Microstructural and electrochemical properties of Ti-doped Al<Subscript>2</Subscript>O<Subscript>3</Subscript> coated LiCoO<Subscript>2</Subscript> films

We studied the microstructural and electrochemical properties of Ti-doped Al₂O₃ (Ti-Al₂O₃) coated LiCoO₂ thin films depending on the Ti composition. The 1.27 at.% Ti-Al₂O₃ coated films had an amorphous structure with better conductivity than that of pure Al₂O₃ films. The Ti-Al₂O₃ coating layer effectively suppressed the dissolution of Co and the formation of lower Li conductivity SEI films at the interface between the LiCoO₂ film and electrolyte. The Ti-Al₂O₃ coating improved the cycling performance and capacity retention at high voltage (4.5 V) of the LiCoO₂ films. The Ti-Al₂O₃ coated LiCoO₂ films showed better electrochemical properties than did the pure Al₂O₃ coated LiCoO₂ films. These results were closely related to the enhanced Li-conductivity and interfacial quality of the Ti-Al₂O₃ film.     

Surface modification of LiNi<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript> with Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> for lithium ion batteries

Cr 2 O 3-coated LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathode materials were synthesized by a novel method. The structure and electrochemical properties of prepared cathode materials were measured using X-ray diffraction (XRD), scanning electron microscopy (SEM), charge-discharge tests, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The measured results indicate that surface coating with 1.0 wt% Cr 2 O 3 does not affect the LiNi 1/3 Co 1/3 Mn 1/3 O 2 crystal structure (α-NaFeO 2 ) of the cathode material compared to the pristine material, the surfaces of LiNi 1/3 Co 1/3 Mn 1/3 O 2 samples are covered with Cr 2 O 3 well, and the LiNi 1/3 Co 1/3 Mn 1/3 O 2 material coated with Cr 2 O 3 has better electrochemical performance under a high cutoff voltage of 4.5 V. Moreover, at room temperature, the initial discharging capacity of LiNi 1/3 Co 1/3 Mn 1/3 O 2 material coated with 1.0 wt.% Cr 2 O 3 at 0.5C reaches 169 mAh·g 1 and the capacity retention is 83.1% after 30 cycles, while that of the bare LiNi 1/3 Co 1/3 Mn 1/3 O 2 is only 160.8 mAh·g 1 and 72.5%. Finally, the coated samples are found to display the improved electrochemical performance, which is mainly attributed to the suppression of the charge-transfer resistance at the interface between the cathode and the electrolyte.     

Structure and electric property comparison between Ge nanoclusters embedded in Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/ZrO<Subscript>2</Subscript>

Metal-insulator-semiconductor (MIS) structures containing Ge nanocrystals embedded in both Al₂O₃ and ZrO₂/Al₂O₃ are fabricated by an ultra-high vacuum electron-beam evaporation method. Secondary ion mass spectroscopy (SIMS) results indicate that Ge embedded in Al₂O₃ diffuses towards the surface of the Al₂O₃ layer after annealing at 800°C in N₂ ambient for 30 min. Ge embedded in ZrO₂/Al₂O₃ is stable, thus inducing less leakage current. Capacitance voltage studies indicate that annealing can effectively passivate the negatively charged trapping centers. Memory effect of the Ge nanoclusters is verified by hysteresis in the C-V curves in the Al₂O₃/Ge+Al₂O₃/Al₂O₃ and ZrO₂/Ge+Al₂O₃/Al₂O₃ samples. This article is based on a presentation in “The 7th Korea-China Workshop On Advanced Materials” organized by the Korea-China Advanced Materials Cooperation Center and the China-Korea Advanced Materials Cooperation Center, held at Ramada Plaza Jeju Hotel, Jeju Island, Korea on August 24–27, 2003.     

