Interface Damping Research Articles

Role of Microstructure on the Shock-Induced Strengthening Behavior of Ti–6Al–4V Alloy

The influence of microstructure on the shock-induced strengthening behavior of Ti–6Al–4V (Ti-64) alloy was systematically investigated through plate impact experiments and quasi-static reload compression tests. Ti-64 displays no enhanced shock-induced strengthening effect at equivalent strain, regardless of the microstructure and shock stress amplitude. However, the shock-induced enhancement ratio is higher in the alloy having the bimodal microstructure with high equiaxed primary α-phase ($$\alpha_{P}$$) volume fraction or the lamellar microstructure with wide α-platelets. The microstructure analyses show that the substructures of the postshock Ti-64 with both bimodal and lamellar microstructures are dominated by planar slip. Dislocations are easier to nucleate, move and tangle in those large-sized α phases, such as equiaxed $$\alpha_{P}$$ and wide α-platelet, leading to the formation of reticular substructures and slip bands. However, the dislocation density is relatively low in the small α plate of the transformed β regions and in the narrow α-platelet, which is attributed to the relaxation of shock stress and consequently to the suppression of dislocation nucleation caused by the obvious grain/phase boundary damping effect. Only a small number of twins were formed in the lamellar microstructure with wide α-platelet, indicating that grain size and interface damping also affect the twinning behavior of Ti-64 under shock loading conditions.

Chemical interface damping for propagating surface plasmon polaritons in gold nanostripes.

Leakage radiation microscopy has been used to examine chemical interface damping (CID) for the propagating surface plasmon polariton (PSPP) modes of Au nanostripes-nanofabricated structures with heights of 40 or 50 nm, widths between 2 and 4 µm, and 100 µm lengths. Real space imaging was used to determine the propagation lengths LSPP of the leaky PSPP modes, and back focal plane measurements generated ω vs k dispersion curves, which yield the PSPP group velocities vg. The combination of these two experiments was used to calculate the PSPP lifetime via T1 = LSPP/vg. The difference in T1 times between bare and thiol coated nanostripes was used to determine the dephasing rate due to CID ΓCID for the adsorbed thiol molecules. A variety of different thiol molecules were examined, as well as nanostripes with different dimensions. The values of ΓCID are similar for the different systems and are an order-of-magnitude smaller than the typical values observed for the localized surface plasmon resonances (LSPRs) of Au nanoparticles. Scaling the measured ΓCID values by the effective path length for electron-surface scattering shows that the CID effect for the PSPP modes of the nanostripes is similar to that for the LSPR modes of nanoparticles. This is somewhat surprising given that PSPPs and LSPRs have different properties: PSPPs have a well-defined momentum, whereas LSPRs do not. The magnitude of ΓCID for the nanostripes could be increased by reducing their dimensions, principally the height of the nanostructures. However, decreasing dimensions for the leaky PSPP mode increases radiation damping, which would make it challenging to accurately measure ΓCID.

Photoinduced electron transfer dynamics of AuNPs and Au@PdNPs supported on graphene oxide probed by dark-field hyperspectral microscopy.

The time scale for interfacial photoinduced electron transfer (PeT) in plasmonic nanoparticles is not well established and the details are still under debate. This has renewed the interest in studying the electron transfer effect from both experimental and theoretical points of view. We present a quantitative analysis of PeT in single spherical gold (Au) and gold@palladium core@shell (Au@Pd) nanoparticles supported on reduced graphene oxide (RGO) using dark-field hyperspectral microscopy (DFHM) and electrochemical impedance spectroscopy (EIS). By studying the plasmon bandwidth in the scattering spectra of single particles and by correlating it to the plasmon damping processes we showed that PeT occurs from the AuNPs to RGO in a 10 fs time scale with a quantum efficiency of 35%. The introduction of a Pd shell on the AuNPs decreases the PeT time, with transfer occurring in as little as 1.7 fs with quantum yield higher than 74%. Furthermore, EIS showed a smaller resistance for PeT on RGO/Au@PdNPs under green light illumination. Our results can improve the understanding of the chemical interface damping process due to PeT in plasmonic nanomaterials and can enable the design of more efficient plasmon enhanced photocatalysts.

