Characterisation of stoichiometric sol–gel mullite by fourier transform infrared spectroscopy

Efficient ion transport mode and stable Li+-interface induced by the introduction of HA-SiO2 in PVDF-based electrolytes for solid-state lithium metal batteries

Polyvinylidene fluoride (PVDF) materials have been widely investigated as polymer matrix for solid polymer electrolytes (SPEs) due to their high dielectric constant, electroactive effect (piezo-, pyro-, and ferroelectricity), and excellent thermal stability. However, the poor interface compatibility caused by highly reactive residual solvents and unsatisfactory ionic conductivity owing to sluggish Li+ transport kinetics are principal bottlenecks impeding the further development of PVDF-based electrolytes. Herein, we design a PVDF-based electrolytes with the assistance of hydrophilic-amorphous silica (HA-SiO2). Result shows that HA-SiO2 can tightly anchor reactive residual solvents on the surface due to its high adsorption energy with [Li(DMF)3]+, which not only dramatically suppresses the severe side reactions between the electrolyte and Li anode, but also provides additional Li+-hopping sites on the surface of HA-SiO2. Meanwhile, the anchored [Li(DMF)3]+ snatch away partial Li+ that should have coordinated with polymer chains, which significantly improve ion transfer efficacy. Benefiting from the unique ion transport mode and enhanced interface stability, the designed PVDF-based electrolytes exhibit a high ionic conductivity (1.28 × 10-4 S cm-1), sufficient Li+ transference number (tLi+ = 0.71) and excellent oxidation resistance (4.9 V vs. Li/Li+) at room temperature.

Hybrid Alumina-Silica Filler for Thermally Conductive Epoxidized Natural Rubber

Thermally conductive composites were prepared based on epoxidized natural rubber (ENR) filled with alumina, silica, and hybrid alumina and silica. The thermal conductivity and mechanical properties were assessed. It was observed that the interactions of polar functional groups in the fillers and epoxy group in ENR supported a fine dispersion of filler in the ENR matrix. The mechanical properties were improved with alumina, silica, and hybrid alumina/silica loadings. The ENR/Silica composite at 50 phr of silica provided the highest 60 shore A hardness, a maximum 100% modulus up to 0.37 MPa, and the highest tensile strength of 27.3 MPa, while ENR/Alumina with 50 phr alumina gave the best thermal conductivity. The hybrid alumina/silica filler at 25/25 phr significantly improved the mechanical properties and thermal conductivity in an ENR composite. That is, the thermal conductivity of the ENR/Hybrid filler was 2.23 W/mK, much higher than that of gum ENR (1.16 W/mK). The experimental results were further analyzed using ANOVA and it was found that the ENR/Hybrid filler showed significant increases in mechanical and thermal properties compared to gum ENR. Moreover, silica in the hybrid composites contributed to higher strength when compared to both gum ENR and ENR/Alumina composites. The hybrid filler system also favors process ability with energy savings. As a result, ENR filled with hybrid alumina/silica is an alternative thermally conductive elastomeric material to expensive silicone rubber, and it could have commercial applications in the fabrication of electronic devices, solar energy conversion, rechargeable batteries, and sensors.

Experimental study on enrichment of heavy metals by modified mullite during co-combustion of lignite with eucalyptus wood

Modifying the content of oxygen vacancies (OVs) has emerged as a crucial approach to tailoring silicate's adsorption properties, microstructure, conductivity, and catalytic performance. Some studies have reported the formation of OVs during ammonia treatment. However, there are limited studies on the production of OV-enriched mullite by treating it with N-containing compounds at low temperatures. In this work, formamide, urea, and ammonium acetate were used as ammonia-assisted reduction modifiers to induce oxygen vacancies in mullite at 30 ℃, 60 ℃, and 90 °C. The aim was to enhance the enrichment effect of heavy metals (Cr, Cu, Mn, Ni, Pb, Zn) during the co-combustion of coal and biomass. The modified mullite was analyzed by using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The results indicated that the particle size of mullite decreased, and the concentration of internal Al3+ ions and oxygen vacancies was enhanced. Coal-biomass-mullite combustion experiments were conducted in a tubular furnace at 900 °C, revealing a significant enhancement in the enrichment of heavy metals during the combustion process, particularly when the modification temperature was 60 °C using ammonium acetate as the modifier. This work holds significant importance for developing novel heavy metal adsorbents and the reduction of pollutant emissions from coal-biomass co-combustion in industrial applications.

Fabrication and synergistically enhanced photocatalytic activity of ternary kaolinite, TiO2, and Al2O3 (K65T30A5) nanocomposite for visible-light-induced degradation of methylene blue and remazol red dye

The ternary photocatalyst ((Al2Si2O5 (OH)4/TiO2/Al2O3) composites (where w/w = 65, 30, and 5 wt%) denoted K65T30A5 were successfully synthesized and examined for their efficiency in removing cationic (Methylene Blue, MB) and anionic (Remazol Red, RR) dye from aqueous medium under visible-light irradiation. A series of nanocomposites with varied wt% of kaolinite, TiO2, and Al2O3 were prepared through sonication followed by calcination at 600 °C. X-ray diffraction (XRD) analysis confirmed the crystallinity of the synthesized materials and established their average crystal size to be 83.87 nm. The morphological structure, composite molecule, and surface properties of the resulting K65T30A5 were characterized using FTIR, FE-SEM, and EDS analyses to confirm the successful fabrication of the nanocomposite. FTIR and EDS elemental mapping analyses confirmed the presence of Al, Si, Ti, and O elements in the nanocomposites. The composites exhibited photocatalytic behaviour across the UV-visible spectra, with values varying from the ultraviolet to the visible region with a sharp increase in reflectance at 510 nm. Near-complete degradation of MB (97.66 %) was achieved within 90 min at pH 9 and a 10 mg/L dye concentration, while RR removal reached 90.66 % within 120 min at pH 3.5 and the same dye concentration under visible light irradiation. The catalyst exhibited robust stability, retaining its efficiency by removing 85.09 % of MB and 80.21 % of RR dye after three reuse cycles. The composite catalyst discussed in this study emerges as a promising material for straightforward fabrication techniques, featuring a high percentage of kaolinite and proving to be a cost-effective solution for large-scale water and wastewater treatment processes.

Sol-Gel Synthesis of Zinc Alumotitanate, Monitoring of Chelation, Hydrolysis, Condensation, and Crystallization Processes

Zinc alumotitanate sorbents with various compositions were prepared through sol-gel synthesis with the use of ethyl acetoacetate as a chelating agent. The formation and decomposition of chelates, providing insight into sol-gel process advancement, have been successfully monitored via 1H NMR, 13C NMR, and FTIR spectroscopy. It has been established that Al(OBus)3 and Ti(OBun)4 react completely with Eaa, forming chelates after 1 h, while after 24 h hydrolysis is already advanced. Hydrolysis is accelerated in the presence of Zn(NO2)3·6H2O, supplying the water needed for hydrolysis. In dried gels, the amount of ethyl acetoacetate is greatly reduced, and it is mainly present unbound. According to XRD analysis, samples with none or less titania are composed of layered double hydroxide, while in samples with greater amounts of titania, crystal nitrates are present. In all samples except those without Al, the spinel phase with variable composition crystallizes.

A long-term study on structural changes in calcium aluminate silicate hydrates

Production of blended cements in which Portland cement is combined with supplementary cementitious materials (SCM) is an effective strategy for reducing the CO₂ emissions during cement manufacturing and achieving sustainable concrete production. However, the high Al₂O₃ and SiO₂ contents of SCM change the chemical composition of the main hydration product, calcium aluminate silicate hydrate (C-A-S-H). Herein, spectroscopic and structural data for C-A-S-H gels are reported in a large range of equilibration times from 3 months up to 2 years and Al/Si molar ratios from 0.001 to 0.2. The ²⁷Al MAS NMR spectroscopy and thermogravimetric analysis indicate that in addition to the C-A-S-H phase, secondary phases such as strätlingite, katoite, Al(OH)₃ and calcium aluminate hydrate are present at Al/Si ≥ 0.03 limiting the uptake of Al in C-A-S-H. More secondary phases are present at higher Al concentrations; their content decreases with equilibration time while more Al is taken up in the C-A-S-H phase. At low Al contents, Al concentrations decrease strongly with time indicating a slow equilibration, in contrast to high Al contents where a clear change in Al concentrations over time was not observed indicating that the equilibrium has been reached faster. The ²⁷Al NMR studies show that tetrahedrally coordinated Al is incorporated in C-A-S-H and its amount increases with the amount of Al present in the solution.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1617/s11527-022-02080-x.

Thermally Insulating, Thermal Shock Resistant Calcium Aluminate Phosphate Cement Composites for Reservoir Thermal Energy Storage

This paper presents the use of hydrophobic silica aerogel (HSA) and hydrophilic fly ash cenosphere (FCS) aggregates for improvements in the thermal insulating and mechanical properties of 100- and 250 °C-autoclaved calcium aluminate phosphate (CaP) cement composites reinforced with micro-glass (MGF) and micro-carbon (MCF) fibers for deployment in medium- (100 °C) and high-temperature (250 °C) reservoir thermal energy storage systems. The following six factors were assessed: (1) Hydrothermal stability of HSA; (2) Pozzolanic activity of the two aggregates and MGF in an alkali cement environment; (3) CaP cement slurry heat release during hydration and chemical reactions; (4) Composite phase compositions and phase transitions; (5) Mechanical behavior; (6) Thermal shock (TS) resistance at temperature gradients of 150 and 225 °C. The results showed that hydrophobic trimethylsilyl groups in trimethylsiloxy-linked silica aerogel structure were susceptible to hydrothermal degradation at 250 °C. This degradation was followed by pozzolanic reactions (PR) of HSA, its dissolution, and the formation of a porous microstructure that caused a major loss in the compressive strength of the composites at 250 °C. The pozzolanic activities of FCS and MGF were moderate, and they offered improved interfacial bonding at cement-FCS and cement-MGF joints through a bridging effect by PR products. Despite the PR of MGF, both MGF and MCF played an essential role in minimizing the considerable losses in compressive strength, particularly in toughness, engendered by incorporating weak HSA. As a result, a FCS/HSA ratio of 90/10 in the CaP composite system was identified as the most effective hybrid insulating aggregate composition, with a persistent compressive strength of more than 7 MPa after three TS tests at a 150 °C temperature gradient. This composite displayed thermal conductivity of 0.28 and 0.35 W/mK after TS with 225 and 150 °C thermal gradients, respectively. These values, below the TC of water (TC water = 0.6 W/mK), were measured under water-saturated conditions for applications in underground reservoirs. However, considering the hydrothermal disintegration of HSA at 250 °C, these CaP composites have potential applications for use in thermally insulating, thermal shock-resistant well cement in a mid-temperature range (100 to 175 °C) reservoir thermal energy storage system.

Hydrophobic Lightweight Cement with Thermal Shock Resistance and Thermal Insulating Properties for Energy-Storage Geothermal Well Systems

This study assessed the possibility of using polymethylhydrosiloxane (PMHS)-treated fly ash cenospheres (FCS) for formulating a thermally insulating and thermal shock (TS)-resistant cementitious blend with calcium aluminate cement. To prevent FCS degradation in an alkaline cement environment at high temperatures, the cenospheres were pre-treated with sodium metasilicate to form silanol and aluminol groups on their surface. These groups participated in a dehydrogenation reaction with the functional ≡Si–H groups within PMHS with the formation of siloxane oxygen-linked M-FCS (M: Al or Si). At high hydrothermal temperatures of 175 and 250 °C, some Si–O–Si and SiCH₃ bonds ruptured, causing depolymerization of the polymer at the FCS surface and hydroxylation of the raptured sites with the formation of silanol groups. Repolymerization through self-condensation between the silanol groups followed, resulting in the transformation of siloxane to low crosslinked silicon-like polymer as a repolymerization-induced product (RIP) without carbon. The RIP provided adequate protection of FCS from pozzolanic reactions (PR), which was confirmed by the decline in zeolites as the products of PR of FCS. Cements with PMHS-treated FCS withstood both hydrothermal and thermal temperature of 250 °C in TS tests, and they also showed improved compressive strength, toughness, and water repellency as well as decreased thermal conductivity. The lubricating properties of PMHS increased the fluidity of lightweight slurries.

