Einsatz der Elektronenstrahl-Mikrosonde bei der Lösung metallurgischer Werkstoffprobleme

The electron-probe microonalysis provides a variety of informations on the condition of mettalic samples within the micro range, which in connection with an appropriate measuring technique enables numerous statements to be made on important metallographic problems. As examples from the operating practice of a high-quality steel plant the identification of structural constituents, determination of microsegregation, investigation of grain boundaries and material defects in steels are explained.     

Untersuchung epitaktischer Molybdänkarbidschichten an Molybdän-(110)-Oberflächen

The initial phases of high temperature (1700 K) carburization of (110) molybdenum surfaces by C₆H₆ at low pressure are examined with low energy electron diffraction (LEED) and emission electron microscopy. After an exposition of about 8 · 10⁻⁵ Torr · sec a (4 × 4) superstructure was observed by means of LEED, interpreted as coincidence lattices with the Mo₂C (10.0) plane parallel to the Mo (110) surface. Heating a sample without further exposition resulted in the appearance of a complex and of a (2 × 2) superstructures. After an exposition of about 2 … 9 · 10⁻³ Torr · sec needle shaped molybdenum carbide crystallites grew on the surface into the [111] and [111] directions. The orientation Mo₂C (10.1) parallel to Mo (110) was concluded from the LEED patterns.     

Elektronenmikroskopische Untersuchungen zur Rißausbreitung bei der Zugverformung gewalzter Molybdän-Einkristalle

The effect of dislocation structure on mechanical properties, crack propagation and fracture was investigated in molybdenum single crystals predeformed by rolling to produce a homogeneously distributed dislocation structure or a cell structure. The rolled crystals were notched and deformed by tension at various temperatures (493, 293 and 193 K). It is shown, that the crystals with cell structure ((111) [112 ] orientation) have the higher strength, but the crystals with homogeneous structure ((001) [110] orientation) are more ductile. In cell structure cracks propagate catastrophically without pronounced necking. The homogeneous structure becomes unstable during tensile loading above the transition temperature, but crack propagation occurs slowly involving complete necking of the crystal. At low temperatures (193 K) cleavage fracture on {100} planes takes place both in the crystals with homogeneous and cell structure.     

Funktionelle Abhängigkeiten der Gleichgewichtsverteilungskoeffizienten in Molybdän

From the deeper investigation of the periodicity of the equilibrium distribution coefficient in molybdenum comes out that k_c values of admixtures (transition metals) in Mo depend on three factors of influence: a) the valence factor (the number of valence electrons), b) the dimension factor (the real or hypotetical melting point of the admixture phase, which is the same as that one of the basic metal Mo—KSC.) From this dependence it is possible to predict the value k_o of the elements in molybdenum, the diagrams of which are not known or inexact.     

Zum Einsatz der quantitativen Lichtmikroskopie bei der Versetzungsdichtebestimmung von GaAs-〈100〉-Kristallen

The linear analysis with the microscope EPIQUANT is applicable to metallographical measurement of the etch pit density of GaAs 〈100〉 crystals. The values of the linear analysis are converting to numbers of particles in the measuring field by means of mathematical-statistical equations. For large etch pit densities the measurement of the percentage fraction of etch pits of the measuring line is more precise as the measurement of the number of particles intersected by the measuring line.     

Einsatz des Spiegel-Elektronenmikroskops zur Untersuchung dielektrischer dünner Schichten

A technique for imaging of charge inhomogeneities in dielectric layers with the aid of the mirror electron microscope is described. The experimental results given being interpreted in a semiquantitative way, are first of all related to silicon oxide evaporation layers.     

Grundlagen der Theorie des Parakristalls und ihre Anwendungsmöglichkeiten bei der Untersuchung der Realstruktur kristalliner Stoffe

A brief review is given concerning the basic ideas of the theory of paracrystals and its practical application in X-ray structure analysis. Moreover, the relationships are discussed which exist between the the ory of paracrystals and the theories of liquids as proposed by ORNSTEIN , ZERNIKE and ZERNIKE , PRINS , and between the theory of paracrystals and the treatment of imperfect crystals as introduced by KRIVOGLAZ .     

Beitrag zum röntgenographischen Nachweis von Phasen mit geringen Volumenanteilen

Following quantum counting statistical considerations relations were derived which enable to estimate the error of integral intensity measurements of weak interferences and the minimal detectable volume parts of minority phases as a function of the measuring conditions and of the given error limits, and to optimize the choice of radiation and monochromatization conditions for the X-ray analysis of minority phases.     

