Binary Aerogels Research Articles

Preparation of Silicon/Iron Binary Aerogel from High Iron Fly Ash and Adsorption of Mine Antimony Wastewater

Preparation of Silicon/Iron Binary Aerogel from High Iron Fly Ash and Adsorption of Mine Antimony Wastewater

Nitrogen-Coordinated borate esters induced entangled heterointerface toward multifunctional Silicone/Phenolic binary aerogel composites

Organosilicone/phsenolic hybrid resin (SiR/PR), which can withstand thermal oxidation, is constantly plagued by significant phase separation during the co-curing process. Herein, coordination interaction between borate esters and siloxane was firstly proposed to achieve domain size below the visible wavelength (20 nm) and homogenous SiR/PBA-PR aerogels. Profiting from the electron-deficient boron element, the weak interactions of matrixes was compensated by nitrogen coordinated borate esters during the rapidly grafting process. The entangled heterointerface inherently endows the integrated “organic–inorganic” hybrid aerogels with hierarchical alveolate structure after oxidative decomposition. As expected, the distributed organosilicone, stabilized by nitrogen coordinated borate esters, shields the organic and carbonaceous components from ubiquitous oxygen-rich heat flow, thereby qualifying the SiR/PBA-PR aerogels with great thermal oxidation stability (R1000,Air > 50 wt%) and specific compressive strength (1400 N·m/kg). Besides, owing to the inherited heterointerface after pyrolysis, SET of pyrolytic sample with 50 % SiR even increase slightly (2.5 %) compared with the reduction of 73 % in SET of that without SiR after flame ablation. This strategy of silicone resin doping in nitrogen-coordinated phenolic resin will pave a way for “organic–inorganic” hybrid materials.

Multifunctional flexible SiO2/BNNBs nanofibrous aerogel for thermal insulation, infrared stealth and sound-absorption

Ceramic nanofibrous aerogels have attracted great interest because of their extraordinary multifunctional properties. Herein, a facile strategy was proposed to create SiO2 nanofibers-BN nanoribbons assembled binary aerogel with excellent temperature-invariant super-flexibility, as well as low thermal conductivity, low infrared radiation and excellent sound absorption properties. In addition, the unique structure of the nanofibers-nanoribbon aerogel acts as the thermal insulation layer, combined with Al foil acting as an infrared reflection layer, forming a component that can effectively hide high infrared targets. The nanofibrous-nanoribbons binary aerogel possess low thermal conductivity (0.0288 W/(m⋅K)) and outstanding sound-absorption ability (NRC value of 0.43), as well as excellent infrared stealth ability, which makes it an ideal candidate for thermal insulation and sound absorption in multi fields.

High-Performance Oxygen Evolution Reaction Electrocatalysts Discovered via High-Throughput Aerogel Synthesis

A combinatorial high-throughput aerogel synthesis method is developed to systematically study the synergistic catalytic effects of multiple non-noble metal elements. A large number of aerogels with different compositions were synthesized and the corresponding ternary phase diagrams of the composition–electrocatalytic performance were constructed. A batch of aerogel catalysts with outstanding catalytic performance and stability for the electrochemical oxygen evolution reaction (OER) were discovered. Amorphous Fe3Co3Ni2-(oxy)hydroxide with excellent electrocatalytic performance (Tafel slope of 49 mV dec–1 and η100 of 421.48 ± 6.41 mV) was found to achieve a mass activity of 611.23 A/gmetal at 1.63 V (vs RHE). X-ray photoemission spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) studies reveal that the incorporation of a third atom (Ni and Ce) into the binary aerogels enlarges the Co–O atomic distance and reduces the average valence state of Co, which in turn speed up the oxygen evolution reaction kinetics. This work puts forward a strategy for high-throughput synthesis and screening of electrocatalysts and provides valuable data sets for future machine learning and prediction of high-performance electrocatalysts.

