitizer should possess a good absorbance in the visible range and strong interaction with the rare-earth ions. In this study silver ions were selected as the sensitizer.

Abnormal IR Spectra of CO Adsorbed on the Surface of Glass Carbon Electrode Modified with Polypyrrole Film with Platinum Microparticles

Abnormal IR spectra of CO adsorbed at the surface of glass carbon electrode modified with polypyrrole film with Pt microparticles are reported.

Tailoring mechanical heterogeneity,nanoscale creep deformation and optical properties of nanostructured Zr-based metallic glass

Metallic glasses are spatially heterogeneous at the nanometer scale.However,the effects of external excitation on their structural and mechanical heterogeneity and the correlation to their properties are still unresolved.Nanoindentation,atomic force microscopy(AFM) and high-resolution transmis sion elec tron micro scopy(HRTEM) were carried out to explore the effects of cryogenic thermal cycling(CTC) on mechanical/structural heterogeneity,nano sc ale creep deformation and optical properties of nano structured metallic glass thin films(MGTFs).The results indicate that CTC treatment alters the distribution fluctuations of hardness/modulus and energy dissipation and results in an increase-then-decrease variation in mechanical heterogeneity.By applying Maxwell-Voigt model,it can be shown that CTC treatment results in a remarkable activation of more defects with longer relaxation time in soft regions but has only a slight effect on defects in hard regions.In addition,CTC treatment increases the transition time from primary-state stage to steady-state stage during creep deformation.The enhanced optical reflectivity of the MGTFs after 15 thermal cycles can be attributed to increased aggregation of Cu and Ni elements.The results of this study shed new light on understanding mechanical/structural heterogeneity and its influence on nanoscale creep deformation and optical characteristics of nanostructured MGTFs,and facilitate the design of high-performance nanostructured MGTFs.

High-Q ring resonators directly written in As2S3 chalcogenide glass films

Planar ring resonator waveguides are fabricated in thin films of As2S3 chalcogenide glass,deposited on silicaon-silicon substrates.Waveguide cores are directly written by scanning the focused illumination of a femtosecond Ti:sapphire laser at a central wavelength of 810 nm,through a two-photon photo-darkening process.A large photoinduced index change of 0.3–0.4 refractive index units is obtained.The radius of the ring resonator is 1.9 mm,corresponding to a transmission free spectral range of 9.1 GHz.A high loaded（intrinsic） Q value of 110,000（180,000） is achieved.The thermal dependence of the resonator transfer function is characterized.The results provide the first report,to the best of our knowledge,of directly written high-Q ring resonators in chalcogenide glass films,and demonstrate the potential of this simple technique towards the fabrication of planar lightguide circuits in these materials.

Role of late transition metals on pitting resistance of Zr-Ti-(Cu, Ni,Co)-Al bulk metallic glasses in 0.6 M NaCl aqueous solution

Four quanternary Zr-based bulk metallic glasses（BMGs）were selected,including the Zr_（46）Ti_2Cu_（45）Al_7,Zr_（61）Ti_2Cu_（25）Al_（12）,Zr_（55）Ti_4Ni_（22）Al_（19）and Zr_（55）Ti_2Co_（28）Al_（15）,due to their robust glass-forming ability and containing a single species of late transition metal（LTM）in compositions.Their pitting resistances in 0.6 M Na Cl aqueous solution were investigated to examine the role of LTM elements in the alloys,with electrochemical measurements,surface morphology observation and x-ray photoelectron spectrometry analysis.It is shown that in comparision with two Cu-bearing BMGs,Zr_（55）Ti_4Ni_（22）Al_（19）and Zr_（55）Ti_2Co_（28）Al_（15）BMGs exhibited significantly superior resistance to pitting.Zr_（61）Ti_2Cu_（25）Al_（12）,Zr_（55）Ti_4Ni_（22）Al_（19）and Zr_（55）Ti_2Co_（28）Al_（15）BMGs manifested distinct passivation behaviour,because of the formation of surface passive film mainly comprising of Zr O_2,Ti O_2and Al_2O_3.However,no significant differences in the electrochemical resistive properties and thicknesses of passive films were found between Zr_（61）Ti_2Cu_（25）Al_（12）and Zr_（55）Ti_4Ni_（22）Al_（19）BMGs.Nevertheless,at the passive film/metal interface,copper enrichment took place in Zr_（61）Ti_2Cu_（25）Al_（12）,whereas the nickel was slightly deficient at the interface in Zr_（55）Ti_4Ni_（22）Al_（19）.During pitting propagation,selective dissolution of the zirconium,titanium and aluminum over the copper took place in Zr_（61）Ti_2Cu_（25）Al_（12）,but it was not the case in Zr_（55）Ti_4Ni_（22）Al_（19）.For the two Cu-bearing BMGs,reduction of passive base metal elements in composition resulted in local selective dissolution,even absence of the passivation.

