Aijie Ma

Enhanced Thermal Conductivity of Epoxy Composites with MWCNTs/AlN Hybrid Filler

To further improve the thermal conductivity of epoxy resin, the multi-walled carbon nanotube/aluminum nitride (MWCNTs/AlN) hybrid filler was employed to prepare thermal conductivity MWCNTs/AlN/epoxy composite by casting process, and the silane coupling reagent of γ-glycidoxy propyl trimethoxy silane(KH-560) was also used to functionalize the surface of MWCNTs and/or AlN. Results revealed that, the thermal conductivity of epoxy resin was improved remarkably with the addition of MWCNTs/AlN hybrid filler, a higher thermal conductivity of 1.04 W/mK could be achieved with 29 wt% MWCNTs/AlN hybrid filler (4 wt% MWCNTs +25 wt% AlN), about 5 times higher than that of native epoxy resin. And the epoxy composite with 29 wt% MWCNTs/AlN hybrid filler possessed better thermal conductivity and mechanical properties than those of single 5 wt% MWCNTs or 40 wt% AlN. The thermal decomposition temperature of MWCNTs/AlN/epoxy composite was increased with the addition of MWCNTs/AlN hybrid filler. For given filler loading, surface treatment of MWCNTs and/or AlN by KH-560 exhibited a positive effect on the thermal conductivity of epoxy composite.

Improved Thermal Conductivity of Silicon Carbide/Carbon Fiber/Epoxy Resin Composites

The surface functionalized silicon carbide/carbon fiber (SiC/CF) hybrid fillers were introduced to improve the thermal conductivities and mechanical properties of the epoxy resin composites. Results revealed that, the thermal conductivities of epoxy resin composites were increased with the increasing volume fraction of SiC, and a higher thermal conductivity of 1.226 W/mK could be achieved with 28 vol% treated SiC/CF hybrid fillers (25 vol% treated SiC +3 vol% treated CF), about 6 times higher than that of native epoxy resin (0.202 W/mK). Both the flexural strength and impact strength of the epoxy resin composites increased up to 5 vol% incorporation, but decreased with the further addition of SiC. However, the electrical conductivity was decreased with the increasing volume fraction of SiC. For a given SiC/CF hybrid fillers loading, the surface functionalized SiC/CF hybrid fillers exhibited a positive effect on the thermal conductivities and mechanical properties of the epoxy resin composites.

Dispersion, Mechanical and Thermal Properties of Epoxy Resin Composites Filled with the Nanometer Carbon Black

The nanometer carbon black (CB) was employed to prepare epoxy resin/carbon black (EP/CB) composites by blending-casting method. The different modified methods of silicone coupling agent were used to improve the dispersion of CB in epoxy resin. The mechanical and thermal properties of EP/CB composites were investigated. Experimental results showed that the mechanical properties increased at first, but decreased with excessive addition of CB. When the mass fraction of CB was 2%, the mechanical properties were maximum. The use of modified CB significantly enhanced the mechanical properties of the composites. For given CB loading, the CB modified by pretreatment method displayed better dispersion in the epoxy resin than that of the direct mixing method. SEM observation revealed that the tensile fracture surface of the composite filled with 2 wt% modified CB held more microcracks than that of 5 wt% modified CB, and the formed microcracks could consume more energy of rupture, finally to have better tensile strength. DSC analysis showed that the glass transition temperature (Tg) of the composites increased with the increasing mass fraction of CB.

The Preparation and Cure Kinetics Researches of Thermal Conductivity Epoxy/AlN Composites

The aluminum nitride (AlN) was employed to prepare epoxy/AlN composites by blending-casting moulding method, two different coupling agents were used to functionalize the surface of AlN. The thermal conductivity and mechanical properties of the composites were investigated. And the cure kinetics of the EP/AlN composites was studied by means of isothermal DSC. Results revealed that the thermal conductivity of EP improved remarkably with the addition of AlN, a higher thermal conductivity of 1.05 W/mK can be achieved with 42 vol% AlN, about 5 times higher than that of native epoxy resin. And the flexural and impact strength of the EP/AlN composites were optimal with 3.3 vol% AlN. The curing process of the EP/AlN composites contained autocatalytic mechanism, the whole process was according with the Kamal model. The presence of AlN did not change the cure reaction mechanism, and had little effecting on the activation energy, but decreased the rate constants kl and k2.

Dually Synergetic Network Hydrogels with Integrated Mechanical Stretchability, Thermal Responsiveness, and Electrical Conductivity for Strain Sensors and Temperature Alertors

The first example of dually synergetic network hydrogel, which has integrated mechanical stretchability, thermal responsiveness, and electrical conductivity, has been constructed by a versatile and topological co-cross-linking approach. Poly( N-isopropylacrylamide) (PNIPAAm) is introduced as the thermally responsive ingredient, and polyaniline (PANI) is selected as the electrically conductive ingredient. PNIPAAm network is cross-linked by double-bond end-capped Pluronic F127 (F127DA). PANI network is doped and cross-linked by phytic acid. These two ingredients are further mechanically interlocked. Due to the integrated multiple functionalities, the topologically co-cross-linked hydrogels, as will be mentioned as F-PNIPAAm/PANI hydrogels, can be fabricated into resistive-type strain sensors. The strain sensors can achieve a gauge factor of 3.92, a response time of 0.4 s, and a sensing stability for at least 350 cycles and can be further applied for monitoring human motions, including motion of two hands, bending of joints, and even swallowing and pulse rate. Moreover, F-PNIPAAm/PANI hydrogels are utilized to construct efficient temperature alertors based on the disconnection of circuits induced by volume shrinkage at high temperature.

Mechanical and Thermal Conductivities of MWCNTs/Si3N4/Epoxy Composites

The treated multiwalled carbon nanotube/silicon nitride (MWCNTs/Si3N4) hybrid fillers were employed to fabricate thermal conductive MWCNTs/Si3N4/epoxy composites. The thermal conductive coefficient of the composites with 45 wt.% treated MWCNTs/Si3N4 hybrid fillers (5 wt.% MWCNTs + 40 wt.% Si3N4) was 2.42 W/mK. The mechanical properties of the composites were optimal with 7 wt.% MWCNTs/Si3N4 hybrid fillers (2 wt.% MWCNTs + 5 wt.% Si3N4). The composites possessed better thermal stabilities than that of native epoxy composites. For the same hybrid fillers loading, the surface treatment of MWCNTs/Si3N4 hybrid fillers exhibited a positive effect on the thermal conductivities of MWCNTs/Si3N4/epoxy composites.

Dual-functional probe based on rhodamine for sequential Cu 2+ and ATP detection in vivo

A rhodamine-based fluorescent probe for Cu2+ and ATP has been designed. The fluorescence intensity/absorbance was significantly enhanced upon the addition of Cu2+ owning to the opening of the spiro-ring of rhodamine, which quickly returned to the original level due to the reconstruction of the probe by the reacting with ATP. Cu2+/ATP-induced fluorescent intensity/aborbance changes showed a good linear relationship with the concentration of Cu2+/ATP in the range of 2-20 μM/0-10 μM with a detection limit of 0.1 μM/1.0 μM. The proposed method is simple in design and fast in operation, and is suitable for the reversible monitoring of Cu2+ and ATP in bioanalytical applications.

Poly(NIPAAm-co-Ru(bpy) 3 2+ ) hydrogels crosslinked by double-bond end-capped Pluronic F127: preparation, properties and coupling with the BZ reaction

Topological network design is an effective way to obtain new functionalities and regulate the properties of stimuli responsive hydrogels. In this work, poly(NIPAAm-co-Ru(bpy)32+) hydrogels (NIPAAm: N-isopropylacrylamide, Ru(bpy)32+: Ruthenium bipyridine complex monomer) crosslinked by amphiphilic triblock copolymers were designed and constructed by a photo-induced gelation method, utilizing double-bond end-capped Pluronic F127 (F127DA) as the crosslinking agent, NIPAAm and Ru(bpy)32+ as the monomers, α-ketoglutaric acid as the photoinitiator and H2O as the solvent. The resulting F127DA crosslinked hydrogels exhibit unique swelling behaviors, mechanical properties, fluorescent behaviors and thermosensitive properties and can be coupled with the BZ reaction. The present example may enrich the family of metal-containing polymer materials and provide clues to develop other functional hydrogels by designing topologically crosslinked network.

Extremely stretchable and electrically conductive hydrogels with dually synergistic networks for wearable strain sensors

Flexible strain sensors are highly used in soft robotics, human–machine interfaces and health monitoring devices. However, it is still a big challenge to construct strain sensors with excellent mechanical properties and broad sensing ranges. In this study, a class of extremely stretchable and electrically conductive hydrogels with dually synergistic networks are fabricated for wearable resistive-type strain sensors. Dually synergistic networks are composed of a soft poly(acrylic acid) (PAA) network and a rigid conductive polyaniline (PANI) network. The PAA network is crosslinked by amphiphilic block copolymers, and the PANI network is chemically doped and ionically crosslinked by phytic acid and these two networks are further interlocked by physical entanglements, hydrogen bonds and ionic interactions. The resulting hydrogels have high tensile strength, controllable conductivity and large tensile deformation (1160%). Moreover, these hydrogels are utilized for fabricating strain sensors with good sensitivity and a wide sensing range (0–1130%). The high performances of hydrogels make such strain sensors suitable for wearable devices monitoring both subtle and large strains induced by human motions, including moving of two hands, bending of joints, conducting of gestures and swallowing.