摘要:

Thermal conductivity measurements have been made on a series of germanium‐silicon alloys. At 300°K for an alloy containing 56 atomic percent Si, the thermal conductivity was found to be six times smaller than the value for pure Ge. Measurements of the thermoelectric power on some alloys are also reported. It is then shown that solid‐solution alloying can significantly increase the figure of merit of thermoelectric materials.

ISSN:0021-8979    

DOI:10.1063/1.1722984

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

This note reports evidence for the existence of vacancy aggregates in Ge crystals. When dislocations are absent over volumes of the order of cubic centimeters the crystal etches much more rapidly than when dislocations are present. This enhanced etching behavior can be eliminated by appropriate heat treatment at 800°C. Ridges of normal etching rate have been observed traversing the rapidly etched areas in ⟨110⟩ directions. Etch figures, usually spiral dislocations, are always associated with these ridges. Ridges are not observed in completely dislocation‐free crystals.

ISSN:0021-8979    

DOI:10.1063/1.1722985

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Electrical resistivities, temperature coefficients of resistivity, and Hall coefficients have been measured on single crystals of hexagonal CaMg2and on polycrystals of cubic MgCu2. The magnitudes of the measured values fall in the range normally observed in metals. In contrast, measured values for the coefficients of thermal expansion are slightly higher than those observed in metallic elements. Appreciable scatter in measured resistivities on different specimens was observed and is presumably due to variations in the degree of crystalline perfection. For CaMg2the measured Hall coefficients and the temperature coefficients of resistivity and of thermal expansion show only a small degree of anisotropy. The sign of the Hall coefficients was found to be positive for CaMg2and negative for MgCu2; this is consistent with previous measurements of magnetic susceptibility made on MgCu2and its alloys.

ISSN:0021-8979    

DOI:10.1063/1.1722986

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Detailed measurements have been made of the dc and rf current distribution in a modulated, magnetically focused electron beam having normalized parameters in the range of values appropriate for practical medium‐power and high‐power klystrons. The ratio of the total rf current to the total dc current in the beam as a function of drift distance was determined experimentally under Brillouin‐flow conditions for selected values of &agr; (the ratio of the rf voltage at the input gap to the dc beam voltage). These experimental values are compared with the results predicted theoretically. Similar experimental results are presented for higher focusing fields. Detailed radial distributions of the dc and rf current were experimentally determined by using an iris (a plate with a small hole) to allow only a small portion of the beam to be selected at any radial position. These measurements were made at various values of &agr; and drift distance. The results for small values of &agr; show, as predicted by theoretical considerations for a modulated Brillouin‐flow beam, that the radial rf current distribution in the beam is the same as that of a beam whose modulation is represented as sinusoidal scallops on a beam of constant (volume) charge density. As either &agr; or the focusing field, or both, are increased, the rf current is no longer confined to the beam periphery but becomes more evenly distributed throughout the beam cross section.

ISSN:0021-8979    

DOI:10.1063/1.1722987

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Experimental information is presented which shows that abruptp+njunctions break down by the Zener internal field emission effect when the base resistivity is low and by ionization avalanche when the base resistivity is high. In intermediate regions of base resistivity both mechanisms are observed in the same junction. The onset of Zener current is accompanied by a drop, of unexplained origin, in the junction collection efficiency for minority carriers photoinjected into the base. Applicability of the Zener theory to abruptp+njunctions is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1722988

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Measurements have been made of the anomalous dispersion occurring in certain types of artificial dielectrics. To a limited extent the dependence of dispersion on array and scattering element geometry has been determined and an attempt made to control dispersion by changing the array configuration. Applications are mentioned briefly.

ISSN:0021-8979    

DOI:10.1063/1.1722989

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

In microanalysis using x‐ray emission excited on the surface of a thick specimen by an electron probe, the minimum volume element which can be analyzed is limited by the size of the electron probe, by fluorescence excitation, and by the penetration and diffusion of the electrons in the specimen. With an electron accelerating voltage of about 30 kv the electrons have an energy of the order of 3 times the critical excitation energy of theKorLx‐ray levels of the target and the minimum volume which can be analyzed (in the absence of strong fluorescence effects) is of the order of 8 cubic microns for a copper target, and is considerably larger than this for targets of low atomic number or density. It is shown that the resolution in this method of analysis can be improved without loss of statistical accuracy or increase in the time of measurement by (1) improving the quality of the electron optics and by (2) selecting the accelerating voltage and electron probe size. The minimum volume element for practical quantitative analysis can thereby be made as small as about 0.2 cubic microns in a copper target. This is obtained by using slightly larger electron probes and lower accelerating voltages than those representative of current practice.

ISSN:0021-8979    

DOI:10.1063/1.1722990

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Water vapor corrosion of a simple soda‐lime glass has been studied in regard to its effect on static fatigue of the same glass. A mechanism of dissolution has been proposed in which alkali ion self‐diffusion controls the initial steps of water corrosion and leads to breakdown of the glass network. Since experiments show that an expansion of a glass network enhances corrosion rate, it is postulated that asymmetrical contitions of expansion around a surface flaw, brought about by applied stress, could lead to growth of the flaw in a preferential direction to bring about delayed failure.

ISSN:0021-8979    

DOI:10.1063/1.1722991

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Static fatigue of a simple soda‐lime glass has been investigated in relation to the sensitivity of this glass to atmospheric corrosion. An analysis of the failure process has been given which is based on the concept that inherent surface flaws grow by corrosive mechanisms to critical dimensions by virtue of a reaction between water vapor in the atmosphere and components of the glass. The rate of this reaction is determined by the stress conditions around local areas and the temperature, pressure, and composition of the surrounding atmosphere. Since the experimental work shows a close relationship between the temperature dependence of the failure process and that of the self diffusion of sodium ion in bulk glass it is concluded that alkali content is responsible for the very low long time strengths of most inorganic glasses.

ISSN:0021-8979    

DOI:10.1063/1.1722992

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The temperature diffuse scattering of x‐rays from a single crystal of &bgr;‐AuZn has been measured at room temperature using a Geiger counter diffractometer and crystal monochromatic CuK&agr;radiation. Acoustical frequency and velocity dispersion curves were obtained for the symmetry axes using the theories of James and Laval. Integrated intensity measurements of Bragg reflections from the alloy gave Debye temperatures of 153°K and 220°K for gold and zinc, respectively. The velocities at infinite wavelength yielded elastic constants ofc11= 5.3c12= 3.5, andc44= 3.0 in units of 1011dynes per cm. An approximate frequency spectrum was calculated.

ISSN:0021-8979    

DOI:10.1063/1.1722993

出版商:AIP    

年代:1958

数据来源: AIP