3D Diffusion Research Articles

High-throughput measurements of interdiffusivities in fcc Co–Ni–Ta alloys at 1373K and 1473K

The composition-dependent interdiffusivities in the fcc Co–Ni–Ta alloys at 1373 K and 1473 K were deduced by using our newly developed numerical inverse scheme that combines two-dimensional (2D) simulations with diffusion triple experiments. This approach largely reduced the experimental efforts by analyzing only one single-phase diffusion triple at each temperature yet covering a much wider composition range than diffusion couples. The reliability of the high-throughput results was firstly verified by reproducing the experimental 2D composition profiles in each triple. In order to further validate the deduced interdiffusivities, several traditional one-dimensional (1D) diffusion couples were also devised, and the widely recognized Sauer-Freise method and Whittle-Green method were then employed to calculate the interdiffusivities for the binaries and at the intersection points within the ternary composition range, respectively. The interdiffusivities extracted from the inverse scheme agree well with those from the traditional approaches, which strongly proves the applicability of the present new scheme. Besides, the constructed main interdiffusivity planes at 1373 K and 1473 K provide an overview of the diffusion behavior in the fcc Co–Ni–Ta system and promote further kinetic studies.

Atomistic Description of Interdroplet Ice-Bridge Formation during Condensation Frosting.

The propagation of frost in an assembly of supercooled dew droplets takes place by the formation of ice protrusions that bridge ice particles and still-liquid droplets. In this work, we develop a Kinetic Monte Carlo (KMC) model to study the formation kinetics of the ice protrusions. The KMC simulations reproduce well the experimental results reported in the literature. The elongation speed of the ice protrusions does not depend on the droplet size but increases when the interdroplet distance decreases, the temperature increases, or the substrate wettability increases. While 2D diffusion of the water molecules on the substrate surface is sufficient to explain the process kinetics, high 3D (vapor) water-molecule concentration can lead to the development of 3D lateral branches on the ice protrusions. A 1D analytical model based on the water-molecule concentration gradient between a droplet and a nearby ice particle reproduces well the simulation results and highlights the relation between the protrusion elongation kinetics and parameters like the interdroplet distance, the water diffusivity, and the concentration gradient. The bridge-formation time has a quadratic dependence on the droplet-ice distance. Comparing the simulations, the analytical model, and the experimental results of the literature, we conclude that the propagation of frost on a flat substrate in an assembly of supercooled dew droplets with interdroplet spacing larger than about 1 μm is limited by water-molecule diffusivity.

Numerical Modeling of Pollutant Transport: Results and Optimal Parameters

In this work, we used three finite difference schemes to solve 1D and 2D convective diffusion equations. The three methods are the Kowalic–Murty scheme, Lax–Wendroff scheme, and nonstandard finite difference (NSFD) scheme. We considered a total of four numerical experiments; in all of these cases, the initial conditions consisted of symmetrical profiles. We looked at cases when the advection velocity was much greater than the diffusion of the coefficient and cases when the coefficient of diffusion was much greater than the advection velocity. The dispersion analysis of the three methods was studied for one of the cases and the optimal value of the time step size k, minimizing the dispersion error at a given value of the spatial step size. From our findings, we conclude that Lax–Wendroff is the most efficient scheme for all four cases. We also show that the optimal value of k computed by minimizing the dispersion error at a given value of a spacial step size gave the lowest l2 and l∞ errors.

Co-Firing Zhundong Coal with Its Gangue: Combustion Performance, Sodium Retention and Ash Fusion Behaviors

Fouling and slagging are intractable ash-related problems for boilers burning high-sodium coals (HSC) to produce electricity or heat. Reduction and resource utilization of solid waste, coal gangues, is urgent because of stringent environmental regulations and economic benefits. Based on the sodium-rich character of Zhundong coal (ZDC) and the mineralogical features of the coal gangues (ZDG), this work investigated their co-firing performance, the sodium retention behaviors as well as the slagging and fouling tendency of the ashes. Results show that combustion performance of ZDC is not reduced despite ofthe lower reactivity of ZDG. The co-firing reaction follows the 3D diffusion model (cylinder symmetry) which probably reflects the gas diffusion of oxygen to combustible matter. During co-firing, the enriched silica and alumina components in ZDG efficiently react with the alkali and alkaline earth metals (sodium, magnesium and calcium) in ZDC to form complex minerals, thus effectively capturing and retaining sodium. The slagging and fouling propensity of ashes are notably reduced. Overall, co-firing provides an alternative means to solve the ash slagging and fouling issues, and also for the reduction and resource utilization of coal gangues.

A simple and efficient strategy to construct Li-rich layered materials with surface layered/spinel heterostructures

In Li-rich layered oxides cathode materials (LR materials), spinel structure was widely introduced to suppress the structure attenuation and voltage decline during cycling. In this study, LR materials with surface layered/spinel heterostructures have been fabricated by a simple high-temperature post-treatment method. The existence of the surface spinel structure in synthesized materials was verified via X-ray diffraction, Raman spectra, and transmission electron microscopy. Moreover, the synthesized materials demonstrated remarkable electrochemical performance, especially their cycling performance. After optimization, the LR-850 samples showed the best electrochemical performances, that is, the capacity retentions are 126.97% at 1 C after 200 cycles and 92.2% at 5 C after 700 cycles, and the discharge-specific capacities are 139.6 mAh·g−1 at 5 C and 111 mAh·g−1 at 10 C, respectively. These electrochemical properties improvements are attributed to the introduction of the surface spinel structure in LR materials which could enhance the structural stability and provide 3D lithium ion diffusion paths.

Stabilization of DNA fork junctions by Smc5/6 complexes revealed by single-molecule imaging.

SMC complexes play key roles in genome maintenance, where they ensure efficient genome replication and segregation. The SMC complex Smc5/6 is a crucial player in DNA replication and repair, yet many molecular features that determine its roles are unclear. Here, we use single-molecule microscopy to investigate Smc5/6's interaction with DNA. We find that Smc5/6 forms oligomers that dynamically redistribute on dsDNA by 1D diffusion and statically bind to ssDNA. Using combined force manipulation and single-molecule microscopy, we generate ssDNA-dsDNA junctions that mimic structures present in DNA repair intermediates or replication forks. We show that Smc5/6 accumulates at these junction sites, stabilizes the fork, and promotes the retention of RPA. Our observations provide a model for the complex's enrichment at sites of replication stress and DNA lesions from where it coordinates the recruitment and activation of downstream repair proteins.

A combinatorial view of stochastic processes: White noise.

White noise is a fundamental and fairly well understood stochastic process that conforms to the conceptual basis for many other processes, as well as for the modeling of time series. Here, we push a fresh perspective toward white noise that, grounded on combinatorial considerations, contributes to giving new interesting insights both for modeling and theoretical purposes. To this aim, we incorporate the ordinal pattern analysis approach, which allows us to abstract a time series as a sequence of patterns and their associated permutations, and introduce a simple functional over permutations that partitions them into classes encoding their level of asymmetry. We compute the exact probability mass function (p.m.f.) of this functional over the symmetric group of degree n, thus providing the description for the case of an infinite white noise realization. This p.m.f. can be conveniently approximated by a continuous probability density from an exponential family, the Gaussian, hence providing natural sufficient statistics that render a convenient and simple statistical analysis through ordinal patterns. Such analysis is exemplified on experimental data for the spatial increments from tracks of gold nanoparticles in 3D diffusion.

A Spatiotemporal Deep Neural Network Useful for Defect Identification and Reconstruction of Artworks Using Infrared Thermography

Assessment of cultural heritage assets is now extremely important all around the world. Non-destructive inspection is essential for preserving the integrity of artworks while avoiding the loss of any precious materials that make them up. The use of Infrared Thermography is an interesting concept since surface and subsurface faults can be discovered by utilizing the 3D diffusion inside the object caused by external heat. The primary goal of this research is to detect defects in artworks, which is one of the most important tasks in the restoration of mural paintings. To this end, machine learning and deep learning techniques are effective tools that should be employed properly in accordance with the experiment's nature and the collected data. Considering both the temporal and spatial perspectives of step-heating thermography, a spatiotemporal deep neural network is developed for defect identification in a mock-up reproducing an artwork. The results are then compared with those of other conventional algorithms, demonstrating that the proposed approach outperforms the others.

A model based study of the drying and shrinkage behavior of a ceramic green body

This work presents a 1D diffusion model to characterize the drying procedure of a ceramic slab with respect to shrinkage. The proposed mathematical framework is comprised of a set of partial–differential and algebraic equations along with moving boundary conditions. The model predictions are compared to experimental data from the literature and a good agreement is accomplished. Afterwards, the parameters of a desorption isotherm equation are estimated based on experimental data from three drying tests, to characterize an industrially used clay material. A parametric analysis is conducted to study the impact of the drying-induced shrinkage on the drying kinetics of the ceramic body. The results indicate that the scale of shrinkage affects the porosity change which in turn, has a great impact on the drying kinetics and the properties distribution along the material. Finally, the drying dynamics of the green ceramic material is studied for a realistic shrinkage scenario, followed by the discussion of the results.

Quartz-hosted inclusions and embayments reveal storage, fluxing, and ascent of the Mesa Falls Tuff, Yellowstone

Quartz-hosted glasses from the Mesa Falls Tuff provide a geochemical window into the pre-eruptive magmatic system from one of Yellowstone's largest-volume caldera-forming eruptions. H2O and CO2 concentrations, along with major and trace elements, were measured in both fully enclosed glass inclusions and partially enclosed embayments in the same quartz crystals. Major elements are largely consistent between the inclusions and embayments, except for K2O and Na2O. Of note, K2O is enriched by ∼1 wt.% in embayment interiors relative to inclusions. Most trace elements are also enriched in the embayment interiors compared to inclusions from the same crystals. Fractionation trends of trace elements are consistent with ∼30-60% crystallization. Quartz-hosted glass inclusions preserve 3.1±0.9 wt.% H2O and 493±227 ppm CO2 whereas embayment interiors have 0.9±0.1 wt.% H2O and 399±229 ppm CO2. The CO2 is roughly similar, but the distinct ∼2 wt.% discrepancy between inclusion and embayment interior H2O contents may have been produced by CO2 fluxing sourced from underplated Yellowstone basalts. H2O gradients within embayments are flat in their interiors and modified by sharp positive gradients near embayment exteriors which were produced by post-eruptive rehydration. CO2 gradients occur as gently sloping concentration gradients that extend inward 150 to 250 μm from the embayment exterior. Finite-difference 1D and 2D diffusion modeling indicates the distribution of H2O and CO2 in embayments was produced by slow, fluid-saturated decompression that preceded rapid ascent during the caldera-forming eruption.

Diffusion Laws and Modified Pascal’s Triangles

Four main diffusion laws: 1D diffusion in a planar bulk sample or random walks along a straight line x=α1t1/2; 3D diffusion or random walks from a point source and forming small spherical particle: x=α2t1/3; 1D+1D diffusion or random walks along a straight plane with simultaneous outflow into balk: x=α3t1/4; 1D+2D diffusion or random walks along a straight line with simultaneous outflow into balk: x=α4t1/6 are analysed theoretically using mathematical modelling and appropriate physical models. Convex shape of the diffusion profile near the top along a dislocation pipe with simultaneous outflow into balk is predicted. It is shown that the cone angle near the top is increasing with time. Literature experimental data are used for analysis.

Study of lateral junction drive-in after annealing in ion implanted HgCdTe

Lateral junction drive-in after annealing in an n on p medium wave HgCdTe was studied. A method through testing the current voltage characteristic of an adjacent injection area was used to directly measure the lateral junction drive-in. The experimental results showed that under a standard annealing condition, the lateral drive-in was about 0.5 μm. While the annealing conditions were 88% and 112% standard temperature, the lateral drive-in were 0 and 3.25 μm, respectively, which showed a strong relationship between temperature and lateral drive-in extent. A 2D diffusion model was developed to account for the temperature dependence of lateral junction drive-in. This work suggests a simple and effective method for lateral drive-in testing and provides a useful 2D model for simulation and optimization of HgCdTe junction formation.

