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Abstract In the present research, we produced porous silicon carbide (SiC) scaffolds with lamellar and uniformly distributed structures by unidirectional and quick freeze casting, respectively. Subsequently, we prepared the ZL205A/SiC composites with lamellar and uniformly distributed structures by infiltrating a molten ZL205A alloy into the porous SiC scaffolds. The influence of freezing speed on the damage-tolerance behavior and the toughening mechanism of the resultant composites were investigated. We found that because of multiple toughening mechanisms, the layered composites exhibited much higher strength and toughness as compared with the uniformly distributed composites. The lamellar composites manifested superior specific modulus and a unique combination of specific strength and toughness, which was comparable to those of titanium and magnesium alloys. We also observed that the thicknesses of alloy layers and SiC lamellae of the composites reduced with decreasing cooling temperature in freeze casting. Furthermore, the refinement of lamellae size at higher freezing speeds caused a decrease in the damage-tolerance ability of the composites because of weak toughening effect. Graphical Abstract Unlabelled Image Highlights • The ZL205A/SiC composites with lamellar and uniformly distributed structures were prepared. • The microstructure of the composite was adjusted by manipulating the freezing rate of the SiC slurry. • Lamellar composites exhibited much higher strength and toughness as compared with the uniformly distributed composites. • The refinement of lamellae size caused a decrease in damage-tolerance ability of the composites. [ABSTRACT FROM AUTHOR]

Silicate-bonded porous SiC scaffolds with lamellar structures were prepared by freeze casting and liquid-phase sintering. It was found that the viscosity and solidification velocity of SiC water-based slurries with 30 vol% solid loading decreased with increasing Al 2 O 3 –MgO (AM) addition. As the AM content increased from 10 to 30 wt%, the lamellae of the sintered scaffolds became denser and the porosity decreased from 69±0.5% to 62±0.5%, while the compressive strength improved from 25±2 to 51±2 MPa. The dynamics of pressureless infiltration for an Al–12 Si–10 Mg alloy on the SiC porous scaffold was measured and the composites with lamellar-interpenetrated structures were successfully produced. Both the compressive strength and the elastic modulus of the composites increased with increasing AM content. The maximum strength reached 952±24 MPa and the highest elastic modulus about 156 GPa, respectively, in a longitudinal direction, increasing about 32% and 11% as compared with those of the composites without AM. [ABSTRACT FROM AUTHOR]

Porous laminated SiC scaffolds with initial solid loadings of 20–40 vol% were prepared by freeze casting and then sintered at 1200 °C for 2 h in air to produce a SiO 2 layer. Subsequently, the preforms were pressureless-infiltrated by an Al–12 wt% Si–10 wt% Mg alloy in a N 2 atmosphere, forming a lamellar-interpenetrated structure in the composites. The resultant composites were investigated by compression tests and ultrasonic pulse echo measurements in the longitudinal and transverse directions, exhibiting weak orthotropic properties. The highest compressive strength (722±35 MPa) was achieved in the samples with 30 vol% SiC in a longitudinal direction and the largest elastic modulus (163 GPa) was exhibited in the 40 vol% SiC composites. [ABSTRACT FROM AUTHOR]

Alloys, especially Mo–Ni alloys, are excellent HER electrocatalysts in alkaline solution. The HER activity of the Mo–Ni alloys can be improved by grafting H2O dissociation promoters (metal oxides or hydroxides) to promote the dissociation of H2O in alkaline solution. However, most of the reported Mo–Ni alloys grafting with H2O dissociation promoters only have simple one-dimensional (1D) structures, which cannot further improve the catalytic performance. Compared with 1D nanomaterials, two-dimensional (2D) nanomaterials have higher specific surface area, electrical conductivity, more exposed active sites and mass transfer channels. Herein, a novel 2D nanosheets self-supporting composite electrocatalyst MoNi4/MoO2.5-NF derived from the NiMoO4 nanosheets was reported for the first time. Benefiting from the unique 2D nanosheets structure and the synergistic effect of each component, the catalyst shows high electrocatalytic HER activity in 1 M KOH solution. The MoNi4/MoO2.5-NF needs overpotential of 49 mV to reach 10 mA cm−2. The HER activity of MoNi4/MoO2.5-NF can be further improved through electrochemical-cycling activation (CV) process. After 10 CV cycles, the overpotential to reach 10 mA cm−2 of the catalyst decreased from 49 to 27 mV and even exceeded 20% Pt/C (32 mV). The improvement of HER performance is attributed to the increase in the electrochemically active surface area, the reduced impedance and Tafel slope after CV process. [ABSTRACT FROM AUTHOR]

