Externally applied stress sign and film elastic properties effects on brittle film fracture

Rectangular stainless steel samples with TiN film deposited on the front lateral surface were loaded in three-point bending to the maximum normal strain of 6%. Scanning electron microscopy showed that vertical cracks appeared in the tension zone when the tensile strain exceeded 1.5%, while horizontal cracks appeared in the compression zone when the compressive strain exceeded –2.9%. Film cracks in the compressive zone originate from the tensile stress imposed by the plastically deformed substrate due to the Poisson’s expansion. Taking plastic deformation and Poisson’s expansion of the substrate in compression into account, theoretical analysis of normal stress distribution along the cracked film segment in compression is presented. Substrate strain and film elastic properties affect film cracking in the compressive zone. At larger compressive strain, some transverse cracks along with buckling cause the film spallation. The presented method is useful for studying brittle film fracture with variable strain levels in a single sample.     

The Morphology and Mechanical Properties of Isotactic Polypropylene Injection-Molded Samples with the Presence of β-Nucleation Agent and Periodical Shear Field

The pressure vibration injection molding (PVIM) method was used to prepare β-nucleated isotactic polypropylene samples (PVIM β-iPP samples); a relatively low, periodical shear was imposed on the polymer melt in the mold at the filling and packing stages. The crystal structures and crystal orientation of the PVIM β-iPP samples were investigated by polarizing light microscopy (PLM), scanning electron microscopy (SEM), and synchrotron two-dimensional wide-angle X-ray diffraction (2D-WAXD). The PLM observations indicated that a cylindrite layer, rather than the transition layer, was found in PVIM β-iPP samples, which is different from the conventional injection-molded (CIM) samples. In addition, the thickness of the oriented layer of the PVIM samples was obviously greater than that of the CIM samples. The SEM observations demonstrated that a large amount of shish-kebab structures appeared in the shear layer of the PVIM β-iPP samples; at the same time, numerous β-spherulites were formed in the core layer. The 2D-WAXD data indicated that orientation homogeneity, to some degree, could be obtained by the periodical shear during PVIM. As a result, the above-mentioned morphology of the PVIM β-iPP samples leads to potentially useful prominent reinforcement and toughening of the material.     

Self-referenced continuous-variable measurement-device-independent quantum key distribution

We propose a scheme to remove the demand of transmitting a high-brightness local oscillator (LO) in continuous-variable measurement-device-independent quantum key distribution (CV-MDI QKD) protocol, which we call as the self-referenced (SR) CV-MDI QKD. We show that our scheme is immune to the side-channel attacks, such as the calibration attacks, the wavelength attacks and the LO fluctuation attacks, which are all exploiting the security loopholes introduced by transmitting the LO. Besides, the proposed scheme waives the necessity of complex multiplexer and demultiplexer, which can greatly simplify the QKD processes and improve the transmission efficiency. The numerical simulations under collective attacks show that all the improvements brought about by our scheme are only at the expense of slight transmission distance shortening. This scheme shows an available method to mend the security loopholes incurred by transmitting LO in CV-MDI QKD.     

Synthesis of a Novel Flame Retardant and Its Synergistic Effect With a Phosphapheanthrene Flame Retardant in Polypropylene/Polyethylene Vinyl Acetate Blends

A novel flame retardant (NSiB) containing nitrogen, silicon and boron was synthesized through reacting of N-(β-aminoethyl)-γ-aminopropyl trimethoxy-silane (KH-792) and boric acid. The structure of NSiB was characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy with energy dispersive spectrometry (SEM-EDS). The effects of NSiB on the flame retardancy and thermal behaviors of polypropylene (PP)/polyethylene vinyl acetate (EVA) blends were investigated by limiting oxygen index value (LOI), vertical burning tests (UL-94) and thermal gravimetric analysis tests (TGA). The results showed that the flame retardancy and thermal stability of PP/EVA blends were improved with the addition of NSiB. When 7.5 wt% DOPO (phosphaphenanthrene) and 0.5 wt% NSiB were incorporated, the LOI value of the PP/EVA blends was 26.9%, and the class V-0 of UL-94 test was passed, as compared to the LOI value of 22.4% and class V-2 of UL-94 test for 8.0 wt% DOPO only and 16.7% and fail, respectively, for the PP/EVA blends alone. The char structure observed by SEM indicated that the surface of the char for the PP/EVA/7.5 wt% DOPO/0.5 wt% NSiB blends had a denser and continuous char structure when compared with that of the PP/EVA blends and PP/EVA/8.0 wt% DOPO blends. These results indicated that there was a good synergistic effect for NSiB and DOPO.     

Strong localization across the metal-insulator transition at the Ag/Si(111)-(√3 × √3)R30° interface

We present the temperature dependent electrical transport measurements of Ag/Si(111)-(√3 × √3)R30° by the in situ micro-four-point probe method integrated with scanning tunneling microscopy. The surface structure characterizations show hexagonal patterns at room temperature, which supports the inequivalent triangle (IET) model. A metal-insulator transition occurs at ～115 K.The lowtemperature transportmeasurements clearly reveal the strong localization characteristics of the insulating phase.