Interlamellar Pores Research Articles

Shrinkage Reduction in Nanopore-Rich Cement Paste Based on Facile Organic Modification of Montmorillonite.

The organic modification of montmorillonite was successfully achieved using cetyltrimethyl ammonium bromide under facile conditions. The modified montmorillonite was subsequently used for the fabrication of montmorillonite-induced nanopore-rich cement paste (MNCP), and the shrinkage behavior and fundamental performance of MNCP were also investigated. The results indicate that alkali cations on a montmorillonite layer surface were exchanged by using CTAB under 80 °C, successfully achieving the organic modification of montmorillonite. As a pore-forming agent, the modified montmorillonite caused a reduction in shrinkage: the 28-day autogenous shrinkage at a design density of 400 kg/m3 and 800 kg/m3 was reduced to 2.05 mm/m and 0.24 mm/m, and the highest reduction percentages during the 28-day drying shrinkage were 68.1% and 62.2%, respectively. The enlarged interlamellar pores and hydrophobic effects caused by the organic modification of montmorillonite aided this process. Organic-modified montmorillonite had a minor influence on dry density and thermal conductivity and could contribute to an enhancement of strength in MNCP.

Ti3C2Tx constrained Sb2S3 composite biomass-derived carbon ribbon film achieves stable sodium storage for flexible quasi-solid full-battery

Optimizing electrode structure, reducing the proportion of inactive substances, and fabricating a flexible free-standing electrode without fluid collection are desirable to enhance the energy density, fast charging, and cycling stability of flexible batteries. In this study, we utilized the biological characteristics of Aspergillus niger to synthesize one-dimensional (1D) Sb2S3 nanoparticle composite N-doped C ribbons. Subsequently, vacuum filtration was employed to blend and assemble these 1D composite C ribbons with Ti3C2Tx nanosheets into a free-standing flexible anode for Sodium-ion batteries (SIBs). Using 1D C ribbons can effectively inhibit the stacking of 2D MXenes, thereby facilitating the penetration of Na+ into Sb2S3@NCR through the interlamellar pores. Ex-situ X-ray photoelectron spectroscopy analyses indicated that the MXene layers were not only physically confined but also effectively suppressed polysulfide diffusion through chemical confinement. Consequently, the energy density and cycling stability of the Sb2S3@NCR composite electrode were enhanced. The Sb2S3@NCR/MXene||CGPFE||NVP@CNF full battery, consisting of an Sb2S3@NCR/MXene anode, free standing NVP@CNF cathode, and PVDF-HFP fiber quasi-solid-state polymer electrolyte prepared via electrospinning, achieved 1,000 stable cycles at a current density of 1 Ag−1. Additionally, the flexible quasi-solid-state bag-type battery could power an LED lamp at a bending angle of 0°–180°.

Effect of heat treatment on the structure, fracture toughness and oxidation behavior of a silicon coating by atmospheric plasma spraying

Silicon coatings produced by atmospheric plasma spraying are used as bond coat in environmental barrier coatings which protect silicon carbide fiber reinforced silicon carbide composites against water vapor induced corrosion at high temperatures. Silicon coatings exhibit structural defects such as interlamellar boundaries, gaps, pores and microcracks, some of which become pathways for oxygen penetration, leading to internal oxidation of the silicon coating. This study was conducted to reduce the pathways for oxygen penetration by heat-treatment under argon atmosphere and investigate the effects of heat-treatment on the structure, fracture toughness and oxidation behavior of the silicon coating. The results show that the structural defects could be reduced by a heat-treatment at T = 1300 °C, which resulted in a lower mass gain of the coating in the initial cycle in a cyclic oxidation test. The fracture toughness of the coating was significantly decreased by the heat-treatment, which led to the formation of microcracks in the coating in the cyclic oxidation test. As a result, the heat-treated coating exhibited a higher mass gain rate than the as-sprayed coating, leading to that both coatings exhibited almost the same mass gain at the end of the cyclic oxidation test of n = 10 cycles.

A Study on Long-Term Oxidation and Thermal Shock Performance of Nanostructured YSZ/NiCrAlY TBC with a Less Dense Bond Coat.

This paper focused on studying the performance of a nanostructured thermal barrier coating (TBC) system deposited by APS, which had a bond coat with inter-lamellar porosities that resulted during the manufacturing process. The higher porosity level of the bond coat was studied as a possible way to keep the thickness of the TGO under control, as it is distributed on a higher surface, thereby reducing the chance of top-coat (TC) spallation during long-term oxidation and high-temperature thermal shock. The TBC system consisted of nanostructured yttria partially stabilized zirconia (YSZ) as a top coat and a conventional NiCrAlY bond coat. Inter-lamellar porosities ensured the development of a TGO distributed on a higher surface without affecting the overall coating performance. Based on long-term isothermal oxidation tests performed at 1150 °C, the inter-lamellar pores do not affect the high resistance of nanostructured TBCs in case of long-term iso-thermal oxidation at 1150 °C. The ceramic layer withstands the high-temperature exposure for 800 h of maintaining without showing major exfoliation. Fine cracks were discovered in the ceramic coating after 400 h of isothermal oxidation, and larger cracks were found after 800 h of exposure. An increase in both ceramic and bond-coat compaction was observed after prolonged high-temperature exposure, and this was sustained by the higher adhesion strength. Moreover, in extreme conditions, under high-temperature thermal shock cycles, the TBC withstands for 1242 cycles at 1200 °C and 555 cycles at 1250 °C.

Tailoring sintering-resistant thermal barrier coatings by considering critical healing width of two-dimensional interlamellar pores

Tailoring sintering-resistant thermal barrier coatings by considering critical healing width of two-dimensional interlamellar pores

Effect of surface roughness and industrial heat treatments on the microstructure and mechanical properties of Ti6Al4V alloy manufactured by laser powder bed fusion in different built orientations

The emergence of powder bed fusion in recent years has made it one of the most demanded additive manufacturing technologies for Ti6Al4V alloys in the biomedical and aerospace industries due to its ease of part fabrication with complex geometry. However, Ti6Al4V components require a post-processing treatment to optimize their mechanical properties for engineering applications. The present study offers an analysis of the effects of different industrial heat treatments (704 °C for 120 min, 740 °C for 130 min) on the microstructure and tensile properties of Ti6Al4V samples manufactured by laser powder bed fusion in different orientations (Z, 45°, XY and XZ). These heat treatments were selected to improve the mechanical properties of the as-built material and to obtain samples representative of real industrial applications. SEM observations illustrated that the α’ martensite grown in the columnar parent β-grains was converted into an α+β mixture after both heat treatments. EBSD showed that the newly formed α phase maintained, inside the parent β grains, the same orientation relationship as the as-built α′ martensite. However, on a macroscopic scale, the α phase exhibited no preferential orientation. The heat-treated samples, which exhibited approximately 10% lower ultimate tensile strength and yield strength than the as built samples but a 10–13% higher elongation, were practically isotropic in their mechanical response. What little anisotropy was left was mainly attributed to few elongated interlamellar pores. The sandblasting process was also investigated; it did not affect the static mechanical properties of the samples but it reduced the Ra values by 25%. Finally, Vickers microhardness vs. strength relationships were studied by considering the α-phase orientation.

Pore characteristics and corresponding controlling factors of the marine shale gas reservoir in the Wufeng-Longmaxi Formation of the Zhaotong shale gas demonstration area

The shale gas reservoir in the Zhaotong national shale gas demonstration area in the southern margin of the Sichuan Basin is mainly developed in the lower member of the Ordovician Wufeng Formation to the Silurian Longmaxi Formation. Shale pore characteristics are the main indicators for evaluating the quality of shale reservoirs and largely determine shale gas productivity. We have qualitatively and quantitatively analyzed pore types and structures through scanning electron microscopy, CO2/N2 adsorption and high-pressure mercury injection experiments, and nuclear magnetic resonance. The pore types of marine shale gas reservoirs in the study area mainly included organic-matter pores and clay mineral interlamellar pores. The pore diameter of the shale reservoir ranged from 0.5 to 35 nm and was concentrated in the range of 2–10 nm, and the main pores were mesopores. Total organic carbon (TOC) content was positively correlated with fractal dimension, which could be used to quantitatively evaluate the complexity and heterogeneity of reservoir pores. The contents of TOC, clay, and siliceous minerals were the main factors controlling the development of shale micropores. The contents of clay minerals and siliceous minerals determined the storage space of shale gas, whereas micropores and mesopores controlled the adsorption capacity of shale.

