| 1. |
- Akhtar, Farid, et al.
(författare)
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TiC-maraging stainless steel composite: microstructure, mechanical and wear properties
- 2006
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Ingår i: Rare Metals. - 1001-0521 .- 1867-7185. ; 25:6, s. 630-635
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Tidskriftsartikel (refereegranskat)abstract
- Particulate TiC reinforced 17-4PH and 465 maraging stainless steel matrix composites were processed by conventional powder metallurgy (P/M). TiC-maraging stainless steel composites with theoretical density >97% were produced using conventional P/M. The microstructure, and mechanical and wear properties of the composites were evaluated. The microstructure of the composites consisted of (core-rim structure) spherical and semi-spherical TiC particles depending on the wettability of the matrix with TiC particles. In TiC-maraging stainless steel composites, 465 stainless steel binder phase showed good wettability with TiC particles. Some microcracks appeared in the composites, indicating the presence of tensile stresses in the composites produced during sintering. The typical properties, hardness, and bend strength were reported for the composites. After heat treatment and aging, an increase in hardness was observed. The increase in hardness was attributed to the aging reaction in maraging stainless steel. The specific wear behavior of the composites strongly depends on the content of TiC particles and their interparticle spacing, and on the heat treatment of the maraging stainless steel.
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| 2. |
- Feng, Peizhong, et al.
(författare)
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Self-propagating high temperature synthesis of MoSi 2 matrix composites
- 2006
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Ingår i: Rare Metals. - 1001-0521 .- 1867-7185. ; 25:3, s. 225-230
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Tidskriftsartikel (refereegranskat)abstract
- MoSi2 is presently regarded as the most important material for electrical heating and as one with huge potential for high temperature structural uses. MoSi2 and MoSi2 matrix composites were prepared by self-propagating high temperature synthesis (SHS). Pure MoSi2 was obtained and a compound of MoSi2 and WSi2 was synthesized in the form of predominant solid solution (Mo, W)Si2. By adding aluminum of 5.5 at.% to Mo-Si, the crystal structure of MoSi2 changed into a mixture of tetragonal CIIb MoSi2 and hexagonal C40 Mo(Si, Al)2. The (Mo, W)Si2-Mo(Si, Al)2-W(Si, Al)2 composite materials were synthesized by adding aluminum of 5.5 at.% to Mo-W-Si. However, if the amount of the added aluminum was not larger than 2.5 at.%, it did not have any significant effect. SHS is an effective technology for synthesis of MoSi2 and MoSi2 matrix composites.
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| 3. |
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| 4. |
- Yang, Ke, et al.
(författare)
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Effect of inner oxidant on self-propagating high-temperature synthesis of MnZn-ferrite powder
- 2006
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Ingår i: Rare Metals. - 1001-0521 .- 1867-7185. ; 25:6: Suppl. 1, s. 553-556
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Tidskriftsartikel (refereegranskat)abstract
- Using KClO3 as an inner oxidant, MnZn-ferrite powder was synthesized by a self-propagating high-temperature synthesis (SHS) process in normal air atmosphere. The effects of the inner oxidant on combustion temperature, combustion velocity, microstructure and the phase of the product were investigated by XRD and SEM, respectively. The results show that a highly ferritized powder can be obtained as well as the highest combustion temperature and the highest combustion velocity when the inner oxidant content m equals 5/4 (k – 1/6).
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| 5. |
- Fan, Mei-Cen, et al.
(författare)
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Room-temperature extraction of individual elements from charged spent LiFePO4 batteries
- 2022
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Ingår i: Rare Metals. - : Springer. - 1001-0521 .- 1867-7185.
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Tidskriftsartikel (refereegranskat)abstract
- Recycling millions of metric tons of spent LiFePO4 batteries would benefit human health while reducing resource depletion and environmental pollution. However, recovering individual elements from the spent batteries without generating waste is challenging. Here, we present a distinctive approach for recycling spent LiFePO4 batteries at room temperature, where water is the only leaching agent consumed. FePO4 and lithium intercalated graphite act as a precursor material for selectively extracting lithium, iron, and phosphorus through charging the LiFePO4 batteries to the delithiated state. NaOH solution extracted Fe from FePO4 within 30 min and regenerated without consumption, similar to a catalyst. Under the optimal leaching conditions (1 mol·L−1 NaOH, 0.5 h, NaOH/Fe molar ratio of 4.5), Fe and P leaching efficiencies achieved 89.1% and 99.2%, respectively. The methodology reflected in this research reduced the material cost per kg cathode material to a fraction of previously published reports, only occupies 6.13% of previous reports. In addition, the method improved the battery recycling revenue calculated by the EverBatt model by 2.31 times and 1.94 times over pyrometallurgical and hydrometallurgical methods. The proposed method allows for the convenient recovery of the elemental components of spent LiFePO4 batteries.
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| 6. |
- Guo, Jia Wei, et al.
