摘要:

Preliminary results are reported of the observation of an intermetallic phase, formed during the oxidation of a 9 wt% Cr-1 wt% Mo steel, the electron diffraction patterns from which exhibit 5 symmetry. The Mo, Fe-rich phase, of approximate composition 37wt% Mo-45wt% Fe-11wt% Cr and 7wt% Si, forms 150μm beneath the oxide scale when the steel is exposed to an atmosphere bf high-pressure CO2at a temperature of 560°C. High-resolution electron microscopy has revealed that the structure of the Mo,Fe-rich phase consists of an intergrowth of microdomains of several phases, which may be interpreted as pentagonal tetrahedrally close-packed (t.c.p.) phases.

ISSN:0950-0839    

DOI:10.1080/09500838808203774

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

We present a discussion of the effect of chemical substitution on the stability of Mackay icosahedra in Al-Mn alloys based on a microscopic model of the total energy of metallic alloys. In particular, we demonstrate why the addition of Si stabilizes both the crystalline α-(Al-Mn-Si) structure and the icosahedral phase of Al-Mn-Si. We predict specific A1 sites which are favourable for Si substitution.

ISSN:0950-0839    

DOI:10.1080/09500838808203775

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The shape of gold crystals inside sapphire has been studied by transmission electron microscopy. 400 keV gold ions were implanted into sapphire (α-Al2O3) at a substrate temperature of 1200°C. The gold ions precipitate as small crystals, which have an ordinary f.c.c. structure and dimensions less than 60 nm. The small gold crystals clearly have faceted outlines. The sides of the outlines are parallel to low-index crystal-planes of sapphire. It has therefore been concluded that the shape of the gold crystals is characterized by the foreign crystal (i.e., sapphire), and that the shape should be a tetradecahedron which consists of two {0001} and twelveplanes of sapphire.

ISSN:0950-0839    

DOI:10.1080/09500838808203776

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

High-resolution structural imaging has been used to show that the great majority of stacking-fault tetrahedra produced in thin foils of electron-irradiated silver are of vacancy nature.

ISSN:0950-0839    

DOI:10.1080/09500838808203777

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

It is shown that in the high-TcYBa2Cu3O∼7superconductor the critical temperature is a function of the orthorhombic distortion (b–a)/aof the unit cell. From the extrapolation of the (b - a)/aratio againstTc, a maximum critical temperature of 66 K for the tetragonal phase of YBa2Cu3O∼7was predicted. From the correlation between the transition width δTcand the orthorhombic distortion there was deduced an upper limit forTc, in the orthorhombic phase of YBa2Cu3O∼7of 94·5K.

ISSN:0950-0839    

DOI:10.1080/09500838808203778

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Conductivity measurements on three disc-shaped n-InSb samples were carried out in magnetic fields up to 70 kG at temperatures down to 40 mK and over a frequency range of 0–105Hz. In the hopping-conduction region the a.c. and d.c. conductivities were found to scale according to:σ(ω, T)/σ(0, T) = f [AωT/σT(0, T)], where ˜ωT and ˜σT are normalized values andfis a universal function obtained by Summerfield. The parameter -log10Ais found to be 3·0±0·2, a value which is predicted by theory for some semiconductor materials with a constant density of states at the Fermi level.

ISSN:0950-0839    

DOI:10.1080/09500838808203779

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0950-0839    

DOI:10.1080/09500838808203780

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor