Subjects -> METALLURGY (Total: 59 journals)
Showing 1 - 10 of 10 Journals sorted alphabetically
Acta Metallurgica Slovaca     Open Access   (Followers: 2)
Advanced Device Materials     Open Access   (Followers: 6)
American Journal of Fluid Dynamics     Open Access   (Followers: 44)
Archives of Metallurgy and Materials     Open Access   (Followers: 9)
Asian Journal of Materials Science     Open Access   (Followers: 4)
Canadian Metallurgical Quarterly     Hybrid Journal   (Followers: 21)
Complex Metals     Open Access   (Followers: 2)
Energy Materials : Materials Science and Engineering for Energy Systems     Hybrid Journal   (Followers: 24)
Graphene and 2D Materials     Open Access   (Followers: 6)
Handbook of Ferromagnetic Materials     Full-text available via subscription   (Followers: 1)
Handbook of Magnetic Materials     Full-text available via subscription   (Followers: 2)
High Temperature Materials and Processes     Open Access   (Followers: 6)
Indian Journal of Engineering and Materials Sciences (IJEMS)     Open Access   (Followers: 11)
International Journal of Metallurgy and Alloys     Full-text available via subscription   (Followers: 2)
International Journal of Metals     Open Access   (Followers: 7)
International Journal of Minerals, Metallurgy, and Materials     Hybrid Journal   (Followers: 12)
International Journal of Mining and Geo-Engineering     Open Access   (Followers: 4)
Ironmaking & Steelmaking     Hybrid Journal   (Followers: 5)
ISIJ International - Iron and Steel Institute of Japan     Full-text available via subscription   (Followers: 26)
Izvestiya Vuzov. Poroshkovaya Metallurgiya i Funktsional’nye Pokrytiya (Proceedings of Higher Schools. Powder Metallurgy аnd Functional Coatings)     Full-text available via subscription   (Followers: 2)
JOM Journal of the Minerals, Metals and Materials Society     Hybrid Journal   (Followers: 35)
Journal of Advanced Joining Processes     Open Access  
Journal of Central South University     Hybrid Journal   (Followers: 1)
Journal of Cluster Science     Hybrid Journal  
Journal of Heavy Metal Toxicity and Diseases     Open Access  
Journal of Iron and Steel Research International     Hybrid Journal   (Followers: 11)
Journal of Materials & Metallurgical Engineering     Full-text available via subscription   (Followers: 2)
Journal of Materials Processing Technology     Hybrid Journal   (Followers: 21)
Journal of Metallurgical Engineering     Open Access   (Followers: 4)
Journal of Sustainable Metallurgy     Hybrid Journal   (Followers: 3)
Materials Science and Metallurgy Engineering     Open Access   (Followers: 7)
Metal Finishing     Full-text available via subscription   (Followers: 20)
Metallurgical and Materials Engineering     Open Access   (Followers: 7)
Metallurgical and Materials Transactions A     Hybrid Journal   (Followers: 42)
Metallurgical and Materials Transactions B     Hybrid Journal   (Followers: 32)
Metallurgical and Materials Transactions E     Full-text available via subscription   (Followers: 2)
Metallurgical Research & Technology     Full-text available via subscription  
Metallurgical Research and Technology     Full-text available via subscription   (Followers: 8)
Metallurgy and Foundry Engineering     Open Access   (Followers: 3)
Mining, Metallurgy & Exploration     Hybrid Journal  
Powder Diffraction     Full-text available via subscription   (Followers: 1)
Powder Metallurgy     Hybrid Journal   (Followers: 35)
Powder Metallurgy and Metal Ceramics     Hybrid Journal   (Followers: 7)
Powder Metallurgy Progress     Open Access   (Followers: 5)
Practical Metallography     Full-text available via subscription   (Followers: 6)
Rare Metals     Hybrid Journal   (Followers: 3)
Revista de Metalurgia     Open Access  
Revista del Instituto de Investigación de la Facultad de Ingeniería Geológica, Minera, Metalurgica y Geográfica     Open Access  
Revista Remetallica     Open Access   (Followers: 1)
Russian Metallurgy (Metally)     Full-text available via subscription   (Followers: 4)
Science and Technology of Welding and Joining     Hybrid Journal   (Followers: 8)
Soldering & Surface Mount Technology     Hybrid Journal   (Followers: 2)
Steel Times lnternational     Partially Free   (Followers: 19)
Transactions of the IMF     Hybrid Journal   (Followers: 14)
Transactions of the Indian Institute of Metals     Hybrid Journal   (Followers: 5)
Tungsten     Hybrid Journal  
Universal Journal of Materials Science     Open Access   (Followers: 3)
Welding in the World     Hybrid Journal   (Followers: 8)
Welding International     Hybrid Journal   (Followers: 11)
Вісник Приазовського Державного Технічного Університету. Серія: Технічні науки     Open Access  
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Rare Metals
Journal Prestige (SJR): 0.454
Citation Impact (citeScore): 1
Number of Followers: 3  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1001-0521 - ISSN (Online) 1867-7185
Published by Springer-Verlag Homepage  [2655 journals]
  • Electrolytes speed up development of zinc batteries
    • PubDate: 2021-04-01
       