(författare)
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2D Co metal-organic framework nanosheet as an oxidase-like nanozyme for sensitive biomolecule monitoring
- 2023
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Ingår i: Rare Metals. - : Springer Science and Business Media LLC. - 1001-0521 .- 1867-7185. ; 42:3, s. 797-805
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Nanozyme-based biomolecules sensitive and quantitative detection is an attractive strategy due to their high chemical, thermal stability and reactive activity. Here, we have synthesized a significant number of two-dimensional (2D) cobalt-metal-organic framework (Co-MOF) nanosheets with oxidase (OXD)-like activity using a facile solvothermal method in one pot for biomolecule monitoring. The synthesized Co-MOF nanosheets exhibit strong stability, higher specific surface area and more active sites due to their MOF structure. Such Co-MOF nanosheets with excellent OXD-like activity show adequate analytical performance in the quantitative determination of dopamine (DA) and glutathione (GSH) with a wider dynamic sensing range and lower detection limits (DA and GSH: 0.24 and 0.067 μmol·L−1, 3σ/slope, where σ is standard deviation of the blank). This work extends the application of 2D-MOF structures in bioassays and brings new insights into the application of OXD-like nanozymes in bioassays. Graphical abstract: [Figure not available: see fulltext.]
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| 7. |
- Hu, Ji-Chong, et al.
(författare)
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Oxidation behavior of Ni-based superalloy GH4738 under tensile stress
- 2024
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Ingår i: Rare Metals. - : NONFERROUS METALS SOC CHINA. - 1001-0521 .- 1867-7185.
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Tidskriftsartikel (refereegranskat)abstract
- Revealing the oxidation behavior of superalloys is crucial for optimizing material properties and extending service life. This study investigated the oxidation behavior of superalloy GH4738 under stress states at 850 degrees C. High-throughput specimens were fabricated to withstand different stresses at the same time. Isothermal oxidation samples were analyzed using the mass gain method to obtain oxidation kinetic curves. The results show that the external stress below 200 MPa could improve the oxidation resistance of the GH4738. With tensile stress increasing, the oxide layer becomes thinner, denser and more complete, while internal oxidation decreases. The tensile stress alters the structure of the external oxide layer from a two-layer to a three-layer configuration. The Cr2O3 oxide layer inhibits the outward diffusion of Ti, leading to Ti enrichment at the oxide-matrix interface and altering the oxidation mechanism of GH4738.
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| 8. |
- Lei, Ying, et al.
(författare)
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Microwave synthesis and enhancement of thermoelectric performance in HfxTi1−xNiSn0.97Sb0.03 half-Heusler bulks
- 2023
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Ingår i: Rare Metals. - : Springer Nature. - 1001-0521 .- 1867-7185. ; 42:11, s. 3780-3786
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Tidskriftsartikel (refereegranskat)abstract
- We obtained TiNiSn-based half-Heusler HfxTi1−xNiSn0.97Sb0.03 bulks with 85%–96% relative densities via 5-min microwave synthesis and 20-min microwave sintering in sealed vacuum. The phase composition and microstructure of samples were characterized by X-ray diffractometer (XRD) and scanning electron microscopy (SEM). Thermoelectric (TE) properties were measured, i.e., Seebeck coefficient (S), electrical resistivity (ρ), and thermal conductivity (κ) through Seebeck coefficient/resistance analysis system (S/RAs) and laser flash thermal analyzer (LFT). The results show that the nearly single phase exists after microwave sintering. The grain sizes and the number of grain boundaries decrease with increase in Hf-doping amount due to an increase in point defects. The matrix grains for Hf0.1Ti0.9NiSn0.97Sb0.03 are ~ 10 μm. The nanoscle pores and precipitates are present as second phases in matrix grain. The real composition for Hf0.1Ti0.9NiSn0.97Sb0.03 matrix grain is Hf3.51Ti28.76Ni34.76Sn31.55Sb1.43. The variation trends of electrical resistivity, Seebeck coefficient, power factor, and thermal conductivity were analyzed in detail. The maximum figure of merit (ZT) of 0.46 is obtained for Hf0.1Ti0.9NiSnSn0.97Sb0.03 at 723 K. The innovation route exhibits advantages for predation of TE bulks when compared to the conventional methods, especially in terms of efficiency while it still maintains TE performance. © 2019, The Nonferrous Metals Society of China and Springer-Verlag GmbH Germany, part of Springer Nature.
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| 9. |
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| 10. |
- Mo, Jin Yong, et al.
(författare)
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First-principle prediction of structural and mechanical properties in NbMoTaWRex refractory high-entropy alloys with experimental validation
- 2022
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Ingår i: Rare Metals. - : Springer Nature. - 1001-0521 .- 1867-7185. ; 41:10, s. 3343-3350
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the effect of Re alloying on the phase composition, crystal structure, and mechanical properties of NbMoTaWRex (x = 0, 0.27, 0.57, 0.92, 1.33) refractory high-entropy alloys (RHEAs) were systematically investigated by combining the calculation of phase diagram (CALPHAD), first-principle calculations and experiment. The theoretical predictions showed good consistency with the experimental results. As the increase in Re content, the theoretical results showed that all considered alloys have a single body-centered cubic (bcc) structure and the lattice constant and ductility were decreased, while the elastic moduli and hardness were improved. To avoid extreme brittleness, a strategic suggestion was given for the design of Re-containing RHEAs in the future.
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| 11. |
- Niu, Li-Ping, et al.
(författare)
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Mechanism of fluidized chlorination reaction of Kenya natural rutile ore
- 2014
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Ingår i: Rare Metals. - : Springer Science and Business Media LLC. - 1001-0521 .- 1867-7185. ; 33:4, s. 485-492
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the thermodynamics and kinetics of nature rutile carbochlorination in a fluidized-bed were investigated. The thermodynamic calculations of TiO2-C-Cl-2 system show that when C is excess in the solid phase, titanium tetrachloride and carbon monoxide can exist stably. At high temperature, the reaction with CO as the product is the dominant reaction. The appropriate reaction conditions are as follows: reaction temperature of 950 A degrees C, reaction time of 40 min, carbon ratio of 30 wt% of rutile, natural rutile particle size of -96 mu m, petroleum coke size of -150 mu m, and chlorine flow of 0.036 m(3)center dot h(-1). Under the above conditions, the reaction conversion rate of TiO2 can reach about 95 %. This paper proposed a reaction rate model, and got a rutile chlorination rate formula, which is generally consistent with the experimental data. For the TiO2-C-Cl-2 system, the reaction rate is dependent on the initial radius of rutile particle, density, and the partial pressures of Cl-2. From 900 to 1,000 A degrees C, the apparent activation energy is 10.569 kJ center dot mol(-1), and the mass diffusion is found to be the main reaction-controlling step. The expression for the chlorine reaction rate in the C-Cl-2 system is obtained, and it depends on the degree of reaction, the partial pressure of Cl-2, and the size of rutile particle.
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| 12. |
- Shi, Zhi Sheng, et al.
(författare)
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Enrichment of Ni–Mo–V via pyrometallurgical reduction from spent hydrogenation catalysts and the multi-reaction mechanism
- 2023
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Ingår i: Rare Metals. - 1001-0521 .- 1867-7185. ; 42:8, s. 2700-2712
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Tidskriftsartikel (refereegranskat)abstract
- Spent hydrogenation catalysts are important secondary resources due to richness in the valuable metals of Ni, Mo and V. Recovery of valuable metals from spent catalysts has high economic value and environmental benefits since they are hazardous wastes as well. Traditional recycling processes including hydrometallurgical leaching and soda roasting-leaching have disadvantages such as generating large amounts of wastewater, long process, and low recovery efficiency of valuable metals. Thus, this paper proposed synergistic enrichment of Ni, Mo and V via pyrometallurgical reduction at 1400–1500 °C. The melting temperature and viscosity of slag were reduced through slag designing by software FactSage 7.1. The phase diagram of Al2O3-CaO-SiO2-Na2O-B2O3 was drawn, and low-temperature region (≤ 1300 °C) was selected as target slag composition. Ni, Mo, and V can be collaborative captured and recovered through the mutual solubility at molten state. Increasing the melting temperature and the amount of CaO, Na2O and C were conducive to improving the metals recovery rates. The kilogram-scale experiments were carried out, and the recovery efficiencies of Ni, Mo and V were 98.3%, 95.3% and 97.9% under optimized conditions: at 1500 °C, with the basicity of 1.0, 13.1 wt% SiO2, 7.0 wt% B2O3, 7.7 wt% Na2O and 20.0 wt% C. The distribution behavior of valuable metals was clarified by investigating the melting process of slag and the reduction in valuable metals. Ni was preferentially reduced and acted as a capturing agent, which captured other metals to form NiMoV alloys. Graphical abstract: [Figure not available: see fulltext.]
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| 13. |
- Wei, Shi-Jie, et al.
(författare)
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Microstructure and magnetocaloric properties of melt-extracted SmGdDyCoAl high-entropy amorphous microwires
- 2024
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Ingår i: Rare Metals. - : Springer Nature. - 1001-0521 .- 1867-7185. ; 43:3, s. 1234-1242
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a systematic investigation of the microstructure and magnetocaloric properties of melt-extracted Sm20Gd20Dy20Co20Al20 high-entropy microwires. The fabricated wires exhibited an amorphous structure, and the temperature interval of the undercooled liquid Delta T was 45 K. The microwires underwent a second-order magnetic transition from a ferromagnetic to a paramagnetic state near the Curie temperature (T-C=52 K). The maximum magnetic entropy change (-Delta S-M(max)), the relative cooling power and the refrigeration capacity reached 6.34 J.kg(-1).K-1, 422.09 J.kg(-1) and 332.94 J.kg(-1), respectively, under a magnetic field change of 5 T. In addition, the temperature-averaged entropy changes with two temperature lifts (3 and 10 K) were 6.32 and 6.27 J.kg(-1).K-1, respectively. The good magnetocaloric performance highlights the significant potential for the Sm20Gd20Dy20Co20Al20 microwires to be used as magnetic refrigerant materials in low-temperature region applications. This work will serve as a valuable reference for future investigations on low-temperature high-entropy magnetocaloric materials.
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