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The aim of this study is to evaluate the usability of new cement (NC) made by the burning of quinary by-product to make commercial binders. Chemical analysis of the by-products and NC as well as X-ray diffraction (XRD) analysis of NC, fineness, density, consistency, and setting time of NC paste, and slump in addition to compressive strength (CS) and splitting tensile strength (STS) of NC concrete (NCC) were conducted. The results suggested that chemical composition of by-products is suitable to make NC binder. The NC contains Ca3SiO5, Ca2SiO5, Ca3Al2O6, and Ca3Al2FeO10. The particles passing through the 200 um Sieve were 56% compared with 52% for Portland cement (PC). The density of the of NC was similar to that of PC. The NC needed 48% more water than PC for normal consistency. The initial and final setting-time of NC was 105 min and 225 min respectively which is much higher than that of PC (15 and 45 min). The slump, compressive strength and splitting tensile strength were slightly lower for concrete containing NC compared with that pf PC concrete. Although the CS and STS of NCC are the lowest, the rate of the CS and STS gain of NCC is greater than that of PCC. It was concluded that NC is a viable alternative to PC for the production of greener concrete. (C) 2021 The Authors. Published by Elsevier B.V.

The possibility of preparing bone substitutes in clinic is demonstrated in this study. With the addition of a small amount of water, the relative density of the calcium sulfate specimen prepared at room temperature became higher than 92%. This value is close to the density of the specimen prepared through conventional sintering at 1100 °C for 1 h. The biaxial strength of the specimen disc can reach 120 MPa. Densification is assisted by the hydration of calcium sulfate hemihydrate to dihydrate wherein coarse hemihydrate particles transformed to fine dihydrate dendrites. Strength is conferred by the entanglement of dendrites and microstructure refinement. The densified calcium sulfate disc remains degradable; its degradation rate in a phosphate buffer saline solution is ~1.6 wt%/day, and the rate remains steady for 28 days.

Atomically thin diamond, also called diamane, is a two-dimensional carbon allotrope and has attracted considerable scientific interest because of its potential physical properties. However, the successful synthesis of a pristine diamane has up until now not been achieved. We demonstrate the realization of a pristine diamane through diamondization of mechanically exfoliated few-layer graphene via compression. Resistance, optical absorption, and X-ray diffraction measurements reveal that hexagonal diamane (h-diamane) with a bandgap of 2.8 ± 0.3 eV forms by compressing trilayer and thicker graphene to above 20 GPa at room temperature and can be preserved upon decompression to ∼1.0 GPa. Theoretical calculations indicate that a (-2110)-oriented h-diamane is energetically stable and has a lower enthalpy than its few-layer graphene precursor above the transition pressure. Compared to gapless graphene, semiconducting h-diamane offers exciting possibilities for carbon-based electronic devices.

Probing the transformation from crystalline form II with 11/3 helical structure to form I with 3/1 helical structure in PB-1 and its nanocomposites is of great importance in both scientific fields and commercial applications. The influence of lamellar thickness on the transformation from form II to form I in isotactic polybutylene-1 (PB-1)/carbon nanotube (CNT) nanocomposites was investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and small-angle X-ray scattering (SAXS) techniques. The crystallization kinetics of PB-1/CNT nanocomposites at different isothermal temperatures (Tc) indicates that CNTs significantly accelerate the nucleation and growth of form II, acting as heterogeneous nucleating agents. However, the influence of CNTs on the form II–I transformation strongly depends on the lamellar thickness obtained at different Tc, verified by the change in melting point (Tm) and the SAXS results for form I. The addition of CNTs accelerates the transformation and elevates the Tm of form I when the Tc is lower than ∼88 °C, and slows the transformation and slightly decreases the Tm when the Tc is higher than ∼88 °C. This is probably due to the fact that the incorporation of CNTs facilitates an increase in lamellar thickness of form II formed at lower Tc but decreases the lamellar thickness of form II formed at higher Tc. Our study illustrates that the lamellar thickness is one of the key points to determine the transformation from form II to form I in PB-1.

This work was conducted to investigate biomimetic micro-textures, mechanical behaviors and intermittent turning performance of textured Al2O3/TiC micro-composite and micro-nano-composite ceramics. Chip characteristics and the geometry features of the structures on the cuticle of Procambarus clarkia were considered in the preparation of the laser-induced biomimetic micro-textures on the composite ceramic surfaces. Characteristics of the biomimetic micro-textures were revealed in terms of geometry, morphology and chemical composition. The connection between the thermal stress resulting from laser pulse and the fractal dimension of the micro-crack on the micro-textures was analyzed and identified. The correlation between the mechanical behaviors (damage and fracture toughness) of the textured composite ceramics and the fractal dimension of the micro-crack was fitted and revealed quantitatively. The performance of the textured composite ceramic tools was pre-evaluated by means of a proposed indicator. Damage, fracture toughness and tool stress were incorporated in the indicator. The indicator and the experimental tool wear were compared for validating the effectiveness of the proposed indicator. It was found that the micro-composite ceramic exhibited greater sensitivity to laser than the micro-nano-composite ceramic did. The damage of the textured micro-composite ceramic was larger than that of the textured micro-nano-composite ceramic when the same laser parameters were utilized in the micro-texture preparation. On the contrary, the fracture toughness of the textured micro-composite ceramic was found to be smaller. There was a negative correlation between the damage of the textured composite ceramic and the fractal dimension of the micro-crack. Conversely, there was a positive correlation between the fracture toughness and the fractal dimension. The performance of the textured micro-nano-composite ceramic tool was better than that of the textured micro-composite ceramic tool. The proposed indicator can be used to predict the combination of laser parameters that resulted in the optimum performance of the textured composite ceramic tool.

Using thermal interface materials (TIMs) is generally considered an effective way to reduce thermal contact resistance. In this paper, effects of surface roughness, temperature and pressure on TIMs’ performance are investigated. A variety of TIMs including thermal pads, carbon-based materials, phase change materials (PCMs) and low-melting-point alloys (LMPAs) are experimentally studied, and their performance is compared with the case without using any TIM. Results indicate that, when pressure is below 0.3 MPa, the interface thermal resistance (ITR) decreases when the pressure increases, but such a trend is not obvious when pressure exceeds 0.3 MPa. The increase of surface roughness causes the ITR of thermal pads and carbon-based materials to increase, but does not affect the performance of PCMs and LMPAs. Interface thermal resistance of carbon-based materials decreases a little as temperature increases and that of thermal pads is not affected by temperature in test range. The ITR of PCMs and LMPAs sharply decreases when temperature exceeds phase change point. When surface roughness is 0.8 μm, thermal contact resistance of aluminum is 189 mm2·K·W−1 at 0.2 MPa and 153 mm2·K·W−1 at 0.4 MPa, but the ITR of thermal pads is 136–395 mm2·K·W−1 at 0.3 MPa and the ITR of one carbon-based material is 165 mm2·K·W−1 at 0.5 MPa.

Bio-inspired fabrication, mechanical characterization and intermittent cutting performance evaluation were conducted for Al2O3/TiC micro-nano-composite ceramic with varying microscopic surfaces. Functions and geometry features of the epidermis were analyzed for two biological species, namely, catharsius molossus and bullhead shark. The biomimetic microscopic texture on ceramic tool surface was designed and fabricated considering tool-chip contact area and chip flow direction. Varying combinations of laser beam angle and spacing were utilized in the fabrication of biomimetic microscopic texture. Microscopic hardness, fracture toughness and fractal dimension of the indentation-induced crack were analyzed and compared for the textured ceramics. A tool performance indicator CP was proposed. Ceramic tool stress in cutting process, mechanical features of the intrinsic microcrack and fractal dimension of the indentation-induced crack were reflected in the indicator. The indicator CP was employed to evaluate the intermittent cutting performance of ceramic tools with different biomimetic microscopic textures. The optimum combination of laser beam angle φ and spacing Ld was found to be 60° and 105 μm. The lowest CP and the lowest experimental tool wear VB appeared at this optimum combination. A proper balance between external loads, micromechanical properties and fracture resistance can be achieved for the textured ceramic tool by using the optimum combination of φ and Ld.

In this paper, the structure of the photosensitive diamines was designed and the method of synthesizing such diamines was investigated. The 1-(3-aminophenyl)-3-(4-aminophenyl)-2-propen-1-one analyzed by elemental analysis and infrared analysis was synthesized through two-step experiments with Aldol condensation and Nitroammoniation process. Through the experiment the optimum reaction conditions are raw material ratio of 1:1, anhydrous ethanol dosage of 60 ml, 10 % NaOH dosage of 10 ml and reaction temperature of 25°C for 4h. The yield was about 55.4 %.

In this paper, both a novel experiment and simulation model was presented to evaluate the performance of a solar still by applying a new shape-stabilized phase change material (SSPCM). The SSPCM was characterized with stable shape, high thermal conductivity and high solar absorption. Firstly, an experiment for solar still with SSPCM was carried out, and the SSPCM used in the experiment got thermal conductivity 1.50 W/m K and solar absorption around 0.94, which can replace the conventional metal absorber plate. Then, a comprehensive heat transfer model for the solar still was built to analyze the effect of melting temperature and thermal conductivity of the SSPCM on the performance of the solar still. The experimental results revealed that the daily productivity of solar still with SSPCM was 3.41 L/m2, 43.3% higher than that of conventional solar still without SSPCM. The simulation results showed that the daily productivity increased from 42% to 53% compared with that of conventional solar still when thermal conductivity of SSPCM increased from 0.2 W/m K to 4.0 W/m K. And increasing the melting temperature of SSPCM from 34 °C to 50 °C improved the percentage of enhancing productivity from 21.5% to 57.5%. Finally, the cost analysis was performed.

A stable graphene anode with high storage Li+ capacity for lithium-ion batteries (LIBs) is to be desired for energy storage. In the present paper, a new scalable method is adopted for preparation of three-dimensional porous graphene microspheres (3DGPM) by a template sacrificing method. The 3DGPM were utilized as an anode for lithium ion batteries (LIBs). The macrostructure of the 3DGPM anode was characterized by the scanning electron microscope, transmission electron microscope and X-ray diffraction. As anode for LIBs, the first discharge/charge capacities of the 3DGPM are 851.1 and 402.4 mAh g−1 at a current density of 0.1 A g−1. The 500th discharge capacity of the 3DGPM anode at a current density of 2 A g−1 is 245.8 mA h g−1. Besides, the 3DGPM exhibit low charge transfer resistance and high Li-ion diffusivities. The porous nanospheres of graphene offer voids for volume expansion and pathways for fast electron transfer during repeated cycling. We believe that the specific micro-/nano-hollow microspherical structure is the main origins of their high electrochemical storage Li performance.

