Gel Precursor Research Articles

A quantitative analysis of dicalcium silicate synthesized via different sol-gel methods

In this paper, the synthesis of dicalcium silicate (C2S) via sol-gel (acid-catalyzed) process including aqueous route, non-aqueous route, and the Pechini method is reported. The composition of C2S (α, β, and γ) polymorphs, by-products, and amorphous content is established by employing QXRD (quantitative X-ray diffraction) studies. The attention has been focused to comprehend assay-amorphous relationships of C2S yield. The intermediate dried gels have been investigated via thermal analysis to monitor changes in the gel structures and precursors at low temperatures. The synthetic parameters including calcination time and temperature, Ca/Si molar ratio and mode of cooling have been optimized to get pure β-C2S with low amorphous content. The dependency of β → γ C2S polymorphic transformation on mean crystallite size (Dcryst) is studied. Overall, the Pechini method exhibits the most promising results for the purity and tuning of β-C2S polymorph. Moreover, the non-aqueous and aqueous routes require calcining the dried gel at a temperature higher than 1200 ℃ due to the presence of CaO precursors as CaCO3. The theoretical calculations of amorphous content have revealed that the change in the stoichiometry from 2.0 to 1.7 Ca/Si ratio is not a viable solution to improve the C2S product yield.

Green Synthesis of Nanostructure CeO2 Using Tea Extract: Characterization and Adsorption of Dye from Aqueous Phase.

Nanostructure CeO2 powders were synthesized using tea waste extract as gel precursor. The as-prepared samples were characterized by thermogravimetric analyzer (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Based on the TGA/DTG analysis, the intermediates of cerium chloride hydrates (CeCl3.4H2O and CeCl3.H2O) and cerium anhydrous (CeCl3) were produced, and the formation temperature of CeO2 was estimated to be 773 K. The cubic fluorite structure of CeO2 was detected to be the predominant species and was completely formed at the calcination temperature of 773K–1073 K with a crystal size between 8.8 and 11.4 nm based on the XRD measurement. Moreover, the main chemical state of ceria on the surface of the synthesized samples was confirmed to be tetravalent ceria by XPS. All samples show a strong Raman signal at a well-defined chemical shift of 463 cm−1 and a significant symmetry feature was observed, suggesting that the tetravalent ceria is the dominant species throughout the bulk sample. All the synthesized CeO2 calcined at different temperatures showed higher adsorption efficiency for Congo red (CR) compared with commercial CeO2. The adsorption efficiency maintained a steady state of more than 95% when the concentration of CR and adsorption temperature were varied in this study. The kinetic analysis showed that the second-order model was the appropriate model to interpret the adsorption behavior of synthesized CeO2. The calculated adsorption capacity derived from the second-order model is in good agreement with the experimental data. The isotherm analysis revealed that the Freundlich and D-R models fit well for the synthesized CeO2 and represent physisorption with a multilayer mechanism. The thermodynamic parameters, including the changes in Gibb's free energy, enthalpy, and entropy, suggested that the adsorption of CR on the synthesized CeO2 sample was a spontaneous and endothermic process.

Sol-gel preparation of ZrO2–Li2Si2O5 ceramics and their sintering properties

Despite zirconia (ZrO2) ceramics and lithium disilicate (Li2Si2O5) glass-ceramics have been widely applied on the market for dental restorations, composites that can combine the advantages of both are still demanded. Here we introduced a ZrO2–Li2Si2O5 ceramic with minimized glass phases that fabricated through a sol-gel method and subsequent pressureless sintering. ZrO2–Li2Si2O5 powders were obtained after the gel precursors were heat treated under 800 °C. The gel-derived powders were molded and pressureless sintered under 900–1000 °C to investigate their sintering properties. From the microstructures of the sintered samples, we knew that the densification process was dominated by the growth of Li2Si2O5 grains instead of the growth of ZrO2 grains. Increasing in Li2Si2O5 content can promote ceramic densification. Interestingly, reactions between ZrO2 and Li2Si2O5 were observed with sintering temperature higher than 916 °C, which can increase the porosity of the ceramics. Therefore, both the content of Li2Si2O5 and sintering temperature should be well adjusted to achieve samples with desired properties. Finally, ceramics with flexural strength of 226 MPa and porosity of 0.4% were achieved from powders with moderate Li2Si2O5 content after sintering at 1000 °C.

Polyphenol-Metal Ion Redox-Induced Gelation System for Constructing Plant Protein Adhesives with Excellent Fluidity and Cold-Pressing Adhesion.

