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It is very challenging to visualize implantable medical devices made of biodegradable polymers in deep tissues. Herein, we designed a novel macromolecular contrast agent with ultrahigh radiopacity (iodinate content > 50%) via polymerizing an iodinated trimethylene carbonate monomer into the two ends of poly(ethylene glycol) (PEG). A set of thermosensitive and biodegradable polyester-PEG-polyester triblock copolymers with varied polyester compositions synthesized by us, which were soluble in water at room temperature and could spontaneously form hydrogels at body temperature, were selected as the demonstration materials. The addition of macromolecular contrast agent did not obviously compromise the injectability and thermogelation properties of polymeric hydrogels, but conferred them with excellent X-ray opacity, enabling visualization of the hydrogels at clinically relevant depths through X-ray fluoroscopy or Micro-CT. In a mouse model, the 3D morphology of the radiopaque hydrogels after injection into different target sites was visible using Micro-CT imaging, and their injection volume could be accurately obtained. Furthermore, the subcutaneous degradation process of a radiopaque hydrogel could be non-invasively monitored in a real-time and quantitative manner. In particular, the corrected degradation curve based on Micro-CT imaging well matched with the degradation profile of virgin polymer hydrogel determined by the gravimetric method. These findings indicate that the macromolecular contrast agent has good universality for the construction of various radiopaque polymer hydrogels, and can nondestructively trace and quantify their degradation in vivo. Meanwhile, the present methodology developed by us affords a platform technology for deep tissue imaging of polymeric materials., Graphical abstract Image 1, Highlights • A universal macromolecular contrast agent with ultrahigh radiopacity was prepared for construction of radiopaque hydrogels. • The location, morphology and volume of the hydrogels in deep tissues could be non-invasively achieved by CT imaging. • The degradation curve of radiopaque hydrogel confirmed by Micro-CT could truly reflect the in vivo fate of virgin hydrogel. • The present methodology is easily extended to other polymer devices for in vivo monitoring at clinically relevant depths.

Researching of high performance and low-cost oxygen reduction reaction (ORR) electrocatalysts is one of the core issues for the rapid development of energy conversion and storage devices. Herein, a N and S dual-doped three-dimensional (3D) interconnected mesoporous carbon catalyst (CNS) was constructed via a facile hydrothermal-pyrolysis strategy. Benefiting from the 3D interconnected mesoporous architecture, CNS was endowed with a fast oxygen mass transfer rate together with plentiful of accessible active centers on the surface. Its ORR half-wave potential (E1/2， 0.87 V) surpasses commercial Pt/C catalyst 50 mV in alkaline media. Its E1/2 negatively shifts only 2 mV after 8000 cycles in half-cell tests. More importantly, the zinc-air battery with CNS as cathode catalyst delivers an excellent high peak power density of 144 mW cm−2. DFT calculation results show that when N and S are co-doped, the spin density of adjacent carbon atoms can be changed, thereby increasing the CNS's binding energy to oxygen and conductivity. The excellent comprehensive performance of CNS undoubtedly discloses its potential practical application in the energy conversation and storage area.

Being the lightest structural metal, Mg is a promising candidate in numerous energy-saving and environmental-friendly applications. The research interest in Mg and its alloys continues to rise in past decades, however, their commercial applications were held back by some longstanding intrinsic difficulties. Belonging to the hexagonal close packed family of metals, Mg has anisotropic slip and twinning systems, leading to strong textures invariably associated with wrought Mg and small strains-to-failure compared to those of current structural metals. Further enhancement of the performance in Mg requires mechanistic understanding of the deformation and innovative design strategies.Microstructure is known to have tremendous influence on the mechanical and functional properties of materials. To shed light on the microstructural design for low density, high strength and formable Mg alloys, the objective of this dissertation is to advance the fundamental understanding of how microstructure affects their mechanical properties. Particular focus is on examining the influence of grain morphology (equiaxed or laminated), grain size (micro- or nano-crystalline), twin mesh features (with or without a high density of intersecting twins) and dilute solute addition of Y in polycrystalline Mg. For this purpose, we designed the experimental strategies leveraging powder metallurgy or surface mechanical treatment approaches to achieve samples with various internal microstructures. Bulk form and in-situ mechanical testing together with multiscale microstructure characterization were carried out on the Mg samples being synthesized.In this dissertation, we have demonstrated strong grain morphology and grain size effects on the active deformation modes in polycrystalline Mg, resulting in a reversed yield strength anisotropy and a large compressive strain >120% at room temperature, in the microlaminated and nanocrystalline Mg, respectively, that have not been observed in conventional Mg. The toughening effect of twin meshes was explored by in-situ TEM nanocompression, and was successfully achieved in a gradient twin meshed Mg polycrystal at the macroscale. Lastly, the alloying effect of Y was analyzed experimentally in regard to the slip and twinning behavior. The difference in activation barriers among the slip modes was reduced by Y addition, and the mobility of twin boundaries may be affected by the segregation of Y atoms on such boundaries.

Due to the poor conversion efficiency and signal-to-noise ratio (SNR) of Electromagnetic Acoustic Transducer (EMAT) testing, the defect detection sensitivity is limited, which restricts the extensive industrial applications. A finite element model for the testing process of a meander-coil EMAT was established that considers the simplified excitation and detection circuits for the EMAT. Based on this model, the effect of the connection methods (parallel or series) of the coils in the generating and receiving EMATs on their generating and receiving efficiency was investigated, and the simulation results were validated experimentally. Subsequently, the pulse compression technique with a 13-bit Barker code was used for the EMAT detection, and improvements of the SNR and range resolution were established through numerical simulation and experimental measurement. The results show that compared with the traditional EMAT design, which comprises single-layer transmitting and receiving coils, the conversion efficiency of the optimized EMAT with two excitation and receiving coils in the parallel connection can be improved by 52.8%. With the application of the Barker-coded pulse compression to detect the ultrasonic A-scan signal with no synchronous average, the SNR of the defect echo can be improved by 9.5 dB compared with the A-scan signal with 128 synchronous averages.

Silk fibroin (SF) protein is versatile for the application of biomaterials due to its excellent mechanical properties, biocompatibility and biodegradability. However, the efficient way to fabricate SF membranes with special structure is still challenging. Here, we develop an efficient and simple way to create SF membranes on the liquid (i.e. subphase) surface. It is essential to prepare highly concentrated SF solution with low surface tension by dissolving the degummed SF powders in 6% (w/v) LiBr/methanol solution by one step. 95 wt% polyethylene glycol (PEG) 200 and 30 wt% (NH4)2SO4 are the subphases, on which the SF solution spreads quickly, generating nonporous and microporous SF membranes (SFM-1 and SFM-2), respectively. PEG 200 causes more ordered molecular packing (β-sheets) in SFM-1. While Fast diffusion and denaturation of SF on (NH4)2SO4 solution lead to the formation of microporous, water-unstable membrane SFM-2. Both membranes have good transparency, hydrophilicty, and mechanical properties. To fabricate antibacterial biomaterials, we design a composite membrane by SFM-1 and SFM-2 sandwiching a layer of hydroxypropyl trimethylammonium chloride chitosan (HACC) to provide antibacterial functions. The sandwich membrane has good cell viability and antibacterial properties, showing potential use for biomedical materials.

This study presents nanorod FeS2@3DGF by in situ synthesized converted from α-FeOOH on the 3D graphene foam (GF) by one-step method. X-ray diffraction (XRD), Scanning electron microscope (SEM), and Transmission electron microscopy (TEM) results show that FeS2 nanorods are evenly distributed above the 3D graphene foam interlayer, forming a grass-like nanostructured composite. The insertion of FeS2 nanorods into the substrate column improves the structural stability of 3D graphene foam to prevent the re-accumulation of nanorods in the process of sodium insertion/extraction process. The nanorods can also shorten the sodium-ion migration path and increase the active region. As the anode electrode materials of sodium-ion battery, FeS2@3DGF has excellent electrochemical performance. The α-FeOOH@3DGF precursor achieved by hydrothermal method creates appropriate morphology of nanorods, which is beneficial for obtaining ultra-small FeS2@3DGF nanorods during sulfidation and electron and sodium ion transferring. Therefore, the FeS2@3DGF capacity keeps 502.2 mAh g−1 up to 250 cycles. The synergistic effect of FeS2 on 3D graphene foam promotes the nanostructure stability of FeS2@3DGF, demonstrating well electrochemical performance of sodium-ion batteries.

Metal fused-coating additive manufacturing composite variable polarity tungsten inert gas (MFCAM & TIG) has the advantages of low cost and high efficiency. Aiming at the difficulty of extracting dimensional information under the arc, a laser band-pass composite filter sensing system is designed according to the intensity and spectral distribution characteristics of arc radiation in the manufacturing process. Aiming at the problem of precision control of forming parts, a fuzzy PID iterative learning strategy is proposed. The results show that the monitoring accuracy of the characteristic size of the deposition layer under the laser-assisted light source is 90.71 %. The error of the control system is less than 0.4 mm and the correction time is less than 3 s. The proposed control strategy improves the control accuracy and convergence speed, and the stable forming specimens by MFCAM & TIG are realized accurately.

A MoSi2 coating was prepared on the Mo1 wire mesh via pack cementation method, and its failure mechanisms under isothermal oxidation and hot-fire test using a hydroxylammonium nitrate based monopropellant were comparatively studied. Under isothermal oxidation at 1300 °C and 1400 °C, degradation of MoSi2 into Mo5Si3 caused failure of the coating, and interdiffusion made a much larger effect relative to oxidation. However, the MoSi2 coating failed because of the synergy of oxidation, ablation, and interdiffusion under hot-fire test. Besides, dissolution of mullite into SiO2 and ablation of high velocity flame contributed to the failure of the coating as well.

Underwater acoustic ranging and detection usually require hydrophones to have high sensitivity at narrowband operating frequencies. Different from traditional sensitization methods with the help of new materials and solid/liquid resonance structure, this paper proposes a low-cost, high-sensitivity hydrophone based on a resonant air cavity containing an affordable MEMS microphone inside to sense the focused acoustic waves transmitted from the external water across the solid shell into the air cavity. Both finite element simulations and experiments are carried out to test its acoustic sensing performances. Resonance frequency and directivity of the proposed hydrophone are determined by the air cavity size and the acoustic mode, but is independent of the solid shell, which facilitates the precise designability. The sensitivity of the developed hydrophone at the resonance frequency is up to −157 dB re 1V/ $\mu $ Pa calibrated by commercial standard hydrophone TC4013. Finally, several further considerations, improvements and applications on the proposed hydrophone are discussed.

An experimental study was conducted to investigate the seismic performance of masonry walls strengthened using hybrid fiber-reinforced reactive powder concrete (HyFRRPC) as a coating. The proposed reinforcement technique was employed to improve the overall strength and structural integrity of the confined masonry wall. In order to guarantee the composite action between the masonry substrate and the coating material, material tests were conducted to achieve an optimal mixture for the HyFRRPC. Then, six full-scaled confined masonry specimens strengthened by HyFRRPCs with varied strengthening configurations were tested under in-plane quasi-static horizontal loading. The test and analysis results indicated that the proposed HyFRRPC-strengthening technique can effectively improve the lateral carrying capacity, displacement ductility, and energy dissipation capacity of masonry walls, and provide an optimal reinforcement. Finally, a simplified analytical model was also proposed for practical application.

Optimizing electrode materials performance and improving the energy density of supercapacitors is a hot research topic. The complex hollow sphere structure material, as a supercapacitor electrode m...

The effect of triphenyl phosphate (TPP) retardant inhibition on flame propagation over the horizontal surface of polymethyl methacrylate (PMMA) has been studied experimentally and numerically. Regarding the flame spread behavior over the surface of PMMA (pure and inhibited by TPP), the following parameters were measured: thermal decomposition with TG / DTG analyzer, the flame spread rate, the pyrolysis zone length, the mass loss rate and spatial distribution of temperature by thermocouples and species concentration in the gas-phase flame by probing mass spectrometry. The previously developed coupled heat and mass transfer mathematical model describing the feedback interaction between flame and solid fuel, as well as volatilization of pyrolysis products, was modified to resolve the effect of TPP on flame spread by introducing the correcting factor of the gas-phase combustion reaction rate relating to the inhibitor concentration in the solid material. Good agreement between the measured and calculated flame spread parameters (flame spread velocity, mass burn-out rate, pyrolysis zone length), as well as a detailed flame structure (gas phase temperature and species concentration), has been obtained for pure PMMA and PMMA+10%TPP. It has been shown that the proposed approach describes a satisfactory retardant effect of TPP on the flame spread over PMMA surface by inhibiting the gas-phase combustion reaction.

Self-aerated technology of valve lintel (SATVL) is widely used in high head navigation lock water delivery system to address the cavitation problem. To optimize the structural parameters of valve intel including the height of the throat ( $ h_1=20\,{\rm mm} $ ) and divergent part enhance ( $ h_2 $ ), the length of the throat part ( $ L_2 $ ) and the divergent part ( $ L_3 $ ), and the diffusion angle ( $ \beta $ ) for better self-aerated performance, the dimensionless structural parameters $ h_2/h_1, L_2/h_1, L_3/h_1 $ and beta were chosen as the variables. The conception of critical self-aerated conditions was proposed via theoretical analysis and experimental verification for the first time, and the slope m of critical self-aerated conditions was taken as the response to assess self-aerated performance. The method of combing Response Surface Methodology (RSM) with Central Composite Design (CCD) was introduced to systematically investigate the effects of the structural parameters on the self-aerated performance. A 1: 1 full-scale slicing physical model and CFD simulations were designed to capture the critical self-aerated conditions. Finally, though multiple regression analysis, a quadratic polynomial equation between m and structural parameters was obtained. It was found that: (i) the results of theoretical analysis and physical model verification confirmed the hypothesis of critical self-aerated conditions. (ii) with the aid of ANOVA, the sensitivity of structural parameters which influenced critical self-aerated conditions is $ {\rm F}(h_2/h_1) > {\rm F}(L_3/h_l) > {\rm F}(\beta) > {\rm F}(L_2/h_1) $ . (iii) the optimal structural parameters are $ h_2/h_1=1.25, L_2/h_1=3.5, L_3/h_1=160 $ and $ \beta =2.5^{\circ} $ . The result indicate that the substantial improvement of self-aerated performance can be achieve by using those optimal structural parameters.

A novel zero-voltage and zero-current switching (ZVZCS) full-bridge (FB) three-level (TL) dc–dc converter is proposed, which can satisfy most requirements of wide operation range high-input dc–dc industrial applications. OFF-voltage on the primary switches can be maintained to $V_{\mathrm {in}}$ /2 by the input capacitors, and no extra primary clamping device is needed. The primary switches can obtain zero-voltage switching (ZVS) or zero-current switching (ZCS) easily. Furthermore, the operation mode can be altered under different output and input conditions, which ensures high efficiency over a wide operation range. The extra MOSFETs have low ON-state resistance and cause less switching loss; thus, the power loss caused by these MOSFETs can be omitted. Furthermore, these components are not inserted into the circuit loop of the input capacitors and primary switches, which may reduce the voltage spike on the primary switches at turn-off instants. The VA rating of the primary switches and input capacitors is identical to that of conventional FB TL dc–dc converters, and the utilization of the dc-link voltage is close to 100%. To evaluate the proposed converter, an industrial application example and some experimental results are also provided.