Insights into the Microstructural Evolution Occurring during Pyrolysis of Metal-Modified Ceramers Studied through Selective SiO2 Removal

Silicon oxycarbide ceramers containing 5% aluminum, zirconium, and cobalt with respect to the total Si amount are prepared from a commercial polysiloxane and molecular precursors and pyrolyzed at temperatures ranging from 500 to 1000 °C. HF etching is carried out to partially digest the silica phase, thus revealing structural characteristics of the materials, which depend upon the incorporated heteroatom. From the structural and textural characterization, it was deduced that when Al enters into the ceramer structure, the crosslinking degree is increased, leading to lower carbon domain size and carbon incorporation as well. On the contrary, the substitution by Zr induced a phase-separated SiO₂-ZrO₂ network with some degree of mesoporosity even at high pyrolysis temperatures. Co, however, forms small carbidic crystallites, which strongly modifies the carbonaceous phase in such a way that even when it is added in a small amount and in combination with other heteroatoms, this transient metal dominates the structural characteristics of the ceramer material. This systematic study of the ceramer compounds allows the identification of the ultimate properties of the polymer-derived ceramic composites.

Converting molecular layer deposited alucone films into Al2O3/alucone hybrid multilayers by plasma densification

Alucones are one of the best-known films in the Molecular Layer Deposition (MLD) field. In this work, we prove that alucone/Al2O3 nanolaminate synthesis can be successfully performed by alternating alucone MLD growth with static O2 plasma exposures. Upon plasma treatment, only the top part of the alucone is densified into Al2O3, while the rest of the film remains relatively unaltered. X-ray reflectivity (XRR) and X-ray photoelectron spectroscopy (XPS) depth profiling show that the process yields a bilayer structure, which remains stable in air. Fourier-transform infrared spectroscopy (FTIR) measurements show that Al2O3 features are generated after plasma treatment, while the original alucone features remain, confirming that plasma treatment results in a bilayer structure. Also, an intermediate carboxylate is created in the interface. Calculations of Al atom density during plasma exposure point towards a partial loss of Al atoms during plasma treatment, in addition to the removal of the glycerol backbone. The effect of different process parameters has been studied. Densification at the highest temperature possible (200 °C) has the best alucone preservation without hindering its thermal stability. In addition, operating at the lowest plasma power is found the most beneficial for the film, but there is a threshold that must be surpassed to achieve successful densification. About 70% of the original alucone film thickness can be expected to remain after densification, but thicker films may result in more diffuse interfaces. Additionally, this process has also been successfully performed in multilayers, showing real potential for encapsulation applications.

Physico-chemical Characterization of Hydrochloric Acid-treated Kaolin Clay: An Industry Approach as a Potential Catalyst

AIMS AND OBJECTIVE

This study explains the FT-IR, XRD, XRF, SEM/EDX, TGA, and DSC/DTA characterization of commercially available kaolin clay. The objective of this paper is to explore the prominent utilization of kandites clay and useful chemical aspects for the modification of kaolin clay minerals.

MATERIALS AND METHODS

The untreated kaolin sample has been procured in this experimental work from AksharChem, Gujrat, India. The kaolin clay was treated with 4M hydrochloric acid. FT-IR, XRD, XRF, SEM/EDX, TGA, and DSC/DTA characterization methods have been used.

RESULTS

Loss on ignition was found at 10.89%. The fingerprint region of the acid-treated sample has broad and more bending vibrations than untreated samples. The high weight percentage of Ti and CaCO3 were spotted in the scanning electron micrograph by both atomic % and weight %. The FT-IR revealed the functional group of Al-O, A1-OH, and Si-O.

CONCLUSION

The morphology indicates that the presences of large particles are in the form of agglomerates. It was found that impurity like scandium vanished and manganese traced by the same atomic % 0.01 of zinc which had no presence after acid treatment. Thermogravimetric analysis indicates the sharp increments in heat flow in-between temperatures 0°C to 200°C and consequently increments in between 500°C to 550°C, a suitable range for the pyrolysis. Low amount of alumina and high amount of silica has been found out. TGA and DTA analysis satisfy the waste plastic valorization temperature ranges.

