Alloy Target Research Articles

Titanium-Doped P-Type WO3 Thin Films for Liquefied Petroleum Gas Detection.

Gas sensors are an important part of smart homes in the era of the Internet of Things. In this work, we studied Ti-doped P-type WO3 thin films for liquefied petroleum gas (LPG) sensors. Ti-doped tungsten oxide films were deposited on glass substrates by direct current reactive magnetron sputtering from a W-Ti alloy target at room temperature. After annealing at 450 °C in N2 ambient for 60 min, p-type Ti-doped WO3 was achieved for the first time. The measurement of the room temperature Hall-effect shows that the film has a resistivity of 5.223 × 103 Ωcm, a hole concentration of 9.227 × 1012 cm−3, and mobility of 1.295 × 102 cm2V−1s−1. X-Ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses reveal that the substitution of W6+ with Ti4+ resulted in p-type conductance. The scanning electron microscope (SEM) images show that the films consist of densely packed nanoparticles. The transmittance of the p-type films is between 72% and 84% in the visible spectra and the optical bandgap is 3.28 eV. The resistance increased when the films were exposed to the reducing gas of liquefied petroleum gas, further confirming the p-type conduction of the films. The p-type films have a quick response and recovery behavior to LPG.

Transformation of Au–Pd alloy nanoparticles to core-shell nanoparticles by electron irradiation

Abstract Present work reports on the electron irradiation induced modification in Au–Pd alloy based spherical shaped nanoparticles in scanning electron microscope (SEM). The Au–Pd alloy thin films were synthesized by DC sputtering of an Au–Pd alloy target and subsequent annealing at 800 °C. The composition and thickness of the as-deposited film was measured by Rutherford Backscattering Spectrometry (RBS). SEM confirmed the formation of spherical shaped Au–Pd alloy nanoparticles in annealed film. In-situ study on the transformation of Au–Pd alloy based spherical shaped nanoparticles to the Au@Au–Pd core-shell nanoparticles during electron irradiation in the SEM was performed. Structural characterizations were carried out by grazing incidence X-ray diffraction (GIXRD) and morphological changes were investigated qualitatively by grazing incidence small angle X-ray scattering (GISAXS) of the annealed film before and after electron irradiation. Theoretical calculations of electron energy loss indicate neither knock-on displacements nor temperature rise are responsible for structural transition observed in present case. It is suggested that electronic-excitations induced atomic displacements may cause spherical to core-shell phase transition.

Electronic and Catalytic Effects of Single-Atom Pd Additives on the Hydrogen Sensing Properties of Co3O4 Nanoparticle Films.

Atomically dispersed Pd additives significantly enhanced the hydrogen sensing performance of a Co3O4 nanoparticle film, and their electronic along with catalytic roles were comprehensively investigated based on a series of systematic experiments. Aggregates of Co3O4 nanoparticles (approximately 3 nm in size) with homogeneously dispersed Pd additives at concentrations in the range of 1-20% (on a molar basis with respect to Co) were generated in the gas phase via reactive pulsed laser ablation of Co-Pd alloy targets in He/O2 mixtures. The form of the Pd could be modified from single atoms to oxide clusters (1-2 nm), and the effects of these additives on the hydrogen sensing properties of thick films prepared by direct deposition were examined. The highest hydrogen sensing performance was obtained at 5% Pd loading, where single Pd atoms were present at the maximum density. Further Pd loading resulted in the formation of Pd oxide clusters and degraded the sensitivity. X-ray photoelectron spectroscopy and Pd K-edge X-ray absorption spectroscopy showed that single Pd atoms in the Pd4+ state at Co3+ sites on the Co3O4 nanoparticle surfaces donated electrons to the Co3O4 valence band. The greater concentration of free electrons led to an increase in the concentration of ionosorbed oxygen under dry air. Consequently, more ionosorbed oxygen was available for reaction with hydrogen, enhancing sensitivity. In situ X-ray absorption spectroscopy data confirmed that approximately 10% of the single Pd atoms in the Pd4+ state were reduced to Pd2+ during exposure to 1000 ppm H2, implying that a Pd4+ ↔ Pd2+ catalytic redox cycle accelerates the water formation reaction during hydrogen sensing. The present results provide deeper insights and understanding of the effects of noble metal additives on gas sensing, while highlighting the unique role of single-atom additives.

Characterization of Al-doped Mn–Co–Ni–O NTC thermistor films prepared by the magnetron co-sputtering approach

Abstract A serial of Al-doped Mn–Co–Ni–O thermistor thin films were prepared by a magnetron co-sputtering system using an Mn1.4Co1.3Ni0.3 alloy target and an Al target. The composition and electrical properties of the thin films could be well controlled by adjusting the sputtering power of the Al target. It was found that the Mn3+, Mn4+, and Co2+ cations at the octahedral sites of the compact and flat films were gradually replaced by the Al3+ cation during doping. The amount of Al dopant in the compound film was easily adjusted by controlling the sputtering power applied to the doping Al target. The experimental results demonstrate that the NTC characters were found in all films. The optimum point (15 W) of Al sputtering power was determined, at which both the maximum material constant B value (4112 K) and the lowest carrier concentration (2.46 × 1014 cm−3) was characterized in the film. The significant enhancement of the B value for NTC thin films can potentially widen the temperature measurement range for sensing applications.

Influence of target dynamics and number of impacts on ballistic performance of 6061-T6 and 7075-T6 aluminum alloy targets

The effect of target condition (static and dynamic) and number of projectile impacts (single and multiple) on the ballistic performance of 6061-T6 Aluminum alloy, 7075-T6 Aluminum alloy and 6061- aluminum alloy Fiber Metal Laminates (FML) have been investigated. Both numerical and experimental approaches were used to predict the nature of target deformation and its kinetic energy absorption. Ballistic experiments were conducted using armor piercing projectiles (APP) of diameter 7.62 mm with velocities ranging between 330 to 450 m/s. Irrespective of the target material (6061-T6 aluminum alloy, 7075-T6 aluminum alloy), non-linear reduction of exit velocity of the projectile was observed for a single plate target. In contrast, large plastic deformation and ‘petaling’ mode of failure was observed for the FML and rubber sandwiched targets. Higher impact energy absorption of the FML target and rubber intruded 7075-T6 aluminum alloy plates is mainly due to the additional resistance offered by the individual layer of metal and fiber. In addition to projectile velocity, when the target (7075-T6 aluminum alloy plate) velocity was varied in the range of 10 to 40 m/s, significant reduction in exit velocity of the projectile was observed compared to static target. This is due the fact that, moving target has altered the penetration behavior of the projectile and additional increase of target velocity caused ‘ricochet’ of the projectile. In addition, when the target was subjected to multiple projectile impacts, gradual reduction of ballistic performance was observed.

Effect of interlayer design on the mechanical properties of AlTiCrN and multilayered AlTiCrN/TiSiN hard coatings

The adhesion strength and mechanical properties of hard coatings on substrates can be improved by adding an interlayer, which is also known as an adhesion, buffer, or seed layer. Cathodic-arc deposition (CAD) of hard coating often results in residual stresses, and the optimized design of the hard coating interlayer helps to reduce residual stress and improve mechanical properties, which is expected to extend the useful life of high speed precision stamping die applications. AlTiCrN transition metal nitride has been used as a protective hard coating because of its high hardness (~36 GPa) and resistance to high temperature oxidation up to 1100 °C. In this study, multicomponent hard coatings of AlTiCrN and AlTiCrN/TiSiN, which in the form of AlTiCrN/TiSiN multilayers, were deposited by cathodic-arc deposition. During the coating process, gradient TiN and CrN were deposited, respectively, as interlayers with different structures to control the residual stress and adhesion strength between the coatings and substrates. AlTiCr and TiSi alloy targets were used to deposit hard AlTiCrN/TiSiN coatings. The multicomponent AlTiCrN/Ti and AlTiCrN/Cr with Ti and Cr interlayers showed high residual stresses of −8 GPa and −8.4 GPa, respectively. The multilayered AlTiCrN/TiSiN coating with intermediate CrN and transition AlTiN/CrN multilayers under the top AlTiCrN/TiSiN multilayers possessed the lowest residual stress (−3 GPa). The residual stress changed by modifying interlayer configuration before the top AlTiCrN/TiSiN multilayers. The design of AlTiCrN/TiSiN multilayered coatings with interlayers of CrN and AlTiCrN/CrN can decrease residual stress and possessed good impact fatigue performance, which can be effective to reduce damage and cracking of hard coatings during cyclic impact loading.

Effects of nitrogen-argon flow ratio on the microstructural and mechanical properties of AlCrN coatings prepared using high power impulse magnetron sputtering

In this study, AlCrN films were deposited from Al70Cr30 alloy targets by high-power impulse magnetron sputtering (HiPIMS). The structural characteristics of the AlCrN films were modulated by performing deposition under various N2/Ar flow ratios. The results indicated that increasing the nitrogen content during deposition leads to corresponding decreases in deposition rate and film thickness, as well as a structural transformation from amorphous to crystalline. A mixture of cubic and hexagonal AlCrN phases was found in the films. Three regions of hardness were observed, and hardness increased with increasing N2/Ar ratio and peaked at 33.6GPa. Good adhesion and wear resistance were observed in all samples.

Processing and characterization of a multibeam sputtered nanocrystalline CoCrFeNi high-entropy alloy film

Physical vapor deposition (PVD) is a well-known route for manufacturing hard coatings. In recent years, PVD has also been applied to create high-entropy alloy (HEA) thin films. HEAs are multicomponent alloys with nearly equal atomic fractions. To achieve the desired composition, typically alloy targets are used in the deposition process. The present work demonstrates that HEA thin films can also be processed using a multiple beam sputtering system in PVD, which does not require preliminary manufacturing of HEA targets, but rather uses commercially pure metal targets. The effectivity of this technique was demonstrated on a nanocrystalline CoCrNiFe HEA film with a thickness of about 1 μm. A part of the compositional gradient sample exhibited equal elemental fractions. The microstructure and the hardness of this part of the PVD film were studied in detail, and the results were compared with those obtained on a bulk nanocrystalline sample having the same chemical composition, but was prepared by the high pressure torsion (HPT) technique. The crystallite size and the texture were characterized by X-ray diffraction, while the hardness was measured by nanoindentation. The PVD film exhibited an exceptionally high hardness of 9.8 ± 0.3 GPa, a value that was notably higher than that determined for the HPT sample (7.3 ± 0.3 GPa). This study also demonstrated the capability of this new multiple beam sputtering technique for the production of compositional gradient samples with a wide range of elemental concentrations, enabling combinatorial analysis of multiple elements high-entropy alloy.

Relationship between target materials and various properties of PLD-made isotropic Nd-Fe-B films

In order to deposit isotropic Nd-Fe-B film magnets on metal substrates, a laser beam with an energy density of approximately 3 J/cm2 was defocused on the surface of Nd-Fe-B sintered targets with three densities of 5.69, 6.14, and 6.64 g/cm3, respectively. The different Nd content (Nd/(Nd + Fe)) between each film and the corresponding targets decreased as the density of the targets increased. We have reported that the deposition using a Nd-Fe-B alloy target under the same laser energy density and T-S distance enabled us to obtain the good transfer of composition from an alloy target to a film. It was clarified that the similar result could be obtained in the use of a sintered target with the density of 6.64 g/cm3. Comparison of magnetic properties, normalized demagnetization curves, and microstructure between the films prepared using a sintered target (6.64 g/cm3) and a Nd-Fe-B alloy target, respectively, was carried out. The values of coercivity and (BH)max of the samples prepared by the sintered target were higher than those of the films prepared using the alloy one. Moreover, the use of a Nd-Fe-B sintered target enabled us to improve the reproducibility of squareness in demagnetization curves. It is considered that the results of comparison are attributed to the different microstructure of the films such as the precipitation due to uneven distribution of α-Fe and Nd elements. We also suppose that the formation of microstructure in each film originates from the microstructure of the corresponding targets.

Three dimensional YSZ interface engineering layer for enhancement of oxygen reduction reactions of low temperature solid oxide fuel cells

In this study, we fabricated three dimensional yttria-stabilized zirconia (YSZ) interface engineering layer (IEL) by using a DC sputtering method to enhance oxygen reduction reactions (ORRs) of low temperature solid oxide fuel cells (LT-SOFCs). In order to deposit three dimensional YSZ IEL, a commercial Y–Zr metal alloy target was sputtered under various deposition pressure conditions (4, 8, 12 Pa) and then annealed at 800 °C for 6 h. Phase transformation of metal alloy Y–Zr to YSZ was identified by X-ray diffraction, X-ray photoelectron spectroscopy and high resolution-transmission electron microscope. The roughness of the three dimensional YSZ IELs were strongly related to the deposition pressure of the sputtering technique. After physical and chemical characterization, electrochemical examinations proved that the three dimensional YSZ IELs efficiently improved the ORR activity by geometrical effects. The fuel cell with the IEL fabricated at 8 Pa condition achieved the best power density (37.9 mW/cm2), which was 30.2% improved performance compared to the fuel cell without IEL (29.1 mW/cm2). Electrochemical impedance spectroscopy investigations also proved that rough three dimensional YSZ IELs efficiently enhance the performance of LT-SOFCs.

Mn-Co-Ni-O thin films prepared by sputtering with alloy target

The thin film of heat-sensitive materials has been widely concerned with the current trend of miniaturization and integration of sensors. In this work, Mn1.56Co0.96Ni0.48O4 (MCNO) thin films were prepared on SiO2/Si substrates by sputtering with Mn–Co–Ni alloy target and then annealing in air at different temperatures (650–900 °C). The X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) analysis indicated that the main crystalline phase of MCNO thin films was spinel crystal structure; the surface of the thin films was very dense and uniform. The electrical properties of the thin films were studied in the temperature range of–5–50 °C. The MCNO thin film with a low room temperature resistance R25 of 71.1 kΩ and a high thermosensitive constant B value of 3305 K was obtained at 750 °C. X-ray photoelectron spectroscopy (XPS) analysis showed that the concentration of Mn3+ and Mn4+ cations in MCNO thin films is the highest when annealing temperature is 750 °C. The complex impedance analysis revealed internal conduction mechanism of the MCNO thin film and the resistance of the thin film was dominated by grain boundary resistance.

Effect of Lode angle incorporation into a fracture criterion in predicting the ballistic resistance of 2024-T351 aluminum alloy plates struck by cylindrical projectiles with different nose shapes

The aim of the present paper is to evaluate the effect of Lode angle incorporation into a fracture criterion when predicting the ballistic resistance of 2024-T351 aluminum alloy plates struck by cylindrical projectiles with different nose shapes through finite element (FE) simulations. To this end ballistic tests in the sub-ordnance impact velocity range were firstly conducted on 9.94 mm thick 2024-T351 aluminum alloy plates using cylindrical projectiles with blunt, hemispherical and ogival nose shapes, a nominal diameter of 12.66 mm, and a nominal mass of 50 g. Ballistic limit velocities (BLVs) for different projectile-target pairs considered were calculated using initial vs. residual velocity data obtained in the experiments. Subsequently FE simulations of the conducted experiments were performed with SIMULIA Abaqus software. In those simulations Johnson–Cook yield criterion with a modified strain hardening law was accompanied with either the Lode-independent Johnson–Cook (JC) fracture criterion or the Lode-dependent modified Mohr–Coulomb (MMC) fracture criterion to describe target material properties. Finally, the predicted ballistic resistance and fracture patterns of the targets were compared with those observed in the experiments. It was found that in the simulations with the Lode-independent JC fracture criterion the BLVs of the targets were overestimated by 18.0–35.1% depending on the projectile nose shape. In the simulations with MMC fracture criterion the BLVs predictions were substantially improved, so that the difference with the experimental results did not exceed 9.0%. Targets failure mechanisms obtained in the simulations with MMC fracture criterion also better match the experiments than those predicted with JC fracture criterion. In the simulations with MMC fracture criterion the targets impacted by the projectiles with blunt and hemispherical noses failed through shear plugging, whereas ogive-nosed projectiles caused ductile hole enlargement and target fragmentation due to its rear side radial fracture and bending of formed short petals with their eventual shear fracture. At the same time the simulations with JC fracture criterion predicted shear plugging for the blunt-nosed projectiles, very small conical plug ejection and target fragmentation due to discing for the hemispherical-nosed projectiles, and ductile hole enlargement for the ogive-nosed projectiles. A detailed analysis of the failure process revealed that in the case of the ogive-nosed and hemispherical-nosed projectiles, respectively, the ductile hole enlargement occurs during the initial stage of the impact and subsequent through-thickness fracture develops causing either fragmentation of the target or its shear plugging failure. The Lode-independent JC fracture criterion overestimates a material fracture strain under shear, thus leading to poor prediction of 2024-T351 aluminum alloy targets ballistic performance in the numerical simulations.

Picosecond laser-induced surface structures on alloys in liquids and their influence on nanoparticle productivity during laser ablation.

The productivity of nanoparticles formed by laser ablation of gold-silver and iron-gold alloy as well as copper and iron-nickel alloy targets in water is correlated with the formation of laser-induced surface structures. At a laser fluence optimized for maximum nanoparticle productivity, it is found that a binary alloy with an equimolar ratio forms laser-induced periodic surface structures (LIPSS) after ablation, if one of the constituent metals also form LIPSS. The ablation rate of nanoparticles linearly depends on the laser fluence if LIPSS is not formed, while a logarithmic trend and a decrease in productivity is evident when LIPSS is formed. To cancel LIPSS formation and recover from this decrease, a change to circularly polarized light is performed and an increase in nanoparticle productivity of more than 30% is observed.

ВЛИЯНИЕ ПРЕДВАРИТЕЛЬНОЙ УЛЬТРАЗВУКОВОЙ ОБРАБОТКИ ТИТАНОВОГО СПЛАВА ВТ6 НА СТРУКТУРУ ПОВЕРХНОСТНОГО СЛОЯ, ПОДВЕРГНУТОГО ИМПЛАНТАЦИИ

The article presents a study on the implantation of silver titanium alloy VT6. It has been shown that ion implantation contributes to the creation of compressive stresses in the surface layer of the target, which makes it possible to increase the endurance indices of the processed alloy under alternating loads. Ultrasonic processing leads to the formation of a nanostructured layer on the surface of a VT6 alloy target. As a result of ultrasonic impact treatment, the structure of the surface layer undergoes significant changes.

Perforation Characteristics of Metal Target plate subjected to PELE

Abstract The perforation tests of 45 # steel target plate and 2A12 aluminium alloy target plate by PELE (the Penetrator with Lateral Efficiency) were carried out in this paper to study the perforation failure characteristics of metal target plate. The macroscopic morphology of perforation on the target plate and the plug was observed, and the perforation wall was cut and polished to observe the distribution and trend of the cracks in the perforation wall by scanning electron microscopy (SEM) and metallographic microscopy. The magnitude and direction of the force produced by PELE on the target during penetration were calculated by numerical simulation. The experimental and numerical results show that, the perforation failure of metal target plate by PELE is different from the ductile perforation by conical-nosed projectile and the punching failure by flat-nosed projectile. The longitudinal cross section of the perforation is funnel-shaped and the shape of the plug is like a circular truncated cone. In the process of penetrating the target plate, the expansion of the filling causes the jacket to exert a force with a certain angle to the direction of projectile movement, which is the main reason for the funnel-shaped perforation and the circular truncated cone shaped plug.

Simulation Study of the Effect of Projectile Length-Diameter Ratio on Anti-Penetration Performance of Composite Armor

We studied the failure modes of 55 g cylindrical projectile penetrating ceramic/titanium alloy/gap/polyethylene/gap/921A steel composite armor structure by numerical simulation, obtained the influence of projectile length-diameter ratio on the anti-penetration performance of structure by analysis. The results showed that, ceramic breaks in-plane and forms ceramic cone, titanium alloy target shows shear failure and bending deformation, 921A steel target shows adiabatic shear failure mode when it is penetrated, bulging when it is not penetrated, the front polyethylene target shows compressive shear deformation, the rear polyethylene target shows bending deformation, and fiber tensile failure is the main failure mode, the impact fiber layer has obvious delamination and degumming phenomenon. Under the same mass condition, the larger the length-diameter ratio of the projectile, the smaller the size of the breach and the greater the penetration depth. With the further increase of the length-diameter ratio, the impact of the projectile on the penetration effect is weakened.

