摘要:

It is shown from step annealing data for the 002 x‐ray diffraction peak that the processes annealing below 200 °C possess a frequency factor ∼1014sec−1, while those processes annealing at higher temperatures possess much lower frequency factors. This is attributed to the lower‐temperature processes being associated with the movement of single carbon interstitial atoms and the higher‐temperature processes being associated with more complex configurations, including clusters of carbon atoms.

ISSN:0021-8979    

DOI:10.1063/1.325556

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Dislocations in solution‐grown ZnSe were observed to climb when exposed to a focused 100‐kV electron beam in an electron microscope. The resulting dislocation networks are complex and are generated in a three‐step sequence: (1) existing dislocations extend their length by forming dipoles, (2) a thin layer of radiation‐damaged material forms at the beam entry surface, and (3) dislocation loops originating at the damaged layer grow into the sample bulk. From a diffraction contrast analysis the loops were determined to be of the extrinsic type. From annealing experiments it is concluded that the beam‐induced climb involves vacancy emission at the dislocation and that the process is energized by electron‐hole recombination.

ISSN:0021-8979    

DOI:10.1063/1.325557

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Theinsitunondestructive determination of the concentration profile in a small epitaxial binary diffusion couple by x‐ray‐diffraction line‐profile analysis is considered. On the basis of the work by Houska and collaborators, a direct method is presented for the determination of the concentration profile from an x‐ray intensity band. The method has the advantages that only a single order of the reflection is required and that neither iterative nor trial and error calculations are necessary as compared to previous methods. It is further shown that linear interpolation between both extremeties of the intensity band is a poor approximation to the actual background profile. The background mainly consists of thermal diffuse scattering (TDS) which peaks at the Bragg positions and may contribute significantly to the integrated intensities measured. An iterative method is proposed to calculate the TDS background. Both the direct method for determining the concentration profile and the calculation and subsequent elimination of the TDS background are applied to experiments with Cu/Ni bicrystals where the copper is either electrocrystallized or deposited from the vapor phase onto the 111 nickel substrate.

ISSN:0021-8979    

DOI:10.1063/1.325558

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

For the purpose of obtaining load‐elongation curves, fused SiO2fibers a few &mgr;m in diameter, which were produced by Nichols’s method, were tested using the tensile‐testing machine which was specially prepared by Hiki and the author. Load‐elongation curves obtained showed nonlinearity which indicates that Young’s modulus becomes larger with increasing strain. Moreover, a distinct elastic hysteresis was observed in which increasing curves have different traces from decreasing ones and return to the origin smoothly. The nonlinearity of load‐elongation curves is explained as the macroscopic appearance of anharmonic interaction between atoms. On the other hand, an elastic hysteresis which has not been observed in metal whiskers is assumed to be caused by complex deformation of a random network of fused SiO2fibers.

ISSN:0021-8979    

DOI:10.1063/1.325559

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The fatigue behavior of optical glass fibers was determined in air at 23°C and 55&percent; relative humidity by the dynamic‐fatigue test technique in which strength is measured as a function of stressing rate. The good correlation found between the fatigue test data and fracture‐mechanics theory indicates that failure is controlled by slow crack growth of preexisting flaws and that fracture‐mechanics theory can be used in making failure predictions for optical glass fibers.

ISSN:0021-8979    

DOI:10.1063/1.325508

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The static and dynamic fatigue of high‐strength glass fibers drawn with a 250‐W CO2laser and coated with a uv‐curable coating is presented and analyzed with respect to current theories. Theories of Charles and those of Wiederhorn and Evans are shown to reduce to a simple expression which accounts for the static‐ and dynamic‐fatigue data. Further, the strength of the coated glass fibers is directly proportional to the inverse temperature.

ISSN:0021-8979    

DOI:10.1063/1.325560

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

An elastic analysis of dislocations in isotropic media has been applied to study the interaction of dislocations on intersecting {111} planes at a coherent twin boundary in the face‐centered‐cubic lattice. The nature of energetically favorable barriers formed by such reactions is determined and their equilibrium separations are given, in addition to the equilibrium separations for the barriers found on intersecting {111} planes in the face‐centered‐cubic structure. The importance of such configurations, and especially the effect of the twin boundary, on work‐hardening behavior is discussed.

ISSN:0021-8979    

DOI:10.1063/1.325561

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

One‐dimensional shock loading, attenuation, and recompression data from gas‐gun experiments on mechanical mixtures of alumina powder and epoxy were used to develop model parameters for stress‐wave propagation. Specimens with 0.42, 0.34, and 0.20 volume fractions of alumina were investigated. Calculations simulating the experiments were performed using an extension of a Maxwell rate‐dependent model which requires definitions of the instantaneous, equilibrium, and relaxation functions as input. Experimental observations indicated the shock‐loading behavior is identifiable with the equilibrium response, and the release wave behavior is closely related to the instantaneous response. To model these effects, for negative strain rates, indicative of expansion, a relaxation time of 0.25 &mgr;s was used; this value gave agreement between the calculated and measured release wave behavior. For positive strain rates, indicative of compression, the relaxation time was permitted to decrease to 0.03 &mgr;s, which caused the shock‐loading response to be dominated by the equilibrium function. Hugoniot data determined from the stress‐wave profiles were compared to effective modulus calculations. This comparison suggests a strength effect which can be interpreted as an interaction between the components. Analysis using a self‐consistent scheme for spherical particles shows good correlation between calculated and measured ultrasonic and Hugoniot intercept wave velocities.

ISSN:0021-8979    

DOI:10.1063/1.325562

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Alkali niobate and tantalate glasses have been prepared by rapid quenching. These glasses exhibit room‐temperature ionic conductivities as high as 10−5(&OHgr; cm)−1and electronic conductivities less than 10−11(&OHgr; cm)−1. In the case of LiNbO3, the glass conductivity is many orders of magnitude greater than that of the single crystal. These conductivities are sufficiently high for rapidly quenched vitreous oxides to be considered for applications as solid electrolytes.

ISSN:0021-8979    

DOI:10.1063/1.325509

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The redistribution of impurities in SOS (silicon‐on‐sapphire) ‐type structures during thermal oxidation is formulated and solved numerically for the nonlinear case when the diffusion coefficient depends on the impurity density. The method of lines is used to reduce the nonlinear boundary‐value problem to a stiff system of initial‐value ordinary differential equations, which is solved by Gear’s method. A computer program based on the numerical solution has been developed and applied to an illustrative example considered previously for the linear problem. The program was then applied to three realistic examples pertaining to the redistribution of ion‐implanted boron impurities in SOS‐type structures during thermal oxidation.

ISSN:0021-8979    

DOI:10.1063/1.325510

出版商:AIP    

年代:1978

数据来源: AIP