摘要:

Amorphous alloys containing nanoscale crystals have been deformedin situin a high-voltage electron microscope. Acceleration in the nucleation and growth of nanoscale crystals has been found at a crack tip during ageing under stress. It has also been revealed that the nanoscale crystals are free from lattice defects after deformation to cracking. These observations suggest that the presence of non-deformable nanoscale crystals plays an important role in the strengthening of amorphous alloys.

ISSN:0950-0839    

DOI:10.1080/09500839508241279

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Hydrogenated amorphous germanium-sulphur (a-G1−xSx: H) alloys have been prepared by the glow-discharge technique from mixtures of hydrogen, germane and sulphur hexafluoride gases. The sulphur content of the films prepared at the powered and the unpowered electrodes varied between 2 and 30 at.%. Addition of sulphur decreases the activation energy of the conductivity from a typical value of 0.5 eV for hydrogenated amorphous germanium (a-Ge: H) to minima of 0.14 and 0.28 eV for the alloys deposited on the unpowered electrode and powered electrode respectively. Concurrent with this, for the cathode-deposited films, the ημτ product of electrons is increased by one order of magnitude to a maximum of 2 × 10−6cm2V−1, and the ambipolar diffusion length decreases from 470 to 350 Å. From these trends, and with a consideration of various additional experimental findings, it is inferred that n-type doping occurs when sulphur is added to a-Ge: H. Sulphur incorporation improves the quality of films prepared at the unpowered electrode as is evident from the optoelectronic properties; the ημτ product increases by more than three orders of magnitude to 10−6cm2V−1, whereas the ambipolar diffusion length is nearly constant at around 400 Å.

ISSN:0950-0839    

DOI:10.1080/09500839508241280

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The metastable magnetic alloy Co10Cu90has been prepared by the conventional melt-spinning technique. The rapid solidification process results in an extended solubility of Co in Cu although some Co particles already have precipitated during quenching. In comparison with conventional ageing methods, Joule heating could also be adopted to fabricate granular Co-Cu alloys with even finer Co particles. The finest size of 4.0nm has been achieved for Co10Cu90alloy after annealing with a currentI= 4 A for 1 rnin. Single-domain behaviour results in a value of coercivity in excess of 40.0 kAm−1for the sample annealed withI= 9.5 A. Below the size of 6.0 nm, Co particles exhibit superparamagnetic behaviour at room temperature, which has been investigated using a superconducting quantum interference device magnetometer. A unique change inMswith annealing current or temperature was discovered.

ISSN:0950-0839    

DOI:10.1080/09500839508241281

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Diffuse scattering of the thermodynamically stable decagonal quasicrystal (QC) Al70Ni15Co15has been measured at a synchrotron radiation source. Perpendicular to the unique ‘periodic’ direction there is an alternating sequence of ‘Bragg’ and (modulated) diffuse layers. Within the zeroth Bragg layer, strong diffuse streaks and diffuse satellite reflections, as well as very weak and slowly varying diffuse scattering, were measured up to high values ofQ. Satellites and diffuse streaks, already known from precession photographs, were explored in theq-scan mode yith a step width of 0.01 inhandk(pseudo-monoclinic setting witha*= 0.081 08 Å−1,b*= 0.081 09 Å−1in the QC plane,c* = 0.245 16 Å−1in the periodic direction,y= 72°). The positions, but not the intensities of all registered satellite reflections obey an overall tenfold symqetry around the Bragg reflection. The satellite vector magnitude ‒qs‒ = 3.3 × 10−2Å−1corresponds to a translational superperiod of the QC substructure with a 30 Å period. First- and second-order satellites were always observed only in pairs around the Bragg reflections, superimposed on the diffuse streaks through the Bragg reflection and the satellites. These observations may be interpreted by lamellar domains extended parallel to the unique axis. The full widths at half-maximum of the satellites are between 1.4 × 10−3and 2.0 × 10−3Å−1, corresponding to correlation lengths between 700 and 500 Å of the domain ordering. The diffuse streaks indicate faults in the regular sequence of the lamellar domains. An additional uniform diffuse background is observed, reflecting a high degree of disorder in the (projected) QC arrangement of the basic columnar-like structural elements.

ISSN:0950-0839    

DOI:10.1080/09500839508241282

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The construction of a two-dimensional and two-colour Penrose tiling known as a grey Penrose tiling is accomplished by using an algorithm comprising the geometrical operations akin to normal crystallographic operations. This method rules out the involvement of selection-making steps based on empirical matching rules as proposed by Li, Dubois and Kuo in a recent publication.

ISSN:0950-0839    

DOI:10.1080/09500839508241283

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor