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Mechanical exfoliation is a facile way for the preparation of two-dimensional (2D) nanoflakes. However, the quality of obtained flakes still needs to be further improved, e.g., the exfoliated size and production yield, which plays a crucial role in practical applications. Here, solvent-assisted method is proposed by introducing chemical solvents in the exfoliations. The impacts of wrinkles and defects existed in the outmost layer of bulk MoS2 crystal are overcome due to the capillary and diffusion forces driven by solvent molecules underlying flakes. Hence, the size and yield of nanoflakes are promoted manifestly. The MoS2 nanoflakes are obtained with the largest area of ~ 1.5 mm2 that is three orders of magnitude bigger than conventional mechanical exfoliation. In addition, the characterizations verify the existence of monolayer which may exhibit intrinsic properties of the MoS2 flakes. Subsequently, MoS2 field-effect transistors are conveniently fabricated by one-step mechanical shadow-mask process. The field-effect mobility of ~ 26 cm2V−1 s−1 and on/off ratio of ~ 106 are achieved. All results indicate that the solvent-assisted exfoliations provide a universal path in the preparation of 2D nanoflakes, which is a fundamental support for the studies of 2D materials and devices. [ABSTRACT FROM AUTHOR]

With the rapid development of artificial intelligence and wearable devices, flexible magnetic sensors have attracted much attention in recent years. In this work, large self-biased 0–3 type poly(vinylidene fluoride-trifluoroethylene)/cobalt ferrite (P(VDF-TrFE)/CoFe2O4) flexible magnetoelectric (ME) composite films are proposed for the development of AC magnetic sensors. P(VDF-TrFE)/CoFe2O4 composite films with CoFe2O4 nanoparticle mass contents from 5 to 30% are successfully fabricated through the solution casting method. The results show that the nanoparticles are homogeneously dispersed in the P(VDF-TrFE) matrix, and the composite films have both excellent ferroelectric and ferromagnetic properties. The P(VDF-TrFE)/CoFe2O4 composite films all exhibit a large ME effect. The ME coefficient reaches 47.1 mV·cm−1·Oe−1 for the film with a CoFe2O4 nanoparticle mass content of 20% at resonance frequency. Moreover, the composite films have a large self-biased ME effect with a maximum value of 20.4 mV·cm−1·Oe−1, which is mainly due to the high remnant magnetization of CoFe2O4 nanoparticles. To evaluate the composite films for application in magnetic sensors, the response of the ME output voltage to an AC magnetic field without a bias DC magnetic field was measured. The good linear correlation coefficient, sensitivity and repeatability indicate that the proposed 0–3 type P(VDF-TrFE)/CoFe2O4 composite film is a promising material for flexible AC magnetic sensors. [ABSTRACT FROM AUTHOR]

Various pollutants in wastewater including water-insoluble oils and water-soluble toxic organic pollutants, have been threatening ecosystems and human health, making wastewater purification difficult. Inspired by the hierarchical structures and chemical compositions of lotus leaf, we combined the usage of polydopamine (PDA) chemistry and photocatalytically active TiO2 to develop a facile approach toward composite PDA-based TiO2 coated mesh with restorable superhydrophobicity. In this procedure, PDA assisted loading of TiO2 nanoparticles onto stainless steel mesh with a result of micro/nanoscale hierarchical surface was achieved via a single-step solvothermal method. After modified with 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane, this mesh became superhydrophobic. The TiO2 coated mesh exhibited enhanced superhydrophobicity, excellent environmental stability, robust chemical resistance and high mechanical durability. Moreover, it has been demonstrated the high separation capacity and extraordinary recyclability for various oils collection from water due to its special surface superhydrophobicity. Importantly, such a mesh possessed photocatalytic activity due to the embedded TiO2, which allowed for the effective degradation of organic pollutants under UV irradiation, representing a plausible way to restore superhydrophobic surface by photocatalytically decomposing the attached contaminants. This investigation suggests a green and facile way to prepare superhydrophobic materials with restored surface wetting property, which will be useful for wastewater purification. [ABSTRACT FROM AUTHOR]

Polyaniline (PANI) multidimensional (MD) structures (i.e., flowers, sheets, and plates) are successfully synthesized by adjusting the dosage of cationic surfactant cetyltrimethylammonium chloride (CTAC) in the range of 0.050-0.50 g in static HCl solution (0.010 M) at room temperature without stirring. CTAC micellar templates consisting of quaternary ammonium cations and binary persulfate anions direct the fabrication of PANI MD structures. On the basis of the employment of CTAC, the effect of pH value on PANI morphologies is investigated in detail, and followed by the obtainment of other PANI structures, including nanobelts, net-like structures, and particulates. Among the PANI MD structures, PANI sheets in micron size have good dispersibility and excellent processability, which are due to the synergistic effect of PANI's suitable size and appropriate CTAC molecules. The results and strategies presented here provide opportunities to obtain good water dispersibility to conduct polymer structures with big size. [ABSTRACT FROM AUTHOR]

