摘要:

Lamellar twins have been observed in the icosahedral phase in Al-Cu-Fe alloy. As indicated by both conventional and convergent-beam electron diffraction and high-resolution lattice fringe pictures, the twins are reflection twins with the twinning plane perpendicular to a fivefold axis of the icosahedral quasilattice.

ISSN:0950-0839    

DOI:10.1080/09500839308243853

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Shear band formation has been studied for the {100} ⟨011⟩ textured f.c.c. metals under uniaxial tension. The variations in Schmid factors as functions of lattice rotation are calculated for each slip system to account for the deformation localization. The 35° shear bands and the transition of textures found in experiments can be explained. The difference of the deformation behaviour between {100}⟨011⟩ and {110}⟨001⟩ crystals is briefly discussed.

ISSN:0950-0839    

DOI:10.1080/09500839308243854

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The spectral dependence of the photogeneration efficiency. η in sublimed undoped C60-C70films has been determined from photoinduced xerographic discharge curves. The dependence of η on the exciting light wavelength from 7250 to 3500Å and electric field are reported. At an applied field of 2–7 × 105V cm−1η is essentially wavelength independent with a value of about 5 × 10−3from 7250 to 5500Å. At shorter wavelengths, η is essentially proportional to the absorption coefficient, rising by more than an order of magnitude to about 6 × 10−2at 3500Å. The difference between the charge-transfer efficiencies of these two regions is discussed in terms of an Onsager surface-mediated dissociation of singlet excitons.

ISSN:0950-0839    

DOI:10.1080/09500839308243855

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Atomic-resolution transmission electron microscopy is used to investigate the microstructure of polycrystalline UPt3. While the host material is the previously reported hexagonal Ni3Sn structure, a second phase having the double-hexagonal Ni3Ti structure is also identified.

ISSN:0950-0839    

DOI:10.1080/09500839308243856

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Presented is a high-resolution scanning electron microscopy study of the mechanical behaviour of GaAs/AlAs superlattices that have been deformed through microindentation. Transverse cleavage through the indentation sites reveals the pattern of the deformed multilayers, showing in particular debonding between the GaAs and AlAs layers, regions of compressive strains of up to 30% and substantial slip on the {111} planes.

ISSN:0950-0839    

DOI:10.1080/09500839308243857

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The fracture surface energy of a dense pure polycrystalline sample of silicon nitride (Si3N4) has been measured at room temperature by the work-of-fracture method on chevron-notched bend bars. Dense specimens were fabricated by hot isostatically pressing highly pure Si3N4starting powder at 1950°C under 180 MPa via glass encapsulation. Annealing experiments at 1750°C in a nitrogen atmosphere were also conducted after sintering in order to release internal residual stresses possibly arising from cooling down under high pressure. A value of 10–7 ± 0–8 J m−2was measured in both as-sintered and annealed specimens. According to fractographic observation and calculation of the theoretical compliance of the notched specimen, the present value is regarded as the intrinsic fracture energy of Si3N4and is to be compared with the markedly higher values commonly measured in alloyed materials.

ISSN:0950-0839    

DOI:10.1080/09500839308243858

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The scanning tunnelling microscopy technique has been successfully used for high-resolution imaging of the C60lattice as well as the submolecular features of the carbon cage of C60molecules. The present study has facilitated further insight into the nanometric defect structure of the C60lattice which is found to be compatible with the f.c.c. structure, and the resolved images of the individual buckyballs are revealed to be distorted.

ISSN:0950-0839    

DOI:10.1080/09500839308243859

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

By using specially prepared specimens of work-hardened mild steel, subsurface deformation patterns around Vickers, conical and spherical indentations of millimetre dimensions have been determined. It has been shown that in no case does the deformation pattern agree with the predictions of the plasticity theory for a rigid-perfectly plastic material; the material flow pattern is also inconsistent with the radial flow models. Also, plastic natural strains of 2±0·01 and 41±0·001 have been estimated at the tips of a Vickers and a conical (included angle, 45°) indentations respectively. In the case of a spherical indentation of sizea/R= 0·5, whereaandRare the radii of contact and the indenter, respectively, the plastic natural strains are estimated to be 0·1 ±0·05 and 0·15±0·06 atz/a= 0·5 and 0·65 respectively, wherezis the distance measured from the undeformed surface along the load axis.

ISSN:0950-0839    

DOI:10.1080/09500839308243860

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An atomic arrangement of an Al-Pd-Mn decagonal quasicrystal with 1·2 nm periodicity has been proposed from high-resolution electron microscopy with the aid of computer simulation. A calculated image from the atomic model reproduced well the features of a high-resolution structure image taken from a thin sample.

ISSN:0950-0839    

DOI:10.1080/09500839308243861

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Irradiation of YBa2Cu3O7-δand Bi2Sr2Ca3Cu3Oxsuperconductors with 300 MeV gold ions leads to the formation of columnar defects along the ion trajectory. These columns consist of amorphized material within the envelope of a displacement-strain field which propagates into the crystal lattice. The morphology of the defects shows a characteristic shape and size depending on the direction of the incident ion with respect to the crystallographic planes of the superconductors. The defects have a circular symmetry for the ion beam directed perpendicular to thea-bplane, while they are larger and elliptical when the beam is parallel to thea-corb-cplanes. A simple model based on the idea of ion-induced localized melting and anisotropic thermal conductivity of these materials helps us to understand the size and shape of these defects.

ISSN:0950-0839    

DOI:10.1080/09500839308243862

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor