Silica Polymer Research Articles

Preparation and carbonation hardening of low calcium CO2 sequestration materials from waste concrete powder and calcium carbide slag

A series of new low calcium CO2 sequestration cementitious materials (LCC) with different Ca/Si ratios were prepared by sintering waste concrete fine powder (WCP) and calcium carbide slag (CCS) at different ratios. Their carbonation reaction activity, carbonation hardening properties, phase assemblages, and microstructure were systematically characterized. The results showed that when the WCP: CCS ratio was 70:30, the compressive strength of LCC reached 38 MPa after carbonation for 24h. With the decrease in the WCP: CCS ratio, the carbonation activity of LCC increased significantly. When the WCP: CCS ratio was 45:55, the compressive strength was increased to 109 MPa. Microstructure tests showed that the minerals of LCC gradually changed from CS and C2AS to C3S2 and C2S. After carbonation, unreacted clinker particles, crystalline CaCO3, and highly polymerized silica formed a dense microstructure, and the impurities of Mg element in the LCC triggered the formation of aragonite.

A non-Newtonian fluid quasi-solid electrolyte designed for long life and high safety Li-O2 batteries

The Li dendrite growth and the liquid electrolyte volatilization under semi-open architecture are intrinsic issues for Li-O2 battery. In this work, we propose a non-Newtonian fluid quasi-solid electrolyte (NNFQSE) SiO2-SO3Li/PVDF-HFP, which has both shear-thinning and shear-thickening properties. The component interactions among the sulfonated silica nanoparticles, liquid electrolyte, and polymer network are beneficial for decent Li+ conductivity and high liquid electrolyte retention without volatilization. Furthermore, NNFQSE exhibits shear-thinning property to eliminate the stress of dendrite growth during repeated cycling. Meanwhile, when the force suddenly increases, such as a high current rate, the NNFQSE may dynamically turn shear-thickening to respond and mechanically stiffen to inhibit the lithium dendrite penetration. By coupling with the NNFQSE, the lithium symmetrical battery can run over 2000 h under 1 mA cm−2 at room temperature, and the quasi-solid Li-O2 battery actualizes long life above 5000 h at 100 mA g−1.

Controlling Superhydrophobicity and Oleophobicity of Polydimethylsiloxane-Coated Silica Hybrid Particles

Hierarchical functional organic-inorganic hybrid particles for versatile control of surface wettability have attracted much attention in a wide range of applications from makeup cosmetics to anti-smudging optoelectronic devices. In this study, superhydrophobic and oleophobic organic-inorganic hybrid particles were prepared by a simple and systematic fabrication strategy using the synergistic combination of commonly available silica particles and polydimethylsiloxanes (PDMSs) with hydrophobic chain ends. Various types of PDMSs with different chain lengths and chemical structures were surface-grafted to silica microparticles through facile physical dispersion and subsequent thermal treatment to form hydrogen bonds or covalent bonds between the inorganic silica and organic PDMS polymers and thus induce a core-shell structure for the hybrid particles, which imparts superhydrophobicity and oleophobicity to the surface of silica particles. The prepared PDMS-coated silica hybrid particles with long PDMS chains exhibited a water contact angle of 151.2° and an oil contact angle of 15.2° due to the rough surface morphology and hydrophobic long-chain effects. Furthermore, the resulting organic-inorganic hybrid particles were thermally stable up to 420 °C. This controlled approach endowed the organic-inorganic hybrid particles with both superhydrophobic and oleophobic surfaces and, therefore, these particles were proven to be suitable for waterproof applications.

Development of carbon capture coating to improve the durability of concrete structures

A novel carbon capture (CC) coating was developed using CO2-activated dicalcium silicate, aiming to enhance the durability of concrete structures and sequestrate CO2. The carbonation products, microstructure and effects validation of the CC coating were investigated. The results showed that the CC coating could achieve a relatively high carbonation degree of 23.3% after 30-min carbonation. The moisture-saturated environment in the CC coating facilitated the formation of a gradient structure with relatively homogeneous carbonation products, i.e. small CaCO3 crystals (calcite, aragonite, and amorphous CaCO3) and highly polymerized silica gel, thereby rapidly densifying the microstructure. The CC coating with a thickness of approximately 200 μm significantly improved the concrete durability (decreasing the capillary water absorption by 20.5% after 30-min carbonation) and exhibited a satisfactory bonding strength (2.74 MPa after 30-min carbonation), which has a promising application scenario in extending the service life of concrete structures and reducing the carbon emissions.

Silicon Nutrition in Plants under Water-Deficit Conditions: Overview and Prospects

Drought is one of the major constraints for sustainable crop production worldwide, especially in arid and semiarid regions. The global warming and climate change scenario has worsened the dilemma of water scarcity, creating an immediate threat to food security. Conserving water resources and exploiting various strategies that enable plants to withstand water deficits need to be urgently addressed. Drought adversely affects plant growth by modulating a range of physio-chemical, metabolic, and molecular processes inside the plant body, which ultimately reduces crop productivity. Besides developing drought-tolerant cultivars, better nutrient management could be a promising strategy to enhance drought tolerance in crop plants. Silicon, a quasi-essential element, is known to play a vital role in improving crop performance under a range of biotic and abiotic stresses. This review discusses the potential of Si application in attenuating the adverse effects of water-deficit stress. Silicon enhances plant growth by improving seed germination, cell membrane stability, carbon assimilation, plant–water relations and osmotic adjustment (by accumulating soluble sugars, proline and glycine betaine). It triggers the activity of antioxidants, promotes the biosynthesis of phytohormones, enhances nutrient acquisition and regulates the activity of vital enzymes in plants under drought stress. Silicon also induces anatomical changes in the plant cell wall through the deposition of polymerized amorphous silica (SiO2-nH2O), thereby improving stem and leaf erectness and reducing lodging. Further, Si-mediated physiological, biochemical and molecular mechanisms associated with drought tolerance in plants and future research prospects have been elucidated.

Experimental determination of quartz solubility in H2O-CaCl2 solutions at 600–900 °C and 0.6–1.4 GPa

Abstract Fluid-mediated calcium metasomatism is often associated with strong silica mobility and the presence of chlorides in solution. To help quantify mass transfer at lower crustal and upper mantle conditions, we measured quartz solubility in H2O-CaCl2 solutions at 0.6–1.4 GPa, 600–900 °C, and salt concentrations to 50 mol%. Solubility was determined by weight loss of single-crystals using hydrothermal piston-cylinder methods. All experiments were conducted at salinity lower than salt saturation. Quartz solubility declines exponentially with added CaCl2 at all conditions investigated, with no evidence for complexing between silica and Ca. The decline in solubility is similar to that in H2O-CO2 but substantially greater than that in H2O-NaCl at the same pressure and temperature. At each temperature, quartz solubility at low salinity (XCaCl2 < 0.1) depends strongly on pressure, whereas at higher XCaCl2 it is nearly pressure independent. This behavior is consistent with a transition from an aqueous solvent to a molten salt near XCaCl2 ~0.1. The solubility data were used to develop a thermodynamic model of H2O-CaCl2 fluids. Assuming ideal molten-salt behavior and utilizing previous models for polymerization of hydrous silica, we derived values for the activity of H2O (aH2O), and for the CaCl2 dissociation factor (α), which may vary from 0 (fully associated) to 2 (fully dissociated). The model accurately reproduces our data along with those of previous work and implies that, at conditions of this study, CaCl2 is largely associated (<0.2) at H2O density <0.85 g/cm3. Dissociation rises isothermally with increasing density, reaching ~1.4 at 600 °C, 1.4 GPa. The variation in silica molality with aH2O in H2O-CaCl2 is nearly identical to that in H2O-CO2 solutions at 800 °C and 1.0 GPa, consistent with the absence of Ca-silicate complexing. The results suggest that the ionization state of the salt solution is an important determinant of aH2O, and that H2O-CaCl2 fluids exhibit nearly ideal molecular mixing over a wider range of conditions than implied by previous modeling. The new data help interpret natural examples of large-scale Ca-metasomatism in a wide range of lower crustal and upper mantle settings.

Polymer-Rich Dense Phase Can Concentrate Metastable Silica Precursors and Regulate Their Mineralization.

Multistep mineralization processes are pivotal in the fabrication of functional materials and are often characterized by far from equilibrium conditions and high supersaturation. Interestingly, such 'nonclassical' mineralization pathways are widespread in biological systems, even though concentrating molecules well beyond their saturation level is incompatible with cellular homeostasis. Here, we show how polymer phase separation can facilitate bioinspired silica formation by passively concentrating the inorganic building blocks within the polymer dense phase. The high affinity of the dense phase to mobile silica precursors generates a diffusive flux against the concentration gradient, similar to dynamic equilibrium, and the resulting high supersaturation leads to precipitation of insoluble silica. Manipulating the chemistry of the dense phase allows to control the delicate interplay between polymer chemistry and silica precipitation. These results connect two phase transition phenomena, mineralization and coacervation, and offer a framework to achieve better control of mineral formation.

Fast Li+ Transport via Silica Network‐Driven Nanochannels in Ionomer‐in‐Framework for Lithium Metal Batteries

AbstractFor the development of all‐solid‐state lithium metal batteries (LMBs), a high‐porous silica aerogel (SA)‐reinforced single‐Li+ conducting nanocomposite polymer electrolyte (NPE) is prepared via two‐step selective functionalization. The mesoporous SA is introduced as a mechanical framework for NPE as well as a channel for fast lithium cation migration. Two types of monomers containing weak‐binding imide anions and Li+ cations are synthesized and used to prepare NPEs, where these monomers are grafted in SA to produce SA‐based NPEs (SANPEs) as ionomer‐in‐framework. This hybrid SANPE exhibits high ionic conductivities (≈10−3 S cm−1), high modulus (≈105 Pa), high lithium transference number (0.84), and wide electrochemical window (>4.8 V). The resultant SANPE in the lithium symmetric cell possesses long‐term cyclic stability without short‐circuiting over 800 h under 0.2 mA cm−2. Furthermore, the LiFePO4|SANPE|Li solid‐state batteries present a high discharge capacity of 167 mAh g−1 at 0.1 C, good rate capability up to 1 C, wide operating temperatures (from −10 to 40 °C), and a stable cycling performance with 97% capacity retention and 100% coulombic efficiency after 75 cycles at 1 C and 25 °C. The SANPE demonstrates a new design principle for solid‐state electrolytes, allowing for a perfect complex between inorganic silica and organic polymer, for high‐energy‐density LMBs.

Experimental Study on Mechanical Properties and Durability of Polymer Silica Fume Concrete with Vinyl Ester Resin.

Polymer concrete, which contains silica fume powder and vinyl ester resin as two replacements for Portland cement, has improved mechanical properties and durability compared to ordinary concrete. Thus, this kind of concrete is considered to be a high-strength concrete that is resistant to corrosion and chemical attacks. In this paper, the effects of the combination of silica fume powder and vinyl ester resin as two Portland cement replacements on the workability and slump value, initial and final water absorption, compressive and tensile strength, and failure and fracture paths of the polymer concrete have been investigated. All investigations have been based on 16 different polymer concrete mixture designs. The results indicate that the optimum percentages for a combination of silica fume and vinyl ester resin, which has the maximum compressive strength (34.26 MPa) and the maximum tensile strength (4.92 MPa), are a combination of 10% silica fume and 5% vinyl ester resin. To evaluate the durability of polymer concrete, the water absorption of all mixture designs has also been measured. Accordingly, the mixture design, which includes a combination of 15% vinyl ester resin and 5% silica fume, has a minimum initial and final water absorption equal to 0.62% and 1.95%, respectively.

Synergistic effect of calcium and magnesium on silica polymerization and colloidal silica fouling in bench-scale reverse osmosis filtration

Synergistic effect of calcium and magnesium on silica polymerization and colloidal silica fouling in bench-scale reverse osmosis filtration

Comparative experiments on a new CaCl2-based composite material and zeolite 13X inside a thermochemical heat storage reactor

Thermal energy storage includes sensible, latent and thermochemical heat storage. The latter is particularly interesting because the heat is stored as a chemical potential, which reduces heat loss in long-term applications. The viability of thermochemical storage systems strongly depends on the energy density of the storage material. The development of high energy density materials is thus essential to achieve compact systems suitable for a wide range of applications. A new sol-gel composite material is investigated here: it is composed of CaCl2 dispersed within a matrix of silica and PEG-600 polymer. Composite materials containing CaCl2 have the highest storage capacities and seem to be the most promising candidates. The aim is to develop a composite that is both efficient and stable. The suitability of the material depends on the ability of the PEG to stabilise calcium chloride and prevent its deliquescence and leakage. The experimental results are compared to those obtained using zeolite 13X, which is a reference adsorbent material.

A hybrid hydrogel constructed using drug loaded mesoporous silica and multiple response copolymer as an intelligent dressing for wound healing of diabetic foot ulcers.

Traditional wound dressings have poor mechanical properties and a single function, which cannot achieve rapid healing of diabetic wounds in a unique physiological microenvironment. In order to develop multifunctional hydrogel dressings with appropriate biological activity to accelerate wound healing and obtain better clinical therapeutic effects, herein we report a hybrid system based on drug loaded mesoporous silica and injectable polymer hydrogels mixed with hypoglycemic drug metformin (Met) as a dressing for diabetic wounds. Firstly, a copolymer with the phenylboronic acid group in the side group, poly(acrylamide-co-dimethylaminopropylacrylamide-co-methacrylamidophenylboronic acid) (abbreviated as PB), was prepared. PB was mixed with polyvinyl alcohol (PVA) to obtain an injectable hydrogel (named PP) with pH/glucose dual responsiveness, which was formed through the combination of the phenylborate group of PB and o-diol of PVA. In another reaction, polydopamine-modified mesoporous silica nanoparticles (MSN@PDA) were prepared and used to adsorb antibiotic tetracycline hydrochloride (TH) to obtain drug-loaded MSN@PDA-TH nanoparticles. Subsequently, the hybrid hydrogel dressing (abbreviated as PP/MSN@PDA-TH/Met) was obtained by mixing PB, PVA, Met and MSN@PDA-TH. The self-healing, rheological and adhesive properties of the hybrid hydrogel were characterized. The results show that the hydrogel dressing has good physical properties. Met and TH were released in vitro in different pH media and glucose environments. The results show that the hydrogel dressing has dual responsiveness towards pH and glucose, and can continuously release metformin and tetracycline, which is conducive to accelerating wound healing. The antimicrobial activity, ROS clearance ability and biocompatibility of the hydrogel dressing were evaluated. The results indicate that the hydrogel dressing was multifunctional. Finally, a full-thickness wound repair model of diabetic mice induced by streptozotocin (STZ) was established. The hybrid hydrogel dressing was applied to the wound surface of mice. The wound healing testing on diabetic mice confirmed that the wound covered with the hybrid hydrogel dressing was completely healed with the formation of the new skin and hair within 9 days to 12 days. Histological analysis indicates that, compared to the PBS control, the hydrogel dressing did not cause significant inflammation in the wound, and a large number of blood vessels, glands and hair follicles appeared. This study provides a good strategy for multi-drug synergistic treatment of diabetic foot ulcers.

SYNTHESIS OF SOL-GEL SILICA: OPTIMIZATION OF SUPPORTS FOR CATALYSTS USING ORANGE BIO-RESIDUES

Citrus bio-residues play an important role in obtaining different materials through the sol-gel method. This method is a friendly technique. These waste consists of organic compounds with a wide variety and chemical reactivity. In this way, it has been recognized that this kind of waste, generated mostly by the food industry, has an important potential to obtain silica to be used as a catalyst support. Provided that the principles of green chemistry and circular economy are present. This work aims to use the peel and juice of orange bio-residues, in acidic hydrolysis to obtain sol-gel silica. FT-IR spectra confirm silica formation according to the centered band at 1070 cm-1. In addition, SEM and TEM images of the synthesized materials were compared to a reference sample to contrast their morphology. Strictly speaking, orange bio-residues promote silica polymerization, due to the availability of complex organic compounds and their abundant acidic contribution.

