The new intermetallic phase Al77Rh15Ru8 is identified in the title system by powder XRD, SEM, and... more The new intermetallic phase Al77Rh15Ru8 is identified in the title system by powder XRD, SEM, and TEM.
The constitution of the Al−Pd−Pt alloy system was studied above 35 at.% Al at 700, 780, 900 and 1... more The constitution of the Al−Pd−Pt alloy system was studied above 35 at.% Al at 700, 780, 900 and 1100 °C. The experiments revealed the formation of wide extensions of the binary Al−Pd and Al−Pt phases but no ternary phases. Continuous regions are probably formed between the isostructural phases Al4TM, Al21TM8, high-temperature AlTM, low-temperature AlTM and Al3TM5 (TM = Pd or Pt). The continuity between the Al3TM2 phases was revealed at 900 °C, while at 1100 °C the regions mutually extended from Al3Ni2 and Al3Pd2 are separated by the ternary extension of Al2Pt. The latter phase was found to dissolve up to 24 at.% Pd, which resulted in a sharp decrease of its Al concentration. The Al−Pd ε-phase was found to extend up to 18 at.% Pt at practically constant Al, while the Al−Pt ξ-phase was found to extend up to 7 at.% Pd.
We report a new phase in the binary SnS system, obtained as highly symmetric nanotetrahedra. Due ... more We report a new phase in the binary SnS system, obtained as highly symmetric nanotetrahedra. Due to the nanoscale size and minute amounts of these particles in the synthesis yield, the structure was exclusively solved using electron diffraction methods. The atomic model of the new phase (a = 11.7 Å, P213) was deduced and found to be associated with the rocksalt-type structure. Kramers-Kronig analysis predicted different optical and electronic properties for the new phase, as compared to α-SnS.
Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials, 2014
The crystal structure of the novel Al77Rh15Ru8 phase (which is an approximant of decagonal quasic... more The crystal structure of the novel Al77Rh15Ru8 phase (which is an approximant of decagonal quasicrystals) was determined using modern direct methods (MDM) applied to automated electron diffraction tomography (ADT) data. The Al77Rh15Ru8 E-phase is orthorhombic [Pbma, a = 23.40 (5), b = 16.20 (4) and c = 20.00 (5) Å] and has one of the most complicated intermetallic structures solved solely by electron diffraction methods. Its structural model consists of 78 unique atomic positions in the unit cell (19 Rh/Ru and 59 Al). Precession electron diffraction (PED) patterns and high-resolution electron microscopy (HRTEM) images were used for the validation of the proposed atomic model. The structure of the E-phase is described using hierarchical packing of polyhedra and a single type of tiling in the form of a parallelogram. Based on this description, the structure of the E-phase is compared with that of the ε6-phase formed in Al-Rh-Ru at close compositions.
ABSTRACT Owing to the individuality of intermetallic compounds, they are regarded as a special cl... more ABSTRACT Owing to the individuality of intermetallic compounds, they are regarded as a special class of materials. As such, there is a need to develop a step-by-step methodology for solution of their structure. The current paper adapts the methodology of structure solution from precession electron diffraction (PED) zonal data for intermetallics. The optimization of PED parameters for structure determination was achieved through the development of the atomic model of a well known Mg17Al12 (β) intermetallic phase. It was concluded that the PED acquisition parameters, the number of unique reflections and the quality of the merging process are the most important parameters that directly influence the correctness of a structure solution. The proposed methodology was applied to the structure solution of a highly complex new Mg48Al36Ag16 phase, which was recently revealed in the Mg–Al–Ag system. The final atomic model consisted of 152 atoms in the unit cell, distributed over 23 unique atomic positions. The correctness of the atomic model was verified by the reasonability of the interatomic distances and coordination polyhedra formed. It was found that the experimental model of Φ-Al17.1Mg53.4Zn29.5 can be assigned as a structure type for the Mg48Al36Ag16 phase. The Δ value, which measures the similarity between two structures, was calculated as 0.040.
