Effect of Heat Treatment on the Microstructure and Strength of Stainless Steel-Clad Plate

Strength of Materials - A 316L/Q345R stainless steel-clad plate after hot rolling was subjected to three heat treatments: rapid cooling, rapid cooling and tempering, high-temperature rapid cooling,...     

A new approach to journal co-citation matrix construction based on the number of co-cited articles in journals

Scientometrics - Co-citation analysis is one of the most important methods in information science. Journal co-citation analysis has been widely used to analyze the relevance, relationship and...     

Multi-Rate Polling: Improve the Performance of Energy Harvesting Backscatter Wireless Networks

In recent years, Researchers have proposed the concept of Energy Harvesting Backscatter Wireless Networks (EHBWN). EHBWN usually consists of one sink and several backscatter nodes. Backscatter nodes harvest energy from their environment and communicate with sink through backscattering the carrier wave transmitted by sink. Although a certain amount of access protocols for Energy Harvesting Wireless Networks have been present, they usually do not take the sink’s receiver sensitivity into account, which makes those protocols unsuitable in practice. In this paper, we first give an analysis of the backscatter channel link budget and the relationship between the effective communication range and uplink data rate. After that, we point out that a single uplink data rate for all the backscatter nodes is no longer suitable due to the constraint of sink receiver sensitivity. Later we propose Multi-rate Polling which divides the network into different uplink data rata regions to make sure the correct packet reception by the sink and improve the network performance. Multi-rate Polling also introduces a parameter K, through adjusting it, we can achieve the trade-off between network throughput and fairness to meet the requirement under various scenarios. We validate Multi-rate Polling under different networks and average harvesting rates through simulation. The result shows that the proposed protocol can effectively improve the network performance and has excellent scalability, which makes it suitable for EHBWN.     

Dynamic Response Solution of Multi-Layered Pavement Structure Under FWD Load Appling the Precise Integration Algorithm

The pavement layered structures are composed of surface layer, road base and multi-layered soil foundation. They can be undermined over time by repeated vehicle loads. In this study, a hybrid numerical method which can evaluate the displacement responses of pavement structures under dynamic falling weight deflectometer (FWD) loads. The proposed method consists of two parts: (a) the dynamic stiffness matrices of the points at the surface in the frequency domain which is based on the domain-transformation and dual vector form equation, and (b) interpolates the dynamic stiffness matrices by a continues rational function of frequency. The mixed variables formulation (MVF) can treat multiple degree of freedom systems with considering the coupling term between degree of freedoms. The accuracy of the developed method has been demonstrated by comparison between the proposed method and published results from the other method. Then the proposed method can be applied as a forward calculation technique to emulate the falling weight deflectometer test for multi-layered pavement structures.     

A study of microstructure and performance of cast Fe–8Cr–2B alloy

The effects of quenching temperature on microstructure and hardness of cast Fe–8Cr–2B alloy containing 0.3 wt% C, 2.0 wt% B, 8.0 wt% Cr, 0.6 wt% Si, and 0.8 wt% Mn were investigated by optical microscopy (OM), scanning electron microscopy (SEM), X‐ray diffraction (XRD), Rockwell hardness and Vickers microhardness testers. The experimental results indicate that the as‐cast microstructure of cast Fe–8Cr–2B alloy consists of M₂B (M = Fe, Cr), M₇(C, B)₃, α‐Fe, and γ‐Fe. The dendritic matrix composed of lath martensite mixed with a small amount of retained austenite, and the netlike boride M₂B distribute in the grain boundary. After quenching between 950 °C and 1100 °C, the netlike eutectic boride are broken up and a new phase‐M₂₃(C, B)₆ which is distributed in the shape of sphere or short rod‐like are precipitated from the matrix. Both the macrohardness and microhardness of specimens increase with the increasing quenching temperature. At about 1050 °C, the hardness reaches the maximum value. However, when the temperature exceeds 1050 °C, the hardness will decrease slightly. With the increase of tempering temperature, the hardness of cast Fe–8Cr–2B alloy quenching from 1050 °C decreases gradually and its impact toughness increases slightly. Crusher hammer made of cast Fe–8Cr–2B alloy quenching from 1050 °C and tempering from 300 °C has good application effect, and its service life improves by 150–180% than that of high manganese steel hammer.     

One‐Step Transfer and Integration of Multifunctionality in CVD Graphene by TiO2/Graphene Oxide Hybrid Layer

We present a straightforward method for simultaneously enhancing the electrical conductivity, environmental stability, and photocatalytic properties of graphene films through one‐step transfer of CVD graphene and integration by introducing TiO₂/graphene oxide layer. A highly durable and flexible TiO₂ layer is successfully used as a supporting layer for graphene transfer instead of the commonly used PMMA. Transferred graphene/TiO₂ film is directly used for measuring the carrier transport and optoelectronic properties without an extra TiO₂ removal and following deposition steps for multifunctional integration into devices because the thin TiO₂ layer is optically transparent and electrically semiconducting. Moreover, the TiO₂ layer induces charge screening by electrostatically interacting with the residual oxygen moieties on graphene, which are charge scattering centers, resulting in a reduced current hysteresis. Adsorption of water and other chemical molecules onto the graphene surface is also prevented by the passivating TiO₂ layer, resulting in the long term environmental stability of the graphene under high temperature and humidity. In addition, the graphene/TiO₂ film shows effectively enhanced photocatalytic properties because of the increase in the transport efficiency of the photogenerated electrons due to the decrease in the injection barrier formed at the interface between the F‐doped tin oxide and TiO₂ layers.     

Effect of lead on formation and dielectric tunability of (Pbx,Sr1? x )0.85Bi0.1TiO3 thin films

(Pb_x,Sr_1−x )_0.85Bi_0.1TiO₃ thin films with the perovskite phase structure were prepared on an ITO glass substrate by sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and an impedance analyzer were respectively used in order to characterize the phase status, morphology and dielectric properties of the thin films. The results show that during the formation process of (Pb_x,Sr_1−x )_0.85Bi_0.1TiO₃ thin films, the nucleus of the perovskite phase are initially formed and then congregated. These aggregated nucleus are then transformed as the perovskite-phase crystalline in the thin film. Finally, the crystalline phase grows and separates gradually to form the perfect crystalline-phase structure. The content of the perovskite phase formed in the thin film under rapid thermal process (RTP) is more than that formed under traditional heat treatment with kinetic equilibrium. This is due to the high active decomposed ions that form the perovskite phase directly when heat-treated by RTP. The formation of the perovskite phase therefore overcomes a much lower barrier under RTP than that under traditional calcinations. The structure of the perovskite phase has a close relation to the ratio of Pb/Sr in the system because of the radius difference between Pb²⁺ and Sr²⁺. The transformation temperature between the cubic and the tetragonal structures of the perovskite phase increases with increasing Pb²⁺ content because the radius of Pb²⁺ is larger than that of Sr²⁺. It appears at room temperature when the content of Pb²⁺/Sr²⁺ is about 40/60 in the thin film. Meanwhile, the tetragonality of the perovskite phase is increased when Pb²⁺ ions increase due to its high polarization. The higher tunability of the (Pb_x,Sr_1−x )_0.85Bi_0.1TiO₃ thin film is exhibited when the film composition is close to the transformation point between the paraelectric and ferroelectric phases. Pb²⁺ ions show a dominant factor to affect the Curie point of the system and then changing tunability. Translated from Journal of Inorganic Materials, 2006, 21(2): 466–472 [译自: 无机材料学报]