Hard carbon with high special capacity has been widely studied as anode for sodium ion batteries (SIBs). Its storage sodium performance still needs to be further improved. Herein, a composite electrode was synthesized through growing V2O5 nanosheet array on free-standing hard carbon fiber fabric by solvothermal reaction. The electrochemical properties of the composite electrode were significantly enhanced compared with pure hard carbon fiber electrode. The composite showed a specific capacity from 241 mA h g−1 at 50 mA g−1 to 77 mA h g−1 at 1000 mA g−1 and a good cycling ability of 184 mA h g−1 after 100 cycles at 100 mA g−1. Except good storage Na ability for V2O5 nannosheets, the improvement of electrochemical performances also benefited from and the synergistic effect from the ability of fast electron transfer of hard carbon and the toleration for Na+ insertion of V2O5 nanosheet array, as well as the inhibitory effect on solid electrolyte interface (SEI) of nanostructure. Additionally, the free-standing electrodes could also increase the energy and power density. This will push the promising hard carbon material used as SIBs anode in practical applications.

Studying the effects of the micro- and meso-scale characteristics of coal-bearing sandstone on its mechanical properties can provide basic data and accumulated experience for the development of technology for the in situ testing of the strength of rock masses. In this paper, the micro- and meso-structures, mineral composition, and elemental contents of 16 kinds of sandstone from three coal mines were studied through X-ray diffraction and polarizing microscope analysis. The stress–strain evolutional characteristics of different sandstone samples were obtained through uniaxial compression, tension, and shear tests under acoustic emission monitoring, and the effect of various micro- and meso-characteristics on the mechanical properties and failure characteristics of the sandstones was investigated. The results show that the strength, elastic modulus, cohesion, and friction coefficient all increase with increasing quartz content and degree of particle contact, and decrease with increasing plagioclase and clay mineral content, especially kaolinite content. The failure mode of sandstone samples is mainly shear failure during uniaxial compression, the larger the particles and the lower the quartz content, the higher the RA value generated near the peak, indicating that more tensile failure occurs. Furthermore, the strength damage model and damage constitutive model are established by acoustic emission measurement data. These results could provide useful reference for the development of intelligent systems for the in situ testing of the mechanical properties of coal and rock masses.

α-Phase hematite photoelectrodes can split water. This material is nontoxic, inexpensive, and chemically stable; its low energy gap of 2.3 eV absorbs light with wavelengths lower than 550 nm, accounting for approximately 30% of solar energy. Previously, we reported polyhedral pseudocubic α-Fe2O3 nanocrystals using a facile hydrothermal route to increase spatial charge separation, enhancing the photocurrent of photocatalytic activity in the water-splitting process. Here, we propose a p-n junction structure in the photoanode of pseudocubic α-Fe2O3 to improve short carrier diffusion length, which limits its photocatalytic efficiency. We dope Zn on top of an Fe2O3 photoanode to form a layer of p-type semiconductor material; Sn is doped from the FTO substrate to form a layer of n-type semiconductor material. The p-n junction, n-type Fe2O3:Sn and p-type Fe2O3:Zn, increase light absorption and charge separation caused by the internal electric field in the p-n junction.

Since the postfire safety of prestressed RPC beams after exposure to elevated temperatures needs to be studied and proved, this paper prepares eight smart prestressed RPC beams with intelligent sensors built in to monitor the internal temperature, force, and strain. The residual bearing tests after fire are carried out. The failure process of the beams under static load with different fire durations cover thickness of tendons, load ratio, bonded and unbonded tendons, and partial prestressing ratio, which are investigated. The load-deflection curves, crack distributions and developments, and strain variations are obtained, in addition to the damage mechanism and failure mode of the beams. The results show that the load-deflection curve of the prestressed RPC beam after fire has obviously three polylines, and the deflection points are where the cracks expand and the tendons yield. The failure procedure is the same as that of under-reinforced beams, while the height of the crushing zone is much lower than that of the balanced-reinforced beam at room temperature. The whole span deformation demonstrates a strong catenary effect, and the midspan deflection is approximately 1/40 of the effective span. The postfire safety of the bonded prestressed RPC beams is superior to that of unbonded prestressed RPC beams. The test results of this paper provide a basis for the safety performance evaluation and control of prestressed RPC beams after fire.

The influence of nanofillers on the crystal transformation from crystal form II to form I of isotactic polybutene-1(PB-1) was investigated by differential scanning calorimetry (DSC), in situ wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) techniques. Two types of silicate clay both having one-dimensional structure, halloysite nanotube (HNT) and palygorskite (PGS), were used as nanofillers of PB-1. PGS accelerates the transformation from crystal form II to I for PB-1 more efficiently than HNT, which is attributed to the lattice match of crystal structure between PGS and form I as confirmed by the WAXD and SAXS tests. Moreover, hydrophobically modified clays MPGS and MHNT were used to improve the miscibility between nanoparticle and PB-1. However, transformation kinetics study indicates that the acceleration effect of MPGS is greatly decreased due to the shield of lattice match although the miscibility of the composites is improved, while that of MHNT is increased due to the improvement of miscibility. These results provide direct evidence that the existence of crystallographic relationships is another important factor to accelerate the crystal transformation from form II to I in PB-1.

