Large Number Of Grain Boundaries Research Articles

Enhancement in interfacial bonding quality of CoCrFeMnNi high-entropy alloy vacuum hot-compression bonding via surface shot peening

Vacuum hot-compression bonding (VHCB) is an advanced solid-state bonding technique. To expand its application in high-entropy alloys (HEAs), a new strategy to enhance the interfacial bonding quality of CoCrFeMnNi HEA VHCB joints by surface shot peening (SP) was proposed, and the effects of SP treatment on the interfacial bonding behavior and mechanical properties of VHCB joints were investigated. The results revealed that SP treatment introduced a nanocrystalline layer and plastic deformation layer with non-uniform strain on the specimen bonding surface, and a hierarchical grain size gradient fine microstructure was formed by a static recrystallization process under the thermal activation condition before VHCB. During the bonding process, the fine microstructure of the SP-treated layer was retained and provided a large number of grain boundaries and dislocations, which facilitated atomic diffusion and plastic flow in the interfacial region and promoted the closure of interfacial voids and the dissolution of interfacial oxide particles. Additionally, interfacial crystallographic and tensile test analyses indicated that the SP treatment induced a multiple interfacial grain boundary (IGB) migration mechanism in the VHCB joints, which dramatically improved the IGB migration level and ultimately led to a complete recovery of the mechanical properties of the CoCrFeMnNi HEA VHCB joints.

Effect of Ni doping on mechanical properties and phase transformation in Co–V–Ga high-temperature shape memory alloys

In the present work, the effects of Ni doping on the microstructure and mechanical properties of Co–V–Ga high-temperature shape memory alloy have been studied. It has been found that γ phase occurs in the form of precipitation or even dendrite microstructure when Ni content continuously increases in the alloy. The composition distribution showed the elements Co and Ni segregated in the γ phase, while elements V and Ga concentrated in the martensite phase. Moreover, the phase transition temperature increased by Ni-doping in Co–V–Ga alloys due to the increase in e/a of the alloy. However, the abundant presence of γ phase hindered the shear phase transformation and created a large number of grain boundaries to reduce Ms temperature when Ni content continuously increased. In addition, electron backscattered diffraction (EBSD) results verified that the presence of γ phase could hinder the expansion of cracks, and improve the strength and plasticity of the alloy. Furthermore, it could be found the shape memory effect could maintain a relatively high recovery rate when Ni content was within a certain extent. However, the shape memory effect of the alloy significantly decreased in the presence of γ phase with dendrite microstructure. The current research results not only clarify the influence of Ni doping on the microstructure and mechanical behavior of Co–V–Ga alloys, but also provide guidance for element doping to prepare high-temperature shape memory alloys (HTSMAs) with excellent performance.

Synthesis, crystal structure, thermal stability, and photovoltaic properties of organic-inorganic hybridized copper-based perovskite single crystals modulated by organics

Organic-inorganic hybridized perovskite have excellent photovoltaic properties, especially Pb-based organic-inorganic perovskite polycrystalline thin films based on Pb-based organic-inorganic perovskite have achieved high power conversion efficiency, but the polycrystalline materials have a large number of grain boundaries and defects, which are susceptible to the influence of water and oxygen, leading to structural degradation, poor stability, high toxicity and slow degradation, which are not friendly to the environment. Therefore, in this paper, two copper-based organic-inorganic hybrid perovskite single crystals (C6H9N2)2CuCl4 and (C6H18N2)2Cu2Cl8 were synthesized by using the method of organic modulation, and were investigated by single-crystal X-ray diffraction, powder X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, thermogravimetric analysis, and UV–vis diffuse reflectance spectroscopy. The samples were analyzed in detail for crystal structure, chemical groups, bond characterization, optical and thermal stability. The results show that (C6H9N2)2CuCl4 and (C6H18N2)2Cu2Cl8 single crystals belong to the C2/c space group of the monoclinic crystal system and the P-1 space group of the triclinic crystal system, respectively. The optical band gap of (C6H9N2)2CuCl4 is 2.45 eV, which is stable up to 179 °C, and that of (C6H18N2)2Cu2Cl8 is 2.47 eV, which is stable up to 163 °C. The thermal stability of the crystals can be regulated by changing the organic cation in the A-site, but the optical band gap of the crystals cannot be regulated significantly.

Crystal Structural Characteristics and Electrical Properties of (Ba0.7Sr0.3-xCax)(Ti0.9Zr0.1)O3 Ceramics Prepared Using the Citrate Gelation Method.

The electrical properties of (Ba0.7Sr0.3-xCax)(Ti0.9Zr0.1)O3 (0 ≤ x ≤ 0.2) (BSCTZ) ceramics prepared using citrate gelation (CG) method were investigated by substituting Ca2+ ions for the Sr2+ sites based on the structural characteristics of the ceramics. BSCTZ was sintered for 3 h at 1300 °C, lower than the temperature (1550 °C) at which the specimens prepared using the solid-state reaction (SSR) method were sintered, which lasted for 6 h. As the amount of substituted Ca2+ ions increased, the unit cell volume of the BSCTZ decreased because of the smaller ionic radius of the Ca2+ ions compared to the Sr2+ ions. The dielectric constant of BaTiO3-based ceramics is imparted by factors such as the tetragonality and B-site bond valence of the ceramics. Although the ceramic tetragonality increased with Ca2+ ion substitution, the x = 0.05 specimens exhibited the highest dielectric constant. The decrease in the dielectric constant of the sintered x > 0.05 specimens was attributed to the increase in the B-site bond valence of the ABO3 perovskite structure. Owing to the large number of grain boundaries, the breakdown voltage (6.6839 kV/mm) of the BSCTZ prepared using the CG method was significantly improved in relation to that (2.0043 kV/mm) of the specimen prepared using the SSR method.

Significant enhancement in high temperature performance of TiAl matrix composites by a novel configuration design

Ti5Si3/TiAl composites were successfully prepared by pressure infiltration and subsequent reactive annealing. Final microstructure of Ti5Si3/TiAl composites was dependent on the reactive annealing temperature, which varied from 1350 °C to 1420 °C, two typical microstructures could be achieved: (i) An unique core-shell structure (Core: fully lamellar α2-Ti3Al/γ-TiAl with in-situ synthesized Ti5Si3 particles predominantly distributed at the interfaces of α2/γ lamellar colonies; Shell: equiaxed γ-TiAl with Ti5Si3 particles distributed in γ grain boundaries); And (ii) A novel quasi-network structure composed of fully lamellar α2/γ and a majority of Ti5Si3 particles with a quasi-network distribution. The formation of the two microstructures could be attributed to the chemical composition heterogeneity which was caused by the difference in interdiffusion rate of Ti and Al elements in different annealing temperatures. The comparative investigations on high temperature tensile properties and creep behavior showed that the core-shell Ti5Si3/TiAl composites exhibited a better specific strength (165 MPa⋅g−1⋅cm3) and higher ultimate tensile strength (633 MPa) at 800 °C, which was 12 % higher than that of the quasi-network Ti5Si3/TiAl composites. While the creep behavior analysis showed that in compassion with equiaxed γ phase, the slip distance of dislocations in fully lamellar α2/γ phase was shorter, impeding the motion of dislocations more effectively. And core-shell Ti5Si3/TiAl composites possessed a large number of grain boundaries concentrating in the shell which became weaker in the high temperature, facilitating the formation of creep pores in the shell and the final premature fracture. Hence, the quasi-network Ti5Si3/TiAl composites containing a higher content of fully lamellar α2/γ exhibited a better creep resistance than that of core-shell Ti5Si3/TiAl composites. More importantly, the steady state creep rate at 750 °C under the fixed stress of 250 MPa of quasi-network Ti5Si3/TiAl composites was relatively low, only 3.305 × 10−8 s−1, comparable to that of third-generation TiAl alloys.

Effect of B on the microstructure and mechanical properties of Cu–Cu joints with in-situ Ag–Cu–Zn–Sn filler metal

With the development of advanced manufacturing, traditional Ag-based filler metals cannot reconcile the contradiction between high performance and complex processing. It also unable to meet the requirements of new materials, new structures and new processes for brazing connection performance. In this paper, based on the Ag–Cu–Zn–Sn flux-cored filler metal, the effect of the addition of B on the microstructure and mechanical properties of Cu–Cu brazing joints was investigated using FESEM‒EDS, EPMA, EBSD, TEM, microindenter and universal tensile testing machine. The results indicated that the microstructure in the brazing seam was mainly composed of Ag (s.s), Cu(s.s) and (Ag + Cu) eutectic. With increasing B content, the grain size and texture strength of Ag(s) and Cu(s) gradually decreased. The refinement of Ag-rich dendrites was mainly due to the enrichment of B atoms around the dendrite, which limited the diffusion of solute atoms in the melt and the release of solidification latent heat in front of the liquid‒solid interface, further inhibiting the growth of Ag-rich dendrites. The refinement behavior of Cu-rich dendrites was mainly attributed to the increase in B content, which reduced the tip radius of Cu-rich dendrites. The mass transfer path of B → B2O3 and B → liquid CuSn alloy → mixed melt of CuSn alloy + solder skin alloy → liquid filler metal in the brazed joint → Cu rich phase and grain boundary in the brazed joint → Ag rich phase and grain boundary in the brazing seam was clarified. The addition of B can improve the microhardness of the brazing seam. The shear strength reached a maximum value of 237.2 MPa when B was added at 2%. The fracture models mainly included intergranular fracture, dimple fracture and cleavage fracture. The strength of brazed joints can be improved by solid solution strengthening, process hardening strengthening and fine grain strengthening. The tangle and jog of dislocations within the crystal, the presence of a large number of grain boundaries and B-rich areas can prevent crack tip extension and enhance the toughness of brazing joints.

Effect of graphene addition on the performance of in-situ (TiC+TiBx)/Ti composite coatings by laser cladding: Microstructure and water droplet erosion resistance

In this study, different amounts of graphene (Gr, 0–2 wt%) were added into Ni60/Ti6Al4V powder mixtures to prepare (TiC+TiBx)/Ti composite coatings on Ti6Al4V substrates by laser cladding. By means of XRD, SEM, EDS, and TEM, the effects of Gr content on the dilution rate, phase composition, microstructure, microhardness and water droplet erosion (WDE) resistance of the coatings were comprehensively analyzed. The results showed that the coatings comprised phases of Ti2Ni, TiC, TiB, TiB2, α-Ti and β-Ti. The increased Gr content precipitated more TiC, providing more heterogeneous nucleation sites for other grains and suppressing the grain growth. The TiC-TiB2 and TiB-TiC intergrowth structures exhibited high load-bearing capacity and contributed to the synergistic hardening and strengthening effects. When the Gr content was 1 wt%, the coating had the highest microhardness of 886.3 HV0.3 and showed the best WDE resistance. The excellent performance of the hard phases, the existence of a large number of grain boundaries and the effect of the skeleton improved the WDE resistance of the coatings.

A significantly improved hydrogen storage performance of nanocrystalline Ti–Fe–Mn–Pr alloy

Improving the activation performance and increasing the hydrogen storage capacity are the main problems faced by TiFe-based alloys. In this paper, alloys with chemical composition Ti1.1-xPrxFe0.8Mn0.2 (x = 0, 0.02, 0.04, 0.06, 0.08) are designed to achieve a reversible hydrogen storage capacity of 1.81 wt% in 15 min, which is close to the theoretical hydrogen storage capacity of TiFe alloy of 1.86 wt%. Alloys with Pr content x ≥ 0.04 can be directly activated without the incubation period. Transmission electron microscopy analysis found that doping Pr introduced TiFe (111) crystal plane with smaller surface energy, makes it easy for hydrogen atoms to diffuse from the surface to interior. Moreover, the addition of Pr significantly refines the grains and introduces a large number of grain boundaries and defects, improving the activation rate and kinetics. The physisorption results show that the specific surface area of the TiFe-based alloy after hydrogen absorption is significantly increased by doping Pr.

On the Intergranular Corrosion Susceptibility of 304 Stainless Steel with Ultrafine Grains and Comparison with Micrometer Austenitic Grains Counterpart

The intergranular corrosion (IGC) susceptibility of ultrafine grains (∼430 nm) and micrometer grains (∼3.1 µm to 9.8 μm) 304 stainless steel obtained by cryogenic rolling and reversion annealing treatments were studied. Transmission electron microscopy results showed that after sensitized treatment at 650°C for 2 h, the micrometer grains were sensitized with many M23C6 precipitates at the grain boundaries, while no precipitates were in the ultrafine grains. The immersion corrosion tests in H2SO4-CuSO4 solution showed that ultrafine grains exhibited weaker IGC attacks than micrometer grains. The double-loop electrochemical potentiokinetic reactivation tests demonstrated the degree of sensitization decreased from 26.61% to 1.52% with the grain ultra-refinement from micrometer to ultrafine. Corrosion studies indicated that the ultrafine grains exhibited lower IGC susceptibility compared with micrometer grains. According to the findings, the large number of grain boundaries generated by grain ultra-refinement inhibited M23C6 precipitates at the grain boundaries during the sensitized process, thereby reducing the susceptibility of ultrafine grains to IGC.

Bridging the inter-grain charge transportviaorganic semiconductors for high-performance thickness-insensitive perovskite solar cells

The solution-processability of perovskite solar cells (PVSCs) reduces the production cost, but renders a multi-crystalline film with a large number of grain boundaries, which hinders the charge transport and induces defects.

Cu-CNTs current collector fabricated by deformation-driven metallurgy for anode-free Li metal batteries

Rechargeable anode-free Li metal batteries (AFLMBs) with improved energy density and reduced cost are beneficial for emission peak and carbon neutralization. Herein, multi-walled carbon nanotubes reinforced Cu matrix composite (Cu-CNTs) enabled by deformation-driven metallurgy (DDM) technology is proposed to retrieve the lithiophilicity of current collectors (CCs) in AFLMBs. Fine-grained Cu-CNTs with a large number of grain boundaries and homogenous distribution of broken CNTs are achieved based on the severe plastic deformation principle since the CNTs inhibit slide of dislocations and migration of grain boundaries. Grain boundaries in fine-grained Cu-CNTs with low-size distribution gradients provide desirable nucleation sites due to their higher disorder and active state. Excellent lithiophilicity of the broken CNTs is exhibited where its layered structure for Li ion insertion contributes to uniform Li deposition. Half cells assembled by Cu-CNTs CC with 2 vol% CNTs display advanced cycling stability with an average coulombic efficiency of 97.8% after 500 cycles at 1.0 mA‧cm−2. Full cells with LiFePO4 cathode possess excellent capacity retention of 69.4% after 100 cycles at 0.5 C. This work provides a novel strategy for fabricating CCs to achieve superior electrochemical performances for future applications of AFLMBs.

Effect of Ni on electrical properties of Ba(Zr,Ce,Y)O3-δ as electrolyte for protonic ceramic fuel cells

NiO is known to promote sinterability and grain growth of the refractory proton conducting ceramic material Ba(Zr,Ce,Y)O3-δ. However, the NiO addition also decreases bulk proton uptake and conductivity. In this work, the influence of NiO addition on the electrochemical properties of Ba1.015Zr0.664Ce0.20Y0.136O3-δ is investigated. For 0.125–1.0 wt% NiO addition, the apparent grain-boundary conductivity increases significantly with NiO content. The largely increased grain size is the main reason for the improved apparent grain-boundary conductivity (the specific grain boundary conductivity does not correlate strongly with NiO content). The bulk conductivity is lower for higher NiO addition, both from decreased proton uptake and proton mobility. STEM-EDX line scans on a large number of grain boundaries show a systematically increased Y content in the boundary region. The local cation composition exhibits a significant scatter, which is expected to contribute to the observed variability of the grain boundary conductivity. STEM-EELS indicates the presence of Ce3+ in the grain boundary regions. Overall, as a good compromise 0.4–0.5 wt% NiO addition is recommended for future electrolyte membrane fabrication for protonic ceramic fuel cells.

Tension-compression fatigue behaviors of uniform and bimodal carbon nanotube/Al-Cu-Mg composites

By introducing the ductile-zones (DZs) without carbon nanotubes (CNTs) into the brittle-zones (BZs) containing CNTs, constructing the bimodal structure, can effectively improve the toughness of CNT reinforced Al (CNT/Al) composites. However, to be applied in the field of aerospace, CNT/Al composites will be required to have high toughness, as well as high fatigue strength. At the present study, the fatigue behaviors of uniform and bimodal CNT/Al composites under the tension-compression state with the stress ratio of −1 were investigated. It was found that CNT rich zones could keep grains stable after the fatigue loading. However, for the bimodal CNT/Al composites, the preferential local deformation occurred in the DZs, which resulted in much lower fatigue strength as compared to the uniform composite. By reducing the grain size of DZs to ultra-fine grain (UFG) level, the large number of grain boundaries within the DZs hindered the directional movement of slip bands, which significantly enhanced the fatigue strength and achieved a higher toughness of bimodal CNT/Al composites. This discovery provides a new strategy for the preparation of high performance CNT/Al composites, and the bimodal CNT/Al composite with UFG DZs is expected to be applied in the aerospace field. • The grain size of CNTs rich zones keeps stable after fatigue loading due to the pinning effect of CNTs on grain boundaries. • The introduction of bimodal structures decreases the tension-compression fatigue life of the CNT/Al-Cu-Mg composites. • The fatigue performance of bimodal CNT/Al-Cu-Mg composite can be improved by refining the grains in the CNT free zones.