Effect of a surface treatment for LiNi<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript> cathode material in lithium secondary batteries

LiNi_1/3Co_1/3Mn_1/3O₂ cathode material was surface-treated to improve its electrochemical performance. Al₂O₃ nanoparticles were coated onto the surface of LiNi_1/3Co_1/3Mn_1/3O₂ powder using a sol-gel method. The as-prepared Al₂O₃ nano-particle was identified as the cubic structure of Al₂O₃. XRD showed that the LiNi_1/3Co_1/3Mn_1/3O₂ structure was not affected by the Al₂O₃ coating. With a coating of 3 wt.% Al₂O₃ on LiNi_1/3Co_1/3Mn_1/3O₂, the cyclic-life performance and rate capability were improved. However, heavier coatings (5 wt.%) on LiNi_1/3Co_1/3Mn_1/3O₂ resulted in a considerable decrease of the discharge capacity and rate capability. The thermal stability of LiNi_1/3Co_1/3Mn_1/3O₂ materials was greatly improved by the 3 wt.% Al₂O₃ coating.     

Microstructure Characterization of the FeAl<Subscript>2</Subscript>O<Subscript>4</Subscript>-Based Nanostructured Composite Coating Synthesized by Plasma Spraying Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/Al Powders

The microstructure of the coating prepared by reactive plasma spraying Fe₂O₃/Al composite powders was characterized by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results indicated that the coating exhibited nanostructured microstructure which consisted of FeAl₂O₄, Fe or Fe solid solution, Al₂O₃ and a little FeAl. In the composite coating, spherical Fe particles (tens of nanometers to hundreds of nanometers) were distributed uniformly within the equiaxed and columnar nanograins FeAl₂O₄ matrix. There were two kinds of Al₂O₃ phases present in the composite coating. One kind was nano-sized Al₂O₃ particles uniformly dispersed within the matrix, forming eutectic structure of (FeAl₂O₄ + γ-Al₂O₃); the other was 1-1.5 μm Al₂O₃ particles embedded individually within the matrix. The composite coating had higher toughness than the conventional microstructured Al₂O₃ coating.     

Effects of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Nano-Particles on Corrosion Performance of Plasma Electrolytic Oxidation Coatings Formed on 6061 Aluminum Alloy

Corrosion resistance improvement of plasma electrolyte oxidation coatings on 6061 aluminum alloy in silicate electrolyte containing Al₂O₃ nano-particles was studied, with particular emphasis on the microstructure, coating growth, and corrosion behavior in 3.5 wt.% NaCl solution. The microstructure of coatings, their thickness, and phase composition were characterized using scanning electron microscopy and x-ray diffraction. All characterization data showed that the maximum coating thickness and lowest amount of porosity were obtained in a low concentration of KOH, a high concentration of Na₂SiO₃, and moderate concentration of Al₂O₃ nano-particles in the electrolyte. This combination describes the optimum plasma electrolytic oxidation electrolyte, which has the best conductivity and oxidizing state, as well as the highest incorporation of electrolyte components in the coating growth process. On the other hand, incorporation and co-deposition of Al₂O₃ nano-particles were more pronounced than SiO₃ ^2? ions in some level of molar concentration, which is due to the higher impact of electron discharge force on the adsorption of Al₂O₃ nano-particles. The electrochemical results showed that the best protective behavior was obtained in the sample having a coat with the lowest porosity and highest thickness.     

Microstructure and Electron Energy-Loss Spectroscopy Analysis of Interface Between Cu Substrate and Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Film Formed by Aerosol Deposition Method

Aerosol deposition method is a technique to form dense films by impacting solid particles on a substrate at room temperature. To clarify the bonding mechanism between AD films and substrates, TEM observation and electron energy-loss spectroscopy (EELS) analysis of the interface between Al₂O₃ AD films and Cu substrates were conducted. The Al₂O₃ film was directly adhered to the Cu substrate without any void or crack. The film was composed of randomly oriented α-Al₂O₃ crystal grains of about 10-20 nm large. At the Al₂O₃/Cu interface, the lattice fringes of the film were recognized, and no interfacial layer with nanometer-order thickness could be found. EELS spectra near O-K edge obtained at the interface had the pre-peak feature at around 528 eV. According to previously reported experiments and theoretical calculations, this suggests interactions between Cu and O in Al₂O₃ at the interface. It is inferred that not only the anchoring effect but also the ionic bonding and covalent bonding that originates from the Cu-O interactions contribute to the bonding between Al₂O₃ AD films and Cu substrates.     

