Network Of Aerogel Research Articles

Porous alumina aerogel with tunable pore structure for facile, ultrasensitive, and reproducible SERS platform

AbstractPorous alumina aerogel synthesized by sol–gel method was used as facile and sensitive surface‐enhanced Raman scattering (SERS) platform. In a simple “drop‐test” SERS detection, low concentration dye solution mixed with silver nanoparticles was directly dropped on the surface of aerogel platform for SERS detection immediately. The pore structure of alumina aerogel was tuned by adding PEG‐400 and varying the gelation temperature. The effects of surface morphology and pore size of alumina aerogel platform on SERS performance of crystal violet (CV) were investigated. The result shows that large specific surface area and interconnected pore network of aerogel are helpful for fast permeation of solution, generation of “hot spots,” and adsorption of probe molecules. The Raman signal of CV was largely enhanced, enabling a detection concentration to 5 × 10−10 M with a SERS enhancement factor of 3.4 × 107. The SERS enhancement of alumina aerogel platform is remarkably improved with the increase of specific surface area and pore size, which is also confirmed by the finite‐difference time‐domain simulation. Moreover, the relative standard deviation of SERS intensity at 1619 cm-1 band for 5 × 10−8 M CV on aerogel platform is about 12%, indicating a good reproducibility.

Particulate Matter Capturing via Naturally Dried ZIF-8/Graphene Aerogels under Harsh Conditions

SummaryParticulate matter (PM) pollution poses a serious threat to the environment and public health. Capture of PM is best performed at the emission source, such as car exhaust exit points, although it is a challenge for filters to work under harsh conditions of high temperatures and flow rate. Here we designed a thermally stable PM filter by in situ anchoring of zeolite imidazole framework-8 (ZIF-8) on a three-dimensional (3D) network of reduced graphene oxide aerogel (rGA) through natural drying. Owing to high specific surface area, well-connected porous network of graphene aerogel, and large number of metal sites from ZIF-8/rGA, the capture efficiencies for PM2.5 and PM10 are over 99.3% and 99.6%, respectively, at ambient conditions, and the efficiencies remain high in harsh conditions (PM2.5 and PM10: >98.8% and >99.1%, respectively, at 200°C at a flow velocity of 30 L/min). The filter can be regenerated by a simple washing process.

A Z-Scheme Polyimide/AgBr@Ag Aerogel with Excellent Photocatalytic Performance for the Degradation of Oxytetracycline.

A novel Z-scheme polyimide (PI)/AgBr@Ag aerogel photocatalyst has been successfully synthesized by combining an in situ precipitation method and a supercritical drying method. The as-prepared PI/AgBr@Ag-50 (50 wt % AgBr@Ag in PI/AgBr@Ag) aerogel photocatalyst exhibited excellent photocatalytic activity for oxytetracycline degradation with a rate constant of 0.025 min-1 , which was 6.9 and 2.6 times higher than that of the PI aerogel or the AgBr@Ag nanoparticles, respectively. More significantly, the PI/AgBr@Ag-50 aerogel photocatalyst showed stable cycling, which could be attributed to the high mechanical strength and 3D network of the PI aerogel. The introduction of AgBr@Ag on PI with a heterojunction structure efficiently promoted the separation of electron-hole pairs by a Z-scheme mechanism. The reduced metallic Ag nanoparticles were found to function as centers for the transfer of electrons from AgBr to PI. This work has revealed a new application for the aerogel PI/AgBr@Ag photocatalyst in environmental protection.

Three-dimensional assembly of building blocks for the fabrication of Pd aerogel as a high performance electrocatalyst toward ethanol oxidation

Porous noble metal nanostructures with highly porous and extended surface areas are a long-desired target in both industry and academia. Among them, noble metal aerogels have emerged as state-of-the-art catalysts and these exceptional structures play crucial roles in various applications such as catalysis, sensors, etc. Until now, various methods have been published for the creation of noble metal aerogels, while their development and synthesis suffer from time-consuming multistep procedures. In this paper, we present an efficient method for the creation of porous three-dimensional network of Pd aerogel by a self-assembly process. This method offers several advantages over other methods such as being one-pot synthesis, simplicity and fast. Pd aerogel is synthesized by reducing H2PdCl4 in the presence of sodium carbonate using glyoxylic acid monohydrate as a reductant agent in a short time followed by supercritical drying. The Pd aerogel serves as an anode catalyst for the electrooxidation reaction of ethanol and exhibits superior electrocatalytic activity and durability compared to Pd/C catalyst. We believe that the Pd aerogel synthesized via this method is a promising catalyst for direct ethanol fuel cells (DEFCs) and will also open large opportunities for other applications.

Porous three-dimensional network of Pd-Cu aerogel toward formic acid oxidation.

New self-assembled architectures have received great interest in nanotechnology, and are a highly desired target in recent studies. Among self-assembled architectures, noble metal aerogels are an important class owing to their collective characters as well as widespread applications. The synthesis of noble metal aerogels still faces several obstacles such as long hydrogel creation time and complicated multistep strategies. In this paper, we propose an efficient and useful approach to create the three-dimensional network of a Pd–Cu aerogel. This way offers a number of advantages including one-pot synthesis, simplicity, and short time to prepare the hydrogel. The Pd–Cu aerogel was prepared by the reduction of H2PdCl4 and CuCl2 in the presence of sodium carbonate by using glyoxylic acid monohydrate as a reducing agent followed by supercritical CO2 drying. The Pd–Cu aerogel was applied as an anode catalyst for electrooxidation process of formic acid, and depicts much higher electrocatalytic activity and durability compared to the Pd/C. We believe that the exceptional three-dimensional nanostructures fabricated by this route are powerful and promising catalysts for application in direct formic acid fuel cells (DFAFCs), which may open great opportunities for widespread applications such as catalysis, sensors, optoelectronics, electrochemical energy systems, etc.

