Ligament Size Research Articles

Morphology Control of Nanoporous Gold Through Selective Dissolution of Au–Ge Eutectic Microstructures

The synthesis of nanoporous gold (np‐Au) through the conventional method of dealloying a more reactive element from AuTherma alloys has been extensively studied and applied in various fields, particularly catalysis. Herein, a novel approach to creating droplet‐like np‐Au through the selective dissolution of Au–Ge eutectic microstructures is explored. This work reveals that adjusting the undercooling of the eutectic melt during solidification allows for the tuning of pore and ligament sizes. It is demonstrated that this undercooling can be modified, either directly or indirectly, by adjusting either the cooling rate or the heterogeneous nucleation site density of the eutectic melt. The findings, aligned with the model based on classical theory for eutectic solidification, elucidate the connection between the tuning of pore and ligament sizes in the eutectic microstructure and the undercooling of the eutectic melt. Importantly, it is established that this phenomenon is applicable across a variety of compositions, including hypereutectic, eutectic, and hypoeutectic. The ability to regulate pore and ligament size in single crystals of np‐Au droplets offers a novel approach to synthesizing catalytic np‐Au crystals with enhanced mechanical and thermal stability compared to conventional methods.

New Electrochemical Approach for Synthesis of Nanoporous Silver

Cu-Ag alloy films were electrodeposited on Au substrates to serve as precursor alloys for synthesizing finely-structured nanoporous Ag (NPS) structures. Two innovative approaches, surface limited redox replacement (SLRR) and defect mediated growth (DMG) along with overpotential deposition (OPD), were comparatively utilized to fabricate Cu-Ag alloy films. The electrolyte for these novel approaches contained Pb2+ ions to serve either as a sacrificial metal to be replaced by the co-depositing Cu and Ag (in SLRR) or as mediating metal to facilitate the 2D growth of both alloy constituents (in DMG). The resulting alloy films from both approaches displayed superior uniformity and miscibility compared to the OPD alloy, as evidenced by electrochemical scanning electron microscopy (SEM) and X-ray diffraction characterization routines. In a subsequent step, NPS structures were generated through the de-alloying of as-deposited Cu-Ag alloys, as illustrated by SEM imaging that revealed ligament and pore sizes with a thickness in the ballpark of 40 nm. Also, surface area measurements done by a Pb underpotential deposition assay suggested a surface enhancement ratio nearly five times higher than that of flat Ag. Furthermore, various de-alloying potentials were assessed to determine the optimal de-alloying potential for the best outcome of the de-alloying process.

A highly structured Au-grafted nanoporous gold for surface-enhanced Raman scattering detection of ferbam

The expansive potential of surface-enhanced Raman scattering (SERS) has been well-established; however, the primary bottleneck hindering its routine analytical and commercial implementation is the poor signal reproducibility and challenges in substrate fabrication. Thus, the current work attempts to synthesize a scalable and reproducible nanoporous gold (npAu) decorated with gold (Au) nanoparticles to generate a highly structured Au@npAu nanocomposite. The substrate fabrication completes via three distinct routes: i) selective dealloying to form npAu on the Au film, ii) the fast deposition (i-t = −0.8 V, t = 10.0 s) of Au atoms across the npAu surface, and finally iii) the precise growth control of the generated Au@npAu by a series of by oxidation-reduction cycles (−0.03 to −0.4 V for 80.0 segments at ν = 50.0 mVs−1). The simulations of the dealloyed npAu and the final Au@npAu nanocomposite showed that the reduced interparticle spacing and ligament size in the Au@npAu nanocomposite is crucial for forming abundant "hot spot" regions with highly concentrated electromagnetic fields. The Au@npAu substrate reproducibility was assessed on 400.0 sites for SERS spectral acquisition with a relative standard deviation of 9.22 %. Furthermore, the Au@npAu was checked under different preparation batches for intra- and inter-day analysis and storage for 20.0 days with good stability. Finally, the substrate was checked for direct SERS detection of ferbam residues with a 4.34 × 10−9 mol L−1 sensitivity and examined in real samples with satisfactory recoveries (97.63 ± 1.95%–99.16 ± 0.24 %). This work offers a promising avenue towards highly reproducible, scalable and universal Au@npAu SERS substrate fabrication in diverse SERS-related applications.

Unraveling the dealloying mechanism of a Au33Fe67 metastable precursor for a low-cost nanoporous gold production

A low-cost Nanoporous Gold (NPG) has been successfully prepared by chemical dealloying of a Au33Fe67 supersaturated solid solution, whose ribbons were obtained by rapid solidification using melt-spinning technique. The dealloying procedures were carried out in 1 M HNO3 at 70 °C for varying durations. As-quenched ribbon and dealloyed samples have been structurally and compositionally investigated using XRD, FESEM and EDS techniques. The obtained NPG is homogeneous with tunable ligament size and shape, easy-to-handle and free-standing. Most notably, a metastable precursor has been favourably obtained from an immiscible Au-Fe system. Furthermore, according to the characterization results, a mechanism of dealloying has been proposed. Pairing Au with cheap and abundant Fe and fabricating an Fe-rich precursor gives an exceedingly cost-effective starting material. No usage of critical raw materials is involved. Then, employing a straight-forward and rapid dealloying procedure to obtain the NPG sample, makes for an overall inexpensive and sustainable production.

Fabrication of three-dimensional bicontinuous porous aluminum by vapor phase dealloying

The development of lightweight, high-specific-surface-area, and exceptionally tough porous aluminum (Al) through dealloying has been consistently captured the attention of the porous metal field. However, widely employed dealloying approaches such as electrochemical dealloying (ECD) and liquid metal dealloying (LMD) face limitations in constructing porous metals with high chemical reactivities. In this study, we employed an emerging vapor phase dealloying (VPD) method, utilizing the differences in saturated vapor pressures among alloy constituents to selectively remove elements with high vapor pressures under optimized temperature and vacuum conditions. The VPD process, characterized by its chemical-free nature and the application of high temperatures, rapidly produces porous Al with varying ligament sizes from the MgZnAl system. The resulting porous Al, distinguished by its crack-free structure and substantial ligament size, exhibits remarkable toughness. The successful fabrication of porous Al using the VPD method effectively bridges the existing gap in generating porous metals with low melting points and high chemical reactivity through ECD and LMD methods. This advancement holds significance for broadening the range of systems and application fields for porous metals.

Mussel‐inspired self‐assembly of silver nanoclusters into multifunctional silver aerogels for enhanced catalytic and bactericidal applications

AbstractSilver nanoclusters (AgNCs) have shown broad application prospects in catalysis, sensing, and biological fields. However, the limited stability of AgNCs has become the main challenge restricting their practical application in complex environments. Herein, a mussel‐inspired, dopamine‐assisted self‐assembly approach is reported to fabricate 3D AgNC aerogels (PDA/AgNCs), which possess significantly enhanced structural stability and synergistic functional properties. The prepared AgNC aerogels display a hierarchical network structure with an ultrafine ligament size of 10.3 ± 1.2 nm and a high specific surface area of 50.7 m2 g−1. The gelation mechanism is elucidated by in‐depth characterization and time‐lapse monitoring of the gelation process vis spectroscopic and microscopic approaches. Owing to the distinct features of aerogels and the synergistic effect of AgNCs and PDA, the fabricated aerogels can not only efficiently decolorize dyes with a faster kinetic than individual AgNCs, but also exhibit remarkable broad‐spectrum antimicrobial activity. Consequently, a conceptual water‐treatment device is established by depositing PDA/AgNC aerogels on the cotton substrate, which shows good performance in both catalytic dye degradation and bacterial killing in the flowing system. This mussel‐inspired self‐assembly strategy has great potential in developing robust AgNC‐based functional materials, which also provides a new guideline for designing sophisticated materials with integrated functions and synergistic properties.

Solvothermal Fabrication of Mesoporous Pd Nano-Corals at Mild Temperature for Alkaline Hydrogen Evolution Reaction.

