Nanostructured magnetic CoNiP electrodeposits: structure-property relationships

Magnetic CoNiP thin film alloys were electrodeposited from chloride baths. The effects of solution composition, solution pH and film thickness on the magnetic properties, microstructure and phases of electrodeposited CoNiP films were investigated. Solution pH and NaH₂PO₂ concentration significantly influenced the magnetic properties of CoNiP deposits. These films when deposited from solutions of pH <2.25 exhibited soft magnetic properties, whereas from solutions of pH >2.25, hard magnetic deposits (H_C,⊥≈2000 Oe and H_C,//≈1000 Oe) were obtained. X-ray diffraction revealed hcp structure consisting of nanocrystalline grains (∼50 nm) with preferred (002) planes as deposit P content and solution pH increased.     

Influence of a cationic surfactant in the properties of cobalt-nickel electrodeposits

The effect of a cationic surfactant, dodecyltrimethylammonium chloride (DTAC) on CoNi electrodeposition process has been analysed. CoNi electrodeposition is greatly modified by the presence of the cationic surfactant in the bath. The DTAC modifies the initial stages of the deposition process and enhances the cobalt percentage in the deposits. Structure and morphology of the deposits are also modified, as the manner that magnetic properties of the electrodeposited films were affected as a consequence of the structural change. The presence of the surfactant in the bath causes changes on the CoNi structure from face-centred cubic (fcc) to close-packed hexagonal (hcp). DTAC incorporation into the deposits is a function of its concentration in the bath. Thus, it is important to be careful with the effects caused by the surfactant on deposits when it assists the particles insertion.     

Electrochemical preparation and magnetic study of Bi–Fe–Co–Ni–Mn high entropy alloy

A facile and efficient synthesis route for the preparation of Bi–Fe–Co–Ni–Mn high entropy alloy films has been firstly reported in this work. The surface of the film is close-grained and the nanorods with high aspect ratios can be obtained by potentiostatic electrodeposition in the DMF (N,N-dimethylformamide)–CH₃CN organic system. The effects of the deposition potential and the molar ratio of Bi(III) to transition metal ions (TMs(II)) in the organic system on the contents of Bi in the HE alloy were investigated. The annealed alloy structure is composed mainly of face-centered-cubic solid solution. The as-deposited alloys show soft magnetic behavior, and the annealed alloys exhibit hard magnetic properties.     

Magnetic properties of nanocrystalline iron group thin film alloys electrodeposited from sulfate and chloride baths

Systematic studies of iron group binary (NiCo and CoFe) and ternary (CoNiFe) thin film alloys relating their magnetic properties with film composition, grain size and the corresponding crystal structure were investigated. Anions influence current efficiencies, magnetic properties, surface morphology and phases of electrodeposited films. Higher current efficiencies in chloride baths compared to sulfate baths were observed for CoFe, NiCo and CoNiFe alloys. The higher deposition current efficiencies in chloride baths were attributed to a catalytic effect. Anion types in CoFe and CoNiFe thin film alloys influenced the microstructures and the resulting magnetic properties (coercivity and squareness). The microstructures of NiCo alloys depend on the deposit Co contents rather than anion types. The surface morphologies of CoFe, NiCo and CoNiFe thin films were independent of anion types. CoFe deposits exhibited relatively smooth surface morphology and turned into fine crystallites with increasing solution Fe⁺² concentration. NiCo deposits showed very smooth surface morphology. CoNiFe deposits had the surface morphology of polyhedral crystallites. The deposit Fe content in CoFe electrodeposits linearly increased with increasing solution Fe⁺² concentration for both chloride and sulfate baths. Similar linear behavior of deposit Co contents was observed in NiCo electrodeposits.     

Electrodeposition of zinc-cobalt alloy from a complexing alkaline glycinate bath

The influence of cobalt on the electrodeposition of zinc onto AISI 1018 steel was studied in weakly alkaline glycine solutions. Thermodynamic calculations were performed to construct predominance-zone diagrams to identify the stability of the zinc and cobalt glycine complexes, and experimental studies of electrochemical behavior and deposit properties were conducted. When zinc is present, cobalt deposition shifts to more negative potentials, producing ZnCo alloys. Two main reduction steps were observed for electrodeposition from the ZnCo bath: the first at low potentials was due to ZnCo electrodeposition. In the second, at more negative potentials, cobalt content in the deposit increased forming a range of intermediate phases, and the hydrogen-evolution reaction became significant. The presence of Co(II) in the bath modified the morphology of the deposits as well as reducing the faradaic metal-deposition efficiency. ZnCo-deposit morphology was modified by the applied current density as well as the metal composition of the coating. X-ray diffraction studies revealed that cobalt oxide or hydroxide is formed during ZnCo electrodeposition, indicating that an elevation of the interfacial pH plays a role in the alloy deposition process.     

Stability of the electrodeposition process for CoPt alloy formation

The stability of the process for electrodeposition of CoPt alloys from ammonium citrate electrolytes containing [Pt(NO₂)₂(NH₃)₂]⁰ as the source of Pt was studied. Voltammetric monitoring of the anodic oxidation of the electrolyte and deposition of CoPt on the cathode showed the effect of the changes of the nature of the Pt complex on the performance of the plating bath. Anodic oxidation of the Pt complex was shown to involve mainly the oxidation of and to some extent NH₃ ligands. The cathodic process is accompanied by reduction of free The reduction of this anion in the bound form is highly inhibited. In contrast, its oxidation at the anode proceeds almost as readily in the bound form as that in the free form.     

Residual stress in Ni-W electrodeposits

In the present work, the residual stress in Ni-W layers electrodeposited from electrolytes based on NiSO₄ and Na₂WO₄, is investigated. Citrate, glycine and triethanolamine were used as complexing agents, enabling complex formation between the nickel ion and tungstate. The results show that the type of complexing agent and the current efficiency have an influence on the residual stress. In all cases, an increase in tensile stress in the deposit with time after deposition was observed. Pulse plating could improve the stress level for the electrolyte containing equal amounts of citrate, glycine and triethanolamine (TEA) as complexing agent. An additive as 1,3,6 naphthalene trisulphonic acid which has a grain refining effect, and chloride, which enables dissolution of metal during the anodic cycle, reduced crack occurrence in the electrodeposits.     

Markov chain model of electrochemical alloy deposition

A new model of the electrochemical alloy deposition has been developed. It is based on the application of the finite Markov chain theory and is called the Markov chain model. The first analytical relationship between the alloy composition (ratio of mol fractions x_A/x_B and the metal ion concentrations in the electrolyte (mol fraction X_A and X_B can be deduced from the model.

     

Electrodeposition and properties of NiW films for MEMS application

The study reports basic investigations on the electroplating and properties of movable NiW microstructures with potential application in MEMS as temporary contacts for IC integration. The NiW layers have been deposited from nickel sulphamate electrolyte (MICROFAB NI-110, Enthone GmbH, Germany) with addition of citric acid stabilized tungsten complex at operating temperature of 50 °C and pH of about 3.0 using direct und pulse current plating regimes. The influence of the electroplating parameters, such as the tungsten concentration in the electrolyte and the current density on the tungsten content in the electroplated alloy, the surface structure and morphology of the deposits, as well as the mechanical properties of the alloy have been thoroughly investigated. The process allows deposition of 12 μm thick homogeneous NiW layers. An essential improvement of the mechanical properties such as micro hardness, elasticity and internal stress compared to that of the pure nickel has been achieved at comparatively low tungsten content of 3.2 wt.%.     

Electrodeposition of magnetic CoPd thin films: Influence of plating condition

The manufacture and properties evaluation of Co-based thin film alloys are extensively studied because of their magnetic properties that make them a critical element in many different applications and devices. Therefore the electrodeposition of CoPd alloy thin films was studied from a chloride bath containing glycine as additive. The cobalt content in the CoPd deposits varied from 6.4 to 94.0 at% by controlling the pH and [Co²⁺]/[Pd²⁺] ratio in the bath. Current efficiencies were independent of the solution pH and bath composition. The morphology of the deposits depended on the applied current density: current densities higher than 50 mA cm⁻² resulted in deposits with a typical cauliflower morphology. For current densities lower than 25 mA cm⁻² cracks was observed. The XRD measurements showed that all CoPd alloys were amorphous. The magnetic properties for CoPd alloys revealed that the coercivity (H_c) values ranged from 84 up to 555 Oe and the magnetic saturation (M_s) from 0 to 1.73 T.     