A new solvent composed of 4-(tert-butyl) cyclohexyl acetate as a dilute agent and HPMDA as a thickener was developed to make micron-sized Ag paste and to bond power semiconductors. The new Ag paste achieved sentinel printing to form sharp Ag patterns with uniform thickness and defined boundaries, which is a key to printing fine pitches in the electronics industry. The electrical resistivity of Ag patterns of 3 μΩ cm was obtained at 280 °C for 30 min. Two Ag-plating copper substrates were successfully bonded with the new Ag paste and the shear strength gradually increased with the bonding temperature. A high strength of 80 MPa was achieved at 280 °C under a small sintering pressure of 0.4 MPa. This value is far higher than the value obtained by using an expensive Ag nanoparticle paste. The detailed mechanism is discussed in this work by comparison with common ethylene glycol solvent. [ABSTRACT FROM AUTHOR]

Polyvinylchloride (PVC) was mechanochemically modified (mmPVC) by a ball mill. The dynamic rheological properties of PVC and mmPVC dope solution [containing PVC/ N, N-dimethyl acetamide (DMAc)/polyethylene glycol 400 (PEG 400)/polyethylene glycol 6000 (PEG 6000)] were studied with the advanced rheometric expansion system of AR1000 at different temperatures (40, 60, and 80 °C). PVC and mmPVC membranes were prepared at different dope solution temperatures (50 and 80 °C), and the structure and permeation of membranes were analyzed. It was showed that homogeneous degree of PVC dope solution deteriorated as temperature increased; while homogeneous degree of mmPVC dope solution improved at 80 °C. Mechanochemical modification led to the forging of hydroxyl group into PVC molecular chains, and the storage modulus ( G′) of modified PVC dope solution increased. The gel point of mmPVC dope solution occurred at 77.3 °C, and the viscosity ( η) increased significantly. As the dope solution temperature increased, the permeation of PVC membrane increased from 158.8 to 236.7 L/(m h); while the permeation of mmPVC membrane decreased from 349.2 to 302.3 L/(m h). [ABSTRACT FROM AUTHOR]

Polyvinylchloride (PVC) powders containing (or not) calcium carbonate were mechanochemically modified using a ball mill. Membranes prepared by phase inversion of the modified PVC were tested by scanning electron microscopy, infrared spectroscopy, thermogravimetry, and differential scanning calorimetry to compare the structure and properties before and after mechanochemical modification. The results showed that after mechanochemical modification, pure water flux of the phase inversion PVC membrane reached up to 378.6 L/(m h), significantly higher than that before modification [123.3 L/(m h)]; calcium carbonate enhanced the dechlorination effect of mechanochemical modification and further increased pure water flux of the membrane to 454.2 L/(m h). Mechanochemical modification increased the tensile strength of the PVC membrane by 4.1 % and decreased crystallinity of the PVC powder by about 34 %. [ABSTRACT FROM AUTHOR]

Harvesting solar energy to convert thermal energy is a promising technology that enables substantial eco-friendly applications to alleviate freshwater and energy crisis. To realize rapid and energy-efficient solar driven steam evaporation, developing efficient photothermal conversion materials are significantly important. Here is a facile approach for constructing a three-dimensional (3D) pillar hydrogel based on FeCoNiCrOx (FCNCO) for effective water treatment. Taking advantage of high solar absorption property and low evaporation enthalpy, the CPH-2S can be capable of achieving surface plasmon resonance assisted water evaporation rates of 2.44 kg m−2 h−1 under 1 sun irradiation. This function endows the evaporator with a light-to-vapor conversion efficiency of 96%, which is induced by an elaborately constructed hydrogel with surface photons trapping and thermal localization capabilities. Meanwhile, the hydrogel exhibits salt resistance in seawater as well as the stability of solar evaporation performance. This work offers a rational design principle to create multi-metal component-based photothermal materials for developing a self-sustainable and solar-powered water-energy platform. [ABSTRACT FROM AUTHOR]