Soy protein (SP) adhesives can resolve several problems with aldehyde-based adhesives, including formaldehyde release and excessive dependence on petroleum-based materials. Nevertheless, their development is hindered by the lack of balance between fluidity and high cold-pressing adhesive strength. A dynamically cross-linked SP adhesive with excellent fluidity and cold-pressing adhesion was developed in this study based on the polyphenol-metal ion redox-induced gelation system. SP was blended with acrylamide (AM), ammonium persulfate (APS), and the tannic acid (TA)-Fe3+ complex to prepare an adhesive gel precursor with good fluidity. In situ gelation of SP adhesive was then achieved via AM polymerization, as initiated by redox between TA and Fe3+. As expected, the prepared adhesive gel exhibited outstanding cold-pressing bonding strength (650 kPa) to the veneers compared to the neat SP adhesive, which has almost no cold-pressing bonding strength to the veneers. The TA-Fe3+ complex induced an in situ gelation system, which endowed the SP adhesive with strong cohesion; the topological entanglement of the adhesive gel in the veneers contributed to tight interfacial combinations. The TA-Fe3+ complex served not only as an accelerator of SP adhesive gelation but also as a "cross-linking core" for the cross-link SP adhesive system. The prepared SP-based adhesive also exhibited outstanding hot-pressing bonding strength and mildew resistance. The proposed polyphenol-metal ion-induced in situ gelation strategy may provide a new approach for developing advanced vegetable protein adhesives to replace aldehyde adhesives.

Obtention and characterization of a hybrid nanocomposite monolith by sol–gel process

A monolithic porous composite was synthesized by sol–gel process, containing the maximum and significant amount of bentonite that allows its use as a filter bed in aqueous effluents treatment. This process is able to apply on an industrial scale.The bentonite used was an efficient adsorbent for various contaminant molecules in aqueous media when is operated in a batch stirred tank, but presents difficulty in the separation stage of suspended particles. In this laboratory-scale work, cylindrical monoliths of 9cm length by 2cm diameter were made that can be used as a filter bed. The primary composite, silica-resin, was prepared by the sol–gel precursor mixture of the partially hydrolyzed tetraethylorthosilicate and a phenol-formaldehyde resin. Bentonite was added to the pre-gelling, obtaining the silica-resin-bentonite composite, made up the gel which is then dried and cured at 270°C. The different composites mineralogical and structurally were evaluated. The preliminary performance of the developed bentonite filter bed showed almost 90% adsorption of diphenylamine, a commercial agrochemical widely used as anti-antiscaldant in postharvest treatment of fruit, and showed that the bentonite conserves its adsorption capacity and controls the swelling of the interlayer space which encourages further research studies applied to water treatment.

Highly Effective Covalently Crosslinked Composite Alginate Cryogels for Cationic Dye Removal.

Currently, macroporous hydrogels have been receiving attention in wastewater treatment due to their unique structures. As a natural polymer, alginate is used to remove cationic dyes due to its sustainable features such as abundance, low cost, processability, and being environmentally friendly. Herein, alginate/montmorillonite composite macroporous hydrogels (cryogels) with high porosity, mechanical elasticity, and high adsorption yield for methylene blue (MB) were generated by the one-step cryogelation technique. These cryogels were synthesized by adding montmorillonite into gel precursor, followed by chemical cross-linking employing carbodiimide chemistry in a frozen state. The as-prepared adsorbents were analyzed by FT-IR, SEM, gel fraction, swelling, uniaxial compression, and MB adsorption tests. The results indicated that alginate/montmorillonite cryogels exhibited high gelation yield (up to 80%), colossal water uptake capacity, elasticity, and effective dye adsorption capacity (93.7%). Maximum adsorption capacity against MB was 559.94 mg g−1 by linear regression of Langmuir model onto experimental data. The Pseudo-Second-Order model was fitted better onto kinetic data compared to the Pseudo-First-Order model. Improved porosity and mechanical elasticity yielding enhanced dye removal capacity make them highly potential alternative adsorbents compared to available alginate/montmorillonite materials for MB removal.

Near-Surface Composition, Structure, and Energetics of TiO2 Thin Films: Characterization of Stress-Induced Defect States in Oxides Prepared via Chemical Vapor Deposition versus Solution Deposition from Sol–Gel Precursors

We present here a comprehensive comparison of near-surface composition, structure, and energetics of compact ultrathin TiO2 thin films deposited by two approaches: (i) chemical vapor deposition (CV...

