Wide Bandwidth Silicon Nitride Strip-Loaded Grating Coupler on Lithium Niobate Thin Film

In this research, a vertical silicon nitride strip-loaded grating coupler on lithium niobate thin film was proposed, designed, and simulated. In order to improve the coupling efficiency and bandwidth, the parameters such as the SiO2 cladding layer thickness, grating period, duty cycle, fiber position, and fiber angle were optimized and analyzed. The alignment tolerances of the grating coupler parameters were also calculated. The maximum coupling efficiency and the −3 dB bandwidth were optimized to 33.5% and 113 nm, respectively. In addition, the grating coupler exhibited a high alignment tolerance.

Operational reliability of suspended facade structures with variable thickness of the cladding layer

The article presents the results of laboratory tests of experimental samples for mechanical safety, aimed at obtaining data pertaining to the performance of protective and decorative brick facade structures on metal substructures. The designs of the samples are atypical, with a different arrangement of bricks in the face layer and with ledges evenly distributed over the surface of the sample. Based on the test results, structure behavior under load, the absolute values of the displacement of the cladding layer, and the values of the bond strength between bricks and mortar were established. During the tests, the displacement of the protective and decorative structure in the direction of the applied load and the values of the forces, corresponding to the strength limit, were recorded.The article addresses the issue of the lack of rules for the design and testing of suspended facade systems made of bricks on metal substructures in the regulatory and technical documentation of the Russian Federation.

Effect of friction stir processing on microstructures and mechanical properties of TIG cladding layer on AA7075

AA7075 is a precipitation strengthened Al-Zn-Mg-Cu alloy which has been widely used. As a common way to repair AA7075 components, tungsten inert gas (TIG) cladding generates coarse grains and defects. In addition, the use of other types of filler wires could lead to insufficient rigidity and strength of the cladding layer. In the present work, friction stir processing (FSP) has been applied to the TIG cladding layer on AA7075 to study the effect of process parameters on microstructures and mechanical properties. The macro/micro structural characteristics, elemental distribution, microhardness distribution and tensile properties have been investigated. The macroscopic defects in TIG cladding layer are eliminated and the size of grains is decreases to around 6 μm by FSP. FSP reduces the compositional difference between the stir zone and the base material. Higher rotational speed promotes the grain refinement while the lower traverse speed benefits the microstructural uniformity. FSP on the TIG weld bead brings improvement in tensile properties and hardness. All the fractures for TIG+FSP samples occur at thermo-mechanically affected zone of the advancing side. The tensile strength of the stir zone increases from 424.2 to 442.8 MPa with the increase in rotational speed and traverse speed.

Defect Formation Mechanism and Performance Study of Laser Cladding Ni/Mo Composite Coating

In order to improve the wear resistance of Cu, a Ni/Mo composite coating was applied on the surface of Cu alloy by means of laser cladding. The laser power was 6000 W, the scanning speed was 5 mm/s and the feed rate was 10 g/min. The transition layer of the Ni layer had three layers, and the surface layer of the Mo layer had two layers. The results showed that the surface of the cladding layer was pure Mo. Due to the fluidity and non-equilibrium solidification of Mo in the molten state, pores and cracks along the grain boundary were observed in the Mo layer. The results showed that the cross-section of cladding layer was divided into a pure Mo layer, Mo-Ni-Cu mixed layer and an Ni-Cu mixed layer. The surface hardness of the Mo layer was 200~460 HV. Ni3Mo was formed at the interface of Mo and Ni. The hardness was improved by Ni3Mo; the maximum hardness was 750 HV. Under the same load and wear time, the wear rate of Cu was three times that of the surface layer.