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The microstructural characterization of duplex Fe-Cr-Ni-based alloy processed through sub-rapid solidification and subsequent solid solution heat treatment was investigated, and the mechanism underlying the phase transformation and the improvement in the tensile properties of the alloy was discussed. A metastable thermodynamic balance emerged immediately during sub-rapid solidification which promoted the multiple phase transformation deviate from equilibrium transformation, e.g., suppressed dendrite δ phase, coupled structure features and constrained constituent diffusion behavior. The phase transformation in subsequent solid solution heat treatment proceeded very quickly, which resulted in decomposition of the primary δ phase and the polymorphic transformation (γ → δ). The solid solution heat treatment also led the change of grain size and shape, crystallographic orientation and constituents' distribution characterization. The application of solid solution heat treatment significantly improves the yield strength from 643.65 to 1014.09 MPa, and the ultimate tensile strength from 729.54 to 1029.31 MPa, corresponding to an increase of 57.55% and 41.09%, respectively. The results showed that the lamellar structures in sub-rapid solidified could give rise to strain concentration during loading and result in performance deterioration, which is different with the adverse effect derived from coarse dendrites in previous research. The underlying mechanism for the enhanced mechanical performance after solid solution heat treatment is discussed. It is demonstrated that the crack propagation and their interaction with individual microstructure features (dislocation, dimple or inclusions) play a vital role in final enhance performance. And the crack propagation is essentially orientation dependent. [ABSTRACT FROM AUTHOR]

Inconel 718 is the most popular nickel-based superalloy and is extensively used in aerospace, automotive, and energy industries owing to its extraordinary thermomechanical properties. The effects of different two-step solid solution treatments on microstructure and δ phase precipitation of Inconel 718 alloy were studied, and the transformation mechanism from γ″ metastable phase to δ phase was clarified. The precipitates were statistically analyzed by X-ray diffractometry. The results show that the δ phase content firstly increased, and then decreased with the temperature of the second-step solid solution. The changes in microstructure and δ phase were studied by scanning electron microscopy and transmission electron microscopy. An intragranular δ phase formed in Inconel 718 alloy at the second-step solid solution temperature of 925°C, and its orientation relationship with γ matrix was determined as [ 1 ¯ 00 ] δ / / [ 01 1 ¯ ] γ and (010)δ//(111)γ. Furthermore, the Vickers hardness of different heat treatment samples was measured, and the sample treated by second-step solid solution at 1010°C reached the maximum hardness of HV 446.84. [ABSTRACT FROM AUTHOR]

The infamous type IV failure within the fine-grained heat-affected zone (FGHAZ) in G115 steel weldments seriously threatens the safe operation of ultra-supercritical (USC) power plants. In this work, the traditional thermo-mechanical treatment was modified via the replacement of hot-rolling with cold rolling, i.e., normalizing, cold rolling, and tempering (NCT), which was developed to improve the creep strength of the FGHAZ in G115 steel weldments. The NCT treatment effectively promoted the dissolution of preformed M23C6 particles and relieved the boundary segregation of C and Cr during welding thermal cycling, which accelerated the dispersed reprecipitation of M23C6 particles within the fresh reaustenitized grains during post-weld heat treatment. In addition, the precipitation of Cu-rich phases and MX particles was promoted evidently due to the deformation-induced dislocations. As a result, the interacting actions between precipitates, dislocations, and boundaries during creep were reinforced considerably. Following this strategy, the creep rupture life of the FGHAZ in G115 steel weldments can be prolonged by 18.6%, which can further push the application of G115 steel in USC power plants. [ABSTRACT FROM AUTHOR]

As a new concrete crack patching technology, microbial self-healing slurries offer favourable characteristics including non-pollution, ecological sustainability and good compatibility with concrete. In this paper, a nano-sio2-modified microbial bacteria liquid, combined with sodium alginate and polyvinyl alcohol, was used to prepare a nano-modified microbial self-healing slurry. This slurry was used to coat concrete under negative pressure in order to verify its restoration effect, and the micromorphology of the resulting microbial mineralization products was observed. The results revealed that patching the concrete using the nano-modified microbial slurry significantly improved its permeability, and increased its carbonization resistance by three times in comparison with the control group. Through a combination of Scanning electron microscopy (SEM) and X-ray diffraction (XRD) observation, it was determined that the microbial mineralization reaction products were mainly calcite crystals, which, integrated with the nano-sio2, sodium alginate and polyvinyl alcohol at the microscopic level, filled the internal pores of concrete, thus improving its durability. Highlights: • Surface crack treatment of concrete using a nano-modified microbial slurry was investigated. • Patching concrete using nano-microbial slurry clearly improved its chloride penetration. • The carbonization of the concrete was three times in comparision with the control group. • The main product of the microbial mineralization reaction was calcite crystal. [ABSTRACT FROM AUTHOR]

To reveal the effects of water vapor on the oxidation mechanism of Al–Zr-based materials, the Al2Zr alloy was oxidized in a wet atmosphere. Water vapor achieves the synchronous oxidation of Al and Zr to form amorphous (Al0.67Zr0.33)O1.66 oxide on the Al2Zr surface. The oxidation kinetics of the Al2Zr alloy is significantly retarded by the presence of water vapor. Compared with the oxygen molecules, water molecules are preferentially adsorbed on the surface, thereby providing fewer oxidizing species for wet oxidation than those for oxygen-involved oxidation. This work provides fundamental insights for surficial protection of structural alloys in humid environments. [ABSTRACT FROM AUTHOR]

G115 martensitic heat-resistant steel has been widely used in high parameter thermal power units because of its excellent mechanical properties and oxidation resistance. The microstructure and mechanical properties of single pass G115 steel welded joints fabricated by different welding currents were investigated in this study. The results show that larger welding current causes the widening of martensite laths, the coarsening of M23C6 carbides and the decrease in Vickers hardness in weld metal. However, welding current will affect evidently the microstructure and Vickers hardness of heat-affected zones only when it reaches to 120 A, which is mainly manifested by larger diameter and lower area fraction of M23C6 carbides and lower Vickers hardness. The tensile strength of welded joint firstly decreases and then increases with the increase in welding current, while the yield strength and elongation firstly increase and then decrease. The welded joint with welding current of 100 A is more recommended, due to the combination of highest yield strength and best ductility. [ABSTRACT FROM AUTHOR]

