Jet pulse electrodeposition and characterization of Ni–AlN nanocoatings in presence of ultrasound

In current study, Ni–AlN nanocoatings were successfully prepared by adopting the jet pulse electrodeposition (JPE) technique with ultrasound. The scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Vickers microhardness test, electrochemical workstation and friction wear tests were utilized to investigate the microstructure, mechanical properties, corrosion degree and wear resistance of the coatings. The results indicated that the Ni–AlN nanocoatings deposited by using ultrasound demonstrated the minimum and most compact surface structure compared to the other coatings. The thicknesses of Ni coating and Ni–AlN nanocoatings were approximately 56 µm. The average atomic percent of Al and Ni elements in the Ni–AlN nano-coating prepared by using ultrasound, were approximately 21.4 at% and 47.5 at%, respectively. The maximum kinetic energy of the jet plating solution was 916 m²/s² during JPE-deposited Ni-AlN nanocoatings including ultrasound. The average micro-hardness value of the nano-coating prepared by using ultrasound equaled 767.9 HV. The Ni–AlN nanocoatings prepared using ultrasound had the minimum E_corr and I_corr values of ? 0.167 V and 6.363 × 10^?6 mA/cm², respectively. In this case, the demonstrated corrosion resistance was the most efficient. The Ni–AlN nanocoatings prepared using ultrasound sustained the minimum friction coefficients and the average friction coefficient was approximately 0.52. In contrast, the JPE-deposited Ni coating presented the maximum friction coefficient, while the average friction coefficient was approximately 1.43.     

Effect of plating parameters on the properties of pulse electrodeposited Ni–TiN thin films

The influence of pulse plating parameters on the microstructure, microhardness, and properties of the Ni–TiN thin films was investigated by transmission electron microscopy (TEM), atomic force microscopy (AFM), X–ray diffraction (XRD), scanning electron microscopy (SEM), and corrosion and wear tests. The results indicated the Ni–TiN thin films prepared via electrodeposition at 4 A/dm² current density to show an optimum microhardness and TiN content values of 984.7 HV and 8.69 wt%, respectively. The average grain sizes of Ni and TiN in the films obtained at 200 Hz were 127.8 and 48.5 nm, respectively. Numerous large pores can be noticed in the films prepared at pulse frequencies of 200 Hz and 500 Hz, whereas only a few small pits are visible on the surface of the Ni–TiN thin films deposited at 800 Hz. The films prepared at 20% duty cycle experienced the least weight loss.     

Fabrication and characterization of in-situ duplex plasma-treated nanocrystalline Ti/AlTiN coatings

Plasma nitriding and plasma-assisted PVD duplex treatment was adopted to improve the load-bearing capacity, fatigue resistance and adhesion of the AlTiN coating. Ion etch-cleaning was applied for better adhesion before plasma nitriding. After plasma nitriding Ti interlayer was in-situ deposited by high power impulse magnetron sputtering (HIPIMS), followed by the AlTiN coating through in-situ deposition by advanced plasma-assisted arc (APA-Arc). The microstructure and properties of the duplex-treated coating were carefully characterized and analyzed. The results show that the thicknesses of the nitriding zone, the γ′-Fe₄N compound layer, the Ti interlayer and the AlTiN top layer with nanocrystalline microstructures are about 60 μm, 2–3 μm, 100 nm and 6.1 μm, respectively. The nitriding rate is about 30 μm/h and the AlTiN coating deposition rate reaches 6.1 μm/h. The interfacial adhesion of the Ti/AlTiN coating is well enhanced by ion etch-cleaning and a Ti interlayer, and the load-bearing capacity is also improved by duplex treatment. In addition, the instinct hardness of the Ti/AlTiN coating reaches 3368HV_0.05 while the wear rate coefficient of 5.394×10⁻⁸ mm⁻³/Nm is sufficiently low. The Ti/AlTiN coating, which possesses a high corrosion potential (E_corr=−104.6 mV) and a low corrosion current density (i_corr=4.769 μA/cm²), shows highly protective efficiency to the substrate.     

Spark plasma sintering of TiN–TiB2 composites

TiN–TiB₂ composites were fabricated by spark plasma sintering at 1773–2573 K. Effects of TiN and TiB₂ content on relative density, microstructure, and mechanical properties were investigated. Above 2373 K, TiN–TiB₂ composites exhibited relative densities over 95%. A high density of 99.7% was obtained at 2573 K with 20–30 vol% TiB₂. Shrinkage of the TiN–70 vol% TiB₂ composite was the highest at 1573–2473 K. For the TiN–70 vol% TiB₂ composite prepared at 1973–2373 K, TiN grains were small, while at 2573 K, TiB₂ became a continuous matrix, in which irregular-shaped TiN dispersed. hBN was formed in the TiN–TiB₂ composite containing 50–60 vol% TiB₂ above 2373 K. The maximum Vickers hardness and fracture toughness obtained for the TiN–80 vol% TiB₂ composite sintered at 2473 K was 26.3 GPa and 4.5 MPa m^1/2, respectively.     

Highly conductive SiC ceramics containing Ti2CN

Highly conductive SiC ceramics were fabricated by sintering β-SiC and TiN powder mixture in N₂ atmosphere. SiC ceramics exhibited decreased electrical resistivity (ρ) with increasing TiN content. X-ray diffraction data indicated that the specimens consisted of β-SiC grains without a detectible secondary phase for low TiN content (≤2 vol%) but contained a Ti₂CN phase as the TiN content increased. The temperature-dependent resistivity ρ(T) of specimens revealed semiconductor-like behavior for TiN content up to 10 vol% and metal-like behavior above 20 vol%. For the specimen with TiN content of 15 vol%, ρ(T) remained almost constant (2.06 ± 0.01 × 10⁻³ Ω cm) in the 4–300 K range. The resistivity of metal-like specimens were as low as 3.5 × 10⁻⁴ Ω cm for TiN content of 20 vol%. For semiconductor-like specimens, ρ(T) was primarily affected by N donors in the β-SiC grains. Metal-like specimens were primarily affected by metallic Ti₂CN clusters.     

Polymer-derived mesoporous Ni/SiOC(H) ceramic nanocomposites for efficient removal of acid fuchsin

In this paper, magnetic porous Ni-modified SiOC(H) ceramic nanocomposites (Ni/SiOC(H)) were successfully prepared via a template-free polymer-derived ceramic route, which involves pyrolysis at 600 °C of nickel-modified allylhydridopolycarbosilane (AHPCS-Ni) precursors synthesized by the reaction of allylhydridopolycarbosilane (AHPCS) with nickel(II)acetylacetonate (Ni(acac)₂). The resultant Ni/SiOC(H) nanocomposites are comprised of in-situ formed nanoscaled Ni socialized with small amounts of NiO and nickel silicides embedded in the amorphous SiOC(H) matrix. The materials show ferromagnetic behavior and excellent magnetic properties with the saturation magnetization in the range of 1.71–7.08 emu g⁻¹. Besides, the Ni/SiOC(H) nanocomposites are predominantly mesoporous with a high BET surface area and pore volume in the range of 253–344 and 0.134–0.185 cm³ g⁻¹, respectively. The measured porosity features cause an excellent adsorption capacity towards a template dye acid fuchsin with the adsorption capacity Q_t at 10 min of 80.7–85.8 mg g⁻¹ and the Q_e at equilibrium of 123.8–129.8 mg g⁻¹.     

Role of spin-glass phase for magnetoresistance enhancement in nickel substituted lanthanum calcium manganite

Effect of Ni substitution in lanthanum calcium manganite (LCMO) has been investigated for change in magnetoresistance (MR). Scanning electron microscopy images revealed decrease in grain size from 3.72 µm to 0.55 µm by Ni substitution. Maximum increase in MR has been found 28% at low temperature (100 K) for x=0.10, Ni substitution at Mn site. Metal insulator transition temperature has been decreased from 253.2 K for x=0.0–90 K for x=0.10. Above x=0.10, Ni substitution no metal-insulator transition temperature appeared due to the presence of porosity in the samples. Ni substitution lowered the magnetic transition temperature from 255 K for x=0.0–125 K for x=0.25. Lowering of irreversible temperature (T_irr) from 250 K for x=0.0–135.4 K for x=0.20 has been obtained by zero field cooled (ZFC) and field cooled (FC) measurements confirm reduction of ferromagnetic clusters and spin-glass phase like behavior due to Ni presence. The spin-glass phase presence allows spin-polarized tunneling even at low magnetic field, which ultimately results in enhancement of MR at low temperature. Core level X-ray photoelectron spectroscopy measurements confirm Ni²⁺ charge state of Ni ions and increase in Mn⁴⁺/Mn³⁺ ratio with increasing Ni content. Increase in resistivity and weakening of ferromagnetism with Ni substitution at Mn site has been observed due to the reduction in grain size and dilution of double exchange interaction.     

Effect of multi-walled carbon nanotubes as reinforced fibres on tribological behaviour of Ni–P electroless coatings

After multi-walled carbon nanotubes (MWNTs) were modified and dispersed uniformly in electrolyte, the MWNTs composite coatings were prepared by electroless deposition. Hardness tests were carried out using a Vickers Hardness indenter. The friction and wear behavior of the Ni–P–MWNTs composite coatings in carbon-steel rings were investigated by using a ring-on-plate wear tester at pure liquid paraffin. Moreover, the friction and wear behavior of nine kinds of wear combinations, which were composed of plates and rings of different composite coatings, were studied. The experimental results indicated that addition of MWNTs would result in an increase in microhardness and an improvement of tribological properties of the Ni–P composite coating significantly. The Ni–P–MWNTs composite coatings revealed lower wear rate and friction coefficient compared with Si–C composite coatings. Moreover, the wear combination, which composed of the Ni–P–MWNTs composite coatings, showed a more excellent ability of friction-reduction and wear resistance than other combinations, and their friction coefficient and wear rate were 0.1087 and 1.49 × 10^− 6 kg/m, respectively.     

Electrical properties and microstructural evolution of ZrO2–Al2O3–TiN nanocomposites prepared by spark plasma sintering

Electroconductive ZrO₂–Al₂O₃–25 vol% TiN ceramic nanocomposites were prepared by spark plasma sintering at 1200 °C for 3 min. The electrical resistivity of the composites decreased from 4.5 × 10^?4 Ω m to 3 × 10^?5 Ω m as the Al₂O₃ content in the ZrO₂–Al₂O₃ matrix increased from 0 to 100 vol%. SEM images graphically presented the microstructural evolution of the composites and a geometrical percolation model was applied to investigate the relationship between the electrical property and the microstructure. The results indicated that the addition of Al₂O₃ to ZrO₂–TiN improved the electrical conductivity of the material by tailoring the structure from “nano–nano” type for ZrO₂–TiN to “micro–nano” type for ZrO₂–Al₂O₃–TiN.     

Synthesis and electrochemical performance of Li4Ti5O12 submicrospheres coated with TiN as anode materials for lithium-ion battery

The TiN coated Li₄Ti₅O₁₂ (LTO) submicrospheres with high electrochemical performance as anode materials for lithium-ion battery were synthesized successfully by solvothermal method and subsequent nitridation process in the presence of ammonia. The XRD results revealed that the crystal structure of LTO did not change after thermal nitridation process. The submicrospheres morphology of LTO and TiN film on the surface of LTO submicrospheres were characterized by FESEM and HRTEM, respectively. XPS result confirmed that a small amount of Ti changed from Ti⁴⁺ to Ti³⁺ after nitridation process, which will increase the electronic conductivity of LTO. Electrochemical results showed that electrochemical performance of TiN coated LTO anode materials compared favorably with that of pure LTO. Also its rate capability and cycling performance were apparently superior to those of pure LTO. The reversible capacity of TiN-LTO is 105.2 mA h g⁻¹ at a current density of 10 C after 100 cycles and maintain 92.9% of its initial discharge capacity, while that of pure LTO is only 83.6 mA h g⁻¹ with a capacity retention of 90.3%. Even at 20 C, the discharge capacity of TiN coated LTO sample is 101.3 mA h g⁻¹, compared with 77.3 mA h g⁻¹ for pristine LTO in the potential range 1.0–2.5 V (vs. Li/Li⁺).     

