摘要:
Directionally solidified gas turbine blades are wildly used in land-based industrial gas turbines for power generation. During long-term service, the harsh service environment causes microstructural and mechanical deterioration of the blades. In order to increase usage and save costs, this study analyzed the microstructure damage in different sections of the blade. Meanwhile, this investigation discussed the optimum rejuvenation heat treatment parameter and applied it to the serviced blade for the lifetime extension. The microstructural analysis indicated that the appropriate solution temperature for the serviced blade is 1205 degrees C. Furthermore, the microstructure of the degraded blade was effectively recovered including the gamma ' dissolution and reprecipitation with the cubic shape, tertiary gamma ' reprecipitation in gamma matrix, part of film-like M23C6 redissolution and dislocation networks were eliminated after rejuvenation heat treatment. In addition, the stress rupture lifetime and the tensile and yield strength were effectively improved by rejuvenation heat treatment.(c) 2023 Elsevier B.V. All rights reserved.
摘要:
In this paper, graphene with low platinum loading was prepared using the thermal expansion method, resulting in uniform dispersion of ultrafine Pt nanoparticles. The synthesized Pt/graphene exhibits a large specific surface area, abundant graphene defects, and homogeneous Pt particles. In 0.1 M KOH, the catalyst exhibits a half-wave potential of 0.84 V (vs. RHE), a limiting current density of 5.66 mA cm-2, and an electron transfer number of 3.9. The performance is close to that of the commercial 20 wt% Pt/C and outperforms the 10 wt% Pt/C. Moreover, it demonstrates better charge transfer kinetics and exceptional stability compared to the commercial 20 wt% Pt/C. This provides a promising avenue for the development of novel Pt-based catalysts.
摘要:
Flow batteries (FBs) are one of the most promising strategies for large-scale energy storage, in which the flow rates of electrolytes are critical to the redox reaction efficiency. However, low-power and energy-efficient strategies to effectively monitor and adjust the flow rates of FBs are great challenges. Here, a liquid metal based thin-film and self-powered triboelectric sensor (LM-TS) to monitor and adjust the real-time electrolyte flow rates in FBs is developed. By integrating the LM-TS with a peristaltic pump (flow rate control unit in FB), the flow rates of electrolytes can be converted into readable electrical output signals. Furthermore, a logical and a control module are adopted to adjust the flow rates of electrolytes automatically after receiving those electrical signals, which are available to guarantee the optimal working condition of FBs. Benefiting from the high conductivity and outstanding ductility of ultrathin LM film, the self-powered LM-TS is endowed with high sensitivity, short response time (9.1 ms), and remarkable cyclic stability (> 20000 cycles) without affecting the normal operation of FBs. This is the first prototype of self-powered adjustment sensor for FBs, which is readily extended to scaled-up FB equipment for intermediate trial and large-scale energy-storage demonstration.
作者机构:
[Hao, Jiayi; Du, Jinchao; Wu, Chun; Wang, Bixia; Xu, Hui; Qin, Wei] Changsha Univ Sci & Technol, Coll Mat Sci & Engn, Changsha 410114, Peoples R China.;[Ma, Zhen] South China Normal Univ, Sch Chem, Guangzhou 510006, Peoples R China.
通讯机构:
[Zhen Ma] S;[Chun Wu; Wei Qin] C;College of Materials Science and Engineering, Changsha University of Science and Technology, Changsha 410114, China<&wdkj&>School of Chemistry, South China Normal University, Guangzhou 510006, China
关键词:
aqueous zinc ion batteries;electrolyte;solvation structure;water in salt
摘要:
Abstract: Zinc as an anode, with low potential (−0.762 V vs. SHE) and high theoretical capacity (820 mAh g−1 or 5854 mAh L−1), shows great promise for energy storage devices. The aqueous zinc ion battery (ZIB) is known as a prospective candidate for large-scale application in the future due to its high safety, environmental friendliness, abundant zinc resources on earth, and low-cost advantages. However, the existence of zinc dendrites and side reactions limit the practical application of ZIBs. Therefore, a lot of effort has been made to improve the performance from aspects including the structure design and surface modification of zinc anodes, regulation of the electrolyte solvation structure, and design of the functional separator. In this review, we attempt to summarize recent advances on the regulation of the electrolyte solvation structure through a number of selected representative works from two aspects: high-concentration salt strategy and electrolyte additives. At the end of this review, the challenges and future development prospects are briefly outlined. Keywords: aqueous zinc ion batteries; electrolyte; solvation structure; water in salt
关键词:
Al alloys;Gradient microstructure;Precipitation;Laser remelting;Strength-ductility synergy
摘要:
Titanium (Ti) is generally known for its limited solid solubility and used as grain refiner in Al-based alloys, accelerating heterogeneous alpha-Al nucleation during solidification. In this study, a newly developed surface modification of pure Al followed by sputtering Ti film (similar to 1 mu m) and subsequent laser remelting has been proposed. Gradient structural features in both grain size and chemical composition have been accomplished in the top surface layer (<10 mu m), showing three typical domains with different grain morphology and Al3Ti nanoprecipitates. The simultaneous increase in strength and ductility is attributed to the strong dislocation-precipitate interaction inside gradient nano-grained top-surface layer, which has been confirmed by the partially dissolved Al3Ti nanoprecipitates induced by deformation. The findings in this work provide a new routine for upgrading mechanical properties through the manipulation of both grain- and chemical-gradients.
关键词:
FeOOH/Zn(OH)2/CoS ferromagnetic nanocomposites;electrochemical performances;magnetic field;stern double layer model
摘要:
In the study, the enhanced electrochemical mechanism of FeOOH/ Zn(OH)2/CoS ferromagnetic nanocomposite in magnetic field is proposed by combining the Stern double layer model with zeta potentials. The promotion of electrolyte ions transfer by the additional magnetic field generated after FZC magnetisation, the change in Warburg impedance and the magnetohydrodynamics effect for the electrochemical performances of FZC nanocomposites are investigated, systematically. Abstract The FeOOH/Zn(OH)2/CoS (FZC) nanocomposites are synthesized and show the outstanding electrochemical properties in both supercapacitor and catalytic hydrogen production. The specific area capacitance reaches 17.04 F cm−2, which is more than ten times higher than that of FeOOH/Zn(OH)2 (FZ) substrate: 1.58 F cm−2). FZC nanocomposites also exhibit the excellent cycling stability with an initial capacity retention rate of 93.6% after 10 000 long‐term cycles. The electrolytic cell (FZC//FZC) assembled with FZC as both anode and cathode in the UOR (urea oxidation reaction)|| HER (hydrogen evolution reaction) coupled system requires a cell voltage of only 1.453 V to drive a current density of 10 mA cm−2. Especially, the electrochemical performances of FZC nanocomposites are enhanced in magnetic field, and the mechanism is proposed based on Stern double layer model at electrode–electrolyte interface (EEI). More electrolyte ions reach the surface of FZC electrode material under Kelvin force, moreover, the warburg impedance of FZC nanocomposites decrease under magnetic field action, which results in the enhanced behaviors for both the energy storage and urea oxidation reaction .
关键词:
3D framework;Biofouling;Electrospun membrane;Membrane bioreactor;Structure enhancing;quorum quenching
摘要:
Bacterial quorum quenching (QQ) is an effective strategy for controlling biofouling in membrane bioreactor (MBR) by interfering the releasing and degradation of signal molecules during quorum sensing (QS) process. However, due to the framework feature of QQ media, the maintenance of QQ activity and the restriction of mass transfer threshold, it has been difficult to design a more stable and better performing structure in a long period of time. In this research, electrospun fiber coated hydrogel QQ beads (QQ-ECHB) were fabricated by using electrospun nanofiber coated hydrogel to strengthen layers of QQ carriers for the first time. The robust porous PVDF 3D nanofiber membrane was coated on the surface of millimeter-scale QQ hydrogel beads. Biocompatible hydrogel entrapping quorum quenching bacteria (sp.BH4) was employed as the core of the QQ-ECHB. In MBR with the addition of QQ-ECHB, the time to reach transmembrane pressure (TMP) of 40 kPa was 4 times longer than conventional MBR. The robust coating and porous microstructure of QQ-ECHB contributed to keeping a lasting QQ activity and stable physical washing effect at a very low dosage (10g beads/5L MBR). Physical stability and environmental-tolerance tests also verified that the carrier can maintain the structural strength and keep the core bacteria stable when suffering long-term cyclic compression and great fluctuations in sewage quality.
