Alloy Target Research Articles

(PEFCE&E 21 Best Student Poster - First Place) Oxygen Reduction Reaction Properties and Microstructures of Pt/Nb:SnO2 Model Catalysts Fabricated on Pt Single Crystal Surfaces

Introduction Considering strong acidic and severe potential fluctuation environments for operating conditions of Polymer Electrolyte Fuel Cells (PEFC), electrochemical degradation of electrode materials, such as elution and/or oxidation, is crucial for development of high-performance electrode materials, e.g., Pt-based nanoparticles (NPs) and C-based supports. Recently, replacing the C-based supports with metal-oxides aimed for improving electrochemical stabilization has attracted much attention. Among the candidates of metal-oxides used as support materials, X (=Nb, Sb, Ta etc.) doped tin dioxide (X:SnO2) shows relatively high electrical conductivity. Actually, Kakinuma et al. [1,2] demonstrated that superior oxygen reduction reaction (ORR) activity and durability of the Pt NPs supported on Nb-doped SnO2 (Pt NPs/Nb:SnO2). The results clearly show that such the metal-oxide supports are one of the powerful candidates for the next-generation cathode materials. Also, it is considered possible to use Nb:SnO2 as a core material (Pt@Nb:SnO2) for highly durable Pt-shell / metal-oxide-core type catalyst, although influences of microstructures of the Pt-based materials and metal-oxide interface on the ORR properties remains unclear. Therefore, in this study, we prepared Pt NPs/Nb:SnO2 and Pt@Nb:SnO2 model catalysts with atomically-controlled Pt/SnO2 interface under ultra-high vacuum (UHV; ~10-8 Pa) and investigated relationship between the surface and interface microstructures of the model catalysts and their ORR properties. Experimental Nb-doped Sn layer with 5 nm thickness was deposited on the surface-cleaned Pt(111) substrate (Ar+-sputtering and annealing) by arc-plasma deposition (APD) of Sn-Nb alloy target (composition ratio 96:4 (at.%)) at the substrate temperature of 300 K. Subsequently, the prepared sample was transferred to a furnace and thermally-oxidized in dry air (Nb:SnO2 / Pt(111)). Then, the Nb:SnO2 / Pt(111) sample was re-introduced into the UHV-chamber, Pt was vacuum-deposited by the APD for Pt NPs / Nb:SnO2 / Pt(111) and by e-beam evaporation for Pt-shell on the Nb:SnO2/Pt(111) (Pt shell / Nb:SnO2 / Pt(111)) (Fig1-(a) and Fig1-(b), respectively). The microstructures of the catalyst model samples were analyzed by STM, cross sectional STEM-EDS, XPS etc. The ORR properties were evaluated by CV and LSV with the RDE method conducted in N2-purged and O2-saturated 0.1 M HClO4, respectively. The ORR activity was evaluated from j k values at 0.9 V vs. RHE by using Koutecky-Levich equation. The electrochemical stability was discussed by the ORR activity changes during applying the potential cycles (PCs) of 0.6-1.0 V vs. RHE (each 3 s) in O2 saturated 0.1 M HClO4 at room temperature. Results and Discussion The STM image (Fig. 2-(a)) of the Pt NPs / Nb:SnO2 / Pt(111) for the Pt/SnO2 model catalyst showed Pt NPs with an average size of 3.6 nm were distributed over the Nb:SnO2 substrate surface. The ORR activity and durability for the Pt NPs / Nb:SnO2 / Pt(111) clearly outperformed relative to the Pt NPs formed on a highly oriented pyrolytic graphite (HOPG)[3] formed under the same Pt deposition condition: increase in Pt particle sizes and size distribution of Pt NPs by the 10000 PCs loading was suppressed compared to that of the Pt NPs / HOPG.A cross-sectional HAADF-STEM image of the Pt-shell / Nb:SnO2 / Pt(111) model core-shell sample (Fig. 2-(b)) reveals that the surface Pt layers with (111) orientation (ca. 2.5 nm in thickness) and SnO2(101) lattice of ca. 4 nm-thick Nb:SnO2 layer are grown on the Pt(111) substrate surface. This is probably due to lattice matching between the Pt(111) (0.48 × 0.56 nm) and SnO2(101) (0.48 × 0.58 nm)(Fig. 2-(c)). Such the lattice matching might correlate with the forementioned suppression of nanoparticle migration [4] in the Pt NPs / Nb:SnO2 / Pt(111) model catalyst. Furthermore, as shown in Fig. 2-(d), the Pt shell / Nb:SnO2 / Pt(111) shows that the ORR activity enhancement factor is at most × 4.1 vs. clean Pt(111) at 500 PCs and × 3.2 even after 5000 PCs loading. The ORR activity enhancement might stem from so-called the ligand effect of Sn and/or Nb on the surface Pt(111) layer through thermal diffusion such the elements into the surface Pt(111) layer during the model catalyst UHV preparation. At the meeting, I will show ORR properties of the Pt / Nb:SnO2 / Pt(110) and discuss influences of the lattice orientations of the surface Pt and underlaid SnO2 layer. Acknowledgement This study was supported by new energy and industrial technology development organization (NEDO) of Japan.Reference[1] K. Kakinuma et al., Electrochim. Acta., 110, 316-324 (2013).[2] K. Kakinuma et al., J. Electrochem. Soc., 165, 15, J3083-J3089 (2018).[3] S. Takahashi et al., Phys. Chem. Chem. Phys., 17, 18638-18644 (2015).[4] M. Wakisaka, et al., Phys. Chem. Chem. Phys., 12, 4184-4190 (2010). Figure 1

