Molybdenum alloy electrodeposits for magnetic actuation

The Influence of Titania Nanoparticles on the Electrodeposition of Ni-Mo-W Composites in Aqueous Electrolytes at Different Electrolyte Temperatures

The electrodeposition of Ni-Mo-W alloys and composites with TiO2 are examined with a rotating Hull cell to better understand the influence of the particle on the deposition composition and morphology. The addition of the TiO2 particle to the electrolyte and deposit, significantly affected the deposit composition when the electrolyte temperature was 650C. Both Ni and Mo composition in the deposit was enhanced, but not due to higher reaction rates. The enhancement was a result of an apparent inhibition by the hydrogen evolving side reaction. The W partial current density was most significantly inhibited. The deposit morphology changed with the addition of TiO2 with a reduction of microcracks compared to the particle-free deposit. The results suggest that the adsorption of the hydrogen intermediate from the side reaction is influenced by the particle, hindering hydrogen desorption, and indirectly affects the partial current densities of the nickel, molybdate and tungstate ion reduction and the morphology.

Molybdenum imidazole citrate and bipyridine homocitrate in different oxidation states – balance between coordinated α-hydroxy and α-alkoxy groups

Oxo and thiomolybdenum(iv/vi) imidazole hydrocitrates K₂{Mo^IV₃O₄(im)₃[Mo^VIO₃(Hcit)]₂}·3im·4H₂O (1), (Him)₂{Mo^IV₃SO₃(im)₃[Mo^VIO₃(Hcit)]₂}·im·6H₂O (2), molybdenum(v) bipyridine homocitrate trans-[(Mo^VO)₂O(H₂homocit)₂(bpy)₂]·4H₂O (3) and molybdenum(vi) citrate (Et₄N)[Mo^VIO₂Cl(H₂cit)]·H₂O (4) (H₄cit = citric acid, H₄homocit = homocitric acid, im = imidazole and bpy = 2,2′-bipyridine) with different oxidation states were prepared. 1 and 2 are the coupling products of [Mo^VIO₃(Hcit)]³⁻ anions and incomplete cubane units [Mo^IV₃O₄]⁴⁺ ([Mo^IV₃SO₃]⁴⁺) with monodentate imidazoles, respectively, where tridentate citrates coordinate with α-hydroxy, α-carboxy and β-carboxy groups, forming pentanuclear skeleton structures. The molybdenum atoms in 1 and 2 show unusual +4 and +6 valences based on charge balances, theoretical bond valence calculations and Mo XPS spectrum. The coordinated citrates in 1 and 2 are protonated with α-hydroxy groups, while 3 and 4 with higher oxidation states of +5 and +6 are deprotonated with α-alkoxy group even under strong acidic condition, respectively. This shows the relationship between the oxidation state and protonation of the α-alkoxy group in citrate or homocitrate, which is related to the protonation state of homocitrate in FeMo-cofactor of nitrogenase. The homocitrate in 3 chelates to molybdenum(v) with bidentate α-alkoxy and monodentate α-carboxy groups. Molybdenum(vi) citrate 4 is only protonated with coordinated and uncoordinated β-carboxy groups. The solution behaviours of 1 and 2 are discussed based on ¹H and ¹³C NMR spectroscopies and cyclic voltammograms, showing no decomposition of the species.

Oxo and thiomolybdenum(iv/vi) citrates, molybdenum(v) homocitrate and molybdenum(vi) citrate were obtained, showing the influence of coordinated α-hydroxy and α-alkoxy groups with different oxidation states.

Electrosynthesis method of CoPt nanoparticles in percolated microemulsions

An electrochemical synthesis of CoPt nanoparticles on Si/Ti/Au substrates has been performed in percolated water-in-oil (w/o) microemulsions to define the nanoparticle size and composition.

Grain boundary segregation and interdiffusion effects in nickel-copper alloys: an effective means to improve the thermal stability of nanocrystalline nickel

Nanocrystalline (nc) Ni films show pronounced grain growth and suffer from concomitant deterioration of their mechanical and magnetic properties after annealing at relatively low temperatures (T(ANN) ≥ 475 K). This constitutes a drawback for their applicability as coatings or in components of miniaturized devices. This work reveals that the thermal stability of nc Ni is significantly improved by controllably alloying Ni with Cu, by means of electrodeposition, to form a Ni(1-x)Cu(x) solid solution. To tune the composition of such nc alloys, Ni(1-x)Cu(x) films are deposited galvanostatically using an electrolytic bath containing Ni and Cu sulfate salts as electroactive species, saccharine as grain-refining agent, and applying current densities ranging from -10 to -40 mA cm(-2). The enhanced thermal stability is ascribed to segregation of a Cu-rich phase at the Ni(1-x)Cu(x) grain boundaries, which acts as a shielding layer against grain growth. As a result, high values of hardness (in excess of 6 GPa) remain in nc Ni(1-x)Cu(x) for x ≥ 0.3, even after annealing at T(ANN) ≥ 575 K. From a magnetic point of view, Ni(1-x)Cu(x) films possess lower coercivity values than pure nc Ni films, both in the as-prepared and annealed states, thus offering potential advantages for certain soft magnetic applications.