Porous Metal Structure Research Articles

Influence of Porosities of 3D Printed Titanium Implants on the Tensile Properties in a Rat Tendon Repair Model.

There is a desire in orthopaedics to have soft tissue, particularly tendon, grow into metallic implants. With the introduction of three-dimensional (3D) printed porous metal implants, we hypothesized that tendons could directly attach to the implants. However, the effects of the porous metal structure on tissue growth and penetration into the pores are unknown. Using a rat model, we investigated the effect of pore size on tendon repair fixation using 3D printed titanium implants. There were three experimental groups of eight Sprague Dawley rats (n = 24) plus control (n = 3). Implants had defined pore sizes of 400µm (n = 8), 700µm (n = 8), and 1000µm (n = 8). A defect was created in the Achilles tendon and the implant positioned between cut ends and secured with suture. Specimens were harvested at twelve weeks. Half the specimens underwent mechanical testing to assess tensile load to failure. The remaining specimens were fixed and processed for hard tissue histological analysis. The average load to failure was 72.6N for controls (SD 10.04), 29.95N for 400µm (SD 17.95), 55.08N for 700µm (SD 13.47), and 63.08N for 1000µm (SD 1.87). The load to failure was generally better in the larger pore sizes. The 700µm and 1000µm specimens performed similarly, while the 400µm showed significant differences vs control (p = 0.039), vs 1000µm (p = 0.010), and approached significance vs 700µm (p = 0.066). There was increasing ingrowth as pore size increased. Histology showed fibrous tendon tissue within and around the implants, with collagen fibers organized in bundles. Tendon repair utilizing implants with 700µm and 1000µm pores exhibited similar load to failure as controls. Using a defined pore structure at the attachment points of tendons to implants may allow predictable tendon ingrowth onto/into an implant at the time of revision arthroplasty.

Development of Novel Surface-Enhanced Raman Spectroscopy-Based Biosensors by Controlling the Roughness of Gold/Alumina Platforms for Highly Sensitive Detection of Pyocyanin Secreted from Pseudomonas aeruginosa.

Pyocyanin is considered a maker of Pseudomonas aeruginosa (P. aeruginosa) infection. Pyocyanin is among the toxins released by the P. aeruginosa bacteria. Therefore, the development of a direct detection of PYO is crucial due to its importance. Among the different optical techniques, the Raman technique showed unique advantages because of its fingerprint data, no sample preparation, and high sensitivity besides its ease of use. Noble metal nanostructures were used to improve the Raman response based on the surface-enhanced Raman scattering (SERS) technique. Anodic metal oxide attracts much interest due to its unique morphology and applications. The porous metal structure provides a large surface area that could be used as a hard template for periodic nanostructure array fabrication. Porous shapes and sizes could be controlled by controlling the anodization parameters, including the anodization voltage, current, temperature, and time, besides the metal purity and the electrolyte type/concentration. The anodization of aluminum foil results in anodic aluminum oxide (AAO) formation with different roughness. Here, we will use the roughness as hotspot centers to enhance the Raman signals. Firstly, a thin film of gold was deposited to develop gold/alumina (Au/AAO) platforms and then applied as SERS-active surfaces. The morphology and roughness of the developed substrates were investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The Au/AAO substrates were used for monitoring pyocyanin secreted from Pseudomonas aeruginosa microorganisms based on the SERS technique. The results showed that the roughness degree affects the enhancement efficiency of this sensor. The high enhancement was obtained in the case of depositing a 30 nm layer of gold onto the second anodized substrates. The developed sensor showed high sensitivity toward pyocyanin with a limit of detection of 96 nM with a linear response over a dynamic range from 1 µM to 9 µM.

High energy absorption design of porous metals using deep learning

Due to its remarkable energy absorption properties, porous metals have widespread applications in engineering. However, the high randomness of pore morphology greatly hinders the effective design and analysis of high energy absorption structures. To address this challenge, this paper first introduces a deep learning-based framework for high energy absorption-oriented design of random porous metals structures. The framework comprises two steps: (i) a generator powered by Wasserstein deep convolutional generative adversarial network is developed to swiftly generate a vast design space (∼one million samples) of porous metals with real random pore morphology. (ii) an inverse search strategy based on convolutional neural network is applied to quickly pick out the optimal structure with the best energy absorption from the design space. Results show that the optimal energy absorption is about 17.71 % higher than the maximum value of initial structures from CT scan. Additionally, a 575-fold increase in computational efficiency is achieved compared to the traversal search using finite element method. Subsequently, the deformation process of the optimal structure is analyzed focusing on the pore morphology and compression performance, showing that random porous metals with uniformly sized pores are capable of withstanding higher stress under the same strain and exhibit no yield band during compression. Inspired by this, a structural homogenization method is introduced and validated to create porous metal structure with stable microstructure evolution, extended plateau stress and high energy absorption.

Simulation and Experimental Investigation of the Effect of Pore Shape on Heat Transfer Behavior of Phase Change Materials in Porous Metal Structures.

With the gradual increase in energy demand in global industrialization, the energy crisis has become an urgent problem. Due to high heat storage density, small volume change, and nearly constant transition temperature, phase change materials (PCMs) provide a promising method to store thermal energy. In this work, we designed and fabricated three kinds of porous metal structures with hexagonal, rectangular, and circular pores and explored the phase change process of PCMs within them. A two-dimensional numerical model was established to investigate the heat transfer process of PCMs within different shapes of porous metal structures and analyze the influence of heat source location on the thermal performance of the thermal storage units. Visualization experiments were also carried out to reveal the melting process of PCMs within different porous metal structures by a digital camera. The results show that paraffin in a porous metal structure with hexagonal pores has the fastest melting rate, while that in a porous metal structure with circular pores has the slowest melting rate. Under the bottom heating mode, the melting time of the paraffin in porous metal structures with hexagonal pores is shortened by 18.6% compared to that in porous metal structures with circular pores. Under the left heating mode, the corresponding melting time is shortened by 16.7%. These findings in this work will offer an effective method to design and optimize the structure of porous metal and improve the thermal properties of PCMs.

Management of Advanced Peri-Implantitis by Guided Bone Regeneration in Combination with Trabecular Metal Fixtures, Two Months after Removal of the Failed Implants: Two-Year Results of a Single-Cohort Clinical Study

Background: Implant replacement is among the treatment options for severe peri-implantitis. The aim of this single-cohort study was to evaluate the feasibility of replacing compromised implants affected by advanced peri-implantitis with new implants with a porous trabecular metal (TM) structure. Materials and Methods: Patients with one or more implants in the posterior region showing a defect depth >50% of implant length, measured from the residual crest, were consecutively included. Two months after implant removal, patients received a TM implant combined with a xenograft and a resorbable membrane. The implant stability quotient (ISQ) was measured at placement and re-assessed five months later (at uncovering), then after 6, 12, and 24 months of function. Marginal bone loss was radiographically evaluated. Results: Twenty consecutive cases were included. One patient dropped out due to COVID-19 infection, and nineteen cases were evaluated up to 24 months. At placement, the mean ISQ was 53.08 ± 13.65 (standard deviation), which increased significantly to 69.74 ± 9.01 after five months of healing (p < 0.001) and to 78.00 ± 7.29 after six months of loading (p < 0.001). Thereafter, the ISQ remained stable for up to 24 months (80.55 ± 4.73). All implants successfully osseointegrated and were restored as planned. After two years, the average marginal bone level change was −0.41 ± 0.38 mm (95% confidence interval −0.60, −0.21), which was limited yet significantly different from the baseline (p < 0.05). Conclusions: The treatment of advanced peri-implant defects using TM implants inserted two months after explantation in combination with guided bone regeneration may achieve successful outcomes up to two years follow-up, even in the presence of low primary stability.