Summary Effective stabilization of lithium metal has been hindered by the exacting requirements for the protection layer. Among all materials, the mechanical strength and electrochemical inertness of diamond is a prime candidate for lithium stabilization. Herein, we successfully rendered this desirable material compatible as lithium metal interface, which strictly satisfied the critical requirements. Our interface possessed the highest modulus among all the lithium coatings (>200 GPa), which can effectively arrest dendrite propagation. Since pinholes are the major failure mechanisms of artificial interfaces, a novel double-layer design was proposed to enhance the defect tolerance, enabling uniform ion flux and mechanical properties as confirmed by both simulation and experiments. Thanks to the multifold advantages of our interface design, high Coulombic efficiency of >99.4% was obtained at 1 mA cm−2; and more than 400 stable cycles were realized in prototypical lithium-sulfur cells with limited lithium, corresponding to an average anode Coulombic efficiency of >99%.

Purpose Laser additive manufacturing (LAM) technology based on powder bed has been used to manufacture complex geometrical components. In this study, IN625 superalloys were fabricated by high-power fiber laser without cracks, bounding errors or porosity. Meanwhile, the objectives of this paper are to systemically investigate the microstructures, micro-hardness and the precipitated Laves phase of deposited-IN625 under different annealing temperatures. Design/methodology/approach The effects of annealing temperatures on the microstructure, micro-hardness and the precipitated Laves phase were studied by optical microscope (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS), selected area electron diffraction (SAED), backscattered electron (BSE) imaging in the SEM and transmission electron microscopy (TEM), respectively. The thermal stability of the dendritic morphology about IN625 superalloys was investigated through annealing at temperatures range from 1,000°C to 1,200°C. Findings It is found that the microstructure of deposited-IN625 was typical dendrite structure. Besides, some Laves phase precipitated in the interdendritic region results in the segregation of niobium and molybdenum. The thermal stability indicate that the morphology of dendrite can be stable up to 1,000°C. With the annealing temperatures increasing from 1,000 to 1,200°C, the Laves phase partially dissolves into the γ-Ni matrix, and the morphology of the remaining Laves phase is changing from irregular shape to rod-like or block-like shape. Research limitations/implications The heat treatment used on the IN625 superalloys is helpful for knowing the evolution of microstructures and precipitated phases thermal stability and mechanical properties. Practical implications Due to the different kinds of application conditions, the original microstructure of the IN625 superalloys fabricated by LAM may not be ideal. So exploring the influence of annealing treatment on IN625 superalloys can bring theory basis and guidance for actual production. Originality/value This study continues valuing the fabrication of IN625 by LAM. It shows the effect of annealing temperatures on the shape, size and distribution of Laves phase and the microstructures of deposited-IN625 superalloys.

The effect of heat treatment on microstructure and mechanical properties (microhardness, wear resistance and impact toughness) of laser additively manufactured AISI H13 tool steel was systemically investigated. To understand the variation of microstructure and mechanical properties under different heat treatments, the as-deposited samples were treated at 350, 450, 550, 600 and 650 °C/2 h, respectively. Microstructure and phase transformation were investigated through optical microscopy, scanning electron microscope and transmission electron microscope. The mechanical properties were characterized by nanoindentation tests, Charpy tests and high-temperature wear tests. The microstructure of as-deposited samples consisted of martensite, ultrafine carbides and retained austenite. After the tempering treatment, the martensite was converted into tempered martensite and some fine alloy carbides which precipitated in the matrix. When treated at 550 °C, the greatest hardness and nanohardness were 600 HV0.3 and 6119.4 MPa due to many needle-like carbides precipitation. The value of hardness increased firstly and then decreased when increasing the temperature. When tempered temperatures exceeded 550 °C, the carbides became coarse, and martensitic matrix recrystallized at the temperature of 650 °C. The least impact energy was 6.0 J at a temperature of 550 °C. Samples tempered at 550 °C had larger wear volume loss than that of others. Wear resistances of all samples under atmospheric condition at 400 °C showed an oxidation mechanism.

M2 high-speed steel samples were fabricated by laser additive manufacturing and tempered at different times at a temperature of 560°C. The microstructures of deposited samples were characterised by...

Color center-containing nanodiamonds have many applications in quantum technologies and biology. Diamondoids, molecular-sized diamonds have been used as seeds in chemical vapor deposition (CVD) growth. However, optimizing growth conditions to produce high crystal quality nanodiamonds with color centers requires varying growth conditions that often leads to ad-hoc and time-consuming, one-at-a-time testing of reaction conditions. In order to rapidly explore parameter space, we developed a microwave plasma CVD technique using a vertical, rather than horizontally oriented stage-substrate geometry. With this configuration, temperature, plasma density, and atomic hydrogen density vary continuously along the vertical axis of the substrate. This variation allowed rapid identification of growth parameters that yield single crystal diamonds down to 10 nm in size and 75 nm diameter optically active center silicon-vacancy (Si-V) nanoparticles. Furthermore, this method may provide a means of incorporating a wide variety of dopants in nanodiamonds without ion irradiation damage.

Adding small nanoparticles (NPs) into polymer melt can lead to a non-Einstein-like decrease in viscosity. However, the underlying mechanism remains a long-standing unsolved puzzle. Here, for an all-polymer nanocomposite formed by linear polystyrene (PS) chains and PS single-chain nanoparticles (SCNPs), we perform large-scale molecular dynamics simulations and experimental rheology measurements. We show that with a fixed (small) loading of the SCNP, viscosity reduction (VR) effect can be largely amplified with an increase in matrix chain length \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$N$$\end{document}N, and that the system with longer polymer chains will have a larger VR. We demonstrate that such \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$N$$\end{document}N-dependent VR can be attributed to the friction reduction experienced by polymer segment blobs which have similar size and interact directly with these SCNPs. A theoretical model is proposed based on the tube model. We demonstrate that it can well describe the friction reduction experienced by melt polymers and the VR effect in these composite systems., Addition of small nanoparticles into polymer melt can lead to decrease in viscosity but the underlying mechanism for such viscosity reduction remains unclear. Here, the authors investigate the reduction in viscosity by large-scale molecular dynamics simulation and experimental rheology measurements for an all-polymer nanocomposite formed by linear polystyrene chains and PS single-chain nanoparticle.

