Pre-existing Porosity Research Articles

Optimization of garnet-type solid-state lithium batteries via synergistic integration of an advanced composite interface for elevated performance

Solid-state batteries (SSBs) represent a pivotal avenue of development owing to their superior energy density and enhanced safety profile. However, the widespread utilization about SSBs confronts challenges such as inadequate interfacial connectivity resulting in high resistance, dendrite formation, and volumetric fluctuations in the lithium metal anode during plating and stripping. In this study, we introduce an innovative and remarkably efficient approach, leveraging the transformative potential of TiN-induced conversion. This method yields a lithium-ion-conductive TiN material concurrently addressing pre-existing porosity. The LiTiN| LLZTO| LiTiN symmetric cell is particularly noteworthy for its remarkable long-term cycle stability, which exceeds 1000 h at 0.2 mA cm−2, and its remarkable critical current density of 1.4 mA cm−2 at 25 °C. By subjecting TiN, the formation of the Li-Ti-N phase is induced, thereby establishing an additional Li3N-conductive layer that significantly enhances battery performance. Of paramount significance is the validation of the exceptional attributes of the composite through the deployment of LiFePO4 (LFP) full cells. In this configuration, the LFP coupled full cell manifests a remarkable discharge rate capacity of about 147 mAh g−1 at 1C, along with a noteworthy discharge capacity retention rate of 90 % even following 1000 charge and discharge cycles. These outcomes underscore the material’s robust lithium affinity and uniform lithium-ion distribution, which together mitigate dendrite growth and enhance the cycle stability of lithium-metal batteries.

Characterisation of Single-Phase Fluid-Flow Heterogeneity Due to Localised Deformation in a Porous Rock Using Rapid Neutron Tomography.

The behaviour of subsurface-reservoir porous rocks is a central topic in the resource engineering industry and has relevant applications in hydrocarbon, water production, and CO sequestration. One of the key open issues is the effect of deformation on the hydraulic properties of the host rock and, specifically, in saturated environments. This paper presents a novel full-field data set describing the hydro-mechanical properties of porous geomaterials through in situ neutron and X-ray tomography. The use of high-performance neutron imaging facilities such as CONRAD-2 (Helmholtz-Zentrum Berlin) allows the tracking of the fluid front in saturated samples, making use of the differential neutron contrast between “normal” water and heavy water. To quantify the local hydro-mechanical coupling, we applied a number of existing image analysis algorithms and developed an array of bespoke methods to track the water front and calculate the 3D speed maps. The experimental campaign performed revealed that the pressure-driven flow speed decreases, in saturated samples, in the presence of pre-existing low porosity heterogeneities and compactant shear-bands. Furthermore, the observed complex mechanical behaviour of the samples and the associated fluid flow highlight the necessity for 3D imaging and analysis.

On the hot embrittlement of continuously-cast and transfer-bar structures in DP600 advanced high-strength steel

Abstract This study reports on ultra-high temperature tensile tests (1300–1480 °C) performed on dual-phase (DP) advanced high-strength steels utilizing a Gleeble 3500 thermo-mechanical simulator. The thermomechanical results of both as-cast (AC) and transfer-bar (TB) material is presented, as well as three different sample geometries, to better comprehend the effect of temperature distribution and stress localization on the reproducibility of data. The results show that presence of pre-existing porosity in the AC structure decreases the ultra-high temperature strength of the material because of voids nucleation, growth and coalescence, while tearing apart of the melt in highly susceptible zones plays an important role to drastically increase the ultra-high temperature embrittlement of the TB material. It is shown that a sample with long-gauge-length (LGL) geometry provides the most consistent reproducibility as compared with other geometries; this is attributed to a combination between gentle stress localization and intensified temperature distribution along the gauge length.

Evaluation of residual stress and corrosion behaviour of electroless plated Ni−P/Ni−Mo−P coatings

Abstract Single Ni−P and Ni−Mo−P coatings as well as duplex Ni−P/Ni−Mo−P coatings with the same compositions were prepared by electroless plating. The residual stresses of the coatings on the surface and cross sections were measured by nanoindentation and AFM analysis, and the corrosion behaviour of the coatings in 10% HCl solution was evaluated by electrochemical methods, to establish the correlation between the residual stresses and corrosion behaviour of the coatings. The results showed that the single Ni−P and duplex Ni−P/Ni−Mo−P coatings presented residual compressive stresses of 241 and 206 MPa respectively, while the single Ni−Mo−P coating exhibited a residual tensile stress of 257 MPa. The residual compressive stress impeded the growth of the pre-existing porosity in the coatings, protecting the integrity of the coating. The duplex Ni−P/Ni−Mo−P coatings had better corrosion resistance than their respective single coating. In addition, the stress states affect the corrosive form of coatings.