Carrier lifetimes in gold–hyperdoped silicon—Influence of dopant incorporation methods and concentration profiles

Incorporating ultrahigh concentrations of deep-level dopants in silicon drastically alters silicon’s optoelectronic properties. Photodiodes built from silicon hyperdoped with gold extend light sensitivity into the shortwave infrared region, far beyond the absorption edge of a pristine silicon sample. Deep-level dopants, however, also enhance carrier recombination; even though hyperdoped silicon has great light absorption properties, short charge carrier lifetime limits its applications. In this work, using terahertz spectroscopy, we investigate the charge carrier lifetime of gold–hyperdoped silicon, where the gold dopants are introduced by either film deposition or ion implantation, followed by pulsed laser melting. Using reactive ion etching, we measure how carrier lifetime changes when dopant concentration profiles are altered. Furthermore, using a 1D diffusion and recombination model, we simulate carrier dynamics when electrons are excited by sub-bandgap light. Our results show that the dopant distribution profile heavily influences excited carrier dynamics. We found that etching improves the half-life by a factor of two. In the short-wave-infrared range, the gold dopants are both light absorption centers and recombination centers. Focusing on optoelectronic properties in the short-wave-infrared region, our results suggest that these samples are over doped—etching much of the gold dopants away has little impact on the number of excited electrons at a later time. Our results suggest that dopant profile engineering is important for building efficient optoelectronic devices using hyperdoped semiconductors.

An Analytical Algorithm for Tensor Tomography From Projections Acquired About Three Axes.

Tensor fields are useful for modeling the structure of biological tissues. The challenge to measure tensor fields involves acquiring sufficient data of scalar measurements that are physically achievable and reconstructing tensors from as few projections as possible for efficient applications in medical imaging. In this paper, we present a filtered back-projection algorithm for the reconstruction of a symmetric second-rank tensor field from directional X-ray projections about three axes. The tensor field is decomposed into a solenoidal and irrotational component, each of three unknowns. Using the Fourier projection theorem, a filtered back-projection algorithm is derived to reconstruct the solenoidal and irrotational components from projections acquired around three axes. A simple illustrative phantom consisting of two spherical shells and a 3D digital cardiac diffusion image obtained from diffusion tensor MRI of an excised human heart are used to simulate directional X-ray projections. The simulations validate the mathematical derivations and demonstrate reasonable noise properties of the algorithm. The decomposition of the tensor field into solenoidal and irrotational components provides insight into the development of algorithms for reconstructing tensor fields with sufficient samples in terms of the type of directional projections and the necessary orbits for the acquisition of the projections of the tensor field.

Force-Extension Curve of a Polymer Chain Entangled with a Static Ring-Shaped Obstacle.

The way to theoretically approach dynamic and static topological constraints of polymer entanglements still presents a great challenge in polymer physics. So far, only the problem of static entanglement with multiple simple objects has been solved in theory by a superspace approach in our previous work. This work is devoted to extending the superspace approach to study a polymer chain entangled with a relatively complicated object-a ring-shaped object with genus one. Taking advantage of the axial symmetry of the model setup, the 3D diffusion equations in the superspace can be numerically solved within the 2D coordinates using a specially designed alternating-direction implicit (ADI) scheme. A series of numerical calculations reveal that the topological entanglement effect of the ring will exert a topological entropy attractive force on the linear chain, which can be used to explain the viscosity-increase phenomenon observed in recent simulations and experiments. Furthermore, the influences of the ring size and the entangling modes on the topological entropy force are also investigated by examining the corresponding force-extension curves. This work, together with our previous work, might pave the path toward the complete formulation of static topological constraints.

Sodium decavanadate encapsulated Mn-BTC POM@MOF as high-capacity cathode material for aqueous sodium-ion batteries

Aqueous sodium-ion batteries are the promising candidates for large scale energy storage applications owing to their cost effectiveness and environmental safety. However, the development of a stable cathode material with high capacity is still a challenging task for the commercial viability of aqueous electrolyte-based sodium-ion batteries. This work demonstrates the development of a hierarchically nanostructured high-capacity cathode material by encapsulating sodium decavanadate Na6V10O28 (NaDV) in the scaffold of manganese-based metal-organic framework Mn-BTC (where BTC is 1,3,5-benzenetricarboxylic acid) by an in situ synthesis. The uniform distribution of NaDV in the pores of Mn-BTC enables the multielectron redox properties of NaDV whereas the diverse 3D diffusion channels, high surface area, and flexible architecture of Mn-BTC ensure high intercalation capacity by suppressing the agglomeration and providing faster ionic diffusion kinetics in the NaDV@Mn-BTC nano-hybrid cathode material. The Mn-BTC framework not only ensures the stabilization of NaDV but also enhances sodium storage capacity by the involvement of Mn in the redox process. The NaDV@Mn-BTC cathode material exhibits high reversible capacity of 137 mAh/g at 1 C rate. High capacity of this cathode material suggests that the development of these nano-hybrid materials is a feasible approach to design high energy cathode materials for aqueous batteries.

