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The wettability of 3 mol% yttria-stabilized zirconia (3YSZ) by molten Cu was noticeably improved by applying a direct current (DC). Furthermore, robust brazing of 3YSZ to a GH3128 superalloy using a Cu filler was achieved within seconds at 1100 °C with the assistance of a DC. When the DC flowed from 3YSZ to GH3128, the shear strength of the joints reached 225 ± 20 MPa at 1 s of energization and increased to 330 ± 30 MPa at 5 s of energization. The formation of Cu51Zr14 at the 3YSZ/Cu interface, the dissolution of Ni into the Cu filler, the dispersive distribution of fine granular (Mo, Cr, W)(Ni, Cu) in the brazing seam and the relief of residual stress by ductile (Cu, Ni) solid solution were crucial for achieving the high-strength joints. This work provides a novel and economical method for ultrafast brazing of zirconia to metals.

The wettability of 3 mol% Y2O3-stabilized ZrO2 (3YSZ) by molten Cu can be greatly improved by applying pulsed currents at 1373 K. The improvement was closely related to current polarity and influenced by duty cycle and frequency. When the Cu/3YSZ interface was under cathodic condition, the wettability was mainly improved by the formation of substoichiometric ZrO2-δ and metallic Zr at the interface. Increasing duty cycle caused the interface to change from forming protrusions to creating depression. Decreasing frequency further deepened the depression. In the opposite polarity, the adsorption and enrichment of oxygen reduced the solid-liquid and liquid-vacuum interfacial energies, thus improving the wettability. Only bubbles formed at the interface. The larger the duty cycle, the more rapidly bubbles formed and escaped. The effect of frequency at this polarity was weak. Overall, this work provides a novel and effective strategy for tailoring the wettability and interfacial chemistry between zirconia and metals.

Conventional reactive air brazing (RAB) of stainless steel (SS) to ceramic components usually encounters Cr oxidation and joint embrittlement problems due to high temperature and long dwelling time. Herein, 3 mol% yttria-stabilized zirconia (3YSZ) and 430 SS were joined using an Ag–CuO filler in seconds at relatively low temperatures (875 °C–1050 °C) with the assistance of a direct current passing through the seam. The applied current promoted the melting of the filler and rapid filling of the gap due to Joule heating effect. Also, it facilitated atomic/ionic transport and interfacial reaction. Key joining parameters including current density, joining time and furnace temperature were investigated, and a maximum joint strength of 158 ± 9 MPa was achieved at a current density of 4 A/cm2 for 30 s at 950 °C, which is approximately 50% higher than that of the RAB joints. The formation of AgCu4Zr and Zr-rich intermetallic phases at the 3YSZ/Ag and Ag/430 SS interfaces, respectively, together with the suppression of the growth of Cr-containing oxide, was responsible for the robust joining.

Rare-earth zirconate ceramics are conventionally sintered at high temperatures for long durations to achieve a full density. Herein, we synthesized and densified five lanthanide-group rare-earth zirconates (Ln2Zr2O7, Ln = La, Nd, Sm, Eu, Gd) containing different numbers of Ln cations in a high-throughput mode using a novel ultrafast high-temperature sintering technique within a cycle of 5 min, and investigated the effects of components on the structure and properties of the resultant ceramics. Under the high-throughput mode, the same sintering conditions make the analysis and comparison of the results more reasonable. The average grain size decreased while hardness and Young’s modulus increased with an increase in the number of the Ln components in the zirconate ceramics. The mechanisms were ascribed to the sluggish diffusion and lattice distortion effect caused by the increase in entropy.

We investigated the wetting of a high-entropy rare-earth oxide, (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr2O7, by a molten 71Ag–27Cu–2Ti (in wt%) alloy using a modified sessile drop method at 1073–1273 K. The wettability shows a first increase and then decrease with increasing temperature, depending on the competition among the adsorption and diffusion of active Ti atoms towards triple line, the consumption of Ti due to interfacial reaction and the migration of oxygen from the substrate bulk to the interface. In addition, the La cations in the high-entropy substrate exhibited noticeable outward diffusion while the other rare-earth cations remained stable due to their different bonding strengths in the lattice. Despite the occurrence of interfacial reaction and selective diffusion, the substrate maintained the high-entropy structure after the reactive wetting.

MnS inclusions in steels usually have many kinds of morphology. It is difficult to accurately obtain the characteristics of inclusions by two-dimensional observation due to the complex morphology o...

AISI 416 steel is a free-cutting stainless steel with a banded structure (BS) that is formed by element segregation, and its secondary phase particles significantly affect its microstructure and properties during the hot working process. In this study, we investigated the formation mechanism of the BS and its relationship with secondary phase particles (MnS and M23C6) in 416 steel by carrying out thermodynamic calculations and high-temperature confocal laser scanning microscopy, electron backscatter diffraction, scanning electron microscopy, and electron probe microanalyzer measurements. The BS was identified to be a delta-ferrite (δ-Fe) phase rich in Cr. In addition, when the volume fraction of δ-Fe was the largest during the solidification process (1392 °C, 1665 K) the BS was most likely to precipitate. The length and width of each grain in the BS were approximately 15 to 20 and 5 μm, respectively. The spacing between the BSs was in the range of 30 to 60 μm. The heat preservation treatment (1170 °C, 1443 K) of the steel could barely improve the shape of the BS. The fine M23C6 particles around the BS enhanced the segregation of Cr and worked with the MnS inclusions to pin the surrounding grains in order to prevent their coarsening during the heat preservation process. The metastable banded structure (MBS) formed near the BS transformed into a martensite phase because the concentration of the segregated Cr in the MBS was not sufficient to stabilize its microstructure. The MnS inclusions pinned and refined the grains and showed four types of distributions, namely between two grain boundaries, between polycrystalline boundaries, within the grains, and throughout the grains.