Greener Monolithic Solid Phase Extraction Biosorbent Based on Calcium Cross-Linked Starch Cryogel Composite Graphene Oxide Nanoparticles for Benzo(a)pyrene Analysis.

Benzo(a)pyrene (BaP) has been recognized as a marker for the detection of carcinogenic polycyclic aromatic hydrocarbons. In this work, a novel monolithic solid-phase extraction (SPE) sorbent based on graphene oxide nanoparticles (GO) in starch-based cryogel composite (GO-Cry) was successfully prepared for BaP analysis. Rice flour and tapioca starch (gel precursors) were gelatinized in limewater (cross-linker) under alkaline conditions before addition of GO (filler) that can increase the ability to extract BaP up to 2.6-fold. BaP analysis had a linear range of 10 to 1000 µgL−1 with good linearity (R2 = 0.9971) and high sensitivity (4.1 ± 0.1 a.u./(µgL−1)). The limit of detection and limit of quantification were 4.21 ± 0.06 and 14.04 ± 0.19 µgL−1, respectively, with excellent precision (0.17 to 2.45%RSD). The accuracy in terms of recovery from spiked samples was in the range of 84 to 110% with no significant difference to a C18 cartridge. GO-Cry can be reproducibly prepared with 2.8%RSD from 4 lots and can be reused at least 10 times, which not only helps reduce the analysis costs (~0.41USD per analysis), but also reduces the resultant waste to the environment.

Removal and recovery of phosphate using a novel calcium silicate hydrate composite starch cryogel

Phosphate is a major pollutant that deteriorates water quality and causes eutrophication, a novel calcium silicate hydrate composite cryogel (Cry-CSH) was thus successfully prepared for phosphate removal and recovery in this work. Calcium silicate hydrate (C–S–H) was mixed with the gel precursor (7.5% w/w) prepared from native starch and limewater (saturated calcium hydroxide solution as the cross-linker). The mixture was frozen and thawed for 3 cycles giving an interconnected macroporous composite. This had C–S–H nanoparticles (75 mg) immobilized on a monolithic floatable cryogel network (2.5 cm diameter × 1.0 cm height) enabling an easier recovery and without the losses that occur when using C–S–H nanoparticles. The phosphate adsorption reaches equilibrium at 120 min with adsorption capacity of 2.50 mgPO43−/gCry-CSH (65.42 mgPO43−/gC–S–H) under optimum conditions. Adsorption equilibrium data were well fit by the Freundlich isotherm model, while kinetic results were well fit by the pseudo second-order model. The calculated activation energy (Ea) of 43.9 kJ/mol indicates chemical adsorption, while a positive change in enthalpy (ΔH0, 19.3 kJ/mol) indicates the endothermic nature of phosphate adsorption. Cry-CSH can remove phosphate from wastewater and effluent samples with excellent removal efficiency (>98%). It can float on water surface for at least 105 days without damage, while its phosphate adsorbed form can be biodegraded within 10 days under soil buried conditions. Thus, this work demonstrated the significant potential of Cry-CSH for practical and environmentally friendly phosphate removal and recovery.

Assessment of Novel MgCe4P6O24 Ceramic Electrolyte in Fabricating Mg-Sensors: Focus on Structure and Electrochemical Impedance Spectroscopy

In this study, a sol-gel process was modified and used to synthesise gel precursors of MgCe4P6O24 ceramic electrolyte. TGA-DSC profiles predicted the calcination temperature of MgCe4P6O24 dried gel precursors at 900 oC. XRD patterns show that a single phase MgCe4P6O24 ceramic electrolyte was formed after the gels were calcined at 900 oC, and there was no phase transformation after the pelletised calcined nanopowders were sintered at 1300 0C. XRD analysis revealed that the dried gel precursor powders calcined at 900 oC shows a monoclinic crystalline phase structure with an average crystallite size of 52±1 nm, which is consistent with results from the high-resolution TEM (HRTEM). Whereas the TGA-DSC profiles show a single phase MgCe4P6O24 ceramic electrolyte at 900 oC, thermodynamic stability of the sintered MgCe4P6O24 ceramic electrolyte is held at 1300 oC. Electrical properties of platinised MgCe4P6O24 ceramic electrolytes analysed using electrochemical impedance spectroscopy (EIS) exhibits an improved bulk ionic conductivity of 10-3 Scm-1 at 744 oC, which is considered suitable as an ionic conductor in fabricating solid-state Mg-sensors.