Constructing three-dimensional NiFe binary aerogel as anodic electrocatalyst for oxygen evolution reaction

Designing highly active and stable anodic electrocatalysts is of great essentiality to improve the efficiency for alkaline water electrolysis. Metal aerogels with three-dimensional structure are developing fast recently as efficient electrocatalysts but research efforts mainly focus on noble metal-based aerogels. Herein, the nonprecious NiFe aerogel is synthesized from a fast metal salt reduction-gelation method. The three-dimensional NiFe aerogel was assembled from nanosized branches, which contained NiFe alloy nanoparticles as the cores and NiFe hydroxide nanosheets as the shells. The porous NiFe aerogel can provide more surface sites and benefit the mass/charge transfer, as well as the low crystallinity in structure can provide more active sites. As the result, this NiFe aerogel demonstrated remarkable electrocatalytic activity with low overpotential of 267 mV at 50 mA cm−2 and good durability for alkaline oxygen evolution reaction, which is among the best transition metal-based OER electrocatalysts. Thus, this NiFe aerogel holds good potentials for alkaline water oxidation and brings a novel member to the family of metal aerogels.

Multilevel Structural Design and Heterointerface Engineering of a Host–Guest Binary Aerogel toward Multifunctional Broadband Microwave Absorption

Multilevel Structural Design and Heterointerface Engineering of a Host–Guest Binary Aerogel toward Multifunctional Broadband Microwave Absorption

Бинарные аэрогели Al2O3-TiO2: синтез с использованием эпоксид-индуцированного золь-гель перехода

A new method for the synthesis of binary aerogels Al2O3-TiO2 by epoxide-mediated route was proposed. The synthesis is conducted in DMF solution, the starting materials for the synthesis are aluminium nitrate and titanium chloride. The obtained homogeneous amorphous aerogels possess high surface (250–750 m2/g) and porosity (86–95 %).

Engineering SiO2–TiO2 binary aerogels for sun protection and cosmetic applications

SiO2‒TiO2 binary aerogels obtained by the methods of low-temperature (carbon dioxide) and high-temperature (isopropanol, hexafluoroisopropanol and methyl tert-butyl ether) supercritical drying are considered as multifunctional cosmetic pigments with high anti-shine power and photoprotective properties. The composition and structure of SiO2–TiO2 aerogels obtained by supercritical drying in various fluids were studied by IR spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, scanning and transmission electron microscopy, and low-temperature nitrogen adsorption. The values of the sun protection factors SPF and UVAPF for the obtained materials are comparable to those of the commercial sunscreens Kronos 1171 and Kronos 2971, and the anti-shine power is approximately 1.5 times higher than that of kaolin-based materials.

The effect of solvent parameters on properties of iron-based silica binary aerogels as adsorbents

The magnetic Fe3O4-SiO2 binary aerogel and nonmagnetic α-Fe2O3-SiO2 binary aerogels are obtained by adjusting the solvent type during the solvothermal reaction and varying the Fe/Si proportion in the sol-gel process. The microstructure, surface charge and the formation mechanism of iron-based silica binary aerogels are analyzed by SEM, zeta potential and BET. The influence of the Fe/Si proportion on the surface group and morphology of binary aerogels is also investigated by FTIR and TEM analysis. The adsorption behavior of the iron-based silica binary aerogels on the Congo Red (CR) dye is also discussed by adsorption kinetics model and adsorption isotherm model. In addition, the effects of pH and initial concentration of the solutions, adsorption time and the maximum adsorption capacities for CR of iron-based silica binary aerogels adsorbents are also discussed, respectively. Moreover, the maximum adsorption capacity of as-prepared magnetic Fe3O4-SiO2 binary aerogels for dyes achieved 489.13 mg g−1, the maximum adsorption capacity of nonmagnetic α-Fe2O3-SiO2 reached 454.55 mg g−1, respectively. Thus, the iron-based silica binary aerogels provides valuable clues for the study of other aerogel materials as adsorbents.

