Slow Diffusion Research Articles

Differentiation of glioma and solitary brain metastasis: a multi-parameter magnetic resonance imaging study using histogram analysis

BackgroundDifferentiation of glioma and solitary brain metastasis (SBM), which requires biopsy or multi-disciplinary diagnosis, remains sophisticated clinically. Histogram analysis of MR diffusion or molecular imaging hasn’t been fully investigated for the differentiation and may have the potential to improve it.MethodsA total of 65 patients with newly diagnosed glioma or metastases were enrolled. All patients underwent DWI, IVIM, and APTW, as well as the T1W, T2W, T2FLAIR, and contrast-enhanced T1W imaging. The histogram features of apparent diffusion coefficient (ADC) from DWI, slow diffusion coefficient (Dslow), perfusion fraction (frac), fast diffusion coefficient (Dfast) from IVIM, and MTRasym@3.5ppm from APTWI were extracted from the tumor parenchyma and compared between glioma and SBM. Parameters with significant differences were analyzed with the logistics regression and receiver operator curves to explore the optimal model and compare the differentiation performance.ResultsHigher ADCkurtosis (P = 0.022), frackurtosis (P<0.001),and fracskewness (P<0.001) were found for glioma, while higher (MTRasym@3.5ppm)10 (P = 0.045), frac10 (P<0.001),frac90 (P = 0.001), fracmean (P<0.001), and fracentropy (P<0.001) were observed for SBM. frackurtosis (OR = 0.431, 95%CI 0.256–0.723, P = 0.002) was independent factor for SBM differentiation. The model combining (MTRasym@3.5ppm)10, frac10, and frackurtosis showed an AUC of 0.857 (sensitivity: 0.857, specificity: 0.750), while the model combined with frac10 and frackurtosis had an AUC of 0.824 (sensitivity: 0.952, specificity: 0.591). There was no statistically significant difference between AUCs from the two models. (Z = -1.14, P = 0.25).ConclusionsThe frac10 and frackurtosis in enhanced tumor region could be used to differentiate glioma and SBM and (MTRasym@3.5ppm)10 helps improving the differentiation specificity.

Influence of Polypyrrole on Phosphorus- and TiO2-Based Anode Nanomaterials for Li-Ion Batteries.

Phosphorus (P) and TiO2 have been extensively studied as anode materials for lithium-ion batteries (LIBs) due to their high specific capacities. However, P is limited by low electrical conductivity and significant volume changes during charge and discharge cycles, while TiO2 is hindered by low electrical conductivity and slow Li-ion diffusion. To address these issues, we synthesized organic-inorganic hybrid anode materials of P-polypyrrole (PPy) and TiO2-PPy, through in situ polymerization of pyrrole monomer in the presence of the nanoscale inorganic materials. These hybrid anode materials showed higher cycling stability and capacity compared to pure P and TiO2. The enhancements are attributed to the electrical conductivity and flexibility of PPy polymers, which improve the conductivity of the anode materials and effectively buffer volume changes to sustain structural integrity during the charge and discharge processes. Additionally, PPy can undergo polymerization to form multi-component composites for anode materials. In this study, we successfully synthesized a ternary composite anode material, P-TiO2-PPy, achieving a capacity of up to 1763 mAh/g over 1000 cycles.

Diffusive Leakage of scCO2 in Shaly Caprocks: Effect of Geochemical Reactivity and Anisotropy

Summary Supercritical carbon dioxide (scCO2) trapping mechanisms within carbon geostorage (CGS) primarily hinge on the upper caprock system, with shales being favored for their fine-grained nature and geological abundance. Experimental assessments of CO2 reactivity in brine-saturated shales reveal microstructural changes, raising concerns about long-term CO2 leakage risks. Existing models of scCO2 transport through caprocks lack consideration for shale anisotropy. This study addresses these gaps by investigating the diffusive properties and propagation of geochemical reactivity in shaly caprocks, accounting for anisotropy. Horizontal and vertical core samples from three shale formations with varying petrophysical characteristics underwent mineralogical, total organic carbon (TOC), porosity, and velocity measurements. scCO2 treatment for up to 3 weeks at 150°F and 3,000 psi was conducted. The propagation of geochemical reactivity was monitored by multiple surface X-ray fluorescence (XRF) measurements and fine polishing. A nuclear magnetic resonance (NMR)-based H2O-D2O fluid exchange protocol was used to quantify effective diffusivities and tortuosities parallel and perpendicular to bedding. Results indicate preferential surface reactivity toward carbonate minerals; however, the apparent reaction diffusivity of the shaly caprock is notably slow (~10−15 m2/s). This aligns with previous experimental and reactive transport modeling studies, emphasizing long timescales for carbonate dissolution reactions to influence shale caprock properties. Shale-effective diffusivities display anisotropy increasing with clay content, where diffusivities parallel to bedding exceed those perpendicular by at least three times. Faster horizontal diffusion in shaly confining zones should be considered when estimating diffusive leakage along faults penetrating these zones, a significant risk in CGS. Post-scCO2 treatment, diffusivity changes vary among samples, increasing within the same order of magnitude in the clay-rich sample. Nonsteady-state modeling of scCO2 diffusion suggests limited caprock penetration over 100 years, with a minimal increase from 5 m to 7 m post-scCO2 treatment for the clay-rich sample. This study extends existing literature observations on the slow molecular diffusion of scCO2 within shaly caprocks, integrating the roles of geochemical reactions and shale anisotropy under the examined conditions.

A mosquito proboscis-inspired cambered microneedle patch for ophthalmic regional anaesthesia

IntroductionOne of the methods for pain management involves the use of local anesthesia, which numbs sensations in specific body regions while maintaining consciousness. ObjectivesConsidering the certain limitations (e.g., pain, the requirement of skilled professionals, or slow passive diffusion) of conventional delivery methods of local anesthetics, developing alternative strategies that offer minimally invasive yet therapeutically effective delivery systems is of great concern for ophthalmic regional anesthesia. Methods and resultsIn this study, a rapidly dissolving cambered microneedle (MNs) patch, composed of poly(vinylpyrrolidone) (PVP) and hyaluronic acid (HA) and served as a delivery system for lidocaine (Lido) in local anesthesia, was developed taking inspiration from the mosquito proboscis’s ability to extract blood unnoticed. The lidocaine-containing MNs patch (MNs@Lido) consisted of 25 microneedles with a four-pronged cone structure (height: 500 μm, base width: 275 μm), arranged in a concentric circle pattern on the patch, and displays excellent dissolubility for effective drug delivery of Lido. After confirming good cytocompatibility, MNs@Lido was found to possess adequate rigidity to penetrate the cornea without causing any subsequent injury, and the created corneal pinhole channels completely self-healed within 24 h. Interestingly, MNs@Lido exhibited effective analgesic effects for local anesthesia on both heel skin and eyeball, with the sustained anesthetic effect lasting for at least 30 min. ConclusionsThese findings indicate that the mosquito proboscis-inspired cambered MNs patch provides rapid and painless local anesthesia, overcoming the limitations of conventional delivery methods of local anesthetics, thus opening up new possibilities in the treatment of ophthalmic diseases.

Use of Rocuronium and Sugammadex for a Patient With Controlled Polymyositis: A Case Report

Muscle relaxants and their reverse drugs should be carefully administered to patients with acute polymyositis and/or dermatomyositis. However, the use of these drugs in controlled polymyositis and/or dermatomyositis is controversial. This case report describes the use of rocuronium and sugammadex in a 27-year-old female patient with controlled polymyositis who was scheduled for minor oral surgery under general anesthesia. General anesthesia was induced rapidly, and 0.66 mg/kg of rocuronium was administered prior to nasotracheal intubation. No additional muscle relaxants were administered during the surgery. At the end of surgery, approximately 2 hours after the rocuronium was administered, her train-of-four (TOF) ratio was still 49%. A dose of 3.3 mg/kg of sugammadex was administered, and it took 12 minutes for the TOF ratio to exceed 90%. The prolonged duration of muscle relaxation in patients with polymyositis may be due to a decrease in skeletal muscle and capillary volume. The slow onset of sugammadex may be caused by slow diffusion of rocuronium from the neuromuscular junction. Patients with polymyositis require close perioperative neuromuscular function monitoring, regardless of their disease control status.

Study on the Performance of Aniline Electrodeposited on MnO2 Nanowire as an Anode for Sodium-Ion Batteries.

Manganese dioxide is an ideal anode for sodium-ion batteries due to its rich crystal shapes. However, its low conductivity, low reversible discharge capacity, slow diffusion kinetics, and poor cyclic stability limit its potential for industrial application. The design of manganese dioxide (MnO2) with various morphologies, such as nanowires, nanorods, and nanoflowers, has proven effective in enhancing its electrochemical performance. Stacking nanowire structures is of interest as they increase the open space by forming an interconnected network, thus facilitating favorable diffusion pathways for sodium ions. Concurrently, the substantial increase in the electrolyte contact area efficiently mitigates the strain induced by the volume expansion associated with the repetitive migration and insertion of sodium ions. Based on previous research, this work presents the structural design of flexible MnO2/polyaniline (MnO2/PANI) nanowires assembled on carbon cloth (CC), an innovation in MnO2 modification. Compared to conventional MnO2 nanowires, the MnO2/PANI nanowires exhibit enhanced structural stability and improved dynamic performance, thereby marking a significant advancement in their material properties. This MnO2/PANI composite exhibits a rate capacity of approximately 200 mA h g-1 after 60 cycles at a current density of 0.1 A g-1, and maintains a rate capacity of 182 mA h g-1 even after 200 cycles under the same current density. This study not only provides new insights into the underlying mechanisms governing energy storage in MnO2/PANI nanowires but also paves the way for their further development and optimization as anodes for sodium-ion batteries, thereby opening up fresh avenues for research and application.

Layered Na2Ti3O7 as an Ultrastable Intercalation-Type Anode for Non-Aqueous Calcium-Ion Batteries.

Calcium ion batteries (CIBs) are a promising energy storage device due to the low redox potential of the Ca metal and the abundant reserves of the Ca element. However, the large radius and divalent nature of Ca2+ lead to its slow ion diffusion kinetics and the lack of suitable electrode materials for Ca storage. Here, a layered structure of Na2Ti3O7 (NTO) is presented as an anode material for nonaqueous CIBs. This NTO anode demonstrates a high discharge capacity of 165 mA h g-1 at 100 mA g-1 and a remarkable capacity retention rate of 80%, even after 2000 cycles at 500 mA g-1, surpassing the performance of all reported intercalation-type anode materials for CIBs. The NTO transfers to layered CaVIINaIXTi3O7 (CNTO) with intercalation of Ca2+ and extraction of Na+ during the first discharge process. Then, the CNTO undergoes the reversible insertion/extraction of Ca2+ during subsequent cycling. Additionally, density functional theory calculations reveal that NTO possesses a rapid two-dimensional diffusion pathway for Ca2+. Moreover, the full CIBs based on NTO as the anode further underscore its potential for CIBs. This work presents promising anode materials for CIBs, offering opportunities to promote the development of high-performance CIBs.

Detection of metastable solid solution in doped LiFePO4 by synchrotron nuclear resonance techniques

In this work we study one of the popular cathode materials based on doped lithium iron phosphate LiFexMn1-xPO4. Synchrotron operando Mössbauer measurements reveal the existence of metastable states at different stages of the charge and discharge processes, with a lifetime in a wide range from 5 to 140 min. The existence of such states is associated with the formation of a metastable solid solution with the composition LiyFexMn1-xPO4 during cycling. Afterwards, this solution dissolves due to the slow diffusion of manganese and iron ions together with lithium. The presence of metastable states and their rapid decay indicate that cycling is not an equilibrium process. The influence of the manganese migration on the mechanism of the cycling process is discussed in this study.

The effect of physical stability and modified gastrointestinal tract behaviour of resveratrol-loaded NLCs encapsulated alginate beads.

Nanostructured lipid carriers (NLC) have low storage and gastrointestinal stability, limiting their applicability. The work aimed to elevate the stability and behaviour of NLC in the alimentary tract by creating an alginate bead. Through the extrusion dropping procedure, Resveratrol (RES)-loaded NLC were efficiently integrated into alginate beads. The incorporation had no significant impact on the particle size, morphology, or inner structure of NLC, as assessed using DLS (Dynamic Light Scattering), SEM (Scanning Electron Microscopy), Differential Scanning Calorimetry (DSC) and FT-IR (Fourier Transform Infra-Red). Incorporating NLC into alginate beads improves its physical stability compared to dispersion of NLC as well as NLC-Sol. An in vitro release investigation found that the NLC-alginate beads released RES more slowly than optimized NLC formulation (RES-NLCs-opt) and NLC-alginate sol. Research on simulated in vitro digestive models revealed that just a small amount of integrated NLC may permeate stomach fluid due to its tiny size. The slow diffusion of NLC from alginate to intestinal fluid prevented aggregation and allowed for gentle hydrolysis of the lipid matrix. Incorporating NLC in alginate beads shows promise for improving stability, modifying gastrointestinal behaviour, and controlling release throughout the process of digestion.

Unveiling the Degradation Mechanism of Sodium Ion Batteries Based on Na4Fe3(PO4)2P2O7 Cathode and Hard Carbon Anode Suggests Anode Particle Size Reduction for Cycling Stability

AbstractTo improve the cycle life of sodium‐ion batteries, it is essential to understand the microscopic processes that lead to cell degradation. The mismatched response time of anode and cathode has profound but poorly understood impact on cycle life. In this work, we combine electrochemical and materials characterization along with electrochemical modeling to investigate the root cause of degradation in sodium‐ion full cells made from Na4Fe3(PO4)2P2O7 (NFPP) cathodes and hard carbon (HC) anode. Our results pinpoint to the slow diffusion of Na in HC as the main cause of diffusional polarization that leads to cathode experiencing high local potentials and ultimately to active material loss over cycling. We demonstrate that by reducing the anode particle size, the diffusional timescales in anode can be matched with that of cathode to improve both extractable capacity as well as cycle life. These observations shed light on non‐intuitive and intricate ways in which cathode and anode can interact with each other to cause degradation in Na‐ion batteries and how microscopic understanding of these cause and effects can help design long lasting batteries.

Inorganic phosphorous availability and mobility in a manufactured soil

Manufactured soils, created by combining various organic and inorganic waste materials and byproducts, may be tailored to specific applications, providing an alternative to the extraction of natural soils. It is important for them to be capable of supporting plant growth without the need for significant management or fertiliser applications, the over-application of which can have adverse environmental effects.We examined the dynamics of phosphorus (P) transformations within a manufactured soil and the implications for nutrient cycling. A freshly prepared manufactured soil (32.5 % composted green waste, 32.5 % composted bark, 25 % horticultural grit, and 10 % lignite clay) was studied over one year in temperature and moisture controlled mesocosms. Leachate was collected to achieve high-resolution monitoring of leached phosphate concentrations.Initially, leached dissolved inorganic phosphorus (DIP) concentrations were low (0.02 ± 0.01 mg P L−1), before increasing by 160 μg P L−1 d−1 over the first 42 days to 5.57 ± 1.23 mg P L−1. After reaching a maximum concentration, DIP concentrations remained relatively consistent, varying by only 1.67 mg P L−1 until day 270. The increase in leached DIP was likely driven by soil organic matter mineralisation and the cleavage of carbon‑phosphorus bonds by the soil microbes to satisfy carbon demand with mineralogical influences, such as a decrease in apatite content, also contributing. Sorption and desorption from soil particles were the processes behind the P loss from the soil, which was followed by slow diffusion and eventual loss via leaching. The fertiliser application on phosphate dynamics resulted in increased DIP leaching.P concentrations observed in the manufactured soil were within the range considered sufficient to support plant growth. However, the mean leached phosphorus concentrations were higher than reported eutrophication thresholds suggesting that these soils may pose a risk to surface waters in their current form.

Synthesis of a Flaky CeO2 with Nanocrystals Used for Polishing.

It is important to adapt the morphology of CeO2 to different applications. A novel flaky CeO2 with nanocrystals was successfully synthesized using the ordinal precipitation method and calcination. The size of the flaky CeO2 was about 10 μm, and the nanocrystals were about 100 nm. Under the action of the precipitant NH4HCO3, Ce3+ nucleated in large quantities. The nanosized crystals gathered into flakes driven by the surface energy. As the calcination temperature increased, the grains grew slowly by mass transfer due to the slow diffusion of reactants. By adding AlOOH to the starting material, the Al3+ doped into the CeO2 increased the content of Ce3+ in the CeO2, which improved the chemical activity of the CeO2. When the starting material's Al:Ce ratio was 5:1, the Ce3+ increased to 31.11% in the CeO2, which provided good application potential in the polishing field. After polishing by the slurry of flaky CeO2 for 1 h, the SiC surface roughness reduced from 464 nm to 11 nm.

Diffusion Mapping with Diffractive Optical Elements for Periodically Patterned Photobleaching.

Fourier transform-fluorescence recovery after photobleaching (FT-FRAP) using a diffractive optical element (DOE) is shown to support distance-dependent diffusion analysis in biologically relevant media. Integration of DOEs enables patterning of a dot array for parallel acquisition of point-bleach FRAP measurements at multiple locations across the field of view. In homogeneous media, the spatial harmonics of the dot array analyzed in the spatial Fourier transform domain yield diffusion recovery curves evaluated over specific well-defined distances. Relative distances for diffusive recovery in the spatial Fourier transform domain are directly connected to the 2D (h,k) Miller indices of the corresponding lattice lines. The distribution of the photobleach power across the entire field of view using a multidot array pattern greatly increases the overall signal power in the spatial FT-domain for signal-to-noise improvements. Derivations are presented for the mathematical underpinnings of FT-FRAP performed with 2D periodicity in the photobleach patterns. Retrofitting of FT-FRAP into instrumentation for high-throughput FRAP analysis (Formulatrix) supports automated analysis of robotically prepared 96-well plates for precise quantification of molecular mobility. Figures of merit are evaluated for FT-FRAP in analysis for both slow diffusion of fluorescent dyes in glassy polymer matrices spanning several days and model proteins and monoclonal antibodies within aqueous solutions recovering in matters of seconds.

Triple engineering boosts high-performance accordion-like vanadium oxide for practical aqueous zinc-ion batteries

Vanadium oxide is one of promising cathode materials for aqueous zinc-ion batteries (ZIBs), but the low electrical conductivity and slow ion diffusion kinetics of vanadium oxide lead to low practical capacity and poor cycling life, which limits further commercialization development. Herein, this study proposes a triple engineering strategy of N-doping, oxygen vacancies and crystal water to achieve the high-performance of V2O5 by a simple stirring method. N doping can improve the electrical conductivity of the materials, oxygen vacancies can modulate the electronic structure, and the crystal water can effectively shield the electrostatic effect. First-principles calculations confirmed that the incorporation of the triple engineering strategies can effectively reduce of the energy band gap and Zn2+ diffusion barrier of V2O5, and promote the intercalation dynamics of Zn2+. As a result, the prepared N-doped V2O5-x·nH2O achieves an outstanding specific capacity of 607.74 mAh/g at 0.1 A/g, and cycling stability. Moreover, based on the above advantages, the practical 21700-type cylindrical battery assembled with this N-doped V2O5-x·nH2O cathode and Zn foil anode, presenting a maximum capacity of 393.5 mAh at 0.4 A. This high performance of vanadium oxide cathode shows a good practical prospect in aqueous cylindrical ZIBs.

Presentation of microstructural diffusion components by color schemes in abdominal organs.

Development of a color scheme representation to facilitate the interpretation of tri-exponential DWI data from abdominal organs, where multi-exponential behavior is more pronounced. Multi-exponential analysis of DWI data provides information about the microstructure of the tissue under study. The tri-exponential signal analysis generates numerous parameter images that are difficult to analyze individually. Summarized color images can simplify at-a-glance analysis. A color scheme was developed in which the slow, intermediate, and fast diffusion components were each assigned to a different red, green, and blue color channel. To improve the appearance of the image, histogram equalization, gamma correction, and white balance were used, and the processing parameters were adjusted. Examples of the resulting color maps of the diffusion fractions of healthy and pathological kidney and prostate are shown. The color maps obtained by the presented method show the merged information of the slow, intermediate, and fast diffusion components in a single view. A differentiation of the different fractions becomes clearly visible. Fast diffusion regimes, such as in the renal hilus, can be clearly distinguished from slow fractions, such as in dense tumor tissue. Combining the diffusion information from tri-exponential DWI analysis into a single color image allows for simplified interpretation of the diffusion fractions. In the future, such color images may provide additional information about the microstructural nature of the tissue under study.

Fabrication of used-tea embedded alginate beads for cationic dye remediation: Synergistic effect of surface adsorption and intraparticle diffusion

Water pollution has become a major concern due to high industrialization and poor waste management policies. Recently, organic contaminants such as dyes are severely influencing environmental conditions and therefore, it must be employed to efficient treatment processes before discarding in waterbodies. In this work, used-tea embedded alginate beads were fabricated as a novel adsorbent for removing a cationic dye (methylene blue, MB). The physical properties of fabricated beads were investigated and also characterized using field emission scanning electron microscope (FESEM), energy dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The highest MB removal efficiency of about 97.38 ± 1.84% was obtained at optimized pH 7 and 25 °C. The adsorption capacity (qe) increased with MB concentration and the pseudo-second-order model exhibited excellent fit. MB adsorption comprises rapid surface adsorption (initial 5 min) and slow inter-particle diffusion (after 5 min). Supporting the Langmuir isotherm indicated the formation of a monolayer of MB on the surface of the beads and the calculated maximum adsorption capacity (qm) was 421.94 mg/g. Negative ΔG (-7.25 kJ/mol) and ΔH (-52.67 kJ/mol) reveal MB removal as a spontaneous and exothermic process. Positive entropy change of ΔS (152.05 J/mol) states increased randomness, facilitating promoted affinity of beads for free MB molecules. A removal efficiency of about 90.40 ± 2.91% was obtained up to 3rd cycle of its reuse, which further decreased to 67.11 ± 1.72% during 5th cycle. The MB adsorption mechanism was investigated by comparing the physiochemical and morphological characteristics of beads before and after MB removal.

Multiscale Scrutinizing Ion Storage Kinetics in Hollow Ni‐Mn Prussian Blue Analogues for Enhanced Capacitive Deionization

AbstractPrussian blue analogues (PBAs) are a class of promising materials for capacitive deionization. However, the kinetic mismatch between their slow ion storage rate and the demand from short‐time desalination severely limits their desalination performance. Here, a group of structure‐tuneable Ni‐Mn PBAs have been developed by a combination strategy of surface‐protected chemical etching and Ostwald ripening to study their ion storage kinetics. Treating them as demos, the characterizations and investigations, e.g., in situ XRD in a three‐electrode system, dynamic impedance, finite element simulation, and DFT calculations etc., reveal that the slow ion diffusion caused by the severe agglomeration of the nanoparticles and the unsuitable lattice parameter controls the final desalination behavior. Therefore, the correspondingly optimized sample (HC‐t) possessing a microscale hollow structure, nanoscale shell thickness, and expanded lattice, displays a fast ion storage kinetics with the ratio of surface‐controlled current as high as 82% at a scan rate of 20 mV s−1. Consequently, it delivers an impressive desalination capacity of 120.8 mg g−1 (2.06 mmol g−1 Na+) with a fast average desalination rate of 0.25 mg g−1 s−1 (0.004 mmol g−1 s−1) at 1.2 V, competitive with those reported in the literature. Moreover, the elucidation of the structure‐performance correlation provides valuable insights for the development and design of next‐generation PBAs for capacitive deionization (CDI).

On the effect of the sun on Kordylewski clouds

In this paper, we focus on the existence of dust clouds moving near the triangular points of the Earth–Moon system, the so-called Kordylewski clouds. The study is based on using some simplified planar models to find possible locations for these clouds. The validity of these predictions is tested by means of numerical simulations on a realistic model. The simplified models are based on the Earth–Moon restricted three-body problem plus the direct gravitational effect of the Sun on the particles (this is the so-called bicircular model), the solar radiation pressure and the Poynting–Robertson effect. The analysis of these models shows that there are some stability regions in the Earth–Moon plane, at some distance of the triangular points. The stability of these regions has been tested numerically in realistic (nonplanar) models. The results show that particles in these regions persist for some time (about a century), but it is very remarkable that many of these particles also escape the Earth–Moon system. If we perform backwards in time numerical simulations we obtain a similar result: particles also escape the Earth–Moon system after a similar time. From this point of view, the clouds are not a stable region in the classical sense of the term, but a region with “slow diffusion” where interplanetary particles stay for some years.

Investigation on the interdiffusion mechanism between single-crystal superalloy and FeCrNiAl-based medium entropy alloys

High and medium entropy alloys (HEAs, MEAs) have emerged as promising candidates for bond-coat materials in the thermal barrier coating systems due to their exceptional oxidation resistance. However, understanding the interdiffusion behavior between these alloys and single-crystal superalloys (SXs) substrates requires further investigation. In this study, diffusion couples were created between SXs and two types of MEAs, namely FeCrNiAl and FeCrNi0.4Al0.4, and the interdiffusion behavior was simulated using the commercial DICTRA code. The results reveal significant interdiffusion at 1100 °C in the couples, attributed to the substantial elemental differences between SXs and MEAs. This led to the formation of the interdiffusion zone (IDZ) and the secondary reaction zone (SRZ). Within the SRZ, phase transformation of SXs occurred, resulting in the precipitation of topologically close-packed (TCP) phases. Three types of TCP phases (σ, μ, and P) were observed. Along the {11¯02} plane of the μ phase, twins and stacking faults have formed. The glide of P phase contributed to the bending of bar-like precipitates. Notably, the amorphization of the σ phase was observed for the first time, suggesting an intermediate state during the phase transformation. Despite elemental differences between the two MEAs, the growth mechanism of IDZ and SRZ, as well as the precipitation of TCP phases, exhibited similarities. This underscores the importance of Cr and Ni diffusion alongside Al diffusion. The pronounced interdiffusion behavior raises concerns about the suitability of 3-d transition metal MEAs as bond-coat materials due to the lack of slow diffusion effect.

Fabrication and enhanced degradation behavior of sinterless porous apatite scaffolds with centrosymmetric structure

The primary component of natural bone minerals, hydroxyapatite (HA), has been the subject of research on materials for bone implants. Sintered HA scaffolds, on the other hand, degrade slowly after implantation and exhibit a high degree of crystallization at high temperatures, making it challenging to match the rate at which new bone grows. In this study, the benefit of self-curing calcium phosphate bone cement was employed to create porous apatite scaffolds without sintering. The lamellar pore structure was created by directional freeze-casting, and the enhanced specific surface area aided the in-situ hydration process. The crystallinity of sinterless porous apatite scaffolds diminishes when the TTCP and DCPD molar ratios drop. When the molar ratio is adjusted to 1:2.25, the crystallinity of the fabricated scaffold is reduced to 63.99 %, and 10.21 % can be degraded in 30 days. The degradation of porous scaffolds in simulated body fluids mainly depends on the rapid dissolution and transformation of solid phase powders in the early hydration reaction and the slow diffusion of the apatite in the later stage. The compressive strength of the porous scaffold is 5.3 MPa and its elastic modulus is 0.68 GPa. After 14 days of degradation, the compressive strength was 4.0 MPa and the elastic modulus was 0.64 GPa, which was still within the applicable range of cancellous bone repair. It has a promising application prospect as a substitute scaffold for absorbable cancellous bone.