As a new type of refrigeration technology, the traveling-wave thermoacoustic refrigerator offers advantages that include high efficiency, reliability and environmental friendliness. To date, because of problems such as low power utilization and high power recovery losses, traveling-wave thermoacoustic refrigerators for use in room temperature applications have not been widely studied. In this paper, following an investigation of the traditional single-stage traveling-wave thermoacoustic refrigerator, a multi-stage traveling-wave thermoacoustic refrigerator is proposed and the working mechanism of this refrigerator is studied numerically using SAGE software. The calculation results show that the proposed multi-stage traveling-wave thermoacoustic refrigerator can enhance the utilization of the input acoustic work effectively, thereby improving the cooling power of the refrigerator with high cooling efficiency. As a result, the cooling power increases from 2.17 kW for a single-stage refrigerator to 6.42 kW for a seven-stage refrigerator, while the acoustic work utilization rate increases from 0.26 to 0.82, and the coefficient of performance changes from 2.60 to 3.19. The calculation results also indicate that three to five stages may be most suitable for the multi-stage traveling-wave thermoacoustic refrigerator when working within the temperature range of interest here by striking a balance between cooling efficiency and cooling power.

The cavitation is ubiquitous in the water delivery system of high hydraulic head navigation locks. This paper studies the choked cavitation characteristics of the gap flows in the valve lintel of the navigation locks and analyzes the critical self-aeration conditions. The cavitation gap flow in the valve lintel is experimentally and numerically investigated. A visualized 1:1 full-scale slicing model is designed, with a high-speed camera, the details of the cavitation flow is captured without the reduced scale effect. Moreover, the numerical simulations are conducted to reveal the flow structures in the gap. The experimental results show that the flow pattern of the gap flow in the valve lintel could be separated into four models, namely, the incipient (1) the developing, (2), the intensive, (3), and the choked (4) cavitation models. The numerical simulation results are consistent with the experimental data. The choked cavitation conditions are crucial to the gap flow in the valve lintel. When the choked cavitation occurs, the gap is entirely occupied by two cavitation cloud sheets. The gap pressure then decreases sharply to the saturated water vapor pressure at the operating temperature. This water vapor pressure is the ultimate negative pressure in the gap that remains unchanged with the continuous decrease of the downstream pressure. The volumetric flow rate reaches a peak, then remains constant, with the further decrease of the pressure ratio or the cavitation number. At the choking point, the volumetric flow rate is proportional to the root mean square of the difference between the upstream pressure (absolute pressure) and the saturated pressure of the water. Moreover, the pressure ratio is linearly correlated with the downstream cavitation number with a slope of (1 + Ϛc).

Aluminium-polymethyl methacrylate-copper (Al-PMMA-Cu) composite coatings were developed using cored wire arc spraying. The bacteria Bacillus sp. was used to evaluate the antifouling performances of the coatings. The microstructures and antifouling mechanisms of the coatings were investigated and discussed. The results show that the composite coatings presented improved antifouling performances, and two antifouling mechanisms were explored. On the one hand, the Cu nano-particles were released to seawater due to corrosion of the Al components, converted to cupric ions, and killed the bacteria. Meanwhile, oxidation of Al was accelerated due to Cu-Al galvanic reaction, and the needle-like corrosion products were formed, which pierced the cell membranes and killed the bacteria. The effects of the PMMA on the electrochemical properties of the coatings were also evaluated. The results show that the sealing function of the PMMA components enhanced the corrosion resistance of the Al-PMMA-Cu coatings. This investigation shed light on one-step construction of antifouling and anticorrosion layers for marine applications.

