Porosity Level Research Articles

Effect of additively manufactured polymeric inserts on impact response of construction safety helmets

Purpose Struck-by accidents (i.e. being hit by a falling object) are a leading cause of traumatic brain injuries in the construction industry. Despite the critical role of hard hats in minimizing such injuries, their overall design has not appreciably changed in decades. Therefore, this study aims to explore the potential benefits of modifying commercially available hard hat designs by incorporating a compliant cantilever and a sacrificial, energy-absorbing structure to enhance their protective capabilities against impacts. Design/methodology/approach This study involved conducting experimental impact tests to obtain the head acceleration attenuation using hard hats with a variety of compliant cantilever lattice insert designs. These lattice inserts were additively manufactured using three polymeric materials, including polylactide (PLA), acrylonitrile butadiene styrene, high-impact polystyrene and three porosity levels. A Hybrid III head/neck assembly was fitted with each hard hat design, and experimental drop tests were conducted using a 1.8-kg steel impactor dropped from 1.83 m. The maximum acceleration and head injury criterion (HIC) values were obtained for each test. Findings Analysis of variance revealed that HIC was significantly reduced for all lattices with 56% porosity (p < 0.023) compared to the control (unmodified) hard hat. The most effective insert was found to be a PLA insert with 56% porosity, which reduced the HIC value by 38% compared to the control (unmodified) hard hat, with a statistically significant p-value of 0.018. Originality/value The data present in this study reveals that simple and inexpensive modifications can be made to existing hard hat designs to reduce injury risk from overhead impacts.

Enhancing the performance of SiC-based varistors through the use of SPS processing and fluxes

SiC varistors, which are used as surge arrestors in high power/high energy applications, often contain high levels of porosity (∼25 %) which can degrade varistor performance. Starting with SiC-clay varistors (∼43 µm grain size SiC) we employed spark plasma sintering (SPS) and flux additions (to enable liquid phase sintering) to reduce the level of porosity and understand its impact on the microstructure and the electrical properties. Sintering by SPS at 1200 °C for 5 min increased the density to 94 % theoretical, increasing energy density capability by almost a factor of 10 (to ∼1100 J cm−3), but the non-linear coefficient (α) fell by 40 % (to 3.5) and breakdown field (Eb) fell by 75 % (to ∼200 V cm−1). Varistors prepared with nepheline syenite as a flux (replacing clay) which were pressureless sintered at 1200 °C had maximum densities of 80 %. The samples in which all the clay was replaced by the flux exhibited exceptional energy density performance (over 10,000 J cm−3) but suffered reductions in other parameters. Using small grain size SiC (∼3 µm) and 40 % syenite flux yielded consistently superior properties: low power range α value 12.2, high power range α value 32.5, breakdown field ∼5880 (V cm−1) and very low leakage currents ∼10−3 (mA/cm2).

Stabilization of porosity in reaction bonded aluminum oxide (RBAO) by coarsening in a reactive atmosphere

A coarsening treatment in an HCl containing atmosphere was performed to stabilize the porosity of Al2O3/ZrO2 composites up to elevated temperatures. There is minimal shrinkage during the reactive coarsening treatment and the porous microstructure is stable during subsequent heat treatments. The reaction bonding of aluminum oxide (RBAO) process was used to fabricate the samples. Coarsening was investigated as a function of initial density (40–60 % TD) and coarsening temperatures (1250–1400 °C). After the HCl coarsening step, samples were sintered in air to determine the effect of coarsening treatment on pore stability. Up to the temperature of the coarsening treatment no further densification is observed. Above the HCl coarsening temperature densification is significantly retarded. Thus, it is shown that the porosity in RBAO can be stabilized by heat treatment in a 10 vol % HCl containing atmosphere. During the coarsening treatment in HCl at 1300 °C, 1350 °C and 1400 °C little densification was observed (Δ ρ ≤ 2 % TD) in comparison with the densities that result from sintering reaction bonded samples in air at 1350 °C (Δ ρ ∼ 5–8 % TD). Therefore, the HCl coarsening is a promising approach to adjust a desired level of porosity for high temperature applications of porous materials. It is postulated that at a given density, the coarsened materials should exhibit increased strength compared to un-coarsened materials due to increased contact area between the particles.