Droplet assisted growth and shaping of alumina and mixed alumina-silicone 1-dimensional nanostructures

Since the discovery of silicone nanofilaments a decade ago, room temperature droplet assisted growth and shaping using silanes has been used to synthesize various silicone-based nanostructures. In the present work, we report an extension of this synthesis technique to synthesize nanostructures of new materials. We have successfully synthesized one-dimensional assemblies of beads or necklaces based on alumina (Al) and mixed alumina-silicone (AlSi) nanostructures exhibiting a similar structure as silicone nanofilaments. The characterization of the synthesized nanostructures was performed using different tools, including scanning and transmission electron microscopy, energy dispersive x-ray spectroscopy, and infrared and NMR spectroscopy. Selected area electron diffraction revealed that the nanostructures are amorphous in nature, and the growth behavior and thermal stability of nanostructures are also discussed.

A novel single-step hydrogenation of 2-imidazolecarboxaldehyde to 2-methylimidazole over Pd-impregnated Al–Ti mixed oxide and kinetics

A novel and clean route for the hydrogenation of 2-imidazolecarboxaldehyde to 2-methylimidazole with high yield and selectivity over a Pd/ATMO catalyst.

Adsorption of fluoride from aqueous solution by fly ash cenospheres modified with paper mill lime mud: Experimental and modeling

Fluoride removal from aqueous solution by adsorption using fly ash cenospheres (FAC) modified with paper mill lime mud (LM) as composite adsorbent had been investigated. The characterization of FAC and composite adsorbent were analyzed by Scanning electron spectroscope (SEM), Energy dispersive spectrometer (EDS), Brunauer emmett teller (BET) and Fourier transform infrared (FTIR), which demonstrated that the porous structure of composite adsorbent was obtained after surface modification. Adsorption of fluoride on modified fly ash cenospheres was fitted with pseudo-second-order model and Langmuir model. Response surface methodology (RSM) was employed to investigate the effects of F^- concentration, pH, adsorbent dosage and temperature on the removal efficiency. Analysis of variance (ANOVA) was used to test the adequacy of the mathematical models. The Nonelectrostatic model of modified fly ash cenospheres adsorbing fluoride was built through the Generalized composite method, indicating that two inner-spherical complexes, ≡SF and ≡SOHF^-, were formed in the adsorption process by means of the ligand exchange and surface complexation. Optimization of the adsorption conditions enabled the realization of the practical needs for fluoride contaminated water.

Textile/Al2O3–TiO2 nanocomposite as an antimicrobial and radical scavenger wound dressing

Improving the antimicrobial activity and radical scavenging ability of a textile-based nanocomposite is the key issue in developing a good and flexible wound dressing.

Sol–gel synthesis of transition-metal ion conjugated alumina-rich mullite nanocomposites with potential mechanical, dielectric and photoluminescence properties

Mechanical, dielectric and photoluminescence properties of transition-metal ions doped mullite nanocomposite synthesized via alkoxide hydrolysis.

Synthesis and characterization of Cu/Ag nanoparticle loaded mullite nanocomposite system: A potential candidate for antimicrobial and therapeutic applications

BACKGROUND

Microbial resistance to antibiotics has triggered the development of nanoscale materials as an alternative strategy. To stabilize these particles an inert support is needed.

METHOD

Porous nanomullite developed by sol-gel route is loaded with copper and silver nanoparticle by simple adsorption method. These nanocomposites are characterized using XRD, FTIR, TEM, SEM, EDAX and UV-visible spectrophotometer. Antibacterial activity of these nanocomposites against Gram positive and Gram negative bacteria are performed by bactericidal kinetics, flow cytometry and MTT assay. The underlying mechanisms behind the antimicrobial property and cell death are also investigated by EPR spectroscopy, intracellular ROS measurement and β-galactosidase assay. The cytocompatibility of the nanocomposites is investigated by cell viability (MTT), proliferation (Alamar blue) and wound healing assay of mammalian fibroblast cell line.

RESULTS

Nanocomposites show a fairly uniform distribution of metal nanoparticle within mullite matrix. They show excellent antibacterial activity. Metal ions/nanoparticle is found to be released from the materials (CM and SM). Treated cells manifested high intracellular oxidative stress and β-galactosidase activity in the growth medium. The effect of nanocomposites on mammalian cell line depends on exposure time and concentration. The scratch assay shows normal cell migration with respect to control.

CONCLUSION

The fabricated nanoparticles possess diverse antimicrobial mechanism and exhibit good cytocompatibility along with wound healing characteristics in mouse fibroblast cell line (L929).

GENERAL SIGNIFICANCE

The newly synthesized materials are promising candidates for the development of antimicrobial ceramic coatings for biomedical devices and therapeutic applications.

The FTIR studies of gels and thin films of Al2O3-TiO2 and Al2O3-TiO2-SiO2 systems

In this work, samples in form of bulk ones and thin films were obtained using the sol-gel method. The bulk samples were heated at different temperatures (500 °C, 850 °C and 1100 °C) corresponding to the annealing process of coatings, deposited on different substrates by dipping and pulling out samples from the proper sol with the stable speed. Thin films of both Al2O3-TiO2 and Al2O3-TiO2-SiO2 systems were deposited on carbon, steel and titanium substrates in two different ways: as single layers obtained from Al2O3 sol, TiO2 sol and Al2O3 sol or deposited as mixed coatings from Al2O3-TiO2 sol as well as Al2O3-TiO2-SiO2 one. All bulk samples were studied by the FTIR spectroscopy and the X-ray diffractometry while thin films were also investigated by the electron microscopy. In the IR spectra of Al2O3-TiO2 samples, as well as gels and coatings, bands due to the vibrations of AlO bonds of the octahedrally and tetrahedrally coordinated aluminum were observed. The IR spectra of samples of Al2O3-TiO2-SiO2 system differ from that of Al2O3-TiO2 ones in presence of bands assigned to the SiO bond vibrations and in positions of bands due to AlO bond vibrations. In all spectra of bulk samples and coatings, the positions of TiO bond vibrations were ascribed basing on the IR spectra of the pure anatase and rutile.

Characterization of ceramic roof tile wastes as pozzolanic admixture

The aim of this work is to study the recycling of tile wastes in the manufacture of blended cements. Cracked or broken ceramic bodies are not accepted as commercial products and, therefore, the unsold waste of the ceramic industry becomes an environment problem. The use of powdered roof tile in cement production, as pozzolanic addition, is reported. The wastes were classified as nonglazed, natural and black glazed tiles. The mineralogy of the powders was controlled by SEM-EDX microscopy, XRD analysis and FTIR spectroscopy. Particle size was checked by laser granulometry. Once the materials were fully characterized, pozzolanic lime consumption tests and Fratini tests were carried out. Different formulations of cement-tile blends were prepared by incorporation of up to 30% weight ratios of recycled waste. The compressive strength of the resulting specimens was measured. The evolution of hydration of the cement-tile blends was analyzed by XRD and FTIR techniques. Vibrational spectroscopy presented accurate evidence of pozzolanic activity. The results of the investigation confirmed the potential use of these waste materials to produce pozzolanic cement.

Surface modifications of alumina-silica glass fiber

A commercial glass fiber with Al(2)O(3) (68.4%) and SiO(2) (27.6%) as major components and CaO, TiO(2), Fe(2)O(3), and CuO as minor components was used as substrate in a silica sol-gel coating process. After cleaning, fiber samples were immersed into tetraethoxysilane (TEOS) at room temperature for 1 h, and then individual fiber samples were soaked into a simulated body fluid (SBF) solution,1 and removed after 5, 10, 15, and 20 days. Zeta potential and Energy Dispersive Spectroscopy (EDS) analyses showed that the fiber surfaces were effectively coated with a silica layer, which improved the formation of an HA layer upon immersion into SBF solution for 5 days. The coating became even more continuous after 10-day immersion. Fourier Transform Infrared Spectroscopic (FTIR) analyses confirmed that the coating layer has P--O vibration bands characteristic of hydroxyapatite (HA) near 1060 and 600 cm(-1).