We achieved the densification of hydroxyapatite (HA) via cold sintering using CaHPO4·2H2O as an additive at temperatures lower than 200 °C and investigated the influences of CaHPO4·2H2O content and temperature on the relative density of cold-sintered HA and its composites. The elastic modulus, compressive strength and flexural strength of the cold-sintered specimens were comparable yet slightly inferior to the level of the dense HA prepared by conventional sintering at temperatures higher than 1000 °C. A possible densification mechanism was proposed for the formation of hydrogen bonds between the CaHPO4 fragments generated by the thermal decomposition of CaHPO4·2H2O and the phosphate groups in HA by water molecules, thus linking the HA particles together. This strategy of achieving dense target product from its hydrated precursors provides an important avenue for the development of cold sintering process.

Pyrochlore-type high-entropy oxides (HEOs) are usually sintered at high temperatures for a long time to achieve full density. Herein, we synthesized pyrochlore-structured (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 HEOs with densities up to 99 % at a furnace temperature of 1200 °C in seconds via reactive flash sintering (RFS). The resultant HEOs achieved compositional uniformity at the atomic level and exhibited superior modulus, hardness and fracture toughness compared to the counterparts prepared by conventional solid-state sintering (at 1600 °C for 6 h). The underlying mechanisms for the ultrafast densification of the RFSed-HEOs were addressed in view of the roles of electric field, rapid heating, external pressure and internal reactions.

Hydroxyapatite (HA)/magnesium (Mg) composites are a promising alternative material for bone repair in load-bearing sites. However, the poor wettability between Mg and HA as well as the extreme sensitivity of Mg to oxidation and high vapor pressure at elevated temperatures makes the preparation of HA/Mg composites rather difficult. Herein, a facile strategy for improving the wettability of HA by Mg was proposed to enable the successful preparation of bio-inspired HA/Mg composites via directional freezing and pressureless infiltration. SiO2 nanoparticles were introduced into the freeze-cast HA scaffold by doping or soaking to promote the spontaneous infiltration of the Mg melt. The resulting HA/Mg composites displayed a delicate biomimetic lamellar structure with alternating ceramic/metal arrangements and demonstrated higher compressive strength (increased by 140%) and wear resistance (increased by 1200%) than porcine bones. In addition, the composites exhibited progressive degradation and surface apatite mineralization in a simulated body fluid environment, making them potentially promising for biomedical applications. This study provides a facile and tailorable method for the design and preparation of novel Mg-matrix composites with bio-inspired structures and biomedical functions.

Conventional ceramic sintering often requires high temperatures and hours of duration to achieve near full density. Herein, we adopted an innovative ultrafast high-temperature sintering (UHS) technique to densify several representative bulk oxides within an isothermal duration of 30 s and a total sintering period of several minutes, and revealed the relationship between ceramic structures and processing parameters. These achievements demonstrate the great potential of the UHS technique in the rapid densification of ceramics. Moreover, this flexible technique is expected to accelerate the material screening rate and facilitate the development of novel materials.

Balancing photovoltaic parameters is very challenging to optimize the device performance of nonfullerene small-molecule acceptor (SMA)-based polymer solar cells (PSCs). We herein employed electron-withdrawing fluorinated or chlorinated 1,1-dicyanomethylene-3-indanone (ICF or ICCl) as the terminal acceptor (A) group to develop two acceptor–donor–acceptor (A–D–A) SMAs, DTCFO-ICF and DTCFO-ICCl, with an electron-rich fluorene-fused dithienocyclopentafluorene as the identical central donor (D) core. Compared with the nonhalogenated counterpart (DTCFO-IC), the two halogenated SMAs possessed a red-shifted absorption spectrum, reduced optical bandgap, and increased charge carrier mobility, but these were accompanied by down-shifted HOMO and LUMO levels, especially for the chlorinated molecule (DTCFO-ICCl). Accordingly, with respect to DTCFO-IC, PSCs based on the two halogenated SMAs with polymer PBDB-T as a donor exhibited an improved Jsc, but a dropped Voc, thus leading to a commensurate power conversion efficiency (PCE) of 6.80% for DTCFO-ICF and an increased PCE of 8.55% for DTCFO-ICCl. To further improve the device performance by means of balancing photovoltaic parameters, polymer PBDB-TF with a lower-lying HOMO level relative to PBDB-T was used to replace PBDB-T as the donor. The PCEs of PBDB-TF-based PSCs were further improved mainly due to the significantly enhanced Voc. Importantly, the DTCFO-ICCl-based PSCs achieved a high PCE of up to 11.03% along with an increased Voc (0.93 V), a further increased Jsc (18.80 mA cm−2), and almost retained FF (63.1%). The enhanced device performance could be attributed to better charge transport and collection abilities, less charge recombination and more optimal active layer morphology. These results argue that combining the halogenation on the A group of an A–D–A acceptor and variation of the paired polymer donor could be an effective strategy to enhance the device efficiency by balancing photovoltaic parameters.

Different cyclization reaction sites on the benzene ring will produce isomers during the cyclization process for the synthesis of small-molecule acceptors. Herein, we developed a structural unit (named BTMe) that can prevent isomerization during cyclization by introducing a methyl into a benzo[b]benzo[4,5]thieno[2,3-d]thiophene (BTBT) unit. Two fused ring electron acceptors (BTMe-C6-2F and BTMe-C8-2F) with the BTMe core were synthesized by changing the length of the side chain. When they were blended with donor PM6, the active layer PM6:BTMe-C8-2F exhibited a more excellent charge transport, phase morphology and π–π stacking, which are beneficial to improve the short-circuit current density (Jsc) and fill factor (FF). Compared with BTMe-C6-2F, the organic solar cell (OSC) based on BTMe-C8-2F exhibited a higher power conversion efficiency (PCE) of 12.72% with a Voc of 0.97 V, a Jsc of 19.65 mA cm−2 and a FF of 66.76%. These results proved that it is a promising approach to achieve a high-performance small-molecule acceptor by changing the length of the side chain and introducing methyl groups to prevent the isomerization of the fused ring core owing to special reaction sites.

