H-Diffusion in the H-Storage TiVMnCr Alloys as Deduced from Absorption and Mechanical Spectroscopy Experiments

2005 ◽  
Vol 885 ◽  
Author(s):  
Giovanni Mazzolai ◽  
Andrea Biscarini ◽  
Bruno Coluzzi ◽  
Fabio Massimo Mazzolai ◽  
Ausonio Tuissi
Keyword(s):  
Solid Solution ◽  
Diffusion Coefficients ◽  
Arrhenius Plot ◽  
Solubility Limit ◽  
Absorption Kinetics ◽  
Mechanical Spectroscopy ◽  
Α Phase

ABSTRACTThe low H content portion of the PCT absorption curves of the 40Ti-xV-(50-x)Mn-10Cr alloys exhibits a plateau, whose pressure has been determined together with the solubility limit of H in the α–phase (solid solution). The chemical (Dc) and Einstein (DE) diffusion coefficients of H have been deduced from H absorption kinetics (273 K-1100 K) and from mechanical spectroscopy (150 K-200 K), which has revealed a Snoek-type of anelastic relaxation. The combined Arrhenius plot of DE and Dc gives the following parameters for H diffusion: W=0.318±0.005 eV, D0=(4±1)×10−7 m2/s (36 V alloy) and W=0.352±0.005 eV, D0=(5±1)10−7 m2/s (32 V alloy).

Nitrogen Diffusion in Niobium under Low Pressure

2014 ◽  
Vol 353 ◽  
pp. 223-227
Author(s):  
Armando Cirilo Souza ◽  
Odila Florêncio ◽  
Carlos Roberto Grandini
Keyword(s):  
Solid Solution ◽  
Partial Pressure ◽  
Diffusion Coefficients ◽  
Solubility Limit ◽  
Nitrogen Diffusion ◽  
Interstitial Concentration ◽  
Relaxation Parameters ◽  
Bcc Structure ◽  
Oscillation Frequencies ◽  
And Diffusion

The interaction among heavy interstitial atoms present in metals with bcc structure is studied using anelastic spectroscopy. This technique makes it possible to obtain information on interstitial concentration, precipitation, solubility limit, and diffusion. The diffusion coefficients of nitrogen in niobium were obtained using the relaxation parameters obtained from anelastic spectroscopy measurements for different oscillation frequencies of the system. The results showed the interstitial diffusion of nitrogen present in solid solution in niobium when submitted to different charges of nitrogen at a temperature of 1373 K and a partial pressure in the order of 10-4Torr. The exponential variation of the pressure experimentally in function of the time was thus obtained.

Diffusion of Nitrogen in Ti-13V-11Cr-3Al Alloys

2009 ◽  
Vol 283-286 ◽  
pp. 38-44 ◽  
Author(s):  
Carlos Roberto Grandini ◽  
Emerson Haruiti Kamimura ◽  
José Roberto Severino Martins ◽  
Hugo Ricardo Zschommler Sandim ◽  
Odila Florêncio
Keyword(s):  
Solid Solution ◽  
Internal Friction ◽  
Diffusion Coefficients ◽  
Crystalline Lattice ◽  
Mechanical Spectroscopy ◽  
Interstitial Concentration ◽  
Exponential Factors ◽  
Friction Measurements ◽  
Internal Friction Spectra ◽  
Interstitial Elements

Metals with a bcc crystalline structure such as Ti-13V-11Cr-3Al alloys have their physical properties significantly changed through the addition of interstitial elements such as oxygen and nitrogen. These metals can dissolve substantial amounts of interstitial elements forming solid solutions. Mechanical spectroscopy measurements constitute a powerful tool for studying interactions of these interstitial elements with other elements that make up the alloy. From these measurements, it is possible to obtain information regarding diffusion, interstitial concentration, interaction between interstitials, and other imperfections of the crystalline lattice. In this paper, Ti-13V-11Cr-3Al alloys with several amount of nitrogen, in a solid solution, were studied using mechanical spectroscopy (internal friction) measurements. The results presented complex internal friction spectra which were resolved in a series of constituent Debye peaks corresponding to different interactions and interstitial diffusion coefficients. Pre-exponential factors and activation energies were calculated for nitrogen in theses alloys.

Diffusion Phenomena of the Oxygen and Nitrogen in Niobium by Mechanical Spectroscopy

2010 ◽  
Vol 297-301 ◽  
pp. 1346-1353
Author(s):  
Odila Florêncio ◽  
Paulo Sergio Silva ◽  
Carlos Roberto Grandini
Keyword(s):  
Diffusion Coefficients ◽  
Short Range ◽  
Annealed Sample ◽  
Relaxation Processes ◽  
Torsion Pendulum ◽  
Mechanical Spectroscopy ◽  
Interstitial Diffusion ◽  
Relaxation Parameters ◽  
Low Concentrations ◽  
Diffusion Phenomena

The short-range diffusion phenomenon (Snoek Effect) was investigated by mechanical spectroscopy measurements between 300 K and 650 K, in a polycrystalline niobium sample, containing oxygen and nitrogen, using a torsion pendulum. Experimental spectra of anelastic relaxation were obtained under three conditions: as-received sample; annealed sample and subsequently annealed in an oxygen atmosphere for three hours at 1170 K in partial pressure of 5x10-5mbar. The experimental spectra obtained were decomposed in elementary Debye peaks and the anelastic relaxation processes were identified. With anelastic relaxation parameters and the lattice parameters, the interstitial diffusion coefficients of the oxygen and nitrogen in niobium were calculated for each kind of preferential occupation (octahedral and tetrahedral). The results were compared with the literature data, and confirmed that the best adjustment is for the preferential occupation octahedral model for low concentrations of interstitial solutes, but at higher concentration of oxygen were observed deviations of experimental data for the interstitial diffusion coefficients of oxygen in niobium when compared with the literature data, this could be related to the possible occurrence of a double occupation of interstitial sites in the niobium lattice by oxygen interstitials.

Activation barriers for oxygen diffusion in polystyrene and polycarbonate glasses: effects of codissolved argon, helium, and nitrogen

1995 ◽  
Vol 73 (11) ◽  
pp. 1831-1840 ◽  
Author(s):  
Bojie Wang ◽  
Peter R. Ogilby
Keyword(s):  
Diffusion Coefficient ◽  
Polymer Matrix ◽  
Diffusion Coefficients ◽  
Oxygen Diffusion ◽  
Arrhenius Plot ◽  
Activation Barrier ◽  
Spectroscopic Technique ◽  
Activation Barriers ◽  
Data Yield ◽  
Diffusion Activation

A recently developed spectroscopic technique was used to determine oxygen diffusion coefficients as a function of temperature for polystyrene and polycarbonate films. Data were recorded at total pressures <300 Torr over the temperature range 5–45 °C under conditions in which argon, helium, and nitrogen, respectively, were copenetrants. In all cases, the presence of the additional gas caused an increase in the oxygen diffusion coefficient. Arrhenius plots of the data yield (a) a diffusion activation barrier, Eact, and (b) a diffusion coefficient, D0, that represents the condition of "barrier-free" gas transport for the temperature domain over which the Arrhenius plot is linear. For all cases examined in both polystyrene and polycarbonate, D0 increased with an increase in the partial pressure of added gas. In polystyrene, the presence of an additional gas did not change Eact. In polycarbonate, Eact obtained in the presence of helium and argon likewise did not differ from that obtained in the absence of the copenetrant. When nitrogen was the added gas, however, a larger value of Eact was obtained. This latter observation is interpreted to reflect the plasticization of polycarbonate by nitrogen. Eact and D0 data are discussed within the context of a model that distinguishes between dynamic and static elements of free volume in the polymer matrix. Keywords: oxygen diffusion, polystyrene, polycarbonate, activation barrier.

Synthesis and characterization of mixed fluorides with PbF2 and ScF3

2005 ◽  
Vol 20 (3) ◽  
pp. 254-258 ◽  
Author(s):  
S. N. Achary ◽  
A. K. Tyagi
Keyword(s):  
Solid Solution ◽  
Phase Equilibria ◽  
Room Temperature ◽  
Unit Cell Volume ◽  
Solubility Limit ◽  
Synthesis And Characterization ◽  
Temperature Phase ◽  
Fluorite Type ◽  
Low Temperature Phase

A series of mixed fluoride compositions with PbF2 and ScF3 were prepared by heating the intimate mixtures of component fluorides at 600 °C for 10 h followed by slowly cooling to room temperature. The products obtained were analyzed by powder XRD to reveal the phases present in them and hence the low-temperature phase equilibria in the PbF2-ScF3 system. The phase equilibria show the fluorite-type solid solution up to the composition of about 15 mol% of ScF3 in the PbF2 lattice. The unit cell volume decreases with increasing ScF3 contents in the fluorite-type solid solutions. Beyond the solubility limit, the biphasic mixture of the cubic fluorite-type solid solution and leftover ScF3 is found to exist.