Synthesis and electrochemical performance of YF<Subscript>3</Subscript>-coated LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> cathode materials for Li-ion batteries

Spinel LiMn₂O₄ cathodes were coated with 1 mol% YF₃. X-ray diffraction (XRD) analyses showed that Y and/or F did not enter the lattice of the LiMn₂O₄ crystal. Transmission electron microscopy (TEM) showed that a compact YF₃ layer of 5–20 nm in thickness was coated onto the surface of LiMn₂O₄ particles. Scanning electron microscopy (SEM) observation showed that the YF₃ coating caused the agglomeration of LiMn₂O₄ particles. The cycling test demonstrated that the YF₃ coating can improve the electrochemical performance of LiMn₂O₄ at both 20 and 55°C. Moreover, YF₃-coated LiMn₂O₄ exhibited an improved rate capability compared with the uncoated one at high rates over 5C. The immersion test in electrolytes showed that YF₃-coated LiMn₂O₄ is more erosion resistant than the uncoated one.     

Corrosion behaviour of polycrystalline Nb<Subscript>2</Subscript>O<Subscript>5</Subscript> thin films and its size effects

This study examines the effect of film thickness ranging from 230 to 404 nm on the corrosion resistance of Nb₂O₅ thin films grown by chemical solution deposition. The films were characterized to obtain the relationships between the deposition parameters and the most relevant physical properties (structural, surface morphology and corrosion resistance). From X-ray diffraction and XPS analyses we can conclude that the films were stoichiometric Nb₂O₅ and crystalline. The internal strain and morphology of the film changes as the number of layers increases indicating a thickness dependent grain size. The surface roughness, corrosion resistance were also affected by the film thickness. Electrochemical impedance spectroscopy (EIS) shows that the thicker film have higher passive and charge transfer resistance than the control samples. These results coating layer of Nb₂O₅ improves the corrosion resistance on an API 5L X80 steel alloy due to the formation of a film on the surface.     

Fabrication and Properties of Plasma-Sprayed Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/ZrO<Subscript>2</Subscript> Composite Coatings

Al₂O₃ /xZrO₂ (where x = 0, 3, 13, and 20 wt.%) composite coatings were deposited onto mild steel substrates by atmospheric plasma spraying of mixed α-Al₂O₃ and nano-sized monoclinic-ZrO₂ powders. Microstructural investigation showed that the coatings comprised well-separated Al₂O₃ and ZrO₂ lamellae, pores, and partially molten particles. The coating comprised mainly of metastable γ-Al₂O₃ and tetragonal-ZrO₂ with trace of original α-Al₂O₃ and monoclinic-ZrO₂ phases. The effect of ZrO₂ addition on the properties of coatings were investigated in terms of microhardness, fracture toughness, and wear behavior. It was found that ZrO₂ improved the fracture toughness, reduced friction coefficient, and wear rate of the coatings.     

Dielectric properties of Ta<Subscript>2</Subscript>O<Subscript>5</Subscript> thin films deposited onto Ti and TiO<Subscript>2</Subscript> layer

The present study describes the dielectric properties of RF sputtered Ta₂O₅ thin films as a function of the buffer layer and annealing condition. The buffer layers were Ti or TiO₂. And the thin film was annealed in various conditions. The X-ray pattern results showed that the phase of the RF sputtered Ta₂O₅ thin films was amorphous and this state was kept stable to RTA (rapid thermal annealing) even at 700°C. Measurements of the electrical and dielectric properties of the reactive sputtered Ta₂O₅ fabricated in two simple metal insulator semiconductor (MIS) structures, (Cu/Ta₂O₅/Ti/Si/Cu and Cu/Ta₂O₅/TiO₂/Si/Cu) indicated that the amorphous Ta₂O₅ grown on Ti possesses a high dielectric constant (30–70) and high leakage current (10⁻¹–10⁻⁴ A/cm²), whereas a relatively low dielectric constant (−10) and low leakage current (−10⁻¹⁰ A/cm²) were observed in the amorphous Ta₂O₅ deposited on the TiO₂ buffer layer. In addition, the leakage current mechanisms of the two amorphous Ta₂O₅ thin films were investigated by plotting the relation of current density (J) vs. applied electric field (E). The Ta₂O₅/Ti film exhibited three dominant conduction mechanism regimes contributed by the Ohmic emission at low electrical field, by the Schottky emission at intermediate field and by the Poole-Frenkel emission at high field. In the case of Ta₂O₅/TiO₂ film, the two conduction mechanisms, the Ohmic and Schottky emissions, governed the leakage current density behavior. The conduction mechanisms at various electric fields applied were related to the diffusion of Ta, Ti and O, followed by the creation of vacancies, in the rapid thermal treated capacitors.     

Cold spray of SiC and Al<Subscript>2</Subscript>O<Subscript>3</Subscript> with soft metal incorporation: A technical contribution

Al + SiC, Al + Al₂O₃ composites as well as pure Al, SiC, and Al₂O₃ coatings were prepared on Si substrates by the cold gas dynamic spray process (CGDS or cold spray). The powder composition of metal (Al) and ceramic (SiC, Al₂O₃) was varied into 1:1 and 10:1 wt.%, respectively. The propellant gas was air heated up to 330 °C and the gas pressure was fixed at 0.7 MPa. SiC and Al₂O₃ have been successfully sprayed producing coatings with more than 50 μm in thickness with the incorporation of Al as a binder. Also, hard ceramic particles showed peening effects on the coating surfaces. In the case of pure Al metal coating, there was no crater formation on hard Si substrates. However, when Al mixed with SiC and Al₂O₃, craters were observed and their quantities and sizes depended on the composition, aggregation and size of raw materials.     

Corrosion Behavior and Microhardness of Ni-P-SiO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Nano-composite Coatings on Magnesium Alloy

In the present work, nano-composites of Ni-P-SiO₂-Al₂O₃ were coated on AZ91HP magnesium alloy. The surface morphology of the nano-composite coating was studied by field emission scanning electron microscopy (FESEM). The amount of SiO₂ in the coating was determined by energy-dispersive analysis of x-ray (EDX), and the crystalline structure of the coating was examined by x-ray diffractometer (XRD). All the experiments concerning the corrosion behavior of the coating carried out in 3.5 wt.% NaCl solution and evaluated by electrochemical impedance spectroscopy (EIS) and polarization technique. The results showed that an incorporation of SiO₂ and Al₂O₃ in Ni-P coating at the SiO₂ concentration of 10 g/Land 14 g/LAl₂O₃ led to the lowest corrosion rate (i _corr = 1.3 µA/cm²), the most positive E _corr and maximum microhardness (496 VH). Furthermore, Ni-P-SiO₂-Al₂O₃ nano-composite coating possesses less porosity than that in Ni-P coating, resulting in improving corrosion resistance.     

Synthesis and characterization of Li<Subscript>1.3</Subscript>Al<Subscript>0.3</Subscript>Ti<Subscript>1.7</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>-coated LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> by wet chemical route

Li_1.3Al_0.3Ti_1.7(PO₄)₃-coated LiMn₂O₄ was prepared by wet chemical route. The phase, surface morphology, and electrochemical properties of the prepared powders were characterized by X-ray diffraction, scanning electron micrograph, and galvanostatic charge-discharge experiments. Li_1.3Al_0.3Ti_1.7(PO₄)₃-coated LiMn₂O₄ has similar X-ray diffraction patterns as LiMn₂O₄. The corner and border of Li_1.3Al_0.3Ti_1.7(PO₄)₃-coated LiMn₂O₄ particles are not as clear as the uncoated one. The two powders show similar values of lithium-ion diffusion coefficient. When cycled at room temperature and 55°C for 40 times at the charge-discharge rate of 0.2C, Li_1.3Al_0.3Ti_1.7(PO₄)₃-coated LiMn₂O₄ shows the capacity retentions of 98.2% and 93.9%, respectively, which are considerably higher than the values of 85.4% and 79.1% for the uncoated one. Both the capacity retention differences between Li_1.3Al_0.3Ti_1.7(PO₄)₃-coated LiMn₂O₄ and LiMn₂O₄ cycling at room temperature and 55°C become larger with the increase of charge-discharge rate. When the charge-discharge rate reaches 2C, the capacity retention of LATP-coated LiMn₂O₄ becomes 8.4% higher than the uncoated LiMn₂O₄ for room temperature cycling, and it becomes 11.1% higher than the latter when cycled at 55°C.     

