Search

• A novel fluorine-containing PINF membrane with high whiteness has been prepared from 6FDA and TFMB via electrospinning technology. • The as-obtained PINF membranes have a high solar reflection of 95.5% (0.4–0.8 µm) and infrared emissivity of 88.0% (8–13 µm). • The PINF membranes display strong UV shielding properties and excellent thermal stability with no obvious weight loss before 500 ℃. • The daytime radiative cooling effect of PINF membranes maintains constant in the aging test for continuous 720 h. Personal daytime radiative cooling (PDRC) materials have high sunlight reflection and high selective emissivity to outer space in the main atmospheric window, demonstrating huge potential in energy-saving for sustainable development. Recently, polymer-based membranes for radiative cooling have been widely reported, due to their easy processing, low cost, and unique optical performance. However, the desired high sunlight reflectance of PDRC materials is easily dampened by environmental aging, high temperature, and ultraviolet (UV) irradiation, resulting in reduced cooling performance for most polymers, adverse to large-scale practical applications. In this work, we demonstrate a novel polyimide nanofiber (PINF) membrane with a fluorine-containing structure via typical electrospinning technology. The resultant PINF membrane exhibits high sunlight reflectance, UV resistance, and excellent thermal stability, rendering anti-aging daytime radiative cooling. The sunlight reflectance of PINF membranes could maintain constant in the aging test for continuous 720 h under outdoor solar irradiation, exhibiting durable and long-term personal daytime radiative cooling performance. [Display omitted] [ABSTRACT FROM AUTHOR]

• Polyimide/silica (PSi) aerogel with integrated double network and anisotropic structure was fabricated. • The PSi aerogel could withstand 500 cyclic compression test in the radial direction with a high silica content of 60 wt%. • The PSi aerogel exhibited ultra-low thermal conductivity of 21.2 mW m−1 K−1 in the radial direction. • The PSi aerogel exhibited structure integrity when subjected to a flame of a propane/butane blowlamp (∼1200 °C). The materials with thermal insulating and fire-retardant properties are highly demanded for architectures to improve the energy efficiency. The applications of conventional inorganic insulating materials such as silica aerogels are restricted by their mechanical fragility and organic insulating materials are either easily ignitable or exhibit unsatisfactory thermal insulation performance. Here, we report an organic/inorganic composite aerogel with integrated double network structure, in which silica constituent homogeneously distribute in the anisotropic polyimide nanofiber aerogel matrix and strong interfacial effect is formed between two components. The integrated binary network endows the polyimide/silica composite aerogels with outstanding compressibility and flexibility even with a high inorganic content of 60%, which can withstand 500 cyclic fatigue tests at a compressive strain of 50% in the radial direction. The resulting composite aerogel exhibits a combination of outstanding insulating performance with a low thermal conductivity (21.2 mW m−1 K−1) and excellent resistance to a 1200 °C flame without disintegration. The high-performance polyimide/silica aerogels can decrease the risk brought by the collapse of reinforced concrete structures in a fire, demonstrating great potential as efficient building materials. [Display omitted] [ABSTRACT FROM AUTHOR]

• Ordered lamellar polyimide-based graphene foam has been constructed. • More lamellar interfaces are formed inside the foam per unit volume. • Lamellar porous structure promotes the layer-by-layer dissipation for incident EMW. • Microwave absorption can be adjusted via controlling microstructure of the foam. The development of high-performance microwave absorption materials with strong absorption capacity and broad bandwidth is highly desirable in the field of electromagnetic pollution protection. Herein, ultralight polyimide-based graphene foam with ordered lamellar structure is precisely designed and controllably constructed by bidirectional freezing process. More lamellar interfaces formed inside the foam per unit volume effectively facilitate the layer-by-layer dissipation for the vertical incident electromagnetic waves, thereby endowing the foam with efficient broadband electromagnetic absorption performance. More importantly, electromagnetic absorption performance can be controllably adjusted by optimizing impedance distribution and microstructure of skeletons. As a result, the optimized foam with an ultralow density of 9.10 mg/cm3 presents a minimum reflection loss value of −61.29 dB at 9.25 GHz and an effective absorption bandwidth of 5.51 GHz (7.06–12.57 GHz, covering the whole X band) when the thickness is 4.75 mm. [Display omitted] [ABSTRACT FROM AUTHOR]

Conventionally, interface effects between polymers and fillers are essential for determining the breakdown strength and energy storage density of polymer-based dielectric composites. In this study, we found that interface effects between different fillers have similar behavior. BN and BaTiO 3 fiber composite fillers with three different interface bonding strengths were successfully achieved by controlling composite processes (BT-fiber/BN < BT-fiber@BN < BT-fiber&BN), and introduced into a polyimide (PI) matrix to form composite films. Considerably enhanced breakdown strength and energy storage density were obtained in BT-fiber&BN/PI composites owing to strong interface bonding, compared to other two composite fillers, which are well supported by the data from the finite element simulation. Specifically, PI composites with only 3 wt% BT-fiber&BN possess an optimized energy storage density of approximately 4.25 J/cm3 at 4343 kV/cm. These results provide an effective way for adjusting and improving the energy storage properties of polymer-based composites. [ABSTRACT FROM AUTHOR]

This paper presents a galvanically isolated dc-dc converter with multi-channel communication exploiting a single isolation transformer. The proposed architecture makes compliant both regulated output power and data transmission on the same isolation physical link by using ASK modulation of the power signal and data/control signal multiplexing. The dc-dc converter consists of two integrated chips fabricated in 0.18- $\mu \text{m}$ BCD and 0.13- $\mu \text{m}$ CMOS technologies, respectively, along with a thick polyimide transformer chip able to comply with reinforced isolation requirements. The dc-dc converter delivers an isolated output power up to 50 mW at 3.3-V output voltage, while providing three data channels with a data rate up to 10 Mb/s. [ABSTRACT FROM AUTHOR]

A polyethylene oxide (PEO)-coated polyimide (PI) membrane was prepared by electrospinning method followed by a dip-coating and drying process for high-performance lithium-ion batteries (LIB). Semicrystal PEO was covered on the surface of the fibers and partially enmeshed in PI matrix, which formed unique porous structures. The pores with an average size of 4.1 µm and a porosity of 90% served as ion transport channels. Compared with the cell with Celgard 2400 membrane, the half-cell using PEO-coated PI membrane as a separator exhibits excellent electrochemical performance both at room temperature and at low temperature. The electrolyte uptaking rate of PEO-coated PI membrane was 170% and the ionic conductivity was 3.83 × 10 –3  S cm –1 . PEO-coated PI membrane possessed 5.3 V electrochemical window. The electrode–electrolyte interfacial resistance was 62.4 Ω. The capacity retention ratios with PEO-coated PI membrane were 86.4% at 5 C and 73.5% at 10 C at 25 °C and 75% at 5 C at 0 °C. Furthermore, the cell using the separator demonstrates excellent capacity retention over cycling. These advanced characteristics would boost the application of the PEO-coated PI membrane for high-power lithium ion battery. [ABSTRACT FROM AUTHOR]

This paper presents the first printed organic 13-MHz RFID on flexible substrate. The proposed solution includes a planar near field antenna bonded to an RFID tag, which is printed on flexible foil using an organic complementary TFT technology. Thanks to an active envelope detector, ASK modulation with modulation depth as low as 20% can be adopted to increase the available input power for the rectifier. The RFID functionality is demonstrated at the internally generated supply voltage of 24 V, for a reading range of 2–5 cm and a bit-rate up to 50 bit/s. With more than 250 transistors on the same foil, this work represents the most complex circuit ever published in a printed organic complementary TFT technology. [ABSTRACT FROM AUTHOR]

Negative thermal expansion (NTE) ZrW2O8 powders were prepared by step-by-step solid-state reaction with ZrO2 and WO3 powders. The coefficient of thermal expansion (CTE) of the as-prepared ZrW2O8 was around −5.08×10−6 K−1 at 20–700°C. Different amounts of ZrW2O8 powders were added in BTDA-ODA polyamic acid to form polyimide/ZrW2O8 composites (PI/ZrW2O8). With the increment of ZrW2O8, experimental results show that ZrW2O8 powders can significantly enhance the thermal stability of the composites, and reduce the thermal expansion. A 50 wt pct ZrW2O8 addition can give rise to a 31% reduction of CTE. It is suggested that the PI/ZrW2O8 composites have potential applications in high performance microelectronic devices. [Copyright &y& Elsevier]