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The prevention of drying-induced cracking is crucial in maintaining the mechanical integrity and functionality of colloidal deposits and coatings. Despite exploring various approaches, controlling drying-induced cracking remains a subject of great scientific interest and practical importance. By introducing chain-like particles composed of the same material and with comparable size into commonly used colloidal suspensions of spherical silica nanoparticles, we can significantly reduce the cracks formed in dried particle deposits and achieve a fivefold increase in the critical cracking thickness of colloidal silica coatings. The mechanism underlying the crack suppression is attributed to the increased porosity and pore sizes in dried particle deposits containing chain-like particle, which essentially leads to reduction in internal stresses developed during the drying process. Meanwhile, the nanoindentation measurements reveal that colloidal deposits with chain-like particles exhibit a smaller reduction in hardness compared to those reported using other cracking suppression approaches. This work demonstrates a promising technique for preparing colloidal coatings with enhanced crack resistance while maintaining desirable mechanical properties. [ABSTRACT FROM AUTHOR]

Most of the available data on diffusion in natural clayey rocks consider tracer diffusion in the absence of a salinity gradient despite the fact that such gradients are frequently found in natural and engineered subsurface environments. To assess the role of such gradients on the diffusion properties of clayey materials, through-diffusion experiments were carried out in the presence and absence of a salinity gradient using salt-diffusion and radioisotope tracer techniques. The experiments were carried out with vermiculite samples that contained equal proportions of interparticle and interlayer porosities so as to assess also the role played by the two types of porosities on the diffusion of water and ions. Data were interpreted using both a classical Fickian diffusion model and with a reactive transport code, CrunchClay that can handle multi-porosity diffusion processes in the presence of charged surfaces. By combining experimental and simulated data, we demonstrated that (i) the flux of water diffusing through vermiculite interlayer porosity was minor compared to that diffusing through the interparticle porosity, and (ii) a model considering at least three types of porous volumes (interlayer, interparticle diffuse layer, and bulk interparticle) was necessary to reproduce consistently the variations of neutral and charged species diffusion as a function of salinity gradient conditions.

We investigated the relationship between porosity and flexoelectricity for aluminum (Al)/polyvinylidene fluoride (PVDF) composites. Neat PVDF, composites of micron aluminum (μAl)/PVDF, and composites of nano aluminum (nAl)/PVDF were 3D printed, and the flexoelectric response was measured using a cantilever beam test setup. Voids (up to 72.4 mm3) were incorporated into the samples by decreasing the infill percent of the 3D printed material. We found that increasing the porosity via millimeter scale voids incorporated into the infill pattern decreased the average effective flexoelectric coefficient relative to the near full-density (100% infill) control samples. This contrasts with other studies that have shown increasing micron scale porosity increases the flexoelectric coefficient. In addition, we measured higher flexoelectric responses for nAl/PVDF than μAl/PVDF as well as for samples printed by the Hyrel 3D SR printer as opposed to the Ender 3 V2 printer. These results indicate that charge generation due to flexoelectricity can be altered by changing parameters such as porosity, particle size of inclusions, or manufacturing method. Smaller voids and fine particles can induce larger strain gradients than larger inhomogeneities, leading to increased flexoelectric coefficients. A competing effect is that more porosity leads to less materials, which can decrease the flexoelectric coefficient. [ABSTRACT FROM AUTHOR]

Reactive burn models for heterogeneous energetic materials (EMs) must account for chemistry as well as microstructure to predict shock-to-detonation transition (SDT). Upon shock loading, the collapse of individual voids leads to ignition of hotspots, which then grow and interact to consume the surrounding material. The sub-grid dynamics of shock-void interactions and hotspot development are transmitted to macro-scale SDT calculations in the form of a global reactive "burn model." This paper presents a physically evocative model, called meso-informed sub-grid source terms for energy localization (MISSEL), to close the macro-scale governing equations for calculating SDT. The model parameters are explicitly related to four measurable physical quantities: two depending on the microstructure (the porosity ϕ and average pore size D ¯ v o i d ), one depending on shock–microstructure interaction (the fraction of critical voids ξ c r ), and the other depending on the chemistry (the burn front velocity V h s ). These quantities are individually quantifiable using a small number of rather inexpensive meso-scale simulations. As constructed, the model overcomes the following problems that hinder the development of meso-informed burn models: (1) the opacity of more sophisticated surrogate/machine-learning approaches for bridging meso- and macro-scales, (2) the rather large number of high-resolution mesoscale simulations necessary to train machine-learning algorithms, and (3) the need for calibration of many free parameters that appear in phenomenological burn models. The model is tested against experimental data on James curves for a specific class of pressed 1,3,5,7-tetranitro-1,3,5,7-tetrazoctane materials. The simple, evocative, and fast-to-construct MISSEL model suggests a route to develop frameworks for physics-informed, simulation-derived meso-informed burn models. [ABSTRACT FROM AUTHOR]

Gas–liquid two-phase stratified flow exists in many industrial processes. Although the flow pattern is simple, the interfacial shear prediction of stratified flow is still the focus of the study. The calculation of the shear stress at the gas–liquid interface is closely related to the measurement of the void fraction and pressure drop of the stratified flow. In this study, a new method for the calculation of interfacial shear stress of gas–liquid two-phase stratified flow is proposed. Differential pressure measurement and planar laser-induced fluorescence technology are combined to obtain important parameters for stratified flow under low-speed flow conditions (Ql = 0.10–0.25 m3/h, Qg = 0.35–1.00 m3/h). The interfacial shear stress is successfully calculated using macroparameters. The uncertainty associated with the calculated parameters using the proposed method is 2.67%, and this study verifies the accuracy of the linear relationship. The method provides a new way to obtain the interfacial shear stress of gas–liquid stratified flow. [ABSTRACT FROM AUTHOR]

Utilizing molecular dynamics simulation, this study aims to explore the phase transformation behavior of porous nanocrystalline (NC) NiTi shape memory alloys (SMAs) when subjected to cyclic deformation. The influences of porosity and cyclic deformation on the phase transformation of NC NiTi SMAs are examined and discussed. The simulation results show that the increase in the porosity and number of cycles leads to a decrease in both the critical phase transformation stress and peak stress whereas an increase in the residual martensite, phase boundary, and interstitial atoms; the related results can be supported by previous experiments. After cyclic deformation, the reduction in the potential energy for the entire system during the tensile phase occurs at an earlier stage, indicating that the martensitic transformation occurs earlier as the number of cycles increases. Notably, the dissipated energy demonstrates a decrease with an increasing number of cycles, and the potential energy during the austenite elastic unloading stage undergoes a transition from a decreasing to an increasing trend due to the presence of residual martensite increasing with the number of cycles. [ABSTRACT FROM AUTHOR]

In this study, the physiomechanical properties of carboxymethylcellulose sodium salt (Na-CMC salt) filler-loaded foam and its impact on the wicking capacity of the foam were investigated in juxtaposition with the increasing tin concentration. According to the study's findings, standard unfilled foam demonstrated no wicking at all, while flexible PU foam filled with Na-CMC salt, even with low porosity and subpar mechanical traits, displayed wicking heights of 4 mm, 3.4 mm, and 2.8 mm in test specimens of thicknesses of 6 mm, 8 mm, and 10 mm. Moreover, filled foam with a higher porosity level exhibited significantly better wicking heights of 11.4 mm, 10.8 mm, and 8.2 mm. The inclusion of CMC filler in the PU foam matrix is the reason for enhanced wicking property in foam. The sample thickness and wicking height trends are consistent among all foams; as foam sample thickness increases, wicking height progressively falls. The correlation between the foam's porosity value and the number of closed cell windows is confirmed by stereomicroscopy and the porosity values. According to this study, the infused filler's characteristics have a greater influence on the foam's wicking capacity than the foam's porosity. This study contributes significant insights into ongoing initiatives to enhance user experience, well-being, and hygiene through innovative and meticulously designed new developed mattress foam using Na-CMC as a filler. Highlights * Co-relation between concentration of tin and infused filler on wicking property. * Standard unfilled foam demonstrated no wicking at all. * Na-CMC salt filled foam displayed wicking heights. * After 15% increase in tin level, mechanical properties of foam degrade. * Wicking depends on nature of infused filler and the foam's porosity. KEYWORDS filler, flexible polyurethane foam, porosity, wicking, 1 | INTRODUCTION Polyurethanes (PU) are polymeric substances with urethane linkages [NH--C(O)--O] produced by the reaction of polyols with hydroxyl (--OH) groups and isocyanates (-N=C= O). (1,2) In the production [...]

The behavior of energetic materials is significantly influenced by the spatial distributions of microstructure heterogeneities and voids. We pursue the concept of Functionally Graded Energetic Materials whose microstructure features (e.g., grain size, grain volume fraction, void size, and void volume fraction) change spatially such that they may allow the behavior of the materials to be tailored. We explore using gradients in the density of voids to alter the detonation behavior of a polymer-bonded explosive (PBX) echoing PBX9501 with HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) grains and Estane binder. Five cases, two graded void distributions from 1% to 10% and 10% to 1% by volume along the length of the sample, and three uniform distributions matching the lowest (1%), average (5.5%), and highest (10%) void densities are considered. An Arrhenius reaction burn model is used to account for the chemical kinetics of HMX. Different detonation behaviors are obtained from the same graded sample when impact loading is from 1% void end and from the 10% void end as well as from the uniform cases. The SDT (shock to detonation transition) behaviors are analyzed in terms of the run distance, the time duration and shock velocity changes over the SDT process. The computational results are presented in the context of available experimental data for PBX9501 with which agreement is obtained through a parametric study. Overall, it is shown that gradients in microstructures of PBX can lead to SDT behaviors different or not obtainable from microstructures without gradients, thereby offering a mechanism for designing and tailoring new materials. [ABSTRACT FROM AUTHOR]

In this study, analytical models for space charge limited current (SCLC) transport in a porous (or disordered) trap-limited dielectric cylindrical configuration are developed. The method used in this paper is first verified by reproducing the well-known analytical results for planar cases developed decades ago based on the traditional approach. By considering the porous solid as a fractional object characterized by a parameter α ≤ 1 , we formulate its fractional capacitance and determine the SCLC transport by using the transit time approach. At α = 1 , it will recover the well-known Mott–Gurney law and Mark–Helfrich law for trap-free and trap-limited cases, respectively. For cylindrical geometry, our findings show an analytical form that is not available from the traditional methods. We anticipate that the proposed analytical model will serve as a useful tool for characterizing the current–voltage measurements in SCLC transport in dielectric breakdown and organic electronics, where spatial porosity of the materials is inevitable. The introduced fractional parameter α extracted from such characterization can facilitate the quantitative determination of the relationship between spatial porosity and charge mobility. [ABSTRACT FROM AUTHOR]

Our study examines 'Finstagramming' as a resistance strategy from influencers trying to circumvent the prescriptive nature and restrictive algorithm of Instagram. Without ever leaving the platform, Finstagram acts as an emancipatory outlet that enables influencers to share more intimate, less-conforming and unpolished content without jeopardising the highly curated, monetizable person-brand of their main account. Through a dual-method qualitative approach of netnography and in-depth interviews, we unravel this paradox of embedded escapism, where influencers toggle between main and Finsta accounts in their pursuit of authenticity. Our findings reveal the porosity of these multiple digital personae and differentiated digital work taking place on the platform. We argue that Finstagram affords a momentary escape from the digital attention economy whilst remaining tethered to socially mediated authenticity markers. [ABSTRACT FROM AUTHOR]

The principle of the conventional ultrasound test states that the detectable voids cannot be smaller than the acoustic wavelength. However, by using effective medium approximation, the fraction of small voids can be estimated by the variation of the effective density. In this study, a non-contacting ultrasound-based porosity fraction mapping methodology is developed for estimated small voids in coal with long operating wavelength in air. This novel ultrasonic technique based on the mechanical properties of coal offers a rapid scan of the effective density mapping and distribution of void fraction over a large sample area, which overcame the limitation of small voids detection in the conventional ultrasound testing. [ABSTRACT FROM AUTHOR]

Three types of mesoporous silicon flakes were fabricated by anodization in methanoic hydrofluoric acid from the same substrates (heavily doped p-type). Even though anodization current density, rinsing, drying method, and storage condition were the same for all three wafers, the resulting porous silicon (PSi) structures had very different properties. They had very different colors. Two of them showed quite high luminescence quantum yields (QYs), confirmed by very long luminescence lifetimes. The highest QY exceeded 50% for a peak photoluminescence wavelength of ∼750 nm. To date, this QY is the highest obtained for PSi and very importantly for silicon with large mesopores, which is typically not highly efficient (as opposed to silicon with small mesopores and microporous silicon). Large mesopores (>15 nm diameter) facilitate impregnation of various substances into luminescent material, such as metals for plasmonics and drugs for theranostics. The differing luminescent properties were correlated to electrolyte temperature during anodization, and evolution of the electrolyte batch (lowering of active fluoride content and buildup of hexafluorosilicate) used to anodize several wafers, whose effects are often overlooked when mass-producing PSi. Supercritical drying and completion of the slow growth of native oxide passivation in the dark leading to different final partially oxidized PSi structures are also important factors for the high QYs obtained. The highest QY was obtained with the structure having the most isolated Si nanocrystals in an amorphous Si oxide tissue. [ABSTRACT FROM AUTHOR]

Defect engineering has been widely applied in the field of photocatalysis, and defects can be used to modify the surface structure and photoelectric properties of catalysts so as to achieve the purpose of regulating the activity and stability of catalysts. However, design of a highly efficient photocatalyst with abundant defects remains a challenging task in current research. Therefore, in this study, graphitic carbon nitride (g-C 3 N 4) with abundant three-coordinated nitrogen (N 3C) vacancies and pore structures was obtained using a facile hydrothermal method with the assistance of glycerol. Under visible light (λ > 420 nm) irradiation, the 50CN (volume ratio of glycerol/water is 50/10) catalyst exhibits a superior CO release rate (4.18 μmol g−1 h−1), which is 12.06 times higher than the reference GCN (0.32 μmol g−1 h−1), and the corresponding apparent quantum yields (AQY) of 50CN is 0.24 %, which is significantly higher than that of GCN (0.045 %). Successful introduction of N 3C vacancies is conducive to broaden light response range of the catalyst, enhancing the separation and migration efficiency of photogenerated charges, and providing more adsorption active sites to promote the adsorption and activation of CO 2 molecules, thus effectively boosting photocatalytic CO 2 reduction activity. In addition, the N 3C vacancies can effectively lower the CO 2 activation energy barrier and reduce the energy consumption required for the reaction. This work offers valuable new insights into defect engineering in g-C 3 N 4 for the development of high-performance photocatalysts for CO 2 reduction. [ABSTRACT FROM AUTHOR]

Ultrafiltration (UF) membranes with excellent dye removal and antibacterial activity are highly desired in dye wastewater treatment, and more importantly environmental protection puts high demands on polymeric membrane materials. In this work, three methacrylate copolymers containing quaternary ammonium salt were synthesized to cast UF membranes. The physicochemical property, structural evolution, dye separation, and antibacterial activity of as‐prepared membranes were systematically investigated. With increased content of the hydrophilic monomer allyl polypropylene glycol (APPG) in the feed, the wettability and positive charge of the resultant membranes were enhanced. Remarkably, the supporting layer of membranes changed from finger‐like pore structure to sponge‐like pore structure by increasing APPG content, and the sponge‐like membranes showed higher retention rates for dyes (99.78% for victoria blue B, 90.49% for methylene blue, and 97.43% for methyl blue) compared with the finger‐like membranes. Besides, the sponge‐like membranes exhibited high rejection for vctoria blue B (>99%) in dye/salt mixture and simultaneously low rejection for salts (<10%), indicating effective selective separation to dye/salt mixture, and also achieved easy regeneration. It was also found that increased hydrophilicity and positive charge endowed membranes with better antibacterial activity. This work will provide an alternative for dye/salt selective separation in dye effluent treatment. [ABSTRACT FROM AUTHOR]

The conventional approach to generate pores in ceramic membranes involves the incorporation of a pore-forming element. However, this method tends to diminish the mechanical properties of the membranes and poses challenges in effectively regulating both pore size and membrane porosity. In this work, low-cost ceramic filtering membranes with enhanced mechanical strength have been successfully prepared mainly from abundant clays and without the need for pore-forming agents. The Porosity and pore size were controlled by adding a finely-grained clay (d 90 = 22 μm) by-product to coarse clay (d 90 = 50 μm) within a specified range of 33–66 wt%. The microstructure evolution of prepared membranes was examined by XRF, FTIR, XRD, SEM, and DTA-TGA analysis, while the technological properties were evaluated by permeability, porosity, density, and mechanical measurements. The findings indicated that the increase in the amount of finely grained clay mixed with coarse clay and the sintering temperature had a synergistic effect on the porosity and pore size of the obtained membranes. The incorporation of finely-grained clays, accompanied by an elevation in sintering temperature, led to a reduction in porosity from 31.3 ± 0.7 % to 6.2 ± 0.5 % and pore size, along with the crystallization of the α-mullite (12 %) and anorthite (30 %) phase with a quartz phase and an improvement in mechanical strength reaching up to 251 ± 3 MPa. A formulation comprising 33 wt% of finely-grained clay by-products and 67 wt% of coarse clay, sintered at 1000 °C, emerged as a promising ultrafiltering membrane with enhanced mechanical strength reaching 120 ± 1 MPa, and a permeability of 1000 L/h.m2 at 1 bar. [ABSTRACT FROM AUTHOR]

High-entropy carbides with tunable crystallization and growth have been demonstrated using single-source precursor derived ceramic route. The in situ nanocrystallization of high-entropy carbide phases, (Ta 0.2 W 0.2 V 0.2 Mo 0.2 Nb 0.2)Si δ C and (Ta 0.167 W 0.167 V 0.167 Mo 0.167 Nb 0.167 Si 0.167)C in amorphous Si-based ceramic matrices was achieved by using polysiloxanes and polycarbosilanes as polymer precursors respectively. The results exemplify a prominent role of the architectures of the polymeric precursors in controlling the structural features of these ceramics at various length scales. In particular, it was observed that high-entropy carbides with rock salt and zinc blende crystal structures were formed when polysiloxanes and polycarbosilanes with different backbone structure were used as polymeric precursors respectively. This is attributed to the thermodynamics of nucleation of the carbidic phases in these nanocomposites. Furthermore, the precursor architecture that dictates free carbon content, influenced nanostructural features and porosity in the material. Therefore, engineering such compositionally complex phases is feasible by selecting suitable polymeric precursors. • Precursor architecture influenced the crystal structure of high-entropy carbides. • Crystal structure dependent on earliest nucleated carbidic phase. • Free carbon played a key role in controlling crystallite size and porosity. [ABSTRACT FROM AUTHOR]

New C/SiC composites with continuous fibers were produced through impregnation of carbon fiber preforms and consolidation by hot pressing. The resulting sintered material was investigated as a potential target for nuclear applications, such as radioisotope production. Desired properties include high porosity and high thermal conductivity to allow isotope release from the targets while working at high temperature. To this end, porosimetry and thermal and mechanical characterizations were conducted up to 1250°C. It was shown that the addition of fibers resulted in high porosity, about 40%, while maintaining a very high thermal conductivity, 40 W/m∙K at 1250°C, a value particularly attractive for the intended application. Emissivity at 1250°C was 0.76, compressive strength at room temperature was 134 MPa, and flexural strength passed from about 90 MPa before thermal conductivity measurements to 50 MPa after the tests. [ABSTRACT FROM AUTHOR]

The refractory alkaline activated materials gained attention in the various engineering and industrial applications due to its environmental and eco-friendly benefits. The present study deals with the evaluation of the effects of nano-ZrO 2, nano-Al 2 O 3 , and nano-TiO 2 particles reinforcement mechanism on the final properties of the geopolymer matrices subjected to thermal treatment from 900 to 1250°C. Three series of composite matrices were obtained by adding 2–8 wt% of nanoparticles content (Al 2 O 3 , TiO 2 and ZrO 2) within the activated mortar and were devoted RAi, RRi and RZi (i = 2, 3, 5 and 8%).The designed composite matrices were characterized using several analytical methods and techniques including the mechanical characterization, mercury intrusion porosimetry (MIP) as well as the microstructural characterization. The results revealed that the use of the high content of nanoparticles (8 wt%) favored formation of a cross-linkage chain around the crystalline phases present within matrices. Their resulting percolation-induced reinforcement acted as supplementary with the interlocked network from the crystalline phases within the matrices to rendering it denser and compact. The matrices with high content of the nanoparticles added exhibited high mechanical properties at 1250°C. Flexural strength and young modulus were 70.7, 52 and 78.4 MPa, and 28.15, 22.61 and 29.86 GPa for RA, RR and RZ series respectively. Furthermore, the formation of the new crystalline phase like cordierite, mullite and leucite contributed to hindering the crack propagation within the matrices and increased the level of crystallization of the matrices by providing a homogeneous and well-dispersed structure. The produced matrices emerged stable at high temperature treatment and therefore could be used as a potential candidate for the materials for elevated temperatures applications. [ABSTRACT FROM AUTHOR]

