Atomic-Scale Design for Enhanced Low Temperature Twinning in ZrCr2-Based Laves Phases

1999 ◽  
Vol 578 ◽  
Author(s):  
W.-Y. Kim ◽  
D.E. Luzzi
Keyword(s):  
Low Temperature ◽  
Room Temperature ◽  
Alloy System ◽  
Deformation Mode ◽  
Systematic Investigation ◽  
Mechanical Twinning ◽  
Atomic Scale ◽  
Laves Phases ◽  
Drastic Effect ◽  
Scale Design

AbstractRecently, we have designed and produced several transition metal Laves phases with low-temperature compressive ductility. These improved alloys demonstrate that manipulation of atomic-scale structure can have a drastic effect on meso-scale deformation behavior. To gain a basic understanding of the role of atomic-scale substitutions on the room temperature mechanical properties, a systematic investigation of the Laves ZrCr2-based alloy system alloyed with Hf, Nb, Ta and Ti was conducted and is reported here. Extensive room temperature ductility was obtained in the Hf-alloyed ternary Laves phase alloy system. Mechanical twinning is found to be the predominant deformation mode at room temperature in this alloy system. It is emphasized that Hf substitution in the Zr sublattice of ZrCr2 may play the most prominent role in changing the local electronic structure resulting in easier twinning.

Deformation Twinning, Slip, Martensite Formation and Crack Inhibition in the B2-Type Zr50Pd35Ru15 Alloy

1991 ◽  
Vol 246 ◽  
Author(s):  
R.M. Waterstrat ◽  
L.A. Bendersky ◽  
R. Kuentzler
Keyword(s):  
Crystal Structure ◽  
Plastic Deformation ◽  
Room Temperature ◽  
Deformation Mode ◽  
Deformation Twinning ◽  
Mechanical Twinning ◽  
Dislocation Slip ◽  
Slip Mode ◽  
Martensite Formation ◽  
Additional Mode

AbstractEnhanced room temperature toughness of the Zr50Pd35Ru15B2 phase alloy was found to be a result of the activation of an additional deformation mode besides the b=[001] dislocation slip mode - {114}-type mechanical twinning. The twinning is a true one, i.e. there is no change in the ordered crystal structure. Another additional mode of plastic deformation, expected for more Pd rich alloys, is the formation of stress-induced martensite. The martensite was found to have a CrBtype structure.

Room-temperature deformation in a Laves phase

1990 ◽  
Vol 5 (1) ◽  
pp. 5-8 ◽  
Author(s):  
J. D. Livingston ◽  
E. L. Hall
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Room Temperature ◽  
Deformation Mode ◽  
Laves Phase ◽  
Temperature Deformation ◽  
Two Phase ◽  
Laves Phases ◽  
Ti Alloys ◽  
Transmission Electron

Transmission electron microscopy of two-phase V-Hf-Nb and V-Hf-Nb-Ti alloys plastically deformed at room temperature shows that {111} (112) twinning is a major deformation mode for the HfV2-based Laves phase. Bands of concentrated shear are also observed. Possible approaches to enhance low-temperature deformability in other Laves phases are discussed.

THE EFFECT OF SOLUTE ON SLIP AND MECHANICAL TWINNING IN IRON ALLOYS

1967 ◽  
Vol 45 (2) ◽  
pp. 541-557 ◽  
Author(s):  
G. F. Bolling ◽  
R. H. Richman
Keyword(s):  
Room Temperature ◽  
Deformation Mode ◽  
Solute Concentration ◽  
Mechanical Twinning ◽  
Extensive Study ◽  
Liquid Distribution ◽  
Initial Flow ◽  
Nucleation Mechanisms ◽  
Dislocation Behavior ◽  
Mechanical Twins

The effects of solute type and concentration upon the nature of, and stresses for, plastic flow in polycrystalline iron solid solutions have been examined. An extensive study was made using Al, Be, Ge, P, Si, and Sn; limited examples with Co, Sb, and Ti are also included. Three experimental observations stand out: (i) At room temperature and lower solute concentration the flow stress for slip increases monotonically with the parameter c|ln km|. Here c is the solute concentration, and the solid–liquid distribution coefficient, km, differentiates the solute type, (ii) At room temperature, there is a transition in the deformation mode from slip to twinning at a concentration that decreases with increasing |ln km|. The actual stresses for mechanical twinning can be compared with those at 77 °K; they are higher and provide a second measure for the deformation-mode transition, (iii) At 77 °K the initial deformation mode is predominantly mechanical twinning, and, below concentrations producing atomic ordering, the initial flow stresses are independent of solute concentration and type.When these observations are accompanied by tests for the propagation-controlled phenomenon of continual mechanical twinning, we deduce the following: (i) and (ii) show that solute promotes mechanical twinning as a consequence of its effect on dislocation behavior, most likely by requiring fast-moving individual dislocations, while (iii) shows that a threshold stress exists for the nucleation of mechanical twins that cannot easily be explained by existing twin-nucleation mechanisms.

