有机-无机复合CdS纳米晶的制备及表征

本文采用液液两相法,在甲苯、甲醇和水两相体系中制备了烷基硫醇和芳杂环硫醇修饰的有机-无机复合的CdS半导体纳米晶.通过紫外可见吸收光谱、X-射线光电子能谱、X-射线粉末衍射、透射电子显微镜、元素分析和热重分析检测手段对样品的结构和组成进行了表征.结果表明:该方法所制备的硫化镉纳米晶是由无机纳米核及通过化学键吸附在其表面的硫醇分子所组成.纳米晶的平均粒径约为5nm,尺寸均匀,稳定性高,在空气中可长时间保存.     

Absorption Properties of Hybrid SnO<Subscript>2</Subscript> Nanocrystal-Carbon Nanotube Structures

Tin oxide (SnO₂) nanocrystals of a few nanometers are of great interest for electronic applications. Here we present a mini-arc plasma method to produce aerosol tin oxide nanocrystals at atmospheric pressure. The product SnO₂ nanocrystals are then assembled onto the external surface of carbon nanotubes (CNTs) to form hybrid SnO₂–CNT structures. The absorption properties of both the SnO₂ nanocrystals and the SnO₂–CNT hybrid structures have been characterized. Quantum size effects have been observed for as-produced SnO₂ nanocrystals. The intrinsic nanoparticle size selection during the assembly process results in a blue shift of the absorption spectrum for hybrid nanostructures.     

Evaluation of HfAlO high-k materials for control dielectric applications in non-volatile memories

In this paper, we evaluate the potentiality of hafnium aluminium oxide (HfAlO) high-k materials for control dielectric application in non-volatile memories. We analyze the electrical properties (conduction and parasitic trapping) of HfAlO single layers and SiO₂/HfAlO/SiO₂ triple layer stacks as a function of the HfAlO thickness and Hf:Al ratio. A particular attention is given to the electrical behaviour of the samples at high temperature, up to 250 °C. Experimental results obtained on silicon nanocrystal memories demonstrate the high advantage of HfAlO based control dielectrics on the memory performances for Fowler-Nordheim operation. Then an analytical model is presented, to simulate the program erase characteristics in the transient regime and at saturation, depending on the high-k control dielectric properties. A very good agreement is obtained between the experimental data and the simulation results.     

Reinforcing effects of aminosilane-functionalized graphene on the tribological and mechanical behaviors of epoxy nanocomposites

In this study, aminopropyl trimethoxysilane as an interfacial modifier was introduced on the surface of graphene (Gr) nanoplatelets. The effects of the silane-modified graphene (SGr) loading (0, 0.05, 0.1, 0.3, and 0.5 wt %) and silane modification on the tensile, compressive, interlaminar shear stress (ILSS), and tribological properties of the epoxy-based nanocomposites were investigated. Out of these specimens, the highest values of ILSS and compressive strength were related to the 0.3 wt % SGr–epoxy nanocomposite. The addition of SGr enhanced the tensile strength and strain to failure only at low contents (i.e., 0.05 wt %). Also, the tensile and compressive moduli were improved, and the highest values were observed at a 0.5 wt % SGr loading. In addition, decreases of approximately 40 and 68% in the coefficient of friction and wear rate, respectively, were observed at a 0.3 wt % SGr loading. Enhanced tensile, compressive, ILSS, and wear properties in the SGr–epoxy specimens were observed compared to those in the Gr–epoxy specimens. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47410.     

Electrorheological behavior of low filled suspensions of highly anisometric montmorillonite particles

The electrorheological (ER) behavior of modified montmorillonite (MMT) suspensions in polydimethylsiloxane is studied. As established by rotational viscometry, the samples with a dispersed phase concentration from 1 to 8 wt % reveal viscous Newtonian behavior and dramatically change their properties to elastic when electric field is applied. The rheological characteristics of the suspensions over 0–7 kV mm⁻¹ range of electric field strengths are also studied. Novel X-ray diffraction method is developed to evaluate the suspension of the filler in a siloxane medium and to calculate the degree of its exfoliation. The dependence of exfoliation degree, dielectric, and ER characteristics on the type of modifier in the MMT structure is considered. Based on the obtained data, a new model of system behavior with the various types of fillers is proposed and the prospects of utilizing MMT as a filler for ER fluids are demonstrated. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47678.     

