Internal architecture of tissue scaffolds plays a significant role in their ability to heal critical-size bone defects. Many studies have investigated these effects but lack isolating architectural features in 3D space, hindering optimization of pore shape to improve bone ingrowth and consequently clinical outcome. To address this challenge, we developed a systematic design strategy and a high-fidelity and -precision ceramic printing technique using a stereolithography desktop printer. We used these techniques to print 5 scaffold architectures with different surface convexities/concavities, pore interconnectivities, and permeabilities, while maintaining the same porosity, average pore size, and surface area. We determined the mechanical effects of the architecture using mechanical tests with in-situ imaging, finite element, and computational fluid dynamic simulations. The effects of architecture on bioactivity and bone ingrowth were determined in a rabbit calvarial critical-size defect model at 12-week implantation, using µ-computed tomography, and histology. The results showed that bone ingrowth is significantly affected by pore interconnectivity in 3D space and maximum fluid permeability in 3D regardless of flow direction, but not permeability in one or few directions. Surface convexity/concavity did not affect bone formation in our 3D scaffolds. Bone ingrowth in scaffolds with highly interconnected pores resulted in a significantly tougher and stronger bioceramic/bone composites, compared to the inherently brittle scaffolds pre-implantation. Our findings provide a rational design of 3D scaffolds architectures for effective translation to the clinic and could be used to predict the tissue regeneration capacity of scaffolds with other architectures or made of other materials. Graphical abstract Download : Download high-res image (162KB) Download : Download full-size image

Binder jet three-dimensional (3D) printing has been extensively developed since the early 1990s and is widely applied in various industrial fields. Binder jetting 3D-printed products have anisotropic mechanical properties; however, no study has provided a systematic explanation of this mechanism. Herein, we propose that the crystal lattice model based on the crystallographic logic can explain the mechanical anisotropy and fracture mode of 3D-printed products based on the nozzle pattern (resolution) of the print head. In this study, calcium sulfate-base powder was hardened by ejecting different amounts of water-base ink, and the crystal phases, mechanical anisotropy, and fracture mode of the cylindrical moldings printed in the x-, y-, and z-directions and in the directions rotated from these axes with a binder jetting 3D printer were investigated. The results revealed that the content of calcium sulfate hemihydrate/dihydrate and the density of the moldings printed in each direction were almost constant, regardless of the ink/volume ratio; however, the content of the formed hemihydrate and amorphous anhydrate calcium sulfate was dependent on the ratio to a certain extent. The mechanical anisotropy and the different fracture modes (crack propagation) of the moldings printed in different directions at a constant lamination thickness were reproducibly observed. The authors found that the direction of the crack propagation represented by a Miller index was affected by the nozzle pattern of the print head. This study provides new insights to comprehensively explain anisotropic mechanical properties of binder jetting 3D-printed products. Graphical abstract Download : Download high-res image (193KB) Download : Download full-size image

Ceramic materials were applied to the area of bone defect treatment for a long time. The structure character and preparation method of ceramic scaffolds are of great importance to the satisfaction of defect repair. Among the myriads of forming methods, 3D printing technology allows to form porous and individualized ceramic scaffolds. Normally the extrusion-based 3D printing technique can only build scaffolds with grid structures, instead of complicated ones. In this study, the tricalcium phosphate/bioglass composite (TCP/BG) scaffold with gyroid structure was successfully and precisely manufactured using digital light processing (DLP) method. The surface characters, mechanical properties, and structural parameters of TCP/BG gyroid scaffold were analyzed. In vivo experiments demonstrated that compared to commercial artificial bone graft manufactured by conventional foaming method, TCP/BG scaffold with gyroid structure could effectively induce bone ingrowth and integration, meanwhile keep the surrounding trabeculae structure as natural. This kind of scaffolds presented great potential in the field of challenging bone defect treatment. Graphical abstract Download : Download high-res image (145KB) Download : Download full-size image