Preparation and Structure-Property Relationship Study of Piezoelectric-Conductive Composite Polymer Nanofiber Materials for Bone Tissue Engineering.

This study aimed to develop Janus-, cross-network-, and coaxial-structured piezoelectric-conductive polymer nanofibers through electrospinning to mimic the piezoelectricity of bone and facilitate the conduction of electrical signals in bone tissue repair. These nanofibers were constructed using the piezoelectric polymer polyvinylidene fluoride, and the conductive fillers reduced graphene oxide and polypyrrole. The influence of structural features on the electroactivity of the fibers was also explored. The morphology and components of the various structural samples were characterized using SEM, TEM, and FTIR. The electroactivity of the materials was assessed with a quasi-static d33 meter and the four-probe method. The results revealed that the piezoelectric-conductive phases were successfully integrated. The Janus-structured nanofibers demonstrated the best electroactivity, with a piezoelectric constant d33 of 24.5 pC/N and conductivity of 6.78 × 10-2 S/m. The tensile tests and MIP measurements showed that all samples had porosity levels exceeding 70%. The tensile strength of the Janus and cross-network structures exceeded that of the periosteum (3-4 MPa), with average pore sizes of 1194.36 and 2264.46 nm, respectively. These properties indicated good mechanical performance, allowing material support while preventing fibroblast invasion. The CCK-8 and ALP tests indicated that the Janus-structured samples were biocompatible and significantly promoted the proliferation of MC3T3-E1 cells.

Numerical evaluation of interwire angle influence on molten pool fluid dynamics and weld defects in tandem NG-GMAW of 5083 aluminum alloy

The impact of interwire angle on the fluid dynamics and weld defects in tandem NG-GMAW of 5083 AlMg alloy was investigated through experimental and simulation methods. The rotating coordinate system was employed to model the inclined arc and arc interaction, while a pulsed Gaussian distribution arc model was adopted to consider factors such as arc heat, arc pressure and drag force. Experimental results demonstrate that different interwire angles lead to different weld formation and varying levels of porosity and pore distribution. A sound weld bead with no formation defect and low porosity was achieved when the interwire angle was set at 10°. Simulation results illustrate the relationship between weld formation, bubble escape and molten pool fluid dynamics under diverse interwire angles. As the interwire angle increases, the weld surface becomes concave. At the interwire angle of 0°, the weld bead surface appears leveled and porosity tends to occur near the sidewalls due to roundabout flows in that region. At an interwire angle of 14°, roundabout flows converge at the central longitudinal section, resulting in significant porosity in this area. However, when the interwire angle is set at 10°, backward flows driven by two arcs suppresses roundabout flow throughout the entire molten pool, leading to a lower percentage of porosity area.

Numerical investigation on the influence of CO2-induced mineral dissolution on hydrogeological and mechanical properties of sandstone using coupled lattice Boltzmann and finite element model

The impact of CO2-induced mineral reactions, specifically the CO2-water-rock interactions, has been widely recognized for its potential to compromise the hydrogeological and mechanical properties of porous media, thereby deteriorating their integrity and mechanical characteristics. This raises concerns regarding the safety of numerous projects such as CO2 geological storage. However, the mechanism underlying the influence of CO2-induced mineral reactions on these parameters is still not fully understood, thereby introducing uncertainty into the reliability of predicted outcomes. Direct pore-scale simulation plays a crucial role in deepening the understanding of CO2 -water-rock interaction and its associated impacts. The present study proposes a novel simulation model that integrates the lattice Boltzmann and finite element methods to simulate the dissolution of calcite in a 3D sandstone sample invaded by saturated CO2 solution, aiming to investigate the resulting evolution of hydrogeological parameters (i.e., porosity and permeability) and mechanical properties (i.e., bulk and shear moduli). The injection rates of reactive fluid (i.e., CO2 solution) were varied in the model to simulate different operational conditions of CO2 geological storage project. The simulation results demonstrate that the decrease in injection velocity inhibits the dissolution of calcite in the middle and downstream regions, concentrating it near the inlet. These distinct modes of calcite dissolution result in differentiated permeability and mechanical properties within rocks possessing identical porosity levels. In general, the increase in fluid injection velocity leads to a more pronounced enhancement in permeability and a greater attenuation in bulk and shear moduli under the same porosity. Thus, it is confirmed that the utilization of porosity is inadequate in accurately characterizing the evolution of rock permeability and mechanical properties resulting from mineral reactions. We ascertain that the application of fractal parameters, i.e., succolarity and fractal dimension, can more precisely depict the progression of permeability and bulk/shear modulus, respectively.

In Ukrainian

The contact wetting is one of the effective methods of studying the adsorption capacity of sorbents. The purpose of the work was to compare the experimentally obtained data on the adsorption capacity of shungite, obtained by the sessile drop method, and the results of modeling the behavior of liquid droplets on heterogeneous surfaces using the Boltzmann lattice method, and to show the suitability of the simplified version of the LBM method that we applied within the framework of a two-dimensional model for modeling complex cases of contact interaction between liquids and sorbent, when it cannot be carried out by the method of contact wetting. The adsorption properties of shungite with regard to the extraction of various impurities from water-alcohol solutions and the capability of the sorbent to recover were investigated by the method of contact wetting and analyzed by involving the data obtained by the methods of nitrogen adsorption, thermogravimetry and IR spectroscopy. It is shown that the adsorption properties of shungite are due to the presence on its surface of hydroxyl functional groups attached to carbon atoms in phenol or enol form, which give the surface hydrophilic characteristics. These groups play a key role in the adsorption of components from the liquid (aqueous) phase due to the formation of a hydrogen bond during the sorption of components from the liquid phase, and are restored after heating in the temperature range of 80–180 °C with the formation of carbon-containing gases and water. It has been found that silanol groups present in shungite do not participate in sorption. Compared to the original shungite sample, the sample after five cycles of adsorption is characterized by a noticeable effect of mass loss (1.8 %) in the temperature range of 80–180 °С. At the same time, the loss of mass is not significant at temperatures below 100 °С. This suggests that the sorbed substances are in the pores and not on the surface of shungite, and they begin to be removed only after heating above 100 °C. The LBM method was used to study fast-moving processes at the meso-level. A comparative analysis of the experimental data obtained by the method of contact wetting with the results of simulation by the Boltzmann lattice method within the framework of the two-dimensional model was carried out. 2D modeling by the LBM method turned out to be an effective means of studying capillary condensation in mesopores, anticipatory wetting of the solid phase, liquid penetration into a porous medium with different topologies, and the formation of anisotropic droplets and anisotropic bridges. The role of mesopores in the sorption process was analyzed by modeling the behavior of liquid droplets on heterogeneous surfaces and using data on the course of adsorption and capillary processes on the surface of a solid phase with different levels of porosity, roughness, and functional composition.

Microfacies and Depositional Environments Analyses of the Hartha Formation at Balad Oil Field, Central Iraq

The Hartha Formation (Late Campanian-Maastrichtian) has been recognized as a potential reservoir for hydrocarbons in various oilfields within the Mesopotamian basin in central Iraq. The formation has conformable upper contact with the overlying Shiranish Formation but unconformable lower contact with the underlying Mushorah Formation. This formation has been stratigraphically divided into two main parts. The lower part is particularly significant as it is recognized as an important stratigraphic unit due to the presence of oil shows. Five subsurface sections and many thin sections of the Hartha Formation (Late Campanian-Maastrichtian) were studied to unravel the depositional facies and environments. The sedimentary microfacies of the Hartha Formation in the Balad oil field include mudstone, wackestone, wackestone to packstone, packstone, Packstone to Grainstone, and Rudstone. These depositional microfacies have been subdivided according to their primary and diagenetic constituents into six sub-microfacies. The microfacies have been deposited in deep shelf margin, open shelf, and foreslope of varying salinities and energy levels. Cementation, dolomitization, compaction and pressure solution (stylolitization ), and dissolution are observed affecting variably both ground mass and particles. These diagenetic processes have both positive and negative effects on porosity types, causing fluctuations in porosity levels. The primary pore types identified within the study wells include interparticle porosity, intercrystal porosity, moldic porosity, vuggy porosity, channel porosity, and fracture porosity.

Review on The Impacts of Biochar and Soil Organic Matter (SOM) Habitation toward the Soil Physico-Chemical Properties Conjugating with Maize (Zea mays) Growth Performance

This study studies the complex relationships between maize growth, soil organic matter, and soil physico-chemcial properties, with an emphasis on biochar. It examines how soil organic matter affects pH, bulk density, Cation Exchange Capacity (CEC), porosity, and nutrient levels. Biochar and soil organic matter increase soil pH by decomposing organic anions. With biochar, increasing soil organic matter concentration reduces bulk density, improving soil structure, porosity, and water retention. By increasing Cation Exchange Capacity (CEC), biochar and soil organic matter improve soil nutrient retention and delivery, which is essential for soil fertility. As a soil organic matter component, biochar provides macro and micronutrients, boosting soil production. The study also highlights the importance of soil porosity in plant growth, with sandy soils having high porosity and leaching susceptibility and soil organic matter. However, loam soils, made of sand, clay, and silt, have a balanced porosity and soil organic matter concentration that makes them ideal for agriculture. These data show how organic matter, and biochar, affect maize growth and soil physico-chemical properties. This finding has major implications for protecting the environment and sustainable agriculture.

Chemical Modifications of Recycled Concrete Aggregate

The necessity for environmental sustainability has prompted the utilization of recycled concrete aggregates (RCA) sourced from structural demolition sites for the production of recycled aggregate concrete (RAC). The primary element impacting the quality of recycled concrete aggregate (RCA) is the mortar paste that adheres to the natural aggregate (NA). The cement mortar adhered to recycled concrete aggregate exhibits higher porosity and water absorption levels, along with reduced strength compared to natural aggregate. These characteristics negatively impact both the mechanical properties and durability of fresh and hardened concrete incorporating recycled concrete aggregate. As a result, it is crucial to enhance the interface by improving the surface of the aggregate or by removing the mortar adhered to the NA. Methods for achieving this include surface modification of the aggregate or removing adhered paste from the natural aggregate (NA). This research includes treatment involving acidic solutions particularly hydrochloric acid (HCl), and sulphuric acid (H2SO4), for mortar layer removal from RCA, analyzing their impact on the mechanical properties of aggregates and durability of concrete incorporating RCA.

Degradable biporous polymeric networks based on 2-methylene-1,3-dioxepane: Towards hierarchically structured materials meant for biomedical applications

For the first time, the preparation of doubly porous “poly(ε-caprolactone)-like” networks through free-radical ring-opening copolymerization of 2-methylene-1,3-dioxepane with divinyl adipate was achieved via a double porogen templating approach. This versatile strategy allowed for the formation of macropores of around 150 μm generated by removal of sieved and sintered NaCl particles in water, while smaller pores in the 1–10 μm range were created by phase separation during the copolymerization process through a syneresis mechanism in the presence of a porogenic solvent. The chemical nature of the as-obtained scaffolds was evidenced by Raman spectroscopy. The two distinct porosity levels could be examined by scanning electron microscopy and mercury intrusion porosimetry. The nature of the porogenic solvent as well as its volume proportion and the amount of crosslinking agent in the polymerization feed allowed for finely tuning the porous features of the micropores. The crucial role of the double porosity of such biporous scaffolds on their water uptake and mechanical properties under compression was assessed by comparing them with their monoporous analogues, while their degradability was investigated in different alkaline aqueous media. The double porosity enabled a synergistic effect regarding the water uptake of the resulting scaffolds when compared to their monoporous counterparts. Doubly porous polymeric materials with appropriate mechanical properties were obtained, possessing high compressibility and shape memory behavior upon consecutive compression cycles. Finally, these materials display degradation rates that could be controlled depending on medium pH.