Nucleation and growth surface conductivity of H-terminated diamond films prepared by DC arc jet CVD

High-quality polycrystalline diamond film has been extremely attractive to many researchers, since the maximum transition frequency (f_T) and the maximum frequency of oscillation (f_max) of polycrystalline diamond electronic devices are comparable to those of single crystalline diamond devices. Besides large deposition area, DC arc jet CVD diamond films with high deposition rate and high quality are one choice for electronic device industrialization. Four inch free-standing diamond films were obtained by DC arc jet CVD using gas recycling mode with deposition rate of 14 μm/h. After treatment in hydrogen plasma under the same conditions for both the nucleation and growth sides, the conductivity difference between them was analyzed and clarified by characterizing the grain size, surface profile, crystalline quality and impurity content. The roughness of growth surface with the grain size about 400 nm increased from 0.869 nm to 8.406 nm after hydrogen plasma etching. As for the nucleation surface, the grain size was about 100 nm and the roughness increased from 0.31 nm to 3.739 nm. The XPS results showed that H-termination had been formed and energy band bent upwards. The nucleation and growth surfaces displayed the same magnitude of square resistance (R_s). The mobility and the sheet carrier concentration of the nucleation surface were 0.898 cm/V s and 10¹³/cm² order of magnitude, respectively; while for growth surface, they were 20.2 cm/V s and 9.97 × 10¹¹/cm², respectively. The small grain size and much non-diamond carbon at grain boundary resulted in lower carrier mobility on the nucleation surface. The high concentration of impurity nitrogen may explain the low sheet carrier concentration on the growth surface. The maximum drain current density and the maximum transconductance (g_m) for MESFET with gate length L_G of 2 μm on H-terminated diamond growth surface was 22.5 mA/mm and 4 mS/mm, respectively. The device performance can be further improved by using diamond films with larger grains and optimizing device fabrication techniques.     

Thermal and electrical conduction in the compaction direction of exfoliated graphite and their relation to the structure

The effects of the compaction and graphite layer preferred orientation on the thermal and electrical conductions in the compaction direction of graphite-flake-based exfoliated graphite have been decoupled. The compact’s electrical and thermal conductivities decrease with increasing compaction (density increasing from 0.047 to 0.67 g/cm³, solid content increasing from 2.1 to 30 vol.%) and preferred orientation. The essentially linear correlation between electrical and thermal conductivities (Wiedemann–Franz Law) is because both conductions are governed by the preferred orientation. With increasing compaction, the fraction (f) of conduction path that is the graphite a-axis decreases from 0.997 to 0.937 and from 0.994 to 0.798 for thermal and electrical conductions respectively. For the solid-part thermal and electrical conductivities to exceed 140 W/(m K) and 60 kS/m respectively, f must exceed 0.95; the highest solid-part conductivities are 550 W/(m K) and 230 kS/m. The compaction-related variation in the solid-part conductivities is large [21–550 W/(m K) and 10–230 kS/m], due to the preferred orientation variation. The through-thickness Lorentz number (7.3 × 10⁻⁶ W Ω/K²) is similar to the in-plane value, being independent of the preferred orientation. At 2–7 vol.% solid, conductivities of 7 W/(m K) and 3 kS/m are obtained for the compact – toward the targets for fuel cell biopolar plates.     

Spark plasma sintering of Al2O3–Ni nanocomposites using Ni nanoparticles produced by rotary chemical vapour deposition

Al₂O₃–Ni nanocomposites were fabricated by spark plasma sintering (SPS) using Ni nanoparticle produced by rotary chemical vapour deposition. Carbon-free Ni nanoparticles were prepared by reacting NiCp₂ with O₂ to form NiO and then reducing to Ni by H₂ for 30 min at 823 K. The highest Ni content and grain size were 7.8 wt.% and 47.7 nm, respectively, using a NiCp₂ supply rate (R_s) of 1.67 × 10⁻⁶ kg s⁻¹. At a sintering temperature (T_SPS) of 1573 K, the hardness of Al₂O₃–3.8 wt.% Ni was 20.5 GPa, around 1 GPa higher than that of monolithic Al₂O₃ sintered at the same temperature. The tensile strength of Al₂O₃–4.6 wt.% Ni was 170 MPa, 60 MPa higher than that of Al₂O₃ sintered at 1573 K.     