Porous metallic nanomaterials exhibit interesting physical and chemical properties, and are widely used in various fields. Traditional fabrication techniques are limited to metallurgy, sintering, electrodeposition, etc., which limit the control of pore size and distribution, and make it difficult to achieve materials with high surface areas. On the other hand, the chemical preparation of metallic nanoparticles is usually carried out with strong reducing agents or at high temperature, resulting in the formation of dispersed particles which cannot evolve into porous metal. In this study, we reported the simple fabrication of coral-like mesoporous Pd nanomaterial (Pd NC) with a ligament size of 4.1 nm. The fabrication was carried out by simple solvothermal reduction at a mild temperature of 135 °C, without using any templates. The control experiments suggested that tetrabutylammonium bromide (TBAB) played a critical role in the Pd(II) reduction into Pd nanoclusters and their subsequent aggregation to form Pd NC, and another key point for the formation of Pd NC is not to use a strong reducing agent. In alkaline water electrolysis, the Pd NC outperforms the monodisperse Pd NPs and the state-of-the-art Pt (under large potentials) for H2 evolution reaction, probably due to its mesoporous structure and large surface area. This work reports a simple and novel method for producing porous metallic nanomaterials with a high utilization efficiency of metal atoms, and it is expected to contribute to the practical preparation of porous metallic nanomaterials by solvothermal reductions.

Bioinspired soft-hard interfaces fabricated by multi-material additive manufacturing: A fracture mechanics investigation using essential work of fracture

This study employs the Essential Work of Fracture (EWF) concept to evaluate the interfacial fracture toughness of bioinspired interfaces between soft and hard polymer phases. The experimental framework utilizes a model material system with Polylactic Acid (PLA) as the hard phase and Thermoplastic Polyurethane (TPU) as the soft phase. Employing the Fused Filament Fabrication (FFF) technique, bioinspired sutural interfaces are created, characterized by interpenetrating soft and hard protrusions. The modulation of a critical parameter in the FFF process enables the variation of interpenetration length of protrusions at the interface, thereby achieving a spectrum of interfacial strength and toughness. The determination of essential work of fracture from double edge notch tension samples, with varied ligament sizes, allows for the specific EWF measurement. This specific EWF is found to align with the initiation value of plane strain interfacial fracture toughness obtained through the Double Cantilever Beam (DCB) test. Therefore, the proposed approach asserts the elimination of the need for complex interfacial fracture tests, such as DCB. A noteworthy discovery is the establishment of a correlation between specific plastic energy dissipation and protrusion length. This correlation suggests an increased plastic dissipation with longer protrusions within the investigated bioinspired interface. Due to this heightened plastic energy dissipation, the shape of the interfacial nominal stress-displacement curves demonstrates substantial dependence on interface morphology, shifting from a triangular to a trapezoidal shape as protrusion length increases. These findings offer valuable insights into the mechanics of bioinspired interfaces, presenting a more efficient and nuanced approach to characterizing their fracture properties.

Effects of structural hierarchy and size on mechanical behavior of nanoporous gold

Nanoporous gold with a hierarchical structure has prospects as an advanced functional material with enhanced mechanical properties, but how the hierarchical structure affects its mechanical properties compared to a unimodal structure has not been revealed. Here, we investigate the mechanical behavior of hierarchically-structured nanoporous gold and unimodally-structured nanoporous gold with the same relative density by micropillar compressive tests in dry and electrolyte environment. The ligament size at the upper-level structure in hierarchically-structured nanoporous gold and the ligament size in unimodally-structured nanoporous gold are kept similar, while having hierarchically-structured samples with ligament sizes of 10 to 50 nm at lower-level structure. We find that hierarchically-structured nanoporous gold shows greater compressive strength and pronounced stress-variation by oxidization of the surface compared to unimodally-structured nanoporous gold. A ligament-size dependency on the lower-level structure in hierarchical samples is observed, with compressive strength and stress variation by surface oxidation increasing as the lower-level ligament size decreases. Three-dimensionally reconstructed structure analysis suggests that the enhanced mechanical properties of hierarchically-structured nanoporous gold are attributed to the better-connected network of ligaments originating from two separated dealloying-coarsening procedures. The influence of dislocation activities depending on characteristic sizes is also discussed to elucidate the distinguished mechanical behavior.

