Role Of Porous Structure Research Articles

Synergistic impact of scan strategy and scan angles in laser powder bed fusion process on mechanical, tribological and cell viability properties of porous 316L SS structure

Poor load bearing ability and concentrated stress within cross-linked porous structures was found to be the major cause for the mechanical and wear failure of SS (Stainless Steel) 316L implants. Therefore, the present study introduces a novel scan pattern to enhance the mechanical and wear properties. Importantly, the role of porous structures on the constituents and formation of Tribo-film regimes under the simulated body fluid (SBF) condition were assessed using the X-ray photoelectron spectroscopy (XPS). Furthermore, the impact of the surface roughness of porous structures on the cell adhesion and cytotoxicity were explored. Various cross-linked porous structures are produced at three different scanning rotation angles (0°, 45°, and 90°) using the Laser powder bed fusion (LPBF) process. Morphology analysis reveals balling and stair-case effects at 0°, controlled for structures built at 45° and 90°. Porous-90° structure exhibits negative skewness and a platykurtic surface with low peaks and more valleys. It demonstrates higher strength with low density due to better particle fusion, net-like structure, and uniform element distribution. X-ray photoelectron spectroscopy (XPS) evaluates the impact of porous structures on Tribo-film regimes in simulated body fluid. Surface roughness effects on cell adhesion and cytotoxicity are also investigated. Cross linked porous structures presented two major compression failure modes include wrinkling and diagonal shearing. The densified structure of Porous-45° reduces contamination and cell death, facilitating stable cell growth. Tribo-film formation and load bearing ability of Porous-90° structure was better than the other structures, due to the cross-linked netlike structure and further more detailed in the XPS study.

Ni-Based Molecular Sieves Nanomaterials for Dry Methane Reforming: Role of Porous Structure and Active Sites Distribution on Hydrogen Production.

Global warming, driven by greenhouse gases like CH4 and CO2, necessitates efficient catalytic conversion to syngas. Herein, Ni containing different molecular sieve nanomaterials are investigated for dry reforming of methane (DRM). The reduced catalysts are characterized by surface area porosity, X-ray diffraction, Raman infrared spectroscopy, CO2 temperature-programmed desorption techniques, and transmission electron microscopy. The active sites over each molecular sieve remain stable under oxidizing gas CO2 during DRM. The reduced 5Ni/CBV10A catalyst, characterized by the lowest silica-alumina ratio, smallest surface area and pore volume, and narrow 8-ring connecting channels, generated the maximum number of active sites on its outer surface. In contrast, the reduced-5Ni/CBV3024E catalyst, with the highest silica-alumina ratio, more than double the surface area and pore volume, 12-ring sinusoidal porous channels, and smallest Ni crystallite, produced the highest H2 output (44%) after 300 min of operation at 700 °C, with a CH4:CO2 = 1:1, P = 1 atom, gas hour space velocity (GHSV) = 42 L gcat-1 h-1. This performance was achieved despite having 25% fewer initial active sites, suggesting that a larger fraction of these sites is stabilized within the pore channels, leading to sustained catalytic activity. Using central composite design and response surface methodology, we successfully optimized the process conditions for the 5Ni/CBV3024E catalyst. The optimized conditions yielded a desirable H2 to CO ratio of 1.00, with a H2 yield of 91.92% and a CO yield of 89.16%, indicating high efficiency in gas production. The experimental results closely aligned with the predicted values, demonstrating the effectiveness of the optimization approach.

The role of porous structure on airfoil turbulence interaction noise reduction

Experiments are performed to investigate the effect of porous treatment structure used at the leading edge on the aerodynamic and aeroacoustic characteristics of a National Advisory Committee for Aeronautics (NACA) 0012 airfoil. Three different triply periodic minimal surface porous structures of constant porosity are studied to explore their effect on the flow field and the relationship between airfoil response and far-field noise. The results show that the ratio between the porous structure pore size and the length scale of the turbulent flow plays an important role in the noise reduction capability of a porous leading edge. Changes to the turbulent flow properties in the vicinity of the airfoil are assessed to characterize the contributing physical behavior responsible for far-field noise manipulation. Velocity field analysis in front of the leading edge demonstrates a pronounced difference among porous structures. Furthermore, close to the airfoil surface and off from the stagnation line, all porous leading edges demonstrate a marked reduction in the low-frequency content of the velocity fluctuations. These results demonstrate the importance of the airfoil leading edge region and not just the stagnation line. The strong link evident in pressure–velocity coherence analysis of the solid airfoil is broken by the introduction of the porous leading edge. Furthermore, the porous leading edges reduce the near-field to far-field pressure coherence in both magnitude and frequency range.

Atomistic Insight into the Role of Porous Structure in Accommodating the Volume Expansion of Silicon Anodes for Lithium-Ion Batteries

Despite possessing high theoretical gravimetric capacity, the practical utilization of silicon anodes for lithium-ion batteries is still challenging because of poor capacity retention caused by massive volume expansion upon lithium insertion. The use of porosity to tackle this issue has widely been scrutinized, and porous silicon materials have been experimentally shown to have improved cycling stability. To provide a fundamental understanding of the structural and chemical evolution, here, we investigate the atomistic behaviors of porous silicon nanowires during lithiation and delithiation by means of a reactive molecular dynamics method. The simulations show that although the porous nanomaterials undergo a large intrinsic volume expansion similar to the non-porous ones, the hollow space available inside the materials can be exploited for lowering the external expansion via the local structure relaxation in the vicinity of the pore. Due to such relaxation, a small pore undergoes structural collapse during the first charge, suggesting that a relatively large pore diameter and a thin wall thickness are required to maintain the porous structural integrity. The simulations also unveil the evolution of the local stresses generated during lithium migration into and out of the materials, which emphasizes the role of porosity in alleviating the induced stresses.

Feasibility of advancing the production of bio-jet fuel via microwave reactor under low reaction temperature

Catalytic reduction of oxygen-containing compounds in palm kernel oil has been studied under H2-free atmosphere condition using microwave system approach over Raney nickel and magnetite activated carbon-based catalysts. The role of porous structure and active O-containing groups of magnetite activated carbon (FeMo/ACB) catalyst during deoxygenation (DO) at 250 °C was investigated. Activated carbon catalysts, obtained from bamboo-derived biochar activation at 800 °C with KOH exhibited large surface area and O-containing group. With the introduction of the FeMo/ACB catalyst, the relative content of bio-jet fuel increased remarkably (∼80%) with the bio-jet fuel selectivity of ∼80%. Noted, the high DO activity also showed strong correlation with the presence of high acidic sites, high porosity and surface on the bamboo-derived carbon support, which in turn allows the active metals Fe-Mo to coat the ACB support thoroughly thus promoting a more efficient DO reaction. In addition, the FeMo/ACB catalyst showed excellent reusability over five consecutive cycles, with hydrocarbon fractions ranging from 62% to 80% and bio-jet fuel selectivity from 65% to 80% and minimum coke formation (< 2 wt%).

Role of porous structure and active O-containing groups of activated biochar catalyst during biomass catalytic pyrolysis

Activated biochar contains developed porosity and is rich in O-containing groups, both of which can allow the biochar to act as a catalyst in biomass catalytic pyrolysis and produce valuable chemicals. In this study, the role of porous structure and active O-containing groups of activated biochar catalyst during biomass pyrolysis at 600 °C was investigated in a fixed-bed reaction system. Activated biochar catalysts, obtained from bamboo-derived biochar activation at 800 °C with KOH, K2CO3, KHCO3, or CH3COOK, exhibited large surface area (SBET) and lots of O-containing groups. With the introduction of the activated biochar catalyst, the bio-oil yield reduced and the gaseous product yield increased, especially for CO, CO2, and CH4. The content of phenols (reaching 67%) and aromatics increased greatly, while content of O-containing compounds and acetic acid significantly reduced. Phenols content exhibited a positive linear correlation with the SBET of the catalyst, while aromatics content showed a negative linear correlation with the SBET. The SBET and active O-containing groups were both reduced after catalytic pyrolysis, especially in the –OH, O–CO, and C–O groups, which showed higher catalytic activity for biomass pyrolysis. Activated biochar catalyst acted both as a catalyst and reactant during catalytic pyrolysis process.

Structural transformations and mechanical properties of porous glasses under compressive loading

The role of porous structure and glass density in the response behavior to compressive deformation of amorphous materials is investigated via molecular dynamics simulations. The disordered, porous structures were prepared by quenching a high-temperature binary mixture below the glass transition point into the phase coexistence region. With decreasing average glass density, the pore morphology in quiescent samples varies from a random distribution of compact voids to complex pore networks embedded in a continuous glass phase. We find that during compressive loading at constant volume, the porous structure is linearly transformed in the elastic regime and the elastic modulus follows a power-law increase as a function of the average glass density. Upon further compression, pores deform significantly and coalesce into large voids leading to formation of domains with nearly homogeneous glass phase, which provides an enhanced resistance to deformation at high strain.

Model of cathode catalyst layers for polymer electrolyte fuel cells: The role of porous structure and water accumulation

The cathode catalyst layer (CCL) is the major competitive ground for reactant transport, electrochemical reaction, and water management in a polymer electrolyte fuel cell (PEFC). Our model, presented here, accounts for the full coupling of random porous morphology, transport properties, and electrochemical conversion in CCLs. It relates spatial distributions of water, oxygen, electrostatic potential, and reaction rates to the effectiveness of catalyst utilization, water handling capabilities, and voltage efficiency. A feedback mechanism, involving the non-linear coupling between liquid water accumulation and oxygen depletion is responsible for the transition from a state of low partial saturation with high voltage efficiency to a state with excessive water accumulation that corresponds to highly non-uniform reaction rate distributions and large voltage losses. The transition between these states could be monotonous or it could involve bistability in the transition region. We introduce stability diagrams as a convenient tool for assessing CCL performance in dependence of composition, porous structure, wetting properties, and operating conditions.

Role of porous structure in char oxidation

The role of the porous structure and its effect on reactivity was studied from changes of macroscopic properties. We present a review of our experimental-modeling effort that concerns porosity and reactivity. Shrinkage gave an understanding into the structure, and occurs becasue of the reduction of microcrystal dimensions. Detailed modeling for the porous structure was developed and reproduced the shrinkage. Fragmentation increased the understanding into the behavior of the porous structure; it depends on the structure geometry and threshold porosity, and has been shown to occur when macroporosity reaches a threshold. Tiny details of the structure were gained from thermal conductivity (TC). A five-time decrease was measured from 0 to 30% burnout, then TC remained constant up to 80% burnout and increased twofold to 100% burnout. Heat transfer calculations using the same model showed an excellent fit to experimental data, indicating that the extent of connectivity between microcrystals is the single most important parameter for TC. The behavior of TC at low conversions is consistent with the reactivity data, since steep changes in TC are accompanied by generating defects which are attributed to active sites.