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In this study, laser cladding on EA4T steel was carried out. The Composition of HAZ of the EA4T steel was analyzed by OM and SEM. The effect of laser cladding on microstructural transformation of HAZ of EA4T steel was discussed. The distribution of alloying elements and the micromechanical properties of the interface were tested. The results show that the microstructures of the laser cladding heat-affected zone of the EA4T steel are mainly lath martensite. The homogenization of austenite and the dissolution of carbides near the interface are not sufficiently developed, and coarse grains are observed. In the fine-grained area of the HAZ, the microstructure is mainly composed of martensite and a small amount of sorbite with a certain orientation. In addition, among all laser cladding conditions, the highest temperature experienced in the HAZ of the EA4T steel plays a decisive role in the evolution of the microstructure and mechanical properties. A sudden change in alloying elements occurs at the junction site, and the grain orientation is clearly found. Moreover, the shear strength of the HAZ increases, whereas the degree of packing decreases.

Carbon nanotubes (CNTs) are an ideal starting material for the development of strong, light‐weight conductors. In this work, we pursued the development of high specific electrical conductivity and high specific strength CNT/metal composites. We started with CNT yarns which had an initial electrical conductivity, σe, of 3.14 MS m‐1 and a density of 1.32 g cm‐3. We brominated the yarns, demonstrating increases in σe, with our best samples reaching σe = 7.00 MS m‐1. To increase the stability of the bromination, we electroplated a Cu layer onto the Br‐doped yarn which led to a stabilization of the conductivity improvement. This was quantified by monitoring periodically the σe of a Br‐doped and metallized CNT yarn over a period of 69 days, during which time the sample was otherwise exposed to ambient conditions. Analysis gives a value 6.15 MS m‐1 for the brominated yarn after metallization which is excellent for CNT yarns. Tensile tests on these Cu/CNT composites showed tensile strengths reaching 700 MPa, Young's modulus values of 22.8 GPa, and specific tensile strength values of 146 kN*m kg‐1 (this latter is 6X that of Cu). Our best CNT‐Cu composites show specific conductivity values comparable with that of Cu but with much higher specific tensile strengths.

Aqueous amine-based CO2 capture is considered as the most mature and applicable CO2 capture method for post-combustion. With the CO2 capture process running for a long time, the degradation of aqu...

A novel surface-enhanced Raman scattering (SERS)-lateral flow assay (LFA) biosensor in combination with catalytic hairpin assembly (CHA) signal amplification has been developed for the analysis of miR-196a-5p and miR-31-5p associated with lung cancer. In the presence of target miRNAs, two hairpin DNAs self-assembled into double-stranded DNA, making biotin molecules on the surface of Au–Ag nanoshuttles (Au–AgNSs) exposed. Therefore, the target enters the next cycle, while SERS complexes were trapped and concentrated on the different test lines (T1 and T2 lines), strongly amplifying the SERS signals. Through the finite difference time domain method, it was proved that the intense electromagnetic field enhancements provided “hot spots” for SERS in the nanogaps between aggregated Au–AgNSs, making Au–AgNSs exhibit excellent SERS performance. The prepared biosensor enabled rapid, sensitive, specific and simultaneous detection of miR-196a-5p and miR-31-5p. The whole detection time was short (40 min), and the detection limits of miR-196a-5p and miR-31-5p were as low as 1.171 nM and 2.251 nM in phosphate buffer, and were 1.681 nM and 2.603 nM in human serum, respectively. For the high accuracy diagnosis of lung cancer, SERS was successfully applied to quantitatively detect these two miRNAs in clinical serum from lung cancer patients at different stages and healthy subjects. The results of the SERS-LFA method were comparable to those of the real-time polymerase chain reaction. The designed multiple signal amplification SERS biosensor would be a very promising alternative tool for miRNA research in the field of biomedical diagnosis, which is of vital importance in the early detection and prevention of lung cancer.

Prussian blue nanoparticles (PBNPs), which belong to the iron-based metal-organic frameworks, are important biomedical agents. Reducing the size of PBNPs can bring improved functional properties, but unfortunately, has been a long-standing challenge. Herein, sub-5 nm ultrasmall PBNPs (USPBNPs) were successfully synthesized by using ethanol/water mixture as the solvent and polyvinyl pyrrolidone (PVP) as the surface capping agent. Adjusting the ethanol/water ratio is not only able to control the nucleation time and size of PBNPs but also tune the conformation of PVP molecules so as to prevent interparticle attachment and enlargement. At an ethanol/water ratio of 3:1, highly stable USPBNPs with a size of ∼3.4 nm were synthesized. Due to their large specific surface area, they demonstrated high peroxidase-like and catalase-like activities, which outperform PBNPs synthesized by a conventional method. In addition, they also showed a high longitudinal relaxation rate (r1) of 1.3 mM-1 S-1, suggesting their potential to be used as T1 MRI agent.

The development of high-performance glucose sensors is an urgent need, especially for diabetes mellitus diagnosis. However, the glucose monitoring is conventionally operated in an invasive finger-prick manner and their noninvasive alternatives largely suffered from the relatively poor sensitivity, selectivity, and stability, resulted from the lack of robust and efficient catalysts. In this paper, we design a concave shaped nitrogen-doped carbon framework embellished with single Co site catalyst (Co SSC) by selectively controlling the etching rate on different facet of carbon substrate, which is beneficial to the diffusion and contact of analyte. The Co SSC prompts a significant improvement in the sensitivity of the solution-gated graphene transistor (SGGT) devices, with three orders of magnitude better than those of SGGT devices without catalysts. Our findings expand the field of single site catalyst in the application of biosensors, diabetes diagnostics and personalized health-care monitoring.

Dissimilar joining of aluminum to steel is an important industrial and academic problem. The present study reports the application of a novel approach in impact welding where a pocket machined on the flyer sheet generates the requisite standoff, enabling joining of commonly used automotive aluminum alloys to high-strength low-alloy (HSLA) steels. The new approach enables impact spot welding of heat treatable AA6111-T4 aluminum (Al) alloy to bare, hot-dip galvanized and e-coated HSLA 340 steel (with local removal of the coating on the faying surface) as well as of high-pressure vacuum die cast Aural 2 Al alloy to hot-dip galvanized HSLA 340 steel. Characterization of the welded samples via lap-shear and coach peel testing demonstrated high joint strengths with button pullout failure modes in all weld pairs. Optical microscopy of the weld cross-sections revealed defect-free joints displaying typical impact welded interface morphology. A significant outcome of the novel impact spot welding approach was the ability to produce joints exhibiting flat external target surfaces with unperturbed coating, a potential enabler for mixed metal joining applications involving pre-treated, e-coated, or painted materials.

Palygorskite (PAL) is a natural fibrous clay mineral which attracted tremendous attention as reinforcing agent to polymers. In this paper, a facile and environmental friendly modification process of PAL by poly acrylic acid (PAA) via in-situ polymerization in PAL/water gel has been reported. The effects of PAA modified PAL (PAA-PAL) on the mechanical and thermal properties of waterborne polyurethane (WPU) nanocomposites have been investigated. Scanning electron microscopy (SEM) demonstrated that the dispersion of PAL has improved dramatically after PAA modification. Tensile tests showed that PAA-PAL has a significant reinforcement effect on WPU matrix. Addition of 10 wt% PAA-PAL, the tensile strength and the Young’s modulus of WPU composites increased 235 % and 388 %, respectively. Furthermore, the thermal stability of WPU also has been distinctly improved via addition of PAA-PAL.

Ethanol dry reformation (EDR) is a chemical process for syngas production, which consumes a greenhouse gas and reduces carbon footprint. We present a mechanistic study of EDR over Rh catalyst based...

在图像处理与分析领域, 深度学习发挥着日渐重要的作用. 我们将深度学习应用于高分辨率透射电子显微镜(HRTEM)图像晶面间距的自动快速测量中, 通过对随机样本数据训练得到具有U型结构的神经网络, 开发了一种新的图像处理方法. 本方法能够自动提取快速傅里叶变换(FFT)图像中的衍射斑点, 进一步在计算机视觉技术的协助下, 可以自动计算与FFT图像中被识别的衍射点相对应的晶格间距, 并与标准晶体结构数据进行比较. 以Fe3O4纳米粒子的HRTEM图像为例, 用本方法进行自动测量的晶格间距与手动测量的晶格间距相比, 误差小于1%. 我们的工作证明了深度学习技术在协助晶体材料发展方面的巨大潜力.

In this reported study, a new Q criterion was proposed to analyze the vortex in three cyclones that had various inlet structures. The Reynolds stress model (RSM) was used to simulate the gas flow, and the Phase Doppler Particle Analyzer (PDPA) was used to measure the fluid velocity. The results showed that the vortex structure was intuitive according to the new isovortex surface that was obtained using the Q criterion. The isovortex surface was found to be distorted and not distributed around the center axis. With the development of flow, the equivalent diameter of the isovortex surface gradually decreased. The magnitude of the vorticity and the vortex lines of axisymmetrical volute inlet (AVI) structure were more uniform and symmetrical than those found into the single tangential inlet (STI) structure and the single volute inlet (SVI) structure.

In this study, a broadband and high gain dielectric-rod end-fire antenna are proposed for applications on both the K and Ka bands. By employing the double-ridged waveguide (DRW) feeding structure which is composed of a coaxial line to tapered DRW transition, a parabolic tapered DRW, and a parabolic-tapered flared parallel waveguide section, the impedance bandwidth of this proposed antenna is broadened to 84.5%. The dielectric-rod with the double circular truncated cone structure acted as the main radiator of the proposed antenna is adopted to achieve higher gains and lower side-lobe levels as compared to the traditional circular cone dielectric-rod, while the four-wedges structure inserted in the waveguide is developed as the matching section of the dielectric-rod to further improve the impedance matching. The measured results show that this antenna can be operated in 17.9–44.1 GHz, and the measured gain changes from 9.9 to 15.5 dBi. Moreover, the radiation patterns are demonstrated with observed end-fire characteristic in the overall operating band.

Iron based nanomedicine (IBNM) has been one powerful diagnostic tool as a magnetic resonance imaging (MRI) contrast agent (CA) in the clinic for years. Conventional IBNMs are generally employed as T2-MRI CAs, but most of them are constrained in clinical indication expansion by magnetic susceptibility artifacts. In comparison, extremely small iron oxide (ESIO) with a core size less than 5 nm has demonstrated the T1-MRI effect, which provides prospects for a Gd-based agent alternative. Nevertheless, currently developed ESIOs for T1-MRI CAs always require harsh conditions such as a high temperature and high boiling point reagent. Moreover, very few of the currently developed ESIOs meet the stringent pharmaceutical standard. Herein, on the basis of a crystal nuclear precipitation-dissolution equilibrium mechanism and outer/inner sphere T1-MRI theory, monodisperse ESIOs with an average size of 3.43 nm (polydispersity index of 0.104) are fabricated using a moderate cooling procedure with mild coprecipitation reaction conditions. The as-synthesized ESIOs display around 3-fold higher T1 MRI signal intensity than that of commercial Ferumoxytol (FMT), comparable to that of Gd-based CAs in vitro. Additionally, the T1-MRI performance of the ESIOs is pH dependent and delivers bright signal augmentation. Eventually, the internalization into mesenchymal stem cells of the ESIO is realized in the absence of a transferring agent. Considering the identical structure and composition of the ESIOs as compared to that of FMT, they could meet the pharmaceutical criteria, thus providing great potential as T1-MRI Cas, for instance as stem cell tracers.

The oxygen evolution reaction (OER) is a critical process involved in various energy related processes. Here, surface engineering of metal foams is achieved by immersing a commercially available metal foam in an aqueous Fe3+ solution at room temperature. This approach provides a facile and scalable one-step strategy to make effective oxygen evolution electrodes, which does not involve any noble metals and does not demand any thermal or electrical energy-intensive steps. The obtained electrodes show low overpotentials of 239–262 mV at 10.0 mA cm−2 in 1 M KOH for the OER. The spontaneous reaction between Fe3+ and metallic cobalt or nickel, along with the spontaneous hydrolytic reaction of the metal ions in the presence of air, induces the formation of edge-rich bimetal hydroxide species on the metal foam surface. Importantly, the as-obtained electrodes also demonstrate excellent stability for more than 70 h. Scaled-up preparation of the foam electrodes is shown with the size of an A4 sheet of paper. Density functional theory calculations reveal that the oxygen vacancies induce the structural distortion of M–OH and electronic structure modulation of M–OOH, thus breaking the scaling relation between ΔGOH and ΔGOOH and improving the catalytic activity. The approach demonstrated here is one of the easy-operation routes for highly active electrocatalytic electrodes towards the OER.

An approach to rationally design optimal alloy catalysts is established using nitric oxide (NO) oxidation as an example. We introduce a quantitative structure-energy equation to predict the chemisorption energies of adsorbates on alloy catalysts. The structure-energy descriptor is used to rationally design Pt-based and Ni-based alloy catalysts for NO oxidation. Full first principles calculations with kinetic simulations demonstrate that these designed catalysts possess much better catalytic performances than the traditional catalysts.

The thermoplastic polymer such as poly(methyl methacrylate) (PMMA), polyetheretherketone (PEEK), and polyimide (PI) is a kind of polymer material with properties of good mechanical strength. It has been widely used in the fields of aerospace, optical engineering, and microfluidics, etc. Thermoplastic polymers are considered to be one of the most promising engineering plastics in the future. Therefore, it is necessary to further study its mechanical properties and machinability, especially in ultra-precision machining. Furthermore, mechanical property and machinability were studied in this work. Through the dynamic mechanical analysis experiment, the elastic modulus and temperature effect of PMMA, PEEK, and PI are analyzed. In addition, the high-speed micromilling experiment is conducted to show that the surface roughness, burrs, and cutting chip characteristics in the high-speed micromilling process. In general, the surface quality of the brittle removal is generally better than that of the viscoelasticity state. The results show that PMMA, PEEK, and PI have good mechanical properties and machinability. Base on the results, the material will be in a viscoelastic state as the temperature increases. The surface quality of the brittle removal is generally better than the viscoelastic state.

Vaporizing foil actuator welding (VFAW) was used to create high strength and fatigue resistant dissimilar welds between NiTi and a brass alloy for the first time. VFAW uses the high pressure resulting from a vaporized aluminum foil to impact weld NiTi to brass. Advanced techniques were used to characterize the structure, mechanical and functional properties of these impact welds. The results show that NiTi/brass welds had solid-state wavy interfaces with no thermally induced defects. The adjoining area of the interfaces were strengthened compared to the base metals. Martensitic transformation temperature ranges were widened in these dissimilar impact welds. Lap shear tests show that the dissimilar NiTi impact welds exhibited a similar pseudoelastic plateau and maximum stress as the NiTi base metal. The resultant joint efficiencies were near 100 % compared to less than 50 % in traditional welding technologies. Cycling tests show that the NiTi/brass impact welds exhibited very similar pseudoelastic responses as the NiTi base metal with less than 0.5 % irrecoverable strains. Dissimilar impact welding of NiTi to brass provides stronger joining and more design flexibility compared to mechanical crimping, positioning the technology to be a solution to producing high strength actuators and sensors.

polycrystalline CuxYyOz are made through solid state reaction. Ferromagnetism is found in this YCuO system at room temperature. The ferromagnetism quite probably originates from Cu2Y2O5 , the Copper Yttrium Oxide. The average magnetic moment per Cu2+ is estimated to be 0.04μB. Itinerant electron magnetism is a rational explaination for the observed ferromagnetism. The experiment shows that the excessive amount of Cu may lead more defects and further distortion in the lattice and decrease the exchange interaction. This reminds us that the Copper Yttrium Oxide is a substance not only should be avoided in fabricating YBCO superconductors but also should be considered as a potential substance of magnetic semiconductor.

Thermally-induced fatigue cracking of steel dies is one of the most common failures in die casting industry. Based on a modified universal slopes equation, a new fatigue life prediction criterion has been developed for die casting processes, correlating the temperature differences during casting cycles and thermal fatigue crack cycles. A laboratory thermal fatigue experiment, undergoing cyclic heating and water cooling, was used to reproduce thermal fatigue cracking. A simple plate sample was tested to fit this new fatigue model criterion, where its heating was achieved by residing in a kiln chamber. Furthermore, a finite element analysis code ProCAST® was used to model the thermal loadings during the test. To further extend the application of this newly developed criterion, a miniature H13 steel insert sample was machined and tested. The sample was designed to be geometrically similar to an actual water jacket insert in an automotive engine block. In addition to the kiln chamber heating, the sample was tested by immersion in A380 melt, which is more characteristic to actual die casting conditions. Based on the test results, the fatigue life prediction model can be used as a practical and efficient tool to predict and improve hot-work tooling life in the die casting and other manufacturing industries.

Due to the potential toxicity of sulfite as widely used food additive, there is urgent need for the development of low-cost, rapid and convenient sensors for sulfite detection. Toward this end, highly sensitive and selective sulfite sensors based on solution gated graphene transistors (SGGTs) was innovatively developed. The performance of the device was significantly improved through the functionalization of the gate electrode with multi-walled carbon nanotubes (MWCNTs). We found that the MWCNT modified SGGT sensor showed an ultra-low detection limit of 30 nM toward sulfite. In addition, we also demonstrated that the SGGT-based sulfite sensor was capable of detecting sulfite content in practical liquor samples with high recovery rate. Considering its low-cost and easy-fabricating features, we believe that the SGGT-based sensor with appropriate functionalization may be applied as a highly potential platform for ultra-sensitive detection of a broad range of important analytes in practical samples for food safety purpose.

Serious Joule heating is expected to bring new reliability challenges in advanced packaging technology and thermomigration of solder joints is regarded as one of critical reliability issues. Recently, Co has been proposed as a candidate for under-bump metallization (UBM) because of its high wettability, great corrosion resistance and lower growth rate of intermetallic compound (IMC) during reflow process as compared to Cu and Ni. In this study, thermomigration behavior of Co/SnAg/Co and Cu/SnAg/Co sandwich structure is investigated. For Co/SnAg/Co structure, faster growth of CoSn3 IMC at the hot end than the cold end is observed and Sn is found to dominate the interfacial growth under a temperature gradient. In contrast to Co/SnAg/Co structure, Cu6Sn5 and Cu3Sn IMCs in Cu/SnAg/Co structure grow faster at the cold end than that at the hot end and Cu is the dominant diffusion species during thermomigration. In addition, no Co signal is detected near Cu substrate under a temperature gradient in Cu/SnAg/Co structure, demonstrating that Co possesses better thermomigration resistance than Cu and Sn.

With the growing need to develop light weight structures joining dissimilar metals is inevitable. Hence a fundamental understanding of the microstructure evolution and bond formation mechanism is necessary. In this work we probe the welded interface in aluminum and steel joined using vaporizing foil actuator welding (VFAW) a novel impact welding process. The goal of such a detailed characterization campaign is to understand the bond formation mechanism. The study shows that the interfacial microstructure has a pronounced hierarchical nature. At the macro scale, the interface is characterized by a wavy interface which is a result of extensive plastic deformation that accompanies the process. Detailed transmission electron microscopy shows evidence for the formation of a liquid film at the interface resulting in significant inter diffusion of Fe. The solidified structure at the interface consisted of crystalline α-Al and an amorphous metastable Al-Fe intermetallic compound similar to the observations in rapid solidification of Al-Fe alloys. The sub-nm scale characterization of the interface using atom probe tomography showed two distinct zones 1. A magnesium (5 at.%) and oxygen (15 at.%) rich (not detectable using energy dispersive spectroscopy) which was probably from the decomposition of the surface oxide film 2. The rapidly solidified reaction zone consisting of primary crystalline α-Al and an amorphous Al-Fe (15 at.%)-O (0.5 at.%)-Si (1.5 at.%). Based on these observations a mechanism for the bond formation is presented.

Inspired by the parallel performing of storage and processing information in biological synapse, artificial synapse that can control ionic and protonic currents are ideal means for attracted tremendous attention as a promising option to break the von Neumann bottleneck. Here we demonstrate an artificial synapse with tunable synaptic behavior based on solution-processed two-dimensional (2D) C3N/polyvinylpyrrolidone (PVPy). The proton modulated memristive characteristics of synaptic device are verified by ambient pressure X-ray photoelectron spectroscopy under different H2O gas atmosphere. The highly proton conducting of C3N/PVPy matrix stems from the hydrogen bonding network between C3N and PVPy, as well as the large amount of ordered nitrogen atoms in C3N. The artificial synapse ensure a direct imitation of short-term and long-term plasticity in biological synapses including excitatory post-synaptic current (EPSC), paired-pulse facilitation (PPF), paired-pulse depression (PPD), PPF following PPD and post-tetanic potentiation (PTP). The C3N/PVPy matrix-based memristor which can mimic the synapse cleft based on proton conducting mechanism may find further applications in artificial intelligence.

In silico design of catalysts has made significant progress in recent decades. Arguably the best one among the used methods is to plot the activity against the adsorption energy of the key intermed...

In this work, a numerical simulation framework based on the finite element method (FEM) with Eulerian formalism is developed to model the high-speed impact between metal plates. The model accounts for the thermomechanical interactions in the process and captures the complex interfacial deformations. A thorough validation of the model is achieved by comparing the wave characteristics obtained from numerical simulations with the experimental results from vaporizing foil actuator welding. The amplitude and wavelength of the interfacial waves and the resulting joint microstructure are shown to depend significantly on the process conditions and the specific material system, which is well captured by the model.

Mimicking biological synapses with resistive random switching memory (RRAM) can lay a concrete foundation for the future of artificial intelligence. RRAMs based on low-cost and solution-processed organic materials provide a competitive approach. Here, we report an artificial synaptic device with a solution-processed small molecule (bis-4-(N-carbazolyl)phenyl)phenylphosphine oxide (BCPO) based RRAM. The BCPO-based RRAM exhibits reproducible resistive switching behavior, a long retention time as well as good thermal tolerance with a sufficient on/off current ratio. In situ Kelvin probe force microscopy (KPFM), conductive atomic force microscopy (C-AFM) and density function theory (DFT) calculations demonstrate that both the redox state and the trap-filled space charge limited current (SCLC) determine the resistive switching of a BCPO-based RRAM. Furthermore, the fabricated device was employed to emulate a biological synapse in which several synaptic functions, including spike-rate-dependent plasticity (SRDP), a transition from short-term plasticity (STP) to long-term plasticity (LTP) and spike-time-dependent plasticity (STDP), were realized. To the best of our knowledge, this is the first successful demonstration of solution-processed small molecules in artificial synaptic devices. The BCPO layer is solution-processed at low temperature which is compatible with a flexible substrate and printable electronics. We believe this electronic synapse will have a wide range of applications in future neuromorphic computing.

The activity of oxygen evolution reaction (OER) catalysts is strongly dependent on the activity of each catalytic site, which can be improved through interactions among the species present, and the number of accessible catalytic sites, which can be increased by downsizing the electrocatalysts. In this study, small sized Fe–Co sulfide nanoclusters (2–3 nm) in situ anchored on carbon were designed and prepared as an OER catalyst. Due to the smaller size, a large number of catalytic sites are exposed. The optimized Fe–Co bimetal sulfide nanoclusters/carbon composite exhibits an overpotential of only 247 mV to deliver a current density of 10 mA cm−2 and a low Tafel slope of 35 mV dec−1. In addition, the formed nanocluster catalyst also showed superior stability without activity decay and metal component dissolution during the OER process. Experimental and theoretical calculations indicate that on the Fe–Co sulfide nanoclusters, Fe sites are preferred to enrich the sulfide surface; surface oxidation will occur during the OER process in alkaline electrolyte forming Fe–Co–S–O species. The electron transfer interactions from Fe to S sites induce stronger acidity on Fe sites, which would facilitate OH− and water adsorption, thus inducing the enhancement of electrocatalytic performance.

An iterative hybrid of finite element boundary integral (FEBI) method and physical optics (PO) is presented for scattering problems of complex structures having junctions with electrically large-scale platform. The treatment of basis functions on the junctions between complex structures and platform is discussed in detail. Moreover, the multilevel fast multipole algorithm and the adaptive cross approximation method are employed to accelerate the solution of FEBI and the computation of interaction between FEBI and PO regions, respectively. Compared with FEBI method, the hybrid method can efficiently reduce the number of unknowns and the computational complexity while preserving acceptable accuracy. In addition, the alternative implementation of FEBI and PO can also maintain good independence of the two methods. Some numerical results are discussed to demonstrate the efficiency and accuracy of the approach.

Resistive random-access memory (RRAM) is the most promising research direction of the next generation non-volatile memory (NVM) devices, and seeking novel materials as the active layer can facilitate RRAM device development. Two-dimensional graphitic carbon nitride (g-C3N4) nanosheets with a mass of carrier trapping sites are employed as the active layer of RRAM devices. Solution processed memory devices show good stability and reliability, and the fabricated g-C3N4-based RRAM devices show a non-volatile behavior and a bipolar switching characteristic with an ON/OFF ratio of 103, a low operation voltage and good retention capability. In addition, by means of controlling the compliance current precisely, multi-level data storage can be realized. The mechanism of the RRAM devices is thought to be carrier trapping assisted hopping, which is verified by atomic force microscopy in the electrical mode. This work demonstrates that g-C3N4 nanosheet based RRAM devices provide a novel direction for low energy and high density data storage devices.

Hydrogen transfer is the fundamental step in electrochemistry involved in water splitting and the hydrogen evolution reaction (HER). However, the nature of this process at the solid-liquid interface has been little studied at the atomic level. In this work, we use ab initio molecular dynamics (AIMD) and umbrella sampling (US), giving us an accurate description of the dynamic processes associated with the solid-liquid environment. Based on this method, the free energy barriers were calculated at the H2O/Pt(111) interface, and a multistep mechanism has been proposed. We find that proton transfer is dictated by the strength of the solid-liquid interaction and the configuration of water molecules above the reaction site. In particular, we show that the surface adsorbed cations, which are confined to the interface above the top site position, act as vessels for enhanced hydrogen transfer to and from the surface. Our results could lead to significant mechanistic consequences for the HER, water splitting and solid-liquid reactions in general.

