In this work, for the first time we fabricated highly self-aligned large-area reduced graphene oxide/poly (vinylidene fluoride-co-hexafluoropropylene) (rLGO/PVDF-HFP) composite films through simple ...solution casting followed by low temperature chemical reduction process. The resulting free-standing rLGO/PVDF-HFP composite thin film revealed excellent electrical conductivity of ∼3000 S/m and ultrahigh in-plane thermal conductivity of ∼19.5 W/mK at rLGO content of 27.2 wt %. This ultrahigh electrical and thermal conductivity were attributed to the good interfacial interaction, effective chemical reduction, high aspect ratio, and preferential orientation of graphene sheets along the film direction. We believe that our new fabrication procedure can be effectively used for large-scale production and commercialization of conductive composite materials for many thermal and electrical conduction applications.
Interactive displays involve the interfacing of a stimuli-responsive sensor with a visual human-readable response. Here, we describe a polymeric electroluminescence-based stimuli-responsive display ...method that simultaneously detects external stimuli and visualizes the stimulant object. This organic light-emitting board is capable of both sensing and direct visualization of a variety of conductive information. Simultaneous sensing and visualization of the conductive substance is achieved when the conductive object is coupled with the light emissive material layer on application of alternating current. A variety of conductive materials can be detected regardless of their work functions, and thus information written by a conductive pen is clearly visualized, as is a human fingerprint with natural conductivity. Furthermore, we demonstrate that integration of the organic light-emitting board with a fluidic channel readily allows for dynamic monitoring of metallic liquid flow through the channel, which may be suitable for biological detection and imaging applications.
Design of materials to be heat-conductive in a preferred direction is a crucial issue for efficient heat dissipation in systems using stacked devices. Here, we demonstrate a facile route to fabricate ...polymer composites with directional thermal conduction. Our method is based on control of the orientation of fillers with anisotropic heat conduction. Melt-compression of solution-cast poly(vinylidene fluoride) (PVDF) and graphene nanoflake (GNF) films in an L-shape kinked tube yielded a lightweight polymer composite with the surface normal of GNF preferentially aligned perpendicular to the melt-flow direction, giving rise to a directional thermal conductivity of approximately 10 W/mK at 25 vol % with an anisotropic thermal conduction ratio greater than six. The high directional thermal conduction was attributed to the two-dimensional planar shape of GNFs readily adaptable to the molten polymer flow, compared with highly entangled carbon nanotubes and three-dimensional graphite fillers. Furthermore, our composite with its density of approximately 1.5 g/cm3 was mechanically stable, and its thermal performance was successfully preserved above 100 °C even after multiple heating and cooling cycles. The results indicate that the methodology using an L-shape kinked tube is a new way to achieve polymer composites with highly anisotropic thermal conduction.
Thermal management of polymeric composites is a crucial issue to determine the performance and reliability of the devices. Here, we report a straightforward route to prepare polymeric composites with ...Cu thin film networks. Taking advantage of the fluidity of polymer melt and the ductile properties of Cu films, the polymeric composites were created by the Cu metallization of PS bead and the hot press molding of Cu-plated PS beads. The unique three-dimensional Cu shell-networks in the PS matrix demonstrated isotropic and ideal conductive performance at even extremely low Cu contents. In contrast to the conventional simple melt-mixed Cu beads/PS composites at the same concentration of 23.0 vol %, the PS composites with Cu shell networks indeed revealed 60 times larger thermal conductivity and 8 orders of magnitude larger electrical conductivity. Our strategy offers a straightforward and high-throughput route for the isotropic thermal and electrical conductive composites.
This study explores the utilization of liquid butadiene rubber (LqBR) as a processing aid in tire tread compounds, as a replacement for treated distillate aromatic extract (TDAE) oil, which is known ...to contribute to the extraction of organic materials during tire aging. Additionally, the influence of the silane-terminated functional group in LqBR and the procedure of LqBR addition are investigated. The results demonstrate a significant reduction in organic extraction when employing silane-terminated LqBR as a processing aid. Moreover, the performance of tire tread compounds is comparable or even superior to those incorporating TDAE oil, particularly when 80 % silane-terminated LqBR is added after the mixing of silica and coupling agent. The enhanced performance is attributed to homogeneous silica dispersion and robust filler-rubber interaction. These findings offer valuable insights into the optimization procedure for developing tire tread compounds utilizing functionalized LqBR as a processing aid, with the aim of improving tire tread applications.
In addition to the demand for stimuli‐responsive sensors that can detect various vital signals in epidermal skin, the development of electronic skin displays that quantitatively detect and visualize ...various epidermal stimuli such as the temperature, sweat gland activity, and conductance simultaneously are of significant interest for emerging human‐interactive electronics used in health monitoring. Herein, a novel interactive skin display with epidermal stimuli electrode (ISDEE) allowing for the simultaneous sensing and display of multiple epidermal stimuli on a single device is presented. It is based on a simple two‐layer architecture on a topographically patterned elastomeric polymer composite with light‐emitting inorganic phosphors, upon which two electrodes are placed with a certain parallel gap. The ISDEE is directly mounted on human skin, which by itself serves as a field‐responsive floating electrode of the display operating under an alternating current (AC). The AC field exerted on the epidermal skin layer depends on the conductance of the skin, which can be modulated based on a variety of physiological skin factors, such as the temperature, sweat gland activity, and pressure. Conductance‐dependent field‐induced electroluminescence is achieved, giving rise to an on‐hand sensing display platform where a variety of human information can be directly sensed and visualized.