The Influence of the Mechanical Compliance of a Substrate on the Morphology of Nanoporous Gold Thin Films.

Nanoporous gold (np-Au) has found its use in applications ranging from catalysis to biosensing, where pore morphology plays a critical role in performance. While the morphology evolution of bulk np-Au has been widely studied, knowledge about its thin-film form is limited. This work hypothesizes that the mechanical compliance of the thin film substrate can play a critical role in the morphology evolution. Via experimental and finite-element-analysis approaches, we investigate the morphological variation in np-Au thin films deposited on compliant silicone (PDMS) substrates of a range of thicknesses anchored on rigid glass supports and compare those to the morphology of np-Au deposited on glass. More macroscopic (10 s to 100 s of microns) cracks and discrete islands form in the np-Au films on PDMS compared to on glass. Conversely, uniformly distributed microscopic (100 s of nanometers) cracks form in greater numbers in the np-Au films on glass than those on PDMS, with the cracks located within the discrete islands. The np-Au films on glass also show larger ligament and pore sizes, possibly due to higher residual stresses compared to the np-Au/PDMS films. The effective elastic modulus of the substrate layers decreases with increasing PDMS thickness, resulting in secondary np-Au morphology effects, including a reduction in macroscopic crack-to-crack distance, an increase in microscopic crack coverage, and a widening of the microscopic cracks. However, changes in the ligament/pore widths with PDMS thickness are negligible, allowing for independent optimization for cracking. We expect these results to inform the integration of functional np-Au films on compliant substrates into emerging applications, including flexible electronics.

Electrochemical Surface Nanostructuring of Ti47Cu38Fe2.5Zr7.5Sn2Si1Ag2 Metallic Glass for Improved Pitting Corrosion Resistance

Ti‐based bulk metallic glasses are envisioned for human implant applications. Yet, while their elevated Cu content is essential for a high glass‐forming ability, it poses biocompatibility issues, necessitating a reduction in near‐surface regions. To address this, surface treatments that simultaneously generate protective and bioactive states, based on nanostructured Ti and Zr‐oxide layers are proposed. An electrochemical pseudo‐dealloying process using the bulk glass‐forming Ti47Cu38Fe2.5Zr7.5Sn2Si1Ag2 alloy is defined. Melt‐spun ribbons are immersed in hot concentrated nitric acid solution, monitoring the anodic polarization behavior. From the current density transient measurements, together with surface studies (field‐emission scanning electron microscopy, transmission electron microscopy, and Auger electron spectroscopy), the surface reactions are described. This nanostructuring process is divided into three stages: passivation, Cu dissolution, and slow oxide growth, leading to homogenous nanoporous and ligament structures. By tuning the applied potential, the pore and ligament sizes, and thickness values are adjusted. According to X‐ray photoelectron spectroscopy, these nanoporous structures are Ti and Zr‐oxides rich in hydrous and nonhydrous states. In a simulated physiological solution, for those treated glassy alloy samples, complete suppression of chloride‐induced pitting corrosion in the anodic regime of water stability is achieved. This high corrosion resistance is similar to that of clinically used cp‐Ti.

Effect of precursor composition and heat-treatment on the morphology and physical properties of Ag nanosponges

Nanoporous silver (np-S) was prepared by free corrosion dealloying of a series of Ag–Al thin films containing between 25 and 73 at.% Al. It was found that precursor composition had an important influence on the nanostructures and morphologies of the np-S. In particular the size of the Ag ligaments systematically decreased from 32 to 13 nm as the Al content was increased over the series. In contrast, there was only a weak effect on pore size, which remained in the range 11–15 nm, with the maximum occurring at about 55 at.% Al. There was however a significant increase in the density of the pores as the Al content of the precursor was increased. The electrical resistivity of the np-S increases with the decrease in ligament size, changing from about 3 × 10−8 Ω m for sponges with ligaments of about 32 nm diameter rising to 30 × 10−8 Ω m for the sponge with the 13 nm ligaments. The surface area of the np-S was estimated by the electrochemical capacitance in KNO3 solutions and was estimated to increase by an order of magnitude compared to a smooth Ag surface. There was a systematic change in the optical properties of the sponges, with a trend towards less metallic behaviour as the ligament size decreased and pore density increased. These changes culminated in the sponge prepared from the 73 at.% Al precursor having non-metallic characteristics with regard to visible and near-infrared light. The volume fraction of metal was estimated to be of the order of 40 ± 5%. Prior annealing of the precursor inhibited dealloying.

