摘要:

The elastic constants of a commercial tungsten carbide cermet (3% cobalt binder) were measured as a function of pressure at room temperature. As pointed out in a recent publication by Ruoff, the pressure dependence of the elastic constants affects the maximum possible pressure which a vessel can contain. This dependence is discussed in light of the present data.

ISSN:0021-8979    

DOI:10.1063/1.1662593

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A transmission electron microscopy study of the interaction between a prismatic dislocation loop and a straight dislocation moving in its glide plane in MgO is reported. The interactions are discussed in terms of Kroupa's theoretical estimates of interaction parameters.

ISSN:0021-8979    

DOI:10.1063/1.1662594

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

With the recent discovery that the addition of copper to thin aluminum films increases the lifetime to electrical failure of the films, a large effort has been made to understand the role of the copper in the process. The present paper describes experiments on various types of thin polycrystalline films designed to understand the solid solution and precipitation effects in the films. It is shown that precipitation is different from the bulk and in turn different from thin‐film work on unsupported single‐crystal films. Possible mechanisms relating copper additions to electromigration lifetime are considered and the effect of total copper distribution in the films is found to be important. Differences in residual gas pressure in the vacuum system can alter precipitation processes.

ISSN:0021-8979    

DOI:10.1063/1.1662595

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The elastic constants, thermal expansion, thermal conductivity, and heat capacity are reported for a new class of laser hosts‐the silicate oxyapatites. For Ca2La8(SiO4)6O2the five independent elastic constants obtained from sound velocity measurements areC11=1.71,C12=0.62,C33=1.71,C44=0.52, andC13=0.39×1012dyn/cm2, the thermal expansion coefficients at 300 K are 8.9×10−6and 6.6×10−6K−1for the [101¯0] and [0001] directions, respectively, and the room‐temperature conductivity is about 0.019 W cm−1K−1. Sound velocity and thermal expansion data suggest a Debye temperature between 400 and 500 K.

ISSN:0021-8979    

DOI:10.1063/1.1662596

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Irradiation of dielectrics with nonpenetrating electron beams generates long‐lasting space charges. A simple experimental and mathematical method is developed for the investigation of charge buildupduringirradiation. Time‐resolved charge measurements carried out with pulsed beams of 1‐MeV electrons, pulse duration of 4×10−5sec, and an average current density of 10−2A/cm2were used to analyze effects of charge leakage caused by radiation‐induced conductivity and electron range reduction caused by retardation of the incident electrons in the internal space‐charge field. Leakage is found to predominate in silica and borosilicate glass while range reduction predominates in polyethylene.

ISSN:0021-8979    

DOI:10.1063/1.1662597

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An expression is derived for the pyroelectric (PE) voltage response to step radiation signals which can be applied up to temperatures close to the Curie pointTcunder a ``small‐signal'' condition. Based on the Curie‐Weiss law and the thermodynamic theory of a second‐order ferroelectric transition, a discussion is given of the temperature dependence of the parameters of the PE voltage response: initial slope, peak value, rise time, and fall time as functions of sample parameters and load resistance. It is found that the PE voltage may reach a maximum close toTc, and expressions are derived for this value as well as for the temperature at which it occurs. These results were checked in detail on 12 samples of single‐crystalline triglycine sulphate for temperatures from 20 °C to the Curie point, and good agreement between theory and experiment was observed. The application of the results to PE detection of ir is considered.

ISSN:0021-8979    

DOI:10.1063/1.1662598

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The densities of the elements have been found to be a periodic function of the atomic number in the same manner as the other properties of elements in the Periodic Table. The existence of pressure‐induced polymorphic transformations in solid elements at room temperature is found to be closely correlated to the periodicity of density, hence, the atomic number. With only the exception of Fe, no phase transformations have been found for 28 solid elements having densities greater than &rgr;=2.8+0.12Z. For elements having densities less than the above value, there might be only two exceptions out of 50 solid elements that do undergo pressure‐induced phase transformations within the range of presently available apparatus. This correlation seems to serve as a better indication for finding a high‐pressure phase than is predicted on the basis of crystal structure, and has led the author to find a high‐pressure phase in Se, Tm, and Lu.

ISSN:0021-8979    

DOI:10.1063/1.1662599

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

CaF2films, 30–1500 Å thick, were vapor deposited at 25–380 °C onto air‐cleaved and vacuum‐cleaved NaCl in residual gas pressures of order 10−5, 10−7, and 10−9Torr. The structures of the films were examined byin situultrahigh‐vacuum reflection high‐energy electron diffraction, conventional transmission electron microscopy, transmission electron diffraction, and surface replication techniques. The films consisted of many crystallites, the complex {110} and {001} orientations of which depended on the deposition parameters. The transition from the complex {110} orientation to the {001} orientation is described in detail in terms of its dependence on the deposition temperature, film thickness, vacuum, and substrate conditions. The {001} orientation was identified with two sets of thin needle‐shaped crystallites oriented at 90° to each other. The {110} orientation was identified with two sets of larger crystals also oriented at 90° to each other. At higher deposition temperatures the larger crystals formed predominantly at cleavage steps on the NaCl substrate, while the needlelike crystals tended to form on the surface of the films.

ISSN:0021-8979    

DOI:10.1063/1.1662600

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Optical spectroscopy has been used to study the interaction of lithium impurity atoms with neutron‐produced defects in silicon. In addition to the divacancy‐associated defect absorption bands at 1.8, 3.46, and 3.61 &mgr;, several additional radiation‐produced infrared absorption bands at 1.36, 1.50, 1.6, 1.94, 2.05, 2.09, 2.14, and 2.4 &mgr; are observed in lithium‐doped silicon, irrespective of the oxygen concentration. In high oxygen concentration Si, a decrease of the (LiO)+vibrational band (9.85 &mgr;) accompanied by an increase of the oxygen interstitial vibrational band (9 &mgr;) is observed after neutron irradiation (at∼ 300 ∘K) and heat treatment (to∼ 150 ∘C). This fact rules out the possibility of the formation of the Li&sngbnd;O‐vacancy defect complex. The presence of Li decreases the production of the oxygen‐vacancy complex. The intensity and the annealing temperature of the divacancy‐associated bands strongly depend upon the Li concentration, and the intensity is found to be substantially lower than that observed for Si not containing Li. The Li defect bands exhibit a saturation in their intensity for (Li) ≈6×1016cm−3. The bands increase in intensity afterT ≳80 ∘Cheat treatment. This is attributed to the dissociation of other simple Li‐associated defects. The results indicate that higher‐order defect complexes are responsible for the bands and the divacancy must be directly involved in the formation of at least one of them. Detailed annealing studies are presented.

ISSN:0021-8979    

DOI:10.1063/1.1662601

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The anisotrpic resistivity of dislocations produced by deformation is measured in high‐purity Al single crystals at liquid‐helium temperature. A network of screw dislocations is produced by twisting a single‐crystal cylindrical Al bar about the [111] direction which was along the axis of the bar. Resistivity parallel to the slip plane is measured by a mutual inductance method and along the crystal axis by a dc potentiometric method using Josephson junctions. Resistivities perpendicular to the specimen axis are found to be greater than those parallel to the specimen axis. The ratio &Dgr;&rgr;ac/&Dgr;&rgr;dc(where &Dgr;&rgr;acand &Dgr;&rgr;dcare the resistivity increments along the directions perpendicular and parallel to specimen axis, respectively) is approximately equal to 1.29.

ISSN:0021-8979    

DOI:10.1063/1.1662602

出版商:AIP    

年代:1973

数据来源: AIP