Compositional dependence of thermal and elastic properties of Cu-Ti-Zr-Ni bulk metallic glasses

Starting from the quaternary Cu47Ti34Zr11Ni8 alloy, the compositional dependence of thermal and elastic properties of Cu-Ti-Zr-Ni alloys was systematically investigated. Quaternary Cu-Ti-Zr-Ni alloys can be cast directly from the melt into copper molds to form fully amorphous strips or rods with the thickness of 3-6 mm. The evidence of the amorphous nature of the cast rods was provided by X-ray spectra. The measured glass transition temperature （Tg） and crystallization temperature （Tx） were obtained for the alloys using differential scanning calorimetry （DSC） at the heating rate of 20 K/s. In the results, the differences between the glass temperature and the crystallization temperature （△Tx=Tx-Tg） are measured with values ranging up to 33-55 K. The reduced glass transition temperature （Trg）, which is the ratio of the glass temperature to the liquidus temperature （T3, is often used as an indication of the glass-forming ability of metallic alloys. For the present Cu-Ti-Zr-Ni alloys, this ratio is typically in the range of 0.5838-0.5959, characteristic of metallic alloys with good glass-forming ability. The elastic constants for several selected alloys were measured using ultrasonic methods. The values of the elastic shear modulus, bulk modulus, and Poisson＇s ratio were also given.

Synthesis of Novel Quaternary Selenide K_2CdSnSe_4

A novel quaternary metal selenide, K2CdSnSe4, was synthesized via a molten-salt reaction at 550 ℃. The compound has a one-dimensional structure containing a chain of ∞^1[CdSnSe4]^2- anions separated by K^＋ cations. The crystal belongs to the space group I-4^-2m, with the unit cell parameters a=0.80298（11） nm, b=0.80298（11） nm, c=0.69217（14） nm, α=β=γ=90°. A reflectance spectroscopy study reveals the nature of the semiconductor with an energy gap of 1.7 eV for the compound and it has a strong optical absorotion in a range of 2--5 eV.

Functionalized activated carbon for the adsorptive removal of perchlorate from water solutions

Two types of activated carbon, namely, Filtrasorb 400 and Nuchar SA, were functionalized by quaternary ammonium salts （quats）, as to enhance perchlorate adsorption. Results showed that the adsorption of quats on Nuchar SA increased with increase in chain length （hydrophobicity） of quats. Filtrasorb 400, however, had limited uptake of long-chain quats such as dodecyl- trimethylammonium and hexadecyltrimethylammoium （HDTMA）. Results indicated that perchlorate removal by the functionalized activated carbon was directly related to the chain length of the modifying quats. Perchlorate removal by functionalized activated carbon increased with increase in chain length of the modifying quats and became less pH-dependent. Modified Nuchar SA had higher overall perchlorate removal capacity than the modified Filtrasorb F400, but was more strongly affected by pH than Filtrasorb 400. Activated carbon treated with HDTMA exhibited the best perchlorate removal capacity among all quats studied. Results indicated that tailoring the activated carbon surface with HDTMA rendered the activated carbon surface positively charged, which resulted in substantial increase in perchlorate removal compared to unfunctionalized activated carbons.