H. Cesiulis

Electrodeposition and properties of NiW, FeW and FeNiW amorphous alloys. A comparative study

Thin, micrometre-thick layers of a new amorphous alloy, FeNiW, have been obtained by electrodeposition. The iron mole fraction, [Fe]/([Fe]+[Ni]), can be changed from 0 to 1, however, the best properties under constant current deposition are obtained for the mole fraction near 0.5. The key, needed properties of the FeW and NiW alloys were transferred to the FeNiW alloy, while the unwanted properties of the two-component alloys were eliminated. The new alloy is hard (1040 HV, for equal percentage of Fe and Ni), smooth, of nice appearance, and of good adherence to both steel and copper. Pulse electroplating further improves the smoothness and uniformity of the electrodeposited layers and allows one to obtain higher tungsten content of up to 35 at.%. X-ray diffractometry, EDX, and chronopotentiometry were used to characterise the new material. The influence of pH and the ratio of concentrations of Fe and Ni in the plating solution was examined.

Modern Trends in Tungsten Alloys Electrodeposition with Iron Group Metals 1

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.

Formation of Nanofibers in Thin Layers of Amorphous W Alloys with Ni, Co, and Fe Obtained by Electrodeposition

Scanning tunneling microscopy (STM) experiments supported by scanning electron microscopy (SEM) pictures and X-ray diffractometry indicate that all electrodeposited amorphous alloys of tungsten with the iron-group metals are in fact of nanofibrous structure. It has been shown that the nanofibers grow perpendicularly to the copper support and, as the thickness of the alloy microlayer grows, group into well-packed bundles. The thickness of the fibers, for 79:21 Ni-W and 75:25 Co-W determined from the STM images, equals 50 A. This number correlates well with the average grain size (40-55 A) calculated, using the Scherrer formula, from the peak broadening seen at the X-ray spectrograms.

The role of mass transfer in the formation of the composition and structure of CoW coatings electrodeposited from citrate solutions

The effect of the hydrodynamic conditions on the electrode process’s rate and the composition and structure of cobalt-tungsten coatings electrodeposited from citrate solutions is studied. The rate of the electrode process depends on the hydrodynamic conditions. However, the electrochemical impedance data do not reveal the presence of slow diffusion processes. The analysis of the electrochemical impedance spectra shows the occurrence of slow adsorption processes, such as an intermediate adsorption stage. It is assumed that the hydrodynamic conditions have a strong effect on the surface state rather than on the mass transfer from the solution’s bulk to the electrode.

Electrodeposition of CoMo and CoMoP alloys from the weakly acidic solutions

INTRODUCTIONThe procedures for the electrodeposition of CoMoalloys have been intensively developed because thesealloys possess premium hardness, high melting point,reasonable resistance to corrosion and wear of thesecoatings [1–5]. Some of them also show catalyticproperties and might be used for hydrogen generation[6–12]. Introduction of 5 to 11 wt % molybdenum intocobalt electrodeposits leads to obtaining of materialswith good lowcoercitivity properties [13–16]. Themagnetic and mechanical properties of CoMo alloysmake them promising for application in the microelectronics, e.g. in microelectromechanical systems(MEMS) applications. The electrochemical forming ofMEMS have many advantages over other physical processes, such as a room temperature operation, lowenergy requirements, fast deposition rates, fairly uniform deposition over complicated shapes, low cost,simple scaleup and easily maintained equipment.MEMS are integrated micro devices or systems combining electrical and mechanical components fabricated using integrated circuit (IC) compatible batchprocessing techniques and range in size from micrometers to millimeters. The properties of the deposit can be“tailored” by controlling solution compositions anddeposition parameters [17]. In this case the depositionprocesses have to be compatible with other MEMS processing operations. The magnetic deposits must havegood adhesion, low stress, corrosion resistance andthermal stability at operating temperatures withoutcontaminating ICs. In addition, the stresses in deposit isimportant factor, because may result cracks or deformations of electroformed MEMS devices.Several types of baths are used for the electrodeposition of Co–Mo films. Co–Mo alloys are depositedfrom citrate and citrate–ammonium electrolytes

Co-W nanocrystalline electrodeposits as barrier for interconnects

This study was performed in order to investigate a possibility to obtain Co-W microbumps via electrochemical routes, because this alloy recently has gained attraction as a novel barrier against copper diffusion. In order to be applied in flip-chip technology, barrier layers should be void-free and uniformly deposited on the entire area of a die to ensure high reliability and high performance of wafer bump-solder interface. To meet these requirements, a set of potentiostatic and galvanostatic electrodeposition was carried out from a citrate electrolyte, at pH 5 and at room temperature. The tests done confirm that void-free Co-W bumps with a uniform tungsten content along the bump can be obtained by potentiostatic and galvanostatic electrodeposition. Successful electrodeposition of Cu/Co-W/Sn layers with good adhesion between them and uniformity on the entire array of bumps also was obtained. The XPS data confirm that electrodeposited Co-W layers can act as a good barrier between Sn and Cu.

