摘要:

The initial sintering kinetics of stoichiometric SmCo5powder containing a samarium‐rich sintering addition (60 wt% Sm plus 40 wt% Co) have been investigated as a function of amount of liquid phase, time, temperature, and particle size. The shrinkage as a function of time exhibits the classical three stages of liquid‐phase sintering, i.e., rearrangement, solution precipitation, and solid phase. The rate‐controlling step during the solution‐precipitation stage corresponds to a phase‐boundary (solid/liquid) reaction leading to dissolution. Evidence for this conclusion is partially based on the logarithm‐shrinkage—logarithm‐time slopes being equal to 1/2 instead of 1/3. A 1/3 slope is predicted by the liquid‐diffusion‐controlled sintering model while the phase‐boundary sintering model predicts a slope of 1/2. An activation energy of 52.8 kcal/mole was obtained for the temperature dependence, and this also suggests a phase‐boundary reaction rather than rate control by diffusion in the liquid phase. The rate of sintering follows anr−1particle‐size dependence instead of anr−4/3dependence, again suggesting that the solution‐precipitation stage of sintering of SmCo5is controlled by a phase‐boundary reaction leading to dissolution.

ISSN:0021-8979    

DOI:10.1063/1.1662663

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The maximum current through multiple Josephson structures as a function of applied magnetic field is presented. Particular emphasis is placed on the Josephson penetration depth effects and geometrical considerations. The symmetrical and asymmetrical current feed two‐, three‐, four‐, and five‐junction gratings are analyzed and discussed. The Josephson penetration depth is shown to control the amplitude of the interference and diffraction patterns of the interference grating. In addition the interior‐junction‐length/interference‐loop‐area product is shown to control the operating mode of the interference grating. The dependence of the magnetic field sensitivity and interference pattern amplitude on the number of junctions is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1662664

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Measurements of the thermal conductivity &lgr; of some stainless steels (AISI types 304, 304L, 310, 321, and U.S. Steel Tenelon) between 0.4 and 1.6 °K, and of the electrical resistivity and magnetic susceptibility below 295 °K are given. Between 0.7 and 1.6 °K, &lgr; depends linearly on temperature and is given to within ±15% for all samples by &lgr;=0.67T(mW/cm °K). All samples show antiferromagnetic order. The susceptibility of Tenelon is about 20×10−6emu for all temperatures below 295 °K and is smaller than that for any of the other samples by over an order of magnitude at 4.2 °K.

ISSN:0021-8979    

DOI:10.1063/1.1662665

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The first observation of localized vibrational modes for an implanted ion in Ge is reported. The localized mode for interstitial oxygen at 856 cm−1and additional weak oxygen‐associated absorption bands between 700 and 850 cm−1have been observed by infrared absorption following oxygen implantation at 200 °C. Infrared detection of the vibrational modes for oxygen implanted into Ge at room temperature is precluded by ion‐induced disorder and by absorption presumably associated with free carriers in the implanted layer.

ISSN:0021-8979    

DOI:10.1063/1.1662666

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Cosputtering of Au and Cr produces polycrystalline thin films in the entire compositional range up to solubility limits of 49 at.% Cr in Au corresponding to the phase diagram of bulk material. Compositions of the Au&sngbnd;Cr system were checked by electron‐probe microanalysis. The change in lattice constant with addition of Cr in Au shows exactly the same deviation from Vegard's law as bulk. The resistivity changes with increasing Cr content are presented and the temperature coefficient is found to be constant in the range ‐150–160°C.

ISSN:0021-8979    

DOI:10.1063/1.1662667

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

This paper reports a new junction‐stripe‐geometry double‐heterostructure laser, in which the active region is defined into narrow stripe by means of diffusion technique. These lasers have good thermal characteristics, and the lowest threshold current density is 3500 A/cm2at continuous operation.

ISSN:0021-8979    

DOI:10.1063/1.1662668

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

In a recent paper, Towle has criticized our studies in which we ralated the coefficient of friction for thin solid lubricant films to a pressure effect on the shear strength of the film material. This a rebuttal to that paper.

ISSN:0021-8979    

DOI:10.1063/1.1662669

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

New transport and low‐frequency current oscillation phenomena have been observed in a photoexcited Bi12GeO20single crystal in the temperature range 77–110 K. These phenomena can be explained on the basis of the relaxation semiconductor regime where the dielectric relaxation time exceeds the minority‐carrier lifetime. Experiments strongly suggest that sublinear dependencies in the current‐voltage characteristic and the current oscillation in the higher bias range are general features of the relaxation regime.

ISSN:0021-8979    

DOI:10.1063/1.1662670

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The potential importance of built‐up films of barium stearate for making dielectric devices has led to the necessity of the study of their ac breakdown characteristics. In the present work, the thickness and frequency dependence of the ac breakdown field has been reported in the thickness range 100–1500 Å and in the frequency region 10–200 kHz. The breakdown field is found to vary with thickness asd–a(&agr;=0.68) and the breakdown voltage is found to increase with increasing thickness and frequency in the specified ranges. Although the experimental results could not be interpreted at present, the results obtained may prove useful in ac device applications of the films.

ISSN:0021-8979    

DOI:10.1063/1.1662671

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Recent applications of steady‐state growth rates to heterogeneous nucleation rates are considered and rejected. The time‐dependent solution of the differential equation governing adsorbed monomer behavior shows that the capture probability approach of Halpern is equivalent to a steady‐state solution.

ISSN:0021-8979    

DOI:10.1063/1.1662672

出版商:AIP    

年代:1973

数据来源: AIP