Origin and Distribution of Grain Dolostone Reservoirs in the Cambrian Longwangmiao Formation, Sichuan Basin, China

Dolostones in the Cambrian Longwangmiao Formation have become one of the most significant gas exploration domains in China. Over a trillion cubic meters of gas reservoirs have been discovered in the Gaoshiti-Moxi area; however, the origins and distribution of the dolostone reservoirs are not well understood. This work discussed the geology and geochemistry of the dolostone reservoirs in the Longwangmiao Formation to determine their origin and distribution. Two understandings are acquired: firstly, a carbonate ramp provided excellent conditions for grain beach deposition, while the presence of a hypersaline lake was favorable for the contemporaneous dolomitization of grain beach deposits. Petrographic and geochemical evidence further confirm that the Longwangmiao dolostone was formed during the contemporaneous stage. Secondly, the reservoir characteristics indicate that the grain beach sediments provide material basis for the development of the Longwangmiao dolostone reservoirs. Reservoir dissolution simulation experiments show that the porosity of the reservoirs was formed by dissolution during contemporaneous and burial stages. The dissolution pores formed during the contemporaneous stage were controlled by sequence interfaces. The large scale dissolution vugs formed during the burial stage subsequently spread along the pre-existing porosity and fracture zones. This study therefore identified that the development of grain dolostone reservoirs in a shallow water ramp under arid climatic conditions generally met the following conditions: (1) reefal beach deposits lay a foundation for reservoir development; (2) superficial conditions are an important determining factor for reservoir porosity; and (3) burial conditions provide environment for porosity preservation and modification.

Ductilization of aluminium alloy 6056 by friction stir processing

The ductility of Al alloys is dictated by the nucleation, growth and coalescence of small internal voids originating from intermetallic particle fracture and from the presence of pre-existing porosity. The ductility is degraded when intermetallic particles are large and clustered. A low ductility adversely impacts both forming operations and the integrity of structural components. Local stirring using a friction stir processing (FSP) tool is shown here to very significantly increase the fracture strain of the Al alloy 6056 sometimes by more than a factor of two while making it more isotropic. Three reasons for the ductilization are unravelled based on 3D microtomography: (i) FSP breaks the large intermetallic particles into smaller, and thus stronger, fragments, (ii) FSP closes the pre-existing porosity; (iii) FSP randomizes the particle distribution. Hence, FSP positively impacts three of the main causes of ductility loss in metallic alloys. From an applicability viewpoint, this method has the potential to locally improve ductility of sheets at locations where forming involves large strains or of structural components at stress concentration points.

Scale and distribution of marine carbonate burial dissolution pores

It is gradually accepted that porosity can be created in burial settings via dissolution by organic acid; TSR derived or hydrothermal fluids. The role of deep-buried carbonate reservoirs is becoming more and more important since the degree and difficulty in petroleum exploration of shallow strata are increasing. A profound understanding of the development scale and prediction of the deep-buried carbonate reservoirs is economically crucial. In addition to the formation mechanism, scale and distribution of burial dissolution pores in burial settings are focused on in recent studies. This paper is based on case studies of deep-buried (>4500 m) carbonate reservoirs from the Tarim Basin and Sichuan Basin. Case studies mentioned includes dissolution simulation experiments proposes that an open system is of crucial importance in the development of large-scale burial dissolution pores, the distribution pattern of which is controlled by lithology, pre-existing porosity, and pore throat structures. These findings provided the basis for evaluation and prediction of deep-buried carbonate reservoirs.

Zn(II), Mn(II) and Sr(II) Behavior in a Natural Carbonate Reservoir System. Part II: Impact of Geological CO2Storage Conditions

Some key points still prevent the full development of geological carbon sequestration in underground formations, especially concerning the assessment of the integrity of such storage. Indeed, the consequences of gas injection on chemistry and petrophysical properties are still much discussed in the scientific community, and are still not well known at either laboratory or field scale. In this article, the results of an experimental study about the mobilization of Trace Elements (TE) during CO2 injection in a reservoir are presented. The experimental conditions range from typical storage formation conditions (90 bar, supercritical CO2 ) to shallower conditions (60 and 30 bar, CO2 as gas phase), and consider the dissolution of the two carbonates, coupled with the sorption of an initial concentration of 10−5 M of Zn(II), and the consequent release in solution of Mn(II) and Sr(II). The investigation goes beyond the sole behavior of TE in the storage conditions: it presents the specific behavior of each element with respect to the pressure and the natural carbonate considered, showing that different equilibrium concentrations are to be expected if a fluid with a given concentration of TE leaks to an upper formation. Even though sorption is evidenced, it does not balance the amount of TE released by the dissolution process. The increase in porosity is clearly evidenced as a linear function of the CO2 pressure imposed for the St-Emilion carbonate. For the Lavoux carbonate, this trend is not confirmed by the 90 bar experiment. A preferential dissolution of the bigger family of pores from the preexisting porosity is observed in one of the samples (Lavoux carbonate) while the second one (St-Emilion carbonate) presents a newly-formed family of pores. Both reacted samples evidence that the pore network evolves toward a tubular network type.

