Talc Research Articles

Investigation of mechanical properties and hydration of low-carbon magnesium and calcium-rich waste powder geopolymer paste

Magnesium and calcium-rich waste powder (MWP) has the potential to be a low-carbon geopolymer cementitious material. This study investigates the mechanical properties and hydration products of low-carbon magnesium and calcium-rich waste powder geopolymer paste (LMWP). The influences of alkali content, calcination temperature, mix proportions of raw materials and curing temperature on the compressive strength and hydration of LMWP were examined. The mechanical properties of LMWP were systematically evaluated by assessing setting time, fluidity, and compressive strength, while the pore structure was analyzed using mercury intrusion porosimetry (MIP). The hydration products and microstructures of LMWP were investigated by XRD, TG-DTG, and SEM-EDS. The results indicated that incorporating 1 % NaOH significantly enhanced the compressive strength of LMWP, whereas thermally activated MWP (800 ℃, 900 ℃) negatively affected compressive strength development. The addition of slag facilitated the reaction of MWP and improved the compressive strength of LMWP. When the slag incorporation reached 40 %, the specimen demonstrated optimal performance with a compressive strength of 27.8 MPa. The pore diameter was predominantly distributed around 10 nm, indicating well-structured porosity. Microstructural analysis revealed that the hydration products are dense calcium magnesium silicate gels (C-M-S-H), which significantly enhanced the compressive strength and optimized pore structure of LMWP. The efficiency of carbon emission reduction achieved by LMWP was evaluated. The findings indicate that, compared to traditional cement-based materials, LMWP reduces cement consumption by over 60 %, significantly decreasing CO2 emissions. This study innovatively utilizes MWP to prepare green and low-carbon geopolymer paste materials, with the aim of replacing cement applications in the construction industry, thereby reducing carbon emissions. It explores new avenues for the low-carbon and green development of the civil engineering sector and contributes to efforts in addressing the global climate crisis.

Hydrophilic Modification of Macroscopically Hydrophobic Mineral Talc and Its Specific Application in Flotation.

Sodium diethyldithiocarbamate (DDTC), a common collector used to enhance the hydrophobicity of minerals in froth flotation, nevertheless weakens the hydrophobicity of the talc surface. To rationalize this anomaly, the interactions of a hydrophobic alkyl group and hydrophilic mineralophilic group (-NCS2-) of heteropolar surfactant DDTC, and a water molecule with the talc (001) surface, were investigated. Herein, DFT simulations found that the talc (001) surface features natural hydrophobicity determined by the competition between adhesion (surface water) and cohesion (water-water interactions). The interaction of the hydrophobic alkyl group of DDTC with the talc surface is more favorable compared to that of the -NCS2- group and H2O, favoring the hydrophilic modification of the talc surface. Additionally, adsorption isotherms, time-of-flight secondary ion mass spectrometry (ToF-SIMS), microflotation tests, and contact angle measurements also indicate that the differences in adsorption orientation of the heteropolar surfactant DDTC on the talc surface enhance the hydrophilicity of the talc surface, leading to a decreased recovery of the talc. This study provides crucial surface chemistry evidence for the selective adsorption of heteropolar surfactants and contributes to the understanding of the mechanism for the efficient flotation separation of molybdenite from talc.

Mg/Si- and Ag-Doped Carbon-Based Media Rainwater Filtration System for Multiple Pollutants Removal.

In this study, the removal performances of a multi-pollutant elimination cartridge system (MPECS) composed of palm shell waste-based activated carbon (PSAC), magnesium (Mg)/silicon (Si)-doped PSAC (Mg/Si-PSAC), and silver (Ag)-doped PSAC (Ag-PSAC) for heavy metals, organic pollutants, and Escherichia coli were investigated. Mg/Si impregnation significantly improved heavy metal removal using PSAC by increasing the surface area and adding more sorption sites to the magnesium silicate nanolayer. Fixed-bed column experiments showed that the MPECS column outperformed PSAC and commercial activated carbon (DJAC), with a 1.5 to 2.0 times higher E. coli removal and a higher removal of organic pollutants and heavy metals. The MPECS column, with its disinfection ability and adsorption of heavy metals and organic matter, is a promising system for removing multiple pollutants from rainwater.

Rapid Micro-Propagation of Disease-Free Hemp (Cannabis sativa L.) to Improve Industrial Production

Hemp (Cannabis sativa L.) is widely used in industrial production due to its pharmacological properties, particularly cannabidiol (CBD). For commercial production, it is essential to have a large-scale propagation that is consistently disease-free and rapid. Thus, this study aims to establish a protocol for exponentially increasing the amount of high CBD hemp variety CA-UP1 by nodal segment via tissue culture method. Initially, with 10-minute surface sterilization with 0.1 % HgCl2, the microbial contamination rate was reduced to its lowest level (approximately 16.67 %) within 7 days. The nodal segments exhibited optimal response to MS media supplemented with 0.5 mg/L TDZ, resulting in a 100 % shoot multiplication rate. The average number of shoots per explant was 4.7 ± 1.57, and the average shoot height was 2.30 ± 0.42 cm at 4 weeks. Following the induction of elongation in MS medium supplemented with charcoal, the seedlings were acclimatized and dipped in a 1,000 ppm IBA solution mixed with talcum powder. The cultivation resulted in a 100 % rooting rate, with an average of 5.6 ± 1.94 roots/explant, an average root length of 5.78 ± 1.96 cm, and an average explant height of 4.32 ± 1.52 cm. The tissue culture protocol can produce over 190 times the quantity of hemp plants compared with the stem cutting technique. The researchers anticipate that this micropropagation protocol will be useful as a rapid and economical alternative for the industrial production of effective C. sativa L. HIGHLIGHTS A 10-minute surface cleaning protocol with a minimal microbiological contamination rate of 16.67 % in the nodal segment. Thidiazuron (TDZ) can stimulate the most significant increase in shoot growth in Cannabis sativa L. variety CA-UP1 when grown on a semi-solid medium. Dispensing talcum powder combined with IBA results in a 70 - 100 % survival percentage by effectively preventing root during the acclimation stage. The following procedures can be implemented micropropagation of hemp for the production of a large quantity of high-quality, disease-free hemp plants with approximately 190 times more than stem cutting method. GRAPHICAL ABSTRACT

Human Supplementation with AM3, Spermidine, and Hesperidin Enhances Immune Function, Decreases Biological Age, and Improves Oxidative-Inflammatory State: A Randomized Controlled Trial.

The positive effect of AM3, spermidine, and hesperidin, which have antioxidant and anti-inflammatory properties, on immunity is known, but their effect on the rate of aging, known as biological age (BA), is unclear. This work aims to test if the intake of a blend of AM3 (150 mg), spermidine (0.6 mg), and hesperidin (50 mg) for 2 months could decrease BA and improve immunity, redox, and inflammatory states. For this, 41 participants (30-63 years) were randomly divided into placebo and supplement groups. The supplement group took two capsules daily with AM3, spermidine, and hesperidin for two months, while the placebo group took capsules containing only calcium phosphate and talcum powder. Before and after the treatment, peripheral blood was collected. Immune function was assessed in leukocytes, redox state in whole-blood cells, erythrocytes, and plasma, and cytokine concentration in both mononuclear cell cultures and plasma. Finally, the Immunity Clock model was applied to determine BA. The results show that the intake of this blend improves the immune functions that constitute the Immunity Clock, decreasing BA by 11 years and reducing the oxidative-inflammatory state of the participants. Therefore, this supplement can be proposed as a strategy to rejuvenate BA and achieve healthy aging.

Chemical and Thermal Changes in Mg3Si2O5 (OH)4 Polymorph Minerals and Importance as an Industrial Material

Serpentine (Mg3Si2O5(OH)4), like quartz, dolomite and magnesite minerals, is a versatile mineral group characterized by silica and magnesium silicate contents with multiple polymorphic phases. Among the phases composed of antigorite, lizardite, and chrysotile, lizardite and chrysotile are the most prevalent phases in the serpentinites studied here. The formation process of serpentinites, which arise from the hydrothermal alteration of peridotites, influences the ratio of light rare earth elements (LREE) to heavy rare earth elements (HREE). In serpentinites, the ratio of light rare earth elements (LREE)/heavy rare earth elements (HREE) provides insights into formation conditions, geochemical evolution, and magmatic processes. The depletion of REE compositions in serpentinites indicates high melting extraction for fore-arc/mantle wedge serpentinites. The studied serpentinites show a depletion in REE concentrations compared to chondrite values, with HREE exhibiting a lesser degree of depletion compared to LREE. The high ΣLREE/ΣHREE ratios of the samples are between 0.16 and 4 ppm. While Ce shows a strong negative anomaly (0.1–12), Eu shows a weak positive anomaly (0.1–0.3). This indicates that fluid interacts significantly with rock during serpentinization, and highly incompatible elements (HIEs) gradually become involved in the serpentinization process. While high REE concentrations indicate mantle wedge serpentinites, REE levels are lower in mid-ocean ridge serpentinites. The enrichment of LREE in the analyzed samples reflects melt/rock interaction with depleted mantle and is consistent with rock–water interaction during serpentinization. The gradual increase in highly incompatible elements (HIEs) suggests that they result from fluid integration into the system and a subduction process. The large differential thermal analysis (DTA) peak at 810–830 °C is an important sign of dehydration, transformation reactions and thermal decomposition, and is compatible with H2O phyllosilicates in the mineral structure losing water at this temperature. In SEM images, chrysotile, which has a fibrous structure, and lizardite, which has a flat appearance, transform into talc as a result of dehydration with increasing temperature. Therefore, the sudden temperature drop observed in DTA graphs is an indicator of crystal form transformation and CO2 loss. In this study, the mineralogical and structural properties and the formation of serpentinites were examined for the first time using thermo-gravimetric analysis methods. In addition, the mineralogical and physical properties of serpentinites can be recommended for industrial use as additives in polymers or in the adsorption of organic pollutants. As a result, the high refractory nature of examined serpentine suggests that it is well-suited for applications involving high temperatures. This includes industries such as metallurgy and steel production, glass manufacturing, ceramic production, and the chemical industry.

Growth regulation in bread wheat via novel bioinoculant formulation

Wheat (Triticum aestivum L.) is one of the most significant crops and the backbone of food security worldwide. However, low wheat production remains a substantial concern in global agricultural systems. It can be attributed to several factors, including adverse climatic conditions, plant disease and poor soil quality. Recent efforts have explored bioinoculant applications as a promising approach to enhance wheat yield, trying to mitigate constraints essential for future wheat production and global food security. This study tested talc powder, wheat biochar, sugarcane bagasse biochar, and farmyard manure as carriers with two endophytic bacterial strains, Burkholderia phytofirmans PsJN and Bacillus spp. MN54 was applied to three wheat varieties (Ujala-16, Zincol-16, and Fathejang-16). The data was recorded at the seedling and maturity growth stages of plants. A pot experiment revealed significant improvements in plant growth following bioinoculant application compared to controls. Notably, the combination of sugarcane bagasse biochar with Bacillus sp. MN54 exhibited the most pronounced effects, promoting internodal length, spike length, tiller number per plant, grain yield per plant, and spikelets per spike. Additionally, talc powder with Bacillus sp. MN54 increased peduncle length, tiller number per plant, and spike length in Fathejang-16. These findings offer valuable insights into optimizing bioinoculant formulations for improved agricultural practices, adapting to climate change, and contributing to ensuring global food security.

Application of Sini Decoction at acupoint on gastrointestinal dysfunction in patients with sepsis: A clinical study.

The occurrence of gastrointestinal dysfunction is widely recognized as a prevalent complication in patients with sepsis. To investigate clinical effect of Sini Decoction at acupoint on gastrointestinal dysfunction in sepsis patients. Seventy-five patients with gastrointestinal dysfunction caused by sepsis were randomly divided into 2 groups. Treatment group received routine Western medicine treatment combined with Sini Decoction at acupoint, while control group treated with talcum powder at acupoint. Treatments in both groups lasted 7 days. Changes in the acute physiology and chronic health evaluation II score, sequential organ failure assessment score, mechanical ventilation duration, the length of Intensive Care Unit (ICU) stay, enteral nutrition tolerance scores, abdominal circumference, gastric residual volume, bowel sounds, and serum index were observed. After treatment, the enteral nutrition tolerance score, abdominal circumference, gastric residual volume, and levels of lactate and interleukin-6 were significantly lower in the treatment group compared to the control group. Bowel sounds were more active and motilin levels were higher in the treatment group. Additionally, the length of ICU stay was significantly shorter in the treatment group than in the control group. Our findings demonstrated that the application of Sini Decoction at acupoints in sepsis patients with gastrointestinal dysfunction can effectively enhance gastrointestinal function, leading to a reduction in ICU stay duration and an improvement in patients' prognosis.

Syndiotactic polypropylene-based elastomer as promising toughening agent for waste appliances-derived polypropylene

The rapid replacement of household appliances has generated a significant amount of waste appliances-derived polypropylene (WAPP), presenting a valuable resource for recycling. However, the long-term use and subsequent thermal processing of WAPP lead to its degradation, significantly impairing its toughness. Herein, syndiotactic polypropylene (sPP) as a novel toughening agent was investigated to achieve the efficient toughing of WAPP. The incorporation of 15 wt% of the sPP-based elastomer increased the impact strength of WAPP to 29.2 kJ/m2 (25 °C), which was 5.7 times that of the unmodified one and 1.9 times that modified with polyolefin elastomers (POE). This inspiring effect originates from the structural similarity between isotactic and syndiotactic polypropylene, which not only achieves a more uniform dispersion of the rubbery phase, but also creates micro voids between the phases due to the incompatibility of sPP and iPP, making it easier for shear bands to form. Further, the contradiction between rigidity and toughness is reconciled by introduction of talcum powder. This comprehensive investigation into the effects of the sPP-based toughening agent on the composite material's properties expands the potential applications of sPP and enhances our understanding of its toughening mechanisms.

Influence of MgO chemical activity on the drying shrinkage of the MgO-SiO2-H2O system

The magnesium silicate hydrate (MgO-SiO2-H2O) system is an innovative eco-friendly cementitious material. However, its poor volume stability and significant shrinkage have curtailed its widespread development and utilization. The primary component for preparing the MgO-SiO2-H2O system, MgO, has a substantial impact on the properties, particularly in relation to volume stability. This research examined the effects of MgO chemical activity on the volume stability of the system. The results suggested that reducing MgO chemical activity and increasing the Mg/Si ratio result in varying reductions in the water loss ratio and drying shrinkage, with the lowest drying shrinkage ratio being 0.913 %, representing a 14.1 % reduction compared to the sample with the highest drying shrinkage ratio. MgO chemical activity affected the shrinkage deformation of the system by influencing the generation rate and content of Mg(OH)2-induced volume expansion. Additionally, the increase in the Mg/Si ratio influenced the content of Mg(OH)2, ultimately reducing drying shrinkage. At an Mg/Si ratio of 1.25, the resulting M-S-H gel resembled a T:O structure, and promoted a higher degree of polymerization of the gel. In contrast, when the Mg/Si ratio is 1.00, the M-S-H gel exhibited characteristics more akin to a T:O:T structure, leading to an even higher degree of polymerization.

Self-Powered Machine-Learning-Assisted Material Identification Enabled by a Thermogalvanic Dual-Network Hydrogel with a High Thermopower.

Wearable devices equipped with high-performance flexible sensors that can identify diverse physical information free from batteries are playing an indispensable role in various fields. However, previous studies on flexible sensors have primarily focused on their elasticity and temperature-sensing capability, with few reports on material identification. In this paper, a thermogalvanic dual-network hydrogel is fabricated with [Fe(CN)6]3-/4- as a redox couple and lithium magnesium silicate, Gdm+ and lithium bromideas key electrolytes to optimize the interconnected porous structure of the gel, which shows excellent mechanical and thermoelectric properties with a thermopower as high as 4.01mV K-1. A self-powered material identification ring is developed based on the temperature-triggered thermoelectric response of the gel in conjunction with machine learning, which can actively infer materials without an external power connection by analyzing the voltage signals correlated with interfacial heat transfer produced upon contact with different materials. The proposed gel ring has important applications for future areas such as human-computer interaction and haptic-associated artificial intelligence.

Surface modification of talc powder by silane functionalized polycarboxylates and its effect on the performance of polyvinyl chloride composite

AbstractIn this work, modified polycarboxylates were prepared by copolymerizing γ‐Methacryloxy propyl trimethoxyl silane (KH‐570) with acrylic acid and allyl polyoxyethylene ether. Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) indicate that silane copolymerized polycarboxylates have been successfully synthesized. The talc powder (TP) modified with synthesized polycarboxylate and modified polycarboxylates was blended with polyvinyl chloride (PVC) to prepare composite films. FTIR and x‐ray photoelectron spectroscopy (XPS) were used to determine changes in the surface properties of unmodified and modified TP. The effects of TP and polycarboxylate‐modified TP on the tensile properties, light transmission and moisture transmission of the PVC composite films were investigated. Compared with untreated TP filled PVC film, the PVC composite films filled with organosilicon polycarboxylate‐modified TP exhibit enhanced tensile strength, light transmittance, barrier, and other properties. Especially, the tensile strength of PVC composite film filled with 7 wt% Si0.5‐PCE modified TP is increased by 19.5% and the elongation at break is increased by 21.6%. In addition, the moisture permeability of the composite film is reduced by a maximum of 80.6% compared with the pure PVC film.

Comparison of composition, properties and modifying effect in epoxy compositions of natural and synthetic diopside-containing fillers

Diopside is one of the key components in various construction materials and can also be used as a filler for epoxy compositions. However, due to the complexity and labor intensity of developing domestic deposits of this calcium magnesium silicate, it is rational to synthesize diopside based on rice husk ash and dolomite and compare its phase composition and properties with diopside concentrate mined in nature.It has been established that the synthesized calcium-magnesium silicate, compared to the natural mineral, contains 10 times more diopside, has a 3 times smaller pore volume and an almost 5 times smaller average particle size, i.e. they differ significantly in both phase and granulometric composition, as well as in porosity.At the same time, both natural and synthetic diopside-containing fillers increase the hardness, wear resistance and viability of epoxy compositions. A filler synthesized on the basis of rice husk ash is more effective in terms of increasing the performance characteristics of epoxy materials.

Computational Mechanistic Analysis of the Formation of the Magnesium Silicate Monomers MgSiO3 and Mg2SiO4.

Silicate grains comprise a large fraction of cosmic dust, motivating a need to understand how they form. The current body of work on silicates generally reflects the abundance of silicate grains, yet models for their formation often do not consider silicate chemistry on the smallest scale, which can form species available for dust grain nucleation processes. In order to expand upon previous attempts to bridge this gap in silicate chemistry, novel gas-phase reaction pathways for the magnesium silicate monomers enstatite (MgSiO3) and forsterite (Mg2SiO4) from MgH, H2O, and SiO are presently computed using highly accurate quantum chemical calculations. MgSiO3 and Mg2SiO4 form through a series of reactions that initially excludes silicon addition, creating the elusive species MgOH and Mg2O prior to further reaction. The formation of the two silicate monomers is expected to be efficient with the primary bottleneck being the amount of MgH available for reaction. The addition of these reactions to cosmic chemical networks will add further clarity to the processes that govern dust formation, most significantly for those occurring within stellar outflows of asymptotic giant branch stars.

Petrology, mineral chemistry and geochemistry of chloritite associated with Neoproterozoic ophiolitic ultramaficsin the Eastern Desert of Egypt, Arabian-Nubian Shield

This study presents for the first time, the field observations, petrography, mineral chemistry and geochemistry of chloritite hosted in the Al-Barramiya Neoproterozoic ophiolite of the Eastern Desert of Egypt, Arabian-Nubian Shield (ANS). The Al-Barramiya ophiolite is one of the most important ophiolitic sequences exposed in the ANS. It is affected by different types of alterations including carbonatization, listvenitization, chloritization and rodingitization. The Al-Barramiya chloritite occurs as thin layers associated with highly serpentinized peridotite. It is a fine-grained rock entirely composed of chlorite (85–95 vol.%) with minor talc and accessory minerals (epidote, rutile, titanite, corundum and opaque minerals). The chlorite minerals in the chloritite are represented mainly by diabantite, while those in the serpentinites include ripidolite. Depending on the chemical composition of the chlorites, the chlorite in chloritite formed at temperatures ranging between 200 and 250°C, which are lower than those of the disseminated chlorite in the serpentinite (310–345oC), indicating their formation in different hydrothermal stages. The chloritite samples are rich in total REE contents (17.9–27.3 ppm) compared with the associated serpentinites (0.69–0.87 ppm). They are characterized by slightly depleted LREE relative to HREE [(La/Lu)n = 0.8–0.9], with a moderately negative Eu-anomaly [(Eu/Eu*)n = 0.4–0.5]. The negative Eu-anomalies are derived from chloritization fluids or reflect the presence of talc in the chloritite. Based on field work, petrography, mineralogical and geochemical data, the studied chloritite has been interpreted as being derived from the associated serpentinized ultramafics by hydrothermal alterations. This is supported by an enrichment of chloritite in compatible trace elements (Cr = 2031–2534 ppm, Ni = 1264–1988 ppm, Co = 76–101 ppm) similar to that which is observed in the associate serpentinite.

Silicate Derived from Phaeodactylum tricornutum for Removal of Polystyrene: Interfacial Effects of Living Organism and Its Derivatives with Nanoplastics.

The deposition of nanoplastics in the environment poses a direct threat to human health through the food chain. There is an urgent need to investigate how they can be effectively removed from water. In this work, the toxic effects of nanopolystyrene (PS) at different concentrations on Phaeodactylum tricornutum (PT) were investigated. The results show that PS affects the cell activity of PT through cell wall adhesion and shading effect and hinders the transmission of light energy, thus inhibiting the growth of PT. Considering that living PT is not suitable for the removal of heterogeneous aggregation of PS, magnesium silicate (MS) was obtained by calcination of PT biomass based on retaining salt. The maximum adsorption capacity of PS by MS was 40.85 mg g-1, which was 10 times higher than that of conventional adsorbents. The presence of competitive anions significantly affects the removal of PS. The application in real water bodies and the reusability of the adsorbents were also verified. By characterizing the materials before and after adsorption, it is found that the adsorption mechanism mainly includes electrostatic attraction, hydrogen bonding, π-π interaction, and complexation between Si-O bond and PS. This study explains the toxic effect of nano-PS on PT and innovatively develops a biomass derivative from diatoms, which provides a novel and feasible strategy for environmental remediation.

Pepgen-P15 delivery to bone: A novel 3D printed scaffold for enhanced bone regeneration

Pepgen-P15 is a combination of an organic hydroxyapatite matrix derived from bovine sources, combined with a synthetic peptide known as P-15. The interaction between α2β1 integrin and the P15 chain triggers both intracellular and extracellular signaling pathways, resulting in the production of growth factors. Three-dimensional (3D) printing has recently emerged as an innovative strategy for developing personalized therapies in bone tissue regeneration. In this research, various ratios of calcium magnesium silicate (bredigite) nanoparticles were used to modify 3D printed scaffolds made of xanthan gum and polycaprolactone (PCL) via fused deposition modeling (FDM). Scaffolds were subsequently treated with an alkaline solution, covered with graphene oxide, and finally, Pepgen-P15 was applied. the effects of xanthan gum were assessed using swellability and contact angle tests. The results indicated that, the prepared scaffolds exhibited suitable degradation rates, mechanical characteristics, and apatite formation. Alizarin red and alkaline phosphatase assays were also conducted to evaluate the scaffolds’ effectiveness in promoting bone cell differentiation during cell culture. Furthermore, the surface of the scaffold was examined to determine the amount of Pepgen-P15 loaded and released. According to the findings, the scaffold composed of 20 % bredigite and 0.3 % graphene oxide, coated with Pepgen-P15, demonstrate optimal mechanical properties, cell adherence, development, and proliferation. Typically, it is a good candidate for use in bone tissue engineering.

Geopolymers made using organic bases. Part III: Cast magnesium, yttrium, and zinc aluminosilicate and silicate ceramics

AbstractIt was shown in Part II of this series of articles that geopolymers synthesized with organic bases could be used as precursors to mullite and mullite + glass composites. A natural next step is to determine whether it is possible to synthesize materials outside the Al2O3·SiO2 and alkali oxide·Al2O3·SiO2 phase systems. Hence, the focus of this study was the use of geopolymer‐like processing to make preceramic bodies with magnesium, yttrium, and zinc aluminosilicate and silicate compositions. These preceramics were successfully fired into monolithic bodies of cordierite, mixed yttrium and aluminum silicates, yttrium disilicate, and willemite. The synthesis of these preceramics employed a guanidine silicate solution, a synthetic oxide powder, and in some cases metakaolin to reach the oxide composition of the ceramic. All solidified within 3 days at 20°C or 50°C, depending on the composition. For the first time, this study showed that Y2O3 and ZnO can react with silicate solutions to give some Y‐O‐Si and Zn‐O‐Si bonding analogous to Al‐O‐Si bonding in geopolymers. These results suggest that other silicate compositions may be possible, such as with the rare earth oxides, which might be valuable to process like a geopolymer rather than by traditional ceramic processing. However, the ceramics made here were generally porous due to the expansion of gases within the sample that were trapped by a viscous liquid phase during firing.

Fracture characteristics and microscopic mechanism of slag-based marine geopolymer mortar prepared with seawater and sea-sand

This study utilized seawater, sea sand, and ternary solid waste to produce marine geopolymer mortar (MGM). 23 groups of MGM samples with varying alkali content and basalt fiber (BF) and polypropylene fiber (PPF) volume fractions, as well as marine cement mortar (MCM), were tested for fracture characteristics. Three initial crack length ratios (a0/h) (0.2, 0.3, and 0.4) were designed. The analysis included load-crack mouth opening displacement (P-CMOD) curves for all specimens, focusing on critical crack length (ac), critical crack tip opening displacement (CTODc), fracture toughness (KSIC), fracture energy (GF), and facture brittleness index (FBI). Results indicated that increasing alkali content enhanced strength and elastic modulus, peak fracture load, critical crack extension length (Δac), and CTODc, while decreasing final CMOD. This was attributed to the increased alkali content, which enhanced the mortar’s density. However, excessive alkali content also led to increased shrinkage damage within the matrix, making it prone to stress concentrations and resulting in brittle failure. Based on the research, it is recommended that the alkali content be controlled within the range of 4–5 %. Hybrid fibers showed superior overall toughness enhancement, increasing KSIC, GF, and FBI by 54.3 %, 95.6 %, and 427.4 %, respectively. This improvement was due to the synergistic effect of BF and PPF, which increased the specimen’s elastic modulus, reduced crack propagation speed, and sustained load-bearing capacity during the later stages of crack development. The fracture toughness of conventional geopolymer mortar was positively correlated with the Ca/Si ratio and was lower than that of MGM. In contrast, MGM’s Ca/Si ratio showed an inverse correlation with KSIC, indicating that phase assemblage governs the fracture resistance of MGM. This is because Cl- in seawater intensified geopolymerization reactions. Interwoven gel structures in MGM, with surface depositions like magnesium aluminosilicate hydrate (M-A-S-H), magnesium silicate hydrate (M-S-H), and silica gel, filled pores, and improved homogeneity, resulting in its superior fracture toughness over conventional geopolymer mortar.

Aluminum and Iron Effects on the Electrical Conductivity of the Dense Hydrous Magnesium Silicate Phase E

AbstractThe electrical conductivity of pure and Al/Fe‐bearing phase E was measured up to 950 K at 15 GPa using a complex impedance spectroscopy. Pure phase E shows comparable conductivity to that of phase D, and a few orders of magnitude higher than that of phase A and super‐hydrous phase B. Al‐bearing phase E does not exhibit a conductivity difference, while a certain amount of incorporated Fe prominently increases its electrical conductivity by a factor of 4. Unlike the sole substitution 2Al3+→Mg2++Si4+ in phase D and H, H+ is likely involved in the substitution. Proton conduction is the dominant conduction mechanism, while small polaron conduction becomes dominant with increasing Fe content. Phase E in subducted slabs at depth of the upper transition zone cannot explain the high electrical conductivity anomalies beneath the Philippine Sea or Northeast China. Other mechanisms such as dehydration of hydrous minerals is needed to account for them.