Porous SiCnw/SiC ceramics with unidirectionally aligned channels produced by freeze-drying and chemical vapor infiltration

The current study introduces a methodology for the fabrication of porous silicon carbide nanowire/silicon carbide (SiCnw/SiC) ceramics with macroscopic unidirectionally aligned channels and reports on their microstructural and mechanical properties. The material was produced by freezing of a water-based slurry of β-SiC nanowires (SiCnw) with control of the ice growth direction. Pores were subsequently generated by sublimation of the columnar ice during freeze-drying. Chemical vapor infiltration (CVI) of SiC into the open pore network of the SiCnw aerogel with unidirectionally aligned channels, resulted in the formation of highly porous SiCnw/SiC ceramics which exhibited a unique microstructure as identified by scanning electron microscopy. The pore size distribution and the mechanical properties of the as-fabricated porous ceramics were examined by mercury intrusion porosimetry and three-point bending and compression tests, respectively, while phase composition was investigated through X-ray diffraction.

Grand Canonical Monte Carlo Simulation of Nitrogen Adsorption in a Silica Aerogel Model

In this paper, the Diffusion Limited Cluster Aggregation (DLCA) method is employed to reconstruct the three-dimensional network of silica aerogel. Then, simulation of nitrogen adsorption at 77 K in silica aerogel is conducted by the Grand Canonical Monte Carlo (GCMC) method. To reduce the computational cost and guarantee accuracy, a continuous-discrete hybrid potential model, as well as an adsorbed layer thickness estimation method, is employed. Four different structures are generated to investigate impacts of specific surface area and porosity on adsorptive capacity. Good agreement with experimental results is found over a wide range of relative pressures, which proves the validity of the model. Specific surface area and porosity mainly affect nitrogen uptake under low pressure and high pressure, respectively.

Fabrication and electrochemical properties of 3D Fe3O4@graphene aerogel composites as lithium-ion battery anodes

A novel facile strategy was developed to prepare the Fe3O4@graphene aerogel (Fe3O4@GA) composites. Fe3O4 nanoparticles were uniformly dispersed into the 3D network of graphene aerogel and the resultant hybrid composites contained meso- and macro-scale pores with high specific surface area (276.9m2g−1) and large pore volume (0.3230cm3g–1). The electrochemical performance revealed that the Fe3O4@GA anode exhibited high reversible capacity (~941.5mAhg−1 at a current density of 100mAg−1), stable cycling performance, and excellent rate capability.

The pore network and the adsorption characteristics of mesoporous silica aerogel: adsorption kinetics on a timescale of seconds

Pore network and adsorption properties of mesoporous silica aerogel: a mechanistic study on the timescale of seconds.

The Effect of pH of the Aging Solution on Microstructure of Silica/Zirconia Aerogel

ZrO2 wet gel was prepared using zirconium n-butoxide as precursor and 1,2-propylene oxide (PO) as a gelation agent in sol-gel process. Then, tetraethoxysilane (TEOS) was used to strengthen the wet gel in aging process. Finally, the monolithic silica/zirconia aerogel was obtained by supercritical fluid drying. N2 adsorption-desorption method, scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR) were used to characterize microstructure of the aerogel. The influence of pH of the aging solution on microstructure of silica/zirconia aerogel was studied. The results indicate that the particle size distribution of SiO2/ZrO2 aerogel was more uniform and less aggregate when aging in acid solution. However, the average pore diameter and particle size of SiO2/ZrO2 aerogel was increased by aging in alkaline solution. Aging in alkaline condition was useful for largening the pore size of SiO2/ZrO2 aerogel, and the maximum specific surface area and pore volume were obtained at pH=9. Meanwhile, different reactions were produced between the acid/alkaline solution and the hydroxyl of SiO2/ZrO2 aerogel, and the ester group/amino group was obtained relatively which can modify the network of aerogel and decrease the shrinkage of aerogel during the supercritical fluid drying.

Multifunctional Structural Supercapacitor Composites Based on Carbon Aerogel Modified High Performance Carbon Fiber Fabric

A novel multifunctional material has been designed to provide excellent mechanical properties while possessing a high electrochemical surface area suitable for electrochemical energy storage: structural carbon fiber fabrics are embedded in a continuous network of carbon aerogel (CAG) to form a coherent but porous monolith. The CAG-modification process was found to be scalable and to be compatible with a range of carbon fiber fabrics with different surface properties. The incorporation of CAG significantly increased the surface area of carbon fiber fabrics, and hence the electrochemical performance, by around 100-fold, resulting in a CAG-normalized specific electrode capacitance of around 62 F g(-1), determined by cyclic voltammetry in an aqueous electrolyte. Using an ionic liquid (IL) electrolyte, the estimated energy density increased from 0.003 to 1 Wh kg(-1), after introducing the CAG into the carbon fiber fabric. 'Proof-of-concept' multifunctional structural supercapacitor devices were fabricated using an IL-modified solid-state polymer electrolyte as a multifunctional matrix to provide both ionic transport and physical support for the primary fibers. Two CAG-impregnated carbon fabrics were sandwiched around an insulating separator to form a functioning structural electrochemical double layer capacitor composite. The CAG-modification not only improved the electrochemical surface area, but also reinforced the polymer matrix surrounding the primary fibers, leading to dramatic improvements in the matrix-dominated composite properties. Increases in in-plane shear strength and modulus, of up to 4.5-fold, were observed, demonstrating that CAG-modified structural carbon fiber fabrics have promise in both pure structural and multifunctional energy storage applications.