查看更多>>摘要：Tin sulfide (SnS_x) thin films deposited by atomic layer deposition (ALD) under various deposition conditions have unique properties. Such films have two phases, tin monosulfide (SnS) and tin disulfide (SnS_2), that depend on the composition ratio of the thin film, and these materials can be applied to a wide range of technologies, such as solar cells, optical sensors, and transistors. In this study, we deposit amorphous tin sulfide thin films at 100 °C using ALD and perform post annealing at various temperatures to control the phase transition from SnS_2 to SnS. The post annealing temperature-dependent phase transition was analyzed through Raman spectroscopy, grazing-incidence X-ray diffraction (GI-XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-vis) spectroscopy, and ultraviolet photoelectron spectroscopy (UPS). Thermodynamic calculations were performed to determine that the initial temperature of the phase transition correspond to the post annealing temperature of 350 °C. The phases and crystal structures of the films annealed at different temperatures were investigated by Raman and GI-XRD. The chemical bonding of the films was analyzed through XPS, revealing that the binding energy of Sn~(4+) states shifted to the lower binding energy of Sn~(2+) states with increasing annealing temperatures. The electronic band structures of the films were calculated by UV-vis and UPS. The band gaps of the 300 °C, 350 °C, 400 °C annealed films were 2.26 eV, 2.05 eV, 1.63 eV, respectively. The tin sulfide thin films had n-type characteristics when annealed at 300 °C, which changed to p-type characteristics when annealed at 350 °C and 400 °C. Through this study, we can investigate phase transition of tin sulfides and correlate fabrication conditions to both n-type and p-type characteristics, which can be applied to synthesize the desired films for application in various devices.
查看更多>>摘要：The hybrid structure of high conductive carbon materials with large capacitive metal compounds is one of promising strategies for achieving high specific capacity, cycling stability, and ultrafast Li-ion storage capability due to their synergistic effects. This article will demonstrate the novel hybrid structure of a zinc oxysulflde (ZnOS) lamination layer on a sulfur (S)-doped carbon nanofiber (SCNF) matrix via an electro-spinning method with sequential atomic layer deposition (ALD) process and will also present the structural advantages for ultrafast Li-ion batteries (LIBs). As a double-anion material, ZnOS has benefits compared with single ZnO and ZnS during the charge/discharge process, which is accompanied with consecutive conversion and alloying reactions. To verify these factors, structural analysis at the atomic scale and various electrochemical properties were evaluated. The resultant ZnOS/SCNF electrode showed superior electrochemical performance such as high specific capacity (672.8 mAh g~(-1) at 100 mA g~(-1)), good capacity retention (87.8% after 100 cycles), and excellent cycling stability (85.4% after 500 cycles). This is attributed to the facilitated kinetic properties including electron and ion transfer efficiency during the electrochemical reactions, accompanied with the ZnOS/SCNF hybrid structure. In this regards, we believe that the ZnOS/SCNF electrode could be a great reference as a promising research strategy for accomplishing ultrafast LIBs.
查看更多>>摘要：The chemistry of metal borohydrides and their derivatives has expanded signficantly during the past decade involving new compositions, structures, and the diversity of associated properties. Here we provide an overview of interesting results mainly from the past few years, discussed relative to previously published results. A range of new synthesis strategies has been developed to obtain pure samples, which has allowed very detailed structural, physical, and chemical investigations. A short overview of mono- and dimetallic borohydrides is provided, including a description of the complete series of rare-earth metal borohydrides and the recently discovered ammonium metal borohydrides, where the latter has attracted interest due to an extreme hydrogen content. Metal borohydrides appear to be the most promising class of materials to achieve high cationic conductivity of divalent metals, and particularly derivatives of metal borohydrides with neutral molecules show promise as future electrolytes for new types of solid-state batteries. Furthermore, metal borohydrides display a wide range of other properties, including optical, magnetic, semi conduction and possibly superconducting properties, and are also used as a new approach for carbon capture and conversion. The aim of the present review is to highlight new trends in properties and provide an outlook with possible future applications. Here, we focus on the more recently discovered materials.