TiN modified SiC with enhanced strength and electrical properties

SiC based composites were manufactured with varying TiN content (0–50 V%) using Al₂O₃ and Y₂O₃ sintering aids. Basic dilatometry measurements were performed to determine when densification begins within the composite system. Samples were consolidated via uni-axial hot pressing at 1900 °C to produce ceramic composites with >98% theoretical density. Electrical measurements show increasing TiN additions reduce resistivity and begin to plateau at 40–50V%. Resistivity decreased from 2.0 × 10⁵ Ω − cm (0% TiN) to 2.0 × 10⁻⁴ Ω − cm (50V% TiN). Flexural strengths were characterized and compared against a baseline (0% TiN) SiC. Strengths increased gradually with TiN content. A maximum strength 921 MPa was observed at 40V% TiN content vs. 616 MPa for the baseline SiC. This was a gain of 50% over baseline. Additions beyond that range did not produce further gains in strength.     

B deficiency in TiB2 and B solid solution in TiN in TiN–TiB2 composites prepared by spark plasma sintering

Dense TiN–TiB₂ composites were prepared by spark plasma sintering at 2573 K using TiN and TiB₂ powders. With increasing TiN content from 60 to 90 vol%, the c-axis length of TiB₂ in the TiN–TiB₂ composites decreased from the stoichiometric value (0.3230 nm) to 0.3227 nm because of B deficiency in TiB₂, whereas the a-axis length of TiB₂ was unchanged from the stoichiometric value of 0.3031 nm. The lattice parameter of TiN increased from the stoichiometric value (0.4243 nm) to 0.4250 nm with increasing TiB₂ content from 0 to 60 vol% because of B solid solution in TiN.     

Electrically conductive ZrO2–TiN composites

1.75 mol% Y₂O₃-stabilized ZrO₂–TiN composites could be fully densified by hot pressing for 1 h at 1550 °C in vacuum under a mechanical pressure of 28 MPa. Composites with 35–95 vol% TiN were investigated and the best mechanical properties, i.e., a Vickers hardness of 14.7 GPa, an indentation toughness of 5.9 MPa m^1/2 and an excellent bending strength of 1674 MPa were obtained with 40 vol% TiN. The active toughening mechanisms were identified and their contribution to the overall composite toughness as function of the TiN content was modelled, experimentally verified and discussed. Transformation toughening was found to be the primary toughening mechanism. The TiN grain size was found to increase with increasing TiN content, resulting in a decreasing hardness and strength. A maximum strength was obtained at 40 vol% TiN. The electrical resistivity of the composites decreases exponentially with increasing TiN content and correlates well with the Polder-Van Santen mixture rule. Thus at around 40 vol% TiN, the conductivity is high enough to allow EDM machining of the composite, therefore avoiding the expensive grinding operation for final shaping and surface finishing of components.     

Film thickness effect on texture and residual stress sign transition in sputtered TiN thin films

Residual stress in thin films and coatings strongly affects their properties and behavior in service. Comprehensive understanding and precise measurements of residual stress are prerequisites for preparing high quality films and coatings. Residual stresses in TiN films with different thickness were measured by X-ray diffraction (XRD) employing the cos²α sin²ψ method with certain optimization. Grazing incidence parallel beam optics was combined with side-inclination geometry using in-house designed sample stage to ensure results accuracy. To validate this method, TiN films with thickness ranging from 1 to 3 µm were deposited on (100) Si single crystal substrates at 300 °C by RF magnetron sputtering. High compressive −2 GPa residual stress was present in the 0.9 µm thick film and decreased with film thickness. Tensile stress of less than 0.3 GPa was present in 2 µm TiN film. Compressive-to-tensile residual stress transition was observed with the film thickness increase. Microstructure change with growth, annihilation of grain boudaries, atomic peening and recovery mechanisms are responsible for the reported stress sign transition.     