Study on thermal conductive PA6 composites with 3-dimensional structured boron nitride hybrids

To develop thermally conductive PA6 composites with the aim of decreasing filler content, structure-complexed fillers were fabricated. This research presented an effective approach by noncovalent functionalization of poly(dopamine) (PDA) followed by silver nanoparticles decoration to fabricate 3-dimensional (3-D) structured boron nitride hybrids (BN@PDA@AgNPs). BN hybrids were then introduced into PA6 to prepare thermally conductive PA6 composites. The results demonstrated that PA6/BN hybrids (PMB) composites exhibited higher thermal conducivity compared with PA6/BN composites, which revealed more effective construction of thermal conductive network in the composites with the addition of 3-D structured fillers. The effects of BN hybrids with different loadings on thermal stability, mechanical property, as well as electrical resistance of the composites were also analyzed. Overall, the prepared PMB composites exhibited outstanding performance in thermal conductivity, thermal stability, mechanical property, while retaining good electrical insulating property, which showed a potential application in electronic packaging fields. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47630.     

Surface texture and barrier performance of poly(lactic acid)–cellulose nanocrystal extruded-cast films

In this study, we assessed the influence of cellulose nanocrystal (CNC) addition level (0.5–2 wt %) on the surface texture, thickness, and barrier properties of poly(lactic acid) (PLA) extruded-cast films. Regardless of the CNC content, the addition of CNC increased the surface average roughness and maximum roughness of the PLA films in both the machine and cross-machine directions because of the presence of CNC agglomerates. The increased roughness resulted in films with uneven thicknesses; this affected their accurate measurements with a conventional micrometer. Rather, accurate thickness measurements were obtained through the density method, a more appropriate thickness measurement method for films with rough surfaces. The permeability values were negatively correlated with the increased crystallinity. Both the water vapor permeability and oxygen permeability (OP) values decreased significantly by approximately 26–45 and 25–50%, respectively, as the CNC content increased from 0.5 to 2 wt % because of the tortuosity effect. The OP values of the neat PLA and composite films remained insensitive to changes in the relative humidity (from 0 to 75%) when they were tested at 23 °C. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47594.     

Facile modification of polysulfone hollow-fiber membranes via the incorporation of well-dispersed iron oxide nanoparticles for protein purification

Protein existence in wastewater is an important issue in wastewater management because proteins are generally present as contaminants and foulants. Hence, in this study, we focused on designing a polysulfone (PSf) hollow-fiber membrane embedded with hydrophilic iron oxide nanoparticles (IONPs) for protein purification by means of ultrafiltration. Before membrane fabrication, the dispersion stability of the IONPs was enhanced by the addition of a stabilizer, namely, citric acid (CA). Next, PSf–IONP–CA nanocomposite hollow-fiber membranes were prepared via a dry–wet spinning process and then characterized in terms of their hydrophilicity and morphology. Ultrafiltration and adsorption experiments were then conducted with bovine serum albumin as a model protein. The results that an IONP/CA weight ratio of 1:20 contributed to the most stable IONP dispersion. It was also revealed that the membrane incorporated with IONP–CA at a weight ratio of 1:20 exhibited the highest pure water permeability (58.6 L m⁻² h⁻¹ bar⁻¹) and protein rejection (98.5%) while maintaining a low protein adsorption (3.3 μg/cm²). The addition of well-dispersed IONPs enhanced the separation features of the PSf hollow-fiber membrane for protein purification. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47502.     

SiO2-modified nanocomposite nanofiltration membranes with high flux and acid resistance

Thin-film nanocomposite (TFN) nanofiltration (NF) membranes with superior properties were prepared using hydrophilic SiO₂ (HGPN-SiO₂) nanoparticles as the inorganic modifying monomer by an interfacial polymerization (IP) process. The effects of HGPN-SiO₂ on the morphology and surface properties of the prepared NF membranes were characterized by attenuated total reflectance–Fourier transform infrared spectroscopy, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, surface zeta potential, and static contact angle. The addition of HGPN-SiO₂ can effectively improve the permeate flux of the NF membranes. When the HGPN-SiO₂ concentration in the aqueous phase was 0.08 wt %, the permeate flux of the TFN-NF membrane was twice that of the pure NF membrane. Furthermore, the acid resistance of the TFN-NF membrane was clearly improved with the addition of HGPN-SiO₂. Under neutral conditions, the TFN-NF membrane showed superior flux and salt rejection stability in a long-running operation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47436.