Viscous flow of the Cu47-Ti34-Zr11-Ni8 glass forming alloy

The viscosity of the Cu47-Ti34-Zr11-Ni8 glass forming alloy was determined by beam bending experiments and by a noncontact oscillating drop technique. These viscosity data can be described with the Vogel-Fulcher-Tammann relation. Using the strong/fragile classification of glasses, Cu47-Ti34-Zr11-Ni8 is more fragile than the strong Zr-Ti-Cu-Ni-Be metallic glass formers

Thermodynamics of Cu47Ti34Zr11Ni8, Zr52.5Cu17.9Ni14.6Al10Ti5 and Zr57Cu15.4Ni12.6Al10Nb5 bulk metallic glass forming alloys

The differences in the thermodynamic functions between the liquid and the crystalline states of three bulk metallic glass forming alloys, Cu47Ti34Zr11Ni8, Zr52.5Cu17.9Ni14.6Al10Ti5, and Zr57Cu15.4Ni12.6Al10Nb5, were calculated. The heat capacity was measured in the crystalline solid, the amorphous solid, the supercooled liquid, and the equilibrium liquid. Using these heat capacity data and the heats of fusion of the alloys, the differences in the thermodynamic functions between the liquid and the crystalline states were determined. The Gibbs free energy difference between the liquid and the crystalline states gives a qualitative measure of the glass forming ability of these alloys. Using the derived entropy difference, the Kauzmann temperatures for these alloys were determined

Crystallization of amorphous Cu47-Ti34-Zr11-Ni8

The results of a study on the crystallization of amorphous Cu47-Ti34-Zr11-Ni8 with the use of differential scanning calorimetry, transmission electron microscopy (TEM), x-ray diffraction, field ion microscopy, atom probe tomography (APT), and small-angle neutron scattering (SANS) are presented. These experimental techniques were used to characterize as-prepared samples and specimens heat treated at different temperatures around the glass transition temperature. APT and SANS show that the alloy decomposes into copper-enriched and titanium-enriched regions prior to nucleation and growth of a crystalline phase. TEM shows that the primary nucleating phase has a face centered cubic structure

CHARACTERIZATION OF PLASTICALLY-INDUCED STRUCTURAL CHANGES IN A Zr-BASED BULK METALLIC GLASS USING POSITRON ANNIHILATION SPECTROCOPY

Flow in metallic glasses is associated with stress-induced cooperative rearrangements of small groups of atoms involving the surrounding free volume. Understanding the details of these rearrangements therefore requires knowledge of the amount and distribution of the free volume and how that distribution evolves with deformation. The present study employs positron annihilation spectroscopy to investigate the free volume change in Zr{sub 58.5}Cu{sub 15.6}Ni{sub 12.8}Al{sub 10.3}Nb{sub 2.8} bulk metallic glass after inhomogeneous plastic deformation by cold rolling and structural relaxation by annealing. Results indicate that the size distribution of open volume sites is at least bimodal. The size and concentration of the larger group, identified as flow defects, changes with processing. Following initial plastic deformation the size of the flow defects increases, consistent with the free volume theory for flow. Following more extensive deformation, however, the size distribution of the positron traps shifts, with much larger open volume sites forming at the expense of the flow defects. This suggests that a critical strain is required for flow defects to coalesce and form more stable nanovoids, which have been observed elsewhere by high resolution TEM. Although these results suggest the presence of three distinct open volume size groups, further analysis indicates that all groups have the same line shape parameter. This is in contrast to the distinctly different interactions observed in crystalline materials with multiple defect types. This similarity may be due to the disordered structure of the glass and positron affinity to particular atoms surrounding open-volume regions

Oxidation of uranium nanoparticles produced via pulsed laser ablation

An experimental apparatus designed for the synthesis, via pulsed laser deposition, and analysis of metallic nanoparticles and thin films of plutonium and other actinides was tested on depleted uranium samples. Five nanosecond pulses from a Nd:YAG laser produced films of {approx}1600 {angstrom} thickness that were deposited showing an angular distribution typical thermal ablation. The films remained contiguous for many months in vacuum but blistered due to induced tensile stresses several days after exposure to air. The films were allowed to oxidize from the residual water vapor within the chamber (2 x 10{sup -10} Torr base pressure). The oxidation was monitored by in-situ analysis techniques including x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and scanning tunneling microscopy (STM) and followed Langmuir kinetics

Phase I study of bortezomib combined with chemotherapy in children with relapsed childhood acute lymphoblastic leukemia (ALL): A report from the therapeutic advances in childhood leukemia (TACL) consortium

Background Outcomes remain poor for children after relapse of acute lymphoblastic leukemia (ALL), especially after early marrow relapse. Bortezomib is a proteasome inhibitor with in vitro synergy with corticosteroids and clinical activity in human lymphoid malignancies. Procedure This is a Phase I study of escalating doses bortezomib administered days 1, 4, 8, and 11, added to 4-drug induction chemotherapy with vincristine, dexamethasone, pegylated L -asparaginase, and doxorubicin (VXLD) in children with relapsed ALL. Results Ten patients were enrolled, five in first marrow relapse, and five in second relapse. Four patients were enrolled at dose level 1 (bortezomib 1 mg/m 2 ). One patient was not evaluable for toxicity because of omitted dexamethasone doses. No dose-limiting toxicity (DLT) was observed. Six patients were enrolled at dose level 2 (bortezomib 1.3 mg/m 2 ). One patient had dose-limiting hypophosphatemia and rhabdomyolysis after 1 dose of bortezomib, and died from a diffuse zygomyces infection on day 17. Five additional patients were enrolled with no subsequent DLTs. As planned, no further dose escalation was pursued. The regimen had predictable toxicity related to the chemotherapy drugs. Two patients had mild peripheral neuropathy (grades 1 and 2). Six of nine evaluable patients (67%) achieved a complete response (CR), and one had a bone marrow CR with persistent central nervous system leukemia. Conclusions The combination of bortezomib (1.3 mg/m 2 ) with VXLD is active with acceptable toxicity in pretreated pediatric patients with relapsed ALL. We are expanding the 1.3 mg/m 2 cohort for a phase II estimate of response. Study registered at ClinicalTrials.gov ( http://clinicaltrials.gov/ct2/show/NCT00440726 ). Pediatr Blood Cancer 2010;55:254–259. © 2010 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77437/1/22456_ftp.pd

Characterization of densified fully stabilized nanometric zirconia by positron annihilation spectroscopy

Fully-stabilized nanometric zirconia samples with varying degrees of porosity and grain sizes were analyzed using the coincidence Doppler broadening mode of the positron annihilation spectroscopy (PAS). A decrease in the low momentum fraction was observed and coincided with a decrease in porosity. In addition to pores, it is proposed that defects in the negatively charges grain boundary space region act as positron trapping centers; their effectiveness decreases with an increase in grain size. It is shown that PAS is sensitive to small grain size differences within the nanometric regime in these oxide materials