Journal of Non-crystalline Solids最新文献

We reported the excellent magnetocaloric effect of a binary Er_67.5Co_32.5 metallic glass (MG) near the hydrogen liquefaction temperature. The binary MG ribbon was fabricated by a melt-spinning method. The Er_67.5Co_32.5 alloy exhibits a better glass formability than most of other rare earth (RE)-Co binary alloys. The maximum magnetic entropy change (−ΔS_m^peak) and refrigeration capacity (RC) of the Er_67.5Co_32.5 amorphous ribbon under 0–5 T reach to 17.47 J/(kg × K) near its Curie temperature (T_c, ∼ 11 K) and 472 J/kg, both of which are rather high among the RE-based MGs with a T_c around 10 K and imply the potential application perspective as magnetic refrigerants for hydrogen liquefaction. The magnetization as well as magnetocaloric behaviors of the binary MG were observed, and the mechanism involved was investigated.

The 1.0 μm ultra-short pulse laser is distinguished by its high energy, short pulse width, and intense peak power density, serving various applications in materials processing and biomedicine. Yb ions play a crucial role in this wavelength range, yet achieving high doping levels in commercial Yb-doped silica fibers is challenging due to their dense network structure. Here, we present the design and fabrication of a fluorophosphate (FP) glass with high thermal shock stability (figure of merit is 0.95), achieved through thermodynamic prediction methods, ion field strength analysis, and glass structure theory. By modifying the composition of high-field-strength cations, we not only alter the fundamental properties of the glass but also enhance its thermomechanical performance. Specifically, Yb³⁺-doped Zn(PO₃)₂-Ba(PO₃)₂-AlF₃-KF FP glass (Yb₁₀-ZBAFP10) exhibits a high emission cross-section (0.74×10⁻²⁰ cm² at ∼1008 nm), a low level of minimum population inversion (β_min=0.09), and minimum pump intensity (I_min=1.75 kW/cm²). Furthermore, it demonstrates a stable fluorescence lifetime within the temperature range of 298 ∼ 473 K. These findings highlight the potential of Yb³⁺-doped FP glass for applications demanding high thermal shock stability, particularly in high repetition rate ultra-short pulse laser systems.

Bulk metallic glass (BMG) possesses a range of desirable properties, including exceptional mechanical, soft magnetic, and catalytic properties, etc. However, to pursuit extensive specific applications, enhancing the corrosion resistance of BMG is required. Herein, an effective method involving ultrasonic vibrations (UV) treatment was proposed to significantly enhance the corrosion resistance of BMG. The self-corrosion potential of UV processed BMG increased by up to 0.14 V in 1 N HCl solution and 0.2 V in 3.5 % NaCl solution, respectively. Additionally, the maximum reduction in corrosion current density for the UV processed BMG in these solutions was 15 % and 20 %, respectively. Micro-morphology results indicated that the UV processed BMG exhibited better pitting resistance. It is found that a denser arrangement of BMG was obtained after UV which resulted in reduced relaxation enthalpy and enhanced corrosion resistance. This work introduces an innovative and convenient method to enhance the corrosion resistance of BMG for engineering applications.

In the field of solid-state lighting, phosphor-in-glass composites (PIGs) containing colorful phosphors can be used to improve the spectral fixation and color rendering indices (CRIs) of phosphor conversion materials. However, PIGs using red nitride phosphors are difficult to produce because the phosphors decompose at high temperatures. Therefore, this study presents a method of producing orange–red PIGs at low temperatures (320 °C) using Y₃Al₅O₁₂:Ce³⁺ and CaAlSiN₃:Eu²⁺ phosphors based on the fluorophosphate glass matrix. Scanning electron microscopy and X-ray diffraction show that the crystalline phases of the phosphors in the PIGs remain intact and independent. The prepared samples can achieve luminescence efficiency up to 92.5 lm/W and ideal CRIs. Therefore, the proposed materials have a wide range of potential applications in high-quality lighting and displays.

The evolution of structure and physical properties was investigated in the (Ag₂S)_x(HgS)_50-x(GeS₂)₅₀ system. It was found that the density increases with increasing silver sulfide. The DSC data show a non-monotonic change of the glass transition temperature, T_g, from 243 °C (x = 0) to 301 °C (x = 50) with the minimum at 231 °C for x = 10 sample. The dual structure of HgS, which consists of the presence of dimorphic tetrahedral and chain forms of HgS, is found to be responsible for the non-monotonic change of the T_g. An increase in silver content leads to a significant enhancement of ionic conductivity from ∼10⁻¹⁴ S.cm⁻¹ (x = 0) to ∼10⁻³ S.cm⁻¹ (x = 50). The gradual structural evaluation is evidenced by the disappearance of the main Raman feature at ≈300 cm⁻¹ related to the Hg-S stretching and the emergence of two contributions for silver-rich glasses at ≈370 cm⁻¹ and at ≈400 cm⁻¹.

