摘要:

Gold and silver single-crystal foils of uniform thickness have been produced by electrolysis. The preparationof gold foils involves three steps: the evaporation of silver onto cleaved mica, the electrodeposition ofgold on silver, and, lastly, the stripping of the gold foil by dissolving the intermediate layer of silver. Silverfoils are prepared by (1) evaporating silver onto cleaved mica, (2) electrodepositing silver on silver, and (3)mechanically stripping the silver foil.

ISSN:0021-8979    

DOI:10.1063/1.1931127

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A chemical etching solution has been found which results in etch pit formation at dislocations in the (100)and (111) surfaces of silver single crystals. Etch pits as small as 500 to 2000 Å may be obtained in the (111)surface of silver permitting the observation of dislocation densities of as high as1010 lines/cm2. The slip bandstructure of deformed silver has been examined by this technique and has been found to be cellular inappearance.

ISSN:0021-8979    

DOI:10.1063/1.1931128

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The acoustic response for waves normally incident upon a burning surface region is analyzed. The combustionprocess involves heat conduction within the solid, an irreversible surface pyrolysis process, and adistributed gas-phase reaction zone with conduction and diffusion. Linear differential equations determiningthe acoustic response are derived for arbitrary frequencies and simplified to a single second-order equationfor the case in which the frequency is small compared to the reciprocal of a characteristic gaseous reactiontime. An approximate analytical solution to this last equation, valid when the over-all activation energyfor the gaseous reaction is large, is shown to yield a simple formula for the admittance, which determinesthe acoustic response. This admittance formula implies that sound waves are attenuated at low frequenciesand, in most cases, amplified only when the frequency approaches the reciprocal of the reaction time. Inparticular, it is inferred that a pure solid ammonium perchlorate deflagration will not amplify acousticvibrations, and therefore, presumably, will not experience oscillatory combustion.

ISSN:0021-8979    

DOI:10.1063/1.1931129

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Light scattering by crystals of potassium chloride grown at the Harshaw Chemical Company and at theNaval Research Laboratory was measured. Scattering by the Harshaw crystals varies with crystal orientationwhile scattering from the NRL crystals does not. The major part of the Harshaw crystal scattering isattributed to vacancy-impurity clouds around dislocations which have the scattering pattern of cylinderswith5×105 Ålength, radius 100–500 Å, and axis parallel to (100) directions. The major part of the NRLcrystal scattering is attributed to impurity precipitates which have the scattering pattern of spheres 1400–1600Å in diameter. Air quenching of the crystals to room temperature from temperatures up to 650°Cproduced marked changes in the scattering. The results of the quench treatments are tentatively interpretedin terms of the migration of defects.

ISSN:0021-8979    

DOI:10.1063/1.1931130

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A possible approach to the development of a low work functionthermionic emitter involves the introduction of shallow donorstates into a matrix having a low electron affinity. It is the intentof this paper to explore the concept of a shallow donor emitterfrom both a general point of view and with specific application tobarium oxide as the host lattice. The problem is discussed in termsof the single-donor model with consideration given the variouscharacteristics which would be required for a practical matrix-additivesystem. Although the electron affinity of BaO has beenestimated to be as low as 0.6 eV, the ordinary oxygen vacancydonor present is a deep level with an ionization energy of about1.4 eV; it yields a work function of 1.4 to 1.5 eV at 1000°K. Bycomparison, a work function of 0.83 eV would be expected forshallow donor BaO at this temperature. The substitution of atripositive rare-earth ion for aBa2+ion in the lattice is presentedas a possible mechanism for the incorporation of an impurity donorcenter. Some speculation is offered concerning the ionizationenergy of this type of donor as well as the associated activationprocess. An attempt was made to observe the donor behavior ofseveral rare-earth ion additives in BaO and also SrO by studyingthe temperature dependence of the effective work function. Datawere secured for La, Gd, Nd, Er, and Eu in BaO, and Eu and Smin SrO at analytical concentrations of from 0.01 to 0.05 mole %While no lowering of the work function is reported, it is clear thatno definitive interpretation of a negative result can be made untilcertain other experimental information becomes available, particularlythe solubility and oxidation state of the additive ion in thematrix crystal.

ISSN:0021-8979    

DOI:10.1063/1.1931131

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Using phenomenological equations in partially inverted form, the operation of galvano-thermomagneticgenerators has been analyzed for six different modes of operation. The efficiency, figure of merit, and geometryoptimization have been investigated. The two-dimensional temperature distribution prevailing ina device arm is also briefly analyzed. For the “longitudinal” case where heat flow and current are colinearin a transverse field,Hz, the mathematical relations conform to the standard theory, except that the transportcoefficients depend onHz. In the “transverse” case where heat flow, current, and magnetic field are mutuallyperpendicular, new expressions are obtained for the figure of merit and device efficiency. Furthermore, inthe latter case the optimal operating conditions are those in which both device arms are made of the samematerial. The results are discussed in the light of some existing experimental data.

ISSN:0021-8979    

DOI:10.1063/1.1931132

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Following the procedure of an earlier paper (Port I) the maximum temperature difference, coefficient ofperformance, figure of merit, optimum current and voltage, and the optimization conditions were obtainedfor galvano-thermomagnetic refrigerators and heat pumps under a variety of operating conditions. It isshown that the coefficients of performance of refrigerators and heat pumps differ by unity. Upper bounds areplaced on the transverse figure of merit and a brief discussion of the main features of the theory is given.

ISSN:0021-8979    

DOI:10.1063/1.1931133

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

An experimental setup is described for measuring the variation of optical power output with gas mixturesin a gas maser oscillator. Experimental results are given for the case of the He-Ne maser. Optical gain inpure neon has been reported by Bennett. With the above setup a pure neon maser oscillator has beenoperated for the first time and the results are given. This setup is particularly convenient in investigatingmaser action in new gases.

ISSN:0021-8979    

DOI:10.1063/1.1931134

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The temperature coefficient of resistance has been obtained for the high pressure phases of silicon, germanium,and several III–V and II–VI compounds having the zinc-blende or wurtzite structure. The high pressurephases of all zinc-blende compounds were metallic. The high pressure phase of CdS is a semiconductor.Data were also obtained on CdSe at room temperature and as a function of temperature. The transitionfound optically is also obtained electrically. The resistance-pressure curve for the high pressure phase hasconsiderable structure. It is metallic.An upper limit for the transition pressures of germanium and GaSb at liquid nitrogen temperature wasestablished.

ISSN:0021-8979    

DOI:10.1063/1.1931135

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The high-field electron emission projection microscope has been used to study the field emission characteristicsof cadmium telluride field emission cathodes. Stable currents were observed which exhibited lightsensitive changes.

ISSN:0021-8979    

DOI:10.1063/1.1931136

出版商:AIP    

年代:1962

数据来源: AIP