A nacre-like magnesium matrix composite with high carbon nanotube (CNT) contents (up to 4.40 wt%) was successfully prepared under the combined effects of bidirectional freeze casting, pressureless infiltration, and hot pressing. The bidirectional freeze casting was carried out to fabricate large-scale parallelly layered CNT scaffolds. The spontaneous infiltration of an AZ91 magnesium alloy was achieved using nano-silica as the wetting promoter, and MgO and Mg 2 Si (reaction products) provided the strength of the as-synthesized composites. Furthermore, the hot pressing increased the average thickness ratio of reinforcing phase/alloy layers in the AZ91/CNT composites from 0.89 (before hot pressing) to 1.46 (after hot pressing) and also significantly improved the specific strength from 142.3 MPa/(g⋅cm−3) to 158.7 MPa/(g⋅cm−3) without sacrificing the specific toughness ((17–18) MPa⋅m1/2/(g⋅cm−3)). The resultant composites were mainly strengthened by CNTs, reaction products, and the strong interfacial bonding between CNTs and the Mg matrix. The key toughening mechanisms for the as-prepared composites were crack deflection, branching, and CNT pull-out. This study provides a new idea for the economical and efficient preparation of lightweight and damage-tolerant composites with high CNT contents. Image 1091852 [ABSTRACT FROM AUTHOR]

Novel bio-inspired ZL205A/SiC composites with a lamellar-interpenetrated structure were successfully fabricated via gas-pressure infiltration of a commercial ZL205A alloy into freeze-cast porous SiC scaffolds. The influences of initial ceramic content (20, 30 and 40 vol%) on the microstructure and damage-tolerance behavior of the resultant composites as well as their toughening mechanism were investigated. With an increase in the ceramic content in the composite, the flexural strength and fracture toughness in the longitudinal direction gradually decreased; whereas, in the transverse direction they showed a first increase and then decrease but their elastic modulus increased. The composites displayed significant damage-tolerance anisotropy, with higher strength and toughness in the longitudinal direction (parallel to the lamellae) than that in the transverse direction (perpendicular to the lamellae). In the longitudinal bending, the ZL205A/20 vol%SiC composite exhibited the maximum flexural strength (760 MPa) and the largest fracture toughness (33.0 MPa m 1/2 ). The excellent damage tolerance of the composites was attributed to multiple toughening mechanisms such as plastic deformation in the matrix alloy, crack blunting, deflection and branching, and uncracked-ligament bridging of the ductile alloy layers. However, in the transverse bending, the crack propagated along the ceramic layer in the composites and thus greatly weakened their damage-tolerance capability. [ABSTRACT FROM AUTHOR]

Lightweight and high-strength AZ91/SiC composites with lamellar structures were successfully prepared by using freeze casting (ice-templating) and reactive infiltration techniques. The infiltration dynamics was measured and activation energy calculated to be 7.74 kJ/mol. The compressive and flexural strengths of the composites with 30 vol% initial solid load reached 743±20 MPa and 599±44 MPa, about 1.8 and 1.5 times of those of the AZ91 alloy, respectively. [ABSTRACT FROM AUTHOR]

A POP-based electrochemical aptasensor has been successfully designed and fabricated, which has outstanding physicochemical stability, reproducibility and reproducibility. Meanwhile, this fabricated aptasensor has ultrahigh selectivity and out-bound sensitivity toward AMP even in various real samples. • An exceptionally stable POP-based electrochemical aptasensor was successfully fabricated and used to detect ampicillin. • This biosensor exhibits the lowest LOD of 1.33 fg·mL–1 (3.30 fM). • This aptasensor has the ability to precisely identify ampicillin in various real samples. A novel porous organic polymer (POP) was designed and prepared by the coupled polymerization of 1, 3, 6, 8-Tetraphenylpyrene and α , α ′-dibromo- p -xylen. The as-synthesized POP is an extended π -conjugation framework with high surface area, excellent stability and large pore cavity, thus bestowing the outstanding carrying capacity of aptamer strands through π-π stacking interaction to rationally fabricate a ultrasensitive electrochemical aptasensor. The biosensor exhibits the lowest limit of detection of 1.33 fg·mL–1 (3.30 fM) for detecting trace ampicillin (AMP) by using electrochemical impedance spectroscopy. Furthermore, this biosensor can accurately monitor AMP in multiple real samples. This work provides the greatly potential applications of POPs in the fabrication of electrochemical biosensors for sensitively detecting antibiotics or other analytes. [ABSTRACT FROM AUTHOR]

The rapid accumulation of CO 2 , as the main component of greenhouse gas, causes the global warming and significant climatic variation along with a series of environmental problems. At the moment, the adsorption and capture of CO 2 is identified as one of the most promising and effective methods to control and reduce CO 2. Hence, it is in urgent need of constructing highly efficient porous materials with excellent stability to capture CO 2. A porous organic polymer (denoted as sf-PTPTCz) is firstly designed and synthesized by the FeCl 3 -trigged oxidative coupling polymerization of tetrakis (4-(9H-carbazol-9-yl)phenyl)methane (TPTCz) via the solvent-free mechanochemical approach, which is an environmentally friendly preparation method and industrialized mass preparation. The as-synthesized porous material is further investigated by 13C solid-state NMR, Fourier transform infrared, powder X-ray diffraction, transmission electron microscope, scanning electron microscope, and gas sorption. By virtue of high surface area and excellent stability, the as-synthesized porous sample exhibits a high CO 2 adsorption ability and an excellent selectivity of CO 2 over N 2. A carbazolic POP with high surface and stability is constructed successfully by the solvent-free mechanochemical approach, which exhibits an outstanding CO 2 sorption ability under the mild condition. Image 1 [ABSTRACT FROM AUTHOR]