Up-Date of a Thermodynamic Database of the ZrO<Subscript>2</Subscript>-Gd<Subscript>2</Subscript>O<Subscript>3</Subscript>-Y<Subscript>2</Subscript>O<Subscript>3</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> System for TBC Applications

The thermodynamic database of the ZrO₂-Gd₂O₃-Y₂O₃-Al₂O₃ system is up-dated taking into account new data on lattice stabilities of ZrO₂, Gd₂O₃ and Y₂O₃ and heat capacity measurements for the monoclinic phase Gd₄Al₂O₉ and phase with garnet structure Gd₃Al₅O₁₂. New data for the heat capacities of Gd₂Zr₂O₇ (pyrochlore) and GdAlO₃ (perovskite) as well as on the enthalpy of formation of fluorite solid solutions (Zr_1−x Gd _x )O_2−x/2 were found to be in good agreement with calculated results. In comparison with the previous assessment, taking into account new experimental data resulted in a change of the melting character of the Gd₄Al₂O₉ phase from a peritectic one to a congruent one in the Gd₂O₃-Al₂O₃ system. Correspondently, in the ternary system ZrO₂-Gd₂O₃-Al₂O₃, the melting character of the three-phase assemblage Gd₂O₃ (B), Gd₄Al₂O₉ and GdAlO₃ changed from eutectic to transition type U. The T ₀-lines for T/M and F/T diffusionless transformations and driving force of partitioning to equilibrium assemblage T + F were calculated in the ZrO₂-Gd₂O₃-Y₂O₃ system.     

Development and Application of Binary Suspensions in the Ternary System Cr<Subscript>2</Subscript>O<Subscript>3</Subscript>-TiO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> for S-HVOF Spraying

Compositions in the system Cr₂O₃-TiO₂-Al₂O₃ are among the most used ceramic materials for thermally sprayed coating solutions. Cr₂O₃ coatings present good sliding wear resistance; Al₂O₃ coatings show excellent insulation behavior and TiO₂ striking corrosion properties. In order to combine these properties, coatings containing more than one oxide are highly interesting. The conventional spraying process is limited to the availability of binary feedstock powders with defined compositions. The use of suspensions offers the opportunity for tailor-made chemical compositions: within the triangle of Cr₂O₃-TiO₂-Al₂O₃, each mixture of oxides can be created. Criteria for the selection of raw materials as well as the relevant aspects for the development of binary suspensions in the Cr₂O₃-TiO₂-Al₂O₃ system to be used as feedstock for thermal spraying are presented. This formulation of binary suspensions required the development of water-based single-oxide suspensions with suitable behavior; otherwise, the interaction between the particles while mixing could lead up to a formation of agglomerates, which affect both the stability of the spray process and the coating properties. For the validation of this formulation procedure, binary Cr₂O₃-TiO₂ and Al₂O₃-TiO₂ suspensions were developed and sprayed using the S-HVOF process. The binary coatings were characterized and discussed in terms of microstructure and microhardness.     

Synthesis and electrochemical performances of LiCoO<Subscript>2</Subscript> recycled from the incisors bound of Li-ion batteries

A new LiCoO₂ recovery technology for Li-ion batteries was studied in this paper. LiCoO₂ was peeled from the Al foil with dimethyl acetamide (DMAC), and then polyvinylidene fluoride (PVDF) and carbon powders in the active material were eliminated by high temperature calcining. Subsequently, Li₂CO₃, LiOH·H₂O and LiAc·2H₂O were added into the recycled powders to adjust the Li/Co molar ratio to 1.00. The new LiCoO₂ was obtained by calcining the mixture at 850°C for 12 h in air. The structure and morphology of the recycled powders and resulting samples were studied by XRD and SEM techniques, respectively. The layered structure of LiCoO₂ synthesized by adding Li₂CO₃ is the best, and it is found to have the best characteristics as a cathode material in terms of charge-discharge capacity and cycling performance. The first discharge capacity is 160 mAh·g⁻¹ between 3.0–4.3 V. The discharge capacity after cycling for 50 times is still 145.2 mAh·g⁻¹.     