Hypercholesterolemia and vascular inflammation are key interconnected contributors to the pathogenesis of atherosclerosis. How hypercholesterolemia initiates vascular inflammation is poorly understood. Here we show in male mice that hypercholesterolemia-driven endothelial activation, monocyte recruitment and atherosclerotic lesion formation are promoted by a crosstalk between macrophages and endothelial cells mediated by the cholesterol metabolite 27-hydroxycholesterol (27HC). The pro-atherogenic actions of macrophage-derived 27HC require endothelial estrogen receptor alpha (ERα) and disassociation of the cytoplasmic scaffolding protein septin 11 from ERα, leading to extranuclear ERα- and septin 11-dependent activation of NF-κB. Furthermore, pharmacologic inhibition of cyp27a1, which generates 27HC, affords atheroprotection by reducing endothelial activation and monocyte recruitment. These findings demonstrate cell-to-cell communication by 27HC, and identify a major causal linkage between the hypercholesterolemia and vascular inflammation that partner to promote atherosclerosis. Interventions interrupting this linkage may provide the means to blunt vascular inflammation without impairing host defense to combat the risk of atherosclerotic cardiovascular disease that remains despite lipid-lowering therapies. Hypercholesterolemia and vascular inflammation both contribute to the pathogenesis of atherosclerosis, but how hypercholesterolemia initiates vascular inflammation is not fully understood. Here the authors report that crosstalk between macrophages and endothelial cells mediated by the cholesterol metabolite 27-hydroxycholesterol drives vascular inflammation and contributes to atherosclerosis in male mice. [ABSTRACT FROM AUTHOR]

With the development of science and technology, the demand for high-performance sintered Nd-Fe-B magnets has increased dramatically. Since the grain refinement has a significant effect on the coercivity of sintered Nd-Fe-B magnets, a low-temperature sintering process using fine powder is proposed to control the grain size to improve the coercivity. Through this method, the grain size of the magnets is controlled to about 3.1 μm, which is smaller than the grain size of the conventionally processed magnet (4.2 μm). As a result, the intrinsic coercivity is increased by 1.24 kOe and the maximum magnetic energy product is increased by 1.23 MGOe, for the same composition. The influence of grain refinement on the magnet performance is studied in detail, which provides a guiding reference for the development of high-performance Nd-Fe-B sintered magnets. [ABSTRACT FROM AUTHOR]

Precipitation evolution and strengthening effect of Al-15wt%Mg2Si-5wt%Cu alloy were studied by characterizing the change of morphology and tensile properties after ageing at 200 °C for various times. At the under-ageing condition (ageing for 0.5 h), metastable θ″, θ′, fine dots and σ phases are formed. After ageing for 1 h (peak-ageing condition), θ″ and θ′ are dominant phases, and the high number density of precipitates produces a significant improvement of the hardness (173 Hv) and ultimate tensile strength (356 MPa). As ageing time is prolonged (ageing for 24 h), plenty of σ phases are formed at the expense of θ"/θ′ phases and act as the main strengthening precipitates. The over-aged microstructure consequently causes a decrease in the hardness (134 Hv) and ultimate tensile strength (311 MPa) of the alloy. [ABSTRACT FROM AUTHOR]

With excellent creep resistance, good high-temperature microstructural stability and good irradiation resistance, oxide dispersion strengthened (ODS) alloys are a class of important alloys that are promising for high-temperature applications. However, plagued by a nerve-wracking fact that the oxide particles tend to aggregate at grain boundary of metal matrix, their improvement effect on the mechanical properties of metal matrix tends to be limited. In this work, we employ a unique in-house synthesized oxide@W core-shell nanopowder as precursor to prepare W-based ODS alloy. After low-temperature sintering and high-energy-rate forging, high-density oxide nanoparticles are dispersed homogeneously within W grains in the prepared alloy, accompanying with the intergranular oxide particles completely disappearing. As a result, our prepared alloy achieves a great enhancement of strength and ductility at room temperature. Our strategy using core-shell powder as precursor to prepare high-performance ODS alloy has potential to be applied to other dispersion-strengthened alloy systems. Aggregation and coarsening of the second-phase oxide particles at grain boundaries have been a bottleneck for improving mechanical properties of oxide-dispersion-strengthened (ODS) alloys. Here the authors employ core-shell nanopowder precursors to achieve uniform dispersion of oxides in ODS alloys. [ABSTRACT FROM AUTHOR]

In the present work, Tungsten (W)/oxide dispersion strengthened (ODS) steel joints were fabricated by the direct solid state diffusion bonding (SSDB) technology with a multistage cooling process, and the microstructure and tensile strength of the bonded interfaces and parent materials were experimentally investigated. The results show that W and ODS steel can be successfully bonded at the temperature ranging from 900 °C to 1050 °C, without severe macroscopic deformation or obvious microscopic defects. Reaction layers generated at the bonded interfaces are evolutive with the bonding temperature, result in different fracture locations of the bonded joints. In the joint bonded at 950 °C, a higher interfacial strength of ~ 234.2 MPa is achieved, due to the formation of nano-scale intermetallic compound FeW. Microstructure of W remains stable after all the SSDB processes, while the lath structure of ODS steel is completely broken and transformed into the equiaxed grains, which should be responsible for the deterioration of strength. When the bonding temperature is higher than 950 °C, the pinning effect of precipitates M23C6 and nano-oxide particles on the movement of dislocations is observed. [ABSTRACT FROM AUTHOR]

The current study has demonstrated that cation dopant segregation at matrix/oxide interface opened up a new route to refine and disperse secondary oxide particles in oxide dispersion-strengthened (ODS) alloys. Thus, a unified theory that explains the physical origins of this interfacial segregation phenomenon is needed for designing ODS alloys with excellent oxide dispersity and ensuing high performance. Here, taking W–Y2O3 system for example, we firstly assess the possible driving forces for cation dopant interfacial segregation based on the experimental observation from Sc3+-, La3+-, Ti4+-, Zr4+- and Hf4+-doped W–Y2O3 alloys. It was suggested that elastic energy, oxygen chemical potential gradient and interfacial energy reduction are three main driving forces for the cation dopant segregation at W/Y2O3 interface. Then, an analytical model was developed in this work to quantitatively calculate the contributions of these three factors to the total segregation energy. Finally, the coupled results are further validated with the density functional theory (DFT)-calculated total segregation energy, and the good consistency confirms again the underlying mechanism behind cation dopant segregation phenomenon in W-based ODS alloy. On this basis, it can be predicted that a chemically expanded lattice and a large oxygen affinity will promote dopant interfacial segregation and enable the microstructure of ODS alloys to be tailored desirably. More importantly, the results and analytical model in our work can provide theoretical guidance for choosing proper cation dopant for other ODS alloys and then enhancing their strength and ductility simultaneously. Besides, the high-temperature instability of secondary oxide particles under extreme working environment also can be solved easily using this method. [ABSTRACT FROM AUTHOR]

A chemically stable Zr(IV)-based metal-organic framework (BUT-17) has been explored for simultaneous adsorption and determination of bisphenol compounds (BPs) in aqueous medium. The prepared BUT-17 possesses a large surface area (2936 m2 g−1) and excellent fluorescent performance. An adsorption capacity of 111 mg g−1 for bisphenol A (BPA) with a rapid adsorption rate (1.76 g mg−1 min−1) is achieved by BUT-17. The excellent adsorption performance could be attributed to the hydrogen bond interaction between BPs and BUT-17. Furthermore, the fluorescent intensity of BUT-17 was quenched up to 92% due to the formation of complexes between BPs and BUT-17. Thus, a BUT-17-based fluorescent sensing method for the rapid determination of BPs has been established with the limit of detection of 10.0 ng mL−1 for BPA and a linear range from 2.0 to 23.0 μg mL−1. These results indicate that as an outstanding multifunctional platform, BUT-17 is promising for the simultaneous removal and determination of BPs in water medium. [ABSTRACT FROM AUTHOR]

Purpose of Review: Scavenger receptor class B type I (SR-BI) serves a key role in the reverse cholesterol transport in the liver as the high-affinity receptor for HDL. SR-BI is abundantly expressed in endothelium, and earlier works indicate that the receptor mediates anti-atherogenic actions of HDL. However, more recent studies uncovered novel functions of endothelial SR-BI as a lipoprotein transporter, which regulates transcellular transport process of both LDL and HDL. This brief review focuses on the unique functions of endothelial SR-BI and how they influence atherogenesis. Recent Findings: Earlier studies indicate that SR-BI facilitates anti-atherogenic actions of HDL through modulation of intracellular signaling to stimulate endothelial nitric oxide synthase. In vivo studies in global SR-BI knockout mice also showed a strong atheroprotective role of the receptor; however, a contribution of endothelial SR-BI to atherosclerosis process in vivo has not been fully appreciated. Recent studies using cultured endothelial cells and in mice with endothelial-specific deletion of the receptor revealed previously unappreciated pro-atherogenic actions of SR-BI, which relates to its ability to deliver LDL into arteries. On the other hand, SR-BI has also been implicated in transport of HDL to the sub-intimal space as a part of reverse cholesterol transport. Summary: SR-BI mediates internalization and transcellular transport of both HDL and LDL, and the cellular and molecular mechanism of the process has just begun to emerge. Harnessing these dual transport functions of the endothelial SR-BI may provide a novel, effective intervention to atherosclerosis. [ABSTRACT FROM AUTHOR]

The evolutionary behaviors of dislocations, sub-grain boundaries (SGBs), and precipitated carbide particles in 9Cr-1.7W-0.1C reduced activation ferritic–martensitic (RAFM) steel were studied by implementing varying levels of roll deformation and tempering processes. The microstructural parameters were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron backscatter diffraction (EBSD). The relationships between these parameters, the deformation levels, and different tempering processes were quantitatively determined. The obtained results demonstrate that both high-level deformation and dual tempering (medium-temperature tempering T1 followed by standard tempering T2) contribute to the refinement of M23C6/MX particles, especially M23C6, due to the greater abundance of nucleation sites for M23C6/MX particles supplied by SGBs. How the correlation among these different microstructural parameters (dislocations, SGBs, and carbide particles) influenced the decreased process of engineering strength both at room temperature (RT) and high temperature was qualitatively and quantitatively discussed. [ABSTRACT FROM AUTHOR]

In the present study, correlation of the microstructure and stress corrosion cracking (SCC) susceptibility in the top, middle and root regions of a multi-pass austenitic stainless steel weld joint fabricated by narrow-gap tungsten inert gas welding (NG-TIG) was investigated by slow strain rate tests (SSRT) following a microstructure characterization. The results show that from the top to root regions in both the heat-affected zone (HAZ) and weld metal (WM), the dislocation density and length fraction of the Σ3 boundaries present a decreased trend, while the grain size, length fraction of LAB and residual strain all increase. By comparing the microstructure of WM with HAZ, δ-ferrite in WM is excessive and continuous while that in HAZ is island-shaped and discontinuous. In addition, larger grain size, lower dislocation density, higher residual strain, lower length fraction of Σ3 boundaries and higher length fraction of RGB are observed in WM. As a result, the SCC susceptibility in various regions of the weld joint follows the order of root regions > middle regions > top regions and WM > HAZ. [ABSTRACT FROM AUTHOR]

The accelerating rate calorimetry is a powerful tool for thermal hazard evaluation. However, the existing kinetics approaches ignore the fact that the thermal inertia is varying during the pseudo-adiabatic reaction because of the changing of the sample's heat capacity and heat loss. To overcome this shortcoming, the expression of the thermal inertia is amended based on the heat balance and transfer in this article. The arithmetic product of the sample's heat capacity and the amended thermal inertia is obtained by merging the kinetic results of the DSC and ARC data. Then, the data from the ARC are corrected and the more reasonable values of the kinetic parameters are computed based on the varying thermal inertia consideration. With the typical n-order and autocatalytic decomposition experiments under the different sample masses, the validity of the proposed kinetic approach is verified. Meanwhile, the hypotheses of the proposed approach are analyzed and discussed in the end of the article. [ABSTRACT FROM AUTHOR]

Although various efforts have been made to develop effective treatments for alveolar bone defect, alveolar regeneration has been emerging as the one with the most potential Herein, we investigated the potential of gelatin methacrylate (GelMA) hydrogels-encapsulated human periodontal ligament stem cells (hPDLSCs) to regenerate alveolar bone. The easy, rapid, and cost-effective nature of GelMA hydrogels makes them a promising mode of stem cell-delivery for clinically relevant alveolar bone regeneration. More importantly, GelMA hydrogels provide an optimal niche for hPDLSCs proliferation, migration and osteogenic differentiation, which are critical for alveolar bone regeneration. In this study, we examined the microstructure of GelMA hydrogels, and identified a highly porous and interconnected network. Compressive test of GelMA hydrogels showed that the stress reached a maximum value of 13.67 ± 0.03 kPa when the strain reached 55%. The maximum values of swelling ratio were 700 ± 47% at the fifth hour. The proliferation rate of hPDLSCs in the GelMA hydrogels resembled that in 2D culture and gradually increased. We established a critical-sized rat model of alveolar bone defects, and applied Micro-CT to assess new bone formation. Compared to the control group, there was substantial bone regeneration in the GelMA + hPDLSCs group at both 4 and 8 weeks after the operation. Histological analysis results were consistent with Micro-CT results. Our study demonstrates that the GelMA hydrogels-encapsulated hPDLSCs have a significant alveolar regenerative potential, and may represent a new strategy for the therapy of alveolar bone defects. [ABSTRACT FROM AUTHOR]

For the Al-alloyed 9Cr-ODS steels consolidated by spark plasma sintering and annealed at 800 °C, the Y-Al-O oxides, interface structure and orientation relationships between the oxides and the matrix are studied by high-resolution transmission electron microscope technique. It is found that the spark plasma sintering can serve as a useful and effective tool to investigate the transition states in complex oxide formation. Monoclinic Y4Al2O9 (YAM), orthorhombic YAlO3 (YAP), cubic Y3Al5O12 (YAG) and Y2O3 nanoparticles are identified. Both YAM and YAG can directly precipitate from the Y2O3 particles. One individual Y2O3 particle will produce several YAM particles, while only one YAG particle can be formed within one Y2O3 particle. The majority of identified Y-Al-O oxides exhibit partially coherent interfaces with the matrix, and multiple orientation relationships are revealed. [ABSTRACT FROM AUTHOR]

With Al addition, dual-phase oxide dispersion strengthened (ODS) steels consisting of martensite and ferrite are fabricated by spark plasma sintering. It is found that Al addition has a negligible effect on martensite lath size, while the amount and size of ferrite grains are related to the Al content. M23C6 (M = Fe, Cr) carbides have been identified within the ferrite grains or along ferrite boundaries. With increasing Al concentration, more fine Y-Al-O oxide nanoparticles are formed. Upon annealing treatment, homogeneous and refined distribution of ferrite grains is obtained, which may involve the particle-stimulated nucleation of recrystallization caused by the large sized M23C6. As Al is increased from 0.05 to 0.1 wt%, the tensile strength of the annealed steel is decreased, as well as its ductility. For the annealed 9Cr-ODS steel containing 0.1 wt% Al, in tensile loading the large sized M23C6 along ferrite boundaries would facilitate the cracking along boundaries between the hard annealed ferrite and soft annealed martensite, producing the mixed fracture of dimple and intergranular fracture. [ABSTRACT FROM AUTHOR]

The titanium carbide nanoparticles attached single-walled carbon nanotubes (TiC-SWCNTs) were mass-produced by an argon-hydrogen direct current arc discharge method using TiO2 and Fe added carbon rod as anode. The composites of TiC-SWCNTs in the paraffin matrix were investigated in the frequency range of 2-18 GHz by a vector network analyzer. The electromagnetic (EM) parameter and reflection loss (RL) properties were simulated by transmission line theory and the microwave absorption mechanisms for the dielectric loss and magnetic loss were discussed in detail. The results indicate that the TiC-SWCNTs prepared by 4 at.% TiO2 added anode exhibited the best microwave absorption property due to better impedance matching, whose RL value reached − 45.6 dB at 14.2 GHz and the absorption bandwidth below − 10 dB was up to 5.7 GHz. Furthermore, the matching thickness of the absorber is 1.8 mm and the filler loading of TiC-SWCNTs in the matrix is 20 wt%. It is expected that the TiC attached SWCNTs nanocomposite will be an excellent candidate for microwave absorption and provide a new idea to prepare weak magnetic EM wave absorber. [ABSTRACT FROM AUTHOR]

The martensitic transformation, microstructural characteristics, and mechanical performance of modified ferritic heat-resistant steels under various austenitizing conditions were investigated by differential scanning calorimetry, microstructural examination, and mechanical tests. When the austenitizing temperature was as high as 1200 °C, a considerable amount of δ-ferrite formed, and the austenite grain size was seen to decrease. Higher austenitizing temperatures were found to promote martensite formation, but retard martensite growth, and the lath width increased as the austenitizing temperature increased. After tempering, rod-like and granular M23C6 carbides appeared within the tempered martensite, the average size and composition of which were dependent on the austenitizing conditions. When the austenitizing temperature was 1050 °C, granular MX with sizes less than 6 nm were identified in the δ-ferrite, while for other austenitizing temperatures, plate MX was inside the δ-ferrite. At 1200 °C, the length of the plate MX was as high as 100 nm, and the number density of plate MX decreased. The steel austenitized at 1150 °C exhibited the best tensile performance. It was found that the presence of a large amount of δ-ferrite would initiate cracking, thereby impeding the tensile strength. [ABSTRACT FROM AUTHOR]

The hot deformation behavior of Nb–V–Ti microalloyed ultra-high strength steel was investigated by isothermal compression at 900–1200 °C with strain rates from 0.01 to 10 s−1. The microstructure evolution and precipitation behavior were studied using an optical microscope and a transmission electron microscope Results indicate that the peak stress of experimental steel increases with increasing the strain rate and decreasing the deformation temperature. The constitutive equation of hot deformation was developed with the activation energy Q being about 407.29 kJ/mol. The processing maps were also obtained to identify the instable regions of the flow behavior and to evaluate the efficiency of hot deformation. The size of dynamically recrystallized grains increases gradually with a decrease in the strain rate. Three types of carbides were identified, namely M3C, rich-Ti MC, and rich-Nb MC. With the increase of the deformation rate, the amounts of carbides increase, and the average sizes of the carbides decrease gradually. [ABSTRACT FROM PUBLISHER]

The CoFe attached single-walled carbon nanotubes (CoFe@SWCNTs) and BaFeO ferrite nanocomposites with different CoFe@SWCNTs weight ratios (1, 3, 5, 7 wt%) were synthesized by a simple combination process. Then, the electromagnetic and microwave absorption properties were systematically investigated by a vector network analyzer in the frequency range of 2-18 GHz. High-quality CoFe@SWCNTs were prepared by a direct current arc discharge method in one-step. BaFeO nanocrystals were synthesized by a nitrate citric acid sol-gel auto-ignition method. The CoFe@SWCNT/BaFeO nanocomposites exhibited an efficient reflection loss (RL) and a wide absorption bandwidth. The minimum RL of −54.13 dB was observed at 11.84 GHz for the nanocomposite (5 wt% CoFe@SWCNTs) with a thickness of 2.8 mm, 3.4 times greater than those without CoFe@SWCNTs, and a broad absorption bandwidth of 4.64 GHz (<−10 dB) was achieved. In addition, the nanocomposite (1 wt% CoFe@SWCNTs) shows a broader effective microwave absorption bandwidth of 7.12 GHz with a thickness of 1.9 mm. The experimental results reveal that the absorbing properties of the nanocomposites are greatly improved by controlling the CoFe@SWCNTs weight ratio and the matching thickness of the absorber. This CoFe@SWCNT/BaFeO nanocomposite is anticipated to be applied in advanced microwave absorbers. [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) nanocomposite of reduced graphene oxide (RGO) and zinc oxide (ZnO) was synthesized by a mild solution-process and a freeze-dried process effectively to keep the whole system fluffy. The BaFeO nanocrystals were synthesized by nitrate citric acid sol-gel auto-ignition method. The electromagnetic and microwave absorption properties of 3D-RGO-ZnO/BaFeO nanocomposites were investigated and this new type 3D material exhibited an efficient reflection loss value and a wide absorption bandwidth. The minimum reflection loss arrives −43.45 dB at 11.52 GHz for 7 wt% of 3D-RGO-ZnO in the nanocomposite with a thickness of 2.0 mm, and the effective absorption bandwidth is larger than 5.8 GHz (the reflection loss below −10 dB). Therefore, the 3D-RGO-ZnO/BaFeO nanocomposites can be considered as an excellent material candidate for microwave absorbers. [ABSTRACT FROM AUTHOR]

Diallyl trisulfide (DATS) protects against apoptosis during myocardial ischemia-reperfusion (MI/R) injury in diabetic state, although the underlying mechanisms remain poorly defined. Previously, we and others demonstrated that silent information regulator 1 (SIRT1) activation inhibited oxidative stress and endoplasmic reticulum (ER) stress during MI/R injury. We hypothesize that DATS reduces diabetic MI/R injury by activating SIRT1 signaling. Streptozotocin (STZ)-induced type 1 diabetic rats were subjected to MI/R surgery with or without perioperative administration of DATS (40 mg/kg). We found that DATS treatment markedly improved left ventricular systolic pressure and the first derivative of left ventricular pressure, reduced myocardial infarct size as well as serum creatine kinase and lactate dehydrogenase activities. Furthermore, the myocardial apoptosis was also suppressed by DATS as evidenced by reduced apoptotic index and cleaved caspase-3 expression. However, these effects were abolished by EX527 (the inhibitor of SIRT1 signaling, 5 mg/kg). We further found that DATS effectively upregulated SIRT1 expression and its nuclear distribution. Additionally, PERK/eIF2α/ATF4/CHOP-mediated ER stress-induced apoptosis was suppressed by DATS treatment. Moreover, DATS significantly activated Nrf-2/HO-1 antioxidant signaling pathway, thus reducing Nox-2/4 expressions. However, the ameliorative effects of DATS on oxidative stress and ER stress-mediated myocardial apoptosis were inhibited by EX527 administration. Taken together, these data suggest that perioperative DATS treatment effectively ameliorates MI/R injury in type 1 diabetic setting by enhancing cardiac SIRT1 signaling. SIRT1 activation not only upregulated Nrf-2/HO-1-mediated antioxidant signaling pathway but also suppressed PERK/eIF2α/ATF4/CHOP-mediated ER stress level, thus reducing myocardial apoptosis and eventually preserving cardiac function. [ABSTRACT FROM AUTHOR]

Glycine (Gly)-doped and Cu-and-Gly-co-doped MgB samples were two-step synthesized by a short 800 °C period followed by sintering at 600 °C for 2 h. In view of the depression of oxidation and the significant reduction of the synthesis time, the sintering efficiency was improved due to the instantaneous high-temperature process, in contrast with the one-step sintered samples at 800 °C. The critical current density was examined to be 5.1 × 10 and 8.4 × 10 A cm at 20 K and 3 T for the Gly-doped and the co-doped samples, respectively. Such enhancement, with respect to the one-step sintered un-doped sample, is attributed to the fine MgO (~20 nm) and MgCu (~10 nm) pinning centers. The MgO and MgCu in the co-doped sample precipitated at the grain boundary and within the grains, respectively. Besides, the residual Mg phase in the Gly-doped sample remained on the surface of the MgB grains, which proved the screw-dislocation growth of the MgB grains, i.e. the grains extended from inner center to outer zone at low temperature. [ABSTRACT FROM AUTHOR]

Recently, we demonstrated that melatonin reduced protein kinase RNA (PKR)-like ER kinase (PERK)-eukaryotic initiation factor 2 alpha (eIF2α)-activating transcription factor-4 (ATF4)-mediated myocardial endoplasmic reticulum (ER) stress and apoptosis during myocardial ischemia-reperfusion (MI/R) injury. However, the underlying mechanisms are still not clear. Myocardial reperfusion injury salvage kinase (RISK) pathway as well as survivor activating factor enhancement (SAFE) pathway are two pivotal intrinsic pro-survival signaling cascades. In this study, we performed in vivo and in vitro experiment to investigate the ameliorative effect of melatonin on ER stress with a focus on RISK and SAFE pathways interaction. Male C57Bl/6 mice received melatonin (300 μg/25 g/day, 3 days before MI/R surgery; 300 μg/25 g, 25 min before the onset of ischemia) pre-treatment with or without the administration of LY294002 (a PI3K/Akt inhibitor), U0126 (an ERK1/2 inhibitor) or AG490 (a STAT3 pathway inhibitor). H9c2 cells were pre-treated with melatonin (100 μM, 8 h) in the presence or absence of LY294002, U0126 or AG490. Compared with the I/R-injured group, melatonin effectively reduced myocardial apoptosis, oxidative stress and improved cardiac function. In addition, melatonin pre-treatment also increased the phosphorylation of Akt, GSK-3β, ERK1/2 and STAT3 and reduced PERK-eIF2α-ATF4-mediated ER stress. However, these effects were blocked by LY294002, U0126 or AG490. Additionally, either LY294002 or U0126 treatment could inhibit STAT3 phosphorylation, whereas AG490 administration also reduced both Akt and ERK1/2 phosphorylation, indicating an interplay exists between RISK and SAFE pathways in melatonin's cardioprotective effect. In summary, our study demonstrates that RISK and SAFE pathways mediate the cardioprotective effect of melatonin against MI/R injury. Melatonin pre-treatment attenuates PERK-eIF2α-ATF4-mediated ER stress and apoptosis during MI/R injury via RISK and SAFE pathways interaction. [ABSTRACT FROM AUTHOR]

To study the hot deformation behavior of the Ti–22Al–25Nb alloy, isothermal compression tests were conducted at the temperature range of 930–1080 °C with strain rates of 0.001–1.0 s−1. Both the strain rate and the deformation temperature have a significant influence on the stress–strain behavior of the Ti–22Al–25Nb alloy. A hyperbolic–sine constitutive equation is established to quantitatively demonstrate the relationship between the parameters involved, and the hot deformation activation energy Q is determined as 621 kJ/mol. To optimize the processing window, a hot processing map is established, which is related to the microstructure evolution in hot working. The lamellar globularization as well as the dynamic recrystallization (DRX) would contribute to the stable regions with high power dissipation, while the adiabatic shear bands would lead to unstable regions. Moreover, an Avrami-type kinetics model is applied to examine the evolution of DRX during isothermal deformation process. [ABSTRACT FROM PUBLISHER]

To investigate the effects of cold rolling on the microstructure, the precipitation behavior and the morphology of δ-phase, Inconel 718 alloy samples with different cold rolling reductions were aged for different periods at temperatures range from 850 °C to 1000 °C. Detailed microstructural observations and quantitative measurements were conducted to characterize the evolution of the δ-phase during aging. The results show that the microstructure consists of large deformed grains as a result of a slow static recovery at the low aging temperatures (850 and 900 °C); whereas the austenite matrix is fully recrystallized at the high aging temperatures (950 and 1000 °C). It is also found that the amount of δ-phase and the number density of spherical δ-phase particles increase with the increase in the degree of cold rolling both at low and high aging temperatures. With respect to different microstructural changes for the cold-rolled samples at the low or the high aging temperatures, two distinct mechanisms have been, respectively, introduced to interpret the changes in the precipitation behavior and the appearance of δ-phase. [ABSTRACT FROM PUBLISHER]

The microstructural evolution of type 347H heat-resistant austenitic steel during long-term aging at 700–900 °C was investigated by using a transmission microscope, a scanning electron microscope, and electron energy spectrum technology. The microstructural examination showed the typical micrographs of MX carbonitrides and M23C6 carbides after aging. The existence of the Z phase (NbCrN) at the grain boundaries during aging was identified. Meanwhile, the possible precipitation sequence of these particles was also confirmed. In the beginning of aging, fine Nb(C,N) precipitates first, then, M23C6 carbides precipitate along the grain boundaries. Finally, the Z phase is also observed at the grain boundaries. Moreover, the influence of isothermal holding temperature on the precipitation of MX carbonitrides and M23C6 carbides was discussed. The various microstructural characterizations showed that the M23C6 carbides and MX carbonitrides precipitate more easily with the increase of aging temperature. Furthermore, the number and the size of MX particles and M23C6 carbides increase when the isothermal holding time is prolonged. [ABSTRACT FROM AUTHOR]

Berberine (BBR) confers cardioprotective effect against myocardial ischemia reperfusion injury (MI/RI). Activation of Notch1/Hairy and enhancer of split 1 (Hes1) signaling also reduces MI/RI. We hypothesize that BBR may protect against MI/RI by modulating Notch1/Hes1-Phosphatase and tensin homolog deleted on chromosome ten (PTEN)/Akt signaling. In this study, male Sprague-Dawley rats were exposed to BBR treatment (200 mg/kg/d) for 2 weeks and then subjected to MI/RI. BBR significantly improved cardiac function recovery and decreased myocardial apoptosis, infarct size, serum creatine kinase and lactate dehydrogenase levels. Furthermore, in cultured H9c2 cardiomyocytes, BBR (50 μmol/L) attenuated simulated ischemia/reperfusion-induced myocardial apoptosis. Both in vivo and in vitro study showed that BBR treatment up-regulates Notch1 intracellular domain, Hes1, Bcl-2 expression and p-Akt/Akt ratio, down-regulates Bax Caspase-3 and cleaved Caspase-3 expression. However, the anti-apoptotic effect conferred by BBR was blocked by Notch1 siRNA, Hes1 siRNA or LY294002 (the specific inhibitor of Akt signaling) in the cultured cardiomyocytes. In summary, our results demonstrate that BBR treatment attenuates MI/RI by modulating Notch1/Hes1-PTEN/Akt signaling. [ABSTRACT FROM AUTHOR]

The influence of aging treatment on the shape memory effect and corrosion resistance of a newly developed Fe–Mn–Si–Cr–Ni-based alloy containing C, N, and V elements was investigated. Results showed that V(CN) and Cr23C6 particles, precipitated during aging, could improve the shape recovery ratio to 72%, compared with that of 21% for the solution treated sample, when the alloy was aged for 24 h. The corrosion behavior in 0.5 M H2SO4 solution was almost the same for all the samples, barring a slight difference in the passivation range. In addition, the passivation current and critical current required for the onset of passivation of the aged samples were almost triple that of the unaged. In 3.5% NaCl solution the corrosion behavior of all aged samples was that of general dissolution with localized attack (pitting), which can be attributed to the micro-cathodic effect of the V(CN) and Cr23C6 particles precipitated during aging. Although the best corrosion resistance in both H2SO4 and NaCl solutions was shown by the solution treated sample, 24 h-aged sample exhibited an improved corrosion resistance, ascribed to the improved chemical homogeneity of the austenite matrix due to long aging time (24 h). [ABSTRACT FROM PUBLISHER]

The corrosion resistance of Sn-0.3Ag-0.9Zn alloy solidified under different cooling rates in 3.5 wt% NaCl solution was evaluated based on potentiodynamic polarization, electrochemical impedance spectroscopy and electrochemical noise. It is found that the corrosion resistance of this alloy improves with the increase of the applied cooling rate, which is attributed to the distinct microstructure. The furnace-cooled and air-cooled alloy with active Zn-rich phase and a microstructure formed by a coarser dendritic array associated with larger size of AgZn intermetallic compounds exhibit a worse corrosion resistance due to a serious galvanic corrosion. Besides, the Mott-Schottky measurement and the X-ray photoelectron spectroscopy were performed to analyze the semiconductor properties and composition of the passive film formed on the surface of the alloy. It confirms that the stability and protective ability of the passive films formed on furnace-cooled and air-cooled alloy are worse than that of water-cooled alloy due to their higher oxygen vacancy defects and concentration of unstable SnO. Furthermore, the major corrosion product on the surface of the Sn-0.3Ag-0.9Zn alloys is tin oxide chloride hydroxide. [ABSTRACT FROM AUTHOR]

Multiferroic materials are currently the subject of intensive research worldwide, because of both their fundamental scientific problems and also possible technological applications. Among a number of candidates in the laboratories, compounds consisting of rare earth and transition metal perovskite oxides have very unusual structural and physical properties. In contrast to the so-called type I multiferroics, ferroelectricity may be induced by magnetic ordering or by applying external fields. In this review, the recent progress on the experimental and theoretical studies of some selected type II multiferroics is presented, with a focus on the perovskite oxides containing rare earth and transition metal elements. The rare earth orthoferrite crystals, rare earth titanate strained film, and rare earth-based superlattices are systematically reviewed to provide a broad overview on their promising electric, magnetic, and structural properties. The recent experimental advances in single-crystal growth by optical floating zone method are also presented. First-principles investigations, either supported by experimental results or awaiting for experimental verifications, are shown to offer useful guidance for the future applications of unconventional multiferroics. [ABSTRACT FROM AUTHOR]

The influence of aging treatment on shape memory effect (SME) and wear resistance of Fe–20Mn–5Si–10Cr–5Ni–0.7V–0.2N (mass%) alloy was investigated. Results showed that vanadium nitride (VN) particles precipitated during aging treatment, and the amount and size of the particles increased with increasing aging time. The sample aged for 8 h exhibited the maximal shape recovery ratio of 74% (compared with that of 16% for unaged) and favorable wear resistance in both dry wear and oil-lubricant wear conditions. The fine VN particles are the key factor to improve the SME by strengthening the alloy and acting as preferential nucleation sites for martensite. However, more and larger particles due to further aging treatment appeared to have negative effects on the SME and wear resistance. After oil-lubricant friction, there existed large amounts of friction-stress-induced ε martensite in the worn surface of the sample. As a result, the wear resistance of samples in oil-lubricant wear condition was remarkably higher than that in dry wear condition. [ABSTRACT FROM PUBLISHER]

Bulk MgB sample with carbon nanotube (CNT)-coated Al addition was prepared by conventional solid-state reaction at 900 °C for 30 min. We investigated the effects of Al and C co-doping on the lattice parameter, the microstructure, and the critical current density of MgB. The substitution of Al and C atoms for the sites of Mg and B in the MgB lattice resulted in dislocations in the MgB grains, which makes great contributions, along with the nanoscale oxide particles, to the enhancement of critical current density at high field (10 A cm, 7 T, 5 K) in the co-doped sample. These results contrasted significantly with the measured values of the pure MgB and Al- and C-doped samples. Co-doping introduced more electrons into MgB and decreased both the parameters c and a of MgB lattice, and the used coating technique delayed and shortened the oxidation process of Mg and Al, leading to the decrease in the size and the content of the oxide. These advantages should be responsible for the enhancement of the critical current density as well. [ABSTRACT FROM AUTHOR]

MgB samples containing 2.5 wt% multi-walled carbon nanotubes (CNTs) and amorphous carbon (nano-C) were sintered at 800 °C. The doped samples were prepared from Mg/CNT and Mg/nano-C composites, which were previously synthesized from coarse Mg and fine Mg by chemical vapor deposition, respectively. We made comparisons between the two samples on the C-doping level, the MgO contents, and the effects of the carbon source on critical current density ( J) by investigating the phase composition, microstructure, and magnetic properties. Compared with pure MgB (coarse Mg), the J performance at high field was improved in the CNT-doped sample (coarse Mg) due to the high C substitution level induced lattice defects as pinning centers. However, J values of the amorphous C-doped sample with sufficient C doping decreased over the entire field in contrast with the pure sample (fine Mg), which exhibited the highest J performance among the samples. This is attributed to the much more MgO impurities, mostly generated during the preparation of Mg/C composites, than the CNT-doped sample. [ABSTRACT FROM AUTHOR]

