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In this study, we used lead zirconate titanate (PZT) aerogels prepared by a solvothermal assisted sol–gel method as raw materials to synthesize PZT aerogel/PVDF composite coatings and PZT aerogel sintered sheets through natural annealing and PVDF composite and hot pressing, respectively, and then combined them with the design principle of a biomimetic shell structure to prepare an alternate coating/sheet structured PZT aerogel piezoelectric composite with natural distinguished mechanical properties. It had excellent piezoelectric properties with a piezoelectric coefficient d33 of 435.15 pC N−1 and d31 of −144.55 pC N−1, excellent electromechanical coupling properties with a planar electromechanical coupling coefficient of 60.14%, low dielectric loss of 0.76% at 40 Hz and low density of 3.04 g cm−3. When used as the piezoelectric material in underwater acoustic transducers (UATs), compared with all kinds of piezoelectric ceramics, it achieved higher piezoelectric and comprehensive mechanical properties, lower dielectric loss, lower density, and electromechanical coupling properties similar to that of Pb-containing piezoelectric ceramics, thus showing extremely promising application prospects in UATs. [ABSTRACT FROM AUTHOR]

A hybrid aerogel structure for hydrogen sensing was produced and tested, which consists of Pd nanoparticles decorated on a TiO 2 aerogel skeleton structure with large specific surface areas and high porosity. The effects of decorated with different contents of Pd nanoparticles on the microstructure of anatase TiO 2 aerogel and the hydrogen response characteristics were investigated. The contribution of the doping of Pd nanoparticles to the specific selectivity of the anatase phase TiO 2 aerogel for hydrogen sensing was investigated. Benefiting from highly interconnected porous networks of aerogel, ultra-large specific surface area, and homogeneous Pd nanoparticles dispersion, the resulting Pd nanoparticle-decorated TiO 2 3D hybrid aerogel hydrogen sensors express high hydrogen sensing performance. The response was 4.8 toward 100 ppm hydrogen at the optimal working temperature of 325 °C, with a short response time (<2 s), short recovery time (<22 s), and high selectivity and long-term stability. A hydrogen-sensitive mechanism is proposed in which metal atom doping causes more oxygen defects in metal oxide semiconductor lattice. The approach of constructing aerogel network structures by decorating metal nanoparticles on metal oxide semiconductors provides a new way to develop gas sensors. • Pd nanoparticles-decorated TiO 2 aerogel structure was prepared by sol-gel method and supercritical drying method for hydrogen sensing. • Very large specific surface areas and highly interconnected porous networks. • Short response time(<2s) and recovery time(<22s) of anatase Pd-modified TiO 2 aerogel structure for hydrogen sensing. • High selectivity of Pd nanoparticles-decorated anatase phase TiO 2 aerogel structure for hydrogen sensing. [ABSTRACT FROM AUTHOR]

SiO 2 aerogel is a promising lightweight and high-efficiency thermal insulation material for applications in construction, industrial, aerospace vehicles, etc., but weak mechanical properties limit its further development and application. In order to overcome this challenge, we combined the design concepts of elastic group's introduction and structural strengthening of cellulose nanofibers with a directed freezing process, and successfully realized an anisotropic and high-strength SiO 2 /cellulose nanofiber composite aerogel. Under the low density of 0.247 g/cm3, the maximum compression strength of the aerogel in the radial direction is as high as 18.08 MPa, corresponding to a high fracture strain of 75.67%, and it also exhibits an excellent fatigue resistance, with only a slight plastic deformation of 6.5% after 100 load-unload cycles at a high compression strain of 50%. In addition, the aerogel exhibits an ultra-low thermal conductivity (0.01714W/(m·K)) in the radial direction, and also has a superhydrophobicity (water contact angle 150.8°) and a long-term hydrophobic stability (saturated mass moisture absorption rate 0.44%). The combination of these properties makes it an ideal material for thermal superinsulation in environments where both integrated mechanical properties and hydrophobic properties are critical. [ABSTRACT FROM AUTHOR]

[Display omitted] • A polybenzoxazine aerogel system with high strength under suitable deformation is designed. • Reversible sacrificial hydrogen bonding enhanced mechanical properties of the polybenzoxazine aerogel are realized. • The polybenzoxazine aerogel withstands more than 300,000 times its own weight under pressure before breaking. • The polybenzoxazine aerogel has a low thermal conductivity of 0.03012 W/(m·K) at 25 °C and 0.03486 W/(m·K) at 150 °C. • The polybenzoxazine aerogel has a hydrophobic angle of 148.7° and a saturated mass moisture absorption rate of about 0.63%. Aerogels are a very attractive class of lightweight and high-efficient thermal insulators, but poor mechanical properties have always been the main obstacle restricting their development and application. In order to overcome this problem, we innovatively used the concept of reversible sacrificial hydrogen bondings strengthening, and successfully synthesized a polybenzoxazine aerogel with outstanding mechanical properties and a lightweight structure. The aerogel (density 0.231 g/cm3 and porosity 90.7 %) exhibits a high compression strength of 14.36 MPa with a suitable deformation capacity of 19.6 % fracture strain, and also shows a relatively good fatigue resistance. In addition, the aerogel has outstanding thermal insulation properties [0.03012 W/(m·K) at 25℃ and 0.03486 W/(m·K) at 150℃] and hydrophobic properties (hydrophobic angle 148.7° and saturated mass moisture absorption rate about 0.63 %), thus it has great prospects for a high-efficiency thermal insulator used in buildings, industries, aerospace vehicles, etc. [ABSTRACT FROM AUTHOR]

Lead zirconate titanate (PZT) aerogels are ideal piezoelectric materials for underwater acoustic transducers (UATs) due to their light structure, but their difficult preparation, poor mechanical properties and poor integrated electrical properties greatly limit their practical applications. In order to overcome these difficulties, we innovatively adopted a solvothermally combined sol-gel method to successfully achieve simple, rapid, and low-cost preparation of PZT aerogels, designed a 0–3 type PZT aerogel/PVDF composite coating to overcome the weak mechanical properties of PZT aerogels, and used SiO 2 aerogels and PZT ceramic powders to improve the ferroelectric and piezoelectric properties of the PZT aerogel/PVDF composite coating, respectively. After verifying that the PZT aerogel/PVDF composite coating modified by 4 wt% SiO 2 aerogels and 30 wt% PZT ceramic powders has the best integrated electrical properties, we prepared its 50-layer combination to further improve the comprehensive properties. The 50-layer composite coating has a moderate piezoelectric constant d 33 of 132.7 pC/N and a high piezoelectric constant d 31 of −33.6 pC/N, a low relative permittivity of 593.7 and a low dielectric loss of 0.85% at 40 Hz, a high Young's modulus of 616.2 MPa, and a density of 1.163 g/cm3 similar to water, indicating that it has surpassed various high-performance Pb-containing piezoelectric ceramics in integrated electrical properties, mechanical properties and acoustic impedance matching with water, which is more in line with the needs of use in UATs. This research offers a new pathway to design a piezoelectric material for UATs with light structure and excellent comprehensive properties. • Solvothermal combined with sol-gel method overcomes the bottleneck that PZT aerogels are difficult to prepare. • PZT aerogel/PVDF composite coating is used to overcome the poor mechanical properties of PZT aerogels. • SiO 2 aerogels and PZT ceramic powders improve the ferroelectric and piezoelectric properties of the composite coating. • The 50-layer composite coating realizes light structure, excellent mechanical and integrated electrical properties. • The 50-layer composite coating shows extremely superior practical significance for UATs. [ABSTRACT FROM AUTHOR]