Al−7Si−5Cu/Al 2 O 3 −ZrO 2 composites with nacre-like structures were prepared via ice-templating and gas pressure infiltration techniques. The composites were subsequently heat-treated at 850 °C for 0, 30, 60, 90 and 120 min to regulate the interfacial reaction between Al and ZrO 2 . The yield of larger (Al 1−m , Si m ) 3 Zr and ZrSi 2 phases increased with longer dwell times. The compressive strength initially increased and then decreased. The highest strength was observed in composites treated for 60 min and reached 1600±40, 1261±30 and 1033±22 MPa at temperatures of 20, 150 and 300 °C, respectively. These values increased by 30−40% as compared to those of the non-treated counterparts and were 2-, 5- and 12-fold more than those of the matrix alloy, respectively, which is demonstrative of the material's excellent load-bearing capacity, particularly at elevated temperatures. [ABSTRACT FROM AUTHOR]

Inspired by nacre, we designed biomimetic metal–ceramic composites in which hard and ductile phases were alternately arranged. We first prepared lamellar-structured TiC scaffolds with 25, 30 and 35 vol% solid loadings using a unidirectional freeze casting technique and then measured wetting and infiltration dynamics for a commercial Al cast alloy, ZL107, with the main composition of Al–7Si–5Cu on the porous TiC scaffold using a modified sessile drop method at 850 °C. The wetting was affected by liquid spreading at horizontal surface and infiltration in depth, while the latter played a dominant role in the decrease in contact angle. On the basis of the wetting results, the lamellar ZL107/TiC composites were successfully fabricated by pressure infiltration of the molten ZL107 alloy into porous TiC scaffolds and their mechanical properties were evaluated. The compressive strength and elastic modulus increased while bending strength decreased with increasing TiC content, giving maximum values of 1166 ± 20 MPa, 205 ± 2 GPa and 363 ± 5 MPa, respectively. Formation of (Al m ,Si 1 − m ) 3 Ti, Al 3 Ti and Al 4 C 3 phases in the composites was presumed to deteriorate the toughness of the composites, leading to brittle fracture under loading. [ABSTRACT FROM AUTHOR]

Highlights: [•] Bismuth telluride alloyed nanorods were synthesized by hydrothermal method. [•] Nanorods with 500nm in length are stacked by nanoplates along the c axis. [•] BiTe and Bi2Te3 domains randomly distributed in the alloyed nanorods. [•] The formation of inhomogeneous nanorods is related to the spiral structure of Te. [•] Thermoelectric properties were measured after consolidating by two sinter methods. [Copyright &y& Elsevier]

Freeze casting is a versatile approach for the design of lamellar metal−ceramic composites with unique combination of strength and toughness. However, previous studies mainly focused on ceramic factors such as content and lamellae structure, seldom concerning the effects of metal property and interfacial structures, which, in practice, are key factors in determining the mechanical performances of the composites. In this work, we prepared three kinds of Al/TiC lamellar-interpenetrated composites with different matrix compositions (pure Al, 6061Al (Al−0.4Cu−1.0Mg−0.6Si) and ZL107 (Al–7Si–5Cu)) via freeze casting and pressure infiltration, aiming at clarifying the roles of matrix property and interfacial reaction on the mechanical properties and fracture mechanisms of the composites. The flexural strengths of pure Al/TiC, 6061Al/TiC and ZL107/TiC composites reached 355 ± 10, 415 ± 15 and 459 ± 18 MPa, while the toughness values (characterized by crack-growth toughness) were 81.0 ± 2.0, 57.6 ± 1.2 and 43.4 ± 1.5 MPa m1/2, respectively. The exceptional damage tolerance of these lamellar composites was attributed to multiple toughening mechanisms such as crack deflection, uncracked-ligament bridging of ductile layers and plastic deformation of the metal matrix. However, the presence of Si in the 6061Al and ZL107 alloys weakened the stability of TiC and promoted interfacial reaction, leading to the formation of a certain number of (Al 1-m , Si m) 3 Ti and Al 4 C 3 , which greatly weakened the toughness of the composites. Due to the combined effects of alloy plasticity, lamellar-interpenetrated structure and interfacial reaction, the fracture of the materials changed from a multiple cracking mode in the Al/TiC composite to a single crack propagating mode in the 6061Al/TiC and ZL107/TiC composites. [ABSTRACT FROM AUTHOR]