Effect of the Cooling Liquid on the Milled Interface in the Combined Process of Milling and Direct Metal Deposition.

The combination of Direct Metal Deposition (DMD) with milling offers numerous advantages for the manufacturing of complex geometry parts demanding high dimensional accuracy and surface quality. To reach this, a process strategy alternation between both processes is often required, leaving the milled surface with a layer of cooling fluid before adding material by DMD. This paper investigates the effect of cooling liquid on the milled interface in the combined process of milling and DMD. Five different interface conditions were examined, employing four distinct cleaning techniques to assess their impact on the quality of the interface. Key metrics analysed included hydrogen content, carbon content, and porosity levels at the interface. Cleaning techniques were evaluated to determine their necessity in enhancing the interface quality in the combined DMD and milling production process. Results from this study provide essential insights into the optimal cleaning requirements for improving the interface integrity in hybrid manufacturing processes, which could lead to more reliable and efficient production methods in industrial applications.

Evaluation of Porosity in AISI 316L Samples Processed by Laser Powder Directed Energy Deposition

Directed energy deposition-laser beam/powder (DED-LB/Powder) is an additive manufacturing process that is gaining popularity in the manufacturing industry due to its numerous advantages, particularly in repairing operations. However, its application is often limited to case studies due to some critical issues that need to be addressed, such as the degree of internal porosity. This paper investigates the effect of the most relevant process parameters of the DED-LB/Powder process on the level and distribution of porosity. Results indicate that, among the process parameters examined, porosity is less affected by travel speed and more influenced by powder mass flow rate and laser power. Additionally, a three-dimensional finite element transient model was introduced, which was able to predict the development and location of lack-of-fusion pores along the building direction.

Insights into Nb-silicide-based in-situ composite processed by electron beam powder bed fusion

This is the first report introducing the idea of processing Nb-silicide-based in-situ composite through electron beam powder bed fusion (PBF-EB). A high energy input together with a line order strategy resulted in cracking, whilst a lower energy input without the line order led to microstructural inhomogeneity characterised by alternating dark- and bright-contrast bands. In samples printed using the line order strategy, long cracks initiated close to the melt pool boundary and propagated into the previous layer. These cracks were due to the weak interface between the primary Nb3Si columnar grains and the equiaxed (Nb,Ti) solid solution phase or Nb3Si-(Nb,Ti) solid solution eutectic structure. The porosity level increased from 0.122 % to 0.547 % with the increase of area average energy input from 2.22 J/mm2 to 6.67 J/mm2. The density decreased to 6.80 g/cm³ in the line order strategy samples due to the presence of cracks, compared to 6.84 g/cm³ in samples without employing the line order strategy. The dark-contrast band consisted of (Nb,Ti) solid solution, Nb3Si and Nb5Si3, while the bright-contrast band was composed of (Nb,Ti) solid solution and Nb3Si. Within the bright-contrast band, a recurring layered microstructural inhomogeneity appeared, with columnar grains at the bottom, whilst fine- and coarse-grained eutectic networks in the middle and upper regions. The Nb3Si phase exhibited a pronounced {001} texture, whereas the (Nb,Ti) solid solution phase displayed a weaker texture. The Nb-silicide-based in-situ composite fabricated through PBF-EB had a microhardness of ∼700 HV0.5. This value is higher than that achieved through conventional means but falls within the mid-range for laser-based additive manufacturing counterparts.

Influence of defect degree on corrosion resistance of graphene coating on titanium alloy

