Papers by Author: Peng Jun Cao

Abstract: The microwave properties of Glass-coated FeCuNbVSiB and CoFeNiSiB microwires/dielectric composite with different microwires diameters were studied. Relative complex permeability and complex permittivity was measured by transmission/reflection (T/R) coaxial line method at the frequency range of 2-18 GHz for composite samples. The results show that the microwave permeability and permittivity increases with the lengthening of the microwires in composite. The microwave permeability, natural resonance frequency and microwave permittivity increase with the decrease of the diameter of the microwires.

Abstract: High-strength Cu-based bulk glassy alloys with a large supercooled liquid region in Cu-Zr-Ti-Ni systems were prepared by means of copper mold casting. The Cu-based bulk glassy alloys samples were tested by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and Instron testing machine. The result indicates, the maximum diameter was 5.0 mm for the Cu₅₅Zr₂₅Ti₁₅Ni₅ bulk glassy alloy. The temperature interval of supercooled liquid region (ΔT_x) is as large as 45.48-70.98 K for the Cu-Zr-Ti-Ni alloy. The Cu-based glassy alloys rods exhibited the very high mechanical properties and the distinct plastic strains. The compressive fracture strength is 2155 MPa, 2026 MPa and 1904 MPa respectively for Cu₅₀Zr₂₅Ti₁₅Ni₁₀, Cu₅₅Zr₂₅Ti₁₅Ni₅ and Cu₅₄Zr₂₂Ti₁₈Ni₆ bulk glassy alloys. The Vickers hardness is respectively 674, 678 and 685 for the Cu₅₀Zr₂₅Ti₁₅Ni₁₀, Cu₅₅Zr₂₅Ti₁₅Ni₅ and Cu₅₄Zr₂₂Ti₁₈Ni₆ bulk glassy alloys. The addition Co element to Cu-Zr-Ti-Ni alloy expand the ΔT_x, the ΔT_x is 74.5 K for Cu₅₀Zr₂₂Ti₁₈Ni₆Co₄ bulk glassy alloys.

Abstract: The magnetic structure of the glass-coated magnetic alloy microwires were modeled based on the main magnetic domain structure and meshed by finite element method. The magnetic spectrum of the magnetic alloy microwires was calculated based on the micromagnetic theory. The simulation results of the magnetic spectrum of glass-coated magnetic alloy microwires showed that the magnetic anisotropy field increase as the magneto-crystalline anisotropy constants increase. The microwave resonance frequency increased accompanied by the reduction of the permeability and the increase of the magnetic anisotropy field of the glass-coated magnetic alloy microwires.

Abstract: The Cu-based bulk glassy alloys in Cu-Zr-Ti-Ni systems were prepared by means of copper mold casting. The structure and corrosion resistance of Cu-based bulk glassy alloys were analyzed by X-ray diffraction (XRD), differential scanning calorimetry (DSC), electrochemistry method, lost weight method. The result indicates the supercooled liquid temperature interval (ΔT_x) is up to 70.98 K for Cu₅₀Zr₂₅Ti₁₅Ni₁₀ bulk glassy alloy. The maximum diameter was up to 5.0 mm for the Cu₅₅Zr₂₅Ti₁₅Ni₅ bulk glassy alloy. For electrochemistry corrosion in 3.5% NaCl solution, self-corrosion electric current density of the Cu₅₀Zr₂₅Ti₁₅Ni₁₀ bulk glassy alloys is obviously lower than that of stainless steel and brass, so corrosion resistance of Cu-based bulk glassy alloys is better than stainless steel and brass at the same corrosion condition. The lost weight method showed that the corrosion rate of brass, stainless steel and glassy alloy is respectively 10.08 g/(m²•h), 6.08 g/(m²•h) and 2.19 g/(m²•h) in the 3% NaCl solution, which also indicates that the corrosion resistance of Cu-based bulk glassy alloys is better than stainless steel and brass. The Cu-based bulk glassy alloys can be used in the special field demanding to have the super high strength, hardness and corrosion resistance.

Abstract: Bulk isotropic and anisotropic Nd_13.5Fe_80.4Ga_0.5B_5.6 and Nd_13.5Fe_80.4Ga_0.5B_5.6/Fe magnets were synthesized by applying spark plasma sintering (SPS) technique. The effect of hot-pressing temperature on the magnetic properties of hot-pressed (HP) and hot-deformed (HD) magnets without additive and with 5% Fe addition was investigated. With increasing sintering temperature for HP magnets, the grain grew gradually. For HD magnets, the optimal magnetic properties could be obtained at hot-pressing temperature 680°C due to the development of desired c-axis texture and uniform microstructure, which resulted from the appropriate and uniform grain size in HP magnets. Fe addition could enhance remanence (B_r) and magnetic energy products ((BH)_m) of HP and HD magnets. However, the maximum magnetic energy product of HD magnets decreased when hot-pressing temperature was higher than 650°C.

Abstract: The atmospheric corrosion has been shown to be an electrochemical process, the atmospheric corrosion behavior of Q235 stell evaluated with ACM (Atmospheric corrosion monitor) electrochemical technique was investigated in the study. The experimental results showed that there existed a close relation between electrochemical data and climatic parameters was confirmed. Taking into consideration accuracy and sensitivity of electrochemical technique, the ISO-standardized time of wetness (TOW) seems to be too conservative. SO2 seems to be more aggressive than chloride on metal corrosion in the early stage of atmospheric corrosion but the complexion reverses in the final stage of atmospheric corrosion. The ratio of corrosion rate from integration of ACM current to corrosion rate from weight loss of test specimens, that is, cell factor is fairly constant at the same test site but varied greatly between test sites. Based on constant cell factors and close relation between electrochemical data and climatic parameters in all test sites, ACM electrochemical technique can evaluate and classify the short-term atmospheric corrosivity as a substitute for gravimetric method, and the verification shows that atmospheric corrosivity classifications according to integration of ACM current and especially to cell factor coincide with the specifications of ISO Standard.