Clay-graphene oxide liquid crystals and their aerogels: synthesis, characterization and properties.

The dispersions containing two kinds of layered solids—graphene oxide (GO) and exfoliated montmorillonite (MMT) were mainly prepared, following which the binary aerogels were synthesized. The results indicate that the formation of liquid crystals (LCs) occurs at lower GO concentration and the birefringence becomes stronger when MMT is introduced into GO dispersion. Sol–gel transition forms in the binary suspensions with different mass fractions of MMT and GO. LCs with highly ordered alignment are observed in the gel and the fraction of LCs obviously increases with the increase in GO concentration. Moreover, the birefringence is observed in MMT–GO binary aerogels with the interconnected three-dimensional porous network, which is attributed to the ordered arrangement of MMT and GO nanosheets in pore walls. Among the aerogels with different MMT/GO ratios, the samples at the ratio of 10 : 1 show better adsorption capacity and removal percentage of cationic and anionic dyes.

In-situ synthesis and textural evolution of the novel carbonaceous SiC/mullite aerogel via polymer-derived ceramics route

Abstract A novel carbonaceous SiC/mullite composite aerogel is derived from catechol-formaldehyde/silica/alumina hybrid aerogel (CF/SiO 2 /AlOOH) via polymer-derived ceramics route (PDCR). The effects of the reactants concentrations on the physicochemical properties of the carbonaceous SiO 2 /Al 2 O 3 aerogel and SiC/mullite aerogel are investigated. The mechanism of the textural and structural evolution for the novel carbonaceous SiC/mullite is further discussed based on the experimental results. Smaller reactants concentration is favorable to formation of mullite. Reactants concentration of 25% is selected as the optimal condition in considering of the mullite formation and bulk densities of the preceramic aerogels. Spherical large silica particles are also produced during heat treatment, and amorphous silica is remained after this reaction. With further heat treatment at 1400 °C, silicon carbide and mullite coexist in the aerogel matrix. The mullite addition decreases the temperature of SiC formation, when compared with the conventional methods. However, after heat treatment at 1450 °C, the amount of mullite begins to decrease due to the further reaction between carbon and mullite, forming more silicon carbide and alumina. The carbonaceous SiC/mullite can be transferred to SiC/mullite binary aerogel after carbon combustion under air atmosphere. The carbonaceous SiC/mullite has a composition of SiC (31%), mullite (19.1%), SiO 2 (14.4%), and carbon (35%). It also possesses a 6.531 nm average pore diameter, high surface area (69.61 m 2 /g), and BJH desorption pore volume (0.1744 cm 3 /g). The oxidation resistance of the carbonaceous SiC/mullite is improved for 85 °C when compared with the carbon based aerogel.

SiO2–TiO2 binary aerogels: Synthesis in new supercritical fluids and study of thermal stability

A comparative analysis of properties of SiO2–TiO2 binary aerogels prepared by supercritical drying using different supercritical fluids (isopropanol, hexafluoroisopropanol, methyl tert-butyl ether, and CO2) has been performed. The use of different supercritical fluids allows preparation of both homogeneous amorphous SiO2–TiO2 binary aerogels (by supercritical drying in hexafluoroisopropanol and CO2) and composite aerogels containing nanocrystalline anatase (by supercritical drying in isopropanol and methyl tert-butyl ether). The thermal treatment of the aerogels at temperatures up to 600°C does not lead to considerable change in the porous structure and phase composition of the aerogels.