Bulk MgB samples containing Cu and YO have been prepared by conventional solid state reaction at 850 °C, and the structure and superconducting properties have been investigated. Differing from the structure in previous studies, a type of novel, layered structure was obtained in Cu/YO-doped MgB sample. Furthermore, the critical current density ( J) at high field (>4 T) was improved compared to undoped, and Cu-doped MgB samples. After analyzing the phase composition, microstructure, and sintering process, it was found that YO and Cu are independent in providing effective pinning centers, and YB impurity should be responsible for the enhancement of J as well as the increased irreversible magnetic field. However, J at low field was slightly worsened, but still maintaining 10 A cm at 0 T, since the intercrystalline connectivity was not seriously deteriorated. Finally, a possible growth model was put forward to describe the formation sequences of the layered structure. It was supposed that the formation of steps at low temperature originated from the coherent relationship between Mg and MgB, while the steps formed at high temperature were related to the pinning effect of secondary phase during the migration of grain boundary. [ABSTRACT FROM AUTHOR]

In present study, the sintering process and superconducting properties of MgB prepared with milled original powders of Mg, B, and 3 at.% Graphite were investigated. It was found that ball-milling treatment of original powders can significantly promote the C substitution for B in MgB crystal lattice, resulting in more lattice distortion. Consequently, the values of J at high fields were improved. Besides, ball-milling also refined MgB grains, which enhances grain boundary pinning and is also contributed to the improved J at high fields. On the other hand, with the milling time prolonging, Mg becomes more active and leads to an obvious increase of MgO impurities during the subsequent sintering process. These MgO impurities would degrade the connectivity between MgB grains and finally lead to slight decrease in J at low fields. [ABSTRACT FROM AUTHOR]

Oxide-dispersion-strengthened (ODS) ferritic steels of Fe-9Cr-0.3Y2O3 and Fe-9Cr-0.2Ti-0.3Y2O3 (in mass) incorporating nanoscale oxide particles, were produced by mechanical milling (MM) followed by hot pressing (HP). Microstructural evolution of these two types of ODS steels were structurally characterized at each step of the elaboration processes by means of scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), and optical microscope. The observations of structure of the mixed powders and the nanoscale oxide particles in both ODS steels after MM indicate that the initial powders, coupled with the original yttria powders, get fractured by severe plastic deformation and ultrafine bcc grains (~20 nm) of the matrix and Y2O3 nanocrystals with irregular edges are formed during MM. The addition of titanium (Ti) promotes the refinement of bcc grains, Y2O3 nanocrystals and the formation of amorphous phase of Y2O3 during MM. TEM observations of these two Oxide-dispersion-strengthened (ODS) steels exhibit a very fine structure of micrometer-scale grains in which large number of nanoscale oxide particles are distributed after HP process. The observation of some unreinforced domains without the nanoscale oxide particles indicates that there still exist inhomogeneous areas, although the size of those oxide particles reaches nanoscale. Threshold stress of the HPped Fe-9Cr-0.2Ti-0.3Y2O3 steel with the relatively homogeneous dispersion was carefully evaluated on the basis of higher magnified images of the nanoscale oxide particles. Different values of threshold stress were obtained due to the various dispersions of the nanoscale oxide particles within different areas. That may be the reason why the threshold stress cannot be clearly obtained by the results of creep tests. [ABSTRACT FROM AUTHOR]

The thermal dilation experiment and the martensite transformation features of modified high Cr ferritic heat-resistant steel upon continuous cooling were explored at various cooling rates. The "spread" martensite transformation model was introduced to investigate the influence of the cooling rate applied on the martensite transformation behaviors. The martensite fraction, martensite formation rate, and the density of martensite laths were obtained as a function of cooling rate. Both the onset and offset temperatures of the martensite transformation decrease with the increase of cooling rate, and the martensite formation rate bursts at the beginning of transformation and then reaches a peak rapidly. The fitted data based on the proposed kinetic model indicated that the aspect ratio of martensite lath decreases, instead the density of martensite laths increases, with the increase of cooling rate. [ABSTRACT FROM AUTHOR]

A simple one-step approach for the preparation of Ag-Fe-decorated single-walled carbon nanotubes (Ag-Fe/SWCNTs) by DC hydrogen arc discharge is presented in this article. The growth of SWCNTs and the attachment of Ag and Fe nanoparticles to the SWCNTs occur simultaneously during the arc discharge evaporation process. It has been confirmed that the Ag and Fe nanoparticles in the diameter range of 1-10 nm are well dispersed and tightly attached to the outer surfaces of SWCNTs. The as-grown Ag-Fe/SWCNTs have been purified by high-temperature hydrogen treatment to remove amorphous carbon and carbon shells. Antibacterial tests show that the antibacterial activity of the purified Ag-Fe/SWCNT hybrid nanoparticles is excellent against Escherichia coli. The percentage of the E. coli killed by 100 μg/ml Ag-Fe/SWCNTs can reach up to 85.1 % at a short residence time of 2 h, suggesting that the purified Ag-Fe/SWCNTs may have potential antibacterial applications. [ABSTRACT FROM AUTHOR]

Double-walled carbon nanotubes (DWCNTs) with high graphitization have been synthesized by hydrogen arc discharge. The obtained DWCNTs have a narrow distribution of diameters of both the inner and outer tubes, and more than half of the DWCNTs have inner diameters in the range 0.6-1.0 nm. Field electron emission from a DWCNT cathode to an anode has been measured, and the emission current density of DWCNTs reached 1 A/cm at an applied field of about 4.3 V/μm. After high-temperature treatment of DWCNTs, long linear carbon chains (C-chains) can be grown inside the ultra-thin DWCNTs to form a novel C-chain@DWCNT nanostructure, showing that these ultra-thin DWCNTs are an appropriate nanocontainer for preparing truly one-dimensional nanostructures with one-atom-diameter. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

First feed support system, which is one of the key technologies of Five hundred meter Aperture Spherical Telescope (FAST) was discussed in this paper. A 1:30 scaled model (20 m × 20 m × 6 m) has been built to make systemic research on the feasibility of the system. The root mean square of pointing error of moving cable car was measured and the displacements of cable car within the wind speed of 8 m/s, which is the maximal wind speed of the place where the FAST will be located, were evaluated. Then the total maximal pointing error of cable car was computed. Experimental results demonstrate that the total pointing error of the cable car is less than 50 cm, the required pointing accuracy error of the system. [ABSTRACT FROM AUTHOR]