Medium- and high-temperature phase change materials are important in the field of heat storage. They usually consist of inorganic salt/ceramic mixtures and require high temperatures for sintering. In this work, cold sintering was applied to fabricate heat storage composites using NaNO3/MgO as a model system. NaNO3 was successfully encapsulated in a MgO skeleton, which maintained stable after 500 melting−freezing cycles. The composites exhibited excellent chemical compatibility and good thermal stability. Moreover, the resultant composites achieved a compressive strength of higher than 100 MPa with relative density over 98% under 75 MPa at low temperatures (≤180 °C) in the presence of 6 wt% water. Compared with the conventional preparation processes that are implemented at high temperatures, this method is very simple, economical and environmentally friendly, and can be applied to the synthesis of other inorganic salt/ceramic phase change materials.

The wettability and reactivity between molten aluminum (Al) and carbon nanotubes (CNTs) are a key issue in the preparation of CNTs-reinforced Al-matrix composites using a solidification route. In this work, we measured the wettability of randomly aligned multi-walled carbon nanotubes (buckypaper) by molten Al at 973–1173 K in a high vacuum using a modified sessile-drop method and examined their interactions using a droplet-sucking technique. The wettability between Al and CNTs is even worse than that of the Al/graphite system. The contact angles are basically larger than 140° and show only a sluggish decrease with time during isothermal dwelling. The chemical stability of CNTs in contact with Al is closely related to their structural integrity. The CNTs with good crystallinity and structural integrity have relatively high chemical stability and exhibit only a weak interfacial reaction with Al at 973 K. However, the stability of structural defective parts is much lower. They are readily eroded by molten Al, leading to the fragmentation of the CNTs. These CNT fragments having an open tubular structure are then rapidly dissolved in molten Al along the axial and radial directions. Simultaneously, a large amount of Al4C3 is formed at the interfaces.

The wettability of TiC by Al alloys plays a key role in the preparation of TiC-reinforced Al matrix composites. Despite some prior work has been reported on this issue, few studies concern the influence of Si. In this work, the effects of Si concentration (0, 7Si, 12Si in wt%) and temperature on the wettability in the Al/TiC system were investigated by a dispensed sessile drop method at 1073–1173 K in a high vacuum. The initial contact angles were 103°–105°, almost independent of temperature, while the final contact angles decreased with increasing temperature. Formation of an Al4C3 phase and adsorption of the displaced [Ti] at the solid–liquid interface were two primary driving forces for the wetting improvement. On the other hand, an increase in the Si concentration greatly weakened the stability of TiC in Al melt, promoted the formation of Al4C3, and thus led to the faster spreading of the liquid in the early wetting stage. However, as the interfacial reaction progressed, the displaced [Ti] was bound by the Si in the Al melt due to their strong chemical affinity, thus weakening the adsorption effect of [Ti] for the wetting. As a consequence, the final apparent wettability of the Al–Si/TiC system was even worse than that of the Al/TiC system, and this situation was more prominent with increasing Si content.

Development of high-performance small-molecular acceptors (SMAs) and an eco-friendly and simple device fabrication procedure is very crucial for scalable production of polymer solar cells (PSCs) in...

We designed a soft Cu-based brazing filler (60Cu–40Ag in wt.%) and investigated its wettability and brazeability with 3 mol% yttria-stabilized zirconia (3YSZ) under direct current (DC) application. Increasing the current intensity dramatically accelerated the spreading rate and decreased the final contact angle. When the DC reached 60 mA, the contact angle decreased from 140° to 50° within 50 s and finally stabilized at 26° in approximately 300 s. The change in the stoichiometry of the 3YSZ substrate and the adsorption of Zr at the triple line were presumably responsible for the electrochemically induced wetting improvement. Furthermore, robust joining of 3YSZ to 304 stainless steel (304 SS) with a shear strength of 215 ± 9 MPa was achieved in only 300 s by applying a DC of 30 mA using this 60Cu–40Ag filler. The AgCu4Zr formed at the 60Cu–40Ag/3YSZ interface was critical for the robust joining. This work provides a novel route for obtaining robust zirconia–metal joints.

We constructed a nacre-inspired laminate-reticular hierarchical architecture in Cu/(TiC−Cr3C2) composites by tuning the wettability between loose freeze-cast ceramic lamellae and Cu melt. This unique architecture takes full advantage of superb intrinsic strength of the ceramic particles and toughness of the metal, stimulating multiple extrinsic toughening mechanisms such as synergistic deformation of the metal and ceramic layers, ductile-ligament bridging and multi-cracking mode. As a consequence, the resultant composites containing ~30 vol% ceramics exhibited exceptional damage-tolerant properties with a fracture toughness of 62.6 ± 1.0 MPa⋅m1/2 and a bending strength of 639 ± 27 MPa.

Multifunctional metal–organic supramolecular hydrogels have achieved great progress nowadays. However, their applications in aqueous batteries for flexible energy storage devices remain limited due...

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 Mg2Si (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.

To develop good rate capability and good cycle stability electrode, hierarchical porous coral-like ZnO/ZnCo2O4/Co3O4 coating was fabricated on a novel 3D straight-through layered copper current collector with one-step solution combustion method and used as self-supporting anode for lithium-ion batteries (LIBs). The coral-like ZnO/ZnCo2O4/Co3O4 coating facilitated the full penetration of the electrolyte and increased the activation rate of the active material. Also, the novel 3D copper current collector has an increased surface area compared to a traditional foam metal, providing an optimal structure for balancing the volume-change tolerance and the energy density of the porous electrode. In addition, the highly oriented structure favors the effective transport of electrons and Li ions within the 3D electrode. As a consequence, high reversible capacity of 1428 mAh g−1 at a current density of 200 mA g−1 after 100 cycles and excellent rate capability of 682 mAh g−1 at 1000 mA g−1 were achieved. This study provides a facile and scalable path toward high-performance self-supporting electrodes for LIBs and demonstrates that the volume density of self-supporting electrodes can be enhanced by increasing surface area of the 3D structured current collector.

High-density hydroxyapatite (HA) compacts were achieved by cold sintering of co-precipitated powders at temperatures lower than 200 °C without addition of any solvent. Critical factors affecting the densification behavior including the source of powders, the type of solvent, applied pressure, sintering temperature and time were investigated. The presence of lattice water together with ion substitution in the co-precipitated HA powders has a significant effect on the densification. A novel viewpoint that is essentially different from classical dissolution−precipitation mechanism in cold sintering was proposed; i.e., the formation of hydrogen bonds between the HA particles plays a critical role in the densification.

Semitransparent polymer solar cells (ST-PSCs) have attracted worldwide attention owing to unique superiority in multiple utilization of incident light. However, the color of ST-PSCs is relatively uniform after fabrication, cannot be dynamically tuned in terms of application requirement. Herein, we demonstrate a high-efficiency ST-PSCs as a smart window, which can be reversibly switched on and off by a gasochromic tungsten trioxide/platinum (WO3/Pt) back reflector layer. The ST-PSCs can be switchable between colored and bleached states with fast response speed of sub-second during hydrogen exposure. Meanwhile, the color and transparency-switching enable light trapping enhancement in long wavelength range, which can systematically improve power conversion efficiency (PCE). As a result, the ST-PSCs contribute a PCE of 10.2% and 9.1% as well as corresponding average visible transmission (AVT) of 25.4% and 33.8% at colored state and bleached state, respectively, which can meet the visual aesthetics requirement well in building integrated photovoltaics. To the best of our knowledge, this is the first example for ST-PSCs that achieve both color-switching and light trapping. Furthermore, the smart windows facing to automobile sunroof are proposed to prove a practical application towards commercialization. We believe that smart windows with gasochromic functions can promise potential opportunities and directions for the future development of ST-PSCs.

The defect of mixed-grain structure with millimeter-grade coarse grains (MCGs) is frequently found in heavy forgings, such as nuclear main pipes manufactured from 316LN steel. Renovation of such kind forgings can only be conducted through recrystallization. However, the allowed deformation is limited because the geometric size of forgings should be maintained during the renovation. For this purpose, the deformation heterogeneity of 316LN steel with mixed-grain structures were studied experimentally, which demonstrated that the MCGs were more inclined to deform than fine grains even if MCGs are with hard orientations. Therefore, a two-stage method was studied to refine MCGs, which takes the advantage of this deformation heterogeneity. The first stage was to impose a limited deformation to the steel at room temperature, suppressing the dynamic recovery and leading the preferentially deformed MCGs to accumulate enough deformation energy storage. The second stage was rapidly heating the deformed materials to realize static recrystallization (SRX). The results showed that the MCGs were completely refined by SRX even if the reduction rate is only 8%. The SRX mechanisms and refining assessments of MCGs under different deformation conditions were discussed. This work, thus, provides an effective method to salvage the heavy structures in engineering.

Fused-ring electron acceptors (FREAs) have attracted immense interest owing to their ability for facile structural modification and good thermal and optical characteristics. Among these acceptors, isomerized building blocks originating from multiple reaction sites affect the electronic structures, morphological properties and resulting photovoltaic performance, but have rarely been studied. Herein, three isomeric FREAs, Z1-aa, Z1-ab, and Z1-bb, were synthesized using different reaction sites of benzo[b]benzo[4,5]thieno[2,3-d]thiophene (BTBT)-based fused-ring cores and were used in organic solar cells (OSCs). As compared to Z1-aa and Z1-ab, Z1-bb exhibited red-shifted absorption and a higher maximum molar extinction coefficient. When blended with PM6, Z1-bb-based OSCs exhibited more balanced charge transport compared to those with the PM6:Z1-aa and PM6:Z1-ab blend films, which favored higher short-circuit current density (Jsc) and fill factor (FF). As a result, the OSC devices based on Z1-bb exhibited a power conversion efficiency (PCE) of 12.66% with Voc = 0.98 V, Jsc = 18.52 mA cm−2, and FF = 70.05%, respectively, which are significantly higher than the values recorded for the Z1-ab-based (PCE of 9.60%) and Z1-aa-based (PCE of 4.56%) devices. These results indicate that the isomerization of a fused-ring core originating from a special reaction site could be a promising approach to achieve high-performance OSCs with high Jsc, Voc, and FF.

Along with the rapidly increasing power conversion efficiency (PCE) of polymer solar cells (PSCs), the stability of PSCs has become one of the crucial issues for the commercial application of this technology. Ternary PSCs exhibit great potential in improving the device efficiency and stability. However, the main cause behind the improvement in the efficiency and stability has been a lack of in-depth investigation. Moreover, the basic working mechanism of ternary solar cells is still ambiguous and it is urgently necessary to further understand it. Here, a small-molecule acceptor (SMA) IDT-OT was developed and introduced into a binary system containing polymer donor PBDB-T (donor) and fullerene acceptor (FA) PC71BM to construct donor/FA/SMA ternary PSCs. The results reveal that the incorporation of IDT-OT into the PBDB-T/PC71BM binary system can improve the PCE up to 9.09% and enhance the thermal stability of the ternary PSCs relative to all the binary systems. In-depth investigations indicate that the enhanced device performance and stability are closely related to an intermixed small-molecule/fullerene acceptor alloy formed by IDT-OT and PC71BM in which the structural nature of the two acceptors is remarkably different. This distinctive alloy system is verified via investigating the dependence of the LUMO energy level and open-circuit voltage on the weight ratio of IDT-OT in the acceptor blend and the miscibility of the two acceptors by morphological characterization and water contact angle measurements. This small-molecule/fullerene acceptor alloy phase is beneficial for improving charge dissociation, collection and transport as well as the carrier mobility, and suppressing bimolecular recombination, thus leading to the increase of Jsc and FF of the ternary PSCs. Interestingly, photoluminescence and donor-free device performance studies demonstrate that there exists not only efficient charge transfer but also Forster resonance energy transfer between PC71BM and IDT-OT, which has rarely been found in previously reported ternary PSCs. Moreover, we suppose the stable active layer morphology benefitting from the formation of this small-molecule/fullerene acceptor alloy as the main reason behind the observed improvement in the thermal stability of the ternary PSCs. This work suggests that introducing an SMA into an FA to form a small-molecule/fullerene acceptor alloy could be a powerful tool to realize high-performance and stable PSCs.

In this contribution, a series of A−π–D−π–A small molecules (SMs), IPY-T-IC, IPY-T-ICCl, and IPY-T-ICF, containing the central donor unit (D) of 6,12-dihydro-diindolo[1,2-b:10,20-e]pyrazine (IPY), the π-conjugated bridge of thiophene, and the end-accepting group (A) of 3-(dic yanomethylidene)indol-1-one, 5,6-dichloro-3-(dicyanomethylidene)indol-1-one, or 5,6-difluoro-3-(dicyanomethylene)indol-1-one, were developed, characterized, and employed as the acceptor materials for polymer solar cells (PSCs). Influences of the different end-accepting groups on thermal properties, spectral absorption, energy levels, photovoltaic performance, and film morphology of these small-molecule acceptors (SMAs) were investigated in detail. These SMAs exhibit an excellent thermal stability and strong crystallization. The absorption spectra of these SMs mainly locate the wavelength between 400 and 700 nm, associated with the optical band gaps in the range of 1.75–1.90 eV. Compared with nonhalogenated IPY-T-IC, the halogenated S...

The wetting of (100), (110) and (111) MgAl2O4 single crystals by molten Al at 1073–1273 K in vacuum was investigated using a dispensed sessile drop method to determine the effect of the substrate orientation on the wettability and reaction in this system. This system is non-wetting in nature. The initial contact angles are generally in the range of 96–106°, slightly decreasing with increasing temperature but without significant dependence on the MgAl2O4 surface orientation. However, the interfacial reaction is sensitive to the MgAl2O4 surface orientation and temperature. No reaction product was observed at 1073 K while the thickness of the Al2O3 product layer was in the order of (100) > (110) > (111) at 1173 K and 1273 K. During the reactive wetting process, significant reconstruction and “whisker growth” occurred at the periphery of the triple line due to the stress created at the substrate surface as a result of volume change between the reactant and product, and the morphology of the “whiskers” was closely related to the MgAl2O4 crystal orientation. The formation of these “whiskers” not only affected the wetting behavior but also weakened the dependence of the wettability on the MgAl2O4 surface orientation.

Electrically actuated movement of liquid metals is quite promising in mechanical engineering and applied physics. However, little work has so far been performed on the effect of current polarity on the actuation of the eutectic gallium–indium (EGaIn) alloy moving on metal substrates. In this work, the spreading of EGaIn on copper (Cu) substrate under different direct-current (DC) polarities in the 0.5 mol/L NaOH solution was investigated, and the underlying mechanisms were addressed. When the Cu substrate was connected to cathode, the wetting was essentially attributed to the reduction in the oxidized surface of the Cu substrate; whereas, under the opposite polarity, the spreading was related to the tension gradient along the EGaIn–solution interface, which induced Marangoni flow, despite the fact that the EGaIn–Cu system was non-wetting in this case.

We proposed a new strategy of combining dynamic freeze casting with pressure infiltration and successfully prepared an antler-bone-inspired gradient metal-ceramic composite. As exemplified by Al-7Si-5Cu/Al2O3, the resultant composite exhibits the unique mechanical properties of being externally hard, strong, and wear-resistant but internally soft and tough owing to its compositional and structural gradients and delicate lamellar microstructures. This study offers a feasible, flexible, and scalable approach to designing and preparing functionally gradient materials with biomimetic structural features and exceptional properties.

Nacre-inspired laminated composites have been proven to possess a unique combination of strength and toughness. In this study, we fabricated nacre-mimetic Cu/TiC composites via unidirectional freezing of aqueous TiC slurries containing different amounts of NiO additives, followed by ice sublimation, carbothermal reduction of NiO to Ni during sintering and then gas-pressure infiltration of the Cu melt. The introduction of Ni greatly facilitated the densification of ceramic lamellae and enhanced the interfacial bonding between Cu and TiC. The resultant composites displayed outstanding damage tolerance and anisotropic electrical conductivities. Specifically, for an ∼31 vol% TiC–Cu composite containing 24 wt% Ni in the ceramic lamellae (based on the TiC content), a fracture toughness (KJc) of 72.5 ± 1.0 MPa·m1/2, work of fracture of 53.4 ± 3.5 kJ/m2, bending strength of 725 ± 11 MPa and longitudinal electrical conductivity of 22.7 MS/m (∼60% of the Cu matrix) were achieved, which were approx. 81%, 536%, 122% and 97% higher than those of the Ni-free composite, respectively. Noticeable toughening was demonstrated to be a consequence of multiple cracking, plastic deformation and uncracked-ligament bridging of the metal layers, as well as crack deflection and blunting. On the other hand, significant strengthening resulted from tailoring the microstructures in the ceramic layers and at the Cu/TiC interface as a result of Ni doping. We believe that the facile strategy adopted herein provides an effective way to solve the problems of wetting and bonding related to metal infiltration and can be readily extended to the preparation of other nacre-inspired metal−ceramic composites.