Agar-based porous electrode and electrolyte for flexible symmetric supercapacitors with ultrahigh energy density

In this work, a symmetric flexible supercapacitor is successfully fabricated using the electrode and electrolyte, which are both derived from source-abundant agar. Agar-based porous carbon electrode is synthesized by foaming and carbonization-activation processes using KHCO3 and HAc as activators. The unique foam-like gel precursor forms during the agar gelation process with simple metathetical reactions, which facilitates the generation of porous structure. Benefitting from the large specific surface area (2134 m2 g−1) and hierarchically porous conductive network, the as-prepared carbon electrode displays a high gravimetric capacitance of 313.7 F g−1 at 0.5 A g−1 and good rate performance in 6 M KOH. Moreover, agar-contained Na2SO4 hydrogel electrolyte is prepared by a simple solvent casting process, and the prepared hydrogel electrolyte shows a broadening electrochemical potential window of 1.8 V and excellent flexibility when used in supercapacitor. The symmetrical flexible aqueous-based supercapacitor that assembled via agar-based porous carbon electrode and agar-based gel electrolyte exhibits an ultrahigh energy density of 22.1 Wh kg−1 at 450 W kg−1. This work provides an effective strategy for preparing both the supercapacitor electrode and electrolyte using the same source, i.e. agar as the starting material, which uncovers a new possibility for the development of flexible capacitors with high energy density.

Influences of alkali metal fluoride and Si/Al ratio on preparation aluminum-rich ZSM-5 zeolite membrane without organic template

Aluminum-rich ZSM-5 zeolite membranes are prepared on α-alumina support through organic template free precursor gels by secondary hydrothermal synthesis, microstructure of the membrane through the different Si/Al ratio and alkali metal fluoride synthesis gel are discussed in this work. Alkali metal fluorides have a significant influence on the synthesis of aluminum-rich ZSM-5 zeolite membranes without organic template, which are realized by the synergistic reaction of the “bridging” and “salting-out” effects. Sodium fluoride and potassium fluoride could produce dense and needle-like zeolites layer on the supports by an extremely low Si/Al ratio synthesis gel (Si/Al <10). When the Si/Al ratio of the initial synthesis gel is 18.52, the compact and prismatic ZSM-5 zeolites are fully covered on the supports with sodium fluoride, potassium fluoride or lithium fluoride. There are few of ZSM-5 zeolites could form on the support by cesium fluoride containing synthesis gel.

Fabrication of fiber-reinforced polymer ceramic composites by wet electrospinning

We propose a novel approach of wet electrospinning to yield fiber-reinforced polymer ceramic composites, where a reactive ceramic precursor gel is used as a collector. We illustrate our approach by generating polyethylene oxide (PEO) fibers in a potassium silicate gel; the gel is later activated using metakaolin to yield a ceramic-0.5 wt% PEO fiber composite. An increase of 29% and 22% is recorded for the fabricated polymer ceramic composites in terms of indentation modulus and indentation hardness respectively. Our initial findings demonstrate the process viability and might lead to a potentially scalable manufacturing approach for fiber-reinforced polymer ceramic composites.

Recovery of High Purity Chlorine by Cu‐Doped Fe2O3 in Nitrogen Containing Carbon Matrix: A Bifunctional Electrocatalyst for HCl Electrolysis

AbstractAn environmentally benign approach towards synthesis of a non‐noble metal and/or metal oxide doped incorporated in nitrogen containing carbon matrix (Cu−Fe2O3/NC) is premeditated in this study. In‐situ incorporation of Cu, Fe2O3 as well as nitrogen into the carbon matrix using a single gel precursor simplified the synthetic route and divulged bifunctional activity assisting chlorine evolution at anode and oxygen reduction reaction at cathodic counterpart during HCl electrolysis. As a result of synergy between Cu and Fe2O3 in N‐ doped carbon matrix, enhanced activity and stability is stimulated. Catalyst optimization was executed by varying the weight percentage of metal reactants added during precursor synthesis (2, 5 and 10 wt. %), which rendered different composition of Cu, Fe2O3 and N in the composite with flake‐like morphology at same thermal treatment conditions. Electrochemical studies were performed in 0.4 M HCl analogous to industrial waste HCl, to investigate the bifunctional activity of catalyst where Cu−Fe2O3 (5 %)/NC came out to be the most active and exhibited long term stability for 24 hours at onset potential of chlorine evolution. It offered a higher current density of 92.1 mA cm−2 at 1.7 V vs. RHE during chlorine evolution and comparable activity to that of benchmark noble metal based catalyst along with more positive onset potential and high diffusion limiting current density of 0.78 V vs. RHE and 6 mA cm−2 during oxygen reduction respectively.

Preparation of Bio-Inert Carbon Nanofiber Scaffold and Its Effect of Postoperative Injury Nursing and Repair of Bone Tissue

In this research, the characteristics of the bioactive glass (AG) and bio-inert carbon nanofibers (Cnano) in the bone formation was explored. The AG was prepared by sol–gel and combined with polyacrylonitrile (PAN) by electrospinning. Then, Cnano loaded with AG nanoparticles was prepared by carbonization. During the preparation process, the material supply ratio of the sol–gel precursor was changed to obtain 3 nanofiber scaffold materials (Canno/AG_01, Canno/AG_02, and Canno/AG_03). First, the release behavior of silicon ions, calcium ions, and phosphorus ions was investigated during the material preparation process, and Transwell was used for cabin culture, so that bone marrow mesenchymal stem cells (BMSCs) did not directly contact the materials. Besides, the expression levels of osteogenic differentiation genes in different culture sites were detected by reverse transcription-polymerase chain reaction (RT-PCR) method. There was an evaluation of the influences of increased AG content on trauma nursing and chondrocyte apoptosis in vitro. Finally, bone marrow blood mononuclear cells (BMWM) combined with Canno/AG materials were used for clinical research on skull repair. In the experiment, the ion dissolution levels of different prepared materials were different, but they had little effect on the proliferation of BMSCs. Canno/AG_02 with the highest level of silicon ion dissolution had good osteogenic differentiation ability, and RT-PCR proved that contact culture could markedly promote the proliferation and differentiation of BMSCs cells based on the prepared fiber morphology and cell contact effect. Moreover, Canno/AG_02 could be used as the wound dressing for skull fracture to achieve the nursing and rehabilitation effect of wound closure and promoting angiogenesis, and BMWM loaded with Canno/AG_02 could accelerate the tissue healing speed of patients with damaged skull defect.

Tailoring the defects of two-dimensional borocarbonitride nanomesh for high energy density micro-supercapacitor

The development of high-performance micro-supercapacitors (MSCs) highlights two-dimensional (2D) carbon materials with pseudocapacitive charge storage capacity. However, improving the electrochemical performances of these electrode materials is still challenging. Here, we synthesized 2D borocarbonitride nanomesh (BCNN) by carbonizng gel precursor of milk powder and boron oxide in 700, 800, and 900 °C, respectively, denoted as BCNN700, BCNN800, and BCNN900, as electrode for MSCs. By tailoring defects and atomic contents of BCNN, the areal capacitance increases from 30.5 mF cm−2 for BCNN700-MSCs to 80.1 mF cm−2 for BCNN900-MSCs with a hydrogel electrolyte. Notably, BCNN900-MSCs can provide a high energy density of 67.6 mWh cm−3with an ion-gel electrolyte, efficiently powering a liquid crystal display for 328 s. In addition, a first principles simulation verifies the effects of the dopants and pores on improving the total capacitance of BCNN by enhancing qauntam capacitance. Therefore, BCNN exhibits tremendous potential for applying on future energy storage devices.

Synthesis and Characterization of ZnO Thin Layers using Sol-Gel Spin Coating Method

The potential of thin layer in many applications has led to research on the development of many new materials and their fabrication methods. This study aimed to synthesize a thin layer of ZnO using the facile and low-cost sol-gel spin coating method. The ZnO thin layer is deposited on a glass substrate and analyzed to observe the influence of the deposition variables such as heating and rotation speed, and its aging. The characterization methods include the identification of the formed phase using X-Ray Diffractometer (XRD), and the microstructure and elemental composition using Scanning Electron Microscopy (SEM) coupled with EDS (Energy Dispersive Spectrometer). The study shows that a thin layer of ZnO is successfully deposited on a glass substrate by heat treatment at temperatures of 300 oC and 500 oC. Furthermore, XRD reveals that higher heating temperatures result in higher diffraction peak intensity. At a heating temperature of 300 °C crystals are formed but are not yet perfectly oriented, while they are at 500 °C. On the other hand, higher spin coating rotation speed gives rise to lower intensity of diffraction peak. The ZnO crystallization is easier to form in the coating process with a lower rotation (1500 rpm). Interestingly, the thin layer is stable over time where there is no significant change in each sample, both in terms of intensity and width of the ZnO crystal peak. The results indicate that gel precursor aged less than two days can form ZnO crystals. Finally, SEM results show that the surface morphology of the ZnO layer heated at 500 oC has an average grain size of 300 nm. Based on the cross-sectional results of SEM shows that the higher the coating rotation speed has resulted the thinner of the ZnO layer, where the thickness of the resulting layer is on order &gt;5 mm.

