Jiayi Zhu

Facile fabrication of flexible graphene/porous carbon microsphere hybrid films and their application in supercapacitors

Graphene/porous carbon microsphere hybrid films were fabricated by vacuum filtration of graphene oxide nanosheets and porous carbon microspheres, followed by reduction, leavening and compressing. The as-prepared hybrid films were characterized by means of scanning electron microscopy, X-ray diffraction, Raman spectroscopy and four-point probe measurements. After reduction and leavening, the leavened foam film displayed a moderate capacitive performance (183 F g−1 at 0.2 A g−1) in KOH aqueous solution. Additionally, over 112.1% of the initial capacitance was retained after repeating the cyclic voltammetry test for 1000 cycles. After compressing, the flexible thin film had a moderate capacitive performance of 144 F g−1 at 0.2 A g−1 for a single electrode and over 99.7% of the initial capacitance. Moreover, the thin film had good capacitive behaviour retainability after multiple cycles of excessive bending experiments.

Facile fabrication of mechanical monolithic polyamide aerogels via a modified sol–gel method

The good-formability polyamide (PA) aerogel via a modified sol–gel technology was facilely fabricated by using melamine and isophthaloyl chloride with the acid-binging agent followed by CO2 supercritical drying. The synthesis procedure was straightforward and simple, relying on no nitrogen-based protective atmosphere. The influences of various parameters, such as the amount of acid-binging agent, reaction temperature and precursor concentration, on the aerogel structure were discussed. The structural properties of PA aerogels were characterized by the scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller methods and Fourier transform infrared spectroscopy. The results indicated that the PA aerogel had a typical three-dimensional porous structure. Due to the moderate mechanical property of the PA aerogel, the aerogel had potential for the use in construction and building materials.Graphical AbstractWe reported that the good-formability polyamide (PA) aerogel via a modified sol–gel technology was facilely fabricated by using melamine and isophthaloyl chloride with the acid-binging agent followed by CO2 supercritical drying. The synthesis procedure was straightforward and simple, relying on no nitrogen-based protective atmosphere. The dimethylacetamide (DMAC) as the acid-binging agent could indeed remove the hydrochloric acid to accelerate the cross-linking degree of the PA prepolymer and improve the formation of a fine porous structure of the PA aerogel. Thus, the specific surface area of the PA aerogel after the addition of acid-binging agent could be enhanced as high as 391 m2/g, higher than that (282 m2/g) of the one without the DMAC. Furthermore, it also showed the influences of various parameters, such as reaction temperature and precursor concentration, on the aerogel structure. According to the structure analysis, the results indicated that the PA aerogel had a typical three-dimensional structure with various porous size. Due to the moderate mechanical property, the PA aerogel had potential for use in construction and building materials.

Facile fabrication of gradient density organic aerogel foams via density gradient centrifugation and UV curing in one-step

Gradient density porous materials have played an important role in areas of aerospace, biomaterials and high-energy absorption experiments. In order to accurately control the process of gradient forming, a new approach was proposed to produce gradient density porous materials. By using dibutyl phthalate as the solvent and benzoin methyl ether as the photoinitiator, gradient density trimethylolpropane trimethacrylate (TMPTMA) foams were fabricated after the density gradient centrifugation, ultraviolet curing and CO2 supercritical drying. The microstructure and density distribution of foams were characterized by nitrogen adsorption, mercury injection apparatus test, scanning electron microscopy, UV–visible absorption spectrum, X-ray phase contrast, and dynamic mechanical analysis. Moreover, the storage modulus of organic foams was significantly improved by the gradient change of foam density. The results indicated that this approach was an effective method for the preparation of gradient density organic foams and could be suitable for producing gradient density porous materials derived from a sol–gel process.Graphical abstractWe presented a new approach for the preparation of gradient density TMPTMA aerogel foams via density gradient centrifugation and UV curing in one-step. It was the first report so far to rationally design and facilely fabricate TMPTMA foams. The results definitively proved the density distribution of a linear gradient for foams. The approach could be simple and suitable for producing other gradient density porous materials derived from a sol–gel process. Different gradient parameters of TMPTMA foams could be obtained by monitoring the target density of mixture solutions, the sloping angle, and the size of the tube, respectively. Furthermore, it could be seen that the method of analyzing absorbance was actually a suitable tool to observe the density distribution of TMPTMA foams, which showed an intuitionistic figure to realize the density distribution. As a result, it could be believed that this approach could be useful for fabrication of gradient density porous materials in future.

Assembly of methylated hollow silica nanospheres toward humidity-resistant antireflective porous films with ultralow refractive indices

Humidity-resistant antireflective (AR) porous films with ultralow refractive indices were prepared via an one-step sol–gel process by assembly of methylated hollow silica nanospheres (HSNs). The hydrophobicity and refractive indices of silica-based AR porous films could be varied between 66.0° and 115.0°, and between 1.08 and 1.14, respectively, by tuning the MTES/TEOS molar ratios. A possible assembly mechanism was proposed according to the microstructure of methylated HSNs and porous films. The various properties of silica-based AR porous films were investigated and the AR porous film could demonstrate a good AR capability of 97.6% and excellent humidity resistance.

