Nowadays, application of nanocrystalline nickel-tungsten (Ni-W) alloys is receiving a great interest because they are an efficient replacement for hard chromium coatings owing to their premium hardness, wear, and corrosion properties. Moreover, heat-treated nanocrystalline Ni-W alloys demonstrate proper mechanical properties as well as thermal stability at high temperatures. The current paper reviews different aspects of electrodeposition, microstructure, corrosion, oxidation, wear, and mechanical properties Ni-W alloys and nano/micro composites. Besides, heat treatment effects on properties and thermal stability of these alloys are also reviewed.

Ni-W electrodeposited coatings: Characterization, properties and applications

Theoretical and applied studies of tungsten alloys with iron group metals (Me-W) are being carried out worldwide, in the light of their versatile applications. The aim of this paper is to provide an overview of the works on electrodeposition of tungsten alloys with iron group metals, their properties and applications. There are 221 papers reviewing on the following theoretical and practical topics: chemistry of electrolytes used for electrodeposition, codeposition mechanisms, and properties of electrodeposited tungsten alloys. In addition, the formation of W(VI) and iron group metal (Me) complexes (polytungstates and complexes of Me(II) and W(VI)) with citrates and OH− is analysed based on the published data and the calculated distribution of species as a function of pH (ranged from 1 to 10) is provided for solutions with/without citrates. The adduced data are correlated with the compositions of electrodeposited alloys. Various codeposition models of tungsten with iron group metals described in the literature are critically discussed as well. The peculiarities of the structure of tungsten alloys and their thermal stability, mechanical, tribological, and magnetic properties, corrosion performance, their applications in hydrogen electrocatalysis, template-assisted deposition into recesses (aimed to obtain micro- and nanostructures) are also reviewed and mapped.

Modern trends in tungsten alloys electrodeposition with iron group metals

The kinetics of the induced codischarge of Mo with Ni in citrate-ammonia electrolytes was investigated by means of polarization and a.c. impedance measurements. Three potential ranges were considered. At low polarization, hydrogen evolution resulting from citrate reduction is the main reaction. The impedance plots exhibit a large capacitive loop with a small high frequency inflection characteristic of the development of a porous layer and a low frequency inductive feature. At intermediate polarization, the partial currents for Ni and Mo discharge increase in the same proportion; the hydrogen evolution is first constant and then rapidly decreases. Then a large low-frequency capacitive feature is observed on the impedance plots, whose size decreases with increasing polarization. At still higher polarization, the Mo discharge becomes increasingly controlled by diffusion which generates an additional capacitive loop. A reaction scheme is proposed which accounts for the polarization data and the major impedance features.

Mechanism of nickel-molybdenum alloy electrodeposition in citrate electrolytes

Electrochemical deposition of Ni–W alloys from ammonia–citrate electrolyte

Interactive, strong interbonding and highly electron conductive nonstoichiometric titanium suboxide catalytic supports, Magneli phases (TinO2n-1, on average Ti4O7), have been used in the electrocatalysis of hydrogen (HELR) and oxygen (OELR) electrode reactions with remarkable consequences and advanced achievements. The theory of hypo-hyper-d-interelectronic bonding of transition metal ions and atoms has been employed for selective ordered grafting and shown to stay in the core of the strong metal−support interaction (SMSI) in heterogeneous catalysis and electrocatalysis, and thereby the substantial cause for the improved synergistic activity of composite (electro)catalysts. The same fundament has been the thermodynamic basis for the thermal production of symmetric intermetallic Laves type phases of nanostructured electrocatalysts, in particular the ones with higher oxophilic properties of hypo-d-elements. Remarkably advanced in electrocatalytic activity, highly monatomically dispersed deposits of Pt upon ...

Susumu Akagi

Papers

Role of Iron-group Metals in the Induced Codeposition of Molybdenum from Aqueous Solution

Role of Iron-group Metals in the Induced Codeposition of Molybdenum from Aqueous Solution