Microporous structure and gas adsorption model of fusain in lignite

Fusain is widely distributed in coal seams and studying its porosity and adsorption capabilities helps clarify the physical properties of coal reservoirs and gas adsorption mechanisms. The microporous structure characteristics and gas adsorption mechanism of fusain in lignite were studied based on methane and CO2 adsorption experiments, combined with nuclear magnetic resonance (13NMR) and high-resolution transmission electron microscopy (HRTEM) measurements. Numerous micropores were found in the sample, and the pore volume and specific surface area were relatively large, which is similar to the results of the micropore test for meta-anthracite. The adsorption capacity of fusain was higher under dry base conditions but significantly lower under air-dry base and equilibrium water conditions. The chemical structure analysis results indicate that the micropores of fusain are mainly the interlamellar pores of the aromatic layers and the pore channels formed by them. Under dry conditions, the water in the microporous structure was removed, which provides an effective space for gas adsorption, resulting in more micropores for CO2 adsorption and a higher methane adsorption capacity. Under wet conditions, the water occupies the adsorption site of methane, which hinders the gas entering the microporous channel of the fusain, resulting in a low adsorption capacity. On comparing the pore structure characteristics of fusain and meta-anthracite, it was found that despite possessing similar chemical structure characteristics of high polycondensation and similar micropore structure, there were clear differences in pore size, and their adsorption properties for methane were different.

Thermal Shock Resistance and Thermal Insulation Capability of Laser-Glazed Functionally Graded Lanthanum Magnesium Hexaluminate/Yttria-Stabilised Zirconia Thermal Barrier Coating.

In this work, functionally graded lanthanum magnesium hexaluminate (LaMgAl11O19)/yttria-stabilised zirconia (YSZ) thermal barrier coating (FG-TBC), in as-sprayed and laser-glazed conditions, were investigated for their thermal shock resistance and thermal insulation properties. Results were compared with those of a dual-layered coating of LaMgAl11O19 and YSZ (DC-TBC). Thermal shock tests at 1100 °C revealed that the as-sprayed FG-TBC had improved thermal stability, i.e., higher cycle lifetime than the as-sprayed DC-TBC due to its gradient architecture, which minimised stress concentration across its thickness. In contrast, DC-TBC spalled at the interface due to the difference in the coefficient of thermal expansion between the LaMgAl11O19 and YSZ layers. Laser glazing improved cycle lifetimes of both the types of coatings. Microstructural changes, mainly the formation of segmentation cracks in the laser-glazed surfaces, provided strain tolerance during thermal cycles. Infrared rapid heating of the coatings up to 1000 °C showed that the laser-glazed FG-TBC had better thermal insulation capability, as interlamellar pores entrapped gas and constrained heat transfer across its thickness. From the investigation, it is inferred that (i) FG-TBC has better thermal shock resistance and thermal insulation capability than DC-TBC and (ii) laser glazing can significantly enhance the overall thermal performance of the coatings. Laser-glazed FG-TBC provides the best heat management, and has good potential for applications that require effective heat management, such as in gas turbines.

Micropore Characteristics and Geological Significance of Shale Reservoirs: Case Study of Fuling Shale Gas in Sichuan Basin, China

Several techniques (such as scanning electron microscopy (SEM) and gas adsorption systems) have been used to study the pore features and structures of shale reservoirs. The available methods and techniques have restricted the specific research on micropores, and the morphology, genesis, volume, and main factors controlling pore characteristics are yet to be analyzed. Currently, there is no systematic understanding of the role that these spaces play in gas storage and flow. As such, our understanding of the spatial connectivity of pores and reserves of shale reservoirs is limited. In this study, the pores of the Fuling shale gas reservoir in the Sichuan Basin were systematically observed by SEM and transmission electron microscopy. Images of pores smaller than 2 nm were captured for the first time, and their morphology and genesis were analyzed by combining these images with the rock mineralogy theory. The pore size distribution characteristics of the reservoir were analyzed by the adsorption-mercury injection method and nuclear magnetic resonance, and the main factors controlling the distribution of different pore sizes were analyzed. The results show that large numbers of micropores were distributed between the mesopores and macropores in the shale reservoir, which mainly consisted intergranular pores, intermolecular pores, interlamellar pores of clay minerals, and organic matter skeleton pores. The development of pores smaller than 1 nm was mainly controlled by the clay mineral content, and the development of pores with a size of approximately 1-2 nm was related to the contents of clay minerals and organic matter. These pores could connect the macropores and mesopores well, which is important for gas storage and flow. In this paper, the types, distribution, and main controlling factors of micropores were studied, and our understanding of the reservoir space was improved from the nanometer level to the Angstrom level, which is important for gas storage and flow process analysis.

