Solid-state interdiffusion reactions in Ni/Ti and Ni/Zr multilayered thin films

We have performed a comparative transmission electron microscopy study of solid-state interdiffusion reactions in multilayered Ni/Zr and Ni/Ti thin films. The Ni-Zr reaction product was amorphous while the Ni-Ti reaction product was a simple intermetallic compound. Because thermodynamic and chemical properties of these two alloy systems are similar, we suggest kinetic origins for this difference in reaction product

Simultaneous planar growth of amorphous and crystalline Ni silicides

We report a solid-state interdiffusion reaction induced by rapid thermal annealing and vacuum furnace annealing in evaporated Ni/Si bilayers. Upon heat treatment of a Ni film overlaid on a film of amorphous Si evaporated from a graphite crucible, amorphous and crystalline silicide layers grow uniformly side by side as revealed by cross-sectional transmission electron microscopy and backscattering spectrometry. This phenomenon contrasts with the silicide formation behavior previously observed in the Ni-Si system, and constitutes an interesting counterpart of the solid-state interdiffusion-induced amorphization in Ni/Zr thin-film diffusion couples. Carbon impurity contained in the amorphous Si film stabilizes the amorphous phase. Kinetic and thermodynamic factors that account for the experimental findings are discussed

Nickel base coating alloy

Zirconium is added to a Ni-30 Al (beta) intermetallic alloy in the range of 0.05 w/o to 0.25 w/o. This addition is made during melting or by using metal powders. The addition of zirconium improves the cyclic oxidation resistance of the alloys at temperatures above 1100 C

Maximum thickness of amorphous NiZr interlayers formed by a solid-state reaction technique

Formation of the equilibrium intermetallic compound NiZr in sputter deposited Ni/Zr diffusion couples is suppressed by the formation of a metastable amorphous NiZr alloy until a critical thickness of the amorphous NiZr interlayer is reached. The temperature dependence of this critical thickness is studied experimentally. A phenomenological model based on the premise of interfacial heterogeneous nucleation is proposed to understand the evolution of Ni/Zr diffusion couples

Parameter analysis of copper-nickel-tungsten prepared via powder metallurgy process for electrical discharge machining of polycrystalline diamond

Polycrystalline Diamond (PCD) tools have an outstanding wear resistance. The electric conductivity of PCD caused by the conductive binding material (Cobalt) makes it possible to machine PCD tools with EDM. Electrode used in EDM of PCD must have better porosity, electrical and thermal conductivity. Therefore, this research presents the works in production of Cu-Ni-W electrode by powder metallurgy route. Production of powder metallurgy parts involve mixing of the powder with additives or lubricants, compacting the mixture and heating the green compacts in an Argon gas furnace so the particle bond to each other. Two levels of full factorial with six centre points and two replication technique was used to study the influence of main and interaction effects of the powder metallurgy parameter. There were four factors involved in this experiment. Factor A which is Type of Cu-Ni; Type A and Type B was defined as categorical factor. Factor B in which Composition of W; 5 Wt.%, 15 Wt. % and 25 Wt.%, was defined as numerical factor. Factor C which is the Compaction load; 7, 8 and 9 tonne and Factor D which is Sintering temperature; 635 ℃, 685 ℃ and 735 ℃ were also defined as numerical factor. Optical Microscope, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) was used to analysed the microstructure and surface morphology of Cu-Ni-W electrode. The best parameter combination to produced better porosity, electrical and thermal conductivity for both Type A and Type B was 5 Wt.% of W, compaction load at 9 tonne and sintering temperature at 735℃. The best response for Type A is 12.65% of porosity, 14.40 IACS% of electrical conductivity and 413.26 W/m.℃ of thermal conductivity. While that, the best response for Type B were 9.36% of porosity, 16.66 IACS% of electrical conductivity and 345.21W/m.℃ of thermal conductivity. From the calculation of Maxwell’s Equation, Type A and Type B had the highest electrical conductivity of 58.48 IACS% and 77.35 IACS% respectively at W content of 5Wt.%. Type A and Type B also had the highest thermal conductivity of 369.86 W/m.℃ and 310.24 W/m.℃ respectively at W content of 5 Wt.%. Besides that, thermal conductivity also increased with the temperature increased until 450℃

Phase equilibria and phase transformations in the Ti-rich corner of the Fe-Ni-Ti system

While the main features of the Fe-Ni-Ti system are well known at low Ti content, literature review of the Ti-rich corner revealed inconsistencies between experimental reports. This investigation presents new experimental results, defined to remove the uncertainties concerning melting behavior and solid-state phase equilibria of the (Ni,Fe)Ti2 phase with the adjacent (Fe,Ni)Ti (B2, CsCl-type structure) and Beta-Ti (A2, W-type) phases. Six samples have been prepared and examined by differential thermal analysis performed in yttria and alumina crucibles, and by scanning electron microscopy in the as-cast state as well as equilibrated at 900°C

Физико-механические свойства керамических и металлокерамических покрытий, нанесенных плазменно-детонационным способом

