NiAl Layer Research Articles

Al-etching-induced defect engineering in NiAl LDHs for promoting multifunctional electrocatalytic oxidations: Water oxidation and urea oxidation

Electrocatalytic water splitting is a promising avenue to produce green hydrogen for future sustainable development. Developing multifunctional catalysts with high-performance toward urea oxidation reaction (UOR) and oxygen evolution reaction (OER) offers a unique approach for simultaneously achieving the degradation of urea-containing wastewater and energy-saving hydrogen production. Ni-based materials are a kind of promising materials for electrocatalysis, since its abundant reserve and tolerance. However, low intrinsic activity and catalytic efficiency hinder its wide application. Here, a defect engineering strategy is developed to create vacancies on NiAl layer double hydroxides (LDHs) catalysts by selectively etching Al ions in strong alkaline solution. The obtained NiAl LDHs with rich defects (D-NiAl LDHs) exhibit good OER performance with overpotential of 264 mV to achieve a current density of 10 mA cm−2 and a Tafel slope of 39.8 mV dec−1. In addition, the D-NiAl LDHs catalysts also show excellent UOR activity using a potential of 1.328 V vs. RHE @ 10 mA cm−2 in alkaline solution. In comparation to NiAl LDHs, the enhanced performance of D-NiAl LDHs toward oxidation of small-molecule OH− and urea could be attributed to electronic regulation of defects and a larger electrochemical surface area. Partially replacing the OER with the UOR, the driving voltage of overall water splitting reduces effectively from 1.856 V to 1.688 V at a current of 100 mA cm−2.

Solidified characteristic and enhanced properties of Al0.5MnFeNiCu0.5/Al–Ni functionally gradient coating fabricated by laser cladding on AZ91HP

To ensure the high entropy effect of the coating, it is necessary to control the dilution of Mg during laser cladding process. Therefore, Al0.5MnFeNiCu0.5/Al–Ni functionally gradient coating was proposed in this work. More remarkable, the design of Al–Ni transition layer effectively prevented the dilution of Mg into Al0.5MnFeNiCu0.5 layer, and relieved physical and chemical differences between Al0.5MnFeNiCu0.5 layer and Mg alloy. Al0.5MnFeNiCu0.5 layer exhibited flower-like grain consisted of BCC phase. Al–Ni remelting layer crystallized as the fine snowflake-like grain. Al–Ni layer presented coarse needle-like grain morphology. Microhardness of Al0.5MnFeNiCu0.5 layer was about 8.2 times more than that of the substrate. Specifically, compared with Mg alloy and Al–Ni layer, the wear volume of Al0.5MnFeNiCu0.5 layer were decreased by 87.83% and 50.38%, respectively. The results of Polarization curve, Nyquist curve and Bode plot indicated that Al0.5MnFeNiCu0.5 layer displayed better corrosion resistance than Al–Ni layer and Mg alloy.

Breakthrough Study of CO2 Adsorption and Regeneration Performance of Mn‐ and Ce‐Doped Ni–Al Layered Double Hydroxides Derived Mixed Oxides in Packed‐Bed Column

AbstractCarbon dioxide (CO2) capture is an important strategy to mitigate greenhouse gas emissions and reduce global warming effects. This study synthesizes two nanomaterials, Ce‐doped Ni–Al mixed metal oxide (CNAO) and Mn‐doped Ni–Al mixed metal oxide (MNAO), from Mn‐ and Ce‐doped Ni–Al‐layered double hydroxides using a co‐precipitation method followed by a calcination process. The materials are characterized using various techniques, such as High‐resolution transmission electron microscopy‐energy dispersive x‐ray spectroscopy/selected area electron dispersion (HRTEM‐EDS/SAED), X‐ray diffraction (XRD), x‐ray photoelectron spectroscopy (XPS), Brunauer‐Emmett‐Teller (BET), and attenuated total reflection Fourier transform infrared (ATR FT‐IR). The CO2 adsorption performance of the materials is evaluated using packed‐bed column experiments at the testing conditions of 13 vol% ± 1 vol% CO2 in N2 simulated flue gas, flow rate of 20 mL min−1, inlet pressure of 14.15 ± 0.1 psi, and temperature of 31 °C ± 2 °C. The results show that both CNAO and MNAO are promising nanomaterials for CO2 capture applications due to their high CO2 adsorption capacity and efficiency. CNAO has a higher saturation capacity of 11.4 mmol g−1 and a longer breakthrough time than MNAO, which has a saturation capacity of 10.0 mmol g−1. The doping of Ce and Mn enhances the CO2 adsorption capacity of the materials compared to the un‐doped Ni–Al mixed oxide. The mechanisms of CO2 adsorption are mainly linearly adsorbed CO2, bidentate, and monodentate or bulk carbonate formation, as revealed by ATR FT‐IR analysis. The regeneration performance results suggest that CNAO is more stable than MNAO under multiple regeneration cycles and more promising material for large‐scale CO2 capture applications.

Combustion-synthesised TiAl/NiAl layered intermetallic composite: synthesis, phase composition, and microstructure

ABSTRACT The joining of different intermetallics (e.g. NiAl, TiAl) is important for high-temperature applications. In this study, self-propagating high-temperature synthesis was used for simultaneous joining of (Ni+Al) and (Ti+Al) layered samples of the stoichiometric compositions. The main advantage of such joining by self-propagating high-temperature synthesis is that it could be done at ambient temperature without the use of a furnace. The applied load during combustion synthesis was used to improve the contact between the Ni-Al and Ti-Al layers. The obtained results demonstrate that TiAl/NiAl intermetallics were successfully joined together with a bonding interface of about 170 μm thickness. XRD analysis has shown that the joining area consists of NiAl, TiAl, Ti3Al, and NiTiAl2 phases. The SEM data analysis of the transition zone of NiAl-TiAl conjunction has revealed that the transition zone consists of several intermediate layers: a polycrystalline NiAl layer; an intermediate layer based on Ni-Al-Ti containing NiTiAl2 phase; a layer based on Ni-Al-Ti with mixed dendritic and eutectic regions; and a polycrystalline TiAl layer.The measured microhardness of the transition zone varies from 3200 up to 13,600 MPa with the maximum microhardness of 1355 ± 45 MPa corresponding to the layer identified as the NiTiAl2 phase.

Preparation of NiAl-AlMg6 Functionally Graded Composite Using the Energy of a Highly Exothermic Ti-C Mixture during Self-Propagating High-Temperature Synthesis.

A functionally graded composite NiAl-AlMg6 was prepared using the pressure of gaseous reaction products (impurity gases) produced during the synthesis of reactive powders in a sealed reactor. It has been shown that this method can be used to prepare a NiAl/AlMg6 composite with both chaotically oriented pores in the NiAl layer and unidirectionally oriented pores (lotus-type pores). The pore shape in NiAl was found to be dependent on the pressure of the impurity gases and hydrogen present in the starting titanium powder. A mechanism for pore formation in NiAl and AlMg6 composite during SHS is proposed. Thus, functionally graded high-temperature composites can be produced by SHS in a sealed reactor using the chemical reaction energy and the pressure of impurity gases and hydrogen. Additionally, minimizing the influence of impurity gases on the contact zone increases the interface area between NiAl and AlMg6.

Modified Ni-Al layer double hydroxides as nanoparticles for self-healing anti-corrosion composite coating

Corrosion is a major concern for metallic structures, leading to significant economic losses and safety risks. Self-healing coatings have recently emerged as a promising solution to mitigate corrosion issues. This research develops a novel self-healing anti-corrosion composite coating using Ni-Al double layer hydroxide (LDHs) modified with phosphate ions as inhibitor. 1 wt% of modified particles were incorporated into the polyurethane (PU) matrix to form a coating (PU-LDH-PO4) and was applied on the carbon steel substrate. Reference coating (PU-LDH-NO3) was also formed for comparison purposes. The LDH serves as a reservoir for the inhibitor, which gradually released in response to corrosion-induced damage. The inhibitor release inhibits the corrosion process and promotes the formation of a protective passive film on the metallic surface. FTIR and FE-SEM coupled with EDS confirmed the successful loading of phosphate ions in the layered structure of Ni-Al LDH. The corrosion resistance of the self-healing composite coating was evaluated by electrochemical impedance spectroscopy (EIS) and salt spray test (SST). These tests demonstrate a higher and more robust inhibition efficiency (98 %) and self-healing effect compared to the reference coating. The enhanced corrosion ability of developed modified coating can be attributed to the effective and controlled release of inhibitor ions as well as the entrapment of aggressive chloride ions (Cl−) through the ion exchange mechanism. This composite coating demonstrated enhanced corrosion resistance and self-healing properties, making it a promising candidate for applications in protecting metallic structures against corrosive environments.

Thermodynamics and kinetics of interdiffusion in Ni//NiAl diffusion couples

The growth behavior of Ni3Al after nucleation at the Ni/NiAl interface was investigated by using macroscopic diffusion couples at low annealing temperatures of 973–1073 K. The thickness and grain size of the Ni3Al phase at different annealing temperatures were statistically analyzed by scanning electron microscopy to evaluate the growth kinetics of the Ni3Al layer. According to the growth rate exponent, the growth of Ni3Al layer to NiAl is almost completely controlled by volume diffusion (VD) when it is above 1023 K, and by boundary diffusion (BD) when it is below 1023 K. In contrast, the growth of Ni3Al into Ni is controlled by VD almost whether at 1023 K or 1073 K. Remarkably, a continuous Al-rich Ni grain layer was formed at the Ni3Al/Ni interface by diffusion-induced recrystallization (DIR), and the experimental results for DIR region of composition and growth behavior were numerically analyzed using the thermodynamic and kinetic models, respectively. The analyses suggest that the composition of the DIR region in the Ni(Al) binary system can be determined by the thermodynamic conditions of the chemical driving force model (CDF model). Additionally, kinetic analysis using the new extended model (NE model) indicates that under current annealing conditions, interface reaction and BD control growth at the moving boundary of the DIR region. Furthermore, the temperature stability range of Ni5Al3 in the Ni//NiAl system was subjected to systematic analysis.

Applications of Ni-Al Layered Double Hydroxide as Oxygen Evolution Reaction Catalysts Synthesized by Liquid Phase Deposition Process

Applications of Ni-Al Layered Double Hydroxide as Oxygen Evolution Reaction Catalysts Synthesized by Liquid Phase Deposition Process

Kinetically and Thermodynamically Favorable Ni–Al Layered Double Hydroxide/Ni-Doped Zn0.5Cd0.5S S-Scheme Heterojunction Triggering Photocatalytic H2 Evolution

Layered double hydroxide (LDH)-based photocatalysts have attracted more attention in photocatalysis due to their low cost, wide band gaps, and adjustable photocatalytic active sites; however, their low photogenerated carrier separation efficiency limits their photocatalytic efficiency. Herein, a NiAl-LDH/Ni-doped Zn0.5Cd0.5S (LDH/Ni-ZCS) S-scheme heterojunction is rationally designed and constructed from kinetically and thermodynamically favorable angles. The 15% LDH/1% Ni-ZCS displays comparable photocatalytic hydrogen evolution (PHE) activity with a rate of 6584.0 μmol g-1 h-1, which exceeds by ∼6.14- and ∼1.73-fold those of ZCS and 1% Ni-ZCS, respectively, and outperforms most of the previously reported LDH-based and metal sulfide-based photocatalysts. In addition, the apparent quantum yield of 15% LDH/1% Ni-ZCS reaches 12.1% at 420 nm. In situ X-ray photoelectron spectroscopy, photodeposition, and theoretical calculation reveal the specific transfer path of photogenerated carriers. On this basis, we propose the possible photocatalytic mechanism. The fabrication of the S-scheme heterojunction not only accelerates the separation of photogenerated carriers but also decreases the activation energy of H2 evolution and improves the redox capacity. Moreover, there are huge amounts of hydroxyl groups distributed on the surface of photocatalysts, which is highly polar and easy to combine with H2O with a large dielectric constant to form a hydrogen bond, which can further accelerate PHE.

Improvement of thermal stability of NiAl via employing Al capping layer for advanced interconnect applications

This letter reports on the study of employing an Al capping layer to improve the thermal stability of NiAl films for advanced interconnect applications. We prepare NiAl films with an Al capping layer of various thicknesses. Transmission electron microscopy analysis of NiAl with a 1 nm thick capping layer annealed at 450 °C discloses an effective suppression of Al out-diffusion from the NiAl layer and hence enhanced thermal stability. Measurement of thickness-dependent resistivity unravels a much slower resistivity increase for the capping layer sample than that of the sample without capping layer and low resistivity below 10 nm (49.7 μΩ·cm for 3.2 nm).

Effects of the Preparation Method on the Dielectric Properties of Ni–Al Layered Double Hydroxides

Ni–Al layered double hydroxides (LDHs) are of interest as functional materials. The effects of preparation methods on the dielectric properties of Ni–Al layered double hydroxides were studied on samples prepared from solution (by coprecipitation and a hydrothermal process) and by plasma technology. The prepared layered structures were characterized by advanced analytical methods. The high ζ potentials of the particles prepared in suspensions evidence their high aggregation stability. X-ray powder diffraction and IR spectroscopy were used to determine the phase composition of samples and to identify the interlayer anion. The plasma between Al and Ni electrodes in distilled bulk water gives rise to the formation of Ni–Al LDHs with hydroxide ion as the interlayer anion. Thermal properties of the structures prepared were studied by thermal analysis. The results of dielectric measurements are presented.

Effects of the Preparation Method on the Dielectric Properties of Ni–Al Layered Double Hydroxides

Effects of the Preparation Method on the Dielectric Properties of Ni–Al Layered Double Hydroxides

Fabrication of highly efficient Au and layered double hydroxide modified g-C3N4 ternary composites for degradation of pharmaceutical drug: Pathways and mechanism

Graphitic carbon nitride (CN), a conjugated polymer widely recognized as a chemically stable and low toxic catalyst for the degradation of organic molecules. But it acquires certain limitations like a limited visible light response, high recombination rate of charge carriers, and lower charge density. To overcome such drawbacks, we synthesized a series of Ni-Al layer double hydroxide (LDH)/CN composites by loading 5–15 wt% of Ni-Al LDH onto CN by electrostatic self-assembly method. Further, Au nanoparticles were deposited photochemically on LDH/CN nanocomposites. The Au/LDH/CN nanocomposites exhibited enhanced photocatalytic degradation of tetracycline (TCH) under visible light. Particularly, the Au/LDH/CN nanocomposite with LDH and Au contents of 10 and 1 wt%, sequentially, displayed the highest degradation, which was much better than that for pure CN. The face-to-face interface between LDH and CN and the electron-accepting capability of Au nanoparticles in Au@LDH/CN boosts the separation and transfer efficiencies of photogenerated charge carriers. The intermediate products formed after the degradation of TCH were detected by LCMS and possible degradation pathways were shown. Based on photoluminescence, scavenging experiments, and LC-MS analysis, a possible mechanism for degradation of TCH on Au@LDH/CN nanocomposite was proposed.

Optimization of Processing Parameter and Mechanical Response Analysis of Advanced Heterogeneous Laminated Composites Using Ni/Al Foils by In Situ Reaction Synthesis.

The advanced heterogeneous laminated composites were successfully fabricated by vacuum hot pressing using Ni and Al foils by in situ solid-state reaction synthesis. The effects of holding time and temperature on the microstructure and phase distribution were analyzed using scanning electron microscopy. Based on the optimized processing parameters, the microstructure and phase transformation, and the relationship between the microstructure and the corresponding mechanical properties were discussed in detail. To clarify the mechanical response of the laminated structure, the deformation microstructure and fracture characteristics were studied by scanning electron microscopy and electron backscatter diffraction. The results indicated that the evolution of the interfacial phases in the laminated composite occurred via the sequence: NiAl3, Ni2Al3, NiAl, and Ni3Al. An interface between the Ni and Ni3Al layers without cracks and voids formed due to the uniform pressure applied during hot pressing. The laminated composites hot pressed under 620 °C/5 MPa/1 h + 1150 °C/10 MPa/2 h exhibited the best ultimate tensile strength of 965 MPa and an elongation of 22.6% at room temperature. Extending the holding time during the second stage of the reaction synthesis decreased the thickness of the Ni3Al layer. This decreased the tensile strength of the laminated composite at 1000 °C but improved the tensile strength at room temperature. Moreover, the layer-thickness relationship of the laminated structure and the matching pattern were important factors affecting the strength and elongation of the laminated composites. The reinforcement form of the materials was not limited to a lamellar structure but could be combined with different forms of reinforcement to achieve continuous reinforcement over a wide range of temperatures.

Gas-phase aluminizing of HP40Nb steel used in reformer tubes: Synthesis, characterization, and its implications for the microstructure and high-temperature creep resistance of the base alloy

This study investigates the microstructure and creep behavior of gas-phase aluminized High-Performance (HP40Nb) steel. Microstructures of coated and base alloy were examined by electron and optical microscopes. Gas-phase aluminizing of HP steel resulted in the formation of a top AlNi layer over an interdiffusion zone (IDZ) on the base alloy. Results also showed that there were hardly any cavities or discontinuities formed in top layer and IDZ during the aluminizing process. The creep test results showed that the gas-phase aluminized steel had significantly a higher minimum creep rate and consequently a shorter time-to-rupture, as compared to uncoated HP40Nb steel. Microscopic examinations revealed that the main reason for the fracture of the steel after the creep test was formation of micro-cavities in the vicinity of carbides and growth of micro-cracks along the grain boundaries and alongside inter-dendritic areas. Also, fractography analysis showed that a quasi-cleavage fracture had occurred for both coated and uncoated steel. The implication of gas-phase aluminizing on creep resistance of coated HP40Nb steel, and its interrelation between the microstructure and observed mechanical properties are discussed and explained through the paper.

Corrosion of Ni–Fe based alloy in chloride molten salts for concentrating solar power containing aluminum as corrosion inhibitor

Chloride molten salt is extremely corrosive at high temperature. Thus, it is significant to study molten salt purification schemes to prevent structural materials from high-temperature corrosion. This paper performed corrosion tests of a Ni–Fe-based materials (HT700 alloy) in ternary chloride molten salt at 800 °C to identify the inhibiting effects of Al powder by using electrochemical methods which included impedance spectroscopy and potentiodynamic polarization, the morphologies and phase composition of HT700 alloy after corrosion tests were determined by scanning electron microscopy equipped with energy dispersive spectroscopy and X-ray diffraction. Addition of Al powder could reduce the corrosion current density of HT700 alloy in chloride molten salt, the Al2O3 layer was formed from the reaction of Al and impurities on the surface of the alloy, and the beneficial effects of Al powder increased with increasing Al content added in the chloride molten salt. There was a diffusion layer beneath the oxide scale resulting from the outwards diffusion of Cr in the alloy, addition of Al could hinder the outwards diffusion of Cr, thus prolong the lifetime of HT700 alloy in the chloride molten salt. Otherwise, a protective Ni3Al layer formed by the inwards diffusion of Al when the content of addition Al reached up to 10 wt%. Therefore, addition of Al powder in ternary chloride molten salt as corrosion inhibitor was feasible, but the content of added Al should be optimized to balance the corrosive and the thermal-physics properties of the chloride molten salt.

Preparation of α-Al2O3/NiAl multilayer coatings on GH3535 superalloy surface by pack cementation and subsequent in-situ oxidation

Tritium would be produced in the Thorium-based Molten Salt Reactor and then quickly penetrate through the structural material of GH3535 superalloy into environment at elevated temperatures. To suppress the permeation of tritium, the α-Al2O3/NiAl multilayer coatings were prepared on GH3535 by pack aluminizing (PCA) and subsequent low vacuum oxidation as tritium permeation barriers. Herein, the effects of PCA process parameters on the composition and structure of the Ni–Al coatings were characterized, simultaneously, the influence of oxidation temperature on the composition and structure of Al2O3 films were analyzed in detail. Experimental results demonstrated that the main phase of the Ni–Al layers is Ni2Al3 (or NiAl) doped with Al86Cr14. Significant amounts of Mo-aluminides were found on the surface of the samples aluminized at 1050 °C. The Ni–Al layers growth kinetic equation under 650–850 °C was empirically obtained as h = 7.07•104W1/2t1/2exp[-7.53•104/RT]. After low vacuum heat-treatment, the α-alumina films with a thickness of approximately 1 μm were formed at 1050 °C for 2 h, densely and non-porously. Meanwhile, the brittle Ni2Al3 in the transition layer was transformed into the tough NiAl, providing a self-healing capability as well as alleviating the thermal mismatch between the coating and the substrate.

Exploring the role of promoters (Au, Cu and Re) in the performance of Ni–Al layered double hydroxides for water-gas shift reaction

Water-gas shift (WGS) reaction is well-known industrial process targeting hydrogen production. Designing well-performing and economically profitable WGS catalysts is the key toward production of pure hydrogen for application in fuel cell processing systems. Promotional role of Au, Cu, or Re in the WGS performance of Ni–Al formulations derived from hydrotalcite precursor was analysed on the basis of deep characterization by BET, XRD, UV–Vis, XPS, and TPR measurements of as-prepared and WGS-tested samples. Additionally, modification by ceria was examined. WGS results revealed that catalyst behaviour was strongly dependent on promoter type. The best performance exhibited gold-promoted Ni–Al layer double hydroxide modified with ceria. This system showed a superior catalytic activity as 99.7% CO conversion at 220 °C that correlated well with significantly enhanced reducibility of support. Although Au-containing CeO2-modified Ni–Al catalyst outperformed WGS activity of Cu- and Re-promoted analogues, stability of Re-containing sample and enhanced activity of Cu-based sample after tests at different reaction conditions manifested promising results. They leave open space for future investigations addressing improved catalyst performance by tuning Re4+/Re7+ redox structures or optimizing catalyst composition.

Molecular dynamics simulations on shock induced plasticity and stacking fault of coherent {001} Ni/Ni3Al laminate composite

Using molecular dynamics (MD) simulations, the shock induced plasticity and stacking fault of coherent {001} Ni/Ni3Al laminate composite based on the interfaces were studied in this work. Firstly, the influences of interfaces on shock wave propagation are studied. The results reveal “reflection-unloading” at the Ni-Ni3Al, but “reflection-loading” at the Ni3Al-Ni. Strong discontinuities of shock wave stress at the interfaces also are revealed, the discontinuities are correlated to the impedance mismatch and elastic-plastic properties of the two materials adjacent to the interfaces. Secondly, the dislocation activities and stacking faults in the Ni3Al layer were obtained through shock simulation of multilayer target, and the interfacial lattice mismatch was studied at the atomic level, the abnormal arrangement of the atomic layers on both sides of the interface was found. Thirdly, since atoms in different directions are not activated at the same time during shock, resulting in dislocation decomposition in two steps. The dislocation sheet composed of Lomer-Cottrell locks and Hirth locks can act as a barriers to dislocation transmission. The phase transition process induced by the shock was also studied. The result showed that the region where the dislocation lines are located first changed from fcc to bcc. With the slip extension of Shockley dislocations, bcc to hcp continued to occur in the stacking fault region.

Magnetron sputtered NiAl/TiBx multilayer thin films

Transition metal diboride-based thin films are currently receiving strong interest in fundamental and applied research. Multilayer thin films based on transition metal diborides are, however, not yet explored in detail. This study presents results on the constitution and microstructure of multilayer thin films composed of TiBx and the intermetallic compound NiAl. Single layer NiAl and TiBx and NiAl/TiBx multilayer thin films with a variation of the individual layer thickness and bilayer period were deposited by D.C. and R.F. magnetron sputtering on silicon substrates. The impact of the operation mode of the sputtering targets on the microstructure of the thin films was investigated by detailed compositional and structural characterization. The NiAl single layer thin films showed an operation mode-dependent growth in a polycrystalline B2 CsCl structure with a cubic lattice with and without preferred orientation. The TiBx single layer thin films exhibited an operation mode independent crystalline structure with a hexagonal lattice and a pronounced (001) texture. These TiBx layers were significantly Ti-deficient and showed B-excess, resulting in stoichiometry in the range TiB2.64–TiB2.72. Both thin film materials were deposited in a regime corresponding with zone 1 or zone T in the structure zone model of Thornton. Transmission electron microscopy studies revealed, however, very homogeneous, dense thin-film microstructures, as well as the existence of dislocation lines in both materials. In the multilayer stacks with various microscale and nanoscale designs, the TiBx layers grew in a similar microstructure with (001) texture, while the NiAl layers were polycrystalline without preferred orientation in microscale design and tended to grow polycrystalline with (211) preferred orientation in nanoscale designs. The dislocation densities at the NiAl/TiBx phase boundaries changed with the multilayer design, suggesting more smooth interfaces for multilayers with microscale design and more disturbed, strained interfaces in multilayers with nanoscale design. In conclusion, the volume fraction of the two-layer materials, their grain size and crystalline structure, and the nature of the interfaces have an impact on the dislocation density and ability to form dislocations in these NiAl/TiBx-based multilayer structures.