Showing papers on "Solid solution published in 2022"

Synergistic Polarization Loss of MoS2‐Based Multiphase Solid Solution for Electromagnetic Wave Absorption

Abstract: Given tunable hybridization structures in solid solutions, fascinating electromagnetic (EM) properties can be achieved for regulating EM wave (EMW) absorption. Herein, a novel metal–organic cooperative interactions method is proposed to manipulate the vacancy, interstitial, substitutional, and heterointerface structures in molybdenum disulfide (MoS2) solid solution simultaneously, thence meeting the synergistic polarization loss on various point and face sites. Assisted by the coordination between Cu2+ and polydopamine (PDA), the effect of Cu modification on MoS2 is highly improved, which further lead to polarization loss on S vacancy, interstitial Cu, substitutional N, and heterointerface between carbon and MoS2. Contributing to the synergetic effect among multiple polarizations, the Cu/C@MoS2 solid solution exhibit ultrahigh EMW absorption performance, of which EMA with twice PDA delivers the effective absorption bandwidth of 7.12 GHz and minimum reflection loss of −48.22 dB (2.5 mm). The energy attenuation of Cu/C@MoS2 improved almost 266.7% and 222.2% than C@MoS2 and Cu@MoS2, respectively. Finally, this work reveals the structural dependency of solid solution materials of EMW absorption and establishes an entirely new polarization loss model.

Effect of CoCrFeNiMn high entropy alloy interlayer on microstructure and mechanical properties of laser-welded NiTi/304SS joint

Abstract: In order to suppress the formation of Fe-Ti IMCs in NiTi SMA/304 SS laser-welded joint and improve the properties of the joint. In this study, NiTi SMA/304 SS dissimilar alloys joints with and without CoCrFeNiMn high entropy alloy interlayer were obtained by micro laser welding process. The effect of CoCrFeNiMn high entropy alloy interlayer on the microstructure and properties of NiTi SMA/304 SS laser-welded joint was investigated systematically. Results showed that the addition of HEA interlayer significantly reduced the formation of the brittle intermetallic compounds (IMCs) such as FeTi phase. The addition of high entropy alloy interlayer promotes the formation of (Fe,Ni) solid solution phase, therefor, the joint with HEA interlayer is composed of (Fe,Ni) solid solution and small amount of FeTi IMCs and B2 phase. On the other hand, the average microhardness of weld metal was decreased from 732 HV to 221 HV by adding the HEA interlayer. The addition of HEA interlayer significantly improves the tensile shear properties of the joint, and the tensile shear load of the joint can reached 175 N, which is 6 times higher than that of the joint without HEA interlayer.

Investigation of microstructure and wear resistance of laser-clad CoCrNiTi and CrFeNiTi medium-entropy alloy coatings on Ti sheet

Abstract: Two medium-entropy alloy coatings (MEACs), CoCrNiTi and CrFeNiTi, were successfully prepared on pure Ti sheet by utilizing pulsed laser cladding. Microstructural characterization reveals that both the MEACs are mainly comprised of BCC solid-solution phase along with interdendritic Cr2Ti Laves phase (C14 type) due to element segregation. Hardness and wear tests show that the CoCrNiTi MEAC has a hardness of 762 ± 32 HV and a specific wear rate of 1.7 × 10−5 mm3·N−1·m−1, and those of the CrFeNiTi MEAC are 820 ± 34 HV and 2.8 × 10−5 mm3·N−1·m−1, respectively, both of which are markedly superior to the pure Ti substrate (114 ± 5 HV and 5.4 × 10−4 mm3·N−1·m−1). Comprehensive analyses suggest that the excellent properties of the MEACs can be attributed to combined strengthening effects of solid-solution, short-range order, grain refinement and the Cr2Ti Laves phase.

Investigation of microstructure and wear resistance of laser-clad CoCrNiTi and CrFeNiTi medium-entropy alloy coatings on Ti sheet

Abstract: Two medium-entropy alloy coatings (MEACs), CoCrNiTi and CrFeNiTi, were successfully prepared on pure Ti sheet by utilizing pulsed laser cladding. Microstructural characterization reveals that both the MEACs are mainly comprised of BCC solid-solution phase along with interdendritic Cr2Ti Laves phase (C14 type) due to element segregation. Hardness and wear tests show that the CoCrNiTi MEAC has a hardness of 762 ± 32 HV and a specific wear rate of 1.7 × 10−5 mm3·N−1·m−1, and those of the CrFeNiTi MEAC are 820 ± 34 HV and 2.8 × 10−5 mm3·N−1·m−1, respectively, both of which are markedly superior to the pure Ti substrate (114 ± 5 HV and 5.4 × 10−4 mm3·N−1·m−1). Comprehensive analyses suggest that the excellent properties of the MEACs can be attributed to combined strengthening effects of solid-solution, short-range order, grain refinement and the Cr2Ti Laves phase.