Transient temperature control performance evaluation of a novel hybrid PCM-based active heat sink

In this study, a novel hybrid PCM-based active heat sink is proposed for temperature control management of transient high heat flux shock electronic devices. The temperature control features of the novel hybrid PCM-based active heat sink are numerically studied under the periodic heat flux condition. Impacts of parameters, including phase-change temperatures, heat transfer coefficient, heat sink parameters, and porosity of the porous metal structure embedded in PCM, are numerically investigated. Then the thermal control performance ratio is evaluated. Results reveal that the innovative hybrid PCM-based active heat sink achieves an outstanding temperature management performance when compared to a heat sink without PCM. And the temperature is reduced by more than 10 K. Increasing the height and width of the heat sink can make the temperature distribution more consistent, but an excessive increase seems unnecessary. Compared with pure PCM, When the porosity of porous metal structure decreases from 0.96 to 0.76, the initial melting time of PCM is delayed by 38.7%, and the solidification time is accelerated by 30.2%.

A comprehensive approach combining gradient porous metal foam and the magnetic field to regulate latent heat storage performance

This study proposes a comprehensive regulation method of gradient porous metal structure combined with the magnetic field to improve the controllability of heat utilization of latent heat thermal energy storage (LHTES) unit. Melting and solidification are considered. The enthalpy porosity method and magnetic force model describe the phase change of phase change material (PCM) and the movement of Fe3O4 nanoparticles under the magnetic field and assume the local thermal non-equilibrium model of metal foam. The numerical model is consistent with the visual experimental results of melting front evolution. The effects of magnetic nanoparticle concentration and gradient porosity on heat transfer and thermal energy change during melting and solidification are numerically studied. The results show that the phase change rate increases with the concentration of nanoparticles. The positive magnetic field further accelerates the phase change and heat energy change. The addition of copper foam considerably shortened the phase change time. The positive magnetic field accelerated the melting and heat energy change rate of PCM in copper foam by 18.2% and 23.1%, but the improvement of solidification was weak. Based on magnetic field promotion, the setting of porosity spacing with different gradients can regulate the phase interface uniformity, total heat energy, and heat energy change rate. Finally, according to different heat utilization scenarios of the LHTES system, this study gives recommended cases to optimize the performance of melting, solidification, and the phase change cycle.

Evaluation of the Elastic Modulus and Plateau Stress of a 2D Porous Aluminum Alloy Based on a Convolutional Neural Network

Porous metals are a new ultra-light material with high specific stiffness, specific strength, and good energy absorption properties. The elastic modulus and plateau stress of porous metals are essential parameters. There have been many studies on the effects of the matrix material, porosity, and pore size on the elastic modulus and plateau stress of porous metals, but few studies can be found on the impact of pore arrangement. The pore arrangement of porous metals cannot be quantitatively described, and the design space of a porous metal structure under the same porosity is vast. With the powerful learning and prediction ability of neural networks, the influence of pore arrangement can be better understood. In this paper, a convolutional neural network was used to explore the impact of pore arrangement on both the elastic modulus and plateau stress of a porous aluminum alloy. Firstly, a finite element method was used to simulate the compression of a porous aluminum alloy to obtain a training sample library. Secondly, a convolutional neural network was built to positively predict the elastic modulus and plateau stress of the porous aluminum alloy. Partial samples were used to select the best training model from five convolutional neural network candidates. Dropout, Batch Normalization, and L2 regularization methods were used to alleviate the over-fitting phenomenon in training. All data in the database were then trained and predicted, and the predicted goodness of fit of the elastic modulus and plateau stress were 0.8785 and 0.5922, respectively. A search method based on the convolutional neural network was then used to iteratively search the database. Under the condition of using a small amount of data, the pore structure with the best elastic modulus and plateau stress in the database could be determined, and the inverse design of a structure with high elastic modulus and plateau stress could be realized.

(Digital Presentation) Electrodeposition of Free-Standing Porous Cu Frameworks for Energy Applications

Recently, a convenient method has been suggested to produce a highly porous metal structure such as Cu using a single-step electrodeposition method [1]. In this approach, hydrogen bubbles are used as dynamic templates during the metal electrodeposition process to create the micro-porous structure. However, the pore walls of the porous layers often grow in ramified dendritic structure, which results in limited mechanical stability and creates challenged for applications in compact devices.In this contribution, a novel approach will be discussed to improve the mechanical stability of these porous structures by employing a second electrodeposition step. This process greatly reduces the number of dendrites within the pore walls making the porous layer more compact and thus improving the mechanical stability significantly. Furthermore, a complete separation of the porous layer from the flat substrate can be achieved by ultrasonication to obtain a free-standing porous Cu framework. Some parameters such as the layer thicknesses and pore sizes can be tuned easily by changing the current density and the electrodeposition time, respectively.The use of thus prepared free-standing porous Cu frameworks will be discussed for photoelectrochemical (PEC) water splitting and CO2 reduction. For the PEC water splitting application, a photoactive Cu2O layer is electrodeposited on the free-standing porous Cu framework. A homogenous coating of the Cu2O can be achieved and the PEC performance shows a significant increase of photocurrents by more than 80 % at 0 V vs. RHE in comparison to the Cu2O planar substrate [2]. For the CO2 reduction application, a large sample with10 cm2 geometric surface area was successfully prepared. The sample was used in a custom-made electrochemical cell with a cation exchange membrane as a separator. CO2 gas in a high humidity environment is transported to the free-standing porous Cu working electrode via a membrane pump in a closed-loop system. Our preliminary results show formation of ethylene and ethane gas using gas chromatography which indicates a successful reduction reaction of the CO2.[1] H.C. Shin., M. Liu. Chem Mater 16:5460–5464 2004. Doi:10.1021/cm048887b[2] M. Kurniawan, M. Stich, M. Marimon, M. Camargo, R. Peipmann, T. Hannappel, A. Bund, J. Mater. Sci. 2021, Doi:10.1007/s10853-021-06058-y

Analytical fin efficiency model for open-cell porous metal fins based on Kelvin cell assumption

Open-cell porous metals are widely used to enhance convective heat transfer of thermal management devices. In this paper, the open-cell porous metal structure was represented by a polyhedron model known as the Kelvin cell, and an analytical model for the efficiency of the porous metal fin attached to an isothermal surface was derived. The forced convective heat transfer coupled with heat conduction through the ligaments of porous metal was analyzed to derive the fin efficiency model. The effects of pore diameter, ligament diameter, and porous metal fin height on the fin efficiency and heat transfer rate of porous metal fins were also investigated. The new analytical fin efficiency model based on the Kelvin cell was compared with the fin efficiency evaluated using computational fluid dynamics analysis results; good agreement was found. The proposed analytical fin efficiency model avoids the numerical calculations required for heat transfer analysis of porous metals used as extended surfaces in many engineering applications such as heat sinks and heat exchangers, and can produce simple but effective results.

Synthesis of Porous Metallic Structure and Its Application for Energy Storage Materials

Porous metal or metal oxide frameworks have been comprehensively applicated to numerous fields such as catalyst, energy storage system, and bio-filtration. Here, we introduce a de-alloying method prior to a facile polymer gel-templating to synthesize a self-supporting porous metal/metal oxide frameworks (e.g. Au, Ag, Ag/CuO, Au/MnO<sub>2</sub>, etc.). The template methods based on polymer gel suggest easy preparation of porous metal/metal oxide frameworks, prepared by heating a metal precursor impregnated in polymer gel. Compared to de-alloying Ag<sub>65</sub>A<sub>35</sub> method, polymer gel based soft template serves numerous advantages as follows; 1) facile fabrication of porous transition metal structure, 2) atom economy, 3) high-loading of precious metals, 4) harmless to human and environment, 5) natural abundance, 6) easy to scale-up and control the pore size by differentiate the polymer content ratio, 7) mild reaction conditions, and 8) structural controllability, 9) cost-effectiveness, etc. We report the methodologies to synthesis bicontinuous metal/ metal oxide architectures, derived from porous gel soft templates, and they are applicated to the energy storage system such as, supercapacitor, pseudocapacitor, and battery.

Hydrophobically/oleophilically guarded powder metallurgical structures and liquid impregnation for ice mitigation

Icing hazards often pose operational and safety challenges. Various surface and coating approaches have been attempted for ice mitigation purposes, but the durability remains an outstanding issue. Inspired by traditional powder metallurgy and slippery icephobic surfaces, a new strategy for slippery liquid-impregnated porous metallic structure (LIPMS) with gradient porosity was proposed in this study for ice mitigation, by directly impregnating selected liquids into sintered porous copper components with hydrophobic/oleophilic guarding consideration. The results indicated that robust LIPMS with desired porosity were obtained, significantly delaying the icing of surface water droplets, providing good frost resistance in a high humid environment, and demonstrating ultra-low ice adhesion strength (less than 1 kPa). It was confirmed that the hydrophobic/oleophilic guarding design significantly improved icephobic durability, attributing to its role in repelling external water and maintaining internal slippery liquid. To offer a comprehensive understanding of icephobic mechanisms and the potentials of LIPMSs, a concept of ice initiation position was also proposed and theoretically discussed. The pivotal factor of icephobic LIPMS is to maintain the icing initiation position at the unfrozen liquid–liquid interface or inside the homogeneous liquid, thus inhibiting icing and facilitating the ice removal.

Design of porous metal collector via bubble template-assisted electrochemical deposition using numerical simulation

Reduction of resistances in next-generation secondary batteries, which considerably affects battery performance under high-rate conditions, is essential to increase their output density. In particular, lithium-ion batteries (LiBs) require sufficient contact between the collector and the composite electrode layer. However, contact is often disrupted due to the absence of strong bonding. This issue can be redressed using a porous metal to fabricate the collector. In this study, a porous metal structure is theoretically designed and optimized for this purpose. To this end, a numerical model is developed to simulate the formation of the structure via the hydrogen bubble template-assisted electrodeposition method. With the model, the effects of electrodeposition on the process of formation were examined. Via simulation, the performance of the proposed porous metal structure is estimated corresponding to each deposition potential, and the validity of the architecture is confirmed based on experimental results. In addition, a gradient structure is designed to serve as a highly conductive collector during particle packing. The effectiveness of the overall architecture is evaluated via numerical simulation and a multi-step process is proposed to fabricate the gradient structure. Experimental results reveal that the optimal proposed structure exhibits 30% higher conductivity compared to conventional alternatives.

A biphenylene nanoribbon-based 3D metallic and ductile carbon allotrope.

Assembling two-dimensional (2D) sheets for three-dimensional (3D) functional materials is of current interest. Motivated by the recent experimental synthesis of 2D biphenylene [Science372 (2021) 852], we propose a new porous 3D metallic carbon structure, named T48-carbon, by using biphenylene nanoribbons as the building block. Based on state-of-the-art theoretical calculations, we find that T48-carbon is not only dynamically, thermally, and mechanically stable, but also energetically more favorable as compared with some other theoretically predicted carbon allotropes. Especially, T48-carbon exhibits mechanical anisotropy, ductility and intrinsic metallicity. A detailed analysis of electronic properties reveals that the metallicity mainly comes from the pz-orbital of sp2-hybridized carbon atoms. This work shows the promise of design and synthesis of 3D biphenylene-based metallic carbon materials with novel properties.