The fusion zone (FZ) of AZ31 alloy typically exhibits undesirable coarse columnar grains, often accompanied by solidification cracks, resulting in a decrease in the mechanical properties of the welded joint. In this work, a novel welding wire containing MgO particles has been developed to promote the columnar-to-equiaxed transition (CET) in TIG-welded AZ31 alloy. The results indicate that the liquid film caused by Al and Zn segregation, along with the high thermal stress induced by columnar grains, is responsible for the formation of solidification cracks. Moreover, cracks are prone to propagate along high-angle grain boundaries exceeding 30°. A fully equiaxed grain structure in the FZ is obtained through MgO modification, with a significant 65.8% reduction in grain size to 70.5 μm from the original coarse columnar dendrites. The high number density of MgO particles and good lattice matching between MgO and the α-Mg matrix, with the orientation relationship of [ 11 2 ¯ 0 ] α - Mg // [ 01 1 ¯ ] MgO and (0002) α - Mg // (111) MgO , are crucial factors contributing to grain refinement, thereby reducing the susceptibility to hot cracking of the welded joint. This study presents an innovative method for promoting CET and suppressing crack formation in the FZ of Mg alloys. [ABSTRACT FROM AUTHOR]

Solar-driven interfacial water evaporation can efficiently utilize abundant and sustainable solar energy to alleviate the scarcity of freshwater resources, which has been recognized as one of the most attractive technologies for purifying seawater and wastewater. However, photothermal evaporation process cannot eliminate pollutions in residual wastewater. Therefore, inducing photocatalytic degradation technology into photothermal evaporation will greatly realize the concurrent freshwater collection and pollution degradation. Herein, bifunctional La0.5Sr0.5CoO3 (LSC5) solar evaporator with various architecture structures is constructed. It is demonstrated that the LSC5 photothermal catalyst has excellent solar absorption and photothermal conversion property. Furthermore, interpenetrating polyvinyl alcohol (PVA) and chitosan (CS) into LSC5 can promote water transport capacity and decrease water evaporation enthalpy. Benefited from these advantages, three-dimensional (3D) solar evaporator comprised of LSC5 and PVA/CS polymer achieves a relatively high evaporation rate of 2.45 kg m−2 h−1 with the photothermal conversion efficiency of 93.0%. Moreover, the LSC5 displays obvious photocatalytic degradation effect on tetracycline pollutants. Therefore, this photothermal–photocatalytic degradation bifunctional hydrogel provides a promising alternative material for comprehensive water purification and pollution elimination. [ABSTRACT FROM AUTHOR]

Traditional isothermal aging treatments could not balance the relationship between mechanical properties and corrosion resistance of ultra-high-strength Al–Zn–Mg–Cu alloys. Therefore, the effect of non-isothermal aging (NIA) treatments on the microstructure and properties of TiC-TiB2 (BC) ceramic particles-reinforced spray-formed 7055 aluminum alloy tungsten inert gas (TIG) weld metal (WM) has been investigated. Weld joints were solid soluted at 475 °C for 2.5 h and quenched in water at 65 °C. Then, they were heated from 100 to 180 °C firstly at the rates of 60, 40, and 20 °C h−1 and cooled from 180 to 100 °C at the rate of 20 °C h−1. The results show that the mechanical properties of WM improve as the variable temperature rates decrease and its corrosion resistance deteriorates. The tensile strength of BC-20 is the best (580 ± 25 MPa), and the corrosion resistance of BC-60 is the best. The NIA treatments promote the formation of narrower precipitate free zones and finer-dispersed precipitates. Therefore, the mechanical properties (565 ± 25 MPa, 4.20 ± 0.21%) and corrosion resistance of BC-40 are excellent in the shorter aging time. [ABSTRACT FROM AUTHOR]

In this paper, we observe for the first time that a metastable beta-Zr in the body-centered cubic (BCC) structure can form via a new phase transformation route. The as-received alpha-Zr in the hexagonal closed-packed (HCP) structure transforms partially to the gamma-Zr in the face-centered cubic (FCC) structure via Shockley partial dislocations during deformation, while the gamma-Zr can continuously transform to the beta-Zr by a uniform shear along the 112 FCC direction on the 111 FCC plane during subsequent hot deformation. The beta phase is in a Pitsch–Schrader relationship ((110) BCC | | (0001) HCP , [ 1 1 ¯ 0 ] BCC | | [ 10 1 ¯ 0 ] HCP) with the matrix alpha phase and in a Nishiyama–Wassermann relationship ((110) BCC | | (1 1 ¯ 1 ¯) FCC , [ 1 1 ¯ 0 ] BCC | | [ 12 1 ¯ ] FCC) , with the gamma phase, both of which have not been reported in Zr previously. Combined with corresponding molecular dynamics simulations, the phase transition mechanism and stability of the beta phase are studied. The results show that the beta-Zr phase can be retained in the gamma phase when the cooling is fast enough. [ABSTRACT FROM AUTHOR]

Although lithium-sulfur (Li-S) batteries are an advanced energy storage system, their development has been impeded due to poor cycling stability and low sulfur utilization. Hollow TiN microspheres with a porous shell were prepared to host sulfur (TiN-S) for use as a Li-S battery cathode. The TiN-S electrode delivered a high capacity of 1206.1 mA h/g at 0.1 C, and a narrow value domain of 1218.2 ± 17.7 mA h/g was obtained from initial discharge capacities of 9 cells. Furthermore, a capacity of 623.3 mA h/g (with a retention of 67.5%) was maintained after 300 progressive cycles at 1 C. The superior cycling performance of the TiN-based cathode can be ascribed to the following: (1) TiN improved the electrical conductivity of the cathode, effectively increasing the active sulfur utilization; (2) the hollow TiN microspheres with pores restricted the soluble polysulfides by both chemical and physical interactions; (3) the large void of the spherical cavity in TiN could accommodate the change in volume of the cathode during the discharge-charge processes. [ABSTRACT FROM AUTHOR]

The solution-aging behavior and properties of spray-formed 7055 aluminum alloy TIG weld metal (WM) reinforced by TiC–TiB2 (BC) ceramic particles are investigated, in detail. Weld joints were subjected to solution at 475 °C for 1, 2.5, and 5 h, followed by the aging process at 120 °C for 0–24 h. The results show that ceramic particles not only restrict the grain coarsening of WM during the heat treatment but also accelerate the solution and age-precipitation behavior. The optimum solution time of ceramic particle-reinforced WM is 2.5 h, which has superior aging kinetics due to the completely dissolved eutectic phases. More importantly, during the aging process, ceramic particles decrease the width of the precipitate free zone and modify the size and distribution of precipitates. With the 475 °C/2.5 h + 120 °C/15 h treatment, the tensile strength (530 ± 15 MPa) and elongation (3.9 ± 0.29%) of BC weld joints are higher than 7055 weld joints (358 ± 20 MPa, 2.38 ± 0.42%). Grain refinement, Zener pinning strengthening, coefficients of thermal expansion mismatch strengthening, and precipitation strengthening are the dominant strengthening mechanisms of ceramic particle-reinforced WM. [ABSTRACT FROM AUTHOR]

The high temperature oxidation behavior of selective laser melting processed IN738LC alloy at different temperatures was studied using isothermal oxidation testing. The phase composition and oxide layer morphology of the oxidation products under various temperature conditions were characterized by X-ray diffraction (XRD), optical microscopy (OM), and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), and the oxidation mechanism was discussed. The results reveal that the oxidation kinetic curves of the deposited samples at 900 and 1000 °C show parabolic law, and the oxidation rate constants kp are 2.54 × 10–4 and 7.68 × 10–4mg2/cm4·h, respectively, where the oxidation products at different temperatures are composed of Al2O3, Cr2O3, and TiO2, which meet the complete oxidation resistance level. Element Cr preferentially oxidizes to produce Cr2O3 during the initial oxidation, Ti atoms at the interface extend the diffusion to the surface of the sample through the Cr2O3 layer to produce TiO2, while the Al atoms rapidly diffuse along the fine columnar grain boundaries toward the oxide–metal interface and finally form a dense Al2O3 layer. The holes formed under the oxide film at 1000 °C will reduce the adhesion between the oxide layer and the substrate, meanwhile adversely affecting the oxidation resistance of the sample. [ABSTRACT FROM AUTHOR]

Activated carbon (AC) has been widely used in the prevention and control of air and water pollution due to its excellent adsorption ability. However, the adsorption capacity of AC for targeting organic compounds is reduced because of the competitive adsorption of water molecules. The current study proposes hydrophobic modification and regeneration of waste AC as a solution to these issues. Using waste AC as raw material, SiO2 particles were introduced to increase its surface roughness and micropores of AC. Nonpolar alkyl chain groups were grafted on the surface of AC to improve its hydrophobic performance, and high-temperature regeneration was used to increase its specific surface area. The experimental results showed that the water contact angle of AC increased from 30° (hydrophilic) to 142° (hydrophobic) after modification, and it maintained an angle of 139° even after high-temperature regeneration. The specific surface area of hydrophobic AC increased from 290 to 1075 m2 g−1 and the equilibrium adsorption capacity of hydrophobic AC for methylene blue is 425.4 mg g−1 after regeneration. AC-adsorbed methylene blue also has excellent hydrophobicity (145°) and high specific surface area (1250 m2 g−1) after being modified and regenerated by the same methods. After being exposed to air for 600 days, the modified AC still has good hydrophobicity (125°). This indicates that our method of hydrophobic modification combined with regeneration has great significance to the recovery and utilization of waste AC. [ABSTRACT FROM AUTHOR]

In the design of composite materials, the properties and failure modes/mechanisms are always of the main concern. In this work, the mechanical properties and failure mechanisms of composite laminates with classical fabric stacking patterns ([(0, 90)]8 and [(0, 90)/(± 45)]4) were systematically investigated through mechanical experiments and FEM (finite element method) numerical simulations. The results show that the tensile modulus and bending modulus of the laminates were reduced by 22.2% and 37% after partially changing the stacking angle to ± 45°, but corresponding elongation and bending displacement were increased by 8.8% and 11.7%, respectively. Bending failure mode changes from complete fracture to partial fracture. Meanwhile, the delamination damage and tow peeling from the matrix increase significantly. FEM simulations on tensile and bending processes of the composites indicate that the ± 45° stacking angle leads to the change of the axial stress direction from SX (0°) to SY (± 45°), which is difficult to be observed from mechanical experiments. The FEM simulation provides a cost effective and efficient way for the structural visual optimization design and failure prediction of the actual composite materials. [ABSTRACT FROM AUTHOR]

Li-ion capacitors (LICs) combine the merits of supercapacitors and batteries, which are usually fabricated by battery-type anode and supercapacitor-type cathode. The main challenge for LICs is to make kinetics balance between anode and cathode. Herein, we created a LIC based on superabsorbent polymer salt-derived carbon-based nanomaterials. By annealing the Mn2+ adsorbed polymer salt precursor, the obtained MnO/C anode with a high specific surface area of 762 m2 g−1 displays a high capacity of 540 mAh g−1 at 0.1 A g−1 and an excellent capacity retention of 80% after 500 cycles. The hierarchical porous carbon cathode is generated by the combined carbonization and KOH activation techniques, which exhibits an excellent capacitive storage performance. After well-matched capacity and kinetic behavior in both anode and cathode, the LIC possesses a high energy density of 97.3 Wh kg−1 and a superior cycle life with 80% capacity retention after 10000 cycles. This work gives a case study to fabricate high-performance energy storage devices by using environmentally friendly electrodes. [ABSTRACT FROM AUTHOR]

The nickel-based superalloy GH4099 was diffusion-bonded with 2-10 μm thick pure nickel interlayer. The joint microstructure was characterized by scanning electron microscopy, electron probe micro-analyzer and electron backscattered diffraction; the joint mechanical properties were evaluated by nanoindentation, tensile and Charpy impact tests. It was observed that with the reduction in interlayer thickness, element distribution and hardness across the joining interface became more homogeneous and subsequently produced sound joints due to the suppression of precipitated carbides on joining interface. The strengths of joints were in the range of the base metal as-received. When bonding time or temperatures increased, the bond line of the 2 μm interlayer joint was partially eliminated by the recrystallization across the joining interface, and the strength and elongation (or the absorbed energy) of the joint were same as (or close to) the base metal which underwent the same heating process. However, due to the microstructure degradation induced by the grain coarsening, the absorbed energy of the 2 μm interlayer joint reaches the maximum when the joint bonded under the moderate condition of 1120 °C and 90 min. [ABSTRACT FROM AUTHOR]

A core-shell structure ZnS nanocomposite was synthesized by wrapping ZnS nanoparticles up in graphene-like nano-cell (GLC@ZnS) through chemical vapor deposition. The morphological and structural characteristics exhibit that the obtained GLC@ZnS composite possesses high-quality ZnS nano-sized particles and laminated graphene-like layers shell. When applied as anode materials for lithium-ion batteries, the GLC@ZnS composite (high ZnS content of 97.2%) with diameter of 30 nm delivers high reversible capacities (1134 mAh g−1 after 100 cycles at 0.5 A g−1, 890 mAh g−1 after 200 cycles at 1.0 A g−1) and excellent rate capability (701 mAh g−1 at 8.0 A g−1). The excellent electrochemical performance of the composite is ascribed to the inclosed graphene-like nano-cell, which could localize the active materials and enhance the exchange of charges and ions. [ABSTRACT FROM AUTHOR]