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Novel silica nanofibrous (SNF) membranes with ultra-softness and enhanced tensile strength were prepared for the first time via an electrospinning technique with a sol–gel solution containing NaCl. By employing NaCl incorporation, the bonding structure was formed between silica nanofibers, which significantly enhanced the tensile strength of the SNF membranes from 3.2 to 5.5 MPa. Meanwhile, the morphology and mechanical properties of the SNF membranes can be finely controlled by tuning the calcination temperature and varying the NaCl content in the precursor solution. Additionally, the proposed mechanism of the softness of the SNF membranes was discussed by in situ SEM analysis during the bending and recovery process. Furthermore, the as-prepared SNF membranes with ultra-softness of 40 mN and relative high tensile strength of 5.5 MPa exhibit an ultra-low thermal conductivity of 0.0058 W m−1 K−1, even lower than air, which suggested them to be promising candidates for bunker clothing. This novel method also provides a new insight into the design and development of other soft ceramic nanofibrous membranes with high tensile strength for various applications.

As engineers strive to develop high-performance filtration membranes with structural alternatives, the challenges and costs of processing often limit creative innovation. Here, we describe a powerful yet economic strategy for fabricating multilevel structured nanofibrous membranes within a single filter medium, which is constructed by the accumulation of bimodal sized and silica nanoparticles (SiO 2 NPs) incorporated electrospun polyacrylonitrile (PAN) nanofibrous membranes. By simply varying the composition of precursor solutions and layer-by-layer assisted stacking structure, individual fibers within the medium can conformally be endowed with non-circular cross section, or rough surface to form a skeletal frame-worked membrane with complimentary filtration efficiency (99.989%) and pressure drop (117 Pa) for 300–500 nm NaCl aerosol particles. The results suggested that this cost-effective filter media could be used as promising materials for a variety of potential applications in respiratory protection equipment, high efficiency particulate air filters, and ultra-low penetration air filters.

Hierarchically structured, superhydrophobic filter medium exhibiting robust filtration performance to airborne particulate were prepared by a facile deposition of electrospun polysulfone/titania nanoparticles (PSU/TiO2 NPs) on a conventional nonwoven substrate. The air permeability, tensile strength and abrasion resistance of pristine PSU fibrous membranes could be finely controlled by regulating the solvent composition and number ratios of jets. By employing the TiO2 NPs incorporation, the pristine PSU fibers were endowed with promising superhydrophobicity with a water contact angle of up to 152°. The quantitative hierarchical roughness analysis using N2 adsorption method has confirmed the major contribution of TiO2 NPs on enhancing the porous structure and surface fractal features with irregular rough structure. Filtration performance studies have revealed that the filtration efficiency and pressure drop of resultant hybrid membranes could be manipulated by tuning the surface composition as well as the hierarchical structures. Furthermore, the as-prepared PSU/TiO2-5 membrane exhibited improved filtration efficiency (99.997%) and pressure drop (45.3 Pa) compared with pristine PSU membrane, which would make them a promising media for fine particle filtration, and a new insight was also provided into the design and development of high performance filter medium based on hierarchical structured fibers.