The pre-film breakup in a high-performance gas turbine combustor is simplified into a two-dimensional and three-dimensional liquid sheet breakup, and the liquid sheet breakup processes, mechanisms and characteristics are investigated under nearly representative operating conditions. First, the two-dimensional flat liquid sheet breakup processes are simulated using a Reynolds-averaged Navier–Stokes (RANS) model and a VOF (volume of fluid) method. The effect of airflow velocity on the liquid sheet breakup distance is analyzed under various high-speed airflow velocities of 80 m/s, 180 m/s and 280 m/s. Then, the three-dimensional liquid sheet breakup processes are simulated using the large eddy simulation (LES)/VOF method, and the variations of the characteristics of both the horizontal liquid sheet and the oblique liquid sheet, such as the breakup process, breakup mode, breakup distance, wave characteristics and liquid sheet thickness, are analyzed. It’s found that for the two-dimensional flat liquid sheet breakup, the liquid sheet breakup distance decreases with the increase of airflow velocity or Weber number (We). When the airflow inlet velocities are 80 m/s (We = 6.13), 180 m/s (We = 220.5) and 280 m/s (We = 741.13), the liquid sheet breakup distances are 22.2 mm, 16.0 mm and 10.5 mm, respectively. An empirical formula of the liquid sheet breakup distance was thus summarized. For the three-dimensional liquid sheet breakup, as the airflow inlet angle increases, the breakup distance is significantly shortened, which is 2.21 mm at 0° and 1.85 mm at 15°, and the oscillation angle of the liquid sheet becomes larger. For the oblique liquid sheet breakup, the liquid sheet breakup mode becomes more complicated and the surface wave fluctuation amplitude increases. The empirical formula prediction values of the liquid sheet breakup distance developed in this study are in good agreement with the numerical results.

Non-precious metal-based electrocatalyst with high activity and stability for efficient hydrogen evolution reaction (HER) is of critical importance toward low-cost and large-scale water splitting. Traditional MoS2 has electrocatalytic hydrogen evolution inertness in alkaline environment, which is detrimental to the adsorption and dissociation of water. Composited with electrocatalyst with good electrical conductivity can enhance its HER activity. In this work, we for the first time construct a carbon-supported hollow heterostructure MoS2@Mo2C composite via two-step calcination and sulfurized process from carbonized Mo2C–Mo3C2 heteronanowires. The results show that the existence of the Mo3C2 phase is the key point to construct the effective heterostructure with hollow morphology. Due to the strong negative hydrogen binding energy for H on surface of Mo2C, the H+ reduction in the MoS2@Mo2C in the Volmer step can be enhanced. Compared with MoS2, MoS2@Mo2C has high electrocatalytic activity for hydrogen evolution with an onset potential of 28 mV, overpotential of 129 mV at the current density of 10 mA cm−2, a small Tafel slope of 78 mV dec−1, and an excellent stability. This work will provide new insights into the design of high-efficiency HER catalysts via interfacial engineering at nanoscale for commercial water splitting.

In the abrasive belt grinding process, there are factors affecting the machining stability, efficiency, and quality. Based on the analysis of the grinding process, the normal force in the contact area between the abrasive belt and the workpiece is a major factor. By comparing constant force and non-constant force grinding, the results imply that keeping the grinding force constant will achieve desired material removal and better surface quality. The phenomenon of over- and under-cutting of the workpieces can also be avoided by a constant normal force. In this article, a controllable and flexible belt grinding mechanism accompanied with a mechanical decoupling control strategy is built and tested. Afterward, a detailed comparison is made between the traditional force-position coupling system and the proposed decoupling control system. The proposed control system suppresses the interference between the position and force control systems. The contact force is directly measured and controlled without detecting the position of other components in the tool system. The complexity of the control system is thereby reduced. Finally, several grinding experiments are carried out. The standard deviation and coefficient of variation of the measured normal force are kept within 0.25 and 0.02, respectively. The experiment results reveal that the mechanical decoupling system performs well in force control compared with the traditional force-position coupling system. In addition, the surface roughness Ra

The poor sintering performance of limonitic laterite hinders its utilization. Hot exhaust-gas recirculation sintering was conducted to improve its sintering performance and intensification mechanism was revealed. Evaluating sinter indices in systematical sinter pot tests were substantially improved with tumble index and productivity increased by 18.01% and 7.22% respectively and solid fuel rate lowered by 13.71%, further proved by extensive industrial application. Effective CO2 emissions reduction and huge economic benefits were realized. The improvement of thermodynamic conditions converted sinter microstructure from large thin-wall pores into small thin-wall or large thick-wall pores. The amount of silico-ferrite of calcium and alumina in sinter pot tests and industrial application was increased from 8.78% to 18.61% and 21.25% respectively. Grains aggregation and growth of hercynite and close adhesion between solid phases and liquid bonding phases were achieved. Hot exhaust-gas recirculation sintering of limonitic laterite contributed to dramatically improving sinter performance and reducing CO2 emission.