查看更多>>摘要：Three dimensional (3D) hybrid nanoarchitecture of two-dimensional (2D) reduced graphene oxide/one dimensional (1D) multiwalled carbon nanotube and zero-dimensional (OD) zirconium oxide (ZrO_2) nano-particles (rGO/MWCNT/ZrO_2) was synthesised by a simple hydrolysis method for high performance supercapacitors. To unlock the properties of individual materials to the maximum, binaries of ZrO_2 with GO and MWCNT were also synthesised. The increased wettability, integrated structure, and the synergistic effect of rGO, MWCNT, and ZrO_2 in rGO/MWCNT/ZrO_2 (GMZ) offer a capacitance of 357 F g~(-1) at 1 A g~(-1) with excellent capacitance retention of 98% across 5000 cycles. 1D structure of MWCNT creates an exceptional conductive network with rGO due to the confinement of electrons and ions without disturbing its electronic structure. The intriguing supercapacitor performance of differently dimensioned framework with ZrO_2 emphasises the engineered orientation and tuning of a designed environment for its appropriateness, uniqueness, and sensitivity to push up enhanced performance.
查看更多>>摘要：Recently, additive manufacturing (AM), being part of IR4.0, received great attention for the fabrication of customized implants with outstanding quality, which are used in hard tissue replacement. For an orthopedic application, the titanium alloy implants, especially those that use Ti-6Al-4V manufactured by selective laser melting (SLM), should facilitate maximum osteointegration between the implant and corresponding bone. However, the superior mechanical characteristics, poor surface integration, antibacterial performance, and readiness of SLM Ti-6Al-4V for use in advanced implants are still not comparable to those of anatomical bone. This review focused on the current issue of stress-shielding limitations in SLM Ti-6Al-4V owing to failures in load-bearing applications. The surface treatment and modification strategy that might improve the osseointegration of the implant were discussed. The corrosion resistance of SLM Ti-6Al-4V which could significantly affect antibacterial capability, improve cell adherence and apatite formation on the bone remodeling surface was also addressed. Finally, the current challenges, prospects and applications for SLM Ti-6Al-4V development were presented.
查看更多>>摘要：BiCuSeO exhibits remarkable low thermal conductivity among oxides. The lone pair of the Bi~(3+) and the point defects brought about by elemental doping are thought to be the origin of the low thermal conductivity. In a recent study, however, the Cu atoms in BiCuSeO play a more significant role in reducing the lattice thermal conductivity than the above two factors. In this work, two series of polycrystalline Bi_(1-x)Ca_xCu_(0.975)SeO (x = 0.025,0.050,0.075,0.100, 0.125,0.150) and Bi_(0.95)Ca_(0.05)Cu_(1-y)SeO (y = 0.015,0.025, 0.035) are synthesized by solid-state reaction. All the materials are of single phase. Point defects introduced by partial elemental substitution and atom vacancy are expected to reduce the lattice thermal conductivity, however, which is not followed by the prediction for Bi_(1-x)Ca_xCu_(0.975)SeO with 0.050 ≤ x ≤0.125 and Bi_(0.95)Ca_(0.05)Cu_(1-y) with y = 0.015,0.025, and 0.035 in the temperature range where the resistivity decreases while the thermopower increases with temperature. This is in sharp contrast with those BiCuSeO with partial elemental substitution or Cu deficiency exhibiting either both the electrical resistivity and thermopower increase or decrease with increasing temperature. Our results support that the Cu atoms in BiCuSeO play a more significant role in reducing the lattice thermal conductivity than the lone pair of the Bi~(3+) and the point defects brought about by elemental doping.