Macroporous polymeric sorbents were synthesized via high internal phase emulsion (HIPE) templating. For this aim, water‐in‐oil (w/o) HIPEs were prepared with 80 vol.% of aqueous internal phase whereas plant‐based β‐myrcene (My) and D‐limonene (Lim) were used as renewable building blocks in the continuous oil phase. Moreover, biocompatible ethylene glycol dimetacrylate (EGDMA) was also added as a crosslinker comonomer. By varying the total volume fraction of My and Lim in the continuous phase composition between 90% and 50%, 14 different HIPE formulations were prepared. After polymerization of HIPE templates 28 different sorbents were obtained depending on the purification procedure (extraction & drying under vacuum or freeze drying). The effect of terpene composition in the obtained sorbents was investigated in terms of cross‐link density (υ), the molecular weight (Mc) and pore morphology. In this context, chemical structures and pore morphologies were characterized by FTIR spectroscopy and SEM analysis, respectively. The Brunauer‐Emmet‐Teller (BET) specific surface area was also measured to determine the relationship between pore morphology and surface area. Based on the characterization results, two sorbents were selected as model for sorption tests. Thereafter, solvent sorption tests were performed by immersing sorbents in either hexane, dichloromethane, deionized water, seawater, solvent/water mixture, or solvent/seawater mixture to determine maximum sorption capacities and determine reusability of the sorbents. Moreover, experimental data was fitted to pseudo‐first order and pseudo second order kinetic models, as well as Freundlich and Langmuir isotherms. In the end, it was found that varying My and Lim ratio is the key parameter of controlling pore morphology and physicochemical properties. Moreover, it was shown that resulting sorbents can be efficiently used in oil/water separation processes repeatedly for several cycles. [ABSTRACT FROM AUTHOR]

Compared with heavy metal catalysts, metal-free catalysts that activate persulfate (PS) for controlling organic pollutants are more economical, environmentally friendly, and safer for human health. Utilizing ZIF-8 particles as templates and polyphosphazene as the precursor, hollow N, P, and O tri-doped carbon microspheres (NPOC) with a hierarchical pore structure were successfully synthesized from ZIF-8@polyphosphazene. Their morphology and structure were investigated by SEM, TEM, TGA, XPS, BET, and FT-IR. Otherwise, NPOC were used as catalysts to activate PS for the oxidative degradation of tetracycline. The dosage of catalyst and oxidant, tetracycline concentration, carbonization temperature, and pH can all have a substantial influence on the oxidative degradation of tetracycline. Free radical testing by EPR reveals that HO˙ and SO4˙− are generated and the radical pathway is dominant in the oxidative degradation process. NPOC exhibited superior catalytic oxidation performance and good reusability, indicating their potential for application for eliminating TC from aqueous solution. [ABSTRACT FROM AUTHOR]

Microfluidic chips hold vast potential for applications in fields such as DNA analysis, drug screening, cell culture and biosensing. However, microfluidic chips are susceptible to disruption and damage from bubbles. Current bubble removal methods suffer from limitations including narrow applicability, poor biocompatibility, limited bubble containment volume, low degassing rates, manufacturing complexity and integration challenges. Addressing these issues, this study presents the development of a bubble filtration microfluidic chip inspired by the stomatal pore structure in plant leaves, which prevents air propagation between conduits. Surface wettability theory and surface tension principles were utilized to investigate the mechanism of bubble filtration by plant stomatal pores. A cellulose/PVA hydrogel was introduced to enable the microfluidic chip to effectively filter bubbles. The design and in situ formation method of the bubble filtration chip were developed, and the chip was fabricated using micro-nanofabrication processes. Performance evaluation of the bubble filtration microfluidic chip demonstrated that with a gel film thickness of 20 μm, the microfluidic chip exhibits high gas leak threshold and minimal flow loss. The resulting biomimetic bubble filtration microfluidic chip features a simple structure, compact size, and independence from auxiliary equipment, making it suitable for portable microfluidic devices. [ABSTRACT FROM AUTHOR]

In this work, the Schwarz primitive unit cell is used as the building block of different types of metastructures for steering and focusing elastic vibrations. The emergence of a Bragg-type bandgap when constructing a two-dimensional plate from such unit cells is experimentally validated. It is demonstrated that increasing both mass and porosity of the Schwarz primitive leads to a decrease in the frequency of the out-of-plane propagating wave targeted in this study. By arranging these modified Schwarz primitive unit cells in constant and graded layouts, two-dimensional plates with an embedded metabarrier and a metalens are numerically designed. The metabarrier protects an interior area of the plate from the propagating waves on a wide frequency band (approx. 1.4–3.4 kHz). Equally, the refractive index profile necessary for gradient index lenses is obtained via a progressive variation of the added mass or, alternatively, the porosity of the unit cell over a rectangular area. For the first time, bending of the out-of-plane mode towards the focusing point is practically validated in a challenging mesoscale experiment requiring the assembly of different three-dimensional printed sections of the plate. The increased porosity design is advantageous not only in terms of overall lightweight, but also towards additive manufacturing as it requires less material. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'. [ABSTRACT FROM AUTHOR]

In this work, a porous Co 3 O 4 anode material with capsule–shaped morphology is prepared by a simple solvothermal method and subsequent heat treatment process in air. The as–synthesized CoCO 3 precursor and Co 3 O 4 sample are systematically studied and analyzed by a series of testing technologies, such as XRD, FTIR, FESEM, (HR)TEM, TGA, XPS and N 2 adsorption/desorption measurement. As negative materials in Li–ion batteries, the Co 3 O 4 active material exhibits high charge/discharge specific capacity, good rate performance and satisfactory cycle stability. The excellent electrochemical properties are inevitably related to the structural characteristics of the electrode material itself, including regular morphology, rich pore structure, large specific surface area, high crystallinity, nanoscale particle size, etc. [ABSTRACT FROM AUTHOR]

Carbon foams (CFs), which can be manufactured from melamine foam (MF) via direct carbonization, are promising spacecraft thermal insulation material due to their excellent performance of sound absorption, low density, high porosity and heat resistance. Carbonization temperature, heating rate and carbonization time are three key elements during the melamine carbon foam process. As an improvement, this study simultaneously researches the impacts of pre-heat treatment on the microstructure, structure parameter, mechanical properties and heat-shielding performance of the melamine-derived carbon foam (MDCF), aiming to explore the best process of MDCF production. The results showed that the cross-linking degree and defects of MF samples were directly improved by pre-heat treatment. Additionally, all MDCF samples retained the three-dimensional mesh open-cell skeleton structure. The MDCF samples obtained by carbonization at 900 °C had the smallest average pore size structure, which performed the compressive stress of 16.8 kPa at 10 % strain and lowest thermal conductivity of 0.0252 W m−1 K−1. To further study the mechanical property and thermal conductivity performance of MDCF samples, the mechanics relationships of the buckling strength and shape variables, as well as thermal conductivity and pore size structure were researched. [ABSTRACT FROM AUTHOR]

Triethanolamine (TEA) has been broadly used as the organic amine conditioning agent to modify the workability of cement-based materials. However, the effect of TEA on the structure and property of porous silicate cement membranes has not been reported. In this paper, TEA was applied to study its effect on parameters of porous silicate cement membranes based on the preparation method combining freeze casting and heat-dry curing, because it is easy to form complexes with cement particles. The effect and acting mechanism of TEA on porous silicate cement membranes were researched using a series of characterizations and molecular dynamics (MD) simulation. Results showed that TEA significantly improved the performance of porous silicate cement membranes. The addition of TEA changed the pore morphology of porous silicate cement membranes from lamellar structures to cellular structures, with mesoporous size distribution focusing on 2.5–4.5 nm at TEA doping ratio of 0.16 wt%. The oil-water separation performance could reach up to 99.6 %. Through comprehensive comparison, the porous silicate cement membrane with 1.0 wt% TEA showed better holistic preponderance of oil-water separation and permeation flux. Quantum chemistry calculation and MD simulation were used to briefly explain the influence of TEA on phase transformation. MD showed that adding TEA changed the morphology and structure of ice crystals. The percentage of the Ih structure significantly increased from 53 % to 86 % after adding TEA. This study might expand the application of TEA in other aspects and enlighten relevant workers in new experimental designs. [Display omitted] • TEA noticeably changed the pore morphology form lamellar to cellular structures. • Cement membranes doped TEA showed excellent separation performance and stability. • Effects of TEA on crystals were analyzed via quantum chemistry and MD simulation. [ABSTRACT FROM AUTHOR]

An analysis is made on the effect of magneto hydrodynamics on poro-circular stepped plates lubricated with micropolar fluid. The modified Reynold's equation leads to the development of a closed form expression for pressure, load sustaining capacity, and squeezing time. The impact of porosity is analyzed using the modified Darcy's equation, and the outcomes are compared with the cases of the presence and absence of porosity on the same circular stepped plate. The external magnetic field influences the bearing's efficiency by increasing the pressure, load sustaining capacity, and squeezing time performance. In the presence of porosity, the pressure, load sustaining capacity and squeezing time decrease compared to the absence of porosity, and the comparisons are shown in the tables. The variation of the highly influenced parameter of the bearing system is represented graphically. [ABSTRACT FROM AUTHOR]

Soybean is a source of high-quality vegetable protein and a suitable substitute for meat protein. However, several factors, including a lengthy cooking process, palatability issues, and digestion concerns, have limited their consumption. Several treatments have been suggested to overcome such issues, including infrared heating, which has many advantages over traditional roasting methods. In this study, the three-dimensional microstructure of soybeans with initial moisture contents (12, 16, 20, and 24% w.b.) and treated at different micronization durations (60, 90, and 120 s) at 180 °C were studied and related to quality parameters including water absorption and hardness of both non-cooked and cooked samples. The water absorption tests demonstrated no significant difference (p > 0.05) between the moisture absorbed for 60, 90, and 120 s micronization with initial moisture levels of 12, 16, and 24%. Yet all soybeans treated for 60 s exhibited significantly different results (p < 0.05) compared to raw counterparts. The highest hardness values were achieved after 60 s treatments on 24% moisturized seeds. As expected, the 20 min cooking time resulted in a considerable reduction in soybean hardness. The X-ray micro-computed tomography (micro-CT) was a powerful non-destructive tool to explore the microstructure of individual soybean seeds. Results of X-ray micro-CT have shown an increase in open porosity with increasing infrared treatment time. Overall, the qualitative and quantitative analysis provided in this study may serve as a basis for developing improved food processing techniques. [ABSTRACT FROM AUTHOR]

As a first attempt, the vibrational behaviors of point supported truncated conical sandwich shells with circumferential stiffeners, graphene platelets reinforced composite porous core and face sheets (GPLRC-PC-FS) are investigated. The point supports are simulated using the conventional elastic translational and rotational springs, which can be easily converted to the classical boundary conditions. The face sheets, porous core and the circumferential stiffeners are co-axially and perfectly bonded, and each of these components are reinforced by uniformly distributed and randomly oriented graphene platelets (GPLs). The motion equations are derived using a zigzag shell theory based on the first-order shear deformation theory (FSDT) in conjunction with the Chebyshev-Ritz method. The results are validated by carrying out the convergence study and performing the comparison studies with existing solutions in the literature. After that, the influences of porosity and its structures, the GPLs weight fraction and geometric dimensions, face sheets, geometric parameters of the shell, boundary conditions, and the stiffener parameters on the results are investigated. The results show that the number of point supports plays an important role on the fundamental frequency of the considered shells. Moreover, it is found that the porosity and its distribution pattern and circumferential stiffeners have considerable effects on the natural frequencies. Also, the results reveal that by adding a very small amount of GPLs, the frequencies increase significantly. [ABSTRACT FROM AUTHOR]

In this study, a novel methodology for the fabrication of gradient porous structures is introduced, predicated upon the phase evolution characteristics of immiscible polymer blends. Initially, a comprehensive flow-phase field dynamics model is developed. This model couples the principles of phase field theory and the dynamics of fluid flow to the two-phase evolution process, facilitating a numerical simulation of the phase evolution. Subsequently, the phase field parameters of model are determined and combined with the temperature field, thereby enabling a targeted and controlled fabrication of gradient porous structures. Finally, the efficacy and practical applicability of the proposed methodology are substantiated through the construction of illustrative examples. This approach, as delineated herein, provides a robust framework for the efficient design and realization of intricate, interconnected gradient porous structures with potential applications in various scientific and engineering domains. [ABSTRACT FROM AUTHOR]

The properties of graphene oxide–detonation nanodiamond composites obtained as a result of heterocoagulation of graphene oxide and hydrogenated detonation nanodiamonds in aqueous mixtures were studied. The resulting composites with different proportions of graphene oxide and detonation nanodiamond were subjected to drying and subsequent heat treatment in a vacuum, converting graphene oxide into graphene. The structure of the composites was studied using electron microscopy and Raman spectroscopy. The specific surface area and porosity of the obtained samples were studied by analyzing nitrogen adsorption isotherms. A model for the composite formation and a possible technology for producing a material based on it with different specific surface area values and pore structure are proposed. It is shown, that the largest possible specific surface area of two-component structures of the «DND/GO» type does not exceed 500 m2·g−1. It was also concluded that it is necessary to achieve a uniform distribution of detonation nanodiamond particles over the surface of graphene sheets. [ABSTRACT FROM AUTHOR]

The global increase in water consumption has led to significant domestic wastewater (DW), with only 55.5% being treated properly. Discharging untreated DW has serious environmental consequences and wastes a valuable resource. Therefore, this study proposed replacing 25%–100% potable water with DW in preparing alkali-activated slag (AAS) mortars. The results indicated that the use of DW promoted the hydration of AAS. Pore structure analysis revealed that DW enhanced the formation of gel pores while reducing mesopores, resulting in a higher elastic modulus and a denser microstructure of AAS mortars. Consequently, the compressive strength of AAS mortars increased by 9.0%–20.3%, and the autogenous shrinkage decreased by 7.5%–34.5%. Moreover, replacing 100% of potable water with DW maximizes its utilization and improves the cost–benefit and eco-efficiency of AAS mortars by 9.4% and 10.0%. These findings demonstrate the feasibility of using DW as mixing water for AAS mortars, offering a sustainable approach to the utilization of DW. [ABSTRACT FROM AUTHOR]

Spent waterglass foundry sand (SWFS) is a major waste in foundry industries and should be disposed of preferentially. Two SWFS subjected to working temperatures of 100°C (SWFS1) and 800°C (SWFS8) were prepared to investigate their effects on the flow, compressive strength, micromechanical properties, and pore structure of alkali-activated slag (AAS). Experimental results confirmed that the overall performance of AAS was determined by the dissolved properties of the dried waterglass coating and the content of SWFS. The flow values of AAS in the first 1 h were increased by adding two SWFS. SWFS1 can release abundant silica tetrahedra into the activation system, contributing to micromechanical and macromechanical properties. The compressive strength of SWFS1 -added AAS mortars was increased by 28.8% to 49.0% at 28 days. In contrast, SWFS8 exerted weaker dissolved properties. The compressive strength of AAS mortars was slightly enhanced and the maximum increment at 28 days was only 8.5%. In summary, this paper confirmed the feasibility of using SWFS as reactive fine aggregates for AAS owing to the dried waterglass coating. [ABSTRACT FROM AUTHOR]

Based on investigated mechanical properties of alkali residue-based foamed concrete (A-FC), this paper presents a comprehensive examination of the microstructural features of A-FC and their impact on compressive properties. A detailed investigation of the compressive performance and pore structure characteristics was conducted through compression tests and low-field nuclear magnetic resonance (NMR) tests. The results demonstrate that the primary pore size in A-FC falls within the microscale, and the pores can be categorized into three types—gel pores, capillary pores, and air voids. In addition, the T2 spectrum of A-FC exhibits three distinct relaxation peaks, each of which is attributed to different water components, i.e., adsorbed water, pore water, and free water. As the pore size, air void ratio, and porosity increase, the compressive strength of A-FC decreases. The main reasons for the increased in strain in low-strength A-FC include compression at the bottom, internal stress dissipation through the pore structure, and changes in the failure mode. [ABSTRACT FROM AUTHOR]

Freeze-thaw resistance ability of concrete is an important issue when evaluating its durability. In this research, the objective was to predict concrete resistance to such cycles by analyzing water absorption based on the critical water saturation theory. In order to achieve this goal, detailed experiments were conducted, including water absorption, pore structure scanning, and mercury intrusion porosimetry of concrete with air-entraining admixture and different fiber content to obtain critical indicators, such as water absorption, porosity, and air void spacing factor, which formed the basis for predicting the service life of concrete. To predict the service life of concrete under freeze-thaw cycles, the critical saturation theory was utilized, taking into account environmental parameters and experimental indexes. The service life of concrete against freeze-thaw using air-entraining admixture and fibers had been calculated quantitatively in this paper. The results show that the predicted service life of concrete with air-entraining admixture was increased by more than 50 times, and using both air-entraining admixture and fiber could increase the service life by more than 80 times, even reaching 249 years. [ABSTRACT FROM AUTHOR]

The hydration reaction mechanism of geopolymers is intimately linked to their composition and structure. Additionally, pore structure characteristics play a vital role in the properties of hardened geopolymer pastes, significantly influencing the material's strength, impermeability, and thermal conductivity. In this study, fly ash geopolymer (FAG) was synthesized by utilizing NaOH, Na2SiO3 , and low-calcium fly ash. The pore structure characteristics of FAGs were analyzed using mercury intrusion porosimetry (MIP), and the fractal dimension of FAGs was calculated using the Menger sponge model (Df) and a fractal model based on thermodynamic relationships (Ds). Fourier infrared spectroscopy (FTIR), thermogravimetric differential thermal (TG/DTA), and scanning electron microscopy secondary electron phase (SEM-SE) were used to test the composition of the hydration products of FAGs and their microscopic morphology. The results showed that after 90 days of maintaining ambient temperature, the porosity of FAG is between 20% and 30%, and the most available pore size is 10–50 nm. The fractal dimension calculated using the analytical model based on thermodynamic relations can more comprehensively determine the pore structure characteristics of FAG. The geopolymerization reaction process of fly ash particles can be categorized into four primary processes, forming an amorphous aluminosilicate gel as the hydration product. [ABSTRACT FROM AUTHOR]

Soil improvement via cement-based stabilizers is often necessary to improve the workability and strength of problematic soils. However, understanding the underlying mechanisms of the stabilization process merits further study, particularly concerning changes in the microscale structure that affect macroscale behavior. Mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) are often paired to characterize the microstructure and pore networks and can be used to quantitatively describe pore structure and surface complexity. Fractal geometry (e.g., fractal dimension and lacunarity) has been shown to provide a quantitative description of structural complexity in nature. Therefore, these fractal geometry fundamentals (fractal dimension and lacunarity) were implemented in the analysis of SEM micrographs and MIP results of a single-mineral kaolinitic soil (SA-1 kaolinite) stabilized with a portland cement stabilizer (portland cement Type I/II) to better understand the evolution of the soil microstructure with curing time. Particle size distributions (PSD) were developed based on image analysis of SEM micrographs collected at curing times of 1, 7, 14, 28, and 90 days. The surface fractal dimension obtained via analysis of MIP results was used to describe changes occurring in the pore network with curing time. The formation of cementitious products was inferred from changes in the PSD as gels first formed and then fused with clay surfaces. Box-counting fractal dimensions and lacunarity showed evidence of particle restructuring with cementation. The transition pore size between intraaggregate and interaggregate pores, obtained via fractal analysis of MIP data, decreased with curing time, indicating the formation of hydration products with stabilization. Using fractal geometry to help analyze the microstructural properties of stabilized clays may lead to better insight into their engineering scale behavior. Practical Applications: Problematic soils pose an expensive problem to engineers and are often treated with cement-based stabilizers to improve strength and decrease compressibility or the potential to deform or collapse. However, the underlying mechanism causing problematic behavior, such as low strength or shrinking and swelling, is not well understood and techniques to characterize these soils at the microscopic level are needed to better prevent the damage posed to infrastructure. The current standard of practice utilizes only qualitative measurements of the soil structure and cannot be used in models attempting to predict clay behavior. Therefore, concepts from fractal geometry were used in this study to provide a quantitative, measured value of the soil and pore surface which can be used in future models. Analysis of images at the microscale provided a quantitative measurement of the change in soil structure as stabilization reactions occurred. Moreover, the geometric parameters obtained showed strong correlations with strength values, indicating the utility of the technique for predicting engineering behavior. The results of this study show promise for adapting the box-counting procedure to other, more complex soils. Additionally, because there was a good correlation between the fractal parameters and strength, the results should be correlated with other soil parameters. [ABSTRACT FROM AUTHOR]

Bentonite, used as a barrier material in landfill systems and the geological disposal of radioactive waste, undergoes various processes such as the cation exchange with landfill leachate and repository groundwater, desiccation shrinkage due to heat released from solid waste or nuclide decay. In the context of these engineering applications, it is crucial to consider the effect of interlayer cation composition on the desiccation-shrinkage behavior of bentonite for assessing the long-term performance of barrier systems. This study investigates this impact by conducting desiccation tests on four different cation-type bentonite samples (i.e., K-, Na-, Ca-, and Mg-bentonite) and elucidating the underlying mechanisms through mercury intrusion porosimetry test, X-ray diffraction analysis, and suction measurements. The results indicate that K-bentonite exhibits the highest water evaporation rate and the lowest shrinkage potential, with no shrinkage cracks detected, and that Na-bentonite evaporates water at a relatively fast rate but presents the most pronounced volumetric shrinkage. In contrast, Ca- and Mg-bentonite have the highest water-retention capacity, and their shrinkage potentials are less than Na-bentonite. An improved shrinkage model is proposed, which is shown to describe the measured shrinkage curves for four types of homoionic bentonite samples. Additionally, the mechanism behind the effect of different interlayer cations was interpreted in terms of the interlayer–cation–water interaction, pore structure evolution, and soil suction variation. [ABSTRACT FROM AUTHOR]

The present study reports the investigation of the influence of naphthalene–camphor binary solvent and the densification process on the pore structure formation of α‐alumina monoliths using the freeze‐casting technique with a freezing temperature control mechanism. Freeze‐casting technique allowed a controlled production of monoliths with high porosity (65%–70%) and distinct pore morphologies based on the adjustment of solvent composition (hypoeutectic, eutectic, and hypereutectic) and sintering time. In general, the longer the sintering time, the greater the average pore diameter (8–10 µm), the larger the grain size (∼319–596 nm), the higher the material density (∼1450–1650 kg/m3), the lower the open porosity (∼60%–49%), the higher the closed porosity (5%–18%), and the greater the compressive strength of the monoliths (hypoeutectic: 23.56 MPa; eutectic: 4.81 MPa; hypereutectic: 23.49 MPa). The study also reveals that the solvent composition directly influenced the alignment of the pore structure, as the pores of the final monolith resemble frozen solvent crystals. Hydraulic tortuosity varied from 1.30 to 1.53 for selected samples. Finally, solvent composition and sintering time proved to be important parameters that should be considered in the manufacturing process of porous ceramic structures via freeze casting. [ABSTRACT FROM AUTHOR]

Maintaining high surface area and porosity at high temperatures is important when considering aerogels for use in thermal management systems. The mesoporous structure of aerogels results in extremely low thermal conductivity, making them lightweight, high performance insulating materials. Maintaining these properties requires innovative routes to suppress sintering and pore collapse as use temperatures rise. The current work aims to improve the pore structure stability of yttria‐stabilized zirconia aerogels by the addition of a SiO2 coating. The functionalization of surface hydroxyl groups by the addition of SiO2 is hypothesized to mitigate condensation reactions, which are a driving force for shrinkage and pore structure collapse. Zirconia aerogels with 0, 10, and 30 mol% yttria (YO1.5) additions were coated in a tetraethyl orthosilicate (TEOS) solution and exposed to temperatures up to 1200°C. Crystal structure, pore structure, and aerogel morphology were investigated to understand changes in aerogel thermal stability. The SiO2 coating exhibited a greater influence on pore stability over yttria concentration, with specific surface area of the coated aerogels being twice that of the uncoated aerogels up to 1000°C. However, the presence of the SiO2 coating promoted rapid sintering and densification at 1200°C, establishing an upper use temperature for SiO2 and a need to develop other coating chemistries. [ABSTRACT FROM AUTHOR]

We prepared yttria‐stabilized zirconia (YSZ) and titania crystalline thin films on polycarbonate (PC) substrates by the sol‐gel transfer technique that we have developed recently. Precursor gel films were deposited by spin‐coating on a polyimide/polyvinylpyrrolidone mixture layer on Si(100) substrates, and then were calcined at 600°C. The spin‐coating and the calcination were cycled, followed by final firing at 600–1000°C, to obtain 140–190 nm thick, YSZ and titania crystalline thin films. The film densification progressed as the final firing temperature increased, where the porosity calculated from the refractive index decreased down to a few percent. The film thus obtained was heated at 190°C on a hot plate, and a PC substrate was pressed on the film to transfer it to the PC substrate. The transferability quantified by image analysis of the film area was found to be significantly different between the YSZ and titania films. In the case of YSZ films, the area of silicon that was fractured and adhered to the transferred film increased significantly with increasing firing temperature, leading to a decrease down to 0% in the fraction of the successful transfer area without such a damage. On the other hand, the fraction of the successful transfer area remained around 90% irrespective of the firing temperature for the titania films. The surface of the titania films that were fired at 800–1000°C and transferred to PC substrates had voids of several tens nm scale, which may have been formed during anatase‐to‐rutile phase transformation. We thought that the reduced titania/Si(100) contact area due to such void formation facilitated the delamination of the titania films from Si(100) substrates. High temperature firing, which promotes crystallization and densification of films, thus affects differently the film transferability to plastic substrates, depending on the type of films. The work also suggested possible use of titania films as release‐assisting layers. [ABSTRACT FROM AUTHOR]

Functionally graded materials with porosity have received increased application in satellites, space vehicles, aircraft, and other transportation systems. The multi-physics coupled modeling technique for structural response analysis remains a big challenge. This paper develops a finite element formulation based on the first-order shear deformation (FOSD) hypothesis for evaluation of the static and dynamic behavior of functionally graded magneto-electro-elastic porous (FG-MEEP) cylindrical shells under thermal loads. Four types of thermal loads such as uniform, linear, sinusoidal, and heat conduction temperature rise are included in the FE model. Furthermore, FG-U, FG-V, FG-O, and FG-X distributions of porosity is considered. The material parameters of FG-MEEP are obtained by modified power law. Two forms of material gradation in the framework of 'B'-rich bottom and 'F'-rich bottom are used. The correctness of the present model is verified by comparing with the results of literature. Finally, parametric studies are adopted to analyze the static and dynamic response of FG-MEEP cylindrical shell by varying functionally graded pattern, gradient index, porosity volume, temperature, porosity distribution, etc. These numerical results can serve as benchmarks for the future study of porous structures in thermal environment. [ABSTRACT FROM AUTHOR]

Developing and designing carbon-free refractory materials is an effective alternative to MgO–C refractory materials to produce large-scale, high-quality, low-carbon special steels. Therefore, in this work, excessive MgO is introduced into MgAlON to prepare a series of MgO–MgAlON composite refractories. The enhancement mechanism of comprehensive performance is systematically evaluated, where MgO as a reinforcer features intergranular phase strengthening and grain boundary purification effects. Besides, the pore structure of MgO–MgAlON composite refractories is also optimized to regulate the molten slag wetting behavior. The results demonstrated that MgO–MgAlON composite refractories have apparent porosity of 13.86%–15.84 %, bulk density of 2.78–2.97 mg cm−3, and compressive strength of 204.17–253.97 MPa. When 42.8 % MgO is introduced, the sample strength retention ratio after thermal shock measurement and slag corrosion experiments are 64 % and 75 %, respectively. Consequently, a cost-effective and feasible reinforcement strategy for MgO–MgAlON composite refractories is proposed, paving the way for. [ABSTRACT FROM AUTHOR]

Resin materials feature exceptional physical properties and inexpensive cost, but unfavorable surface characteristics, such as low wear resistance and poor erosion wear performance, render them tough to satisfy greater demands. The potential option is to prepare supersonic plasma sprayed Al 2 O 3 -13 wt%TiO 2 /Al 2 O 3 -phenolic resin (AT13/Al 2 O 3 -PF) coating on the surface of the resin matrix. AT13 feedstocks are classified into two types: Al 2 O 3 -13 wt%TiO 2 powder prepared by the agglomeration granulation process (AT13-1) and the mixture of spherical Al 2 O 3 and TiO 2 (approximately 13 wt%) powder (AT13-2). The effect of component dispersion on mechanical and tribological characteristics of coatings was thoroughly investigated, as well as the solid particle erosion wear behavior of coatings. The results illustrated that the evenly dispersed TiO 2 phase in AT13-1 coating was prone to homogenize the coating structure, resulting in better tribological characteristics than AT13-2 coating, although erosion wear performance was inferior to AT13-2 coating. The wear rate of AT13-1 coating was 1.36 × 10−5 mm3 (N m)−1, which was 1/21 times that of AT13-2 coating. At the 60° erosion angle, the high porosity of AT13-1 coating resulted in hard phase cracking or hard phase debonding. The high microhardness of AT13-2 coating reduced erosion wear at the 90° erosion angle. [ABSTRACT FROM AUTHOR]

Porous mullite ceramics exhibit exceptional mechanical and thermal properties in high-temperature environments, making them suitable for applications in thermal insulation. However, a notable challenge associated with high porosity is the tendency for increased sintering shrinkage during the sintering process. The sintering shrinkage can lead to unpredictable cracking and deformation, negatively impacting the final properties of the porous ceramics. In this study, porous mullite ceramics were fabricated using aluminium powder, alumina powder, and silica sol through foam-gelcasting and freeze-drying methods. The oxidative expansion of the aluminium powder was employed to offset the sintering shrinkage. The influence of alumina powder content on the microstructure and properties of porous mullite ceramics was investigated. Particularly, at the alumina content of 50 wt%, the porous mullite ceramics exhibited near-zero sintering shrinkage (0.3%). These ceramics demonstrated high porosity ranging from 78.9% to 83.3%, accompanied with low thermal conductivity (0.24-0.29 W/(m·K)) and great mechanical properties (0.51-1.02 MPa). The temperature difference over 750 °C revealed porous ceramics get excellent thermal stability as ideal lightweight high-temperature thermal insulation materials. This innovative approach presents a novel idea for fabricating complex net-shape porous mullite ceramic components with enhancing yield and low cost. • Near-zero sintering shrinkage porous mullite ceramics were prepared by foam-gelcasting combined with freeze-drying. • The microstructure and properties of porous mullite ceramics was tailored by the ratio of alumina and aluminium. • High porosity, low thermal conductivity and excellent thermal insulation performance were achieved. [ABSTRACT FROM AUTHOR]

Tight carbonate reservoirs are complicated by their vast heterogeneity, which is attributed to diagenetic and depositional processes. The new discovery of natural gas in the tight carbonate reservoir of the Upper Cretaceous Kawagarh Formation (KF− UC) in Pakistan makes it crucial to study the factors controlling reservoir properties. This study investigated the sedimentology and reservoir characteristics of KF− UC using integrated petrography, scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS), and petrophysical techniques. The microfacies analysis of KF− UC indicates mudstone and wackestone, identified in the proximal and distal outer ramp settings of the homoclinal carbonate ramp. Diagenetic processes such as compaction, micritization, dolomitization, cementation, neomorphism, and dissolution, which represent meteoric and marine phreatic mixing zones and burial diagenetic settings, have modified the reservoir characteristics of KF− UC. The net porosity of KF− UC could be enhanced by dolomitization, dissolution, and fracturing, making it a better petroleum reservoir. With an average porosity of 2.3%, microporosities such as intercrystalline/interparticle, intracrystalline/intraparticle, vuggy, and fracture were identified in KF− UC, designating it as a tight carbonate reservoir. The outcrop and well data exhibit excellent correlation; nevertheless, the well’s net pay is inadequate due to the influence of complex tectonic structures along significant faults within the study area. Furthermore, the results of this study were compared with the Gurpi Formation of Zagros Basin, Iran, and the Aruma Formation of Central Saudi Arabia, highlighting similar sedimentological characteristics, thus emphasizing the need to initiate such projects in other regions with similar settings to further strengthen petroleum exploration. [ABSTRACT FROM AUTHOR]

Hierarchical cellular ceramics have attracted considerable interest due to their versatility and unique physico-mechanical effectiveness for advanced applications. Tailorable alumina foams with low shrinkage were fabricated through an innovative combination of 3D printing and sacrificial templating with low environmental footprint. The viscoelastic pastes were formulated using the aqueous-based solution of binder, dispersant, and plasticizer with different volumes of α-alumina and lightweight hollow microspheres (HMs) as a template. The solid-to-liquid ratio increased 53–80 vol% with the inclusion of HMs for printable rheology. Cellular architectures of alumina were structured through a material extrusion-based technique and then thermally treated at 1200 °C. Finally, the alumina monoliths achieved a ∼55–93 % porosity with three different types of adjustable pores, produced by combining 3D printing, burning of templates, and inter-particle voids. The HMs generated spherical pores (7–47 µm) in the printing struts with reduced CO 2 emissions compared to conventional sacrificial porogens during the burnout process. [Display omitted] • Alumina monolith appears a density of 0.31 g/cc with tailorable pores of 93 %. • Aqueous-based pastes are designed using lightweight hollow microspheres template. • The 3D printing paste is formulated with a solids-loading of up to 80 vol%. • Foam with three different sizes pore is fabricated by 3D printing and microspheres. • The study is an ecological approach for lightweight low shrinkage alumina foam. [ABSTRACT FROM AUTHOR]

For marine soft soil under the periodic wave loading, the pore water content in soil suffering dry-wet cycle for a long time, which affects its microstructure and macroscopic mechanical strength, resulting in insufficient bearing capacity and excessive deformation of soft soil. To reveal the microstructural characteristics and strength attenuation law of marine soft soil under dry-wet cycle condition, electron microscopy scanning and direct shear tests under different times of dry-wet cycles were carried out, and the mathematical equations of pore structure and strength parameters were established based on fractal theory. The research results showed that: (1) The pore structure changed considerably after the first dry-wet cycle, and then changed gently with the increase of dry-wet cycle times, which was reflected by the fractal dimension D value decreases to a constant value gradually. (2) The shear strength of the soil diminishes with an increase in the number of dry-wet cycle times, and the maximum attenuation occurs after the first dry-wet cycle. (3) The relationship between cohesion (c), internal friction angle (φ), and fractal dimension (D) is exponential, with the curve shapes being concave and convex, respectively. [ABSTRACT FROM AUTHOR]

Despite the many advantages that additive technologies have over subtractive ones, low porosity levels, good mechanical properties, and low residual stresses remain the most pressing issues that need further research. In particular, the latter can cause a mismatch between the desired geometry and the geometry that can be achieved. In this work, a process window for the Laser Powder Bed Fusion (LPBF) process of Ti-6Al-4V alloys, has been identified. The micro-warping phenomenon, which causes the deformation of the printed part during the printing job and the failure of the process, was taken into account together with the parts' strength, ductility, and porosity. The occurrence of micro-warping phenomena was assessed by the new Warping Alert (WA) parameter, which depends on the parameters P and v. It was found that, before balling, micro-warping limits the process window in the laser power (P) – laser velocity (v) plane. However, optimal mechanical performances can be found in the proximity of the micro-warping zone, thus making it extremely important to determine the WA threshold value to the process design. [ABSTRACT FROM AUTHOR]