My CV includes my honors, awards and memberships in different societies plus history of my resear... more My CV includes my honors, awards and memberships in different societies plus history of my research career starting in 1960 after I received my BS degree from New York University's campus in the Bronx.
Direct and visible evidence was obtained for long-range migration of self-interstitial atoms (SIA... more Direct and visible evidence was obtained for long-range migration of self-interstitial atoms (SIAs) in Stage II of three different ion-irradiated platinum(gold) alloys (Pt/0.1 at% Au, Pt/0.62 at% Au and Pt/4.0 at% Au). Field-ion microscope (FIM) specimens of the alloys were irradiated in-situ with 30 keV W/sup +/ or Pt/sup +/ ions at a tip temperature of 35 to 40 K at approximately 2.10/sup -9/ torr. Direct observation of the surface of the FIM specimens during isochronal warming experiments to 100 K showed that a flux of SIAs crossed the specimen's surfaces between 40 and 100 K. The spectrum for each alloy consisted of two recovery peaks (substages II/sub B/ and II/sub C/). The results are explained on the basis of an impurity delayed diffusion mechanism employing a two-level trapping model.
Journal of Physics E: Scientific Instruments, 1968
A 0-4 kv pulse amplifier has been constructed for field ion microscopy. The circuit employed was ... more A 0-4 kv pulse amplifier has been constructed for field ion microscopy. The circuit employed was a triode amplifier, powered by a 5 kv full-wave voltage doubler, triggered by a General Radio 1217-B pulse generator and capacitively coupled to the field ion microscope via a 30 kv, 0.01 μF capacitor. The circuit produces either negative or positive field evaporation pulses. The usable minimum pulse time was found to be in the range 10-20 μs for this amplifier design.
ABSTRACTTernary carbide precipitates improve the high-temperature creep strength of 2-phase TiAl ... more ABSTRACTTernary carbide precipitates improve the high-temperature creep strength of 2-phase TiAl alloys. The perovskite (P-type) Ti3 AlC nucleates at relatively low temperatures (750 deg. C), whereas hexagonal (H-type) Ti2AlC precipitates occur at somewhat higher temperatures. Calculations are performed, based on first- principles-local-density-functional theory, of the interface structure and energy of these two carbides with a 7-TiAl matrix. Calculations are first done on coherent interfaces, and approximate corrections are then made for the effect of misfit. The perovskite is known to form needle-shaped precipitates oriented along the c-axis of the host. Our calculations yield a relatively low energy for the (100) perovskite-host interface, which is a favorable orientation owing to its low misfit, and because the terminating carbide layer for the coherent interface is pseudomorphic with the host. Predictions are given for the critical thickness for coherence and the critical nucl...
ABSTRACTThe amorphous(a)-to-crystalline (c) phase transition has been studied in electron(e-) and... more ABSTRACTThe amorphous(a)-to-crystalline (c) phase transition has been studied in electron(e-) and/or ion irradiated silicon (Si). The irradiations were performed in i n the Argonne High Voltage Microscope-Tandem Facility The irradia ion of Si, at <10 K, with 1-MeV e- to a fluence of 14 dpa failed to induce the c-to-a transition. Whereas an irradiation, at <10 K, with 1.0 or 1.5-MeV Kr+ ions induced the c-to-a transition by a fluence of ≈0.37 dpa. Alternatively a dual irradiation, at 10 K, with 1.0-MeV e and 1.0 or 1.5-MeV Kr+ to a Kr+ fluence of 1.5 dpa -- where the ratio of the displacement rates for e- to ions was ≈0.5--resulted in the Si specimen retaining a degree of crystallinity. These results are discussed in terms of the degree of dispersion of point defects in the primary state of radiation damage and the mobilities of point defects.
A review is presented of field ion microscope applications in studies of point defect distributio... more A review is presented of field ion microscope applications in studies of point defect distribution in irradiated metals. FIM results on the primary state of radiation damage in neutron and ion-irradiated iridium and tungsten, at both room-temperature and 78/sup 0/K, showed that it consists of: (1) isolated vacancies; (2) depleted zones; (3) compact vacancy clusters of voids; and (4) dislocation loops. The fraction of vacancies stored in the dislocation loops represented a small fraction of the total vacancy concentration; in the case of tungsten it was approximately 10 percent. These FIM observations provide a simple explanation of the low yield-factor, determined by transmission electron microscopy, for a number of ion-irradiated metals.
Atomistic Monte Carlo simulations utilizing many-body embedded atom method (EAM) potentials have ... more Atomistic Monte Carlo simulations utilizing many-body embedded atom method (EAM) potentials have been carried out for a series of symmetrical [001] twist boundaries in Pt-3 at.% Ni and Ni-3 at.% Pt alloy bicrystals at 850 K throughout the misorientation range 0° to 45°. The results demonstrate enhancement of the solute-atom concentration at twist boundaries for both alloys; the interfacial Gibbsian excess is a factor of two greater on the Ni-rich side of the phase diagram. The spatial distributions of solute atoms in the vicinity of the interfaces are found to be markedly different on the two sides of the Ni-Pt phase diagram. For low-angle boundaries on the Pt-rich side solute atoms tend to segregate in hourglass-like regions along the cores of the primary grain boundary screw dislocations, while in the case of Ni-3 at.% Pt they occupy bipyramidal regions centered on the cells of the dislocation grid. The former behavior explains the oscillatory solute-atom concentration profiles no...