Structural characteristics and photocatalytic activity of ambient pressure dried SiO2/TiO2 aerogel composites by one-step solvent exchange/surface modification

An ambient pressure synthesis of SiO2/TiO2 binary aerogel was prepared through the low-cost precursors of titanium tetrachloride (TiCl4) and sodium silicate (Na2O·nSiO2). After gelation, solvent exchange and surface modification were performed simultaneously and the modified gel was finally dried under ambient pressure. Microstructural analyses by transmission electron microscope (TEM) indicate that fabricated SiO2/TiO2 aerogel composite shows similar sponge-like nanostructure as silica aerogel, and the Brunauer–Emmett–Teller (BET) analysis shows that the specific surface area of the composite reaches 605 m2/g, and the average pore size is 9.7 nm. Such binary aerogel exhibits significant photocatalytic performance in this paper for treating model pollutant of methyl orange (MO), and the decolorizing efficiency of MO is detected as 84.9% after 210 mins exposure to UV light irradiation. Degraded gel suspends in the water so as to separate from solution for reuse, and after 4 times recycling, 70% degradation efficiency can be easily reached when composite catalyzed system is exposed for 210 mins under UV irradiation.

Methyl tert-butyl ether as a new solvent for the preparation of SiO2–TiO2 binary aerogels

SiO2–TiO2 binary aerogels have been synthesized for the first time using methyl tert-butyl ether as supercritical fluid. It has been shown that the aerogels prepared in methyl tert-butyl ether and isopropanol contain nanocrystalline anatase and that amorphous SiO2–TiO2 aerogels with a homogeneous distribution of their components can be obtained in CO2. A considerable contribution to the large specific surface area of the aerogels is made by micropores, especially when supercritical drying is carried out in CO2 and isopropanol.

Preparation and characterization of equimolar SiO2–Al2O3–TiO2 ternary aerogel beads

Crack-free mesoporous equimolar SiO2–Al2O3–TiO2 ternary aerogel beads have been synthesized and characterized. Silica sol, alumina sol, and titania sol were synthesized individually to prevent the formation of inhomogeneous structure due to the different hydrolization and polymerization rate of individual precursor. After mixing these three types of acidic sols, SiO2–Al2O3–TiO2 ternary beads were prepared by the ball dropping method. The ternary aerogel beads were typically mesoporous, showing high surface area (305 m2 g−1), large pore volume (1.32 cm3 g−1), and high surface acid amount (0.884 mmol NH3 g−1). Moreover, the acid sites of the ternary aerogel beads showed higher thermal stability than those of binary aerogel beads. Gradient drying (GD), supercritical drying (SD), ambient drying (AD), extended aging (EA) and hydrophobic modifying drying (HM) have been employed to investigate the effects of drying method on the characteristics of the aerogel beads. The surface areas of the ternary aerogel beads obtained by different drying methods decrease in the sequence EA > HM > GD > SD > AD. The ternary aerogel beads have been characterized by scanning electron microscopy, nitrogen adsorption, X-ray powder diffraction, Fourier-transform infrared spectroscopy (FTIR), solid-state NMR, temperature-programmed desorption measurements, pyridine adsorption FTIR, and differential scanning calorimetry.

Anatase–silica composite aerogels: a nanoparticle-based approach

Herein we present the synthesis of anatase–silica aerogels based on the controlled gelation of preformed nanoparticle mixtures. The monolithic aerogels with macroscopic dimensions show large specific surface areas, and high and uniform porosities. The major advantage of such a particle-based approach is the great flexibility in pre-defining the compositional and structural features of the final aerogels before the gelation process by fine-tuning the properties of the titania and silica building blocks (e.g., size, composition and crystallinity) and their relative ratio in the dispersion. Specific surface functionalization enables control over the interaction between the nanoparticles and thus over their distribution in the aerogel. Positively charged titania nanoparticles are co-assembled with negatively charged Stoeber particles, resulting in a binary aerogel with a crystalline anatase and amorphous silica framework directly after supercritical drying without any calcination step. Titania–silica aerogels combine the photocatalytic activity of the anatase nanoparticles with the extensive silica chemistry available for silica surface functionalization.

