Hyperbranched Poly(ester-enamine) from Spontaneous Amino-yne Click Reaction for Stabilization of Gold Nanoparticle Catalysts

Hyperbranched polymers have garnered much attention due to attractive properties and wide applications, such as drug‐controlled release, stimuli‐responsive nano‐objects, photosensitive materials and catalysts. Herein, two types of novel hyperbranched poly(ester‐enamine) (hb‐PEEa) were designed and synthesized via the spontaneous amino‐yne click reaction of A2 monomer (1, 3‐bis(4‐piperidyl)‐propane (A2a) or piperazine (A2b)) and B3 monomer (trimethylolpropanetripropiolate). According to Flory's hypothesis, gelation is an intrinsic problem in an ideal A2+B3 polymerization system. By controlling the polymerization conditions, such as monomer concentration, molar ratio and rate of addition, a non‐ideal A2+B3 polymerization system can be established to avoid gelation and to synthesize soluble hb‐PEEa. Due to abundant unreacted alkynyl groups in periphery, the hb‐PEEa can be further functionalized by different amino compounds or their derivates. The as‐prepared amphiphilic PEG‐hb‐PEEa copolymer can readily self‐assemble into micelles in water, which can be used as surfactant to stabilize Au nanoparticles (AuNPs) during reduction of NaBH4 in aqueous solution. As a demonstration, the as‐prepared PEG‐hb‐PEEa‐supported AuNPs demonstrate good dispersion in water, solvent stability and remarkable catalytic activity for reduction of nitrobenzene compounds

Structural and Magnetic Properties of Ni81Fe19 Thin Film Grown on Si(001) Substrate via Single Graphene Layer

We prepared magnetic thin films Ni81Fe19 on single-crystal Si(001) substrates via single graphene layer through magnetron sputtering for Ni81Fe19 and chemical vapor deposition for graphene. Structural investigation showed that crystal quality of Ni81Fe19 thin films was significantly improved with insertion of graphene layer compared with that directly grown on Si(001) substrate. Furthermore, saturation magnetization of Ni81Fe19/graphene/Si(001) heterostructure increased to 477 emu/cm3 with annealing temperature Ta=400°C, which is much higher than values of Ni81Fe19/Si(001) heterostructures with Ta ranging from 200°C to 400°C

WDM-compatible multimode optical switching system-on-chip

The development of optical interconnect techniques greatly expands the communication bandwidth and decreases the power consumption at the same time. It provides a prospective solution for both intra-chip and inter-chip links. Herein reported is an integrated wavelength-division multiplexing (WDM)-compatible multimode optical switching system-on-chip (SoC) for large-capacity optical switching among processors. The interfaces for the input and output of the processor signals are electrical, and the on-chip data transmission and switching process are optical. It includes silicon-based microring optical modulator arrays, mode multiplexers/de-multiplexers, optical switches, microring wavelength de-multiplexers and germanium-silicon high-speed photodetectors. By introducing external multi-wavelength laser sources, the SoC achieved the function of on-chip WDM and mode-division multiplexing (MDM) hybrid-signal data transmission and switching on a standard silicon photonics platform. As a proof of concept, signals with a 25 Gbps data rate are implemented on each microring modulator of the fabricated SoC. We illustrated 25 × 3 × 2 Gbps on-chip data throughput with two-by-two multimode switching functionality through implementing three wavelength-channels and two mode-channel hybrid-multiplexed signals for each multimode transmission waveguide. The architecture of the SoC is flexible to scale, both for the number of supported processors and the data throughput. The demonstration paves the way to a large-capacity multimode optical switching SoC

Assessment of Interaction Behaviors of Cement-Emulsified Asphalt Based on Micro-Morphological and Macro-Rheological Approaches

Cement emulsified asphalt composite binder (CEACB) plays a determining role in the construction of cold recycled asphalt pavements. Understanding the interaction behaviors of cement-emulsified asphalt is very essential to promote the serviceability of CEACB. The objective of this study was to explore the interaction behaviors and mechanism of cement-emulsified asphalt associated with microstructural characteristics and to assess the interaction ability of cement-emulsified asphalt by performing macro-rheological measurements. Firstly, the physico-chemical interaction of cement-emulsified asphalt was qualitatively discussed by analyzing the difference of characteristic peaks based on Fourier transform infrared (FTIR) spectrometer. Secondly, the micro-morphological evolution behaviors of CEACB attributing to the cement-emulsified asphalt interaction were investigated by using a fluorescence microscope (FM) and laser particle size analyzer (LPSA). Thirdly, the microstructural characteristics of CEACB were studied by observing the spatial network structure through the scanning electron microscopy (SEM). Finally, the macro-rheological index based on dynamic rheological shear (DSR) test was proposed to evaluate the interaction ability of cement-emulsified asphalt. The results show that the cement-emulsified asphalt interaction is merely a physical blending process due to the occurrence of no new characteristic peaks in the FTIR spectrum except for cement hydration products. The cement-emulsified asphalt interaction in early-age CEACB could be reflected by the aggregation process among asphalt droplets and the adsorption action of cement particles to asphalt droplets. A reasonable ratio of cement to emulsified asphalt could promote the formation of the denser spatial network structure of CEACB along with cement hydration products growing and interweaving with asphalt films. The K-B-G* index based on macro-rheological properties of CEACB with full consideration of cement hydration process is very suitable for evaluating the interaction ability of cement-emulsified asphalt under the condition of different cement proportions and curing time. The research would provide the support for understanding the natural properties of CEACB and promote the improvement of the mechanical performance of cold recycled asphalt pavements

The Interdiffusion Behavior of NiCoCrAlYHf Coating Deposited by Arc Ion Plating on Carburized Ni-Based Single Crystal Superalloy

In the present study, arc ion plating (AIP) was used to prepare a NiCoCrAlYHf coating (HY5 coating) on a carburized third-generation single-crystal superalloy DD10. The interdiffusion behavior of the carburized superalloy with an HY5 coating was investigated for a 1000 h oxidation time at 1100 °C. Carburization enhanced the interfacial bonding force and improved the microstructure of the NiCoCrAlYHf coating. An interdiffusion zone (IDZ) formed after a 300 h oxidation time, and the formation of a carburized layer effectively suppressed an inward diffusion of cobalt, aluminium, and chromium to the DD10 superalloy as well as an outward diffusion of nickel and refractory elements for instance rhenium and tungsten to the HY5 coating that occurred in static air at 1100 °C. The roles of the carburized layer in affecting thermal cyclic oxidation and element interdiffusion were studied. Subsequently, a modified form of the Boltzmann–Matano analysis was used to present the interdiffusion coefficients of aluminium

Use of MD Simulation for Investigating Diffusion Behaviors between Virgin Asphalt and Recycled Asphalt Mastic

The study aims at investigating diffusion behaviors between virgin asphalt and recycled asphalt mastic (RAM) at an atomistic scale. Firstly, a mutual diffusion model of virgin asphalt–RAM considering the actual mass ratio of filler to asphalt binder (F/A) condition was developed by molecular dynamic (MD)simulation. Secondly, the indexes of relative concentration (RC), radial distribution function (RDF) and mean square displacement (MSD) were used to analyze the molecular arrangement characteristics of polar components in the diffusion processes at different temperatures. Then, the blending efficiency of virgin asphalt–RAM was evaluated by Fick’s second law and the binding energy. The results indicate that the reliability of the RAM model was validated by thermodynamics properties. The results of RC and RDF show that the diffusion direction of virgin asphalt–RAM is not changed by the presence of mineral fillers. However, it will inhibit the occurrence of diffusion behaviors, and the aggregation of molecules in the blending zone increases due to the adsorption of mineral fillers, which would become a barrier to molecular diffusion. The development of MSD indicates that the diffusion coefficients of molecules in both virgin–aged asphalt and virgin asphalt–RAM are on the rise with the increase in temperature. Compared with the virgin–aged asphalt, the molecular migration speed in virgin asphalt–RAM is relatively slow. According to Fick’s second law and the binding energy, diffusion behaviors are dominated by the nonpolar components. The existence of mineral fillers has the greatest effect on the nonpolar components in diffusion. It is suggested that rejuvenator containing more aromatic components should be added or the temperature controlled within 433.15–443.15 K to promote blending efficiency. The research results contribute to a deeper understanding about diffusion behaviors of virgin asphalt–RAM, serving as a benchmark for further study of rejuvenation using computational experiments