Effect of Nano-Si<Subscript>3</Subscript>N<Subscript>4</Subscript> Additives and Plasma Treatment on the Dry Sliding Wear Behavior of Plasma Sprayed Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-8YSZ Ceramic Coatings

In this paper, the effect of nano-Si₃N₄ additives and plasma treatment on the wear behavior of Al₂O₃-8YSZ ceramic coatings was studied. Nano-Al₂O₃, nano-8YSZ (8 wt.% Y₂O₃-stabilized ZrO₂) and nano-Si₃N₄ powders were used as raw materials to fabricate four types of sprayable feedstocks. Plasma treatment was used to improve the properties of the feedstocks. The surface morphologies of the ceramic coatings were observed. The mechanical properties of the ceramic coatings were measured. The dry sliding wear behavior of the Al₂O₃-8YSZ coatings with and without Si₃N₄ additives was studied. Nano-Si₃N₄ additives and plasma treatment can improve the morphologies of the coatings by prohibiting the initiation of micro-cracks and reducing the unmelted particles. The hardness and bonding strength of AZSP (Al₂O₃-18 wt.% 8YSZ-10 wt.% Si₃N₄-plasma treatment) coating increased by 79.2 and 44% compared to those of AZ (Al₂O₃-20 wt.% 8YSZ) coating. The porosity of AZSP coating decreased by 85.4% compared to that of AZ coating. The wear test results showed that the addition of nano-Si₃N₄ and plasma treatment could improve the wear resistance of Al₂O₃-8YSZ coatings.     

Studies on Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/ZrO<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> high K gate dielectrics applied in a fully depleted SOI MOSFET

Al₂O₃/ZrO₂/Al₂O₃ gate stacks were prepared on ultrathin SOI (Silicon on insulator) substrates by ultrahigh vacuum electron beam evaporation and post-annealed in N₂ at 450°C for 30 min. Three clear nanolaminate layered structure of Al₂O₃(2.1 nm)/ZrO₂(3.5 nm)/Al₂O₃(2.3 nm) was observed with a high-resolution cross-sectional transmission electron microscope (HR-XTEM). High frequency capacitance voltage (C-V) characteristics of a fully depleted (FD) SOI MOS capacitor at 1 and 5 MHz were studied. The minority carriers determine the high frequency C-V properties, which is opposite to the case of bulk MOS capacitors. The series resistance of the SOI substrate is found to be the determinant factor of the high frequency characteristics of FD SOI MOS capacitors. This article is based on a presentation in “The 7th Korea-China Workshop on Advanced Materials” organized by the Korea-China Advanced Materials Cooperation Center and the China-Korea Advanced Materials Cooperation Center, held at Ramada Plaza Jeju Hotel, Jeju Island, Korea on August 24≈27, 2003.     

Effect of Surface Roughness and Structure Features on Tribological Properties of Electrodeposited Nanocrystalline Ni and Ni/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Coatings

Metal matrix composite coatings obtained by electrodeposition are one of the ways of improving the surfaces of materials to enhance their durability and properties required in different applications. This paper presents an analysis of the surface topography, microstructure and properties (residual stresses, microhardness, wear resistance) of Ni/Al₂O₃ nanocomposite coatings electrodeposited on steel substrates from modified Watt’s-type baths containing various concentrations of Al₂O₃ nanoparticles and a saccharin additive. The residual stresses measured in the Ni/Al₂O₃ coatings decreased with an increasing amount of the co-deposited ceramics. It was established that the addition of Al₂O₃ powder significantly improved the coatings’ microhardness. The wear mechanism changed from adhesive-abrasive to abrasive with a rising amount of Al₂O₃ particles and coating microhardness. Nanocomposite coatings also exhibited a lower coefficient of friction than that of a pure Ni-electrodeposited coating. The friction was found to depend on the surface roughness, and the smoother surfaces gave lower friction coefficients.