Electrophoretic deposition (EPD) is an effective method for preparing graphene coatings with dense and uniform characteristics on complex-shaped substrates, but defects in graphene coatings prepared by EPD are unavoidable, which affects the corrosion resistance of graphene coatings. This study investigates the effect of defect levels(i.e. ID/IG values in Raman spectroscopy analysis) on the corrosion resistance of graphene coatings on titanium alloys by varying EPD parameters and graphene raw material sizes to prepare coatings with different defect levels. Raman spectroscopy and scanning electron microscopy were used to characterize and measure the defect degree of graphene coatings. Open-circuit potential analysis, electrochemical impedance spectroscopy (EIS) and polarization analysis of dynamic potential were used to study the corrosion properties and anti-corrosion mechanism of graphene coatings.The results show that the graphene coating has lower defect level at an electrophoresis voltage of 60 V, deposition time of 20 min, and graphene flakes size of 1 μm achieving a corrosion current density as low as 0.06 μA/cm2. This study reveals the corrosion resistance mechanism of graphene coatings with different defect levels. Graphene coatings with large porosity and defect levels are easily penetrated by corrosive media and then corrode in contact with the substrate. This research provides insights into developing graphene coatings with low defect levels and high compactness, which will significantly enhance the anti-corrosion efficiency of titanium alloys.

Karakteristik Fisik, Kimia, Fungsional, dan Sensori Nasi Gurih Instan Dibandingkan dengan Nasi Putih Instan

Variations of processing rice into cooked rice had long been developed. One of the rice products that had been widely circulated in the community was savory rice. Savory rice with an instantization processed was more practical in serving. This research aimed to determine the physical, chemical, functional, and sensory characteristics of instant savory rice compared to instant white rice. The stages of processing instant savory rice included washing, soaking, cooking, freezing, and drying. The freezing process was carried out at -20 °C for 24 h. The drying process for instant savory rice used a fluidized bed dryer for 3 h. Instant white rice was used as a control. The porosity level of instant savory rice was lower than instant white rice as indicated by the yield (95.77%), bulk density (0.57 g/mL), rehydration time (14.34 min), rehydration ratio (2.86), expansion volume ratio (2.26), and water absorption capacity (69.50%). Instant savory rice contained moisture content (8.48%), ash content (3.93%), fat content (5.56%), protein content (7.54%), and starch digestibility (54.84%) which was higher than instant white rice. Instant savory rice had carbohydrate content (82.97%), amylose content (32.39%), amylopectin content (46.59%), starch content (79.98%), and resistant starch content (1.90%) lower than instant white rice. In terms of sensory test results revealed that instant savory rice after rehydration was preferred by consumers compared to instant white rice regarding color, aroma, taste, texture, and overall with a score of 5.39-5.84.

Process parameters for enhanced microstructure and composition of as-sprayed Yb2Si2O7 environmental barrier coatings via atmospheric plasma spray

Achieving high crystallinity levels, dense, crack-free microstructures with near-stoichiometric phase composition and controlled secondary phase formation are crucial for enhancing the performance of environmental barrier coatings (EBCs). To investigate the impact of APS process parameters on the as-sprayed crystallinity, microstructure, and phase composition of Yb2Si2O7 EBCs, various spraying conditions were explored by adjusting torch power, nozzle size, powder feedrate, stand-off distance, and adding a shroud attachment to the torch. The velocity of particles controlled the density of the EBCs by an interplay between deposition efficiency and splat flattening ratios. Increasing nozzle size from 5/16″ to 1/2″ reduced particle velocity by up to 40 %, resulting in improved deposition efficiencies, porosity levels and coating thickness. However, larger nozzles led to higher silicon evaporation and up to 8 wt% more stable Yb2SiO5 (I2/a) secondary phase was formed. Increasing the stand-off distance from 50 mm had minimal effect on microstructure, but metastable Yb2SiO5 (P21/c) was detected (up to 9 wt%) at longer stand-off distances of 100 and 150 mm. Raising the powder feedrate from 15 gr/min to 60 gr/min improved deposition efficiency (up to 9 %) and density (up to 15 %) of EBCs, yet resulted in higher silicon-depleted phase formation (up to 12 wt%). Adding a shroud to the torch nozzle exit led to severe silicon evaporation and formation of up to 42 wt% and 6 wt% of Yb2SiO5 (I2/a) and Yb2O3, respectively. Moreover, due to the shroud's funnelling effect on smaller particles as well as particle overheating, porous microstructures with up to 28 % porosity levels were formed. High levels of crystallinity (∼75–91 %) were achieved in the as-sprayed condition for all the coatings, indicating real-time crystallization during spraying in all the spraying conditions.