Coating behavior and surface hardening of Pd_(77)Cu_6Si_(17) thin film metallic glass on AZ31 magnesium alloy

Pd77Cu6Si17(PCS) thin film metallic glasses(TFMGs) with high glass forming ability and hardness were selected as a hard coating for improving the surface hardness of AZ31 magnesium alloy. Both microindentation and nanoindentation tests were conducted on specimens with various PCS film thicknesses from 30 to 2000 nm. The apparent hardness and the relative indentation depth(β) were integrated using a quantitative model. The interaction parameters involved and relative hardness values were extracted from iterative calculations. According to the results, surface hardness can be enhanced greatly by PCS TFMGs in the shallow region, followed by gradual decrease with increasing β ratio. In addition, specimens with thinner coatings(e.g., 200nm) showed greater substrate-film interaction and those with thick coatings(e.g., 2000nm) became prone to film cracking. The optimum TFMG coating thickness in this study was estimated to be around 200 nm.

Self-assembling nacre-like high-strength and extremely tough polymer composites with new toughening mechanism

Achieving high strength,deformability and toughness in polymers is important for practical industrial applications.This has remained challenging because of the mutually opposing effects of improvements to each of these properties.Here,a self-assembling nacre-like polymer composite is designed to achieve ex-tremely tough with increasing strength.This special design significantly improved polymer’s mechanical properties,including an ultra-high fracture strain of 1180%,a tensile strength of 55.4 MPa and a toughness of 506.9 MJ/m^(3),which far exceed the highest values previously reported for polymer composites.This ex-cellent combination of properties can be attributed to a novel toughening mechanism,achieved by the synergy of the domain-limiting effect of metallic glass fragments with the strain-gradient-induced orien-tation and crystallisation within the polymer during stretching.Our approach opens a promising avenue for designing robust polymer materials in armour and aerospace engineering for a range of innovative applications.

Formation mechanism of surface oxide layer of grain-oriented silicon steel

The surface oxide layer of grain-oriented electrical steels was investigated by scanning electron microscopy.The formation mechanism and the influence on the glass film of the surface oxide layer were analyzed by the calculation of thermodynamics and kinetics.The surface oxide layer with 2.3μm in thickness is mainly composed of SiO_(2),a small amount of FeO and Fe_(2)SiO_(4).During the formation of surface oxide layer,the restriction factor was the diffusion of O in the oxide layer.At the initial stage of the decarburization annealing,FeO would be formed on the surface layer.SiO_(2) and silicate particles rapidly nucleated,grew and formed a granular oxide layer in the subsurface.As the oxidation layer thickens,the nucleation of new particles decreases,and the growth of oxide particles would be dominant.A lamellar oxide layer was formed between the surface oxide layer and the steel matrix,and eventually formed a typical three-layer structure.During the high temperature annealing,MgO mainly reacted with SiO_(2) and Fe_(2)SiO_(4) in the surface oxide layer to form Mg2SiO_(4) and Fe_(2)SiO_(4) would respond first,thus forming the glass film with average thickness of 4.87μm.