Using weak beam electron microscopy the stacking fault energy (SFE) of III‐V compounds is determined by measuring the dissociation width of edge dislocations. The SFE corrected for the lattice parameters is given in meV/atom for GaAs, GaP, GaSb, InAs, InP, and InSb. As expected there is a strong correlation of the SFE with the ionicity of the bond. The different plasticity of the compounds is traced back to different dislocation velocities.
Structure, morphology, and elemental composition as well as the size-selectivity of the ion transport behavior
of ultrathin membranes of iron(III) hexacyanoferrate(II) (FeIIIHCFII), iron(II) hexacyanoferrate(III) (FeIIHCFIII),
cobalt(II) hexacyanoferrate(III) (CoIIHCFIII), and nickel(II) hexacyanoferrate(III) (NiIIHCFIII) are described.
The membranes were prepared upon multiple sequential adsorption of metal cations and hexacyanometalate
anions on porous polymer supports. Scanning electron and scanning force microscopy indicate that the
membranes of the complex salts consist of a multitude of small, densely packed particles with diameter in
the 10−100 nm range. Energy-dispersive X-ray analysis indicates that the iron hexacyanoferrate (Prussian
blue) membranes consist of the potassium-rich, so-called “soluble” modification, KFe[Fe(CN)6], while the
membranes of the analogous complex salts consist of a mixture of the potassium-rich and potassium-free
modification. The porous, zeolitic structure of the inorganic complex salts was permeable for ions with a
small Stokes radius such as Cs+, K+, and Cl-, whereas large hydrated ions such as Na+, Li+, Mg2+, or SO4
2-
were blocked. Ion separation became progressively more effective, if the number of complex layers increased.
The highest separation factors α(CsCl/NaCl) and α(KCl/NaCl) of 7.7 and 5.9, respectively, were found for
the FeIIIHCFII membrane subjected to a hundred dipping cycles. Membranes of iron(II), cobalt(II), and nickel(II) hexacyanoferrate(III) were also useful for ion separation, but the α values were lower. Effects on the ion
flux rates caused by the feed concentration and the polyelectrolyte precoating of the support are also discussed.
Spin precession of channeled particles in bent crystals has been observed for the first time. Polarized I"*" were channeled using bent Si crystals. These crystals provided an effective magnetic field of 45 T which resulted in a measured spin precession of 60° ±17°. This agrees with the prediction of 62° ± 2° using the world average of Z"*" magnetic moment measurements. This new technique gives a I"*" magnetic moment of (2.40 ± 0.46 ± 0.40)/X7v, where the quoted uncertainties are statistical and systematic, respectively. We see no evidence of depolarization in the channeling process. PACS numbers: 13.40.Fn, 14.20.Jn, 61.80.MkChanneling of high-energy particles in bent crystals has been observed in the momentum range [1-5] of 1.7-800 GeV/c. This technique has already found applications [3][4][5] in the deflection of high-energy beams. Another possibly important application of channeling is the precession of the spin of a polarized particle. This may allow the measurement of magnetic moments in distances of only a few cm. The lifetimes [6] of baryons containing charm quarks are so short that they travel only a few centimeters even at the highest available accelerator energies. Because of these short lifetimes, classical spin precession techniques using conventional magnets would produce negligibly small spin precession angles.It was pointed out by Baryshevskii [7] and Pondrom [8] that the magnetic moments of particles should precess if they were channeled in a bent crystal. The detailed precession theory has been developed by Lyuboshits [9] and Kim [10]. In a curved crystal the electrostatic field of the atomic planes deflecting the particle transforms into a magnetic field in the particle's rest frame. Thus the spin precession angle ^ is [9]
A new method of measuring dislocation velocities in the bulk by TEM is presented. Jogs on dislocations are strong obstacles against dislocation motion during a low temperature deformation. They can be used as markers for the initial course of the dislocation lines and allow to measure the paths travelled by the free dislocation segments between the jogs. First results for the activation energy of the motion of screws and 60° dislocations (2 eV) and for the edges (1.8 eV) are reported. An edge dislocation is assumed to be a series of geometrical kinks. Its motion is interpreted as the collective motion of kinks and the activation energy is tentatively attributed to the kink migration energy.
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