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1.
S. P. Belyaev R. F. Konopleva I. V. Nazarkin A. I. Razov V. L. Soloveĭ V. A. Chekanov 《Physics of the Solid State》2007,49(10):1969-1972
The recovery of inelastic strains in Ti-Ni alloy samples irradiated in a nuclear reactor under isothermal conditions was studied. Before irradiation, the cylindrical samples were compressed to a residual strain of 3–6% in the martenstici state at room temperature. The samples were irradiated at a temperature of 45°C, which does not exceed the temperature of the onset of the reverse martensitic transformation A S . Irradiation with a fastneutron fluence of 5 × 1020 cm?2 is established to result in the recovery of the residual strain. The value of the recoverable strain is comparable to that observed under the conditions of the shape memory effect on heating of the deformed alloy and even somewhat exceeds it. The obtained data show that neutron irradiation can induce the shape-memory effect in the TiNi alloy. This is due to a decrease in the temperatures of the martensitic transformations under irradiation. 相似文献
2.
Samples of F/M steel HT9 were irradiated to 20?dpa at 420°C, 440°C and 470°C in a transmission electron microscope with 1?MeV Kr ions so that the microstructure evolution could be followed in situ and characterised as a function of dose. Dynamic observations of irradiation-induced defect formation and evolution were made at the different temperatures. Irradiation-induced loops were characterised in terms of their Burgers vector, size and density as a function of dose and similar observations and trends were found at the three temperatures: (i) both a/2 <111> and a <100> loops are observed; (ii) in the early stage of irradiation, the density of irradiation-induced loops increases with dose (0–4?dpa) and then decreases at higher doses (above 4?dpa), (iii) the dislocation line density shows an inverse trend to the loop density with increasing dose: in the early stages of irradiation, the pre-existing dislocation lines are lost by climb to the surfaces while at higher doses (above 4?dpa), the build-up of new dislocation networks is observed along with the loss of the radiation-induced dislocation loops to dislocation networks; (iv) at higher doses, the decrease of number of loops affects more the a/2 <111> loop population; the possible loss mechanisms of the a/2 <111> loops are discussed. Also, the ratio of a <100> to a/2 <111> loops is found to be similar to cases of bulk irradiation of the same alloy using 5?MeV Fe2+ ions to similar doses of 20?dpa at similar temperatures. 相似文献
3.
Abstract High-purity nickel was irradiated with 2 MeV electrons at temperatures below 80 K to a dose of 1 × 1023 e?/m2 in the as-prepared state and after charging with H or D. By means of magnetic after-effect measurements relaxations of anisotropic radiation-induced defects and of defect-hydrogen complexes were investigated in the temperature range between 4.2 and 500 K. The isochronal annealing behaviour of these relaxations and the isochronal recovery of the residual resistivity was measured simultaneously on the same specimens. At temperatures below the hydrogen mobility (< 160 K) in charged irradiated specimens relaxation maxima are observed at 45, 100, 115 and 140 K which show no isotope shift for H and D charging. The maxima below 160 K are explained by defect-hydrogen complexes, where radiation-induced defects reorient around immobile hydrogen atoms. Above 160 K, where hydrogen atoms get mobile, in charged irradiated specimens a broad relaxation maximum appears at 170 K which shows an inverse isotope shift for H and D charging. This 170 K maximum anneals in Stage III. A hydrogen diffusion maximum observed in charged specimens at 215 K prior to irradiation is missing after electron irradiation. The 170 K relaxation is explained by defect-hydrogen complexes, where hydrogen atoms reorient around immobile radiation-induced defects while the long-range hydrogen diffusion is suppressed by these defects. In such relaxation measurements hydrogen and deuterium atoms are used as a “probe” to investigate radiation-induced defects. 相似文献
4.
Kinetics of radiation damage and martensitic transformations in TiNi alloys irradiated with neutrons
S. P. Belyaev A. E. Volkov R. F. Konopleva I. V. Nazarkin A. I. Razov V. L. Solovei V. A. Chekanov 《Physics of the Solid State》2001,43(11):2158-2164
The variation of the temperatures of martensitic transformations and the rate of radiation damage in TiNi alloys were studied upon irradiation with reactor neutrons. The irradiation was performed at temperatures of 120 and 335 K. In the process of irradiation, electrical resistance of the alloys was measured continuously and thermal cycling through the temperature range of martensitic transformations was carried out. The transformation temperatures were shown to decrease at different rates with increasing irradiation fluence. The electrical resistance increases linearly with increasing neutron fluence to 6.7×1018 cm?2 irrespective of the irradiation temperature. Deviation from a linear dependence is only observed when the irradiation leads to a change in the phase state of the alloy. The rate of the resistance increase only slightly depends on the irradiation temperature. In martensite, it is greater by a factor of 2–4 than that in austenite. Mechanisms of irradiation-induced modification of the structure of TiNi alloys that explain the experimental data obtained are discussed. 相似文献
5.
