超临界乙醇制备TiO_2/石墨烯纳米复合材料及其表征

以氧化石墨为载体、钛酸异丙酯为前驱体,利用超临界乙醇的超临界性能和还原性,制得了晶型完善的锐钛矿TiO2/石墨烯纳米复合材料。通过红外光谱(FTIR)、X射线光电子能谱(XPS)对采用Hummers法制得的氧化石墨(GO)进行表征;同时利用透射电子显微镜(TEM)、X射线衍射仪(XRD)对TiO2/石墨烯纳米复合材料进行研究。结果表明:成功制得了氧化石墨(GO)和晶型完善的锐钛矿TiO2/石墨烯纳米复合材料,并且发现二氧化钛在石墨烯纳米片层上呈现为有规则的颗粒,分散均匀,平均粒径为8.24nm。     

Interpenetrating polymer network/functionalized-reduced graphene oxide nanocomposite: As an advanced functional material

In this report, smart polyurethane-polystyrene interpenetrating polymer network (IPN)-based nanocomposites were fabricated using simultaneous polymerization technique with different doses of functionalized reduced graphene oxide (f-RGO). RGO was functionalized with monoglyceride of sunflower oil in the presence of toluene diisocyanate. Successful functionalization of RGO was supported by Fourier-transform infrared spectroscopy, X-Ray diffraction, and transmission electron microscopy analyses. Most interestingly, the fabricated IPN-based nanocomposites showed significant enhancements in mechanical (tensile strength: 165%; elongation at break: 198%; toughness: 340%) and thermal (thermally stable up to 262°C) properties upon incorporation of 1 weight% of f-RGO. Moreover, the fabricated nanocomposites exhibited outstanding chemical resistance, self-cleaning behavior through surface hydrophobicity (static contact angle: 125.6–136.5°), multi-stimuli responsive shape memory effect (100% recovery within 33–44 s by microwave and 265–308 s by sunlight) and thermally actuated artificial muscle-like behavior. Therefore, the studied smart nanocomposites with the aforementioned properties hold significant potential for possible advanced applications.     

Thermal,mechanical and γ-ray shielding properties of micro- and nano-Ta2O5 loaded DGEBA epoxy resin composites

In this work, we have investigated the synergistic effect of micro- and nano-Ta₂O₅ fillers in the epoxy matrix on the thermal, mechanical, and radioprotective properties of the composites. Morphological analysis revealed uniform dispersion of fillers in the matrix. Both the thermal stability and tensile properties of matrices have enhanced in the presence of fillers. Although the nanocomposites showed significantly higher tensile strength and Youngs modulus compared to micro-composites, the enhancement in these properties was predominant at low loadings. Dynamic mechanical analysis indicated good interfacial adhesion and positive reinforcing effect on the matrix even at higher loading (30 wt%) of nano-Ta₂O₅. γ-Ray attenuation studies performed in the energy range of 0.356–1.332 MeV revealed better γ-ray shielding ability of nanocomposites compared to microcomposites at same weight fraction of fillers. In particular, γ-ray attenuation at 0.356 MeV for 30 wt% nano-Ta₂O₅ loaded epoxy composite was enhanced by around 13% compared to the microcomposite at the same loading. Increased surface-to-volume ratio of nanofillers and consequent increase in matrix-filler adhesion and radiation-matter interaction have manifested in an overall enhancement in the thermal, mechanical, dynamic mechanical, and radiation shielding characteristics of nano-Ta₂O₅/epoxy composites, proving them as promising γ-ray shields.     

Melt extrusion and blow molding parts-per-million POSS interspersed the macromolecular network and simultaneously enhanced thermomechanical and barrier properties of polyolefin films

There has been the expectation that polymers filled with small concentrations of nanosized particles will exhibit superior thermomechanical properties. We demonstrate that dispersing parts-per-million (ppm) polyhedral oligomeric silsesquioxane (POSS) nanochemicals by melt extrusion with polyolefins increased the tensile Young's modulus, yield stress, and toughness of blow molded and extruded films without penalizing extensibility, which is common to polymers reinforced with nano/microparticles. Transmission electron microscopy showed that the key to mechanical reinforcement is the spatial distribution of POSS at ca. single nanocage thus enabling interspersion of the macromolecular network. The thermal stability, water contact angle, and oxygen transmission of the films were also enhanced enabling a single component food package capable to keep food without decay for two weeks. The physical properties are improved when the nanoparticle size <D> is about the size of the virtual tube diameter d_t, that is, <D>/d_t ≈ 1. The enhancement of physical properties by placing the nanoparticle in the free space of the molecular network is a new paradigm in engineering polymer nanocomposites and opens opportunities for recyclable single component packaging films and tunable lightweight engineering and biomimetic materials.     

Polystyrene and poly(methyl methacrylate) interfaces reinforced with diblock carbon nanotubes

An asymmetric double cantilever beam test was used to determine the ability of carbon nanotubes with varying chemistry along their lengths, that is, diblock nanotubes, to compatibilize the polystyrene/poly(methyl methacrylate) (PS/PMMA) interface. PS molecules were grafted primarily to one of the blocks to cause that block to migrate to the PS phase since otherwise both blocks would prefer to reside in PMMA. Fracture toughnesses increased monotonically with increasing diblock carbon nanotube concentration and maximum values were like those for block copolymer-reinforced interfaces while single-chemistry nanotubes showed no reinforcing effect. However, the abrupt increase in fracture toughness with added compatibilizer indicative of a transition to crazing was not found consistent with nanotubes suppressing crazing in homopolymers. Scanning electron microscopy images of the fractured surfaces show agglomerates of carbon nanotubes present which are likely limiting the efficacy of carbon nanotubes at toughening the interface.     

Chemiresistor sensor using elastomer-functionalized carbon nanotube nanocomposites for the detection of gasoline spills

Two types of multi-walled carbon nanotube (MWNT)-based elastomer nanocomposites are used as a sensor material for the detection of gasoline spills by applying the interdigitated electrode (IDE) device. MWNT-g-polyisoprene (PI) and Si-MWNT/natural rubber (NR) are prepared by applying “grafting-from” and “grafting-to” process, respectively. When compared based on the identical condition of gasoline sensing test, the maximum response value to the exposure of gasoline is 17.5 for MWNT-g-PI sensor and 12.9 for Si-MWNT/NR sensor, which reach the maximum in less than 3 min. The MWNT-g-PI sensor selectively detects gasoline, and its response is completely reversible. It shows that the longer chain length of PI brings about the larger response of MWNT-g-PI sensor to gasoline. The sensitivity of MWNT-g-PI sensor highly depends on both how much gasoline is exposed to the sensor and what bias voltage is applied to the IDE device. The IDE sensor using MWNT-g-PI nanocomposites effectively detects gasoline spills.     

Effects of nanosized metallic palladium loading and calcination on characteristics of composite silica

1　INTRODUCTIONThemotivationfortheresearchoncolloidalmet alparticlesstemmedfromtheiruniqueelectro opticalandelectrochemicalproperties[13] .Duringthe pastfew years,aflurryofactivityhasbeendirectedto wardsthepreparationofnanosizedmetallicparticlesduetolargeenhancementinthephysicalpropertiesofnanostructuredcompositescomparedtothebulk[4 6 ] .Therefore ,size dependentchangesinband gapener gy ,excited stateelectronicbehaviorandopticalspec traaregenerateddrasticallyfromthoseknownforthemolecularan…     

Effect of ball milling process on the microstructure of titanium-nanohydroxyapatite composite powder

Titaninm-nanohydroxyapatite （Ti-nHA） composite powders, composed of titanium with 10 vol.% and 20 vol.% of nano-hydroxyapatite, were milled in a planetary ball mill using alcohol media to avoid excessive heat. XRD and SEM were performed for characterization of the microstructure, and the homogeneity of Ti/HA nanocomposite powder was evaluated by EPMA with prolonged ball milling time. The results show that under the condition of wet milling, the grain size of Ti-nHA composite powders is decreased with the increase in ball milling time and the amount of the addition of nHA. While for milling of 30 h, the nanocomposite powder with free structure, which consists of the nano-hydroxyapatite （nHA） particles and titanium （Ti） phase, is obtained. Three stages of milling can be observed from the dement mapping of Ti, Ca, and P by EPMA; meanwhile, it is found that the nHA would be more homogenously distributed after milling for 30 h.     

High‐Performance Piezoelectric Nanogenerators with Imprinted P(VDF‐TrFE)/BaTiO3 Nanocomposite Micropillars for Self‐Powered Flexible Sensors

Piezoelectric nanogenerators with large output, high sensitivity, and good flexibility have attracted extensive interest in wearable electronics and personal healthcare. In this paper, the authors propose a high‐performance flexible piezoelectric nanogenerator based on piezoelectrically enhanced nanocomposite micropillar array of polyvinylidene fluoride‐trifluoroethylene (P(VDF‐TrFE))/barium titanate (BaTiO₃) for energy harvesting and highly sensitive self‐powered sensing. By a reliable and scalable nanoimprinting process, the piezoelectrically enhanced vertically aligned P(VDF‐TrFE)/BaTiO₃ nanocomposite micropillar arrays are fabricated. The piezoelectric device exhibits enhanced voltage of 13.2 V and a current density of 0.33 µA cm^?2, which an enhancement by a factor of 7.3 relatives to the pristine P(VDF‐TrFE) bulk film. The mechanisms of high performance are mainly attributed to the enhanced piezoelectricity of the P(VDF‐TrFE)/BaTiO₃ nanocomposite materials and the improved mechanical flexibility of the micropillar array. Under mechanical impact, stable electricity is stably generated from the nanogenerator and used to drive various electronic devices to work continuously, implying its significance in the field of consumer electronic devices. Furthermore, it can be applied as self‐powered flexible sensor work in a noncontact mode for detecting air pressure and wearable sensors for detecting some human vital signs including different modes of breath and heartbeat pulse, which shows its potential applications in flexible electronics and medical sciences.