ISSN:0232-1300    

DOI:10.1002/crat.2170170515

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170170516

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170170517

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170170518

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe mechanical behaviour of fatigued pure nickel monocrystals oriented for single slip was studied in push‐pull tests at room temperature. Especially the cyclic hardening curves, the cyclic stress‐strain curve and the shape changes of the hysteresis loops were investigated in the range of the plastic resolved shear strain amplitude, γap, between 10‐10and 10‐2. In this range the cyclic stress‐strain curve exhibits a plateau which is related to plastic strain localization in persistent slip bands (PSBs) developing within the residual “matrix” volume. Using a two‐phase model the cyclic saturation mechanical behaviour of the PSB and the matrix volumes has been determined. An explanation has been given of the constant plateau stress τBof the cyclic stress‐strain curve by taking into account the nucleation stress for PSBs depending on the plastic resolved shear strain amplitude of the matrix volume. Further, the propagation rate of PSBs after strain amplitude increase in the plateau range has been calculated by applying

ISSN:0232-1300    

DOI:10.1002/crat.2170170502

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe usual classification of nitrides into ionic, metallic, diamond like, and covalent phases is refined by analyzing the spatial correlation of the valence electrons (bcorrelation) and of the peripheral core electrons (ccorrelation). When the valence electrons of the N‐atoms take part in thebcorrelation then the octet rule is obeyed and ionic or covalent nitrides are formed; when the valence electrons of the N‐atoms take part in theccorrelation then either azides or metallic interstitial structures are formed, depending on whether the metal contributes sp electrons or d electrons into theccorrelation. The interstitial nitrides with NaCl structure owe their stability to the participation of an additionalecorrelation in the binding. The occurrence of stacking homeotypes of the NaCl structure is related to theccorrelation which is filled by d electrons of the T‐atoms and by the valence electrons of the N‐atoms. The Bnnitrides follow the octet rule which stabilizes the B3N compounds at the equiatomic composition. The diamond type is not formed, instead the related ZnO (H2.2) type is formed as a cC̃correlation may become stable here. The analysis of the binding in Si3N4shows that the structural transformation Si3N4· h → Si3N4· r is caused by increasing Hund insertion with decreasing temperature. The possibility of the present binding classification confirms that the two‐correlations model is a valence model als

ISSN:0232-1300    

DOI:10.1002/crat.2170170503

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe relationship between partitions of the three‐dimensional space into Dirichlet domains of morphological points and the face forms observed on crystals will here be examined. Dirichlet domains, the central points of which are to be found on the exterior net plane, can be connected two or one‐dimensionally through face‐sharing or they occur as isolated groups. If the crystal faces are arranged according to the proportion of these surface polyeder on the total surface of the net plane, the order of rank of barite and cerussite agree excellently with the experimental observations. The packings of space filling polyeder allow conclusions on growth mecha

ISSN:0232-1300    

DOI:10.1002/crat.2170170504

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe formation of shallow cavities on the faces of zinc (and cadmium) single crystals after reaching some critical size during growth from vapours in inert gas (Ar, H2) atmosphere has been discussed. New experimental facts concerning cavity form and the diffusion origin cause of the phenomenon have been reported. A satisfactory good semi‐quantitative agreement with the theoretically predicted critical sizes (CHERNOV, CAHN) has been found as a result of the precise discussion of the experimental results. The conclusion has been drawn that the diffusion in the parent phase plays unambigously a decisive role by the formation of the morphological peculiarities during vapour growth in inert gas atmospher

ISSN:0232-1300    

DOI:10.1002/crat.2170170505

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe influence of cleavage steps and low angle boundaries on the results of conductivity and Hall measurements by Van der Pauw's method are investigated and some criterions for evidence of sample inhomogeneities by the assumption of symmetrical sample shape and contact arrangement formulated. Hall voltage is less influenced by cleavage steps, so that the determination of carrier concentration is nearly correct also in strongly disturbed samples. Conductivity and carrier mobility measurements in the usus usual calculation procedure will lead to considerable errors. By one pair of contacts only for conductivity as well as for Hall measurements, the influences of inhomogeneities cannot be distinguished from volume effects of the sample.

ISSN:0232-1300    

DOI:10.1002/crat.2170170506

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractTiS1.7crystals have been grown by vapour transport technique employing a two‐zone furnace with the temperatures of reaction and growth zone maintained at 1073 K and 973 K, respectively. We have measured the variation of electrical conductivity (s̀) with temperature (T) of TiS1.7single crystals. It has been found that the conductivity increases at temperaturesT>433 K, which provides convincing evidence that the TiS1.7crystal is a semiconductor. Another electronic characteristic of TiS1.7crystals observed in the present investigation is the occurrence of voltage controlled negative resistance (VCNR) at a field of 32.1 V cm‐1to 35.7 V cm‐1. All the polytypes of TiS1.7were found to exhibit VCNR nearly at the same field which indicates that the VCNR is polytype independent property. The occurrence of VCNR has been explained on the intervally transfer of electrons in the conductio

ISSN:0232-1300    

DOI:10.1002/crat.2170170507

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY