A new carbon structure in annealed film coatings of the carbon–lead system

Carbon–lead solid solutions coexisting with amorphous carbon have been obtained for the first time in a film coating deposited by ion-plasma sputtering. During subsequent vacuum annealing of carbon–lead films containing more than 68.5 at % Pb, this element almost completely evaporates to leave an amorphous carbon coating on a substrate. During annealing at 1100°C, this amorphous carbon crystallizes into a new hexagonal lattice with unit cell parameters a = 0.7603 nm and c = 0.8168 nm. Characteristic X-ray diffraction data for the identification of this phase are determined.

     

New Mo3Pb phase with a15 structure formed in solid solutions of film molybdenum-lead system

Ion-plasma sputtering and codeposition of Mo and Pb ultrafine particles have been used for the first time to prepare solid solutions that are alloys over the whole composition range of the binary system, which were obtained in the form of coatings; this confirms the thermal-fluctuation melting and coalescence of small particles. When coatings are formed by molybdenum and lead nanolayers less than 1 nm thick, the mutual dissolution of the components with the formation of solid solutions in each other takes place; in this case, beginning from a concentration of ～25 at % Pb in the alloy, lead atoms give their crystal symmetry for the formed lattice. A new phase was found that was prepared directly in the course formation; it was identified as the Mo₃Pb compound with the A15 body-centered cubic structure. X-ray diffraction data for the identification of the phases were determined. The upper temperature limit of the existence of the Mo₃Pb compound has been found and the unit cell whose volume is 0.1290 nm³ has been constructed.     

New NbCd<Subscript>2</Subscript> Phase in Niobium–Cadmium Coating Films

Solid solutions in the form of alloy coatings have been obtained for the first time in the Cd concentration range of 64.5% using ion-plasma sputtering and the codeposition of Nb and Cd ultrafine particles. This supports thermal fluctuation melting and the coalescence of fine particles. A coating of niobium and cadmium layers less than 2 nm thick at 68 at % Cd results in the formation of a new phase identified as NbCd2. The tetragonal fcc phase with lattice parameters a = 0.84357 nm and c = 0.54514 nm forms directly during film coating. XRD data for the identification of the intermetallic compound have been determined. The thermal stability of the NbCd2 intermetallic compound is limited by 200°C. The properties of the synthesized NbCd2 phase are typical of semiconductors.     

Nanocomposite protective coatings based on Ti–N–Cr/Ni–Cr–B–Si–Fe,their structure and properties

The first results of manufacturing and investigations of a new type of nanocomposite protective coatings are presented. They were manufactured using a combination of two technologies: plasma-detonation coating deposition with the help of plasma jets and thin coating vacuum-arc deposition. We investigated structure, morphology, physical and mechanical properties of the coatings of 80–90 μm thickness, as well as defined the hardness, elastic Young modulus and their corrosion resistance in different media. Grain dimensions of the nanocomposite coatings on Ti–N–Cr base varied from 2.8 to 4 nm. The following phases and compounds formed as a result of plasma interaction with the thick coating surface were found in the coatings: Ti–N–Cr (200), (220), γ-Ni₃–Fe, a hexagonal Cr₂–Ti, Fe₃–Ni, (Fe, Ni)N and the following Ti–Ni compounds: Ti₂Ni, Ni₃Ti, Ni₄Ti, etc. We also found that the nanocomposite coating microhardness increased to H = 31.6 ± 1.1 GPa. The Young elastic modulus was determined to be E = 319 ± 27 GPa – it was derived from the loading–unloading curves. The protective coating demonstrated the increased corrosion resistance in acidic and alkaline media in comparison with that of the stainless steel substrate.     

Some Physical Properties of the New Intermetallic Compound NbCd2

Semiconductors - Solid solutions of cadmium in niobium and NbCd2 phase are formed by magnetron sputtering and coprecipitation on substrates moving relative to the flow of Nb and Cd particles. The...     