  • Stacking fault, dislocation dissociation, and twinning in Pt 3 Hf
           compounds: a DFT study
    • Abstract: The Pt3Hf compound plays a decisive role in strengthening Pt–Hf alloy systems. Evaluating the stacking fault, dislocation dissociation, and twinning mechanisms in Pt3Hf is the first step in understanding its plastic behavior. In this work, the generalized stacking fault energies (GSFE), including the complex stacking fault (CSF), the superlattice intrinsic stacking fault (SISF), and the antiphase boundary (APB) energies, are calculated using first-principles calculations. The dislocation dissociation, deformation twinning, and yield behavior of Pt3Hf are discussed based on GSFE after their incorporation into the Peierls-Nabarro model. We found that the unstable stacking fault energy (γus) of (111)APB is lower than that of SISF and (010) APB, implying that the energy barrier and critical stress required for (111)APB generation are lower than those required for (010)APB formation. This result indicates that the \(a\left\langle {1\bar{1}0} \right\rangle\) superdislocation will dissociate into two collinear \({a \mathord{\left/ {\vphantom {a 2}} \right. \kern-0pt} 2}\left\langle {1\bar{1}0} \right\rangle\) superpartial dislocations. The \({a \mathord{\left/ {\vphantom {a 2}} \right. \kern-0pt} 2}\left\langle {1\bar{1}0} \right\rangle\) dislocation could further dissociate into a \({a \mathord{\left/ {\vphantom {a 6}} \right. \kern-0pt} 6}\left\langle {\bar{1}\bar{1}2} \right\rangle\) Shockley dislocation and a \({a \mathord{\left/ {\vphantom {a 3}} \right. \kern-0pt} 3}\left\langle {2\bar{1}\bar{1}} \right\rangle\) super-Shockley dislocation connected by a SISF, which results in an APB → SISF transformation. The study also discovered that Pt3Hf exhibits normal yield behavior, although the cross-slip of a \({a \mathord{\left/ {\vphantom {a 2}} \right. \kern-0pt} 2}\left\langle {1\bar{1}0} \right\rangle\) dislocation is not forbidden, and the anomalous yield criterion is satisfied. Moreover, it is observed that the energy barrier and critical stress for APB formation increases with increasing pressure and decreases as the temperature is elevated. When the temperature rises above 1400 K, the \({a \mathord{\left/ {\vphantom {a 2}} \right. \kern-0pt} 2}\left\langle {1\bar{1}0} \right\rangle\) dislocation slipping may change from the {111} planes to the {100} planes. Graphical abstract
      PubDate: 2021-04-01
       
  • Corrosion evolution and behaviour of Al–2.1Mg–1.6Si alloy in
           chloride media
    • Abstract: Owing to the importance of finding better methods and technologies for protecting against corrosion of aluminium alloys, research into the electrochemical characteristics of the corrosion is an ongoing concern. In this paper, the corrosion behaviour of Al–Mg–Si alloys in 3.5 wt% NaCl solution was investigated using multiple methods, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), potentiodynamic polarisation measurement and electrochemical impedance spectroscopy (EIS). The results suggest that corrosion begins with dealloying of Mg, followed by conversion of MgSi particles into Al–Fe–Mn–Si particles. The corrosion rate increased until it reached a peak and then decreased. The increase in the corrosion rate may be attributed to an increased electrochemical driving force, which is produced by anodic dissolution between the matrix and residual MgSi particles. Additionally, the thin re-deposited layer of inert elements also plays an important role in accelerating the anodic process of the corrosion pit. The passivated corrosion pit and narrowed intergranular corrosion (IGC) pathway cause the area of active dissolution to decrease, thus reducing the corrosion rate.
      PubDate: 2021-04-01
       
  • Microstructure, fracture behavior, in vitro corrosion resistance, and
           cytotoxicity of Zn–Mg/Mg–Zn–HAp laminated composites produced by
           spark plasma sintering
    • Abstract: Ideal biodegradable materials exhibit suitable degradation rates and sufficient mechanical properties for their specific application. With these parameters in mind, Zn–Mg/Mg–Zn–hydroxyapatite (HAp) laminated composites were designed and fabricated by spark plasma sintering. This paper describes the structure, mechanical properties, in vitro corrosion resistance, and cytotoxicity of the Zn–Mg/Mg–Zn–HAp laminated composites. The compressive strength and elastic moduli of the laminated composites matched that of cortical bone and could effectively reduce the stress shielding effect as an implant with good biomechanical compatibility. Analysis of the fracture path and morphology after fracture toughness tests indicated that the Zn–Mg/Mg–Zn–HAp laminated composites exhibited significant capacity to prevent crack propagation, improving the fracture toughness. In vitro degradation experiments showed that the design of the laminated structure can provide a gradient degradation rate for the material. Furthermore, the laminated composites exhibited excellent biocompatibility and are promising candidates for orthopedic implants.
      PubDate: 2021-04-01
       
  • Microstructure, magnetic properties of hexagonal barium ferrite powder
           based on calcination temperature and holding time
    • Abstract: In this paper, single-phase and fine-grain hexagonal barium ferrite powder was prepared based on the optimal calcination condition. The influence of calcination conditions including temperature and holding time on microstructure and magnetic properties of powder were studied in detail. Firstly, θ–2θ scan X-ray diffraction (XRD) results reveal that it is hard to obtain single phase of powder when the calcination temperature is lower than 850 °C. In addition, the calcination time for single phase of barium ferrite powder was reduced with the increase in calcination temperature. Scanning electron microscopy (SEM) images and magnetic hysteresis loops show that the condition of low temperature and long holding time is beneficial for obtaining homogeneous size of grain and excellent magnetic properties. Consequently, hexagonal barium ferrite powder with uniform grain size of ~ 180 nm, high purity and excellent magnetic properties is obtained at optimal calcination condition of 850 °C–10.0 h.
      PubDate: 2021-04-01
       
  • Photocatalytic and photochemical processes of AgCl/TiO 2 studied with a
           fully integrated X-ray photoelectron spectrometer
    • Abstract: A fully integrated X-ray photoelectron spectrometer (XPS) was employed for the investigation of the separation processes and recombination behaviors of photogenerated electrons and holes on the surface of AgCl and ultra-small nano-titanium oxide cluster composite photocatalyst (AgCl/TiO2). A facile route, by direct colloidal synthesis, for preparing AgCl/TiO2 with high stability and enhanced visible light (Vis) driven catalytic activity was reported. The photocatalytic activity of AgCl/TiO2, which revealed that the photo-degradation rate of the as-prepared AgCl/TiO2 was nearly 10.5 times higher than that of bare AgCl, was evaluated by applying it to the photo-degradation of methyl orange (MO) in water solution. Moreover, AgCl/TiO2 exhibited an outstanding long-term stability during ten cycles of photo-degradation. The band gap of AgCl decreased from 3.25 to 2.85 eV because of the ultra-small nano-TiO2 clusters that were pinned to its surface. The results indicate that the band gap narrowing and surface plasmon resonance (SPR) of Ag (0) were two major contributors to the enhancement of the photocatalytic activity of AgCl/TiO2 by improving the utilization of Vis. In situ XPS analysis was, therefore, certified as a beneficial method to explore the catalytic mechanism of photocatalysts. Graphic abstract
      PubDate: 2021-04-01
       
  • Improvement in irradiation resistance of FeCu alloy by pre-deformation
           through introduction of dense point defect sinks
    • Abstract: The irradiation resistance of pre-deformed FeCu alloy was studied using a 3 MeV Fe ion irradiation experiment at room temperature in comparison with that of the as-received sample. Nanoindentation and atom probe tomography (APT) were used to characterize the mechanical properties and solute distribution. The stress–strain curve obtained by nanoindentation shows that the yield strength (σ0.2) of the pre-deformed sample is unexpectedly reduced with an increase in the irradiation dose to five displacements per atom (dpa). We suggest that it results both from the decrease in the dislocation density and the suppression of defects during irradiation. APT shows that the nucleation of the Cu cluster is suppressed; however, its growth is promoted in the pre-deformed sample, resulting in the formation of sparse and coarse clusters at 1 dpa irradiation. These coarse Cu clusters were then unexpectedly refined to finer grains with an increase in the irradiation dose to 5 dpa. Theoretically, the improvement in the resistance to irradiation in the pre-deformed sample is attributed to the dense point-defect sinks, that is, the dislocations and grain boundaries introduced by pre-deformation. In addition, the contributions of the dislocations and grain boundaries to the sink strength are estimated for both the as-received and pre-deformed samples. The results indicate that dislocations, rather than grain boundaries, play a major role after deformation. Graphic abstract
      PubDate: 2021-04-01
       
  • Multi-core–shell-structured LiFePO 4 @Na 3 V 2 (PO 4 ) 3 @C composite
           for enhanced low-temperature performance of lithium-ion batteries
    • Abstract: In this work, a multi-core–shell-structured LiFePO4@Na3V2(PO4)3@C (LFP@NVP@C) composite was successfully designed and prepared to address inferior low-temperature performance of LiFePO4 cathode for lithium-ion batteries. Transmission electron microscopy (TEM) confirms the inner NVP and outer carbon layers co-existed on the surface of LFP particle. When evaluated at low-temperature operation, LFP@NVP@C composite exhibits an evidently enhanced electrochemical performance in term of higher capacity and lower polarization, compared with LFP@C. Even at − 10 °C with 0.5C, LFP@NVP@C delivers a discharge capacity of ca. 96.9 mAh·g−1 and discharge voltage of ca. 3.3 V, which is attributed to the beneficial contribution of NVP coating. NASICON-structured NVP with an open framework for readily insertion/desertion of Li+ will effectively reduce the polarization for the electrochemical reactions of the designed LFP@NVP@C composite. Graphic abstract
      PubDate: 2021-04-01
       
  • Fabrication of nano-grained negative temperature coefficient thermistors
           with high electrical stability
    • Abstract: Dense nano-grained Ni0.7Mn2.3O4 negative temperature coefficient (NTC) thermistors were fabricated by a novel two-step sintering approach that combines rapid sintering and principle of conventional two-step sintering technique. Samples were sintered at 1042 °C for 30 s in the first rapid step and then at 850–950 °C for 20 h in the second soaking step. Crystal phase, microstructure and electrical properties of sintered samples were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), resistance temperature relationship and aging performance. Sintered samples show a single-phase cubic spinel structure and indicate a high relative density ranging from 84% to 91% of the theoretical density. Moreover, average grain sizes of sintered samples under SEM are distributed between 254 and 570 nm. Meanwhile, the resistivity and the aging coefficient significantly decrease when soaking sintering temperature rises. In addition, the obtained material constant (B) ranges from 3931 to 3981 K. Ni0.7Mn2.3O4-3 (soaking at 900 °C) and Ni0.7Mn2.3O4-4 (soaking at 950 °C) present little aging behavior, implying great electrical stability.
      PubDate: 2021-04-01
       
  • When thermoelectric materials come across with magnetism
    • Abstract: Nowadays, thermoelectric materials have attracted a lot of attention as they can directly convert heat into electricity and vice versa. However, while strenuous efforts have been made, those conventional strategies are still inevitably going to meet their performance optimization limits. For this reason, brand new strategies are badly needed to achieve further enhancement. Here, the roles played by magnetism in recent advances of thermoelectric optimization are concluded. Firstly, magnetic thermoelectric materials can just be treated like other normal materials because the use of universal optimization strategies can still get good results. So, it is not a situation which is all or nothing and the tactics of using magnetism for thermoelectric optimization can coexist with other strategies. Besides, through magnetic doping, we can introduce and adjust magnetism in materials for further optimization. Magnetism provides more possibilities in thermoelectric optimization as it can directly influence the spin states in materials. Furthermore, in the form of magnetic second-phase nanoclusters, magnetism can be introduced to thermoelectric materials to conquer the dilemma that the solid solubility of many magnetic ions in thermoelectric materials is too low to have any significant effect on thermoelectric properties. Finally, when exposed to an external magnetic field, topological materials can rely on its unique band structures to optimize. Graphic
      PubDate: 2021-04-01
       
  • Reoxidation process and corrosion behavior of TA15 alloy by laser ablation
    • Abstract: The thermal oxide layer formed of TA15 alloy has poor corrosion resistance. In this paper, the changes of the elements and components on the surface after laser ablation with different energy densities (E) were researched. The formation process and corrosion behavior of laser-generated oxide layer were clarified. As E increases, the oxygen content decreases from 8.52% to 5.43% and then increases to 11.89%. The surface oxide layer changes from TiO2(R) (i.e., rutile) to Ti2O3 + TiO2(R) and finally becomes TiO2(R) + TiO2(A) (i.e., anatase). The TiO2(R) gasification was confirmed by calculating the surface temperature rise. The surface reoxidation process was illustrated by a thermodynamically calculated ∆G-T(i.e., the Gibbs free energy changes with temperature). When E ≥ 17.5 J·cm−2, the oxide layer exhibits an agitated morphology, and oxide falls off at the bottom. As E increases, the corrosion rate decreases first and then increases. With energy density of 8.75 J·cm−2, the surface corrosion rate was 20.43 times slower than that of the untreated sample. The impedance spectrum and equivalent resistance results also prove the best corrosion resistance at 8.75 J·cm−2. The corrosion behavior of the oxide layer is analyzed from the properties of the oxide layer components and the reaction products with the electrolyte. Graphic abstract
      PubDate: 2021-04-01
       
  • Improving interface adhesion in TiNi wire/shape memory epoxy composites
           using carbon nanotubes
    • Abstract: In order to increase both the interfacial strength and interphase region strength between TiNi wires and shape memory epoxy, a novel interface structure including aminated CNTs was designed. The morphology shows that after electroplating and etching, continuous and homogeneous concave–convex layers form on the surface of as-treated TiNi wires, meanwhile aminated CNTs were planted on the surface which could react with shape memory epoxy at the interface region. The interfacial shear strength increases first with the CNT content rising but then a dramatic drop happens, and the maximum is obtained at CNT content of 0.6 g·L−1, which is about twice the result of acid etching TiNi wires.
      PubDate: 2021-04-01
       
  • Leakage current characteristics of SrTiO 3 /LaNiO 3 /Ba 0.67 Sr 0.33 TiO 3
           /SrTiO 3 heterostructure thin films
    • Abstract: There is an urgent demand to explore new approaches of improving the electric breakdown strength of the ferroelectric thin-film capacitor without the degradation of the high dielectric constant. In this work, LaNiO3/Ba0.67Sr0.33TiO3 (LNO/BST) thin film and SrTiO3(STO)/LNO/BST/SrTiO3 (STO) were prepared by using radio frequency (RF) magnetron sputtering technique and ultrathin STO insulator layers were inserted between the LNO/BST and metal electrodes (Au or Pt) to improve the electric breakdown strength and the leakage current of the LNO/BST thin film. X-ray diffraction (XRD) and scanning electron microscopy (SEM) investigations revealed that these multilayer thin films show compact, smooth and uniform morphologies. The leakage current density of STO/LNO/BST/STO thin film was decreased by one order of magnitude and breakdown strength of STO/LNO/BST/STO thin film was enhanced from 0.72 to 1.26 MV·cm−1 compared with that of LNO/BST thin film. Moreover, the dielectric constant of the STO/LNO/BST/STO thin film keeps at the same level as that of LNO/BST thin film, and dielectric loss of the STO/LNO/BST/STO thin film was decreased slightly compared with that of LNO/BST thin film.
      PubDate: 2021-04-01
       
  • Experimental isothermal section phase diagram of Ho–Fe–In at 773 K
           and magnetic properties of Ho 12 Fe 2.08 In 2.92 alloy
    • Abstract: The isothermal section of the Ho–Fe–In system at 773 K has been constructed by X-ray powder diffraction. One known structure ternary compound Er12Fe2In3-type Ho12Fe2In3 has been confirmed. At the same time, solid solutions are not detected in Ho–Fe–In system at 773 K. The magnetic transition and magnetocaloric effect of Ho12Fe2.08In2.92 alloy with Er12Fe2In3-type structure were investigated by magnetic susceptibility and isothermal magnetization measurements. One normal antiferromagnetic–paramagnetic transition and another abnormal one are discovered at 18 and 76 K in ground state, respectively. Owing to a first-order field-induced metamagnetic transition (antiferromagnetic–ferromagnetic) at/below the Néel temperature of 18 K), the negative entropy changes are observed at corresponding temperature. There is only a second-order ferromagnetic–paramagnetic transition near Curie temperature (TC), the maximum entropy change ( \( \Delta S_{ {\rm max} } \) ) values are − 6.14 J·kg−1·K−1 at 3 K and 7.88 J·kg−1·K−1 at 28 K in a field range of 0–7 T. The reversible relative cooling power corresponding to negative entropy change can reach about 600 J·kg−1 in an wide operating temperature region \( \Delta T_{\text{cycl}} \)  = 74 K from 16 to 90 K, which suggests that Ho12Fe2.08In2.92 could be a potential material for magnetic refrigeration in the corresponding temperature range. Graphic abstract
      PubDate: 2021-04-01
       
  • The microstructural evolution and wear properties of Ni60/high-aluminum
           bronze composite coatings with directional structure
    • Abstract: The directional structure of Ni60/high-aluminum bronze composite coating was formed using induction remelting and forced cooling. The microstructural evolution and the characteristics of interface growth were studied. The results showed that the remelted coating formed metallurgical bonding with the substrate. The microstructures changed from plane crystal to dendrite, cellular dendrite, fine cellular dendrite, and then to dendrite again with the increase in the cooling rate. The crystal grew along the heat flow direction and had (111) and (200) preferred orientations when the cooling rate was 1.886 ml·min−1·mm−2. The plane crystal, dendrite and cellular dendrite were mainly composed of compounds and solid solutions with Ni, Fe and Cu, and they were surrounded by strengthening phases composed of Cr, C and B. The grain boundary of directional structure coatings showed the characteristic of regular eutectic growth, but grain boundary of remelted coating presented characteristic of divorced eutectic growth. The wear resistance of directional structure coatings is better than that of remelted coating.
      PubDate: 2021-04-01
       
  • Hydrothermal calcification surface modification of biomedical tantalum
    • Abstract: Tantalum (Ta) as a new type of medical metal is now utilized in several orthopedic applications due to its excellent fracture toughness and workability, high corrosion resistance, good biocompatibility and X-ray visibility, but it lacks bioactivity. Therefore, pure Ta was hydrothermally calcified in CaHPO4 solution at 120–200 °C here for bioactive surface modification. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Raman spectroscopy analyses show that thin tantalum oxide film with a few calcium phosphate precipitates is formed at the surface after the treatment at 200 °C. The hydrothermally treated sample has good hydrophilicity and corrosion resistance evidenced by the water contact angle measurement and the potentiodynamic polarization test, respectively, and it can induce the formation of apatite layer after soaked in the simulated body fluid for 1 week. The present method would be applicable for bioactive surface modification of tantalum implants with irregular shapes and even porous structure. Graphic abstract
      PubDate: 2021-04-01
       