Technology of a novel conidia-tablet formulation and packaging type to increase Beauveria bassiana (Hypocreales: Ophiocordycipitaceae) shelf life at room temperature

Description of the subject. This study describes development of mycoinsecticide formulations containing dry conidia of the entomopathogenic fungus Beauveria bassiana combined with various inert excipients in tablet form to facilitate conidia dispersion in water and to maintain viability during storage. Objectives. This study aimed to evaluate the tablet formation of B. bassiana conidia associated with different inert excipient under direct compression in a hydraulic press. Method. Evaluation and validation of the mechanical and storage properties of conidial tablets in different types of packaging. Results. The tablet formulation containing 30% conidia (active ingredient) and 70% cornstarch (inert excipient) displayed satisfactory results regarding mechanical resistance and dispersion in water. This tablet exhibited hardness and friability of 173.94 N and 0.34%, respectively. The tablet disintegration rate in water occurred in 2 min, presenting a rapid dispersion of 109 conidia∙ml-1. Tablet stored in polyethylene pot with polymerized silica exhibited viability ≥ 80% over 180 days storage (25-28 °C). Conclusions. The formulation-packaging binomial is promising, considering the physical-chemical tablet parameters and the viability data. The conidia:cornstarch tablet type formulation provides a relevant cost-benefit ratio of a simple production process of a bioinsecticide, besides the use of low-cost adjuvant and packaging (polyethylene pot). Considering that most biopesticide products require storage under refrigeration, this work becomes important since the formulation remained viable for 180-days storage under room temperature conditions.

Enantiomeric Separation by Capillary Electro chromatography with a Novel β-cyclodextrin-hyperbranched Carbosilane–silica Polymer Coating

A new type of β-cyclodextrin-modified hyperbranched carbosilane (β-CD@HBC) stationary phase was synthesized by combining hyperbranched carbosilane with the -OH group of β-cyclodextrin, and then the β-CD@HBC was used as astationary phase to fix it on the inner wall of capillary column, application in chiral drug separation. The chromatographic behaviour of the stationary phase was studied. The preliminary test results showed that the β-CD@HBC coated OT column has the ability to separate a variety of enantiomers, such as clenbuterol, ibuprofen, enrofloxacin, hlorpheniramine, isoproterenol hydrochloride, epinephrine, Phenylalanine, and Ketoprofen. The β-CD@HBC coated OT column has good repeatability and stability. The relative standard deviations (RSD) between runs, between days, and between columns were less than 1.5%, 1.86%, and 4.83%, respectively. This paper shows that hyperbranched polymers have great potential and advantages in the application of capillary electrochromatography for chiral separation.

Ultrahigh magnetic resonance contrast switching with water gated polymer-silica nanoparticles.

Very high T1 magnetic resonance imaging (MRI) switches can be obtained with pH-responsive polymer-coated paramagnetic mesoporous silica nanoparticles (MSNs), as the local environment traverses the pKa of the polymer coat (Δr1 ∼ 50 mM-1 s-1 at 1.5 T and Δr1 ∼ 22 mM-1 s-1 at 3 T). We assign these characteristics to a strong peripheral hydration capping at the mesopores, impacting channel-confined water mobility such that outer sphere contributions to contrast are greatly enhanced.

Nanoscale Mg-Depleted Layers Slow Carbonation of Forsterite (Mg2SiO4) When Water Is Limited

Passivation of silicate surfaces by accumulated reaction products is an obstacle to efficient CO2 mineralization. In this study, we investigate a unique passivation effect during the carbonation of the basalt mineral forsterite (Mg2SiO4) in humid supercritical CO2 (50 °C, 90 bar). Using in situ high-pressure infrared spectroscopy, we demonstrate that dissolution of forsterite into a thin water film slows significantly after reaction for ≈24 h, even under far-from-equilibrium conditions. 29Si magic angle spinning nuclear magnetic resonance spectroscopy detects a highly polymerized amorphous silica at this stage. On the basis of transmission electron microscopy and energy dispersive X-ray spectroscopy, we show that the silica is present as a Mg-depleted layer that is just 2–3 nm thick on the reacted forsterite particles. The decrease in the level of forsterite dissolution in the presence of an extraordinarily thin Mg-depleted layer can be strongly linked to properties of the thin fluid film at the surface, highlighting the importance of water during mineral carbonation. This study furthers our understanding of silicate mineral carbonation under select low-water, humidified fluid conditions relevant to basaltic geologic reservoirs, recovery of critical elements by carbonation of mafic ores, and sequestration of atmospheric CO2 by enhanced rock weathering.

Modelling and optimization of reinforced nano silica polymer

Materials used to make the various parts should be able to withstand the wear and tear for longer product life. Polymers are preferred to use for some of the applications because of its lesser weight and its thermophysical and Mechanical properties. The present work is to investigate the abrasive rate of reinforced nano silica composite which is extracted from sugar cane bagas by pin on disc testing. The factors influences the abrasive rate of the composites are predicted by multilinear regression analysis. The impact of each parameter of reinforcement, input load and sliding speed on abrasive behavior is identified by analysis of variance.It is identified that in the dry sliding, wear of the epoxy silica composite is inversely proportional to thickness and constituents of reinforcement. The weight bearing strength of the exopy has been improved with the addition of nano silica. Micro-structural study is done by SEM to investigate the wear behaviour of epoxy nano silica composite with Non-lubricant sliding circumstances.

Early and middle stages of multicomponent cement hydration under the effect of geothermal water and increased temperatures

The study of early and middle stages of hydration in the systems composed of Portland cement Class G (PC) – silica fume (SF) – metakaolin (MK) and PC – SF – blast furnace slag (BFS) was performed by Isothermal calorimetry, Thermogravimetric, X-ray diffraction, and Fourier Transform Infrared analyses in the mid-IR region. The influence of composition, temperature (25, 60, and 80 °C), and hydration media (water and geothermal solution) was investigated. Geothermal solution delayed main hydration, however, considering the times of the calorimetric maxima at 25 °C, it led to the formation of hydration products with more polymerized structures in larger amounts than during the hydration process using water. At higher temperatures, the deceleration effect of the geothermal solution became less evident, nevertheless higher degree of silica polymerization and more hydration products were found in samples that were hydrated in water. Regardless of the hydration temperature, the hydration carried out in geothermal solution became more effective already after 40 h. The effect of fine additives advanced by higher temperatures resulted in accelerated hydration represented by faster depletion of gypsum. The presence of SO4-AFm and CO3-AFm phases was confirmed during the deceleration period of the hydration process using water and geothermal solution, respectively.

Reducing carbonation degradation and enhancing elastic properties of calcium silicate hydrates using biomimetic molecules

This study presents a novel way of reducing the carbonation-induced degradation of CSH using organic molecules. Synthetic CSH batches were prepared with the addition of l-aspartic acid and polydopamine. The effects of these molecules on the synthesized CSH before and after carbonation were monitored using various experimental techniques, including 29Si NMR, TEM, nanoindentation, and FTIR. It was observed that, without the presence of biomimetic molecules, CSH was converted to a fully polymerized silica gel after 168 h of carbonation, as evident by the presence of Q3 and Q4 species in 29Si NMR spectra. On the other hand, biomimetic molecules modified CSH retained the original chain-like arrangements even after 28 days of carbonation, as identified by the presence of Q1 and Q2 species in 29Si NMR spectra. Additionally, the biomimetic molecules modification increased the elastic modulus of CSH by 3–9 times, which were further increased upon carbonation.