Massive interstitial solid solution alloys achieve near-theoretical strength

Abstract: Interstitials, e.g., C, N, and O, are attractive alloying elements as small atoms on interstitial sites create strong lattice distortions and hence substantially strengthen metals. However, brittle ceramics such as oxides and carbides usually form, instead of solid solutions, when the interstitial content exceeds a critical yet low value (e.g., 2 at.%). Here we introduce a class of massive interstitial solid solution (MISS) alloys by using a highly distorted substitutional host lattice, which enables solution of massive amounts of interstitials as an additional principal element class, without forming ceramic phases. For a TiNbZr-O-C-N MISS model system, the content of interstitial O reaches 12 at.%, with no oxides formed. The alloy reveals an ultrahigh compressive yield strength of 4.2 GPa, approaching the theoretical limit, and large deformability (65% strain) at ambient temperature, without localized shear deformation. The MISS concept thus offers a new avenue in the development of metallic materials with excellent mechanical properties.

Universal Solution Synthesis of Sulfide Solid Electrolytes Using Alkahest for All‐Solid‐State Batteries

Abstract: The wet‐chemical processability of sulfide solid electrolytes (SEs) provides intriguing opportunities for all‐solid‐state batteries. Thus far, sulfide SEs are wet‐prepared either from solid precursors suspended in solvents (suspension synthesis) or from homogeneous solutions using SEs (solution process) with restricted composition spaces. Here, a universal solution synthesis method for preparing sulfide SEs from precursors, not only Li2S, P2S5, LiCl, and Na2S, but also metal sulfides (e.g., GeS2 and SnS2), fully dissolved in an alkahest: a mixture solvent of 1,2‐ethylenediamine (EDA) and 1,2‐ethanedithiol (EDT) (or ethanethiol). Raman spectroscopy and theoretical calculations reveal that the exceptional dissolving power of EDA–EDT toward GeS2 is due to the nucleophilicity of the thiolate anions that is strong enough to dissociate the GeS bonds. Solution‐synthesized Li10GeP2S12, Li6PS5Cl, and Na11Sn2PS12 exhibit high ionic conductivities (0.74, 1.3, and 0.10 mS cm−1 at 30 °C, respectively), and their application for all‐solid‐state batteries is successfully demonstrated.

Crystal Structure Control of Binary and Ternary Solid-Solution Alloy Nanoparticles with a Face-Centered Cubic or Hexagonal Close-Packed Phase.

Abstract: The crystal structure significantly affects the physical and chemical properties of solids. However, the crystal structure-dependent properties of alloys are rarely studied because controlling the crystal structure of an alloy at the same composition is extremely difficult. Here, for the first time, we successfully demonstrate the synthesis of binary Ru-Pt (Ru/Pt = 7:3) and Ru-Ir (Ru/Ir = 7:3) and ternary Ru-Ir-Pt (Ru/Ir/Pt = 7:1.5:1.5) solid-solution alloy nanoparticles (NPs) with well-controlled hexagonal close-packed (hcp) and face-centered cubic (fcc) phases, through the chemical reduction method. The crystal structure control is realized by precisely tunning the reduction speeds of the metal precursors. The effect of the crystal structure on the catalytic performance of solid-solution alloy NPs is systematically investigated. Impressively, all the hcp alloy NPs show superior electrocatalytic activities for the hydrogen evolution reaction in alkaline solution compared with the fcc alloy NPs. In particular, hcp-RuIrPt exhibits extremely high intrinsic (mass) activity, which is 3.1 (3.2) and 6.7 (6.9) times enhanced compared to that of fcc-RuIrPt and commercial Pt/C.

Optical, thermal, and mechanical properties of (Y1−xScx)2O3 transparent ceramics

Abstract: Abstract Sesquioxides such as Y 2 O 3 and Sc 2 O 3 are important optical materials, but the fabrication of their transparent ceramics remains a challenge due to the ultra-high melting point of over 2400 ° C. In this work, a series of (Y 1− x Sc x ) 2 O 3 transparent ceramics were successfully fabricated by a simple vacuum sintering process without any sintering additives, and the effect of scandium (Sc) content ( x ) on the crystal structure and optical/thermal/mechanical properties was evaluated. Y 2 O 3 and Sc 2 O 3 form a complete solid solution with a cubic bixbyite structure. The formation of (Y 1− x Sc x ) 2 O 3 solid solution promotes the densification of ceramics, leading to the realization of high transparency close to the theoretical transmittance over a wide wavelength range of 0.35–8 µm. In particular, the in-line transmittance in the range of 0.6–6 µm remains above 80% for (Y 1− x Sc x ) 2 O 3 with x = 0.23–0.31, while the pristine Y 2 O 3 and Sc 2 O 3 are opaque. Moreover, the mechanical properties including Vickers hardness ( HV ), fracture toughness ( K IC ), and biaxial flexural strength ( δ b ) are evidently enhanced due to the solid solution strengthening, while the thermal conductivity ( k ) is reduced due to the reduction of photon free path. This study demonstrates that forming of solid solution is a facile and universal approach for preparing sesquioxide transparent ceramics with high optical and mechanical quality.

Ultrafast high-temperature synthesis and densification of high-entropy carbides

Abstract: Recently, high-entropy carbides have attracted great attention due to their remarkable component complexity and excellent properties. However, the high melting points and low self-diffusion coefficients of carbides lead to the difficulties in forming solid solution and sintering densification. In this work, six dense multicomponent carbides (containing 5–8 cations) were prepared by a novel ultrafast high-temperature sintering (UHS) technique within a full period of 6 min, and three of them formed a single-phase high-entropy solid solution. The solid solubility of the UHSed multicomponent carbides was highly sensitive to the compositional variation. The presence of Cr3C2 liquid had significant contributions to the formation of solid solution and the densification of multicomponent carbides. All UHSed multicomponent carbides exhibited high hardness, which, unexpectedly, did not simply increase with increasing number of the components. The highest nanohardness with a value of 36.6 ± 1.5 GPa was achieved in the (Ti1/5Cr1/5Nb1/5Ta1/5V1/5)Cx high-entropy carbide. This work is expected to expedite the development of high-entropy carbides and broaden the application of UHS in the synthesis and densification of advanced ceramics.

Effect of Additive Elements (x = Cr, Mn, Zn, Sn) on the Phase Evolution and Thermodynamic Complexity of AlCuSiFe-x High Entropy Alloys Fabricated via Powder Metallurgy

Abstract: In this study, equimolar AlCuSiFe-x (x = Cr, Mn, Zn, Sn) HEAs were fabricated by mechanical alloying (MA) and spark plasma sintering methods (SPS). The MA was performed for 45 h followed by densification of powder compacts at 650 °C. The results revealed the formation of dual face-centered cubic (FCC) and body-centered cubic (BCC) structures in AlCuSiFe-x (x = Zn, Sn) while a single BCC solid solution was noticed in AlCuSiFe-x (x = Cr, Mn). After SPS treatment, AlCuSiFeSn alloy contained FCC with CuxSny while AlCuSiFe–Zn changed to FCC + BCC structure. Similarly, AlCuSiFeCr and AlCuSiFeMn showed the formation of BCC + FCC with additional σ- and µ-phases in the HEA matrix. The calculated thermodynamic parameters of HEAs also supported the formation of different solid-solution phases in each of the above HEAs. It was found that HEAs with the additive elements Sn and Zn tend to have major FCC phases, while those with Cr and Mn give rise to major BCC with brittle σ- and µ-phase, which further improves their mechanical strength.

Tunable Electrical Conductivity and Simultaneously Enhanced Thermoelectric and Mechanical Properties in n‐type Bi2Te3

Abstract: The recent growing energy crisis draws considerable attention to high‐performance thermoelectric materials. n‐type bismuth telluride is still irreplaceable at near room temperature for commercial application, and therefore, is worthy of further investigation. In this work, nanostructured Bi2Te3 polycrystalline materials with highly enhanced thermoelectric properties are obtained by alkali metal Na solid solution. Na is chosen as the cation site dopant for n‐type polycrystalline Bi2Te3. Na enters the Bi site, introducing holes in the Bi2Te3 matrix and rendering the electrical conductivity tunable from 300 to 1800 Scm–1. The solid solution limit of Na in Bi2Te3 exceeds 0.3 wt%. Owing to the effective solid solution, the Fermi level of Bi2Te3 is properly regulated, leading to an improved Seebeck coefficient. In addition, the scattering of both charge carriers and phonons is modulated, which ensured a high‐power factor and low lattice thermal conductivity. Benefitting from the synergistic optimization of both electrical and thermal transport properties, a maximum figure of merit (ZT) of 1.03 is achieved at 303 K when the doping content is 0.25 wt%, which is 70% higher than that of the pristine sample. This work disclosed an effective strategy for enhancing the performance of n‐type bismuth telluride‐based alloy materials.