Fabrication of Binary Niobium Alloys with Low-Melting Metals by the Deposition of Nanoparticles

Binary alloys of niobium with tin, lead, and cadmium are fabricated by the deposition of nanosized metal particles atomized in low-pressure plasma using the thermal-fluctuation melting effect. This effect implies the residence of a small particle in a quasi-liquid state to a certain critical size which, if is exceeded due to vapor condensation or merging (coalescence) with other quasi-liquid particles, leads to the droplet crystallization. Critical sizes are found at which the particles situated in a quasi-liquid state are able to coalescence and formation the alloy–solid solution. They are 2.1–2.2 nm for Nb, 0.4 nm for Sn, 0.6 nm for Pb, and 3.2 nm for Cd. The occurrence boundary of solid solutions of metals in niobium is determined by the following concentrations, at %: Sn 25.5, Pb 23.0, and Cd 64.5. The solid solution is based on the crystal lattice of matrix metal—niobium, in which lead, cadmium, and tin atoms are arranged. In connection with the fact that the sizes of atoms of incorporated metals differ from these for matrix niobium, the lattice parameters of the matrix (Nb) change and additional stresses appear in it up to the lattice destruction. The parameters of the bcc lattice of solid solutions increase with an increase in concentrations of Pb, Cd, and Sn in connection with their atomic sizes more when compared with niobium. The change in the growth rate of the crystal lattice is caused by the change in the schematic of the arrangement of impurity atoms in the matrix niobium lattice for alloys with lead and cadmium. Based on the critical particle sizes of metals, the magnitudes of the surface tension at the crystal–melt boundary are evaluated. They are as follows, J/m2: 1.17–1.22 for Nb, 1.15 × 10–2 for Sn, 1.48 × 10–2 for Pb, and 0.142 for Cd. The fabrication of alloys of refractory niobium with tin, lead, and cadmium is an example of using the size effect when fabricating new materials.     

Structure of sputter-deposited films of β-tantalum-aluminum alloys

Ion-plasma sputtering and the codeposition of ultradisperse particles of Ta and Al have been used to prepare solid solutions in the entire range of concentrations of the binary system in the form of alloy coatings. The formation of the solid solution of these alloys directly in the process of codeposition confirms the theory of the thermofluctuation melting of small particles and coalescence of quasi-liquid clusters of subcritical size. Upon the formation of coatings via the deposition of nanolayers of tantalum of less than 0.8 nm for β-Ta and 1.1 nm for Al, the spontaneous mutual dissolution of the components occurs with the formation of solid solutions of one metal in the other. Beginning with a concentration of ～85 at % Al in the alloy, Al atoms control the type of symmetry of the arising lattice. An increase in the characteristic dimensions (thickness of sublayers) of tantalum and aluminum leads to the appearance of solid solutions of these metals in these coatings in addition to the β tantalum and aluminum phases, as well as of amorphous regions and superlattices formed by nanoclusters of one metal in the matrix of the other. It has been established that the formation of these superlattices is controlled by the size factor.     

Structure and phase composition of deposited tantalum–carbon films

Ion plasma sputtering and the subsequent codeposition of ultrafine tantalum and carbon particles were used to prepare coatings with 4.6–71.5 at % C. Structural studies of the coatings showed the existence of carbon solid solutions in β Ta at carbon contents to 4.6 at %, carbon solid solutions in α Ta at carbon contents of 4.6–10.3 at %, and direct synthesis of TaC at carbon contents of 44.7–71.5 at %. During heat treatments to 700°C, the substantial concentration widening of regions of the existence of Ta₂C and TaC was found. The lattice parameters of hexagonal Ta₂C and fcc TaC carbides were determined for composition ranges of the existence of phases during heating to 700°C. Upon heating above 600°C, the progressive transition of quasiamorphous Ta₂C carbide into the crystalline Ta₂C carbide was found to take place. The possibility of applying the direct synthesis of TaC carbide in engineering was noted.     

Synthesis of Porous Tungsten from Tungsten–Cadmium Film Coatings

Solid solutions (alloys) with a Cd concentration of 50.3–76.3 at % were synthesized for the first time in the form of coatings by ion–plasma sputtering and codeposition of ultrafine W and Cd particles. When coatings were formed by tungsten and cadmium nanolayers, the components dissolved mutually to produce solid solutions of one metal in the other. A solid solution of cadmium in tungsten was synthesized at Cd concentrations up to 60.9 at %. At a cadmium concentration of 68.6 at % in the coating, the crystalline structure of cadmium with an admixture of amorphous tungsten was produced. At 800°C, tungsten evaporated from tungsten–cadmium coatings to form porous tungsten. The results of examination of materials fabricated on the basis of porous tungsten are planned to be used in practice.     

Whisker microcrystals on the surface of tantalum–cadmium alloy films

Technical Physics Letters - Whiskers crystals were discovered in the tantalum–cadmium (56.6 at % Cd) solid solutions formed by in-turn deposition of the superfine tantalum and cadmium...