Properties of electrodeposited nanocrystalline Ni-B alloy films

The influence of the boron content on the various properties of nanocrystalline Ni-B alloy produced by electrodeposition was investigated. The considerable reduction in grain size was observed with increasing boron content. The internal stress was tensile and increased linearly with increasing boron content. Hardness increased up to 750 Hv at 2 at.% boron and then kept the value to 11 at.% boron for as-plated Ni-B coatings.The hardness of Ni-B films increased considerably due to the intermetallic Ni₃B precipitation by the heat treatment and maximum hardness of each coating increases with boron content. Wear resistance decreased with increasing the boron content because of high friction coefficient and brittle fracture of coating with high content of boron.     

CoPt nanoscale structures with different geometry prepared by electrodeposition for modulation of their magnetic properties

Different nanoscale structures of CoPt have been prepared by electrodeposition. Nonmagnetic materials were used in all cases, so that the substrates did not interfere in the magnetic properties of the deposits. Thin films of 200–300 nm-thick were obtained on glass/ITO substrates; nanoparticles of 150 nm of diameter were obtained over silicon; nanowires of 100–200 nm of diameter and 14 μm length were obtained by using polycarbonate membranes sputtered with Au. All deposited geometries had a fixed composition (68–71 wt.% Pt) and crystalline structure typical of Co-hcp, distorted due to platinum incorporation. A study of the magnetic properties of the different geometries was performed. Dramatic changes in magnetism have been detected, related to the shape of the nanostructures: nanowires presented the lowest coercivity (330–700 Oe), thin films had a coercivity value of 850 Oe, while nanoparticles had the highest coercivity (2040 Oe). These coercivity variations were caused by different anisotropy contributions, depending on the geometry. The corrosion resistance test has been performed to determine the viability of the prepared nanostructures, nanostructures with higher exposed surface area had increase tendency to oxidation.     

锡锌合金镀层的耐蚀性

锡锌合金镀层相对于钢铁基体为阳极性镀层，本文比较了不同含锌量的锡锌合金镀层、锌镀层和镉镀层在5％氯化钠溶液中的电位、中性盐雾试验以及二氧化硫加速腐蚀试验结果。锡锌合金镀层的耐蚀性优于锌、镉镀层，含锌25％（质量分数）的锡锌合金镀层的耐蚀性最高。     

Fe–Pt magnetic multilayers by electrochemical deposition

A series of magnetically soft/hard bilayers (BL) and multilayers with various sublayer thickness and configurations were prepared by electrodeposition from an alkaline solution using potential modulated waveforms and successive thermal annealing. In the as-deposited conditions the equiatomic layers grow with a face centered cubic FCC structure, and the Fe-rich ones with a body-centered cubic BCC structure. Annealing induces partial transformations of both structures to a L1₀ FCT phase. The coercivity of bilayers after annealing at or above 450 °C shows a maximum when the Fe-rich layer thickness is 10 nm; this configuration yields up to 45% increase in coercivity compared with single layers of 15 nm equiatomic Fe–Pt. Multilayer structures with fixed 5 or 10 nm Fe-rich layers show a coercivity enhancement similar to that of bilayers, suggesting that a bilayer structure is sufficient to facilitate magnetic hardening while minimizing the overall structure thickness. Either BLs or multilayers with 5 nm thick Fe-rich layers show a single phase magnetization behavior, behaving like a rigid magnet; those with 10 nm thick Fe-rich layers show instead a two stage magnetization switching, implying partial exchange decoupling.     

Electrodeposition of copper–magnetite magnetic composite films

Electrodeposition was demonstrated to be useful for the preparation of copper–magnetite magnetic composites. An acidic bath was tested for the incorporation of nanometric magnetite (Fe₃O₄) particles into an electrodeposited copper matrix. Cationic surfactant (dodecyltrimethylammonium chloride—DTAC) was used to keep particles suspended in the electrolyte as well as to assist magnetite incorporation. The influence of several parameters (bath temperature, deposition technique, stirring regimes and deposition conditions) on composites composition was analysed. Low stirring rate, moderate temperature (15 °C) and an applied magnetic field provided a greater incorporation of magnetite. Field emission scanning electron microscopy revealed magnetite distribution through the deposit thickness. Electrodeposited composites showed ferromagnetic behaviour. Magnetic force microscopy showed a magnetic response for the composites.     