Herein, we adopted a simple way to fabricate nacre-inspired “brick-and-mortar”-structured composites with freeze-cast alumina and pure Al. The ceramic layer thickness (2.5–16.6 μm) and alumina volume fraction (8–48%, resulting from the volume shrinkage of the scaffolds after sintering) were controlled by varying the slurry concentration (5, 10, 15 and 20 vol%). The Al/8 vol% Al2O3 composite, with a relatively thick metal layer (24.8 ± 5.7 μm) and low density (2.78 g/cm3), exhibited a bending strength of 319 ± 13 MPa and fracture toughness of 138 ± 7 MPa m1/2. Compared to the Al/8 vol% Al2O3 composite, the Al/20–48 vol% Al2O3 composites had higher bending strengths (332–368 MPa) but lower fracture toughness values (87–41 MPa m1/2). The relationships between the cracking modes and structural features in the composites were discussed to account for the strengthening and toughening mechanisms. This work provides new ideas and solutions concerning the design and fabrication of nacre-mimetic metal-ceramic composites.

In the present study, the wettability between liquid iron with two different Al contents and MgO Al2O3 binary substrates was studied in reducing atmosphere. The contact angles between liquid iron with 18 ppm Al and MgO, MgO·Al2O3, Al2O3 were 133.5°, 113.7°, 126.9° respectively. With the variation of the substrate composition, the contact angles for the intermediate binary phases of the three components (MgO, MgO·Al2O3, Al2O3) obeyed the Cassie theory. In the experiment using iron with 370 ppm Al, all the contact angles were higher than that using low Al-containing iron. The surface of the iron drop was covered with an oxide layer, which mainly consisted of many small particles. With the variation of the substrate gradually from MgO to Al2O3, the composition of the oxide layer changed from MgO·Al2O3 to CaO Al2O3. The formation of the oxide layer prevented the spreading of liquid iron, leading to the increase of the contact angle.

The effects of current polarity, temperature and current intensity on the wettability of 3 mol% yttria-partially stabilized zirconia (3Y-PSZ) by molten 72Ag–28Cu were investigated using a direct current (DC)-coupled sessile drop method. The wettability was significantly improved with the assistance of a DC, especially when 3Y-PSZ was connected to anode. Noticeably, the contact angle rapidly decreased from 143° to smaller than 20° when the current intensity was larger than +10 mA. The wettability also showed abnormal dependence on temperature, presumably due to the competition between nucleation and growth of the m(AgCu4Zr) phase at the interface. The mechanisms for the significant improvement in the wettability under the DC application were ascribed to the formation of substoichiometric ZrO2-δ, the release and adsorption of metallic Zr, and the formation of wettable m(AgCu4Zr) phase at the interface. The DC-assisted wetting provides a new strategy for the rapid and robust joining of 3Y-PSZ to metals.

Ion implantation has played a unique role in the fabrication of optical waveguide devices. Tb3+-doped aluminum borosilicate (TDAB) glass has been considered as an important magneto-optical material. In this work, near-infrared waveguides have been manufactured by the (5.5 + 6.0) MeV C3+ ion implantation with doses of (4.0 + 8.0) × 1013 ions·cm-2 in the TDAB glass. The modes propagated in the TDAB glass waveguide were recorded by a prism-coupling system. The finite-difference beam propagation method (FD-BPM) was carried out to simulate the guiding characteristics of the TDAB glass waveguide. The TDAB glass waveguide allows the light propagation with a single-mode at 1.539 μm and can serve as a potential candidate for future waveguide isolators.

Wetting of SiC by Al alloys is a key issue in the preparation of SiC-reinforced Al matrix composites. The wettability could be improved by alloying of Al, yet controversial results widely exist in the literature. We investigated the effects of four important alloying elements (Si, Cu, Ti and Mg) and their concentrations on the wettability in the Al/SiC system using a dispensed sessile-drop method. The results demonstrate that Si could weaken or even inhibit the formation of Al4C3 and substantially improve the wettability via an adsorption effect; Cu slightly deteriorates the wettability, but alleviates the formation of Al4C3 by decreasing the activity of Al; Ti strongly adsorbs at the solid−liquid interface, forming TiCx instead of Al4C3, and thus significantly improves the wettability; Mg may also favor the wettability due to its help in the disruption of the oxide film covering the Al surface via evaporation and its strong affinity for the silica film on the SiC surface; but for a clean Al/SiC system, the effect of Mg is essentially limited. In addition, the evaporation of Mg always leads to a reduction in the drop volume, which causes a decrease in the apparent contact angle, but this effect is usually neglected.