Boosted activity of Cu/SiO2 catalyst for furfural hydrogenation by freeze drying

The biomass valorization is of great importance as an alternative for the production of transport fuels and fine chemicals. Furfural hydrogenation to furfuryl alcohol is a prevailing industrial route for the utilization of hemicellulose component of biomass. The toxicity of the chromium species in commercial copper chromite catalyst for furfuryl alcohol production motivates the development of efficient chromium-free catalyst. Thus, a highly efficient silica supported copper catalyst is developed in this study. The catalyst is prepared by freeze drying of a gel precursor that is synthesized by ammonia evaporation, followed by calcination and H2 reduction. The catalyst exhibits higher furfural hydrogenation activity than oven dried catalyst, commercial copper chromite catalyst and a plant supplied commercial silica supported copper catalyst. The catalyst also shows good stability. The superior performance of the freeze dried catalyst has resulted from its developed pore structure and higher amount of Cu0 as well as Cu+ active sites.

Photonic Curing of Solution-Processed Oxide Semiconductors with Efficient Gate Absorbers and Minimal Substrate Heating for High-Performance Thin-Film Transistors.

In this study, photonic curing is used to rapidly and effectively convert metal-oxide sol–gels to realize high-quality thin-film transistors (TFTs). Photonic curing offers advantages over conventional thermal processing methods such as ultrashort processing time and compatibility with low-temperature substrates. However, previous work on photonically cured TFTs often results in significant heating of the entire substrate rather than just the thin film at the surface. Here, sol–gel indium zinc oxide (IZO)-based TFTs are photonically cured with efficient gate absorbers requiring as few as five pulses using intense white light delivering radiant energy up to 6 J cm–2. Simulations indicate that the IZO film reaches a peak temperature of ∼590 °C while the back of the substrate stays below 30 °C. The requirements and design guidelines for photonic curing metal-oxide semiconductors for high-performance TFT applications are discussed, focusing on the importance of effective gate absorbers and optimized pulse designs to efficiently and effectively cure sol–gel films. This process yields TFTs with a field-effect mobility of 21.8 cm2 V–1 s–1 and an Ion/Ioff ratio approaching 108, which exceeds the performance of samples annealed at 500 °C for 1 h. This is the best performance and highest metal-oxide conversion for photonically cured oxide TFTs achieved to date that does not significantly heat the entire thickness of the substrate. Importantly, the conversion from sol–gel precursors to the semiconducting metal-oxide phase during photonic curing is on par with thermal annealing, which is a significant improvement over previous pulsed-light processing work. The use of efficient gate absorbers also allows for the reduction in the number of pulses and efficient sol–gel conversion.

Synthesis of bulk silicon oxynitride glass through nitridation of SiO2 aerogels and determination of Tg

AbstractThe development of transparent glass for use in high‐temperature applications is continuing. In this study, we synthesized bulk silicon oxynitride glasses (a‐Si(O,N)x) through the nitridation of SiO2 aerogels containing methyl (CH3‐) groups and evaluated their bulk properties, including their glass transition temperature (Tg). Tetramethyl orthosilicate and methyltrimethoxysilane were added into the precursor gels, and those gels were subjected to a supercritical CO2 drying process. The presence of CH3‐group in the gel avoided cracking during ammonolysis at 750°C–1400°C, and the transparency of the gel was remained even after ammonolysis at 1300°C. The ammonolysis successfully introduced nitrogen into the gels even at relatively low temperatures, for example, 750°C, and the highest nitrogen content (11.7 mass%) was achieved in the gel after ammonolysis at 1300°C. As the nitrogen‐related signals in electron spectroscopy indicated presence of nitride ions (N3−) after ammonolysis and the infrared absorption signals attributed to Si–N bonds were enhanced with the increase of nitrogen concentration, we successfully obtained oxynitride glasses. Those oxynitride glasses showed increase of Tg with their nitrogen concentration.