  • Up-conversion of Nd 3+ /Yb 3+ /Tm 3+ tri-doped CaTeO 3 compound under
           excitation of 808 nm
    • Abstract: Nd3+/Yb3+/Tm3+ tri-doped CaTeO3 compounds were prepared by a solid-state reaction method. Bright blue up-conversion (UC) luminescence at around 476 nm, which corresponds to the Tm3+: 1G4 → 3H6 transition, was observed under 808-nm excitation. The Nd3+ → Yb3+ → Tm3+ energy transfer process was responsible for the strong blue up-conversion emission in the tri-doped phosphor. The Tm3+ blue up-conversion emission intensity was strongly dependent on the concentrations of Yb3+ and Nd3+. The possible up-conversion mechanisms for the Nd3+/Yb3+/Tm3+ tri-doped CaTeO3 phosphor are discussed, based on the Nd3+ and Yb3+ concentration-dependent UC spectra, near-infrared luminescence spectra and luminescence decay curves.
      PubDate: 2021-04-01
       
  • Overview of composition and technique process study on 2:17-type Sm–Co
           high-temperature permanent magnet
    • Abstract: Sm–Co permanent magnets are widely used in aerospace equipments, tubes, sensors and hybrid electric vehicles due to their excellent magnetic properties at both room and high temperatures. Compared to that of Nd–Fe–B magnets, the capability of reliably operating at temperatures up to 500 °C is the biggest preponderance of Sm–Co permanent magnets. However, the reliable high-temperature magnetic properties are susceptible to composition and technique processes. So, appropriate composition and matched technique processes are prerequisites for good high-temperature magnetic properties. This review mainly emphasizes the influences of Sm, Fe, Cu and Zr contents and technique processes on development of high-temperature performance and discusses the controversial high-temperature coercivity mechanism of 2:17-type high-temperature Sm–Co magnets.
      PubDate: 2021-04-01
       
  • Thermal stability of bimodal grain structure in a cobalt-based superalloy
           subjected to high-temperature exposure
    • Abstract: The present work investigates the thermal stability and mechanical properties of a Co–20Cr–15W–10Ni (wt%) alloy with a bimodal grain (BG) structure. The BG structure consisting of fine grains (FGs) and coarse grains (CGs) is thermally stable under high-temperature exposure treatments of 760 °C for 100 h and 870 °C for 100–1000 h. The size of both FGs and CGs remains no significant changes after thermal exposure treatments. The microstructural stability is associated with the slow kinetics of grain growth and the pinning of carbides. The thermal stability enables to maintain the BG structures, leading to the same mechanical properties as the sample without thermal exposure treatment. In particular, the BG alloy samples after thermal exposure treatment exhibit superior mechanical properties of both high strength and high ductility compared to the unimodal grain (UG) structured ones. The BG structure of the alloy samples after thermal exposure is capable of avoiding severe loss of ductility and retaining high strength. More specifically, the ductility of the BG alloy samples after thermal exposure treatments of 870 °C for 500–1000 h is ten times higher (44.6% vs. 3.5% and 52.6% vs. 5.0%) than that of the UG ones. The finding in the present work may give new insights into high-temperature applications of the Co–20Cr–15W–10Ni alloy and other metallic materials with a BG structure. Graphical abstract
      PubDate: 2021-04-01
       
  • Growth and characterization of ZnTe single crystal via a novel Te flux
           vertical Bridgman method
    • Abstract: In this work, an II–VI group semiconductor zinc telluride (ZnTe) single crystal is prepared by a novel vertical Bridgman method using Te as flux. The initial mole ratio of Zn/Te = 3:7 is designed for raw material synthesis. ZnTe polycrystalline combined with rich Te is effectively fabricated through rocking technique at 1100 °C. A Φ 25 mm × 65 mm ZnTe boule is successfully grown under a ~ 40 °C·cm−1 temperature gradient with a growth speed of 5 mm·day−1. The as-grown ZnTe crystal has a standard 1:1 stoichiometric ratio and pure F43m phase structure. The maximum transmittance perpendicular to (110) plane is about 64%, and the band gap (Eg) is tested to be 2.225 eV. Terahertz (THz) examination results demonstrate that the time of the highest THz signal is around 17 ps and the frequency of the highest THz transmission is about 0.78 THz, implying that the ZnTe crystal grown by the present Te flux vertical Bridgman method has a good feasibility for THz application. Graphic abstract
      PubDate: 2021-04-01
       
 
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