摘要:

An investigation was made of the mobility and types of point defect introduced in platinum by deformation in liquid nitrogen, quenching into water from 1600°c, or reactor irradiation at 50°c. In all cases the activation energy for motion of the defect was determined from measurements of electrical resistivity. Measurements of density, hardness, and x-ray line broadening were also made where applicable.

ISSN:0031-8086    

DOI:10.1080/14786436008235837

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

Diffraction patterns of low energy electrons produced by a (111) face of a crystal of nickel have been accelerated sufficiently to show on a fluorescent screen, where they can be photographed. Various gases at low controlled pressures have been admitted to a clean surface, and the arrangements of atoms or molecules upon the surface deduced from their diffraction patterns. Molecules of CO are adsorbed at low pressures as monolayers. They form a single two-dimensional crystal having a spacing between molecules double that between surface nickel atoms; these molecules are completely removed from the surface by heating to 175°c. Experiments with nitrogen have produced a polycrystalline monolayer having the same structure as the CO crystal. (Because of low sticking probability adequate experiments to prove that the layer is really nitrogen are difficult and have not yet been satisfactorily completed. A new type of experimental equipment seems to be required which is now being constructed.) Crystal growth in this monolayer is induced by heating to 125°c; heating above 200°c results in transformation into one or the other of two polymorphic forms either of which is more stable than the original structure; heating to 300°c results in melting the monolayer without removing it, the crystalline structure returning upon cooling. Oxygen can be adsorbed in a layer several atoms or molecules thick; this shows no structure until annealed at 125°c after which the structure is that of the most complex of the polymorphic forms assigned to nitrogen; this complex structure is polycrystalline with very small individual crystals; its diffraction pattern is unchanged when the oxygen is reduced to a single monolayer by heating. No diffraction pattern has been obtained from hydrogen, although the presence of hydrogen is proved by rise in pressure when the crystal is subsequently heated.

ISSN:0031-8086    

DOI:10.1080/14786436008235838

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

A study has been made of the effect of 1 MeV electron irradiation on the mechanical properties of lithium fluoride single crystals tested in compression. The yield point, σ has been shown to vary with the irradiation dose, φ, according to the law σ=σu+A[1-exp (-Bφ)]1/2, where σu,AandBare constants. This relationship has been derived theoretically by considering the passage of dislocations through radiation induced obstacles dispersed in the slip plane, together with the capture of point defects by existing obstacles. The empirical relationship, σ=kφ1/3, previously used for radiation hardening in metals, is capable of representing only the medium dose results, but clearly does not fit at either low or high doses.

ISSN:0031-8086    

DOI:10.1080/14786436008235839

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

The scattering of electrons and x-rays by stacking faults is due to a phase change in the diffraction by crystal planes which do not lie parallel to the fault. A simple model of the process in copper estimates a resistivityp≃1 × 10−12β ohm-cm for a total stacking fault density of β cm−1on all planes. A wave matching calculation in which Tamm surface waves are used confirms the order of magnitude of the effect and is also in agreement with the prediction of the simple model that the distance over which scattering from two faults could interfere is less than the lattice spacing. These results are consistent with the available experimental data and it is concluded that the effect explains the resistivity caused by extended dislocations in cold worked metals and by tetrahedra of stacking faults in quenched metals.

ISSN:0031-8086    

DOI:10.1080/14786436008235840

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

The optical constants of liquid silver have been measured in the infra-red between wave numbers 4000 and 17000 cm−1. The results are compared with the Drude theory and lead to a value of about 1.1 for the effective number of free electrons per atom. The electrical conductivity of the surface layer, calculated from optical constants, differs by less than 10% from the bulk conductivity. Some results on the temperature variation of the optical constants are presented. The optical constants of liquid copper have also been measured at two wave numbers in the infra-red.

ISSN:0031-8086    

DOI:10.1080/14786436008235841

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

Residual electrical resistivity has been used as an index of the damage present in tungsten irradiated in a nuclear reactor at 4°K and 77°K. A comparison was made between four different types of specimen prepared from cold-drawn wire respectively annealed before irradiation at 2000, 1500, 800°c and not at all. A fifth type of specimen was prepared from wire in a different state of purity.

ISSN:0031-8086    

DOI:10.1080/14786436008235842

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

ISSN:0031-8086    

DOI:10.1080/14786436008235843

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

ISSN:0031-8086    

DOI:10.1080/14786436008235844

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

Manual of Mathematical Physies. By PAUL I. RICHARDS. (London : Pergamon, 1960.) [Pp. 486.] £53 10s. Od.

ISSN:0031-8086    

DOI:10.1080/14786436008235845

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

ISSN:0031-8086    

DOI:10.1080/14786436008235846

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor