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Showing 1 to 20 of 24 for “"Activation volume"”.
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Primary creep of polycrystalline copper and determination of the activation volume
… between the moving and forest dislocations. The activation volume is found to be inversely proportional to the strain, and to increase with temperature. These effects are discussed in terms of the dislocation density and the stacking fault width.
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Activation volumes of carbon diffusion in F.C.C. iron-nickel alloys
… technique was used to determine the activation volume of carbon diffusion, ΔV, in six fcc iron-nickel alloys. Measurements were made at temperatures ranging from 68ºC to 90ºC and pressures up to six kilobars on samples having a nickel content between 31 and 63 at. %. A maximum …
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Effect of pressure on ionic conductivity in rubidium silver iodide and silver iodide
… samples, up to pressures of 6 kbar. The activation volumes for motion in cr-RbAg4I5 and B-RbAgI5, respectively, are -0.4 ±.2 cm3/mole and -0.2 ±.l cm3/mole. In 4a-AgI, the motion volume increases from 0.56 ±.l cm3 /mole at 435 K to 0.8 ±.l cm3/mole at 623 K. These values are unusually …
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The Influence of Pressure on The Low-Temperature Kinetics of Myoglobin
… is first pressurized and then frozen, the total volume change for the reaction can be resolved into an activation volume component and a conformational volume component. Strong evidence requiring both conformational volume and activation volume components was found. Over the pressure range …
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Stress effects on atomistic kinetic transitions
… applied to a kinetic transition impacts the activation enthalpy. To this end, the activation energy, scalar activation volume, and tensorial activation volume were studied for several kinetic transition types. This computational study used the nudged elastic band method to find the activation …
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The effect of high pressure on self-diffusion in beta-titanium
… to decrease with pressure, indicating a positive activation volume. This result is in contradiction of earlier reports of negative activation volumes for diffusion of Fe in S-Ti and U in y-U. The value obtained for the activation volume for self-diffusion in S-Ti is approximately 3.6 ± 1.0 …
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Magnetic properties of block-copolymer fabricated cobalt nanodots and nanowires at elevated temperatures
… 200°Cand no more than 10nm deep when above 200°C Activation volume calculations could not be accurately calculated, suggesting an activation volume 10!! times the volume of one nanodots. To characterize magnetic features present in the nanowires from block copolymer fabrication, magnetic force …
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Strain rate and temperature dependent mechanical behavior of nanocrystalline gold
… stress-strain curves were used to calculate activation volumes for two film thicknesses (0.85 μm, and 1.75 μm), which were 4.5b3 and 8.1b3, at strain rates smaller than 10-4 s-1 and 12.5b3 and 14.6b3 at strain rates higher than 10-4 s-1. The reduced activation volume and increased strain rate …
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Effect of ion irradiation on the rate dependence of plastic deformation of extruded Zr-2.5%Nb
… hardening, strain rate sensitivity and apparent activation volume were investigated. The effects of Zr+ ion-implantation occurring at 300°C, simulating irradiation-induced damage, and the strain rate of loading on these properties were also investigated. Two methods of testing were performed: …
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Characterizing Plastic Deformation Mechanisms in Metal Thin Films using In Situ Transmission Electron Microscopy Nanomechanics
… strength is generally attributed to the high volume of grain boundaries (GB) which impede conventional dislocation glide. Unfortunately, the increase in strength is accompanied by a decrease in ductility. NC and UFG metals also exhibit an increase in strain-rate sensitivity and decrease in …
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High Pressure Effects on the Dynamics and Kinetics of Two Model Biochemical Systems
… NMR inversion transfer, and the apparent activation volumes of exchange determined. Hydrogen exchange between NMA and water serves as a model for amide-water hydrogen exchange in peptides and proteins which is sensitive to the local environment of the protons and is used to probe …
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Stress-mediated reaction pathways for dislocation nucleation in copper
… that the common structural conception of activation volume for dislocation nucleation does not apply for all stresses and in general over-predicts the stress-dependence of activation by considering only the shear displacement of the critical defect.
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Experimental constraints on the rheological behavior of olivine at upper mantle conditions
… pressure effect on the strength of olivine (an activation volume of 14 ± 3 cm3/mol), as well as pioneering in situ measurements of fabric development, slip system transitions, and stress heterogeneity.
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Organic materials with acenoid and iptycene structures
… of high-pressure on reactions with a negative activation volume. A pyridinium p-toluenesulfonate catalyzed dehydration reaction of the D-A polymer led to a novel aromatic ladder polymer, poly(iptycene), which is soluble in common organic solvents and stable up to 350 oC.
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Multiscale In-Situ Characterization of Crystal Orientation, Temperature, and Microstructure Effects on Creep Defromation of Pure Magnesium and Mg-Al-RE Alloys
… creep tests at 25, 100, and 180 ˚C. Analysis of activation energy, activation volume, and athermal flow stress indicates that creep is dominated by obstacle-limited dislocation glide, while higher temperatures promote dynamic recovery. The final part studies high pressure die cast (HPDC) AE44 …
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Hierarchical Assembly Strategy and Multiscale Structural Origin of Exceptional Mechanical Performance In Nacre
… can be directly related to the localized plastic activation volume. Nacre's hierarchical energy-dissipation mechanism under dynamic compression loading comes from a mechanical optimization derived from its inherently multiscale functional structure design.</p>
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Time dependence in fine-particle systems
… texture and a distribution of particle volumes. The coercivity, (i.e. the magnitude of the field that will just reduce the magnetisation of a saturated system to zero), is an important parameter used for characterising a recording medium, and consequently studies of its time dependence …
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Photoconductivity studies of the ferrocyanide ion under high pressure
… aqueous solution, was interpreted in terms of an activation volume model. The photoaquation data for both the aqueous and the alcoholic solutions agreed with a hypothetical mechanism whereby ligand-to-metal bond-breaking, and solvent-to-metal bond-formation, are effectively simultaneous. The …
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Imaging and Understanding Atomic-Scale Adhesion and Wear: Quantitative investigations Using in situ TEM
… custom analysis routines to resolve tip shape, volume changes, and adhesive forces with unprecedented resolution. From in situ adhesion tests, a novel method was developed to extract the work of adhesion (0.66±0.14 J/m^2) and range of adhesion (0.25±0.06 nm) between silicon and diamond. The …
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Silicon and oxygen self-diffusion in forsterite and implications to upper-mantle rheology
… small negative pressure dependence with an activation volume of 1.7±0.4 cm3/mol. The activation energy is found to be 410±30 kJ/mol. LogDSi at 1600 and 1800 K at ambient pressure are -19.7±0.4 and -18.1±0.3 (DSi in m2/s), respectively, which are ~2.4 orders of magnitude higher than those …
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