Open Porosity Research Articles

Performance of self-compacting concrete with treated rice husk ash at different curing temperatures

Self-compacting concrete (SCC) is currently gaining traction as a replacement to conventional vibrated concrete. Its distinct microstructure leads to varied mechanical behaviour under different curing temperatures. In the past various supplementary cementitious materials (SCMs) were used in SCC to investigate their respective effects on the performance. However, there has been no systematic studies conducted to determine the effect of different curing temperature on the sensitivity reaction of rice husk ash (RHA) in SCC. This research focuses on high-strength SCC with SCMs such as RHA, silica fume (SF), fly ash (FA), and ground granulated blast-furnace slag (GGBS), exploring their applicability for concrete structures under varying curing temperatures. Heat of hydration, compressive strength and open porosity of SCC specimens were assessed at various temperature. Results indicate high curing temperatures expedite the hydration and pozzolanic reaction, refining the microstructure and increasing the early-age concrete strength, but compromising the long-term performance, potentially mitigated by the use of SCMs. Conversely, lower curing temperature, impedes hydration leading to gradual strength gain, particularly with SCMs, yet yielding significant strength increases at later concrete age. SCMs presence and curing temperature significantly influence maturity function-based strength predictions, impacting strength trends in the samples studied.

Additive manufacturing of alumina refractories by binder jetting

In this work, refractory components based on alumina were produced by binder jetting using a large-scale 3D printer. The formulation contained several particle fractions up to a grain size of 3 mm, equal to the printer resolution. The binder system contained fine dead burnt magnesia, milled citric acid and reactive alumina, which were added to the aggregate mixture to create the powder bed. Deionized water was deposited from the printer's nozzles and triggered the binding reaction between the magnesia and citric acid. After 24 h, the printed samples were removed from the powder bed, dried and sintered at 1600 °C for 5 h. Reactive alumina contributed to the in situ creation of magnesium aluminate spinel at high temperature. The samples were characterized in terms of Young's modulus of elasticity, bending and compressive strength in 2 directions (parallel and perpendicular to the printing direction). The broken parts were used to investigate physical properties such as the open porosity and bulk density. The microstructure was studied by means of computed tomography. Finally, powder samples were used to determine the phase composition at different stages of production by means of XRD.

Characteristic parameters and radon exhalation rates of aerated concrete blocks

ObjectiveTo understand the characteristic parameters and radon exhalation rates of aerated concrete blocks. MethodsA total of 39 nationally inspected samples were measured. Their dry density was determined based on their mass and volumes, their porosities were measured on the principle of volumetric expansion, and their radium content was determined using a high-purity germanium (HPGe) detector for gamma-ray spectroscopy. Furthermore, their diffusion lengths were quantified by establishing a combined cumulative and diffusion chamber, and their radon exhalation rates were measured through closed-box testing using a continuous radon monitor. ResultsThe aerated concrete blocks exhibited dry densities ranging from 464 to 840 ​kg/m3 [average: (654.0 ​± ​82.5) kg/m3], open porosities from 67.1 ​% to 81.1 % [average: (74.3 ​± ​3.3) %, radium (226Ra) content from 12.3 to 136 Bq/kg [average: (63.0 ​± ​30.4) Bq/kg], diffusion lengths from 0.49 to 1.01 ​m [average: (0.70 ​± ​0.15) m], and radon exhalation rates from 0.6 to 22.8 Bq·m−2·h−1 [average: (7.3 ​± ​5.3) Bq·m−2·h−1]. ConclusionAerated concrete blocks exhibit significantly higher porosities, diffusion lengths, and radon exhalation rates than traditional concrete and clay bricks. These blocks might contribute to the high indoor radon concentration observed in modern buildings in China.

Highly Porous Co-Al Intermetallic Created by Thermal Explosion Using NaCl as a Space Retainer.

Co-Al porous materials were fabricated by thermal explosion (TE) reactions from Co and Al powders in a 1:1 ratio using NaCl as a space retainer. The effects of the NaCl content on the temperature profiles, phase structure, volume change, density, pore distribution and antioxidation behavior were investigated. The results showed that the sintered product of Co and Al powders was solely Co-Al intermetallic, while the final product was Co4Al13 with an abundant Co phase and minor Co2Al5 and Co-Al phases after added NaCl dissolved out, due to the high Tig and low Tc. The open porosity of sintered Co-Al compound was sensibly improved to 79.5% after 80 wt.% of the added NaCl dissolved out. Moreover, porous Co-Al intermetallic exhibited an inherited pore structure, including large pores originating from the dissolution of NaCl and small pores in the matrix caused by volume expansion due to TE reaction. The interconnected large and small pores make the open cellular Co-Al intermetallic suitable for broad application prospects in liquid-gas separation and filtration.

Investigation of End-of-Life Chrome-Magnesia Refractories Using X-Ray Computed Tomography

The lifespan of refractory linings is a major industrial concern for safety, on-line availability, and financial reasons. In copper smelting, batchwise operating matte converters are the furnaces that pose the greatest challenge when it comes to refractory wear and lining life. In this work, the structure and morphology of used magnesia–chrome bricks were studied using X-ray computed tomography and mineralogical techniques. The bricks were taken from various locations of an end-of-life brick lining of an industrial Peirce–Smith converter, after a normal campaign at Boliden Harjavalta smelter (Finland). The results show that it is possible to visualize in 3D, e.g., porosity, metal-containing phases, and refractory magnesia in the used bricks. Different digital images, such as cross-sections and average volume fractions, were used as a non-destructive method to characterize the bricks’ internal structure. The metal/matte infiltration in the open porosity was found to differ based on the location in the converter, with some bricks having no metal/matte infiltration and the tuyere line showing metal/matte infiltration at a depth of about 100 mm from the hot face.

Use of a Glaciogene Marine Clay (Ilulissat, Greenland) in a Pilot Production of Red Bricks.

Uplifted occurrences of fine-grained glaciogene marine sediments are found throughout the northern hemisphere. These sediments could be used to produce local construction materials, to rely less on imported construction materials from southern regions. In this study, a representative occurrence from Ilulissat, West Greenland, was investigated as a potential resource for local brick production. The study comprised three parts: (1) raw material characterization based on grain size distribution, major element chemistry, including total carbon, sulfur, and chloride concentrations, mineralogy, morphology, and Atterberg limits; (2) the production of test bricks at a Danish brickwork; and (3) testing of the bricks based on total shrinkage, water absorption, hygroscopic adsorption, open porosity, bulk density, compression strength, and mineralogy. The bricks produced proved to have excellent compression strength, low open porosity, and low water absorption. The shrinkage could be reduced by adding 10% chamotte to the marine sediment. Based on the investigated properties, this indicates that this type of clay is highly suitable as a resource for bricks.

Preparation of graphite/silicon carbide based on SLS/LSI and study of properties

In this paper, graphite/silicon carbide composites with an integrated structure–function were prepared by selective laser sintering (SLS) and liquid silicon infiltration (LSI). The study investigated the influence of different factors on the microstructure, mechanical properties, and thermal conductivity of graphite/silicon carbide composites. The results demonstrated that the open porosity of the precast body gradually decreased with an increase in the content of mesocarbon microbeads (MCMB), while the carbon content gradually increased. The density, mechanical strength, and thermal conductivity (TC) of the composites initially increased, followed by a subsequent decrease. In the absence of MCMB, micropores and a significant amount of free silicon were observed within the composite after LSI, leading to reduced density and mechanical properties. Conversely, the inclusion of 20 wt% MCMB led to the elimination of micropores and free silicon within the composite, resulting in the highest density and TC values of 2.52 g/cm3 and 73.22 W/m·K, respectively. The measured TC values were consistent with those calculated by the Effective Medium Theory Model (EMT). At a 40 wt% addition, micropores and free silicon reappeared within the composites, leading to a decrease in density and properties. Furthermore, the calculated values of the five thermal conductivity models were found to be higher than the measured values. This paper presents a further improvement in the process of preparing graphite-ceramic composites with a complex structure, achieved by controlling the amount of MCMB added. This contributes to the subsequent research.

Investigating the effect of polymer additives on the rheology of SiC/clay paste for use in Direct Ink Writing method

AbstractIn this study, we investigated the impact of polyethylene glycol, sodium carboxymethyl cellulose, and polyvinyl alcohol on the rheological behavior, printability, and mechanical/physical properties of 3D‐printed scaffolds for high‐temperature applications using SiC/clay ceramic paste. Employing the Direct Ink Writing method, varying concentrations of each polymer (PEG: 2.5%–10% weight, CMC: .6%–1.8% weight, PVA: .25%–1% weight) were incorporated into the composition. The resulting SiC/clay paste, with adjusted additive content, was used to 3D‐print scaffold structures through Direct Ink Writing. Sintering of clay‐bonded SiC samples were carried out at 1300°C for 1 h in an ambient atmosphere. The research revealed that altering the additive amounts significantly influenced the rheological behavior, mechanical properties, and physical characteristics of the printed specimens. Notably, the ideal properties with additive concentrations (10% wt PEG, 1% wt PVA, and .6% CMC) were identified, providing the best outcomes in terms of printability and firing results. High density samples with 2.09, 1.93, and 1.79 g/cm3, high compression strength of 20.82, 14.5 and 12.53 MPa with 32.26%, 42.5%, and 52.63% open porosity for samples containing PVA, CMC, and PEG modifiers were obtained, respectively. Additionally, the study led to the development of a high solid loading printable paste with an 80% weight.

Analysis of porous alkali activated materials using bauxite residue as principal precursor

Bauxite residue is a red-hued and mineral-rich material that is released from the production of alumina during the Bayer process. There are large areas of land across the world dedicated to the storage of this underutilized material. The growing nature of the alumina-producing industry implies that the production of bauxite residue will increase, which necessitates solutions for valorizing bauxite residue. One area of research involves using bauxite residue as a precursor in preparation of porous alkali activated materials and the novelty of the study is to make porous alkali-activated material with bauxite residue. Porous AAMs have applications as industrial adsorbents and as insulating materials. This study focused on the pore analysis of AAMs prepared with a high proportion of bauxite residue and fly ash addition, using varying percentages of hydrogen peroxide and added water to form the pore structure, with hydrogen peroxide and water acting as a “green reagent”. The sample containing the highest percentage of added water displayed the highest open porosity, with the sample consisting of large millipores and the widest distribution of pore sizes out of all the samples. The samples containing only hydrogen peroxide displayed a uniform distribution of smaller pores as measured by nitrogen adsorption. The study describes a process to create highly porous AAMs in low temperatures using a limited number of constituents. Furthermore, it optimizes the variation of hydrogen peroxide and added water to tailor the pore character depending on the desired application of the material, with only as much as 3 % hydrogen peroxide needed for porosity. The porous alkali-activated bauxite residue has the potential to be used as insulating material in the building.

Mineral trioxide aggregate obturation quality with two obturation techniques in severe curved root canals – a micro-CT study

BackgroundThe existence of voids within the mineral trioxide aggregate (MTA) composition is one of the factors that can influence the treatment outcome. The primary objective of this study was to quantitatively assess and compare the MTA orthograde obturation quality in severe curved root canals using two different MTA compaction techniques: manual compaction with K-file, or Auger technique using micro-computed tomography (micro-CT) imaging.MethodsFor this study, 26 mandibular first molar teeth with severely curved mesiobuccal root canals were selected. These samples were randomly divided into two groups. All root canals were instrumented using ProTaper Gold rotary files up to the F3 file at the working length. In one group, OrthoMTA was compacted using a stainless steel K-file, while in the other group, the Auger technique was employed for compaction into the root canals. Once the MTA had completely set, the filled root canals were subjected to scanning using a high-resolution micro-CT scanner. The porosity volume was determined as a percentage in relation to the overal volume of the canal, and the collected data were subjected to analysis using SPSS software, with the significance level set at P < 0.05.ResultsThe two techniques had no significant difference in open, closed, and total mean porosity. In both groups, the mean of open porosity was significantly more than closed porosity.ConclusionsAccording to the results of the present study, neither of these two techniques is preferred to the other, and factors such as working time, etc., can be considered to choose the more appropriate clinical technique.

The Contribution of Nano-Alumina to Ultra-High-Performance Cement-Based Systems.

In the last decades, nano-silica (NS), nano-alumina (NA), and nano-calcium oxide (NC) particles have been incorporated into cementitious materials, and it seems that each one of them contributes uniquely to the materials' properties. This research explores the influence of each nanomaterial on the fresh properties of cement pastes and their compressive strength evolution over one year. Low proportions (1.5% by weight) of nanomaterials were added to cement pastes, and their fresh properties, such as heat of hydration and X-ray diffraction patterns in the first hours, were analyzed. The compressive strength and open porosity were also measured long-term. The acceleration of hydration heat in NA-cement pastes is linked to enhanced hydration product formation at early ages. Among the tested nanomaterials, NA increased compressive strength by 10% at later ages. Although the fresh properties of NC-cement pastes remained unaffected, their open porosity decreased by 54% at 28 days. In contrast, the increase in heat of hydration in NS-cement pastes did not result in significant strength improvement. Based on these findings, NA was selected for ultra-high-performance cement (UHPC)-based material use. Its incorporation not only preserved the ultra-high-performance (UHP) properties but also provided additional benefits such as an increase in compressive strength under a CO2 atmosphere. Through detailed analysis, this research establishes that nano-alumina incorporation optimizes the microstructural development and compressive strength of ultra-high-performance cement-based systems, presenting a novel advancement in enhancing the mechanical properties and durability of these materials under various environmental conditions.

Structural optimization on heat transfer characteristics in polyurethane foam film melting process by deflagration method

Flexible polyurethane foam (FPUF) is extensively utilized in various industrial sectors, due to its distinctive porosity. The deflagration approach is a prevalent method employed to reticulate polyurethane foam. The open porosity of the polymer, along with its reticular framework, significantly shape the structure of FPUF and consequently impact its mechanical properties. This study investigates the impacts of two pivotal parameters, pore size and film thickness, on the open porosity of the foam film. The heat transfer characteristics are studied by standard k-ε model coupling with the melting-solidification model based on the enthalpy-porosity method analysis model, and nine PUF models are selected as the evaluation objects. The experimental results indicate that the reticulation effect is more favorable when the open porosity ranges from 0.7 to 0.85. Based on these findings, the parameters with large variation degrees have a greater influence on the melting process of FPUF film. Furthermore, FPUF composites characterized by thicker films and smaller pores demonstrate a remarkable reticulation performance. The insights garnered from this study hold promise for advancing the comprehension of the underlying mechanisms governing FPUF deflagration, thereby facilitating the optimization of its structural applications in industrial domains.

Integrating multiple microstructure and water distribution visual analysis to reveal the moisture release and quality deterioration of precooked beef during freezing-thawing-reheating processes

Prepared dishes are becoming an increasingly important part of diets, while most studies focus on the flavor. In this study, the moisture loss induced by structure changes of precooked beef during freezing-thawing-reheating process was investigated. The myowater trapped and released by ‘myenteric channels’ and ‘water reservoir’ were observed by integrated multiple microstructure and water distribution visual analysis. X-ray results showed an increase in total porosity and the close porosity transfer to open porosity during freezing-thawing-reheating. The weight loss of frozen-reheated (FR) and frozen-thawed-reheated (FTR) samples was 6.34% and 7.69%, respectively. Although freezing-thawing did not significantly affect the moisture loss, magnetic resonance image (MRI) showed that the ‘free water’ temporarily existed in interfibrous spaces after thawing and leaked out during reheating. Directly reheating avoided the myowater redistribution and muscle extension mediated, which reduced moisture loss. These results provide a reference for quality control of prepared dishes during the industrial supply chain.

Simulation of Electrical Conductivity of Porous Composite Electrodes for Solid Oxide Cells Using a Monte Carlo 3D Equivalent Electronic Circuit Networks

Solid oxide cells (SOCs) show high potential in energy conversion applications necessary for the decarbonization of the economy. Their advantage consists in ability to operate at high temperatures, reaching up to 900 °C. Firstly, it results in accelerated electrode reactions kinetics, secondly, in favorable thermodynamic conditions decreasing the equilibrium voltage of the water splitting. As a result, SOCs are attractive candidates for both efficient electrolysis and fuel cell applications, offering a robust solution in the pursuit of clean energy. However, the elevated operational temperature also introduces material challenges that hinder the competitiveness of SOCs.Porous gas diffusion electrodes are used to accomplish the desired electrode reactions. Considering conventional exclusively electron-conductive electrode materials, triple phase boundary (TPB) is required for the reactions to take place – a simultaneous contact of electron-conductive, ion-conductive and gaseous phase. While the electrode and electrolyte phases are solid, the gaseous phase is represented by open porosity in the electrode body. TPB is located exclusively at the contact area of electrode and electrolyte components in the case of single-phase electrodes, limiting the electrode electrocatalytic performance. To avoid the limitation by TPB length, composite electrodes are frequently used. Due to the involvement of the ionically conductive phase, they exhibit improved electrocatalytic capabilities.Electrolyte phase, however, usually exhibits 4 orders of magnitude lower electrical conductivity than the electron-conductive phase, while gaseous phase is electrically non-conductive. Thus, an improper phase composition and morphology of the composites can lead to a significant drop in their electrical conductivity and thus in the cell performance. Simple and reliable method for the conductivity value prediction is up to now missing. At the same time, experimental determination is both expensive and time-consuming. The goal of this study was to develop simple, fast and reliable method for prediction of electrical conductivity of the porous electron-ion conductor composites.The key feature of the presented approach lies in the minimal requirements for input parameters. Only electrode phase composition and bulk electrical conductivity of each phase are required. Based on the input composition, the model generates a 3D artificial specimen, a domain discretized into cubic voxels each assigned randomly to a specific phase. The resulting structure is substituted with an equivalent circuit network with electric elements corresponding to the electrochemical properties of the material components: specific resistivity of electrical conductors and polarization resistance / capacitance of electrochemical reaction at material interface. In-silica electrochemical impedance spectroscopy measurement is performed by solving charge balance following Kirchhoff’s current law for multiple frequency values. Resulting impedance spectrum is fitted in order to obtain Ohmic and polarization resistance and the capacitance of the artificial specimen. This procedure is averaged over a large number of artificial specimens in a Monte Carlo manner.Conventionally used oxygen electrode composite material lanthanum strontium manganite (LSM) mixed with yttria-stabilized zirconia (YSZ) was used to produce validation dataset. LSM:YSZ powder mixtures of compositions between 1:0 and 0:1, chosen to produce samples of various degree of LSM percolation, were homogenized. The mixtures were fired at 1150 °C. Electrical conductivity of the pellets was determined at temperatures between 600 and 800 °C using electrochemical impedance spectroscopy.Experimental data obtained were confronted to the model results. The model demonstrated very good accuracy for a porosity value of up to 55%. Significant error was observed in the porosity range between 55% and 68%. Finally, the model failed to generate an artificial specimen with a porosity of 75%. As it was found, the limited applicability of the model for the materials characteristic for high porosity was caused by the coalescence of the void phase. This shortcoming of the model was solved by implementing morphological parameter describing degree of void phase coalescence in the electrode structure. Due to this modification, model allows to gain valuable information on the microstructure of the studied composite material on the base of the experimentally determined conductivity data.This work introduces a novel modelling approach with minimal amount of input parameters, streamlining the prediction of electrical conductivity of porous electron-ion conductor composites. This simplified yet effective methodology holds great promise for efficiently characterizing and optimizing materials for energy conversion applications, offering a valuable tool for advancing research in the field.This publication was supported by the project "The Energy Conversion and Storage", funded as project No. CZ.02.01.01/00/22_008/0004617 by Programme Johannes Amos Commenius, call Excellent Research.

Development of eco-efficient limestone calcined clay cement (LC3) mortars by a multi-step experimental design

Calcined clays and calcium carbonates can be used to reduce clinker factor in blended cements, offering significant economic and environmental benefits. Limestone calcined clay cements (LC3) combine them as supplementary cementitious materials (SCMs) for delivering a sustainable alternative to conventional Ordinary Portland Cement products, with envisioned applications in construction and rehabilitation of historical buildings.This study reports a chemometric approach to the development of LC3 mortars, targeting to minimize clinker content while maintaining or improving the technical characteristics. To evaluate their performance, apparent density, modulus of elasticity, open porosity, water absorption, flexural and compressive strength have been considered as responses. Multiple Linear Regression (MLR) and Principal Component Analysis (PCA) were employed in a three-step mixture-process design allowing to obtain LC3 mixtures with a 21 wt% reduction in clinker while achieving notable enhancements in the physical properties (open porosity −9% and water absorption −10 %), along with commendable increases in compressive strength (+17 %) when compared to benchmark mortars produced without SCMs. The successful integration of multivariate techniques in designing sustainable building materials is showcased, highlighting the potential of chemometric methodologies to reduce the environmental impact as well as to increase the performance of building materials.

Ablation and mechanical behavior of reusable Cf/SiC-ZrC with a gradient-structured matrix produced by reactive melt infiltration

Cf/SiC-ZrC renowned for its outstanding performance as a thermal protectant, has gaining widespread recognition. Recent research on this system has emphasized the development of a cost-effective and reusable version with increased thickness for extended use in thick-walled thermal structural components. Ablation resistance, high strength retention, and high thermal conductivity are crucial for successful aircraft reentry. In this study, a low-cost reactive melt infiltration (RMI) method is developed for preparing dense and high-performance large-thickness Cf/SiC-ZrC (L-Cf/SiC-ZrC) with a gradient-structured matrix. The use of a fine weave-pierced fabric preform structure enhances both the structural integrity and thermal conductivity of Cf/SiC-ZrC in the thickness direction. Simultaneously, the gradient-structured matrix, with appropriate contents of surficial ZrC and SiC exhibits erosion resistance, where the internal core with a high SiC content ensures remarkable strength retention. This unique matrix-structure design is achieved by integrating porous C with a single-stage pore structure and a high degree of graphitization degree, and a Si-Zr alloy with a unique composition. The 20 mm thick Cf/SiC-ZrC obtained via RMI has a density of 2.79 g/cm3 with an open porosity of 5.65 % and flexural strength of 224.3 ± 5.4 MPa. Under a heat flux of 4.186 MW/m2, Cf/SiC-ZrC exhibits an ablation rate of −0.004 mm/s after 60 s, demonstrating its resilience against ablation damage. Moreover, the post-ablation strength (166.0 ± 4.4 MPa) exceeds that of reported Cf/SiC-ZrC congeners, highlighting the robust load-bearing capability.

Evaluating building stones: Physical-mechanical changes from high-temperature fire and water cooling

Heritage sites built with natural stone are at risk from fires, which can alter stone properties and compromise its structural integrity. Over 60 studies in the past three decades have examined fire impact on natural stone, providing insights for their prevention and restoration. The primary objectives are to develop effective strategies to mitigate fire risks, protect heritage structures, and ensure the preservation of our cultural legacy. Two noteworthy Portuguese limestones used as heritage building materials: Lioz (LL) and grey Ançã stone (GAS), were studied regarding the effect of high-temperature exposure for simulating fire at 200 °C, 400 °C and 600 °C, followed by cooling in water to reproduce fire extinguish in natural stone buildings. The findings provided insights into how the different temperatures impact the stone morphological, physical and mechanical properties. Color measurements (CIE L*a*b*) showed a color difference from 3 to 32 %; SEM-EDS confirmed microstructure modifications after fire exposure with cracks formation and intragranular porosity development. Among the diverse physical and mechanical properties of the stones, uniaxial compressive strength decreased from 1 to 33 %, Leeb D hardness decreased up to 12.2 %, lowering in open porosity was detected in the range 70–289 % and ultrasound speed propagation were significantly affected after thermal cycle at 600 °C with a negative variation reaching 49 %. Results from TGA show a loss of mass due to retained water (∼40 °C) and loss of hydration water at ∼ 120 °C in both limestones. The total mass loss (∼42–∼44 %) is associated with the loss of H2O, CO2. In conclusion, stones with higher toughness and compression strength exhibited reduced damage at high temperatures due to their enhanced resistance to fracturing under stress. As limestone's mechanical strength decreases under high temperatures, it's advisable to increase its thickness to ensure sufficient support for loads and intended conditions of use. The deficiency of analysis on limestone's mechanical decay from fire reveals a significant knowledge gap regarding the complete extent of damage and deterioration in stone heritage structures.

Generation mechanism of Si–Y–B-Yb ceramics with enhanced water-oxygen corrosion resistance

This study systematically investigates the influence of preparation temperature on microstructure and generation mechanism of Si–Y–B-Yb ceramics as anti-corrosion matrix. Main phases of Si–Y–B-Yb ceramics are Y/YbB4, YSi2, and Si, where Y/YbB4 is derived from the reaction between YSi2 and YbB6. With increase in preparation temperature, open porosity of Si–Y–B-Yb ceramics gradually decreases, reaching 0.24 % at 1350 °C, and internal phases transform from a dispersed distribution to clearly defined boundary state. Based on this, high-temperature water-oxygen corrosion behavior of Si–Y–B-Yb ceramics is characterized in 50 vol% H2O+50 vol% O2 environment at 1250 °C for 100 h. In this corrosive environment, silicate phase appears on the surface of Si–Y–B-Yb ceramics. With prolonged corrosion time, silicate phase gradually forms more complete protective layer, hindering further corrosion by water-oxygen environment. These results demonstrate the feasibility of proposed Si–Y–B-Yb materials for corrosion protection.

Preparation of lightweight foam glass-ceramics from copper slag tailings: Secondary aluminum slag as pore-forming agent

To address metallurgical waste residue pollution, this study utilized copper slag tailings (CST) and waste glass (WG) as primary raw materials, with secondary aluminum dross (SAD) as a pore-forming agent, to produce lightweight spontaneous foam glass-ceramics. The effects of raw material ratios, sintering temperature (1120–1160 °C), and sintering time (0–40 min) on foam glass-ceramics properties were investigated, elucidating the correlations between various properties. Under optimal preparation conditions (CST: WG: SAD = 7:11:2, sintered at 1150 °C for 20 min), the foam glass-ceramics exhibited a bulk density of 0.41 g/m³, compressive strength of 2.32 MPa, open porosity of 61.02 %, 2-h water absorption of 83.76 %, and mean pore size of 3.12 mm. The sintering process transformed raw materials into substances like diopside subsilic ferrian, which enhanced the strength of lightweight foam glass-ceramics. Harmful substances in the raw materials can be immobilized within the internal structure of foam glass-ceramics, ensuring excellent environmental safety. Additionally, comprehensive characterization was conducted on the foam glass-ceramics, elucidating their composition, structure, and pore-forming mechanisms.

Synthesis and characterization of biodegradable Kraft lignin-based hydrophilic phenol formaldehyde foams

Phenol formaldehyde foams, extensively utilized in wide range of applications face challenges due to depleting petroleum resources and adverse environmental concerns. This study explores a promising shift to biobased alternatives, specifically investigating the use of Kraft lignin (KL) by replacing about 10 to 50% phenol content to synthesize open-cell hydrophilic phenolic foams. The produced foams undergo comprehensive testing to evaluate wetting properties, porosity, mechanical strength, and biodegradation potential. Remarkably, foams with a high percentage of Kraft lignin exhibit outstanding physical and wetting characteristics. Notably, substituting 50% of phenol with KL gave rise to a foam with a density of 40 kg/m3, open cell porosity of about 100%, water absorption capacity of 2100%, and an average water uptake rate of 0.9 cm3/s. Furthermore, these lignin-substituted foams display enhanced biodegradability compared with their petroleum-based counterparts. The foam with the 40% phenol substitution exhibits the highest weight loss of approximately 68% in 15 days during the biodegradation test. The biodegradation was further confirmed using scanning electron microscopy and FT-IR analysis of the degraded samples.