My CV includes my honors, awards and memberships in different societies plus history of my resear... more My CV includes my honors, awards and memberships in different societies plus history of my research career starting in 1960 after I received my BS degree from New York University's campus in the Bronx.
Direct and visible evidence was obtained for long-range migration of self-interstitial atoms (SIA... more Direct and visible evidence was obtained for long-range migration of self-interstitial atoms (SIAs) in Stage II of three different ion-irradiated platinum(gold) alloys (Pt/0.1 at% Au, Pt/0.62 at% Au and Pt/4.0 at% Au). Field-ion microscope (FIM) specimens of the alloys were irradiated in-situ with 30 keV W/sup +/ or Pt/sup +/ ions at a tip temperature of 35 to 40 K at approximately 2.10/sup -9/ torr. Direct observation of the surface of the FIM specimens during isochronal warming experiments to 100 K showed that a flux of SIAs crossed the specimen's surfaces between 40 and 100 K. The spectrum for each alloy consisted of two recovery peaks (substages II/sub B/ and II/sub C/). The results are explained on the basis of an impurity delayed diffusion mechanism employing a two-level trapping model.
Journal of Physics E: Scientific Instruments, 1968
A 0-4 kv pulse amplifier has been constructed for field ion microscopy. The circuit employed was ... more A 0-4 kv pulse amplifier has been constructed for field ion microscopy. The circuit employed was a triode amplifier, powered by a 5 kv full-wave voltage doubler, triggered by a General Radio 1217-B pulse generator and capacitively coupled to the field ion microscope via a 30 kv, 0.01 μF capacitor. The circuit produces either negative or positive field evaporation pulses. The usable minimum pulse time was found to be in the range 10-20 μs for this amplifier design.
ABSTRACTTernary carbide precipitates improve the high-temperature creep strength of 2-phase TiAl ... more ABSTRACTTernary carbide precipitates improve the high-temperature creep strength of 2-phase TiAl alloys. The perovskite (P-type) Ti3 AlC nucleates at relatively low temperatures (750 deg. C), whereas hexagonal (H-type) Ti2AlC precipitates occur at somewhat higher temperatures. Calculations are performed, based on first- principles-local-density-functional theory, of the interface structure and energy of these two carbides with a 7-TiAl matrix. Calculations are first done on coherent interfaces, and approximate corrections are then made for the effect of misfit. The perovskite is known to form needle-shaped precipitates oriented along the c-axis of the host. Our calculations yield a relatively low energy for the (100) perovskite-host interface, which is a favorable orientation owing to its low misfit, and because the terminating carbide layer for the coherent interface is pseudomorphic with the host. Predictions are given for the critical thickness for coherence and the critical nucl...
ABSTRACTThe amorphous(a)-to-crystalline (c) phase transition has been studied in electron(e-) and... more ABSTRACTThe amorphous(a)-to-crystalline (c) phase transition has been studied in electron(e-) and/or ion irradiated silicon (Si). The irradiations were performed in i n the Argonne High Voltage Microscope-Tandem Facility The irradia ion of Si, at <10 K, with 1-MeV e- to a fluence of 14 dpa failed to induce the c-to-a transition. Whereas an irradiation, at <10 K, with 1.0 or 1.5-MeV Kr+ ions induced the c-to-a transition by a fluence of ≈0.37 dpa. Alternatively a dual irradiation, at 10 K, with 1.0-MeV e and 1.0 or 1.5-MeV Kr+ to a Kr+ fluence of 1.5 dpa -- where the ratio of the displacement rates for e- to ions was ≈0.5--resulted in the Si specimen retaining a degree of crystallinity. These results are discussed in terms of the degree of dispersion of point defects in the primary state of radiation damage and the mobilities of point defects.
A review is presented of field ion microscope applications in studies of point defect distributio... more A review is presented of field ion microscope applications in studies of point defect distribution in irradiated metals. FIM results on the primary state of radiation damage in neutron and ion-irradiated iridium and tungsten, at both room-temperature and 78/sup 0/K, showed that it consists of: (1) isolated vacancies; (2) depleted zones; (3) compact vacancy clusters of voids; and (4) dislocation loops. The fraction of vacancies stored in the dislocation loops represented a small fraction of the total vacancy concentration; in the case of tungsten it was approximately 10 percent. These FIM observations provide a simple explanation of the low yield-factor, determined by transmission electron microscopy, for a number of ion-irradiated metals.
Atomistic Monte Carlo simulations utilizing many-body embedded atom method (EAM) potentials have ... more Atomistic Monte Carlo simulations utilizing many-body embedded atom method (EAM) potentials have been carried out for a series of symmetrical [001] twist boundaries in Pt-3 at.% Ni and Ni-3 at.% Pt alloy bicrystals at 850 K throughout the misorientation range 0° to 45°. The results demonstrate enhancement of the solute-atom concentration at twist boundaries for both alloys; the interfacial Gibbsian excess is a factor of two greater on the Ni-rich side of the phase diagram. The spatial distributions of solute atoms in the vicinity of the interfaces are found to be markedly different on the two sides of the Ni-Pt phase diagram. For low-angle boundaries on the Pt-rich side solute atoms tend to segregate in hourglass-like regions along the cores of the primary grain boundary screw dislocations, while in the case of Ni-3 at.% Pt they occupy bipyramidal regions centered on the cells of the dislocation grid. The former behavior explains the oscillatory solute-atom concentration profiles no...
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