摘要:

The residual stress in films formed by vacuum sublimation of bulk silicon monoxide has been studied as a function of the angle of incidence of the evaporant. Using a source temperature of 1350–1400°C and a system total pressure of ∼2×10−6Torr, a pronounced dependence of stress on angle of incidence and a distinct stress anisotropy was observed. The stress in thexdirection (i.e., perpendicular to the direction of the evaporant irrespective of substrate orientation) increases from 4×108dyn/cm2for normal incidence to 14×108dyn/cm2for an incident angle of ∼50° and then decreases to 4×108dyn/cm2for an incident angle of 80°. The stress in theydirection (i.e., perpendicular to thexdirection) is peaked at ∼30° at a value of 13×108dyn/cm2and then decreases to ∼0.5×108dyn/cm2at 80°. Films formed at normal incidence are quite stable and not susceptible to the effects of water vapor. However, films formed by depositing at grazing incident angles (>30°) are very unstable and invariably buckle and rupture when exposed to atmospheres of water vapor. Substrate temperature, film thickness, and inert residual gases were found to have little effect on the stress and stability of films deposited at an angle of incidence of 45°. When a lower source temperature (<1200°C) is used and a high partial pressure (10−4Torr) of water vapor is present during deposition, the resulting highly oxidized films show a compressive stress (∼2×108dyn/cm2) and very little dependence on the angle of incidence. These films are stable when exposed to higher partial pressures of water vapor.

ISSN:0021-8979    

DOI:10.1063/1.1702611

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The method described uses an eddy current concentrator to focus the energy of an rf magnetic field on a small part of a ¼‐in.‐diam rod. Zone melting has been carried out at temperatures above 2600°C, and can probably be extended to temperatures above 3000°C. The advantages of this method over some others used in the same temperature range are that it can be carried out under an inert gas atmosphere instead of a vacuum, and uses for its power supply conventional 450‐kc induction heating equipment.

ISSN:0021-8979    

DOI:10.1063/1.1702612

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The problem of noise‐ (and, as a special case, signal‐) wave propagation along a drifting, one‐dimensional electron stream with a half‐Maxwellian velocity distribution is analyzed. The integral equation resulting from the linearized Boltzmann equation is intractable in its exact form and so, heretofore, has succumbed only to machine computation. In this paper closed‐form solutions are obtained through the use of a simplified kernel. This approximation, although it limits the analysis to beams with small relative velocity spreads and small ratios of plasma frequency to operating frequency, is yet innocuous enough not to mask the main effects.The noise current and voltage are found to consist of three wave terms: a ballistic wave describing the injected noisy ``test particle,'' a slow space‐charge wave and an aggregate of fast space‐charge ``waves'' which decays,en masse, with distance because of phase mixing. This aggregate is approximately representable by a single fast wave with exponential damping. Far downstream the noise power spectra (&psgr;,&PHgr;,&Pgr;,S) lose their familiar sinusoidal pattern and settle to constant values. Along the entire beam the positive rf noise power,S+&Pgr;, is invariant.

ISSN:0021-8979    

DOI:10.1063/1.1702613

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Smooth bore cannons were used to produce plane collisions between plates of Armco iron. Projectile velocities ranged from 60 to 400 m/sec. Time resolved measurements of the target free‐surface velocities indicate that the dynamic yielding process is time dependent on a submicrosecond time scale. The shape of the Hugoniot curve in the pressure‐volume plane up to 80 kbars shows that true hydrostatic equilibrium has not yet been established behind the elastic wave. On the other hand the substantially constant free‐surface velocities behind the plastic front indicate that the material cannot be far from equilibrium after a short time. Some data on the rarefaction sound speed in the high pressure region are interpreted to imply a value very near 6 km/sec.

ISSN:0021-8979    

DOI:10.1063/1.1702614

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Transmission electron microscopy and microbeam x‐ray techniques were used to study the substructure developed in pure, polycrystalline aluminum during constant strain fatigue. A complete study was made at strain amplitude ±0.002 over the cycle range 0–100 000 cycles. During the first several thousand cycles, the substructure varies considerably from grain to grain, depending on orientation. In general, dislocations initially cluster along {111} glide planes during the first few hundred cycles. By 2000–3000 cycles subgrain boundaries have formed along {111}, {100}, and {110} planes. Large numbers of dislocation loops are seen in and near the boundaries. As cycling proceeds to fracture, the dislocation density in these boundaries and the misorientation between the subgrains increases. The average subgrain volume decreases from ∼25 &mgr;3at 5000 cycles to ∼8 &mgr;3at 100 000 cycles. Subgrains were formed at all strain levels which were investigated, the lowest being ±0.0005; however, the rate of formation decreases rapidly as the strain is lowered. A model of fatigue hardening is proposed based on these observations, and the relation to fatigue fracture is discussed briefly.

ISSN:0021-8979    

DOI:10.1063/1.1702615

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A new method of studying the surface states of silicon is described. Essentially it involves applying porous graphite contacts top‐type silicon and exposing the samples to various inversion‐layer producing gaseous ambients. A voltage pulse is applied to the sample and the resulting current pulse is a measure of the density of charge states. From such data it was found that the number of water‐vapor‐induced surface states onp‐type silicon was 5×1012/cm2. For any sample this value was reduced ∼50% by using ammonia instead of water vapor. Tests using widely differing electrode particle sizes resulted in no change in the measured density of states. By applying a small dc bias (∼1 V at <1 mA) to control the surface potential it is possible to continuously extend the current envelope or reduce it to a small capacitive spike. The total charge, at fixed bias, is a constant, independent of applied voltage amplitude.

ISSN:0021-8979    

DOI:10.1063/1.1702616

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The crystallographic polarity of the noncentrosymmetric material zincite (ZnO) has been determined by a rapid x‐ray absorption edge method. The polarity results have been correlated to marked differences in etching behavior and crystal morphology in opposite polar directions of ZnO crystals. These differences are shown to be consistent with the proposed surface bonding model for AII‐BVIcompounds. Crystal morphology is shown to be a useful criterion to indicate crystallographic polarity in well‐formed wurtzite‐type crystals.

ISSN:0021-8979    

DOI:10.1063/1.1702617

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Single crystals of cobalt ferrite were grown from a melt having the composition 95% CoFe2O4−5% NaFeO2by weight, under an oxygen pressure of 1650 psig and a temperature of 1590°C. Chemical analysis indicated that the crystals contained no Fe2+and 3 parts per 10 000 sodium.

ISSN:0021-8979    

DOI:10.1063/1.1702618

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Fourteen sample compositions, representing combinations of As2Te3and Tl2Se with Sb2Te3, Bi2Te3, or Sb2Se3, were prepared and tested. A number of the samples were amorphous while others were diphasal including both amorphous and crystalline phases. The material parameters were structure dependent with room temperature parameters ranging from 7.2×10−4–1.8×103&OHgr;‐cm in resistivity, 3.1–1040 &mgr;V/°K in Seebeck coefficient magnitude, and 3.6–19.0 mW/cm‐deg in thermal conductivity.

ISSN:0021-8979    

DOI:10.1063/1.1702619

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

End losses of an inviscid magnetohydrodynamic channel having tensor conductivity and segmented electrodes have been calculated for a magnetohydrodynamic power generator of this geometry. It was found that the constant‐current configuration is more efficient than the constant potential difference case. The efficiencies increase with increasing Hall effect, but constant magnitude extensions to the magnetic field have very little effect. The theoretical efficiency for an aspect ratio of 10 and &ohgr;&tgr;=2 is only 74%.

ISSN:0021-8979    

DOI:10.1063/1.1702620

出版商:AIP    

年代:1963

数据来源: AIP