Role of chemical interface damping for tuning chemical enhancement in resonance surface-enhanced Raman scattering of plasmonic gold nanorods

Chemical interface damping in plasmonic gold nanoparticles is closely connected with chemical enhancement in resonance SERS.

Test of spin pumping into proximity-polarized Pt by in-phase and out-of-phase pumping in Py/Pt/Py

Spin pumping into proximity-polarized Pt was investigated by magnetic damping studies of Permalloy(Py)/Pt and Py/Pt/Py structures for a Pt thickness range of $0l{d}_{\mathrm{Pt}}l3$ nm. The observed exponential increase in damping with increasing ${d}_{\mathrm{Pt}}$ in Py/Pt is consistent with previous studies of single crystal Fe/Pt. However, at present there are no studies of magnetic double layer structures, ferromagnet/Pt/ferromagnet. The main reason is that the presence of an induced magnetic moment in Pt, by proximity effect, leads to a strong interlayer exchange coupling. Proximity effect has so far not been addressed in the framework of spin pumping. Due to the ferromagnetic interlayer exchange coupling mediated by Pt, the magnetic response of the Py/Pt/Py structure results in optical (out-of-phase) and acoustic (in-phase) resonance modes. The magnetic damping of both modes has a different dependence on ${d}_{\mathrm{Pt}}$ than that of the Py/Pt structure. The study of Py/Pt/Py is sensitive to both the magnitude and phase of spin pumping and thus provides a stringent test of validity for spin-pumping theory for systems with proximity magnetism. We found that the results in Py/Pt and Py/Pt/Py can be self-consistently interpreted by a standard spin pumping theory with ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{g}}_{\ensuremath{\uparrow}\ensuremath{\downarrow}}=4.3\ifmmode\times\else\texttimes\fi{}{10}^{15}\ifmmode\pm\else\textpm\fi{}0.4\ifmmode\times\else\texttimes\fi{}{10}^{15}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$ and ${\ensuremath{\lambda}}_{\mathrm{sd}}=1.1\ifmmode\pm\else\textpm\fi{}0.1$ nm. We found no evidence of any additional contributions to the interface damping.

Колебания вязкой трехслойной жидкости в неподвижном баке

Due to the continued research into chemistry, biology, pharmaceutics and rocket space technology, interest in the study of the dynamics of layered fluids has increased significantly. The paper focuses on oscillations of a three-layer viscous fluid, gives the formulation of the viscous fluid free oscillations problem. Within the research, we determined natural frequencies and damping coefficients of oscillations of the three-layer viscous fluid in a cylindrical vessel by means of the boundary layer method and a mechanical analog. Oscillations of the three-layer viscous fluid were considered as joint oscillations of two partial hydrodynamic systems, one of which corresponds to oscillations of the upper and middle viscous fluids, and the other one - to oscillations of the middle and lower fluids. Then, we determined the coefficients of viscous resistance in partial hydrodynamic systems of a two-layer viscous fluid. Using the mechanical analog of oscillations of the three-layer liquid, we derived the characteristic equation for determining natural frequencies of the hydrodynamic system under consideration. Next, we calculated the dependency of natural frequencies and liquid-liquid interface damping coefficients on the height of the middle layer and the density of the upper fluid. Finally, we analyzed and compared theoretical calculations with the results obtained by other researchers and experimental investigation. The paper gives the results of experimental studies of oscillations of the three-layer fluid in a stationary cylindrical tank.

Spin Pumping in Asymmetric Fe50Pt50/Cu/Fe20Ni80 Trilayer Structure

Herein, spin transport dynamics across asymmetric Fe50Pt50/Cu/Fe20Ni80 soft‐magnetic trilayer structure is reported and thereby modulation of magnetic parameters including damping and effective field is determined by means of the angular dependence of broadband ferromagnetic resonance measurements. At distinct precession of individual magnetic layer, spin‐pumping is found to be prevalent with expected linewidth increase. Mutual precession for wide range of resonance configuration reveals a collective reduction in anisotropy field of around 200 mT for both Fe50Pt50 and Fe20Ni80 systems. Subsequent observation of no‐excess interface damping shows the possible control of spin‐pumping effect by tuning the net flow of spin‐current in a multilayer structure. These experimental findings have significance for microwave devices that require tunable anisotropy field in magnetic multilayers.

An Experimental Study for the Cyclic Interface Properties of the EPS–sand Mixtures Reinforced with Geogrid

Design and analysis of geosynthetic-reinforced soil structures subjected to repeated loading (e.g. compaction, traffic and earthquake loads) require a proper understanding of the cyclic soil–geosynthetic interface behaviour. This research is undertaken to study the interface properties between sand-expanded polystyrene (EPS) mixtures and geogrid reinforcement under cyclic loading. A series of cyclic tests is performed and the influences of normal stresses, cyclic shear amplitudes and number of cycles are studied. The experiments are conducted using a large-scale direct shear test device allowing to perform displacement-controlled cyclic tests. Accordingly, the influence of the aforementioned parameters on interface shear stiffness and damping ratio is discussed. The results of the experiments showed that adding 0.9% EPS beads to the sand bed leads to the decrease in interface shear stiffness by 30% to 63%, depending on the shear displacement amplitude. In contrast, for the same EPS content ratio, the interface damping increases roughly twice, irrespective of the applied shear displacement amplitude. The value of hardening factor was also found to increase with cycle number under different normal stress levels.

Tuning Chemical Interface Damping: Interfacial Electronic Effects of Adsorbate Molecules and Sharp Tips of Single Gold Bipyramids.

The optimization of the localized surface plasmon resonance (LSPR)-decaying channels of hot-electrons is essential for efficient optical and photochemical processes. Understanding and having the ability to control chemical interface damping (CID) channel contributions will bring about new possibilities for tuning the efficiency of plasmonic hot-electron energy transfer in artificial devices. In this scanning electron microscopy-correlated dark-field scattering study, the CID was controlled by focusing on the electronic nature of disubstituted benzene rings acting as adsorbates, as well as the effects of sharp tips on gold bipyramids (AuBPs) with similar aspect ratios to those of gold nanorods. The results showed that the sharp tips on single AuBPs, as well as the electronic effects of the adsorbate molecules, increase the interfacial contact between the nanoparticles and adsorbate molecules. Electron withdrawing groups (EWGs) on the adsorbates induce larger homogeneous LSPR line widths compared to those of electron donating groups (EDGs). Depending on the location (ortho, meta, and para) of the EDG, the effect of benzene rings with an EDG, which was considered to be induced by sulfur atoms bound to the nanoparticle surface, is weakened by the back transfer of electrons facilitated by the difference in the availability of the electrons of the EDG. Therefore, this study reports that the CID in the LSPR total decay channels can be tuned by controlling the electron withdrawing and electron donating features of adsorbate molecules with the surface topology of metal.

Modelling of SAW-PDMS acoustofluidics: physical fields and particle motions influenced by different descriptions of the PDMS domain.

In modelling acoustofluidic chips actuated by surface acoustic waves (SAWs) and using polydimethylsilane (PDMS) as a channel material, reduced models are often adopted to describe the acoustic behaviors of PDMS. Here, based on a standing SAW (SSAW) acoustophoresis chip, we compared three different descriptions of a PDMS chamber and looked into in-chamber physical fields and ensuing particle motion processes through finite element (FE) simulations. Specifically, the PDMS domain was considered as an elastic solid material, a non-flow fluid, and a lossy wall, respectively. The major findings include: (a) the shear waves that propagated in a solid PDMS wall did not influence the in-chamber pressure and ARF fields severely, but induced an observable difference in the acoustic streaming (AS) patterns, and distinctly changed the trajectories of polystyrene particles, especially those whose radii were below 1.5 μm; and (b) the equivalent damping coefficients were linearly dependent on the SAW frequency, characterized by a fixed loss per wavelength, indicating the wave leakage at the interface being the main source of the transmission loss of SAWs. Meanwhile, the acoustic radiation force (ARF) can be overestimated when describing PDMS as a lossy wall, especially at the bottom corners of the chamber, which could cause inaccurate predictions of the motion of big particles. Based on the damping mechanism, a rough protocol is provided for scaling of pressure fields between different models. Some suggestions for device designs and operations are also given based on the obtained findings.

Single-particle correlation study: chemical interface damping induced by biotinylated proteins with sulfur in plasmonic gold nanorods.

Plasmonic gold nanoparticles can be an efficient source of hot electrons that can transfer to adsorbed molecules for photochemistry, followed by broadening of the homogeneous localized surface plasmon resonance (LSPR) linewidth. Although chemical interface damping (CID) is one of the main decay processes, it is the most poorly understood damping mechanism in gold nanoparticles. Herein, to better understand CID and to find new functional groups that can induce CID as an alternative to thiol groups (-SH, sulfhydryl groups), we carried out scanning electron microscopy (SEM) correlated dark-field (DF) scattering studies of gold nanorods (AuNRs) at the single-particle level. We found that biotin with sulfur can lead to strong plasmon damping in single AuNRs. We chose biotin in this study because it is widely used as a linker that can selectively bind to streptavidin in many biological sensing experiments. We further demonstrated the possibility of real-time detection of biological molecules, specifically biotinylated BSA proteins, by means of CID in single AuNRs. Therefore, this study allows us to gain a deeper insight into how adsorbate molecules with sulfur affect CID, which is an important step toward developing a CID-based LSPR biosensor to detect real biological molecules having sulfur or thiol groups without interference from the medium dielectric constant in single AuNRs.

Influence of the capping material on pyridine-induced chemical interface damping in single gold nanorods.

Chemical interface damping (CID) is one of the plasmon decay processes that occur in gold nanoparticles. With the aim of exploring new functional groups that can induce CID as an alternative to thiol groups, we performed dark-field (DF) scattering studies of gold nanorods (AuNRs) using pyridine as adsorbate. We found that the adsorption of pyridine molecules on single AuNRs though nitrogen-gold interactions leads to an increase of the localized surface plasmon resonance (LSPR) linewidth. However, pyridine molecules were not adsorbed effectively on AuNR surfaces having a capping reagent. This study allows us to gain insight into the effect and role of the capping reagent in pyridine-induced CID. Furthermore, pyridine was revealed to induce a strong CID through the interaction of the nitrogen atom with the Au surface, provided the capping material was previously removed from the AuNRs by oxygen plasma treatment. Finally, we demonstrated that CID could be used to sense pyridine and its derivatives in real-time.

Gilbert damping in FeCo alloy: From weak to strong spin disorder

We study systematically the Gilbert damping of FeCo alloy from first-principles scattering calculations. For collinear magnetization, the nonmonotonic concentration dependence of the reported Gilbert damping is reproduced. At Co-rich concentration, the Gilbert damping in the faced-centred-cubic phase is found to be a half to a third of that in the body-centred-cubic phase for the same alloy concentration. Spin-wave increases the Gilbert damping in the form consistent with the previously discovered spin pumping in noncollinear magnetization. We also consider the Gilbert damping with strong spin disorder that significantly reduces the total magnetization from its saturation magnetization. In such cases, the dimensionless Gilbert damping parameter tends to diverge near the ferromagnetic-paramagnetic phase transition point while the damping frequency saturates and therefore is more appropriate to describe the damping in magnetization dynamics with strong spin disorder. The spin-mixing conductance that gives rise to the interface damping enhancement is almost unaffected by spin waves or strong spin fluctuation even near the transition point.

The Sensitivity of Surface Plasmon Resonance Damping for Colloidal Silver Nanoparticles

The impact of environmental conditions (ionic strength and type of electrolytes) on the damping of surface plasmon resonance spectra of silver nanoparticles (AgNPs) colloids suspensions were investigated. This study is structured for analyzing the interaction of three different sized (20, 50, and 80 nm) silver nanoparticles, which electrostatically stabilized (sodium citrate) with non-adsorbent media (e.g. NaCl and NaOH). The absorption spectra were observed using a UV-visible / NIR spectrophotometer in the range of 300 – 1000 nm. Taking advantage of the sensitivity of surface plasmon resonance (SPR) on the refractive index of the surrounding medium on the silver nanoparticles, the role of ionic media’s refractive index in changing the sensitivity of SPR on damping and plasmon resonance shift were investigated experimentally and compared with theory results thoroughly. The results of experiment revealed that the absorption spectra are blue shifted, due to the increase in perturbation of conduction electron density of AgNPs when the electron density of surrounding media increases and electrons transfer from Cl- or OH- ions to the NPs. The results of sensitivity of SPR damping corroborate the assumption that the damping of resonance strongly depend on type and concentration of ionic surrounding media (chemical interface damping). It is demonstrated that the sensitivity of SPR damping is depended on primary particle size.

Gold Ultrathin Nanorods with Controlled Aspect Ratios and Surface Modifications: Formation Mechanism and Localized Surface Plasmon Resonance.

We synthesized gold ultrathin nanorods (AuUNRs) by slow reductions of gold(I) in the presence of oleylamine (OA) as a surfactant. Transmission electron microscopy revealed that the lengths of AuUNRs were tuned in the range of 5-20 nm while keeping the diameter constant (∼2 nm) by changing the relative concentration of OA and Au(I). It is proposed on the basis of time-resolved optical spectroscopy that AuUNRs are formed via the formation of small (<2 nm) Au spherical clusters followed by their one-dimensional attachment in OA micelles. The surfactant OA on AuUNRs was successfully replaced with glutathionate or dodecanethiolate by the ligand exchange approach. Optical extinction spectroscopy on a series of AuUNRs with different aspect ratios (ARs) revealed a single intense extinction band in the near-IR (NIR) region due to the longitudinal localized surface plasmon resonance (LSPR), the peak position of which is red-shifted with the AR. The NIR bands of AuUNRs with AR < 5 were blue-shifted upon the ligand exchange from OA to thiolates, in sharp contrast to the red shift observed in the conventional Au nanorods and nanospheres (diameter >10 nm). This behavior suggests that the NIR bands of thiolate-protected AuUNRs with AR < 5 are not plasmonic in nature, but are associated with a single-electron excitation between quantized states. The LSPR band was attenuated by thiolate passivation that can be explained by the direct decay of plasmons into an interfacial charge transfer state (chemical interface damping). The LSPR wavelengths of AuUNRs are remarkably longer than those of the conventional AuNRs with the same AR, demonstrating that the miniaturization of the diameter to below ∼2 nm significantly affects the optical response. The red shift of the LSPR band can be ascribed to the increase in the effective mass of electrons in AuUNRs.

Effects of Semi-solid Isothermal Heat Treatment on Microstructures and Damping Capacities of Fly Ash Cenosphere/AZ91D Composites

The fly ash cenosphere/AZ91D composites were successfully prepared and isothermally heat-treated at different temperatures for different time. The effects of semi-solid isothermal heat treatment on the microstructures and damping capacities of fly ash cenosphere/AZ91D composites were investigated. With the increase in isothermal temperature or holding time, the small liquid droplets within grains increased in size but decreased in quantity. The average size and shape factor of Mg2Si particles increased with the rise of isothermal temperature. The damping capacities of the composites were improved by isothermal heat treatment. At room temperature, the composites after heat treatment at 520 and 550 °C had a higher damping capacity due to interface damping when the strain amplitude was lower than about 8.8 × 10−5, and the composite after heat treatment at 580 °C had a better damping capacity because of the dislocation damping under the condition of high strain amplitude. The damping capacities of the composites increased with the rise of the test temperature, and the damping mechanisms varied depending on different test temperatures. The interface damping played an important role when the test temperature was below about 100 °C, and the dislocation damping and grain boundary damping took effect with the rise of test temperature.

Effect of alloying elements on microstructure, mechanical and damping properties of Cr-Mn-Fe-V-Cu high-entropy alloys

A series of new Cr-Mn-Fe-V-Cu high-entropy alloys were prepared by arc melting and suction casting. It is found that with the addition of Cu, the structure of the alloys evolved from BCC + BCC1 phases to BCC + FCC phases. With increase of Cu, the volume fraction of the Cu-Mn-rich FCC phase increased, and the morphology of the FCC phase transformed from granular particles to long strips and blocks. Compared with other reported HEAs, the Cr-Mn-Fe-V-Cu HEAs exhibit a good balance between strength and ductility. The CrMn0.3FeVCu0.06 alloy with granular FCC particles exhibits the highest compressive yield strength (1273 MPa) and excellent ductility (εf = 50.7%). Quantitative calculations for different strengthening mechanisms demonstrate that dislocation and precipitate strengthening are responsible for high strength of the CrMn0.3FeVCu0.06 alloy, while the solid solution strengthening effect is very low because of its small atomic-size difference. In addition, the CrMn0.3FeVCu0.06 alloy exhibits good damping capacity due to its high dislocation and interface damping effects. Therefore, the dislocation density and distribution of FCC phase are the crucial factors for improvement of both mechanical properties and damping capacity of the HEAs.

Damping Vibration Behavior of Viscoelastic Porous Nanocrystalline Nanobeams Incorporating Nonlocal–Couple Stress and Surface Energy Effects

Damping vibration analysis of multi-phase viscoelastic nanocrystalline nanobeams on viscoelastic medium is carried out accounting for nano-grains and nano-voids sizes. For the first time, a contribution of nonlocal, couple stress and surface energy effects is applied for vibration analysis of nanocrystalline nanobeams. In fact, couple stress theory considers grains microrotations, while nonlocal elasticity theory considers long-range interactions between the particles. Viscoelastic medium is described as infinite parallel springs as well as shear and viscous layers. Hamilton’s principle is employed to derive the governing equations and the related boundary conditions which are solved applying differential transform method. The frequencies are compared with those of nonlocal and couple stress-based beams. It is observed that damping frequencies of a nanocrystalline nanobeam are significantly influenced by the grain size, grain rotations, porosities, interface, damping coefficient, surface energy, nonlocality and structural damping.

Chemical interface damping of single gold nanorods with low sensitivity to the medium dielectric constant

Herein, we present scanning electron microscopy (SEM) correlated dark-field (DF) scattering studies of single gold nanorods (AuNRs). We demonstrate the effect of refractive index variation of the surrounding medium on the localized surface plasmon resonance (LSPR) linewidth in single AuNRs. The LSPR linewidth remains almost constant while increasing the dielectric constant of the medium, which is further verified by discrete dipole approximation (DDA) calculations. Furthermore, we demonstrate how thiol binding affects the LSPR linewidth of the longitudinal surface plasmon of single AuNRs. The thiol resulted in both a red shift and a strong damping with an increased LSPR linewidth.

Chemical Interface Damping Depends on Electrons Reaching the Surface.

Metallic nanoparticles show extraordinary strong light absorption near their plasmon resonance, orders of magnitude larger compared to nonmetallic nanoparticles. This "antenna" effect has recently been exploited to transfer electrons into empty states of an attached material, for example to create electric currents in photovoltaic devices or to induce chemical reactions. It is generally assumed that plasmons decay into hot electrons, which then transfer to the attached material. Ultrafast electron-electron scattering reduces the lifetime of hot electrons drastically in metals and therefore strongly limits the efficiency of plasmon induced hot electron transfer. However, recent work has revived the concept of plasmons decaying directly into an interfacial charge transfer state, thus avoiding the intermediate creation of hot electrons. This direct decay mechanism has mostly been neglected, and has been termed chemical interface damping (CID). CID manifests itself as an additional damping contribution to the homogeneous plasmon line width. In this study, we investigate the size dependence of CID by following the plasmon line width of gold nanorods during the adsorption process of thiols on the gold surface with single particle spectroscopy. We show that CID scales inversely with the effective path length of electrons, i.e., the average distance of electrons to the surface. Moreover, we compare the contribution of CID to other competing plasmon decay channels and predict that CID becomes the dominating plasmon energy decay mechanism for very small gold nanorods.