The Nature of Anomalous Particles (Granules) in Rapidly Quenched PREP Powders: I. A Multiscale Study of the Heating Zone of the Rotating Electrode Used to Obtain the Rapidly Quenched PREP Ni-Based Superalloy Powder

The uniformity of composition of rapidly quenched PREP particles of the powder of high temperature Ni-based superalloys and stainless steels is characterized by an important feature—the occurrence of anomalous particles (granules) with a significantly different content, mainly of microalloying interstitial elements, carbon and boron, as well as active carbide- and boride-forming alloying elements. A detailed multi-scale experimental study of the heating zone of the crater of the Ni-based superalloy electrode after its use to obtain rapidly quenched PREP powder was carried out in order to find the nature and mechanisms of the formation of anomalous granules. Direct nuclear physics methods of activation autoradiography on carbon, track autoradiography on boron, metallography, SEM, EDX, OIM were used. In the electrode crater, the heat-affected zone (HAZ) and the partially melted zone (PMZ) were detected. Intense migration of boron to the electrode surface due to the formation of thermal macrocracks was also revealed. The behavior of carbon is determined by the formation of a thin layer of melt on the surface of the crater. The features of the evolution of the terminal solidification region TSR and incipiently melted regions IMR, the main type of heterogeneity of the composition of the dendritic structure of Ni-based superalloys and stainless steels, are revealed. The interrelation of the evolution of these areas is established, which is a consequence of the thermodynamic principle of the reversibility of the processes of solidification and melting, respectively, in the smelting of an ingot electrode and in the process of subsequent atomization. The analysis of the influence of the behavior of boron, carbon, and the characteristics of the crater structure on the nature and mechanism of the formation of anomalous granules using the PREP method for producing rapidly quenched powder of the Ni-based superalloy is performed.

     

Relaxation processes in self-assembling triads based on porphyrin Zn-heterodimers

The directional self-assembly of nanosized, structurally organized triads is implemented in methylcyclohexane at 295 K, which is based on the two-point extra coordination of nonsymmetric, covalently bound heterodimers of Zn porphyrins to bipyridyl-substituted porphyrin free-base extra ligands. Based on experimental data and theoretical calculations, the structural organization is determined and information on the energetics of electronic interactions of components is obtained and the rate constants of the directional energy transfer (k ^ET ∼ 10¹¹ s⁻¹) and photoinduced electron transfer (k ^PET ∼ 2.7 × 10⁹ s⁻¹) are determined. The effects of the orientation of interacting macrocycles, the intercenter distances and the solvent temperature on the efficiency of relaxation processes in the triad is investigated.     

The experimental determination of the impact parameter dependence of inelastic energy loss of channeled ions

Using the channeling technique, the impact parameter dependence of inelastic energy loss of fast He and N ions in Si has been measured.     

Deuteron photodisintegration within the Bethe-Salpeter formalism: Effects of negative-energy components

Relativistic covariance requires that an analysis of the reaction γd → pn within a field-theoretical model of the nucleon-nucleon interaction involve negative-energy states. Relativistic effects and the contributions of negative-energy states in the Bethe-Salpeter amplitude to the differential cross section, the asymmetry of linearly polarized photons, and tensor asymmetries of the target deuteron are estimated on the basis of the Bethe-Salpeter formalism as applied to describing the interaction of an electromagnetic field with a two-nucleon system. It is found that the contribution of such states becomes sizable with increasing photon energy, but that it does not change the general qualitative behavior of observables as functions of angles.     

Radiation-Chemical Synthesis of Perfluorinated Tetrafluoroethylene Telomers

High Energy Chemistry - The kinetics of radiation-initiated telomerization of tetrafluoroethylene in perfluoromethylcyclohexane and perfluoro-1,3-dimethylcyclohexane has been studied, and new...     

New data on the composition of products of ultrasonic irradiation of graphite in <Emphasis Type="Italic">N</Emphasis>-methylpyrrolidone

It has been found that ultrasonic irradiation of graphite in N-methylpyrrolidone is accompanied by the formation of polymer nanoparticles. These particles form aggregates with n-layered graphene particles, the formation of which prevents graphene particles from precipitation during centrifugation.     

Justification of the Kirchhoff hypotheses and error estimation for two-dimensional models of anisotropic and inhomogeneous plates, including laminated plates

Asymptotic analysis of the problem describing deformation ofa thin cylindrical plate with clamped lateral side is performed.The problem is considered under the most general statement withthe plate being laminated and consisting of an arbitrary numberof nonhomogeneous and anisotropic (21 elastic moduli) layers.Explicit integral representations of the differential operatorswhich form the two-dimensional model of the plate are derived.In the case when the elastic moduli of each of the layers areconstant, these integral representations turn into algebraicones. The asymptotic procedure is justified with the help ofa weighted inequality of Korn's type. The error estimates obtainedgive a rigorous mathematical proof of both of Kirchhoff's hypotheses(kinematic and static) and shed light on the well-known intrinsicinconsistency of two of the hypotheses.     

Study of the physical sputtering of a carbon-ceramic composite by ion bombardment

The results of experimental study and computer simulation of SG-P-0.1 carbon-ceramic composite sputtering under 30 keV Ar⁺ ion irradiation at normal incidence are presented. A comparison with the simulation data shows that taking into account the nanometric wave-like relief well describes an approximately threefold increase in the sputtering yield observed in the experiment in comparison to the smooth surface calculation.     

Reaction of hydrogen gas with C60 at elevated pressure and temperature: hydrogenation and cage fragmentation

Products of the reaction of C(60) with H(2) gas have been monitored by high-resolution atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry (APPI FT-ICR MS), X-ray diffraction, and IR spectroscopy as a function of hydrogenation period. Samples were synthesized at 673 K and 120 bar hydrogen pressure for hydrogenation periods between 300 and 5000 min, resulting in the formation of hydrofullerene mixtures with hydrogen content ranging from 1.6 to 5.3 wt %. Highly reduced C(60)H(x) (x > 36-40) and products of their fragmentation were identified in these samples by APPI FT-ICR MS. A sharp change in structure was observed for samples with at least 5.0 wt % of hydrogen. Low-mass (300-500 Da) hydrogenation products not observed by prior field desorption (FD) FT-ICR MS were detected by APPI FT-ICR MS and their elemental compositions obtained for the first time. Synthetic and analytical fragmentation pathways are discussed.