Using an optical fiber to both excite the nitrogen-vacancy (NV) center in diamond and collect its fluorescence is essential to build NV-based endoscope-type sensor. Such endoscope-type sensor can reach inaccessible fields for traditional NV-based sensors built by bulky optical components and extend the application areas. Since single NV's fluorescence is weak and can easily be buried in fluorescence from optical fiber core's oxide defects excited by the green laser, fixing a micrometer size diamond containing high-density NVs rather than a nanodiamond containing single NV or several NVs on the apex of an optical fiber to build an endoscope-type sensor is more implementable. Unfortunately, due to small numerical aperture (NA), most of the optical fibers have a low fluorescence collection efficiency, which limits the sensitivity and spatial resolution of the NV-based endoscope-type sensor. Here, using a tapered optical fiber (TOF) tip, we significantly improve the efficiency of the laser excitation and fluorescence collection of the NV ensembles in diamond. This could potentially enhance the sensitivity and spatial resolution of the NV-based endoscope-type sensor. Numerical calculations show that the TOF tip delivers a high NA and has a high NV excitation and fluorescence collection efficiency. Experiments demonstrate that such TOF tip can obtain up to over 7-fold excitation efficiency and over 15-fold fluorescence collection efficiency of that from a flat-ended fiber (non-TOF) tip.

In order to control the grain size during hot forming, grain growth behavior of a pre-extruded Mg-6Zn magnesium alloy and its correlation with solute and second phase distribution were investigated. Isothermal annealing was conducted on a Gleeble-1500 thermo-mechanical simulator. The mean grain size Dg of each annealed specimen was measured by the quantitative metallography technique. The grain growth kinetics of the Mg-6Zn alloy annealed at 473–623 K was obtained as D g 4 − D g 0 4 = 2.25 × 10 11 exp ( − 95450 / R T ) t by the least square linear regression method. The deviation of grain growth exponent n = 4 from the theoretical value of 2 may be attributed to the presence of solute zinc and second phases which will retard the boundary migration. Microscopic observations show that the non-uniform distribution of grain size for samples pre-extruded or annealed at low temperatures is closely related to the non-uniform distribution of fine and dispersed second phases but not to the non-uniform distribution of solute zinc. This indicates that second phase pinning effect plays an important role in microstructure refinement.

The microstructure evolutions and mechanical properties of a heterogeneous Mg88Y8Zn4 (in at.%) alloy during multi-pass equal channel angular pressing (ECAP) were systematically investigated in this work. The results show that four phases, i.e. α-Mg, 18R long period stacking ordered (LPSO) phase, Mg24Y5 and Y-rich phase, are present in cast alloy. During ECAP, dynamic recrystallization (DRX) occurs and the diameter of DRXed α-Mg grains decreases to 0.8 µm. Moreover, precipitation of lamellar 14H LPSO structure is developed within α-Mg phase. Both the refinement of α-Mg grains and precipitation of 14H LPSO contribute to the increase in micro-hardness from 98 HV to 135 HV for α-Mg. In addition, a simplified model describing the evolution of 18R LPSO phase is established, which illustrates that 18R undergoes a four-step morphological evolution with increasing strains during ECAP, i.e. original lath → bent lath → cracked lath → smaller particles. Compression test results indicate that the alloy has been markedly strengthened after multi-pass ECAP, and the main reason for the significantly enhanced mechanical properties could be ascribed to the DRXed α-Mg grains, newly precipitated 14H lamellas, 18R kinking and refined 18R particles.

A novel scheme for a perfect hyperbolic metamaterial (HMM) absorber is proposed, and experimental verification is provided. It has been shown previously that tapered HMM stacks can provide adiabatic waveguiding over a wide spectral range and thus are an ideal opaque absorber. Here, nontapered shape-optimized HMM absorbers are proposed, which facilitates the fabrication and promotes the large-area applications such as thermophotovoltaics (TPV). In the synthesis of the optimal patterns, we use 5-harmonic rigorously coupled wave analysis (RCWA) and experimental trials to shorten the trial-and-error time. The best pattern provides an averaged broadband experimental absorption of 88.38% over λ = 1 μm to λ = 2 μm, which is comparable to the state-of-the-art experimental effort using tapered HMM. The nontapered nature can be easier to fabricate from the semiconductor processing viewpoint. The physics behind the pattern-optimized HMM cavity is the broadband light coupling by the air-cavity and the unbounded photonic density of the states (PDOS) associated with the HMM. The topology optimized air cavity effectively couples the incident photons into the metal-dielectric stacking, eliminating the need of sidewall tapers. We believe the proposed topology-optimization methodology benefits the future design of compact metamaterial perfect absorbers (MPA), sensors, antenna, and thermophotovoltaic emitters, and absorbers.

Compared with conventional solar cells, thermophotovoltaics (TPV) can be more efficient and, thus, exceeds the detailed balance efficiency limit. In particular, the emitter of TPV is a critical design since it determines whether the thermalization loss can be reduced and whether the sub-band-gap radiation can be suppressed, as far as the photovoltaic (PV) process is concerned. In this paper, we propose a selective planar emitter composed of alternating ultrathin metal and dielectric layers. An aperiodic dielectric stacking is designed to tailor the emission spectrum by shaping the emission peak and by adjusting the emission wavelength. We show that the peak emission wavelength $(\lambda_{\mathrm{emission}})$ is adjustable from $\lambda=1500\ \text{nm}$ to $\lambda=2500\ \text{nm}$ . Furthermore, the long-wavelength cutoff is very sharp for our proposed emitter structure, and the absorption is suppressed to 0.1 beyond the cutoff. The preliminary experiment is also conducted to fulfill the concept of a fully planar ultrathin refractory metal emitter design, and the result is similar to the calculated ones. We believe that the planar thermal emitter based on ultrathin metals and aperiodic dielectric stacking is very promising for future thermal emission applications since it requires no lithography and etching, provides strong peak emission power, and possesses wide wavelength scalability.

This paper proposes a novel high-power supply rejection ratio (high-PSRR) high-order curvature-compensated CMOS bandgap voltage reference (BGR) in SMIC 0.18 μm CMOS process. Three kinds of current are added to a conventional BGR in order to improve the temperature drift within wider temperature range, which include a piecewise-curvature- corrected current in high temperature range, a piecewise-curvature-corrected current in low temperature range and a proportional-to-absolute-temperature T1.5 current. The high-PSRR characteristic of the proposed BGR is achieved by adopting the technique of pre-regulator. Simulation results shows that the temperature coefficient of the proposed BGR with pre-regulator is 8.42×10−6/°C from −55 °C to 125 °C with a 1.8 V power supply voltage. The proposed BGR with pre-regulator achieves PSRR of −123.51 dB, −123.52 dB, −88.5 dB and −50.23 dB at 1 Hz, 100 Hz, 100 kHz and 1 MHz respectively.

An effective strategy to improve the conductivity of MnO2-based electrodes is to combine them with some conductive materials, such as metal or carbon-based materials. In this work, Ag nanoparticles decorated MnO2/Sulfonated Graphene composite with 3D macroporous structure (3D Ag–MnO2/SG) was synthesized and their performance as electrode material in supercapacitors was studied. The improved conductivity and the elaborate design of 3D porous structure allowed the 3D Ag–MnO2/SG electrode to possess enhanced electrochemical performance. For example, the electrochemical testing results demonstrated that the 3D Ag–MnO2/SG presents a capacitance of 537 F g−1 at 0.5 A g−1, which is much higher than that of MnO2 (∼172 F g−1). Moreover, the 3D Ag–MnO2/SG electrode delivers a higher capacity retention rate in high current density and smaller charge transfer resistance than that of MnO2, which is contributed by the synergistic effect from the Ag nanoparticles and the 3D porous SG.

In the past, perfect metamaterial absorbers (PMAs) have required nanolithography patterning to boost broadband absoprtion. Tapered structures, in particular, are shown to achieve close-to-unity absorption over broadband using adiabatic light coupling. A nontapered PMA is desirable due to the fact that it is easier to fabricate using regular lithography techniques. This facilitates the scalability to large-area photonic applications such as thermophotovoltaics. In this work, we propose a fully planarized design with ultrathin metallic films for broadband PMAs. The design provides close-to-unity absorbance over a wide spectral range and is wavelength scalable from middle ultraviolet to long wavelength infrared. The planarized design is extremely easy to fabricate, and it requires no lithography nor etching. The design can be used with different moderate-extinction metals such as tungsten, titanium, tantalum, and nickel. The physics is that the thin layer of the moderate-extinction metal allows photons to penetrate through itself. The insertion of the dielectric between thin metal layers is necessary to spatially separate the ultrathin metallic thin film to boost the effect of thin-film absorption. As far as the bandwidth normalized to center wavelength is concerned, we believe that the experimental result demonstrated here shows the broadest bandwidth to date.

We propose an extremely simple multiple-metal metamaterial perfect absorber (MPA). The dimension of our proposed design is only 221 nm for the visible wavelength range from 400 to 700 nm. This is comparable with past efforts on MPAs using plasmonics at the same wavelength range, whereas the plasmonic excitation is absent in our proposal. A unity broadband absorption can be achieved with ultrathin metallic films. In addition, the wavelength scalability is possible using our design, and the fully planar simple configuration facilitates large-area photonic design without the need for lithography and etching. The physics is the field penetration and the field absorption for the photons at different wavelength ranges using different metallic layers. We also show that the adjustment of the individual layer thickness is critical to attaining a perfect wave impedance matching to vacuum. The titanium (Ti), nickel (Ni), and aluminum (Al) triple-metal configuration is used to demonstrate the concept experimentally, and a close match to the theoretical result is observed. The absorption band can be further widened with more stacking layers with various metals. We believe that the proposed design is very promising in the aspects of simple processing and scalable for large-area broadband unity absorption. It thus improves the future implementation of MPAs and facilitates a wide range of relevant applications.

Fixing a diamond containing a high density of Nitrogen-Vacancy (NV) center ensembles on the apex of a multimode optical fiber (MMF) extends the applications of NV-based endoscope sensors. Replacing the normal MMF with a tapered MMF (MMF-taper) has enhanced the fluorescence (FL) collection efficiency from the diamond and achieved a high spatial resolution NV-based endoscope. The MMF-taper's high FL collection efficiency is the direct result of multiple internal reflections in the tapered region caused by silica, which has a higher refractive index (RI) than the surrounding air. However, for applications involving fluidic environments whose RI is close to or higher than that of the silica, the MMF-taper loses its FL collection significantly. Here, to overcome this challenge, we replaced the MMF-taper with an ultra-high numerical aperture (NA) microstructured optical fiber (MOF) which is tapered and sealed its air capillaries at the tapered end. Since the end-sealed air capillaries along the tapered MOF (MOF-taper) have isolated the MOF core from the surrounding medium, the core retains its high FL collection and NV excitation efficiency in liquids regardless of their RI values. Such a versatile NV-based endoscope could potentially find broad applications in fluidic environments where many biological processes and chemical reactions occur., 4 pages, 5 figures

The coexistence of thin and thick lamellae of form II in isotactic polybutylene-1 (PB-1) was obtained by isothermal crystallization at high temperature (100 °C) and subsequent cooling, and then the transformation from coexisted thin and thick lamellae of form II to form I was investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), in-situ wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS), to understand the dependence of lamellar thickness on the transformation from form II to form I. It is seen that the transformation of thick lamellae is always superior to that of thin lamellae. The crystal transformation time is shortened to ∼ 48 h for the samples with only thick lamellae of form II, which also weakens the retardance of form II to form I transition at late stage. By directly observing the crystalline morphology via POM, we find that crystalline form II formed at higher isothermal temperatures possesses loose and irregular spherulites, which facilitates the transition in contrast with the dense and regular spherulites formed at lower temperatures. Moreover, the large temperature difference during cooling from higher isothermal temperature to room temperature also accelerates the transformation due to increasing internal stress. Our work builds up connections among the crystalline morphology, the lamellar thickness, and the transformation behavior, which may help understand the crystalline transformation from form II to form I in PB-1.

Infrared imagine seeker is an important development direction of ground-to-groung ballistic missle terminal guidance technology, but it’s derection probability is vulnerable to target/background characteristic detector performance field of view and other factors. In order to improve the ability of infrared seeker to adapt to complex battlefield environment, a new design principle of infrared dual-band seeker is introduced. The whole system adopts dual band design, and uses image fusion technology to enrich the information difference between target and background features. In addition, the design of large and small dual field of view can further improve the target interception and accurate recognition and tracking ability of seeker. The working principle of infrared seeker is analyzed, and the optical design idea and image fusion method are introduced. Through index analysis and calculation, the infrared seeker meets the system requirements, which can provide reference for future ballistic missle seeker design

We demonstrate cavity-enhanced Raman emission from a single atomic defect in a solid. Our platform is a single silicon-vacancy center in diamond coupled with a monolithic diamond photonic crystal cavity. The cavity enables an unprecedented frequency tuning range of the Raman emission (100 GHz) that significantly exceeds the spectral inhomogeneity of silicon-vacancy centers in diamond nanostructures. We also show that the cavity selectively suppresses the phonon-induced spontaneous emission that degrades the efficiency of Raman photon generation. Our results pave the way towards photon-mediated many-body interactions between solid-state quantum emitters in a nanophotonic platform.

The dielectric mirror is an important optical component for optoelectronic devices, passive photonic devices, and solar cells. Unfortunately, the reflection bandwidth of distributed Bragg reflectors (DBRs) and high-index contrast mirrors (HCGs) are limited by the index contrast of the material system used. Here, an aperiodic design for dielectric mirrors is proposed, and it is shown that for a fixed index contrast, the bandwidth of the reflection band can be arbitrarily widened by simply incorporating more dielectric layers. This is pronouncedly different from the fixed bandwidth of HCGs and DBRs. The physics behind the broadband reflection for the aperiodic stacking is identified as the photonic bandgap widening due to the annihilation of the quasi-guided modes in nonperiodic structures. This observation applies very well to aperiodic auto-cloned 3-D photonic crystal reflectors, to aperiodic DBRs, and even to diffuse dielectric mirrors that have recently emerged to be very promising for solar cells due to their zero plasmonic absorption nature. Experimentally, the white paint diffuse medium reflectors are applied to SiGe solar cells to confirm their high reflectance and the feasibility of enhancing solar cell efficiency.

Measuring temperature in nanoscale spatial resolution either at or far from equilibrium is of importance in many scientific and technological applications. Although negatively charged nitrogen-vacancy (NV(-)) centers in diamond have recently emerged as a promising nanometric temperature sensor, the technique has been applied only under steady state conditions so far. Here, we present a three-point sampling method that allows real-time monitoring of the temperature changes over ±100 K and a pump-probe-type experiment that enables the study of nanoscale heat transfer with a temporal resolution of better than 10 μs. The utility of the time-resolved luminescence nanothermometry was demonstrated with 100 nm fluorescent nanodiamonds spin-coated on a glass substrate and submerged in gold nanorod solution heated by a near-infrared laser, and the validity of the measurements was verified with finite-element numerical simulations. The combined theoretical and experimental approaches will be useful to implement time-resolved temperature sensing in laser processing of materials and even for devices in operation at the nanometer scale.

Arrays of identical and individually addressable qubits lay the foundation for the creation of scalable quantum hardware such as quantum processors and repeaters. Silicon-vacancy (SiV) centers in diamond offer excellent physical properties such as low inhomogeneous broadening, fast photon emission, and a large Debye–Waller factor. The possibility for all-optical ultrafast manipulation and techniques to extend the spin coherence times makes them promising candidates for qubits. Here, we have developed arrays of nanopillars containing single (SiV) centers with high yield, and we demonstrate ultrafast all-optical complete coherent control of the excited state population of a single SiV center at the optical transition frequency. The high quality of the chemical vapor deposition (CVD) grown SiV centers provides excellent spectral stability, which allows us to coherently manipulate and quasi-resonantly read out the excited state population of individual SiV centers on picosecond timescales using ultrafast optical pulses. This work opens new opportunities to create a scalable on-chip diamond platform for quantum information processing and scalable nanophotonics applications.