Densification and mechanical properties of cBN–TiN–TiB2 composites prepared by spark plasma sintering of SiO2-coated cBN powder

cBN–TiN–TiB₂ composites were fabricated by spark plasma sintering at 1773–1973 K using cubic boron nitride (cBN) and SiO₂-coated cBN (cBN(SiO₂)) powders. The effect of SiO₂ coating, cBN content and sintering temperature on the phase composition, densification and mechanical properties of the composites was investigated. SiO₂ coating on cBN powder retarded the phase transformation of cBN in the composites up to 1873 K and facilitated viscous sintering that promoted the densification of the composites. Sintering at 1873 K, without the SiO₂ coating, caused the relative density and Vickers hardness of the composite to linearly decrease from 96.2% to 79.8% and from 25.3 to 4.4 GPa, respectively, whereas the cBN(SiO₂)–TiN–TiB₂ composites maintained high relative density (91.0–96.2%) and Vickers hardness (17.9–21.0 GPa) up to 50 vol% cBN. The cBN(SiO₂)–TiN–TiB₂ composites had high thermal conductivity (60 W m⁻¹ K⁻¹ at room temperature) comparable to the TiN–TiB₂ binary composite.     

Substrate effect on wear resistant transition metal nitride hard coatings: Microstructure and tribo-mechanical properties

Four types of different hard transition metal nitrides (TMN:ZrN, CrN, WN and TiN) coatings were deposited on Si (100) and 316LN stainless steel substrates using DC magnetron sputtering. A comprehensive study of microstructure and substrate dependent tribo-mechanical properties of TMN coatings was carried out. Higher hardness (H) and elastic modulus (E) were obtained for WN (H=40 GPa and E=440 GPa) and TiN (H=30 GPa and E=399 GPa) coatings. This is related to the formation of (100) and (111) preferred orientations in WN and TiN coatings, respectively. However, the less hardness and elastic modulus were obtained for ZrN and CrN coatings where (200) orientation is preferred. Remarkably, low friction coefficient (0.06–0.57) and higher wear resistance in the coatings deposited on steel substrates are directly associated with the higher resistance to plastic deformation (H³/E²) and the presence of intrinsic compressive stress. Three body wear modes enhanced the friction coefficient (0.15–0.62) and the wear rate in the coatings deposited on Si substrates. This is primarily associated with low fracture toughness of brittle single crystalline Si (100) substrates. Steel-on-steel contact was dominated in ZrN/steel sliding system. This occurs due to the severe adhesive wear mode of steel ball, whereas, the abrasive wear modes were attained for the CrN, WN and TiN coatings sliding against steel balls.     

Wear mechanisms of TiN–TiB2 ceramic in sliding against alumina from room temperature to 700 °C

TiN–TiB₂ ceramic was prepared by the reactive hot-pressing method using titanium and BN powders as raw materials. The friction and wear properties of TiN–TiB₂ ceramic were evaluated in sliding against alumina ball from room temperature to 700 °C in air. The TiN–TiB₂ ceramic has a relative density of 98.6%, a flexural strength of 731.9 MPa and a fracture toughness of 8.5 MPa m^1/2 at room temperature. The TiN–TiB₂ ceramic exhibits a distinct decrease in friction coefficient at 700 °C as contrasted with the friction data obtained at room temperature and 400 °C. Wear mechanisms of TiN–TiB₂ ceramic depend mainly upon testing temperature at identical applied loads. Lubricious oxidized products caused by thermal oxidation provide excellent lubrication effects and greatly reduce the friction coefficient of TiN–TiB₂ ceramic at 700 °C. However, abrasive wear and tribo-oxidation are the dominant wear mechanisms of TiN–TiB₂ ceramic at 400 °C. Mechanical polishing effect and removal of micro-fractured grains play important roles during room-temperature wear tests.