In order to study the effect of ionization seed mass fraction on gas plasma jet deflection, Cs2CO3 was selected as ionization seed, and the combustion temperature and conductivity in chemical equilibrium were calculated by Chemkin software. A calculation scheme for mixed combustion of methane with air and Cs2CO3 at initial temperature T0 = 300 K and initial pressure p0 = 1.04 × 105 Pa is determined. The gas temperature and conductivity were calculated when the mass fraction of ionization seed was 1%, 5% and 10%, respectively. According to the calculation results, the quantitative relationship between conductivity and temperature was fitted. The results showed that the fifth-order polynomial had good fitting accuracy for three different seed mass fraction schemes, and high conductivity could be obtained by keeping the excess air coefficient near 0.9. The plasma jet deflection experiments under different working conditions were carried out on a thrust-vector test rig controlled by MHD. The effect of jet deflection is analyzed. The results showed that at the same temperature, the higher the mass fraction of ionization seed is, the higher the conductivity is, the greater the Lorentz force on the plasma is, and the larger the jet deflection angle is. The calculation results can provide theoretical basis for the corresponding experimental research.

BaTiO3:100xZnO composite ceramics with different ZnO particle sizes were prepared by using a conventional solid-state method. Phase constitution, microstructure and dielectric properties of BaTiO3:100xZnO composite ceramics are investigated. Compared to micrometer scaled ZnO particles, nanometer scaled ZnO particles tend to agglomerate at lower ZnO contents in the BaTiO3:100xZnO composite ceramics. The introduction of ZnO in BaTiO3 leads to the reduction of grain size, decrease of the tetragonality and shift of phase transition temperature. The optimum composition is BaTiO3 with 20 wt. % nanometer scaled ZnO particles, which has stable permittivity and low dielectric loss from -100 to 160 °C. The stable dielectric properties are proposed to be beneficiated from the stress induced multi-phase coexistence.

The purpose of this paper is to elaborate the non-linear collapse of externally pressurized resin toroidal and cylindrical shells, along with a comparison between a toroid and cylinder. For this pu...

Bimetallic clusters have aroused increased attention because of the ability to tune their own properties by changing size, shape, and doping. In present work, a structural search of the global minimum for divalent bimetal Be2Mgn (n = 1–20) clusters are performed by utilizing CALYPSO structural searching method with subsequent DFT optimization. We investigate the evolution of geometries, electronic properties, and nature of bonding from small to medium-sized clusters. It is found that the structural transition from hollow 3D structures to filled cage-like frameworks emerges at n = 10 for Be2Mgn clusters, which is obviously earlier than that of Mgn clusters. The Be atoms prefer the surface sites in small cluster size, then one Be atom tend to embed itself inside the magnesium motif. At the number of Mg larger than eighteen, two Be atoms have been completely encapsulated by caged magnesium frameworks. In all Be2Mgn clusters, the partial charge transfer from Mg to Be takes place. An increase in the occupations of the Be-2p and Mg-3p orbitals reveals the increasing metallic behavior of Be2Mgn clusters. The analysis of stability shows that the cluster stability can be enhanced by Be atoms doping and the Be2Mg8 cluster possesses robust stability across the cluster size range of n = 1–20. There is s-p hybridization between the Be and Mg atoms leading to stronger Be-Mg bonds in Be2Mg8 cluster. This finding is supported by the multi-center bonds and Mayer bond order analysis.