Facile fabrication of multifunctional monolithic polyamide aerogels

The polyamide (PA) aerogels with good-formability via a sol–gel technology were facilely fabricated by using melamine and aroyl chloride followed by CO2 supercritical drying. The synthesis procedure was straightforward and simple, relying on no nitrogen-based protective atmosphere. The influences of aroyl chloride monomer on the gelation time and aerogel structure were discussed. The structural properties of PA aerogels were characterized by the scanning electron microscopy (SEM) and Brunauer–Emmett–Teller methods (BET). The results indicated that the PA aerogels had a typical three-dimensional porous structure. The PA aerogels exhibited well multifunctional properties, such as flame resistance, thermal insulation, dielectric characteristics and mechanical properties. Due to well multifunctional properties, the PA aerogels had potential for the use in construction and building materials.

Facile fabrication of machinable low-density moisture-resistant silica aerogels

Low-density moisture-resistant silica aerogels with enhanced mechanical strength were obtained by combining with the aging of the teteraehoxysilane (TEOS)-based alcogels in the TEOS/ethanol solution and the modification in the hexamethyldisilazane (HMDS)/ethanol solution. This route introduced less organic impurities into as-prepared aerogels and their mechanical strength was also enhanced. The linear volume shrinkage of the modified wet gels reached as low as 3.6% during supercritical drying. Thus, the aerogels had appropriate mechanical strength to be adapted the requirements of applications with various shapes. Moreover, the densities of silica aerogels maintained stable after modification by high concentration HMDS, suggesting excellent moisture resistance.

Synthesis and properties of melamine–starch hybrid aerogels cross-linked with formaldehyde

We reported the synthesis of melamine–starch–formaldehyde aerogels by using starch and melamine cross-linked with formaldehyde. The gelation time of melamine–starch–formaldehyde gels prepared at different concentrations and ratios of reactants, pH and heating temperature were studied and discussed. The results indicated that the gelation time reduced with the increase of reactant concentrations and heating temperature, and decrease of starch/melamine–formaldehyde mass ratio and pH. The structural properties of melamine–starch–formaldehyde aerogels were also characterized by the field emission scanning electron microscopy, the Brunauer-Emmett-Teller methods, the X-ray diffraction, the fourier transform infrared spectroscopy, and the dynamic mechanical analyzer. It was found that all the melamine–starch–formaldehyde aerogels showed a typical three-dimensional porous structure and their surface areas decreased with increase of the density. Furthermore, the compressive stress as a function of strain was measured to study the mechanical properties of the melamine–starch–formaldehyde aerogels. Because of potentially lower cost, the high surface areas, relatively large pore volume, low-bulk densities and excellent mechanical performance, the melamine–starch–formaldehyde aerogels would have potential for use in construction and building materials.Graphic AbstractMSF aerogels were successfully prepared. The starch/MF mass ratio played an important role in the gelation and structural properties. The gelation process became faster with the increase of starch/MF mass ratios. The MSF-1 aerogel has a large surface area (384.6 m2/g), highly ordered mesopores with uniform pore size (17.9 nm) and pore volume (1.63 cm3/g). To study the mechanical properties of the hybrid aerogel, it was found that the MSF-1 aerogel possessed excellent elasticity and mechanical durability.

Thermal stability, solubility, and fluorescence property of poly(arylene ether ketone)s bearing N-arylenebenzimidazole units

A series of novel random poly(arylene ether ketone)s containing N-arylenebenzimidazolyl groups with precise structures in high yields were synthesized from 2-(2′-hydroxyphenyl) benzimidazole and 4,4′-dihydroxybenzophenone with 4,4′-difluorobenzophenone via nucleophilic substitution polycondensation reaction using sulfolane as a solvent. The reaction was carried out at 210 °C in the presence of anhydrous potassium carbonate. The structures of the resulted polymers were characterized by means of FT-IR, 1H NMR spectroscopy, and elemental analysis, and the results were largely consistent with the proposed structure. X-ray diffraction studies revealed that the incorporation of N-arylenebenzimidazolyl groups decreased the crystallinity of the resulted polymers. As the benzimidazole unit content in the copolymer increased, the solubility and thermal behavior of the prepared polymers improved. The novel poly(arylene ether ketone)s exhibited glass transition temperatures (Tgs) in the range 188–237°C, and there was a good linearity relationship between Tg values and the content of benzimidazolyl groups. The 5% decomposition temperatures were within the range of 512–539 °C in nitrogen and 496–540 °C in air indicating their good thermal stability. Tensile tests of the films showed that these polymers have desirable mechanical properties. Moreover, the resulting polymers showed good fluorescence properties.

Rapid Fabrication of Low-Density Porous Tin Monolith via Hydrogen Bulb Dynamics Templates

Low-density porous tin monolith with the pteridophyta leaf-like structure was fast fabricated by a facile route via the electrochemical deposition process via hydrogen bulb dynamics templates within less than 1min. The samples were characterized by scanning electron microscope, X-ray diffraction and so on. The results indicated that the deposited tin porous structure could be easily controlled to form film or monolith by adjusting the tin precursor concentration and surfactant content.

Template-Method Synthesis of High-Surface-Area Monolithic Carbon Aerogels and Their Applications for Hydrogen and Deuterium Adsorption

In this work, novel monolithic carbon aerogels obtained by using a polymer template method were characterized and evaluated for their applications in the hydrogen and deuterium adsorption capacity. The properties (i.e., surface area, pore size distribution, hydrogen and deuterium adsorption capacities, etc.) of the carbon aerogels were affected by the polymer templates. The results showed that the carbon aerogel with the molar ratio of polyacrylic acid (PAA) to zinc chloride (ZnCl2) being 0.75:40 was featured the highest surface area (1806 m2/g) and had the highest hydrogen adsorption capacity. Moreover, the deuterium adsorption capacity of the carbon aerogel was to be further elucidated.