Survival of mouse blastocysts after low-temperature preservation under high pressure

2004 ◽  
Vol 52 (4) ◽  
pp. 479-487 ◽  
Author(s):  
Cs. Pribenszky ◽  
M. Molnár ◽  
S. Cseh ◽  
L. Solti
Keyword(s):  
Phase Transition ◽  
Hydrostatic Pressure ◽  
Low Temperature ◽  
High Hydrostatic Pressure ◽  
Room Temperature ◽  
Freezing Point ◽  
Significant Loss ◽  
Embryo Cryopreservation ◽  
Subzero Temperatures ◽  
Survival Capacity

Cryoinjuries are almost inevitable during the freezing of embryos. The present study examines the possibility of using high hydrostatic pressure to reduce substantially the freezing point of the embryo-holding solution, in order to preserve embryos at subzero temperatures, thus avoiding all the disadvantages of freezing. The pressure of 210 MPa lowers the phase transition temperature of water to -21°C. According to the results of this study, embryos can survive in high hydrostatic pressure environment at room temperature; the time embryos spend under pressure without significant loss in their survival could be lengthened by gradual decompression. Pressurisation at 0°C significantly reduced the survival capacity of the embryos; gradual decompression had no beneficial effect on survival at that stage. Based on the findings, the use of the phenomena is not applicable in this form, since pressure and low temperature together proved to be lethal to the embryos in these experiments. The application of hydrostatic pressure in embryo cryopreservation requires more detailed research, although the experience gained in this study can be applied usefully in different circumstances.

Photophysical properties of N719 and Z907 dyes, benchmark sensitizers for dye-sensitized solar cells, at room and low temperature

2021 ◽  
Vol 23 (10) ◽  
pp. 6182-6189
Author(s):  
Dariusz M. Niedzwiedzki
Keyword(s):  
Solar Cells ◽  
Low Temperature ◽  
Optical Spectroscopy ◽  
Room Temperature ◽  
Photophysical Properties ◽  
Dye Sensitized Solar Cells ◽  
Time Resolved ◽  
Dye Sensitized ◽  
Sensitized Solar Cells

Photophysical properties of N719 and Z907, benchmark Ru-dyes used as sensitizers in dye-sensitized solar cells, were studied by static and time-resolved optical spectroscopy at room temperature and 160 K.

Transition Insulator-Metal and Antiferromagnetic-Paramagnetic Cu Doped in La0.47Ca0.53MnO3

2015 ◽  
Vol 1123 ◽  
pp. 73-77 ◽  
Author(s):  
Yohanes Edi Gunanto ◽  
K. Sinaga ◽  
B. Kurniawan ◽  
S. Poertadji ◽  
H. Tanaka ◽  
...  
Keyword(s):  
High Resolution ◽  
Low Temperature ◽  
Magnetic Structure ◽  
Room Temperature ◽  
Paramagnetic Phase ◽  
Perovskite Manganites ◽  
Antiferromagnetic Phase ◽  
Temperature Transition ◽  
Cu Doping ◽  
Metal State

The study of the perovskite manganites La0.47Ca0.53Mn1-xCuxO3 with x = 0, 0.06, 0.09, and 0.13 has been done. The magnetic structure was determined using high-resolution neutron scattering at room temperature and low temperature. All samples were paramagnetic at room temperature and antiferromagnetic at low temperature. Using the SQUID Quantum Design, the samples showed that the doping of the insulating antiferromagnetic phase La0.47Ca0.53MnO3 with Cu doping resulted in the temperature transition from an insulator to metal state, and an antiferromagnetic to paramagnetic phase. The temperature transition from an insulator to metal state ranged from 23 to 100 K and from 200 to 230 K for the transition from an antiferromagnetic to paramagnetic phase.

Molecule-Based Magnets—An Overview

MRS Bulletin ◽  
2000 ◽  
Vol 25 (11) ◽  
pp. 21-30 ◽  
Author(s):  
Joel S. Miller ◽  
Arthur J. Epstein
Keyword(s):  
Low Temperature ◽  
Vapor Deposition ◽  
Room Temperature ◽  
Chemical Vapor ◽  
Magnetic Ordering ◽  
Low Density ◽  
Materials Properties ◽  
The Common ◽  
New Processing ◽  
Very High

Molecule-based magnets are a broad, emerging class of magnetic materials that expand the materials properties typically associated with magnets to include low density, transparency, electrical insulation, and low-temperature fabrication, as well as combine magnetic ordering with other properties such as photoresponsiveness. Essentially all of the common magnetic phenomena associated with conventional transition-metal and rare-earth-based magnets can be found in molecule-based magnets. Although discovered less than two decades ago, magnets with ordering temperatures exceeding room temperature, very high (∼27.0 kOe or 2.16 MA/m) and very low (several Oe or less) coercivities, and substantial remanent and saturation magnetizations have been achieved. In addition, exotic phenomena including photoresponsiveness have been reported. The advent of molecule-based magnets offers new processing opportunities. For example, thin-film magnets can be prepared by means of low-temperature chemical vapor deposition and electrodeposition methods.

Infrared spectra of the ammonium ion in crystals. Part VIII. Spectroscopic criteria of highly-bent hydrogen bonds

1980 ◽  
Vol 58 (9) ◽  
pp. 867-874 ◽  
Author(s):  
Osvald Knop ◽  
Wolfgang J. Westerhaus ◽  
Michael Falk
Keyword(s):  
Low Temperature ◽  
Hydrogen Bonds ◽  
Infrared Spectra ◽  
Room Temperature ◽  
Ammonium Ion ◽  
Temperature Transition ◽  
Increasing Temperature

Available evidence suggests that (1) the stretching frequencies of highly-bent hydrogen bonds decrease with increasing temperature, regardless of whether the bonds are static or dynamic in character, to a single acceptor or to several competing acceptors; and (2) departures from symmetric trifurcation (or bifurcation) toward asymmetric situations lower the stretching frequency. In further support of these criteria isotopic probe ion spectra between 10 K and room temperature have been obtained for taurine and for trigonal (NH4)2MF6 (M = Si, Ge, Sn, Ti). Evidence of a low-temperature transition at 100(10) K in trigonal (NH4)2SnF6 is presented, and existence of the previously reported transition at 38.6 K in trigonal (NH4)2SiF6 is confirmed. Symmetry changes associated with these transitions are discussed.

Sign in / Sign up

Export Citation Format

Share Document