A multi-phase-field model of topological pattern formation during electrochemical dealloying of binary alloys

Porous metal structures produced by electrochemical dealloying have been extensively studied for use in various applications that require high surface areas. A new comprehensive multi-phase-field (MPF) model is proposed to study topological porous patterns formed by spontaneously etching a bulk binary alloy that involves electrochemical reactions, bulk and surface diffusion, ion transport, applied electrode potential, and charge conservation. The governing equations for the alloy-porous cluster-electrolyte system account for a generalized Butler-Volmer electrochemical reaction and are in accordance with the classical nucleation theory. Based on a quantitative examination of the effects of electrode potential and precursor composition, the simulation results reproduce typical phenomena including passive surface dealloying, active porosity evolution, critical potential, and characteristic length scale in two-dimension (2-D) and three-dimension (3-D). To consider more complicated dealloying systems, the evolutions of a bimodal porous metal structure, nanocomposite, and nested porous network with a structured hierarchy are investigated. The proposed model can be a useful tool for understanding and predicting the morphology evolution of diverse porous structures during electrochemical dealloying.

Mechanical behavior, damage mode and mechanism of AlSi10Mg porous structure manufactured by selective laser melting

In order to correctly understand the mechanical behavior, damage mode and damage mechanism of AlSi10Mg optimized structure under compressive load, a series of experimental and simulation studies were carried out. The stress-strain response, bearing capacity, energy absorption characteristics, damage mode and mechanism of the structure are analyzed and discussed. The results show that AlSi10Mg porous structure has obvious strain hardening effect, but no obvious strain rate effect. The volume fraction of AlSi10Mg porous structure increased from 9.43% to 22.15%, and its bearing strength increased from 22.34 MPa to 50.98 MPa. The optimized design structure is complex in this paper, which eliminates undesirable failure modes, and the benefit of high specific energy absorption is retained. The experimental and simulation results show that shear failure is the main cause of structural damage, and the normal of the failure section and the load action direction are roughly inclined at an angle of 45° ∼ 55°. The research results can provide an important reference for the optimal design of porous metal structure.

Toward Achieving High Kinetics in Anodeless Li2S Battery: Surface Modification of Cu Current Collector

AbstractAn anodeless Li2S is a promising battery system, which increases volumetric energy density. However, a severe capacity fading in the anodeless Li2S is observed at a high current density. Here, it is reported that the surface properties of Cu electrode significantly affect kinetics and cycle stability via controlling Li nucleation and Li metal deposition morphology. A native oxide on the surface increases the Li nucleation underpotential and makes porous Li metal structure because its reaction with the polysulfides during cycles leads to the formation of Li2SO4 and the reduction in the polysulfides. After removing the native oxide, the anodeless Li2S cell achieves a fast kinetics up to 10 C (11.66 A g−1) with 312 mAh g−1 and stable cycling (120 cycles at 1 C). Furthermore, high‐loading Li2S (4.5 mg cm−2) anodeless cell is demonstrated by using the modified Cu electrode without the native oxide, achieving good capacity retention for 50 cycles at C/3 and 484 mAh g−1 at reasonable high rate of 1 C. The findings pave the possible way for the practical application of the anodeless Li2S battery that has high energy density and fast kinetics.

Porous Noble Metal Electrocatalysts: Synthesis, Performance, and Development.

Active sites (intrinsic activity, quantity, and distribution), electron transfer, and mass diffusion are three important factors affecting the performance of electrocatalysts. Composed of highly active components which are built into various network structures, porous noble metal is an inherently promising electrocatalysts. In recent years, great efforts have been made to explore new efficient synthesis methods and establish structural-performance relationships in the field of porous noble metal electrocatalysis. In this review, the very recent progress in strategies for preparing porous noble metal, including innovation and deeper understanding of traditional methods is summarized. A discussion of relationship between porous noble metal structure and electrocatalytic performance, such as accessibility of active sites, connectivity of skeleton structures, channels dimensions, and hierarchical structures, is provided.

Design a novel integrated screw for minimally invasive atlantoaxial anterior transarticular screw fixation: a finite element analysis

PurposeTo design a new type of screw for minimally invasive atlantoaxial anterior transarticular screw (AATS) fixation with a diameter that is significantly thicker than that of traditional screws, threaded structures at both ends, and a porous metal structure in the middle. The use of a porous metal structure can effectively promote bone fusion and compensate for the disadvantages of traditional AATSs in terms of insufficient fixation strength and difficulty of bone fusion. The biomechanical stability of this screw was verified through finite element analysis. This instrument may provide a new surgical option for the treatment of atlantoaxial disorders.MethodsAccording to the surgical procedure, the new type of AATS was placed in a three-dimensional atlantoaxial model to determine the setting of relevant parameters such as the diameter, length, and thread to porous metal ratio of the structure. According to the results of measurement, the feasibility and safety of the new AATS were verified, and a representative finite element model of the upper cervical vertebrae was chosen to establish, and the validity of the model was verified. Then, finite element-based biomechanical analysis was performed using three models, i.e., atlantoaxial posterior pedicle screw fixation, traditional atlantoaxial AATS fixation, and atlantoaxial AATS fixation with the new type of screw, and the biomechanical effectiveness of the novel AATS was verified.ResultsBy measuring the atlantoaxial parameters, the atlantoaxial CT data of the representative 30-year-old normal adult male were selected to create a personalized 3D printing AATS screw. In this case, the design parameters of the new screw were determined as follows: diameter, 6 mm; length of the head thread structure, 10 mm; length of the middle porous metal structure, 8 mm (a middle porous structure containing an annular cylinder ); length of the tail thread structure, 8 mm; and total length, 26 mm. Applying the same load conditions to the atlantoaxial complex along different directions in the established finite element models of the three types of atlantoaxial fusion modes, the immediate stability of the new AATS is similar with Atlantoaxial posterior pedicle screw fixation.They are both superior to traditional atlantoaxial anterior screw fixation.The maximum local stress on the screw head in the atlantoaxial anterior surgery was less than those of traditional atlantoaxial anterior surgery.ConclusionsBy measuring relevant atlantoaxial data, we found that screws with a larger diameter can be used in AATS surgery, and the new AATS can make full use of the atlantoaxial lateral mass space and increase the stability of fixation. The finite element analysis and verification revealed that the biomechanical stability of the new AATS was superior to the AATS used in traditional atlantoaxial AATS fixation. The porous metal structure of the new AATS may promote fusion between atlantoaxial joints and allow more effective bone fusion in the minimally invasive anterior approach surgery.

Experimental and numerical investigation on thermal performance enhancement of phase change material embedding porous metal structure with cubic cell

Phase change material (PCM) is a promising candidate for application to thermal energy storage. However, low thermal conductivity hinders its wide application. In this paper, a porous metal structure (PMS) with cubic cell is used to enhance the thermal performance of PCM, in which additive manufacturing (AM) as advanced manufacturing technology enables the fast and precise fabrication of PMS with a controlled structure and material. A visualized experiment setup is built to investigate the thermal performance of PCM with and without PMS, including solid-liquid interface, temperature variation, and total melting time. To examine the heat transfer characteristics and clarify the role of PMS in the melting process, a three-dimensional numerical model is developed based on the pore-scale numerical simulation method. The experimental results illustrate that embedding PMS can significantly improve the thermal performance of PCM, e.g., the total melting time can be shortened by 38% compared with that for PCM without PMS. The numerical results are in good agreement with experimental results, which indicates that heat transfer characteristics can be predicted using pore-scale numerical simulation. The numerical results show that the temperature field of PCM with PMS is more uniform and heat transfer mechanics is different for PCM with and without PMS. In addition, PMS made of highly thermally conductive materials significantly enhances the thermal performance of PCM. Due to structure and material controllability of porous material fabricated by AM, this study highlights the capacity and potential of PMS as a heat transfer enhancer.