Beyond Li-ion batteries, one of the most promising technology is the Lithium-Sulphur (Li-S) not only for its higher theoretical energy density (about 2600 Wh kg−1) but because sulfur is relatively inexpensive and non-toxic. However, the Li-S battery suffers from “shuttle effect” of polysulfides. Thus, restricting shuttling means increasing cell performance and durability. DFT calculations showed that graphitic carbon nitride (g-C3N4) exhibits strong interactions with Li2S (e.g. superior to graphene-like carbon) and acts as polysulfides trapping agent. In this work, the role of g-C3N4, synthetized from different precursor and at different polycondensation temperatures was systematically studied, using a double layer approach for the electrode preparation, which ensures direct interaction between g-C3N4 and soluble lithium-polysulfides. This systematic study confirms the importance of the morphological and superficial properties of the material. In particular, carbon nitride from urea precursor remarkably improves the performance of the sulphur cathode, increasing the specific capacity of the cell by 25% and improving its useful life over 500 cycles. According to the morphological characterization and the XPS analysis, benefits are achieved from polycondensation of urea at 550°C. The obtained g-C3N4 shows the highest proportion of -NH2 species on the surface, which favours the interaction with polysulfides. Graphical abstract Download : Download high-res image (186KB) Download : Download full-size image

Mn‒Cu-based shape memory alloys have great potential owing to their excellent shape memory properties, high damping capacity, low production cost, and ease of fabrication. In this study, a selective laser melting (SLM) technique was used to design and manufacture a series of high-manganese Mn‒xCu (x=10–40 wt.%) alloys by blending the elemental powders. Spinodal decomposition and martensitic transformation of the alloys during SLM and heat treatment (HT) processes were investigated and correlated with the tensile, damping, and shape memory properties of the alloys. The results showed that γ‒(Mn, Cu) was the main constituent phase in all of samples subjected to SLM only (hereafter as-SLMed) and the SLMed + HTed Mn‒Cu alloys. The effect of the chemical composition and manufacturing process on the phase structural evolution of the Mn‒Cu alloys were monitored. The spinodal decomposition, martensitic transformation and α-Mn precipitation reactions occurred in the as-SLMed Mn‒xCu samples with x = 15–20 wt.%, x < 30 wt.%, and x < 15 wt.%, respectively. The tensile properties of the as-SLMed Mn‒xCu alloys followed a general downward trend with increasing Mn content, while the corresponding damping capacity and shape memory recovery strain showed the opposite trend. HT can promote spinodal decomposition and martensitic transformation to form an equiaxed γ‒(Mn, Cu) grain, parallel twin plate structure, tweed microstructure, and α-Mn precipitate in the alloys. The SLMed + HTed Mn‒30% Cu alloy displayed a better combination of tensile properties (764, 540 MPa, and 12.5%), damping capacity (tan δ = 0.072 at a strain amplitude of 900 × 10−6), and one-way and two-way (εsme = 1.6% and εtw = 0.7% under the pre-bending strain of 10%) shape memory properties. In addition, the performance of the as-SLMed Mn‒xCu (x = 15–20 wt.%) and SLMed + HTed Mn‒xCu (x = 30 wt.%) alloys is comparable with and even superior to those of multi-component and commercial Mn‒Cu-based alloys, respectively. Graphical abstract Graphical abstract Download : Download high-res image (284KB) Download : Download full-size image

Identifying efficient and low-cost catalysts for electrocatalytic and photocatalytic hydrogen evolution reaction (HER) is critical for renewable energies, yet it remains an immense challenge. Through density functional theory calculations, we systematically investigate the great potential of 30 single-atom catalysts (SACs), namely single-atom-anchored g-CN (M/g-CN), toward electrocatalytic and photocatalytic HER in all pH intervals. Through Gibbs free energy (ΔGH*) calculations, electrical conductivity as well as water dissociation kinetic analysis, six M/g-CN (M = Sc, Ti, V, Ga, Sn, Au) are identified as pH universal electrocatalysts for HER. After excluding the influence of charge and solvation on ΔGH*, M/g-CN (M = V, Ga, Sn, Au) can still be regarded as potential pH universal electrocatalysts for HER. In addition, by combination of band structures with ΔGH* assessments, five M/g-CN (M = Ti, Ni, Ru, Pd, Os) are expected to be pH universal photocatalysts for HER. In particular, Ti/g-CN and Pd/g-CN possess favorable solar light harvesting and proton reducing kinetics, which can be regarded as the essential photo-electro integrated catalysts for HER. Moreover, employing machine learning method, the activity origin for HER on SACs is unveiled, and it is demonstrated that the charge transfer plays the decisive impact accompanied by the synergy effect from a series of structural characteristics. This work gives a new approach to design and search potential HER catalysts. Graphical abstract Download : Download high-res image (143KB) Download : Download full-size image

PtSx, as a more recent 2D material that aroused extensive research interests, has been applied in electronic and optoelectronic devices because of its excellent electronic characteristics and commendable stability. However, the synthesis of large-scale uniform PtSx remains a challenge. Here we studied a modified chemical vapor deposition (CVD) method to grow large-scale uniform PtSx films on SiO2/Si and c-plane sapphire substrates, which can avoid some disadvantages of the mechanical exfoliation method in the device fabrication. The large area uniform PtSx films are achieved through Pt sulfurization using H2S gas, replacing the sulfur powder in traditional methods, as the sulfur source. The material characterizations successfully proved that our modified CVD method is feasible and repeatable, and the PtSx film can be synthesized on different substrates. The PtSx photodevices show good photoresponse properties with a wide spectrum response range. The PtSx/sapphire device shows a better photoresponse in terms of the detectivity (9.17 × 109 Jones) and the responsivity (0.31 A W−1) than that of the PtSx/SiO2/Si device in our experiment, as well as one-year air stability, which may be caused by the different PtSx film quality due to a lattice mismatch difference between the PtSx and the different substrates. The results offer the design and synthesis technology for large-scale, uniform, and stable PtSx film, as well as an example of photoresponse-enhanced devices which could be generalizable to other transition metal dichalcogenides (TMDCs) and devices for future development and applications. Graphical abstract Download : Download high-res image (142KB) Download : Download full-size image

Highlights • A hybrid consisting of NiSe crystalline and MoSex amorphous structure was designed and synthesized. The various heterogeneous interfaces in this structure contributed to promote the electrochemical catalytic reaction. In particular, the stability is greatly improved, while the activity is not significantly decreased. The obtained electrochemical performances are superior to the most previous reports from transition metal catalysts. • To reveal the underlying mechanism, the density functional theory calculation was employed to investigate the Gibbs free energy, electronic states and intermediates desorption. The results show that crystalline/amorphous hetero-phase structure can reduce the Gibbs free energy difference and increase the occupation densities of electronic states. • The high catalytic activity for hydrogen and oxygen evolution reaction (HER and OER) was achieved in this work. In this work, a novel hetero-phase interface structure (NiMoSe/NF-2), consisting of crystalline (NiSe) and amorphous (MoSex), was constructed by annealing Ni0.85Se/MoSex hybrid (NiMoSe/NF-1), synthesized through hydrothermal and selenylation steps. For hydrogen evolution and oxygen evolution reaction, the NiMoSe/NF-2 exhibited an overpotential of 91 mV (10 mA cm−2) and 307 mV (100 mA cm−2) with the Tafel slope of 48.1 mV dec−1 and 30.9 mV dec−1, respectively, superior to NiMoSe/NF-1. Meanwhile, much higher stability with 10 and 14 h tests was also respectively achieved for HER and OER. Using the NiMoSe/NF-2 as anode and cathode, the electrolyzer showed a long-time stability up to 14 h with the current density of 100 mA cm−2 at the potential of 1.91 V for overall water splitting. The density functional theory calculation validates that the crystalline/amorphous hetero-phase structure remarkably reduces the Gibbs free energy difference for both HER/OER and the increased occupation densities of electronic states near Fermi level accelerated charge transfer rate during electrocatalytic process. The hydrogen and oxygen intermediates desorption are facilitated by the downshift of Ni d-band center. The proposed crystalline/amorphous hetero-phase structure is prospective for designing bifunctional catalysts for water splitting. Graphical abstract An in-situ grown 3D bimetal ternary selenides (NiMoSe/NF-2) nanowire array was successfully fabricated through a high-temperature phase transition strategy for the first time. The crystalline NiSe in NiMoSe/NF-2 transformed from Ni0.85Se phase and the amorphous MoSex construct an interfacial balance, resulting in a bifunctional electrocatalyst for overall water splitting with strengthened stability without activity degradation. Download : Download high-res image (154KB) Download : Download full-size image