Accelerated structural ordering during liquid metal dealloying and its effect on thermal coarsening of nanoporous refractory alloys

Nanoporous non-noble metals with attractive properties can be fabricated by liquid metal dealloying (LMD). However, further refinement of the ligament size of nanoporous metals produced by LMD is desired because this high-temperature process induces rapid ligament coarsening. Herein, we fabricate nanoporous refractory metals and alloys by LMD. The molybdenum (Mo)-tantalum (Ta) alloy with the smallest ligament size of the specimens contains a B2 ordered structure, whereas the other specimens possess disordered structures. It is proposed that the B2 ordering of the Mo-Ta alloy suppresses ligament coarsening by restricting the surface diffusion of atoms during LMD. The Mo-Ta alloy with B2 ordered structure exists in a previously inaccessible low-temperature region of the related phase diagram, illustrating that LMD can enable access to new materials. Our results indicate that materials with refined ligaments may be obtained by LMD promoting the formation of ordered structures.

Size effects in fatigue crack growth in confined volumes: A microbending case study on nanocrystalline nickel

Mechanical size effects are a well known phenomenon when the sample volume is reduced or the characteristic length of the microstructure is changed. While size effects in micropillar compression (smaller is stronger) or due to grain refinement (Hall-Petch) are well understood, this is less so in fracture mechanics. Given this lack of knowledge, the main question addressed in this work is: What happens to the fatigue crack growth properties when extrinsic size effects play a role? To answer this question, nanocrystalline nickel cantilevers, ranging in width from 5 to ▪, were subjected to fatigue crack growth. The crack growth rates and stress intensity factors were calculated and the Paris exponent in the stable crack growth regime was determined. It was found that the results scatter more strongly for the smaller cantilevers compared to the larger cantilevers. Results are interpreted in terms of plastic zone size and ligament size which are found to be critical for small cantilevers.

New record of Philometra species from the marine edible fish Terapon jarbua collected from the Sindh, Arabian Sea, Pakistan.

Diseases in fish due to helminth parasites, especially Philometra species, are the primary worry in aquaculture. Philometra are responsible for health problem in fishes they directly affect fish growth and population parameters. A comprehensive survey was conducted involving the examination of the marine fish species Terapon jarbua, gathered from the coastal waters of Sindh, Pakistan In this research different Philometra species from marine fish Terapon jarbua during 2021 and 2022. Philometra nematodes, belonging to the family Philometridae, are common parasitic organisms inhabiting both marine and freshwater environments. Their prevalence, particularly when existing in high numbers within host organisms, can lead to severe and potentially lethal consequences. Employing light microscopy techniques, diverse species of Philometra were identified, including Philometra teraponi, P. jarbuai, P. arabiai, P. karachii, and P. awarii, localized primarily within the ovaries of the host fish. A total of 140 fish samples were examined and 76 were infected. The intensity of infected fish was 54.28%. The identification process encompassed meticulous analysis of crucial parameters, such as body size, esophagus length, positioning of the nerve ring, dimensions of the ventriculus, and ligament size. Intriguingly, the parasites were found in varying contexts; while some were free within the ovaries, others were embedded within tissues, inducing severe muscular dystrophy. This research presents novel findings of Philometra nematodes in the marine waters of Pakistan, extending their host and geographical distribution records. Future studies are needed to better evaluate and describe the dynamics and the epidemiology of Philometra infection in wild and cultured fish species.

Employing Electrochemical Potential Cycling to Controlling Surface to Volume Ratio of Nanoporous Gold and Photoelectron Injection into Electrolyte

Nanoporous metals made by alloy corrosion are bicountinuous porous networks that possess nanoscale ligaments and pores and thus a large surface-to-volume ratio. Their ligament and pore size can be tuned between a few nanometers and several microns via thermal annealing [1], which makes them attractive material systems for a variety of applications, including catalysis, sensing, and energy storage. In particular, dealloying-derived nanoporous metals, present novel opportunities for exploring the impact of surfaces on electro-photocatalytic activity of metallic nanostructures [2]. Yet, achieving the ligament and pore sizes in the dealloyed metallic networks below 10 nm, which is especially crucial for understanding an efficient electrochemical charge transfer, is challenging so far.In this study, we demonstrate a successful fabrication of nanoporous gold (npAu) thin films via electrochemical dealloying with the ligament size down below 10 nm on quartz substrate. We study the material by means of in situ photoelectrochemical setup while simultaneously varying the electrode potential in 0.5 M H2SO4 electrolyte. To probe the size effect on the photocurrent response, we exploit cyclic voltammetry (CV) in order to promote coarsening of the ligaments of npAu networks. By varying a number of CV cycles, we were able to induce subtle changes in the ligament size, therefore modifying the surface-to-volume ratio of the nanoporous metals at the lower limit of the nanoscale.Our results show that this approach provides an excellent foundation for future optical investigations of surface effects on the internal quantum efficiency of high-surface area metallic photoelectrodes.Our study demonstrates that modifying the surface-to-volume ratio of the sample by electrochemistry allows us to control the hot electron generation and injection processes in nanoscale plasmonic systems. Moreover, the internal quantum efficiency of the npAu network photoelectrode is significantly influenced by the size of its ligaments. In contrast to prior findings that suggested efficiency would level off with decreasing ligament size [3], we have observed a continuous nonlinear increase in quantum efficiency as the ligament size decreased from 16 to 8 nm. This result is attributed to the increase in absorption by the electrons colliding with the surface (Landau damping) and increase of emission of this electrons into the electrolyte due to possibility of multiple collisions with the surface.

Silver-Rich Clusters Reveal the Initial Size of Nanoscale Network during Dealloying Via Kinetic Monte Carlo Simulation

As residues of the master alloy that survived corrosion, the silver-rich clusters of nanoporous gold (NPG) fabricated by dealloying affect the functional properties of the material. Also, they are representative of the initial nanoscale network established at the beginning of dealloying. The evolution of silver-rich clusters during dealloying at different potentials is investigated via kinetic Monte Carlo simulations [1]. Our simulations show that the dealloying consists of two characteristic processes: (i) the primary process produces an initial three-dimensional bicontinuous network with silver-rich clusters embedded in the ligaments and pure gold covered on ligaments' surface. See Fig.1(a). (ii) the secondary process coarsens the ligaments and further dissolves silver from the ligaments. See Fig.1(b). The size of silver-rich clusters, L Ag, scales with that of ligaments, L lig, during primary dealloying for all studied potentials (Fig.1(c)). Both sizes decrease with increasing dealloying potential. The trends in size and potential are consistent with a Gibbs-Thompson-type relation (dash-dotted line in Fig.1(c)). Yet, the size of silver clusters remains invariant when the ligament size increases during secondary dealloying. Our simulations reveal that the survived clusters provided a way to measure the initial ligament size.Fig.1. Renderings of slicing the NPG structure at different dealloying time (a-b) and the size evolution during primary dealloying (c) (Ref.[1]): (a) the primary dealloying establishes the initial 3D nanoscale network, (b) the secondary dealloying dissolves Ag clusters and coarsens ligaments, (c) inverse of Ag cluster size, L Ag and of ligament size, L lig, during primary dealloying as a function of dealloying potential, Φ.Reference:[1] Y. Li, B.-N. D. Ngô, J. Markmann, J. Weissmüller. Evolution of length scales and of chemical heterogeneity during primary and secondary dealloying, Acta Materialia, (2021) 117424. Figure 1

Ligament rotation-dominated creep in stochastic bicontinuous nanoporous metallic glass

Bicontinuous nanoporous metallic glasses (BNPMGs) are promising candidates in functional applications such as energy storage, sensors, and fuel cells. The time-dependent deformation strongly affects their long-term in-service performance. This study investigates the tensile creep behavior and its underlying deformation mechanisms of Cu50Zr50 BNPMGs through molecular dynamics simulations. The creep-recovery fatigue behavior is revealed. Our results manifest that both the transient and steady creep strengths increase with the solid fraction. The transient strength is larger for smaller ligament sizes, but the steady creep strength has very mild sensitivity to the ligament size. The generalized Kelvin model, consisting of two Kelvin units and one Maxwell unit connected in series, can accurately predict the creep and recovery curves. The rotation of individual ligaments, rather than atomic diffusion, is the dominant creep mechanism. During creep, the shear transformation zones are mainly developed on the ligament surface, and the strain in the ligament core is relatively smaller. The creep stress exponent has no definite relation with the creep mechanism and decreases with the increasing solid fraction. With the increase in the creep-recovery cycle number, the creep rate decreases, and the recovery procedure makes a milder impact on the creep response.

Correlation Between the Severity of Multifidus Fatty Degeneration and the Size of Ossification of Posterior Longitudinal Ligament at Each Spinal Level.

This study aimed to investigate the correlation between ossification of the posterior longitudinal ligament (OPLL) size and multifidus fatty degeneration (MFD), hypothesizing that larger OPLL sizes are associated with worse MFD. One hundred four patients with cervical OPLL who underwent surgery were screened. OPLL occupying diameter and area ratios, the severity of MFD using the Goutallier classification, and range of motion (ROM) of cervical flexion-extension (ΔCobb) were measured. Correlation analyses between OPLL size, MFD severity, and ΔCobb were conducted. MFD severity was compared for each OPLL type using one-way analysis of variance. The final clinical data from 100 patients were analyzed. The average Goutallier grade of C2-7 significantly correlated with the average OPLL diameter and area occupying ratios, and OPLL involved vertebral level (r = 0.58, p < 0.01; r = 0.40, p < 0.01; r = 0.47, p < 0.01, respectively). The OPLL size at each cervical level significantly correlated with MFD of the same or 1-3 adjacent levels. ΔCobb angle was negatively correlated with the average Goutallier grade (r = -0.31, p < 0.01) and average OPLL occupying diameter and area ratios (r = -0.31, p < 0.01; r = -0.35, p < 0.01, respectively). Patients with continuous OPLL exhibited worse MFD than those with segmental OPLL (p < 0.01). OPLL size is clinically correlated with MFD and cervical ROM. OPLL at one spinal level affects MFD at the same and 1-3 adjacent spinal levels. The worsening severity of MFD is associated with the longitudinal continuity of OPLL.

Metrics for the characteristic length scale in the random bicontinuous microstructure of nanoporous gold

Nanoporous gold (NPG) made by dealloying exemplifies materials with random bicontinuous microstructures that can be approximated by leveled-wave type models. As a distinguishing feature, the characteristic length scale – often quantified by the “ligament size” L – of NPG may be tuned over several orders of magnitude while the microstructural geometry retains a high degree of self-similarity. It is therefore essential to have at hand accurate procedures for determining the size by experiment and to match it to analogous size metrics of model scenarios. Working with a set of NPG samples of widely different size, we compare ligament size distributions determined by analysis of scanning electron micrographs to those of the leveled-wave model. The model is representative of various material types with random bicontinuous microstructures. The size distribution is remarkably uniform over the cross-section of experimental samples. Furthermore, the distribution evolves self-similarly upon coarsening, and the normalized distribution width agrees closely to that of the model. A measure for size determined by the electrochemical capacitance ratio method correlates well with L. This supports a protocol for converting between the two measures. As a dimensionless factor characteristic of the microstructural geometry of random dual phase microstructures, the product of L and the specific surface area is found consistent between experiment and model. The findings suggest conversion factors between the various metrics, and they advertise the combination of NPG and the leveled-wave model as a showcase for characterizing the characteristic length scale of random bicontinuous microstructures.