Freeze casting has been widely used in the preparation of nacre-inspired composites because of its prominent advantages in controlling the fine structure of ceramic scaffolds. However, the ceramic-phase content in composites prepared by this method is much lower than that in nacre due to the limitations of the dispersion and viscosity of the ceramic slurry. In this work, we combined the ideas of freeze casting and in-situ reaction to prepare nacre-inspired lamellar composites with high hard-phase contents. We first prepared the TiO2-−SiO2 porous scaffold with an initial solid loading of 20 vol% via unidirectional freeze casting and then infiltrated it with a 6061Al alloy. During the reaction process, the TiO2-SiO2 layers were progressively transformed into Al2O3 layers, and the Al layers were transformed into Al3Ti. Composites with different hard-phase volume fractions (approx. 29%, 38%, 52% and 65%) and different interfacial bonding strengths could be obtained by altering the infiltration temperature. Increases in the hard-phase content and the interfacial bonding strength substantially enhanced the bending and compressive strengths of the composites, with maximum values of 350 MPa and 854 MPa, respectively, achieved in the composites with approx. 65 vol% hard phases. However, the highest fracture toughness of 42.9 MPa m1/2 and maximum fracture work of 3.6 kJ/m2 appeared when the hard-phase content in the composite was approx. 38 vol%, sharing an appropriate interfacial bonding strength. A robust interface favors stress transfer but impedes crack deflection, while a weak interface fails to bear loads, even though it is conducive to crack deflection. A moderately-strong interface together with a considerable amount of layered soft phase contributes to the generation of multiple-cracking, and thereby greatly toughens the metal−ceramic composite.

The strength and toughness of a material are generally two mutually exclusive properties. Optimization of these properties can be realized by regulating microstructures based on a bio-inspired idea. Herein, we used gelatin as a pore-regulating agent to investigate the effect of microstructural transition from “nacre-like” lamellae to “honeycomb-like” reticulae on the mechanical properties of metal–ceramic composites. By introducing different quantities of gelatin into SiC slurries during freeze casting and infiltrating the sintered SiC scaffolds with pure molten Al, we prepared the Al/SiC (88/12 in volume) composites with variable yet controllable microstructures and further demonstrated that the desired properties could be achieved by tailoring their microstructures. Specifically, the Al/SiC composites with a fully laminated structure exhibited optimal fracture toughness (KJc) of 51.9 ± 2.9 MPa m1/2 while those with a three-dimensional reticular structure displayed peak three-point flexural strength of 371 ± 6 MPa. The relationship between the microstructures and mechanical properties of the composites was addressed based on material strengthening and toughening mechanisms.

The construction of a hierarchically ordered “brick-and-mortar” structure with a high content of “brick” phase is a key challenge in the preparation of nacre-mimetic composites. Herein, inspired by the transverse cracks in the ceramic lamellae after freeze-drying caused by the secondary nucleation of ice crystals during directional freezing of water-based ceramic slurry, we propose a new idea to use these structural defects and an in-situ reaction to construct composites with a nacre-like “brick-and-mortar” structure and high hard-phase content. This uses ice-templating to first prepare lamellar TiO2 scaffolds with transverse cracks that separated the ceramic lamellae into “brick” whose size was controlled by adjusting the initial ceramic particle size (50, 300, and 700 nm). After the reactive infiltration, these cracks were filled with molten Al, leading to the formation of a “brick-and-mortar” structure with a high hard-phase content (86 vol%). The increasing ceramic particle size reduced the hard-phase content but significantly increased the aspect ratio (height/width) of the ceramic “brick” and the fracture toughness. The excellent damage tolerance was attributed to multiple toughening mechanisms, i.e., multiple cracking, crack deflection, and uncracked-ligament bridging of the metal layers. The existence of “mortar” increased the probability of the formation of multiple cracking.

Taking account of the fascinating properties of photovoltaic materials with conjugated side chains and the great influence of side-chain engineering on molecular structures and optoelectronic properties, we herein successfully developed three novel A–D–A (A = acceptor unit, D = donor unit) type small molecular acceptors (SMAs), IDTV-PhIC, m-IDTV-PhIC, and IDTV-ThIC, based on a methylene-modified indacenodithiophene (IDT) donor building block (IDTV), in which four flanking aryls were introduced as the conjugated side chains by grafting onto the two ethylene bridges of the IDT unit. The effects of the conjugated side chain and its type (phenyl vs. thienyl) as well as the substitution position (para vs. meta) on the molecular structures, physicochemical properties, charge transport properties, film morphology and photovoltaic performance of these SMAs have been investigated systematically. Compared to the control molecule IDT-PhIC based on IDT, the three IDTV-based acceptors exhibit extended conjugation in the vertical direction, which can enlarge the π-electron delocalization region along the molecular backbone and thus broaden the absorption spectra, reduce the bandgaps and elevate energy levels. Additionally, the conjugated side chains far away from the framework of the IDTV segment can enhance the rigidity, resulting in decreased solubility and improved charge transport properties of the SMAs. Because of the synergistic effects of changing the conjugated side-chain type and substitution position, m-IDTV-PhIC with meta-hexyloxyphenyl as the conjugated side chains exhibits relatively good solubility, a broad absorption spectrum and a high-lying LUMO energy level, moderate molecular planarity and better charge transport properties and film morphology, which are beneficial for achieving higher Voc, Jsc, and FF in devices compared to the control IDT-PhIC and the other IDTV-based SMAs IDTV-PhIC and IDTV-ThIC. As a result, among these acceptors, a polymer solar cell (PSC) fabricated with m-IDTV-PhIC as an acceptor and polymer PBDB-T as the donor delivers the best PCE of 5.85% with both the highest Voc (0.99 V) and Jsc (11.58 mA cm−2). This work not only provides a simple and effective strategy for developing new A–D–A type SMAs with conjugated side chains but also proves that the side-chain modification is an effective approach to optimize photovoltaic performance of the acceptors in PSCs.