高比表面积Al2O3-TiO2二元气凝胶小球的制备

以拟薄水铝石和水合硫酸氧钛为前驱体，水为溶剂，采用溶胶–凝胶、烃氨成球法、老化和控制干燥制备出大比表面积的AlO2-TiO2复合气凝胶小球。研究其理化性质并考察了不同铝钛组成及温度对孔结构和酸量的影响。采用了SEM、XRD、FT-IR、NMR、N2吸附–脱附法、NH3-TPD等手段对所制得的复合氧化物进行了表征。结果显示，复合氧化物中TiO2为锐钛矿型，Al2O3为无定形。通过混合溶胶共水解缩聚及老化和控制干燥，使不同铝/钛比的二元气凝胶小球的比表面积均达到200 m2/g以上，总酸量达到0.8 mmol NH3/g以上。不同铝/钛比的二元气凝胶小球比表面积和酸量相近，孔径可通过铝/钛比调整。 Crack-free and high surface area mesoporous alumina-titania binary aerogel beads have been synthesized by sol-gel technology, the ball dropping method (BDM), extended aging and gradient drying method with pseudo boehmite and dehydrate titanyl sulfate as precursors and water as solvent. The effects of composition and calcination temperature on pore structure and acid amounts have been investigated and discussed. The binary aerogel beads have been charac-terized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier-transform infrared spectros-copy (FT-IR), solid state nuclear magnetic resonance (NMR), nitrogen adsorption/desorption analysis and ammonia- temperature programmed desorption (TPD). The obtained aerogel beads show surface area of 200 m2/g and acid amounts of 0.8 mmol NH3/g respectively. The binary aerogel beads with different constitutes show similar specific sur-face area and acid amounts. The pore size of aerogel beads can be modified by changing composition and calcination temperature.

Recent Study on Nano TiO2 Photocatalyst: A Review in Modification, Synthsis Technique, and Operation Parameters

Nano TiO2 as a potential photocatalyst has been widely studied and used in many fields including environmental decontamination, sterilization and fuel cells. Some efforts, including improvements by doping, synthesis technique and operation parameter, have been made to enhance its performance. In this paper, the new progresses in these studies have been reviewed. Keywords: TiO2, photocatalyst, doping, aerogel, performance improvement, Narrow Band Gap Semiconductor, HPLC, Co-Doping, TiO2 Aeorgels, Binary Aerogels, Recent Study on Nano TiO2 Photocatalyst: A Review in Modification, Synthsis Technique, and Operation Parameters

Water assisted synthesis of clean single-walled carbon nanotubes over a Fe 2O 3/Al 2O 3 binary aerogel catalyst

Water assisted synthesis of clean single-walled carbon nanotubes over a Fe 2O 3/Al 2O 3 binary aerogel catalyst

Preparation and application of nanoglued binary titania–silica aerogel

Nanoglued binary titania (TiO 2)–silica (SiO 2) aerogel, as a novel type of photocatalyst, has been synthesized on glass substrates. Using an about-to-gel SiO 2 sol as nanoglue, anatase TiO 2 aerogel was immobilized into a three-dimensional mesoporous network of the SiO 2. Factorial designs were employed to optimize both TiO 2 aerogel and binary TiO 2–SiO 2 aerogel synthesis. Characterization of the as-prepared TiO 2 and binary samples by surface area, porosity, and surface chemical composition showed that the photocatalysts were high-surface-area nanoporous materials, with a Ti 4+ valency. The binary aerogel exhibited high photocatalytic activity for the degradation of methylene blue (MB) under simulated solar light; the reaction followed the pseudo first-order Langmuir–Hinshelwood (L–H) kinetic model. Fluorescence spectroscopy revealed that the hydroxyl ( OH) radical was formed during the illumination of the binary TiO 2–SiO 2 aerogel in a solution of probe molecules, which corroborates the probable mechanism of hydroxyl radical oxidation of contaminants in photocatalytic reactions.