V. A. Vazhenin A. P. Potapov V. B. Guseva M. Yu. Artyomov 《Physics of the Solid State》2009,51(5):917-923
An EPR study of two phases of manganese-doped lanthanum gallate (with a first-order structural transition occurring at 430 K) has revealed Gd3+, Fe3+, and Mn4+ centers at room temperature and 438 K. The parameters of spin Hamiltonians are determined for the Gd3+, Fe3+, and Mn4+ rhombohedral centers in the high-temperature phase (with no other centers found here) and for the monoclinic center Gd3+ in the low-temperature phase. Both in the orthorhombic and in the rhombohedral phase, crystallographic twins (or ferroelastic domains) are observed. 相似文献
6.
Goddard PA Singleton J McDonald RD Harrison N Lashley JC Harima H Suzuki MT 《Physical review letters》2005,94(11):116401
AuZn undergoes a shape-memory transition at 67 K. The de Haas-van Alphen effect persists to 100 K enabling the observation of a change in the quantum oscillation spectrum indicative of a catastrophic Fermi surface reconstruction at the transition. The coexistence of both Fermi surfaces at low temperatures suggests an intrinsic phase separation in the bulk of the material. In addition, Dingle analysis reveals a sharp change in the scattering mechanism at a threshold cyclotron radius, attributable to the underlying microstructure driving the shape-memory effect. 相似文献
7.
A thin film of dilute Fe (0.008)-doped Sb0.95Se0.05 alloy was grown on silicon substrate using the thermal evaporation technique. This film was irradiated with swift heavy ions (SHIs) Ag+15 having 200?MeV energy at ion fluences of 1?×?1012 and 5?×?1012 ions per cm2, respectively. The thickness of the thin film was ~500?nm. We study the effect of irradiation on structural, electrical, surface morphology and magnetic properties of this film using grazing angle XRD (GAXRD), DC resistivity, atomic force microscopy (AFM) and magnetic force microscopy (MFM), respectively. GAXRD suggests that no significant change is observed in this system due to SHI irradiation. The average crystallite size increases with fluence, whereas the AFM image shows the rms roughness decreases due to irradiation with respect to the un-irradiated thin film. The MFM image shows that the magnetic interaction in irradiated film decreases due to the irradiation effect. Although the un-irradiated sample shows metal to semiconducting transition, but after irradiation with fluence of 5?×?1012 ions per cm2, the sharpness of the metal to semiconducting phase transition is observed to increase dramatically at ~300?K. This characteristic of the thin film makes it a promising candidate for an electrical switching device after irradiation. 相似文献
8.
E. Chappel M.D. Núñez-Regueiro G. Chouteau O. Isnard C. Darie 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(4):615-622
NaNiO2 has been studied by neutron-powder diffraction, magnetic susceptibility and submillimeter wave ESR. The monoclinic structure
at room temperature is characterised by a ferrodistorsive orbital ordering due to the Jahn-Teller (JT) effect of the Ni3+ ions in the low spin state. NaNiO2 undergoes a structural transition at around 480 K, above which the orbital ordering disappears. The high temperature phase
is rhombohedral with the layered -NaFeO2 structure ( space group). The magnetic susceptibility exhibits hysteresis and we observe a change of the Curie-Weiss law parameters above
the JT transition. The anisotropy of the g-factor at 200 K can be attributed to the JT effect which favours the orbital occupation. Finally, the interplay between the magnetic and structural properties of NaNiO2 and Li1-xNi1+xO2 is discussed.
Received 29 May 2000 相似文献
9.
Conversion Electron Mössbauer Spectroscopy, (CEMS), has been used to study ion-beam-induced mass transport and phase formation in the Fe/Al bilayer system. In a previous work it was shown that ion irradiation in the same system with noble gases (Ar+, Kr2+, and Xe3+) leaded to the formation of non intermetallic phases when the samples were kept at 77 and 300 K during the bombardments. On the other hand, intermetallic phases were observed for irradiations at substrate temperature of 500 K. The last experimental condition for phase formation corresponds to a lower temperature than conventional thermal treatment needs to reach the same phase. Here, the irradiation conditions were devised to account intermediate substrate temperatures, namely 200 and 400 K, in order to identify the effect of the implantation dose in the phase formation. The intermetallic phases observed in the samples submitted to irradiations at substrate temperature of 500 K, are now formed by even lower temperature-400 K. The results also show a threshold dose of irradiation above which the intermetallic phases are formed. These observations are discussed in terms of a superposition of collision cascades. 相似文献
10.
Abstract The non-stoichiometric solution Ln1?xSrxMnO3-δ□δ was prepared by the classic ceramic method. The physical properties as crystallographic, magnetic and electrical properties were studied. A structural phase transition from rhombohedral to orthorhombic was observed at a concentration of Mn4+ between 10% and 15% per Mn atom in the unit formula. The magnetic properties are very sensitive to the presence of vacancies at the oxygen sites. The non-stoichiometric, samples change from metallic to insulating behaviour depending on their vacancy concentration. In the semiconductor phase, the activation energy value changes with the structural phase, increasing in the rhombohedral phase and decreasing in the orthorhombic phase. 相似文献
11.
ABSTRACTA Fe-based multi-component alloy, 60Fe-12Cr-10Mn-15Cu-3Mo, which presents higher yield stress than typical stainless steels (such as 304, 316, and 340), was used to investigate the thermal stability of irradiation-induced defects. Neutron irradiation was carried out at approximately 323 and 643?K using up to 1.3 × 10?3 and 4.5 × 10?4 dpa (displacements per atom), respectively. While no defects were accumulated at the high temperature of 643?K, single vacancies were formed after irradiation at the low temperature of 323?K to 1.3 × 10?3 dpa, and the vacancies became mobile at 423?K. As a result, vacancy clusters were formed. However, as the annealing temperature increased the size of vacancy clusters decreased. Coincidence Doppler broadening measurements indicated that Cu precipitates were the sites of vacancy cluster formation, and the recovery of vacancy clusters became prominent while annealing the irradiated sample at temperatures higher than 423?K. Recovery of vacancy clusters at 573?K, which was not a high temperature, was also observed even in the sample that was irradiated using 2.5?MeV Fe ions at room temperature to 0.6 dpa at damage peak. 相似文献
12.
A. Ruggiero S. Libertino F. Roccaforte F. La Via L. Calcagno 《Applied Physics A: Materials Science & Processing》2006,82(3):543-547
The effects of ion irradiation defects on the carrier concentration of 6H-SiC epitaxial layer were studied by current–voltage
(I–V), capacitance.-voltage (C–V) measurements, thermally stimulated capacitance and deep level transient spectroscopy. The
defects were produced by irradiation with 10 MeV C+ at a fluence of 1011 ions/cm2 and subsequent thermal annealings were carried out in the temperature range 500–1700 K under N2 flux.
I–V and C–V measurements reveal the presence of a high defect concentration after irradiation and annealing at temperature
lower than 1000 K. Thermally stimulated capacitance measurements show that some of the defects induce a deactivation of the
nitrogen donor, while some of the generated defects, behaving as donor-like traps, contribute to increase the material free
carrier concentration at temperatures above their freezing point.
Deep level transient spectroscopy measurements performed in the temperature range 150–450 K show the presence of several overlapping
traps after ion irradiation and annealing at 1000 K: these traps suffer a recovery and a transformation at higher temperatures.
The annealing of all traps at temperatures as high as 1700 K allows one to completely restore the n-type conductivity. The
defects mainly responsible of the observed change in the carrier concentration are identified.
PACS 73.30.+y; 61.80.Jh; 61.82.Fk; 85.30.Hi 相似文献
13.
Thermal annealing, irradiation with electrons (25-300 keV), and irradiation with photons (hν = 2.33-3.88 eV) have been used to stimulate the crystallization of isolated amorphous zones in Si, Ge, GaAs, GaP and InP. Transmission electron microscopy and computer image analysis were used to determine the crystallization processes. For all materials, thermally stimulated crystallization occurred only at temperatures above 373 K. The electron-stimulated crystallization rate is sensitive to the electron energy. Initially, the rate decreases with increasing energy until it reaches a minimum at about one half the threshold displacement energy and then it increases. It is insensitive to the irradiation temperature between 90 and 300 K and to the crystal orientation. The effective diameter of the amorphous zone initially shrinks linearly with increasing electron dose. For the laser-induced crystallization experiments the crystallization rate in Si, but not in Ge, was sensitive to the temperature, with a faster rate occurring at 300 K than at 90 K. The photon and electron stimulated crystallization results indicate that a non-displacive mechanism causes bond breakage at the amorphous-crystalline interface. The re-formation of these interfacial bonds is responsible for the amorphous-to-crystalline transition. 相似文献
14.