The activity of oxygen evolution reaction (OER) catalysts is strongly dependent on the activity of each catalytic site, which can be improved through interactions among the species present, and the number of accessible catalytic sites, which can be increased by downsizing the electrocatalysts. In this study, small sized Fe–Co sulfide nanoclusters (2–3 nm) in situ anchored on carbon were designed and prepared as an OER catalyst. Due to the smaller size, a large number of catalytic sites are exposed. The optimized Fe–Co bimetal sulfide nanoclusters/carbon composite exhibits an overpotential of only 247 mV to deliver a current density of 10 mA cm−2 and a low Tafel slope of 35 mV dec−1. In addition, the formed nanocluster catalyst also showed superior stability without activity decay and metal component dissolution during the OER process. Experimental and theoretical calculations indicate that on the Fe–Co sulfide nanoclusters, Fe sites are preferred to enrich the sulfide surface; surface oxidation will occur during the OER process in alkaline electrolyte forming Fe–Co–S–O species. The electron transfer interactions from Fe to S sites induce stronger acidity on Fe sites, which would facilitate OH− and water adsorption, thus inducing the enhancement of electrocatalytic performance.

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.

Semitransparent polymer solar cells (ST-PSCs) have become novel photovoltaic technologies because of their extensive applications such as in building integrated photovoltaics (BIPV); however, their power conversion efficiency (PCE) is still lagging behind that of opaque PSCs mainly due to insufficient light harvesting. Herein, we demonstrated high-efficiency ST-PSCs by controlling the optical Tamm state (OTS) formed at the interface between thin silver (Ag) electrodes and extra added layer (EAL)/one-dimensional photonic crystals (1DPCs). The transmission groove of Ag/EAL/1DPCs was gradually red-shifted and broadened by tuning the position and intensity of the OTS; this resulted in a PCE as high as 9.36 ± 0.16% and an average visible transmission (AVT) of 14.31 ± 0.65% in the visible range along with tailor-made color. Simulation results obtained by transfer matrix modeling (TMM) demonstrated that the photoelectric field intensity could be redistributed by controlling the OTS; this led to an enhancement in the absorption of the ST-PSCs. We believe that the light management method of controlling the OTS can have the significant promise to speed up the commercial applications of colorized ST-PSCs in BIPVs.

This study proposes an analogous active suspension system consisting of an air spring with adjustable spring coefficient K and a hydraulic damper with adjustable damping coefficient C. This system changes the spring coefficient K of the suspension system by adjusting the internal pressure of the air spring. It also changes the displacement and changes the chassis height of the vehicle. In the damping part, the internal diaphragm of the hydraulic damper is rotated by the motor to adjust the damping coefficient of the suspension system damper, so as to achieve the purpose of damping and stabilizing the vehicle body. In this study, the relationship between the force and displacement was measured by simulating a quarter of the actual vehicle's weight on the air spring of the suspension system with the payload spring pressurized, and the characteristics of the air spring were learned. In addition, the dynamic simulation of the analogous active suspension system is performed by inputting the pavement function characteristics to understand the dynamic response of the suspension system to the vehicle, and then the air spring and the hydraulic damper are adjusted to achieve the most appropriate riding condition.

A novel technique termed cold sintering process (CSP) was introduced for the preparation of high-performance chitosan/hydroxyapatite bulk materials. The chitosan/hydroxyapatite nanocomposite powders were first synthesized by co-precipitation in an alkaline aqueous solution and then pressed at 100°C under 600 MPa to yield a relative density over 90%. The effects of key processing parameters including sintering temperature, pressure, dwelling time and composition on the densification behavior were investigated and the densification mechanisms were explored. The flexural and compressive strengths of the cold-sintered samples were significantly higher than those prepared by conventional cold pressing. Moreover, the cold-sintered samples showed good biological activity in a simulated body fluid environment. Overall, this work demonstrates that CSP is a simple yet effective and economical method for the development of high-performance organic/inorganic bio-composites.

Directionally aligned prismatic and lamellar porous alumina scaffolds with a high strength-to-density ratio were fabricated from submicron Al2O3 powders and a tiny quantity of nanoscale TiO2 sintering aids by freeze casting using TBA and water as solvents. Both freezing temperature (− 10 °C, − 50 °C, − 90 °C) and sintering temperature (1300 °C, 1350 °C, 1400 °C) were varied to adjust pore parameters while a low solid loading (15 vol%) was maintained to ensure high porosity. This paper describes and compares the microstructures, porosity, pore size, wall thickness and compressive behavior of the scaffolds with two typical pore morphologies (lamella and honeycomb), which help to identify their scope of application and to unveil the relationship between pore morphology and mechanical property to optimize the material performance. The failure modes of these two types of scaffolds under compression were simulated. The TBA-based 1 wt% TiO2-containing alumina scaffolds with dense ceramic walls that were freeze-cast at − 90 °C and sintered at 1400 °C exhibited a compressive strength of 160 MPa with a porosity of 59%, indicating lightweight and high-strength characteristics.

In this work, a low-cost technique combining MIG welding and lateral powder injection was developed to fabricate B4C particles-reinforced aluminum matrix composite (AMC) layer on a T6 heat-treated 7075 aluminum alloy (AA7075-T6) substrate. The AMC layer was 6-7 mm thick and well bonded to the substrate. The B4C particles were dispersed throughout the AMC layer with an average content of approximately 7 vol.%. No significant reaction products existed either at the particle–matrix interface or in the Al-matrix. In pin-on-disk dry sliding wear tests against Al2O3 grinding wheels, the AMC layer exhibited excellent wear resistance with volume wear rate approximately 1/10-3/10 that of the quenched AISI 1045 steel and only approximately 2-7% that of the AA7075-T6 alloy under the same wear conditions. A small addition of ceramic particles can greatly improve wear resistance, suggesting that this technique has good prospects for a wide variety of applications.