Sintered Metal Fibers Research Articles

Co-doped carbon nitride nanosheets supported on SMFs for peroxymonosulfate activation to degrade tetracycline

For the treatment of antibiotics contained wastewater, developing a highly efficient catalyst is key to peroxymonosulfate (PMS) activation and antibiotics degradation. In this work, nitrogen-doped carbon nanosheets (NCS) coated sintered metal fibers (SMFs) catalyst was designed and developed, which could positively promote the contacting efficiency between PMS, TC and catalysts. In specific, by the dip-coating of SMFs in the cobalt-contained dicyandiamide formaldehyde resin and the following pyrolyzing coordinated polymer procedure, it was possible to create a Co-doped NCS catalyst supported on SMFs. NCS with abundant exposed surface active sites could result in a relatively higher catalytic activity. Microscopy studies confirmed the presence of stacked NCS with high Co active sites loading, which was anchored on the surface of SMFs. The developed Co NCS/SMFs catalyst exhibited a highly degradation efficiency of 96% in 240 min. Effects of operating parameters (including PMS concentration and solution pH) on the TC elimination efficicency were also investigated. Additionally, Co NCS/SMFs exhibited good PMS activation activity in the wide pH range of 2.0–9.0, and acceptable recyclability with over 86% TC removal efficiency after five cycles test. According to SEM, XRD and XPS results, highly exposed active metal sites, O defects, Co-Nx sites and reactivity of Co0 in Co NCS/SMFs played an important role in the enhancement of degradation efficiency. Finally, radical inhibition experiment and corresponding EPR test revealedthe presence of SO4∙−, ∙OH, O2∙− and 1O2 in the TC degradation system, in which singlet oxygen (1O2) was demonstrated to be the dominating reactive species for PMS activation and TC degradation. This work provided an efficient strategy for developing robust monolithic lamellar catalyst for the continuous PMS activated degradation of TC.

Heuristic Approaches Based on Modified Three-Parameter Model for Inverse Acoustic Characterisation of Sintered Metal Fibre Materials

Modelling of sound propagation in porous media generally requires the knowledge of several transport properties of the materials. In this study, a three-parameter analytical model that links microstructure properties of sintered metal fibre materials and non-acoustical parameters of the JCAL model is used and modified, and two heuristic approaches based on the established model for inverse acoustic characterisation of fibrous metal felts are developed. The geometric microstructure of sintered fibrous metals is simplified to derive the relationship between pores and fibre diameters. The new set of transport parameters in the modified three-parameter model can cover two controllable parameters during the fabrication process of fibrous metals. With two known transport parameters, six sintered specimens are characterised using a deterministic algorithm, and a satisfactory result is achieved in fitting the normalised surface impedance measured by an acoustic measurement system. Moreover, the forward evaluation shows that our modified three-parameter theoretical model is capable of yielding accurate results for the sintered metal fibre materials. A numerical investigation of the complete inverse acoustic characterisation of fibrous metals by a global non-deterministic algorithm indicates that inversion from two porous material properties is preferable to the normalised surface impedance.

Cobalt Oxide Synthesis via Flame Spray Pyrolysis as Anode Electrocatalyst for Alkaline Membrane Water Electrolyzer.

Nanostructured cobalt oxide powders as electro catalysts for the oxygen evolution reaction (OER) in an alkaline membrane electrolysis cell (AME) were prepared by flame spray synthesis (FS); an AME’s anode was then produced by depositing the FS prepared cobalt oxide powders on an AISI-316 sintered metal fiber by the electrophoretic deposition (EPD) method. FS powders and the composite electrode were characterized by SEM, XRD, and XPS analysis. The electrode showed an increase in the OER catalytic activity in a KOH 0.5 M solution with respect to commercial materials commonly applied in alkaline electrolysis, demonstrating that the flame spray synthesis of nanoparticles combined with the electrophoretic deposition technique represent an effective methodology for producing an anodic catalyst for alkaline membrane electrolyzers.

In Situ X‐Ray Tomography of Sintered Metal Fiber Felts Exhibiting Auxetic Effect under Tension and Compression

Sintered metal fiber felts (SMFFs) are kinds of the strongest auxetic materials to date, but there are significant differences in the reported auxeticities, due to the lack of investigation on the fabrication process. This study is performed to analyze the influence of fabrication process and structural features on the auxetic effect exhibited by SMFFs. The sequence of compression and sintering processes determines the volume density of the interfiber-sintered joints and the resulting Poisson's ratio behavior under tension and compression. The SMFFs with a low volume density exhibit strong auxetic effect under tension and achiev a positive Poisson's ratio under compression because of the weak interfiber layer bonding. In contrast, the felts with a high density of interfiber joints reveal a relatively weak auxetic effect under both tension and compression. Moreover, an increase in the thickness and a decrease in the porosity reduce the auxetic effect. In addition, in situ X-Ray tomography of the tensile testing is performed to elucidate the mechanism of the auxetic effect. To explain the observed Poisson's ratio behavior under tension and compression, periodical finite-element modeling with real mesostructures is performed. Herein, a new insight into the relationship between the structure features and the Poisson's ratio behaviors is given.

3D Composite Nickel-Cobalt Oxides on Sintered Metal Fiber Mesh for Electrocatalytic and Pseudocapacitive Applications

Enhancement of specific surface area is known to improve performance of electrocatalytic system by intensifying the oxygen evolution (OER) process. In this work, nickel-cobalt oxides were formed on Bekipor ST 20AL3 3D stainless steel mesh, achieving a large surface area and high electric conductivity. Layer-by-layer potentiostatic electrodeposition was carried out in one solution by applying different potential values for individual cobalt and nickel oxide layer formation to ensure uniform distribution on each mesh filament. Hydroxide coatings were then thermally treated at 473–1073 K to obtain spinel-type oxides. X-ray diffraction analysis indicated three oxides—NiO, Co3O4 and NiCo2O4—as the main products obtained after annealing at 473–773 K. Surface morphology investigated by scanning electron microscopy showed a uniform coverage of each filament with lamellar nickel-cobalt oxides. The electrochemically active surface area of the films was determined by employing cyclic voltammetry of a ferricyanide/ferrocyanide redox system, which revealed a significant impact of annealing on the surface activity. Electrocatalytic performance tests indicated that annealing at 673 K significantly enhanced nickel-cobalt activity in OER, with overpotential of 536 mV at 10 mA cm−2, while further treatment had a detrimental effect. The coating was able to maintain this activity during long-term stability tests with no signs of surface damage. Galvanostatic charge/discharge measurements revealed a complex charge storing mechanism of nickel-cobalt oxide coatings, combining properties of batteries and supercapacitors. The highest energetic parameters achieved in this work were demonstrated by a coating annealed at 473 K (specific capacitance 769 F g−1, specific energy 312 W h kg−1, and specific power 750 W kg−1), along with great stability, maintaining 98% of its initial specific capacitance after 300 cycles.

Platinum Nanoparticles on Sintered Metal Fibers Are Efficient Structured Catalysts in Partial Methane Oxidation into Synthesis Gas.

Efficient structured catalysts of partial methane oxidation into synthesis gas were obtained by electrochemical modification of the surface of sintered FeCrAl alloy fibers in an ionic liquid BMIM-NTf2 with further introduction of platinum nanoparticles. It was shown that etching and electrochemical modification of sintered FeCrAl alloy fibers result in a decrease of the surface aluminum content. With an increase of the reaction temperature to 900 °C, the methane conversion reaches 90% and the selectivity to CO increases significantly to achieve 98%. The catalysts with a Pt loading of 1 × 10–4 wt % demonstrate high activity and selectivity as well as TOF in synthesis gas production by the CH4 + O2 reaction at 850–900 °C. To trace the composition and structure evolution of the catalysts, XRD and SEM methods were used.

Structured Fe3O4-doped ordered mesoporous carbon catalyst supported on sintered metal fibers for intensifying phenol degradation

Microfibrous-structured catalysts are materials that address the mass/heat transfer limitation and achieve catalytic process intensification, showing great promise for enabling practical environmental catalysis such as continuous wastewater treatment process. In this work, Fe3O4-doped ordered mesoporous carbon (OMC) catalyst supported on porous sintered metal fibers (Fe-OMC/SMFs) was prepared using a new yet simple “one-pot” method and used as a Fenton-like heterogeneous catalyst. The obtained catalysts were carefully characterized by TGA-DTG, BET, XRD, SEM-EDS, XPS and H2-TPR techniques. Structured reactor was designed and developed using developed microfibrous-structured catalysts, demonstrating an excellent catalytic performance for continuous heterogeneous Fenton oxidation of phenol. Specifically, both phenol and H2O2 conversions increased slightly as carbonization temperatures increasing from 400 to 1000°C. Compared to Fe-OMC pellet catalyst, the developed structured catalyst showed an improved catalytic activity (i.e. ∼100 % phenol/H2O2 conversions), and remarkable long-term stability (i.e. ∼100 % phenol conversion over a 7-h longevity test). Additionally, the developed Fe-OMC/SMFs catalyst showed Fe leaching amounts of ∼10mgL−1 during reaction, being significantly lower than that of Fe-OMC pellet catalyst (i.e. ∼500mgL−1). Experimental results revealed that well-dispersed Fe3O4 nanoparticles in OMC and three-dimensional microfibrous networks and large void volume of SMFs support are significantly benefit to enhance mass transfer and contacting efficiency between active sites and reactants, and thus achieve the process intensification of catalytic degradation of phenol.

Effective removal of fluorescent microparticles as Cryptosporidium parvum surrogates in drinking water treatment by metallic membrane

The diarrhoea-causing parasitic protozoan Cryptosporidium parvum (C. parvum) cannot be efficiently removed by conventional drinking water treatment and poses a biological threat to public health. To ensure the biological safety, three kinds of metallic membranes, laminating metal mesh filter, non-woven metal filter and sintered metal fiber filter were employed to compare their properties. The results showed that the sintered membrane possessed the best filtration performance and lowest membrane resistance among three metallic membranes. Therefore, the sintered membrane was selected for subsequent experiments. Due to the low infectious dose of C. parvum and sophisticated detection methods, fluorescent particle tracers, Crypto-tracer-1, were chosen as a feasible surrogate was proposed to investigate the removal efficiency of sintered membrane for C. parvum. The results indicated that the tracer log removal value (LRV) ranged between 5.1 and 5.4 log10 under different filtration flux, which equivalently means that C. parvum could be completely removed and further tests are needed to confirm the results obtained using C. parvum. Furthermore, a pilot-scale study was performed for 10 weeks in full-scale drinking water treatment systems. The turbidity could be efficiently removed (outlet water of membrane was 0.08 ± 0.04 NTU) and the average transmembrane pressure recovery rate was 84.6% after physical backwash. Fouling mechanism analysis indicated that the interaction energy between foulants and membrane material became stronger over time. The practical operation results showed that sintered membrane performed well in continuous operation for a long time and also had a good anti-pollution ability. These findings could facilitate application of metallic membrane in drinking water treatment.

Design and evaluation of a sintered metal fiber filter for gasoline direct injection engine exhaust aftertreatment

A novel metal fiber gasoline particulate filter (GPF) is designed and evaluated as a potential improvement to the traditional automotive wall flow substrate. A procedure based on single fiber efficiency theory and the Kuwabara flow model for fibrous filter media is developed to optimize filter design. The prototype design is derived from two constraints, namely to maximize PM removal efficiency while minimizing filter backpressure. Metal fibers are chosen that tolerate gasoline engine exhaust temperatures and pleating is used to fulfill size limits dictated by vehicle space constraints. Two prototypes are evaluated by vehicle and engine dynamometer testing. These tests reveal PM filtration efficiencies of greater than 78% for both the FTP and US06 drive cycles, with an average backpressure of approximately 1 kPa over a US06 drive cycle on a 2.0 L GDI light duty vehicle. Measured PM removal efficiencies at constant exhaust temperature and flowrate agree well with model predictions. Backpressure predictions agree withs measurements after accounting for GPF entrance and exit effects. The metal fiber GPF performance is discussed relative to the current state of the art wall flow filters and the limited literature data on metal foam filters. Whereas the fibrous media offers excellent efficiency and backpressure penalty, achieving surface areas comparable to wall flow substrates remains a challenge for practical implementation.

Gas Diffusion Layers in Fuel Cells and Electrolysers: A Novel Semi-Empirical Model to Predict Electrical Conductivity of Sintered Metal Fibres

This paper introduces novel empirical as well as modified models to predict the electrical conductivity of sintered metal fibres and closed-cell foams. These models provide a significant improvement over the existing models and reduce the maximum relative error from as high as just over 30% down to about 10%. Also, it is shown that these models provide a noticeable improvement for closed-cell metal foams. However, the estimation of electrical conductivity of open-cell metal foams was improved marginally over previous models. Sintered porous metals are widely used in electrochemical devices such as water electrolysers, unitised regenerative fuel cells (URFCs) as gas diffusion layers (GDLs), and batteries. Having a more accurate prediction of electrical conductivity based on variation by porosity helps in better modelling of such devices and hence achieving improved designs. The models presented in this paper are fitted to the experimental results in order to highlight the difference between the conductivity of sintered metal fibres and metal foams. It is shown that the critical porosity (maximum achievable porosity) can play an important role in sintered metal fibres to predict the electrical conductivity whereas its effect is not significant in open-cell metal foams. Based on the models, the electrical conductivity reaches zero value at 95% porosity rather than 100% for sintered metal fibres.

Thickness effect on mechanical behavior of auxetic sintered metal fiber sheets

Sintered metal fiber sheets (MFSs) made by sequential-overlap method are transversely isotropic open-cell cellular materials with paper-like fiber network architectures, which exhibit auxeticity and are promising for various potential applications due to the reentrant micro-structure. The thickness effect on the out-of-plane auxeticity (negative Poisson's ratio) of MFSs samples of 2–20 mm thick subjected to in-plane tensile loading is investigated with digital image correlation technique. Furthermore, the deformation modes of fibers within MFSs during various loading stages are examined with X-ray tomography. It is found that in addition to the straightening of reentrant fibers, fiber layers with defects and joints failure induced slippage between adjacent layers leads to local shear and results in unique umbrella-like local deformation termed umbrella effect, which gradually dominates the auxeticity during tensile loading. Although remarkably increasing lateral deformation, the umbrella effect significantly diminishes the in-plane mechanical performance such as rigidity and strength. In particular, this effect is suppressed by sample thickness: the overall performance tends to stabilize with sample thickness greater than a certain value, provided that the MFS is uniform with all fibers randomly distributed. The finding facilitates wider application of auxetic MFSs with further understanding on the relationship between the thickness effect and performance.

Electrocatalytic and pseudocapacitive properties of cobalt (hydro)oxide films on sintered metal fiber filter

Cobalt (hydro)oxide films on Bekipor ST 20AL3 sintered metal fiber were formed by electrochemical deposition under galvanostatic conditions using different electrolyte baths (nitrate, acetate and chloride). Cobalt oxide films were prepared via thermal treatment of as-deposited specimens at 673 K. Electroactive surface area of as-deposited and annealed films was estimated using oxidation–reduction system containing ferricyanide/ferrocyanide. Electrocatalytic and pseudocapacitive properties of the prepared films were investigated using 0.1 M NaOH aqueous solutions. The maximum specific capacitance of 1324 F g−1 was observed for α-Co(OH)2 films electrodeposited from nitrate-containing electrolyte. Similarly, the highest electrocatalytic activity and stability in oxygen evolution reaction (OER) was determined to be characteristic for Co3O4 films derived from nitrate bath.

A semi-analytical model for the influence of temperature on sound propagation in sintered metal fiber materials

A semi-analytical model is developed to predict the influence of temperature on the sound absorbing performance of sintered metal fiber materials (SMFMs) by extending the Johnson-Champoux-Allard-Lafarge (JCAL) model. In this model, three micro-structure factors of the SMFMs – the Kozeny number and the thermal and viscous shape factors – are calculated by applying the multi-scale asymptotic method (MAM), and the temperature effect is taken into account by considering the variations of the thermo-physical parameters of saturated air with temperature. Key transport parameters (e.g., viscous and thermal permeability, tortuosity, viscous and thermal characteristic lengths) are then directly determined by fiber diameter and porosity of the material. High-efficiency of the semi-analytical model is demonstrated for estimating the influence of topological parameters upon sound absorption under different temperatures. The transport parameters obtained by the proposed model agree well with those calculated using fully numerical simulations. Also, the model predictions are in accordance with existing experimental measurements at different temperatures. The model reveals not only the underlying mechanisms of temperature effect on sound propagation in porous metals, but also provides a theoretical guideline for the sound absorption application of SMFMs in high temperature environments.

Evaluation of metallic filter media for sub-micrometer soot particle removal at elevated temperature

ABSTRACTSoot particle removal performance of two types of metallic filter media, sintered metal powder and sintered metal fiber, is experimentally evaluated as potential improvements to conventional ceramic filtration media for gasoline direct injection (GDI) engine PM after-treatment application. Soot collection efficiency and flow resistance of several grades of metallic media are measured at temperatures of 25, 350, and 650°C and a range of representative filtration velocities for sub-micrometer soot particles generated from a propane flame. Theoretical collection efficiency based on single fiber efficiency theory shows good agreement with experimental data for nearly spherical KCl particles at 350°C. Improved collection efficiency is observed for soot particles in the interception-dominated size range above ∼100 nm due to enhanced interception length. Soot collection is slightly enhanced at higher temperature, which is consistent with model predictions. Sintered metal fiber media are found capable of ...

2D Model and 3D Reconstitution of Sintered Metal Fibers by Surface Diffusion

Abstract According to the sections of sintered junction of two metal fibers, which are oval-oval geometry structure in different directions, an oval-oval model was developed based on the traditional surface diffusion mathematical model. This model was numerically solved by a level set method to achieve the 2D simulations of two sintered metal fibers. Moreover, the 3D reconstitution method was proposed to depict the complex 3D geometrical structure of sintered junction. The 2D simulations and 3D reconstitution results of two metal fibers with the fiber angle 30° well agree with the experimental ones, which imply that the 2D model and 3D reconstitution method are correct. In addition, the numerical simulation results show that the growth rate of sintered neck along the directions taken from the bisector of obtuse angle to the bisector of acute angle is increased.

Effects of porosity and wire diameter on pressure drop and heat transfer characteristics of sintered metal fiber

Effects of porosity and wire diameter on pressure drop and heat transfer characteristics of sintered metal fiber

A novel adsorption module with fiber heat exchangers: Performance analysis based on driving temperature differences

A main focus of recent R&D on adsorption modules for thermally driven heat pumps and chillers has been to enhance the volume specific power output while maintaining a reasonable coefficient of performance (COP).An adsorption module using a new type of heat exchanger based on aluminum sintered metal fiber structures brazed on flat fluid channels has been developed. The heat exchangers for adsorber/desorber and evaporator/condenser are identically constructed. The adsorption heat exchanger is coated with a silico-alumino phosphate (SAPO-34) by a partial support transformation direct crystallization (PST) [1]. Both components are placed in a vacuum tight housing using a valve-free configuration. Water is used as adsorptive.The experimental characterization of the module shows a high volume specific power (up to 82 W/litre module for cooling, 320 W/litre for heating). Although no heat is recovered between ad- and desorption cycle, a COP of almost 0.4 is reached for cooling and 1.4 for heating.Driving temperature differences are defined for the analysis of the heat exchanger performance. The evaporator/condenser shows extremely good performance with about 240 W/K specific evaporation power per litre of heat exchanger, while the adsorber is limiting the module performance.

Sound absorption coefficient optimization of gradient sintered metal fiber felts

An optimization method for sound absorption of gradient (multi-layered) sintered metal fiber felts is presented. The theoretical model based on dynamic flow resistivity is selected to calculate the sound absorption coefficient of the sintered metal fiber felts since it only requires three key morphological parameters: fiber diameter, porosity and layer thickness. The model predictions agree well with experimental measurements. Objective functions and constraint conditions are then set up to optimize separately the distribution of porosity, fiber diameter, and simultaneous porosity and fiber diameter in the metal fiber. The optimization problem for either a sole frequency or a pre-specified frequency range is solved using a genetic algorithm method. Acoustic performance comparison between optimized and non-optimized metal fibers is presented to confirm the effectiveness of the optimization method. Gradient sintered metal fiber felts hold great potential for noise control applications particularly when stringent restriction is placed on the total volume and/or weight of sound absorbing material allowed to use.

金属繊維焼結体を流路に用いた固体高分子形セルによるメタノールの電気分解に関する研究

There is a possibility that the electrolysis of methanol can be a efficient hydrogen production methode due to a very low theoretical electrolysis voltage of methanol. This paper describes the investigation on the hydrogen production in an electrolyzer cell employing a newly developed flow fields made with sintered metal fiber. The sintered metal fiber flow field can supply reactants whole area of electrode. Results show that the flow field has higher performance than conventioned metal wire structure flow field and the performance tends to increase by reducing the porosity of sintered metal fiber.

Research on a Direct Methanol Fuel Cell with Sintered Metal Fiber Porous Flow Fields for Even Supply of Reactants

Research on a Direct Methanol Fuel Cell with Sintered Metal Fiber Porous Flow Fields for Even Supply of Reactants