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Ni–P(–SiC) composite coatings were successfully deposited on 70 vol% SiCp/Al composite by electroless plating. The surface microstructures and the phase structures of the Ni–P(–SiC) coatings were examined and analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) before and after heat-treatment at 200–400 °C for 2 h. The thermal diffusivity of the deposited samples and the interface adhesion between the coating and the substrate were investigated. The experimental results show that SiC content in the coatings increases obviously and XRD peaks are enhanced with SiC content in the bath increasing from 3 to 9 g·L−1. After heat-treatment, the surface of the coating becomes smoother and no diffusion layer is produced at the interface. A new phase Ni3P forms in the coating during heat-treatment at 400 °C. The critical load (Lc) of Ni–P–SiC composite coating on SiCp/Al composite reaches the maximum value of 84.9 N with SiC content of 3 g·L−1 after heat-treatment at 200 °C and more or less decreases with the increase in SiC content and heat-treatment temperature. The thermal diffusivity of deposited samples gradually increases as the temperature increases; however, it reduces firstly and then climbs with the increase in SiC content. [ABSTRACT FROM AUTHOR]

Geometric error is the main obstacle that affects the quasi-static accuracy of horizontal boring machine tools. To improve quasi-static performance, the error terms of all position-independent geometric errors (PIGEs) and position-dependent geometric errors (PDGEs) must be measured and identified precisely. This study proposes a novel method for measuring and identifying the above two types of geometric errors based on double ballbar for the rotary axis. The error terms of the linear axis are identified from the measurement model based on the exponential product method and a preset measure trajectory, and the measure coordinate system is combined with the reference coordinate to lower the uncertainty in the identification accuracy. Then, the elastic net method and improved weight function IGG3-LTS method are established to identify the PIGEs and PDGEs of the rotary and linear axes, respectively. This method has the advantage that measurement with the built-in sensor method synchronously does not interfere with the running state of the machine tool, and neither the inaccuracy of reference-frame misalignment nor installation error of the measuring instrument affects the geometric error identification results of the linear axis. Moreover, all PIGEs and PDGEs, particular to the rotary axis of the horizontal boring machine tool, are determined accurately. The measurement and identification strategy is demonstrated by experimental comparison on a four-axis precision horizontal boring machine tool. The minimum compensation rate of each precision index of the test specimen is 40.0%, the average compensation rate is 52.7%, and the maximum compensation rate is 62.5%. [ABSTRACT FROM AUTHOR]

The recirculating planetary roller screw mechanism (RPRSM) is a transmission mechanism that engages the screw and nut threaded by multiple grooved rollers. In this paper, firstly, the design method of RPRSM nut threadless area is proposed, and the equations related to the structural parameters of nut threadless area are derived. On this basis, the cross-section design method of roller, screw and nut is constructed according to the actual situation of engagements between the screw/nut and the roller. By adjusting the gap between the two beveled edges and that between the arc and the beveled edge, the accuracy of the thread engagements between the screw/nut and the roller can be improved. Secondly, to ensure the engagements of the screw/nut and the roller, the distance equation from the center surface of the different rollers to the end surface of cam ring is given. Thirdly, combined with the working principle and structural composition of RPRSM, the component model is established according to its relevant structural parameters, and the virtual assembly is completed. Finally, the 3D model is imported into the ADAMS simulation software for multi-rigid body dynamics. The dynamic characteristic is analyzed, and the simulated values are compared with the theoretical values. The results show that the contact forces between the screw/nut and the roller are sinusoidal, mainly due to the existence of a small gap between the roller and the carrier. The maximum collision forces between the roller and cam ring are independent from load magnitude. Normally, the collision force between the roller and the carrier increases as the load increases. When RPRSM is in the transmission process, the roller angular speed in nut threadless area begins to appear abruptly, and the position of the maximum change is at the contact between the roller and the convex platform of cam ring. The design of the nut threadless area and the proposed virtual assembly method can provide a theoretical guidance for RPRSM research, as well as a reference for overall performance optimization. [ABSTRACT FROM AUTHOR]

The core-shell structural nano-TiO@Fe micro-sized photocatalysts were prepared by a precipitation method followed with a hydrothermal treatment. The results indicate that the sheet-like nano-TiO particles are evenly coated on the surface of micro-sized Fe particles to form a core-shell structure with a specific surface area of 31.7 m/g. These composite particles possess combined properties of nano-TiO and zero-valent Fe, which make the TiO@Fe photocatalyst exhibit high photocatalytic activity to remove the phenol pollutant under visible light and have the magnetic property to be easily recycled from treated waters. This magnetically separable photocatalyst can be reused over 20 times with a removal efficiency above 90 %. Graphical abstract: [ABSTRACT FROM AUTHOR]

An FeMo-alloy-doped β-SiAlON (FeMo/β-SiAlON) composite was fabricated via a reaction-bonding method using raw materials of Si, AlO, AlN, FeMo, and SmO. The effects of FeMo on the microstructure and mechanical properties of the composite were investigated. Some properties of the composite, including its bending strength at 700°C and after oxidization at 700°C for 24 h in air, thermal shock resistance and corrosion resistance to molten aluminum, were also evaluated. The results show that the density, toughness, bending strength, and thermal shock resistance of the composite are obviously improved with the addition of an FeMo alloy. In addition, other properties of the composite such as its high-temperature strength and oxidized strength are also improved by the addition of FeMo alloy, and its corrosion resistance to molten aluminum is maintained. These findings indicate that the developed FeMo/β-SiAlON composite exhibits strong potential for application to molten aluminum environments. [ABSTRACT FROM AUTHOR]

Ni-base metal-intermetallic laminate composites were obtained from in situ reaction synthesis between Ni and Al foils by utilizing plasma activated sintering. The effects of Ni foil thickness on the microstructure and tensile properties of the composites were investigated. The results show that the phases forming during reaction synthesis are independent of the starting thickness of the Ni foils. However, thicker reacted layers are obtained in the samples fabricated from 100 μm Ni foils (Ni100) than those obtained in the samples from 50 μm Ni foils (Ni50) when treated at the same process. The tensile strength of Ni100 samples increases with the temperature increasing at the expense of ductility. Dissimilarly, Ni50 composites treated at higher temperatures exhibit enhanced strength and ductility. Both Ni50 and Ni100 laminate fracture in a similar mechanism. Cracking first occurs in the brittle intermetallic layers. These original cracks result in shear bands in Ni layers emitted from the crack tips, and thus producing local stress concentration, which initiates new cracks in adjacent intermetallic layers. The multiplication of cracks and shear bands leads to the failure of the laminates. [ABSTRACT FROM AUTHOR]