通讯机构:
[Chen, CS ] C;Changsha Univ Sci & Technol, Coll Mat Sci & Engn, Changsha 410114, Peoples R China.
关键词:
Graphene oxide;Quaternary material;Microwave synthesis;Photocatalytic H 2-production
摘要:
To enhance the photocatalytic H2 production capacity of reduced graphene oxide/CdS/ single crystal ZnO nanorod (RGOCZ) ternary material, Ce-organic framework [UiO66-(Ce)]/ rGO/CdS/single crystal ZnO nanorod (URGOCZ) quaternary material was prepared by microwave-assisted co-precipitation method, and the influence of UiO66-(Ce) content on the photocatalytic performance of quaternary material was analyzed. The experimental study shows that RGOCZ ternary material is anchored in the surface of the UiO66-(Ce), and the photocatalytic H2 evolution capacity of RGOCZ ternary material is enhanced by UiO66(Ce) significantly. When 15 mL UiO66-(Ce) solution (0.4 g/L) is added, the photocatalytic H2 evolution efficiency of 15URGOCZ quaternary material reaches 10.55 mmol g-1 h-1.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
摘要:
Styrene/1,3-diene copolymers are widely used in rubber tires, adhesives, waterproof materials, automotive parts and others. However, their oil resistance, compatibility with polar materials, and poor adhesion limit their applications. Polarization modification strategy can further expand the application field of such materials. In this paper, a series of strictly alternating copolymers were synthesized in cyclohexane via living and controlled anionic alternating copolymerization of styrene derivatives (including styrene (ST), p-methylstyrene (MST), p-tert-butylstyrene (TBS), and 1,1-diphenylethylene (DPE)) with 1,3-pentadiene (PD) using n-BuLi initiator. The above-mentioned alternating copolymers were epoxidized in cycloamyl methyl ether (CPME, green solvent) using m-Chloroperoxybenzoic acid (m-CPBA) as the oxygen source. The H-1 NMR and FTIR results showed that the degree of epoxidation (DE) of the alternating copolymers was controllable and the cross-linking gels can be avoided (determined by solubility experiment), and the DE of nearly 100% could be achieved by optimizing processes. As for these PD-based alternating copolymers, the type of substituents on rigid benzene rings has a certain impact on the epoxidation rate as well as the DE. DSC results showed that not only the high steric hindrance groups in polymer side chains but also the epoxidation strategy can greatly improve the heat resistance of the product.
通讯机构:
[Qin, Wei] C;College of Materials Science and Engineering, Changsha University of Science and Technology, Changsha 410114, China. Electronic address:
摘要:
Due to the large ionic radius and associated slow reaction kinetics of potassium ions, it is a major chal-lenge to find suitable anode materials for potassium-ion batteries. Herein, we design porous antimony -based nanofibres via a simple, low-cost and large scalable method to promote the electrochemical per-formance of potassium-ion batteries. Unlike those traditionally treated in inert atmospheres, using the different decomposition processes of polyacrylonitrile and polyvinylpyrrolidone in air, we obtain anti-mony trioxide embedded in porous carbon nanofibres (Sb2O3@PCN). The porous structure can promote the permeation of electrolyte into electrode materials and increase the active sites of the redox reaction. The porous carbonaceous fibre skeleton structure establishes a fast ion transport channel and enhances the kinetic performance. In a concentrated 5 M potassium bis(fluorosulfonyl)-imide/dimethyl carbonate electrolyte, Sb2O3@PCN exhibits a stable discharge specific capacity of 437.3 mAh g-1 at a current density of 100 mA g-1 after 50 cycles, which is much higher than that treated in a N2 atmosphere (247.5 mAh g-1). This method provides a new approach for the preparation of efficient potassium-ion battery electrode materials. (c) 2022 Elsevier Inc. All rights reserved.
通讯机构:
[Lu, ZP ; Wu, Y] U;[Lei, ZF ] H;Univ Sci & Technol Beijing, Beijing Adv Innovat Ctr Mat Genome Engn, State Key Lab Adv Met & Mat, Beijing 100083, Peoples R China.;Hunan Univ, Coll Mat Sci & Engn, Changsha 410082, Peoples R China.
摘要:
Oxygen solute strengthening is an effective strategy to harden alloys, yet, it often deteriorates the ductility. Ordered oxygen complexes (OOCs), a state between random interstitials and oxides, can simultaneously enhance strength and ductility in high-entropy alloys. However, whether this particular strengthening mechanism holds in other alloys and how these OOCs are tailored remain unclear. Herein, we demonstrate that OOCs can be obtained in bcc (body-centered-cubic) Ti-Zr-Nb medium-entropy alloys via adjusting the content of Nb and oxygen. Decreasing the phase stability enhances the degree of (Ti, Zr)-rich chemical short-range orderings, and then favors formation of OOCs after doping oxygen. Moreover, the number density of OOCs increases with oxygen contents in a given alloy, but adding excessive oxygen (>3.0 at.%) causes grain boundary segregation. Consequently, the tensile yield strength is enhanced by ~75% and ductility is substantially improved by ~164% with addition of 3.0 at.% O in the Ti-30Zr-14Nb MEA. Ordered oxygen complexes (OOCs) endow a unique interstitial strengthening mechanism for simultaneously enhancing strength and ductility in HEAs. Here, the authors demonstrate whether such mechanism can be extended to other alloy systems and how the formation of OOCs is tailored.
通讯机构:
[Jianxiao Yang; Ruixuan Tan] H;Hunan Province Key Laboratory for Advanced Carbon Materials and Applied Technology, College of Materials Science and Engineering, Hunan University, Changsha 410082, China
摘要:
Abstract: Lightweight, high-temperature-resistant carbon-bonded carbon fiber (CBCF) composites with excellent thermal insulation properties are desirable materials for thermal protection systems in military and aerospace applications. Here, glucose was introduced into the polyacrylamide hydrogel to form the glucose-polyacrylamide (Glu-PAM) hydrogel. The CBCF composites were prepared using the Glu-PAM hydrogel as a brand-new binder, and the synergistic effect between glucose and acrylamide was investigated. The results showed the Glu-PAM hydrogel could limit the foaming of glucose and enhance the carbon yield of glucose. Meanwhile, the dopamine-modified chopped carbon fiber could be uniformly mixed by high-speed shearing to form a slurry with the Glu-PAM hydrogel. Finally, the slurry was successfully extruded and molded to prepare CBCF composites with a density of 0.158~0.390 g cm−3 and excellent thermal insulation performance and good mechanical properties. The compressive strength of CBCF composites with a density of 0.158 g cm−3 in the Z direction is 0.18 MPa, and the thermal conductivity in the Z direction at 25 °C and 1200 °C is 0.10 W m−1 k−1 and 0.20 W m−1 k−1, respectively. This study provided an efficient, environment-friendly, and cost-effective strategy for the preparation of CBCF composites. Keywords: carbon-bonded carbon fiber composites; glucose-polyacrylamide hydrogel; chopped carbon fiber; extrusion-injection molding; thermal conductivity
摘要:
In this study, the intrinsic heterogeneous grain structure derived from the special temperature gradient in additive manufacturing and the intragranular precipitation were utilized for constructing a high-strength Al-Mg-Sc-Zr alloy. The alternative distribution of the coarse-grained (CG) layer in the middle of the molten pool and ultrafine-grained (UFG) layer at the boundary between the adjacent two molten pools were produced by using laser powder bed fusion (L-PBF) technology. High contents of Sc and Zr elements were introduced into the Al-Mg alloy, which contributed to the stabilization of UFG boundaries in the form of sub-micro primary Al3(Sc, Zr) particles and resulted in the formation of supersaturated Sc and Zr solid solutions in CG. The afterward aging treatment or well-controlled hot isostatic pressing (HIP) induced uniform precipitation of the high-density nano-scale coherent Al3(Sc, Zr) phase in CG. The HIP also promoted a significant decrease in porosity of the alloy and resulted in a combination of high ultimate tensile strength of 560 MPa and elongation of 12 % of the L-PBF Al-Mg-Sc-Zr alloy. The high strength of the alloy was attributed to the hierarchical formation of the Sc-rich phase, exerting a "dragging effect" on intergranular boundary migration as well as a "pinning effect" on intragranular dislocation sliding. (c) 2023 Elsevier B.V. All rights reserved.
通讯机构:
[Yonggang Tong] C;College of Automobile and Mechanical Engineering, Changsha University of Science and Technology, Changsha, People’s Republic of China
摘要:
Developing advanced materials with excellent mechanical properties and high-temperature oxidation performance are important to the potential application in high-temperature structural parts. In the paper, CoCrNiAlxY (x = 0.2, 0.6, 1.0 and 1.4) middle entropy alloys were prepared, and the effects of Al content on the microstructure, mechanical properties and oxidation behavior at 1200 degrees C of CoCrNiAlxY middle entropy alloys were studied. The phase of CoCrNiAlxY alloys is changing from FCC to BCC with increasing Al content; thereinto, CoCrNiAl0.6Y alloy forms duplex FCC plus BCC phase structure. The hardness and fracture strength of CoCrNiAlxY (x = 0.2, 0.6, 1.0) alloys increase with increasing Al content. When Al content is 1.4, the hardness and fracture strength of CoCrNiAl1.4Y alloy decrease, which result from the tiny variation of alloy microstructure. The oxidation behavior at 1200 degrees C of CoCrNiAlxY alloys confirms that compact aluminum oxide film can be formed on the CoCrNiAl0.6Y alloy, which slows down the oxidation rate of the alloy. The CoCrNiAl0.6Y alloy has the best oxidation resistance with lower oxidation rate of 1.467 x 10(-11) g(2)/(cm(4) s).
作者机构:
[Jiang, Yong; Lu, Anxian; Lin, Xiangtao; Jiang, Y; Wang, Zhikai; Liu, Songxuan; Jiang, Xingxing; Liu, Lidan] Cent South Univ, Sch Mat Sci & Engn, Changsha 410083, Peoples R China.;[Ning, Tianxiang] Changsha Univ Sci & Technol, Sch Mat Sci & Engn, Changsha 410114, Peoples R China.;[Ning, Tianxiang] Hunan LEED Elect Ink Co Ltd, Zhuzhou 412000, Hunan, Peoples R China.
通讯机构:
[Lu, AX ; Jiang, Y; Ning, TX ] C;Cent South Univ, Sch Mat Sci & Engn, Changsha 410083, Peoples R China.;Changsha Univ Sci & Technol, Sch Mat Sci & Engn, Changsha 410114, Peoples R China.
关键词:
Ga 2 O 3 modifier;Glass ceramic;Crystallization behavior;Fluorescence properties
摘要:
This paper focuses on the effects of Ga2O3/GeO2 ratios and heat treatment on the structure, crystallization and fluorescence properties of Gd2O3-Ga2O3-GeO2-Nd2O3 glass system. According to the results, the glass network's structural stability suffers when the ratio of Ga2O3/GeO2 is low. As the ratio of Ga2O3/GeO2 continues to increase, Ga3+ ions are transformed into [GaO4] to participate in the construction of the glass network structure. The principal phase of glass-ceramics is GdGaGe2O7, and the secondary phase is Ga4GeO8, GeO2 and Gd3Ga5O12. Moreover, the glasses with high content of Ga2O3 is easier to prepare translucent glass-ceramics with uniform grain distribution and size. The emission spectrum intensity of glass-ceramics is obviously improved compared with that of glasses. In addition, it is found that the emission peak of Nd3+ ions generated by 4F3/2 -> 4I11/2 electron transition is stably redshifted from 1060 nm to 1088 nm by microcrystallization, which means a small range of spectrum is adjustable.
摘要:
In this work, a Cu@Co catalyst with dilatation strain is prepared for low‐concentration NO electroreduction, and it exhibits high NH3 yield of 627.20 µg h‐1 cm‐2 and Faradaic efficiency of 76.54%. The assembled Zn‐NO battery using Cu@Co as cathode achieves a power density of 3.08 mW cm−2, which can simultaneously realize NO removal, NH3 green synthesis, and electricity output. Abstract Electrocatalytic reduction of nitric oxide (NO) to ammonia (NH3) is a clean and sustainable strategy to simultaneously remove NO and synthesize NH3. However, the conversion of low concentration NO to NH3 is still a huge challenge. In this work, the dilatation strain between Cu and Co interface over Cu@Co catalyst is built up and investigated for electroreduction of low concentration NO (volume ratio of 1%) to NH3. The catalyst shows a high NH3 yield of 627.20 µg h−1 cm−2 and a Faradaic efficiency of 76.54%. Through the combination of spherical aberration‐corrected transmission electron microscopy and geometric phase analyses, it shows that Co atoms occupy Cu lattice sites to form dilatation strain in the xy direction within Co region. Further density functional theory calculations and NO temperature‐programmed desorption (NO‐TPD) results show that the surface dilatation strain on Cu@Co is helpful to enhance the NO adsorption and reduce energy barrier of the rate‐determining step (*NO to *NOH), thereby accelerating the catalytic reaction. To simultaneously realize NO exhaust gas removal, NH3 green synthesis, and electricity output, a Zn‐NO battery with Cu@Co cathode is assembled with a power density of 3.08 mW cm−2 and an NH3 yield of 273.37 µg h−1 cm−2.
期刊:
Journal of Materials Chemistry A,2023年11(27):14720-14727 ISSN:2050-7488
通讯作者:
Yuan, D;Zhang, YZ;Zhang, HT
作者机构:
[Yao, Hong; Yuan, D; Li, Yuhang; Yuan, Du; Liu, Xiangjie; Li, Xin] Changsha Univ Sci & Technol, Coll Mat Sci & Engn, Changsha 410004, Hunan, Peoples R China.;[Wong, Ming Wah; Chen, Yingqian] Natl Univ Singapore, Dept Chem, Block S8,3 Sci Dr 3, Singapore 117543, Singapore.;[Zhang, Yizhou; Zhang, YZ] Nanjing Univ Informat Sci & Technol, Inst Adv Mat & Flexible Elect IAMFE, Sch Chem & Mat Sci, Nanjing 210044, Peoples R China.;[Zhang, Haitao] Chinese Acad Sci, Inst Proc Engn, Beijing 100190, Peoples R China.
通讯机构:
[Zhang, YZ ] N;[Yuan, D ; Zhang, HT ] C;Changsha Univ Sci & Technol, Coll Mat Sci & Engn, Changsha 410004, Hunan, Peoples R China.;Nanjing Univ Informat Sci & Technol, Inst Adv Mat & Flexible Elect IAMFE, Sch Chem & Mat Sci, Nanjing 210044, Peoples R China.;Chinese Acad Sci, Inst Proc Engn, Beijing 100190, Peoples R China.
摘要:
Electrolyte design provides a fundamental solution to address the irreversibility and instability of metallic Zn anodes for the fast-developing zinc-ion batteries, considering the increasing issue of their sustainability. Herein, a cellulose-complexing approach was developed for a ZnCl2-based eutectic electrolyte to reconstruct Zn2+ coordination, tune water activity and regulate the solid-electrolyte interface (SEI). In the case of deficient water, the oxygen atoms from the glucose unit were revealed to coordinate directly with Zn2+, resulting in the participation of cellulose in the solvation shell of Zn2+, with a change in the hydrogen-bond network, where water transformed into the bulk state. The reshaped Zn2+ coordination with sluggish water activity led to a widened electrochemical window and promising ion transport in the complex electrolyte. Endowed with a dissolution-regeneration induced in situ SEI with inorganic-organic characteristics, dendrite-free Zn stripping/plating were achieved at a high current density of 50 mA cm(-2) and 50 mA h cm(-2) for 2000 h, with a high depth-of-discharge of 85%. The complex electrolyte was demonstrated to be beneficial for the long-term cycling stability of the activated carbon/Zn cell compared to its ZnCl2 eutectic electrolyte counterpart. Further, an artificial SEI was fabricated via electrochemical deposition using the electrolyte, possessing the merits of organic-dominant characteristics. The developed approach provides a facile route to prepare novel zinc electrolytes towards a high utilization rate of Zn.
通讯机构:
[Liu, Z; Liu, Z ; Guo, ZH ; Bai, L ] N;Nanchang Hangkong Univ, Natl Def Key Disciplines Lab Light Alloy Proc Sci, Nanchang 330063, Jiangxi, Peoples R China.;Nanchang Hangkong Univ, Sch Aeronaut Mfg Engn, Nanchang 330063, Jiangxi, Peoples R China.;NanChang JiaoTong Inst, Nanchang 330100, Jiangxi, Peoples R China.
关键词:
Electron beam direct energy deposition;Anisotropy;Uniform elongation;Columnar morphology;Ti–6Al–4V alloy
摘要:
Additive manufactured titanium alloys are generally characterized by columnar grain structures along the vertical direction (VD), thereby causing a relative lower plasticity in the horizontal direction (HD) than that in the VD direction. However, herein we report that such columnar grain structures in the Ti-6Al-4V alloy produced by electron beam direct energy deposition (EB DED) can induce a superior uniform elongation in the HD direction than that in the other loading directions (22.5 degrees ,45 degrees, 67.5 degrees and VD directions). Besides the orientation of alpha laths with a favorable soft and hard match when the loading direction is along the HD, such anisotropic plasticity also can be attributed to the columnar grain structures which can also effectively prevent dislocation slip and suppress the necking of the HD sample, thereby triggering a greater work-hardening rate and strain hardening exponent in the stage of uniform deformation, and increasing the uniform elongation in the HD. The greater total elongation in the VD is mainly reflected in its higher non-uniform elongation, rather than uniform elongation, which is mainly caused by the alpha laths possessing easily activated basal slip system inducing strain softening. As for the 22.5 degrees and 45 degrees samples, most of the alpha laths under such loading directions present hard orientation, thereby leading to both lower non-uniform elongation and total elongation. The above information offers a deeper understanding about anisotropic plasticity in additive manufactured titanium alloys, thereby providing a theoretical basis for optimizing the consistency of mechanical properties.
摘要:
Layered Ni-rich transition metal oxides (LiNixCoyMnzO2, x + y + z = 1, NCM) are regarded as promising cathodes for high-energy Li-ion batteries, due to merits of large capacity and low cost. However, the formed microcracks during cycling can lead to severe structural degradation, rapidly deteriorating properties of NCM cathode. To solve this problem, an enhanced mechanical strength strategy triggered by regulating the grain size of precursor has been successfully proposed, which is aimed at improving the structural stability of NCM cathode. It is found that NCM cathode featured with small grain size (NCM-S) exhibits a strong mechanical property for hindering structural deterioration. Detailedly, the strong external compression rupture strength triggered by grain size effect and decreased internal stress originating from mitigated H2-H3 phase transition are both beneficial for synergistically suppressing the generation of microcracks. Benefiting from the unique architecture, the NCM-S cathode delivers a remarkable initial discharge capacity of 192.6 mAh g(-1) at 0.1C and excellent capacity retention of 82.8 % after 300 cycles at 1C. This work powerfully provides a mechanistic perspective based on the regulating precursor grain size for impeding the structure collapse, which is beneficial for purposefully engineering the high-performance Ni-rich cathodes in electric vehicles.