В обзоре представлены результаты исследований структуры и свойств покрытий из Al₂O₃ - Cr₂О₃,Cr₃C₂–Ni и WC-Co, нанесенных на подложку из металлов с помощью плазменно-детонационной технологии. Показано, что в покрытиях из Al₂O₃ образуется 60% γ-фазы Al₂O₃ , 30% α-фазы, остальное – метастабильные и аморфные фазы ( β, η, и θ-модификации Al₂O₃ ). Переходной слой состоит из интерметаллидов FeAl с размерами кристаллитов (20-40) нм. В составе покрытия из смешанной керамики образуются α-, β-, γ-Al₂O₃ , и интерметаллид AlFe. Средний размер кристаллов от 100 до 350 нм. В данном покрытии также присутствуют фазы Cr₂О₃ и CrО₃ с размерами кристаллитов от 150 до 500 нм. В покрытии их WC-Co обнаружено формирование следующих фаз: W₂C, Co₇W₆ , Co₃W, W и Co. Средний размер кристаллов WC с ГПУ-решеткой составляет 150 нм, а кобальта 25 нм. На границах кристаллитов наблюдаются частицы фаз W₃Cо₃С. В покрытии на основе металлокерамики (твердый сплав Cr₃C₂-Ni) обнаружено формирование фаз CrO, Cr₃C₂, Cr₃Ni₂, Cr₇C₃ , Cr, Ni. Твердость покрытий из твердых сплавов составляет от 10,1 (Cr₃C₂-Ni) до 19,8 ГПа для WC-Со покрытия.В огляді представлені результати досліджень структури та властивостей покрить на основі Al₂O₃-Cr2 O3 , Cr₃C₂-Ni та WC-Co, нанесених на підкладинку з металів за допомогою плазмово- детонаційної технології. Доведено, що в покриттях із Al₂O₃ утворюється 60% γ-фази Al₂O₃ , 30 % α-фази, решта – метастабільні та аморфні фази ( β, η, та θ-модифікації Al₂O₃ ). Перехідний шар складається із інтерметалідів FeAl з розмірами кристалів (20 – 40) нм. В складі покриття зі змішаної кераміки утворюються α-, β-, γ-Al₂O₃ та інтерметалід FeAl. Середній розмір кристалів від 150 до 500 нм. В покриттях із WC-Co виявлено формування наступних фаз: W₂C, Co₇W₆ , Co₃W, W та Co. Середній розмір кристалів WC з ГЩУ- решіткою складає 150 нм, а кобальта 25 нм. На межах кристалів спостерігаються частинки фаз W₃Cо₃С. В покритті на основі металокераміки (твердий сплав Cr3 -C2 -Ni) виявлено формування фаз CrO, Cr₃C, Cr₃Ni₂ , Cr₇C₃, Cr, Ni. Твердість покриттів із твердих сплавів складає від 10,1 (Cr3 -C2 -Ni) до 19,8 ГПа для WC-Co-покриття.The review presents the investigation results on the structure and properties of Al₂O₃ -Cr₂О₃, Cr₃C₂-Ni and WC-Co coatings which were deposited to a metal substrate using the plasma-detonation technology. It was demonstrated that 60% of Al₂O₃ γ-phase, 30% of α-phase, and metastable and amorphous phases (β, η, θ, and σ-modifications of Al₂O₃ ) as the rest were formed in Al₂O₃ coatings. The transition layer was composed of intermetalloids FeAl with crystallite dimensions 20 to 40nm. In the mixed ceramic coatings Al₂O₃ α-, β-, γ-Al₂O₃ and AlFe intermetalloid were formed. The average crystal dimensions were 100 to 350nm. In the coating phases Cr2 O3 and CrO3 phases were also present, the crystallites dimensions varying from 150 to 500 nm. The following phases were found in the coating: W₂C, Co₇W₆ , Co₃W, W and Co. The average W crystals dimension with the fcc-lattice was 150nm, and 25nm for cobalt. Near the crystallite boundaries the particles of W₃Cо₃С phases of about 15nm dimension were observed. The formation of CrO, Cr₃C₂, Cr₃Ni₂ , Cr₇C₃ , Cr, and Ni phases was found in the coatings on the metal-ceramic base (a hard Cr3 -C2 -Ni alloy). The hardness of the hard-alloy coatings was from 10.1GPa for Cr₃C₂-Ni and 19.8 GPa for WC-Co coating

Исследование диффузии Ni по поверхности W авторадиографическим методом

В работе исследовалась диффузия Ni по поверхности кристаллов W. Эта система на протяжении долгого времени привлекает большое внимание исследователей в области физики металлов и порошковой металлургии, так как оказывается, что весьма малые добавки Ni существенно влияют на характер пластической деформации кристаллов W и процесс спекания вольфрамовых порошков

Superconductivity in carbon nanotubes coupled to transition metal atoms

The electronic structures of zig-zag and arm-chair single-walled carbon nanotubes interacting with a transitional-metal atomic nanowire of Ni have been determined. The Ni nanowire creates a large electron density of states (DOS)at the Fermi energy. The dependence of the enhanced DOS on the spin state and positioning of the transition-metal wire(inside or outside the nanotube) is studied. Preliminary estimates of the electron-phonon interaction suggest that such systems may have a superconducting transition temperature of $\sim$ 10-50 K. The signs of superconductivity seen in ``ropes'' of nanotubes may also be related to the effect of intrinsic transition-metal impurities.Comment: 4 pages and two figure

Elastic-plastic fracture toughness of electrodeposited Ni-W thick films using in-situ microcantilever bend tests

Nanocrystalline materials have been shown to exhibit properties superior to their coarse-grained counterparts. Nanocrystalline Ni-W is no exception and is a promising replacement for nanocrystalline Ni and hard chromium, with prospect in the electronics, microfabrication technology, automobile, and aerospace industries. In spite of having desirable properties, Ni-W exhibits a certain brittleness that if not mitigated, could lead to premature failure. This study investigates the fracture behavior of Ni-W and establishes structure-property relationships via correlation to the microstructure. Due to non-negligible plastic yielding, conventional linear elastic fracture mechanics was insufficient in quantifying the fracture toughness, and novel elastic-plastic fracture mechanics had to be used. Please click Additional Files below to see the full abstract