Friction and wear of copper rubbed with lubrication in wide range of loads and sliding velocities... more Friction and wear of copper rubbed with lubrication in wide range of loads and sliding velocities were studied. The results of friction and wear experiments are presented as the Stribeck curve where the boundary lubrication (BL), mixed (ML) and elasto-hydrodynamic lubrication (EHL) regions are considered. The structural state of subsurface layers in different lubricant regions is studied by X-ray photoelectron
A ternary orthorhombic phase (Pbma, a=2.34, b=1.62 and c=2.00nm) was revealed around the Al77Rh15... more A ternary orthorhombic phase (Pbma, a=2.34, b=1.62 and c=2.00nm) was revealed around the Al77Rh15Ru8 composition. It is structurally related to the Al–Rh and Al–Pd ɛ-phases.
Friction and wear of copper rubbed in the presence of lubricants over a wide range of loads and s... more Friction and wear of copper rubbed in the presence of lubricants over a wide range of loads and sliding velocities were studied. The results of friction and wear experiments in the boundary lubrication (BL) and elastohydrodynamic lubrication (EHL) regimes are briefly considered. The structural state of subsurface layers in different lubricant regions is studied by optical, transmission and scanning microscopy analysis. Dislocation density and Burgers vector of individual dislocations in EHL and BL lubricant regimes were determined. A laminated structure with thin and elongated grains is formed in the EHL region. A range of nanocrystalline structures with grain sizes of 20-100 nm is formed in the surface layers in the BL region. Strong plastic deformation (SPD) of thin surface layers under friction is accompanied by formation of shear bands in sublayers of contact spots. Nanohardness at thin surface layers is compared for surfaces rubbed under different lubricant regimes. The hardness of thin surface layers saturates after repeated sliding of Cu and is close to the hardness of nanocrystalline Cu produced by various SPD processes.
Partial 1100, 1000, 900 and 700°C isothermal sections of the Al–Rh–Ru phase diagram were determin... more Partial 1100, 1000, 900 and 700°C isothermal sections of the Al–Rh–Ru phase diagram were determined. The isostructural binary AlRu and AlRh phases probably form a continuous β-range of the CsCl-type solid solutions. The Al9Rh2 and C-Al5Rh2 dissolve up to 4.5 and 13at.% Ru, while Al13Ru4 and Al2Ru dissolve up to 14.5 and 8at.% Rh, respectively. A ternary orthorhombic structure (Pbma,
The new intermetallic phase Al77Rh15Ru8 is identified in the title system by powder XRD, SEM, and... more The new intermetallic phase Al77Rh15Ru8 is identified in the title system by powder XRD, SEM, and TEM.
The constitution of the Al−Pd−Pt alloy system was studied above 35 at.% Al at 700, 780, 900 and 1... more The constitution of the Al−Pd−Pt alloy system was studied above 35 at.% Al at 700, 780, 900 and 1100 °C. The experiments revealed the formation of wide extensions of the binary Al−Pd and Al−Pt phases but no ternary phases. Continuous regions are probably formed between the isostructural phases Al4TM, Al21TM8, high-temperature AlTM, low-temperature AlTM and Al3TM5 (TM = Pd or Pt). The continuity between the Al3TM2 phases was revealed at 900 °C, while at 1100 °C the regions mutually extended from Al3Ni2 and Al3Pd2 are separated by the ternary extension of Al2Pt. The latter phase was found to dissolve up to 24 at.% Pd, which resulted in a sharp decrease of its Al concentration. The Al−Pd ε-phase was found to extend up to 18 at.% Pt at practically constant Al, while the Al−Pt ξ-phase was found to extend up to 7 at.% Pd.
We report a new phase in the binary SnS system, obtained as highly symmetric nanotetrahedra. Due ... more We report a new phase in the binary SnS system, obtained as highly symmetric nanotetrahedra. Due to the nanoscale size and minute amounts of these particles in the synthesis yield, the structure was exclusively solved using electron diffraction methods. The atomic model of the new phase (a = 11.7 Å, P213) was deduced and found to be associated with the rocksalt-type structure. Kramers-Kronig analysis predicted different optical and electronic properties for the new phase, as compared to α-SnS.
Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials, 2014
The crystal structure of the novel Al77Rh15Ru8 phase (which is an approximant of decagonal quasic... more The crystal structure of the novel Al77Rh15Ru8 phase (which is an approximant of decagonal quasicrystals) was determined using modern direct methods (MDM) applied to automated electron diffraction tomography (ADT) data. The Al77Rh15Ru8 E-phase is orthorhombic [Pbma, a = 23.40 (5), b = 16.20 (4) and c = 20.00 (5) Å] and has one of the most complicated intermetallic structures solved solely by electron diffraction methods. Its structural model consists of 78 unique atomic positions in the unit cell (19 Rh/Ru and 59 Al). Precession electron diffraction (PED) patterns and high-resolution electron microscopy (HRTEM) images were used for the validation of the proposed atomic model. The structure of the E-phase is described using hierarchical packing of polyhedra and a single type of tiling in the form of a parallelogram. Based on this description, the structure of the E-phase is compared with that of the ε6-phase formed in Al-Rh-Ru at close compositions.
ABSTRACT Owing to the individuality of intermetallic compounds, they are regarded as a special cl... more ABSTRACT Owing to the individuality of intermetallic compounds, they are regarded as a special class of materials. As such, there is a need to develop a step-by-step methodology for solution of their structure. The current paper adapts the methodology of structure solution from precession electron diffraction (PED) zonal data for intermetallics. The optimization of PED parameters for structure determination was achieved through the development of the atomic model of a well known Mg17Al12 (β) intermetallic phase. It was concluded that the PED acquisition parameters, the number of unique reflections and the quality of the merging process are the most important parameters that directly influence the correctness of a structure solution. The proposed methodology was applied to the structure solution of a highly complex new Mg48Al36Ag16 phase, which was recently revealed in the Mg–Al–Ag system. The final atomic model consisted of 152 atoms in the unit cell, distributed over 23 unique atomic positions. The correctness of the atomic model was verified by the reasonability of the interatomic distances and coordination polyhedra formed. It was found that the experimental model of Φ-Al17.1Mg53.4Zn29.5 can be assigned as a structure type for the Mg48Al36Ag16 phase. The Δ value, which measures the similarity between two structures, was calculated as 0.040.
Friction and wear of copper rubbed with lubrication in wide range of loads and sliding velocities... more Friction and wear of copper rubbed with lubrication in wide range of loads and sliding velocities were studied. The results of friction and wear experiments are presented as the Stribeck curve where the boundary lubrication (BL), mixed (ML) and elasto-hydrodynamic lubrication (EHL) regions are considered. The structural state of subsurface layers in different lubricant regions is studied by X-ray photoelectron
A ternary orthorhombic phase (Pbma, a=2.34, b=1.62 and c=2.00nm) was revealed around the Al77Rh15... more A ternary orthorhombic phase (Pbma, a=2.34, b=1.62 and c=2.00nm) was revealed around the Al77Rh15Ru8 composition. It is structurally related to the Al–Rh and Al–Pd ɛ-phases.
Friction and wear of copper rubbed in the presence of lubricants over a wide range of loads and s... more Friction and wear of copper rubbed in the presence of lubricants over a wide range of loads and sliding velocities were studied. The results of friction and wear experiments in the boundary lubrication (BL) and elastohydrodynamic lubrication (EHL) regimes are briefly considered. The structural state of subsurface layers in different lubricant regions is studied by optical, transmission and scanning microscopy analysis. Dislocation density and Burgers vector of individual dislocations in EHL and BL lubricant regimes were determined. A laminated structure with thin and elongated grains is formed in the EHL region. A range of nanocrystalline structures with grain sizes of 20-100 nm is formed in the surface layers in the BL region. Strong plastic deformation (SPD) of thin surface layers under friction is accompanied by formation of shear bands in sublayers of contact spots. Nanohardness at thin surface layers is compared for surfaces rubbed under different lubricant regimes. The hardness of thin surface layers saturates after repeated sliding of Cu and is close to the hardness of nanocrystalline Cu produced by various SPD processes.
Partial 1100, 1000, 900 and 700°C isothermal sections of the Al–Rh–Ru phase diagram were determin... more Partial 1100, 1000, 900 and 700°C isothermal sections of the Al–Rh–Ru phase diagram were determined. The isostructural binary AlRu and AlRh phases probably form a continuous β-range of the CsCl-type solid solutions. The Al9Rh2 and C-Al5Rh2 dissolve up to 4.5 and 13at.% Ru, while Al13Ru4 and Al2Ru dissolve up to 14.5 and 8at.% Rh, respectively. A ternary orthorhombic structure (Pbma,
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Papers by Shmuel Samuha