Pingsheng Yu

Pressure effects on mechanical properties of bulk metallic glass

The effects of high pressure (up to 5GPa) on the mechanical properties of a typical Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass (BMG) have been investigated. It is found that the high-pressure pretreatment at room temperature can significantly improve the mechanical performance of the BMG. Particularly, the compressive plasticity of the BMG can be increased as large to as 12% by 4.5GPa pressure pretreatment. The origin of the pressure effect on mechanical properties is studied.

Thulium-based bulk metallic glass

We report the formation and properties of a thulium-based bulk metallic glass (BMG). Compared with other known rare-earth (RE) based BMGs, Tm-based BMGs show features of excellent glass formation ability, considerable higher elastic modulus, smaller Poisson’s ratio, high mechanical strength, and intrinsic brittleness. The reasons for the different properties between the Tm-based and other RE-based BMGs are discussed. It is expected that the Tm-based glasses with the unique properties are appropriate candidates for studying some important issues in BMGs.

Near-infrared broadband luminescence in Bi2O3-GeO2 binary glass system

Near-infrared broadband luminescence from 1100 to 1600 nm was observed in Bi2O3-GeO2 binary glasses. The strongest emission can be observed with 30 mol % Bi2O3 when pumped at 808 nm. The lifetimes of all samples are longer than 200 μs. The glass network was studied by Raman spectra and Bi+ ions are proposed as the infrared luminescence centers in this glass system. Thermal treatment in air results in partly oxidation of Bi+ to Bi2+.

Understanding exceptional thermodynamic and kinetic stability of amorphous sulfur obtained by rapid compression

Amorphous sulfur (a-S) with excellent stability is obtained by rapid compression method. The prepared a-S has a single glassy phase and exhibits a wide supercooled liquid region of 112 K and much high thermal and kinetic stability at room temperature compared to that of conventional a-S fabricated by quenched method. The substantial improved thermal and kinetic stability is attributed to low energy state induced by rapid compressing process. The stable a-S is a model system for facilitating the studies of the nature of glasses and supercooled liquids.

Broadband photoluminescence of Bi2O3–GeO2 binary systems: glass, glass-ceramics and crystals

Ultra-broadband emission covering 1000?1800 and 1800?3020?nm of Bi2O3?GeO2 binary system materials, from glass to glass-ceramics to crystals, is presented in this paper. This is the first time, to our best knowledge, that broadband photoluminescence of BGO crystals (including Bi4Ge3O12 and Bi12GeO20) in the range of 1800?3020?nm has been realized. HRTEM, XPS and XANES have been used to investigate the effects of the valence states and the structure environment of bismuth on the emission properties of Bi2O3?GeO2 binary system materials. Bi2+ and Bi+ are proposed as the emission centers of the photoluminescence peaks at 1060 and 1300?nm, respectively. The broadband emission from 1800 to 3020?nm originates from bismuth clusters. Bi2O3?GeO2 binary system materials could be promising laser materials in the field of full-band optical fiber communication amplifiers, ultra-fast lasers and diode pumped solid state lasers, due to their broadband emission spectra and their feasibility of synthesis and drawing into fibers.

Study on spectroscopic properties and effects of tungsten ions in 2Bi2O3-3GeO2/SiO2 glasses.

The 2Bi2O3-3GeO2/SiO2 glass samples have been prepared by the conventional melt quenching technique. XRD patterns, absorption spectra, excitation-emission spectra and Raman measurements were utilized to characterize the synthesized glasses. When substitute SiO2 for GeO2, the 0.4Bi2O3-(0.4-0.1)GeO2-(0.2-0.5)SiO2 glasses exhibit strong emission centered at about 475nm (under 300nm excitation), and the decay constants are within the scope of 20-40ns. W doping into 2Bi2O3-3SiO2 glass could increase the emission intensity of 470nm, and the W-doped 2Bi2O3-3SiO2 glass has shown another emission at about 433nm with much shorter decay time (near 10ns). The 2Bi2O3-3GeO2/SiO2 glass system could be the possible candidate for scintillator in high energy physics applications.