The family of Co-based Heusler compounds contains promising candidates for spintronic applications regarding their predicted Half-Metal-Magnetic nature, ultra-low magnetic damping coefficients, high curie temperatures and tunable electronic properties. Here we focused on the transport properties of Co2MnSi thin films with thickness in the range of 4-44 nm exhibiting magnetic damping in the 10-4 - 10-3 range. The goals of this study are to examine the impact of the peculiar electronic band structure on the transport properties, to identify the temperature-dependent scattering process, and to extract robust conduction parameters to exploit this material in magnetoelectric devices. In order to undoubtedly correlate all results, the full study has been performed on the same series of samples. Scanning transmission electron microscopy experiments were performed to check the chemically-ordered L21 phase in our films, and also allowed us to identify misfit dislocations generated at the interface with the substrate. The variation of the resistivity with film thickness was measured at different temperatures. The results are examined under the Fuchs and Sondheimer model which allowed us to extract the electron mean free path in Co2MnSi in the temperature range 5 – 300 K. Values for the residual resistivity, Debye temperature, and distance between the Fermi energy and the conduction band for minority spins were obtained from the fit of the resistivity versus temperatures curves. A negative AMR ratio was measured for all the samples which confirmed the Half-metallic nature of the Co2MnSi films. The determination of the ordinary Hall coefficient alloys allowed us to extract the carrier concentration and carrier mobility and their dependency on the temperature. Finally, scaling of the anomalous Hall coefficient with the longitudinal resistivity was performed indicating that skew scattering is the dominant temperature-dependent scattering mechanism in our films. Graphical abstract Download : Download high-res image (173KB) Download : Download full-size image

The repair of critical-sized bone defects remains challenging. Natural polysaccharide-based hydrogels (NPHs) have shown great promise for facilitating bone defect healing, but limited by osteogenesis, mechanical strength and stability. Here we prepared a water-soluble methacrylic anhydride-co-phosphate modified chitosan (CSMAP) incorporated MgO nanoparticles to form a pergel, and followed by introduction of acrylamide to construct a double-network hydrogel (CSMAP-MgO). We found that Mg2+ released from CSMAP-MgO hydrogel in a stable and sustained manner in 30 days and the compressive strength was maintained and the compressive modulus was even enhanced during immersion in PBS for 28 days. Moreover, the CSMAP-MgO hydrogel was superior in promoting in vitro calcium phosphate deposition, MC3T3-E1 cell proliferation, osteogenic differentiation, and mineralization compared to Magnesium free groups. At 12 weeks post-implantation into a rat critical-sized calvarial defect, the CSMAP-MgO hydrogel promoted significantly more new bone formation compared to CSMAP and non-treated groups. Thus, the CSMAP-MgO hydrogel has great promising as a bone filling material. Graphical abstract Download : Download high-res image (248KB) Download : Download full-size image