Influence of magnetic field and gravity on the morphology of zinc fractal electrodeposits

We present a comprehensive study of growth of zinc fractal electrodeposits in a flat electrochemical cell considering the effects of applied voltage, electrode shape and thickness, ion concentration and applied magnetic field for both concentric and parallel electrode geometries. The effect of gravity is also considered in vertical cells. ‘Phase diagrams’ set out the variety of morphologies achievable at different voltages and concentrations for both electrode geometries. Electron microscope analysis indicates that the deposits are built from individual micron-sized crystallites. The system is modelled numerically using a number of modifications to the diffusion-limited aggregation (DLA) model to introduce migration and convection. Experimentally observed morphologies are reproduced numerically for horizontal and vertical, concentric and parallel electrode cells. Each occupied numerical site represents not an individual atom, but the point of nucleation and growth of an individual zinc crystallite containing ∼10¹⁰ atoms.     

Effects of electrodeposition potential on the corrosion properties of bis-1,2-[triethoxysilyl] ethane films on aluminum alloy

Bis-1,2-[triethoxysilyl] ethane (BTSE) films were prepared on 2024-T3 alloys by using potentiostatic method for corrosion protection. This work mainly investigated the effects of electrodeposition potential on the corrosion properties of silane films. Films prepared at cathodic potentials display an improvement in corrosion inhibition properties, while those prepared at anodic potentials present the deterioration of protectiveness. In the case of cathodic deposition, when the potential shifts negatively from the open-circuit potential (OCP), corrosion protection of the obtained films initially increases and then decreases, with the optimal deposition potential at −0.8 V/SCE. As indicated in scanning electron microscopy (SEM) images, films deposited at the optimum potential present the most uniform and compact morphologies. In addition, steady-state polarization and current-time curves have been also recorded on Al alloys in BTSE solutions during the deposition, respectively.     

A ZnO thin-film driven microcantilever for nanoscale actuation and sensing

Zinc oxide (ZnO) thin film as a piezoelectric material for microelectromechanical system (MEMS) actuators and sensors was evaluated. ZnO thin films were deposited using radio frequency (RF) magnetron sputtering. Process parameters such as gas ratio, working pressure, and RF power were optimized for crystalline structure. The ZnO thin films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Good quality of ZnO thin films was further confirmed by a high transverse piezoelectric coefficient d ₃₁. A microcantilever was then designed, fabricated, and characterized. Design formulas of resonant frequency, actuation, and sensing sensitivities were derived. The resonant frequency was determined by an impedance analyzer. Tip deflection on nanometer level was demonstrated with the cantilever used as an actuator. The actuation sensitivity was found to be 12.2 nm/V. As a sensor, the cantilever was calibrated against a reference accelerometer. The sensing sensitivity was characterized to be 46 mV/g. The characterization results were compared with design specifications. The differences were caused mainly by thickness control in etching. This study showed that ZnO is a promising piezoelectric material for MEMS actuators and sensors in terms of excellent process compatibility and good piezoelectric performance.     

Bi electrodeposition under magnetic field

Bi was galvanostatically electrodeposited in a hydrochloric acid solution in the presence and absence of a 0.5 T field. The effects of magnetohydrodynamics (MHD) convection were focused on the concentration overpotential as well as the current efficiency. The morphological and microstructural variation of electrodeposited Bi thin film was also investigated. Dendritic growth enhanced at higher current density was considerably suppressed by superimposition of a 0.5 T field, while the effect on the crystal microstructure was not confirmed.     

Electrodeposition of low-stress high magnetic moment Fe-rich FeCoNi thin films

Low-stress high magnetic moment Fe-rich FeCoNi thin films were electrodeposited from acidic chloride baths to investigate the effects of the deposition temperature, solution pH and l-ascorbic acid on film morphology, crystal structure, magnetic properties and film stress. As the deposition temperatures were increased from 23 to 70 °C, the film stress in the FeCoNi films decreased from 260 to 28 MPa at pH 1.5 in the absence of l-ascorbic acid. The film stresses further decreased to approximately 0 MPa when solution pH was increased to 2.15. However, the plating baths became unstable at pH higher than 2.15 because of precipitate formation. On increasing the deposition temperature, the deposit Fe content in the FeCoNi thin films decreased from 83 to 72 atomic percent (at.%) and the Co content increased from 17 to 27 at.%. In the case of the deposit Ni content, it slightly increased with increasing deposition temperature. From the XRD analysis, the change of the preferred planes from the bcc (1 1 0) to bcc (2 0 0) with increasing deposition temperatures was observed. It is believed that the changes in the grain size and the incorporation of impurities during electrodeposition influenced the stress of the FeCoNi films. The presence of l-ascorbic acid enhanced the stability of the baths at high pH meanwhile reducing current efficiencies. With increasing deposit Ni content, magnetic saturation (B_S) and parallel squareness slightly decreased and increased, respectively.