An interactive skin display is demonstrated with an epidermal stimuli electrode, allowing for simultaneous sensing and display on a single device. The device is directly mounted on skin, which by itself serves as a field‐responsive floating electrode. The alternating current (AC) field exerted on the epidermal depends on the conductance, giving rise to an on‐hand multimode and multifunctional sensing display.
For changing environmental circumstances, interactive structural color (SC) observation is a promising strategy to store and express external information. SCs based on self-assembled block copolymer ...(BCP) photonic crystals have been a research focus due to their facile and diverse nanostructures relying on the volume ratio of blocks. Their unique nano-architectonics can reflect incident light due to constructive interference of the two different dielectric constituents. Their excellent ability to change nano-architectonics in response to external stimuli (i.e. humidity, temperature, pH, and mechanical force) allows for a programmable and stimuli-interactive BCP SC display. In this review, recent advances in programmable and stimuli-interactive SC displays with the 1-dimensional self-assembled BCP nano-architectonics are comprehensively discussed. First, this review focuses on the development of programmable BCP SCs that can store various information. Second, stimuli-interactive BCP SCs capable of responding reversibly to external stimuli are also addressed. Particularly, reversible BCP SC changes are suitable for rewritable displays and emerging human-interactive BCP SC displays that detect various human information through changes in electric signals with the simultaneous alteration of the BCP SCs. Based on previously reported literature, the current challenges in this research field are further discussed, and the perspective for future development is presented in terms of material, nano-architectonics, and process.
In this paper, we report the high-temperature and high-voltage (HV) insulation characteristics of the polypropylene (PP) blend with highly packed elastomeric domains that showed excellent mechanical ...toughness in our previous study to find its suitability as insulation material for power cable applications. The main focus lies on tensile properties with thermal aging, thermomechanical behavior corresponding to the thermal transition, high-temperature volume resistivity and DC dielectric strength, and space charge accumulation behavior of the PP blend in comparison to the crosslinked polyethylene (XLPE). Our PP blend having low elastic modulus of approximately 266.9 MPa exhibited high tensile strength and elongation at break, and high-temperature stability as well. Using this PP blend, not only good HV insulating performances in volume resistivity and DC breakdown strength (BDS) were obtained similar to XLPE, but also adequate values were obtained at high temperature, even at 110 °C, which was not possible with XLPE. However, there was space charge accumulation and electric field distortion in the PP blend like XLPE, which needs to be suppressed. Therefore, our PP blend is expected to have the potential to replace existing XLPE as insulation materials for future HV power cables.
•The PPHE exhibits mechanical properties and thermal stability suitable for high-voltage power cable applications.•Decrease in the tensile properties in the PPHE are not significant after accelerated aging test as well as long-term stability test.•The PPHE exhibits high volume resistivity and DC breakdown strength even at 110 °C, which is not possible with XLPE.
We report a flame retardant epoxy nanocomposite reinforced with 9,10-dihydro-9-oxa-10-phosphaphenantrene-10-oxide (DOPO)-tethered SiO2 (DOPO-t-SiO2) hybrid nanoparticles (NPs). The DOPO-t-SiO2 NPs ...were successfully synthesized through surface treatment of SiO2 NPs with (3-glycidyloxypropyl)trimethoxysilane (GPTMS), followed by a click reaction between GPTMS on SiO2 and DOPO. The epoxy nanocomposites with DOPO-t-SiO2 NPs as multifunctional additive exhibited not only high flexural strength and fracture toughness but also excellent flame retardant properties and thermal stability, compared to those of pristine epoxy and epoxy nanocomposites with a single additive of SiO2 or DOPO, respectively. Our approach allows a facile, yet effective strategy to synthesize a functional hybrid additive for developing flame retardant nanocomposites.
In this study, Bi0.5Sb1.5Te3.0 (BST) nanoparticles (NPs) with high crystallinities were synthesized via a mechanochemical process (MCP). X-ray diffraction (XRD), and Raman and X-ray photoelectron ...spectroscopy (XPS) spectra of the BST NPs showed that the Bi, Sb, and Te powders successfully formed BiSbTe phase and transmission electron microscopy (TEM) images, verifying the high crystallinity and smaller size, albeit agglomerated. The as-synthesized BST NPs with agglomerated clusters were ground into smaller sizes of approximately 41.8 nm with uniform distribution through a simple wet-milling process during 7 days. The thermal conduction behaviors of bulk alloys fabricated by spark plasma sintering (SPS) of the BST NPs were studied by comparing those of samples fabricated from as-synthesized BST NPs and a BST ingot. The thermal conductivities (κ) of the BST nanocomposites were significantly reduced by introducing BST NPs with smaller grain sizes and finer distributions in the temperature range from 300 to 500 K. The BST nanocomposites fabricated from wet-milled BST NPs offered ultralow κ values of 0.84 W m−1 K−1 at approximately 398 K.
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