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1.
Elżbieta Godlewska M. Mitoraj F. Devred B. E. Nieuwenhuys 《Journal of Thermal Analysis and Calorimetry》2007,88(1):225-230
A Ti–45.9Al–8Nb
(at%) alloy with a lamellar structure (γ+α2)
was oxidised in air at 700, 800, 850 and 900°C in isothermal and thermal
cycling conditions. The reaction progress was followed by thermogravimetric
measurements. In isothermal conditions the oxidation kinetics followed approximately
a parabolic rate law and the rate constants ranged from about 10–12
kg2 m–4 s–1
at 700°C to 10–10 kg2
m–4 s–1
at 900°C. The oxide scales were built of Al2O3
and TiO2, the former being the main component of the
outermost layer. The oxidation behaviour of Ti–45.9Al–8Nb was
referred to a commercial titanium alloy, WT4 (Ti–6Al–1Mn), and
selected oxidation-resistant alloys. 相似文献
2.
3.
4.
Hermse CG van Bavel AP Nieuwenhuys BE Lukkien JJ van Santen RA Jansen AP 《Langmuir : the ACS journal of surfaces and colloids》2005,21(18):8302-8311
Lateral adsorbate-adsorbate interactions result in variation of the desorption rate constants with coverage. This effect can be studied in great detail from the shape of a multi-isotherm. To produce the multi-isotherm, the temperature is increased in a (semi)stepwise fashion to some temperature, followed by maintaining this temperature for a prolonged time. Then, the temperature is stepped to a higher value and held constant at this new temperature. This cycle is continued until all of the adsorbates have desorbed. Using a detailed kinetic Monte Carlo model and an optimization algorithm based on Evolutionary Strategy, we are able to reproduce the shape of the experimentally measured multi-isotherm of nitrogen on Rh(111) and obtain the lateral interactions between the nitrogen atoms. 相似文献
5.
The adsorption, desorption and decomposition of CO on Rh surfaces have been investigated using field emission microscopy and thermal desorption spectroscopy. Thermal dissociation of CO cannot be detected on clean Rh surfaces at pressures up to 10?1 Torr and temperatures below 1000 K. This holds also for atomically rough surfaces like (210). CO dissociation can be promoted under the influence of an electron beam directed to the surface, a high electric field in the presence of CO in the gas phase and by means of discharge techniques. The growth of crystallites formed by CO dissociation and the diffusion of carbon into the bulk has been followed as a function of temperature and surface structure. The tip regions around (110) are very active in these processes. Carbon crystallites on these surfaces disappear around 1000 K by diffusion into the lattice whereas crystallites present around (311) surfaces persist up to 1150 K. The results are discussed in relation to the activity of Rh in CO/H2 reactions. 相似文献
6.
Galli F Ramakrishnan S Taniguchi T Nieuwenhuys GJ Mydosh JA Geupel S Ludecke J van Smaalen S 《Physical review letters》2000,85(1):158-161
We report the observation of a new type of charge-density wave (CDW) in the large magnetic-moment rare-earth intermetallic compound, Er5Ir4Si10, which then orders magnetically at low temperatures. Single crystal x-ray diffraction shows the development of a 1D incommensurate CDW at 155 K, which then locks into a purely commensurate state below 55 K. The well-localized Er3+ moments are antiferromagnetically ordered below 2.8 K. We observe very sharp anomalies in the specific heat at 145 and 2.8 K, signifying the bulk nature of these transitions. Our data suggest the coexistence of strongly coupled CDW with local-moment antiferromagnetism in Er5Ir4Si10. 相似文献
7.
A. S. Prokhorov V. B. Anzin D. A. Vitukhnovskiĭ E. S. Zhukova I. E. Spektor B. P. Gorshunov S. Vongtragool M. B. S. Hesselberth J. Aarts G. J. Nieuwenhuys M. Dumm D. Faltermeier S. Kaiser S. Yasin M. Dressel N. Drichko 《Journal of Experimental and Theoretical Physics》2006,103(6):887-896
The electrodynamic response of spin glasses (in the form of thin AuFe films) in the terahertz frequency range has been studied using backward-wave oscillator (BWO) spectroscopy (10–40 cm?1) and optical ellipsometry (5000–33000 cm?1) techniques at temperatures from 5 to 295 K. The room-temperature dynamic conductivity spectra of AuFe films are typical of metals and can be described within the framework of the Drude theory of conduction by free charge carriers. Changes in the microscopic parameters of charge carriers in AuFe films with increasing iron content, which are related to additional scattering of carriers on the impurity magnetic moments, have been studied on the quantitative level, including the carrier relaxation frequency and characteristic time, plasma frequency, and conductivity. It is established that the spin-glass phase at a temperature of ~5 K exhibits dispersion of the conductivity in the frequency range 10–40 cm?1, which can be related to the appearance of a mobility gap in the subsystem of free electrons involved in the RKKY interaction between magnetic centers (Fe atoms). 相似文献
8.
L.P. Le R.H. Heffner J.D. Thompson G.J. Nieuwenhuys D.E. Maclaughlin P.C. Canfield B.K. Cho A. Amato R. Feyerherm F.N. Gygax A. Schenck 《Hyperfine Interactions》1997,104(1-4):49-54
The muon‐spin‐relaxation technique has been utilized to characterize the magnetic properties of the borocarbide compounds
RNi2B2C ( R=\,Tm, Er, Ho and Dy), which exhibit coexistence of superconductivity and magnetism. Some general features of their magnetic
ground‐state and unusual results obtained in the Ho, Tm and Dy systems are discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
Origin of the spatiotemporal oscillations observed during the NO + H2 reaction on a Rh field emitter
The main purpose of the study described in the present paper was to obtain more detailed information on the mechanism of the spatiotemporal oscillations found recently by field emission microscopy for the NO + H2 reaction on a Rh tip. These oscillations are related to the kinetics of the reaction over a Rh wire. There are two kinetic regions of the steady-state reaction. The oscillations are attributed to the reversible transition between these kinetic regions. The observed sharp moving wave can be ascribed to the hydrogenation of a nitrogen layer, followed by fast combination and/or decomposition of the adsorbed intermediate NH and restoring of its surface coverage by the NO + H2 interaction. Surface defects and, probably, grain boundaries are responsible for the initiation of the chemical waves in the course of the sustained oscillations. 相似文献
10.
S. Süllow G. J. Nieuwenhuys A. A. Menovsky J. A. Mydosh 《Zeitschrift für Physik B Condensed Matter》1997,104(2):185-188
We present the physical properties of the new intermetallic compound UNi2Ga3. This compound crystallizes in the hexagonal CaCu5-structure, and bulk experiments (specific heat c p, susceptibility X, magnetization M and resistivity ρ) indicate the system to undergo a magnetic transition at 9.5 K. No superconductivity is observed down to 50 mK. The magnetic transition in UNi2Ga3 closely resembles that of the incommensurably ordered state in the related heavy-fermion superconductor UNi2Al3. In addition, and independently from the conditions for sample preparation, we found indications for a considerable degree of lattice disorder, likely due to structural Ga/Ni disorder. We discuss our results, particularly the absence of superconductivity in UNi2Ga3, in comparison to UNi2Al3. 相似文献