Takeyuki Okada 《辐射效应与固体损伤》2013,168(1):337-342
Abstract Irradiation of KI near 150 K with KrCl excimer laser irradiation (hv=5. 58 eV) produces V centers causing V2 and V3 bands. The two bands exhibit 100-type dichroism. In KI containing V centers, the 111 cm?1 Raman signal attributed to I3- molecular ions is observed. Under KrCl excimer laser irradiation at low temperatures, resonance Raman scattering effects have been also studied for KI, NaI and LiI. 相似文献
15.
V. V. Ovchinnikov N. V. Gushchina F. F. Makhin’ko L. S. Chemerinskaya A. R. Shkol’nikov S. M. Mozharovskii A. V. Filippov L. I. Kaigorodova 《Russian Physics Journal》2007,50(2):177-186
Using electron microscopy it was found that irradiation of clad cold-worked specimens made of commercial aluminium-lithium
alloy 1441 by the Ar
+ ions of energy 40 keV at low doses of irradiation (1015 cm−2, irradiation time 1 s, T < 70 °C) and ion-current density of about 100 μA/cm2 results in the transformation of the cellular structure formed in the alloy under deformation. As the dose of irradiation
is increased up to 1016 cm−2, a transition from a cellular to a subgrain structure close to a polygonal one is observed. The efficiency of the process
is increased with ion-current density. Furthermore, under ion irradiation at increased ion-current densities, the β′(Al
3
Zr) and Al
8
Fe
2
Si particles present in the deformed alloy dissolve, and disperse particles of a new Al
2
LiMg phase of platelet shape are formed. The changes in the dislocation structure and phase composition in alloy 1441 are observed
several seconds after irradiation not only in the surface layer adjacent to the ion incorporation band but also through the
thickness of the specimen tens of thousands times greater than ion projective ranges.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 73–81, February, 2007. 相似文献
16.
Abstract The displacive transition in La is studied in the pressure range up to 26 GPa and under temperatures up to 630 K with angular dispersive X-ray diffraction at the ESRF and with energy dispersive X-ray diffraction in HASYLAB to elucidate further details of this transition with an extension of the transition line up to 22.5(5) GPa and 590(10) K and a determination of the order parameter down to a level of η ≈=5· 10?4. 相似文献
17.
A. U. Sheleg V. G. Gurtovoi V. V. Shevtsova S. N. Mustafaeva E. M. Kerimova 《Physics of the Solid State》2012,54(9):1870-1874
The dependences of the permittivity and electrical conductivity of TlInS2 and TlGaS2 single crystals on the temperature and electron beam irradiation dose have been studied. It has been established that, as the electron irradiation dose increases, the electrical conductivity σ significantly increases, whereas the permittivity ? decreases over the entire temperature range covered (80–320 K). It has been shown that anomalies in the form of maxima in the temperature dependences σ(T) and ?(T) are observed in the regions characteristic of phase transitions in TlInS2. Irradiation of the TlInS2 and TlGaS2 crystals with electrons to doses of 1015 and 1016 cm?2 does not affect their phase transition temperatures. The dispersion curves of the permittivity ? of the TlGaS2 crystal have been constructed. 相似文献
18.
Abstract The change in electrical properties of TGS crystals due to induced defects created by fast neutron irradiation of two different energies (2 and 14 MeV) and different integrated neutron fluxes have been studied in the vicinity of phase transition. It is observed that the electrical conductivity increases with increase of neutron fluence up to 1.7 × 1010 n · cm?2 and the values of the relative change of electrical conductivity in case of 2 MeV are higher than that of 14 MeV neutrons at the same neutron fluence (φ) 相似文献
19.
V. S. Pokatilov A. S. Sigov V. V. Pokatilov A. O. Konovalova 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(8):1115-1117
Single-phase rhombohedral perovskites (Bi0.9Sr0.1)FeO3 were studied by Mössbauer spectroscopy at temperatures of 293, 87, and 680 K. The Neel temperature T N = 652 ± 2 K of the magnetic transition was measured. Three states of trivalent iron ions in the octahedral states were discovered. Substitution of Sr2+ for 0.1 mol % Bi3+ breaks the spatially spin-modulated structure. 相似文献
20.
The rearrangement was investigated of crystallographic domains in the antiferromagnetic pseudo-tetragonal phase in CoO (Néel temperature: 293 K) when the domains were driven by a magnetic field. A rearrangement is generally observed in ferromagnetic shape-memory alloys. The rearrangement was found to occur at temperatures between 170 K and 293 K, but not at temperatures below 170 K. In order to determine the reason for such a difference, the shear stress driven by a magnetic field, τ mag, was calculated and compared with the shear stress required for twinning plane movement, τ req. It was found that τ mag is equal to or larger than τ req whenever the rearrangement of crystallographic domains occurs due to the application of a magnetic field, and vice versa. This observation is similar to past observations in the case of many ferromagnetic shape-memory alloys. 相似文献