Nanocrystalline Phase Research Articles

Tailoring the amorphous-nanocrystalline structures of TiNbZrNx films towards improving the anti-corrosion and mechanical properties by controlling nitrogen flow ratio

Multi-principal element alloy (MPEA) films demonstrate superior corrosion resistance and tribological properties, which have substantial potential for applications in marine engineering equipment. In this study, the TiNbZrNx MPEA nitride films were successfully deposited on 316 L austenitic stainless steel by direct current (DC) magnetron sputtering at various nitrogen flow ratio (RN2). The phase, composition, microstructure, corrosion and mechanical behaviors were investigated in detail. The results showed that the phase transitioned from amorphous to amorphous/nanocrystalline as RN2 increased. The TiNbZrNx films deposited at RN2 = 0.15–0.4 exhibited better corrosion performance in the electrochemical and salt spray tests. The RN2 = 0.4 film presented the optimal corrosion resistance, with the lowest self-corrosion current density (0.249 μA/cm2) and the largest passivation zone (from OCP to >1.2 VSCE). The amorphous/nanocrystalline film deposited at RN2 = 0.2 showed a remarkable nanohardness of 7.03 GPa and adhesion strength of 18.86 N. The strengthening effect can be attributed to the interstitial dissolution of nitrogen atoms among the metal atoms. The formation of nitride nanocrystalline phases and the existence of interfaces can effectively improve the plastic deformation ability of amorphous alloy films. This work provides theoretical guidance for the development of MPEA nitride films with tunable properties for key moving parts in marine equipment.

Mechanical alloying and phase transition of immiscible Al/Zn system during high-pressure torsion

Two half-disk samples of pure Al and pure Zn were mechanically alloyed via high-pressure torsion (HPT) processing, followed by post-deformation annealing (PDA). The microstructure evolution of the Al–Zn alloy was studied by scanning electron microscopy, transmission electron microscopy and molecular dynamics (MD) simulations. The results indicated that the HPT-processed Al/Zn assembly was presented as a mixture of nanocrystalline and amorphous phases. The deformation-induced special orientation of (0001)Al//(111)Zn facilitated the interatomic diffusion, and the dislocation density reached 2.17×1017 m−2 under the pinning effect of high solid solubility. Nanocrystalline, high diffusion degree, and high local dislocation density may primarily accounted for the crystalline-to-amorphous transformation in Al–Zn alloy. Moreover, the results indicated a bimodal grain size distribution of 150–250 nm and 500–900 nm, and Zn atoms were enriched at the grain boundaries, upon subsequent PDA. Under the effect of this special heterogeneous microstructure, the prepared alloy exhibited an excellent plasticity with 160% of tensile elongation.

Microstructure and hydrogen storage property of as-milled La–Y–Mg–Ni alloy

To improve the hydrogen storage property of La–Y–Mg–Ni alloy, the La1.7Y0.3Mg16Ni alloys with an amorphous and nanocrystalline structure were prepared by ball milling the as-cast alloy for 5–30 h. The effects of microstructure on hydrogen storage property and its mechanism were analyzed. The results show that with prolonging milling time, the crystallinity, grain size and particle size decrease and the amorphous phases increase. The dual regulation of the nanocrystalline and amorphous phases results in the hydrogen storage kinetic property increasing at first and declining later. The 15 h-milled alloy gets the best hydrogenation and dehydrogenation kinetic property, which can absorb 3.10 wt.% hydrogen gas in 10 min at 373 K and has the lowest dehydrogenation activation energy of 71.2 kJ/mol. The thermodynamic property of the alloys milled for different time shows a little change, and the 15 h-milled alloy has the lowest dehydrogenation enthalpy change of 72.9 kJ/mol.

