摘要:

On a gas of ∼104protons, contained at ∼10−11Torr in a parabolic rf trap of depthD¯between 2.6 and 10.4 V, equilibrium temperatureskTi≃0.1eD¯and storage timesT≃100 sec were measured ordinarily, both apparently determined by ``evaporation'' processes. When cooling the ions by coupling their disordered oscillatory heat motion to anLCcircuit at room temperature,Tidropped another factor of 3 to as low as 900°K andTincreased to ∼3000 sec.

ISSN:0021-8979    

DOI:10.1063/1.1658214

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The magnetization curves to 7000 Oe at 2° and 4.2°K of magnesiowu¨stites with 1 to 5 cat.% Fe++have more curvature and a lower extrapolated saturation magnetization (using the Brillouin function) than expected for isolated Fe++ions. This behavior indicates Fe++ion clustering. The magnetization data were used to computen¯, the average number of Fe++per cluster, andJ¯, the average total angular momentum quantum number per cluster taking the isolated Fe++ion value forg. The observedJ¯'s showed that the Fe++&sngbnd;Fe++near‐neighbor interaction is ferromagnetic. The cluster size increased with Fe++content butJ¯/n¯decreased due to the predominance of the second‐near‐neighbor antiferromagnetic interaction. When magnesiowu¨stites containing 9 and more cat.% Fe were cooled from room temperature to 4.2° or 2°K in an applied magnetic field, the magnetization curves, which showed a small amount of hysteresis, were not symmetric about the origin. The shifted hysteresis was attributed to exchange coupling between neighboring ferromagnetic and antiferromagnetic regions. The antiferromagnetic order persists to rather low concentrations of Fe++(TNfor 9 cat.% Fe++is above 8°K), further evidence for Fe++clustering. Published values of the thermodynamic activities show a positive deviation from Raoult's law and thus a nonrandom clustered configuration is expected.

ISSN:0021-8979    

DOI:10.1063/1.1658215

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

An extensive study has been made on the growth and characterization of single‐crystal magnesium aluminate spinel. This material has received attention as a superior substrate for epitaxial silicon‐integrated electronic devices. Large spinel single crystals within the compositional range MgO:Al2O3&sngbnd;MgO:3Al2O3, have been successfully grown by flame fusion using a modern three‐tube post‐mix‐type Verneuil burner. Substrate wafers of (111), (100), and (110) orientations were prepared for silicon epitaxy. Surface preparation of the substrates was studied, including mechanical polishing, hydrogen annealing, and chemical etching. The composition, lattice parameter, crystalline perfection, mechanical hardness, thermal stability, and dielectric properties of the spinel single crystals have been characterized by various techniques in an effort to obtain a basic understanding for substrate use of this material system. Some trends in the dependence of these properties on composition were observed. In particular, the thermal stability increases with decreasing Al content in the spinel system. It was found that the spinel crystals with alumina content up to MgO:2.5Al2O3are thermally stable and exhibit no cracking and/or exsolution behavior to at least 1200°C, which is the temperature commonly used for fabricating many silicon devices. However, the ease of growth and the mechanical stability decrease with decreasing Al content in spinel. A post‐growth annealing treatment enhances the mechanical stability and prevents formation of cracks during cutting. Substrates within the compositional range of MgO:1.5Al2O3&sngbnd;MgO:2.5Al2O3are suitable for silicon epitaxy, and the choice of the optimum substrate composition depends on the specific conditions for processing of the silicon devices.

ISSN:0021-8979    

DOI:10.1063/1.1658216

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Compressive surface layers were formed on sapphire rods. The methods included glazing and quenching, formation of Al2O3&sngbnd;Cr2O3solid solution surface layers, and formation of mullite and calcium aluminate surface layers. The presence of the compressive stresses was demonstrated by slotted rod tests. Substantial improvements in flexural strength and thermal shock resistance were observed. The highest average flexural strength was obtained by glazing and quenching and was 340 000 psi. The strengths were measured in the ``as‐treated'' and ``as‐treated and abraded'' conditions. The abraded samples retain a substantial portion of the improved strength.

ISSN:0021-8979    

DOI:10.1063/1.1658217

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The lattice parameters of the body‐centered cubic phase (martensite) and the face‐centered cubic phase (austenite) were determined for a series of Fe&sngbnd;Ni alloys. Compositions ranged from pure Fe to Fe‐35 at.% Ni. Careful film and diffractometer Debye‐Scherrer techniques on powder and bulk samples and computerized calculations and error analyses were employed. Results indicate that the martensite lattice parameter reaches a maximum between 10 and 20 at.% Ni and the room‐temperature lattice parameter of the face‐centered cubic phase has a maximum in alloys having greater than 35 at.% Ni.

ISSN:0021-8979    

DOI:10.1063/1.1658218

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The electrical resistivity of irons containing different levels of impurity have been measured at 77° and 293°K for a range of grain sizes. The resistivity of a given iron is found to vary with the grain diameter (dmm) as &rgr; =A+Blog(1/d).AandBare both temperature dependent, increasing with increasing temperature. With increasing impurity content, the parameterAincreases andBdecreases. Thus the purer iron shows a larger variation of resistivity with grain size than the less pure material. The observed relationship can only be explained in terms of a grain‐boundary scattering process if the effective width of the boundaries is much greater than is usually believed.

ISSN:0021-8979    

DOI:10.1063/1.1658219

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A simple method for the preparation of free surface single crystals of mercury is presented. X‐ray orientation determination and formation of electrical contacts are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1658220

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Fatigue crack propagation in metals may exhibit two consecutive modes: an initial crystallographic shear mode (Stage I) followed by a noncrystallographic tensile mode (Stage II). The mode of cracking is assumed to be governed by the character of slip in the vicinity of the crack tip, i.e., Stage I is the result of co‐planar reversible slip, while Stage II is associated with homogeneous, ``wavy'' slip. The slip character is, in turn, assumed to depend upon the likelihood of screw dislocations to cross slip out of the primary slip planes, which requires recombination of the Shockley partials. Thus the transition from Stage I to Stage II is postulated to occur when the separation of the partials, influenced by the crack‐tip stress field and the material's stacking‐fault energy, is reduced to the order of the Burger's vector. A continuous dislocation distribution representing the crack and plastic zones is used to analyze the transition from Stage I to Stage II. In the model, the closest screw dislocation in the plastic zone adjacent to the crack tip is dissociated into discrete partial dislocations, while the dislocations representing the crack and remaining plastic zone are presented as a continuous distribution of dislocations. Although it was found that the separation of partials is very sensitive to the ratio of the applied stress to the yield stress and the stacking‐fault energy, the separation isnotsignificantly reduced as the crack length increases. It is therefore concluded that strong obstacles to dislocation movement or dislocation entanglements would be required ahead of the crack to effect recombination of the partials. This result implies that a transition in the mode of crack growth shouldnotbe observed in single crystals of metals which display planar slip characteristics.

ISSN:0021-8979    

DOI:10.1063/1.1658221

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The mechanical behavior of OFHC copper at strain rates from 10−3to 103sec−1at 300°, 420°, and 590°K was investigated. The strain rate behavior of copper can be divided into two regions. Below 10 sec−1the dislocation motion is thermally activated over forest dislocation barriers. Above 103sec−1, a linear relationship between stress and strain rate was observed indicating the presence of a viscous damping mechanism. The stress level &tgr;Bthat must be exceeded in order to obtain viscous behavior depends on the work‐hardened state of the copper. The mobile dislocation density in the viscous damping region was found to be (1) independent of strain rate, (b) only a small fraction (10−5) of the total dislocation density, (c) independent of strain, and (d) increased with increasing temperature. These deductions are discussed in terms of the dislocation multiplication and annihilation mechanism.

ISSN:0021-8979    

DOI:10.1063/1.1658222

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The results of measurements of the rate of arrival of defects at dislocations in copper doped with varying amounts of oxygen are presented. The defects were created continuously during the measurement by gamma‐irradiation, and the arrival of defects at the dislocations was detected by measuring the dislocation damping. The rate of arrival of the stage III defect at the dislocations was not affected by the oxygen content of the copper. This result indicates that the binding energy between oxygen and the stage III defect is considerably less than the motion energy of the defect. Some evidence for a significant binding between oxygen and another defect (presumably the vacancy) created by the irradiation is presented.

ISSN:0021-8979    

DOI:10.1063/1.1658223

出版商:AIP    

年代:1969

数据来源: AIP