Влияние фазовых превращений на взаимодействие алюминиевых сплавов при скоростях более 9 km/s

The introduction of an aluminum jet with a speed of 8 - 11 km / s into an aluminum alloy target is being investigated. An analysis of the kinetics and parameters of penetration, the surface of the cavity after the introduction suggests that at speeds of more than 9 km / s the hydrodynamic nature of the penetration is violated due to the melting of interacting metals. The results of the study are intended to develop screen protection of spacecraft from the most dangerous fragments of space debris.

Long-term stability and disappearing anode effects during reactive DC and pulsed bipolar magnetron sputtering of Al2O3

Reactive magnetron sputtering is a well-established technique to deposit compound films with different composition. Target poisoning influences the process stability and gives rise to hysteresis effects. Recently, a double S-shaped hysteresis curve has been reported, meaning two values of discharge voltage correspond to one defined value of the reactive gas partial pressure. In the present study, the long-term stability of the hysteresis behavior was studied in an industrial system equipped with a mass spectrometer, an optical emission spectrometer and an external anode. Cycles of decreasing and increasing the target voltage have been repeated several times for single Al alloy target DC sputtering and bipolar pulsed sputtering. In the first case, changes in the hysteresis S-shaped curve depending on time were detected indicating that the system moves towards the poisoned mode meaning higher currents at low voltages and vice versa. When an external additional anode is opened, the system instantly reacts by moving closer to the metallic mode. All of our observations indicate that the long-term behavior is caused by the effect of a disappearing anode and corresponding effects on the plasma medium. Bipolar sputtering reduces considerably the effects of disappearing anode, but a long time evolution can still be seen.

A Novel Method for Notable Reducing Phase Transition Temperature of VO2 Films for Smart Energy Efficient Windows.

Although Vanadium dioxide (VO2) has a potential application value for smart energy efficient windows because of its unique phase transition characteristic, there are still many obstacles that need to be overcome. One challenge is to reduce its high transition temperature (ζc = 68 °C) to near room temperature without causing its phase transition performance degradation. In this paper, a novel method was employed that covered a 3 nm ultra-thin heavy Cr-doped VO2 layer on the pure VO2 films. Compared with the as-grown pure VO2, obviously, phase transition temperature decreasing from 59.5 °C to 48.0 °C was observed. Different from previous doping techniques, almost no phase transition performance weakening occurred. Based on the microstructure and electrical parameters measurement results, the mechanism of ζc reducing was discussed. The upper ultra-thin heavy Cr-doped layer may act as the induced role of phase transition. With temperature increasing, carrier concentration increased from the upper heavy Cr-doped layer to the bottom pure VO2 layer by diffusion, and induced the carrier concentration reach to phase transition critical value from top to bottom gradually. The present method is not only a simpler technique, but also avoids expensive alloy targets.

Unraveling the Surface Chemistry and Structure in Highly Active Sputtered Pt3Y Catalyst Films for the Oxygen Reduction Reaction.

Platinum is the most widely used and best performing sole element for catalyzing the oxygen reduction reaction (ORR) in low-temperature fuel cells. Although recyclable, there is a need to reduce the amount used in current fuel cells for their extensive uptake in society. Alloying platinum with rare-earth elements such as yttrium can provide an increase in activity of more than seven times, reducing the amount of platinum and the total amount of catalyst material required for the ORR. As yttrium is easily oxidized, exposure of the Pt-Y catalyst layer to air causes the formation of an oxide layer that can be removed during acid treatment, leaving behind a highly active pure platinum overlayer. This paper presents an investigation of the overlayer composition and quality of Pt3Y films sputtered from an alloy target. The Pt3Y catalyst surface is investigated using synchrotron radiation X-ray photoelectron spectroscopy before and after acid treatment. A new substoichiometric oxide component is identified. The oxide layer extends into the alloy surface, and although it is not completely removed with acid treatment, the catalyst still achieves the expected high ORR activity. Other surface-sensitive techniques show that the sputtered films are smooth and bulk X-ray diffraction reveals many defects and high microstrain. Nevertheless, sputtered Pt3Y exhibits a very high activity regardless of the film's oxide content and imperfections, highlighting Pt3Y as a promising catalyst. The obtained results will help to support its integration into fuel cell systems.