Phase Transformations in Layered Composites Based on Zr, Nb, Ta or Ti Sheet Explosively Welded to Stainless Steel Plate

The composites based on reactive metals (Zr, Ta, Nb, Ti) sheets explosively welded to stainless steel plates were investigated using X-ray synchrotron radiation, TEM and SEM to characterize phase transformations in near-the-interface layers. SEM and TEM investigations of the solidified melt regions unveiled amorphous and nanocrystalline non-equilibrium phases of variable chemical compositions, incorporating elements from the joined components. Phase analysis in layers near the interface carried out using high-resolution synchrotron radiation show predominantly reflections coming from the main elements of parent sheets/plates. Nevertheless, a closer look at the diffraction patterns shows the presence of reflections coming from the phases based on the two-component equilibrium phase diagrams. The measurements performed at the interface, but including only the steel plate, revealed significant amounts of α-Fe, γ-Fe and ε-Fe phases. Their appearance was attributed to the high pressure and fast cooling rates, which promoted a martensitic transformation in steel.

Effect of electrodeposited Cu interlayer thickness on characterizations and adhesion force of Ni/Cu/Ni coatings on polyetherimide composite substrates

Polyetherimide (PEI) composite is an engineering plastic with excellent performance. After metallization, the metalized PEI composite has some unique properties, such as electromagnetic shielding and high electrical conductivity. In this study, a composite coating of Ni/Cu/Ni was produced on the surface of a PEI composite substrate. Nickel and copper layers were plated by electroless and electrodeposition, respectively. The influences of copper interlayer thickness and heat treatment on the adhesion state of the multilayer coatings on the substrate were studied. The morphology and phase of the composite coatings were determined by optical microscopy, scanning electronic microscopy and X-ray diffraction, respectively. The surface roughness and contact angles of the samples before and after sandblasting were measured by surface profile-meter and goniometer, respectively. The electrical resistivity and adhesion state of the composite coatings were determined by multimeter and the tape test, respectively. The results show that Ni/7.54 μm Cu/Ni and Ni/58.6 μm Cu/Ni multilayer deposits were produced on the substrates. The top surface of the coating with a thin 7.54 μm-Cu interlayer was much rougher than that of a coating with a thick 58.6 μm-Cu interlayer. The initial alkaline electroless nickel layer with 5.8 ± 0.5% phosphorus was composed of a mixture of amorphous and nanocrystalline phases. The Cu interlayer consisted of a face-centered cubic crystalline structure. The phosphorus contents of the top nickel layers for samples #1 and #2 were composed of 6.53 ± 0.4 wt% and 3.52 ± 0.21 wt%, respectively. An increase in Cu interlayer thickness for the composite coating resulted in an increase in electrical resistivity. The average microhardness values of Ni/7.54 μm Cu/Ni PEI composite and the Ni/58.6 μm Cu/Ni PEI composite were about 300 HV0.1 and 244.2 HV0.1, respectively. The adhesion state of the Ni/7.54 μm Cu/Ni and Ni/58.6 μm Cu/Ni PEI composites could be classified as grade 5B and 3B, respectively. The adhesion force of the Ni/58.6 μm Cu/Ni multilayer on the substrate can be improved by heat treatment at 200 °C for 4 h.

Dynamics of Cu–Zr metallic glass devitrification under ultrafast laser excitation revealed by atomistic modeling

The physics of metallic glass local devitrification employing ultrafast laser irradiation is the cradle of complex phenomena that are still not understood despite its applicative potential in material processing for nanotechnology. This paper reports a theoretical simulation combining the two temperature model and classical molecular dynamics simulations to unravel the mechanisms that lead to the localized phase transition in Cu–Zr metallic glass. According to observations, the initial composition of amorphous samples plays an essential role, in addition to nonequilibrium thermodynamic processes caused by the laser energy deposition that alters the atomic environment. We further demonstrate that specific compositions devitrify despite its high glass-forming ability. The thermodynamic conditions fostering the emergence of a stable nanocrystalline phase are clearly established. The compressive pressure wave and the rapid heating process caused by ultrafast laser energy deposition synergistically contribute to disrupt the microstructure of the glass significantly, thereby initiating the devitrification process. Results are discussed using additional classical MD simulations that provide valuable insights for interpreting the distinct contributions of temperature and pressure to the phase transformation. Finally, the impact of the formed nanocrystals on the phononic thermal conductivity of the alloy is presented confirming the potential application of the laser-induced devitrification process for the development of a new generation of nanoarchitectured materials.

Corrosion mode evaluation of Fe-based glassy alloys with metalloid elements by electrochemical noise (EN)

The corrosion mode and passivation behavior of Fe60(P0.3C0.7)40 and Fe83(P0.3C0.7)17 ribbons (Fe60 and Fe83) in 0.6 M NaCl were studied using various techniques. The decrement of P and C could weaken the glass formation ability (GFA) and raise the liquidus temperature of the alloys. Electrochemical noise (EN) and microstrucure investigations show that Fe60 exhibits a local corrosion mode and forms a stable and dense passivation film with a higher corrosion resistance, and Fe83 displays a combination of local and global corrosion modes and has a lower corrosion resistance. Controlling the precipitation of nanocrystalline phases and increasing the POx content in the passivation film have a significant impact on improving the corrosion resistance of Fe-based glassy alloys.

Microstructure, Multi-Phase and Corrosion Resistance of Amorphous Phase Reinforced Multi-Layer Fabricated by Laser beam

Abstract The Fe-Cr-B-Si deposited layers were prepared on the titanium alloy by the laser melting deposition (LMD) or the laser cladding (LC) technology. The microstructure of the clad layer and the deposition bulk was characterized by the scanning electron microscopy, transmission electron microscopy and electron-backscattered diffraction. The single clad layer was primarily composed of the amorphous phase (APs), the fraction of APs decreased with increasing of the LMD layer thickness due to the heat accumulation, producing the crystalline phases. Parts of the nanocrystalline phases (NPs) were produced due to the characteristics of a laser-induced pool (LIP), producing the deposition bulk with the good metallurgy bond between the adjacent laser fabricated layers. The corrosion resistance of the deposition bulk was enhanced due to the production of the oxides and hydroxides, forming a passive film to enhance the corrosion resistance.

Silk fibroin-based green colloidal silver nanoparticle synthesis and their antibacterial and anticancer properties

Aqueous silk fibroin (SF), derived from Bombyx mori silk, was used to synthesize colloidal silver nanoparticles (AgNPs) in situ under white light and at ambient temperature. A characteristic surface plasmon resonance (SPR) band at 425–435 nm from the UV–Vis spectrum provided evidence of the formation of AgNPs by UV–Visible spectroscopy. The nanoparticles that were synthesized were spherical with smooth surfaces, as evidenced by the transmission electron microscope (TEM) photographs. The size of the particles was between 35 and 40 nm. Additionally, X-ray diffraction (XRD) investigation supports the existence of silver's nanocrystalline phase with FCC crystal structure. The human bacterial pathogens Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) were significantly inhibited by the biogenic silver nanoparticles' antibacterial activity. The synthesized nanoparticles also show an excellent anti-cancer activity in lowest dosage.

Exploring the energy landscape and crystal structures of CrSi2N4

AbstractThe Cr−Si−N system is of great interest for materials with advanced tribological and mechanical properties. So far, experimental data have been reported on Cr−Si−N coating, nanocrystalline phases, and thin films, together with theoretically predicted 1D and 2D hetero‐structures, and 3D bulk Cr2SiN4 modifications. This study predicts possible bulk Cr−Si−N phases with the composition CrSi2N4. A multi‐methodological approach has been employed to explore the system's energy landscape, where global optimization was combined with data mining and the Primitive Cell for Atom Exchange (PCAE) method. Local optimization of the structure candidates was performed on the DFT level using the GGA‐PBE and the LDA‐PZ approximation. The ten energetically most favorable structure candidates discovered in the CrSi2N4 chemical system mostly exhibited monoclinic symmetry but with a variety of structural features, from zeolite‐like structures to polytypic behavior. Finally, the bulk modulus of these possible modifications was computed for a pressure range of up to 10 GPa.

Effect of the Annealing Conditions on the Formation of a Nanocrystalline Phase in TiOx Films

Effect of the Annealing Conditions on the Formation of a Nanocrystalline Phase in TiOx Films

Ieffect of Ultrasonic Impact Treatment on the Microstructure and Fatigue Life of 3<i>D</i>-Printed Titanium Alloy Ti–6Al–4V

Abstract—Using a hard alloy (Co–WC) striker, ultrasonic impact treatment (UTT) of Ti–6Al–4V alloy samples obtained by electron-beam wire additive technology was carried out. Using X-ray diffraction analysis and transmission electron microscopy, it has been shown that UTT leads to the appearance of compressive macrostresses in the surface layers of the sample, elastic microdeformation in the crystal lattice of the alpha-phase, to the formation of a gradient structure from nanocrystalline at a depth of 5 μm to a submicrocrystalline structure of the alpha-phase at a depth from 15 to 40 microns.A nanocrystalline phase of titanium oxides is formed in the grains of the alpha phase. UTT leads to an increase in microhardness and fatigue life. A fractographic analysis of specimen fractures after cyclic tension in the low-cycle fatigue regime has been carried out.

Combination of titanium dioxide and polyhedral oligomeric silsesquioxane nanofillers to boost mechanical and rheological properties of polyolefins: Recycling possibility

Recycling of polyolefins has become a on-demand route to avoid its environmental threats. Nevertheless, drop of properties after re-extrusion necessitates use of reinforcing agents to compensate for poor mechanical properties. The incorporation of nanoparticles into plastics can boost their mechanical and rheological properties due to the hard nanocrystalline phases. This study aims to promote and identify a polyolefin-based nanocomposite by combination of TiO2 and polyhedral oligomeric silsesquioxane (POSS) at concentration of 1, 3, and 6 wt% in a twin-screw extruder. The nanocomposites were characterized for mechanical and rheological properties. Overall, the results showed that the mechanical properties were improved by adding particles up to 6 wt% loadings. The magnitude of this effect was dependent on the nanofiller weight fraction and particle size. Well-dispersion and, as a result, enhancing the viscosity, modulus, and hardness in the sample containing 3 wt% TiO2 and 3 wt%. POSS was due to the presence of hydroxyl functional groups on its surface. Glass transition temperature and crystallinity of the samples did not show a significant change due to the neutral role of nanoparticle nucleation in the matrix.

Greening Industrially Applied Toxic Cadmium Plating with γ‐Ni2Zn11 Alloy in Deep Eutectic Solvents: Promising Electroplating Efficiency and Chemical Corrosion Resistance

Cadmium is an industrially applied plating metal used in aerospace applications, but electrodeposition of cadmium is toxic, and current production method will soon be banned. Therefore, electrodeposition of alternative alloys in environmentally friendly solutions is an attractive research area. An additive‐free, nonaqueous, deep eutectic solvent (DES) containing Ni and Zn halide salts is developed in a greener environmental method. Gamma‐phase nanocrystalline Ni2Zn11 is coated onto hot‐rolled mild steel via pulse reverse current (PRC) in the developed nonaqueous solvent. The employed DES’ relatively low viscosity and sufficient conductivity enable the simultaneous reduction of Ni2+ and Zn2+ cations on microelectrode. Electrochemical quartz crystal microbalance (eQCM) analysis proves the absence of the commonly reported problem of electrode blocking during electrodeposition, revealing an efficiency of 86.07%. Appropriate PRC parameters are applied for scaled macroelectrode deposition. The plating profile exhibits 20 μm‐thick alloy deposition without cracks around 3 h. Scanning electron microscopy–electron‐dispersive spectroscopy and X‐ray diffraction analyses reveal that 15.5 wt% Ni is in the nanograin phase, and all crystal planes belong to the γ‐Ni2Zn11 phase, which is needed as an alternative to cadmium plating. Hardness and corrosion tests performed on the γ‐Ni2Zn11 coating reveal better hardness and corrosion resistance with supporting morphological evidence.

Integration of hardness and toughness in (CuNiTiNbCr)Nx high entropy films through nitrogen-induced nanocomposite structure

The high-entropy alloy films show excellent comprehensive properties and have great application prospects in space, polar, deep-sea exploration. Compared with traditional ceramic films, the application of high-entropy alloy films is limited by the relative low hardness. In this paper, based on the nanocomposite structure formation principle in thermodynamics, we design the nanocomposite (CuNiTiNbCr)Nx films (HEFs). The introduced N atoms react with Ti, Nb, Cr to form (TiNbCr)N phase (accompanied by Cu and Ni segregation), and the structure of the HEFs changes from amorphous to a nanocomposite structure of CuNi-rich amorphous matrix-(TiNbCr)N nanocrystalline phase. The nanocomposite HEFs exhibit high hardness, high toughness, and excellent wear performance. These results indicate that nanocomposite HEFs have potential applications in the field of extreme environmental wear protection.

Giant Energy Density via Mechanically Tailored Relaxor Ferroelectric Behavior of Pzt Thick Film.

Relaxor ferroelectrics (RFEs) are being actively investigated for energy storage applications due to their large electric-field-induced polarization with slim hysteresis and fast energy charging-discharging capability. Here, w e report a novel nanograin engineering approach based upon high kinetic energy deposition for mechanically inducing the RFE behavior in a normal ferroelectric Pb(Zr0.52 Ti0.48 )O3 (PZT), which results in simultaneous enhancement in the dielectric breakdown strength (EDBS ) and polarization. Mechanically transformed relaxor thick films with 4μm thickness exhibited an exceptional EDBS of 540 MV/m and reduced hysteresis with large unsaturated polarization (103.6 μC/cm2 ), resulting in a record high energy storage density of 124.1 J/cm3 and a power density of 64.5 MW/cm3 . This fundamental advancement is correlated with the generalized nanostructure design that comprises of nanocrystalline phases embedded within the amorphous matrix. Microstructure-tailored ferroelectric behavior overcomes the limitations imposed by traditional compositional design methods and provides a feasible pathway for realization of high-performance energy storage materials. This article is protected by copyright. All rights reserved.

Effect of Rapid Thermal Annealing on Si-Based Dielectric Films Grown by ICP-CVD.

Silicon nitride, silicon oxide, and silicon oxynitride thin films were deposited on the Si substrate by inductively coupled plasma chemical vapor deposition and annealed at 1100 °C for 3 min in an Ar environment. Silicon nitride and silicon oxide films deposited at ratios of the reactant flow rates of SiH4/N2 = 1.875 and SiH4/N2O = 3, respectively, were Si-rich, while Si excess for the oxynitride film (SiH4/N2/N2O = 3:2:2) was not found. Annealing resulted in a thickness decrease and structural transformation for SiOx and SiNx films. Nanocrystalline phases of Si as well as α- and β-Si3N4 were found in the annealed silicon nitride film. Compared to oxide and nitride films, the oxynitride film is the least susceptible to change during annealing. The relationship between the structure, composition, and optical properties of the Si-based films has been revealed. It has been shown that the calculated optical parameters (refractive index, extinction coefficient) reflect structural peculiarities of the as-deposited and annealed films.

Photocatalytic Performance of Sol-Gel Prepared TiO2 Thin Films Annealed at Various Temperatures.

Titanium dioxide (TiO2) in the form of thin films has attracted enormous attention for photocatalysis. It combines the fundamental properties of TiO2 as a large bandgap semiconductor with the advantage of thin films, making it competitive with TiO2 powders for recycling and maintenance in photocatalytic applications. There are many aspects affecting the photocatalytic performance of thin film structures, such as the nanocrystalline size, surface morphology, and phase composition. However, the quantification of each influencing aspect needs to be better studied and correlated. Here, we prepared a series of TiO2 thin films using a sol-gel process and spin-coated on p-type, (100)-oriented silicon substrates with a native oxide layer. The as-deposited TiO2 thin films were then annealed at different temperatures from 400 °C to 800 °C for 3 h in an ambient atmosphere. This sample synthesis provided systemic parameter variation regarding the aspects mentioned above. To characterize thin films, several techniques were used. Spectroscopic ellipsometry (SE) was employed for the investigation of the film thickness and the optical properties. The results revealed that an increasing annealing temperature reduced the film thickness with an increase in the refractive index. Atomic force microscopy (AFM) was utilized to examine the surface morphology, revealing an increased surface roughness and grain sizes. X-ray diffractometry (XRD) and UV-Raman spectroscopy were used to study the phase composition and crystallite size. The annealing process initially led to the formation of pure anatase, followed by a transformation from anatase to rutile as the annealing temperature increased. An overall enhancement in crystallinity was also observed. The photocatalytic properties of the thin films were tested using the photocatalytic decomposition of acetone gas in a home-built solid (photocatalyst)-gas (reactant) reactor. The composition of the gas mixture in the reaction chamber was monitored using in situ Fourier transform infrared spectroscopy. Finally, all of the structural and spectroscopic characteristics of the TiO2 thin films were quantified and correlated with their photocatalytic properties using a correlation matrix. This provided a good overview of which film properties affect the photocatalytic efficiency the most.

Nanocatalyst for carbon monoxide oxidation based on palladium(II), copper(II) salts, and carbon fiber material

The phase composition, textural, and activity of catalysts for the carbon monoxide low-temperature oxidation based on two series of non-woven carbon fiber material samples CFM-I and CFM-II, and K2PdCl4, Cu(NO3)2, KBr basic components were studied in this work. Catalysts and CFMs were studied by XRD, nitrogen and water vapor adsorption/desorption, and atomic absorption spectrophotometry methods. It has been found that the basic components K2PdCl4 and Cu(NO3)2 deposited on a microporous carbon surface undergo changes and form an X-ray amorphous Pd0 phase and a paratacamite—Cu2(OH)3Cl nanocrystalline phase. The catalysts were tested at carbon monoxide initial concentrations of 300 mg/m3 with an effective contact time of the catalyst with the gas–air mixture from 0.12 to 0.50 s. Catalysts provide air purification from CO to concentrations below MPCCO (20 mg/m3) and can be used in respiratory devices. The maximum catalytic activity is observed when the content of palladium in the catalyst is 1.70⋅10−4 mol/g and the content of copper (ІІ) is 4.68⋅10−4 mol/g.

Design of amorphous-nanocrystalline films of TiAlCrNbZrx multi-component alloy: The effect of Zr on the corrosion resistance and mechanical properties

In this study, amorphous/nanocrystalline TiAlCrNbZrx (x = 0, 0.3, 0.7, 1) multi-component alloy films have been successfully prepared on the surface of 316L stainless steel using direct current magnetron sputtering technique. The composition, microstructure, corrosion and mechanical properties, especially the effect of Zr content and structure on the properties, are discussed in detail. X-ray diffraction (XRD) and transmission electron microscopy (TEM) data revealed the presence of nanocrystalline phases among the amorphous phase. The results showed that the amorphous phase can effectively mitigate corrosion, while the nanocrystals can improve the mechanical properties and adhesion of the films as the Zr content increased. The lattice distortion caused by the incorporation of large atomic Zr contributed to a significant change in the film structure. TiAlCrNbZr films with the most nanocrystals showed better plastic deformation ability, while TiAlCrNbZr0.3 has a suitable amorphous/nanocrystal ratio, good corrosion resistance, and excellent mechanical properties.