Properties of porous magnesia‐stabilized zirconia ceramics fabricated by slurry infiltration into polyurethane foam

AbstractThis paper brings out an innovation in fabricating porous magnesia‐stabilized zirconia components by infiltrating free‐flowing suspension into polyurethane foam. The process enables the production of samples with different levels of porosity and pore structure by easily controlling the amount of slurry infiltrated into the foam. The process uses Isobam, a nontoxic binder, which makes the fabrication simple and environment‐friendly. Samples with five different levels of total porosity ranging from 41.7% to 62.4% were fabricated. Microstructural studies revealed multimodal pore structure comprising both open and closed porosities. Measurements on thermal properties and compressive strength of the samples showed that the sample with the lowest porosity exhibited a thermal conductivity of 0.495 W/mK and a compressive strength of 45.7 MPa. The measured values of thermal conductivity of the samples with different porosity levels could be described by modified effective medium theory. Present work opens up enormous possibilities for economical industrial production of porous magnesia‐stabilized zirconia components for biomedical and thermal insulation applications.

Structural effects on thermal conductivity of micro-thick Li4Ti5O12-based anode

This study investigates the structural effects on the cross-plane thermal conductivity of Li4Ti5O12-based anode active material. Three structures are investigated: a basic structure consisting of LiBr/LiCl/Li4Ti5O12, polyvinylidene difluoride, and Super P (sample #1); a structure without Li4Ti5O12 (sample #2); and a structure without LiBr/LiCl (sample #3). Despite its high porosity level (77%), sample #1 exhibits higher thermal conductivity than sample #3 (64% porosity) in both air and vacuum conditions, potentially due to the extra structural bonding provided by LiBr/LiCl. The observed difference in cross-plane thermal conductivity between air and vacuum conditions provides insights into the configuration of the anode's active material in the heat transfer direction. The lower limit corresponds to the parallel thermal circuit configuration of active material and air, which is the product of the sample's porosity and thermal conductivity of air. Our analysis suggests that in sample #2, the anode's active material and air inside the pores demonstrate a more serial configuration, while in sample #3, they exhibit a more parallel configuration in the heat transfer direction. However, the thermal conductivity difference observed for sample #1 falls below the theoretical lower bound indicating significant thermal radiation within the pores. Furthermore, the in-plane thermal conductivity is predominantly controlled by the copper foil. Sample #2 exhibits the lowest in-plane thermal conductivity. This is attributed to the severe oxidization of the copper foil by LiBr/LiCl, which is confirmed by structure characterization.

Exploring the Potential of MIM-Manufactured Porous NiTi as a Vascular Drug Delivery Material.

Porous nickel-titanium (NiTi) manufactured using metal injection molding (MIM) has emerged as an innovative generation of drug-loaded stent materials. However, an increase in NiTi porosity may compromise its mechanical properties and cytocompatibility. This study aims to explore the potential of porous NiTi as a vascular drug delivery material and evaluate the impact of porosity on its drug loading and release, mechanical properties, and cytocompatibility. MIM, combined with the powder space-holder method, was used to fabricate porous NiTi alloys with three porosity levels. The mechanical properties of porous NiTi were assessed, as well as the surface cell growth capability. Furthermore, by loading rapamycin nanoparticles onto the surface and within the pores of porous NiTi, we evaluated the in vitro drug release behavior, inhibitory effect on cell proliferation, and inhibition of neointimal hyperplasia in vivo. The results demonstrated that an increase in porosity led to a decrease in the mechanical properties of porous NiTi, including hardness, tensile strength, and elastic modulus, and a decrease in the surface cell growth capability, affecting both cell proliferation and morphology. Concurrently, the loading capacity and release duration of rapamycin were extended with increasing porosity, resulting in enhanced inhibitory effects on cell proliferation in vitro and inhibition of neointimal hyperplasia in vivo. In conclusion, porous NiTi holds promise as a desirable vascular drug delivery material, but a balanced consideration of the influence of porosity on both mechanical properties and cytocompatibility is necessary to achieve an optimal balance among drug-loading and release performance, mechanical properties, and cytocompatibility.