Mechanical compaction and strain localization in Bleurswiller sandstone

AbstractWe performed a systematic investigation of mechanical compaction and strain localization in Bleurswiller sandstone. Our data show that the effective pressure principle can be applied in both the brittle faulting and cataclastic flow regimes, with an effective pressure coefficient close to but somewhat less than 1. Under relatively high confinement, the samples typically fail by development of compaction bands. X‐ray computed tomography (CT) was used to resolve preexisting porosity clusters, as well as the initiation and propagation of the compaction bands in deformed samples. Synthesis of the CT and microstructural data indicates that there is no casual relation between collapse of the porosity clusters in Bleurswiller sandstone and nucleation of the compaction bands. Instead, the collapsed porosity clusters may represent barriers for the propagation of compaction localization, rendering the compaction bands to propagate along relatively tortuous paths so as to avoid the porosity clusters. The diffuse and tortuous geometry of compaction bands results in permeability reduction that is significantly lower than that associated with compaction band formation in other porous sandstones. Our new data confirm that Bleurswiller sandstone stands out as the only porous sandstone associated with a compactive cap that is linear, and our CT and microstructural observation show that it is intimately related to collapse of the porosity clusters. We demonstrate that the anomalous linear caps and their slopes are in agreement with a micromechanical model based on the collapse of a spherical pore embedded in an elastic‐plastic matrix that obeys the Coulomb failure criterion.

The porosity origin of dolostone reservoirs in the Tarim, Sichuan and Ordos basins and its implication to reservoir prediction

Origin of dolostone remained a controversial subject, although numerous dolomitization models had been proposed to date. Because of the dolomitization’s potential to be hydrocarbon reservoirs, one debatable issue was the role of dolomitization in porosity construction or destruction. Based upon case studies of dolostone reservoirs in various geological settings such as evaporative tidal flat (Ordos Basin, NW China), evaporative platform (Sichuan Basin, SW China), and burial and hydrothermal diagenesis (Tarim Basin, NW China), here we systematically discuss the origin of porosity in dolostone reservoirs. Contrary to traditional concepts, which regarded dolomitization as a significant mechanism for porosity creation, we found two dominant factors controlling reservoir development in dolostones, i.e., porosity inherited from precursor carbonates and porosity resulted from post-dolomitization dissolution. Actually, dolomitization rarely had a notable effect on porosity creation but rather in many cases destroyed pre-existing porosity such as saddle dolostone precipitation in vugs and fractures. Porosity in dolostones associated with evaporative tidal flat or evaporative platform was generally created by subaerial dissolution of evaporites and/or undolomitized components. Porosity in burial dolostones was inherited mostly from precursor carbonates, which could be enlarged due to subsequent dissolution. Intercrystalline porosity in hydrothermal dolostones was either formed during dolo- mitization or inherited from precursor carbonates, whereas dissolution-enlarged intercrystalline pores and/or vugs were usually interpreted to be the result of hydrothermal alteration. These understandings on dolostone porosity shed light on reservoir prediction. Dolostone reservoirs associated with evaporative tidal flat were laterally distributed as banded or quasi-stratified shapes in evaporite-bearing dolostones, and vertically presented as multi-interval patterns on tops of shallowing-upward cycles. Dolostone reservoirs associated with evaporative platform commonly occurred along epiplatforms or beneath evaporite beds, and vertically presented as multi-interval patterns in dolostones and/or evaporite-bearing dolostones of reef/shoal facies. Constrained by primary sedimentary facies, burial dolostone reservoirs were distributed in dolomitized, porous sediments of reef/shoal facies, and occurred vertically as multi-interval patterns in crystalline dolostones on tops of shallowing-upward cycles. Hydrothermal dolomitization was obviously controlled by conduits (e.g., faults, unconformities), along which lenticular reservoirs could develop.

Pore behaviour during semi-solid alloy compression: Insights into defect creation under pressure

The pre-existing porosity behaviour of globular semi-solid Al–Cu alloys during uniaxial compression is quantified during time-resolved synchrotron tomography at ∼64% and ∼93% solid. At ∼64% solid, both tortuous and round pores exist before deformation, respectively persisting and closing during compression, while at ∼93% solid, pre-existing tortuous pores open under compressive axial strain. It is demonstrated that pore behaviour reflects the immediate grain neighbourhood where the semi-solid alloy acts as a granular material, and that pore opening results from shear-induced dilation during uniaxial compression.

Experiments and modeling of variably permeable carbonate reservoir samples in contact with CO2-acidified brines

Reactive experiments were performed to expose sample cores from the Arbuckle carbonate reservoir to CO2-acidified brine under reservoir temperature and pressure conditions. The samples consisted of dolomite with varying quantities of calcite and silica/chert. The timescales of monitored pressure decline across each sample (and concurrent increases in permeability) in response to CO2 exposure, as well as the amount of and nature of dissolution features, varied widely among these three experiments. For all samples cores, the experimentally measured initial permeability was at least one order of magnitude or more lower than the values estimated from downhole methods. Nondestructive X-ray computed tomography (XRCT) imaging revealed dissolution features including “wormholes,” removal of fracture-filling crystals, and widening of pre-existing pore spaces. In the injection zone sample, multiple fractures may have contributed to the high initial permeability of this core and restricted the distribution of CO2-induced mineral dissolution. In contrast, the pre-existing porosity of the baffle zone sample was much lower and less connected, leading to a lower initial permeability and contributing to the development of a single dissolution channel. While calcite may make up only a small percentage of the overall sample composition, its location and the effects of its dissolution have an outsized effect on permeability responses to CO2 exposure. The XRCT data presented here are informative for building the model domain for numerical simulations of these experiments but require calibration by higher resolution means to confidently evaluate different porosity-permeability relationships.

The characterization and interpretation of ductile fracture mechanisms in AL2024-T351 using X-ray and focused ion beam tomography

This paper describes an experimental investigation into the mechanism of ductile fracture in the aluminum alloy AL2024-T351 using a combination of synchrotron X-ray and focused ion beam tomography. Microstructural features that influence fracture at the micro- and nanoscale were characterized in virgin material in three-dimensions. The nature and volume fraction of ductile damage was then quantified as a function of distance below the fracture surfaces of tested notched and fatigue pre-cracked laboratory specimens. In both specimens the ductile fracture process initiates with the brittle fracture of large irregular intermetallic particles at low levels of plastic strain. With increasing plasticity, the resulting voids grow and combine with pre-existing porosity to increase the overall void volume fraction. Once a critical void volume fraction is attained, final failure occurs by the fracture or decohesion of dispersoids from the matrix, initiating a second population of nanoscale voids, which interlinks the larger voids. The critical void volume fraction for coalescence and the distribution of ductile damage below the fracture surface is markedly different between blunt-notched and pre-cracked specimens, with notched specimens exhibiting a significantly lower critical void volume fraction and a more extensive distribution of ductile damage below the fracture surface than is observed in pre-cracked specimens. This observation, related to the gradients in stress triaxiality and plastic strain in each specimen type, has important implications for the calibration of ductile damage mechanics models against notched-specimen data and their use to predict crack behavior in engineering structures.

Microstructural Characterization of a Polycrystalline Nickel-Based Superalloy Processed via Tungsten-Intert-Gas-Shaped Metal Deposition

Recent trials have produced tungsten-inert-gas (TIG)-welded structures of a suitable scale to allow an evaluation of the technique as an economic and commercial process for the manufacture of complex aeroengine components. The employment of TIG welding is shown to have specific advantages over alternative techniques based on metal inert gas (MIG) systems. Investigations using the nickel-based superalloy 718 have shown that TIG induces a smaller weld pool with less compositional segregation. In addition, because the TIG process involves a pulsed power source, a faster cooling rate is achieved, although this rate, in turn, compromises the deposition rate. The microstructures produced by the two techniques differ significantly, with TIG showing an absence of the detrimental delta and Laves phases typically produced by extended periods at a high temperature using MIG. Instead, an anisotropic dendritic microstructure was evident with a preferred orientation relative to the axis of epitaxy. Niobium was segregated to the interdendritic regions. A fine-scale porosity was evident within the microstructure with a maximum diameter of approximately 5 μm. This porosity often was found in clusters and usually was associated with the interdendritic regions. Subsequent postdeposition heat treatment was shown to have no effect on preexisting porosity and to have a minimal effect on the microstructure.

The reliability of polished porcelain stoneware tiles

The flexural strength and the Young’s modulus of as fired and polished porcelain stoneware tiles were investigated. Bending tests were carried out on suitable specimens, cut from five commercial products before and after polishing. The differences found in the flexural strength data were evaluated by the analysis of variance and the determination of the Weibull parameters. The results showed that: (i) the as fired tiles and the corresponding polished tiles cannot be always considered the same material and (ii) the data scattering is usually greater for the polished products, i.e., the reliability of the polished products, in terms of the Weibull modulus m, decreases. The results, supported by microstructural observations, surface roughness and Vickers hardness measurements, were directly attributed to the severe damage induced by the first step of machining, i.e., calibrating or grinding. Young’s modulus data showed a clear dependence on the pre-existing porosity, i.e., the production process, rather than on the machining induced damage. It was also shown that the conditions and the characteristics of the polished working surfaces strongly depend on the microstructure of the as fired material.