Achieving excellent corrosion resistance properties of 7075 Al alloy via ultrasonic surface rolling treatment

The corrosion resistance of 7075 aluminum (Al) alloy treated by ultrasonic surface rolling process (USRP) in a chloride environment was studied in this work. The effects of different USRP passes on the surface state (surface roughness and residual stress), surface microstructure, and corrosion resistance of this alloy were investigated through microstructural characterization, stress relaxation, immersion testing and electrochemical measurement. The results revealed that all USRP-treated samples demonstrated significantly improved corrosion resistance. However, the main factors that led to this performance enhancement were not the same. After 3 USRP treatment passes, the reduction in surface roughness and the increase in surface compressive residual stress improved the corrosion resistance of the 7075 Al alloy. After 7 USRP passes, the larger number of grain boundaries caused by surface grain nanocrystallization led to the rapid enrichment of passive elements, which formed a dense passive film on the alloy surface. At the same time, the dissolution of precipitates and the disappearance of precipitation-free zones (PFZ) reduced the corrosion caused by anodic dissolution. Meanwhile, the primary mechanism that controlled the corrosion rate was transformed from the surface state to the surface microstructure, which further improved the corrosion resistance of the 7075 Al alloy. • In our work, the surface state and surface microstructure of 7075 aluminum alloy are tailored by changing the ultrasonic rolling passes. • The corrosion resistance of 7075 Al alloy is significantly improved by ultrasonic surface rolling process (USRP) in this study. • The effects of surface roughness, residual stress, surface nanocrystalline and precipitates on the corrosion resistance of 7075 Al alloy after USRP are studied by stress relaxation and surface roughness analysis.

Nanocrystalline graphene for ultrasensitive surface-enhanced Raman spectroscopy

The development of ultrasensitive and biocompatible Surface-Enhanced Raman Spectroscopy (SERS) substrates, able to provide uniform and reproducible signals, has become a focus of study in the last decade. Graphene, with his advantageous properties, such as photoluminescence quenching of fluorescent dyes, chemical inertness and biocompatibility, allows to overcome many important limitations of conventional metal SERS substrates. In this work, we develop ultrasensitive graphene substrates by ethanol Chemical Vapor Deposition (CVD). Large-area thin films composed of nanosized sp2 grains surrounded by disordered regions are obtained by lowering the growth temperature from the standard 1070 °C to 700 °C. Our substrates are able to detect trace amounts of molecules, down to 6·10−11 M, which is the lowest concentration that has been achieved in Graphene-Enhanced Raman Spectroscopy (GERS) with rhodamine 6G (R6G) as probe molecule. This outstanding result is attributable to two main features: i) more efficient charge transfer due to the energy level matching between R6G and the nanocrystalline graphene film; ii) large number of grain boundaries acting as “trapping sites” for the molecules.

Inorganic cesium lead mixed halide based perovskite solar materials modified with functional silver iodide

Inorganic CsPbIBr2 perovskites have recently attracted enormous attention as a viable alternative material for optoelectronic applications due to their higher efficiency, thermal stability, suitable bandgap, and proper optical absorption. However, the CsPbIBr2 perovskite films fabricated using a one-step deposition technique is usually comprised of small grain size with a large number of grain boundaries and compositional defects. In this work, silver iodide (AgI) will be incorporated as an additive into the CsPbIBr2 perovskite precursor solution to prepare the unique perovskite CsI(PbBr2)1-x(AgI)x. The AgI additive in the precursor solution works as a nucleation promoter which will help the perovskite to grow and merge into a continuous film with reduced defects. With detailed characterizations, we found that incorporating AgI additive resulted in a uniform perovskite film with fewer grain boundaries, increased grain size, crystallinity, optical absorption while decreasing carrier recombination and trap density. Using the AgI in an optimum amount, we fabricated CsPbIBr2 perovskite solar cells (PSCs) with a simple structure and achieved a power conversion efficiency (PCE) of 7.2% with a reduced hysteresis index. This work offers an alternative approach towards preparing high-quality CsPbIBr2 perovskite films for solar cells with higher stability and other optoelectronic applications.

Superior fracture toughness in a high-strength austenitic steel with heterogeneous lamellar microstructure

The development of steels with a combination of high strength, ductility, and toughness has been highly desirable for structural applications. Here we achieve high fracture toughness (129 MPa m½) in a high-strength (∼1.5 GPa yield strength) and ductile (∼37% uniform elongation) austenitic stainless steel. Through cold rolling, flash annealing, and tempering processes, the steel displays a heterogeneous lamellar microstructure that is comprised of reversed austenite (RA) lamellae with high-density dislocations and partially recrystallized austenite (PRA) lamellae with sub-micron grains. The lamellar interfaces are prior-austenite grain boundaries (PAGBs) with thin layer precipitates. Intrinsically, a large number of grain boundaries hinder the propagation of cracks, enhancing fracture resistance in PRA lamellae. The dislocation cells in the RA lamellae act as soft barriers to crack propagation, blunting the crack tips and reducing the adverse effect of high-density dislocations on fracture toughness. Extrinsically, the toughening mechanisms include the deep expansion of dimples in the PRA lamellae, the interfacial delamination of lamellar interfaces, and transformation-induced plasticity (TRIP) effect. Our study may promote the development of high-strength and high-toughness austenitic steels and alloys for structural applications.

Improving the oxidation resistance of SIMP steel to liquid Pb-Bi eutectic by shot peening treatments

A gradient nano- and submicron-structured surface layer of SIMP steel was produced by means of shot peening (SP). Compared with the original samples, corrosion experiments at 550℃ for various durations (120 h-1218 h) in liquid LBE showed that the oxidation resistance of the SP samples is significantly improved by shot peening, owing to the enhanced diffusivity of Cr by the large number of grain boundaries and dislocations introduced by shot peening, making it easier to form enhanced Cr-rich oxides. The magnetite layer of the SP samples has higher compactness, giving it better resistance to exfoliation than that of CG samples.

Effects of Sm implantation on the structure and magnetic properties of polar ZnO films

The present study reports a large ferromagnetism obtained by implanting Sm ions in Zn-polar and O-polar ZnO films prepared by molecular beam epitaxy (MBE) on sapphire substrates. X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and superconducting quantum interference device (SQUID) measurements were carried out to characterize the structure, surface morphology, elemental chemical states and magnetic properties of the Sm-doped polar ZnO films. XRD and AFM show that the doped ions in Zn-polar films are located at the grain boundary, while the doping ions in the O-polar films are incorporated into the grains. The magnetic moment for the as-implanted O-polar film is higher than that of the Zn-polar film. After annealing at 600 ℃ for 30 mins., there is a clear reduction in the saturation magnetization for the O-polar film, while the magnetic moment of the Zn-polar film shows little change. Raman and XPS results show that a large number of grain boundaries in the O-polar films are repaired and O vacancy (Vo) defects are reduced. We concluded that the magnetization of polar ZnO film after annealing is attributed to the combined effects of the Vo defects introduced by implantation and the local moments associated with the Sm ions.

Dispersed Cu-Sn Nanoparticles Confined in Nanowire Carbon Fibers for Electrochemical CO2 Reduction

Electrochemical reduction of CO2 (ECRCO2) into useful products, such as formic acid and carbon monoxide, is a fascinating approach for CO2 fixation as well as energy storage. Cu-Sn nanoparticles are attractive catalysts for highly selective ECRCO2 into HCOOH. but still suffer from high overpotential, low current density, and poor stability. Here, a low-cost one-dimensional (1D) Cu-Sn nanoparticle with nanowire carbon fiber (NCF) structure is synthesized and shows superior selectivity for HCOOH products. Using the NCF Cu-Sn nanoparticles as the ECRCO2 catalyst, very high Faradaic efficiency of HCOOH (>96%) can be achieved at a wide potential range from −0.90 to −1.35 V versus RHE, thus substantially suppressing the hydrogen evolution reaction. The electrocatalyst also exhibits excellent long-term stability. The improved catalytic activity of the NCF Cu-Sn nanoparticles indicates that higher surface area and large number of grain boundaries can effectively enhance the ECRCO2 activity. Synthesized via a facile and low-cost electrospinning technology, the reduced NCF Cu-Sn nanoparticles can serve as a promising electrocatalyst for efficient CO2 to HCOOH conversion.