Untersuchung der Ausscheidungsverhältnisse von schmelzgegossenen hochaluminiumoxidhaltigen feuerfesten Materialien

The relation between the conditions of crystallisation and grain texture of fused refractory bricks with high contents of aluminium oxide ist investigated. The results make clear that bricks with small contents of a glass phase have to becooled down slowly, thus avoiding a strongly disturbed growth of the corundum crystals in larger areas of the brick. A fast solidification process caused by rapid cooling does not result in a defined growth of dendrites and in the formation of a stable equilibrium state.     

Strukturuntersuchungen an Oberflächenschichten spanend bearbeiteter Molybdän-Einkristalle

Molybdenum single crystals were used as model samples for gross machining operations (turning). The damaged surface layer was studied by reflection electron diffraction and transmission electron microscopy (TEM). Near the machined surface the material was found to be polycrystalline, the transition to the single crystal state occurs within the range from 2 to 5 μm. Pronounced plastic deformations are ranging to a depth of about 150 μm below the surface. The transition to the undisturbed single crystal occurs within the range from 150 to 300 μm.     

Emissionsmikroskopische Untersuchungen zur Änderung der Sekundärelektronenemission bei der plastischen Verformung

Both the electron optical image contrast and the electron current density of all crystal grains decrease by plastic deformation of polycrystalline samples in a secondary electron emission microscope with conventional high vacuum. As a presumption both the sample temperature and the vacuum must be so high that the secondary electron yield does not change during the variation of these parameters. After recrystallisation the electron current densities of the crystallites with preserved orientation return to those of the initial stage. From these results it follows that a connection exists between secondary electron yield and crystal lattice perfection. A qualitative explanation of this connection is tried.     

Elektronenmikroskopische Beobachtung von Zonenachsen-Interferenzmustern in verbogenen Molybdänfolien

The paper reports on many beam patterns at 150 and 200 kV observed in saucershaped single crystal molybdenum foils if the incident electron beam is parallel to a low index zone axis. Feasible applications are discussed.     

Berechnung der Übersättigung bei der Kristallisation von InAs aus der Gasphase

It is proved that under experimental conditions for the growing of InAs crystals from the vapour phase the partial supersaturation of indium monoiodide corresponding to the difference of partial pressure of InJ_(g) in the source and in the crystallisation zones, can serve as a quantitative process parameter granting predictions on process development and results in a wide range of ruling conditions. Experiments confirmed the conclusions postulated on the base of quantitative analysis of the transport process. The analysis enables to controll the process parameters of crystal growth by chemical transport.     

Untersuchung der Kinetik der Kristallisation unterkühlter Schmelzen

Experimental arrangement and a method are given to investigate the kinetics of solidification of supercooled liquids in thin layers. The kinetics of isothermal phase transformation of supercooled melts of betol are investigated between 0° and 85°C. Kinetic curves present the course of phase transformation in this range. It is stated that the process of isothermal solidification can sufficiently be described by the equation S_π = S₀ [1 − exp (− a τ^b)], b lying between 2 and 3. Compared with the theoretical value the experimental one is lowered, this being explained by the presence of active impurities and their exhaustion during the process of solidification.     

Automatische Intensitätsoptimierung bei der Röntgentopographie

For routine investigations of crystal defects in semiconductor wafers the scanning-oscillating-technique turned out to be insufficient. In the following article an electronic adjusting mechanism is described which guarantees a maximum of intensity during the wafer translation. Thus the time of exposure can be remarkably reduced.     

Zum Einfluß des Primärionenstrahlprofils bei der Monolagenanalyse mittels der Methode SIMS

The influence of the primary ion beam profile on the secondary ion currents has been investigated by the SIMS method. The results obtained by Benninghoven concerning the destruction of monolayers could be generalized for the conditions existing in some SIMS devices, namely that the primary ion beam profile is not rectangular, that means, the current density of the irradiation disc is not constant. Moreover, an analytical formula has been given in order to eliminate numerically the so-called „crater effect”︁ existing at the estimation of depth profiles by means of such a stationary primary ion beam of not rectangular profile. Using experimental curves obtained by investigations of the oxidation of (100) CrNi steel surface by means of the SIMS method, it was demonstrated how to carry out a quantitative analysis.     

Untersuchung der Kühlkristallisation in einer Flüssigkeitsgeysir-Anlage

The application of gas-liquid spouted bed process for crystallization was studied. In using the same model material, the results obtained were compared with crystallization tests of other intensive processes. It was stated that in the gas-liquid spouted bed there was no difference between temperatures of air and liquid. The decrease in temperature of the warm liquid was caused by the evaporation at first, and the relative humidity of outlet air was found about 70%. Based on the correlations between the process parameters and particle size of crystals technological circumstances for manufacturing crystals having predetermined particle size was elaborated. The process — using appropriate technological parameters — can be applied for producing narrow (homogeneous) fraction of crystalline products of different size.