Bulk metallic glasses (BMGs) show limited plasticity at room temperature. However, BMGs usually exhibit superplasticity and high plastic forming ability in their supercooled liquid region (SLR). The rheological behavior of BMGs in SLR is vitally important to their thermoplastic forming process. In contrast to the ductile BMGs, thermoplastic deformation behavior of brittle BMGs is rarely reported. In present work, the rheological behavior of two brittle BMGs with high glass forming ability Cu_44.25Ag_14.75Zr₃₆Ti₅ and Ti_32.8Zr_30.2Cu₉Ni_5.3Be_22.7 was investigated on Gleeble3500. The two BMGs can deform homogeneously depending on the temperature and strain rate. According to the high value of m (strain rate sensitivity index), which is the most important mechanical characteristic of a superplastic material, the two BMGs show superplasticity in their SLR with m ≥ 0.3. Based on the free volume model, their activation volumes are calculated as 0.263∼0.486 nm³ and 1.261∼1.650 nm³, indicating the minimum displacement clusters with average 26∼48 and 91∼127 atoms, for Cu_44.25Ag_14.75Zr₃₆Ti₅ and Ti_32.8Zr_30.2Cu₉Ni_5.3Be_22.7, respectively. Thus, the two investigated brittle BMGs can be thermoplastic processed in the SLR and the deformation maps are given. BMG Cu_44.25Ag_14.75Zr₃₆Ti₅ shows better machinable property than Ti_32.8Zr_30.2Cu₉Ni_5.3Be_22.7. Compared to the ductile BMGs, no Newtonian flow is found for the two investigated brittle BMGs.

A viscosity model based on CALPHAD principles, considering the influences of associates in multicomponent melts, was developed. A strategy for determining CALPHAD-type viscosity parameters in systems lacking experimental data was proposed, which combines the Kozlov-Romanov-Petrov model and thermodynamic descriptions. This model and strategy were applied to analyze viscosities in Mg-Al-Zn-Sn-Bi melts. The viscosity expressions of pure melts were initially assessed based on the available experimental data. Subsequently, the Arrhenius viscosities of Mg₃Bi₂, Mg₂Sn, and MgZn₂ associates were determined by integrating thermal-physical properties into Kaptay equation. Viscosity parameters for 10 sub-binary and sub-ternary systems within Mg-Al-Zn-Sn-Bi system were examined. A comparison between predicted and measured viscosities confirmed the accuracy of the model. Isothermal viscosities in all sub-ternary melts were calculated to assess the impact of alloying elements on viscosity. Additionally, viscosities in AZ91 alloys with Bi and Sn additions were predicted, demonstrating an increase in viscosity with higher Bi or Sn content.

Glasses in the system BaO – La₂O₃ – Ga₂O₃ – GeO₂ and Langasite crystalline phases with the same stoichiometry have been studied considering the possible use of these glasses for laser-induced space-selective growth of crystalline architectures in the glass compositions. For better understanding of mechanisms involved in such controlled crystallization process, crystalline and glass compounds with same stoichiometry and different La/Ba ratios have been synthesized to compare their local structure. Solid-state Nuclear Magnetic Resonance evidence 4- and 5-coordinated gallium units in the glass matrix, denying unambiguously the formation of 6-coordinated gallium sites observed in crystalline phases. Moreover vibrational spectroscopies suggest a link between a 3D network formed by 4- and 5-coordinated gallium, connected to each other and to 4- coordinated Q4 and Q3 germanium units in the glass and their congruent crystallization. The transition from 4- and 5-coordinated gallium to 6-coordinated gallium sites observed in Langasite crystalline phases remains not still elucidated.

Combined with the pendant drop method and infrared and Raman spectroscopic detection, the effect of the basicity on the density and surface tension properties and the structure of CaO-SiO₂–10 % Fe_xO slag was investigated. With increasing basicity from 0.5 to 1, it is found that the density and surface tension values increase at the same temperature. Meanwhile, the complex structures of Si-O groups in the slag depolymerize, the area proportion of [FeO₆]^9- units decreases from 13.0 % to 8.3 % and that of [FeO₄]^5- units increases significantly from 2.9 % to 18.6 %. The key factor determining the area proportion and structural evolution of [FeO₆]^9- and [FeO₄]^5- units is the basicity rather than the relative contents of Fe²⁺ and Fe³⁺ ions. Overall, the slag polymerization degree depends on the structures of Si-O groups rather than on those of Fe-O groups, which leads to increases in the density and surface tension with increasing basicity.

Developing low-cost, and efficient oxygen evolution reaction (OER) electrodes with high flexibility is critical for hydrogen production. Here, flexible noble-metal-free Fe-based metallic glassy OER electrodes were fabricated via an electrochemical dealloying method combined with a dipping process. The sample requires a low overpotential of 258 mV to achieve a current density of 10 mA cm⁻² in 1 M KOH solution, and the Tafel slope is 51.7 mV/dec. Galvanostatic test proved the excellent electrochemical stability of the electrodes. The highly efficient performance mainly originated from the high-energy disordered amorphous microstructure combined with the doping effect of nickel. Furthermore, the unique double-layer structure of the nanoporous surface covered with amorphous sheets increased the contact area of the samples. The ductile amorphous matrix together with the amorphous sheets tightly bonded on the nanoporous layer results in high flexibility of the electrodes. Our work provides a simple strategy to fabricate flexible amorphous OER electrodes.