A magnetic internal heating single-precursor approach was exploited to fabricate higher quality Prussian blue nanoparticles (PBNPs) with excellent crystallinity, dispersibility and uniformity. Furthermore, the magnetic properties and MRI contrast effect were improved. Subsequently, significantly increased nanoenzyme activity has been demonstrated.

The formation of surface oxides on metal surfaces is not only important in materials science, but also of significance in heterogeneous catalysis due to the fact that during most oxidation reactions the metal catalysts are inevitably oxidized, which may cause dramatic consequences in the reactions. In this work, we perform a thorough investigation on the formation of surface oxides on Pd(211) using advanced first principles calculations. A detailed mechanism of the surface oxide formation is revealed: starting from simple O chemisorption, the step sites of Pd(211) are oxidized by formation of local linear O-Pd-O oxide structures and then planar Pd-O4 structures as the O coverage is increased; the local oxide structures spread out to yield a surface oxide layer, and finally 3-dimesional oxide forms with the increase of the degree of surface oxidation. The structures of O-Pd-O and Pd-O4 are revealed to be the basic units for oxide formation and can be considered as the oxide seeds. The origin of the oxide seed formation is identified, and the understanding of the oxide formation process is provided. A simple equation is derived, which describes the general trend of O vacancy formation in the oxides. The equation may be of great use for understanding oxide formation on Pd surfaces.

Neuromorphic computing could tackle the inherent limitations of traditional von Neumann architecture in devoted machine learning applications. Nevertheless, implementation of a transistor-based artificial synapse which is the fundamental building block for mimicking the functions of biological synapses remains challenging owing to the nonlinear and asymmetric weight update protocol and fast saturation within the initial few pulses. Here, a three-terminal photoactive synapse is proposed based on black phosphorus (BP)–ZnO hybrid nanoparticles (NPs) with a combination of an electronic mode and a photoactive mode. By the electronic mode, the channel conductance can be manipulated by charge trapping inside the thin BP–ZnO NPs which ensures an enlarged variation margin and the realization of 4 synaptic weight levels, while optical modulation of the excitatory and inhibitory synaptic weights with symmetry and linearity variation was realized, since an extended energy threshold of photon absorption and accelerated dissipation of excitons can be achieved in the BP–ZnO hybrid NPs. Crucially, we can modulate the synaptic weight simply by varying the wavelength of the light source (365, 520, and 660 nm) and achieve an extended synaptic weight change of 400% within 10 optical pulses. This study proposes an extremely simple and powerful system with multiple forms of synaptic plasticity resembling an analogue of a natural biological synapse due to the broadband response of the BP–ZnO hybrid NPs.

The main development challenge of low temperature hybrid bonding technology is the oxidation of Cu surface. The schemes to achieve the high-quality surface condition of Cu before bonding is urgently demanded. In this study, four acid solutions, including sulfuric acid (H 2 SO 4 ), hydrochloric acid (HCl), acetic acid (CH 3 COOH) and citric acid (C 6 H 8 O 7 ), were chosen as wet pretreatment approaches to remove Cu oxides based on the respective chemical reactions. To investigate the influence of these acid solutions on bonding surface, different acid immersion times are examined and the XPS analysis is conducted to check the surface component composition. Next, thermal compression bonding (TCB) is conducted after the Cu oxide removal process, followed by various analyses, including SAT analysis to validate bonding results, FIB and SEM analyses to inspect bonding interface, and pull test to measure bonding strength. The results of analyses verify the ability of different wet pretreatment to improve Cu-Cu bonding.

An innovative surface-enhanced Raman spectroscopy and lateral flow assay (SERS-LFA) biosensor combined with aptamer recognition had been developed for the convenient, rapid, sensitive and accurate detection of thrombin and platelet-derived growth factor-BB (PDGF-BB) associated with prostate cancer simultaneously. During the biosensor operation, thrombin and PDGF-BB in the sample were recognized and combined by thiol-modified aptamers immobilized on Au-Ag hollow nanoparticles (Au-Ag HNPs) surface and biotinylated aptamers immobilized on the test lines of the biosensor. Thus, thrombin and PDGF-BB were simultaneously captured between detection aptamers and capture aptamers in a sandwich structure. Finite difference time domain simulation confirmed that 'hot spots' appeared at the gaps of Au-Ag HNPs dimer in the enhanced electromagnetic field compared to that of a single Au-Ag HNP, indicating that the aggregated Au-Ag HNPs owned a good SERS signal amplification effect. The detection limits of thrombin and PDGF-BB in human plasma were as low as 4.837 pg ml-1and 3.802 pg ml-1, respectively. Moreover, the accuracy of the biosensor which was applied to detect thrombin and PDGF-BB in prostate cancer plasma had been verified. This designed biosensor had broad application prospects in the clinical diagnosis of prostate cancer.

In this study, an asymmetric Cu-polymer hybrid bonding technology was successfully developed at 200 °C, which uses SU-8 for polymer bonding and Au passivation for Cu bonding. The polymer bonding performance was investigated by the analyses of sat, SEM and pulling test, indicating that bonding with the best quality was achieved at 200 °C. With the Au passivation layer capping on the Cu surface, a low temperature Cu-Cu bonding process can be realized at 200 °C. After demonstrating the bonding process with single material, a chip-level hybrid bonding structure was fabricated and bonded successfully. The hybrid bonding interface was observed by the SEM images, showing that both of the metal and polymer region were well bonded. Furthermore, the electrical properties and reliability performance were analyzed by electrical measurements with a modified Kelvin structure and after un-biased highly accelerated stress test for 168 hours. The bonded structure can still maintain excellent electrical property about 10−7 Ω•cm2. Based on the bonding results, this research provides a practical concept for low temperature hybrid bonding in 3D integration.

Gate-grounded tunnel field effect transistors (ggTFETs) are considered as basic electrostatic discharge (ESD) protection devices in TFET-integrated circuits. ESD test method of transmission line pulse is used to deeply analyze the current characteristics and working mechanism of Conventional TFET ESD impact. On this basis, a SiGe Source/Drain PNN (P+N+N+) tunnel field effect transistors (TFET) was proposed, which was simulated by Sentaurus technology computer aided design (TCAD) software. Simulation results showed that the trigger voltage of SiGe PNN TFET was 46.3% lower, and the failure current was 13.3% higher than Conventional TFET. After analyzing the simulation results, the parameters of the SiGe PNN TFET were optimized. The single current path of the SiGe PNN TFET was analyzed and explained in the case of gate grounding.

Vaporizing foil actuator (VFA) is an impulse or high-speed manufacturing technology using electrically driven rapid vaporization of thin conductors to produce short-duration pressure pulses of high magnitude. This impulse technique has been implemented for various applications such as high strain rate forming, shearing, collision welding, and springback calibration. VFA technology for manufacturing processes potentially offers improved accuracy, reliability, and environmental safety and creates opportunities to design new products by joining similar and dissimilar material combinations. The paper includes the results of industrially relevant “work-in-progress” research with the VFA tool. The applications of the process, mainly regarding advanced manufacturing such as metal-matrix composite (MMC) welding, axisymmetric welding, and impact-mediated additive manufacturing processes, are presented and discussed. The applications of the method characterize adequate responses to support the manufacturing process.

The use of a chemical explosive mixture to augment the vaporizing foil actuator (VFA) and laser impact welding (LIW) processes is introduced in this study. A liquid explosive known as Picatinny liquid explosive (PLX) was used to augment the capabilities of both the VFA and LIW processes. The 304 stainless steel flyers 3 mm thick driven by PLX augmented VFA and unaugmented VFA are compared. Similarly, 0.442 mm thick Al3003 flyers driven by laser impact and PLX augmented laser impact are compared. In all cases, a photon Doppler velocimetry (PDV) system was used to collect the velocity–time profiles of the flyers. All PLX augmented experiments showed increases in both flyer acceleration and peak velocity over the same time scales as the unaugmented experiments. This indicates that the PLX-provided impulse occurs at the same time as the VFA/laser impulse. The augmented VFA experiments showed a 28% velocity increase over the unaugmented experiments at 10 kJ input energy. The augmented laser impact process exhibited peak flyer velocities 236% higher than laser impact using only the laser. Here we demonstrate that chemical augmentation is capable of significantly increasing flyer velocities for both VFA and LIW at the same input energies and under similar conditions. This development should expand the repertoire of flyer materials and thicknesses that can be impact welded by VFA and LIW.

In this paper, we present the design of a triple-band metamaterial polarization converter based on substrate integrated waveguide (SIW) technology. The converter consists of periodic U-shaped slot elements etched on copper-clad plates which are surrounded by SIW cavities. The proposed converter combines the traditional transmission-type polarization converter with SIW to achieve 90° rotation from y polarized wave to x polarized wave. The simulation results show that the polarization conversion efficiency is very high at the operating frequencies of 6.82GHz, 9.4GHz and 12.04GHz, close to 100%. The polarization converter has the advantages of multi-frequency., high efficiency and easy manufacture, and has great application value.

Many important physical phenomena are governed by intense mechanical shock and impulse. These can be used in material processing and manufacturing. Examples include the compaction or shearing of materials in ballistic, meteor, or other impacts, spallation in armor and impact to induce phase and residual stress changes. The traditional methods for measuring very high strain rate behavior usually include gas-guns that accelerate flyers up to km/s speeds over a distance of meters. The throughput of such experiments is usually limited to a few experiments per day and the equipment is usually large, requiring specialized laboratories. Here, a much more compact method based on the Vaporizing Foil Actuator (VFA) is used that can accelerate flyers to over 1 km/s over a few mm of travel is proposed for high throughput testing in a compact system. A system with this primary driver coupled with Photonic Doppler Velocimetry (PDV) is demonstrated to give insightful data in powder compaction allowing measurements of shock speed, spall testing giving fast and reasonable estimates of spall strength, and impact welding providing interface microstructure as a function of impact angle and speed. The essential features of the system are outlined, and it is noted that this approach can be extended to other dynamic tests as well.

With the post-combustion CO2 capture process running for a long time, the degradation of aqueous amine-based is inevitable. Unfortunately, a simple and effective way to increase the economic feasibility of CO2 capture process after accumulated degradation products remains absent, and little attention has been paid to the real effect of degradation products on the CO2 capture performance in aqueous amine solutions. We propose a simple experimental and computational method that can evaluate the performance and regeneration energy of solvent after change. The method can determine key degradation products that affecting the performance of solvent, so as to guide the selective removal of degradation products and improve solvent performance.

Defects introduced during the growth process greatly affect the device performance of two-dimensional (2D) materials. Here we demonstrate the applicability of employing machine-learning-based analysis to distinguish the monolayer continuous film and defect areas of molybdenum disulfide (MoS2) using position-dependent information extracted from its Raman spectra. The random forest method can analyze multiple Raman features to identify samples, making up for the problem of not being able to effectively identify by using just one certain variable with high recognition accuracy. Even some dispersed nucleation site defects can be predicted, which would commonly be ignored under an optical microscope because of the lower optical contrast. The successful application for classification and analysis highlights the potential for implementing machine learning to tap the depth of classical methods in 2D materials research.

Poly(methyl methacrylate) (PMMA) is of growing interest in the application of microfluidic devices and high precision optical elements due to its excellent moldability and formability. Micromilling is one of the micromachining methods which has been extensively used to manufacture polymer components. In this study, a high-speed micromilling method was used to manufacture polymer with high form accuracy and surface quality. The processing temperature effects on the surface quality were investigated in detail. The dynamic mechanical analysis (DMA) experiment was used to study the material mechanical property under different temperatures. According to the DMA results, the PMMA sample is in the glass and viscoelastic state during the milling process. The cutting chips under various processing temperatures are classified into three kinds according to their shapes: roll, sheet, and sinter. The surface roughness of samples with sheet and roll cutting chips is smaller than that of sinter cutting chips. To obtain a better machining bottom surface and edge shape, the processing temperature below 70 &deg, C is recommended according to the results. This work is of great value for the study of polymer removal mechanism and optimization of processing parameters for the industry.

Though membranes with pore size larger than 1 μm are much desired to increase the permeate flux of membrane distillation (MD), the vulnerability of large-pore-size membranes to pore wetting results in the penetration of saline water and consequent failure of MD operation. We report modification of large-pore-size membranes by chemically vapor deposited nanocoatings to achieve both high salt rejection and high permeate flux. The chemical vapor modification not only led to enhanced surface hydrophobicity and increased liquid entry pressure in membranes, but also significantly improved membrane wetting resistance at high temperature. Membranes with 1.0 and 2.0 μm pore size were successfully used for MD desalination with salt rejection higher than 99.99% achieved. Enlarging the pore size from 0.2 μm to 2.0 μm contributed to 48–73% enhancement in the permeate flux of the modified membranes. The modified large-pore-size membranes maintained the high permeate flux at elevated saline concentration and extended the operation time.

A novel dual-polarized transmissive/absorptive frequency-selective rasorber (FSR) with an ultrawide absorption spectrum covering both the X- and Ku-bands is proposed in this paper. The FSR is constructed from a bottom lossless transmission layer and a top lossy absorption layer, in which a resistor-loaded incurved square loop strip line structure is utilized to obtain an ultrawide absorption band. To quantitatively analyze its operation principle, an accurate equivalent circuit model of the proposed FSR was developed. A 2D prototype was designed, assembled, fabricated, and measured. The FSR exhibits an absorption band that ranges from 8.1 to 19.1 GHz (81%) under normal incidence, whereas the passband insertion loss at 4.5 GHz is less than 0.45 dB. The total thickness of the FSR is only 5.1 mm, which keeps low profile characteristics. The simulation agrees well with the measured results.

In order to achieve accurate detection and evaluation of the freshness of fish samples, high sensitivity and selectivity of histamine sensors based on solution-gated graphene transistors (SGGT) have been successfully developed. By using graphene (Gra), multi-walled carbon nanotubes (MWNT) and gold nanoparticles (AuNP) to functionalize the gate electrode, the electrocatalytic performance of the device can be significantly improved. We have found that graphene, MWNT and AuNP modified SGGT sensors exhibit an ultra-low detection limit of 100 nM for histamine, a linear range of 3 μM–100 μM. We have also demonstrated that the SGGT-based histamine sensor has a high recovery rate and is capable of assessing the histamine content of actual fish samples in a fast and accurate manner. Considering the superior performance of the SGGT-based histamine sensor, it can be readily extended to histamine determination in many other real food samples for their freshness assessment.

Core-shell semiconductor quantum dots (QDs) are one of the biggest nanotechnology successes so far. In particular, type-I QDs with straddling band offset possess the ability to enhance the charge carriers capturing which is useful for memory application. Here, the type-I core-shell QD-based bipolar resistive switching (RS) memory with anomalous multiple SET and RESET processes was demonstrated. The synergy and competition between space charge limited current conduction (arising from charge trapping in potential well of type-I QDs) and electrochemical metallization (ECM, originating from redox reaction of Ag electrode) process were employed for modulating the RS behavior. Through utilizing stochastic RS mechanisms in QD-based devices, four situations of RS behaviors can be classified into three states in Markov chain for implementing the application of a true random number generator. Furthermore, a 6 × 6 cross-bar array was demonstrated to realize the generation of random letters with case distinction.