Microstructural investigation of plasma sprayed ceramic coatings focusing on the effect of the splat boundary for SOFC sealing applications using peridynamics

The present study employs a continuum mechanics approach called peridynamics to investigate the deformation as well as the damage behaviour of a 2D microstructure obtained from a plasma sprayed ceramic coating used in solid oxide fuel cell (SOFC) sealing systems. Due to the production process, plasma sprayed ceramic materials possess typical microstructural features, such as globular pores, interlamellar pores as well as microcracks, which are orientated along the splat boundaries parallel or perpendicular to the spraying direction. Several studies postulated a splat interface or boundary, which influences the effective mechanical behaviour of such a microstructure without increasing the observable porosity. By means of an image analysis technique a splat interface was identified and considered as a separate phase in the simulation models. Based on this procedure, a microstructural model of a plasma sprayed ceramic coating of a SOFC sealing system is investigated. The simulation results are compared to experimental and analytical results. These micromechanical simulations show that structural defects influence the crack initiation as well as the crack propagation while interconnecting these defects. Typical crack mechanisms, such as crack deflection, crack shielding or multiple cracking, are observed. Additionally, an anisotropy of the effective mechanical properties is observed in this heterogeneous material, which is generally expected for plasma sprayed materials. As a result, considering the splat boundary in the simulations increases the anisotropy of the mechanical behaviour, decreases stiffness as well as the strength and influences the crack pattern strongly.

Bentonite microstructure and saturation evolution in wetting–drying cycles evaluated using ESEM, MIP and WRC measurements

In this paper, the microstructure of the Czech bentonite B75 was investigated by three methods: water retention curve (WRC) measurements, mercury intrusion porosimetry (MIP) measurements and environmental scanning electron microscopy (ESEM) investigation. The experiments were performed on samples at various compaction levels (between 1·27 and 1·90 g/cm3) and at various suctions (between 3·3 and 290 MPa) along both drying and wetting hydraulic paths. In the ESEM observations, target relative humidities (and thus total suctions) were imposed directly in the ESEM chamber to observe the effect of the hydraulic path on the microstructure. Apart from the inter-lamellar pores, which are not accessible to the adopted experimental techniques, two pore families were identified: micropores and macropores. The transition pore size between the micropores and macropores was found to be suction dependent. The microporosity was practically insensitive to compaction and only the largest micropores were sensitive to suction. Smaller macropores were sensitive to compaction only, whereas larger macropores were sensitive to both compaction and suction. It was observed that, during wetting from the as-compacted state, the macropores remained completely dry up to very low values of suction, whereas the micropores were found to be unsaturated up to the suctions between 10 to 60 MPa. Both macropores and micropores contributed to sample volume changes during drying and wetting. Although the microstructural volume change appeared to be reversible, the macrostructure exhibited permanent deformation.

Thermal properties and phase stability of Yttria-Stabilized Zirconia (YSZ) coating deposited by Air Plasma Spray onto a Ni-base superalloy

Thermal properties and microstructure characterization of Yttria Stabilized Zirconia (YSZ) Thermal Barrier Coatings (TBCs) deposited by Air Plasma Spray (APS) onto a Ni-base superalloy (Inconel 625) were studied. Two separate sets of tests were performed. The first one consisted in Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) performed over free-standing TC samples detached from TBCs. The second one included the analysis of the cross section of samples heat treated at 1100°C with holding times of 600, 1000, and 1700h. The TC porosity was analyzed for different heat treatment conditions so that inter-lamellar, intra-lamellar and globular pores, as well as cracks, were identified and quantified independently. An initial porosity reduction related to inter-lamellar and intra-lamellar pores, as well as cracks, was observed during the first 600h of heat treatment, due to sintering. However, porosity continually increased during heat treatment from 600 to 1700h driven by volumetric changes associated to phase transformations. During this period, yttrium diffused from the metastable tetragonal phase favoring the transformation to cubic phase while monoclinic phase transformed after cooling from the yttrium-depleted tetragonal phase. Energy absorption curves and the variation of heat capacity with temperature were also determined and correlated to microstructural changes.

List of Abstracts

. Production efficiency as well as the reduction of energy consumption and waste are the main drivers for the improvement of large-scale production in chemical industry. In addition, the demand for new processes – these days especially related to the chemical energy conversion as basis for the Energiewende – are additional triggers for innovation. Catalysis, well recognized by the public e.g. in form of the 3-way automobile catalyst, plays an important role for about 90% of all processes in chemical industry. The development of new and improved catalysts is a challenge for chemists – as is the search for new structural materials for mechanical engineers. Due to the often-necessary noble and thus expensive metals (e.g. palladium) in many catalysts, structural and chemical function have been developed separately in the two communities. Recent progress in catalytically active materials allows replacing expensive noble metals in selected catalytic processes by significant cheaper elements [1]. This offers the new perspective to combine structural and chemical functionality by innovative materials. Within this area, intermetallic compounds with their peculiar combination of crystal and electronic structure [2], represent an interesting class of materials to address this vision as will be shown in the contribution.

Properties evolution of plasma-sprayed La2Zr2O7 coating induced by pore structure evolution during thermal exposure

To study the inter-lamellar pores evolution under thermal exposure and how it affects the coating properties, free standing atmospheric plasma sprayed (APS) La2Zr2O7 (LZO) coating was subjected to thermal exposure at the temperatures of 1200°C and 1300°C for different durations. It was found that APS LZO coating experiences a rapid sintering during the early 5–20h of thermal exposure. Such microstructure evolution behavior was attributed to the presence of the lamellar structure, which contains most 2D pores with a small inter-lamellar spacing. As a result, the density, inter-lamellar bonding ratio, mechanical properties and thermal conductivity of the LZO coating remarkably increase in about 20h of thermal exposure. It was revealed that the evolution of the properties of the APS LZO coating during high temperature exposure is mainly ascribed to the shape change of the inter-lamellar pores for the formation of grain bridging in inter-lamellar pores.

Methodology for studying the composition of non-interlamellar pore water in compacted bentonite

AbstractMany safety functions required of the compacted bentonite buffer in the KBS-3 concept rely on processes influenced by the composition of the pore water. Important safety-relevant processes are related to the bentonite buffer,e.g.swelling, precipitation and dissolution reactions, and transport of water, colloids and ions. One of the methods used in analysing pore water in compacted bentonite is the ‘squeezing technique’. Various possible artefacts which can occur during squeezing, such as mixing of different pore-water types, dissolution of accessory minerals and cation exchange, need special attention.The present work describes the methodology for studying the composition of the non-interlamellar pore water by combining squeezing methods, chemical analyses, microstructure measurements and geochemical modelling. Four different maximum pressures were used to squeeze the compacted bentonite pore water. The origin of the pore water was studied by analysing the bentonite microstructure both before and after squeezing using SAXS and NMR, the cation exchange and dissolution reactions were studied by chemical analyses and geochemical modelling.The pore-water yield increased from 32 to 48 wt.% from the initial amount of porewater in the samples when the maximum squeezing pressure was increased from 60 MPa to 120 MPa. About 35 wt.% of the water collected originated from the interlamellar (IL) pores. The ratio between IL and non-IL pore waters as well as the composition of the squeezed porewater was constant in the squeezing-pressure range used. The results of microstructural measurements by SAXS were in perfect agreement with previous studies (e.g.Muurinen & Carlsson, 2013). The dissolving accessory minerals have an effect on the ratio of the cations in the squeezed solution while the migration of anions in bentonite seems to be diffusion limited. According to geochemical modelling the chloride concentration of the non-IL pore water in compacted bentonite before squeezing was 0.34 Mgreater than in the squeezed pore water due to the mixing of two main water types.

High Heat Insulating Thermal Barrier Coating Designed with Large Two-Dimensional Inter-lamellar Pores

Atmospheric plasma-sprayed ceramic coatings with a lamellar structure exhibit low thermal conductivity. However, high-temperature exposure causes sintering, which heals inter-lamellar two-dimensional (2D) pores and intra-splat pores. Such sintering effect increases the thermal conductivity of the coatings and consequently reduces the thermal insulation ability of TBCs. In this study, inter-lamellar 2D pores with a large opening width were introduced into the La2Zr2O7 (LZO) coating through the spraying of a LZO-SrO coating and the removal of the SrO splats in water. Then, the conventional LZO coating and the porous LZO coating were subjected to high-temperature exposure at 1300 °C, for different durations. It was found that the 2D pores resulting from SrO splats present little healing during high-temperature exposure, while the conventional 2D inter-lamellar pores with a small opening width heal rapidly. Thus, the thermal conductivity of the conventional LZO coating increased rapidly, while the unhealed 2D pores in the highly porous LZO coating contributed to the coating low thermal conductivity. The present results indicated that a high heat insulating thermal barrier coating with high stability can be fabricated though the introduction of inter-lamellar 2D pores with large opening width.

Morphology and Size Evolution of Interlamellar Two-Dimensional Pores in Plasma-Sprayed La2Zr2O7 Coatings During Thermal Exposure at 1300 °C

La2Zr2O7 (LZO) is widely expected to be one of the promising thermal barrier coating materials for application in high-temperature conditions (1200 °C). However, high-temperature exposure causes sintering which heals interlamellar two-dimensional (2D) pores and intrasplat pores. This sintering effect increases the stiffness and thermal conductivity of thermal barrier coatings, consequently reducing their durability. In this study, to reveal the possible critical opening of 2D pores above which they are free from sintering, LZO coating and splat were deposited by atmospheric plasma spraying and were exposed to 1300 °C for different durations. Thereafter, the evolution of the parameters of residual 2D pores in the coating and the surface morphology of LZO splat were characterized. It was found that there is a critical opening width for 2D pores above which grain bridging does not occur across the gaps. Accordingly, pores with an opening larger than this critical width are free from sintering across the 2D pores despite surface roughening of splats, whereas pores with an opening less than the critical width sinter rapidly at the early stage of thermal exposure through the formation of grain bridges.

Sintering of bi-porous titanium dioxide scaffolds: Experimentation, modeling and simulation

Highly bimodal pore size distributions are found in ceramic scaffolds prepared by freeze casting (ice templating). The scaffolds, with preferred orientation in the ice crystal growth direction, have large interlamellar pores between the scaffold walls and small intergranular pores within the walls. The constitutive equations based on a continuum theory of sintering are used in a finite element analysis of the sintered scaffolds. The calculations employed a model of large isolated pores surrounded by a shell containing small pores. During sintering at 1173 to 1773K the scaffold walls densified first, followed by wall closure at higher temperatures. Excellent agreement is found between the predicted and measured porosity. The compressive strength and elastic modulus depend on the fraction of interlamellar porosity, not the total porosity, indicating that the scaffold wall strength does not affect these properties.

セラミック溶射皮膜構造評価法としてのキャビテーション・エロージョン試験の有効性

The microstructure of plasma sprayed ceramic coatings is characterized by the existence of splats along with other morphological features such as interlamellar and globular pores, intrasplat microcracks and splat boundaries. These various process-dependant micro- defects extremely influence physical and mechanical properties such as thermal conductivity and elastic modulus and then influence coating behavior. In this approach, the process involved in the cavitation erosion of plasma sprayed ceramic coatings have been studied using the ultrasonic vibratory technique. The weight loss occurring during fifteen minute intervals of exposure to cavitational erosion was determined, the surface of specimens and the wear debris were examined by Scanning electron microscopy (SEM). The results suggest that the improvement in coating performance could be achieved by controlling the effective contact between lamellae of which the coating is made up using the plasma spray conditions, such as sufficient preheat, short standoff distance and slow gun traversing movement.