查看更多>>摘要：The interphase of composites is a vital element in controlling the overall performance. Herein, the SiC nanowires (SiC_(nw)) were grown on the interface of the SiC fiber (SiC_f)/Si_3N_4 composites and successfully achieved the integration of enhanced mechanical and electromagnetic wave (EMW) absorption performance. The introduction of SiC_(nw) made the bonding between the SiCf and Si_3N_4 matrix more appropriate, thereby enhancing the mechanical properties. The defects, stacking faults, twin boundaries and heterogeneous interfaces in SiC_(nw) improved the dielectric loss of the composites, which was beneficial to the consumption of EMW energy. Notably, the SiCf/SiC_(nw)/Si_3N_4 composite containing 1.8 vol% SiC_(nw) demonstrated the optimal mechanical and EMW absorption properties, reaching a flexural strength of 333 ± 29 MPa, a minimum reflection coefficient (RC_(min)) value of- 51.4 dB with a thickness of 3.2 mm and an effective absorption bandwidth (EAB) of 3.5 GHz with a thickness of 2.8 mm. Besides, the fracture mechanism and EMW absorption mechanism are also discussed. This work provides a potential new way to prepare lightweight, stable, and high-performance EMW absorbing materials for aviation and aerospace.
查看更多>>摘要：Poor tribocorrosion resistance of Ti and its alloys remains as a concern for load-bearing biomedical implants. Despite being an effective method to improve tribocorrosion resistance, titanium matrix composites (TMCs) have yet to be used in this type of applications. In-situ TiB (titanium boride) and TiC (titanium carbide) reinforcement phases have been considered as one of the best options to produce TMCs once these phases present high compatibility and strong interfacial bonding with Ti. Although the effect of these phases on the mechanical properties of Ti has been thoroughly researched in the last years, their effect on corrosion, tribocorrosion and biocompatibility of Ti is yet to be fully understood. In this work, in-situ Ti-TiB-TiC_x composites obtained by reactive hot pressing showed identical corrosion response compared to the unreinforced Ti but displayed improved tribocorrosion behaviour. Under 0.5 N load, composites presented as average a reduction of 51% in wear volume loss and under 10 N the reduction was up to 93%. Early biological tests showed promising results, as composites were biocompatible and induced osteoblasts spreading and possibly proliferation most probably due to composite chemistry and surface hardness.
查看更多>>摘要：In this work, a novel Cu decorated Fe_3O_4@ CeOHCO_3 nanocomposite (Cu-Fe_3O_4@CeOHCO_3) has been prepared by a one-step hydrothermal method. Fabricating into the electrode, the electrochemical properties of the prepared materials were characterized by cyclic voltammetry (CV), galvano-static charge-discharge (GCD) test and electrochemical impedance spectroscopy (EIS). The specific capacitance of the Cu-Fe_3O_4@ CeOHCO_3 electrode was 324.7 F g~(-1) at a current density of 1.0 A g~(-1) with a capacitive retention of 88.3% after 1000 charge-discharge cycles. The assembled asymmetric supercapacitor(ASC) device can provide an energy density of 35.4 W h kg~(-1) with a high power density of 781.9 W kg~(-1). DFT calculations prove that the surface modification of Cu functions significantly in modulating the electronic structure and super-capacitive properties of CeOHCO_3. Our self-assembled Cerium-based composite may initiate the suitability for energy storage devices and provides a valuable reference for the fabrication in sodium Ion supercapacitors.
查看更多>>摘要：Nanoporous silver (NPS) with a three-dimensional (3D) bicontinuous ligament/pore structure can be fabricated in different ways and with different treatments. Thermal treatments before or after dealloying can have a considerable impact on the dealloying process. High-temperature oxidation (HTO) has been researched as a method to tune the process of NPS fabrication. In this work, X-ray diffraction and X-ray photoelectron spectroscopy characterizations were used to identify the phase after HTO and dealloying. Copper oxide was found in the precursor alloy after HTO, which could be the key factor that would influence the mechanism of NPS fabrication. Scanning electron microscopy and transmission electron microscopy were executed to characterize the pathway of forming NPS and research the difference between HTO specimens and the as-cast sample. This demonstrated that, compared to the free corrosion pathway, the diffusion method of Ag atoms was different under HTO pretreatment, which was the predominant factor causing a larger 3D bicontinuous ligament/pore structure. Finally, the microstructure of the final NPS pretreated with HTO for 3 min was much more homogeneous than that of the others, and when the pretreatment time of HTO reached 5 min, the ligament/pore structure almost collapsed.
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