Evaluation of the potential of pelletized enzyme-treated Ginkgo leaf residues for use as a solid fuel

Converting biowaste to solid fuel pellets is an efficient and environmental-friendly way for forestry residues utilization. Here, we investigated the effect of enzyme treatment on the quality and combustion characteristics of Ginkgo leaf residues (GLRs) pellets. The results indicated that compared with the untreated control sample (T1), the GLRs treated with 100 (T2) and 200 mg/g (T3) concentrations of cellulase enzyme were coarser and cracked with enhanced specific surface area. GLRs heating value increased from 17.8 to 18.9 and 19.3 MJ/kg for T2 and T3, respectively. Increase in pellet durability (from 73.4 to 80.8%) and hardness (from 0.8 to 1.3) as compared to T1 pellets. The energy consumption of all pellets kept in a low range of 15.1–16.1 J. The kinetics analysis found that the activation energy of T3 pellet decreased from 45.5 to 34.2 kJ/mol in the first order reaction model and from 95.8 to 77.8 kJ/mol in the 3D diffusion model compared to T1. Further, molecular dynamics simulation suggested the enzyme treatment was effective in disorganizing the crystalline cellulose chains, which not only improved the extraction efficiency of bioactive components in Ginkgo leaves, but also promoted the acquisition of high-quality GLRs for manufacturing solid fuel pellets.

Studies of Synthesis Temperature Effects on Cubic Lithated-Spinel to Layered Phase Transformation and Electrochemical Performance of LiMn0.5Ni0.5O2 Cathode Materials

Recently, our group has reported a novel Li-ion battery cathode, ‘LT-LiMn0.5Ni0.5O2’, where LT refers to its relatively low synthesis temperature (400 °C). By collecting high energy X-ray diffraction and high-angle, annular-dark-field (HAADF) scanning-transmission electron microscopy (STEM) data, we confirm that the LT-LiMn0.5Ni0.5O2 features a unique partially disordered rock salt structure with predominant lithiated-spinel-like character. The electrochemical data indicates that the Li/LT-LiMn0.5Ni0.5O2 cells shows good cycle stability when operate between 2.5-5.0V. The 1st cycle specific discharge capacity was determined to be 225mAh/g. Two distinct voltage plateaus can be identified at approximately at ~4.6 V and ~3.5 V during discharge. The ~1 voltage separation of the plateaus is caused by the octahedral and tetrahedral site energy difference during lithium extraction and insertion.1 The discovery of LT-LiMn0.5Ni0.5O2 not only expand the compositional space for the known lithated-spinel family but also provide a practical way to increase the operational capacity of traditional spinels such like LiMn2O4 and LiMn1.5Ni0.5O2.2-5 It is well known that when synthesized at 900°C, LiMn0.5Ni0.5O2 features a layered structure.6 The existence of lithated-spinel like LiMn0.5Ni0.5O2 at low temperature (400°C) immediately raise another question: How does the synthesis temperature affect the structure and electrochemical performance of LiMn0.5Ni0.5O2? We synthesized a series of different temperature of LiMn0.5Ni0.5O2 powders. By collecting high energy X-ray diffraction and high-resolution transmission electron microscopy (HR-TEM) data, we confirm that, the LiMn0.5Ni0.5O2 exhibits a lithated spinel → disordered layered → ordered layered structure transformation as temperature increase from 400-900 °C. The Rietveld refinements results also reveals a gradual decrease of the Li/Ni exchange ratio accompanied by the synthesis temperature changes. The evolution of specific discharge capacity for different temperature LiMn0.5Ni0.5O2 shows a parabola-like curve behavior with the lowest discharge capacity at 700 °C. This unique behavior is likely to be related to the diffusion channels reconstruction along with the structure changes. 3D diffusion channels are incorporated with 2D diffusion channels at low temperature (400°C) for lithated-spinel LiMn0.5Ni0.5O2. Within the middle temperature range (500°C-700°C), the 3D channels destroy rapidly while 2D diffusion channels are not well established due to the highly disorder ratio resulting in a decrease of capacity. At higher temperature (800-900°C), the 2D diffusion channels are more well established enabling an increase of the capacity. Shi, B.; Gim, J.; Li, L.; Wang, C.; Vu, A.; Croy, J. R.; Thackeray, M. M.; Lee, E., LT-LiMn 0.5 Ni 0.5 O 2: a unique co-free cathode for high energy Li-ion cells. Chemical Communications 2021, 57 (84), 11009-11012.Thackeray, M. M.; Lee, E.; Shi, B.; Croy, J. R., Review–From LiMn2O4 to Partially-Disordered Li2MnNiO4: The Evolution of Lithiated-Spinel Cathodes for Li-Ion Batteries. Journal of The Electrochemical Society 2022, 169 (2), 020535.Gummow, R.; Thackeray, M.; David, W.; Hull, S., Structure and electrochemistry of lithium cobalt oxide synthesised at 400 C. Materials research bulletin 1992, 27 (3), 327-337.Lee, E.; Blauwkamp, J.; Castro, F. C.; Wu, J.; Dravid, V. P.; Yan, P.; Wang, C.; Kim, S.; Wolverton, C.; Benedek, R., Exploring lithium-cobalt-nickel oxide spinel electrodes for≥ 3.5 V Li-ion cells. ACS applied materials & interfaces 2016, 8 (41), 27720-27729.Lee, E.; Kwon, B. J.; Dogan, F.; Ren, Y.; Croy, J. R.; Thackeray, M. M., Lithiated Spinel LiCo1–x Al x O2 as a Stable Zero-Strain Cathode. ACS Applied Energy Materials 2019, 2 (9), 6170-6175.Yang, X.-Q.; McBreen, J.; Yoon, W.-S.; Grey, C. P., Crystal structure changes of LiMn0. 5Ni0. 5O2 cathode materials during charge and discharge studied by synchrotron based in situ XRD. Electrochemistry communications 2002, 4 (8), 649-654

Security enhancement of a W-band millimeter-wave signal based on 3D Hilbert scrambling and diffusion.

A physical layer enhancement scheme of the W-band millimeter-wave signal based on chaotic grouping and segmentation encryption, 3D Hilbert scrambling, and diffusion is proposed in this paper. Chaotic grouping and segmentation bit-level encryption can enhance the randomness of data and enlarge the key space. 3D Hilbert scrambling and chaotic diffusion are performed in symbol and subcarrier domains. The correlation of data can be effectively reduced after encryption. The analyses show that the key space of the proposed scheme can reach ∼10152. The encrypted W-band millimeter-wave signal can be successfully transmitted in the orthogonal frequency division multiplexing (OFDM) radio-over-fiber (RoF) system of 50-km standard single-mode fiber (SSMF) and 3-m wireless channel, and the experimental results demonstrate that the proposed scheme can enhance the security of the system without negatively affecting transmission performance.

Search and processing of Holliday junctions within long DNA by junction-resolving enzymes

Resolution of Holliday junctions is a critical intermediate step of homologous recombination in which junctions are processed by junction-resolving endonucleases. Although binding and cleavage are well understood, the question remains how the enzymes locate their substrate within long duplex DNA. Here we track fluorescent dimers of endonuclease I on DNA, presenting the complete single-molecule reaction trajectory for a junction-resolving enzyme finding and cleaving a Holliday junction. We show that the enzyme binds remotely to dsDNA and then undergoes 1D diffusion. Upon encountering a four-way junction, a catalytically-impaired mutant remains bound at that point. An active enzyme, however, cleaves the junction after a few seconds. Quantitative analysis provides a comprehensive description of the facilitated diffusion mechanism. We show that the eukaryotic junction-resolving enzyme GEN1 also undergoes facilitated diffusion on dsDNA until it becomes located at a junction, so that the general resolution trajectory is probably applicable to many junction resolving enzymes.