Carbon nanotubes (CNTs) possesses decent optical properties and thus can be considered as a candidate for perfect absorbers due to their close-to-air refractive index and minimal extinction. However, weak absorption in porous materials, due to the low extinction coefficients, requires an inevitably thick absorption layer (∼100 μm) for the perfect opaque absorbers. Thus, the requirement of large thicknesses of CNTs prohibits them from being used as miniaturized integrated photonic devices. Here, we propose an electrophoretic deposited (EPD) CNT resonant cavity structure on tantalum (Ta) to enhance optical absorption. Efficient random light scattering along with the resonant cavity structure using Ti/SiO2 stacking enhances the absorption in our proposed EPD-CNT film while maintaining the total device thickness to

External light trapping has been proposed as an alternative to internal light trapping. The advantage is that the electrical and optical characteristics can be designed separately. This enhances the degree of improvement that nano-photonics can contribute to the solar cell efficiency and J SC . In this work, we use diffuse trench reflectors with down-conversion polymer to demonstrate the concepts of a low-cost, widely applicable scheme for the external light trap. A >50% enhancement of the J SC can be observed with proper designs and configurations. The proposed external light trap can be applied to nearly all thin-film solar cell technologies since the external optical components do not affect the electrical diode characteristic of the solar cells. The efficient external light trap is attributed to the high reflectance of the disuse mirror and its wide-angle diffractions, optical confinement due to the trench reflector, and the additional short-wavelength spectral enhancement by the down-conversion mechanism.

In this work, we develop the process flow for nano-imprinted metamaterial patterns for perovskite solar cell light trapping. Nanoimprint can be scaled for large-area photovoltaics at low cost, compared to conventional lithography techniques. While conventional grating is normally underneath the solar cell active layers, the degraded electrical characteristic can be a problem. On the other hand, the external light trapping separates the electrical and optical designs and, therefore, it is more promising for complex photonic management without sacrificing the diode characteristics. We demonstrate the concept by perovskite solar cells with metamaterial patterns. Imprinting a deeper metamaterial pattern is suggested to enhance the far field effect for further efficiency improvement.

Solar cell nano-structured anti-reflection coatings based on graded index (GI) and mode coupling are all proposed to significantly reduce the reflection from semiconductor–air interface. In this work, it is shown that purely graded index approach can lead to degradation of long wavelength absorption by eliminating quasi-guided mode excitation. The reason is that the physically graded layer not only provides low reflectance path from air to semiconductor, but also from semiconductor to air, leading to photon escape. This results in out-coupling of photons from the semiconductor to air. On the other hand, anti-reflection coating based on mode coupling does not suffer from degraded long wavelength absorption and it is capable of acting as one-way photon pass coating. It is found that the sidewall thickness of mode coupling anti-reflection coating has significant impact on its effectiveness for antireflection, and therefore the selection of process methods is critical for its low reflectance. It is proposed that the purely graded index coating is more suitable for wafer-based photovoltaics where full absorption is possible by two photon traces. The mode coupling coating is suitable for both wafer-based photovoltaics and thin-film photovoltaics since it provides not only low reflectance but also long wavelength quasi-guided mode excitations. In the end, new types of anti-reflection coating and light trapping structure are proposed to further enhance the performance. © 2014 Elsevier B.V. All rights reserved.

In this work, we have successfully demonstrated the rear side passivation technology applied to multi-crystalline p-type wafers. The AlOx/SiNx stack was selected as rear side passivation layer combined with suitable laser opening source and metallization materials. The performance of multi-crystalline cell reached an efficiency level of 18%-19% applying this technology and the light induced degradation and module power output performance are attractive compared with current cell type.

We discuss the progress in integration of nanodiamonds with photonic devices for quantum optics applications. Experimental results in GaP, SiO2 and SiC-nanodiamond platforms show that various regimes of light and matter interaction can be achieved by engineering color center systems through hybrid approaches. We present our recent results on the growth of color center-rich nanodiamond on prefabricated 3C-SiC microdisk resonators. These hybrid devices achieve up to five-fold enhancement of diamond color center light emission and can be employed for integrated quantum photonics.

Among quantum sensors, the single nitrogen-vacancy (NV) defect in diamond has the highest sensitivity-to-size factor. For instance, a single-NV spin when used as a magnetometer could achieve sensitivities of the order of nT/Hz, while the dimensions of the sensor are merely atomic in size. The sensitivity is limited only by the photon shot noise. One method to boost the magnetometer sensitivity to pico-tesla scales is to use many NV defect centers as an ensemble sensor [Phys. Rev. X5, 041001 (2015)PRXHAE2160-330810.1103/PhysRevX.5.041001]. However, during the absorption-emission (fluorescence) optical cycles, the NV centers transfer a portion of the irradiation laser energy into phonons and heat the diamond matrix. This results in unintended fluorescence decrease, spin resonance lines shifts, and fluctuations. Hence, the advantages gained by packing a high density of NV centers are significantly reduced. Here we investigate the heat generation of ensemble NV centers in micrometer-sized diamond under 532 nm laser irradiation and its effects pertaining to sensing applications. These investigations help us to find strategies that mitigate the detrimental effects of heating and yet permits the use of ensemble NV defects for improved metrology applications.