Water Absorption Characteristics of Obatanpa and Mamaba Maize Hybrids (Zea mays)

2006 ◽  
Vol 2 (3) ◽  
Author(s):  
Ahmad Addo ◽  
Ato Bart-Plange ◽  
Komla Dzisi
Keyword(s):  
Zea Mays ◽  
Diffusion Coefficient ◽  
Water Absorption ◽  
Diffusion Coefficients ◽  
Type Equation ◽  
Water Diffusion ◽  
Energy Of Activation ◽  
Absorption Kinetics ◽  
Maize Hybrids ◽  
Absorption Characteristics

Water absorption characteristics of two newly-released maize hybrids, Obatanpa and Mamaba, during soaking were measured at four temperatures of 30, 40, 50 and 60ºC. The absorption kinetics followed the Fick's law of diffusion during the first hours of soaking. The values determined for water diffusion coefficients varied from 7.31 x 10-12 to 9.33 x 10-12 m2/s and from 6.30 x 10-12 to 8.25 x 10-12 m2/s for Obatanpa and Mamaba respectively. An Arrhenius–type equation was used to relate the diffusion coefficient of Obatanpa and Mamaba to temperature, and the energy of activation for Obatanpa and Mamaba was estimated. The values determined were 6.54 kJ/mol and 6.82 kJ/mol for Obatanpa and Mamaba respectively.

Effect of the Solid-Solution Treatment on the Die-Casting Structures and Properties of Commercial RE-AZ91D Mg Alloy

2014 ◽  
Vol 1061-1062 ◽  
pp. 13-16
Author(s):  
Zhi Chao Liu ◽  
Yao Li ◽  
Jun Jie Yang
Keyword(s):  
Solid Solution ◽  
Tensile Strength ◽  
Die Casting ◽  
Solution Treatment ◽  
Treatment Temperature ◽  
Elongation Ratio ◽  
Β Phase ◽  
Solid Solution Treatment ◽  
Α Phase ◽  
Structures And Properties

Effect of the solid-solution treatment on the structures and properties of the die-casting AZ91D alloy with mixed rare-earth elements was explored.The results show that the the tensile strength and the elongation ratio δ have been improved by solid-solution treatment.The higher the treatment temperature was,the better the improvement were.With the increase of the temperature,the content of β phase was lower when those of M-RE compound and the refinement α phase were higher.The tensile strength can reach 304.74Mpa and the elongation ratio can reach 11% after the solid-solution treatment of 370°C×16h.

Silicon nitride: Enthalpy of formation of the α- and β-polymorphs and the effect of C and O impurities

1999 ◽  
Vol 14 (5) ◽  
pp. 1959-1968 ◽  
Author(s):  
Jian-jie Liang ◽  
Letitia Topor ◽  
Alexandra Navrotsky ◽  
Mamoru Mitomo
Keyword(s):  
Solid Solution ◽  
Enthalpy Of Formation ◽  
Solution Calorimetry ◽  
Molar Enthalpy ◽  
Solid Solution Series ◽  
Solution Series ◽  
Α Phase ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
The Enthalpy Of Formation

High-temperature oxidative drop solution calorimetry was used to measure the enthalpy of formation of α− and β−Si3N4. Two different solvents, molten alkali borate (48 wt% LiBO2 · 52 wt% NaBO2) at 1043 and 1073 K and potassium vanadate (K2O · 3V2O5) at 973 K, were used, giving the same results. Pure α− and β−Si3N4 polymorphs have the same molar enthalpy of formation at 298 K of −850.9 ± 22.4 and −852.0 ± 8.7 kJ/mol, respectively. The unit cell dimensions of impure α−Si3N4 samples depend linearly on the O and C impurity contents, and so does the molar enthalpy of formation. The energetic stability of the α−Si3N4phase decreases when the sample contains O and C impurities. The experimental evidence strongly suggests that the impurities dissolve into the α−Si3N4 structure to form a (limited) isostructural solid solution series but that this solid solution series is energetically less stable than a mechanical mixture of pure (α or β) Si3N4, SiO2, and SiC. Thus, the α-phase is not stabilized by impurities and is probably always metastable.

The Measurement of Concentration Dependent Diffusion Coefficients in the Solid-solution Alloy Pd-Y*

1993 ◽  
Vol 181 (Part_1_2) ◽  
pp. 125-131 ◽  
Author(s):  
P. R. Stonadge ◽  
M. J. Benham ◽  
D. K. Ross ◽  
C. Manwaring ◽  
I. R. Harris
Keyword(s):  
Solid Solution ◽  
Diffusion Coefficients ◽  
Solid Solution Alloy
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