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Oxidizing anneals have been carried out to test the stability of nickel precipitates previously formed in MgO:Ni by thermochemical reduction. The annealed crystals have been examined by transmission electron microscopy (TEM) and cathodoluminescence (CL). Both techniques, TEM and CL, reveal that the nickel precipitates become unstable under oxidizing annealing at temperatures 1223 K for 30 min. Cathodoluminescence results are analyzed on the basis of anion vacancy complexes and Ni2+ transitions. 相似文献
2.
R. da Silveira A. Boukour Ch. Leclercq-Willain 《The European Physical Journal A - Hadrons and Nuclei》2000,7(4):503-506
We present a simple method which enables us to identify the occurence of a forward glory in heavy ion scattering data. The
method is successfully applied to the elastic scattering data of 12C (65 MeV), 13C (60 MeV), 15N (85 MeV) and 16O (75 MeV) on 28Si.
Received: 2 July 1999 / Revised version: 3 December 1999 相似文献
3.
Evidence of precipitation in MgO:Co crystals after reducing heat treatments at temperatures near or above 1375 K is given. Thermochemically reduced crystals have been examined by transmission electron microscopy (TEM) and cathodoluminescence scanning electron microscopy (CL-SEM). TEM observations show the spatial and size distribution of particles to be very inhomogeneous and associated with complex structures of dislocations. These structures are developed during the thermochemical reduction of the crystals. The CL results are analyzed on the basis of anion vacancy complexes. 相似文献
4.
M.G. Nijkamp J.E.M.J. Raaymakers A.J. van Dillen K.P. de Jong 《Applied Physics A: Materials Science & Processing》2001,72(5):619-623
A survey is presented of the storage capacities of a large number of different adsorbents for hydrogen at 77 K and 1 bar.
Results are evaluated to examine the feasibility and perspectives of transportable and reversible storage systems based on
physisorption of hydrogen on adsorbents. It is concluded that microporousadsorbents, e.g. zeolites and activated carbons,
display appreciable sorption capacities. Based on their micropore volume (∼1 ml/g) carbon-based sorbents display the largest
adsorption, viz. 238 ml (STP)/g, at the prevailing conditions. Optimization of sorbent and adsorption conditions is expected
to lead to adsorption of ∼560 ml (STP)/g, close to targets set for mobile applications.
Received: 9 January 2001 / Accepted: 27 January 2001 / Published online: 23 March 2001 相似文献
5.
S. Amoruso M. Armenante V. Berardi R. Bruzzese N. Spinelli 《Applied Physics A: Materials Science & Processing》1997,65(3):265-271
-2 ). The interpretation of the ion TOF distributions in terms of theoretical shifted Maxwell–Boltzmann distributions produces
a good agreement with the experimental data. This has allowed us to infer the ion flow velocity and temperature associated
with the measured TOF distributions, as well as the ion kinetic energies as a function of the laser fluence. We have also
studied the total ion yield at different laser fluences. Our results show that all the plume parameters investigated are increasing
functions of the laser fluence until a saturation plateau is reached at high fluences (>20 Jcm-2). We ascribe this saturation behav
iour to strong absorption and partial, or total, reflection of the laser light by the hot plasma produced by the leading edge
of the intense laser pulse. This interpretation is supported by a semi-quantitative analysis of the laser photon absorption
and ionization mechanisms in Al plasma, at both laser wavelengths.
Received: 6 January 1997/Accepted: 14 March 1997 相似文献
6.
D.Y. Noh H.C. Kang T.Y. Seong J.H. Je H.K. Kim 《Applied Physics A: Materials Science & Processing》1998,67(3):343-346
3 /MgO(100) films was studied in synchrotron X-ray scattering experiments. In the thin epitaxial films, the tetragonal distortion
of the ferroelectric phase and the transition temperature were significantly reduced. In sharp contrast to the reported mixture
of the a-type and the c-type domains in thicker films, the 250-Å-thick film was purely composed of the c-type domains in the
tetragonal phase. We attribute the suppression of the transition to the substrate effect, which prefers the c-type domains
near the interface, and reduces the tetragonal distortion to minimize the strain energy caused by the lattice mismatch.
Received: 1 November 1997/Accepted: 5 January 1998 相似文献
7.
We calculate the ground state of the half-filled Hubbard model and its energy by starting from a spindensity wave approximation and improving it by incorporating transverse spin fluctuations. The calculations are done by employing a projection method. The quality of the proposed approximation is particularly high for intermediate and large Coulomb repulsionU, where it exceeds considerably e.g. that of the Gutzwiller projected spin-density wave state. To ordert
2/U (wheret is the hopping matrix element), our approximation is shown to be equivalent to a recent Coupled Cluster calculation for the Heisenberg antiferromagnet. Finally we show how to ordert
2/U the linear spin-wave approximation for the Heisenberg antiferromagnet may be obtained. 相似文献
8.
Bismuth-borate glasses doped with some rare earth ions were studied with respect to the density, molar volume and the elastic moduli, Poisson’s ratio, Debye temperature, microhardness, softening temperature, acoustic impedance, diffusion constant and latent heat of melting. Ultrasonic velocities were measured by the pulse echo overlap technique at a frequency of 10 MHz and at room temperature. From these velocities and density values, various elastic moduli were calculated. The correlation of elastic stiffness, the cross link density, and the fractal bond connectivity of these glasses are discussed. The derived experimental values of shear modulus, bulk modulus, Young’s modulus, and Poisson’s ratio for our glasses are compared with the theoretically calculated values in terms of the bond compression model and Makishima-Mackenize theory. 相似文献
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