Effect of Ni content on the microstructure and mechanical properties of TiNiN coatings

Incorporation of Ni can have intriguing effects on the phase composition, microstructure and mechanical characteristics of titanium nitride coatings synthesised by physical vapour deposition. In this investigation, a series of TiNiN coatings, with varying Ni contents, were deposited onto Si substrates using the filtered vacuum cathodic arc method by changing the composition of the TiNi alloy target. The aim of this study is to investigate the effect of Ni concentration (as controlled by composition of the target material) on the phase composition, microstructure and mechanical behaviour of these TiNiN coatings. A transition from a fine columnar structure, at low Ni contents (∼2 at.%), to a much finer equiaxed structure at higher Ni concentrations (≥4 at.%) was noted. A maximum hardness value of ∼ 32.4 GPa was attained in the coating containing a Ni concentration of ∼ 4 at.%, which was ascribed to the synergistic effects of solid solution hardening, grain refinement and the presence of a high compressive residual stress. In addition, the density of macroparticles generated in these TiNiN coatings during arc deposition was shown to be inversely related to the melting temperature of the target material.

Analytical and FEM Analyses of High-Speed Impact Behaviour of Al 2024 Alloy

The present work investigates the impact behaviour of Al 2024-T3 alloy using FEM analysis performed through LS DYNA software. Johnson–Cookvisco-plastic model is used to study the ballistic impact resistance of target Al alloy impacted by a rigid steel cylindrical projectile. The tensile properties of Al 2024-T3 alloy reported in the literature are used to estimate the J.C. model parameters. Impact velocities within a range of 50 m/s–900 m/s of the projectile were triggered onto Al alloy target thicknesses in the range of 3.18 mm–6.35 mm. To understand the accuracy of the FEM model, an analytical model proposed by Chen et al. for blunt-nosed projectiles on the ductile targets was used to compare with the obtained residual velocities from FEM simulations. It was observed that the ballistic limit velocities have led to the highest energy absorption behaviour of the Al 2024-T3 alloy for an impact velocity of 183 m/s and a 6.35 mm target thickness. The ballistic limit velocities have increased from 97 m/s to 183 m/s for the considered thickness range of 3.18 mm–6.35 mm. The impact failure was observed to have a petalling formation with two petals for thinner targets, while a full-fledged plugging with no petal formation for the 4.00 mm and 6.35 mm target thicknesses was observed.

Composites to Produce a Material with Zero Absolute Thermopower S = 0 or a Thermopower Switch between S = 0 and S ≠ 0.

From the theory of two-phase composites it is concluded that in the concentration dependence of the Seebeck coefficient S a kink can occur precisely at absolute if the two phases have different kinds of carriers, electrons and holes, and if the phase grains are spherical without preferred orientations and arranged in a symmetrical fashion. This feature, indeed found to be realized in amorphous CrSi thin films deposited by ion beam sputtering from Cr-Si alloy targets, can be applied to make reference standards for at room temperature and even at higher temperatures. Additionally, it may be used to design a thermopower switch between and . It is also concluded that the structure realized in any alloy during solidification does not only depend on the diffusion mobility of the atoms and on the existence of a (relative) minimum in the Gibbs’ free energy. It depends also on the fact whether this structure is compatible with the demand that (spatial) continuity of the entropy and energy flux densities and their gradients is saved during the solidification process.

Fabrication of a 3.5-GHz Solidly Mounted Resonator by Using an AlScN Piezoelectric Thin Film

In this study, a 3.5-GHz solidly mounted resonator (SMR) was developed by doping scandium in aluminum nitride to form AlScN as the piezoelectric thin film. Molybdenum (Mo) of 449 nm thickness and silicon dioxide (SiO2) of 371 nm thickness were used as the high and low acoustic impedance films, respectively, which were alternately stacked on a silicon substrate to form a Bragg reflector. Then, an alloy target with atomic ratio of 15% Sc was adopted to deposit the piezoelectric AlScN thin film on the Bragg reflector, using a radio frequency magnetron sputtering system. The characteristics of the c-axis orientation of the AlScN thin films were optimized by adjusting sputtering parameters as sputtering power of 250 W, sputtering pressure of 20 mTorr, nitrogen gas ratio of 20%, and substrate temperature of 300 °C. Finally, a metal top electrode was coated to form a resonator. The X-ray diffraction (XRD) analysis showed that the diffraction peak angles of the AlScN film shifted towards lower angles in each crystal phase, compared to those of AlN film. The energy dispersive X-ray spectrometer (EDX) analysis showed that the percentage of scandium atom in the film is about 4.5%, regardless of the sputtering conditions. The fabricated resonator exhibited a resonance frequency of 3.46 GHz, which was a small deviation from the preset resonance frequency of 3.5 GHz. The insertion loss of −10.92 dB and the electromechanical coupling coefficient of 2.24% were obtained. As compared to the AlN-based device, the AlScN-based resonator exhibited an improved electromechanical coupling coefficient by about two times.

Texture and Microstructure Evolution of Ultra-High Purity Cu-0.1Al Alloy under Different Rolling Methods

The microstructure and texture distribution of ultra-high purity Cu-0.1Al alloy target play a key role in the quality of the sputtering film. The Cu-0.1Al alloy sheets were processed by unidirectional (UR) and cross rolling (CR), and X-ray diffraction (XRD), and electron backscatter diffraction (EBSD) technologies were adopted to observe the texture and microstructure evolution. XRD results reveal that the texture types vary greatly in UR and CR due to the change of strain path. As the strain increases to 90%, S texture occupies the most, followed by copper texture in the UR sample, while brass texture dominates the most in the CR sample. Additionally, the orientation density of texture does not increase significantly with the increase of strain but shows a downward trend both in UR and CR modes. EBSD analysis demonstrates that compared with UR, the deformation microstructure in CR is more uniform, and the layer spacing between the deformation bands is smaller, which can reduce the local-region stress concentration. After the completion of recrystallization, the difference in average grain size between the UR and CR-annealed samples is not significant, and the recrystallized grains become much finer with the increase of strain, while more equiaxed grains can be observed in CR-annealed samples.

Theoretical analysis of ionization of spherical aluminum alloy projectile impacting aluminum alloy target in hypervelocity impact

A two-stage light gas gun is used to accelerate the sphere 6061 aluminum projectiles to a speed range of 2.3-6.3 km/s in an almost vacuum environment. Spectrometer and pyrometer are adopted to measure the time-frequency characteristics of the collision-generated spectra when 6061 aluminum projectiles impact on 6061 aluminum targets with thicknesses varying from 1 mm to 26 mm. Based on the thermal ionization, theories of the single and the secondary collision are established. Experimental spectra show that threshold velocities of evaporation and plasma phase transition are 2.45 km/s and 4.7 km/s when spherical aluminum alloy projectile impacts on aluminum alloy target. Theoretical calculation demonstrates that neither the single impact nor the secondary impact of debris or secondary compression in the oblique direction can explain the ionization at low-speed impact. The threshold velocity of ionization, however, calculated by the combined secondary collision both in the oblique and horizontal direction during the impact of spherical projectile colliding on the target is most reasonable to explain the plasma produced by relatively low-speed hypervelocity impact.

Structure and magnetic properties of Fe-Co alloy nanoparticles synthesized by pulsed-laser inert gas condensation

Fe-Co alloy nanoparticles of different compositions (Fe content of 76, 51, and 30 at%), along with pure Fe and Co nanoparticles, were prepared by pulsed-laser inert gas condensation, consisting in laser ablation of Fe-Co alloy targets under helium atmosphere. From the morphological point of view, the obtained nanoparticles have nearly spherical shape, follow a lognormal size distribution and exhibit little aggregation. X-ray diffraction and high-resolution electron microscopy coupled with electron energy loss spectroscopy show that the Fe-Co nanoparticles are single crystals with body-centered cubic structure. Furthermore, in the majority of nanoparticles the composition is highly uniform across the whole diameter and there is little variation in composition from one nanoparticle to another. Exposure to non-inert atmosphere leads to the formation of a core@shell metal@oxide morphology characterized by a spinel oxide shell of 2–3 nm around the metallic alloy core. All samples display a ferromagnetic behavior, characterized by a hysteretic magnetization loop. The saturation magnetization attains a maximum value of 2.43 Bohr magnetons per atom for Fe content of 76 at%, in agreement with the Slater-Pauling curve for alloys of 3d elements. Instead, the coercive field, ranging from 29 to 60 kA m−1, is much larger than the reported values for polycrystalline bulk Fe-Co compounds and monotonically increases from pure Fe to pure Co. These results demonstrate that pulsed-laser inert gas condensation allows to prepare high-quality nanoalloys with tailorable magnetic properties, overcoming the limitations of thermal evaporation methods with respect to compositional control.

High temperature (up to 1200 °C) thermal-mechanical stability of Si and Ni doped CrN framework coatings

High temperature thermal-mechanical stability of tribological thin coatings is extremely important to a large number of applications in modern industries. DC magnetron sputtering of single metallic element (Cr, Si) and alloy (Ni:Cr) targets formed transition metal nitrides film coatings, CrSiN and CrNiN onto M2 steel. High temperature in-situ synchrotron X-ray diffraction, in the range 25 °C–700 °C, obtained experimental data for a range of structural and mechanical properties. Furthermore, experimental room temperature Nanoindentation measurements, made before and after the in-situ heating cycle, provided corresponding hardness and shear modulus results. The structural results identified microstructure and phase transformation changes, while the mechanical results identified microstrain, hardness, elastic modulus and deformation resistance properties of the coatings. Density functional theory (DFT) and quasi-harmonic approximation (QHA) modelled the high temperature thermal and mechanical properties such as: Young's modulus, shear modulus and thermal expansion coefficients (populated up to 1200 °C). Estimates of hardness are made by correlating the bulk phase hardness and shear modulus, of the CrN and Ni phases, as a function of temperature. Results indicate that Si doping enhances the hardness of the CrN framework, increasing from 29 to 36 GPa and improves the coatings elastic modulus, and resistance to deformation. However the addition of Ni reduced these properties. Furthermore, formation of (Cr,Si)N and Ni(Cr) solid solutions is inferred from DFT, Rietveld and lattice constant analysis.

Development of Near Gold-Colored TixZr1-xN Nano Thin Films by Arc Ion Plating.

A gold plating technique with wet chemical solution is widely used to make different metallic colors for various industrial applications. However, it results in environmental pollution due to the generation of contaminated water, and it is also an expensive process. As an alternative approach, it is often desirable to use the Physical Vapor Deposition coating method that does not generate such pollution, and to use cheaper material to imitate gold colors. In this letter, target materials consisting of Ti-Zr alloy are employed to realize tens of nanometers thickness metallic thin film that can produce a metallic color that is close to that of natural gold. TiZrN thin films with a thickness ranging (2,000 to 4,000) nm are formed on a substrate using Arc Ion Plating. The results showed that the thin films exhibited an adhesion force of 50 N or more and a hardness of 1,500 Hv or more under a -100 V bias condition, and various gold colors could be realized by changing the ratio of Ti and Zr element of the alloy target.

Laser-generated high entropy metallic glass nanoparticles as bifunctional electrocatalysts

High entropy metallic glass nanoparticles (HEMG NPs) are very promising materials for energy conversion due to the wide tuning possibilities of electrochemical potentials offered by their multimetallic character combined with an amorphous structure. Up until now, the generation of these HEMG NPs involved tedious synthesis procedures where the generated particles were only available on highly specialized supports, which limited their widespread use. Hence, more flexible synthetic approaches to obtain colloidal HEMG NPs for applications in energy conversion and storage are highly desirable. We utilized pulsed laser ablation of bulk high entropy alloy targets in acetonitrile to generate colloidal carbon-coated CrCoFeNiMn and CrCoFeNiMnMo HEMG NPs. An in-depth analysis of the structure and elemental distribution of the obtained nanoparticles down to single-particle levels using advanced transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) methods revealed amorphous quinary and senary alloy phases with slight manganese oxide/hydroxide surface segregation, which were stabilized within graphitic shells. Studies on the catalytic activity of the corresponding carbon-HEMG NPs during oxygen evolution and oxygen reduction reactions revealed an elevated activity upon the incorporation of moderate amounts of Mo into the amorphous alloy, probably due to the defect generation by atomic size mismatch. Furthermore, we demonstrate the superiority of these carbon-HEMG NPs over their crystalline analogies and highlight the suitability of these amorphous multi-elemental NPs in electrocatalytic energy conversion.

Improvement on synaptic properties of WO x -based memristor by doping Ti into WO x

Doping Ti into WO x is widely used to improve the performance of various WO x -based devices. However, Ti-doped WO x (Ti:WO x ) based memristors have not been investigated in depth, especially regarding their synaptic properties. In this report, Ti:WO x films are deposited by sputtering WTi alloy target in Ar + O2 atmosphere, in which the substrates are not heated, avoiding the precipitation of TiO2 phase. As-grown Ti:WO x films exhibit polymorphous crystallized structures, originating from the topological deformation of WO6 octahedron by replacing W with Ti. Furthermore, the memristor with the structure of W/Ti:WO x / indium-doped tin oxide demonstrates typical synaptic properties, including the controllable synapse weight update by adjusting the input pulse amplitude, interval, as well as the transformation from the paired-pulse facilitation to the paired-pulse depression. Moreover, the higher Ti–O band energy leads to smaller hysteresis loop areas of its current–voltage (I–V) curves, which may mean better synaptic performances, such as higher resolution. Additionally, contrary to other metal-oxide based memristors, our device conductance increases by applying positive voltage scans or a series of positive pulses on the metal electrode. Otherwise, it will decrease. With I–V fitting and the energy-band diagrams, we analyzed deep carrier transport processes, revealing a unique synaptic mechanism.

Penetration Damaging Behavior of ATI425 Titanium Alloy

The penetration damaging behavior of ATI425 titanium alloy was studied by 7.62 mm diameter armor piercing projectiles. The damage characteristics and the mechanism were analyzed by observing and analyzing the craters of ATI425 titanium alloy target. It can be found that local temperature-rise of the target plate occurred, even sputtering phenomenon in the opening stage. The shear bands extended upward along the cater wall could be seen in the stable stage. The large non-homogeneous deformation in adiabatic shear bands caused microcracks and micropores. A large number of macro-cracks were observed on the side wall and at the bottom of the crater.

Microstructure, Hardness, and Elastic Modulus of a Multibeam-Sputtered Nanocrystalline Co-Cr-Fe-Ni Compositional Complex Alloy Film

A nanocrystalline Co-Cr-Ni-Fe compositional complex alloy (CCA) film with a thickness of about 1 micron was produced by a multiple-beam-sputtering physical vapor deposition (PVD) technique. The main advantage of this novel method is that it does not require alloy targets, but rather uses commercially pure metal sources. Another benefit of the application of this technique is that it produces compositional gradient samples on a disk surface with a wide range of elemental concentrations, enabling combinatorial analysis of CCA films. In this study, the variation of the phase composition, the microstructure (crystallite size and defect density), and the mechanical performance (hardness and elastic modulus) as a function of the chemical composition was studied in a combinatorial Co-Cr-Ni-Fe thin film sample that was produced on a surface of a disk with a diameter of about 10 cm. The spatial variation of the crystallite size and the density of lattice defects (e.g., dislocations and twin faults) were investigated by X-ray diffraction line profile analysis performed on the patterns taken by synchrotron radiation. The hardness and the elastic modulus were measured by the nanoindentation technique. It was found that a single-phase face-centered cubic (fcc) structure was formed for a wide range of chemical compositions. The microstructure was nanocrystalline with a crystallite size of 10–27 nm and contained a high lattice defect density. The hardness and the elastic modulus values measured for very different compositions were in the ranges of 8.4–11.8 and 182–239 GPa, respectively.

Effect of the methane flow ratio on the structural and mechanical properties of high-entropy alloy co-doped DLC films

High-entropy alloy is co-doped in diamond-like carbon films by sputtering using a single (AlCrNbSiTiV) target. This study analyzed the effects of methane flow rates [Rm = CH4/(Ar + CH4) flow ratio], which varied in the range from 16 to 24%, on the morphological, phase structures, mechanical characteristics and tribological behavior of diamond-like carbon films. The diamond-like carbon film is characterized using Raman spectroscopy, nano-indentation, high-resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and scratch testing. As a result, the element concentration in the diamond-like carbon films is quite near to the High-entropy alloy target composition, and the metal content of co-doped diamond-like carbon films decreases as the fraction of the methane reactive gas increases. For a monotonically increasing Rm flow ratio, the position of the G-peak is downshifted to a low wavenumber, a decrease in ID/IG ratio suggests a decrease in sp2/sp3 ratio, which is associated with the decrease in the fraction of graphite and the more disordered carbon structure. An increase in the Rm flow ratio results in increased hardness (H) and elastic modulus (E) and a decreased friction coefficient, wear rate, H3/E2 and H/E. Cutting tests using a tool coated in a diamond-like carbon film shows the cutter life was extended.

Microstructure and Magnetron Sputtering Properties of W/Re Alloy Targets Fabricated by Vacuum Sintering

Microstructure and Magnetron Sputtering Properties of W/Re Alloy Targets Fabricated by Vacuum Sintering

A 3D printing route to fabrication of ZrCuSi alloy target for ZrCuSiN nanocomposite thin films

The present study demonstrates a simple and robust strategy for fabricating nanocomposite thin films with high quality using a multi-component ZrCuSi single target. The ZrCuSi target was produced by using computer numerical control (CNC) based direct energy deposition (i.e., 3D printing). The influence of the energy density on morphological features and porosity of the ZrCuSi target surface was closely examined at a certain range of the energy density (75–225 J/mm3). X-ray diffractometer (XRD) and scanning electron microscopy (SEM) were applied for confirming the presence of the preferable crystallographic orientation and elucidating the morphological features of the nanocomposite target. In addition, functional nanocomposite thin films deposited from the ZrCuSi target presented in the current study were characterized. A scratch test and field-emission SEM (FE-SEM) revealed the adhesion properties and the morphological features of the nanocomposite coatings. Therefore, this work is highly expected to provide a facile and robust way to fabrication of e multi-component functional targets based ZrN, thereby envisioning usefulness of the nanocomposite coatings for automotive engine parts and various other wear protection applications.

Anti-reflective and wetting properties of femtosecond pulsed laser textured Al alloy surfaces

The effects of laser surface texturing of aluminium alloy targets on the morphologies, wetting properties, and anti-reflection were studied. The parallel micro-trenches with a period of 50 µm were processed by fs-laser line scanning with different laser pulse fluences and laser scanning speeds. The laser textured surfaces showed some micro-cracks, micro-bumps, and micro-porous structures with some nanoparticles decoration. The water wetting response of the samples was measured by static contact angle measurements. With high laser fluence irradiation, the laser-textured Al alloy surfaces exhibited hydrophilic characteristics, while that of low laser fluence irradiation showed hydrophobic characteristics. Furthermore, the anti-reflection performance in the spectral range of 200–1200 nm with the value lower than 5% was obtained at high laser fluence irradiation. The results imply the potential applications of these surfaces in a variety of fields.

Impact of the target material surface layer on neutron yield and target lifetime of the neutron tube

The neutron yield and target lifetime of a neutron tube are affected by the target materials, the oxide layer and the overcoat layer on the target film. Target lifetime can be improved by adopting alloy instead of pure titanium. The neutron yields of pure titanium target and 200 nm oxide titanium target are simulated by SRIM, which are in good agreement with the experimental results. The neutron yield and target lifetime are calculated at different deuterium energy and alloy targets with variable surface layers. The protective overcoat layers include Pd, Ni and Al. The simulated results show that oxide layer reduces the neutron yield, and the thicker the oxide layer is, the less the neutron yield is. The target lifetime is increased by using the alloy targets, in which the scandium-titanium alloys has a higher lifetime. Meanwhile, depositing a protective overcoat on the target film surface can increase the neutron yield and extend the target lifetime of the neutron tube. In order to meet the requirements of long lifetime and high yield neutron tubes in different applications, the target was optimized theoretically.

Insights into microstructural evolution and deformation behaviors of a gradient textured AZ31B Mg alloy plate under hypervelocity impact

We have for the first time elucidated the microstructural evolution and deformation behaviors of a gradient textured AZ31B Mg alloy plate under the ultrahigh strain rate of ~106 s−1 that is generated by a two-stage light gas gun with the hypervelocities of 1.6−4.4 km s−1. The hypervelocity impact cratering behaviors indicate that the cratering deformation of AZ31B Mg alloy is mainly affected by the inertia and strength of the target material. The crater prediction equation of AZ31B Mg alloy target under impact velocity of 5 km s−1 is given. The 2017Al projectile completely melts in the Mg alloy target plate at the impact velocities of 3.8 km s−1 and 4.4 km s−1, and the microstructural evolution around the crater is: dynamic recrystallization zone, high-density twinning zone, low-density twinning zone, and Mg alloy matrix. It is found that the dynamic recrystallization, twinning and cracking are the main deformation behaviors for the AZ31B Mg alloy to absorb the shock wave energy and release the stress generated by the hypervelocity impact. The main plastic deformation mechanisms of the Mg alloy target during hypervelocity impact are twinning and dislocation slip. Microstructure analysis shows the interactions of twins-twins, dislocations-dislocations, and twins-dislocations determine the strain hardening during the hypervelocity impact process, which eventually contributes the dynamic mechanical properties. The evolution of microhardness around the crater further demonstrates the microstructural evolutions and their interactions under the hypervelocity impacts.