As an advanced additive manufacturing technology, laser cladding has become a research hotspot in the fields of rapid manufacturing and surface modification in recent years. The quality of the cladding layer directly depends on the choice of process parameters. In order to obtain high quality cladding layer, the effects of laser power, scanning speed, and powder feeding rate on the quality of JG-3 iron-based powder cladding layer were studied by interaction orthogonal experiments. Three-dimensional measurement laser microscopy (3D MLM) and variance analysis were used to analyze the results. It was found that the interaction between laser power and powder feeding rate directly affects the optimum process parameters. Laser power 750 W, scanning speed 420 mm/min, and powder feeding rate 6.96 g/min were selected as the optimum process parameters. Scanning electron microscope (SEM), X-ray diffraction (XRD), and Thermo-Calc software were used to analyze the microstructure, phase composition, and solidification process of the coating, and compared with the experimental results. The results show that under the optimum process parameters, a dense crack-free and non-porous coating was obtained. The coating can be divided into three areas: coating zone (CZ), bonding zone (BZ), and heat affected zone (HAZ). The CZ is composed of α-Fe, Cr2B, Fe2B, and Cr23C6 phases. The calculated results obtained from the Thermo-Calc software are in good agreement with the experimental data. It is beneficial to the coating design for a desirable microstructure and mechanical properties.

This article provides a systematic study on the resorcinol–formaldehyde (RF) resin coating via a sol–gel process with focus on surface modification of the core. With colloidal SiO2 particles as the...

Traditional contact lenses bring convenience for ophthalmic drug delivery. However, either as contact lenses or as drug carriers, traditional materials have still some drawbacks in the field. Therefore, a transparent film was designed and investigated for the application of therapeutic contact lenses. Chitosan (CS)/graphene oxide (GO) composite film and CS film were fabricated with acceptable transparent and tensile properties by simple casting flow method. Although swelling ratio of CS/GO composite film was higher than that of CS film with significant difference, both formed films had suitable swelling ratio for contact lens application. Both CS/GO composite film and CS film exhibited typical CS infrared characteristic peaks. CS/GO composite film had significant greater breaking strength than CS film, but its elongation at break was a little lower than CS film. Either CS/GO composite film or CS film exhibited good hydrophilic property with a contact angle of around 20 degree. Ofloxacin as a model drug was loaded into films by adsorption diffusion method. Loaded drug amount in CS/GO composite film was a little larger than that in CS film, but without significant difference. The drug release behaviors from CS/GO composite film or CS film were investigated and revealed that the loaded drug could be controlled to release in the first hour. Two kinds of cells were used to evaluate the biocompatibility of films by in vitro method. It was found that both CS/GO composite film and CS film could support human umbilical vein endothelial cell (HUVEC) growth. But for human epidermal fibroblasts (HSF) cells, CS/GO composite film could promote HSF cells growth and proliferation much better than CS film.

To make use of broad spectrum solar energy remains a main target in the photoelectrochemical area. Novel promising photoelectrode CeO2:Fe/Yb/Er nanomaterials supported on upconversion nanomaterials doped with transition-metal ions are reported to improve broad spectrum absorption and scattering properties in dye-sensitized solar cells (DSSCs) for the first time. The results demonstrate that the materials have stronger upconversion luminescence than CeO2:Yb/Er samples when the Fe3+ ion doping concentration is 2 mol% and 33.5% higher photoelectric conversion efficiency than a pure P25 electrode, which are attributed to the special light scattering properties and excellent dye adsorption capacity of the CeO2:Fe/Yb/Er nanomaterials. Accordingly, doping Fe3+ transition metal ions in the upconversion material CeO2:Yb/Er provides a new research idea for improving the photoelectric conversion efficiency of DSSCs.

Understanding the irradiation hardening effect of structural steels under various irradiation conditions plays an important role in developing advanced nuclear systems. Such being the case, a crystal plasticity model for body-centered cubic (BCC) crystal based on the density of dislocations and irradiation defects is summarized and numerically implemented in this paper. Based on this model, nano-indentation hardness of Chinese A508-3 steels with ion irradiation is calculated. Very good agreement is observed between simulation and experimental data of several different irradiation doses subjected to various operating temperatures, from which, it can be concluded that indentation hardness increases with increasing irradiation dose at both room temperature and high temperature. Consequently, the validity of this model has been proved properly, and furthermore, the model established in this paper could guide the study of irradiation hardening effect and temperature effect to some extent. Keywords: Crystal plasticity, Nano-indentation, Hardness, Irradiation hardening, Ion irradiation