[en] Zr₄₈Nb₈Cu₁₄Ni₁₂Be₁₈ bulk metallic glass (BMG) with excellent glass-forming ability was prepared by water quenching method. The BMG exhibits high glass transition temperature T_g and onset crystallization temperature T_x, compared with Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5 BMG. The crystallization processes, change of elastic constants, and density and hardness in the crystallization process were studied by using X-ray diffraction, differential scanning calorimetry and acoustic method. The shear modulus, Poisson ratio, density and hardness are found to be sensitive to the crystallization process. A striking softening of long-wavelength transverse acoustic phonons in the BMG relative to its crystallized state is observed. The linear expansion coefficient, determined by a dilatometer method, is α_TG=1.04x10^-5 K^-1 (300-656 K) for the BMG and α_TC=1.11x10^-5 K^-1 (356-890 K) for the crystalline alloy. The Mie potential function and the equation of state of the BMG are determined from the expansion coefficient and acoustic experiments

[en] Acoustic velocities, elastic constants and thermodynamic parameters upon pressure up to 2 GPa of typical Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5 bulk metallic glass (BMG) have been studied by using a pulse echo overlap method. The results indicate that the glass forming ability (GFA) has a relation with the elastic constants for a glass forming system. The compression curve of the BMG is interposed among its components, and the BMG exhibits small volume changes upon pressure, confirming that the BMG has similar atomic close-packed configurations with elements which may closely related to the origin of its excellent GFA

[en] A family of holmium-based bulk metallic glasses (BMGs) with high glass-forming ability is obtained. The Ho-based BMGs exhibit much larger elastic moduli and high thermal stability in contrast to other known rare-earth (RE)-based BMGs. In particular, the BMGs show a large value of fragility. It is expected that the hard RE-based glasses with high glass-forming ability and fragile behaviors make them the appropriate candidate for glass transition study

[en] The aging behavior and the stability of a Ce₆₈Al₁₀Cu₂₀Fe₂ bulk metallic glass (BMG) with low glass transition temperature T_g have been investigated upon isothermal annealing near T_g. The annealing time-dependent acoustic velocities, density, elastic constants, and thermodynamic parameters are determined to monitor the structural and properties changes upon aging, and the structural relaxation progress is monitored by the change of enthalpy recovery after annealing. It is found that BMG with T_g near room temperature has high thermal and property stabilities. Stable BMG provides an ideal system to investigate relaxation and supercooled liquid state in alloys

[en] The pressure-volume (P-V) relation of Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5 bulk metallic glass (BMG) at room temperature has been studied using a piston-cylinder high-pressure apparatus up to 4.5 GPa. The equation of state of the BMG is determined. As the first equation of state of the BMG, it is compared with other crystalline solids, and the differences are phenomenologically explained. The experimental results indicate the BMG contains a large amount of vacancylike free volume

[en] We report cerium-based bulk metallic glasses with an exceptionally low glass transition temperature T_g, similar to or lower than that of many polymers. We demonstrate that, in near-boiling water, these materials can be repeatedly shaped, and can thus be regarded as metallic plastics. Their resistance to crystallization permits extended forming times above T_g and ensures an adequate lifetime at room temperature. Such materials, combining polymerlike thermoplastic behavior with the distinctive properties of metallic glasses, are highly unusual for metallic alloys and have great potential in applications and can also facilitate studies of the supercooled liquid state

[en] Crystallization of a Cu₆₀Zr₂₀Hf₁₀Ti₁₀ bulk metallic glass in the entire supercooled liquid region (SLR) is studied using an in situ x-ray diffraction with synchrotron radiation under high pressure and a differential scanning calorimeter at ambient pressure. The temperature-time-transition diagrams under ambient and high pressure are determined and compared, and the phase evolution of the crystallization with time is in situ exhibited under high pressure. We find that the crystallization in the temperature regime near glass transition temperature and near melting temperature in SLR cannot be described by a single crystallization mechanism in the entire SLR under high pressure. The effects of pressure on the crystallization of the BMG are explored

[en] The pressure dependence of crystallization in Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5 bulk metallic glass has been studied by means of high-pressure annealing close to and beyond the glass transition temperature, using differential scanning calorimetry and x-ray diffraction. The results reveal that high pressure markedly decreases the crystallization temperature of the glass. It is deduced that high-pressure annealing can promote crystal nucleation by decreasing the work of formation of the critical nucleus, but it also restrains crystal growth by decreasing the diffusion velocity of atoms. (author). Letter-to-the-editor

[en] A novel miniature cylindrical combustor, whose chamber wall is made of porous material, has been designed and experimented for reducing heat loss and enhancing flame stability. The combustor has the function of reducing wall heat loss, extending residence time and avoiding radical chemical quenching with a self-thermal insulation concept in which heat loss reduction is obtained by the opposite flow directions between thermal energy transfer and mass flow. The methane/air mixture flames formed in the chamber are blue and tubular in shape. Between the flames and the porous wall, there is a thin unburned film that plays a significant role in reducing the flames' heat loss and keeping the flames stable. The porous wall temperature was 150-400 deg. C when the temperatures of the flames and exhaust gas were more than 1200 deg. C. When the equivalence ratio φ < 1.0, the methane conversion ratio was above 95%; the combustion efficiency was near 90%; and the overall sidewall heat loss was less than 15% in the 1.53 cm³ chamber. Moreover, its combustion efficiency is stable in a wider combustion load (input power) range.

[en] A centimeter magnitude thermoelectric (TE) power generation system based on a plat-flame micro combustor burning DME (dimethyl ether) has been developed. The chamber wall of this micro combustor was made of two parallel sintered porous plates which acted as mixture inlet. The main virtue of this combustor is that it can keep combustor wall at lower temperature for reducing heat loss when sustaining a stable flame. Experimental test results showed it was feasible to obtain stable DME/air premixed flame at lean combustion situations in the micro combustor. The combustion load of this 0.48 cm³ chamber capacity was 20-200 W at equivalence ratio φ = 0.6. Though the flame temperature was above 1000 ^oC, the combustor's wall temperature was near 600 ^oC lower than flame temperature. In the demonstrated TE power generation system which integrated the plat-flame micro combustor, a heat spreader had good effect on uniforming the hot side temperature field of TE modules. Cooled by water and with 150 W input power at φ = 0.7, the system produced 10 V output at open circuit and 4 V at 10 Ω load. The maximum power output was above 2 W, and the maximum overall chemical-electric energy conversion efficiency was 1.25%.