Cobalt-Molybdenum-Phosphorus Alloys: Electroplating and Corrosion Properties

The relation between the composition, morphology, and corrosion resistance of the electrolytic CoMoP coatings plated at various current densities from citrate baths containing ammonia or hydrazine and various amounts of sodium hypophosphite is studied. Phosphorus was included in the coatings as a result of the electrochemical reduction of hypophosphite ions. Ternary Co-Mo-P alloys containing up to 26 at % Mo and up to 3 at % P were electroplated. Coatings of the highest quality were obtained from a bath containing hydrazine admixture at a temperature of 50°C. Corrosion resistance of CoMoP coatings increases with an increase in the Mo content and a certain decrease in the phosphorus amount in the deposit. The best protective properties were demonstrated by coatings obtained at higher concentrations of sodium hypophosphite and high deposition current densities when CoMoP alloys containing 23 ± 2 at % Mo and up to 1.5 at % P were formed.

Electrodeposition and corrosion behaviour of nanostructured cobalt-tungsten alloys coatings

Theoretical and practical studies of tungsten alloys with iron group metals continue to be carried out because of their unique combination of tribological, magnetic and electrical properties. The electrodeposition of Co–W alloys was performed in a citrate–borate solution at pH 5–8; t = 20 and 60°C. The electrochemical corrosion was studied in 0.01 M H2SO4, and stainless steel was selected as a substrate. For the mapping of the properties alloy deposits having various contents of W (2.4–30 at.-%) and crystallite size varying from polycrystalline (<60 nm) to ‘amorphous-like’ (2–5 nm) were prepared. Co–W alloys possessing the highest corrosion resistance should contain 17–24 at.-% of W, i.e. have a structure close to intermetallic phase Co3W. The corrosion occurs via an intermediate adsorbed stage by forming oxygen-containing compounds; the estimated thickness of the adsorbed layer varies in the range 0–1.6 Å.

Tribological behaviour of mineral and rapeseed oils containing iron particles

Purpose – The purpose of this paper is to investigate the tribological behaviour of commercially available SAE 10 mineral and rapeseed oils containing Fe particles synthesized directly in the oil phase. Design/methodology/approach – Sub-micron Fe particles (50-340 nm) were synthesized by wet chemical reduction reaction of FeSO4 by sodium borohydride in the rapeseed and mineral oils in the presence of surfactant: block copolymer (ENB 90R4) or oxyethylated alcohol (OS-20). A four-ball wear tribometer was used to investigate the tribological properties of mineral and rapeseed oil: coefficient of friction (COF), wear scar diameter and wear loss. Viscosity measurements of oil solutions and determination of synthesized Fe particles size were performed as well. Findings – The presence of Fe particles (0.1 weight per cent) in the rapeseed and mineral oils caused the little change in the COF but resulted in marked improvement of anti-wear property. The oils containing Fe particles with slightly higher viscosity ar...

Influence of fluor‐oligomers on the structural and tribological properties of steel surface at the rolling friction

Purpose – The purpose of this paper is to investigate the influence of fluor‐oligomeric coat on the mechanical properties of steel surface, as well as the chemical interaction of fluor‐oligomeric films with surface and theoretical‐phenomenological interpretation of structural processes in friction surface.Design/methodology/approach – Four groups of specimens were studied: two groups of specimens without any wear tests – initial steel specimen as control version and a specimen which was ten times coated by fluor‐oligomer, and two groups of specimens, which were tribologically tested for one million cycles – without any coating and coated specimens. Closed kinematical profile scheme roller‐roller of steel 45 was chosen for tribological tests. Wear of friction surface after those tests was investigated. The interaction between fluor‐oligomer and iron was studied by means of Mossbauer spectroscopy. The micro‐hardness of matrix was also measured.Findings – Affecting the surface of steel by the fluor‐oligomer ...